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Sample records for alkaline earth element

  1. 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.

  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. 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

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. 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

  10. 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

  11. 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)).

  12. 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

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. 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

  8. 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...

  9. 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...

  10. 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...

  11. 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...

  12. 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...

  13. 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.

  14. 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.

  15. Scarcity of rare earth elements.

    PubMed

    de Boer, M A; Lammertsma, K

    2013-11-01

    Rare earth elements (REEs) are important for green and a large variety of high-tech technologies and are, therefore, in high demand. As a result, supply with REEs is likely to be disrupted (the degree of depends on the REE) in the near future. The 17 REEs are divided into heavy and light REEs. Other critical elements besides REEs, identified by the European Commission, are also becoming less easily available. Although there is no deficiency in the earth's crust of rare earth oxides, the economic accessibility is limited. The increased demand for REEs, the decreasing export from China, and geopolitical concerns on availability contributed to the (re)opening of mines in Australia and the USA and other mines are slow to follow. As a result, short supply of particularly terbium, dysprosium, praseodymium, and neodymium is expected to be problematic for at least the short term, also because they cannot be substituted. Recycling REEs from electronic waste would be a solution, but so far there are hardly any established REE recycling methods. Decreasing the dependency on REEs, for example, by identifying possible replacements or increasing their efficient use, represents another possibility.

  16. 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.

  17. Rare earth elements: end use and recyclability

    USGS Publications Warehouse

    Goonan, Thomas G.

    2011-01-01

    Rare earth elements are used in mature markets (such as catalysts, glassmaking, lighting, and metallurgy), which account for 59 percent of the total worldwide consumption of rare earth elements, and in newer, high-growth markets (such as battery alloys, ceramics, and permanent magnets), which account for 41 percent of the total worldwide consumption of rare earth elements. In mature market segments, lanthanum and cerium constitute about 80 percent of rare earth elements used, and in new market segments, dysprosium, neodymium, and praseodymium account for about 85 percent of rare earth elements used. Regardless of the end use, rare earth elements are not recycled in large quantities, but could be if recycling became mandated or very high prices of rare earth elements made recycling feasible.

  18. 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.

  19. Recycling of Rare Earth Elements

    NASA Astrophysics Data System (ADS)

    Lorenz, Tom; Bertau, Martin

    2017-01-01

    Any development of an effective process for rare earth (RE) recycling has become more and more challenging, especially in recent years. Since 2011, when commodity prices of REs had met their all-time maximum, prices have dropped rapidly by more than 90 %. An economic process able to offset these fluctuations has to take unconventional methods into account beside well-known strategies like acid/basic leaching or solvent extraction. The solid-state chlorination provides such an unconventional method for mobilizing RE elements from waste streams. Instead of hydrochloric acid this kind of chlorination decomposes NH4Cl thermally to release up to 400 °C hot HCl gas. After cooling the resulting solid metal chlorides may be easily dissolved in pH-adjusted water. Without producing strongly acidic wastes and with NH4Cl as cheap source for hydrogen chloride, solid-state chlorination provides various advantages in terms of costs and disposal. In the course of the SepSELSA project this method was examined, adjusted and optimized for RE recycling from fluorescent lamp scraps as well as Fe14Nd2B magnets. Thereby many surprising influences and trends required various analytic methods to examine the reasons and special mechanisms behind them.

  20. 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.

  1. 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.

  2. 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%.

  3. 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.

  4. Rare Earth Element Mines, Deposits, and Occurrences

    USGS Publications Warehouse

    Orris, Greta J.; Grauch, Richard I.

    2002-01-01

    Data on rare earth (including yttrium) mines, deposits, and occurrences were compiled as part of an effort by the USGS and the University of Arizona Center for Mineral Resources to summarize current knowledge on the supply and demand outlook and related topics for this group of elements. Economic competition and environmental concerns are increasingly constraining the mining and processing of rare earths from the Mountain Pass mine in California. For many years, the deposit at Mountain Pass was the world's dominant source of rare earth elements and the United States was essentially self-sufficient. Starting approximately 10 years ago, the U.S. has become increasingly dependent (> 90 percent of separated rare earths) upon imports from China, now the dominant source of rare earths. A knowledge of the known economic and noneconomic sources of rare earths is basic to evaluating the outlook for rare earth supply and associated issues.

  5. Moving KML geometry elements within Google Earth

    NASA Astrophysics Data System (ADS)

    Zhu, Liang-feng; Wang, Xi-feng; Pan, Xin

    2014-11-01

    During the process of modeling and visualizing geospatial information on the Google Earth virtual globe, there is an increasing demand to carry out such operations as moving geospatial objects defined by KML geometry elements horizontally or vertically. Due to the absence of the functionality and user interface for performing the moving transformation, it is either hard or impossible to interactively move multiple geospatial objects only using the existing Google Earth desktop application, especially when the data sets are in large volume. In this paper, we present a general framework and associated implementation methods for moving multiple KML geometry elements within Google Earth. In our proposed framework, we first load KML objects into the Google Earth plug-in, and then extract KML geometry elements from the imported KML objects. Subsequently, we interactively control the movement distance along a specified orientation by employing a custom user interface, calculate the transformed geographic location for each KML geometry element, and adjust geographic coordinates of the points in each KML objects. And finally, transformed KML geometry elements can be displayed in Google Earth for 3D visualization and spatial analysis. A key advantage of the proposed framework is that it provides a simple, uniform and efficient user interface for moving multiple KML geometry elements within Google Earth. More importantly, the proposed framework and associated implementations can be conveniently integrated into other customizable Google Earth applications to support interactively visualizing and analyzing geospatial objects defined by KML geometry elements.

  6. Mineral resource of the month: rare earth elements

    USGS Publications Warehouse

    ,

    2011-01-01

    The article provides information on rare earth elements, which are group of 17 natural metallic elements. The rare earth elements are scandium, yttrium and lanthanides and classified into light rare earth elements (LREE) and heavy rate earth elements (HREE). The principal ores of the rare earth elements are identified. An overview of China's production of 97 percent of the rare earths in the world is provided. Commercial applications of rare earths are described.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. Trace element distribution coefficients in alkaline series. [Titanites; bitite

    SciTech Connect

    Lemarchand, F.; Villemant, B.; Calas, G.

    1987-05-01

    Mineral/groundmass partition coefficients for U, Th, Zr, Hf, Ta, Rb, REE, Co and Sc have been systematically measured in olivine, clinopyroxene, amphibole, biotite, Ti-magnetites, titanite, zircon and feldspars, in basaltic to trachytic lavas from alkaline series (Velay, Chaine des Puys: Massif Central, France and Fayal: Azores). Average partition coefficients are defined within the experimental uncertainty for limited compositional ranges (basalt-hawaiite, mugearites, benmoreite-trachyte), and are useful for trace element modelling. The new results for U, Th, Ta, Zr and Hf partition coefficients show contrasting behaviour. They can thus be used as ''key elements'' for identifying fractionating mineral phases in differentiation processes (e.g. Ta and Th for amphibole and mica). Partition coefficient may be calculated using the two-lattice model suggested by NIELSEN (1985). Such values show a considerably reduced chemical dependence in natural systems, relative to weight per cent D values. The residual variations may be accounted for by temperature or volatile influence. This calculation greatly enhances modelling possibilities using trace elements for comparing differentiation series as well as for predicting the behaviour of elements during magmatic differentiation.

  17. 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.

  18. Ferromagnetism in ZnO doped with alkaline elements

    NASA Astrophysics Data System (ADS)

    Wang, Yiren; Piao, Jingyuan; Xin, Guozhong; Lu, Yunhao; Ao, Zhimin; Bao, Nina; Ding, Jun; Li, Sean; Yi, Jiabao

    We have observed room temperature ferromagnetism (RTFM) in ZnO doped with alkaline elements Using first-principles calculations we found the magnetization in these systems is originated from the O2p hole states around Zn vacancies. Calculations indicate that the formation energy of Zn vacancies alone is rather high while further investigation indicates the formation can be much stabilized by the alkaline dopants in the form of defect complexes. By calculating the formation energy of concerned defects and complexes, we found the role of the dopants that under a certain doping concentration: Zn vacancy, substitutional and interstitial dopants can form a defect complex, which can lower formation energy, therefore stabilizing Zn vacancies. Moreover K dopants have shown unique functions on the ferromagnetism since the substitutional K can induce magnetic moments to the system by forming partial zinc vacancy via lattice distortion. Hence K doped ZnO can be magnetic at low doping concentrations. Experimentally, Li, Na doped ZnO films and K doped ZnO nanorods with different doping levels are synthesized, RTFM can be observed in all these systems. The magnetization is found to be greatly influenced by the doping concentrations. The experimental results have shown good consistence with our theoretical calculations. Our studies can inspire the defect induced ferromagnetism as a new route for the fabrication of new diluted magnetic semiconductors.

  19. 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.

  20. [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.

  1. Rare earth element scavenging in seawater

    NASA Astrophysics Data System (ADS)

    Byrne, Robert H.; Kim, Ki-Hyun

    1990-10-01

    Examinations of rare earth element (REE) adsorption in seawater, using a variety of surface-types, indicated that, for most surfaces, light rare earth elements (LREEs) are preferentially adsorbed compared to the heavy rare earths (HREEs). Exceptions to this behavior were observed only for silica phases (glass surfaces, acid-cleaned diatomaceous earth, and synthetic SiO 2). The affinity of the rare earths for surfaces can be strongly affected by thin organic coatings. Glass surfaces which acquired an organic coating through immersion in Tampa Bay exhibited adsorptive behavior typical of organic-rich, rather than glass, surfaces. Models of rare earth distributions between seawater and carboxylate-rich surfaces indicate that scavenging processes which involve such surfaces should exhibit a strong dependence on pH and carbonate complexation. Scavenging models involving carboxylate surfaces produce relative REE abundance patterns in good general agreement with observed shale-normalized REE abundances in seawater. Scavenging by carboxylate-rich surfaces should produce HREE enrichments in seawater relative to the LREEs and may produce enrichments of lanthanum relative to its immediate trivalent neighbors. Due to the origin of distribution coefficients as a difference between REE solution complexation (which increases strongly with atomic number) and surface complexation (which apparently also increases with atomic number) the relative solution abundance patterns of the REEs produced by scavenging reactions can be quite complex.

  2. What about the rare-earth elements

    Technology Transfer Automated Retrieval System (TEKTRAN)

    There is insufficient understanding of the nutritional physiology of pecan trees and orchards; thus, affecting nutmeat yield and quality, disease resistance and alternate bearing. An analysis of the rare-earth element composition of pecan and related hickory cousins found that they hyperaccumulate ...

  3. 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

  4. Trace elemental imaging of rare earth elements discriminates tissues at microscale in flat fossils.

    PubMed

    Gueriau, Pierre; Mocuta, Cristian; Dutheil, Didier B; Cohen, Serge X; Thiaudière, Dominique; Charbonnier, Sylvain; Clément, Gaël; Bertrand, Loïc

    2014-01-01

    The interpretation of flattened fossils remains a major challenge due to compression of their complex anatomies during fossilization, making critical anatomical features invisible or hardly discernible. Key features are often hidden under greatly preserved decay prone tissues, or an unpreparable sedimentary matrix. A method offering access to such anatomical features is of paramount interest to resolve taxonomic affinities and to study fossils after a least possible invasive preparation. Unfortunately, the widely-used X-ray micro-computed tomography, for visualizing hidden or internal structures of a broad range of fossils, is generally inapplicable to flattened specimens, due to the very high differential absorbance in distinct directions. Here we show that synchrotron X-ray fluorescence spectral raster-scanning coupled to spectral decomposition or a much faster Kullback-Leibler divergence based statistical analysis provides microscale visualization of tissues. We imaged exceptionally well-preserved fossils from the Late Cretaceous without needing any prior delicate preparation. The contrasting elemental distributions greatly improved the discrimination of skeletal elements material from both the sedimentary matrix and fossilized soft tissues. Aside content in alkaline earth elements and phosphorus, a critical parameter for tissue discrimination is the distinct amounts of rare earth elements. Local quantification of rare earths may open new avenues for fossil description but also in paleoenvironmental and taphonomical studies.

  5. Trace Elemental Imaging of Rare Earth Elements Discriminates Tissues at Microscale in Flat Fossils

    PubMed Central

    Gueriau, Pierre; Mocuta, Cristian; Dutheil, Didier B.; Cohen, Serge X.; Thiaudière, Dominique; Charbonnier, Sylvain; Clément, Gaël; Bertrand, Loïc

    2014-01-01

    The interpretation of flattened fossils remains a major challenge due to compression of their complex anatomies during fossilization, making critical anatomical features invisible or hardly discernible. Key features are often hidden under greatly preserved decay prone tissues, or an unpreparable sedimentary matrix. A method offering access to such anatomical features is of paramount interest to resolve taxonomic affinities and to study fossils after a least possible invasive preparation. Unfortunately, the widely-used X-ray micro-computed tomography, for visualizing hidden or internal structures of a broad range of fossils, is generally inapplicable to flattened specimens, due to the very high differential absorbance in distinct directions. Here we show that synchrotron X-ray fluorescence spectral raster-scanning coupled to spectral decomposition or a much faster Kullback-Leibler divergence based statistical analysis provides microscale visualization of tissues. We imaged exceptionally well-preserved fossils from the Late Cretaceous without needing any prior delicate preparation. The contrasting elemental distributions greatly improved the discrimination of skeletal elements material from both the sedimentary matrix and fossilized soft tissues. Aside content in alkaline earth elements and phosphorus, a critical parameter for tissue discrimination is the distinct amounts of rare earth elements. Local quantification of rare earths may open new avenues for fossil description but also in paleoenvironmental and taphonomical studies. PMID:24489809

  6. 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.

  7. Rare earth elements and permanent magnets (invited)

    NASA Astrophysics Data System (ADS)

    Dent, Peter C.

    2012-04-01

    Rare earth (RE) magnets have become virtually indispensible in a wide variety of industries such as aerospace, automotive, electronics, medical, and military. RE elements are essential ingredients in these high performance magnets based on intermetallic compounds RECo5, RE2TM17 (TM: transition metal), and RE2TM14B. Rare earth magnets are known for their superior magnetic properties—high induction, and coercive force. These properties arise due to the extremely high magnetocrystalline anisotropy made possible by unique 3d-4f interactions between transition metals and rare earths. For more than 40 years, these magnets remain the number one choice in applications that require high magnetic fields in extreme operating conditions—high demagnetization forces and high temperature. EEC produces and specializes in RECo5 and RE2TM17 type sintered magnets. Samarium and gadolinium are key RE ingredients in the powder metallurgical magnet production processes which include melting, crushing, jet milling, pressing, sintering, and heat treating. The magnetic properties and applications of these magnets will be discussed. We will also briefly discuss the past, current, and future of the permanent magnet business. Currently, over 95% of all pure rare earth oxides are sourced from China, which currently controls the market. We will provide insights regarding current and potential new magnet technologies and designer choices, which may mitigate rare earth supply chain issues now and into the future.

  8. 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.

  9. 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.

  10. Note: Portable rare-earth element analyzer using pyroelectric crystal

    SciTech Connect

    Imashuku, Susumu Fuyuno, Naoto; Hanasaki, Kohei; Kawai, Jun

    2013-12-15

    We report a portable rare-earth element analyzer with a palm-top size chamber including the electron source of a pyroelectric crystal and the sample stage utilizing cathodoluminescence (CL) phenomenon. The portable rare-earth element analyzer utilizing CL phenomenon is the smallest reported so far. The portable rare-earth element analyzer detected the rare-earth elements Dy, Tb, Er, and Sm of ppm order in zircon, which were not detected by scanning electron microscopy-energy dispersive X-ray spectroscopy analysis. We also performed an elemental mapping of rare-earth elements by capturing a CL image using CCD camera.

  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. Anthropogenic Cycles of Rare Earth Elements

    NASA Astrophysics Data System (ADS)

    Du, X.; Graedel, T. E.

    2009-12-01

    This research will develop quantitatively resolved anthropogenic cycles and in-use stocks for the rare earth metals specifically cerium, lanthanum and dysprosium in Japan, China, and the U.S. for the year of 2007. Rare earth elements (REE) is a group of 17 scare metals widely used in a growing number of emerging technologies and have been in high demand for emerging technologies as raw materials during past the three decades. New market participants from newly industrializing countries, primarily China, have had strong impacts on the demand of share. Consequently, the importance to sustain a reliable, steady, uninterrupted supply on global market triggered comprehensive research to recognize and understand the life cycles of rare earths. Moreover, because China plays a dominant role in mining production since 1990, it requires the assessment for the countries, which are almost completely dependent on imports from China with respect to rare earth resources. The study aims to analyze the flows and stocks of rare earth elements individually as elemental form in spite of their natural geological co-occurrence and mixed composition in applications. By applying the method of Material Flow Analysis (MFA) work has been done on evaluating current and historical flows of specific technologically significant materials, for example, copper, zinc, nickel, etc., determining the stocks available in different types of reservoirs (e.g., lithosphere, in-use) and the flows among the reservoirs, developing scenarios of possible futures of metal use, and assessing the environmental and policy implications of the results. Therefore, REE as a new target deserves inclusion because of its potential demand-supply conflict and importance to secure the competitive advantage of technical innovation in future. This work will generate a quantitatively resolved anthropogenic life cycle and in-use stocks for REE for the main target countries for a chosen year, 2007, providing flows and stocks from

  14. 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.

  15. 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.

  16. 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.

  17. 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,…

  18. Tipping elements in the Earth's climate system

    SciTech Connect

    Lenton, T.M.; Held, H.; Lucht, W.; Rahmstorf, S.; Kriegler, E. |; Hall, J.W.; Schellnhuber, H.J. |

    2008-02-12

    The term 'tipping point' commonly refers to a critical threshold at which a tiny perturbation can qualitatively alter the state or development of a system. Here the authors introduce the term 'tipping element' to describe large-scale components of the Earth system that may pass a tipping point. They critically evaluate potential policy-relevant tipping elements in the climate system under anthropogenic forcing, drawing on the pertinent literature and a recent international workshop to compile a short list, and they assess where their tipping points lie. An expert elicitation is used to help rank their sensitivity to global warming and the uncertainty about the underlying physical mechanisms. Then the authors explain how, in principle, early warning systems could be established to detect the proximity of some tipping points.

  19. Magmatic (silicates/saline/sulfur-rich/CO2) immiscibility and zirconium and rare-earth element enrichment from alkaline magma chamber margins : Evidence from Ponza Island, Pontine Archipelago, Italy

    USGS Publications Warehouse

    Belkin, H.E.; de Vivo, B.; Lima, A.; Torok, K.

    1996-01-01

    incompatible elements.

  20. Alkaline chemistry of transuranium elements and technetium and the treatment of alkaline radioactive wastes

    SciTech Connect

    Delegard, C.H.; Peretrukhin, V.F.; Shilov, V.P.; Pikaev, A.K.

    1995-05-01

    Goal of this survey is to generalize the known data on fundamental physical-chemical properties of TRUs and Tc, methods for their isolation, and to provide recommendations that will be useful for partitioning them from alkaline high-level wastes.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Rare earth elements in river waters

    NASA Technical Reports Server (NTRS)

    Goldstein, Steven J.; Jacobsen, Stein B.

    1988-01-01

    To characterize the input to the oceans of rare earth elements (REE) in the dissolved and the suspended loads of rivers, the REE concentrations were measured in samples of Amazon, Indus, Mississippi, Murray-Darling, and Ohio rivers and in samples of smaller rivers that had more distinct drainage basin lithology and water chemistry. It was found that, in the suspended loads of small rivers, the REE pattern was dependent on drainage basin geology, whereas the suspended loads in major rivers had relatively uniform REE patterns and were heavy-REE depleted relative to the North American Shale composite (NASC). The dissolved loads in the five major rivers had marked relative heavy-REE enrichments, relative to the NASC and the suspended material, with the (La/Yb)N ratio of about 0.4 (as compared with the ratio of about 1.9 in suspended loads).

  6. 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.

  7. 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.

  8. Rare Earth Elements in Global Aqueous Media

    NASA Astrophysics Data System (ADS)

    Noack, C.; Karamalidis, A.; Dzombak, D. A.

    2012-12-01

    We are examining the occurrence and abundance of rare earth elements (REE) associated with produced waters from shale gas development, and factors controlling aqueous REE concentrations in geochemical environments, to provide information for: (1) potential recovery of REE as a valuable byproduct, and (2) utilization of unique REE signatures as a risk assessment tool. REE include the lanthanide series of elements - excluding short-lived, radioactive promethium - and yttrium. These elements are critical to a wide variety of high-tech, energy efficient applications such as phosphors, magnets, and batteries. Escalating costs of REE resulting from divergent supply and demand patterns motivates the first goal. The second goal relates to the search for a reliable, naturally occurring tracer to improve understanding of fluid migration and water-rock interactions during hydraulic fracturing and natural gas recovery. We compiled data from 100 studies of REE occurrence and concentrations in groundwaters, ocean waters, river waters, and lake waters. In the groundwater systems documented, total dissolved REE concentrations ranged over eight orders of magnitude; however the average concentrations across the lanthanides varied by less than two orders of magnitude. This leads to exceptional inter-element correlations, with a median correlation coefficient greater than 0.98, implying potential usefulness of REE ratios for groundwater signatures. Reports describing reactions governing REE solubilization were also investigated. We assembled information about important solution chemistries and performed equilibrium modeling using PHREEQC to examine common hypotheses regarding the factors controlling REE compositions. In particular, effects of pH, Eh, and common complexing ligands were evaluated. Produced and connate waters of the Marcellus shale are well characterized for their major chemical elements. There is a dearth of knowledge, however, regarding the occurrence of REE in

  9. 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.

  10. 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.

  11. 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.

  12. Google Earth locations of USA and seafloor hydrothermal vents with associated rare earth element data

    SciTech Connect

    Andrew Fowler

    2016-02-10

    Google Earth .kmz files that contain the locations of geothermal wells and thermal springs in the USA, and seafloor hydrothermal vents that have associated rare earth element data. The file does not contain the actual data, the actual data is available through the GDR website in two tier 3 data sets entitled "Compilation of Rare Earth Element Analyses from US Geothermal Fields and Mid Ocean Ridge (MOR) Hydrothermal Vents" and "Rare earth element content of thermal fluids from Surprise Valley, California"

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Rare earths and other trace elements in Luna 16 soil.

    NASA Technical Reports Server (NTRS)

    Helmke, P. A.; Haskin, L. A.

    1972-01-01

    An analysis has been made of four small samples of material brought to earth by the Luna 16 mission, with the aim to determine rare earths and other trace elements in these samples. The analytical results are tabulated, and the rare earth abundances are compared with the average for chondrites. A comparison is also made with the results of similar analyses of Apollo samples.

  3. How PNNL Extracts Rare Earth Elements from Geothermal Brine

    SciTech Connect

    2016-07-12

    By looking at a problem at a nanoscale level, PNNL researchers are developing an economic way to extract valuable rare earth elements from geothermal fluids. This novel approach may help meet the high demand for rare earth elements that are used in many clean energy technologies.

  4. 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.

  5. Rare earth element diffusion in natural enstatite

    NASA Astrophysics Data System (ADS)

    Cherniak, Daniele J.; Liang, Yan

    2007-03-01

    diopside [Van Orman, J.A., Grove, T.L., Shimizu, N., 2001. Rare earth element diffusion in diopside; influence of temperature, pressure, and ionic radius, and an elastic model for diffusion in silicates. Contrib. Mineral. Petrol.141, 687-703]. These differences in diffusive behavior of REE between diopside and enstatite, as well as Eu 2+ and Eu 3+ in enstatite, can result in significant REE fractionation between coexisting pyroxenes during partial melting, melt migration, and subsolidus reequilibration processes in the Earth's mantle and that of the Moon.

  6. Rare earth elements in Hamersley BIF minerals

    NASA Astrophysics Data System (ADS)

    Alibert, Chantal

    2016-07-01

    Minerals from the Hamersley banded iron formation, Western Australia, were analyzed for Y and rare earth elements (YREEs) by laser ablation ICP-MS to investigate diagenetic pathways, from precursor phases to BIF minerals. One group of apatites carries the seawater REE signature, giving evidence that P and REEs, thoroughly scavenged from the water column by Si-ferrihydrite particles, were released upon microbial Fe3+ reductive dissolution of Si-ferrihydrite in pore-water and finally sequestered mainly in authigenic apatite. The absence of fractionation between apatite and seawater suggests that REE were first incorporated into an amorphous calcium phosphate as fully hydrated cations, i.e. as outer-sphere complexes. The iron oxides and carbonates carry only a small fraction of the whole-rock REE budget. Their REE patterns are distinctly enriched in Yb and show some M-type tetrad effect consistent with experimental Kd(REE) between solid and saline solution with low carbonate ion concentrations. It is deduced that hematite formed at an incipient stage of Fe2+-catalyzed dissolution of Si-ferrihydrite, via a dissolution-reprecipitation pathway. The REE pattern of greenalite, found as sub-micron particles in quartz in a chert-siderite sample, is consistent with its authigenic origin by precipitation in pore-water after dissolution of a small amount of Si-ferrihydrite. Magnetite carries very low YREEs (ppb-level), has an homogeneous pattern distinctly enriched in the mid-REEs compared to hematite, and includes a late population depleted in light-REEs, Ba and As. Magnetite forming aggregates and massive laminae is tentatively interpreted as reflecting some fluid-aided hematite-magnetite re-equilibration or transformation at low-grade metamorphic temperatures.

  7. 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

  8. [Content of rare earth elements in wild Hypericum japonicum Thunb].

    PubMed

    Wei, Zhen-Lin; Rui, Yu-Kui; Tian, Zhi-Huan

    2009-06-01

    Rare earth elements are important nutritional elements for human health, and today more and more attention has been paid to the effective components in Chinese traditional medicine, especially to rare earth elements. Fifteen rare earth elements in wild hypericum japonicum Thunb were analyzed by the methods of ICP-MS. The results showed that the concentrations of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Tm, Lu and Y ranged from 6 ng x g(-1) x DW to 14 522 ng x g(-1) x DW, and among them the concentrations of La, Ce and Nd were higher than 2 000 ng x g(-1) x DW. Compared with the concentration of rare earth elements in rice, corn, wheat and barley, the total concentration of rare earth elements in hypericum japonicum Thunb was much higher, which could be the mechanism of curative effect of hypericum japonicum Thunb on liverish diseases. The character of elements and the content of rare earth elements in soil should be responsible for the difference, but the distributive mechanism of rare earth elements in hypericum japonicum Thunb should be further studied.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. Alkali element constraints on Earth-Moon relations

    NASA Technical Reports Server (NTRS)

    Norman, M. D.; Drake, M. J.; Jones, J. H.

    1994-01-01

    Given their range of volatilities, alkali elements are potential tracers of temperature-dependent processes during planetary accretion and formation of the Earth-Moon system. Under the giant impact hypothesis, no direct connection between the composition of the Moon and the Earth is required, and proto-lunar material does not necessarily experience high temperatures. Models calling for multiple collisions with smaller planetesimals derive proto-lunar materials mainly from the Earth's mantle and explicitly invoke vaporization, shock melting and volatility-related fractionation. Na/K, K/Rb, and Rb/Cs should all increase in response to thermal volatization, so theories which derive the Moon substantially from Earth's mantle predict these ratios will be higher in the Moon than in the primitive mantle of the Earth. Despite the overall depletion of volatile elements in the Moon, its Na/K and K/Rb are equal to or less than those of Earth. A new model presented here for the composition of Earth's continental crust, a major repository of the alkali elements, suggests the Rb/Cs of the Moon is also less than that of Earth. Fractionation of the alkali elements between Earth and Moon are in the opposite sense to predictions based on the relative volatilities of these elements, if the Moon formed by high-T processing of Earth's mantle. Earth, rather than the Moon, appears to carry a signature of volatility-related fractionation in the alkali elements. This may reflect an early episode of intense heating on Earth with the Moon's alkali budget accreting from cooler material.

  16. Earth, Air, Fire and Water in Our Elements

    ERIC Educational Resources Information Center

    Lievesley, Tara

    2007-01-01

    The idea that everything is made of the four "elements", earth, air, fire and water, goes back to the ancient Greeks. In this article, the author talks about the origins of ideas about the elements. The author provides an account that attempts to summarise thousands of years of theoretical development of the elements in a thousand words or so.

  17. Rare earth element enrichment using membrane based solvent extraction

    NASA Astrophysics Data System (ADS)

    Makertiharta, I. G. B. N.; Dharmawijaya, P. T.; Zunita, M.; Wenten, I. G.

    2017-01-01

    The chemical, catalytic, electrical, magnetic, and optical properties of rare earth elements are required in broad applications. Rare earth elements have similar physical and chemical properties thus it is difficult to separate one from each other. Rare earth element is relatively abundant in earth's crust but rarely occur in high concentrated deposits. Traditionally, ion-exchange and solvent extraction techniques have been developed to separate and purify single rare earth solutions or compounds. Recently, membrane starts to gain attention for rare earth separation by combining membrane and proven technologies such as solvent extraction. Membrane-based process offers selective, reliable, energy efficient and easy to scale up separation. During membrane-based separation process, one phase passes through membrane pores while the other phase is rejected. There is no direct mixing of two phases thus the solvent loss is very low. Membrane can also lower solvent physical properties requirement (viscosity, density) and backmixing, eliminate flooding phenomenon and provide large interfacial area for mass transfer. This paper will summarize research efforts in developing membrane technology for rare earth element separation. Special attention will be given to solvent extraction related process as the commonly used method for rare earth element separation. Furthermore, membrane configuration and its potentials will also be discussed.

  18. 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.

  19. 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

  20. 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.

  1. 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.

  2. 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

  3. Implications of Competition for Rare Earth Elements (REE) in Africa

    DTIC Science & Technology

    2011-03-15

    Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202- 4302. Respondents should be aware that...2010). 3 Marc Humphries , ―Rare Earth Elements: The Global Supply Chain,‖ Congressional Research Service Report for Congress R41347 (September 30...101026_Verrastro_Geopolitics_web.pdf (accessed October 14, 2010). 10 Humphries , ―Rare Earth Elements: The Global Supply Chain,‖ (September 30, 2010): 4

  4. 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.

  5. 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

  6. 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.

  7. Competition between humic acid and carbonates for rare earth elements complexation.

    PubMed

    Pourret, Olivier; Davranche, Mélanie; Gruau, Gérard; Dia, Aline

    2007-01-01

    The competitive binding of rare earth elements (REE) to humic acid (HA) and carbonates was studied experimentally at various pH and alkalinity values by combining ultrafiltration and inductively coupled plasma mass spectrometry techniques. The results show that the REE species occur as binary humate or carbonate complexes but not as ternary REE-carbonate-humate as previously proposed. The results also reveal the strong pH and alkalinity dependence of the competition as well as the existence of a systematic fractionation across the REE series. Specifically, carbonate complexation is at a maximum at pH 10 and increase with increasing alkalinity and with the atomic number of the REE (LuCO(3)>LaCO(3)). Modeling of the data using Model VI and recently published stability constants for complexation of REE by humic acid well reproduced the experimental data, confirming the ability of Model VI to accurately determine REE speciation in natural waters. This modeling also confirms the reliability of recently published stability constants. This work shed more light not only on the competition between carbonates and HA for REE complexation but also on the reliability of WHAM 6 and Model VI for calculating the speciation of REE with organic matter in alkaline organic-rich water.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. 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.

  2. Rare earth elements in synthetic zircon. 1. synthesis, and rare earth element and phosphorus doping.

    SciTech Connect

    Hanchar, J. M.; Finch, R. J.; Hoskin, W. O.; Watson, E. B.; Cherniak, D. J.; Mariano, A. N.; Chemical Engineering; George Washington Univ.; Univ. of Canterbury; Australian National Univ.; Rensselaer Polytechnic Inst.

    2001-05-01

    Sedimentary mineral assemblages commonly contain detrital zircon crystals as part of the heavy-mineral fraction. Age spectra determined by U-Pb isotopic analysis of single zircon crystals within a sample may directly image the age composition--but not the chemical composition--of the source region. Rare earth element (REE) abundances have been measured for zircons from a range of common crustal igneous rock types from different tectonic environments, as well as kimberlite, carbonatite, and high-grade metamorphic rocks, to assess the potential of using zircon REE characteristics to infer the rock types present in sediment source regions. Except for zircon with probable mantle affinities, zircon REE abundances and normalized patterns show little intersample and intrasample variation. To evaluate the actual variation in detrital zircon REE composition in a true sediment of known mixed provenance, zircons from a sandstone sample from the Statfjord Formation (North Sea) were analyzed. Despite a provenance including high-grade metasediment and granitoids and a range in zircon age of 2.82 b.y., the zircon REEs exhibit a narrow abundance range with no systematic differences in pattern shape. These evidences show zircon REE patterns and abundances are generally not useful as indicators of provenance.

  3. Bioleaching of rare earth elements from monazite sand.

    PubMed

    Brisson, Vanessa L; Zhuang, Wei-Qin; Alvarez-Cohen, Lisa

    2016-02-01

    Three fungal strains were found to be capable of bioleaching rare earth elements from monazite, a rare earth phosphate mineral, utilizing the monazite as a phosphate source and releasing rare earth cations into solution. These organisms include one known phosphate solubilizing fungus, Aspergillus niger ATCC 1015, as well as two newly isolated fungi: an Aspergillus terreus strain ML3-1 and a Paecilomyces spp. strain WE3-F. Although monazite also contains the radioactive element Thorium, bioleaching by these fungi preferentially solubilized rare earth elements over Thorium, leaving the Thorium in the solid residual. Adjustments in growth media composition improved bioleaching performance measured as rare earth release. Cell-free spent medium generated during growth of A. terreus strain ML3-1 and Paecilomyces spp. strain WE3-F in the presence of monazite leached rare earths to concentrations 1.7-3.8 times those of HCl solutions of comparable pH, indicating that compounds exogenously released by these organisms contribute substantially to leaching. Organic acids released by the organisms included acetic, citric, gluconic, itaconic, oxalic, and succinic acids. Abiotic leaching with laboratory prepared solutions of these acids was not as effective as bioleaching or leaching with cell-free spent medium at releasing rare earths from monazite, indicating that compounds other than the identified organic acids contribute to leaching performance.

  4. MaRGEE: Move and Rotate Google Earth Elements

    NASA Astrophysics Data System (ADS)

    Dordevic, Mladen M.; Whitmeyer, Steven J.

    2015-12-01

    Google Earth is recognized as a highly effective visualization tool for geospatial information. However, there remain serious limitations that have hindered its acceptance as a tool for research and education in the geosciences. One significant limitation is the inability to translate or rotate geometrical elements on the Google Earth virtual globe. Here we present a new JavaScript web application to "Move and Rotate Google Earth Elements" (MaRGEE). MaRGEE includes tools to simplify, translate, and rotate elements, add intermediate steps to a transposition, and batch process multiple transpositions. The transposition algorithm uses spherical geometry calculations, such as the haversine formula, to accurately reposition groups of points, paths, and polygons on the Google Earth globe without distortion. Due to the imminent deprecation of the Google Earth API and browser plugin, MaRGEE uses a Google Maps interface to facilitate and illustrate the transpositions. However, the inherent spatial distortions that result from the Google Maps Web Mercator projection are not apparent once the transposed elements are saved as a KML file and opened in Google Earth. Potential applications of the MaRGEE toolkit include tectonic reconstructions, the movements of glaciers or thrust sheets, and time-based animations of other large- and small-scale geologic processes.

  5. Modeling rammed earth wall using discrete element method

    NASA Astrophysics Data System (ADS)

    Bui, T.-T.; Bui, Q.-B.; Limam, A.; Morel, J.-C.

    2016-03-01

    Rammed earth is attracting renewed interest throughout the world thanks to its "green" characteristics in the context of sustainable development. Several research studies have thus recently been carried out to investigate this material. Some of them attempted to simulate the rammed earth's mechanical behavior by using analytical or numerical models. Most of these studies assumed that there was a perfect cohesion at the interface between earthen layers. This hypothesis proved to be acceptable for the case of vertical loading, but it could be questionable for horizontal loading. To address this problem, discrete element modeling seems to be relevant to simulate a rammed earth wall. To our knowledge, no research has been conducted thus far using discrete element modeling to study a rammed earth wall. This paper presents an assessment of the discrete element modeling's robustness for rammed earth walls. Firstly, a brief description of the discrete element modeling is presented. Then the parameters necessary for discrete element modeling of the material law of the earthen layers and their interfaces law following the Mohr-Coulomb model with a tension cut-off and post-peak softening were given. The relevance of the model and the material parameters were assessed by comparing them with experimental results from the literature. The results showed that, in the case of vertical loading, interfaces did not have an important effect. In the case of diagonal loading, model with interfaces produced better results. Interface characteristics can vary from 85 to 100% of the corresponding earthen layer's characteristics.

  6. Systematic variation of rare-earth elements in cerium-earth minerals

    USGS Publications Warehouse

    Murata, K.J.; Rose, H.J.; Carron, M.K.; Glass, J.J.

    1957-01-01

    In a continuation of a study reported previously, rare-earth elements and thorium have been determined in monazite, allanite, cerite, bastnaesite, and a number of miscellaneous cerium-earth minerals. A quantity called sigma (???), which is the sum of the atomic percentages of La, Ce, and Pr, is proposed as an index of composition of all cerium-earth minerals with respect to the rare-earth elements. The value of ??? for all of the minerals analysed falls between 58 and 92 atomic per cent. Monazites, allanites, and cerites cover the entire observed range, whereas bastnaesites are sharply restricted to the range between 80 and 92 atomic per cent. The minimum value of ??? for a cerium-earth mineral corresponds to the smallest possible unit-cell size of the mineral. In monazite, this structurally controlled minimum value of ??? is estimated to be around 30 atomic per cent. Neodymium, because of its abundance, and yttrium, because of its small size, have dominant roles in contraction of the structure. In the other direction, the limit of variation in composition will be reached when lanthanum becomes the sole rare-earth element in a cerium-earth mineral. Cerium-earth minerals from alkalic rocks are all characterized by values of ??? greater than 80 atomic per cent, indicating that the processes that formed these rocks were unusually efficient in fractionating the rare-earth elements-efficient in the sense that a highly selected assemblage is produced without eliminating the bulk of these elements. Analyses of inner and outer parts of two large crystals of monazite from different deposits show no difference in ??? in one crystal and a slightly smaller value of ??? in the outer part of the other crystal compared to the inner part. The ??? of monazites from pegmatites that intrude genetically related granitic rocks in North Carolina is found to be either higher or lower than the ??? of monazites in the intruded host rock. These results indicate that the fractionation of the

  7. Alkali elements in the Earth's core: Evidence from enstatite meteorites

    NASA Technical Reports Server (NTRS)

    Lodders, K.

    1995-01-01

    The abundances of alkali elements in the Earth's core are predicted by assuming that accretion of the Earth started from material similar in composition to enstatite chondrites and that enstatite achondrites (aubrites) provide a natural laboratory to study core-mantle differentiation under extremely reducing conditions. If core formation on the aubrite parent body is comparable with core formation on the early Earth, it is found that 2600 (+/- 1000) ppm Na, 550 (+/- 260) ppm K, 3.4 (+/- 2.1) ppm Rb, and 0.31 (+/- 0.24) ppm Cs can reside in the Earth's core. The alkali-element abundances are consistent with those predicted by independent estimates based on nebula condensation calculations and heat flow data.

  8. SEPARATION OF TRANSURANIC ELEMENTS FROM RARE EARTH COMPOUNDS

    DOEpatents

    Kohman, T.P.

    1961-11-21

    A process of separating neptunium and plutonium values from rare earths and alkaline earth fission products present on a solid mixed actinide carrier (Th or U(IV) oxalate or fluoride) --fission product carrier (LaF/sub 3/, CeF/sub 3/, SrF/sub 2/, CaF/sub 2/, YF/sub 3/, La oxalate, cerous oxalate, Sr oxalate, Ca oxalate or Y oxalate) by extraction of the actinides at elevated temperature with a solution of ammonium fluoride and/or ammonium oxalate is described. Separation of the fission-product-containing carriers from the actinide solution formed and precipitation of the neptunium and plutonium from the solution with mineral acid are also accomplished. (AEC)

  9. 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

  10. Rare Earth elements as sediment tracers in Mangrove ecosystems

    NASA Astrophysics Data System (ADS)

    Ramanathan, A. L.; Swathi, S.

    2013-05-01

    Rare earth elements have been widely used as geochemical source fingerprints of rocks and sediments to study processes involving cosmo-chemistry, igneous petrology, tectonic setting and for investigations of water-rock interactions and weathering processes including transport of weathering products to the oceans.Many studies have addressed the use of REEs in investigating the environmental impact of human activity and demonstrated that the REE natural distribution in sediment from densely industrialised and populated regions can be altered by anthropogenic influences.The coastal wetlands like Mangroves are ultimate sinks for all the material derived from the terrestrial and marine environment.The high productivity and low ratio of sediment respiration to net primary production gives mangrove sediments the potential for long-term sequestration of these pollutants/metals before reaching the coastal ocean. Geochemical study of REE in these sedimentary systems is useful for determining the nature of the biogeochemical processes. In particular, REE show a great sensitivity to pH changes, redox conditions and adsorption/ desorption reactions. So, they may be used as markers of discharge provenance, weathering processes, changes in environmental conditions in the water and sediments of Mangrove/wetland systems. Our study aims to establish the abundance, distribution and enrichment of REEs to track the sediment sources and biogeochemical processes occurring in the mangrove environment.Core sediments were collected from the different environmental settings within the Pichavaram mangrove area.Higher REE concentration in Pichavaram sediments indicated greater input from sources like terrestrial weathering and anthropogenic activities which in turn are affected by saline mixing and dynamic physico-chemical processes occurring in the mangrove environment. REE enrichment order was attributed to the alkaline pH (7-8.5) and reducing conditions prevailing in the mangrove

  11. Modelling of Rare Earth Elements Complexation With Humic Acid

    NASA Astrophysics Data System (ADS)

    Pourret, O.; Davranche, M.; Gruau, G.; Dia, A.

    2006-12-01

    The binding of rare earth elements (REE) to humic acid (HA) was studied by combining Ultrafiltration and ICP- MS techniques. REE-HA complexation experiments were performed at various pH conditions (ranging from 2 to 10.5) using a standard batch equilibration method. Results show that the amount of REE bound to HA strongly increase with increasing pH. Moreover, a Middle REE (MREE) downward concavity is evidenced by REE distribution patterns at acidic pH. Modelling of the experimental data using Humic Ion Binding Model VI provided a set of log KMA values (i.e. the REE-HA complexation constants specific to Model VI) for the entire REE series. The log KMA pattern obtained displays a MREE downward concavity. Log KMA values range from 2.42 to 2.79. These binding constants are in good agreement with the few existing datasets quantifying the binding of REE with humic substances except a recently published study which evidence a lanthanide contraction effect (i.e. continuous increase of the constant from La to Lu). The MREE downward concavity displayed by REE-HA complexation pattern determined in this study compares well with results from REE-fulvic acid (FA) and REE-acetic acid complexation studies. This similarity in the REE complexation pattern shapes suggests that carboxylic groups are the main binding sites of REE in HA. This conclusion is further supported by a detailed review of published studies for natural, organic-rich, river- and ground-waters which show no evidence of a lanthanide contraction effect in REE pattern shape. Finally, application of Model VI using the new, experimentally determined log KMA values to World Average River Water confirms earlier suggestions that REE occur predominantly as organic complexes (> 60 %) in the pH range between 5-5.5 and 7-8.5 (i.e. in circumneutral pH waters). The only significant difference as compared to earlier model predictions made using estimated log KMA values is that the experimentally determined log KMA values

  12. Magnetic Nanofluid Rare Earth Element Extraction Process Report, Techno Economic Analysis, and Results for Geothermal Fluids

    SciTech Connect

    Pete McGrail

    2016-03-14

    This GDR submission is an interim technical report and raw data files from the first year of testing on functionalized nanoparticles for rare earth element extraction from geothermal fluids. The report contains Rare Earth Element uptake results (percent removal, mg Rare Earth Element/gram of sorbent, distribution coefficient) for the elements of Neodymium, Europium, Yttrium, Dysprosium, and Cesium. A detailed techno economic analysis is also presented in the report for a scaled up geothermal rare earth element extraction process. All rare earth element uptake testing was done on simulated geothermal brines with one rare earth element in each brine. The rare earth element uptake testing was conducted at room temperature.

  13. Determination of thorium and of rare earth elements in cerium earth minerals and ores

    USGS Publications Warehouse

    Carron, M.K.; Skinner, D.L.; Stevens, R.E.

    1955-01-01

    The conventional oxalate method for precipitating thorium and the rare earth elements in acid solution exhibits definite solubilities of these elements. The present work was undertaken to establish conditions overcoming these solubilities and to find optimum conditions for precipitating thorium and the rare earth elements as hydroxides and sebacates. The investigations resulted in a reliable procedure applicable to samples in which the cerium group elements predominate. The oxalate precipitations are made from homogeneous solution at pH 2 by adding a prepared solution of anhydrous oxalic acid in methanol instead of the more expensive crystalline methyl oxalate. Calcium is added as a carrier. Quantitative precipitation of thorium and the rare earth elements is ascertained by further small additions of calcium to the supernatant liquid, until the added calcium precipitates as oxalate within 2 minutes. Calcium is removed by precipitating the hydroxides of thorium and rare earths at room temperature by adding ammonium hydroxide to pH > 10. Thorium is separated as the sebacate at pH 2.5, and the rare earths are precipitated with ammonium sebacate at pH 9. Maximum errors for combined weights of thorium and rare earth oxides on synthetic mixtures are ??0.6 mg. Maximum error for separated thoria is ??0.5 mg.

  14. 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.

  15. 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.

  16. 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

  17. Rare Earth Elements in National Defense: Background, Oversight Issues, and Options for Congress

    DTIC Science & Technology

    2011-03-31

    light rare earths (lanthanum, cerium, praseodymium , neodymium, promethium, samarium) and heavy rare earths (europium, gadolinium, terbium, dysprosium...rare earth elements cerium, lanthanum, praseodymium , and neodymium. However, the Mountain Pass mine will not immediately be able to refine rare earth

  18. Multi-objective optimization of chromatographic rare earth element separation.

    PubMed

    Knutson, Hans-Kristian; Holmqvist, Anders; Nilsson, Bernt

    2015-10-16

    The importance of rare earth elements in modern technological industry grows, and as a result the interest for developing separation processes increases. This work is a part of developing chromatography as a rare earth element processing method. Process optimization is an important step in process development, and there are several competing objectives that need to be considered in a chromatographic separation process. Most studies are limited to evaluating the two competing objectives productivity and yield, and studies of scenarios with tri-objective optimizations are scarce. Tri-objective optimizations are much needed when evaluating the chromatographic separation of rare earth elements due to the importance of product pool concentration along with productivity and yield as process objectives. In this work, a multi-objective optimization strategy considering productivity, yield and pool concentration is proposed. This was carried out in the frame of a model based optimization study on a batch chromatography separation of the rare earth elements samarium, europium and gadolinium. The findings from the multi-objective optimization were used to provide with a general strategy for achieving desirable operation points, resulting in a productivity ranging between 0.61 and 0.75 kgEu/mcolumn(3), h(-1) and a pool concentration between 0.52 and 0.79 kgEu/m(3), while maintaining a purity above 99% and never falling below an 80% yield for the main target component europium.

  19. Heterogeneous accretion and the moderately volatile element budget of Earth.

    PubMed

    Schönbächler, M; Carlson, R W; Horan, M F; Mock, T D; Hauri, E H

    2010-05-14

    Several models exist to describe the growth and evolution of Earth; however, variables such as the type of precursor materials, extent of mixing, and material loss during accretion are poorly constrained. High-precision palladium-silver isotope data show that Earth's mantle is similar in 107Ag/109Ag to primitive, volatile-rich chondrites, suggesting that Earth accreted a considerable amount of material with high contents of moderately volatile elements. Contradictory evidence from terrestrial chromium and strontium isotope data are reconciled by heterogeneous accretion, which includes a transition from dominantly volatile-depleted to volatile-rich materials with possibly high water contents. The Moon-forming giant impact probably involved the collision with a Mars-like protoplanet that had an oxidized mantle, enriched in moderately volatile elements.

  20. Forms of rare earth elements' sorption by quartz and goethite in the presence of bacteria Rhodopseudomonas palustris

    NASA Astrophysics Data System (ADS)

    Perelomov, L. V.; Perelomova, I. V.; Yoshida, S.

    2009-12-01

    The adsorption of a mixture of 16 isotopes of 14 rare earth elements (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) present in the initial solution in equal concentrations by quartz and goethite in the presence of bacteria Rhodopseudomonas palustris was studied under different acidity conditions. The solution pH was apparently the leading factor in the interaction of rare earth ions with the surface of mineral and biological sorbents. These interactions were controlled by electrostatic forces in acid (pH 4) and neutral (pH 7) solutions; the precipitation of elements from the solution was the predominant mechanism under alkaline conditions (pH 9). Microorganisms affected the adsorption of lanthanides by quartz in the entire pH range under study, especially at pH 7. In the presence of bacteria, the adsorption of the elements studied by goethite increased in an acid solution, remained unchanged under neutral conditions, and slightly decreased under alkaline conditions. Microorganisms increased the concentration of nonexchangeable forms of the elements adsorbed on the surface of quartz and goethite, which could be due to the formation of low-soluble complexes of rare earth elements with organic substances produced by bacteria.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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).

  8. 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.

  9. Amphibole-melt trace element partitioning of fractionating calc-alkaline magmas in the lower crust: an experimental study

    NASA Astrophysics Data System (ADS)

    Nandedkar, Rohit H.; Hürlimann, Niklaus; Ulmer, Peter; Müntener, Othmar

    2016-09-01

    Amphibole is one of the most important hydrous minerals of the middle and lower continental crust and plays a key role in the formation of intermediate to silica-rich magmas. This study reports a consistent set of amphibole trace element partition coefficients derived from fractional crystallization experiments at 0.7 GPa in a piston cylinder apparatus. Starting materials were doped with trace elements on the 20-40 ppm level and measured using laser ablation (LA)-ICP-MS. Amphibole is stable from 1010 to 730 °C and systematically changes its composition from pargasite to magnesiohornblende to cummingtonite, while coexisting liquids vary from andesite to dacite and rhyolite. Amphibole-liquid partition coefficients increase systematically with decreasing temperature and increasing SiO2 in the liquid. Potassium displays an inverse behavior and partitioning decreases with decreasing temperature. Rare earth element (REE) partition coefficients, assumed to occupy the M4 site within the amphibole structure, increase continuously up to one order of magnitude. The calculated lattice parameters, ideal cation radius ( r 0) and Young's modulus ( E) remain nearly constant with decreasing temperature. The high-field strength elements Zr and Hf that occupy the M2 site of the amphibole structure reveal a fivefold increase in partition coefficients with decreasing temperature and constant lattice parameters r 0 and E. Partition coefficients correlate with edenite, tschermaks and cummingtonite exchange vectors indicating that the maximum partition coefficient ( D 0) for an ideal cation radius increases with decreasing edenite component, while the latter decreases linearly with temperature. Regressing Amph/L D Ca against trace elements results in fair to excellent correlations ( r 2 0.55-0.99) providing a predictive tool to implement the trace element partition coefficients in numerical geochemical modeling. Our data result in positive correlations between Amph/L D Nb/Ta and Amph/L D

  10. REDISTRIBUTION OF ALKALINE ELEMENTS IN ASSOCIATION WITH AQUEOUS ACTIVITY IN THE EARLY SOLAR SYSTEM

    SciTech Connect

    Hidaka, Hiroshi; Higuchi, Takuya; Yoneda, Shigekazu E-mail: s-yoneda@kahaku.go.jp

    2015-12-10

    It is known that the Sayama meteorite (CM2) shows an extensive signature for aqueous alteration on the meteorite parent body, and that most of the primary minerals in the chondrules are replaced with phyllosilicates as the result of the aqueous alteration. In this paper, it is confirmed from the observation of two-dimensional Raman spectra that a part of olivine in a chondrule collected from the Sayama chondrite is serperntinized. Ion microprobe analysis of the chondrule showed that alkaline elements such as Rb and Cs are heterogeneously redistributed in the chondrule. The result of higher Rb and Cs contents in serpentinized phases in the chondrule rather than in other parts suggested the selective adsorption of alkaline elements into the serpentine in association with early aqueous activity on the meteorite parent body. Furthermore Ba isotopic analysis provided variations of {sup 135}Ba/{sup 138}Ba and {sup 137}Ba/{sup 138}Ba in the chondrule. This result was consistent with our previous isotopic data suggesting isotopic evidence for the existence of the presently extinct nuclide {sup 135}Cs in the Sayama meteorite, but the abundance of {sup 135}Cs in the solar system remains unclear because of large analytical uncertainties.

  11. 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.

  12. Coal fly ash as a resource for rare earth elements.

    PubMed

    Franus, Wojciech; Wiatros-Motyka, Małgorzata M; Wdowin, Magdalena

    2015-06-01

    Rare earth elements (REE) have been recognised as critical raw materials, crucial for many clean technologies. As the gap between their global demand and supply increases, the search for their alternative resources becomes more and more important, especially for the countries which depend highly on their import. Coal fly ash (CFA), which when not utilised is considered waste, has been regarded as the possible source of many elements, including REE. Due to the increase in the energy demand, CFA production is expected to grow, making research into the use of this material a necessity. As Poland is the second biggest coal consumer in the European Union, the authors have studied different coal fly ashes from ten Polish power plants for their rare earth element content. All the fly ashes have a broadly similar distribution of rear earth elements, with light REE being dominant. Most of the samples have REE content relatively high and according to Seredin and Dai (Int J Coal Geol 94: 67-93, 2012) classification can be considered promising REE raw materials.

  13. Uncovering the end uses of the rare earth elements.

    PubMed

    Du, Xiaoyue; Graedel, T E

    2013-09-01

    The rare earth elements (REE) are a group of fifteen elements with unique properties that make them indispensable for a wide variety of emerging and conventional established technologies. However, quantitative knowledge of REE remains sparse, despite the current heightened interest in future availability of the resources. Mining is heavily concentrated in China, whose monopoly position and potential restriction of exports render primary supply vulnerable to short term disruption. We have drawn upon the published literature and unpublished materials in different languages to derive the first quantitative annual domestic production by end use of individual rare earth elements from 1995 to 2007. The information is illustrated in Sankey diagrams for the years 1995 and 2007. Other years are available in the supporting information. Comparing 1995 and 2007, the production of the rare earth elements in China, Japan, and the US changed dramatically in quantities and structure. The information can provide a solid foundation for industries, academic institutions and governments to make decisions and develop strategies.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. 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.

  20. Contamination in the Rare-Earth Element Orthophosphate Reference Samples

    PubMed Central

    Donovan, John J.; Hanchar, John M.; Picolli, Phillip M.; Schrier, Marc D.; Boatner, Lynn A.; Jarosewich, Eugene

    2002-01-01

    Several of the fourteen rare-earth element (plus Sc and Y) orthophosphate standards grown at Oak Ridge National Laboratory in the 1980s and widely distributed by the Smithsonian Institution’s Department of Mineral Sciences, are significantly contaminated by Pb. The origin of this impurity is the Pb2P2O7 flux that is derived from the thermal decomposition of PbHPO4. The lead pyrophosphate flux is used to dissolve the oxide starting materials at elevated temperatures (≈1360 °C) prior to the crystal synthesis. Because these rare-earth element standards are extremely stable under the electron beam and considered homogenous, they have been of enormous value to electron probe micro-analysis (EPMA). The monoclinic, monazite structure, orthophosphates show a higher degree of Pb incorporation than the tetragonal xenotime structure, orthophosphates. This paper will attempt to describe and rationalize the extent of the Pb contamination in these otherwise excellent materials. PMID:27446762

  1. 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

  2. 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.

  3. Compositional and phase relations among rare earth element minerals

    NASA Technical Reports Server (NTRS)

    Burt, D. M.

    1990-01-01

    This paper discusses the compositional and phase relationships among minerals in which rare earth elements (REE) occur as essential constituents (e.g., bastnaesite, monazite, xenotime, aeschynite, allanite). Particular consideration is given to the vector representation of complex coupled substitutions in selected REE-bearing minerals and to the REE partitioning between minerals as related to the acid-base tendencies and mineral stabilities. It is shown that the treatment of coupled substitutions as vector quantities facilitates graphical representation of mineral composition spaces.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. 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

  10. [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.

  11. Uncovering the global life cycles of the rare earth elements.

    PubMed

    Du, Xiaoyue; Graedel, T E

    2011-01-01

    The rare earth elements (REE) are a group of fifteen elements with unique properties that make them indispensable for a wide variety of emerging, critical technologies. Knowledge of the life cycles of REE remains sparse, despite the current heightened interest in their future availability. Mining is heavily concentrated in China, whose monopoly position and potential restriction of exports render primary supplies vulnerable to short and long-term disruption. To provide an improved perspective we derived the first quantitative life cycles (for the year 2007) for ten REE: lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), and yttrium (Y). Of these REE, Ce and Nd in-use stocks are highest; the in-use stocks of most REE show significant accumulation in modern society. Industrial scrap recycling occurs only from magnet manufacture. We believe there is no post-customer recycling of any of these elements.

  12. Uncovering the Global Life Cycles of the Rare Earth Elements

    NASA Astrophysics Data System (ADS)

    Du, Xiaoyue; Graedel, T. E.

    2011-11-01

    The rare earth elements (REE) are a group of fifteen elements with unique properties that make them indispensable for a wide variety of emerging, critical technologies. Knowledge of the life cycles of REE remains sparse, despite the current heightened interest in their future availability. Mining is heavily concentrated in China, whose monopoly position and potential restriction of exports render primary supplies vulnerable to short and long-term disruption. To provide an improved perspective we derived the first quantitative life cycles (for the year 2007) for ten REE: lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), and yttrium (Y). Of these REE, Ce and Nd in-use stocks are highest; the in-use stocks of most REE show significant accumulation in modern society. Industrial scrap recycling occurs only from magnet manufacture. We believe there is no post-customer recycling of any of these elements.

  13. The Earth Based Ground Stations Element of the Lunar Program

    NASA Technical Reports Server (NTRS)

    Gal-Edd, Jonathan; Fatig, Curtis; Schier, James; Lee, Charles

    2007-01-01

    The Lunar Architecture Team (LAT) is responsible for developing a concept for building and supporting a lunar outpost with several exploration capabilities such as rovers, colonization, and observatories. The lunar outpost is planned to be located at the Moon's South Pole. The LAT Communications and Navigation Team (C&N) is responsible for defining the network infrastructure to support the lunar outpost. The following elements are needed to support lunar outpost activities: A Lunar surface network based on industry standard wireless 802.xx protocols, relay satellites positioned 180 degrees apart to provide South Pole coverage for the half of the lunar 28-day orbit that is obscured from Earth view, earth-based ground stations deployed at geographical locations 120 degrees apart. This paper will focus on the Earth ground stations of the lunar architecture. Two types of ground station networks are discussed. One provides Direct to Earth (DTE) support to lunar users using Kaband 23/26Giga-Hertz (GHz) communication frequencies. The second supports the Lunar Relay Satellite (LRS) that will be using Ka-band 40/37GHz (Q-band). This paper will discuss strategies to provide a robust operational network in support of various lunar missions and trades of building new antennas at non-NASA facilities, to improve coverage and provide site diversification for handling rain attenuation.

  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. 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.

  16. 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.

  17. Germanium and Rare Earth Element accumulation in woody bioenergy crops

    NASA Astrophysics Data System (ADS)

    Hentschel, Werner

    2016-04-01

    Germanium and REEs are strategic elements that are used for high tech devices and engineered systems, however these elements are hardly concentrated into mineable ore deposits. Since these elements occur widely dispersed in the earth crust with concentrations of several mgṡkg-1 (Ge 1.6 mgṡkg-1, Nd 25 mgṡkg-1) a new possibility to gain these elements could be phytomining, a technique that uses plants to extract elements from soils via their roots. Since knowledge about accumulating plant species is quite limited we conducted research on the concentrations of strategic elements in wood and leaves of fast growing tree species (Salix spec., Populus spec., Betula pendula, Alnus glutinosa, Fraxinus excelsior, Acer pseudoplatanus). In total 35 study sites were selected in the mining affected area around Freiberg (Saxony, Germany), differing in their species composition and degree of contamination with toxic trace metals (Pb, As, Cd). On each site plant tissues (wood and leaves, respectively) of different species were sampled. In addition soil samples were taken from a soil depth of 0 - 30 cm and 30 - 60 cm. The aim of our work was to investigate correlations between the concentrations of the target elements in plant tissues and soil characteristics like pH, texture, nutrients and concentrations in six operationally defined soil fractions (mobile, acid soluble, oxidizable, amorphic oxides, crystalline oxides, residual or siliceous). Concentrations of elements in soil extracts and plant tissues were measured with ICP-MS. The element Nd was selected as representative for the group of REEs, since this element showed a high correlation with the concentrations of the other REE We found that the concentration of Nd in the leaves (0.31 mgṡkg-1Nd) were several times higher than in herbaceous species (0.05 mgṡkg-1 Nd). The concentration of Ge in leaves were ten times lower than that of Nd whereas in herbaceous species Nd and Ge were in equal magnitude. Within the tree

  18. 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.

  19. Rare earth element patterns in biotite, muscovite and tourmaline minerals

    SciTech Connect

    Laul, J.C.; Lepel, E.A.

    1986-04-21

    Rare earth element concentrations in the minerals biotite and muscovite from the mica schist country rocks of the Etta pegmatite and tourmalines from the Bob Ingersoll pegmatite have been measured by INAA and CNAA. The concentrations range from 10/sup -4/ g/g to 10/sup -10g//sub g/. The REE patterns of biotite, muscovite and tourmaline reported herein are highly fractionated from light to heavy REE. The REE concentrations in biotite and muscovite are high and indigenous. The pegmatite tourmalines contain low concentrations of REE. Variations in tourmaline REE patterns reflect the geochemical evolution of pegmatite melt/fluid system during crystallization.

  20. Compositional and phase relations among rare earth element minerals

    NASA Technical Reports Server (NTRS)

    Burt, D. M.

    1989-01-01

    A review is presented that mainly treats minerals in which the rare-earth elements are essential constituents, e.g., bastnaesite, monazite, xenotime, aeschynite, allanite. The chemical mechanisms and limits of REE substitution in some rock-forming minerals (zircon, apatite, titanite, garnet) are also derived. Vector representation of complex coupled substitutions in selected REE-bearing minerals is examined and some comments on REE-partitioning between minerals as related to acid-based tendencies and mineral stabilities are presented. As the same or analogous coupled substitutions involving the REE occur in a wide variety of mineral structures, they are discussed together.

  1. Standard reference water samples for rare earth element determinations

    USGS Publications Warehouse

    Verplanck, P.L.; Antweiler, R.C.; Nordstrom, D.K.; Taylor, H.E.

    2001-01-01

    Standard reference water samples (SRWS) were collected from two mine sites, one near Ophir, CO, USA and the other near Redding, CA, USA. The samples were filtered, preserved, and analyzed for rare earth element (REE) concentrations (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) by inductively coupled plasma-mass spectrometry (ICP-MS). These two samples were acid mine waters with elevated concentrations of REEs (0.45-161 ??g/1). Seventeen international laboratories participated in a 'round-robin' chemical analysis program, which made it possible to evaluate the data by robust statistical procedures that are insensitive to outliers. The resulting most probable values are reported. Ten to 15 of the participants also reported values for Ba, Y, and Sc. Field parameters, major ion, and other trace element concentrations, not subject to statistical evaluation, are provided.

  2. 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

  3. 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.

  4. 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.

  5. Mimicking the magnetic properties of rare earth elements using superatoms.

    PubMed

    Cheng, Shi-Bo; Berkdemir, Cuneyt; Castleman, A W

    2015-04-21

    Rare earth elements (REs) consist of a very important group in the periodic table that is vital to many modern technologies. The mining process, however, is extremely damaging to the environment, making them low yield and very expensive. Therefore, mimicking the properties of REs in a superatom framework is especially valuable but at the same time, technically challenging and requiring advanced concepts about manipulating properties of atom/molecular complexes. Herein, by using photoelectron imaging spectroscopy, we provide original idea and direct experimental evidence that chosen boron-doped clusters could mimic the magnetic characteristics of REs. Specifically, the neutral LaB and NdB clusters are found to have similar unpaired electrons and magnetic moments as their isovalent REs (namely Nd and Eu, respectively), opening up the great possibility in accomplishing rare earth mimicry. Extension of the superatom concept into the rare earth group not only further shows the power and advance of this concept but also, will stimulate more efforts to explore new superatomic clusters to mimic the chemistry of these heavy atoms, which will be of great importance in designing novel building blocks in the application of cluster-assembled nanomaterials. Additionally, based on these experimental findings, a novel "magic boron" counting rule is proposed to estimate the numbers of unpaired electrons in diatomic LnB clusters.

  6. Accumulation of rare earth elements by siderophore-forming Arthrobacter luteolus isolated from rare earth environment of Chavara, India.

    PubMed

    Emmanuel, E S Challaraj; Ananthi, T; Anandkumar, B; Maruthamuthu, S

    2012-03-01

    In this study, Arthrobacter luteolus, isolated from rare earth environment of Chavara (Quilon district, Kerala, India), were found to produce catechol-type siderophores. The bacterial strain accumulated rare earth elements such as samarium and scandium. The siderophores may play a role in the accumulation of rare earth elements. Catecholate siderophore and low-molecular-weight organic acids were found to be present in experiments with Arthrobacter luteolus. The influence of siderophore on the accumulation of rare earth elements by bacteria has been extensively discussed.

  7. Bacterial Cell Surface Adsorption of Rare Earth Elements

    NASA Astrophysics Data System (ADS)

    Jiao, Y.; Park, D.; Reed, D.; Fujita, Y.; Yung, M.; Anderko, A.; Eslamimanesh, A.

    2015-12-01

    Rare earth elements (REE) play a critical role in many emerging clean energy technologies, including high-power magnets, wind turbines, solar panels, hybrid/electric vehicle batteries and lamp phosphors. In order to sustain demand for such technologies given current domestic REE shortages, there is a need to develop new approaches for ore processing/refining and recycling of REE-containing materials. To this end, we have developed a microbially-mediated bioadsorption strategy with application towards enrichment of REE from complex mixtures. Specifically, the bacterium Caulobacter crescentus was genetically engineered to display lanthanide binding tags (LBTs), short peptides that possess high affinity and specificity for rare earth elements, on its cell surface S-layer protein. Under optimal conditions, LBT-displayed cells adsorbed greater than 5-fold more REE than control cells lacking LBTs. Competition binding experiments with a selection of REEs demonstrated that our engineered cells could facilitate separation of light- from heavy- REE. Importantly, binding of REE onto our engineered strains was much more favorable compared to non-REE metals. Finally, REE bound to the cell surface could be stripped off using citrate, providing an effective and non-toxic REE recovery method. Together, this data highlights the potential of our approach for selective REE enrichment from REE containing mixtures.

  8. Emissions of alkaline elements calcium, magnesium, potassium, and sodium from open sources in the contiguous United States

    SciTech Connect

    Gillette, D.A. ); Stensland, G.J.; Williams, A.L.; Barnard, W.; Gatz, D. ); Sinclair, P.C. ); Johnson, T.C. )

    1992-12-01

    Models of dust emissions by wind erosion (including winds associated with regional activity as well as dust devils) and vehicular disturbances of unpaved roads were developed, calibrated, and used to estimate alkaline dust emissions from elemental soil and road composition data. Emissions from tillage of soils were estimated form the work of previous researchers. The area of maximum dust production by all of those sources is the area of the old Dust Bowl' of the 1930s (the panhandles of Texas and Oklahoma, eastern New Mexico and Colorado, and western Kansas). The areas of maximum alkaline dust production are the arid southwest, the Dust Bowl,' and the midwestern-mideastern states from Iowa to Pennsylvania. Our calculations show that calcium is the dominant alkaline element produced by open sources' (sources too great in extent to be controlled by enclosure or ducting). Although the largest dust mass source is wind erosion (by winds associated with regional activity and convective activity), the largest producer of the alkaline component is road dust because the abundance of alkaline materials in road coverings (which include crushed limestone) is significantly higher than for soils. Comparing the above estimated sources of alkaline material with inventories of SO[sub 2] and NO[sub x] emissions by previous investigators gives the rough approximation that alkaline emission rates are of the order of the SO[sub 2] + NO[sub x] emissions in the western United States and that they are much smaller than SO[sub 2] + NO[sub x] in the eastern United States. This approximation is substantiated by data on Ca/(SO[sub 4] + NO[sub 3]) for wet deposition for National Atmospheric Deposition Program sites. 53 refs., 9 figs., 2 tabs.

  9. Field experiment determinations of distribution coefficients of actinide elements in alkaline lake environments

    SciTech Connect

    Simpson, H.J.; Trier, R.M.; Li, Y.-H.; Anderson, R.F.; Herczeg, A.L.

    1984-08-01

    Measurements of the radioisotope concentrations of a number of elements (Am, Pu, U, Pa, Th, Ac, Ra, Po, Pb, Cs, and Sr) in the water and sediments of a group of alkaline (pH = 9-10), saline lakes demonstrate greatly enhanced soluble-phase concentrations of elements with oxidation states of (III)-(VI) as the result of complexing by carbonate ion. Ratios of soluble radionuclide concentrations in Mono Lake to those in seawater ((CO/sub 3//sup 2 -/) in Mono Lake = 200 times that of seawater) were: Pu(approx. =10), /sup 238/U(approx. =150), /sup 231/Pa, /sup 228/Th, /sup 230/Th(approx. =10/sup 3/), and /sup 232/Th(approx. =10/sup 5/). Effective distribution coefficients of these radionuclides in high CO/sub 3//sup 2 -/ environments are several orders of magnitude lower (i.e., less particle reactive) than in most other natural waters. The importance of CO/sub 3//sup 2 -/ ion on effective K/sub d/ values was also strongly suggested by laboratory experiments in which most of the dissolved actinide elements became adsorbed to particles after a water sample normally at a pH of 10 was acidified, stripped of all CO/sub 2/, and then returned to pH 10 by adding NH/sub 4/OH. Furthermore, the effect of complexation by organic ligands is of secondary importance in the presence of appreciable carbonate ion concentration. Neither pure phase solubility calculations nor laboratory scale K/sub d/ determinations accurately predicted the measured natural system concentrations. Therefore, measurements of the distribution of radionuclides in natural systems are essential for assessment of the likely fate of potential releases from high level waste repositories to groundwater. 50 references, 31 figures, 43 tables.

  10. Mobility of elements during K-metasomatism of volcanic rocks by alkaline, saline brines

    SciTech Connect

    Chapin, C.E. )

    1992-01-01

    Silicic ignimbrites and interbedded mafic lavas of Oligocene age were altered by alkaline, saline brines in the Popotosa basin of the Rio Grande rift near Socorro, New Mexico. Alteration was toward a fine-grained assemblage of adularia + hematite [+-] quartz irrespective of initial rock composition. Elevated [delta][sup 18]O and the occurrence of zeolites, gypsum, and salt casts in overlying play a deposits indicates that the altering fluids were basin brines. Preliminary analysis of secondary inclusions in fractured quartz phenocrysts indicates temperatures near 100 C and salinities near 20 wt. % NaCl equivalent. To test element mobility, pairs of fresh and altered samples from each of 7 ignimbrite units plus 4 samples of interbedded mafic lavas were analyzed by XRF, INAA, and AA. The elements showing the greatest mobility during alteration of ignimbrites are listed below along with their enrichment factors (altered rock/fresh rock). Ignimbrites: enriched--K[sub 2]O 1.99, Rb 1.89, Ba 1.43, As 12.14, Sb 18.30, Pb 1.23; depleted--Na[sub 2]O 0.25, MgO 0.57, CaO 0.27, MnO 0.50, P[sub 2]O[sub 5] 0.75, Sr 0.54, Li 0.57, U 0.78, Br 0.67, Cu 0.90, Zn 0.69. The dramatic enrichment of As and Sb in both ignimbrites and mafic lavas indicates that these elements are highly mobile in oxidizing basin brine systems. K-metasomatism is a common type of alteration in rift basins, detachment terranes, aquifers through which brines have migrated.

  11. Diagenetic uptake of rare earth elements by conodont apatite

    NASA Astrophysics Data System (ADS)

    Zhang, L.; Algeo, T. J.; Cao, L.; Zhao, L.; Chen, Z. Q.; Li, Z.

    2015-12-01

    The rare earth element (REE) composition of bioapatite has long been used as a proxy for ancient seawater chemistry and paleomarine environmental reconstruction, based on the assumption of preservation of a hydrogenous (seawater-derived) REE signal. Recent work, however, has begun to question the provenance of REEs in conodonts, emphasizing the importance of REEs released by the lithogenous fraction of the sediment and subsequently adsorbed onto conodont apatite in the burial environment. Here, we investigate patterns of REE and trace-element abundance in conodonts and their host sediments from the Early to Late Ordovician Huanghuachang and Chenjiahe sections of Hubei Province, South China. Several lines of evidence indicate that REEs in the conodont samples were acquired mainly from clay minerals in the host sediment during burial diagenesis: (1) REEs in conodonts show a strong positive correlation to Th and other lithogenic elements; (2) conodonts and whole-rock samples show general patterns of REE and trace-element enrichment that are highly similar to each other and bear no resemblance to seawater elemental concentrations; (3) similar patterns are observed in Triassic conodonts and whole-rock samples; and (4) Y/Ho ratios in conodonts are mostly <40 (mean ~33), values that are consistent with derivation of >90% of REEs from lithogenous sources. Conodonts show pronounced middle rare earth element (MREE) enrichment, a pattern that is unambiguously of diagenetic origin owing to its association with lower Y/Ho ratios. With increasing MREE enrichment of conodont samples, U concentrations and LaN/YbN ratios shift from high to low, and Mn concentrations from low to high. These patterns suggest that conodont diagenesis was initiated at shallow burial depths under suboxic conditions (i.e., in the zone of Mn(IV) and Fe(III) reduction) but continued at greater burial depths, with most acquisition of secondary REEs at later diagenetic stages. Our findings indicate that (1

  12. The History and Use of Our Earth's Chemical Elements: A Reference Guide (by Robert E. Krebs)

    NASA Astrophysics Data System (ADS)

    Bracken, Reviewed By Jeffrey D.

    1999-04-01

    Greenwood Press: Westport, CT, 1998. 282 pp + 25 pp glossary + 37 pp index. 15.9 x 24.1 cm. ISBN 0-313-30123-9. $39.95. This book is an excellent resource for chemical educators at the high school and college levels. The format of the text is consistent and the writing style is clear and concise, making it ideally suited for student use also. The first three chapters serve to introduce the reader to a brief history of chemistry, early models of the atom, and the development of the periodic table. Names of the contributing scientists are mentioned whenever necessary, but the overall purpose of these introductory chapters is simply to lay a foundation for the subsequent seven chapters. A complete glossary of important scientific terms mentioned in the text should allow beginning students to use this book without feeling overwhelmed. Each entry for the 112 elements contains the following information: elemental symbol, atomic number, period, common valence, atomic weight, natural state, common isotopes, properties, characteristics, abundance, natural sources, history, common uses and compounds, and safety hazards. This information is well organized, with clear headings and separate sections making the book extremely user-friendly. Readers can easily obtain the information they desire without having to skim the full entry for a chosen element. One very nice feature of this book is that the elements entries are arranged by their locations in the periodic table. For example, chapter 4 contains the alkali metals and alkaline earth metals. This organizational scheme allows one to quickly see the patterns and trends within groups of elements. This format is significantly better than arranging the elements in alphabetical order, which places the entry for sodium far removed from the entries for lithium and potassium. I would highly recommend this book to high school teachers and college chemistry professors. It is well written and is an excellent source of information for

  13. Speciation of adsorbed yttrium and rare earth elements on oxide surfaces

    NASA Astrophysics Data System (ADS)

    Piasecki, Wojciech; Sverjensky, Dimitri A.

    2008-08-01

    The distribution of yttrium and the rare earth elements (YREE) between natural waters and oxide mineral surfaces depends on adsorption reactions, which in turn depend on the specific way in which YREE are coordinated to mineral surfaces. Recent X-ray studies have established that Y 3+ is adsorbed to the rutile (1 1 0) surface as a distinctive tetranuclear species. However, the hydrolysis state of the adsorbed cation is not known from experiment. Previous surface complexation models of YREE adsorption have suggested two to four cation hydrolysis states coexisting on oxide surfaces. In the present study, we investigate the applicability of the X-ray results to rare earth elements and to several oxides in addition to rutile using the extended triple-layer surface complexation model. The reaction producing a hydrolyzed tetranuclear surface species 4>SOH+M+2HO=(>SOH)2_M(OH)2++4H was found to account for a significant fraction of the adsorbed Y 3+, La 3+, Nd 3+, Gd 3+, and Yb 3+ on rutile, hematite, alumina and silica over wide ranges of pH and ionic strength. Where adsorption data were available as a function of surface coverage for hematite and silica, an additional reaction involving a mononuclear species could be used to account for the higher surface coverages. However, it is also possible that some of the higher surface coverage data refer to surface precipitation rather than adsorption. The results of the present study provide an internally consistent basis for describing YREE adsorption which could be used to investigate more complex systems in which YREE compete both in aqueous solution and on mineral surfaces with alkaline earths and ligands such as carbonate, sulfate, chloride and organic species, in order to build a predictive adsorption model applicable to natural waters.

  14. Behavior of Rare Earth Elements in Fractured Aquifers

    NASA Astrophysics Data System (ADS)

    Lee, S.; Kim, Y.; Lee, K.

    2003-12-01

    An understanding of the geochemistry of potential host rocks is very important in the site evaluation for construction of an underground geologic repository for radioactive waste. Because of similar valence and ionic radii and high similarity in electronic structure with trivalent actinides (such as Am3+ and Cm3+), the rare earth elements (REEs) have been used to predict the behavior of actinide-series elements in solution. For Am and Cm, which occur only in the trivalent states in most waste-disposal repository environments, the analogy with the REEs is particularly relevant. Krauskopf calculated the retardation factors for radionuclides in various rock materials based on some compiled data. But, in general, because the transuranic actinides do not occur naturally in appreciable quantities, their behaviors in repository environments cannot be predicted from evidence of their movement in geologic environments (mainly in groundwater) over geologic timespans. Predictions about long-term future behavior of transuranic actinides have therefore been made by extrapolation from short-term observations of their chemical properties in laboratory experiments or in field tests, but such extrapolation is fraught with uncertainty. In order to verify the behavior of Eu in various geological environments, we estimated the abundance of rare earth elements in three gneiss bodies originated from different geological environments and volcanic tuff. We also carried out some leaching experiment of fracture-filling calcite precipitated due to changes of geochemical environment in paleo-groundwater. Of the three gneisses, two gneisses are granitic-granodioritic origin and the other is tonaltic-trondjemitic origin. As a result, we could observe that Eu had a close relationship with fracture-filling calcite precipitation due to water-rock interaction. Our results show that Eu is the most variable element of REEs for the hydrogeological environment such as change of oxidation-reduction and

  15. The chemistry of rare earth elements in the solar nebula

    NASA Technical Reports Server (NTRS)

    Larimer, J. W.; Bartholomay, H. A.; Fegley, B.

    1984-01-01

    The high concentration of rare earth elements (REE) in primitive CaS suggests that the REE along with the other normally lithophile elements form stable sulfides under the unusual conditions which existed during the formation of enstatite chrondites. In order to acquire a more quantitative framework in which to interpret these data, the behavior of the REE in systems with solar, or slightly fractionated solar, composition is being studied. These new data introduce modest changes in the behavior of some of the REE when compared to previous studies. For example, the largest differences are in the stabilities of the gaseous monoxides of Ce, Eu, Tb, Ho, and Tm, all of which now appear to be less stable than previously thought, and YbO(g) which is somewhat more stable. Much more significant are the changes in REE distribution in the gas phase in fractionated systems, especially those made more reducing by changing the C/O ratio from the solar value of 0.6 to about 1.0. In almost all cases, the exceptions being Eu, Tm and Yb whose elemental gaseous species dominate, the monosulfides become more abundant. Moreover, the solid oxides of Eu, Tm and Yb become less stable under more reducing conditions which, in effect, should reduce the condensation temperature of all REE in more reduced systems.

  16. Revisiting the rare earth elements in foraminiferal tests [rapid communication

    NASA Astrophysics Data System (ADS)

    Haley, Brian A.; Klinkhammer, Gary P.; Mix, Alan C.

    2005-10-01

    Are the rare earth elements (REEs) in foraminifera a valuable proxy for use in paleoceanographic and climate change studies? In order to investigate this, we attempted a comprehensive study of REEs in planktonic and benthic foraminifera. Several different cleaning protocols were tested. Although the hydroxylamine used to clean all foraminifera in this study removes an unidentified source of REE contamination, it seems to remobilize metal oxides that are otherwise unaffected in flow-through dissolution. The calculated REE distribution coefficients, KD(REE)s, are between 100 and 500 for both planktonic and benthic foraminifera. These KDs are high compared to other elements in biogenic calcite but can be explained through a general model of element incorporation during foraminiferal calcification. From data taken from eight core tops in the southeast Pacific, we conclude that the REEs in planktonic foraminifera are, indeed, useful as a proxy for upper ocean water mass and mixed layer biogenic productivity. Alternatively, the REEs in benthic foraminifera are useful as a proxy for carbon flux to the sea floor. These proxies should be robust down core unless the sediments have undergone anoxic diagenesis, which stabilizes Fe carbonate thus overprinting the primary REE signature. However, it is clear from REE distributions in foraminiferal tests if anoxic conditions have occurred.

  17. Lunar anorthosites: rare-Earth and other elemental abundances.

    PubMed

    Wakita, H; Schmitt, R A

    1970-11-27

    Elemental abundances of major (Ti, Al, Fe, and Ca), minor (Na, Mn, and Cr), and trace elements [14 rare-earth elements (REE), Y, In, Cd, Rb, Cs, Ba, Co, and Sc] in lunar anorthosites separated from Apollo 11 sample 10085 coarse fines have been determined by means of instrumental and radiochemical neutron activation analysis. The REE distribution pattern of lunar anorthosites, relative to ordinary chondrites, has a positive Eu anomaly. On the assumption that (i) the lunar composition is similar to that of ordinary chondritic meteorites low in total Fe ( approximately 13 percent); (ii) lunar anorthosites are derived from highland cratering events and are representative of the highlands; and (iii) the moon differentiated into olivine, hypersthene, and basaltic and anorthositic phases, and plagioclase crysstallization began after approximately 93 percent solidification, then mass balance calculations yield approximately 30-kilometer and approximately 10-kilometer thicknesses for the lunar highlands for the melting and chemical differentiation of the entire moon and of the upper 200 kilometers, respectively. Corresponding thicknesses of the basaltic basement rocks were approximately 5 kilometers and approximately 2 kilometers, respectively. Alternatively, if the anorthosites of this study are representative of the highlands and the onset of plagioclase crystallization occurred after approximately 50 percent solidification of the initially melted moon, calculations with REE and Ba partition coefficients suggest that the REE and Ba abundances in the primeval moon were similar to those observed in basaltic achondrites.

  18. 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.

  19. 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.

  20. The elements of the Earth's magnetism and their secular changes between 1550 and 1915

    NASA Technical Reports Server (NTRS)

    Fritsche, H.

    1983-01-01

    The results of an investigation about the magnetic agents outside the Earth's surface as well as the Earth's magnetic elements for the epochs 1550, 1900, 1915 are presented. The secular changes of the Earth's magnetic elements during the time interval 1550 - 1900 are also included.

  1. Enhanced phytoextraction of germanium and rare earth elements - a rhizosphere-based approach

    NASA Astrophysics Data System (ADS)

    Wiche, Oliver

    2016-04-01

    Germanium (Ge) and rare earth elements (REEs) are economically valuable raw materials that have become an integral part of our modern high tech society. While most of these elements are not actually rare in terms of general amounts in the earth's crust, they are rarely found in sufficient abundances in single locations for their mining to be economically viable. The average concentration of Ge in soils is estimated at 1.6 μg g-1. The REEs comprise a group of 16 elements including La, the group of lanthanides and Y that are abundant in the earth crust with concentrations varying from 35 μg g-1 (La), 40 μg g-1 (Nd), 6 μg g-1 (Gd) and 3.5 μg g-1 (Er) to 0.5 μg g-1 in Tm. Thus, a promising chance to improve supply of these elements could be phytomining. Unfortunately, bioavailability of Ge and REEs in soils appears to be low, in particular in neutral or alkaline soils. A sequential dissolution analysis of 120 soil samples taken from the A-horizons of soils in the area of Freiberg (Saxony, Germany) revealed that only 0.2% of total Ge and about 0.5% of La, Nd, Gd and Er of bulk concentrations were easily accessible by leaching with NH4-acetate (pH 7). Most of the investigated elements were bound to Fe-/Mn-oxides and silicates and were therefore only poorly available for plant uptake. Here we report an environmentally friendly approach for enhanced phytoextraction of Ge and REEs from soils using mixed cultures of plant species with efficient mechanisms for the acquisition of nutrients in the rhizosphere. The rhizosphere is characterized as the zone in soil sourrounding a plant root that consists of a gradient in chemical, physical and biological soil properties driven by rhizodeposits like carboxylates and protons. Some species like white lupin (Lupinus albus) are able to excrete large amounts of organic acid anions(predominantly citrate and malate) and show a particularly high potential for the acidification of the rhizosphere. In our experiments, mixed cultures

  2. The Marine Geochemistry of the Rare Earth Elements

    DTIC Science & Technology

    1983-09-01

    C3): 2045-2056. BACON, M.P., P.G. BREWER, D.W. SPENCER, T.W. MURRAY & T. GODDARD (1980). Lead - 210 , polonium - 210 , manganese and iron in the Cariaco...191 La and Pr 197 Ce: its oxidation and reduction 197 Eu 207 4.5. Conclusions 210 CHAPTER 5. Behaviour of the Rare Earth Elements in anoxic waters of...0.142 140Ce(n, )14ICe 0.58 0.48 2.89 0.0053 41Pr(n,e.)142Pr 11.5 14.1 57.4 0.17 l46Nd(n,a-)l47Nd 1.4 3.2 6.98 0.0039 152Sni(n,a)153Sm 210 2530 1047

  3. Rare earth elements in parasol mushroom Macrolepiota procera.

    PubMed

    Falandysz, Jerzy; Sapkota, Atindra; Mędyk, Małgorzata; Feng, Xinbin

    2017-04-15

    This study aimed to investigate occurrence and distribution of 16 rare earth elements (REEs) in edible saprobic mushroom Macrolepiota procera, and to estimate possible intake and risk to human consumer. Mushrooms samples were collected from sixteen geographically diverse sites in the northern regions of Poland. The results showed that for Ce as the most abundant among the RREs in edible caps, the mean concentration was at 0.18±0.29mgkg(-1)dry biomass. The mean concentration for Σ16 REEs determined in caps of fungus was 0.50mgkg(-1)dry biomass and in whole fruiting bodies was 0.75mgkg(-1)dry biomass. From a point of view by consumer, the amounts of REEs contained in edible caps of M. procera could be considered small. Hence, eating a tasty caps of this fungus would not result in a health risk for consumer because of exposure to the REEs.

  4. Rare Earth elements in individual minerals in Shergottites

    NASA Technical Reports Server (NTRS)

    Wadhwa, Meenakshi; Crozaz, Ghislaine

    1993-01-01

    Shergottites (i.e., Shergotty, Zagami, EETA79001, ALHA77005, and LEW88516) are an important set of achondrites because they comprise the majority of the SNC group of meteorites (nine, in total, known to us), which are likely to be samples of the planet Mars. Study of these meteorites may therefore provide valuable information about petrogenetic processes on a large planetary body other than Earth. Rare earth element (REE) distributions between various mineral phases were found to be useful in geochemically modeling the petrogenesis of various rock types (terrestrial and meteoritic). However, with the exception of a few ion microprobe studies and analyses of mineral separates, there has previously not been any comprehensive effort to characterize and directly compare REE in individual minerals in each of the five known shergottites. Ion microprobe analyses were made on thin sections of each of the shergottites. Minerals analyzed were pyroxenes (pigeonite and augite), maskelynite, and whitlockite. The REE concentrations in each mineral type in each shergottite is given.

  5. Core-Mantle Partitioning of Volatile Elements and the Origin of Volatile Elements in Earth and Moon

    NASA Technical Reports Server (NTRS)

    Righter, K.; Pando, K.; Danielson, L.; Nickodem, K.

    2014-01-01

    Depletions of siderophile elements in mantles have placed constraints on the conditions on core segregation and differentiation in bodies such as Earth, Earth's Moon, Mars, and asteroid 4 Vesta. Among the siderophile elements there are a sub-set that are also volatile (volatile siderophile elements or VSE; Ga, Ge, In, As, Sb, Sn, Bi, Zn, Cu, Cd), and thus can help to constrain the origin of volatile elements in these bodies, and in particular the Earth and Moon. One of the fundamental observations of the geochemistry of the Moon is the overall depletion of volatile elements relative to the Earth, but a satisfactory explanation has remained elusive. Hypotheses for Earth include addition during accretion and core formation and mobilized into the metallic core, multiple stage origin, or addition after the core formed. Any explanation for volatile elements in the Earth's mantle must also be linked to an explanation of these elements in the lunar mantle. New metal-silicate partitioning data will be applied to the origin of volatile elements in both the Earth and Moon, and will evaluate theories for exogenous versus endogenous origin of volatile elements.

  6. Effects of rare earth elements on the distribution of mineral elements and heavy metals in horseradish.

    PubMed

    Wang, Lihong; Huang, Xiaohua; Zhou, Qing

    2008-09-01

    In order to investigate the effects of rare earth elements (REEs) on horseradish, the distribution of the mineral elements and heavy metals in different organs of horseradish have been studied by using inductively coupled plasma-atomic emission spectrometry (ICP-AES). Meanwhile, three variable major parameters, namely the concentration of REEs, the type of REEs, and the growth stage of plant were chosen. The results indicated that the test REEs, Ce(III) and Tb(III), could be accumulated in leaves, stems and roots of horseradish. In addition, we found that the content of mineral elements was increased in horseradish treated with 20mgl(-1) of Ce(III), but not those with the 20mgl(-1) of Tb(III). Moreover, the content of mineral elements in horseradish was decreased with the increasing concentration of REEs (100, 300mgl(-1)). Furthermore, we found that there were the opposite effects on the content of the heavy metals in horseradish treated with REEs. Finally, we found that the effect of REEs on the accumulation of REEs, and the content of mineral elements or heavy metals of horseradish during vigorous growth stage, no matter positive or negative, was more obvious than that of the other growth stages. These results demonstrated that the distribution behaviors of mineral elements and heavy metals in horseradish can be affected by the type and concentration of REEs, and the growth period of plant.

  7. Separation/Preconcentration Techniques for Rare Earth Elements Analysis

    NASA Astrophysics Data System (ADS)

    Hu, Bin; He, Man; Chen, Beibei; Jiang, Zucheng

    2016-10-01

    The main aim of this chapter exactly characterizes the contribution. The analytical chemistry of the rare earth elements (REEs) very often is highly complicated and the determination of a specific element is impossible without a sample pre-concentration. Sample preparation can be carried out either by separation of the REEs from the matrix or by concentrating the REEs. The separation of REEs from each other is mainly made by chromatography. At the beginning of REE analysis, the method of precipitation/coprecipitation was applied for the treatment of REE mixtures. The method is not applicable for the separation of trace amounts of REEs. The majority of the methods used are based on the distribution of REEs in a two-phase system, a liquid-liquid or a liquid-solid system. Various techniques have been developed for the liquid-liquid extraction (LLE), in particular the liquid phase micro-extraction. The extraction is always combined with a pre-concentration of the REEs in a single drop of extractant or in a hollow fiber filled with the extractant. Further modified techniques for special applications and for difficult REE separation have been developed. Compared to the LLE, the solid phase micro-extraction is preferred. The method is robust and easy to handle, in which the solid phase loaded with the REEs can be used directly for subsequent determination methods. At present, very new solid materials, like nanotubes, are developed and tested for solid phase extraction.

  8. Pb and rare earth element diffusion in xenotime

    NASA Astrophysics Data System (ADS)

    Cherniak, D. J.

    2006-05-01

    Diffusion of Pb and the rare earth elements Sm, Dy and Yb have been characterized in synthetic xenotime under dry conditions. The synthetic xenotime was grown via a Na 2CO 3-MoO 3 flux method. The sources of diffusant for the rare earth diffusion experiments were REE phosphate powders, with experiments run using sources containing a single REE. For Pb, the source consisted a mixture of YPO 4 and PbTiO 3. Experiments were performed by placing source and xenotime in Pt capsules, and annealing capsules in 1 atm furnaces for times ranging from 30 min to several weeks, at temperatures from 1000 to 1500 °C. The REE and Pb distributions in the xenotime were profiled by Rutherford Backscattering Spectrometry (RBS). The following Arrhenius relations are obtained for diffusion in xenotime, normal to (101): D=1.5×10exp⁡(-441±12 kJmol/R⁢T)ms.D=9.0×10exp⁡(-349±16 kJmol/R⁢T)ms.D=3.9×10exp⁡(-362±13 kJmol/R⁢T)ms. Diffusivities among the REE do not differ greatly in xenotime over the investigated temperature range, in contrast to findings for the REE in zircon [Cherniak, D.J., Hanchar, J.M., Watson, E.B., 1997. Rare earth diffusion in zircon. Chem. Geol. 134, 289-301.], where the LREE diffuse more slowly, and with higher activation energies for diffusion, than the heavier rare earths. In zircon, these differences among diffusion of the rare earths are attributed to the relatively large size of the REE with respect to Zr, for which they likely substitute in the zircon lattice. With the systematic increase in ionic radius from the heavy to lighter REE, this size mismatch becomes more pronounced and diffusivities of the LREE are as consequence slower. Although xenotime is isostructural with zircon, the REE are more closely matched in size to Y, so in xenotime this effect appears much smaller and the REE diffuse at similar rates. In addition, the process of diffusion in xenotime likely involves simple REE + 3 → Y + 3 exchange, without charge compensation as needed

  9. Rare earth element analysis indicates micropollutants in an urban estuary

    NASA Astrophysics Data System (ADS)

    Mohajerin, T. J.; Johannesson, K. H.; Kolker, A.; Burdige, D. J.; Chevis, D.

    2011-12-01

    Rare earth element analysis of Bayou Bienvenue waters shows anomalously high gadolinium, Gd, concentrations relative to its nearest neighbors in the REE series, europium and terbium. The anomalously high Gd concentrations indicate anthropogenic input from waste-water treatment plants in the area as anthropogenic Gd input can be traced back to its use as a contrast agent in magnetic resonance imaging in hospitals. Others have shown that anomalously high levels of Gd in natural waters are likely to be associated with other micropollutants that also occur in hospital effluent and that are not removed in the wastewater treatment process, including pharmaceuticals in the form of steroids, antihistamines, and antibiotics. Estuaries serve as many important ecological roles and have been shown to act as a filter for pollutants. To better understand the transport, biogeochemical cycling, and ultimate fate of trace elements in estuaries, I collected surface water samples from Bayou Bienvenue, a wetland triangle that covers an area of 427 acres directly adjacent to New Orleans, Louisiana. Water samples from Bayou Bienvenue were collected along the salinity gradient and subsequently filtered through progressively smaller pore-size filters. The resulting fractions were analyzed for trace element concentions, including the REEs, by magnetic sector ICP-MS. The attached figure shows the Gd anomaly present in the particulate (>0.45μm) fraction. Upper continental crust (UCC)-normalized plots of colloidal REEs (0.02μm - 0.45μm) fraction is lacking this anomaly indicating anthropogenic Gd is found chiefly in the particulate fraction in Bayou Bienvenue. No clear relationship between Gd concentration and salinity was apparent.

  10. Rare Earth Elements reveal past earthquakes on limestone normal faults

    NASA Astrophysics Data System (ADS)

    Manighetti, I.; Boucher, E.; Chauvel, C.; Schlagenhauf, A.; Benedetti, L.

    2009-12-01

    In 2008, we suggested that the chemical composition of the rocks which form well preserved, seismically exhumed fault scarps might record past major earthquakes (Carcaillet et al., 2008) because those scarp surfaces consist of a vertical succession of zones that have been exposed at different times by the repeating earthquakes, thus weathered over different time spans. In this pioneer study, we validated this hypothesis using the changes in chemical compositions (major and trace elements) of 15 carbonate rock samples collected from the base to the top of the seismically exhumed, 10 m-high Magnola normal fault scarp (Abruzzes, Central Italy). However, the number of available samples was insufficient to fully assess the validity of the model. Here we present trace element data on 27 additional samples collected systematically every 25 cm along the Magnola scarp, as well as on 7 scarp samples buried below the colluvium hence representing the first 4 meters of the scarp before exhumation. The scarp rocks buried in the first meter of the ground appear significantly enriched in Rare Earth elements (REE): they contain 60% more REE than the rocks located either deeper in the ground or immediately above the ground level. This concentration peak most probably results from enrichment of the scarp rocks by interaction with the impurity-doped, acidic, upper soil. Above the ground surface and along the scarp, most element concentrations (70%) decrease up-dip, generally by more than 50%; we attribute this trend to leaching and dissolution-recrystallization of purer calcite through time. The top of the scarp having been exposed for a longer period of time, its surface lost more of the trace elements contained in the rocks. However, the upward decrease in REE contents is not linear and 4 REE concentration peaks can be recognized along the exposed scarp. The position of these 4 peaks coincide with the zones identified by Schlagenhauf et al. (2009) and Palumbo et al. (2004) as

  11. 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.

  12. Trace element geochemistry and genesis of Precambrian sub-alkaline mafic dikes from the central Indian craton: evidence for mantle metasomatism

    NASA Astrophysics Data System (ADS)

    Srivastava, Rajesh K.; Singh, R. K.

    2004-07-01

    Precambrian mafic dikes transect the Archaean granite gneisses of the southern Bastar craton, Central India. On the basis of high-field strength elements, the Bastar mafic dike swarms were sub-divided into an earlier BD1 and a later BD2 system. The BD1 set comprises amphibolites, whereas the BD2 set consists of dolerites/metadolerites. On the basis of field relationships and available age data for enveloping granite rocks, the BD1 dikes are regarded as middle Archaean in age and BD2 dikes are Paleoproterozoic (˜1.8 Ga). The silica and total-alkalis contents of dikes of both swarms classified them mostly as sub-alkaline basalts. The BD1 dikes are low Ti+Fe and high-Mg olivine to quartz normative rocks, whereas the BD2 dikes are predominantly quartz normative with relatively high Ti+Fe and low-Mg contents. The high-field strength element concentrations are relatively higher in the BD2 dikes than in the BD1 dikes for comparable values of MgO and/or Cr. Judging from the geochemical data, these dikes probably were not contaminated by crustal components. The geochemistry and field observations clearly suggest a continental rift environment for the emplacement of both BD1 and BD2 dikes. Rare-earth element patterns and compatible-incompatible trace element modelling suggest that the two swarms were derived from distinctly different sub-alkaline basaltic magmas. The middle Archaean BD1 dikes were derived from ˜15-20% batch melting of a depleted lherzolite mantle source; in contrast, the Paleoproterozoic BD2 dikes were derived from ˜7-10% batch melting of a relatively enriched mantle source. A post Archaean increase in the thickness of metasomatized mantle lithosphere is the probable cause of mantle enrichment.

  13. Rare earth elements exploitation, geopolitical implications and raw materials trading

    NASA Astrophysics Data System (ADS)

    Chemin, Marie-Charlotte

    2015-04-01

    Rare earth elements (REE) correspond to seventeen elements of the periodic table. They are used in high technology, cracking, electric cars' magnet, metal alloy for batteries, and also in phone construction or ceramics for electronic card. REEs are an important resource for high technology. This project targets 16 years old students in the subject "personalized aid" and will last six weeks. The purpose of this project is to develop autonomy and research in groups for a transdisciplinary work. This project gathers knowledge in geology, geography and economics. During the first session students analyze the geology applications of the REE. They begin the analysis with learning the composition in different rocks such as basalt and diorite to make the link with crystallization. Then they compare it with adakite to understand the formation of these rocks. In the second session, they study REE exploitation. We can find them as oxides in many deposits. The principal concentrations of rare earth elements are associated with uncommon varieties of igneous rocks, such as carbonatites. They can use Qgis, to localize this high concentration. In the third session, they study the environmental costs of REE exploitation. Indeed, the exploitation produces thorium and carcinogenic toxins: sulphates, ammonia and hydrochloric acid. Processing one ton of rare earths produces 2,000 tons of toxic waste. This session focuses, first, on Baotou's region, and then on an example they are free to choose. In the fourth session, they study the geopolitical issues of REE with a focus on China. In fact this country is the largest producer of REE, and is providing 95% of the overall production. REE in China are at the center of a geopolitical strategy. In fact, China implements a sort of protectionism. Indeed, the export tax on REE is very high so, as a foreign company, it is financially attractive to establish a manufacturing subsidiary in China in order to use REE. As a matter of fact

  14. Targeting heavy rare earth elements in carbonatite complexes

    NASA Astrophysics Data System (ADS)

    Broom-Fendley, S.; Wall, F.; Gunn, A. G.; Dowman, E.

    2012-04-01

    The world's main sources of the rare earth elements (REE) are concentrated in carbonatite complexes. These have the advantages of high grade and tonnage, combined with low thorium contents, yet they are generally enriched in light rare earths (LREE). The heavy rare earths (HREE, which include Eu-Lu and Y) are more highly sought after because of their role in new and green technologies. HREE are predominantly extracted from ion-adsorption clays in China. These are small, low grade deposits, which are often illegally mined by artisans. Increased government control, environmental legislation and local demand for REE in China have led to high prices and global concerns about the security of supply of the HREE. Alternative sources of the HREE are poorly documented. We present a review of such targets, including: (1) 'abnormal' carbonatites; (2) areas around LREE-rich complexes such as breccia, fenite and latter stage veins; and (3) weathered carbonatites. At Lofdal, Namibia, carbonatite dykes contain xenotime-(Y) together with LREE minerals. The original chemistry of the carbonatite magma, coupled with late-stage magma and fluid evolution, seem to be controlling factors [1, 2]. The Khibina carbonatite, Kola Peninsula, Russia, is an example of where early LREE carbonatites become increasing HREE-enriched as magmas evolve to carbo-hydrothermal fluids [3]. Around carbonatite complexes in Malawi HREE enrichment can be found in breccia and in fenite. Breccia around Songwe shows areas with high Y/La ratios within the matrix caused by narrow zones of xenotime enrichment. Fenite around Kangankunde and Chilwa Island has higher HREE:LREE ratios than the carbonatite [4]. At weathered complexes, such as at Mount Weld in Western Australia, changes in both HREE concentration and LREE:HREE ratios are observed. In currently unworked sections of the deposit, the HREE mineral churchite (YPO4.H2O) has formed concentrations due to groundwater flow [5]. These areas of enrichment are

  15. Rare earth elements as a fingerprint of soil components solubilization

    NASA Astrophysics Data System (ADS)

    Davranche, M.; Grybos, M.; Gruau, G.; Pédrot, M.; Dia, A.

    2009-04-01

    The retention of rare earth element (REE) in the soil profile are mainly controlled by three factors, (i) the stability of the primary REE-carrying minerals, (ii) the presence of secondary phases as clays and Fe- and Mn-oxyhydroxides and (ii) the concentration of colloidal organic matter (OM). Considering that each soil phases (mineral or organic) displays (ii) various surface properties, such as specific area, surface sites density and nature and (ii) their own REE distribution inherited from the rock weathering, their mobilization through various chemical reactions (dissolution, colloidal release….) may involve the development of various shaped REE patterns in the soil solutions. REE fractionation from the different soil phases may therefore be used to identify the response of the soil system to a particular chemical process such as reductive and/or acidic dissolution. To test this purpose, an organic-rich wetland soil sample was incubated under anaerobic condition at both pH 5 and uncontrolled pH. The REE patterns developed in the soil solution were then compared to the REE patterns obtained through either aerobic at pH 3 and 7 incubations or a chemical reduction experiment (using hydroxylamine). REE patterns in anaerobic and aerobic at pH 7 experiments exhibited the same middle rare earth element (MREE) downward concavity significant of the complexation of REE with soil OM. By contrast, under acidic condition, the REE pattern exhibited a positive Eu anomaly due to the dissolution of soil feldspar. Finally, REE pattern obtained from the chemical reducing experiment showed an intermediary flat shape corresponding to a mixing between the soil organic and mineral phases dissolution. The comparison of the various REE pattern shapes allowed to conclude that (i) biological reduction of wetland soil involved amorphous Fe(III) colloids linked to OM and, (ii) that the REE mobility was controlled by the dynamic of OM in wetland soil. They also evidence the potential of

  16. Rare earth elements in scleractinian cold-water corals

    NASA Astrophysics Data System (ADS)

    Raddatz, J.; Liebetrau, V.; Hathorne, E. C.; Rüggeberg, A.; Dullo, W.; Frank, M.

    2012-12-01

    The Rare Earth Elements (REE) have a great potential to trace continental input, particle scavenging and the oxidation state of seawater. These REE are recorded in the skeleton of the cosmopolitan cold-water corals Lophelia pertusa. Here we use an online preconcentration ICP-MS method (Hathorne et al. 2012) to measure REE concentrations in seawater and associated cold-water coral carbonates in order to investigate their seawater origin. Scleractinian cold-water corals were collected in-situ and alive and with corresponding seawater samples covering from the European Continental Margin. The seawater REE patterns are characterized by the typical negative cerium anomaly of seawater, but are distinct for the northern Norwegian Margin and the Oslo Fjord, probably related to continental input. Initial results for the corresponding coral samples suggest that these distinct REE patterns of ambient seawater are recorded by the coral skeletons although some fractionation during incorporation into the aragonite occurs. This indicates that scleractinian cold-water corals can serve as a valuable archive for seawater derived REE signatures, as well radiogenic Nd isotope compositions. In a second step we analysed fossil coral samples from various locations, which were oxidatively and reductively cleaned prior to analysis. Initial results reveal that sediment-buried fossil (early Pleistocene to Holocene) coral samples from the Norwegian Margin and the Porcupine Seabight (Challenger Mound, IODP Site 1317) do not show the expected seawater REE patterns. In particular, the fossil coral-derived REE patterns lack a negative cerium anomaly suggesting that fossil coral-REE patterns do not represent ambient seawater. Thus, we suggest that the oxidative-reductive cleaning method widely used for cleaning of marine carbonates such as foraminifera prior to measurements of seawater-derived trace metal and isotope compositions are not sufficient for REE and Nd isotopes in sediment-buried coral

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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)].

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. Geochemical behavior of rare earth elements and other trace elements in the Amazon River

    NASA Astrophysics Data System (ADS)

    Merschel, Gila; Bau, Michael; Dantas, Elton Luiz

    2014-05-01

    Rivers transport large amounts of dissolved and suspended particulate material from the catchment area to the oceans and are a major source of trace metals to seawater. The Amazon River is the world's largest river and supplies approximately 20% of the oceans' freshwater (Molinier et al., 1997). However, the behavior of trace elements, especially particle-reactive elements such as the rare earth elements (REE), within the river as well as in the estuary is not well constrained and rather little is known about their transport mechanisms. This study aims at understanding the transport properties of particle-reactive elements in the Amazon River and some of its major tributaries, including the Rio Solimões, Rio Negro, Tapajos, Xingu and Jari Rivers. Samples were taken at 12 stations, seven of which were located in the Amazon mainstream, while the other five stations sampled its tributaries. To account for the effects of variable discharge, the samples were collected during periods of high and low discharge. We present data for major and trace elements, including REE, of the dissolved and suspended load of these samples. First results indicate that the shale-normalized REE pattern of the dissolved load (filtered through 0.2 µm membranes) of the Amazon mainstream and the Rio Solimões confirm earlier studies (Elderfield et al., 1990; Gerard et al., 2003) and show an enrichment of the middle REE relative to the light and heavy REE (LaSN/GdSN: 0.25 - 0.32; GdSN/YbSN: 1.54 - 1.78). In contrast to the Amazon mainstream and the Rio Solimões, which are considered to be whitewater rivers, blackwater rivers, such as the Rio Negro, have a flat REE pattern with higher REE concentrations than whitewater rivers. The third water-type found in the Amazon Basin is clearwater, e.g. Rio Tapajos, with REE patterns in between those of the other two types, i.e. LaSN/GdSN: 0.55 - 0.70; GdSN/YbSN: 1.26 - 1.55. A similar behavior can be identified for other major and trace elements. While

  12. Automated Quantitative Rare Earth Elements Mineralogy by Scanning Electron Microscopy

    NASA Astrophysics Data System (ADS)

    Sindern, Sven; Meyer, F. Michael

    2016-09-01

    Increasing industrial demand of rare earth elements (REEs) stems from the central role they play for advanced technologies and the accelerating move away from carbon-based fuels. However, REE production is often hampered by the chemical, mineralogical as well as textural complexity of the ores with a need for better understanding of their salient properties. This is not only essential for in-depth genetic interpretations but also for a robust assessment of ore quality and economic viability. The design of energy and cost-efficient processing of REE ores depends heavily on information about REE element deportment that can be made available employing automated quantitative process mineralogy. Quantitative mineralogy assigns numeric values to compositional and textural properties of mineral matter. Scanning electron microscopy (SEM) combined with a suitable software package for acquisition of backscatter electron and X-ray signals, phase assignment and image analysis is one of the most efficient tools for quantitative mineralogy. The four different SEM-based automated quantitative mineralogy systems, i.e. FEI QEMSCAN and MLA, Tescan TIMA and Zeiss Mineralogic Mining, which are commercially available, are briefly characterized. Using examples of quantitative REE mineralogy, this chapter illustrates capabilities and limitations of automated SEM-based systems. Chemical variability of REE minerals and analytical uncertainty can reduce performance of phase assignment. This is shown for the REE phases parisite and synchysite. In another example from a monazite REE deposit, the quantitative mineralogical parameters surface roughness and mineral association derived from image analysis are applied for automated discrimination of apatite formed in a breakdown reaction of monazite and apatite formed by metamorphism prior to monazite breakdown. SEM-based automated mineralogy fulfils all requirements for characterization of complex unconventional REE ores that will become

  13. Rare Earth Element Partitioning in Lunar Minerals: An Experimental Study

    NASA Technical Reports Server (NTRS)

    McIntosh, E. C.; Rapp, J. F.; Draper, D. S.

    2016-01-01

    The partitioning behavior of rare earth elements (REE) between minerals and melts is widely used to interpret the petrogenesis and geologic context of terrestrial and extra-terrestrial samples. REE are important tools for modelling the evolution of the lunar interior. The ubiquitous negative Eu anomaly in lunar basalts is one of the main lines of evidence to support the lunar magma ocean (LMO) hypothesis, by which the plagioclase-rich lunar highlands were formed as a flotation crust during differentiation of a global-scale magma ocean. The separation of plagioclase from the mafic cumulates is thought to be the source of the Eu depletion, as Eu is very compatible in plagioclase. Lunar basalts and volcanic glasses are commonly depleted in light REEs (LREE), and more enriched in heavy REEs (HREE). However, there is very little experimental data available on REE partitioning between lunar minerals and melts. In order to interpret the source of these distinctive REE patterns, and to model lunar petrogenetic processes, REE partition coefficients (D) between lunar minerals and melts are needed at conditions relevant to lunar processes. New data on D(sub REE) for plagioclase, and pyroxenes are now available, but there is limited available data for olivine/melt D(sub REE), particularly at pressures higher than 1 bar, and in Fe-rich and reduced compositions - all conditions relevant to the lunar mantle. Based on terrestrial data, REE are highly incompatible in olivine (i.e. D much less than 1), however olivine is the predominant mineral in the lunar interior, so it is important to understand whether it is capable of storing even small amounts of REE, and how the REEs might be fractionatied, in order to understand the trace element budget of the lunar interior. This abstract presents results from high-pressure and temperature experiments investigating REE partitioning between olivine and melt in a composition relevant to lunar magmatism.

  14. Effects of spraying rare earths on contents of rare Earth elements and effective components in tea.

    PubMed

    Wang, Dongfeng; Wang, Changhong; Ye, Sheng; Qi, Hongtao; Zhao, Guiwen

    2003-11-05

    Rare earth (RE) fertilizer is widely applied in China to increase the yield and the quality of crops including tea. However, the effects of spraying RE fertilizer on the contents of rare earth elements (REE) and effective components in tea are unknown. The results from basin and field experiments show that the values of the REE concentrations in new shoots of tea plants and the concentration of REE in the soil (REE/REEs) either from control basins or from treatment basins were smaller than those in other parts of tea plant and similar between control and treatment. The longer the interval between spraying RE fertilizer and picking the shoots of tea plants, the less the effects from spraying. About 80% summation operator REE (the sum of the concentrations of 15 REE) in tea, whether it came from spraying or not, was insoluble in the infusion. About 10% the soluble REE of summation operator REE in tea infusion was bound to polysaccharide, and the amount of REE bound polysaccharide decreased over time. At least a 25 day safety interval is needed between spraying and picking if the microelement fertilizer is used, in order to enhance tea output and to ensure tea safety.

  15. Size distribution of rare earth elements in coal ash

    USGS Publications Warehouse

    Scott, Clinton T.; Deonarine, Amrika; Kolker, Allan; Adams, Monique; Holland, James F.

    2015-01-01

    Rare earth elements (REEs) are utilized in various applications that are vital to the automotive, petrochemical, medical, and information technology industries. As world demand for REEs increases, critical shortages are expected. Due to the retention of REEs during coal combustion, coal fly ash is increasingly considered a potential resource. Previous studies have demonstrated that coal fly ash is variably enriched in REEs relative to feed coal (e.g, Seredin and Dai, 2012) and that enrichment increases with decreasing size fractions (Blissett et al., 2014). In order to further explore the REE resource potential of coal ash, and determine the partitioning behavior of REE as a function of grain size, we studied whole coal and fly ash size-fractions collected from three U.S commercial-scale coal-fired generating stations burning Appalachian or Powder River Basin coal. Whole fly ash was separated into , 5 um, to 5 to 10 um and 10 to 100 um particle size fractions by mechanical shaking using trace-metal clean procedures. In these samples REE enrichments in whole fly ash ranges 5.6 to 18.5 times that of feedcoals. Partitioning results for size separates relative to whole coal and whole fly ash will also be reported. 

  16. Spectroscopy of Luminescent Crystals Containing Rare Earth Elements

    NASA Astrophysics Data System (ADS)

    Chen, Meng-Ling; Lii, Kwang-Hwa; Chang, Bor-Chen

    2013-06-01

    We have studied the spectroscopy of luminescent crystals containing rare earth elements such as KEuGe_2O_6, Cs_3EuSi_6O_{15}, K_4[(UO_2)Eu_2(Ge_2O_7)_2], and R_2(C_8H_{10}O_4)_3 (R= Y, Tb, or Eu). The emission and excitation spectra of these compounds were recorded at ambient temperature. These spectra are consistent with the structures which were determined by single crystal X-ray diffraction. Crystals containing hybrid luminescent centers were also synthesized and interesting energy transfer mechanisms were observed. For example, dramatic luminescence quenching was found in KEu_xNd_{1-x}Ge_2O_6 (x= 0.98, 0.96, 0.94, and 0.84) as well as in Cs_3Eu_{0.98}Nd_{0.02}Si_6O_{15}, while different compositions of Y_xEu_yTb_{2-x-y}(C_8H_{10}O_4)_3 exhibit different emission colors. Emission lifetimes were also measured for these compounds, and the results shed light on the energy transfer mechanisms. Detailed results of our research will be presented. P.-L. Chen, P.-Y. Chiang, H.-C. Yeh, B.-C. Chang, and K.-H. Lii, Dalton Trans., 1721 (2008). M.-Y. Hung, Y.-H. Chen, B.-C. Chang, and K.-H. Lii, Chem. Mater. 17, 5743 (2005).

  17. 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

  18. 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).

  19. Rare earth element budgets in subduction-zone fluids

    NASA Astrophysics Data System (ADS)

    Tsay, A.; Zajacz, Z.; Sanchez-Valle, C.

    2012-12-01

    Subduction zone fluids play a fundamental role in the geochemical cycle of the Earth. The nature and composition of these fluids are determined by complex processes and still poorly understood. As a result of a variety of metasomatic and partial melting events, arc-related magmas display a typical trace element abundance spectrum, in which the rare earth elements' (REE) signature is an important record of petrogenetic processes. Therefore, investigating the behavior of REE in fluids at high pressure (P) and temperature (T) conditions is crucial for constraining fluid composition, as well as understanding subduction-zone processes in general. However, up to date, the experimental studies on REE solubility and speciation are limited to quite low P-T conditions (300 °C, saturated water vapor pressure) [1]. The theoretical predictions of the stability of REE complexes have been performed up to 350 °C [2] and 1000 °C, 0.5 GPa [3] by the extrapolation of thermodynamic data obtained at ambient conditions. In this study we present new experimental data on REE silicate (REE2Si2O7) solubility in aqueous quartz saturated fluids, containing various ligands, at conditions relevant for subducting slabs (600, 700, 800 °C, 2.6 GPa). The aim of the experiments was to investigate the relative effect of temperature and ligands on the solubility of REE. The experiments were conducted in an end-loaded piston-cylinder apparatus and the fluids were in situ sampled at P-T in the form of primary fluid inclusions in quartz [4]. The gold capsule was typically loaded with a chip of synthetic REE silicate (La,Nd,Gd,Dy,Er,Yb)2Si2O7, an aqueous fluid (~20 wt.%) and a piece of natural quartz. During the experiment (24-48 h) a thermal gradient along the capsule promoted intensive dissolution of quartz at the hottest part and precipitation of new quartz at the cooler part of the capsule, allowing the primary fluid inclusions to be trapped (~30-50 μm). Rubidium and cesium were added to the

  20. Investigating Rare Earth Element Systematics in the Marcellus Shale

    NASA Astrophysics Data System (ADS)

    Yang, J.; Torres, M. E.; Kim, J. H.; Verba, C.

    2014-12-01

    The lanthanide series of elements (the 14 rare earth elements, REEs) have similar chemical properties and respond to different chemical and physical processes in the natural environment by developing unique patterns in their concentration distribution when normalized to an average shale REE content. The interpretation of the REE content in a gas-bearing black shale deposited in a marine environment must therefore take into account the paleoredox conditions of deposition as well as any diagenetic remobilization and authigenic mineral formation. We analyzed 15 samples from a core of the Marcellus Shale (Whipkey ST1, Greene Co., PA) for REEs, TOC, gas-producing potential, trace metal content, and carbon isotopes of organic matter in order to determine the REE systematics of a black shale currently undergoing shale gas development. We also conducted a series of sequential leaching experiments targeting the phosphatic fractions in order to evaluate the dominant host phase of REEs in a black shale. Knowledge of the REE system in the Marcellus black shale will allow us to evaluate potential REE release and behavior during hydraulic fracturing operations. Total REE content of the Whipkey ST1 core ranged from 65-185 μg/g and we observed three distinct REE shale-normalized patterns: middle-REE enrichment (MREE/MREE* ~2) with heavy-REE enrichment (HREE/LREE ~1.8-2), flat patterns, and a linear enrichment towards the heavy-REE (HREE/LREE ~1.5-2.5). The MREE enrichment occurred in the high carbonate samples of the Stafford Member overlying the Marcellus Formation. The HREE enrichment occurred in the Union Springs Member of the Marcellus Formation, corresponding to a high TOC peak (TOC ~4.6-6.2 wt%) and moderate carbonate levels (CaCO3 ~4-53 wt%). Results from the sequential leaching experiments suggest that the dominant host of the REEs is the organic fraction of the black shale and that the detrital and authigenic fractions have characteristic MREE enrichments. We present our

  1. Recovery and Separation of Rare Earth Elements Using Salmon Milt

    PubMed Central

    Takahashi, Yoshio; Kondo, Kazuhiro; Miyaji, Asami; Watanabe, Yusuke; Fan, Qiaohui; Honma, Tetsuo; Tanaka, Kazuya

    2014-01-01

    Recycling rare earth elements (REEs) used in advanced materials such as Nd magnets is important for the efficient use of REE resources when the supply of several REEs is limited. In this work, the feasibility of using salmon milt for REE recovery and separation was examined, along with the identification of the binding site of REEs in salmon milt. Results showed that (i) salmon milt has a sufficiently high affinity to adsorb REEs and (ii) the adsorption capacity of the milt is 1.04 mEq/g, which is comparable with that of commercial cation exchange resin. Heavier REEs have higher affinity for milt. A comparison of stability constants and adsorption patterns of REEs discussed in the literature suggests that the phosphate is responsible for the adsorption of REE in milt. The results were supported by dysprosium (Dy) and lutetium (Lu) LIII-edge extended x-ray absorption fine structure (EXAFS) spectroscopy. The REE-P shell was identified for the second neighboring atom, which shows the importance of the phosphate site as REE binding sites. The comparison of REE adsorption pattern and EXAFS results between the milt system and other adsorbent systems (cellulose phosphate, Ln-resin, bacteria, and DNA-filter hybrid) revealed that the coordination number of phosphate is correlated with the slope of the REE pattern. The separation column loaded with milt was tested to separate REE for the practical use of salmon milt for the recovery and separation of REE. However, water did not flow through the column possibly because of the hydrophobicity of the milt. Thus, sequential adsorption–desorption approach using a batch-type method was applied for the separation of REE. As an example of the practical applications of REE separation, Nd and Fe(III) were successfully separated from a synthetic solution of Nd magnet waste by a batch-type method using salmon milt. PMID:25490035

  2. Attenuation of rare earth elements in a boreal estuary

    NASA Astrophysics Data System (ADS)

    Åström, Mats E.; Österholm, Peter; Gustafsson, Jon Petter; Nystrand, Miriam; Peltola, Pasi; Nordmyr, Linda; Boman, Anton

    2012-11-01

    This study focuses on attenuation of rare earth elements (REE) when a boreal creek, acidified and loaded with REE and other metals as a result of wetland drainage, empties into a brackish-water estuary (salinity < 6‰). Surface water was collected in a transect from the creek mouth to the outer estuary, and settling (particulate) material in sediment traps moored at selected locations in the estuary. Ultrafiltration, high-resolution ICP-MS and modeling were applied on the waters, and a variety of chemical reagents were used to extract metals from the settling material. Aluminium, Fe and REE transported by the acidic creek were extensively removed in the inner/central estuary where the acidic water was neutralised, whereas Mn was relatively persistent in solution and thus redistributed to particles and deposited further down the estuary. The REE removal was caused by several contemporary mechanisms: co-precipitation with oxyhydroxides (mainly Al but also Fe), complexation with flocculating humic substances and sorption to suspended particles. Down estuary the dissolved REE pool, remaining after removal, was fractionated: the <1 kDa pool became depleted in the middle REE and the colloidal (0.45 μm-1 kDa) pool depleted in the middle and heavy REE. This fractionation was controlled by the removal process, such that those REE with highest affinity for the settling particles became most depleted in the remaining dissolved pool. Modeling, based on Visual MINTEQ version 3.0 and the Stockholm Humic Model after revision and updating, predicted that the dissolved (<0.45 μm) REE pool in the estuary is bound almost entirely to humic substances. Acid sulphate soils, the source of the REE and other metals in the creek water, are widespread on coastal plains worldwide and therefore the REE attenuation patterns and mechanisms identified in the studied estuary are relevant for recognition of similar geochemical processes and conditions in a variety of coastal locations.

  3. Core-Mantle Partitioning of Volatile Siderophile Elements and the Origin of Volatile Elements in the Earth

    NASA Technical Reports Server (NTRS)

    Nickodem, K.; Righter, K.; Danielson, L.; Pando, K.; Lee, C.

    2012-01-01

    There are currently several hypotheses on the origin of volatile siderophile elements in the Earth. One hypothesis is that they were added during Earth s accretion and core formation and mobilized into the metallic core [1], others claim multiple stage origin [2], while some hypothesize that volatiles were added after the core already formed [3]. Several volatile siderophile elements are depleted in Earth s mantle relative to the chondrites, something which continues to puzzle many scientists. This depletion is likely due to a combination of volatility and core formation. The Earth s core is composed of Fe and some lighter constituents, although the abundances of these lighter elements are unknown [4]. Si is one of these potential light elements [5] although few studies have analyzed the effect of Si on metal-silicate partitioning, in particular the volatile elements. As, In, Ge, and Sb are trace volatile siderophile elements which are depleted in the mantle but have yet to be extensively studied. The metal-silicate partition coefficients of these elements will be measured to determine the effect of Si. Partition coefficients depend on temperature, pressure, oxygen fugacity, and metal and silicate composition and can constrain the concentrations of volatile, siderophile elements found in the mantle. Reported here are the results from 13 experiments examining the partitioning of As, In, Ge, and Sb between metallic and silicate liquid. These experiments will examine the effect of temperature, and metal-composition (i.e., Si content) on these elements in or-der to gain a greater understanding of the core-mantle separation which occurred during the Earth s early stages. The data can then be applied to the origin of volatile elements in the Earth.

  4. Miocene Coral Skeleton Rare Earth Element Patterns Reflect River Discharge

    NASA Astrophysics Data System (ADS)

    Mertz-Kraus, R.; Brachert, T. C.; Jochum, K. P.

    2010-12-01

    Rare Earth Element (REE) patterns of modern coral skeletons usually reflect the REE composition of ambient seawater which is characterized by heavy REE enriched relative to light REE with NASC (North American Shale Composite) normalized La/Lu ratios of typically <0.4. The REE concentration in coral aragonite is enriched by 3 to 4 orders of magnitude compared to ambient seawater. Here we report trace element data including REE of coral skeletons of Late Miocene age (~9 Ma, Tortonian) from Crete (Eastern Mediterranean). Analyses were done using a 213 nm Nd:YAG laser coupled to an Element2 ICP-MS along the growth axis of the coral skeletons. The profiles show that Ba/Ca ratios have a seasonally induced pattern with high values around the winter months which are identified by δ18O analyses. REE/Ca ratios co-vary with Ba/Ca ratios. Since the Ba/Ca ratio is a proxy used to monitor river discharge, the co-variation suggests the REE/Ca ratio to be a proxy of comparable quality. NASC-normalized REE patterns of the Tortonian corals have negative Ce anomalies like modern corals. However, the Tortonian corals have REE patterns highly enriched in LREE with (La/Lu)N ratios of 4 to 30 which is 1 to 2 orders of magnitude higher compared to modern corals. Al concentrations are low (<10 ppm) and do not correlate with REE concentrations indicating an insignificant fraction of terrigenous material included in the skeleton. Applying distribution coefficients typical for modern corals, the REE composition of the Tortonian ambient water yields (La/Lu)N of about 2 to 16. This range can be explained by binary mixing of modern Eastern Mediterranean sea surface water ((La/Lu)N=0.35, sea surface salinity (SSS) ~38 ‰) with highly LREE-enriched river water ((La/Lu)N >3, salinity ~0.5 ‰) transporting suspended and colloid phases, also highly enriched, especially in LREE, at a ratio of ~9 (seawater):1 (river water). The river water component is considered because paleoenvironmental

  5. PROCESS FOR SEPARATING AMERICIUM AND CURIUM FROM RARE EARTH ELEMENTS

    DOEpatents

    Baybarz, R.D.; Lloyd, M.H.

    1963-02-26

    This invention relates to methods of separating americium and curium values from rare earth values. In accordance with the invention americium, curium, and rare earth values are sorbed on an anion exchange resin. A major portion of the rare earth values are selectively stripped from the resin with a concentrated aqueous solution of lithium chloride, and americium, curium, and a minor portion of rare earth values are then stripped from the resin with a dilute aqueous solution of lithium chloride. The americium and curium values are further purified by increasing the concentration of lithium chloride in the solution to at least 8 molar and selectively extracting rare earth values from the resulting solution with a monoalkylphosphoric acid. (AEC)

  6. Geochemical behaviour of trace elements during fractional crystallization and crustal assimilation of the felsic alkaline magmas of the state of Rio de Janeiro, Brazil.

    PubMed

    Motoki, Akihisa; Sichel, Susanna E; Vargas, Thais; Melo, Dean P; Motoki, Kenji F

    2015-01-01

    This paper presents geochemical behaviour of trace elements of the felsic alkaline rocks of the state of Rio de Janeiro, Brazil, with special attention of fractional crystallization and continental crust assimilation. Fractionation of leucite and K-feldspar increases Rb/K and decreases K2O/(K2O+Na2O). Primitive nepheline syenite magmas have low Zr/TiO2, Sr, and Ba. On the Nb/Y vs. Zr/TiO2 diagram, these rocks are projected on the field of alkaline basalt, basanite, and nephelinite, instead of phonolite. Well-fractionated peralkaline nepheline syenite has high Zr/TiO2 but there are no zircon. The diagrams of silica saturation index (SSI) distinguish the trends originated form fractional crystallization and crustal assimilation. In the field of SSI<-200, Zr/TiO2 and Ba/Sr have negative correlations to SSI in consequence of fractional crystallization. In the field of SSI>-200, they show positive correlations due to continental crust assimilation. Total REEs (Rare Earth Elements) is nearly 10 times that of granitic rocks, but LaN/SmN and LaN/YbN are similar. REE trend is linear and Eu anomaly is irrelevant. The pegmatitic liquid generated by country rock partial melting is SiO2-oversaturated and peraluminous with high Ba, Sr, Ba/Sr, Zr/TiO2, and SSI, with high content of fluids. This model justifies the peraluminous and SiO2-oversaturated composition of the rocks with relevant effects of continental crust assimilation.

  7. 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.

  8. Relative sensitivity of rare earth elements in spark-source mass spectrometry.

    PubMed

    Roaldset, E

    1970-07-01

    A method for calculating the relative sensitivity factors for the rare earth elements in geological material is outlined. A close correlation is found between the relative sensitivity factors calculated and isotopic mass and the first ionization potential for the elements. The points are grouped in the vicinity of a regression line, which may be used to determine the relative sensitivity factors for all the rare earth elements.

  9. 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.

  10. Biogeochemistry of the rare-earth elements with particular reference to hickory trees

    USGS Publications Warehouse

    Robinson, W.O.; Bastron, H.; Murata, K.J.

    1958-01-01

    Hickory trees concentrate the rare-earth elements in their leaves to a phenomenal degree and may contain as much as 2300 p.p.m. of total rare earths based on the dry weight of the leaves. The average proportions of the individual elements (atomic percent of the total rare-earth elements) in the leaves are: Y 36, La 16, Ce 14, Pr 2, Nd 20, Sm 1, Eu 0.7, Gd 3, Tb 0.6, Dy 3, Ho 0.7, Er 2, Tm 0.2, Yb 1, and Lu 0.2. The similarity in the proportions of the rare-earth elements in the leaves and in the exchange complex of the soil on which the hickory trees grow indicates that the trees do not fractionate the rare earths appreciably. The variation of the rare-earth elements in the leaves and soils can be explained generally in terms of the relative abundance of the cerium group and the yttrium group, except for the element cerium. The large fluctuations in the proportion of cerium [Ce/(La + Nd) atomic ratios of 0.16 to 0.86] correlate with oxidation-reduction conditions in the soil profile. The substitution of dilute H2SO3 for dilute HC1 in the determination of available rare-earth elements brings about a large increase in the proportion of cerium that is extracted from an oxygenated subsoil. These relationships strongly suggest that quadrivalent cerium is present in oxygenated subsoil and is less available to plants than the other rare-earth elements that do not undergo such a change in valence. A few parts per billion of rare-earth elements have been detected in two samples of ground water. ?? 1958.

  11. Review of rare earth element concentrations in oil shales of the Eocene Green River Formation

    USGS Publications Warehouse

    Birdwell, Justin E.

    2012-01-01

    Concentrations of the lanthanide series or rare earth elements and yttrium were determined for lacustrine oil shale samples from the Eocene Green River Formation in the Piceance Basin of Colorado and the Uinta Basin of Utah. Unprocessed oil shale, post-pyrolysis (spent) shale, and leached shale samples were examined to determine if oil-shale processing to generate oil or the remediation of retorted shale affects rare earth element concentrations. Results for unprocessed Green River oil shale samples were compared to data published in the literature on reference materials, such as chondritic meteorites, the North American shale composite, marine oil shale samples from two sites in northern Tibet, and mined rare earth element ores from the United States and China. The Green River oil shales had lower rare earth element concentrations (66.3 to 141.3 micrograms per gram, μg g-1) than are typical of material in the upper crust (approximately 170 μg g-1) and were also lower in rare earth elements relative to the North American shale composite (approximately 165 μg g-1). Adjusting for dilution of rare earth elements by organic matter does not account for the total difference between the oil shales and other crustal rocks. Europium anomalies for Green River oil shales from the Piceance Basin were slightly lower than those reported for the North American shale composite and upper crust. When compared to ores currently mined for rare earth elements, the concentrations in Green River oil shales are several orders of magnitude lower. Retorting Green River oil shales led to a slight enrichment of rare earth elements due to removal of organic matter. When concentrations in spent and leached samples were normalized to an original rock basis, concentrations were comparable to those of the raw shale, indicating that rare earth elements are conserved in processed oil shales.

  12. Rare-earth elements enrichment of Pacific seafloor sediments: the view from volcanic islands of Polynesia

    NASA Astrophysics Data System (ADS)

    Melleton, Jérémie; Tuduri, Johann; Pourret, Olivier; Bailly, Laurent; Gisbert, Thierry

    2014-05-01

    Rare-earth elements (REEs) are key metals for «green» technologies such as energy saving lamps or permanent magnets used in, e.g., wind turbines, hard disk drives, portable phone or electric or hybrid vehicles. Since several years, world demand for these metals is therefore drastically increasing. The quasi-monopolistic position of China, which produces around 95 % of global REEs production, generates risks for the industries that depend on a secure supply of REEs. In response, countries are developing and diversifying their supply sources, with new mining projects located outside China and efforts in the area of REEs recycling. Most of these projects focus on deposits related to carbonatites and alkaline-peralkaline magmatism, which are generally enriched in light REEs (LREEs) compared to the heavy REEs (HREEs)-enriched deposits of the ion-adsorption types, located in southern China. However, a recent study revealed new valuable resources corresponding to seafloor sediments located in the south-eastern and north-central Pacific. The deep-sea mud described by these authors show a higher HREE/LREE ratio than ion-adsorption deposits, a feature which significantly increases their economic interest. The authors suggest mid-ocean ridge hydrothermal activity as an explanation to this anomalous enrichment. However, several contributions have documented considerable REEs enrichment in basalts and peridotitic xenoliths from French Polynesia. Several arguments have been exposed in favour of a supergene origin, with a short migration, suggesting that REEs were collected from weathered basalts. The Tahaa volcanic island (Sous-le-Vent Island, Society Archipelago, French Polynesia) is the first location where such enrichment has been described. New petrographic and mineralogical investigations confirm a supergene mobilization of this abnormal occurrence. REE-bearing minerals (mainly phosphates of the rhabdophane group) are primarily located within basalt vesicles but also in

  13. RARE EARTH ELEMENTS: A REVIEW OF PRODUCTION, PROCESSING, RECYCLING, AND ASSOCIATED ENVIRONMENTAL ISSUES

    EPA Science Inventory

    Rare earth elements (REEs) are a group of 15 chemical elements in the periodic table, specifically the lanthanides. Two other elements, scandium and yttrium, have a similar physiochemistry to the lanthanides, are commonly found in the same mineral assemblages, and are often refe...

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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

  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. Binding in alkali and alkaline-earth tetrahydroborates: Special position of magnesium tetrahydroborate

    NASA Astrophysics Data System (ADS)

    Łodziana, Zbigniew; van Setten, Michiel J.

    2010-01-01

    Compounds of light elements and hydrogen are currently extensively studied due to their potential application in the field of hydrogen or energy storage. A number of new interesting tetrahydroborates that are especially promising due to their very high gravimetric hydrogen content were recently reported. However, the determination and understanding of their complex crystalline structures has created considerable debate. Metal tetrahydroborates, in general, form a large variety of structures ranging from simple for NaBH4 to very complex for Mg(BH4)2 . Despite the extensive discussion in the literature no clear explanation has been offered for this variety so far. In this paper we analyze the structural and electronic properties of a broad range of metal tetrahydroborates and reveal the factors that determine their structure: ionic bonding, the orientation of the BH4 groups, and the coordination number of the metal cation. We show, in a simple way, that the charge transfer in the metal tetrahydroborates rationally explains the structural diversity of these compounds. Being ionic systems, the metal tetrahydroborates fall into the classification of Linus Pauling. By using the ionic radius for the BH4 group as determined in this paper, this allows for structural predictions for new and mixed compounds.

  2. Rare earth elements and neodymium isotopes in sedimentary organic matter

    NASA Astrophysics Data System (ADS)

    Freslon, Nicolas; Bayon, Germain; Toucanne, Samuel; Bermell, Sylvain; Bollinger, Claire; Chéron, Sandrine; Etoubleau, Joel; Germain, Yoan; Khripounoff, Alexis; Ponzevera, Emmanuel; Rouget, Marie-Laure

    2014-09-01

    We report rare earth element (REE) and neodymium (Nd) isotope data for the organic fraction of sediments collected from various depositional environments, i.e. rivers (n = 25), estuaries (n = 18), open-ocean settings (n = 15), and cold seeps (n = 12). Sedimentary organic matter (SOM) was extracted using a mixed hydrogen peroxide/nitric acid solution (20%-H2O2-0.02 M-HNO3), after removal of carbonate and oxy-hydroxide phases with dilute hydrochloric acid (0.25 M-HCl). A series of experimental tests indicate that extraction of sedimentary organic compounds using H2O2 may be complicated occasionally by partial dissolution of sulphide minerals and residual carbonates. However, this contamination is expected to be minor for REE because measured concentrations in H2O2 leachates are about two-orders of magnitude higher than in the above mentioned phases. The mean REE concentrations determined in the H2O2 leachates for samples from rivers, estuaries, coastal seas and open-ocean settings yield relatively similar levels, with ΣREE = 109 ± 86 ppm (mean ± s; n = 58). The organic fractions leached from cold seep sediments display even higher concentration levels (285 ± 150 ppm; mean ± s; n = 12). The H2O2 leachates for most sediments exhibit remarkably similar shale-normalized REE patterns, all characterized by a mid-REE enrichment compared to the other REE. This suggests that the distribution of REE in leached sedimentary organic phases is controlled primarily by biogeochemical processes, rather than by the composition of the source from which they derive (e.g. pore, river or sea-water). The Nd isotopic compositions for organic phases leached from river sediments are very similar to those for the corresponding detrital fractions. In contrast, the SOM extracted from marine sediments display εNd values that typically range between the εNd signatures for terrestrial organic matter (inferred from the analysis of the sedimentary detrital fractions) and marine organic matter

  3. High-level extracellular production of alkaline polygalacturonate lyase in Bacillus subtilis with optimized regulatory elements.

    PubMed

    Zhang, Junjiao; Kang, Zhen; Ling, Zhenmin; Cao, Wenlong; Liu, Long; Wang, Miao; Du, Guocheng; Chen, Jian

    2013-10-01

    The present work aims to construct a robust recombinant Bacillus subtilis to achieve secretory production of alkaline polygalacturonate lyase (PGL). First, 6 signal peptides (amyX, bpr, vpr, yvgO, wapA and nprE) were screened with a semi-rational approach and comparatively investigated their effects on the production of PGL. The signal peptide bpr directed efficient PGL secretory expression and increased PGL titer to 313.7 U mL(-1). By optimizing and applying strong promoter P43 and Shine-Dalgarno sequence, higher titer of 446.3 U mL(-1) PGL was achieved. Finally, the capacity of the recombinant B. subtilis WB43CB was evaluated with a fed-batch strategy in 3 L fermentor. The PGL titer reached 632.6 U mL(-1) with a productivity of 17.6 U mL(-1) h(-1), which was the highest secretory production of PGL by the B. subtilis system. The recombinant B. subtilis strain WB43CB constructed in the present work has great potential in production of alkaline PGL.

  4. Rare Earth Element Partition Coefficients from Enstatite/Melt Synthesis Experiments

    NASA Technical Reports Server (NTRS)

    Schwandt, Craig S.; McKay, Gordon A.

    1997-01-01

    Enstatite (En(80)Fs(19)Wo(01)) was synthesized from a hypersthene normative basaltic melt doped at the same time with La, Ce, Nd, Sm, Eu, Dy, Er, Yb and Lu. The rare earth element concentrations were measured in both the basaltic glass and the enstatite. Rare earth element concentrations in the glass were determined by electron microprobe analysis with uncertainties less than two percent relative. Rare earth element concentrations in enstatite were determined by secondary ion mass spectrometry with uncertainties less than five percent relative. The resulting rare earth element partition signature for enstatite is similar to previous calculated and composite low-Ca pigeonite signatures, but is better defined and differs in several details. The partition coefficients are consistent with crystal structural constraints.

  5. Core-Mantle Partitioning of Volatile Elements and the Origin of Volatile Elements in Earth and Moon

    NASA Technical Reports Server (NTRS)

    Righter, Kevin; Pando, K.; Danielson, L.; Nickodem, K.

    2014-01-01

    Depletions of volatile siderophile elements (VSE; Ga, Ge, In, As, Sb, Sn, Bi, Zn, Cu, Cd) in mantles of Earth and Moon, constrain the origin of volatile elements in these bodies, and the overall depletion of volatile elements in Moon relative to Earth. A satisfactory explanation has remained elusive [1,2]. We examine the depletions of VSE in Earth and Moon and quantify the amount of depletion due to core formation and volatility of potential building blocks. We calculate the composition of the Earth's PUM during continuous accretion scenarios with constant and variable fO2. Results suggest that the VSE can be explained by a rather simple scenario of continuous accretion leading to a high PT metal-silicate equilibrium scenario that establishes the siderophile element content of Earth's PUM near the end of accretion [3]. Core formation models for the Moon explain most VSE, but calculated contents of In, Sn, and Zn (all with Tc < 750 K) are all still too high after core formation, and must therefore require an additional process to explain the depletions in the lunar mantle. We discuss possible processes including magmatic degassing, evaporation, condensation, and vapor-liquid fractionation in the lunar disk.

  6. Input impedance and gain of monopole elements with disk ground planes on flat earth

    NASA Astrophysics Data System (ADS)

    Weiner, M. M.

    1990-12-01

    This paper extends previously reported results for a quarterwave monopole element on a disk ground plane in free space to the case where the disk ground plane rests on flat earth. Numerical results are obtained by utilizing Richmond's method of moments computer program for disk ground planes over flat earth.

  7. Trace Element Inputs to the Upper West Pacific from Nd Isotopes and Rare Earth Elements

    NASA Astrophysics Data System (ADS)

    Behrens, M. K.; Pahnke, K.; Schnetger, B.; Brumsack, H. J.

    2015-12-01

    Neodymium isotopes (143Nd/144Nd, expressed as ɛNd) and rare earth element (REE) concentrations in the ocean trace water mass transport and margin-seawater exchange processes. The distinct ɛNd and REE signatures of the lithogenic components of margin sediments of the West Pacific allow characterization of trace element inputs to the Pacific Ocean. We present dissolved ɛNdand REE concentrations from twelve vertical profiles of a transect from South Korea to Fiji. Near South Korea, surface waters are marked by unradiogenic ɛNd (as low as -7.3), high REE concentrations (e.g., Nd = 15.3 pmol/kg) and low salinity. Towards the open ocean, these parameters gradually change towards typical Pacific open ocean values (ɛNd = -3.3, [Nd] = 5.55 pmol/kg). Subsurface waters show REE depletions, followed by the typical REE increase with increasing water depth. These distributions indicate trace element input near South Korea and enhanced subsurface scavenging, as indicated by strong heavy REE to light REE fractionation. In the tropical West Pacific (10°N-15°S), high surface and subsurface water ɛNd values (+0.7) and positive Eu anomalies trace the influence of volcanic islands. Yet, absolute REE concentrations are extremely low at these depths (e.g., Nd = 2.77 pmol/kg). Using shale-normalized Nd/Er and Ho/Dy ratios, that show a much stronger surface to subsurface decrease in coastal waters compared to the open ocean, we suggest enhanced scavenging in this area. Eastward flowing intermediate waters (NPIW, AAIW) have ɛNd values up to +1.9 (NPIW) and +3.7 (AAIW) higher than those entering the tropical West Pacific from north and south, respectively. Modified ɛNd at intermediate depths and no change in REE patterns suggest that boundary exchange along volcanic island margins modifies the seawater ɛNd without changing the REE budget.

  8. Development of a critically evaluated thermodynamic database for the systems containing alkaline-earth oxides

    NASA Astrophysics Data System (ADS)

    Shukla, Adarsh

    In a thermodynamic system which contains several elements, the phase relationships among the components are usually very complex. Especially, systems containing oxides are generally very difficult to investigate owing to the very high experimental temperatures and corrosive action of slags. Due to such difficulties, large inconsistencies are often observed among the available experimental data. In order to investigate and understand the complex phase relationships effectively, it is very useful to develop thermodynamic databases containing optimized model parameters giving the thermodynamic properties of all phases as functions of temperature and composition. In a thermodynamic optimization, adjustable model parameters are calculated using, simultaneously, all available thermodynamic and phase-equilibrium data in order to obtain one set of model equations as functions of temperature and composition. Thermodynamic data, such as activities, can aid in the evaluation of the phase diagrams, and information on phase equilibria can be used to deduce thermodynamic properties. Thus, it is frequently possible to resolve discrepancies in the available data. From the model equations, all the thermodynamic properties and phase diagrams can be back-calculated, and interpolations and extrapolations can be made in a thermodynamically correct manner. The data are thereby rendered self-consistent and consistent with thermodynamic principles, and the available data are distilled into a small set of model parameters, ideal for computer storage. As part of a broader research project at the Centre de Recherche en Calcul Thermochimique (CRCT), Ecole Polytechnique to develop a thermodynamic database for multicomponent oxide systems, this thesis deals with the addition of components SrO and BaO to the existing multicomponent database of the SiO2-B2O3-Al2O 3-CaO-MgO system. Over the years, in collaboration with many industrial companies, a thermodynamic database for the SiO2-B2O 3-Al2O3-Ca

  9. Experimental Parameters Affecting Stripping of Rare Earth Elements from Loaded Sorptive Media in Simulated Geothermal Brines

    SciTech Connect

    Dean Stull

    2016-05-24

    Experimental results from several studies exploring the impact of pH and acid volume on the stripping of rare earth elements (REEs) loaded onto ligand-based media via an active column. The REEs in this experiment were loaded onto the media through exposure to a simulated geothermal brine with known mineral concentrations. The data include the experiment results, rare earth element concentrations, and the experimental parameters varied.

  10. (BRI) Direct and Inverse Design Optimization of Magnetic Alloys with Minimized Use of Rare Earth Elements

    DTIC Science & Technology

    2016-02-02

    AFRL-AFOSR-VA-TR-2016-0091 (BRI) Direct and Inverse Design Optimization of Magnetic Alloys with Minimized Use of Rare Earth Elements George...2012 – 31/10/2015 4. TITLE AND SUBTITLE (BRI) Direct and Inverse Design Optimization of Magnetic Alloys with Minimized Use of Rare Earth Elements... Science and Eng., Raleigh, NC (Profs. Justin Schwartz and Carl C. Koch). Their team performed all manufacturing and experimental measurements. 14

  11. Magnetic properties in α-MnO2 doped with alkaline elements

    PubMed Central

    Tseng, Li-Ting; Lu, Yunhao; Fan, Hai Ming; Wang, Yiren; Luo, Xi; Liu, Tao; Munroe, Paul; Li, Sean; Yi, Jiabao

    2015-01-01

    α-MnO2 nanotubes were fabricated using a hydrothermal technique. Li, Na and K ions were introduced into MnO2 nanotubes to tailor their magnetic properties. It was found that with a doping concentration lower than 12 at%, the nanotubes showed ferromagnetic-like ordering at low temperature (<50 K), while antiferromagnetic coupling dominated their physical behavior with doping concentrations beyond 12 at%. Such experimental phenomenon was in very good agreement with associated first principle calculations. The ferromagnetic-like ordering originates from the breaking of equivalence between two different Mn-O octahedrals in α-MnO2 due to the filling of alkaline ions in the tunnels. Both small charge transfer and lattice distortion play important roles in the ferromagnetic ordering. PMID:25766870

  12. 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.

  13. 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%).

  14. An Integrated Rare Earth Elements Supply Chain Strategy

    DTIC Science & Technology

    2011-02-24

    Disruption in the global supply of rare earths poses a significant concern for America‘s energy security and clean energy objectives, its future defense...World Trade Organization rules by limiting clean energy imports, while incentivizing clean energy exports.54 If accurate, this speculation supports...resource scarcity and secure our supply chains. The NSS further declares the U.S. ―has a window of opportunity to lead in the development of clean energy technology

  15. 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.

  16. Clinopyroxene with diverse origins in alkaline basalts from the western Pannonian Basin: Implications from trace element characteristics

    NASA Astrophysics Data System (ADS)

    Jankovics, M. Éva; Taracsák, Zoltán; Dobosi, Gábor; Embey-Isztin, Antal; Batki, Anikó; Harangi, Szabolcs; Hauzenberger, Christoph A.

    2016-10-01

    Clinopyroxene crystals of various origins occur in the unusually crystal- and xenolith-rich alkaline basalts of the Bondoró-hegy and the Füzes-tó scoria cone, which are the youngest eruptive centres in the Bakony-Balaton Highland Volcanic Field, western Pannonian Basin. The clinopyroxenes show diverse textural and zoning features as well as highly variable major and trace element chemistry. Xenocryst, megacryst and phenocryst crystal populations can be distinguished on the basis of their compositional differences. The trace element patterns of green clinopyroxene cores display a large range in composition and indicate that most of them have a metamorphic origin. Most of them were incorporated from lower crustal mafic granulite wall rocks, while only a few of them are of magmatic origin representing pyroxenite (Type II) cumulates. The colourless clinopyroxene xenocrysts reflect the texturally and geochemically diverse nature of the subcontinental lithospheric mantle beneath the studied area, mainly representing regions characterised by various stages of metasomatism. The colourless and green megacrysts are genetically related to each other, having crystallised as early and late crystallisation products, respectively, from petrogenetically related melts as part of a fractional crystallisation sequence. These melts represent earlier alkaline basaltic magmas (as represented by the Type II xenoliths), having stalled and crystallised near the crust-mantle boundary in the uppermost part of the mantle. This serves as evidence that the deep magmatic systems beneath monogenetic volcanic fields are complex, involving several phases of melt generation, accumulation and fractionation at variable depths. We show that in situ trace element analysis is necessary in order to unravel the origins and relationships of the diverse clinopyroxene populations. Such studies significantly contribute to our understanding of the ascent histories of alkaline basaltic magmas and provide

  17. 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

  18. 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.

  19. Partitioning of rare earth elements, yttrium, and some major elements among source rocks, liquid and vapor of Larderello-Travale geothermal field, Tuscany (Central Italy)

    NASA Astrophysics Data System (ADS)

    Möller, P.; Dulski, P.; Morteani, G.

    2003-01-01

    Rare earth elements (REE), yttrium and some major element concentrations have been measured in the high-enthalpy fluids (HEF) of several geothermal wells and the fluid's source rocks in the Larderello-Travale area (Tuscany/Central Italy). The REE and Y abundances in the HEF range from 0.1 to about 10 pmol/kg and are slightly higher in the HEF originating from evaporite/carbonate sequences (Calcare Cavernoso) than in those from phyllites. The resulting REY distribution factors between HEF and source rocks, appKdsource-rockHEF defined as the ratios of REY/Ca in both phases, range from <0.01 to 0.03 and 0.03 to 0.1 for phyllites and evaporite-limestone sequences (Calcare Cavernoso), respectively. REE+Y are more retained by the source rocks than Ca. HEF show no inherited and, with exception of a small Y anomaly, no acquired anomalies. This indicates a static equilibrium between HEF and the source rocks. The absence of any Eu anomalies points to temperatures less than 250°C in the source region. The small negative Y anomalies are the result of Y depletion in the rock fractions taking part in the water-rock interaction. Due to depressurization of the HEF to about 120°C and 2 bars, a liquid and a vapor phase is produced, which were sampled for the determination of the REE+Y partitioning between the two phases. The apparent partition factors between vapor and liquid appDliquidvapor of REE+Y range between 0.05 to 0.2 and about 3 for HEF originating from the phyllites and evaporites/carbonates, respectively. Among all ionic species determined, only NH 4+ has an apparent partition factor appDliquidvapor above one. In general, REY partition more easily into the vapor phase than the earth alkaline and alkaline elements. No significant correlation of REE+Y in the vapor phase with any of the determined ionic species could be detected. This probably points to the dominant presence of ion pairing such as REY(OH) 3o or REYO(OH) o.

  20. 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.

  1. Rare earth element recycling from waste nickel-metal hydride batteries.

    PubMed

    Yang, Xiuli; Zhang, Junwei; Fang, Xihui

    2014-08-30

    With an increase in number of waste nickel-metal hydride batteries, and because of the importance of rare earth elements, the recycling of rare earth elements is becoming increasingly important. In this paper, we investigate the effects of temperature, hydrochloric acid concentration, and leaching time to optimize leaching conditions and determine leach kinetics. The results indicate that an increase in temperature, hydrochloric acid concentration, and leaching time enhance the leaching rate of rare earth elements. A maximum rare earth elements recovery of 95.16% was achieved at optimal leaching conditions of 70°C, solid/liquid ratio of 1:10, 20% hydrochloric acid concentration, -74μm particle size, and 100min leaching time. The experimental data were best fitted by a chemical reaction-controlled model. The activation energy was 43.98kJ/mol and the reaction order for hydrochloric acid concentration was 0.64. The kinetic equation for the leaching process was found to be: 1-(1-x)(1/3)=A/ρr0[HCl](0.64)exp-439,8008.314Tt. After leaching and filtration, by adding saturated oxalic solution to the filtrate, rare earth element oxalates were obtained. After removing impurities by adding ammonia, filtering, washing with dilute hydrochloric acid, and calcining at 810°C, a final product of 99% pure rare earth oxides was obtained.

  2. Rare-earth elements in the Permian Phosphoria Formation: Paleo proxies of ocean geochemistry

    USGS Publications Warehouse

    Piper, D.Z.; Perkins, R.B.; Rowe, H.D.

    2007-01-01

    The geochemistry of deposition of the Meade Peak Member of the Phosphoria Formation (MPM) in southeast Idaho, USA, a world-class sedimentary phosphate deposit of Permian age that extends over 300,000 km2, is ascertained from its rare earth element (REE) composition. Ratios of REE:Al2O3 suggest two sources-seawater and terrigenous debris. The seawater-derived marine fraction identifies bottom water in the Phosphoria Sea as O2-depleted, denitrifying (suboxic) most of the time, and seldom sulfate-reducing (anoxic). This interpretation is supported by earlier research that showed progressively greater ratios in the marine sediment fraction of Cr:Ni>V:Ni???Mo:Ni, relative to their ratios in seawater; for which marine Cr, V, and Mo can have a dominantly O2-depleted bottom-water source and Ni a photic-zone, largely algal, source. The water chemistry was maintained by a balance between bacterial oxidation of organic matter settling through the water column, determined largely by primary productivity in the photic zone, and the flux of oxidants into the bottom water via advection of seawater from the open ocean. Samples strongly enriched in carbonate fluorapatite, the dominant REE host mineral, have variable Er/Sm, Tm/Sm, and Yb/Sm ratios. Their distribution may represent greater advection of seawater between the Phosphoria Sea and open ocean during deposition of two ore zones than a center waste and greater upwelling of nutrient-enriched water into the photic zone. However, the mean rate of deposition of marine Ni, a trace nutrient of algae, and PO43-, a limiting nutrient, indicate that primary productivity was probably high throughout the depositional history. An alternative interpretation of the variable enrichments of Er, Tm, and Yb, relative to Sm, is that they may reflect temporally variable carbonate alkalinity of open-ocean seawater in Permian time. A more strongly negative Ce anomaly for all phosphatic units than the Ce anomaly of modern pelletal phosphate is

  3. Preconcentration and determination of rare-earth elements in iron-rich water samples by extraction chromatography and plasma source mass spectrometry (ICP-MS).

    PubMed

    Hernández González, Carolina; Cabezas, Alberto J Quejido; Díaz, Marta Fernández

    2005-11-15

    A 100-fold preconcentration procedure based on rare-earth elements (REEs) separation from water samples with an extraction chromatographic column has been developed. The separation of REEs from matrix elements (mainly Fe, alkaline and alkaline-earth elements) in water samples was performed loading the samples, previously acidified to pH 2.0 with HNO(3), in a 2ml column preconditioned with 20ml 0.01M HNO(3). Subsequently, REEs were quantitatively eluted with 20ml 7M HNO(3). This solution was evaporated to dryness and the final residue was dissolved in 10ml 2% HNO(3) containing 1mugl(-1) of cesium used as internal standard. The solution was directly analysed by inductively coupled plasma mass spectrometry (ICP-MS), using ultrasonic nebulization, obtaining quantification limits ranging from 0.05 to 0.10 ngl(-1). The proposed method has been applied to granitic waters running through fracture fillings coated by iron and manganese oxy-hydroxides in the area of the Ratones (Cáceres, Spain) old uranium mine.

  4. Experimental productivity rate optimization of rare earth element separation through preparative solid phase extraction chromatography.

    PubMed

    Knutson, Hans-Kristian; Max-Hansen, Mark; Jönsson, Christian; Borg, Niklas; Nilsson, Bernt

    2014-06-27

    Separating individual rare earth elements from a complex mixture with several elements is difficult and this is emphasized for the middle elements: Samarium, Europium and Gadolinium. In this study we have accomplished an overloaded one-step separation of these rare earth elements through preparative ion-exchange high-performance liquid chromatography with an bis (2-ethylhexyl) phosphoric acid impregnated column and nitric acid as eluent. An inductively coupled plasma mass spectrometry unit was used for post column element detection. The main focus was to optimize the productivity rate, subject to a yield requirement of 80% and a purity requirement of 99% for each element, by varying the flow rate and batch load size. The optimal productivity rate in this study was 1.32kgSamarium/(hmcolumn(3)), 0.38kgEuropium/(hmcolumn(3)) and 0.81kgGadolinium/(hmcolumn(3)).

  5. Highly siderophile element constraints on accretion and differentiation of the Earth-Moon system.

    PubMed

    Day, James M D; Pearson, D Graham; Taylor, Lawrence A

    2007-01-12

    A new combined rhenium-osmium- and platinum-group element data set for basalts from the Moon establishes that the basalts have uniformly low abundances of highly siderophile elements. The data set indicates a lunar mantle with long-term, chondritic, highly siderophile element ratios, but with absolute abundances that are over 20 times lower than those in Earth's mantle. The results are consistent with silicate-metal equilibrium during a giant impact and core formation in both bodies, followed by post-core-formation late accretion that replenished their mantles with highly siderophile elements. The lunar mantle experienced late accretion that was similar in composition to that of Earth but volumetrically less than (approximately 0.02% lunar mass) and terminated earlier than for Earth.

  6. 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.

  7. Vanadium oxide bronzes containing rare-earth elements

    SciTech Connect

    Volkov, V.L.; Zubkov, V.G.; Fedyukov, A.S.; Zainulin, Yu.G.

    1988-05-01

    We attempted to make phases having the general formula Ln/sub x/V/sub 2/O/sub 5/ (Ln = La, Eu, Yb) without success; the specimens usually consisted of three phases: the rare-earth orthovanadate LnVO/sub 4/, vanadium(V) oxide, and VO/sub 2/. To shift the process to give Ln/sub x/V/sub 2/O/sub 5/, heat treatment was applied to mixtures of the initial high-purity substances. The x-ray patterns were recorded with a DRON-UM1 apparatus with Cr K..cap alpha.. radiation and were processed by the Poroshok program. The IR spectra were recorded with UR-20 spectrometer with oil mulls.

  8. Mobile DNA Elements: The Seeds of Organic Complexity on Earth.

    PubMed

    Habibi, Laleh; Pedram, Mehrdad; AmirPhirozy, Akbar; Bonyadi, Khadijeh

    2015-10-01

    Mobile DNA or transposable elements (TEs) are genomic sequences capable of moving themselves independently into different parts of the genome. Viral invasion of eukaryotic genomes is assumed to be the main source of TEs. Selfish transposition of these elements could be a serious threat to the host cell, as they can insert themselves into the middle of coding genes and/or induce genomic instability. In response, through millions of years of evolution, cells have come up with various mechanisms such as genomic imprinting, DNA methylation, heterochromatin formation, and RNA interference to deactivate them. Interestingly, these processes have also greatly contributed to important cellular functions involved in cell differentiation, development, and differential gene expression. Propagation of TE copies during the course of evolution have resulted in increasing the genome size and providing proper space and flexibility in shaping the genome by creating new genes and establishing essential cellular structures such as heterochromatin, centromere, and telomeres. Yet, these elements are mostly labeled for playing a role in pathogenesis of human diseases. Here, we attempt to introduce TEs as factors necessary for making us human rather than just selfish sequences or obligatory guests invading our DNA.

  9. [Application of ICP-MS to Detect Rare Earth Elements in Three Economic Macroalgaes in China].

    PubMed

    Zhao, Yan-fang; Shang, De-rong; Zhai, Yu-xiu; Ning, Jin-song; Ding, Hai-yan; Sheng, Xiao-feng

    2015-11-01

    In order to investigate the content and distribution of rare earth elements (REE) in main economic macroalgaes in our country, fifteen rare earth elements in three economic macroalgaes (including 30 samples of kelp, 30 samples of laver and 15 samples of Enteromorpha) were detected using ICP-MS method. Results showed that the total content of REE in different species of macroalgaes was different. The highest total content of REE was in Enteromorpha (16,012.0 ng · g⁻¹), while in kelp and laver, the total REE was similar for two macroalgaes (3887.4 and 4318.1 ng · g⁻¹ respectively). The content of fifteen rare earth elements in kelp ranged from 7.9 to 1496.4 ng · g⁻¹; in laver, it ranged from 8.2 to 1836.6 ng · g⁻¹. For Enteromorpha, the concentration of 15 rare earth elements were between 19.2 and 6014.5 ng · g⁻¹. In addition, the content and distribution of different rare earth elements in different macroalgaes was also different. For kelp, the highest content of REE was Ce (1 496.4 ng · g⁻¹), and the second was La (689.1 ng · g⁻¹). For laver, the highest was Y (1836.6 ng · g⁻¹), and the second was Ce (682.2 ng · g⁻¹). For Enteromorpha, the highest was Ce (6014.5 ng · g⁻¹), and the second was La (2902.9 ng · g⁻¹). Present results also showed that three macroalgaes accumulated the light rare earth elements much more than the high rare earth elements. The light rare earth elements occupied 90.9%, 87.3% and 91.1% for kelp, laver and Enteromorpha respectively. The result that the Enteromorpha had high content of rare earth elements could provide important support for opening new research directions for the utilization of Enteromorpha.

  10. Research of the entry of rare earth elements Eu3+ and La3+ into plant cell.

    PubMed

    Gao, Yongsheng; Zeng, Fuli; Yi, An; Ping, Shi; Jing, Lanhua

    2003-03-01

    Whether rare earth elements can enter into plant cells remains controversial. This article discusses the ultracellular structural localization of lanthanum (La(3+)) and europium (Eu(3+)) in the intact plant cells fed by rare earth elements Eu(3+) and La(3+). Eu-TTA fluorescence analysis of the plasmalemma, cytoplast, and mitochondria showed that Eu(3+) fluorescence intensities in such structures significantly increased. Eu(3+) can directly enter or be carried by the artificial ion carrier A23187 into plant cells through the calcium ion (Ca(2+)) channel and then partially resume the synthesis of amaranthin in the Amaranthus caudatus growing in the dark. Locations of rare earth elements La(3+) and Eu(3+) in all kinds of components of cytoplasmatic organelles were determined with transmission electron microscope, scanning electron microscope, and energy-dispersive X-ray microanalysis. The results of energy-dispersive X-ray microanalysis indicated that Eu(3+) and La(3+) can be absorbed into plant cells and bind to the membranes of protoplasm, chloroplast, mitochondrion, cytoplast, and karyon. These results provide experimental evidence that rare earth elements can be absorbed into plant cells, which would be the basis for interpreting physiological and biochemical effects of rare earth elements on plant cells.

  11. Rare earths and other trace elements in Apollo 14 samples.

    NASA Technical Reports Server (NTRS)

    Helmke, P. A.; Haskin, L. A.; Korotev, R. L.; Ziege, K. E.

    1972-01-01

    REE and other trace elements have been determined in igneous rocks 14053, 14072, and 14310, in breccias 14063 and 14313, and in fines 14163. All materials analyzed have typical depletions of Eu except for feldspar fragments from the breccias and igneous fragments from 14063. Igneous rocks 14072 and 14053 have REE concentrations very similar to Apollo 12 basalts; 14310 has the highest REE concentrations yet observed for a large fragment of lunar basalt. The effects of crystallization of a basaltic liquid as a closed system on the concentrations of Sm and Eu in feldspar are considered. Small anorthositic fragments may have originated by simple crystallization from very highly differentiated basalt (KREEP) or by closed-system crystallization in a less differentiated starting material. Application of independent models of igneous differentiation to Sm and Eu in massive anorthosite 15415 and to Sm and Eu in lunar basalts suggests a common starting material with a ratio of concentrations of Sm and Eu about the same as that in chondrites and with concentrations of those elements about 15 times enriched over chondrites.

  12. Rare earth elements upon assessment of reasons of the geophagy in Sikhote-Alin region (Russian Federation), Africa and other world regions.

    PubMed

    Panichev, Alexander M; Popov, Vladimir K; Chekryzhov, Igor Yu; Seryodkin, Ivan V; Stolyarova, Tatiana A; Zakusin, Sergey V; Sergievich, Alexandr A; Khoroshikh, Pavel P

    2016-12-01

    Rocks eaten by wild animals on the Bolshoy Shanduyskiy kudur in the Sikhote-Alin region (Russian Federation) are zeolite-clay mineral complexes-products of weathering of zeolitized vitric tuffs of rhyolite composition, deposited in aqueous medium within the volcanic caldera of about 55 million years ago. By composition of rock-forming oxides, the tuffs refer to high-potassium calc-alkaline series. In trace elements of most favorite kudurites of the Bolshoy Shanduyskiy kudur, there are significantly increased contents of most of rare earth elements (2-5 times in comparison with surrounding rocks). The results of our analysis of geological and geochemical data on kudurs and kudurites in another part of the Sikhote-Alin, as well as on other regions of the world (particularly, in Africa and Indonesia), taking into account new data on the prevalence of rare earth elements in living matter and their medical and biological properties, enable us to consider the version of causal connection of the geophagy with rare earth elements.

  13. Volume characteristics and element transfer of fenite aureoles: a case study from the Iivaara alkaline complex, Finland

    NASA Astrophysics Data System (ADS)

    Sindern, Sven; Kramm, Ulrich

    2000-03-01

    Fenitization in granodioritic rocks has been investigated taking the Iivaara alkaline complex (Finland) as a case study. Five main fenitization reactions responsible for the transition from a granodioritic precursor mineral assemblage to a syenitic or even cancrinite-syenitic mineral assemblage of the fenites are set up. An assessment of element transfer and volume change associated with each of these reactions indicates a general volume loss of about 20% due to fenitization. High activities of Na, Ca, Mg and Fe as well as a low H 2O/CO 2 ratio in the fenitizing fluid phase are indicated. Si, which is the main component released from the precursor rock, was redistributed within the aureole and formed pyroxene dominated mineral assemblages in a reaction with the fenitizing fluid. These vein-type pyroxenites can be found cross-cutting all fenite types. Compositional data of aegirine augite in the fenites reveal disequilibria and feldspar compositions point to minimum temperatures for the production of fenites with syenitic compositions of 660°C and also indicate fast cooling. A Sr isotope characterization of the fenites allows assessment of minimum fluid-rock weight-ratios in the fenite aureole of 0.023-2.3. The element transfer scheme developed in this study is applicable to other localities since many aureoles formed in granitic to granodioritic host rocks have petrographic characteristics similar to the Iivaara fenites.

  14. Levels of major and trace elements, including rare earth elements, and ²³⁸U in Croatian tap waters.

    PubMed

    Fiket, Željka; Rožmarić, Martina; Krmpotić, Matea; Benedik, Ljudmila

    2015-05-01

    Concentrations of 46 elements, including major, trace, and rare earth elements, and (238)U in Croatian tap waters were investigated. Selected sampling locations include tap waters from various hydrogeological regions, i.e., different types of aquifers, providing insight into the range of concentrations of studied elements and (238)U activity concentrations in Croatian tap waters. Obtained concentrations were compared with the Croatian maximum contaminant levels for trace elements in water intended for human consumption, as well as WHO and EPA drinking water standards. Concentrations in all analyzed tap waters were found in accordance with Croatian regulations, except tap water from Šibenik in which manganese in concentration above maximum permissible concentration (MPC) was measured. Furthermore, in tap water from Osijek, levels of arsenic exceeded the WHO guidelines and EPA regulations. In general, investigated tap waters were found to vary considerably in concentrations of studied elements, including (238)U activity concentrations. Causes of variability were further explored using statistical methods. Composition of studied tap waters was found to be predominately influenced by hydrogeological characteristics of the aquifer, at regional and local level, the existing redox conditions, and the household plumbing system. Rare earth element data, including abundances and fractionation patterns, complemented the characterization and facilitated the interpretation of factors affecting the composition of the analyzed tap waters.

  15. Genesis of the central zone of the Nolans Bore rare earth element deposit, Northern Territory, Australia

    NASA Astrophysics Data System (ADS)

    Schoneveld, Louise; Spandler, Carl; Hussey, Kelvin

    2015-08-01

    The Nolans Bore rare earth element (REE) deposit consists of a network of fluorapatite-bearing veins and breccias hosted within Proterozoic granulites of the Reynolds Range, Central Australia. Mineralisation is divided into three zones (north, central, and south-east), with the north and south-east zones consisting of massive REE-bearing fluorapatite veins, with minor brecciation and carbonate infill. The central zone is distinctively different in mineralogy and structure; it features extensive brecciation, a high allanite content, and a large, epidote-rich enveloping alteration zone. The central zone is a reworking of the original solid apatite veins that formed during the Chewings Orogeny at ca. 1525 Ma. These original apatite veins are thought to derive from phosphate-rich magmatic-hydrothermal fluid exsolved from as-yet unrecognised alkaline magmatic bodies at depth. We define four ore breccia types (BX1-4) in the central zone on the basis of detailed petrological and geochemical analysis of drillcore and thin sections. BX1 ore comprises fluorapatite with minor crackle brecciation with carbonate infill and resembles ore of the north and south-east zones. Breccia types BX2, BX3, and BX4 represent progressive stages of ore brecciation and development of calc-silicate mineral (amphibole, epidote, allanite, calcite) infill. Comparison of bulk ore sample geochemistry between breccia types indicates that REEs were not mobilised more than a few centimetres during hydrothermal alteration and brecciation. Instead, most of the REEs were partitioned from the original REE fluorapatite into newly formed allanite, REE-poor fluorapatite and minor REE carbonate in the breccias. Negative europium (Eu) anomalies in the breccia minerals are accounted for by a large positive Eu anomaly in epidote from the alteration zones surrounding the ore breccias. This observation provides a direct link between ore recrystallisation and brecciation, and the formation of the alteration halo in

  16. U.S. trade dispute with China over rare earth elements

    NASA Astrophysics Data System (ADS)

    Showstack, Randy

    2012-03-01

    The U.S. government has brought a new trade case against China over rare earth elements (REE) as well as tungsten and molybdenum, President Barack Obama announced on 13 March. Japan and the European Union also have taken similar actions against China about REEs, which are a group of 17 chemically similar metallic elements that are used in a variety of electronic, optical, magnetic, and catalytic applications. REEs are plentiful in the Earth's crust, although China currently has about 37% of the world's reserves and accounts for more than 95% of the world's production of the elements, according to the British Geological Survey. The United States has requested consultations with China at the World Trade Organization (WTO) concerning "China's unfair export restraints on rare earths, as well as tungsten and molybdenum," the Office of the United States Trade Representative announced in a 13 March statement.

  17. Alkali element depletion by core formation and vaporization on the early Earth

    NASA Technical Reports Server (NTRS)

    Lodders, K.; Fegley, B., Jr.

    1994-01-01

    The depletion of Na, K, Rb, and Cs in the Earth's upper mantle and crust relative to their abundances in chondrites is a long standing problem in geochemistry. Here we consider two commonly invoked mechanisms, namely core formation, and vaporization, for producing the observed depletions. Our models predict that a significant percentage of the Earth's bulk alkali element inventory is in the core (30 percent for Na, 52 percent for K, 74 percent for Rb, and 92 percent for Cs). These predictions agree with independent estimates from nebular volatility trends and (for K) from terrestrial heat flow data. Our models also predict that vaporization and thermal escape during planetary accretion are unlikely to produce the observed alkali element depletion pattern. However, loss during the putative giant impact which formed the Moon cannot be ruled out. Experimental, observational, and theoretical tests of our predictions are also described. Alkali element partitioning into the Earth's core was modeled by assuming that alkali element partitioning during core formation on the aubrite parent body (APB) is analogous to that on the early Earth. The analogy is reasonable for three reasons. First, the enstatite meteorites are the only known meteorites with the same oxygen isotope systematics as the Earth-Moon system. Second, the large core size of the Earth and the V depletion in the mantle requires accretion from planetesimals as reduced as the enstatite chondrites. Third, experimental studies of K partitioning between silicate and metal plus sulfide show that more K goes into the metal plus sulfide at higher pressures than at one atmosphere pressure. Thus partitioning in the relatively low pressure natural laboratory of the APB is a good guide to alkali elemental partitioning during the growth of the Earth.

  18. 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.

  19. Addressing Rare-Earth Element Criticality: An Example from the Aviation Industry

    NASA Astrophysics Data System (ADS)

    Ku, Anthony Y.; Dosch, Christopher; Grossman, Theodore R.; Herzog, Joseph L.; Maricocchi, Antonio F.; Polli, Drew; Lipkin, Don M.

    2014-11-01

    Rare-earth (RE) elements are enablers for a wide range of technologies, including high-strength permanent magnets, energy-efficient lighting, high-temperature thermal barrier coatings, and catalysts. While direct material substitution is difficult in many of these applications because of the specific electronic, optical, or electrochemical properties imparted by the individual rare-earth elements, we describe an example from the aviation industry where supply chain optimization may be an option. Ceramic matrix composite engine components require environmental barrier coatings (EBCs) to protect them from extreme temperatures and adverse reactions with water vapor in the hot gas path. EBC systems based on rare-earth silicates offer a unique combination of environmental resistance, thermal expansion matching, thermal conductivity, and thermal stability across the service temperature window. Several pure rare-earth silicates and solid solutions have been demonstrated in EBC applications. However, all rely on heavy rare-earth elements (HREEs) for phase stability. This article considers the possibility of using separation tailings containing a mixture of HREEs as a source material in lieu of using the high-purity HREE oxides. This option arises because the desired properties of RE-silicate EBCs derive from the average cation size rather than the electronic properties of the individual rare-earth cations. Because separation tailings have not incurred the costs associated with the final stages of separation, they offer an economical alternative to high-purity oxides for this emerging application.

  20. Development of Electronic Tongue for Detection of Rare Earth Elements in Natural Surroundings

    NASA Astrophysics Data System (ADS)

    Sarkar, Subrata; Purkait, Monirul; Roy, Jayanta Kumar; Datta, C.; Bhattacharyya, Nabarun; Sarkar, D.; Datta, Jagannath; Chowdhury, D. P.

    2011-09-01

    The rare earth elements (like lanthanum) and other metals like zirconium, arsenic, potassium, copper etc. are some of the elements, which are found in the natural surrounding. Since these metals have immense utility in the field of medical science, energy efficient electronic devices, nuclear energy domain, early and easy detection of such metals is very important. In the present work, voltammetric electronic tongue for detection and quantitative determination of these elements has been explored. A sensor array comprising of noble metals (like gold, iridium, rhodium etc) has been developed and it exhibits remarkable sensitivity and promising results for detection and analysis of these elements.

  1. 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.

  2. Rare Earth Element Fractionation During Evaporation of Chondritic Material

    NASA Astrophysics Data System (ADS)

    Wang, J.; Davis, A. M.; Clayton, R. N.

    1993-07-01

    Evaporation experiments suggest that enrichments in the heavy isotopes of oxygen, magnesium, and silicon in some CAIs are caused by kinetic effects during evaporation [1]. Volatility-fractionated REE patterns found in some CAIs have been modeled with some success using equilibrium thermodynamics [2,3], but little is known about kinetic effects on REE patterns. We have begun an investigation of REE fractionation under conditions where large isotope effects are produced by the kinetic isotope effect. We synthesized a starting material containing CI chondritic relative proportions of MgO, Al2O3, SiO2, CaO, TiO2, and FeO, and doped it with 100 ppm each of the REE. Samples of this material were evaporated in a vacuum furnace [4] at 10^-6 torr and 1800 or 2000 degrees C for periods of a few seconds to 5 hr. The mass fraction evaporated ranged from 7.6 to 95.4%. Most residues consist of olivine and glass. Chemical compositions of the residues were determined by electron and ion microprobe. Results for selected elements are shown in Fig. 1. There is no significant evaporation of Ca, Al, and Ti up to 95% mass loss; the evaporation behavior of Mg, Si, and Fe is similar to that found by Hashimoto [5]. There is no significant evaporation of most of the REE up to 95% mass loss. Ce is much more volatile than the other REE under these conditions: a tenfold negative Ce anomaly developed between 60 and 70% mass loss and the anomaly reached 5 X 10^-4 at 95% mass loss. A small Pr anomaly (50% Pr loss) also appeared in the highest-mass-loss residue. Thermodynamic calculations show that Ce has approximately the same volatility as other LREE under solar nebular oxygen fugacity, but is much more volatile than the other REE under oxidizing conditions [6]. We suspect that conditions in the residue in our vacuum evaporation experiments became oxidizing because evaporation reactions involving most major element oxides involve release of oxygen. The four known HAL-type hibonite

  3. 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.

  4. [Geochemical characteristics of rare earth elements on sunflower growing area in the west of Jilin Province].

    PubMed

    Li, Shu-Jie; Dou, Sen; Wang, Li-Min; Liu, Zhao-Shun

    2011-07-01

    Soil and plant samples were collected from the sunflower growing area in the west of Jilin province. A variety of ancillary methods were used to determine the soil element content. Then the rare earth elements geochemistry in soil was studied, and the correlation of REEs in this region with other elements and the quality of plant was investigated. The results show that, (1) REE content of the soil in Nong'an is relatively higher to those in Daan and Tongyu. Distribution pattern of rare earth elements in soil for the right tilt of the light rare earth enrichment patterns which is consistent with the national distribution pattern of rare earth elements; (2) REE contents in the three studying areas in the soil are different, and this primarily relates to the soil parent materials; (3) The REEs which positively correlate with soil available potassium are Se, Fe2O3, Ti, P, Mn, Cu, Zn, Cr, Mo, B, F. The protein content of sunflower seeds has a negative correlation with REE. With the exception of Lu, all REEs show a similar correlation.

  5. Rare earth element content of thermal fluids from Surprise Valley, California

    DOE Data Explorer

    Andrew Fowler

    2015-09-23

    Rare earth element measurements for thermal fluids from Surprise Valley, California. Samples were collected in acid washed HDPE bottles and acidified with concentrated trace element clean (Fisher Scientific) nitric acid. Samples were pre-concentratated by a factor of approximately 10 using chelating resin with and IDA functional group and measured on magnetic sector ICP-MS. Samples include Seyferth Hot Springs, Surprise Valley Resort Mineral Well, Leonard's Hot Spring, and Lake City Mud Volcano Boiling Spring.

  6. Determination of rare-earth elements in Luna 16 regolith sample by chemical spectral method

    NASA Technical Reports Server (NTRS)

    Stroganova, N. S.; Ryabukhin, V. A.; Laktinova, N. V.; Ageyeva, L. V.; Galkina, I. P.; Gatinskaya, N. G.; Yermakov, A. N.; Karyakin, A. V.

    1974-01-01

    An analysis was made of regolith from layer A of the Luna 16 sample for rare earth elements, by a chemical spectral method. Chemical and ion exchange concentrations were used to determine the content of 12 elements and Y at the level 0.001 to 0.0001 percent with 10 to 15 percent reproducibility of the emission determination. Results within the limits of reproducibility agree with data obtained by mass spectra, activation, and X-ray fluorescent methods.

  7. Imaging Earth's Interior based on Spectral-Element and Adjoint Methods (Invited)

    NASA Astrophysics Data System (ADS)

    Tromp, J.; Zhu, H.; Bozdag, E.

    2013-12-01

    We use spectral-element and adjoint methods to iteratively improve 3D tomographic images of Earth's interior, ranging from global to continental to exploration scales. The spectral-element method, a high-order finite-element method with the advantage of a diagonal mass matrix, is used to accurately calculate three-component synthetic seismograms in a complex 3D Earth model. An adjoint method is used to numerically compute Frechét derivatives of a misfit function based on the interaction between the wavefield for a reference Earth model and a wavefield obtained by using time-reversed differences between data and synthetics at all receivers as simultaneous sources. In combination with gradient-based optimization methods, such as a preconditioned conjugate gradient or L-BSGF method, we are able to iteratively improve 3D images of Earth's interior and gradually minimize discrepancies between observed and simulated seismograms. Various misfit functions may be chosen to quantify these discrepancies, such as cross-correlation traveltime differences, frequency-dependent phase and amplitude anomalies as well as full-waveform differences. Various physical properties of the Earth are constrained based on this method, such as elastic wavespeeds, radial anisotropy, shear attenuation and impedance contrasts. We apply this method to study seismic inverse problems at various scales, from global- and continental-scale seismic tomography to exploration-scale full-waveform inversion.

  8. Radioluminescence and thermoluminescence of rare earth element and phosphorus-doped zircon

    SciTech Connect

    Karali, T.; Can, N.; Townsend, P.D.; Rowlands, A.P.; Hanchar, J.M.

    2000-06-01

    The radioluminescence and thermoluminescence spectra of synthetic zircon crystals doped with individual trivalent rare earth element (REE) ions (Pr, Sm, Eu, Gd, Dy, Ho, Er, and Yb) and P are reported in the temperature range 25 to 673 K. Although there is some intrinsic UV/blue emission from the host lattice, the dominant signals are from the rare-earth sites, with signals characteristic of the REE{sup 3+} states. The shapes of the glow curves are different for each dopant, and there are distinct differences between glow peak temperatures for different rare-earth lines of the same element. Within the overall set of signals there are indications of linear trends in which some glow peak temperatures vary as a function of the ionic size of the rare earth ions. The temperature shifts of the peaks are considerable, up to 200{degree}, and much larger than those cited in other rare-earth-doped crystals of LaF{sub 3} and Bi{sub 4}Ge{sub 3}O{sub 12}. The data clearly suggest that the rare-earth ions are active both in the trapping and luminescence steps, and hence the TL occurs within localized defect complexes that include REE{sup 3+} ions.

  9. Genetic implications of minor-element and Sr-isotope geochemistry of alkaline rock complexes in the Wet Mountains area, Fremont and Custer counties, Colorado

    USGS Publications Warehouse

    Armbrustmacher, T.J.; Hedge, C.E.

    1982-01-01

    Concentrations of Rb, Sr, and REE (rare earth elements), and Sr-isotopic ratios in rocks of the Cambrian alkaline complexes in the Wet Mountains area, Colorado, show that rocks formed as end-products of a variety of magmas generated from different source materials. The complexes generally contain a bimodal suite of cumulus mafic-ultramafic rocks and younger leucocratic rocks that include nepheline syenite and hornblende-biotite syenite in the McClure Mountain Complex, nepheline syenite pegmatite in the Gem Park Complex, and quartz syenite in the complex at Democrat Creek. The nepheline syenite and hornblende-biotite syenite at McClure Mountain (535??5m.y.) are older than the syenitic rocks at Democrat Creek (511??8m.y.). REE concentrations indicate that the nepheline syenite at McClure Mountain cannot be derived from the hornblende-biotite syenite, which it intrudes, or from the associated mafic-ultramafic rocks. REE also indicate that mafic-ultramafic rocks at McClure Mountain have a source distinct from that of the mafic-ultramafic rocks at Democrat Creek. In the McClure Mountain Complex, initial87Sr/86Sr ratios for mafic-ultramafic rocks (0.7046??0.0002) are similar to those of hornblende-biotite syenite (0.7045??0.0002), suggesting a similar magmatic source, whereas ratios for carbonatites (0.7038??0.0002) are similar to those of nepheline syenite (0.7038??0.0002). At Democrat Creek, initial ratios of syenitic rocks (0.7032??0.0002) and mafic-ultramafic rocks (0.7028??0.0002) are different from those of corresponding rocks at McClure Mountain. ?? 1982 Springer-Verlag.

  10. Composition of the earth's upper mantle. I - Siderophile trace elements in ultramafic nodules

    NASA Technical Reports Server (NTRS)

    Morgan, J. W.; Wandless, G. A.; Petrie, R. K.; Irving, A. J.

    1981-01-01

    The considered investigation is concerned with a reexamination of the question of the distribution of siderophile elements in the earth's upper mantle, taking into account a more unified data base which is now available. A comprehensive suite of ultramafic inclusions was collected as part of the Basaltic Volcanism Study Project and has been analyzed by instrument neutron activation analysis for major, minor, and some lithophile trace elements. In addition, 18 of these rocks and the important sheared garnet lherzolite PHN 1611 have been analyzed by means of radiochemical neutron activation analysis for 7 siderophile elements (Au, Ge, Ir, Ni, Os, Pd, and Re) and 9 volatile elements (Ag, Bi, Cd, In, Sb, Se, Te, Tl, and Zn). The siderophile element data reveal interesting inter-element correlations, which were not apparent from the compiled abundance tables of Ringwood and Kesson (1976) and Chou (1978).

  11. Fluid rare earth element anlayses from wells RN-12 and RN-19, Reykjanes, Iceland

    SciTech Connect

    Andrew Fowler

    2015-07-24

    Results for fluid rare earth elment analyses from Reykjanes wells RN-12 and RN-19. The data have not been corrected for flashing. Samples preconcetrated using chelating resin with IDA functional group (InertSep ME-1). Analyzed using and Element magnetic sctor ICP-MS.

  12. Interactions between exogenous rare earth elements and phosphorus leaching in packed soil columns

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Rare earth elements (REEs) increasingly used in agriculture as an amendment for crop growth may help to lessen environmental losses of phosphorus (P) from heavily fertilized soils. The vertical transport characteristics of P and REEs, lanthanum (La), neodymium (Nd), samarium (Sm), and cerium (Ce), w...

  13. Compilation of Rare Earth Element Analyses from US Geothermal Fields and Mid Ocean Ridge Hydrothermal Vents

    SciTech Connect

    Andrew Fowler

    2015-10-01

    Compilation of rare earth element and associated major and minor dissolved constituent analytical data for USA geothermal fields and global seafloor hydrothermal vents. Data is in original units. Reference to and use of this data should be attributed to the original authors and publications according to the provisions outlined therein.

  14. Method to Recover Media Ligand Losses During Sorption of Rare Earth Elements from Simulated Geothermal Brines

    SciTech Connect

    Dean Stull

    2016-05-24

    This document describes the method and results of an in-situ experiment used to confirm that ligand bleed from a sorptive media can be contained. The experiment focused on maintaining the media's sorption of rare earth elements (REE) obtained from a simulated geothermal brine doped with known mineral concentrations.

  15. Technical Information Resource on Rare Earth Elements Now Available to Public and Private Sector Stakeholders

    EPA Science Inventory

    A new EPA technical information resource, “Rare Earth Elements: A Review of Production, Processing, Recycling, and Associated Environmental Issues” has been produced as an introductory resource for those interested in learning more about REE mining and alternatives to meet demand...

  16. Preliminary study on using rare earth elements to trace non-point source phosphorous loss

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The environmental fate of phosphorus (P) is of concern as P is a primary cause of freshwater eutrophication. Rare earth elements (REEs) have been successfully used in the analysis of soil erosion and pollutant sources, as well as in the analysis of mineral genesis. To better understand the potential...

  17. Tracing sediment movement on semi-arid watershed using Rare Earth Elements 1988

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A multi-tracer method employing rare earth elements (REE) was used to determine sediment yield and to track sediment movement in a small semiarid watershed. A 0.33 ha watershed near Tombstone, AZ was divided into five morphological units, each tagged with one of five REE oxides. Relative contributi...

  18. 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.

  19. 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.

  20. Geochemical characteristics of rare earth elements in soil of the Ditru Massif, Eastern Carpathians, Romania

    NASA Astrophysics Data System (ADS)

    Ion, Adriana

    2013-04-01

    The present paper describes the level of rare earth elements in soils developed from Ditrău massif area for evaluating of the background of these elements and accurate assessment of environmental impact. Also this paper contributed to understanding the important role of parent rocks in pedogenic processes. The Ditrău Alkaline Massif represent an intrusion body with a internal zonal structure, which was emplaced into pre-Alpine metamorphic rocks of the Bucovinian nappe complex close the Neogene - Quaternary volcanic arc of the Calimani-Guurghiu- Harghita Mountain chain. The center of massif was formed by nepheline syenite, which is surrounded by syenite and monazonite. North-western and north-eastern marginal sectors are composed of hornblende gabbro/hornblendite, alkali diorite, monzodiorite, monzosyenites and alkali granite. Small discrete ultramafic bodies (kaersutite-bearing peridotite, olivine, pyroxenite and hornblendite) and alkali gabbros occur in the Jolotca area. All this rocks are cut by late-stage dykes with a large variety of composition including tinguaite, phonolite, nepheline syenite, microsyenite, and aplite. The types of soils predominant in this zone are lithosoils. These soils are shallow developed, have low content in organic matter and reflects mineralogical and geochemical composition of the bedrock. The soil samples were collected from 70 location for all type of representative rocks (approximately 10 soil sampling points for each type of rock). The samples were analyzed by inductively coupled plasma mass spectrometry (ICP-MS). The pH values of these samples varied from 3.6 to 7.3, in general, the soils from massif area are acid or weakly acidic. The pH controls the abundance of REE in soil, the concentration of REE increases with decreasing pH values. In soil samples analyzed the contents of REE follow the order: Ce > La > Nd > Pr > Sm > Eu > Gd > Dy > Yb > Er > Tb > Ho >Tm. ∑ REE varied from 52.59 μg g-1 to 579.2 μg g-1 , the average

  1. Rare earth element patterns as correlation tools and tectonic indicators for the Paleogene Dillon Volcanics, southwestern Montana

    SciTech Connect

    McDowell, R.J.; Fritz, W.J.; Ghazi, A.M. . Dept. of Geology)

    1993-04-01

    The Dillon Volcanics of the Paleogene Renova Formation consist of epiclastic, pyroclastic, and volcanic rocks. The latter are composed of alkaline and transitional basalts and rhyolites. Major and trace element variation diagrams indicate that both rock types had a similar parent magma source, and that the rhyolites were mainly derived from a basaltic parent magma. This is confirmed by very similar rare earth element (REE) patterns. The REE patterns are typical of continental rift zone volcanics, and indicate that bimodal rift zone volcanism occurred in a back-arc setting 30 m.y. before basin-and-range extension. Subsequent normal faulting, combined with Neogene erosion, has separated the dillon Volcanics into isolated outcrops that cannot be accurately correlated in the field. Major and trace element compositional trends are not good correlation tools, but chondrite-normalized REE patterns are almost parallel for the rhyolites and can be used to correlate now-isolated outcrops. REE patterns for the basalts do not show the same degree of similarity, but their patterns do indicate a common magmatic source. REE patterns for continental rift settings typically show enrichment in light REE's, reflecting derivation from a light REE-enriched mantle source such as sub-continental lithosphere. As eruption of the Dillon volcanics was partly contemporaneous with arc volcanism related to the Laramide orogeny, the sub-continental lithosphere may have been enriched in light REE's bu subduction zone fluids derived from the down-going Farallon plate. However, it might not be possible to distinguish continental rift zone volcanics from continental back-arc basin volcanics. The authors favor the latter model because of the chronologic and geographic relationship of the dillon Volcanics with nearby continental arc volcanic fields.

  2. 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

  3. Concentrations of rare-earth elements in soils of the Prioksko-Terrasnyi state biospheric reserve

    NASA Astrophysics Data System (ADS)

    Perelomov, L. V.; Asainova, Zh. S.; Yoshida, S.; Ivanov, I. V.

    2012-10-01

    The concentrations of rare-earth elements were studied in the profiles of soddy podburs and mucky-humus gley soils. The soil horizons differed significantly in the contents of Corg (0-26%), the physical clay (<0.01 mm) fraction (3-31%), the acidity (pH 4 to 5.5), and the presence/absence of Al-Fe-humus accumulations. The most significant relationship was observed between the concentrations of rare-earth elements and the physical clay content, particularly for Nd: x(Nd, mg/kg) = 7 + 1.6 y (fraction <0.01 mm, %). Weak biogenic accumulations in the upper horizons were observed for Nd, Ce, and Dy; Nd, Pr, and La accumulated in the Al-Fe-humus illuvial horizon. The concentrations of rare-earth elements in the studied soils formed the following sequence (mg/kg): Nd (20-101)-Ce (10-44)-La, Sm, Gd, Dy, Yb (3-20)-Pr (1-4)-Ho (0.1-0.4)-Tm, Lu, and Tl (0.0). A clear trend was observed to higher contents of even-numbered elements as compared with odd-numbered elements, excluding La.

  4. Scanning Electron Microscope-Cathodoluminescence Analysis of Rare-Earth Elements in Magnets.

    PubMed

    Imashuku, Susumu; Wagatsuma, Kazuaki; Kawai, Jun

    2016-02-01

    Scanning electron microscope-cathodoluminescence (SEM-CL) analysis was performed for neodymium-iron-boron (NdFeB) and samarium-cobalt (Sm-Co) magnets to analyze the rare-earth elements present in the magnets. We examined the advantages of SEM-CL analysis over conventional analytical methods such as SEM-energy-dispersive X-ray (EDX) spectroscopy and SEM-wavelength-dispersive X-ray (WDX) spectroscopy for elemental analysis of rare-earth elements in NdFeB magnets. Luminescence spectra of chloride compounds of elements in the magnets were measured by the SEM-CL method. Chloride compounds were obtained by the dropwise addition of hydrochloric acid on the magnets followed by drying in vacuum. Neodymium, praseodymium, terbium, and dysprosium were separately detected in the NdFeB magnets, and samarium was detected in the Sm-Co magnet by the SEM-CL method. In contrast, it was difficult to distinguish terbium and dysprosium in the NdFeB magnet with a dysprosium concentration of 1.05 wt% by conventional SEM-EDX analysis. Terbium with a concentration of 0.02 wt% in an NdFeB magnet was detected by SEM-CL analysis, but not by conventional SEM-WDX analysis. SEM-CL analysis is advantageous over conventional SEM-EDX and SEM-WDX analyses for detecting trace rare-earth elements in NdFeB magnets, particularly dysprosium and terbium.

  5. Study on Orbital Decay of Near Earth Satellites with KS Orthogonal Elements

    NASA Astrophysics Data System (ADS)

    Ps, Sandeep

    STUDY ON ORBITAL DECAY OF NEAR EARTH SATELLITES WITH KS ORTHOGONAL ELEMENTS SANDEEP P S The knowledge of satellite orbit decay and its expected life prior to launch is necessary for mission planning purpose. Several sets of data for various parametric studies is sought quite often, it is necessary to minimize computational time involved for generating decay predictions, keeping the prediction accuracy normally good. A number of factors play dominant role in perturbation modelling for near earth satellites such as oblateness of the Earth, presence of the atmosphere, luni-solar attraction and solar radiation pressure. This paper concerns with the study of orbital decay of near earth satellites with KS orthogonal elements, which provide accurate orbit predictions at low computational time. Perturbations considered are due to oblateness of the Earth and the atmospheric drag. The Earth’s zonal harmonic terms J2 to J6 are included and the drag is modeled with an analytical diurnally oblate atmosphere. Effect of Earth’s geomagnetic and solar activity is included in density and density scale height computations. JACCHIA77 atmospheric model is utilized. The developed software is validated with the orbital data of decayed objects taken from www.space-track.org.

  6. Siderophile Element Compositions of Lunar Impact Breccias: Implications for the Cataclysm and Early Earth

    NASA Astrophysics Data System (ADS)

    Norman, M.; Bennett, V.; Ryder, G.

    2001-12-01

    Highly siderophile element signatures of the two main textural and compositional groups of Apollo 17 impact melt breccias (poikilitics and aphanites) are consistent with EH chondrite impactor(s). Similar siderophile element signatures in both types of breccias implies either that multiple EH chondritic impactors were delivered to the Serenitatis region of the Moon within a narrow time interval, or that the two groups of breccias are petrogenetically related to a single impact event. To the extent that these breccias can be linked with the Serenitatis basin-forming event, this identifies one type of planetesimal responsible for creating a large nearside lunar basin, possibly during a terminal cataclysm. Owing to its larger size and greater gravitational focusing, the Earth would have experienced a significantly greater cratering rate (20x) and mass accretion rate (100x) compared to the Moon. If there was a terminal cataclysm, the Earth must have been hit by several large impacts during the crucial period in which the oldest preserved continental crust was forming and early life was evolving. If EH chondrites are found to be an important population for creating the 3.8 to 4.0 Ga lunar basins, their fractionated HSE pattern may have contributed to mantle heterogeneity on Earth. However, the dry and highly reduced nature of EH chondrites would preclude a significant contribution from these planetesimals to the volatile budget of the Earth and the oxidation of the terrestrial mantle. Additional studies of highly siderophile elements in lunar impact breccias and ancient terrestrial rocks are needed to establish the composition of infalling planetesimals on the early Earth and Moon, and the contribution of large impact events to the subsequent evolution of the Earth and other terrestrial planets.

  7. Isomorphous Substitution of Rare-Earth Elements in Lacunary Apatite Pb8Na2(PO4)6.

    PubMed

    Get'man, Evgeni I; Loboda, Stanislav N; Ignatov, Alexey V; Prisedsky, Vadim V; Abdul Jabar, Mohammed A B; Ardanova, Lyudmyla I

    2016-03-07

    The substitution of rare-earth elements (REEs) for Pb in the lacunary apatite Pb8Na2(PO4)6 with void structural channels was studied by means of powder X-ray diffraction (including the Rietveld refinement), scanning electron microscopy, energy-dispersive X-ray microanalysis, and IR spectroscopy and also measurements of the electrical conductivity. The substitution limits (xmax in Pb8-xLnxNa2(PO4)6Ox/2) at 800 °C were found to decrease with the atomic number of the REE from 1.40 for La to 0.12 for Yb with a rapid drop from light to heavy lanthanides (between Gd and Tb). The REE atoms substitute for Pb predominantly at Pb2 sites of the apatite structure according to the scheme 2Pb(2+) + □ → 2Ln(3+) + O(2-), where □ is a vacancy in the structural channel. The substitution in lacunary apatite produces quite different changes in the structural parameters compared with broadly studied alkaline-earth hydroxyapatites. In spite of the much lower ionic radii of REE than that of Pb(2+), the mean distances ⟨Pb1-O⟩ somewhat increase, whereas the distances ⟨Pb2-Pb2⟩ and ⟨Pb2-O4⟩ do not change considerably with the degree of substitution. This implies control of the substitution by not only spatial and charge accommodation of REE ions but also the availability of a stereochemically active 6s(2) electron pair on Pb(2+). The high-temperature electrical conductivity shows dependence on the degree of substitution with a minimum at x = 0.2 indicative of a possible change of the type of conductivity.

  8. Heavy metals and rare earth elements source-sink in some Egyptian cigarettes as determined by neutron activation analysis.

    PubMed

    Nada, A; Abdel-Wahab, M; Sroor, A; Abdel-Haleem, A S; Abdel-Sabour, M F

    1999-07-01

    Heavy metals and rare earth elements in two types of cigarettes were studied. The contents of trace elements were determined by using delayed neutron activation analysis. In the present study 11 elements have been detected in popular and fine brand cigarettes marketed in Egypt. Evaluation of these elements with their potential hazards for smokers is briefly discussed. The material balance (source and sink) for each element was determined. Also the ratio of element recovery to the total amount was assessed.

  9. Structural Responses and Finite Element Modeling of Hakka Tulou Rammed Earth Structures

    NASA Astrophysics Data System (ADS)

    Sranislawski, Daniel

    Hakka Tulous are rammed earth structures that have survived the effects of aging and natural elements upwards of even over a thousand years. These structures have housed the Hakka people of the Fujian Province, China in natural yet modern housing that has provided benefits over newer building materials. The key building material, rammed earth, which is used for the walls of the Hakka Tulou structures, has provided structural stability along with thermal comfort to the respective inhabitants of the Hakka Tulous. Through material testing and analysis this study has examined how the Tulou structures have maintained their structural stability while also providing thermal comfort. Reports of self healing cracks in the rammed earth walls were also analyzed for their validity in this study. The study has found that although the story of the self healing crack cannot be validated, there is reason to believe that with the existence of lime, some type of autogenous healing could occur on a small scale. The study has also found, through the use of nondestructive testing, that both the internal wooden systems (flooring, roof, and column support) and the rammed earth walls, are still structurally sound. Also, rammed earth's high thermal mass along with the use of sufficient shading has allowed for a delay release of heat energy from the walls of the Tulous, thus providing thermal comfort that can be felt during both night and day temperatures. The Hakka Tulou structures have been found to resist destruction from natural disasters such as strong earthquakes even when more modern construction has not. Through finite element modeling, this study has shown that the high volume of rammed earth used in the construction of the Hakka Tulous helps dissipate lateral force energy into much lower stresses for the rammed earth wall. This absorption of lateral force energy allows the rammed earth structures to survive even the strongest of earthquakes experienced in the region. The Hakka

  10. Distributions of 14 elements on 60 selected absorbers from two simulant solutions (acid-dissolved sludge and alkaline supernate) for Hanford HLW Tank 102-SY

    SciTech Connect

    Marsh, S.F.; Svitra, Z.V.; Bowen, S.M.

    1993-10-01

    Sixty commercially available or experimental absorber materials were evaluated for partitioning high-level radioactive waste. These absorbers included cation and anion exchange resins, inorganic exchangers, composite absorbers, and a series of liquid extractants sorbed on porous support-beads. The distributions of 14 elements onto each absorber were measured from simulated solutions that represent acid-dissolved sludge and alkaline supernate solutions from Hanford high-level waste (HLW) Tank 102-SY. The selected elements, which represent fission products (Ce, Cs, Sr, Tc, and Y); actinides (U, Pu, and Am); and matrix elements (Cr, Co, Fe, Mn, Zn, and Zr), were traced by radionuclides and assayed by gamma spectrometry. Distribution coefficients for each of the 1680 element/absorber/solution combinations were measured for dynamic contact periods of 30 min, 2 h, and 6 h to provide sorption kinetics information for the specified elements from these complex media. More than 5000 measured distribution coefficients are tabulated.

  11. Concentrations and health risk assessment of rare earth elements in vegetables from mining area in Shandong, China.

    PubMed

    Zhuang, Maoqiang; Zhao, Jinshan; Li, Suyun; Liu, Danru; Wang, Kebo; Xiao, Peirui; Yu, Lianlong; Jiang, Ying; Song, Jian; Zhou, Jingyang; Wang, Liansen; Chu, Zunhua

    2017-02-01

    To investigate the concentrations of rare earth elements in vegetables and assess human health risk through vegetable consumption, a total of 301 vegetable samples were collected from mining area and control area in Shandong, China. The contents of 14 rare earth elements were determined by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). The total rare earth elements in vegetables from mining and control areas were 94.08 μg kg(-1) and 38.67 μg kg(-1), respectively, and the difference was statistically significant (p < 0.05). The leaf vegetable had the highest rare earth elements concentration (984.24 μg kg(-1) and 81.24 μg kg(-1) for mining and control areas, respectively) and gourd vegetable had the lowest rare earth elements concentration (37.34 μg kg(-1) and 24.63 μg kg(-1) for mining and control areas, respectively). For both areas, the rare earth elements concentration in vegetables declined in the order of leaf vegetable > taproot vegetable > alliaceous vegetable > gourd vegetable. The rare earth elements distribution patterns for both areas were characterized by enrichment of light rare earth elements. The health risk assessment demonstrated that the estimated daily intakes (0.69 μg kg(-1) d(-1) and 0.28 μg kg(-1) d(-1) for mining and control areas, respectively) of rare earth elements through vegetable consumption were significantly lower than the acceptable daily intake (70 μg kg(-1) d(-1)). The damage to adults can be neglected, but more attention should be paid to the effects of continuous exposure to low levels of rare earth elements on children.

  12. Thermal effects on rare earth element and strontium isotope chemistry in single conodont elements

    NASA Astrophysics Data System (ADS)

    Armstrong, H. A.; Pearson, D. G.; Griselin, M.

    2001-02-01

    A low-blank, high sensitivity isotope dilution, ICP-MS analytical technique has been used to obtain REE abundance data from single conodont elements weighing as little as 5 μg. Sr isotopes can also be measured from the column eluants enabling Sr isotope ratios and REE abundance to be determined from the same dissolution. Results are comparable to published analyses comprising tens to hundreds of elements. To study the effects of thermal metamorphism on REE and strontium mobility in conodonts, samples were selected from a single bed adjacent to a basaltic dyke and from the internationally used colour alteration index (CAI) "standard set." Our analyses span the range of CAI 1 to 8. Homogeneous REE patterns, "bell-shaped" shale-normalised REE patterns are observed across the range of CAI 1 to 6 in both sample sets. This pattern is interpreted as the result of adsorption during early diagenesis and could reflect original seawater chemistry. Above CAI 6 REE patterns become less predictable and perturbations from the typical REE pattern are likely to be due to the onset of apatite recrystallisation. Samples outside the contact aureole of the dyke have a mean 87Sr/ 86Sr ratio of 0.708165, within the broad range of published mid-Carboniferous seawater values. Our analysis indicates conodonts up to CAI 6 record primary geochemical signals that may be a proxy for ancient seawater.

  13. Highly siderophile elements were stripped from Earth's mantle by iron sulfide segregation.

    PubMed

    Rubie, David C; Laurenz, Vera; Jacobson, Seth A; Morbidelli, Alessandro; Palme, Herbert; Vogel, Antje K; Frost, Daniel J

    2016-09-09

    Highly siderophile elements (HSEs) are strongly depleted in the bulk silicate Earth (BSE) but are present in near-chondritic relative abundances. The conventional explanation is that the HSEs were stripped from the mantle by the segregation of metal during core formation but were added back in near-chondritic proportions by late accretion, after core formation had ceased. Here we show that metal-silicate equilibration and segregation during Earth's core formation actually increased HSE mantle concentrations because HSE partition coefficients are relatively low at the high pressures of core formation within Earth. The pervasive exsolution and segregation of iron sulfide liquid from silicate liquid (the "Hadean matte") stripped magma oceans of HSEs during cooling and crystallization, before late accretion, and resulted in slightly suprachondritic palladium/iridium and ruthenium/iridium ratios.

  14. A deposit model for carbonatite and peralkaline intrusion-related rare earth element deposits: Chapter J in Mineral deposit models for resource assessment

    USGS Publications Warehouse

    Verplanck, Philip L.; Van Gosen, Bradley S.; Seal, Robert R., II; McCafferty, Anne E.

    2014-01-01

    The greatest environmental challenges associated with carbonatite and peralkaline intrusion-related rare earth element deposits center on the associated uranium and thorium. Considerable uncertainty exists around the toxicity of rare earth elements and warrants further investigation. The acid-generating potential of carbonatites and peralkaline intrusion-related deposits is low due to the dominance of carbonate minerals in carbonatite deposits, the presence of feldspars and minor calcite within the alkaline intrusion deposits, and only minor quantities of potentially acid-generating sulfides. Therefore, acid-drainage issues are not likely to be a major concern associated with these deposits. Uranium has the potential to be recovered as a byproduct, which would mitigate some of its environmental effects. However, thorium will likely remain a waste-stream product that will require management since progress is not being made towards the development of thorium-based nuclear reactors in the United States or other large scale commercial uses. Because some deposits are rich in fluorine and beryllium, these elements may be of environmental concern in certain locations.

  15. Thulium anomalies and rare earth element patterns in meteorites and Earth: Nebular fractionation and the nugget effect

    NASA Astrophysics Data System (ADS)

    Dauphas, Nicolas; Pourmand, Ali

    2015-08-01

    This study reports the bulk rare earth element (REEs, La-Lu) compositions of 41 chondrites, including 32 falls and 9 finds from carbonaceous (CI, CM, CO and CV), enstatite (EH and EL) and ordinary (H, L and LL) groups, as well as 2 enstatite achondrites (aubrite). The measurements were done in dynamic mode using multi-collector inductively coupled plasma mass spectrometers (MC-ICPMS), allowing precise quantification of mono-isotopic REEs (Pr, Tb, Ho and Tm). The CI-chondrite-normalized REE patterns (LaN/LuN; a proxy for fractionation of light vs. heavy REEs) and Eu anomalies in ordinary and enstatite chondrites show more scatter in more metamorphosed (petrologic types 4-6) than in unequilibrated (types 1-3) chondrites. This is due to parent-body redistribution of the REEs in various carrier phases during metamorphism. A model is presented that predicts the dispersion of elemental and isotopic ratios due to the nugget effect when the analyzed sample mass is limited and elements are concentrated in minor grains. The dispersion in REE patterns of equilibrated ordinary chondrites is reproduced well by this model, considering that REEs are concentrated in 200 μm-size phosphates, which have high LaN/LuN ratios and negative Eu anomalies. Terrestrial rocks and samples from ordinary and enstatite chondrites display negative Tm anomalies of ∼-4.5% relative to CI chondrites. In contrast, CM, CO and CV (except Allende) show no significant Tm anomalies. Allende CV chondrite shows large excess Tm (∼+10%). These anomalies are similar to those found in group II refractory inclusions in meteorites but of much smaller magnitude. The presence of Tm anomalies in meteorites and terrestrial rocks suggests that either (i) the material in the inner part of the solar system was formed from a gas reservoir that had been depleted in refractory dust and carried positive Tm anomalies or (ii) CI chondrites are enriched in refractory dust and are not representative of solar composition for

  16. Analytical approach using KS elements to near-earth orbit predictions including drag

    NASA Astrophysics Data System (ADS)

    Sharma, Ram Krishnan

    1991-04-01

    An analytical theory for the motion of near-earth satellite orbits with the air drag effect is evolved in terms of the KS elements, using an analytical oblate exponential atmospheric density model. Due to the symmetry of the KS element equations, only one of the eight equations is integrated analytically to acquire the state vector at the close of each revolution. In the numerical studies performed, it is shown that after 100 revolutions, with a ballistic coefficient of 50, a maximum difference of 39 meters is found in the semimajor axis comparison for a very small eccentricity (0.001) instance having an initial perigee height of 391.425 km.

  17. Bishop tuff revisited: new rare Earth element data consistent with crystal fractionation.

    PubMed

    Cameron, K L

    1984-06-22

    The Bishop Tuff of eastern California is the type example of a high-silica rhyolite that, according to Hildreth, supposedly evolved by liquid-state differentiation. New analyses establish that the Bishop Tuff "earlyllate" rare earth element trend reported by Hildreth mimics the relations between groundmass glasses and whole rocks for allanite-bearing pumice. Differences in elemental concentrations between whole rock and groundmass are the result of phenocryst precipitation; thus the data of Hildreth are precisely those expected to result from crystal fractionation.

  18. Trace elements and rare earth elements in wet deposition of Lijiang, Mt. Yulong region, southeastern edge of the Tibetan Plateau.

    PubMed

    Guo, Junming; Kang, Shichang; Huang, Jie; Sillanpää, Mika; Niu, Hewen; Sun, Xuejun; He, Yuanqing; Wang, Shijing; Tripathee, Lekhendra

    2017-02-01

    In order to investigate the compositions and wet deposition fluxes of trace elements and rare earth elements (REEs) in the precipitation of the southeastern edge of the Tibetan Plateau, 38 precipitation samples were collected from March to August in 2012 in an urban site of Lijiang city in the Mt. Yulong region. The concentrations of most trace elements and REEs were higher during the non-monsoon season than during the monsoon season, indicating that the lower concentrations of trace elements and REEs observed during monsoon had been influenced by the dilution effect of increased precipitation. The concentrations of trace elements in the precipitation of Lijiang city were slightly higher than those observed in remote sites of the Tibetan Plateau but much lower than those observed in the metropolises of China, indicating that the atmospheric environment of Lijiang city was less influenced by anthropogenic emissions, and, as a consequence, the air quality was still relatively good. However, the results of enrichment factor and principal component analysis revealed that some anthropogenic activities (e.g., the increasing traffic emissions from the rapid development of tourism) were most likely important contributors to trace elements, while the regional/local crustal sources rather than anthropogenic activities were the predominant contributors to the REEs in the wet deposition of Lijiang city. Our study was relevant not only for assessing the current status of the atmospheric environment in the Mt. Yulong region, but also for specific management actions to be implemented for the control of atmospheric inputs and the health of the environment for the future.

  19. A possible new host mineral of large-ion elements in the Earth's deep interior

    NASA Astrophysics Data System (ADS)

    Kawai, K.; Tsuchiya, T.

    2015-12-01

    The radiogenic heat production as well as the secular cooling is essential in order to better understand the thermal history and dynamics in the Earth. Potassium is thought to be one of the important radioactive elements in the Earth's interior. Although these elements are concentrated in the continental and oceanic crusts due to chemical differentiations through partial melting at plate boundaries due to their large ion-radii, they have been considered to return into the deep mantle accompanied with subducting slab through time . However, since there are few studies on host minerals of potassium in the high P,T condition, it has yet to be clear how much and where host rocks of such radioactive elements exist in the Earth. Hence, it is important to understand the fate of the potassium-bearing phase subducted into the deep Earth's interior. Here we have studied the high-pressure stability and elasticity of KMg2Al5SiO12 hexagonal aluminous phase (K-Hex with three different size of cation cites, by means of the density functional computation method. Results indicate that the K-Hex phase remains mechanically stable up to 150 GPa and also energetically more stable than an isochemical form with the calcium-ferrite (K-CF) and calcium-titanate (K-CT) type structure with two different size of cation cites. In addition, when the spinel composition coexists with the K-hollandite (K-Hol) phase, which is ), which is considered to be able to host potassium the K-Hex phase becomes more stable than the K-Hol phase at pressures above ~27 GPa. These demonstrate that the Hex phase is substantially stable in the lower mantle, suggesting that it could be a potential host of potassium and other incompatible large-ion elements.

  20. Transport of rare earth element-tagged soil particles in response to thunderstorm runoff.

    PubMed

    Matisoff, G; Ketterer, M E; Wilson, C G; Layman, R; Whiting, P J

    2001-08-15

    The downslope transport of rare earth element-tagged soil particles remobilized during a spring thunderstorm was studied on both a natural prairie and an agricultural field in southwestern Iowa (U.S.A.). A technique was developed for tagging natural soils with the rare earth elements Eu, Tb, and Ho to approximately 1,000 ppm via coprecipitation with MnO2. Tagged material was replaced in target locations; surficial soil samples were collected following precipitation and runoff; and rare earth element concentrations were determined by inductively coupled plasma mass spectrometry. Diffusion and exponential models were applied to the concentration-distance data to determine particle transport distances. The results indicate that the concentration-distance data are well described by the diffusion model, butthe exponential model does not simulate the rapid drop-off in concentrations near the tagged source. Using the diffusion model, calculated particle transport distances at all hillside locations and at both the cultivated and natural prairie sites were short, ranging from 3 to 73 cm during this single runoff event. This study successfully demonstrates a new tool for studying soil erosion.

  1. 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.

  2. 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.

  3. 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

  4. 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.

  5. Highly siderophile elements in Earth's mantle as a clock for the Moon-forming impact.

    PubMed

    Jacobson, Seth A; Morbidelli, Alessandro; Raymond, Sean N; O'Brien, David P; Walsh, Kevin J; Rubie, David C

    2014-04-03

    According to the generally accepted scenario, the last giant impact on Earth formed the Moon and initiated the final phase of core formation by melting Earth's mantle. A key goal of geochemistry is to date this event, but different ages have been proposed. Some argue for an early Moon-forming event, approximately 30 million years (Myr) after the condensation of the first solids in the Solar System, whereas others claim a date later than 50 Myr (and possibly as late as around 100 Myr) after condensation. Here we show that a Moon-forming event at 40 Myr after condensation, or earlier, is ruled out at a 99.9 per cent confidence level. We use a large number of N-body simulations to demonstrate a relationship between the time of the last giant impact on an Earth-like planet and the amount of mass subsequently added during the era known as Late Accretion. As the last giant impact is delayed, the late-accreted mass decreases in a predictable fashion. This relationship exists within both the classical scenario and the Grand Tack scenario of terrestrial planet formation, and holds across a wide range of disk conditions. The concentration of highly siderophile elements (HSEs) in Earth's mantle constrains the mass of chondritic material added to Earth during Late Accretion. Using HSE abundance measurements, we determine a Moon-formation age of 95 ± 32 Myr after condensation. The possibility exists that some late projectiles were differentiated and left an incomplete HSE record in Earth's mantle. Even in this case, various isotopic constraints strongly suggest that the late-accreted mass did not exceed 1 per cent of Earth's mass, and so the HSE clock still robustly limits the timing of the Moon-forming event to significantly later than 40 Myr after condensation.

  6. A Study on Removal of Rare Earth Elements from U.S. Coal Byproducts by Ion Exchange

    NASA Astrophysics Data System (ADS)

    Rozelle, Peter L.; Khadilkar, Aditi B.; Pulati, Nuerxida; Soundarrajan, Nari; Klima, Mark S.; Mosser, Morgan M.; Miller, Charles E.; Pisupati, Sarma V.

    2016-03-01

    Rare earth elements are known to occur in low concentrations in U.S. coals and coal byproducts. These low concentrations may make rare earth element recovery from these materials unattractive, using only physical separation techniques. However, given the significant production of rare earths through ion exchange extraction in China, two U.S. coal byproducts were examined for ion extraction, using ammonium sulfate, an ionic liquid, and a deep eutectic solvent as lixiviants. Extraction of rare earth elements in each case produced high recoveries of rare earth elements to the solution. This suggests that in at least the cases of the materials examined, U.S. coal byproducts may be technically suitable as REE ores. More work is required to establish economic suitability.

  7. 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.

  8. Complementary rare earth element patterns in unique achondrites, such as ALHA 77005 and shergottites, and in the earth

    NASA Technical Reports Server (NTRS)

    Ma, M.-S.; Schmitt, R. A.; Laul, J. C.

    1982-01-01

    Abundances of major, minor, and trace elements are determined in the Antarctic achondrite Allan Hills (ALHA) 77005 via sequential instrumental and radiochemical neutron activation analysis. The rare earth element (REE) abundances of ALHA 77005 reveal a unique chondritic normalized pattern; that is, the REEs are nearly unfractionated from La to Pr at approximately 1.0X chondrites, monotonically increased from Pr to Gd at approximately 3.4X with no Eu anomaly, nearly unfractionated from Gd and Ho and monotonically decreased from Ho to Lu at approximately 2.2X. It is noted that this unique REE pattern of ALHA 77005 can be modeled by a melting process involving a continuous melting and progressive partial removal of melt from a light REE enriched source material. In a model of this type, ALHA 77005 could represent either a crystallized cumulate from such a melt or the residual source material. Calculations show that the parent liquids for the shergottites could also be derived from a light REE enriched source material similar to that for ALHA 77005.

  9. Siku: A Sea Ice Discrete Element Method Model on a Spherical Earth

    NASA Astrophysics Data System (ADS)

    Kulchitsky, A. V.; Hutchings, J. K.; Johnson, J.

    2014-12-01

    Offshore oil and gas exploration and production activities in the Beaufort and Chukchi Seas can be significantly and adversely affected by sea ice. In the event of an oil spill, sea ice complicates the tracking of ice/oil trajectories and can hinder cleanup operations. There is a need for a sea ice dynamics model that can accurately simulate ice pack deformation and failure to improve the ability to track ice/oil trajectories and support oil response operations. A discrete element method (DEM) model, where each ice floe is represented by discrete elements that are initially bonded (frozen) together will be used to address the difficulty continuum modeling approaches have with representing discrete phenomena in sea ice, such as the formation of leads and ridges. Each discrete element in the DEM is a rigid body driven by environmental forcing (wind, current and Coriolis forces) and interaction forces with other discrete elements (compression, shear, tension, bond rupture and regrowth). We introduce a new DEM model ``Siku'', currently under development, to simulate ice drift of an ice floe on a spherical Earth. We will present initial free-drift results. Siku is focused on improving sea ice interaction mechanics and providing an accurate geometrical representation needed for basin scale and regional simulations. Upon completion, Siku will be an open source GNU GPL licensed user friendly program with embedded python capability for setting up simulations "scenarios" and coupling with other models to provide forcing fields. We use a unique quaternion representation for position and orientation of polygon sea-ice elements that use a second order integration scheme of sea-ice element motion on the Earth's sphere that does not depend on the location of the element and, hence, avoids numerical problems near the pole.

  10. Mining and Exploitation of Rare Earth Elements in Africa as an Engagement Strategy in US Africa Command

    DTIC Science & Technology

    2011-06-17

    Globalsecurity.org, 2010, 2. 3 Geology.com, “REE Rare Earth Elements and their Uses,” Geology.com, http://geology.com/ articles /rare-earth-elements/ (accessed...controversy for decades.36 Jasper, in his article “Engineered Extinction” specifically mentions U.S. rare earth mining. He details the impact that...35 Justin Rohrlich, “How China Came to Dominate the Rare Earths Market,” December 29, 2010, http://www.minyanville.com/businessmarkets/ articles

  11. Normalized rare earth elements in water, sediments, and wine: identifying sources and environmental redox conditions

    USGS Publications Warehouse

    Piper, David Z.; Bau, Michael

    2013-01-01

    The concentrations of the rare earth elements (REE) in surface waters and sediments, when normalized on an element-by-element basis to one of several rock standards and plotted versus atomic number, yield curves that reveal their partitioning between different sediment fractions and the sources of those fractions, for example, between terrestrial-derived lithogenous debris and seawater-derived biogenous detritus and hydrogenous metal oxides. The REE of ancient sediments support their partitioning into these same fractions and further contribute to the identification of the redox geochemistry of the sea water in which the sediments accumulated. The normalized curves of the REE that have been examined in several South American wine varietals can be interpreted to reflect the lithology of the bedrock on which the vines may have been grown, suggesting limited fractionation during soil development.

  12. Bioleaching of rare earth and radioactive elements from red mud using Penicillium tricolor RM-10.

    PubMed

    Qu, Yang; Lian, Bin

    2013-05-01

    The aim of this work is to investigate biological leaching of rare earth elements (REEs) and radioactive elements from red mud, and to evaluate the radioactivity of the bioleached red mud used for construction materials. A filamentous, acid-producing fungi named RM-10, identified as Penicillium tricolor, is isolated from red mud. In our bioleaching experiments by using RM-10, a total concentration of 2% (w/v) red mud under one-step bioleaching process was generally found to give the maximum leaching ratios of the REEs and radioactive elements. However, the highest extraction yields are achieved under two-step bioleaching process at 10% (w/v) pulp density. At pulp densities of 2% and 5% (w/v), red mud processed under both one- and two-step bioleaching can meet the radioactivity regulations in China.

  13. Experimental partitioning of rare earth elements and scandium among armalcolite, ilmenite, olivine and mare basalt liquid

    NASA Technical Reports Server (NTRS)

    Irving, A. J.; Merrill, R. B.; Singleton, D. E.

    1978-01-01

    An experimental study was carried out to measure partition coefficients for two rare-earth elements (Sm and Tm) and Sc among armalcolite, ilmenite, olivine and liquid coexisting in a system modeled on high-Ti mare basalt 74275. This 'primitive' sample was chosen for study because its major and trace element chemistry as well as its equilibrium phase relations at atmospheric pressure are known from previous studies. Beta-track analytical techniques were used so that partition coefficients could be measured in an environment whose bulk trace element composition is similar to that of the natural basalt. Partition coefficients for Cr and Mn were determined in the same experiments by microprobe analysis. The only equilibrium partial melting model appears to be one in which ilmenite is initially present in the source region but is consumed by melting before segregation of the high-Ti mare basalt liquid from the residue.

  14. Multi-element including rare earth content of lichens, bark, soils, and waste following industrial closure.

    PubMed

    Rusu, Ana-Maria; Chimonides, P D James; Jones, Gary C; Garcia-Sanchez, Raquel; Purvis, O William

    2006-08-01

    The fate of rare earth and other rare elements entering the environment is largely unknown. The lichen Hypogymnia physodes was transplanted over a 40 km long transect centered on a major metallurgical waste dump close to the Zlatna town center two weeks after smelter closure. Lichens, bark, soil, and waste dump materials were analyzed for 56 elements (including REE). Lichen and bark multi-element compositions were alike, reflecting fixation of elements of environmental concern and the ability for tree canopies to concentrate substances leading to enhanced deposition to both lichens and bark. Higher REE enrichment in lichens than in soil confirm efficient fixation in lichens. The negative europium anomaly in lichens and soil, similar to that in upper crust, confirm a strong crustal influence on lichen signatures across the transect area. Multi-element analysis supports the view that epiphytic lichens, unlike trees, are not influenced by lower groundwater, and they are excellent indicators for REE and other rare elements entering the surface environment, difficult to detect by conventional means.

  15. Quantification of rare earth elements using laser-induced breakdown spectroscopy

    DOE PAGES

    Martin, Madhavi; Martin, Rodger C.; Allman, Steve; ...

    2015-10-21

    In this paper, a study of the optical emission as a function of concentration of laser-ablated yttrium (Y) and of six rare earth elements, europium (Eu), gadolinium (Gd), lanthanum (La), praseodymium (Pr), neodymium (Nd), and samarium (Sm), has been evaluated using the laser-induced breakdown spectroscopy (LIBS) technique. Statistical methodology using multivariate analysis has been used to obtain the sampling errors, coefficient of regression, calibration, and cross-validation of measurements as they relate to the LIBS analysis in graphite-matrix pellets that were doped with elements at several concentrations. Each element (in oxide form) was mixed in the graphite matrix in percentages rangingmore » from 1% to 50% by weight and the LIBS spectra obtained for each composition as well as for pure oxide samples. Finally, a single pellet was mixed with all the elements in equal oxide masses to determine if we can identify the elemental peaks in a mixed pellet. This dataset is relevant for future application to studies of fission product content and distribution in irradiated nuclear fuels. These results demonstrate that LIBS technique is inherently well suited for the future challenge of in situ analysis of nuclear materials. Finally, these studies also show that LIBS spectral analysis using statistical methodology can provide quantitative results and suggest an approach in future to the far more challenging multielemental analysis of ~ 20 primary elements in high-burnup nuclear reactor fuel.« less

  16. Quantification of rare earth elements using laser-induced breakdown spectroscopy

    SciTech Connect

    Martin, Madhavi; Martin, Rodger C.; Allman, Steve; Brice, Deanne; Wymore, Ann; Andre, Nicolas

    2015-10-21

    In this paper, a study of the optical emission as a function of concentration of laser-ablated yttrium (Y) and of six rare earth elements, europium (Eu), gadolinium (Gd), lanthanum (La), praseodymium (Pr), neodymium (Nd), and samarium (Sm), has been evaluated using the laser-induced breakdown spectroscopy (LIBS) technique. Statistical methodology using multivariate analysis has been used to obtain the sampling errors, coefficient of regression, calibration, and cross-validation of measurements as they relate to the LIBS analysis in graphite-matrix pellets that were doped with elements at several concentrations. Each element (in oxide form) was mixed in the graphite matrix in percentages ranging from 1% to 50% by weight and the LIBS spectra obtained for each composition as well as for pure oxide samples. Finally, a single pellet was mixed with all the elements in equal oxide masses to determine if we can identify the elemental peaks in a mixed pellet. This dataset is relevant for future application to studies of fission product content and distribution in irradiated nuclear fuels. These results demonstrate that LIBS technique is inherently well suited for the future challenge of in situ analysis of nuclear materials. Finally, these studies also show that LIBS spectral analysis using statistical methodology can provide quantitative results and suggest an approach in future to the far more challenging multielemental analysis of ~ 20 primary elements in high-burnup nuclear reactor fuel.

  17. Quantification of rare earth elements using laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Martin, Madhavi; Martin, Rodger C.; Allman, Steve; Brice, Deanne; Wymore, Ann; Andre, Nicolas

    2015-12-01

    A study of the optical emission as a function of concentration of laser-ablated yttrium (Y) and of six rare earth elements, europium (Eu), gadolinium (Gd), lanthanum (La), praseodymium (Pr), neodymium (Nd), and samarium (Sm), has been evaluated using the laser-induced breakdown spectroscopy (LIBS) technique. Statistical methodology using multivariate analysis has been used to obtain the sampling errors, coefficient of regression, calibration, and cross-validation of measurements as they relate to the LIBS analysis in graphite-matrix pellets that were doped with elements at several concentrations. Each element (in oxide form) was mixed in the graphite matrix in percentages ranging from 1% to 50% by weight and the LIBS spectra obtained for each composition as well as for pure oxide samples. Finally, a single pellet was mixed with all the elements in equal oxide masses to determine if we can identify the elemental peaks in a mixed pellet. This dataset is relevant for future application to studies of fission product content and distribution in irradiated nuclear fuels. These results demonstrate that LIBS technique is inherently well suited for the future challenge of in situ analysis of nuclear materials. These studies also show that LIBS spectral analysis using statistical methodology can provide quantitative results and suggest an approach in future to the far more challenging multielemental analysis of ~ 20 primary elements in high-burnup nuclear reactor fuel.

  18. Spectral Analysis of Rare Earth Elements using Laser-Induced Breakdown Spectroscopy

    SciTech Connect

    Martin, Madhavi Z; Fox, Dr. Richard V; Miziolek, Andrzej W; DeLucia, Frank C; Andre, Nicolas O

    2015-01-01

    There is growing interest in rapid analysis of rare earth elements (REEs) both due to the need to find new natural sources to satisfy increased demand in their use in various electronic devices, as well as the fact that they are used to estimate actinide masses for nuclear safeguards and nonproliferation. Laser-Induced Breakdown Spectroscopy (LIBS) appears to be a particularly well-suited spectroscopy-based technology to rapidly and accurately analyze the REEs in various matrices at low concentration levels (parts-per-million). Although LIBS spectra of REEs have been reported for a number of years, further work is still necessary in order to be able to quantify the concentrations of various REEs in realworld complex samples. LIBS offers advantages over conventional solution-based radiochemistry in terms of cost, analytical turnaround, waste generation, personnel dose, and contamination risk. Rare earth elements of commercial interest are found in the following three matrix groups: 1) raw ores and unrefined materials, 2) as components in refined products such as magnets, lighting phosphors, consumer electronics (which are mostly magnets and phosphors), catalysts, batteries, etc., and 3) waste/recyclable materials (aka e-waste). LIBS spectra for REEs such as Gd, Nd, and Sm found in rare earth magnets are presented.

  19. Spectral Analysis of Rare Earth Elements using Laser-Induced Breakdown Spectroscopy

    SciTech Connect

    Martin, Madhavi Z; Fox, Dr. Richard V; Miziolek, Andrzej W; DeLucia, Frank C; Andre, Nicolas O

    2015-01-01

    There is growing interest in rapid analysis of rare earth elements (REEs) both due to the need to find new natural sources to satisfy increased demand in their use in various electronic devices, as well as the fact that they are used to estimate actinide masses for nuclear safeguards and nonproliferation. Laser-Induced Breakdown Spectroscopy (LIBS) appears to be a particularly well-suited spectroscopy-based technology to rapidly and accurately analyze the REEs in various matrices at low concentration levels (parts-per-million). Although LIBS spectra of REEs have been reported for a number of years, further work is still necessary in order to be able to quantify the concentrations of various REEs in real-world complex samples. LIBS offers advantages over conventional solution-based radiochemistry in terms of cost, analytical turnaround, waste generation, personnel dose, and contamination risk. Rare earth elements of commercial interest are found in the following three matrix groups: 1) raw ores and unrefined materials, 2) as components in refined products such as magnets, lighting phosphors, consumer electronics (which are mostly magnets and phosphors), catalysts, batteries, etc., and 3) waste/recyclable materials (aka e-waste). LIBS spectra for REEs such as Gd, Nd, and Sm found in rare earth magnets are presented.

  20. Rare earth elements recycling from waste phosphor by dual hydrochloric acid dissolution.

    PubMed

    Liu, Hu; Zhang, Shengen; Pan, Dean; Tian, Jianjun; Yang, Min; Wu, Maolin; Volinsky, Alex A

    2014-05-15

    This paper is a comparative study of recycling rare earth elements from waste phosphor, which focuses on the leaching rate and the technical principle. The traditional and dual dissolution by hydrochloric acid (DHA) methods were compared. The method of dual dissolution by hydrochloric acid has been developed. The Red rare earth phosphor (Y0.95Eu0.05)2O3 in waste phosphor is dissolved during the first step of acid leaching, while the Green phosphor (Ce0.67Tb0.33MgAl11O19) and the Blue phosphor (Ba0.9Eu0.1MgAl10O17) mixed with caustic soda are obtained by alkali sintering. The excess caustic soda and NaAlO2 are removed by washing. The insoluble matter is leached by the hydrochloric acid, followed by solvent extraction and precipitation (the DHA method). In comparison, the total leaching rate of the rare earth elements was 94.6% by DHA, which is much higher than 42.08% achieved by the traditional method. The leaching rate of Y, Eu, Ce and Tb reached 94.6%, 99.05%, 71.45%, and 76.22%, respectively. DHA can decrease the consumption of chemicals and energy. The suggested DHA method is feasible for industrial applications.

  1. Geochemical fractions of rare earth elements in soil around a mine tailing in Baotou, China

    PubMed Central

    Wang, Lingqing; Liang, Tao

    2015-01-01

    Rare earth mine tailing dumps are environmental hazards because tailing easily leaches and erodes by water and wind. To assess the influence of mine tailing on the geochemical behavior of rare earth elements (REEs) in soil, sixty-seven surface soil samples and three soil profile samples were collected from different locations near China’s largest rare earth mine tailing. The total concentration of REEs in surface soils ranged from 156 to 5.65 × 104 mg·kg−1 with an average value of 4.67 × 103 mg·kg−1, which was significantly higher than the average value in China (181 mg·kg−1). We found obvious fractionation of both light and heavy REEs, which was supported by the North American Shale Composite (NASC) and the Post-Archean Average Australian Shale (PAAS) normalized concentration ratios calculated for selected elements (LaN/YbN, LaN/SmN and GdN/YbN). A slightly positive Ce anomaly and a negative Eu anomaly were also found. For all 14 REEs in soils, enrichment was intensified by the mine tailing sources and influenced by the prevailing wind. PMID:26198417

  2. Spectral analysis of rare earth elements using laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Martin, Madhavi Z.; Fox, Robert V.; Miziolek, Andrzej W.; DeLucia, Frank C.; André, Nicolas

    2015-06-01

    There is growing interest in rapid analysis of rare earth elements (REEs) both due to the need to find new natural sources to satisfy increased demand in their use in various electronic devices, as well as the fact that they are used to estimate actinide masses for nuclear safeguards and nonproliferation. Laser-Induced Breakdown Spectroscopy (LIBS) appears to be a particularly well-suited spectroscopy-based technology to rapidly and accurately analyze the REEs in various matrices at low concentration levels (parts-per-million). Although LIBS spectra of REEs have been reported for a number of years, further work is still necessary in order to be able to quantify the concentrations of various REEs in realworld complex samples. LIBS offers advantages over conventional solution-based radiochemistry in terms of cost, analytical turnaround, waste generation, personnel dose, and contamination risk. Rare earth elements of commercial interest are found in the following three matrix groups: 1) raw ores and unrefined materials, 2) as components in refined products such as magnets, lighting phosphors, consumer electronics (which are mostly magnets and phosphors), catalysts, batteries, etc., and 3) waste/recyclable materials (aka e-waste). LIBS spectra for REEs such as Gd, Nd, and Sm found in rare earth magnets are presented.

  3. Spectral Analysis of Rare Earth Elements using Laser-Induced Breakdown Spectroscopy

    SciTech Connect

    Madhavi Z. Martin; Robert V. Fox; Andrzej W. Miziolek; Frank C. DeLucia, Jr.; Nicolas Andre

    2001-05-01

    There is growing interest in rapid analysis of rare earth elements (REEs) both due to the need to find new natural sources to satisfy increased demand in their use in various electronic devices, as well as the fact that they are used to estimate actinide masses for nuclear safeguards and nonproliferation. Laser-Induced Breakdown Spectroscopy (LIBS) appears to be a particularly well-suited spectroscopy-based technology to rapidly and accurately analyze the REEs in various matrices at low concentration levels (parts-per-million). Although LIBS spectra of REEs have been reported for a number of years, further work is still necessary in order to be able to quantify the concentrations of various REEs in realworld complex samples. LIBS offers advantages over conventional solution-based radiochemistry in terms of cost, analytical turnaround, waste generation, personnel dose, and contamination risk. Rare earth elements of commercial interest are found in the following three matrix groups: 1) raw ores and unrefined materials, 2) as components in refined products such as magnets, lighting phosphors, consumer electronics (which are mostly magnets and phosphors), catalysts, batteries, etc., and 3) waste/recyclable materials (aka e-waste). LIBS spectra for REEs such as Gd, Nd, and Sm found in rare earth magnets are presented.

  4. Geochemical fractions of rare earth elements in soil around a mine tailing in Baotou, China.

    PubMed

    Wang, Lingqing; Liang, Tao

    2015-07-22

    Rare earth mine tailing dumps are environmental hazards because tailing easily leaches and erodes by water and wind. To assess the influence of mine tailing on the geochemical behavior of rare earth elements (REEs) in soil, sixty-seven surface soil samples and three soil profile samples were collected from different locations near China's largest rare earth mine tailing. The total concentration of REEs in surface soils ranged from 156 to 5.65 × 10(4) mg·kg(-1) with an average value of 4.67 × 10(3) mg·kg(-1), which was significantly higher than the average value in China (181 mg·kg(-1)). We found obvious fractionation of both light and heavy REEs, which was supported by the North American Shale Composite (NASC) and the Post-Archean Average Australian Shale (PAAS) normalized concentration ratios calculated for selected elements (La(N)/Yb(N), La(N)/Sm(N) and Gd(N)/Yb(N)). A slightly positive Ce anomaly and a negative Eu anomaly were also found. For all 14 REEs in soils, enrichment was intensified by the mine tailing sources and influenced by the prevailing wind.

  5. Deep-sea mud in the Pacific Ocean as a potential resource for rare-earth elements

    NASA Astrophysics Data System (ADS)

    Kato, Yasuhiro; Fujinaga, Koichiro; Nakamura, Kentaro; Takaya, Yutaro; Kitamura, Kenichi; Ohta, Junichiro; Toda, Ryuichi; Nakashima, Takuya; Iwamori, Hikaru

    2011-08-01

    World demand for rare-earth elements and the metal yttrium--which are crucial for novel electronic equipment and green-energy technologies--is increasing rapidly. Several types of seafloor sediment harbour high concentrations of these elements. However, seafloor sediments have not been regarded as a rare-earth element and yttrium resource, because data on the spatial distribution of these deposits are insufficient. Here, we report measurements of the elemental composition of over 2,000 seafloor sediments, sampled at depth intervals of around one metre, at 78 sites that cover a large part of the Pacific Ocean. We show that deep-sea mud contains high concentrations of rare-earth elements and yttrium at numerous sites throughout the eastern South and central North Pacific. We estimate that an area of just one square kilometre, surrounding one of the sampling sites, could provide one-fifth of the current annual world consumption of these elements. Uptake of rare-earth elements and yttrium by mineral phases such as hydrothermal iron-oxyhydroxides and phillipsite seems to be responsible for their high concentration. We show that rare-earth elements and yttrium are readily recovered from the mud by simple acid leaching, and suggest that deep-sea mud constitutes a highly promising huge resource for these elements.

  6. 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.

  7. Neutron Activation Analysis of the Rare Earth Elements (REE) - With Emphasis on Geological Materials

    NASA Astrophysics Data System (ADS)

    Stosch, Heinz-Günter

    2016-08-01

    Neutron activation analysis (NAA) has been the analytical method of choice for rare earth element (REE) analysis from the early 1960s through the 1980s. At that time, irradiation facilitieswere widely available and fairly easily accessible. The development of high-resolution gamma-ray detectors in the mid-1960s eliminated, formany applications, the need for chemical separation of the REE from the matrix material, making NAA a reliable and effective analytical tool. While not as precise as isotopedilution mass spectrometry, NAA was competitive by being sensitive for the analysis of about half of the rare earths (La, Ce, Nd, Sm, Eu, Tb, Yb, Lu). The development of inductively coupled plasma mass spectrometry since the 1980s, together with decommissioning of research reactors and the lack of installation of new ones in Europe and North America has led to the rapid decline of NAA.

  8. Biological availability and environmental behaviour of Rare Earth Elements in soils of Hesse, Central Germany

    NASA Astrophysics Data System (ADS)

    Loell, M.; Duering, R.-A.; Felix-Henningsen, P.

    2009-04-01

    Rare earth elements (REEs) comprise a group of 17 transition metals with very similar chemical and physical properties. They include the elements scandium (Sc), yttrium (Y) and lanthanum (La) and the 14 elements (cerium to lutetium) that follow La in the periodic table. Their average abundance in the earth's crust varies from 0,01 to 0,02% so they are as common as Cu and Pb. Beside their widespread use in industry, REEs are applied in Chinese agriculture. Their beneficial effects both on crop yield and on animal production are reported in various investigations. As a result - by using microelement fertilisers and manure - REEs enter the pedosphere while their fate and behaviour in the environment up to now remains unexamined. The first aim of our investigation was to evaluate the concentration of REEs in agricultural used soils in central Germany (Hesse) by ICP-MS. In addition to their total concentration (aqua regia digestion) their bioavailable contents - determined by EDTA (potentially available fraction) and ammonium nitrate extraction (mobile fraction) - were analysed. The occurrence of the three REE fractions in different soils will be discussed and influencing soil properties (e.g. pH-value, content of clay and organic carbon) will be revealed. Additionally the uptake of REEs by grassland plants was determined and resulting transfer factors will be presented.

  9. Geochemistry of rare earth elements in basalts from the Walvis Ridge: implications for its origin and evolution

    NASA Astrophysics Data System (ADS)

    Humphris, Susan E.; Thompson, Geoffrey

    1983-12-01

    Selected basalts from a suite of dredged and drilled samples (IPOD sites 525, 527, 528 and 530) from the Walvis Ridge have been analysed to determine their rare earth element (REE) contents in order to investigate the origin and evolution of this major structural feature in the South Atlantic Ocean. All of the samples show a high degree of light rare earth element (LREE) enrichment, quite unlike the flat or depleted patterns normally observed for normal mid-ocean ridge basalts (MORBs). Basalts from Sites 527, 528 and 530 show REE patterns characterised by an arcuate shape and relatively low (Ce/Yb) N ratios (1.46-5.22), and the ratios show a positive linear relationship to Nb content. A different trend is exhibited by the dredged basalts and the basalts from Site 525, and their REE patterns have a fairly constant slope, and higher (Ce/Yb) N ratios (4.31-8.50). These differences are further reflected in the ratios of incompatible trace elements, which also indicate considerable variations within the groups. Mixing hyperbolae for these ratios suggest that simple magma mixing between a "hot spot" type of magma, similar to present-day volcanics of Tristan da Cunha, and a depleted source, possibly similar to that for magmas being erupted at the Mid-Atlantic Ridge, was an important process in the origin of parts of the Walvis Ridge, as exemplified by Sites 527, 528 and 530. Site 525 and dredged basalts cannot be explained by this mixing process, and their incompatible element ratios suggest either a mantle source of a different composition or some complexity to the mixing process. In addition, the occurrence of different types of basalt at the same location suggests there is vertical zonation within the volcanic pile, with the later erupted basalts becoming more alkaline and more enriched in incompatible elements. The model proposed for the origin and evolution of the Walvis Ridge involves an initial stage of eruption in which the magma was essentially a mixture of

  10. Investigation of recovery and recycling of rare earth elements from waste fluorescent lamp phosphors

    NASA Astrophysics Data System (ADS)

    Eduafo, Patrick Max

    Characterization techniques and experimental measurements were used to evaluate a process for recycling rare earth elements (REEs) from spent fluorescent lamp phosphors. QEMSCAN analysis revealed that over 60% of the rare earth bearing minerals was less than 10 microm. A representative sample of the as-received feed contained 14.59 wt% total rare earth elements (TREE) and upon sieving to below 75 microm, the grade increased to 19.60 wt% REE with 98.75% recovery. Based on experimental work, a new process for extracting the chief REEs from end of life fluorescent lamps has been developed. The proposed flowsheet employs a three-stage leaching and precipitation process for selective extraction and recovery of the REEs. Hydrochloric acid was used as lixiviant in batch leach experiments on the phosphor powder. The maximum extraction obtained was 100% for both yttrium and europium under the following leaching conditions: 2.5 M HCl, 70°C, 1 hour, 180 g/L and 600 rpm. However, the solubility of cerium, lanthanum and terbium remained low at these conditions. Kinetic data of the leaching of yttrium and europium showed best fit to the logarithmic rate expression of the empirical model of leaching. Activation energy was calculated to be 77.49 kJ/mol for Y and 72.75 kJ/mol for Eu in the temperature range of 298 to 343 K. Precipitation tests demonstrate that at least 50% excess the stoichiometric amount of oxalic acid is needed to recover yttrium and europium efficiently to produce a pure (Y, Eu) mixed oxide. Total recovery of the REEs was achieved even at very low pH or without any base added. Over 99% pure mixed rare earth oxide at 99% recovery has been attained. An economic assessment of the developed process using operating and capital cost have be undertaken and based on the analysis of the three economic scenarios, two are economic and one is non-economic.

  11. Origin of Volatiles in Earth: Indigenous Versus Exogenous Sources Based on Highly Siderophile, Volatile Siderophile, and Light Volatile Elements

    NASA Technical Reports Server (NTRS)

    Righter, K.; Danielson, L.; Pando, K. M.; Marin, N.; Nickodem, K.

    2015-01-01

    Origin of Earth's volatiles has traditionally been ascribed to late accretion of material after major differentiation events - chondrites, comets, ice or other exogenous sources. A competing theory is that the Earth accreted its volatiles as it was built, thus water and other building blocks were present early and during differentiation and core formation (indigenous). Here we discuss geochemical evidence from three groups of elements that suggests Earth's volatiles were acquired during accretion and did not require additional sources after differentiation.

  12. On the origin of falling-tone chorus elements in Earth's inner magnetosphere

    NASA Astrophysics Data System (ADS)

    Breuillard, H.; Agapitov, O.; Artemyev, A.; Krasnoselskikh, V.; Le Contel, O.; Cully, C. M.; Angelopoulos, V.; Zaliznyak, Y.; Rolland, G.

    2014-12-01

    Generation of extremely/very low frequency (ELF/VLF) chorus waves in Earth's inner magnetosphere has received increased attention recently because of their significance for radiation belt dynamics. Though past theoretical and numerical models have demonstrated how rising-tone chorus elements are produced, falling-tone chorus element generation has yet to be explained. Our new model proposes that weak-amplitude falling-tone chorus elements can be generated by magnetospheric reflection of rising-tone elements. Using ray tracing in a realistic plasma model of the inner magnetosphere, we demonstrate that rising-tone elements originating at the magnetic equator propagate to higher latitudes. Upon reflection there, they propagate to lower L-shells and turn into oblique falling tones of reduced power, frequency, and bandwidth relative to their progenitor rising tones. Our results are in good agreement with comprehensive statistical studies of such waves, notably using magnetic field measurements from THEMIS (Time History of Events and Macroscale Interactions during Substorms) spacecraft. Thus, we conclude that the proposed mechanism can be responsible for the generation of weak-amplitude falling-tone chorus emissions.

  13. Rare earth elements geochemistry in springs from Taftan geothermal area SE Iran

    NASA Astrophysics Data System (ADS)

    Shakeri, Ata; Ghoreyshinia, Sayedkazem; Mehrabi, Behzad; Delavari, Morteza

    2015-10-01

    Concentrations of rare earth elements (REEs) were determined in springs and andesitic-dacitic rocks of Taftan geothermal field. Hydrochemical results of major ions indicate that thermal springs are Na-SO4-Cl and Ca-SO4-Cl types. Concentrations of REEs are in ranges of 10- 4 to 1.2 and 49 to ~ 62 times of chondrite for springwater and rock samples, respectively. The thermal (STS and TTS) and the cold (APS) springs with low pH values exhibit a very high REE contents (0.64 to 3.15 mg/l). Saturation index indicates that Fe and Al phases can control dissolved REE concentration in FTS and PF cold springs. The speciation of REE complexes indicates dominant presence of LnSO4+ and free ion in the Taftan thermal springs. In APS cold spring with pH ~ 4, fluoride complexes are dominate over the free ion and sulfate species, while in PF and FTS cold springs with pH 6.4 and 7, respectively, carbonate complexes (LnCO3+) are predominant species. Chondrite-normalized pattern for the low-pH waters show very distinctive gull-wing patterns, characteristic feature of acid-sulfate geothermal systems, and are similar to those of the host rocks. Chemical characteristics of rare earth elements in spring and volcanic rock samples indicate that REEs are originated from the andesitic-dacitic host rocks. Whole-rock-normalized REE patterns and petrographic evidences show that rare earth elements leached mainly from marginal alteration of minerals and matrix decomposition in volcanic rocks. In chondrite-normalized REE patterns, significant negative Eu anomaly in the cold springs compare to the thermal and acidic springs indicates that alteration of plagioclase is more intense in the later, corresponding to increasing in temperature and acidic state of reactant water.

  14. Selective liquid chromatographic separation of yttrium from heavier rare earth elements using acetic acid as a novel eluent.

    PubMed

    Kifle, Dejene; Wibetoe, Grethe

    2013-09-13

    One of the major difficulties in the rare earth elements separation is purification of yttrium from heavy rare earth elements. Thus, an HPLC method using acetic acid as novel eluent was explored for selective separation of yttrium form the heavy rare earth elements. When acetic acid is used as a mobile phase yttrium eluted with the lighter lanthanides. This is contrary to its relative position amongst heavier lanthanides when eluents commonly used for separation of rare earth elements were employed. The shift in elution position of yttrium with acetic acid as eluent may reflect a relatively lower stability constant of the yttrium-AcOH complex (in the same order as for the lighter lanthanides) compared to the corresponding AcOH complexes with heavy lanthanides, enabling selective separation of yttrium from the latter. The method was successfully used for selective separation of yttrium in mixed rare earth sample containing about 80% of yttrium and about 20% of heavy rare earth oxides. Thus, the use of AcOH as eluent is an effective approach for separating and determining the trace amounts of heavy rare earth elements in large amounts of yttrium matrix. Separation was performed on C18 column by running appropriate elution programs. The effluent from the column was monitored with diode array detector at absorbance wavelength of 658nm after post column derivatization with Arsenazo III.

  15. Standardless EDXRF application for quantification of thorium (Th), uranium (U) and rare earth elements (REEs) in various Malaysian rare earth ores

    NASA Astrophysics Data System (ADS)

    Ruf, Mohd Izzat Fahmi Mohd; Bahri, Che Nor Aniza Che Zainul; AL-Areqi, Wadeeah M.; Majid, Amran Ab.

    2016-11-01

    Our local rare earth ores contained substantial amount of Thorium and Uranium which the level exceed permissible limit adopted by Malaysia and many importing nation. X-ray fluorescence technique has been applied for determination of thorium (Th), uranium (U) and rare earth elements (REEs) in Malaysian rare earth ores as it's recognized as viable tool. XRF has been widely used in detecting elemental composition of unknown materials both qualitative and quantitatively because of its wide range of element detection alongside the non-destructive analytical technique with great accuracy and precision. Four types of minerals sample which is monazite, xenotime, ilmenite and zircon were collected from `amang' factory located in famous city of mining, Ipoh and analyzed using EDXRF.

  16. Unveiling the effects of post-deposition treatment with different alkaline elements on the electronic properties of CIGS thin film solar cells.

    PubMed

    Pianezzi, Fabian; Reinhard, Patrick; Chirilă, Adrian; Bissig, Benjamin; Nishiwaki, Shiro; Buecheler, Stephan; Tiwari, Ayodhya N

    2014-05-21

    Thin film solar cells with a Cu(In,Ga)Se2 (CIGS) absorber layer achieved efficiencies above 20%. In order to achieve such high performance the absorber layer of the device has to be doped with alkaline material. One possibility to incorporate alkaline material is a post deposition treatment (PDT), where a thin layer of NaF and/or KF is deposited onto the completely grown CIGS layer. In this paper we discuss the effects of PDT with different alkaline elements (Na and K) on the electronic properties of CIGS solar cells. We demonstrate that whereas Na is more effective in increasing the hole concentration in CIGS, K significantly improves the pn-junction quality. The beneficial role of K in improving the PV performance is attributed to reduced recombination at the CdS/CIGS interface, as revealed by temperature dependent J-V measurements, due to a stronger electronically inverted CIGS surface region. Computer simulations with the software SCAPS are used to verify this model. Furthermore, we show that PDT with either KF or NaF has also a distinct influence on other electronic properties of the device such as the position of the N1 signal in admittance spectroscopy and the roll-over of the J-V curve at low temperature. In view of the presented results we conclude that a model based on a secondary diode at the CIGS/Mo interface can best explain these features.

  17. Use of X-ray Fluorescence Analysis for the Determination of Rare Earth Elements

    NASA Astrophysics Data System (ADS)

    Schramm, Rainer

    2016-09-01

    X-ray fluorescence spectrometry (XRF) is a powerful tool for the analysis of solid material. That is the reason why the technique was applied for the determination of rare earth elements (REEs) since about 1970. At present, energy-dispersive XRF and wavelength-dispersive XRF are used for the analysis of pressed powder pellets or fused Li-borate beads containing REEs. The production of reliable results can only be achieved by careful optimization of the parameter, in particular the selection of spectral lines. The quantification is based on a calibration realized by using reference samples.

  18. Influence of rare earth elements (Nd, Sm, Gd) on the physicochemical properties of ges crystal

    NASA Astrophysics Data System (ADS)

    Madatov, R. S.; Alekperov, A. S.; Magerramova, Dzh. A.

    2015-11-01

    Layered semiconductors (including GeS), which are widely used in modern electronics, are of great interest for researchers. New GeS-based devices have been developed for holographic recording, optical processing, and storage of information. In the last few years, American scientists have developed a unique GeS-based device that makes it possible to accumulate an immense amount of solar energy. The introduction of rare earth elements (REEs) facilitates the healing of metal and chalcogenide vacancies, removes polytypism, and enhances interlayer interaction.

  19. Rare-Earth Elements in Lighting and Optical Applications and Their Recycling

    NASA Astrophysics Data System (ADS)

    Song, Xin; Chang, Moon-Hwan; Pecht, Michael

    2013-10-01

    Rare-earth elements (REEs) are used in lighting and optical applications to enable color and light adjustment, miniaturization, and energy efficiency. Common applications of REEs include phosphors for light-emitting diodes, lasers, and electronic video displays. This article reviews how REEs are widely used in these applications. However, supply constraints, including rising prices, environmental concerns over mining and refining processes, and China's control over the supply of the vast majority of REEs, are of concern for manufacturers. In view of these supply constraints, this article discusses ways for manufacturers of lighting and optical devices to identify potential substitutes and recycling methods for REEs.

  20. Studies of rare earth element distribution and action in human erythrocyte and animal hepatocyte by PIXE

    NASA Astrophysics Data System (ADS)

    Wu, Y. P.; Mi, Y.; Shen, H.; Yao, H. Y.; Cheng, Y.; Wang, X.; Zhang, J. X.

    2002-04-01

    PIXE analysis is applied to investigate a long-term disputed issue whether the rare earth element (REE) can enter the cell across the cell membrane or not. It has been illustrated that REE could travel across the biomembrane into the cells by cell studies in vitro as well as in studies of animals fed with REEs diet. The binding of REE by membrane changes its permeability and makes intracellular ion transportable. Entrance of REEs may influence the cellular function. In addition, the REE distribution and behavior in cell are discussed.

  1. 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.

  2. Effects of rare earth elements and REE-binding proteins on physiological responses in plants.

    PubMed

    Liu, Dongwu; Wang, Xue; Chen, Zhiwei

    2012-02-01

    Rare earth elements (REEs), which include 17 elements in the periodic table, share chemical properties related to a similar external electronic configuration. REEs enriched fertilizers have been used in China since the 1980s. REEs could enter the cell and cell organelles, influence plant growth, and mainly be bound with the biological macromolecules. REE-binding proteins have been found in some plants. In addition, the chlorophyll activities and photosynthetic rate can be regulated by REEs. REEs could promote the protective function of cell membrane and enhance the plant resistance capability to stress produced by environmental factors, and affect the plant physiological mechanism by regulating the Ca²⁺ level in the plant cells. The focus of present review is to describe how REEs and REE-binding proteins participate in the physiological responses in plants.

  3. Geochemistry of rare earth elements in Permian coals from the Huaibei Coalfield, China

    USGS Publications Warehouse

    Zheng, Lingyun; Liu, Gaisheng; Chou, C.-L.; Qi, C.; Zhang, Y.

    2007-01-01

    The rare earth elements (REEs) in coals are important because of: (a) REE patterns can be an indicator of the nature of source rocks of the mineral matter as well as sedimentary environments; (b) REEs abundance in coal may have industrial-significance. In this study, a total of thirty-four samples of Permian coal, partings, roof, and floor were collected from the Huaibei Coalfield, Anhui Province, China. Abundances of rare earth elements (REEs) and other elements in the samples were determined by inductively coupled-plasma mass spectrometry (ICP-MS) and inductively coupled-plasma atomic emission spectrometry (ICP-AES). The results show that the REEs are enriched in coals in the Huaibei Coalfield as compared with Chinese and U.S. coals and the world coal average. Coals in the Lower Shihezi Formation (No. 7, 5, and 4 Coals) and Upper Shihezi Formation (No. 3) have higher REE abundances than the coals in Shanxi Formation (No. 10). Magmatic intrusion resulted in high enrichment of REEs concentrations in No. 5 and 7 Coals. The REE abundances are positively correlated with the ash content. The mineral matter in these coals is mainly made up of clay minerals and carbonates. The REEs are positively correlated with lithophile elements including Si, Al, Ti, Fe, and Na, which are mainly distributed in clay minerals, indicating that REEs are contained mainly in clay minerals. The REE abundances in coals normalized by the ash are higher than that in partings. REEs abundances of coals cannot be accounted for by the REE content in the mineral matter, and some REEs associated with organic matter in coals. ?? 2007 Elsevier Ltd. All rights reserved.

  4. Geochemistry of rare earth elements in Permian coals from the Huaibei Coalfield, China

    NASA Astrophysics Data System (ADS)

    Zheng, Liugen; Liu, Guijian; Chou, Chen-Lin; Qi, Cuicui; Zhang, Ying

    2007-10-01

    The rare earth elements (REEs) in coals are important because of: (a) REE patterns can be an indicator of the nature of source rocks of the mineral matter as well as sedimentary environments; (b) REEs abundance in coal may have industrial-significance. In this study, a total of thirty-four samples of Permian coal, partings, roof, and floor were collected from the Huaibei Coalfield, Anhui Province, China. Abundances of rare earth elements (REEs) and other elements in the samples were determined by inductively coupled-plasma mass spectrometry (ICP-MS) and inductively coupled-plasma atomic emission spectrometry (ICP-AES). The results show that the REEs are enriched in coals in the Huaibei Coalfield as compared with Chinese and U.S. coals and the world coal average. Coals in the Lower Shihezi Formation (No. 7, 5, and 4 Coals) and Upper Shihezi Formation (No. 3) have higher REE abundances than the coals in Shanxi Formation (No. 10). Magmatic intrusion resulted in high enrichment of REEs concentrations in No. 5 and 7 Coals. The REE abundances are positively correlated with the ash content. The mineral matter in these coals is mainly made up of clay minerals and carbonates. The REEs are positively correlated with lithophile elements including Si, Al, Ti, Fe, and Na, which are mainly distributed in clay minerals, indicating that REEs are contained mainly in clay minerals. The REE abundances in coals normalized by the ash are higher than that in partings. REEs abundances of coals cannot be accounted for by the REE content in the mineral matter, and some REEs associated with organic matter in coals.

  5. Determination of rare earth elements in high purity rare earth oxides by liquid chromatography, thermionic mass spectrometry and combined liquid chromatography/thermionic mass spectrometry

    NASA Astrophysics Data System (ADS)

    Stijfhoorn, D. E.; Stray, H.; Hjelmseth, H.

    1993-03-01

    A high-performance liquid Chromatographie (HPLC) method for the determination of rare earth elements in rocks has been modified and used for the determination of rare earth elements (REE) in high purity rare earth oxides. The detection limit was 1-1.5 ng or 2-3 mg/kg when a solution corresponding to 0.5 mg of the rare earth oxide was injected. The REE determination was also carried out by adding a mixture of selected REE isotopes to the sample and analysing the collected HPLC-fractions by mass spectrometry (MS) using a thermionic source. Since the matrix element was not collected, interference from this element during the mass spectrometric analysis was avoided. Detection limits as low as 0.5 mg/kg could then be obtained. Detection limits as low as 0.05 mg/kg were possible by MS without HPLC-pre-separation, but this approach could only be used for those elements that were not affected by the matrix. Commercial samples of high purity Nd 2O 3, Gd 2O 3 and Dy 2O 3 were analysed in this study, and a comparison of results obtained by HPLC, combined HPLC/MS and direct MS are presented.

  6. 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.

  7. Rare earth element components in atmospheric particulates in the Bayan Obo mine region.

    PubMed

    Wang, Lingqing; Liang, Tao; Zhang, Qian; Li, Kexin

    2014-05-01

    The Bayan Obo mine, located in Inner Mongolia, China, is the largest light rare earth body ever found in the world. The research for rare earth elements (REEs) enrichment in atmospheric particulates caused by mining and ore processing is fairly limited so far. In this paper, atmospheric particulates including total suspended particulate (TSP) matter and particles with an equivalent aerodynamic diameter less than 10 μm (PM10) were collected around the Bayan Obo mine region, in August 2012 and March 2013, to analyze the levels and distributions of REEs in particles. The total concentrations of REEs for TSP were 149.8 and 239.6 ng/m(3), and those for PM10 were 42.8 and 68.9 ng/m(3), in August 2012 and March 2013, respectively. Enrichment factor was calculated for all 14 REEs in the TSP and PM10 and the results indicated that REEs enrichment in atmosphere particulates was caused by anthropogenic sources and influenced by the strong wind in springtime. The spatial distribution of REEs in TSP showed a strong gradient concentration in the prevailing wind direction. REE chondrite normalized patterns of TSP and PM10 were similar and the normalized curves inclined to the right side, showing the conspicuous fractionation between the light REEs and heavy REE, which supported by the chondrite normalized concentration ratios calculated for selected elements (La(N)/Yb(N), La(N)/Sm(N), Gd(N)/Yb(N)).

  8. Uptake and effect of rare earth elements on gene expression in Methylosinus trichosporium OB3b

    DOE PAGES

    Gu, Wenyu; Farhan Ul Haque, Muhammad; DiSpirito, Alan A.; ...

    2016-05-12

    It is well-known that M. trichosporium OB3b has two forms of methane monooxygenase responsible for the initial conversion of methane to methanol, a cytoplasmic (soluble) methane monooxygenase (sMMO) and a membrane-associated (particulate) methane monooxygenase (pMMO) and that copper strongly regulates expression of these alternative forms of MMO. More recently, it has been discovered that M. trichosporium OB3b has multiple types of the methanol dehydrogenase (MeDH), i.e. the Mxa-MeDH and Xox-MeDH, and the expression of these two forms is regulated by the availability of the rare earth element, cerium. Here we extend these studies and show that lanthanum, praseodymium, neodymium andmore » samarium also regulate expression of alternative forms of MeDH. The effect of these rare earth elements on MeDH expression, however, was only observed in the absence of copper. Further, a mutant of M. trichosporium OB3b where the Mxa-MeDH was knocked out was able to grow in the presence of lanthanum, praseodymium and neodymium, but was not able to grow in the presence of samarium. In conclusion, collectively these data suggest that multiple levels of gene regulation by metals exist in M. trichosporium OB3b but that copper overrides the effect of other metals by an as yet unknown mechanism.« less

  9. Rare earth elements in soils from selected areas on the Island of Hawaii

    SciTech Connect

    Barnard, W.M.; Halbig, J.B.

    1985-07-01

    Fifty soil samples for the wet, windward (east) side and dry, leeward (west) side of the Island of Hawaii were analyzed for La, Ce, Sm, Eu, Yb, and Lu by neutron activation/gamma-ray spectroscopic analysis. Data on concentrations in each sample are listed and analyzed statistically for soil samples collected from the western slope of Kohala Mountain, the western coastal plain of Mauna Kea, and the Northeastern coastal plain of Maunal Loa. Rare earth element (REE) concentrations are two to six times greater in soils from the western, dry side of the island, and good statistical correlation is exhibited among the samples for pairs of individual REEs. In the organic-rich soils of the east side, correlations are poor but are markedly improved when sample weights are adjusted for weight due to organic matter and water in soil colloids. If the mean compositions of selected rock samples from the Hawaii Reference Suite are representative of the compositions of the parent materials, REEs in the soils are moderately enriched (up to two times, based on oven-dry weights). Rare earth element concentrations in the island's western soils are as much as two times greater than the mean REE values of common sedimentary rocks worldwide; however, they are well within the concentration ranges of soils of continental origin. The eastern soils tend to have less La and Ce, but similar amounts of the middle and heavy REEs.

  10. While China's dominance in rare earths dips, concerns remain about these and other elements

    NASA Astrophysics Data System (ADS)

    Showstack, Randy

    2012-05-01

    China's dominance in the production of rare earth elements (REEs) peaked with that nation producing 97% of them in 2010; this number already has dipped to 90% in 2012 as mines in other nations are coming online, according to REE expert Karl Gschneidner Jr., a professor at Iowa State University's Ames Laboratory. Chinese production could drop to 60% by 2014, with production increasing at mines in the United States and other countries, he said. However, this reduction in China's share of REE production does not signal an end to the production crisis in REEs and other critical minerals, Gschneidner and others noted during a 1 May panel discussion on critical materials shortages at the AGU Science Policy Conference in Washington, D. C. REEs are a group of 17 chemically similar metallic elements used in a variety of electronic, optical, magnetic, and catalytic applications, and despite their name, they are relatively plentiful in the Earth's crust. China's control of known REE reserves has dropped from 75% in 1975 to 30.9% in 2012, with other regions also having large reserves, including the Commonwealth of Independent States (some former Soviet Republic states), the United States, and Australia, according to Gschneidner. Critical minerals are mineral commodities that are particularly important for a nation's economy or national defense that could potentially face supply disruptions.

  11. Seawater rare-earth element patterns preserved in apatite of Pennsylvanian conodonts?

    NASA Astrophysics Data System (ADS)

    Bright, Camomilia A.; Cruse, Anna M.; Lyons, Timothy W.; MacLeod, Kenneth G.; Glascock, Michael D.; Ethington, Raymond L.

    2009-03-01

    Past workers have used rare-earth element patterns recorded in biogenic apatite as proxies for original seawater chemistry. To explore the potency of this approach, we analyzed Pennsylvanian conodonts from limestones, gray shales, and black shales of the Fort Scott and Pawnee formations (Desmoinesian) and Swope and Dennis formations (Missourian) in Kansas, Missouri, and Iowa, U.S.A. Analysis of individual platform conodonts from seven taxa using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) revealed a consistent enrichment in the middle rare-earth elements (MREE). Analogous MREE enrichment has been observed in authigenic apatite and bulk samples of phosphate-rich black shales from the same formations. Importantly, however, phosphate-depleted shales intimately associated with the P-rich intervals are relatively depleted in MREE. These antithetic patterns argue convincingly for secondary migration from the bulk sediment into the phosphate, and the extent of MREE enrichment in the conodonts is correlated positively with the total REE content. MREE enrichment in conodonts does not vary systematically as a function of lithology, stratigraphic level, conodont genus, geographic location, or with independent estimates of paleoredox conditions in the bottom waters. Collectively, these results argue for postmortem (diagenetic) REE uptake resulting in a pronounced (and progressive) MREE enrichment. Any cerium anomalies, if initially present, were masked by diagenetic uptake of REE. Paleoenvironmental interpretations of conodont REE, particularly for samples exhibiting MREE enrichment, should therefore be viewed with caution.

  12. Composition, characteristic and activity of rare earth element-bound polysaccharide from tea.

    PubMed

    Wang, D; Wang, C; Zhao, G; Wei, Z; Tao, Y; Liang, X

    2001-09-01

    The compositions and structural characteristics of rare earth elements-bound polysaccharides from tea (REE-TPS) were studied with the methods of Inductively Coupled Plasma Mass Spectrometry (ICP-MS), Gas Chromatography (GC) and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. The results show that polysaccharide from tea (TPS) was a sort of glycoprotein and coordinated with Rare Earth Elements (REE) closely. The sugar fraction was composed of Rha, Ara, Xyl, Fuc, Glc, and Gal. There existed almost all natural amino acids with Glx, Asx, and Hyp as the major parts in the protein fraction. The REEs in REE-TPS were mainly composed of La, Ce, and Nd, especially, more than 75% of them was La. The coordination atom of the first coordination shell of La in REE-TPS was oxygen, the coordination number of which was 6, and the average distance between the atoms was 2.52 A. The second shell was formed from sulfur atoms, the coordination number and the average distance were 3 and 2.91 A, respectively. The bio-experiments show that REE-TPS could decrease the content of blood glucose in mice significantly.

  13. Rare earth elements--a new generation of growth promoters for pigs?

    PubMed

    He, M L; Rambeck, W A

    2000-01-01

    The present study which includes two feeding experiments was performed to investigate a possible performance enhancing effect of rare earth elements (REF) in piglets. This performance enhancing effect has been described in the Chinese literature for a long time, however, it was never tested under "western conditions". In the first feeding experiment 72 piglets at a mean BW of 7.3 kg were allotted to a control and to 4 REE groups at different levels of lanthanum chloride or an REE mixture containing mainly chlorides of lanthanum, cerium and praseodymium. The experimental period lasted 5 weeks. Positive effects of REE were found on body weight gain as well as on feed conversion ratio of the piglets. Compared to the control group, the daily weight gain was improved by 2 to 5% and feed conversion was better by up to 7%. These effects were, however, not significant. In the second feeding experiment, piglets (mean BW 17.3 kg) were fed for 8 weeks with a similar REE mixture. Significant positive effects of REE were found on both body weight gain and on feed conversion ratio by 19% and 10%, respectively. This is the first time that a performance enhancing effect of REE in pigs under western feeding conditions has been shown. Since the use of antibiotics as growth promoters in animal feed has been restricted in the European Union recently, rare earth elements might be of interest as new, safe and inexpensive alternative performance enhancers.

  14. Behavior and distribution of heavy metals including rare Earth elements, thorium, and uranium in sludge from industry water treatment plant and recovery method of metals by biosurfactants application.

    PubMed

    Gao, Lidi; Kano, Naoki; Sato, Yuichi; Li, Chong; Zhang, Shuang; Imaizumi, Hiroshi

    2012-01-01

    In order to investigate the behavior, distribution, and characteristics of heavy metals including rare earth elements (REEs), thorium (Th), and uranium (U) in sludge, the total and fractional concentrations of these elements in sludge collected from an industry water treatment plant were determined and compared with those in natural soil. In addition, the removal/recovery process of heavy metals (Pb, Cr, and Ni) from the polluted sludge was studied with biosurfactant (saponin and sophorolipid) elution by batch and column experiments to evaluate the efficiency of biosurfactant for the removal of heavy metals. Consequently, the following matters have been largely clarified. (1) Heavy metallic elements in sludge have generally larger concentrations and exist as more unstable fraction than those in natural soil. (2) Nonionic saponin including carboxyl group is more efficient than sophorolipid for the removal of heavy metals in polluted sludge. Saponin has selectivity for the mobilization of heavy metals and mainly reacts with heavy metals in F3 (the fraction bound to carbonates) and F5 (the fraction bound to Fe-Mn oxides). (3) The recovery efficiency of heavy metals (Pb, Ni, and Cr) reached about 90-100% using a precipitation method with alkaline solution.

  15. Toward understanding early Earth evolution: Prescription for approach from terrestrial noble gas and light element records in lunar soils

    PubMed Central

    Ozima, Minoru; Yin, Qing-Zhu; Podosek, Frank A.; Miura, Yayoi N.

    2008-01-01

    Because of the almost total lack of geological record on the Earth's surface before 4 billion years ago, the history of the Earth during this period is still enigmatic. Here we describe a practical approach to tackle the formidable problems caused by this lack. We propose that examinations of lunar soils for light elements such as He, N, O, Ne, and Ar would shed a new light on this dark age in the Earth's history and resolve three of the most fundamental questions in earth science: the onset time of the geomagnetic field, the appearance of an oxygen atmosphere, and the secular variation of an Earth–Moon dynamical system. PMID:19001263

  16. Recovery of rare earth elements from the sulfothermophilic red alga Galdieria sulphuraria using aqueous acid.

    PubMed

    Minoda, Ayumi; Sawada, Hitomi; Suzuki, Sonoe; Miyashita, Shin-ichi; Inagaki, Kazumi; Yamamoto, Takaiku; Tsuzuki, Mikio

    2015-02-01

    The demand for rare earth elements has increased dramatically in recent years because of their numerous industrial applications, and considerable research efforts have consequently been directed toward recycling these materials. The accumulation of metals in microorganisms is a low-cost and environmentally friendly method for the recovery of metals present in the environment at low levels. Numerous metals, including rare earth elements, can be readily dissolved in aqueous acid, but the efficiency of metal biosorption is usually decreased under the acidic conditions. In this report, we have investigated the use of the sulfothermophilic red alga Galdieria sulphuraria for the recovery of metals, with particular emphasis on the recovery of rare earth metals. Of the five different growth conditions investigated where G. sulphuraria could undergo an adaptation process, Nd(III), Dy(III), and Cu(II) were efficiently recovered from a solution containing a mixture of different metals under semi-anaerobic heterotrophic condition at a pH of 2.5. G. sulphuraria also recovered Nd(III), Dy(III), La(III), and Cu(II) with greater than 90% efficiency at a concentration of 0.5 ppm. The efficiency remained unchanged at pH values in the range of 1.5-2.5. Furthermore, at pH values in the range of 1.0-1.5, the lanthanoid ions were collected much more efficiently into the cell fractions than Cu(II) and therefore successfully separated from the Cu(II) dissolved in the aqueous acid. Microscope observation of the cells using alizarin red suggested that the metals were accumulating inside of the cells. Experiments using dead cells suggested that this phenomenon was a biological process involving specific activities within the cells.

  17. Distribution characteristics of rare earth elements in children's scalp hair from a rare earths mining area in southern China.

    PubMed

    Tong, Shi-Lu; Zhu, Wang-Zhao; Gao, Zhao-Hua; Meng, Yu-Xiu; Peng, Rui-Ling; Lu, Guo-Cheng

    2004-01-01

    In order to demonstrate the validity of using scalp hair rare earth elements (REEs) content as a biomarker of human REEs exposure, data were collected on REEs exposure levels from children aged 11-15 years old and living in an ion-adsorptive type light REEs (LREEs) mining and surrounding areas in southern China. Sixty scalp hair samples were analyzed by ICP-MS for 16 REEs (La Lu, Y and Sc). Sixteen REEs contents in the samples from the mining area (e.g., range: La: 0.14-6.93 microg/g; Nd: 0.09-5.27 microg/g; Gd: 12.2-645.6ng/g; Lu: 0.2-13.3 ng/g; Y: 0.03-1.27 microg/g; Sc: 0.05-0.30 microg/g) were significantly higher than those from the reference area (range: La: 0.04-0.40 microg/g; Nd: 0.04-0.32 microg/g; Gd: 8.3-64.6 ng/g; Lu: 0.4-3.3ng/g; Y: 0.03-0.29 microg/g; Sc: 0.11-0.36 microg/g) and even much higher than those published in the literature. The distribution pattern of REEs in scalp hair from the mining area was very similar to that of REEs in the mine and the atmosphere shrouding that area. In conclusion, the scalp hair REEs contents may indicate not only quantitatively but also qualitatively (distribution pattern) the absorption of REEs from environmental exposure into human body. The children living in this mining area should be regarded as a high-risk group with REEs (especially LREEs) exposure, and their health status should be examined from a REEs health risk assessment perspective.

  18. Earth Observatory Satellite system definition study. Report no. 5: System design and specifications. Part 1: Observatory system element specifications

    NASA Technical Reports Server (NTRS)

    1974-01-01

    The performance, design, and quality assurance requirements for the Earth Observatory Satellite (EOS) Observatory and Ground System program elements required to perform the Land Resources Management (LRM) A-type mission are presented. The requirements for the Observatory element with the exception of the instruments specifications are contained in the first part.

  19. The possible role of hydrogen in the substitution of rare earth elements into zircon

    NASA Astrophysics Data System (ADS)

    Hinton, R.; MacDonald, R.; Macgarvie, D.; Tindle, A.; Harley, S.

    2003-04-01

    Ion microprobe measurements have been made of trace element concentrations in zircon and surrounding fresh glass of 5 recently erupted rhyolites. In particular analyses have included not only rare earth elements (REE), but many of the elements that have been suggested to be incorporated into zircon. Y and the REE elements were found to be the dominant trace elements in the zircon and these elements varied by over an order of magnitude between grains despite a relatively constant REE content in the surrounding glasses. Strong correlations were observed between Y and all other REE except Ce and Eu. As has been previously observed, the REE partitioning coefficients (zircon/glass) increased strongly from La to Lu. The Ce partitioning was significantly higher than the neighbouring REE (as this element dominantly substitutes as the 4+ ion). Whereas it has been previously demonstrated that xenotime substitution occurs in zircon it is clear that in some strongly zoned crystals the P content is insufficient to permit complete charge balance. In the zircons analysed here there also appears to be insufficient P to permit charge balance. The P_2O_5 did not exceed 0.15 wt.% yet the total Y and REE oxide concentrations ranged up to about 2 wt.%. Concentrations of other trace elements were invariably very low (Li, Na, K, Be, Mg, Ca, Sr and Ba) less than 7 ppm and Al less than 5 ppm wt. Sc, Ti and Fe were less than 40 ppm wt. and V, Cr and Mn less than 1 ppm wt. F concentrations (7 to 200 ppm wt.) correlated poorly with Y and the REE but were about an order of magnitude too low to permit any major charge coupling with the REE. Although no zircon water standard was available, initial estimates of the water content suggest that the zircons contained between 0.01 to 0.09 wt.% H_2O (background approximately 0.008 wt.% H_2O). Somewhat surprisingly the H contents displayed a very good correlation with the Y (and REE) content. Further, although low, these water concentrations appear to

  20. Composition of the earth's upper mantle-I. Siderophile trace elements in ultramafic nodules

    USGS Publications Warehouse

    Morgan, J.W.; Wandless, G.A.; Petrie, R.K.; Irving, A.J.

    1981-01-01

    Seven siderophile elements (Au, Ge, Ir, Ni, Pd, Os, Re) were determined by radiochemical neutron activation analysis in 19 ultramafic rocks, which are spinel lherzollites-xenoliths from North and Central America, Hawaii and Australia, and garnet Iherzolitexenoliths from Lesotho. Abundances of the platinum metals are very uniform in spinel lherzolites averaging 3.4 ?? 1.2 ppb Os, 3.7 ?? 1.1 ppb Ir, and 4.6 ?? 2.0 ppb Pd. Sheared garnet lherzolite PHN 1611 has similar abundances of these elements, but in 4 granulated garnet lherzolites, abundances are more variable. In all samples, the Pt metals retain cosmic ( Cl-chondrite) ratios. Abundances of Au and Re vary more than those of Pt metals, but the Au/Re ratio remains close to the cosmic value. The fact that higher values of Au and Re approach cosmic proportions with respect to the Pt metals, suggests that Au and Re have been depleted in some ultramafic rocks from an initially chondrite-like pattern equivalent to about 0.01 of Cl chondrite abundances. The relative enrichment of Au and Re in crustal rocks is apparently the result of crust-mantle fractionation and does not require a special circumstance of core-mantle partitioning. Abundances of moderately volatile elements Ni, Co and Ge are very uniform in all rocks, and are much higher than those of the highly siderophile elements Au, Ir, Pd, Os and Re. When normalized to Cl chondrites, abundances of Ni and Co are nearly identical, averaging 0.20 ?? 0.02 and 0.22 ?? 0.02, respectively; but Ge is only 0.027 ?? 0.004. The low abundance of Ge relative to Ni and Co is apparently a reflection of the general depletion of volatile elements in the Earth. The moderately siderophile elements cannot be derived from the same source as the highly siderophile elements because of the marked difference in Cl chondrite-normalized abundances and patterns. We suggest that most of the Ni, Co and Ge were enriched in the silicate by the partial oxidation of pre-existing volatile-poor Fe

  1. Effect of the addition of low rare earth elements (lanthanum, neodymium, cerium) on the biodegradation and biocompatibility of magnesium.

    PubMed

    Willbold, Elmar; Gu, Xuenan; Albert, Devon; Kalla, Katharina; Bobe, Katharina; Brauneis, Maria; Janning, Carla; Nellesen, Jens; Czayka, Wolfgang; Tillmann, Wolfgang; Zheng, Yufeng; Witte, Frank

    2015-01-01

    Rare earth elements are promising alloying element candidates for magnesium alloys used as biodegradable devices in biomedical applications. Rare earth elements have significant effects on the high temperature strength as well as the creep resistance of alloys and they improve magnesium corrosion resistance. We focused on lanthanum, neodymium and cerium to produce magnesium alloys with commonly used rare earth element concentrations. We showed that low concentrations of rare earth elements do not promote bone growth inside a 750 μm broad area around the implant. However, increased bone growth was observed at a greater distance from the degrading alloys. Clinically and histologically, the alloys and their corrosion products caused no systematic or local cytotoxicological effects. Using microtomography and in vitro experiments, we could show that the magnesium-rare earth element alloys showed low corrosion rates, both in in vitro and in vivo. The lanthanum- and cerium-containing alloys degraded at comparable rates, whereas the neodymium-containing alloy showed the lowest corrosion rates.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Investigation on the co-precipitation of transuranium elements from alkaline solutions by the method of appearing reagents

    SciTech Connect

    Krot, N.; Shilov, V.; Bessonov, A.; Budantseva, N.; Charushnikova, I.; Perminov, V.; Astafurova, L.

    1996-06-06

    Highly alkaline radioactive waste solutions originating from production of plutonium for military purposes are stored in underground tanks at the U.S. Department of Energy Hanford Site. The purification of alkaline solutions from neptunium and plutonium is important in the treatment and disposal of these wastes. This report describes scoping tests with sodium hydroxide solutions, where precipitation techniques were investigated to perform the separation. Hydroxides of iron (III), manganese (II), cobalt (II, III), and chromium (III); manganese (IV) oxide, and sodium uranate were investigated as carriers. The report describes the optimum conditions that were identified to precipitate these carriers homogeneously throughout the solution by reductive, hydrolytic, or catalytic decomposition of alkali-soluble precursor compounds by a technique called the Method of Appearing Reagents. The coprecipitation of pentavalent and hexavalent neptunium and plutonium was investigated for the candidate agents under optimum conditions and is described in this report along with the following results. Plutonium coprecipitated well with all tested materials except manganese (IV) oxide. Neptunium only coprecipitated well with uranate. The report presents a hypothesis to explain these behaviors. Further tests with more complex solution matrices must be performed.

  8. On Re-Entry Prediction of Near Earth Objects with Genetic Algorithm Using KS Elements

    NASA Astrophysics Data System (ADS)

    Sharma, R. K.; Anilkumar, A. K.; Xavier James Raj, M.; Sabarinath, A.

    2009-03-01

    The accurate orbit prediction of the near-Earth objects is an important requirement for the re-entry and the life time estimation. The method of Kustaanheimo and Stiefel (KS) total energy element equations is one of the powerful methods for orbit prediction. Recently, due to the reentries of large number of risk objects, which posses threat to the human life and property, a great concern is developed in the space scientific community. Consequently, the prediction of risk objects re-entry time and location has got much importance for the proper planning of mitigation strategies and hazard assessment. This paper discusses an integrated procedure for orbit life time prediction combining the KS elements and genetic algorithm (GA). The orbit prediction is carried out by numerically integrating the KS element equations. In this methodology, the ballistic coefficient is estimated from a set of observed orbital parameters in terms of the Two Line Elements (TLE) by minimizing the variance of the predicted re-entry time from different TLE using GA. A software, KSGEN, systematically developed in-house using KS elements and genetic algorithm is utilized for predicting the re-entry time of the risk objects. This software has been effectively used for the prediction of the re-entry time in the past seven re-entry exercise campaigns conducted by the Inter Agency Space Debris Coordination Committee (IADC). The predicted re-entry time matched quite well with the actual re-entry time for all the seven IADC re-entry campaigns. A detailed analysis is carried out with two case studies.

  9. Cracking the Code of Soil Genesis. The Early Role of Rare Earth Elements

    NASA Astrophysics Data System (ADS)

    Zaharescu, D. G.; Dontsova, K.; Burghelea, C. I.; Maier, R. M.; Huxman, T. E.; Chorover, J.

    2014-12-01

    Soil is terrestrial life support system. Its genesis involves tight interactions between biota and mineral surfaces that mobilize structural elements into biogeochemical cycles. Of all chemical elements rare earth elements (REE) are a group of 16 non-nutrient elements of unusual geochemical similarity and present in all components of the surface environment. While much is known about the role of major nutrients in soil development we lack vital understanding of how early biotic colonization affects more conservative elements such as REE. A highly controlled experiment was set up at University of Arizona's Biosphere-2 that tested the effect of 4 biological treatments, incorporating a combination of microbe, grass, mycorrhiza and uninoculated control on REE leaching and uptake in 4 bedrock substrates: basalt, rhyolite, granite and schist. Generally the response of REE to biota presence was synergistic. Variation in total bedrock chemistry could explain major trends in pore water REE. There was a fast transition from chemistry-dominated to a biota dominated environment in the first 3-4 months of inoculation/seeding which translated into increase in REE signal over time. Relative REE abundances in water were generally reflected in plant concentrations, particularly in root, implying that below ground biomass is the main sync of REE in the ecosystem. Mycorrhiza effect on REE uptake in plant organs was significant and increased with infection rates. Presence of different biota translated into subtle differences in REE release, reveling potential biosignatures of biolota-rock colonization. The results thus bring fundamental insight into early stages non-nutrient cycle and soil genesis.

  10. Levels of platinum group elements and rare-earth elements in wild mushroom species growing in Poland.

    PubMed

    Mleczek, Mirosław; Niedzielski, Przemysław; Kalač, Pavel; Siwulski, Marek; Rzymski, Piotr; Gąsecka, Monika

    2016-01-01

    Due to limited data-describing abilities of mushrooms to accumulate platinum group elements (PGEs) and rare-earth elements (REEs), the aim of this study was to determine, by inductively coupled plasma optical emission spectrometry followed by microwave-assisted sample digestion by nitric acid, the content of these elements in 20 mushroom species (10 above ground and 10 growing on wood), mostly edible, collected near a busy trunk road. The highest content of PGEs in above-ground mushroom species was observed in Lepista gilva and Suillus bovinus fruit bodies (0.38 ± 0.05 and 0.37 ± 0.03 mg kg(-1) DW, respectively), while in mushrooms growing on wood, the highest content was observed in Pleurotus ostreatus (0.35 ± 0.04 mg kg(-1) DW). The mean content of PGEs for both these groups was 0.23 ± 0.08 and 0.26 ± 0.07 mg kg(-1) DW, respectively. The highest content of REEs in Suillus luteus and Tricholoma equestra was 5.03 ± 0.50 and 2.18 ± 0.56 mg kg(-1) DW, respectively, but within mushrooms growing on wood in Ganoderma applanatum fruiting bodies it was 4.19 ± 0.78 mg kg(-1) DW. Mean contents of REEs were 1.39 ± 1.21 and 1.61 ± 0.97 mg kg(-1) DW in above-ground species and species growing on wood, respectively. Generally, the group of mushroom species growing on wood was capable of slightly higher accumulation of both REEs and PGEs. No limits have been established for both the groups until now.

  11. The effect of diagenesis and fluid migration on rare earth element distribution in pore fluids of the northern Cascadia accretionary margin

    USGS Publications Warehouse

    Kim, Ji-Hoon; Torres, Marta E.; Haley, Brian A.; Kastner, Miriam; Pohlman, John W.; Riedel, Michael; Lee, Young-Joo

    2012-01-01

    Analytical challenges in obtaining high quality measurements of rare earth elements (REEs) from small pore fluid volumes have limited the application of REEs as deep fluid geochemical tracers. Using a recently developed analytical technique, we analyzed REEs from pore fluids collected from Sites U1325 and U1329, drilled on the northern Cascadia margin during the Integrated Ocean Drilling Program (IODP) Expedition 311, to investigate the REE behavior during diagenesis and their utility as tracers of deep fluid migration. These sites were selected because they represent contrasting settings on an accretionary margin: a ponded basin at the toe of the margin, and the landward Tofino Basin near the shelf's edge. REE concentrations of pore fluid in the methanogenic zone at Sites U1325 and U1329 correlate positively with concentrations of dissolved organic carbon (DOC) and alkalinity. Fractionations across the REE series are driven by preferential complexation of the heavy REEs. Simultaneous enrichment of diagenetic indicators (DOC and alkalinity) and of REEs (in particular the heavy elements Ho to Lu), suggests that the heavy REEs are released during particulate organic carbon (POC) degradation and are subsequently chelated by DOC. REE concentrations are greater at Site U1325, a site where shorter residence times of POC in sulfate-bearing redox zones may enhance REE burial efficiency within sulfidic and methanogenic sediment zones where REE release ensues. Cross-plots of La concentrations versus Cl, Li and Sr delineate a distinct field for the deep fluids (z > 75 mbsf) at Site U1329, and indicate the presence of a fluid not observed at the other sites drilled on the Cascadia margin. Changes in REE patterns, the presence of a positive Eu anomaly, and other available geochemical data for this site suggest a complex hydrology and possible interaction with the igneous Crescent Terrane, located east of the drilled transect.

  12. Siderophile and chalcophile element abundances in oceanic basalts, Pb isotope evolution and growth of the earth's core

    NASA Technical Reports Server (NTRS)

    Newsom, H. E.; White, W. M.; Jochum, K. P.; Hofmann, A. W.

    1986-01-01

    The hypothesis that the mantle Pb isotope ratios reflect continued extraction of Pb into the earth's core over geologic time is evaluated by studying the depeletion of chalcophile and siderophile elements in the mantle. Oceanic basalt samples are analyzed in order to determine the Pb, Sr, and Nd isotropic compositions and the abundances of siderophile and chalcophile elements and incompatible lithophile elements. The data reveal that there is no systematic variation of siderophile or chalcophile element abundances relative to abundances of lithophile elements and the Pb/Ce ratio of the mantle is constant. It is suggested that the crust formation involves nonmagmatic and magmatic processes.

  13. 'Nano' Morphology and Element Signatures of Early Life on Earth: A New Tool for Assessing Biogenicity

    NASA Technical Reports Server (NTRS)

    Oehler, D. Z.; Mostefaoui, S.; Meibom, A.; Selo, M.; McKay, D. S.; Robert, F.

    2006-01-01

    The relatively young technology of NanoSIMS is unlocking an exciting new level of information from organic matter in ancient sediments. We are using this technique to characterize Proterozoic organic material that is clearly biogenic as a guide for interpreting controversial organic structures in either terrestrial or extraterrestrial samples. NanoSIMS is secondary ion mass spectrometry for trace element and isotope analysis at sub-micron resolution. In 2005, Robert et al. [1] combined NanoSIMS element maps with optical microscopic imagery in an effort to develop a new method for assessing biogenicity of Precambrian structures. The ability of NanoSIMS to map simultaneously the distribution of organic elements with a 50 nm spatial resolution provides new biologic markers that could help define the timing of life s development on Earth. The current study corroborates the work of Robert et al. and builds on their study by using NanoSIMS to map C, N (as CN), S, Si and O of both excellently preserved microfossils and less well preserved, non-descript organics in Proterozoic chert from the ca. 0.8 Ga Bitter Springs Formation of Australia.

  14. Accumulation of rare earth elements in human bone within the lifespan.

    PubMed

    Zaichick, Sofia; Zaichick, Vladimir; Karandashev, Vasilii; Nosenko, Sergey

    2011-02-01

    For the first time, the contents of rare earth elements (REEs) in a rib bone of a healthy human were determined. The mean value of the contents of Ce, Dy, Er, Gd, La, Nd, Pr, Sm, Tb, and Yb (10 elements out of 17 total REEs), as well as the upper limit of means for Ho, Lu, Tm, and Y (4 elements) were measured in the rib bone tissue of 38 females and 42 males (15 to 55 years old) using inductively coupled plasma mass spectrometry (ICP-MS). We found age-related accumulation of REEs in the bone tissue of healthy individuals who lived in a non-industrial region. It was calculated that during a lifespan the content of REEs in a skeleton of non-industrial region residents may increase by one to two orders of magnitude. Using our results as indicative normal values and published data we estimated relative Gd accumulation in the bone tissue of patients according to magnetic resonance imaging with contrast agent and La accumulation in the bone tissue of patients receiving hemodialysis after treatment with lanthanum carbonate as a phosphate binder. It was shown that after such procedures contents of Gd and La in the bone tissue of patients are two to three orders of magnitude higher than normal levels. In our opinion, REEs incorporation may affect bone quality and health similar to other potentially toxic trace metals. The impact of elevated REEs content on bone physiology, biochemistry and morphology requires further investigation.

  15. Rare earth elements in sinters from the geothermal waters (hot springs) on the Tibetan Plateau, China

    NASA Astrophysics Data System (ADS)

    Feng, Jin-Liang; Zhao, Zhen-Hong; Chen, Feng; Hu, Hai-Ping

    2014-10-01

    The mineralogical and geochemical composition of sinters from the geothermal areas on the Tibetan Plateau was determined. They occur as siliceous, salty and calcareous sinters but biogenic siliceous sinters were also found. The analyses indicate that there are no distinct inter -element relationships between individual rare earth elements (REEs) and other elements. Formed from the same geothermal water, the mineralogical and chemical composition of the sinters is influenced by their genesis and formation conditions. The REE distributions depend on the origin of the sinters. Fe-Mn phases in sinters tend to scavenge more REEs from geothermal water. Neither the REE fractionation nor the Ce anomaly seems to be associated with Fe-Mn phases in the sinters. The fourth tetrads of some sinters display weak W-type (concave) effects. In contrast, the third tetrads present large effects in some sinters due to positive Gd anomalies. The origin of the positive Eu anomalies in some sinters seems to be caused by preferential dissolution of feldspars during water-rock interaction. The complexing ligands in geothermal water may contribute significantly to the fractionation of REEs in sinters. The dominant CO32- and HCO3- complexing in geothermal water favors enrichment of heavy REEs in calcareous sinters.

  16. [Speciation and distribution characters of rare earth elements in the Baotou Section of the Yellow River].

    PubMed

    He, Jiang; Mi, Na; Kuang, Yun-chen; Fan, Qing-yun; Wang, Xia; Guan, Wei; Li, Gui-hai; Li, Chao-sheng; Wang, Xi-wei

    2004-03-01

    As a whole of water column, suspended matter and surface sediment in the mainstream and the branch taking up industry wastewater, speciation and distribution characters of rare earth elements (REEs) were investigated systemically in the Baotou section of the Yellow River. This study shows that rare earth elements in the mainstream of the Baotou section of the Yellow River mainly exist in suspended particles, and the dissolved contents are in extremely minute quantities. REEs mainly exist in dissolved particles in the branch taking up industry wastewater, and suspended sigma REE and dissolved sigma REE are obviously higher than those in the mainstream. The change of sigma REE of dissolved particles in water phase along the Baotou section of the Yellow River is very similar to that of sigma REE of suspended particles, and consistent along the main river, it is that sigma REE increase appreciably from the control profile to the keystone discharged section, come to a head in the D site and reduce in the E site. This distribution pattern indicates pile industry wastewater of Baotou to rare earth elements in the mainstream of the Yellow River, particularly LREE. The REE distribution in the mainstream of the Baotou section of the Yellow River is the same, with LREE enrichment and Eu depletion. But LREE origin of D site is different from the other sites by excursion of LREE distribution curve and other geochemical parameters, they are origin of industry wastewater piled, otherwise the other four sites are origin of loess altiplano. And HREE are origin of loess altiplano in all the sites. The speciation characteristics of REE in the sediments and suspended matter are quite similar with the amount in as follows: residual > bound to carbonates, bound to Fe-Mn oxides > bound to organic matter > exchangeable. REEs exchangeable in surface sediment and suspended matter in the branch taking up industry wastewater are higher than those in the mainstream, it confirms that REEs in

  17. Strontium isotopes and rare-earth element geochemistry of hydrothermal carbonate deposits from Lake Tanganyika, East Africa

    SciTech Connect

    Barrat, J.A.; Boulegue, J.; Tiercelin, J.J.; Lesourd, M.

    2000-01-01

    At Cape Banza (North Tanganyika Lake), fluids and aragonite chimneys have been collected many times since the discovery of this sublacustrine field in 1987. This sampling has been investigated here for the Sr isotopic compositions and the rare-earth element features of the carbonates and a few fluid samples. The {sup 87}Sr/{sup 86}Sr ratios of the chimneys indicate that they have precipitated from a mixture of lake water (more than 95%) and hydrothermal fluids. No zoning in the chimneys was detected with the Sr data. For the rare-earth elements, the situation is more complex. The external walls of the chimneys are rare-earth-element-poor (La {approx} 500 ppb, Yb {approx} 200 ppb, La/Yb = 2 to 3.4). Their shale normalized rare-earth element patterns suggest that they are in equilibrium with the inferred carbonate-depositing fluids. The rare-earth element concentrations of the internal walls of the chimneys are significantly light rare earth elements (LREE)-enriched with La contents sometimes up to 5 ppm. The authors suggest that they contain more vent-fluid rare-earth elements than the external wall samples, possibly adsorbed on the surface of growing crystals or simply hosted by impurities. It was not possible to constrain the nature of these phases, but the variations of the compositions of the internal wall materials of the active chimneys with time, as well as data obtained on an inactive chimney indicate that this rare-earth element excess is mobile. Partition coefficients were calculated between the external wall aragonite and carbonate-depositing fluid. The results are strikingly similar to the values obtained by Sholkovitz and Shen (1995) on coral aragonite, and suggest that there is no significant biologic effect on the incorporation of rare-earth elements into coral aragonite and that the various carbonate complexes involved Me(CO{sub 3}{sup +}) complexes are the main LREE carriers in seawater instead of Me(CO{sub 3}){sub 2}{sup {minus}} in Banza fluids

  18. Liquid Inclusions in Heat-Resistant Steel Containing Rare Earth Elements

    NASA Astrophysics Data System (ADS)

    Li, Yandong; Liu, Chengjun; Zhang, Tongsheng; Jiang, Maofa; Peng, Cheng

    2017-04-01

    Abundant thermodynamic data of pure substances were incorporated in the coupled thermodynamic model of inclusion precipitation and solute micro-segregation during the solidification of heat-resistant steel containing rare earth elements. The liquid inclusions Ce2 x Al2 y Si1- x-y O z (0 < x < 1, 0 < y < x and z = 1 - x - y) were first introduced to ensure the model more accurately. And the computational method for generation Gibbs free energy of liquid inclusions in molten steel was given. The accuracy of accomplished model was validated through plant trials, lab-scale experiments, and the data published in the literature. The comparisons of results calculated by FactSage with the model were also discussed. Finally, the stable area of liquid inclusions was predicted and the liquid inclusions with larger size were found in the preliminary experiments.

  19. Binary rare earth element-Ni/Co metallic glasses with distinct β-relaxation behaviors

    SciTech Connect

    Zhu, Z. G.; Wang, Z.; Wang, W. H.

    2015-10-21

    We report the formation of a series of rare earth element (RE)-Ni/Co binary metallic glasses (MGs) with unusual distinct β-relaxation peak compared with that of most of the reported MGs which usually exhibit as an excess wing or a shoulder. The β-relaxation behavior of RE-Ni/Co MGs is sensitive to the composition and the atomic radii of the RE and can be tuned through changing the fraction of RE-Ni (or Co) atomic pairs. The novel RE-Ni/Co MGs with distinct β-relaxation can serve as model system to investigate the nature of the β-relaxation as well as its relations with other physical and mechanical properties of MGs.

  20. Rare earths, other trace elements and iron in Luna 20 samples.

    NASA Technical Reports Server (NTRS)

    Helmke, P. A.; Blanchard, D. P.; Jacobs, J. W.; Haskin, L.; Haskin, A.

    1973-01-01

    The results of the analysis by neutron activation of six samples from the Luna 20 mission and one sample of less than 1 mm fines from Apollo 16 are reported. The concentrations of the rare-earth elements (REE) in the samples of fines from Luna 20 and Apollo 16 are less than those found for corresponding materials from the mare areas but a negative Eu anomaly is still present. The concentrations of the REE in fines from Luna 20 are only about two-thirds as great as in the sample of Apollo 16 fines, but the concentration of Co, Sc and Cr are greater by factors ranging from 1.5 to 2.3.

  1. Geochemistry of rare earth elements in a passive treatment system built for acid mine drainage remediation.

    PubMed

    Prudêncio, Maria Isabel; Valente, Teresa; Marques, Rosa; Sequeira Braga, Maria Amália; Pamplona, Jorge

    2015-11-01

    Rare earth elements (REE) were used to assess attenuation processes in a passive system for acid mine drainage treatment (Jales, Portugal). Hydrochemical parameters and REE contents in water, soils and sediments were obtained along the treatment system, after summer and winter. A decrease of REE contents in the water resulting from the interaction with limestone after summer occurs; in the wetlands REE are significantly released by the soil particles to the water. After winter, a higher water dynamics favors the AMD treatment effectiveness and performance since REE contents decrease along the system; La and Ce are preferentially sequestered by ochre sludge but released to the water in the wetlands, influencing the REE pattern of the creek water. Thus, REE fractionation occurs in the passive treatment systems and can be used as tracer to follow up and understand the geochemical processes that promote the remediation of AMD.

  2. Study on the electrochemical extraction of rare earth elements from FLINAK

    SciTech Connect

    Long, Dewu; Huang, Wei; Jiang, Feng; Tian, Lifang; Li, Qingnuan

    2013-07-01

    Electrochemical behaviors of rare earth elements, such as NdF{sub 3}, GdF{sub 3}, SmF{sub 3}, YF{sub 3}, and EuF{sub 3}, were investigated in a LiF-NaF-KF (46.5-11.5-42.0 mol %, FLINAK, m. p. 454 Celsius degrees) solvent. The results indicated that it is possible to extract Nd, Gd and Y directly by electrochemical deposition since the reductions of those cations to metal are located in the electrochemical window of the FLINAK eutectic, while the reductions of Sm and Eu metal are out of the range of the medium. Subsequently electro-deposition of Nd was carried out with two kinds of cathodic materials, namely, an inert cathode, Pt, and a reactive electrode, Cu. The collected products were characterized by various techniques revealing that a Nd-rich product was obtained. (authors)

  3. Predictive model for ionic liquid extraction solvents for rare earth elements

    NASA Astrophysics Data System (ADS)

    Grabda, Mariusz; Oleszek, Sylwia; Panigrahi, Mrutyunjay; Kozak, Dmytro; Eckert, Franck; Shibata, Etsuro; Nakamura, Takashi

    2015-12-01

    The purpose of our study was to select the most effective ionic liquid extraction solvents for dysprosium (III) fluoride using a theoretical approach. Conductor-like Screening Model for Real Solvents (COSMO-RS), based on quantum chemistry and the statistical thermodynamics of predefined DyF3-ionic liquid systems, was applied to reach the target. Chemical potentials of the salt were predicted in 4,400 different ionic liquids. On the base of these predictions set of ionic liquids' ions, manifesting significant decrease of the chemical potentials, were selected. Considering the calculated physicochemical properties (hydrophobicity, viscosity) of the ionic liquids containing these specific ions, the most effective extraction solvents for liquid-liquid extraction of DyF3 were proposed. The obtained results indicate that the COSMO-RS approach can be applied to quickly screen the affinity of any rare earth element for a large number of ionic liquid systems, before extensive experimental tests.

  4. Naturally occurring radionuclides and rare earth elements in weathered Japanese soil samples

    NASA Astrophysics Data System (ADS)

    Sahoo, Sarata; Hosoda, Masahiro; Prasad, Ganesh; Takahashi, Hiroyuki; Sorimachi, Atsuyuki; Ishikawa, Tetsuo; Tokonami, Shinji; Uchida, Shigeo

    2013-08-01

    The activity concentrations of 226Ra and 228Ac in weathered Japanese soils from two selected prefectures have been measured using a γ-ray spectroscopy system with high purity germanium detector. The uranium, thorium, and rare earth elements (REEs) concentrations were determined from the same soil samples using inductively coupled plasma mass spectrometry (ICP-MS). For example, granitic rocks contain higher amounts of U, Th, and light REEs compared to other igneous rocks such as basalt and andesites. Therefore, it is necessary to understand the interaction between REEs and nature of soils since soils are complex heterogeneous mixture of organic and inorganic solids, water, and gases. In this paper, we will discuss about distribution pattern of 238U and 232Th along with REEs in soil samples of weathered acid rock (granite) collected from two prefectures of Japan: Hiroshima and Miyagi.

  5. Rare earth and trace element geochemistry of a fragment of Jurassic seafloor, Point Sal, California

    NASA Technical Reports Server (NTRS)

    Menzies, M.; Blanchard, D.; Brannon, J.; Korotev, R.

    1977-01-01

    Rocks from an ophiolite suite once on the seafloor were analyzed for rare earth elements (REE), Sc, Co, Na2O, Cr, Zn and FeO. Strontium isotope exchange noted in some of the lavas is attributed to basalt-seawater interaction; the Ce abundance in smectite- and zeolite-bearing lavas may also be due to prolonged exposure to seawater. The higher grades of metamorphic rock, however, show no variation from the usual flat or slightly light REE depleted profiles. Plutonic igneous rock, all light REE depleted, have total REE abundances varying by a factor of 100 between the dunites and diorites. In order of decreasing REE abundance are hornblende, clinopyroxene, plagioclase, orthopyroxene and olivine. Calculations of REE contents of liquids in equilibrium with early cumulative clinopyroxenes suggest that the parent to the stratiform sequence was more depleted in light REE than the parent to the lava pile.

  6. Lagrangian finite element analysis of the penetration of earth penetrating weapons

    SciTech Connect

    Rosinsky, R.W.

    1985-11-22

    Buried targets, such as hardened missile silos, that are resistant to the effects of air blast from above-ground or surface-burst explosions may be vulnerable to the effects of ground motion produced by nearby underground explosions. An earth penetrating weapon (EPW) is being developed to exploit this phenomena. To design the EPW system, loads on the weapon due to the penetration event must be determined. This paper presents the methodology for performing Lagrangian finite-element analysis of the penetration event in two and three dimensions. In order to describe the methodology, results from analyses done for a particular EPW impacting a particular target medium are presented. The results for impacts with nonzero angles of incidence and nonzero angles of attack show the importance of being able to calculate three dimensional penetration loads. 62 figs.

  7. Behavior of Rare Earth Element In Geothermal Systems; A New Exploration/Exploitation Tool

    SciTech Connect

    Scott A. Wood

    2002-01-28

    The goal of this four-year project was to provide a database by which to judge the utility of the rare earth elements (REE) in the exploration for and exploitation of geothermal fields in the United States. Geothermal fluids from hot springs and wells have been sampled from a number of locations, including: (1) the North Island of New Zealand (1 set of samples); (2) the Cascades of Oregon; (3) the Harney, Alvord Desert and Owyhee geothermal areas of Oregon; (4) the Dixie Valley and Beowawe fields in Nevada; (5) Palinpion, the Philippines: (6) the Salton Sea and Heber geothermal fields of southern California; and (7) the Dieng field in Central Java, Indonesia. We have analyzed the samples from all fields for REE except the last two.

  8. The distribution of Sr and REE between diopside and silicate liquid. [Rare Earth Elements

    NASA Technical Reports Server (NTRS)

    Grutzeck, M.; Kridelbaugh, S.; Weill, D.

    1974-01-01

    Experimental determination of the distribution coefficients in diopside-liquid pairs for strontium and nine rare-earth elements in the system CaMgSi2O6-NaAlSi3O8-CaAl2Si2O8. In experiments in air at 1265 C it is found that most of the Sr(2+), Eu(2+), and RE(3+) ions substitute for Ca(2+) and, in addition, a coupled substitution of Al(3+) for Si(4+) occurs. All of the trace ions considered are found to be excluded from the diopside lattice relative to the liquid. In the case of the trivalent ions the exclusion is much more pronounced for La and Ce, which have ionic radii larger than that of Ca(2+) in 8-fold oxygen coordination. Divalent Sr and Eu with even larger radii are also strongly excluded.

  9. Bioelectrical activity of the central nervous system among populations in a rare earth element area.

    PubMed

    Zhu, W; Xu, S; Shao, P; Zhang, H; Wu, D; Yang, W; Feng, J

    1997-04-01

    Auditory brainstem electric response (ABR) and somatosensory evoked potential (SEP) of 21 subjects (41 ears) among villagers in a rare earth element (REE) area in Gan County, Jiangxi, China, were studied. No difference in ABR between the subjects from the REE area and the control group was noted. However, the conduction detected by SEP from the median nerve to the thalamus (P15) was shortened (P < 0.05), especially to the first-grade primary somatosensory responsive region (S1) (P < 0.01) and the amplitude of S1 decreased (P < 0.05), indicating that REE was difficult to accumulate in the brainstem, but it was susceptible to cerebral cortex, thus causing sub-clinical damage. This condition was confirmed in the animal experiment. It was suggested that the toxicity through long-term intake of small doses of REE might not be negligible, and the hazard of REE environments should be investigated.

  10. Predictive model for ionic liquid extraction solvents for rare earth elements

    SciTech Connect

    Grabda, Mariusz; Oleszek, Sylwia; Panigrahi, Mrutyunjay; Kozak, Dmytro; Shibata, Etsuro; Nakamura, Takashi; Eckert, Franck

    2015-12-31

    The purpose of our study was to select the most effective ionic liquid extraction solvents for dysprosium (III) fluoride using a theoretical approach. Conductor-like Screening Model for Real Solvents (COSMO-RS), based on quantum chemistry and the statistical thermodynamics of predefined DyF{sub 3}-ionic liquid systems, was applied to reach the target. Chemical potentials of the salt were predicted in 4,400 different ionic liquids. On the base of these predictions set of ionic liquids’ ions, manifesting significant decrease of the chemical potentials, were selected. Considering the calculated physicochemical properties (hydrophobicity, viscosity) of the ionic liquids containing these specific ions, the most effective extraction solvents for liquid-liquid extraction of DyF{sub 3} were proposed. The obtained results indicate that the COSMO-RS approach can be applied to quickly screen the affinity of any rare earth element for a large number of ionic liquid systems, before extensive experimental tests.

  11. X-ray fluorescence analysis of rare earth elements in rocks using low dilution glass beads.

    PubMed

    Nakayama, Kenichi; Nakamura, Toshihiro

    2005-07-01

    Major and trace elements (Na, Mg, Al, Si, P, K, Ca, Ti, Mn, Fe, Rb, Sr, Y, Zr, La, Ce, Pr, Nd, Sm, Gd, Dy, Th and U) in igneous rocks were assayed with fused lithium borate glass beads using X-ray fluorescence spectrometry. Low dilution glass beads, which had a 1:1 sample-to-flux ratio, were prepared for determination of rare earth elements. Complete vitrification of 1:1 mixture required heating twice at 1200 degrees C with agitation. Extra pure reagents containing determinants were used for calibrating standards instead of the rock standard. The calibration curves of the 23 elements showed good linearity. Furthermore, the lower limits of detection corresponding to three times the standard deviation for blank measurements were 26 mass ppm for Na2O, 6.7 for MgO, 4.5 for Al2O3, 4.5 for SiO2, 18 for P2O5, 1.1 for K2O, 4.0 for CaO, 3.9 for TiO2, 1.6 for MnO, 0.8 for Fe2O3, 0.5 for Rb, 0.2 for Sr, 0.4 for Y, 0.5 for Zr, 3.3 for La, 6.5 for Ce, 2.7 for Pr, 2.1 for Nd, 1.7 for Sm, 0.7 for Gd, 2.7 for Dy, 0.5 for Th, and 0.6 for U. Using the present method, we determined the contents of these 23 elements in four rhyolitic and granitic rocks from Japan.

  12. Constraints on Hadean zircon protoliths from oxygen isotopes, Ti-thermometry, and rare earth elements

    NASA Astrophysics Data System (ADS)

    Trail, Dustin; Mojzsis, Stephen J.; Harrison, T. Mark; Schmitt, Axel K.; Watson, E. Bruce; Young, Edward D.

    2007-06-01

    We report zircon oxygen isotope ratios and reconnaissance Ti-in-zircon concentrations, guided by cathodoluminescence image studies, for detrital zircons up to 4.34 Ga from the Narryer Gneiss Complex of Western Australia. Zircon oxygen isotope results bolster the view that some Hadean (>3.85 Ga) zircon source melts were enriched in heavy oxygen, a sensitive proxy for melt contamination by sediments altered in liquid water. Zircon crystallization temperatures calculated from Ti concentration in pre-3.8 Ga zircons yield values around 680°C in all cases except for one lower value in a 4.0 Ga grain. Elevated zircon δ18O values reported here and elsewhere, combined with low minimum-melt crystallization temperatures, and analysis of zircon/melt partitioning of rare earth elements (REEs) provide mutually consistent lines of evidence that the Hadean Earth supported an evolved rock cycle which included formation of granitic water-saturated melts, extensive continental crust, hydrosphere-lithosphere interactions, and sediment recycling within the first 150 million years of planet formation.

  13. Planktonic foraminiferal rare earth elements as a potential new aeolian dust proxy

    NASA Astrophysics Data System (ADS)

    Chou, C.; Liu, Y.; Lo, L.; Wei, K.; Shen, C.

    2012-12-01

    Characteristics of rare earth elements (REEs) have widely been used as important tracers in many fields of earth sciences, including lithosphere research, environmental change, ocean circulation and other natural carbonate materials. Foraminiferal test REE signatures have been suggested to reflect ambient seawater conditions and serve as valuable proxies in the fields of paleoceanography and paleoclimate. Here we present a 60-kyr planktonic foraminifera Globigerinoides ruber (white, 250-300 μm) REE record of a sediment core MD05-2925 (9°20.61'S, 151°27.61'E, water depth 1660 m) from the Solomon Sea. The REE diagram shows two dominant sources of local seawater and nearby terrestrial input. The variability of foraminiferal REE/Ca time series is different from Mg/Ca-inferred sea surface temperature and δ18O records during the past 60-kyr. This inconsistency suggests that planktonic foraminiferal REE content cannot result only from changes in ice volume and temperature. Synchroneity between high planktonic foraminiferal REE content and Antarctic ice core dust amount record implies the same dust sources, probably from Australia or mainland China. Our results suggest that foraminiferal REE can potentially be as a new dust proxy and record dry/humid conditions at the source area.

  14. Bioadsorption of Rare Earth Elements through Cell Surface Display of Lanthanide Binding Tags.

    PubMed

    Park, Dan M; Reed, David W; Yung, Mimi C; Eslamimanesh, Ali; Lencka, Malgorzata M; Anderko, Andrzej; Fujita, Yoshiko; Riman, Richard E; Navrotsky, Alexandra; Jiao, Yongqin

    2016-03-01

    With the increasing demand for rare earth elements (REEs) in many emerging clean energy technologies, there is an urgent need for the development of new approaches for efficient REE extraction and recovery. As a step toward this goal, we genetically engineered the aerobic bacterium Caulobacter crescentus for REE adsorption through high-density cell surface display of lanthanide binding tags (LBTs) on its S-layer. The LBT-displayed strains exhibited enhanced adsorption of REEs compared to cells lacking LBT, high specificity for REEs, and an adsorption preference for REEs with small atomic radii. Adsorbed Tb(3+) could be effectively recovered using citrate, consistent with thermodynamic speciation calculations that predicted strong complexation of Tb(3+) by citrate. No reduction in Tb(3+) adsorption capacity was observed following citrate elution, enabling consecutive adsorption/desorption cycles. The LBT-displayed strain was effective for extracting REEs from the acid leachate of core samples collected at a prospective rare earth mine. Our collective results demonstrate a rapid, efficient, and reversible process for REE adsorption with potential industrial application for REE enrichment and separation.

  15. Rare earth elements in human hair from a mining area of China.

    PubMed

    Wei, Binggan; Li, Yonghua; Li, Hairong; Yu, Jiangping; Ye, Bixiong; Liang, Tao

    2013-10-01

    Rare earth minerals have been mined for more than 50 years in Inner Mongolia of China. In the mining area rare earth elements (REE) may be significantly accumulated in humans. Therefore, the aim of this paper is to characterize the REE concentrations in hair of local residents. REE concentrations in hair of 118 subjects were determined. The results showed that the mean concentrations of the determined REE in the hair of both females and males were usually higher from mining area than from control area. The mean concentrations of all the fifteen REE were much higher in hair of males than in hair of females from mining area. This suggested that males might be more sensitive to REE than females. In addition, the mean contents of the REE in hair of miners, particularly light REE (La, Ce, Pr and Nd), were usually much higher than the values in hair of non-miners from both mining area and control area, indicating that the miners were exposed to higher concentrations of REE in occupational environment. Among age groups, the relationships between REE concentrations and age groups showed that more and more concentrations of light REE accumulated in body of both females and males with age until 60 years, while heavy REE concentrations decreased with age in males who were exposed to low concentrations of heavy REE.

  16. Rare earth elements and hypertension risk among housewives: A pilot study in Shanxi Province, China.

    PubMed

    Wang, Bin; Yan, Lailai; Huo, Wenhua; Lu, Qun; Cheng, Zixi; Zhang, Jingxu; Li, Zhiwen

    2017-01-01

    Studies have shown that residents living near rare earth mining areas have high concentrations of rare earth elements (REEs) in their hair. However, the adverse effects of REEs on human health have rarely been the focus of epidemiological studies. The goal of this study was to evaluate the relationship between REEs in hair and the risk of hypertension in housewives. We recruited 398 housewives in Shanxi Province, China, consisting of 163 women with hypertension (cases) and 235 healthy women without hypertension (controls). We analyzed 15 REEs (lanthanum (La), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), Yttrium (Y), cerium (Ce), praseodymium (Pr), and neodymium (Nd)) and calcium (Ca) accumulated in housewives hair over a period of two years. The results revealed that, with the exception of Eu, concentrations of the REEs in hair were higher in the cases than in the controls. The univariate odds ratios (ORs) of the 14 REEs were >1, and four of the REEs (Dy, Tm, Yb, and Y) also had adjusted ORs > 1. The increasing dose-response trends of the four REEs further indicated the potential for increased hypertension risk. Moreover, the REEs were negatively correlated with Ca content in hair. These results might suggest an antagonistic effect of REEs on Ca in the human body. It was concluded that high intake of REEs might increase the risk of hypertension among housewives.

  17. Bioadsorption of rare earth elements through cell surface display of lanthanide binding tags

    SciTech Connect

    Park, Dan M.; Reed, David W.; Yung, Mimi C.; Eslamimanesh, Ali; Lencka, Malgorzata M.; Anderko, Andrzej; Fujita, Yoshiko; Riman, Richard E.; Navrotsky, Alexandra; Jiao, Yongqin

    2016-02-02

    In this study, with the increasing demand for rare earth elements (REEs) in many emerging clean energy technologies, there is an urgent need for the development of new approaches for efficient REE extraction and recovery. As a step toward this goal, we genetically engineered the aerobic bacterium Caulobacter crescentus for REE adsorption through high-density cell surface display of lanthanide binding tags (LBTs) on its S-layer. The LBT-displayed strains exhibited enhanced adsorption of REEs compared to cells lacking LBT, high specificity for REEs, and an adsorption preference for REEs with small atomic radii. Adsorbed Tb3+ could be effectively recovered using citrate, consistent with thermodynamic speciation calculations that predicted strong complexation of Tb3+ by citrate. No reduction in Tb3+ adsorption capacity was observed following citrate elution, enabling consecutive adsorption/desorption cycles. The LBT-displayed strain was effective for extracting REEs from the acid leachate of core samples collected at a prospective rare earth mine. Our collective results demonstrate a rapid, efficient, and reversible process for REE adsorption with potential industrial application for REE enrichment and separation.

  18. Bioadsorption of rare earth elements through cell surface display of lanthanide binding tags

    DOE PAGES

    Park, Dan M.; Reed, David W.; Yung, Mimi C.; ...

    2016-02-02

    In this study, with the increasing demand for rare earth elements (REEs) in many emerging clean energy technologies, there is an urgent need for the development of new approaches for efficient REE extraction and recovery. As a step toward this goal, we genetically engineered the aerobic bacterium Caulobacter crescentus for REE adsorption through high-density cell surface display of lanthanide binding tags (LBTs) on its S-layer. The LBT-displayed strains exhibited enhanced adsorption of REEs compared to cells lacking LBT, high specificity for REEs, and an adsorption preference for REEs with small atomic radii. Adsorbed Tb3+ could be effectively recovered using citrate,more » consistent with thermodynamic speciation calculations that predicted strong complexation of Tb3+ by citrate. No reduction in Tb3+ adsorption capacity was observed following citrate elution, enabling consecutive adsorption/desorption cycles. The LBT-displayed strain was effective for extracting REEs from the acid leachate of core samples collected at a prospective rare earth mine. Our collective results demonstrate a rapid, efficient, and reversible process for REE adsorption with potential industrial application for REE enrichment and separation.« less

  19. 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.

  20. TerraFERMA: The Transparent Finite Element Rapid Model Assembler for multiphysics problems in Earth sciences

    NASA Astrophysics Data System (ADS)

    Wilson, Cian R.; Spiegelman, Marc; van Keken, Peter E.

    2017-02-01

    We introduce and describe a new software infrastructure TerraFERMA, the Transparent Finite Element Rapid Model Assembler, for the rapid and reproducible description and solution of coupled multiphysics problems. The design of TerraFERMA is driven by two computational needs in Earth sciences. The first is the need for increased flexibility in both problem description and solution strategies for coupled problems where small changes in model assumptions can lead to dramatic changes in physical behavior. The second is the need for software and models that are more transparent so that results can be verified, reproduced, and modified in a manner such that the best ideas in computation and Earth science can be more easily shared and reused. TerraFERMA leverages three advanced open-source libraries for scientific computation that provide high-level problem description (FEniCS), composable solvers for coupled multiphysics problems (PETSc), and an options handling system (SPuD) that allows the hierarchical management of all model options. TerraFERMA integrates these libraries into an interface that organizes the scientific and computational choices required in a model into a single options file from which a custom compiled application is generated and run. Because all models share the same infrastructure, models become more reusable and reproducible, while still permitting the individual researcher considerable latitude in model construction. TerraFERMA solves partial differential equations using the finite element method. It is particularly well suited for nonlinear problems with complex coupling between components. TerraFERMA is open-source and available at http://terraferma.github.io, which includes links to documentation and example input files.

  1. A major light rare-earth element (LREE) resource in the Khanneshin carbonatite complex, southern Afghanistan

    USGS Publications Warehouse

    Tucker, Robert D.; Belkin, Harvey E.; Schulz, Klaus J.; Peters, Stephen G.; Horton, Forrest; Buttleman, Kim; Scott, Emily R.

    2012-01-01

    The rapid rise in world demand for the rare-earth elements (REEs) has expanded the search for new REE resources. We document two types of light rare-earth element (LREE)-enriched rocks in the Khanneshin carbonatite complex of southern Afghanistan: type 1 concordant seams of khanneshite-(Ce), synchysite-(Ce), and parisite-(Ce) within banded barite-strontianite alvikite, and type 2 igneous dikes of coarse-grained carbonatite, enriched in fluorine or phosphorus, containing idiomorphic crystals of khanneshite-(Ce) or carbocernaite. Type 1 mineralized barite-strontianite alvikite averages 22.25 wt % BaO, 4.27 wt % SrO, and 3.25 wt % ∑ LREE2O3 (sum of La, Ce, Pr, and Nd oxides). Type 2 igneous dikes average 14.51 wt % BaO, 5.96 wt % SrO, and 3.77 wt % ∑ LREE2O3. A magmatic origin is clearly indicated for the type 2 LREE-enriched dikes, and type 1 LREE mineralization probably formed in the presence of LREE-rich hydrothermal fluid. Both types of LREE mineralization may be penecontemporaneous, having formed in a carbonate-rich magma in the marginal zone of the central vent, highly charged with volatile constituents (i.e., CO2, F, P2O5), and strongly enriched in Ba, Sr, and the LREE. Based on several assumptions, and employing simple geometry for the zone of LREE enrichment, we estimate that at least 1.29 Mt (million metric tonnes) of LREE2O3 is present in this part of the Khanneshin carbonatite complex.

  2. Geology and market-dependent significance of rare earth element resources

    NASA Astrophysics Data System (ADS)

    Simandl, G. J.

    2014-12-01

    China started to produce rare earth elements (REEs) in the 1980s, and since the mid-1990s, it has become the dominant producer. Rare earth element export quotas first introduced by the Chinese government in the early 2000s were severely reduced in 2010 and 2011. This led to strong government-created disparity between prices within China and the rest of the world. Industrialized countries identified several REEs as strategic metals. Because of rapid price increases of REE outside of China, we have witnessed a world-scale REE exploration rush. The REE resources are concentrated in carbonatite-related deposits, peralkaline igneous rocks, pegmatites, monazite ± apatite veins, ion adsorption clays, placers, and some deep ocean sediments. REE could also be derived as a by-product of phosphate fertilizer production, U processing, mining of Ti-Zr-bearing placers, and exploitation of Olympic Dam subtype iron oxide copper gold (IOCG) deposits. Currently, REEs are produced mostly from carbonatite-related deposits, but ion adsorption clay deposits are an important source of heavy REE (HREE). Small quantities of REE are derived from placer deposits and one peralkaline intrusion-related deposit. The ideal REE development targets would be located in a politically stable jurisdiction with a pro-mining disposition such as Canada and Australia. REE grade, HREE/light REE (LREE) ratio of the mineralization, tonnage, mineralogy, and permissive metallurgy are some of the key technical factors that could be used to screen potential development projects. As REEs are considered strategic metals from economic, national security, and environmental points of view, technical and economic parameters alone are unlikely to be used in REE project development decision-making. Recycling of REE is in its infancy and unless legislated, in the short term, it is not expected to contribute significantly to the supply of REE.

  3. Natural radioactivity and rare earth elements in feldspar samples, Central Eastern desert, Egypt.

    PubMed

    Walley El-Dine, Nadia; El-Shershaby, Amal; Afifi, Sofia; Sroor, Amany; Samir, Eman

    2011-05-01

    The pegmatite bodies of the Eastern Desert of Egypt are widely distributed especially along the Marsa-Alam-Idfu road. The Abu Dob area covers about 150km(2) of the Arabian Nubian shield at the central part of the Eastern Desert of Egypt. Most of the pegmatite is zoned; the zonation starts with milky quartz at the core followed by alkali feldspar at the margins. The feldspars vary in color from rose to milky and in composition from K-feldspar to Na-feldspar, sometimes interactions of both types are encountered. Thirteen feldspar samples were collected from different locations in the Abu Dob area for measuring the natural radioactivity of (238)U, (232)Th and (40)K using an HPGe detector. The variation in concentration of radionuclides for the area under investigation can be classified into regions of high, medium and low natural radioactivity. The average concentration in BqKg(-1) has been observed to be from 9.5 to 183675.7BqKg(-1) for (238)U, between 6.1 and 94,314.2BqKg(-1) for (232)Th and from 0 to 7894.6BqKg(-1) for (40)K. Radium equivalent activities (Ra(eq)), dose rate (D(R)) and external hazard (H(ex)) have also been determined. In the present work, the concentration of rare earth elements are measured for two feldspar samples using two techniques, Environmental Scanning Electron microscope XIL 30 ESEM, Philips, and Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). The existence of rare earth elements in this area are very high and can be used in different important industries.

  4. Evaluation of rare earth elements in groundwater of Lagos and Ogun States, Southwest Nigeria.

    PubMed

    Ayedun, H; Arowolo, T A; Gbadebo, A M; Idowu, O A

    2016-06-11

    Rare earth elements in our environment are becoming important because of their utilization in permanent magnets, lamp phosphors, superconductors, rechargeable batteries, catalyst, ceramics and other applications. This study was conducted to evaluate the level of rare earth elements (REE) and the variability of their anomalous behavior in groundwater samples collected from Lagos and Ogun States, Southwest, Nigeria. REE concentrations were determined in 170 groundwater samples using inductively coupled plasma-mass spectrometry, while the physicochemical parameters were determined using standard methods. Lagos State groundwater is enriched with REE [sum REEs range (mean ± SD)]; [0.365-488 (69.5 ± 117)] µg L(-1) than Ogun State groundwater [sum REEs range (mean ± SD)]; [1.14-232 (22.6 ± 41.1)] µg L(-1). Boreholes are more enriched with REEs than wells. Significant (P < 0.05) positive correlation (R = Pearson) was recorded in Lagos State groundwater between sum REEs and Fe (R = 0.55). However, there were no significant correlations between sum REEs, pH (R = 0.073) and HCO3(2-) (R = 0.157) in Ogun State groundwater. Chondrite-normalized plot shows that Lagos groundwater exhibits positive Ce anomaly, while Ogun State groundwater does not. The source of REE in Lagos State may be from the ocean and leaching from wastes dumpsites, while the source in Ogun State groundwater may be from the rocks.

  5. Trace element partitioning in rock forming minerals of co-genetic, subduction-related alkaline and tholeiitic mafic rocks in the Ural Mountains, Russia

    NASA Astrophysics Data System (ADS)

    Krause, J.; Brügmann, G. E.; Pushkarev, E. V.

    2009-04-01

    The partitioning of trace elements between rock forming minerals in igneous rocks is largely controlled by physical and chemical parameters e.g. temperature, pressure and chemical composition of the minerals and the coexisting melt. In the present study partition coefficients for REE between hornblende, orthopyroxene, feldspars, apatite and clinopyroxene in a suite of co-genetic alkaline and tholeiitic mafic rocks from the Ural Mountains (Russia) were calculated. The results give insights to the influence of the chemical composition of the parental melt on the partitioning behaviour of the REE. Nepheline-bearing, alkaline melanogabbros (tilaites) are assumed to represent the most fractionated products of the melt that formed the ultramafic cumulates in zoned mafic-ultramafic complexes in the Ural Mountains. Co-genetic with the latter is a suite of olivine gabbros, gabbronorites and hornblende gabbros formed from a tholeiitic parental melt. Negative anomalies for the HFSE along with low Nb and Ta contents and a positive Sr anomaly indicate a subduction related origin of all parental melts. The nepheline gabbros consist predominantly of coarse-grained clinopyroxene phenocrysts in a matrix of fine grained clinopyroxene, olivine, plagioclase, K-feldspar and nepheline with accessory apatite. The tholeiitic gabbros have equigranular to porphyric textures with phenocrysts of olivine, pyroxene and hornblende in a plagioclase rich matrix with olivine hornblende, pyroxene and accessory apatite. Element concentrations of adjacent matrix grains and rims of phenochrysts were measured with LA-ICPMS. The distribution of REE between hornblende and clinopyroxene in the tholeiitic rocks is similar for most of the elements (DHbl•Cpx(La-Tm) = 2.7-2.8, decreasing to 2.6 and 2.4 for Yb and Lu, respectively). These values are about two times higher than published data (e.g. Ionov et al. 1997). Partition coefficients for orthopyroxene/clinopyroxene systematically decrease from the HREE

  6. Structural Elements in a Persistent Identifier Infrastructure and Resulting Benefits for the Earth Science Community

    NASA Astrophysics Data System (ADS)

    Weigel, T.; Toussaiant, F.; Stockhause, M.; Höck, H.; Kindermann, S.; Lautenschlager, M.; Ludwig, T.

    2012-12-01

    We propose a wide adoption of structural elements (typed links, collections, trees) in the Handle System to improve identification and access of scientific data, metadata and software as well as traceability of data provenance. Typed links target the issue of data provenance as a means to assess the quality of scientific data. Data provenance is seen here as a directed acyclic graph with nodes representing data and vertices representing derivative operations (Moreau 2010). Landing pages can allow a human user to explore the provenance graph back to the primary unprocessed data, thereby also giving credit to the original data producer. As in Earth System Modeling no single infrastructure with complete data lifecycle coverage exists, we propose to split the problem domain in two parts. Project-specific infrastructures such as the German project C3-Grid or the Earth System Grid Federation (ESGF) for CMIP5 data are aware of data and data operations (Toussaint et al. 2012) and can thus detect and accumulate single nodes and vertices in the provenance graph, assigning Handles to data, metadata and software. With a common schema for typed links, the provenance graph is established as downstream infrastructures refer incoming Handles. Data in this context is for example hierarchically structured Earth System model output data, which receives DataCite DOIs only for the most coarse-granular elements. Using Handle tree structures, the lower levels of the hierarchy can also receive Handles, allowing authors to more precisely identify the data they used (Lawrence et al. 2011). We can e.g. define a DOI for just the 2m-temperature variable of CMIP5 data across many CMIP5 experiments or a DOI for model and observational data coming from different sources. The structural elements should be implemented through Handle values at the Handle infrastructure level for two reasons. Handle values are more durable than downstream websites or databases, and thus the provenance chain does not

  7. Seawater-derived rare earth element addition to abyssal peridotites during serpentinization

    NASA Astrophysics Data System (ADS)

    Frisby, Carl; Bizimis, Michael; Mallick, Soumen

    2016-04-01

    Serpentinized abyssal peridotites are evidence for active communication between the Earth's hydrosphere and the upper mantle, where exchange and retention of both major and trace elements occur. Bulk rock Nd isotopes in serpentinized abyssal peridotites imply interaction of seawater with the peridotite. In contrast, the Nd isotopes of clinopyroxenes from serpentinized abyssal peridotites retain their primary magmatic signature. It is currently unclear if, how and where seawater-derived Nd and other REE are being added or exchanged with the mantle peridotite minerals during serpentinization. To remedy this knowledge gap, we present in situ trace and major element concentrations, bulk rock and sequential leaching experiment trace element concentrations as well as Nd, Sr isotope data on refertilized and depleted serpentinized abyssal peridotites from the Southwest Indian Ridge. The secondary serpentine matrix and magnetite veins in these peridotites have elevated LREE concentrations, with variable negative Ce anomalies and large Rb, Sr, Pb and U enrichments that resemble seawater trace element patterns. The LREE concentrations in the serpentine phase are higher than those expected for the primary mantle mineralogy (olivine, orthopyroxene) based on data from relic clinopyroxenes and equilibrium partition coefficients. These data are consistent with seawater-derived REE addition to the peridotite during serpentinization. The bulk rocks have more radiogenic Sr and more unradiogenic Nd isotopes than their clinopyroxene (up to 8 εNd units lower than clinopyroxene). Sequential leaching experiments designed to mobilize secondary carbonates and Fe-oxides show even more unradiogenic Nd isotope ratios in the leachates than the bulk rock and clinopyroxene, approaching seawater compositions (up to 15 εNd units lower than clinopyroxene). Mass balance calculations using trace elements or Nd isotopes suggest that up to 30% of the bulk peridotite Nd budget is of seawater origin and

  8. The importance of sulfur for the behavior of highly-siderophile elements during Earth's differentiation

    NASA Astrophysics Data System (ADS)

    Laurenz, Vera; Rubie, David C.; Frost, Daniel J.; Vogel, Antje K.

    2016-12-01

    The highly siderophile elements (HSEs) are widely used as geochemical tracers for Earth's accretion and core formation history. It is generally considered that core formation strongly depleted the Earth's mantle in HSEs, which were subsequently replenished by a chondritic late veneer. However, open questions remain regarding the origin of suprachondritic Ru/Ir and Pd/Ir ratios that are thought to be characteristic for the primitive upper mantle. In most core-formation models that address the behavior of the HSEs, light elements such as S entering the core have not been taken into account and high P-T experimental data for S-bearing compositions are scarce. Here we present a comprehensive experimental study to investigate the effect of increasing S concentration in the metal on HSE metal-silicate partitioning at 2473 K and 11 GPa. We show that the HSEs become less siderophile with increasing S concentrations in the metal, rendering core-forming metal less efficient in removing the HSEs from the mantle if S is present. Furthermore, we investigated the FeS sulfide-silicate partitioning of the HSEs as a function of pressure (7-21 GPa) and temperature (2373-2673 K). The sulfide-silicate partition coefficient for Pt increases strongly with P, whereas those for Pd, Ru and Ir all decrease. The combined effect is such that above ∼20 GPa Ru becomes less chalcophile than Pt, which is opposite to their behavior in the metal-silicate system where Ru is always more siderophile than Pt. The newly determined experimental results are used in a simple 2-stage core formation model that takes into account the effect of S on the behavior of the HSEs during core formation. Results of this model show that segregation of a sulfide liquid to the core from a mantle with substantial HSE concentrations plays a key role in reproducing Earth's mantle HSE abundances. As Ru and Pd are less chalcophile than Pt and Ir at high P-T, some Ru and Pd remain in the mantle after sulfide segregation

  9. Tracing irradiation-induced defect state of monazite by photoluminescence of rare Earth elements

    NASA Astrophysics Data System (ADS)

    Panczer, G.; Seydoux-Guillaume, A. M.; Montel, J. M.; Champagnon, B.

    2003-04-01

    Natural monazite is known in contrast to zircon, to almost never be found in the metamict state (Ewing, 1975) despite the fact that it received intensive radiation doses during geologic history by U and Th incorporation. Radiation damages in natural monazite seems to be limited to isolated domains within the crystal (Meldrum et al., 1998). Such property controlled the fact that the monazite lattice is easily healed even at low temperature as it was shown by TEM, XRD and Raman spectrometry (Seydoux-Guillaume et al., 2002). In order to estimate the degree of disorder and the healing of defects we used trivalent neodymium as an internal luminescent probe (Gaft et al., 2001). As a matter of fact the radiative electronic transitions of rare earth elements are very sensible to the short-range crystallographic order around them. Three natural monazites thermally untreated and quenched at 450, 500, 700, 800 and 1000^oC were analyzed under 514 nm Argon laser excitation with a Renishaw microspectrometer. Nd3+ emission was recorded in the range of 750 nm to 1 μm. The ^4F3/2 rightarrow ^4I9/2 transition parameters (position and width) show that 1) the position of the Stark levels do not change during thermal treatment, and 2) that the emission line widths decrease continuously (from 25 to 37%) from room temperature to 1000^oC. These results indicates that before annealing, sub sites of Nd were present with slight different environments induced by internal irradiation induced displacement of ions around them (short range disorder). After thermal treatment a continuous reorganization of the lattice occurs up to 1000^oC with quite strong rearrangement of the environment around the rare-earth leading to a decrease of the Nd sub site number. Thus, the luminescent probe reveals that defect healing continue at much higher temperatures than what was previously reported indicating that luminescence is a very sensible tool to appreciate the degree of disorder in mineral phases. Gaft M

  10. The Nolans Bore rare-earth element-phosphorus-uranium mineral system: geology, origin and post-depositional modifications

    NASA Astrophysics Data System (ADS)

    Huston, David L.; Maas, Roland; Cross, Andrew; Hussey, Kelvin J.; Mernagh, Terrence P.; Fraser, Geoff; Champion, David C.

    2016-08-01

    Nolans Bore is a rare-earth element (REE)-U-P fluorapatite vein deposit hosted mostly by the ~1805 Ma Boothby Orthogneiss in the Aileron Province, Northern Territory, Australia. The fluorapatite veins are complex, with two stages: (1) massive to granular fluorapatite with inclusions of REE silicates, phosphates and (fluoro)carbonates, and (2) calcite-allanite with accessory REE-bearing phosphate and (fluoro)carbonate minerals that vein and brecciate the earlier stage. The veins are locally accompanied by narrow skarn-like (garnet-diopside-amphibole) wall rock alteration zones. SHRIMP Th-Pb analyses of allanite yielded an age of 1525 ± 18 Ma, interpreted as the minimum age of mineralisation. The maximum age is provided by a ~1550 Ma SHRIMP U-Pb age for a pegmatite that predates the fluorapatite veins. Other isotopic systems yielded ages from ~1443 to ~345 Ma, implying significant post-depositional isotopic disturbance. Calculation of initial ɛNd and 87Sr/86Sr at 1525 Ma and stable isotope data are consistent with an enriched mantle or lower crust source, although post-depositional disturbance is likely. Processes leading to formation of Nolans Bore began with north-dipping subduction along the south margin of the Aileron Province at 1820-1750 Ma, producing a metasomatised, volatile-rich, lithospheric mantle wedge. About 200 million years later, near the end of the Chewings Orogeny, this reservoir and/or the lower crust sourced alkaline low-degree partial melts which passed into the mid- and upper-crust. Fluids derived from these melts, which may have included phosphatic melts, eventually deposited the Nolans Bore fluorapatite veins due to fluid-rock interaction, cooling, depressurisation and/or fluid mixing. Owing to its size and high concentration of Th (2500 ppm), in situ radiogenic heating caused significant recrystallisation and isotopic resetting. The system finally cooled below 300 °C at ~370 Ma, possibly in response to unroofing during the Alice Springs

  11. Developing alternative resources of rare earth elements in Europe - EURARE and the red mud challenge

    NASA Astrophysics Data System (ADS)

    Deady, Eimear; Mouchos, Evangelos; Goodenough, Kathryn; Wall, Frances; Williamson, Ben

    2015-04-01

    Rare earth elements (REE) are considered to be highly "critical" by the European Commission [1], owing to the concentration of global supply [2] and their use in a wide range of emerging technologies (e.g. smart phones, electric cars and wind turbines). The main source of REE is the mineral bastnäsite, which is primarily extracted from carbonatites. Alternative resources of REE have been identified in a variety of other environments such as alluvial placers, bauxites and ore tailings. The EURARE project (www.eurare.eu), funded by the European Commission, aims to improve understanding of potential REE resources in Europe with the overall objective of establishing the basis for a European REE industry. As a part of this project, alternative sources of rare earth elements in Europe are being considered. REE have been identified as being particularly enriched in karst-bauxites and hence in the red muds generated as a waste product from the processing of these bauxites to alumina through the Bayer process [3]. Karst-bauxites are widely distributed with deposits known across the Mediterranean and with intermittent exploitation occurring over many decades. REE become concentrated in the bauxite deposits by the bauxitisation process and are retained due to the geochemical barrier created by the limestone bedrock below. This can result in several processes, including the crystallisation of authigenic REE-bearing minerals, the accumulation of residual phases and the adsorption of ions onto clays and other mineral surfaces [4]. Red muds produced from alumina processing represent a potentially important concentration of REE as it has been demonstrated that the REE pass through the alumina extraction process into the waste, and the total REE concentrations are typically enriched by a factor of two compared with the original bauxite ore [5]. Bauxites and red muds from the Parnassus Ghiona region of Greece [6] and the Seydişehir-Akseki region of Turkey have been assessed as

  12. Subduction Zone Redox and the Deep Earth Cycles of Sulfur and Chalcophile Elements

    NASA Astrophysics Data System (ADS)

    Canil, D.

    2013-12-01

    Subduction at convergent plate margins is a return flux to the mantle of rocks influenced by weathering, hydrothermal activity, atmospheric exchange, or bio-mineralization in the exosphere. The latter exogenic processes modify the long-term abundance and behaviour of certain elements in the deeper earth that can be traced over time in the chemistry of mantle-derived magmas. The redox budget of subduction is controlled by the flux of oxidized versus reduced forms of Fe, S, H, or C, and impacts the long-term evolution of oxygen on the planet, critical for life in the exosphere. In particular, the sulfur cycle is specifically tied to the evolution of oxygen on Earth's surface over time and critical to biogeochemical cycles on the surface. The behaviour of sulfur in the exogenic system is well-studied and fairly well understood using sedimentary records. An originally sulfidic ocean on Earth gave way with time and oxygenation to one that is sulfate dominated over the last two billion years. In contrast, far less is known of the deep earth cycle of S, and more so its history. The record of the endogenic cycle can only be monitored via what comes out of the mantle (magmas and their gases), or what goes down via subduction (hydrothermally-altered or weathered subducted lithosphere). Interest in the endogenic cycle of S is not new but several outstanding conundrums remain for sulfur in arc magmas that point to the importance of the subduction process. A hitherto ignored component of the paradox of the sulfur cycle is the sedimentary veneer that sits atop the subducted oceanic basalt crust. Compilations show only 0.12 wt% S in altered ocean basalt crust, but up to 10 times that amount in oceanic sediments, tied to their Fe content (in pyrite). These abundances may seem trivial, but the behaviour of this small amount of S in subduction is not fully appreciated and its oxidation potential in the arc mantle is enormous. The conversion of subducted sulfide to sulfate is a 8

  13. A new fungal isolate, Penidiella sp. strain T9, accumulates the rare earth element dysprosium.

    PubMed

    Horiike, Takumi; Yamashita, Mitsuo

    2015-05-01

    With an aim to develop a highly efficient method for the recovery of rare earth elements (REEs) by using microorganisms, we attempted to isolate dysprosium (Dy)-accumulating microorganisms that grow under acidic conditions from environmental samples containing high concentrations of heavy metals. One acidophilic strain, T9, which was isolated from an abandoned mine, decreased the concentration of Dy in medium that contained 100 mg/liter Dy to 53 mg/liter Dy after 3 days of cultivation at pH 2.5. The Dy content in the cell pellet of the T9 strain was 910 μg/mg of dry cells. The T9 strain also accumulated other REEs. Based on the results of 28S-D1/D2 rRNA gene sequencing and morphological characterization, we designated this fungal strain Penidiella sp. T9. Bioaccumulation of Dy was observed on the cell surface of the T9 strain by elemental mapping using scanning electron microscopy-energy dispersive X-ray spectroscopy. Our results indicate that Penidiella sp. T9 has the potential to recover REEs such as Dy from mine drainage and industrial liquid waste under acidic conditions.

  14. Rare earth elements and select actinoids in the Canadian House Dust Study.

    PubMed

    Rasmussen, P E; Levesque, C; Chénier, M; Gardner, H D

    2017-03-17

    Nationally representative baseline data are presented for rare earth elements (REE), thorium (Th) and uranium (U) in house dust sampled from 1025 urban homes, in units of concentrations (μg g(-1) ), loadings (μg m(-2) ), and loading rates (ng m(-2)  d(-1) ). Spearman rank correlations indicate that, in addition to outdoor sources, consumer products and building materials can influence indoor dust concentrations of REE, Th, and U. Correlations (P<.01) with numbers of occupants, dogs, and cats suggest soil track-in. Correlations (P<.01) with hardwood floors suggest release of REE additives used in pigments and coatings during daily wear and tear. Concentrations of light REE are elevated in smokers' homes compared to non-smokers' homes (P<.001), suggesting that a key source is "mischmetal," the REE alloy used in cigarette-lighter flints. Indoor sources include geological impurities in raw materials used in consumer products, such as U and Th impurities in bentonite clay used in cat litter, and REE impurities in phosphates used for a variety of applications including dog food and building materials. Median gastric bioaccessibility (pH 1.5) of most REE in dust ranges from about 20% to 29%. Household vacuum samples correlate with fresh dust samples from the same homes (P<.001 for all investigated elements).

  15. Analytical Approach Using KS Elements to Near-Earth Orbit Predictions Including Drag

    NASA Astrophysics Data System (ADS)

    Krishnan Sharma, Ram

    1991-04-01

    A new analytical theory for the motion of near-Earth satellite orbits with the air drag effect is developed in terms of the KS elements, utilizing an analytical oblate exponential atmospheric density model. Due to the symmetry of the KS element equations, only one of the eight equations is integrated analytically to obtain the state vector at the end of each revolution. This is a uniqueness of the present theory. The series expansions include up to quadratic terms in e (eccentricity) and c (a small parameter dependent on the flattening of the atmosphere). Numerical studies are done with six test cases, selected to cover a wide range of eccentricity and semi-major axis, and a comparison of the three orbital parameters: semi-major axis, eccentricity and argument of perigee perturbed by the air drag with oblate atmosphere is made up to 100 revolutions with the numerically integrated values. The comparison is quite satisfactory. After 100 revolutions, with a ballistic coefficient of 50, a maximum difference of 39 metres is found in the semi-major axis comparison for a very small eccentricity (0.001) case having an initial perigee height of 391.425 km. One important advantage of the present theory is that it is singularity free, a problem faced by the analytical theories developed from the Lagrange's planetary equations. Another advantage is that the state vector is known after each revolution.

  16. A New Fungal Isolate, Penidiella sp. Strain T9, Accumulates the Rare Earth Element Dysprosium

    PubMed Central

    Horiike, Takumi

    2015-01-01

    With an aim to develop a highly efficient method for the recovery of rare earth elements (REEs) by using microorganisms, we attempted to isolate dysprosium (Dy)-accumulating microorganisms that grow under acidic conditions from environmental samples containing high concentrations of heavy metals. One acidophilic strain, T9, which was isolated from an abandoned mine, decreased the concentration of Dy in medium that contained 100 mg/liter Dy to 53 mg/liter Dy after 3 days of cultivation at pH 2.5. The Dy content in the cell pellet of the T9 strain was 910 μg/mg of dry cells. The T9 strain also accumulated other REEs. Based on the results of 28S-D1/D2 rRNA gene sequencing and morphological characterization, we designated this fungal strain Penidiella sp. T9. Bioaccumulation of Dy was observed on the cell surface of the T9 strain by elemental mapping using scanning electron microscopy-energy dispersive X-ray spectroscopy. Our results indicate that Penidiella sp. T9 has the potential to recover REEs such as Dy from mine drainage and industrial liquid waste under acidic conditions. PMID:25710372

  17. Ecosystem Composition Controls the Fate of Rare Earth Elements during Incipient Soil Genesis.

    PubMed

    Zaharescu, Dragos G; Burghelea, Carmen I; Dontsova, Katerina; Presler, Jennifer K; Maier, Raina M; Huxman, Travis; Domanik, Kenneth J; Hunt, Edward A; Amistadi, Mary K; Gaddis, Emily E; Palacios-Menendez, Maria A; Vaquera-Ibarra, Maria O; Chorover, Jon

    2017-02-23

    The rare earth elements (REE) are increasingly important in a variety of science and economic fields, including (bio)geosciences, paleoecology, astrobiology, and mining. However, REE distribution in early rock-microbe-plant systems has remained elusive. We tested the hypothesis that REE mass-partitioning during incipient weathering of basalt, rhyolite, granite and schist depends on the activity of microbes, vascular plants (Buffalo grass), and arbuscular mycorrhiza. Pore-water element abundances revealed a rapid transition from abiotic to biotic signatures of weathering, the latter associated with smaller aqueous loss and larger plant uptake. Abiotic dissolution was 39% of total denudation in plant-microbes-mycorrhiza treatment. Microbes incremented denudation, particularly in rhyolite, and this resulted in decreased bioavailable solid pools in this rock. Total mobilization (aqueous + uptake) was ten times greater in planted compared to abiotic treatments, REE masses in plant generally exceeding those in water. Larger plants increased bioavailable solid pools, consistent with enhanced soil genesis. Mycorrhiza generally had a positive effect on total mobilization. The main mechanism behind incipient REE weathering was carbonation enhanced by biotic respiration, the denudation patterns being largely dictated by mineralogy. A consistent biotic signature was observed in La:phosphate and mobilization: solid pool ratios, and in the pattern of denudation and uptake.

  18. Ecosystem Composition Controls the Fate of Rare Earth Elements during Incipient Soil Genesis

    NASA Astrophysics Data System (ADS)

    Zaharescu, Dragos G.; Burghelea, Carmen I.; Dontsova, Katerina; Presler, Jennifer K.; Maier, Raina M.; Huxman, Travis; Domanik, Kenneth J.; Hunt, Edward A.; Amistadi, Mary K.; Gaddis, Emily E.; Palacios-Menendez, Maria A.; Vaquera-Ibarra, Maria O.; Chorover, Jon

    2017-02-01

    The rare earth elements (REE) are increasingly important in a variety of science and economic fields, including (bio)geosciences, paleoecology, astrobiology, and mining. However, REE distribution in early rock-microbe-plant systems has remained elusive. We tested the hypothesis that REE mass-partitioning during incipient weathering of basalt, rhyolite, granite and schist depends on the activity of microbes, vascular plants (Buffalo grass), and arbuscular mycorrhiza. Pore-water element abundances revealed a rapid transition from abiotic to biotic signatures of weathering, the latter associated with smaller aqueous loss and larger plant uptake. Abiotic dissolution was 39% of total denudation in plant-microbes-mycorrhiza treatment. Microbes incremented denudation, particularly in rhyolite, and this resulted in decreased bioavailable solid pools in this rock. Total mobilization (aqueous + uptake) was ten times greater in planted compared to abiotic treatments, REE masses in plant generally exceeding those in water. Larger plants increased bioavailable solid pools, consistent with enhanced soil genesis. Mycorrhiza generally had a positive effect on total mobilization. The main mechanism behind incipient REE weathering was carbonation enhanced by biotic respiration, the denudation patterns being largely dictated by mineralogy. A consistent biotic signature was observed in La:phosphate and mobilization: solid pool ratios, and in the pattern of denudation and uptake.

  19. Distribution of rare earth elements in soil and grape berries of Vitis vinifera cv. "Glera".

    PubMed

    Pepi, Salvatore; Sansone, Luigi; Chicca, Milvia; Marrocchino, Elena; Vaccaro, Carmela

    2016-08-01

    The renowned Vitis vinifera L. cultivar "Glera" (Magnoliopsida Vitaceae) has been grown for hundreds of years in the Italian regions of Veneto and Friuli to produce the sparkling Prosecco wine, with controlled designation of origin (DOC). We evaluated the relationship among the concentrations of rare earth elements (REE) in soil and in "Glera" grape berries in vineyards belonging to five different localities in the Veneto alluvial plain, all included in the DOC area of Prosecco. The concentration of REE in samples of soil and juice or solid residues of grape berries was determined by inductively coupled plasma mass spectrometry (ICP-MS), and the index of bioaccumulation was calculated to define the specific assimilation of these elements from soil to grape berries. The concentration of REE in soil samples allowed an identification of each locality examined, and REE were mostly detected in solid grape berry residues in comparison to juice. These data may be useful to associate REE distribution in soil and grape berries to a specific geographical origin, in order to prevent fraudulent use of wine denomination labels.

  20. Using rare earth element tracers and neutron activation analysis to study rill erosion process.

    PubMed

    Li, Mian; Li, Zhan-bin; Ding, Weng-feng; Liu, Pu-ling; Yao, Wen-yi

    2006-03-01

    Spatially averaged soil erosion data provide little information on the process of rill erosion. The dynamically varied data on the temporal and spatial distributions in the rill erosion process are needed to better understand the erosion process and reveal its innate characteristics. The objectives of this study were to examine the feasibility and effectiveness of rare earth element (REE) tracers and the neutron activation analysis (NAA) method on the study of the rill erosion process and to reveal quantitatively the relationships and characteristics of temporal and spatial distributions of sediment yield in rill erosion. Four REEs were used to study the changeable process of rill erosion at 4 slope positions. Four water inflow rates were applied to a 0.3 x 5 m soil bed at 3 slopes of 10.5%, 15.8% and 21.2% in scouring experiments. All of the runoff was collected in the experiment. Each sample was air-dried and well mixed. Then 20 g of each sample was sieved through 100-mesh and about a 50 mg sample was weighed for analysis of the four elemental compositions by NAA. Results indicate that the REE tracers and NAA method can be used to not only quantitatively determine soil erosion amounts on different slope segments, but also to reveal the changeable process of rill erosion amount. All of the relative errors of the experimental results were less than 25%, which is considered satisfactory on the study of rill erosion process.

  1. Concomitant Leaching and Electrochemical Extraction of Rare Earth Elements from Monazite.

    PubMed

    Maes, Synthia; Zhuang, Wei-Qin; Rabaey, Korneel; Alvarez-Cohen, Lisa; Hennebel, Tom

    2017-02-07

    Rare earth elements (REEs) have become increasingly important in modern day technologies. Unfortunately, their recycling is currently limited, and the conventional technologies for their extraction and purification are exceedingly energy and chemical intensive. New sustainable technologies for REE extraction from both primary and secondary resources would be extremely beneficial. This research investigated a two-stage recovery strategy focused on the recovery of neodymium (Nd) and lanthanum (La) from monazite ore that combines microbially based leaching (using citric acid and spent fungal supernatant) with electrochemical extraction. Pretreating the phosphate-based monazite rock (via roasting) dramatically increased the microbial REE leaching efficiency. Batch experiments demonstrated the effective and continued leaching of REEs by recycled citric acid, with up to 392 mg of Nd L(-1) and 281 mg of La L(-1) leached during seven consecutive 24 h cycles. Neodymium was further extracted in the catholyte of a three-compartment electrochemical system, with up to 880 mg of Nd L(-1) achieved within 4 days (at 40 A m(-2)). Meanwhile, the radioactive element thorium and counterions phosphate and citrate were separated effectively from the REEs in the anolyte, favoring REE extraction and allowing sustainable reuse of the leaching agent. This study shows a promising technology that is suitable for primary ores and can further be optimized for secondary resources.

  2. Geochemistry of the rare earth elements in ferromanganese nodules from DOMES Site A, northern equatorial Pacific

    USGS Publications Warehouse

    Calvert, S.E.; Piper, D.Z.; Baedecker, P.A.

    1987-01-01

    The distribution of rare earth elements (REE) in ferromanganese nodules from DOMES Site A has been determined by instrumental neutron activation methods. The concentrations of the REE vary markedly. Low concentrations characterize samples from a depression (the valley), in which Quaternary sediments are thin or absent; high concentrations are found in samples from the surrounding abyssal hills (the highlands) where the Quaternary sediment section is relatively thick. Moreover, the valley nodules are strongly depleted in the light trivalent REE (LREE) and Ce compared with nodules from the highlands, some of the former showing negative Ce anomalies. The REE abundances in the nodules are strongly influenced by the REE abundances in coexisting bottom water. Some controls on the REE chemistry of bottom waters include: a) the more effective removal of the LREE relative to the HREE from seawater because of the greater degree of complexation of the latter elements with seawater ligands, b) the very efficient oxidative scavenging of Ce on particle surfaces in seawater, and c) the strong depletion of both Ce and the LREE in, or a larger benthic flux of the HREE into, the Antarctic Bottom Water (AABW) which flows through the valley. The distinctive REE chemistry of valley nodules is a function of their growth from geochemically evolved AABW. In contrast, the REE chemistry of highland nodules indicates growth from a local, less evolved seawater source. ?? 1987.

  3. Uranium, thorium and rare earth elements in macrofungi: what are the genuine concentrations?

    PubMed

    Borovička, Jan; Kubrová, Jaroslava; Rohovec, Jan; Randa, Zdeněk; Dunn, Colin E

    2011-10-01

    Concentrations of uranium, thorium and rare earth elements (REE) in 36 species of ectomycorrhizal (26 samples) and saprobic (25 samples) macrofungi from unpolluted sites with differing bedrock geochemistry were analyzed by inductively coupled plasma mass spectrometry (ICP-MS). Analytical results are supported by use of certified reference materials (BCR-670, BCR-667, NIST-1575a) and the reliability of the determination of uranium was verified by epithermal neutron activation analysis (ENAA). It appears that data recently published on these elements are erroneous, in part because of use of an inappropriate analytical method; and in part because of apparent contamination by soil particles resulting in elevated levels of thorium and REE. Macrofungi from unpolluted areas, in general, did not accumulate high levels of the investigated metals. Concentrations of uranium and thorium were generally below 30 and 125 μg kg(-1) (dry weight), respectively. Concentrations of REE in macrofungi did not exceed 360 μg kg(-1) (dry weight) and their distribution more or less followed the trend observed in post-Archean shales and loess.

  4. Ecosystem Composition Controls the Fate of Rare Earth Elements during Incipient Soil Genesis

    PubMed Central

    Zaharescu, Dragos G.; Burghelea, Carmen I.; Dontsova, Katerina; Presler, Jennifer K.; Maier, Raina M.; Huxman, Travis; Domanik, Kenneth J.; Hunt, Edward A.; Amistadi, Mary K.; Gaddis, Emily E.; Palacios-Menendez, Maria A.; Vaquera-Ibarra, Maria O.; Chorover, Jon

    2017-01-01

    The rare earth elements (REE) are increasingly important in a variety of science and economic fields, including (bio)geosciences, paleoecology, astrobiology, and mining. However, REE distribution in early rock-microbe-plant systems has remained elusive. We tested the hypothesis that REE mass-partitioning during incipient weathering of basalt, rhyolite, granite and schist depends on the activity of microbes, vascular plants (Buffalo grass), and arbuscular mycorrhiza. Pore-water element abundances revealed a rapid transition from abiotic to biotic signatures of weathering, the latter associated with smaller aqueous loss and larger plant uptake. Abiotic dissolution was 39% of total denudation in plant-microbes-mycorrhiza treatment. Microbes incremented denudation, particularly in rhyolite, and this resulted in decreased bioavailable solid pools in this rock. Total mobilization (aqueous + uptake) was ten times greater in planted compared to abiotic treatments, REE masses in plant generally exceeding those in water. Larger plants increased bioavailable solid pools, consistent with enhanced soil genesis. Mycorrhiza generally had a positive effect on total mobilization. The main mechanism behind incipient REE weathering was carbonation enhanced by biotic respiration, the denudation patterns being largely dictated by mineralogy. A consistent biotic signature was observed in La:phosphate and mobilization: solid pool ratios, and in the pattern of denudation and uptake. PMID:28230202

  5. 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)

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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 A