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Sample records for alkali aluminosilicate glasses

  1. Alkali aluminosilicate melts and glasses: structuring at the middle range order of amorphous matter

    NASA Astrophysics Data System (ADS)

    Le Losq, C.; neuville, D. R.

    2012-12-01

    Rheological properties of silicate melts govern both magma ascension from the mantle to the surface of the earth and volcanological eruptions styles and behaviours. It is well known that several parameters impact strongly these properties, such as for instance the temperature, pressure, chemical composition and volatiles concentration, finally influencing eruptive behaviour of volcanoes. In this work, we will focus on the Na2O-K2O-Al2O3-SiO2 system, which is of a prime importance because it deals with a non-negligible part of natural melts, like for instance the Vesuvius (Italy) or Erebus (Antartica) magmas. In an oncoming paper in Chemical Geology (Le Losq and Neuville, 2012), we have communicated results of the study of mixing Na-K in tectosilicate melts containing a high concentration of silica (≥75mol%). In the present communication, we will enlarge this first point of view to tectosilicate melts presenting a lower silica concentration. We will first present our viscosity data, and then the Adam and Gibbs theory that allows theoretically modelling Na-K mixing in aluminosilicate melts by using the so-called "mixed alkali effect". On the basis of the rheological results, the Na-K mixing cannot be explained with the ideal "mixed alkali effect", which involves random exchange of Na-K cationic pairs. To go further and as rheological properties are directly linked with structural properties, we will present our first results obtained by Raman and NMR spectroscopy. These last ones provide important structural pieces of information on the polymerization state of glasses and melts, and also on the environment of tetrahedrally coordinated cations. Rheological and structural results all highlight that Na and K are not randomly distributed in aluminosilicate glasses and melts networks. Na melts present a network with some channels and a non-random distribution of Al and Si. K networks are different. They also present a non-random distribution of Al and Si, but in two sub

  2. Structural Role of Alkali Cations in Calcium Aluminosilicate Glasses as Examined Using Oxygen-17 Solid-State Nuclear Magnetic Resonance Spectroscopy

    NASA Astrophysics Data System (ADS)

    Sukenaga, Sohei; Kanehashi, Koji; Shibata, Hiroyuki; Saito, Noritaka; Nakashima, Kunihiko

    2016-08-01

    The structural roles of alkali and calcium cations are important for understanding the physical and chemical properties of aluminosilicate melts and glasses. Recently, oxygen-17 nuclear magnetic resonance (17O NMR) studies of calcium-sodium aluminosilicate glasses showed that these structural roles are not randomly given, but rather each cation has its own preferential role. However, the relationship between cation type and role preference in calcium aluminosilicate glass is not completely understood. In the present study, the structural roles of lithium, sodium, and potassium cations in selected calcium aluminosilicate glasses are investigated using 17O solid-state NMR experiments. Data from these experiments clearly show that potassium cations have a notably stronger tendency to act as charge compensators within the network structure, compared to sodium and lithium cations. The result of 17O NMR experiment also showed that sodium and lithium cations in part act as network modifier alongside with calcium cations.

  3. Ring distributions in alkali- and alkaline-earth aluminosilicate framework glasses- a raman spectroscopic study

    USGS Publications Warehouse

    Sharma, S.K.; Philpotts, J.A.; Matson, D.W.

    1985-01-01

    Raman spectra of crystalline polymorphs of a number of tectosilicate minerals having various sizes of smallest rings of TO4 tetrahedra (T = Si, Al) have been investigated to identify the bands that are sensitive indicators of the smallest rings in the network. The information obtained from the Raman spectra of tectosilicate minerals (e.g., SiO2 polymorphs, NaAlSi3O8 (Ab), NaAlSiO4 (Ne), KAlSi3O8 (Or), and KAlSi2O6 (Lc)) is used to interpret the Raman spectra of the isochemical glasses. It is shown that the frequency of the dominant ??s (TOT) band in the spectra of both crystals and glasses is related to the dominant size of TO4 rings in the structure. In agreement with previous X-ray RDF work, it is found that in the glasses of Ab and Jd (NaAlSi2O6) compositions, six-membered rings of TO4 tetrahedra predominate. The Raman spectrum of Or glass, however, indicates that clusters of intermixed four- and six-membered rings of TO4 tetrahedra, similar to those existing in crystalline leucite, are also present in the glass. Raman evidence indicates that four-membered rings of TO4 tetrahedra predominate in the glass of An composition. Similarly, the higher frequency of the ??s (TOT) band in the spectrum of Ne glass as compared with the frequency the ??s (TOT) band in the spectra of crystalline cargenieite and nephelite indicates either an admixture of the four- and six-membered rings or the puckering of six-membered rings in the glass structure. ?? 1985.

  4. Photoelastic response of alkaline earth aluminosilicate glasses.

    PubMed

    Smedskjaer, Morten M; Saxton, Scott A; Ellison, Adam J; Mauro, John C

    2012-02-01

    Understanding the structural origins of the photoelastic response in oxide glasses is important for discovering new families of zero-stress optic glasses and for developing a predictive physical model. In this Letter, we have investigated the composition dependence of the stress optic coefficient C of 32 sodium aluminosilicate glasses with different types of alkaline earth oxides (MgO, CaO, SrO, and BaO). We find that most of the composition dependence of the stress optic response can be captured by a linear regression model and that the individual contributions from the alkaline earths to C depend on the alkaline earth-oxygen bond metallicity. High bond metallicity is required to allow bonds to be distorted along both the bonding direction and perpendicular to it. These findings are valuable for understanding the photoelastic response of oxide glasses.

  5. Structure and rheological properties in alkali aluminosilicate melts

    NASA Astrophysics Data System (ADS)

    Le Losq, Charles; Neuville, Daniel

    2010-05-01

    Rheological properties of silicate melts govern both magma ascension from the mantle to the surface of the earth and volcanological eruptions styles and behaviors. In this mind, it is very important to understand which parameters influence these properties. Up to now, we know for example that viscosity of silicate melts is dependent of temperature, pressure and chemical composition. In this work, we will focus on the Na2O-K2O-Al2O3-SiO2 system, which is of a prime importance because it deals with a non-negligible part of natural melts like haplogranitic rhyolitic alkali magmas. We will first present our viscosity measurements and some modelisation concepts based on the Adam and Gibbs theory. From configurational entropy theory we obtain some macroscopic information's that we can link to the structure of glasses and melts. In this mind, we have investigated them with Raman and NMR spectroscopies. These spectroscopies provide information on speciation and polymerization of glasses and melts. We will present and discuss structural and rheological variations as a function of temperature and chemical change.

  6. Crystallization of a barium-aluminosilicate glass

    NASA Technical Reports Server (NTRS)

    Drummond, C. H., III; Lee, W. E.; Bansal, N. P.; Hyatt, M. J.

    1989-01-01

    The crystallization of a celsian glass composition was investigated as a possible high-temperature ceramic matrix material. Heat treatments invariably resulted in crystallization of the hexaclesian phase unless a flux, such as lithia, was added or a nucleating agent used (e.g., celsian seeds). TEM analysis revealed complex microstructures. Glasses with Mo additions contained hexacelsian, mullite, and an Mo-rich glass. Li2O additions stabilized celsian but mullite and Mo-rich glass were still present.

  7. Mixed alkali effect in nonconventional alkali gallotitanate glasses

    SciTech Connect

    Miyaji, Fumiaki; Hasegawa, Shinya; Yoko, Toshinobu; Sakka, Sumio . Inst. for Chemical Research)

    1993-02-01

    The mixed alkali effect on electrical conductivity, that is, the reduction of conductivity due to alkali mixing, was observed in Na[sub 2]O-K[sub 2]O-Ga[sub 2]O[sub 3]-TiO[sub 2] glasses, which are nonconventional in the sense that glass-forming oxides defined by Zachariasen are not involved. The magnitude of the reduction in conductivity of the present glasses due to alkali mixing was similar to that of corresponding mixed alkali silicate and phosphate glasses. The activation energy for electrical conduction showed a maximum around the composition Na/(Na + K) = 0.5, where the conductivity was at a minimum.

  8. Effects of Thermal and Pressure Histories on the Chemical Strengthening of Sodium Aluminosilicate Glass

    NASA Astrophysics Data System (ADS)

    Svenson, Mouritz; Thirion, Lynn; Youngman, Randall; Mauro, John; Bauchy, Mathieu; Rzoska, Sylwester; Bockowski, Michal; Smedskjaer, Morten

    2016-03-01

    Glasses can be chemically strengthened through the ion exchange process, wherein smaller ions in the glass (e.g., Na+) are replaced by larger ions from a salt bath (e.g., K+). This develops a compressive stress (CS) on the glass surface, which, in turn, improves the damage resistance of the glass. The magnitude and depth of the generated CS depends on the thermal and pressure histories of the glass prior to ion exchange. In this study, we investigate the ion exchange-related properties (mutual diffusivity, CS, and hardness) of a sodium aluminosilicate glass, which has been densified through annealing below the initial fictive temperature of the glass or through pressure-quenching from the glass transition temperature at 1 GPa prior to ion exchange. We show that the rate of alkali interdiffusivity depends only on the density of the glass, rather than on the applied densification method. However, we also demonstrate that for a given density, the increase in CS and increase in hardness induced by ion exchange strongly depends on the densification method. Specifically, at constant density, the CS and hardness values achieved through thermal annealing are larger than those achieved through pressure-quenching. These results are discussed in relation to the structural changes in the environment of the network-modifier and the overall network densification.

  9. Crystallization Kinetics of Calcium-magnesium Aluminosilicate (CMAS) Glass

    NASA Technical Reports Server (NTRS)

    Wiesner, Valerie L.; Bansal, Narottam P.

    2015-01-01

    The crystallization kinetics of a calcium-magnesium aluminosilicate (CMAS) glass with composition relevant for aerospace applications, like air-breathing engines, were evaluated using differential thermal analysis (DTA) in powder and bulk forms. Activation energy and frequency factor values for crystallization of the glass were evaluated. X-ray diffraction (XRD) was used to investigate the onset of crystallization and the phases that developed after heat treating bulk glass at temperatures ranging from 690 to 960 deg for various times. Samples annealed at temperatures below 900 deg remained amorphous, while specimens heat treated at and above 900 deg exhibited crystallinity originating at the surface. The crystalline phases were identified as wollastonite (CaSiO3) and aluminum diopside (Ca(Mg,Al) (Si,Al)2O6). Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were employed to examine the microstructure and chemical compositions of crystalline phases formed after heat treatment.

  10. Thermodynamic assessment of hydrothermal alkali feldspar-mica-aluminosilicate equilibria

    USGS Publications Warehouse

    Sverjensky, D.A.; Hemley, J.J.; d'Angelo, W. M.

    1991-01-01

    The thermodynamic properties of minerals retrieved from consideration of solid-solid and dehydration equilibria with calorimetric reference values, and those of aqueous species derived from studies of electrolytes, are not consistent with experimentally measured high-temperature solubilities in the systems K2O- and Na2O-Al2O3-SiO2-H2O-HCl (e.g., K-fs - Ms - Qtz - K+ - H+). This introduces major inaccuracies into the computation of ionic activity ratios and the acidities of diagenetic, metamorphic, and magmatic hydrothermal fluids buffered by alkali silicate-bearing assemblages. We report a thermodynamic analysis of revised solubility equilibria in these systems that integrates the thermodynamic properties of minerals obtained from phase equilibria studies (Berman, 1988) with the properties of aqueous species calculated from a calibrated equation of state (Shock and Helgeson, 1988). This was achieved in two separate steps. First, new values of the free energies and enthalpies of formation at 25??C and 1 bar for the alkali silicates muscovite and albite were retrieved from the experimental solubility equilibria at 300??C and Psat. Because the latter have stoichiometric reaction coefficients different from those for solid-solid and dehydration equilibria, our procedure preserves exactly the relative thermodynamic properties of the alkali-bearing silicates (Berman, 1988). Only simple arithmetic adjustments of -1,600 and -1,626 (??500) cal/mol to all the K- and Na-bearing silicates, respectively, in Berman (1988) are required. In all cases, the revised values are within ??0.2% of calorimetric values. Similar adjustments were derived for the properties of minerals from Helgeson et al. (1978). Second, new values of the dissociation constant of HCl were retrieved from the solubility equilibria at temperatures and pressures from 300-600??C and 0.5-2.0 kbars using a simple model for aqueous speciation. The results agree well with the conductance-derived dissociation

  11. Mixed alkaline earth effect in the compressibility of aluminosilicate glasses.

    PubMed

    Smedskjaer, Morten M; Rzoska, Sylwester J; Bockowski, Michal; Mauro, John C

    2014-02-01

    The mixed modifier effect (MME) in oxide glasses manifests itself as a non-additive variation in certain properties when one modifier oxide species is substituted by another one at constant total modifier content. However, the structural and topological origins of the MME are still under debate. This study provides new insights into the MME by investigating the effect of isostatic compression on density and hardness of mixed MgO/CaO sodium aluminosilicate glasses. This is done using a specially designed setup allowing isostatic compression of bulk glass samples up to 1 GPa at elevated temperature. A mixed alkaline earth effect is found in the compressibility and relative change of hardness, viz., a local maximum of density as a function of Mg/Ca ratio appears following compression, whereas a local minimum of hardness in the uncompressed glasses nearly disappears after compression. Moreover, the densification of these glasses is found to occur at temperatures much below the glass transition temperature, indicating that a non-viscous mechanism is at play. This is further supported by the fact that density relaxes in a stretched exponential manner upon subsequent annealing at ambient pressure with an exponent of ∼0.62. This is close to the Phillips value of 3/5 for relaxation in three dimensions when both short- and long-range interactions are activated.

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

    NASA Astrophysics Data System (ADS)

    Musil, Sean

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

  13. DuraLith Alkali-Aluminosilicate Geopolymer Waste Form Testing for Hanford Secondary Waste

    SciTech Connect

    Gong, W. L.; Lutz, Werner; Pegg, Ian L.

    2011-07-21

    The primary objective of the work reported here was to develop additional information regarding the DuraLith alkali aluminosilicate geopolymer as a waste form for liquid secondary waste to support selection of a final waste form for the Hanford Tank Waste Treatment and Immobilization Plant secondary liquid wastes to be disposed in the Integrated Disposal Facility on the Hanford Site. Testing focused on optimizing waste loading, improving waste form performance, and evaluating the robustness of the waste form with respect to waste variability.

  14. Selective laser densification of lithium aluminosilicate glass ceramic tapes

    NASA Astrophysics Data System (ADS)

    Zocca, Andrea; Colombo, Paolo; Günster, Jens; Mühler, Thomas; Heinrich, Jürgen G.

    2013-01-01

    Tapes, cast by blade deposition of a lithium aluminosilicate glass slurry, were sintered using a YAG-fiber laser, with the aim of finding suitable parameters for an additive manufacturing process based on layer-wise slurry deposition and selective laser densification. The influence of the laser parameters (output power and scan velocity) on the sintering was evaluated, by scanning electron microscopy and by X-ray diffraction, on the basis of the quality of the processed layer. Well densified samples could be obtained only in a small window of values for the output power and the scan velocity. The measurement of the width of a set of single scanned lines allowed also to estimate the minimum resolution of the system along the layer plane.

  15. Corrosion behavior of sodium aluminosilicate glasses and crystals

    NASA Astrophysics Data System (ADS)

    Hamilton, James Patrick

    1999-12-01

    A comprehensive study of the effects of structure and composition on the pH-dependent corrosion behavior of sodium-aluminosilicate glasses and crystals at 25°C, was investigated by a combination of various solution and surface analysis techniques. These techniques were used to measure solution stoichiometry relative to the glass and crystal, surface composition, surface layer thickness, and structure of the surface layer. The room temperature dissolution rates of glasses and crystals with the albite composition (NaAlSi3O8) were essentially identical over the acidic-weakly basic pH region. Differences in density and tetrahedral ring structure between the glass and crystal structures, however, led to more extensive Na and Al depletion from the glass surface. Nevertheless, the outermost 17A of the glass and crystal surface were compositionally similar, suggesting that this region of the solid controls the dissolution rate. The corrosion behavior of glasses in the NBO (Na2O-xAl 2O3-(3-x)SiO2) and mineral (Na2O-Al 2O3-y SiO2) series were investigated over the pH range of 1--12. The NBO glass series tested the effects of alumina and non-bridging oxygen (NBO) concentration on corrosion behavior without any change in soda content. The mineral glass series tested the effect of Al/Si ratio on corrosion behavior in glasses with fully polymerized structures and no NBO sites. The elimination of some NBO sites by the initial addition of alumina to the glass with x = 0.0 composition caused a significant reduction in the dissolution rate. However, the dissolution rates of glasses with x > 0.2 (in the NBO series) and all glasses in the mineral series were controlled by Al-O-Si and Si-O-Si bonding. In the NBO series, NBO concentration controlled the formation and thickness of leached surface layers. In the absence of NBO sites, Al-O-Si and Si-O-Si bonding controlled the leaching behavior. Transformation of the glass surfaces during corrosion at any pH led to the formation leached

  16. Compressibility of magnesium silicate glasses in comparison with those of aluminosilicate glasses

    NASA Astrophysics Data System (ADS)

    Kuryaeva, R. G.

    2013-10-01

    The refractive index of the Na2MgSi6O14 glass in the pressure range up to 6.0 GPa has been measured using a polarization-interference microscope and an apparatus with diamond anvils. The changes in relative density which characterize the compressibility of the glass have been estimated in the pressure range under investigation from the measured refractive indices within the framework of the theory of photoelasticity. The results have been compared with the data previously obtained for the NaAlSi3O8 and CaAl2Si6O16 glasses. A comparison of the changes in relative density of the aluminosilicate and magnesium silicate glasses has been demonstrated that the difference in the compressibility is not so much significant as should be expected from the replacement of network-forming ions by modifiers ions. Estimated by different methods the degree of depolymerization of the Na2MgSi6O14 glass (NBO/T ≅ 0.2) is compared to those for the aluminosilicate glasses. The decrease in the compressibility in the series NaAlSi3O8, CaAl2Si6O16, Na2MgSi6O14 glasses is in agreement with an increase of the degree of depolymerization in the same series.

  17. Cellular morphology of organic-inorganic hybrid foams based on alkali alumino-silicate matrix

    NASA Astrophysics Data System (ADS)

    Verdolotti, Letizia; Liguori, Barbara; Capasso, Ilaria; Caputo, Domenico; Lavorgna, Marino; Iannace, Salvatore

    2014-05-01

    Organic-inorganic hybrid foams based on an alkali alumino-silicate matrix were prepared by using different foaming methods. Initially, the synthesis of an inorganic matrix by using aluminosilicate particles, activated through a sodium silicate solution, was performed at room temperature. Subsequently the viscous paste was foamed by using three different methods. In the first method, gaseous hydrogen produced by the oxidization of Si powder in an alkaline media, was used as blowing agent to generate gas bubbles in the paste. In the second method, the porous structure was generated by mixing the paste with a "meringue" type of foam previously prepared by whipping, under vigorous stirring, a water solution containing vegetal proteins as surfactants. In the third method, a combination of these two methods was employed. The foamed systems were consolidated for 24 hours at 40°C and then characterized by FTIR, X-Ray diffraction, scanning electron microscopy (SEM) and compression tests. Low density foams (˜500 Kg/m3) with good cellular structure and mechanical properties were obtained by combining the "meringue" approach with the use of the chemical blowing agent based on Si.

  18. Cellular morphology of organic-inorganic hybrid foams based on alkali alumino-silicate matrix

    SciTech Connect

    Verdolotti, Letizia; Capasso, Ilaria; Lavorgna, Marino; Liguori, Barbara; Caputo, Domenico; Iannace, Salvatore

    2014-05-15

    Organic-inorganic hybrid foams based on an alkali alumino-silicate matrix were prepared by using different foaming methods. Initially, the synthesis of an inorganic matrix by using aluminosilicate particles, activated through a sodium silicate solution, was performed at room temperature. Subsequently the viscous paste was foamed by using three different methods. In the first method, gaseous hydrogen produced by the oxidization of Si powder in an alkaline media, was used as blowing agent to generate gas bubbles in the paste. In the second method, the porous structure was generated by mixing the paste with a “meringue” type of foam previously prepared by whipping, under vigorous stirring, a water solution containing vegetal proteins as surfactants. In the third method, a combination of these two methods was employed. The foamed systems were consolidated for 24 hours at 40°C and then characterized by FTIR, X-Ray diffraction, scanning electron microscopy (SEM) and compression tests. Low density foams (∼500 Kg/m{sup 3}) with good cellular structure and mechanical properties were obtained by combining the “meringue” approach with the use of the chemical blowing agent based on Si.

  19. Flux Decoupling and Chemical Diffusion in Redox Dynamics in Aluminosilicate Melts and Glasses (Invited)

    NASA Astrophysics Data System (ADS)

    Cooper, R. F.

    2010-12-01

    Measurements of redox dynamics in silicate melts and glasses suggest that, for many compositions and for many external environments, the reaction proceeds and is rate-limited by the diffusive flux of divalent-cation network modifiers. Application of ion-backscattering spectrometry either (i) on oxidized or reduced melts (subsequently quenched before analysis) or (ii) on similarly reacted glasses, both of basalt-composition polymerization, demonstrates that the network modifiers move relative to the (first-order-rigid) aluminosilicate network. Thus, the textures associated with such reactions are often surprising, and frequently include metastable or unstable phases and/or spatial compositional differences. This response is only possible if the motion of cations can be decoupled from that of anions. In many cases, decoupling is accomplished by the presence in the melt/glass of transition-metal cations, whose heterovalency creates distortions in the electronic band structure resulting in electronic defects: electron “holes” in the valence band or electrons in the conduction band. (The prevalence of holes or electrons being a function of bulk chemistry and oxygen activity.) These electronic species make the melt/glass a “defect semiconductor.” Because (a) the critical issue in reaction dynamics is the transport coefficient (the product of species mobility and species concentration) and (b) the electronic species are many orders of magnitude more mobile than are the ions, very low concentrations of transition-metal ions are required for flux decoupling. For example, 0.04 at% Fe keeps a magnesium aluminosilicate melt/glass a defect semiconductor down to 800°C [Cook & Cooper, 2000]. Depending on composition, high-temperature melts can see ion species having a high-enough transport coefficient to allow decoupling, e.g., alkali cations in a basaltic melt [e.g., Pommier et al., 2010]. In this presentation, these ideas will be illustrated by examining redox dynamics

  20. Formic acid, ethanol in vycor glass, and water in aluminosilicate zeolites

    SciTech Connect

    Loong, C.K.; Trouw, F.; Iton, L.E.

    1993-11-01

    We present results of incoherent inelastic neutron-scattering experiments on formic acid, ethanol in vycor glass, and water in aluminosilicate zeolites performed at Argonne`s spallation neutron source, IPNS. The forming and breaking of hydrogen bonds are discussed in terms of translational and rotational diffusion, and vibrational footprints of various molecular species in these systems.

  1. Hydration effects on the structural and vibrational properties of yttrium aluminosilicate glasses for in situ radiotherapy.

    PubMed

    Malik, Jahangir; Tilocca, Antonio

    2013-11-21

    The performances of silicate glasses as containment matrices or vectors of radioactive ions in nuclear waste storage and in situ radiotherapy are influenced by the effect of interstitial water on the glass durability. In order to assess how hydration determines changes to atomistic structural features which control the glass degradation, we have carried out molecular dynamics simulations of a typical yttrium aluminosilicate (YAS) glass employed in radiotherapy, incorporating different water contents. The analysis of the models allows us to discuss the way in which hydroxyl groups are distributed in the glass structure and modify or disrupt the aluminosilicate glass network. Hydration affects the silicate and aluminate connectivity to a different extent, resulting in a different degree of disruption (depolymerization) of the Si and Al network. The simulations also highlight a strong tendency of all hydrated compositions to form Y(3+)- and OH(-)-rich domains, separated from the aluminosilicate matrix. The implications of these structural effects for the durability and ion release behavior of the glass are discussed, as well as the vibrational signatures of the various hydrous species identified in the models. PMID:24206236

  2. Hafnium in peralkaline and peraluminous boro-aluminosilicate glass, and glass subcomponents: a solubility study.

    SciTech Connect

    Davis, Linda L.; Darab, John G.; Qian, Maoxu; Zhao, Donggao; Palenik, Christopher S.; Li, Hong; Strachan, Denis M.; Li, Liyu

    2003-10-15

    A relationship between the solubility of hafnia (HfO2) and the host glass composition was explored by determining the solubility limits of HfO2 in peralkaline and peraluminous borosilicate glasses in the system SiO2-Al2O3-B2O3-Na2O, and in glasses in the system SiO2-Na2O-Al2O3 in air at 1450 C. The only Hf-bearing phase to crystallize in the peralkaline borosilicate melts is hafnia, while in the boron-free melts sodium-hafnium silicates crystallize. All peraluminous borosilicate melts crystallize hafnia, but the slightly peraluminous glasses also have sector-zoned hafnia crystals that contain Al and Si. The more peraluminous borosilicate glasses also crystallize a B-containing mullite. The general morphology of the hafnia crystals changes as peralkalinity (Na2O/(Na2O+Al2O3)) decreases, as expected in melts with increasing viscosity. In all of the glasses with Na2O > Al2O3, the solubility of hafnia is linearly and positively correlated with Na2O/(Na2O + Al2O3) or Na2O - Al2O3 (excess sodium), despite the presence of 5 to 16 mol% B2O3. The solubility of hafnia is higher in the sodium-aluminum borosilicate glasses than in the sodium-aluminosilicate glasses, suggesting that the boron is enhancing the effect that excess sodium has on the incorporation of Hf into the glass structure. The results of this solubility study are compared to other studies of high-valence cation solubility in B-free silicate melts. From this, for peralkaline B-bearing glasses, it is shown that, although the solubility limits are higher, the solution behavior of hafnia is the same as in B-free silicate melts previously studied. By comparison, also, it is shown that in peraluminous melts, there must be a different solution mechanism for hafnia: different than for peralkaline sodium-aluminum borosilicate glasses and different than for B-free silicate melts studied by others.

  3. Fictive temperature-independent density and minimum indentation size effect in calcium aluminosilicate glass

    NASA Astrophysics Data System (ADS)

    Gross, T. M.; Tomozawa, M.

    2008-09-01

    Using the calcium aluminosilicate system a glass was developed that exhibits fictive temperature-independent density by creating an intermediate glass between normal and anomalous glasses. Normal glass, such as soda-lime silicate glass, exhibits decreasing density with increasing fictive temperature while anomalous glass, such as silica glass, exhibits increasing density with increasing fictive temperature. This intermediate glass composition was found to exhibit the minimum indentation size effect during indentation hardness testing. It appears that the indentation size effect is correlated with a deformation-induced fictive temperature increase, which is accompanied by a density change and hardness change in the vicinity of the indentation. It is suggested from these observations that indentation size effect originates from the energy required to create interfaces and defects such as shear bands, subsurface cracks, and point defects near the indenter-specimen boundary, which accompany the volume change.

  4. Fictive temperature-independent density and minimum indentation size effect in calcium aluminosilicate glass

    SciTech Connect

    Gross, T. M.; Tomozawa, M.

    2008-09-15

    Using the calcium aluminosilicate system a glass was developed that exhibits fictive temperature-independent density by creating an intermediate glass between normal and anomalous glasses. Normal glass, such as soda-lime silicate glass, exhibits decreasing density with increasing fictive temperature while anomalous glass, such as silica glass, exhibits increasing density with increasing fictive temperature. This intermediate glass composition was found to exhibit the minimum indentation size effect during indentation hardness testing. It appears that the indentation size effect is correlated with a deformation-induced fictive temperature increase, which is accompanied by a density change and hardness change in the vicinity of the indentation. It is suggested from these observations that indentation size effect originates from the energy required to create interfaces and defects such as shear bands, subsurface cracks, and point defects near the indenter-specimen boundary, which accompany the volume change.

  5. Intrinsic differences in atomic ordering of calcium (alumino)silicate hydrates in conventional and alkali-activated cements

    SciTech Connect

    White, Claire E.; Daemen, Luke L.; Hartl, Monika; Page, Katharine

    2015-01-15

    The atomic structures of calcium silicate hydrate (C–S–H) and calcium (–sodium) aluminosilicate hydrate (C–(N)–A–S–H) gels, and their presence in conventional and blended cement systems, have been the topic of significant debate over recent decades. Previous investigations have revealed that synthetic C–S–H gel is nanocrystalline and due to the chemical similarities between ordinary Portland cement (OPC)-based systems and low-CO{sub 2} alkali-activated slags, researchers have inferred that the atomic ordering in alkali-activated slag is the same as in OPC–slag cements. Here, X-ray total scattering is used to determine the local bonding environment and nanostructure of C(–A)–S–H gels present in hydrated tricalcium silicate (C{sub 3}S), blended C{sub 3}S–slag and alkali-activated slag, revealing the large intrinsic differences in the extent of nanoscale ordering between C–S–H derived from C{sub 3}S and alkali-activated slag systems, which may have a significant influence on thermodynamic stability, and material properties at higher length scales, including long term durability of alkali-activated cements.

  6. Infrared and Raman spectroscopic studies on alkali borate glasses: evidence of mixed alkali effect.

    PubMed

    Padmaja, G; Kistaiah, P

    2009-03-19

    A lithium-potassium-borate glass system containing manganese and iron cations has been thoroughly investigated in order to obtain information about the mixed alkali effect and the structural role of both the manganese and iron in such glass hosts. Mixed alkali borate glasses of the (30 - x)Li(2)O - xK(2)O - 10CdO/ZnO - 59B(2)O(3) (x = 0, 10, 15, 20, and 30) doped with 1MnO(2)/1Fe(2)O(3) system were prepared by a melt quench technique. The amorphous phase of the prepared glass samples was confirmed from their X-ray diffraction. The spectroscopic properties of glass samples were studied using infrared (IR) and Raman spectroscopic techniques. The density of all the prepared glasses was measured using Archimedes principle. Molar volumes were estimated from the density data. IR spectra of these glasses revealed a dramatic variation of three- and four-coordinated boron structures as a function of mixed alkali concentration. The vibrations due to Li-O, K-O, and MnO(4)/FeO(4) arrangements are consistent in all the compositions and show a nonlinear variation in the intensity with alkali content. Raman spectra of different alkali combinations with CdO and ZnO present drastic changes in the intensity of various Raman bands. The observation of disappearance and reappearance of IR and Raman bands as a function of various alkali concentrations is an important result pertaining to the mixed alkali effect in borate glasses. Acting as complementary spectroscopic techniques, both types of measurements, IR and Raman, revealed that the network structure of the studied glasses is mainly based on BO(3) and BO(4) units placed in different structural groups, the BO(3) units being dominant. The measured IR and Raman spectra of different glasses are used to clarify the optical properties of the present glasses correlating them with their structure and composition. PMID:19235995

  7. Cooperative luminescence and absorption in ytterbium doped aluminosilicate glass optical fibres and preforms

    NASA Astrophysics Data System (ADS)

    Ryan, Tom G.; Jackson, Stuart D.

    2007-05-01

    The cooperative luminescence and absorption properties of Yb 3+ doped aluminosilicate glass optical fibres and preforms are investigated in detail. In accordance with previous investigations, both the visible cooperative luminescence and the infrared luminescence decay measurements have been resolved into a single exponential decay component. We show that for a glass with similar Yb 3+ dopant concentration but more Al 3+, the glass emits less visible luminescence. Absorption loss measurements completed on fibre samples revealed a broad absorption in the 350-500 nm range, which we propose is due to a combination of Yb 2+ absorption and cooperative absorption from Yb 3+ ion pairs.

  8. Electric field-induced softening of alkali silicate glasses

    SciTech Connect

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

    2015-11-02

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

  9. Chemical durability of soda-lime-aluminosilicate glass for radioactive waste vitrification

    SciTech Connect

    Eppler, F.H.; Yim, M.S.

    1998-09-01

    Vitrification has been identified as one of the most viable waste treatment alternatives for nuclear waste disposal. Currently, the most popular glass compositions being selected for vitrification are the borosilicate family of glasses. Another popular type that has been around in glass industry is the soda-lime-silicate variety, which has often been characterized as the least durable and a poor candidate for radioactive waste vitrification. By replacing the boron constituent with a cheaper substitute, such as silica, the cost of vitrification processing can be reduced. At the same time, addition of network intermediates such as Al{sub 2}O{sub 3} to the glass composition increases the environmental durability of the glass. The objective of this study is to examine the ability of the soda-lime-aluminosilicate glass as an alternative vitrification tool for the disposal of radioactive waste and to investigate the sensitivity of product chemical durability to variations in composition.

  10. Effects of the degree of polymerization on the structure of sodium silicate and aluminosilicate glasses and melts: An 17O NMR study

    NASA Astrophysics Data System (ADS)

    Lee, Sung Keun; Stebbins, Jonathan F.

    2009-02-01

    Revealing the atomic structure and disorder in oxide glasses, including sodium silicates and aluminosilicates, with varying degrees of polymerization, is a challenging problem in high-temperature geochemistry as well as glass science. Here, we report 17O MAS and 3QMAS NMR spectra for binary sodium silicate and ternary sodium aluminosilicate glasses with varying degrees of polymerization (Na 2O/SiO 2 ratio and Na 2O/Al 2O 3 ratio), revealing in detail the extent of disorder (network connectivity and topological disorder) and variations of NMR parameters with the glass composition. In binary sodium silicate glasses [Na 2O- k(SiO 2)], the fraction of non-bridging oxygens (NBOs, Na-O-Si) increases with the Na 2O/SiO 2 ratio ( k), as predicted from the composition. The 17O isotropic chemical shifts ( 17O δiso) for both bridging oxygen (BO) and NBO increase by about 10-15 ppm with the SiO 2 content (for k = 1-3). The quadrupolar coupling products of BOs and NBOs also increase with the SiO 2 content. These trends suggest that both NBOs and BOs strongly interact with Na; therefore, the Na distributions around BOs and NBOs are likely to be relatively homogenous for the glass compositions studied here, placing some qualitative limits on the extent of segregation of alkali channels from silica-enriched regions as suggested by modified random-network models. The peak width (in the isotropic dimension) and thus bond angle and length distributions of Si-O-Si and Na-O-Si increase with the SiO 2 content, indicating an increase in the topological disorder with the degree of polymerization. In the ternary aluminosilicate glasses [Na 2O] x[Al 2O 3] 1-xSiO 2, the NBO fraction decreases while the Al-O-Si and Al-O-Al fractions apparently increase with increasing Al 2O 3 content. The variation of oxygen cluster populations suggests that deviation from "Al avoidance" is more apparent near the charge-balanced join (Na/Al = 1). The Si-O-Si fraction, which is closely related to the activity

  11. Water solubility in calcium aluminosilicate glasses investigated by first principles techniques

    SciTech Connect

    Bouyer, Frederic; Geneste, Gregory; Ispas, Simona; Kob, Walter; Ganster, Patrick

    2010-12-15

    First-principles techniques have been employed to study the reactivity of water into a calcium aluminosilicate glass. In addition to the well known hydrolysis reactions Si-O-Si+H{sub 2}O{yields}Si-OH+Si-OH and Si-O-Al+H{sub 2}O{yields}Si-OH+Al-OH, a peculiar mechanism is found, leading to the formation of an AlO{sub 3}-H{sub 2}O entity and the breaking of Al-O-Si bond. In the glass bulk, most of the hydrolysis reactions are endothermic. Only a few regular sites are found reactive (i.e. in association with an exothermic reaction), and in that case, the hydrolysis reaction leads to a decrease of the local disorder in the amorphous vitreous network. Afterwards, we suggest that ionic charge compensators transform into network modifiers when hydrolysis occurs, according to a global process firstly suggested by Burnham in 1975. Our theoretical computations provide a more general model of the first hydrolysis steps that could help to understand experimental data and water speciation in glasses. -- Graphical Abstract: Reactivity within glass bulk: structures obtained after hydrolyses reactions (endothermic and exothermic processes) and mechanisms involving Si-OH, Al-OH, Si-OH-Al groups within aluminosilicates glasses (through ab initio molecular dynamics): formation of the Si-OH-Al entity coupled with an H exchange-Frederic Bouyer and Gregory Geneste. Display Omitted

  12. A Novel Conversion Process for Waste Slag: The Preparation of Aluminosilicate Glass with Evaluation of the Dielectric Properties from Blast Furnace Slag

    NASA Astrophysics Data System (ADS)

    Li, Sheng; Huang, Sanxi; Liu, Hongting; Wu, Fengnian; Chang, Ziyuan; Yue, Yunlong

    2015-11-01

    In this paper, aluminosilicate glass was prepared from blast furnace slag and quartz sand. Fourier transform infrared, differential scanning calorimetry and density measurements were carried out to investigate the effects of SiO2 on the aluminosilicate glass network rigidity. The results indicate that glass structure would be enhanced if more SiO2 was introduced into the glass system. Meanwhile, both the glass transition temperature ( T g) and the glass crystallization temperature ( T c) increase slightly; the increase in density of the glass being further evidence of the enhancement in glass network rigidity. Dielectric measurements show that the dielectric constant and dielectric loss decrease with more SiO2. The properties of the prepared aluminosilicate glasses are comparable to those of E glass, indicating that blast furnace slags are suitable for producing aluminosilicate glass with low dielectric constant and dielectric loss.

  13. Effect of water on the heat capacity of polymerized aluminosilicate glasses and melts

    NASA Astrophysics Data System (ADS)

    Bouhifd, M. Ali; Whittington, Alan; Roux, Jacques; Richet, Pascal

    2006-02-01

    The effect of water on heat capacity has been determined for four series of hydrated synthetic aluminosilicate glasses and supercooled liquids close to albite, phonolite, trachyte, and leucogranite compositions. Heat capacities were measured at atmospheric pressure by differential scanning calorimetry for water contents between 0 and 4.9 wt % from 300 K to about 100 K above the glass transition temperature ( Tg). The partial molar heat capacity of water in polymerized aluminosilicate glasses, which can be considered as independent of composition, is =-122.319+341.631×10-3T+63.4426×105/T2 (J/mol K). In liquids containing at least 1 wt % H 2O, the partial molar heat capacity of water is about 85 J/mol K. From speciation data, the effects of water as hydroxyl groups and as molecular water have tentatively been estimated, with partial molar heat capacities of 153 ± 18 and 41 ± 14 J/mol K, respectively. In all cases, water strongly increases the configurational heat capacity at Tg and exerts a marked depressing effect on Tg, in close agreement with the results of viscosity experiments on the same series of glasses. Consistent with the Adam and Gibbs theory of relaxation processes, the departure of the viscosity of hydrous melts from Arrhenian variations correlates with the magnitude of configurational heat capacities.

  14. Structure and properties of sodium aluminosilicate glasses from molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Xiang, Ye; Du, Jincheng; Smedskjaer, Morten M.; Mauro, John C.

    2013-07-01

    Addition of alumina to sodium silicate glasses considerably improves the mechanical properties and chemical durability and changes other properties such as ionic conductivity and melt viscosity. As a result, aluminosilicate glasses find wide industrial and technological applications including the recent Corning® Gorilla® Glass. In this paper, the structures of sodium aluminosilicate glasses with a wide range of Al/Na ratios (from 1.5 to 0.6) have been studied using classical molecular dynamics simulations in a system containing around 3000 atoms, with the aim to understand the structural role of aluminum as a function of chemical composition in these glasses. The short- and medium-range structures such as aluminum coordination, bond angle distribution around cations, Qn distribution (n bridging oxygen per network forming tetrahedron), and ring size distribution have been systematically studied. In addition, the mechanical properties including bulk, shear, and Young's moduli have been calculated and compared with experimental data. It is found that aluminum ions are mainly four-fold coordinated in peralkaline compositions (Al/Na < 1) and form an integral part of the rigid silicon-oxygen glass network. In peraluminous compositions (Al/Na > 1), small amounts of five-fold coordinated aluminum ions are present while the concentration of six-fold coordinated aluminum is negligible. Oxygen triclusters are also found to be present in peraluminous compositions, and their concentration increases with increasing Al/Na ratio. The calculated bulk, shear, and Young's moduli were found to increase with increasing Al/Na ratio, in good agreement with experimental data.

  15. Alkali-lead-iron phosphate glass and associated method

    DOEpatents

    Boatner, Lynn A.; Sales, Brian C.; Franco, Sofia C. S.

    1994-01-01

    A glass composition and method of preparation utilizes a mixture consisting of phosphorus oxide within the range of about 40 to 49 molar percent, lead oxide within the range of about 10 to 25 molar percent, iron oxide within the range of about 10 to 17 molar percent and an alkali oxide within the range of about 23 to 30 molar percent. The glass resulting from the melting and subsequent solidifying of the mixture possesses a high degree of durability and a coefficient of thermal expansion as high as that of any of a number of metals. Such features render this glass highly desirable in glass-to-metal seal applications.

  16. Alkali-lead-iron phosphate glass and associated method

    DOEpatents

    Boatner, L.A.; Sales, B.C.; Franco, S.C.S.

    1994-03-29

    A glass composition and method of preparation utilizes a mixture consisting of phosphorus oxide within the range of about 40 to 49 molar percent, lead oxide within the range of about 10 to 25 molar percent, iron oxide within the range of about 10 to 17 molar percent and an alkali oxide within the range of about 23 to 30 molar percent. The glass resulting from the melting and subsequent solidifying of the mixture possesses a high degree of durability and a coefficient of thermal expansion as high as that of any of a number of metals. Such features render this glass highly desirable in glass-to-metal seal applications. 6 figures.

  17. Chemical Compatibility of Barium-Calcium-Aluminosilicate Based Sealing Glasses with Heat Resistant Alloys

    SciTech Connect

    Yang, Zhenguo; Weil, K. Scott; Meinhardt, Kerry D.; Stevenson, Jeffry W.; Paxton, Dean M.; Xia, Guanguang; Kim, Dong-Sang

    2003-01-02

    In most planar SOFC stacks operating at an intermediate temperature (700-800 degrees C), the interconnect is typically made from a ferritic stainless steel and has to be hermitically sealed to its adjacent components, such as the ceramic PEN (Positive electrode-Electrolyte-Negative electrode) by a sealing glass. To large extent the seal performance relies on the chemical compatibility of the sealing glass with the metallic interconnect. In this study, a barium-calcium-aluminosilicate (BCAS) based glass-ceramic, specifically developed as a sealant in SOFC stacks, and a ferritic stainless steel (446) were chosen as examples to investigate the chemical interactions or corrosions at the sealing glass interface with the ferritic stainless steels. Evaluation of the interfaces of coupon joints indicated that interactions between the BCAS glass-ceramic and the ferritic stainless steel depended on the exposure conditions. At the edges of joints, where oxygen or air was accessible, the interaction often led to the formation of BaCrO4, while in the interior of the joints, chromium or chromia dissolved into the glass to form a thin layer of chromium rich solid solution. It was also found that, in the interior of the joints, the interaction often resulted in the formation of pores aligning along the interface. The pore formation along the interface of sealing glass and ferritic stainless steel however could be avoided through a pre-heat treatment of the ferriitc stainless steel.

  18. Optical Properties of Tm(3+) Ions in Alkali Germanate Glass

    NASA Technical Reports Server (NTRS)

    Walsh, Brian M.; Barnes, Norman P.; Reichle, Donald J.; Jiang, Shibin

    2006-01-01

    Tm-doped alkali germanate glass is investigated for use as a laser material. Spectroscopic investigations of bulk Tm-doped germanate glass are reported for the absorption, emission and luminescence decay. Tm:germanate shows promise as a fiber laser when pumped with 0.792 m diodes because of low phonon energies. Spectroscopic analysis indicates low nonradiative quenching and pulsed laser performance studies confirm this prediction by showing a quantum efficiency of 1.69.

  19. Striking role of non-bridging oxygen on glass transition temperature of calcium aluminosilicate glass-formers

    SciTech Connect

    Bouhadja, M.; Jakse, N.; Pasturel, A.

    2014-06-21

    Molecular dynamics simulations are used to study the structural and dynamic properties of calcium aluminosilicate, (CaO-Al{sub 2}O{sub 3}){sub 1−x}(SiO{sub 2}){sub x}, glass formers along three joins, namely, R = 1, 1.57, and 3, in which the silica content x can vary from 0 to 1. For all compositions, we determined the glass-transition temperature, the abundances of the non-bridging oxygen, triclusters, and AlO{sub 5} structural units, as well as the fragility from the temperature evolution of the α-relaxation times. We clearly evidence the role played by the non-bridging oxygen linked either to Al atoms or Si atoms in the evolution of the glass-transition temperature as well as of the fragility as a function of silica content along the three joins.

  20. Strong UV absorption and visible luminescence in ytterbium-doped aluminosilicate glass under UV excitation.

    PubMed

    Engholm, M; Norin, L; Aberg, D

    2007-11-15

    A broad visible luminescence band and characteristic IR luminescence of Yb(3+) ions are observed under UV excitation in ytterbium-doped aluminosilicate glass. Samples made under both oxidizing and reducing conditions are analyzed. A strong charge-transfer absorption band in the UV range is observed for glass samples containing ytterbium. Additional absorption bands are observed for the sample made under reducing conditions, which are associated with f-d transitions of divalent ytterbium. The visible luminescence band is attributed to 5d-4f emission from Yb(2+) ions, and the IR luminescence is concluded to originate from a relaxed charge-transfer transition. The findings are important to explain induced optical losses (photodarkening) in high-power fiber lasers. PMID:18026305

  1. Synthesis and characterization of inorganic polymers from the alkali activation of an aluminosilicate

    NASA Astrophysics Data System (ADS)

    González, C. P.; Montaño, A. M.; González, A. K.; Ríos, C. A.

    2014-06-01

    This paper presents the results of the synthesis and characterization of inorganic polymers (IP) from aluminosilicates: bentonite (BT) and pumice (PP). The synthesis of IP, was carried out by two methods involving alkaline activation, at room temperature and 80 ± 5 °C, using as activating agent sodium silicate both commercial and analytical (Na2SiO3). Sodium hydroxide (NaOH) at 3 M, 7 M and 12 M was added. A lower degree of polymerization was obtained by using analytical precursors subjected to room temperature and 80 ± 5°C. Replacement of heating by the use of the commercial activating agent with greater alkalinity allows the formation of a 3D network. The materials were structurally characterized by FTIR spectroscopy with Attenuated Reflectance (ATR), Scanning Electron Microscope (SEM) and X -ray diffraction (DRX).

  2. Theory of corrosion of alkali-borosilicate glass

    SciTech Connect

    Clark, D.E.; Hench, L.L.

    1983-01-01

    The alkali-borosilicate (ABS) system provides the basis for a wide variety of commercially important products among which are the nuclear waste glasses. Although a large number of investigations have been undertaken in the last five years, the corrosion mechanisms of the ABS glasses have not been characterized nearly as well as for the soda-lime-silicate (NCS) glasses commonly used for containers. It is well known that the corrosion of the latter glasses involves ion exchange, network dissolution, and precipitation mechanisms resulting in the development of one of five types of surface films. In the present paper we compare the corrosion behavior to the ABS and NCS glasses and discuss our current understanding of ABS glass corrosion in terms of mechanisms, kinetics, surface film formation and thermodynamics.

  3. Chemical Interactions of Barium-Calcium-Aluminosilicate Based Sealing Glasses with Oxidation Resistant Alloys

    SciTech Connect

    Yang, Z Gary ); Stevenson, Jeffry W. ); Meinhardt, Kerry D. )

    2003-04-04

    In most planar SOFC stack designs, the interconnect, which is typically made from an oxidation resistant alloy, potentially including austenitic chromia-forming, ferritic chromia-forming, and alumina-forming alloys, has to be hermitically sealed to its adjacent components, usually by a sealing glass. To maintain the structural stability and minimize the degradation of stack performance, the sealing glass must be chemically compatible with the alloy used for the interconnect. In this work, Nicrofer6025, AISI446 and a Fecralloy were selected as examples of austenitic chromia-forming, ferritic chromia-forming, and alumina-forming alloys, respectively. Their chemical compatibility with a barium-calcium-aluminosilicate (BCAS) based glass, specifically developed as a sealant in SOFC stacks, was evaluated. It was found that the BCAS sealing glass interacted chemically with both the chromia-forming alloys and the alumina-forming alloys. The extent and nature of the interactions and their final products depended on the matrix alloy compositions, the exposure conditions and/or proximity of the glass/alloy interface to the ambient air. These interactions and their mechanisms will be discussed with the assistance of thermodynamic modeling.

  4. Synthesis and Properties of a Barium Aluminosilicate Solid Oxide Fuel Cell Glass-Ceramic Sealant

    SciTech Connect

    Meinhardt, Kerry D.; Kim, Dong-Sang; Chou, Y. S.; Weil, K. Scott

    2008-07-15

    A series of barium aluminosilicate glasses modified with CaO and B2O3, were prepared and evaluated with respect to their suitability in sealing planar solid oxide fuel cells (SOFCs). At a target operating temperature of 750ºC, the long-term CTE of one particular composition (35 mol% BaO, 15 mol% CaO, 10 mol% B2O3, 5 mol% Al2O3, bal. SiO2) was found to be particularly stable, due to devitrification to a mixture of glass and ceramic phases. This sealant composition exhibits minimal chemical interaction with the yttria-stabilized zirconia electrolyte, yet forms a strong bond with this material. Interactions with metal components were found to be more extensive and depended on the composition of the metal oxide scale that formed during sealing. Generally alumina-scale formers exhibited a more compact reaction zone with the glass than chromia-scale forming alloys. Mechanical measurements conducted on the bulk glass-ceramic and on seals formed using these materials indicate that the sealant is anticipated to display adequate long-term strength for most conventional stationary SOFC applications.

  5. Chemical Compatibility of Barium-Calcium-Aluminosilicate Based Sealing Glasses with Heat Resistant Alloys

    SciTech Connect

    Yang, Z Gary; Weil, K. Scott; Meinhardt, Kerry D.; Stevenson, Jeffry W.; Paxton, Dean M.; Xia, Gordon; Kim, Dong-Sang

    2003-09-15

    Over the past several years, advances in the design and fabrication of planar SOFCs have led to a steady reduction in the temperatures necessary for their operation. Consequently, it appears more realistic now to use low cost heat resistant alloys for interconnect sub-components in the SOFC stack. Considering these materials requirements, heat resistant alloys, which overall demonstrate oxidation resistance at elevated temperatures, could be potential candidates. Overall, the heat resistant alloys of interest may include superalloys and the stainless steels. Depending whether a chromia or alumina scale forms on the alloy surface for protection, these heat resistant alloys can be also classified into chromia or alumina formers, repetitively. To help screening alloys and understanding the interface of sealing glass, a couple of alloy compositions have been carefully chosen as a reprehensive of different groups of alloys for the study on their chemical compatibility with a barium-aluminosilicate base glass. These alloys selected are AL 29-4, Nicrofer 6025, and Fecralloy, representing chromia forming stainless steels, superalloys and alumina formers, respectively. Results of chemical and microstructural analyses on sealing glass interfaces with different alloys will be presented, and accordingly, the applicability of alloys in terms of sealing glass chemical compatibility will be discussed. Possible means of modification on alloys for an improved applicability will be elaborated as well.

  6. The role of Al3+ on rheology and structural changes in sodium silicate and aluminosilicate glasses and melts

    NASA Astrophysics Data System (ADS)

    Le Losq, Charles; Neuville, Daniel R.; Florian, Pierre; Henderson, Grant S.; Massiot, Dominique

    2014-02-01

    Because of their importance in both the geosciences and the glass-making industry, alkali aluminosilicate melts have been the focal point of many past studies, but despite progress many problems remain unresolved, such as the complex behaviour of the thermodynamic properties of aluminium-rich alkali silicate melts. This paper presents a study of Na2O-Al2O3-SiO2 glasses and melts, containing 75 mol% SiO2 and different Al/(Al + Na) ratios. Their structure has been investigated by using Raman spectroscopy, as well as, 23Na, 27Al and 29Si 1D MAS NMR spectroscopy. Results confirm the role change of Na+ cations from network modifier to charge compensator in the presence of Al3+ ions. In addition, polymerization increases with increase of the Al/(Al + Na) ratio. These structural changes explain the observed variations in the viscosity of these melts. The viscosity data in turn allow us to calculate the configurational entropy of melts at the glass transition temperature [the Sconf(Tg)]. The variations of the Sconf(Tg) are strongly nonlinear, with sharp increases and decreases depending on the Al/(Al + Na) ratio. More importantly, a strong increase of the Sconf(Tg) is observed when a few Al2O3 is added to sodium silicate melt. A strong decrease is observed after crossing the tectosilicate join, when Al/(Al + Na) > 0.5 and when Al3+ ions are present in fivefold coordination, Al[5], in the glass. Furthermore, in situ27Al NMR spectra of the peraluminous melt show a clear increase of the Al[5] concentration with increasing temperature. When considered in combination with melt fragility and heat capacity, our data demonstrate that Al[5] is clearly a transient unit at high temperature in highly polymerized tectosilicate and peraluminous melts. However, when present in glasses, Al[5] increases the stability of the aluminosilicate network, hence the Tg of glasses. This could be explained by the ability of Al[5] to carry threefold coordinated oxygen atoms in its first coordination

  7. Network cation coordination in aluminoborosilicate and Mg- aluminosilicate glasses: pressure effects in recovered structural changes and densification

    NASA Astrophysics Data System (ADS)

    Bista, S.; Stebbins, J. F.; Sisson, T. W.; Hankins, W. B.

    2015-12-01

    In this study, we compare the aluminum and boron coordination of glass samples recovered from piston-cylinder experiments carried out at 1 to 3 GPa and near to their ambient glass transition temperature (Tg), which we have found gives a more accurate picture of high pressure structural changes than experiments involving quenching from above the liquidus, as large pressure drops can occur in the latter. Aluminoborosilicate glasses with excess modifier (Ca, La and Y- aluminoborosilicate) quenched from melts at 1-3 GPa were studied with B-11 and Al-27 MAS NMR to assess relative effects on two different network cations. Structural changes in the Y-aluminoborosilicate are dramatic, going from mostly AlO4 at low pressure to mostly AlO5 and AlO6 at 3 GPa. Large increases in BO4 (vs. BO3) are also seen. Mg-aluminosilicate glasses, both tectosilicate (Mg2Al4Si6O20) and with excess modifier composition (Mg3Al2Si6O18) quenched from melts at 1-3 GPa pressure were studied with Al-27 MAS NMR. In contrast to our previous study (Bista et al., Am. Min., in press) of jadeite glass, where only 0.5% of fivefold aluminum was seen in glass recovered from 3 GPa, five and six fold aluminum species increase significantly with increasing pressure in both Mg aluminosilicate glass compositions studied here. We observe that the tectosilicate Mg aluminosilicate glass has more higher coordinated aluminum than the excess modifier containing composition in the pressure range in our study. In the previous study (Bista et al., in press) of jadeite and calcium aluminosilicate (Ca3Al2Si6O18) glasses, 6-8% densification was observed in glasses recovered from 3 GPa. In this study of Mg aluminosilicate glasses, we observe 12% densification in glasses recovered from 3 GPa. Both types of observation confirm that structural and density changes with pressure are enhanced by higher field strength modifier cations, and will be especially important in Mg- and Fe-rich mantle melts.

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

    SciTech Connect

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

    2014-03-28

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

  9. In situ structural analysis of calcium aluminosilicate glasses under high pressure

    NASA Astrophysics Data System (ADS)

    Muniz, R. F.; de Ligny, D.; Martinet, C.; Sandrini, M.; Medina, A. N.; Rohling, J. H.; Baesso, M. L.; Lima, S. M.; Andrade, L. H. C.; Guyot, Y.

    2016-08-01

    In situ micro-Raman spectroscopy was used to investigate the structural evolution of OH--free calcium aluminosilicate glasses, under high pressure and at room temperature. Evaluation was made of the role of the SiO2 concentration in percalcic join systems, for Al/(Al  +  Si) in the approximate range from 0.9 to 0.2. Under high pressure, the intensity of the main band related to the bending mode of bridging oxygen ({ν\\text{B}} [T-O-T], where T  =  Si or Al) decreased gradually, suggesting that the bonds were severely altered or even destroyed. In Si-rich glasses, compression induced a transformation of Q n species to Q n-1. In the case of Al-rich glass, the Al in the smallest Q n units evolved from tetrahedral to higher-coordinated Al ([5]Al and [6]Al). Permanent structural changes were observed in samples recovered from the highest pressure of around 15 GPa and, particularly for Si-rich samples, the recovered structure showed an increase of three-membered rings in the Si/Al tetrahedral network.

  10. In situ structural analysis of calcium aluminosilicate glasses under high pressure

    NASA Astrophysics Data System (ADS)

    Muniz, R. F.; de Ligny, D.; Martinet, C.; Sandrini, M.; Medina, A. N.; Rohling, J. H.; Baesso, M. L.; Lima, S. M.; Andrade, L. H. C.; Guyot, Y.

    2016-08-01

    In situ micro-Raman spectroscopy was used to investigate the structural evolution of OH‑-free calcium aluminosilicate glasses, under high pressure and at room temperature. Evaluation was made of the role of the SiO2 concentration in percalcic join systems, for Al/(Al  +  Si) in the approximate range from 0.9 to 0.2. Under high pressure, the intensity of the main band related to the bending mode of bridging oxygen ({ν\\text{B}} [T-O-T], where T  =  Si or Al) decreased gradually, suggesting that the bonds were severely altered or even destroyed. In Si-rich glasses, compression induced a transformation of Q n species to Q n‑1. In the case of Al-rich glass, the Al in the smallest Q n units evolved from tetrahedral to higher-coordinated Al ([5]Al and [6]Al). Permanent structural changes were observed in samples recovered from the highest pressure of around 15 GPa and, particularly for Si-rich samples, the recovered structure showed an increase of three-membered rings in the Si/Al tetrahedral network.

  11. Steam Reforming Technology Demonstration for Conversion of DOE Sodium-Bearing Tank Wastes at Idaho National Laboratory into a Leach-Resistant Alkali Aluminosilicate Waste Form

    SciTech Connect

    Ryan, K.; Bradley Mason, J.; Evans, B.; Vora, V.; Olson, A.

    2008-07-01

    The patented THOR{sup R} fluidized-bed steam reforming (FBSR) technology was selected by the U.S. Department of Energy (DOE) for treatment of sodium-bearing waste (SBW) in the Integrated Waste Treatment Unit (IWTU), currently under construction at the Idaho National Laboratory (INL) Site.1 SBW is an acidic waste created primarily from cleanup of the fuel reprocessing equipment at the Idaho Nuclear Technology and Engineering Center (INTEC) at the INL. The SBW contains high concentrations of nitric acid, and alkali and aluminum nitrates, along with many other inorganic compounds, including substantial levels of radionuclides. As part of the implementation of the THOR{sup R} process at INTEC, an engineering-scale technology demonstration (ESTD) was conducted using a specially designed pilot plant located at Hazen Research, Inc. in Golden Colorado. This ESTD confirmed the efficacy of the THOR{sup R} FBSR process to convert the SBW into a granular carbonate-based waste form suitable for disposal at the Waste Isolation Pilot Plant (WIPP). DOE authorized, as a risk reduction measure, the performance of an additional ESTD to demonstrate the production of an insoluble mineralized product, in the event that an alternate disposition path is required. The additional ESTD was conducted at the Hazen Research facility using the THOR{sup R} process and the same SBW simulant employed previously. An alkali aluminosilicate mineral product was produced that exhibited excellent leach resistance and chemical durability. The demonstration established general system operating parameters for a full-scale facility; provided process off-gas data that confirmed operation within regulatory limits; determined that the mineralized product exhibits superior leach resistance and durability, compared to Environmental Assessment (EA) and Low-activity Reference Material (LRM) glasses, as indicated by the Product Consistency Test (PCT); ascertained that Cs and Re (a surrogate for Tc) were non

  12. The role of Al3+ on rheology and structural changes in sodium silicate and aluminosilicate glasses and melts

    NASA Astrophysics Data System (ADS)

    Le Losq, Charles; Neuville, Daniel R.; Florian, Pierre; Henderson, Grant S.; Massiot, Dominique

    2014-02-01

    Because of their importance in both the geosciences and the glass-making industry, alkali aluminosilicate melts have been the focal point of many past studies, but despite progress many problems remain unresolved, such as the complex behaviour of the thermodynamic properties of aluminium-rich alkali silicate melts. This paper presents a study of Na2O-Al2O3-SiO2 glasses and melts, containing 75 mol% SiO2 and different Al/(Al + Na) ratios. Their structure has been investigated by using Raman spectroscopy, as well as, 23Na, 27Al and 29Si 1D MAS NMR spectroscopy. Results confirm the role change of Na+ cations from network modifier to charge compensator in the presence of Al3+ ions. In addition, polymerization increases with increase of the Al/(Al + Na) ratio. These structural changes explain the observed variations in the viscosity of these melts. The viscosity data in turn allow us to calculate the configurational entropy of melts at the glass transition temperature [the Sconf(Tg)]. The variations of the Sconf(Tg) are strongly nonlinear, with sharp increases and decreases depending on the Al/(Al + Na) ratio. More importantly, a strong increase of the Sconf(Tg) is observed when a few Al2O3 is added to sodium silicate melt. A strong decrease is observed after crossing the tectosilicate join, when Al/(Al + Na) > 0.5 and when Al3+ ions are present in fivefold coordination, Al[5], in the glass. Furthermore, in situ27Al NMR spectra of the peraluminous melt show a clear increase of the Al[5] concentration with increasing temperature. When considered in combination with melt fragility and heat capacity, our data demonstrate that Al[5] is clearly a transient unit at high temperature in highly polymerized tectosilicate and peraluminous melts. However, when present in glasses, Al[5] increases the stability of the aluminosilicate network, hence the Tg of glasses. This could be explained by the ability of Al[5] to carry threefold coordinated oxygen atoms in its first coordination

  13. Synthesis and studies on microhardness of alkali zinc borate glasses

    SciTech Connect

    Subhashini, Bhattacharya, Soumalya Shashikala, H. D. Udayashankar, N. K.

    2014-04-24

    The mixed alkali effect on zinc borate glasses have been reported. The glass systems of nominal composition 10Zn+xLi{sub 2}O+yNa{sub 2}O+80B{sub 2}O{sub 3} (x = y = 0, 5, 10, 15 mol%) were prepared using standard melt quenching method. The structural, physical and mechanical properties of the samples have been studied using X-ray diffraction(XRD), density measurement and Vickers hardness measurement, respectively. A consistent increase in the density was observed, which explains the role of the modifiers (Li{sub 2}O and Na{sub 2}O) in the network modification of borate structure. The molar volume is decreasing linearly with the alkali concentration, which is attributed to the conversion of tetrahedral boron (BO{sub 4/2}){sup −} into (BO{sub 3/2}){sup −}. The microhardness studies reveals the anisotropy nature of the material. It further confirms that the samples belong to hard glass category.

  14. 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).

  15. Surface of a calcium aluminosilicate glass by classical and ab initio molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Ganster, Patrick; Benoit, Magali; Delaye, Jean-Marc; Kob, Walter

    We present the structural properties of thin films of a calcium aluminosilicate glass generated by classical molecular dynamics (MD). The films are generated by two methods: in the first, the films are created in the liquid state and quenched to 300 K; in the second, the films are generated at room temperature. Depending on the method, film thickness and surface roughness are different but the main structural characteristics of the films are similar. The atomic concentration appears to be inhomogeneous from the center of the films to the surface and new structural entities are present at the film surfaces. The surfaces are depleted in calcium atoms and are enriched in aluminum atoms. This atomic arrangement induces a de-polymerized area under the surface. At the surface, all structural properties are modified in comparison with those of the bulk: interatomic distances, angular distributions, ring size, coordinations. In order to confirm the surface properties, we relaxed a surface using ab initio molecular dynamics. Some modifications appear but they do not significantly change the results obtained by classical MD, validating the use of interatomic potentials for the study of such films.

  16. Scaling behavior in the conductivity of alkali oxide glasses

    SciTech Connect

    Sidebottom, D.L.; Green, P.F.; Brow, R.K.

    1995-11-01

    Although the frequency dependent conductivity, {sigma}({omega}), of ion-containing glasses displays power law dispersion ({sigma}({omega}) {approx} {omega}{sup n}) that can usually be described by a master curve, several findings have suggested that this scaling fails at low temperatures as indicated by a temperature dependence of the scaling exponent, n. The authors investigate this behavior in the frequency range between 1 Hz and 10{sup 6} Hz for a different materials including alkali metaphosphate glasses and a polymer. They identify two distinct regimes of conductive behavior, {sigma}{sub {vert_bar}} and {sigma}{sub {parallel}}. The first, {sigma}{sub {vert_bar}}, is strongly temperature dependent and appears to obey a master curve representation. The second, {sigma}{sub {parallel}}, exhibits only a weak temperature dependence with a roughly linear frequency dependence. A strong depression of {sigma}{sub {vert_bar}} occurs for the mixed alkali case, but {sigma}{sub {parallel}} is unaffected and occurs at roughly the same location in all the alkali compositions studied. They propose that {sigma}{sub {parallel}} does not arise from cation motion, but rather originates from a second mechanisms likely involving small distortions of the underlying glassy matrix. This assignment of {sigma}{sub {parallel}} is further supported by the roughly universal location of {sigma}{sub {parallel}}, to within an order of magnitude, of a variety of materials, including a polymer electrolyte and a doped crystal. Since {sigma}{sub {vert_bar}}(T) and {sigma}{sub {parallel}}(T {approx} const.) are viewed as separate phenomena, the temperature dependence of the scaling exponent is shown to result merely from a superposition of these two contributions and does not indicate any intrinsic failure of the scaling property of {sigma}{sub {vert_bar}}.

  17. Modeling the Structure of Complex Aluminosilicate Glasses: The Effect of Zinc Addition.

    PubMed

    Bernasconi, Andrea; Dapiaggi, Monica; Pavese, Alessandro; Agostini, Giovanni; Bernasconi, Maurizio; Bowron, Daniel T

    2016-03-10

    An empirical potential structure refinement of neutron and X-ray diffraction data combined with extended absorption fine structure evidence has been applied to the investigation of two distinct sets of complex aluminosilicate glasses containing different quantities of zinc. Data come from (i) neutron and X-ray total scattering experiments, which have been performed at the ISIS neutron spallation source (SANDALS beamline) and at the European Synchrotron Radiation Facility (ID11 beamline), and (ii) EXAFS experiments which have been performed at the European Synchrotron Radiation Facility (BM23 beamline). By careful examination of the modeled ensemble of atoms, a wide range of structural information has been extracted: coordination numbers, bond distances, cluster sizes, type of oxygen sharing, and the preference of large cations to adopt a charge-compensating role. The first series of glasses, which is characterized by a fixed network modifier element content (i.e., Na), shows how the introduction of Zn at the expense of Si and Al network forming elements does not significantly alter the polymerization degree, as a result of its dominant 4-fold coordination. In the case of the second series, which is characterized by fixed network forming element content (i.e., Si and Al), it is shown how the replacement of a network modifier element (i.e., Ca) with the introduction of Zn does not change the propensity of Zn to be mainly 4-fold coordinated by promoting the network. Where appropriate the experimental results have been compared with classical theoretical approaches such as stoichiometric models based on Zachariasen's rules and computational routines. PMID:26848740

  18. Barium oxide, calcium oxide, magnesia, and alkali oxide free glass

    DOEpatents

    Lu, Peizhen Kathy; Mahapatra, Manoj Kumar

    2013-09-24

    A glass composition consisting essentially of about 10-45 mole percent of SrO; about 35-75 mole percent SiO.sub.2; one or more compounds from the group of compounds consisting of La.sub.2O.sub.3, Al.sub.2O.sub.3, B.sub.2O.sub.3, and Ni; the La.sub.2O.sub.3 less than about 20 mole percent; the Al.sub.2O.sub.3 less than about 25 mole percent; the B.sub.2O.sub.3 less than about 15 mole percent; and the Ni less than about 5 mole percent. Preferably, the glass is substantially free of barium oxide, calcium oxide, magnesia, and alkali oxide. Preferably, the glass is used as a seal in a solid oxide fuel/electrolyzer cell (SOFC) stack. The SOFC stack comprises a plurality of SOFCs connected by one or more interconnect and manifold materials and sealed by the glass. Preferably, each SOFC comprises an anode, a cathode, and a solid electrolyte.

  19. Structural, vibrational, and elastic properties of a calcium aluminosilicate glass from molecular dynamics simulations: The role of the potential

    SciTech Connect

    Bauchy, M.

    2014-07-14

    We study a calcium aluminosilicate glass of composition (SiO{sub 2}){sub 0.60}(Al{sub 2}O{sub 3}){sub 0.10}(CaO){sub 0.30} by means of molecular dynamics. To this end, we conduct parallel simulations, following a consistent methodology, but using three different potentials. Structural and elastic properties are analyzed and compared to available experimental data. This allows assessing the respective abilities of the potentials to produce a realistic glass. We report that, although all these potentials offer a reasonable glass structure, featuring tricluster oxygen atoms, their respective vibrational and elastic predictions differ. This allows us to draw some general conclusions about the crucial role, or otherwise, of the interaction potential in silicate systems.

  20. Resonant excited state absorption and relaxation mechanisms in Tb3+-doped calcium aluminosilicate glasses: an investigation by thermal mirror spectroscopy.

    PubMed

    Bianchi, G S; Zanuto, V S; Astrath, F B G; Malacarne, L C; Terra, I A A; Catunda, T; Nunes, L A O; Jacinto, C; Andrade, L H C; Lima, S M; Baesso, M L; Astrath, N G C

    2013-11-15

    Resonant excited state absorption (ESA) and relaxation processes in Tb(3+)-doped aluminosilicate glasses are quantitatively evaluated. A model describing the excitation steps and upconversion emission is developed and applied to interpret the results from laser-induced surface deformation using thermal mirror spectroscopy. The fluorescence quantum efficiency of level (5)D(4) was found to be close to unity and concentration independent while, for the level (5)D(3), it decreases with Tb(3+) concentration. Emission spectroscopy measurements supported these results. ESA cross sections are found to be more than three orders of magnitude higher than the ground state absorption cross section. PMID:24322101

  1. ALKALI/ AKALINE-EARTH CONTENT EFFECTS ON PROPERTIES OF HIGH-ALUMINA NUCLEAR WASTE GLASSES

    SciTech Connect

    McCloy, John S.; Rodriguez, Carmen P.; Windisch, Charles F.; Leslie, Clifford J.; Schweiger, Michael J.; Riley, Brian J.; Vienna, John D.

    2010-10-01

    A series of high alumina (>20 mass %) borosilicate glasses have been made and characterized based on the assumption that the primary modifier cation field strength plays a significant role in mediating glass structure of nuclear waste glasses. Any crystallization upon quenching or after heat treatment at 950 °C for 24 hours was identified and quantified by X-ray diffraction. Particular note was take of any aluminosilicates formed, such as those in the nepheline group (MAlSiO4 where M=K, Na, Li), as these remove multiple glass-formers from the network upon crystallization. The relative roles of potassium, sodium, lithium, calcium, and magnesium on glass structure and crystallization in high alumina glasses were explored using Raman and infrared vibrational spectroscopy. Strong evidence was found for the importance of 4 membered rings in glasses with 10 mol % alkaline earths (Ca, Mg).

  2. Alkali-aggregate reactivity of typical siliceious glass and carbonate rocks in alkali-activated fly ash based geopolymers

    NASA Astrophysics Data System (ADS)

    Lu, Duyou; Liu, Yongdao; Zheng, Yanzeng; Xu, Zhongzi; Shen, Xiaodong

    2013-08-01

    For exploring the behaviour of alkali-aggregate reactivity (AAR) in alkali-activated geopolymeric materials and assessing the procedures for testing AAR in geopolymers, the expansion behaviour of fly ash based geopolymer mortars with pure silica glass and typical carbonate rocks were studied respectively by curing at various conditions, i.e. 23°C and 38°C with relative humidity over 95%, immersed in 1M NaOH solution at 80°C. Results show that, at various curing conditions, neither harmful ASR nor harmful ACR was observed in geopolymers with the criteria specified for OPC system. However, with the change of curing conditions, the geopolymer binder and reactive aggregates may experience different reaction processes leading to quite different dimensional changes, especially with additional alkalis and elevated temperatures. It suggests that high temperature with additional alkali for accelerating AAR in traditional OPC system may not appropriate for assessing the alkali-aggregate reactivity behaviour in geopolymers designed for normal conditions. On the other hand, it is hopeful to control the dimensional change of geopolymer mortar or concrete by selecting the type of aggregates and the appropriate curing conditions, thus changing the harmful AAR in OPC into beneficial AAR in geopolymers and other alkali-activated cementitious systems.

  3. Chemical Compatibility of Barium-Calcium-Aluminosilicate Based Sealing Glasses with Ferritic Stainless Steel Interconnect in SOFCs

    SciTech Connect

    Yang, Z Gary; Meinhardt, Kerry D.; Stevenson, Jeffry W.

    2003-08-01

    In most planar SOFC stack designs, the interconnect, which is typically made from a ferritic stainless steel, is hermitically sealed to the ceramic PEN (Positive electrode-Electrolyte-Negative electrode) by a sealing glass. To maintain the structural stability and minimize degradation of the stack performance, the sealing glass must be chemically compatible with the stainless steel interconnect. In this study, a barium-calcium-aluminosilicate (BCAS) based glass-ceramic, specifically developed as a sealant in SOFC stacks, and a ferritic stainless steel (446) were selected as examples to increase the understanding the chemical compatibility issues in SOFC. Evaluation of the interfaces of coupon joints indicated that interactions between the BCAS glass-ceramic and the ferritic stainless steel was dependent on the exposure conditions. At the edges of joints, where oxygen or air was accessible, the interaction often led to the formation of BaCrO4, while in the interior of the joints, chromium or chromia dissolved into the glass to form a thin layer of chromium rich solid solution. It was also found that, in the interior of the joints, the interaction often resulted in the formation of pores aligned along the interface. It appears the pore formation along the interface can be avoided through a pre-heat treatment.

  4. Communication: Dimensionality of the ionic conduction pathways in glass and the mixed-alkali effect.

    PubMed

    Novy, Melissa; Avila-Paredes, Hugo; Kim, Sangtae; Sen, Sabyasachi

    2015-12-28

    A revised empirical relationship between the power law exponent of ac conductivity dispersion and the dimensionality of the ionic conduction pathway is established on the basis of electrical impedance spectroscopic (EIS) measurements on crystalline ionic conductors. These results imply that the "universal" ac conductivity dispersion observed in glassy solids is associated with ionic transport along fractal pathways. EIS measurements on single-alkali glasses indicate that the dimensionality of this pathway D is ∼2.5, while in mixed-alkali glasses, D is lower and goes through a minimum value of ∼2.2 when the concentrations of the two alkalis become equal. D and σ display similar variation with alkali composition, thus suggesting a topological origin of the mixed-alkali effect.

  5. Communication: Dimensionality of the ionic conduction pathways in glass and the mixed-alkali effect.

    PubMed

    Novy, Melissa; Avila-Paredes, Hugo; Kim, Sangtae; Sen, Sabyasachi

    2015-12-28

    A revised empirical relationship between the power law exponent of ac conductivity dispersion and the dimensionality of the ionic conduction pathway is established on the basis of electrical impedance spectroscopic (EIS) measurements on crystalline ionic conductors. These results imply that the "universal" ac conductivity dispersion observed in glassy solids is associated with ionic transport along fractal pathways. EIS measurements on single-alkali glasses indicate that the dimensionality of this pathway D is ∼2.5, while in mixed-alkali glasses, D is lower and goes through a minimum value of ∼2.2 when the concentrations of the two alkalis become equal. D and σ display similar variation with alkali composition, thus suggesting a topological origin of the mixed-alkali effect. PMID:26723583

  6. Thermal history effects on electrical relaxation and conductivity for potassium silicate glass with low alkali concentrations

    NASA Technical Reports Server (NTRS)

    Angel, Paul W.; Hann, Raiford E.; Cooper, Alfred R.

    1993-01-01

    Electrical response measurements from 10 Hz to 100 kHz between 120 and 540 C were made on potassium-silicate glasses with alkali oxide contents of 2, 3, 5 and 10 mol percent. Low alkali content glasses were chosen in order to try to reduce the Coulombic interactions between alkali ions to the point that frozen structural effects from the glass could be observed. Conductivity and electrical relaxation responses for both annealed and quenched glasses of the same composition were compared. Lower DC conductivity (sigma(sub DC)) activation energies were measured for the quenched compared to the annealed glasses. The two glasses with the lowest alkali contents exhibited a non-Arrhenius concave up curvature in the log(sigma(sub DC)) against 1/T plots, which decreased upon quenching. A sharp decrease in sigma(sub DC) was observed for glasses containing K2O concentrations of 5 mol percent or less. The log modulus loss peak (M'') maximum frequency plots against 1/T all showed Arrhenius behavior for both annealed and quenched samples. The activation energies for these plots closely agreed with the sigma(sub DC) activation energies. A sharp increase in activation energy was observed for both series as the potassium oxide concentration decreased. Changes in the electrical response are attributed to structural effects due to different alkali concentrations. Differences between the annealed and quenched response are linked to a change in the distribution of activation energies (DAE).

  7. Optical absorption of Co 2+ in gel-derived aluminosilicate glass-ceramics

    NASA Astrophysics Data System (ADS)

    Duan, Xiulan; Yuan, Duorong; Cheng, Xiufeng; Wang, Xinqiang

    2006-07-01

    Pure and Co 2+-doped aluminosilicate gels were prepared by the sol-gel method from two different aluminum salts, aluminum-iso-propoxide and aluminum nitrate, and heat-treated at 40-1200 °C. Visible and near-infrared (NIR) absorption spectra of the heated samples were studied. When the heat-treatment temperature was 1100 °C, Co 2+-doped aluminosilicate samples, obtained by using aluminum-iso-propoxide, crystallized to Al 2O 3 nanocrystals and exhibited a broad absorption band in the range of 1200-1600 nm, which is characteristic of tetrahedral Co 2+ ions in crystals. The existence of the broad absorption band has allowed us to consider this kind of material as possible candidate for passive Q-switched materials in the NIR region. While the sample prepared from aluminum nitrate was amorphous when heated to 1200 °C.

  8. Aluminosilicate melts and glasses at 1 to 3 GPa: Temperature and pressure effects on recovered structural and density changes

    USGS Publications Warehouse

    Bista, S; Stebbins, Jonathan; Hankins, William B.; Sisson, Thomas W.

    2015-01-01

    In the pressure range in the Earth’s mantle where many basaltic magmas are generated (1 to 3 GPa) (Stolper et al. 1981), increases in the coordination numbers of the network-forming cations in aluminosilicate melts have generally been considered to be minor, although effects on silicon and particularly on aluminum coordination in non-bridging oxygen-rich glasses from the higher, 5 to 12 GPa range, are now well known. Most high-precision measurements of network cation coordination in such samples have been made by spectroscopy (notably 27Al and 29Si NMR) on glasses quenched from high-temperature, high-pressure melts synthesized in solid-media apparatuses and decompressed to room temperature and 1 bar pressure. There are several effects that could lead to the underestimation of the extent of actual structural (and density) changes in high-pressure/temperature melts from such data. For non-bridging oxygen-rich sodium and calcium aluminosilicate compositions in the 1 to 3 GPa range, we show here that glasses annealed near to their glass transition temperatures systematically record higher recovered increases in aluminum coordination and in density than samples quenched from high-temperature melts. In the piston-cylinder apparatus used, rates of cooling through the glass transition are measured as very similar for both higher and lower initial temperatures, indicating that fictive temperature effects are not the likely explanation of these differences. Instead, transient decreases in melt pressure during thermal quenching, which may be especially large for high initial run temperatures, of as much as 0.5 to 1 GPa, may be responsible. As a result, the equilibrium proportion of high-coordinated Al in this pressure range may be 50 to 90% greater than previously estimated, reaching mean coordination numbers (e.g., 4.5) that are probably high enough to significantly affect melt properties. New data on jadeite (NaAlSi2O6) glass confirm that aluminum coordination increase

  9. Effect of alkali addition on DC conductivity and thermal properties of vanadium-bismo-borate glasses

    SciTech Connect

    Khasa, S. Dahiya, M. S.; Agarwal, A.

    2014-04-24

    The DC Conductivity and Differential Thermal Analysis of glasses with composition (30−x)Li{sub 2}O⋅xV{sub 2}O{sub 5}⋅20Bi{sub 2}O{sub 3}⋅50B{sub 2}O{sub 3}(x=15, 10, 5) has been carried out in order to study the effect of replacing the Transition Metal Oxide (TMO) with alkali oxide. A significant increase in the DC conductivity has been observed with increase in alkali content. Again the thermal measurements have shown the decrease in both glass transition temperature (T{sub g}) and crystallization temperature (T{sub x}). The Glass Stability (GS) and Glass Forming Ability (GFA) have also been calculated and these also were found to decrease with increase in alkali oxide content at the cost of TMO.

  10. ``Cooperativity blockage'' in the mixed alkali effect as revealed by molecular-dynamics simulations of alkali metasilicate glass

    NASA Astrophysics Data System (ADS)

    Habasaki, Junko; Ngai, K. L.; Hiwatari, Yasuaki

    2004-07-01

    The relaxation dynamics of a complex interacting system can be drastically changed when mixing with another component having different dynamics. In this work, we elucidate the effect of the less mobile guest ions on the dynamics of the more mobile host ions in mixed alkali glasses by molecular-dynamics (MD) simulations. One MD simulation was carried out on lithium metasilicate glass with the guest ions created by freezing some randomly chosen lithium ions at their initial locations at 700 K. A remarkable slowing down of the dynamics of the majority mobile Li ions was observed both in the self-part of the density-density correlation function, Fs(k,t), and in the mean-squared displacements. On the other hand, there is no significant change in the structure. The motion of the Li ions in the unadulterated Li metasilicate glass is dynamically heterogeneous. In the present work, the fast and slow ions were divided into two groups. The number of fast ions, which shows faster dynamics (Lévy flight) facilitated by cooperative jumps, decreases considerably when small amount of Li ions are frozen. Consequently there is a large overall reduction of the mobility of the Li ions. The result is also in accordance with the experimental finding in mixed alkali silicate glasses that the most dramatic reduction of ionic conductivity occurs in the dilute foreign alkali limit. Similar suppression of the cooperative jumps is observed in the MD simulation data of mixed alkali system, LiKSiO3. Naturally, the effect found here is appropriately described as "cooperativity blockage." Slowing down of the motion of Li ions also was observed when a small number of oxygen atoms chosen at random were frozen. The effect is smaller than the case of freezing some the Li ions, but it is not negligible. The cooperativity blockage is also implemented by confining the Li metasilicate glass inside two parallel walls formed by freezing Li ions in the same metasilicate glass. Molecular-dynamics simulations

  11. The influence of alkali and alkaline earths on the working range for bioactive glasses.

    PubMed

    Brink, M

    1997-07-01

    Viscosity-temperature dependence has been investigated for glasses in a system where bioactive compositions are found. A glass is called bioactive when living bone can bond to it. In this work, high-temperature microscopy was used to determine viscosity-temperature behaviour for 40 glasses in the system Na2O-K2O-MgO-CaO-B2O3-P2O5-SiO2. The silica content in the glasses was 39-70 wt% % All glasses containing < 54 mol % SiO2 devitrified during the viscosity measurements. Generally, glasses that devitrified contained more alkali but less alkaline earths than glasses with a large working range. A working range is the temperature interval at which forming of a glass can take place. This temperature interval can, for bioactive glasses, be enlarged by decreasing the amount of alkali, especially Na2O, in the glass and by increasing the amount of alkaline earths, especially MgO. Optionally, B2O3 and P2O5 can be added to the glass. An enlarged working range is a prerequisite for an expanded medical use of bioactive glasses as e.g., sintered and blown products, and fibers. PMID:9212395

  12. PLUTONIUM SOLUBILITY IN HIGH-LEVEL WASTE ALKALI BOROSILICATE GLASS

    SciTech Connect

    Marra, J.; Crawford, C.; Fox, K.; Bibler, N.

    2011-01-04

    The solubility of plutonium in a Sludge Batch 6 (SB6) reference glass and the effect of incorporation of Pu in the glass on specific glass properties were evaluated. A Pu loading of 1 wt % in glass was studied. Prior to actual plutonium glass testing, surrogate testing (using Hf as a surrogate for Pu) was conducted to evaluate the homogeneity of significant quantities of Hf (Pu) in the glass, determine the most appropriate methods to evaluate homogeneity for Pu glass testing, and to evaluate the impact of Hf loading in the glass on select glass properties. Surrogate testing was conducted using Hf to represent between 0 and 1 wt % Pu in glass on an equivalent molar basis. A Pu loading of 1 wt % in glass translated to {approx}18 kg Pu per Defense Waste Processing Facility (DWPF) canister, or about 10X the current allowed limit per the Waste Acceptance Product Specifications (2500 g/m{sup 3} of glass or about 1700 g/canister) and about 30X the current allowable concentration based on the fissile material concentration limit referenced in the Yucca Mountain Project License Application (897 g/m{sup 3}3 of glass or about 600 g Pu/canister). Based on historical process throughput data, this level was considered to represent a reasonable upper bound for Pu loading based on the ability to provide Pu containing feed to the DWPF. The task elements included evaluating the distribution of Pu in the glass (e.g. homogeneity), evaluating crystallization within the glass, evaluating select glass properties (with surrogates), and evaluating durability using the Product Consistency Test -- Method A (PCT-A). The behavior of Pu in the melter was evaluated using paper studies and corresponding analyses of DWPF melter pour samples.The results of the testing indicated that at 1 wt % Pu in the glass, the Pu was homogeneously distributed and did not result in any formation of plutonium-containing crystalline phases as long as the glass was prepared under 'well-mixed' conditions. The

  13. Crystallization Kinetics of Barium and Strontium Aluminosilicate Glasses of Feldspar Composition

    NASA Technical Reports Server (NTRS)

    Hyatt, Mark J.; Bansal, Narottam P.

    1994-01-01

    Crystallization kinetics of BaO.Al2O3.2SiO2 (BAS) and SrO.Al2O3.2SiO2 (SAS) glasses in bulk and powder forms have been studied by non-isothermal differential scanning calorimetry (DSC). The crystal growth activation energies were evaluated to be 473 and 451 kJ/mol for bulk samples and 560 and 534 kJ/mol for powder specimens in BAS and SAS glasses, respectively. Development of crystalline phases on thermal treatments of glasses at various temperatures has been followed by powder x-ray diffraction. Powder samples crystallized at lower temperatures than the bulk and the crystallization temperature was lower for SAS glass than BAS. Crystallization in both glasses appeared to be surface nucleated. The high temperature phase hexacelsian, MAl2Si2O8 (M = Ba or Sr), crystallized first by nucleating preferentially on the glass surface. Also, monoclinic celsian does not nucleate directly in the glass, but is formed at higher temperatures from the transformation of the metastable hexagonal phase. In SAS the transformation to monoclinic celsian occurred rapidly after 1 h at 1100 C. In contrast, in BAS this transformation is sluggish and difficult and did not go to completion even after 10 h heat treatment at 1400 C. The crystal growth morphologies in the glasses have been observed by optical microscopy. Some of the physical properties of the two glasses are also reported.

  14. Cation-network interactions in binary alkali metal borate glasses. A far-infrared study

    SciTech Connect

    Kamitsos, E.I.; Karakassides, M.A.; Chryssikos, G.D.

    1987-10-22

    The far-infrared spectra of compositions probing the glass-forming regions of all five binary alkali metal borate systems chi M/sub 2/O x (1 - chi)B/sub 2/O/sub 3/ (0 < chi less than or equal to 0.40, M = Na; and 0 < chi less than or equal to 0.35, M = K, Rb, Cs) have been measured and analyzed to systematically study the alkali metal cation-network interactions and their compositional dependence. Band deconvolution of the measured spectra showed the presence of two distinct distributions of alkali metal cation sites in Li, Na, and K glasses. Similar results have been obtained for rubidium and cesium borate glasses of compositions chi > 0.25. One distribution of cation sites has been observed for the lower alkali metal content Rb and Cs glasses. The fractions of cations in the two different network sites have also been evaluated. The squares of the frequencies of the cation-motion bands were found to vary linearly with composition, and exhibit kinks at chi similarly ordered 20, for all but the Cs glasses. This behavior was explained on the basis of the network structural changes known to occur at this composition.

  15. Structure of glasses containing transition metal ions. Progress report, February 1, 1979-January 31, 1980

    SciTech Connect

    White, W B; Furukawa, T; Tsong, I S.T.; Fox, K; Herman, J S; Houser, C; Nelson, C

    1980-02-01

    New normal coordinate calculations were used to relate the vibrational frequencies of silicate glasses to Si-O force constants. These appear to account for the observed frequency shifts with degree of silica polymerization. Raman spectroscopy has been used to elucidate the structure of sodium borosilicate glasses and of sodium aluminosilicate glasses. Structures of compositionally complex glasses can be understood if spectra are measured on many glasses spaced at small compositional intervals. Optical absorption spectra were used to investigate the structural setting of iron in alkali silicate glasses. Research on the alkali-hydrogen exchange in alkali silicate glasses was completed and additional work on ternary glasses is under way. A series of appendices present completed work on the structural investigations of alkali borosilicate glasses, on the structural setting of transition metal ions in glasses, and on the diffusion of hydrogen in alkali silicate glasses.

  16. Influence of Y2O3 on the structure and properties of calcium magnesium aluminosilicate glasses

    NASA Astrophysics Data System (ADS)

    Mahdy, Ebrahim A.; Ibrahim, S.

    2012-11-01

    Glasses were prepared whose composition is defined by the formula: 25CaOsbnd 20MgOsbnd xY2O3sbnd (9-x) Al2O3sbnd 46SiO2 mol.% (0 ⩽ x ⩾ 3). To investigate the relation between the structural change and compositional variation by introducing Y2O3 instead of Al2O3, the glasses were analyzed by Fourier transform Infrared (FT-IR) analysis and differential thermal analysis (DTA). The density, molar volume, hardness and the chemical durability were measured and calculated. The FTIR spectra were recorded in the spectral range from 400 to 4000 cm-1 and showed significant depolymerization of silicate groups and hence resulting in a net decrease of local symmetry. Introducing yttrium in the glasses increases both glass transition (Tg) and softening (Ts) temperatures. The obtained Vicker's microhardness, the density values and the chemical stability data were increased by addition Y2O3 instead of Al2O3 in the glasses. The resulting data were greatly correlated to the role played by the cations present in the glass structure.

  17. Modifier interaction and mixed-alkali effect in bond constraint theory applied to ternary alkali metaphosphate glasses

    NASA Astrophysics Data System (ADS)

    Poletto Rodrigues, Bruno; Deubener, Joachim; Wondraczek, Lothar

    2016-05-01

    Introducing an interaction parameter γ, we implement modifier interaction and the mixed-alkali effect into bond constraint theory, and apply this extension for simplistic property prediction on ternary phosphate glasses. The severity of the mixed alkali effect results from the interplay of two simultaneous contributions: Bond constraints on the modifier species soften or stiffen with decreasing or increasing γ, respectively. When the modifier size is not too dissimilar the decrease in γ reflects that the alkali ions can easily migrate between different sites, forcing the network to continuously re-accommodate for any subsequent distortions. With increasing size difference, migration becomes increasingly difficult without considerable network deformation. This holds even for smaller ions, where the sluggish dynamics of the larger constituent result in blocking of the fast ion movement, leading to the subsequent increase in γ. Beyond a certain size difference in the modifier pair, a value of γ exceeding unity may indicate the presence of steric hindrance due to the large surrounding modifiers impeding the phosphate network to re-accommodate deformation.

  18. Crystallization and properties of Sr-Ba aluminosilicate glass-ceramic matrices

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Hyatt, Mark J.; Drummond, Charles H., III

    1991-01-01

    Powders of roller quenched (Sr,Ba)O-Al2O3-2SiO2 glasses of various compositions were uniaxially pressed into bars and hot isostatically pressed at 1350 C for 4 hours or cold isostatically pressed and sintered at different temperatures between 800 to 1500 C for 10 or 20 hours. Densities, flexural strengths, and linear thermal expansion were measured for three compositions. The glass transition and crystallization temperatures were determined by Differential Scanning Calorimetry (DSC). The liquidus and crystallization temperature from the melt were measured using high temperature Differential Thermal Analysis (DTA). Crystalline phases formed on heat treatment of the glasses were identified by powder X ray diffraction. In Sr containing glasses, the monoclinic celsian phase always crystallized at temperatures above 1000 C. At lower temperatures, the hexagonal analog formed. The temperature for orthorhombic to hexagonal structural transformation increased monotonically with SrO content, from 327 C for BaO-Al2O3-2SiO2 to 758 C for SrO-Al2O3-2SiO2. These glass powders can be sintered to almost full densities and monoclinic celsian phase at a relatively low temperature of 1100 C.

  19. Color tunability with temperature and pump intensity in Yb3+/Tm3+ codoped aluminosilicate glass under anti-Stokes excitation.

    PubMed

    Silva, W F; Eliel, G S N; dos Santos, P V; de Araujo, M T; Vermelho, M V D; Udo, P T; Astrath, N G C; Baesso, M L; Jacinto, C

    2010-07-21

    Pump and thermally induced color tunabilities were demonstrated in Yb(3+)/Tm(3+) codoped low silica calcium aluminosilicate (LSCAS) glass under anti-Stokes excitation at 1.064 microm. The effects of pump intensity and sample's temperature on the upconversion emissions and mainly on the color tunabilities (from 800 to 480 nm) were investigated. The results revealed a 20- and a threefold reductions at 800/480 nm ratio as, respectively, the pump intensity and sample's temperature were increased from 27 to 700 kW/cm(2) and from 296 to 577 K. These behaviors with pump intensity and temperature (a strong increase of the 480 nm emission in comparison with the 800 nm one) were attributed to the several efficient processes occurring in the LSCAS system (Yb(3+)-->Tm(3+) energy-transfer processes, easy saturations of the Yb(3+) and Tm(3+) excited states, and radiative emissions). Besides these assigns, the temperature dependence is mainly assigned to the temperature-dependent effective absorption cross section of the ytterbium sensitizer through the so-called multiphonon-assisted anti-Stokes excitation process. Theoretical analyses and fits of the experimental data provided quantitative information. PMID:20649337

  20. Electrical behavior of aluminosilicate glass-ceramic sealants and their interaction with metallic solid oxide fuel cell interconnects

    NASA Astrophysics Data System (ADS)

    Goel, Ashutosh; Tulyaganov, Dilshat U.; Kharton, Vladislav V.; Yaremchenko, Aleksey A.; Ferreira, José M. F.

    A series of alkaline-earth aluminosilicate glass-ceramics (GCs) were appraised with respect to their suitability as sealants for solid oxide fuel cells (SOFCs). The parent composition with general formula Ca 0.9MgAl 0.1La 0.1Si 1.9O 6 was modified with Cr 2O 3 and BaO. The addition of BaO led to a substantial decrease in the total electrical conductivity of the GCs, thus improving their insulating properties. BaO-containing GCs exhibited higher coefficient of thermal expansion (CTE) in comparison to BaO-free GCs. An extensive segregation of oxides of Ti and Mn, components of the Crofer22 APU interconnect alloy, along with negligible formation of BaCrO 4 was observed at the interface between GC/interconnects diffusion couples. Thermal shock resistance and gas-tightness of GC sealants in contact with yttria-stabilized zirconia electrolyte (8YSZ) was evaluated in air and water. Good matching of CTE and strong, but not reactive, adhesion to the solid electrolyte and interconnect, in conjunction with a high level of electrical resistivity, are all advantageous for potential SOFC applications.

  1. Relations among nonbridging oxygen, optical properties, optical basicity, and color center formation in CaO-MgO aluminosilicate glasses

    SciTech Connect

    Novatski, A.; Steimacher, A.; Medina, A. N.; Bento, A. C.; Baesso, M. L.; Andrade, L. H. C.; Lima, S. M.; Guyot, Y.; Boulon, G.

    2008-11-01

    In this study the relations among nonbridging oxygen (NBO), optical properties, optical basicity, and color center formation in CaO-MgO aluminosilicate glasses were studied. Samples containing (in mol %) 35.9-57.5 of CaO, 16-27.7 of Al{sub 2}O{sub 3}, 7.9-41.6 of SiO{sub 2}, and 6.5-6.9 of MgO were measured by optical absorption and excitation, luminescence, and Raman spectroscopy. The results showed that when the SiO{sub 2} content was increased, the absorption edge shifted toward lower wavelengths and the bonds between O{sup 2-} ions and cations became more covalent. These observations were confirmed by Raman results that showed a decrease in the number of NBO per silicon tetrahedron as a function of SiO{sub 2} content. The results indicate that the effects of higher NBO concentration are the narrowing of the band gap energy and the delocalization of O{sup 2-} electrons, which facilitates the O{sup 2-} electrons to be trapped by anion vacancies and, consequently, forming color centers. The relationship between color center formation and SiO{sub 2} content was confirmed by optical spectroscopic measurements under UV radiation.

  2. Color tunability with temperature and pump intensity in Yb3+/Tm3+ codoped aluminosilicate glass under anti-Stokes excitation.

    PubMed

    Silva, W F; Eliel, G S N; dos Santos, P V; de Araujo, M T; Vermelho, M V D; Udo, P T; Astrath, N G C; Baesso, M L; Jacinto, C

    2010-07-21

    Pump and thermally induced color tunabilities were demonstrated in Yb(3+)/Tm(3+) codoped low silica calcium aluminosilicate (LSCAS) glass under anti-Stokes excitation at 1.064 microm. The effects of pump intensity and sample's temperature on the upconversion emissions and mainly on the color tunabilities (from 800 to 480 nm) were investigated. The results revealed a 20- and a threefold reductions at 800/480 nm ratio as, respectively, the pump intensity and sample's temperature were increased from 27 to 700 kW/cm(2) and from 296 to 577 K. These behaviors with pump intensity and temperature (a strong increase of the 480 nm emission in comparison with the 800 nm one) were attributed to the several efficient processes occurring in the LSCAS system (Yb(3+)-->Tm(3+) energy-transfer processes, easy saturations of the Yb(3+) and Tm(3+) excited states, and radiative emissions). Besides these assigns, the temperature dependence is mainly assigned to the temperature-dependent effective absorption cross section of the ytterbium sensitizer through the so-called multiphonon-assisted anti-Stokes excitation process. Theoretical analyses and fits of the experimental data provided quantitative information.

  3. Method of producing a silicon carbide fiber reinforced strontium aluminosilicate glass-ceramic matrix composite

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P. (Inventor)

    1995-01-01

    A SrO-Al2O3-2SrO2 (SAS) glass ceramic matrix is reinforced with CVD SiC continuous fibers. This material is prepared by casting a slurry of SAS glass powder into tapes. Mats of continuous CVD-SiC fibers are alternately stacked with the matrix tapes. This tape-mat stack is warm-pressed to produce a 'green' composite. Organic constituents are burned out of the 'green' composite, and the remaining interim material is hot pressed.

  4. Silicon carbide fiber reinforced strontium aluminosilicate glass-ceramic matrix composite

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam (Inventor)

    1992-01-01

    A SrO-Al2O3 - 2SrO2 (SAS) glass ceramic matrix is reinforced with CVD SiC continuous fibers. This material is prepared by casting a slurry of SAS glass powder into tapes. Mats of continuous CVD-SiC fibers are alternately stacked with the matrix tapes. This tape-mat stack is warm-pressed to produce a 'green' composite. Organic constituents are burned out of the 'green' composite, and the remaining interim material is hot pressed.

  5. Disorder and the extent of polymerization in calcium silicate and aluminosilicate glasses: O-17 NMR results and quantum chemical molecular orbital calculations

    NASA Astrophysics Data System (ADS)

    Lee, Sung Keun; Stebbins, Jonathan F.

    2006-08-01

    Estimation of the framework connectivity and the atomic structure of depolymerized silicate melts and glasses (NBO/T > 0) remains a difficult question in high-temperature geochemistry relevant to magmatic processes and glass science. Here, we explore the extent of disorder and the nature of polymerization in binary Ca-silicate and ternary Ca-aluminosilicate glasses with varying NBO/T (from 0 to 2.67) using O-17 NMR at two different magnetic fields of 9.4 and 14.1 T in conjunction with quantum chemical calculations. Non-random distributions among framework cations (Si and Al) are demonstrated in the variation of relative populations of oxygen sites with NBO/T. The proportion of non-bridging oxygen (NBO, Ca-O-Si) in the binary and ternary aluminosilicate glasses increases with NBO/T. While the trend is consistent with predictions from composition, the detailed fractions apparently deviate from the predicted values, suggesting further complications in the nature of polymerization. The proportion of each bridging oxygen in the glasses also varies with NBO/T. The fractions of Al-O-Si and Al-O-Al increase with increasing polymerization as CaO is replaced with Al 2O 3, while that of Si-O-Si seems to decrease, implying that activity of silica may decrease from calcium silicate to polymerized aluminosilicates (X=constant). Quantum chemical molecular orbital calculations based on density functional theory show that a silicate chain with Al-NBO (Ca-O-Al) has an energy penalty (calculated cluster energy difference) of about 108 kJ/mol compared with the cluster with Ca-O-Si, consistent with preferential depolymerization of Si-networks, reported in an earlier O-17 NMR study [Allwardt, J., Lee, S.K., Stebbins, J.F., 2003. Bonding preferences of non-bridging oxygens in calcium aluminosilicate glass: Evidence from O-17 MAS and 3QMAS NMR on calcium aluminate glass. Am. Mineral.88, 949-954]. These prominent types of non-randomness in the distributions suggest significant chemical

  6. Evidence of energy transfer in an aluminosilicate glass codoped with Si nanoaggregates and Er{sup 3+} ions

    SciTech Connect

    Enrichi, F.; Mattei, G.; Sada, C.; Trave, E.; Pacifici, D.; Franzo, G.; Priolo, F.; Iacona, F.; Prassas, M.; Falconieri, M.; Borsella, E.

    2004-10-01

    The enhancement of the Er{sup 3+} ions' photoluminescence (PL) emission at 1.54 {mu}m in a Si and Er coimplanted aluminosilicate glass is investigated in detail. A postimplantation thermal treatment has been performed to recover the damage induced by the implantation process and to promote Si aggregation. It will be shown that 1 h treatment in N{sub 2} atmosphere is not sufficient to induce Si precipitation for temperatures up to 500 deg. C. Nevertheless, the most intense Er{sup 3+} PL emission at 1.54 {mu}m is achieved after a thermal treatment at 400 deg. C. Such emission has been investigated by pumping in and out of resonance, showing a very efficient energy transfer process in the whole excitation wavelength range (360-515 nm). These results suggest that good energy transfer mediators could be small Si aggregates and not only crystalline clusters. For the best performing sample, the effective Er excitation cross section has been measured to be higher than 10{sup -17} cm{sup 2} at 379 and 390 nm and about 2x10{sup -16} cm{sup 2} at 476 nm, that is, several orders of magnitude higher than the Er direct absorption cross section (of the order of 10{sup -21} cm{sup 2} in this glass). Moreover the coefficient of cooperative upconversion has been evaluated to be 2.7x10{sup -18} cm{sup 3} s{sup -1}. The structural and optical properties of this material are discussed and compared to those found for Si and Er codoped silica.

  7. Crystallization and properties of Sr-Ba aluminosilicate glass-ceramic matrices

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Hyatt, Mark J.; Drummond, Charles H., III

    1991-01-01

    Powders of roller quenched (Sr,Ba)O-Al2O3-2SiO2 glasses of various compositions were uniaxially pressed into bars and hot isostatically pressed at 1350 C for 4 hours or cold isostatically pressed and sintered at different temperatures between 800 to 1500 C for 10 or 20 hours. Densities, flexural strengths, and linear thermal expansion were measured for three compositions. The glasss transition and crystallization temperatures were determined by Differential Scanning Calorimetry (DSC). The liquidus and crystallization temperature from the melt were measured using high temperature Differential Thermal Analysis (DTA). Crystalline phases formed on heat treatment of the glasses were identified by powder x ray diffraction. In Sr containing glasses, the monoclinic celsian phase always crystallized at temperatures above 1000 C. At lower temperatures, the hexagonal analog formed. The temperature for orthorhombic to hexagonal structure transformation increased monotonically with SrO content, from 327 C for BaO-Al2O3-2SiO2 to 758 C for SrO-Al2O3-2SiO2. These glass powders can be sintered to almost full densities and monoclinic celsian phase at a relatively low temperature of 1100 C.

  8. Spectroscopic properties of Er{sup 3+}- and Yb{sup 3+}-doped soda-lime silicate and aluminosilicate glasses

    SciTech Connect

    Hehlen, M.P.; Cockroft, N.J.; Gosnell, T.R.; Bruce, A.J.

    1997-10-01

    A spectroscopic investigation of an extensive series of Er{sup 3+}-doped and Er{sup 3+},Yb{sup 3+}-codoped soda-lime-silicate (SL) and aluminosilicate (AS) glasses is presented. Compared to SL glasses, 4f transitions in AS glasses show higher oscillator strengths, larger inhomogeneous broadening, and smaller crystal-field splittings of the respective excited-state multiplets. The Er{sup 3+} excited-state relaxation dynamics is adequately described by a combination of the Judd-Ofelt model and the energy-gap law. With the exception of {sup 4}I{sub 13/2}, multiphonon relaxation is dominant for all excited states, making it possible to efficiently pump the 1.55 {mu}m {sup 4}I{sub 13/2}{r_arrow}{sup 4}I{sub 15/2} emission by excitation of {sup 4}I{sub 11/2} at around 980 nm. The absolute {sup 4}I{sub 13/2} luminescence quantum yield, for low 980-nm excitation density ({approximately}5W/cm{sup 2}), {eta}, is {approximately}0.9 at 0.4 mol{percent} Er{sub 2}O{sub 3} and drops to about 0.65 upon increasing Er{sub 2}O{sub 3} to 1.2 mol{percent}, indicating the onset of energy-transfer processes. Samples with high OH{sup {minus}} impurity concentration suffer from significantly higher quenching of {sup 4}I{sub 13/2} luminescence at higher Er{sup 3+} concentrations. Energy migration to the minority of Er{sup 3+} ions coordinated to OH{sup {minus}}, followed by efficient multiphonon relaxation accounts for this effect. At low excitation densities, the strong near-infrared absorption of Yb{sup 3+} in combination with efficient Yb{r_arrow}Er energy transfer increases the {sup 4}I{sub 13/2} population density in Yb{sup 3+},Er{sup 3+}-codoped samples by up to 2 orders of magnitude compared to equivalent samples without Yb{sup 3+}. (Abstract Truncated)

  9. Structure, biodegradation behavior and cytotoxicity of alkali-containing alkaline-earth phosphosilicate glasses.

    PubMed

    Kansal, Ishu; Reddy, AlluAmarnath; Muñoz, Francisco; Choi, Seong-Jun; Kim, Hae-Won; Tulyaganov, Dilshat U; Ferreira, José M F

    2014-11-01

    We report on the effect of sodium on the structure, chemical degradation and bioactivity of glasses in the CaO-MgO-SiO2-P2O5-CaF2 system. The (29)Si and (31)P magic angle spinning-nuclear magnetic resonance spectroscopy of melt-quenched glasses with varying Na2O/MgO ratios exhibit a silicate glass network with the dominance of Q(2)(Si) units and phosphorus mainly forming orthophosphate species. Sodium incorporation in the glasses did not induce a significant structural change in the silicate network, while it did influence the phosphate environment due to its lower ionic field strength in comparison with that of magnesium. The apatite forming ability of glasses has been investigated by immersion of glass powders in simulated body fluid (SBF) for time durations varying between 1h and 7 days while their chemical degradation has been studied in Tris-HCl in accordance with ISO-10993-14. Increasing Na(+)/Mg(2+) ratio caused a decrease in the chemical durability of glasses and in the apatite forming ability especially during initial steps of interaction between glass and SBF solution. The cellular responses were observed in vitro on bulk glass samples using mouse-derived pre-osteoblastic MC3T3-E1 cell line. The preliminary study suggested that the increasing alkali-concentration in glasses led to cytotoxicity in the cell culture medium.

  10. Structure, biodegradation behavior and cytotoxicity of alkali-containing alkaline-earth phosphosilicate glasses.

    PubMed

    Kansal, Ishu; Reddy, AlluAmarnath; Muñoz, Francisco; Choi, Seong-Jun; Kim, Hae-Won; Tulyaganov, Dilshat U; Ferreira, José M F

    2014-11-01

    We report on the effect of sodium on the structure, chemical degradation and bioactivity of glasses in the CaO-MgO-SiO2-P2O5-CaF2 system. The (29)Si and (31)P magic angle spinning-nuclear magnetic resonance spectroscopy of melt-quenched glasses with varying Na2O/MgO ratios exhibit a silicate glass network with the dominance of Q(2)(Si) units and phosphorus mainly forming orthophosphate species. Sodium incorporation in the glasses did not induce a significant structural change in the silicate network, while it did influence the phosphate environment due to its lower ionic field strength in comparison with that of magnesium. The apatite forming ability of glasses has been investigated by immersion of glass powders in simulated body fluid (SBF) for time durations varying between 1h and 7 days while their chemical degradation has been studied in Tris-HCl in accordance with ISO-10993-14. Increasing Na(+)/Mg(2+) ratio caused a decrease in the chemical durability of glasses and in the apatite forming ability especially during initial steps of interaction between glass and SBF solution. The cellular responses were observed in vitro on bulk glass samples using mouse-derived pre-osteoblastic MC3T3-E1 cell line. The preliminary study suggested that the increasing alkali-concentration in glasses led to cytotoxicity in the cell culture medium. PMID:25280692

  11. Wetting of single crystal mullite by borosilicate and yttrium-aluminosilicate glasses and wetting phenomena of steels containing aluminum and titanium

    NASA Astrophysics Data System (ADS)

    Eldred, Benjamin Todd

    This dissertation consists of two major sections. The first section concerns the wetting of single crystal mullite by borosilicate and yttrium-aluminosilicate glasses. The borosilicate glass showed poor wetting and interacted only moderately with the substrate. The yttrium-aluminosilicate glass interacted strongly with mullite and showed very good wetting. Balanced chemical equations between each glass and mullite were derived from EDS data. Wetting was found to be dependent on the crystallographic orientation of the substrate, in agreement with previous studies of the surface energy of mullite. The second section concerns the wetting phenomena of steels containing aluminum and titanium. A modified sessile drop technique was used to investigate the wetting of steels containing aluminum and/or titanium as a function of furnace atmosphere. It was found that the steel chemistry and furnace atmosphere had little effect on wetting except in the case of a particular ultra-low carbon steel containing both aluminum and titanium. This steel was found to show significantly lower contact angles than any other steel tested when it was in an atmosphere of pure hydrogen. As nitrogen was added to the atmosphere, the contact angle increased monotonically and irreversibly. The interaction between aluminum, titanium, and nitrogen is explained in terms of first-order interaction coefficients available in thermodynamic literature.

  12. Alkali-silica reactivity of expanded glass granules in structure of lightweight concrete

    NASA Astrophysics Data System (ADS)

    Bumanis, G.; Bajare, D.; Locs, J.; Korjakins, A.

    2013-12-01

    Main component in the lightweight concrete, which provides its properties, is aggregate. A lot of investigations on alkali silica reaction (ASR) between cement and lightweight aggregates have been done with their results published in the academic literature. Whereas expanded glass granules, which is relatively new product in the market of building materials, has not been a frequent research object. Therefore lightweight granules made from waste glass and eight types of cement with different chemical and mineralogical composition were examined in this research. Expanded glass granules used in this research is commercially available material produced by Penostek. Lightweight concrete mixtures were prepared by using commercial chemical additives to improve workability of concrete. The aim of the study is to identify effect of cement composition to the ASR reaction which occurs between expanded glass granules and binder. Expanded glass granules mechanical and physical properties were determined. In addition, properties of fresh and hardened concrete were determined. The ASR test was processed according to RILEM AAR-2 testing recommendation. Tests with scanning electron microscope and microstructural investigations were performed for expanded glass granules and hardened concrete specimens before and after exposing them in alkali solution.

  13. Raman Analysis of Perrhenate and Pertechnetate in Alkali Salts and Borosilicate Glasses

    SciTech Connect

    Gassman, Paul L.; McCloy, John S.; Soderquist, Chuck Z.; Schweiger, Michael J.

    2014-01-03

    Sodium borosilicate glasses containing various concentrations of rhenium or technetium were fabricated, and their vibrational spectra studied using a Raman microscope. Spectra were interpreted with reference to new high resolution measurements of alkali pertechnetates and perrhenates NaReO4, KReO4, NaTcO4, and KTcO4. At low concentrations of ReO4- or TcO4-, glass spectra show weak peaks superimposed on a dominant spectrum of glass characteristic of silicate and borate network vibrations. At high concentrations, sharp peaks characteristic of crystal field splitting and C4h symmetry dominate the spectra of glasses, indicating alkali nearby tetrahedral Re or Tc. Often peaks indicative of both the K and Na pertechnetates/ perrhenates are evident in the Raman spectrum, with the latter being favored at high additions of the source chemical, since Na is more prevalent in the glass and ion exchange takes place. These results have significance to immobilization of nuclear waste containing radioactive 99Tc in glass for ultimate disposal.

  14. Sodium sulfate corrosion of silicon carbide fiber-reinforced lithium aluminosilicate glass-ceramic matrix composites. Master's thesis

    SciTech Connect

    Maldia, L.C.

    1993-12-01

    Sodium sulfate hot corrosion of a SiC fiber-reinforced lithium aluminosilicate (LAS) glass-ceramic matrix composite was studied using Scanning Electron Microscope (SEM) and X-ray Diffraction (XRD). Changes in the microstructural chemical composition of the specimens were investigated. The samples provided by Naval Air Warfare Center (NAWC), Warminster, PA were grouped as follows: (1) as-received, (2) Na2SO4 salt-coated and heat-treated in oxygen, (3) noncoated and heat-treated in oxygen, (4) Na2SO4. Salt-coated and heat-treated in argon, and (5) noncoated and heat-treated in argon. Heat treatment was performed by NAWC for 100 hours at 900 deg C. Experimental data obtained indicated that the presence of Na2SO4 in an oxidative environment resulted in rapid corrosion of the matrix and SiC fibers and in the latter rings of SiO2 replaced what had previously been SiC. There was very limited degradation of the fibers and matrix exposed at the surface in the noncoated sample heat-treated in oxygen and in the salt-coated sample heat-treated in argon. A significant reduction in the amount of mullite in the matrices of all heat-treated samples was observed. Mullite dissolved into either the glassy phase or into the Beta-spodumene matrix. Lastly, the presence of distinct magnesium silicate crystalline phases in the salt-coated and heat-treated in oxygen sample implies that the MgO at the surface reacted with the SiO2 in the matrix.

  15. Alkali-free bioactive glasses for bone tissue engineering: a preliminary investigation.

    PubMed

    Goel, Ashutosh; Kapoor, Saurabh; Rajagopal, Raghu Raman; Pascual, Maria J; Kim, Hae-Won; Ferreira, José M F

    2012-01-01

    An alkali-free series of bioactive glasses has been designed and developed in the glass system CaO-MgO-SiO(2)-P(2)O(5)-CaF(2) along the diopside (CaMgSi(2)O(6))-fluorapatite (Ca(5)(PO(4))(3)F)-tricalcium phosphate (3CaO·P(2)O(5)) join. The silicate network in all the investigated glasses is predominantly coordinated in Q(2) (Si) units, while phosphorus tends to remain in an orthophosphate (Q(0)) environment. The in vitro bioactivity analysis of glasses has been made by immersion of glass powders in simulated body fluid (SBF) while chemical degradation has been studied in Tris-HCl in accordance with ISO-10993-14. Some of the investigated glasses exhibit hydroxyapatite formation on their surface within 1-12 h of their immersion in SBF solution. The sintering and crystallization kinetics of glasses has been investigated by differential thermal analysis and hot-stage microscopy, respectively while the crystalline phase evolution in resultant glass-ceramics has been studied in the temperature range of 800-900°C using powder X-ray diffraction and scanning electron microscopy. The alkaline phosphatase activity and osteogenic differentiation for glasses have been studied in vitro on sintered glass powder compacts using rat bone marrow mesenchymal stem cells. The as-designed glasses are ideal candidates for their potential applications in bone tissue engineering in the form of bioactive glasses as well as glass/glass-ceramic scaffolds.

  16. Functionalized Amorphous Aluminosilicates

    NASA Astrophysics Data System (ADS)

    Mesgar, Milad

    Alkali treated aluminosilicate (geopolymer) was functionalized by surfactant to increase the hydrophobicity for making Pickering emulsion for the first part of this work. In the first part of this study, alkali treated metakaolin was functionalized with cetyltrimethylammonium bromide ((C16H33)N(CH 3)3Br, CTAB). The electrostatic interaction between this quaternary ammonium and the surface of the aluminosilicate which has negative charge has taken place. The particles then were used to prepare Pickering emulsion. The resulting stable dispersions, obtained very fast at very simple conditions with low ratio of aluminosilicate to liquid phase. In the second part, the interaction between geopolymer and glycerol was studied to see the covalent grafting of the geopolymer for making geopolymer composite. The composite material would be the basis material to be used as support catalyst, thin coating reagent and flame retardant material and so on, Variety of techniques, Thermogravimetric (TGA), Particle-induced X-ray emission (PIXE), FTIR, Solid state NMR, Powder X-ray diffraction (PXRD), BET surface area, Elemental analysis (CHN), TEM, SEM and Optical microscopy were used to characterize the functionalized geopolymer.

  17. Mixed alkali effect in glasses containing MnO{sub 2}

    SciTech Connect

    Reddy, M. Sudhakara; Rajiv, Asha; Veeranna Gowda, V. C.; Chakradhar, R. P. S.; Reddy, C. Narayana

    2013-02-05

    Glass systems of the composition xLi{sub 2}O-(25-x)K{sub 2}O-70(0.4ZnO+0.6P{sub 2}O{sub 5})+5MnO{sub 2} (x = 4,8,12,16 and 20 mol %) have been prepared by melt quenching technique. The thermal and mechanical properties of the glasses have been evaluated as a function of mixed alkali content. Glass transition temperature and Vickers's hardness of the glasses show a pronounced deviation from linearity at 12 mol%Li{sub 2}O. Theoretically estimated elastic moduli of the glasses show small positive deviations from linearity. MAE in these properties has been attributed to the localized changes in the glass network. The absorption spectra of Mn{sup 2+} ions in these glasses showed strong broad absorption band at 514 nm corresponding to the transition {sup 6}A{sub 1g}(S){yields}{sup 4}T{sub 1g}(G), characteristic of manganese ions in octahedral symmetry. The fundamental absorption edge in UV region is used to study the optical transitions and electronic band structure. From UV absorption edge, optical band gap energies have been evaluated. Band gap energies of the glasses have exhibited MAE and shows minimum value for 12 mol%Li{sub 2}O glass.

  18. Alkali oxide containing mesoporous bioactive glasses: synthesis, characterization and in vitro bioactivity.

    PubMed

    Vaid, Chitra; Murugavel, Sevi

    2013-03-01

    We report, for the first time, the synthesis of sodium oxide containing mesoporous bioactive quaternary glasses and compared with two different mesoporous ternary silicate systems by modified sol-gel process. With the aid of three different glass systems, a systematic analysis has been made on phosphorous-bearing (P-bearing) and phosphorous-free (P-free) mesoporous bioactive glasses to investigate the role of phosphorus on in vitro bioactivity of various silicate glasses with constant alkali oxide content. The combined use of multiple analytical techniques XRD, FTIR, SEM, nitrogen adsorption/desorption analysis before and after soaking in the SBF solution allowed us to establish strong correlation between composition, pore structure and bioactivity. We find that the P-bearing mesoporous glasses show the rapid hydroxycarbonate apatite (HCA) crystallization than P-free mesoporous glasses independent of calcium content. The present study reveals that the presence of phosphorous jointly with calcium in the bioactive glass system significantly enhances the rate of apatite formation as well as crystallization of apatite phase. Additionally, we find that a glass with sodium orthophosphate rich phase enhances the solubility when immersed in SBF and further accelerate the kinetics of apatite formation. The influences of the chemical composition and their superior textural properties on bioactivity are explained in terms of the unique structure of mesoporous bioactive glasses.

  19. Alkali-free bioactive glasses for bone tissue engineering: A preliminary investigation

    SciTech Connect

    Goel, Ashutosh; Kapoor, Saurabh; Rajagopal, Raghu R.; Pascual, Maria J.; Kim, Hae-Won; Ferreira, Jose M.

    2011-08-25

    An alkali-free series of bioactive glasses has been designed and developed in the glass system CaO-MgO-SiO2-P2O5-CaF2 along diopside (CaMgSi2O6) – fluorapatite [Ca5(PO4)3F] – tricalcium phosphate (3CaO•P2O5) join. The silicate network in all the investigated glasses is predominantly coordinated in Q2 (Si) units while phosphorus tends to remain in orthophosphate (Q0) environment. The in vitro bioactivity analysis of glasses has been made by immersion of glass powders in simulated body fluid (SBF) while chemical degradation has been studied in Tris-HCl in accordance with ISO-10993-14. Some of the investigated glasses exhibit hydroxyapatite (HA) formation on their surface with in 1-12 h of their immersion in SBF solution. The sintering and crystallization kinetics of glasses has been investigated by differential thermal analysis (DTA) and hot-stage microscopy (HSM), respectively while the crystalline phase evolution in resultant glass-ceramics (GCs) has been studied in the temperature range of 800-900 oC using powder X-ray diffraction (XRD) and scanning electron microscope (SEM). The cell growth and osteogenic differentiation for glasses has been studied in vitro on sintered glass powder compacts using rat bone marrow mesenchymal stem cells. The as designed glasses are ideal candidates for their potential applications in bone tissue engineering in the form of bioactive glasses as well as glass/GC scaffolds.

  20. On the induction of homogeneous bulk crystallization in Eu-doped calcium aluminosilicate glass by applying simultaneous high pressure and temperature

    NASA Astrophysics Data System (ADS)

    Muniz, R. F.; de Ligny, D.; Le Floch, S.; Martinet, C.; Rohling, J. H.; Medina, A. N.; Sandrini, M.; Andrade, L. H. C.; Lima, S. M.; Baesso, M. L.; Guyot, Y.

    2016-06-01

    From initial calcium aluminosilicate glass, transparent glass-ceramics have been successfully synthesized under simultaneous high pressure and temperature (SHPT). Possible homogeneous volumetric crystallization of this glassy system, which was not achieved previously by means of conventional heat treatment, has been put in evidence with a SHPT procedure. Structural, mechanical, and optical properties of glass and glass-ceramic obtained were investigated. Raman spectroscopy and X-ray diffraction allowed to identify two main crystalline phases: merwinite [Ca3Mg(SiO4)2] and diopside [CaMgSi2O6]. A Raman scanning profile showed that the formation of merwinite is quite homogeneous over the bulk sample. However, the sample surface also contains significant diopside crystals. Instrumented Berkovich nanoindentation was applied to determine the effect of SHPT on hardness from glass to glass-ceramic. For Eu-doped samples, the broadband emission due to 4f65d1 → 4f7 transition of Eu2+ was studied in both host systems. Additionally, the 5D0 → 7FJ transition of Eu3+ was used as an environment probe in the pristine glass and the glass-ceramic.

  1. Coupled ion redistribution and electronic breakdown in low-alkali boroaluminosilicate glass

    SciTech Connect

    Choi, Doo Hyun; Randall, Clive Furman, Eugene Lanagan, Michael

    2015-08-28

    Dielectrics with high electrostatic energy storage must have exceptionally high dielectric breakdown strength at elevated temperatures. Another important consideration in designing a high performance dielectric is understanding the thickness and temperature dependence of breakdown strengths. Here, we develop a numerical model which assumes a coupled ionic redistribution and electronic breakdown is applied to predict the breakdown strength of low-alkali glass. The ionic charge transport of three likely charge carriers (Na{sup +}, H{sup +}/H{sub 3}O{sup +}, Ba{sup 2+}) was used to calculate the ionic depletion width in low-alkali boroaluminosilicate which can further be used for the breakdown modeling. This model predicts the breakdown strengths in the 10{sup 8}–10{sup 9 }V/m range and also accounts for the experimentally observed two distinct thickness dependent regions for breakdown. Moreover, the model successfully predicts the temperature dependent breakdown strength for low-alkali glass from room temperature up to 150 °C. This model showed that breakdown strengths were governed by minority charge carriers in the form of ionic transport (mostly sodium) in these glasses.

  2. Nepheline crystallization in boron-rich alumino-silicate glasses as investigated by multi-nuclear NMR, Raman, & Mössbauer spectroscopies

    SciTech Connect

    Mccloy, John S.; Washton, Nancy M.; Gassman, Paul L.; Marcial, Jose; Weaver, Jamie L.; Kukkadapu, Ravi K.

    2015-02-01

    A spectroscopic study was conducted on 6 complex simulant nuclear waste glasses using multi-nuclear NMR, Raman and Mössbauer spectroscopies to explore the role of glass-forming elements Si, Al, B, along with Na and Fe and to understand their connectivity with the goal of understanding melt structure precursors to deleterious feldspathoid nepheline-like crystals formation. NMR showed the appearance of two sites for Al, Si, and Na in the samples which crystallized significant amounts of nepheline, and B speciation changed, typically resulting in more B(IV) after nepheline crystallization. Raman spectroscopy suggested a major part of the glass structure is composed of metaborate chains or rings, thus significant numbers of non-bridging oxygens and a separation of the borate from the alumino-silicate network. Mössbauer combined with Fe redox chemical measurements showed that Fe plays a minor role in these glasses, mostly as Fe3+, but that iron oxide spinel forms with nepheline in all cases. Models of the glass network, speciation of B, and allocation of non-bridging oxygens were computed. The Yun-Dell-Bray model failed to predict the observed high concentration of NBO necessary to explain the metaborate features in the Raman spectra, and it largely over-estimated B(IV) fraction. The model assuming Na-Al-Si moieties and using experimental B(IV) fraction predicted a large amount of NBO consistent with Raman spectra. An alternative notation for appreciating the glass network is suggested and then used to investigate the changes the glass due to crystallization of sodium nepheline and the residual glass network. From a theoretical standpoint, it may be preferred to picture nuclear waste glasses by the Lebedev theory of glass structure where “microcrystallites” of ordered nuclei (or embryos) exist in the matrix of more disordered glass.

  3. Crystallization of LiAlSiO4 Glass in Hydrothermal Environments at Gigapascal Pressures-Dense Hydrous Aluminosilicates.

    PubMed

    Spektor, Kristina; Fischer, Andreas; Häussermann, Ulrich

    2016-08-15

    High-pressure hydrothermal environments can drastically reduce the kinetic constraints of phase transitions and afford high-pressure modifications of oxides at comparatively low temperatures. Under certain circumstances such environments allow access to kinetically favored phases, including hydrous ones with water incorporated as hydroxyl. We studied the crystallization of glass in the presence of a large excess of water in the pressure range of 0.25-10 GPa and at temperatures from 200 to 600 °C. The p and T quenched samples were analyzed by powder X-ray diffraction, scanning electron microscopy, and IR spectroscopy. At pressures of 0.25-2 GPa metastable zeolite Li-ABW and stable α-eucryptite are obtained at low and high temperatures, respectively, with crystal structures based on tetrahedrally coordinated Al and Si atoms. At 5 GPa a new, hydrous phase of LiAlSiO4, LiAlSiO3(OH)2 = LiAlSiO4·H2O, is produced. Its crystal structure was characterized from single-crystal X-ray diffraction data (space group P21/c, a = 9.547(3) Å, b = 14.461(5) Å, c = 5.062(2) Å, β = 104.36(1)°). The monoclinic structure resembles that of α-spodumene (LiAlSi2O6) and constitutes alternating layers of chains of corner-condensed SiO4 tetrahedra and chains of edge-sharing AlO6 octahedra. OH groups are part of the octahedral Al coordination and extend into channels provided within the SiO4 tetrahedron chain layers. At 10 GPa another hydrous phase of LiAlSiO4 with presently unknown structure is produced. The formation of hydrous forms of LiAlSiO4 shows the potential of hydrothermal environments at gigapascal pressures for creating truly new materials. In this particular case it indicates the possibility of generally accessing pyroxene-type aluminosilicates with crystallographic amounts of hydroxyl incorporated. This could also have implications to geosciences by representing a mechanism of water storage and transport in the depths of the Earth. PMID:27482770

  4. Crystallization of LiAlSiO4 Glass in Hydrothermal Environments at Gigapascal Pressures-Dense Hydrous Aluminosilicates.

    PubMed

    Spektor, Kristina; Fischer, Andreas; Häussermann, Ulrich

    2016-08-15

    High-pressure hydrothermal environments can drastically reduce the kinetic constraints of phase transitions and afford high-pressure modifications of oxides at comparatively low temperatures. Under certain circumstances such environments allow access to kinetically favored phases, including hydrous ones with water incorporated as hydroxyl. We studied the crystallization of glass in the presence of a large excess of water in the pressure range of 0.25-10 GPa and at temperatures from 200 to 600 °C. The p and T quenched samples were analyzed by powder X-ray diffraction, scanning electron microscopy, and IR spectroscopy. At pressures of 0.25-2 GPa metastable zeolite Li-ABW and stable α-eucryptite are obtained at low and high temperatures, respectively, with crystal structures based on tetrahedrally coordinated Al and Si atoms. At 5 GPa a new, hydrous phase of LiAlSiO4, LiAlSiO3(OH)2 = LiAlSiO4·H2O, is produced. Its crystal structure was characterized from single-crystal X-ray diffraction data (space group P21/c, a = 9.547(3) Å, b = 14.461(5) Å, c = 5.062(2) Å, β = 104.36(1)°). The monoclinic structure resembles that of α-spodumene (LiAlSi2O6) and constitutes alternating layers of chains of corner-condensed SiO4 tetrahedra and chains of edge-sharing AlO6 octahedra. OH groups are part of the octahedral Al coordination and extend into channels provided within the SiO4 tetrahedron chain layers. At 10 GPa another hydrous phase of LiAlSiO4 with presently unknown structure is produced. The formation of hydrous forms of LiAlSiO4 shows the potential of hydrothermal environments at gigapascal pressures for creating truly new materials. In this particular case it indicates the possibility of generally accessing pyroxene-type aluminosilicates with crystallographic amounts of hydroxyl incorporated. This could also have implications to geosciences by representing a mechanism of water storage and transport in the depths of the Earth.

  5. Cation mass dependence of the nearly constant dielectric loss in alkali triborate glasses.

    PubMed

    Rivera, A; León, C; Varsamis, C P E; Chryssikos, G D; Ngai, K L; Roland, C M; Buckley, L J

    2002-03-25

    Electrical ac conductivity measurements on alkali triborate glasses ( M2O x 3B2O3, M = Li, Na, K, and Rb) were performed at temperatures down to 8 K and frequencies up to 1 GHz. All samples show a nearly constant dielectric loss (NCL), at the limit of high frequencies and/or low temperatures. The magnitude of the NCL is found to decrease as m(-1/3) with increasing alkali ion mass m. This quantitative result for the NCL, closely related to the mean-square displacement of ions, indicates that the origin of the NCL might be related to vibrational relaxation of the ions in the anharmonic potentials that cage them, and the cage is decaying very slowly with time. PMID:11909481

  6. Quantification of the boron speciation in alkali borosilicate glasses by electron energy loss spectroscopy

    PubMed Central

    Cheng, Shaodong; Yang, Guang; Zhao, Yanqi; Peng, MingYing; Skibsted, Jørgen; Yue, Yuanzheng

    2015-01-01

    Transmission electron microscopy and related analytical techniques have been widely used to study the microstructure of different materials. However, few research works have been performed in the field of glasses, possibly due to the electron-beam irradiation damage. In this paper, we have developed a method based on electron energy loss spectroscopy (EELS) data acquisition and analyses, which enables determination of the boron speciation in a series of ternary alkali borosilicate glasses with constant molar ratios. A script for the fast acquisition of EELS has been designed, from which the fraction of BO4 tetrahedra can be obtained by fitting the experimental data with linear combinations of the reference spectra. The BO4 fractions (N4) obtained by EELS are consistent with those from 11B MAS NMR spectra, suggesting that EELS can be an alternative and convenient way to determine the N4 fraction in glasses. In addition, the boron speciation of a CeO2 doped potassium borosilicate glass has been analyzed by using the time-resolved EELS spectra. The results clearly demonstrate that the BO4 to BO3 transformation induced by the electron beam irradiation can be efficiently suppressed by doping CeO2 to the borosilicate glasses. PMID:26643370

  7. Investigation of luminescence and spectroscopic properties of Nd3+ions in cadmium alkali borate glasses

    NASA Astrophysics Data System (ADS)

    Mohan, Shaweta; Thind, Kulwant Singh

    2016-07-01

    Neodymium doped cadmium alkali borate glasses having composition 20CdOsbnd 20R2Osbnd 59.5H3BO3sbnd 0.5Nd2O3; (R = Li, Na and K) were prepared by conventional melt-quenching technique. The amorphous nature of the glasses was confirmed by X-ray diffraction studies. The physical properties such as density, refractive index, molar volume, rare earth ion concentration etc. were determined. Optical absorption and fluorescence spectra were recorded. The Judd-Ofelt theory was applied on the optical absorption spectra of the glasses to evaluate the three phenomenological intensity parameters Ω2, Ω4 and Ω6. These parameters were in turn used to predict the radiative properties such as the radiative transition probability (A), radiative lifetime (τR) and branching ratio (βR) for the fluorescent levels of Nd3+ ion in the present glass series. The lasing efficiency of the prepared glasses has been characterized by the spectroscopic quality factor (Ω4/Ω6), the value of which is in the range of 0.2-1.5, typical for Nd3+ in different laser hosts. The variation of Ω2 with the change in alkali oxide has been attributed to the changes in the asymmetry of the ligand field at the rare earth ion site. The shift of the hypersensitive bands, study of the oscillator strengths and the variation of the spectral profile of the transition 4I9/2 → 4F7/2 + 4S3/2 indicate a maximum covalency of Ndsbnd O bond for glass with potassium ions. From the fluorescence spectra, peak wavelength (λp), effective line widths (Δλeff) and stimulated emission cross-section (σp) have been obtained for the three transitions 4F3/2 → 4I9/2,4F3/2 → 4I11/2 and4F3/2 → 4I13/2 of Nd3+ ion. The relatively high values of σp obtained for Nd3+ in present glass system suggest that these materials can be considered as suitable candidates for laser applications. The glass with potassium ions shows the highest value of the stimulated emission cross-section.

  8. Glass corrosion in natural environment

    NASA Technical Reports Server (NTRS)

    Thorpe, Arthur N.

    1989-01-01

    A series of studies of the effects of solutes which appear in natural aqueous environments, specifically Mg and Al, under controlled conditions, permit characterization of the retardation of silicate glass leaching in water containing such solutes. In the case of Mg the interaction with the glass appears to consist of exchange with alkali ions present in the glass to a depth of several microns. The effect of Al can be observed at much lower levels, indicating that the mechanism in the case of Al involves irreversible formation of aluminosilicate species at the glass surface.

  9. Compliant alkali silicate sealing glass for solid oxide fuel cell applications: thermal cycle stability and chemical compatibility

    SciTech Connect

    Chou, Y. S.; Thomsen, Edwin C.; Williams, Riley T.; Choi, Jung-Pyung; Canfield, Nathan L.; Bonnett, Jeff F.; Stevenson, Jeffry W.; Shyam, Amit; Lara-Curzio, E.

    2011-03-01

    An alkali silicate glass (SCN-1) is currently being evaluated as a candidate sealing glass for solid oxide fuel (SOFC) applications. The glass containing ~17 mole% alkalis (K2O and Na2O) remains vitreous and compliant during SOFC operation, unlike conventional SOFC sealing glasses, which experience substantial devitrification after the sealing process. The non-crystallizing compliant sealing glass has lower glass transition and softening temperatures since the microstructure remains glassy without significant crystallite formation, and hence can relieve or reduce residual stresses and also has the potential for crack healing. Sealing approaches based on compliant glass will also need to satisfy all the mechanical, thermal, chemical, physical, and electrical requirements for SOFC applications, not only in bulk properties but also at sealing interfaces. In this first of a series of papers we will report the thermal cycle stability of the glass when sealed between two SOFC components, i.e., a NiO/YSZ anode supported YSZ bilayer and a coated ferritic stainless steel interconnect material. High temperature leak rates were monitored versus thermal cycles between 700-850oC using back pressures ranging from 0.2 psi to 1.0 psi. Isothermal stability was also evaluated in a dual environment consisting of flowing dilute H2 fuel versus ambient air. In addition, chemical compatibility at the alumina and YSZ interfaces was examined with scanning electron microscopy and energy dispersive spectroscopy. The results shed new light on the topic of SOFC glass seal development.

  10. H2O/OH ratio determination in hydrous aluminosilicate glasses by static proton NMR and the effect of chemical shift anisotropy.

    PubMed

    Riemer, T; Schmidt, B; Behrens, H; Dupree, R

    2000-04-01

    Static 1H NMR spectra of hydrous NaAlSi3O8 glasses have been acquired at low temperature (140 K) in order to quantitatively determine OH and H2O concentrations. Since both components overlap in the spectra, an unambiguous determination of the line shapes is required. The structurally bonded hydroxyl groups are well described by a Gaussian line and the water molecules exhibit a Pake doublet-like line shape due to the strong proton-proton dipolar interaction. However, at proton resonance frequencies used in this study (360 MHz), the Pake doublet has an asymmetric line shape due to chemical shift anisotropy (CSA), which is significant and must be included in any simulation in order to reproduce the experimental line shape successfully. The simulations for rigid water molecules dissolved in our hydrous aluminosilicate glasses result in a CSA of 30+/-5 ppm and a dipolar interaction constant of 63.8+/-2.5 kHz (i.e., dipolar coupling constant (DCC) of 42.6+/-1.7 kHz), corresponding to a proton-proton distance of r(ij) = 154+/-2 pm. In contrast to earlier work, water speciation obtained from the simulations of our 1H NMR spectra are in excellent agreement with those obtained from infrared (IR) spectroscopy.

  11. Investigation of doped calcium aluminosilicate glass: A coupling between thermal-expansion and thermal-diffusion models for assessment of nonradiative relaxation time and characteristic diffusion time

    NASA Astrophysics Data System (ADS)

    Souza Filho, N. E.; Nogueira, A. C.; Rohling, J. H.; Baesso, M. L.; Medina, A. N.; Siqueira, A. P. L.; Sampaio, J. A.; Vargas, H.; Bento, A. C.

    2009-11-01

    This paper discusses the use of photoacoustic models to obtain the nonradiative relaxation time (τ) and characteristic diffusion time (τβ) for a sample showing visible absorption bands from fluorescent ion-doped low-silica calcium aluminosilicate glass. Two models allowing phase shift analyses, the thermal-expansion and thermal-diffusion models, are briefly reviewed. These models have limitations when the photoacoustic signal depends on both factors, in a coupling mechanism. An alternative model is proposed to take both thermal expansion and thermal diffusion into account with a single temperature solution for the heat-coupled differential equation. This model is simulated for absorbing samples near the thermally thick region. The model is applied to Eu-V codoped glass showing intermediate signal dependence from ω-1.0 to ω-3/2. The nonradiative time and characteristic diffusion time are derived with 33<τ(ms)<39, and τβ(ms)˜70 ms for the Eu-ion and 340<τβ(ms)<710 for the V-ion. Four absorption bands were analyzed (280, 350, 420, and 600 nm), which showed a signal dependence from ω-1.1 to ω-1.52. Absorption coefficients were derived from τβ in the range of 15<β(cm-1)<51, which agreed fairly well with spectrophotometer data for the same ions.

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

    NASA Astrophysics Data System (ADS)

    Riley, Brian J.; Rieck, Bennett T.; McCloy, John S.; Crum, Jarrod V.; Sundaram, S. K.; Vienna, John D.

    2012-05-01

    Tellurite glasses have historically been shown to host large concentrations of halides. They are here considered for the first time as a waste form for immobilizing chloride wastes, such as may be generated in the proposed molten alkali salt electrochemical separations step in nuclear fuel reprocessing. Key properties of several tellurite glasses are determined to assess acceptability as a chloride waste form. TeO2 glasses with other oxides (PbO, Al2O3 + B2O3, WO3, P2O5, or ZnO) were fabricated with and without 10 mass% of a simulated (non-radioactive) mixed alkali, alkaline-earth, and rare earth chloride waste. Measured chemical durability is compared for the glasses, as determined by the product consistency test (PCT), a common standardized chemical durability test often used to validate borosilicate glass waste forms. The glass with the most promise as a waste form is the TeO2-PbO system, as it offers good halide retention, a low sodium release (by PCT) comparable with high-level waste silicate glass waste forms, and a high storage density.

  13. Thorium and cerium chemical behaviour in ion-irradiated alkali-borosilicate glasses

    NASA Astrophysics Data System (ADS)

    Trocellier, P.; Haddi, A.; Poissonnet, S.; Bonnaillie, P.; Serruys, Y.

    2006-08-01

    Simple alkali-borosilicate glasses containing SiO2-B2O3-Li2O-Na2O and only one or two transition metal oxides (CeO2 and/or ThO2) have been synthesized by melting the stoichiometric powder mixture at 1100 °C in a platinum crucible. Thorium and cerium were used as chemical analogs of minor actinides (Pu and Am). Th is a purely tetravalent element, although Ce can be tetravalent or trivalent. Glass samples were submitted to aqueous leaching tests at 90 °C in deionised water for one week, with or without having previously been ion-irradiated. The irradiation experiments were conducted in the nuclear energy loss regime. Kr ions supplied by a 1 MV electrostatic Van de Graaff accelerator, were used to produce displacement cascades in the first hundreds of nanometers beneath the sample's surfaces. The leached samples were then characterized by scanning electron microscopy (SEM), electron microprobe analysis (EMA) and ion beam analytical (IBA) methods: Rutherford backscattering spectrometry and elastic recoil detection analysis (RBS and ERDA), proton-induced X-ray or gamma ray emission (PIXE and PIGE). Th and Ce are shown to be enriched in the near surface region of leached glasses due to the extremely low solubility of their hydroxides. The effect of surface damage on the chemical behaviour of Th and Ce is then detailed. The possibility for Ce(IV) to be reduced as Ce(III) during ion-irradiation just before leaching and its consequences on the relative solubility of corresponding chemical species is discussed in terms of hydroxide solubility thermodynamical equilibria.

  14. Structure of hydrous aluminosilicate glasses along the diopside anorthite join: A comprehensive one- and two-dimensional 1H and 27Al NMR study

    NASA Astrophysics Data System (ADS)

    Xue, Xianyu; Kanzaki, Masami

    2008-05-01

    We have taken a systematic approach utilizing advanced solid-state NMR techniques to gain new insights into the controversial issue concerning the dissolution mechanisms of water in aluminosilicate melts (glasses). A series of quenched anhydrous and hydrous (˜2 wt% H 2O) glass samples along the diopside (Di, CaMgSi 2O 6)—anorthite (An, CaAl 2Si 2O 8) join with varying An components (0, 20, 38, 60, 80, and 100 mol %) have been studied. A variety of NMR techniques, including one-dimensional (1D) 1H and 27Al MAS NMR, and 27Al → 1H cross-polarization (CP) MAS NMR, as well as two-dimensional (2D) 1H double-quantum (DQ) MAS NMR, 27Al triple-quantum (3Q) MAS NMR, and 27Al → 1H heteronuclear correlation NMR (HETCOR) and 3QMAS/HETCOR NMR, have been applied. These data revealed the presence of SiOH, free OH ((Ca,Mg)OH) and AlOH species in the hydrous glasses, with the last mostly interconnected with Si and residing in the more polymerized parts of the structure. Thus, there are no fundamental differences in water dissolution mechanisms for Al-free and Al-bearing silicate melts (glasses), both involving two competing processes: the formation of SiOH/AlOH that is accompanied by the depolymerization of the network structure, and the formation of free OH that has an opposite effect. The latter is more important for depolymerized compositions corresponding to mafic and ultramafic magmas. Aluminum is dominantly present in four coordination (Al IV), but a small amount of five-coordinate Al (Al V) is also observed in all the anhydrous and hydrous glasses. Furthermore, six-coordinate Al (Al VI) is also present in most of the hydrous glasses. As Al of higher coordinations are favored by high pressure, Al VIOH and Al VOH may become major water species at higher pressures corresponding to those of the Earth's mantle.

  15. Probing silicon and aluminium chemical environments in silicate and aluminosilicate glasses by solid state NMR spectroscopy and accurate first-principles calculations

    NASA Astrophysics Data System (ADS)

    Gambuzzi, Elisa; Pedone, Alfonso; Menziani, Maria Cristina; Angeli, Frédéric; Caurant, Daniel; Charpentier, Thibault

    2014-01-01

    Silicon and aluminium chemical environments in silicate and aluminosilicate glasses with compositions 60SiO2·20Na2O·20CaO (CSN), 60SiO2·20Al2O3·20CaO (CAS), 78SiO2·11Al2O3·11Na2O (NAS) and 60SiO2·10Al2O3·10Na2O·20CaO (CASN) have been investigated by 27Al and 29Si solid state magic angle spinning (MAS) and multiple quantum MAS (MQMAS) nuclear magnetic resonance (NMR) experiments. To interpret the NMR data, first-principles calculations using density functional theory were performed on structural models of these glasses. These models were generated by Shell-model molecular dynamics (MD) simulations. The theoretical NMR parameters and spectra were computed using the gauge including projected augmented wave (GIPAW) method and spin-effective Hamiltonians, respectively. This synergetic computational-experimental approach offers a clear structural characterization of these glasses, particularly in terms of network polymerization, chemical disorder (i.e. Si and Al distribution in second coordination sphere) and modifier cation distributions. The relationships between the local structural environments and the 29Si and 27Al NMR parameters are highlighted, and show that: (i) the isotropic chemical shift of both 29Si and 27Al increases of about +5 ppm for each Al added in the second sphere and (ii) both the 27Al and 29Si isotropic chemical shifts linearly decrease with the reduction of the average Si/Al-O-T bond angle. Conversely, 27Al and 29Si NMR parameters are much less sensitive to the connectivity with triple bridging oxygen atoms, precluding their indirect detection from 27Al and 29Si NMR.

  16. Evaluation of alkali concentration in conditions relevant to oxygen/natural gas glass furnaces by laser-induced breakdown spectroscopy.

    SciTech Connect

    Walsh, Peter M.; Molina, Alejandro; Shaddix, Christopher R.; Blevins, Linda Gail; Sickafoose, Shane M.

    2005-01-01

    A number of industrial combustion systems are adopting oxygen-enhanced firing to improve heat transfer characteristics and reduce emissions. The exhaust gas from these systems is dominated by H2O and CO2 and therefore has substantially different gas properties from traditional combustion exhaust. In the past, laser-induced breakdown spectroscopy (LIBS) has been successfully used for the evaluation of alkali aerosol concentrations in air-based combustion systems. This paper presents results of LIBS measurements of alkali concentrations in a laboratory calibration setup and in an oxygen/natural gas container glass furnace. It shows how both gas conditions (composition and temperature) and the molecular form of the alkali species affect the LIBS signals. The paper proposes strategies for mitigating these effects in future applications of LIBS in oxygen-enhanced combustion systems.

  17. Effects of Fiber Content on Mechanical Properties of CVD SiC Fiber-Reinforced Strontium Aluminosilicate Glass-Ceramic Composites

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.

    1996-01-01

    Unidirectional CVD SiC(f)(SCS-6) fiber-reinforced strontium aluminosilicate (SAS) glass-ceramic matrix composites containing various volume fractions, approximately 16 to 40 volume %, of fibers were fabricated by hot pressing at 1400 C for 2 h under 27.6 MPa. Monoclinic celsian, SrAl2Si2O8, was the only crystalline phase formed, with complete absence of the undesired hexacelsian phase, in the matrix. Room temperature mechanical properties were measured in 3-point flexure. The matrix microcracking stress and the ultimate strength increased with increase in fiber volume fraction, reached maximum values for V(sub f) approximately equal to 0.35, and degraded at higher fiber loadings. This degradation in mechanical properties is related to the change in failure mode, from tensile at lower V(sub f) to interlaminar shear at higher fiber contents. The extent of fiber loading did not have noticeable effect on either fiber-matrix debonding stress, or frictional sliding stress at the interface. The applicability of micromechanical models in predicting the mechanical properties of the composites was also examined. The currently available theoretical models do not appear to be useful in predicting the values of the first matrix cracking stress, and the ultimate strength of the SCS-6/SAS composites.

  18. Heat conductivity of LiF-NaF-Al(PO{sub 3}){sub 3} mixed-alkali glasses

    SciTech Connect

    Il`in, A.A.; Pronkin, A.A.

    1995-03-01

    Described is the heat conductivity of LiF-NaF-Al(PO{sub 3}){sub 3} mixed-alkali phosphate glasses. The percentage of NaF was varied to measure the density, mean sound velocity, Debye temperature, thermal oscillation frequency, and heat conductivity coefficient at different molar fractions. Correlation between the heat conductivity and the Debye temperature show the same regularity of variation in these parameters as for most crystalline substances.

  19. Role of glass structure in defining the chemical dissolution behavior, bioactivity and antioxidant properties of zinc and strontium co-doped alkali-free phosphosilicate glasses.

    PubMed

    Kapoor, Saurabh; Goel, Ashutosh; Tilocca, Antonio; Dhuna, Vikram; Bhatia, Gaurav; Dhuna, Kshitija; Ferreira, José M F

    2014-07-01

    We investigated the structure-property relationships in a series of alkali-free phosphosilicate glass compositions co-doped with Zn(2+) and Sr(2+). The emphasis was laid on understanding the structural role of Sr(2+) and Zn(2+) co-doping on the chemical dissolution behavior of glasses and its impact on their in vitro bioactivity. The structure of glasses was studied using molecular dynamics simulations in combination with solid state nuclear magnetic resonance spectroscopy. The relevant structural properties are then linked to the observed degradation behavior, in vitro bioactivity, osteoblast proliferation and oxidative stress levels. The apatite-forming ability of glasses has been investigated by X-ray diffraction, infrared spectroscopy and scanning electron microscopy-energy-dispersive spectroscopy after immersion of glass powders/bulk in simulated body fluid (SBF) for time durations varying between 1h and 14 days, while their chemical degradation has been studied in Tris-HCl in accordance with ISO 10993-14. All the glasses exhibit hydroxyapatite formation on their surface within 1-3h of their immersion in SBF. The cellular responses were observed in vitro on bulk glass samples using human osteosarcoma MG63 cell line. The dose-dependent cytoprotective effect of glasses with respect to the concentration of zinc and strontium released from the glasses is also discussed. PMID:24709542

  20. Role of glass structure in defining the chemical dissolution behavior, bioactivity and antioxidant properties of zinc and strontium co-doped alkali-free phosphosilicate glasses.

    PubMed

    Kapoor, Saurabh; Goel, Ashutosh; Tilocca, Antonio; Dhuna, Vikram; Bhatia, Gaurav; Dhuna, Kshitija; Ferreira, José M F

    2014-07-01

    We investigated the structure-property relationships in a series of alkali-free phosphosilicate glass compositions co-doped with Zn(2+) and Sr(2+). The emphasis was laid on understanding the structural role of Sr(2+) and Zn(2+) co-doping on the chemical dissolution behavior of glasses and its impact on their in vitro bioactivity. The structure of glasses was studied using molecular dynamics simulations in combination with solid state nuclear magnetic resonance spectroscopy. The relevant structural properties are then linked to the observed degradation behavior, in vitro bioactivity, osteoblast proliferation and oxidative stress levels. The apatite-forming ability of glasses has been investigated by X-ray diffraction, infrared spectroscopy and scanning electron microscopy-energy-dispersive spectroscopy after immersion of glass powders/bulk in simulated body fluid (SBF) for time durations varying between 1h and 14 days, while their chemical degradation has been studied in Tris-HCl in accordance with ISO 10993-14. All the glasses exhibit hydroxyapatite formation on their surface within 1-3h of their immersion in SBF. The cellular responses were observed in vitro on bulk glass samples using human osteosarcoma MG63 cell line. The dose-dependent cytoprotective effect of glasses with respect to the concentration of zinc and strontium released from the glasses is also discussed.

  1. Alkali Silicate Glass Coatings for Mitigating the Risks of Tin Whiskers

    NASA Astrophysics Data System (ADS)

    Hillman, Dave; Wilcoxon, Ross; Lower, Nate; Grossman, Dan

    2015-12-01

    Alkali silicate glass (ASG) coatings were investigated as a possible method for inhibiting tin whisker initiation and growth. The aqueous-based ASG formulations used in this study were deposited with equipment and conditions that are typical of those used to apply conventional conformal coatings. Processes for controlling ASG coating properties were developed, and a number of ASG-based coating combinations were applied to test components with pure tin surfaces. Coatings were applied both in a laboratory environment at Rockwell Collins and in a manufacturing environment at Plasma Ruggedized Solutions. Testing in elevated humidity/temperature environments and subsequent inspection of the test articles identified coating combinations that inhibited tin whisker growth as well as other material combinations that actually accelerated tin whisker growth. None of the coatings evaluated in this study, including conventional acrylic and Parylene conformal coatings, completely prevented the formation of tin whiskers. Two of the coatings were particularly effective at reducing the risks of whisker growth, albeit through different mechanisms. Parylene conformal coating almost, but not completely, eliminated whisker formation, and only a few tin whiskers were found on these surfaces during the study. A composite of ASG and alumina nanoparticles inhibited whisker formation to a lesser degree than Parylene, but did disrupt whisker growth mechanisms so as to inhibit the formation of long, and more dangerous, tin whiskers. Additional testing also demonstrated that the conformal coatings had relatively little effect on the dielectric loss of a stripline test structure operating at frequencies over 30 GHz.

  2. Chemical Vapor Deposited SiC (SCS-0) Fiber-Reinforced Strontium Aluminosilicate Glass-Ceramic Composites

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.

    1997-01-01

    Unidirectional SrO Al2O3 2SiO2 glass-ceramic matrix composites reinforced with uncoated Chemical Vapor Deposited (CVD) SiC (SCS-0) fibers have been fabricated by hot-pressing under appropriate conditions using the glass-ceramic approach. Almost fully dense composites having a fiber volume fraction of 0.24 have been obtained. Monoclinic celsian, SrAl2Si2O8, was the only crystalline phase observed in the matrix by x-ray diffraction. No chemical reaction was observed between the fiber and the matrix after high temperature processing. In three-point flexure, the composite exhibited a first matrix cracking stress of approx. 231 +/- 20 MPa and an ultimate strength of 265 +/- 17 MPa. Examination of fracture surfaces revealed limited short length fiber pull-out. From fiber push-out, the fiber/matrix interfacial debonding and frictional strengths were evaluated to be approx. 17.5 +/- 2.7 MPa and 11.3 +/- 1.6 MPa, respectively. Some fibers were strongly bonded to the matrix and could not be pushed out. The micromechanical models were not useful in predicting values of the first matrix cracking stress as well as the ultimate strength of the composites.

  3. High thermal neutron flux effects on structural and macroscopic properties of alkali-borosilicate glasses used as neutron guide substrate

    NASA Astrophysics Data System (ADS)

    Boffy, R.; Peuget, S.; Schweins, R.; Beaucour, J.; Bermejo, F. J.

    2016-05-01

    The behaviour of four alkali-borosilicate glasses under homogeneous thermal neutron irradiation has been studied. These materials are used for the manufacturing of neutron guides which are installed in most facilities as devices to transport neutrons from intense sources such as nuclear reactors or spallation sources up to scientific instruments. Several experimental techniques such as Raman, NMR, SANS and STEM have been employed in order to understand the rather different macroscopic behaviour under irradiation of materials that belong to a same glass family. The results have shown that the remarkable glass shrinking observed for neutron doses below 0.5 ·1018 n/cm2 critically depends upon the presence of domains where silicate and borate network do not mix.

  4. Chemical durability of alkali-borosilicate glasses studied by analytical SEM, IBA, isotopic-tracing and SIMS

    NASA Astrophysics Data System (ADS)

    Trocellier, P.; Djanarthany, S.; Chêne, J.; Haddi, A.; Brass, A. M.; Poissonnet, S.; Farges, F.

    2005-10-01

    Simple and complex alkali-borosilicate glasses were submitted to aqueous corrosion at room temperature, 60 and 90 °C in solutions with pH ranging between 0 and 12. Analytical scanning electron microscopy (SEM), ion beam analysis (IBA) techniques, isotopic tracing and secondary ion mass-depth profiling (SIMS) have been used to investigate the variations of the surface composition of glass. In acidic medium, the glass surface is generally covered by a thick hydrated silica layer, mobile elements like Li, Na and B and transition elements (Fe, Zr, Mo, etc.) are strongly depleted. Near pH 7, relative enrichments of aluminium, iron and rare earths are shown together with strong Li, Na and B depletions. In basic medium, the glass surface exhibits relative enrichments of the major part of transition metals (from Cr to U) whereas mobile elements seem to be kept close to their nominal concentration level at the glass surface and Si is severely impoverished. Hydrogen incorporated at the glass surface after leaching is much more immobile in neutral and basic media than in acid medium.

  5. Identifying glass compositions in fly ash

    NASA Astrophysics Data System (ADS)

    Aughenbaugh, Katherine; Stutzman, Paul; Juenger, Maria

    2016-01-01

    In this study, four Class F fly ashes were studied with a scanning electron microscope; the glassy phases were identified and their compositions quantified using point compositional analysis with k-means clustering and multispectral image analysis. The results showed that while the bulk oxide contents of the fly ashes were different, the four fly ashes had somewhat similar glassy phase compositions. Aluminosilicate glasses (AS), calcium aluminosilicate glasses (CAS), a mixed glass, and, in one case, a high iron glass were identified in the fly ashes. Quartz and iron crystalline phases were identified in each fly ash as well. The compositions of the three main glasses identified, AS, CAS, and mixed glass, were relatively similar in each ash. The amounts of each glass were varied by fly ash, with the highest calcium fly ash containing the most of calcium-containing glass. Some of the glasses were identified as intermixed in individual particles, particularly the calcium-containing glasses. Finally, the smallest particles in the fly ashes, with the most surface area available to react in alkaline solution, such as when mixed with portland cement or in alkali-activated fly ash, were not different in composition than the large particles, with each of the glasses represented. The method used in the study may be applied to a fly ash of interest for use as a cementing material in order to understand its potential for reactivity.

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

    SciTech Connect

    Sato, K.; Hatta, T.

    2015-03-07

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

  7. Structure of glasses containing transition metal ions. Progress report, February 1, 1980-January 31, 1981

    SciTech Connect

    White, W.B.; Fox, K.; Herman, J.S.; Houser, C.; Nelson, C.

    1981-01-01

    This research is concerned with the structure and properties of insulator glasses, particularly as these are modified by transition metal ions in solution. This progress report spans a one-year period and describes the status of the work two-thirds into the sixth contract year. Work on the host glasses has been concentrated on the alkali borosilicate, alkali aluminosilicate and alkali-gallia-silicate glasses. The main interest here is the structure setting for aluminum. The optical absorption spectra of nickel and iron in a variety of glasses have been examined. Utilization of luminescence in addition to optical absorption spectra has permitted the identification of several iron arrangements in glass. The investigation of diffusion processes, particularly hydrogen diffusion, by sputter-induced photon spectrometry (SIPS) has moved from qualitative demonstration to quantitative calculation.

  8. [Raman active vibrations of aluminosilicates].

    PubMed

    Pan, Feng; Yu, Xue-hui; Mo, Xuan-xue; You, Jing-lin; Wang, Chen; Chen, Hui; Jiang, Guo-chang

    2006-10-01

    Raman spectra of aluminosilicate minerals, namely kyanite, andalusite, and sillimanite and K2O-Al2O3-SiO2 glasses were recorded. Four alumino-silicon tetrahedral model clusters were calculated by self-consistent (SCF) molecular orbital ab-ini-tio calculation of the quantum chem (QC) method. The result shows a decrease tendency in Raman frequencies in the 800-1200 cm(-1) frequency region with increase in four-coordinated Al content, which is assigned to the Si--Onb symmetry stretching vibrations. The Raman spectra in the 700-800 cm(-1) frequency region is attributed to Al-Onb symmetry stretching vibrations. PMID:17205741

  9. [Raman active vibrations of aluminosilicates].

    PubMed

    Pan, Feng; Yu, Xue-hui; Mo, Xuan-xue; You, Jing-lin; Wang, Chen; Chen, Hui; Jiang, Guo-chang

    2006-10-01

    Raman spectra of aluminosilicate minerals, namely kyanite, andalusite, and sillimanite and K2O-Al2O3-SiO2 glasses were recorded. Four alumino-silicon tetrahedral model clusters were calculated by self-consistent (SCF) molecular orbital ab-ini-tio calculation of the quantum chem (QC) method. The result shows a decrease tendency in Raman frequencies in the 800-1200 cm(-1) frequency region with increase in four-coordinated Al content, which is assigned to the Si--Onb symmetry stretching vibrations. The Raman spectra in the 700-800 cm(-1) frequency region is attributed to Al-Onb symmetry stretching vibrations.

  10. Structure of Alkali Borate Glasses at High Pressure: B and Li K-Edge Inelastic X-Ray Scattering Study

    SciTech Connect

    Lee, Sung Keun; Eng, Peter J.; Mao, Ho-kwang; Meng, Yue; Shu, Jinfu

    2008-06-16

    We report the first in situ boron K-edge inelastic x-ray scattering (IXS) spectra for alkali borate glasses (Li{sub 2}B{sub 4}O{sub 7}) at high pressure up to 30 GPa where pressure-induced coordination transformation from three-coordinated to four-coordinated boron was directly probed. Coordination transformation (reversible upon decompression) begins around 5 GPa and the fraction of four-coordinated boron increases with pressure from about 50% (at 1 atm) to more than 95% (at 30 GPa) with multiple densification mechanisms, evidenced by three distinct pressure ranges for (d{sup [4]}B/dP){sub T}. The lithium K-edge IXS spectrum for Li-borate glasses at 5 GPa shows IXS features similar to that at 1 atm, suggesting that the Li environment does not change much with pressure up to 5 GPa. These results provide improved understanding of the structure of low-z glass at high pressure.

  11. Investigation of emulsified, acid and acid-alkali catalyzed mesoporous bioactive glass microspheres for bone regeneration and drug delivery.

    PubMed

    Miao, Guohou; Chen, Xiaofeng; Dong, Hua; Fang, Liming; Mao, Cong; Li, Yuli; Li, Zhengmao; Hu, Qing

    2013-10-01

    Acid-catalyzed mesoporous bioactive glass microspheres (MBGMs-A) and acid-alkali co-catalyzed mesoporous bioactive glass microspheres (MBGMs-B) were successfully synthesized via combination of sol-gel and water-in-oil (W/O) micro-emulsion methods. The structural, morphological and textural properties of mesoporous bioactive glass microspheres (MBGMs) were characterized by various techniques. Results show that both MBGMs-A and MBGMs-B exhibit regularly spherical shape but with different internal porous structures, i.e., a dense microstructure for MBGMs-A and internally porous structure for MBGMs-B. (29)Si NMR data reveal that MGBMs have low polymerization degree of silica network. The in vitro bioactivity tests indicate that the apatite formation rate of MBGMs-B was faster than that of MBGMs-A after soaking in simulated body fluid (SBF) solution. Furthermore, the two kinds of MBGMs have similar storage capacity of alendronate (AL), and the release behaviors of AL could be controlled due to their unique porous structure. In conclusion, the microspheres are shown to be promising candidates as bone-related drug carriers and filling materials of composite scaffold for bone repair.

  12. Investigation of emulsified, acid and acid-alkali catalyzed mesoporous bioactive glass microspheres for bone regeneration and drug delivery.

    PubMed

    Miao, Guohou; Chen, Xiaofeng; Dong, Hua; Fang, Liming; Mao, Cong; Li, Yuli; Li, Zhengmao; Hu, Qing

    2013-10-01

    Acid-catalyzed mesoporous bioactive glass microspheres (MBGMs-A) and acid-alkali co-catalyzed mesoporous bioactive glass microspheres (MBGMs-B) were successfully synthesized via combination of sol-gel and water-in-oil (W/O) micro-emulsion methods. The structural, morphological and textural properties of mesoporous bioactive glass microspheres (MBGMs) were characterized by various techniques. Results show that both MBGMs-A and MBGMs-B exhibit regularly spherical shape but with different internal porous structures, i.e., a dense microstructure for MBGMs-A and internally porous structure for MBGMs-B. (29)Si NMR data reveal that MGBMs have low polymerization degree of silica network. The in vitro bioactivity tests indicate that the apatite formation rate of MBGMs-B was faster than that of MBGMs-A after soaking in simulated body fluid (SBF) solution. Furthermore, the two kinds of MBGMs have similar storage capacity of alendronate (AL), and the release behaviors of AL could be controlled due to their unique porous structure. In conclusion, the microspheres are shown to be promising candidates as bone-related drug carriers and filling materials of composite scaffold for bone repair. PMID:23910338

  13. Compliant alkali silicate sealing glass for solid oxide fuel cell applications: the effect of protective alumina coating on electrical stability in dual environment

    SciTech Connect

    Chou, Y. S.; Choi, Jung-Pyung; Stevenson, Jeffry W.

    2012-12-01

    An alkali-containing silicate glass was recently proposed as a potential sealant for solid oxide fuel cells (SOFC). The glass contains appreciable amount of alkalis and retains its glassy microstructure at elevated temperatures over time. It is more compliant as compared to conventional glass-ceramics sealants and could potentially heal cracks during thermal cycling. In previous papers the thermal cycle stability, thermal stability and chemical compatibility were reported with yttria-stabilized zirconia (YSZ) electrolyte and YSZ-coated ferritic stainless steel interconnect. In this paper, we report the electrical stability of the compliant glass with aluminized AISI441 interconnect material under DC load in dual environment at 700-800oC. Apparent electrical resistivity was measured with a 4-point method for the glass sealed between two aluminized AISI441 metal coupons as well as plain AISI441 substrates. The results showed good electrical stability with the aluminized AISI441 substrate, while unstable behavior was observed for un-coated substrates. In addition, interfacial microstructure was examined with scanning electron microscopy and correlated with the measured resistivity results. Overall, the alumina coating demonstrated good chemical stability with the alkali-containing silicate sealing glass under DC loading.

  14. The Structural Role of Zr within Alkali Borosilicate Glasses for Nuclear Waste Immobilisation

    SciTech Connect

    A Connelly; N Hyatt; K Travis; R Hand; E Maddrell; R Short

    2011-12-31

    Zirconium is a key constituent element of High Level nuclear Waste (HLW) glasses, occurring both as a fission product and a fuel cladding component. As part of a wider research program aimed at optimizing the solubility of zirconium in HLW glasses, we have investigated the structural chemistry of zirconium in such materials using X-ray Absorption Spectroscopy (XAS). Zirconium K-edge XAS data were acquired from several inactive simulant and simplified waste glass compositions, including a specimen of blended Magnox/UO{sub 2} fuel waste glass. These data demonstrate that zirconium is immobilized as (octahedral) six-fold coordinate ZrO{sub 6} species in these glasses, with a Zr-O contact distance of 2.09 {angstrom}. The next nearest neighbors of the Zr species are Si at 3.42 {angstrom} and possibly Na at 3.44 {angstrom}, no next nearest neighbor Zr could be resolved.

  15. Determination of the valence band structure of an alkali phosphorus oxynitride glass: A synchrotron XPS study on LiPON

    NASA Astrophysics Data System (ADS)

    Schwöbel, André; Precht, Ruben; Motzko, Markus; Carrillo Solano, Mercedes A.; Calvet, Wolfram; Hausbrand, René; Jaegermann, Wolfram

    2014-12-01

    Lithium phosphorus oxynitride (LiPON) is a solid state electrolyte commonly used in thin film batteries (TFBs). Advanced TFBs face the issue of detrimental electrode-electrolyte interlayer formation, related to the electronic structure of the interface. In this contribution, we study the valence band structure of LiPON using resonant photoemission and synchrotron photoemission with variable excitation energies. The identification of different valence band features is done according to the known valence band features of meta- and orthophosphates. Additionally we compare our results with partial density of states simulations from literature. We find that the valence band structure is similar to the known metaphosphates with an additional contribution of nitrogen states at the top of the valence band. From the results we conclude that synchrotron X-ray photoemission (XPS) is a useful tool to study the valence band structure of nitridated alkali phosphate glasses.

  16. Compliant alkali silicate sealing glass for solid oxide fuel cell applications: Combined stability in isothermal ageing and thermal cycling with YSZ coated ferritic stainless steels

    SciTech Connect

    Chou, Y. S.; Thomsen, Edwin C.; Choi, Jung-Pyung; Stevenson, Jeffry W.

    2012-01-01

    An alkali-containing silicate glass (SCN-1) is currently being evaluated as a candidate sealing glass for solid oxide fuel cell (SOFC) applications. The glass contains about 17 mole% alkalis (K+Na) and has low glass transition and softening temperatures. It remains vitreous and compliant around 750-800oC after sealing without substantial crystallization, as contrary to conventional glass-ceramic sealants, which experience rapid crystallization after the sealing process. The glassy nature and low characteristic temperatures can reduce residual stresses and result in the potential for crack healing. In a previous study, the glass was found to have good thermal cycle stability and was chemically compatible with YSZ coating during short term testing. In the current study, the compliant glass was further evaluated in a more realistic way in that the sealed glass couples were first isothermally aged for 1000h followed by thermal cycling. High temperature leakage was measured. The chemical compatibility was also investigated with powder mixtures at 700 and 800oC to enhance potential interfacial reaction. In addition, interfacial microstructure was examined with scanning electron microscopy and evaluated with regard to the leakage and chemical compatibility results.

  17. Multilevel tunnelling systems and fractal clustering in the low-temperature mixed alkali-silicate glasses.

    PubMed

    Jug, Giancarlo; Paliienko, Maksym

    2013-01-01

    The thermal and dielectric anomalies of window-type glasses at low temperatures (T < 1 K) are rather successfully explained by the two-level systems (2LS) standard tunneling model (STM). However, the magnetic effects discovered in the multisilicate glasses in recent times, magnetic effects in the organic glasses, and also some older data from mixed (SiO₂)(1-x) (K₂O)(x) and (SiO₂)(1-x) (Na₂O)(x) glasses indicate the need for a suitable extension of the 2LS-STM. We show that--not only for the magnetic effects, but also for the mixed glasses in the absence of a field--the right extension of the 2LS-STM is provided by the (anomalous) multilevel tunnelling systems (ATS) proposed by one of us for multicomponent amorphous solids. Though a secondary type of TS, different from the standard 2LS, was invoked long ago already, we clarify their physical origin and mathematical description and show that their contribution considerably improves the agreement with the experimental data. In spite of dealing with low-temperature properties, our work impinges on the structure and statistical physics of glasses at all temperatures. PMID:23861652

  18. Multilevel tunnelling systems and fractal clustering in the low-temperature mixed alkali-silicate glasses.

    PubMed

    Jug, Giancarlo; Paliienko, Maksym

    2013-01-01

    The thermal and dielectric anomalies of window-type glasses at low temperatures (T < 1 K) are rather successfully explained by the two-level systems (2LS) standard tunneling model (STM). However, the magnetic effects discovered in the multisilicate glasses in recent times, magnetic effects in the organic glasses, and also some older data from mixed (SiO₂)(1-x) (K₂O)(x) and (SiO₂)(1-x) (Na₂O)(x) glasses indicate the need for a suitable extension of the 2LS-STM. We show that--not only for the magnetic effects, but also for the mixed glasses in the absence of a field--the right extension of the 2LS-STM is provided by the (anomalous) multilevel tunnelling systems (ATS) proposed by one of us for multicomponent amorphous solids. Though a secondary type of TS, different from the standard 2LS, was invoked long ago already, we clarify their physical origin and mathematical description and show that their contribution considerably improves the agreement with the experimental data. In spite of dealing with low-temperature properties, our work impinges on the structure and statistical physics of glasses at all temperatures.

  19. Microprobes aluminosilicate ceramic membranes

    DOEpatents

    Anderson, Marc A.; Sheng, Guangyao

    1993-01-01

    Methods have been developed to make mixed alumina-silicate and aluminosilicate particulate microporous ceramic membranes. One method involves the making of separate alumina and silica sols which are then mixed. Another method involves the creation of a combined sol with aluminosilicate particles. The resulting combined alumina and silica membranes have high surface area, a very small pore size, and a very good temperature stability.

  20. Structural investigation and electron paramagnetic resonance of vanadyl doped alkali niobium borate glasses.

    PubMed

    Agarwal, A; Sheoran, A; Sanghi, S; Bhatnagar, V; Gupta, S K; Arora, M

    2010-03-01

    Glasses with compositions xNb(2)O(5).(30-x)M(2)O.69B(2)O(3) (where M=Li, Na, K; x=0, 4, 8 mol%) doped with 1 mol% V(2)O(5) have been prepared using normal melt quench technique. The IR transmission spectra of the glasses have been studied over the range 400-4000 cm(-1). The changes caused by the addition of Nb(2)O(5) on the structure of these glasses have been reported. The electron paramagnetic resonance spectra of VO(2+) ions in these glasses have been recorded in X-band (9.14 GHz) at room temperature (300 K). The spin Hamiltonian parameters, dipolar hyperfine coupling parameter and Fermi contact interaction parameter have been calculated. It is observed that the resultant resonance spectra contain hyperfine structures (hfs) due to V(4+) ions which exist as VO(2+) ions in octahedral coordination with a tetragonal compression in the present glasses. The tetragonality of V(4+)O(6) complex decreases with increasing concentration of Nb(2)O(5). The 3d(xy) orbit contracts with increase in Nb(2)O(5):M(2)O ratio. Values of the theoretical optical basicity, Lambda(th), have also been reported.

  1. Compliant alkali silicate sealing glass for solid oxide fuel cell applications: Combined stability in isothermal ageing and thermal cycling with YSZ coated ferritic stainless steels

    NASA Astrophysics Data System (ADS)

    Chou, Yeong-Shyung; Thomsen, E. C.; Choi, J.-P.; Stevenson, J. W.

    2012-01-01

    An alkali silicate glass (SCN-1) is being evaluated as a candidate sealant for solid oxide fuel cell (SOFC) applications. The glass contains about 17 wt.% alkalis (K + Na) and has low glass transition and softening temperatures. It remains vitreous and compliant after sealing without substantial crystallization, as contrary to conventional glass-ceramic sealant. The glassy nature and low characteristic temperatures can reduce residual stresses and result in the potential for crack healing. In a previous study, the glass was found to have good thermal cycle stability and was chemically compatible with yttria stabilized zirconia (YSZ) coating during short term testing. In this study, the compliant glass was further evaluated in a more realistic way in that the sealed couples were first isothermally aged for 1000 h followed by thermal cycling. High temperature leakage was measured. Chemical compatibility was also investigated with powder mixtures to enhance potential interfacial reaction. In addition, interfacial microstructure was examined with scanning electron microscopy and evaluated with regard to the leakage and chemical compatibility results. Overall the compliant sealing glass showed desirable chemical compatibility with YSZ coated metallic interconnect of minimum reaction and hermetic behavior at 700-750 °C in dual environment.

  2. Silicate species of water glass and insights for alkali-activated green cement

    SciTech Connect

    Jansson, Helén; Bernin, Diana; Ramser, Kerstin

    2015-06-15

    Despite that sodium silicate solutions of high pH are commonly used in industrial applications, most investigations are focused on low to medium values of pH. Therefore we have investigated such solutions in a broad modulus range and up to high pH values (∼14) by use of infrared (IR) spectroscopy and silicon nuclear magnetic resonance ({sup 29}Si-NMR). The results show that the modulus dependent pH value leads to more or less charged species, which affects the configurations of the silicate units. This in turn, influences the alkali-activation process of low CO{sub 2} footprint cements, i.e. materials based on industrial waste or by-products.

  3. Silicate species of water glass and insights for alkali-activated green cement

    NASA Astrophysics Data System (ADS)

    Jansson, Helén; Bernin, Diana; Ramser, Kerstin

    2015-06-01

    Despite that sodium silicate solutions of high pH are commonly used in industrial applications, most investigations are focused on low to medium values of pH. Therefore we have investigated such solutions in a broad modulus range and up to high pH values (˜14) by use of infrared (IR) spectroscopy and silicon nuclear magnetic resonance (29Si-NMR). The results show that the modulus dependent pH value leads to more or less charged species, which affects the configurations of the silicate units. This in turn, influences the alkali-activation process of low CO2 footprint cements, i.e. materials based on industrial waste or by-products.

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

    NASA Astrophysics Data System (ADS)

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

    1996-07-01

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

  5. Fe(3+) ions in alkali lead tetraborate glasses--an electron paramagnetic resonance and optical study.

    PubMed

    Chakradhar, R P Sreekanth; Sivaramaiah, G; Rao, J Lakshmana; Gopal, N O

    2005-11-01

    Glass systems of composition 90R(2)B(4)O(7)+9PbO+1Fe(2)O(3) (R=Li, Na and K) and 90Li(2)B(4)O(7)+(10-x)PbO+xFe(2)O(3) (x=0.5, 1, 3, 4, 5, 7 and 9 mol %) have been investigated by means of electron paramagnetic resonance (EPR) and optical absorption techniques. The EPR spectra exhibit three resonance signals at g approximately 6.0, 4.2 and 2.0. The resonances at g approximately 6.0 and 4.2 are attributed to Fe(3+) ions in rhombic and axial symmetry sites, respectively. The g approximately 2.0 resonance signal is due to two or more Fe(3+) ions coupled together with dipolar interaction. The EPR spectra of 1 mol % of Fe(2)O(3) doped in lithium lead tetraborate glass samples have been studied at different temperatures (123-433 K). The intensity of g approximately 4.2 resonance signal decreases and the intensity of g approximately 2.0 resonance signal increases with the increase of temperature. The line widths are found to be independent of temperature. The EPR spectra exhibit a marked concentration dependence on iron content. A decrease in intensity for the resonance signal at g approximately 4.2 with increase in iron content for more than 4 mol % has been observed in lithium lead tetraborate glass samples and this has been attributed to the formation of Fe(3+) ion clusters in the glass samples. The paramagnetic susceptibility (chi) is calculated from the EPR data at various temperatures and the Curie constant (C) has been evaluated from 1/chi versus T graph. The optical absorption spectrum of Fe(3+) ions in lithium lead tetraborate glasses exhibits three bands characteristic of Fe(3+) ions in an octahedral symmetry. The crystal field parameter D(q) and the Racah interelectronic repulsion parameters B and C have also been evaluated. The value of interelectronic repulsion parameter B (825 cm(-1)) obtained in the present work suggests that the bonding is moderately covalent.

  6. Compliant alkali silicate sealing glass for solid oxide fuel cell applications: the effect of protective YSZ coating on electrical stability in dual environment

    SciTech Connect

    Chou, Y. S.; Thomsen, Edwin C.; Choi, Jung-Pyung; Stevenson, Jeffry W.

    2012-03-15

    Recently, compliant sealing glass has been proposed as a potential candidate sealant for solid oxide fuel cell (SOFC) applications. In a previous paper, the thermal stability and chemical compatibility were reported for a compliant alkali-containing silicate glass sealed between anode supported YSZ bi-layer and YSZ-coated stainless steel interconnect. In this paper, we will report the electrical stability of the compliant glass under a DC load and dual environment at 700-800 degrees C. Apparent electrical resistivity was measured with a 4-point method for the glass sealed between two plain SS441 metal coupons or YSZ-coated aluminized substrates. The results showed instability with plain SS441 at 800 degrees C, but stable behavior of increasing resistivity with time was observed with the YSZ coated SS441. In addition, results of interfacial microstructure analysis with scanning electron microscopy will be correlated with the measured resistivity results. Overall, the YSZ coating demonstrated chemically stability with the alkali-containing compliant silicate sealing glass under electrical field and dual environments.

  7. Multi-phase glass-ceramics as a waste form for combined fission products: alkalis, alkaline earths, lanthanides, and transition metals

    SciTech Connect

    Crum, Jarrod V.; Turo, Laura A.; Riley, Brian J.; Tang, Ming; Kossoy, Anna

    2012-04-01

    In this study, multi-phase silicate-based glass-ceramics were investigated as an alternate waste form for immobilizing non-fissionable products from used nuclear fuel. Currently, borosilicate glass is the waste form selected for immobilization of this waste stream, however, the low thermal stability and solubility of MoO{sub 3} in borosilicate glass translates into a maximum waste loading in the range of 15-20 mass%. Glass-ceramics provide the opportunity to target durable crystalline phases, e.g., powellite, oxyapatite, celsian, and pollucite, that will incorporate MoO{sub 3} as well as other waste components such as lanthanides, alkalis, and alkaline earths at levels 2X the solubility limits of a single-phase glass. In addition a glass-ceramic could provide higher thermal stability, depending upon the properties of the crystalline and amorphous phases. Glass-ceramics were successfully synthesized at waste loadings of 42, 45, and 50 mass% with the following glass additives: B{sub 2}O{sub 3}, Al{sub 2}O{sub 3}, CaO and SiO{sub 2} by slow cooling form from a glass melt. Glass-ceramics were characterized in terms of phase assemblage, morphology, and thermal stability. The targeted phases: powellite and oxyapatite were observed in all of the compositions along with a lanthanide borosilicate, and cerianite. Results of this initial investigation of glass-ceramics show promise as a potential waste form to replace single-phase borosilicate glass.

  8. Entropy and structure of silicate glasses and melts

    USGS Publications Warehouse

    Richet, P.; Robie, R.A.; Hemingway, B.S.

    1993-01-01

    Low-temperature adiabatic Cp measurements have been made on NaAlSi2O6, MgSiO3, Ca3Al2Si3O12 and Ca1.5Mg1.5Al2Si3O12 glasses. Above about 50 K, these and previous data show that the heat capacity is an additive function of composition to within ??1% throughout the investigated glassforming part of the system CaO-MgO-Al2O3-SiO2. In view of the determining role of oxygen coordination polyhedra on the low-temperature entropy, this is interpreted as indicating that Si and Al are tetrahedrally coordinated in all these glasses, in agreement with structural data; whereas Ca and Mg remain octahedrally coordinated. In contrast, heat capacities and entropies are not additive functions of composition for alkali aluminosilicates, indicating increases in the coordination numbers of alkali elements from about six to nine when alumina is introduced. A thermochemical consequence of additivity of vibrational entropies of glasses is that entropies of mixing are essentially configurational for calcium and magnesium aluminosilicate melts. For alkali-bearing liquids, it is probable that vibrational entropies contribute significantly to entropies of mixing. At very low temperatures, the additive nature of the heat capacity with composition is less well followed, likely as a result of specific differences in medium-range order. ?? 1993.

  9. Intumescence and pore structure of alkali-activated volcanic glasses upon exposure to high temperatures

    NASA Astrophysics Data System (ADS)

    Erdogan, S. T.

    2015-12-01

    Structures formed with ground perlite, a natural volcanic glass, activated with NaOH solutions, are shown to possess the ability to expand up to ~225 % of their original volumes upon exposure to temperatures in the 200-600 °C range. Porous solid with 3-7 MPa compressive strength and ˜450 kg/m3 or higher density are obtained. The observed expansion is believed to occur due to a loss of silanol condensation water, as vapor and is accompanied by an up to ~20 % loss in mass. A drop in pH to near-neutral values supports this idea. The size and total amount of pores in the final solid are controlled by concentration of the NaOH solution and thermal processing conditions. The pores formed are observed to be ~1-10 μm to mm-sized. The ability of perlite-based solids to intumesce over specific temperature ranges could be beneficial in applications where absorption of thermal energy is necessary, such as passive fire protection.

  10. Generation of alkali-free and high-proton concentration layer in a soda lime glass using non-contact corona discharge

    SciTech Connect

    Ikeda, Hiroshi; Sakai, Daisuke; Nishii, Junji; Funatsu, Shiro; Yamamoto, Kiyoshi; Suzuki, Toshio; Harada, Kenji

    2013-08-14

    Formation mechanisms of alkali-free and high-proton concentration surfaces were investigated for a soda lime glass using a corona discharge treatment under an atmospheric pressure. Protons produced by high DC voltage around an anode needle electrode were incorporated into a sodium ion site in the anode side glass. The sodium ion was swept away to the cathode side as a charge carrier. Then it was discharged. The precipitated sodium was transformed to a Na{sub 2}CO{sub 3} powder when the surface contacted with air. The sodium ion in the glass surface layer of the anode side was replaced completely by protons. The concentration of OH groups in the layer was balanced with the amount of excluded sodium ions. The substitution reaction of sodium ions with protons tends to be saturated according to a square root function of time. The alkali depletion layer formation rate was affected by the large difference in mobility between sodium ions and protons in the glass.

  11. Alkali-silica reactions of mortars produced by using waste glass as fine aggregate and admixtures such as fly ash and Li2CO3.

    PubMed

    Topçu, Ilker Bekir; Boğa, Ahmet Raif; Bilir, Turhan

    2008-01-01

    Use of waste glass or glass cullet (GC) as concrete aggregate is becoming more widespread each day because of the increase in resource efficiency. Recycling of wastes is very important for sustainable development. When glass is used as aggregate in concrete or mortar, expansions and internal stresses occur due to an alkali-silica reaction (ASR). Furthermore, rapid loss in durability is generally observed due to extreme crack formation and an increase in permeability. It is necessary to use some kind of chemical or mineral admixture to reduce crack formation. In this study, mortar bars are produced by using three different colors of glass in four different quantities as fine aggregate by weight, and the effects of these glass aggregates on ASR are investigated, corresponding to ASTM C 1260. Additionally, in order to reduce the expansions of mortars, 10% and 20% fly ash (FA) as mineral admixture and 1% and 2% Li(2)CO(3) as chemical admixture are incorporated by weight in the cement and their effects on expansion are examined. It is observed that among white (WG), green (GG) and brown glass (BG) aggregates, WG aggregate causes the greatest expansion. In addition, expansion increases with an increase in amount of glass. According to the test results, it is seen that over 20% FA and 2% Li(2)CO(3) replacements are required to produce mortars which have expansion values below the 0.2% critical value when exposed to ASR. However, usages of these admixtures reduce expansions occurring because of ASR.

  12. Specialty glass raw materials: Status and developments

    SciTech Connect

    Bauer, R.J.; Gray, S.L.

    1996-12-31

    The authors highlight several key raw materials used in the specialty glass industry. The focus here is to update changes and shifts underway in the worldwide availability and processes that will impact both costs and efficient use of these products. The glass types that use these materials generally are those other than container, float, and fiber glass. Those high-volume consumers of glass raw materials are discussed in a companion paper in this volume. In the specialty glass field, the batch materials involve minerals, and the chemicals derived from them, which are less readily available domestically. These are much more critically defined by specifications of assay, contamination, and particle size, resulting in their being more expensive. They are seldom commodity products. The scope of materials for this fragmented industry includes those for leads, borosilicates, aluminosilicates, opals, sealing and frit glasses, optical glass, ophthalmic glass, cathode ray tubes (CRTs) for TV and display, and glass-ceramics as major segments. They use lead oxides, nearly all the alkalies and alkaline earth portions of the periodic table, as well as rare earths, transition element oxides, phosphates, boron minerals and chemicals, zircon, zinc, most of the halogens, and many of the anions. They often require very special particle size specifications. The requirements for these batch materials are often based on chemistry, the absence of contaminants that impact melting, very wide ranges of the electromagnetic spectrum, glass homogeneity, and freedom from solid and gaseous inclusions down to ppm levels in both size and number.

  13. Results of Aluminosilicate Inhibitor Testing

    SciTech Connect

    Wilmarth, W.R.

    2001-06-27

    The aluminosilicate scale in the 2H Evaporator has precluded operation since late 1999. The chemistry of scale formation is known but the mechanism(s) for deposition are not well understood. Tests have been conducted to determine if chemical agents could prevent aluminosilicate formation under conditions similar to Tank 43H. Additionally, particle growth inhibition is also tested.

  14. Lithium alumino-silicate ion source development

    NASA Astrophysics Data System (ADS)

    Roy, Prabir Kumar; Seidl, Peter A.; Kwan, Joe W.; Greenway, Wayne G.; Waldron, William L.; Wu, James K.; Mazaheri, Kavous

    2009-11-01

    We report experimental progress on Li+ source development in preparation for warm dense matter heating experiments. To uniformly heat targets to electron-volt temperatures for the study of warm dense matter, we are pursuing the use of a low (E < 5 MeV) kinetic energy singly ionized lithium beam and a thin target. Two kinds of lithium (Li+) alumino-silicate ion sources, β-spodumene and β-eucryptite, each of area 0.31 cm2, have been fabricated for ion emission measurements. These surface ionization sources are heated to 1200 to 1300 C where they preferentially emit singly ionized alkali ions. Tight process controls were necessary in preparing and sintering the alumino-silicate to the porous tungsten substrate to produce an emitter that gives uniform ion emission, sufficient current density and low beam emittance. Current density limit of the two kinds have been measured, and ion species identification of possible contaminants has been verified with a Wien (E x B) filter.

  15. Mechanisms of optical losses in the {sup 5}D{sub 4} and {sup 5}D{sub 3} levels in Tb{sup 3+} doped low silica calcium aluminosilicate glasses

    SciTech Connect

    Santos, J. F. M. dos; Terra, I. A. A.; Nunes, L. A. O.; Catunda, T.; Astrath, N. G. C.; Guimarães, F. B.; Baesso, M. L.

    2015-02-07

    Trivalent Tb-doped materials exhibit strong emission in the green and weak emission in the UV-blue levels. Usually, this behavior is attributed to the cross relaxation (CR) process. In this paper, the luminescence properties of Tb{sup 3+}-doped low silica calcium aluminosilicate glasses are analyzed for UV (λ{sub exc} = 325 nm) and visible (488 nm) excitations. Under 325 nm excitation, the intensity of green luminescence increases proportionally to Tb{sup 3+} concentration. However, the blue luminescence intensity is strongly reduced with the increase of concentration from 0.5–15.0 wt. %. In the case of 488 nm excitation, a saturation behavior of the green emission is observed at intensities two orders of magnitude smaller than expected for bleaching of the ground state population. Using a rate equation model, we showed that this behavior can be explained by an excited state absorption cross section two orders of magnitude larger than the ground state absorption. The blue emission is much weaker than expected from our rate equations (325 nm and 488 nm excitation). We concluded that only the CR process cannot explain the overall feature of measured luminescence quenching in the wide range of Tb{sup 3+} concentrations. Cooperative upconversion from a pair of excited ions ({sup 5}D{sub 3}:{sup 5}D{sub 3} or {sup 5}D{sub 3}:{sup 5}D{sub 4}) and other mechanisms involving upper lying states (4f5d, charge transfer, host matrix, defects, etc.) may play a significant role.

  16. Solubilizing functionalized molecular aluminosilicates.

    PubMed

    Rascón-Cruz, Fernando; Huerta-Lavorie, Raúl; Jancik, Vojtech; Toscano, Rubén Alfredo; Cea-Olivares, Raymundo

    2009-02-21

    Molecular aluminosilicate Al(SH)(micro-O)Si(OH)(O(t)Bu)(2) ( = [HC{C(Me)N(Ar)}(2)](-), Ar = 2,6-(i)Pr(2)C(6)H(3)) has been prepared from Al(SH)(2) and ((t)BuO)(2)Si(OH)(2) in high yield. When reacted with one equiv. of water, the unique aluminosilicate containing two terminal hydroxy groups Al(OH.THF)(mu-O)Si(OH)(O(t)Bu)(2) can be isolated. However, when is reacted with the bulkier silanol ((t)BuO)(3)SiOH, no reaction is observed. The desired Al(SH)(micro-O)Si(O(t)Bu)(3) can be prepared in a two-step synthesis between AlH(2) and ((t)BuO)(3)SiOH giving first Al(H)(micro-O)Si(O(t)Bu)(3), which reacts further with elemental sulfur to give as the only product. Direct hydrolysis of was conducted to obtain Al(OH)(micro-O)Si(O(t)Bu)(3), however, such hydrolysis always resulted in a complete decomposition of the starting material. Therefore we used boric acid, which condenses in non-polar solvents and slowly evolve water, to hydrolyze to under mild conditions. Compounds , and have been characterized by single-crystal X-ray diffraction.

  17. Influence of ZnO/MgO substitution on sintering, crystallisation, and bio-activity of alkali-free glass-ceramics.

    PubMed

    Kapoor, Saurabh; Goel, Ashutosh; Correia, Ana Filipa; Pascual, Maria J; Lee, Hye-Young; Kim, Hae-Won; Ferreira, José M F

    2015-08-01

    The present study reports on the influence of partial replacement of MgO by ZnO on the structure, crystallisation behaviour and bioactivity of alkali-free bioactive glass-ceramics (GCs). A series of glass compositions (mol%): 36.07 CaO-(19.24-x) MgO-x ZnO-5.61 P2O5-38.49 SiO2-0.59 CaF2 (x=2-10) have been synthesised by melt-quench technique. The structural changes were investigated by solid-state magic angle spinning nuclear magnetic resonance (MAS-NMR), X-ray diffraction and differential thermal analysis. The sintering and crystallisation behaviours of glass powders were studied by hot-stage microscopy and differential thermal analysis, respectively. All the glass compositions exhibited good densification ability resulting in well sintered and mechanically strong GCs. The crystallisation and mechanical behaviour were studied under non-isothermal heating conditions at 850 °C for 1h. Diopside was the primary crystalline phase in all the GCs followed by fluorapatite and rankinite as secondary phases. Another phase named petedunnite was identified in GCs with ZnO content >4 mol. The proliferation of mesenchymal stem cells (MSCs) and their alkaline phosphatase activity (ALP) on GCs was revealed to be Zn-dose dependent with the highest performance being observed for 4 mol% ZnO.

  18. Results of Aluminosilicate Formation Testing

    SciTech Connect

    Wilmarth, W.R.

    2001-09-11

    The purpose of this work was to examine several experimental parameters of the formation of aluminosilicates under several tank chemistries, examine the conversion of crystalline phases, and determine inherent solubilities of certain crystal phases.

  19. Sorption of cesium and strontium from mineralized aqueous solutions on natural aluminosilicates modified by ferrocyanides of heavy metals

    SciTech Connect

    Panasyugin, A.S.; Trofimenko, N.E.; Masherova, N.P.; Rat`ko, A.I.; Golikova, N.I.

    1994-03-10

    The sorption behavior of natural aluminosilicates (bentonite and clinoptilolite) and aluminosilicates modified by ferrocyanides of heavy metals has been studied relative to radionuclides {sup 137}Cs and {sup 90}Sr in the presence of various quantities of alkali and alkaline-earth ions (e.g. surface waters). It has been shown that the distribution coefficients of the modified samples may exceed 100 for Sr{sup 2+} and 10,000 for Cs{sup +}; however, with a concentration of mineral background over 1.0 g{center_dot}liter, the competing ions strongly depress the sorption properties of the aluminosilicates.

  20. Optical Properties of K2O-Li2O-WO3-B2O3 Glasses: Evidence of Mixed Alkali Effect

    NASA Astrophysics Data System (ADS)

    Edukondalu, Avula; Sripathi, T.; Kareem Ahmmad, Shaik; Rahman, Syed; Sivakumar, K.

    2016-10-01

    Glass with compositions xK2O-(30 - x)Li2O-10WO3-60B2O3 for 0 ≤ x ≤ 30 mol.% have been prepared using the normal melt quenching technique. The optical reflection and absorption spectra were recorded at room temperature in the wavelength range 300-800 nm. From the absorption edge studies, the values of the optical band gap (E opt) and Urbach energy (ΔE) have been evaluated. The values of E opt and ΔE vary non-linearly with composition parameter, showing the mixed alkali effect. The dispersion of the refractive index is discussed in terms of the single oscillator Wemple Di-Domenico model.

  1. The Yb-doped aluminosilicate fibers photodarkening mechanism based on the charge-transfer state excitation

    NASA Astrophysics Data System (ADS)

    Rybaltovsky, A. A.; Bobkov, K. K.; Velmiskin, V. V.; Umnikov, A. A.; Shestakova, I. A.; Guryanov, A. N.; Likhachev, M. E.; Bubnov, M. M.; Dianov, E. M.

    2014-03-01

    We have studied the photodarkening effect in fiber preforms with an ytterbium-doped aluminosilicate glass core. The room-temperature stable Yb2+ ions formation in the glass matrix under both UV- and NIR-pumping irradiation was revealed by the method of absorption spectra analysis and the fluorescence spectroscopy technique. Comparative studies of preforms and crystals samples luminescence spectra, obtained under UV-excitation, were performed. A general mechanism of Yb2+ ions and aluminium oxygen-hole centers (Al-OHC) formation as a result of photoinduced process of Yb3+ ions excitation to "charge-transfer state" (CTS) was found for both Yb:YAG crystal and aluminosilicate glass.

  2. The development of a potassium-sulfide glass fiber cell and studies on impurities in alkali metal-sulfur cells

    NASA Technical Reports Server (NTRS)

    Tsang, F. Y.

    1977-01-01

    Potassium sulfur rechargeable cells, having as the electrolyte the thin walls of hollow glass fibers made from permeable glass, were developed. The cells had short lives, probably due to the construction materials and impurities in the potassium. The effect of the impurities in the analogous NA-S system was studied. Calcium, potassium, and NaOH/oxide impurities caused increased resistance or corrosion of the glass fibers. For long lived cell operation, the Na must contain less than 1 ppm Ca and less than a few ppm of hydroxide/oxide. Up to 150 ppm K can be tolerated. After purification of the Na anolyte, cell lifetimes in excess of 1000 deep charge-discharge cycles or over 8 months on continuous cycling at 10-30 percent depth of discharge were obtained.

  3. Measurements of alkali concentrations in an oxygen-natural gas-fired soda-lime-silica glass furnace

    SciTech Connect

    S. G. Buckley; P. M. Walsh; D. w. Hahn; R. J. Gallagher; M. K. Misra; J. T. Brown; F. Quan; K. Bhatia; V. I. Henry; R. D. Moore

    1999-10-18

    Sodium species vaporized from melting batch and molten glass in tank furnaces are the principal agents of corrosion of superstructure refractory and main contributors to emissions of particulate matter from glass melting. The use of oxygen in place of air for combustion of natural gas reduces particulate emissions, but is thought to accelerate corrosion in some melting tanks. Methods for measuring sodium are under investigation as means for identifying the volatilization, transport, and deposition mechanisms and developing strategies for control. Three separate methods were used to measure the concentrations of sodium species at various locations in an oxygen-natural gas-fired soda-lime-silica glass melting tank. Measurements were made inside the furnace using the absorption of visible light and in the flue duct using Laser-Induced Breakdown Spectroscopy (LIBS). Measurements in both the furnace and flue were also made by withdrawing and analyzing samples of the furnace gas.

  4. 21 CFR 182.2727 - Sodium aluminosilicate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Sodium aluminosilicate. 182.2727 Section 182.2727 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD... Sodium aluminosilicate. (a) Product. Sodium aluminosilicate (sodium silicoaluminate). (b) Tolerance....

  5. 21 CFR 582.2727 - Sodium aluminosilicate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Sodium aluminosilicate. 582.2727 Section 582.2727 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Sodium aluminosilicate. (a) Product. Sodium aluminosilicate (sodium silicoaluminate). (b) Tolerance....

  6. 21 CFR 182.2727 - Sodium aluminosilicate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Sodium aluminosilicate. 182.2727 Section 182.2727 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD... Sodium aluminosilicate. (a) Product. Sodium aluminosilicate (sodium silicoaluminate). (b) Tolerance....

  7. 21 CFR 582.2727 - Sodium aluminosilicate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Sodium aluminosilicate. 582.2727 Section 582.2727 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Sodium aluminosilicate. (a) Product. Sodium aluminosilicate (sodium silicoaluminate). (b) Tolerance....

  8. 21 CFR 582.2727 - Sodium aluminosilicate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Sodium aluminosilicate. 582.2727 Section 582.2727 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Sodium aluminosilicate. (a) Product. Sodium aluminosilicate (sodium silicoaluminate). (b) Tolerance....

  9. 21 CFR 182.2727 - Sodium aluminosilicate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Sodium aluminosilicate. 182.2727 Section 182.2727 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD... Sodium aluminosilicate. (a) Product. Sodium aluminosilicate (sodium silicoaluminate). (b) Tolerance....

  10. 21 CFR 182.2727 - Sodium aluminosilicate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Sodium aluminosilicate. 182.2727 Section 182.2727...) SUBSTANCES GENERALLY RECOGNIZED AS SAFE Anticaking Agents § 182.2727 Sodium aluminosilicate. (a) Product. Sodium aluminosilicate (sodium silicoaluminate). (b) Tolerance. This substance is generally recognized...

  11. 21 CFR 182.2727 - Sodium aluminosilicate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Sodium aluminosilicate. 182.2727 Section 182.2727 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD... Sodium aluminosilicate. (a) Product. Sodium aluminosilicate (sodium silicoaluminate). (b) Tolerance....

  12. 21 CFR 582.2727 - Sodium aluminosilicate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Sodium aluminosilicate. 582.2727 Section 582.2727 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Sodium aluminosilicate. (a) Product. Sodium aluminosilicate (sodium silicoaluminate). (b) Tolerance....

  13. 21 CFR 582.2727 - Sodium aluminosilicate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Sodium aluminosilicate. 582.2727 Section 582.2727 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Sodium aluminosilicate. (a) Product. Sodium aluminosilicate (sodium silicoaluminate). (b) Tolerance....

  14. 40 CFR 721.633 - Aluminosilicates, phospho-.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Aluminosilicates, phospho-. 721.633... Substances § 721.633 Aluminosilicates, phospho-. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as Aluminosilicates, phospho- (PMN P-98-1275; CAS...

  15. 40 CFR 721.633 - Aluminosilicates, phospho-.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Aluminosilicates, phospho-. 721.633... Substances § 721.633 Aluminosilicates, phospho-. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as Aluminosilicates, phospho- (PMN P-98-1275; CAS...

  16. 40 CFR 721.633 - Aluminosilicates, phospho-.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Aluminosilicates, phospho-. 721.633... Substances § 721.633 Aluminosilicates, phospho-. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as Aluminosilicates, phospho- (PMN P-98-1275; CAS...

  17. 40 CFR 721.633 - Aluminosilicates, phospho-.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Aluminosilicates, phospho-. 721.633... Substances § 721.633 Aluminosilicates, phospho-. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as Aluminosilicates, phospho- (PMN P-98-1275; CAS...

  18. 40 CFR 721.633 - Aluminosilicates, phospho-.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Aluminosilicates, phospho-. 721.633... Substances § 721.633 Aluminosilicates, phospho-. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as Aluminosilicates, phospho- (PMN P-98-1275; CAS...

  19. Development of Li+ alumino-silicate ion source

    SciTech Connect

    Roy, P.K.; Seidl, P.A.; Waldron, W.; Greenway, W.; Lidia, S.; Anders, A.; Kwan, J.

    2009-04-21

    To uniformly heat targets to electron-volt temperatures for the study of warm dense matter, one strategy is to deposit most of the ion energy at the peak of energy loss (dE/dx) with a low (E< 5 MeV) kinetic energy beam and a thin target[1]. Lower mass ions have a peak dE/dx at a lower kinetic energy. To this end, a small lithium (Li+) alumino-silicate source has been fabricated, and its emission limit has been measured. These surface ionization sources are heated to 1000-1150 C where they preferentially emit singly ionized alkali ions. Alumino-silicates sources of K+ and Cs+ have been used extensively in beam experiments, but there are additional challenges for the preparation of high-quality Li+ sources: There are tighter tolerances in preparing and sintering the alumino-silicate to the substrate to produce an emitter that gives uniform ion emission, sufficient current density and low beam emittance. We report on recent measurements ofhigh ( up to 35 mA/cm2) current density from a Li+ source. Ion species identification of possible contaminants is being verified with a Wien (E x B) filter, and via time-of-flight.

  20. A structural investigation of the alkali metal site distribution within bioactive glass using neutron diffraction and multinuclear solid state NMR.

    PubMed

    Martin, Richard A; Twyman, Helen L; Rees, Gregory J; Smith, Jodie M; Barney, Emma R; Smith, Mark E; Hanna, John V; Newport, Robert J

    2012-09-21

    The atomic-scale structure of Bioglass and the effect of substituting lithium for sodium within these glasses have been investigated using neutron diffraction and solid state magic angle spinning (MAS) NMR. Applying an effective isomorphic substitution difference function to the neutron diffraction data has enabled the Na-O and Li-O nearest-neighbour correlations to be isolated from the overlapping Ca-O, O-(P)-O and O-(Si)-O correlations. These results reveal that Na and Li behave in a similar manner within the glassy matrix and do not disrupt the short range order of the network former. Residual differences are attributed solely to the variation in ionic radius between the two species. Successful simplification of the 2 < r (Å) < 3 region via the difference method has enabled all the nearest neighbour correlations to be deconvolved. The diffraction data provides the first direct experimental evidence of split Na-O nearest-neighbour correlations in these melt quench bioactive glasses, and an analogous splitting of the Li-O correlations. The observed correlations are attributed to the metal ions bonded either to bridging or to non-bridging oxygen atoms. (23)Na triple quantum MAS (3QMAS) NMR data corroborates the split Na-O correlations. The structural sites present will be intimately related to the release properties of the glass system in physiological fluids such as plasma and saliva, and hence to the bioactivity of the material. Detailed structural knowledge is therefore a prerequisite for optimizing material design. PMID:22868255

  1. Water behaviour in nanoporous aluminosilicates.

    PubMed

    Smirnov, Konstantin S; Bougeard, Daniel

    2010-07-21

    This paper briefly reviews results of molecular dynamics simulation studies of water confined in nanoporous aluminosilicates. The behaviour of confined molecules is shown to be influenced by the nature of the host structure, and the size and the topology of the voids. For some of the systems discussed the ambiguity in results of different modelling studies call for the use of extended potential and structural models. Thus, the use of polarizable force fields was shown to be necessary to take into account the variation of the molecular dipole of confined molecules in different environments. PMID:21399287

  2. Water behaviour in nanoporous aluminosilicates.

    PubMed

    Smirnov, Konstantin S; Bougeard, Daniel

    2010-07-21

    This paper briefly reviews results of molecular dynamics simulation studies of water confined in nanoporous aluminosilicates. The behaviour of confined molecules is shown to be influenced by the nature of the host structure, and the size and the topology of the voids. For some of the systems discussed the ambiguity in results of different modelling studies call for the use of extended potential and structural models. Thus, the use of polarizable force fields was shown to be necessary to take into account the variation of the molecular dipole of confined molecules in different environments.

  3. Ultrastable Mesoporous Aluminosilicates by Grafting Routes.

    PubMed

    Mokaya

    1999-10-01

    A combination of postsynthesis grafting and hydrothermal treatment offers an excellent route for the synthesis of ultrastable mesoporous aluminosilicates with enhanced acidity and catalytic activity. The stability observed (>150 h in boiling water; 4 h at 1000 degrees C) is, for mesoporous silicates, remarkable. Unusually the hydrothermal treatment is beneficial with respect to the use of the stable aluminosilicates as solid acid catalysts.

  4. Alumino-silicate ion sources for accelerator applications

    SciTech Connect

    Warwick, A.I.

    1985-04-01

    As part of the program of Heavy Ion Fusion Accelerator Research at the Lawrence Berkeley Laboratory, ion sources have been developed using thermionic emitters of singly charged alkali metal ions. These emitters are flat surfaces of alumino-silicate, loaded with the appropriate ion. They have become convenient and reliable sources producing pulsed beams of very low emittance. Thermionic emission of ions from alumino-silicates has been known for a very long time. Here the author focuses on the practical application as accelerator ion sources. The author discusses the fabrication and heating of large area emitters, uniformity of emission and the maximum ion current density which can be extracted under space charge limited conditions, with zero electric field on the emitter surface. Results are presented for Na, K and Cs ions showing maximum space charge limited current densities of 25, 40 and 120 mAcm/sup -2/ respectively. In the case of cesium the author has produced a 5 mA beam at a kinetic energy of 200 keV with normalized emittance 1.2 x 10/sup -7/ ..pi.. m rad.

  5. Spectroscopy and laser action of rhodamine 6G doped aluminosilicate xerogels

    SciTech Connect

    McKiernan, J.M.; Yamanaka, S.A.; Dunn, B.; Zink, J.I. )

    1990-07-26

    Rhodamine 6G (R6G) doped aluminosilicate glass synthesized by the sol-gel method exhibits laser action. Transparent 5 mm {times} 5 mm {times} 10 mm monoliths were used as cast in a simple laser cavity. This new material was pumped at rates of up to 25 Hz and was still active after as many as 40,000 pump pulses. Luminescence and free-running laser spectra are measured. The dependence of the R6G doped aluminosilicate dye laser output on the number of pump pulses and the pump pulse energy is discussed.

  6. Aluminosilicate Precipitation Impact on Uranium

    SciTech Connect

    WILMARTH, WILLIAM

    2006-03-10

    Experiments have been conducted to examine the fate of uranium during the formation of sodium aluminosilicate (NAS) when wastes containing high aluminate concentrations are mixed with wastes of high silicate concentration. Testing was conducted at varying degrees of uranium saturation. Testing examined typical tank conditions, e.g., stagnant, slightly elevated temperature (50 C). The results showed that under sub-saturated conditions uranium is not removed from solution to any large extent in both simulant testing and actual tank waste testing. This aspect was not thoroughly understood prior to this work and was necessary to avoid criticality issues when actual tank wastes were aggregated. There are data supporting a small removal due to sorption of uranium on sites in the NAS. Above the solubility limit the data are clear that a reduction in uranium concentration occurs concomitant with the formation of aluminosilicate. This uranium precipitation is fairly rapid and ceases when uranium reaches its solubility limit. At the solubility limit, it appears that uranium is not affected, but further testing might be warranted.

  7. Method of handling radioactive alkali metal waste

    DOEpatents

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

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

  8. Method of handling radioactive alkali metal waste

    DOEpatents

    Wolson, Raymond D.; McPheeters, Charles C.

    1980-01-01

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

  9. Beneficiation of aluminosilicate and magnesia secondary refractories

    SciTech Connect

    Baranovskii, N.I.; Klyachin, V.V.; Rogozina, V.G.; Bortnikova, N.V.

    1987-09-01

    This article provides a comprehensive description of the recycling, magnetic separation, and utilization of waste refractories comprised of aluminosilicate and magnesia refractories along with data on the properties pertinent to the efficiency of the recycling process.

  10. Shape selectivity extending to ordered supermicroporous aluminosilicates.

    PubMed

    Fu, Wen Hua; Liang, Xiao Min; Zhang, Haidong; Wang, Yi Meng; He, Ming Yuan

    2015-01-28

    In the synthesis of polyoxymethylene dimethyl ethers (PODEn) catalyzed by ordered supermicroporous aluminosilicates, shape selectivity was observed and the high selectivity for target products (PODE3-8) was attributed to the particular pore diameter.

  11. Microstructural and phase evolution in metakaolin geopolymers with different activators and added aluminosilicate fillers

    NASA Astrophysics Data System (ADS)

    Sarkar, Madhuchhanda; Dana, Kausik; Das, Sukhen

    2015-10-01

    This work aims to investigate the microstructural and phase evolution of alkali activated metakaolin products with different activators and added aluminosilicate filler phases. The added filler phases have different reactivity to the alkali activated metakaolin system. Microstructural evolution in the alkali activated products has been investigated by X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Field Emission Scanning Electron Microscope (FESEM). Variation in strength development in alkali activated metakaolin products was followed by compressive strength measurement test. Microstructural study shows that in case of metakaolin with NaOH activator crystalline sodalite formed in all the product samples irrespective of the added filler phases. The microstructure of these NaOH activated products investigated by FESEM showed crystalline and inhomogeneous morphology. Mixed activator containing both NaOH and sodium silicate in a fixed mass ratio formed predominantly amorphous phase. Microstructure of these samples showed more homogeneity than that of NaOH activated metakaolin products. The study further shows that addition of α-Al2O3 powder, non reactive phase to the alkali activated metakaolin system when used in larger amount increased crystalline phase in the matrix. α-Al2O3 powder addition increased the compressive strength of the product samples for both the activator compositions. Added phase of colloidal silica, reactive to the alkali activated metakaolin system when used in larger amount was found to increase amorphous nature of the matrix. Addition of colloidal silica influenced the compressive strength property differently with different activator compositions.

  12. Glass microspheres

    SciTech Connect

    Day, D.E.; Ehrhardt, G.J.

    1988-12-06

    This patent describes a glass microsphere having a diameter of about 54 micrometers or less and adapted for radiation therapy of a mammal. The glass consists of essentially an yttrium oxide-aluminosilicate glass composition lying substantially within a quadrilateral region of the ternary composition diagram of the yttria-alumina-silica system, the quadrilateral region being defined by its four corners having the following combination of weight proportions of the components: 20% silica, 10% alumina, 70% yttria; 70% silica, 10% alumina, 20% yttria; 70% silica, 20% alumina, 10% yttria; and 20% silica, 45% alumina, 35% yttria, the glass having a chemical durability such that subsequent to irradiation and administration of the microsphere to the mammal, the mircosphere will not release a significant amount of yttrium-90 into the mammal's system.

  13. Alkali activation of halloysite for adsorption and release of ofloxacin

    NASA Astrophysics Data System (ADS)

    Wang, Qin; Zhang, Junping; Wang, Aiqin

    2013-12-01

    Halloysite nanotubes are promising vehicles for the controlled release of drug molecules. Here, we systematically investigated the effects of alkali activation on the physicochemical properties, structure and morphology of halloysite nanotubes by XRD, FTIR, SEM and TEM, etc. Afterwards, the adsorption and in vitro release properties of halloysite for cationic ofloxacin (OFL) were evaluated. The results indicate that alkali activation dissolves amorphous aluminosilicate, free silica and alumina, which results in the increase in pore volume and pore size. OFL is adsorbed onto halloysite via electrostatic interaction and complexation. Alkali activation could increase the adsorption capacity of halloysite for OFL and prolong release of the adsorbed OFL compared with the natural halloysite. Thus, alkali activation of halloysite is an effective protocol to improve the adsorption and prolong release for cationic drug molecules.

  14. Geopolymers and Related Alkali-Activated Materials

    NASA Astrophysics Data System (ADS)

    Provis, John L.; Bernal, Susan A.

    2014-07-01

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

  15. An investigation of waste glass-based geopolymers supplemented with alumina

    NASA Astrophysics Data System (ADS)

    Christiansen, Mary U.

    An increased consideration of sustainability throughout society has resulted in a surge of research investigating sustainable alternatives to existing construction materials. A new binder system, called a geopolymer, is being investigated to supplement ordinary portland cement (OPC) concrete, which has come under scrutiny because of the CO2 emissions inherent in its production. Geopolymers are produced from the alkali activation of a powdered aluminosilicate source by an alkaline solution, which results in a dense three-dimensional matrix of tetrahedrally linked aluminosilicates. Geopolymers have shown great potential as a building construction material, offering similar mechanical and durability properties to OPC. Additionally, geopolymers have the added value of a considerably smaller carbon footprint than OPC. This research considered the compressive strength, microstructure and composition of geopolymers made from two types of waste glass with varying aluminum contents. Waste glass shows great potential for mainstream use in geopolymers due to its chemical and physical homogeneity as well as its high content of amorphous silica, which could eliminate the need for sodium silicate. However, the lack of aluminum is thought to negatively affect the mechanical performance and alkali stability of the geopolymer system. 39 Mortars were designed using various combinations of glass and metakaolin or fly ash to supplement the aluminum in the system. Mortar made from the high-Al glass (12% Al2O3) reached over 10,000 psi at six months. Mortar made from the low-Al glass (<1% Al2O3) did not perform as well and remained sticky even after several weeks of curing, most likely due to the lack of Al which is believed to cause hardening in geopolymers. A moderate metakaolin replacement (25-38% by mass) was found to positively affect the compressive strength of mortars made with either type of glass. Though the microstructure of the mortar was quite indicative of mechanical

  16. Influence of mixed alkali on the spectral properties of vanadyl ions doped xNa{sub 2}O-(30 - x)K{sub 2}O-60B{sub 2}O{sub 3} glasses-an EPR and optical study

    SciTech Connect

    Sreekanth Chakradhar, R.P. . E-mail: chakra72@physics.iisc.ernet.in; Ramesh, K.P.; Rao, J.L.; Ramakrishna, J.

    2005-06-15

    Electron paramagnetic resonance (EPR) and optical investigations have been performed in the mixed alkali borate xNa{sub 2}O-(30 - x)K{sub 2}O-60B{sub 2}O{sub 3} (5 {<=} x {<=} 25) glasses doped with 10 mol% of vanadyl ions in order to look for the effect of 'mixed alkalis' on the spectral properties of the glasses. The observed EPR spectra have structures for x > 5 mol% which are characteristic of a hyperfine interaction arising from an unpaired electron with the {sup 51}V nucleus and it builds up in intensity as x increases. It is observed that the mixed alkali play a significant role in accommodating the vanadyl ions in these mixed alkali glasses and for x > 5 mol%, shows a well resolved hyperfine structure typical for isolated VO{sup 2+} ions. The spin-Hamiltonian parameters (g and A), the dipolar hyperfine coupling parameter (P) and Fermi contact interaction parameter (k) have been evaluated. It is observed that the spin-Hamiltonian parameters do not vary much with the change in composition. It is observed that with increase of x, an increase occurs in tetragonal distortion for VO{sup 2+}. The number of spins (N) participating in resonance and the paramagnetic susceptibility ({chi}) have been calculated. It is observed that N and {chi} increase with x. The optical bandgap energies evaluated for these glasses slightly increase with x and reach a maximum around x = 20 and thereafter decrease showing the mixed alkali effect. Optical band gap energies obtained in the present work vary from 2.73 to 3.10 eV for both the direct and indirect transitions. The physical parameters of the glasses are also determined with respect to the composition.

  17. Phase evolution of Na2O-Al2O3-SiO2-H2O gels in synthetic aluminosilicate binders.

    PubMed

    Walkley, Brant; San Nicolas, Rackel; Sani, Marc-Antoine; Gehman, John D; van Deventer, Jannie S J; Provis, John L

    2016-04-01

    This study demonstrates the production of stoichiometrically controlled alkali-aluminosilicate gels ('geopolymers') via alkali-activation of high-purity synthetic amorphous aluminosilicate powders. This method provides for the first time a process by which the chemistry of aluminosilicate-based cementitious materials may be accurately simulated by pure synthetic systems, allowing elucidation of physicochemical phenomena controlling alkali-aluminosilicate gel formation which has until now been impeded by the inability to isolate and control key variables. Phase evolution and nanostructural development of these materials are examined using advanced characterisation techniques, including solid state MAS NMR spectroscopy probing (29)Si, (27)Al and (23)Na nuclei. Gel stoichiometry and the reaction kinetics which control phase evolution are shown to be strongly dependent on the chemical composition of the reaction mix, while the main reaction product is a Na2O-Al2O3-SiO2-H2O type gel comprised of aluminium and silicon tetrahedra linked via oxygen bridges, with sodium taking on a charge balancing function. The alkali-aluminosilicate gels produced in this study constitute a chemically simplified model system which provides a novel research tool for the study of phase evolution and microstructural development in these systems. Novel insight of physicochemical phenomena governing geopolymer gel formation suggests that intricate control over time-dependent geopolymer physical properties can be attained through a careful precursor mix design. Chemical composition of the main N-A-S-H type gel reaction product as well as the reaction kinetics governing its formation are closely related to the Si/Al ratio of the precursor, with increased Al content leading to an increased rate of reaction and a decreased Si/Al ratio in the N-A-S-H type gel. This has significant implications for geopolymer mix design for industrial applications. PMID:26911317

  18. Phase evolution of Na2O-Al2O3-SiO2-H2O gels in synthetic aluminosilicate binders.

    PubMed

    Walkley, Brant; San Nicolas, Rackel; Sani, Marc-Antoine; Gehman, John D; van Deventer, Jannie S J; Provis, John L

    2016-04-01

    This study demonstrates the production of stoichiometrically controlled alkali-aluminosilicate gels ('geopolymers') via alkali-activation of high-purity synthetic amorphous aluminosilicate powders. This method provides for the first time a process by which the chemistry of aluminosilicate-based cementitious materials may be accurately simulated by pure synthetic systems, allowing elucidation of physicochemical phenomena controlling alkali-aluminosilicate gel formation which has until now been impeded by the inability to isolate and control key variables. Phase evolution and nanostructural development of these materials are examined using advanced characterisation techniques, including solid state MAS NMR spectroscopy probing (29)Si, (27)Al and (23)Na nuclei. Gel stoichiometry and the reaction kinetics which control phase evolution are shown to be strongly dependent on the chemical composition of the reaction mix, while the main reaction product is a Na2O-Al2O3-SiO2-H2O type gel comprised of aluminium and silicon tetrahedra linked via oxygen bridges, with sodium taking on a charge balancing function. The alkali-aluminosilicate gels produced in this study constitute a chemically simplified model system which provides a novel research tool for the study of phase evolution and microstructural development in these systems. Novel insight of physicochemical phenomena governing geopolymer gel formation suggests that intricate control over time-dependent geopolymer physical properties can be attained through a careful precursor mix design. Chemical composition of the main N-A-S-H type gel reaction product as well as the reaction kinetics governing its formation are closely related to the Si/Al ratio of the precursor, with increased Al content leading to an increased rate of reaction and a decreased Si/Al ratio in the N-A-S-H type gel. This has significant implications for geopolymer mix design for industrial applications.

  19. Dissolution and Separation of Aluminum and Aluminosilicates

    SciTech Connect

    McFarlane, Joanna; Benker, Dennis; DePaoli, David W.; Felker, Leslie Kevin; Mattus, Catherine H.

    2015-12-19

    The selection of an aluminum alloy for target irradiation affects post-irradiation target dissolution and separations. Recent tests with aluminum alloy 6061 yielded greater than expected precipitation in the dissolver, forming up to 10 wt.% solids of aluminum hydroxides and aluminosilicates. Aluminosilicate dissolution presents challenges in a number of different areas, metals extraction from minerals, flyash treatment, and separations from aluminum alloys. We present experimental work that attempts to maximize dissolution of aluminum metal, along with silicon, magnesium, and copper impurities, through control of temperature, the rate of reagent addition, and incubation time. Aluminum phase transformations have been identified as a function of time and temperature, using X-ray diffraction. Solutions have been analyzed using wet chemical methods and X-ray fluorescence. Our data have been compared with published calculations of aluminum phase diagrams. Approaches are given to enhance the dissolution of aluminum and aluminosilicate phases in caustic solution.

  20. Dissolution and Separation of Aluminum and Aluminosilicates

    DOE PAGES

    McFarlane, Joanna; Benker, Dennis; DePaoli, David W.; Felker, Leslie Kevin; Mattus, Catherine H.

    2015-12-19

    The selection of an aluminum alloy for target irradiation affects post-irradiation target dissolution and separations. Recent tests with aluminum alloy 6061 yielded greater than expected precipitation in the dissolver, forming up to 10 wt.% solids of aluminum hydroxides and aluminosilicates. Aluminosilicate dissolution presents challenges in a number of different areas, metals extraction from minerals, flyash treatment, and separations from aluminum alloys. We present experimental work that attempts to maximize dissolution of aluminum metal, along with silicon, magnesium, and copper impurities, through control of temperature, the rate of reagent addition, and incubation time. Aluminum phase transformations have been identified as amore » function of time and temperature, using X-ray diffraction. Solutions have been analyzed using wet chemical methods and X-ray fluorescence. Our data have been compared with published calculations of aluminum phase diagrams. Approaches are given to enhance the dissolution of aluminum and aluminosilicate phases in caustic solution.« less

  1. 21 CFR 582.2729 - Hydrated sodium calcium aluminosilicate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Hydrated sodium calcium aluminosilicate. 582.2729... Agents § 582.2729 Hydrated sodium calcium aluminosilicate. (a) Product. Hydrated sodium calcium aluminosilicate (sodium calcium silicoaluminate). (b) Tolerance. This substance is generally recognized as...

  2. 21 CFR 182.2729 - Sodium calcium aluminosilicate, hydrated.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Sodium calcium aluminosilicate, hydrated. 182.2729... § 182.2729 Sodium calcium aluminosilicate, hydrated. (a) Product. Hydrated sodium calcium aluminosilicate (sodium calcium silicoaluminate). (b) Tolerance. This substance is generally recognized as...

  3. 21 CFR 182.2729 - Sodium calcium aluminosilicate, hydrated.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Sodium calcium aluminosilicate, hydrated. 182.2729... (CONTINUED) SUBSTANCES GENERALLY RECOGNIZED AS SAFE Anticaking Agents § 182.2729 Sodium calcium aluminosilicate, hydrated. (a) Product. Hydrated sodium calcium aluminosilicate (sodium calcium...

  4. 21 CFR 582.2729 - Hydrated sodium calcium aluminosilicate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Hydrated sodium calcium aluminosilicate. 582.2729... Agents § 582.2729 Hydrated sodium calcium aluminosilicate. (a) Product. Hydrated sodium calcium aluminosilicate (sodium calcium silicoaluminate). (b) Tolerance. This substance is generally recognized as...

  5. 21 CFR 582.2729 - Hydrated sodium calcium aluminosilicate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Hydrated sodium calcium aluminosilicate. 582.2729... Agents § 582.2729 Hydrated sodium calcium aluminosilicate. (a) Product. Hydrated sodium calcium aluminosilicate (sodium calcium silicoaluminate). (b) Tolerance. This substance is generally recognized as...

  6. 21 CFR 582.2729 - Hydrated sodium calcium aluminosilicate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Hydrated sodium calcium aluminosilicate. 582.2729... Agents § 582.2729 Hydrated sodium calcium aluminosilicate. (a) Product. Hydrated sodium calcium aluminosilicate (sodium calcium silicoaluminate). (b) Tolerance. This substance is generally recognized as...

  7. 21 CFR 182.2729 - Sodium calcium aluminosilicate, hydrated.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Sodium calcium aluminosilicate, hydrated. 182.2729... § 182.2729 Sodium calcium aluminosilicate, hydrated. (a) Product. Hydrated sodium calcium aluminosilicate (sodium calcium silicoaluminate). (b) Tolerance. This substance is generally recognized as...

  8. 21 CFR 182.2729 - Sodium calcium aluminosilicate, hydrated.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Sodium calcium aluminosilicate, hydrated. 182.2729... § 182.2729 Sodium calcium aluminosilicate, hydrated. (a) Product. Hydrated sodium calcium aluminosilicate (sodium calcium silicoaluminate). (b) Tolerance. This substance is generally recognized as...

  9. 21 CFR 582.2729 - Hydrated sodium calcium aluminosilicate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Hydrated sodium calcium aluminosilicate. 582.2729... Agents § 582.2729 Hydrated sodium calcium aluminosilicate. (a) Product. Hydrated sodium calcium aluminosilicate (sodium calcium silicoaluminate). (b) Tolerance. This substance is generally recognized as...

  10. 21 CFR 182.2729 - Sodium calcium aluminosilicate, hydrated.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Sodium calcium aluminosilicate, hydrated. 182.2729... § 182.2729 Sodium calcium aluminosilicate, hydrated. (a) Product. Hydrated sodium calcium aluminosilicate (sodium calcium silicoaluminate). (b) Tolerance. This substance is generally recognized as...

  11. Secondary Ion Mass Spectrometry of Zeolite Materials: Observation of Abundant Aluminosilicate Oligomers Using an Ion Trap

    SciTech Connect

    Groenewold, Gary Steven; Kessinger, Glen Frank; Scott, Jill Rennee; Gianotto, Anita Kay; Appelhans, Anthony David; Delmore, James Edward

    2000-12-01

    Oligomeric oxyanions were observed in the secondary ion mass spectra (SIMS) of zeolite materials. The oxyanions have the general composition AlmSinO2(m+n)H(m-1)- (m + n = 2 to 8) and are termed dehydrates. For a given mass, multiple elemental compositions are possible because (Al + H) is an isovalent and isobaric substitute for Si. Using 18 keV Ga+ as a projectile, oligomer abundances are low relative to the monomers. Oligomer abundance can be increased by using the polyatomic projectile ReO4- (~5 keV). Oligomer abundance can be further increased using an ion trap (IT-) SIMS; in this instrument, long ion lifetimes (tens of ms) and relatively high He pressure result in significant collisional stabilization and increased high-mass abundance. The dehydrates rapidly react with adventitious H2O present in the IT-SIMS to form mono-, di-, and trihydrates. The rapidity of the reaction and comparison to aluminum oxyanion hydration suggest that H2O adds to the aluminosilicate oxyanions in a dissociative fashion, forming covalently bound product ions. In addition to these findings, it was noted that production of abundant oligomeric aluminosilicates could be significantly increased by substituting the countercation (NH4+) with the larger alkali ions Rb+ and Cs+. This constitutes a useful tactic for generating large aluminosilicate oligomers for surface characterization and ion-molecule reactivity studies.

  12. Super ionic conductive glass

    DOEpatents

    Susman, Sherman; Volin, Kenneth J.

    1984-01-01

    An ionically conducting glass for use as a solid electrolyte in a power or secondary cell containing an alkali metal-containing anode and a cathode separated by an alkali metal ion conducting glass having an ionic transference number of unity and the general formula: A.sub.1+x D.sub.2-x/3 Si.sub.x P.sub.3-x O.sub.12-2x/3, wherein A is a network modifier for the glass and is an alkali metal of the anode, D is an intermediate for the glass and is selected from the class consisting of Zr, Ti, Ge, Al, Sb, Be, and Zn and X is in the range of from 2.25 to 3.0. Of the alkali metals, Na and Li are preferred and of the intermediate, Zr, Ti and Ge are preferred.

  13. Super ionic conductive glass

    DOEpatents

    Susman, S.; Volin, K.J.

    Described is an ionically conducting glass for use as a solid electrolyte in a power or secondary cell containing an alkali metal-containing anode and a cathode separated by an alkali metal ion conducting glass having an ionic transference number of unity and the general formula: A/sub 1 + x/D/sub 2-x/3/Si/sub x/P/sub 3 - x/O/sub 12 - 2x/3/, wherein A is a network modifier for the glass and is an alkali metal of the anode, D is an intermediate for the glass and is selected from the class consisting of Zr, Ti, Ge, Al, Sb, Be, and Zn and X is in the range of from 2.25 to 3.0. Of the alkali metals, Na and Li are preferred and of the intermediate, Zr, Ti and Ge are preferred.

  14. Glass/BNNT Composite for Sealing Solid Oxide Fuel Cells

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Hurst, Janet B.; Choi, Sung R.

    2007-01-01

    A material consisting of a barium calcium aluminosilicate glass reinforced with 4 weight percent of boron nitride nanotubes (BNNTs) has shown promise for use as a sealant in planar solid oxide fuel cells (SOFCs).

  15. Charge-transfer state excitation as the main mechanism of the photodarkening process in ytterbium-doped aluminosilicate fibres

    SciTech Connect

    Bobkov, K K; Rybaltovsky, A A; Vel'miskin, V V; Likhachev, M E; Bubnov, M M; Dianov, E M; Umnikov, A A; Gur'yanov, A N; Vechkanov, N N; Shestakova, I A

    2014-12-31

    We have studied photodarkening in ytterbium-doped fibre preforms with an aluminosilicate glass core. Analysis of their absorption and luminescence spectra indicates the formation of stable Yb{sup 2+} ions in the glass network under IR laser pumping at a wavelength λ = 915 nm and under UV irradiation with an excimer laser (λ = 193 nm). We have performed comparative studies of the luminescence spectra of the preforms and crystals under excitation at a wavelength of 193 nm. The mechanism behind the formation of Yb{sup 2+} ions and aluminium – oxygen hole centres (Al-OHCs), common to ytterbium-doped YAG crystals and aluminosilicate glass, has been identified: photoinduced Yb{sup 3+} charge-transfer state excitation. (optical fibres)

  16. Charge-transfer state excitation as the main mechanism of the photodarkening process in ytterbium-doped aluminosilicate fibres

    NASA Astrophysics Data System (ADS)

    Bobkov, K. K.; Rybaltovsky, A. A.; Vel'miskin, V. V.; Likhachev, M. E.; Bubnov, M. M.; Dianov, E. M.; Umnikov, A. A.; Gur'yanov, A. N.; Vechkanov, N. N.; Shestakova, I. A.

    2014-12-01

    We have studied photodarkening in ytterbium-doped fibre preforms with an aluminosilicate glass core. Analysis of their absorption and luminescence spectra indicates the formation of stable Yb2+ ions in the glass network under IR laser pumping at a wavelength λ = 915 nm and under UV irradiation with an excimer laser (λ = 193 nm). We have performed comparative studies of the luminescence spectra of the preforms and crystals under excitation at a wavelength of 193 nm. The mechanism behind the formation of Yb2+ ions and aluminium - oxygen hole centres (Al-OHCs), common to ytterbium-doped YAG crystals and aluminosilicate glass, has been identified: photoinduced Yb3+ charge-transfer state excitation.

  17. Atomic-scale models of early-stage alkali depletion and SiO2-rich gel formation in bioactive glasses.

    PubMed

    Tilocca, Antonio

    2015-01-28

    Molecular dynamics simulations of Na(+)/H(+)-exchanged 45S5 Bioglass® models reveal that a large fraction of the hydroxyl groups introduced into the proton-exchanged, hydrated glass structure do not initially form covalent bonds with Si and P network formers but remain free and stabilised by the modifier metal cations, whereas substantial Si-OH and P-OH bonding is observed only at higher Na(+)/H(+) exchange levels. The strong affinity between free OH groups and modifier cations in the highly fragmented 45S5 glass structure appears to represent the main driving force for this effect. This suggests an alternative direct route for the formation of a repolymerised silica-rich gel in the early stages of the bioactive mechanism, not considered before, which does not require sequential repeated breakings of Si-O-Si bonds and silanol condensations.

  18. Alteration layer formation of Ca- and Zn-oxide bearing alkali borosilicate glasses for immobilisation of UK high level waste: A vapour hydration study

    NASA Astrophysics Data System (ADS)

    Cassingham, N. J.; Corkhill, C. L.; Stennett, M. C.; Hand, R. J.; Hyatt, N. C.

    2016-10-01

    The UK high level nuclear waste glass modified with CaO/ZnO was investigated using the vapour phase hydration test, performed at 200 °C, with the aim of understanding the impact of the modification on the chemical composition and microstructure of the alteration layer. Experiments were undertaken on non-modified and CaO/ZnO-modified base glass, with or without 25 wt% of simulant Magnox waste calcine. The modification resulted in a dramatic reduction in gel layer thickness and also a reduction in the reaction rate, from 3.4 ± 0.3 g m-2 d-1 without CaO/ZnO modification to 0.9 ± 0.1 g m-2 d-1 with CaO/ZnO. The precipitated phase assemblage for the CaO/ZnO-modified compositions was identified as hydrated Ca- and Zn-bearing silicate phases, which were absent from the non-modified counterpart. These results are in agreement with other recent studies showing the beneficial effects of ZnO additions on glass durability.

  19. Alkali metal nitrate purification

    DOEpatents

    Fiorucci, Louis C.; Morgan, Michael J.

    1986-02-04

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

  20. A new SiC-whisker-reinforced lithium aluminosilicate composite

    SciTech Connect

    Xue, L.A.; Chen, Iwei . Dept. of Materials Science and Engineering)

    1993-11-01

    The glass-ceramic matrix of the well-known lithium aluminosilicate (LAS)/SiC composite is usually formulated near the spodumene composition. The authors report a new composition which is rich in alumina and lean in silica and lithia. This formulation offers a new option of converting the glass-ceramic matrix to a mullite/alumina matrix upon annealing above 1,400 C, and hence better creep resistance and other high-temperature mechanical properties. Using a transient-phase processing method that they developed previously for the superplastic forming of mullite, the authors are able to hot-press a composite containing 30 vol% SiC whiskers at [approximately]1,350 C to achieve full density. Flexural strength measurements up to 1,400 C have confirmed the improved high-temperature strength and creep resistance over conventional LAS. The fracture toughness is also higher than that of LAS. The results suggest that the new composition may be chosen as a better candidate matrix for SiC-fiber-reinforced composites.

  1. Evaluation of Uranium Coprecipitation with Sodium Aluminosilicate Phases

    SciTech Connect

    Oji, Lawrence N.; Williams, Adrienne L.

    2004-02-15

    Batch laboratory experiments performed to evaluate uranium incorporation into aluminosilicate structures during synthesis are described. This research was conducted in response to plant problems related to the accumulation of uranium with aluminosilicates in low-level radioactive waste evaporators. Conditions that favor precipitation of aluminosilicates also foster uranium solid precipitation, so it is difficult to attribute problems with uranium accumulation to, for example, only the formation of the aluminosilicates. Infrared spectra show that sodium uranates, uranium silicates, and other uranium solids are formed during the synthesis of sodium aluminosilicates structures in the presence of uranium. Both amorphous and sodalite aluminosilicate phases, unlike the zeolite A phase, show appreciable affinity for uranium incorporation during their formation in the presence of uranium.

  2. High temperature alkali corrosion of ceramics in coal gas

    SciTech Connect

    Pickrell, G.R.; Sun, T.; Brown, J.J.

    1992-05-27

    High temperature alkali corrosion has been known to cause premature failure of ceramic components used in advanced high temperature coal combustion systems such as coal gasification and clean-up, coal fired gas turbines, and high efficiency heat engines. The objective of this research is to systematically evaluate the alkali corrosion resistance of the most commonly used structural ceramics including silicon carbide, silicon nitride, cordierite, mullite, alumina, aluminum titanate, zirconia, and fireclay glass. The study consists of identification of the alkali reaction products (phase equilibria) and the kinetics of the alkali reactions as a function of temperature and time.

  3. High temperature alkali corrosion of ceramics in coal gas

    SciTech Connect

    Pickrell, G.R.; Sun, T.; Brown, J.J.

    1991-11-30

    High temperature alkali corrosion has been known to cause premature failure of ceramic components used in advanced high temperature coal combustion systems such as coal gasification and clean-up, coal fired gas turbines, and high efficiency heat engines. The objective of this program is to systematically evaluate the alkali corrosion resistance of the most commonly used structural ceramics including silicon carbide, silicon nitride, cordierite, mullite, alumina, aluminum titanate, zirconia, and fireclay glass. The study consists of identification of the alkali reaction products (phase equilibria) and the kinetics of the alkali reactions as a function of temperature and time.

  4. High temperature alkali corrosion of ceramics in coal gas

    SciTech Connect

    Pickrell, G.R.; Sun, T.; Brown, J.J.

    1992-08-29

    High temperature alkali corrosion has been known to cause premature failure of ceramic components used in advanced high temperature coal combustion systems such as coal gasification and clean-up, coal fired gas turbines, and high efficiency heat engines. The objective of this research is to systematically evaluate the alkali corrosion resistance of the most commonly used structural ceramics including silicon carbide, silicon nitride, cordierite, mullite, alumina, aluminum titanate, zirconia, and fireclay glass. The study consists of identification of the alkali reaction products (phase equilibria) and the kinetics of the alkali reactions as a function of temperature and time.

  5. Electrochemical devices utilizing molten alkali metal electrode-reactant

    DOEpatents

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

    1985-07-10

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

  6. Electrochemical devices utilizing molten alkali metal electrode-reactant

    DOEpatents

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

    1986-01-01

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

  7. Solubility and solution mechanisms of chlorine in aluminosilicate melts at high pressure and high temperature

    NASA Astrophysics Data System (ADS)

    Dalou, C.; Mysen, B. O.

    2012-12-01

    We address the effect of alkalies and aluminum on the solution behavior of Cl by combining solubility measurements of Cl and Raman data of Cl-bearing peralkaline aluminosilicate glasses (quenched melt). Six compositions along the join Na2Si3O7(NS3)-Na2(NaAl)3O7 and six compositions along the join K2Si3O7(KS3)-K2(KAl)3O7 were used. In order to isolate potential effects of Al/(Al+Si) from changes on melt polymerization, Al2O3 was exchanged with SiO2 in a charge-balanced form, NaAlO2 and KaAlO2 thus keeping approximately constant NBO/T (0.65 ± 0.02) for all melts (assuming Al3+ in 4-fold coordination in the melts). Starting materials were doped with 5wt% Cl in the form of PdCl2, which releases Cl2 as its gaseous phase during experiment. Samples were synthetized on piston-cylinder apparatus at 1600°C - 1.5 GPa. At the end of the experiments, Pd forms little spheres (1-2 μm) that for most part dissolves into the capsule. Chlorine oversaturation in the melts is ensured by the observation of bubbles in the quenched samples. The Cl solubility in Na-bearing systems is about twice that of the than in K-bearing system and may, therefore, be negatively correlated with ionic radius of the metal cation.. The solubility also decreases with Al/(Al+Si). In NS3 system, it decreases from 4.01 ± 0.13 wt% of Cl in Al-free systems to 1.87 ± 0.19 wt% of Cl for an Al/Al+Si ratio of 0.34. In KS3 system, this decrease is from 2.23 ± 0.08 wt% of Cl in Al-free systems to 0.62 ± 0.05 wt% of Cl for an Al/Al+Si ratio of 0.36. In Al-free systems, preliminary Raman data show the appearance of a peak around 465cm-1, that we assigned to alkali-Cl bonding. The intensity of this 465cm-1 peak increases with Al content confirming the role of Al in Cl solution mechanism.We also identify the molecular Cl peak at 1540cm-1. The peak can be detected only in Al-bearing melts. The Al substitution for Si results in increased abundance of three-dimensional cages on the melt structure into which molecular

  8. Calcium-magnesium Aluminosilicate (CMAS) Interactions with Advanced Environmental Barrier Coating Material

    NASA Technical Reports Server (NTRS)

    Wiesner, Valerie L.; Bansal, Narottam P.

    2015-01-01

    Particulates, like sand and volcanic ash, threaten the development of robust environmental barrier coatings (EBCs) that protect next-generation silicon-based ceramic matrix composite (CMC) turbine engine components from harsh combustion environments during service. The siliceous particulates transform into molten glassy deposits of calcium-magnesium aluminosilicate (CMAS) when ingested by an aircraft engine operating at temperatures above 1200C. In this study, a sample of desert sand was melted into CMAS glass to evaluate high-temperature interactions between the sand glass and an advanced EBC material. Desert sand glass was added to the surface of hot-pressed EBC substrates, which were then heated in air at temperatures ranging from 1200C to 1500C. Scanning electron microscopy and X-ray energy-dispersive spectroscopy were used to evaluate microstructure and phase compositions of specimens and the CMASEBC interface after heat treatments.

  9. Use of precalciners to remove alkali from raw materials in the cement industry. Final report, July 1978-July 1980

    SciTech Connect

    Gartner, E.M.

    1980-07-01

    The objective of this work was to develop an efficient means of removing alkali metal compounds (alkalies) from high-alkali aluminosilicate raw materials of the type commonly used as part of cement raw mixes in order to increase the energy efficiency of cement manufacture. The intention of this project was to determine whether the high-alkali raw materials could be pyroprocessed separately to remove the alkalies before they entered the rotary kiln, where they would be mixed with the other raw feed components. If this could be achieved, considerable savings could be made in the energy required to remove alkalies, compared to conventional methods in which the cement raw mix must be treated as a whole. Two different methods of alkali removal were examined, namely, vaporization of alkalies at relatively low temperatures; and alkali-rich melt separation at relativey high temperatures. The results showed that the removal of alkalies by pyroprocessing of high-alkali raw feed components separate from the other cement raw mix components is not likely to be a practical alternative to the best available conventional precalciner technology. (LCL)

  10. Uranium and Aluminosilicate Surface Precipitation Tests

    SciTech Connect

    Hu, M.Z.

    2002-11-27

    The 2H evaporator at the Savannah River Site has been used to treat an aluminum-rich waste stream from canyon operations and a silicon-rich waste stream from the Defense Waste Processing Facility. The formation of aluminosilicate scale in the evaporator has caused significant operational problems. Because uranium has been found to accumulate in the aluminosilicate solids, the scale deposition has introduced criticality concerns as well. The objective of the tests described in this report is to determine possible causes of the uranium incorporation in the evaporator scale materials. The scope of this task is to perform laboratory experiments with simulant solutions to determine if (1) uranium can be deposited on the surfaces of various sodium aluminosilicate (NAS) forms and (2) aluminosilicates can form on the surfaces of uranium-containing solids. Batch experiments with simulant solutions of three types were conducted: (1) contact of uranium solutions/sols with NAS coatings on stainless steel surfaces, (2) contact of uranium solutions with NAS particles, and (3) contact of precipitated uranium-containing particles with solutions containing aluminum and silicon. The results show that uranium can be incorporated in NAS solids through encapsulation in bulk agglomerated NAS particles of different phases (amorphous, zeolite A, sodalite, and cancrinite) as well as through heterogeneous deposition on the surfaces of NAS coatings (amorphous and cancrinite) grown on stainless steel. The results also indicate that NAS particles can grow on the surfaces of precipitated uranium solids. Particularly notable for evaporator operations is the finding that uranium solids can form on existing NAS scale, including cancrinite solids. If NAS scale is present, and uranium is in sufficient concentration in solution to precipitate, a portion of the uranium can be expected to become associated with the scale. The data obtained to date on uranium-NAS affinity are qualitative. A necessary

  11. Evaluation of Uranium Co-precipitations with Sodium Aluminosilicate Phases

    SciTech Connect

    Oji, L.N.

    2003-06-24

    This paper describes batch laboratory experiments performed to evaluate uranium incorporation into aluminosilicate structures during synthesis. This research was conducted in response to plant problems related to the accumulation of uranium with aluminosilicates in low-level radioactive waste evaporators. We have found that conditions which favor precipitation of aluminosilicates also foster uranium solid precipitation, so it is difficult to attribute problems with uranium accumulation to say just the formation of the aluminosilicates. Infrared spectra shows that sodium uranates, uranium silicates and other uranium solids are formed during the synthesis of sodium aluminosilicates structures in the presence of uranium. Both amorphous and sodalite aluminosilcate phases, unlike zeolite A phase, show appreciable affinity for uranium incorporation during their formation in the presence of uranium.

  12. 29Si NMR study of structural ordering in aluminosilicate geopolymer gels.

    PubMed

    Duxson, Peter; Provis, John L; Lukey, Grant C; Separovic, Frances; van Deventer, Jannie S J

    2005-03-29

    A systematic series of aluminosilicate geopolymer gels was synthesized and then analyzed using 29Si magic-angle spinning nuclear magnetic resonance (MAS NMR) in combination with Gaussian peak deconvolution to characterize the short-range ordering in terms of T-O-T bonds (where T is Al or Si). The effect of nominal Na2O/(Na2O + K2O) and Si/Al ratios on short-range network ordering was quantified by deconvolution of the 29Si MAS NMR spectra into individual Gaussian peaks representing different Q4(mAl) silicon centers. The deconvolution procedure developed in this work is applicable to other aluminosilicate gel systems. The short-range ordering observed here indicates that Loewenstein's Rule of perfect aluminum avoidance may not apply strictly to geopolymeric gels, although further analyses are required to quantify the degree of aluminum avoidance. Potassium geopolymers appeared to exhibit a more random Si/Al distribution compared to that of mixed-alkali and sodium systems. This work provides a quantitative account of the silicon and aluminum ordering in geopolymers, which is essential for extending our understanding of the mechanical strength, chemical and thermal stability, and fundamental structure of these systems.

  13. Nanostructure of gel-derived aluminosilicate materials.

    PubMed

    Sinkó, Katalin; Hüsing, Nicola; Goerigk, Günter; Peterlik, Herwig

    2008-02-01

    In the present work, aluminosilicate aerogels prepared under various conditions were compared with respect to their nanostructures and porosity. The purpose of this investigation was to find a suitable way to predict the final product structure and to tailor a required texture. Several Al and Si precursors (Al nitrate, Al isopropoxide, Al acetate, tetraethoxysilane (TEOS), and sodium silicate) were used in our examinations; the solvent content (water and alcohols), surfactants, as well as the catalysts were varied. In addition, the aerogels were subjected to various heat treatments. Hybrid aerogels were synthesized by the addition of different polymers (poly(acrylic acid), polyvinyl acetate, and polydimethylsiloxane). Aluminosilicate and hybrid aerogel structures were investigated by 27Al MAS NMR, SAXS, SEM, and porosity measurements. Loose fractal structures with a good porosity and high Al incorporation can be achieved from TEOS and Al nitrate or isopropoxide via a sol-gel preparation route. The use of Al acetate led to compact aerogel structures independently of the Si precursor, the pH, and the catalyst.

  14. Calculation of the 13C NMR shieldings of the C0 2 complexes of aluminosilicates

    NASA Astrophysics Data System (ADS)

    Tossell, J. A.

    1995-04-01

    13C NMR shieldings have been calculated using the random-phase-approximation, localized-orbital local-origins version of ab initio coupled Hartree-Fuck perturbation theory for CO 2 and and for several complexes formed by the reaction of CO 2 with molecular models for aluminosilicate glasses, H 3TOT'H3 3-n, T,T' = Si,Al. Two isomeric forms of the CO 2-aluminosilicate complexes have been considered: (1) "CO 2-like" complexes, in which the CO 2 group is bound through carbon to a bridging oxygen and (2) "CO 3-like" complexes, in which two oxygens of a central CO 3 group form bridging bonds to the two TH 3 groups. The CO 2-like isomer of CO 2-H 3SiOSiH 3 is quite weakly bonded and its 13C isotropic NMR shielding is almost identical to that in free CO 2. As Si is progressively replaced by Al in the - H terminated aluminosilicate model, the CO 2-like isomers show increasing distortion from the free CO 2 geometry and their 13C NMR shieldings decrease uniformly. The calculated 13C shielding value for H 3AlO(CO 2)AlH 3-2 is only about 6 ppm larger than that calculated for point charge stabilized CO 3-2. However, for a geometry of H 3SiO(CO 2) AlH 3-1, in which the bridging oxygen to C bond length has been artificially increased to that found in the - OH terminated cluster (OH) 3SiO(CO 2)Al(OH) 3-1, the calculated 13C shielding is almost identical to that for free CO 2. The CO 3-like isomers of the CO 2-aluminosili-cate complexes show carbonate like geometries and 13C NMR shieldings about 4-9 ppm larger than those of carbonate for all T,T' pairs. For the Si,Si tetrahedral atom pair the CO 2-like isomer is more stable energetically, while for the Si,Al and Al,Al cases the CO 3-like isomer is more stable. Addition of Na + ions to the CO 3-2 or H 3AlO(CO 2)AlH 3-2 complexes reduces the 13C NMR shieldings by about 10 ppm. Complexation with either Na + or CO 2 also reduces the 29Si NMR shieldings of the aluminosilicate models, while the changes in 27Al shielding with Na + or CO 2

  15. Characterization of Uranium Solids Precipitated with Aluminosilicates

    SciTech Connect

    DUFF, MC

    2004-04-29

    At the Savannah River Site (SRS), the High-Level Waste (HLW) Tank Farms store and process high-level liquid radioactive wastes from the Canyons and recycle water from the Defense Waste Processing Facility. The waste is concentrated using evaporators to minimize the volume of space required for HLW storage. Recently, the 2H Evaporator was shutdown due to the crystallization of sodium aluminosilicate (NAS) solids (such as cancrinite and sodalite) that contained close to 10 weight percent of elementally-enriched uranium (U). Prior to extensive cleaning,the evaporator deposits resided on the evaporator walls and other exposed internal surfaces within the evaporator pot. Our goal is to support the basis for the continued safe operation of SRS evaporators and to gain more information that could be used to help mitigate U accumulation during evaporator operation.

  16. Evaluation of the Incorporation of Uranium into Sodium Aluminosilicate Phases

    SciTech Connect

    Oji, L.N.

    2003-03-26

    This report describes batch laboratory experiments performed to determine the relative amounts of uranium incorporated in aluminosilicate structures during synthesis. The findings summarized here are based on laboratory experiments, which involved the synthesis of sodium aluminosilicates (NAS) structures, amorphous, zeolites A and sodalite phases in the presence of depleted uranium and the analytical search for incorporated uranium in NAS internal structures after synthesis. These studies will support the basis for continued operation of evaporators at the Savannah River Site (SRS).

  17. Stabilization/solidification of hazardous and radioactive wastes with alkali-activated cements.

    PubMed

    Shi, Caijun; Fernández-Jiménez, A

    2006-10-11

    This paper reviews progresses on the use of alkali-activated cements for stabilization/solidification of hazardous and radioactive wastes. Alkali-activated cements consist of an alkaline activator and cementing components, such as blast furnace slag, coal fly ash, phosphorus slag, steel slag, metakaolin, etc., or a combination of two or more of them. Properly designed alkali-activated cements can exhibit both higher early and later strengths than conventional portland cement. The main hydration product of alkali-activated cements is calcium silicate hydrate (CSH) with low Ca/Si ratios or aluminosilicate gel at room temperature; CSH, tobmorite, xonotlite and/or zeolites under hydrothermal condition, no metastable crystalline compounds such as Ca(OH)(2) and calcium sulphoaluminates exist. Alkali-activated cements also exhibit excellent resistance to corrosive environments. The leachability of contaminants from alkali-activated cement stabilized hazardous and radioactive wastes is lower than that from hardened portland cement stabilized wastes. From all these aspects, it is concluded that alkali-activated cements are better matrix for solidification/stabilization of hazardous and radioactive wastes than Portland cement.

  18. Secondary Waste Form Screening Test Results—Cast Stone and Alkali Alumino-Silicate Geopolymer

    SciTech Connect

    Pierce, Eric M.; Cantrell, Kirk J.; Westsik, Joseph H.; Parker, Kent E.; Um, Wooyong; Valenta, Michelle M.; Serne, R. Jeffrey

    2010-06-28

    PNNL is conducting screening tests on the candidate waste forms to provide a basis for comparison and to resolve the formulation and data needs identified in the literature review. This report documents the screening test results on the Cast Stone cementitious waste form and the Geopolymer waste form. Test results suggest that both the Cast Stone and Geopolymer appear to be viable waste forms for the solidification of the secondary liquid wastes to be treated in the ETF. The diffusivity for technetium from the Cast Stone monoliths was in the range of 1.2 × 10-11 to 2.3 × 10-13 cm2/s during the 63 days of testing. The diffusivity for technetium from the Geopolymer was in the range of 1.7 × 10-10 to 3.8 × 10-12 cm2/s through the 63 days of the test. These values compare with a target of 1 × 10-9 cm2/s or less. The Geopolymer continues to show some fabrication issues with the diffusivities ranging from 1.7 × 10-10 to 3.8 × 10-12 cm2/s for the better-performing batch to from 1.2 × 10-9 to 1.8 × 10-11 cm2/s for the poorer-performing batch. In the future more comprehensive and longer term performance testing will be conducted, to further evaluate whether or not these waste forms will meet the regulation and performance criteria needed to cost-effectively dispose of secondary wastes.

  19. Carbon dioxide in silica-undersaturated melt Part II: Effect of CO2 on quenched glass structure

    NASA Astrophysics Data System (ADS)

    Morizet, Yann; Paris, Michael; Gaillard, Fabrice; Scaillet, Bruno

    2014-11-01

    Despite CO2 is the second most abundant volatile species implied in magmatic systems, its impact on the molecular structure of aluminosilicate glasses in complex systems is currently not well-constrained. Inasmuch, whether CO2 induces an increase in glass polymerization or not is yet not clear for complex glass compositions. Using the set of nephelinite glass samples investigated in Part I (Morizet et al., 2014), in which the CO2 solubility and speciation have been constrained as a function of the #K (molar K2O/K2O + Na2O), we have conducted a thorough investigation of the change in the silicate network structure associated to CO2 dissolution. The change in silicate structure has been studied as a function of volatiles solubility (CO2 up to 4.5 wt.%, H2O up to 3 wt.%) as well as a function of the #K (between 0 and 0.75) of the glasses. We used 29Si Solid-State NMR for probing the silicon local environment in the quenched glasses. We observe that in such depolymerized nephelinite compositions the exchange between Na and K in volatile-free glasses induces a change in the glass structure attributed to the Mixed Alkali Effect (MAE) invoked in previous works. The observed changes might be related to geometric changes in the glass structure (change in network species bond lengths or angles). The addition of H2O only produces a negligible change in the degree of polymerization being probed by the constant NBO/T (Non-Bridging Oxygen per Tetrahedron) as H2O is added to volatile-free glasses. In contrast, we observed that the addition of CO2 induces a strong change in the glass structure which might be interpreted as an increase in polymerization. Alternatively, considering the identified CO2 dissolution mechanism (mostly as non-bridging carbonates units), the glass structure changes might reflect an apparent glass polymerization through the creation of Si-O-C bonds rather a true polymerization through the creation of Si-O-Si bonds.

  20. Channel waveguides in glass via silver-sodium field-assisted ion exchange

    NASA Technical Reports Server (NTRS)

    Forrest, K.; Pagano, S. J.; Viehmann, W.

    1986-01-01

    Multimode channel waveguides have been formed in sodium aluminosilicate glass by field-assisted diffusion of Ag(+) ions from vacuum-evaporated Ag films. The two-dimensional refractive index profiles of the waveguides were controlled by varying the diffusion time, the diffusion temperature, and the electric field strength. Estimates of the diffusion rate through a strip aperture were obtained, assuming the electric field was strong 120-240 V/mm. The maximum change in refractive index in the sodium aluminosilicate glasses was estimated near 65 percent of the change in soda-lime silicate glass. The physical properties of the glasses are given in a table.

  1. Alkali metal ionization detector

    DOEpatents

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

    1978-01-01

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

  2. Catalytic pyrolysis using UZM-44 aluminosilicate zeolite

    SciTech Connect

    Nicholas, Christopher P; Boldingh, Edwin P

    2013-12-17

    A new family of aluminosilicate zeolites designated UZM-44 has been synthesized. These zeolites are represented by the empirical formula Na.sub.nM.sub.m.sup.k+T.sub.tAl.sub.1-xE.sub.xSi.sub.yO.sub.z where "n" is the mole ratio of Na to (Al+E), M represents a metal or metals from zinc, Group 1, Group 2, Group 3 and or the lanthanide series of the periodic table, "m" is the mole ratio of M to (Al+E), "k" is the average charge of the metal or metals M, T is the organic structure directing agent or agents, and E is a framework element such as gallium. The process involves contacting a carbonaceous biomass feedstock with UZM-44 at pyrolysis conditions to produce pyrolysis gases comprising hydrocarbons. The catalyst catalyzes a deoxygenation reaction converting oxygenated hydrocarbons into hydrocarbons and removing the oxygen as carbon oxides and water. A portion of the pyrolysis gases is condensed to produce low oxygen biomass-derived pyrolysis oil.

  3. Catalytic pyrolysis using UZM-44 aluminosilicate zeolite

    SciTech Connect

    Nicholas, Christopher P; Boldingh, Edwin P

    2014-04-29

    A new family of aluminosilicate zeolites designated UZM-44 has been synthesized. These zeolites are represented by the empirical formula. Na.sub.nM.sub.m.sup.k+T.sub.tAl.sub.1-xE.sub.xSi.sub.yO.sub.z where "n" is the mole ratio of Na to (Al+E), M represents a metal or metals from zinc, Group 1, Group 2, Group 3 and or the lanthanide series of the periodic table, "m" is the mole ratio of M to (Al+E), "k" is the average charge of the metal or metals M, T is the organic structure directing agent or agents, and E is a framework element such as gallium. The process involves contacting a carbonaceous biomass feedstock with UZM-44 at pyrolysis conditions to produce pyrolysis gases comprising hydrocarbons. The catalyst catalyzes a deoxygenation reaction converting oxygenated hydrocarbons into hydrocarbons and removing the oxygen as carbon oxides and water. A portion of the pyrolysis gases is condensed to produce low oxygen biomass-derived pyrolysis oil.

  4. Characterization of Uranium Solids Precipitated with Aluminosilicates

    SciTech Connect

    DUFF, MC

    2004-01-09

    At the Savannah River Site (SRS), the High-Level Waste (HLW) Tank Farms store and process high-level liquid radioactive wastes from the Canyons and recycle water from the Defense Waste Processing Facility. The waste is concentrated using evaporators to minimize the volume of space required for HLW storage. Recently, the 2H Evaporator was shutdown due to the crystallization of sodium aluminosilicate (NAS) solids (such as cancrinite and sodalite) that contained close to 10 weight percent of elementally-enriched uranium (U). Prior to extensive cleaning,the evaporator deposits resided on the evaporator walls and other exposed internal surfaces within the evaporator pot. Our goal is to support the basis for the continued safe operation of SRS evaporators and to gain more information that could be used to help mitigate U accumulation during evaporator operation. To learn more about the interaction between U(VI) and NAS in HLW salt solutions, we performed several fundamental studies to examine the mechanisms of U accumulation with NAS in highly caustic solutions. This larger group of studies focused on the following processes: co-precipitation/structural incorporation, sorption, and precipitation (with or without NAS), which will be reviewed in this presentation. We will present and discuss local atomic structural characterization data about U that has been co-precipitated with NAS solids (such as amorphous zeolite precursor material and sodalite) using X-ray absorption fine-structure (XAFS) spectroscopic techniques.

  5. Uranium Sorption on Sodium Aluminosilicates and Gibbsite

    SciTech Connect

    Duff, M.C.

    2003-02-11

    At the Savannah River Site (SRS), the High-Level Waste (HLW) Tank Farms store and process high-level liquid radioactive wastes from the Canyons and recycle water from the Defense Waste Processing Facility (DWPF). The waste is concentrated using evaporators to minimize the volume of space required for HLW storage. After evaporation, the waste concentrate is transferred to one or more receipt storage tanks. Recently, the 2H Evaporator was shutdown due to the crystallization of sodium aluminosilicates (NAS) solids that contained elementally enriched uranium (U) precipitates. The scale deposits resided on the evaporator walls and other exposed internal surfaces within the evaporator pot. Little is known about U interactions with NAS in HLW solutions. Hence, this research was conducted to improve our basic understanding of one possible mechanism for U accumulation in the evaporators and in other SRS process areas. These studies will help support the basis for the continued safe operation of SRS evaporators and provide information on other issues associated with U behavior in the tank farms. For example, the knowledge of such fundamental information could help mitigate U accumulation during evaporator operation and optimize saltcake dissolution.

  6. Boron Nitride Nanotubes-Reinforced Glass Composites

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam; Hurst, Janet B.; Choi, Sung R.

    2005-01-01

    Boron nitride nanotubes of significant lengths were synthesized by reaction of boron with nitrogen. Barium calcium aluminosilicate glass composites reinforced with 4 weight percent of BN nanotubes were fabricated by hot pressing. Ambient-temperature flexure strength and fracture toughness of the glass-BN nanotube composites were determined. The strength and fracture toughness of the composite were higher by as much as 90 and 35 percent, respectively, than those of the unreinforced glass. Microscopic examination of the composite fracture surfaces showed pullout of the BN nanotubes. The preliminary results on the processing and improvement in mechanical properties of BN nanotube reinforced glass matrix composites are being reported here for the first time.

  7. Electromagnetic and Mechanical Properties of Silica-Aluminosilicates Plasma Sprayed Composite Coatings

    NASA Astrophysics Data System (ADS)

    Cipri, F.; Bartuli, C.; Valente, T.; Casadei, F.

    2007-12-01

    The physico-chemical and thermo-mechanical properties of aluminosilicate ceramics (high-melting point, low thermal expansion coefficient, excellent thermal shock resistance, low-density and good corrosion resistance) make this class of materials a good option for high-temperature structural applications. Al2O3-SiO2 compounds show an excellent refractory behavior allowing a wide use as wear-resistant thermal barrier coatings, in metallurgical and glass plants and in high temperature heat exchangers. Moreover, the low values of thermal expansion coefficient and of complex permittivity allow to extend the use of this ceramic for microelectronic devices, radome for antennas and electromagnetic windows for microwaves and infrared. The present article presents the results of an extensive experimental activity carried out to produce thick aluminosilicate coatings by plasma-spray technique. The APS deposition parameters were optimized on the basis of a surface response approach, as specified by design of experiments (DoE) methodologies. Samples were tested for phase composition, total porosity, microstructure, microhardness, deposition efficiency, fracture toughness, and modulus of rupture. Finally, coatings were characterized for their particularly interesting electromagnetic properties: complex permittivity was measured at microwave frequency using a network analyzer with wave guide.

  8. The effect of TiO2/aluminosilicate nanocomposite additives on the mechanical and thermal properties of polyacrylic coatings

    NASA Astrophysics Data System (ADS)

    Nosrati, Rahimeh; Olad, Ali

    2015-12-01

    The commercial grade polyacrylic latex was modified in order to prepare a mechanical and thermal improved coating. TiO2/Ag-exchanged-aluminosilicate nanocomposites with montmorillonite, zeolite-A and clinoptilolite aluminosilicates were prepared and used as additive in the matrix of polyacrylic latex to achieve a coating with proper mechanical and thermal properties. X-ray diffraction patterns and FESEM were used to characterize the composition, structure, and morphology of the nanocomposite additives. Polyacrylic coatings modified by TiO2/Ag-exchanged-aluminosilicate nanocomposite additives showed higher adhesion strength and hardness compared to unmodified commercial grade polyacrylic coatings. Differential Scanning Calorimetry (DSC) analysis showed lower glass transition temperature for modified polyacrylic coatings than that of unmodified polyacrylic coatings. The tensile tests were also carried out for unmodified and modified polyacrylic coatings. According to the results, the modified polyacrylic based coating with TiO2/Ag-exchanged-clinoptilolite nanocomposite additive was the best coating considering most of useful properties.

  9. Spectroscopic studies of aluminosilicate formation in tank waste simulants

    SciTech Connect

    Su, Y.; Wang, L.; Bunker, B.C.; Windisch, C.F.

    1997-12-31

    Aluminosilicates are one of the major class of species controlling the volume of radioactive high-level waste that will be produced from future remediation at Hanford site. Here the authors present studies of the phases and structures of aluminosilicates as a function of sludge composition using X-ray powder diffraction, solid state {sup 27}Al and {sup 29}Si NMR, and Raman spectroscopy. The results show that the content of NaNO{sub 3} in solution has significant effects on the nature of the insoluble aluminosilicate phases produced. It was found that regardless of the initial Si:Al ratio, nitrate cancrinite was the main phase formed in the solution with pH of 13.5 and 5 M NaNO{sub 3}. However, at lower NaNO{sub 3} concentration with initial Si:Al ratios of 1.1, 2.2, and 11.0 in the solutions, a range of aluminosilicate zeolites was produced with Si:Al ratios of 1.1, 1.3, and 1.5, respectively. Lowering the solution pH appears to promote the formation of amorphous aluminosilicates. The results presented here are important for the prediction of the solubility and dissolution rate of Al in tank wastes.

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

    NASA Technical Reports Server (NTRS)

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

    1966-01-01

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

  11. Mesostructured silica and aluminosilicate carriers for oxytetracycline delivery systems.

    PubMed

    Berger, D; Nastase, S; Mitran, R A; Petrescu, M; Vasile, E; Matei, C; Negreanu-Pirjol, T

    2016-08-30

    Oxytetracycline delivery systems containing various MCM-type silica and aluminosilicate with different antibiotic content were developed in order to establish the influence of the support structural and textural properties and aluminum content on the drug release profile. The antibiotic molecules were loaded into the support mesochannels by incipient wetness impregnation method using a drug concentrated aqueous solution. The carriers and drug-loaded materials were investigated by small- and wide-angle XRD, FTIR spectroscopy, TEM and N2 adsorption-desorption isotherms. Faster release kinetics of oxytetracycline from uncalcined silica and aluminosilicate supports was observed, whereas higher drug content led to lower delivery rate. The presence of aluminum into the silica network also slowed down the release rate. The antimicrobial assays performed on Staphylococcus aureus clinical isolates showed that the oxytetracycline-loaded materials containing MCM-41-type mesoporous silica or aluminosilicate carriers inhibited the bacterial development. PMID:26861688

  12. Mesostructured silica and aluminosilicate carriers for oxytetracycline delivery systems.

    PubMed

    Berger, D; Nastase, S; Mitran, R A; Petrescu, M; Vasile, E; Matei, C; Negreanu-Pirjol, T

    2016-08-30

    Oxytetracycline delivery systems containing various MCM-type silica and aluminosilicate with different antibiotic content were developed in order to establish the influence of the support structural and textural properties and aluminum content on the drug release profile. The antibiotic molecules were loaded into the support mesochannels by incipient wetness impregnation method using a drug concentrated aqueous solution. The carriers and drug-loaded materials were investigated by small- and wide-angle XRD, FTIR spectroscopy, TEM and N2 adsorption-desorption isotherms. Faster release kinetics of oxytetracycline from uncalcined silica and aluminosilicate supports was observed, whereas higher drug content led to lower delivery rate. The presence of aluminum into the silica network also slowed down the release rate. The antimicrobial assays performed on Staphylococcus aureus clinical isolates showed that the oxytetracycline-loaded materials containing MCM-41-type mesoporous silica or aluminosilicate carriers inhibited the bacterial development.

  13. Nanoscale encapsulation: the structure of cations in hydrophobic microporous aluminosilicates

    SciTech Connect

    Wasserman, S.R.; Yuchs, S.E.; Giaquinta, D.; Soderholm, L.; Song, Kang

    1996-10-01

    Hydrophobic microporous aluminosilicates, created by organic surface modification of inherently hydrophilic materials such as zeolites and clays, are currently being investigated as storage media for hazardous cations. Use of organic monolayers to modify the surface of an aluminosilicate after introducing an ion into the zeolite/clay reduces the interaction of water with the material. Resulting systems are about 20 times more resistant to leaching of stored ion. XAS spectra from the encapsulated ion demonstrate that byproducts from the organic modifier can complex with the stored cation. This complexation can result in a decreased affinity of the cation for the aluminosilicate matrix. Changing the organic modifier eliminates this problem. XAS spectra also indicate that the reactivity and speciation of the encapsulated ion may change upon application of the hydrophobic layer.

  14. Analysis of early medieval glass beads - Glass in the transition period

    NASA Astrophysics Data System (ADS)

    Šmit, Žiga; Knific, Timotej; Jezeršek, David; Istenič, Janka

    2012-05-01

    Glass beads from graves excavated in Slovenia and dated archaeologically to the 7th-10th century AD were analysed by the combined PIXE-PIGE method. The results indicate two groups of glass; natron glass made in the Roman tradition and glass made with alkalis from the ash of halophytic plants, which gradually replaced natron glass after c. 800 AD. The alkalis used in the second group of glass seem to be in close relation to a variant of the Venetian white glass that appeared several centuries later. The origin of this glass may be traced to glass production in Mesopotamia and around the Aral Sea. All the mosaic beads with eye decoration, as well as most of the drawn-segmented and drawn-cut beads analysed, are of plant-ash glass, which confirms their supposed oriental origin.

  15. Synthesis and characterization of aluminosilicate catalyst impregnated by nickel oxide

    NASA Astrophysics Data System (ADS)

    Maulida, Iffana Dani; Sriatun, Taslimah

    2015-09-01

    Aluminosilicate as a catalyst has been synthesized by pore-engineering using CetylTrimethylAmmonium-Bromide (CTAB) as templating agent. It can produce bigger aluminosilicate pore therefore it will be more suitable for bulky molecule. The aims of this research are to synthesize aluminosilicate supported by Nickel, using CTAB surfactant as templating agent for larger pore radius than natural zeolite and characterize the synthesis product, consist of total acid sites and surface area characteristic. This research has been done with following steps. First, making sodium silicate and sodium aluminate. Second, aluminosilicate was synthesized by direct methods, calcined at 550, 650 and 750°C variation temperature, characterized product by X-RD and FTIR spectrometer. Third, NiCl2 was impregnated to the aluminosilicate that has the best cristallinity and main TO4 functional groups product (550 sample). Variation of NiCl2:aluminosilicate (w/w) ratio were 25%:75%, 50%:50% and 75%:25%. Last but not least characterization of catalytic properties was performed. It comprised total acidity test (gravimetric method) and Surface Area Analyzer. The result shows that the product synthesized by direct method at 550oC calcination temperature has the best cristallinity and main functional groups of TO4. The highest total acid sites was 31.6 mmole/g (Imp-A sample). Surface Area Analyzer shows that Imp-B sample has the best pore distribution and highest total pore volume and specific surface area with value 32.424 cc/g and 46.8287 m2/g respectively. We can draw the conclusion that the most potential catalyst is Imp-A sample compared to Imp-B and Imp-C because it has the highest total acid sites. However the most effective catalyst used for product selectivity was Imp-B sample among all samples.

  16. Replacement of glass in the Nakhla meteorite by berthierine: Implications for understanding the origins of aluminum-rich phyllosilicates on Mars

    NASA Astrophysics Data System (ADS)

    Lee, Martin R.; Chatzitheodoridis, Elias

    2016-09-01

    A scanning and transmission electron microscope study of aluminosilicate glasses within melt inclusions from the Martian meteorite Nakhla shows that they have been replaced by berthierine, an aluminum-iron serpentine mineral. This alteration reaction was mediated by liquid water that gained access to the glasses along fractures within enclosing augite and olivine grains. Water/rock ratios were low, and the aqueous solutions were circumneutral and reducing. They introduced magnesium and iron that were sourced from the dissolution of olivine, and exported alkalis. Berthierine was identified using X-ray microanalysis and electron diffraction. It is restricted in its occurrence to parts of the melt inclusions that were formerly glass, thus showing that under the ambient physico-chemical conditions, the mobility of aluminum and silicon were low. This discovery of serpentine adds to the suite of postmagmatic hydrous silicates in Nakhla that include saponite and opal-A. Such a variety of secondary silicates indicates that during aqueous alteration compositionally distinct microenvironments developed on sub-millimeter length scales. The scarcity of berthierine in Nakhla is consistent with results from orbital remote sensing of the Martian crust showing very low abundances of aluminum-rich phyllosilicates.

  17. Replacement of glass in the Nakhla meteorite by berthierine: Implications for understanding the origins of aluminum-rich phyllosilicates on Mars

    NASA Astrophysics Data System (ADS)

    Lee, Martin R.; Chatzitheodoridis, Elias

    2016-07-01

    A scanning and transmission electron microscope study of aluminosilicate glasses within melt inclusions from the Martian meteorite Nakhla shows that they have been replaced by berthierine, an aluminum-iron serpentine mineral. This alteration reaction was mediated by liquid water that gained access to the glasses along fractures within enclosing augite and olivine grains. Water/rock ratios were low, and the aqueous solutions were circumneutral and reducing. They introduced magnesium and iron that were sourced from the dissolution of olivine, and exported alkalis. Berthierine was identified using X-ray microanalysis and electron diffraction. It is restricted in its occurrence to parts of the melt inclusions that were formerly glass, thus showing that under the ambient physico-chemical conditions, the mobility of aluminum and silicon were low. This discovery of serpentine adds to the suite of postmagmatic hydrous silicates in Nakhla that include saponite and opal-A. Such a variety of secondary silicates indicates that during aqueous alteration compositionally distinct microenvironments developed on sub-millimeter length scales. The scarcity of berthierine in Nakhla is consistent with results from orbital remote sensing of the Martian crust showing very low abundances of aluminum-rich phyllosilicates.

  18. Solid oxide fuel cell having a glass composite seal

    SciTech Connect

    De Rose, Anthony J.; Mukerjee, Subhasish; Haltiner, Jr., Karl Jacob

    2013-04-16

    A solid oxide fuel cell stack having a plurality of cassettes and a glass composite seal disposed between the sealing surfaces of adjacent cassettes, thereby joining the cassettes and providing a hermetic seal therebetween. The glass composite seal includes an alkaline earth aluminosilicate (AEAS) glass disposed about a viscous glass such that the AEAS glass retains the viscous glass in a predetermined position between the first and second sealing surfaces. The AEAS glass provides geometric stability to the glass composite seal to maintain the proper distance between the adjacent cassettes while the viscous glass provides for a compliant and self-healing seal. The glass composite seal may include fibers, powders, and/or beads of zirconium oxide, aluminum oxide, yttria-stabilized zirconia (YSZ), or mixtures thereof, to enhance the desirable properties of the glass composite seal.

  19. Aluminosilicate and aluminosilicate based polymer composites: Present status, applications and future trends

    NASA Astrophysics Data System (ADS)

    Lopes, A. C.; Martins, P.; Lanceros-Mendez, S.

    2014-08-01

    Aluminosilicates have traditionally been important materials for applications related to adsorbents, water softeners, catalysis and mechanical and thermal reinforcement due to their high surface area, excellent thermal/hydrothermal stability, high shape-selectivity and superior ion-exchange ability. Recently, their use as polymer fillers has allowed to increasingly extending their application range to innovative areas such as medical and biological fields as well as in sensors, filtration membranes, energy storage and novel catalysis routes. Further, the large versatility and tailoring possibilities of both filler and matrix indicates this area as one of the enabling key technologies of the near future. This work summarizes the main developments up to date in this increasingly interesting field, focuses on the main applications already developed as well as on the key challenges for the near future.

  20. Recycling of aluminosilicate waste: Impact onto geopolymer formation

    NASA Astrophysics Data System (ADS)

    Essaidi, N.; Gharzouni, A.; Vidal, L.; Gouny, F.; Joussein, E.; Rossignol, S.

    2015-07-01

    Geopolymers are innovative ecomaterials resulting from the activation of an aluminosilicate source by an alkaline solution. Their properties depend on the used raw materials. This paper focuses on the possibility to obtain geopolymer materials with aluminosilicate laboratory waste. The effect of these additions on the geopolymer properties was studied by FTIR spectroscopy and mechanical test. It was evidenced a slowdown of the polycondensation reaction as well as the compressive strength due to the addition of laboratory waste which decreases the Si/K ratio of mixture.

  1. Alkali metal ion battery with bimetallic electrode

    SciTech Connect

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

    2015-04-07

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

  2. Methods of recovering alkali metals

    DOEpatents

    Krumhansl, James L; Rigali, Mark J

    2014-03-04

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

  3. XANES and Raman spectrometry on glasses and crystals in the CAS system.

    NASA Astrophysics Data System (ADS)

    Neuville, N.; Cormier, C.; Flank, F.; Massiot, M.

    2003-04-01

    XANES and Raman spectrometry on glasses and crystals in the CAS system. DANIEL R. NEUVILLE1, LAURENT CORMIER2 ANNE-MARIE FLANK3 and DOMINIQUE MASSIOT4 1Laboratoire de physico-chimie des fluides géologiques, IPGP-CNRS-UMR7047, 4 place Jussieu, 75252 Paris 2Laboratoire de Minéralogie et de Cristallographie, Universités PARIS 6 et 7, IPGP, UMR CNRS 7590, 4 place Jussieu, 75252 Paris 3Laboratoire pour l’Utilisation du Rayonnement Electromagnétique, Bat. 209D, B.P. 34, 91898, Orsay Cedex France 4UPR 4212, CNRS-CRMHT1d, avenue de la recherche scientifique F-45071 Orléans Cedex 2. Calcium aluminate and aluminosilicate glasses are attractive materials for a wide range of technical applications due to their highly refractory nature, their excellent optical and mechanical properties. The CaO-Al2O3-SiO2 system (CAS) is remarkable since glasses with very few SiO2 content can be synthesized, contrary to alkali or Mg aluminosilicate glasses. We have synthesized more than 40 different glasses in the CAS system using quenching method and 15 glasses using laser heating. These glasses were studied using a Raman spectrometer T64000 from Jobin-Yvon-Dilor company, X-ray absorption spectroscopy at Si, Al, Ca K edges the SA32 and D44 beamlines at LURE and NMR-700MHz. Cormier et al (2000) have shown using X-ray and neutron diffraction that aluminium is in 4-fold coordination in this ternary system. In this present study, we present Raman and XANES obtained at room temperature for these glasses. On the join SiO2-CaAl2O4 glass, we observed a decrease in Raman frequency with increasing CaAl2O4 content for all the bands. In particular, we observed a big decrease in frequency for the T4 band near 1150 cm-1 assigned to T-O0 in T4 units. This decrease suggests that aluminium substitutes principally for Si4+ in the fully polymerized structural units (TO2) according with Neuville and Mysen (1996). On the join SiO2-Ca3Al2O7 (R=CaO/AL2O3=3), we observed a decrease for all bands with

  4. Glasses, ceramics, and composites from lunar materials

    NASA Technical Reports Server (NTRS)

    Beall, George H.

    1992-01-01

    A variety of useful silicate materials can be synthesized from lunar rocks and soils. The simplest to manufacture are glasses and glass-ceramics. Glass fibers can be drawn from a variety of basaltic glasses. Glass articles formed from titania-rich basalts are capable of fine-grained internal crystallization, with resulting strength and abrasion resistance allowing their wide application in construction. Specialty glass-ceramics and fiber-reinforced composites would rely on chemical separation of magnesium silicates and aluminosilicates as well as oxides titania and alumina. Polycrystalline enstatite with induced lamellar twinning has high fracture toughness, while cordierite glass-ceramics combine excellent thermal shock resistance with high flexural strengths. If sapphire or rutile whiskers can be made, composites of even better mechanical properties are envisioned.

  5. Chlor-Alkali Technology.

    ERIC Educational Resources Information Center

    Venkatesh, S.; Tilak, B. V.

    1983-01-01

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

  6. Effect of silicate modulus and metakaolin incorporation on the carbonation of alkali silicate-activated slags

    SciTech Connect

    Bernal, Susan A.; Mejia de Gutierrez, Ruby; Provis, John L.; Rose, Volker

    2010-06-15

    Accelerated carbonation is induced in pastes and mortars produced from alkali silicate-activated granulated blast furnace slag (GBFS)-metakaolin (MK) blends, by exposure to CO{sub 2}-rich gas atmospheres. Uncarbonated specimens show compressive strengths of up to 63 MPa after 28 days of curing when GBFS is used as the sole binder, and this decreases by 40-50% upon complete carbonation. The final strength of carbonated samples is largely independent of the extent of metakaolin incorporation up to 20%. Increasing the metakaolin content of the binder leads to a reduction in mechanical strength, more rapid carbonation, and an increase in capillary sorptivity. A higher susceptibility to carbonation is identified when activation is carried out with a lower solution modulus (SiO{sub 2}/Na{sub 2}O ratio) in metakaolin-free samples, but this trend is reversed when metakaolin is added due to the formation of secondary aluminosilicate phases. High-energy synchrotron X-ray diffractometry of uncarbonated paste samples shows that the main reaction products in alkali-activated GBFS/MK blends are C-S-H gels, and aluminosilicates with a zeolitic (gismondine) structure. The main crystalline carbonation products are calcite in all samples and trona only in samples containing no metakaolin, with carbonation taking place in the C-S-H gels of all samples, and involving the free Na{sup +} present in the pore solution of the metakaolin-free samples. Samples containing metakaolin do not appear to have the same availability of Na{sup +} for carbonation, indicating that this is more effectively bound in the presence of a secondary aluminosilicate gel phase. It is clear that claims of exceptional carbonation resistance in alkali-activated binders are not universally true, but by developing a fuller mechanistic understanding of this process, it will certainly be possible to improve performance in this area.

  7. Modelling studies of water in crystalline nanoporous aluminosilicates.

    PubMed

    Bougeard, Daniel; Smirnov, Konstantin S

    2007-01-14

    The paper presents a review of molecular modelling studies of hydrated nanoporous aluminosilicates (zeolites and clays) performed during the last decade. A special emphasis is set on the calculation of the dynamical quantities and collective properties of the confined water. Some new results concerning the behaviour of water molecules in the siliceous silicalite and zeolite beta structures are presented.

  8. 27Al-->1H cross-polarization in aluminosilicates.

    PubMed

    Kolodziejski, W; Corma, A

    1994-06-01

    Solid-state nuclear magnetic resonance (NMR) cross-polarization (CP) from 27Al to 1H was set on kaolinite, verified by a variable-contact time experiment and applied to ultrastable zeolite Y. The technique is useful for the selective NMR observation of AlOH sites in aluminosilicates, especially those from extraframework species in zeolites.

  9. Enhancement of ion mobility in aluminosilicate-polyphosphazene nanocomposites

    SciTech Connect

    Hutchison, J.C.; Bissessur, R.; Shriver, D.F.

    1997-09-01

    Nanocomposites of poly(bis-(2(2-methoxyethoxy)ethoxy)phosphazene) (MEEP) or cryptand[2.2.2] with the aluminosilicate Na-montmorillonite (NaMont) were studied to develop new solid electrolytes with high conductivity and a unity cation transport number. An aluminosilicate was chosen because the low basicity of the Si-O-Al framework should minimize ion pairing. To further reduce ion pairing, solvating molecules or polymers such as cryptand[2.2.2] or MEEP were introduced into the aluminosilicate. When compared to pristine Na-montmorillonite, impedance spectroscopy indicates an increase in conductivity of up to 100 for MEEP{center_dot}NaMont intercalates, and of 50 for cryptand[2.2.2]{center_dot}NaMont intercalates. The MEEP{center_dot}NaMont intercalate exhibits high ionic conductivity anisotropy with respect to the montmorillonite layers ({sigma}{sub para.}/{sigma}{sub perp.} = 100), which is consistent with increased tortuosity of the cation diffusion path perpendicular to the structure layers. The temperature dependence of the conductivity suggests that cation transport is coupled to segmental motion of the intercalated polymer, as observed previously for simple polymer-salt complexes. Nanocomposites of solvating polymers or molecules with aluminosilicates provide a promising new direction in solid-state electrolytes.

  10. Hydrothermal alkali metal recovery process

    DOEpatents

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

    1980-01-01

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

  11. Structure and mechanical properties of aluminosilicate geopolymer composites with Portland cement and its constituent minerals

    SciTech Connect

    Tailby, Jonathan; MacKenzie, Kenneth J.D.

    2010-05-15

    The compressive strengths and structures of composites of aluminosilicate geopolymer with the synthetic cement minerals C{sub 3}S, beta-C{sub 2}S, C{sub 3}A and commercial OPC were investigated. All the composites showed lower strengths than the geopolymer and OPC paste alone. X-ray diffraction, {sup 29}Si and {sup 27}Al MAS NMR and SEM/EDS observations indicate that hydration of the cement minerals and OPC is hindered in the presence of geopolymer, even though sufficient water was present in the mix for hydration to occur. In the absence of SEM evidence for the formation of an impervious layer around the cement mineral grains, the poor strength development is suggested to be due to the retarded development of C-S-H because of the preferential removal from the system of available Si because geopolymer formation is more rapid than the hydration of the cement minerals. This possibility is supported by experiments in which the rate of geopolymer formation is retarded by the substitution of potassium for sodium, by the reduction of the alkali content of the geopolymer paste or by the addition of borate. In all these cases the strength of the OPC-geopolymer composite was increased, particularly by the combination of the borate additive with the potassium geopolymer, producing an OPC-geopolymer composite stronger than hydrated OPC paste alone.

  12. Alkaline solution/binder ratio as a determining factor in the alkaline activation of aluminosilicates

    SciTech Connect

    Ruiz-Santaquiteria, C.; Fernandez-Jimenez, A.; Palomo, A.

    2012-09-15

    This study investigates the effect of the alkaline solution/binder (S/B) ratio on the composition and nanostructure of the reaction products generated in the alkaline activation of aluminosilicates. The experiments used two mixtures of fly ash and dehydroxylated white clay and for each of these, varying proportions of the solution components. The alkali activator was an 8 M NaOH solution (with and without sodium silicate) used at three S/B ratios: 0.50, 0.75 and 1.25. The {sup 29}Si, {sup 27}Al MAS NMR and XRD characterisation of the reaction products reveal that for ratios nearest the value delivering suitable paste workability, the reaction-product composition and structure depend primarily on the nature and composition of the starting materials and the alkaline activator used. However, when an excess alkaline activator is present in the system, the reaction products tend to exhibit SiO{sub 2}/Al{sub 2}O{sub 3} ratios of approximately 1, irrespective of the composition of the starting binder or the alkaline activator.

  13. Alkali-vapor lasers

    NASA Astrophysics Data System (ADS)

    Zweiback, J.; Komashko, A.; Krupke, W. F.

    2010-02-01

    We report on the results from several of our alkali laser systems. We show highly efficient performance from an alexandrite-pumped rubidium laser. Using a laser diode stack as a pump source, we demonstrate up to 145 W of average power from a CW system. We present a design for a transversely pumped demonstration system that will show all of the required laser physics for a high power system.

  14. Chemical and mechanical consequences of environmental barrier coating exposure to calcium-magnesium-aluminosilicate.

    SciTech Connect

    Harder, B.; Ramirez-Rico, J.; Almer, J. D.; Kang, L.; Faber, K.

    2011-06-01

    The success of Si-based ceramics as high-temperature structural materials for gas turbine applications relies on the use of environmental barrier coatings (EBCs) with low silica activity, such as Ba{sub 1-x}Sr{sub x}Al{sub 2}Si{sub 2}O{sub 8} (BSAS), which protect the underlying components from oxidation and corrosion in combustion environments containing water vapor. One of the current challenges concerning EBC lifetime is the effect of sandy deposits of calcium-magnesium-aluminosilicate (CMAS) glass that melt during engine operation and react with the EBC, changing both its composition and stress state. In this work, we study the effect of CMAS exposure at 1300 C on the residual stress state and composition in BSAS-mullite-Si-SiC multilayers. Residual stresses were measured in BSAS multilayers exposed to CMAS for different times using high-energy X-ray diffraction. Their microstructure was studied using a combination of scanning electron microscopy and transmission electron microscopy techniques. Our results show that CMAS dissolves the BSAS topcoat preferentially through the grain boundaries, dislodging the grains and changing the residual stress state in the topcoat to a nonuniform and increasingly compressive stress state with increasing exposure time. The presence of CMAS accelerates the hexacelsian-to-celsian phase transformation kinetics in BSAS, which reacts with the glass by a solution-reprecipitation mechanism. Precipitates have crystallographic structures consistent with Ca-doped celsian and Ba-doped anorthite.

  15. Transformation of Aluminosilicate Wet Gel to Solid State

    NASA Astrophysics Data System (ADS)

    Sinkó, Katalin; Pöppl, László

    2002-04-01

    Optically clear, homogeneous, monolithic aluminosilicate gels were prepared directly from solutions of inorganic aluminum salt, tetraethoxysilane, and alcohol. The dried aluminosilicate gels show new special properties, e.g. piezoelectricity and variable porosity (1-2000 m 2/g) due to the fractal-like gel structure. Ceramic products, which keep the chemical bonds and structure of the gels, were produced by heat treatment at 300-350°C. The processes that occurred during heat treatment were investigated by thermal analysis and mass spectrometry. The temperature limits of the gel state were determined by differential scanning calorimetry and small angle X-ray scattering. The collapse of the gel structure began around 350°C; however, the amorphous character remained until the temperature (ca. 970°C) of the phase transmission.

  16. Aluminosilicates and senile plaque formation in Alzheimer's disease.

    PubMed

    Candy, J M; Oakley, A E; Klinowski, J; Carpenter, T A; Perry, R H; Atack, J R; Perry, E K; Blessed, G; Fairbairn, A; Edwardson, J A

    1986-02-15

    Aluminium and silicon were found to be colocalised in the central region of senile plaque cores in studies with energy dispersive X-ray microanalysis. The distribution of these elements was similar in cores isolated from the cerebral cortex of patients with senile dementia of the Alzheimer type and in cores studied in situ from tissue sections from the cerebral cortex of presenile and senile patients with Alzheimer's disease, and elderly, mentally normal patients. High-resolution solid-state nuclear magnetic resonance techniques showed aluminium and silicon to be present as aluminosilicates. The presence of aluminosilicates at the centre of senile plaque cores contrasts with the distribution of other inorganic constituents and suggests that they may be involved in the initiation or early stages of senile plaque formation.

  17. Mesoporous aluminosilicate ropes with improved stability from protozeolitic nanoclusters

    NASA Astrophysics Data System (ADS)

    Zheng, Junlin; Kong, Dejin; Yang, Weimin; Xie, Zaiku; Wu, Dong; Sun, Yuhan

    2007-02-01

    Mesoporous aluminosilicate ropes with improved hydrothermal stability have been prepared through S +X -I + route via self-assembly of protozeolitic nanoclusters with cetyltrimethylammonium bromides (CTAB) template micelles in HNO 3 solution. SEM observation confirmed that high-yield aluminosilicate ropes could be produced under proper HNO 3 concentration. NO 3- ions had strong binding strength to the CTA + ions and tended to form more elongated surfactant micelles, thus fibrous products were fabricated under the direction of these long rod micelles in shearing flow. At the same time, the NO 3- ions combining with CTA + ions generated more active (CTA +NO 3-) assembly, which effectively catalysed the polymerization of protozeolitic nanoclusters with large volume into highly ordered mesostructures. Compared with normal MCM-41 silica synthesized through S +X -I + route in acidic media, the hydrothermal stability was improved considerably. These protozeolitic nanoclusters survived strongly acidic media and entered into mesostructured framework, which contributed to the improvement of hydrothermal stability.

  18. Hard x-ray nanotomography of amorphous aluminosilicate cements.

    SciTech Connect

    Provis, J. L.; Rose, V.; Winarski, R. P.; van Deventer, J. S. J.

    2011-08-01

    Nanotomographic reconstruction of a sample of low-CO{sub 2} 'geopolymer' cement provides the first three-dimensional view of the pore structure of the aluminosilicate geopolymer gel, as well as evidence for direct binding of geopolymer gel onto unreacted fly ash precursor particles. This is central to understanding and optimizing the durability of concretes made using this new class of binder, and demonstrates the value of nanotomography in providing a three-dimensional view of nanoporous inorganic materials.

  19. Gel nanostructure in alkali-activated binders based on slag and fly ash, and effects of accelerated carbonation

    SciTech Connect

    Bernal, Susan A.; Provis, John L.; Walkley, Brant; San Nicolas, Rackel; Gehman, John D.; Brice, David G.; Kilcullen, Adam R.; Duxson, Peter; Deventer, Jannie S.J. van

    2013-11-15

    Binders formed through alkali-activation of slags and fly ashes, including ‘fly ash geopolymers’, provide appealing properties as binders for low-emissions concrete production. However, the changes in pH and pore solution chemistry induced during accelerated carbonation testing provide unrealistically low predictions of in-service carbonation resistance. The aluminosilicate gel remaining in an alkali-activated slag system after accelerated carbonation is highly polymerised, consistent with a decalcification mechanism, while fly ash-based binders mainly carbonate through precipitation of alkali salts (bicarbonates at elevated CO{sub 2} concentrations, or carbonates under natural exposure) from the pore solution, with little change in the binder gel identifiable by nuclear magnetic resonance spectroscopy. In activated fly ash/slag blends, two distinct gels (C–A–S–H and N–A–S–H) are formed; under accelerated carbonation, the N–A–S–H gel behaves comparably to fly ash-based systems, while the C–A–S–H gel is decalcified similarly to alkali-activated slag. This provides new scope for durability optimisation, and for developing appropriate testing methodologies. -- Highlights: •C-A-S-H gel in alkali-activated slag decalcifies during accelerated carbonation. •Alkali-activated fly ash gel changes much less under CO{sub 2} exposure. •Blended slag-fly ash binder contains two coexisting gel types. •These two gels respond differently to carbonation. •Understanding of carbonation mechanisms is essential in developing test methods.

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

    NASA Astrophysics Data System (ADS)

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

    1999-11-01

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

  1. Mesoporous aluminosilicate ropes with improved stability from protozeolitic nanoclusters

    SciTech Connect

    Zheng Junlin; Kong Dejin; Yang Weimin; Xie Zaiku; Wu Dong; Sun Yuhan

    2007-02-15

    Mesoporous aluminosilicate ropes with improved hydrothermal stability have been prepared through S{sup +}X{sup -}I{sup +} route via self-assembly of protozeolitic nanoclusters with cetyltrimethylammonium bromides (CTAB) template micelles in HNO{sub 3} solution. SEM observation confirmed that high-yield aluminosilicate ropes could be produced under proper HNO{sub 3} concentration. NO{sub 3} {sup -} ions had strong binding strength to the CTA{sup +} ions and tended to form more elongated surfactant micelles, thus fibrous products were fabricated under the direction of these long rod micelles in shearing flow. At the same time, the NO{sub 3} {sup -} ions combining with CTA{sup +} ions generated more active (CTA{sup +}NO{sub 3} {sup -}) assembly, which effectively catalysed the polymerization of protozeolitic nanoclusters with large volume into highly ordered mesostructures. Compared with normal MCM-41 silica synthesized through S{sup +}X{sup -}I{sup +} route in acidic media, the hydrothermal stability was improved considerably. These protozeolitic nanoclusters survived strongly acidic media and entered into mesostructured framework, which contributed to the improvement of hydrothermal stability. - Graphical abstract: Mesoporous aluminosilicate ropes with enhanced hydrothermal stability were fabricated from protozeolitic nanoclusters through S{sup +}X{sup -}I{sup +} route in HNO{sub 3} solution under the direction of CTAB templates.

  2. Relationship between texture and acidic properties of aluminosilicates and the conditions of their preparation

    SciTech Connect

    Grzechowiak, E.R.; Masalska, A.

    1986-04-01

    A study has been made of the method of pH adjustment in the precipitation of hydrogel in relation to its influence on the texture and acidic properties of alumino-silicates. It has been established that large-pore aluminosilicates can be obtained from neutral solutions. X-ray diffraction analysis of aluminosilicates has shown that the method of pH adjustment also affects their phase composition.

  3. Experimental Modeling of Peridotite Melting with Alkali-Carbonate Fluid at P = 3.9 GPa, T=1250°C

    NASA Astrophysics Data System (ADS)

    Kostyuk, Anastasia; Gorbachev, Nikolay; Nekrasov, Alexey

    2014-05-01

    The close association of alkaline and ultramafic rocks with carbonatites, apatite and sulfide mineralization, as well as features of the melt compositions, tell us about the mantle source and the importance of alkaline-carbonate fluids in the genesis of these rocks. Experimental modeling of formation of alkali silicate, carbonate and sulfide melts was carried out in the system peridotite-alkaline-carbonate fluid (K, Na)2CO3 with additives of apatite, nickel-containing pyrrhotite, ilmenite and zircon as accessory minerals at P= 3.9 GPa and T=1250°C. Composition of coexisting melts, phase relationships, behavior of titanium, phosphorus, sulfur and zircon have been studied in this system. Liquidus association of phlogopite-clinopyroxene-zircon-X-phase (not diagnosed titanium and phosphorus-containing aluminosilicate phase) cemented by intergranular silicate glass with inclusions of carbonate and sulphide phases at partial (10%) melting of peridotite. Morphology, composition and relations of silicate glass, carbonate and sulfide globules indicate the existence of immiscible silicate, carbonate and sulfide melts at the experimental conditions. The composition of the silicate melt is phonolite, carbonate melt - significantly calcium composition with an admixture of alkali metal and silicate components. Solubility of zircon in silicate melt reached up to 0.8 wt.% of ZrO2, in coexisting carbonate melt - up to 1.5 wt.%. Absence of ilmenite and apatite in the experimental samples due to their high solubility in the coexisting phases. Concentration of TiO2 and P2O5 in silicate melt reached 2 wt. %. The concentration of TiO2 in the carbonate melt up to 1.7 wt.% and P2O5 up to 14 wt.%. The sulfur concentration in these melts does not exceed 0.2 wt.%. Concentrators of titanium and phosphorus among liquidus minerals were X-phase and phlogopite - 8 wt.% TiO2 and up to 3 wt.% P2O5 in the X-phase; up to 6 wt.% TiO2 and up to 2.5 wt.% of P2O5 in the phlogopite. The distribution

  4. Energetics of formation of alkali and ammonium cobalt and zinc phosphate frameworks

    SciTech Connect

    Le, So-Nhu; Navrotsky, Alexandra

    2008-01-15

    Alkali and ammonium cobalt and zinc phosphates show extensive polymorphism. Thermal behavior, relative stabilities, and enthalpies of formation of KCoPO{sub 4}, RbCoPO{sub 4}, NH{sub 4}CoPO{sub 4}, and NH{sub 4}ZnPO{sub 4} polymorphs are studied by differential scanning calorimetry, high-temperature oxide melt solution calorimetry, and acid solution calorimetry. {alpha}-KCoPO{sub 4} and {gamma}-KCoPO{sub 4} are very similar in enthalpy. {gamma}-KCoPO{sub 4} slowly transforms to {alpha}-KCoPO{sub 4} near 673 K. The high-temperature phase, {beta}-KCoPO{sub 4}, is 5-7 kJ mol{sup -1} higher in enthalpy than {alpha}-KCoPO{sub 4} and {gamma}-KCoPO{sub 4}. HEX phases of NH{sub 4}CoPO{sub 4} and NH{sub 4}ZnPO{sub 4} are about 3 kJ mol{sup -1} lower in enthalpy than the corresponding ABW phases. There is a strong relationship between enthalpy of formation from oxides and acid-base interaction for cobalt and zinc phosphates and also for aluminosilicates with related frameworks. Cobalt and zinc phosphates exhibit similar trends in enthalpies of formation from oxides as aluminosilicates, but their enthalpies of formation from oxides are more exothermic because of their stronger acid-base interactions. Enthalpies of formation from ammonia and oxides of NH{sub 4}CoPO{sub 4} and NH{sub 4}ZnPO{sub 4} are similar, reflecting the similar basicity of CoO and ZnO. - Graphical abstract: Relationship between enthalpy of formation from oxides and acid-base interaction for cobalt phosphates, zinc phosphates, and aluminosilicates with related frameworks. They exhibit similar trends, but the enthalpies of formation of phosphates are more exothermic than those of aluminosilicates because of stronger acid-base interactions.

  5. PROCESS OF RECOVERING ALKALI METALS

    DOEpatents

    Wolkoff, J.

    1961-08-15

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

  6. Impact of Alkali Source on Vitrification of SRS High Level Waste

    SciTech Connect

    LAMBERT, D. P.; MILLER, D. H.; PEELER, D. K.; SMITH, M. E.; STONE, M. E.

    2005-09-08

    The Defense Waste Processing Facility (DWPF) Savannah River Site is currently immobilizing high level nuclear waste sludge by vitrification in borosilicate glass. The processing strategy involves blending a large batch of sludge into a feed tank, washing the sludge to reduce the amount of soluble species, then processing the large ''sludge batch'' through the DWPF. Each sludge batch is tested by the Savannah River National Laboratory (SRNL) using simulants and tests with samples of the radioactive waste to ''qualify'' the batch prior to processing in the DWPF. The DWPF pretreats the sludge by first acidifying the sludge with nitric and formic acid. The ratio of nitric to formic acid is adjusted as required to target a final glass composition that is slightly reducing (the target is for {approx}20% of the iron to have a valence of two in the glass). The formic acid reduces the mercury in the feed to elemental mercury which is steam stripped from the feed. After a concentration step, the glass former (glass frit) is added as a 50 wt% slurry and the batch is concentrated to approximately 50 wt% solids. The feed slurry is then fed to a joule heated melter maintained at 1150 C. The glass must meet both processing (e.g., viscosity and liquidus temperature) and product performance (e.g., durability) constraints The alkali content of the final waste glass is a critical parameter that affects key glass properties (such as durability) as well as the processing characteristics of the waste sludge during the pretreatment and vitrification processes. Increasing the alkali content of the glass has been shown to improve the production rate of the DWPF, but the total alkali in the final glass is limited by constraints on glass durability and viscosity. Two sources of alkali contribute to the final alkali content of the glass: sodium salts in the waste supernate and sodium and lithium oxides in the glass frit added during pretreatment processes. Sodium salts in the waste supernate

  7. Considerations of Glass Sealing SOFC Stacks

    SciTech Connect

    Yang, Z Gary; Weil, K. Scott; Meinhardt, Kerry D.; Paxton, Dean M.; Stevenson, Jeffry W.

    2003-08-31

    Due to their TEC matching to PEN components, excellent oxidation resistance, low cost and good fabricability, stainless steels have been used as the interconnect materials in planar SOFC. For being hermetical, the stainless steel interconnect ought to be sealed to YSZ electrolyte and/or another piece of metallic interconnect, usually using a sealing glass. The seal performance, which is critical factor to determine the reliability and durability of SOFC stack, largely depends on the chemical compatibility between the sealing glass and stainless steel. In this work, the ferritic stainless steel 446 and a barium-aluminosilicate base glass have been taken as an example for metallic interconnects and sealing glass, respectively, and the corrosion at the interface of metal and sealing glass has been investigated and understood. The methodology and results of the microscopic analysis and thermodynamic modeling will be presented, and the mechanism of corrosion at the interface will be discussed as well.

  8. High temperature alkali corrosion of ceramics in coal gas. Quarterly progress report No. 12, June 1--August 31, 1994

    SciTech Connect

    Pickrell, G.R.; Brown, J.J.

    1994-09-01

    High temperature alkali corrosion has been known to cause premature failure of ceramic components used in advanced high temperature coal combustion systems such as coal gasification and clean-up, coal fired gas turbines, and high efficiency heat engines. The objective of this research is to evaluate the alkali corrosion resistance of the most commonly used structural ceramics including silicon carbide, silicon nitride, cordierite, mullite, alumina, aluminum titanate, zirconia, and fireclay glass. The study consists of identification of the alkali reaction products (phase equilibria) and the kinetics of the alkali reactions.

  9. High temperature alkali corrosion of ceramics in coal gas. Quarterly progress report No. 3, March 1, 1992--May 31, 1992

    SciTech Connect

    Pickrell, G.R.; Sun, T.; Brown, J.J.

    1992-05-27

    High temperature alkali corrosion has been known to cause premature failure of ceramic components used in advanced high temperature coal combustion systems such as coal gasification and clean-up, coal fired gas turbines, and high efficiency heat engines. The objective of this research is to systematically evaluate the alkali corrosion resistance of the most commonly used structural ceramics including silicon carbide, silicon nitride, cordierite, mullite, alumina, aluminum titanate, zirconia, and fireclay glass. The study consists of identification of the alkali reaction products (phase equilibria) and the kinetics of the alkali reactions as a function of temperature and time.

  10. High temperature alkali corrosion of ceramics in coal gas. Quarterly progress report No. 1, September 1, 1991--November 31, 1991

    SciTech Connect

    Pickrell, G.R.; Sun, T.; Brown, J.J.

    1991-11-30

    High temperature alkali corrosion has been known to cause premature failure of ceramic components used in advanced high temperature coal combustion systems such as coal gasification and clean-up, coal fired gas turbines, and high efficiency heat engines. The objective of this program is to systematically evaluate the alkali corrosion resistance of the most commonly used structural ceramics including silicon carbide, silicon nitride, cordierite, mullite, alumina, aluminum titanate, zirconia, and fireclay glass. The study consists of identification of the alkali reaction products (phase equilibria) and the kinetics of the alkali reactions as a function of temperature and time.

  11. High temperature alkali corrosion of ceramics in coal gas. Quarterly progress report No. 4, June 1, 1992--August 31, 1992

    SciTech Connect

    Pickrell, G.R.; Sun, T.; Brown, J.J.

    1992-08-29

    High temperature alkali corrosion has been known to cause premature failure of ceramic components used in advanced high temperature coal combustion systems such as coal gasification and clean-up, coal fired gas turbines, and high efficiency heat engines. The objective of this research is to systematically evaluate the alkali corrosion resistance of the most commonly used structural ceramics including silicon carbide, silicon nitride, cordierite, mullite, alumina, aluminum titanate, zirconia, and fireclay glass. The study consists of identification of the alkali reaction products (phase equilibria) and the kinetics of the alkali reactions as a function of temperature and time.

  12. In situ Brillouin study of sodium alumino silicate glasses under pressure

    NASA Astrophysics Data System (ADS)

    Sonneville, C.; De Ligny, D.; Mermet, A.; Champagnon, B.; Martinet, C.; Henderson, G. H.; Deschamps, T.; Margueritat, J.; Barthel, E.

    2013-08-01

    The in situ elastic and plastic behaviors of sodium aluminosilicate glasses with different degrees of depolymerization were analyzed using Brillouin spectroscopy. The observed elastic anomaly progressively vanished with depolymerization. The densification process appears to be different from that observed in pure silica glass. In the plastic regime of densified glasses hysteresis loops were observed and related to modification of the local silicon environment facilitated by the addition of sodium.

  13. Purification of alkali metal nitrates

    DOEpatents

    Fiorucci, Louis C.; Gregory, Kevin M.

    1985-05-14

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

  14. Alkali metal and alkali earth metal gadolinium halide scintillators

    DOEpatents

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

    2016-08-02

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

  15. Alkali hydrolysis of trinitrotoluene.

    PubMed

    Karasch, Christian; Popovic, Milan; Qasim, Mohamed; Bajpai, Rakesh K

    2002-01-01

    Data for alkali hydrolysis of 2,4,6-trinitrotoluene (TNT) in aqueous solution at pH 12.0 under static (pH-controlled) as well as dynamic (pH-uncontrolled) conditions are reported. The experiments were conducted at two different molar ratios of TNT to hydroxyl ions at room temperature. The TNT disappeared rapidly from the solution as a first-order reaction. The complete disappearance of aromatic structure from the aqueous solution within 24 h was confirmed by the ultraviolet-visible (UV-VIS) spectra of the samples. Cuvet experiments in a UV-VIS spectrophotometer demonstrated the formation of Meisenheimer complex, which slowly disappeared via formation of aromatic compounds with fewer nitro groups. The known metabolites of TNT were found to accumulate only in very small quantities in the liquid phase.

  16. MAS-NMR studies of lithium aluminum silicate (LAS) glasses and glass-ceramics having different Li{sub 2}O/Al{sub 2}O{sub 3} ratio

    SciTech Connect

    Ananthanarayanan, A.; Kothiyal, G.P.; Montagne, L.; Revel, B.

    2010-01-15

    Emergence of phases in lithium aluminum silicate (LAS) glasses of composition (wt%) xLi{sub 2}O-71.7SiO{sub 2}-(17.7-x)Al{sub 2}O{sub 3}-4.9K{sub 2}O-3.2B{sub 2}O{sub 3}-2.5P{sub 2}O{sub 5} (5.1<=x<=12.6) upon heat treatment were studied. {sup 29}Si, {sup 27}Al, {sup 31}P and {sup 11}B MAS-NMR were employed for structural characterization of both LAS glasses and glass-ceramics. In glass samples, Al is found in tetrahedral coordination, while P exists mainly in the form of orthophosphate units. B exists as BO{sub 3} and BO{sub 4} units. {sup 27}Al NMR spectra show no change with crystallization, ruling out the presence of any Al containing phase. Contrary to X-ray diffraction studies carried out, {sup 11}B (high field 18.8 T) and {sup 29}Si NMR spectra clearly indicate the unexpected crystallization of a borosilicate phase (Li,K)BSi{sub 2}O{sub 6}, whose structure is similar to the aluminosilicate virgilite. Also, lithium disilicate (Li{sub 2}Si{sub 2}O{sub 5}), lithium metasilicate (Li{sub 2}SiO{sub 3}) and quartz (SiO{sub 2}) were identified in the {sup 29}Si NMR spectra of the glass-ceramics. {sup 31}P NMR spectra of the glass-ceramics revealed the presence of Li{sub 3}PO{sub 4} and a mixed phase (Li,K){sub 3}PO{sub 4} at low alkali concentrations. - Graphical Abstract: The {sup 11}B MAS-NMR spectra of lithium aluminum silicate (LAS) glass-ceramics indicating the formation of Li/KBSiO{sub 6} phase. This phase is isostructural with virgilite and cannot be distinguished in X-ray diffractograms.

  17. Characterisation of frequency doubling in Eu(2+) doped aluminosilicate fibres

    NASA Technical Reports Server (NTRS)

    Driscoll, T. J.; Lawandy, N. M.; Killian, A.; Rienhart, L.; Morse, T. F.

    1991-01-01

    The results of a series of experiments on efficient second-harmonic generation in a fiber with a Eu(2+)-doped aluminosilicate core are reported. The fiber was prepared by the seeding method with CW mode-locked radiation at 1.06 micron and produced ultrastable peak conversion efficiencies of 0.001 during mode-locked readout. Experiments were performed to determine the IR preparation intensity dependence, the stability of the output, and the type of erasure mechanisms which occur. The results are compared with those of germanosilicate fibers and some similarities and differences are discussed.

  18. Relation of the acidity of amorphous aluminosilicates with their activity and selectivity in isomerization of xylenes

    SciTech Connect

    Zadymov, V.V.; Lupina, M.I.; Kaliko, M.A.

    1981-01-01

    Conversion of m-xylene on amorphous aluminosilicates is determined by overall surface acidity. The formation of acid centres with pK a greater than or equal toapprox. =-10 as a result of heat-steam treatment of aluminosilicates and a reduction in the number of strong centres increases selectivity in isomerization of m-xylene.

  19. Applications of high resolution NMR to geochemistry: crystalline, glass, and molten silicates

    SciTech Connect

    Schneider, E.

    1985-11-01

    The nuclear spin interactions and the associated quantum mechanical dynamics which are present in solid state NMR are introduced. A brief overview of aluminosilicate structure is presented and crystalline structure is then reviewed, with emphasis on the contributions made by /sup 29/Si NMR spectroscopy. The local structure of glass aluminosilicates as observed by NMR, is presented with analysis of the information content of /sup 29/Si spectra. A high-temperature (to 1300/sup 0/C) NMR spectroscopic investigation of the local environment and dynamics of molecular motion in molten aluminosilicates is described. A comparison is made of silicate liquid, glass, and crystalline local structure. The atomic and molecular motions present in a melt are investigated through relaxation time (T/sub 1/ and T/sub 2/) measurements as a function of composition and temperature for /sup 23/Na and /sup 29/Si.

  20. Upgrading platform using alkali metals

    SciTech Connect

    Gordon, John Howard

    2014-09-09

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

  1. Glass/Ceramic Composites for Sealing Solid Oxide Fuel Cells

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Choi, Sung R.

    2007-01-01

    A family of glass/ceramic composite materials has been investigated for use as sealants in planar solid oxide fuel cells. These materials are modified versions of a barium calcium aluminosilicate glass developed previously for the same purpose. The composition of the glass in mole percentages is 35BaO + 15CaO + 5Al2O3 + 10B2O3 + 35SiO2. The glass seal was found to be susceptible to cracking during thermal cycling of the fuel cells. The goal in formulating the glass/ ceramic composite materials was to (1) retain the physical and chemical advantages that led to the prior selection of the barium calcium aluminosilicate glass as the sealant while (2) increasing strength and fracture toughness so as to reduce the tendency toward cracking. Each of the composite formulations consists of the glass plus either of two ceramic reinforcements in a proportion between 0 and 30 mole percent. One of the ceramic reinforcements consists of alumina platelets; the other one consists of particles of yttria-stabilized zirconia wherein the yttria content is 3 mole percent (3YSZ). In preparation for experiments, panels of the glass/ceramic composites were hot-pressed and machined into test bars.

  2. Effective Sequestration of Clostridium difficile Protein Toxins by Calcium Aluminosilicate.

    PubMed

    Sturino, Joseph M; Pokusaeva, Karina; Carpenter, Robert

    2015-12-01

    Clostridium difficile is a leading cause of antibiotic-associated diarrhea and the etiologic agent responsible for C. difficile infection. Toxin A (TcdA) and toxin B (TcdB) are nearly indispensable virulence factors for Clostridium difficile pathogenesis. Given the toxin-centric mechanism by which C. difficile pathogenesis occurs, the selective sequestration with neutralization of TcdA and TcdB by nonantibiotic agents represents a novel mode of action to prevent or treat C. difficile-associated disease. In this preclinical study, we used quantitative enzyme immunoassays to determine the extent by which a novel drug, calcium aluminosilicate uniform particle size nonswelling M-1 (CAS UPSN M-1), is capable of sequestering TcdA and TcdB in vitro. The following major findings were derived from the present study. First, we show that CAS UPSN M-1 efficiently sequestered both TcdA and TcdB to undetectable levels. Second, we show that CAS UPSN M-1's affinity for TcdA is greater than its affinity for TcdB. Last, we show that CAS UPSN M-1 exhibited limited binding affinity for nontarget proteins. Taken together, these results suggest that ingestion of calcium aluminosilicate might protect gastrointestinal tissues from antibiotic- or chemotherapy-induced C. difficile infection by neutralizing the cytotoxic and proinflammatory effects of luminal TcdA and TcdB.

  3. Rationale for windshield glass system specification requirements for shuttle orbiter

    NASA Technical Reports Server (NTRS)

    Hayashida, K.; King, G. L.; Tesinsiky, J.; Wittenburg, D. R.

    1972-01-01

    A preliminary procurement specification for the space shuttle orbiter windshield pane, and some of the design considerations and rationale leading to its development are presented. The windshield designer is given the necessary methods and procedures for assuring glass pane structural integrity by proof test. These methods and procedures are fully developed for annealed and thermally tempered aluminosilicate, borosilicate, and soda lime glass and for annealed fused silica. Application of the method to chemically tempered glass is considered. Other considerations are vision requirements, protection against bird impact, hail, frost, rain, and meteoroids. The functional requirements of the windshield system during landing, ferrying, boost, space flight, and entry are included.

  4. XAFS Studies of Silver Environments in Ion-Exchanged Glasses

    SciTech Connect

    Yang, X. C.; Dubiel, M.

    2007-02-02

    The X-ray absorption fine structure (XAFS) technique was used to analyze the structural geometry of Ag atoms introduced into soda-lime silicate glass and soda aluminosilicate glass by ion-exchange methods. The results show that Ag+ ions in aluminosilicate glass are coordinated by about two oxygens and the nearest-neighbor Ag-O distance increases when the Ag+-for-Na+ ion-exchange ratio is larger than 0.47. When the exchange ratio is low, the introduced Ag+ ions are stabilized at the non-bridge oxygen (NBO) site with a Ag-O distance of 2.20 A, and the Na+ ions in the AlO4 site are exchanged by Ag+ ions after full replacement of the NBO sites with a Ag-O distance of 2.28 A. The disorder of Ag-O coordination increases with increasing ion-exchange ratio in aluminosilicate glass where Ag+ ions are coordinated by NBO and bridge oxygen (BO)

  5. Chlorine, in the Presence of Iron, Does Indeed Decrease the Viscosity of Aluminosilicate Melts

    NASA Astrophysics Data System (ADS)

    Webb, S. L.

    2012-12-01

    The effect of volatiles on melt rheology is investigated here, as the degassing of magma before an eruption usually leads to an increase in magma viscosity; and therefore increases the probability of an explosive eruption. There is not a large amount of data on the effect of chlorine on viscosity. It would appear, however, that chlorine increases the viscosity of peralkaline sodium-aluminosilicate melts, and decreases the viscosity of peraluminous sodium-aluminosilicate melts. These different effects of chlorine on viscosity indicate that the chlorine sits in different structural sites in peraluminous and peralkaline melts. In previous studies of rheology in this laboratory, we have shown that chlorine does indeed increase the viscosity of a phonolite analog Na2O-CaO-Al2O3-SiO2 melt. In this study, we have extended our investigation of the rheology of chlorine-bearing melts to basaltic compositions. The melt composition used here is that of a basaltic glass taken from the mid-Atlantic Ridge at 3000 m depth during the Venture Cruise (Ireland) of 2011. The viscosities were determined using the micropenetration technique in the 109-1012 Pa s range at temperatures 600-800 C. It was found that the addition of 0.6 wt% Cl resulted in a 0.5 log unit decrease in viscosity. A synthetic haplo-basaltic melt with the iron replaced by Mg and the Al was also synthesized. The addition of 0.3 wt% chlorine to this melt resulted in a 0.3 log unit increase in viscosity; as observed previously for Fe-free peralkaline melts. Based on these viscosity data it would appear that the effect of chlorine on rheology is a function of the composition of the melt, and that the structural site taken by chlorine varies as a function of the presence or absence of iron. The addition of chlorine to the iron-bearing melt, increased the Fe2+/Fetot from 0.30 to 0.45. This indicates that the presence of chlorine results in an energetic preference for Fe2+ in the melt structure. Thus, it is not so much the

  6. Analysis of aluminosilicate particles in biological matrices using histochemistry and X-ray microanalysis.

    PubMed

    Powell, J J

    2002-06-01

    Aluminosilicates are a group of ubiquitous environmental particles that, in some cases, have been implicated in human disease. Characterisation of aluminosilicates in tissue samples requires, first, their in situ identification and, secondly, analysis of their aluminium and silicon content or, at least, aluminium:silicon ratio. Here, histochemical staining, microscopy and X-ray microanalysis were investigated as potential methods for the detection of aluminosilicates in biological samples. In contrast to aluminium phosphate or hydroxide, aluminosilicates were refractory to histochemical staining for aluminium. However, using electron microscopy, back scattered electrons allowed identification of aluminosilicates in tissue-like (gelatine) sections. X-ray microanalysis, using conventional peak:background ratios, did not provide a sufficiently accurate assessment of the aluminium content of various standard aluminosilicates to allow their identification. However, the similar spectral energies of aluminium and silicon allowed spectral peak heights to be directly compared and, using simple standards, aluminium:silicon ratios were found for a range of reference particles. Application of this technique should allow the localisation and identification of aluminosilicates in biological samples.

  7. SODIUM ALUMINOSILICATE FOULING AND CLEANING OF DECONTAMINATED SALT SOLUTION COALESCERS

    SciTech Connect

    Poirier, M; Thomas Peters, T; Fernando Fondeur, F; Samuel Fink, S

    2008-10-28

    During initial non-radioactive operations at the Modular Caustic Side Solvent Extraction Unit (MCU), the pressure drop across the decontaminated salt solution coalescer reached {approx}10 psi while processing {approx}1250 gallons of salt solution, indicating possible fouling or plugging of the coalescer. An analysis of the feed solution and the 'plugged coalescer' concluded that the plugging was due to sodium aluminosilicate solids. MCU personnel requested Savannah River National Laboratory (SRNL) to investigate the formation of the sodium aluminosilicate solids (NAS) and the impact of the solids on the decontaminated salt solution coalescer. Researchers performed developmental testing of the cleaning protocols with a bench-scale coalescer container 1-inch long segments of a new coalescer element fouled using simulant solution. In addition, the authors obtained a 'plugged' Decontaminated Salt Solution coalescer from non-radioactive testing in the MCU and cleaned it according to the proposed cleaning procedure. Conclusions from this testing include the following: (1) Testing with the bench-scale coalescer showed an increase in pressure drop from solid particles, but the increase was not as large as observed at MCU. (2) Cleaning the bench-scale coalescer with nitric acid reduced the pressure drop and removed a large amount of solid particles (11 g of bayerite if all aluminum is present in that form or 23 g of sodium aluminosilicate if all silicon is present in that form). (3) Based on analysis of the cleaning solutions from bench-scale test, the 'dirt capacity' of a 40 inch coalescer for the NAS solids tested is calculated as 450-950 grams. (4) Cleaning the full-scale coalescer with nitric acid reduced the pressure drop and removed a large amount of solid particles (60 g of aluminum and 5 g of silicon). (5) Piping holdup in the full-scale coalescer system caused the pH to differ from the target value. Comparable hold-up in the facility could lead to less effective

  8. Dynamic Reduction of FeO-Bearing, Anhydrous Aluminosilicate Melts

    NASA Astrophysics Data System (ADS)

    Everman, R. L.; Cooper, R. F.

    2004-12-01

    We have studied the reduction dynamics of FeO-bearing aluminosilicate melts at oxygen activities sufficiently low to form metallic iron. The experiments involved reacting droplets, suspended from refractory metal wires, with a high-temperature ( ˜1400oC), controlled-oxygen-activity environment maintained by a dynamic CO:CO2 buffer. In the case of an FeO-doped magnesium aluminosilicate ("Fe-MAS") melt ( ˜5 mol% FeO) exposed to an oxygen activity of 2x10-13 ("QIF-2"; CO:CO2=240:1), the reduction dynamic is rate-limited by chemical diffusion of Mg2+: oxygen chemically ablates from the free surface and the network-modifying cations diffuse inward, charge-compensated by a counterflux of electron holes (the "semiconductor condition" holds for diffusion dynamics in this melt [e.g., Cook and Cooper, 2000]); nm-scale crystals of pure α -Fe nucleate at an internal front. Diffusion of an oxygen species is not involved. In the case of FeO-doped calcium-magnesium aluminosilicate (Fe-CMAS) melt ( ˜8 mol% FeO) exposed to an oxygen activity of 2x10-15 (QIF-4; CO:CO2=1750:1), the dynamic changes: molten Fe-C-Si alloy droplets form near the surface, and bubbles are seen to form internally, truncating at an internal front. Further, the reaction occurs more slowly than that seen for the similarly polymerized Fe-MAS melt. The results suggests that molecular CO diffuses inward, consuming electron holes so as to form carbonate ion species in the melt [cf. Brooker et al., 2001]. Quenching produces a driving potential to reverse the internal reduction reaction, so creating the bubbles. Consumption of the electron holes by reaction with the carbon species dramatically reduces the reduction-to-metal kinetics. Brooker RA, Kohn SC, Holloway JR, McMillan PF (2001) Chem Geol 174:241-254; Cook GB, Cooper RF (2000) Am Mineral 85:397-406

  9. NOVEL REFRACTORY MATERIALS FOR HIGH ALKALI, HIGH TEMPERATURE ENVIRONMENTS

    SciTech Connect

    Hemrick, James Gordon; Smith, Jeffrey D; O'Hara, Kelley; Rodrigues-Schroer, Angela; Colavito,

    2012-08-01

    A project was led by Oak Ridge National Laboratory (ORNL) in collaboration with a research team comprised of the academic institution Missouri University of Science and Technology (MS&T), and the industrial company MINTEQ International, Inc. (MINTEQ), along with representatives from the aluminum, chemical, glass, and forest products industries. The project was to address the need for new innovative refractory compositions by developing a family of novel MgO-Al 2O3, MgAl2O4, or other similar spinel structured or alumina-based unshaped refractory compositions (castables, gunnables, shotcretes, etc.) utilizing new aggregate materials, bond systems, protective coatings, and phase formation techniques (in-situ phase formation, altered conversion temperatures, accelerated reactions, etc). This family of refractory compositions would then be tailored for use in high-temperature, high-alkaline industrial environments like those found in the aluminum, chemical, forest products, glass, and steel industries. Both practical refractory development experience and computer modeling techniques were used to aid in the design of this new family of materials. The newly developed materials were expected to offer alternative material choices for high-temperature, high-alkali environments that were capable of operating at higher temperatures (goal of increasing operating temperature by 100-200oC depending on process) or for longer periods of time (goal of twice the life span of current materials or next process determined service increment). This would lead to less process down time, greater energy efficiency for associated manufacturing processes (more heat kept in process), and materials that could be installed/repaired in a more efficient manner. The overall project goal was a 5% improvement in energy efficiency (brought about through a 20% improvement in thermal efficiency) resulting in a savings of 3.7 TBtu/yr (7.2 billion ft3 natural gas) by the year 2030. Additionally, new

  10. Cathodoluminescence Characterization of Maskelynite and Alkali Feldspar in Shergottite (Dhofar 019)

    SciTech Connect

    Kayama, M.; Nakazato, T.; Nishido, H.; Ninagawa, K.; Gucsik, A.

    2009-08-17

    Dhofar 019 is classified as an olivine-bearing basaltic shergottite and consists of subhedral grains of pyroxene, olivine, feldspar mostly converted to maskelynite and minor alkali feldspar. The CL spectrum of its maskelynite exhibits an emission band at around 380 nm. Similar UV-blue emission has been observed in the plagioclase experimentally shocked at 30 and 40 GPa, but not in terrestrial plagioclase. This UV-blue emission is a notable characteristic of maskelynite. CL spectrum of alkali feldspar in Dhofar 019 has an emission bands at around 420 nm with no red emission. Terrestrial alkali feldspar actually consists of blue and red emission at 420 and 710 nm assigned to Al-O{sup -}-Al and Fe{sup 3+} centers, respectively. Maskelynite shows weak and broad Raman spectral peaks at around 500 and 580 cm{sup -1}. The Raman spectrum of alkali feldspar has a weak peak at 520 cm{sup -1}, whereas terrestrial counterpart shows the emission bands at 280, 400, 470, 520 and 1120 cm{sup -1}. Shock pressure on this meteorite transformed plagioclase and alkali feldspar into maskelynite and almost glass phase, respectively. It eliminates their luminescence centers, responsible for disappearance of yellow and/or red emission in CL of maskelynite and alkali feldspar. The absence of the red emission band in alkali feldspar can also be due to the lack of Fe{sup 3+} in the feldspar as it was reported for some lunar feldspars.

  11. XPS study of distribution of elements between surface and volume in aluminosilicate catalysts and adsorbents

    SciTech Connect

    Chukin, G.D.; Grishin, S.A.; Kulikov, A.S.; Nefedov, B.K.; Surin, S.A.

    1986-02-01

    X-ray photoelectron spectroscopy (XPS) has been used in an investigation of the distribution of aluminum and sodium on the surface and in the volume of amorphous aluminosilicates. It has been shown that in the Na form of the aluminosilicates, the sodium and aluminum ions are localized preferentially on the surface. When the Na/sup +/ ions are replaced by protons, there is a change in the electronic state of the near-surface atoms in the aluminosilicates. Information on acidic centers that has been obtained by IR spectroscopy is consistent with the XPS data.

  12. Low melting high lithia glass compositions and methods

    DOEpatents

    Jantzen, Carol M.; Pickett, John B.; Cicero-Herman, Connie A.; Marra, James C.

    2003-09-23

    The invention relates to methods of vitrifying waste and for lowering the melting point of glass forming systems by including lithia formers in the glass forming composition in significant amounts, typically from about 0.16 wt % to about 11 wt %, based on the total glass forming oxides. The lithia is typically included as a replacement for alkali oxide glass formers that would normally be present in a particular glass forming system. Replacement can occur on a mole percent or weight percent basis, and typically results in a composition wherein lithia forms about 10 wt % to about 100 wt % of the alkali oxide glass formers present in the composition. The present invention also relates to the high lithia glass compositions formed by these methods. The invention is useful for stabilization of numerous types of waste materials, including aqueous waste uranium oxides The decrease in melting point achieved by the present invention desirably prevents volatilization of hazardous or radioactive species during vitrification.

  13. Sorption of cesium ions by nanostructured calcium aluminosilicates

    NASA Astrophysics Data System (ADS)

    Gordienko, P. S.; Shabalin, I. A.; Yarusova, S. B.; Suponina, A. P.; Zhevtun, I. G.

    2016-10-01

    Data on the sorption properties of synthetic calcium aluminosilicates (CASes) with Al: Si ratios of 2: 2, 2: 6, and 2: 10, fabricated within the multicomponent system CaCl2-AlCl3-KOM-SiO2-H2O, are presented. Isotherms of the sorption of Cs+ ions from aqueous solutions with Cs+ concentrations of 0.2 to 6.0 mmol L-1 are analyzed. The CAS maximum sorption capacity and the Langmuir constants are determined. Kinetic data are obtained, and the energy of cation-exchange activation upon the sorption of Cs+ ions is determined. The effect of a salt background (1% KCl + 6% NaCl) has on the values of distribution coefficient ( K d) and the degree of Cs+ ion removal is established.

  14. The aluminosilicate fraction of North Pacific manganese nodules

    USGS Publications Warehouse

    Bischoff, J.L.; Piper, D.Z.; Leong, K.

    1981-01-01

    Nine nodules collected from throughout the deep North Pacific were analyzed for their mineralogy and major-element composition before and after leaching with Chester-Hughes solution. Data indicate that the mineral phillipsite accounts for the major part (> 75%) of the aluminosilicate fraction of all nodules. It is suggested that formation of phillipsite takes place on growing nodule surfaces coupled with the oxidation of absorbed manganous ion. All the nodules could be described as ternary mixtures of amorphous iron fraction (Fe-Ti-P), manganese oxide fraction (Mn-Mg Cu-Ni), and phillipsite fraction (Al-Si-K-Na), these fractions accounting for 96% of the variability of the chemical composition. ?? 1981.

  15. Adsorption of β-galactosidase on silica and aluminosilicate adsorbents

    NASA Astrophysics Data System (ADS)

    Atyaksheva, L. F.; Dobryakova, I. V.; Pilipenko, O. S.

    2015-03-01

    It is shown that adsorption of β-galactosidase of Aspergillus oryzae fungi on mesoporous and biporous silica and aluminosilicate adsorbents and the rate of the process grow along with the diameter of the pores of the adsorbent. It is found that the shape of the adsorption isotherms changes as well, depending on the texture of the adsorbent: the Michaelis constant rises from 0.3 mM for the enzyme in solution to 0.4-0.5 mM for the enzyme on a surface in the hydrolysis of o-nitrophenyl-β-D-galactopyranoside. It is concluded that β-galactosidase displays its maximum activity on the surface of biporous adsorbents.

  16. Amphiphilic properties of poly(oxyalkylene)amine-intercalated smectite aluminosilicates.

    PubMed

    Lin, Jiang-Jen; Chen, Yu-Min

    2004-05-11

    Layered aluminosilicates, including synthetic fluorine mica and natural montmorillonite (MMT), were intercalated with poly(oxypropylene)-polyamine quaternary salts with a 230-5000 molecular weight range. The X-ray basal spacing of these silicates had been expanded from 13.5 to 83.7 A for the synthetic mica and to 92.0 A for MMT. The relative silicate dimensions (300-1000 nm for synthetic mica and 80-100 nm for MMT) were ascertained by direct TEM observations in the case of the co-intercalated synthetic mica and MMT mixtures with Mw = 2000 quaternary ammonium salts. The tailored organic incorporation of synthetic mica and MMT clays could alter these hydrophilic clays, making them amphiphilic, and enable the lowering of toluene/water interfacial tension to 2.0 mN/m at the critical concentration of 0.1 wt %.

  17. Hydrothermal alkali metal catalyst recovery process

    DOEpatents

    Eakman, James M.; Clavenna, LeRoy R.

    1979-01-01

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

  18. High temperature alkali corrosion of ceramics in coal gas. Quarterly progress report {number_sign}9: September 1--December 1, 1993

    SciTech Connect

    Pickrell, G.R.; Sun, T.; Brown, J.J.

    1993-12-01

    High temperature alkali corrosion has been known to cause premature failure of ceramic components used in advanced high temperature coal combustion systems such as coal gasification and clean-up, coal fired gas turbines, and high efficiency heat engines. The objective of this research is to systematically evaluate the alkali corrosion resistance of the most commonly used structural ceramics including silicon carbide, silicon nitride, cordierite, mullite, alumina, aluminum titanate, zirconia, and fireclay glass. The study consists of identification of the alkali reaction products (phase equilibria) and the kinetics of the alkali reactions.

  19. Irradiation study of PNNL synthesized glass-ceramics

    SciTech Connect

    Kossoy-simakov, Anna-eden; Tang, Ming; Valdez, James A; Usov, Igor O; Sickafus, Kurt E

    2011-01-18

    Two types of glass-ceramic were investigated: (1) for immobilization of Ln, alkali, and alkaline earths (GC4); and (2) same as above + high (7%) molybdenum content (Mo7) multiphase specimens. The purpose was to study the radiation stability of PNNL synthesized glass-ceramics and changes in microstructure/phase composition.

  20. X-ray microtomography shows pore structure and tortuosity in alkali-activated binders

    SciTech Connect

    Provis, John L.; Myers, Rupert J.; White, Claire E.; Rose, Volker; Deventer, Jannie S.J. van

    2012-06-15

    Durability of alkali-activated binders is of vital importance in their commercial application, and depends strongly on microstructure and pore network characteristics. X-ray microtomography ({mu}CT) offers, for the first time, direct insight into microstructural and pore structure characteristics in three dimensions. Here, {mu}CT is performed on a set of sodium metasilicate-activated fly ash/slag blends, using a synchrotron beamline instrument. Segmentation of the samples into pore and solid regions is then conducted, and pore tortuosity is calculated by a random walker method. Segmented porosity and diffusion tortuosity are correlated, and vary as a function of slag content (slag addition reduces porosity and increases tortuosity), and sample age (extended curing gives lower porosity and higher tortuosity). This is particularly notable for samples with {>=} 50% slag content, where a space-filling calcium (alumino)silicate hydrate gel provides porosity reductions which are not observed for the sodium aluminosilicate ('geopolymer') gels which do not chemically bind water of hydration.

  1. Use of natural and synthetic aluminosilicates in decontamination of feed contaminated by fungi and micotoxins.

    PubMed

    Kołacz, R; Dobrzański, Z; Kulok, M

    2004-01-01

    The contamination of feed with micotoxin has been a serious problem in animal nutrition. Many existing methods of decontamination are not satisfying due to the toxicological safety and health quality of the fodder materials. It stimulates the scientists to search for the new methods. The use of sorbents in the form of natural and synthetic aluminosilicates is a promising direction. The efficacy of aluminosilicates towards aflatoxins has been proved. However, their influence on other micotoxins is not that obvious. According to the last investigations, the use of aluminosilicates in nutrition does not cause any side effects and widespread pathological effects are observed only when dosage is incorrect. Regarding the analyses that were published, it can be supposed that the addition of several different aluminosilicates is a sufficient protection against mycotoxicoses.

  2. Healing of lithographically introduced flaws in glass and glass containing ceramics

    SciTech Connect

    Ackler, H.D.

    1992-12-01

    The morphological evolution of cylindrical pores or ``channels`` and crack-like cavities in glass and glass-containing ceramics at elevated temperatures was studied. The systems studied were: Coming 7056 alkali borosilicate glass, soda-lime glass (microscope slides), a commercially available 96% Al{sub 2}O{sub 3}with {approx}5--10% intergranular glass, 96% Al{sub 2}O{sub 3} bonded to sapphire, and a model sapphire/glass/sapphire system fabricated by diffusion bonding etched and unetched pieces of sapphire onto which 30--50 nm of SiO{sub 2} had been sputter deposited. These systems span a broad range of glass contents, and permit observation of healing behavior with varying glass content. The results were compared with analytical models and results of similar studies in completely crystalline systems.

  3. Healing of lithographically introduced flaws in glass and glass containing ceramics

    SciTech Connect

    Ackler, H.D.

    1992-12-01

    The morphological evolution of cylindrical pores or channels'' and crack-like cavities in glass and glass-containing ceramics at elevated temperatures was studied. The systems studied were: Coming 7056 alkali borosilicate glass, soda-lime glass (microscope slides), a commercially available 96% Al[sub 2]O[sub 3]with [approx]5--10% intergranular glass, 96% Al[sub 2]O[sub 3] bonded to sapphire, and a model sapphire/glass/sapphire system fabricated by diffusion bonding etched and unetched pieces of sapphire onto which 30--50 nm of SiO[sub 2] had been sputter deposited. These systems span a broad range of glass contents, and permit observation of healing behavior with varying glass content. The results were compared with analytical models and results of similar studies in completely crystalline systems.

  4. Process for direct conversion of reactive metals to glass

    DOEpatents

    Rajan, John B.; Kumar, Romesh; Vissers, Donald R.

    1990-01-01

    Radioactive alkali metal is introduced into a cyclone reactor in droplet form by an aspirating gas. In the cyclone metal reactor the aspirated alkali metal is contacted with silica powder introduced in an air stream to form in one step a glass. The sides of the cyclone reactor are preheated to ensure that the initial glass formed coats the side of the reactor forming a protective coating against the reactants which are maintained in excess of 1000.degree. C. to ensure the formation of glass in a single step.

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

    SciTech Connect

    Joshi, Ashok V.; Balagopal, Shekar; Pendelton, Justin

    2011-12-13

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

  6. Process for recovering alkali metals and sulfur from alkali metal sulfides and polysulfides

    DOEpatents

    Gordon, John Howard; Alvare, Javier

    2016-10-25

    Alkali metals and sulfur may be recovered from alkali monosulfide and polysulfides in an electrolytic process that utilizes an electrolytic cell having an alkali ion conductive membrane. An anolyte solution includes an alkali monosulfide, an alkali polysulfide, or a mixture thereof and a solvent that dissolves elemental sulfur. A catholyte includes molten alkali metal. Applying an electric current oxidizes sulfide and polysulfide in the anolyte compartment, causes alkali metal ions to pass through the alkali ion conductive membrane to the catholyte compartment, and reduces the alkali metal ions in the catholyte compartment. Liquid sulfur separates from the anolyte solution and may be recovered. The electrolytic cell is operated at a temperature where the formed alkali metal and sulfur are molten.

  7. Alkali and transition metal phospholides

    NASA Astrophysics Data System (ADS)

    Bezkishko, I. A.; Zagidullin, A. A.; Milyukov, V. A.; Sinyashin, O. G.

    2014-06-01

    Major tendencies in modern chemistry of alkali and transition metal phospholides (phosphacyclopentadienides) are systematized, analyzed and generalized. Basic methods of synthesis of these compounds are presented. Their chemical properties are considered with a special focus on their complexing ability. Potential applications of phospholides and their derivatives are discussed. The bibliography includes 184 references.

  8. Utilization of calcite and waste glass for preparing construction materials with a low environmental load.

    PubMed

    Maeda, Hirotaka; Imaizumi, Haruki; Ishida, Emile Hideki

    2011-11-01

    In this study, porous calcite materials are hydrothermally treated at 200 °C using powder compacts consisting of calcite and glasses composed of silica-rich soda-lime. After treatment, the glasses are converted into calcium aluminosilicate hydrates, such as zeolite phases, which increase their strength. The porosity and morphology of new deposits of hydrothermally solidified materials depend up on the chemical composition of glass. The use of calcite and glass in the hydrothermal treatment plays an important role in the solidification of calcite without thermal decomposition. PMID:21794973

  9. Effects of Anions on Local Structure of Al and Si in Aluminosilicates.

    PubMed

    Miyazaki; Yokoyama

    1999-06-15

    Three kinds of amorphous aluminosilicates were synthesized by coprecipitation of silicic acid with aluminum hydroxide in the presence of different inorganic ions: sulfate, chloride, and nitrate. Although the bulk composition of the aluminosilicates obtained was not affected by anion species, their DTA spectra were significantly different, suggesting that their structures also differ. The local structure of Al and Si in the aluminosilicates was studied in detail by 27Al and 29Si MAS NMR. From the 27Al MAS NMR spectra and comparison between 29Si HD- and CP-MAS NMR spectra, it was concluded that the aluminosilicate obtained in the presence of sulfate ions has only a montmorillonite-like structure, whereas in the cases of chloride and nitrate, the solids are composed of three phases: aluminum hydroxide, silica, and the montmorillonite-like aluminosilicate. The difference in the local structure of Al and Si in the aluminosilicates was explained by the difference in interaction between the anions and aluminum ions. Copyright 1999 Academic Press.

  10. Effects of anions on local structure of Al and Si in aluminosilicates

    SciTech Connect

    Miyazaki, Akane; Yokoyama, Takushi

    1999-06-15

    Three kinds of amorphous aluminosilicates were synthesized by coprecipitation of silicic acid with aluminum hydroxide in the presence of different inorganic ions: sulfate, chloride, and nitrate. Although the bulk composition of the aluminosilicates obtained was not affected by anion species, their DTA spectra were significantly different, suggesting that their structures also differ. The local structure of Al and Si in the aluminosilicates was studied in detail by {sup 27}Al and {sup 29}Si MAS NMR. From the {sup 27}Al MAS NMR spectra and comparison between {sup 29}Si HD- and CP-MAS NMR spectra, it was concluded that the aluminosilicate obtained in the presence of sulfate ions has only a montmorillonite-like structure, whereas in the cases of chloride and nitrate, the solids are composed of three phases: aluminum hydroxide, silica, and the montmorillonite-like aluminosilicate. The difference in the local structure of Al and Si in the aluminosilicates was explained by the difference in interaction between the anions and aluminum ions.

  11. A New Titanium-Bearing Calcium Aluminosilicate Phase. 1; Meteoritic Occurrences and Formation in Synthetic Systems

    NASA Technical Reports Server (NTRS)

    Paque, Julie M.; Beckett, John R.; Barber, David J.; Stolper, Edward M.

    1994-01-01

    A new titanium-bearing calcium aluminosilicate mineral has been identified in coarse-grained calcium-aluminum-rich inclusions (CAIs) from carbonaceous chondrites. The formula for this phase, which we have temporarily termed "UNK," is Ca3Ti(AlTi)2(Si,Al)3O14, and it is present in at least 8 of the 20 coarse-grained CAIs from the Allende CV3 chondrite examined as part of this project. The phase occurs in Types A and B1 inclusions as small tabular crystals oriented along two mutually perpendicular planes in melilite. UNK crystallizes from melts in dynamic crystallization experiments conducted in air from four bulk compositions modeled after Types A, B1, B2 and C inclusions. Cooling rates resulting in crystallization of UNK ranged from 0.5 to 200 C/h from maximum (initial) temperatures of 1375 to 1580 C. Only below 1190 C does UNK itself begin to crystallize. To first order, the presence or absence of UNK from individual experiments can be understood in terms of the compositions of residual melts and nucleation probabilities. Compositions of synthetic and meteoritic LINK are very similar in terms of major oxides, differing only in the small amounts of trivalent Ti (7-13% of total Ti) in meteoritic samples. UNK crystallized from the Type A analog is similar texturally to that found in CAls, although glass, which is typically associated with synthetic UN& is not observed in meteoritic occurrences. A low Ti end-member of UNK ("Si-UNK") with a composition new that of Ca3Al2Si4O14 was produced in a few samples from the Type B1 analog. This phase has not been found in the meteoritic inclusions.

  12. FTIR Analysis of Alkali Activated Slag and Fly Ash Using Deconvolution Techniques

    NASA Astrophysics Data System (ADS)

    Madavarapu, Sateesh Babu

    The studies on aluminosilicate materials to replace traditional construction materials such as ordinary Portland cement (OPC) to reduce the effects caused has been an important research area for the past decades. Many properties like strength have already been studied and the primary focus is to learn about the reaction mechanism and the effect of the parameters on the formed products. The aim of this research was to explore the structural changes and reaction product analysis of geopolymers (Slag & Fly Ash) using Fourier transform infrared spectroscopy (FTIR) and deconvolution techniques. Spectroscopic techniques give valuable information at a molecular level but not all methods are economic and simple. To understand the mechanisms of alkali activated aluminosilicate materials, attenuated total reflectance (ATR) FTIR has been used where the effect of the parameters on the reaction products have been analyzed. To analyze complex systems like geopolymers using FTIR, deconvolution techniques help to obtain the properties of a particular peak attributed to a certain molecular vibration. Time and temperature dependent analysis were done on slag pastes to understand the polymerization of reactive silica in the system with time and temperature variance. For time dependent analysis slag has been activated with sodium and potassium silicates using two different `n'values and three different silica modulus [Ms- (SiO2 /M2 O)] values. The temperature dependent analysis was done by curing the samples at 60°C and 80°C. Similarly fly ash has been studied by activating with alkali hydroxides and alkali silicates. Under the same curing conditions the fly ash samples were evaluated to analyze the effects of added silicates for alkali activation. The peak shifts in the FTIR explains the changes in the structural nature of the matrix and can be identified using the deconvolution technique. A strong correlation is found between the concentrations of silicate monomer in the

  13. Geopolymers prepared from DC plasma treated air pollution control (APC) residues glass: properties and characterisation of the binder phase.

    PubMed

    Kourti, Ioanna; Devaraj, Amutha Rani; Bustos, Ana Guerrero; Deegan, David; Boccaccini, Aldo R; Cheeseman, Christopher R

    2011-11-30

    Air pollution control (APC) residues have been blended with glass-forming additives and treated using DC plasma technology to produce a high calcium aluminosilicate glass (APC glass). This has been used to form geopolymer-glass composites that exhibit high strength and density, low porosity, low water absorption, low leaching and high acid resistance. The composites have a microstructure consisting of un-reacted residual APC glass particles imbedded in a complex geopolymer and C-S-H gel binder phase, and behave as particle reinforced composites. The work demonstrates that materials prepared from DC plasma treated APC residues have potential to be used to form high quality pre-cast products.

  14. Valorization of sugarcane bagasse ash: producing glass-ceramic materials.

    PubMed

    Teixeira, S R; Magalhães, R S; Arenales, A; Souza, A E; Romero, M; Rincón, J M

    2014-02-15

    Some aluminosilicates, for example mullite and wollastonite, are very important in the ceramic and construction industries. The most significant glass-ceramic for building applications has wollastonite as the main crystal phase. In this work we report on the use of sugarcane bagasse ash (SCBA) to produce glass-ceramics with silicates as the major crystalline phases. The glasses (frits) were prepared by mixing ash, limestone (calcium and magnesium carbonates) and potassium carbonate as the fluxing agent. X-ray fluorescence was used to determine the chemical composition of the glasses and their crystallization was assessed by using thermal analysis (DTA/DSC/TGA) and X-ray diffraction. The results showed that glass-ceramic material can be produced with wollastonite as the major phase, at a temperature lower than 900 °C. PMID:24463731

  15. Valorization of sugarcane bagasse ash: producing glass-ceramic materials.

    PubMed

    Teixeira, S R; Magalhães, R S; Arenales, A; Souza, A E; Romero, M; Rincón, J M

    2014-02-15

    Some aluminosilicates, for example mullite and wollastonite, are very important in the ceramic and construction industries. The most significant glass-ceramic for building applications has wollastonite as the main crystal phase. In this work we report on the use of sugarcane bagasse ash (SCBA) to produce glass-ceramics with silicates as the major crystalline phases. The glasses (frits) were prepared by mixing ash, limestone (calcium and magnesium carbonates) and potassium carbonate as the fluxing agent. X-ray fluorescence was used to determine the chemical composition of the glasses and their crystallization was assessed by using thermal analysis (DTA/DSC/TGA) and X-ray diffraction. The results showed that glass-ceramic material can be produced with wollastonite as the major phase, at a temperature lower than 900 °C.

  16. Characterization of Glass-Like Fragments from the 3714 Building

    SciTech Connect

    Buck, Edgar C.

    2010-02-23

    This report describes characterization of a sample obtained from the 3714 building in the 300 Area. Characterization of this unknown material was required for the demonolition activities in the 300 Area. The object of the study was to dertermine the nature of the material, composition, possible structure, evidence for hazards components. The green material is a sodium alumino-silicate glass. This conclusion is based on the composition provided by SEM-EDS, and the images that suggest a glass-like morphology. Further analysis with Ramin and/or infrared could be used to determine the presence of any organics.

  17. Formation and durability of hydrated layers for several oxide glasses

    SciTech Connect

    Nishii, Junji; Akai, Tomoko; Yamashita, Masaru; Yamanaka, Hiroshi; Wakabayashi, Hajimu

    1995-12-31

    Formations and durabilities of hydrated layers were compared between a soda-aluminosilicate (NAS), a soda-lime-aluminosilicate (NCAS) and a soda-lime-alumino-borosilicate (NCABS) glasses. The first step of the study was to prepare the optically transparent hydrated layers on the surface of specimens by an autoclave (400 C, 20 kgf/cm{sup 2}) treatment. Distributions of OH groups in hydrated layers were analyzed by an etch sectioning and FTIR measurement. The rates of hydration of the glasses were in the order NAS {much_gt} NCAS > NCABS. The hydration of the NCABS glass, which is a modified nuclear waste glass, required the treatment longer than those of the NAS and NCAS glasses. In the second step, the authors investigated the durabilities of hydrated layers by immersing the specimens into a distilled water at 100 C. The dissolutions of hydrated layers were confirmed for each glass. The dissolution rates of hydrated layers were in the order NCAS > NCABS {much_gt} NAS. It has become apparent by an XPS analysis that the highest durability of the hydrated NAS glass was due to the formation of a sodium free Al{sub 2}O{sub 3}-SiO{sub 2} layer on the surface. The hydrated layer of the NCAS glass, while the sodium ions were almost leached out during immersion, dissolved to water most quickly than those of other glasses. In the hydrated layer of the NCABS glass, a half amount of sodium and boron ions remained and inhibited the dissolution of hydrated layer.

  18. X-ray-absorption spectroscopic investigation of alkali and alkaline earth catalysts in coal gasification. Final report, January 1987-September 1989

    SciTech Connect

    Huggins, F.E.; Shah, N.; Huffman, G.P.

    1990-04-01

    The structures of alkali and alkaline-earth metal catalyst species in lignite and polymer chars and during pyrolysis pretreatment and char gasification have been investigated using ambient and newly-developed, in situ XAFS spectroscopic techniques. The XAFS data, which were obtained at the Stanford Synchrotron Radiation Laboratory, were supplemented by char characterization and reactivity measurements made at the Pennsylvania State University. The findings of the investigation are as follows: (i) the catalytic species, as introduced to the char or lignite, is an atomically-dispersed, metal-ion-oxygen-anion complex, and remains a metal-oxygen complex throughout pyrolysis and gasification; (ii) the catalyst species transforms to a bulk oxide species during pyrolysis pretreatment; (iii) during gasification, the catalyst species rapidly transforms to bulk alkali carbonate in the case of the alkali-metal species and slowly to calcium oxide in the case of the calcium species; (iv) higher catalyst loadings results in an increased number of catalytic sites, rather than any structural variation of the catalyst site due to concentration effects; and (v) reaction of alkali with aluminosilicates (from clays) or silica is the major catalyst poisoning reaction, unless the coal is demineralized in which case the alkali may react with residual halide from HCl or HF used to clean the coal. Such poisoning reactions were not demonstrated for calcium-oxygen species.

  19. The metapelitic garnet biotite muscovite aluminosilicate quartz (GBMAQ) geobarometer

    NASA Astrophysics Data System (ADS)

    Wu, Chun-Ming; Zhao, Guochun C.

    2007-09-01

    In this contribution we have empirically calibrated the garnet-biotite-muscovite-aluminosilicate-quartz (GBMAQ) barometer using low- to medium-high-pressure, mid-grade metapelites. Application of the barometer suggests that the GBMAQ and GASP barometers show quite similar pressure estimates. Furthermore, metapelites within thermal contact aureole or very limited geographic area show no meaningful pressure diversity determined by the GBMAQ and GASP barometers which is the geological reality. The random error of the GBMAQ barometer is expected to be around ± 0.8 kbar, and this barometer shows no systematic bias with respect to either pressure, or temperature, or Al VI in muscovite, or Fe in biotite, or Fe in garnet. The GBMAQ barometer is thermodynamically consistent with the garnet-biotite geothermometer because they share the same activity models of both garnet and biotite. This barometer is especially useful for assemblages with Ca-poor garnet or Ca-poor plagioclase or plagioclase-absent metapelites. Application of this barometer beyond the calibration ranges, i.e., P- T range and chemical ranges of the minerals, is not encouraged.

  20. Electro-optical parameters of bond polarizability model for aluminosilicates.

    PubMed

    Smirnov, Konstantin S; Bougeard, Daniel; Tandon, Poonam

    2006-04-01

    Electro-optical parameters (EOPs) of bond polarizability model (BPM) for aluminosilicate structures were derived from quantum-chemical DFT calculations of molecular models. The tensor of molecular polarizability and the derivatives of the tensor with respect to the bond length are well reproduced with the BPM, and the EOPs obtained are in a fair agreement with available experimental data. The parameters derived were found to be transferable to larger molecules. This finding suggests that the procedure used can be applied to systems with partially ionic chemical bonds. The transferability of the parameters to periodic systems was tested in molecular dynamics simulation of the polarized Raman spectra of alpha-quartz. It appeared that the molecular Si-O bond EOPs failed to reproduce the intensity of peaks in the spectra. This limitation is due to large values of the longitudinal components of the bond polarizability and its derivative found in the molecular calculations as compared to those obtained from periodic DFT calculations of crystalline silica polymorphs by Umari et al. (Phys. Rev. B 2001, 63, 094305). It is supposed that the electric field of the solid is responsible for the difference of the parameters. Nevertheless, the EOPs obtained can be used as an initial set of parameters for calculations of polarizability related characteristics of relevant systems in the framework of BPM.

  1. SODIUM ALUMINOSILICATE SOLIDS AFFINITY FOR CESIUM AND ACTINIDES

    SciTech Connect

    Peters, T; Bill Wilmarth, B; Samuel Fink, S

    2007-07-31

    Washed sodium-aluminosilicate (NAS) solids at initial concentrations of 3.55 and 5.4 g/L sorb or uptake virtually no cesium over 288 hours, nor do any NAS solids generated during that time. These concentrations of solids are believed to conservatively bound current and near-term operations. Hence, the NAS solids should not have affected measurements of the cesium during the mass transfer tests and there is minimal risk of accumulating cesium during routine operations (and hence posing a gamma radiation exposure risk in maintenance). With respect to actinide uptake, it appears that NAS solids sorb minimal quantities of uranium - up to 58 mg U per kg NAS solid. The behavior with plutonium is less well understood. Additional study may be needed for radioactive operations relative to plutonium or other fissile component sorption or trapping by the solids. We recommend this testing be incorporated in the planned tests using samples from Tank 25F and Tank 49H to extend the duration to bound expected inventory time for solution.

  2. Ageing characteristics of aluminium alloy aluminosilicate discontinuous fiber reinforced composites

    SciTech Connect

    Nath, D.; Singh, V.

    1999-03-05

    Development of continuous fiber reinforced metal matrix composites is aimed at providing high specific strength and stiffness needed for aerospace and some critical high temperature structural applications. Considerable efforts have been made, during the last decade, to improve the strength of age-hardening aluminium alloy matrix composites by suitable heat treatment. It has also been well established that age-hardenable aluminium alloy composites show accelerated ageing behavior because of enhanced dislocation density at the fiber/matrix interface resulting from thermal expansion mismatch between ceramic fiber and the metal matrix. The accelerated ageing of aluminium alloy composites either from dislocation density or the residual stress, as a result of thermal expansion mismatch is dependent on the size of whisker and particulate. Investigations have also been made on the effect of volume fraction of particulate on the ageing behavior of aluminium alloys. The present investigation is concerned with characterization of age-hardening behavior of an Al-Si-Cu-Mg(AA 336) alloy alumino-silicate discontinuous fiber-reinforced composites (referred to as aluminium MMCs in the present text) being developed for automotive pistons. An effort is made to study the effect of volume fraction of the reinforcement on age-hardening behavior of this composite.

  3. Protein adsorption to multi-component glasses

    NASA Astrophysics Data System (ADS)

    Hall, Matthew Micah

    2003-07-01

    The adsorption of human serum albumin (HSA) to sodium silicate, soda lime silicate (SLS), and sodium aluminosilicate (SAS) glass microspheres was investigated using sodiumdodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) in conjunction with a colloidal silver stain for visualization. The 30 Na2O·70 SiO2 composition could not be evaluated due to an apparent chemical interference that occurred during silver staining. This inhibitory effect was attributed to the extensive corrosion that occurred during the protein elution and caused an elevation in the pH of the solution. The remaining glass compositions were sufficiently durable for further study. The HSA adsorption capacity of SLS glass microspheres containing 70 and 80 mol% SiO2 increased as CaO was substituted for Na2O. An abrupt decrease in the HSA adsorption capacity was observed for SLS glasses containing 60 mol% SiO2. A similar trend was observed for the SAS glass microspheres, although the SAS glasses adsorbed less HSA than the SLS glasses containing equivalent molar percentages of SiO2. The initial increase in HSA adsorption capacity for SLS and SAS glasses containing 70 and 80 MOM SiO2 was attributed to the introduction of positive charges into the glass surfaces via Ca2+ and Al3+ cations. The decrease in HSA adsorption capacity for SLS and SAS glasses containing 60 mol% SiO2 may be due to an enhanced affinity between the glasses and HSA, resulting in a "flattened" conformation that limits the total accessible area for adsorption.

  4. Alkali metal/sulfur battery

    DOEpatents

    Anand, Joginder N.

    1978-01-01

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

  5. Detecting Nanophase Weathering Products with CheMin: Reference Intensity Ratios of Allophane, Aluminosilicate Gel, and Ferrihydrite

    NASA Technical Reports Server (NTRS)

    Rampe, E. B.; Bish, D. L.; Chipera, S. J.; Morris, R. V.; Achilles, C. N.; Ming, D W.; Blake, D. F.; Anderson, R. C.; Bristow, T. F.; Crisp, A.; DesMarais, D. J.; Downs, R. T.; Farmer, J. D.; Morookian, J. M.; Morrison, S. M.; Sarrazin, P.; Spanovich, N.; Stolper, E. M.; Treiman, A. H.; Vaniman, D. T.; Yen, A. S.

    2013-01-01

    X-ray diffraction (XRD) data collected of the Rocknest samples by the CheMin instrument on Mars Science Laboratory suggest the presence of poorly crystalline or amorphous materials [1], such as nanophase weathering products or volcanic and impact glasses. The identification of the type(s) of X-ray amorphous material at Rocknest is important because it can elucidate past aqueous weathering processes. The presence of volcanic and impact glasses would indicate that little chemical weathering has occurred because glass is highly susceptible to aqueous alteration. The presence of nanophase weathering products, such as allophane, nanophase iron-oxides, and/or palagonite, would indicate incipient chemical weathering. Furthermore, the types of weathering products present could help constrain pH conditions and identify which primary phases altered to form the weathering products. Quantitative analysis of phases from CheMin data is achieved through Reference Intensity Ratios (RIRs) and Rietveld refinement. The RIR of a mineral (or mineraloid) that relates the scattering power of that mineral (typically the most intense diffraction line) to the scattering power of a separate mineral standard such as corundum [2]. RIRs can be calculated from XRD patterns measured in the laboratory by mixing a mineral with a standard in known abundances and comparing diffraction line intensities of the mineral to the standard. X-ray amorphous phases (e.g., nanophase weathering products) have broad scattering signatures rather than sharp diffraction lines. Thus, RIRs of X-ray amorphous materials are calculated by comparing the area under one of these broad scattering signals with the area under a diffraction line in the standard. Here, we measured XRD patterns of nanophase weathering products (allophane, aluminosilicate gel, and ferrihydrite) mixed with a mineral standard (beryl) in the CheMinIV laboratory instrument and calculated their RIRs to help constrain the abundances of these phases in

  6. Upconversion in erbium-doped transparent glass ceramics

    NASA Astrophysics Data System (ADS)

    Jones, Gina Christine

    2005-11-01

    Transparent glass ceramics (TGCs) are a class of materials that are composed of a robust glass matrix which is densely embedded with nanometer-sized fluoride crystals: In bulk, fluoride materials tend to have poor handling and mechanical properties, and can be expensive to produce. In contrast, the forming and handling properties of the TGC are similar to those of the precursor, glass, and are engineered to be robust and mechanically stable. Rare earth ions can be incorporated into the TGC during manufacture and can become partially segregated into the crystalline phase. There they experience the low-phonon energy environment of the fluoride nanocrystallite, which induces long energy level lifetimes and enhanced frequency upconversion. Therefore, rare earth doped TGCs can have the spectroscopic properties of a crystal with the durability of an aluminosilicate glass. Upconversion fluorescence is studied for an aluminosilicate TGC containing LaF3 nanocrystallites and doped with an erbium density of 1.7 x 1020 CM-3. Time gated fluorescence and excitation spectra as well as photoluminescence decays are used to find the nature and origin of this fluorescence. It is determined that energy transfer upconversion occurs only in the nanocrystallite phase and sequential two-photon absorption upconversion occurs in both glass and crystal phases.

  7. Glass sealing

    SciTech Connect

    Brow, R.K.; Kovacic, L.; Chambers, R.S.

    1996-04-01

    Hernetic glass sealing technologies developed for weapons component applications can be utilized for the design and manufacture of fuel cells. Design and processing of of a seal are optimized through an integrated approach based on glass composition research, finite element analysis, and sealing process definition. Glass sealing procedures are selected to accommodate the limits imposed by glass composition and predicted calculations.

  8. Glass transition temperature and conductivity in Li2O and Na2O doped borophosphate glasses

    NASA Astrophysics Data System (ADS)

    Ashwajeet, J. S.; Sankarappa, T.; Ramanna, R.; Sujatha, T.; Awasthi, A. M.

    2015-08-01

    Two alkali doped Borophosphate glasses in the composition, (B2O3)0.2. (P2O5)0.3. (Na2O)(0.5-x). (Li2O)x, where x = 0.05 to 0.50 were prepared by standard melt quenching method at 1200K. Non-crystalline nature was confirmed by XRD studies. Room temperature density was measured by Archimedes principle. DC conductivity in the temperature range from 300K to 575K has been measured. Samples were DSC studied in the temperature range from 423K to 673K and glass transition temperature was determined. Glass transition temperature passed through minima for Li2O con.2centration between 0.25 and 0.30 mole fractions. Activation energy of conduction has been determined by analyzing temperature variation of conductivity determining Arrhenius law. Conductivity passed through minimum and activation passed through maximum for Li2O content from 0.25 to 0.30 mole fractions. Glass transition temperature passed through minimum for the same range of Li2O content. These results revealed mixed alkali effect taking place in these glasses. It is for the first time borophosphate glasses doped with Li2O and Na2O have been studied for density and dc conductivity and, the mixed alkali effect (MAE) has been observed.

  9. Durabiliy of two simulated nuclear waste glasses, a frit glass, and tektite in aqueous solutions: Final report, Volume I

    SciTech Connect

    Hagen, D.A.; Altstetter, C.J.; Brown, S.D.

    1988-05-01

    High level nuclear waste is commonly incorporated into glass for disposal. Therefore the long term aqueous durability of the waste glass is important. The leaching behavior of three simulated nuclear waste glasses (AH10, AH165, and Frit 165) and a natural glass (tektite) were examined using nuclear reaction analysis, leachate solution analysis, and microscopy. The three simulated waste glasses developed hydrated layers which increased in thickness by t/sup /1/2//. The hydrated layer in Frit 165 reached a constant thickness of about one micron. Alkali were preferentially removed from the Frit 165 and AH10. The tektite corroded by slow uniform dissolution. 94 refs., 68 figs., 13 tabs.

  10. Aluminosilicate Formation in High Level Waste Evaporators: A Mechanism for Uranium Accumulation

    SciTech Connect

    Wilmarth, W.R.

    2002-02-08

    High level waste Evaporators at the Savannah River Site (SRS) process radioactive waste to concentrate supernate and thus conserve tank space. In June of 1997, difficulty in evaporator operation was initially observed. This operational difficulty evidenced itself as a plugging of the evaporator's gravity drain line (GDL). The material blocking the GDL was determined to be a sodium aluminosilicate. Following a mechanical cleaning of the GDL, the evaporator was returned to service until October 1999. At this time massive deposits were discovered in the evaporator pot. As a result of the changes in evaporator chemistry and the resulting formation of aluminosilicate deposits in the evaporator, a comprehensive research and development program has been undertaken. This program is underway in order to assist in understanding the new evaporator chemistry and gain insight into the deposition phenomena. Key results from testing in FY01 have demonstrated that the chemistry of the evaporator feed favors aluminosilicate formation. Both the reaction kinetics and particle growth of the aluminosilicate material under SRS evaporator conditions has been demonstrated to occur within the residence times utilized in the SRS evaporator operation. Batch and continuous-flow experiments at known levels of supersaturation have shown a significant correlation between the deposition of aluminosilicates and mixing intensity in the vessel. Advances in thermodynamic modeling of the evaporator chemistry have been accomplished. The resulting thermodynamic model has been related to the operational history of the evaporator, is currently assisting in feed selection, and could potentially assist in expanding the operating envelopes technical baselines for evaporator operation.

  11. The BRAG and GM2003 Models for Glass Dissolution

    SciTech Connect

    Aertsens, Marc

    2007-07-01

    The GM2003 model extends the r(t) glass dissolution model with water diffusion through the diffusion layer. Boron and alkali diffusion through the diffusion layer is described by introducing a retention factor K{sub d,i} between boron/alkali and water in the diffusion layer. Introducing a boron/alkali diffusion coefficient, the BRAG model describes boron/alkali diffusion in the diffusion layer as well. It is shown that both models are consistent with each other and an expression is derived for the boron/alkali diffusion coefficient (BRAG) as a function of both parameters of GM2003: the retention factor K{sub d,i} and the water diffusion coefficient D{sub H{sub 2}}{sub O} in the diffusion layer. From dissolution data only, it is possible to fit the value for the boron/alkali diffusion coefficient in the diffusion layer but due to correlations the individual values of both parameters K{sub d,i} and DH{sub 2}O of GM2003 cannot be determined. From theoretical considerations follows that the K{sub d,i} value for boron/alkali should be slightly larger than 0.1 kg/liter. A user friendly code for the BRAG model allows automatic fits of glass dissolution data in water. (authors)

  12. Aqueous dissolution of sodium aluminosilicate geopolymers derived from metakaolin

    NASA Astrophysics Data System (ADS)

    Aly, Z.; Vance, E. R.; Perera, D. S.

    2012-05-01

    In dilute aqueous solutions, the elemental releases of Na, Al and Si from a metakaolin-based sodium aluminosilicate geopolymer were not very sensitive to pH in the range of 4-10 but increased outside this range, particularly on the acidic side. To minimise pH drifts, experiments were carried out using small amounts of graded powders in relatively large volumes of water. In deionised water, the Na dissolution rate in 7 days was dominant and increased by at least a factor of ˜4 on heating from 18 to 90 °C, with greater increases in the extractions of Al and Si. At 18 °C the elemental extractions in deionised water increased approximately linearly with time over the 1-7 days period. Further exposure led to a slower extraction into solution for Na and Si, with a decrease in extraction of Al. It was deduced that framework dissolution was important in significantly acidic or alkaline solutions, but that contributions from water transfer from pores to elemental extractions were present, even at low temperatures in neutral solutions. It was also deduced from the Na release data that the Na leaching kinetics of geopolymer in deionised water (dilute solutions) followed the pseudo-second-order kinetic model and the pseudo-second-order rate constant evaluated. Contact with KCl, KHCO3, and pH ˜6 and 10 potassium phthalate buffer solutions gave rise to a high degree of Na+ ↔ K+ exchange and rendered the framework ions less leachable in water.

  13. Chemiluminescence from excited c 2- -alkali cation complexes formed in alkali atom-halocarbon flames

    NASA Astrophysics Data System (ADS)

    Lin, K. K.; Balling, L. C.; Wright, J. J.

    1987-01-01

    Vapor phase reactions between alkali atoms and several halocarbon molecules containing C-C bonds have been observed to produce chemiluminescence which appears to originate from C 2-- (alkali) + complexes.

  14. Space processing of chalcogenide glasses

    NASA Technical Reports Server (NTRS)

    Larsen, D. C.; Ali, M. A.

    1975-01-01

    Chalcogenide glasses are discussed as good infrared transmitters, possessing the strength, corrosion resistance, and scale-up potential necessary for large 10.6-micron windows. The disadvantage of earth-produced chalcogenide glasses is shown to be an infrared absorption coefficient which is unacceptably high relative to alkali halides. This coefficient is traced to optical nonhomogeneities resulting from environmental and container contamination. Space processing is considered as a means of improving the infrared transmission quality of chalcogenides and of eliminating the following problems: optical inhomogeneities caused by thermal currents and density fluctuation in the l-g earth environment; contamination from the earth-melting crucible by oxygen and other elements deleterious to infrared transmission; and, heterogeneous nucleation at the earth-melting crucible-glass interface.

  15. Synthesis and Luminescence Properties of Transparent Nanocrystalline GdF3:Tb Glass-Ceramic Scintillator

    PubMed Central

    Lee, Gyuhyon; Savage, Nicholas; Wagner, Brent; Zhang, Yuelan; Jacobs, Benjamin; Menkara, Hisham; Summers, Christopher; Kang, Zhitao

    2014-01-01

    Transparent glass-ceramic containing rare-earth doped halide nanocrystals exhibits enhanced luminescence performance. In this study, a glass-ceramic with Tb doped gadolinium fluoride nanocrystals embedded in an aluminosilicate glass matrix is investigated for X-ray imaging applications. The nanocrystalline glass-ceramic scintillator was prepared by a melt-quench method followed by an anneal. The GdF3:Tb nanocrystals precipitated within the oxide glass matrix during the processing and their luminescence and scintillation properties were investigated. In this nanocomposite scintillator system, the incorporation of high atomic number Gd compound into the glass matrix increases the X-ray stopping power of the glass scintillator, and effective energy transfer between Gd3+ and Tb3+ ions in the nanocrystals enhances the scintillation efficiency. PMID:24610960

  16. Synthesis and Luminescence Properties of Transparent Nanocrystalline GdF3:Tb Glass-Ceramic Scintillator.

    PubMed

    Lee, Gyuhyon; Savage, Nicholas; Wagner, Brent; Zhang, Yuelan; Jacobs, Benjamin; Menkara, Hisham; Summers, Christopher; Kang, Zhitao

    2014-03-01

    Transparent glass-ceramic containing rare-earth doped halide nanocrystals exhibits enhanced luminescence performance. In this study, a glass-ceramic with Tb doped gadolinium fluoride nanocrystals embedded in an aluminosilicate glass matrix is investigated for X-ray imaging applications. The nanocrystalline glass-ceramic scintillator was prepared by a melt-quench method followed by an anneal. The GdF3:Tb nanocrystals precipitated within the oxide glass matrix during the processing and their luminescence and scintillation properties were investigated. In this nanocomposite scintillator system, the incorporation of high atomic number Gd compound into the glass matrix increases the X-ray stopping power of the glass scintillator, and effective energy transfer between Gd(3+) and Tb(3+) ions in the nanocrystals enhances the scintillation efficiency.

  17. Glass Ceramic Formulation Data Package

    SciTech Connect

    Crum, Jarrod V.; Rodriguez, Carmen P.; McCloy, John S.; Vienna, John D.; Chung, Chul-Woo

    2012-06-17

    A glass ceramic waste form is being developed for treatment of secondary waste streams generated by aqueous reprocessing of commercial used nuclear fuel (Crum et al. 2012b). The waste stream contains a mixture of transition metals, alkali, alkaline earths, and lanthanides, several of which exceed the solubility limits of a single phase borosilicate glass (Crum et al. 2009; Caurant et al. 2007). A multi-phase glass ceramic waste form allows incorporation of insoluble components of the waste by designed crystallization into durable heat tolerant phases. The glass ceramic formulation and processing targets the formation of the following three stable crystalline phases: (1) powellite (XMoO4) where X can be (Ca, Sr, Ba, and/or Ln), (2) oxyapatite Yx,Z(10-x)Si6O26 where Y is alkaline earth, Z is Ln, and (3) lanthanide borosilicate (Ln5BSi2O13). These three phases incorporate the waste components that are above the solubility limit of a single-phase borosilicate glass. The glass ceramic is designed to be a single phase melt, just like a borosilicate glass, and then crystallize upon slow cooling to form the targeted phases. The slow cooling schedule is based on the centerline cooling profile of a 2 foot diameter canister such as the Hanford High-Level Waste canister. Up to this point, crucible testing has been used for glass ceramic development, with cold crucible induction melter (CCIM) targeted as the ultimate processing technology for the waste form. Idaho National Laboratory (INL) will conduct a scaled CCIM test in FY2012 with a glass ceramic to demonstrate the processing behavior. This Data Package documents the laboratory studies of the glass ceramic composition to support the CCIM test. Pacific Northwest National Laboratory (PNNL) measured melt viscosity, electrical conductivity, and crystallization behavior upon cooling to identify a processing window (temperature range) for melter operation and cooling profiles necessary to crystallize the targeted phases in the

  18. Regenerable activated bauxite adsorbent alkali monitor probe

    DOEpatents

    Lee, Sheldon H. D.

    1992-01-01

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

  19. Regenerable activated bauxite adsorbent alkali monitor probe

    DOEpatents

    Lee, S.H.D.

    1992-12-22

    A regenerable activated bauxite adsorber alkali monitor probe for field applications to provide reliable measurement of alkali-vapor concentration in combustion gas with special emphasis on pressurized fluidized-bed combustion (PFBC) off-gas. More particularly, the invention relates to the development of a easily regenerable bauxite adsorbent for use in a method to accurately determine the alkali-vapor content of PFBC exhaust gases. 6 figs.

  20. Volcanic glasses, their origins and alteration processes

    USGS Publications Warehouse

    Friedman, I.; Long, W.

    1984-01-01

    Natural glass can be formed by volcanic processes, lightning (fulgarites) burning coal, and by meteorite impact. By far the most common process is volcanic - basically the glass is rapidly chilled molten rock. All natural glasses are thermodynamically unstable and tend to alter chemically or to crystallize. The rate of these processes is determined by the chemical composition of the magma. The hot and fluid basaltic melts have a structure that allows for rapid crystal growth, and seldom forms glass selvages greater than a few centimeters thick, even when the melt is rapidly cooled by extrusion in the deep sea. In contrast the cooler and very viscous rhyolitic magmas can yield bodies of glass that are tens of meters thick. These highly polymerized magmas have a high silica content - often 71-77% SiO2. Their high viscosity inhibits diffusive crystal growth. Basalt glass in sea water forms an alteration zone called palagonite whose thickness increases linearly with time. The rate of diffusion of water into rhyolitic glass, which follows the relationship - thickness = k (time) 1 2, has been determined as a function of the glass composition and temperature. Increased SiO2 increases the rate, whereas increased CaO, MgO and H2O decrease the rate. The activation energy of water diffusion varies from about 19 to 22 kcal/mol. for the glasses studied. The diffusion of alkali out of rhyolite glass occurs simultaneously with water diffusion into the glass. The rate of devitrification of rhyolitic glass is a function of the glass viscosity, which in turn is a function of water content and temperature. Although all of the aforementioned processes tend to destroy natural glasses, the slow rates of these processes, particularly for rhyolitic glass, has allowed samples of glass to persist for 60 million years. ?? 1984.

  1. Glass capable of ionic conduction and method of preparation

    DOEpatents

    Susman, S.; Boehm, L.; Volin, K.J.; Delbecq, C.J.

    1982-05-06

    Sulfide glasses capable of conducting alkali metal ions are prepared from a nonmetal glass former such as GeS/sub 2/, B/sub 2/S/sub 2/ and SiS/sub 2/ in mixture with a glass modifier such as Na/sub 2/S or another alkali metal sulfide. A molten mixture of the constituents is rapidly quenched to below the glass transition temperature by contact with a metal mold. The rapid quench is sufficient to prevent crystallization and permit solidification as an amorphous solid mixture. An oxygen-free atmosphere is maintained over the mixture to prevent oxidation. A new glass system of (1 - X) Na/sub 2/O:XB/sub 2/S/sub 3/ is disclosed.

  2. Glass capable of ionic conduction and method of preparation

    DOEpatents

    Susman, Sherman; Boehm, Leah; Volin, Kenneth J.; Delbacq, Charles J.

    1985-01-01

    Sulfide glasses capable of conducting alkali metal ions are prepared from a nonmetal glass former such as GeS.sub.2, B.sub.2 S.sub.3 and SiS.sub.2 in mixture with a glass modifier such as Na.sub.2 S or another alkali metal sulfide. A molten mixture of the constituents is rapidly quenched to below the glass transition temperature by contact with a metal mold. The rapid quench is sufficient to prevent crystallization and permit solidification as an amorphous solid mixture. An oxygen-free atmosphere is maintained over the mixture to prevent oxidation. A new glass system of (1-X) Na.sub.2 O:XB.sub.2 S.sub.3 is disclosed.

  3. Glass capable of ionic conduction and method of preparation

    DOEpatents

    Susman, S.; Delbecq, C.J.; Volin, K.J.; Boehm, L.

    1984-02-21

    Sulfide glasses capable of conducting alkali metal ions are prepared from a nonmetal glass former such as GeS[sub 2], B[sub 2]S[sub 3] and SiS[sub 2] in mixture with a glass modifier such as Na[sub 2]S or another alkali metal sulfide. A molten mixture of the constituents is rapidly quenched to below the glass transition temperature by contact with a metal mold. The rapid quench is sufficient to prevent crystallization and permit solidification as an amorphous solid mixture. An oxygen-free atmosphere is maintained over the mixture to prevent oxidation. A new glass system of (1-X) Na[sub 2]O:XB[sub 2]S[sub 3] is disclosed. 4 figs.

  4. Glass capable of ionic conduction and method of preparation

    DOEpatents

    Susman, Sherman; Delbecq, Charles J.; Volin, Kenneth J.; Boehm, Leah

    1984-01-01

    Sulfide glasses capable of conducting alkali metal ions are prepared from a nonmetal glass former such as GeS.sub.2, B.sub.2 S.sub.3 and SiS.sub.2 in mixture with a glass modifier such as Na.sub.2 S or another alkali metal sulfide. A molten mixture of the constituents is rapidly quenched to below the glass transition temperature by contact with a metal mold. The rapid quench is sufficient to prevent crystallization and permit solidification as an amorphous solid mixture. An oxygen-free atmosphere is maintained over the mixture to prevent oxidation. A new glass system of (1-X) Na.sub.2 O:XB.sub.2 S.sub.3 is disclosed.

  5. Borosilicate glass alteration driven by magnesium carbonates

    NASA Astrophysics Data System (ADS)

    Debure, M.; Frugier, P.; De Windt, L.; Gin, S.

    2012-01-01

    The alteration of simplified synthetic glass, representative of the French reference nuclear glass R7T7, in presence of hydromagnesite has been experimentally investigated and modeled. Magnesium in solution is known to potentially enhance glass alteration; nuclear glass clayed host rocks contain magnesium and can dissolve to maintain the concentration of magnesium in solution. For modeling purposes, it was suitable to study a simple system. Hydromagnesite was therefore chosen as a simple model mineral in order to check the influence of an Mg-rich mineral on glass alteration. Since the models use thermodynamic and kinetic parameters measured in pure water and pH-buffered solutions, changing the solution composition or adding minerals is a key step towards the validation of the modeling assumptions before using the model for predictive purposes. Experiments revealed that glass alteration is enhanced in presence of hydromagnesite. Modeling was performed using the GRAAL model implemented within the CHESS/HYTEC reactive transport code. Modeling proved useful both for explaining the mechanisms involved and quantifying the impact on glass alteration: Mg coming from hydromagnesite dissolution reacts with Si provided by the glass in order to form magnesium silicates. This reaction decreases the pH down to neutral conditions where magnesium silicates are more soluble than at the natural alkali pH imposed by glass or hydromagnesite dissolution. The driving force of the magnesium silicate precipitation is eventually the interdiffusion of alkali within the altered amorphous glass layer as this mechanism consumes protons. The model's ability to describe the concentrations of elements in solution and formed solids whatever the glass/hydromagnesite ratio strongly supports the basic modeling hypothesis.

  6. Effect of host glass matrix on structural and optical behavior of glass-ceramic nanocomposite scintillators

    NASA Astrophysics Data System (ADS)

    Brooke Barta, M.; Nadler, Jason H.; Kang, Zhitao; Wagner, Brent K.; Rosson, Robert; Kahn, Bernd

    2013-12-01

    Composite scintillator systems have received increased attention in recent years due to their promise for merging the radioisotope discrimination capabilities of single crystal scintillators with the high throughput scanning capabilities of portal monitors. However, producing the high light yield required for good energy resolution has proven challenging as scintillation photons are often scattered by variations in refractive index and agglomerated scintillator crystals within the composite. This investigation sought to mitigate these common problems by using glass-ceramic nanocomposite materials systems in which nanoscale scintillating crystallites are precipitated in a controlled manner from a transparent glass matrix. Precipitating crystallites in situ precludes nanoparticle agglomeration, and limiting crystallite size to 50 nm or less mitigates the effect of refractive index mismatch between the crystals and host glass. Cerium-doped gadolinium bromide (GdBr3(Ce)) scintillating crystals were incorporated into sodium-aluminosilicate (NAS) and alumino-borosilicate (ABS) host glass matrices, and the resulting glass-ceramic structures and luminescence behavior were characterized. The as-cast glass from the ABS system displayed a highly ordered microstructure that produced the highest luminescence intensity (light yield) of the samples studied. However, heat treating to form the glass-ceramic precipitated rare-earth oxide crystallites rather than rare-earth halides. This degraded light yield relative to the unaged sample.

  7. Evidence for lithium-aluminosilicate supersaturation of pegmatite-forming melts

    NASA Astrophysics Data System (ADS)

    Maneta, Victoria; Baker, Don R.; Minarik, William

    2015-07-01

    New experimental data on the solubility of lithium (Li) at spodumene (LiAlSi2O6) and petalite (LiAlSi4O10) saturation at 500 MPa and 550-750 °C reveal evidence for lithium supersaturation of pegmatite-forming melts before the formation of Li-aluminosilicates. The degree of Li enrichment in granitic melts can reach ~11,000 ppm above the saturation value before the crystallization of Li-aluminosilicate minerals at lower temperatures. Comparison of the experimental results with the spodumene-rich Moblan pegmatite (Quebec) is consistent with extreme Li enrichment of the pegmatite-forming melt prior to emplacement, which cannot be explained with equilibrium crystallization of Li-aluminosilicates from a common granitic melt. The results of this study support the model of disequilibrium fractional crystallization through liquidus undercooling as the most plausible mechanism for the generation of such Li-rich ore resources.

  8. Highly acidic mesostructured aluminosilicates assembled from surfactant-mediated zeolite hydrolysis products.

    PubMed

    Wang, Hui; Liu, Yu; Pinnavaia, Thomas J

    2006-03-16

    The surfactant-mediated hydrolysis of ZSM-5 zeolite affords five-membered ring subunits that can be readily incorporated into the framework walls of a hexagonal mesostructured aluminosilicate, denoted MSU-Z. The five-membered ring subunits, which are identifiable by infrared spectroscopy, impart unprecedented acidity to the mesostructure, as judged by cumene cracking activity at 300 degrees C. Most notably, MSU-Z aluminosilicate made through the base hydrolysis of ZSM-5 in the presence of cetyltrimethylammonium ions exhibits a cumene conversion of 73%, which is 6.7-fold higher than the conversion provided by a conventional MCM-41. This approach to stabilizing zeolitic subunits through surfactant-mediated hydrolysis of zeolites appears to be general. The hydrolysis of USY zeolite under analogous hydrolytic conditions also affords zeolitic fragments that boost the acidity of the mesostructure in comparison to equivalent compositions prepared from conventional aluminosilicate precursors.

  9. Synthesis and immobilization of silver nanoparticles on aluminosilicate nanotubes and their antibacterial properties

    NASA Astrophysics Data System (ADS)

    Ipek Yucelen, G.; Connell, Rachel E.; Terbush, Jessica R.; Westenberg, David J.; Dogan, Fatih

    2016-04-01

    A novel colloidal method is presented to synthesize silver nanoparticles on aluminosilicate nanotubes. The technique involves decomposition of AgNO3 solution to Ag nanoparticles in the presence of aluminosilicate nanotubes at room temperature without utilizing of reducing agents or any organic additives. Aluminosilicate nanotubes are shown to be capable of providing a unique chemical environment, not only for in situ conversion of Ag+ into Ag0, but also for stabilization and immobilization of Ag nanoparticles. The synthesis strategy described here could be implemented to obtain self-assembled nanoparticles on other single-walled metal oxide nanotubes for unique applications. Finally, we demonstrated that nanotube/nanoparticle hybrid show strong antibacterial activity toward Gram-positive Staphylococcus epidermidis and Gram-negative Escherichia coli.

  10. Quantum-chemical investigation of mechanism of dehydroxylation of crystalline and amorphous aluminosilicates

    SciTech Connect

    Senchenya, I.N.; Chuvylkin, N.D.; Kazanskii, V.B.

    1986-07-01

    Within the framework of the cluster approach and the semiempirical SCF MO LCAO method in the CNDO/BW valence approximation, possible pathways have been compared for the dehydroxylation of aluminosilicate systems. It has been shown that dehydroxylation as a result of splitting of a water molecule from an acidic bridge hydroxyl group and a more basic terminal group Al-OH is the most energyfavorable. Apparently, such a dehydroxylation pathway is primarily characteristic for amorphous aluminosilicates. Typical of crystalline aluminosilicates at moderate heat-treating temperature is dehydroxylation through splitting of a water molecule from an acidic bridge hydroxyl group and a neutral Si-OH group; at higher temperatures, there is a possible pathway of dehydroxylation of highsilica zeolites as a result of condensation of two acidic surface hydroxyls.

  11. Li+ alumino-silicate ion source development for the Neutralized Drift Compression Experiment (NDCX)

    SciTech Connect

    Roy, Prabir K.; Greenway, Wayne G.; Kwan, Joe W.; Seidl, Peter A.; Waldron, William L.; Wu, James K.

    2010-10-01

    We report results on lithium alumino-silicate ion source development in preparation for warmdense-matter heating experiments on the new Neutralized Drift Compression Experiment (NDCXII). The practical limit to the current density for a lithium alumino-silicate source is determined by the maximum operating temperature that the ion source can withstand before running into problems of heat transfer, melting of the alumino-silicate material, and emission lifetime. Using small prototype emitters, at a temperature of ~;;1275 oC, a space-charge-limited Li+ beam current density of J ~;;1 mA/cm2 was obtained. The lifetime of the ion source was ~;;50 hours while pulsing at a rate of 0.033 Hz with a pulse duration of 5-6 mu s.

  12. Interface Induced Growth and Transformation of Polymer-Conjugated Proto-Crystalline Phases in Aluminosilicate Hybrids: A Multiple-Quantum (23)Na-(23)Na MAS NMR Correlation Spectroscopy Study.

    PubMed

    Brus, Jiri; Kobera, Libor; Urbanova, Martina; Doušová, Barbora; Lhotka, Miloslav; Koloušek, David; Kotek, Jiří; Čuba, Pavel; Czernek, Jiri; Dědeček, Jiří

    2016-03-22

    Nanostructured materials typically offer enhanced physicochemical properties because of their large interfacial area. In this contribution, we present a comprehensive structural characterization of aluminosilicate hybrids with polymer-conjugated nanosized zeolites specifically grown at the organic-inorganic interface. The inorganic amorphous Al-O-Si framework is formed by alkali-activated low-temperature transformation of metakaoline, whereas simultaneous copolymerization of organic comonomers creates a secondary epoxide network covalently bound to the aluminosilicate matrix. This secondary epoxide phase not only enhances the mechanical integrity of the resulting hybrids but also introduces additional binding sites accessible for compensating negative charge on the aluminosilicate framework. This way, the polymer network initiates growth and subsequent transformation of protocrystalline short-range ordered zeolite domains that are located at the organic-inorganic interface. By applying an experimental approach based on 2D (23)Na-(23)Na double-quantum (DQ) MAS NMR spectroscopy, we discovered multiple sodium binding sites in these protocrystalline domains, in which immobilized Na(+) ions form pairs or small clusters. It is further demonstrated that these sites, the local geometry of which allows for the pairing of sodium ions, are preferentially occupied by Pb(2+) ions during the ion exchange. The proposed synthesis protocol thus allows for the preparation of a novel type of geopolymer hybrids with polymer-conjugated zeolite phases suitable for capturing and storage of metal cations. The demonstrated (23)Na-(23)Na DQ MAS NMR combined with DFT calculations represents a suitable approach for understanding the role of Na(+) ions in aluminositicate solids and related inorganic-organic hybrids, particularly their specific arrangement and clustering at interfacial areas.

  13. Alkali-Metal Spin Maser.

    PubMed

    Chalupczak, W; Josephs-Franks, P

    2015-07-17

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

  14. Alkali-Metal Spin Maser

    NASA Astrophysics Data System (ADS)

    Chalupczak, W.; Josephs-Franks, P.

    2015-07-01

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

  15. Alkali Activated Systems: Understanding the Influence of Curing Conditions and Activator Type/Chemistry on the Mechanical Strength and Chemical Structure of Fly Ash/Slag Systems

    NASA Astrophysics Data System (ADS)

    Chowdhury, Ussala

    The alkali activation of aluminosilicate materials as binder systems derived from industrial byproducts have been extensively studied due to the advantages they offer in terms enhanced material properties, while increasing sustainability by the reuse of industrial waste and byproducts and reducing the adverse impacts of OPC production. Fly ash and ground granulated blast furnace slag are commonly used for their content of soluble silica and aluminate species that can undergo dissolution, polymerization with the alkali, condensation on particle surfaces and solidification. The following topics are the focus of this thesis: (i) the use of microwave assisted thermal processing, in addition to heat-curing as a means of alkali activation and (ii) the relative effects of alkali cations (K or Na) in the activator (powder activators) on the mechanical properties and chemical structure of these systems. Unsuitable curing conditions instigate carbonation, which in turn lowers the pH of the system causing significant reductions in the rate of fly ash activation and mechanical strength development. This study explores the effects of sealing the samples during the curing process, which effectively traps the free water in the system, and allows for increased aluminosilicate activation. The use of microwave-curing in lieu of thermal-curing is also studied in order to reduce energy consumption and for its ability to provide fast volumetric heating. Potassium-based powder activators dry blended into the slag binder system is shown to be effective in obtaining very high compressive strengths under moist curing conditions (greater than 70 MPa), whereas sodium-based powder activation is much weaker (around 25 MPa). Compressive strength decreases when fly ash is introduced into the system. Isothermal calorimetry is used to evaluate the early hydration process, and to understand the reaction kinetics of the alkali powder activated systems. A qualitative evidence of the alkali

  16. Glass tube of high dielectric constant and low dielectric loss for external electrode fluorescent lamps

    SciTech Connect

    Cho, Guangsup; Shin, Myeong-Ju; Jeong, Jong-Mun; Kim, Jung-Hyun; Hong, Byoung-Hee; Koo, Je-Huan; Kim, YunKi; Choi, Eun-Ha; Fechner, Joerg; Letz, Martin; Ott, Franz

    2007-12-01

    A glass tube of aluminosilicate glass, with high dielectric constant K{approx}6.0 and low dielectric loss tan {delta}{approx}8.0x10{sup -4}, was investigated for the external electrode fluorescent lamps (EEFLs) of a dielectric barrier discharge. Compared with conventional EEFLs made out of borosilicate glass tubes with K{approx}(4.9-5.3) and tan {delta}{approx}(2.3-2.4)x10{sup -3}, the efficiency of the aluminosilicate EEFL increases by 15%-25% even at high luminance above 20 000 cd/m{sup 2} and the pinhole stability of the aluminosilicate EEFL also improves remarkably. In a soda-lime glass EEFL with a high dielectric loss tan {delta}{approx}7.0x10{sup -3}, the luminance and pinhole stability deteriorate even with a high dielectric constant K{approx}7.2 at room temperature, because the value of tan {delta} escalates as the temperature on the external electrode increases due to the dielectric heat dissipation.

  17. Aflatoxin adsorbent capacity of two Mexican aluminosilicates in experimentally contaminated chick diets.

    PubMed

    Márquez Márquez, R N; Tejada de Hernandez, I

    1995-01-01

    To study the aflatoxin-adsorbent capacity of two Mexican aluminosilicates (ALS) identified as Atapulgita (AT) and Füller earth (FE), these ALS were compared with a commercial aluminosilicate, Novasil (NV), at two concentrations (0.05 and 1.0%) added to chick diets with 55% of experimentally contaminated corn (200 micrograms/kg). Eight treatments were studied with two replicates for treatment and four chicks per cage. Results (weight gain, feed efficiency, gross and microscopic pathology) at 3 weeks showed that both Mexican ALS were as efficient as the commercial material in protecting chicks against the aflatoxin toxicity. PMID:7664939

  18. Aflatoxin adsorbent capacity of two Mexican aluminosilicates in experimentally contaminated chick diets.

    PubMed

    Márquez Márquez, R N; Tejada de Hernandez, I

    1995-01-01

    To study the aflatoxin-adsorbent capacity of two Mexican aluminosilicates (ALS) identified as Atapulgita (AT) and Füller earth (FE), these ALS were compared with a commercial aluminosilicate, Novasil (NV), at two concentrations (0.05 and 1.0%) added to chick diets with 55% of experimentally contaminated corn (200 micrograms/kg). Eight treatments were studied with two replicates for treatment and four chicks per cage. Results (weight gain, feed efficiency, gross and microscopic pathology) at 3 weeks showed that both Mexican ALS were as efficient as the commercial material in protecting chicks against the aflatoxin toxicity.

  19. Calculation of the Aluminosilicate Half-Life Formation Time in the 2H Evaporator

    SciTech Connect

    Fondeur, F.F.

    2000-09-21

    The 2H Evaporator contains large quantities of aluminosilicate solids deposited on internal fixtures. The proposed cleaning operations will dissolve the solids in nitric acid. Operations will then neutralize the waste prior to transfer to a waste tank. Combining recent calculations of heat transfer for the 2H Evaporator cleaning operations and laboratory experiments for dissolution of solid samples from the pot, the authors estimated the re-formation rate for aluminosilicates during cooling. The results indicate a half-life formation of 17 hours when evaporator solution cools from 60 degrees C and 9 hours when cooled from 90 degrees C.

  20. Chemical durability of simulated nuclear glasses containing water

    SciTech Connect

    Li, H.; Tomozawa, M.

    1995-04-01

    The chemical durability of simulated nuclear waste glasses having different water contents was studied. Results from the product consistency test (PCT) showed that glass dissolution increased with water content in the glass. This trend was not observed during MCC-1 testing. This difference was attributed to the differences in reactions between glass and water. In the PCT, the glass network dissolution controlled the elemental releases, and water in the glass accelerated the reaction rate. On the other hand, alkali ion exchange with hydronium played an important role in the MCC-1. For the latter, the amount of water introduced into a leached layer from ion-exchange was found to be much greater than that of initially incorporated water in the glass. Hence, the initial water content has no effect on glass dissolution as measured by the MCC-1 test.

  1. Strength enhancement of Nicalon-reinforced lithium aluminosilicate containing a Ta(2)O(5) second phase

    NASA Astrophysics Data System (ADS)

    Villalobos, Guillermo R.

    The purpose of this study was to follow up the preliminary results of a previous thesis which appeared to indicate that the addition of Tasb2Osb5 to the matrix of a Nicalon fiber reinforced lithium aluminosilicate glass ceramic composite increased the mechanical properties of the resulting composites. The strength increase was attributed to the presence of a TaC platelet phase in the matrix material. The TaC was thought to be a result of the reaction between the Tasb2Osb5 additions and soluble CO from the hot press atmosphere used in the densification of the composites. These preliminary results (the strength increase and TaC formation) were a side experiment to a larger work and consequently were not rigorously investigated. The present work showed that the CO did react with Tasb2Osb5 to form TaC, but only as a surface coating. The surface coating reached a terminal thickness of 5-10 mum after 1 h at 1400sp°C. There was no evidence of soluble CO reacting to form TaC in the matrix. What was previously thought to be TaC platelets appears to be a two phase eutectic structure of beta-spodumene and Tasb2Osb5. When the Tasb2Osb5 content was increased to 15%, Tasb2Osb5 crystals were formed in addition to the eutectic structure. The formation of the eutectic structure could be suppressed in samples containing less than 3.5% Tasb2Osb5 by cooling at 10sp°C/min. Cooling rates of 1sp°C/min promoted the two phase structure. The interfacial shear strength and flexural strength did not appreciably increase with Tasb2Osb5 additions. Increasing the hot pressing time did increase the interfacial shear strength, but resulted in lower flexural strengths and less graceful failure modes. There was great variation in the flexural strength of the composites which increased with increasing Tasb2Osb5 content. With the very limited sample size of the preliminary study the large variation may have suggested a trend which did not statistically exist.

  2. Determination of the Structure of Vitrified Hydroceramic/CBC Waste Form Glasses Manufactured from DOE Reprocessing Waste

    SciTech Connect

    Scheetz, B.E.; White, W. B.; Chesleigh, M.; Portanova, A.; Olanrewaju, J.

    2005-05-31

    The selection of a glass-making option for the solidification of nuclear waste has dominated DOE waste form programs since the early 1980's. Both West Valley and Savannah River are routinely manufacturing glass logs from the high level waste inventory in tank sludges. However, for some wastes, direct conversion to glass is clearly not the optimum strategy for immobilization. INEEL, for example, has approximately 4400 m{sup 3} of calcined high level waste with an activity that produces approximately 45 watts/m{sup 3}, a rather low concentration of radioactive constituents. For these wastes, there is value in seeking alternatives to glass. An alternative approach has been developed and the efficacy of the process demonstrated that offers a significant savings in both human health and safety exposures and also a lower cost relative to the vitrification option. The alternative approach utilizes the intrinsic chemical reactivity of the highly alkaline waste with the addition of aluminosilicate admixtures in the appropriate proportions to form zeolites. The process is one in which a chemically bonded ceramic is produced. The driving force for reaction is derived from the chemical system itself at very modest temperatures and yet forms predominantly crystalline phases. Because the chemically bonded ceramic requires an aqueous medium to serve as a vehicle for the chemical reaction, the proposed zeolite-containing waste form can more adequately be described as a hydroceramic. The hydrated crystalline materials are then subject to hot isostatic pressing (HIP) which partially melts the material to form a glass ceramic. The scientific advantages of the hydroceramic/CBC approach are: (1) Low temperature processing; (2) High waste loading and thus only modest volumetric bulking from the addition of admixtures; (3) Ability to immobilize sodium; (4) Ability to handle low levels of nitrate (2-3% NO{sub 3}{sup -}); (5) The flexibility of a vitrifiable waste; and (6) A process that

  3. Water Content of Lunar Alkali Fedlspar

    NASA Technical Reports Server (NTRS)

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

    2016-01-01

    Detection of indigenous hydrogen in a diversity of lunar materials, including volcanic glass, melt inclusions, apatite, and plagioclase suggests water may have played a role in the chemical differentiation of the Moon. Spectroscopic data from the Moon indicate a positive correlation between water and Th. Modeling of lunar magma ocean crystallization predicts a similar chemical differentiation with the highest levels of water in the K- and Th-rich melt residuum of the magma ocean (i.e. urKREEP). Until now, the only sample-based estimates of water content of KREEP-rich magmas come from measurements of OH, F, and Cl in lunar apatites, which suggest a water concentration of < 1 ppm in urKREEP. Using these data, predict that the bulk water content of the magma ocean would have <10 ppm. In contrast, estimate water contents of 320 ppm for the bulk Moon and 1.4 wt % for urKREEP from plagioclase in ferroan anorthosites. Results and interpretation: NanoSIMS data from granitic clasts from Apollo sample 15405,78 show that alkali feldspar, a common mineral in K-enriched rocks, can have approx. 20 ppm of water, which implies magmatic water contents of approx. 1 wt % in the high-silica magmas. This estimate is 2 to 3 orders of magnitude higher than that estimated from apatite in similar rocks. However, the Cl and F contents of apatite in chemically similar rocks suggest that these melts also had high Cl/F ratios, which leads to spuriously low water estimates from the apatite. We can only estimate the minimum water content of urKREEP (+ bulk Moon) from our alkali feldspar data because of the unknown amount of degassing that led to the formation of the granites. Assuming a reasonable 10 to 100 times enrichment of water from urKREEP into the granites produces an estimate of 100-1000 ppm of water for the urKREEP reservoir. Using the modeling of and the 100-1000 ppm of water in urKREEP suggests a minimum bulk silicate Moon water content between 2 and 20 ppm. However, hydrogen loss was

  4. Technetium (VII) Co-precipitation with Framework Aluminosilicates

    SciTech Connect

    Harsh, James B.; Dickson, Johnbull Otah; Pierce, Eric M.; Bargar, John

    2015-07-13

    Technetium-99 (99Tc), a long-lived radionuclide, is one of the most widespread contaminants within the Hanford subsurface. At some depths, it is only extractable with strong acids, suggesting incorporation into a solid phase. We hypothesized that Tc may have coprecipitated with feldspathoid aluminosilicates under waste tanks that had leaked caustic solutions into the vadose zone. Our objectives were to determine if Tc could be incorporated into the feldspathoids cancrinite and sodalite and under what conditions coprecipitation could occur. Our hypothesis was that sodalite was more likely to incorporate and retain Tc. Our approach was to use known methods of feldspathoid formation in solutions resembling those in Hanford waste tanks contacting sediments in terms of major ion (Na, NO3, OH, Al(OH)4, and Si(OH)4 concentrations. In some cases, Al and Si were supplied from zeolite. We used perrhenate (ReO4) as a surrogate for pertechnetate (TcO4) to avoid the radioactivity. The major findings of this study were 1) ReO4 could be incorporated into either sodalite or cancrinite but the concentration in the solid was < 1% of the competing ion Cl, NO3, or NO2. 2) The small amount of ReO4 incorporated was not exchangeable with NO3 or NO2. 3) In sodalite, NO3 was highly preferred over ReO4 but significant Re-sodalite was formed when the mole fraction in solution (Re/Re+N) exceeded 0.8. 4) A nonlinear relation between the unit cell parameter and amount of Re incorporated suggested that a separate Re-sodalite phase was formed rather than a solid solution. 5) We determined that sodalite preference for sodalite in the presence of different anions increased with the ionic size of the competing anion: Cl < CO3 < NO3 < SO4 < MnO4 < WO4 and significant incorporation did not occur unless the difference in anion radii was less than 12%. 6) Re(VII) was not significantly reduced to Re(IV) under the conditions of this experiment and Re appeared to be a good surrogate for Tc under oxidizing

  5. The alkali metals: 200 years of surprises.

    PubMed

    Dye, James L

    2015-03-13

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

  6. The alkali metals: 200 years of surprises.

    PubMed

    Dye, James L

    2015-03-13

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

  7. Process for the disposal of alkali metals

    DOEpatents

    Lewis, Leroy C.

    1977-01-01

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

  8. Purification of sulfide-alkali effluent with the aid of ionizing radiation. [Gamma radiation

    SciTech Connect

    Petryaev, E.P.; Gerasimovich, O.A.; Kovalevskaya, A.M.; Plyuto, I.Ch.; Shlyk, V.G.

    1984-03-01

    The treatment of sulfide-alkali effluent under the effect of ionizing radiation was investigated. The source was an LMB-..gamma..-1M ..gamma..-apparatus with /sup 137/Cs source. The dose rate was 52 rad/s. Irradiation was done in glass ampules and in vessels allowing bubbling with air and irradiation to be carried out at the same time. 7 references, 1 figure, 1 table.

  9. Glasses in coarse-grained micrometeorites

    NASA Astrophysics Data System (ADS)

    Varela, M. E.; Kurat, G.

    2009-06-01

    Micrometeorites (MMs, interplanetary dust particles with 25 - 500 μm diameters) carry the main mass of extraterrestrial matter that is captured by Earth. The coarse-grained MMs mainly consist of olivine aggregates, which - as their counterparts in CC chondrites - also contain pyroxenes and glass. We studied clear glasses in four coarse-grained crystalline MMs (10M12, M92-6b, AM9, and Mc7-10), which were collected from the ice at Cap Prudhomme, Antarctica. Previous studies of glasses (e.g., glass inclusions trapped in olivine and clear mesostasis glass) in carbonaceous and ordinary chondrites showed that these phases could keep memory of the physical-chemical conditions to which extraterrestrial matter was exposed. Here we compare the chemical compositions of MM glasses and glasses from CM chondrites with that in experimentally heated objects from the Allende CV chondrite and with glasses from cometary particles. Our results show that MMs were heated to variable degrees (during entry through the terrestrial atmosphere), which caused a range from very little chemical modification of the glass to total melting of the precursor object. Such modifications include dissolution of minerals in the melted glass precursor and some loss of volatile alkali elements. The chemical composition of all precursor glasses in the MMs investigated is not primitive such as glasses in CM and CR chondrite objects. It shows signs of pre-terrestrial chemical modification, e.g., metasomatic enrichments in Na and Fe 2+ presumably in the solar nebula. Glasses of MMs heated to very low degree have a chemical composition indistinguishable from that of glasses in comet Wild 2 particles; giving additional evidence that interplanetary dust (e.g., Antarctic MMs) possibly represents samples from comets.

  10. A highly crystalline microporous hybrid organic-inorganic aluminosilicate resembling the AFI-type zeolite.

    PubMed

    Bellussi, Giuseppe; Millini, Roberto; Montanari, Erica; Carati, Angela; Rizzo, Caterina; Parker, Wallace O; Cruciani, Giuseppe; de Angelis, Alberto; Bonoldi, Lucia; Zanardi, Stefano

    2012-07-28

    ECS-14, a crystalline microporous hybrid organic-inorganic aluminosilicate, has been synthesized by using 1,4-bis-(triethoxysilyl)-benzene (BTEB) as a source of silica. Its structure contains a system of linear channels with 12-membered ring openings, running along the [001] direction, resembling the pore architecture of the AFI framework type. PMID:22717682

  11. EFFECT OF IMPURITIES ASSOCIATED WITH ALUMINOSILICATES ON ARSENIC SORPTION AND OXIDATION

    EPA Science Inventory

    Arsenite, As(III), and arsenate, As(V), are of increasing environmental concern. Risk assessment and risk management of arsenic contaminated sites requires a better understanding of arsenic-mineral interactions. Aluminosilicate minerals, such as feldspars and clays, are the mos...

  12. Direct aerosol synthesis of large-pore amorphous mesostructured aluminosilicates with superior acid-catalytic properties.

    PubMed

    Pega, Stéphanie; Boissière, Cédric; Grosso, David; Azaïs, Thierry; Chaumonnot, Alexandra; Sanchez, Clément

    2009-01-01

    An old dream comes true: A direct and environmentally benign synthetic strategy was developed for the aerosol-based mass production of large-pore mesostructured aluminosilicate powders (see TEM image). Although amorphous, some powders exhibit higher activity towards m-xylene isomerization and lower coke formation than a Y-zeolite based industrial reference catalyst.

  13. Epoxide ring-opening and Meinwald rearrangement reactions of epoxides catalyzed by mesoporous aluminosilicates.

    PubMed

    Robinson, Mathew W C; Davies, A Matthew; Buckle, Richard; Mabbett, Ian; Taylor, Stuart H; Graham, Andrew E

    2009-06-21

    Mesoporous aluminosilicates efficiently catalyze the ring-opening of epoxides to produce beta-alkoxyalcohols in high yields under extremely mild reaction conditions. These materials also catalyze the corresponding Meinwald rearrangement in non-nucleophilic solvents to give aldehydes which can be trapped in situ to provide the corresponding acetals in an efficient tandem process.

  14. High-aluminum-affinity silica is a nanoparticle that seeds secondary aluminosilicate formation.

    PubMed

    Jugdaohsingh, Ravin; Brown, Andy; Dietzel, Martin; Powell, Jonathan J

    2013-01-01

    Despite the importance and abundance of aluminosilicates throughout our natural surroundings, their formation at neutral pH is, surprisingly, a matter of considerable debate. From our experiments in dilute aluminum and silica containing solutions (pH ~ 7) we previously identified a silica polymer with an extraordinarily high affinity for aluminium ions (high-aluminum-affinity silica polymer, HSP). Here, further characterization shows that HSP is a colloid of approximately 2.4 nm in diameter with a mean specific surface area of about 1,000 m(2) g(-1) and it competes effectively with transferrin for Al(III) binding. Aluminum binding to HSP strongly inhibited its decomposition whilst the reaction rate constant for the formation of the β-silicomolybdic acid complex indicated a diameter between 3.6 and 4.1 nm for these aluminum-containing nanoparticles. Similarly, high resolution microscopic analysis of the air dried aluminum-containing silica colloid solution revealed 3.9 ± 1.3 nm sized crystalline Al-rich silica nanoparticles (ASP) with an estimated Al:Si ratio of between 2 and 3 which is close to the range of secondary aluminosilicates such as imogolite. Thus the high-aluminum-affinity silica polymer is a nanoparticle that seeds early aluminosilicate formation through highly competitive binding of Al(III) ions. In niche environments, especially in vivo, this may serve as an alternative mechanism to polyhydroxy Al(III) species binding monomeric silica to form early phase, non-toxic aluminosilicates.

  15. Feed Preparation for Source of Alkali Melt Rate Tests

    SciTech Connect

    Stone, M. E.; Lambert, D. P.

    2005-02-26

    The purpose of the Source of Alkali testing was to prepare feed for melt rate testing in order to determine the maximum melt-rate for a series of batches where the alkali was increased from 0% Na{sub 2}O in the frit (low washed sludge) to 16% Na{sub 2}O in the frit (highly washed sludge). This document summarizes the feed preparation for the Source of Alkali melt rate testing. The Source of Alkali melt rate results will be issued in a separate report. Five batches of Sludge Receipt and Adjustment Tank (SRAT) product and four batches of Slurry Mix Evaporator (SME) product were produced to support Source of Alkali (SOA) melt rate testing. Sludge Batch 3 (SB3) simulant and frit 418 were used as targets for the 8% Na{sub 2}O baseline run. For the other four cases (0% Na{sub 2}O, 4% Na{sub 2}O, 12% Na{sub 2}O, and 16% Na{sub 2}O in frit), special sludge and frit preparations were necessary. The sludge preparations mimicked washing of the SB3 baseline composition, while frit adjustments consisted of increasing or decreasing Na and then re-normalizing the remaining frit components. For all batches, the target glass compositions were identical. The five SRAT products were prepared for testing in the dry fed melt-rate furnace and the four SME products were prepared for the Slurry-fed Melt-Rate Furnace (SMRF). At the same time, the impacts of washing on a baseline composition from a Chemical Process Cell (CPC) perspective could also be investigated. Five process simulations (0% Na{sub 2}O in frit, 4% Na{sub 2}O in frit, 8% Na{sub 2}O in frit or baseline, 12% Na{sub 2}O in frit, and 16% Na{sub 2}O in frit) were completed in three identical 4-L apparatus to produce the five SRAT products. The SRAT products were later dried and combined with the complementary frits to produce identical glass compositions. All five batches were produced with identical processing steps, including off-gas measurement using online gas chromatographs. Two slurry-fed melter feed batches, a 4% Na

  16. Glass Artworks

    NASA Technical Reports Server (NTRS)

    1988-01-01

    Several NASA technologies have played part in growth and cost containment of studio glass art, among them a foam type insulation developed to meet a need for lightweight material that would reduce flame spread in aircraft fire. Foam comes in several forms and is widely used by glass artists, chiefly as an insulator for the various types of ovens used in glass working. Another Spinoff is alumina crucibles to contain molten glass. Before alumina crucibles were used, glass tanks were made of firebrick which tended to erode under high temperatures and cause impurities; this not only improved quality but made the process more cost effective. One more NASA technology that found its way into glass art working is a material known as graphite board, a special form of graphite originally developed for rocket motor applications. This graphite is used to exact compound angles and creates molds for poured glass artworks of dramatic design.

  17. Measurement of alkali in PFBC exhaust

    SciTech Connect

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

    1992-11-01

    This project supports the DOE/METC Fossil Energy Program for the development of PFBC technology. Based on the analytical activated-bauxite sorber-bed technique, we are developing the RABSAM as an altemative to the on-line alkali analyzer for field application. As shown in Fig. 1, the RABSAM is a sampling probe containing a regenerable activated-bauxite adsorbent (RABA). It can be inserted directly into the PFBC exhaust duct and requires no HTHP sampling line. Alkali vapors are captured by the adsorbent purely through physical adsorption. The adsorbent is regenerated by a simple water-leaching process, which also recovers the adsorbed alkalis. The alkali analysis of the leachate by atomic absorption (AA) provides a basis for calculating the time-averaged alkali-vapor concentration in the PFBC exhaust. If the RABA is to use commercial grade activated bauxite, the clay impurities in activated bauxite can react with alkali vapors and, therefore, need to be either removed or deactivated. In earlier work, a 6M-LiCl-solution impregnation technique was shown to deactivate these impurities in fresh activated bauxite [8]. During this year, RABA prepared by this technique was tested in a pressurized alkali-vapor sorption test unit to determine its NaCl-vapor capture efficiency and the regenerability of the sorbent by water extraction. Results of this study are presented and discussed.

  18. Measurement of alkali in PFBC exhaust

    SciTech Connect

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

    1992-01-01

    This project supports the DOE/METC Fossil Energy Program for the development of PFBC technology. Based on the analytical activated-bauxite sorber-bed technique, we are developing the RABSAM as an altemative to the on-line alkali analyzer for field application. As shown in Fig. 1, the RABSAM is a sampling probe containing a regenerable activated-bauxite adsorbent (RABA). It can be inserted directly into the PFBC exhaust duct and requires no HTHP sampling line. Alkali vapors are captured by the adsorbent purely through physical adsorption. The adsorbent is regenerated by a simple water-leaching process, which also recovers the adsorbed alkalis. The alkali analysis of the leachate by atomic absorption (AA) provides a basis for calculating the time-averaged alkali-vapor concentration in the PFBC exhaust. If the RABA is to use commercial grade activated bauxite, the clay impurities in activated bauxite can react with alkali vapors and, therefore, need to be either removed or deactivated. In earlier work, a 6M-LiCl-solution impregnation technique was shown to deactivate these impurities in fresh activated bauxite [8]. During this year, RABA prepared by this technique was tested in a pressurized alkali-vapor sorption test unit to determine its NaCl-vapor capture efficiency and the regenerability of the sorbent by water extraction. Results of this study are presented and discussed.

  19. Glass Research

    NASA Technical Reports Server (NTRS)

    Weinberg, M. C.

    1985-01-01

    Research efforts span three general areas of glass science: glass refining, gel-derived glasses, and nucleation and crystallization of glasses. Gas bubbles which are present in a glass product are defects which may render the glass totally useless for the end application. For example, optical glasses, laser host glasses, and a variety of other specialty glasses must be prepared virtually defect free to be employable. Since a major mechanism of bubble removal, buoyant rise, is virtually inoperative in microgravity, glass fining will be especially difficult in space. On the other hand, the suppression of buoyant rise and the ability to perform containerless melting experiments in space allows the opportunity to carry out several unique bubble experiments in space. Gas bubble dissolution studies may be performed at elevated temperatures for large bubbles with negligible bubble motion. Also, bubble nucleation studies may be performed without the disturbing feature of heterogeneous bubble nucleation at the platinum walls. Ground based research efforts are being performed in support of these potential flight experiments.

  20. Diode pumped alkali vapor fiber laser

    DOEpatents

    Payne, Stephen A.; Beach, Raymond J.; Dawson, Jay W.; Krupke, William F.

    2007-10-23

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

  1. Diode pumped alkali vapor fiber laser

    DOEpatents

    Payne, Stephen A.; Beach, Raymond J.; Dawson, Jay W.; Krupke, William F.

    2006-07-26

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

  2. Alkali Silicate Vehicle Forms Durable, Fireproof Paint

    NASA Technical Reports Server (NTRS)

    Schutt, John B.; Seindenberg, Benjamin

    1964-01-01

    The problem: To develop a paint for use on satellites or space vehicles that exhibits high resistance to cracking, peeling, or flaking when subjected to a wide range of temperatures. Organic coatings will partially meet the required specifications but have the inherent disadvantage of combustibility. Alkali-silicate binders, used in some industrial coatings and adhesives, show evidence of forming a fireproof paint, but the problem of high surface-tension, a characteristic of alkali silicates, has not been resolved. The solution: Use of a suitable non-ionic wetting agent combined with a paint incorporating alkali silicate as the binder.

  3. Advancements in flowing diode pumped alkali lasers

    NASA Astrophysics Data System (ADS)

    Pitz, Greg A.; Stalnaker, Donald M.; Guild, Eric M.; Oliker, Benjamin Q.; Moran, Paul J.; Townsend, Steven W.; Hostutler, David A.

    2016-03-01

    Multiple variants of the Diode Pumped Alkali Laser (DPAL) have recently been demonstrated at the Air Force Research Laboratory (AFRL). Highlights of this ongoing research effort include: a) a 571W rubidium (Rb) based Master Oscillator Power Amplifier (MOPA) with a gain (2α) of 0.48 cm-1, b) a rubidium-cesium (Cs) Multi-Alkali Multi-Line (MAML) laser that simultaneously lases at both 795 nm and 895 nm, and c) a 1.5 kW resonantly pumped potassium (K) DPAL with a slope efficiency of 50%. The common factor among these experiments is the use of a flowing alkali test bed.

  4. Preliminary report on a glass burial experiment in granite

    SciTech Connect

    Clark, D.E.; Zhu, B.F.; Robinson, R.S.; Wicks, G.G.

    1983-01-01

    Preliminary results of a two-year burial experiment in granite are discussed. Three compositions of simulated alkali borosilicate waste glasses were placed in boreholes approximately 350 meters deep. The glass sample configurations include mini-cans (stainless steel rings into which glass has been cast) and pineapple slices (thin sections from cylindrical blocks). Assemblies of these glass samples were prepared by stacking them together with granite, compacted bentonite and metal rings to provide several types of interfaces that are expected to occur in the repository. The assemblies were maintained at either ambient mine temperature (8 to 10/sup 0/C) or 90/sup 0/C. The glasses were analyzed before burial and after one month storage at 90/sup 0/C. The most extensive surface degradation occurred on the glasses interfaced with bentonite. In general, very little attack was observed on glass surfaces in contact with the other materials. The limited field and laboratory data are compared.

  5. The Impact of the Source of Alkali on Sludge Batch 3 Melt Rate (U)

    SciTech Connect

    Smith, M

    2005-04-01

    Previous Savannah River National Laboratory (SRNL) melt rate tests in support of the Defense Waste Processing Facility (DWPF) have indicated that improvements in melt rate can be achieved through an increase in the total alkali of the melter feed. Higher alkali can be attained by the use of an ''underwashed'' sludge, a high alkali frit, or a combination of the two. Although the general trend between melt rate and total alkali (in particular Na{sub 2}O content) has been demonstrated, the question of ''does the source of alkali (SOA) matter?'' still exists. Therefore the purpose of this set of tests was to determine if the source of alkali (frit versus sludge) can impact melt rate. The general test concept was to transition from a Na{sub 2}O-rich frit to a Na{sub 2}O-deficient frit while compensating the Na{sub 2}O content in the sludge to maintain the same overall Na{sub 2}O content in the melter feed. Specifically, the strategy was to vary the amount of alkali in frits and in the sludge batch 3 (SB3) sludge simulant (midpoint or baseline feed was SB3/Frit 418 at 35% waste loading) so that the resultant feeds had the same final glass composition when vitrified. A set of SOA feeds using frits ranging from 0 to 16 weight % Na{sub 2}O (in 4% increments) was first tested in the Melt Rate Furnace (MRF) to determine if indeed there was an impact. The dry-fed MRF tests indicated that if the alkali is too depleted from either the sludge (16% Na{sub 2}O feed) or the frit (the 0% Na{sub 2}O feed), then melt rate was negatively impacted when compared to the baseline SB3/Frit 418 feed currently being processed at DWPF. The MRF melt rates for the 4 and 12% SOA feeds were similar to the baseline SB3/Frit 418 (8% SOA) feed. Due to this finding, a smaller subset of SOA feeds that could be processed in the DWPF (4 and 12% SOA feeds) was then tested in the Slurry-fed Melt Rate Furnace (SMRF). The results from a previous SMRF test with SB3/Frit 418 (Smith et al. 2004) were used as the

  6. Alkali metal for ultraviolet band-pass filter

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  7. Scintillating glass fiber-optic neutron sensors

    NASA Astrophysics Data System (ADS)

    Abel, K. H.; Arthur, R. J.; Bliss, M.

    1994-04-01

    Pacific Northwest Laboratory (PNL) has fabricated cerium-activated lithium silicate scintillating fibers via a hot-downdraw process. These fibers, which, as produced, typically have a transmission length (e(sup -1) length) of greater than 2 meters, are found to undergo aging when subjected to room air. The aging, which is complete in a few weeks, reduces the transmission length to the order of 0.5 meter. Because of the high alkali content of the glass (on the order of 20-30 mole percent lithia), we have attributed this aging to aqueous corrosion at the polymer cladding/glass interface. Changes in transmission with chemical treatment of the surface support the corrosion model. Fiber transmission performance has been preserved by modifying the hot-downdraw to a double crucible to produce glass-on-glass waveguides.

  8. Computer Simulations of Supercooled Liquids and Glasses

    NASA Astrophysics Data System (ADS)

    Kob, Walter

    Glasses are materials that are ubiquitous in our daily life. We find them in such diverse items as window pans, optical fibers, computer chips, ceramics, all of which are oxide glasses, as well as in food, foams, polymers, gels, which are mainly of organic nature. Roughly speaking glasses are solid materials that have no translational or orientational order on the scale beyond O(10) diameters of the constituent particles (atoms, colloids, …) [1]. Note that these materials are not necessarily homogeneous since, e.g., alkali-glasses such as Na2O-SiO2 show (disordered!) structural features on the length scale of 6-10 Å (compare to the interatomic distance of 1-2 Å) and gels can have structural inhomogeneities that extend up to macroscopic length scales.

  9. Alkali Metal Salts with Designable Aryltrifluoroborate Anions.

    PubMed

    Iwasaki, Kazuki; Yoshii, Kazuki; Tsuzuki, Seiji; Matsumoto, Hajime; Tsuda, Tetsuya; Kuwabata, Susumu

    2016-09-01

    Aryltrifluoroborate ([ArBF3](-)) has a designable basic anion structure. Various [ArBF3](-)-based anions were synthesized to create novel alkali metal salts using a simple and safe process. Nearly 40 novel alkali metal salts were successfully obtained, and their physicochemical characteristics, particularly their thermal properties, were elucidated. These salts have lower melting points than those of simple inorganic alkali halide salts, such as KCl and LiCl, because of the weaker interactions between the alkali metal cations and the [ArBF3](-) anions and the anions' larger entropy. Moreover, interestingly, potassium cations were electrochemically reduced in the potassium (meta-ethoxyphenyl)trifluoroborate (K[m-OEtC6H4BF3]) molten salt at 433 K. These findings contribute substantially to furthering molten salt chemistry, ionic liquid chemistry, and electrochemistry. PMID:27510799

  10. Alkali Metal Handling Practices at NASA MSFC

    NASA Technical Reports Server (NTRS)

    Salvail, Patrick G.; Carter, Robert R.

    2002-01-01

    NASA Marshall Space Flight Center (MSFC) is NASA s principle propulsion development center. Research and development is coordinated and carried out on not only the existing transportation systems, but also those that may be flown in the near future. Heat pipe cooled fast fission cores are among several concepts being considered for the Nuclear Systems Initiative. Marshall Space Flight Center has developed a capability to handle high-purity alkali metals for use in heat pipes or liquid metal heat transfer loops. This capability is a low budget prototype of an alkali metal handling system that would allow the production of flight qualified heat pipe modules or alkali metal loops. The processing approach used to introduce pure alkali metal into heat pipe modules and other test articles are described in this paper.

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  12. Alkali basalts and enclosed ultramafic xenoliths near Ushuaia, Tierra Del Fuego, Argentina.

    PubMed

    Acevedo, Rogelio Daniel

    2016-01-01

    At the southernmost part of Tierra del Fuego a few outcrops and erratic boulders of alkali basaltic rocks with ultramafic enclaves have been studied. Alkali basalt plugs or pipes hitherto identified are scarce, and host rocks are constituted by slates that belong to Mesozoic deposition. The petrography, texture and composition of the basalt and xenoliths were investigated by petrographic microscope and electron microprobe analysis. Xenocrysts of amphibole and alkali feldspar, phenocrysts of nepheline, olivine, spinel, phlogopite and Fe-Ti minerals (10 %) and a diversity of xenoliths, mainly lherzolitic, pyroxenite and wehrlitic nodules (15 %), but also from metamorphic rocks provenance, are contained in the basalt groundmass (75 %). This finer-grained material is made up of laths or needles of plagioclase, pyroxene, opaque minerals, apatite and glass, with intersertal, hyalopilitic and pilotaxitic. Locally, rock has an even granoblastic texture. Former amygdules are filled by analcite, zeolites, sodalite and calcite. The normative classification, based on nepheline content, conclude that this rock is an alkali basalt. The chemical classification, considering immobile elements as Zr/TiO2 versus Nb/Y indicate an alkali basalt too and plots over the TAS diagram fall in the foidite (Na-rich or nephelinite) and basanite fields. The REE patterns are fractionated (La/Yb primitive mantle normalized is approximately 30). The K-Ar isotopic technique on individual macrocrysts gave ages of 146 ± 5 Ma (amphibole) and 127 ± 4 Ma (alkali feldspar); and K-Ar whole rock datum reported 8.3 ± 0.3 Ma. Nevertheless, fertile samples show geochemical features typical of deep derived material thus, based on the position in the actual tectonic setting, indicate that the basalt is older than its isotopic age. PMID:27610313

  13. Alkali basalts and enclosed ultramafic xenoliths near Ushuaia, Tierra Del Fuego, Argentina.

    PubMed

    Acevedo, Rogelio Daniel

    2016-01-01

    At the southernmost part of Tierra del Fuego a few outcrops and erratic boulders of alkali basaltic rocks with ultramafic enclaves have been studied. Alkali basalt plugs or pipes hitherto identified are scarce, and host rocks are constituted by slates that belong to Mesozoic deposition. The petrography, texture and composition of the basalt and xenoliths were investigated by petrographic microscope and electron microprobe analysis. Xenocrysts of amphibole and alkali feldspar, phenocrysts of nepheline, olivine, spinel, phlogopite and Fe-Ti minerals (10 %) and a diversity of xenoliths, mainly lherzolitic, pyroxenite and wehrlitic nodules (15 %), but also from metamorphic rocks provenance, are contained in the basalt groundmass (75 %). This finer-grained material is made up of laths or needles of plagioclase, pyroxene, opaque minerals, apatite and glass, with intersertal, hyalopilitic and pilotaxitic. Locally, rock has an even granoblastic texture. Former amygdules are filled by analcite, zeolites, sodalite and calcite. The normative classification, based on nepheline content, conclude that this rock is an alkali basalt. The chemical classification, considering immobile elements as Zr/TiO2 versus Nb/Y indicate an alkali basalt too and plots over the TAS diagram fall in the foidite (Na-rich or nephelinite) and basanite fields. The REE patterns are fractionated (La/Yb primitive mantle normalized is approximately 30). The K-Ar isotopic technique on individual macrocrysts gave ages of 146 ± 5 Ma (amphibole) and 127 ± 4 Ma (alkali feldspar); and K-Ar whole rock datum reported 8.3 ± 0.3 Ma. Nevertheless, fertile samples show geochemical features typical of deep derived material thus, based on the position in the actual tectonic setting, indicate that the basalt is older than its isotopic age.

  14. Reflection of thermal Cs atoms grazing a polished glass surface

    SciTech Connect

    Anderson, A.; Haroche, S.; Hinds, E.A.; Jhe, W.; Meschede, D.; Moi, L.

    1986-10-01

    We present an experimental study which shows that a large fraction (> or =50%) of thermal Cs atoms are nearly specularly reflected by polished glass surfaces at grazing incidence. This effect is interesting in the context of projects aimed at storing cold alkali-metal atoms in boxes.

  15. Desulfurizing Coal With an Alkali Treatment

    NASA Technical Reports Server (NTRS)

    Ravindram, M.; Kalvinskas, J. J.

    1987-01-01

    Experimental coal-desulfurization process uses alkalies and steam in fluidized-bed reactor. With highly volatile, high-sulfur bituminous coal, process removed 98 percent of pyritic sulfur and 47 percent of organic sulfur. Used in coal liquefaction and in production of clean solid fuels and synthetic liquid fuels. Nitrogen or steam flows through bed of coal in reactor. Alkalies react with sulfur, removing it from coal. Nitrogen flow fluidizes bed while heating or cooling; steam is fluidizing medium during reaction.

  16. Studies of the surface charge of amorphous aluminosilicates using surface complexation models.

    PubMed

    Jara, Alejandra A; Goldberg, Sabine; Mora, M L

    2005-12-01

    Synthetic noncrystalline aluminosilicates with variable charge, similar to allophanes present naturally in volcanic soils, were studied. The surface charge behavior was determined by zero point charge (ZPC) measured by electrophoretic mobility (isoelectric points, IEP) and determined by potentiometric titration (point of zero salt effect, PZSE). The ZPC calculated by Parks model (ZPC(c)), compared with IEP values, showed that the aluminosilicate (AlSi) surface was slightly enriched by AlOH (34% Al(2)O(3) and 66% SiO(2)) compared with the bulk composition (29% Al(2)O(3) and 71% SiO(2)). For aluminosilicate coated with iron oxide (AlSiFe) the ZPC(c) (4.4) was lower than the IEP (8.46), showing that the surface composition is formed mainly from iron oxide. The PZSE values for AlSi and AlSiFe were 6.2 and 4.8, respectively. The differences between the IEP and PZSE are attributed to the formation of Si-O-Fe or Si-O-Al bonds; therefore, the reactivity of Fe and Al atoms was modified on the surface. Two mechanistic models, the constant capacitance model (CCM) and the triple layer model (TLM), using the program FITEQL 3.2 were able to describe the surface behavior of both synthetic aluminosilicates. The acidity constants determined using both models for the aluminosilicates showed differences with respect to pure oxide, mainly attributed to the presence of SiOH sites on the internal surfaces. The ionic strength showed a good relation with the parameters obtained using the CCM (pK(int)(a1), pK(int)(a2) and capacitance values) and the TLM (pK(int)(a1), pK(int)(a2), pK(int)(Cl-), pK(int)(K+), and inner capacitance) for both aluminosilicates. However, the TLM was able to describe the acidity and complexation constants better since it considered the formation of the outer sphere complex between the background electrolyte and the surface. Then, the TLM makes it possible to describe real systems.

  17. Structure of rhenium-containing sodium borosilicate glass

    SciTech Connect

    Goel, Ashutosh; McCloy, John S.; Windisch, Charles F.; Riley, Brian J.; Schweiger, Michael J.; Rodriguez, Carmen P.; Ferreira, Jose M.

    2013-03-01

    A series of sodium borosilicate glasses were synthesized with increasing fractions of KReO4 or Re2O7, to 10000 ppm (1 mass%) target Re in glass, to assess the effects of large concentrations of rhenium on glass structure and to estimate the solubility of technetium, a radioactive component in typical low active waste nuclear waste glasses. Magic angle spinning nuclear magnetic resonance (MAS-NMR), Fourier transform infrared (FTIR) spectroscopy, and Raman spectroscopy were performed to characterize the glasses as a function of Re source additions. In general, silicon was found coordinated in a mixture of Q2 and Q3 structural units, while Al was 4-coordinated and B was largely 3-coordinate and partially 4-coordinated. The rhenium source did not appear to have significant effects on the glass structure. Thus, at the up to the concentrations that remain in dissolved in glass, ~3000 ppm Re by mass maximum. , the Re appeared to be neither a glass-former nor a strong glass modifier., Rhenium likely exists in isolated ReO4- anions in the interstices of the glass network, as evidenced by the polarized Raman spectrum of the Re glass in the absence of sulfate. Analogous to SO42-¬ in similar glasses, ReO4- is likely a network modifier and forms alkali salt phases on the surface and in the bulk glass above solubility.

  18. Long-term product consistency test of simulated 90-19/Nd HLW glass

    NASA Astrophysics Data System (ADS)

    Gan, X. Y.; Zhang, Z. T.; Yuan, W. Y.; Wang, L.; Bai, Y.; Ma, H.

    2011-01-01

    Chemical durability of 90-19/Nd glass, a simulated high-level waste (HLW) glass in contact with the groundwater was investigated with a long-term product consistency test (PCT). Generally, it is difficult to observe the long term property of HLW glass due to the slow corrosion rate in a mild condition. In order to overcome this problem, increased contacting surface ( S/ V = 6000 m -1) and elevated temperature (150 °C) were employed to accelerate the glass corrosion evolution. The micro-morphological characteristics of the glass surface and the secondary minerals formed after the glass alteration were analyzed by SEM-EDS and XRD, and concentrations of elements in the leaching solution were determined by ICP-AES. In our experiments, two types of minerals, which have great impact on glass dissolution, were found to form on 90-19/Nd HLW glass surface when it was subjected to a long-term leaching in the groundwater. One is Mg-Fe-rich phyllosilicates with honeycomb structure; the other is aluminosilicates (zeolites). Mg and Fe in the leaching solution participated in the formation of phyllosilicates. The main components of phyllosilicates in alteration products of 90-19/Nd HLW glass are nontronite (Na 0.3Fe 2Si 4O 10(OH) 2·4H 2O) and montmorillonite (Ca 0.2(Al,Mg) 2Si 4O 10(OH) 2·4H 2O), and those of aluminosilicates are mordenite ((Na 2,K 2,Ca)Al 2Si 10O 24·7H 2O)) and clinoptilolite ((Na,K,Ca) 5Al 6Si 30O 72·18H 2O). Minerals like Ca(Mg)SO 4 and CaCO 3 with low solubility limits are prone to form precipitant on the glass surface. Appearance of the phyllosilicates and aluminosilicates result in the dissolution rate of 90-19/Nd HLW glass resumed, which is increased by several times over the stable rate. As further dissolution of the glass, both B and Na in the glass were found to leach out in borax form.

  19. Influence of Boehmite Precursor on Aluminosilicate Aerogel Pore Structure, Phase Stability and Resistance to Densification at High Temperatures

    NASA Technical Reports Server (NTRS)

    Hurwitz, Frances I.; Guo, Haiquan; Newlin, Katy N.

    2011-01-01

    Aluminosilicate aerogels are of interest as constituents of thermal insulation systems for use at temperatures higher than those attainable with silica aerogels. It is anticipated that their effectiveness as thermal insulators will be influenced by their morphology, pore size distribution, physical and skeletal densities. The present study focuses on the synthesis of aluminosilicate aerogel from a variety of Boehmite (precursors as the Al source, and tetraethylorthosilicate (TEOS) as the Si source, and the influence of starting powder on pore structure and thermal stability.

  20. Characterization of high cesium containing glass-bonded ceramic waste forms.

    SciTech Connect

    Lambregts, M. J.; Frank, S. M.

    2003-10-03

    High cesium containing glass-bonded ceramic waste form samples were prepared and characterized to identify possible cesium phases present in glass-bonded ceramic waste forms developed for the containment of fission product bearing salts. Major phases of the waste forms are sodalite and glass. A combination of powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and nuclear magnetic resonance spectroscopy (NMR) were used to study the multiphase nature of these waste forms. Cesium was found to be present in the higher loaded waste forms in a cesium aluminosilicate phase with an analcime structure and a 1:1 Si:Al ratio, a pollucite phase, and also in the glass phase. The glass phase contains the majority of the cesium at lower loadings, however some pollucite also remains. Cesium was not detected in the sodalite phase of any of the samples.

  1. Metallic glasses.

    PubMed

    Greer, A L

    1995-03-31

    Amorphous metallic alloys, relative newcomers to the world of glasses, have properties that are unusual for solid metals. The metallic glasses, which exist in a very wide variety of compositions, combine fundamental interest with practical applications. They also serve as precursors for exciting new nanocrystalline materials. Their magnetic (soft and hard) and mechanical properties are of particular interest.

  2. Strength Improvement of Glass Substrates by Using Surface Nanostructures

    NASA Astrophysics Data System (ADS)

    Kumar, Amarendra; Kashyap, Kunal; Hou, Max T.; Yeh, J. Andrew

    2016-05-01

    Defects and heterogeneities degrade the strength of glass with different surface and subsurface properties. This study uses surface nanostructures to improve the bending strength of glass and investigates the effect of defects on three glass types. Borosilicate and aluminosilicate glasses with a higher defect density than fused silica exhibited 118 and 48 % improvement, respectively, in bending strength after surface nanostructure fabrication. Fused silica, exhibited limited strength improvement. Therefore, a 4-μm-deep square notch was fabricated to study the effect of a dominant defect in low defect density glass. The reduced bending strength of fused silica caused by artificial defect increased 65 % in the presence of 2-μm-deep nanostructures, and the fused silica regained its original strength when the nanostructures were 4 μm deep. In fragmentation tests, the fused silica specimen broke into two major portions because of the creation of artificial defects. The number of fragments increased when nanostructures were fabricated on the fused silica surface. Bending strength improvement and fragmentation test confirm the usability of this method for glasses with low defect densities when a dominant defect is present on the surface. Our findings indicate that nanostructure-based strengthening is suitable for all types of glasses irrespective of defect density, and the observed Weibull modulus enhancement confirms the reliability of this method.

  3. Thermochemical study of rare earth and nitrogen incorporation in glasses

    NASA Astrophysics Data System (ADS)

    Zhang, Yahong

    Rare earth containing aluminosilicate, borosilicate, aluminate and nitrogen containing aluminosilicate glasses are technically important materials. They have extraordinary physical and chemical properties such as high glass transition temperature, very low electrical conductivity, and excellent chemical stability. These unique properties lead to applications as coatings on metals and ceramics, optical fibers, semiconductors, and nuclear waste containment materials. In addition, such systems contain the most widely used additives for sintering of Si3N4, SiAlON and SiC ceramics for high temperature applications. Thermodynamic properties and the relations among energetics, structure and bonding are essential to controlling processing parameters to synthesize, at lower cost, materials having better properties. Earlier investigations mainly pertained to specific physical properties of rare-earth doped oxide and oxynitride glasses. Work on the thermodynamic stability and materials compatibility has been very sparse. High temperature solution calorimetry in molten oxide solvents is a powerful tool for the thermodynamic study of refractory materials. With implementation and improvement, this technique has been applied to the first measurement of enthalpies of formation of RE-Si-Al-O glasses, REAlO3 glasses, RE-Si-Al-O-N glasses, and Si3N 4 and Ge3N4 with high pressure spinel structure. The first successful synthesis of REAlO3 glasses has been achieved by containerless melting. Their large enthalpies of crystallization confirm that they are reluctant glass formers. For glasses along the 2REAlO3 -3SiO2 join, the strongly negative heats of mixing support the absence of miscibility gaps except possibly at very high silica content. Energetic evidence has been presented for incipient phase-ordered regions in Gd- or Hf-containing sodium alumino-borosilicate glasses for plutonium immobilization. Linear relations between enthalpies of formation of RESiAlON glasses from elements and

  4. Alzheimer's disease may begin in the nose and may be caused by aluminosilicates.

    PubMed

    Roberts, E

    1986-01-01

    Genetic factors may interact with aging changes in the nasal mucociliary apparatus to increase the probability that ubiquitously occurring aluminosilicates may enter sensory neurons of the olfactory epithelium and spread transneuronally to several olfactory-related areas of the brain, thereby initiating changes that eventually result in neuronal damage typical of Alzheimer's disease. A speculative sequence of events is suggested by which neuronally-contained aluminosilicates might cleave or otherwise alter a normal cellular protein in such a manner that aggregates would arise that could interfere with cellular function and which also could act in a pseudo-infective manner, relaxing translational and transcriptional controls in the synthesis of the native protein. Some relevant experiments and potential therapies arising from the hypothesis presented are discussed.

  5. Maximizing the catalytic function of hydrogen spillover in platinum-encapsulated aluminosilicates with controlled nanostructures.

    PubMed

    Im, Juhwan; Shin, Hyeyoung; Jang, Haeyoun; Kim, Hyungjun; Choi, Minkee

    2014-02-25

    Hydrogen spillover has been studied for several decades, but its nature, catalytic functions and even its existence remain topics of vigorous debate. This is a consequence of the lack of model catalysts that can provide direct evidences of the existence of hydrogen spillover and simplify the catalytic interpretation. Here we use platinum encapsulated in a dense aluminosilicate matrix with controlled diffusional properties and surface hydroxyl concentrations to elucidate the catalytic functions of hydrogen spillover. The catalytic investigation and theoretical modelling show that surface hydroxyls, presumably Brønsted acids, are crucial for utilizing the catalytic functions of hydrogen spillover on the aluminosilicate surface. The catalysts with optimized nanostructure show remarkable activities in hydro-/dehydrogenation, but virtually no activity for hydrogenolysis. This distinct chemoselectivity may be beneficial in industrially important hydroconversions such as propane dehydrogenation to propylene because the undesired hydrogenolysis pathway producing light hydrocarbons of low value (methane and ethane) is greatly suppressed.

  6. Oxidative damage in Alzheimer's dementia, and the potential etiopathogenic role of aluminosilicates, microglia and micronutrient interactions.

    PubMed

    Evans, P H; Yano, E; Klinowski, J; Peterhans, E

    1992-01-01

    While evidence implicating free radical oxidative processes in the etiopathogenesis of Alzheimer's dementia is accumulating, the specific cellular and biochemical mechanisms involved remain to be identified. The potential pathogenic role of microglial cells in neurodegenerative processes is indicated by the finding that purified murine microglial cells exposed in vitro to various model aluminosilicate particles stimulate the generation of tissue-injurious free radical reactive oxygen metabolites. Analogous inorganic aluminosilicate deposits have been reported to occur in the core of the characteristic senile plaques found in the brains of Alzheimer disease subjects. The possible modulation of free radical oxidative activity by antioxidant micronutrients and pharmacological agents, provides a rational basis for further preventative and therapeutic clinical investigations.

  7. Surface and interface investigation of aluminosilicate biomaterial by the “in vivo” experiments

    NASA Astrophysics Data System (ADS)

    Oudadesse, H.; Derrien, A. C.; Martin, S.; Chaair, H.; Cathelineau, G.

    2008-11-01

    Porous mixtures of aluminosilicate/calcium phosphate have been studied for biomaterials applications. Aluminosilicates formed with an inorganic polymeric constitution present amorphous zeolites because of their 3D network structure and present the ability to link to bone matrix. Amorphous geopolymers of the potassium-poly(sialate)-nanopolymer type were synthesised at low temperature and studied for their use as potential biomaterials. They were mixed with 13% weight of calcium phosphate like biphasic hydroxyapatite and β-tricalcium phosphate. In this study, " in vivo" experiments were monitored to evaluate the biocompatibility, the surface and the interface behaviour of these composites when used as bone implants. Moreover, it has been demonstrated using histological and physicochemical studies that the developed materials exhibited a remarkable bone bonding when implanted in a rabbit's thighbone for a period of 1 month. The easy synthesis conditions (low temperature) of this composite and the fast intimate links with bone constitute an improvement of synthetic bone graft biomaterial.

  8. Amphiphilic Organic-Inorganic Hybrid Zeotype Aluminosilicate like a Nanoporous Crystallized Langmuir-Blodgett Film.

    PubMed

    Ikeda, Takuji; Hiyoshi, Norihito; Matsuura, Shun-ichi; Kodaira, Tetsuya; Nakaoka, Takuma; Irisa, Ami; Kawano, Miki; Yamamoto, Katsutoshi

    2015-06-26

    A new organic-inorganic hybrid zeotype compound with amphiphilic one-dimensional nanopore and aluminosilicate composition was developed. The framework structure is composed of double aluminosilicate layers and 12-ring nanopores; a hydrophilic layer pillared by Q(2) silicon atom species and a lipophilic layer pillared by phenylene groups are alternately stacked, and 12-ring nanopores perpendicularly penetrate the layers. The framework topology looks similar to that of an AFI-type zeolite but possesses a quasi-multidimensional pore structure consisting of a 12-ring channel and intersecting small pores equivalent to 8-rings. The hybrid material with alternately laminated lipophilic and hydrophilic nanospaces can be assumed as a crystallized Langmuir-Blodgett film. It demonstrates microporous adsorption for both hydrophilic and lipophilic adsorptives, and its outer surface tightly adsorbs lysozyme whose molecular size is much larger than its micropore opening. Our results suggest the possibility of designing porous adsorbent with high amphipathicity.

  9. Mechanical and microstructural properties of alkali-activated fly ash geopolymers.

    PubMed

    Komljenović, M; Bascarević, Z; Bradić, V

    2010-09-15

    This paper investigates the properties of geopolymer obtained by alkali-activation of fly ash (FA), i.e. the influence of characteristics of the representative group of FA (class F) from Serbia, as well as that of the nature and concentration of various activators on mechanical and microstructural properties of geopolymers. Aqueous solutions of Ca(OH)(2), NaOH, NaOH+Na(2)CO(3), KOH and sodium silicate (water glass) of various concentrations were used as alkali activators. It was established that the nature and concentration of the activator was the most dominant parameter in the alkali-activation process. In respect of physical characteristics of FA, the key parameter was fineness. The geopolymer based on FA with the highest content of fine particles (<43 microm), showed the highest compressive strength in all cases. Regardless of FA characteristics, nature and concentration of the activator, the alkali-activation products were mainly amorphous. The formation of crystalline phases (zeolites) occurred in some cases, depending on the reaction conditions. The highest compressive strength was obtained using sodium silicate. Together with the increase of sodium silicate SiO(2)/Na(2)O mass ratio, the atomic Si/Al ratio in the reaction products was also increased. Under the experimental conditions of this investigation, high strength was directly related to the high Si/Al ratio.

  10. Alkali-Activated Aluminium-Silicate Composites as Insulation Materials for Industrial Application

    NASA Astrophysics Data System (ADS)

    Dembovska, L.; Bajare, D.; Pundiene, I.; Bumanis, G.

    2015-11-01

    The article reports on the study of thermal stability of alkali-activated aluminium- silicate composites (ASC) at temperature 800-1100°C. ASC were prepared by using calcined kaolinite clay, aluminium scrap recycling waste, lead-silicate glass waste and quartz sand. As alkali activator, commercial sodium silicate solution modified with an addition of sodium hydroxide was used. The obtained alkali activation solution had silica modulus Ms=1.67. Components of aluminium scrap recycling waste (aluminium nitride (AlN) and iron sulphite (FeSO3)) react in the alkali media and create gases - ammonia and sulphur dioxide, which provide the porous structure of the material [1]. Changes in the chemical composition of ASC during heating were identified and quantitatively analysed by using DTA/TG, dimension changes during the heating process were determined by using HTOM, pore microstructure was examined by SEM, and mineralogical composition of ASC was determined by XRD. The density of ASC was measured in accordance with EN 1097-7. ASC with density around 560 kg/m3 and heat resistance up to 1100°C with shrinkage less than 5% were obtained. The intended use of this material is the application as an insulation material for industrial purposes at elevated temperatures.

  11. Mechanical and microstructural properties of alkali-activated fly ash geopolymers.

    PubMed

    Komljenović, M; Bascarević, Z; Bradić, V

    2010-09-15

    This paper investigates the properties of geopolymer obtained by alkali-activation of fly ash (FA), i.e. the influence of characteristics of the representative group of FA (class F) from Serbia, as well as that of the nature and concentration of various activators on mechanical and microstructural properties of geopolymers. Aqueous solutions of Ca(OH)(2), NaOH, NaOH+Na(2)CO(3), KOH and sodium silicate (water glass) of various concentrations were used as alkali activators. It was established that the nature and concentration of the activator was the most dominant parameter in the alkali-activation process. In respect of physical characteristics of FA, the key parameter was fineness. The geopolymer based on FA with the highest content of fine particles (<43 microm), showed the highest compressive strength in all cases. Regardless of FA characteristics, nature and concentration of the activator, the alkali-activation products were mainly amorphous. The formation of crystalline phases (zeolites) occurred in some cases, depending on the reaction conditions. The highest compressive strength was obtained using sodium silicate. Together with the increase of sodium silicate SiO(2)/Na(2)O mass ratio, the atomic Si/Al ratio in the reaction products was also increased. Under the experimental conditions of this investigation, high strength was directly related to the high Si/Al ratio. PMID:20554110

  12. High-Aluminum-Affinity Silica Is a Nanoparticle That Seeds Secondary Aluminosilicate Formation

    PubMed Central

    Jugdaohsingh, Ravin; Brown, Andy; Dietzel, Martin; Powell, Jonathan J.

    2013-01-01

    Despite the importance and abundance of aluminosilicates throughout our natural surroundings, their formation at neutral pH is, surprisingly, a matter of considerable debate. From our experiments in dilute aluminum and silica containing solutions (pH ~ 7) we previously identified a silica polymer with an extraordinarily high affinity for aluminium ions (high-aluminum-affinity silica polymer, HSP). Here, further characterization shows that HSP is a colloid of approximately 2.4 nm in diameter with a mean specific surface area of about 1,000 m2 g-1 and it competes effectively with transferrin for Al(III) binding. Aluminum binding to HSP strongly inhibited its decomposition whilst the reaction rate constant for the formation of the β-silicomolybdic acid complex indicated a diameter between 3.6 and 4.1 nm for these aluminum-containing nanoparticles. Similarly, high resolution microscopic analysis of the air dried aluminum-containing silica colloid solution revealed 3.9 ± 1.3 nm sized crystalline Al-rich silica nanoparticles (ASP) with an estimated Al:Si ratio of between 2 and 3 which is close to the range of secondary aluminosilicates such as imogolite. Thus the high-aluminum-affinity silica polymer is a nanoparticle that seeds early aluminosilicate formation through highly competitive binding of Al(III) ions. In niche environments, especially in vivo, this may serve as an alternative mechanism to polyhydroxy Al(III) species binding monomeric silica to form early phase, non-toxic aluminosilicates. PMID:24349573

  13. One-step synthesis of hydrothermally stable mesoporous aluminosilicates with strong acidity

    SciTech Connect

    Yang Dongjiang; Xu Yao Wu Dong; Sun Yuhan

    2008-09-15

    Using tetraethylorthosilicate (TEOS), polymethylhydrosiloxane (PMHS) and aluminium isopropoxide (AIP) as the reactants, through a one-step nonsurfactant route based on PMHS-TEOS-AIP co-polycondensation, hydrothermally stable mesoporous aluminosilicates with different Si/Al molar ratios were successfully prepared. All samples exclusively showed narrow pore size distribution centered at 3.6 nm. To assess the hydrothermal stability, samples were subjected to 100 deg. C distilled water for 300 h. The boiled mesoporous aluminosilicates have nearly the same N{sub 2} adsorption-desorption isotherms and the same pore size distributions as those newly synthesized ones, indicating excellent hydrothermal stability. The {sup 29}Si MAS NMR spectra confirmed that PMHS and TEOS have jointly condensed and CH{sub 3} groups have been introduced into the materials. The {sup 27}Al MAS NMR spectra indicated that Al atoms have been incorporated in the mesopore frameworks. The NH{sub 3} temperature-programmed desorption showed strong acidity. Due to the existence of large amount of CH{sub 3} groups, the mesoporous aluminosilicates obtained good hydrophobicity. Owing to the relatively large pore and the strong acidity provided by the uniform four-coordinated Al atoms, the excellent catalytic performance for 1,3,5-triisopropylbenzene cracking was acquired easily. The materials may be a profitable complement for the synthesis of solid acid catalysts. - Graphical abstract: Based on the nonsurfactant method, a facile one-step synthesis route has been developed to prepare methyl-modified mesoporous aluminosilicates that possessed hydrothermal stability and strong acidity.

  14. Adsorption into mineral mesopores as a stabilization mechanism for organic matter on aluminosilicates

    SciTech Connect

    Mayer, L.M. . Dept. of Oceanography)

    1992-01-01

    Measurements of mineral specific surface area and total organic carbon (TOC) indicate that many marine shelf and estuarine sediments, and aluminosilicate soils, have a TOC content equivalent to a monolayer of organic matter covering all mineral surfaces. Density separations of discrete organic particulates from mineral-associated OC are consistent with a primarily adsorbed nature foremost of TOC. Nitrogen gas adsorption data also suggest extensive organic coatings on the mineral grains. Downcore analyses indicate that sediments with TOC starting in excess of monolayer-equivalent (ME) levels decay with core depth to the ME level and then markedly slow their OC loss rate--i.e., the ME level determines the refractory background concentration of TOC. Pore size distributions of marine sediments, determined by nitrogen adsorption or mercury porosimetry, indicate that most surface area of minerals is to be found in pores of < 10 nm diameter. These observations lead to the hypothesis that organic matter is stabilized on aluminosilicate minerals by adsorption into pores too small to allow entry or functioning of the hydrolytic enzymes responsible for OC degradation. This hypothesis is consistent with, but does not require, humification reactions as necessary for OC stabilization. The ME levels of TOC found in continental platform aluminosilicates hence represent a cap on the amount of organic matter that can be protected in this manner and thus attain a residence time of > 1,000 y. Stabilization of higher levels of TOC, as in acid soils or anoxic sediments, presumably results from protection by different mechanisms.

  15. Mesoporous aluminosilicates with ordered hexagonal structure, strong acidity, and extraordinary hydrothermal stability at high temperatures.

    PubMed

    Zhang, Z; Han, Y; Xiao, F S; Qiu, S; Zhu, L; Wang, R; Yu, Y; Zhang, Z; Zou, B; Wang, Y; Sun, H; Zhao, D; Wei, Y

    2001-05-30

    Highly ordered hexagonal mesoporous aluminosilicates (MAS-5) with uniform pore sizes have been successfully synthesized from assembly of preformed aluminosilcate precursors with cetyltrimethylammonium bromide (CTAB) surfactant. The aluminosilicate precursors were obtained by heating, at 100--140 degrees C for 2--10 h, aluminasilica gels at the Al(2)O(3)/SiO(2)/TEAOH/H(2)O molar ratios of 1.0/7.0--350/10.0--33.0/500--2000. Mesoporous MAS-5 shows extraordinary stability both in boiling water (over 300 h) and in steam (800 degrees C for 2 h). Temperature-programmed desorption of ammonia shows that the acidic strength of MAS-5 is much higher than that of MCM-41 and is comparable to that of microporous Beta zeolite. In catalytic cracking of 1,3,5-triisopropylbenzene and alkylation of isobutane with butene, MAS-5 exhibits greater catalytic activity and selectivity, as compared with MCM-41 and HZSM-5. The MAS-5 samples were characterized with infrared, UV--Raman, and NMR spectroscopy and numerous other techniques. The results suggest that MAS-5 consists of both mesopores and micropores and that the pore walls of MAS-5 contain primary and secondary structural building units, similar to those of microporous zeolites. Such unique structural features might be responsible for the observed strong acidity and high thermal stability of the mesoporous aluminosilicates with well-ordered hexagonal symmetry.

  16. STUDIES OF POTENTIAL INHIBITORS OF SODIUM ALUMINOSILICATE SCALES IN HIGH-LEVEL WASTE EVAPORATION

    SciTech Connect

    Wilmarth, B; Lawrence Oji, L; Terri Fellinger, T; David Hobbs, D; Nilesh Badheka, N

    2008-02-27

    The Savannah River Site (SRS) has 49 underground storage tanks used to store High Level Waste (HLW). The tank space in these tanks must be managed to support the continued operation of key facilities. The reduction of the tank volumes in these tanks are accomplished through the use of three atmospheric pressure HLW evaporators. For a decade, evaporation of highly alkaline HLW containing aluminum and silicates has produced sodium aluminosilicate scales causing both operation and criticality hazards in the 2H Evaporator System. Segregation of aluminum-rich wastes from silicate-rich wastes minimizes the amount of scale produced and reduces cleaning expenses, but does not eliminate the scaling nor increases operation flexibility in waste process. Similar issues have affected the aluminum refining industry for many decades. Over the past several years, successful commercial products have been identified to eliminate aluminosilicate fouling in the aluminum industry, but have not been utilized in a nuclear environment. Laboratory quantities of three proprietary aluminosilicate scale inhibitors have been produced and been shown to prevent formation of scales. SRNL has been actively testing these potential inhibitors to examine their radiation stability, radiolytic degradation behaviors, and downstream impacts to determine their viability within the HLW system. One of the tested polymers successfully meets the established criteria for application in the nuclear environment. This paper will describe a summary of the methodology used to prioritize laboratory testing protocols based on potential impacts/risks identified for inhibitor deployment at SRS.

  17. Impact Of Sodium Oxalate, Sodium Aluminosilicate, and Gibbsite/Boehmite on ARP Filter Performance

    SciTech Connect

    Poirier, M.; Burket, P.

    2015-11-01

    The Savannah River Site (SRS) is currently treating radioactive liquid waste with the Actinide Removal Process (ARP) and the Modular Caustic Side Solvent Extraction Unit (MCU). Recently, the low filter flux through the ARP of approximately 5 gallons per minute has limited the rate at which radioactive liquid waste can be treated. Salt Batch 6 had a lower processing rate and required frequent filter cleaning. Savannah River Remediation (SRR) has a desire to understand the causes of the low filter flux and to increase ARP/MCU throughput. SRR requested SRNL to conduct bench-scale filter tests to evaluate whether sodium oxalate, sodium aluminosilicate, or aluminum solids (i.e., gibbsite and boehmite) could be the cause of excessive fouling of the crossflow or secondary filter at ARP. The authors conducted the tests by preparing slurries containing 6.6 M sodium Salt Batch 6 supernate, 2.5 g MST/L slurry, and varying concentrations of sodium oxalate, sodium aluminosilicate, and aluminum solids, processing the slurry through a bench-scale filter unit that contains a crossflow primary filter and a dead-end secondary filter, and measuring filter flux and transmembrane pressure as a function of time. Among the conclusions drwn from this work are the following: (1) All of the tests showed some evidence of fouling the secondary filter. This fouling could be from fine particles passing through the crossflow filter. (2) The sodium oxalate-containing feeds behaved differently from the sodium aluminosilicate- and gibbsite/boehmite-containing feeds.

  18. A-thermal elastic behavior of silicate glasses.

    PubMed

    Rabia, Mohammed Kamel; Degioanni, Simon; Martinet, Christine; Le Brusq, Jacques; Champagnon, Bernard; Vouagner, Dominique

    2016-02-24

    Depending on the composition of silicate glasses, their elastic moduli can increase or decrease as function of the temperature. Studying the Brillouin frequency shift of these glasses versus temperature allows the a-thermal composition corresponding to an intermediate glass to be determined. In an intermediate glass, the elastic moduli are independent of the temperature over a large temperature range. For sodium alumino-silicate glasses, the a-thermal composition is close to the albite glass (NaAlSi3O8). The structural origin of this property is studied by in situ high temperature Raman scattering. The structure of the intermediate albite glass and of silica are compared at different temperatures between room temperature and 600 °C. When the temperature increases, it is shown that the high frequency shift of the main band at 440 cm(-1) in silica is a consequence of the cristobalite-like alpha-beta transformation of 6-membered rings. This effect is stronger in silica than bond elongation (anharmonic effects). As a consequence, the elastic moduli of silica increase as the temperature increases. In the albite glass, the substitution of 25% of Si(4+) ions by Al(3+) and Na(+) ions decreases the proportion of SiO2 6-membered rings responsible for the silica anomaly. The effects of the silica anomaly balance the anharmonicity in albite glass and give rise to an intermediate a-thermal glass. Different networks, formers or modifiers, can be added to produce different a-thermal glasses with useful mechanical or chemical properties.

  19. A-thermal elastic behavior of silicate glasses.

    PubMed

    Rabia, Mohammed Kamel; Degioanni, Simon; Martinet, Christine; Le Brusq, Jacques; Champagnon, Bernard; Vouagner, Dominique

    2016-02-24

    Depending on the composition of silicate glasses, their elastic moduli can increase or decrease as function of the temperature. Studying the Brillouin frequency shift of these glasses versus temperature allows the a-thermal composition corresponding to an intermediate glass to be determined. In an intermediate glass, the elastic moduli are independent of the temperature over a large temperature range. For sodium alumino-silicate glasses, the a-thermal composition is close to the albite glass (NaAlSi3O8). The structural origin of this property is studied by in situ high temperature Raman scattering. The structure of the intermediate albite glass and of silica are compared at different temperatures between room temperature and 600 °C. When the temperature increases, it is shown that the high frequency shift of the main band at 440 cm(-1) in silica is a consequence of the cristobalite-like alpha-beta transformation of 6-membered rings. This effect is stronger in silica than bond elongation (anharmonic effects). As a consequence, the elastic moduli of silica increase as the temperature increases. In the albite glass, the substitution of 25% of Si(4+) ions by Al(3+) and Na(+) ions decreases the proportion of SiO2 6-membered rings responsible for the silica anomaly. The effects of the silica anomaly balance the anharmonicity in albite glass and give rise to an intermediate a-thermal glass. Different networks, formers or modifiers, can be added to produce different a-thermal glasses with useful mechanical or chemical properties. PMID:26815634

  20. Freeze-thawing behaviour of highly concentrated aqueous alkali chloride-glucose systems.

    PubMed

    Kajiwara, K; Motegi, A; Murase, N

    2001-01-01

    The freeze-thawing behaviour of highly concentrated aqueous alkali chloride-glucose systems was investigated by differential scanning calorimetry (DSC). In the aqueous NaCl-glucose solution system, single or double glass transitions followed by the corresponding devitrification exotherms were observed during rewarming. In the aqueous KCl-glucose solution system, on the other hand, a single glass transition followed by an exotherm was observed during rewarming. The presence of double glass transitions observed for a certain composition of the aqueous NaCl-glucose solution was taken as an evidence for the liquid-liquid immiscibility at low temperatures. Two kinds of crystallisation accompanied by exotherms during rewarming were identified by X-ray diffraction as ice and ice/NaCl x 2H(2)O, or ice/KCl eutectic component. PMID:11788873

  1. Use of recycled glass for concrete masonry blocks. Final report

    SciTech Connect

    Meyer, C.; Baxter, S.

    1997-11-01

    A two-year research project was conducted to study the technical and economic feasibility of using mixed-color crushed waste glass for concrete masonry. From a technical standpoint, two problems had to be confronted. First, it was known that the silica in glass is highly reactive in the alkaline environment of portland cement concrete. Second, there was the possibility of strength loss, as crushed glass particles with smooth surfaces were substituted for regular aggregate. Both problems were solved in the course of this research. It was found that waste glass ground to mesh size No. 30 or smaller does not exhibit any expansion due to alkali-silica reaction (ASR). Another significant research finding was that very finely ground glass exhibits pozzolanic properties and therefore is suitable as a partial replacement for portland cement. The economic feasibility of concrete block masonry with glass both as aggregate and cement substitution was evaluated and found to be encouraging.

  2. High-Intensity Plasma Glass Melter Final Technical Report

    SciTech Connect

    Gonterman, J. Ronald; Weinstein, Michael A.

    2006-10-27

    frits. Exploratory melts of non-glassy materials, such as wollastonite, zirconium silicate, and alumino-silicate melts were successfully done indicating that plasma melting has potential application beyond glass. Experimental results were generated that show the high quality of plasma-melted fiberglass compositions, such as E-glass, can result in good fiberizing performance. Fiberizing performance and tensile strength data were achieved during the project to support this conclusion. High seed counts are a feature of the current lab scale melter and must be dealt with via other means, since fining work was outside the scope of this project.

  3. Triple stack glass-to-glass anodic bonding for optogalvanic spectroscopy cells with electrical feedthroughs

    SciTech Connect

    Daschner, R.; Kübler, H.; Löw, R.; Pfau, T.; Baur, H.; Frühauf, N.

    2014-07-28

    We demonstrate the use of an anodic bonding technique for building a vacuum tight vapor cell for the use of Rydberg spectroscopy of alkali atoms with thin film electrodes on the inside of the cell. The cell is fabricated by simultaneous triple stack glass-to-glass anodic bonding at 300 °C. This glue-free, low temperature sealing technique provides the opportunity to include thin film electric feedthroughs. The pressure broadening is only limited by the vapor pressure of rubidium and the lifetime is at least four months with operating temperatures up to 230 °C.

  4. Triple stack glass-to-glass anodic bonding for optogalvanic spectroscopy cells with electrical feedthroughs

    NASA Astrophysics Data System (ADS)

    Daschner, R.; Kübler, H.; Löw, R.; Baur, H.; Frühauf, N.; Pfau, T.

    2014-07-01

    We demonstrate the use of an anodic bonding technique for building a vacuum tight vapor cell for the use of Rydberg spectroscopy of alkali atoms with thin film electrodes on the inside of the cell. The cell is fabricated by simultaneous triple stack glass-to-glass anodic bonding at 300 °C. This glue-free, low temperature sealing technique provides the opportunity to include thin film electric feedthroughs. The pressure broadening is only limited by the vapor pressure of rubidium and the lifetime is at least four months with operating temperatures up to 230 °C.

  5. DIET of alkali atoms from mineral surfaces

    NASA Astrophysics Data System (ADS)

    Yakshinskiy, B. V.; Madey, T. E.

    2003-03-01

    To investigate mechanisms for the origin of alkalis in the atmosphere of the Moon, we are studying the electron- and photon-stimulated desorption (ESD and PSD) of K atoms from model mineral surfaces (SiO 2 films), and ESD and PSD of Na atoms from a lunar basalt sample. X-ray photoelectron spectroscopy demonstrates the existence of traces of Na in the lunar sample. To obtain an increased signal for detailed measurements of desorption parameters (appearance thresholds, yields), a fractional monolayer of Na is deposited onto the lunar sample surface. An alkali atom detector based on surface ionization and a time-of-flight technique are used for DIET measurements, together with a pulsed electron gun, and a mechanically chopped and filtered mercury arc light source. We find that bombardment of the alkali covered surfaces by UV photons or by electrons with energies E>4 eV causes desorption of "hot" alkali atoms. The results are consistent with the model based on charge transfer from the substrate to adsorbate which was developed to explain our previous measurements of sodium desorption from a silica surface and desorption of K atoms from water ice. The data support the suggestion that PSD by UV solar photons is a dominant source process for alkalis in the tenuous lunar atmosphere.

  6. Monte Carlo simulations of phosphate polyhedron connectivity in glasses

    SciTech Connect

    ALAM,TODD M.

    2000-01-01

    Monte Carlo simulations of phosphate tetrahedron connectivity distributions in alkali and alkaline earth phosphate glasses are reported. By utilizing a discrete bond model, the distribution of next-nearest neighbor connectivities between phosphate polyhedron for random, alternating and clustering bonding scenarios was evaluated as a function of the relative bond energy difference. The simulated distributions are compared to experimentally observed connectivities reported for solid-state two-dimensional exchange and double-quantum NMR experiments of phosphate glasses. These Monte Carlo simulations demonstrate that the polyhedron connectivity is best described by a random distribution in lithium phosphate and calcium phosphate glasses.

  7. Monte Carlo Simulations of Phosphate Polyhedron Connectivity in Glasses

    SciTech Connect

    ALAM,TODD M.

    1999-12-21

    Monte Carlo simulations of phosphate tetrahedron connectivity distributions in alkali and alkaline earth phosphate glasses are reported. By utilizing a discrete bond model, the distribution of next-nearest neighbor connectivities between phosphate polyhedron for random, alternating and clustering bonding scenarios was evaluated as a function of the relative bond energy difference. The simulated distributions are compared to experimentally observed connectivities reported for solid-state two-dimensional exchange and double-quantum NMR experiments of phosphate glasses. These Monte Carlo simulations demonstrate that the polyhedron connectivity is best described by a random distribution in lithium phosphate and calcium phosphate glasses.

  8. Glass electrolytes

    SciTech Connect

    Not Available

    1984-06-25

    The objective of this research is a glass electrolyte for use in sodium/sulfur batteries that has a low resistivity (100 ohm-cm at 300/sup 0/C) and is stable in the cell environment. Experiments in this program are focussed on glasses in the quaternary system: soda, alumina, zirconia and silica. The FY 1983 research on glass analogs of NASICON, parallel thermodynamic calculations, and a review of the literature in the areas of glass conductivity and corrosion resistance led to selection of this system for more detailed investigation. The main program elements are: (1) conductivity measurements at 300 to 500/sup 0/C; (2) differential thermal analysis for determination of glass-transition and crystallization temperatures; (3) static corrosion tests at 400/sup 0/C using Na, Na/sub 2/S/sub 4/, and S; (4) mechanical strength and fracture toughness measurements; and (5) sodium/sulfur cell tests at 350/sup 0/C. Elements (1) and (2) are nearly completed; element (3) is being initiated using the glasses prepared for (1) and (2), and elements (4) and (5) will begin in the first and second quarters of FY 1985, respectively. Fourteen quaternary glasses having a broad range of compositions have been made. The resistivities of these glasses at 300/sup 0/C extended from 130 to 3704 ohm-cm; the activation energies for conduction extended from 0.488 to 0.684 eV, and the glass transition temperatures extended from 397 to 685/sup 0/C. Through a multiple linear regression analysis of these data response surfaces were generated for resistivity, activation energy for conduction, and glass transition temperature over the composition region within the quaternary system that is bounded by SiO/sub 2/, Na/sub 2/O/sub 3/, Na/sub 2/AlO/sub 4/ and Na/sub 2/ZrO/sub 3/. These response surfaces indicated a new region of high conductivity and high glass transition temperature in the neighborhood of 42% soda, 31% silica and 27% alumina plus zirconia.

  9. Refractories for high-alkali environments

    SciTech Connect

    Rau, A.W.; Cloer, F.

    1996-01-01

    There are two reliable and cost-effective tests for evaluating refractory materials. They are used to determine which refractory products allow greater variance in fuel type with respect to alkali environment for coal-fired applications. Preselection of a particular refractory is important because of down-time cost for premature failure. One test is a variation of the standard alkali cup test. The second involves reacting test specimens with the contaminant, followed by physical properties testing to determine degree of degradation and properties affected. The alkali cup test rates products using a relative numerical scale based upon visual appearance. This test indicates the presence and relative degree of chemical attack to the refractory. The physical properties test determines the specific properties affected by the given contaminant.

  10. Alkali metal vapors - Laser spectroscopy and applications

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

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

  11. A thermochemical study of glasses and crystals along the joins silica-calcium aluminate and silica-sodium aluminate

    NASA Astrophysics Data System (ADS)

    Navrotsky, Alexandra; Peraudeau, Gilles; McMillan, Paul; Coutures, Jean-Pierre

    1982-11-01

    Enthalpies of solution in molten 2PbO · B 2O 3 at 985 K are reported for series of glasses xCa0.5AlO2-(1- x) SiO2 ( O ≤ x ≤ 0.99) and xNaAlO2-(1- x) SiO2 (0 ≤ x ≤ 0.56). The data are compared to values for the corresponding crystalline aluminosilicates and to preliminary data for systems containing KAlO 2 and Mg 0.5AlO 2. The enthalpies of mixing of glasses become more exothermic with increasing basicity of the mono- or divalent oxide. The tendency toward immiscibility on the silica-rich side, indicated by the shape of the heat of mixing curve between x = 0 and x = 0.4, is pronounced in the calcium aluminate system, but not in the sodium aluminate system. The shape of the heat of mixing curve, which is roughly symmetrical about x = 0.5, can be rationalized in terms of glass structure by considering essentially random substitution of Si and Al on a continuous three dimensional tetrahedral framework, with stabilization arising from electrostatic interactions between aluminum and the nonframework cation balancing the destabilizing effects arising from perturbation of the aluminosilicate framework by the nonframework cation. These trends are consistent with the variation of physical properties of aluminosilicate melts.

  12. Utilization of recycled glass derived from cathode ray tube glass as fine aggregate in cement mortar.

    PubMed

    Ling, Tung-Chai; Poon, Chi-Sun

    2011-08-30

    Rapid advances in the electronic industry led to an excessive amount of early disposal of older electronic devices such as computer monitors and old televisions (TV) before the end of their useful life. The management of cathode ray tubes (CRT), which have been a key component in computer monitors and TV sets, has become a major environmental problem worldwide. Therefore, there is a pressing need to develop sustainable alternative methods to manage hazardous CRT glass waste. This study assesses the feasibility of utilizing CRT glass as a substitute for natural aggregates in cement mortar. The CRT glass investigated was an acid-washed funnel glass of dismantled CRT from computer monitors and old TV sets. The mechanical properties of mortar mixes containing 0%, 25%, 50%, 75% and 100% of CRT glass were investigated. The potential of the alkali-silica reaction (ASR) and leachability of lead were also evaluated. The results confirmed that the properties of the mortar mixes prepared with CRT glass was similar to that of the control mortar using sand as fine aggregate, and displayed innocuous behaviour in the ASR expansion test. Incorporating CRT glass in cement mortar successfully prevented the leaching of lead. We conclude that it is feasible to utilize CRT glass in cement mortar production.

  13. Utilization of recycled glass derived from cathode ray tube glass as fine aggregate in cement mortar.

    PubMed

    Ling, Tung-Chai; Poon, Chi-Sun

    2011-08-30

    Rapid advances in the electronic industry led to an excessive amount of early disposal of older electronic devices such as computer monitors and old televisions (TV) before the end of their useful life. The management of cathode ray tubes (CRT), which have been a key component in computer monitors and TV sets, has become a major environmental problem worldwide. Therefore, there is a pressing need to develop sustainable alternative methods to manage hazardous CRT glass waste. This study assesses the feasibility of utilizing CRT glass as a substitute for natural aggregates in cement mortar. The CRT glass investigated was an acid-washed funnel glass of dismantled CRT from computer monitors and old TV sets. The mechanical properties of mortar mixes containing 0%, 25%, 50%, 75% and 100% of CRT glass were investigated. The potential of the alkali-silica reaction (ASR) and leachability of lead were also evaluated. The results confirmed that the properties of the mortar mixes prepared with CRT glass was similar to that of the control mortar using sand as fine aggregate, and displayed innocuous behaviour in the ASR expansion test. Incorporating CRT glass in cement mortar successfully prevented the leaching of lead. We conclude that it is feasible to utilize CRT glass in cement mortar production. PMID:21705136

  14. Low melting high lithia glass compositions and methods

    DOEpatents

    Jantzen, Carol M.; Pickett, John B.; Cicero-Herman, Connie A.; Marra, James C.

    2004-11-02

    The invention relates to methods of vitrifying waste and for lowering the melting point of glass forming systems by including lithia formers in the glass forming composition in significant amounts, typically from about 0.16 wt % to about 11 wt %, based on the total glass forming oxides. The lithia is typically included as a replacement for alkali oxide glass formers that would normally be present in a particular glass forming system. Replacement can occur on a mole percent or weight percent basis, and typically results in a composition wherein lithia forms about 10 wt % to about 100 wt % of the alkali oxide glass formers present in the composition. The present invention also relates to the high lithia glass compositions formed by these methods. The invention is useful for stabilization of numerous types of waste materials, including aqueous waste streams, sludge solids, mixtures of aqueous supernate and sludge solids, combinations of spent filter aids from waste water treatment and waste sludges, supernate alone, incinerator ash, incinerator offgas blowdown, or combinations thereof, geological mine tailings and sludges, asbestos, inorganic filter media, cement waste forms in need of remediation, spent or partially spent ion exchange resins or zeolites, contaminated soils, lead paint, etc. The decrease in melting point achieved by the present invention desirably prevents volatilization of hazardous or radioactive species during vitrification.

  15. Low melting high lithia glass compositions and methods

    DOEpatents

    Jantzen, Carol M.; Pickett, John B.; Cicero-Herman, Connie A.; Marra, James C.

    2003-10-07

    The invention relates to methods of vitrifying waste and for lowering the melting point of glass forming systems by including lithia formers in the glass forming composition in significant amounts, typically from about 0.16 wt % to about 11 wt %, based on the total glass forming oxides. The lithia is typically included as a replacement for alkali oxide glass formers that would normally be present in a particular glass forming system. Replacement can occur on a mole percent or weight percent basis, and typically results in a composition wherein lithia forms about 10 wt % to about 100 wt % of the alkali oxide glass formers present in the composition. The present invention also relates to the high lithia glass compositions formed by these methods. The invention is useful for stabilization of numerous types of waste materials, including aqueous waste streams, sludge solids, mixtures of aqueous supernate and sludge solids, combinations of spent filter aids from waste water treatment and waste sludges, supernate alone, incinerator ash, incinerator offgas blowdown, or combinations thereof, geological mine tailings and sludges, asbestos, inorganic filter media, cement waste forms in need of remediation, spent or partially spent ion exchange resins or zeolites, contaminated soils, lead paint, etc. The decrease in melting point achieved by the present invention desirably prevents volatilization of hazardous or radioactive species during vitrification.

  16. Low melting high lithia glass compositions and methods

    DOEpatents

    Jantzen, Carol M.; Pickett, John B.; Cicero-Herman, Connie A.; Marra, James C.

    2000-01-01

    The invention relates to methods of vitrifying waste and for lowering the melting point of glass forming systems by including lithia formers in the glass forming composition in significant amounts, typically from about 0.16 wt % to about 11 wt %, based on the total glass forming oxides. The lithia is typically included as a replacement for alkali oxide glass formers that would normally be present in a particular glass forming system. Replacement can occur on a mole percent or weight percent basis, and typically results in a composition wherein lithia forms about 10 wt % to about 100 wt % of the alkali oxide glass formers present in the composition. The present invention also relates to the high lithia glass compositions formed by these methods. The invention is useful for stabilization of numerous types of waste materials, including aqueous waste streams, sludge solids, mixtures of aqueous supernate and sludge solids, combinations of spent filter aids from waste water treatment and waste sludges, supernate alone, incinerator ash, incinerator offgas blowdown, or combinations thereof, geological mine tailings and sludges, asbestos, inorganic filter media, cement waste forms in need of remediation, spent or partially spent ion exchange resins or zeolites, contaminated soils, lead paint, etc. The decrease in melting point achieved by the present invention desirably prevents volatilization of hazardous or radioactive species during vitrification.

  17. Reuse of ground waste glass as aggregate for mortars.

    PubMed

    Corinaldesi, V; Gnappi, G; Moriconi, G; Montenero, A

    2005-01-01

    This work was aimed at studying the possibility of reusing waste glass from crushed containers and building demolition as aggregate for preparing mortars and concrete. At present, this kind of reuse is still not common due to the risk of alkali-silica reaction between the alkalis of cement and silica of the waste glass. This expansive reaction can cause great problems of cracking and, consequently, it can be extremely deleterious for the durability of mortar and concrete. However, data reported in the literature show that if the waste glass is finely ground, under 75mum, this effect does not occur and mortar durability is guaranteed. Therefore, in this work the possible reactivity of waste glass with the cement paste in mortars was verified, by varying the particle size of the finely ground waste glass. No reaction has been detected with particle size up to 100mum thus indicating the feasibility of the waste glass reuse as fine aggregate in mortars and concrete. In addition, waste glass seems to positively contribute to the mortar micro-structural properties resulting in an evident improvement of its mechanical performance.

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

    DOEpatents

    Soung, W.Y.

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

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

    DOEpatents

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

    1978-01-01

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

  20. Solubility of a resin-modified glass ionomer cement.

    PubMed

    Quackenbush, B M; Donly, K J; Croll, T P

    1998-01-01

    Thirty standardized discs were fabricated from a resin-modified glass ionomer cement (Vitremer -3M) using three different powder/liquid ratios. All specimens were immediately weighed. Specimens were stored in artificial saliva for thirty days. Twice each day the specimens received a 30-min. artificial caries challenge (pH 4.4) and were returned to artificial saliva. At the end of the thirty-day experimental period, the specimens were dried and weighed again. Duncan's Multiple Range Test indicated that the 145 mg powder/35 mg liquid ratio had significantly less weight loss than the 145 mg powder/105 mg liquid ratio (p < 0.05). The results appear to demonstrate that solubility decreases as the aluminosilicate glass powder increases. PMID:9795733

  1. Corrosion behavior of a glass-bonded sodalite ceramic waste form and its constituents.

    SciTech Connect

    Lewis, M. A.; Ebert, W. L.; Morss, L.

    1999-06-18

    A ceramic waste form (CWF) of glass bonded sodalite is being developed as a waste form for the long-term immobilization of fission products and transuranic elements from the U.S. Department of Energy's activities on spent nuclear fuel conditioning. A durable waste form was prepared by hot isostatic pressing (HIP) a mixture of salt-loaded zeolite powders and glass frit. During HIP the zeolite is converted to sodalite, and the resultant CWF is been completed for durations of up to 182 days. Four dissolution modes were identified: dissolution of free salt, dissolution of the aluminosilicate matrix of sodalite and the accompanying dissolution of occluded salt, dissolution of the boroaluminosilicate matrix of the glass, and ion exchange. Synergies inherent to the CWF were identified by comparing the results of the tests with pure glass and sodalite with those of the composite CWF.

  2. Properties of Desert Sand and CMAS Glass

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Choi, Sung R.

    2014-01-01

    As-received desert sand from a Middle East country has been characterized for its phase composition and thermal stability. X-ray diffraction analysis showed the presence of quartz (SiO2), calcite (CaCO3), gypsum (CaSO4.2H2O), and NaAlSi3O8 phases in as-received desert sand and showed weight loss of approx. 35 percent due to decomposition of CaCO3 and CaSO4.2H2O when heated to 1400 C. A batch of as-received desert sand was melted into calcium magnesium aluminosilicate (CMAS) glass at approx. 1500 C. From inductively coupled plasma-atomic emission spectrometry, chemical composition of the CMAS glass was analyzed to be 27.8CaO-4MgO-5Al2O3-61.6SiO2-0.6Fe2O3-1K2O (mole percent). Various physical, thermal and mechanical properties of the glass have been evaluated. Bulk density of CMAS glass was 2.69 g/cc, Young's modulus 92 GPa, Shear modulus 36 GPa, Poisson's ratio 0.28, dilatometric glass transition temperature (T (sub g)) 706 C, softening point (T (sub d)) 764 C, Vickers microhardness 6.3 +/- 0.4 GPa, indentation fracture toughness 0.75 +/- 0.15 MPa.m (sup 1/2), and coefficient of thermal expansion (CTE) 9.8 x 10 (exp -6)/degC in the temperature range 25 to 700 C. Temperature dependence of viscosity has also been estimated from various reference points of the CMAS glass using the Vogel-Fulcher-Tamman (VFT) equation. The glass remained amorphous after heat treating at 850 C for 10 hr but crystallized into CaSiO3 and Ca-Mg-Al silicate phases at 900 C or higher temperatures. Crystallization kinetics of the CMAS glass has also been investigated by differential thermal analysis (DTA). Activation energies for the crystallization of two different phases in the glass were calculated to be 403 and 483 kJ/mol, respectively.

  3. 40 CFR 721.1878 - Alkali metal alkyl borohydride (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

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

  4. 40 CFR 721.1878 - Alkali metal alkyl borohydride (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

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

  5. 40 CFR 721.1878 - Alkali metal alkyl borohydride (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Alkali metal alkyl borohydride... Specific Chemical Substances § 721.1878 Alkali metal alkyl borohydride (generic). (a) Chemical substance... alkali metal alkyl borohydride (PMN P-00-1089) is subject to reporting under this section for...

  6. 40 CFR 721.1878 - Alkali metal alkyl borohydride (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

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

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

    Code of Federal Regulations, 2013 CFR

    2013-07-01

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

  8. 40 CFR 721.4660 - Alcohol, alkali metal salt.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

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

  9. 40 CFR 721.4660 - Alcohol, alkali metal salt.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

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

  10. 40 CFR 721.4660 - Alcohol, alkali metal salt.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

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

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

    Code of Federal Regulations, 2013 CFR

    2013-07-01

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

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

    Code of Federal Regulations, 2012 CFR

    2012-07-01

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

  13. 40 CFR 721.5278 - Substituted naphthalenesulfonic acid, alkali salt.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ..., alkali salt. 721.5278 Section 721.5278 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.5278 Substituted naphthalenesulfonic acid, alkali salt. (a) Chemical... as a substituted naphthalenesulfonic acid, alkali salt (PMN P-95-85) is subject to reporting...

  14. 40 CFR 721.5278 - Substituted naphthalenesulfonic acid, alkali salt.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ..., alkali salt. 721.5278 Section 721.5278 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.5278 Substituted naphthalenesulfonic acid, alkali salt. (a) Chemical... as a substituted naphthalenesulfonic acid, alkali salt (PMN P-95-85) is subject to reporting...

  15. 40 CFR 721.5278 - Substituted naphthalenesulfonic acid, alkali salt.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ..., alkali salt. 721.5278 Section 721.5278 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.5278 Substituted naphthalenesulfonic acid, alkali salt. (a) Chemical... as a substituted naphthalenesulfonic acid, alkali salt (PMN P-95-85) is subject to reporting...

  16. 40 CFR 721.8900 - Substituted halogenated pyridinol, alkali salt.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ..., alkali salt. 721.8900 Section 721.8900 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.8900 Substituted halogenated pyridinol, alkali salt. (a) Chemical... as substituted halogenated pyridinols, alkali salts (PMNs P-88-1271 and P-88-1272) are subject...

  17. 40 CFR 721.5278 - Substituted naphthalenesulfonic acid, alkali salt.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ..., alkali salt. 721.5278 Section 721.5278 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.5278 Substituted naphthalenesulfonic acid, alkali salt. (a) Chemical... as a substituted naphthalenesulfonic acid, alkali salt (PMN P-95-85) is subject to reporting...

  18. 40 CFR 721.5278 - Substituted naphthalenesulfonic acid, alkali salt.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ..., alkali salt. 721.5278 Section 721.5278 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.5278 Substituted naphthalenesulfonic acid, alkali salt. (a) Chemical... as a substituted naphthalenesulfonic acid, alkali salt (PMN P-95-85) is subject to reporting...

  19. 40 CFR 721.8900 - Substituted halogenated pyridinol, alkali salt.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ..., alkali salt. 721.8900 Section 721.8900 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.8900 Substituted halogenated pyridinol, alkali salt. (a) Chemical... as substituted halogenated pyridinols, alkali salts (PMNs P-88-1271 and P-88-1272) are subject...

  20. 40 CFR 721.8900 - Substituted halogenated pyridinol, alkali salt.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ..., alkali salt. 721.8900 Section 721.8900 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.8900 Substituted halogenated pyridinol, alkali salt. (a) Chemical... as substituted halogenated pyridinols, alkali salts (PMNs P-88-1271 and P-88-1272) are subject...

  1. 40 CFR 721.8900 - Substituted halogenated pyridinol, alkali salt.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ..., alkali salt. 721.8900 Section 721.8900 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.8900 Substituted halogenated pyridinol, alkali salt. (a) Chemical... as substituted halogenated pyridinols, alkali salts (PMNs P-88-1271 and P-88-1272) are subject...

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

    SciTech Connect

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

    2014-11-18

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

  3. Computational studies of solid-state alkali conduction in rechargeable alkali-ion batteries

    DOE PAGES

    Deng, Zhi; Mo, Yifei; Ong, Shyue Ping

    2016-03-25

    The facile conduction of alkali ions in a crystal host is of crucial importance in rechargeable alkali-ion batteries, the dominant form of energy storage today. In this review, we provide a comprehensive survey of computational approaches to study solid-state alkali diffusion. We demonstrate how these methods have provided useful insights into the design of materials that form the main components of a rechargeable alkali-ion battery, namely the electrodes, superionic conductor solid electrolytes and interfaces. We will also provide a perspective on future challenges and directions. Here, the scope of this review includes the monovalent lithium- and sodium-ion chemistries that aremore » currently of the most commercial interest.« less

  4. Ingestion of caustic alkali farm products.

    PubMed

    Neidich, G

    1993-01-01

    Since the Poison Prevention Packaging Act took effect, the number of ingestions of caustic alkali from household products has been significantly reduced. Commercial caustic alkalis used on farms, however, were not included in this legislation. Fourteen children over a 5 year period were seen after ingestion of commercial caustic alkalis used on farms. Seven of the children had ingested liquid pipeline cleaners and seven had ingested solid agents used for a variety of reasons. Six of seven children ingesting liquid agents did so from nonoriginal containers into which the caustic had been transferred for convenience. All seven children ingesting solid agents did so from the original container. Eight of the 14 children were found to have second-degree or worse esophageal involvement. Both solid and liquid caustic agents used commercially on farms can cause significant morbidity. Development of a child-resistant container for daily transfer of liquid pipeline agents could be helpful in preventing injuries from liquid pipeline cleaners. Pediatric gastroenterologists as well as primary care physicians in rural areas should be familiar with this type of injury and should take an active role in instructing parents of children living on farms to prevent such injuries. Extension of the Poison Prevention Packaging Act to caustic alkalis used on farms needs to be considered. PMID:8433244

  5. Terahertz radiation in alkali vapor plasmas

    SciTech Connect

    Sun, Xuan; Zhang, X.-C.

    2014-05-12

    By taking advantage of low ionization potentials of alkali atoms, we demonstrate terahertz wave generation from cesium and rubidium vapor plasmas with an amplitude nearly one order of magnitude larger than that from nitrogen gas at low pressure (0.02–0.5 Torr). The observed phenomena are explained by the numerical modeling based upon electron tunneling ionization.

  6. Ingestion of caustic alkali farm products.

    PubMed

    Neidich, G

    1993-01-01

    Since the Poison Prevention Packaging Act took effect, the number of ingestions of caustic alkali from household products has been significantly reduced. Commercial caustic alkalis used on farms, however, were not included in this legislation. Fourteen children over a 5 year period were seen after ingestion of commercial caustic alkalis used on farms. Seven of the children had ingested liquid pipeline cleaners and seven had ingested solid agents used for a variety of reasons. Six of seven children ingesting liquid agents did so from nonoriginal containers into which the caustic had been transferred for convenience. All seven children ingesting solid agents did so from the original container. Eight of the 14 children were found to have second-degree or worse esophageal involvement. Both solid and liquid caustic agents used commercially on farms can cause significant morbidity. Development of a child-resistant container for daily transfer of liquid pipeline agents could be helpful in preventing injuries from liquid pipeline cleaners. Pediatric gastroenterologists as well as primary care physicians in rural areas should be familiar with this type of injury and should take an active role in instructing parents of children living on farms to prevent such injuries. Extension of the Poison Prevention Packaging Act to caustic alkalis used on farms needs to be considered.

  7. The Additive Coloration of Alkali Halides

    ERIC Educational Resources Information Center

    Jirgal, G. H.; and others

    1969-01-01

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

  8. Cohesive Energy of the Alkali Metals.

    ERIC Educational Resources Information Center

    Poole, R. T.

    1980-01-01

    Describes a method, considered appropriate for presentation to undergraduate students in materials science and related courses, for the calculation of cohesive energies of the alkali metals. Uses a description based on the free electron model and gives results to within 0.1 eV of the experimental values. (Author/GS)

  9. Development of a Composite Non-Electrostatic Surface Complexation Model Describing Plutonium Sorption to Aluminosilicates

    SciTech Connect

    Powell, B A; Kersting, A; Zavarin, M; Zhao, P

    2008-10-28

    Due to their ubiquity in nature and chemical reactivity, aluminosilicate minerals play an important role in retarding actinide subsurface migration. However, very few studies have examined Pu interaction with clay minerals in sufficient detail to produce a credible mechanistic model of its behavior. In this work, Pu(IV) and Pu(V) interactions with silica, gibbsite (Aloxide), and Na-montmorillonite (smectite clay) were examined as a function of time and pH. Sorption of Pu(IV) and Pu(V) to gibbsite and silica increased with pH (4 to 10). The Pu(V) sorption edge shifted to lower pH values over time and approached that of Pu(IV). This behavior is apparently due to surface mediated reduction of Pu(V) to Pu(IV). Surface complexation constants describing Pu(IV)/Pu(V) sorption to aluminol and silanol groups were developed from the silica and gibbsite sorption experiments and applied to the montmorillonite dataset. The model provided an acceptable fit to the montmorillonite sorption data for Pu(V). In order to accurately predict Pu(IV) sorption to montmorillonite, the model required inclusion of ion exchange. The objective of this work is to measure the sorption of Pu(IV) and Pu(V) to silica, gibbsite, and smectite (montmorillonite). Aluminosilicate minerals are ubiquitous at the Nevada National Security Site and improving our understanding of Pu sorption to aluminosilicates (smectite clays in particular) is essential to the accurate prediction of Pu transport rates. These data will improve the mechanistic approach for modeling the hydrologic source term (HST) and provide sorption Kd parameters for use in CAU models. In both alluvium and tuff, aluminosilicates have been found to play a dominant role in the radionuclide retardation because their abundance is typically more than an order of magnitude greater than other potential sorbing minerals such as iron and manganese oxides (e.g. Vaniman et al., 1996). The sorption database used in recent HST models (Carle et al., 2006

  10. Contribution of aluminas and aluminosilicates to the formation of PCDD/Fs on fly ashes.

    PubMed

    Potter, Phillip M; Dellinger, Barry; Lomnicki, Slawomir M

    2016-02-01

    Chlorinated aromatics undergo surface-mediated reactions with metal oxides to form Environmentally Persistent Free Radicals (EPFRs) which can further react to produce polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Previous work using laboratory-made fly ash surrogates composed of transition metal oxides deposited on silica powder has confirmed their ability to mimic fly ash in the production of PCDD/Fs. However, little is known about the propensity of aluminas and aluminosilicates, other components of fly ash, to form PCDD/Fs. A fly ash sample containing both alumina and mullite, an aluminosilicate, was tested for PCDD/F formation ability and compared to PCDD/F yields from the thermal degradation of 2-monochlorophenol (2-MCP) precursor over γ-alumina, α-alumina, and mullite. A packed-bed flow reactor was used to investigate the thermal degradation of 2-MCP over the various catalysts at 200-600 °C. Fly ash gave similar PCDD/F yields to surrogates made with similar transition metal content. γ-alumina, which is thermodynamically unfavorable, was very catalytically active and gave low PCDD/F yields despite a high destruction of 2-MCP. Mullite and α-alumina, the thermodynamically favorable form of alumina, yielded higher concentrations of dioxins and products with a higher degree of chlorine substitution than γ-alumina. The data suggest that certain aluminas and aluminosilicates, commonly found in fly ash, are active catalytic surfaces in the formation of PCDD/Fs in the post-flame cool zones of combustion systems and should be considered as additional catalytic surfaces active in the process. PMID:26615490

  11. Efficient adsorbents of nanoporous aluminosilicate monoliths for organic dyes from aqueous solution.

    PubMed

    El-Safty, Sherif A; Shahat, Ahmed; Awual, Md Rabiul

    2011-07-01

    Growing public awareness on the potential risk to humans of toxic chemicals in the environment has generated demand for new and improved methods for toxicity assessment and removal, rational means for health risk estimation. With the aim of controlling nanoscale adsorbents for functionality in molecular sieving of organic pollutants, we fabricated cubic Im3m mesocages with uniform entrance and large cavity pores of aluminosilicates as highly promising candidates for the colorimetric monitoring of organic dyes in an aqueous solution. However, a feasible control over engineering of three-dimensional (3D) mesopore cage structures with uniform entrance (~5 nm) and large cavity (~10 nm) allowed the development of nanoadsorbent membranes as a powerful tool for large-quantity and high-speed (in minutes) adsorption/removal of bulk molecules such as organic dyes. Incorporation of high aluminum contents (Si/Al=1) into 3D cubic Im3m cage mesoporous silica monoliths resulted in small, easy-to-use optical adsorbent strips. In such adsorption systems, natural surfaces of active acid sites of aluminosilicate strips strongly induced both physical adsorption of chemically responsive dyes and intraparticle diffusion into cubic Im3m mesocage monoliths. Results likewise indicated that although aluminosilicate strips with low Si/Al ratios exhibit distortion in pore ordering and decrease in surface area and pore volume, enhancement of both molecular converges and intraparticle diffusion onto the network surfaces and into the pore architectures of adsorbent membranes was achieved. Moreover, 3D mesopore cage adsorbents are reversible, offering potential for multiple adsorption assays.

  12. Contribution of aluminas and aluminosilicates to the formation of PCDD/Fs on fly ashes.

    PubMed

    Potter, Phillip M; Dellinger, Barry; Lomnicki, Slawomir M

    2016-02-01

    Chlorinated aromatics undergo surface-mediated reactions with metal oxides to form Environmentally Persistent Free Radicals (EPFRs) which can further react to produce polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Previous work using laboratory-made fly ash surrogates composed of transition metal oxides deposited on silica powder has confirmed their ability to mimic fly ash in the production of PCDD/Fs. However, little is known about the propensity of aluminas and aluminosilicates, other components of fly ash, to form PCDD/Fs. A fly ash sample containing both alumina and mullite, an aluminosilicate, was tested for PCDD/F formation ability and compared to PCDD/F yields from the thermal degradation of 2-monochlorophenol (2-MCP) precursor over γ-alumina, α-alumina, and mullite. A packed-bed flow reactor was used to investigate the thermal degradation of 2-MCP over the various catalysts at 200-600 °C. Fly ash gave similar PCDD/F yields to surrogates made with similar transition metal content. γ-alumina, which is thermodynamically unfavorable, was very catalytically active and gave low PCDD/F yields despite a high destruction of 2-MCP. Mullite and α-alumina, the thermodynamically favorable form of alumina, yielded higher concentrations of dioxins and products with a higher degree of chlorine substitution than γ-alumina. The data suggest that certain aluminas and aluminosilicates, commonly found in fly ash, are active catalytic surfaces in the formation of PCDD/Fs in the post-flame cool zones of combustion systems and should be considered as additional catalytic surfaces active in the process.

  13. Metallic nanoparticles and their medicinal potential. Part II: aluminosilicates, nanobiomagnets, quantum dots and cochleates.

    PubMed

    Loomba, Leena; Scarabelli, Tiziano

    2013-09-01

    Metallic miniaturization techniques have taken metals to nanoscale size where they can display fascinating properties and their potential applications in medicine. In recent years, metal nanoparticles such as aluminium, silicon, iron, cadmium, selenium, indium and calcium, which find their presence in aluminosilicates, nanobiomagnets, quantum dots (Q-dots) and cochleates, have caught attention of medical industries. The increasing impact of metallic nanoparticles in life sciences has significantly advanced the production techniques for these nanoparticles. In this Review, the various methods for the synthesis of nanoparticles are outlined, followed by their physicochemical properties, some recent applications in wound healing, diagnostic imaging, biosensing, assay labeling, antimicrobial activity, cancer therapy and drug delivery are listed, and finally their toxicological impacts are revised. The first half of this article describes the medicinal uses of two noble nanoparticles - gold and silver. This Review provides further information on the ability of aluminum, silicon, iron, selenium, indium, calcium and zinc to be used as nanoparticles in biomedical sciences. Aluminosilicates find their utility in wound healing and antibacterial growth. Iron-oxide nanoparticles enhance the properties of MRI contrast agents and are also used as biomagnets. Cadmium, selenium, tellurium and indium form the core nanostructures of tiny Q-dots used in cellular assay labeling, high-resolution cell imaging and biosensing. Cochleates have the bivalent nano ions calcium, magnesium or zinc imbedded in their structures and are considered to be highly effective agents for drug and gene delivery. The aluminosilicates, nanobiomagnets, Q-dots and cochleates are discussed in the light of their properties, synthesis and utility.

  14. Characterization of enameled glass excavated from Laem Pho, southern Thailand

    NASA Astrophysics Data System (ADS)

    Dhanmanonda, W.; Won-in, K.; Tancharakorn, S.; Tantanuch, W.; Thongleurm, C.; Kamwanna, T.; Dararutana, P.

    2012-07-01

    Laem Pho in Surat Thani, southern province of Thailand is one of the most important historic site on the eastern shore of the Gulf of Thailand. In this work, the enameled glass fragments which looked-like Islamic glass mainly excavated from this site were analyzed using SEM-EDS, PIXE and μ-XRF, in order to understand the chemical composition by comparing the archaeological data and topology. The structure of the enameled decoration was also studied. The resulting data indicated that high-magnesia alkali-lime silicate glass was produced. The presence of transition metals such as copper, iron and manganese were affected on the glass colorations. Typological classifications, technological observations and comparative studies serve to clarify the development and cultural inter-relationships of various glass objects along the trade and exchange networks in ancient maritime.

  15. Pinhole Glasses

    NASA Astrophysics Data System (ADS)

    Colicchia, Giuseppe; Hopf, Martin; Wiesner, Hartmut; Zollman, Dean

    2008-01-01

    Eye aberrations are commonly corrected by lenses that restore vision by altering rays before they pass through the cornea. Some modern promoters claim that pinhole glasses are better than conventional lenses in correcting all kinds of refractive defects such as myopia (nearsighted), hyperopia (farsighted), astigmatisms, and presbyopia. Do pinhole glasses really give better vision? Some ways to use this question for motivation in teaching optics have been discussed. For this column we include a series of experiments that students can complete using a model of the eye and demonstrate issues related to pinhole vision correction.

  16. Potential Sites for Ice Nucleation on Aluminosilicate Clay Minerals and Related Materials.

    PubMed

    Freedman, Miriam Arak

    2015-10-01

    Few aerosol particles in clouds nucleate the formation of ice. The surface sites available for nucleus formation, which can include surface defects and functional groups, determine in part the activity of an aerosol particle toward ice formation. Although ice nucleation on particles has been widely studied, exploration of the specific sites at which the initial germ forms has been limited, but is important for predicting the microphysical properties of clouds, which impact climate. This Perspective focuses on what is currently known about surface sites for ice nucleation on aluminosilicate clay minerals, which are commonly found in ice residuals, as well as related materials. PMID:26722881

  17. A coarse-graining approach for the proton complex in protonated aluminosilicates.

    PubMed

    Calero, S; Lobato, M D; García-Pérez, E; Mejías, J A; Lago, S; Vlugt, T J H; Maesen, T L M; Smit, B; Dubbeldam, D

    2006-03-30

    We have developed a computational framework for the adsorption of linear alkanes in protonated aluminosilicates. These zeolites contain trace amounts of water that form hydrated proton complexes. The presence of hydrated protons makes the simulations at the fully atomistic level difficult. Instead of constructing an elaborate and complex model, we show that an approach based on a coarse-graining of the proton-complex accurately describes the available experimental isotherms, Henry coefficients, heats of adsorption, and oxygen-proton distances. Our approach is supported by MP2 quantum mechanical simulations. The model gives remarkably good agreement with experimental data beyond the initial calibration set.

  18. Facile Fabrication of Uniform Polyaniline Nanotubes with Tubular Aluminosilicates as Templates

    NASA Astrophysics Data System (ADS)

    Zhang, Long; Liu, Peng

    2008-08-01

    The uniform polyaniline (PANI) nanotubes, with inner diameter, outer diameter, and tubular thickness of 40, 60, and 10 nm, respectively, were prepared successfully by using natural tubular aluminosilicates as templates. The halloysite nanotubes were coated with PANI via the in situ chemical oxidation polymerization. Then the templates were etched with HCl/HF solution. The PANI nanotubes were characterized using FTIR, X-ray diffraction, and transmission electron microscopy. The conductivity of the PANI nanotubes was found to be 1.752 × 10-5 (Ω·cm)-1.

  19. Potential Sites for Ice Nucleation on Aluminosilicate Clay Minerals and Related Materials.

    PubMed

    Freedman, Miriam Arak

    2015-10-01

    Few aerosol particles in clouds nucleate the formation of ice. The surface sites available for nucleus formation, which can include surface defects and functional groups, determine in part the activity of an aerosol particle toward ice formation. Although ice nucleation on particles has been widely studied, exploration of the specific sites at which the initial germ forms has been limited, but is important for predicting the microphysical properties of clouds, which impact climate. This Perspective focuses on what is currently known about surface sites for ice nucleation on aluminosilicate clay minerals, which are commonly found in ice residuals, as well as related materials.

  20. Ultrapure glass optical waveguide development in microgravity by the sol-gel process

    NASA Technical Reports Server (NTRS)

    Mukherjee, S. P.

    1980-01-01

    The alkali-borosilicate system was selected as the glass system for the preparation of ultrapure low loss glasses suitable for optical communication. The effect of different oxide contents on the absorption loss was critically reviewed. One composition was chosen to develop the gel preparation procedure in the alkali-borosilicate system. In addition, several procedures for the preparation of gels based on two different approaches were developed. The influence of different preparation parameters were investigated qualitatively. Several conclusions are drawn from the results.