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Sample records for alkaline earth halides

  1. Alkaline and alkaline earth metal phosphate halides and phosphors

    DOEpatents

    Lyons, Robert Joseph; Setlur, Anant Achyut; Cleaver, Robert John

    2012-11-13

    Compounds, phosphor materials and apparatus related to nacaphite family of materials are presented. Potassium and rubidium based nacaphite family compounds and phosphors designed by doping divalent rare earth elements in the sites of alkaline earth metals in the nacaphite material families are descried. An apparatus comprising the phosphors based on the nacaphite family materials are presented herein. The compounds presented is of formula A.sub.2B.sub.1-yR.sub.yPO.sub.4X where the elements A, B, R, X and suffix y are defined such that A is potassium, rubidium, or a combination of potassium and rubidium and B is calcium, strontium, barium, or a combination of any of calcium, strontium and barium. X is fluorine, chlorine, or a combination of fluorine and chlorine, R is europium, samarium, ytterbium, or a combination of any of europium, samarium, and ytterbium, and y ranges from 0 to about 0.1.

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

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

    SciTech Connect

    Boatner, Lynn A; Ramey, Joanne Oxendine; Kolopus, James A; Neal, John S; Cherepy, Nerine; Payne, Stephen A.; Beck, P; Burger, Arnold; Rowe, E; Bhattacharya, P.

    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.

  4. Recent advances in tailoring the aggregation of heavier alkaline earth metal halides, alkoxides and aryloxides from non-aqueous solvents.

    PubMed

    Fromm, Katharina M

    2006-11-21

    This overview on one of the subjects treated in our group deals with the synthesis and study of low-dimensional polymer and molecular solid state structures formed with alkaline earth metal ions in non-aqueous solvents. We have chosen several synthetic approaches in order to obtain such compounds. The first concept deals with the "cutting out" of structural fragments from a solid state structure of a binary compound, which will be explained with reference to BaI2. Depending on the size and concentration of oxygen donor ligands, used as chemical scissors on BaI2, three-, two-, one- and zero-dimensional derived adducts of BaI2 are obtained, comparable to a structural genealogy tree for BaI2. A second part deals with the supramolecular approach for the synthesis of low dimensional polymeric compounds based on alkaline earth metal iodides, obtained by the combination of metal ion coordination with hydrogen bonding between the cationic complexes and their anions. Certain circumstances allow rules to be established for the prediction of the dimensionality of a given compound, contributing to the fundamental problem of structure prediction in crystal engineering. A third section describes a synthetic approach for generating pure alkaline earth metal cage compounds as well as alkali and alkaline earth mixed metal clusters. A first step deals with different molecular solvated alkaline earth metal iodides which are investigated as a function of the ligand size in non-aqueous solvents. These are then reacted with some alkali metal compound in order to partially or totally eliminate alkali iodide and to form the targeted clusters. These unique structures of ligand stabilized metal halide, hydroxide and/or alkoxide and aryloxide aggregates are of interest as potential precursors for oxide materials and as catalysts. Approaches to two synthetic methods of the latter, sol-gel and (MO)CVD (metal-organic chemical vapour deposition), are investigated with some of our compounds. (D

  5. Effect of metal cation replacement on the electronic structure of metalorganic halide perovskites: Replacement of lead with alkaline-earth metals

    NASA Astrophysics Data System (ADS)

    Pazoki, Meysam; Jacobsson, T. Jesper; Hagfeldt, Anders; Boschloo, Gerrit; Edvinsson, Tomas

    2016-04-01

    Organic and inorganic lead halogen perovskites, and in particular, C H3N H3Pb I3 , have during the last years emerged as a class of highly efficient solar cell materials. Herein we introduce metalorganic halogen perovskite materials for energy-relevant applications based on alkaline-earth metals. Based on the classical notion of Goldschmidt's rules and quantum mechanical considerations, the three alkaline-earth metals, Ca, Sr, and Ba, are shown to be able to exchange lead in the perovskite structure. The three alkaline-earth perovskites, C H3N H3Ca I3,C H3N H3Sr I3 , and C H3N H3Ba I3 , as well as the reference compound, C H3N H3Pb I3 , are in this paper investigated with density functional theory (DFT) calculations, which predict these compounds to exist as stable perovskite materials, and their electronic properties are explored. A detailed analysis of the projected molecular orbital density of states and electronic band structure from DFT calculations were used for interpretation of the band-gap variations in these materials and for estimation of the effective masses of the electrons and holes. Neglecting spin-orbit effects, the band gap of MACa I3,MASr I3 , and MABa I3 were estimated to be 2.95, 3.6, and 3.3 eV, respectively, showing the relative change expected for metal cation exchange. The shifts in the conduction band (CB) edges for the alkaline-earth perovskites were quantified using scalar relativistic DFT calculations and tight-binding analysis, and were compared to the situation in the more extensively studied lead halide perovskite, C H3N H3Pb I3 , where the change in the work function of the metal is the single most important factor in tuning the CB edge and band gap. The results show that alkaline-earth-based organometallic perovskites will not work as an efficient light absorber in photovoltaic applications but instead could be applicable as charge-selective contact materials. The rather high CB edge and the wide band gap together with the large

  6. Absorption Coefficient of Alkaline Earth Halides.

    DTIC Science & Technology

    1980-04-01

    levels . As a natural consequence, the magnitude of the absorption coefficient is the key parameter in selecting laser window materials. Over the past...of as can be achieved through improved crystal growing techniques and surface polishing. 2.5. Urbach’s Rule A central question for the development of...high absorption levels , inaccuracies progressively increasing with decreasing absorption level , a natural consequence of decreasing in instrumental

  7. Alkali metal and alkali earth metal gadolinium halide scintillators

    DOEpatents

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

    2016-08-02

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

  8. Alkaline earth filled nickel skutterudite antimonide thermoelectrics

    DOEpatents

    Singh, David Joseph

    2013-07-16

    A thermoelectric material including a body centered cubic filled skutterudite having the formula A.sub.xFe.sub.yNi.sub.zSb.sub.12, where A is an alkaline earth element, x is no more than approximately 1.0, and the sum of y and z is approximately equal to 4.0. The alkaline earth element includes guest atoms selected from the group consisting of Be, Mb, Ca, Sr, Ba, Ra and combinations thereof. The filled skutterudite is shown to have properties suitable for a wide variety of thermoelectric applications.

  9. Alkaline earth metal catalysts for asymmetric reactions.

    PubMed

    Kobayashi, Shū; Yamashita, Yasuhiro

    2011-01-18

    The group 2 alkaline earth metals calcium (Ca), strontium (Sr), and barium (Ba) are among the most common elements on Earth, abundant in both the sea and the Earth's crust. Although they are familiar in our daily lives, their application to organic synthesis has, so far, been limited. Some particularly useful properties of these elements include (i) low electronegativity, (ii) a stable oxidation state of +2, meaning that they can potentially form two covalent bonds with anions, and (iii) the ability to occupy a variety of coordination sites due to their large ionic radius. Furthermore, the alkaline earth metals, found between the group 1 and group 3 elements, show mild but significant Lewis acidity, which can be harnessed to control coordinative molecules via a Lewis acid-base interaction. Taken together, these characteristics make the metals Ca, Sr, and Ba very promising components of highly functionalized acid-base catalysts. In this Account, we describe the development of chiral alkaline earth metal catalysts for asymmetric carbon-carbon bond-forming reactions. Recently prepared chiral alkaline earth metal complexes have shown high diastereo- and enantioselectivities in fundamental and important chemical transformations. We chose chiral bisoxazoline (Box) derivatives bearing a methylene tether as a ligand for chiral modification. These molecules are very useful because they can covalently coordinate to alkaline earth metals in a bidentate fashion through deprotonation of the tether portion. It was found that chiral calcium-Box complexes could successfully promote catalytic asymmetric 1,4-addition and [3 + 2] cycloaddition reactions with high diastereo- and enantioselectivities. Both the calcium-Box complexes and chiral strontium-bis-sulfonamide and chiral barium-BINOLate complexes could catalyze asymmetric 1,4-addition reactions with high enantioselectivities. Furthermore, we designed a calcium-neutral coordinative ligand complex as a new type of chiral alkaline

  10. The alkaline earth intercalates of molybdenum disulfide

    NASA Technical Reports Server (NTRS)

    Somoano, R. B.; Hadek, V.; Rembaum, A.; Samson, S.; Woollam, J. A.

    1975-01-01

    Molybdenum disulfide has been intercalated with calcium and strontium by means of the liquid ammonia technique. Chemical, X-ray, and superconductivity data are presented. The X-ray data reveal a lowering of crystal symmetry and increase of complexity of the structure upon intercalation with the alkaline earth metals. The Ca and Sr intercalates start to superconduct at 4 and 5.6 K, respectively, and show considerable anisotropy regarding the critical magnetic field.

  11. Alkaline earth cation extraction from acid solution

    DOEpatents

    Dietz, Mark; Horwitz, E. Philip

    2003-01-01

    An extractant medium for extracting alkaline earth cations from an aqueous acidic sample solution is described as are a method and apparatus for using the same. The separation medium is free of diluent, free-flowing and particulate, and comprises a Crown ether that is a 4,4'(5')[C.sub.4 -C.sub.8 -alkylcyclohexano]18-Crown-6 dispersed on an inert substrate material.

  12. Oxidation catalysts on alkaline earth supports

    DOEpatents

    Mohajeri, Nahid

    2017-03-21

    An oxidation catalyst includes a support including particles of an alkaline earth salt, and first particles including a palladium compound on the support. The oxidation catalyst can also include precious metal group (PMG) metal particles in addition to the first particles intermixed together on the support. A gas permeable polymer that provides a continuous phase can completely encapsulate the particles and the support. The oxidation catalyst may be used as a gas sensor, where the first particles are chemochromic particles.

  13. Diclofenac salts. III. Alkaline and earth alkaline salts.

    PubMed

    Fini, Adamo; Fazio, Giuseppe; Rosetti, Francesca; Angeles Holgado, M; Iruín, Ana; Alvarez-Fuentes, Josefa

    2005-11-01

    Diclofenac salts containing the alkaline and two earth alkaline cations have been prepared and characterized by scanning electron microscopy (SEM) and EDAX spectroscopy; and by thermal and thermogravimetric analysis (TGA): all of them crystallize as hydrate when precipitated from water. The salts dehydrate at room temperature and more easily on heating, but recovery the hydration, when placed in a humid environment. X-ray diffraction spectra suggest that on dehydration new peaks appear on diffractograms and the lattice of the salts partially looses crystallinity. This phenomenon is readily visible in the case of the calcium and magnesium salts, whose thermograms display a crystallization exotherm, before melting or decomposing at temperatures near or above 200 degrees C; these last salts appear to form solvates, when prepared from methanol. The thermogram of each salt shows a complex endotherm of dehydration about 100 degrees C; the calcium salt displays two endotherms, well separated at about 120 and 160 degrees C, which disappear after prolonged heating. Decomposition exotherms, before or soon after the melting, appear below 300 degrees C. The ammonium salt is thermally unstable and, when heated to start dehydration, dissociates and leaves acidic diclofenac.

  14. Method of increasing the sulfation capacity of alkaline earth sorbents

    DOEpatents

    Shearer, J.A.; Turner, C.B.; Johnson, I.

    1980-03-13

    A system and method for increasing the sulfation capacity of alkaline earth carbonates to scrub sulfur dioxide produced during the fluidized bed combustion of coal in which partially sulfated alkaline earth carbonates are hydrated in a fluidized bed to crack the sulfate coating and convert the alkaline earth oxide to the hydroxide. Subsequent dehydration of the sulfate-hydroxide to a sulfate-oxide particle produces particles having larger pore size, increased porosity, decreased grain size and additional sulfation capacity. A continuous process is disclosed.

  15. Method of increasing the sulfation capacity of alkaline earth sorbents

    DOEpatents

    Shearer, John A.; Turner, Clarence B.; Johnson, Irving

    1982-01-01

    A system and method for increasing the sulfation capacity of alkaline earth carbonates to scrub sulfur dioxide produced during the fluidized bed combustion of coal in which partially sulfated alkaline earth carbonates are hydrated in a fluidized bed to crack the sulfate coating and convert the alkaline earth oxide to the hydroxide. Subsequent dehydration of the sulfate-hydroxide to a sulfate-oxide particle produces particles having larger pore size, increased porosity, decreased grain size and additional sulfation capacity. A continuous process is disclosed.

  16. Observation of vapor pressure enhancement of rare-earth metal-halide salts in the temperature range relevant to metal-halide lamps

    SciTech Connect

    Curry, J. J.; Henins, A.; Hardis, J. E.; Estupinan, E. G.; Lapatovich, W. P.; Shastri, S. D.

    2012-02-20

    Total vapor-phase densities of Dy in equilibrium with a DyI{sub 3}/InI condensate and Tm in equilibrium with a TmI{sub 3}/TlI condensate have been measured for temperatures between 900 K and 1400 K. The measurements show strong enhancements in rare-earth vapor densities compared to vapors in equilibrium with the pure rare-earth metal-halides. The measurements were made with x-ray induced fluorescence on the sector 1-ID beam line at the Advanced Photon Source. The temperature range and salt mixtures are relevant to the operation of metal-halide high-intensity discharge lamps.

  17. Study of point defects in alkaline-earth sulfides

    SciTech Connect

    Pandey, R.; Kunz, A.B.; Vail, J.M.

    1988-11-01

    The results of a computer simulation study of point defects including vacancy, interstitial, and F/sup +/ center in alkaline-earth sulfides are presented. The study is based on ICECAP/HADES simulation procedures and uses empirical interionic potentials obtained from the analysis of macroscopic data for these materials. The results predict the dominance of Schottky disorder and suggest that vacancy migration predominates in alkaline-earth sulfides. Furthermore, the calculated F/sup +/ center absorption energy is in good agreement with the experimental data deduced from the optical stimulated studies in these materials.

  18. Tuning NaYF4 Nanoparticles through Alkaline Earth Doping

    PubMed Central

    Chen, Xian; Peng, Dengfeng; Wang, Feng

    2013-01-01

    Phase and size of lanthanide-doped nanoparticles are the most important characteristics that dictate optical properties of these nanoparticles and affect their technological applications. Herein, we present a systematic study to examine the effect of alkaline earth doping on the formation of NaYF4 upconversion nanoparticles. We show that alkaline earth doping has a dual function of tuning particle size of hexagonal phase NaYF4 nanoparticles and stabilizing cubic phase NaYF4 nanoparticles depending on composition and concentration of the dopant ions. The study described here represents a facile and general strategy to tuning the properties of NaYF4 upconversion nanoparticles. PMID:28348353

  19. 40 CFR 721.4668 - Hydrated alkaline earth metal salts of metalloid oxyanions.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Hydrated alkaline earth metal salts of... Specific Chemical Substances § 721.4668 Hydrated alkaline earth metal salts of metalloid oxyanions. (a... hydrated alkaline earth metal salts of metalloid oxyanions (PMN P-94-1557) is subject to reporting...

  20. 40 CFR 721.4668 - Hydrated alkaline earth metal salts of metalloid oxyanions.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Hydrated alkaline earth metal salts of... Specific Chemical Substances § 721.4668 Hydrated alkaline earth metal salts of metalloid oxyanions. (a... hydrated alkaline earth metal salts of metalloid oxyanions (PMN P-94-1557) is subject to reporting...

  1. 40 CFR 721.4668 - Hydrated alkaline earth metal salts of metalloid oxyanions.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Hydrated alkaline earth metal salts of... Specific Chemical Substances § 721.4668 Hydrated alkaline earth metal salts of metalloid oxyanions. (a... hydrated alkaline earth metal salts of metalloid oxyanions (PMN P-94-1557) is subject to reporting...

  2. 40 CFR 721.4668 - Hydrated alkaline earth metal salts of metalloid oxyanions.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Hydrated alkaline earth metal salts of... Specific Chemical Substances § 721.4668 Hydrated alkaline earth metal salts of metalloid oxyanions. (a... hydrated alkaline earth metal salts of metalloid oxyanions (PMN P-94-1557) is subject to reporting...

  3. 40 CFR 721.4668 - Hydrated alkaline earth metal salts of metalloid oxyanions.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Hydrated alkaline earth metal salts of... Specific Chemical Substances § 721.4668 Hydrated alkaline earth metal salts of metalloid oxyanions. (a... hydrated alkaline earth metal salts of metalloid oxyanions (PMN P-94-1557) is subject to reporting...

  4. Specialties of distributions of alkaline-earth metals in coal

    SciTech Connect

    Fan Jinchuan; Fan Minqiang

    1997-12-31

    Four different ranks of coal have been sampled and separated into different density fractions by Float-Sink. The contents of some trace elements in each density fraction has been analyzed by ICAP. The analyzed data show that the alkaline-earth metals (Be, Sr, and Ba) have their special distributions in coal: Be and Sr may exist in the form of organic matter. Ba often has the highest content in the middle density fraction (1.4--1.5). The relative relationship between ash (or sulfur) and the trace element in a certain type of coal was obtained by using linear regression approach. Results show that there is no significant correlation between the contents of ash or sulfur and those of Be, Sr, and Ba. On the other hand, the linear regression was done among the trace elements of 17 types of coal. The results also show that there is no significant correlation between ash or sulfur and alkaline-earth metals.

  5. Theoretical study of the alkali and alkaline-earth monosulfides

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    Ab initio calculations have been used to obtain accurate spectroscopic constants for the X2Pi and A2Sigma(+) states of the alkali sulfides and the X1Sigma(+), a3Pi, and A1Pi states of the alkaline-earth sulfides. In contrast to the alkali oxides, the alkali sulfides are found to have X2Pi ground states, due to the larger electrostatic interaction. Dissociation energies of 3.27 eV for BeS, 2.32 eV for MgS, 3.29 eV for CaS, and 3.41 eV for SrS have been obtained for the X1Sigma(+) states of the alkaline-earth sulfides, in good agreement with experimental results. Core correlation is shown to increase the Te values for the a3Pi and A1Pi states of MgS, CaS, and SrS.

  6. Steady-state superradiance with alkaline-earth-metal atoms

    SciTech Connect

    Meiser, D.; Holland, M. J.

    2010-03-15

    Alkaline-earth-metal-like atoms with ultranarrow transitions open the door to a new regime of cavity quantum electrodynamics. That regime is characterized by a critical photon number that is many orders of magnitude smaller than what can be achieved in conventional systems. We show that it is possible to achieve superradiance in steady state with such systems. We discuss the basic underlying mechanisms as well as the key experimental requirements.

  7. Proposal for Laser Cooling of Alkaline Earth Monoalkoxide Free Radicals

    NASA Astrophysics Data System (ADS)

    Baum, Louis; Kozyryev, Ivan; Matsuda, Kyle; Doyle, John M.

    2016-05-01

    Cold samples of polyatomic molecules will open new avenues in physics, chemistry, and quantum science. Non-diagonal Franck-Condon factors, technically challenging wavelengths, and the lack of strong electronic transitions inhibit direct laser cooling of nonlinear molecules. We identify a scheme for optical cycling in certain molecules with six or more atoms. Replacing hydrogen in alcohols with an alkaline earth metal (M) leads to alkaline earth monoalkoxide free radicals (MOR), which have favorable properties for laser cooling. M-O bond is very ionic, so the metal orbitals are slightly affected by the nature of R on the ligand. Diagonal Franck-Condon factors, laser accessible transitions, and a small hyperfine structure make MOR molecules suitable for laser cooling. We explore a scheme for optical cycling on the A - X transition of SrOCH3 . Molecules lost to dark vibrational states will be repumped on the B - X transition. Extension to larger species is possible through expansion of the R group since transitions involve the promotion of the metal-centered nonbonding valence electron. We will detail our estimations of the Franck-Condon factors, simulations of the cooling process and describe progress towards the Doppler cooling of MOR polyatomics.

  8. Recent advances in Rydberg physics using alkaline-earth atoms

    NASA Astrophysics Data System (ADS)

    Dunning, F. B.; Killian, T. C.; Yoshida, S.; Burgdörfer, J.

    2016-06-01

    In this brief review, the opportunities that the alkaline-earth elements offer for studying new aspects of Rydberg physics are discussed. For example, the bosonic alkaline-earth isotopes have zero nuclear spin which eliminates many of the complexities present in alkali Rydberg atoms, permitting simpler and more direct comparison between theory and experiment. The presence of two valence electrons allows the production of singlet and triplet Rydberg states that can exhibit a variety of attractive or repulsive interactions. The availability of weak intercombination lines is advantageous for laser cooling and for applications such as Rydberg dressing. Excitation of one electron to a Rydberg state leaves behind an optically active core ion allowing, for high-L states, the optical imaging of Rydberg atoms and their (spatial) manipulation using light scattering. The second valence electron offers the possibility of engineering long-lived doubly excited states such as planetary atoms. Recent advances in both theory and experiment are highlighted together with a number of possible directions for the future.

  9. Enhanced Magnetic Trap Loading for Alkaline-Earth Atoms

    NASA Astrophysics Data System (ADS)

    Reschovsky, Benjamin J.; Barker, Daniel S.; Pisenti, Neal C.; Campbell, Gretchen K.

    2016-05-01

    We report on a technique to improve the continuous loading of atomic strontium into a magnetic trap from a Magneto-Optical Trap (MOT). This is achieved by adding a depumping laser addressing the 3P1 level. For the 3P1 -->3S1 (688-nm) transition in strontium, the depumping laser increases atom number in the magnetic trap and subsequent cooling stages by up to 65 % for the bosonic isotopes and up to 30 % for the fermionic isotope. We optimize this trap loading strategy with respect to the 688-nm laser detuning, intensity, and beam size. To understand the results, we develop a one-dimensional rate equation model of the system, which is in good agreement with the data. We discuss the use of other transitions in strontium for accelerated trap loading and the application of the technique to other alkaline-earth-like atoms.

  10. Structural diversity of alkaline-earth 2,5-thiophenedicarboxylates

    NASA Astrophysics Data System (ADS)

    Balendra; Ramanan, Arunachalam

    2017-03-01

    Exploration of the structural landscape of the system containing divalent alkaline-earth metal ion (Mg, Ca and Sr) with the rigid 2,5-thiophenedicarboxylic acid (TDC) under varying solvothermal condition (DMF, DMA and DEF) yielded five new crystals: [Mg(TDC) (DEF)2(H2O)1/2] (1), [Ca(TDC) (DMA)] (2), [Ca(TDC) (DMA) (H2O)] (3), [Sr(TDC) (DMA)] (4) and [Sr(TDC) (DMA) (H2O)] (5) and two known solids. Single crystal structures of all the solids are characteristic of extended coordination interaction between metal and carboxylate ions. While the smaller magnesium ion crystallized into a 2D coordination polymer, the larger calcium and strontium compounds resulted into the growth of 3D metal organic frameworks. All the solids show blue emission arising from intra ligand charge transfer.

  11. The MCVD synthesis and characterization of water tolerant fiber optic waveguides based on alkaline earth-doped silicas

    NASA Astrophysics Data System (ADS)

    Farley, Kevin F.

    Optical fibers that transmit throughout the entire telecommunications spectrum (1.2--1.7 mum) are presently manufactured by the removal of hydrogen or OH from the host preform glass. Hydrogen-oxygen torches are utilized in the conventional preform manufacturing process, but result in the formation of hydroxyls in germanium-doped silica fiber. The hydroxyl species generate unacceptably high losses for long haul telecommunications systems. This thesis has explored an alternative strategy for reducing OH-related absorption in silica-based glasses. Alkaline earth modifiers have been introduced via the modified chemical vapor deposition (MCVD) process to successfully damp out and dramatically reduce the extrinsic attenuation associated with both water and hydrogen. Specifically, alkaline earth ions were introduced into alumino-silicate glasses to form MgO-Al2O3-SiO2, CaO-Al 2O3-SiO2, and SrO-Al2O3-SiO 2 compositions. The utilization of halide precursors based on the vapor delivery of rare earths was incorporated into the existing MCVD set-up to fabricate these optical preforms. Both the bulk preforms and fibers drawn from them were characterized to determine relevant optical properties, including the attenuation, index profiles and extinction coefficients arising from OH in each host. The data indicate that modification of the silica glass structure through the additions of modifying ions can significantly reduce OH related absorption. For example, the doping of alkaline earth ions decreased the extinction coefficient measured at the 1.39 mum) OH overtone, to values < 0.2 L/(mol*cm). Prompt gamma activation analysis (PGAA) measurements conducted at the National Institute of Standards and Technology (NIST) found OH concentrations in the glasses in the range from 10 to 27.5 ppm. The alkaline earth-doped fibers exhibited lower OH absorption at 1.39 mum) than germanium and aluminum-doped reference fibers. Fibers doped with either magnesium, calcium or strontium displayed up

  12. Chemistry of soluble β-diketiminatoalkaline-earth metal complexes with M-X bonds (M=Mg, Ca, Sr; X=OH, Halides, H).

    PubMed

    Sarish, Sankaranarayana Pillai; Nembenna, Sharanappa; Nagendran, Selvarajan; Roesky, Herbert W

    2011-03-15

    Victor Grignard's Nobel Prize-winning preparation of organomagnesium halides (Grignard reagents) marked the formal beginning of organometallic chemistry with alkaline earth metals. Further development of this invaluable synthetic route, RX+Mg→RMgX, with the heavier alkaline earth metals (Ca and Sr) was hampered by limitations in synthetic methodologies. Moreover, the lack of suitable ligands for stabilizing the reactive target molecules, particularly with the more electropositive Ca and Sr, was another obstacle. The absence in the literature, until just recently, of fundamental alkaline earth metal complexes with M-H, M-F, and M-OH (where M is the Group 2 metal Mg, Ca, or Sr) bonds amenable for organometallic reactions is remarkable. The progress in isolating various unstable compounds of p-block elements with β-diketiminate ligands was recently applied to Group 2 chemistry. The monoanionic β-diketiminate ligands are versatile tools for addressing synthetic challenges, as amply demonstrated with alkaline earth complexes: the synthesis and structural characterization of soluble β-diketiminatocalcium hydroxide, β-diketiminatostrontium hydroxide, and β-diketiminatocalcium fluoride are just a few examples of our contribution to this area of research. To advance the chemistry beyond synthesis, we have investigated the reactivity and potential for applications of these species, for example, through the demonstration of dip coating surfaces with CaCO(3) and CaF(2) with solutions of the calcium hydroxide and calcium fluoride complexes, respectively. In this Account, we summarize some recent developments in alkaline earth metal complex chemistry, particularly of Mg, Ca, and Sr, through the utilization of β-diketiminate ligands. We focus on results generated in our laboratory but give due mention to work from other groups as well. We also highlight the closely related chemistry of the Group 12 element Zn, as well as the important chemistry developed by other groups

  13. Alkaline Earth Core Level Photoemission Spectroscopy of High-Temperature Superconductors

    NASA Technical Reports Server (NTRS)

    Vasquez, R.

    1993-01-01

    This paper examines photoemission measurements of the alkaline Earth core levels of high-temperature superconductors and related materials, models that seek to explain the large negative shifts observed relative to the corresponding alkaline Earth metals, and the effect of lattice site disorder on the core level spectra and the presence or absence of intrinsic surface peaks.

  14. Monte Carlo simulations of electron thermalization in alkali iodide and alkaline-earth fluoride scintillators

    NASA Astrophysics Data System (ADS)

    Wang, Zhiguo; Xie, YuLong; Campbell, Luke W.; Gao, Fei; Kerisit, Sebastien

    2012-07-01

    A Monte Carlo model of electron thermalization in inorganic scintillators, which was developed and applied to CsI in a previous publication [Wang et al., J. Appl. Phys. 110, 064903 (2011)], is extended to another material of the alkali halide class, NaI, and to two materials from the alkaline-earth halide class, CaF2 and BaF2. This model includes electron scattering with both longitudinal optical (LO) and acoustic phonons as well as the effects of internal electric fields. For the four pure materials, a significant fraction of the electrons recombine with self-trapped holes and the thermalization distance distributions of the electrons that do not recombine peak between approximately 25 and 50 nm and extend up to a few hundreds of nanometers. The thermalization time distributions of CaF2, BaF2, NaI, and CsI extend to approximately 0.5, 1, 2, and 7 ps, respectively. The simulations show that the LO phonon energy is a key factor that affects the electron thermalization process. Indeed, the higher the LO phonon energy is, the shorter the thermalization time and distance are. The thermalization time and distance distributions show no dependence on the incident γ-ray energy. The four materials also show different extents of electron-hole pair recombination due mostly to differences in their electron mean free paths (MFPs), LO phonon energies, initial densities of electron-hole pairs, and static dielectric constants. The effect of thallium doping is also investigated for CsI and NaI as these materials are often doped with activators. Comparison between CsI and NaI shows that both the larger size of Cs+ relative to Na+, i.e., the greater atomic density of NaI, and the longer electron mean free path in NaI compared to CsI contribute to an increased probability for electron trapping at Tl sites in NaI versus CsI.

  15. Monte Carlo simulations of electron thermalization in alkali iodide and alkaline-earth fluoride scintillators

    SciTech Connect

    Wang Zhiguo; Gao Fei; Kerisit, Sebastien; Xie Yulong; Campbell, Luke W.

    2012-07-01

    A Monte Carlo model of electron thermalization in inorganic scintillators, which was developed and applied to CsI in a previous publication [Wang et al., J. Appl. Phys. 110, 064903 (2011)], is extended to another material of the alkali halide class, NaI, and to two materials from the alkaline-earth halide class, CaF{sub 2} and BaF{sub 2}. This model includes electron scattering with both longitudinal optical (LO) and acoustic phonons as well as the effects of internal electric fields. For the four pure materials, a significant fraction of the electrons recombine with self-trapped holes and the thermalization distance distributions of the electrons that do not recombine peak between approximately 25 and 50 nm and extend up to a few hundreds of nanometers. The thermalization time distributions of CaF{sub 2}, BaF{sub 2}, NaI, and CsI extend to approximately 0.5, 1, 2, and 7 ps, respectively. The simulations show that the LO phonon energy is a key factor that affects the electron thermalization process. Indeed, the higher the LO phonon energy is, the shorter the thermalization time and distance are. The thermalization time and distance distributions show no dependence on the incident {gamma}-ray energy. The four materials also show different extents of electron-hole pair recombination due mostly to differences in their electron mean free paths (MFPs), LO phonon energies, initial densities of electron-hole pairs, and static dielectric constants. The effect of thallium doping is also investigated for CsI and NaI as these materials are often doped with activators. Comparison between CsI and NaI shows that both the larger size of Cs{sup +} relative to Na{sup +}, i.e., the greater atomic density of NaI, and the longer electron mean free path in NaI compared to CsI contribute to an increased probability for electron trapping at Tl sites in NaI versus CsI.

  16. Improvement of thermoelectric properties of alkaline-earth hexaborides

    SciTech Connect

    Takeda, Masatoshi . E-mail: takeda@mech.nagaokaut.ac.jp; Terui, Manabu; Takahashi, Norihito; Ueda, Noriyoshi

    2006-09-15

    Thermoelectric (TE) and transport properties of alkaline-earth hexaborides were examined to investigate the possibility of improvement in their TE performance. As carrier concentration increased, electrical conductivity increased and the absolute value of the Seebeck coefficient decreased monotonically, while carrier mobility was almost unchanged. These results suggest that the electrical properties of the hexaboride depend largely on carrier concentration. Thermal conductivity of the hexaboride was higher than 10 W/m K even at 1073 K, which is relatively high among TE materials. Alloys of CaB{sub 6} and SrB{sub 6} were prepared in order to reduce lattice thermal conductivity. Whereas the Seebeck coefficient and electrical conductivity of the alloys were intermediate between those of CaB{sub 6} and SrB{sub 6} single phases, the thermal conductivities of the alloys were lower than those of both single phases. The highest TE performance was obtained in the vicinity of Ca{sub 0.5}Sr{sub 0.5}B{sub 6}, indicating that alloying is effective in improving the performance. - Graphical abstract: Thermoelectric figure-of-merit, ZT, for (Ca,Sr)B{sub 6} alloys. The highest ZT value of 0.35 at 1073 K was obtained due to effective reduction of thermal conductivity by alloying.

  17. Effect of alkaline-earth ions on the dynamics of alkali ions in bismuthate glasses

    NASA Astrophysics Data System (ADS)

    Dutta, A.; Ghosh, A.

    2005-12-01

    The effect of alkaline earth ions on the dynamics of Li+ ions in bismuthate glasses has been studied in the temperature range 353-503K and in the frequency range 10Hz-2MHz . The dc conductivity increases and activation energy decreases with the increase of a particular alkaline earth content for the glasses with a fixed alkali content. The increased modification of the network due to the increase in alkaline earth content in the compositions is responsible for the increasing conductivity. Also the compositions with smaller alkaline earth ions were found to exhibit higher conductivity. Although the conductivity increases with the decrease of ionic radii of alkaline earth ions, the activation energy shows a maximum for the Sr ion. The electric modulus and the conductivity formalisms have been employed to study the relaxation dynamics of charge carriers in these glasses. The alkali ions were observed to change their dynamics with the change of the alkaline earth ions. The same anomalous trend for activation energy for the conductivity relaxation frequency and the hopping frequency was also observed for glasses containing SrO. It was also observed that the mobile lithium ion concentrations are independent of nature of alkaline earth ions in these glasses.

  18. Physical and electrochemical properties of alkaline earth doped, rare earth vanadates

    SciTech Connect

    Adijanto, Lawrence; Balaji Padmanabhan, Venu; Holmes, Kevin J.; Gorte, Raymond J.; Vohs, John M.

    2012-06-15

    The effect of partial substitution of alkaline earth (AE) ions, Sr{sup 2+} and Ca{sup 2+}, for the rare earth (RE) ions, La{sup 3+}, Ce{sup 3+}, Pr{sup 3+}, and Sm{sup 3+}, on the physical properties of REVO{sub 4} compounds were investigated. The use of the Pechini method to synthesize the vanadates allowed for high levels of AE substitution to be obtained. Coulometric titration was used to measure redox isotherms for these materials and showed that the addition of the AE ions increased both reducibility and electronic conductivity under typical solid oxide fuel cell (SOFC) anode conditions, through the formation of compounds with mixed vanadium valence. In spite of their high electronic conductivity, REVO{sub 4}-yttira stabilized zirconia (YSZ) composite anodes exhibited only modest performance when used in SOFCs operating with H{sub 2} fuel at 973 K due to their low catalytic activity. High performance was obtained, however, after the addition of a small amount of catalytically active Pd to the anode. - Graphical abstract: Coulometric titration isotherms for ({open_square}) LaVO{sub 4}, ( White-Circle ) PrVO{sub 4}, ( Lozenge ) CeVO{sub 4}, ( Black-Up-Pointing-Triangle ) Ce{sub 0.7}Sr{sub 0.3}VO{sub 3.85}, and ( Black-Square ) Ce{sub 0.7}Ca{sub 0.3}VO{sub 3.85}, at 973 K. Highlights: Black-Right-Pointing-Pointer Infiltration procedures were used to prepare SOFC anodes from various vanadates. Black-Right-Pointing-Pointer Doping of Alkaline Earth to Rare Earth Vanadates showed to improve conductivity and chemical stability. Black-Right-Pointing-Pointer Alkaline Earth Doped Rare Earth Vanadates-YSZ composites showed conductivities as high as 5 S cm{sup -1} at 973 K. Black-Right-Pointing-Pointer As with other ceramic anodes, the addition of a catalyst was required to achieve low anode impedance.

  19. Physical and electrochemical properties of alkaline earth doped, rare earth vanadates

    NASA Astrophysics Data System (ADS)

    Adijanto, Lawrence; Balaji Padmanabhan, Venu; Holmes, Kevin J.; Gorte, Raymond J.; Vohs, John M.

    2012-06-01

    The effect of partial substitution of alkaline earth (AE) ions, Sr2+ and Ca2+, for the rare earth (RE) ions, La3+, Ce3+, Pr3+, and Sm3+, on the physical properties of REVO4 compounds were investigated. The use of the Pechini method to synthesize the vanadates allowed for high levels of AE substitution to be obtained. Coulometric titration was used to measure redox isotherms for these materials and showed that the addition of the AE ions increased both reducibility and electronic conductivity under typical solid oxide fuel cell (SOFC) anode conditions, through the formation of compounds with mixed vanadium valence. In spite of their high electronic conductivity, REVO4-yttira stabilized zirconia (YSZ) composite anodes exhibited only modest performance when used in SOFCs operating with H2 fuel at 973 K due to their low catalytic activity. High performance was obtained, however, after the addition of a small amount of catalytically active Pd to the anode.

  20. Atomistic simulation of defects in alkaline-earth fluorohalide crystals

    NASA Astrophysics Data System (ADS)

    Baetzold, Roger C.

    1987-12-01

    Defect properties of BaFBr, BaFCl, and SrFCl were calculated using the atomistic simulation technique. Two-body potentials were developed starting from potentials in related crystals or calculated by the electron-gas method and then fit to minimize strain in the equilibrium structure. Agreement of calculated elastic, dielectric, and cohesive properties with available experimental and theoretical data was reasonable. Generally, Frenkel energies for the larger-size halogen ion were less than for the fluorine ion and less than the Schottky energy for the metal, fluoride, and other halide ions set. A Schottky energy for vacancies of the metal ion and two of the larger-size halide ions was small. Energies of formation of Vk and H centers were computed with the aid of thermodynamic cycles. The most stable Vk center forms on the halide ion site where the Madelung potential is most favorable for holes. H centers occupy off-center sites in these low-symmetry materials. Stable geometries are discussed.

  1. Release characteristics of alkali and alkaline earth metallic species during biomass pyrolysis and steam gasification process.

    PubMed

    Long, Jiang; Song, Hu; Jun, Xiang; Sheng, Su; Lun-Shi, Sun; Kai, Xu; Yao, Yao

    2012-07-01

    Investigating the release characteristics of alkali and alkaline earth metallic species (AAEMs) is of potential interest because of AAEM's possible useful service as catalysts in biomass thermal conversion. In this study, three kinds of typical Chinese biomass were selected to pyrolyse and their chars were subsequently steam gasified in a designed quartz fixed-bed reactor to investigate the release characteristics of alkali and alkaline earth metallic species (AAEMs). The results indicate that 53-76% of alkali metal and 27-40% of alkaline earth metal release in pyrolysis process, as well as 12-34% of alkali metal and 12-16% of alkaline earth metal evaporate in char gasification process, and temperature is not the only factor to impact AAEMs emission. The releasing characteristics of AAEMs during pyrolysis and char gasification process of three kinds of biomass were discussed in this paper.

  2. More arrows in the quiver: new pathways and old problems with heavy alkaline earth metal diphenylmethanides.

    PubMed

    Alexander, Jacob S; Ruhlandt-Senge, Karin

    2004-03-05

    Progress in the field of sigma-bonded alkaline earth organometallics has been handicapped by numerous complications, such as high reactivity, low solubility, and the limited availability of suitable starting materials. Here we present two synthetic methods, hydrocarbon elimination and desilylation, as alternative routes into this chemistry. A novel barium diphenylmethanide was prepared using these routes delineating that both methods provide a powerful, versatile synthetic access route to an extended library of organometallic alkaline earth derivatives.

  3. Process for preparing higher oxides of the alkali and alkaline earth metals

    NASA Technical Reports Server (NTRS)

    Sadhukhan, P.; Bell, A. (Inventor)

    1978-01-01

    High purity inorganic higher oxides of the alkali and alkaline earth metals are prepared by subjecting the hydroxide of the alkali and alkaline earth metal to a radio frequency discharge sustained in oxygen. The process is particulary adaptable to the production of high purity potassium superoxide by subjecting potassium hydroxide to glow discharge sustained in oxygen under the pressure of about 0.75 to 1.00 torr.

  4. Medical imaging scintillators from glass-ceramics using mixed rare-earth halides

    NASA Astrophysics Data System (ADS)

    Beckert, M. Brooke; Gallego, Sabrina; Ding, Yong; Elder, Eric; Nadler, Jason H.

    2016-10-01

    Recent years have seen greater interest in developing new luminescent materials to replace scintillator panels currently used in medical X-ray imaging systems. The primary areas targeted for improvement are cost and image resolution. Cost reduction is somewhat straightforward in that less expensive raw materials and processing methods will yield a less expensive product. The path to improving image resolution is more complex because it depends on several properties of the scintillator material including density, transparency, and composition, among others. The present study focused on improving image resolution using composite materials, known as glass-ceramics that contain nanoscale scintillating crystallites formed within a transparent host glass matrix. The small size of the particles and in-situ precipitation from the host glass are key to maintaining transparency of the composite scintillator, which ensures that a majority of the light produced from absorbed X-rays can actually be used to create an image of the patient. Because light output is the dominating property that determines the image resolution achievable with a given scintillator, it was used as the primary metric to evaluate performance of the glass-ceramics relative to current scintillators. Several glass compositions were formulated and then heat treated in a step known as "ceramization" to grow the scintillating nanocrystals, whose light output was measured in response to a 65 kV X-ray source. Performance was found to depend heavily on the thermal history of the glass and glass-ceramic, and so additional studies are required to more precisely determine optimal process temperatures. Of the compositions investigated, an alumino-borosilicate host glass containing 56mol% scintillating rare-earth halides (BaF2, GdF3, GdBr3, TbF3) produced the highest recorded light output at nearly 80% of the value recorded using a commercially-available GOS:Tb panel as a reference.

  5. Coordination chemistry of the alkaline earth metal ions with Zwitterionic forms of the Schift bases. X-Ray studies and other spectroscopic properties

    NASA Astrophysics Data System (ADS)

    Tajmir-Riahi, H. A.; Lotfipoor, M.

    The non-ionized forms of tetradentate Schiff bases NN'-ethylenebis(salicylideneimine), H 2L and NN'-propane-1,3-diylbis(salicylideneimine), H 2L' react with hydrated alkaline earth halide and nitrate to give complexes of the type: M(H 2L)Cl 2· nH 2O [M = Mg(II), Ca(II), Sr(II); n = 0-4], M(H 2L) 2Cl 2 [M = Ca(II), Sr(II), M(H 2L) nBr 2 [M = Ca(II), Sr(II); n = 2, 3 and Mg 2(H 2L) 3Br 4], M(H 2L) nI 2 [M = Mg(II), Ca(II), Sr(II), Ba(II); n = 2, 3)], M(H 2L) n(NO 3) 2 and M(H 2L') n(NO 1) 2[M = Mg(II), Ca(II); n = 1, 2)]. Because of distinct spectral similarities with structurally known Ca(H 2L')(NO 3) 2 compound, the Schiff bases are coordinated through the negatively charged phenolic oxygen atoms and not the nitrogen atoms of the azomethine groups, which carry the protons transferred from phenolic groups on complexation. Halide and nitrate are coordinated to the central metal ion except in 2:1 nitrato complexes where the presence of both ionic and coordinated nitrate groups are evident and also in 3:1 halide complexes where the presence of non-coordinated halide cannot be excluded. X-Ray powder photographs showed no marked similarities between Ca(H 2L')(NO 3) 2 and Mg(H 2L')(NO 3) 2 while there are some isomorphic features between the same types of halide complexes. Infrared spectra and other structural information revealed the polymeric nature of the complexes. Therefore the coordination numbers exhibited by the alkaline earth metal cations would be 4, 6 or 8 in these series of Schiff base complexes.

  6. Structure and ionic diffusion of alkaline-earth ions in mixed cation glasses

    SciTech Connect

    Konstantinou, Konstantinos; Sushko, Petr; Duffy, Dorothy M.

    2015-08-15

    A series of mixed cation silicate glasses of the composition A2O – 2MO – 4SiO2, with A=Li,Na,K and M=Ca,Sr,Ba has been investigated by means of molecular dynamics simulations in order to understand the effect of the nature of the cations on the mobility of the alkaline-earth ions within the glass network. The size of the alkaline-earth cation was found to affect the inter-atomic distances, the coordination number distributions and the bond angle distributions , whereas the medium-range order was almost unaffected by the type of the cation. All the alkaline-earth cations contribute to lower vibrational frequencies but it is observed that that there is a shift to smaller frequencies and the vibrational density of states distribution gets narrower as the size of the alkaline-earth increases. The results from our modeling for the ionic diffusion of the alkaline-earth cations are in a qualitative agreement with the experimental observations in that there is a distinct correlation between the activation energy for diffusion of alkaline earth-ions and the cation radii ratio. An asymmetrical linear behavior in the diffusion activation energy with increasing size difference is observed. The results can be described on the basis of a theoretical model that relates the diffusion activation energy to the electrostatic interactions of the cations with the oxygens and the elastic deformation of the silicate network.

  7. [Broad excitation band alkaline-earth silicate luminescent materials activated by rare earth and its applications].

    PubMed

    Xia, Wei; Lei, Ming-Kai; Luo, Xi-Xian; Xiao, Zhi-Guo

    2008-01-01

    Series of novel broad excitation band phosphors M2 MgSis O7 : Eu, Dy(M = Ca, Sr) were prepared by a high temperature solid-state reaction method. The crystal structure of compound was characterized. And the effects of part substitution of alkaline-earth on crystal structure, photoluminescence spectra and luminescence properties were also investigated. It is found that the excitation band of silicate luminescent materials extend to visible region and they exhibit yellow, green and blue long after-glow luminescence after excited by ultraviolet or visible light. Ca MgSi O7 : Eu, Dy luminescent materials can be excited effectively under the 450-480 nm range and exhibit a strong emission at 536 nm, nicely combining with blue light emitted by InGaN chips to produce white light. This promises the silicate luminescent materials a potential yellow phosphor for white LED.

  8. Dynamics of dipolar defects in rare earth-doped alkaline-earth fluoride crystals

    NASA Astrophysics Data System (ADS)

    Charnock, Forrest Taylor

    Alkaline-earth fluoride crystals such as SrF2 provide an excellent sample material for investigating the physics of point defects in crystal lattices. High quality crystals are easily grown, and they readily accept many dopant ions into the lattice, particularly rare earth ions. Rare earth dopant ions (typically trivalent) occupy substitutional sites in the lattice by replacing a Sr2+ ion. Due to the extra charge of the rare earth ion, charge compensation is often provided by an extra fluoride ion (F--) located in a nearby interstitial position. If located in the nearest-neighbor (nn) interstitial position, it forms a defect with C4n symmetry; if located in the next-nearest-neighbor (nnn) intersitial position, it forms a defect with C3n symmetry. Given sufficient thermal energy, this interstitial F ion can move to adjacent interstitial sites and hence reorient the defect. The rate w at which the ion moves from one interstitial site to another is well described by a simple Arrhenius expression: w=n0e-E/kT , where n0 is the attack frequency of the F-- and E is the activation energy. This motion can profoundly affect both the electronic polarizability of the material and the polarization of light emitted or absorbed by the rare earth ion. This thesis describes the normal mode motion of interstitial ions which may occupy either nn or nnn interstitial sites. Using electron paramagnetic resonance (EPR), I observed the relative populations of nn and nnn defects in SrF2 doped with Gd3+ as a function of temperature. These measurements show that dipolar reorientation of the nnn F occurs through the nn interstitial position. Not all interstitial F-- motion is thermally driven. Fluorescence depolarization measurements of SrF2:Pr3+ indicate that optically stimulating a Pr3+ may induce interstitial motion of a nn F--. Such motion was confirmed by showing that nn defects in SrF2:Pr3+ may be polarized at very low temperatures when the sample is illuminated with resonant light. I

  9. Rare-earth-doped bifunctional alkaline-earth metal fluoride nanocrystals via a facile microwave-assisted process.

    PubMed

    Pang, Min; Liu, Dapeng; Lei, Yongqian; Song, Shuyan; Feng, Jing; Fan, Weiqiang; Zhang, Hongjie

    2011-06-20

    Rare-earth-doped magnetic-optic bifunctional alkaline-earth metal fluoride nanocrystals have been successfully synthesized via a facile microwave-assisted process. The as-prepared nanocrystals were monodisperse and could form stable colloidal solutions in polar solvents, such as water and ethanol. They show bright-green fluorescence emisson. Furthermore, Gd(3+)-doped ones exhibit paramagnetic behavior at room temperature and superparamagnetic behavior at 2 K.

  10. Charge-separated and molecular heterobimetallic rare earth-rare earth and alkaline earth-rare earth aryloxo complexes featuring intramolecular metal-pi-arene interactions.

    PubMed

    Deacon, Glen B; Junk, Peter C; Moxey, Graeme J; Ruhlandt-Senge, Karin; St Prix, Courtney; Zuniga, Maria F

    2009-01-01

    Treatment of a rare earth metal (Ln) and a potential divalent rare earth metal (Ln') or an alkaline earth metal (Ae) with 2,6-diphenylphenol (HOdpp) at elevated temperatures (200-250 degrees C) afforded heterobimetallic aryloxo complexes, which were structurally characterised. A charge-separated species [(Ln'/Ae)(2)(Odpp)(3)][Ln(Odpp)(4)] was obtained for a range of metals, demonstrating the similarities between the chemistry of the divalent rare earth metals and the alkaline earth metals. The [(Ln'/Ae)(2)(Odpp)(3)](+) cation in the heterobimetallic structures is unusual in that it consists solely of bridging aryloxide ligands. A molecular heterobimetallic species [AeEu(Odpp)(4)] (Ae = Ca, Sr, Ba) was obtained by treating an alkaline earth metal and Eu metal with HOdpp at elevated temperatures. Similarly, [BaSr(Odpp)(4)] was prepared by treating Ba metal and Sr metal with HOdpp. Treatment of [Ba(2)(Odpp)(4)] with [Mg(Odpp)(2)(thf)(2)] in toluene afforded [Ba(2)(Odpp)(3)][Mg(Odpp)(3)(thf)]. Analogous solution-based syntheses were not possible for [(Ln'/Ae)(2)(Odpp)(3)][Ln(Odpp)(4)] complexes, for which the free-metal route was essential. As a result of the absence of additional donor ligands, the crystal structures of the heterobimetallic complexes feature extensive pi-Ph-metal interactions involving the pendant phenyl groups of the Odpp ligands, thus enabling the large electropositive metal atoms to attain coordination saturation. The charge-separated heterobimetallic species were purified by extraction with toluene/thf mixtures at ambient temperature (Ba-containing compounds) or by extraction with toluene under pressure above the boiling point of the solvent (other products). In donor solvents, heterobimetallic complexes other than those containing barium were found to fragment into homometallic species.

  11. Depolarizing collisions with hydrogen: Neutral and singly ionized alkaline earths

    SciTech Connect

    Manso Sainz, Rafael; Ramos, Andrés Asensio; Bueno, Javier Trujillo; Aguado, Alfredo

    2014-06-20

    Depolarizing collisions are elastic or quasielastic collisions that equalize the populations and destroy the coherence between the magnetic sublevels of atomic levels. In astrophysical plasmas, the main depolarizing collider is neutral hydrogen. We consider depolarizing rates on the lowest levels of neutral and singly ionized alkali earths Mg I, Sr I, Ba I, Mg II, Ca II, and Ba II, due to collisions with H°. We compute ab initio potential curves of the atom-H° system and solve the quantum mechanical dynamics. From the scattering amplitudes, we calculate the depolarizing rates for Maxwellian distributions of colliders at temperatures T ≤ 10,000 K. A comparative analysis of our results and previous calculations in the literature is completed. We discuss the effect of these rates on the formation of scattering polarization patterns of resonant lines of alkali earths in the solar atmosphere, and their effect on Hanle effect diagnostics of solar magnetic fields.

  12. IUPAC-NIST Solubility Data Series. 79. Alkali and Alkaline Earth Metal Pseudohalides

    NASA Astrophysics Data System (ADS)

    Hála, Jiri

    2004-03-01

    This volume presents solubility data of azides, cyanides, cyanates, and thiocyanates of alkali metals, alkaline earth metals, and ammonium. Covered are binary and ternary systems in all solvents. No solubility data have been found for some of the compounds of alkali metals, alkaline metals, and ammonium. These include beryllium and magnesium azides, lithium, rubidium cesium, ammonium, and alkaline earth cyanates and cyanides, and beryllium thiocyanate. Likewise, no solubility data seem to exist for selenocyanates of the mentioned metals and ammonium. The literature has been covered up to the middle of 2001, and there was a great effort to have the literature survey as complete as possible. The few documents which remained unavailable to the editor, and could not be included in the volume, are listed in the Appendix. For some compounds it was not possible to show the Chemical Abstracts registry numbers since these have not been assigned. For this reason, the registry number index is incomplete.

  13. Systematic studies of the mass spectrometric properties of alkaline earth metal cationized amino acids and peptides

    NASA Astrophysics Data System (ADS)

    Küjckelmann, Ulrich; Müller, Dietrich; Weber, Carsten

    1997-07-01

    The results of a systematic study of the gas phase interactions of α-amino acids and peptides (4-15 amino acids) with alkaline earth metals, observed with mass spectrometric techniques, are presented. Furthermore, a model for the cationization with calcium at the C-terminal amino acid arginine in rotaviral polypeptides is presented.

  14. Recent developments in the field of organic heterobimetallic compounds of the alkaline-earth metals.

    PubMed

    Westerhausen, Matthias

    2006-10-28

    Heterobimetallic compounds of the alkaline-earth metals show a wide structural variety with strongly differing reactivity patterns. The combination of magnesium and alkali metal amides yields cyclic molecules with an extreme high reactivity which often are considered as "inverse crowns" with the metal atoms as coordination sites for Lewis bases. In other metallates of the alkaline-earth metals an activation of alkyl groups succeeds. In alkaline-earth metal zincates an inverse coordination of the type M(2)[(mu-R)(2)ZnR](2) is observed and the alkyl groups are in bridging positions between zinc and the s-block metals thus forming a very reactive M-C-Zn three-center-two-electron bond. Furthermore, the metals of the carbon group form alkaline-earth metal-silicon, -germanium and -tin bonds or, in the presence of very strong Lewis bases, even solvent-separated ion pairs. For electronegative substituents at tin an inverse coordination mode such as M[(mu-R)(2)SnR](2) is observed.

  15. Homoleptic alkaline earth metal bis(trifluoromethanesulfonyl)imide complex compounds obtained from an ionic liquid.

    PubMed

    Babai, Arash; Mudring, Anja-Verena

    2006-04-17

    The first homoleptic alkaline earth bis(trifluoromethanesulfonyl)imide (Tf2N) complexes [mppyr]2[Ca(Tf2N)4], [mppyr]2[Sr(Tf2N)4], and [mppyr][Ba(Tf2N)3] were crystallized from a solution of the respective alkaline earth bis(trifluoromethanesulfonyl)imide and the ionic liquid [mppyr][Tf2N] (mppyr = 1,1-N-methyl-N-propylpyrrolidinium). In the calcium and strontium compounds, the alkaline earth metal (AE) is coordinated by four bidentately chelating Tf2N ligands to form isolated (distorted) square antiprismatic [AE(Tf2N)4]2- complexes which are separated by N-methyl-N-propylpyrrolidinium cations. In contrast, the barium compound, [mppyr][Ba(Tf2N)3], forms an extended structure. Here the alkaline earth cation is surrounded by six oxygen atoms belonging to three Tf2N- anions which coordinate in a bidentate chelating fashion. Three further oxygen atoms of the same ligands are linking the Ba2+ cations to infinite (infinity)(1)[Ba(Tf2N)3] chains.

  16. Coordination Chemistry of Alkali and Alkaline-Earth Cations with Macrocyclic Ligands.

    ERIC Educational Resources Information Center

    Dietrich, Bernard

    1985-01-01

    Discusses: (l) alkali and alkaline-earth cations in biology (considering naturally occurring lonophores, their X-ray structures, and physiochemical studies); (2) synthetic complexing agents for groups IA and IIA; and (3) ion transport across membranes (examining neutral macrobicyclic ligands as metal cation carriers, transport by anionic carriers,…

  17. An alkaline tin(II) halide compound Na3Sn2F6Cl: Synthesis, structure, and characterization

    NASA Astrophysics Data System (ADS)

    Gong, Pifu; Luo, Siyang; Huang, Qian; Yang, Yi; Jiang, Xingxing; Liang, Fei; Chen, Chuangtian; Lin, Zheshuai

    2017-04-01

    A new alkali tin(II) halide compound, Na3Sn2F6Cl, is synthesized by hydrothermal method. This compound crystallizes trigonally in space group of R-3c (167), and processes a zero-dimensional (0D) structure consisted of Na+ cations, Cl- anions and the isolated [SnF3]- trigonal pyramids in which the stereochemically active 5s2 lone pair electrons are attached to the Sn2+ cations. Interestingly, the [SnF3]- trigonal pyramids are parallel arranged in the a-b plane, while oppositely arranged in line with rotation along the c- axis. Moreover, the energy bandgap, thermal stability and electronic structure of Na3Sn2F6Cl are characterized and the results reveal that this compound has and indirect bandgap of 3.88 eV and is stable under 270 °C.

  18. Metal Based Synthetic Strategies and the Examination of Structure Determining Factors in Alkaline Earth Metal Compounds

    NASA Astrophysics Data System (ADS)

    Takahashi, Yuriko

    Last decades have witnessed a large expansion of the organometallic heavier alkaline earth metal species. However, continued growth of this promising area of chemistry has been slowed by severe restrictions and limitations in viable synthetic methodologies leading to difficulties in preparing and characterizing the target compounds. There is clearly a need for the further development of synthetic methodologies and detailed structure function analysis that will promote the further advancement of organoalkaline earth metal chemistry in applications as diverse as materials chemistry and catalysis. This thesis work greatly extends the synthetic options currently available towards organoalkaline earth metal species by introducing redox transmetallation protolysis (RTP), a reaction based on the readily available Ph3Bi as a non-toxic transmetallation agent. Based on a straightforward one-pot procedure and work-up, Ph3Bi based RTP presents a powerful synthetic alternative for the facile preparation of a large variety of heavy alkaline earth metal compounds. The second part of the thesis explores the effect of secondary non covalent interactions on the coordination chemistry as well as thermal properties of a series of novel alkali, alkaline earth, rare earth as well as heterobimetallic alkali/alkaline earth fluoroalkoxides. These compounds showcase the significance of non-covalent M···F-C and agostic interactions on metal stabilization and structural features, providing critical input on ligand design for the design of advanced metal organic vapor deposition (MOCVD) precursor materials. This work also showcases the impact of M···F-C interactions over M---co-ligand coordination, a critical precursor design element as well.

  19. Carbonatite and alkaline intrusion-related rare earth element deposits–A deposit model

    USGS Publications Warehouse

    Verplanck, Philip L.; Van Gosen, Bradley S.

    2011-01-01

    The rare earth elements are not as rare in nature as their name implies, but economic deposits with these elements are not common and few deposits have been large producers. In the past 25 years, demand for rare earth elements has increased dramatically because of their wide and diverse use in high-technology applications. Yet, presently the global production and supply of rare earth elements come from only a few sources. China produces more than 95 percent of the world's supply of rare earth elements. Because of China's decision to restrict exports of these elements, the price of rare earth elements has increased and industrial countries are concerned about supply shortages. As a result, understanding the distribution and origin of rare earth elements deposits, and identifying and quantifying our nation's rare earth elements resources have become priorities. Carbonatite and alkaline intrusive complexes, as well as their weathering products, are the primary sources of rare earth elements. The general mineral deposit model summarized here is part of an effort by the U.S. Geological Survey's Mineral Resources Program to update existing models and develop new descriptive mineral deposit models to supplement previously published models for use in mineral-resource and mineral-environmental assessments. Carbonatite and alkaline intrusion-related REE deposits are discussed together because of their spatial association, common enrichment in incompatible elements, and similarities in genesis. A wide variety of commodities have been exploited from carbonatites and alkaline igneous rocks, such as rare earth elements, niobium, phosphate, titanium, vermiculite, barite, fluorite, copper, calcite, and zirconium. Other enrichments include manganese, strontium, tantalum, thorium, vanadium, and uranium.

  20. Ab initio study of the alkali and alkaline-earth monohydroxides

    NASA Technical Reports Server (NTRS)

    Bauschlicher, C. W., Jr.; Langhoff, S. R.; Partridge, H.

    1986-01-01

    A systematic study of the structures and dissociation energies of all the alkali and alkaline-earth monohydroxides is conducted. A theoretical model for determining accurate dissociation energies of ionic molecules is discussed. The obtained theoretical structures and dissociation energies of the alkali and alkaline-earth monohydroxides, respectively, are compared with experimental data. It is found that the theoretical studies of the bending potentials of BeOH, MgOH, and CaOH reveal the different admixture of covalent character in these systems. The BeOH molecule with the largest degree of covalent character is found to be bent (theta equals 147 deg). The MgOH is also linear. The theoretical dissociation energies for the alkali and akaline-earth hydroxides are thought to be accurate to 0.1 eV.

  1. Rare-Earth Tri-Halide Methanol-Adduct Single-Crystal Scintillators for Gamma Ray and Neutron Detection - 8/17/09

    SciTech Connect

    Boatner, Lynn A; Wisniewski, D.; Neal, John S; Bell, Zane W; Ramey, Joanne Oxendine; Kolopus, James A; Chakoumakos, Bryan C; Custelcean, Radu; Wisniewska, Monika; Peña, K. E.

    2009-01-01

    Cerium activated rare-earth tri- halides represent a well-known family of high performance inorganic rare-earth scintillators - including the high-light-yield, high-energy-resolution scintillator, cerium-doped lanthanum tribromide. These hygroscopic inorganic rare-earth halides are currently grown as single crystals from the melt - either by the Bridgman or Czochralski techniques slow and expensive processes that are frequently characterized by severe cracking of the material due to anisotropic thermal stresses and cleavage effects. We have recently discovered a new family of cerium-activated rare-earth metal organic scintillators consisting of tri-halide methanol adducts of cerium and lanthanum namely CeCl3(CH3OH)4 and LaBr3(CH3OH)4:Ce. These methanol-adduct scintillator materials can be grown near room temperature from a methanol solution, and their high solubility is consistent with the application of the rapid solution growth methods that are currently used to grow very large single crystals of potassium dihydrogen phosphate. The structures of these new rare-earth metal-organic scintillating compounds were determined by single crystal x-ray refinements, and their scintillation response to both gamma rays and neutrons, as presented here, was characterized using different excitation sources. Tri-halide methanol-adduct crystals activated with trivalent cerium apparently represent the initial example of a solution-grown rare-earth metal-organic molecular scintillator that is applicable to gamma ray, x-ray, and fast neutron detection.

  2. Alkali or alkaline earth metal promoted catalyst and a process for methanol synthesis using alkali or alkaline earth metals as promoters

    DOEpatents

    Tierney, John W.; Wender, Irving; Palekar, Vishwesh M.

    1995-01-01

    The present invention relates to a novel route for the synthesis of methanol, and more specifically to the production of methanol by contacting synthesis gas under relatively mild conditions in a slurry phase with a heterogeneous catalyst comprising reduced copper chromite impregnated with an alkali or alkaline earth metal. There is thus no need to add a separate alkali or alkaline earth compound. The present invention allows the synthesis of methanol to occur in the temperature range of approximately 100.degree.-160.degree. C. and the pressure range of 40-65 atm. The process produces methanol with up to 90% syngas conversion per pass and up to 95% methanol selectivity. The only major by-product is a small amount of easily separated methyl formate. Very small amounts of water, carbon dioxide and dimethyl ether are also produced. The present catalyst combination also is capable of tolerating fluctuations in the H.sub.2 /CO ratio without major deleterious effect on the reaction rate. Furthermore, carbon dioxide and water are also tolerated without substantial catalyst deactivation.

  3. Alkali or alkaline earth metal promoted catalyst and a process for methanol synthesis using alkali or alkaline earth metals as promoters

    DOEpatents

    Tierney, J.W.; Wender, I.; Palekar, V.M.

    1995-01-31

    The present invention relates to a novel route for the synthesis of methanol, and more specifically to the production of methanol by contacting synthesis gas under relatively mild conditions in a slurry phase with a heterogeneous catalyst comprising reduced copper chromite impregnated with an alkali or alkaline earth metal. There is thus no need to add a separate alkali or alkaline earth compound. The present invention allows the synthesis of methanol to occur in the temperature range of approximately 100--160 C and the pressure range of 40--65 atm. The process produces methanol with up to 90% syngas conversion per pass and up to 95% methanol selectivity. The only major by-product is a small amount of easily separated methyl formate. Very small amounts of water, carbon dioxide and dimethyl ether are also produced. The present catalyst combination also is capable of tolerating fluctuations in the H[sub 2]/CO ratio without major deleterious effect on the reaction rate. Furthermore, carbon dioxide and water are also tolerated without substantial catalyst deactivation.

  4. Ab initio calculations on the positive ions of the alkaline-earth oxides, fluorides, and hydroxides

    NASA Technical Reports Server (NTRS)

    Partridge, H.; Langhoff, S. R.; Bauschlicher, C. W., Jr.

    1986-01-01

    Theoretical dissociation energies are presented for the alkaline-earth fluoride, hydroxide, and oxide positive ions that are considered to be accurate to 0.1-0.2 eV. The r(e) for the positive ions are found to be consistently shorter than the corresponding neutrals by 0.07 + or -0.02 A. The bonding in the ground states is demonstrated to be of predominantly M + 2 X - character. The a 3 Pi and A 1 Pi are found to lie considerably above the X 1 Sigma + ground states of the alkaline-earth fluoride and hydroxide positive ions. The overall agreement of the theoretical ionization potentials with the available experimental appearance potentials is satisfactory; these values should represent the most accurate and consistent set available.

  5. Effects of inherent alkali and alkaline earth metallic species on biomass pyrolysis at different temperatures.

    PubMed

    Hu, Song; Jiang, Long; Wang, Yi; Su, Sheng; Sun, Lushi; Xu, Boyang; He, Limo; Xiang, Jun

    2015-09-01

    This work aimed to investigate effects of inherent alkali and alkaline earth metallic species (AAEMs) on biomass pyrolysis at different temperatures. The yield of CO, H2 and C2H4 was increased and that of CO2 was suppressed with increasing temperature. Increasing temperature could also promote depolymerization and aromatization reactions of active tars, forming heavier polycyclic aromatic hydrocarbons, leading to decrease of tar yields and species diversity. Diverse performance of inherent AAEMs at different temperatures significantly affected the distribution of pyrolysis products. The presence of inherent AAEMs promoted water-gas shift reaction, and enhanced the yield of H2 and CO2. Additionally, inherent AAEMs not only promoted breakage and decarboxylation/decarbonylation reaction of thermally labile hetero atoms of the tar but also enhanced thermal decomposing of heavier aromatics. Inherent AAEMs could also significantly enhance the decomposition of levoglucosan, and alkaline earth metals showed greater effect than alkali metals.

  6. IUPAC-NIST Solubility Data Series. 95. Alkaline Earth Carbonates in Aqueous Systems. Part 2. Ca

    SciTech Connect

    De Visscher, Alex; Vanderdeelen, Jan

    2012-06-15

    The alkaline earth carbonates are an important class of minerals. This article is part of a volume in the IUPAC-NIST Solubility Data Series that compiles and critically evaluates solubility data of the alkaline earth carbonates in water and in simple aqueous electrolyte solutions. Part 1 outlined the procedure adopted in this volume, and presented the beryllium and magnesium carbonates. Part 2, the current paper, compiles and critically evaluates the solubility data of calcium carbonate. The chemical forms included are the anhydrous CaCO{sub 3} types calcite, aragonite, and vaterite, the monohydrate monohydrocalcite (CaCO{sub 3}{center_dot} H{sub 2}O), the hexahydrate ikaite (CaCO{sub 3}{center_dot}6H{sub 2}O), and an amorphous form. The data were analyzed with two model variants, and thermodynamic data of each form consistent with each of the models and with the CODATA key values for thermodynamics are presented.

  7. Surface energetics of alkaline-earth metal oxides: Trends in stability and adsorption of small molecules

    NASA Astrophysics Data System (ADS)

    Bajdich, Michal; Nørskov, Jens K.; Vojvodic, Aleksandra

    2015-04-01

    We present a systematic theoretical investigation of the surface properties, stability, and reactivity of rocksalt type alkaline-earth metal oxides including MgO, CaO, SrO, and BaO. The accuracy of commonly used exchange-correlation density functionals (LDA, PBE, RPBE, PBEsol, BEEF-vdW, and hybrid HSE) and random-phase approximation (RPA) is evaluated and compared to existing experimental values. Calculated surface energies of the four most stable surface facets under vacuum conditions, the (100) surface, the metal and oxygen terminated octopolar (111), and the (110) surfaces, exhibit a monotonic increase in stability from MgO to BaO. On the MgO(100) surface, adsorption of CO, NO, and CH4 is characterized by physisorption while H2O chemisorbs, which is in agreement with experimental findings. We further use the on-top metal adsorption of CO and NO molecules to map out the surface energetics of each alkaline-earth metal oxide surface. The considered functionals all qualitatively predict similar adsorption energy trends. The ordering between the adsorption energies on different surface facets can be attributed to differences in the local geometrical surface structure and the electronic structure of the metal constituent of the alkaline-earth metal oxide. The striking observation that CO adsorption strength is weaker than NO adsorption on the (100) terraces as the period of the alkaline-earth metal in the oxide increases is analyzed in detail in terms of charge redistribution within the σ and π channels of adsorbates. Finally, we also present oxygen adsorption and oxygen vacancy formation energies in these oxide systems.

  8. Properties of the triplet metastable states of the alkaline-earth-metal atoms

    SciTech Connect

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

    2004-11-01

    The static and dynamic properties of the alkaline-earth-metal atoms in their metastable state are computed in a configuration interaction approach with a semiempirical model potential for the core. Among the properties determined are the scalar and tensor polarizabilities, the quadrupole moment, some of the oscillator strengths, and the dispersion coefficients of the van der Waals interaction. A simple method for including the effect of the core on the dispersion parameters is described.

  9. Energetics of alkali and alkaline earth ion-exchanged zeolite A

    DOE PAGES

    Sun, Hui; Wu, Di; Liu, Kefeng; ...

    2016-06-30

    Alkali and alkaline earth ion-exchanged zeolite A samples were synthesized in aqueous exchange media. They were thoroughly studied by powder X-ray diffraction (XRD), electron microprobe (EMPA), thermogravimetric analysis and differential scanning calorimetry (TG-DSC), and high temperature oxide melt solution calorimetry. The hydration energetics and enthalpies of formation of these zeolite A materials from constituent oxides were determined. Specifically, the hydration level of zeolite A has a linear dependence on the average ionic potential (Z/r) of the cation, from 0.894 (Rb-A) to 1.317 per TO2 (Mg-A). The formation enthalpies from oxides (25 °C) range from –93.71 ± 1.77 (K-A) to –48.02more » ± 1.85 kJ/mol per TO2 (Li-A) for hydrated alkali ion-exchanged zeolite A, and from –47.99 ± 1.20 (Ba-A) to –26.41 ± 1.71 kJ/mol per TO2 (Mg-A) for hydrated alkaline earth ion-exchanged zeolite A. As a result, the formation enthalpy from oxides generally becomes less exothermic as Z/r increases, but a distinct difference in slope is observed between the alkali and the alkaline earth series.« less

  10. Energetics of alkali and alkaline earth ion-exchanged zeolite A

    SciTech Connect

    Sun, Hui; Wu, Di; Liu, Kefeng; Guo, Xiaofeng; Navrotsky, Alexandra

    2016-06-30

    Alkali and alkaline earth ion-exchanged zeolite A samples were synthesized in aqueous exchange media. They were thoroughly studied by powder X-ray diffraction (XRD), electron microprobe (EMPA), thermogravimetric analysis and differential scanning calorimetry (TG-DSC), and high temperature oxide melt solution calorimetry. The hydration energetics and enthalpies of formation of these zeolite A materials from constituent oxides were determined. Specifically, the hydration level of zeolite A has a linear dependence on the average ionic potential (Z/r) of the cation, from 0.894 (Rb-A) to 1.317 per TO2 (Mg-A). The formation enthalpies from oxides (25 °C) range from –93.71 ± 1.77 (K-A) to –48.02 ± 1.85 kJ/mol per TO2 (Li-A) for hydrated alkali ion-exchanged zeolite A, and from –47.99 ± 1.20 (Ba-A) to –26.41 ± 1.71 kJ/mol per TO2 (Mg-A) for hydrated alkaline earth ion-exchanged zeolite A. As a result, the formation enthalpy from oxides generally becomes less exothermic as Z/r increases, but a distinct difference in slope is observed between the alkali and the alkaline earth series.

  11. Alkaline earth metal doped tin oxide as a novel oxygen storage material

    SciTech Connect

    Dong, Qiang; Yin, Shu; Yoshida, Mizuki; Wu, Xiaoyong; Liu, Bin; Miura, Akira; Takei, Takahiro; Kumada, Nobuhiro; Sato, Tsugio

    2015-09-15

    Alkaline earth metal doped tin oxide (SnO{sub 2}) hollow nanospheres with a diameter of 50 nm have been synthesized successfully via a facial solvothermal route in a very simple system composed of only ethanol, acetic acid, SnCl{sub 4}·5H{sub 2}O and A(NO{sub 3}){sub 2}·xH{sub 2}O (A = Mg, Ca, Sr, Ba). The synthesized undoped SnO{sub 2} and A-doped SnO{sub 2} hollow nanospheres were characterized by the oxygen storage capacity (OSC), X-ray diffraction, transmission electron microscopy and the Brunauer–Emmet–Teller (BET) technique. The OSC values of all samples were measured using thermogravimetric-differential thermal analysis. The incorporation of alkaline earth metal ion into tin oxide greatly enhanced the thermal stability and OSC. Especially, Ba-doped SnO{sub 2} hollow nanospheres calcined at 1000 °C for 20 h with a BET surface area of 61 m{sup 2} g{sup −1} exhibited the considerably high OSC of 457 μmol-O g{sup −1} and good thermal stability. Alkaline earth metal doped tin oxide has the potential to be a novel oxygen storage material.

  12. The Effect of Alkaline Earth Metal on the Cesium Loading of Ionsiv(R) IE-910 and IE-911

    SciTech Connect

    Fondeur, F.F.

    2001-01-16

    This study investigated the effect of variances in alkaline earth metal concentrations on cesium loading of IONSIV(R) IE-911. The study focused on Savannah River Site (SRS) ''average'' solution with varying amounts of calcium, barium and magnesium.

  13. Nano porous alkaline earth metal silicates as free fatty acid adsorbents from Crude Palm Oil (CPO)

    NASA Astrophysics Data System (ADS)

    Masmur, Indra; Sembiring, Seri Bima; Bangun, Nimpan; Kaban, Jamaran; Putri, Nabila Karina

    2017-01-01

    Free fatty acids(FFA) from Crude Palm Oil (CPO) have been adsorbed by alkaline earth metal silicate (M-silicate : M = Mg, Ca, Sr and Ba) adsorbents in ethanol using batch method. The adsorbents were prepared from the chloride salts of alkaline metals and Na2SiO3. The resulting white solid of the alkaline earth metal silicates were then heated at 800°C for 3 hours to enlarge their porosities. All adsorbents were characterized by SEM-EDX, XRD and BET. The EDX spectrum of SEM-EDX showed the appearance of all elements in the adsorbents, and the XRD spectrum of all adsorbents showed that they have crystobalite structure. The porosity of the adsorbents calculated by BET method showed that the porosities of the adsorbents range from 2.0884 - 2.0969 nm. All the adsorbents were used to adsorb the FFA from CPO containing 4.79%, 7.3%, 10.37% and 13.34% of FFA. The ratio of adsorbent to CPO to be used in adsorption of FFA from CPO were made 1:1, 1:2 and 1:3, with adsorption time of 1 hour. We found that the maximum adsorption of FFA from CPO was given by Ca-Silicate adsorbent which was between 69.86 - 94.78%, while the lowest adsorption was shown by Mg-silicate adsorbent which was 49.32 -74.53%.

  14. Intermolecular hydroamination of vinylarenes by iminoanilide alkaline-earth catalysts: a computational scrutiny of mechanistic pathways.

    PubMed

    Tobisch, Sven

    2014-07-14

    A thorough computational exploration of the mechanistic intricacies of the intermolecular hydroamination (HA) of vinylarenes by a recently reported class of kinetically stabilised iminoanilide [{N^N}Ae{N(SiMe3)2}⋅(THF)n] alkaline-earth amido compounds (Ae = Ca, Sr, Ba) is presented. Two distinct mechanistic pathways for catalytic HA mediated by alkaline-earth and rare-earth compounds have emerged over the years that account equally well for the specific features of the process. On one hand, a concerted proton-assisted pathway to deliver the amine product in a single step can be invoked and, on the other, a stepwise σ-insertive pathway that comprises a rapid, reversible migratory olefin insertion step linked to a less facile, irreversible Ae-C alkyl bond aminolysis. The results of the study presented herein, which employed a heavily benchmarked and reliable DFT methodology, supports a stepwise σ-insertive pathway that involves fast and reversible migratory C=C bond insertion into the polar Ae-N pyrrolido σ bond. This proceeds with strict 2,1 regioselectivity via a highly polarised four-centre transition state (TS) structure, linked to irreversible intramolecular Ae-C bond aminolysis of the alkaline-earth alkyl intermediate as the energetically favourable mechanism. Turnover-limiting aminolysis is consistent with the significant KIE measured; the DFT-derived effective barrier matches the Eyring parameter empirically determined for the best-performing {N^N}Ba(NR2) catalyst gratifyingly well. It also predicts the observed trend in reactivity (Ca

  15. Theoretical investigation of the structures, stabilities, and NLO responses of calcium-doped pyridazine: alkaline-earth-based alkaline salt electrides.

    PubMed

    Wang, Yin-Feng; Huang, Jiangen; Jia, Li; Zhou, Guangpei

    2014-02-01

    Currently, whether alkaline-earth-doped compounds with electride characteristics are novel candidates for high-performance nonlinear optical (NLO) materials is unknown. In this paper, using quantum chemical computations, we show that: when doping calcium atoms into a family of alkaline-substituted pyridazines, alkaline-earth-based alkaline salt electrides M-H₃C₄N₂⋯Ca (M=H, Li, and K) with distended excess electron clouds are formed. Interestingly, from the triplet to the singlet state, the chemical valence of calcium atom changes from +1 to 0, and the dipole moment direction (μ₀) of the molecule reverses for each M-H₃C₄N₂⋯Ca. Changing pyridazine from without (H₄C₄N₂⋯Ca) to with one alkaline substituent (M-H₃C₄N₂⋯Ca, M=Li and K), the ground state changes from the triplet to the singlet state. The alkaline earth metal doping effect (electride effect) and alkaline salt effect on the static first hyperpolarizabilities (β₀) demonstrates that (1) the β₀ value is increased approximately 1371-fold from 2 (pyridazine, H₄C₄N₂) to 2745au (Ca-doped pyridazine, H₄C₄N₂⋯Ca), (2) the β₀ value is increased approximately 1146-fold from 2 in pyridazine (H₄C₄N₂) to 2294au in an Li-substituted pyridazine (Li-H₃C₄N₂), and (3) the β₀ value is increased 324-(M=Li) and 106-(M=K) fold from 826 (MLi) and 2294au (MK) to 268,679 (M=Li) and 245,878au (M=K), respectively, from the alkalized pyridazine (M-H₃C₄N₂) to the Ca-doped pyridazine (M-H₃C₄N₂⋯Ca). These results may provide a new means for designing high-performance NLO materials.

  16. Quantum phase transition of alkaline-earth fermionic atoms confined in an optical superlattice

    NASA Astrophysics Data System (ADS)

    Silva-Valencia, J.; Franco, R.; Figueira, M. S.

    2013-03-01

    Using the density matrix renormalization group method, we evaluate the spin and charge gaps of alkaline-earth fermionic atoms in a periodic one-dimensional optical superlattice. The number of delocalized atoms is equal to the lattice size and we consider an antiferromagnetic coupling between delocalized and localized atoms. We found a quantum phase transition from a Kondo insulator spin liquid state without confining potential to a charge-gapped antiferromagnetic state with nonzero potential. For each on-site coupling, there is a critical potential point for which the spin gap vanishes and its value increases linearly with the local interaction.

  17. Single-stage sub-Doppler cooling of alkaline earth atoms.

    PubMed

    Xu, Xinye; Loftus, Thomas H; Dunn, Josh W; Greene, Chris H; Hall, John L; Gallagher, Alan; Ye, Jun

    2003-05-16

    We report the first experimental study of sub-Doppler cooling in alkaline earth atoms (87Sr) enabled by the presence of nuclear spin-originated magnetic degeneracy in the atomic ground state. Sub-Doppler cooling in a sigma(+)-sigma(-) configuration is achieved despite the presence of multiple, closely spaced excited states. This surprising result is confirmed by an expanded multilevel theory of the radiative cooling force. Detailed investigations of system performance have shed new insights into (sigma(+)-sigma(-)) cooling dynamics and will likely play an important role in the future development of neutral atom-based optical frequency standards.

  18. Wide-band-gap, alkaline-earth-oxide semiconductor and devices utilizing same

    DOEpatents

    Abraham, Marvin M.; Chen, Yok; Kernohan, Robert H.

    1981-01-01

    This invention relates to novel and comparatively inexpensive semiconductor devices utilizing semiconducting alkaline-earth-oxide crystals doped with alkali metal. The semiconducting crystals are produced by a simple and relatively inexpensive process. As a specific example, a high-purity lithium-doped MgO crystal is grown by conventional techniques. The crystal then is heated in an oxygen-containing atmosphere to form many [Li].degree. defects therein, and the resulting defect-rich hot crystal is promptly quenched to render the defects stable at room temperature and temperatures well above the same. Quenching can be effected conveniently by contacting the hot crystal with room-temperature air.

  19. Liquefaction process for solid carbonaceous materials containing alkaline earth metal humates

    DOEpatents

    Epperly, William R.; Deane, Barry C.; Brunson, Roy J.

    1982-01-01

    An improved liquefaction process wherein wall scale and particulate agglomeration during the liquefaction of solid carbonaceous materials containing alkaline earth metal humates is reduced and/or eliminated by subjecting the solid carbonaceous materials to controlled cyclic cavitation during liquefaction. It is important that the solid carbonaceous material be slurried in a suitable solvent or diluent during liquefaction. The cyclic cavitation may be imparted via pressure cycling, cyclic agitation and the like. When pressure cycling or the like is employed an amplitude equivalent to at least 25 psia is required to effectively remove scale from the liquefaction vessel walls.

  20. Studies on the interactions between purified bovine caseins and alkaline-earth-metalions

    PubMed Central

    Dickson, I. R.; Perkins, D. J.

    1971-01-01

    1. Alkaline-earth-metal cations at low concentrations form soluble complexes with bovine caseins. The relative order of binding capacities is: Mg2+>Ca2+>Ba2+>Sr2+. 2. The cations interact with both free ionized carboxyl groups of aspartic acid and glutamic acid and with monoester phosphate groups covalently bound to serine and threonine; at low concentrations of the cations interactions are predominantly with the phosphate groups. 3. The order of binding capacities for purified components of the casein complex is: αs1-casein>β-casein>κ-casein. PMID:5166590

  1. Measurements of the mobility of alkaline earth ions in liquid xenon

    NASA Astrophysics Data System (ADS)

    Jeng, S.-C.; Fairbank, W. M., Jr.; Miyajima, M.

    2009-02-01

    The mobility of alkaline earth ions, Mg+, Ca+, Sr+ and Ba+, in liquid xenon is measured for the first time. The mobility of Tl+ is also determined for comparison with a measurement by other researchers. The Atkins cluster model for positive ions in non-polar liquids, based on the electrostriction effect, gives general agreement with the magnitude of the mobility values. This is some evidence that the positive ions form a snowball rather than a bubble structure in liquid xenon. However, the temperature dependence of the mobility does not match well with the Atkins theory, so there are still open theoretical questions on the nature of the environment of alkaline earth ions in liquid xenon. The lower mobility of Mg+ and Ba+ may be explained by a better size match to interstitial and substitutional sites, respectively, in solid Xe. These measurements are motivated by the development of a new technique to search for neutrino masses through 0νββ decay of 136Xe. A key component of one version of the proposed experiment is tagging of 136Ba+ daughter ions in liquid 136Xe by laser-induced fluorescence.

  2. Atomic hydrogen in. gamma. -irradiated hydroxides of alkaline-earth elements

    SciTech Connect

    Spitsyn, V.I.; Yurik, T.K.; Barsova, L.I.

    1982-04-01

    Atomic hydrogen is an important intermediate product formed in the radiolysis of compounds containing X-H bonds. H atoms have been detected in irradiated matrices of H/sub 2/ and inert gases at 4/sup 0/K, in irradiated ice and frozen solutions of acids in irradiated salts and in other systems. Here results are presented from a study of the ESR spectra of H atoms generated in polycrystalline hydroxides of alkaline-earth elements that have been ..gamma..-irradiated at 77/sup 0/K, after preliminary treatment at various temperatures. For the first time stabilization of atomic hydrogen in ..gamma..-irradiated polycrystalline alkaline-earth element hydroxides has been detected. Depending on the degree of dehydroxylation, several types of hydrogen atoms may be stabilized in the hydroxides, these hydrogen atoms having different radiospectroscopic parameters. In the magnesium-calcium-strontium-barium hydroxide series, a regular decrease has been found in the hfi constants for H atoms with the cations in the immediate surroundings. A direct proportionality has been found between the parameters ..delta..A/A/sub 0/ and the polarizability of the cation.

  3. Temperature-induced collapse of alkaline Earth cation-polyacrylate anion complexes.

    PubMed

    Lages, Sebastian; Schweins, Ralf; Huber, Klaus

    2007-09-06

    Polyacrylate anions are used to inhibit CaCO3 precipitation and may be a promising additive to control formation of inorganic nanoparticles. The origin of this applicability lies in specific interactions between the alkaline earth cations and the carboxylate functions along the polyacrylate chains. In the absence of CO32- anions, these interactions eventually cause precipitation of polyelectrolytes. Extended investigation of dilute sodium polyacrylate solutions approaching this precipitation threshold revealed a dramatic shrinking of the PA coil dimensions once the threshold is reached (Eur. Phys. J. E 2001, 5, 117). Recent isothermal calorimetric titration experiments by Antonietti et al. (Macromolecules 2004, 37, 3444) indicated that the driving force of this precipitation is entropic in nature. In the present work, we investigated the impact of temperature on the structural changes of dissolved polyacrylate chains decorated with alkaline earth cations. To this end, large polyacrylate chains were brought close to the precipitation threshold by the addition of distinct amounts of Ca2+ or Sr2+ cations. The resulting structural intermediates were then subjected to temperature variations in the range of 15 degrees C

  4. Tungstate-ferrates of some alkali and alkaline-earth metals

    SciTech Connect

    Gruba, A.I.; Danileiko, L.A.; Moroz, Ya.A.; Zyats, M.N.

    1988-02-01

    Tungstate-ferrates of some alkali and alkaline-earth metals with the ratio Fe:W = 2:11, the iron ions in which are found in two types of coordination, tetrahedral and octahedral, were synthesized. The similarity of the IR spectra of the compounds obtained and known compounds with the anion structure of the Keggin type with the composition M/sub X/(XZW/sub 11/O/sub 40/H/sub m/) x nH/sub 2/O indicates that their heteropolyanions are isostructural. The thermal stability of the compounds studied and the structure of the products of thermolysis depend on the charge and radius of the extrasphere cation. When the ratio of the radii of the extrasphere cation of the alkali or alkaline-earth metal to the radius of the ion of the central 3d element, appearing in the coordination sphere of the heteropolytungstates, exceeds 1.6, the most likely products of thermolysis of heteropolycompounds are the compounds of the pyrochlore family and tungsten bronzes.

  5. Matrix diffusion of some alkali- and alkaline earth-metals in granitic rock

    SciTech Connect

    Johansson, H.; Byegaard, J.; Skarnemark, G.; Skaalberg, M.

    1997-12-31

    Static through-diffusion experiments were performed to study the diffusion of alkali- and alkaline earth-metals in fine-grained granite and medium-grained Aespoe-diorite. Tritiated water was used as an inert reference tracer. Radionuclides of the alkali- and alkaline earth-metals (mono- and divalent elements which are not influenced by hydrolysis in the pH-range studied) were used as tracers, i.e., {sup 22}Na{sup +}, {sup 45}Ca{sup 2+} and {sup 85}Sr{sup 2+}. The effective diffusivity and the rock capacity factor were calculated by fitting the breakthrough curve to the one-dimensional solution of the diffusion equation. Sorption coefficients, K{sub d}, that were derived from the rock capacity factor (diffusion experiments) were compared with K{sub d} determined in batch experiments using crushed material of different size fractions. The results show that the tracers were retarded in the same order as was expected from the measured batch K{sub d}. Furthermore, the largest size fraction was the most representative when comparing batch K{sub d} with K{sub d} evaluated from the diffusion experiments. The observed effective diffusivities tended to decrease with increasing cell lengths, indicating that the transport porosity decreases with increasing sample lengths used in the diffusion experiments.

  6. Three-photon process for producing a degenerate gas of metastable alkaline-earth-metal atoms

    NASA Astrophysics Data System (ADS)

    Barker, D. S.; Pisenti, N. C.; Reschovsky, B. J.; Campbell, G. K.

    2016-05-01

    We present a method for creating a quantum degenerate gas of metastable alkaline-earth-metal atoms. This has yet to be achieved due to inelastic collisions that limit evaporative cooling in the metastable states. Quantum degenerate samples prepared in the 1S0 ground state can be rapidly transferred to either the 3P2 or 3P0 state via a coherent three-photon process. Numerical integration of the density-matrix evolution for the fine structure of bosonic alkaline-earth-metal atoms shows that transfer efficiencies of ≃90 % can be achieved with experimentally feasible laser parameters in both Sr and Yb. Importantly, the three-photon process can be set up such that it imparts no net momentum to the degenerate gas during the excitation, which will allow for studies of metastable samples outside the Lamb-Dicke regime. We discuss several experimental challenges to successfully realizing our scheme, including the minimization of differential ac Stark shifts between the four states connected by the three-photon transition.

  7. A 3-photon process for producing degenerate gases of metastable alkaline-earth atoms

    NASA Astrophysics Data System (ADS)

    Barker, Daniel S.; Pisenti, Neal C.; Reschovsky, Benjamin J.; Campbell, Gretchen K.

    2016-05-01

    We present a method for creating quantum degenerate gases of metastable alkaline-earth atoms. A degenerate gas in any of the 3 P metastable states has not previously been obtained due to large inelastic collision rates, which are unfavorable for evaporative cooling. Samples prepared in the 1S0 ground state can be rapidly transferred to either the 3P2 or 3P0 state via a coherent 3-photon process. Numerical integration of the density matrix evolution for the fine structure of bosonic alkaline-earth atoms shows that transfer efficiencies of ~= 90 % can be achieved with experimentally feasible laser parameters in both Sr and Yb. Importantly, the 3-photon process does not impart momentum to the degenerate gas during excitation, which allows studies of these metastable samples outside the Lamb-Dicke regime. We discuss several experimental challenges to the successful realization of our scheme, including the minimization of differential AC Stark shifts between the four states connected by the 3-photon transition.

  8. Theoretical study of the alkaline-earth metal superoxides BeO2 through SrO2

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    Three competing bonding mechanisms have been identified for the alkaline-earth metal superoxides: these result in a change in the optimal structure and ground state as the alkaline-earth metal becomes heavier. For example, BeO2 has a linear 3Sigma(-)g ground-state structure, whereas both CaO2 and SrO2 have C(2v)1A1 structures. For MgO2, the theoretical calculations are less definitive, as the 3A2 C(2v) structure is computed to lie only about 3 kcal/mol above the 3Sigma(-)g linear structure. The bond dissociation energies for the alkaline-earth metal superoxides have been computed using extensive Gaussian basis sets and treating electron correlation at the modified coupled-pair functional or coupled-cluster singles and doubles level with a perturbational estimate of the triple excitations.

  9. Bond-length distributions for ions bonded to oxygen: alkali and alkaline-earth metals

    PubMed Central

    Gagné, Olivier Charles; Hawthorne, Frank Christopher

    2016-01-01

    Bond-length distributions have been examined for 55 configurations of alkali-metal ions and 29 configurations of alkaline-earth-metal ions bonded to oxygen, for 4859 coordination polyhedra and 38 594 bond distances (alkali metals), and for 3038 coordination polyhedra and 24 487 bond distances (alkaline-earth metals). Bond lengths generally show a positively skewed Gaussian distribution that originates from the variation in Born repulsion and Coulomb attraction as a function of interatomic distance. The skewness and kurtosis of these distributions generally decrease with increasing coordination number of the central cation, a result of decreasing Born repulsion with increasing coordination number. We confirm the following minimum coordination numbers: [3]Li+, [3]Na+, [4]K+, [4]Rb+, [6]Cs+, [3]Be2+, [4]Mg2+, [6]Ca2+, [6]Sr2+ and [6]Ba2+, but note that some reported examples are the result of extensive dynamic and/or positional short-range disorder and are not ordered arrangements. Some distributions of bond lengths are distinctly multi-modal. This is commonly due to the occurrence of large numbers of structure refinements of a particular structure type in which a particular cation is always present, leading to an over-representation of a specific range of bond lengths. Outliers in the distributions of mean bond lengths are often associated with anomalous values of atomic displacement of the constituent cations and/or anions. For a sample of [6]Na+, the ratio U eq(Na)/U eq(bonded anions) is partially correlated with 〈[6]Na+—O2−〉 (R 2 = 0.57), suggesting that the mean bond length is correlated with vibrational/displacement characteristics of the constituent ions for a fixed coordination number. Mean bond lengths also show a weak correlation with bond-length distortion from the mean value in general, although some coordination numbers show the widest variation in mean bond length for zero distortion, e.g. Li+ in [4]- and [6]-coordination, Na+ in [4]- and [6

  10. Structure elucidation of alkaline earth impregnated MCM-41 type mesoporous materials obtained by direct synthesis: An experimental and theoretical study

    NASA Astrophysics Data System (ADS)

    Paz, Gizeuda L.; Silva, Francisco das Chagas M.; Araújo, Maciel M.; Lima, Francisco das Chagas A.; Luz, Geraldo E.

    2014-06-01

    In this work, MCM-41 were synthesized hydrothermally and functionalized with calcium and strontium salts by direct method, using the Si/M = 50 molar ratio, in order to elucidate the way as the alkaline earth is incorporated on MCM-41 molecular sieve. The materials were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, nitrogen adsorption-desorption and theoretical calculations by DFT method. Experimental results and computer simulations showed that the alkaline earths were incorporated on MCM-41 through a complex structure, which negatively influences on basic sites formation.

  11. Impacts of artificial ocean alkalinization on the carbon cycle and climate in Earth system simulations

    NASA Astrophysics Data System (ADS)

    González, Miriam Ferrer; Ilyina, Tatiana

    2016-06-01

    Using the state-of-the-art emissions-driven Max Planck Institute Earth system model, we explore the impacts of artificial ocean alkalinization (AOA) with a scenario based on the Representative Concentration Pathway (RCP) framework. Addition of 114 Pmol of alkalinity to the surface ocean stabilizes atmospheric CO2 concentration to RCP4.5 levels under RCP8.5 emissions. This scenario removes 940 GtC from the atmosphere and mitigates 1.5 K of global warming within this century. The climate adjusts to the lower CO2 concentration preventing the loss of sea ice and high sea level rise. Seawater pH and the carbonate saturation state (Ω) rise substantially above levels of the current decade. Pronounced differences in regional sensitivities to AOA are projected, with the Arctic Ocean and tropical oceans emerging as hot spots for biogeochemical changes induced by AOA. Thus, the CO2 mitigation potential of AOA comes at a price of an unprecedented ocean biogeochemistry perturbation with unknown ecological consequences.

  12. Theoretical study of the alkaline-earth (LiBe)+ ion: structure, spectroscopy and dipole moments

    NASA Astrophysics Data System (ADS)

    Ghanmi, C.; Farjallah, M.; Berriche, H.

    2017-03-01

    We study theoretically the structure and spectroscopic properties of the alkali alkaline-earth (LiBe)+ ion. The potential energy curves and their spectroscopic parameters, permanent and transition dipole moments are determined with a quantum chemistry approach. The (LiBe)+ ion is modelled as two valence electron system moving in the field of Be2+ and Li+ cores, which are described by pseudopotentials. In addition, effective core-polarization potentials are included to correct the energy. The molecular calculations are performed using a standard quantum chemistry approach based on the pseudopotential model, Gaussian basis sets, effective core polarization potentials, and full configuration interaction (CI) calculations. The precision of our spectroscopic parameters are discussed by comparison with currently available theoretical results. A rather good agreement is observed for the ground and first excited states. The permanent dipole moments reveal many abrupt changes, which are localized at particular distances corresponding to the positions of the avoided crossings.

  13. Prolonged QT Syndrome and Seizure Secondary to Alkaline Earth Metal Deficiency: A Case Report.

    PubMed

    McKinney, A; Keegan, B C

    2011-01-01

    Introduction. Alkaline earth metal deficiency is recognized as a cause of both seizure and long QT syndrome. Their deficiency can have significant repercussions on the function of cells, tissues, and organs of the body. An understanding of the role of electrolytes allows an appreciation of the significance of depleted levels on cell function. Case Report. A 65-year-old lady was admitted with symptoms of chest discomfort, vomiting, increased stoma output, and dizziness. Two days following admission she suffered a tonic-clonic seizure. ECG review demonstrated a prolonged QTc interval, raising the possibility of an underlying Torsades de Pointes as the precipitant. This was attributed to electrolyte disturbance arising as a result of multiple aetiologies. Discussion. This paper highlights the multisystem effects of electrolyte disturbance, with emphasis upon its role in precipitating cardiac arrhythmia and neurological symptoms.

  14. Alkaline earth metal cation exchange: effect of mobile counterion and dissolved organic matter.

    PubMed

    Indarawis, Katrina; Boyer, Treavor H

    2012-04-17

    The goal of this research was to provide an improved understanding of the interactions between alkaline earth metals and DOM under conditions that are encountered during drinking water treatment with particular focus on cation exchange. Both magnetically enhanced and nonmagnetic cation exchange resins were converted to Na, Mg, Ca, Sr, and Ba mobile counterion forms as a novel approach to investigate the exchange behavior between the cations and the interactions between the cations and DOM. The results show that cation exchange is a robust process for removal of Ca(2+) and Mg(2+) considering competition with cations on the resin surface and presence of DOM. DOM was actively involved during the cation exchange process through complexation, adsorption, and coprecipitation reactions. In addition to advancing the understanding of ion exchange processes for water treatment, the results of this work are applicable to membrane pretreatment to minimize fouling, treatment of membrane concentrate, and precipitative softening.

  15. Hydration process of alkaline-earth metal atoms in water clusters

    NASA Astrophysics Data System (ADS)

    Okai, Nobuhiro; Ishikawa, Haruki; Fuke, Kiyokazu

    2005-10-01

    Ionization potentials (IPs) of water clusters containing alkaline-earth metal atoms are measured by a photoionization threshold method to examine the hydration process of the metal atoms in clusters. IPs of Mg(H 2O) n and Ca(H 2O) n are found to decrease with increasing n and become constant at 3.18 eV for n ⩾ 9 and n ⩾ 8, respectively. The observed constant IP agrees with an estimated photoelectric threshold (3.2 eV) of bulk ice. From the comparison with the results on the theoretical calculations as well as the IPs for alkali atom-water clusters, the anomalous size dependence of IPs is ascribed to the formation of an ion-pair state.

  16. Linear alkaline earth metal phosphinate coordination polymers: synthesis and structural characterization.

    PubMed

    Rood, Jeffrey A; Huttenstine, Ashley L; Schmidt, Zachery A; White, Michael R; Oliver, Allen G

    2014-06-01

    Reaction of alkaline earth metal salts with diphenylphosphinic acid in dimethylformamide solvent afforded four coordination polymers: [Mg3(O2PPh2)6(DMF)2]·2DMF (I), [Ca(O2PPh2)2(DMF)2] (II), [Sr(O2PPh2)2(DMF)2] (III) and [Ba(O2PPh2)2(DMF)2] (IV) (where DMF is N,N-dimethylformamide). Single-crystal X-ray diffraction revealed that all four compounds produce linear chain structures in the solid state, with the Ca, Sr and Ba forming isostructural crystals. The bulk materials were characterized by FT-IR and (1)H NMR spectroscopy and elemental analyses.

  17. Magnetic crystals and helical liquids in alkaline-earth fermionic gases

    PubMed Central

    Barbarino, Simone; Taddia, Luca; Rossini, Davide; Mazza, Leonardo; Fazio, Rosario

    2015-01-01

    The joint action of a magnetic field and of interactions is crucial for the appearance of exotic quantum phenomena, such as the quantum Hall effect. Owing to their rich nuclear structure, equivalent to an additional synthetic dimension, one-dimensional alkaline-earth(-like) fermionic gases with synthetic gauge potential and atomic contact repulsion may display similar related properties. Here we show the existence and the features of a hierarchy of fractional insulating and conducting states by means of analytical and numerical methods. We demonstrate that the gapped states are characterized by density and magnetic order emerging solely for gases with effective nuclear spin larger than 1/2, whereas the gapless phases can support helical modes. We finally argue that these states are related to an unconventional fractional quantum Hall effect in the thin-torus limit and that their properties can be studied in state-of-the-art laboratories. PMID:26350624

  18. Methanol synthesis using a catalyst combination of alkali or alkaline earth salts and reduced copper chromite

    DOEpatents

    Tierney, J.W.; Wender, I.; Palekar, V.M.

    1995-01-24

    The present invention relates to a novel route for the synthesis of methanol, and more specifically to the production of methanol by contacting synthesis gas under relatively mild conditions in a slurry phase with a catalyst combination comprising reduced copper chromite and basic alkali salts or alkaline earth salts. The present invention allows the synthesis of methanol to occur in the temperature range of approximately 100--160 C and the pressure range of 40--65 atm. The process produces methanol with up to 90% syngas conversion per pass and up to 95% methanol selectivity. The only major by-product is a small amount of easily separated methyl formate. Very small amounts of water, carbon dioxide and dimethyl ether are also produced. The present catalyst combination also is capable of tolerating fluctuations in the H[sub 2]/CO ratio without major deleterious effect on the reaction rate. Furthermore, carbon dioxide and water are also tolerated without substantial catalyst deactivation.

  19. Methanol synthesis using a catalyst combination of alkali or alkaline earth salts and reduced copper chromite

    DOEpatents

    Tierney, John W.; Wender, Irving; Palekar, Vishwesh M.

    1995-01-01

    The present invention relates to a novel route for the synthesis of methanol, and more specifically to the production of methanol by contacting synthesis gas under relatively mild conditions in a slurry phase with a catalyst combination comprising reduced copper chromite and basic alkali salts or alkaline earth salts. The present invention allows the synthesis of methanol to occur in the temperature range of approximately 100.degree.-160.degree. C. and the pressure range of 40-65 atm. The process produces methanol with up to 90% syngas conversion per pass and up to 95% methanol selectivity. The only major by-product is a small amount of easily separated methyl formate. Very small amounts of water, carbon dioxide and dimethyl ether are also produced. The present catalyst combination also is capable of tolerating fluctuations in the H.sub.2 /CO ratio without major deleterious effect on the reaction rate. Furthermore, carbon dioxide and water are also tolerated without substantial catalyst deactivation.

  20. Quantum Degenerate Mixtures of Alkali and Alkaline-Earth-Like Atoms

    SciTech Connect

    Hara, Hideaki; Takasu, Yosuke; Yamaoka, Yoshifumi; Doyle, John M.; Takahashi, Yoshiro

    2011-05-20

    We realize simultaneous quantum degeneracy in mixtures consisting of the alkali and alkaline-earth-like atoms Li and Yb. This is accomplished within an optical trap by sympathetic cooling of the fermionic isotope {sup 6}Li with evaporatively cooled bosonic {sup 174}Yb and, separately, fermionic {sup 173}Yb. Using cross-thermalization studies, we also measure the elastic s-wave scattering lengths of both Li-Yb combinations, |a{sub {sup 6}Li-{sup 174}Yb}|=1.0{+-}0.2 nm and |a{sub {sup 6}Li-{sup 173}Yb}|=0.9{+-}0.2 nm. The equality of these lengths is found to be consistent with mass-scaling analysis. The quantum degenerate mixtures of Li and Yb, as realized here, can be the basis for creation of ultracold molecules with electron spin degrees of freedom, studies of novel Efimov trimers, and impurity probes of superfluid systems.

  1. First hyperpolarizability of cyclooctatetraene modulated by alkali and alkaline earth metals.

    PubMed

    Roy, Ria Sinha; Mondal, Avijit; Nandi, Prasanta K

    2017-03-01

    In the present investigation, the first hyperpolarizability of alkali and alkaline earth metal derivatives of cyclooctatetraene (COT) has been calculated using BHHLYP and CAM-B3LYP functional for 6-311++G(d,p), 6-311++G(3df,3pd), and aug-pc 2 basis sets. Introduction of Na/K atoms at the axial position of COT and Li, Na, K/Be, Mg, Ca metal atoms and cyanide groups at the equatorial sites leads to lager enhancement of first hyperpolarizability. The ring charge density can account for the variation of first hyperpolarizability. The two state model has been invoked to explain the variation of first hyperpolarizability.

  2. Alkaline-earth metal hydrides as novel host lattices for Eu(II) luminescence.

    PubMed

    Kunkel, Nathalie; Kohlmann, Holger; Sayede, Adlane; Springborg, Michael

    2011-07-04

    Luminescence of divalent europium has been investigated for the first time in metal hydrides. A complete solid-solution series was found for the pseudobinary system Eu(x)Sr(1-x)H(2) [a = 637.6(1) pm -12.1(3)x pm, b = 387.0(1)-6.5(2)x pm, c = 732.2(2)-10.1(4)x pm]. Europium-doped alkaline-earth hydrides Eu(x)M(1-x)H(2) (M = Ca, Sr, Ba) with a small europium concentration (x = 0.005) exhibit luminescence with maximum emission wavelengths of 764 nm (M = Ca), 728 nm (M = Sr), and 750 nm (M = Ba); i.e., the emission energy of divalent europium shows an extremely large red shift compared to the emission energies of fluorides or oxides. Theoretical calculations (LDA+U) confirm decreasing band gaps with increasing europium content of the solid solutions.

  3. Relationship between microstructure and efficiency of lithium silicate scintillating glasses: The effect of alkaline earths

    SciTech Connect

    Bliss, M.; Craig, R.A.; Sunberg, D.S.; Weber, M.J.

    1996-12-31

    Lithium silicate glasses containing Ce{sup 3+} are known to be scintillators. Glasses in this family in which the Li is enriched ({sup 6}Li) are used as neutron detectors. The addition of Mg to this glass is known to increase the scintillation efficiency. We have found that substituting other alkaline earths results in a monotonic decrease of the scintillation efficiency with increasing atomic number. The total variation in scintillation efficiency from Mg to Ba is nearly a factor of 3. Prior experiments with this glass family show small differences in Raman and fluorescence spectra; evidence from thermoluminescence experiments indicates that the scintillation efficiency is most strongly correlated with structural effects in the neighborhood of the Ce{sup 3+} activator ion. The results of low-temperature studies of fluorescence and thermoluminescence of these glasses will be reported.

  4. Effect of Composition and Impurities on the Phosphorescence of Green-Emitting Alkaline Earth Aluminate Phosphor

    PubMed Central

    Kim, Doory; Kim, Han-Eol; Kim, Chang-Hong

    2016-01-01

    Recent improvements to SrAl2O4:Eu2+, Dy3+ phosphors have enabled the use of luminescent hosts with a stable crystal structure and high physical and chemical stability, thus overcoming the bottleneck in the applicability of ZnS:Cu phosphors. However, enhancement of afterglow lifetime and brightness in SrAl2O4:Eu2+, Dy3+ phosphors remains a challenging task. Here, we have improved the afterglow characteristics in terms of persistence time and brightness by a systematic investigation of the composition of Eu-doped alkaline earth aluminate SrAl2O4:Eu2+, Dy3+ crystals. We found that a Dy3+/Eu2+ ratio of ~2.4 and ~0.935 mol Eu2+ (per mol of SrAl2O4) gave the brightest and longest emissions (11% and 9% increase for each). Doping with Si4+ also resulted in a slight increase in brightness up to ~15%. Doping with alkali metal or alkaline earth metal significantly enhanced the phosphorescence intensity. In particular, doping with 0.005 mol Li+ (per mol of SrAl2O4) alone boosted the phosphorescence intensity to 239% of the initial value, as compared to that observed for the non-doped crystal, while doping with 0.01 mol Mg2+ and 0.005 mol Li+ (per 1 mol SrAl2O4) boosted the phosphorescence intensity up to 313% of the initial value. The results of this investigation are expected to act as a guideline for the synthesis of bright and long persistent phosphors, and facilitate the development of persistent phosphors with afterglow characteristics superior to those of conventional phosphors. PMID:26731086

  5. Alkaline earth-based coordination polymers derived from a cyclotriphosphazene-functionalized hexacarboxylate

    NASA Astrophysics Data System (ADS)

    Ling, Yajing; Bai, Dongjie; Feng, Yunlong; He, Yabing

    2016-10-01

    Combination of hexakis(4-carboxylatephenoxy)cyclotriphosphazene with alkaline earth ions of increasing ionic radii (Mg2+, Ca2+ and Ba2+) under different solvothermal conditions yielded three new coordination polymers, and their crystal structures were determined by single-crystal X-ray diffraction analysis. The magnesium compound displays a three dimensional (3D) network structure constructed from the deprotonated ligand and the secondary building block Mg(COO)4, which can be rationalized as a (4,6)-connected topological net with the Schläfli symbol of (44·62)3(49·66)2. The calcium compound consists of 1D infinite "Ca-O" inorganic chains connected by the deprotonated ligands to from a 3D framework. The barium compound exhibits a 3D framework in which 1D "Ba-O" inorganic chains are connected together by the deprotonated organic linkers. Due to the semi-rigid nature, the ligand adopts distinctly different conformations in the three compounds. The metal ions' influence exerted on the final structure of the resulting coordination polymers is also discussed. When the radii of alkaline earth ions increases descending down the group from Mg(II) to Ba(II), the coordination number becomes larger and more versatile: from 6 in the magnesium compound, to 6,7 and 10 in the calcium compound, and to 8 and 9 in the barium compound, thus substantially influencing the resulting final framework structures. Also, the photophysical properties were investigated systematically, revealing that the three compounds are photoluminscent in the solid state at room temperature. This work demonstrates that although the multiplicity of conformation in the hexacarboxylate ligand based on the inorganic scaffold cyclotriphosphazene makes it difficult to predict how this ligand will form extended network, but provides unique opportunities for the formation of diverse inorganic-organic hybrids exhibiting rich structural topologies.

  6. Optical and electronic properties of conductive ternary nitrides with rare- or alkaline-earth elements

    NASA Astrophysics Data System (ADS)

    Kassavetis, S.; Hodroj, A.; Metaxa, C.; Logothetidis, S.; Pierson, J. F.; Patsalas, P.

    2016-12-01

    Conductive nitrides, such as TiN, are key engineering materials for electronics, photonics, and plasmonics; one of the essential issues for such applications is the ability of tuning the conduction electron density, the resistivity, and the electron scattering. While enhancing the conduction electron density and blueshifting the intraband absorption towards the UV were easily achieved previously, reducing the conduction electron density and redshifting the intraband absorption into the infrared are still an open issue. The latter is achieved in this work by alloying TiN by rare earth (RE = Sc, Y, La) or alkaline earth (AE = Mg, Ca) atoms in Ti substitutional positions. The produced TixRE1-xN and TixAE1-xN thin film samples were grown by a hybrid arc evaporation/sputtering process, and most of them are stable in the B1 cubic structure. Their optical properties were studied in an extensive spectral range by spectroscopic ellipsometry. The ellipsometric spectra were analyzed and quantified by the Drude-Lorentz model, which provided the conduction electron density, the electron mean free path, and the resistivity. The observed interband transitions are firmly assigned, and the optical and electrical properties of TixRE1-xN and TixAE1-xN are quantitatively correlated with their composition and crystal structure.

  7. Eu(2+)-Activated Alkaline-Earth Halophosphates, M5(PO4)3X:Eu(2+) (M = Ca, Sr, Ba; X = F, Cl, Br) for NUV-LEDs: Site-Selective Crystal Field Effect.

    PubMed

    Kim, Donghyeon; Kim, Sung-Chul; Bae, Jong-Seong; Kim, Sungyun; Kim, Seung-Joo; Park, Jung-Chul

    2016-09-06

    Eu(2+)-activated M5(PO4)3X (M = Ca, Sr, Ba; X = F, Cl, Br) compounds providing different alkaline-earth metal and halide ions were successfully synthesized and characterized. The emission peak maxima of the M5(PO4)3Cl:Eu(2+) (M = Ca, Sr, Ba) compounds were blue-shifted from Ca to Ba (454 nm for Ca, 444 nm for Sr, and 434 nm for Ba), and those of the Sr5(PO4)3X:Eu(2+) (X = F, Cl, Br) compounds were red-shifted along the series of halides, F → Cl → Br (437 nm for F, 444 nm for Cl, and 448 nm for Br). The site selectivity and occupancy of the activator ions (Eu(2+)) in the M5(PO4)3X:Eu(2+) (M = Ca, Sr, Ba; X = F, Cl, Br) crystal lattices were estimated based on theoretical calculation of the 5d → 4f transition energies of Eu(2+) using LCAO. In combination with the photoluminescence measurements and theoretical calculation, it was elucidated that the Eu(2+) ions preferably enter the fully oxygen-coordinated sites in the M5(PO4)3X:Eu(2+) (M = Ca, Sr, Ba; X = F, Cl, Br) compounds. This trend can be well explained by "Pauling's rules". These compounds may provide a platform for modeling a new phosphor and application in the solid-state lighting field.

  8. Gamma ray spectroscopy employing divalent europium-doped alkaline earth halides and digital readout for accurate histogramming

    DOEpatents

    Cherepy, Nerine Jane; Payne, Stephen Anthony; Drury, Owen B.; Sturm, Benjamin W.

    2016-02-09

    According to one embodiment, a scintillator radiation detector system includes a scintillator, and a processing device for processing pulse traces corresponding to light pulses from the scintillator, where the processing device is configured to: process each pulse trace over at least two temporal windows and to use pulse digitization to improve energy resolution of the system. According to another embodiment, a scintillator radiation detector system includes a processing device configured to: fit digitized scintillation waveforms to an algorithm, perform a direct integration of fit parameters, process multiple integration windows for each digitized scintillation waveform to determine a correction factor, and apply the correction factor to each digitized scintillation waveform.

  9. Gamma ray spectroscopy employing divalent europium-doped alkaline earth halides and digital readout for accurate histogramming

    DOEpatents

    Cherepy, Nerine Jane; Payne, Stephen Anthony; Drury, Owen B; Sturm, Benjamin W

    2014-11-11

    A scintillator radiation detector system according to one embodiment includes a scintillator; and a processing device for processing pulse traces corresponding to light pulses from the scintillator, wherein pulse digitization is used to improve energy resolution of the system. A scintillator radiation detector system according to another embodiment includes a processing device for fitting digitized scintillation waveforms to an algorithm based on identifying rise and decay times and performing a direct integration of fit parameters. A method according to yet another embodiment includes processing pulse traces corresponding to light pulses from a scintillator, wherein pulse digitization is used to improve energy resolution of the system. A method in a further embodiment includes fitting digitized scintillation waveforms to an algorithm based on identifying rise and decay times; and performing a direct integration of fit parameters. Additional systems and methods are also presented.

  10. Theoretical study of Ti0 and Pb+ centers in alkali halide and alkaline earth fluoride type crystals

    NASA Astrophysics Data System (ADS)

    Andriessen, J.; Postma, H.

    1987-04-01

    A theoretical study has been carried out on the hfi of Pb+ defects in KCl, CaF2 and BaF2 using an earlier developed crystal field model. Experimental results can be explained in the same way as was done for Tl0 in KCl. However some parameters seem to have a less physical meaning than in the case of Tl0. A new method is in progress using the ASW band structure procedure in order to estimate genuine solid state effects. Preliminary results are encouraging.

  11. Alkaline earth metal fluxes for the growth of single crystal oxides

    NASA Astrophysics Data System (ADS)

    Ramirez, Daniel

    Oxide ceramics are materials with a wide range of properties. Insulators are most common, however semiconductors, strongly correlated electron materials, and even superconductors are all relevant oxide materials. Here we seek to synthesize novel oxide single crystal phases and study their properties using an alkaline earth metal flux technique. The specific flux techniques are new, and we will seek to understand the capabilities of these fluxes as a novel synthesis tool. The use of a barium metal flux to grow single crystal oxides is rather counterintuitive, but is exemplified further with the growth of europium monoxide (Fm3¯m #225, Z = 4). Eu1-xBaxO single crystals (x = 0.01 - 0.25) are grown and studied for their ferromagnetic properties. A new oxide phase Ba2Eu2P2O (P4/mbm #127, Z = 2) has also been synthesized from the same method, and may potentially be studied as a ferromagnetic semiconductor based on preliminary observations. Other examples of single crystal oxide phases grown from barium metal flux includes Ba2TeO (P4/nmm #129, Z = 2), BaLn2O4 (Ln = La - Lu) (Pnma #62, Z = 4), and Ba3Yb2O 5Te (P4/mmm #123 Z = 1). The new crystal phases Ba3Ln2O5Cl 2 (Ln = Sm - Lu, Y) are synthesized using a reactive barium metal flux. Single crystal x-ray diffraction is used to determine their structures with space group (I4/mmm #139, Z = 2) related to the Ruddlesden-Popper structure type. The unit cell dimensions range from a = 4.46(6) A and c = 24.87(6) A for Ba3Gd2O5Cl2 to a = 4.35(6) A and c = 24.57(6) A for Ba3Lu2O 5Cl2 with the dimensions following the expected lanthanide contraction trends. The magnetic properties of these materials are studied and related to their structures. The use of alkaline earth fluxes such as magnesium or calcium based fluxes are also briefly considered for their capabilities to produce novel mixed anion phases. A calcium flux is shown to produce the novel semimetals Ca 4TeOH4 and Ca3Ca1-xEuxTeOH 4 (I4/mmm #139, Z = 2), and highly reducing

  12. METHOD OF MAKING ALLOYS OF SECOND RARE EARTH SERIES METALS

    DOEpatents

    Baker, R.D.; Hayward, B.R.

    1963-01-01

    >This invention relates to a process for alloying the second rare earth series metals with Mo, Nb, or Zr. A halide of the rare earth metal is mixed with about 1 to 20 at.% of an oxide of Mo, Nb, or Zr. Iodine and an alkali or alkaline earth metal are added, and the resulting mixture is heated in an inert atmosphere to 350 deg C. (AEC)

  13. Bond ionicity of alkaline-earth oxides studied by low-energy D+ scattering

    NASA Astrophysics Data System (ADS)

    Souda, R.; Yamamoto, K.; Hayami, W.; Aizawa, T.; Ishizawa, Y.

    1994-08-01

    Low-energy D+ scattering is employed to explore the nature of the bonding of polycrystalline alkaline-earth oxides MgO, CaO, SrO, and BaO, with particular emphasis on the investigation of the ionicity of the topmost-layer atoms. Increasing ionicity as one goes to the heavier cations is concluded from the probability of the resonance neutraliztion of the D+ ions, which is consistent with the conventional chemical arguments based on electronegativity scales but is in apparent contradiction to the results of recent ab initio cluster-model calculations. It is also concluded that the metallic Ba layer is formed rather patchily on the BaO surface after the heat treatment up to 1000 °C. This is probably because free Ba atoms, being supplied by the reaction of BaO with the Ta substrate, are precipitated at the BaO surface. Another example is concerned with the interactions of the Ba adatoms with Si(001) and Pt(111) surfaces; Ba is found to have marked covalency with the substrate atoms.

  14. CP(N - 1) quantum field theories with alkaline-earth atoms in optical lattices

    NASA Astrophysics Data System (ADS)

    Laflamme, C.; Evans, W.; Dalmonte, M.; Gerber, U.; Mejía-Díaz, H.; Bietenholz, W.; Wiese, U.-J.; Zoller, P.

    2016-07-01

    We propose a cold atom implementation to attain the continuum limit of (1 + 1) -d CP(N - 1) quantum field theories. These theories share important features with (3 + 1) -d QCD, such as asymptotic freedom and θ-vacua. Moreover, their continuum limit can be accessed via the mechanism of dimensional reduction. In our scheme, the CP(N - 1) degrees of freedom emerge at low energies from a ladder system of SU(N) quantum spins, where the N spin states are embodied by the nuclear Zeeman states of alkaline-earth atoms, trapped in an optical lattice. Based on Monte Carlo results, we establish that the continuum limit can be demonstrated by an atomic quantum simulation by employing the feature of asymptotic freedom. We discuss a protocol for the adiabatic preparation of the ground state of the system, the real-time evolution of a false θ-vacuum state after a quench, and we propose experiments to unravel the phase diagram at non-zero density.

  15. Crystal and defect chemistry influences on band gap trends in alkaline earth perovskites

    SciTech Connect

    Lee, Soonil; Woodford, William H.; Randall, Clive A.

    2008-05-19

    A number of perovskites with A-site alkaline earth chemistries being Ca, Sr, and Ba, and tetravalent cations including Ce, Zr, and Ti are measured for optical band gap and found to vary systematically with tolerance factor and lattice volume within limits defined by the chemistry of the octahedral site. This paper also focuses on the BaTiO{sub 3} system, considering equilibrated nonstoichiometries, and determines the changes in band gap with respect to Ba/Ti ratios. It was found that the optical band gap changes in the solid solution regime and is invariant in the second phase regions, as would be expected. In the cases of Ba/Ti<1.0, the variation in band gap scales with lattice volume, but in the Ba/Ti>1.0 stoichiometries, there is a distinct Urbach tail and the trend with lattice volume no longer holds. It is inferred that the V{sub Ti}{sup q}prime-2V{sub O} partial Schottky complex controls the band gap trend with Ba-rich nonstoichiometries.

  16. Collective non-equilibrium spin exchange in cold alkaline-earth atomic clocks

    NASA Astrophysics Data System (ADS)

    Acevedo, Oscar Leonardo; Rey, Ana Maria

    2016-05-01

    Alkaline-earth atomic (AEA) clocks have recently been shown to be reliable simulators of two-orbital SU(N) quantum magnetism. In this work, we study the non-equilibrium spin exchange dynamics during the clock interrogation of AEAs confined in a deep one-dimensional optical lattice and prepared in two nuclear levels. The two clock states act as an orbital degree of freedom. Every site in the lattice can be thought as populated by a frozen set of vibrational modes collectively interacting via predominantly p-wave collisions. Due to the exchange coupling, orbital state transfer between atoms with different nuclear states is expected to happen. At the mean field level, we observe that in addition to the expected suppression of population transfer in the presence of a large magnetic field, that makes the single particle levels off-resonance, there is also an interaction induced suppression for initial orbital population imbalance. This suppression resembles the macroscopic self-trapping mechanism seen in bosonic systems. However, by performing exact numerical solutions and also by using the so-called Truncated Wigner Approximation, we show that quantum correlations can significantly modify the mean field suppression. Our predictions should be testable in optical clock experiments. Project supported by NSF-PHY-1521080, JILA-NSF-PFC-1125844, ARO, AFOSR, and MURI-AFOSR.

  17. Process for depositing epitaxial alkaline earth oxide onto a substrate and structures prepared with the process

    DOEpatents

    McKee, Rodney A.; Walker, Frederick J.

    1996-01-01

    A process and structure involving a silicon substrate utilize molecular beam epitaxy (MBE) and/or electron beam evaporation methods and an ultra-high vacuum facility to grow a layup of epitaxial alkaline earth oxide films upon the substrate surface. By selecting metal constituents for the oxides and in the appropriate proportions so that the lattice parameter of each oxide grown closely approximates that of the substrate or base layer upon which oxide is grown, lattice strain at the film/film or film/substrate interface of adjacent films is appreciably reduced or relieved. Moreover, by selecting constituents for the oxides so that the lattice parameters of the materials of adjacent oxide films either increase or decrease in size from one parameter to another parameter, a graded layup of films can be grown (with reduced strain levels therebetween) so that the outer film has a lattice parameter which closely approximates that of, and thus accomodates the epitaxial growth of, a pervoskite chosen to be grown upon the outer film.

  18. The Characterization of Eu2+-Doped Mixed Alkaline-Earth Iodide Scintillator Crystals

    SciTech Connect

    Neal, John S; Boatner, Lynn A; Ramey, Joanne Oxendine; Wisniewski, D.; Kolopus, James A; Cherepy, Nerine; Payne, Stephen A.

    2011-01-01

    The high-performance inorganic scintillator, SrI2:Eu2+, when activated with divalent europium in the concentration range of 3 to 6%, has shown great promise for use in applications that require high-energy-resolution gamma-ray detection. We have recently grown and tested crystals in which other alkaline-earth ions have been partially substituted for Sr ions. Specifically, europium-doped single crystals have been grown in which up to 30 at % of the strontium ions have been substituted for either by barium, magnesium, or calcium ions. In the case of the strontium iodide scintillator host, a material that is characterized by an orthorhombic crystal structure, there are three other column IIA elements that are obvious choices for investigations whose purpose is to realize potential improvements in the performance of SrI2:Eu2+-based scintillators via the replacement of strontium ions with either Mg2+, Ca2+, or Ba2+. Light yields of up to 81,400 photons/MeV with an associated energy resolution of 3.7% (fwhm for 662 keV gamma-rays) have been observed in the case of a partial substitution of Ba2+ for Sr2+. The measured decay times ranged from 1.1 to 2.0 s, while the peak emission wavelengths ranged from 432 to 438 nm.

  19. Alkaline earth silicate wools - A new generation of high temperature insulation.

    PubMed

    Brown, Robert C; Harrison, Paul T C

    2012-11-01

    Intensive study of the natural asbestiform minerals that cause human diseases, and the consequent understanding of their hazardous characteristics, has enabled the development of manufactured fibres whose physical and/or chemical properties, in particular as they relate to biopersistence, have been adjusted to minimize possible harm to health. A strong driver for the developmentof new high temperature insulation materials wasthe perception of the toxicity of refractory ceramic fibres (RCF)and their classification in the EU as a category 2 carcinogen under Directive 67/548/EEC. Such classification carries with it the requirement for substitution by less hazardous materials. This paper focuses on the development of alkaline earth silicate (AES) wools as a new class of high temperature insulation with the capability of such substitution in a number of applications. These wools have only a low potential to cause harm because they do not persist in lung tissue once deposited, and have produced minimal effects in experimental test systems. AES wools are increasingly being used in a wide range of high temperature applications.

  20. Mixed alkali effect on the spectroscopic properties of alkali-alkaline earth oxide borate glasses

    NASA Astrophysics Data System (ADS)

    Srinivas, G.; Ramesh, B.; Shareefuddin, Md.; Chary, M. N.; Sayanna, R.

    2016-05-01

    The mixed alkali and alkaline earth oxide borate glass with the composition xK2O - (25-x) Li2O-12.5BaO-12.5MgO-50B2O3 (x = 0, 5, 10, 15, 20 and 25mol %) and doped with 1mol% CuO were prepared by the melt quenching technique. From the optical absorption spectra the optical band gap, electronic polarizability(α02-), interaction parameter (A), theoretical and experimental optical basicity (Λ) values were evaluated. From the Electron Paramagnetic Resonance (EPR) spectral data the number of spins (N) and susceptibility (χ) were evaluated. The values of (α02-), and (Λ) increases with increasing of K2O content and electronic polarizability and interaction parameter show opposite behaviuor which may be due to the creation of non-bridging oxygens and expansion of borate network. The reciprocal of susceptibility (1/χ) and spin concentration (N) as a function of K2O content, varied nonlinearly which may be due to creation of non-bridging oxygens in the present glass system. This may be attributed to mixed alkali effect (MAE).

  1. Heavy water reactions with alkaline-earth metal dications in the gas phase

    NASA Astrophysics Data System (ADS)

    Feil, Stefan; Koyanagi, Greg K.; Bohme, Diethard K.

    2009-02-01

    Room temperature rate coefficients and product distributions are reported for the reactions initiated in D2O with dications of the alkaline-earth metals Mg, Ca, Sr and Ba. The measurements were performed with a selected-ion flow tube (SIFT) tandem mass spectrometer and electrospray ionization (ESI). Mg2+ reacts with water by a fast electron transfer leading to charge separation with a rate coefficient of 1.4 × 10-9 cm3 molecule-1 s-1. Ca2+ reacts with D2O in a first step to form the adduct Ca2+(D2O), with an effective bimolecular rate coefficient of 2.3 × 10-11 cm3 molecule-1 s-1, which then undergoes rapid charge separation by deuteron transfer to form CaOD+ and D3O+ in a second step with k = 7.9 × 10-10 cm3 molecule-1 s-1. The CaOD+ ion reacts further by clustering up to five more D2O molecules. Sr2+ clusters up to eight D2O molecules and Ba2+ up to seven D2O molecules, with the first addition of D2O being rate determining in each case and the last addition being distinctly slower, as might be expected from a transition in the occupation of the added water molecules from an inner to an outer hydration shell.

  2. Optimizing the performance of bandpass photon detectors for inverse photoemission: Transmission of alkaline earth fluoride window crystals

    SciTech Connect

    Thiede, Christian Schmidt, Anke B.; Donath, Markus

    2015-08-15

    Bandpass photon detectors are widely used in inverse photoemission in the isochromat mode at energies in the vacuum-ultraviolet spectral range. The energy bandpass of gas-filled counters is usually formed by the ionization threshold of the counting gas as high-pass filter and the transmission cutoff of an alkaline earth fluoride window as low-pass filter. The transmission characteristics of the window have, therefore, a crucial impact on the detector performance. We present transmission measurements in the vacuum-ultraviolet spectral range for alkaline earth fluoride window crystals in the vicinity of the transmission cutoff as a function of crystal purity, surface finish, surface contamination, temperature, and thickness. Our findings reveal that the transmission characteristics of the window crystal and, thus, the detector performance depend critically on these window parameters.

  3. The contents of alkali and alkaline earth metals in soils of the southern Cis-Ural region

    NASA Astrophysics Data System (ADS)

    Asylbaev, I. G.; Khabirov, I. K.

    2016-01-01

    The contents and distribution patterns of alkali and alkaline earth metals in soils and rocks of the southern Cis-Ural region were studied. A database on the contents of these metals was developed, the soils were classified with respect to their provision with these metals, and corresponding schematic maps showing their distribution in soils of the region were compiled. It was found that the contents of these metals decrease from east to west (from the Yuryuzan-Aisk Piedmont Plain to the Ufa Plateau and to the Belebeevsk Upland), and their distribution patterns change. Among alkali metals, the highest accumulation in the soils is typical of potassium, sodium, and cesium; among alkaline earth metals, of strontium and barium.

  4. Spin-Orbit-Coupled Correlated Metal Phase in Kondo Lattices: An Implementation with Alkaline-Earth Atoms

    NASA Astrophysics Data System (ADS)

    Isaev, L.; Schachenmayer, J.; Rey, A. M.

    2016-09-01

    We show that an interplay between quantum effects, strong on-site ferromagnetic exchange interaction, and antiferromagnetic correlations in Kondo lattices can give rise to an exotic spin-orbit coupled metallic state in regimes where classical treatments predict a trivial insulating behavior. This phenomenon can be simulated with ultracold alkaline-earth fermionic atoms subject to a laser-induced magnetic field by observing dynamics of spin-charge excitations in quench experiments.

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

    SciTech Connect

    Guo, W.; Ma, H.A.; Jia, X.

    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.

  6. 5 d-4 f luminescence of Nd3+, Gd3+, Er3+, Tm3+, and Ho3+ ions in crystals of alkaline earth fluorides

    NASA Astrophysics Data System (ADS)

    Radzhabov, E. A.; Prosekina, E. A.

    2011-09-01

    The vacuum ultraviolet emission spectra of alkaline-earth fluoride (CaF2, SrF2, BaF2) crystals with rare earth impurity ions (Nd, Gd, Er, Tm, Ho) have been investigated. The main luminescence bands are described well by the transitions from the lowest excited 5 d state to different 4 f levels of rare earth ions.

  7. The significance of secondary interactions during alkaline earth-promoted dehydrogenation of dialkylamine-boranes.

    PubMed

    Bellham, Peter; Anker, Mathew D; Hill, Michael S; Kociok-Köhn, Gabriele; Mahon, Mary F

    2016-09-21

    a modified mechanism for group 2-mediated dimethylamine borane dehydrocoupling that is dependent on the intermediacy of key derivatives of the [NMe2·BH3](-) and [NMe2BH2NMe2BH3](-) anions but does not require the formation of high energy alkaline earth hydride intermediates. Although these results are specifically focussed on the applications of alkaline earth species, this mechanistic insight may also be relevant to other redox-inactive main group element-based systems and to our understanding of hydrogen evolution from saline derivatives of ammonia borane.

  8. Ocean-Based Alkalinity Enhancement: Mitigation Potential, Side Effects and the Fate of Added Alkalinity Assessed in an Earth System Model

    NASA Astrophysics Data System (ADS)

    Gonzalez, M. F.; Ilyina, T.

    2014-12-01

    Artificial ocean alkalinization (AOA) has been proposed as a mean to mitigate climate change and ocean acidification. Whilst the mitigation potential of this geo-engineering technology may sound promising, it poses environmental risks. Within the Priority Program "Climate Engineering" of the German Science Foundation (DFG), we investigate the mitigation potential of AOA to reduce atmospheric CO2 and counteract the consequences of ocean acidification. We are particularly interested in the residence time of the added alkalinity at the ocean surface because it must stay in the upper ocean in order to increase the oceanic CO2 uptake. The mitigation potential, risks and the unintended consequences of this geo-engineering method are also exhaustively studied. These questions are tackled through the analysis of different alkalinity enhancement scenarios in the state-of-the-art Earth system model of the Max Planck Institute for Meteorology (MPI-ESM) in a configuration based on the fifth phase of the Coupled Model Intercomparison Project (CMIP5). Model scenarios are designed so that AOA is performed to keep the atmospheric CO2 concentrations similar to values of the stabilization scenario RCP4.5, while fossil fuel CO2 emissions follow the pathway of the high-CO2 scenario RCP8.5. Alkalinity is added globally into the upper 12 meters of the ocean in different seasons and years. We found that on the time scale of relevance (i.e. from years to decades), season and location are key aspects to take into account in the implementation of AOA. This is because of inhomogeneous vertical mixing of added alkalinity due to the mixed layer depth which is established by the season. We also show that the rate of addition greatly determines impact and outcome of this geo-engineering method. Changes driven by the implementation of this method in the ocean biogeochemistry are also discussed. For instance, the associated changes in the carbon cycle, marine oxygen levels, saturation state of

  9. Novel alkaline earth copper germanates with ferro and antiferromagnetic S=1/2 chains

    SciTech Connect

    Brandao, Paula; Reis, Mario S; Gai, Zheng; Moreira Dos Santos, Antonio F

    2013-01-01

    Two new alkaline earth copper(II) germanates were hydrothermally synthesized: CaCuGeO4 center dot H2O (1) and BaCu2Ge3O9 center dot H2O (2), and their structures determined by single crystal X-ray diffraction. Compound (1) crystallizes in space group P2(1)/c with a=5.1320(2) angstrom, b=16.1637(5) angstrom, c=5.4818(2) angstrom, beta=102.609(2)degrees, V=443.76(3) angstrom(3) and Z=4. This copper germanate contains layers of composition [CuGeO4](infinity)(2-) comprising CuO4 square planes and GeO4 tetrahedra with calcium and water molecules in the inter-layer space. Compound (2) crystallizes in the Cmcm space group with a=5.5593(3) angstrom, b=10.8606(9) angstrom, c=13.5409(8) angstrom, V=817.56(9) angstrom(3) and Z=4. This structure contains GeO6 and CuO6 octahedra as well as GeO4 tetrahedra, forming a three-dimensional network of interconnecting six-membered ring channels. The magnetic susceptibility for both samples can be interpreted as S=1/2 chains, in agreement with the copper topology observed in the crystal structure. The susceptibility of (1) exhibits a Bonner-Fisher type behavior, resulting from antiferromagnetic intra-chain interactions without three-dimensional ordering down to 5 K-the lowest measured temperature. This observation, together with the absence of super-exchange paths between the copper chains, make this system particularly promising for the study of low dimensional magnetism. The magnetic properties of (2) show a very weak ferromagnetic near-neighbor interaction along the chain. In this compound a peak the chi T plot seems to indicate the onset of interchain antiferromagentic correlations. However, no ordering temperature is detected in the susceptibility data.

  10. Accumulation of alkaline earth metals by the green macroalga Bryopsis maxima.

    PubMed

    Takahashi, Shigekazu; Aizawa, Kyoko; Nakamura, Saki; Nakayama, Katsumi; Fujisaki, Shingo; Watanabe, Soichiro; Satoh, Hiroyuki

    2015-04-01

    Twenty-five days after the disaster at the Fukushima Daiichi nuclear power plant in 2011, we collected samples of the green macroalga Bryopsis maxima from the Pacific coast of Japan. Bryopsis maxima is a unicellular, multinuclear, siphonous green macroalga. Radiation analysis revealed that B. maxima emitted remarkably high gamma radiation of (131)I, (134)Cs, (137)Cs, and (140)Ba as fission products of (235)U. Interestingly, B. maxima contained naturally occurring radionuclides derived from (226)Ra and (228)Ra. Analysis of element content revealed that B. maxima accumulates many ocean elements, especially high quantities of the alkaline earth metals Sr (15.9 g per dry-kg) and Ba (3.79 g per dry-kg), whereas Ca content (12.5 g per dry-kg) was lower than that of Sr and only 61 % of the mean content of 70 Japanese seaweed species. Time-course analysis determined the rate of radioactive (85)Sr incorporation into thalli to be approximately 0.13 g Sr per dry-kg of thallus per day. Subcellular fractionation of B. maxima cells showed that most of the (85)Sr was localized in the soluble fraction, predominantly in the vacuole or cytosol. Given that (85)Sr radioactivity was permeable through a dialysis membrane, the (85)Sr was considered to be a form of inorganic ion and/or bound with a small molecule. Precipitation analysis with sodium sulfate showed that more than 70% of the Sr did not precipitate as SrSO4, indicating that a proportion of the Sr may bind with small molecules in B. maxima.

  11. ION EXCHANGE IN FUSED SALTS. II. THE DISTRIBUTION OF ALKALI METAL AND ALKALINE EARTH IONS BETWEEN CHABAZITE AND FUSED LINO3, NANO3, AND KNO3,

    DTIC Science & Technology

    ION EXCHANGE, SALTS ), (*ALKALI METALS, ION EXCHANGE), (*ALKALINE EARTH METALS, ION EXCHANGE), (*NITRATES, ION EXCHANGE), SODIUM , CALCIUM, POTASSIUM...BARIUM, RUBIDIUM, CESIUM, LITHIUM COMPOUNDS, SODIUM COMPOUNDS, POTASSIUM COMPOUNDS, DISTRIBUTION, MINERALS, IONS

  12. [Effect of bivalent alkaline earth fluorides introduction on thermal stability and spectroscopic properties of Er3+/Tm3+ /Yb3+ co-doped oxyfluorogermanate glasses].

    PubMed

    Hu, Yue-bo; Zhang, Xin-na; Zhou, Da-li; Jiao, Qing; Wang, Rong-fei; Huang, Jin-feng; Long, Xiao-bo; Qiu, Jian-bei

    2012-01-01

    Transparent Er3+/Tm3+ /Yb3+ co-doped oxyfluorogermanate glasses alone containing MgF2, CaF2, SrF2 or BaF2 and nano-glass-ceramics only containing BaF2 were prepared. The thermal stabilities and the up-conversion emission properties of the samples were investigated. Analyses of absorbance spectra reveal that the UV cutoff band moves slightly to shortwave band with the doping bivalent cation mass increasing. The results show that the emission color can be adjusted by changing the alkaline earth cation species in the glass matrixes, especially as Mg2+ is concerned, and the emission intensity can increase notably by heating the glass containing alkaline-earth fluoride into glass ceramic containing alkaline-earth fluoride nanocrystals or increasing the content of bivalent alkaline earth fluorides.

  13. Influence of doping with alkaline earth metals on the optical properties of thermochromic VO2

    NASA Astrophysics Data System (ADS)

    Dietrich, Marc K.; Kramm, Benedikt G.; Becker, Martin; Meyer, Bruno K.; Polity, Angelika; Klar, Peter J.

    2015-05-01

    Thin films of doped VO2 were deposited, analyzed, and optimized with regard to their solar energy transmittance (Tsol) and visible/luminous light transmittance (Tlum) which are important parameters in the context of smart window applications in buildings. The doping with alkaline earth metals (AEM) like Mg, Ca, Sr, or Ba increased both Tsol and Tlum due to a bandgap widening and an associated absorption edge blue-shift. Thereby, the brown-yellowish color impression of pure VO2 thin films, which is one major hindrance limiting the usage of VO2 as thermochromic window coating, was overcome. Transparent thin films with excellent switching behavior were prepared by sputtering. Highly doped V1-xMexO2 (Me = Ca, Sr, Ba) kept its excellent thermochromic switching behavior up to x(Me) = Me/(Me + V) = 10 at. % doping level, while the optical bandgap energy was increased from 1.64 eV for undoped VO2 to 2.38 eV for x(Mg) = 7.7 at. %, 1.85 eV for x(Ca) = 7.4 at. %, 1.84 eV for x(Sr) = 6.4 at. % and 1.70 eV for x(Ba) = 6.8 at. %, as well as the absorption edge is blue shifted by increasing AEM contents. Also, the critical temperature ϑc, at which the semiconductor-to-metal transition (SMT) occurs, was decreased by AEM doping, which amounted to about -0.5 K/at. % for all AEM on average. The critical temperature was determined by transmittance-temperature hysteresis measurements. Furthermore, Tsol and Tlum were calculated and were found to be significantly enhanced by AEM doping. Tlum increased from 32.0% in undoped VO2 to 43.4% in VO2 doped with 6.4 at. % Sr. Similar improvements were found for other AEM. The modulation of the solar energy transmittance ΔTsol, which is the difference of the Tsol values in the low and high temperature phase, was almost constant or even slightly increased when the doping level was increased up to about 10 at. % Ca, Sr, or Ba.

  14. Overview of the crystal chemistry of the actinide chalcogenides: incorporation of the alkaline-earth elements.

    PubMed

    Mesbah, Adel; Prakash, Jai; Ibers, James A

    2016-10-18

    This review focuses on the results of exploratory syntheses of alkaline-earth-metal actinide chalcogenides Ak-An-Q (Ak = Ba, Sr; An = Th, U; Q = S, Se, and Te). About thirty new compounds are described. Although the basic building blocks of their structures are usually AnQ6 octahedra and AkQ8 bicapped trigonal prisms, these are combined in diverse ways to afford eleven new structure types. The structures reconfirm the prevailing presence of An(4+) in chalcogenides, although some of the compounds discovered are mixed An(4+)/An(5+) systems, and a few contain only An(5+). The tendency of the chalcogens to form Q-Q bonds is again evident from the presence of S-S single bonds and infinite Te-Te-Te linear chains. The latter possess interatomic distances of lengths greater than that of a Te-Te single bond but less than that of a Te-Te van der Waals interaction. Assignment of formal oxidation states in compounds containing these chains is arbitrary at best. Addition of metal atoms (M) affords quaternary structures, some of which show remarkable flexibility in the positions of the An and M atoms, and in such compounds the nature of the M elements influences directly the dimensionality of the resultant structure. The presence of adventitious oxygen, often from etching of the fused-silica tubes by oxyphilic An elements, results in new quintary compounds that show remarkable structural variations with change of M. The compounds discussed have shown transport and electronic structures that range from metallic-like to semiconducting. We find, with the exception of BaUSe3, when comparisons can be made that the values of the calculated band gaps are reasonably close but usually lower than the experimentally derived values. Thus the method used, in particular the HSE functional, has been generally successful on these 5f actinides. This is an important result because in the absence of suitable crystals, and hence experimental measurements, it still may be possible to offer credible

  15. Unified mechanism of alkali and alkaline earth catalyzed gasification reactions of carbon by CO2 and H2O

    USGS Publications Warehouse

    Chen, S.G.; Yang, R.T.

    1997-01-01

    From molecular orbital calculations, a unified mechanism is proposed for the gasification reactions of graphite by CO2 and H2O, both uncatalyzed and catalyzed by alkali and alkaline earth catalysts. In this mechanism, there are two types of oxygen intermediates that are bonded to the active edge carbon atoms: an in-plane semiquinone type, Cf(O), and an off-plane oxygen bonded to two saturated carbon atoms that are adjacent to the semiquinone species, C(O)Cf(O). The rate-limiting step is the decomposition of these intermediates by breaking the C-C bonds that are connected to Cf(O). A new rate equation is derived for the uncatalyzed reactions, and that for the catalyzed reactions is readily available from the proposed mechanism. The proposed mechanism can account for several unresolved experimental observations: TPD and TK (transient kinetics) desorption results of the catalyzed systems, the similar activation energies for the uncatalyzed and catalyzed reactions, and the relative activities of the alkali and alkaline earth elements. The net charge of the edge carbon active site is substantially changed by gaining electron density from the alkali or alkaline earth element (by forming C-O-M, where M stands for metal). The relative catalytic activities of these elements can be correlated with their abilities of donating electrons and changing the net charge of the edge carbon atom. As shown previously (Chen, S. G.; Yang, R. T. J. Catal. 1993, 141, 102), only clusters of the alkali compounds are active. This derives from the ability of the clusters to dissociate CO2 and H2O to form O atoms and the mobility of the dissociated O atoms facilitated by the clusters.

  16. Tris(pyrazolyl)methanides of the alkaline earth metals: influence of the substitution pattern on stability and degradation.

    PubMed

    Müller, Christoph; Koch, Alexander; Görls, Helmar; Krieck, Sven; Westerhausen, Matthias

    2015-01-20

    Trispyrazolylmethanides commonly act as strong tridentate bases toward metal ions. This expected coordination behavior has been observed for tris(3,4,5-trimethylpyrazolyl)methane (1a), which yields the alkaline-earth-metal bis[tris(3,4,5-trimethylpyrazolyl)methanides] of magnesium (1b), calcium (1c), strontium (1d), and barium (1e) via deprotonation of 1a with dibutylmagnesium and [Ae{N(SiMe3)2}2] (Ae = Mg, Ca, Sr, and Ba, respectively). Barium complex 1e degrades during recrystallization that was attempted from aromatic hydrocarbons and ethers. In these scorpionate complexes, the metal ions are embedded in distorted octahedral coordination spheres. Contrarily, tris(3-thienylpyrazolyl)methane (2a) exhibits a strikingly different reactivity. Dibutylmagnesium is unable to deprotonate 2a, whereas [Ae{N(SiMe3)2}2] (Ae = Ca, Sr, and Ba) smoothly metalates 2a. However, the primary alkaline-earth-metal bis[tris(3-thienylpyrazolyl)methanides] of Ca (2c), Sr (2d), and Ba (2e) represent intermediates and degrade under the formation of the alkaline-earth-metal bis(3-thienylpyrazolates) of calcium (3c), strontium (3d), and barium (3e) and the elimination of tetrakis(3-thienylpyrazolyl)ethene (4). To isolate crystalline compounds, 3-thienylpyrazole has been metalated, and the corresponding derivatives [(HPz(Tp))4Mg(Pz(Tp))2] (3b), dinuclear [(tmeda)Ca(Pz(Tp))2]2 (3c), mononuclear [(pmdeta)Sr(Pz(Tp))2] (3d), and [(hmteta)Ba(Pz(Tp))2] (3e) have been structurally characterized. Regardless of the applied stoichiometry, magnesiation of thienylpyrazole 3a with dibutylmagnesium yields [(HPz(Tp))4Mg(Pz(Tp))2] (3b), which is stabilized in the solid state by intramolecular N-H···N···H-N hydrogen bridges. The degradation of [Ae{C(Pz(R))3}2] (R = Ph and Tp) has been studied by quantum chemical methods, the results of which propose an intermediate complex of the nature [{(Pz(R))2C}2Ca{Pz(R)}2]; thereafter, the singlet carbenes ([:C(Pz(R))2]) dimerize in the vicinity of the alkaline

  17. The effect of alkaline earth metal ion dopants on photocatalytic water splitting by NaTaO(3) powder.

    PubMed

    Iwase, Akihide; Kato, Hideki; Kudo, Akihiko

    2009-01-01

    Alkaline earth metal ions (Ca, Sr, and Ba) are doped into a NaTaO(3) photocatalyst, yielding fine particles and surface structures with nanometer-scale "steps." The formation of the surface nanostep structure depends on the amount of doped Sr and Ba. The photocatalytic water splitting over NaTaO(3) is enhanced: NaTaO(3) doped with 0.5 and 1.0 mol % of Sr shows high activities for photocatalytic water splitting without loading of a co-catalyst, and the photocatalytic activity is further improved by loading with a NiO co-catalyst.

  18. Luminescence properties of Eu-activated alkaline and alkaline-earth silicate Na{sub 2}Ca{sub 3}Si{sub 6}O{sub 16}

    SciTech Connect

    Wang, Jing; Huang, Yanlin; Wang, Xigang; Qin, Lin; Seo, Hyo Jin

    2014-07-01

    Highlights: • A novel yellow-emitting alkaline and alkaline-earth silicate Na{sub 2}Ca{sub 3}Si{sub 6}O{sub 16}:Eu{sup 2+} was first developed. • Under excitation with UV or near UV light the silicate presents broad emission band centered at 580 nm. - Abstract: Yellow-emitting phosphors of Na{sub 2}Ca{sub 3}Si{sub 6}O{sub 16}:Eu{sup 2+} was prepared by wet chemistry sol–gel method. X-ray powder diffraction and SEM measurements were applied to characterize the structure and morphology, respectively. The luminescence properties were investigated by the photoluminescence excitation and emission spectra, decay curve (lifetimes), CIE coordinates and the internal quantum efficiencies. The excitation spectra can match well with the emission light of near UV-LED chips (360–400 nm). Na{sub 2}Ca{sub 3}Si{sub 6}O{sub 16}:Eu{sup 2+} presents a symmetric emission band from 4f{sup 6}5d{sup 1} ⟶ 4f{sup 7}({sup 8}S{sub 7/2}) transitions of Eu{sup 2+} ions on doping below 3.0 mol%. On increasing Eu-doping levels, the sample contains two kinds of emission centers, i.e., Eu{sup 2+} and Eu{sup 3+} ions, which present the characteristic broad band (5d ⟶ 4f) and narrower (4f ⟶ 4f) luminescence lines, respectively. The energy transfer, the luminescence thermal stability (activation energy ΔE for thermal quenching) and luminescence mechanism of Na{sub 2}Ca{sub 3}Si{sub 6}O{sub 16}:Eu{sup 2+} phosphors were discussed by analyzing the relationship between the luminescence characteristics and the crystal structure.

  19. Synthesis and Characterization of Alkaline-Earth Metal (Ca, Sr, and Ba) Doped Nanodimensional LaMnO3 Rare-Earth Manganites

    NASA Astrophysics Data System (ADS)

    Asma, Khalid; Saadat, Anwar Siddiqi; Affia, Aslam

    2013-07-01

    The substitution of divalent cations of alkaline-earth elements in nanodimensional structures of rare-earth manganites produces advanced materials with potential electrical and magnetic functionalities. A systematic investigation of La0.65A0.35MnO3 (A = Ca, Sr, Ba) materials synthesized with a modified citrate route adopting ethanol dehydration has been undertaken. The structural and morphological analyses are carried out by using x-ray diffraction and scanning electron microscopy, respectively. Resistivity measurements are performed in variation with temperature to study the electrical transport properties which are found to vary with the size of the A-site cationic radius. Room temperature magnetic measurements are carried out to investigate the type of magnetic phase present in materials. The stability of the magnetic phase and coercivity are found to be dependent on the size of nanocrystallites.

  20. Thermodynamic stability of perovskites and related compounds in some alkaline earth-transition metal-oxygen systems

    NASA Astrophysics Data System (ADS)

    Yokokawa, Harumi; Sakai, Natsuko; Kawada, Tatsuya; Dokiya, Masayuki

    1991-09-01

    The thermodynamic properties of some alkaline earth ( A)-transition metal ( M) perovskites and K 2NiF 4 compounds have been collected, analyzed, and utilized to examine their stabilities by constructing the chemical potential diagrams of a log [ {a(A)}/{a(M)}] vs log P(O 2) plot. A thermodynamic analysis was performed on the dissociation reaction of K 2NiF 4 compounds ( A2MO 4) into perovskites ( AMO 3) and alkaline earth oxides ( AO) using empirical correlations between stabilization energy and tolerance factor. It has been found that the softness of calcium ions, which shrink markedly with decreasing coordination number from 12 to 9, makes the calcium K 2NiF 4 compounds (Ca 2MO 4) relatively less stable with increasing radius of the transition metal ions, r( M4+). This destabilization related to the coordination-number-dependent radii implies that when compared with the strontium perovskites, the calcium analogous perovskites may have a smaller number of oxygen vacancies, because the formation of oxygen vacancies should be accompanied with a decrease in coordination number of A-site ions.

  1. Binding and selectivity of phenazino-18-crown-6-ether with alkali, alkaline earth and toxic metal species: A DFT study

    NASA Astrophysics Data System (ADS)

    Islam, Nasarul; Chimni, Swapandeep Singh

    2017-02-01

    The interactions of phenazino-crown ether ligands with alkali, alkaline earth and selected toxic species were investigated using density functional theory modelling by employing B3PW91/6-311G ++ (d, p) level of theory. The complex stability was analysed in terms of binding energies, perturbation energies, position of highest molecular orbital and energy gap values. In general, the complexes formed by P18C6-1a ligand with metal cations were found to be more stable than those with P18C6-1b. Among alkali and alkaline earth metals complexes having highest stability was observed for the complex formed by P18C6-1a with Be2+. Computational calculations of P18C6 ligand with toxic metal ions reveals that the P18C6-Cr6+ metal complexes acquire envelop like geometry, leading to higher binding energy values. Comparing the binding energies of neutral and monocations of Ag and Hg, the former had higher value both in neutral as well as monocation state. Thus, the stability of metal complexes is determined not only by the ligand but also by the type of metal ion. In solvent systems the stability constants of metal complexes were found increasing with decreasing permittivity of the solvent. This reflects the inherited polar character of the protic solvents stabilises the cation, resulting in decrease of effective interaction of ligand with the metal ion.

  2. Three interesting coordination compounds based on metalloligand and alkaline-earth ions: Syntheses, structures, thermal behaviors and magnetic property

    NASA Astrophysics Data System (ADS)

    Zhou, Qiang; Qian, Jun; Zhang, Chi

    2016-09-01

    Based on metalloligand LCu ([Cu(2,4-pydca)2]2-, 2,4-pydca2- = pyridine-2,4-dicarboxylate) and alkaline-earth ions (Ca2+, Sr2+, and Ba2+), three interesting coordination compounds, [Ca(H2O)7][LCu·H2O]·H2O (1), {Sr[LCu·H2O]·4H2O}n (2), and {Ba[LCu·H2O]·8H2O}n (3), have been synthesized and well-characterized by elemental analysis, infrared spectroscopy, thermogravimetric and single-crystal X-ray diffraction analysis. X-ray crystallographic studies reveal that 1 features a discrete 0D coordination compound, while 2 and 3 exhibit the 2D network and 1D chain structures, respectively. Compound 2 is constructed from {LCu}2 dimers connected with {Sr2} units, which is fabricated by two Sr2+ ions bridged via two μ2-O bridges, while compound 3 is formed by 1D {Ba}n chain linked with metalloligands LCu and exhibits an interesting sandwich like chain structure. It is noted that the coordination numbers of alkaline-earth ions are in positive correlation with their radiuses. Moreover, the magnetic property of compound 2 has been studied.

  3. Oxidation behavior of Cr(III) during thermal treatment of chromium hydroxide in the presence of alkali and alkaline earth metal chlorides.

    PubMed

    Mao, Linqiang; Gao, Bingying; Deng, Ning; Liu, Lu; Cui, Hao

    2016-02-01

    The oxidation behavior of Cr(III) during the thermal treatment of chromium hydroxide in the presence of alkali and alkaline earth metal chlorides (NaCl, KCl, MgCl2, and CaCl2) was investigated. The amounts of Cr(III) oxidized at various temperatures and heating times were determined, and the Cr-containing species in the residues were characterized. During the transformation of chromium hydroxide to Cr2O3 at 300 °C approximately 5% of the Cr(III) was oxidized to form intermediate compounds containing Cr(VI) (i.e., CrO3), but these intermediates were reduced to Cr2O3 when the temperature was above 400 °C. Alkali and alkaline earth metals significantly promoted the oxidation of Cr(III) during the thermal drying process. Two pathways were involved in the influences the alkali and alkaline earth metals had on the formation of Cr(VI). In pathway I, the alkali and alkaline earth metals were found to act as electron transfer agents and to interfere with the dehydration process, causing more intermediate Cr(VI)-containing compounds (which were identified as being CrO3 and Cr5O12) to be formed. The reduction of intermediate compounds to Cr2O3 was also found to be hindered in pathway I. In pathway II, the alkali and alkaline earth metals were found to contribute to the oxidation of Cr(III) to form chromates. The results showed that the presence of alkali and alkaline earth metals significantly increases the degree to which Cr(III) is oxidized during the thermal drying of chromium-containing sludge.

  4. Half metallic ferromagnetism in alkaline-earth metal nitrides XN (X=Ca, Sr and Ba): A first principles study

    NASA Astrophysics Data System (ADS)

    Palanichamy, R. Rajeswara; Priyanga, G. Sudha; Cinthia, A. Jemmy; Murugan, A.; Meenaatci, A. T. Asvini; Iyakutti, K.

    2013-11-01

    The structural, electronic, mechanical and magnetic properties of 3 alkaline-earth metal nitrides (XN: X=Ca, Sr, and Ba) are investigated by the first principles calculations based on density functional theory using the Vienna ab-initio simulation code. At ambient pressure all the 3 nitrides are stable in the ferromagnetic state with a cubic NaCl structure. The calculated lattice parameters are in good agreement with the available results. The electronic structure reveals that these materials are half metallic ferromagnets at normal pressure. A pressure-induced structural phase transition from NaCl (B1) to CsCl (B2) phase is observed in CaN, SrN and BaN. On further increasing the pressure, a half metallic to metallic transition is also observed in these nitrides. Ferromagnetism is quenched in all the 3 nitrides at high pressures.

  5. Two-band superfluidity and intrinsic Josephson effect in alkaline-earth-metal Fermi gases across an orbital Feshbach resonance

    NASA Astrophysics Data System (ADS)

    Iskin, M.

    2016-07-01

    We first show that the many-body Hamiltonian governing the physical properties of an alkaline-earth 173Yb Fermi gas across the recently realized orbital Feshbach resonance is exactly analogous to that of two-band s -wave superconductors with contact interactions; i.e., even though the free-particle bands have a tunable energy offset in between and are coupled by a Josephson-type attractive interband pair scattering, the intraband interactions have exactly the same strength. We then introduce two intraband order parameters within the BCS mean-field approximation and investigate the competition between their in-phase and out-of-phase (i.e., the so-called π -phase) solutions in the entire BCS-BEC evolution at zero temperature.

  6. High-T sub c thin films on low microwave loss alkaline-rare-earth-aluminate crystals

    SciTech Connect

    Sobolewski, R.; Gierlowski, P.; Kula, W.; Zarembinski, S.; Lewandowski, S.J.; Berkowski, M.; Pajaczkowska, A. ); Gorshunov, B.P.; Lyudmirsky, D.B.; Sirotinsky, O.I. )

    1991-03-01

    This paper reports on the alkaline-rare-earth aluminates (K{sub 2}NiF{sub 4}-type perovskites) which are an excellent choice as the substrate material for the growth of high-T{sub c} thin films suitable for microwave and far-infrared applications. The CaNdAlO{sub 4}, and SrLaAlO{sub 4} single crystals have been grown by Czochralski pulling and fabricated into the form of (001) oriented wafers. The Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O films deposited on these substrates by a single-target magnetron sputtering exhibited very good superconducting and structural properties.

  7. Cyclotron dynamics of a Kondo singlet in a spin-orbit-coupled alkaline-earth-metal atomic gas

    NASA Astrophysics Data System (ADS)

    Jiang, Bo-Nan; Lv, Hao; Wang, Wen-Li; Du, Juan; Qian, Jun; Wang, Yu-Zhu

    2014-11-01

    We propose a scheme to investigate the interplay between the Kondo-exchange interaction and the quantum spin Hall effect with ultracold fermionic alkaline-earth-metal atoms trapped in two-dimensional optical lattices using ultracold collision and laser-assisted tunneling. In the strong Kondo-coupling regime, although the loop trajectory of the mobile atom disappears, collective dynamics of an atom pair in two clock states can exhibit an unexpected spin-dependent cyclotron orbit in a plaquette, realizing the quantum spin Hall effect of the Kondo singlet. We demonstrate that the collective cyclotron dynamics of the spin-zero Kondo singlet is governed by an effective Harper-Hofstadter model in addition to second-order diagonal tunneling.

  8. Physical and optical absorption studies of Fe3+ - ions doped lithium borate glasses containing certain alkaline earths

    NASA Astrophysics Data System (ADS)

    Bhogi, Ashok; Kumar, R. Vijaya; Kistaiah, P.

    2016-05-01

    Iron ion doped lithium borate glasses with the composition 15RO-25Li2O-59B2O3-1Fe2O3 (where R= Ca, Sr and Ba) have been prepared by the conventional melt quenching technique and characterized to investigate the physical and optical properties using XRD, density, molar volume and UV-Visible spectroscopy. The optical absorption spectra exhibit a band at around 460 nm which is assigned to 6A1g(S) → 4Eg (G) of Fe3+ ions with distorted octahedral symmetry. From ultraviolet absorption edges, the optical band gap and Urbach energies have been evaluated. The effect of alkaline earths on these properties is discussed.

  9. Alkaline earth lead and tin compounds Ae2Pb, Ae2Sn, Ae = Ca, Sr, Ba, as thermoelectric materials.

    PubMed

    Parker, David; Singh, David J

    2013-10-01

    We present a detailed theoretical study of three alkaline earth compounds Ca2Pb, Sr2Pb and Ba2Pb, which have undergone little previous study, calculating electronic band structures and Boltzmann transport and bulk moduli using density functional theory. We also study the corresponding tin compounds Ca2Sn, Sr2Sn and Ba2Sn. We find that these are all narrow band gap semiconductors with an electronic structure favorable for thermoelectric performance, with substantial thermopowers for the lead compounds at temperature ranges from 300 to 800 K. For the lead compounds, we further find very low calculated bulk moduli-roughly half of the values for the lead chalcogenides, suggestive of soft phonons and hence low lattice thermal conductivity. All these facts indicate that these materials merit experimental investigation as potential high performance thermoelectrics. We find good potential for thermoelectric performance in the environmentally friendly stannide materials, particularly at high temperature.

  10. Methanol synthesis using a catalyst combination of alkali or alkaline earth salts and reduced copper chromite for methanol synthesis

    DOEpatents

    Tierney, John W.; Wender, Irving; Palekar, Vishwesh M.

    1993-01-01

    The present invention relates to a novel route for the synthesis of methanol, and more specifically to the production of methanol by contacting synthesis gas under relatively mild conditions in a slurry phase with a catalyst combination comprising reduced copper chromite and basic alkali salts or alkaline earth salts. The present invention allows the synthesis of methanol to occur in the temperature range of approximately 100.degree.-160.degree. C. and the pressure range of 40-65 atm. The process produces methanol with up to 90% syngas conversion per pass and up to 95% methanol selectivity. The only major by-product is a small amount of easily separated methyl formate. Very small amounts of water, carbon dioxide and dimethyl ether are also produced. The present catalyst combination also is capable of tolerating fluctuations in the H.sub.2 /CO ratio without major deleterious effect on the reaction rate. Furthermore, carbon dioxide and water are also tolerated without substantial catalyst deactivation.

  11. Dispersion coefficients for H and He interactions with alkali-metal and alkaline-earth-metal atoms

    SciTech Connect

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

    2003-12-01

    The van der Waals coefficients C{sub 6}, C{sub 8}, and C{sub 10} for H and He interactions with the alkali-metal (Li, Na, K, and Rb) and alkaline-earth-metal (Be, Mg, Ca, and Sr) atoms are determined from oscillator strength sum rules. The oscillator strengths were computed using a combination of ab initio and semiempirical methods. The dispersion parameters generally agree with close to exact variational calculations for Li-H and Li-He at the 0.1% level of accuracy. For larger systems, there is agreement with relativistic many-body perturbation theory estimates of C{sub 6} at the 1% level. These validations for selected systems attest to the reliability of the present dispersion parameters. About half the present parameters lie within the recommended bounds of the Standard and Certain compilation [J. Chem. Phys. 83, 3002 (1985)].

  12. Alkaline earth lead and tin compounds Ae2Pb, Ae2Sn, Ae=Ca,Sr,Ba, as thermoelectric materials

    SciTech Connect

    Parker, David S; Singh, David J

    2013-01-01

    We present a detailed theoretical study of three alkaline earth compounds Ca2Pb, Sr2Pb and Ba2Pb, which have undergone little previous study, calculating electronic band structures and Boltzmann transport and bulk moduli using density functional theory. We also study the corresponding tin compounds Ca2 Sn, Sr2 Sn and Ba2 Sn. We find that these are all narrow band gap semiconductors with an electronic structure favorable for thermoelectric performance, with substantial thermopowers for the lead compounds at temperature ranges from 300 to 800 K. For the lead compounds, we further find very low calculated bulk moduli - roughly half of the values for the lead chalcogenides, suggestive of soft phonons and hence low lattice thermal conductivity. All these facts indicate that these materials merit experimental investigation as potential high performance thermoelectrics. We find good potential for thermoelectric performance in the environmentally friendly stannide materials, particularly at high temperature.

  13. Heteroleptic alkyl and amide iminoanilide alkaline earth and divalent rare earth complexes for the catalysis of hydrophosphination and (cyclo)hydroamination reactions.

    PubMed

    Liu, Bo; Roisnel, Thierry; Carpentier, Jean-François; Sarazin, Yann

    2013-09-27

    [{N^N}M(X)(thf)n] alkyl (X=CH(SiMe3)2) and amide (X=N(SiMe3)2) complexes of alkaline earths (M=Ca, Sr, Ba) and divalent rare earths (Yb(II) and Eu(II) ) bearing an iminoanilide ligand ({N^N}(-)) are presented. Remarkably, these complexes proved to be kinetically stable in solution. X-ray diffraction studies allowed us to establish size-structure trends. Except for one case of oxidation with [{N^N}Yb(II){N(SiMe3)2}(thf)], all these complexes are stable under the catalytic conditions and constitute effective precatalysts for the cyclohydroamination of terminal aminoalkenes and the intermolecular hydroamination and intermolecular hydrophosphination of activated alkenes. Metals with equal sizes across alkaline earth and rare earth families display almost identical apparent catalytic activity and selectivity. Hydrocarbyl complexes are much better catalyst precursors than their amido analogues. In the case of cyclohydroamination, the apparent activity decreases with metal size: Ca>Sr>Ba, and the kinetic rate law agrees with R(CHA) =k[precatalyst](1)[aminoalkene](1). The intermolecular hydroamination and hydrophosphination of styrene are anti-Markovnikov regiospecific. In both cases, the apparent activity increases with the ionic radius (Ca

  14. EPR and optical absorption studies of Cu{sup 2+} ions in alkaline earth alumino borate glasses

    SciTech Connect

    Ramesh Kumar, V.; Rao, J.L. . E-mail: jlrao46@yahoo.co.in; Gopal, N.O.

    2005-08-11

    Electron paramagnetic resonance (EPR) and optical absorption spectra of Cu{sup 2+} ions in alkaline earth alumino borate glasses doped with different concentrations of CuO have been studied. The EPR spectra of all the glasses exhibit the resonance signals, characteristic of Cu{sup 2+} ions present in axially elongated octahedral sites. The number of spins participating in the resonance has been calculated as a function of temperature for calcium alumino borate (CaAB) glass doped with 0.1 mol% of CuO. From the EPR data, the paramagnetic susceptibility ({chi}) was calculated at different temperatures (T) and from the 1/{chi}-T graph, the Curie temperature of the glass has been evaluated. The optical absorption spectra of all the glasses show a single broad band, which has been assigned to the {sup 2}B{sub 1g} {yields} {sup 2}B{sub 2g} transition of the Cu{sup 2+} ions. The variation in the intensity of optical absorption with the ionic radius of the alkaline earth ion has been explained based on the Coulombic forces. By correlating the EPR and optical absorption spectral data, the nature of the in-plane {sigma} bonding between Cu{sup 2+} ion and the ligands is estimated. From the fundamental ultraviolet absorption edges of the glasses, the optical energy gap (E {sub opt}) and the Urbach energy ({delta}E) are evaluated. The variation in E {sub opt} and {delta}E is explained based on the number of defect centers in the glass.

  15. Structural, electronic and mechanical properties of alkaline earth metal oxides MO (M=Be, Mg, Ca, Sr, Ba)

    NASA Astrophysics Data System (ADS)

    Cinthia, A. Jemmy; Priyanga, G. Sudha; Rajeswarapalanichamy, R.; Iyakutti, K.

    2015-04-01

    The structural, electronic and mechanical properties of alkaline earth metal oxides MO (M=Be, Mg, Ca, Sr, Ba) in the cubic (B1, B2 and B3) phases and in the wurtzite (B4) phase are investigated using density functional theory calculations as implemented in VASP code. The lattice constants, cohesive energy, bulk modulus, band structures and the density of states are computed. The calculated lattice parameters are in good agreement with the experimental and the other available theoretical results. Electronic structure reveals that all the five alkaline earth metal oxides exhibit semiconducting behavior at zero pressure. The estimated band gaps for the stable wurtzite phase of BeO is 7.2 eV and for the stable cubic NaCl phases of MgO, CaO, SrO and BaO are 4.436 eV, 4.166 eV, 4.013 eV, and 2.274 eV respectively. A pressure induced structural phase transition occurs from wurtzite (B4) to NaCl (B1) phase in BeO at 112.1 GPa and from NaCl (B1) to CsCl (B2) phase in MgO at 514.9 GPa, in CaO at 61.3 GPa, in SrO at 42 GPa and in BaO at 14.5 GPa. The elastic constants are computed at zero and elevated pressures for the B4 and B1 phases for BeO and for the B1 and B2 phases in the case of the other oxides in order to investigate their mechanical stability, anisotropy and hardness. The sound velocities and the Debye temperatures are calculated for all the oxides using the computed elastic constants.

  16. Design of ternary alkaline-earth metal Sn(II) oxides with potential good p-type conductivity

    SciTech Connect

    Du, Mao -Hua; Singh, David J.; Zhang, Lijun; Li, Yuwei; Xu, Qiaoling; Ma, Yanming; Zheng, Weitao

    2016-04-19

    Oxides with good p-type conductivity have been long sought after to achieve high performance all-oxide optoelectronic devices. Divalent Sn(II) based oxides are promising candidates because of their rather dispersive upper valence bands caused by the Sn-5s/O-2p anti-bonding hybridization. There are so far few known Sn(II) oxides being p-type conductive suitable for device applications. Here, we present via first-principles global optimization structure searches a material design study for a hitherto unexplored Sn(II)-based system, ternary alkaline-earth metal Sn(II) oxides in the stoichiometry of MSn2O3 (M = Mg, Ca, Sr, Ba). We identify two stable compounds of SrSn2O3 and BaSn2O3, which can be stabilized by Sn-rich conditions in phase stability diagrams. Their structures follow the Zintl behaviour and consist of basic structural motifs of SnO3 tetrahedra. Unexpectedly they show distinct electronic properties with band gaps ranging from 1.90 (BaSn2O3) to 3.15 (SrSn2O3) eV, and hole effective masses ranging from 0.87 (BaSn2O3) to above 6.0 (SrSn2O3) m0. Further exploration of metastable phases indicates a wide tunability of electronic properties controlled by the details of the bonding between the basic structural motifs. Lastly, this suggests further exploration of alkaline-earth metal Sn(II) oxides for potential applications requiring good p-type conductivity such as transparent conductors and photovoltaic absorbers.

  17. Sign Changes in the Electric Dipole Moment of Excited States in Rubidium-Alkaline Earth Diatomic Molecules

    NASA Astrophysics Data System (ADS)

    Pototschnig, Johann V.; Lackner, Florian; Hauser, Andreas W.; Ernst, Wolfgang E.

    2015-06-01

    In a recent series of combined experimental and theoretical studies we investigated the ground state and several excited states of the Rb-alkaline earth molecules RbSr and RbCa. The group of alkali-alkaline earth (AK-AKE) molecules has drawn attention for applications in ultracold molecular physics and the measurement of fundamental constants due to their large permanent electric and magnetic dipole moments in the ground state. These properties should allow for an easy manipulation of the molecules and simulations of spin models in optical lattices. In our studies we found that the permanent electric dipole moment points in different directions for certain electronically excited states, and changes the sign in some cases as a function of bond length. We summarize our results, give possible causes for the measured trends in terms of molecular orbital theory and extrapolate the tendencies to other combinations of AK and AKE - elements. F. Lackner, G. Krois, T. Buchsteiner, J. V. Pototschnig, and W. E. Ernst, Phys. Rev. Lett., 2014, 113, 153001; G. Krois, F. Lackner, J. V. Pototschnig, T. Buchsteiner, and W. E. Ernst, Phys. Chem. Chem. Phys., 2014, 16, 22373; J. V. Pototschnig, G. Krois, F. Lackner, and W. E. Ernst, J. Chem. Phys., 2014, 141, 234309 J. V. Pototschnig, G. Krois, F. Lackner, and W. E. Ernst, J. Mol. Spectrosc., in Press (2015), doi:10.1016/j.jms.2015.01.006 M. Kajita, G. Gopakumar, M. Abe, and M. Hada, J. Mol. Spectrosc., 2014, 300, 99-107 A. Micheli, G. K. Brennen, and P. Zoller, Nature Physics, 2006, 2, 341-347

  18. Design of ternary alkaline-earth metal Sn(II) oxides with potential good p-type conductivity

    DOE PAGES

    Du, Mao -Hua; Singh, David J.; Zhang, Lijun; ...

    2016-04-19

    Oxides with good p-type conductivity have been long sought after to achieve high performance all-oxide optoelectronic devices. Divalent Sn(II) based oxides are promising candidates because of their rather dispersive upper valence bands caused by the Sn-5s/O-2p anti-bonding hybridization. There are so far few known Sn(II) oxides being p-type conductive suitable for device applications. Here, we present via first-principles global optimization structure searches a material design study for a hitherto unexplored Sn(II)-based system, ternary alkaline-earth metal Sn(II) oxides in the stoichiometry of MSn2O3 (M = Mg, Ca, Sr, Ba). We identify two stable compounds of SrSn2O3 and BaSn2O3, which can bemore » stabilized by Sn-rich conditions in phase stability diagrams. Their structures follow the Zintl behaviour and consist of basic structural motifs of SnO3 tetrahedra. Unexpectedly they show distinct electronic properties with band gaps ranging from 1.90 (BaSn2O3) to 3.15 (SrSn2O3) eV, and hole effective masses ranging from 0.87 (BaSn2O3) to above 6.0 (SrSn2O3) m0. Further exploration of metastable phases indicates a wide tunability of electronic properties controlled by the details of the bonding between the basic structural motifs. Lastly, this suggests further exploration of alkaline-earth metal Sn(II) oxides for potential applications requiring good p-type conductivity such as transparent conductors and photovoltaic absorbers.« less

  19. Theoretical Studies of the Spin Hamiltonian Parameters and Local Distortions for Cu2+ in Alkaline Earth Lead Zinc Phosphate Glasses

    NASA Astrophysics Data System (ADS)

    Wang, Bo-Kun; Wu, Shao-Yi; Yuan, Zi-Yi; Liu, Zi-Xuan; Jiang, Shi-Xin; Liu, Zheng; Yao, Zi-Jian; Teng, Bao-Hua; Wu, Ming-He

    2016-08-01

    The spin Hamiltonian parameters and local structures are theoretically studied for Cu2+-doped alkaline earth lead zinc phosphate (RPPZ, R=Mg, Ca, Sr, and Ba) glasses based on the high-order perturbation calculations for a tetragonally elongated octahedral 3d9 cluster. The relative elongation ratios are found to be ρ≈3.2%, 4.4%, 4.6%, and 3.3% for R=Mg, Ca, Sr, and Ba, respectively, because of the Jahn-Teller effect. The whole decreasing crystal-field strength Dq and orbital reduction factor k from Mg to Sr are ascribed to the weakening electrostatic coulombic interactions and the increasing probability of productivity of nonbridge oxygen (and hence increasing Cu2+-O2- electron cloud admixtures) under PbO addition, respectively, with increasing alkali earth ionic radius. The anomalies (the largest Dq and the next highest k among the systems) for R=Ba are attributed to the cross linkage of this large cation in the network. The overall increasing order (Mg≤Ba

  20. Structural diversity in binuclear complexes of alkaline earth metal ions with 4,6-diacetylresorcinol

    NASA Astrophysics Data System (ADS)

    Shebl, Magdy; Khalil, Saied M. E.; Taha, A.; Mahdi, M. A. N.

    2012-11-01

    A new series of binuclear and mixed-ligand complexes with the general formula: [M 2(LO)yClz]; where M = Mg(II), Ca(II), Sr(II) and Ba(II); H2L = 4,6-diacetylresorcinol, the secondary ligand L' = acetylacetone (acac), 8-hydroxyquinoline (8-HQ) or 2,2'-bipyridyl (Bipy), n = 0-2, m = 1, 2, x = 0, 1, 2, 4, y = 0, 2, 4, 5 and z = 0-2; have been synthesized. They have been characterized by the analytical and spectral methods (IR, 1H NMR and mass) as well as TGA and molar conductivity measurements. The spectroscopic and conductance data suggested that the H2L ligand behaves as a neutral, monobasic or dibasic tetradentate ligand, depending on the basicity of the secondary ligand, through the two phenolic and two carbonyl groups. Binuclear octahedral geometry has been assigned to all of the prepared complexes in various molar ratios 2:2; 2:2:2; 1:2:1 and 1:2:4 (L:M:L'). Molecular orbital calculations were performed for the ligands and their complexes using Hyperchem 7.52 program on the bases of PM3 level and the results were correlated with the experimental data. The ligand and some of its alkaline metal(II) complexes showed antibacterial activity towards some of Gram-positive and Gram-negative bacteria, yeast (Candida albicans) and fungus (Aspergillus fumigatus).

  1. The Silver Halides

    ERIC Educational Resources Information Center

    Sahyun, M. R. V.

    1977-01-01

    Illustrates the type of fractional bonding for solid silver halides. Treats the silver halides as electron excess compounds, and develops a model of a localized bonding unit that may be iterated in three dimensions to describe the bulk phase. (MLH)

  2. Recent progress on earth abundant hydrogen evolution reaction and oxygen evolution reaction bifunctional electrocatalyst for overall water splitting in alkaline media

    NASA Astrophysics Data System (ADS)

    Jamesh, Mohammed Ibrahim

    2016-11-01

    Electrochemical water-splitting is one of the promising ways for producing clean chemical fuel (Hydrogen) while cheap-earth-abundant-bifunctional-electrocatalyst is one of the possible way for improving the overall cost efficiency of water-splitting. This paper reviews the chemical state, hydrogen and oxygen evolution reaction activity in alkaline media, overall water-splitting performance in alkaline media, stability, and possible-factors for improving its efficiency of various kinds of recently reported electrocatalyst such as Ni-P, Co-P, Ni-Co-P, graphene-Co-P, O/N/C-Co/Ni, Ni-S, B-Ni/Co, Ni-Co, Mo, Se, Fe, Mn/Zn/Ti, and metal-free based earth-abundant-bifunctional-electrocatalyst. This paper also reviews and highlights the remarkable water splitting performance of the earth-abundant-bifunctional-electrocatalyst those exhibit better or well comparable with Pt/C//RuO2.

  3. Halogen-abstraction reactions from chloromethane and bromomethane molecules by alkaline-earth monocations.

    PubMed

    Redondo, Pilar; Largo, Antonio; Rayón, Víctor Manuel; Molpeceres, Germán; Sordo, José Ángel; Barrientos, Carmen

    2014-08-14

    The reactions, in the gas phase, between alkali-earth monocations (Mg(+), Ca(+), Sr(+), Ba(+)) and CH3X (X = Cl, Br) have been theoretically studied. The stationary points on the potential energy surfaces were characterized at the Density Functional Theory level on the framework of the mPW1K functional with the QZVPP Ahlrichs's basis sets. A complementary kinetics study has also been performed using conventional/variational microcanonical transition state theory. In the reactions of Mg(+) with either chloro- or bromomethane the transition structure lies in energy clearly above the reactants rendering thermal activation of CH3Cl or CH3Br extremely improbable. The remaining reactions are exothermic and barrierless processes; thus carbon-halogen bonds in chloro- or bromomethane can be activated by calcium, strontium or barium monocations to obtain the metal halogen cation and the methyl radical. The Mulliken population analysis for the stationary points of the potential energy surfaces supports a "harpoon"-like mechanism for the halogen-atom abstraction processes. An analysis of the bonding situation for the stationary points on the potential energy surface has also been performed in the framework of the quantum theory of atoms in molecules.

  4. A new N-hydroxyethyliminodiacetic acid modified core-shell silica phase for chelation ion chromatography of alkaline earth, transition and rare earth elements.

    PubMed

    McGillicuddy, Nicola; Nesterenko, Ekaterina P; Nesterenko, Pavel N; Stack, Elaine M; Omamogho, Jesse O; Glennon, Jeremy D; Paull, Brett

    2013-12-20

    Bare core-shell silica (1.7μm) has been modified with iminodiacetic acid functional groups via standard silane chemistry, forming a new N-hydroxyethyliminodiacetic acid (HEIDA) functionalised core-shell stationary phase. The column was applied in high-performance chelation ion chromatography and evaluated for the retention of alkaline earth, transition and heavy metal cations. The influence of nitric acid eluent concentration, addition of complexing agent dipicolinic acid, eluent pH and column temperature on the column performance was investigated. The efficiencies obtained for transition and heavy metal cations (and resultant separations) were comparable or better than those previously obtained for alternative fully porous silica based chelation stationary phases, and a similarly modified monolithic silica column, ranging from ∼15 to 56μm HETP. Increasing the ionic strength of the eluent with the addition of KNO3 (0.75M) and increasing the column temperature (70°C) facilitated the isocratic separation of a mixture of 14 lanthanides and yttrium in under 12min, with HETP averaging 18μm (7μm for Ce(III)).

  5. Structures and stabilities of alkaline earth metal peroxides XO2 (X=Ca, Be, Mg) studied by a genetic algorithm

    SciTech Connect

    Zhao, Xin; Nguyen, Manh Cuong; Wang, Cai-Zhuang; Ho, Kai-Ming

    2013-09-17

    The structures and stabilities of alkaline earth metal peroxides XO2 (X = Ca, Be, Mg) were studied using an adaptive genetic algorithm (GA) for global structure optimization in combination with first-principles calculations. From the adaptive GA search, we obtained an orthorhombic structure for CaO2 with 12 atoms in the unit cell, which is energetically more favorable than the previously proposed structures. Reaction energy of the decomposition CaO2 → CaO + 1/2O2 determined by density functional theory (DFT) calculation shows that this orthorhombic calcium peroxide structure is thermodynamically stable. The simulated X-ray diffraction (XRD) pattern using our predicted structure is in excellent agreement with experimental data. We also show that crystal phase BeO2 is unlikely to exist under normal conditions. MgO2 has a cubic pyrite structure, but it is not stable against decomposition: MgO2 → MgO + 1/2O2.

  6. X-ray Diffraction Studies of the Structure and Thermochemistry of Alkaline-Earth Oxide-Coated Thermionic Cathodes

    NASA Technical Reports Server (NTRS)

    Karikari, E. K.; Bassey, E.; Wintucky, Edwin G.

    1998-01-01

    NASA LeRC has a broad, active cathode technology development program in which both experimental and theoretical studies are being employed to further development of thermionic cathodes for use as electron sources in vacuum devices for communications and other space applications. One important type of thermionic cathode under development is the alkaline-earth oxide-coated (BaO, SrO, CaO) cathode. Significant improvements in the emission characteristics of this cathode have been obtained through modification of the chemical composition and morphology of the oxide coating, with the best result thus far coming from the addition of In2O3 and Sc2O3. Whereas the In2O3 produces a finer, more uniform particle structure, the exact chemical state and role of the Sc2O3 in the emission enhancement is unknown. The purpose of this cooperative agreement is to combine the studies of the surface chemistry and electron emission at NASA LeRC of chemically modified oxide coatings with a study of the thermochemistry and crystal structure using X-ray diffraction equipment and expertise at Clark Atlanta University (CAU). The study at CAU is intended to provide the description and understanding of the structure and thermochemistry needed for further improvement and optimization of the modified coatings. A description of the experimental procedure, preliminary X-ray diffraction test results, together with the design of an ultrahigh vacuum chamber necessary for high temperature thermochemistry studies will be presented.

  7. Selective oxidation of methanol to hydrogen over gold catalysts promoted by alkaline-earth-metal and lanthanum oxides.

    PubMed

    Hereijgers, Bart P C; Weckhuysen, Bert M

    2009-01-01

    A series of alumina-supported gold catalysts was investigated for the CO-free production of hydrogen by partial oxidation of methanol. The addition of alkaline-earth metal oxide promoters resulted in a significant improvement of the catalytic performance. The methanol conversion was ca. 85 % with all studied catalyst materials, however, the selectivity for hydrogen increased from 15 % to 51 % when going from the unpromoted to a BaO-promoted catalyst. The formation of the undesired byproducts CO, methane, and dimethyl ether was considerably reduced as well. The observed trend in catalyst performance follows the trend in increasing basicity of the studied promoter elements, indicating a chemical effect of the promoter material. Superior catalytic performance, in terms of H(2) and CO selectivity, was obtained with a Au/La(2)O(3) catalyst. At 300 degrees C the hydrogen selectivity reached 80 % with only 2 % CO formation, and the catalyst displayed a stable performance over at least 24 h on-stream. Furthermore, the formation of CO was found to be independent of the oxygen concentration in the feed. The commercial lanthanum oxide used in this study had a low specific surface area, which led to the formation of relative large gold particles. Therefore, the catalytic activity could be enhanced by decreasing the gold particle size through deposition on lanthanum oxide supported on high-surface-area alumina.

  8. Synergetic effect of alkaline earth metal oxides and iron oxides on the degradation of hexachlorobenzene and its degradation pathway.

    PubMed

    Su, Guijin; Liu, Yexuan; Huang, Linyan; Shi, Yali; Zhang, Aiqian; Zhang, Lixia; Liu, Wenbin; Gao, Lirong; Zheng, Minghui

    2013-01-01

    The degradation of hexachlorobenzene (HCB) was carried out over physical mixtures of a series of alkaline earth metal oxides (MO: M=Mg, Ca, Sr, Ba) and iron oxides with different crystal types (Fe(x)O(y):Fe(2)O(3) or Fe(3)O(4)) at 300°C. These physical mixtures all showed a synergetic effect toward the degradation of HCB. A range of degradation products were identified by various methods, including tri- to penta-chlorobenzenes by gas chromatography/mass spectrometry (GC-MS), tri- to penta-chlorophenols, tetrachlorocatechol (TCC) and tetrachlorohydroquinone (TCHQ) by GC-MS after derivatization, and formic and acetic acids by ion chromatography. Two degradation pathways, hydrodechlorination and oxidative degradation, appear to occur competitively. However, more sequential chlorinated benzene and phenol congeners were formed over mixed MO/Fe(3)O(4) than over mixed MO/Fe(2)O(3) under the same conditions. The oxidative reaction dominated over mixed MO/Fe(2)O(3) and was promoted as the major reaction by the synergetic effect, while both the oxidative and hydrodechlorination reactions were important over mixed MO/Fe(3)O(4), and both pathways are remarkably promoted by the synergetic effect. The enhanced hydrodechlorination may be attributed to free electrons generated by the transformation of Fe(3)O(4) into Fe(2)O(3), and hydrogen provided by water adsorbed on the MO.

  9. Cardiac ryanodine receptor: Selectivity for alkaline earth metal cations points to the EF-hand nature of luminal binding sites.

    PubMed

    Gaburjakova, Jana; Gaburjakova, Marta

    2016-06-01

    A growing body of evidence suggests that the regulation of cardiac ryanodine receptor (RYR2) by luminal Ca(2+) is mediated by luminal binding sites located on the RYR2 channel itself and/or its auxiliary protein, calsequestrin. The localization and structure of RYR2-resident binding sites are not known because of the lack of a high-resolution structure of RYR2 luminal regions. To obtain the first structural insight, we probed the RYR2 luminal face stripped of calsequestrin by alkaline earth metal divalents (M(2+): Mg(2+), Ca(2+), Sr(2+) or Ba(2+)). We show that the RYR2 response to caffeine at the single-channel level is significantly modified by the nature of luminal M(2+). Moreover, we performed competition experiments by varying the concentration of luminal M(2+) (Mg(2+), Sr(2+) or Ba(2+)) from 8 mM to 53 mM and investigated its ability to compete with 1mM luminal Ca(2+). We demonstrate that all tested M(2+) bind to exactly the same RYR2 luminal binding sites. Their affinities decrease in the order: Ca(2+)>Sr(2+)>Mg(2+)~Ba(2+), showing a strong correlation with the M(2+) affinity of the EF-hand motif. This indicates that the RYR2 luminal binding regions and the EF-hand motif likely share some structural similarities because the structure ties directly to the function.

  10. Dissolution of glass wool, rock wool and alkaline earth silicate wool: morphological and chemical changes in fibers.

    PubMed

    Campopiano, Antonella; Cannizzaro, Annapaola; Angelosanto, Federica; Astolfi, Maria Luisa; Ramires, Deborah; Olori, Angelo; Canepari, Silvia; Iavicoli, Sergio

    2014-10-01

    The behavior of alkaline earth silicate (AES) wool and of other biosoluble wools in saline solution simulating physiological fluids was compared with that of a traditional wool belonging to synthetic vitreous fibers. Morphological and size changes of fibers were studied by scanning electron microscopy (SEM). The elements extracted from fibers were analyzed by inductively coupled plasma atomic emission spectrometry. SEM analysis showed a larger reduction of length-weighted geometric mean fiber diameter at 4.5 pH than at 7.4 pH. At the 7.4 pH, AES wool showed a higher dissolution rate and a dissolution time less than a few days. Their dissolution was highly non-congruent with rapid leaching of calcium. Unlike rock wool, glass wool dissolved more rapidly at physiological pH than at acid pH. Dissolution of AES and biosoluble rock wool is accompanied by a noticeable change in morphology while by no change for glass wool. Biosoluble rock wool developed a leached surface with porous honeycomb structure. SEM analysis showed the dissolution for glass wool is mainly due to breakage transverse of fiber at pH 7.4. AES dissolution constant (Kdis) was the highest at pH 7.4, while at pH 4.5 only biosoluble rockwool 1 showed a higher Kdis.

  11. First-Principles Calculation of Solution Energy of Alkaline-Earth Metal Elements to BaTiO3

    NASA Astrophysics Data System (ADS)

    Moriwake, Hiroki; Hirayama, Tsukasa; Ikuhara, Yuichi; Tanaka, Isao

    2007-10-01

    Quantitative analysis of the solution energy of alkaline-earth metal elements to perovskite-type BaTiO3 was carried out by a first-principles calculation combined with thermodynamics theory. The solution energies of neutral solute and a compensated solute with an oxygen vacancy were systematically calculated. They were obtained for two cation sites and four thermodynamical conditions with different chemical potentials of constituent atoms. Both Ca and Sr preferably occupy the Ba site of BaTiO3. On the other hand, Mg occupies the Ti site. This corresponds well to the widely accepted experimental findings regarding site preference. Moreover, under the condition of coexising BaO, CaO and BaTiO3, energy difference between the Ba-site solution and O-vacancy compensated Ti-site solution of Ca ions has been found to be smaller than that of Sr. Under this condition, the O-vacancy compensated Ti-site solution of Ca should be favorable compared with that of Sr. The same number of oxygen vacancies as Ca ions occupying Ti sites can be introduced. This also explains well experimental feature of the Ca-doped BaTiO3-based nonreducible multilayer ceramics capacitor (MLCC) materials regarding solution site of the Ca ion and abundance of O-vacancy.

  12. CO2 gasification reactivity of biomass char: catalytic influence of alkali, alkaline earth and transition metal salts.

    PubMed

    Lahijani, Pooya; Zainal, Zainal Alimuddin; Mohamed, Abdul Rahman; Mohammadi, Maedeh

    2013-09-01

    This study investigates the influence of alkali (Na, K), alkaline earth (Ca, Mg) and transition (Fe) metal nitrates on CO2 gasification reactivity of pistachio nut shell (PNS) char. The preliminary gasification experiments were performed in thermogravimetric analyzer (TGA) and the results showed considerable improvement in carbon conversion; Na-char>Ca-char>Fe-char>K-char>Mg-char>raw char. Based on TGA studies, NaNO3 (with loadings of 3-7 wt%) was selected as the superior catalyst for further gasification studies in bench-scale reactor; the highest reactivity was devoted to 5 wt% Na loaded char. The data acquired for gasification rate of catalyzed char were fitted with several kinetic models, among which, random pore model was adopted as the best model. Based on obtained gasification rate constant and using the Arrhenius plot, activation energy of 5 wt% Na loaded char was calculated as 151.46 kJ/mol which was 53 kJ/mol lower than that of un-catalyzed char.

  13. A Density Functional Theory Study of Codoping Characteristics of Sulfur with Alkaline Earth in Delafossite CuAlO2

    NASA Astrophysics Data System (ADS)

    Liu, Qi-Jun; Qin, Han; Liu, Zheng-Tang

    2016-04-01

    The structural, electronic properties and formation energies of sulfur and alkaline earth codoped delafossite CuAlO2 have been investigated using the first-principles density functional theory calculations. Our results reveal that the volume of codoping systems increases with the increasing atomic radius of metal atoms. The formation energies under different growth conditions have been calculated, showing that the codoping systems are formed easily under O-rich growth conditions. Electronic band structures and density of states have been obtained. The decreased bandgaps, enhanced covalence and appearance of electron acceptors after codoping are all good for p-type conductivity. Supported by the National Natural Science Foundation of China under Grant Nos. 11347199, 51402244, and 11547311, the Specialized Research Fund for Doctoral Program of Higher Education of China under Grant No. 20130184120028, the Fundamental Research Fund for the Central Universities, China under Grant Nos. 2682014CX084, 2682014ZT30, and 2682014ZT31, and the fund of the State Key Laboratory of Solidification Processing in NWPU under Grant No. SKLSP201511

  14. Amido-based potassium-alkaline earth metallates--synthesis and structures of heterobimetallic complexes of heavy s-block elements.

    PubMed

    Glock, Carsten; Görls, Helmar; Westerhausen, Matthias

    2011-08-28

    The metathesis reaction of potassium N-isopropylanilide with alkaline earth metal diiodides of calcium, strontium and barium in a molar ratio of 4:1 yields the corresponding alkaline earth metalates of the type [(THF)(n)K(μ-NPhiPr)(2)Ae(μ-NPhiPr)(2)K(THF)(n)] (1: Ae = Ca, n = 2). Stabilization and crystallization of such derivatives succeeds after exchange of the THF ligands by multidentate amino bases such as tetramethylethylenediamine (TMEDA) or pentamethyldiethylenetriamine (PMDETA). The influence of the size and hardness of the alkaline earth metal center on the molecular structures is studied with [(L)K(μ-NPhiPr)(2)Ae(μ-NPhiPr)(2)K(L)] (2: Ae = Ca, L = TMEDA; 3: Ae = Sr, L = TMEDA; 4: Ae = Sr, L = PMDETA; and 5: Ae = Ba, L = PMDETA). The molecular structures are dominated by (attractive and repulsive) electrostatic and steric factors leading to a shortening of the non-bonding AeK distances from calcium to barium.

  15. Monitoring of photoluminescence decay by alkali and alkaline earth metal cations using a photoluminescent bolaamphiphile self-assembly as an optical probe.

    PubMed

    Kim, Sunhyung; Kwak, Jinyoung; Lee, Sang-Yup

    2014-05-01

    Photoluminescence (PL) decay induced by the displacement of an ionic fluorescence component, Tb(3+), with alkali and alkaline earth metal cations was investigated using photoluminescent spherical self-assemblies as optical probes. The photoluminescent spherical self-assembly was prepared by the self-organization of a tyrosine-containing bolaamphiphile molecule with a photosensitizer and Tb(3+) ion. The lanthanide ion, Tb(3+), electrically bound to the carboxyl group of the bolaamphiphile molecule, was displaced by alkali and alkaline earth metal cations that had stronger electrophilicity. The PL of the self-assembly decayed remarkably due to the substitution of lanthanide ions with alkali and alkaline earth metal cations. The PL decay showed a positive correlation with cation concentration and was sensitive to the cation valency. Generally, the PL decay was enhanced by the electrophilicity of the cations. However, Ca(2+) showed greater PL decay than Mg(2+) because Ca(2+) could create various complexes with the carboxyl groups of the bolaamphiphile molecule. Microscopic and spectroscopic investigations were conducted to study the photon energy transfer and displacement of Tb(3+) by the cation exchange. This study demonstrated that the PL decay by the displacement of the ionic fluorescent compound was applied to the detection of various cations in aqueous media and is applicable to the development of future optical sensors.

  16. Multidimensional (0D to 3D) Alkaline-Earth Metal Diphosphonates: Synthesis, Structural Diversity, and Luminescence Properties.

    PubMed

    Senthil Raja, Duraisamy; Lin, Pin-Chun; Liu, Wei-Ren; Zhan, Jun-Xiang; Fu, Xin-Yi; Lin, Chia-Her

    2015-05-04

    A series of new alkaline-earth metal diphosphonate frameworks were successfully synthesized under solvothermal reaction condition (160 °C, 3 d) using 1-hydroxyethylidene-1,1-diphosphonic acid (CH3C(OH)(H2PO3)2, hedpH4) as a diphosphonate building block and Mg(II), Ca(II), Sr(II), or Ba(II) ions as alkaline-earth metal ion centers in water, dimethylformamide, and/or EtOH media. These diphosphonate frameworks, (H2NMe2)4[Mg(hedpH2)3]·3H2O (1), (H2NMe2)2[Ca(hedpH2)2] (2), (H2NMe2)2[Sr3(hedpH2)4(H2O)2] (3), and [Ba3(hedpH2)3]·H2O (4) exhibited interesting structural topologies (zero-, one-, two-, and three-dimensional (0D, 1D, 2D, and 3D, respectively)), which are mainly depending on the metal ions and the solvents used in the synthesis. The single-crystal analysis of these newly synthesized compounds revealed that 1 was a 0D molecule, 2 has 1D chains, 3 was a 3D molecule, and 4 has 2D layers. All compounds were further characterized using thermogravimetric analysis, solid-state (31)P NMR, powder X-ray diffraction analysis, UV-vis spectra, and infrared spectroscopy. In addition, Eu(III)- and Tb(III)-doped compounds of 1-4, namely, (H2NMe2)4[Ln(x)Mg(1-x)(hedpH2)2(hedpH(2-x))]·3H2O (1Ln), (H2NMe2)2[Ln(x)Ca(1-x)(hedpH2)(hedpH(2-x))] (2Ln), (H2NMe2)2[Ln(x)Sr(3-x)(hedpH2)3(hedpH(2-x))(H2O)2] (3Ln), and [Ln(x)Ba(3-x)(hedpH2)2(hedpH(2-x))]·H2O (4Ln) (where Ln = Eu, Tb), were synthesized, and their photoluminescence properties were studied. The quantum yield of 1Eu-4Eu was measured with reference to commercial red phosphor, Y2O2S:Eu(3+) (YE), and the quantum yield of terbium-doped compounds 1Tb-4Tb was measured with reference to commercial green-emitting phosphor CeMgAl10O17:Tb(3+). Interestingly, the compound 2Eu showed very high quantum yield of 92.2%, which is better than that of the reference commercial red phosphor, YE (90.8%).

  17. Separation of alkali, alkaline earth and rare earth cations by liquid membranes containing macrocyclic carriers. Third progress report, September 1, 1980-April 1, 1981

    SciTech Connect

    Christensen, J.J.

    1981-04-15

    The overall objective of this project is to study the use of liquid membrane systems employing macrocyclic ligand carriers in making separations among metal cations. During the third year of the project, work continued in the development of a mathematical model to describe cation transport. The model was originally developed to describe the relationship between cation transport rate (J/sub M/) and the cation-macrocycle stability constant (K). The model was tested by determining the rates of transport of alkali and alkaline earth cations through chloroform membranes containing carrier ligands where the stability constants for their reaction with cations in methanol were known. From the results, it is clear that the model correctly describes the dependence of J/sub M/ on log K. The model also correctly describes the effect of cation concentration and carrier concentration on cation transport rates, as detailed in the previous progress report. During the third year of the project, the transport model was expanded so as to apply to competitive transport of cations from mixtures of two cations in the source aqueous phase. Data were collected under these conditions and the ability of the model to predict the flux of each cation was tested. Representative data of this type are presented along with corresponding data which were obtained when each cation was transported by the same carrier from a source phase containing only that cation. Comparison of transport rates determined under the two experimental conditions indicates that the relationship between the two sets of data is complex. To date, a few of these data involving transport from binary cation mixtures have been tested against the transport model. It was found that the model correctly predicts the cation fluxes from cation mixtures. These preliminary results indicate that the transport model can successfully predict separation factors when cation mixtures are used.

  18. Discrete divalent rare-earth cationic ROP catalysts: ligand-dependent redox behavior and discrepancies with alkaline-earth analogues in a ligand-assisted activated monomer mechanism.

    PubMed

    Liu, Bo; Roisnel, Thierry; Maron, Laurent; Carpentier, Jean-François; Sarazin, Yann

    2013-03-18

    The first solvent-free cationic complexes of the divalent rare-earth metals, [{RO}RE(II) ](+) [A](-) (RE(II) =Yb(II) , 1; Eu(II) , 2) and [{LO}RE(II) ](+) [A](-) ([A](-) =[H2 N{B(C6 F5 )3 }2 ](-) ; RE(II) =Yb(II) , 3; Eu(II) , 4), have been prepared by using highly chelating monoanionic aminoether-fluoroalkoxide ({RO}(-) ) and aminoether-phenolate ({LO}(-) ) ligands. Complexes 1 and 2 are structurally related to their alkaline-earth analogues [{RO}AE](+) [A](-) (AE=Ca, 5; Sr, 6). Yet, the two families behave very differently during catalysis of the ring-opening polymerization (ROP) of L-lactide (L-LA) and trimethylene carbonate (TMC) performed under immortal conditions with excess BnOH as an exogenous chain-transfer agent. The ligand was found to strongly influence the behavior of the RE(II) complexes during ROP catalysis. The fluoroalkoxide RE(II) catalysts 1 and 2 are not oxidized under ROP conditions, and compare very favorably with their Ca and Sr congeners 5 and 6 in terms of activity (turnover frequency (TOF) in the range 200-400 molL-LA (molEu  h(-1) )) and control over the parameters during the immortal ROP of L-LA (Mn,theor ≈Mn,SEC , Mw /Mn <1.05). The Eu(II) -phenolate 4 provided one of the most effective ROP cationic systems known to date for L-LA polymerization, exhibiting high activity (TOF up to 1 880 molL-LA ⋅(molEu  h)(-1) ) and good control (Mw /Mn =1.05). By contrast, upon addition of L-LA the Yb(II) -phenolate 3 immediately oxidizes to inactive RE(III) species. Yet, the cyclic carbonate TMC was rapidly polymerized by combinations of 3 (or even 1) and BnOH, revealing excellent activities (TOF=5000-7000 molTMC ⋅(molEu  h)(-1) ) and unusually high control (Mn,theor ≈Mn,SEC , Mw /Mn <1.09); under identical conditions, the calcium derivative 5 was entirely inert toward TMC. Based on experimental and kinetic data, a new ligand-assisted activated monomer ROP mechanism is suggested, in which the so-called ancillary ligand plays a

  19. DEVELOPMENT OF GLASS COMPOSITIONS TO IMMOBILIZE ALKALI, ALKALINE EARTH, LANTHANIDE AND TRANSITION METAL FISSION PRODUCTS FROM NUCLEAR FUEL REPROCESSING

    SciTech Connect

    Marra, J.; Billings, A.

    2009-06-24

    The Advanced Fuel Cycle Initiative (AFCI) waste management strategy revolves around specific treatment of individual or groups of separated waste streams. A goal for the separations processes is to efficiently manage the waste to be dispositioned as high level radioactive waste. The Advanced Fuel Cycle Initiative (AFCI) baseline technology for immobilization of the lanthanide (Ln) and transition metal fission product (TM) wastes is vitrification into a borosilicate glass. A current interest is to evaluate the feasibility of vitrifying combined waste streams to most cost effectively immobilize the wastes resulting from aqueous fuel reprocessing. Studies showed that high waste loadings are achievable for the Ln only (Option 1) stream. Waste loadings in excess of 60 wt % (on a calcined oxide basis) were demonstrated via a lanthanide borosilicate (LaBS) glass. The resulting glasses had excellent relative durability as determined by the Product Consistency Test (PCT). For a combined Ln and TM waste stream glass (Option 2), noble metal solubility was found to limit waste loading. However, the measured PCT normalized elemental releases for this glass were at least an order of magnitude below that of Environmental Assessment (EA) glass. Current efforts to evaluate the feasibility of vitrifying combined Ln, TM, alkali (Cs is the primary radionuclide of concern) and alkaline earth (Sr is the primary radionuclide of concern) wastes (Option 3) have shown that these approaches are feasible. However, waste loading limitations with respect to heat load (Cs/Sr loading), molybdenum solubility and/or noble metal solubility will likely be realized and must be considered in determining the cost effectiveness of these approaches.

  20. Honeycomb-shaped coordination polymers based on the self-assembly of long flexible ligands and alkaline-earth ions

    SciTech Connect

    Lian, Chen; Liu, Liu; Guo, Xu; Long, Yinshuang; Jia, Shanshan; Li, Huanhuan; Yang, Lirong

    2016-01-15

    Two novel coordination polymers, namely, [Ca(NCP){sub 2}]{sub ∞} (I) and [Sr(NCP){sub 2}]{sub ∞} (II) were synthesized under hydrothermal conditions based on 2-(4-carboxyphenyl)imidazo(4,5-f)-(1,10)phenanthroline (HNCP) and characterized by elemental analysis, infrared spectrometry, X-ray powder diffraction and single crystal X-ray diffraction. Findings indicate that I and II are isomorphous and isostructural, containing the unit of M(NCP{sup −}){sub 4} (M=Ca(II) and Sr(II)), based on which to assemble into three-dimensional (3D) porous 4-fold interpenetration honeycomb-shaped neutral coordination polymers (CPs). Between the adjacent lamellar structures in I and II, there exist π–π interactions between the pyridine rings belonging to phenanthroline of NCP{sup −} which stabilize the frameworks. Both I and II display stronger fluorescence emissions as well as high thermal stability. - Graphical abstract: One-dimensional nanotubular channels with the cross dimension of 37.1959(20)×23.6141(11)Å{sup 2} in the three-dimensional honeycomb-shaped coordination network of II are observed. The topological analysis of II indicates that there exists a typical diamond framework possessing large adamantanoid cages, which containing four cyclohexane-shaped patterns in chair conformations. - Highlights: • Two isomorphous and isostructural coordination polymers based on flexible ligand and two alkaline-earth metal salts have been synthesized and characterized. • Structural analysis indicates that I and II are assembled into 3D porous honeycomb-shaped metal-organic frameworks. • Both I and II display stronger fluorescence emissions and higher thermal stability.

  1. Designing mixed metal halide ammines for ammonia storage using density functional theory and genetic algorithms.

    PubMed

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

    2014-09-28

    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 release the stored ammonia in one step, at temperatures suitable for system integration with polymer electrolyte membrane fuel cells (PEMFC). We use genetic algorithms (GAs) to search for materials containing up to three different metals (alkaline-earth, 3d and 4d) and two different halides (Cl, Br and I) - almost 27,000 combinations, and have identified novel mixtures, with significantly improved storage capacities. The size of the search space and the chosen fitness function make it possible to verify that the found candidates are the best possible candidates in the search space, proving that the GA implementation is ideal for this kind of computational materials design, requiring calculations on less than two percent of the candidates to identify the global optimum.

  2. The synthesis and crystal structures of the first rare-earth alkaline-earth selenite chlorides MNd 10(SeO 3) 12Cl 8 ( M=Ca and Sr)

    NASA Astrophysics Data System (ADS)

    Berdonosov, P. S.; Olenev, A. V.; Dolgikh, V. A.; Lightfoot, P.

    2007-11-01

    Two new alkaline-earth Nd selenite chlorides MNd 10(SeO 3) 12Cl 8 ( M=Ca, Sr) were obtained using crystal growth from alkaline-earth chloride melts in quartz tubes. These new compounds crystallize in the orthorhombic system in space group C cca (#68). The compounds were studied by energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction. It was shown that both compounds adopt the same structure type, constructed by complex [M 11(SeO 3) 12] 8+ slabs separated by chloride anion layers perpendicular to the longest cell parameter. The SeO 3 groups show a pyramidal shape and may be described as SeO 3E tetrahedra. Such SeO 3 groups decorate the Nd-O skeletons forming the [M 11(SeO 3) 12] 8+ slabs.

  3. High-pressure densified solid solutions of alkaline earth hexaborides (Ca/Sr, Ca/Ba, Sr/Ba) and their high-temperature thermoelectric properties

    SciTech Connect

    Gürsoy, M.; Takeda, M.; Albert, B.

    2015-01-15

    Solid solutions of alkaline earth hexaborides were synthesized and densified by spark plasma sintering at 100 MPa. The high-temperature thermoelectric properties (Seebeck coefficients, electrical and thermal diffusivities, heat capacities) were measured between room temperature and 1073 K. CaB{sub 6}, SrB{sub 6}, BaB{sub 6} and the ternary hexaborides Ca{sub x}Sr{sub 1−x}B{sub 6}, Ca{sub x}Ba{sub 1−x}B{sub 6}, Sr{sub x}Ba{sub 1−x}B{sub 6} (x = 0.25, 0.5, 0.75) are n-type conducting compounds over the whole compositional and thermal ranges. The values of the figure of merit ZT for CaB{sub 6} (ca. 0.3 at 1073 K) were found to be significantly increased compared to earlier investigations which is attributed to the densification process. - Highlights: • Solid solutions of alkaline earth hexaborides were synthesized. • High-temperature thermoelectric properties of mixed calcium borides are excellent. • Spark plasma source densification results in high ZT values. • Borides are rare-earth free and refractory materials.

  4. Removal of toxic and alkali/alkaline earth metals during co-thermal treatment of two types of MSWI fly ashes in China.

    PubMed

    Yu, Jie; Qiao, Yu; Jin, Limei; Ma, Chuan; Paterson, Nigel; Sun, Lushi

    2015-12-01

    This study aims to vaporize heavy metals and alkali/alkaline earth metals from two different types of fly ashes by thermal treatment method. Fly ash from a fluidized bed incinerator (HK fly ash) was mixed with one from a grate incinerator (HS fly ash) in various proportions and thermally treated under different temperatures. The melting of HS fly ash was avoided when treated with HK fly ash. Alkali/alkaline earth metals in HS fly ash served as Cl-donors to promote the vaporization of heavy metals during thermal treatment. With temperature increasing from 800 to 900°C, significant amounts of Cl, Na and K were vaporized. Up to 1000°C in air, less than 3% of Cl and Na and less than 5% of K were retained in ash. Under all conditions, Cd can be vaporized effectively. The vaporization of Pb was mildly improved when treated with HS fly ash, while the effect became less pronounced above 900°C. Alkali/alkaline earth metals can promote Cu vaporization by forming copper chlorides. Comparatively, Zn vaporization was low and only slightly improved by HS fly ash. The low vaporization of Zn could be caused by the formation of Zn2SiO4, ZnFe2O4 and ZnAl2O4. Under all conditions, less than 20% of Cr was vaporized. In a reductive atmosphere, the vaporization of Cd and Pb were as high as that in oxidative atmosphere. However, the vaporization of Zn was accelerated and that of Cu was hindered because the formation of Zn2SiO4, ZnFe2O4 and ZnAl2O4 and copper chloride was depressed in reductive atmosphere.

  5. Identifying calcium sources at an acid deposition-impacted spruce forest: A strontium isotope, alkaline earth element multi-tracer approach

    USGS Publications Warehouse

    Bullen, T.D.; Bailey, S.W.

    2005-01-01

    Depletion of calcium from forest soils has important implications for forest productivity and health. Ca is available to fine feeder roots from a number of soil organic and mineral sources, but identifying the primary source or changes of sources in response to environmental change is problematic. We used strontium isotope and alkaline earth element concentration ratios of trees and soils to discern the record of Ca sources for red spruce at a base-poor, acid deposition-impacted watershed. We measured 87Sr/86Sr and chemical compositions of cross-sectional stemwood cores of red spruce, other spruce tissues and sequential extracts of co-located soil samples. 87Sr/86Sr and Sr/Ba ratios together provide a tracer of alkaline earth element sources that distinguishes the plant-available fraction of the shallow organic soils from those of deeper organic and mineral soils. Ca/Sr ratios proved less diagnostic, due to within-tree processes that fractionate these elements from each other. Over the growth period from 1870 to 1960, 87Sr/86Sr and Sr/Ba ratios of stemwood samples became progressively more variable and on average trended toward values that considered together are characteristic of the uppermost forest floor. In detail the stemwood chemistry revealed an episode of simultaneous enhanced uptake of all alkaline earth elements during the growth period from 1930 to 1960, coincident with reported local and regional increases in atmospheric inputs of inorganic acidity. We attribute the temporal trends in stemwood chemistry to progressive shallowing of the effective depth of alkaline earth element uptake by fine roots over this growth period, due to preferential concentration of fine roots in the upper forest floor coupled with reduced nutrient uptake by roots in the lower organic and upper mineral soils in response to acid-induced aluminum toxicity. Although both increased atmospheric deposition and selective weathering of Ca-rich minerals such as apatite provide possible

  6. Electronic structure, optical properties and bonding in alkaline earth halo-fluoride scintillators: BaClF, BaBrF and BaIF

    SciTech Connect

    Yedukondalu, N.; Babu, K. Ramesh; Bheemalingam, Ch.; Singh, David J; Vaitheeswaran, G.; Kanchana, V.

    2011-01-01

    We report first-principles studies of the structural, electronic, and optical properties of the alkaline-earth halofluorides, BaXF (X = Cl, Br, and I), including pressure dependence of structural properties. The band structures show clear separation of the halogen p derived valence bands into higher binding energy F and lower binding energy X derived manifolds reflecting the very high electronegativity of F relative to the other halogens. Implications of this for bonding and other properties are discussed. We find an anisotropic behavior of the structural parameters especially of BaIF under pressure. The optical properties on the other hand are almost isotropic, in spite of the anisotropic crystal structures.

  7. Identifying the presence of a disulfide linkage in peptides by the selective elimination of hydrogen disulfide from collisionally activated alkali and alkaline earth metal complexes.

    PubMed

    Kim, Hugh I; Beauchamp, J L

    2008-01-30

    We report a new method for identifying disulfide linkages in peptides using mass spectrometry. This is accomplished by collisional activation of singly charged cationic alkali and alkaline earth metal complexes, which results in the highly selective elimination of hydrogen disulfide (H2S2). Complexes of peptides possessing disulfide bonds with sodium and alkaline earth metal are generated using electrospray ionization (ESI). Isolation followed by collision induced dissociation (CID) of singly charged peptide complexes results in selective elimination of H2S2 to leave newly formed dehydroalanine residues in the peptide. Further activation of the product yields sequence information in the region previously short circuited by the disulfide bond. For example, singly charged magnesium and calcium ion bound complexes of [Lys8]-vasopressin exhibit selective elimination of H2S2 via low-energy CID. Further isolation of the product followed by CID yields major b- and z-type fragments revealing the peptide sequence in the region between the newly formed dehydroalanine residues. Numerous model peptides provide mechanistic details for the selective elimination of H2S2. The process is initiated starting with a metal stabilized enolate anion at Cys, followed by cleavage of the S-C bond. An examination of the peptic digest of insulin provides an example of the application of the selective elimination of H2S2 for the identification of peptides with disulfide linkages. The energetics and mechanisms of H2S2 elimination from model compounds are investigated using density functional theory (DFT) calculations.

  8. Indirect ultraviolet detection of alkaline earth metal ions using an imidazolium ionic liquid as an ultraviolet absorption reagent in ion chromatography.

    PubMed

    Liu, Yong-Qiang; Yu, Hong

    2017-02-20

    A convenient and versatile method was developed for the separation and detection of alkaline earth metal ions by ion chromatography with indirect UV detection. The chromatographic separation of Mg(2+) , Ca(2+) , and Sr(2+) was performed on a carboxylic acid base cation exchange column using imidazolium ionic liquid/acid as the mobile phase, in which the imidazolium ionic liquid acted as an UV-absorption reagent. The effects of imidazolium ionic liquids, detection wavelength, acids in the mobile phase, and column temperature on the retention of Mg(2+) , Ca(2+) , and Sr(2+) were investigated. The main factors influencing the separation and detection were the background UV absorption reagent and the concentration of hydrogen ion in ion chromatography with indirect UV detection. The successful separation and detection of Mg(2+) , Ca(2+) , and Sr(2+) within 14 min were achieved using the selected chromatographic conditions, and the detection limits (S/N = 3) were 0.06, 0.12, and 0.23 mg/L, respectively. A new separation and detection method of alkaline earth metal ions by ion chromatography with indirect UV detection was developed, and the application range of ionic liquids was expanded.

  9. Origin of low sodium capacity in graphite and generally weak substrate binding of Na and Mg among alkali and alkaline earth metals.

    PubMed

    Liu, Yuanyue; Merinov, Boris V; Goddard, William A

    2016-04-05

    It is well known that graphite has a low capacity for Na but a high capacity for other alkali metals. The growing interest in alternative cation batteries beyond Li makes it particularly important to elucidate the origin of this behavior, which is not well understood. In examining this question, we find a quite general phenomenon: among the alkali and alkaline earth metals, Na and Mg generally have the weakest chemical binding to a given substrate, compared with the other elements in the same column of the periodic table. We demonstrate this with quantum mechanics calculations for a wide range of substrate materials (not limited to C) covering a variety of structures and chemical compositions. The phenomenon arises from the competition between trends in the ionization energy and the ion-substrate coupling, down the columns of the periodic table. Consequently, the cathodic voltage for Na and Mg is expected to be lower than those for other metals in the same column. This generality provides a basis for analyzing the binding of alkali and alkaline earth metal atoms over a broad range of systems.

  10. Origin of low sodium capacity in graphite and generally weak substrate binding of Na and Mg among alkali and alkaline earth metals

    NASA Astrophysics Data System (ADS)

    Liu, Yuanyue; Merinov, Boris V.; Goddard, William A., III

    2016-04-01

    It is well known that graphite has a low capacity for Na but a high capacity for other alkali metals. The growing interest in alternative cation batteries beyond Li makes it particularly important to elucidate the origin of this behavior, which is not well understood. In examining this question, we find a quite general phenomenon: among the alkali and alkaline earth metals, Na and Mg generally have the weakest chemical binding to a given substrate, compared with the other elements in the same column of the periodic table. We demonstrate this with quantum mechanics calculations for a wide range of substrate materials (not limited to C) covering a variety of structures and chemical compositions. The phenomenon arises from the competition between trends in the ionization energy and the ion-substrate coupling, down the columns of the periodic table. Consequently, the cathodic voltage for Na and Mg is expected to be lower than those for other metals in the same column. This generality provides a basis for analyzing the binding of alkali and alkaline earth metal atoms over a broad range of systems.

  11. Binary technetium halides

    NASA Astrophysics Data System (ADS)

    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

  12. Halide Free M(BH4)2 (M = Sr, Ba, and Eu) Synthesis, Structure, and Decomposition.

    PubMed

    Sharma, Manish; Didelot, Emilie; Spyratou, Alexandra; Lawson Daku, Latévi Max; Černý, Radovan; Hagemann, Hans

    2016-07-18

    Borohydrides have attained high interest in the past few years due to their high volumetric and gravimetric hydrogen content. Synthesis of di/trimetallic borohydride is a way to alter the thermodynamics of hydrogen release from borohydrides. Previously reported preparations of M(BH4)2 involved chloride containing species such as SrCl2. The presence of residual chloride (or other halide) ions in borohydrides may change their thermodynamic behavior and their decomposition pathway. Pure monometallic borohydrides are needed to study decomposition products without interference from halide impurities. They can also be used as precursors for synthesizing di/trimetallic borohydrides. In this paper we present a way to synthesize halide free alkaline earth metal (Sr, Ba) and europium borohydrides starting with the respective hydrides as precursors. Two novel high temperature polymorphs of Sr and Eu borohydrides and four polymorphs of Ba borohydride have been characterized by synchrotron X-ray powder diffraction, thermal analysis, and Raman and infrared spectroscopy and supported by periodic DFT calculations. The decomposition routes of these borohydrides have also been investigated. In the case of the decomposition of strontium and europium borohydrides, the metal borohydride hydride (M(BH4)H3, M = Sr, Eu) is observed and characterized. Periodic DFT calculations performed on room temperature Ba(BH4)2 revealed the presence of bidentate and tridentate borohydrides.

  13. Alkaline earth imidazolate coordination polymers by solvent free melt synthesis as potential host lattices for rare earth photoluminescence: (x)(∞)[AE(Im)2(ImH)(2-3)], Mg, Ca, Sr, Ba, x = 1-2.

    PubMed

    Zurawski, Alexander; Rybak, J-Christoph; Meyer, Larissa V; Matthes, Philipp R; Stepanenko, Vladimir; Dannenbauer, Nicole; Würthner, Frank; Müller-Buschbaum, Klaus

    2012-04-14

    The series of alkaline earth elements magnesium, calcium, strontium and barium yields single crystalline imidazolate coordination polymers by reactions of the metals with a melt of 1H-imidazole: (1)(∞)[Mg(Im)(2)(ImH)(3)] (1), (2)(∞)[AE(Im)(2)(ImH)(2)], AE = Ca (2), Sr (3), and (1)(∞)[Ba(Im)(2)(ImH)(2)] (4). No additional solvents were used for the reactions. Co-doping experiments by addition of the rare earth elements cerium, europium and terbium were carried out. They indicate (2)(∞)[Sr(Im)(2)(ImH)(2)] as a possible host lattice for cerium(III) photoluminescence showing a blue emission and thus a novel blue emitting hybrid material phosphor 3:Ce(3+). Co-doping with europium and terbium is also possible but resulted in formation of (3)(∞)[Sr(Im)(2)]:Ln, Ln = Eu and Tb (5), with both exhibiting green emission of either Eu(2+) or Tb(3+). The other alkaline earth elements do not show acceptance of the rare earth ions investigated and a different structural chemistry. For magnesium and barium one-dimensional strand structures are observed whereas calcium and strontium give two-dimensional network structures. Combined with an increase of the ionic radii of AE(2+) the coordinative demand is also increasing from Mg(2+) to Ba(2+), reflected by four different crystal structures for the four elements Mg, Ca, Sr, Ba in 1-4. Different linkages of the imidazolate ligands result in a change from complete σ-N coordination in 1 to additional η(5)-π coordination in 4. The success of co-doping with different lanthanide ions is based on a match in the chemical behaviour and cationic radii. The use of strontium for host lattices with imidazole is a rare example in coordination chemistry of co-doping with small amounts of luminescence centers and successfully reduces the amount of high price rare earth elements in hybrid materials while maintaining the properties. All compounds are examples of pure N-coordinated coordination polymers of the alkaline earth metals and were

  14. Dispersion coefficients for the interactions of the alkali-metal and alkaline-earth-metal ions and inert-gas atoms with a graphene layer

    NASA Astrophysics Data System (ADS)

    Kaur, Kiranpreet; Arora, Bindiya; Sahoo, B. K.

    2015-09-01

    Largely motivated by a number of applications, the van der Waals dispersion coefficients C3 of the alkali-metal ions Li+,Na+,K+, and Rb+, the alkaline-earth-metal ions Ca+,Sr+,Ba+, and Ra+, and the inert-gas atoms He, Ne, Ar, and Kr with a graphene layer are determined precisely within the framework of the Dirac model. For these calculations, we evaluate the dynamic polarizabilities of the above atomic systems very accurately by evaluating the transition matrix elements employing relativistic many-body methods and using the experimental values of the excitation energies. The dispersion coefficients are given as functions of the separation distance of an atomic system from the graphene layer and the ambiance temperature during the interactions. For easy extraction of these coefficients, we give a logistic fit to the functional forms of the dispersion coefficients in terms of the separation distances at room temperature.

  15. Low pressure ion chromatography with a low cost paired emitter-detector diode based detector for the determination of alkaline earth metals in water samples.

    PubMed

    Barron, Leon; Nesterenko, Pavel N; Diamond, Dermot; O'Toole, Martina; Lau, King Tong; Paull, Brett

    2006-09-01

    The use of a low pressure ion chromatograph based upon short (25 mm x 4.6 mm) surfactant coated monolithic columns and a low cost paired emitter-detector diode (PEDD) based detector, for the determination of alkaline earth metals in aqueous matrices is presented. The system was applied to the separation of magnesium, calcium, strontium and barium in less than 7min using a 0.15M KCl mobile phase at pH 3, with post-column reaction detection at 570 nm using o-cresolphthalein complexone. A comparison of the performance of the PEDD detector with a standard laboratory absorbance detector is shown, with limits of detection for magnesium and calcium using the low cost PEDD detector equal to 0.16 and 0.23 mg L(-1), respectively. Finally, the developed system was used for the determination of calcium and magnesium in a commercial spring water sample.

  16. Alkaline earth metal-based metal-organic framework: hydrothermal synthesis, X-ray structure and heterogeneously catalyzed Claisen-Schmidt reaction.

    PubMed

    Saha, Debraj; Maity, Tanmoy; Koner, Subratanath

    2014-09-14

    Two alkaline earth metal-based carboxylate systems, [Mg(HL)(H2O)2]n (1) and [Ca(H2L)2]n (2) (H3L = chelidamic acid) have been hydrothermally synthesized, and characterized by single-crystal X-ray diffraction, IR, elemental analysis, and thermo-gravimetric analysis. Compound 1 has a 2D structure incorporating two water molecules. The dehydrated species, 1a, generated from 1 by removal of the coordinated water, has been characterized by thermo-gravimetric analysis, IR, elemental analysis and variable temperature powder X-ray diffraction. Both 1 and its dehydrated species 1a catalyze the Claisen-Schmidt reaction under heterogeneous conditions, but 1a is a more effective catalyst under environmentally friendly conditions. The catalyst can readily be recovered and reused in successive cycles without detectable loss of activity. Compound 2 has a 3D structure and is thermally stable up to 540 °C, but is inactive catalytically.

  17. Calculation of thermodynamic potentials with the inclusion of fractional occupation numbers and investigation of FCC-BCC structural phase transitions in alkaline-earth metals

    NASA Astrophysics Data System (ADS)

    Pozhivatenko, V. V.

    2013-10-01

    The smearing near the Fermi level has been taken into account in the calculations of the thermodynamic characteristics of metals in order to improve the convergence of the performed calculations and to increase the quality of the obtained results. The choice of the smearing parameter usually has not been explained, although the results of the calculations differ significantly for different values of this parameter. Possible schemes for calculating the thermodynamic potentials with the inclusion of the smearing parameter and additional parameters of the volume and energy shifts have been considered. The influence of these parameters on the calculations of the thermodynamic properties of alkaline-earth metals under pressure and on the description of the structural phase transition has been analyzed.

  18. The coordination complex structures and hydrogen bonding in the three-dimensional alkaline earth metal salts (Mg, Ca, Sr and Ba) of (4-aminophenyl)arsonic acid.

    PubMed

    Smith, Graham; Wermuth, Urs D

    2017-01-01

    (4-Aminophenyl)arsonic acid (p-arsanilic acid) is used as an antihelminth in veterinary applications and was earlier used in the monosodium salt dihydrate form as the antisyphilitic drug atoxyl. Examples of complexes with this acid are rare. The structures of the alkaline earth metal (Mg, Ca, Sr and Ba) complexes with (4-aminophenyl)arsonic acid (p-arsanilic acid) have been determined, viz. hexaaquamagnesium bis[hydrogen (4-aminophenyl)arsonate] tetrahydrate, [Mg(H2O)6](C6H7AsNO3)·4H2O, (I), catena-poly[[[diaquacalcium]-bis[μ2-hydrogen (4-aminophenyl)arsonato-κ(2)O:O']-[diaquacalcium]-bis[μ2-hydrogen (4-aminophenyl)arsonato-κ(2)O:O

  19. Adsorption of alkali, alkaline-earth, simple and 3d transition metal, and nonmetal atoms on monolayer MoS{sub 2}

    SciTech Connect

    Li, X. D.; Fang, Y. M.; Wu, S. Q. E-mail: wsq@xmu.edu.cn; Zhu, Z. Z. E-mail: wsq@xmu.edu.cn

    2015-05-15

    Single adsorption of different atoms on pristine two-dimensional monolayer MoS{sub 2} have been systematically investigated by using density functional calculations with van der Waals correction. The adatoms cover alkali metals, alkaline earth metals, main group metal, 3d-transition metals, coinage metal and nonmetal atoms. Depending on the adatom type, metallic, semimetallic or semiconducting behavior can be found in direct bandgap monolayer MoS{sub 2}. Additionally, local or long-range magnetic moments of two-dimensional MoS{sub 2} sheet can also attained through the adsorption. The detailed atomic-scale knowledge of single adsorption on MoS{sub 2} monolayer is important not only for the sake of a theoretical understanding, but also device level deposition technological application.

  20. Determination of rare earth elements, uranium and thorium in geological samples by ICP-MS, using an automatic fusion machine as an alkaline digestion tool.

    NASA Astrophysics Data System (ADS)

    Granda, Luis; Rivera, Maria; Velasquez, Colon; Barona, Diego; Carpintero, Natalia

    2014-05-01

    At the present time, rare earth elements deposits have became in strategic resources for extraction of raw materials in order to manufacture high tech devices (computers, LCD, cell phones, batteries for hybrid vehicles, fiber optics and wind turbines) (1).The appropriate analytical determination of the REE ( rare earth elements) in sediment and rock samples , is important to find potential deposits and to recognize geological environments for identifying possible alterations and mineral occurrences. The alkaline fusion, which aim is to move the entire sample from solid to liquid state by forming water soluble complexes of boron and lithium, as a previous procedure for the determination of these elements, usually takes a lot of time due to the complexity of the analysis phase and by the addition of other reagents (Tm and HF ) (2) to compensate the lack of strict temperature control. The objective of this work is to develop an efficient alternative to alkaline digestion using an electrical fusion machine, which allows to create temperature programs with advanced process control and supports up to 5 samples simultaneously, which generates a reproducibility of the method and results during the melting step. Additionally, this new method permits the processing of a larger number of samples in a shorter time. The samples analyzed in this method were weighed into porcelain crucibles and subjected to calcination for 4 hours at 950 ° C in order to determine the Lost on Ignition (LOI ) , that serves to adjust the analytical results and to preserve the shelf life of the platinum ware. Subsequently, a fraction of the calcined sample was weighed into platinum crucibles and mixed with ultra-pure lithium metaborate ( flux ) 1:4 . The crucible was then placed in the fusion machine, which was programmed to take the sample from room temperature to 950 ° C in five minutes, make a small ramp to 970 ° C maintain that temperature for five minutes and download the melt in a 10 % v / v

  1. Syntheses and characterization of energetic compounds constructed from alkaline earth metal cations (Sr and Ba) and 1,2-bis(tetrazol-5-yl)ethane

    SciTech Connect

    Xia Zhengqiang; Chen Sanping; Wei Qing; Qiao Chengfang

    2011-07-15

    Two new energetic compounds, [M(BTE)(H{sub 2}O){sub 5}]{sub n} (M=Sr(1), Ba(2)) [H{sub 2}BTE=1,2-bis(tetrazol-5-yl)ethane], have been hydrothermally synthesized and structurally characterized. Single-crystal X-ray diffraction analyses reveal that they are isomorphous and exhibit 2D (4,4) net framework, generated by 4-connected Sr{sub 2}(H{sub 2}O){sub 10}/Ba{sub 2}(H{sub 2}O){sub 10} SBUs linked up by two independent binding modes of H{sub 2}BTE, and the resulting 2D structure is interconnected by hydrogen-bond and strong face to face {pi}-{pi} stacking interactions between two tetrazole rings to lead to a 3D supramolecular architecture. DSC measurements show that they have significant catalytic effects on thermal decomposition of ammonium perchlorate. Moreover, the photoluminescence properties, thermogravimetric analyses, and flame colors of the as-prepared compounds are also investigated in this paper. - Graphical abstract: Two novel 2D isomorphous alkaline earth metal complexes were assembled by 4-connected Sr{sub 2}(H{sub 2}O){sub 10}/Ba{sub 2}(H{sub 2}O){sub 10} SBUs and two independent binding modes of H{sub 2}BTE ligands, and the catalytic performances toward thermal decomposition of ammonium perchlorate and photoluminescent properties of them were investigated. Highlights: > Two novel alkaline earth energetic coordination polymers have been prepared.{yields} Both structures are layered based on 4-connected Sr{sub 2}(H{sub 2}O){sub 10}/Ba{sub 2}(H{sub 2}O){sub 10} SBUs and two distinct H{sub 2}BTE coordination modes.{yields} The dehydrated products of the compounds possess good thermostability and significant catalytic effects on thermal decomposition of AP.

  2. Rapid hydrolysis of model phosphate diesters by alkaline-earth cations in aqueous DMSO: speciation and kinetics.

    PubMed

    Taran, Olga; Medrano, Felipe; Yatsimirsky, Anatoly K

    2008-12-14

    Kinetics of the cleavage of two phosphate diesters, bis(4-nitrophenyl) phosphate and 2-hydroxypropyl 4-nitrophenyl phosphate and a triester, 4-nitrophenyl diphenyl phosphate, in the presence of Mg(II), Ca(II) and Sr(II) were studied in 90% vol. DMSO at 37 degrees C. The alkaline hydrolysis of the triester was inhibited by all cations, but with both phosphodiesters strong catalytic effects were observed. Potentiometric titrations of metal perchlorates by Bu4N(OH) revealed formation of M2(OH)3+, M(OH)+, M(OH)2 and M2(OH)5- species. Rate constants for phosphodiester cleavage by individual species were obtained from analysis of rate-concentration profiles. Observed first-order rate constants in the presence of 1-2 mM Mg(II) or Ca(II) in neutral and weakly basic solutions were 10(8)-10(11) times higher than those for background hydrolysis at the same pH while in water additions of up to 50 mM metal produced <100-fold accelerations. Possible structures of DMSO solvated catalyst-substrate complexes were modeled by DFT calculations with Mg(II). The increased catalytic activity in 90% DMSO is attributed to stronger association of hydroxide ions and anionic phosphodiesters with metal ions and to preferable solvation of cations by DMSO, which creates favorable for reaction anhydrous microenvironment in the coordination sphere of the catalyst.

  3. Lack of marked cyto- and genotoxicity of cristobalite in devitrified (heated) alkaline earth silicate wools in short-term assays with cultured primary rat alveolar macrophages.

    PubMed

    Ziemann, Christina; Harrison, Paul T C; Bellmann, Bernd; Brown, Robert C; Zoitos, Bruce K; Class, Philippe

    2014-02-01

    Alkaline earth silicate (AES) wools are low-biopersistence high-temperature insulation wools. Following prolonged periods at high temperatures they may devitrify, producing crystalline silica (CS) polymorphs, including cristobalite, classified as carcinogenic to humans. Here we investigated the cytotoxic and genotoxic significance of cristobalite present in heated AES wools. Primary rat alveolar macrophages were incubated in vitro for 2 h with 200 µg/cm² unheated/heated calcium magnesium silicate wools (CMS1, CMS2, CMS3; heat-treated for 1 week at, or 4 weeks 150 °C below, their respective classification temperatures) or magnesium silicate wool (MS; heated for 24 h at 1260 °C). Types and quantities of CS formed, and fiber size distribution and shape were determined by X-ray diffraction and electron microscopy. Lactate dehydrogenase release and alkaline and hOGG1-modified comet assays were used, ± aluminum lactate (known to quench CS effects), for cytotoxicity/genotoxicity screening. Cristobalite content of wools increased with heating temperature and duration, paralleled by decreases in fiber length and changes in fiber shape. No marked cytotoxicity, and nearly no (CMS) or only slight (MS) DNA-strand break induction was observed, compared to the CS-negative control Al₂O₃, whereas DQ12 as CS-positive control was highly active. Some samples induced slight oxidative DNA damage, but no biological endpoint significantly correlated with free CS, quartz, or cristobalite. In conclusion, heating of AES wools mediates changes in CS content and fiber length/shape. While changes in fiber morphology can impact biological activity, cristobalite content appears minor or of no relevance to the intrinsic toxicity of heated AES wools in short-term assays with rat alveolar macrophages.

  4. Dissolution stoichiometry and adsorption of alkali and alkaline earth elements to the acid-reacted wollastonite surface at 25°C

    NASA Astrophysics Data System (ADS)

    Xie, Zhixin; Walther, John V.

    1994-06-01

    The Ca 2+/H + exchange reaction on the wollastonite surface was investigated at 25°C with both short-term (<2.5 h) and long-term (>48 h) dissolution studies. In acidic solutions, the dissolution of wollastonite is nonstoichiometric with a greater release of Ca than Si relative to the wollastonite stoichiometry. Both short-term and long-term Ca 2+/H + exchange reaction stoichiometries are 0.5. Rapid desorption of Ca 2+ from the surface of untreated wollastonite caused a rise of the suspension pH to about 10 in a couple of minutes. Therefore, potentiometric titrations were performed with an acidreacted wollastonite where most surface detachable Ca 2+ had been removed. Addition of alkali and alkaline earth metal chloride solutions to the acid-reacted wollastonite suspension results in a pH decrease with K +> Na + > Ba 2+ > Mg 2+ > Ca 2+ in equal molal solutions. This suggests that the cations in these solutions are adsorbed to the wollastonite surface. Surface protonation properties of the acid-reacted wollastonite are found to be similar to those of microporous silica but with the point of zero salt effect (pzse) of 4.5-5.5 rather than the 3.0 of microporous silica. The surface protonation-deprotonation as a function of pH is modeled with a one-site double layer model which includes Na adsorption from the background electrolyte to reasonable accuracy. The adsorption of CrO 42-, MoO 42-, Ca 2+, Mg 2+, Ba 2+, and Na + from aqueous solutions to the acidreacted wollastonite/water interface was determined as a function of the pH and ionic strength of the solution. CrO 42- and MoO 42- were not adsorbed to the wollastonite surface at pH above 3. The extent of cation adsorption increases with increasing pH and decreases with increasing ionic strength. Ca 2+ adsorption depends on both the surface area of wollastonite and total amount of Ca 2+ in the suspension. For alkaline earth metals at the same concentration, the adsorption sequence is Ba 2+> Ca 2+> Mg 2+. At pH 8.5, the

  5. The long-range non-additive three-body dispersion interactions for the rare gases, alkali, and alkaline-earth atoms.

    PubMed

    Tang, Li-Yan; Yan, Zong-Chao; Shi, Ting-Yun; Babb, James F; Mitroy, J

    2012-03-14

    The long-range non-additive three-body dispersion interaction coefficients Z(111), Z(112), Z(113), and Z(122) are computed for many atomic combinations using standard expressions. The atoms considered include hydrogen, the rare gases, the alkali atoms (up to Rb), and the alkaline-earth atoms (up to Sr). The term Z(111) arising from three mutual dipole interactions is known as the Axilrod-Teller-Muto coefficient or the DDD (dipole-dipole-dipole) coefficient. Similarly, the terms Z(112), Z(113), and Z(122) arise from the mutual combinations of dipole (1), quadrupole (2), and octupole (3) interactions between atoms and they are sometimes known, respectively, as dipole-dipole-quadrupole, dipole-dipole-octupole, and dipole-quadrupole-quadrupole coefficients. Results for the four Z coefficients are given for the homonuclear trimers, for the trimers involving two like-rare-gas atoms, and for the trimers with all combinations of the H, He, and Li atoms. An exhaustive compilation of all coefficients between all possible atomic combinations is presented as supplementary data.

  6. CO2 capture properties of alkaline earth metal oxides and hydroxides: A combined density functional theory and lattice phonon dynamics study

    NASA Astrophysics Data System (ADS)

    Duan, Yuhua; Sorescu, Dan C.

    2010-08-01

    By combining density functional theory and lattice phonon dynamics, the thermodynamic properties of CO2 absorption/desorption reactions with alkaline earth metal oxides MO and hydroxides M(OH)2 (where M=Be,Mg,Ca,Sr,Ba) are analyzed. The heats of reaction and the chemical potential changes of these solids upon CO2 capture reactions have been calculated and used to evaluate the energy costs. Relative to CaO, a widely used system in practical applications, MgO and Mg(OH)2 systems were found to be better candidates for CO2 sorbent applications due to their lower operating temperatures (600-700 K). In the presence of H2O, MgCO3 can be regenerated into Mg(OH)2 at low temperatures or into MgO at high temperatures. This transition temperature depends not only on the CO2 pressure but also on the H2O pressure. Based on our calculated results and by comparing with available experimental data, we propose a general computational search methodology which can be used as a general scheme for screening a large number of solids for use as CO2 sorbents.

  7. Heating temperature dependence of Cr(III) oxidation in the presence of alkali and alkaline earth salts and subsequent Cr(VI) leaching behavior.

    PubMed

    Verbinnen, Bram; Billen, Pieter; Van Coninckxloo, Michiel; Vandecasteele, Carlo

    2013-06-04

    In this paper, the temperature dependence of Cr(III) oxidation in high temperature processes and the subsequent Cr(VI) leaching was studied using synthetic mixtures. It was experimentally shown that in the presence of alkali and alkaline earth salts, oxidation of Cr(III) takes place, consistent with thermodynamic calculations. Heating of synthetic mixtures of Cr2O3 and Na, K, or Ca salts led to elevated leaching of Cr(VI); in the presence of Na, more than 80% of the initial Cr(III) amount was converted to Cr(VI) at 600-800 °C. Kinetic experiments allowed explanation of the increase in Cr(VI) leaching for increasing temperatures up to 600-800 °C. After reaching a maximum in Cr(VI) leaching at temperatures around 600-800 °C, the leaching decreased again, which could be explained by the formation of a glassy phase that prevents leaching of the formed Cr(VI). By way of illustration, Cr(VI) formation and leaching was evaluated for a case study, the fabrication of ceramic material from contaminated sludge. Based on the proposed reaction mechanisms, countermeasures to prevent Cr oxidation (addition of NH4H2PO4, heating under inert atmosphere) were proposed and successfully tested for synthetic mixtures and for the case study.

  8. Volatilisation of alkali and alkaline earth metallic species during the pyrolysis of biomass: differences between sugar cane bagasse and cane trash.

    PubMed

    Keown, Daniel M; Favas, George; Hayashi, Jun-ichiro; Li, Chun-Zhu

    2005-09-01

    Sugar cane bagasse and cane trash were pyrolysed in a novel quartz fluidised-bed/fixed-bed reactor. Quantification of the Na, K, Mg and Ca in chars revealed that pyrolysis temperature, heating rate, valence and biomass type were important factors influencing the volatilisation of these alkali and alkaline earth metallic (AAEM) species. Pyrolysis at a slow heating rate (approximately 10 K min(-1)) led to minimal (often <20%) volatilisation of AAEM species from these biomass samples. Fast heating rates (>1000 K s(-1)), encouraging volatile-char interactions with the current reactor configuration, resulted in the volatilisation of around 80% of Na, K, Mg and Ca from bagasse during pyrolysis at 900 degrees C. Similar behaviour was observed for monovalent Na and K with cane trash, but the volatilisation of Mg and Ca from cane trash was always restricted. The difference in Cl content between bagasse and cane trash was not sufficient to fully explain the difference in the volatilisation of Mg and Ca.

  9. Mechanochemical synthesis, structure, and properties of solid solutions of alkaline earth metal fluorides: Ma1-xMbxF2 (M: Ca, Sr, Ba)

    NASA Astrophysics Data System (ADS)

    Heise, M.; Scholz, G.; Düvel, A.; Heitjans, P.; Kemnitz, E.

    2016-10-01

    The capability of mechanochemical synthesis for the formation of solid solutions of alkaline earth metal fluorides Ma1-xMbxF2 (M: Ca, Sr, Ba) was tested by fluorination of metal acetates and metal hydroxides with ammonium fluoride directly at milling. Evidence was found for a mutual substitution of cations on their lattice positions in Ca1-xSrxF2 and Ba1-xSrxF2 samples. For the Ba/Ca-system this synthesis route is only partially successful. X-ray diffraction and 19F MAS NMR spectroscopy were used to characterize all samples concerning their crystal structure and local fluorine coordination. Calculations of 19F chemical shifts with the superposition model along with probability calculations for the intensity of the individual 19F lines, performed in dependence on the molar composition of the samples, perfectly agree with the experimental findings. The fluoride ion conductivity of as-prepared samples, determined by temperature dependent DC conductivity measurements, is significantly higher than those of crystalline binary fluorides. Moreover, a higher F- ion conductivity is observed for samples with higher mixing grade in the Ca/Sr-and the Ba/Sr-systems.

  10. PREPARATION OF HALIDES OF PLUTONIUM

    DOEpatents

    Garner, C.S.; Johns, I.B.

    1958-09-01

    A dry chemical method is described for preparing plutonium halides, which consists in contacting plutonyl nitrate with dry gaseous HCl or HF at an elevated temperature. The addition to the reaction gas of a small quantity of an oxidizing gas or a reducing gas will cause formation of the tetra- or tri-halide of plutonium as desired.

  11. Halide laser glasses

    SciTech Connect

    Weber, M.J.

    1982-01-14

    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 Nd/sup 3 +/ 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 /sup 4/F/sub 3/2/ ..-->.. /sup 4/I/sub 11/2/ lasing transition.

  12. Ca12InC13-x and Ba12InC18H4: alkaline-earth indium allenylides synthesized in AE/Li flux (AE = Ca, Ba).

    PubMed

    Blankenship, Trevor V; Dickman, Matthew J; van de Burgt, Lambertus J; Latturner, Susan E

    2015-02-02

    Two new complex main-group metal carbides were synthesized from reactions of indium, carbon, and a metal hydride in metal flux mixtures of an alkaline earth (AE = Ca, Ba) and lithium. Ca(12)InC(13-x) and Ba(12)InC(18)H(4) both crystallize in cubic space group Im3̅ [a = 9.6055(8) and 11.1447(7) Å, respectively]. Their related structures are both built on a body-centered-cubic array of icosahedral clusters comprised of an indium atom and 12 surrounding alkaline-earth cations; these clusters are connected by bridging monatomic anions (either H(-) or C(4-)) and allenylide anions, C(3)(4-). The allenylide anions were characterized by Raman spectroscopy and hydrolysis studies. Density of states and crystal orbital Hamilton population calculations confirm that both compounds are metallic.

  13. Interaction of Rydberg atoms in circular states with the alkaline-earth Ca(4s{sup 2}) and Sr(5s{sup 2}) atoms

    SciTech Connect

    Mironchuk, E. S.; Narits, A. A.; Lebedev, V. S.

    2015-11-15

    The resonant mechanism of interaction of alkaline-earth atoms having a low electron affinity to Rydberg atoms in circular (l = vertical bar m vertical bar = n–1) and near-circular states has been studied. To describe the dynamics of resonant processes accompanied by nonadiabatic transitions between ionic and Rydberg covalent terms of a quasimolecule, an approach based on the integration of coupled equations for the probability amplitudes has been developed taking into account the possibility of the decay of an anion in the Coulomb field of the positive ionic core of a highly excited atom. The approach involves the specific features of the problem associated with the structure of the wavefunction of a Rydberg electron in states with high orbital angular momenta l ∼ n–1. This approach provides a much more accurate description of the dynamics of electronic transitions at collisions between atoms than that within the modified semiclassical Landau–Zener model. In addition, this approach makes it possible to effectively take into account many channels of the problem. The cross sections for resonant quenching of Rydberg states of the Li(nlm) atom with given principal n, orbital l = n–1, and magnetic m quantum numbers at thermal collisions with the Ca(4s{sup 2}) and Sr(5s{sup 2}) atoms have been calculated. The dependences of the results on n, m, and angle α between the relative velocity of the atoms and the normal to the plane of the orbit of the Rydberg electron have been obtained. The influence of orientational effects on the efficiency of the collisional destruction of circular and near-circular states has been studied. The results indicate a higher stability of such states to their perturbations by neutral particles as compared to usually studied nl states with low values of l (l ≪ n)

  14. Fullerene-C60 and crown ether doped on C60 sensors for high sensitive detection of alkali and alkaline earth cations

    NASA Astrophysics Data System (ADS)

    Zaghmarzi, Fatemeh Alipour; Zahedi, Mansour; Mola, Adeleh; Abedini, Saboora; Arshadi, Sattar; Ahmadzadeh, Saeed; Etminan, Nazanin; Younesi, Omran; Rahmanifar, Elham; Yoosefian, Mehdi

    2017-03-01

    Fullerenes are effective acceptor components with high electron affinity for charge transfer. The significant influences of chemical adsorption of the cations on the electrical sensitivity of pristine C60 and 15-(C2H4O)5/C60 nanocages could be the basis of new generation of electronic sensor design. The density functional theory calculation for alkali and alkaline earth cations detection by pristine C60 and 15-(C2H4O)5/C60 nanocages are considered at B3LYP level of theory with 6-31 G(d) basis set. The quantum theory of atoms in molecules analysis have been performed to understand the nature of intermolecular interactions between the cations and nanocages. Also, the natural bond orbital analysis have been performed to assess the intermolecular interactions in detail. Furthermore, the frontier molecular orbital, energy gap, work function, electronegativity, number of transferred electron (∆N), dipole moment as well as the related chemical hardness and softness are investigated and calculated in this study. The results show that the adsorption of cations (M=Na+, K+, Mg2+ and Ca2+) are exothermic and the binding energy in pristine C60 nanocage and 15-(C2H4O)5/C60 increases with respect to the cations charge. The results also denote a decrease in the energy gap and an increase in the electrical conductivity upon the adsorption process. In order to validate the obtained results, the density of state calculations are employed and presented in the end as well.

  15. Unimolecular and hydrolysis channels for the detachment of water from microsolvated alkaline earth dication (Mg2+, Ca2+, Sr2+, Ba2+) clusters

    SciTech Connect

    Miliordos, Evangelos; Xantheas, Sotiris S.

    2014-02-07

    We examine theoretically the three channels that are associated with the detachment of a single water molecule from the aqueous clusters of the alkaline earth dications, [M(H2O)n]2+, M = Mg, Ca, Sr, Ba, n ≤ 6. These are the unimolecular water loss (M2+(H2O)n-1 + H2O) and the two hydrolysis channels resulting to the loss of hydronium ([MOH(H2O)n-2]+ + H3O+) and Zundel ([MOH(H2O)n-3]+ + H3O+(H2O)) cations. The Potential Energy Curves (PECs) corresponding to those three channels were constructed at the Møller-Plesset second order perturbation (MP2) level of theory with basis sets of double- and triple-ζ quality. We furthermore investigated the water and hydronium loss channels from the mono-hydroxide water clusters with up to four water molecules, [MOH(H2O)n]+, 1 ≤ n ≤ 4. Our results indicate the preference of the hydronium loss and possibly the Zundel cation loss channels for the smallest size clusters, whereas the unimolecular water loss channel is preferred for the larger ones as well as the mono-hydroxide clusters. Although the charge separation (hydronium and Zundel cation loss) channels produce more stable products when compared to the ones for the unimolecular water loss, they also require the surmounting of high energy barriers, a fact that makes the experimental observation of fragments related to these hydrolysis channels difficult.

  16. Absorption spectroscopy of heavy alkaline earth metals Ba and Sr in rare gas matrices—CCSD(T) calculations and atomic site occupancies

    SciTech Connect

    Davis, Barry M.; McCaffrey, John G.

    2016-01-28

    Isolation of the heavier alkaline earth metals Ba and Sr in the solid rare gases (RGs) Ar, Kr, and Xe is analysed with absorption spectroscopy and interpreted partly with the assistance of ab initio calculations of the diatomic M ⋅ RG ground state interaction potentials. The y{sup 1}P←a{sup 1}S resonance transitions in the visible spectral region are used to compare the isolation conditions of these two metal atom systems and calcium. Complex absorption bands were recorded in all three metal atom systems even after extensive sample annealing. Coupled cluster calculations conducted on the ground states of the nine M ⋅ RG diatomics (M = Ca, Sr, and Ba; RG = Ar, Kr, and Xe) at the coupled cluster single, double, and non-iterative triple level of theory revealed long bond lengths (>5 Å) and shallow bound regions (<130 cm{sup −1}). All of the M ⋅ RG diatomics have bond lengths considerably longer than those of the rare gas dimers, with the consequence that isolation of these metal atoms in a single substitutional site of the solid rare gas is unlikely, with the possible exception of Ca/Xe. The luminescence of metal dimer bands has been recorded for Ba and Sr revealing very different behaviours. Resonance fluorescence with a lifetime of 15 ns is observed for the lowest energy transition of Sr{sub 2} while this transition is quenched in Ba{sub 2}. This behaviour is consistent with the absence of vibrational structure on the dimer absorption band in Ba{sub 2} indicating lifetime broadening arising from efficient relaxation to low-lying molecular states. More extensive 2D excitation-emission data recorded for the complex site structures present on the absorption bands of the atomic Ba and Sr systems will be presented in future publications.

  17. Absorption spectroscopy of heavy alkaline earth metals Ba and Sr in rare gas matrices--CCSD(T) calculations and atomic site occupancies.

    PubMed

    Davis, Barry M; McCaffrey, John G

    2016-01-28

    Isolation of the heavier alkaline earth metals Ba and Sr in the solid rare gases (RGs) Ar, Kr, and Xe is analysed with absorption spectroscopy and interpreted partly with the assistance of ab initio calculations of the diatomic M ⋅ RG ground state interaction potentials. The y(1)P ← a(1)S resonance transitions in the visible spectral region are used to compare the isolation conditions of these two metal atom systems and calcium. Complex absorption bands were recorded in all three metal atom systems even after extensive sample annealing. Coupled cluster calculations conducted on the ground states of the nine M ⋅ RG diatomics (M = Ca, Sr, and Ba; RG = Ar, Kr, and Xe) at the coupled cluster single, double, and non-iterative triple level of theory revealed long bond lengths (>5 Å) and shallow bound regions (<130 cm(-1)). All of the M ⋅ RG diatomics have bond lengths considerably longer than those of the rare gas dimers, with the consequence that isolation of these metal atoms in a single substitutional site of the solid rare gas is unlikely, with the possible exception of Ca/Xe. The luminescence of metal dimer bands has been recorded for Ba and Sr revealing very different behaviours. Resonance fluorescence with a lifetime of 15 ns is observed for the lowest energy transition of Sr2 while this transition is quenched in Ba2. This behaviour is consistent with the absence of vibrational structure on the dimer absorption band in Ba2 indicating lifetime broadening arising from efficient relaxation to low-lying molecular states. More extensive 2D excitation-emission data recorded for the complex site structures present on the absorption bands of the atomic Ba and Sr systems will be presented in future publications.

  18. Characterization of Surface and Bulk Nitrates of γ-Al2O3-Supported Alkaline Earth Oxides using Density Functional Theory

    SciTech Connect

    Mei, Donghai; Ge, Qingfeng; Kwak, Ja Hun; Kim, Do Heui; Verrier, Christelle M.; Szanyi, Janos; Peden, Charles HF

    2009-05-14

    “Surface" and "bulk" nitrates formed on a series of alkaline earth oxides (AEOs), AE(NO3)2, were investigated using first-principles density functional theory calculations. The formation of these surface and bulk nitrates was modeled by the adsorption of NO2+NO3 pairs on gamma-Al2O3-supported monomeric AEOs (MgO, CaO, SrO, and BaO) and on the extended AEO(001) surfaces, respectively. The calculated vibrational frequencies of the surface and bulk nitrates based on our proposed models are in good agreement with experimental measurements of AEO/gamma-Al2O3 materials after prolonged NO2 exposure. This indicates that experimentally observed "surface" nitrates are most likely formed with isolated two dimensional (including monomeric) AEO clusters on the gamma-Al2O3 substrate, while the "bulk" nitrates are formed on exposed (including (001)) surfaces (and likely in the bulk as well) of large three dimensional AEO particles supported on the gamma-Al2O3 substrate. Also in line with the experiments, our calculations show that the low and high frequency components of the vibrations for both surface and bulk nitrates are systematically red shifted with the increasing basicity and cationic size of the AEOs. The adsorption strengths of NO2+NO3 pairs are nearly the same for the series of alumina-supported monomeric AEOs, while the adsorption strengths of NO2+NO3 pairs on the AEO surfaces increase in the order of MgO < CaO < SrO ~ BaO. Compared to the NO2+NO3 pair that only interacts with monomeric AEOs, the stability of NO2+NO3 pairs that interact with both the monomeric AEO and the gamma-Al2O3 substrate is enhanced by about 0.5 eV. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

  19. Alkaline Earth Metal Zirconate Perovskites MZrO3 (M=Ba(2+), Sr(2+), Ca(2+)) Derived from Molecular Precursors and Doped with Eu(3+) Ions.

    PubMed

    Drąg-Jarząbek, Anna; John, Łukasz; Petrus, Rafał; Kosińska-Klähn, Magdalena; Sobota, Piotr

    2016-03-24

    The effect of alkaline earth metal alkoxides on the protonation of zirconocene dichloride was investigated. This approach enabled the design of compounds with preset molecular structures for generating high-purity binary metal oxide perovskites MZrO3 (M=Ba(2+), Sr(2+), Ca(2+)). Single-source molecular precursors [Ba4 Zr2 (μ6 -O)(μ3 ,η(2)-OR)8 (OR)2(η(2) -HOR)2 (HOR)2 Cl4], [Sr4 Zr2 (μ6 -O)(μ3 ,η(2)-OR)8 (OR)2 (HOR)4 Cl4], [Ca4 Zr2 (μ6-O)(μ3 ,η(2)-OR)8 (OR)2 Cl4], and [Ca6 Zr2 (μ2 ,η(2)-OR)12 (μ-Cl)2 (η(2) -HOR)4 Cl6 ]⋅8 CH2 Cl2 were prepared via elimination of the cyclopentadienyl ring from Cp2 ZrCl2 as CpH in the presence of M(OR)2 and alcohol ROH (ROH=CH3OCH2 CH2OH) as a source of protons. The resulting complexes were characterized by elemental analysis, IR and NMR spectroscopy, and single-crystal X-ray diffraction. The compounds were then thermally decomposed to MCl2 /MZrO3 mixtures. Leaching of MCl2 from the raw powder with deionized water produced highly pure perovskite-like oxide particles of 40-80 nm in size. Luminescence studies on Eu(3+)-doped MZrO3 revealed that the perovskites are attractive host lattices for potential applications in display technology.

  20. Selective trans-membrane transport of alkali and alkaline earth cations through graphene oxide membranes based on cation-π interactions.

    PubMed

    Sun, Pengzhan; Zheng, Feng; Zhu, Miao; Song, Zhigong; Wang, Kunlin; Zhong, Minlin; Wu, Dehai; Little, Reginald B; Xu, Zhiping; Zhu, Hongwei

    2014-01-28

    Graphene and graphene oxide (G-O) have been demonstrated to be excellent filters for various gases and liquids, showing potential applications in areas such as molecular sieving and water desalination. In this paper, the selective trans-membrane transport properties of alkali and alkaline earth cations through a membrane composed of stacked and overlapped G-O sheets ("G-O membrane") are investigated. The thermodynamics of the ion transport process reveal that the competition between the generated thermal motions and the interactions of cations with the G-O sheets results in the different penetration behaviors to temperature variations for the considered cations (K(+), Mg(2+), Ca(2+), and Ba(2+)). The interactions between the studied metal atoms and graphene are quantified by first-principles calculations based on the plane-wave-basis-set density functional theory (DFT) approach. The mechanism of the selective ion trans-membrane transportation is discussed further and found to be consistent with the concept of cation-π interactions involved in biological systems. The balance between cation-π interactions of the cations considered with the sp(2) clusters of G-O membranes and the desolvation effect of the ions is responsible for the selectivity of G-O membranes toward the penetration of different ions. These results help us better understand the ion transport process through G-O membranes, from which the possibility of modeling the ion transport behavior of cellular membrane using G-O can be discussed further. The selectivity toward different ions also makes G-O membrane a promising candidate in areas of membrane separations.

  1. Promoting alkali and alkaline-earth metals on MgO for enhancing CO2 capture by first-principles calculations.

    PubMed

    Kim, Kiwoong; Han, Jeong Woo; Lee, Kwang Soon; Lee, Won Bo

    2014-12-07

    Developing next-generation solid sorbents to improve the economy of pre- and post-combustion carbon capture processes has been challenging for many researchers. Magnesium oxide (MgO) is a promising sorbent because of its moderate sorption-desorption temperature and low heat of sorption. However, its low sorption capacity and thermal instability need to be improved. Various metal-promoted MgO sorbents have been experimentally developed to enhance the CO2 sorption capacities. Nevertheless, rigorous computational studies to screen an optimal metal promoter have been limited to date. We conducted first-principles calculations to select metal promoters of MgO sorbents. Five alkali (Li-, Na-, K-, Rb-, and Cs-) and 4 alkaline earth metals (Be-, Ca-, Sr-, and Ba-) were chosen as a set of promoters. Compared with the CO2 adsorption energy on pure MgO, the adsorption energy on the metal-promoted MgO sorbents is higher, except for the Na-promoter, which indicates that metal promotion on MgO is an efficient approach to enhance the sorption capacities. Based on the stabilized binding of promoters on the MgO surface and the regenerability of sorbents, Li, Ca, and Sr were identified as adequate promoters among the 9 metals on the basis of PW91/GGA augmented with DFT+D2. The adsorption energies of CO2 on metal-promoted MgO sorbents for Li, Ca, and Sr atoms are -1.13, -1.68, and -1.48 eV, respectively.

  2. Silver-halide gelatin holograms

    NASA Astrophysics Data System (ADS)

    Chang, B. J.; Winick, K.

    1980-05-01

    The use of a silver-halide gelatin for volume phase holograms having a wide spectral response and lower exposure requirements than alternatives and using commercially available silver salts, is proposed. The main difference between the dichromated gelatin and silver-halide processes is the creation of a hologram latent image, which is given in the form of a hardness differential between exposed and unexposed regions in the silver halide hologram; the differential is in turn created by the reaction products of either tanning development or tanning bleach, which harden the gelatin with link-bonds between molecules.

  3. Rare earth gas laser

    DOEpatents

    Krupke, W.F.

    1975-10-31

    A high energy gas laser with light output in the infrared or visible region of the spectrum is described. Laser action is obtained by generating vapors of rare earth halides, particularly neodymium iodide or, to a lesser extent, neodymium bromide, and disposing the rare earth vapor medium in a resonant cavity at elevated temperatures; e.g., approximately 1200/sup 0/ to 1400/sup 0/K. A particularly preferred gaseous medium is one involving a complex of aluminum chloride and neodymium chloride, which exhibits tremendously enhanced vapor pressure compared to the rare earth halides per se, and provides comparable increases in stored energy densities.

  4. Actinide halide complexes

    SciTech Connect

    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.

  5. METHOD OF PREPARING METAL HALIDES

    DOEpatents

    Hendrickson, A.V.

    1958-11-18

    The conversion of plutonium halides from plutonium peroxide can be done by washing the peroxide with hydrogen peroxide, drying the peroxide, passing a dry gaseous hydrohalide over the surface of the peroxide at a temperature of about lOO icient laborato C until the reaction rate has stabillzed, and then ralsing the reaction temperature to between 400 and 600 icient laborato C until the conversion to plutonium halide is substantially complete.

  6. Silver-Halide Gelatin Holograms.

    DTIC Science & Technology

    1980-02-01

    PREPARATION OF R-10 TYPE BLEACHES Stock Solution A: Distilled water - 500 ml Ammonium dichromate - 20g Concentrated sulfuric acid - 14 ml Distilled water to...for the preparation of a bleach solution 5 Rinse in running water for 15 seconds Red Light 6 Soak in 0.5% ammonium dichromate for 5 minutes Red Light...those of con- ventional dichromated gelatin holograms, can be formed employing commercial silver-halide films. Major advantages of silver-halide

  7. Chemical composition of modern and fossil Hippopotamid teeth and implications for paleoenvironmental reconstructions and enamel formation - Part 2: Alkaline earth elements as tracers of watershed hydrochemistry and provenance

    NASA Astrophysics Data System (ADS)

    Brügmann, G.; Krause, J.; Brachert, T. C.; Stoll, B.; Weis, U.; Kullmer, O.; Ssemmanda, I.; Mertz, D. F.

    2012-03-01

    For reconstructing environmental change in terrestrial realms the geochemistry of fossil bioapatite in bones and teeth is among the most promising applications. This study demonstrates that alkaline earth elements in enamel of Hippopotamids, in particular Ba and Sr are tracers for water provenance and hydrochemistry. The studied specimens are molar teeth from Hippopotamids found in modern and fossil lacustrine settings of the Western Branch of the East African Rift system (Lake Kikorongo, Lake Albert, and Lake Malawi) and from modern fluvial environments of the Nile River. Concentrations in enamel vary by ca. two orders of magnitude for Ba (120-9336 μg g-1) as well as for Sr (9-2150 μg g-1). Concentration variations in enamel are partly induced during post-mortem alteration and during amelogenesis, but the major contribution originates from the variable water chemistry in the habitats of the Hippopotamids which is dominated by the lithologies and weathering processes in the watershed areas. Amelogenesis causes a distinct distribution of Ba and Sr in modern and fossil enamel, in that element concentrations increase along profiles from the outer rim towards the enamel-dentin junction by a factor of 1.3-1.5. These elements are well correlated with MgO and Na2O in single specimens, thus suggesting that their distribution is determined by a common, single process. Presuming that the shape of the tooth is established at the end of the secretion process and apatite composition is in equilibrium with the enamel fluid, the maturation process can be modeled by closed system Rayleigh crystallization. Enamel from many Hippopotamid specimens has Sr/Ca and Ba/Ca which are typical for herbivores, but the compositions extend well into the levels of plants and carnivores. Within enamel from single specimens these element ratios covary and provide a specific fingerprint of the Hippopotamid habitat. All specimens together, however, define subparallel trends with different Ba

  8. Chemical composition of modern and fossil hippopotamid teeth and implications for paleoenvironmental reconstructions and enamel formation - Part 2: Alkaline earth elements as tracers of watershed hydrochemistry and provenance

    NASA Astrophysics Data System (ADS)

    Brügmann, G.; Krause, J.; Brachert, T. C.; Stoll, B.; Weis, U.; Kullmer, O.; Ssemmanda, I.; Mertz, D. F.

    2012-11-01

    This study demonstrates that alkaline earth elements in enamel of hippopotamids, in particular Ba and Sr, are tracers for water provenance and hydrochemistry in terrestrial settings. The studied specimens are permanent premolar and molar teeth found in modern and fossil lacustrine sediments of the Western Branch of the East African Rift system (Lake Kikorongo, Lake Albert, and Lake Malawi) and from modern fluvial environments of the Nile River. Concentrations in enamel vary by two orders of magnitude for Ba (120-9336 μg g-1) as well as for Sr (9-2150 μg g-1). The variations are partially induced during post-mortem alteration and during amelogenesis, but the major contribution originates ultimately from the variable water chemistry in the habitats of the hippopotamids which is controlled by the lithologies and weathering processes in the watershed areas. Amelogenesis causes a distinct distribution of MgO, Ba and Sr in modern and fossil enamel, in that element concentrations increase along profiles from the outer rim towards the enamel-dentin junction by a factor of 1.3-1.9. These elements are well correlated in single specimens, thus suggesting that their distribution is determined by a common, single process, which can be described by closed system Rayleigh crystallization of bioapatite in vivo. Enamel from most hippopotamid specimens has Sr/Ca and Ba/Ca which are typical for herbivores. However, Ba/Sr ranges from 0.1 to 3 and varies on spatial and temporal scales. Thus, Sr concentrations and Ba/Sr in enamel differentiate between habitats having basaltic mantle rocks or Archean crustal rocks as the ultimate sources of Sr and Ba. This provenance signal is modulated by climate change. In Miocene to Pleistocene enamel from the Lake Albert region, Ba/Sr decreases systematically with time from 2 to 0.5. This trend can be correlated with changes in climate from humid to arid, in vegetation from C3 to C4 biomass as well as with increasing evaporation of the lake water

  9. Methyl Halide Production by Fungi

    NASA Astrophysics Data System (ADS)

    Dailey, G. D.; Varner, R. K.; Blanchard, R. O.; Sive, B. C.; Crill, P. M.

    2005-12-01

    Methyl chloride (CH3Cl), methyl bromide (CH3Br) and methyl iodide (CH3I) are methyl halide gases that contribute significant amounts of halogen radicals to the atmosphere. In an effort to better understand the global budget of methyl halides and their impact on the atmosphere, we need to identify the natural sources in addition to the known anthropogenic sources of these compounds. We are investigating the role of fungi in the production of methyl halides in the soils and wetlands in southern New Hampshire, USA. Previous research has shown that wood decay fungi and ectomycorrhizal fungi, which are within a group of fungi called basidiomycetes, emit methyl halides. In our study, measurements of headspace gas extracted from flasks containing fungi grown in culture demonstrate that a variety of fungi, including basidiomycetes and non-basidiomycetes, emit methyl halides. Our research sites include four ecosystems: an agricultural field, a temperate forest, a fresh water wetland, and coastal salt marshes. We have collected and isolated fungi at each site by culturing tissue samples of fruiting bodies and plant material, by using wood baits, and from the direct culture of soil. We compared the rates of methyl halide emissions from the fungi in the four ecosystems. In addition, we measured emissions from previously assayed fungal isolates after reintroducing them to sterilized soils that were collected from their original environments. Fungal biomass was determined by substrate-induced respiration (SIR). The emission rate by the fungus was determined by a linear regression of the concentration of methyl halide in the sample headspace over time divided by the fungal biomass.

  10. Actinide halide complexes

    DOEpatents

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

    1992-11-24

    A compound is described 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 are described including admixing the actinide metal in an aprotic Lewis base as a coordinating solvent in the presence of a halogen-containing oxidant.

  11. Actinide halide complexes

    DOEpatents

    Avens, Larry R.; Zwick, Bill D.; Sattelberger, Alfred P.; Clark, David L.; Watkin, John G.

    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.

  12. Charge Compensation in RE3+ (RE = Eu, Gd) and M+ (M = Li, Na, K) Co-Doped Alkaline Earth Nanofluorides Obtained by Microwave Reaction with Reactive Ionic Liquids Leading to Improved Optical Properties

    SciTech Connect

    Lorbeer, C; Behrends, F; Cybinska, J; Eckert, H; Mudring, Anja -V

    2014-01-01

    Alkaline earth fluorides are extraordinarily promising host matrices for phosphor materials with regard to rare earth doping. In particular, quantum cutting materials, which might considerably enhance the efficiency of mercury-free fluorescent lamps or SC solar cells, are often based on rare earth containing crystalline fluorides such as NaGdF4, GdF3 or LaF3. Substituting most of the precious rare earth ions and simultaneously retaining the efficiency of the phosphor is a major goal. Alkaline earth fluoride nanoparticles doped with trivalent lanthanide ions (which are required for the quantum cutting phenomenon) were prepared via a microwave assisted method in ionic liquids. As doping trivalent ions into a host with divalent cations requires charge compensation, this effect was thoroughly studied by powder X-ray and electron diffraction, luminescence spectroscopy and 23Na, 139La and 19F solid state NMR spectroscopy. Monovalent alkali ions were codoped with the trivalent lanthanide ions to relieve stress and achieve a better crystallinity and higher quantum cutting abilities of the prepared material. 19F-magic angle spinning (MAS)-NMR-spectra, assisted by 19F{23Na} rotational echo double resonance (REDOR) studies, reveal distinct local fluoride environments, the populations of which are discussed in relation to spatial distribution and clustering models. In the co-doped samples, fluoride species having both Na+ and La3+ ions within their coordination sphere can be identified and quantified. This interplay of mono- and trivalent ions in the CaF2 lattice appears to be an efficient charge compensation mechanism that allows for improved performance characteristics of such co-doped phosphor materials.

  13. {sup 1}H and {sup 23}Na MAS NMR spectroscopy of cationic species in CO{sub 2} selective alkaline earth metal porous silicoaluminophosphates prepared via liquid and solid state ion exchange

    SciTech Connect

    Arevalo-Hidalgo, Ana G.; Dugar, Sneha; Fu, Riqiang; Hernandez-Maldonado, Arturo J.

    2012-07-15

    The location of extraframework cations in Sr{sup 2+} and Ba{sup 2+} ion-exchanged SAPO-34 was estimated by means of {sup 1}H and {sup 23}Na MAS NMR spectroscopy and spectral deconvolution. Incorporation of the alkaline earth metal cations onto the SAPO framework was achieved via liquid state ion exchange, coupled partial detemplation/solid-state ion exchange, and combination of both techniques. MAS NMR revealed that the level of ion exchange was limited by the presence of protons and sodium cations near hexagonal prisms (site SI), which are relatively difficult to exchange with the alkaline earth metal due to steric and charge repulsion criteria. In addition, the presence of ammonium cations in the supercages facilitated the exchange of otherwise tenacious hydrogen as corroborated by unit cell compositional data as well as enhanced CO{sub 2} adsorption at low partial pressures. The extraframework ammonium species were produced from partial detemplation of the structure-directing agent employed for the SAPO-34 synthesis, tetraethylammonium. - Graphical abstract: MAS NMR was used to elucidate the position the cationic species in alkaline earth metal exchanged silicoaluminophosphates. These species played a significant role during the ion exchange process and, therefore, the materials ultimate CO{sub 2} adsorption performance. Highlights: Black-Right-Pointing-Pointer Location of extraframework Sr{sup 2+} or Ba{sup 2+} cations was estimated by means of {sup 1}H and {sup 23}Na MAS NMR. Black-Right-Pointing-Pointer Level of Sr{sup 2+} or Ba{sup 2+} ion exchange was limited by the presence of protons and sodium cations. Black-Right-Pointing-Pointer Presence of ammonium cations in the supercages facilitated the exchange. Black-Right-Pointing-Pointer Sr{sup 2+} and Ba{sup 2+} ion exchanged SAPOs are outstanding CO{sub 2} adsorbents.

  14. Radiochemical synthesis of pure anhydrous metal halides

    NASA Technical Reports Server (NTRS)

    Philipp, W. H.; Marsik, S. J.; May, C. E.

    1973-01-01

    Method uses radiation chemistry as practical tool for inorganic preparations and in particular deposition of metals by irradiation of their aqueous metal salt solutions with high energy electrons. Higher valence metal halide is dissolved in organic liquid and exposed to high energy electrons. This causes metal halide to be reduced to a lower valence metal halide.

  15. Preparation of cerium halide solvate complexes

    SciTech Connect

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

    2013-08-06

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

  16. Optical properties of halide and oxide compounds including the excitonic effects

    NASA Astrophysics Data System (ADS)

    Shwetha, G.; Kanchana, V.

    2014-04-01

    We have studied the optical properties of alkali halide and alkaline-earth oxide compounds including the excitonic effects by using the newly developed bootstrap kernel approximation for the exchange-correlation kernel of the Time-Dependent Density Functional Theory (TD-DFT) implemented in Full-Potential Linearized Augmented Plane Wave (FP-LAPW) method in the elk code. The bootstrap calculations are computationally less expensive and give results the same quality as the Bethe-Salpeter equation. We found improved results when compared to normal Density Functional Theory calculations, and observed results are comparable with the experiments. The lower energy peak of imaginary part of dielectric spectra shifts to lower energy regions as we move from MgO to BaO indicating the decrease in the band gap of these compounds from MgO to BaO. In all the studied compounds, the lower energy peak of the imaginary part of dielectric function is due to the transition from halogen p or oxide p states to metal derived s/d states.

  17. First-principles study of fission product (Xe, Cs, Sr) incorporation and segregation in alkaline earth metal oxides, HfO2, and MgO-HfO2 interface

    SciTech Connect

    Liu, Xiang-yang; Uberuaga, Blas P; Sickafus, Kurt E

    2008-01-01

    In order to close the nuclear fuel cycle, advanced concepts for separating out fission products are necessary. One approach is to use a dispersion fuel form in which a fissile core is surrounded by an inert matrix that captures and immobilizes the fission products from the core. If this inert matrix can be easily separated from the fuel, via e.g. solution chemistry, the fission products can be separated from the fissile material. We examine a surrogate dispersion fuel composition, in which hafnia (HfO{sub 2}) is a surrogate for the fissile core and alkaline earth metal oxides are used as the inert matrix. The questions of fission product incorporation in these oxides and possible segregation behavior at interfaces are considered. Density functional theory based calculations for fission product elements (Xe, Sr, and Cs) in these oxides are carried out. We find smaller incorporation energy in hafnia than in MgO for Cs and Sr, and Xe if variation of charge state is allowed. We also find that this trend is reversed or reduced for alkaline earth metal oxides with large cation sizes. Model interfacial calculations show a strong tendency of segregation from bulk MgO to MgO-HfO{sub 2} interfaces.

  18. Influences of alkaline earth metal substitution on the crystal structure and physical properties of magnetic RuSr1.9A0.1GdCu2O8 (A = Ca, Sr, and Ba) superconductors.

    PubMed

    Hur, Su Gil; Park, Dae Hoon; Hwang, Seong-Ju; Kim, Seung Joo; Lee, J H; Lee, Sang Young

    2005-11-24

    We have investigated the effect of alkaline earth metal substitution on the crystal structure and physical properties of magnetic superconductors RuSr(1.9)A(0.1)GdCu(2)O(8) (A = Ca, Sr, and Ba) in order to probe an interaction between the magnetic coupling of the RuO(2) layer and the superconductivity of the CuO(2) layer. X-ray diffraction and X-ray absorption spectroscopic analyses demonstrate that the isovalent substitution of Sr ions with Ca or Ba ions makes it possible to tune the interlayer distance between the CuO(2) and the RuO(2) layers. From the measurements of electrical resistance and magnetic susceptibility, it was found that, in contrast to negligible change of magnetization, both of the alkaline earth metal substitutions lead to a notable depression of zero-resistance temperature T(c) (DeltaT(c) approximately 17-19 K). On the basis of the absence of a systematic correlation between the T(c) and the interlayer distance/magnetization, we have concluded that the internal magnetic field of the RuO(2) layer has insignificant influence on the superconducting property of the CuO(2) layer in the ruthenocuprate.

  19. Organometal Halide Perovskite Artificial Synapses.

    PubMed

    Xu, Wentao; Cho, Himchan; Kim, Young-Hoon; Kim, Young-Tae; Wolf, Christoph; Park, Chan-Gyung; Lee, Tae-Woo

    2016-07-01

    Organometal halide perovskite synaptic devices are fabricated; they emulate important working principles of a biological synapse, including excitatory postsynaptic current, paired-pulse facilitation, short-term plasticity, long-term plasticity, and spike-timing dependent plasticity. These properties originate from possible ion migration in the ion-rich perovskite matrix. This work has extensive applicability and practical significance in neuromorphic electronics.

  20. Alkaline quinone flow battery.

    PubMed

    Lin, Kaixiang; Chen, Qing; Gerhardt, Michael R; Tong, Liuchuan; Kim, Sang Bok; Eisenach, Louise; Valle, Alvaro W; Hardee, David; Gordon, Roy G; Aziz, Michael J; Marshak, Michael P

    2015-09-25

    Storage of photovoltaic and wind electricity in batteries could solve the mismatch problem between the intermittent supply of these renewable resources and variable demand. Flow batteries permit more economical long-duration discharge than solid-electrode batteries by using liquid electrolytes stored outside of the battery. We report an alkaline flow battery based on redox-active organic molecules that are composed entirely of Earth-abundant elements and are nontoxic, nonflammable, and safe for use in residential and commercial environments. The battery operates efficiently with high power density near room temperature. These results demonstrate the stability and performance of redox-active organic molecules in alkaline flow batteries, potentially enabling cost-effective stationary storage of renewable energy.

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

    SciTech Connect

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

    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.

  2. A set of alkali and alkaline-earth coordination polymers based on the ligand 2-(1H-benzotriazol-1-yl) acetic acid: Effects the radius of metal ions on structures and properties

    SciTech Connect

    Wang, Jin-Hua; Tang, Gui-Mei; Qin, Ting-Xiao; Yan, Shi-Chen; Wang, Yong-Tao; Cui, Yue-Zhi; Weng Ng, Seik

    2014-11-15

    Four new metal coordination complexes, namely, [Na(BTA)]{sub n} (1), [K{sub 2}(BTA){sub 2}(μ{sub 2}-H{sub 2}O)]{sub n} (2), and [M(BTA){sub 2}(H{sub 2}O){sub 2}]{sub n} (M=Ca(II) and Sr(II) for 3 and 4, respectively) [BTA=2-(1H-benzotriazol-1-yl) acetic anion], have been obtained under hydrothermal condition, by reacting the different alkali and alkaline-earth metal hydroxides with HBTA. Complexes 1–4 were structurally characterized by X-ray single-crystal diffraction, EA, IR, PXRD, and thermogravimetry analysis (TGA). These complexes display low-dimensional features displaying various two-dimensional (2D) and one-dimensional (1D) coordination motifs. Complex 1 displays a 2D layer with the thickness of 1.5 nm and possesses a topologic structure of a 11 nodal net with Schläfli symbol of (3{sup 18}). Complex 2 also shows a thick 2D sheet and its topologic structure is a 9 nodes with Schläfli symbol of (3{sup 11}×4{sup 2}). Complexes 3 and 4 possess a 1D linear chain and further stack via hydrogen bonding interactions to generate a three-dimensional supramolecular architecture. These results suggest that both the coordination preferences of the metal ions and the versatile nature of this flexible ligand play a critical role in the final structures. The luminescent spectra show strong emission intensities in complexes 1–4, which display violet photoluminescence. Additionally, ferroelectric, dielectric and nonlinear optic (NLO) second-harmonic generation (SHG) properties of 2 are discussed in detail. - Graphical abstract: A set of alkali and alkaline-earth metal coordination polymers were hydrothermally synthesized by 2-(1H-benzotriazol-1-yl)acetic acid, displaying interesting topologic motifs from two-dimension to one-dimension and specific physical properties. - Highlights: • Alkali and alkaline-earth metal coordination polymers have been obtained. • The ligand 2-(1H-benzotriazol-1-yl)acetic acid has been adopted. • The two-dimensional and one

  3. TRANSURANIC METAL HALIDES AND A PROCESS FOR THE PRODUCTION THEREOF

    DOEpatents

    Fried, S.

    1951-03-20

    Halides of transuranic elements are prepared by contacting with aluminum and a halogen, or with an aluminum halide, a transuranic metal oxide, oxyhalide, halide, or mixture thereof at an elevated temperature.

  4. Metal halide perovskite light emitters

    PubMed Central

    Kim, Young-Hoon; Cho, Himchan; Lee, Tae-Woo

    2016-01-01

    Twenty years after layer-type metal halide perovskites were successfully developed, 3D metal halide perovskites (shortly, perovskites) were recently rediscovered and are attracting multidisciplinary interest from physicists, chemists, and material engineers. Perovskites have a crystal structure composed of five atoms per unit cell (ABX3) with cation A positioned at a corner, metal cation B at the center, and halide anion X at the center of six planes and unique optoelectronic properties determined by the crystal structure. Because of very narrow spectra (full width at half-maximum ≤20 nm), which are insensitive to the crystallite/grain/particle dimension and wide wavelength range (400 nm ≤ λ ≤ 780 nm), perovskites are expected to be promising high-color purity light emitters that overcome inherent problems of conventional organic and inorganic quantum dot emitters. Within the last 2 y, perovskites have already demonstrated their great potential in light-emitting diodes by showing high electroluminescence efficiency comparable to those of organic and quantum dot light-emitting diodes. This article reviews the progress of perovskite emitters in two directions of bulk perovskite polycrystalline films and perovskite nanoparticles, describes current challenges, and suggests future research directions for researchers to encourage them to collaborate and to make a synergetic effect in this rapidly emerging multidisciplinary field. PMID:27679844

  5. Counterion influence on the vibrational wavenumbers in ternary and quaternary metal hydride salts, A2MH6 (A = alkali metal, alkaline earth, and lanthanides; M = Ir, Fe, Ru, Os, Pt, Mn).

    PubMed

    Gilson, Denis F R; Moyer, Ralph O

    2012-02-06

    The wavenumbers of the ν(3) metal-hydrogen stretching mode (T(1u)) in the IR spectra of both ternary and quaternary hexahydrido salts of transition metals from groups 7 to 10 ([Mn(I)H(6)](5-), [Fe(II)H(6)](4-), [Ru(II)H(6)](4-), [Os(II)H(6)](4-), [Ir(III)H(6)](3-), and [Pt(IV)H(6)](2-)) depend linearly upon the ionization energies of the counterions (alkali metal, alkaline earth, and lanthanide) with a separate line for each metal. This relationship provides quantitative support for the charge-transfer mechanism for explaining the stabilities of these compounds.

  6. Effect of alkaline earth oxides on the physical and spectroscopic properties of Dy3+- doped Li2O-B2O3 glasses for white emitting material application

    NASA Astrophysics Data System (ADS)

    Shamshad, L.; Rooh, G.; Kirdsiri, K.; Srisittipokakun, N.; Damdee, B.; Kim, H. J.; Kaewkhao, J.

    2017-02-01

    Li2O-MO-B2O3:0.5Dy2O3 glasses mixed with four different alkaline earth modifier oxides MgO, CaO, SrO and BaO were synthesized by melt quench technique. Their physical properties like density, molar volume and refractive index were measured at room temperature and the effect of alkaline earth modifier oxides were studied. Also, optical absorption and photoluminescence spectra of these glasses have been acquired at room temperature. The Judd-Ofelt theory was effectively used to characterize these spectra and spectral intensities (ƒcal), Judd-Ofelt intensity parameters (Ω2, Ω4 and Ω6) and certain radiative properties have been determined. Radiative life-times (τR), branching ratios (βcal), and emission cross-sections (σp) and optical gain parameters (σp × τR) were calculated from the Judd-Ofelt intensity parameters and the variation in these parameters with the variation of glass matrix are discussed. Yellow/Blue (Y/B) ratio and chromacity color coordinates (x,y) are calculated from the emission spectra which indicates the white light generation from all the investigated samples. The correlated color temperature (CCT) for the studied glasses is found to be 4418 K. The fluorescence decay time (τexp) of the 4F9/2 level of Dy3+ has been measured from the decay profiles and compared with calculated lifetimes (τcal). Among all the studied glass matrices, the glass containing BaO exhibits high value of branching ratio, large emission cross-section and high optical gain parameter for 6F9/2 → 6H13 at 575 nm. The results indicates the suitability of all the studied glasses for laser action and white light generation.

  7. Cohesive Energy-Lattice Constant and Bulk Modulus-Lattice Constant Relationships: Alkali Halides, Ag Halides, Tl Halides

    NASA Technical Reports Server (NTRS)

    Schlosser, Herbert

    1992-01-01

    In this note we present two expressions relating the cohesive energy, E(sub coh), and the zero pressure isothermal bulk modulus, B(sub 0), of the alkali halides. Ag halides and TI halides, with the nearest neighbor distances, d(sub nn). First, we show that the product E(sub coh)d(sub 0) within families of halide crystals with common crystal structure is to a good approximation constant, with maximum rms deviation of plus or minus 2%. Secondly, we demonstrate that within families of halide crystals with a common cation and common crystal structure the product B(sub 0)d(sup 3.5)(sub nn) is a good approximation constant, with maximum rms deviation of plus or minus 1.36%.

  8. Synthesis of aryl halides via organoborane chemistry

    SciTech Connect

    Kabalka, G.W.; Sastry, K.A.R.; Sastry, U.; Somayaji, V.

    1982-01-01

    A method for the rapid synthesis of a variety of substituted aryl halides by the reaction of organoboranes with halide ions in the presence of chloramine-T is described in detail. The products were purified by column chromatography on silica gel using a mixture of petroleum ether-ethyl acetate as eluent.

  9. Freeze Enhanced Halate Halide Reactions

    NASA Astrophysics Data System (ADS)

    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. Hygroscopicity Evaluation of Halide Scintillators

    SciTech Connect

    Zhuravleva, M; Stand, L; Wei, H; Hobbs, C. L.; Boatner, Lynn A; Ramey, Joanne Oxendine; Burger, Arnold; Rowe, E; Bhattacharya, P.; Tupitsyn, E; Melcher, Charles L

    2014-01-01

    A collaborative study of relative hygroscopicity of anhydrous halide scintillators grown at various laboratories is presented. We have developed a technique to evaluate moisture sensitivity of both raw materials and grown crystals, in which the moisture absorption rate is measured using a gravimetric analysis. Degradation of the scintillation performance was investigated by recording gamma-ray spectra and monitoring the photopeak position, count rate and energy resolution. The accompanying physical degradation of the samples exposed to ambient atmosphere was photographically recorded as well. The results were compared with ben

  11. Abiotic Formation of Methyl Halides in the Terrestrial Environment

    NASA Astrophysics Data System (ADS)

    Keppler, F.

    2011-12-01

    Methyl chloride and methyl bromide are the most abundant chlorine and bromine containing organic compounds in the atmosphere. Since both compounds have relatively long tropospheric lifetimes they can effectively transport halogen atoms from the Earth's surface, where they are released, to the stratosphere and following photolytic oxidation form reactive halogen gases that lead to the chemical destruction of ozone. Methyl chloride and methyl bromide account for more than 20% of the ozone-depleting halogens delivered to the stratosphere and are predicted to grow in importance as the chlorine contribution to the stratosphere from anthropogenic CFCs decline. Today methyl chloride and methyl bromide originate mainly from natural sources with only a minor fraction considered to be of anthropogenic origin. However, until as recently as 2000 most of the methyl chloride and methyl bromide input to the atmosphere was considered to originate from the oceans, but investigations in recent years have clearly demonstrated that terrestrial sources such as biomass burning, wood-rotting fungi, coastal salt marshes, tropical vegetation and organic matter degradation must dominate the atmospheric budgets of these trace gases. However, many uncertainties still exist regarding strengths of both sources and sinks, as well as the mechanisms of formation of these naturally occurring halogenated gases. A better understanding of the atmospheric budget of both methyl chloride and methyl bromide is therefore required for reliable prediction of future ozone depletion. Biotic and abiotic methylation processes of chloride and bromide ion are considered to be the dominant pathways of formation of these methyl halides in nature. In this presentation I will focus on abiotic formation processes in the terrestrial environment and the potential parameters that control their emissions. Recent advances in our understanding of the abiotic formation pathway of methyl halides will be discussed. This will

  12. Vapor-liquid partitioning of alkaline earth and transition metals in NaCl-dominated hydrothermal fluids: An experimental study from 360 to 465 °C, near-critical to halite saturated conditions

    NASA Astrophysics Data System (ADS)

    Pester, Nicholas J.; Ding, Kang; Seyfried, William E.

    2015-11-01

    Multi-phase fluid flow is a common occurrence in magmatic hydrothermal systems; and extensive modeling efforts using currently established P-V-T-x properties of the NaCl-H2O system are impending. We have therefore performed hydrothermal flow experiments (360-465 °C) to observe vapor-liquid partitioning of alkaline earth and first row transition metals in NaCl-dominated source solutions. The data allow extraction of partition coefficients related to the intrinsic changes in both chlorinity and density along the two-phase solvus. The coefficients yield an overall decrease in vapor affinity in the order Cu(I) > Na > Fe(II) > Zn > Ni(II) ⩾ Mg ⩾ Mn(II) > Co(II) > Ca > Sr > Ba, distinguished with 95% confidence for vapor densities greater than ∼0.2 g/cm3. The alkaline earth metals are limited to purely electrostatic interactions with Cl ligands, resulting in an excellent linear correlation (R2 > 0.99) between their partition coefficients and respective ionic radii. Though broadly consistent with this relationship, relative behavior of the transition metals is not well resolved, being likely obscured by complex bonding processes and the potential participation of Na in the formation of tetra-chloro species. At lower densities (at/near halite saturation) partitioning behavior of all metals becomes highly non-linear, where M/Cl ratios in the vapor begin to increase despite continued decreases in chlorinity and density. We refer to this phenomenon as "volatility", which is broadly associated with substantial increases in the HCl/NaCl ratio (eventually to >1) due to hydrolysis of NaCl. Some transition metals (e.g., Fe, Zn) exhibit volatility prior to halite stability, suggesting a potential shift in vapor speciation relative to nearer critical regions of the vapor-liquid solvus. The chemistry of deep-sea hydrothermal fluids appears affected by this process during magmatic events, however, our results do not support suggestions of subseafloor halite precipitation

  13. Kinetic study of the α-tocopherol-regeneration reaction of ubiquinol-10 in methanol and acetonitrile solutions: notable effect of the alkali and alkaline earth metal salts on the reaction rates.

    PubMed

    Mukai, Kazuo; Oi, Masanori; Ouchi, Aya; Nagaoka, Shin-ichi

    2012-03-01

    A kinetic study of regeneration reaction of α-tocopherol (α-TocH) by ubiquinol-10 has been performed in the presence of four kinds of alkali and alkaline earth metal salts (LiClO(4), NaClO(4), NaI, and Mg(ClO(4))(2)) in methanol and acetonitrile solutions, using double-mixing stopped-flow spectrophotometry. The second-order rate constants (k(r)'s) for the reaction of α-tocopheroxyl (α-Toc•) radical with ubiquinol-10 increased and decreased notably with increasing concentrations of metal salts in methanol and acetonitrile, respectively. The k(r) values increased in the order of no metal salt < NaClO(4) ~ NaI < LiClO(4) < Mg(ClO(4))(2) at the same concentration of metal salts in methanol. On the other hand, in acetonitrile, the k(r) values decreased in the order of no metal salt > NaClO(4) ~ NaI > LiClO(4) > Mg(ClO(4))(2) at the same concentration of metal salts. The metal salts having a smaller ionic radius of cation and a larger charge of cation gave a larger k(r) value in methanol, and a smaller k(r) value in acetonitrile. The effect of anion was almost negligible in both the solvents. Notable effects of metal cations on the UV-vis absorption spectrum of α-Toc• radical were observed in aprotic acetonitrile solution, suggesting complex formation between α-Toc• and metal cations. On the other hand, effects of metal cations were negligible in protic methanol, suggesting that the complex formation between α-Toc• and metal cations is hindered by the hydrogen bond between α-Toc• and methanol molecules. The difference between the reaction mechanisms in methanol and acetonitrile solutions was discussed on the basis of the results obtained. High concentrations of alkali and alkaline earth metal salts coexist with α-TocH and ubiquinol-10 in plasma, blood, and many tissues, suggesting the contribution of the metal salts to the above regeneration reaction in biological systems.

  14. Synthesis, crystal and band structures, and optical properties of a new lanthanide-alkaline earth tellurium(IV) oxide: La{sub 2}Ba(Te{sub 3}O{sub 8})(TeO{sub 3}){sub 2}

    SciTech Connect

    Jiang Hailong; Kong Fang; Mao Jianggao

    2007-05-15

    A new quaternary lanthanide alkaline-earth tellurium(IV) oxide, La{sub 2}Ba(Te{sub 3}O{sub 8})(TeO{sub 3}){sub 2}, has been prepared by the solid-state reaction and structurally characterized. The compound crystallizes in monoclinic space group C2/c with a=19.119(3), b=5.9923(5), c=13.2970(19) A, {beta}=107.646(8){sup o}, V=1451.7(3) A{sup 3} and Z=4. La{sub 2}Ba(Te{sub 3}O{sub 8})(TeO{sub 3}){sub 2} features a 3D network structure in which the cationic [La{sub 2}Ba(TeO{sub 3}){sub 2}]{sup 4+} layers are cross-linked by Te{sub 3}O{sub 8} {sup 4-} anions. Both band structure calculation by the DFT method and optical diffuse reflectance spectrum measurements indicate that La{sub 2}Ba(Te{sub 3}O{sub 8})(TeO{sub 3}){sub 2} is a wide band-gap semiconductor. - Graphical abstract: A new quaternary lanthanide alkaline-earth tellurium(IV) oxide, La{sub 2}Ba(Te{sub 3}O{sub 8})(TeO{sub 3}){sub 2}, has been prepared by the solid-state reaction and structurally characterized. The structure of La{sub 2}Ba(Te{sub 3}O{sub 8})(TeO{sub 3}){sub 2} is 3D network in which the cationic [La{sub 2}Ba(TeO{sub 3}){sub 2}]{sup 4+} layers are cross-linked by Te{sub 3}O{sub 8} {sup 4-} anions. Both band structure calculation by the DFT method and optical diffuse reflectance spectrum measurements indicate that La{sub 2}Ba(Te{sub 3}O{sub 8})(TeO{sub 3}){sub 2} is a wide band-gap semiconductor.

  15. IR spectroscopy of aqueous alkali halide solutions: Pure salt-solvated water spectra and hydration numbers

    NASA Astrophysics Data System (ADS)

    Max, Jean-Joseph; Chapados, Camille

    2001-08-01

    Extrapolation techniques were used to obtain pure salt-solvated water spectra from the attenuated total reflection infrared spectra (ATR-IR) of aqueous solutions of the nine alkali halide salts LiCl, NaCl, KCl, CsCl, NaBr, KBr, NaI, KI, and CsI and the alkaline-earth chloride salt MgCl2. These salts ionize completely in water. The ions by themselves do not absorb in the IR, but their interactions with water can be observed and analyzed. A pure salt-solvated water spectrum is easier to analyze than that of a combined solution of pure water and salt-solvated water. Although the salt-solvated water spectra examined have distinctive signatures, they can be classified in three categories: those similar to NaCl; those not similar to NaCl; and MgCl2, in a class by itself. Each of the pure salt-solvated water spectra differs from that of liquid water, though the number of bands is the same. From the Gaussian band fitting, we found that the positions of the bands were fairly constant, whereas their intensities differed. The salt hydration numbers were determined: for NaCl, KCl, NaBr, KBr, and CsI solutions it is 5; for KI and MgCL2 it is 4; for NaI it is 3.5; for CsCl it is 3; and for LiCl it is 2. From these results we found that each pair of ions (monoatomic ions) of the ten salt solutions studied are close bound and form a complex in a cluster organization with a fixed number of water molecules.

  16. Shallow halogen vacancies in halide optoelectronic materials

    DOE PAGES

    Shi, Hongliang; Du, Mao -Hua

    2014-11-05

    Halogen vacancies (VH) are usually deep color centers (F centers) in halides and can act as major electron traps or recombination centers. The deep VH contributes to the typically poor carrier transport properties in halides. However, several halides have recently emerged as excellent optoelectronic materials, e.g., CH3NH3PbI3 and TlBr. Both CH3NH3PbI3 and TlBr have been found to have shallow VH, in contrast to commonly seen deep VH in halides. In this paper, several halide optoelectronic materials, i.e., CH3NH3PbI3, CH3NH3SnI3 (photovoltaic materials), TlBr, and CsPbBr3, (gamma-ray detection materials) are studied to understand the material chemistry and structure that determine whether VHmore » is a shallow or deep defect in a halide material. It is found that crystal structure and chemistry of ns2 ions both play important roles in creating shallow VH in halides such as CH3NH3PbI3, CH3NH3SnI3, and TlBr. The key to identifying halides with shallow VH is to find the right crystal structures and compounds that suppress cation orbital hybridization at VH, such as those with long cation-cation distances and low anion coordination numbers, and those with crystal symmetry that prevents strong hybridization of cation dangling bond orbitals at VH. Furthermore, the results of this paper provide insight and guidance to identifying halides with shallow VH as good electronic and optoelectronic materials.« less

  17. Shallow halogen vacancies in halide optoelectronic materials

    NASA Astrophysics Data System (ADS)

    Shi, Hongliang; Du, Mao-Hua

    2014-11-01

    Halogen vacancies (VH ) are usually deep color centers (F centers) in halides and can act as major electron traps or recombination centers. The deep VH contributes to the typically poor carrier transport properties in halides. However, several halides have recently emerged as excellent optoelectronic materials, e.g., C H3N H3Pb I3 and TlBr. Both C H3N H3Pb I3 and TlBr have been found to have shallow VH , in contrast to commonly seen deep VH in halides. In this paper, several halide optoelectronic materials, i.e., C H3N H3Pb I3 , C H3N H3Sn I3 (photovoltaic materials), TlBr, and CsPbB r3 (gamma-ray detection materials) are studied to understand the material chemistry and structure that determine whether VH is a shallow or deep defect in a halide material. It is found that crystal structure and chemistry of n s2 ions both play important roles in creating shallow VH in halides such as C H3N H3Pb I3 , C H3N H3Sn I3 , and TlBr. The key to identifying halides with shallow VH is to find the right crystal structures and compounds that suppress cation orbital hybridization at VH , such as those with large cation-cation distances and low anion coordination numbers and those with crystal symmetry that prevents strong hybridization of cation dangling bond orbitals at VH . The results of this paper provide insight and guidance to identifying halides with shallow VH as good electronic and optoelectronic materials.

  18. Hydrothermal synthesis and crystal structure of two new hydrated alkaline earth metal borates Sr3B6O11(OH)2 and Ba3B6O11(OH)2.

    PubMed

    Heyward, Carla; McMillen, Colin; Kolis, Joseph

    2012-04-02

    Two new hydrated borates Sr(3)B(6)O(11)(OH)(2) (1) and Ba(3)B(6)O(11)(OH)(2) (2) were hydrothermally synthesized. Their structures were determined by single-crystal X-ray diffraction and further characterized by IR, powder XRD, and DSC/TGA. Compound 1 crystallizes in the triclinic space group P-1 with unit cell parameters of a = 6.6275(13) Å, b = 6.6706(13) Å, c = 11.393(2) Å, α = 91.06(3)°, β = 94.50(3)°, and γ = 93.12(3)°, while compound 2 crystallizes in the noncentrosymmetric monoclinic space group Pc with a = 6.958(14) Å, b = 7.024(14) Å, c = 11.346(2) Å, and β = 90.10(3)°. In spite of the differences in symmetry and packing of the borate chains, both structures consist of the same fundamental building block (FBB) of a [B(6)O(11)(OH)(2)](-6) unit and three unique alkaline earth metal atoms.

  19. Spin-Spin Interactions in the Oxides A(3)M'MO(6) (M = Rh, Ir; A = Ca, Sr; M' = Alkaline Earth, Zn, Cd, Na) of the K(4)CdCl(6) Structure Type Examined by Electronic Structure Calculations.

    PubMed

    Lee, K.-S.; Koo, H.-J.; Whangbo, M.-H.

    1999-05-03

    The oxides A(3)M'MO(6) (M = Rh, Ir; A = Ca, Sr; M' = alkaline earth, Zn, Cd) of the K(4)CdCl(6) structure type consist of isolated (MO(6))(8)(-) octahedral anions and exhibit an antiferromagnetic ordering at low temperatures. The spin-spin interactions in these oxides, Ca(3)NaMO(6) (M = Ir, Ru), and Sr(3)NaRuO(6) were examined by calculating how strongly the t(2g)-block levels of adjacent (MO(6))((6+)(n)()())(-) (n = 1, 2) anions interact in the presence and absence of the intervening cations A(2+) and M' (n)()(+) (n = 1, 2). Our calculations show that the spin-spin interactions in these oxides are three-dimensional, and the superexchange interactions occur mainly through the short intrachain and interchain M-O.O-M linkages. When the M(n)()(+) cation is very small compared with the A(2+) cation, the intrachain interaction is substantially stronger than the interchain interaction. The opposite is found when the sizes of the M(n)()(+) and A(2+) cations become similar.

  20. Binding to Redox-Inactive Alkali and Alkaline Earth Metal Ions Strongly Deactivates the C-H Bonds of Tertiary Amides toward Hydrogen Atom Transfer to Reactive Oxygen Centered Radicals.

    PubMed

    Salamone, Michela; Carboni, Giulia; Mangiacapra, Livia; Bietti, Massimo

    2015-09-18

    The effect of alkali and alkaline earth metal ions on the reactions of the cumyloxyl radical (CumO(•)) with N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMA) was studied by laser flash photolysis. In acetonitrile, a >2 order of magnitude decrease in the rate constant for hydrogen atom transfer (HAT) from the C-H bonds of these substrates (kH) was measured after addition of Li(+). This behavior was explained in terms of a strong interaction between Li(+) and the oxygen atom of both DMF and DMA that increases the extent of positive charge on the amide, leading to C-H bond deactivation toward HAT to the electrophilic radical CumO(•). Similar effects were observed after addition of Ca(2+), which was shown to strongly bind up to four equivalents of the amide substrates. With Mg(2+), weak C-H deactivation was observed for the first two substrate equivalents followed by stronger deactivation for two additional equivalents. No C-H deactivation was observed in DMSO after addition of Li(+) and Mg(2+). These results point toward the important role played by metal ion Lewis acidity and solvent Lewis basicity, indicating that C-H deactivation can be modulated by varying the nature of the metal cation and solvent and allowing for careful control over the HAT reactivity of amide substrates.

  1. Effect of high-energy electron irradiation in an electron microscope column on fluorides of alkaline earth elements (CaF2, SrF2, and BaF2)

    NASA Astrophysics Data System (ADS)

    Nikolaichik, V. I.; Sobolev, B. P.; Zaporozhets, M. A.; Avilov, A. S.

    2012-03-01

    The effect of high-energy (150 eV) electron irradiation in an electron microscope column on crystals of fluorides of alkaline earth elements CaF2, SrF2, and BaF2 is studied. During structural investigations by electron diffraction and electron microscopy, the electron irradiation causes chemical changes in MF2 crystals such as the desorption of fluorine and the accumulation of oxygen in the irradiated area with the formation of oxide MO. The fluorine desorption rate increases significantly when the electron-beam density exceeds the threshold value of ˜2 × 103 pA/cm2). In BaF2 samples, the transformation of BaO into Ba(OH)2 was observed when irradiation stopped. The renewal of irradiation is accompanied by the inverse transformation of Ba(OH)2 into BaO. In the initial stage of irradiation of all MF2 compounds, the oxide phase is in the single-crystal state with a lattice highly matched with the MF2 matrix. When the irradiation dose is increased, the oxide phase passes to the polycrystalline phase. Gaseous products of MF2 destruction (in the form of bubbles several nanometers in diameter) form a rectangular array with a period of ˜20 nm in the sample.

  2. Vibronic transitions in the alkali-metal (Li, Na, K, Rb) - alkaline-earth-metal (Ca, Sr) series: A systematic analysis of de-excitation mechanisms based on the graphical mapping of Frank-Condon integrals

    NASA Astrophysics Data System (ADS)

    Pototschnig, Johann V.; Meyer, Ralf; Hauser, Andreas W.; Ernst, Wolfgang E.

    2017-02-01

    Research on ultracold molecules has seen a growing interest recently in the context of high-resolution spectroscopy and quantum computation. After forming weakly bound molecules from atoms in cold collisions, the preparation of molecules in low vibrational levels of the ground state is experimentally challenging, and typically achieved by population transfer using excited electronic states. Accurate potential energy surfaces are needed for a correct description of processes such as the coherent de-excitation from the highest and therefore weakly bound vibrational levels in the electronic ground state via couplings to electronically excited states. This paper is dedicated to the vibrational analysis of potentially relevant electronically excited states in the alkali-metal (Li, Na, K, Rb)- alkaline-earth metal (Ca,Sr) diatomic series. Graphical maps of Frank-Condon overlap integrals are presented for all molecules of the group. By comparison to overlap graphics produced for idealized potential surfaces, we judge the usability of the selected states for future experiments on laser-enhanced molecular formation from mixtures of quantum degenerate gases.

  3. Oxidation of hydrogen halides to elemental halogens

    DOEpatents

    Rohrmann, Charles A.; Fullam, Harold T.

    1985-01-01

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

  4. Reflection silver-halide gelatin holograms

    NASA Astrophysics Data System (ADS)

    Usanov, Yuri E.; Vavilova, Ye. A.; Kosobokova, N. L.; Shevtsov, Michail K.

    1991-02-01

    A new principle of reflection silverhalide gelatin (SHG) holograms generation is presented. The formation mechanism of the micro-cavity structure of holographic gratings is investigated. Based on the principle discussed here three methods of processing are suggested for making highly efficient SHG reflection holograms in the blue the green and the red regions of spectra with properties similar to those of conventional dichromated gelatin (DCG) holograms. 2. SHG HOLOGRAMS AND ANALYSIS OF THE PRINCIPAL OF THEIR FABRICATION Optical properties of DCG holograms and high light sensitivity of silver halide materials in the whole visible spectrum range can be combined in SHG holograms in which light field interference pattern recording is realized on silver halide grains while the light diffraction during the reconstruction takes place on a gelatin layer similar to DCG layer having a refractive index modulation. There exist a number of methods for transforming a ''silver'' structure into refracted index modulation structure. They are based on selective hardening of silver-halide layer gelatin. According to Pennington et. al. [1] selective hardening takes place as a result of the effect of laser or UV light on a silver halide developed fixed bleached and ammonium dichromate sensitized. A gelatin in isophase grating planes is hardened to a less degree that between planes due to high adsorption of a halide silver. After the removal of halide silver from the layer during the next fixing process

  5. Epitaxial Halide Perovskite Lateral Double Heterostructure.

    PubMed

    Wang, Yiping; Chen, Zhizhong; Deschler, Felix; Sun, Xin; Lu, Toh-Ming; Wertz, Esther A; Hu, Jia-Mian; Shi, Jian

    2017-03-28

    Epitaxial III-V semiconductor heterostructures are key components in modern microelectronics, electro-optics, and optoelectronics. With superior semiconducting properties, halide perovskite materials are rising as promising candidates for coherent heterostructure devices. In this report, spinodal decomposition is proposed and experimentally implemented to produce epitaxial double heterostructures in halide perovskite system. Pristine epitaxial mixed halide perovskites rods and films were synthesized via van der Waals epitaxy by chemical vapor deposition method. At room temperature, photon was applied as a knob to regulate the kinetics of spinodal decomposition and classic coarsening. By this approach, halide perovskite double heterostructures were created carrying epitaxial interfaces and outstanding optical properties. Reduced Fröhlich electron-phonon coupling was discovered in coherent halide double heterostructure, which is hypothetically attributed to the classic phonon confinement effect widely existing in III-V double heterostructures. As a proof-of-concept, our results suggest that halide perovskite-based epitaxial heterostructures may be promising for high-performance and low-cost optoelectronics, electro-optics, and microelectronics. Thus, ultimately, for practical device applications, it may be worthy to pursue these heterostructures via conventional vapor phase epitaxy approaches widely practised in III-V field.

  6. Alkaline sorbent injection for mercury control

    DOEpatents

    Madden, Deborah A.; Holmes, Michael J.

    2002-01-01

    A mercury removal system for removing mercury from combustion flue gases is provided in which alkaline sorbents at generally extremely low stoichiometric molar ratios of alkaline earth or an alkali metal to sulfur of less than 1.0 are injected into a power plant system at one or more locations to remove at least between about 40% and 60% of the mercury content from combustion flue gases. Small amounts of alkaline sorbents are injected into the flue gas stream at a relatively low rate. A particulate filter is used to remove mercury-containing particles downstream of each injection point used in the power plant system.

  7. Alkaline sorbent injection for mercury control

    DOEpatents

    Madden, Deborah A.; Holmes, Michael J.

    2003-01-01

    A mercury removal system for removing mercury from combustion flue gases is provided in which alkaline sorbents at generally extremely low stoichiometric molar ratios of alkaline earth or an alkali metal to sulfur of less than 1.0 are injected into a power plant system at one or more locations to remove at least between about 40% and 60% of the mercury content from combustion flue gases. Small amounts of alkaline sorbents are injected into the flue gas stream at a relatively low rate. A particulate filter is used to remove mercury-containing particles downstream of each injection point used in the power plant system.

  8. Dimming of metal halide lamps

    NASA Astrophysics Data System (ADS)

    Schurer, Kees

    1994-03-01

    We ran some tests on the effect of dimming of metal halide (MH) lamps upon the stability and the spectral quality of the light output. Lamps used were a new Philips lamp HPI-T 250W, a similar Philips lamp with a few thousand burning hours and a new Osram lamp HQI-T 250W/D. The ballast was a BBC type DJ 250/2KS, the starter a BAS TORGI type MZN 250 SE and the dimmer an Elstrom Control System type ERHQ-T 250. Power was derived from a Philips stabilizer, type PE 1602. Lamp output was monitored with a PAR meter. Spectra were taken at 100% and at 50% output as measured with the PAR meter. Lamps were allowed to stabilize at any setting for 30 minutes before measurements were made. Lamp manufacturers advise against dimming for fear of poor stability and intolerable changes of the spectrum. However, none of the lamps showed a decrease in stability, no flicker or wandering of the discharge, and the changes of the spectrum were not negligible, but certainly not dramatic. Lamps of either manufacture retain their white color, relative peak heights of spectral lines did shift, but no gaps in the spectrum occurred. Spectra taken at 50% with 30 minutes intervals coincided. Differences between the new and the older Philips lamp were noticeable, but not really significant.

  9. Dimming of metal halide lamps

    NASA Technical Reports Server (NTRS)

    Schurer, Kees

    1994-01-01

    We ran some tests on the effect of dimming of metal halide (MH) lamps upon the stability and the spectral quality of the light output. Lamps used were a new Philips lamp HPI-T 250W, a similar Philips lamp with a few thousand burning hours and a new Osram lamp HQI-T 250W/D. The ballast was a BBC type DJ 250/2KS, the starter a BAS TORGI type MZN 250 SE and the dimmer an Elstrom Control System type ERHQ-T 250. Power was derived from a Philips stabilizer, type PE 1602. Lamp output was monitored with a PAR meter. Spectra were taken at 100% and at 50% output as measured with the PAR meter. Lamps were allowed to stabilize at any setting for 30 minutes before measurements were made. Lamp manufacturers advise against dimming for fear of poor stability and intolerable changes of the spectrum. However, none of the lamps showed a decrease in stability, no flicker or wandering of the discharge, and the changes of the spectrum were not negligible, but certainly not dramatic. Lamps of either manufacture retain their white color, relative peak heights of spectral lines did shift, but no gaps in the spectrum occurred. Spectra taken at 50% with 30 minutes intervals coincided. Differences between the new and the older Philips lamp were noticeable, but not really significant.

  10. Alkali-metal/alkaline-earth-metal fluorine beryllium borate NaSr3Be3B3O9F4 with large nonlinear optical properties in the deep-ultraviolet region

    NASA Astrophysics Data System (ADS)

    Reshak, A. H.; Huang, Hongwei; Kamarudin, H.; Auluck, S.

    2015-02-01

    The linear optical response and second harmonic generation (SHG) in alkali-metal/alkaline-earth-metal fluorine beryllium borate NaSr3Be3B3O9F4 are investigated by means of density functional theory. Calculations are performed using four types of exchange correlations: Ceperley-Alder local density approximation, Perdew Burke and Ernzerhof general gradient approximation, Engel-Vosko generalized gradient approximation, and the recently modified Becke-Johnson potential (mBJ). The mBJ approach brings the calculated band gap (7.20 eV) in excellent agreement with the experimental one (7.28 eV). The calculated values of the uniaxial anisotropy δɛ=-0.076 and the birefringence Δn (0 ) =0.052 indicate considerable anisotropy in the linear optical properties, which makes it favorable for the second harmonic generation. The dominant component of the second harmonic generation is χ111(2)(ω) . The value of |χ111(2)(ω) | is about 1.2 pm/V at λ = 1064 nm in agreement with previous calculations. To analyze the origin of the high SHG of NaSr3Be3B3O9F4 single crystals, we have correlated the features of |χ111(2)(ω) | spectra with the features of ɛ2(ω) spectra as a function of ω/2 and ω. From the calculated dominant component |χ111(2)(ω) | , we find that the microscopic first hyperpolarizability, β111 , the vector components along the dipole moment direction is 0.5 × 10-30 esu at static limit and 0.6 × 10-30 esu at λ = 1064 nm.

  11. The influence of different alkaline earth oxides on the structural and optical properties of undoped, Ce-doped, Sm-doped, and Sm/Ce co-doped lithium alumino-phosphate glasses

    NASA Astrophysics Data System (ADS)

    Othman, H. A.; Arzumanyan, G. M.; Möncke, D.

    2016-12-01

    Undoped, singly Sm doped, Ce doped, and Sm/Ce co-doped lithium alumino-phosphate glasses with different alkaline earth modifiers were prepared by melt quenching. The structure of the prepared glasses was investigated by FT-IR and Raman, as well as by optical spectroscopy. The effect of the optical basicity of the host glass matrix on the added active dopants was studied, as was the effect doping had on the phosphate structural units. The optical edge shifts toward higher wavelengths with an increase in the optical basicity due to the increased polarizability of the glass matrix, but also with increasing CeO2 concentration as a result of Ce3+/Ce4+ inter valence charge transfer (IV-CT) absorption. The optical band gap for direct and indirect allowed transitions was calculated for the undoped glasses. The glass sample containing Mg2+ modifier ions is found to have the highest value (4.16 eV) for the optical band gap while Ba2+ has the lowest value (3.61 eV). The change in the optical band gap arises from the structural changes and the overall polarizability (optical basicity). Refractive index, molar refractivity Rm and molar polarizability αm values increase with increasing optical basicity of the glasses. The characteristic absorption peaks of Sm3+ were also investigated. For Sm/Ce co-doped glasses, especially at high concentration of CeO2, the absorption of Ce3+ hinders the high energy absorption of Sm3+ and this effect becomes more obvious with increasing optical basicity.

  12. Structural effects in molecular metal halides.

    PubMed

    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

  13. Shallow halogen vacancies in halide optoelectronic materials

    SciTech Connect

    Shi, Hongliang; Du, Mao -Hua

    2014-11-05

    Halogen vacancies (VH) are usually deep color centers (F centers) in halides and can act as major electron traps or recombination centers. The deep VH contributes to the typically poor carrier transport properties in halides. However, several halides have recently emerged as excellent optoelectronic materials, e.g., CH3NH3PbI3 and TlBr. Both CH3NH3PbI3 and TlBr have been found to have shallow VH, in contrast to commonly seen deep VH in halides. In this paper, several halide optoelectronic materials, i.e., CH3NH3PbI3, CH3NH3SnI3 (photovoltaic materials), TlBr, and CsPbBr3, (gamma-ray detection materials) are studied to understand the material chemistry and structure that determine whether VH is a shallow or deep defect in a halide material. It is found that crystal structure and chemistry of ns2 ions both play important roles in creating shallow VH in halides such as CH3NH3PbI3, CH3NH3SnI3, and TlBr. The key to identifying halides with shallow VH is to find the right crystal structures and compounds that suppress cation orbital hybridization at VH, such as those with long cation-cation distances and low anion coordination numbers, and those with crystal symmetry that prevents strong hybridization of cation dangling bond orbitals at VH. Furthermore, the results of this paper provide insight and guidance to identifying halides with shallow VH as good electronic and optoelectronic materials.

  14. The Remarkable Reactivity of Aryl Halides with Nucleophiles

    ERIC Educational Resources Information Center

    Bunnett, Joseph F.

    1974-01-01

    Discusses the reactivity of aryl halides with nucleophilic or basic reagents, including nucleophilic attacks on carbon, hydrogen, halogen, and arynes. Suggestions are made concerning revisions of the sections on aryl halide chemistry courses and the corresponding chapters in textbooks. (CC)

  15. Positron elastic scattering from alkaline earth targets

    NASA Astrophysics Data System (ADS)

    Poveda, Luis A.; Assafrão, Denise; Mohallem, José R.

    2016-07-01

    A previously reported model potential approach [Poveda et al., Phys. Rev. A 87, 052702 (2013)] was extended to study low energy positron elastic scattering from beryllium and magnesium. The cross sections were computed for energies ranging from 10-5 eV up to well above the positronium formation threshold. The present results are in good agreement with previous reports, including the prediction of a p-wave resonance in the cross section for magnesium. The emergence of this shape resonance is connected to a trend observed in the evolution of the partial wave cross section in going from Be to Mg target. This trend lead us to speculate that a sharp d-wave resonance should be observed in positron elastic scattering from calcium. The positron-target binding energies are investigated in detail, both using the scattering information and by direct computation of the bound state energies using the model potentials. Contribution to the Topical Issue "Advances in Positron and Electron Scattering", edited by Paulo Limao-Vieira, Gustavo Garcia, E. Krishnakumar, James Sullivan, Hajime Tanuma and Zoran Petrovic.Supplementary material in the form of one pdf file available from the Journal web page at http://dx.doi.org/10.1140/epjd/e2016-70120-y

  16. Alkaline earth stannates: The next silicon?

    SciTech Connect

    Ismail-Beigi, Sohrab Ahn, Charles H.; Walker, Frederick J.; Cheong, Sang-Wook; Rabe, Karin M.

    2015-06-01

    Semiconductor materials are being used in an increasingly diverse array of applications, with new device concepts being proposed each year for solar cells, flat-panel displays, sensors, memory, and spin transport. This rapid progress of invention outpaces the development of new semiconductor materials with the required properties and performance. In many applications, high carrier mobility at room temperature is required in addition to specific functional properties critical to the device concept. We review recent developments on high mobility stannate perovskite oxide materials and devices.

  17. Electrical Resistivity of Alkaline Earth Elements.

    DTIC Science & Technology

    1976-12-01

    and Alloys ," Volume 12 of Thermophysical Properties of Matter - The TPRC Data Series, Plenum Press, New York, 1440 pp., 1975. (T80643) 2. Matthiessen, A...1964. (E17556) 48. Seth, R. S. and Woods, S. B., "Electrical Resistivity and Deviations from Matthiessen’s Rule in Dilute Alloys of Aluminum , Cadmium...Resistance of Dilute Magnesium and Aluminum Alloys at Low Temperature," Can. J. of Phys. 38(3), 376-84, 1960. (E14737) 57. Schofield, F. H., "The

  18. PARAMAGNETIC PROPERTIES OF THE ALKALINE EARTH FLUORIDES.

    DTIC Science & Technology

    constants for Mn(2+) in CaF2 and SrF2 were measured over the temperature range 77 to 850K. In both cases the magnitude of the hyperfine coupling constant...decreases with increasing temperature; and the temperature dependance is stronger for SrF2 . The results have been interpreted using the Simanek-Orbach theory of a phonon-induced hyperfine field. (Author)

  19. Method for recovering hydrocarbons from molten metal halides

    DOEpatents

    Pell, Melvyn B.

    1979-01-01

    In a process for hydrocracking heavy carbonaceous materials by contacting such carbonaceous materials with hydrogen in the presence of a molten metal halide catalyst to produce hydrocarbons having lower molecular weights and thereafter recovering the hydrocarbons so produced from the molten metal halide, an improvement comprising injecting into the spent molten metal halide, a liquid low-boiling hydrocarbon stream is disclosed.

  20. Atomic Resolution Imaging of Halide Perovskites.

    PubMed

    Yu, Yi; Zhang, Dandan; Kisielowski, Christian; Dou, Letian; Kornienko, Nikolay; Bekenstein, Yehonadav; Wong, Andrew B; Alivisatos, A Paul; Yang, Peidong

    2016-12-14

    The radiation-sensitive nature of halide perovskites has hindered structural studies at the atomic scale. We overcome this obstacle by applying low dose-rate in-line holography, which combines aberration-corrected high-resolution transmission electron microscopy with exit-wave reconstruction. This technique successfully yields the genuine atomic structure of ultrathin two-dimensional CsPbBr3 halide perovskites, and a quantitative structure determination was achieved atom column by atom column using the phase information of the reconstructed exit-wave function without causing electron beam-induced sample alterations. An extraordinarily high image quality enables an unambiguous structural analysis of coexisting high-temperature and low-temperature phases of CsPbBr3 in single particles. On a broader level, our approach offers unprecedented opportunities to better understand halide perovskites at the atomic level as well as other radiation-sensitive materials.

  1. Recent advances in technetium halide chemistry.

    PubMed

    Poineau, Frederic; Johnstone, Erik V; Czerwinski, Kenneth R; Sattelberger, Alfred P

    2014-02-18

    Transition metal binary halides are fundamental compounds, and the study of their structure, bonding, and other properties gives chemists a better understanding of physicochemical trends across the periodic table. One transition metal whose halide chemistry is underdeveloped is technetium, the lightest radioelement. For half a century, the halide chemistry of technetium has been defined by three compounds: TcF6, TcF5, and TcCl4. The absence of Tc binary bromides and iodides in the literature was surprising considering the existence of such compounds for all of the elements surrounding technetium. The common synthetic routes that scientists use to obtain binary halides of the neighboring elements, such as sealed tube reactions between elements and flowing gas reactions between a molecular complex and HX gas (X = Cl, Br, or I), had not been reported for technetium. In this Account, we discuss how we used these routes to revisit the halide chemistry of technetium. We report seven new phases: TcBr4, TcBr3, α/β-TcCl3, α/β-TcCl2, and TcI3. Technetium tetrachloride and tetrabromide are isostructural to PtX4 (X = Cl or Br) and consist of infinite chains of edge-sharing TcX6 octahedra. Trivalent technetium halides are isostructural to ruthenium and molybdenum (β-TcCl3, TcBr3, and TcI3) and to rhenium (α-TcCl3). Technetium tribromide and triiodide exhibit the TiI3 structure-type and consist of infinite chains of face-sharing TcX6 (X = Br or I) octahedra. Concerning the trichlorides, β-TcCl3 crystallizes with the AlCl3 structure-type and consists of infinite layers of edge-sharing TcCl6 octahedra, while α-TcCl3 consists of infinite layers of Tc3Cl9 units. Both phases of technetium dichloride exhibit new structure-types that consist of infinite chains of [Tc2Cl8] units. For the technetium binary halides, we studied the metal-metal interaction by theoretical methods and magnetic measurements. The change of the electronic configuration of the metal atom from d(3) (Tc

  2. Venus: Halide cloud condensation and volatile element inventories

    NASA Technical Reports Server (NTRS)

    Lewis, J. S.; Fegley, B., Jr.

    1982-01-01

    Several Venus cloud condensates, including A12C16 as well as halides, oxides and sulfides of arsenic and antimony, are assessed for their thermodynamic and geochemical plausibility. Aluminum chloride can confidently be ruled out, and condensation of arsenic sulfides on the surface will cause arsenic compounds to be too rare to produce the observed clouds. Antimony may conceivably be sufficiently volatile, but the expected molecular form is gaseous SbS, not the chloride. Arsenic and antimony compounds in the atmosphere will be regulated at very low levels by sulfide precipitation, irrespective of the planetary inventory of As and Sb. Thus the arguments for a volatile-deficient origin for Venus based on the depletion of water and mercury (relative to Earth) cannot be tested by a search for atmospheric arsenic or antimony.

  3. Multiline operation of mercury halide lasers

    SciTech Connect

    Kushawaha, M.; Mahmood, M.

    1988-01-01

    Emission spectrum of the (B-X) band system of HgX radicals (X=chlorine, bromine, iodine) was observed by passing electrical discharge through flowing vapors of mercury halides. The emission intensity of the most intense band of the (B-X) system of these radicals was observed to decrease in the presence of other mercury halide vapors at temperatures higher than 130C. Laser action was observed from the (B-X) transition of mercurous chloride, mercurous bromide, and mercurous iodide radicals by electrical discharge pumping of mercuric chloride, mercuric bromide and mercuric iodide vapors individually.

  4. Calculation of the melting point of alkali halides by means of computer simulations.

    PubMed

    Aragones, J L; Sanz, E; Valeriani, C; Vega, C

    2012-09-14

    In this paper, we study the liquid-solid coexistence of NaCl-type alkali halides, described by interaction potentials such as Tosi-Fumi (TF), Smith-Dang (SD), and Joung-Cheatham (JC), and compute their melting temperature (T(m)) at 1 bar via three independent routes: (1) liquid/solid direct coexistence, (2) free-energy calculations, and (3) Hamiltonian Gibbs-Duhem integration. The melting points obtained by the three routes are consistent with each other. The calculated T(m) of the Tosi-Fumi model of NaCl is in good agreement with the experimental value as well as with other numerical calculations. However, the other two models considered for NaCl, SD and JC, overestimate the melting temperature of NaCl by more than 200 K. We have also computed the melting temperature of other alkali halides using the Tosi-Fumi interaction potential and observed that the predictions are not always as close to the experimental values as they are for NaCl. It seems that there is still room for improvement in the area of force-fields for alkaline halides, given that so far most models are still unable to describe a simple yet important property such as the melting point.

  5. New alkaline earth-zirconium oxalates M2Zr(C 2O 4) 4· nH 2O ( M=Ba, Sr, Ca) synthesis, crystal structure and thermal behavior

    NASA Astrophysics Data System (ADS)

    Chapelet-Arab, B.; Nowogrocki, G.; Abraham, F.; Grandjean, S.

    2004-11-01

    Three new alkaline earth-zirconium oxalates M2Zr(C 2O 4) 4· nH 2O have been synthesized by precipitation methods for M=Ba, Sr, Ca. For each compound the crystal structure was determined from single crystals obtained by controlled diffusion of M 2+ and Zr 4+ ions through silica gel containing oxalic acid. Ba 2Zr(C 2O 4) 4·7H 2O, monoclinic, space group C2/c, a=9.830(2), b=29.019(6), c=9.178(2) Å, β=122.248(4) °, V=2214.2(8) Å, Z=4, R=0.0427; Sr 2Zr(C 2O 4) 4·11H 2O, tetragonal, space group I41/acd, a=16.139(4), c=18.247(6) Å, V=4753(2) Å,Z=8, R=0.0403; Ca 2Zr(C 2O 4) 4·5H 2O, orthorhombic, space group Pna2 1, a=8.4181(5), b=15.8885(8), c=15.8885(8) Å, V=2125(2) Å, Z=4, R=0.0622. The structures of the three compounds consist of chains of edge-shared MO 6(H 2O) x ( x=2 or 3) polyhedra connected to ZrO 8 polyhedra through oxalate groups. Depending on the arrangement of chains, the ZrO 8 polyhedron geometry (dodecahedron or square antiprism) and the connectivity, two types of three-dimensional frameworks are obtained. For the smallest M2+ cations (Sr 2+, Ca 2+), large tunnels are obtained, running down the c direction of the unit cell, which can accommodate zeolitic water molecules. For the largest Ba 2+ cation, the second framework is formed and is closely related to that of Pb 2Zr(C 2O 4) 4· nH 2O. The decomposition at 800°C into strontium carbonate, barium carbonate or calcium oxide and MZrO 3 ( M=Sr, Ba, Ca) perovskite is reported from thermal analyses studies and high temperature X-ray powder diffraction.

  6. New alkaline earth-zirconium oxalates M{sub 2}Zr(C{sub 2}O{sub 4}){sub 4}.nH{sub 2}O (M=Ba, Sr, Ca) synthesis, crystal structure and thermal behavior

    SciTech Connect

    Chapelet-Arab, B.; Abraham, F. . E-mail: francis.abraham@ensc-lille.fr; Grandjean, S.

    2004-11-01

    Three new alkaline earth-zirconium oxalates M{sub 2}Zr(C{sub 2}O{sub 4}){sub 4}.nH{sub 2}O have been synthesized by precipitation methods for M=Ba, Sr, Ca. For each compound the crystal structure was determined from single crystals obtained by controlled diffusion of M{sup 2+} and Zr{sup 4+} ions through silica gel containing oxalic acid. Ba{sub 2}Zr(C{sub 2}O{sub 4}){sub 4}.7H{sub 2}O, monoclinic, space group C2/c, a=9.830(2), b=29.019(6), c=9.178(2)A, {beta}=122.248(4){sup o}, V=2214.2(8)A3, Z=4, R=0.0427; Sr{sub 2}Zr(C{sub 2}O{sub 4}){sub 4}.11H{sub 2}O, tetragonal, space group I41/acd, a=16.139(4), c=18.247(6)A, V=4753(2)A3, Z=8, R=0.0403; Ca{sub 2}Zr(C{sub 2}O{sub 4}){sub 4}.5H{sub 2}O, orthorhombic, space group Pna2{sub 1}, a=8.4181(5), b=15.8885(8), c=15.8885(8)A, V=2125(2)A3, Z=4, R=0.0622. The structures of the three compounds consist of chains of edge-shared MO{sub 6}(H{sub 2}O){sub x} (x=2 or 3) polyhedra connected to ZrO{sub 8} polyhedra through oxalate groups. Depending on the arrangement of chains, the ZrO{sub 8} polyhedron geometry (dodecahedron or square antiprism) and the connectivity, two types of three-dimensional frameworks are obtained. For the smallest M{sup 2+} cations (Sr{sup 2+}, Ca{sup 2+}), large tunnels are obtained, running down the c direction of the unit cell, which can accommodate zeolitic water molecules. For the largest Ba{sup 2+} cation, the second framework is formed and is closely related to that of Pb{sub 2}Zr(C{sub 2}O{sub 4}){sub 4}.nH{sub 2}O. The decomposition at 800{sup o}C into strontium carbonate, barium carbonate or calcium oxide and MZrO{sub 3} (M=Sr, Ba, Ca) perovskite is reported from thermal analyses studies and high temperature X-ray powder diffraction.

  7. The Additive Coloration of Alkali Halides

    ERIC Educational Resources Information Center

    Jirgal, G. H.; and others

    1969-01-01

    Describes the construction and use of an inexpensive, vacuum furnace designed to produce F-centers in alkali halide crystals by additive coloration. The method described avoids corrosion or contamination during the coloration process. Examination of the resultant crystals is discussed and several experiments using additively colored crystals are…

  8. Molecular compressibility of some halides in alcohols

    NASA Technical Reports Server (NTRS)

    Serban, C.; Auslaender, D.

    1974-01-01

    After measuring ultrasonic velocity and density, the molecular compressibility values from Wada's formula were calculated, for alkali metal halide solutions in methyl, ethyl, butyl, and glycol alcohol. The temperature and concentration dependence were studied, finding deviations due to the hydrogen bonds of the solvent.

  9. Mechanical resistance of silver halide infrared fibers

    NASA Astrophysics Data System (ADS)

    Barkay, Nitzan; Katzir, Abraham

    1992-01-01

    Flexibility resistance of silver-halide infrared fibers was investigated in the plastic bending regime, which is especially useful for internal medical applications. The CO2 laser transmission of the fibers was measured in several positions while being bent. The fibers have been found to operate even after large plastic deformations, and values for various fibers and bending conditions are reported.

  10. Localized corrosion in halides other than chlorides

    SciTech Connect

    Koch, G.H.

    1995-12-31

    This literature survey characterizes the effects of non-chloride halides on localized corrosion. It includes published material and unpublished data obtained through a questionnaire. Chapters cover Stainless Steels, Nickel, Titanium, and Zirconium. The engineer can use this information for material selection.

  11. Chemistry of Halide Window Growth

    DTIC Science & Technology

    1976-02-01

    found that the minimum-melting solid solution of NaBr and KBr prepared under RAP conditions does not retain phase homogeneity below the melting point...Canyon Road, Malibu. California 90265, during the period 1 April 1974 through 30 September 1975, under Contract F33615-74-C- 5115. Project...earth fluorides 17 3 Temperature dependence of the decay constant (k) for the depolymerization of TFE under various atmospheres 20 4 Infrared

  12. Ionic alkali halide XUV laser feasibility study

    SciTech Connect

    Yang, T.T.; Gylys, V.T.; Bower, R.D.; Harris, D.G.; Blauer, J.A.; Turner, C.E.; Hindy, R.N.

    1989-11-10

    The objective of this work is to assess the feasibility of a select set of ionic alkali halide XUV laser concepts by obtaining the relevant kinetic and spectroscopic parameters required for a proof-of-principle and conceptual design. The proposed lasers operate in the 80--200 nm spectral region and do not require input from outside radiation sources for their operation. Frequency up-conversion and frequency mixing techniques and therefore not considered in the work to be described. An experimental and theoretical study of a new type of laser operating in the extreme ultraviolet wavelength region has been conducted. The lasing species are singly ionized alkali halide molecules such as Rb{sup 2+}F{sub {minus}}, Rb{sup 2+}Br{sup {minus}} and Cs{sup 2+}F{sup {minus}}. These species are similar in electronic structure to the rare gas halide excimers, such as XeF and Krf, except that the ionic molecules emit at wavelengths of 80--200 nm, much shorter than the conventional rare-gas halide excimer laser. The radiative lifetime of these molecules are typically near 1 ns, which is about an order of magnitude shorter than that for rare-gas halide systems. The values of the cross section for stimulated emission are on the order of 1 {times} 10{sup {minus}16}cm{sup 2}. Because of the fundamental similarity to existing UV lasers, these systems show promise as a high power, efficient XUV lasers. 55 refs., 50 figs., 5 tabs.

  13. Anodes for alkaline electrolysis

    DOEpatents

    Soloveichik, Grigorii Lev

    2011-02-01

    A method of making an anode for alkaline electrolysis cells includes adsorption of precursor material on a carbonaceous material, conversion of the precursor material to hydroxide form and conversion of precursor material from hydroxide form to oxy-hydroxide form within the alkaline electrolysis cell.

  14. Transport of Soil Halides through Rice Paddies: A Viable Mechanism for Rapid Dispersion of the Soil Halide Reservoir

    NASA Astrophysics Data System (ADS)

    Redeker, K. R.; Manley, S.; Wang, N.; Cicerone, R.

    2002-05-01

    On short time scales (1-10 years) soil halide concentrations have been assumed to be primarily driven by leaching and deposition processes. Recent results however, have shown that terrestrial plants volatilize soil halides in the form of methyl halides. Emissions of methyl chloride, methyl bromide and methyl iodide represent major pathways for delivery of inorganic halogen radicals to the atmosphere. Inorganic halogen radicals destroy ozone in the stratosphere and modify the oxidative capacity of the lower atmosphere. We have previously shown that rice paddies emit methyl halides and that emissions depend on growth stage of the rice plant as well as field water management. We show here that rice grown in a greenhouse at UCI is capable of volatilizing and/or storing up to 30%, 5%, and 10% of the available chloride, bromide and iodide within the top meter of soil. The percent of plant tissue halide volatilized as methyl halide over the course of the season is calculated to be 0.05%, 0.25% and 85.0% for chloride, bromide and iodide. We compare our greenhouse soil halide concentrations to other commercial rice fields around the world and estimate the e-folding time for soil halides within each region. We suggest that rice agriculture is the driving removal mechanism for halides within rice paddies and that terrestrial plants play a larger role in global cycling of halides than previously estimated.

  15. Morphology-Controlled Synthesis of Organometal Halide Perovskite Inverse Opals.

    PubMed

    Chen, Kun; Tüysüz, Harun

    2015-11-09

    The booming development of organometal halide perovskites in recent years has prompted the exploration of morphology-control strategies to improve their performance in photovoltaic, photonic, and optoelectronic applications. However, the preparation of organometal halide perovskites with high hierarchical architecture is still highly challenging and a general morphology-control method for various organometal halide perovskites has not been achieved. A mild and scalable method to prepare organometal halide perovskites in inverse opal morphology is presented that uses a polystyrene-based artificial opal as hard template. Our method is flexible and compatible with different halides and organic ammonium compositions. Thus, the perovskite inverse opal maintains the advantage of straightforward structure and band gap engineering. Furthermore, optoelectronic investigations reveal that morphology exerted influence on the conducting nature of organometal halide perovskites.

  16. Flame inhibition by hydrogen halides - Some spectroscopic measurements

    NASA Technical Reports Server (NTRS)

    Lerner, N. R.; Cagliostro, D. E.

    1973-01-01

    The far-ultraviolet absorption spectrum of an air-propane diffusion flame inhibited with hydrogen halides has been studied. Plots of the absorption of light by hydrogen halides as a function of position in the flame and also as a function of the amount of hydrogen halide added to the flame have been obtained. The hydrogen halides are shown to be more stable on the fuel side of the reaction zone than they are on the air side. Thermal diffusion is seen to be important in determining the concentration distribution of the heavier hydrogen halides in diffusion flames. The relationship between the concentration distribution of the hydrogen halides in the flame and the flame inhibition mechanism is discussed.

  17. Lanthanide-halide based humidity indicators

    DOEpatents

    Beitz, James V.; Williams, Clayton W.

    2008-01-01

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

  18. Chiral Alkyl Halides: Underexplored Motifs in Medicine

    PubMed Central

    Gál, Bálint; Bucher, Cyril; Burns, Noah Z.

    2016-01-01

    While alkyl halides are valuable intermediates in synthetic organic chemistry, their use as bioactive motifs in drug discovery and medicinal chemistry is rare in comparison. This is likely attributable to the common misconception that these compounds are merely non-specific alkylators in biological systems. A number of chlorinated compounds in the pharmaceutical and food industries, as well as a growing number of halogenated marine natural products showing unique bioactivity, illustrate the role that chiral alkyl halides can play in drug discovery. Through a series of case studies, we demonstrate in this review that these motifs can indeed be stable under physiological conditions, and that halogenation can enhance bioactivity through both steric and electronic effects. Our hope is that, by placing such compounds in the minds of the chemical community, they may gain more traction in drug discovery and inspire more synthetic chemists to develop methods for selective halogenation. PMID:27827902

  19. Process and composition for drying of gaseous hydrogen halides

    DOEpatents

    Tom, Glenn M.; Brown, Duncan W.

    1989-08-01

    A process for drying a gaseous hydrogen halide of the formula HX, wherein X is selected from the group consisting of bromine, chlorine, fluorine, and iodine, to remove water impurity therefrom, comprising: contacting the water impurity-containing gaseous hydrogen halide with a scavenger including a support having associated therewith one or more members of the group consisting of: (a) an active scavenging moiety selected from one or more members of the group consisting of: (i) metal halide compounds dispersed in the support, of the formula MX.sub.y ; and (ii) metal halide pendant functional groups of the formula -MX.sub.y-1 covalently bonded to the support, wherein M is a y-valent metal, and y is an integer whose value is from 1 to 3; (b) corresponding partially or fully alkylated compounds and/or pendant functional groups, of the metal halide compounds and/or pendant functional groups of (a); wherein the alkylated compounds and/or pendant functional groups, when present, are reactive with the gaseous hydrogen halide to form the corresponding halide compounds and/or pendant functional groups of (a); and M being selected such that the heat of formation, .DELTA.H.sub.f of its hydrated halide, MX.sub.y.(H.sub.2 O).sub.n, is governed by the relationship: .DELTA.H.sub.f .gtoreq.n.times.10.1 kilocalories/mole of such hydrated halide compound wherein n is the number of water molecules bound to the metal halide in the metal halide hydrate. Also disclosed is an appertaining scavenger composition and a contacting apparatus wherein the scavenger is deployed in a bed for contacting with the water impurity-containing gaseous hydrogen halide.

  20. Interpulse kinetics in copper and copper halide lasers

    NASA Technical Reports Server (NTRS)

    Harstad, K. G.

    1983-01-01

    The various rate processes that govern the interpulse relaxation in metal vapor and metal halide vapor lasers are considered. Computer calculations indicate that the rapid metastable levels relaxation observed in copper and copper halide laser experiments requires the existence of a relatively small resonance in the cross section for metastable excitation or deexcitation near threshold. The accurate calculation of interpulse relaxation requires knowledge of rate constants presently not well known; this is especially so for metal halide lasers.

  1. Lanthanide doped strontium-barium cesium halide scintillators

    DOEpatents

    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.

  2. Alkaline battery operational methodology

    DOEpatents

    Sholklapper, Tal; Gallaway, Joshua; Steingart, Daniel; Ingale, Nilesh; Nyce, Michael

    2016-08-16

    Methods of using specific operational charge and discharge parameters to extend the life of alkaline batteries are disclosed. The methods can be used with any commercial primary or secondary alkaline battery, as well as with newer alkaline battery designs, including batteries with flowing electrolyte. The methods include cycling batteries within a narrow operating voltage window, with minimum and maximum cut-off voltages that are set based on battery characteristics and environmental conditions. The narrow voltage window decreases available capacity but allows the batteries to be cycled for hundreds or thousands of times.

  3. Making and Breaking of Lead Halide Perovskites.

    PubMed

    Manser, Joseph S; Saidaminov, Makhsud I; Christians, Jeffrey A; Bakr, Osman M; Kamat, Prashant V

    2016-02-16

    A new front-runner has emerged in the field of next-generation photovoltaics. A unique class of materials, known as organic metal halide perovskites, bridges the gap between low-cost fabrication and exceptional device performance. These compounds can be processed at low temperature (typically in the range 80-150 °C) and readily self-assemble from the solution phase into high-quality semiconductor thin films. The low energetic barrier for crystal formation has mixed consequences. On one hand, it enables inexpensive processing and both optical and electronic tunability. The caveat, however, is that many as-formed lead halide perovskite thin films lack chemical and structural stability, undergoing rapid degradation in the presence of moisture or heat. To date, improvements in perovskite solar cell efficiency have resulted primarily from better control over thin film morphology, manipulation of the stoichiometry and chemistry of lead halide and alkylammonium halide precursors, and the choice of solvent treatment. Proper characterization and tuning of processing parameters can aid in rational optimization of perovskite devices. Likewise, gaining a comprehensive understanding of the degradation mechanism and identifying components of the perovskite structure that may be particularly susceptible to attack by moisture are vital to mitigate device degradation under operating conditions. This Account provides insight into the lifecycle of organic-inorganic lead halide perovskites, including (i) the nature of the precursor solution, (ii) formation of solid-state perovskite thin films and single crystals, and (iii) transformation of perovskites into hydrated phases upon exposure to moisture. In particular, spectroscopic and structural characterization techniques shed light on the thermally driven evolution of the perovskite structure. By tuning precursor stoichiometry and chemistry, and thus the lead halide charge-transfer complexes present in solution, crystallization

  4. Defects in perovskite-halides and their effects in solar cells

    NASA Astrophysics Data System (ADS)

    Ball, James M.; Petrozza, Annamaria

    2016-11-01

    Solar cells based on perovskite-halide light absorbers have a unique set of characteristics that could help alleviate the global dependence on fossil fuels for energy generation. They efficiently convert sunlight into electricity using Earth-abundant raw materials processed from solution at low temperature. Thus, they offer potential for cost reductions compared with or in combination with other photovoltaic technologies. Nevertheless, to fully exploit the potential of perovskite-halides, several important challenges must be overcome. Given the nature of the materials — relatively soft ionic solids — one of these challenges is the understanding and control of their defect structures. Currently, such understanding is limited, restricting the power conversion efficiencies of these solar cells from reaching their thermodynamic limit. This Review describes the state of the art in the understanding of the origin and nature of defects in perovskite-halides and their impact on carrier recombination, charge-transport, band alignment, and electrical instability, and provides a perspective on how to make further progress.

  5. Mechanism and Selectivity in Nickel-Catalyzed Cross-Electrophile Coupling of Aryl Halides with Alkyl Halides

    PubMed Central

    Biswas, Soumik; Weix, Daniel J.

    2013-01-01

    The direct cross-coupling of two different electrophiles, such as an aryl halide with an alkyl halide, offers many advantages over conventional cross-coupling methods that require a carbon nucleophile. Despite its promise as a versatile synthetic strategy, a limited understanding of the mechanism and origin of cross selectivity has hindered progress in reaction development and design. Herein, we shed light on the mechanism for the nickel-catalyzed cross-electrophile coupling of aryl halides with alkyl halides and demonstrate that the selectivity arises from an unusual catalytic cycle that combines both polar and radical steps to form the new C-C bond. PMID:23952217

  6. [Emissions of methyl halides from coastal salt marshes: A review].

    PubMed

    Xie, Wen-xia; Zhao, Quan-sheng; Cui, Yu-qian; Du, Hui-na; Ye, Si-yuan

    2015-11-01

    Methyl halides are the major carrier of halogens in the atmosphere, and they play an important role in tropospheric and stratospheric ozone depletion. Meanwhile, methyl halides can act as greenhouse gases in the atmosphere, and they are also environmentally significant because of their toxicity. Coastal salt marshes, the important intertidal ecosystems at the land-ocean interface, have been considered to be a large potential natural source of methyl halides. In this paper, the research status of the natural source or sink of methyl halides, the mechanisms of their emission from coastal salt marshes and affecting factors were summarized. In view of this, the following research fields need to be strengthened in the future: 1) Long time-scale and large region-range researches about the emission of methyl halides and the evaluation of their source and sink function, 2) Accurate quantification of contribution rates of different plant species and various biological types to fluxes of methyl halides, 3) Further researches on effects of the tidal fluctuation process and flooding duration on methyl halides emission, 4) Effects of the global change and human activities on methyl halides emission.

  7. How specific halide adsorption varies hydrophobic interactions.

    PubMed

    Stock, Philipp; Müller, Melanie; Utzig, Thomas; Valtiner, Markus

    2016-03-11

    Hydrophobic interactions (HI) are driven by the water structure around hydrophobes in aqueous electrolytes. How water structures at hydrophobic interfaces and how this influences the HI was subject to numerous studies. However, the effect of specific ion adsorption on HI and hydrophobic interfaces remains largely unexplored or controversial. Here, the authors utilized atomic force microscopy force spectroscopy at well-defined nanoscopic hydrophobic interfaces to experimentally address how specific ion adsorption of halide ions as well as NH4 (+), Cs(+), and Na(+) cations alters interaction forces across hydrophobic interfaces. Our data demonstrate that iodide adsorption at hydrophobic interfaces profoundly varies the hydrophobic interaction potential. A long-range and strong hydration repulsion at distances D > 3 nm, is followed by an instability which could be explained by a subsequent rapid ejection of adsorbed iodides from approaching hydrophobic interfaces. In addition, the authors find only a weakly pronounced influence of bromide, and as expected no influence of chloride. Also, all tested cations do not have any significant influence on HI. Complementary, x-ray photoelectron spectroscopy and quartz-crystal-microbalance with dissipation monitoring showed a clear adsorption of large halide ions (Br(-)/I(-)) onto hydrophobic self-assembled monolayers (SAMs). Interestingly, iodide can even lead to a full disintegration of SAMs due to specific and strong interactions of iodide with gold. Our data suggest that hydrophobic surfaces are not intrinsically charged negatively by hydroxide adsorption, as it was generally believed. Hydrophobic surfaces rather interact strongly with negatively charged large halide ions, leading to a surface charging and significant variation of interaction forces.

  8. Development of novel growth methods for halide single crystals

    NASA Astrophysics Data System (ADS)

    Yokota, Yuui; Kurosawa, Shunsuke; Shoji, Yasuhiro; Ohashi, Yuji; Kamada, Kei; Yoshikawa, Akira

    2017-03-01

    We developed novel growth methods for halide scintillator single crystals with hygroscopic nature, Halide micro-pulling-down [H-μ-PD] method and Halide Vertical Bridgman [H-VB] method. The H-μ-PD method with a removable chamber system can grow a single crystal of halide scintillator material with hygroscopicity at faster growth rate than the conventional methods. On the other hand, the H-VB method can grow a large bulk single crystal of halide scintillator without a quartz ampule. CeCl3, LaBr3, Ce:LaBr3 and Eu:SrI2 fiber single crystals could be grown by the H-μ-PD method and Eu:SrI2 bulk single crystals of 1 and 1.5 inch in diameter could be grown by the H-VB method. The grown fiber and bulk single crystals showed comparable scintillation properties to the previous reports using the conventional methods.

  9. Alkali Halide Nanotubes: Structure and Stability

    PubMed Central

    Fernandez-Lima, Francisco A.; Henkes, Aline Verônica; da Silveira, Enio F.; Nascimento, Marco Antonio Chaer

    2013-01-01

    Accurate density functional theory (DFT) and coupled-cluster (CCSD) calculations on a series of (LiF)n=2,36 neutral clusters suggest that nanotube structures with hexagonal and octagonal transversal cross sections show stability equal to or greater than that of the typical cubic form of large LiF crystals. The nanotube stability was further corroborated by quantum dynamic calculations at room temperature. The fact that stable nanotube structures were also found for other alkali halides (e.g., NaCl and KBr) suggests that this geometry may be widely implemented in material sciences. PMID:24376901

  10. Nanoscale investigation of organic - inorganic halide perovskites

    NASA Astrophysics Data System (ADS)

    Cacovich, S.; Divitini, G.; Vrućinić, M.; Sadhanala, A.; Friend, R. H.; Sirringhaus, H.; Deschler, F.; Ducati, C.

    2015-10-01

    Over the last few years organic - inorganic halide perovskite-based solar cells have exhibited a rapid evolution, reaching certified power conversion efficiencies now surpassing 20%. Nevertheless the understanding of the optical and electronic properties of such systems on the nanoscale is still an open problem. In this work we investigate two model perovskite systems (based on iodine - CH3NH3PbI3 and bromine - CH3NH3PbBr3), analysing the local elemental composition and crystallinity and identifying chemical inhomogeneities.

  11. Research Update: Luminescence in lead halide perovskites

    NASA Astrophysics Data System (ADS)

    Srimath Kandada, Ajay Ram; Petrozza, Annamaria

    2016-09-01

    Efficiency and dynamics of radiative recombination of carriers are crucial figures of merit for optoelectronic materials. Following the recent success of lead halide perovskites in efficient photovoltaic and light emitting technologies, here we review some of the noted literature on the luminescence of this emerging class of materials. After outlining the theoretical formalism that is currently used to explain the carrier recombination dynamics, we review a few significant works which use photoluminescence as a tool to understand and optimize the operation of perovskite based optoelectronic devices.

  12. Improved processing for silver halide pulse holography

    NASA Astrophysics Data System (ADS)

    Mikhailov, Viktor N.; Son, Jung-Young; Grinevitskaya, Olga V.; Lee, Hyuk-Soo; Choi, Yong-Jin

    1996-04-01

    Using of an improved developer with optical latensification allowed to significantly increase exposure sensitivity of currently in use silver halide materials. Transmission large-scale holograms (30 X 40 cm2) of diffused objects have been recorded under pulse exposure of about 6.5 X 10-6 J/cm2 for VRP and of about 2 X 10-6 J/cm2 for Agfa-Gavaert 8E56HD, in both cases without appreciable contrast deterioration. Results of the first experiments on pulse reflection holography are also discussed.

  13. Synthesis of lithium cobaltate in halide melts

    NASA Astrophysics Data System (ADS)

    Modenov, D. V.; Dokutovich, V. N.; Khokhlov, V. A.; Antonov, B. D.; Kochedykov, V. A.; Zakir'yanova, I. D.

    2013-02-01

    A new method for the synthesis of lithium cobaltate LiCoo2 in salt melts is proposed and tested. The method is based on the oxidation of halide ions with molecular oxygen in Li X-CoCl2 mixtures ( X = Cl, Br, I). The chemical and phase compositions of the prepared powders and the crystal structure of the synthesized compound are studied by Fourier transform infrared spectroscopy and X-ray diffraction analysis. The average size of LiCoO2 crystallites is estimated from the X-ray diffraction data.

  14. Strong Turbulence in Alkali Halide Negative Ion Plasmas

    NASA Astrophysics Data System (ADS)

    Sheehan, Daniel

    1999-11-01

    Negative ion plasmas (NIPs) are charge-neutral plasmas in which the negative charge is dominated by negative ions rather than electrons. They are found in laser discharges, combustion products, semiconductor manufacturing processes, stellar atmospheres, pulsar magnetospheres, and the Earth's ionosphere, both naturally and man-made. They often display signatures of strong turbulence^1. Development of a novel, compact, unmagnetized alkali halide (MX) NIP source will be discussed, it incorporating a ohmically-heated incandescent (2500K) tantulum solenoid (3cm dia, 15 cm long) with heat shields. The solenoid ionizes the MX vapor and confines contaminant electrons, allowing a very dry (electron-free) source. Plasma densities of 10^10 cm-3 and positive to negative ion mass ratios of 1 <= fracm_+m- <= 20 are achievable. The source will allow tests of strong turbulence theory^2. 1 Sheehan, D.P., et al., Phys. Fluids B5, 1593 (1993). 2 Tsytovich, V. and Wharton, C.W., Comm. Plasma Phys. Cont. Fusion 4, 91 (1978).

  15. Corrosion and corrosion inhibition of Al and some alloys in sulphate solutions containing halide ions investigated by an impedance technique

    NASA Astrophysics Data System (ADS)

    Rehim, Sayed S. Abdel; Hassan, Hamdi H.; Amin, Mohammed A.

    2002-02-01

    This paper reports the results of impedance measurements on the corrosion behaviour of pure Al, (Al+6%Cu) and (Al+6%Si) alloys in Na 2SO 4 solutions in the absence and presence of NaCl, NaBr and NaI under the influence of various experimental variables at the open circuit potential (OCP). We find that in the absence of halide ions the rates of corrosion of the three Al samples are enhanced with increasing concentration, acidity, and alkalinity of the Na 2SO 4 solution and in the presence of halide ions. The corrosion resistance increases in the order Al<(Al+6%Cu)<(Al+6%Si). The aggressiveness of the halide ions towards the corrosion of Al and its two alloys increases in the order: I -

  16. 10 CFR 429.54 - Metal halide lamp ballasts and fixtures.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 3 2014-01-01 2014-01-01 false Metal halide lamp ballasts and fixtures. 429.54 Section... CONSUMER PRODUCTS AND COMMERCIAL AND INDUSTRIAL EQUIPMENT Certification § 429.54 Metal halide lamp ballasts... are applicable to metal halide lamp ballasts; and (2) For each basic model of metal halide...

  17. 10 CFR 429.54 - Metal halide lamp ballasts and fixtures.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 10 Energy 3 2013-01-01 2013-01-01 false Metal halide lamp ballasts and fixtures. 429.54 Section... CONSUMER PRODUCTS AND COMMERCIAL AND INDUSTRIAL EQUIPMENT Certification § 429.54 Metal halide lamp ballasts... are applicable to metal halide lamp ballasts; and (2) For each basic model of metal halide...

  18. 10 CFR 429.54 - Metal halide lamp ballasts and fixtures.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 3 2012-01-01 2012-01-01 false Metal halide lamp ballasts and fixtures. 429.54 Section... CONSUMER PRODUCTS AND COMMERCIAL AND INDUSTRIAL EQUIPMENT Certification § 429.54 Metal halide lamp ballasts... are applicable to metal halide lamp ballasts; and (2) For each basic model of metal halide...

  19. Finding New Perovskite Halides via Machine learning

    NASA Astrophysics Data System (ADS)

    Pilania, Ghanshyam; Balachandran, Prasanna V.; Kim, Chiho; Lookman, Turab

    2016-04-01

    Advanced materials with improved properties have the potential to fuel future technological advancements. However, identification and discovery of these optimal materials for a specific application is a non-trivial task, because of the vastness of the chemical search space with enormous compositional and configurational degrees of freedom. Materials informatics provides an efficient approach towards rational design of new materials, via learning from known data to make decisions on new and previously unexplored compounds in an accelerated manner. Here, we demonstrate the power and utility of such statistical learning (or machine learning) via building a support vector machine (SVM) based classifier that uses elemental features (or descriptors) to predict the formability of a given ABX3 halide composition (where A and B represent monovalent and divalent cations, respectively, and X is F, Cl, Br or I anion) in the perovskite crystal structure. The classification model is built by learning from a dataset of 181 experimentally known ABX3 compounds. After exploring a wide range of features, we identify ionic radii, tolerance factor and octahedral factor to be the most important factors for the classification, suggesting that steric and geometric packing effects govern the stability of these halides. The trained and validated models then predict, with a high degree of confidence, several novel ABX3 compositions with perovskite crystal structure.

  20. Finding new perovskite halides via machine learning

    SciTech Connect

    Pilania, Ghanshyam; Balachandran, Prasanna V.; Kim, Chiho; Lookman, Turab

    2016-04-26

    Advanced materials with improved properties have the potential to fuel future technological advancements. However, identification and discovery of these optimal materials for a specific application is a non-trivial task, because of the vastness of the chemical search space with enormous compositional and configurational degrees of freedom. Materials informatics provides an efficient approach toward rational design of new materials, via learning from known data to make decisions on new and previously unexplored compounds in an accelerated manner. Here, we demonstrate the power and utility of such statistical learning (or machine learning, henceforth referred to as ML) via building a support vector machine (SVM) based classifier that uses elemental features (or descriptors) to predict the formability of a given ABX3 halide composition (where A and B represent monovalent and divalent cations, respectively, and X is F, Cl, Br, or I anion) in the perovskite crystal structure. The classification model is built by learning from a dataset of 185 experimentally known ABX3 compounds. After exploring a wide range of features, we identify ionic radii, tolerance factor, and octahedral factor to be the most important factors for the classification, suggesting that steric and geometric packing effects govern the stability of these halides. As a result, the trained and validated models then predict, with a high degree of confidence, several novel ABX3 compositions with perovskite crystal structure.

  1. Intriguing Optoelectronic Properties of Metal Halide Perovskites.

    PubMed

    Manser, Joseph S; Christians, Jeffrey A; Kamat, Prashant V

    2016-11-09

    A new chapter in the long and distinguished history of perovskites is being written with the breakthrough success of metal halide perovskites (MHPs) as solution-processed photovoltaic (PV) absorbers. The current surge in MHP research has largely arisen out of their rapid progress in PV devices; however, these materials are potentially suitable for a diverse array of optoelectronic applications. Like oxide perovskites, MHPs have ABX3 stoichiometry, where A and B are cations and X is a halide anion. Here, the underlying physical and photophysical properties of inorganic (A = inorganic) and hybrid organic-inorganic (A = organic) MHPs are reviewed with an eye toward their potential application in emerging optoelectronic technologies. Significant attention is given to the prototypical compound methylammonium lead iodide (CH3NH3PbI3) due to the preponderance of experimental and theoretical studies surrounding this material. We also discuss other salient MHP systems, including 2-dimensional compounds, where relevant. More specifically, this review is a critical account of the interrelation between MHP electronic structure, absorption, emission, carrier dynamics and transport, and other relevant photophysical processes that have propelled these materials to the forefront of modern optoelectronics research.

  2. Methyl halide production associated with kelp

    NASA Technical Reports Server (NTRS)

    Dastoor, Minoo N.; Manley, Steven L.

    1985-01-01

    Methyl halides (MeX) are important trace constituents of the atmosphere because they, mostly MeCl, have a major impact on the atmospheric ozone layer. Also, MeCl may account for 5 pct. of the total Cl budget and MeI may have a central role in the biogeochemical cycling of iodine. High MeI concentrations were found in seawater from kelp beds and it has been suggested that MeI is produced by kelps and that MeI and MeBr along with numerous other halocarbons were released by non-kelp marine macroalgae. The objective was to determine if kelps (and other seaweeds) are sources of MeX and to assess their contribution to the estimated global source strength (EGSS) of MeX. Although the production of MeX appears to be associated with kelp, microbes involved with kelp degradation also produce MeX. Microbial MeX production may be of global significance. The microbial MeX production potential, assuming annual kelp production equals kelp degradation and 100 pct. conversion of kelp halides to MeX, is approx. 2 x the EGSS. This is not achieved but indicates that microbial production of MeX may be of global significance.

  3. Finding new perovskite halides via machine learning

    DOE PAGES

    Pilania, Ghanshyam; Balachandran, Prasanna V.; Kim, Chiho; ...

    2016-04-26

    Advanced materials with improved properties have the potential to fuel future technological advancements. However, identification and discovery of these optimal materials for a specific application is a non-trivial task, because of the vastness of the chemical search space with enormous compositional and configurational degrees of freedom. Materials informatics provides an efficient approach toward rational design of new materials, via learning from known data to make decisions on new and previously unexplored compounds in an accelerated manner. Here, we demonstrate the power and utility of such statistical learning (or machine learning, henceforth referred to as ML) via building a support vectormore » machine (SVM) based classifier that uses elemental features (or descriptors) to predict the formability of a given ABX3 halide composition (where A and B represent monovalent and divalent cations, respectively, and X is F, Cl, Br, or I anion) in the perovskite crystal structure. The classification model is built by learning from a dataset of 185 experimentally known ABX3 compounds. After exploring a wide range of features, we identify ionic radii, tolerance factor, and octahedral factor to be the most important factors for the classification, suggesting that steric and geometric packing effects govern the stability of these halides. As a result, the trained and validated models then predict, with a high degree of confidence, several novel ABX3 compositions with perovskite crystal structure.« less

  4. Alkaline flooding injection strategy

    SciTech Connect

    French, T.R.; Josephson, C.B.

    1992-03-01

    The objective of this project is to improved alkali-surfactant flooding methods, and this includes determining the proper design of injection strategy. Several different injection strategies have been used or suggested for recovering heavy oils with surfactant-enhanced alkaline flooding methods. Oil recovery was compared for four different injection strategies: (1) surfactant followed by polymer, (2) surfactant followed by alkaline polymer, (3) alkaline surfactant followed by polymer, and (4) alkali, surfactant, and polymer mixed in a single formulation. The effect of alkaline preflush was also studied under two different conditions. All of the oil recovery experiments were conducted under optimal conditions with a viscous, non-acidic oil from Hepler (KS) oil field. The coreflood experiments were conducted with Berea sandstone cores since field core was not available in sufficient quantity for coreflood tests. The Tucker sand of Hepler field is a Class I fluvial dominated deltaic reservoir, as classified by the Department of Energy, which has been selected as the site of a DOE-sponsored field pilot test.

  5. Nickel-Catalyzed Borylation of Halides and Pseudo-Halides with Tetrahydroxydiboron [B2(OH)4

    PubMed Central

    Molander, Gary A.; Cavalcanti, Livia N.; García-García, Carolina

    2013-01-01

    Arylboronic acids are gaining increased importance as reagents and target structures in a variety of useful applications. Recently, the palladium-catalyzed synthesis of arylboronic acids employing the atom economical tetrahydroxydiboron (BBA) reagent has been reported. The high cost associated with palladium, combined with several limitations of both palladium and copper-catalyzed processes, prompted us to develop an alternative method. Thus, the nickel-catalyzed borylation of aryl and heteroaryl halides and pseudo-halides using tetrahydroxydiboron (BBA) has been formulated. The reaction proved to be widely functional group tolerant and applicable to a number of heterocyclic systems. To the best of our knowledge, the examples presented here represent the only effective Ni-catalyzed Miyaura borylations conducted at room temperature. PMID:23777538

  6. Unraveling the Role of Monovalent Halides in Mixed-Halide Organic-Inorganic Perovskites.

    PubMed

    Deepa, Melepurath; Ramos, F Javier; Shivaprasad, S M; Ahmad, Shahzada

    2016-03-16

    The performance of perovskite solar cells is strongly influenced by the composition and microstructure of the perovskite. A recent approach to improve the power conversion efficiencies utilized mixed-halide perovskites, but the halide ions and their roles were not directly studied. Unraveling their precise location in the perovskite layer is of paramount importance. Here, we investigated four different perovskites by using X-ray photoelectron spectroscopy, and found that among the three studied mixed-halide perovskites, CH3 NH3 Pb(I0.74 Br0.26 )3 and CH3 NH3 PbBr3-x Clx show peaks that unambiguously demonstrate the presence of iodide and bromide in the former, and bromide and chloride in the latter. The CH3 NH3 PbI3-x Clx perovskite shows anomalous behavior, the iodide content far outweighs that of the chloride; a small proportion of chloride, in all likelihood, resides deep within the TiO2 /absorber layer. Our study reveals that there are many distinguishable structural differences between these perovskites, and that these directly impact the photovoltaic performances.

  7. Metal halide perovskites for energy applications

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Eperon, Giles E.; Snaith, Henry J.

    2016-06-01

    Exploring prospective materials for energy production and storage is one of the biggest challenges of this century. Solar energy is one of the most important renewable energy resources, due to its wide availability and low environmental impact. Metal halide perovskites have emerged as a class of semiconductor materials with unique properties, including tunable bandgap, high absorption coefficient, broad absorption spectrum, high charge carrier mobility and long charge diffusion lengths, which enable a broad range of photovoltaic and optoelectronic applications. Since the first embodiment of perovskite solar cells showing a power conversion efficiency of 3.8%, the device performance has been boosted up to a certified 22.1% within a few years. In this Perspective, we discuss differing forms of perovskite materials produced via various deposition procedures. We focus on their energy-related applications and discuss current challenges and possible solutions, with the aim of stimulating potential new applications.

  8. Tellurium halide IR fibers for remote spectroscopy

    NASA Astrophysics Data System (ADS)

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

    1994-07-01

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

  9. Passive particle dosimetry. [silver halide crystal growth

    NASA Technical Reports Server (NTRS)

    Childs, C. B.

    1977-01-01

    Present methods of dosimetry are reviewed with emphasis on the processes using silver chloride crystals for ionizing particle dosimetry. Differences between the ability of various crystals to record ionizing particle paths are directly related to impurities in the range of a few ppm (parts per million). To understand the roles of these impurities in the process, a method for consistent production of high purity silver chloride, and silver bromide was developed which yields silver halides with detectable impurity content less than 1 ppm. This high purity silver chloride was used in growing crystals with controlled doping. Crystals were grown by both the Czochalski method and the Bridgman method, and the Bridgman grown crystals were used for the experiments discussed. The distribution coefficients of ten divalent cations were determined for the Bridgman crystals. The best dosimeters were made with silver chloride crystals containing 5 to 10 ppm of lead; other impurities tested did not produce proper dosimeters.

  10. Bleaching mechanism of silver halide photochromic glasses

    NASA Astrophysics Data System (ADS)

    Caurant, D.; Gourier, D.; Vivien, D.; Prassas, M.

    1993-02-01

    Thermal bleaching of silver halide photochromic glasses is studied by electron paramagnetic resonance spectroscopy of photoinduced CuII centers. During exposure to ultraviolet light, the only stable CuII species is the (CuIIVAg)A center, which is a CuII-silver vacancy complex with the vacancy in a nearest position. In the dark, this center rapidly decays via two parallel channels. The first involves the dissociation of the complex by displacement of the vacancy along a [110] direction, with an activation energy E3=0.44 eV and a frequency factor k30=3.4×105 s-1. The second channel involves the conversion of the (CuIIVAg)A center into a (CuIICl-VAg)B center, where the silver vacancy is in the next nearest position along the [100] direction. This process occurs with an activation energy E1=0.44 eV and a frequency factor k10=3.1×105 s-1. The (CuIICl-VAg)B center slowly decays by a vacancy hopping mechanism, with an activation energy E2=0.22 eV and a frequency factor k20=4.6 s-1. To explain these two decay channels, it is proposed that the (CuIIVAg)A and (CuIICl-VAg)B centers annihilate via the formation of a CuI ion and a neutral complex (AgIIVAg)A which migrates to the surface of the silver halide particle, where electron-hole recombination occurs.

  11. Nitrogen isotope evidence for alkaline lakes on late Archean continents

    NASA Astrophysics Data System (ADS)

    Stüeken, E. E.; Buick, R.; Schauer, A. J.

    2015-02-01

    Nitrogen isotope ratios in ancient sedimentary rocks are generally interpreted as a proxy for metabolic nitrogen pathways and the redox state of the water column. Fractionation processes occurring under anoxic, alkaline conditions during the dissociation of NH4+ to H+ and volatile NH3 are frequently overlooked, although this mechanism imparts large isotopic fractionations. Here we propose that NH3 volatilization is largely responsible for δ15N values of up to + 50 ‰ at high C/N ratios in the late Archean Tumbiana Formation. This sequence of sedimentary rocks represents a system of lakes that formed on subaerial flood basalts and were partly filled by basaltic volcanic ash. Aqueous alteration of volcanic glass followed by evaporative concentration of ions should have led to the development of high alkalinity with a pH of 9 or higher, as in modern analogues. In this sedimentologically unusual setting, nitrogen isotope ratios thus provide indirect evidence for the oldest alkaline lake system in the rock record. These very heavy lacustrine δ15N values contrast markedly with those of Archean marine sedimentary rocks, making a Precambrian "soda ocean" unlikely. Today, alkaline lakes are among the most productive ecosystems on Earth. Some nutrients, in particular molybdenum, are more soluble at high pH, and certain prebiotic reactions would likely have been favored under alkaline conditions in similar settings earlier in Earth's history. Hence alkaline lakes in the Archean could have been significant for the origin and early evolution of life.

  12. Electronic and Ionic Transport Dynamics in Organolead Halide Perovskites.

    PubMed

    Li, Dehui; Wu, Hao; Cheng, Hung-Chieh; Wang, Gongming; Huang, Yu; Duan, Xiangfeng

    2016-07-26

    Ion migration has been postulated as the underlying mechanism responsible for the hysteresis in organolead halide perovskite devices. However, the electronic and ionic transport dynamics and how they impact each other in organolead halide perovskites remain elusive to date. Here we report a systematic investigation of the electronic and ionic transport dynamics in organolead halide perovskite microplate crystals and thin films using temperature-dependent transient response measurements. Our study reveals that thermally activated ionic and electronic conduction coexist in perovskite devices. The extracted activation energies suggest that the electronic transport is easier, but ions migrate harder in microplates than in thin films, demonstrating that the crystalline quality and grain boundaries can fundamentally modify electronic and ionic transport in perovskites. These findings offer valuable insight on the electronic and ionic transport dynamics in organolead halide perovskites, which is critical for optimizing perovskite devices with reduced hysteresis and improved stability and efficiency.

  13. Advanced alkaline water electrolysis

    NASA Astrophysics Data System (ADS)

    Wakabayashi, N.; Torikai, E.; Kawami, Y.; Takenaka, H.

    Results are presented of experimental studies of possible separators and electrodes for use in advanced, high-temperature, high-pressure alkaline water electrolyzers. Material evaluations in alkaline water electrolyzers at temperatures from 100 to 120 C have shown a new type polytetrafluoroethylene membrane impregnated with potassium titanate to be the most promising when the separator is prepared by the hydrothermal treatment of a porous PFTE membrane impregnated with hydrated titanium oxide. Measurements of cell voltages in 30% KOH at current densities from 5 to 100 A/sq dm at temperatures up to 120 C with nickel electrodes of various structures have shown the foamed nickel electrode, with an average pore size of 1-1.5 mm, to have the best performance. When the foamed nickel is coated by fine powdered nickel, carbonyl nickel or Raney nickel to increase electrode surface areas, even lower cell voltages were found, indicating better performance.

  14. The sulphate-reduction alkalinity pump tested

    NASA Astrophysics Data System (ADS)

    Meister, Patrick; Petrishcheva, Elena

    2016-04-01

    Carbonate precipitation has been suggested to be induced by alkalinity increase during sulphate reduction under anoxic conditions. This mechanism may explain the formation of carbonate deposits in shallow marine environments, either within a redox stratified sediment inhabited by phototrophic microbial mats or in shallow water within the photic zone where sulphidic water is upwelling onto the shelf. The alkalinity pump may work as long as the sulphide is not reoxidized to sulphate, a process that would acidify the surrounding. The alkalinity effect of sulphate reduction was recently tested by Aloisi (2008) for microbial mats using a model approach. He found that sulphate reduction does not significantly increase or even decrease carbonate saturation and is unlikely to have played a significant role through Earth history. The model considers many environmental factors, including the effect of carbonate precipitation itself on the carbonate equilbrium and on the alkalinity. We used a modified version of Aloisi's (2008) model to simulate the saturation states of aragonite, calcite and dolomite without the effects of carbonate precipitation. This is necessary to evaluate the effect of microbial metabolisms exclusively on carbonate saturation, since carbonate precipitation is only the consequence, but not the cause of oversaturation. First results show that the saturation state is increased in the zone of phototrophic CO2 uptake. In contrast, the saturation state is strongly decreased in the zone where dissolved oxygen overlaps with dissolved sulphide. Aerobic sulphide oxidation consumes most of the HS- and dissipates most of the alkalinity produced in the sulphate reduction zone below. Hence, our results are consistent with the findings of Aloisi (2008), and they even more clearly show that sulphate reduction does not induce carbonate precipitation nor contributes to carbonate precipitation in combination with phototrophic CO2 uptake. The alkalinity effect of sulphate

  15. Substrate inhibition competes with halide inhibition in polyphenol oxidase.

    PubMed

    Lim, Giselle Grace Fernando; Imura, Yuki; Yoshimura, Etsuro

    2012-10-01

    Polyphenol oxidase (PPO) is a ubiquitous enzyme important in the food industry. Although PPO activity followed Michaelis-Menten kinetics at catechol concentrations of up to 1 mM, it slowly decreased at catechol concentrations above 2 mM. This result indicated that in addition to the active site (site A), the enzyme possesses a second catechol-binding site (site B) that exerts an inhibitory effect on PPO activity. Halides inhibit PPO activity in such a way that substrate inhibition is lessened when halide concentration is increased. Furthermore, elevated concentrations of catechol diminished the degree of inhibition by halides. These findings suggest that halides also bind to site B to inhibit PPO activity. A steady-state kinetic analysis demonstrated that the dissociation constant between catechol and PPO depended on the binding of halides to site B. The dissociation constants were greatest when chloride bound to the site. Bromide and iodide yielded lower dissociation constants, in that order. These data indicate that the binding of halide to site B modulated the structure of site A, thereby exerting an inhibitory effect.

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

    SciTech Connect

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

    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.

  17. Double-chamber electrode for spectrochemical determination of chlorine and other halogens

    USGS Publications Warehouse

    de Paiva, Azevedo; Specht, A.W.; Harner, R.S.

    1954-01-01

    A double-chamber, graphite electrode, suitable for d.c. arc determination of halogens by means of the alkaline earth halide bands, is described. An upper chamber holds the alkaline earth compound and an interconnected, lower chamber holds the halogen compound. This arrangement assures that there will be an abundance of alkaline earths in the arc by the time the halogen is volatilized from the lower chamber, and thereby promotes maximum emission of the alkaline earth halide bands. ?? 1954.

  18. Alkaline regenerative fuel cell systems for energy storage

    SciTech Connect

    Schubert, F.H.; Reid, M.A.; Martin, R.E.

    1981-01-01

    This paper presents the results of a preliminary design study of a Regenerative Fuel Cell Energy Storage system for application to future low-earth orbit space missions. This high energy density storage system is based on state-of-the-art alkaline electrolyte cell technology and incorporates dedicated fuel cell and electrolysis cell modules. 11 refs.

  19. Carbon cycling and snowball Earth.

    PubMed

    Goddéris, Yves; Donnadieu, Yannick

    2008-12-18

    The possibility that Earth witnessed episodes of global glaciation during the latest Precambrian challenges our understanding of the physical processes controlling the Earth's climate. Peltier et al. suggest that a 'hard snowball Earth' state may have been prevented owing to the release of CO(2) from the oxidation of dissolved organic carbon (DOC) in the ocean as the temperature decreased. Here we show that the model of Peltier et al. is not self-consistent as it implies large fluctuations of the ocean alkalinity content without providing any processes to account for it. Our findings suggest that the hard snowball Earth hypothesis is still valid.

  20. Ultrabroad Photoluminescence and Electroluminescence at New Wavelengths from Doped Organometal Halide Perovskites.

    PubMed

    Zhou, Yang; Yong, Zi-Jun; Zhang, Kai-Cheng; Liu, Bo-Mei; Wang, Zhao-Wei; Hou, Jing-Shan; Fang, Yong-Zheng; Zhou, Yi; Sun, Hong-Tao; Song, Bo

    2016-07-21

    Doping of semiconductors by introducing foreign atoms enables their widespread applications in microelectronics and optoelectronics. We show that this strategy can be applied to direct bandgap lead-halide perovskites, leading to the realization of ultrawide photoluminescence (PL) at new wavelengths enabled by doping bismuth (Bi) into lead-halide perovskites. Structural and photophysical characterization reveals that the PL stems from one class of Bi doping-induced optically active center, which is attributed to distorted [PbI6] units coupled with spatially localized bipolarons. Additionally, we find that compositional engineering of these semiconductors can be employed as an additional way to rationally tune the PL properties of doped perovskites. Finally, we accomplished the electroluminescence at cryogenic temperatures by using this system as an emissive layer, marking the first electrically driven devices using Bi-doped photonic materials. Our results suggest that low-cost, earth-abundant, solution-processable Bi-doped perovskite semiconductors could be promising candidate materials for developing optical sources operating at new wavelengths.

  1. Charge carrier mobility in hybrid halide perovskites.

    PubMed

    Motta, Carlo; El-Mellouhi, Fedwa; Sanvito, Stefano

    2015-08-03

    The charge transport properties of hybrid halide perovskites are investigated with a combination of density functional theory including van der Waals interaction and the Boltzmann theory for diffusive transport in the relaxation time approximation. We find the mobility of electrons to be in the range 5-10 cm(2)V(-1)s(-1) and that for holes within 1-5 cm(2)V(-1)s(-1), where the variations depend on the crystal structure investigated and the level of doping. Such results, in good agreement with recent experiments, set the relaxation time to about 1 ps, which is the time-scale for the molecular rotation at room temperature. For the room temperature tetragonal phase we explore two possible orientations of the organic cations and find that the mobility has a significant asymmetry depending on the direction of the current with respect to the molecular axis. This is due mostly to the way the PbI3 octahedral symmetry is broken. Interestingly we find that substituting I with Cl has minor effects on the mobilities. Our analysis suggests that the carrier mobility is probably not a key factor in determining the high solar-harvesting efficiency of this class of materials.

  2. Ultrathin Colloidal Cesium Lead Halide Perovskite Nanowires.

    PubMed

    Zhang, Dandan; Yu, Yi; Bekenstein, Yehonadav; Wong, Andrew B; Alivisatos, A Paul; Yang, Peidong

    2016-10-12

    Highly uniform single crystal ultrathin CsPbBr3 nanowires (NWs) with diameter of 2.2 ± 0.2 nm and length up to several microns were successfully synthesized and purified using a catalyst-free colloidal synthesis method followed by a stepwise purification strategy. The NWs have bright photoluminescence (PL) with a photoluminescence quantum yield (PLQY) of about 30% after surface treatment. Large blue-shifted UV-vis absorption and PL spectra have been observed due to strong two-dimensional quantum confinement effects. A small angle X-ray scattering (SAXS) pattern shows the periodic packing of the ultrathin NWs along the radial direction, demonstrates the narrow radial distribution of the wires, and emphasizes the deep intercalation of the surfactants. Despite the extreme aspect ratios of the ultrathin NWs, their composition and the resulting optical properties can be readily tuned by an anion-exchange reaction with good morphology preservation. These bright ultrathin NWs may be used as a model system to study strong quantum confinement effects in a one-dimensional halide perovskite system.

  3. Perspectives on organolead halide perovskite photovoltaics

    NASA Astrophysics Data System (ADS)

    Hariz, Alex

    2016-07-01

    A number of photovoltaic technologies have been developed for large-scale solar-power production. The single-crystal first-generation photovoltaic devices were followed by thin-film semiconductor absorber layers layered between two charge-selective contacts, and more recently, by nanostructured or mesostructured solar cells that utilize a distributed heterojunction to generate charge carriers and to transport holes and electrons in spatially separated conduits. Even though a number of materials have been trialed in nanostructured devices, the aim of achieving high-efficiency thin-film solar cells in such a manner as to rival the silicon technology has yet to be attained. Organolead halide perovskites have recently emerged as a promising material for high-efficiency nanoinfiltrated devices. An examination of the efficiency evolution curve reveals that interfaces play a paramount role in emerging organic electronic applications. To optimize and control the performance in these devices, a comprehensive understanding of the contacts is essential. However, despite the apparent advances made, a fundamental theoretical analysis of the physical processes taking place at the contacts is still lacking. However, experimental ideas, such as the use of interlayer films, are forging marked improvements in efficiencies of perovskite-based solar cells. Furthermore, issues of long-term stability and large-area manufacturing have some way to go before full commercialization is possible.

  4. Color silver halide hologram production and mastering

    NASA Astrophysics Data System (ADS)

    Bjelkhagen, Hans I.; Huang, Qiang

    1997-04-01

    Color reflection holograms recorded with the Denisyuk geometry have been demonstrated by the recently formed HOLOS Corporation in New Hampshire. The Slavich red-green-blue (RGB) sensitized ultra-high resolution silver halide emulsion was used for the hologram recording. The employed laser wavelengths were 647 nm, 532 nm, and 476 nm, generated by an argon ion, a frequency doubled Nd:YAG, and a krypton ion laser, respectively. A beam combination mechanism with dichroic filters enabled a simultaneous RGB exposure, which made the color balance and overall exposure energy easy to control as well as simplifying the recording procedure. HOLOS has been producing limited edition color holograms in various sizes from 4' X 5' to 12' X 16'. A 30 foot long optical table and high power lasers will enable HOLOS to record color holograms up to the size of one meter square in the near future. Various approaches have been investigated in generating color hologram masters which have sufficiently high diffraction efficiency to contact copy the color images onto photopolymer materials. A specially designed test object including the 1931 CIE chromaticity diagram, a rainbow ribbon cable, pure yellow dots, and a cloisonne elephant was used for color recording experiments. In addition, the Macbeth Color Checker chart was used. Both colorimetric evaluation and scattering noise measurements were performed using the PR-650 Photo Research SpectraScan SpectraCalorimeter.

  5. Charge carrier mobility in hybrid halide perovskites

    PubMed Central

    Motta, Carlo; El-Mellouhi, Fedwa; Sanvito, Stefano

    2015-01-01

    The charge transport properties of hybrid halide perovskites are investigated with a combination of density functional theory including van der Waals interaction and the Boltzmann theory for diffusive transport in the relaxation time approximation. We find the mobility of electrons to be in the range 5–10 cm2V−1s−1 and that for holes within 1–5 cm2V−1s−1, where the variations depend on the crystal structure investigated and the level of doping. Such results, in good agreement with recent experiments, set the relaxation time to about 1 ps, which is the time-scale for the molecular rotation at room temperature. For the room temperature tetragonal phase we explore two possible orientations of the organic cations and find that the mobility has a significant asymmetry depending on the direction of the current with respect to the molecular axis. This is due mostly to the way the PbI3 octahedral symmetry is broken. Interestingly we find that substituting I with Cl has minor effects on the mobilities. Our analysis suggests that the carrier mobility is probably not a key factor in determining the high solar-harvesting efficiency of this class of materials. PMID:26235910

  6. Mn(2+)-Doped Lead Halide Perovskite Nanocrystals with Dual-Color Emission Controlled by Halide Content.

    PubMed

    Liu, Wenyong; Lin, Qianglu; Li, Hongbo; Wu, Kaifeng; Robel, István; Pietryga, Jeffrey M; Klimov, Victor I

    2016-11-16

    Impurity doping has been widely used to endow semiconductor nanocrystals with novel optical, electronic, and magnetic functionalities. Here, we introduce a new family of doped NCs offering unique insights into the chemical mechanism of doping, as well as into the fundamental interactions between the dopant and the semiconductor host. Specifically, by elucidating the role of relative bond strengths within the precursor and the host lattice, we develop an effective approach for incorporating manganese (Mn) ions into nanocrystals of lead-halide perovskites (CsPbX3, where X = Cl, Br, or I). In a key enabling step not possible in, for example, II-VI nanocrystals, we use gentle chemical means to finely and reversibly tune the nanocrystal band gap over a wide range of energies (1.8-3.1 eV) via postsynthetic anion exchange. We observe a dramatic effect of halide identity on relative intensities of intrinsic band-edge and Mn emission bands, which we ascribe to the influence of the energy difference between the corresponding transitions on the characteristics of energy transfer between the Mn ion and the semiconductor host.

  7. Lead Halide Perovskites and Other Metal Halide Complexes As Inorganic Capping Ligands for Colloidal Nanocrystals

    PubMed Central

    2014-01-01

    Lead halide perovskites (CH3NH3PbX3, where X = I, Br) and other metal halide complexes (MXn, where M = Pb, Cd, In, Zn, Fe, Bi, Sb) have been studied as inorganic capping ligands for colloidal nanocrystals. We present the methodology for the surface functionalization via ligand-exchange reactions and the effect on the optical properties of IV–VI, II–VI, and III–V semiconductor nanocrystals. In particular, we show that the Lewis acid–base properties of the solvents, in addition to the solvent dielectric constant, must be properly adjusted for successful ligand exchange and colloidal stability. High luminescence quantum efficiencies of 20–30% for near-infrared emitting CH3NH3PbI3-functionalized PbS nanocrystals and 50–65% for red-emitting CH3NH3CdBr3- and (NH4)2ZnCl4-capped CdSe/CdS nanocrystals point to highly efficient electronic passivation of the nanocrystal surface. PMID:24746226

  8. Halide eutectic growth experiment MA-131

    NASA Technical Reports Server (NTRS)

    Yue, A. S.; Yue, B. K.; Lee, J. Y. M.

    1976-01-01

    Fiberlike sodium chloride/lithium fluoride eutectic mixtures have been produced on earth and in space by the directional solidification technique. Macroscopic and microscopic examinations were made on longitudinal and transverse sections of Apollo Soyuz Test Project space grown and earth grown ingots. It was found that samples grown in space have a higher percentage of fibers alined with the growth axis. The enhanced alinement of fibers is attributed to the absence of convection currents in the liquid during solidification. Optical transmittance measurements of transverse sections of the space grown and earth grown ingots were performed with an infrared spectrometer. For a given sample thickness, the highest transmittance was obtained from ingots grown in space. For samples of different thicknesses, grown either in space or on earth, it was found that the thinner the sample, the higher the transmittance. This is in agreement with the general optical property of transparent materials.

  9. Vitrification of IFR and MSBR halide salt reprocessing wastes

    SciTech Connect

    Siemer, D.D.

    2013-07-01

    Both of the genuinely sustainable (breeder) nuclear fuel cycles (IFR - Integral Fast Reactor - and MSBR - Molten Salt Breeder Reactor -) studied by the USA's national laboratories would generate high level reprocessing waste (HLRW) streams consisting of a relatively small amount ( about 4 mole %) of fission product halide (chloride or fluoride) salts in a matrix comprised primarily (about 95 mole %) of non radioactive alkali metal halide salts. Because leach resistant glasses cannot accommodate much of any of the halides, most of the treatment scenarios previously envisioned for such HLRW have assumed a monolithic waste form comprised of a synthetic analog of an insoluble crystalline halide mineral. In practice, this translates to making a 'substituted' sodalite ('Ceramic Waste Form') of the IFR's chloride salt-based wastes and fluoroapatite of the MSBR's fluoride salt-based wastes. This paper discusses my experimental studies of an alternative waste management scenario for both fuel cycles that would separate/recycle the waste's halide and immobilize everything else in iron phosphate (Fe-P) glass. It will describe both how the work was done and what its results indicate about how a treatment process for both of those wastes should be implemented (fluoride and chloride behave differently). In either case, this scenario's primary advantages include much higher waste loadings, much lower overall cost, and the generation of a product (glass) that is more consistent with current waste management practices. (author)

  10. Hemibonding of hydroxyl radical and halide anion in aqueous solution.

    PubMed

    Yamaguchi, Makoto

    2011-12-29

    Molecular geometries and properties of the possible reaction products between the hydroxyl radical and the halide anions in aqueous solution were investigated. The formation of two-center three-electron bonding (hemibonding) between the hydroxyl radical and halide anions (Cl, Br, I) was examined by density functional theory (DFT) calculation with a range-separated hybrid (RSH) exchange-correlation functional. The long-range corrected hybrid functional (LC-ωPBE), which have given quantitatively satisfactory results for odd electron systems and excited states, was examined by test calculations for dihalogen radical anions (X(2)(-); X = Cl, Br, I) and hydroxyl radical-water clusters. Equilibrium geometries with hemibonding between the hydroxyl radical and halide anions were located by including four hydrogen-bonded water molecules. Excitation energies and oscillator strengths of σ-σ* transitions calculated by the time-dependent DFT method showed good agreement with observed values. Calculated values of the free energy of reaction on the formation of hydroxyl halide radical anion from the hydroxyl radical and halide anion were endothermic for chloride but exothermic for bromide and iodide, which is consistent with experimental values of equilibrium constants.

  11. Process for oxidation of hydrogen halides to elemental halogens

    DOEpatents

    Lyke, Stephen E.

    1992-01-01

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

  12. Two Dimensional Organometal Halide Perovskite Nanorods with Tunable Optical Properties.

    PubMed

    Aharon, Sigalit; Etgar, Lioz

    2016-05-11

    Organo-metal halide perovskite is an efficient light harvester in photovoltaic solar cells. Organometal halide perovskite is used mainly in its "bulk" form in the solar cell. Confined perovskite nanostructures could be a promising candidate for efficient optoelectronic devices, taking advantage of the superior bulk properties of organo-metal halide perovskite, as well as the nanoscale properties. In this paper, we present facile low-temperature synthesis of two-dimensional (2D) lead halide perovskite nanorods (NRs). These NRs show a shift to higher energies in the absorbance and in the photoluminescence compared to the bulk material, which supports their 2D structure. X-ray diffraction (XRD) analysis of the NRs demonstrates their 2D nature combined with the tetragonal 3D perovskite structure. In addition, by alternating the halide composition, we were able to tune the optical properties of the NRs. Fast Fourier transform, and electron diffraction show the tetragonal structure of these NRs. By varying the ligands ratio (e.g., octylammonium to oleic acid) in the synthesis, we were able to provide the formation mechanism of these novel 2D perovskite NRs. The 2D perovskite NRs are promising candidates for a variety of optoelectronic applications, such as light-emitting diodes, lasing, solar cells, and sensors.

  13. Halide Perovskites: Poor Man's High-Performance Semiconductors.

    PubMed

    Stoumpos, Constantinos C; Kanatzidis, Mercouri G

    2016-07-01

    Halide perovskites are a rapidly developing class of medium-bandgap semiconductors which, to date, have been popularized on account of their remarkable success in solid-state heterojunction solar cells raising the photovoltaic efficiency to 20% within the last 5 years. As the physical properties of the materials are being explored, it is becoming apparent that the photovoltaic performance of the halide perovskites is just but one aspect of the wealth of opportunities that these compounds offer as high-performance semiconductors. From unique optical and electrical properties stemming from their characteristic electronic structure to highly efficient real-life technological applications, halide perovskites constitute a brand new class of materials with exotic properties awaiting discovery. The nature of halide perovskites from the materials' viewpoint is discussed here, enlisting the most important classes of the compounds and describing their most exciting properties. The topics covered focus on the optical and electrical properties highlighting some of the milestone achievements reported to date but also addressing controversies in the vastly expanding halide perovskite literature.

  14. Regeneration of zinc halide catalyst used in the hydrocracking of polynuclear hydrocarbons

    DOEpatents

    Gorin, Everett

    1978-01-01

    Improved recovery of spent molten zinc halide hydro-cracking catalyst is achieved in the oxidative vapor phase regeneration thereof by selective treatment of the zinc oxide carried over by the effluent vapors from the regeneration zone with hydrogen halide gas under conditions favoring the reaction of the zinc oxide with the hydrogen halide, whereby regenerated zinc halide is recovered in a solids-free state with little loss of zinc values.

  15. Advanced technology for extended endurance alkaline fuel cells

    NASA Astrophysics Data System (ADS)

    Sheibley, D. W.; Martin, R. A.

    Advanced components have been developed for alkaline fuel cells with a view to the satisfaction of NASA Space Station design requirements for extended endurance. The components include a platinum-on-carbon catalyst anode, a potassium titanate-bonded electrolyte matrix, a lightweight graphite electrolyte reservoir plate, a gold-plated nickel-perforated foil electrode substrate, a polyphenylene sulfide cell edge frame material, and a nonmagnesium cooler concept. When incorporated into the alkaline fuel cell unit, these components are expected to yield regenerative operation in a low earth orbit Space Station with a design life greater than 5 years.

  16. Advanced technology for extended endurance alkaline fuel cells

    NASA Technical Reports Server (NTRS)

    Sheibley, D. W.; Martin, R. A.

    1987-01-01

    Advanced components have been developed for alkaline fuel cells with a view to the satisfaction of NASA Space Station design requirements for extended endurance. The components include a platinum-on-carbon catalyst anode, a potassium titanate-bonded electrolyte matrix, a lightweight graphite electrolyte reservoir plate, a gold-plated nickel-perforated foil electrode substrate, a polyphenylene sulfide cell edge frame material, and a nonmagnesium cooler concept. When incorporated into the alkaline fuel cell unit, these components are expected to yield regenerative operation in a low earth orbit Space Station with a design life greater than 5 years.

  17. 40 CFR 721.10181 - Halide salt of an alkylamine (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Halide salt of an alkylamine (generic... Specific Chemical Substances § 721.10181 Halide salt of an alkylamine (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as halide salt...

  18. 40 CFR 721.10181 - Halide salt of an alkylamine (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Halide salt of an alkylamine (generic... Specific Chemical Substances § 721.10181 Halide salt of an alkylamine (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as halide salt...

  19. 40 CFR 721.10181 - Halide salt of an alkylamine (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Halide salt of an alkylamine (generic... Specific Chemical Substances § 721.10181 Halide salt of an alkylamine (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as halide salt...

  20. 40 CFR 721.10181 - Halide salt of an alkylamine (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Halide salt of an alkylamine (generic... Specific Chemical Substances § 721.10181 Halide salt of an alkylamine (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as halide salt...

  1. 40 CFR 721.10181 - Halide salt of an alkylamine (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Halide salt of an alkylamine (generic... Specific Chemical Substances § 721.10181 Halide salt of an alkylamine (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as halide salt...

  2. 10 CFR 431.322 - Definitions concerning metal halide lamp ballasts and fixtures.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 3 2010-01-01 2010-01-01 false Definitions concerning metal halide lamp ballasts and... FOR CERTAIN COMMERCIAL AND INDUSTRIAL EQUIPMENT Metal Halide Lamp Ballasts and Fixtures § 431.322 Definitions concerning metal halide lamp ballasts and fixtures. Ballast efficiency means, in the case of...

  3. 75 FR 5544 - Energy Conservation Program: Energy Conservation Standards for Metal Halide Lamp Fixtures: Public...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-03

    ... for Metal Halide Lamp Fixtures: Public Meeting and Availability of the Framework Document AGENCY... conservation standards for certain metal halide lamp fixtures. This document announces that the period for... metal halide lamp fixtures and provide docket number EERE-2009-BT-STD-0018 and/or RIN number 1904-...

  4. 10 CFR Appendix B to Subpart S to... - Certification Report for Metal Halide Lamp Ballasts

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 10 Energy 3 2011-01-01 2011-01-01 false Certification Report for Metal Halide Lamp Ballasts B... PROGRAM FOR CERTAIN COMMERCIAL AND INDUSTRIAL EQUIPMENT Metal Halide Lamp Ballasts and Fixtures Pt. 431, Subpt. S, App. B Appendix B to Subpart S to Part 431—Certification Report for Metal Halide Lamp...

  5. 10 CFR Appendix A to Subpart S of... - Compliance Statement for Metal Halide Lamp Ballasts

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 10 Energy 3 2011-01-01 2011-01-01 false Compliance Statement for Metal Halide Lamp Ballasts A... PROGRAM FOR CERTAIN COMMERCIAL AND INDUSTRIAL EQUIPMENT Metal Halide Lamp Ballasts and Fixtures Pt. 431, Subpt. S, App. A Appendix A to Subpart S of Part 431—Compliance Statement for Metal Halide Lamp...

  6. Metal-halide mixtures for latent heat energy storage

    NASA Technical Reports Server (NTRS)

    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.

  7. Electrochemical Doping of Halide Perovskites with Ion Intercalation.

    PubMed

    Jiang, Qinglong; Chen, Mingming; Li, Junqiang; Wang, Mingchao; Zeng, Xiaoqiao; Besara, Tiglet; Lu, Jun; Xin, Yan; Shan, Xin; Pan, Bicai; Wang, Changchun; Lin, Shangchao; Siegrist, Theo; Xiao, Qiangfeng; Yu, Zhibin

    2017-01-24

    Halide perovskites have recently been investigated for various solution-processed optoelectronic devices. The majority of studies have focused on using intrinsic halide perovskites, and the intentional incoporation of dopants has not been well explored. In this work, we discovered that small alkali ions, including lithium and sodium ions, could be electrochemically intercalated into a variety of halide and pseudohalide perovskites. The ion intercalation caused a lattice expansion of the perovskite crystals and resulted in an n-type doping of the perovskites. Such electrochemical doping improved the conductivity and changed the color of the perovskites, leading to an electrochromism with more than 40% reduction of transmittance in the 450-850 nm wavelength range. The doped perovskites exhibited improved electron injection efficiency into the pristine perovskite crystals, resulting in bright light-emitting diodes with a low turn-on voltage.

  8. Impurity segregation in zone-refined precursors for crystalline halide scintillators

    NASA Astrophysics Data System (ADS)

    Swider, S.; Lam, S.; Motakef, S.; Donohoe, E.; Coers, L.; Taylor, S.; Spencer, S.

    2015-06-01

    Successful growth of halide scintillator crystals depends on a supply of ultra-high purity (UHP) precursor materials. Metallic interstitials and substitutions may provide traps that quench luminescence. Oxygen impurities can create competing compounds within a matrix, such as oxyhalides, that disrupt crystallinity and nucleate cracks. Using mass spectroscopy and oxygen combustion analysis, we analyzed impurities in SrI2, EuI2, and YCl3 precursors before and after zone refining. The data show most alkali and alkali earth impurities segregated easily. However, with the exception of iron, many transition metals were incorporated into the solid. Reliable oxygen measurements proved difficult to achieve. Additional oxygen was measured in nitrates and sulfates, via ion chromatography. Zone refining reduced the overall impurity content, but levels remained above a 10 ppm target.

  9. Thermodynamic reactivity, growth and characterization of mercurous halide crystals

    NASA Technical Reports Server (NTRS)

    Singh, N. B.; Gottlieb, M.; Henningsen, T.; Hopkins, R. H.; Mazelsky, R.; Singh, M.; Glicksman, M. E.; Paradies, C.

    1992-01-01

    Thermodynamic calculations were carried out for the Hg-X-O system (X = Cl, Br, I) to identify the potential sources of contamination and relative stability of oxides and oxy-halide phases. The effect of excess mercury vapor pressure on the optical quality of mercurous halide crystal was studied by growing several mercurous chloride crystals from mercury-rich composition. The optical quality of crystals was examined by birefringence interferometry and laser scattering studies. Crystals grown in slightly mercury-rich composition showed improved optical quality relative to stoichiometric crystals.

  10. Activation volumes in lead halides and other solids

    NASA Astrophysics Data System (ADS)

    Alexopoulos, K.; Lazaridou, M.; Varotsos, P.

    1986-02-01

    Conductivity measurements of PbCl2 and PbBr2 under pressure have been carried out by Oberschmidt and Lazarus. The migration and activation volumes scale with the corresponding enthalpies in a manner predetermined by the bulk properties. By considering the existing data for a large variety of solids (rare-gas solids, lithium halides, lead halides, SrF2, and olivine) in which the defect enthalpies vary by two orders of magnitude we conclude that there is a curve which connects in a unified manner the point-defect data with the bulk properties.

  11. The effects of halide anions on the dielectric response of potassium halide solutions in visible, UV and far UV region.

    PubMed

    Shagieva, F M; Boinovich, L B

    2013-06-07

    Based on the experimentally measured dispersion of refractive indices, we studied the effects of halide anions on the dielectric response of potassium halide solutions in the visible, UV and far UV regions. It was shown that a specific ion effect according to the Hofmeister series is clearly demonstrated for the visible range of spectra. For the near-, mid-, and far UV ranges of spectra, the specific ion effect essentially depends on solution concentration and temperature. The influence of ions on the behavior of dynamic dielectric permittivity of a solution is discussed on the basis of ion/water and ion/ion electrostatic and electrodynamic interactions and hydration shell structure.

  12. FTIR study of matrix-isolated halides of dysprosium and thulium and their gaseous heterocomplexes with alkali halides

    SciTech Connect

    Feltrin, A.; Cesaro, S.N.

    1996-06-01

    Vibrational spectra of dysprosium and thulium chlorides, bromides, and iodides isolated in argon have been studied for the first time. The appearance of a single band, even in heavy deposits, suggested a planar geometry for all the samples examined. The complexity of Dy and Tm chlorides spectra, partly because of isotopic patterns, required a reinvestigation of NdCl{sub 3} isolated in argon and have been explained by comparison. Vapors in equilibrium over heated equimolar mixtures of a number of Dy, Tm, and Nd halides with alkali halides trapped in argon have been also investigated. FTIR measurements gave experimental evidence for the formation of gaseous heterocomplexes whose geometry is discussed.

  13. Mesozoic mafic alkaline magmatism of southern Scandinavia

    NASA Astrophysics Data System (ADS)

    Tappe, Sebastian

    2004-11-01

    More than 100 volcanic necks in central Scania (southern Sweden) are the product of Jurassic continental rift-related mafic alkaline magmatism at the southwest margin of the Baltic Shield. They are mainly basanites, with rarer melanephelinites. Both rock groups display overlapping primitive Mg-numbers, Cr and Ni contents, steep chondrite-normalized rare earth element patterns (LaN /YbN = 17 27) and an overall enrichment in incompatible elements. However, the melanephelinites are more alkaline and have stronger high field strength element enrichment than the basanites. The existence of distinct primary magmas is also indicated by heterogeneity in highly incompatible element ratios (e.g. Zr/Nb, La/Nb). Trace element modelling indicates that the magmas were generated by comparably low degrees of melting of a heterogeneous mantle source. Such a source can best be explained by a metasomatic overprint of the mantle lithosphere by percolating evolved melts. The former existence of such alkaline trace element-enriched melts can be demonstrated by inversion of the trace element content of green-core clinopyroxenes and anorthoclase which occur as xenocrysts in the melanephelinites and are interpreted as being derived from crystallization of evolved mantle melts. Jurassic magmatic activity in Scania was coeval with the generation of nephelinites in the nearby Egersund Basin (Norwegian North Sea). Both Scanian and North Sea alkaline magmas share similar trace element characteristics. Mantle enrichment processes at the southwest margin of the Baltic Shield and the North Sea Basin generated trace element signatures similar to those of ocean island basalts (e.g. low Zr/Nb and La/Nb) but there are no indications of plume activity during the Mesozoic in this area. On the contrary, the short duration of rifting, absence of extensive lithospheric thinning, and low magma volumes argue against a Mesozoic mantle plume. It seems likely that the metasomatic imprint resulted from the

  14. Structural Characterization of Methanol Substituted Lanthanum Halides

    PubMed Central

    Boyle, Timothy J.; Ottley, Leigh Anna M.; Alam, Todd M.; Rodriguez, Mark A.; Yang, Pin; Mcintyre, Sarah K.

    2010-01-01

    The first study into the alcohol solvation of lanthanum halide [LaX3] derivatives as a means to lower the processing temperature for the production of the LaBr3 scintillators was undertaken using methanol (MeOH). Initially the de-hydration of {[La(µ-Br)(H2O)7](Br)2}2 (1) was investigated through the simple room temperature dissolution of 1 in MeOH. The mixed solvate monomeric [La(H2O)7(MeOH)2](Br)3 (2) compound was isolated where the La metal center retains its original 9-coordination through the binding of two additional MeOH solvents but necessitates the transfer of the innersphere Br to the outersphere. In an attempt to in situ dry the reaction mixture of 1 in MeOH over CaH2, crystals of [Ca(MeOH)6](Br)2 (3) were isolated. Compound 1 dissolved in MeOH at reflux temperatures led to the isolation of an unusual arrangement identified as the salt derivative {[LaBr2.75•5.25(MeOH)]+0.25 [LaBr3.25•4.75(MeOH)]−0.25} (4). The fully substituted species was ultimately isolated through the dissolution of dried LaBr3 in MeOH forming the 8-coordinated [LaBr3(MeOH)5] (5) complex. It was determined that the concentration of the crystallization solution directed the structure isolated (4 concentrated; 5 dilute) The other LaX3 derivatives were isolated as [(MeOH)4(Cl)2La(µ-Cl)]2 (6) and [La(MeOH)9](I)3•MeOH (7). Beryllium Dome XRD analysis indicated that the bulk material for 5 appear to have multiple solvated species, 6 is consistent with the single crystal, and 7 was too broad to elucidate structural aspects. Multinuclear NMR (139La) indicated that these compounds do not retain their structure in MeOD. TGA/DTA data revealed that the de-solvation temperatures of the MeOH derivatives 4 – 6 were slightly higher in comparison to their hydrated counterparts. PMID:20514349

  15. Alkaline battery, separator therefore

    NASA Technical Reports Server (NTRS)

    Schmidt, George F. (Inventor)

    1980-01-01

    An improved battery separator for alkaline battery cells has low resistance to electrolyte ion transfer and high resistance to electrode ion transfer. The separator is formed by applying an improved coating to an electrolyte absorber. The absorber, preferably, is a flexible, fibrous, and porous substrate that is resistant to strong alkali and oxidation. The coating composition includes an admixture of a polymeric binder, a hydrolyzable polymeric ester and inert fillers. The coating composition is substantially free of reactive fillers and plasticizers commonly employed as porosity promoting agents in separator coatings. When the separator is immersed in electrolyte, the polymeric ester of the film coating reacts with the electrolyte forming a salt and an alcohol. The alcohol goes into solution with the electrolyte while the salt imbibes electrolyte into the coating composition. When the salt is formed, it expands the polymeric chains of the binder to provide a film coating substantially permeable to electrolyte ion transfer but relatively impermeable to electrode ion transfer during use.

  16. Semiempirical and DFT Investigations of the Dissociation of Alkyl Halides

    ERIC Educational Resources Information Center

    Waas, Jack R.

    2006-01-01

    Enthalpy changes corresponding to the gas phase heats of dissociation of 12 organic halides were calculated using two semiempirical methods, the Hartree-Fock method, and two DFT methods. These calculated values were compared to experimental values where possible. All five methods agreed generally with the expected empirically known trends in the…

  17. On the Boiling Points of the Alkyl Halides.

    ERIC Educational Resources Information Center

    Correia, John

    1988-01-01

    Discusses the variety of explanations in organic chemistry textbooks of a physical property of organic compounds. Focuses on those concepts explaining attractive forces between molecules. Concludes that induction interactions play a major role in alkyl halides and other polar organic molecules and should be given wider exposure in chemistry texts.…

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

    DOEpatents

    Newby, Billie J.

    1979-01-01

    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.

  19. Kinetic Studies of the Solvolysis of Two Organic Halides

    ERIC Educational Resources Information Center

    Duncan, J. A.; Pasto, D. J.

    1975-01-01

    Describes an undergraduate organic chemistry laboratory experiment which utilizes the solvolysis of organic halides to demonstrate first and second order reaction kinetics. The experiment also investigates the effect of a change of solvent polarity on reaction rate, common-ion and noncommon-ion salt effects, and the activation parameters of a…

  20. Students' understanding of alkyl halide reactions in undergraduate organic chemistry

    NASA Astrophysics Data System (ADS)

    Cruz-Ramirez de Arellano, Daniel

    Organic chemistry is an essential subject for many undergraduate students completing degrees in science, engineering, and pre-professional programs. However, students often struggle with the concepts and skills required to successfully solve organic chemistry exercises. Since alkyl halides are traditionally the first functional group that is studied in undergraduate organic chemistry courses, establishing a robust understanding of the concepts and reactions related to them can be beneficial in assuring students' success in organic chemistry courses. Therefore, the purpose of this study was to elucidate and describe students' understanding of alkyl halide reactions in an undergraduate organic chemistry course. Participants were interviewed using a think-aloud protocol in which they were given a set of exercises dealing with reactions and mechanisms of alkyl halide molecules in order to shed light on the students' understanding of these reactions and elucidate any gaps in understanding and incorrect warrants that may be present. These interviews were transcribed and analyzed using qualitative inquiry approaches. In general, the findings from this study show that the students exhibited gaps in understanding and incorrect warrants dealing with: (1) classifying substances as bases and/or nucleophiles, (2) assessing the basic or nucleophilic strength of substances, (3) accurately describing the electron movement of the steps that take place during alkyl halide reaction mechanisms, and (4) assessing the viability of their proposed reactive intermediates and breakage of covalent bonds. In addition, implications for teaching and future research are proposed.

  1. Students' Understanding of Alkyl Halide Reactions in Undergraduate Organic Chemistry

    ERIC Educational Resources Information Center

    Cruz-Ramirez de Arellano, Daniel

    2013-01-01

    Organic chemistry is an essential subject for many undergraduate students completing degrees in science, engineering, and pre-professional programs. However, students often struggle with the concepts and skills required to successfully solve organic chemistry exercises. Since alkyl halides are traditionally the first functional group that is…

  2. Early Earth

    NASA Astrophysics Data System (ADS)

    Brown, M.

    2015-05-01

    Earth has continents, subduction and mobile lid plate tectonics, but details of the early evolution are poorly understood. Here I summarize the Hadean-Archean record, review evidence for a hotter Earth and consider geodynamic models for early Earth.

  3. The Alkaline Dissolution Rate of Calcite.

    PubMed

    Colombani, Jean

    2016-07-07

    Due to the widespread presence of calcium carbonate on Earth, several geochemical systems, among which is the global CO2 cycle, are controlled to a large extent by the dissolution and precipitation of this mineral. For this reason, the dissolution of calcite has been thoroughly investigated for decades. Despite this intense activity, a consensual value of the dissolution rate of calcite has not been found yet. We show here that the inconsistency between the reported values stems mainly from the variability of the chemical and hydrodynamic conditions of measurement. The spreading of the values, when compared in identical conditions, is much less than expected and is interpreted in terms of sample surface topography. This analysis leads us to propose benchmark values of the alkaline dissolution rate of calcite compatible with all the published values, and a method to use them in various chemical and hydrodynamic contexts.

  4. The alkaline and alkaline-carbonatite magmatism from Southern Brazil

    NASA Astrophysics Data System (ADS)

    Ruberti, E.; Gomes, C. D. B.; Comin-Chiaramonti, P.

    2015-12-01

    Early to Late Cretaceous lasting to Paleocene alkaline magmatism from southern Brazil is found associated with major extensional structural features in and around the Paraná Basin and grouped into various provinces on the basis of several data. Magmatism is variable in size, mode of occurrence and composition. The alkaline rocks are dominantly potassic, a few occurrences showing sodic affinity. The more abundant silicate rocks are evolved undersaturated to saturated in silica syenites, displaying large variation in igneous forms. Less evolved types are restricted to subvolcanic environments and outcrops of effusive suites occur rarely. Cumulatic mafic and ultramafic rock types are very common, particularly in the alkali-carbonatitic complexes. Carbonatite bodies are represented by Ca-carbonatites and Mg-carbonatites and more scarcely by Fe-carbonatites. Available radiometric ages for the alkaline rocks fit on three main chronological groups: around 130 Ma, subcoveal with the Early Cretaceous flood tholeiites of the Paraná Basin, 100-110 Ma and 80-90 Ma (Late Cretaceous). The alkaline magmatism also extends into Paleocene times, as indicated by ages from some volcanic lavas. Geochemically, alkaline potassic and sodic rock types are distinguished by their negative and positive Nb-Ta anomalies, respectively. Negative spikes in Nb-Ta are also a feature common to the associated tholeiitic rocks. Sr-Nd-Pb systematics confirm the contribution of both HIMU and EMI mantle components in the formation of the alkaline rocks. Notably, Early and Late Cretaceous carbonatites have the same isotopic Sr-Nd initial ratios of the associated alkaline rocks. C-O isotopic Sr-Nd isotopic ratios indicate typical mantle signature for some carbonatites and the influence of post-magmatic processes in others. Immiscibility of liquids of phonolitic composition, derived from mafic alkaline parental magmas, has been responsible for the origin of the carbonatites. Close association of alkaline

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

    NASA Technical Reports Server (NTRS)

    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.

  6. Spectroscopic effects of disorder and vibrational localization in mixed-halide metal-halide chain solids

    SciTech Connect

    Love, S.P.; Scott, B.; Worl, L.A.; Huckett, S.C.; Saxena, A.; Huang, X.Z.; Bishop, A.R.; Swanson, B.I.

    1993-02-01

    Resonance Raman techniques, together with lattice-dynamics and Peierls-Hubbard modelling, are used to explore the electronic and vibrational dynamics of the quasi-one-dimensional metal-halogen chain solids [Pt(en){sub 2}][R(en){sub 2}X{sub 2}](ClO{sub 4}){sub 4}, (en = C{sub 2}H{sub 8}N{sub 2} and X=Cl, Br), abbreviated ``PLX.`` The mixed-halide materials PtCl{sub 1-x}Br{sub x} and PtCl{sub 1-x}I{sub x} consist of long mixed chains with heterojunctions between segments of the two constituent materials. Thus, in addition to providing mesoscale modulation of the chain electronic states, they serve as prototypes for elucidating the properties to be expected for macroscopic heterojunctions of these highly nonlinear materials. Once a detailed understanding of the various local vibrational modes occurring in these disordered solids is developed, the electronic structure of the chain segments and junctions can be probed by tuning the Raman excitation through their various electronic resonances.

  7. Optical Properties of Alkaline Earth Ions Doped Bismuth Borate Glasses

    SciTech Connect

    Kundu, Virender; Dhiman, R. L.; Maan, A. S.; Goyal, D. R.

    2011-07-15

    The optical properties of glasses with composition xLi{sub 2}O(30-x)Bi{sub 2}O{sub 3}-70B{sub 2}O{sub 3}; x = 0, 5, 10, 15 and 20 mol %, prepared by normal melt quench technique were investigated by means of UV-VIS measurement. It was observed that the optical band gap of the present glass system decreases with increasing Li{sub 2}O content up to 15 mol%, and with further increase in lithium oxide content i.e. x>15 mol% the optical band gap increases. It was also observed that the present glass system behaves as an indirect band gap semiconductor.

  8. Synthesis and Characterization of Alkaline-Earth Indium Sulfides

    DTIC Science & Technology

    1990-06-01

    CaS and In2S3 in an evacuated silica ampule, has the normal spinel structure (a = 10.77 ).1 This report is surprising, since the large Ca 2 + ion would...Ca3.1In6.6S13, 4 has been synthesized as yellow whiskers by iodine transport of a mixture of CaS and In2S3 . An X-ray single-crystal structure determination 5...mixture of CaS (Cerac 99.99%) and In2S3 (prepared from In(NO3)3 and H2S at 750’C) was pre-reacted in a graphite crucible in an evacuated silica

  9. Dissolution of alkaline earth sulfates in the presence of montmorillonite

    USGS Publications Warehouse

    Eberl, D.D.; Landa, E.R.

    1985-01-01

    In a study of the effect of montmorillonite on the dissolution of BaSO4 (barite), SrSO4 (celestite), and 226Ra from U mill tailings, it was found that: (1) More of these substances dissolve in an aqueous system that contains montmorillonite than dissolve in a similar system without clay, due to the ion exchange properties of the clay; (2) Na-montmorillonite is more effective in aiding dissolution than is Ca-montmorillonite; (3) the amount of Ra that moves from mill tailings to an exchanger increases as solution sulfate activity decreases. Leaching experiments suggest that 226Ra from H2SO4-circuit U mill tailings from Edgemont, South Dakota, is not present as pure Ra sulfate or as an impurity in anhydrite or gypsum; it is less soluble, and probably occurs as a trace constituent in barite.

  10. Aluminum/alkaline earth metal composites and method for producing

    DOEpatents

    Russell, Alan M; Anderson, Iver E; Kim, Hyong J; Freichs, Andrew E

    2014-02-11

    A composite is provided having an electrically conducting Al matrix and elongated filaments comprising Ca and/or Sr and/or Ba disposed in the matrix and extending along a longitudinal axis of the composite. The filaments initially comprise Ca and/or Sr and/or Ba metal or allow and then may be reacted with the Al matrix to form a strengthening intermetallic compound comprising Al and Ca and/or Sr and/or Ba. The composite is useful as a long-distance, high voltage power transmission conductor.

  11. Soft-mode transitions of alkaline-earth 122 pnictides

    NASA Astrophysics Data System (ADS)

    Widom, Michael; Quader, Khandker

    A -122 pnictides (A=Ca, Sr, Ba) exhibit three pressure-driven transitions: a first order enthalpic transition at PH from the striped AFM orthorhombic (OR) to a tetragonal (T) or a collapsed tetragonal (cT) phase; a transition at PM >PH from the metastable AFM OR to a T or cT phase; a Lifshitz transition at PL that causes T to collapse to a cT phase. Transitions at PH and PL were previously examined through total energy and band structure calculations. Here we address the transition at PM, beyond which the metastable AFM OR state ceases to exist. We show this transition occurs through a loss of elastic stability caused by softening of a shear mode associated with stretching along the c-axis. Simultaneously, magnetism and orthorhombicity approach limiting values with an approximately square-root singularity. Together these suggest a strong magneto-elastic coupling that may be relevant to a further understanding of the A-122-pnictides under pressure. This work was supported in part by the DOE under Grant DE-SC0014506.

  12. Synthesis and acid digestion of biomorphic ceramics: determination of alkaline and alkaline earth ions.

    PubMed

    Bosch Ojeda, Catalina; Sánchez Rojas, Fuensanta; Cano Pavón, José Manuel

    2007-09-01

    Ceramic and glass are some of the more recent engineering materials and those that are most resistant to environmental conditions. They belong to advanced materials in that they are being developed for the aerospace and electronics industries. In the last decade, a new class of ceramic materials has been the focus of particular attention. The materials were produced with natural, renewable resources (wood or wood-based products). In this work, we have synthesised a new biomorphic ceramic material from oak wood and Si infiltration. After the material characterization, we have optimized the dissolution of the sample by acid attack in an oven under microwave irradiation. Experimental designs were used as a multivariate strategy for the evaluation of the effects of varying several variables at the same time. The optimization was performed in two steps using factorial design for preliminary evaluation and a Draper-Lin design for determination of the critical experimental conditions. Five variables (time, power, volume of HNO3, volume H2SO4 and volume of HF) were considered as factors and as a response the concentration of different metal ions in the optimization process. Interactions between analytical factors and their optimal levels were investigated using a Draper-Lin design.

  13. Methods and Mechanisms for Cross-Electrophile Coupling of Csp2 Halides with Alkyl Electrophiles

    PubMed Central

    2016-01-01

    Conspectus Cross-electrophile coupling, the cross-coupling of two different electrophiles, avoids the need for preformed carbon nucleophiles, but development of general methods has lagged behind cross-coupling and C–H functionalization. A central reason for this slow development is the challenge of selectively coupling two substrates that are alike in reactivity. This Account describes the discovery of generally cross-selective reactions of aryl halides and acyl halides with alkyl halides, the mechanistic studies that illuminated the underlying principles of these reactions, and the use of these fundamental principles in the rational design of new cross-electrophile coupling reactions. Although the coupling of two different electrophiles under reducing conditions often leads primarily to symmetric dimers, the subtle differences in reactivity of aryl halides and alkyl halides with nickel catalysts allowed for generally cross-selective coupling reactions. These conditions could also be extended to the coupling of acyl halides with alkyl halides. These reactions are exceptionally functional group tolerant and can be assembled on the benchtop. A combination of stoichiometric and catalytic studies on the mechanism of these reactions revealed an unusual radical-chain mechanism and suggests that selectivity arises from (1) the preference of nickel(0) for oxidative addition to aryl halides and acyl halides over alkyl halides and (2) the greater propensity of alkyl halides to form free radicals. Bipyridine-ligated arylnickel intermediates react with alkyl radicals to efficiently form, after reductive elimination, new C–C bonds. Finally, the resulting nickel(I) species is proposed to regenerate an alkyl radical to carry the chain. Examples of new reactions designed using these principles include carbonylative coupling of aryl halides with alkyl halides to form ketones, arylation of epoxides to form β-aryl alcohols, and coupling of benzyl sulfonate esters with aryl

  14. Energetics of Amino Acid Synthesis in Alkaline Hydrothermal Environments.

    PubMed

    Kitadai, Norio

    2015-12-01

    Alkaline hydrothermal systems have received considerable attention as candidates for the origin and evolution of life on the primitive Earth. Nevertheless, sufficient information has not yet been obtained for the thermodynamic properties of amino acids, which are necessary components for life, at high temperatures and alkaline pH. These properties were estimated using experimental high-temperature volume and heat capacity data reported in the literature for several amino acids, together with correlation algorithms and the revised Helgeson-Kirkham-Flowers (HKF) equations of state. This approach enabled determination of a complete set of the standard molal thermodynamic data and the revised HKF parameters for the 20 protein amino acids in their zwitterionic and ionization states. The obtained dataset was then used to evaluate the energetics of amino acid syntheses from simple inorganic precursors (CO2, H2, NH3 and H2S) in a simulated alkaline hydrothermal system on the Hadean Earth. Results show that mixing between CO2-rich seawater and the H2-rich hydrothermal fluid can produce energetically favorable conditions for amino acid syntheses, particularly in the lower-temperature region of such systems. Together with data related to the pH and temperature dependences of the energetics of amino acid polymerizations presented in earlier reports, these results suggest the following. Hadean alkaline hydrothermal settings, where steep pH and temperature gradients may have existed between cool, slightly acidic Hadean ocean water and hot, alkaline hydrothermal fluids at the vent-ocean interface, may be energetically the most suitable environment for the synthesis and polymerization of amino acids.

  15. Energetics of Amino Acid Synthesis in Alkaline Hydrothermal Environments

    NASA Astrophysics Data System (ADS)

    Kitadai, Norio

    2015-12-01

    Alkaline hydrothermal systems have received considerable attention as candidates for the origin and evolution of life on the primitive Earth. Nevertheless, sufficient information has not yet been obtained for the thermodynamic properties of amino acids, which are necessary components for life, at high temperatures and alkaline pH. These properties were estimated using experimental high-temperature volume and heat capacity data reported in the literature for several amino acids, together with correlation algorithms and the revised Helgeson-Kirkham-Flowers (HKF) equations of state. This approach enabled determination of a complete set of the standard molal thermodynamic data and the revised HKF parameters for the 20 protein amino acids in their zwitterionic and ionization states. The obtained dataset was then used to evaluate the energetics of amino acid syntheses from simple inorganic precursors (CO2, H2, NH3 and H2S) in a simulated alkaline hydrothermal system on the Hadean Earth. Results show that mixing between CO2-rich seawater and the H2-rich hydrothermal fluid can produce energetically favorable conditions for amino acid syntheses, particularly in the lower-temperature region of such systems. Together with data related to the pH and temperature dependences of the energetics of amino acid polymerizations presented in earlier reports, these results suggest the following. Hadean alkaline hydrothermal settings, where steep pH and temperature gradients may have existed between cool, slightly acidic Hadean ocean water and hot, alkaline hydrothermal fluids at the vent-ocean interface, may be energetically the most suitable environment for the synthesis and polymerization of amino acids.

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

    DOEpatents

    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.

  17. Alkali Halide Microstructured Optical Fiber for X-Ray Detection

    NASA Technical Reports Server (NTRS)

    DeHaven, S. L.; Wincheski, R. A.; Albin, S.

    2014-01-01

    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.

  18. Laser Direct Write Synthesis of Lead Halide Perovskites

    SciTech Connect

    Chou, Stanley S.; Swartzentruber, Brian S.; Janish, Matthew T.; Meyer, Kristin C.; Biedermann, Laura B.; Okur, Serdal; Burckel, D. Bruce; Carter, C. Barry; Kaehr, Bryan

    2016-09-05

    Lead halide perovskites are increasingly considered for applications beyond photovoltaics, for example, light emission and detection, where an ability to pattern and prototype microscale geometries can facilitate the incorporation of this class of materials into devices. In this study, we demonstrate laser direct write of lead halide perovskites, a remarkably simple procedure that takes advantage of the inverse dependence between perovskite solubility and temperature by using a laser to induce localized heating of an absorbing substrate. We also demonstrate arbitrary pattern formation of crystalline CH3NH3PbBr3 on a range of substrates and fabricate and characterize a microscale photodetector using this approach. This direct write methodology provides a path forward for the prototyping and production of perovskite-based devices.

  19. Laser Direct Write Synthesis of Lead Halide Perovskites

    DOE PAGES

    Chou, Stanley S.; Swartzentruber, Brian S.; Janish, Matthew T.; ...

    2016-09-05

    Lead halide perovskites are increasingly considered for applications beyond photovoltaics, for example, light emission and detection, where an ability to pattern and prototype microscale geometries can facilitate the incorporation of this class of materials into devices. In this study, we demonstrate laser direct write of lead halide perovskites, a remarkably simple procedure that takes advantage of the inverse dependence between perovskite solubility and temperature by using a laser to induce localized heating of an absorbing substrate. We also demonstrate arbitrary pattern formation of crystalline CH3NH3PbBr3 on a range of substrates and fabricate and characterize a microscale photodetector using this approach.more » This direct write methodology provides a path forward for the prototyping and production of perovskite-based devices.« less

  20. Gaseous NH3 Confers Porous Pt Nanodendrites Assisted by Halides

    PubMed Central

    Lu, Shuanglong; Eid, Kamel; Li, Weifeng; Cao, Xueqin; Pan, Yue; Guo, Jun; Wang, Liang; Wang, Hongjing; Gu, Hongwei

    2016-01-01

    Tailoring the morphology of Pt nanocrystals (NCs) is of great concern for their enhancement in catalytic activity and durability. In this article, a novel synthetic strategy is developed to selectively prepare porous dendritic Pt NCs with different structures for oxygen reduction reaction (ORR) assisted by NH3 gas and halides (F−, Cl−, Br−). The NH3 gas plays critical roles on tuning the morphology. Previously, H2 and CO gas are reported to assist the shape control of metallic nanocrystals. This is the first demonstration that NH3 gas assists the Pt anisotropic growth. The halides also play important role in the synthetic strategy to regulate the formation of Pt NCs. As-made porous dendritic Pt NCs, especially when NH4F is used as a regulating reagent, show superior catalytic activity for ORR compared with commercial Pt/C catalyst and other previously reported Pt-based NCs. PMID:27184228

  1. Double Charged Surface Layers in Lead Halide Perovskite Crystals.

    PubMed

    Sarmah, Smritakshi P; Burlakov, Victor M; Yengel, Emre; Murali, Banavoth; Alarousu, Erkki; El-Zohry, Ahmed M; Yang, Chen; Alias, Mohd S; Zhumekenov, Ayan A; Saidaminov, Makhsud I; Cho, Namchul; Wehbe, Nimer; Mitra, Somak; Ajia, Idris; Dey, Sukumar; Mansour, Ahmed E; Abdelsamie, Maged; Amassian, Aram; Roqan, Iman S; Ooi, Boon S; Goriely, Alain; Bakr, Osman M; Mohammed, Omar F

    2017-03-08

    Understanding defect chemistry, particularly ion migration, and its significant effect on the surface's optical and electronic properties is one of the major challenges impeding the development of hybrid perovskite-based devices. Here, using both experimental and theoretical approaches, we demonstrated that the surface layers of the perovskite crystals may acquire a high concentration of positively charged vacancies with the complementary negatively charged halide ions pushed to the surface. This charge separation near the surface generates an electric field that can induce an increase of optical band gap in the surface layers relative to the bulk. We found that the charge separation, electric field, and the amplitude of shift in the bandgap strongly depend on the halides and organic moieties of perovskite crystals. Our findings reveal the peculiarity of surface effects that are currently limiting the applications of perovskite crystals and more importantly explain their origins, thus enabling viable surface passivation strategies to remediate them.

  2. Laser Direct Write Synthesis of Lead Halide Perovskites.

    PubMed

    Chou, Stanley S; Swartzentruber, Brian S; Janish, Matthew T; Meyer, Kristin C; Biedermann, Laura B; Okur, Serdal; Burckel, D Bruce; Carter, C Barry; Kaehr, Bryan

    2016-10-06

    Lead halide perovskites are increasingly considered for applications beyond photovoltaics, for example, light emission and detection, where an ability to pattern and prototype microscale geometries can facilitate the incorporation of this class of materials into devices. Here we demonstrate laser direct write of lead halide perovskites, a remarkably simple procedure that takes advantage of the inverse dependence between perovskite solubility and temperature by using a laser to induce localized heating of an absorbing substrate. We demonstrate arbitrary pattern formation of crystalline CH3NH3PbBr3 on a range of substrates and fabricate and characterize a microscale photodetector using this approach. This direct write methodology provides a path forward for the prototyping and production of perovskite-based devices.

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

    PubMed

    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.

  4. Enhanced Born charge and proximity to ferroelectricity in thallium halides

    NASA Astrophysics Data System (ADS)

    Du, Mao-Hua; Singh, David J.

    2010-04-01

    Electronic-structure and lattice-dynamics calculations on thallium halides show that the Born effective charges in these compounds are more than twice larger than the nominal ionic charges. This is a result of cross-band-gap hybridization between Tlp and halogen- p states. The large Born charges cause giant splitting between longitudinal and transverse-optic phonon modes, bringing the lattice close to ferroelectric instability. Our calculations indeed show that cubic TlBr develops ferroelectric instabilities upon lattice expansion starting at 2%. It is remarkable that the apparently ionic thallium halides with a simple cubic CsCl structure and large differences in electronegativity between cations and anions can be very close to ferroelectricity. This can lead to effective screening of defects and impurities that would otherwise be strong carrier traps and may therefore contribute to the relatively good carrier transport properties in TlBr radiation detectors.

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

    SciTech Connect

    DeHaven, S. L. E-mail: russel.a.wincheski@nasa.gov; Wincheski, R. A. E-mail: russel.a.wincheski@nasa.gov; Albin, S.

    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.

  6. Oxidative alkoxylation of phosphine in alcohol solutions of copper halides

    NASA Astrophysics Data System (ADS)

    Polimbetova, G. S.; Borangazieva, A. K.; Ibraimova, Zh. U.; Bugubaeva, G. O.; Keynbay, S.

    2016-08-01

    The phosphine oxidation reaction with oxygen in alcohol solutions of copper (I, II) halides is studied. Kinetic parameters, intermediates, and by-products are studied by means of NMR 31P-, IR-, UV-, and ESR- spectroscopy; and by magnetic susceptibility, redox potentiometry, gas chromatography, and elemental analysis. A reaction mechanism is proposed, and the optimum conditions are found for the reaction of oxidative alkoxylation phosphine.

  7. Copper-catalyzed arylation of alkyl halides with arylaluminum reagents

    PubMed Central

    Shrestha, Bijay

    2015-01-01

    Summary We report a Cu-catalyzed coupling between triarylaluminum reagents and alkyl halides to form arylalkanes. The reaction proceeds in the presence of N,N,N’,N’-tetramethyl-o-phenylenediamine (NN-1) as a ligand in combination with CuI as a catalyst. This catalyst system enables the coupling of primary alkyl iodides and bromides with electron-neutral and electron-rich triarylaluminum reagents and affords the cross-coupled products in good to excellent yields. PMID:26734088

  8. Organolead Halide Perovskites for Low Operating Voltage Multilevel Resistive Switching.

    PubMed

    Choi, Jaeho; Park, Sunghak; Lee, Joohee; Hong, Kootak; Kim, Do-Hong; Moon, Cheon Woo; Park, Gyeong Do; Suh, Junmin; Hwang, Jinyeon; Kim, Soo Young; Jung, Hyun Suk; Park, Nam-Gyu; Han, Seungwu; Nam, Ki Tae; Jang, Ho Won

    2016-08-01

    Organolead halide perovskites are used for low-operating-voltage multilevel resistive switching. Ag/CH3 NH3 PbI3 /Pt cells exhibit electroforming-free resistive switching at an electric field of 3.25 × 10(3) V cm(-1) for four distinguishable ON-state resistance levels. The migration of iodine interstitials and vacancies with low activation energies is responsible for the low-electric-field resistive switching via filament formation and annihilation.

  9. Catalytic Diversity in Alkaline Hydrothermal Vent Systems on Ocean Worlds

    NASA Astrophysics Data System (ADS)

    Cameron, Ryan D.; Barge, Laura; Chin, Keith B.; Doloboff, Ivria J.; Flores, Erika; Hammer, Arden C.; Sobron, Pablo; Russell, Michael J.; Kanik, Isik

    2016-10-01

    Hydrothermal systems formed by serpentinization can create moderate-temperature, alkaline systems and it is possible that this type of vent could exist on icy worlds such as Europa which have water-rock interfaces. It has been proposed that some prebiotic chemistry responsible for the emergence of life on Earth and possibly other wet and icy worlds could occur as a result ofredox potential and pH gradients in submarine alkaline hydrothermal vents (Russell et al., 2014). Hydrothermal chimneys formed in laboratory simulations of alkaline vents under early Earth conditions have precipitate membranes that contain minerals such as iron sulfides, which are hypothesized to catalyze reduction of CO2 (Yamaguchi et al. 2014, Roldan et al. 2014) leading to further organic synthesis. This CO2 reduction process may be affected by other trace components in the chimney, e.g. nickel or organic molecules. We have conducted experiments to investigate catalytic properties of iron and iron-nickel sulfides containing organic dopants in slightly acidic ocean simulants relevant to early Earth or possibly ocean worlds. We find that the electrochemical properties of the chimney as well as the morphology/chemistry of the precipitate are affected by the concentration and type of organics present. These results imply that synthesis of organics in water-rock systems on ocean worlds may lead to hydrothermal precipitates which can incorporate these organic into the mineral matrix and may affect the role of gradients in alkaline vent systems.Therefore, further understanding on the electroactive roles of various organic species within hydrothermal chimneys will have important implications for habitability as well as prebiotic chemistry. This work is funded by NASA Astrobiology Institute JPL Icy Worlds Team and a NAI Director's Discretionary Fund award.Yamaguchi A. et al. (2014) Electrochimica Acta, 141, 311-318.Russell, M. J. et al. (2014), Astrobiology, 14, 308-43.Roldan, A. (2014) Chem. Comm. 51

  10. Iron-catalyzed homocoupling of aryl halides and derivatives in the presence of alkyllithiums.

    PubMed

    Toummini, Dounia; Ouazzani, Fouad; Taillefer, Marc

    2013-09-20

    Direct synthesis of biaryl derivatives from aryl halides takes place under very mild temperature conditions by using a ligand-free iron catalytic system. The procedure, which proceeds via an in situ quantitative aryl halide exchange with alkyllithiums, allows for excellent control of the reactivity and is in line with the sustainable development. The method is also applicable to styryl and benzyl halides and to phenylacetylene.

  11. Fundamentals of Digital Photography 1. Silver Halide Photography and Digital Photography

    NASA Astrophysics Data System (ADS)

    Toyoda, Kenji

    A major difference between silver halide photography and digital photography lies in the way of processing image data. Parallel processing of the whole image area can be accomplished in silver halide photography. However, image data must be processed serially in digital photography, and this serial processing of image data is called "scan". In silver halide photography, an almighty device "film" does everything from signal conversion, signal processing to signal storage. But separate devices take each role in digital photography.

  12. Excited State Kinetics of Mercury Halides and Mixtures with N2 and Xe.

    DTIC Science & Technology

    1983-11-28

    methylmercury and mercuric halides . Room t~m~era- ture quenehing rate constants and rate constants for production of HgX(B z ) were measured. Evidence...1311 (1982) Rite constants for the production of excited state products from the reaction of Xe( P ) with several methylmercury and mercuric halides ...v - 0, 1) and Xe( P ) with serveral mercuric and methylmercury halids haVe been simulated to asiign the HgX(B) vibrational * distributions. The

  13. Effects of halides on plasmid-mediated silver resistance in Escherichia coli.

    PubMed

    Gupta, A; Maynes, M; Silver, S

    1998-12-01

    Silver resistance of sensitive Escherichia coli J53 and resistance plasmid-containing J53(pMG101) was affected by halides in the growth medium. The effects of halides on Ag+ resistance were measured with AgNO3 and silver sulfadiazine, both on agar and in liquid. Low concentrations of chloride made the differences in MICs between sensitive and resistant strains larger. High concentrations of halides increased the sensitivities of both strains to Ag+.

  14. Effects of Halides on Plasmid-Mediated Silver Resistance in Escherichia coli

    PubMed Central

    Gupta, Amit; Maynes, Maria; Silver, Simon

    1998-01-01

    Silver resistance of sensitive Escherichia coli J53 and resistance plasmid-containing J53(pMG101) was affected by halides in the growth medium. The effects of halides on Ag+ resistance were measured with AgNO3 and silver sulfadiazine, both on agar and in liquid. Low concentrations of chloride made the differences in MICs between sensitive and resistant strains larger. High concentrations of halides increased the sensitivities of both strains to Ag+. PMID:9835606

  15. Solid-state 207Pb NMR studies of mixed lead halides, PbFX (X=Cl, Br, or I).

    PubMed

    Glatfelter, Alicia; Dybowski, Cecil; Kragten, David D; Bai, Shi; Perry, Dale L; Lockard, Jenny

    2007-04-01

    Solid-state 207Pb NMR studies have been conducted on mixed lead(II) halides of the type PbFX, where X=Cl, Br, or I. NMR data for the mixed halides are compared to the solid-state NMR data for the divalent, binary lead halides, PbX2 (X=F, Cl, Br, I). The NMR data are evaluated in the context of the structures of the compounds and the effects of the mixed halides on the electronic structure of the divalent lead. Data sets for the mixed halides are discussed and compared to those for the regular lead(II) halides.

  16. Fluorescent Properties of Manganese Halide Benzothiazole Inorganic-Organic Hybrids.

    PubMed

    Yu, Hui; Mei, YingXuan; Wei, ZhenHong; Mei, GuangQuan; Cai, Hu

    2016-11-01

    The reaction of manganese (II) halides MnX2 and benzothiazole (btz) in the concentrated acids HX (X = Cl, Br) at 80 °C resulted in the formation of two inorganic-organic hybrid complexes: [(btz)2(MnX4)]·2H2O (X = Cl, 1; X = Br, 2). Both compounds showed green luminescence and exhibited moderate quantum yields of 43.17 % for 1 and 26.18 % for 2, which were directly originated from the tetrahedral coordination of Mn(2+) ion. Two organic - inorganic hybrids [(btz)2(MnX4)]·2H2O based on MnCl2, benzothiazole and halide acids emitted green light with the moderate quantum efficiencies when excited by 365 nm light. Graphical abstract Two organic-inorganic hybrids [(btz)2(MnX4)]·2H2O based on MnCl2, benzothiazole and halide acids emitted green light with the moderate quantum efficiencies when excited by 365 nm light.

  17. Deciphering Halogen Competition in Organometallic Halide Perovskite Growth

    DOE PAGES

    Keum, Jong Kahk; Ovchinnikova, Olga S.; Chen, Shiyou; ...

    2016-03-01

    Organometallic halide perovskites (OHPs) hold great promise for next-generation, low-cost optoelectronic devices. During the chemical synthesis and crystallization of OHP thin films a major unresolved question is the competition between multiple halide species (e.g. I-, Cl-, Br-) in the formation of the mixed halide perovskite crystals. Whether Cl- ions are successfully incorporated into the perovskite crystal structure or alternatively, where they are located, is not yet fully understood. Here, in situ X-ray diffraction measurements of crystallization dynamics are combined with ex situ TOF-SIMS chemical analysis to reveal that Br- or Cl- ions can promote crystal growth, yet reactive I- ionsmore » prevent them from incorporating into the lattice of the final perovskite crystal structure. The Cl- ions are located in the grain boundaries of the perovskite films. These findings significantly advance our understanding of the role of halogens during synthesis of hybrid perovskites, and provide an insightful guidance to the engineering of high-quality perovskite films, essential for exploring superior-performance and cost-effective optoelectronic devices.« less

  18. Deciphering Halogen Competition in Organometallic Halide Perovskite Growth

    SciTech Connect

    Keum, Jong Kahk; Ovchinnikova, Olga S.; Chen, Shiyou; Du, Mao-Hua; Ivanov, Ilia N; Rouleau, Christopher; Geohegan, David B.; Xiao, Kai

    2016-03-01

    Organometallic halide perovskites (OHPs) hold great promise for next-generation, low-cost optoelectronic devices. During the chemical synthesis and crystallization of OHP thin films a major unresolved question is the competition between multiple halide species (e.g. I-, Cl-, Br-) in the formation of the mixed halide perovskite crystals. Whether Cl- ions are successfully incorporated into the perovskite crystal structure or alternatively, where they are located, is not yet fully understood. Here, in situ X-ray diffraction measurements of crystallization dynamics are combined with ex situ TOF-SIMS chemical analysis to reveal that Br- or Cl- ions can promote crystal growth, yet reactive I- ions prevent them from incorporating into the lattice of the final perovskite crystal structure. The Cl- ions are located in the grain boundaries of the perovskite films. These findings significantly advance our understanding of the role of halogens during synthesis of hybrid perovskites, and provide an insightful guidance to the engineering of high-quality perovskite films, essential for exploring superior-performance and cost-effective optoelectronic devices.

  19. Lasing in robust cesium lead halide perovskite nanowires

    PubMed Central

    Eaton, Samuel W.; Lai, Minliang; Gibson, Natalie A.; Wong, Andrew B.; Dou, Letian; Ma, Jie; Wang, Lin-Wang; Leone, Stephen R.; Yang, Peidong

    2016-01-01

    The rapidly growing field of nanoscale lasers can be advanced through the discovery of new, tunable light sources. The emission wavelength tunability demonstrated in perovskite materials is an attractive property for nanoscale lasers. Whereas organic–inorganic lead halide perovskite materials are known for their instability, cesium lead halides offer a robust alternative without sacrificing emission tunability or ease of synthesis. Here, we report the low-temperature, solution-phase growth of cesium lead halide nanowires exhibiting low-threshold lasing and high stability. The as-grown nanowires are single crystalline with well-formed facets, and act as high-quality laser cavities. The nanowires display excellent stability while stored and handled under ambient conditions over the course of weeks. Upon optical excitation, Fabry–Pérot lasing occurs in CsPbBr3 nanowires with an onset of 5 μJ cm−2 with the nanowire cavity displaying a maximum quality factor of 1,009 ± 5. Lasing under constant, pulsed excitation can be maintained for over 1 h, the equivalent of 109 excitation cycles, and lasing persists upon exposure to ambient atmosphere. Wavelength tunability in the green and blue regions of the spectrum in conjunction with excellent stability makes these nanowire lasers attractive for device fabrication. PMID:26862172

  20. Properties of volume reflection silver-halide gelatin holograms

    NASA Astrophysics Data System (ADS)

    Kosobokova, N. L.; Usanov, Yuri E.; Shevtsov, Michail K.

    1991-02-01

    Three schemes of realization of micro-cavity method of processing silver halide photomaterials for silver-halide gelatin holograms (SHG) generation are proposed. Factors affecting diffraction efficiency replay wavelength shift and selectivity are discussed. 2. EXPERIMENTAL RESULTS In the previous paper on this issue the principle of SHG hologram formation based on a difference of speed hardening of gelatin mass in a photolayer and in a thin cover of gelatin absorbed on silver or silver halide grains was formulated. The investigation of " swelling" factor for layers both containing and not containing solid grains verified the difference in the hardening degree of these layers and demonstrated a possibility of using this phenomenon for the generation of SHG holograms. As a result we proposed three methods of transforming the structure of distribution of solid particles of a layer into the structure of micro-cavity distribution. Processing procedures realizing the micro-cavity (MC) methods are presented in Fig. l. As seen in Fig. l the differentiating feature of each method is the type of grain in a layer during its hardening. In the course of realization of methods MC-l MC-2 and MC-3 a layer to be hardened contains metallic developed silver rehalogenated silver and silver resulting after reversal bleaching of developed silver respectively. The common feature of all methods is dehydration procedure which results in producing micro cavities in the places of removed silver or silver salt grains.

  1. Far Infrared Optical Spectroscopy of Alkali Halide-Polymer Composites

    NASA Astrophysics Data System (ADS)

    McWhirter, J. T.; Broderick, S. D.; Rodriguez, G. A.

    1998-03-01

    Composite samples of small (dimension < 10 =B5m) alkali halide crystallites in a polymer matrix (low density polyethylene and polytetrafluoroethylene) have been prepared. The far infrared optical spectra of these samples are presented, spanning a temperature range of 300 to <10 K, and a dominant absorption feature due to absorption by the transverse optic phonon of the alkali halide constituent is observed. An effective medium analysis of the samples, using the Maxwell-Garnett model, is shown to accurately reproduce the main absorption feature, but requires a shape factor for the inclusion geometry corresponding to flat, plate-like inclusions, and a plausible explanation for such a geometry is proposed. The temperature dependence of the frequency and linewidth of the absorption peak is presented. The temperature shift of the line-center-frequency is found to be adequately described by a quasiharmonic description of the transverse optic phonon energy shift of the alkali halide due to lattice thermal expansion, using published values for the mode Gruneisen parameter and the temperature dependence of the lattice thermal coefficient. In contrast, the linewidth (phonon lifetime) of the composite samples is roughly twice as large as that observed for thin film and bulk crystals, and has a much stronger temperature dependence as well.

  2. Lasing in robust cesium lead halide perovskite nanowires.

    PubMed

    Eaton, Samuel W; Lai, Minliang; Gibson, Natalie A; Wong, Andrew B; Dou, Letian; Ma, Jie; Wang, Lin-Wang; Leone, Stephen R; Yang, Peidong

    2016-02-23

    The rapidly growing field of nanoscale lasers can be advanced through the discovery of new, tunable light sources. The emission wavelength tunability demonstrated in perovskite materials is an attractive property for nanoscale lasers. Whereas organic-inorganic lead halide perovskite materials are known for their instability, cesium lead halides offer a robust alternative without sacrificing emission tunability or ease of synthesis. Here, we report the low-temperature, solution-phase growth of cesium lead halide nanowires exhibiting low-threshold lasing and high stability. The as-grown nanowires are single crystalline with well-formed facets, and act as high-quality laser cavities. The nanowires display excellent stability while stored and handled under ambient conditions over the course of weeks. Upon optical excitation, Fabry-Pérot lasing occurs in CsPbBr3 nanowires with an onset of 5 μJ cm(-2) with the nanowire cavity displaying a maximum quality factor of 1,009 ± 5. Lasing under constant, pulsed excitation can be maintained for over 1 h, the equivalent of 10(9) excitation cycles, and lasing persists upon exposure to ambient atmosphere. Wavelength tunability in the green and blue regions of the spectrum in conjunction with excellent stability makes these nanowire lasers attractive for device fabrication.

  3. Method for producing hydrocarbon fuels from heavy polynuclear hydrocarbons by use of molten metal halide catalyst

    DOEpatents

    Gorin, Everett

    1979-01-01

    In a process for hydrocracking heavy polynuclear carbonaceous feedstocks to produce lighter hydrocarbon fuels by contacting the heavy feedstocks with hydrogen in the presence of a molten metal halide catalyst, thereafter separating at least a substantial portion of the carbonaceous material associated with the reaction mixture from the spent molten metal halide and thereafter regenerating the metal halide catalyst, an improvement comprising contacting the spent molten metal halide catalyst after removal of a major portion of the carbonaceous material therefrom with an additional quantity of hydrogen is disclosed.

  4. Systematic analysis of the unique band gap modulation of mixed halide perovskites.

    PubMed

    Kim, Jongseob; Lee, Sung-Hoon; Chung, Choong-Heui; Hong, Ki-Ha

    2016-02-14

    Solar cells based on organic-inorganic hybrid metal halide perovskites have been proven to be one of the most promising candidates for the next generation thin film photovoltaic cells. Mixing Br or Cl into I-based perovskites has been frequently tried to enhance the cell efficiency and stability. One of the advantages of mixed halides is the modulation of band gap by controlling the composition of the incorporated halides. However, the reported band gap transition behavior has not been resolved yet. Here a theoretical model is presented to understand the electronic structure variation of metal mixed-halide perovskites through hybrid density functional theory. Comparative calculations in this work suggest that the band gap correction including spin-orbit interaction is essential to describe the band gap changes of mixed halides. In our model, both the lattice variation and the orbital interactions between metal and halides play key roles to determine band gap changes and band alignments of mixed halides. It is also presented that the band gap of mixed halide thin films can be significantly affected by the distribution of halide composition.

  5. Experimental versus expected halide-ion size differences; structural changes in three series of isotypic bismuth chalcogenide halides.

    PubMed

    Keller, Egbert; Krämer, Volker

    2006-06-01

    Experimentally determined halide-ion size differences are compared with expected size differences in the three series of isotypic bismuth chalcogenide halide compounds, KBi(6)O(9)X (X = Cl, Br and I), BiOX (X = F, Cl, Br and I) and BiSX (X = Cl, Br and I). The strong deviations observed can be assigned to steric strain caused by the heterogeneity of the bond-valence pattern and (for BiOX) to anion-anion repulsion and a change in the connectivity scheme. Some special features of the BiOF structure and the question of "isotypism" within the BiOX series are briefly discussed. Structural changes within the BiSX series are analysed.

  6. When can ocean acidification impacts be detected from decadal alkalinity measurements?

    NASA Astrophysics Data System (ADS)

    Carter, B. R.; Frölicher, T. L.; Dunne, J. P.; Rodgers, K. B.; Slater, R. D.; Sarmiento, J. L.

    2016-04-01

    We use a large initial condition suite of simulations (30 runs) with an Earth system model to assess the detectability of biogeochemical impacts of ocean acidification (OA) on the marine alkalinity distribution from decadally repeated hydrographic measurements such as those produced by the Global Ship-Based Hydrographic Investigations Program (GO-SHIP). Detection of these impacts is complicated by alkalinity changes from variability and long-term trends in freshwater and organic matter cycling and ocean circulation. In our ensemble simulation, variability in freshwater cycling generates large changes in alkalinity that obscure the changes of interest and prevent the attribution of observed alkalinity redistribution to OA. These complications from freshwater cycling can be mostly avoided through salinity normalization of alkalinity. With the salinity-normalized alkalinity, modeled OA impacts are broadly detectable in the surface of the subtropical gyres by 2030. Discrepancies between this finding and the finding of an earlier analysis suggest that these estimates are strongly sensitive to the patterns of calcium carbonate export simulated by the model. OA impacts are detectable later in the subpolar and equatorial regions due to slower responses of alkalinity to OA in these regions and greater seasonal equatorial alkalinity variability. OA impacts are detectable later at depth despite lower variability due to smaller rates of change and consistent measurement uncertainty.

  7. Alkali-metal/alkaline-earth-metal fluorine beryllium borate NaSr{sub 3}Be{sub 3}B{sub 3}O{sub 9}F{sub 4} with large nonlinear optical properties in the deep-ultraviolet region

    SciTech Connect

    Reshak, A. H.; Huang, Hongwei; Kamarudin, H.; Auluck, S.

    2015-02-28

    The linear optical response and second harmonic generation (SHG) in alkali-metal/alkaline-earth-metal fluorine beryllium borate NaSr{sub 3}Be{sub 3}B{sub 3}O{sub 9}F{sub 4} are investigated by means of density functional theory. Calculations are performed using four types of exchange correlations: Ceperley-Alder local density approximation, Perdew Burke and Ernzerhof general gradient approximation, Engel-Vosko generalized gradient approximation, and the recently modified Becke-Johnson potential (mBJ). The mBJ approach brings the calculated band gap (7.20 eV) in excellent agreement with the experimental one (7.28 eV). The calculated values of the uniaxial anisotropy δε=−0.076 and the birefringence Δn(0)=0.052 indicate considerable anisotropy in the linear optical properties, which makes it favorable for the second harmonic generation. The dominant component of the second harmonic generation is χ{sub 111}{sup (2)}(ω). The value of |χ{sub 111}{sup (2)}(ω)| is about 1.2 pm/V at λ = 1064 nm in agreement with previous calculations. To analyze the origin of the high SHG of NaSr{sub 3}Be{sub 3}B{sub 3}O{sub 9}F{sub 4} single crystals, we have correlated the features of |χ{sub 111}{sup (2)}(ω)| spectra with the features of ε{sub 2}(ω) spectra as a function of ω/2 and ω. From the calculated dominant component |χ{sub 111}{sup (2)}(ω)|, we find that the microscopic first hyperpolarizability, β{sub 111}, the vector components along the dipole moment direction is 0.5 × 10{sup −30} esu at static limit and 0.6 × 10{sup −30} esu at λ = 1064 nm.

  8. Zinc electrode in alkaline electrolyte

    SciTech Connect

    McBreen, J.

    1995-12-31

    The zinc electrode in alkaline electrolyte is unusual in that supersaturated zincate solutions can form during discharge and spongy or mossy zinc deposits can form on charge at low overvoltages. The effect of additives on regular pasted ZnO electrodes and calcium zincate electrodes is discussed. The paper also reports on in situ x-ray absorption (XAS) results on mossy zinc deposits.

  9. Earth Resources

    ERIC Educational Resources Information Center

    Brewer, Tom

    1970-01-01

    Reviews some of the more concerted, large-scale efforts in the earth resources areas" in order to help the computer community obtain insights into the activities it can jointly particpate in withthe earth resources community." (Author)

  10. Nucleotide sequences encoding a thermostable alkaline protease

    DOEpatents

    Wilson, David B.; Lao, Guifang

    1998-01-01

    Nucleotide sequences, derived from a thermophilic actinomycete microorganism, which encode a thermostable alkaline protease are disclosed. Also disclosed are variants of the nucleotide sequences which encode a polypeptide having thermostable alkaline proteolytic activity. Recombinant thermostable alkaline protease or recombinant polypeptide may be obtained by culturing in a medium a host cell genetically engineered to contain and express a nucleotide sequence according to the present invention, and recovering the recombinant thermostable alkaline protease or recombinant polypeptide from the culture medium.

  11. Nucleotide sequences encoding a thermostable alkaline protease

    DOEpatents

    Wilson, D.B.; Lao, G.

    1998-01-06

    Nucleotide sequences, derived from a thermophilic actinomycete microorganism, which encode a thermostable alkaline protease are disclosed. Also disclosed are variants of the nucleotide sequences which encode a polypeptide having thermostable alkaline proteolytic activity. Recombinant thermostable alkaline protease or recombinant polypeptide may be obtained by culturing in a medium a host cell genetically engineered to contain and express a nucleotide sequence according to the present invention, and recovering the recombinant thermostable alkaline protease or recombinant polypeptide from the culture medium. 3 figs.

  12. Origin of halides (Cl- and Br-) and of their stable isotopes (d37Cl and d81Br) at the Tournemire URL (France) - Experimental and numerical approach

    NASA Astrophysics Data System (ADS)

    Bachir-Bey, Nassim; Matray, Jean-Michel

    2014-05-01

    This work is part of research conducted by the Institute of Radiological and Nuclear Safety (IRSN) on the geological disposal of High-Level and Intermediate-Level Long-Lived (HL-ILLL) radioactive waste in deep clayrocks. In France, the choice of the potential host rock for the geological storage is focused on the Callovian-Oxfordian (COx) of Meuse/Haute-Marne from its low permeability, capacity for self- sealing, high sorption and ability to radionuclide (RN) transport by diffusion. IRSN, which plays an expert role for ASN has its own underground research laboratory in a clayrock which has strong analogies to the COx. This is the Toarcian/Domerian clayrock located at Tournemire in southern Aveyron in France. The purpose of this study was to assess the transfer of RN in the Tournemire clayrock through the study of halides contents and of their stable isotopes (Cl-, Br-, Cl-/Br-, d37Cl, d81Br). The approach used was multiple and consisted for halides to: 1) Assess their stock in different fractions of the rock by applying several techniques including i) alkaline fusion for their total stock, ii) leaching to access their stock in porewater and to mineral phases sensitive to dissolution iii) cubic diffusion for their stock in porewater, 2) Get their diffusive transport parameters of a selection of samples from the upper Toarcian by cubic diffusion experiments modelled using the Hytec transport code developed by Mines ParisTech and 3) Model their transport after palaeohydrogeological known changes of the Tournemire massif. The experimental approach, conducted at the LAME lab, did not lead to an operational protocol for the alkaline fusion due to an incomplete rock dissolution. Leaching was used to characterize the concentrations of halides in the fractions of pore water and of minerals sensitive to dissolution. The results show levels of halides much higher than those of pore water with very low Cl/Br ratios likely resulting from the dissolution of mineral species. The

  13. A review of bacterial methyl halide degradation: biochemistry, genetics and molecular ecology

    USGS Publications Warehouse

    McDonald, I.R.; Warner, K.L.; McAnulla, C.; Woodall, C.A.; Oremland, R.S.; Murrell, J.C.

    2002-01-01

    Methyl halide-degrading bacteria are a diverse group of organisms that are found in both terrestrial and marine environments. They potentially play an important role in mitigating ozone depletion resulting from methyl chloride and methyl bromide emissions. The first step in the pathway(s) of methyl halide degradation involves a methyltransferase and, recently, the presence of this pathway has been studied in a number of bacteria. This paper reviews the biochemistry and genetics of methyl halide utilization in the aerobic bacteria Methylobacterium chloromethanicum CM4T, Hyphomicrobium chloromethanicum CM2T, Aminobacter strain IMB-1 and Aminobacter strain CC495. These bacteria are able to use methyl halides as a sole source of carbon and energy, are all members of the α-Proteobacteria and were isolated from a variety of polluted and pristine terrestrial environments. An understanding of the genetics of these bacteria identified a unique gene (cmuA) involved in the degradation of methyl halides, which codes for a protein (CmuA) with unique methyltransferase and corrinoid functions. This unique functional gene, cmuA, is being used to develop molecular ecology techniques to examine the diversity and distribution of methyl halide-utilizing bacteria in the environment and hopefully to understand their role in methyl halide degradation in different environments. These techniques will also enable the detection of potentially novel methyl halide-degrading bacteria.

  14. Artificial Synapses: Organometal Halide Perovskite Artificial Synapses (Adv. Mater. 28/2016).

    PubMed

    Xu, Wentao; Cho, Himchan; Kim, Young-Hoon; Kim, Young-Tae; Wolf, Christoph; Park, Chan-Gyung; Lee, Tae-Woo

    2016-07-01

    A synapse-emulating electronic device based on organometal halide perovskite thin films is described by T.-W. Lee and co-workers on page 5916. The device successfully emulates important characteristics of a biological synapse. This work extends the application of organometal halide perovskites to bioinspired electronic devices, and contributes to the development of neuromorphic electronics.

  15. Thermal battery. [solid metal halide electrolytes with enhanced electrical conductance after a phase transition

    DOEpatents

    Carlsten, R.W.; Nissen, D.A.

    1973-03-06

    The patent describes an improved thermal battery whose novel design eliminates various disadvantages of previous such devices. Its major features include a halide cathode, a solid metal halide electrolyte which has a substantially greater electrical conductance after a phase transition at some temperature, and a means for heating its electrochemical cells to activation temperature.

  16. THE DETERMINATION OF TOTAL ORGANIC HALIDE IN WATER: AN INTERLABORATORY COMPARATIVE STUDY OF TWO METHODS

    EPA Science Inventory

    Total organic halide (TOX) analyzers are commonly used to measure the amount of dissolved halogenated organic byproducts in disinfected waters. Because of the lack of information on the identity of disinfection byproducts, rigorous testing of the dissolved organic halide (DOX) pr...

  17. Intermolecular Addition of Glycosyl Halides to Alkenes Mediated by Visible Light

    DTIC Science & Technology

    2010-08-25

    Visible light, an amine reductant, and a Ru(bpy)32+ photocatalyst can be used to mediate the addition of glycosyl halides into alkenes to synthesize...and a Ru(bpy)32+ photocatalyst can be used to mediate the addition of glycosyl halides into alkenes to synthesize important C-glycosides. This method

  18. Cross coupling of magnesium diacetylenides with functional allylic and halide-containing compounds catalyzed by transition metal complexes

    SciTech Connect

    Dzhemilev, U.M.; Ibragimov, A.G.; Saraev, R.A.

    1986-08-20

    An efficient method has been developed for the synthesis of 1,4-enynes, conjugated acetylenes and aryl acetylenes by the cross coupling of magnesium diacetylenides with allyl ethers and esters, alkyl halides, allyl halides, aryl halides, allyl sulfides, and allylsulfones, using Ni and Pd complexes as the catalyst.

  19. 10 CFR 431.324 - Uniform test method for the measurement of energy efficiency of metal halide ballasts.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... energy efficiency of metal halide ballasts. (b) Testing and Calculations. Energy Conservation Standards ... efficiency of metal halide ballasts. 431.324 Section 431.324 Energy DEPARTMENT OF ENERGY ENERGY CONSERVATION ENERGY EFFICIENCY PROGRAM FOR CERTAIN COMMERCIAL AND INDUSTRIAL EQUIPMENT Metal Halide Lamp Ballasts...

  20. Method for producing hydrocarbon fuels and fuel gas from heavy polynuclear hydrocarbons by the use of molten metal halide catalysts

    DOEpatents

    Gorin, Everett

    1979-01-01

    In a process for hydrocracking heavy polynuclear carbonaceous feedstocks to produce lighter hydrocarbon fuels by contacting the heavy feedstocks with hydrogen in the presence of a molten metal halide catalyst in a hydrocracking zone, thereafter separating at least a major portion of the lighter hydrocarbon fuels from the spent molten metal halide and thereafter regenerating the spent molten metal halide by incinerating the spent molten metal halide by combustion of carbon and sulfur compounds in the spent molten metal halide in an incineration zone, the improvement comprising: (a) contacting the heavy feedstocks and hydrogen in the presence of the molten metal halide in the hydrocracking zone at reaction conditions effective to convert from about 60 to about 90 weight percent of the feedstock to lighter hydrocarbon fuels; (b) separating at least a major portion of the lighter hydrocarbon fuels from the spent molten metal halide; (c) contacting the spent molten metal halide with oxygen in a liquid phase gasification zone at a temperature and pressure sufficient to vaporize from about 25 to about 75 weight percent of the spent metal halide, the oxygen being introduced in an amount sufficient to remove from about 60 to about 90 weight percent of the carbon contained in the spent molten metal halide to produce a fuel gas and regenerated metal halide; and (d) incinerating the spent molten metal halide by combusting carbon and sulfur compounds contained therein.

  1. Characterization of silver halide fiber for modal filtering on mid-infrared: imaging, nulling, and spectral transmission

    NASA Astrophysics Data System (ADS)

    Grille, R.; Labadie, L.; Kern, P.; Martin, G.; Arezki, B.

    2008-07-01

    One of the critical issues for nulling interferometry breadboards for exo-earth detection relies on the possibility to manufacture and properly characterize optical waveguides that present suitable single mode behaviors in the foreseen spectral range (4-20 μm). We developed a dedicated bench for the characterization of available guides for the considered spectral range, in particulary silver halide fibers. This interferometric bench achieves modal characterization in nulling mode and spectral transmission in Fourier Transform spectrometer mode, defining the single mode domain of the components. We present the experimental setup and its performances. We present also some characterization of their single-mode behavior according to the injection conditions. These measurements are very useful for the conception of optimized components.

  2. Calcium phosphate cements with strontium halides as radiopacifiers.

    PubMed

    López, Alejandro; Montazerolghaem, Maryam; Engqvist, Håkan; Ott, Marjam Karlsson; Persson, Cecilia

    2014-02-01

    High radiopacity is required to monitor the delivery and positioning of injectable implants. Inorganic nonsoluble radiopacifiers are typically used in nondegradable bone cements; however, their usefulness in resorbable cements is limited due to their low solubility. Strontium halides, except strontium fluoride, are ionic water-soluble compounds that possess potential as radiopacifiers. In this study, we compare the radiopacity, mechanical properties, composition, and cytotoxicity of radiopaque brushite cements prepared with strontium fluoride (SrF2 ), strontium chloride (SrCl2 ·6H2 O), strontium bromide (SrBr2 ), or strontium iodide (SrI2 ). Brushite cements containing 10 wt % SrCl2 ·6H2 O, SrBr2 , or SrI2 exhibited equal to or higher radiopacity than commercial radiopaque cements. Furthermore, the brushite crystal lattice in cements that contained the ionic radiopacifiers was larger than in unmodified cements and in cements that contained SrF2 , indicating strontium substitution. Despite the fact that the strontium halides increased the solubility of the cements and affected their mechanical properties, calcium phosphate cements containing SrCl2 ·6H2 O, SrBr2 , and SrI2 showed no significant differences in Saos-2 cell viability and proliferation with respect to the control. Strontium halides: SrCl2 ·6H2 O, SrBr2 , and SrI2 may be potential candidates as radiopacifiers in resorbable biomaterials although their in vivo biocompatibility, when incorporated into injectable implants, is yet to be assessed.

  3. The secondary alkaline zinc electrode

    NASA Astrophysics Data System (ADS)

    McLarnon, Frank R.; Cairns, Elton J.

    1991-02-01

    The worldwide studies conducted between 1975 and 1990 with the aim of improving cell lifetimes of secondary alkaline zinc electrodes are overviewed. Attention is given the design features and characteristics of various secondary alkaline zinc cells, including four types of zinc/nickel oxide cell designs (vented static-electrolyte, sealed static-electrolyte, vibrating-electrode, and flowing-electrolyte); two types of zinc/air cells (mechanically rechargeable consolidated-electrode and mechanically rechargeable particulate-electrode); zinc/silver oxide battery; zinc/manganese dioxide cell; and zinc/ferric cyanide battery. Particular consideration is given to recent research in the fields of cell thermodynamics, zinc electrodeposition, zinc electrodissolution, zinc corrosion, electrolyte properties, mathematical and phenomenological models, osmotic pumping, nonuniform current distribution, and cell cycle-life perforamnce.

  4. Development of alkaline fuel cells.

    SciTech Connect

    Hibbs, Michael R.; Jenkins, Janelle E.; Alam, Todd Michael; Janarthanan, Rajeswari; Horan, James L.; Caire, Benjamin R.; Ziegler, Zachary C.; Herring, Andrew M.; Yang, Yuan; Zuo, Xiaobing; Robson, Michael H.; Artyushkova, Kateryna; Patterson, Wendy; Atanassov, Plamen Borissov

    2013-09-01

    This project focuses on the development and demonstration of anion exchange membrane (AEM) fuel cells for portable power applications. Novel polymeric anion exchange membranes and ionomers with high chemical stabilities were prepared characterized by researchers at Sandia National Laboratories. Durable, non-precious metal catalysts were prepared by Dr. Plamen Atanassovs research group at the University of New Mexico by utilizing an aerosol-based process to prepare templated nano-structures. Dr. Andy Herrings group at the Colorado School of Mines combined all of these materials to fabricate and test membrane electrode assemblies for single cell testing in a methanol-fueled alkaline system. The highest power density achieved in this study was 54 mW/cm2 which was 90% of the project target and the highest reported power density for a direct methanol alkaline fuel cell.

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

    SciTech Connect

    Moore, David T.; Sai, Hiroaki; Wee Tan, Kwan; Estroff, Lara A.; Wiesner, Ulrich

    2014-08-01

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

  6. Metal-halide mixtures for latent heat energy storage

    NASA Technical Reports Server (NTRS)

    Chen, K.; Manvi, R.

    1981-01-01

    Some candidates for alkali metal and alkali halide mixtures suitable for thermal energy storage at temperatures 600 C are identified. A solar thermal system application which offer advantages such as precipitation of salt crystals away from heat transfer surfaces, increased thermal conductivity of phase change materials, corrosion inhibition, and a constant monotectic temperature, independent of mixture concentrations. By using the lighters, metal rich phase as a heat transfer medium and the denser, salt rich phase as a phase change material for latent heat storage, undesirable solidification on the heat transfer surface may be prevented, is presented.

  7. Casting of Halide and Fluoride Alloys for Laser Windows

    DTIC Science & Technology

    1974-10-15

    a lower temperature (900CC) or by annealing at 1000° C under a better vacuum or under a partial pressure of teflon vapor providing a purifying...castings (3 in. diameter) of SrF2 have been produced with low optical absorption coefficients pi, 5.25 jim. High qurlity CaF2 castings have been...Waltham, Massachusetts under Contract No. F19628-74-C-0148 entitled "Casting of Halide and Fluoride Alloys for Laser Windows. " This work is

  8. Heavy ion passive dosimetry with silver halide single crystals

    NASA Technical Reports Server (NTRS)

    Childs, C. B.; Parnell, T. A.

    1972-01-01

    A method of detecting radiation damage tracks due to heavy particles in large single crystals of the silver halides is described. The tracks, when made visible with a simple electrical apparatus, appear similar to tracks in emulsions. The properties of the crystals, the technique of printing out the tracks, and evidence concerning the threshold energy for registering particles indicates that this method may find application in heavy ion dosimetry. The method has been found to be sensitive to stopping He nuclei and relativistic M group cosmic rays. Some impurities strongly influence the printout of the tracks, and the effects of these impurities are discussed.

  9. Volatile species in halide-activated-diffusion coating packs

    NASA Technical Reports Server (NTRS)

    Bianco, Robert; Rapp, Robert A.; Jacobson, Nathan S.

    1992-01-01

    An atmospheric pressure sampling mass spectrometer was used to identify the vapor species generated in a halide-activated cementation pack. Pack powder mixtures containing a Cr-Al binary masteralloy powder, an NH4Cl activator salt, and either ZrO2 or Y2O3 (or neither) were analyzed at 1000 C. Both the equilibrium calculations for the pack and mass spectrometer results indicated that volatile AlCl(x) and CrCl(y) species were generated by the pack powder mixture; in packs containing the reactive element oxide, volatile ZrCl(z) and YCl(w) species were formed by the conversion of their oxide sources.

  10. Discover Earth

    NASA Technical Reports Server (NTRS)

    Steele, Colleen

    1998-01-01

    Discover Earth is a NASA-sponsored project for teachers of grades 5-12, designed to: (1) enhance understanding of the Earth as an integrated system; (2) enhance the interdisciplinary approach to science instruction; and (3) provide classroom materials that focus on those goals. Discover Earth is conducted by the Institute for Global Environmental Strategies in collaboration with Dr. Eric Barron, Director, Earth System Science Center, The Pennsylvania State University; and Dr. Robert Hudson, Chair, the Department of Meteorology, University of Maryland at College Park. The enclosed materials: (1) represent only part of the Discover Earth materials; (2) were developed by classroom teachers who are participating in the Discover Earth project; (3) utilize an investigative approach and on-line data; and (4) can be effectively adjusted to classrooms with greater/without technology access. The Discover Earth classroom materials focus on the Earth system and key issues of global climate change including topics such as the greenhouse effect, clouds and Earth's radiation balance, surface hydrology and land cover, and volcanoes and climate change. All the materials developed to date are available on line at (http://www.strategies.org) You are encouraged to submit comments and recommendations about these materials to the Discover Earth project manager, contact information is listed below. You are welcome to duplicate all these materials.

  11. Axial segregation in metal halide lamps under varying gravity conditions during parabolic flights

    NASA Astrophysics Data System (ADS)

    Flikweert, A. J.; van Kemenade, M.; Nimalasuriya, T.; Haverlag, M.; Kroesen, G. M. W.; Stoffels, W. W.

    2006-04-01

    Metal-halide lamps have high efficiencies. These lamps often contain rare-earth additives (in our case dysprosium iodide) which radiate very efficiently in the visible spectrum. Colour separation is a problem in these lamps; this is caused by axial segregation of these additives as a result of diffusion and convection. To vary the effect of convection, parabolic flights were performed with micro-gravity (0g) and hyper-gravity (~1.8g) phases. During these flights, the atomic dysprosium density was measured by means of laser absorption spectroscopy. In addition, the lamp voltage, which is strongly influenced by the total amount of Dy in the lamp, was measured. The Dy density and axial segregation are dependent on the gravity. The dynamic lamp behaviour during the parabolas was investigated: the dysprosium density and lamp voltage followed the gravity variations. When entering the micro-gravity phase, the axial diffusion time constant is the slowest time constant; it is proportional to the mercury pressure in the lamp.

  12. Electronic and Optical Properties of Luminescent Centers in Halides and Oxides

    NASA Astrophysics Data System (ADS)

    Du, Mao-Hua

    2014-03-01

    Luminescent materials, such as phosphors and scintillators, are widely used for fluorescent lighting, laser, medical imaging, nuclear material detection, etc. . The luminescence is usually activated by impurities (or activators), which act as luminescence centers. The activators are typically multi-valent ions that insert multiple electronic states in the band gap of the host material. In this talk, first-principles calculations of electronic structure and optical transitions are shown for a wide range of activators, including rare-earth ions (e.g., Ce3+, Eu2+) , ns2 ions (the ions that have outer electronic configurations of ns2, such as Tl+, Pb2+, Bi3+) , and transition-metal ions (e.g., Mn4+) , in a large number of halides and oxides. The results reveal how the activator-ligand hybridization affects the emission energy and the luminescence mechanism. New phosphors and scintillators are proposed based on the chemical trends emerging from the calculations of a large number of materials.

  13. Tunable Near-Infrared Luminescence in Tin Halide Perovskite Devices.

    PubMed

    Lai, May L; Tay, Timothy Y S; Sadhanala, Aditya; Dutton, Siân E; Li, Guangru; Friend, Richard H; Tan, Zhi-Kuang

    2016-07-21

    Infrared emitters are reasonably rare in solution-processed materials. Recently, research into hybrid organo-lead halide perovskite, originally popular in photovoltaics,1-3 has gained traction in light-emitting diodes (LED) due to their low-cost solution processing and good performance.4-9 The lead-based electroluminescent materials show strong colorful emission in the visible region, but lack emissive variants further in the infrared. The concerns with the toxicity of lead may, additionally, limit their wide-scale applications. Here, we demonstrate tunable near-infrared electroluminescence from a lead-free organo-tin halide perovskite, using an ITO/PEDOT:PSS/CH3NH3Sn(Br1-xIx)3/F8/Ca/Ag device architecture. In our tin iodide (CH3NH3SnI3) LEDs, we achieved a 945 nm near-infrared emission with a radiance of 3.4 W sr(-1) m(-2) and a maximum external quantum efficiency of 0.72%, comparable with earlier lead-based devices. Increasing the bromide content in these tin perovskite devices widens the semiconductor bandgap and leads to shorter wavelength emissions, tunable down to 667 nm. These near-infrared LEDs could find useful applications in a range of optical communication, sensing and medical device applications.

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

    PubMed

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

    2014-07-21

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

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

    NASA Astrophysics Data System (ADS)

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

    2004-06-01

    The present paper reports the dislocation unpinning model of acoustic emis- sion (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_{s} for surface annihilation of dislocations and the pinning time tau_{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.

  16. Pressure variation of melting temperatures of alkali halides

    NASA Astrophysics Data System (ADS)

    Arafin, Sayyadul; Singh, Ram N.

    2017-02-01

    The melting temperatures of alkali halides (LiCl, LiF, NaBr, NaCl, NaF, NaI, KBr, KCl, KF, KI, RbBr, RbCl, RbI and CsI) have been evaluated over a wide range of pressures. The solid-liquid transition of alkali halides is of considerable significance due to their huge industrial applications. Our formalism requires a priori knowledge of the bulk modulus and the Grüneisen parameter at ambient conditions to compute Tm at high pressures. The computed values are in very good agreement with the available experimental results. The formalism can satisfactorily be used to compute Tm at high pressures where the experimental data are scanty. Most of the melting curves (Tm versus P) exhibit nonlinear variation with increasing pressure having curvatures downward and exhibit a maximum in some cases like NaCl, RbBr, RbCl and RbI. The values of Tmmax and Pmax corresponding to the maxima of the curves are given.

  17. X-ray Scintillation in Lead Halide Perovskite Crystals

    PubMed Central

    Birowosuto, M. D.; Cortecchia, D.; Drozdowski, W.; Brylew, K.; Lachmanski, W.; Bruno, A.; Soci, C.

    2016-01-01

    Current technologies for X-ray detection rely on scintillation from expensive inorganic crystals grown at high-temperature, which so far has hindered the development of large-area scintillator arrays. Thanks to the presence of heavy atoms, solution-grown hybrid lead halide perovskite single crystals exhibit short X-ray absorption length and excellent detection efficiency. Here we compare X-ray scintillator characteristics of three-dimensional (3D) MAPbI3 and MAPbBr3 and two-dimensional (2D) (EDBE)PbCl4 hybrid perovskite crystals. X-ray excited thermoluminescence measurements indicate the absence of deep traps and a very small density of shallow trap states, which lessens after-glow effects. All perovskite single crystals exhibit high X-ray excited luminescence yields of >120,000 photons/MeV at low temperature. Although thermal quenching is significant at room temperature, the large exciton binding energy of 2D (EDBE)PbCl4 significantly reduces thermal effects compared to 3D perovskites, and moderate light yield of 9,000 photons/MeV can be achieved even at room temperature. This highlights the potential of 2D metal halide perovskites for large-area and low-cost scintillator devices for medical, security and scientific applications. PMID:27849019

  18. X-ray Scintillation in Lead Halide Perovskite Crystals

    NASA Astrophysics Data System (ADS)

    Birowosuto, M. D.; Cortecchia, D.; Drozdowski, W.; Brylew, K.; Lachmanski, W.; Bruno, A.; Soci, C.

    2016-11-01

    Current technologies for X-ray detection rely on scintillation from expensive inorganic crystals grown at high-temperature, which so far has hindered the development of large-area scintillator arrays. Thanks to the presence of heavy atoms, solution-grown hybrid lead halide perovskite single crystals exhibit short X-ray absorption length and excellent detection efficiency. Here we compare X-ray scintillator characteristics of three-dimensional (3D) MAPbI3 and MAPbBr3 and two-dimensional (2D) (EDBE)PbCl4 hybrid perovskite crystals. X-ray excited thermoluminescence measurements indicate the absence of deep traps and a very small density of shallow trap states, which lessens after-glow effects. All perovskite single crystals exhibit high X-ray excited luminescence yields of >120,000 photons/MeV at low temperature. Although thermal quenching is significant at room temperature, the large exciton binding energy of 2D (EDBE)PbCl4 significantly reduces thermal effects compared to 3D perovskites, and moderate light yield of 9,000 photons/MeV can be achieved even at room temperature. This highlights the potential of 2D metal halide perovskites for large-area and low-cost scintillator devices for medical, security and scientific applications.

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

    SciTech Connect

    Kiss, Péter T.; Baranyai, András

    2014-09-21

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

  20. Two-Dimensional Halide Perovskites: Tuning Electronic Activities of Defects.

    PubMed

    Liu, Yuanyue; Xiao, Hai; Goddard, William A

    2016-05-11

    Two-dimensional (2D) halide perovskites are emerging as promising candidates for nanoelectronics and optoelectronics. To realize their full potential, it is important to understand the role of those defects that can strongly impact material properties. In contrast to other popular 2D semiconductors (e.g., transition metal dichalcogenides MX2) for which defects typically induce harmful traps, we show that the electronic activities of defects in 2D perovskites are significantly tunable. For example, even with a fixed lattice orientation one can change the synthesis conditions to convert a line defect (edge or grain boundary) from electron acceptor to inactive site without deep gap states. We show that this difference originates from the enhanced ionic bonding in these perovskites compared with MX2. The donors tend to have high formation energies and the harmful defects are difficult to form at a low halide chemical potential. Thus, we unveil unique properties of defects in 2D perovskites and suggest practical routes to improve them.

  1. Long-lived charge carrier dynamics in polymer/quantum dot blends and organometal halide perovskites

    NASA Astrophysics Data System (ADS)

    Nagaoka, Hirokazu

    Solution-processable semiconductors offer a potential route to deploy solar panels on a wide scale, based on the possibility of reduced manufacturing costs by using earth-abundant materials and inexpensive production technologies, such as inkjet or roll-to-roll printing. Understanding the fundamental physics underlying device operation is important to realize this goal. This dissertation describes studies of two kinds of solar cells: hybrid polymer/PbS quantum dot solar cells and organometal halide perovskite solar cells. Chapter two discusses details of the experimental techniques. Chapter three and four explore the mechanisms of charge transfer and energy transfer spectroscopically, and find that both processes contribute to the device photocurrent. Chapter four investigates the important question of how the energy level alignment of quantum dot acceptors affects the operation of hybrid polymer/quantum dot solar cells, by making use of the size-tunable energy levels of PbS quantum dots. We observe that long-lived charge transfer yield is diminished at larger dot sizes as the energy level offset at the polymer/quantum dot interface is changed through decreasing quantum confinement using a combination of spectroscopy and device studies. Chapter five discusses the effects of TiO2 surface chemistry on the performance of organometal halide perovskite solar cells. Specifically, chapter five studies the effect of replacing the conventional TiO2 electrode with Zr-doped TiO2 (Zr-TiO2). We aim to explore the correlation between charge carrier dynamics and device studies by incorporating zirconium into TiO2. We find that, compared to Zr-free controls, solar cells employing Zr-TiO2 give rise to an increase in overall power conversion efficiency, and a decrease in hysteresis. We also observe longer carrier lifetimes and higher charge carrier densities in devices on Zr-TiO2 electrodes at microsecond times in transient photovoltage experiments, as well as at longer persistent

  2. ELECTROLYTIC PROCESS FOR PRODUCING METALS

    DOEpatents

    Kopelman, B.; Holden, R.B.

    1961-06-01

    A method is described for reducing beryllium halides to beryllium. The beryllfum halide fs placed in an eutectic mixture of alkali halides and alkaline earth halides. The constituents of this eutectic bath are so chosen that it has a melting point less than the boiling point of mercury, which acts as a cathode for the system. The beryllium metal is then deposited in the mercury upon electrolysis.

  3. Petrogenesis of coeval silica-saturated and silica-undersaturated alkaline rocks: Mineralogical and geochemical evidence from the Saima alkaline complex, NE China

    NASA Astrophysics Data System (ADS)

    Zhu, Yu-Sheng; Yang, Jin-Hui; Sun, Jin-Feng; Zhang, Ji-Heng; Wu, Fu-Yuan

    2016-03-01

    A combined study of zircon U-Pb ages, mineral chemistry, whole-rock elements and Sr-Nd-Hf isotopes was carried out for the Saima alkaline complex in the northeastern China, in order to investigate the source and petrogenesis of coeval silica-saturated and silica-undersaturated alkaline rocks. The Saima alkaline complex consists of nepheline syenites, quartz-bearing syenites and alkaline volcanic rocks (i.e., phonolite and trachyte), with minor mafic dikes and carbonatitic veins. Laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) and secondary ion mass spectrometry (SIMS) zircon U-Pb dating gives consistent ages of 230-224 Ma for these rocks, suggesting that they are coeval. All alkaline rocks in the Saima complex are enriched in large ion lithophile elements (LILEs) and light rare earth elements (LREEs), and depleted in high field strength elements (HFSEs) with significant negative Nb, Ta and Ti anomalies. Geochemical data and Sr-Nd-Hf isotopic compositions indicate that the various alkaline rocks were all derived from partial melting of an ancient, re-enriched lithospheric mantle in the garnet stability field, but experienced variable siliceous- or carbonate-rich crustal contamination. Based on petrographic evidence, mineral compositions, and whole-rock geochemical data, two distinct magmatic evolutionary trends are proposed to explain the coeval emplacement of the various rock types within the Saima alkaline complex. The silica-undersaturated rocks (nepheline syenites and phonolites) result from alkali feldspar + apatite + titanite crystal fractionation of an alkaline mafic parental melt combined with assimilation of marine carbonate host rocks. In contrast, the generation of silica-saturated rocks (quartz-bearing syenites and trachytes) may be attributed to subsequent and continued clinopyroxene + apatite + biotite crystal fractionation coupled with assimilation of siliceous sediments.

  4. Using Perovskite Nanoparticles as Halide Reservoirs in Catalysis and as Spectrochemical Probes of Ions in Solution.

    PubMed

    Doane, Tennyson L; Ryan, Kayla L; Pathade, Laxmikant; Cruz, Kevin J; Zang, Huidong; Cotlet, Mircea; Maye, Mathew M

    2016-06-28

    The ability of cesium lead halide (CsPbX3; X = Cl(-), Br(-), I(-)) perovskite nanoparticles (P-NPs) to participate in halide exchange reactions, to catalyze Finkelstein organohalide substitution reactions, and to colorimetrically monitor chemical reactions and detect anions in real time is described. With the use of tetraoctylammonium halide salts as a starting point, halide exchange with the P-NPs was performed to calibrate reactivity, stability, and extent of ion exchange. The exchange of CsPbI3 with Cl(-) or Br(-) causes a significant blue-shift in absorption and photoluminescence, whereas reacting I(-) with CsPbBr3 causes a red-shift of similar magnitudes. With the high local halide concentrations and the facile nature of halide exchange in mind, we then explored the ability of P-NPs to catalyze organohalide exchange in Finkelstein like reactions. Results indicate that the P-NPs serve as excellent halide reservoirs for substitution of organohalides in nonpolar media, leading to not only different organohalide products, but also a complementary color change over the course of the reaction, which can be used to monitor kinetics in a precise manner. The merits of using P-NP as spectrochemical probes for real time assaying is then expanded to other anions which can react with, or result in unique, classes of perovskites.

  5. Using Perovskite Nanoparticles as Halide Reservoirs in Catalysis and as Spectrochemical Probes of Ions in Solution

    DOE PAGES

    Doane, Tennyson L.; Ryan, Kayla L.; Pathade, Laxmikant; ...

    2016-05-05

    The ability of cesium lead halide (CsPbX3; X = Cl–, Br–, I–) perovskite nanoparticles (P-NPs) to participate in halide exchange reactions, to catalyze Finkelstein organohalide substitution reactions, and to colorimetrically monitor chemical reactions and detect anions in real time is described. With the use of tetraoctylammonium halide salts as a starting point, halide exchange with the P-NPs was performed to calibrate reactivity, stability, and extent of ion exchange. Also, the exchange of CsPbI3 with Cl– or Br– causes a significant blue-shift in absorption and photoluminescence, whereas reacting I– with CsPbBr3 causes a red-shift of similar magnitudes. With the high localmore » halide concentrations and the facile nature of halide exchange in mind, we then explored the ability of P-NPs to catalyze organohalide exchange in Finkelstein like reactions. Results indicate that the P-NPs serve as excellent halide reservoirs for substitution of organohalides in nonpolar media, leading to not only different organohalide products, but also a complementary color change over the course of the reaction, which can be used to monitor kinetics in a precise manner. Finally, the merits of using P-NP as spectrochemical probes for real time assaying is then expanded to other anions which can react with, or result in unique, classes of perovskites.« less

  6. Rainbow Earth.

    ERIC Educational Resources Information Center

    Arizona State Dept. of Library and Archives, Phoenix.

    The environment is a great concern in the 1990s, and everyone needs to work at maintaining our planet. The 1992 Arizona State Library Reading Program, "Rainbow Earth," provides children with many techniques they can use to help the Earth. This reading program guide provides information on the following: goals, objectives, and evaluation;…

  7. Earth tides

    SciTech Connect

    Harrison, J.C.

    1984-01-01

    Nineteen papers on gravity, tilt, and strain tides are compiled into this volume. Detailed chapters cover the calculation of the tidal forces and of the Earth's response to them, as well as actual observations of earth tides. Partial Contents: On Earth tides. The tidal forces: Tidal Forces. New Computations of the Tide-Generating Potential. Corrected Tables of Tidal Harmonics. The Theory of Tidal Deformations. Body Tides on an Elliptical, Rotating, Elastic and Oceanless Earth, Deformation of the Earth by Surface Loads. Gravimetric Tidal Loading Computed from Integrated Green's Functions. Tidal Friction in the Solid Earth. Loading Tides Versus Body Tides. Lunar Tidal Acceleration from Earth Satellite Orbit Analysis. Observations: gravity. Tidal Gravity in Britain: Tidal Loading and the Spatial Distribution of the Marine Tide. Tidal Loading along a Profile Europe-East Africa-South Asia-Australia and the Pacific Ocean. Detailed Gravity-Tide Spectrum between One and Four Cycles per Day. Observations: tilt and strain. Cavity and Topographic Effects in Tilt and Strain Measurement. Observations of Local Elastic Effects on Earth Tide Tilts and Strains.

  8. Alkaline fuel cell performance investigation

    NASA Technical Reports Server (NTRS)

    Martin, R. E.; Manzo, M. A.

    1988-01-01

    An exploratory experimental fuel cell test program was conducted to investigate the performance characteristics of alkaline laboratory research electrodes. The objective of this work was to establish the effect of temperature, pressure, and concentration upon performance and evaluate candidate cathode configurations having the potential for improved performance. The performance characterization tests provided data to empirically establish the effect of temperature, pressure, and concentration upon performance for cell temperatures up to 300 F and reactant pressures up to 200 psia. Evaluation of five gold alloy cathode catalysts revealed that three doped gold alloys had more that two times the surface areas of reference cathodes and therefore offered the best potential for improved performance.

  9. First examples of hybrids based on polyoxometalates, metal halide clusters and organic ligands

    SciTech Connect

    Wang Lamei; Fan Yong; Wang Yan; Xiao Lina; Hu Yangyang; Peng Yu; Wang Tiegang; Gao Zhongmin; Zheng Dafang; Cui Xiaobing; Xu Jiqing

    2012-07-15

    Two new organic-inorganic compounds based on polyoxometalates, metal halide clusters and organic ligands: [BW{sub 12}O{sub 40}]{sub 2}[Cu{sub 2}(Phen){sub 4}Cl](H{sub 2}4, 4 Prime -bpy){sub 4}{center_dot}H{sub 3}O{center_dot}5H{sub 2}O (1) and [HPW{sub 12}O{sub 40}][Cd{sub 2}(Phen){sub 4}Cl{sub 2}](4, 4 Prime -bpy) (2) (Phen=1, 10-phenanthroline, bpy=bipyridine), have been prepared and characterized by IR, UV-vis, XPS, XRD and single crystal X-ray diffraction analyses. Crystal structure analyses reveal that compound 1 is constructed from [BW{sub 12}O{sub 40}]{sup 5-}, metal halide clusters [Cu{sub 2}(Phen){sub 4}Cl]{sup +}and 4, 4 Prime -bpy ligands, while compound 2 is constructed from [PW{sub 12}O{sub 40}]{sup 3-}, metal halide cluster [Cd{sub 2}(Phen){sub 4}Cl{sub 2}]{sup 2+} and 4, 4 Prime -bpy ligands. Compound 1 and compound 2 are not common hybrids based on polyoxometalates and metal halide clusters, they also contain dissociated organic ligands, therefore, compound 1 and 2 are the first examples of hybrids based on polyoxometalates, metal halide clusters and organic ligands. - Graphical Abstract: Two new compounds have been synthesized and characterized. Structure analyses revealed that the two compounds are the first examples of hybrids based on polyoxometalates, metal halide clusters and organic ligands. Highlights: Black-Right-Pointing-Pointer First examples of hybrids based on polyoxometalates, metal halide clusters and organic ligands. Black-Right-Pointing-Pointer Two different kinds of metal halide clusters. Black-Right-Pointing-Pointer Supramolecular structures based on polyoxometalates, metal halide clusters and organic ligands. Black-Right-Pointing-Pointer Hybridization of three different of building blocks.

  10. Optical and Spectral Studies on β Alanine Metal Halide Hybrid Crystals

    NASA Astrophysics Data System (ADS)

    Sweetlin, M. Daniel; Selvarajan, P.; Perumal, S.; Ramalingom, S.

    2011-10-01

    We have synthesized and grown β alanine metal halide hybrid crystals viz. β alanine cadmium chloride (BACC), an amino acid transition metal halide complex crystal and β alanine potassium chloride (BAPC), an amino acid alkali metal halide complex crystal by slow evaporation method. The grown crystals were found to be transparent and have well defined morphology. The optical characteristics of the grown crystals were carried out with the help of UV-Vis Spectroscopy. The optical transmittances of the spectrums show that BAPC is more transparent than BACC. The Photoluminescence of the materials were determined by the Photoluminescent Spectroscopy

  11. Vaporisation and thermal decomposition of dialkylimidazolium halide ion ionic liquids.

    PubMed

    Lovelock, Kevin R J; Armstrong, James P; Licence, Peter; Jones, Robert G

    2014-01-28

    Vaporisation and liquid phase thermal decomposition, TD, of two halide ion ionic liquids, 1-octyl-3-methylimidazolium chloride, [C8C1Im]Cl, and 1-octyl-3-methylimidazolium iodide, [C8C1Im]I, are investigated using temperature programmed desorption (TPD) line of sight mass spectrometry (LOSMS) at ultra-high vacuum (UHV). The ability to use MS to distinguish between vaporisation and TD allows the thermodynamics/kinetics of both vaporisation and TD to be investigated within the same experiments. Vaporisation of both halide ion ionic liquids is demonstrated. For both [C8C1Im]Cl and [C8C1Im]I the vapour is shown to be composed of neutral ion pairs (NIPs). The enthalpy of vaporisation at temperature T, ΔvapHT, was experimentally determined as ΔvapH455 = 151 ± 10 kJ mol(-1) for [C8C1Im]Cl and ΔvapH480 = 149 ± 8 kJ mol(-1) for [C8C1Im]I. Extrapolation of ΔvapHT to the reference temperature, 298 K, gave ΔvapH298 = 166 ± 10 kJ mol(-1) for [C8C1Im]Cl and ΔvapH298 = 167 ± 8 kJ mol(-1) for [C8C1Im]I, higher than most ΔvapH298 values measured to date for other [C8C1Im](+)-containing ionic liquids. In addition, predictions of ΔvapH298 for other halide ion ionic liquids are made. Liquid phase TD is shown to proceed via nucleophilic substitution to give two sets of products: 1-octylimidazole and methylhalide, and 1-methylimidazole and 1-octylhalide. The activation energy of TD at a temperature T, Ea,TD,T, is measured for the nucleophilic substitution of [C8C1Im]I to give methyliodide; Ea,TD,480 = 136 ± 15 kJ mol(-1). Ea,TD,T is measured for the nucleophilic substitution of [C8C1Im]Cl to give methylchloride; Ea,TD,455 = 132 ± 10 kJ mol(-1). The fact that ΔvapHT and Ea,TD,T are the same (within error) for both ionic liquids is commented upon, and conclusions are drawn as to the thermal stability of these ionic liquids.

  12. Latest Mesozoic-Early Cenozoic Continental Extension and Related Alkaline Magmatism in Central Anatolia, Turkey

    NASA Astrophysics Data System (ADS)

    Kadioglu, Y. K.

    2009-04-01

    The Central Anatolian crystalline complex (CACC) in Turkey includes a suite of latest Mesozoic-early Cenozoic plutonic rocks intruding the metamorphic and ophiolitic basement rocks. The intrusive rocks consist of three groups of granitoid, syenitoid, and gabbroids plutons. The granitoid units occur around the periphery of the CACC as large plutonic bodies, whereas the syenitoid assemblages crop out in the inner part of the CACC as small plutons. All the felsic plutons are crosscut by the gabbroid rocks in the region. The alkaline rocks of the CACC change in composition from nordmarkite through pulaskite to lusitanite, and are made of silica-saturated and silica-undersaturated magmas. The silica under-saturated alkaline rocks have gradual contacts with the silica-saturated alkaline rocks and constitute the main component of the alkaline rocks in the CACC. Nepheline, pseudoleucite, cancrinite, nosean, melanite and arfvedsonite are the main typical mineral compositions of the silica-undersaturated alkaline rocks. The leucite- and pseudoleucite-bearing rocks have porphyritic textures intruding the other main subunits of the alkaline rocks at high topographic elevations in the region. They are mostly composed of foid syenite, monzosyenite, monzodiorite and include rare amount of monzogabbro and foidolite. Each subunit has a transitional contact with the others and is crosscut by alkali feldspar foid syenite veins. Felsic dykes intrude the alkaline rock units and fluorite-bearing hydrothermal veins, which manifest themselves as alteration zones. The alkaline rocks have an abundance of xenolithic enclaves but lack any magma mixing-mingling produced enclaves. Normalized elemental patterns of the analyzed alkaline rocks show a slight enrichment in large ion lithophile elements (LILE) and light rare earth elements relatively to high field strength elements (HFSE) and heavy rare earth elements (HREE). The less fluid mobile, LILE and LREE concentration in the alkaline rocks

  13. Alkaline detergent recycling via ultrafiltration

    SciTech Connect

    Steffani, C.; Meltzer, M.

    1995-06-01

    The metal finishing industry uses alkaline cleaners and detergents to remove oils and dirt from manufactured parts, often before they are painted or plated. The use of these cleaners has grown because environmental regulations are phasing out ozone depleting substances and placing restrictions on the use and disposal of many hazardous solvents. Lawrence Livermore National Laboratory is examining ultrafiltration as a cleaning approach that reclaims the cleaning solutions and minimizes wastes. The ultrafiltration membrane is made from sheets of polymerized organic film. The sheets are rolled onto a supporting frame and installed in a tube. Spent cleaning solution is pumped into a filter chamber and filtered through the membrane that captures oils and dirt and allows water and detergent to pass. The membrane is monitored and when pressure builds from oil and dirt, an automatic system cleans the surface to maintain solution flow and filtration quality. The results show that the ultrafiltration does not disturb the detergent concentration or alkalinity but removed almost all the oils and dirt leaving the solution in condition to be reused.

  14. Martian alkaline basites chemically resemble basic rocks of the Lovozero alkaline massif, Kola peninsula

    NASA Astrophysics Data System (ADS)

    Kochemasov, G.

    The comparative wave planetology [1, 5] successfully overcomes the most principal martian test having now analyses of alkaline rocks from Columbia Hills [2, 3, 4]. This kind of rocks was predicted earlier on basis of the wave paradigm having stated that "the higher planetary relief range - the higher density difference between lithologies composing hypsometrically (tectonically) contrasting blocks [5]. This paradigm declares that "celestial bodies are dichotomic"(Theorem 1), "celestial bodies are sectoral" (Theorem 2), "celestial bodies are granular"(Theorem 3), "angular momenta of different level blocks tend to be equal" (Theorem 4)[1, 5]. Mars is a typical terrestrial planet but the farthest from Sun and thus with the smallest tide effects. Nevertheless it has the highest relief range and seems to be most distorted (ellipsoid in shape) and broken by deep fissures. The wave approach explains this by a warping action of standing waves of 4 ortho- and diagonal directions - they are the longest and highest in the martian case. These interfering warping waves caused by the elliptic keplerian orbits implying periodically changing accelerations and inertia-gravity forces produce inevitable tectonic dichotomy (the fundamental wave 1 long 2πR), sectoring (wave 2, πR, and other overtones), granulation. A granule size depends on an orbital frequency: the higher frequency the smaller granule. The Earth's granule, as a scale, is πR/4 (see it in NASA's PIA04159), Venus ` πR/6, Mercury's πR/16, Mars' πR/2 (the sizes are strictly tied to orb. fr.). Along with the granule sizes increase relief ranges ( Mercury ˜5 km, Venus 14, Earth 20, Mars ˜30) and compositional (density) difference between lowland and highland lithologies [5]. The lowland compositions become Fericher and denser: enstatite (Mercury), Mg-basalt (Venus), tholeiite (Earth), Fe-basalt (Mars). The highland compositions get less dense, lighter: anorthosite, alkaline basalt, andesite and conditional "albitite

  15. Recent progress and challenges of organometal halide perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Yang, Liyan; Barrows, Alexander T.; Lidzey, David G.; Wang, Tao

    2016-02-01

    We review recent progress in the development of organometal halide perovskite solar cells. We discuss different compounds used to construct perovskite photoactive layers, as well as the optoelectronic properties of this system. The factors that affect the morphology of the perovskite active layer are explored, e.g. material composition, film deposition methods, casting solvent and various post-treatments. Different strategies are reviewed that have recently emerged to prepare high performing perovskite films, creating polycrystalline films having either large or small grain size. Devices that are constructed using meso-superstructured and planar architectures are summarized and the impact of the fabrication process on operational efficiency is discussed. Finally, important research challenges (hysteresis, thermal and moisture instability, mechanical flexibility, as well as the development of lead-free materials) in the development of perovskite solar cells are outlined and their potential solutions are discussed.

  16. Recent progress and challenges of organometal halide perovskite solar cells.

    PubMed

    Yang, Liyan; Barrows, Alexander T; Lidzey, David G; Wang, Tao

    2016-02-01

    We review recent progress in the development of organometal halide perovskite solar cells. We discuss different compounds used to construct perovskite photoactive layers, as well as the optoelectronic properties of this system. The factors that affect the morphology of the perovskite active layer are explored, e.g. material composition, film deposition methods, casting solvent and various post-treatments. Different strategies are reviewed that have recently emerged to prepare high performing perovskite films, creating polycrystalline films having either large or small grain size. Devices that are constructed using meso-superstructured and planar architectures are summarized and the impact of the fabrication process on operational efficiency is discussed. Finally, important research challenges (hysteresis, thermal and moisture instability, mechanical flexibility, as well as the development of lead-free materials) in the development of perovskite solar cells are outlined and their potential solutions are discussed.

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

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

    PubMed

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

    2015-06-01

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

  19. Fast Photoconductive Responses in Organometal Halide Perovskite Photodetectors.

    PubMed

    Wang, Fei; Mei, Jingjing; Wang, Yunpeng; Zhang, Ligong; Zhao, Haifeng; Zhao, Dongxu

    2016-02-03

    Inorganic semiconductor-based photodetectors have been suffering from slow response speeds, which are caused by the persistent photoconductivity of semiconductor materials. For realizing high speed optoelectronic devices, the organometal halide perovskite thin films were applied onto the interdigitated (IDT) patterned Au electrodes, and symmetrical structured photoconductive detectors were achieved. The detectors were sensitive to the incident light signals, and the photocurrents of the devices were 2-3 orders of magnitude higher than dark currents. The responsivities of the devices could reach up to 55 mA W(1-). Most importantly, the detectors have a fast response time of less than 20 μs. The light and bias induced dipole rearrangement in organometal perovskite thin films has resulted in the instability of photocurrents, and Ag nanowires could quicken the process of dipole alignment and stabilize the photocurrents of the devices.

  20. Inorganic Halide Perovskites for Efficient Light-Emitting Diodes.

    PubMed

    Yantara, Natalia; Bhaumik, Saikat; Yan, Fei; Sabba, Dharani; Dewi, Herlina A; Mathews, Nripan; Boix, Pablo P; Demir, Hilmi Volkan; Mhaisalkar, Subodh

    2015-11-05

    Lead-halide perovskites have transcended photovoltaics. Perovskite light-emitting diodes (PeLEDs) emerge as a new field to leverage on these fascinating semiconductors. Here, we report the first use of completely inorganic CsPbBr3 thin films for enhanced light emission through controlled modulation of the trap density by varying the CsBr-PbBr2 precursor concentration. Although pure CsPbBr3 films can be deposited from equimolar CsBr-PbBr2 and CsBr-rich solutions, strikingly narrow emission line (17 nm), accompanied by elongated radiative lifetimes (3.9 ns) and increased photoluminescence quantum yield (16%), was achieved with the latter. This is translated into the enhanced performance of the resulting PeLED devices, with lower turn-on voltage (3 V), narrow electroluminescence spectra (18 nm) and higher electroluminescence intensity (407 Cd/m(2)) achieved from the CsBr-rich solutions.

  1. Giant photostriction in organic–inorganic lead halide perovskites

    PubMed Central

    Zhou, Yang; You, Lu; Wang, Shiwei; Ku, Zhiliang; Fan, Hongjin; Schmidt, Daniel; Rusydi, Andrivo; Chang, Lei; Wang, Le; Ren, Peng; Chen, Liufang; Yuan, Guoliang; Chen, Lang; Wang, Junling

    2016-01-01

    Among the many materials investigated for next-generation photovoltaic cells, organic–inorganic lead halide perovskites have demonstrated great potential thanks to their high power conversion efficiency and solution processability. Within a short period of about 5 years, the efficiency of solar cells based on these materials has increased dramatically from 3.8 to over 20%. Despite the tremendous progress in device performance, much less is known about the underlying photophysics involving charge–orbital–lattice interactions and the role of the organic molecules in this hybrid material remains poorly understood. Here, we report a giant photostrictive response, that is, light-induced lattice change, of >1,200 p.p.m. in methylammonium lead iodide, which could be the key to understand its superior optical properties. The strong photon-lattice coupling also opens up the possibility of employing these materials in wireless opto-mechanical devices. PMID:27044485

  2. Giant photostriction in organic-inorganic lead halide perovskites

    NASA Astrophysics Data System (ADS)

    Zhou, Yang; You, Lu; Wang, Shiwei; Ku, Zhiliang; Fan, Hongjin; Schmidt, Daniel; Rusydi, Andrivo; Chang, Lei; Wang, Le; Ren, Peng; Chen, Liufang; Yuan, Guoliang; Chen, Lang; Wang, Junling

    2016-04-01

    Among the many materials investigated for next-generation photovoltaic cells, organic-inorganic lead halide perovskites have demonstrated great potential thanks to their high power conversion efficiency and solution processability. Within a short period of about 5 years, the efficiency of solar cells based on these materials has increased dramatically from 3.8 to over 20%. Despite the tremendous progress in device performance, much less is known about the underlying photophysics involving charge-orbital-lattice interactions and the role of the organic molecules in this hybrid material remains poorly understood. Here, we report a giant photostrictive response, that is, light-induced lattice change, of >1,200 p.p.m. in methylammonium lead iodide, which could be the key to understand its superior optical properties. The strong photon-lattice coupling also opens up the possibility of employing these materials in wireless opto-mechanical devices.

  3. The Effect of Radiation "Memory" in Alkali-Halide Crystals

    NASA Astrophysics Data System (ADS)

    Korovkin, M. V.; Sal'nikov, V. N.

    2017-01-01

    The exposure of the alkali-halide crystals to ionizing radiation leads to the destruction of their structure, the emergence of radiation defects, and the formation of the electron and hole color centers. Destruction of the color centers upon heating is accompanied by the crystal bleaching, luminescence, and radio-frequency electromagnetic emission (REME). After complete thermal bleaching of the crystal, radiation defects are not completely annealed, as the electrons and holes released from the color centers by heating leave charged and locally uncompensated defects. Clusters of these "pre centers" lead to electric microheterogeneity of the crystal, the formation of a quasi-electret state, and the emergence of micro-discharges accompanied by radio emission. The generation of REME associated with residual defectiveness, is a manifestation of the effect of radiation "memory" in dielectrics.

  4. Evaluation of low melting halide systems for battery applications

    NASA Astrophysics Data System (ADS)

    Mamantov, G.; Perrovic, C.

    1981-03-01

    This three year program involves evaluation of selected low temperature molten salt solvent systems containing inorganic and/or organic chlorides and bromides for battery applications. The research involves determination of the liquidus temperatures, the specific electrical conductivity, and the electrochemical span of selected halide systems. Characterization of the solvent species by Raman spectroscopy, vapor pressure measurements, and the electrochemical study of a few cathode and anode systems will be undertaken for the most promising solvent systems. The research during the second year of this project involved the determination of liquidus temperatures and/or specific electrical conductivities for a number of binary and ternary molten salt systems containing AlCl3, AlBr3, SbCl3, FeCl3, and GaCl3.

  5. Material Innovation in Advancing Organometal Halide Perovskite Functionality.

    PubMed

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

    2015-12-03

    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.

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

    PubMed Central

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

    2015-01-01

    The efficiency of perovskite solar cells (PSCs) has been improved from 9.7 to 19.3%, with the highest value of 20.1% achieved in 2014. Such a high photovoltaic performance can be attributed to optically high absorption characteristics and balanced charge transport properties with long diffusion lengths of the hybrid lead halide perovskite materials. In this review, some fundamental details of hybrid lead iodide perovskite materials, various fabrication techniques and device structures are described, aiming for a better understanding of these materials and thus highly efficient PSC devices. In addition, some advantages and open issues are discussed here to outline the prospects and challenges of using perovskites in commercial photovoltaic devices. PMID:27877815

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

    NASA Astrophysics Data System (ADS)

    Beléndez, A.; Neipp, C.; Pascual, I.

    1998-10-01

    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 the familiar Agfa 8E75 HD emulsion under the same recording and processing conditions. Theoretical results obtained using Buschmann's weakly scattering model are also compared. Our investigations reveal that high quality SHSG transmission holograms with high spatial frequencies and an almost flat spatial frequency response may be obtained using the new BB-640 plates.

  8. Semiphysical development of holograms recorded in silver halide emulsions

    NASA Astrophysics Data System (ADS)

    Banyasz, Istvan; Belendez, Augusto; Pascual, Inmaculada V.; Fimia, Antonio

    2000-10-01

    In the course of experiments on measurement of the effects of processing on nonlinear characteristics of silver halide holograms recorded in Agfa-gevaert 8E75HD emulsions we found that, under certain circumstances, the AAC developer acted as a semi-physical developer instead of the normal chemical developing action. The developed and fixed holograms were of low optical density (<0.5) and of high diffraction efficiency (up to 15%). Phase contrast microscopy revealed that very clean phase gratings were obtained. This effect of the AAC developer was due to the replacement of one of its components, sodium carbonate of purest grade with that of for analysis grade of the same company.

  9. Direct current ballast circuit for metal halide lamp

    NASA Technical Reports Server (NTRS)

    Lutus, P. (Inventor)

    1981-01-01

    A direct current ballast circuit for a two electrode metal halide lamp is described. Said direct current ballast circuit includes a low voltage DC input and a high frequency power amplifier and power transformer for developing a high voltage output. The output voltage is rectified by diodes and filtered by inductor and capacitor to provide a regulated DC output through commutating diodes to one terminal of the lamp at the output terminal. A feedback path from the output of the filter capacitor through the bias resistor to power the high frequency circuit which includes the power amplifier and the power transformer for sustaining circuit operations during low voltage transients on the input DC supply is described. A current sensor connected to the output of the lamp through terminal for stabilizing lamp current following breakdown of the lamp is described.

  10. Enhanced Quantum Efficiency From Hybrid Cesium Halide/Copper Photocathode

    SciTech Connect

    Kong, Lingmei; Joly, Alan G.; Droubay, Timothy C.; Gong, Yu; Hess, Wayne P.

    2014-04-28

    The quantum efficiency of Cu is found to increase dramatically when coated by a CsI film and then irradiated by a UV laser. Over three orders of magnitude quantum efficiency enhancement at 266 nm is observed in CsI/Cu(100), indicating potential application in future photocathode devices. Upon laser irradiation, a large work function reduction to a value less than 2 eV is also observed, significantly greater than for similarly treated CsBr/Cu(100). The initial QE enhancement, prior to laser irradiation, is attributed to interface interaction, surface cleanliness and the intrinsic properties of the Cs halide film. Further QE enhancement following activation is attributed to formation of inter-band states and Cs metal accumulation at the interface induced by laser irradiation.

  11. Potential function and dissociation energy of alkali halide

    NASA Astrophysics Data System (ADS)

    Srivastava, Abhay P.; Pandey, Anjani K.; Pandey, Brijesh K.

    2016-05-01

    Dissociation energy of some alkali halides have been calculated by using different interaction potential function such as Born-Mayer, Varshani-Shukla and L5 potential model. The theoretical calculation is compared with experimental values. The Result shows that the values of dissociation energy as calculated by using different potential models have an equal amount of deviation with experimental values. The above said deviation with experimental values can be explained by consideration of rotational-vibrational coupling between the constituents of molecules in the limelight of molecular spectroscopy. Findings of present work suggest that the existing potential model need to be reviewed in view of the correction factors solely depending on the rotational, vibrational and electronic coupling between the constituents of molecules.

  12. Metal halide arc discharge lamp having short arc length

    NASA Technical Reports Server (NTRS)

    Muzeroll, Martin E. (Inventor)

    1994-01-01

    A metal halide arc discharge lamp includes a sealed light-transmissive outer jacket, a light-transmissive shroud located within the outer jacket and an arc tube assembly located within the shroud. The arc tube assembly includes an arc tube, electrodes mounted within the arc tube and a fill material for supporting an arc discharge. The electrodes have a spacing such that an electric field in a range of about 60 to 95 volts per centimeter is established between the electrodes. The diameter of the arc tube and the spacing of the electrodes are selected to provide an arc having an arc diameter to arc length ratio in a range of about 1.6 to 1.8. The fill material includes mercury, sodium iodide, scandium tri-iodide and a rare gas, and may include lithium iodide. The lamp exhibits a high color rendering index, high lumen output and high color temperature.

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

    PubMed

    Neipp, C; Pascual, I; Beléndez, A

    1999-03-10

    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.

  14. Theory of hydrogen migration in organic-inorganic halide perovskites.

    PubMed

    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.

  15. Theoretical study of the scandium and yttrium halides

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    The X1Sigma(+) ground states and a3Delta excited states of the diatomic halides of Sc and Y are characterized theoretically, using the SDCI coupled-pair functional method and the state-averaged CASSCF method to determine the spectroscopic constants and related properties. The techniques employed are discussed, and the results are presented in extensive tables. The dissociation energies are given as D0 = 6.00 eV for ScF, 4.55 eV for ScCl, 3.90 eV for ScBr, 6.72 eV for YF, 5.36 eV for YCl, and 4.74 eV for YBr.

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

    PubMed

    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 CH3NH3PbI(3-x)Cl(x) 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.

  17. Discover Earth

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Discover Earth is a NASA-funded project for teachers of grades 5-12 who want to expand their knowledge of the Earth system, and prepare to become master teachers who promote Earth system science in their own schools, counties, and throughout their state. Participants from the following states are invited to apply: Connecticut, Delaware, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, and Washington, DC. Teachers selected for the project participate in a two-week summer workshop conducted at the University of Maryland, College Park; develop classroom-ready materials during the workshop for broad dissemination; conduct a minimum of two peer training activities during the coming school year; and participate in other enrichment/education opportunities as available and desired. Discover Earth is a team effort that utilizes expertise from a range of contributors, and balances science content with hands-on classroom applications.

  18. Earth Rotation

    NASA Technical Reports Server (NTRS)

    Dickey, Jean O.

    1995-01-01

    The study of the Earth's rotation in space (encompassing Universal Time (UT1), length of day, polar motion, and the phenomena of precession and nutation) addresses the complex nature of Earth orientation changes, the mechanisms of excitation of these changes and their geophysical implications in a broad variety of areas. In the absence of internal sources of energy or interactions with astronomical objects, the Earth would move as a rigid body with its various parts (the crust, mantle, inner and outer cores, atmosphere and oceans) rotating together at a constant fixed rate. In reality, the world is considerably more complicated, as is schematically illustrated. The rotation rate of the Earth's crust is not constant, but exhibits complicated fluctuations in speed amounting to several parts in 10(exp 8) [corresponding to a variation of several milliseconds (ms) in the Length Of the Day (LOD) and about one part in 10(exp 6) in the orientation of the rotation axis relative to the solid Earth's axis of figure (polar motion). These changes occur over a broad spectrum of time scales, ranging from hours to centuries and longer, reflecting the fact that they are produced by a wide variety of geophysical and astronomical processes. Geodetic observations of Earth rotation changes thus provide insights into the geophysical processes illustrated, which are often difficult to obtain by other means. In addition, these measurements are required for engineering purposes. Theoretical studies of Earth rotation variations are based on the application of Euler's dynamical equations to the problem of finding the response of slightly deformable solid Earth to variety of surface and internal stresses.

  19. Earth materials and earth dynamics

    SciTech Connect

    Bennett, K; Shankland, T.

    2000-11-01

    In the project ''Earth Materials and Earth Dynamics'' we linked fundamental and exploratory, experimental, theoretical, and computational research programs to shed light on the current and past states of the dynamic Earth. Our objective was to combine different geological, geochemical, geophysical, and materials science analyses with numerical techniques to illuminate active processes in the Earth. These processes include fluid-rock interactions that form and modify the lithosphere, non-linear wave attenuations in rocks that drive plate tectonics and perturb the earth's surface, dynamic recrystallization of olivine that deforms the upper mantle, development of texture in high-pressure olivine polymorphs that create anisotropic velocity regions in the convecting upper mantle and transition zone, and the intense chemical reactions between the mantle and core. We measured physical properties such as texture and nonlinear elasticity, equation of states at simultaneous pressures and temperatures, magnetic spins and bonding, chemical permeability, and thermal-chemical feedback to better characterize earth materials. We artificially generated seismic waves, numerically modeled fluid flow and transport in rock systems and modified polycrystal plasticity theory to interpret measured physical properties and integrate them into our understanding of the Earth. This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL).

  20. Digital Earth

    NASA Astrophysics Data System (ADS)

    de La Beaujardiere, J.

    2001-05-01

    Digital Earth (DE) seeks to make geospatial information broadly and easily available. Vast amounts of natural and cultural information are gathered about the Earth, but it is often difficult to find needed data, to share knowledge across disciplines, and to combine information from several sources. DE defines a framework for interoperability by selecting relevant open standards from the information technology community. These standards specify the technical means by which publishers can provide or sell their data, and by which client applications can find and access data in an automated fashion. The standardized DE framework enables many types of clients--from web browsers to museum kiosks to research-grade virtual environments--to use a common geospatial information infrastructure. Digital Earth can benefit Earth system education in general, and DLESE in particular, in several ways. First, educators, students and creators of instructional material will benefit from standardized access to georeferenced data. Secondly, educational lesson plans that focus on a region or aspect of the Earth can themselves be considered geospatial information resources that could be cataloged and retrieved through DE. Finally, general public knowledge about our planet will by increased by Digital Earth.