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Sample records for crystalline silicate zeolite

  1. A highly crystalline layered silicate with three-dimensionally microporous layers

    NASA Astrophysics Data System (ADS)

    Jeong, Hae-Kwon; Nair, Sankar; Vogt, Thomas; Dickinson, L. Charles; Tsapatsis, Michael

    2003-01-01

    Layered silicates with three-dimensional microporosity within the layers have the potential to enable new applications in catalysis, adsorption and ion-exchange. Until now no such materials have been reported. However, here we present the synthesis and structure of AMH-3, a silicate with three-dimensionally microporous layers, obtained in high purity and crystallinity. AMH-3 is composed of silicate layers containing eight-membered rings in all three principal crystal directions, and spaced by strontium cations, sodium cations and water molecules. Because of its three-dimensional pore structure, acid and thermal stability, this layered material could find applications in polymer-silicate composites for membrane applications, for synthesis of combined microporous-mesoporous materials, and for the formation of new zeolites and microporous films. Its existence also opens new possibilities for the synthesis of other layered silicates with multidimensional microporous framework layers.

  2. Properties of cometary crystalline silicate before and after perihelion passage

    NASA Astrophysics Data System (ADS)

    Ootsubo, Takafumi

    2013-01-01

    Crystalline silicate is sometimes observed in comets as an 11.3-micron resonant emission feature, and may be used for probing the early solar nebula. Because the formation of the crystalline silicate requires high temperature, they are thought to be born from amorphous silicate at the inner region, and then transported toward the outer regions where comets were born. This transportation can produce the difference in the crystalline fraction in the cometary silicate dust between two dynamical types of comets, Oort-cloud comets (OCs) and Ecliptic comets (ECs), due to the different heliocentric distances of their birth places. The study of peak wavelengths in crystalline features is important to investigate the conditions of the crystalline silicate formation as well. Thus far, we don't have enough OC samples, while we have observed several ECs. Fortunately, we can observe three comets in this semester. In particular, C/2012 S1 (ISON) is a bright sungrazing comet, and we might expect possible splitting and exposing of pristine materials inside the nucleus after its perihelion passage. Observations at pre- and post-perihelion provide us precious information on the dust evolution of the comet. The comet C/2012 S1 (ISON), along with two other comets, is an unparalleled target for this study.

  3. Application of thermodynamics to silicate crystalline solutions

    NASA Technical Reports Server (NTRS)

    Saxena, S. K.

    1972-01-01

    A review of thermodynamic relations is presented, describing Guggenheim's regular solution models, the simple mixture, the zeroth approximation, and the quasi-chemical model. The possibilities of retrieving useful thermodynamic quantities from phase equilibrium studies are discussed. Such quantities include the activity-composition relations and the free energy of mixing in crystalline solutions. Theory and results of the study of partitioning of elements in coexisting minerals are briefly reviewed. A thermodynamic study of the intercrystalline and intracrystalline ion exchange relations gives useful information on the thermodynamic behavior of the crystalline solutions involved. Such information is necessary for the solution of most petrogenic problems and for geothermometry. Thermodynamic quantities for tungstates (CaWO4-SrWO4) are calculated.

  4. The leading role of association in framework modification of highly siliceous zeolites with adsorbed methylamine.

    PubMed

    Han, Ai-Jie; Guo, Juan; Yu, Hui; Zeng, Yu; Huang, Yue-Fang; He, He-Yong; Long, Ying-Cai

    2006-03-13

    Affinity index (AT value), adsorption heat, X-ray diffraction (XRD), and 13C and 29Si magic-angle spinning (MAS) NMR, FTIR, and Raman spectroscopies were used to study the interaction of highly siliceous MFI-, FAU-, and FER-type zeolites with adsorbed methylamine (MA). Compared with the data for methanol, the much higher AT values and adsorption heats, and significant changes in XRD patterns, 29Si MAS NMR spectra, and FTIR spectra for the zeolites after adsorption of MA, revealed a strong hydrogen-bonding interaction between the perfect framework of the zeolites and the adsorbed MAs. This interaction results from the fact that the H atom of the amine group attacks the [Si-O] framework to form a Si-OHN bond, which leads to the appearance of Si-N bonds in the zeolites at 323 K. Therefore, the zeolite framework can be modified with MA under mild conditions. The highly siliceous MFI zeolite and the H-ZSM-5 zeolite with SiO2/Al2O3=31:1 were modified with MA and investigated by temperature-programmed desorption of CO2. The modified zeolites exhibited greatly enhanced basic properties in comparison with those of the raw materials. The influence of defects in the zeolite on the adsorption and the interaction with MA is discussed.

  5. Synthesis of crystalline silicate ZSM-11

    SciTech Connect

    Beck, J.S.; Schlenker, J.D.

    1993-05-25

    A method for synthesizing crystalline material exhibiting a characteristic X-ray diffraction pattern including d-spacing maxima values is described, in Angstroms, as follows: 11.2 [plus minus] 0.2, 10.1 [plus minus] 0.2; 6.73 [plus minus] 0.2; 5.61 [plus minus] 0.1; 5.03 [plus minus] 0.1; 4.62 [plus minus] 0.1; 4.39 [plus minus] 0.08; 3.86 [plus minus] 0.07; 3.73 [plus minus] 0.07; 3.49 [plus minus] 0.07; (3.07, 3.00 [plus minus] 0.05); 2.01 [plus minus] 0.02; which comprises (i) preparing a mixture capable of forming said material, said mixture comprising sources of alkali or alkaline earth metal (M), an oxide of trivalent element (X), an oxide of tetravalent element (Y), water and C[sub n]N[sup +](CH[sub 3])[sub 3], wherein n = 9, 10, 11 or 12, directing agent (R), and having a composition in terms of mole ratios within the following ranges: X[sub 2]O[sub 3]/YO[sub 2] - 0 to .05; H[sub 2]O/YO[sub 2] - 10 to 200; OH[sup [minus

  6. INTERSTELLAR SILICATE DUST IN THE z = 0.89 ABSORBER TOWARD PKS 1830-211: CRYSTALLINE SILICATES AT HIGH REDSHIFT?

    SciTech Connect

    Aller, Monique C.; Kulkarni, Varsha P.; Som, Debopam; York, Donald G.; Welty, Daniel E.; Vladilo, Giovanni

    2012-03-20

    We present evidence of a >10{sigma} detection of the 10 {mu}m silicate dust absorption feature in the spectrum of the gravitationally lensed quasar PKS 1830-211, produced by a foreground absorption system at redshift 0.886. We have examined more than 100 optical depth templates, derived from both observations of Galactic and extragalactic sources and laboratory measurements, in order to constrain the chemical structure of the silicate dust. We find that the best fit to the observed absorption profile is produced by laboratory crystalline olivine, with a corresponding peak optical depth of {tau}{sub 10} = 0.27 {+-} 0.05. The fit is slightly improved upon by including small contributions from additional materials, such as silica, enstatite, or serpentine, which suggests that the dust composition may consist of a blend of crystalline silicates. Combining templates for amorphous and crystalline silicates, we find that the fraction of crystalline silicates needs to be at least 95%. Given the rarity of extragalactic sources with such a high degree of silicate crystallinity, we also explore the possibility that the observed spectral features are produced by amorphous silicates in combination with other molecular or atomic transitions, or by foreground source contamination. While we cannot rule out these latter possibilities, they lead to much poorer profile fits than for the crystalline olivine templates. If the presence of crystalline interstellar silicates in this distant galaxy is real, it would be highly unusual, given that the Milky Way interstellar matter contains essentially only amorphous silicates. It is possible that the z = 0.886 absorber toward PKS 1830-211, well known for its high molecular content, has a unique star-forming environment that enables crystalline silicates to form and prevail.

  7. Zeolites

    NASA Technical Reports Server (NTRS)

    1992-01-01

    Zeolites are crystalline aluminosilicates that have complex framework structures. However, there are several features of zeolite crystals that make unequivocal structure determinations difficult. The acquisition of reliable structural information on zeolites is greatly facilitated by the availability of high-quality specimens. For structure determinations by conventional diffraction techniques, large single-crystal specimens are essential. Alternatively, structural determinations by powder profile refinement methods relax the constraints on crystal size, but still require materials with a high degree of crystalline perfection. Studies conducted at CAMMP (Center for Advanced Microgravity Materials Processing) have demonstrated that microgravity processing can produce larger crystal sizes and fewer structural defects relative to terrestrial crystal growth. Principal Investigator: Dr. Albert Sacco

  8. Iridium Complexes and Clusters in Dealuminated Zeolite HY: Distribution between Crystalline and Impurity Amorphous Regions

    SciTech Connect

    Martinez-Macias, Claudia; Xu, Pinghong; Hwang, Son-Jong; Lu, Jing; Chen, Cong-Yan; Browning, Nigel D.; Gates, Bruce C.

    2014-07-08

    Dealuminated zeolite HY was used to support Ir(CO)2 complexes formed from Ir(CO)2(C5H7O2). Infrared and X-ray absorption spectra and atomic-resolution electron microscopy images identify these complexes, and the images and 27Al NMR spectra identify impurity amorphous regions in the zeolite where the iridium is more susceptible to aggregation than in the crystalline regions. The results indicate a significant stability limitation of metal in amorphous impurity regions of zeolites.

  9. Calcium-aluminum-silicate-hydrate "cement" phases and rare Ca-zeolite association at Colle Fabbri, Central Italy

    NASA Astrophysics Data System (ADS)

    Stoppa, F.; Scordari, F.; Mesto, E.; Sharygin, V. V.; Bortolozzi, G.

    2010-06-01

    Very high temperature, Ca-rich alkaline magma intruded an argillite formation at Colle Fabbri, Central Italy, producing cordierite-tridymite metamorphism in the country rocks. An intense Ba-rich sulphate-carbonate-alkaline hydrothermal plume produced a zone of mineralization several meters thick around the igneous body. Reaction of hydrothermal fluids with country rocks formed calcium-silicate-hydrate (CSH), i.e., tobermorite-afwillite-jennite; calcium-aluminum-silicate-hydrate (CASH) — "cement" phases - i.e., thaumasite, strätlingite and an ettringite-like phase and several different species of zeolites: chabazite-Ca, willhendersonite, gismon-dine, three phases bearing Ca with the same or perhaps lower symmetry of phillipsite-Ca, levyne-Ca and the Ca-rich analogue of merlinoite. In addition, apophyllite-(KF) and/or apophyllite-(KOH), Ca-Ba-carbonates, portlandite and sulphates were present. A new polymorph from the pyrrhotite group, containing three layers of sphalerite-type structure in the unit cell, is reported for the first time. Such a complex association is unique. Most of these minerals are specifically related to hydration processes of: (1) pyrometamorphic metacarbonate/metapelitic rocks (natural analogues of cement clinkers); (2) mineralization between intrusive stocks and slates; and (3) high-calcium, alkaline igneous rocks such as melilitites and foidites as well as carbonatites. The Colle Fabbri outcrop offers an opportunity to study in situ complex crystalline overgrowth and specific crystal chemistry in mineral phases formed in igneous to hydrothermal conditions.

  10. Highly crystalline Zeolite-A from flyash of bituminous and lignite coal combustion.

    PubMed

    Rayalu, S S; Udhoji, J S; Munshi, K N; Hasan, M Z

    2001-11-16

    Flyash is being generated in voluminous amounts by large scale coal combustion process. It poses a serious threat to thermal power industries specifically, in India, wherein the percent of utilisation of flyash is very poor (3-5%). In view of this problem, newer methods of its disposal and utilisation are being explored. The synthesis of zeolite from flyash appears to be one of the most promising alternatives as it has emphasis on value addition to waste material. Flyashes originating from different sources of coal differ in their characteristics and have implications in this work on Zeolite-A production. These factors have been thoroughly investigated and the conditions favourable for formation of Zeolite-A have been delineated. The reactivity of flyash towards zeolite formation is directly dependent on the SiO(2)/Al(2)O(3) ratio, Fe(2)O(3) and CaO content. Amongst the flyashes investigated, so far the sub-bituminous coal based flyash with SiO(2)/Al(2)O(3) ratio of 3.47 appears to be a suitable substrate for Zeolite-A synthesis. These zeolites have been characterised with respect to XRD crystallinity, calcium binding capacity (CBC) and sorption capacity, wherein the crystallinity ranges from 50 to 100%, the CBC ranges from 290 to 560meq/100g and sorption capacity ranges from 16.6 to 23.8%.

  11. Feasible conversion of solid waste bauxite tailings into highly crystalline 4A zeolite with valuable application

    SciTech Connect

    Ma, Dongyang; Wang, Zhendong; Guo, Min; Zhang, Mei; Liu, Jingbo

    2014-11-15

    Highlights: • Concept to convert waste to valuable product is carried out in this study. • An industrially feasible and cost-effective approach was developed and optimized. • Highly crystalline and well-defined zeolite was produced under moderate conditions. • The zeolite derived from the bauxite tailings displayed high ion exchange capacity. • Bauxite tailings have potential application in heavy metal ions adsorbent. - Abstract: Bauxite tailings are a major type of solid wastes generated in the flotation process. The waste by-products caused significant environmental impact. To lessen this hazardous effect from poisonous mine tailings, a feasible and cost-effective solution was conceived and implemented. Our approach focused on reutilization of the bauxite tailings by converting it to 4A zeolite for reuse in diverse applications. Three steps were involved in the bauxite conversion: wet-chemistry, alkali fusion, and crystallization to remove impurities and to prepare porous 4A zeolite. It was found that the cubic 4A zeolite was single phase, in high purity, with high crystallinity and well-defined structure. Importantly, the 4A zeolite displayed maximum calcium ion exchange capacity averaged at 296 mg CaCO{sub 3}/g, comparable to commercially-available zeolite (310 mg CaCO{sub 3}/g) exchange capacity. Base on the optimal synthesis condition, the reaction yield of zeolite 4A from bauxite tailings achieved to about 38.43%, hence, this study will provide a new paradigm for remediation of bauxite tailings, further mitigating the environmental and health care concerns, particularly in the mainland of PR China.

  12. Defect sites in highly siliceous HZSM-5 zeolites: A study performed by alumination and IR spectroscopy

    SciTech Connect

    Yamagishi, Kouji; Namba, Seitaro; Yashima, Tatsuaki )

    1991-01-24

    The concentration of oxygen atoms on defect sites in a highly siliceous HZSM-5 type zeolite was estimated by the {sup 18}O-exchange reaction between C{sup 18}O{sub 2} and the zeolite. The concentration of oxygen atoms on defect sites could be controlled by means of changes of the gel composition and of the use of various silica sources in the hydrothermal synthesis. The relationship between the concentration of oxygen atoms on defect sites in a highly siliceous HZSM-5 and the concentration of aluminum introduced into the framework of the HZSM-5 by an alumination was examined. The concentration of the framework aluminum was the same as one-fourth that of the oxygen atoms on defect sites. These results suggest that the defect sites into which aluminum atoms are introduced tetrahedrally can be identified with hydroxyl nests that consist of four silanol groups. The existence of hydroxyl nests could be confirmed by IR spectroscopy. From the {sup 18}O-exchange reaction and IR measurements, the authors conclude that the sharp band at 3,740 cm{sup {minus}1} can be attributed to both isolated SiOH groups on the external surface and intracrystalline isolated SiOH groups and that the broad band at 3,505 cm{sup {minus}1} can be attributed to the SiOH groups in hydroxyl nests.

  13. [Aluminum coordination and active sites on aluminas, Y-zeolites and pillared layered silicates]. Progress report

    SciTech Connect

    Fripiat, J.J.

    1994-02-01

    This report is organized in four sections. In the first the authors will outline structural features which are common to all fine grained alumina, as well as to non-framework alumina in zeolites. This section will be followed by a study of the surface vs. bulk coordination of aluminum. The third section will deal with measurement of the number of acid sites and the scaling of their strength. The fourth and last section will describe three model reactions: the isomerization of 1-butene and of 2 cis-butene; the isomerization and disproportionation of oxtho-xylene; and the transformation of trichloroethane into vinyl chloride followed by the polymerization of the vinyl chloride. The relationship between chemical activity and selectivity and what is known of the local structure of the active catalytic sites will be underlined. Other kinds of zeolites besides Y zeolite have been studied. Instead of the aluminum pillared silicates they found it more interesting to study the substitution of silicon by aluminum in a layered structure containing a permanent porosity (aluminated sepiolite).

  14. A SPITZER INFRARED SPECTROGRAPH DETECTION OF CRYSTALLINE SILICATES IN A PROTOSTELLAR ENVELOPE

    SciTech Connect

    Poteet, Charles A.; Megeath, S. Thomas; Fischer, William J.; Bjorkman, Jon E.; Watson, Dan M.; Remming, Ian S.; McClure, Melissa K.; Calvet, Nuria; Hartmann, Lee; Tobin, John J.; Sargent, Benjamin A.; Muzerolle, James; Furlan, Elise; Allen, Lori E.; Ali, Babar

    2011-06-01

    We present the Spitzer Space Telescope Infrared Spectrograph spectrum of the Orion A protostar HOPS-68. The mid-infrared spectrum reveals crystalline substructure at 11.1, 16.1, 18.8, 23.6, 27.9, and 33.6 {mu}m superimposed on the broad 9.7 and 18 {mu}m amorphous silicate features; the substructure is well matched by the presence of the olivine end-member forsterite (Mg{sub 2}SiO{sub 4}). Crystalline silicates are often observed as infrared emission features around the circumstellar disks of Herbig Ae/Be stars and T Tauri stars. However, this is the first unambiguous detection of crystalline silicate absorption in a cold, infalling, protostellar envelope. We estimate the crystalline mass fraction along the line of sight by first assuming that the crystalline silicates are located in a cold absorbing screen and secondly by utilizing radiative transfer models. The resulting crystalline mass fractions of 0.14 and 0.17, respectively, are significantly greater than the upper limit found in the interstellar medium ({approx}<0.02-0.05). We propose that the amorphous silicates were annealed within the hot inner disk and/or envelope regions and subsequently transported outward into the envelope by entrainment in a protostellar outflow.

  15. Feasible conversion of solid waste bauxite tailings into highly crystalline 4A zeolite with valuable application.

    PubMed

    Ma, Dongyang; Wang, Zhendong; Guo, Min; Zhang, Mei; Liu, Jingbo

    2014-11-01

    Bauxite tailings are a major type of solid wastes generated in the flotation process. The waste by-products caused significant environmental impact. To lessen this hazardous effect from poisonous mine tailings, a feasible and cost-effective solution was conceived and implemented. Our approach focused on reutilization of the bauxite tailings by converting it to 4A zeolite for reuse in diverse applications. Three steps were involved in the bauxite conversion: wet-chemistry, alkali fusion, and crystallization to remove impurities and to prepare porous 4A zeolite. It was found that the cubic 4A zeolite was single phase, in high purity, with high crystallinity and well-defined structure. Importantly, the 4A zeolite displayed maximum calcium ion exchange capacity averaged at 296 mg CaCO3/g, comparable to commercially-available zeolite (310 mg CaCO3/g) exchange capacity. Base on the optimal synthesis condition, the reaction yield of zeolite 4A from bauxite tailings achieved to about 38.43%, hence, this study will provide a new paradigm for remediation of bauxite tailings, further mitigating the environmental and health care concerns, particularly in the mainland of PR China.

  16. Aluminum coordination and active sites on aluminas, Y zeolites and pillared silicates

    SciTech Connect

    Fripiat, J.J.

    1992-01-01

    Effort was continued to characterize the nature of the Al species responsible for Lewis acidity in zeolites and in aluminas by NMR. While numerous techniques have been successful for scaling the acid strength of Broensted sites, the situation is not satisfactory for the Lewis acid sites. Initial rate of dehydrochlorination of 1,1,1-trichloroethane is sensitive to strength of Lewis acid sites. N-Butene isomerization has been extended to the new aluminas obtained from nano-sized precursors. O-Xylene isomerization was carried out in a recirculation reactor on H-mordenite samples containing Lewis or Broensted acid sites; effects of H[sub 2] and NO were also investigated. Cracking of methylcyclohexane and 3-methylpentane was investigated by EPR on H-mordenite. Sepiolite, a Mg silicate with zeolitic channels, had Al substituted for Si; the negative charge is balanced by, say, VO[sup 2+]. Transformation of ethanol into butadiene on this dual-function catalyst appears to result from a Prins reaction between acetaldeyde formed on the redox sites and ethylene resulting from dehydration of ethanol on Lewis sites.

  17. Cooked GEMS - Insights into the Hot Origins of Crystalline Silicates in Circumstellar Disks and the Cold Origins of GEMS

    NASA Technical Reports Server (NTRS)

    Brownlee, D. E.; Joswiak, D. J.; Bradley, J. P.; Matrajt, G.; Wooden, D. H.

    2005-01-01

    The comparison of interstellar, circumstellar and primitive solar nebula silicates has led to a significant conundrum in the understanding of the nature of solid materials that begin the planet forming processes. Crystalline silicates are found in circumstellar regions around young stars and also evolved stars ejecting particles into the interstellar medium (ISM) but they are not seen in the interstellar medium itself, the source material for star and planet formation. Crystalline silicates are minor to major components of all known early solar system materials that have been examined as meteorites or interplanetary dust samples. The strong presence of Mg-rich crystalline silicates in Oort cloud comets and their minor presence in some Kuiper belt comets is also indicated by 11.2 m peak in approx. 10 microns "silicate" infrared feature. This evidence strongly indicates that Mg-rich crystalline silicates were abundant components of the solar nebula disk out to at least 10 AU, and present out to 30 AU.

  18. Discrete dipole approximation models of chrystalline forsterite: Applications to cometary crystalline silicates

    NASA Astrophysics Data System (ADS)

    Lindsay, Sean Stephen

    The shape, size, and composition of crystalline silicates observed in comet comae and external proto-planetary disks are indicative of the formation and evolution of the dust grains during the processes of planetary formation. In this dissertation, I present the 3 -- 40 mum absorption efficiencies( Qabs) of irregularly shaped forsterite crystals computed with the discrete dipole approximation (DDA) code DDSCAT developed by Draine and Flatau and run on the NASA Advanced Supercomputing facility Pleiades. An investigation of grain shapes ranging from spheroidal to irregular indicate that the strong spectral features from forsterite are sensitive to grain shape and are potentially degenerate with the effects of crystal solid state composition (Mg-content). The 10, 11, 18, 23, and 33.5 mum features are found to be the most crystal shape sensitive and should be avoided in determining Mg-content. The distinct spectral features for the three shape classes are connected with crystal formation environment using a condensation experiment by (Kobatake et al., 2008). The condensation experiment demonstrates that condensed forsterite crystal shapes are dependent on the condensation environmental temperature. I generate DDSCAT target analog shapes to the condensed crystal shapes. These analog shapes are represented by the three shape classes: 1) equant, 2) a, c-columns, and 3) b-shortened platelets. Each of these shape classes exhibit distinct spectral features that can be used to interpret grain shape characteristics from 8 --- 40 mum spectroscopy of astronomical objects containing crystalline silicates. Synthetic spectral energy distributions (SEDs) of the coma of Hale-Bopp at rh = 2.8 AU are generated by thermally modeling the flux contributions of 5 mineral species present in comets. The synthetic SEDs are constrained using a chi2- minimization technique. The mineral species are amorphous carbon, amorphous pyroxene, amorphous olivine, crystalline enstatite, and crystalline

  19. Infrared spectra of crystalline phase ices condensed on silicate smokes at T less than 20 K

    NASA Astrophysics Data System (ADS)

    Moore, Marla H.; Ferrante, Robert F.; Hudson, Reggie L.; Nuth, Joseph A., III; Donn, Bertram

    1994-06-01

    Infrared spectra of H2O, CH3OH, and NH3 condensed at T less than 20 K on amorphous silicate smokes reveal that predominantly crystalline phase ice forms directly on deposit. Spectra of these molecules condensed on aluminum substrates at T less than 20 K indicate that amorphous phase ice forms. On aluminum, crystalline phase H2O and CH3OH are formed by annealing amorphous deposits to 155 K and 130 K, respectively (or by direct deposit at these temperatures); crystalline NH3 is formed by direct deposit at 88 K. Silicate smokes are deposited onto aluminum substrates by evaporation of SiO solid or by combustion of SiH4 with O2 in flowing H2 followed by vapor phase nucleation and growth. Silicate smokes which are oxygen-deficient may contain active surface sites which facilitate the amorphous-to-crystalline phase transition during condensation. Detailed experiments to understand the mechanism are currently in progress. The assumption that amorphous phase ice forms routinely on grains at T less than 80 K is often used in models describing the volatile content of comets or in interpretations of interstellar cloud temperatures. This assumption needs to be reexamined in view of these results.

  20. Infrared spectra of crystalline phase ices condensed on silicate smokes at T less than 20 K

    NASA Technical Reports Server (NTRS)

    Moore, Marla H.; Ferrante, Robert F.; Hudson, Reggie L.; Nuth, Joseph A., III; Donn, Bertram

    1994-01-01

    Infrared spectra of H2O, CH3OH, and NH3 condensed at T less than 20 K on amorphous silicate smokes reveal that predominantly crystalline phase ice forms directly on deposit. Spectra of these molecules condensed on aluminum substrates at T less than 20 K indicate that amorphous phase ice forms. On aluminum, crystalline phase H2O and CH3OH are formed by annealing amorphous deposits to 155 K and 130 K, respectively (or by direct deposit at these temperatures); crystalline NH3 is formed by direct deposit at 88 K. Silicate smokes are deposited onto aluminum substrates by evaporation of SiO solid or by combustion of SiH4 with O2 in flowing H2 followed by vapor phase nucleation and growth. Silicate smokes which are oxygen-deficient may contain active surface sites which facilitate the amorphous-to-crystalline phase transition during condensation. Detailed experiments to understand the mechanism are currently in progress. The assumption that amorphous phase ice forms routinely on grains at T less than 80 K is often used in models describing the volatile content of comets or in interpretations of interstellar cloud temperatures. This assumption needs to be reexamined in view of these results.

  1. High Silicate Crystalline-to-Amorphous Ratios in Comets C/2001 Q4 (NEAT) and Hale-Bopp

    NASA Technical Reports Server (NTRS)

    Wooden, D. H.; Harker, D. E.; Wodward, C. E.

    2004-01-01

    Crystalline silicates, by their apparent absence in the ISM, are dust grains that experienced high temperatures in the solar nebula. Mg-rich crystalline silicates formed either by condensation from hot nebular gases (1450 K) or by the annealing of Mg-rich amorphous silicates (approximately 1000 K) in shocks in the 5-10AU region or by radial transport into and out of the hot inner zones, e.g., T(sub d) greater than 1000K at r(sub h) less than 5AU, 10(exp -6) -10(exp -5) solar mass per year, alpha = 10(exp -4) of the early solar nebula. Mg-rich crystalline silicates are found in interplanetary dust particles (IDPs) and produce IR spectral features in many Oort cloud comets. In May 2004, we discovered strong crystalline silicate features in the dynamically new Oort cloud comet C/2001 Q4 (NEAT). Thermal emission modeling of comets Q4 and C/1995 O1 (Hale-Bopp) demonstrate that both these comets have similar, high silicate crystalline-toamorphous ratios of 2.4 and 2.1, respectively, indicating that these icy planetesimals aggregated from similar reservoirs of material or that crystalline silicates were widely distributed within the comet-forming zone. This argues for efficient annealing mechanisms and radial mixing.

  2. High Silicate Crystalline-to-Amorphous Ratios in Comets C/2001 Q4 (NEAT) and Hale-Bopp

    NASA Technical Reports Server (NTRS)

    Wooden, D. H.; Harker, D. E.; Woodward, C. E.

    2004-01-01

    Crystalline silicates, by their apparent absence in the ISM, are dust grains that experienced high temperatures in the solar nebula. Mg-rich crystalline silicates formed either by condensation from hot nebular gases (1450 K) or by the annealing of Mg-rich amorphous silicates (approx. 1000 K) in shocks in the 5-10 AU region or by radial transport into and out of the hot inner zones, e.g., T(sub d) > 1000 K at r(sub h) < 5 AU, 10(exp -6) - 10(exp -5) M(sub O)/yr, alpha = 10(exp -4) of the early solar nebula. Mg-rich crystalline silicates are found in interplanetary dust particles (IDPs) and produce IR spectral features in many Oort cloud comets. In May 2004, we discovered strong crystalline silicate features in the dynamically new Oort cloud comet C/2001 Q4 (NEAT). Thermal emission modeling of comets Q4 and C/1995 O1 (Hale-Bopp) demonstrate that both these comets have similar, high silicate crystalline-to-amorphous ratios of 2.4 and 2.1, respectively, indicating that these icy planetesimals aggregated from similar reservoirs of material or that crystalline silicates were widely distributed within the comet-forming zone. This argues for efficient annealing mechanisms and radial mixing.

  3. Antimicrobial effects of silver zeolite, silver zirconium phosphate silicate and silver zirconium phosphate against oral microorganisms

    PubMed Central

    Saengmee-anupharb, Sirikamon; Srikhirin, Toemsak; Thaweboon, Boonyanit; Thaweboon, Sroisiri; Amornsakchai, Taweechai; Dechkunakorn, Surachai; Suddhasthira, Theeralaksna; Kamaguchi, Arihide

    2013-01-01

    Objective To evaluate the antimicrobial activities of silver inorganic materials, including silver zeolite (AgZ), silver zirconium phosphate silicate (AgZrPSi) and silver zirconium phosphate (AgZrP), against oral microorganisms. In line with this objective, the morphology and structure of each type of silver based powders were also investigated. Methods The antimicrobial activities of AgZ, AgZrPSi and AgZrP were tested against Streptococcus mutans, Lactobacillus casei, Candida albicans and Staphylococcus aureus using disk diffusion assay as a screening test. The minimum inhibitory concentration (MIC) and minimum lethal concentration (MLC) were determined using the modified membrane method. Scanning electron microscope and X-ray diffraction were used to investigate the morphology and structure of these silver materials. Results All forms of silver inorganic materials could inhibit the growth of all test microorganisms. The MIC of AgZ, AgZrPSi and AgZrP was 10.0 g/L whereas MLC ranged between 10.0–60.0 g/L. In terms of morphology and structure, AgZrPSi and AgZrP had smaller sized particles (1.5–3.0 µm) and more uniformly shaped than AgZ. Conclusions Silver inorganic materials in the form of AgZ, AgZrPSi and AgZrP had antimicrobial effects against all test oral microorganisms and those activities may be influenced by the crystal structure of carriers. These results suggest that these silver materials may be useful metals applied to oral hygiene products to provide antimicrobial activity against oral infection. PMID:23570016

  4. A Systematic Search for the Spectra with Features of Crystalline Silicates in the Spitzer IRS Enhanced Products

    NASA Astrophysics Data System (ADS)

    Chen, Rui; Luo, Ali; Liu, Jiaming; Jiang, Biwei

    2016-06-01

    The crystalline silicate features are mainly reflected in infrared bands. The Spitzer Infrared Spectrograph (IRS) collected numerous spectra of various objects and provided a big database to investigate crystalline silicates in a wide range of astronomical environments. We apply the manifold ranking algorithm to perform a systematic search for the spectra with crystalline silicate features in the Spitzer IRS Enhanced Products available. In total, 868 spectra of 790 sources are found to show the features of crystalline silicates. These objects are cross-matched with the SIMBAD database as well as with the Large Sky Area Multi-object Fiber Spectroscopic Telescope (LAMOST)/DR2. The average spectrum of young stellar objects shows a variety of features dominated either by forsterite or enstatite or neither, while the average spectrum of evolved objects consistently present dominant features of forsterite in AGB, OH/IR, post-AGB, and planetary nebulae. They are identified optically as early-type stars, evolved stars, galaxies and so on. In addition, the strength of spectral features in typical silicate complexes is calculated. The results are available through CDS for the astronomical community to further study crystalline silicates.

  5. Combined experimental and computational NMR study of crystalline and amorphous zeolitic imidazolate frameworks.

    PubMed

    Baxter, Emma F; Bennett, Thomas D; Mellot-Draznieks, Caroline; Gervais, Christel; Blanc, Frédéric; Cheetham, Anthony K

    2015-10-14

    Zeolitic imidazolate frameworks (ZIFs) have attracted great interest in recent years due to their high chemical and thermal stability with promising applications in gas storage and separations. We investigate the structures of three different crystalline ZIFs - ZIF-4, ZIF-8, ZIF-zni - and their amorphous counterparts using high field (13)C and (15)N CP MAS NMR. The high field (20 T) allows for the observation of all crystallographically independent carbon and nitrogen atoms in the crystalline ZIFs. Combining our experimental results with density functional theory calculations enabled the assignment of all chemical shifts. The crystalline spectra reveal the potential of high field NMR to distinguish between two ZIF polymorphs, ZIF-4 and ZIF-zni, with identical [Zn(C3H3N2)2] chemical compositions. (13)C and (15)N CP MAS NMR data obtained for the amorphous ZIFs clearly showed signal broadening upon amorphization, confirming the retention of chemical composition and the structural similarity of amorphous ZIF-4 and ZIF-zni. In the case of amorphous ZIF-8, we present evidence for the partial de-coordination of the 2-methyl imidazole linker.

  6. Combined experimental and computational NMR study of crystalline and amorphous zeolitic imidazolate frameworks.

    PubMed

    Baxter, Emma F; Bennett, Thomas D; Mellot-Draznieks, Caroline; Gervais, Christel; Blanc, Frédéric; Cheetham, Anthony K

    2015-10-14

    Zeolitic imidazolate frameworks (ZIFs) have attracted great interest in recent years due to their high chemical and thermal stability with promising applications in gas storage and separations. We investigate the structures of three different crystalline ZIFs - ZIF-4, ZIF-8, ZIF-zni - and their amorphous counterparts using high field (13)C and (15)N CP MAS NMR. The high field (20 T) allows for the observation of all crystallographically independent carbon and nitrogen atoms in the crystalline ZIFs. Combining our experimental results with density functional theory calculations enabled the assignment of all chemical shifts. The crystalline spectra reveal the potential of high field NMR to distinguish between two ZIF polymorphs, ZIF-4 and ZIF-zni, with identical [Zn(C3H3N2)2] chemical compositions. (13)C and (15)N CP MAS NMR data obtained for the amorphous ZIFs clearly showed signal broadening upon amorphization, confirming the retention of chemical composition and the structural similarity of amorphous ZIF-4 and ZIF-zni. In the case of amorphous ZIF-8, we present evidence for the partial de-coordination of the 2-methyl imidazole linker. PMID:26351979

  7. A study of binary adsorption of aromatics in completely siliceous zeolite ZSM-5 by FT-Raman spectroscopy.

    PubMed

    Havenga, Edward A; Huang, Yining

    2005-09-29

    In the present work, binary adsorption of p-xylene and toluene in completely siliceous zeolite ZSM-5 was examined by FT-Raman spectroscopy in combination with powder X-ray diffraction. The results indicate that at total loadings of < or = 4 molecules per unit cell (u.c.) both p-xylene and toluene molecules prefer to reside at the intersections of straight and zigzag channels. The structure of the sorbate/sorbent complexes likely belongs to orthorhombic. At high loadings of 7 and 8 molecules/u.c., the framework of the zeolite transforms to another orthorhombic phase. In this high-loaded phase, toluene molecules are distributed evenly in both the channel intersection and the midsection of straight channel. Although p-xylene has access to both the channel intersection and the zigzag channel, it does show a slight preference for the channel intersection. The adsorptive behavior of these aromatics at intermediate total loadings of 5 and 6 molecules/u.c. is more complicated because the zeolitic framework is a mixture of two different orthorhombic phases.

  8. 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.

  9. A memory diffusion model for molecular anisotropic diffusion in siliceous β-zeolite.

    PubMed

    Ji, Xiangfei; An, Zhuanzhuan; Yang, Xiaofeng

    2016-01-01

    A memory diffusion model of molecules on β-zeolite is proposed. In the model, molecular diffusion in β-zeolites is treated as jumping from one adsorption site to its neighbors and the jumping probability is a compound probability which includes that provided by the transitional state theory as well as that derived from the information about which direction the target molecule comes from. The proposed approach reveals that the diffusivities along two crystal axes on β-zeolite are correlated. The model is tested by molecular dynamics simulations on diffusion of benzene and other simple molecules in β-zeolites. The results show that the molecules with larger diameters fit the prediction much better and that the "memory effects" are important in all cases.

  10. Aluminum coordination and active sites on aluminas, Y zeolites and pillared silicates. Progress report, January 31, 1992--January 31, 1993

    SciTech Connect

    Fripiat, J.J.

    1992-12-31

    Effort was continued to characterize the nature of the Al species responsible for Lewis acidity in zeolites and in aluminas by NMR. While numerous techniques have been successful for scaling the acid strength of Broensted sites, the situation is not satisfactory for the Lewis acid sites. Initial rate of dehydrochlorination of 1,1,1-trichloroethane is sensitive to strength of Lewis acid sites. N-Butene isomerization has been extended to the new aluminas obtained from nano-sized precursors. O-Xylene isomerization was carried out in a recirculation reactor on H-mordenite samples containing Lewis or Broensted acid sites; effects of H{sub 2} and NO were also investigated. Cracking of methylcyclohexane and 3-methylpentane was investigated by EPR on H-mordenite. Sepiolite, a Mg silicate with zeolitic channels, had Al substituted for Si; the negative charge is balanced by, say, VO{sup 2+}. Transformation of ethanol into butadiene on this dual-function catalyst appears to result from a Prins reaction between acetaldeyde formed on the redox sites and ethylene resulting from dehydration of ethanol on Lewis sites.

  11. Crystalline Silicates in Comets: Modeling Irregularly-Shaped Forsterite Crystals and Its Implications on Condensation Conditions

    NASA Technical Reports Server (NTRS)

    Wooden, Diane H.; Lindsay, Sean S.

    2011-01-01

    Crystalline silicates in comets are a product of the condensation in the hot inner regions (T > or approx. equals 1400 K [1]) of our proto-planetary disk or annealing at somewhat lower temperatures (T > or approx. equals 1000-1200 K) [2, 3, 4] in shocks coupled with disk evolutionary processes that include radial transport of crystals from their formation locations out to the cold outer regions where comet nuclei formed. The grain shape of forsterite (crystals) could be indicative of their formation pathways at high temperatures through vapor-solid condensation or at lower temperatures through vapor-liquid-solid formation and growth [5, 6, 7]. Experiments demonstrate that crystals that formed from a rapidly cooled highly supersaturated silicate vapor are characterized by bulky, platy, columnar/needle and droplet shapes for values of temperature and supersaturation, T and sigma, of 1000-1450 C and < 97, 700-1000 C and 97-161, 580-820 C and 131-230, and <500 C and > 230, respectively [7]. The experimental columnar/needle shapes, which form by vapor-liquid-solid at lower temperatures (<820 C), are extended stacks of plates, where the extension is not correlated with an axial direction: columnar/needles may be extended in the c-axis or a-axis direction, can change directions, and/or are off-kilter or a bit askew extending in a combination of the a- and c-axis direction.

  12. Zealous zeolites

    SciTech Connect

    Hairston, D.W.

    1996-07-01

    Zeolites have made significant inroads in fluid cracking catalysts for gasoline and have pushed phosphates out of laundry detergents. But these crystalline aluminosilicate structures are just beginning to make their mark in chemical processes and environmental applications. Ideally suited for work as molecular sieves and catalysts, zeolites sport uniform surface pores and channels that are receptive only to molecules of a specific size and shape. This high selectivity makes zeolites a good alterative to some of the conventional products used for chemical reaction and filtration. One of the most potentially lucrative markets for zeolites is chemical catalyst replacements for liquid acids, such as hydrofluoric acid and sulfuric acid, and aluminum chloride in a number of alkylation and acrylation reactions. Zeolites are also being considered for oligomerization,isomerization, amination and condensation processes for the manufacture of chemical intermediates. The paper discusses the market and manufacturers of zeolites, justifying the cost of converting to zeolite catalysts, and natural zeolites.

  13. Absorption at 11 μm in the interstellar medium and embedded sources: evidence for crystalline silicates

    NASA Astrophysics Data System (ADS)

    Wright, Christopher M.; Do Duy, Tho; Lawson, Warrick

    2016-04-01

    An absorption feature is occasionally reported around 11 μm in astronomical spectra, including those of forming stars. Candidate carriers include water ice, polycyclic aromatic hydrocarbons, silicon carbide, crystalline silicates or even carbonates. All are known constituents of cosmic dust in one or more types of environments, though not necessarily together. In this paper, we present new ground-based 8-13 μm spectra of one evolved star, several embedded young stellar objects and a background source lying behind a large column of the interstellar medium (ISM) towards the Galactic Centre. Our observations, obtained at a spectral resolution of ˜100, are compared with previous lower resolution data, as well as data obtained with the Infrared Space Observatory (ISO) on these and other targets. By presenting a subset of a larger sample, our aim is to establish the reality of the feature and subsequently speculate on its carrier. All evidence points towards crystalline silicate. For instance, the 11 μm band profile is well matched with the emissivity of crystalline olivine. Furthermore, the apparent association of the absorption feature with a sharp polarization signature in the spectrum of two previously reported cases suggests a carrier with a relatively high band strength compared to amorphous silicates. If true, this would either set back the evolutionary stage in which silicates are crystallized, either to the embedded phase or even before within the ISM, or else the silicates ejected from the outflows of evolved stars retain some of their crystalline identity during their long residence in the ISM.

  14. The influence of hydrothermal temperature and time toward crystallinity of zeolite X supported on glass wool for CO2 adsorption

    NASA Astrophysics Data System (ADS)

    Anggita, R. K. Wardani; Yuniar, V. T. P.; Aini, W. T.; Nurul, W.

    2016-04-01

    In this study, the influence of hydrothermal temperature and time at zeolite X supported on glasswool were investigated. The results of characterization using XRD showed that a single phase zeolite X with highest crystallinity was obtained when hydrothermal temperature and time at 100°C during 24 hours (ZXF100-24H). The CO2 adsorption capacity of ZXF100-24H has reached up to 10.15 wt. %. Kinetics of CO2 adsorption onto zeolite X supported on glasswool was investigated using pseudo-first-order, pseudo-second-order and intra-particle diffusion kinetic models. After evaluating three kinetic models for CO2 adsorption at adsorption temperatures of 30°C, 40°C and 50°C, it was found that intra-particle diffusion kinetic model provided the best fitting for the adsorption data. Furthermore, the thermodynamic parameters of CO2 adsorption were obtained as follows, Gibbs free energy change (ΔG°) are -0.409 kJ/mol at 30°C, -0.274 kJ/mol at 40°C and -0.138 kJ/mol at 50 °C, whereas the enthalpy change (ΔH°) is -4.53 kJ/mol and the entropy change (ΔS°) is -0.0135 kJ/(mol K).

  15. A vibrational spectroscopic study of the silicate mineral harmotome - (Ba,Na,K)1-2(Si,Al)8O16ṡ6H2O - A natural zeolite

    NASA Astrophysics Data System (ADS)

    Frost, Ray L.; López, Andrés; Wang, Lina; Romano, Antônio Wilson; Scholz, Ricardo

    2015-02-01

    The mineral harmotome (Ba,Na,K)1-2(Si,Al)8O16ṡ6H2O is a crystalline sodium calcium silicate which has the potential to be used in plaster boards and other industrial applications. It is a natural zeolite with catalytic potential. Raman bands at 1020 and 1102 cm-1 are assigned to the SiO stretching vibrations of three dimensional siloxane units. Raman bands at 428, 470 and 491 cm-1 are assigned to OSiO bending modes. The broad Raman bands at around 699, 728, 768 cm-1 are attributed to water librational modes. Intense Raman bands in the 3100 to 3800 cm-1 spectral range are assigned to OH stretching vibrations of water in harmotome. Infrared spectra are in harmony with the Raman spectra. A sharp infrared band at 3731 cm-1 is assigned to the OH stretching vibration of SiOH units. Raman spectroscopy with complimentary infrared spectroscopy enables the characterization of the silicate mineral harmotome.

  16. The optical constants of crystalline silicate particles in mid- and far-infrared

    NASA Astrophysics Data System (ADS)

    Suto, Hiroshi; Koike, Chiyoe; Shibai, Hiroshi; Tuchiyama, Akira; Mizutani, Kohei

    The optical constants from the mid to far infrared region are presented for the crystalline silicate particles with submicron size, i.e. olivine, forsterite, clinopyroxene and orthopyroxene particles which are considered as major constituents of interplanetary, interstellar and circumstellar dust. The olivine, clinoproxene and orthopyroxene are natural from Ichinomegata, Akita and have the following characteristics, olivine: (Mg_0.90Fe_0.10)_2SiO_2(Fo_90), rho = 3.36g/cm^3 clinopyroxene: Ca(Mg,Fe,Al)(Si,Al)_2O_6 Mg / (Mg+Fe) = 0.90 - 0.92, Al_2O_3 = 1.9 - 4.9 wt%, rho = 3.28 g/cm^3 orthopyroxene: (Mg,Fe,Al)(Si,Al)O_3 3.36g / cm^3 Mg / (Mg+Fe) = 0.89 - 0.90, Al_2O_3 = 3.3 - 4.0 wt%, rho = 3.32 g/cm^3 The forsterite (Mg_2SiO_4, [Mg / (Mg+Fe) = 1]) is synthesized by the CZ method (Takei 1976). The optical constants have been derived from the transmission spectra of the particles with use of Kramers-Kronig relation (Rouleau and Martin 1991). The transmissions from 5 microns to 30 microns and 25 microns to 100 microns were measured respectively for KBr pellets and polyethylene sheets containing the particles. Under Rayleigh approximation (lambda gg particle size) the imaginary part of the polarizability A per unit volume has a form of A = (epsilon/epsilon_h-1) / ((epsilon/epsilon_h-1)L+1) where epsilon: dielectric constant of particle, epsilon_h: dielectric constant of host medium and L: shape parameter of dust with assumption of homogeneous spheroid. The imaginary part of A is proportional to the transmission T as Aimg = lambda/{(2pi nhost)} rho/M ln (1/T). Imaginary part of A at infrared region are given from our measurements, and with applying Kramers-Kronig relation to the polarizability the real part of A can be derived, then the optical constants of particles are evaluated from equation of A. The silicate's strong absorption features around 10 microns and 11 microns were measured for the particles placed on the surface of KBr or glass plate (not embedded in KBr

  17. PETROLOGIC CONSTRAINTS ON AMORPHOUS AND CRYSTALLINE MAGNESIUM SILICATES: DUST FORMATION AND EVOLUTION IN SELECTED HERBIG Ae/Be SYSTEMS

    SciTech Connect

    Rietmeijer, Frans J. M.; Nuth, Joseph A.

    2013-07-01

    The Infrared Space Observatory, Spitzer Space Telescope, and Herschel Space Observatory surveys provided a wealth of data on the Mg-silicate minerals (forsterite, enstatite), silica, and ''amorphous silicates with olivine and pyroxene stoichiometry'' around Herbig Ae/Be stars. These incredible findings do not resonate with the mainstream Earth Sciences because of (1) disconnecting ''astronomical nomenclature'' and the long existing mineralogical and petrologic terminology of minerals and amorphous materials, and (2) the fact that Earth scientists (formerly geologists) are bound by the ''Principle of Actualism'' that was put forward by James Hutton (1726-1797). This principle takes a process-oriented approach to understanding mineral and rock formation and evolution. This paper will (1) review and summarize the results of laboratory-based vapor phase condensation and thermal annealing experiments, (2) present the pathways of magnesiosilica condensates to Mg-silicate mineral (forsterite, enstatite) formation and processing, and (3) present mineralogical and petrologic implications of the properties and compositions of the infrared-observed crystalline and amorphous dust for the state of circumstellar disk evolution. That is, the IR-observation of smectite layer silicates in HD142527 suggests the break-up of asteroid-like parent bodies that had experienced aqueous alteration. We discuss the persistence of amorphous dust around some young stars and an ultrafast amorphous to crystalline dust transition in HD 163296 that leads to forsterite grains with numerous silica inclusions. These dust evolution processes to form forsterite, enstatite {+-} tridymite could occur due to amorphous magnesiosilica dust precursors with a serpentine- or smectite-dehydroxylate composition.

  18. Petrologic Constraints on Amorphous and Crystalline Magnesium Silicates: Dust Formation and Evolution in Selected Herbig Ae/Be Systems

    NASA Astrophysics Data System (ADS)

    Rietmeijer, Frans J. M.; Nuth, Joseph A.

    2013-07-01

    The Infrared Space Observatory, Spitzer Space Telescope, and Herschel Space Observatory surveys provided a wealth of data on the Mg-silicate minerals (forsterite, enstatite), silica, and "amorphous silicates with olivine and pyroxene stoichiometry" around Herbig Ae/Be stars. These incredible findings do not resonate with the mainstream Earth Sciences because of (1) disconnecting "astronomical nomenclature" and the long existing mineralogical and petrologic terminology of minerals and amorphous materials, and (2) the fact that Earth scientists (formerly geologists) are bound by the "Principle of Actualism" that was put forward by James Hutton (1726-1797). This principle takes a process-oriented approach to understanding mineral and rock formation and evolution. This paper will (1) review and summarize the results of laboratory-based vapor phase condensation and thermal annealing experiments, (2) present the pathways of magnesiosilica condensates to Mg-silicate mineral (forsterite, enstatite) formation and processing, and (3) present mineralogical and petrologic implications of the properties and compositions of the infrared-observed crystalline and amorphous dust for the state of circumstellar disk evolution. That is, the IR-observation of smectite layer silicates in HD142527 suggests the break-up of asteroid-like parent bodies that had experienced aqueous alteration. We discuss the persistence of amorphous dust around some young stars and an ultrafast amorphous to crystalline dust transition in HD 163296 that leads to forsterite grains with numerous silica inclusions. These dust evolution processes to form forsterite, enstatite ± tridymite could occur due to amorphous magnesiosilica dust precursors with a serpentine- or smectite-dehydroxylate composition.

  19. Structural, Dielectric, and Interface Properties of Crystalline Barium Silicate Films on Si(100): A Robust High-κ Material

    NASA Astrophysics Data System (ADS)

    Islam, S.; Hofmann, K. R.; Feldhoff, A.; Pfnür, H.

    2016-05-01

    The quality and crystallinity of ultrathin dielectric layers depend crucially on the details of interface formation and chemical stability. Using a combination of photoelectron (XPS) and electron-energy-loss spectroscopy, low-energy electron-diffraction, and transmission electron microscopy (TEM), we show that crystalline epitaxial layers of Ba2 SiO4 can be grown on Si(100) substrates from evaporated Ba in oxygen background atmosphere at 650 °C . Since the silicate is chemically by far more stable than the oxides of Si and Ba, an atomically sharp interface with no interface oxide is formed, as confirmed by XPS and TEM. However, the interface is rough on the atomic scale. dc and frequency-dependent electrical measurements reveal a relative dielectric constant of 22.8, low hysteresis in C V measurements, and low leakage currents but still fairly high interface trap densities.

  20. Effect of silicate minerals (zeolite, bentonite, kaolin, granite) on in vitro fermentation of amorphous cellulose, meadow hay, wheat straw and barley.

    PubMed

    Váradyová, Zora; Baran, Miroslav; Siroka, Peter; Styriaková, Iveta

    2003-01-01

    The objective of the present experiment was to determine the effects of addition of silicate minerals, zeolite (Z), bentonite (B), kaolin (K), granite (G) on the rumen fermentation parameters, total gas, methane, total and individual volatile fatty acids (VFA) and hydrogen recovery in rumen fluid inoculum from sheep. Different materials (0.25 g) meadow hay (MH), wheat straw (WS), barley (BA) and amorphous cellulose (AC) were used as substrates. Silicate minerals (0.1 g) were added to the fermentation bottles containing substrates and rumen fluid inoculum and incubated for 72 h in vitro. The gas production technique simulates fermentation in the rumen was used to determine fermentation parameters. The total gas production was significantly higher compared to control for MH plus B (MHB), MH plus G (MHG), WS plus Z (WSZ), WS plus B (WSB), WS plus K (WSK), WS plus G (WSG), AC plus B (ACB), AC plus G (ACG), BA plus Z (BAZ), BA plus B (BAB), BA plus K (BAK), BA plus granite (BAG). Significant differences of the methane production were found between the controls, WSG, BAB and BAK. The total VFA concentration was increased in ACG (83.1 mM). The acetate: propionate (A:P) ratio of the control and additives ranged between 3.1 and 3.6 for MH, 2.7 and 3.5 for WS, 1.6 and 1.8 for AC and 2.3 and 2.9 for BA. It was concluded that the silicate minerals had no appreciable effect on the methane production, however, they support the microbial metabolism by influencing (bentonite, granite) and slightly influencing (zeolite, kaolin) the rumen fermentation.

  1. 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

  2. X‐ray Excited Optical Fluorescence and Diffraction Imaging of Reactivity and Crystallinity in a Zeolite Crystal: Crystallography and Molecular Spectroscopy in One

    PubMed Central

    Ristanović, Zoran; Hofmann, Jan P.; Richard, Marie‐Ingrid; Jiang, Tao; Chahine, Gilbert A.; Schülli, Tobias U.; Meirer, Florian

    2016-01-01

    Abstract Structure–activity relationships in heterogeneous catalysis are challenging to be measured on a single‐particle level. For the first time, one X‐ray beam is used to determine the crystallographic structure and reactivity of a single zeolite crystal. The method generates μm‐resolved X‐ray diffraction (μ‐XRD) and X‐ray excited optical fluorescence (μ‐XEOF) maps of the crystallinity and Brønsted reactivity of a zeolite crystal previously reacted with a styrene probe molecule. The local gradients in chemical reactivity (derived from μ‐XEOF) were correlated with local crystallinity and framework Al content, determined by μ‐XRD. Two distinctly different types of fluorescent species formed selectively, depending on the local zeolite crystallinity. The results illustrate the potential of this approach to resolve the crystallographic structure of a porous material and its reactivity in one experiment via X‐ray induced fluorescence of organic molecules formed at the reactive centers. PMID:27478278

  3. X‐ray Excited Optical Fluorescence and Diffraction Imaging of Reactivity and Crystallinity in a Zeolite Crystal: Crystallography and Molecular Spectroscopy in One

    PubMed Central

    Ristanović, Zoran; Hofmann, Jan P.; Richard, Marie‐Ingrid; Jiang, Tao; Chahine, Gilbert A.; Schülli, Tobias U.; Meirer, Florian

    2016-01-01

    Abstract Structure–activity relationships in heterogeneous catalysis are challenging to be measured on a single‐particle level. For the first time, one X‐ray beam is used to determine the crystallographic structure and reactivity of a single zeolite crystal. The method generates μm‐resolved X‐ray diffraction (μ‐XRD) and X‐ray excited optical fluorescence (μ‐XEOF) maps of the crystallinity and Brønsted reactivity of a zeolite crystal previously reacted with a styrene probe molecule. The local gradients in chemical reactivity (derived from μ‐XEOF) were correlated with local crystallinity and framework Al content, determined by μ‐XRD. Two distinctly different types of fluorescent species formed selectively, depending on the local zeolite crystallinity. The results illustrate the potential of this approach to resolve the crystallographic structure of a porous material and its reactivity in one experiment via X‐ray induced fluorescence of organic molecules formed at the reactive centers. PMID:27145171

  4. Lyotropic liquid crystalline L3 phase silicated nanoporous monolithic composites and their production

    DOEpatents

    McGrath, Kathryn M.; Dabbs, Daniel M.; Aksay, Ilhan A.; Gruner, Sol M.

    2003-10-28

    A mesoporous ceramic material is provided having a pore size diameter in the range of about 10-100 nanometers produced by templating with a ceramic precursor a lyotropic liquid crystalline L.sub.3 phase consisting of a three-dimensional, random, nonperiodic network packing of a multiple connected continuous membrane. A preferred process for producing the inesoporous ceramic material includes producing a template of a lyotropic liquid crystalline L.sub.3 phase by mixing a surfactant, a co-surfactant and hydrochloric acid, coating the template with an inorganic ceramic precursor by adding to the L.sub.3 phase tetramethoxysilane (TMOS) or tetraethoxysilane (TEOS) and then converting the coated template to a ceramic by removing any remaining liquids.

  5. Towards a full understanding of the nature of Ni(II) species and hydroxyl groups over highly siliceous HZSM-5 zeolite supported nickel catalysts prepared by a deposition-precipitation method.

    PubMed

    Chen, Bao-Hui; Chao, Zi-Sheng; He, Hao; Huang, Chen; Liu, Ya-Juan; Yi, Wen-Jun; Wei, Xue-Ling; An, Jun-Fang

    2016-02-14

    Highly siliceous HZSM-5 zeolite supported nickel catalysts prepared by a deposition-precipitation (D-P) method were characterized by Fourier transform infrared (FT-IR), hydrogen temperature programmed reduction (H2-TPR), X-ray diffraction (XRD), N2-absorption/desorption, field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and (27)Al magic-angle nuclear magnetic resonance (MAS NMR) techniques. The results showed that the D-P of nickel species occurred predominantly on the internal surface of highly siliceous HZSM-5 zeolite, in which the internal silanol groups located on the hydroxylated mesopores or nanocavities played a key role. During the D-P process, nickel hydroxide was first deposited-precipitated via olation/polymerization of neutral hydroxoaqua nickel species over the HZSM-5 zeolite. With the progress of the D-P process, 1 : 1 nickel phyllosilicate was formed over the HZSM-5 via the hetero-condensation/polymerization between charged hydroxoaqua nickel species and monomer silicic species generated due to the partial dissolution of the HZSM-5 framework. The 1 : 1 nickel phyllosilicate could also be generated via the hydrolytic adsorption of hydroxoaqua nickel species and their subsequent olation condensation. After calcination, the deposited-precipitated nickel hydroxide was decomposed into nickel oxide, while the 1 : 1 nickel phyllosilicate was transformed into 2 : 1 nickel phyllosilicate. According to the above mechanism, Ni(ii) species were present both in the form of nickel oxide and 2 : 1 nickel phyllosilicate, which were mutually separated from each other, being highly dispersed over HZSM-5 zeolite.

  6. A novel class of nonlinear optical materials based on host-guest composites: zeolites as inorganic crystalline hosts.

    PubMed

    Kim, Hyun Sung; Pham, Tung Cao Thanh; Yoon, Kyung Byung

    2012-05-16

    The demand for nonlinear optical (NLO) materials with exceptional NLO properties is very large, and hence the search for such materials should be continued not only to enhance their functions in current applications but also to help expedite the materialization of photonics in which photons instead of electrons are used for signal processing, transmission, and storage. This article summarizes the preparation, characteristics, and the future perspectives of novel second order nonlinear optical (2NLO) materials prepared by orientation-controlled incorporation of 2NLO molecules into zeolite channels and third order nonlinear optical (3NLO) materials prepared by compartmentalization of very small (<1.3 nm) PbS QDs within zeolite nanopores under different environments, and the novel chemistry newly unveiled during the preparation of novel zeolite based NLO materials.

  7. Rapid synthesis of beta zeolites

    SciTech Connect

    Fan, Wei; Chang, Chun -Chih; Dornath, Paul; Wang, Zhuopeng

    2015-08-18

    The invention provides methods for rapidly synthesizing heteroatom containing zeolites including Sn-Beta, Si-Beta, Ti-Beta, Zr-Beta and Fe-Beta. The methods for synthesizing heteroatom zeolites include using well-crystalline zeolite crystals as seeds and using a fluoride-free, caustic medium in a seeded dry-gel conversion method. The Beta zeolite catalysts made by the methods of the invention catalyze both isomerization and dehydration reactions.

  8. IRAS 15099-5856: REMARKABLE MID-INFRARED SOURCE WITH PROMINENT CRYSTALLINE SILICATE EMISSION EMBEDDED IN THE SUPERNOVA REMNANT MSH15-52

    SciTech Connect

    Koo, Bon-Chul; Kim, Hyun-Jeong; Im, Myungshin; McKee, Christopher F.; Suh, Kyung-Won; Moon, Dae-Sik; Lee, Ho-Gyu; Onaka, Takashi; Burton, Michael G.; Hiramatsu, Masaaki; Bessell, Michael S.; Gaensler, B. M.; Lee, Jae-Joon; Jeong, Woong-Seob; Tatematsu, Ken'ichi; Kawabe, Ryohei; Ezawa, Hajime; Kohno, Kotaro; Wilson, Grant; Yun, Min S.

    2011-05-01

    We report new mid-infrared (MIR) observations of the remarkable object IRAS 15099-5856 using the space telescopes AKARI and Spitzer, which demonstrate the presence of prominent crystalline silicate emission in this bright source. IRAS 15099-5856 has a complex morphology with a bright central compact source (IRS1) surrounded by knots, spurs, and several extended ({approx}4') arc-like filaments. The source is seen only at {>=}10 {mu}m. The Spitzer mid-infrared spectrum of IRS1 shows prominent emission features from Mg-rich crystalline silicates, strong [Ne II] 12.81 {mu}m, and several other faint ionic lines. We model the MIR spectrum as thermal emission from dust and compare with the Herbig Be star HD 100546 and the luminous blue variable R71, which show very similar MIR spectra. Molecular line observations reveal two molecular clouds around the source, but no associated dense molecular cores. We suggest that IRS1 is heated by UV radiation from the adjacent O star Muzzio 10 and that its crystalline silicates most likely originated in a mass outflow from the progenitor of the supernova remnant (SNR) MSH 15-52. IRS1, which is embedded in the SNR, could have been shielded from the SN blast wave if the progenitor was in a close binary system with Muzzio 10. If MSH 15-52 is a remnant of Type Ib/c supernova (SN Ib/c), as has been previously proposed, this would confirm the binary model for SN Ib/c. IRS1 and the associated structures may be the relics of massive star death, as shaped by the supernova explosion, the pulsar wind, and the intense ionizing radiation of the embedded O star.

  9. Zeolite exposure and associated pneumoconiosis

    SciTech Connect

    Casey, K.R.; Shigeoka, J.W.; Rom, W.N.; Moatamed, F.

    1985-06-01

    Naturally occurring zeolite minerals are aluminum silicates widespread in the earth's crust. Several of these minerals have fibrous forms and have been implicated as a possible cause of benign and malignant diseases of the lung and pleura in Turkey. This report describes a patient, living in an area of Nevada rich in zeolites, who presented with idiopathic pleural thickening and pulmonary fibrosis associated with extensive pulmonary deposition of zeolites.

  10. A vibrational spectroscopic study of the silicate mineral analcime - Na2(Al4SiO4O12)·2H2O - A natural zeolite

    NASA Astrophysics Data System (ADS)

    Frost, Ray L.; López, Andrés; Theiss, Frederick L.; Romano, Antônio Wilson; Scholz, Ricardo

    2014-12-01

    We have studied the mineral analcime using a combination of scanning electron microscopy with energy dispersive spectroscopy and vibrational spectroscopy. The mineral analcime Na2(Al4SiO4O12)·2H2O is a crystalline sodium silicate. Chemical analysis shows the mineral contains a range of elements including Na, Al, Fe2+ and Si. The mineral is characterized by intense Raman bands observed at 1052, 1096 and 1125 cm-1. The infrared bands are broad; nevertheless bands may be resolved at 1006 and 1119 cm-1. These bands are assigned to SiO stretching vibrational modes. Intense Raman band at 484 cm-1 is attributed to OSiO bending modes. Raman bands observed at 2501, 3542, 3558 and 3600 cm-1 are assigned to the stretching vibrations of water. Low intensity infrared bands are noted at 3373, 3529 and 3608 cm-1. The observation of multiple water bands indicate that water is involved in the structure of analcime with differing hydrogen bond strengths. This concept is supported by the number of bands in the water bending region. Vibrational spectroscopy assists with the characterization of the mineral analcime.

  11. Cesium titanium silicate and method of making

    DOEpatents

    Balmer, M.L.

    1997-01-07

    The invention is the new material, a ternary compound of cesium, silica, and titania, together with a method of making the ternary compound, cesium titanium silicate pollucite. More specifically, the invention is Cs{sub 2}Ti{sub 2}Si{sub 4}O{sub 13} pollucite which is a new crystalline phase representing a novel class of Ti-containing zeolites. Compositions contain relatively high Cs{sub 2}O and TiO{sub 2} loadings and are durable glass and ceramic materials. The amount of TiO{sub 2} and Cs{sub 2} that can be incorporated into these glasses and crystalline ceramics far exceeds the limits set for the borosilicate high level waste glass. 10 figs.

  12. Cesium titanium silicate and method of making

    DOEpatents

    Balmer, Mari L.

    1997-01-01

    The invention is the new material, a ternary compound of cesium, silica, and titania, together with a method of making the ternary compound, cesium titanium silicate pollucite. More specifically, the invention is Cs.sub.2 Ti.sub.2 Si.sub.4 O.sub.13 pollucite which is a new crystalline phase representing a novel class of Ti-containing zeolites. Compositions contain relatively high Cs.sub.2 O and TiO.sub.2 loadings and are durable glass and ceramic materials. The amount of TiO.sub.2 and Cs.sub.2 that can be incorporated into these glasses and crystalline ceramics far exceeds the limits set for the borosilicate high level waste glass.

  13. Radiation effects and annealing kinetics in crystalline silicates, phosphates and complex Nb-Ta-Ti oxides. FInal Report

    SciTech Connect

    Ewing, R.C.

    1987-08-10

    Interaction of heavy particles (alpha-recoil nuclei, fission fragments, implanted ions) with ceramics is complex because they have a wide range of structure types, complex compositions and chemical bonding is variable. Radiation damage can produce diverse results, but most commonly, crystalline periodic materials become either polycrystalline or aperiodic (metamict state). We studied the transition from crystalline to aperiodic state in natural materials that have been damaged by alpha recoil nuclei in the U and Th decay series and in synthetic, analogous structure types which have been amorphized by ion implantation. Transition from crystalline to aperiodic was followed by analysis of XRD, high resolution TEM, and EXAFS/XANE spectroscopy. Use of these techniques with increasing dose provided data on an increasing finer scale as the damage process progressed.

  14. Lack of Evidence of In-Situ Decay of Aluminum-26 in a FeO-Poor Ferromagnesian Crystalline Silicate Particle, Pyxie, from Comet Wild 2

    NASA Technical Reports Server (NTRS)

    Nakashima, D.; Ushikubo, T.; Weisberg, M. K.; Zolensky, M. E.; Ebel, D. S.; Kita, N. T.

    2014-01-01

    One of the important discoveries from the Stardust mission is the observation of crystalline silicate particles that resemble Ca, Al-rich inclusions (CAIs) and chondrules in carbonaceous chondrites], which suggests radial transport of high temperature solids from the inner to the outer solar nebula regions and capture by accreting cometary objects. The Al-Mg isotope analyses of CAI-like and type II chondrule-like particles revealed no excess of Mg-26 derived from in-situ decay of Al-26 (Tau)(sub 1/2) = 0.705Myr; ), suggesting late formation of these particles. However, the number of Wild 2 particles analyzed for Al-Mg isotopes is still limited (n = 3). In order to better understand the timing of the formation of Wild 2 particles and possible radial transport in the protoplanetary disk, we performed SIMS (Secondary Ion Mass Spectrometer) Al-Mg isotope analyses of plagioclase in a FeO-poor ferromagnesian Wild 2 particle, which is the most abundant type among crystalline Wild 2 particles.

  15. Predictive model for Pb(II) adsorption on soil minerals (oxides and low-crystalline aluminum silicate) consistent with spectroscopic evidence

    NASA Astrophysics Data System (ADS)

    Usiyama, Tomoki; Fukushi, Keisuke

    2016-10-01

    Mobility of Pb(II) in surface condition is governed by adsorption processes on soil minerals such as iron oxides and low-crystalline aluminum silicates. The adsorption effectiveness and the surface complex structures of Pb(II) vary sensitively with solution conditions such as pH, ionic strength, Pb(II) loading, and electrolyte anion type. This study was undertaken to construct a quantitative model for Pb(II) on soil minerals. It can predict the adsorption effectiveness and surface complex structures under any solution conditions using the extended triple layer model (ETLM). The Pb(II) adsorption data for goethite, hydrous ferric oxide (HFO), quartz, and low-crystalline aluminum silicate (LCAS) were analyzed with ETLM to retrieve the surface complexation reactions and these equilibrium constants. The adsorption data on goethite, HFO and quartz were referred from reports of earlier studies. Those data for LCAS were measured under a wide range of pH, ionic strength and Pb(II) loadings in NaNO3 and NaCl solutions. All adsorption data can be reasonably regressed using ETLM with the assumptions of inner sphere bidentate complexation and inner sphere monodentate ternary complexation with electrolyte anions, which are consistent with previously reported spectroscopic evidence. Predictions of surface speciation under widely various solution conditions using ETLM revealed that the inner sphere bidentate complex is the predominant species at neutral to high pH conditions. The inner sphere monodentate ternary complex becomes important at low pH, high surface Pb(II) coverage, and high electrolyte concentrations, of which the behavior is consistent with the spectroscopic observation. Comparisons of the obtained adsorption constants on goethite, HFO and quartz exhibited good linear relations between the reciprocals of dielectric constants of solids and adsorption constants. Those linear relations support predictions of the adsorption constants of all oxides based on Born

  16. Crystalline Membranes

    NASA Technical Reports Server (NTRS)

    Tsapatsis, Michael (Inventor); Lai, Zhiping (Inventor)

    2008-01-01

    In certain aspects, the invention features methods for forming crystalline membranes (e.g., a membrane of a framework material, such as a zeolite) by inducing secondary growth in a layer of oriented seed crystals. The rate of growth of the seed crystals in the plane of the substrate is controlled to be comparable to the rate of growth out of the plane. As a result, a crystalline membrane can form a substantially continuous layer including grains of uniform crystallographic orientation that extend through the depth of the layer.

  17. Synthesis and testing of nanosized zeolite Y

    NASA Astrophysics Data System (ADS)

    Karami, Davood

    This work focuses on the synthesis and testing of nanosized zeolite Y. The synthesis formulations of faujasite-type structure of zeolite Y prepared in nanosized form are described. The synthetic zeolite Y is the most widely employed for the preparation of fluid catalytic cracking (FCC) catalysts. The synthesis of zeolite Y is very complicated process. The mean particle size of zeolite Y is 1800 nm. The major challenge of this work involved reducing this average particle size to less than 500 nm. The preliminary experiments were conducted to obtain the pure zeolite Y using the soluble silicates as a silica source. This was achieved by applying the experimental design approach to study the effects of many parameters. The ageing time turned out to be the most significant variable affecting product purity. Based on the preliminary results, a detailed investigation was carried out to determine the effects of silica-alumina precursor preparations on zeolite Y synthesis. Aluminosilicate precursors were prepared by gelling and precipitation of soluble silicate. The as-prepared precursors were used for the hydrothermal synthesis of zeolite Y. The procedure of the precipitation of soluble silicate yielded pure zeolite Y at the conventional synthesis conditions. The extent of purity of zeolite Y depends on the surface areas of aluminosilicate precursors. A novel approach to zeolite Y synthesis was employed for the preparation of the pure nanosized zeolite Y. This was achieved by applying the method of impregnation of precipitated silica. This novel method of impregnation for zeolite Y preparation allows eliminating the vigorous agitation step required for the preparation of a homogeneous silica solution, thereby simplifying the synthesis of zeolite Y in one single vessel. In case of the synthesis of nanosized zeolite Y, the effect of varying the organic templates on the formation of nanosized particles of zeolite Y was investigated, while all other reaction parameters were

  18. Observation of azo chromophore fluorescence and phosphorescence emissions from DBH by applying exclusively the orbital confinement effect in siliceous zeolites devoid of charge-balancing cations.

    PubMed

    Márquez, Francisco; Martí, Vicente; Palomares, Emilio; García, Hermenegildo; Adam, Waldemar

    2002-06-26

    The molecular orbital (MO) confinement theory predicts that the HOMO and LUMO of an organic guest may become distorted when the dimensions of the host cavity approach closely those of the MO (Corma, A.; García, H.; Sastre, G.; Viruela, P. M. J. Phys. Chem. B 1997, 101, 4575-4582). Generally, quantum chemical calculations assume that the MO extends over all the space. However, the fact that a molecule is confined within a restricted cavity might impose certain limits to its MO. In agreement with this theory, we have observed for the first time the phosphorescence emission from 2,3-diazabicyclo[2.2.1]hept-2-ene (DBH) upon incorporation in zeolites devoid of charge-balancing cations, even at room temperature. This observation may be rationalized on the basis of two possible effects: (i) Decrease of the HOMO-LUMO gap induced by confinement of the azo np* chromophore favors ISC, and (ii) inhibition of radiationless deactivation pathway by the immobilization of DBH within the zeolite host favors long lifetimes.

  19. Synthesis of hierarchical micro/mesoporous structures via solid-aqueous interface growth: zeolitic imidazolate framework-8 on siliceous mesocellular foams for enhanced pervaporation of water/ethanol mixtures.

    PubMed

    Sue, Yu-Chain; Wu, Jhe-Wei; Chung, Shao-En; Kang, Chao-Hsiang; Tung, Kuo-Lun; Wu, Kevin C-W; Shieh, Fa-Kuen

    2014-04-01

    A new hierarchical micro/mesoporous composite is synthesized via direct growth of microporous zeolitic imidazolate framework-8 (ZIF-8) on siliceous mesocellular foams (MCF). Depending on different synthetic conditions, ZIF-8 with two different particle sizes, i.e., ZIF-8 microparticles and ZIF-8 nanoparticles, were successfully formed on the external surface of amine-functionalized MCF (denoted as microZIF-8@MCF and nanoZIF-8@MCF, respectively). The synthesized hierarchical micro/mesoporous ZIF-8@MCF structures were characterized with several spectroscopic techniques including X-ray diffraction (XRD), solid-state NMR, and FT-IR and electron microscopic techniques (scanning electron microscope, SEM, and transmission electron microscopy, TEM). In addition, the pervaporation measurements of the liquid water/ethanol mixture show that nanoZIF-8@MCF/PVA (poly(vinyl alcohol) mixed-matrix membrane exhibits enhanced performance both on the permeability and separation factor. Compared to conventional routes for chemical etching, this study demonstrates a promising and simple strategy for synthesizing novel hierarchical porous composites exhibiting both advantages of mesoporous materials and microporous materials, which is expected to be useful for gas adsorption, separation, and catalysis.

  20. Vapor Phase Transport Synthesis of Zeolites from Sol-Gel Precursors

    SciTech Connect

    THOMA,STEVEN G.; NENOFF,TINA M.

    2000-07-14

    A study of zeolite crystallization from sol-gel precursors using the vapor phase transport synthesis method has been performed. Zeolites (ZSM-5, ZSM-48, Zeolite P, and Sodalite) were crystallized by contacting vapor phase organic or organic-water mixtures with dried sodium silicate and dried sodium alumino-silicate gels. For each precursor gel, a ternary phase system of vapor phase organic reactant molecules was explored. The vapor phase reactant mixtures ranged from pure ethylene diamene, triethylamine, or water, to an equimolar mixture of each. In addition, a series of gels with varied physical and chemical properties were crystallized using the same vapor phase solvent mixture for each gel. The precursor gels and the crystalline products were analyzed via Scanning Electron Microscopy, Electron Dispersive Spectroscopy, X-ray mapping, X-ray powder diffraction, nitrogen surface area, Fourier Transform Infrared Spectroscopy, and thermal analyses. The product phase and purity as a function of the solvent mixture, precursor gel structure, and precursor gel chemistry is discussed.

  1. Growth of zeolite crystals in the microgravity environment of space

    NASA Technical Reports Server (NTRS)

    Sacco, A., Jr.; Sand, L. B.; Collette, D.; Dieselman, K.; Crowley, J.; Feitelberg, A.

    1986-01-01

    Zeolites are hydrated, crystalline aluminosilicates with alkali and alkaling earth metals substituted into cation vacancies. Typically zeolite crystals are 3 to 8 microns. Larger cyrstals are desirable. Large zeolite crystals were produced (100 to 200 microns); however, they have taken restrictively long times to grow. It was proposed if the rate of nucleation or in some other way the number of nuclei can be lowered, fewer, larger crystals will be formed. The microgravity environment of space may provide an ideal condition to achieve rapid growth of large zeolite crystals. The objective of the project is to establish if large zeolite crystals can be formed rapidly in space.

  2. Early age hydration and pozzolanic reaction in natural zeolite blended cements: Reaction kinetics and products by in situ synchrotron X-ray powder diffraction

    SciTech Connect

    Snellings, R.; Mertens, G.; Cizer, O.; Elsen, J.

    2010-12-15

    The in situ early-age hydration and pozzolanic reaction in cements blended with natural zeolites were investigated by time-resolved synchrotron X-ray powder diffraction with Rietveld quantitative phase analysis. Chabazite and Na-, K-, and Ca-exchanged clinoptilolite materials were mixed with Portland cement in a 3:7 weight ratio and hydrated in situ at 40 {sup o}C. The evolution of phase contents showed that the addition of natural zeolites accelerates the onset of C{sub 3}S hydration and precipitation of CH and AFt. Kinetic analysis of the consumption of C{sub 3}S indicates that the enveloping C-S-H layer is thinner and/or less dense in the presence of alkali-exchanged clinoptilolite pozzolans. The zeolite pozzolanic activity is interpreted to depend on the zeolite exchangeable cation content and on the crystallinity. The addition of natural zeolites alters the structural evolution of the C-S-H product. Longer silicate chains and a lower C/S ratio are deduced from the evolution of the C-S-H b-cell parameter.

  3. Reclaiming silver from silver zeolite

    SciTech Connect

    Reimann, G.A.

    1991-10-01

    Silver zeolite is used to capture radioiodines from air cleaning systems in some nuclear facilities at the Idaho National Engineering Laboratory. It may become radioactively contaminated and/or poisoned by hydrocarbon vapors, which diminishes its capacity for iodine. Silver zeolite contains up to 38 wt% silver. A pyrometallurgical process was developed to reclaim the silver before disposing of the unserviceable zeolite as a radioactive waste. A flux was formulated to convert the refractory aluminosilicate zeolite structure into a low-melting fluid slag, with Na{sub 2}O added as NAOH instead of Na{sub 2}CO{sub 3} to avoid severe foaming due to CO{sub 2} evolution. A propane-fired furnace was built to smelt 45 kg charges at 1300C in a carbon-bonded silicon carbide crucible. A total of 218 kg (7000 tr oz) of silver was reclaimed from 1050 kg of unserviceable zeolite. Silver recoveries of 97% were achieved, and the radioisotopes were fixed as stable silicates in a vitreous slag that was disposed of as a low level waste. Recovered silver was refined using oxygen and cast into 100 tr oz bars assaying 99.8+% silver and showing no radioactive contamination.

  4. Reclaiming silver from silver zeolite

    SciTech Connect

    Reimann, G.A.

    1991-10-01

    Silver zeolite is used to capture radioiodines from air cleaning systems in some nuclear facilities at the Idaho National Engineering Laboratory. It may become radioactively contaminated and/or poisoned by hydrocarbon vapors, which diminishes its capacity for iodine. Silver zeolite contains up to 38 wt% silver. A pyrometallurgical process was developed to reclaim the silver before disposing of the unserviceable zeolite as a radioactive waste. A flux was formulated to convert the refractory aluminosilicate zeolite structure into a low-melting fluid slag, with Na[sub 2]O added as NAOH instead of Na[sub 2]CO[sub 3] to avoid severe foaming due to CO[sub 2] evolution. A propane-fired furnace was built to smelt 45 kg charges at 1300C in a carbon-bonded silicon carbide crucible. A total of 218 kg (7000 tr oz) of silver was reclaimed from 1050 kg of unserviceable zeolite. Silver recoveries of 97% were achieved, and the radioisotopes were fixed as stable silicates in a vitreous slag that was disposed of as a low level waste. Recovered silver was refined using oxygen and cast into 100 tr oz bars assaying 99.8+% silver and showing no radioactive contamination.

  5. [What a physician should know about zeolites].

    PubMed

    Boranić, M

    2000-01-01

    Zeolites are natural and synthetic hydrated crystalline aluminosilicates endowed with absorptive and ion exchange properties. They have found numerous and multifarous applications--in industry as catalysts and absorbents, in water sanitation for the removal of ammonia and heavy metals, in agriculture as fertilizers, and in animal husbandry as the absorbents of excreted material and as food additives. Medical applications have included the use in filtration systems for anesthesia or dialysis and as the contrast materials in NMR imaging. Recently, zeolite powders for external use have found application as deodorants, antimycotic agents and wound dressings. Peroral use of encapsulated zeolite powders enriched with vitamins, oligoelements or other ingredients has been claimed to exert beneficial medical effects. Ingestion of zeolites may be considered analogous to the clay eating (geophagia), considered in traditional medicine as a remedy for various illnesses. Being amphoteric, zeolites are partly soluble in acid or alkaline media, but within the physiological pH range the solubility is generally low. Minimal amounts of free aluminium or silicium from the ingested zeolites are resorbed from the gut. The bulk of ingested zeolite probably remains undissolved in the gut. In view of the ion exchange properties, zeolites may be expected to change the ionic content, pH and buffering capacity of the gastrointestinal secretions and to affect the transport through the intestinal epithelium. In addition, zeolites could affect the bacterial flora and the resorption of bacterial products, vitamins and oligoelements. The contact of zeolite particles with gastrointestinal mucosa may elicit the secretion of cytokines with local and systemic actions. Reactive silicium ions might react with biomolecules of the intestinal epithelium, and if resorbed, do so in other cells. Mutagenic and carcinogenic effects of zeolite particles have been described, resembling such effects of asbestos

  6. Novel Approach for Clustering Zeolite Crystal Structures.

    PubMed

    Lach-Hab, M; Yang, S; Vaisman, I I; Blaisten-Barojas, E

    2010-04-12

    Informatics approaches play an increasingly important role in the design of new materials. In this work we apply unsupervised statistical learning for identifying four framework-type attractors of zeolite crystals in which several of the zeolite framework types are grouped together. Zeolites belonging to these super-classes manifest important topological, chemical and physical similarities. The zeolites form clusters located around four core framework types: LTA, FAU, MFI and the combination of EDI, HEU, LTL and LAU. Clustering is performed in a 9-dimensional space of attributes that reflect topological, chemical and physical properties for each individual zeolite crystalline structure. The implemented machine learning approach relies on hierarchical top-down clustering approach and the expectation maximization method. The model is trained and tested on ten partially independent data sets from the FIZ/NIST Inorganic Crystal Structure Database.

  7. Prediction of Zeolite Framework Types by a Machine Learning Approach

    NASA Astrophysics Data System (ADS)

    Yang, Shujiang; Lach-Hab, Mohammed; Vaisman, Iosif; Blaisten-Barojas, Estela

    2009-03-01

    Zeolites are microporous crystalline materials with highly regular framework structures consisting of molecular-sized pores and channels. Characteristic framework types of zeolites are traditionally determined by the combined information of coordination sequences and vertex symbols. Here we present a machine learning model for classifying zeolite crystals according to their framework types. An eighteen-dimensional feature vector is defined including topological descriptors and physical/chemical properties of zeolite crystals [Microporous and Mesoporous Materials 117, 339 (2009)]. Trained with crystallographic data of known zeolites, the new model can predict the framework types of unknown zeolite crystals with up to 98 % accuracy. Compared with conventional methods, the machine learning model is more robust handling crystal disorder and/or crystal defects in a more effective manner. This model can be adapted for classifying and clustering other crystalline species.

  8. Synthesis of NaY zeolite on preformed kaolinite spheres. Evolution of zeolite content and textural properties with the reaction time

    SciTech Connect

    Basaldella, E.I.; Bonetto, R.; Tara, J.C. )

    1993-04-01

    The synthesis of NaY zeolite was carried out on fired kaolinite microspheres. Changes in porosity, chemical composition, and crystallinity of the solid show zeolite growth on both internal and external microsphere surfaces. It was also observed that, as a consequence of the alkaline treatment, the SiO[sub 2]/Al[sub 2]O[sub 3] ratio in the solid diminishes prior to the appearance of the zeolite, but increases when the zeolite begins to crystallize.

  9. Properties of Zeolite A Obtained from Powdered Laundry Detergent: An Undergraduate Chemistry Experiment

    NASA Astrophysics Data System (ADS)

    Lindquist, David A.; Smoot, Alison L.

    1997-05-01

    Zeolites, crystalline porous aluminosilicates, are valued for their ability to absorb ions and molecules as well as function as catalysts. A number of laboratory experiments using zeolites filtered from a suspension of powdered laundry detergent are described. The various experiments illustrate the myriad uses of zeolites as desiccants, ion exchange materials, and catalysts.

  10. 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.

  11. Understanding silicate hydration from quantitative analyses of hydrating tricalcium silicates.

    PubMed

    Pustovgar, Elizaveta; Sangodkar, Rahul P; Andreev, Andrey S; Palacios, Marta; Chmelka, Bradley F; Flatt, Robert J; d'Espinose de Lacaillerie, Jean-Baptiste

    2016-01-01

    Silicate hydration is prevalent in natural and technological processes, such as, mineral weathering, glass alteration, zeolite syntheses and cement hydration. Tricalcium silicate (Ca3SiO5), the main constituent of Portland cement, is amongst the most reactive silicates in water. Despite its widespread industrial use, the reaction of Ca3SiO5 with water to form calcium-silicate-hydrates (C-S-H) still hosts many open questions. Here, we show that solid-state nuclear magnetic resonance measurements of (29)Si-enriched triclinic Ca3SiO5 enable the quantitative monitoring of the hydration process in terms of transient local molecular composition, extent of silicate hydration and polymerization. This provides insights on the relative influence of surface hydroxylation and hydrate precipitation on the hydration rate. When the rate drops, the amount of hydroxylated Ca3SiO5 decreases, thus demonstrating the partial passivation of the surface during the deceleration stage. Moreover, the relative quantities of monomers, dimers, pentamers and octamers in the C-S-H structure are measured. PMID:27009966

  12. Understanding silicate hydration from quantitative analyses of hydrating tricalcium silicates.

    PubMed

    Pustovgar, Elizaveta; Sangodkar, Rahul P; Andreev, Andrey S; Palacios, Marta; Chmelka, Bradley F; Flatt, Robert J; d'Espinose de Lacaillerie, Jean-Baptiste

    2016-03-24

    Silicate hydration is prevalent in natural and technological processes, such as, mineral weathering, glass alteration, zeolite syntheses and cement hydration. Tricalcium silicate (Ca3SiO5), the main constituent of Portland cement, is amongst the most reactive silicates in water. Despite its widespread industrial use, the reaction of Ca3SiO5 with water to form calcium-silicate-hydrates (C-S-H) still hosts many open questions. Here, we show that solid-state nuclear magnetic resonance measurements of (29)Si-enriched triclinic Ca3SiO5 enable the quantitative monitoring of the hydration process in terms of transient local molecular composition, extent of silicate hydration and polymerization. This provides insights on the relative influence of surface hydroxylation and hydrate precipitation on the hydration rate. When the rate drops, the amount of hydroxylated Ca3SiO5 decreases, thus demonstrating the partial passivation of the surface during the deceleration stage. Moreover, the relative quantities of monomers, dimers, pentamers and octamers in the C-S-H structure are measured.

  13. Understanding silicate hydration from quantitative analyses of hydrating tricalcium silicates

    PubMed Central

    Pustovgar, Elizaveta; Sangodkar, Rahul P.; Andreev, Andrey S.; Palacios, Marta; Chmelka, Bradley F.; Flatt, Robert J.; d'Espinose de Lacaillerie, Jean-Baptiste

    2016-01-01

    Silicate hydration is prevalent in natural and technological processes, such as, mineral weathering, glass alteration, zeolite syntheses and cement hydration. Tricalcium silicate (Ca3SiO5), the main constituent of Portland cement, is amongst the most reactive silicates in water. Despite its widespread industrial use, the reaction of Ca3SiO5 with water to form calcium-silicate-hydrates (C-S-H) still hosts many open questions. Here, we show that solid-state nuclear magnetic resonance measurements of 29Si-enriched triclinic Ca3SiO5 enable the quantitative monitoring of the hydration process in terms of transient local molecular composition, extent of silicate hydration and polymerization. This provides insights on the relative influence of surface hydroxylation and hydrate precipitation on the hydration rate. When the rate drops, the amount of hydroxylated Ca3SiO5 decreases, thus demonstrating the partial passivation of the surface during the deceleration stage. Moreover, the relative quantities of monomers, dimers, pentamers and octamers in the C-S-H structure are measured. PMID:27009966

  14. Thermodynamic modeling of natural zeolite stability

    SciTech Connect

    Chipera, S.J.; Bish, D.L.

    1997-06-01

    Zeolites occur in a variety of geologic environments and are used in numerous agricultural, commercial, and environmental applications. It is desirable to understand their stability both to predict future stability and to evaluate the geochemical conditions resulting in their formation. The use of estimated thermodynamic data for measured zeolite compositions allows thermodynamic modeling of stability relationships among zeolites in different geologic environments (diagenetic, saline and alkaline lakes, acid rock hydrothermal, basic rock, deep sea sediments). This modeling shows that the relative cation abundances in both the aqueous and solid phases, the aqueous silica activity, and temperature are important factors in determining the stable zeolite species. Siliceous zeolites (e.g., clinoptilolite, mordenite, erionite) present in saline and alkaline lakes or diagenetic deposits formed at elevated silica activities. Aluminous zeolites (e.g., natrolite, mesolite/scolecite, thomsonite) formed in basic rocks in association with reduced silica activities. Likewise, phillipsite formation is favored by reduced aqueous silica activities. The presence of erionite, chabazite, and phillipsite are indicative of environments with elevated potassium concentrations. Elevated temperature, calcic water conditions, and reduced silica activity help to enhance the laumontite and wairakite stability fields. Analcime stability increases with increased temperature and aqueous Na concentration, and/or with decreased silica activity.

  15. Inclusion of polyaniline filaments in zeolite molecular sieves

    SciTech Connect

    Enzel, P.; Bein, T. )

    1989-08-24

    Polyaniline has been synthesized in the channels of mordenite (one-dimensional) and zeolite Y (three-dimensional). Aniline was diffused from hexane solution into dehydrated zeolite pores containing different concentrations of framework hydroxyl groups. Addition of (NH{sub 4}){sub 2}S{sub 2}O{sub 8} to an aqueous suspension of the loaded zeolites afforded intrazeolite polyaniline chains, as demonstrated by FTIR, electronic absorption data, and recovery of the included polymer. Stoichiometric, kinetic, XPS, and microscopic data and the absence of bulk conductivity of the polymer/zeolite powders lead to the conclusion that the polymer is formed inside the host channel system. While the polyaniline chains in mordenite channels appear to be more highly oxidized than in Y zeolite, both systems show spectroscopic features typical of emeraldine base and emeraldine salt polymers. The polyaniline/zeolite hybrids represent a new class of materials containing synthetic conductors encapsulated in crystalline inorganic hosts with channel systems of molecular dimensions.

  16. Synthesis and catalytic applications of combined zeolitic/mesoporous materials

    PubMed Central

    Vernimmen, Jarian; Cool, Pegie

    2011-01-01

    Summary In the last decade, research concerning nanoporous siliceous materials has been focused on mesoporous materials with intrinsic zeolitic features. These materials are thought to be superior, because they are able to combine (i) the enhanced diffusion and accessibility for larger molecules and viscous fluids typical of mesoporous materials with (ii) the remarkable stability, catalytic activity and selectivity of zeolites. This review gives an overview of the state of the art concerning combined zeolitic/mesoporous materials. Focus is put on the synthesis and the applications of the combined zeolitic/mesoporous materials. The different synthesis approaches and formation mechanisms leading to these materials are comprehensively discussed and compared. Moreover, Ti-containing nanoporous materials as redox catalysts are discussed to illustrate a potential implementation of combined zeolitic/mesoporous materials. PMID:22259762

  17. A pair distribution function analysis of zeolite beta

    SciTech Connect

    Martinez-Inesta, M.M.; Peral, I.; Proffen, T.; Lobo, R.F.

    2010-07-20

    We describe the structural refinement of zeolite beta using the local structure obtained with the pair distribution function (PDF) method. A high quality synchrotron and two neutron scattering datasets were obtained on two samples of siliceous zeolite beta. The two polytypes that make up zeolite beta have the same local structure; therefore refinement of the two structures was possible using the same experimental PDF. Optimized structures of polytypes A and B were used to refine the structures using the program PDFfit. Refinements using only the synchrotron or the neutron datasets gave results inconsistent with each other but a cyclic refinement with the two datasets gave a good fit to both PDFs. The results show that the PDF method is a viable technique to analyze the local structure of disordered zeolites. However, given the complexity of most zeolite frameworks, the use of both X-ray and neutron radiation and high-resolution patterns is essential to obtain reliable refinements.

  18. Factors that Determine Zeolite Stability in Hot Liquid Water.

    PubMed

    Zhang, Lu; Chen, Kuizhi; Chen, Banghao; White, Jeffery L; Resasco, Daniel E

    2015-09-16

    The susceptibility of zeolites to hot liquid water may hamper their full utilization in aqueous phase processes, such as those involved in biomass conversion and upgrading reactions. Interactions of zeolites with water strongly depend on the presence of hydrophilic moieties including Brønsted acid sites (BAS), extraframework cations, and silanol defects, which facilitate wetting of the surface. However, it is not clear which of these moieties are responsible for the susceptibility of zeolites to liquid water. Previous studies have offered contradictory explanations because the role of each of these characteristics has not been investigated independently. In this work, a systematic comparison has been attempted by relating crystallinity losses to the variation of each of the five zeolite characteristics that may influence their stability in liquid water, including number of BAS, Si-O-Si bonds, framework type, silanol defects, and extraframework Al. In this study, we have systematically monitored the crystallinity changes of a series of HY, H-ZSM-5, and H-β zeolite samples with varying Si/Al ratio, density of BAS, zeolite structure, and density of silanol defects upon exposure to liquid water at 200 °C. The results of this comparison unambiguously indicate that the density of silanol defects plays the most crucial role in determining susceptibility of zeolites to hot liquid water. By functionalizing the silanol defects with organosilanes, the hydrophobicity of defective zeolite is increased and the tolerance to hot liquid water is significantly enhanced. PMID:26301890

  19. Synthesis of zeolite as ordered multicrystal arrays.

    PubMed

    Lee, Jin Seok; Lee, Yun-Jo; Tae, Eunju Lee; Park, Yong Soo; Yoon, Kyung Byung

    2003-08-01

    Zeolites are crystalline nanoporous aluminosilicates widely used in industry. In order for zeolites to find applications as innovative materials, they need to be organized into large two- and three-dimensional (2D and 3D) arrays. We report that uniformly aligned polyurethane films can serve as templates for the synthesis of uniformly aligned 2D and possibly 3D arrays of silicalite-1 crystals, in which the orientations of the crystals are controlled by the nature of the polymers. We propose that the supramolecularly organized organic-inorganic composites that consist of the hydrolyzed organic products and the seed crystals are responsible for this phenomenon.

  20. ZEOLITES: EFFECTIVE WATER PURIFIERS

    EPA Science Inventory

    Zeolites are known for their adsorption, ion exchange and catalytic properties. Various natural zeolites are used as odor and moisture adsorbents and water softeners. Due to their acidic nature, synthetic zeolites are commonly employed as solid acid catalysts in petrochemical ind...

  1. Zeolite-like liquid crystals

    PubMed Central

    Poppe, Silvio; Lehmann, Anne; Scholte, Alexander; Prehm, Marko; Zeng, Xiangbing; Ungar, Goran; Tschierske, Carsten

    2015-01-01

    Zeolites represent inorganic solid-state materials with porous structures of fascinating complexity. Recently, significant progress was made by reticular synthesis of related organic solid-state materials, such as metal-organic or covalent organic frameworks. Herein we go a step further and report the first example of a fluid honeycomb mimicking a zeolitic framework. In this unique self-assembled liquid crystalline structure, transverse-lying π-conjugated rod-like molecules form pentagonal channels, encircling larger octagonal channels, a structural motif also found in some zeolites. Additional bundles of coaxial molecules penetrate the centres of the larger channels, unreachable by chains attached to the honeycomb framework. This creates a unique fluid hybrid structure combining positive and negative anisotropies, providing the potential for tuning the directionality of anisotropic optical, electrical and magnetic properties. This work also demonstrates a new approach to complex soft-matter self-assembly, by using frustration between space filling and the entropic penalty of chain extension. PMID:26486751

  2. Improved Catalysts for Heavy Oil Upgrading Based on Zeolite Y Nanoparticles Encapsulated Stable Nanoporous Host

    SciTech Connect

    Conrad Ingram; Mark Mitchell

    2007-09-30

    The objective of this project is to synthesize nanocrystals of highly acidic zeolite Y nanoclusters, encapsulate them within the channels of mesoporous (nanoporous) silicates or nanoporous organosilicates, and evaluate the 'zeolite Y/Nanoporous host' composites as catalysts for the upgrading of heavy petroleum feedstocks. In comparison to conventionally-used zeolite Y catalysts of micron size particles, the nanocrystals (< 100 nm particle size) which contain shorter path lengths, are expected to allow faster diffusion of large hydrocarbon substrates and the catalysis products within and out of the zeolite's channels and cages (<1 nm size). This is expected to significantly reduce deactivation of the catalyst and to prolong their period of reactivity. Encapsulating zeolite Y nanocrystals within the nanoporous materials is expected to protect its external surfaces and pore entrances from being blocked by large hydrocarbon substrates, since these substrates will initially be converted to small molecules by the nanoporous host (a catalyst in its own right). The project consisted of four major tasks as follows: (1) synthesis of the nanoparticles of zeolite Y (of various chemical compositions) using various techniques such as the addition of organic additives to conventional zeolite Y synthesis mixtures to suppress zeolite Y crystal growth; (2) synthesis of nanoporous silicate host materials of up to 30 nm pore diameter, using poly (alkylene oxide) copolymers which when removed will yield a mesoporous material; (3) synthesis of zeolite Y/Nanoporous Host composite materials as potential catalysts; and (4) evaluation of the catalyst for the upgrading of heavy petroleum feedstocks.

  3. Zeolite catalysis: technology

    SciTech Connect

    Heinemann, H.

    1980-07-01

    Zeolites have been used as catalysts in industry since the early nineteen sixties. The great majority of commercial applications employ one of three zeolite types: zeolite Y; Mordenite; ZSM-5. By far the largest use of zeolites is in catalytic cracking, and to a lesser extent in hydrocracking. This paper reviews the rapid development of zeolite catalysis and its application in industries such as: the production of gasoline by catalytic cracking of petroleum; isomerization of C/sub 5/ and C/sub 6/ paraffin hydrocarbons; alkylation of aromatics with olefins; xylene isomerization; and conversion of methanol to gasoline.

  4. 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.

  5. IN SITU INFRARED MEASUREMENTS OF FREE-FLYING SILICATE DURING CONDENSATION IN THE LABORATORY

    SciTech Connect

    Ishizuka, Shinnosuke; Kimura, Yuki; Sakon, Itsuki

    2015-04-20

    We developed a new experimental system for infrared (IR) measurements on free-flying nucleating nanoparticles in situ and applied it to studies on silicate particles. We monitored the condensation of magnesium-bearing silicate nanoparticles from thermally evaporated magnesium and silicon monoxide vapor under an atmosphere of oxygen and argon. The IR spectrum of newly condensed particles showed a spectral feature for non-crystalline magnesium-bearing silicate that is remarkably consistent with the IR spectrum of astronomically observed non-crystalline silicate around oxygen-rich evolved stars. The silicate crystallized at <500 K and eventually developed a high crystallinity. Because of the size effects of nanoparticles, the silicate would be expected to be like a liquid at least during the initial stages of nucleation and growth. Our experimental results therefore suggest decreasing the possible formation temperature of crystalline silicates in dust formation environments with relatively higher pressure.

  6. In Situ Infrared Measurements of Free-flying Silicate during Condensation in the Laboratory

    NASA Astrophysics Data System (ADS)

    Ishizuka, Shinnosuke; Kimura, Yuki; Sakon, Itsuki

    2015-04-01

    We developed a new experimental system for infrared (IR) measurements on free-flying nucleating nanoparticles in situ and applied it to studies on silicate particles. We monitored the condensation of magnesium-bearing silicate nanoparticles from thermally evaporated magnesium and silicon monoxide vapor under an atmosphere of oxygen and argon. The IR spectrum of newly condensed particles showed a spectral feature for non-crystalline magnesium-bearing silicate that is remarkably consistent with the IR spectrum of astronomically observed non-crystalline silicate around oxygen-rich evolved stars. The silicate crystallized at <500 K and eventually developed a high crystallinity. Because of the size effects of nanoparticles, the silicate would be expected to be like a liquid at least during the initial stages of nucleation and growth. Our experimental results therefore suggest decreasing the possible formation temperature of crystalline silicates in dust formation environments with relatively higher pressure.

  7. Zeolite membranes from kaolin

    SciTech Connect

    Karle, B.G.; Brinker, C.J. |; Phillips, M.L.F.

    1996-07-01

    Zeolite films are sought as components of molecular sieve membranes. Different routes used to prepare zeolite composite membranes include growing zeolite layers from gels on porous supports, depositing oriented zeolites on supports, and dispersing zeolites in polymeric membranes. In most cases, it is very difficult to control and avoid the formation of cracks and/or pinholes. The approach to membrane synthesis is based on hydrothermally converting films of layered aluminosilicates into zeolite films. The authors have demonstrated this concept by preparing zeolite A membranes on alumina supports from kaolin films. The authors have optimized the process parameters not only for desired bulk properties, but also for preparing thin (ca. 5 {micro}m), continuous zeolite A films. Scanning electron microscopy shows highly intergrown zeolite A crystals over most of the surface area of the membrane, but gas permeation experiments indicate existence of mesoporous defects and/or intercrystalline gaps. It has been demonstrated that the thickness of the final zeolite A membrane can be controlled by limiting the amount of precursor kaolin present in the membrane.

  8. Biological and therapeutic effects of ortho-silicic acid and some ortho-silicic acid-releasing compounds: New perspectives for therapy

    PubMed Central

    2013-01-01

    Silicon (Si) is the most abundant element present in the Earth's crust besides oxygen. However, the exact biological roles of silicon remain unknown. Moreover, the ortho-silicic acid (H4SiO4), as a major form of bioavailable silicon for both humans and animals, has not been given adequate attention so far. Silicon has already been associated with bone mineralization, collagen synthesis, skin, hair and nails health atherosclerosis, Alzheimer disease, immune system enhancement, and with some other disorders or pharmacological effects. Beside the ortho-silicic acid and its stabilized formulations such as choline chloride-stabilized ortho-silicic acid and sodium or potassium silicates (e.g. M2SiO3; M= Na,K), the most important sources that release ortho-silicic acid as a bioavailable form of silicon are: colloidal silicic acid (hydrated silica gel), silica gel (amorphous silicon dioxide), and zeolites. Although all these compounds are characterized by substantial water insolubility, they release small, but significant, equilibrium concentration of ortho-silicic acid (H4SiO4) in contact with water and physiological fluids. Even though certain pharmacological effects of these compounds might be attributed to specific structural characteristics that result in profound adsorption and absorption properties, they all exhibit similar pharmacological profiles readily comparable to ortho-silicic acid effects. The most unusual ortho-silicic acid-releasing agents are certain types of zeolites, a class of aluminosilicates with well described ion(cation)-exchange properties. Numerous biological activities of some types of zeolites documented so far might probably be attributable to the ortho-silicic acid-releasing property. In this review, we therefore discuss biological and potential therapeutic effects of ortho-silicic acid and ortho-silicic acid -releasing silicon compounds as its major natural sources. PMID:23298332

  9. Biological and therapeutic effects of ortho-silicic acid and some ortho-silicic acid-releasing compounds: New perspectives for therapy.

    PubMed

    Jurkić, Lela Munjas; Cepanec, Ivica; Pavelić, Sandra Kraljević; Pavelić, Krešimir

    2013-01-01

    Silicon (Si) is the most abundant element present in the Earth's crust besides oxygen. However, the exact biological roles of silicon remain unknown. Moreover, the ortho-silicic acid (H4SiO4), as a major form of bioavailable silicon for both humans and animals, has not been given adequate attention so far. Silicon has already been associated with bone mineralization, collagen synthesis, skin, hair and nails health atherosclerosis, Alzheimer disease, immune system enhancement, and with some other disorders or pharmacological effects. Beside the ortho-silicic acid and its stabilized formulations such as choline chloride-stabilized ortho-silicic acid and sodium or potassium silicates (e.g. M2SiO3; M= Na,K), the most important sources that release ortho-silicic acid as a bioavailable form of silicon are: colloidal silicic acid (hydrated silica gel), silica gel (amorphous silicon dioxide), and zeolites. Although all these compounds are characterized by substantial water insolubility, they release small, but significant, equilibrium concentration of ortho-silicic acid (H4SiO4) in contact with water and physiological fluids. Even though certain pharmacological effects of these compounds might be attributed to specific structural characteristics that result in profound adsorption and absorption properties, they all exhibit similar pharmacological profiles readily comparable to ortho-silicic acid effects. The most unusual ortho-silicic acid-releasing agents are certain types of zeolites, a class of aluminosilicates with well described ion(cation)-exchange properties. Numerous biological activities of some types of zeolites documented so far might probably be attributable to the ortho-silicic acid-releasing property. In this review, we therefore discuss biological and potential therapeutic effects of ortho-silicic acid and ortho-silicic acid -releasing silicon compounds as its major natural sources.

  10. Zeolite thin films: from computer chips to space stations.

    PubMed

    Lew, Christopher M; Cai, Rui; Yan, Yushan

    2010-02-16

    Zeolites are a class of crystalline oxides that have uniform and molecular-sized pores (3-12 A in diameter). Although natural zeolites were first discovered in 1756, significant commercial development did not begin until the 1950s when synthetic zeolites with high purity and controlled chemical composition became available. Since then, major commercial applications of zeolites have been limited to catalysis, adsorption, and ion exchange, all using zeolites in powder form. Although researchers have widely investigated zeolite thin films within the last 15 years, most of these studies were motivated by the potential application of these materials as separation membranes and membrane reactors. In the last decade, we have recognized and demonstrated that zeolite thin films can have new, diverse, and economically significant applications that others had not previously considered. In this Account, we highlight our work on the development of zeolite thin films as low-dielectric constant (low-k) insulators for future generation computer chips, environmentally benign corrosion-resistant coatings for aerospace alloys, and hydrophilic and microbiocidal coatings for gravity-independent water separation in space stations. Although these three applications might not seem directly related, they all rely on the ability to fine-tune important macroscopic properties of zeolites by changing their ratio of silicon to aluminum. For example, pure-silica zeolites (PSZs, Si/Al = infinity) are hydrophobic, acid stable, and have no ion exchange capacity, while low-silica zeolites (LSZs, Si/Al < 2) are hydrophilic, acid soluble, and have a high ion exchange capacity. These new thin films also take advantage of some unique properties of zeolites that have not been exploited before, such as a higher elastic modulus, hardness, and heat conductivity than those of amorphous porous silicas, and microbiocidal capabilities derived from their ion exchange capacities. Finally, we briefly discuss our

  11. Zeolite thin films: from computer chips to space stations.

    PubMed

    Lew, Christopher M; Cai, Rui; Yan, Yushan

    2010-02-16

    Zeolites are a class of crystalline oxides that have uniform and molecular-sized pores (3-12 A in diameter). Although natural zeolites were first discovered in 1756, significant commercial development did not begin until the 1950s when synthetic zeolites with high purity and controlled chemical composition became available. Since then, major commercial applications of zeolites have been limited to catalysis, adsorption, and ion exchange, all using zeolites in powder form. Although researchers have widely investigated zeolite thin films within the last 15 years, most of these studies were motivated by the potential application of these materials as separation membranes and membrane reactors. In the last decade, we have recognized and demonstrated that zeolite thin films can have new, diverse, and economically significant applications that others had not previously considered. In this Account, we highlight our work on the development of zeolite thin films as low-dielectric constant (low-k) insulators for future generation computer chips, environmentally benign corrosion-resistant coatings for aerospace alloys, and hydrophilic and microbiocidal coatings for gravity-independent water separation in space stations. Although these three applications might not seem directly related, they all rely on the ability to fine-tune important macroscopic properties of zeolites by changing their ratio of silicon to aluminum. For example, pure-silica zeolites (PSZs, Si/Al = infinity) are hydrophobic, acid stable, and have no ion exchange capacity, while low-silica zeolites (LSZs, Si/Al < 2) are hydrophilic, acid soluble, and have a high ion exchange capacity. These new thin films also take advantage of some unique properties of zeolites that have not been exploited before, such as a higher elastic modulus, hardness, and heat conductivity than those of amorphous porous silicas, and microbiocidal capabilities derived from their ion exchange capacities. Finally, we briefly discuss our

  12. Delaminated zeolites: Combining the benefits of zeolites and mesoporous materials for catalytic uses

    SciTech Connect

    Corma, A.; Fornes, V.; Martinez-Triguero, J.; Pergher, S.B.

    1999-08-15

    The delamination of the layered precursor of the MCM-22 zeolite (MWW structure) affords monolayers of a crystalline aluminosilicate with more than 700 m{sup 2}/g of a well defined external surface formed by cups of 0.7 x 0.7 nm. In this layered structure the circular 10-member-ring microporous system is preserved. The resultant material presents the strong acidity and stability characteristic of the zeolites but, at the same time, offers the high accessibility to large molecules characteristic of the amorphous aluminosilicates. The cracking behavior during the process of small and large molecules has been compared with that of the zeolite MCM-22 and pillared laminar precursor MCM-36.

  13. Mechanism of hierarchical porosity development in MFI zeolites by desilication: the role of aluminium as a pore-directing agent.

    PubMed

    Groen, Johan C; Peffer, Louk A A; Moulijn, Jacob A; Pérez-Ramírez, Javier

    2005-08-19

    The role of the concentration and the nature of aluminium in the creation of hierarchical porosity in both commercial and synthesized MFI zeolites have been investigated through controlled mesoporosity development by desilication in alkaline medium. Framework aluminium controls the process of framework silicon extraction and makes desilication selective towards intracrystalline mesopore formation. An optimal molar Si/Al ratio in the range 25-50 has been identified; this leads to an optimal mesoporosity centred around 10 nm and mesopore surface areas of up to 235 m(2) g(-1) while preserving the intrinsic crystalline and acidic properties. At lower framework Si/Al ratios the relatively high Al content inhibits Si extraction and hardly any mesopores are created, while in highly siliceous ZSM-5 unselective extraction of framework Si induces formation of large pores. The existence of framework Al sites in different T positions that are more or less susceptible to the alkaline treatment, and the occurrence of re-alumination, are tentative explanations for the remarkable behaviour of Al in the desilication process. The presence of substantial extra framework Al, obtained by steam treatment, inhibits Si extraction and related mesopore formation; this is attributed to re-alumination of the extraframework Al species during the alkaline treatment. Removal of extraframework Al species by mild oxalic acid treatment restores susceptibility to desilication, which is accompanied by formation of larger mesopores due to the enhanced Si/Al ratio in the acid-treated zeolite.

  14. Growth of large zeolite crystals in space

    SciTech Connect

    Sacco, A. Jr.; Dixon, A.; Thompson, R.; Scott, G.; Ditr, J.

    1988-01-01

    Synthesis studies performed using close analogs of triethanolamine (TEA) have shown that all three hydroxyl groups and the amine group in this molecule are necessary to provide nucleation suppression. Studies using C-13 nuclear magnetic resonance (NMR) revealed that the hydroxyl ions and the amine group are involved in the formation of an aluminum complex. It was also shown that silicate species do not interact this way with TEA in an alkaline solution. These results suggest that successful aluminum complexation leads to nucleation in zeolite-A crystallization.

  15. Growth of large zeolite crystals in space

    NASA Technical Reports Server (NTRS)

    Sacco, A., Jr.; Dixon, A.; Thompson, R.; Scott, G.; Ditr, J.

    1988-01-01

    Synthesis studies performed using close analogs of triethanolamine (TEA) have shown that all three hydroxyl groups and the amine group in this molecule are necessary to provide nucleation suppression. Studies using C-13 nuclear magnetic resonance (NMR) revealed that the hydroxyl ions and the amine group are involved in the formation of an aluminum complex. It was also shown that silicate species fo not interact this way with TEA in an alkaline solution. These results suggest that successful aluminum complexation leads to nucleation in zeolite-A crystallization.

  16. Wet gringing of zeolite in stirred media mill

    NASA Astrophysics Data System (ADS)

    Mucsi, G.; Bohács, K.

    2016-04-01

    In the present study the results of systematic experimental series are presented with the specific goal of optimizing the zeolite nanoparticles' production using a wet stirred media mill. The diameter of the grinding media as well as the rotor velocity were varied in the experiments. Particle size distribution and "outer" specific surface area of the ground samples were measured by a laser particle size analyser. Additionally, BET, XRD and FT-IR analyses were performed for the characterization of the "total" specific surface area as well as the crystalline and material structure, respectively. Based on the results of the laboratory experiments it was found that wet stirred media milling provided significant reductions in the particle size of zeolite. Furthermore, the crystallinity of the samples also decreased, so not only the physical but the mineralogical characteristics of zeolite can be controlled by stirred media milling.

  17. Thermodynamics of rock forming crystalline solutions

    NASA Technical Reports Server (NTRS)

    Saxena, S. K.

    1971-01-01

    Analysis of phase diagrams and cation distributions within crystalline solutions as means of obtaining thermodynamic data on rock forming crystalline solutions is discussed along with some aspects of partitioning of elements in coexisting phases. Crystalline solutions, components in a silicate mineral, and chemical potentials of these components were defined. Examples were given for calculating thermodynamic mixing functions in the CaW04-SrW04, olivine-chloride solution, and orthopyroxene systems.

  18. Dispersible Exfoliated Zeolite Nanosheets and Their Application as a Selective Membrane

    SciTech Connect

    Varoon, Kumar; Zhang, Xueyi; Elyassi, Bahman; Brewer, Damien D.; Gettel, Melissa; Kumar, Sandeep; Lee, J. Alex; Maheshwari, Sundeep; Mittal, Anudha; Sung, Chun-Yi; Cococcioni, Matteo; Francis, Lorraine F.; McCormick, Alon V.; Mkhoyan, K. Andre; Tsapatsis, Michael

    2011-10-06

    Thin zeolite films are attractive for a wide range of applications, including molecular sieve membranes, catalytic membrane reactors, permeation barriers, and low-dielectric-constant materials. Synthesis of thin zeolite films using high-aspect-ratio zeolite nanosheets is desirable because of the packing and processing advantages of the nanosheets over isotropic zeolite nanoparticles. Attempts to obtain a dispersed suspension of zeolite nanosheets via exfoliation of their lamellar precursors have been hampered because of their structure deterioration and morphological damage (fragmentation, curling, and aggregation). We demonstrated the synthesis and structure determination of highly crystalline nanosheets of zeolite frameworks MWW and MFI. The purity and morphological integrity of these nanosheets allow them to pack well on porous supports, facilitating the fabrication of molecular sieve membranes.

  19. Antimicrobial properties of zeolite-X and zeolite-A ion-exchanged with silver, copper, and zinc against a broad range of microorganisms.

    PubMed

    Demirci, Selami; Ustaoğlu, Zeynep; Yılmazer, Gonca Altın; Sahin, Fikrettin; Baç, Nurcan

    2014-02-01

    Zeolites are nanoporous alumina silicates composed of silicon, aluminum, and oxygen in a framework with cations, water within pores. Their cation contents can be exchanged with monovalent or divalent ions. In the present study, the antimicrobial (antibacterial, anticandidal, and antifungal) properties of zeolite type X and A, with different Al/Si ratio, ion exchanged with Ag(+), Zn(2+), and Cu(2+) ions were investigated individually. The study presents the synthesis and manufacture of four different zeolite types characterized by scanning electron microscopy and X-ray diffraction. The ion loading capacity of the zeolites was examined and compared with the antimicrobial characteristics against a broad range of microorganisms including bacteria, yeast, and mold. It was observed that Ag(+) ion-loaded zeolites exhibited more antibacterial activity with respect to other metal ion-embedded zeolite samples. The results clearly support that various synthetic zeolites can be ion exchanged with Ag(+), Zn(2+), and Cu(2+) ions to acquire antimicrobial properties or ion-releasing characteristics to provide prolonged or stronger activity. The current study suggested that zeolite formulations could be combined with various materials used in manufacturing medical devices, surfaces, textiles, or household items where antimicrobial properties are required.

  20. First principles derived, transferable force fields for CO2 adsorption in Na-exchanged cationic zeolites.

    PubMed

    Fang, Hanjun; Kamakoti, Preeti; Ravikovitch, Peter I; Aronson, Matthew; Paur, Charanjit; Sholl, David S

    2013-08-21

    The development of accurate force fields is vital for predicting adsorption in porous materials. Previously, we introduced a first principles-based transferable force field for CO2 adsorption in siliceous zeolites (Fang et al., J. Phys. Chem. C, 2012, 116, 10692). In this study, we extend our approach to CO2 adsorption in cationic zeolites which possess more complex structures. Na-exchanged zeolites are chosen for demonstrating the approach. These methods account for several structural complexities including Al distribution, cation positions and cation mobility, all of which are important for predicting adsorption. The simulation results are validated with high-resolution experimental measurements of isotherms and microcalorimetric heats of adsorption on well-characterized materials. The choice of first-principles method has a significant influence on the ability of force fields to accurately describe CO2-zeolite interactions. The PBE-D2 derived force field, which performed well for CO2 adsorption in siliceous zeolites, does not do so for Na-exchanged zeolites; the PBE-D2 method overestimates CO2 adsorption energies on multi-cation sites that are common in cationic zeolites with low Si/Al ratios. In contrast, a force field derived from the DFT/CC method performed well. Agreement was obtained between simulation and experiment not only for LTA-4A on which the force field fitting is based, but for other two common adsorbents, NaX and NaY.

  1. Formulation of cracking catalyst based on zeolite and natural clays

    SciTech Connect

    Aliev, R.R.; Lupina, M.I.

    1995-11-01

    Domestically manufactured cracking catalysts are based on a synthetic amorphous aluminosilicate matrix and Y zeolite. A multistage {open_quotes}gel{close_quotes} technology is used in manufacturing the catalysts. The process includes mixing solutions of sodium silicate and acidic aluminum sulfate, forming, syneresis, and activation of the beaded gel. In the manufacture of bead catalysts, the next steps in the process are washing, drying, and calcining; in the manufacture of microbead catalysts, the next steps are dispersion and formation of a hydrogel slurry, spray-drying, and calcining. The Y zeolite is either introduced into the alumina-silica sol in the stage of forming the beads, or introduced in the dispersion stage. With the aim of developing an active and selective cracking catalyst based on Y zeolite and natural clays, with improved physicomechanical properties, the authors carried out a series of studies, obtaining results that are set forth in the present article.

  2. Zeolites: Exploring Molecular Channels

    SciTech Connect

    Arslan, Ilke; Derewinski, Mirek

    2015-05-22

    Synthetic zeolites contain microscopic channels, sort of like a sponge. They have many uses, such as helping laundry detergent lather, absorbing liquid in kitty litter, and as catalysts to produce fuel. Of the hundreds of types of zeolites, only about 15 are used for catalysis. PNNL catalysis scientists Ilke Arslan and Mirek Derewinksi are studying these zeolites to understand what make them special. By exploring the mystery of these microscopic channels, their fundamental findings will help design better catalysts for applications such as biofuel production.

  3. Diagram of Zeolite Crystals

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The Center for Advanced Microgravity Materials Processing (CAMMP) in Cambridge, MA, a NASA-sponsored Commercial Space Center, is working to improve zeolite materials for storing hydrogen fuel. CAMMP is also applying zeolites to detergents, optical cables, gas and vapor detection for environmental monitoring and control, and chemical production techniques that significantly reduce by-products that are hazardous to the environment. Depicted here is one of the many here complex geometric shapes which make them highly absorbent. Zeolite experiments have also been conducted aboard the International Space Station

  4. Hierarchical zeolites from class F coal fly ash

    NASA Astrophysics Data System (ADS)

    Chitta, Pallavi

    Fly ash, a coal combustion byproduct is classified as types class C and class F. Class C fly ash is traditionally recycled for concrete applications and Class F fly ash often disposed in landfills. Class F poses an environmental hazard due to disposal and leaching of heavy metals into ground water and is important to be recycled in order to mitigate the environmental challenges. A major recycling option is to reuse the fly ash as a low-cost raw material for the production of crystalline zeolites, which serve as catalysts, detergents and adsorbents in the chemical industry. Most of the prior literature of fly ash conversion to zeolites does not focus on creating high zeolite surface area zeolites specifically with hierarchical pore structure, which are very important properties in developing a heterogeneous catalyst for catalysis applications. This research work aids in the development of an economical process for the synthesis of high surface area hierarchical zeolites from class F coal fly ash. In this work, synthesis of zeolites from fly ash using classic hydrothermal treatment approach and fusion pretreatment approach were examined. The fusion pretreatment method led to higher extent of dissolution of silica from quartz and mullite phases, which in turn led to higher surface area and pore size of the zeolite. A qualitative kinetic model developed here attributes the difference in silica content to Si/Al ratio of the beginning fraction of fly ash. At near ambient crystallization temperatures and longer crystallization times, the zeolite formed is a hierarchical faujasite with high surface area of at least 360 m2/g. This work enables the large scale recycling of class F coal fly ash to produce zeolites and mitigate environmental concerns. Design of experiments was used to predict surface area and pore sizes of zeolites - thus obviating the need for intense experimentation. The hierarchical zeolite catalyst supports tested for CO2 conversion, yielded hydrocarbons

  5. Composite zeolite membranes

    DOEpatents

    Nenoff, Tina M.; Thoma, Steven G.; Ashley, Carol S.; Reed, Scott T.

    2002-01-01

    A new class of composite zeolite membranes and synthesis techniques therefor has been invented. These membranes are essentially defect-free, and exhibit large levels of transmembrane flux and of chemical and isotopic selectivity.

  6. Role of ammonium fluoride in crystallization process of beta zeolite

    NASA Astrophysics Data System (ADS)

    Jon, Hery; Oumi, Yasunori; Itabashi, Keiji; Sano, Tsuneji

    2007-09-01

    The addition of Na + cations to the starting gel prepared using NH 4F significantly prolonged the crystallization time of beta zeolite. However, in the case of pure silica beta zeolite an addition of more NH 4F reduced the crystallization time by one-half. From 29Si MAS NMR measurements, the signal attributed to pentacoordinated silicon was found to be more pronounced for pure silica beta zeolite in the presence of Na + cations even in the solid phase with low crystallinity, as compared to that in the absence of Na + cations. Considering the results of theoretical calculation, because of more energetically stable state of Na +[SiO 4/2F] - species, it could be presumed that Na +[SiO 4/2F] - species might exist in pure silica beta zeolite. Furthermore, as confirmed by 19F MAS NMR measurements tetraethylammonium fluoride (TEAF) species were enclathrated intact in solid phase during the initial crystallization stage. This suggests that TEAF species are required for the formation of beta zeolite framework, in other words, as "SDA" which conditions the formation of kinetically favored phase, i.e., beta zeolite. Moreover, since part of TEA + cations is replaced by sodium cations, forming Na +[SiO 4/2F] - species, the amount of TEA +[SiO 4/2F] - species involved in either nucleation or crystal growth decreases and thus the crystallization time becomes longer.

  7. Sol-gel synthesis and luminescence of unexpected microrod crystalline Ca 5La 5(SiO 4) 3(PO 4) 3O 2:Dy 3+ phosphors employing different silicate sources

    NASA Astrophysics Data System (ADS)

    Yan, Bing; Huang, Honghua

    2007-08-01

    Ca5La5(SiO4)3(PO4)3O2 doped with Dy3+ were synthesized by sol-gel technology with hybrid precursor employed four different silicate sources, 3-aminopropyl-trimethoxysilane (APMS), 3-aminopropyl-triethoxysilane (APES), 3-aminopropyl-methyl-diethoxysilane (APMES) and tetraethoxysilane (TEOS), respectively. The SEM diagraphs show that there exist some novel unexpected morphological structures of microrod owing to the crosslinking reagents than TEOS as silicate source for their amphipathy template effect. X-ray pictures confirm that Ca5La5(SiO4)3(PO4)3O2:Dy3+ compound is formed by a pure apatitic phase. The Dy3+ ions could emit white light in Ca5La5(SiO4)3(PO4)3O2 compound, and the ratio of Y/B is 1.1, when the Dy3+ doped concentration is 1.0 mol%.

  8. Characterizing Amorphous Silicates in Extraterrestrial Materials

    NASA Astrophysics Data System (ADS)

    Fu, X.; Wang, A.; Krawczynski, M. J.

    2015-12-01

    Amorphous silicates are common in extraterrestrial materials. They are seen in the matrix of carbonaceous chondrites as well as in planetary materials. Tagish Lake is one of the most primitive carbonaceous meteorites in which TEM and XRD analyses found evidence for poorly crystalline phyllosilicate-like species; Raman spectra revealed amorphous silicates with variable degree of polymerization and low crystallinity. On Mars, CheMin discovered amorphous phases in all analyzed samples, and poorly crystalline smectite in mudstone samples. These discoveries pose questions on the crystallinity of phyllosilicates found by remote sensing on Mars, which is directly relevant to aqueous alteration during geologic history of Mars. Our goal is to use spectroscopy to better characterize amorphous silicates. We use three approaches: (1) using silicate glasses synthesized with controlled chemistry to study the effects of silicate polymerization and (2) using phyllosilicates synthesized with controlled hydrothermal treatment to study the effect of crystallinity on vibrational spectroscopy, finally (3) to use the developed correlations in above two steps to study amorphous phases in meteorites, and those found in future missions to Mars. In the 1st step, silicate glasses were synthesized from pure oxides in a range of NBO/T ratios (from 0 to 4). Depending on the targeted NBO/T and composition of mixed oxides, temperatures for each experiment fell in a range from 1260 to 1520 °C, run for ~ 4 hrs. The melt was quenched in liquid N2 or water. Homogeneity of glass was checked under optical microscopy. Raman spectra were taken over 100 spots on small chips free of bubbles and crystals. We have observed that accompanying an increase of NBO/T, there is a strengthening and a position shift of the Raman peak near 1000 cm-1 (Si-Onon-bridging stretching mode), and the weakening of broad Raman peaks near 500 cm-1 (ring breathing mode) and 700cm-1 (Si-Obridging-Si mode). We are building the

  9. Hydraulic conductivity of compacted zeolites.

    PubMed

    Oren, A Hakan; Ozdamar, Tuğçe

    2013-06-01

    Hydraulic conductivities of compacted zeolites were investigated as a function of compaction water content and zeolite particle size. Initially, the compaction characteristics of zeolites were determined. The compaction test results showed that maximum dry unit weight (γ(dmax)) of fine zeolite was greater than that of granular zeolites. The γ(dmax) of compacted zeolites was between 1.01 and 1.17 Mg m(-3) and optimum water content (w(opt)) was between 38% and 53%. Regardless of zeolite particle size, compacted zeolites had low γ(dmax) and high w(opt) when compared with compacted natural soils. Then, hydraulic conductivity tests were run on compacted zeolites. The hydraulic conductivity values were within the range of 2.0 × 10(-3) cm s(-1) to 1.1 × 10(-7) cm s(-1). Hydraulic conductivity of all compacted zeolites decreased almost 50 times as the water content increased. It is noteworthy that hydraulic conductivity of compacted zeolite was strongly dependent on the zeolite particle size. The hydraulic conductivity decreased almost three orders of magnitude up to 39% fine content; then, it remained almost unchanged beyond 39%. Only one report was found in the literature on the hydraulic conductivity of compacted zeolite, which is in agreement with the findings of this study.

  10. Structural analysis of hierarchically organized zeolites

    NASA Astrophysics Data System (ADS)

    Mitchell, Sharon; Pinar, Ana B.; Kenvin, Jeffrey; Crivelli, Paolo; Kärger, Jörg; Pérez-Ramírez, Javier

    2015-10-01

    Advances in materials synthesis bring about many opportunities for technological applications, but are often accompanied by unprecedented complexity. This is clearly illustrated by the case of hierarchically organized zeolite catalysts, a class of crystalline microporous solids that has been revolutionized by the engineering of multilevel pore architectures, which combine unique chemical functionality with efficient molecular transport. Three key attributes, the crystal, the pore and the active site structure, can be expected to dominate the design process. This review examines the adequacy of the palette of techniques applied to characterize these distinguishing features and their catalytic impact.

  11. Structural analysis of hierarchically organized zeolites

    PubMed Central

    Mitchell, Sharon; Pinar, Ana B.; Kenvin, Jeffrey; Crivelli, Paolo; Kärger, Jörg; Pérez-Ramírez, Javier

    2015-01-01

    Advances in materials synthesis bring about many opportunities for technological applications, but are often accompanied by unprecedented complexity. This is clearly illustrated by the case of hierarchically organized zeolite catalysts, a class of crystalline microporous solids that has been revolutionized by the engineering of multilevel pore architectures, which combine unique chemical functionality with efficient molecular transport. Three key attributes, the crystal, the pore and the active site structure, can be expected to dominate the design process. This review examines the adequacy of the palette of techniques applied to characterize these distinguishing features and their catalytic impact. PMID:26482337

  12. Preparation of functionalized zeolitic frameworks

    DOEpatents

    Yaghi, Omar M.; Hayashi, Hideki; Banerjee, Rahul; Park, Kyo Sung; Wang, Bo; Cote, Adrien P.

    2014-08-19

    The disclosure provides zeolitic frameworks for gas separation, gas storage, catalysis and sensors. More particularly the disclosure provides zeolitic frameworks (ZIFs). The ZIF of the disclosure comprises any number of transition metals or a homogenous transition metal composition.

  13. Preparation of functionalized zeolitic frameworks

    DOEpatents

    Yaghi, Omar M; Furukawa, Hiroyasu; Wang, Bo

    2013-07-09

    The disclosure provides zeolitic frameworks for gas separation, gas storage, catalysis and sensors. More particularly the disclosure provides zeolitic frameworks (ZIFs). The ZIF of the disclosure comprises any number of transition metals or a homogenous transition metal composition.

  14. Preparation of functionalized zeolitic frameworks

    DOEpatents

    Yaghi, Omar M; Hayashi, Hideki; Banerjee, Rahul; Park, Kyo Sung; Wang, Bo; Cote, Adrien P

    2012-11-20

    The disclosure provides zeolitic frameworks for gas separation, gas storage, catalysis and sensors. More particularly the disclosure provides zeolitic frameworks (ZIFs). The ZIF of the disclosure comprises any number of transition metals or a homogenous transition metal composition.

  15. Noble gas adsorption in two-dimensional zeolites: a combined experimental and density functional theory study

    NASA Astrophysics Data System (ADS)

    Wang, Mengen; Zhong, Jianqiang; Boscoboinik, Jorge Anibal; Lu, Deyu

    Zeolites are important industrial catalysts with porous three-dimensional structures. The catalytically active sites are located inside the pores, thus rendering them inaccessible for surface science measurements. We synthesized a two-dimensional (2D) zeolite model system, consisting of an (alumino)silicate bilayer weakly bound to a Ru (0001) surface. The 2D zeolite is suitable for surface science studies; it allows a detailed characterization of the atomic structure of the active site and interrogation of the model system during the catalytic reaction. As an initial step, we use Ar adsorption to obtain a better understanding of the atomic structure of the 2D zeolite. In addition, atomic level studies of rare gas adsorption and separation by zeolite are important for its potential application in nuclear waste sequestration. Experimental studies found that Ar atoms can be trapped inside the 2D-zeolite, raising an interesting question on whether Ar atoms are trapped inside the hexagonal prism nano-cages or at the interface between the (alumino)silicate bilayer and Ru(0001), or both. DFT calculations using van der Waals density functionals were carried out to determine the preferred Ar adsorption sites and the corresponding adsorption energies. This research used resources of the Center for Functional Nanomaterials, which is a U.S. DOE Office of Science Facility, at Brookhaven National Laboratory under Contract No. DE-SC0012704.

  16. Phosphorus Equilibria Among Mafic Silicate Phases

    NASA Technical Reports Server (NTRS)

    Berlin, Jana; Xirouchakis, Dimitris

    2002-01-01

    Phosphorus incorporation in major rock-forming silicate minerals has the following implications: (1) Reactions between phosphorus-hosting major silicates and accessory phosphates, which are also major trace element carriers, may control the stability of the latter and thus may affect the amount of phosphorus and other trace elements released to the coexisting melt or fluid phase. (2) Less of a phosphate mineral is needed to account for the bulk phosphorus of planetaty mantles. (3) During partial melting of mantle mineral assemblages or equilibrium fractional crystallization of basaltic magmas, and in the absence or prior to saturation with a phosphate mineral, silicate melts may become enriched in phosphorus, especially in the geochemically important low melt fraction regime, Although the small differences in the ionic radii of IVp5+, IVSi4+, and IV Al3+ makes phosphoms incorporation into crystalline silicates perhaps unsurprising, isostructural silicate and phosphate crystalline solids do not readily form solutions, e.g., (Fe, Mg)2SiO4 vs. LiMgPO4, SiO)2 VS. AlPO4. Nonetheless, there are reports of, poorly characterized silico-phosphate phases in angrites , 2-4 wt% P2O5 in olivine and pyroxene grains in pallasites and reduced terestrial basalts which are little understood but potentially useful, and up to 17 wt% P2O5 in olivine from ancient slags. However, such enrichments are rare and only underscore the likelihood of phosphoms incorporation in silicate minerals. The mechanisms that allow phosphorus to enter major rock-forming silicate minerals (e.g., Oliv, Px, Gt) remain little understood and the relevant data base is limited. Nonetheless, old and new high-pressure (5-10 GPa) experimental data suggest that P2O5 wt% decreases from silica-poor to silica-rich compositions or from orthosilicate to chain silicate structures (garnet > olivine > orthopyroxene) which implies that phosphorus incorporation in silicates is perhaps more structure-than site-specific. The

  17. Energetic Processing of Interstellar Silicate Grains by Cosmic Rays

    SciTech Connect

    Bringa, E M; Kucheyev, S O; Loeffler, M J; Baragiola, R A; Tielens, A G Q M; Dai, Z R; Graham, G; Bajt, S; Bradley, J; Dukes, C A; Felter, T E; Torres, D F; van Breugel, W

    2007-03-28

    While a significant fraction of silicate dust in stellar winds has a crystalline structure, in the interstellar medium nearly all of it is amorphous. One possible explanation for this observation is the amorphization of crystalline silicates by relatively 'low' energy, heavy ion cosmic rays. Here we present the results of multiple laboratory experiments showing that single-crystal synthetic forsterite (Mg{sub 2}SiO{sub 4}) amorphizes when irradiated by 10 MeV Xe{sup ++} ions at large enough fluences. Using modeling, we extrapolate these results to show that 0.1-5.0 GeV heavy ion cosmic rays can rapidly ({approx}70 Million yrs) amorphize crystalline silicate grains ejected by stars into the interstellar medium.

  18. Mimicking high-silica zeolites: highly stable germanium- and tin-rich zeolite-type chalcogenides.

    PubMed

    Lin, Qipu; Bu, Xianhui; Mao, Chengyu; Zhao, Xiang; Sasan, Koroush; Feng, Pingyun

    2015-05-20

    High-silica zeolites, as exemplified by ZSM-5, with excellent chemical and thermal stability, have generated a revolution in industrial catalysis. In contrast, prior to this work, high-silica-zeolite-like chalcogenides based on germanium/tin remained unknown, even after decades of research. Here six crystalline high-germanium or high-tin zeolite-type sulfides and selenides with four different topologies are reported. Their unprecedented framework compositions give these materials much improved thermal and chemical stability with high surface area (Langmuir surface area of 782 m(2)/g(-1)) comparable to or better than zeolites. Among them, highly stable CPM-120-ZnGeS allows for ion exchange with diverse metal or complex cations, resulting in fine-tuning in porosity, fast ion conductivity, and photoelectric response. Being among the most porous crystalline chalcogenides, CPM-120-ZnGeS (exchanged with Cs(+) ions) also shows reversible adsorption with high capacity and affinity for CO2 (98 and 73 cm(3) g(-1) at 273 and 298 K, respectively, isosteric heat of adsorption = 40.05 kJ mol(-1)). Moreover, CPM-120-ZnGeS could also function as a robust photocatalyst for water reduction to generate H2. The overall activity of H2 production from water, in the presence of Na2S-Na2SO3 as a hole scavenger, was 200 μmol h(-1)/(0.10 g). Such catalytic activity remained undiminished under illumination by UV light for as long as measured (200 h), demonstrating excellent resistance to photocorrosion even under intense UV radiation.

  19. Mg/Fe FRACTIONATION IN CIRCUMSTELLAR SILICATE DUST INVOLVED IN CRYSTALLIZATION

    SciTech Connect

    Murata, K.; Takakura, T.; Chihara, H.; Koike, C.; Tsuchiyama, A.

    2009-05-10

    Infrared astronomical observations of oxygen-rich young and evolved stars show that only magnesium-rich crystalline silicates exist in circumstellar regions, and iron, one of the most important dust-forming elements, is extremely depleted. The compositional characteristic of circumstellar crystalline silicates is fundamentally different from that of primitive extraterrestrial materials in our solar system, such as chondritic meteorites and interplanetary dust particles. Amorphous silicates are ubiquitous and abundant in space, and are a promising carrier of iron. However, since the first detection of crystalline silicates, there has been an unsolved inconsistency due to differing compositions of coexisting crystalline and amorphous phases, considering that amorphous silicates have been expected to be precursors of these crystals. Here we show the first experimental evidence that Fe-depleted olivine can be formed by crystallization via thermal heating of FeO-bearing amorphous silicates under subsolidus conditions. Mg/Fe fractionation involved in crystallization makes possible to coexist Mg-rich crystalline silicates with Fe-bearing amorphous silicates around stars.

  20. Silicate volcanism on Io

    NASA Astrophysics Data System (ADS)

    Carr, M. H.

    1986-03-01

    This paper is mainly concerned with the nature of volcanic eruptions on Io, taking into account questions regarding the presence of silicates or sulfur as principal component. Attention is given to the generation of silicate magma, the viscous dissipation in the melt zone, thermal anomalies at eruption sites, and Ionian volcanism. According to the information available about Io, it appears that its volcanism and hence its surface materials are dominantly silicic. Several percent of volatile materials such as sulfur, but also including sodium- and potassium-rich materials, may also be present. The volatile materials at the surface are continually vaporized and melted as a result of the high rates of silicate volcanism.

  1. Optical Properties of Astronomical Silicates in the Far-infrared

    NASA Technical Reports Server (NTRS)

    Rinehart, Stephen A,; Benford, Dominic J.; Dwek, Eli; Henry, Ross M.; Nuth, Joseph A., III; Silverberg, Robert f.; Wollack, Edward J.

    2008-01-01

    Correct interpretation of a vast array of astronomical data relies heavily on understanding the properties of silicate dust as a function of wavelength, temperature, and crystallinity. We introduce the QPASI-T (Optical Properties of Astronomical Silicates with Infrared Techniques) project to address the need for high fidelity optical characterization data on the various forms of astronomical dust. We use two spectrometers to provide extinction data for silicate samples across a wide wavelength range (from the near infrared to the millimeter). New experiments are in development that will provide complementary information on the emissivity of our samples, allowing us to complete the optical characterization of these dust materials. In this paper, we present initial results from several materials including amorphous iron silicate, magnesium silicate and silica smokes, over a wide range of temperatures, and discuss the design and operation of our new experiments.

  2. Structure and properties of ITQ-8: a hydrous layer silicate with microporous silicate layers.

    PubMed

    Marler, Bernd; Müller, Melanie; Gies, Hermann

    2016-06-21

    ITQ-8 is a new hydrous layer silicate (HLS) with a chemical composition of [C4H8(C7H13N)2]8 [Si64O128(OH)16]·48H2O per unit cell. The synthesis of ITQ-8 was first described in 2002 by Díaz-Cabañas et al., the structure of this material, however, remained unsolved at that time. Physico-chemical characterization using solid-state NMR spectroscopy, SEM, TG-DTA, and FTIR spectroscopy confirmed that ITQ-8 is a layer silicate. The XRD powder pattern was indexed in the monoclinic system with lattice parameters of a0 = 35.5168(5) Å, b0 = 13.3989(2) Å, c0 = 16.0351(2) Å, β = 106.74(2)°. The crystal structure was solved by simulated annealing. Rietveld refinement of the structure in space group C2/c converged to residual values of RBragg = 0.023, RF = 0.022 and chi(2) = 2.3 confirming the structure model. The structure of ITQ-8 contains silicate layers with a topology that resembles a (11-1) section of the framework of zeolite levyne. So far, this layer topology is unique among layer silicates. The layer can be regarded as made up of 4-, 6-, double-six and 8-rings which are interconnected to form cup-like "half-cages". Unlike other HLSs, which possess impermeable silicate layers, ITQ-8 contains 8-rings pores with a free diameter of 3.5 Å × 3.4 Å and can be regarded as a "small-pore layer silicate". In the crystal structure, the organic cations, 1,4-diquiniclidiniumbutane, used as structure directing agents during synthesis are intercalated between the silicate layers. Clusters (bands) of water molecules which are hydrogen bonded to each other and to the terminal Si-OH/Si-O(-) groups are located between the organic cations and interconnect the silicate layers. ITQ-8 is a very interesting material as precursor for the synthesis of microporous framework silicates by topotactic condensation or interlayer expansion reactions leading to 3D micro-pore systems which may be useful in applications as e.g. catalysts, catalyst supports and adsorbents of for separation. PMID

  3. Synthesis, deposition and characterization of magnesium hydroxide nanostructures on zeolite 4A

    SciTech Connect

    Koh, Pei-Yoong; Yan, Jing; Ward, Jason; Koros, William J.; Teja, Amyn S.; Xu, Bo

    2011-03-15

    Research highlights: {yields} Reports a simple precipitation-growth method to produce nanostructures of Mg(OH){sub 2} on the surface of zeolite 4A. {yields} Able to control the growth of the nanostructures by manipulating the experimental procedure. {yields} Able to deposit Mg(OH){sub 2} onto specific sites namely bridging hydroxyl protons (SiOHAl) on the surface of zeolite 4A. -- Abstract: The precipitation and self-assembly of magnesium hydroxide Mg(OH){sub 2} nanopetals on dispersed zeolite 4A particles was investigated. Mg(OH){sub 2}/zeolite nanocomposites were produced from magnesium chloride solutions and characterized via X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Fourier transform infrared analysis (FTIR), and solid state NMR. It was determined that Mg(OH){sub 2} interacted with bridging hydroxyl protons (SiOHAl) on the zeolite surface, but not with silanol or aluminol groups. NMR analysis showed that 13% of the tetrahedral Al sites on the zeolite were converted to octahedral Al. The zeolite structure and crystallinity remained intact after treatment, and no dealumination reactions were detected. This suggests that the deposition-precipitation process at ambient conditions is a facile method for controlling Mg(OH){sub 2} nanostructures on zeolites.

  4. Ionization and protonation of aromatic diamines by sorption in zeolites

    NASA Astrophysics Data System (ADS)

    Marquis, S.; Moissette, A.; Brémard, C.; Vezin, H.

    2003-06-01

    In situ diffuse reflectance UV visible, Raman scattering and EPR spectroscopies were used to monitor spontaneous ionization of N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) by direct exposure to dehydrated M nZSM-5 zeolite (M=Na +, H +; n=0,3,6). The TMPD •+ radical cation is found to be generated in low yield in purely siliceous silicalite-1 whereas TMPD •+ is generated in high yield in aluminated Na nZSM-5 and H nZSM-5. The ejected electron is also characterized though electronic absorption spectra. The charge separation was found to be persistent over several months. The tight fit between the shape of TMPD and the pore size of straight channels of zeolites is considered to be the main factor responsible for the stabilization of the TMPD radical ion by preventing rapid electron back transfer. Within Na nZSM-5, the amounts of TMPD •+ and trapped electron were found to decrease over long time and to recombine to molecular TMPD. In contrast, in acidic H nZSM-5 zeolite the charge recombination generates diprotonated TMPDH 22+ occluded species. Furthermore, within H nZSM-5, protonation appears competitive to the ionization efficiency of zeolite.

  5. Pioneering In Situ Recrystallization during Bead Milling: A Top-down Approach to Prepare Zeolite A Nanocrystals.

    PubMed

    Anand, Chokkalingam; Yamaguchi, Yudai; Liu, Zhendong; Ibe, Sayoko; Elangovan, Shanmugam P; Ishii, Toshihiro; Ishikawa, Tsuyoshi; Endo, Akira; Okubo, Tatsuya; Wakihara, Toru

    2016-07-05

    Top-down approach has been viewed as an efficient and straightforward method to prepare nanosized zeolites. Yet, the mechanical breaking of zeolite causes amorphization, which usually requires a post-milling recrystallization to obtain fully crystalline nanoparticles. Herein we present a facile methodology to prepare zeolite nanocrystals, where milling and recrystallization can be performed in situ. A milling apparatus specially designed to work under conditions of high alkalinity and temperature enables the in situ recrystallization during milling. Taking zeolite A as an example, we demonstrate its size reduction from ~3 μm to 66 nm in 30 min, which is quite faster than previous methods reported. Three functions, viz., miniaturization, amorphization and recrystallization were found to take effect concurrently during this one-pot process. The dynamic balance between these three functions was achieved by adjusting the milling period and temperature, which lead to the tuning of zeolite A particle size. Particle size and crystallinity of the zeolite A nanocrystals were confirmed by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and water adsorption-desorption. This work presents a pioneering advancement in this field of nanosized zeolites, and will facilitate the mass production as well as boost the wide applications of nanosized zeolites.

  6. Pioneering In Situ Recrystallization during Bead Milling: A Top-down Approach to Prepare Zeolite A Nanocrystals

    NASA Astrophysics Data System (ADS)

    Anand, Chokkalingam; Yamaguchi, Yudai; Liu, Zhendong; Ibe, Sayoko; Elangovan, Shanmugam P.; Ishii, Toshihiro; Ishikawa, Tsuyoshi; Endo, Akira; Okubo, Tatsuya; Wakihara, Toru

    2016-07-01

    Top-down approach has been viewed as an efficient and straightforward method to prepare nanosized zeolites. Yet, the mechanical breaking of zeolite causes amorphization, which usually requires a post-milling recrystallization to obtain fully crystalline nanoparticles. Herein we present a facile methodology to prepare zeolite nanocrystals, where milling and recrystallization can be performed in situ. A milling apparatus specially designed to work under conditions of high alkalinity and temperature enables the in situ recrystallization during milling. Taking zeolite A as an example, we demonstrate its size reduction from ~3 μm to 66 nm in 30 min, which is quite faster than previous methods reported. Three functions, viz., miniaturization, amorphization and recrystallization were found to take effect concurrently during this one-pot process. The dynamic balance between these three functions was achieved by adjusting the milling period and temperature, which lead to the tuning of zeolite A particle size. Particle size and crystallinity of the zeolite A nanocrystals were confirmed by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and water adsorption-desorption. This work presents a pioneering advancement in this field of nanosized zeolites, and will facilitate the mass production as well as boost the wide applications of nanosized zeolites.

  7. Pioneering In Situ Recrystallization during Bead Milling: A Top-down Approach to Prepare Zeolite A Nanocrystals.

    PubMed

    Anand, Chokkalingam; Yamaguchi, Yudai; Liu, Zhendong; Ibe, Sayoko; Elangovan, Shanmugam P; Ishii, Toshihiro; Ishikawa, Tsuyoshi; Endo, Akira; Okubo, Tatsuya; Wakihara, Toru

    2016-01-01

    Top-down approach has been viewed as an efficient and straightforward method to prepare nanosized zeolites. Yet, the mechanical breaking of zeolite causes amorphization, which usually requires a post-milling recrystallization to obtain fully crystalline nanoparticles. Herein we present a facile methodology to prepare zeolite nanocrystals, where milling and recrystallization can be performed in situ. A milling apparatus specially designed to work under conditions of high alkalinity and temperature enables the in situ recrystallization during milling. Taking zeolite A as an example, we demonstrate its size reduction from ~3 μm to 66 nm in 30 min, which is quite faster than previous methods reported. Three functions, viz., miniaturization, amorphization and recrystallization were found to take effect concurrently during this one-pot process. The dynamic balance between these three functions was achieved by adjusting the milling period and temperature, which lead to the tuning of zeolite A particle size. Particle size and crystallinity of the zeolite A nanocrystals were confirmed by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and water adsorption-desorption. This work presents a pioneering advancement in this field of nanosized zeolites, and will facilitate the mass production as well as boost the wide applications of nanosized zeolites. PMID:27378145

  8. Pioneering In Situ Recrystallization during Bead Milling: A Top-down Approach to Prepare Zeolite A Nanocrystals

    PubMed Central

    Anand, Chokkalingam; Yamaguchi, Yudai; Liu, Zhendong; Ibe, Sayoko; Elangovan, Shanmugam P.; Ishii, Toshihiro; Ishikawa, Tsuyoshi; Endo, Akira; Okubo, Tatsuya; Wakihara, Toru

    2016-01-01

    Top-down approach has been viewed as an efficient and straightforward method to prepare nanosized zeolites. Yet, the mechanical breaking of zeolite causes amorphization, which usually requires a post-milling recrystallization to obtain fully crystalline nanoparticles. Herein we present a facile methodology to prepare zeolite nanocrystals, where milling and recrystallization can be performed in situ. A milling apparatus specially designed to work under conditions of high alkalinity and temperature enables the in situ recrystallization during milling. Taking zeolite A as an example, we demonstrate its size reduction from ~3 μm to 66 nm in 30 min, which is quite faster than previous methods reported. Three functions, viz., miniaturization, amorphization and recrystallization were found to take effect concurrently during this one-pot process. The dynamic balance between these three functions was achieved by adjusting the milling period and temperature, which lead to the tuning of zeolite A particle size. Particle size and crystallinity of the zeolite A nanocrystals were confirmed by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and water adsorption-desorption. This work presents a pioneering advancement in this field of nanosized zeolites, and will facilitate the mass production as well as boost the wide applications of nanosized zeolites. PMID:27378145

  9. Formation of Magnesium Silicates is Limited around Evolved Stars

    NASA Astrophysics Data System (ADS)

    Kimura, Yuki; Nuth, J. A., III

    2009-05-01

    Laboratory experiments suggest that magnesium silicide (Mg2Si) grains could be produced in the hydrogen dominant gas outflow from evolved stars in addition to amorphous oxide minerals. Astronomical observations have shown the existence of abundant silicate grains around evolved stars and we have long realized that most of the silicate grains are amorphous, based on the observed infrared features. Only high mass loss stars show the feature attributed to magnesium-rich crystalline silicate about 10-20 % respect to total silicates, so far. The lower degree of crystallinity observed in silicates formed in outflows of lower mass-loss-rate stars might be caused by the formation of magnesium silicide in this relatively hydrogen-rich environment. As a result of predominant distribution of magnesium into the silicide, the composition of interstellar amorphous silicates could be magnesium poor compared with silicon. Indeed, the chemical composition of isotopically anomalous GEMS (glass with embedded metal and sulfides) is magnesium poor with respect to a forsteritic composition (Floss et al. 2006; Keller & Messenger 2007). Infrared observations suggest that there is little or no crystalline forsterite in interstellar environments while there is an abundance of crystalline forsterite in our Solar System. If the forsterite is a result of the oxidation of interstellar magnesium silicide, then it is clear both why crystalline forsterite is stoichiometric olivine and why the chemical composition of isotopically anomalous GEMS is magnesium poor with respect to a forsteritic composition. In addition, it may also explain why the chemical composition of olivine is iron poor. Unfortunately, magnesium silicide has never been detected via astronomical observation or in the analysis of primitive meteorites. I would suggest that future analysis of meteorites and theoretical calculations could confirm the possibility of the formation of magnesium silicide grains around evolved stars.

  10. IMPROVED CATALYSTS FOR HEAVY OIL UPGRADING BASED ON ZEOLITE Y NANOPARTICLES ENCAPSULATED IN STABLE NANOPOROUS HOSTS

    SciTech Connect

    Conrad Ingram

    2003-09-03

    The focus of this project is to improve the catalytic performance of zeolite Y for petroleum hydrocracking by synthesizing nanoparticles of the zeolite ({approx}20-25 nm) inside nanoporous silicate or aluminosilicate hosts. The encapsulated zeolite nanoparticles are expected to possess reduced diffusional path lengths, hence hydrocarbon substrates will diffuse in, are converted and the products quickly diffused out. This is expected to prevent over-reaction and the blocking of the zeolite pores and active sites will be minimized. In this phase of the project, procedures for the synthesis of ordered nanoporous silica, such as SBA-15, using block copolymers and nonionic surfactant were successful reproduced. Expansion of the pores sizes of the nanoporous silica using trimethylbenzene is suggested based on shift in the major X-Ray Diffraction peak in the products to lower 2 angles compared with the parent SBA-15 material. The synthesis of ordered nanoporous materials with aluminum incorporated in the predominantly silicate framework was attempted but is not yet successful, and the procedures needs will be repeated and modified as necessary. Nanoparticles of zeolite Y of particle sizes in the range 40 nm to 120 nm were synthesized in the presence of TMAOH as the particle size controlling additive.

  11. Pyrolytic Synthesis of Carbon Nanotubes from Sucrose on a Mesoporous Silicate

    NASA Technical Reports Server (NTRS)

    Abdel-Fattah, Tarek; Siochi, Mia; Crooks, Roy

    2005-01-01

    Multiwall carbon nanotubes were synthesized from sucrose by a pyrolytic technique using mesoporous MCM-41 silicate templates without transition metal catalysts. The Nanotubes were examined in the carbon/silicate composite and after dissolution of the silicate. High resolution transmission electron microscopy study of the multiwall nanotubes showed them to be 15 nm in diameter, 200 nm in length and close-ended. There was variation in crystallinity with some nanotubes showing disordered wall structures.

  12. Zeolite crystal growth in space

    NASA Technical Reports Server (NTRS)

    Sacco, Albert, Jr.; Thompson, Robert W.; Dixon, Anthony G.

    1991-01-01

    The growth of large, uniform zeolite crystals in high yield in space can have a major impact on the chemical process industry. Large zeolite crystals will be used to improve basic understanding of adsorption and catalytic mechanisms, and to make zeolite membranes. To grow large zeolites in microgravity, it is necessary to control the nucleation event and fluid motion, and to enhance nutrient transfer. Data is presented that suggests nucleation can be controlled using chemical compounds (e.g., Triethanolamine, for zeolite A), while not adversely effecting growth rate. A three-zone furnace has been designed to perform multiple syntheses concurrently. The operating range of the furnace is 295 K to 473 K. Teflon-lined autoclaves (10 ml liquid volume) have been designed to minimize contamination, reduce wall nucleation, and control mixing of pre-gel solutions on orbit. Zeolite synthesis experiments will be performed on USML-1 in 1992.

  13. Effect of ultrasound energy on the zeolitization of chemical extracts from fused coal fly ash.

    PubMed

    Bukhari, Syed Salman; Rohani, Sohrab; Kazemian, Hossein

    2016-01-01

    This paper investigates the effects of ultrasound (UTS) energy at different temperatures on the zeolitization of aluminosilicate constituents of coal fly ash. UTS energy irradiated directly into the reaction mixture utilizing a probe immersed into the reaction mixture, unlike previously reported works that have used UTS baths. Controlled synthesis was also conducted at constant stirring and at the same temperatures using conventional heating. The precursor reaction solution was obtained by first fusing the coal fly ash with sodium hydroxide at 550°C followed by dissolution in water and filtration. The synthesized samples were characterized by XRF, XRD, SEM and TGA. The crystallinity of crystals produced with UTS assisted conversion compared to conventional conversion at 85°C was twice as high. UTS energy also reduced the induction time from 60 min to 40 min and from 80 min to 60 min for reaction temperatures of 95°C and 85°C, respectively. Prolonging the UTS irradiation at 95°C resulted in the conversion of zeolite-A crystals to hydroxysodalite, which is a more stable zeolitic phase. It was found that at 85°C coupled with ultrasound energy produced the best crystalline structure with a pure single phase of zeolite-A. It has been shown that crystallization using UTS energy can produce zeolitic crystals at lower temperatures and within 1h, dramatically cutting the synthesis time of zeolite. PMID:26384882

  14. Effect of ultrasound energy on the zeolitization of chemical extracts from fused coal fly ash.

    PubMed

    Bukhari, Syed Salman; Rohani, Sohrab; Kazemian, Hossein

    2016-01-01

    This paper investigates the effects of ultrasound (UTS) energy at different temperatures on the zeolitization of aluminosilicate constituents of coal fly ash. UTS energy irradiated directly into the reaction mixture utilizing a probe immersed into the reaction mixture, unlike previously reported works that have used UTS baths. Controlled synthesis was also conducted at constant stirring and at the same temperatures using conventional heating. The precursor reaction solution was obtained by first fusing the coal fly ash with sodium hydroxide at 550°C followed by dissolution in water and filtration. The synthesized samples were characterized by XRF, XRD, SEM and TGA. The crystallinity of crystals produced with UTS assisted conversion compared to conventional conversion at 85°C was twice as high. UTS energy also reduced the induction time from 60 min to 40 min and from 80 min to 60 min for reaction temperatures of 95°C and 85°C, respectively. Prolonging the UTS irradiation at 95°C resulted in the conversion of zeolite-A crystals to hydroxysodalite, which is a more stable zeolitic phase. It was found that at 85°C coupled with ultrasound energy produced the best crystalline structure with a pure single phase of zeolite-A. It has been shown that crystallization using UTS energy can produce zeolitic crystals at lower temperatures and within 1h, dramatically cutting the synthesis time of zeolite.

  15. Hydrogen storage in Chabazite zeolite frameworks.

    PubMed

    Regli, Laura; Zecchina, Adriano; Vitillo, Jenny G; Cocina, Donato; Spoto, Giuseppe; Lamberti, Carlo; Lillerud, Karl P; Olsbye, Unni; Bordiga, Silvia

    2005-09-01

    We have recently highlighted that H-SSZ-13, a highly siliceous zeolite (Si/Al = 11.6) with a chabazitic framework, is the most efficient zeolitic material for hydrogen storage [A. Zecchina, S. Bordiga, J. G. Vitillo, G. Ricchiardi, C. Lamberti, G. Spoto, M. Bjørgen and K. P. Lillerud, J. Am. Chem. Soc., 2005, 127, 6361]. The aim of this new study is thus to clarify both the role played by the acidic strength and by the density of the polarizing centers hosted in the same framework topology in the increase of the adsorptive capabilities of the chabazitic materials towards H2. To achieve this goal, the volumetric experiments of H2 uptake (performed at 77 K) and the transmission IR experiment of H2 adsorption at 15 K have been performed on H-SSZ-13, H-SAPO-34 (the isostructural silico-aluminophosphate material with the same Brønsted site density) and H-CHA (the standard chabazite zeolite: Si/Al = 2.1) materials. We have found that a H2 uptake improvement has been obtained by increasing the acidic strength of the Brønsted sites (moving from H-SAPO-34 to H-SSZ-13). Conversely, the important increase of the Brønsted sites density (moving from H-SSZ-13 to H-CHA) has played a negative role. This unexpected behavior has been explained as follows. The additional Brønsted sites are in mutual interaction via H-bonds inside the small cages of the chabazitic framework and for most of them the energetic cost needed to displace the adjacent OH ligand is higher than the adsorption enthalpy of the OH...H2 adduct. From our work it can be concluded that proton exchanged chabazitic frameworks represent, among zeolites, the most efficient materials for hydrogen storage. We have shown that a proper balance between available space (volume accessible to hydrogen), high contact surface, and specific interaction with strong and isolated polarizing centers are the necessary characteristics requested to design better materials for molecular H2 storage.

  16. Hydrogen storage in Chabazite zeolite frameworks.

    PubMed

    Regli, Laura; Zecchina, Adriano; Vitillo, Jenny G; Cocina, Donato; Spoto, Giuseppe; Lamberti, Carlo; Lillerud, Karl P; Olsbye, Unni; Bordiga, Silvia

    2005-09-01

    We have recently highlighted that H-SSZ-13, a highly siliceous zeolite (Si/Al = 11.6) with a chabazitic framework, is the most efficient zeolitic material for hydrogen storage [A. Zecchina, S. Bordiga, J. G. Vitillo, G. Ricchiardi, C. Lamberti, G. Spoto, M. Bjørgen and K. P. Lillerud, J. Am. Chem. Soc., 2005, 127, 6361]. The aim of this new study is thus to clarify both the role played by the acidic strength and by the density of the polarizing centers hosted in the same framework topology in the increase of the adsorptive capabilities of the chabazitic materials towards H2. To achieve this goal, the volumetric experiments of H2 uptake (performed at 77 K) and the transmission IR experiment of H2 adsorption at 15 K have been performed on H-SSZ-13, H-SAPO-34 (the isostructural silico-aluminophosphate material with the same Brønsted site density) and H-CHA (the standard chabazite zeolite: Si/Al = 2.1) materials. We have found that a H2 uptake improvement has been obtained by increasing the acidic strength of the Brønsted sites (moving from H-SAPO-34 to H-SSZ-13). Conversely, the important increase of the Brønsted sites density (moving from H-SSZ-13 to H-CHA) has played a negative role. This unexpected behavior has been explained as follows. The additional Brønsted sites are in mutual interaction via H-bonds inside the small cages of the chabazitic framework and for most of them the energetic cost needed to displace the adjacent OH ligand is higher than the adsorption enthalpy of the OH...H2 adduct. From our work it can be concluded that proton exchanged chabazitic frameworks represent, among zeolites, the most efficient materials for hydrogen storage. We have shown that a proper balance between available space (volume accessible to hydrogen), high contact surface, and specific interaction with strong and isolated polarizing centers are the necessary characteristics requested to design better materials for molecular H2 storage. PMID:16240032

  17. Low-temperature crystallization of silicate dust in circumstellar disks.

    PubMed

    Molster, F J; Yamamura, I; Waters, L B; Tielens, A G; de Graauw, T; de Jong, T; de Koter, A; Malfait, K; van den Ancker, M E; van Winckel, H; Voors, R H; Waelkens, C

    1999-10-01

    Silicate dust in the interstellar medium is observed to be amorphous, yet silicate dust in comets and interplanetary dust particles is sometimes partially crystalline. The dust in disks that are thought to be forming planets around some young stars also appears to be partially crystalline. These observations suggest that as the dust goes from the precursor clouds to a planetary system, it must undergo some processing, but the nature and extent of this processing remain unknown. Here we report observations of highly crystalline silicate dust in the disks surrounding binary red-giant stars. The dust was created in amorphous form in the outer atmospheres of the red giants, and therefore must be processed in the disks to become crystalline. The temperatures in these disks are too low for the grains to anneal; therefore, some low-temperature process must be responsible. As the physical properties of the disks around young stars and red giants are similar, our results suggest that low-temperature crystallization of silicate grains also can occur in protoplanetary systems.

  18. Abu Zenima synthetic zeolite for removing iron and manganese from Assiut governorate groundwater, Egypt

    NASA Astrophysics Data System (ADS)

    Farrag, Abd El Hay Ali; Abdel Moghny, Th.; Mohamed, Atef Mohamed Gad; Saleem, Saleem Sayed; Fathy, Mahmoud

    2016-06-01

    Groundwater in Upper Egypt especially in Assiut Governorate is considered the second source of fresh water and used for drinking, agriculture, domestic and industrial purposes. Unfortunately, it is characterized by high concentrations of iron and manganese ions. The study aimed at synthesizing zeolite-4A from kaolinite for removing the excess iron and manganese ions from Assiut Governorate groundwater wells. Therefor, the kaolinite was hydrothermally treated through the metakaolinization and zeolitization processes to produce crystalline zeolite-4A. The chemical composition of crystalline zeolite-4A and its morphology were then characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Then the column experiments were conducted to study the performance of crystalline salt-4A as ion exchange and investigate their operating parameters and regeneration conditions. Thomas and Yoon-Nelson models were applied to predict adsorption capacity and the time required for 50 % breakthrough curves. The effects of initial concentrations of 600 and 1000 mg L-1 for Fe2+ and Mn2+, feed flow rate of 10-30 ml/min, and height range of 0.4-1.5 cm on the breakthrough behavior of the adsorption system were determined. The obtained results indicated that the synthesized zeolite-A4 can remove iron and manganese ions from groundwater to the permissible limit according to the standards drinking water law.

  19. Improved zeolitic isocracking catalysts

    SciTech Connect

    Dahlberg, A.J.; Habib, M.M.; Moore, R.O.; Law, D.V.; Convery, L.J.

    1995-09-01

    Chevron Research Company introduced the first low pressure, low temperature catalytic hydrocracking process--ISOCRACKING--in 1959. Within the last four years, Chevron has developed and commercialized three new zeolitic ISOCRACKING catalysts. ICR 209 is Chevron`s latest noble metal ISOCRACKING catalyst. It offers improved liquid yield stability, longer life, and superior polynuclear aromatics control compared to its predecessor. ICR 209`s high hydrogenation activity generates the highest yields of superior quality jet fuel of any zeolitic ISOCRACKING catalyst. The second new ISOCRACKING catalyst, ICR 208, is a base metal catalyst which combines high liquid selectivity and high light naphtha octane in hydrocrackers operating for maximum naphtha production. ICR 210 is another new base metal catalyst which offers higher liquid yields and longer life than ICR 208 by virtue of a higher hydrogenation-to-acidity ratio. Both ICR 208 and ICR 210 have been formulated to provide higher liquid yield throughout the cycle and longer cycle length than conventional base metal/zeolite catalysts. This paper will discuss the pilot plant and commercial performances of these new ISOCRACKING catalysts.

  20. Effect of chemical environment on the dynamics of water confined in calcium silicate minerals: natural and synthetic tobermorite.

    PubMed

    Monasterio, Manuel; Gaitero, Juan J; Manzano, Hegoi; Dolado, Jorge S; Cerveny, Silvina

    2015-05-01

    Confined water in the slit mesopores of the mineral tobermorite provides an excellent model system for analyzing the dynamic properties of water confined in cement-like materials. In this work, we use broadband dielectric spectroscopy (BDS) to analyze the dynamic of water entrapped in this crystalline material. Two samples, one natural and one synthetic, were analyzed, and despite their similar structure, the motion of confined water in their zeolitic cavity displays considerably different behavior. The water dynamics splits into two different behaviors depending on the chemical nature of the otherwise identical structural environment: water molecules located in areas where the primary building units are SiO4 relax slowly compared to water molecules located in cavities built with both AlO4 and SiO4. Compared to water confined in regular porous systems, water restricted in tobermorite is slower, indicating that the mesopore structure induces high disorder in the water structure. A comparison with water confined in the C-S-H gel is also discussed in this work. The strong dynamical changes in water due to the presence of aluminum might have important implications in the chemical transport of ions within hydrated calcium silicates, a process that governs the leaching and chemical degradation of cement.

  1. Zeolite formation from coal fly ash and its adsorption potential

    SciTech Connect

    Duangkamol Ruen-ngam; Doungmanee Rungsuk; Ronbanchob Apiratikul; Prasert Pavasant

    2009-10-15

    The possibility in converting coal fly ash (CFA) to zeolite was evaluated. CFA samples from the local power plant in Prachinburi province, Thailand, were collected during a 3-month time span to account for the inconsistency of the CFA quality, and it was evident that the deviation of the quality of the raw material did not have significant effects on the synthesis. The zeolite product was found to be type X. The most suitable weight ratio of sodium hydroxide (NaOH) to CFA was approximately 2.25, because this gave reasonably high zeolite yield with good cation exchange capacity (CEC). The silica (Si)-to-aluminum (Al) molar ratio of 4.06 yielded the highest crystallinity level for zeolite X at 79% with a CEC of 240 meq/100 g and a surface area of 325 m{sup 2}/g. Optimal crystallization temperature and time were 90{sup o}C and 4 hr, respectively, which gave the highest CEC of approximately 305 meq/100 g. Yields obtained from all experiments were in the range of 50-72%. 29 refs., 5 tabs., 7 figs.

  2. X-ray photoelectron spectroscopic investigation of nanocrystalline calcium silicate hydrates synthesised by reactive milling

    SciTech Connect

    Black, Leon . E-mail: l.black@shu.ac.uk; Garbev, Krassimir; Beuchle, Guenter; Stemmermann, Peter; Schild, Dieter

    2006-06-15

    X-ray photoelectron spectroscopy (XPS) has been used to analyse a series of mechanochemically synthesised, nanocrystalline calcium silicate hydrates (C-S-H). The samples, with Ca/Si ratios of 0.2 to 1.5, showed structural features of C-S-H(I). XPS analysis revealed changes in the extent of silicate polymerisation. Si 2p, Ca 2p and O 1s spectra showed that, unlike for the crystalline calcium silicate hydrate phases studied previously, there was no evidence of silicate sheets (Q{sup 3}) at low Ca/Si ratios. Si 2p and O 1s spectra indicated silicate depolymerisation, expressed by decreasing silicate chain length, with increasing C/S. In all spectra, peak narrowing was observed with increasing Ca/Si, indicating increased structural ordering. The rapid changes of the slope of FWHM of Si 2p, {delta} {sub Ca-Si} and {delta} {sub NBO-BO} as function of C/S ratio indicated a possible miscibility gap in the C-S-H-solid solution series between C/S 5/6 and 1. The modified Auger parameter ({alpha}') of nanocrystalline C-S-H decreased with increasing silicate polymerisation, a trend already observed studying crystalline C-S-H. Absolute values of {alpha}' were shifted about - 0.7 eV with respect to crystalline phases of equal C/S ratio, due to reduced crystallinity.

  3. Preparation and gas permeabilities of zeolite membranes

    SciTech Connect

    Jinqu Wang; Yongfeng Wang; Shuanshi Fan

    1994-12-31

    Zeolites with less than 10 {angstrom} pore are desirable membrane materials, due to their crystallinity, resistance to high temperature, and chemical inertness. A variety of new membranous materials were synthesized composed of a continuous intergrowth of 5-50 micrometer type A, X, Y, or ZSM-5 crystals. The membranes were crystallized under hydrothermal conditions at 90 to 220{degrees}C on the external surface of a porous ceramics. The reagents used were aluminum sulphate, water glass (20.1 wt% SiO{sub 2}, 6.09 wt% Na{sub 2}O, 73.8 wt% water), sodium hydroxide, sulphuric acid, deionized water and templating agents. The molar composition was: 0.1-0.5 Na{sub 2}O:1 SiO{sub 2}:0.04-0.05 Al{sub 2}O{sub 3}:20-60H{sub 2}O.

  4. Solid-state radioluminescent zeolite-containing composition and light sources

    DOEpatents

    Clough, Roger L.; Gill, John T.; Hawkins, Daniel B.; Renschler, Clifford L.; Shepodd, Timothy J.; Smith, Henry M.

    1992-01-01

    A new type of RL light source consisting of a zeolite crystalline material, the intralattice spaces of which a tritiated compound and a luminophore are sorbed, and which material is optionally further dispersed in a refractive index-matched polymer matrix.

  5. Synthesis of Foam-Shaped Nanoporous Zeolite Material: A Simple Template-Based Method

    ERIC Educational Resources Information Center

    Saini, Vipin K.; Pires, Joao

    2012-01-01

    Nanoporous zeolite foam is an interesting crystalline material with an open-cell microcellular structure, similar to polyurethane foam (PUF). The aluminosilicate structure of this material has a large surface area, extended porosity, and mechanical strength. Owing to these properties, this material is suitable for industrial applications such as…

  6. Crystal Structure and Chemical Composition of a Presolar Silicate from the Queen Elizabeth Range 99177 Meteorite

    NASA Technical Reports Server (NTRS)

    Nguyen, A. N.; Keller, L. P.; Rahman, Z.; Messenger, S.

    2013-01-01

    Mineral characterization of presolar silicate grains, the most abundant stardust phase, has provided valuable information about the formation conditions in circumstellar environments and in super-nova (SN) outflows. Spectroscopic observations of dust around evolved stars suggest a majority of amor-phous, Mg-rich olivine grains, but crystalline silicates, most of which are pyroxene, have also been observed [1]. The chemical compositions of hundreds of presolar silicates have been determined by Auger spectroscopy and reveal high Fe contents and nonstoichiometric compositions intermediate to olivine and pyroxene [2-6]. The unexpectedly high Fe contents can partly be attributed to secondary alteration on the meteorite parent bodies, as some grains have Fe isotopic anomalies from their parent stellar source [7]. Only about 35 presolar silicates have been studied for their mineral structures and chemical compositions by transmission electron microscopy (TEM). These grains display a wide range of compositions and structures, including crystalline forsterite, crystalline pyroxene, nanocrystalline grains, and a majority of amorphous nonstoichiometric grains. Most of these grains were identified in the primitive Acfer 094 meteorite. Presolar silicates from this meteorite show a wide range of Fe-contents, suggestive of secondary processing on the meteorite parent body. The CR chondrite QUE 99177 has not suffered as much alteration [8] and displays the highest presolar silicate abundance to date among carbonaceous chondrites [3, 6]. However, no mineralogical studies of presolar silicates from this meteorite have been performed. Here we examine the mineralogy of a presolar silicate from QUE 99177.

  7. Laboratory studies of the infrared small-particle extinction of amorphous silicates

    NASA Technical Reports Server (NTRS)

    Kraetschmer, W.

    1986-01-01

    The broad interstellar IR extinction features located at 9.7 and 18 microns wavelength are believed to originate from silicate dust grains. Cosmic abundances suggest that the silicate should have a chemical composition similar to that of olivine, (Mg,Fe)2 SiO4. Olivine is a very common terrestrial silicate mineral of crystalline structure. However, crystalline olivine grains do not fit the interstellar features well. Based on spectroscopic data obtained in laboratory studies and astronomical observations it was concluded that the interstellar silicate grains consist of a material with amorphous rather than crystalline structure. The astronomical arguments and the results obtained in our laboratory experiments which support this view are reviewed.

  8. European Microgravity Facilities for ZEOLITE Experiments on the International Space Station

    NASA Astrophysics Data System (ADS)

    Pletser, V.; Minster, O.; Kremer, S.; Kirschhock, C.; Martens, J.; Jacobs, P.

    2002-01-01

    Synthetic zeolites are complex porous silicates. Zeolites are applied as catalysts, adsorbents and sensors. Whereas the traditional applications are situated in the petrochemical area, zeolite catalysis and related zeolite-based technologies have a growing impact on the economics and sustainability of products and processes in a growing number of industrial sectors, including environmental protection and nanotechnology. A Sounding Rocket microgravity experiment led to significant insight in the physical aggregation patterns of zeolitic nanoscopic particles and the occurrence of self-organisation phenomena when undisturbed by convection. The opportunity of performing longer microgravity duration experiments on zeolite structures was recently offered in the frame of a Taxi-Flight to the ISS in November 2002 organized by Belgium and ESA. Two facilities are currently under development for this flight. One of them will use the Microgravity Science Glovebox (MSG) in the US Lab. Destiny to achieve thermal induced self-organization of different types of Zeosil nanoslabs by heating and cooling. The other facility will be flown on the ISS Russian segment and will allow to form Zeogrids at ambient temperature. On the other hand, the European Space Agency (ESA) is studying the possibility of developing a dedicated insert for zeolite experiments to be used with the optical and diagnostic platform of the Protein Crystallisation Diagnostic Facility (PCDF), that will fly integrated in the European Drawer Rack on the Columbus Laboratory starting in 2004. This paper will present the approach followed by ESA to prepare and support zeolite investigations in microgravity and will present the design concept of these three facilities.

  9. Hydrothermal alteration and zeolitization of the Fohberg phonolite, Kaiserstuhl Volcanic Complex, Germany

    NASA Astrophysics Data System (ADS)

    Weisenberger, Tobias Björn; Spürgin, Simon; Lahaye, Yann

    2014-11-01

    The subvolcanic Fohberg phonolite (Kaiserstuhl Volcanic Complex, Germany) is an economic zeolite deposit, formed by hydrothermal alteration of primary magmatic minerals. It is mined due to the high (>40 wt%) zeolite content, which accounts for the remarkable zeolitic physicochemical properties of the ground rock. New mineralogical and geochemical studies are carried out (a) to evaluate the manifestation of hydrothermal alteration, and (b) to constrain the physical and chemical properties of the fluids, which promoted hydrothermal replacement. The alkaline intrusion is characterized by the primary mineralogy: feldspathoid minerals, K-feldspar, aegirine-augite, wollastonite, and andradite. The rare-earth elements-phase götzenite is formed during the late-stage magmatic crystallization. Fluid-induced re-equilibration of feldspathoid minerals and wollastonite caused breakdown to a set of secondary phases. Feldspathoid minerals are totally replaced by various zeolite species, calcite, and barite. Wollastonite breakdown results in the formation of various zeolites, calcite, pectolite, sepiolite, and quartz. Zeolites are formed during subsolidus hydrothermal alteration (<150 °C) under alkaline conditions. A sequence of Ca-Na-dominated zeolite species (gonnardite, thomsonite, mesolite) is followed by natrolite. The sequence reflects an increase in and decrease in of the precipitating fluid. Low radiogenic 87Sr/86Sr values indicate a local origin of the elements necessary for secondary mineral formation from primary igneous phases. In addition, fractures cut the intrusive body, which contain zeolites, followed by calcite and a variety of other silicates, carbonates, and sulfates as younger generations. Stable isotope analysis of late-fracture calcite indicates very late circulation of meteoric fluids and mobilization of organic matter from surrounding sedimentary units.

  10. Oxygen and hydrogen isotope geochemistry of zeolites

    NASA Technical Reports Server (NTRS)

    Karlsson, Haraldur R.; Clayton, Robert N.

    1990-01-01

    Oxygen and hydrogen isotope ratios for natural samples of the zeolites analcime, chabazite, clinoptilolite, laumontite, mordenite, and natrolite have been obtained. The zeolite samples were classified into sedimentary, hydrothermal, and igneous groups. The ratios for each species of zeolite are reported. The results are used to discuss the origin of channel water, the role of zeolites in water-rock interaction, and the possibility that a calibrated zeolite could be used as a low-temperature geothermometer.

  11. Interstellar silicate analogs for grain-surface reaction experiments: Gas-phase condensation and characterization of the silicate dust grains

    SciTech Connect

    Sabri, T.; Jäger, C.; Gavilan, L.; Lemaire, J. L.; Vidali, G.; Henning, T.

    2014-01-10

    Amorphous, astrophysically relevant silicates were prepared by laser ablation of siliceous targets and subsequent quenching of the evaporated atoms and clusters in a helium/oxygen gas atmosphere. The described gas-phase condensation method can be used to synthesize homogeneous and astrophysically relevant silicates with different compositions ranging from nonstoichiometric magnesium iron silicates to pyroxene- and olivine-type stoichiometry. Analytical tools have been used to characterize the morphology, composition, and spectral properties of the condensates. The nanometer-sized silicate condensates represent a new family of cosmic dust analogs that can generally be used for laboratory studies of cosmic processes related to condensation, processing, and destruction of cosmic dust in different astrophysical environments. The well-characterized silicates comprising amorphous Mg{sub 2}SiO{sub 4} and Fe{sub 2}SiO{sub 4}, as well as the corresponding crystalline silicates forsterite and fayalite, produced by thermal annealing of the amorphous condensates, have been used as real grain surfaces for H{sub 2} formation experiments. A specifically developed ultra-high vacuum apparatus has been used for the investigation of molecule formation experiments. The results of these molecular formation experiments on differently structured Mg{sub 2}SiO{sub 4} and Fe{sub 2}SiO{sub 4} described in this paper will be the topic of the next paper of this series.

  12. The safety of synthetic zeolites used in detergents.

    PubMed

    Fruijtier-Pölloth, Claudia

    2009-01-01

    Synthetic zeolites are replacing phosphates as builders in laundry detergents; workers and consumers may, therefore, increasingly be exposed to these materials and it is important to assess their safety. This article puts mechanistic, toxicological and exposure data into context for a safety assessment. Zeolites are hygroscopic compounds with ion-exchanging properties. They may partially decompose under acidic conditions such as in the stomach releasing sodium ions, silicic acid and aluminum salts. The intact molecule is not bioavailable after oral intake or exposure through the dermal and inhalational routes. Under current conditions of manufacture and use, no systemic toxicity is to be expected from neither the intact molecule nor the degradation products; a significant effect on the bioavailability of other compounds is not likely. Zeolites may cause local irritation. It is, therefore, important to minimise occupational exposure. The co-operation of detergent manufacturers with the manufacturers of washing machines is necessary to find the right balance between environmental aspects such as energy and water savings and the occurrence of detergent residues on textiles due to insufficient rinsing.

  13. Theoretical maximal storage of hydrogen in zeolitic frameworks.

    PubMed

    Vitillo, Jenny G; Ricchiardi, Gabriele; Spoto, Giuseppe; Zecchina, Adriano

    2005-12-01

    Physisorption and encapsulation of molecular hydrogen in tailored microporous materials are two of the options for hydrogen storage. Among these materials, zeolites have been widely investigated. In these materials, the attained storage capacities vary widely with structure and composition, leading to the expectation that materials with improved binding sites, together with lighter frameworks, may represent efficient storage materials. In this work, we address the problem of the determination of the maximum amount of molecular hydrogen which could, in principle, be stored in a given zeolitic framework, as limited by the size, structure and flexibility of its pore system. To this end, the progressive filling with H2 of 12 purely siliceous models of common zeolite frameworks has been simulated by means of classical molecular mechanics. By monitoring the variation of cell parameters upon progressive filling of the pores, conclusions are drawn regarding the maximum storage capacity of each framework and, more generally, on framework flexibility. The flexible non-pentasils RHO, FAU, KFI, LTA and CHA display the highest maximal capacities, ranging between 2.86-2.65 mass%, well below the targets set for automotive applications but still in an interesting range. The predicted maximal storage capacities correlate well with experimental results obtained at low temperature. The technique is easily extendable to any other microporous structure, and it can provide a method for the screening of hypothetical new materials for hydrogen storage applications.

  14. Calcium silicate insulation structure

    DOEpatents

    Kollie, Thomas G.; Lauf, Robert J.

    1995-01-01

    An insulative structure including a powder-filled evacuated casing utilizes a quantity of finely divided synthetic calcium silicate having a relatively high surface area. The resultant structure-provides superior thermal insulating characteristics over a broad temperature range and is particularly well-suited as a panel for a refrigerator or freezer or the insulative barrier for a cooler or a insulated bottle.

  15. Determination of the Modal Abundance of Nano-Scale Amorphous Silicate Using Selected Area Electron Diffraction Mapping

    NASA Astrophysics Data System (ADS)

    De Gregorio, B. T.; Stroud, R. M.; Abreu, N.; Howard, K.

    2016-08-01

    Electron diffraction patterns provide an estimate of the relative abundance of amorphous and crystalline nano-scale phases. We map out the distribution of amorphous silicate in two fine-grained chondrule rims from ALH 77307.

  16. Synthesis of NaP zeolite at room temperature and short crystallization time by sonochemical method.

    PubMed

    Pal, Pameli; Das, Jugal K; Das, Nandini; Bandyopadhyay, Sibdas

    2013-01-01

    NaP zeolite nano crystals were synthesized by sonochemical method at room temperature with crystallization time of 3h. For comparison, to insure the effect of sonochemical method, the hydrothermal method at conventional synthesis condition, with same initial sol composition was studied. NaP zeolites are directly formed by ultrasonic treatment without the application of autogenous pressure and also hydrothermal treatment. The effect of ultrasonic energy and irradiation time showed that with increasing sonication energy, the crystallinity of the powders decreased but phase purity remain unchanged. The synthesized powders were characterized by XRD, IR, DTA TGA, FESEM, and TEM analysis. FESEM images revealed that 50 nm zeolite crystals were formed at room temperature by using sonochemical method. However, agglomerated particles having cactus/cabbage like structure was obtained by sonochemical method followed by hydrothermal treatment. In sonochemical process, formation of cavitation and the collapsing of bubbles produced huge energy which is sufficient for crystallization of zeolite compared to that supplied by hydrothermal process for conventional synthesis. With increasing irradiation energy and time, the crystallinity of the synthesized zeolite samples increased slightly.

  17. Single Molecule Nanospectroscopy Visualizes Proton-Transfer Processes within a Zeolite Crystal

    PubMed Central

    2016-01-01

    Visualizing proton-transfer processes at the nanoscale is essential for understanding the reactivity of zeolite-based catalyst materials. In this work, the Brønsted-acid-catalyzed oligomerization of styrene derivatives was used for the first time as a single molecule probe reaction to study the reactivity of individual zeolite H-ZSM-5 crystals in different zeolite framework, reactant and solvent environments. This was accomplished via the formation of distinct dimeric and trimeric fluorescent carbocations, characterized by their different photostability, as detected by single molecule fluorescence microscopy. The oligomerization kinetics turned out to be very sensitive to the reaction conditions and the presence of the local structural defects in zeolite H-ZSM-5 crystals. The remarkably photostable trimeric carbocations were found to be formed predominantly near defect-rich crystalline regions. This spectroscopic marker offers clear prospects for nanoscale quality control of zeolite-based materials. Interestingly, replacing n-heptane with 1-butanol as a solvent led to a reactivity decrease of several orders and shorter survival times of fluorescent products due to the strong chemisorption of 1-butanol onto the Brønsted acid sites. A similar effect was achieved by changing the electrophilic character of the para-substituent of the styrene moiety. Based on the measured turnover rates we have established a quantitative, single turnover approach to evaluate substituent and solvent effects on the reactivity of individual zeolite H-ZSM-5 crystals. PMID:27709925

  18. The growth of zeolites A, X and mordenite in space

    NASA Technical Reports Server (NTRS)

    Sacco, Albert, Jr.; Bac, N.; Coker, E. N.; Dixon, A. G.; Warzywoda, J.; Thompson, R. W.

    1994-01-01

    Zeolites are a class of crystalline aluminosilicate materials that form the backbone of the chemical process industry worldwide. They are used primarily as adsorbents and catalysts and support to a significant extent the positive balance of trade realized by the chemical industry in the United States (around $19 billion in 1991). The magnitude of their efforts can be appreciated when one realizes that since their introduction as 'cracking catalysts' in the early 1960's, they have saved the equivalent of 60 percent of the total oil production from Alaska's North Slope. Thus the performance of zeolite catalysts can have a profound effect on the U.S. economy. It is estimated that a 1 percent increase in yield of the gasoline fraction per barrel of oil would represent a savings of 22 million barrels of crude oil per year, representing a reduction of $400 million in the United States' balance of payments. Thus any activity that results in improvement in zeolite catalyst performance is of significant scientific and industrial interest. In addition, due to their 'stability,' uniformity, and, within limits, their 'engineerable' structures, zeolites are being tested as potential adsorbents to purify gases and liquids at the parts-per-billion levels needed in today's electronic, biomedical, and biotechnology industries and for the environment. Other exotic applications, such as host materials for quantum-confined semiconductor atomic arrays, are also being investigated. Because of the importance of this class of material, extensive efforts have been made to characterize their structures and to understand their nucleation and growth mechanisms, so as to be able to custom-make zeolites for a desired application. To date, both the nucleation mechanics and chemistry (such as what are the 'key' nutrients) are, as yet, still unknown for many, if not all, systems. The problem is compounded because there is usually a 'gel' phase present that is assumed to control the degree of

  19. Copper-containing zeolite catalysts

    DOEpatents

    Price, G.L.; Kanazirev, V.

    1996-12-10

    A catalyst useful in the conversion of nitrogen oxides or in the synthesis of nitriles or imines from amines, is formed by preparing an intimate mechanical mixture of a copper (II)-containing species, such as CuO or CuCl{sub 2}, or elemental copper, with a zeolite having a pore mouth comprising 10 oxygen atoms, such as ZSM-5, converting the elemental copper or copper (II) to copper (I), and driving the copper (I) into the zeolite.

  20. Copper-containing zeolite catalysts

    DOEpatents

    Price, Geoffrey L.; Kanazirev, Vladislav

    1996-01-01

    A catalyst useful in the conversion of nitrogen oxides or in the synthesis of nitriles or imines from amines, formed by preparing an intimate mechanical mixture of a copper (II)-containing species, such as CuO or CuCl.sub.2, or elemental copper, with a zeolite having a pore mouth comprising 10 oxygen atoms, such as ZSM-5, converting the elemental copper or copper (II) to copper (I), and driving the copper (I) into the zeolite.

  1. IMPROVED CATALYSTS FOR HEAVY OIL UPGRADING BASED ON ZEOLITE Y NANOPARTICLES ENCAPSULATED IN STABLE NANOPOROUS HOSTS

    SciTech Connect

    Conrad Ingram; Mark Mitchell

    2004-06-30

    The focus of this project is to improve the catalytic performance of zeolite Y for heavy petroleum hydrocracking by synthesizing nanoparticles of the zeolite ({approx}20-30 nm) inside nanoporous silicate or aluminosilicate hosts of similar pore diameters. The encapsulated zeolite nanoparticles are expected to possess pores of reduced diffusional path lengths, hence hydrocarbon substrates will diffuse in, are converted and the products quickly diffused out. This is expected to prevent over-reaction, hence minimizing pore blockage and active sites deactivation. In this phase of the project, research activities were focused on refining procedures to: (a) improve the synthesis of ordered, high surface area nanoporous silica, such as SBA-15, with expanded pore size using trimethylbenzene as additive to the parent SBA-15 synthesis mixture; and (b) reduce the particle size of zeolite Y such that they can be effectively incorporated into the nanoporous silicas. The synthesis of high surface ordered nanoporous silica containing enlarged pores of diameter of 25 nm (larger than the standard size of 8.4 nm) using trimethylbenzene as a pore size expander was accomplished. The synthesis of zeolite Y nanoparticles with median pore size of approximately 50 nm (smaller than the 80 nm typically obtained with TMAOH) using combined TMABr/TMAOH as organic additives was also accomplished.

  2. IMPROVED CATALYSTS FOR HEAVY OIL UPGRADING BASED ON ZEOLITE Y NANOPARTICLES ENCAPSULATED STABLE NANOPOROUS HOST

    SciTech Connect

    Conrad Ingram; Mark Mitchell

    2005-03-21

    The objectives of this project are to synthesis nanocrystals of highly acidic zeolite Y, encapsulate them within the channels of mesoporous (nanoporous) silicates or nanoporous organosilicates and evaluate the ''zeolite Y/Nanoporous host'' composites as catalysts for the upgrading of heavy petroleum feedstocks. Our results to date are summarized as follows. The synthesis of high surface ordered nanoporous silica of expanded pore diameter of 25 nm (larger than the standard size of 8.4 nm) using trimethylbenzene as a pore size expander was accomplished. The synthesis of zeolite Y nanoparticles with median pore size of approximately 50 nm (smaller than the 80 nm typically obtained with TMAOH) using combined TMABr/TMAOH as organic additives was also accomplished. The successful synthesis of zeoliteY/Nanoporous host composite materials by sequential combination of zeolite precursors and nanoporous material precursor mixtures was implied based on results from various characterization techniques such as X-Ray diffraction, infrared spectra, thermal analysis, porosimetry data. The resulting materials showed pore sizes up to 11 nm, and infrared band at 570 cm{sup -1} suggesting the presence of both phases. Work in the immediate future will be focused on the following three areas: (1) Further characterization of all-silica and aluminosilicate mesoporous materials with expanded pore sizes up to 30 nm will continue; (2) Research efforts to reduce the average particle size of zeolite nanoparticles down to 35-30 nm will continue; (3) Further synthesis of polymer-SBA15 nanocomposites will be conducted by changing the amount and chemistry of the zeolitic precursors added; and (4) Investigation on the catalytic properties of the materials using probe catalytic reactions (such as cumene cracking), followed by catalytic testing for heavy oil conversion.

  3. The Mineralogy of Circumstellar Silicates Preserved in Cometary Dust

    NASA Technical Reports Server (NTRS)

    Keller, L. P.; Messenger, S.

    2010-01-01

    Interplanetary dust particles (IDPs) contain a record of the building blocks of the solar system including presolar grains, molecular cloud material, and materials formed in the early solar nebula. Cometary IDPs have remained relatively unaltered since their accretion because of the lack of parent body thermal and aqueous alteration. We are using coordinated transmission electron microscope (TEM) and ion microprobe studies to establish the origins of the various components within cometary IDPs. Of particular interest is the nature and abundance of presolar silicates in these particles because astronomical observations suggest that crystalline and amorphous silicates are the dominant grain types produced in young main sequence stars and evolved O-rich stars. Five circumstellar grains have been identified including three amorphous silicate grains and two polycrystalline aggregates. All of these grains are between 0.2 and 0.5 micrometers in size. The isotopic compositions of all five presolar silicate grains fall within the range of presolar oxides and silicates, having large (17)O-enrichments and normal (18)O/(16)O ratios (Group 1 grains from AGB and RG stars). The amorphous silicates are chemically heterogeneous and contain nanophase FeNi metal and FeS grains in a Mg-silicate matrix. Two of the amorphous silicate grains are aggregates with subgrains showing variable Mg/Si ratios in chemical maps. The polycrystalline grains show annealed textures (equilibrium grains boundaries, uniform Mg/Fe ratios), and consist of 50-100 nm enstatite and pyrrhotite grains with lesser forsterite. One of the polycrystalline aggregates contains a subgrain of diopside. The polycrystalline aggregates form by subsolidus annealing of amorphous precursors. The bulk compositions of the five grains span a wide range in Mg/Si ratios from 0.4 to 1.2 (avg. 0.86). The average Fe/Si (0.40) and S/Si (0.21) ratios show a much narrower range of values and are approximately 50% of their solar

  4. Small-angle neutron scattering studies of the template-mediated crystallization of ZSM-5 type zeolite

    SciTech Connect

    Iton, L.E.; Brun, T.O.; Epperson, J.E. . Materials Science and Technology Div.); Trouw, F. . Intense Pulsed Neutron Source Program); White, J.W.; Henderson, S.J. )

    1988-03-01

    Small-angle neutron scattering is a useful new approach to the study of zeolite crystallization from aluminosilicate gels and the action of template molecules. It has been applied to gels for synthesis of zeolite ZSM-5 using tetrapropylammonium ions as templates where the scattering length densities of the gel particles and their texture were determined using contrast variation methods. Gels formulated from soluble silicate incorporate template molecules promptly into an amorphous embryonic'' structure and crystallization ensues via a solid hydrogel transformation mechanism. Gels formulated from colloidal silica show different scattering behavior, and a liquid phase transport mechanism is inferred. 8 refs., 4 figs., 2 tabs.

  5. Cost-effective two-stage varying-temperature rapid crystallization of zeolite T and SAPO-34

    NASA Astrophysics Data System (ADS)

    Yin, Xiaoyan; Chu, Naibo; Lu, Xuewei; Li, Zhongfang; Guo, Hong

    2016-05-01

    In this paper, zeolite T and SAPO-34 have been synthesized by two-stage varying temperature crystallization method (TVTC method). The feature of this method is dividing the hydrothermal process into two steps. The first step is lower temperature treatment which is favorable for the crystals nucleation and the second step is higher temperature treatment which is helpful to the crystals growth. The advantage of this method is that it greatly reduces the crystallization time and particle size compared to conventional constant temperature crystallization method (CCTC method). The influences of different initial and final temperatures on the zeolite crystallinity, morphology and particle size have been investigated in detail. Ultimately, the optimal crystallization conditions of zeolite T and SAPO-34 using this method have been summarized. The samples prepared with TVTC method and CCTC method also have been contrasted. With TVTC method, the synthesis time of zeolite T crystals is reduced from 7 days to 4 days and the synthesis time of SAPO-34 crystals is reduced from 48 h to 16 h. Furthermore, the sample prepared by TVTC method has higher crystallinity compared with the sample prepared by CCTC method. The particle size distributions of samples prepared by two methods have strongly confirmed that TVTC method is beneficial to form uniform and small zeolite particles. This paper provides an efficient and economical route to the industrial preparation of zeolite T and SAPO-34.

  6. Silicates in Alien Asteroids

    NASA Technical Reports Server (NTRS)

    2009-01-01

    This plot of data from NASA's Spitzer Space Telescopes shows that asteroid dust around a dead 'white dwarf' star contains silicates a common mineral on Earth. The data were taken primarily by Spitzer's infrared spectrograph, an instrument that breaks light apart into its basic constituents. The yellow dots show averaged data from the spectrograph, while the orange triangles show older data from Spitzer's infrared array camera. The white dwarf is called GD 40.

  7. Thermochemistry of Silicates

    NASA Technical Reports Server (NTRS)

    Costa, Gustavo; Jacobson, Nathan

    2015-01-01

    The thermodynamic properties of vapor and condensed phases of silicates are crucial in many fields of science. These quantities address fundamental questions on the formation, stability, transformation, and physical properties of silicate minerals and silicate coating compositions. Here the thermodynamic activities of silica and other species in solid solution have been measured by the analysis of the corresponding high temperature vapors using Knudsen Effusion Mass Spectrometry (KEMS). In first set of experiments KEMS has been used to examine the volatility sequence of species (Fe, SiO, Mg, O2 and O) present in the vapor phase during heating of fosterite-rich olivine (Fo93Fa7) up to 2400 C and to measure the Fe, SiO and Mg activities in its solid solution. The data of fosterite-rich olivine are essential for thermochemical equilibrium models to predict the atmospheric and surface composition of hot, rocky exoplanets (Lava Planets). In the second set of experiments the measured thermodynamic activities of the silica in Y2O3-SiO2 and Yb2O3-SiO2 systems are used to assess their reactivity and degradation recession as environmental barrier coatings (EBCs) in combustion environments (e.g. non-moveable parts of gas turbine engine).

  8. Selective preparation of zeolite X and A from flyash and its use as catalyst for biodiesel production.

    PubMed

    Volli, Vikranth; Purkait, M K

    2015-10-30

    This work discusses the utilization of flyash for synthesis of heterogeneous catalyst for transesterification. Different types of zeolites were synthesized from alkali fusion followed by hydrothermal treatment of coal flyash as source material. The synthesis conditions were optimized to obtain highly crystalline zeolite based on degree of crystallinity and cation exchange capacity (CEC). The effect of CEC, acid treatment, Si/Al ratio and calcination temperature (800, 900 and 1000 °C) on zeolite formation was also studied. Pure, single phase and highly crystalline zeolite was obtained at flyash/NaOH ratio (1:1.2), fusion temperature (550 °C), fusion time (1 h), hydrothermal temperature (110 °C) and hydrothermal time (12h). The synthesized zeolite was ion-exchanged with potassium and was used as catalyst for transesterification of mustard oil to obtain a maximum conversion of 84.6% with 5 wt% catalyst concentration, 12:1 methanol to oil molar ratio, reaction time of 7 h at 65 °C. The catalyst was reused for 3 times with marginal reduction in activity.

  9. Core-shell strain structure of zeolite microcrystals.

    PubMed

    Cha, Wonsuk; Jeong, Nak Cheon; Song, Sanghoon; Park, Hyun-jun; Thanh Pham, Tung Cao; Harder, Ross; Lim, Bobae; Xiong, Gang; Ahn, Docheon; McNulty, Ian; Kim, Jungho; Yoon, Kyung Byung; Robinson, Ian K; Kim, Hyunjung

    2013-08-01

    Zeolites are crystalline aluminosilicate minerals featuring a network of 0.3-1.5-nm-wide pores, used in industry as catalysts for hydrocarbon interconversion, ion exchangers, molecular sieves and adsorbents. For improved applications, it is highly useful to study the distribution of internal local strains because they sensitively affect the rates of adsorption and diffusion of guest molecules within zeolites. Here, we report the observation of an unusual triangular deformation field distribution in ZSM-5 zeolites by coherent X-ray diffraction imaging, showing the presence of a strain within the crystal arising from the heterogeneous core-shell structure, which is supported by finite element model calculation and confirmed by fluorescence measurement. The shell is composed of H-ZSM-5 with intrinsic negative thermal expansion whereas the core exhibits a different thermal expansion behaviour due to the presence of organic template residues, which usually remain when the starting materials are insufficiently calcined. Engineering such strain effects could have a major impact on the design of future catalysts. PMID:23832126

  10. An emulsion-based droplet hydrothermal synthesis method for the production of uniform sized zeolite nanocrystals.

    PubMed

    Sharma, Pankaj; Han, Moon Hee; Cho, Churl Hee

    2014-05-15

    A droplet based new hydrothermal synthesis method for nano-zeolite synthesis in bulk amount with uniform size, shape and morphology is presented. The proposed process addresses the limitation and shortcomings of droplet based microfluidic reactors and conventional hydrothermal methods. The process has been designed on the concept of mixing two immiscible solutions at high speed which then produces nano/submicron size droplets. Confinement within the droplet provides uniform heat transfer, enhanced mass transfer to growing crystal, chaotic advection within droplet facilitate rapid mixing, prevent the contact between growing crystals etc. Fine-tuned nano-cubic LTA zeolite crystals of size ∼100 nm with uniform morphology and size distribution were prepared. Just within 4h of reaction time (aging+crystallization) well shaped cubic crystals with high crystallinity and size uniformity can be synthesized by the proposed synthesis process. Diffraction and electron microscopic studies reveal the high phase purity and size uniformity of as-synthesized LTA zeolite particles.

  11. Crystals as molecules: postsynthesis covalent functionalization of zeolitic imidazolate frameworks.

    PubMed

    Morris, William; Doonan, Christian J; Furukawa, Hiroyasu; Banerjee, Rahul; Yaghi, Omar M

    2008-09-24

    A new crystalline zeolitic imidazolate framework, ZIF-90, was prepared from zinc(II) nitrate and imidazolate-2-carboxyaldehyde (ICA) and found to have the sodalite-type topology. Its 3D porous framework has an aperture of 3.5 A and a pore size of 11.2 A. The pores are decorated by the aldehyde functionality of ICA which has allowed its transformation to the alcohol functionality by reduction with NaBH4 and its conversion to imine functionality by reaction with ethanolamine to give ZIF-91 and ZIF-92, respectively. The N2 adsorption isotherm of ZIF-90 shows a highly porous material with calculated Langmuir and BET surface areas of 1320 and 1270 m2 g(-1). Both functionalized ZIFs retained high crystallinity and in addition ZIF-91 maintained permanent porosity (surface areas: 1070 and 1010 m2 g(-1)).

  12. Translational dynamics of water in a nanoporous layered silicate

    SciTech Connect

    Nair, Sankar; Chowdhuri, Zema; Peral, Inmaculada; Neumann, Dan A.; Dickinson, L. Charles; Tompsett, Geoffrey; Jeong, Hae-Kwon; Tsapatsis, Michael

    2005-03-01

    Neutron time-of-flight and backscattering spectroscopy have been used to study the translational diffusion of water molecules in the unusual layered material AMH-3, which consists of (zeolitelike) three-dimensionally nanoporous silicate layers spaced by (claylike) interlayer regions. The synthesis of AMH-3 and its characterization by {sup 29}Si NMR, Raman, and infrared spectroscopy, are described. An analysis of quasielastic neutron scattering (QENS) spectra using the random jump diffusion model reveals two translational diffusive motions clearly separated in time scales: a fast process (D{approx}10{sup -9} m{sup 2}/s at 300 K), and a much slower process (D{approx}10{sup -11} m{sup 2}/s at 300 K). Considering the structural model of AMH-3 and the transport properties extracted from the QENS data, it is suggested that the slower motion corresponds to diffusion by water molecules in the interlayer spaces whereas the fast process involves diffusion in the silicate layer. This first investigation of transport phenomena in nanoporous layered silicates like AMH-3 indicates that they have the potential to offer mass transport properties different from zeolite materials and layered clays.

  13. Translational dynamics of water in a nanoporous layered silicate

    NASA Astrophysics Data System (ADS)

    Nair, Sankar; Chowdhuri, Zema; Peral, Inmaculada; Neumann, Dan A.; Dickinson, L. Charles; Tompsett, Geoffrey; Jeong, Hae-Kwon; Tsapatsis, Michael

    2005-03-01

    Neutron time-of-flight and backscattering spectroscopy have been used to study the translational diffusion of water molecules in the unusual layered material AMH-3, which consists of (zeolitelike) three-dimensionally nanoporous silicate layers spaced by (claylike) interlayer regions. The synthesis of AMH-3 and its characterization by Si29 NMR, Raman, and infrared spectroscopy, are described. An analysis of quasielastic neutron scattering (QENS) spectra using the random jump diffusion model reveals two translational diffusive motions clearly separated in time scales: a fast process ( Dtilde 10-9m2/s at 300 K), and a much slower process ( Dtilde 10-11m2/s at 300 K). Considering the structural model of AMH-3 and the transport properties extracted from the QENS data, it is suggested that the slower motion corresponds to diffusion by water molecules in the interlayer spaces whereas the fast process involves diffusion in the silicate layer. This first investigation of transport phenomena in nanoporous layered silicates like AMH-3 indicates that they have the potential to offer mass transport properties different from zeolite materials and layered clays.

  14. Zeolite synthesis: an energetic perspective.

    PubMed

    Zwijnenburg, Martijn A; Bromley, Stefan T

    2010-11-21

    Taking |D(H(2)O)(x)|[AlSiO(4)] based materials (where D is Li, Na, K, Rb or Cs) as an archetypal aluminosilicate system, we use accurate density functional theory calculations to demonstrate how the substitution of silicon cations in silica, with pairs of aluminium and (alkali metal) cations, changes the energetic ordering of different competing structure-types. For large alkali metal cations we further show that the formation of porous aluminosilicate structures, the so-called zeolites, is energetically favored. These findings unequivocally demonstrate that zeolites can be energetic preferred reaction products, rather than being kinetically determined, and that the size of the (hydrated) cations in the pore, be it inorganic or organic, is critical for directing zeolite synthesis.

  15. Zeolite synthesis: an energetic perspective.

    PubMed

    Zwijnenburg, Martijn A; Bromley, Stefan T

    2010-11-21

    Taking |D(H(2)O)(x)|[AlSiO(4)] based materials (where D is Li, Na, K, Rb or Cs) as an archetypal aluminosilicate system, we use accurate density functional theory calculations to demonstrate how the substitution of silicon cations in silica, with pairs of aluminium and (alkali metal) cations, changes the energetic ordering of different competing structure-types. For large alkali metal cations we further show that the formation of porous aluminosilicate structures, the so-called zeolites, is energetically favored. These findings unequivocally demonstrate that zeolites can be energetic preferred reaction products, rather than being kinetically determined, and that the size of the (hydrated) cations in the pore, be it inorganic or organic, is critical for directing zeolite synthesis. PMID:20938518

  16. A new approach to evaluate natural zeolite ability to sorb lead (Pb) from aqueous solutions

    NASA Astrophysics Data System (ADS)

    Drosos, Evangelos I. P.; Karapanagioti, Hrissi K.

    2013-04-01

    Lead (Pb) is a hazardous pollutant commonly found in aquatic ecosystems. Among several methods available, the addition of sorbent amendments to soils or sediments is attractive, since its application is relatively simple, while it can also be cost effective when a low cost and re-usable sorbent is used; e.g. natural zeolites. Zeolites are crystalline aluminosilicates with a three-dimensional structure composed of a set of cavities occupied by large ions and water molecules. Zeolites can accommodate a wide variety of cations, such as Na+, K+, Ca2+, Mg2+, which are rather loosely held and can readily be exchanged for others in an aqueous solution. Natural zeolites are capable of removing cations, such as lead, from aqueous solutions by ion exchange. There is a wide variation in the cation exchange capacity (CEC) of natural zeolites because of the different nature of various zeolites cage structures, natural structural defects, adsorbed ions, and their associated gangue minerals. Naturally occurring zeolites are rarely pure and are contaminated to varying degrees by other minerals, such as clays and feldspars, metals, quartz, or other zeolites as well. These impurities affect the CEC even for samples originated from the same region but from a different source. CEC of the material increases with decreasing impurity content. Potentially exchangeable ions in such impurities do not necessarily participate in ion exchange mechanism, while, in some cases, impurities may additionally block the access to active sites. For zeoliferous rocks having the same percentage of a zeolitic phase, the CEC increases with decreasing Si/Al ratio, as the more Si ions are substituted by Al ions, the more negative the valence of the matrix becomes. Sodium seems to be the most effective exchangeable ion for lead. On the contrary, it is unlikely that the potassium content of the zeolite would be substituted. A pretreatment with high concentration solutions of Na, such as 2 M NaCl, can

  17. Hydration characteristics and environmental friendly performance of a cementitious material composed of calcium silicate slag.

    PubMed

    Zhang, Na; Li, Hongxu; Zhao, Yazhao; Liu, Xiaoming

    2016-04-01

    Calcium silicate slag is an alkali leaching waste generated during the process of extracting Al2O3 from high-alumina fly ash. In this research, a cementitious material composed of calcium silicate slag was developed, and its mechanical and physical properties, hydration characteristics and environmental friendly performance were investigated. The results show that an optimal design for the cementitious material composed of calcium silicate slag was determined by the specimen CFSC7 containing 30% calcium silicate slag, 5% high-alumina fly ash, 24% blast furnace slag, 35% clinker and 6% FGD gypsum. This blended system yields excellent physical and mechanical properties, confirming the usefulness of CFSC7. The hydration products of CFSC7 are mostly amorphous C-A-S-H gel, rod-like ettringite and hexagonal-sheet Ca(OH)2 with small amount of zeolite-like minerals such as CaAl2Si2O8·4H2O and Na2Al2Si2O8·H2O. As the predominant hydration products, rod-like ettringite and amorphous C-A-S-H gel play a positive role in promoting densification of the paste structure, resulting in strength development of CFSC7 in the early hydration process. The leaching toxicity and radioactivity tests results indicate that the developed cementitious material composed of calcium silicate slag is environmentally acceptable. This study points out a promising direction for the proper utilization of calcium silicate slag in large quantities.

  18. Pockels effect of silicate glass-ceramics: Observation of optical modulation in Mach-Zehnder system.

    PubMed

    Yamaoka, Kazuki; Takahashi, Yoshihiro; Yamazaki, Yoshiki; Terakado, Nobuaki; Miyazaki, Takamichi; Fujiwara, Takumi

    2015-07-17

    Silicate glass has been used for long time because of its advantages from material's viewpoint. In this paper, we report the observation of Pockels effect by Mach-Zehnder interferometer in polycrystalline ceramics made from a ternary silicate glass via crystallization due to heat-treatment, i.e., glass-ceramics. Since the silicate system is employed as the precursor, merits of glass material are fully utilized to fabricate the optical device component, in addition to that of functional crystalline material, leading us to provide an electro-optic device, which is introducible into glass-fiber network.

  19. Pockels effect of silicate glass-ceramics: Observation of optical modulation in Mach–Zehnder system

    PubMed Central

    Yamaoka, Kazuki; Takahashi, Yoshihiro; Yamazaki, Yoshiki; Terakado, Nobuaki; Miyazaki, Takamichi; Fujiwara, Takumi

    2015-01-01

    Silicate glass has been used for long time because of its advantages from material’s viewpoint. In this paper, we report the observation of Pockels effect by Mach–Zehnder interferometer in polycrystalline ceramics made from a ternary silicate glass via crystallization due to heat-treatment, i.e., glass-ceramics. Since the silicate system is employed as the precursor, merits of glass material are fully utilized to fabricate the optical device component, in addition to that of functional crystalline material, leading us to provide an electro-optic device, which is introducible into glass-fiber network. PMID:26184722

  20. Enhanced selectivity of zeolites by controlled carbon deposition

    DOEpatents

    Nenoff, Tina M.; Thoma, Steven G.; Kartin, Mutlu

    2006-05-09

    A method for carbonizing a zeolite comprises depositing a carbon coating on the zeolite pores by flowing an inert carrier gas stream containing isoprene through a regenerated zeolite at elevated temperature. The carbonized zeolite is useful for the separation of light hydrocarbon mixtures due to size exclusion and the differential adsorption properties of the carbonized zeolite.

  1. IMPROVED CATALYSTS FOR HEAVY OIL UPGRADING BASED ON ZEOLITE Y NANOPARTICLES ENCAPSULATED IN STABLE NANOPOROUS HOST

    SciTech Connect

    Conrad Ingram; Mark Mitchell

    2005-03-31

    The objectives of this project are to synthesis nanocrystals of highly acidic zeolite Y, encapsulate them within the channels of mesoporous (nanoporous) silicates or nanoporous organosilicates and evaluate the ''zeolite Y/Nanoporous host'' composites as catalysts for the upgrading of heavy petroleum feedstocks. Our results to date are summarized as follows. The synthesis of high surface ordered nanoporous silica of expanded pore diameter of 25 nm (larger than the standard size of 8.4 nm) using trimethylbenzene as a pore size expander was accomplished. The synthesis of zeolite Y nanoparticles with median pore size of approximately 50 nm (smaller than the 80 nm typically obtained with TMAOH) using combined TMABr/TMAOH as organic additives was also accomplished. The successful synthesis of zeoliteY/Nanoporous host composite materials by sequential combination of zeolite precursors and nanoporous material precursor mixtures was implied based on results from various characterization techniques such as X-Ray diffraction, infrared spectra, thermal analysis, porosimetry data. The resulting materials showed pore sizes up to 11 nm, and infrared band at 570 cm{sup -1} suggesting the presence of both phases. New results indicated that good quality highly ordered nanoporous silica host can be synthesized in the presence of zeolite Y seed precursor depending on the amount of precursor added. Preliminary research on the catalytic performance of the materials is underway. Probe acid catalyzed reactions, such as the cracking of cumene is currently being conducted. Work in the immediate future will be focused on the following three areas: (1) Further characterization of all-silica and aluminosilicate mesoporous materials with expanded pore sizes up to 30 nm will continue; (2) Research efforts to reduce the average particle size of zeolite nanoparticles down to 35-30 nm will continue; (3) Further synthesis of ZeoliteY/Nanoporous host composite catalysts of improved structural and

  2. One-pot pseudomorphic crystallization of mesoporous porous silica to hierarchical porous zeolites

    SciTech Connect

    Xing, Jun-Ling; Jiang, Shu-Hua; Pang, Jun-Ling; Yuan, En-Hui; Ma, Xiao-Jing; Lam, Koon-Fung; Xue, Qing-Song; Zhang, Kun

    2015-09-15

    Hierarchically porous silica with mesopore and zeolitic micropore was synthesized via pseudomorphic crystallization under high-temperature hydrothermal treatment in the presence of cetyltrimethylammonium tosylate and tetrapropylammonium ions. A combined characterization using small-angle X-ray diffraction (XRD), nitrogen adsorption, high-resolution transmission electron microscopy (TEM), thermogravimetric analysis (TG), and elemental analysis showed that dual templates, CTA{sup +} and TPA{sup +} molecules, can work in a cooperative manner to synthesize mesoporous zeolite in a one-pot system by precisely tuning the reaction conditions, such as reaction time and temperature, and type and amount of heterometal atoms. It is found that the presence of Ti precursor is critical to the successful synthesis of such nanostructure. It not only retards the nucleation and growth of crystalline MFI domains, but also acts as nano-binder or nano-glue to favor the assembly of zeolite nanoblocks. - Graphical abstract: Display Omitted - Highlights: • A facile method to synthesize mesoporous zeolites with hierarchical porosity was presented. • It gives a new insight into keeping the balance between mesoscopic and molecular ordering in hierarchical porous materials. • A new understanding on the solid–solid transformation mechanism for the synthesis of titanosilicate zeolites was proposed.

  3. A Highly Ion-Selective Zeolite Flake Layer on Porous Membranes for Flow Battery Applications.

    PubMed

    Yuan, Zhizhang; Zhu, Xiangxue; Li, Mingrun; Lu, Wenjing; Li, Xianfeng; Zhang, Huamin

    2016-02-24

    Zeolites are crystalline microporous aluminosilicates with periodic arrangements of cages and well-defined channels, which make them very suitable for separating ions of different sizes, and thus also for use in battery applications. Herein, an ultra-thin ZSM-35 zeolite flake was introduced onto a poly(ether sulfone) based porous membrane. The pore size of the zeolite (ca. 0.5 nm) is intermediary between that of hydrated vanadium ions (>0.6 nm) and protons (<0.24 nm). The resultant membrane can thus be used to perfectly separate vanadium ions and protons, making this technology useful in vanadium flow batteries (VFB). A VFB with a zeolite-coated membrane exhibits a columbic efficiency of >99 % and an energy efficiency of >81 % at 200 mA cm(-2), which is by far the highest value ever reported. These convincing results indicate that zeolite-coated membranes are promising in battery applications.

  4. A Highly Ion-Selective Zeolite Flake Layer on Porous Membranes for Flow Battery Applications.

    PubMed

    Yuan, Zhizhang; Zhu, Xiangxue; Li, Mingrun; Lu, Wenjing; Li, Xianfeng; Zhang, Huamin

    2016-02-24

    Zeolites are crystalline microporous aluminosilicates with periodic arrangements of cages and well-defined channels, which make them very suitable for separating ions of different sizes, and thus also for use in battery applications. Herein, an ultra-thin ZSM-35 zeolite flake was introduced onto a poly(ether sulfone) based porous membrane. The pore size of the zeolite (ca. 0.5 nm) is intermediary between that of hydrated vanadium ions (>0.6 nm) and protons (<0.24 nm). The resultant membrane can thus be used to perfectly separate vanadium ions and protons, making this technology useful in vanadium flow batteries (VFB). A VFB with a zeolite-coated membrane exhibits a columbic efficiency of >99 % and an energy efficiency of >81 % at 200 mA cm(-2), which is by far the highest value ever reported. These convincing results indicate that zeolite-coated membranes are promising in battery applications. PMID:26822866

  5. A novel magnetic 4A zeolite adsorbent synthesised from kaolinite type pyrite cinder (KTPC)

    NASA Astrophysics Data System (ADS)

    Wang, Weiqing; Feng, Qiming; Liu, Kun; Zhang, Guofan; Liu, Jing; Huang, Yang

    2015-01-01

    As a solid waste, kaolinite type pyrite cinder (KTPC) is a special pyrite cinder, its mineral components include metakaolin and magnetite, and the chemical compositions of these minerals include SiO2, Al2O3, FeO and Fe2O3. In this study, a novel magnetic 4A zeolite adsorbent was synthesised from KTPC using the hydrothermal method, and the optimum hydrothermal synthesis conditions were investigated using X-ray diffraction (XRD) and by determining the specific surface area (SSA) and the saturated cation exchange adsorption capacity (SCEAC) to Cs+. Under the optimum hydrothermal synthesis conditions, the magnetic 4A zeolite adsorbent can be synthesised with high crystallinity, and the SSA and SCEAC to Cs+ are 24.49 m2/g and 106.63 mg/g, respectively. The further characterisations of pore size distribution, scanning electron microscopy (SEM), energy dispersive X-ray (EDX), thermogravimetry-derivative thermogravimetry-differential thermal analysis (TG-DTG-DTA), Fourier transform infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM) were performed. The results revealed that magnetic particles are coated onto the zeolite surface and further form magnetic aggregates, and the existing magnetic particles in KTPC do not change their crystal structure and do not affect the synthesis of the 4A zeolite. In addition, the synthesised 4A zeolite adsorbent can be used as a magnetic adsorbent in wastewater treatment with high magnetic sensitivity and is thermally stable up to approximately 900 °C.

  6. A comparison of the amorphization of zeolitic imidazolate frameworks (ZIFs) and aluminosilicate zeolites by ball-milling.

    PubMed

    Baxter, Emma F; Bennett, Thomas D; Cairns, Andrew B; Brownbill, Nick J; Goodwin, Andrew L; Keen, David A; Chater, Philip A; Blanc, Frédéric; Cheetham, Anthony K

    2016-03-14

    X-ray diffraction has been used to investigate the kinetics of amorphization through ball-milling at 20 Hz, for five zeolitic imidazolate frameworks (ZIFs) - ZIF-8, ZIF-4, ZIF-zni, BIF-1-Li and CdIF-1. We find that the rates of amorphization for the zinc-containing ZIFs increase with increasing solvent accessible volume (SAV) in the sequence ZIF-8 > ZIF-4 > ZIF-zni. The Li-B analogue of the dense ZIF-zni amorphizes more slowly than the corresponding zinc phase, with the behaviour showing a correlation with their relative bulk moduli and SAVs. The cadmium analogue of ZIF-8 (CdIF-1) amorphizes more rapidly than the zinc counterpart, which we ascribe primarily to its relatively weak M-N bonds as well as the higher SAV. The results for the ZIFs are compared to three classical zeolites - Na-X, Na-Y and ZSM-5 - with these taking up to four times longer to amorphize. The presence of adsorbed solvent in the pores is found to render both ZIF and zeolite frameworks more resistant to amorphization. X-ray total scattering measurements show that amorphous ZIF-zni is structurally indistinguishable from amorphous ZIF-4 with both structures retaining the same short-range order that is present in their crystalline precursors. By contrast, both X-ray total scattering measurements and (113)Cd NMR measurements point to changes in the local environment of amorphous CdIF-1 compared with its crystalline CdIF-1 precursor.

  7. A comparison of the amorphization of zeolitic imidazolate frameworks (ZIFs) and aluminosilicate zeolites by ball-milling.

    PubMed

    Baxter, Emma F; Bennett, Thomas D; Cairns, Andrew B; Brownbill, Nick J; Goodwin, Andrew L; Keen, David A; Chater, Philip A; Blanc, Frédéric; Cheetham, Anthony K

    2016-03-14

    X-ray diffraction has been used to investigate the kinetics of amorphization through ball-milling at 20 Hz, for five zeolitic imidazolate frameworks (ZIFs) - ZIF-8, ZIF-4, ZIF-zni, BIF-1-Li and CdIF-1. We find that the rates of amorphization for the zinc-containing ZIFs increase with increasing solvent accessible volume (SAV) in the sequence ZIF-8 > ZIF-4 > ZIF-zni. The Li-B analogue of the dense ZIF-zni amorphizes more slowly than the corresponding zinc phase, with the behaviour showing a correlation with their relative bulk moduli and SAVs. The cadmium analogue of ZIF-8 (CdIF-1) amorphizes more rapidly than the zinc counterpart, which we ascribe primarily to its relatively weak M-N bonds as well as the higher SAV. The results for the ZIFs are compared to three classical zeolites - Na-X, Na-Y and ZSM-5 - with these taking up to four times longer to amorphize. The presence of adsorbed solvent in the pores is found to render both ZIF and zeolite frameworks more resistant to amorphization. X-ray total scattering measurements show that amorphous ZIF-zni is structurally indistinguishable from amorphous ZIF-4 with both structures retaining the same short-range order that is present in their crystalline precursors. By contrast, both X-ray total scattering measurements and (113)Cd NMR measurements point to changes in the local environment of amorphous CdIF-1 compared with its crystalline CdIF-1 precursor. PMID:26575842

  8. DIRECT LABORATORY ANALYSIS OF SILICATE STARDUST FROM RED GIANT STARS

    SciTech Connect

    Vollmer, Christian; Hoppe, Peter; Brenker, Frank E.

    2009-07-20

    We performed combined focused ion beam/transmission electron microscopy studies to investigate the chemistry and structure of eight presolar silicate grains that were previously detected by NanoSIMS oxygen isotope mapping of the carbonaceous chondrite Acfer 094. The analyzed presolar silicates belong to the O isotope Groups I/II ({sup 17}O-enriched and {sup 18}O-depleted) and therefore come from 1-2.5 M{sub sun} asymptotic giant branch stars of close-to-solar or slightly lower-than-solar metallicity. Three grains are amorphous, Mg-rich, and show a variable, but more pyroxene-like composition. Most probably, these grains have formed under circumstellar low-temperature conditions below the crystallization temperature. Three grains are Fe-bearing glasses similar to the 'glass with embedded metal and sulfides' (GEMS) grains found in interplanetary dust particles. However, two of the meteorite GEMS grains from this study lack comparatively large ({approx}>20 nm) Fe-rich inclusions and have sulfur contents <1 at.%, which is different than observed for the majority of GEMS grains. These grains likely condensed under strong non-equilibrium conditions from an Si-enriched gas. One olivine is characterized by a crystalline core and an amorphous, more Fe-rich rim, which is probably the result of interstellar medium sputtering combined with Mg removal. The detection of another olivine with a relatively high Fe content (Mg no. 0.9) shows that circumstellar crystalline silicates are more Fe-rich than astrophysical models usually suggest. The overall predominance of olivine among the crystalline silicate stardust population compared to pyroxene indicates preferential formation or survival of this type of mineral. As pyroxene is indeed detected in circumstellar outflows, it remains to be seen how this result is compatible with astrophysical observations and experimental data.

  9. Multiple-quantum NMR studies of spin clusters in liquid crystals and zeolites

    SciTech Connect

    Pearson, J. . Dept. of Chemistry Lawrence Berkeley Lab., CA )

    1991-07-01

    This work will describe the use of MQ NMR to study spin clusters in anisotropic materials. A technique known as multiple-quantum spin counting was used to determine average spin cluster sizes liquid crystalline materials and in faujacitic zeolites containing aromatic hydrocarbons. The first half of the thesis will describe MQ NMR and the MQ spin counting technique, and the second half of the thesis will describe the actual experiments and their results.

  10. Hydrogen Selective Exfoliated Zeolite Membranes

    SciTech Connect

    Tsapatsis, Michael; Daoutidis, Prodromos; Elyassi, Bahman; Lima, Fernando; Iyer, Aparna; Agrawal, Kumar; Sabnis, Sanket

    2015-04-06

    The objective of this project was to develop and evaluate an innovative membrane technology at process conditions that would be representative of Integrated Gasification Combined Cycle (IGCC) advanced power generation with pre-combustion capture of carbon dioxide (CO2). This research focused on hydrogen (H2)-selective zeolite membranes that could be utilized to separate conditioned syngas into H2-rich and CO2-rich components. Both experiments and process design and optimization calculations were performed to evaluate the concept of ultra-thin membranes made from zeolites nanosheets. In this work, efforts in the laboratory were made to tackle two fundamental challenges in application of zeolite membranes in harsh industrial environments, namely, membrane thickness and membrane stability. Conventional zeolite membranes have thicknesses in the micron range, limiting their performance. In this research, we developed a method for fabrication of ultimately thin zeolite membranes based on zeolite nanosheets. A range of layered zeolites (MWW, RWR, NSI structure types) suitable for hydrogen separation was successfully exfoliated to their constituent nanosheets. Further, membranes were made from one of these zeolites, MWW, to demonstrate the potential of this group of materials. Moreover, long-term steam stability of these zeolites (up to 6 months) was investigated in high concentrations of steam (35 mol% and 95 mole%), high pressure (10 barg), and high temperatures (350 °C and 600 °C) relevant to conditions of water-gas-shift and steam methane reforming reactions. It was found that certain nanosheets are stable, and that stability depends on the concentration of structural defects. Additionally, models that represent a water-gas-shift (WGS) membrane reactor equipped with the zeolite membrane were developed for systems studies. These studies had the aim of analyzing the effect of the membrane reactor integration into IGCC plants

  11. Analyses of Cometary Silicate Crystals: DDA Spectral Modeling of Forsterite

    NASA Technical Reports Server (NTRS)

    Wooden, Diane

    2012-01-01

    Comets are the Solar System's deep freezers of gases, ices, and particulates that were present in the outer protoplanetary disk. Where comet nuclei accreted was so cold that CO ice (approximately 50K) and other supervolatile ices like ethane (C2H2) were preserved. However, comets also accreted high temperature minerals: silicate crystals that either condensed (greater than or equal to 1400 K) or that were annealed from amorphous (glassy) silicates (greater than 850-1000 K). By their rarity in the interstellar medium, cometary crystalline silicates are thought to be grains that formed in the inner disk and were then radially transported out to the cold and ice-rich regimes near Neptune. The questions that comets can potentially address are: How fast, how far, and over what duration were crystals that formed in the inner disk transported out to the comet-forming region(s)? In comets, the mass fractions of silicates that are crystalline, f_cryst, translate to benchmarks for protoplanetary disk radial transport models. The infamous comet Hale-Bopp has crystalline fractions of over 55%. The values for cometary crystalline mass fractions, however, are derived assuming that the mineralogy assessed for the submicron to micron-sized portion of the size distribution represents the compositional makeup of all larger grains in the coma. Models for fitting cometary SEDs make this assumption because models can only fit the observed features with submicron to micron-sized discrete crystals. On the other hand, larger (0.1-100 micrometer radii) porous grains composed of amorphous silicates and amorphous carbon can be easily computed with mixed medium theory wherein vacuum mixed into a spherical particle mimics a porous aggregate. If crystalline silicates are mixed in, the models completely fail to match the observations. Moreover, models for a size distribution of discrete crystalline forsterite grains commonly employs the CDE computational method for ellipsoidal platelets (c:a:b=8

  12. UTILITY OF ZEOLITES IN HAZARDOUS METAL REMOVAL FROM WATER

    EPA Science Inventory

    Zeolites are well known for their ion exchange, adsorption and acid catalysis properties. Different inorganic pollutants have been removed from water at room temperature by using synthetic zeolites. Zeolite Faujasite Y has been used to remove inorganic pollutants including arseni...

  13. Tailored zeolites for the removal of metal oxyanions: overcoming intrinsic limitations of zeolites.

    PubMed

    Figueiredo, Hugo; Quintelas, Cristina

    2014-06-15

    This review aims to present a global view of the efforts conducted to convert zeolites into efficient supports for the removal of heavy metal oxyanions. Despite lacking affinity for these species, due to inherent charge repulsion between zeolite framework and anionic species, zeolites have still received considerable attention from the scientific community, since their versatility allowed tailoring them to answer specific requirements. Different processes for the removal and recovery of toxic metals based on zeolites have been presented. These processes resort to modification of the zeolite surface to allow direct adsorption of oxyanions, or by combination with reducing agents for oxyanions that allow ion-exchange with the converted species by the zeolite itself. In order to testify zeolite versatility, as well as covering the wide array of physicochemical constraints that oxyanions offer, chromium and arsenic oxyanions were selected as model compounds for a review of treatment/remediation strategies, based on zeolite modification.

  14. Crystalline and Crystalline International Disposal Activities

    SciTech Connect

    Viswanathan, Hari S.; Chu, Shaoping; Reimus, Paul William; Makedonska, Nataliia; Hyman, Jeffrey De'Haven; Karra, Satish; Dittrich, Timothy M.

    2015-12-21

    This report presents the results of work conducted between September 2014 and July 2015 at Los Alamos National Laboratory in the crystalline disposal and crystalline international disposal work packages of the Used Fuel Disposition Campaign (UFDC) for DOE-NE’s Fuel Cycle Research and Development program.

  15. On the Filling Process Forming Silicic Segregations

    NASA Astrophysics Data System (ADS)

    Zavala, K.; Marsh, B. D.

    2001-05-01

    Interdigitating silicic lenses are particularly well developed and well exposed in the Ferrar Dolerites of the McMurdo Dry Valleys, Antarctica. Silicic segregations are texturally splotchy, have sharp upper contacts, and diffuse lower contacts that grade into normal dolerite. What is unusual about these 1- 2 m lenses is that the background sill shows very little compositional variation and yet the silicic segregations show wide compositional variation. In particular, silica content varies between 47 and 68%, and thus produces for the sill overall a bimodal composition. We have analyzed over 100 segregation samples in order to investigate the nature of the filling process. Previous work (Zavala & Marsh, 1999) has shown that segregations have compositions that correspond to interstitial liquid present at crystallinities between 59 and 63 % and temperatures between 1135° and 1115° . Additionally, it was noted that the large segregation lenses are not homogeneous and exhibit cyclic variations in silica content. This observation lead to the current study, in which new samples from the Peneplain Sill (235 to 241) show remarkable correlations between segregation texture, stratigraphic position and silica enrichment. Incompatibles like Zr indicate relatively low 35 to 40% concentrations of melt at the point of segregation extraction, which supports the notion that segregations formed by withdrawal of interstitial melt into tears as the solidification front (SF) became gravitationally unstable. The details of the filling process can also be gauged using chemical profiles normalized to segregation thickness. One group shows distinct multiple smaller cycles of silica enrichment versus depth, which suggests successive stages of opening. The other group shows a strong enrichment in silica followed by a steady decay to the base. The general form of this latter pattern measures the gradient in melt composition immediately below the segregation at the time of infilling. From

  16. Synthesis, structure, and carbon dioxide capture properties of zeolitic imidazolate frameworks.

    PubMed

    Phan, Anh; Doonan, Christian J; Uribe-Romo, Fernando J; Knobler, Carolyn B; O'Keeffe, Michael; Yaghi, Omar M

    2010-01-19

    Zeolites are one of humanity's most important synthetic products. These aluminosilicate-based materials represent a large segment of the global economy. Indeed, the value of zeolites used in petroleum refining as catalysts and in detergents as water softeners is estimated at $350 billion per year. A major current goal in zeolite chemistry is to create a structure in which metal ions and functionalizable organic units make up an integral part of the framework. Such a structure, by virtue of the flexibility with which metal ions and organic moieties can be varied, is viewed as a key to further improving zeolite properties and accessing new applications. Recently, it was recognized that the Si-O-Si preferred angle in zeolites (145 degrees ) is coincident with that of the bridging angle in the M-Im-M fragment (where M is Zn or Co and Im is imidazolate), and therefore it should be possible to make new zeolitic imidazolate frameworks (ZIFs) with topologies based on those of tetrahedral zeolites. This idea was successful and proved to be quite fruitful; within the last 5 years over 90 new ZIF structures have been reported. The recent application of high-throughput synthesis and characterization of ZIFs has expanded this structure space significantly: it is now possible to make ZIFs with topologies previously unknown in zeolites, in addition to mimicking known structures. In this Account, we describe the general preparation of crystalline ZIFs, discussing the methods that have been developed to create and analyze the variety of materials afforded. We include a comprehensive list of all known ZIFs, including structure, topology, and pore metrics. We also examine how complexity might be introduced into new structures, highlighting how link-link interactions might be exploited to effect particular cage sizes, create polarity variations between pores, or adjust framework robustness, for example. The chemical and thermal stability of ZIFs permit many applications, such as the

  17. Synthesis, structure, and carbon dioxide capture properties of zeolitic imidazolate frameworks.

    PubMed

    Phan, Anh; Doonan, Christian J; Uribe-Romo, Fernando J; Knobler, Carolyn B; O'Keeffe, Michael; Yaghi, Omar M

    2010-01-19

    Zeolites are one of humanity's most important synthetic products. These aluminosilicate-based materials represent a large segment of the global economy. Indeed, the value of zeolites used in petroleum refining as catalysts and in detergents as water softeners is estimated at $350 billion per year. A major current goal in zeolite chemistry is to create a structure in which metal ions and functionalizable organic units make up an integral part of the framework. Such a structure, by virtue of the flexibility with which metal ions and organic moieties can be varied, is viewed as a key to further improving zeolite properties and accessing new applications. Recently, it was recognized that the Si-O-Si preferred angle in zeolites (145 degrees ) is coincident with that of the bridging angle in the M-Im-M fragment (where M is Zn or Co and Im is imidazolate), and therefore it should be possible to make new zeolitic imidazolate frameworks (ZIFs) with topologies based on those of tetrahedral zeolites. This idea was successful and proved to be quite fruitful; within the last 5 years over 90 new ZIF structures have been reported. The recent application of high-throughput synthesis and characterization of ZIFs has expanded this structure space significantly: it is now possible to make ZIFs with topologies previously unknown in zeolites, in addition to mimicking known structures. In this Account, we describe the general preparation of crystalline ZIFs, discussing the methods that have been developed to create and analyze the variety of materials afforded. We include a comprehensive list of all known ZIFs, including structure, topology, and pore metrics. We also examine how complexity might be introduced into new structures, highlighting how link-link interactions might be exploited to effect particular cage sizes, create polarity variations between pores, or adjust framework robustness, for example. The chemical and thermal stability of ZIFs permit many applications, such as the

  18. Mesoporous MFI zeolites by microwave induced assembly between sulfonic acid functionalized MFI zeolite nanoparticles and alkyltrimethylammonium cationic surfactants.

    PubMed

    Jin, Hailian; Ansari, Mohd Bismillah; Park, Sang-Eon

    2011-07-14

    Mesoporous MFI zeolites (ZSM-5, TS-1, S-1) having intracrystalline mesoporosity within zeolite crystals were synthesized by microwave induced assembly through the ionic interaction between the sulfonic acid functionalized MFI zeolite nanoparticles and alkyltrimethylammonium cationic surfactants.

  19. The impact of aqueous medium on zeolite framework integrity

    SciTech Connect

    Vjunov, Aleksei; Fulton, John L.; Camaioni, Donald M.; Hu, Jian Z.; Burton, Sarah D.; Arslan, Ilke; Lercher, Johannes A.

    2015-05-12

    Understanding the zeolite framework stability in aqueous phase is crucial to develop stable catalysts. Al K–edge, extended X–ray absorption fine structure and 27Al MAS NMR spectroscopies in combination with DFT calculations have been used to monitor both qualitative and quantitative structural changes of two well–characterized samples with BEA structure. The effects of various properties on stability were explored, including Al concentration, Al distribution, particle size and structural defects. As the samples were degraded by treatment in hot liquid water, the local structure about the Al T–site remained mostly intact, including the Al–O–Si angles and bond distances, while the nano–scale crystalline structure as measured by XRD and TEM was disrupted. The combined data suggest a three–step mechanism in which, initially, the HBEA framework crystallinity decreases via hydrolysis of T–O bonds along polymorph stacking faults and inter–grain boundaries in a mode similar to crack propagation in glass. With prolonged exposure, amorphization occurs via hydrolysis of surface Si–OH groups propagating inward through the zeolite lattice. In parallel, cracks propagate within the crystalline micro–domains along paths through specific T–O–T groups. Authors thank B. W. Arey (PNNL) for HIM measurements, T. Huthwelker for support during Al XAFS measurements at the Swiss Light Source (PSI, Switzerland) and M. Y. Hu (PNNL) for support during NMR experiments. This work was supported by the U. S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. NMR experiments were performed at the Environmental Molecular Science Laboratory, a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research, and Physical Science Laboratory both located at Pacific Northwest National Laboratory (PNNL). PNNL is a multi–program national laboratory

  20. Effect of metal loading processes on the stability and thermal transformation of Co{sup 2+}- and Cu{sup 2+}-zeolite Y prepared from Egyptian kaolin

    SciTech Connect

    EL-Mekkawi, Doaa M. Selim, Mohamed M.

    2012-07-15

    This paper aims to assess the effect of the transition metals (TM) loading procedure on the incorporation of Co{sup 2+} and Cu{sup 2+} in zeolite Y, and their relevance to stability of the zeolite, particularly with respect to the thermal transformation to the spinel phases. In this work, zeolite Y prepared from Egyptian kaolin was used. XRF, XRD, TEM, UV/visible absorption measurements, and atomic absorption analyses in addition to the visual observations are recorded. XRF has been used to investigate the materials composition. TEM and XRD indicate the presence of nanoparticle spinel upon the calcination of the TM-zeolites at 1000 Degree-Sign C. In addition to spinel particles, XRD shows the formation of metal oxides, SiO{sub 2} and alumino-silicate phases. According to the transition metal and the cation loading process, different phases were detected. UV/visible absorption measurements and the visual observations are used to determine the experimental condition of the highest spinel content. It has been noticed that the experimental conditions of the metal sorption processes greatly affect the phase transformation. Stability and thermal transformation of zeolite depend on the initial concentration of the transition cation solutions and the number of loading cycles. - Highlights: Black-Right-Pointing-Pointer We study the effects of loading procedure in the incorporation of TM in zeolite Y. Black-Right-Pointing-Pointer Synthetic zeolite Y prepared from Egyptian kaolin has been used. Black-Right-Pointing-Pointer The type of TM affects the stability and thermal transformation of zeolite. Black-Right-Pointing-Pointer Loading processes affect the stability and thermal transformation of zeolite.

  1. Synthesis of ‘unfeasible’ zeolites

    NASA Astrophysics Data System (ADS)

    Mazur, Michal; Wheatley, Paul S.; Navarro, Marta; Roth, Wieslaw J.; Položij, Miroslav; Mayoral, Alvaro; Eliášová, Pavla; Nachtigall, Petr; Čejka, Jiří; Morris, Russell E.

    2016-01-01

    Zeolites are porous aluminosilicate materials that have found applications in many different technologies. However, although simulations suggest that there are millions of possible zeolite topologies, only a little over 200 zeolite frameworks of all compositions are currently known, of which about 50 are pure silica materials. This is known as the zeolite conundrum—why have so few of all the possible structures been made? Several criteria have been formulated to explain why most zeolites are unfeasible synthesis targets. Here we demonstrate the synthesis of two such ‘unfeasible’ zeolites, IPC-9 and IPC-10, through the assembly-disassembly-organization-reassembly mechanism. These new high-silica zeolites have rare characteristics, such as windows that comprise odd-membered rings. Their synthesis opens up the possibility of preparing other zeolites that have not been accessible by traditional solvothermal synthetic methods. We envisage that these findings may lead to a step change in the number and types of zeolites available for future applications.

  2. Increased thermal conductivity monolithic zeolite structures

    DOEpatents

    Klett, James; Klett, Lynn; Kaufman, Jonathan

    2008-11-25

    A monolith comprises a zeolite, a thermally conductive carbon, and a binder. The zeolite is included in the form of beads, pellets, powders and mixtures thereof. The thermally conductive carbon can be carbon nano-fibers, diamond or graphite which provide thermal conductivities in excess of about 100 W/mK to more than 1,000 W/mK. A method of preparing a zeolite monolith includes the steps of mixing a zeolite dispersion in an aqueous colloidal silica binder with a dispersion of carbon nano-fibers in water followed by dehydration and curing of the binder is given.

  3. Synthesis, characterization and catalytic activity of indium substituted nanocrystalline Mobil Five (MFI) zeolite

    SciTech Connect

    Shah, Kishor Kr.; Nandi, Mithun; Talukdar, Anup K.

    2015-06-15

    Highlights: • In situ modification of the MFI zeolite by incorporation of indium. • The samples were characterized by XRD, FTIR, TGA, UV–vis (DRS), SAA, EDX and SEM. • The incorporation of indium was confirmed by XRD, FT-IR, UV–vis (DRS), EDX and TGA. • Hydroxylation of phenol reaction was studied on the synthesized catalysts. - Abstract: A series of indium doped Mobil Five (MFI) zeolite were synthesized hydrothermally with silicon to aluminium and indium molar ratio of 100 and with aluminium to indium molar ratios of 1:1, 2:1 and 3:1. The MFI zeolite phase was identified by XRD and FT-IR analysis. In XRD analysis the prominent peaks were observed at 2θ values of around 6.5° and 23° with a few additional shoulder peaks in case of all the indium incorporated samples suggesting formation of pure phase of the MFI zeolite. All the samples under the present investigation were found to exhibit high crystallinity (∼92%). The crystallite sizes of the samples were found to vary from about 49 to 55 nm. IR results confirmed the formation of MFI zeolite in all cases showing distinct absorbance bands near 1080, 790, 540, 450 and 990 cm{sup −1}. TG analysis of In-MFI zeolites showed mass losses in three different steps which are attributed to the loss due to adsorbed water molecules and the two types TPA{sup +} cations. Further, the UV–vis (DRS) studies reflected the position of the indium metal in the zeolite framework. Surface area analysis of the synthesized samples was carried out to characterize the synthesized samples The analysis showed that the specific surface area ranged from ∼357 to ∼361 m{sup 2} g{sup −1} and the pore volume of the synthesized samples ranged from 0.177 to 0.182 cm{sup 3} g{sup −1}. The scanning electron microscopy studies showed the structure of the samples to be rectangular and twinned rectangular shaped. The EDX analysis was carried out for confirmation of Si, Al and In in zeolite frame work. The catalytic activities of

  4. Trends in the adsorption and reactivity of hydrogen on magnesium silicate nanoclusters.

    PubMed

    Oueslati, Ichraf; Kerkeni, Boutheïna; Bromley, Stefan T

    2015-04-14

    We study nanoclusters of Mg-rich olivine and pyroxene (having (MgO)6(SiO2)3 and (MgO)4(SiO2)4 compositions) with respect to their reactivity towards hydrogen atoms, using density functional calculations. Ultrasmall silicate particles are fundamental intermediates in cosmic dust grain formation and processing, and are thought to make up a significant mass fraction of the grain population. Due to their nanoscale dimensions and high surface area to bulk ratios, they are likely to also have a disproportionately large influence on surface chemistry in the interstellar medium. This work investigates the potential role of silicate nanoclusters in vital interstellar hydrogen-based chemistry by studying atomic H adsorption and H2 formation. Our extensive set of calculations confirm the generality of a Brønsted-Evans-Polanyi (BEP) relation between the H2 reaction barrier and the 2Hchem binding energy, suggesting it to be independent of silicate dust grain shape, size, crystallinity and composition. Our results also suggest that amorphous/porous grains with forsteritic composition would tend to dissociate H2, but relatively Mg-poor silicate grains (e.g. enstatite composition) and/or more crystalline/compact silicate grains would tend to catalyse H2 formation. The high structural thermostability of silicate nanoclusters with respect to the heat released during exothermic H2 formation reactions is also verified.

  5. Microsphere zeolite materials derived from coal fly ash cenospheres as precursors to mineral-like aluminosilicate hosts for 135,137Cs and 90Sr

    NASA Astrophysics Data System (ADS)

    Vereshchagina, Tatiana A.; Vereshchagin, Sergei N.; Shishkina, Nina N.; Vasilieva, Nataly G.; Solovyov, Leonid A.; Anshits, Alexander G.

    2013-06-01

    Hollow microsphere zeolite materials with a bilayered zeolite/glass crystalline shell bearing NaP1 zeolite were synthesized by the hydrothermal treatment of coal fly ash cenospheres (Si/Al = 2.7) in an alkaline medium. Cs+ and/or Sr2+ forms of zeolitized cenospheres with the different Cs+ and/or Sr2+ loading were prepared by the ion exchange from nitrate solutions. The resulted (Cs,Na)P1, (Sr,Na)P1 and (Cs,Sr,Na)P1 bearing microsphere zeolites were converted to glass ceramics by heating at 900-1000 °C. The differential scanning calorimetry and quantitative phase analysis were used to monitor the solid-phase transformation of the initial and ion exchanged zeolite materials. It was established that the final solidified forms of Cs+ and/or Sr2+ are glass-crystalline ceramic materials based on pollucite-nepheline, Sr-feldspar-nepheline and Sr-feldspar-pollucite composites including ˜60 wt.% of the major host phases (pollucite, Sr-feldspar) and 10-20 wt.% of glass. The 137Cs leaching rate of 4.1 × 10-7 g cm-2 day-1 was determined for the pollucite glass-ceramic according to Russian State Standard (GOST) No. 52126 P-2003 (7 day, 25 °C, distilled water).

  6. Analysis of a Sheet Silicate.

    ERIC Educational Resources Information Center

    Adams, J. M.; Evans, S.

    1980-01-01

    Describes a student project in analytical chemistry using sheet silicates. Provides specific information regarding the use of phlogopite in an experiment to analyze samples for silicon, aluminum, magnesium, iron, potassium, and fluoride. (CS)

  7. Ion implantation in silicate glasses

    SciTech Connect

    Arnold, G.W.

    1993-12-01

    This review examines the effects of ion implantation on the physical properties of silicate glasses, the compositional modifications that can be brought about, and the use of metal implants to form colloidal nanosize particles for increasing the nonlinear refractive index.

  8. Experiments on metal-silicate plumes and core formation.

    PubMed

    Olson, Peter; Weeraratne, Dayanthie

    2008-11-28

    Short-lived isotope systematics, mantle siderophile abundances and the power requirements of the geodynamo favour an early and high-temperature core-formation process, in which metals concentrate and partially equilibrate with silicates in a deep magma ocean before descending to the core. We report results of laboratory experiments on liquid metal dynamics in a two-layer stratified viscous fluid, using sucrose solutions to represent the magma ocean and the crystalline, more primitive mantle and liquid gallium to represent the core-forming metals. Single gallium drop experiments and experiments on Rayleigh-Taylor instabilities with gallium layers and gallium mixtures produce metal diapirs that entrain the less viscous upper layer fluid and produce trailing plume conduits in the high-viscosity lower layer. Calculations indicate that viscous dissipation in metal-silicate plumes in the early Earth would result in a large initial core superheat. Our experiments suggest that metal-silicate mantle plumes facilitate high-pressure metal-silicate interaction and may later evolve into buoyant thermal plumes, connecting core formation to ancient hotspot activity on the Earth and possibly on other terrestrial planets. PMID:18826918

  9. Experiments on metal-silicate plumes and core formation.

    PubMed

    Olson, Peter; Weeraratne, Dayanthie

    2008-11-28

    Short-lived isotope systematics, mantle siderophile abundances and the power requirements of the geodynamo favour an early and high-temperature core-formation process, in which metals concentrate and partially equilibrate with silicates in a deep magma ocean before descending to the core. We report results of laboratory experiments on liquid metal dynamics in a two-layer stratified viscous fluid, using sucrose solutions to represent the magma ocean and the crystalline, more primitive mantle and liquid gallium to represent the core-forming metals. Single gallium drop experiments and experiments on Rayleigh-Taylor instabilities with gallium layers and gallium mixtures produce metal diapirs that entrain the less viscous upper layer fluid and produce trailing plume conduits in the high-viscosity lower layer. Calculations indicate that viscous dissipation in metal-silicate plumes in the early Earth would result in a large initial core superheat. Our experiments suggest that metal-silicate mantle plumes facilitate high-pressure metal-silicate interaction and may later evolve into buoyant thermal plumes, connecting core formation to ancient hotspot activity on the Earth and possibly on other terrestrial planets.

  10. 21 CFR 172.410 - Calcium silicate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Calcium silicate. 172.410 Section 172.410 Food and... PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Anticaking Agents § 172.410 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be safely used in food in accordance with...

  11. 21 CFR 172.410 - Calcium silicate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Calcium silicate. 172.410 Section 172.410 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Agents § 172.410 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be...

  12. 21 CFR 172.410 - Calcium silicate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Calcium silicate. 172.410 Section 172.410 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Agents § 172.410 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be...

  13. 21 CFR 172.410 - Calcium silicate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Calcium silicate. 172.410 Section 172.410 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Agents § 172.410 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be...

  14. Zeolites Remove Sulfur From Fuels

    NASA Technical Reports Server (NTRS)

    Voecks, Gerald E.; Sharma, Pramod K.

    1991-01-01

    Zeolites remove substantial amounts of sulfur compounds from diesel fuel under relatively mild conditions - atmospheric pressure below 300 degrees C. Extracts up to 60 percent of sulfur content of high-sulfur fuel. Applicable to petroleum refineries, natural-gas processors, electric powerplants, and chemical-processing plants. Method simpler and uses considerably lower pressure than current industrial method, hydro-desulfurization. Yields cleaner emissions from combustion of petroleum fuels, and protects catalysts from poisoning by sulfur.

  15. Nanocrystalline Zeolites: Synthesis, Mechanism, and Applications

    NASA Astrophysics Data System (ADS)

    Severance, Michael Andrew

    Nanocrystalline zeolite particles are becoming an important material in many technical applications (e.g. zeolite membranes). Synthetic methods that minimize the zeolite crystal diameter, while providing a narrow particle size distribution, are of primary importance in these technical applications. However, there are several limitations to currently existing synthetic routes aimed at producing nanozeolites and zeolite membrane devices. For example, zeolite growth in these contexts typically requires days to weeks at high temperature to crystallize. Despite excellent performance of zeolite membranes in several separation applications, the long synthesis times required undermine any practical application of these technologies. This work focuses on chemical manipulation of zeolite nucleation processes in sol gel systems in effort to address such limitations. The primary findings indicate that careful control of the nucleation stage of a clear zeolite synthesis (optically transparent sol gel) allow the formation of zeolite Y nanocrystals less than 50 nm in diameter with a polydispersity index less than 0.2. Furthermore, chemical perturbations made during the nucleation stage of zeolite Y hydrogel synthesis is shown to accelerate crystal growth by a factor of 3-4, depending on the specific sol gel chemistry. These findings are applied to the nanocrystal seeding and rapid hydrothermal growth of zeolite Y membranes on inexpensive polymeric supports. A novel synthetic method is developed to this end. Also, the chemical and physical properties of monodisperse nanocrystalline zeolite Y synthesized herein are explored by electrochemical impedance spectroscopy. It is found that the particle interface plays an important role in the ionic conductivity of nanocrystalline zeolites in contrast to their larger zeolite counterparts in analogy to other ceramic and metal oxide ion conductors. Finally, the possibility to produce novel organic and inorganic composite systems through

  16. Physical, Chemical and Structural Evolution of Zeolite-Containing Waste Forms Produced from Metakaolinite and Calcined Sodium Bearing Waste (HLW and/or LLW)

    SciTech Connect

    Grutzeck, Michael W.

    2005-06-27

    Zeolites are extremely versatile. They can adsorb liquids and gases and serve as cation exchange media. They occur in nature as well cemented deposits. The ancient Romans used blocks of zeolitized tuff as a building material. Using zeolites for the management of radioactive waste is not a new idea, but a process by which the zeolites can be made to act as a cementing agent is. Zeolitic materials are relatively easy to synthesize from a wide range of both natural and man-made substances. The process under study is derived from a well known method in which metakaolin (an impure thermally dehydroxylated kaolinite heated to {approx}700 C containing traces of quartz and mica) is mixed with sodium hydroxide (NaOH) and reacted in slurry form (for a day or two) at mildly elevated temperatures. The zeolites form as finely divided powders containing micrometer ({micro}m) sized crystals. However, if the process is changed slightly and only just enough concentrated sodium hydroxide solution is added to the metakaolinite to make a thick crumbly paste and then the paste is compacted and cured under mild hydrothermal conditions (60-200 C), the mixture will form a hard ceramic-like material containing distinct crystalline tectosilicate minerals (zeolites and feldspathoids) imbedded in an X-ray amorphous hydrated sodium aluminosilicate matrix. Due to its lack of porosity and vitreous appearance we have chosen to call this composite a ''hydroceramic''.

  17. Synthesis and Properties of Nanoparticle Forms Saponite Clay, Cancrinite Zeolite and Phase Mixtures Thereof.

    PubMed

    Shao, Hua; Pinnavaia, Thomas J

    2010-09-01

    The low-temperature synthesis (90°C) of nanoparticle forms of a pure phase smectic clay (saponite) and zeolite (cancrinite) is reported, along with phase mixtures thereof. A synthesis gel corresponding to the Si:Al:Mg unit cell composition of saponite (3.6:0.40:3.0) and a NaOH/Si ratio of 1.39 affords the pure phase clay with disordered nanolayer stacking. Progressive increases in the NaOH/Si ratio up to a value of 8.33 results in the co-crystallization of first garronite and then cancrinite zeolites with nanolath morphology. The resulting phase mixtures exhibit a compound particulate structure of intertwined saponite nanolayers and cancrinite nanolaths that cannot be formed through physical mixing of the pure phase end members. Under magnesium-free conditions, pure phase cancrinite nanocrystals are formed. The Si/Al ratio of the reaction mixture affects the particle morphology as well as the chemical composition of the cancrinite zeolite. Ordinarily, cancrinite crystallizes with a Si/Al ratio of 1.0, but a silicon-rich form of the zeolite (Si/Al=1.25) is crystallized at low temperature from a silica rich synthesis gel, as evidenced by (29)Si NMR spectroscopy and XEDS-TEM. Owing to the exceptionally high external surface areas of the pure phase clay (875 m(2)/g) and zeolite end members (8.9 - 40 m(2)/g), as well as their unique mixed phase composites (124 - 329 m(2)/g), these synthetic derivatives are promising model nanoparticles for studies of the bioavailability of poly-aromatic hydrocarbons immobilized in silicate bearing sediments and soils.

  18. UTILITY OF ZEOLITES IN ARSENIC REMOVAL FROM WATER

    EPA Science Inventory

    Zeolites are well known for their ion exchange and adsorption properties. So far the cation exchanger properties of zeolites have been extensively studied and utilized. The anion exchanger properties of zeolites are less studied. Zeolite Faujasite Y has been used to remove arseni...

  19. Phosphatation of zeolite H-ZSM-5: a combined microscopy and spectroscopy study.

    PubMed

    van der Bij, Hendrik E; Aramburo, Luis R; Arstad, Bjørnar; Dynes, James J; Wang, Jian; Weckhuysen, Bert M

    2014-02-01

    A variety of phosphated zeolite H-ZSM-5 samples are investigated by using a combination of Fourier transfer infrared (FTIR) spectroscopy, single pulse (27)Al, (29)Si, (31)P, (1)H-(31)P cross polarization (CP), (27)Al-(31)P CP, and (27)Al 3Q magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy, scanning transmission X-ray microscopy (STXM) and N2 physisorption. This approach leads to insights into the physicochemical processes that take place during phosphatation. Direct phosphatation of H-ZSM-5 promotes zeolite aggregation, as phosphorus does not penetrate deep into the zeolite material and is mostly found on and close to the outer surface of the zeolite, acting as a glue. Phosphatation of pre-steamed H-ZSM-5 gives rise to the formation of a crystalline tridymite AlPO4 phase, which is found in the mesopores of dealuminated H-ZSM-5. Framework aluminum species interacting with phosphorus are not affected by hydrothermal treatment. Dealuminated H-ZSM-5, containing AlPO4 , retains relatively more framework Al atoms and acid sites during hydrothermal treatment than directly phosphated H-ZSM-5.

  20. Dealumination of hexagonal (EMT)/cubic (FAU) zeolite intergrowth materials: A SEM and HRTEM study

    SciTech Connect

    Ohsuna, Tetsu; Watanabe, Denjiro; Terasaki, Osamu; Anderson, M.W.; Carr, S.W.

    1994-12-01

    The aim of this paper is to describe the effects of mild dealumination of the end members (FAU, EMT) and intergrowths produced using crown ethers on the nature of the resultant zeolite. The end members and intergrowths were prepared as described previously and dealuminated according to the following procedure. The intergrowth was prepared from a mixture of crown ethers; 66% 18-crown-6 and 33% 15-crown-5 to give an ordered intergrowth. The zeolites were first calcined to remove the crown ether template (600{degree}C, flowing air, 16 h) and then exchanged with ammonium ions. The zeolite (6 g) was slurried in ammonium acetate solution (450 cm{sup 3}, 0.8 M), and to this was added slowly 15.6 cm{sup 3} of ammonium hexafluorosilicate solution (0.5 M). The mixture was stirred at 75{degree}C for 3 h. The zeolite was collected and carefully washed with water (3 x 100 cm{sup 3}). The dealuminated samples were characterized by {sup 29}Si and {sup 27}Al MAS NMR, X-ray powder diffraction and adsorption measurements. These data indicate that the resultant materials are highly crystalline and showed no signs of structural degradation both in short-range order ({sup 27}Al, {sup 29}Si MAS NMR) and long-range order (XRD). However, the SEM and high-resolution images were particularly informative.

  1. Comparative pathology of silicate pneumoconiosis.

    PubMed Central

    Brambilla, C.; Abraham, J.; Brambilla, E.; Benirschke, K.; Bloor, C.

    1979-01-01

    A simple pneumoconiosis with lamellar birefringent crystals was observed in animals dying in the San Diego Zoo. We studied 100 autopsies from 11 mammalian and eight avian species. In mammals, mild pulmonary lesions comprised crystal-laden macrophages in alveoli and lymphatics. Interstitial fibrosis was present in 20% of cases. There were no nodules. In birds, dust retention produced large granulomas around tertiary bronchi without fibrosis. Mineralogic analysis using scanning and transmission electron microscopy showed most of the crystals to be silicates. Ninety percent were complex silicates, with aluminum-potassium silicates comprising 70% of the analyzed particles. Electron and x-ray diffraction showed the silicates to be muscovite mica and its hydrothermal degradation product, ie, illite clay. This mica was also present on filtration membranes of atmospheric air samples obtained from the San Diego Zoo. The amount of dust retention was related to the animal's age, anatomic or ecologic variances, and length of stay in the San Diego Zoo. Its semidesert atmosphere is rich in silicates, which are inhaled and deposited in the lungs. Similar mica-induced lesions are found in humans living in this region or the Southwest of the USA. This simple pneumoconiosis is likely to be widespread in human populations living in desert or semidesert climates. Images Figure 9 Figure 10 Figure 7 Figure 8 Figure 5 Figure 6 Figure 1 Figure 2 Figure 3 Figure 4 PMID:223447

  2. Stardust silicates from primitive meteorites.

    PubMed

    Nagashima, Kazuhide; Krot, Alexander N; Yurimoto, Hisayoshi

    2004-04-29

    Primitive chondritic meteorites contain material (presolar grains), at the level of a few parts per million, that predates the formation of our Solar System. Astronomical observations and the chemical composition of the Sun both suggest that silicates must have been the dominant solids in the protoplanetary disk from which the planets of the Solar System formed, but no presolar silicates have been identified in chondrites. Here we report the in situ discovery of presolar silicate grains 0.1-1 microm in size in the matrices of two primitive carbonaceous chondrites. These grains are highly enriched in 17O (delta17O(SMOW) > 100-400 per thousand ), but have solar silicon isotopic compositions within analytical uncertainties, suggesting an origin in an oxygen-rich red giant or an asymptotic giant branch star. The estimated abundance of these presolar silicates (3-30 parts per million) is higher than reported for other types of presolar grains in meteorites, consistent with their ubiquity in the early Solar System, but is about two orders of magnitude lower than their abundance in anhydrous interplanetary dust particles. This result is best explained by the destruction of silicates during high-temperature processing in the solar nebula.

  3. Stardust silicates from primitive meteorites.

    PubMed

    Nagashima, Kazuhide; Krot, Alexander N; Yurimoto, Hisayoshi

    2004-04-29

    Primitive chondritic meteorites contain material (presolar grains), at the level of a few parts per million, that predates the formation of our Solar System. Astronomical observations and the chemical composition of the Sun both suggest that silicates must have been the dominant solids in the protoplanetary disk from which the planets of the Solar System formed, but no presolar silicates have been identified in chondrites. Here we report the in situ discovery of presolar silicate grains 0.1-1 microm in size in the matrices of two primitive carbonaceous chondrites. These grains are highly enriched in 17O (delta17O(SMOW) > 100-400 per thousand ), but have solar silicon isotopic compositions within analytical uncertainties, suggesting an origin in an oxygen-rich red giant or an asymptotic giant branch star. The estimated abundance of these presolar silicates (3-30 parts per million) is higher than reported for other types of presolar grains in meteorites, consistent with their ubiquity in the early Solar System, but is about two orders of magnitude lower than their abundance in anhydrous interplanetary dust particles. This result is best explained by the destruction of silicates during high-temperature processing in the solar nebula. PMID:15118720

  4. In-situ application of Ultrasonic Pulse Velocity measurements to determine the degree of zeolitic alteration of ignimbrites

    NASA Astrophysics Data System (ADS)

    Evren Çubukçu, H.; Yurdakul, Yasin; Erkut, Volkan; Akkaş, Efe; Akın, Lütfiye; Ulusoy, İnan; Şen, Erdal

    2016-04-01

    The velocity of P-waves passing through a rock body is strongly dependent on the petrographical properties such as texture, crystallinity, porosity and fracture network. For this reason, the measurement of ultrasonic pulse velocities (UPV) has been widely used in various applications interested in mechanical properties of solid rock bodies. An ignimbrite is a deposit of pyroclastic density current originating from an explosive volcanic eruption and comprises of vitric volcanic ash, free crystals, juvenile magma fragments (pumice) and accidental xenoliths. The complex nature of the componentry of ignimbrites also exhibits spatial variation depending on the location of deposition. Furthermore, both syn- and post-depositional processes (i.e. welding, alteration etc.) may have drastic impact on the mechanical characteristics of the ignimbrites. Alteration can be defined as the devitrification and the crystallization of vitric components and the transformation of pre-existing minerals of the ignimbrite into new minerals under changing thermodynamic conditions. In this context, zeolitization is an alteration process in which metastable (vitric) components of an ignimbrite body are replaced by zeolite group of minerals under low temperature and pressure induced by hydrothermal activity. The crystallization of zeolite minerals in the pore space promotes an increase in crystallinity and therefore a decrease in porosity. Hence, the velocity of P-waves passing through a zeolitized ignimbrite will be considerably higher compared to those in unaltered counterparts. Within the scope of a TUBİTAK project (No:113Y439) in which the alteration properties of Cappadocian Ignimbrites (Nevşehir, Turkey) are being investigated, in-situ UPV measurements have been performed using a portable pulse test instrument. The acquired velocity data has been correlated with the modal proportions of secondary zeolite minerals obtained by SEM-EDS. The results demonstrate that the measured P

  5. Low-voltage bendable pentacene thin-film transistor with stainless steel substrate and polystyrene-coated hafnium silicate dielectric.

    PubMed

    Yun, Dong-Jin; Lee, Seunghyup; Yong, Kijung; Rhee, Shi-Woo

    2012-04-01

    The hafnium silicate and aluminum oxide high-k dielectrics were deposited on stainless steel substrate using atomic layer deposition process and octadecyltrichlorosilane (OTS) and polystyrene (PS) were treated improve crystallinity of pentacene grown on them. Besides, the effects of the pentacene deposition condition on the morphologies, crystallinities and electrical properties of pentacene were characterized. Therefore, the surface treatment condition on dielectric and pentacene deposition conditions were optimized. The pentacene grown on polystyrene coated high-k dielectric at low deposition rate and temperature (0.2-0.3 Å/s and R.T.) showed the largest grain size (0.8-1.0 μm) and highest crystallinity among pentacenes deposited various deposition conditions, and the pentacene TFT with polystyrene coated high-k dielectric showed excellent device-performance. To decrease threshold voltage of pentacene TFT, the polystyrene-thickness on high-k dielectric was controlled using different concentration of polystyrene solution. As the polystyrene-thickness on hafnium silicate decreases, the dielectric constant of polystyrene/hafnium silicate increases, while the crystallinity of pentacene grown on polystyrene/hafnium silicate did not change. Using low-thickness polystyrene coated hafnium silicate dielectric, the high-performance and low voltage operating (<5 V) pentacene thin film transistor (μ: ~2 cm(2)/(V s), on/off ratio, >1 × 10(4)) and complementary inverter (DC gains, ~20) could be fabricated.

  6. Studies on the formation of hierarchical zeolite T aggregates with well-defined morphology in different template systems

    NASA Astrophysics Data System (ADS)

    Yin, Xiaoyan; Chu, Naibo; Lu, Xuewei; Li, Zhongfang; Guo, Hong

    2016-01-01

    In this paper, the disk-like and pumpkin-like hierarchical zeolite T aggregates consisted of primary nano-grains have been hydrothermally synthesized with and without the aid of the second template. The first template is used with tetramethylammonium hydroxide (TMAOH) and the second template is used with triethanolamine (TEA) or polyving akohol (PVA). A combination of characterization techniques, including XRD, SEM, TEM and N2 adsorption-desorption to examine the crystal crystallinity, morphology and surface properties of hierarchical zeolite T aggregates. In the single-template preparation process, the two-step varying-temperature treatment has been used to improve the meso-porosity of zeolite T aggregates. In the double-template preparation process, the amounts of PVA or TEA on the crystallinity, morphology and meso-porosity of zeolite T aggregates have been studied. It has been proved that the interstitial voids between the primary grains of aggregates are the origin of additional mesopores of samples. The micro- and meso-porosities of samples prepared with and without the second template have been contrasted in detail at last. In particular, the sample synthesized with the addition of PVA presents a hierarchical pore structure with the highest Sext value of 122 m2/g and Vmeso value of 0.255 cm3/g.

  7. CuO nanoparticles incorporated in hierarchical MFI zeolite as highly active electrocatalyst for non-enzymatic glucose sensing.

    PubMed

    Dong, Junping; Tian, Taolei; Ren, Linxiao; Zhang, Yuan; Xu, Jiaqiang; Cheng, Xiaowei

    2015-01-01

    A hierarchical MFI zeolite, with typical micro/meso bimodal pore structures, was prepared by desilication method. CuO nanoparticles (NPs) were incorporated into the hierarchical MFI zeolite by impregnation method. CuO/hierarchical zeolite composites were characterized by X-ray diffraction, transmission electron microscopy and nitrogen sorption. It is shown that the CuO nanoparticles are mostly dispersed in the mesopores with remaining of the crystallinity and morphology of the host zeolite. CuO nanoparticles located in hierarchical zeolite exhibit the excellent electrocatalytic performances to oxidation of glucose in alkaline media. The electrocatalytic activity enhances with increasing the loading content of CuO from 5% to 15%. The composites were fabricated for nonenzyme glucose sensing. Under the optimal conditions, the sensor shows a wide linear range from 5×10(-7) to 1.84×10(-2) M with a low detection limit of 3.7×10(-7) M. The sensor also exhibits good repeatability, long-term stability as well as high selectivity against interfering species. PMID:25499226

  8. CuO nanoparticles incorporated in hierarchical MFI zeolite as highly active electrocatalyst for non-enzymatic glucose sensing.

    PubMed

    Dong, Junping; Tian, Taolei; Ren, Linxiao; Zhang, Yuan; Xu, Jiaqiang; Cheng, Xiaowei

    2015-01-01

    A hierarchical MFI zeolite, with typical micro/meso bimodal pore structures, was prepared by desilication method. CuO nanoparticles (NPs) were incorporated into the hierarchical MFI zeolite by impregnation method. CuO/hierarchical zeolite composites were characterized by X-ray diffraction, transmission electron microscopy and nitrogen sorption. It is shown that the CuO nanoparticles are mostly dispersed in the mesopores with remaining of the crystallinity and morphology of the host zeolite. CuO nanoparticles located in hierarchical zeolite exhibit the excellent electrocatalytic performances to oxidation of glucose in alkaline media. The electrocatalytic activity enhances with increasing the loading content of CuO from 5% to 15%. The composites were fabricated for nonenzyme glucose sensing. Under the optimal conditions, the sensor shows a wide linear range from 5×10(-7) to 1.84×10(-2) M with a low detection limit of 3.7×10(-7) M. The sensor also exhibits good repeatability, long-term stability as well as high selectivity against interfering species.

  9. Zeolites on Mars: Prospects for Remote Sensing

    NASA Technical Reports Server (NTRS)

    Gaffney, E. S.; Singer, R. B.; Kunkle, T. D.

    1985-01-01

    The Martian surface composition measured by Viking can be represented by several combinations of minerals incorporating major fractions of zeolites known to occur in altered mafic rocks and polar soils on Earth. The abundant occurrence of zeolites on Mars is consistent with what is known about both the physical and chemical environment of that planet. The laboratory reflectance spectra (0.65 to 2.55 microns) of a number of relatively pure zeolite minerals and some naturally occurring zeolite-clay soils were measured. All of the spectra measured are dominated by strong absorption near 1.4 and 1.9 microns and a steep reflectance drop longward of about 2.2 microns, all of which are due to abundant H2O. Weaker water overtone bands are also apparent, and in most cases there is spectral evidence for minor Fe(3+). In these features the zeolite spectra are similar to spectra of smectite clays which have abundant interlayer water. The most diagnostic difference between clay and zeolite spectra is the total absence in the zeolites of the weak structural OH absorption.

  10. Quantification of thickness and wrinkling of exfoliated two-dimensional zeolite nanosheets

    PubMed Central

    Kumar, Prashant; Agrawal, Kumar Varoon; Tsapatsis, Michael; Mkhoyan, K. Andre

    2015-01-01

    Some two-dimensional (2D) exfoliated zeolites are single- or near single-unit cell thick silicates that can function as molecular sieves. Although they have already found uses as catalysts, adsorbents and membranes precise determination of their thickness and wrinkling is critical as these properties influence their functionality. Here we demonstrate a method to accurately determine the thickness and wrinkles of a 2D zeolite nanosheet by comprehensive 3D mapping of its reciprocal lattice. Since the intensity modulation of a diffraction spot on tilting is a fingerprint of the thickness, and changes in the spot shape are a measure of wrinkling, this mapping is achieved using a large-angle tilt-series of electron diffraction patterns. Application of the method to a 2D zeolite with MFI structure reveals that the exfoliated MFI nanosheet is 1.5 unit cells (3.0 nm) thick and wrinkled anisotropically with up to 0.8 nm average surface roughness. PMID:25958985

  11. Uniform Catalytic Site in Sn-beta Zeolite Determined using X-ray Absorption Fine Structure

    SciTech Connect

    Bare,S.; Kelly, S.; Sinkler, W.; Low, J.; Modica, F.; Valencia, S.; Corma, A.; Nemeth, L.

    2005-01-01

    The Sn silicate zeolite, Sn-{beta}, has been shown to be an efficient, selective heterogeneous catalyst for Baeyer-Villiger oxidations. Using primarily a multishell fit to extended X-ray absorption fine structure (EXAFS) data, we show that the Sn does not randomly insert into the {beta}-zeolite structure but rather occupies identical, specific, crystallographic sites. These sites are the T5/T6 sites in the six-membered rings. Moreover, the Sn is substituted in pairs on opposite sides of these six-membered rings. We believe that it is the specific, uniform crystallographic location of the Sn in the crystal structure that leads to sites with uniform catalytic activity, and consequently to the high chemical selectivity demonstrated for this catalyst. This manifests itself in the almost enzyme-like selectivity of this catalyst in Baeyer-Villiger oxidations. This uniform site distribution of the Sn suggests that there is likely a symbiotic relationship between the structure-directing agent in the zeolite synthesis and the Sn heteroatoms during the framework formation.

  12. Synthesis, characterization and energetics of zeolites

    NASA Astrophysics Data System (ADS)

    Sun, Pingping

    Zeolites are microporous aluminosilicates, and Al or Si can be substituted by other elements, such as Ge, Ga, or P. Zeolites have been studied for more than two hundred years, because of their wide application and importance in mineralogy and technology. With high acidity and special pore system, zeolite beta (IZA code BEA) receives much attention. In the dissertation, the formation and dehydration enthalpy of cation exchanged zeolite beta, Li/Na/K/Rb/Cs/Mg/Ca/Sr/Ba -BEA 14 (14 is the Si/Al ratio), Mg/Ca - BEA 4 (4 is the Si/Al ratio), were studied by high-temperature oxide melt solution calorimetry. From an energetic point of view, zeolites beta are less stable than other zeolites of similar Si/Al ratio and cation content. Their enthalpies of formation and dehydration become more endothermic with increasing average ionic potential of the cations in the channels. The unfavorable enthalpy of low silica Mg-BEA 4 and Ca-BEA 4 suggests a possible energy barrier in their direct synthesis. The formation and partial molar dehydration enthalpy of Li-BEA 3 and Na-BEA 3.67 are also investigated by high temperature calorimetry. The partial molar dehydration enthalpies are a linear function of water content. Molecular mechanics simulations explore the cation and water molecule positions in the framework at several water contents. Ga substitution is of great interest due to the special catalytic character of Ga zeolites and the directing agent effect of Ga atoms. The energetics of gallosilicate zeolites Ga-NaSOD, Ga-NaFAU, Ga-NaNAT, Ga-KNAT, Ga-KLTL and Ga-KTUN-1 were studied. The lattice parameters and adsorbed water content increase after Ga substitution of Al. Compared to analogous aluminosilicate zeolites, the gallosilicate zeolites have a similar dehydration enthalpy per mole of tetrahedra, but a less endothermic dehydration enthalpy per mole of water. The gallosilicate zeolites also have less exothermic formation enthalpies from oxide components. The energetics of Ga

  13. Copper-Exchanged Zeolite L Traps Oxygen

    NASA Technical Reports Server (NTRS)

    Sharma, Pramod K.; Seshan, Panchalam K.

    1991-01-01

    Brief series of simple chemical treatments found to enhance ability of zeolite to remove oxygen from mixture of gases. Thermally stable up to 700 degrees C and has high specific surface area which provides high capacity for adsorption of gases. To increase ability to adsorb oxygen selectively, copper added by ion exchange, and copper-exchanged zeolite reduced with hydrogen. As result, copper dispersed atomically on inner surfaces of zeolite, making it highly reactive to oxygen, even at room temperature. Reactivity to oxygen even greater at higher temperatures.

  14. Photochemical charge separation in zeolites: Electron transfer dynamics, nanocrystals and zeolitic membranes. Final technical report

    SciTech Connect

    Dutta, Prabir K.

    2001-09-30

    Aluminosilicate zeolites provide an excellent host for photochemical charge separation. Because of the constraints provided by the zeolite, the back electron transfer from the reduced acceptor to the oxidized sensitizer is slowed down. This provides the opportunity to separate the charge and use it in a subsequent reaction for water oxidation and reduction. Zeolite-based ruthenium oxide catalysts have been found to be efficient for the water splitting process. This project has demonstrated the usefulness of zeolite hosts for photolytic splitting of water.

  15. Lithologic mapping of silicate rocks using TIMS

    NASA Technical Reports Server (NTRS)

    Gillespie, A. R.

    1986-01-01

    Common rock-forming minerals have thermal infrared spectral features that are measured in the laboratory to infer composition. An airborne Daedalus scanner (TIMS) that collects six channels of thermal infrared radiance data (8 to 12 microns), may be used to measure these same features for rock identification. Previously, false-color composite pictures made from channels 1, 3, and 5 and emittance spectra for small areas on these images were used to make lithologic maps. Central wavelength, standard deviation, and amplitude of normal curves regressed on the emittance spectra are related to compositional information for crystalline igneous silicate rocks. As expected, the central wavelength varies systematically with silica content and with modal quartz content. Standard deviation is less sensitive to compositional changes, but large values may result from mixed admixture of vegetation. Compression of the six TIMS channels to three image channels made from the regressed parameters may be effective in improving geologic mapping from TIMS data, and these synthetic images may form a basis for the remote assessment of rock composition.

  16. Silicates in Ultraluminous Infrared Galaxies

    NASA Astrophysics Data System (ADS)

    Sirocky, M. M.; Levenson, N. A.; Elitzur, M.; Spoon, H. W. W.; Armus, L.

    2008-05-01

    We analyze the mid-infrared (MIR) spectra of ultraluminous infrared galaxies (ULIRGs) observed with the Spitzer Space Telescope's Infrared Spectrograph. Dust emission dominates the MIR spectra of ULIRGs, and the reprocessed radiation that emerges is independent of the underlying heating spectrum. Instead, the resulting emission depends sensitively on the geometric distribution of the dust, which we diagnose with comparisons of numerical simulations of radiative transfer. Quantifying the silicate emission and absorption features that appear near 10 and 18 μm requires a reliable determination of the continuum, and we demonstrate that including a measurement of the continuum at intermediate wavelength (between the features) produces accurate results at all optical depths. With high-quality spectra, we successfully use the silicate features to constrain the dust chemistry. The observations of the ULIRGs and local sight lines require dust that has a relatively high 18 μm/10 μm absorption ratio of the silicate features (around 0.5). Specifically, the cold dust of Ossenkopf et al. is consistent with the observations, while other dust models are not. We use the silicate feature strengths to identify two families of ULIRGs, in which the dust distributions are fundamentally different. Optical spectral classifications are related to these families. In ULIRGs that harbor an active galactic nucleus, the spectrally broad lines are detected only when the nuclear surroundings are clumpy. In contrast, the sources of lower ionization optical spectra are deeply embedded in smooth distributions of optically thick dust.

  17. Amended Silicated for Mercury Control

    SciTech Connect

    James Butz; Thomas Broderick; Craig Turchi

    2006-12-31

    Amended Silicates{trademark}, a powdered, noncarbon mercury-control sorbent, was tested at Duke Energy's Miami Fort Station, Unit 6 during the first quarter of 2006. Unit 6 is a 175-MW boiler with a cold-side electrostatic precipitator (ESP). The plant burns run-of-the-river eastern bituminous coal with typical ash contents ranging from 8-15% and sulfur contents from 1.6-2.6% on an as-received basis. The performance of the Amended Silicates sorbent was compared with that for powdered activated carbon (PAC). The trial began with a period of baseline monitoring during which no sorbent was injected. Sampling during this and subsequent periods indicated mercury capture by the native fly ash was less than 10%. After the baseline period, Amended Silicates sorbent was injected at several different ratios, followed by a 30-day trial at a fixed injection ratio of 5-6 lb/MMACF. After this period, PAC was injected to provide a comparison. Approximately 40% mercury control was achieved for both the Amended Silicates sorbent and PAC at injection ratios of 5-6 lbs/MMACF. Higher injection ratios did not achieve significantly increased removal. Similar removal efficiencies have been reported for PAC injection trials at other plants with cold-side ESPs, most notably for plants using medium to high sulfur coal. Sorbent injection did not detrimentally impact plant operations and testing confirmed that the use of Amended Silicates sorbent does not degrade fly ash quality (unlike PAC). The cost for mercury control using either PAC or Amended Silicates sorbent was estimated to be equivalent if fly ash sales are not a consideration. However, if the plant did sell fly ash, the effective cost for mercury control could more than double if those sales were no longer possible, due to lost by-product sales and additional cost for waste disposal. Accordingly, the use of Amended Silicates sorbent could reduce the overall cost of mercury control by 50% or more versus PAC for locations where fly

  18. FORMATION OF COSMIC CRYSTALS IN HIGHLY SUPERSATURATED SILICATE VAPOR PRODUCED BY PLANETESIMAL BOW SHOCKS

    SciTech Connect

    Miura, H.; Yamada, J.; Tsukamoto, K.; Nozawa, J.; Tanaka, K. K.; Yamamoto, T.; Nakamoto, T.

    2010-08-10

    Several lines of evidence suggest that fine silicate crystals observed in primitive meteorite and interplanetary dust particles (IDPs) nucleated in a supersaturated silicate vapor followed by crystalline growth. We investigated evaporation of {mu}m-sized silicate particles heated by a bow shock produced by a planetesimal orbiting in the gas in the early solar nebula and condensation of crystalline silicate from the vapor thus produced. Our numerical simulation of shock-wave heating showed that these {mu}m-sized particles evaporate almost completely when the bow shock is strong enough to cause melting of chondrule precursor dust particles. We found that the silicate vapor cools very rapidly with expansion into the ambient unshocked nebular region; for instance, the cooling rate is estimated to be as high as 2000 K s{sup -1} for a vapor heated by a bow shock associated with a planetesimal of radius 1 km. The rapid cooling of the vapor leads to nonequilibrium gas-phase condensation of dust at temperatures much lower than those expected from the equilibrium condensation. It was found that the condensation temperatures are lower by a few hundred K or more than the equilibrium temperatures. This explains the results of the recent experimental studies of condensation from a silicate vapor that condensation in such large supercooling reproduces morphologies similar to those of silicate crystals found in meteorites. Our results strongly suggest that the planetesimal bow shock is one of the plausible sites for formation of not only chondrules but also other cosmic crystals in the early solar system.

  19. Tetraethylenepentamine embedded zeolite A for carbon dioxide adsorption.

    PubMed

    Kim, Young-Ki; Mo, Yong-Hwan; Lee, Jun; You, Hyo-Sang; Yi, Chang-Keun; Park, Young Cheol; Park, Sang-Eon

    2013-04-01

    Tetraethylenepentamine (TEPA) embedded zeolite A crystals were synthesized by using TEPA and the preformed zeolite A precursor under the microwave irradiation. The presence of TEPA in zeolite A crystal was confirmed by TG analysis and FTIR, Raman spectra. The CO2 adsorptive behavior of TEPA embedded zeolite A samples was investigated by CO2 isotherms measured at 25 degrees C comparing with zeolite A. The optimum CO2 sorption capacity was found in the case of 7.5% TEPA embedded zeolite A, which showed 3.75 mmol g(-1) where as the zeolite A showed less CO2 adsorption capacity of 2.88 mmol g(-1). The adsorption capacity of TEPA embedded Zeolite A was sustained up to 90% during 4 cycles of temperature swing adsorption (TSA) from 40 degrees C to 140 degrees C, indicating that the TEPA embedded Zeolite A was found to be useful as one of the application to solid amine adsorbent for CO2.

  20. TRANSMISSION ELECTRON MICROSCOPY OF Al-RICH SILICATE STARDUST FROM ASYMPTOTIC GIANT BRANCH STARS

    SciTech Connect

    Vollmer, Christian; Hoppe, Peter; Brenker, Frank E.

    2013-05-20

    We report on transmission electron microscopy (TEM) investigations of two mineralogically unusual stardust silicates to constrain their circumstellar condensation conditions. Both grains were identified by high spatial resolution nano secondary ion mass spectrometry (NanoSIMS) in the Acfer 094 meteorite, one of the most pristine carbonaceous chondrites available for study. One grain is a highly crystalline, highly refractory (Fe content < 0.5 at%), structurally undisturbed orthopyroxene (MgSiO{sub 3}) with an unusually high Al content (1.8 {+-} 0.5 at%). This is the first TEM documentation of a single crystal pyroxene within the complete stardust silicate data set. We interpret the microstructure and chemistry of this grain as being a direct condensate from a gas of locally non-solar composition (i.e., with a higher-than-solar Al content and most likely also a lower-than-solar Mg/Si ratio) at (near)-equilibrium conditions. From the overabundance of crystalline olivine (six reported grains to date) compared to crystalline pyroxene (only documented as a single crystal in this work) we infer that formation of olivine over pyroxene is favored in circumstellar environments, in agreement with expectations from condensation theory and experiments. The second stardust silicate consists of an amorphous Ca-Si rich material which lacks any crystallinity based on TEM observations in which tiny (<20 nm) hibonite nanocrystallites are embedded. This complex assemblage therefore attests to the fast cooling and rapidly changing chemical environments under which dust grains in circumstellar shells form.

  1. 21 CFR 582.2437 - Magnesium silicate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Magnesium silicate. 582.2437 Section 582.2437 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Magnesium silicate. (a) Product. Magnesium silicate. (b) Tolerance. 2 percent. (c) Limitations,...

  2. 21 CFR 582.2437 - Magnesium silicate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Magnesium silicate. 582.2437 Section 582.2437 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Magnesium silicate. (a) Product. Magnesium silicate. (b) Tolerance. 2 percent. (c) Limitations,...

  3. 21 CFR 182.2437 - Magnesium silicate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Magnesium silicate. 182.2437 Section 182.2437 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Magnesium silicate. (a) Product. Magnesium silicate. (b) Tolerance. 2 percent. (c) Limitations,...

  4. 21 CFR 182.2437 - Magnesium silicate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Magnesium silicate. 182.2437 Section 182.2437 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Magnesium silicate. (a) Product. Magnesium silicate. (b) Tolerance. 2 percent. (c) Limitations,...

  5. 21 CFR 182.2437 - Magnesium silicate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Magnesium silicate. 182.2437 Section 182.2437 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Magnesium silicate. (a) Product. Magnesium silicate. (b) Tolerance. 2 percent. (c) Limitations,...

  6. 21 CFR 582.2437 - Magnesium silicate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Magnesium silicate. 582.2437 Section 582.2437 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Magnesium silicate. (a) Product. Magnesium silicate. (b) Tolerance. 2 percent. (c) Limitations,...

  7. 21 CFR 582.2437 - Magnesium silicate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Magnesium silicate. 582.2437 Section 582.2437 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Magnesium silicate. (a) Product. Magnesium silicate. (b) Tolerance. 2 percent. (c) Limitations,...

  8. 21 CFR 582.2227 - Calcium silicate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Calcium silicate. 582.2227 Section 582.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c)...

  9. 21 CFR 582.2227 - Calcium silicate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Calcium silicate. 582.2227 Section 582.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c)...

  10. 21 CFR 182.2227 - Calcium silicate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Calcium silicate. 182.2227 Section 182.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c)...

  11. 21 CFR 182.2227 - Calcium silicate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Calcium silicate. 182.2227 Section 182.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c)...

  12. 21 CFR 582.2227 - Calcium silicate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Calcium silicate. 582.2227 Section 582.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c)...

  13. 21 CFR 182.2227 - Calcium silicate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Calcium silicate. 182.2227 Section 182.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c)...

  14. 21 CFR 582.2227 - Calcium silicate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Calcium silicate. 582.2227 Section 582.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c)...

  15. 21 CFR 182.2227 - Calcium silicate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Calcium silicate. 182.2227 Section 182.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c)...

  16. 21 CFR 582.2227 - Calcium silicate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Calcium silicate. 582.2227 Section 582.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c)...

  17. 21 CFR 582.2437 - Magnesium silicate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Magnesium silicate. 582.2437 Section 582.2437 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Magnesium silicate. (a) Product. Magnesium silicate. (b) Tolerance. 2 percent. (c) Limitations,...

  18. 21 CFR 182.2437 - Magnesium silicate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Magnesium silicate. 182.2437 Section 182.2437 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Magnesium silicate. (a) Product. Magnesium silicate. (b) Tolerance. 2 percent. (c) Limitations,...

  19. On the Filling Process Forming Silicic Segregations: Porous Flow Experiments

    NASA Astrophysics Data System (ADS)

    Zavala, K.; Marsh, B. D.

    2002-05-01

    Silicic segregations are only observed in the upper parts of large diabase sill, lava lakes and gabbroic intrusions. The segregations often have sharp upper contacts and diffuse lower contacts that grade into the host rock texture. We have analyzed over 100 segregation samples from the Ferrar Dolerites of the McMurdo Dry Valleys Antarctica, to investigate the nature of the infilling process. These segregations have compositions that correspond to interstitial liquid present at crystallinities between 59 and 63% and temperatures between 1135o C and 1115 oC. Stratigraphic position, size, textures, and chemical composition relations indicate that silicic segregation represent a form of bimodal differentiation produced by the physical tearing of the upper Solidification Front (SF) due to gravitational instability, (SFI). Previous work (Zavala & Marsh, 2001) showed that large segregations, which are chemically and texturally non-homogeneous and have non-monotonic Si02 profiles form by multiple infilling episodes. In contrast, smaller segregations have homogeneous textures and chemical profiles, formed by perhaps longer single episode of infilling. Because the rate of melt flow forming these segregations is controlled by the resistance to flow through the crystalline matrix we performed a series of porous media flow experiments to investigate the details of the melt transport dynamics of the infilling process.

  20. Energetic feedback in galaxies: Processing of interstellar silicate grains by cosmic rays

    SciTech Connect

    Bringa, E M; Kucheyev, S O; Loeffler, M J; Baragiola, R A; Tielens, A G W M; Dai, Z R; Graham, G; Bajt, S; Bradley, J P; Dukes, C A; Felter, T E; Torres, D F; van Breugel, W

    2006-05-10

    The formation and evolution of stars and galaxies is a complex process that involves the cooling and collapse of dense interstellar clouds as well as energetic feedback on these clouds. Interstellar dust grains are central to the radiative transfer, thermal balance, and molecular processes in these clouds and can provide an important diagnostic. Hence, the effects of energetic processing of interstellar dust may have significant consequences. r This may be studied in our own Galaxy, where observations have shown that an appreciable fraction of silicates formed in the outflows from red giants and supergiants have a crystalline structure. Yet, the fraction of crystalline silicates in the interstellar medium is very small, pointing towards an efficient crystalline crystalline-to to-amorphous conversion process. Here we report experimental and modeling results that show that relatively ''low'' energy (0.1 - 5.0 GeV) heavy ion cosmic rays can rapidly ({approx}70 Million yrs) amorphize crystalline silicate grains ejected by stars into the interstellar medium. The implications of this are briefly discussed. We also examine the effects of cosmic ray processing of silicates in the solar system and in stellar debris disks. In the latter systems, cosmic ray processing may play a role for grains trapped in resonance with planetary companions. We speculate that energetic processing of interstellar dust is likely to be even more important in s star forming galaxies, which have higher cosmic ray fluxes due to tar their much larger star formation rates and their emerging active black holes with associated jets.

  1. Topological crystalline insulator nanostructures.

    PubMed

    Shen, Jie; Cha, Judy J

    2014-11-01

    Topological crystalline insulators are topological insulators whose surface states are protected by the crystalline symmetry, instead of the time reversal symmetry. Similar to the first generation of three-dimensional topological insulators such as Bi₂Se₃ and Bi₂Te₃, topological crystalline insulators also possess surface states with exotic electronic properties such as spin-momentum locking and Dirac dispersion. Experimentally verified topological crystalline insulators to date are SnTe, Pb₁-xSnxSe, and Pb₁-xSnxTe. Because topological protection comes from the crystal symmetry, magnetic impurities or in-plane magnetic fields are not expected to open a gap in the surface states in topological crystalline insulators. Additionally, because they have a cubic structure instead of a layered structure, branched structures or strong coupling with other materials for large proximity effects are possible, which are difficult with layered Bi₂Se₃ and Bi₂Te₃. Thus, additional fundamental phenomena inaccessible in three-dimensional topological insulators can be pursued. In this review, topological crystalline insulator SnTe nanostructures will be discussed. For comparison, experimental results based on SnTe thin films will be covered. Surface state properties of topological crystalline insulators will be discussed briefly.

  2. Three Mile Island zeolite vitirification demonstration program

    SciTech Connect

    Siemens, D.H.; Knowlton, D.E.; Shupe, M.W.

    1981-06-01

    The cleanup of the high-activity-level water at Three Mile Island (TMI) provides an opportunity to further develop waste management technology. Approximately 790,000 gallons of high-activity-level water at TMI's Unit-2 Nuclear Power Station will be decontaminated at the site using the submerged demineralizer system (SDS). In the SDS process, the cesium and strontium in the water are sorbed onto zeolite that is contained within metal liners. The Department of Energy has asked the Pacific Northwest Laboratory (PNL) to take a portion of the zeolite from the SDS process and demonstrate, on a production scale, that this zeolite can be vitrified using the in-can melting process. This paper is a brief overview of the TMI zeolite vitrification program. The first section discusses the formulation of a glass suitable for immobilizing SDS zeolite. The following section describes a feed system that was developed to feed zeolite to the in-can melter. It also describes the in-can melting process and the government owned facilities in which the demonstrations will take place. Finally, the schedule for completing the program activities is outlined.

  3. Probing zeolites by vibrational spectroscopies.

    PubMed

    Bordiga, Silvia; Lamberti, Carlo; Bonino, Francesca; Travert, Arnaud; Thibault-Starzyk, Frédéric

    2015-10-21

    This review addresses the most relevant aspects of vibrational spectroscopies (IR, Raman and INS) applied to zeolites and zeotype materials. Surface Brønsted and Lewis acidity and surface basicity are treated in detail. The role of probe molecules and the relevance of tuning both the proton affinity and the steric hindrance of the probe to fully understand and map the complex site population present inside microporous materials are critically discussed. A detailed description of the methods needed to precisely determine the IR absorption coefficients is given, making IR a quantitative technique. The thermodynamic parameters of the adsorption process that can be extracted from a variable-temperature IR study are described. Finally, cutting-edge space- and time-resolved experiments are reviewed. All aspects are discussed by reporting relevant examples. When available, the theoretical literature related to the reviewed experimental results is reported to support the interpretation of the vibrational spectra on an atomic level.

  4. The zeolite deposits of Greece

    USGS Publications Warehouse

    Stamatakis, M.G.; Hall, A.; Hein, J.R.

    1996-01-01

    Zeolites are present in altered pyroclastic rocks at many localities in Greece, and large deposits of potential economic interest are present in three areas: (1) the Evros region of the province of Thrace in the north-eastern part of the Greek mainland; (2) the islands of Kimolos and Poliegos in the western Aegean; and (3) the island of Samos in the eastern Aegean Sea. The deposits in Thrace are of Eocene-Oligocene age and are rich in heulandite and/or clinoptilolite. Those of Kimolos and Poliegos are mainly Quaternary and are rich in mordenite. Those of Samos are Miocene, and are rich in clinoptilolite and/or analcime. The deposits in Thrace are believed to have formed in an open hydrological system by the action of meteoric water, and those of the western Aegean islands in a similar way but under conditions of high heat flow, whereas the deposits in Samos were formed in a saline-alkaline lake.

  5. Crystalline Silica Primer

    USGS Publications Warehouse

    ,

    1992-01-01

    substance and will present a nontechnical overview of the techniques used to measure crystalline silica. Because this primer is meant to be a starting point for anyone interested in learning more about crystalline silica, a list of selected readings and other resources is included. The detailed glossary, which defines many terms that are beyond the scope of this publication, is designed to help the reader move from this presentation to a more technical one, the inevitable next step.

  6. Salt-occluded zeolite waste forms: Crystal structures and transformability

    SciTech Connect

    Richardson, J.W. Jr.

    1996-12-31

    Neutron diffraction studies of salt-occluded zeolite and zeolite/glass composite samples, simulating nuclear waste forms loaded with fission products, have revealed complex structures, with cations assuming the dual roles of charge compensation and occlusion (cluster formation). These clusters roughly fill the 6--8 {angstrom} diameter pores of the zeolites. Samples are prepared by equilibrating zeolite-A with complex molten Li, K, Cs, Sr, Ba, Y chloride salts, with compositions representative of anticipated waste systems. Samples prepared using zeolite 4A (which contains exclusively sodium cations) as starting material are observed to transform to sodalite, a denser aluminosilicate framework structure, while those prepared using zeolite 5A (sodium and calcium ions) more readily retain the zeolite-A structure. Because the sodalite framework pores are much smaller than those of zeolite-A, clusters are smaller and more rigorously confined, with a correspondingly lower capacity for waste containment. Details of the sodalite structures resulting from transformation of zeolite-A depend upon the precise composition of the original mixture. The enhanced resistance of salt-occluded zeolites prepared from zeolite 5A to sodalite transformation is thought to be related to differences in the complex chloride clusters present in these zeolite mixtures. Data relating processing conditions to resulting zeolite composition and structure can be used in the selection of processing parameters which lead to optimal waste forms.

  7. A new method for As(V) removal from waters by precipitation of mimetite Pb5(AsO4)3Cl on Pb-activated zeolite

    NASA Astrophysics Data System (ADS)

    Manecki, Maciej; Buszkiewicz, Urszula

    2016-04-01

    A new method for removal of arsenate AsO43- ions from aqueous solutions is proposed. The principle of the method stems from precipitation of very insoluble crystalline lead arsenate apatite (mimetite Pb5(AsO4)3Cl) induced by bringing in contact Pb-activated zeolite and As-contaminated water in the presence of Cl-. Zeolite is activated by sorption of Pb2+ followed by washing with water to remove the excess of Pb and to desorbe weakly adsorbed ions. Lead adsorbed on zeolite is bound strong enough to prevent desorption by water but weak enough to undergo desorption induced by heterogeneous precipitation of mimetite nanocrystals on the surface of zeolite. The experiment consisted of two steps. In the first step, aliquots of 0.5 g of natural clinoptilolite zeolite (from Zeocem a.s., Bystré, Slovak Republic) were reacted with 40 mL of solutions containing 20, 100, 500, and 2000 mg Pb/L (pH =4.5; reaction for 30 minutes followed by centrifugation). The amount of Pb sorbed was calculated from the drop of Pb concentration in solution. Centrifuged zeolite was washed three times by mixing with 10 mL of DDI water, followed by centrifugation. No Pb was detected in the water after second washing. Wet pulp resulting from this stage was exposed to solutions containing 70 mg/L Cl- and various concentrations of AsO43- (2 and 100 mg As/L; pH=4). Complete removal of As was observed for 2 mg As/L solutions mixed with zeolite-20 and zeolite-100. The precipitation of mimetite Pb5(AsO4)3Cl in the form of hexagonal crystals ca. 0.25 μm in size was observed using SEM/EDS. This work is partially funded by AGH research grant no 11.11.140.319.

  8. Modifying Silicates for Better Dispersion in Nanocomposites

    NASA Technical Reports Server (NTRS)

    Campbell, Sandi

    2005-01-01

    An improved chemical modification has been developed to enhance the dispersion of layered silicate particles in the formulation of a polymer/silicate nanocomposite material. The modification involves, among other things, the co-exchange of an alkyl ammonium ion and a monoprotonated diamine with interlayer cations of the silicate. The net overall effects of the improved chemical modification are to improve processability of the nanocomposite and maximize the benefits of dispersing the silicate particles into the polymer. Some background discussion is necessary to give meaning to a description of this development. Polymer/silicate nanocomposites are also denoted polymer/clay composites because the silicate particles in them are typically derived from clay particles. Particles of clay comprise layers of silicate platelets separated by gaps called "galleries." The platelet thickness is 1 nm. The length varies from 30 nm to 1 m, depending on the silicate. In order to fully realize the benefits of polymer/silicate nanocomposites, it is necessary to ensure that the platelets become dispersed in the polymer matrices. Proper dispersion can impart physical and chemical properties that make nanocomposites attractive for a variety of applications. In order to achieve nanometer-level dispersion of a layered silicate into a polymer matrix, it is typically necessary to modify the interlayer silicate surfaces by attaching organic functional groups. This modification can be achieved easily by ion exchange between the interlayer metal cations found naturally in the silicate and protonated organic cations - typically protonated amines. Long-chain alkyl ammonium ions are commonly chosen as the ion-exchange materials because they effectively lower the surface energies of the silicates and ease the incorporation of organic monomers or polymers into the silicate galleries. This completes the background discussion. In the present improved modification of the interlayer silicate surfaces

  9. Evidence of yttrium silicate inclusions in YSZ-porcelain veneers.

    PubMed

    Stoner, Brian R; Griggs, Jason A; Neidigh, John; Piascik, Jeffrey R

    2014-04-01

    This report introduces the discovery of crystalline defects that can form in the porcelain veneering layer when in contact with yttria-stabilized zirconia (YSZ). The focus was on dental prostheses and understanding the defects that form in the YSZ/porcelain system; however the data reported herein may have broader implications toward the use and stability of YSZ-based ceramics in general. Specimens were cut from fully sintered YSZ plates and veneering porcelain was applied (<1 mm thick) to one surface and fired under manufacturer's recommended protocol. Scanning electron microscopy (SEM) with integrated electron dispersive X-ray (EDAX) was used for microstructural and elemental analysis. EDAX, for chemical analysis and transmission electron diffraction (TED) for structural analysis were both performed in the transmission electron microscope (TEM). Additionally, in order to spatially resolve Y-rich precipitates, micro-CT scans were conducted at varying depths within the porcelain veneer. Local EDAX (SEM) was performed in the regions of visible inclusions and showed significant increases in yttrium concentration. TEM specimens also showed apparent inclusions in the porcelain and selected area electron diffraction was performed on these regions and found the inclusions to be crystalline and identified as either yttrium-silicate (Y2 SiO5 ) or yttrium-disilicate (Y2 Si2 O7 ). Micro-CT data showed that yttrium-silicate precipitates were distributed throughout the thickness of the porcelain veneer. Future studies are needed to determine whether many of the premature failures associated with this materials system may be the result of crystalline flaws that form as a result of high temperature yttrium diffusion near the surfaces of YSZ.

  10. Silicate condensation in Mira variables

    NASA Astrophysics Data System (ADS)

    Gail, Hans-Peter; Scholz, Michael; Pucci, Annemarie

    2016-06-01

    Context. The formation of dust in winds of cool and highly evolved stars and the rate of injection of dust into the interstellar medium is not yet completely understood, despite the importance of the process for the evolution of stars and galaxies. This holds in particular for oxygen-rich stars, where it is still not known which process is responsible for the formation of the necessary seed particles of their silicate dust. Aims: We study whether the condensation of silicate dust in Mira envelopes could be caused by cluster formation by the abundant SiO molecules. Methods: We solve the dust nucleation and growth equations in the co-moving frame of a fixed mass element for a simplified model of the pulsational motions of matter in the outer layers of a Mira variable, which is guided by a numerical model for Mira pulsations. It is assumed that seed particles form through the clustering of SiO. The calculation of the nucleation rate is based on published experimental data. The quantity of dust formed is calculated via a moment method and the calculation of radiation pressure on dusty gas is based on a dirty silicate model. Results: Dust nucleation occurs in the model at the upper culmination of the trajectory of a gas parcel where it stays for a considerable time at low temperatures. Subsequent dust growth occurs during the descending part of the motion and continues after the next shock reversed motion. It is found that sufficient dust forms that radiation pressure exceeds the gravitational pull of the stars such that the mass element is finally driven out of the star. Conclusions: Nucleation of dust particles by clustering of the abundant SiO molecules could be the mechanism that triggers silicate dust formation in Miras.

  11. Optimizing the crystallinity and acidity of H-SAPO-34 by fluoride for synthesizing Cu/SAPO-34 NH3-SCR catalyst.

    PubMed

    Ma, Jing; Si, Zhichun; Wu, Xiaodong; Weng, Duan; Ma, Yue

    2016-03-01

    A series of H-SAPO-34 zeolites were synthesized by a hydrothermal method in fluoride media. The as-synthesized H-SAPO-34 zeolites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 physisorption, temperature-programmed desorption of NH3 (NH3-TPD) and nuclear magnetic resonance (NMR) measurements. The results showed that a certain concentration of F(-) anions promoted the nucleation and crystallization of H-SAPO-34. The H-SAPO-34 synthesized in the fluoride media showed high crystallinity, uniform particle size distribution, large specific surface area and pore volume, and enhanced acidity. Therefore, Cu/SAPO-34 based on the fluoride-assisted zeolite showed a broadened temperature window for the selective catalytic reduction of NO by NH3 (NH3-SCR) reaction due to the enhanced acidity of the zeolite and the improved dispersion of copper species. PMID:26969071

  12. Optimizing the crystallinity and acidity of H-SAPO-34 by fluoride for synthesizing Cu/SAPO-34 NH3-SCR catalyst.

    PubMed

    Ma, Jing; Si, Zhichun; Wu, Xiaodong; Weng, Duan; Ma, Yue

    2016-03-01

    A series of H-SAPO-34 zeolites were synthesized by a hydrothermal method in fluoride media. The as-synthesized H-SAPO-34 zeolites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 physisorption, temperature-programmed desorption of NH3 (NH3-TPD) and nuclear magnetic resonance (NMR) measurements. The results showed that a certain concentration of F(-) anions promoted the nucleation and crystallization of H-SAPO-34. The H-SAPO-34 synthesized in the fluoride media showed high crystallinity, uniform particle size distribution, large specific surface area and pore volume, and enhanced acidity. Therefore, Cu/SAPO-34 based on the fluoride-assisted zeolite showed a broadened temperature window for the selective catalytic reduction of NO by NH3 (NH3-SCR) reaction due to the enhanced acidity of the zeolite and the improved dispersion of copper species.

  13. Use of zeolitized pumice waste as a water softening agent.

    PubMed

    Arrigo, I; Catalfamo, P; Cavallari, L; Di Pasquale, S

    2007-08-17

    Important pumice quarries are located on the island of Lipari (Italy) where an intense activity of extraction, transformation and trade of pumice takes place. Nevertheless, the finest fraction amounting to about 60% of mined pumice is discarded and disposed off in open-sky pits. This implies economic losses for mining industries and environmental problems for neighbouring villages. In order to find a sustainable use of this waste, we resumed and improved an old extractive process with aqueous sodium alkali, where a sodium silicate concentrated solution was produced together with an unextracted residue partially converted into zeolite P in Na+ form and now we are searching for suitable applications of this residue. In this paper, we relate about its use as a low cost water softening agent on the basis of results obtained from several tests both in batch systems and column. They show that, at room temperature, the residue works well with calcium and badly with magnesium, whereas, at 60 degrees C, also the affinity toward Mg ions increases to acceptable levels. Repeated regenerations of the residue with concentrated NaCl solutions do not appreciably compromise the performance. The limits for the possible use as water softening agent are defined.

  14. Structural Characterization of Crystalline Ice Nanoclusters

    NASA Technical Reports Server (NTRS)

    Blake, David

    2000-01-01

    Water ice nanoclusters are useful analogs for studying a variety of processes that occur within icy grains in the extraterrestrial environment. The surface of ice nanoclusters prepared in the laboratory is similar to the surface of interstellar ice grains. In cold molecular clouds, the silicate cores of interstellar grains are typically approx. 100 nm in diameter and have a coating of impure amorphous water ice. Depositional, thermal and radiolytic processes leave the surface and subsurface molecules in a disordered state. In this state, structural defects become mobile and reactions of trapped gases and small molecules can occur. The large surface area of nanocluster deposits relative to their bulk allows for routine observation of such surface-mediated processes. Furthermore, the disordered surface and subsurface layers in nanocluster deposits mimic the structure of amorphous ice rinds found on interstellar dust grains. Transmission Electron Microscopy (TEM has been used tn characterize the crystallinity, growth mechanism, and size distribution of nanoclusters formed from a mixture of water vapor with an inert carrier gas that has been rapidly cooled to 77K. E M imaging reveals a Gaussian size distribution around a modal diameter that increases from approx. 15 to 30 nm as the percentage of water vapor within the mixture increases from 0.5 to 2.007, respectively . TEM bright and dark field imaging also reveals the crystalline nature of the clusters. h4any of the clusters show a mosaic structure in which crystalline domains originate at the center Other images show mirror planes that are separated by approx. 10 nm. Electron diffraction patterns of these clusters show that the clusters are composed of cubic ice with only a small hexagonal component. Further, the crystalline domain size is approximately the same as the modal diameter suggesting that the clusters are single crystals.

  15. Calcium hydroxide: its role in the fracture of tricalcium silicate paste.

    PubMed

    Berger, R L

    1972-02-11

    The large areas of crystalline calcium hydroxide [Ca(OH)(2)] formed during the hydration of tricalcium silicate (Ca(3)SiO(5)) correspond to low-porosity regions in the hydrated paste. During the early stage of hydration, areas between Ca(OH)(2) crystals which consist of Ca(3)SiO(5) particles bonded together by calcium silicate hydrate represent the high-porosity portion of the paste. Because of the presence of Ca(OH)(2), fracture in the hardened paste during this period propagates preferentially through the areas bonded by the calcium silicate hydrate phase and around the Ca(OH)(8), crystals. Calcium hydroxide also acts as a crack arrester. The influence of Ca(OH)(2) on fracture diminishes with increased hydration.

  16. Improved epitaxy of ultrathin praseodymia films on chlorine passivated Si(111) reducing silicate interface formation

    SciTech Connect

    Gevers, S.; Bruns, D.; Weisemoeller, T.; Wollschlaeger, J.; Flege, J. I.; Kaemena, B.; Falta, J.

    2010-12-13

    Ultrathin praseodymia films have been deposited on both Cl-passivated and nonpassivated Si(111) substrates by molecular beam epitaxy. Comparative studies on the crystallinity and stoichiometry are performed by x-ray photoelectron spectroscopy, x-ray standing waves, and x-ray reflectometry. On nonpassivated Si(111) an amorphous silicate film is formed. In contrast, praseodymia deposited on Cl-passivated Si(111) form a well-ordered crystalline film with cubic-Pr{sub 2}O{sub 3} (bixbyite) structure. The vertical lattice constant of the praseodymia film is increased by 1.4% compared to the bulk value. Furthermore, the formation of an extended amorphous silicate interface layers is suppressed and confined to only one monolayer.

  17. Liquid crystalline composites containing phyllosilicates

    DOEpatents

    Chaiko, David J.

    2004-07-13

    The present invention provides phyllosilicate-polymer compositions which are useful as liquid crystalline composites. Phyllosilicate-polymer liquid crystalline compositions of the present invention can contain a high percentage of phyllosilicate while at the same time be transparent. Because of the ordering of the particles liquid crystalline composite, liquid crystalline composites are particularly useful as barriers to gas transport.

  18. The asteroid albedo scale. II - Laboratory polarimetry of dark carbon-bearing silicates

    NASA Technical Reports Server (NTRS)

    Zellner, B.; Lebertre, T.; Day, K.

    1977-01-01

    Laboratory reflection polarimetry is presented for eight samples of artificial, poorly crystalline magnesian silicates with varying admixtures of carbon black. The polarimetric slope-albedo law saturates for geometric albedos lower than about 0.05, and good agreement with the telescopic polarization-phase curves of C-type asteroids is found for albedos as low as 0.02. Thus the conclusion from thermal radiometry is confirmed that the C objects are very dark, darker than any known carbonaceous chondrite.

  19. Fly ash zeolite catalyst support for Fischer-Tropsch synthesis

    NASA Astrophysics Data System (ADS)

    Campen, Adam

    This dissertation research aimed at evaluating a fly ash zeolite (FAZ) catalyst support for use in heterogeneous catalytic processes. Gas phase Fischer-Tropsch Synthesis (FTS) over a fixed-bed of the prepared catalyst/FAZ support was identified as an appropriate process for evaluation, by comparison with commercial catalyst supports (silica, alumina, and 13X). Fly ash, obtained from the Wabash River Generating Station, was first characterized using XRD, SEM/EDS, particle size, and nitrogen sorption techniques. Then, a parametric study of a two-step alkali fusion/hydrothermal treatment process for converting fly ash to zeolite frameworks was performed by varying the alkali fusion agent, agent:flyash ratio, fusion temperature, fused ash/water solution, aging time, and crystallization time. The optimal conditions for each were determined to be NaOH, 1.4 g NaOH: 1 g fly ash, 550 °C, 200 g/L, 12 hours, and 48 hours. This robust process was applied to the fly ash to obtain a faujasitic zeolite structure with increased crystallinity (40 %) and surface area (434 m2/g). Following the modification of fly ash to FAZ, ion exchange of H+ for Na+ and cobalt incipient wetness impregnation were used to prepare a FTS catalyst. FTS was performed on the catalysts at 250--300 °C, 300 psi, and with a syngas ratio H2:CO = 2. The HFAZ catalyst support loaded with 11 wt% cobalt resulted in a 75 % carbon selectivity for C5 -- C18 hydrocarbons, while methane and carbon dioxide were limited to 13 and 1 %, respectively. Catalyst characterization was performed by XRD, N2 sorption, TPR, and oxygen pulse titration to provide insight to the behavior of each catalyst. Overall, the HFAZ compared well with silica and 13X supports, and far exceeded the performance of the alumina support under the tested conditions. The successful completion of this research could add value to an underutilized waste product of coal combustion, in the form of catalyst supports in heterogeneous catalytic processes.

  20. Monitoring early zeolite formation via in situ electrochemical impedance spectroscopy.

    PubMed

    Brabants, G; Lieben, S; Breynaert, E; Reichel, E K; Taulelle, F; Martens, J A; Jakoby, B; Kirschhock, C E A

    2016-04-01

    Hitherto zeolite formation has not been fully understood. Although electrochemical impedance spectroscopy has proven to be a versatile tool for characterizing ionic solutions, it was never used for monitoring zeolite growth. We show here that EIS can quantitatively monitor zeolite formation, especially during crucial early steps where other methods fall short. PMID:27020096

  1. Monitoring early zeolite formation via in situ electrochemical impedance spectroscopy.

    PubMed

    Brabants, G; Lieben, S; Breynaert, E; Reichel, E K; Taulelle, F; Martens, J A; Jakoby, B; Kirschhock, C E A

    2016-04-01

    Hitherto zeolite formation has not been fully understood. Although electrochemical impedance spectroscopy has proven to be a versatile tool for characterizing ionic solutions, it was never used for monitoring zeolite growth. We show here that EIS can quantitatively monitor zeolite formation, especially during crucial early steps where other methods fall short.

  2. Pure Silica Zeolite Beta Membrane: A Potential Low Dielectric Constant Material For Microprocessor Application

    NASA Astrophysics Data System (ADS)

    Fong, Yeong Yin; Bhatia, Subhash

    The semiconductor industry needs low dielectric constant (low k-value) materials for more advance microprocessor and chips by reducing the size of the device features. In fabricating these contents, a new material with lower k-value than conventional silica (k = 3.9-4.2) is needed in order to improve the circuit performance. The choice of the inorganic zeolite membrane is an attractive option for low k material and suitable for microprocessor applications. A pure silica zeolite beta membrane was synthesized and coated on non-porous stainless steel support using insitu crystallization in the presence of tetraethylammonium hydroxide, TEA (OH), as structure directing agent, fumed silica, HF and deionized water at pH value of 9. The crystallization was carried out for the duration of 14 days under hydrothermal conditions at 130°C. The membrane was characterized by thermogravimetric analysis (TGA), nitrogen adsorption and Scanning Electron Microscope (SEM). SEM results show a highly crystalline; with a truncated square bipyramidal morphology of pure silica zeolite beta membrane strongly adhered on the non-porous stainless steel support. In the present work, the k-value of the membrane was measured as 2.64 which make it suitable for the microprocessor applications.

  3. Production of biofuel from waste cooking palm oil using nanocrystalline zeolite as catalyst: process optimization studies.

    PubMed

    Taufiqurrahmi, Niken; Mohamed, Abdul Rahman; Bhatia, Subhash

    2011-11-01

    The catalytic cracking of waste cooking palm oil to biofuel was studied over different types of nano-crystalline zeolite catalysts in a fixed bed reactor. The effect of reaction temperature (400-500 °C), catalyst-to-oil ratio (6-14) and catalyst pore size of different nanocrystalline zeolites (0.54-0.80 nm) were studied over the conversion of waste cooking palm oil, yields of Organic Liquid Product (OLP) and gasoline fraction in the OLP following central composite design (CCD). The response surface methodology was used to determine the optimum value of the operating variables for maximum conversion as well as maximum yield of OLP and gasoline fraction, respectively. The optimum reaction temperature of 458 °C with oil/catalyst ratio=6 over the nanocrystalline zeolite Y with pore size of 0.67 nm gave 86.4 wt% oil conversion, 46.5 wt% OLP yield and 33.5 wt% gasoline fraction yield, respectively. The experimental results were in agreement with the simulated values within an experimental error of less than 5%.

  4. Catalytically active and hierarchically porous SAPO-11 zeolite synthesized in the presence of polyhexamethylene biguanidine.

    PubMed

    Liu, Yan; Qu, Wei; Chang, Weiwei; Pan, Shuxiang; Tian, Zhijian; Meng, Xiangju; Rigutto, Marcello; van der Made, Alexander; Zhao, Lan; Zheng, Xiaoming; Xiao, Feng-Shou

    2014-03-15

    Hierarchically porous SAPO-11 zeolite (H-SAPO-11) is rationally synthesized from a starting silicoaluminophosphate gel in the presence of polyhexamethylene biguanidine as a mesoscale template. The sample is well characterized by XRD, N2 sorption, SEM, TEM, NMR, XPS, NH3-TPD, and TG techniques. The results show that the sample obtained has good crystallinity, hierarchical porosity (mesopores at ca. 10 nm and macropores at ca. 50-200 nm), high BET surface area (226 m(2)/g), large pore volume (0.25 cm(3)/g), and abundant medium and strong acidic sites (0.36 mmol/g). After loading Pt (0.5 wt.%) on H-SAPO-11 by using wet impregnation method, catalytic hydroisomerization tests of n-dodecane show that the hierarchical Pt/SAPO-11 zeolite exhibits high conversion of n-dodecane and enhanced selectivity for branched products as well as reduced selectivity for cracking products, compared with conventional Pt/SAPO-11 zeolite. This phenomenon is reasonably attributed to the presence of hierarchical porosity, which is favorable for access of reactants on catalytically active sites. The improvement in catalytic performance in long-chain paraffin hydroisomerization over Pt/SAPO-11-based catalyst is of great importance for its industrial applications in the future.

  5. Molecular simulations and experimental studies of zeolites

    NASA Astrophysics Data System (ADS)

    Moloy, Eric C.

    Zeolites are microporous aluminosilicate tetrahedral framework materials that have symmetric cages and channels with open-diameters between 0.2 and 2.0 nm. Zeolites are used extensively in the petrochemical industries for both their microporosity and their catalytic properties. The role of water is paramount to the formation, structure, and stability of these materials. Zeolites frequently have extra-framework cations, and as a result, are important ion-exchange materials. Zeolites also play important roles as molecular sieves and catalysts. For all that is known about zeolites, much remains a mystery. How, for example, can the well established metastability of these structures be explained? What is the role of water with respect to the formation, stabilization, and dynamical properties? This dissertation addresses these questions mainly from a modeling perspective, but also with some experimental work as well. The first discussion addresses a special class of zeolites: pure-silica zeolites. Experimental enthalpy of formation data are combined with molecular modeling to address zeolitic metastability. Molecular modeling is used to calculate internal surface areas, and a linear relationship between formation enthalpy and internal surface areas is clearly established, producing an internal surface energy of approximately 93 mJ/m2. Nitrate bearing sodalite and cancrinite have formed under the caustic chemical conditions of some nuclear waste processing centers in the United States. These phases have fouled expensive process equipment, and are the primary constituents of the resilient heels in the bottom of storage tanks. Molecular modeling, including molecular mechanics, molecular dynamics, and density functional theory, is used to simulate these materials with respect to structure and dynamical properties. Some new, very interesting results are extracted from the simulation of anhydrous Na6[Si6Al 6O24] sodalite---most importantly, the identification of two distinct

  6. Erupted silicic cumulates in large ignimbrites

    NASA Astrophysics Data System (ADS)

    Bachmann, O.; Deering, C. D.; Huber, C.; Dufek, J.

    2011-12-01

    If chemical diversity in igneous rocks is dominated by crystal-liquid separation in open-system magma reservoirs, a significant number of crystal accumulation zones must be preserved in the crust and upper mantle. Such cumulates are conspicuous in mafic lithologies (MOR, layered mafic intrusions, lower crustal arc sections), but have rarely been described and/or are controversial in the silicic upper crust. Although it is possible to recognize signs of crystal accumulations in plutonic exposures, the fact that these batholiths are typically: 1) at least several millions of years old, 2) multi-stage, 3) deformed and 4) biased towards the youngest intrusive episodes, some ambiguity remains in how to interpret geochemical and textural observations. We have chosen to explore large zoned ignimbrites, which represent an instantaneous evacuation of an upper crustal magma reservoir, to isolate potential crystal accumulation zones. Late-erupted, crystal-rich scoria with unusual chemistries (e.g., high Ba, Zr, Eu/Eu*) have been found in multiple examples of these zoned ignimbrites around the world, including the 900+ km3 Ammonia Tanks and Carpenter Ridge Tuffs, both erupted during the Tertiary magmatic flare-up in the Western USA. As already suggested for the 7700 BP Crater Lake ignimbrite, such crystal-rich scoria have mineralogical and geochemical characteristics that are most convincingly explained by accumulation of low temperature minerals as highly-evolved melt escapes upward and pools at the top of large crystalline mushes. To account for the eruption of such crystal-rich zones (technically uneruptible with >50vol% crystals), some melting of low-temperature mineral phases is required; evidence for resorption textures in sanidine and quartz is commonplace in these scoria. The presence of mafic enclaves and/or mingling textures in such scoria indicate that recharge from below ultimately drove melting of part of the mineral assemblage within the cumulate rootzone, while

  7. Development of Desiccant System using Wakkanai Siliceous Shale

    NASA Astrophysics Data System (ADS)

    Nakabayashi, Saya; Nagano, Katsunori; Nakamura, Makoto; Togawa, Junya; Kurokawa, Asami

    The aim of this study is to develop a desiccant system using Wakkanai siliceous shale. A honeycombed desiccant rotor containing this shale's powder and chlorides was made and evaluated. However a specific surface area and a pore volume were smaller than a silica-gel rotor or a zeolite rotor, the maximum amount of water adsorption was twice as other rotors. We have verified the function of this desiccant rotor concerning adsorption and desorption of moisture from the draft experiments. The rotor containing the shale could adsorb moisture stably in the cyclic test, and be regenerated by 40°C air under this experimental condition. This means that the exhaust heat from the heat pump can be used for regenerating rotor. Furthermore, the numerical simulation was carried out on the assumption that this rotor was used for a dehumidification for the residential air conditioning in Tokyo. This rotor could adsorb 37.1% moisture of the required dehumidification amount for the hottest day in 2008. When we employed a pre-cooling before dehumidification, the amount of adsorption increased to 66.2%.

  8. Catalytic crystallization of ices by small silicate smokes at temperatures less than 20K

    NASA Technical Reports Server (NTRS)

    Moore, M.; Ferrante, R.; Hudson, R.; Tanabe, T.; Nuth, J.

    1993-01-01

    Samples of methanol and water ices condensed from the vapor onto aluminum substrates at low temperatures (below approximately 80 K) form amorphous ices; annealing at temperatures in excess of 140-155 K is usually required to convert such amorphous samples to crystalline ices. However, we have found that when either methanol or water vapor is deposited on to aluminum substrates that have been coated with a thin (0.1-0.5 mm) layer of amorphous silicate smoke, the ices condense in crystalline form. We believe that crystalline ice forms as the result of energy liberated at the ice/silicate interface perhaps due to weak bonding of the ice at defect sites on the grains and the very high surface to volume ratio and defect density of these smokes. Annealing of amorphous water ice mixed with more volatile components such as methane, carbon monoxide, etc., has been suggested as an efficient way to produce clatherates in the outer solar nebula and thus explain the volatile content of comets and icy satellites of the outer planets. This hypothesis may need to be re-examined if amorphous ice does not form on cold silicate grains.

  9. Crystalline molecular flasks.

    PubMed

    Inokuma, Yasuhide; Kawano, Masaki; Fujita, Makoto

    2011-05-01

    A variety of host compounds have been used as molecular-scale reaction vessels, protecting guests from their environment or restricting the space available around them, thus favouring particular reactions. Such molecular 'flasks' can endow guest molecules with reactivities that differ from those in bulk solvents. Here, we extend this concept to crystalline molecular flasks, solid-state crystalline networks with pores within which pseudo-solution-state reactions can take place. As the guest molecules can spontaneously align along the walls and channels of the hosts, structural changes in the substrates can be directly observed by in situ X-ray crystallography during reaction. Recently, this has enabled observation of the molecular structures of transient intermediates and other labile species, in the form of sequential structural snapshots of the chemical transformation. Here, we describe the principles, development and applications of crystalline molecular flasks.

  10. Synthesis of novel perfluoroalkylglucosides on zeolite and non-zeolite catalysts.

    PubMed

    Nowicki, Janusz; Mokrzycki, Łukasz; Sulikowski, Bogdan

    2015-01-01

    Perfluoroalkylglucosides comprise a very important class of fluorine-containing surfactants. These compounds can be synthesized by using the Fisher reaction, starting directly from glucose and the required perfluoroalcohols. We wish to report on the use of zeolite catalysts of different structure and composition for the synthesis of perfluoroalkylglucosides when using glucose and 1-octafluoropentanol as substrates. Zeolites of different pore architecture have been chosen (ZSM-5, ZSM-12, MCM-22 and Beta). Zeolites were characterized by XRD, nitrogen sorption, scanning electron microscopy (SEM) and solid-state 27Al MAS NMR spectroscopy. The activity of the zeolite catalysts in the glycosidation reaction was studied in a batch reactor at 100 °C below atmospheric pressure. The performance of zeolites was compared to other catalysts, an ion-exchange resin (Purolite) and a montmorillonite-type layered aluminosilicate. The catalytic performance of zeolite Beta was the highest among the zeolites studied and the results were comparable to those obtained over Purolite and montmorillonite type catalysts.

  11. [Research on the mineral phase and component of non-crystalline and nano-crystalline corrosion products on bronzes unearthed from Shang Tomb in Xingan].

    PubMed

    Cheng, Xiao-lin; Pan, Lu

    2012-05-01

    The patinas on bronzes in Shang Tomb of Xingan were powdery, pale green, which were more like "bronze disease", but the mineral composition of patinas was not paratacamite or atacamite. Micro X-ray diffraction (XRD) and high performance transmission electroscope (HTEM) showed that the patinas were mainly composed of non-crystalline and nano-crystalline SnO2, and the size of nano-crystalline particle was in the range of 4-5.7 nm; Moreover, the energy-dispersive X-ray spectrometry showed that element tin is the primary ingredient of the sample, as well as little copper, silicon, lead and iron were detected. By studying the crystal lattice stripe image of the nanometer SnO2, it was deduced that the chemical formula of nano-crystalline SnO2 did not include other elements; The Raman spectrum of the sample showed that there were not any characteristic peaks of SnO2, the spectrum was more like non-crystalline SnO2, and the weak and broad peak of 973 cm(-1) indicated that the sample may contain silicate grains, It was inferred that little of copper, silicon, lead and iron should exist in the form of non-crystalline silicate particles.

  12. Topological crystalline insulators.

    PubMed

    Fu, Liang

    2011-03-11

    The recent discovery of topological insulators has revived interest in the band topology of insulators. In this Letter, we extend the topological classification of band structures to include certain crystal point group symmetry. We find a class of three-dimensional "topological crystalline insulators" which have metallic surface states with quadratic band degeneracy on high symmetry crystal surfaces. These topological crystalline insulators are the counterpart of topological insulators in materials without spin-orbit coupling. Their band structures are characterized by new topological invariants. We hope this work will enlarge the family of topological phases in band insulators and stimulate the search for them in real materials.

  13. Preparation, Processing, and Characterization of Oriented Polycrystalline Zeolite and Aluminophosphate Membranes

    NASA Astrophysics Data System (ADS)

    Stoeger, Jared Andrew

    Since the advent of zeolite membranes, speculation on their industrial applicability has been closely monitored, although widespread commercialization has been hampered by limitations in fabrication and post-synthesis processing. Economical, energy-efficient technology breakthroughs require an evaluation of a range of material candidates which show robustness and reliability. Straightforward manufacturing techniques should be devised to generate thousands of square meters of membrane area; however, this demands control of structural characteristics on the scale of nanometers. As described in this dissertation, the path forward will be forged by exploiting the intrinsic crystalline properties of zeolites or aluminophosphates for the next advancement in membrane technology. A facile method is described for the preparation of silicalite-1 (MFI zeolite type) membranes using the secondary growth technique on symmetric porous stainless steel tubes. Activation through rapid thermal processing (RTP), a lamp-based heat-treatment process used as a critical fabrication step in silicon integrated circuit manufacturing, is proven to reduce the density of non-zeolitic transport pathways which are detrimental to high-resolution molecular sieving. RTP-treated membranes are shown to have enhanced performance in the binary separation of vapor-phase isomers (p-/o-xylene), gas-phase isomers (n-/i-butane), and alcohol/water when compared to membranes activated at a much slower heating rate but otherwise similarly-prepared. The performance is discussed in the context of the market potential for industrially-attractive separations: the recovery of p-xylene from an isomeric mixture or alcohol biofuels from aqueous post-fermentation streams. Hydrothermal growth techniques for the preparation and characterization of continuous aluminophosphate (AFI zeolite type) membranes with a preferential crystallographic alignment on porous alpha-Al2O3 disc supports are demonstrated. A mechanism is

  14. Cumulate Fragments in Silicic Ignimbrites

    NASA Astrophysics Data System (ADS)

    Bachmann, O.; Ellis, B. S.; Wolff, J.

    2014-12-01

    Increasingly, studies are concluding that silicic ignimbrites are the result of the amalgamation of multiple discrete magma batches. Yet the existence of discrete batches presents a conundrum for magma generation and storage; if silicic magma batches are not generated nearly in situ in the upper crust, they must traverse, and reside within, a thermally hostile environment with large temperature gradients, resulting in low survivability in their shallow magmatic hearths. The Snake River Plain (Idaho, USA) is a type example of this 'multi-batch' assembly with ignimbrites containing multiple populations of pyroxene crystals, glass shards, and crystal aggregates. The ubiquitous crystal aggregates hint at a mechanism to facilitate the existence of multiple, relatively small batches of rhyolite in the upper crust. These aggregates contain the same plagioclase, pyroxene, and oxide mineral compositions as single phenocrysts of the same minerals in their host rocks, but they have significantly less silicic bulk compositions and lack quartz and sanidine, which occur as single phenocrysts in the deposits. This implies significant crystallization followed by melt extraction from mushy reservoir margins. The extracted melt then continues to evolve (crystallizing sanidine and quartz) while the melt-depleted margins provide an increasingly rigid and refractory network segregating the crystal-poor batches of magma. The hot, refractory, margins insulate the crystal-poor lenses, allowing (1) extended residence in the upper crust, and (2) preservation of chemical heterogeneities among batches. In contrast, systems that produce cumulates richer in low-temperature phases (quartz, K-feldspars, and/or biotite) favour remelting upon recharge, leading to less segregation of eruptible melt pockets and the formation of gradationally zoned ignimbrites. The occurrence of similar crystal aggregates from a variety of magmatic lineages suggests the generality of this process.

  15. Models for silicate melt viscosity

    NASA Astrophysics Data System (ADS)

    Giordano, D.; Russell, K.; Moretti, R.; Mangiacapra, A.; Potuzak, M.; Romano, C.; Dingwell, D. B.

    2004-12-01

    The prediction of viscosity in silicate liquids, over the range of temperatures and compositions encountered in nature, remains one of the most challenging and elusive goals in Earth Sciences. Recent work has demonstrated that there are now sufficient experimental measurements of melt viscosity to create new viscosity models to replace previous Arrhenian models [1],[2] and extend the compositional range of more recent non-Arrhenian models [3]. Most recently, [4] have developed an empirical strategy for accurately predicting viscosities over a very wide range of anhydrous silicate melt compositions (e.g., rhyolite to basanite). Future models that improve upon this work, will probably extend the composition range of the model to consider, at least, H2O and other volatile components and may utilize a compositional basis that reflects melt structure. In preparation for the next generation model, we explore the attributes of the three most common equations that could be used to model the non-Arrhenian viscosity of multicomponent silicate melts. The equations for the non-Arrhenian temperature dependence of viscosity (η ) include: a) Vogel-Fulcher-Tammann (VFT): log η = A + B/(T - C) b) Adam and Gibbs (AG): log η = A + B/[T log (T/C)], and c) Avramov (Av): log η = A + [B/T]α We use an experimental database of approximately 900 high-quality viscosity measurements on silicate melts to test the ability of each equation to capture the experimental data. These equations have different merits [5]. VFT is purely empirical in nature. The AG model has a quasi-theoretical basis that links macroscopic transport properties directly to thermodynamic properties via the configurational entropy. Lastly, the model proposed by Avramov adopts a form designed to relate the fit parameter (α ) to the fragility of the melt. [1] Shaw, H.R., 1972. Am J Science, 272, 438-475. [2] Bottinga Y. and Weill, D., 1972. Am J Science, 272, 438-475. [3] Hess, K.U. and Dingwell, D.B, 1996, Am Min, 81

  16. Basaltic injections into floored silicic magma chambers

    NASA Astrophysics Data System (ADS)

    Wiebe, R. A.

    Recent studies have provided compelling evidence that many large accumulations of silicic volcanic rocks erupted from long-lasting, floored chambers of silicic magma that were repeatedly injected by basaltic magma. These basaltic infusions are commonly thought to play an important role in the evolution of the silicic systems: they have been proposed as a cause for explosive silicic eruptions [Sparks and Sigurdsson, 1977], compositional variation in ash-flow sheets [Smith, 1979], mafic magmatic inclusions in silicic volcanic rocks [Bacon, 1986], and mixing of mafic and silicic magmas [Anderson, 1976; Eichelberger, 1978]. If, as seems likely, floored silicic magma chambers have frequently been invaded by basalt, then plutonic bodies should provide records of these events. Although plutonic evidence for mixing and commingling of mafic and silicic magmas has been recognized for many years, it has been established only recently that some intrusive complex originated through multiple basaltic injections into floored chambers of silicic magma [e.g., Wiebe, 1974; Michael, 1991; Chapman and Rhodes, 1992].

  17. Tailoring polymer properties with layered silicates

    NASA Astrophysics Data System (ADS)

    Xu, Liang

    Polymer layered silicate nanocomposites have found widespread applications in areas such as plastics, oil and gas production, biomedical, automotive and information storage, but their successful commercialization critically depends on consistent control over issues such as complete dispersion of layered silicate into the host polymer and optimal interaction between the layered silicates and the polymers. Polypropylene is a commercially important polymer but usually forms intercalated structures with organically modified layered silicate upon mixing, even it is pre-treated with compatibilizing agent such as maleic anhydride. In this work, layered silicate is well dispersed in ammonium modified polypropylene but does not provide sufficient reinforcement to the host polymer due to poor interactions. On the other hand, interactions between maleic anhydride modified polypropylene and layered silicate are fine tuned by using a small amount of maleic anhydride and mechanical strength of the resultant nanocomposites are significantly enhanced. In particular, the melt rheological properties of layered silicate nanocomposites with maleic anhydride functionalized polypropylene are contrasted to those based on ammonium-terminated polypropylene. While the maleic anhydride treated polypropylene based nanocomposites exhibit solid-like linear dynamic behavior, consistent with the formation of a long-lived percolated nanoparticle network, the single-end ammonium functionalized polypropylene based nanocomposites demonstrated liquid-like behavior at comparable montmorillonite concentrations. The differences in the linear viscoelasticity are attributed to the presence of bridging interaction in maleic anhydride functionalized nanocomposites, which facilitates formation of a long-lived silicate network mediated by physisorbed polymer chains. Further, the transient shear stress of the maleic anhydride functionalized nanocomposites in start-up of steady shear is a function of the shear

  18. Synthesis, Structure, and Carbon Dioxide Capture Properties of Zeolitic Imidazolate Frameworks

    SciTech Connect

    Phan, Anh; Doonan, Christian J.; Uribe-Romo, Fernando J.; Knobler, Carolyn B.; O’Keeffe, Michael; Yaghi, Omar M.

    2010-01-19

    Zeolites are one of humanity’s most important synthetic products. These aluminosilicate-based materials represent a large segment of the global economy. Indeed, the value of zeolites used in petroleum refining as catalysts and in detergents as water softeners is estimated at $350 billion per year. A major current goal in zeolite chemistry is to create a structure in which metal ions and functionalizable organic units make up an integral part of the framework. Such a structure, by virtue of the flexibility with which metal ions and organic moieties can be varied, is viewed as a key to further improving zeolite properties and accessing new applications. Recently, it was recognized that the Si-O-Si preferred angle in zeolites (145°) is coincident with that of the bridging angle in the M-Im-M fragment (where M is Zn or Co and Im is imidazolate), and therefore it should be possible to make new zeolitic imidazolate frameworks (ZIFs) with topologies based on those of tetrahedral zeolites. This idea was successful and proved to be quite fruitful; within the last 5 years over 90 new ZIF structures have been reported. The recent application of high-throughput synthesis and characterization of ZIFs has expanded this structure space significantly: it is now possible to make ZIFs with topologies previously unknown in zeolites, in addition to mimicking known structures. In this Account, we describe the general preparation of crystalline ZIFs, discussing the methods that have been developed to create and analyze the variety of materials afforded. We include a comprehensive list of all known ZIFs, including structure, topology, and pore metrics. We also examine how complexity might be introduced into new structures, highlighting how link-link interactions might be exploited to effect particular cage sizes, create polarity variations between pores, or adjust framework robustness, for example. The chemical and thermal stability of ZIFs permit many applications, such as the

  19. Towards a sustainable manufacture of hierarchical zeolites.

    PubMed

    Verboekend, Danny; Pérez-Ramírez, Javier

    2014-03-01

    Hierarchical zeolites have been established as a superior type of aluminosilicate catalysts compared to their conventional (purely microporous) counterparts. An impressive array of bottom-up and top-down approaches has been developed during the last decade to design and subsequently exploit these exciting materials catalytically. However, the sustainability of the developed synthetic methods has rarely been addressed. This paper highlights important criteria to ensure the ecological and economic viability of the manufacture of hierarchical zeolites. Moreover, by using base leaching as a promising case study, we verify a variety of approaches to increase reactor productivity, recycle waste streams, prevent the combustion of organic compounds, and minimize separation efforts. By reducing their synthetic footprint, hierarchical zeolites are positioned as an integral part of sustainable chemistry.

  20. Hydrogen Purification Using Natural Zeolite Membranes

    NASA Technical Reports Server (NTRS)

    DelValle, William

    2003-01-01

    The School of Science at Universidad del Turabo (UT) have a long-lasting investigation plan to study the hydrogen cleaning and purification technologies. We proposed a research project for the synthesis, phase analysis and porosity characterization of zeolite based ceramic perm-selective membranes for hydrogen cleaning to support NASA's commitment to achieving a broad-based research capability focusing on aerospace-related issues. The present study will focus on technology transfer by utilizing inorganic membranes for production of ultra-clean hydrogen for application in combustion. We tested three different natural zeolite membranes (different particle size at different temperatures and time of exposure). Our results show that the membranes exposured at 900 C for 1Hr has the most higher permeation capacity, indicated that our zeolite membranes has the capacity to permeate hydrogen.

  1. Studies of anions sorption on natural zeolites.

    PubMed

    Barczyk, K; Mozgawa, W; Król, M

    2014-12-10

    This work presents results of FT-IR spectroscopic studies of anions-chromate, phosphate and arsenate - sorbed from aqueous solutions (different concentrations of anions) on zeolites. The sorption has been conducted on natural zeolites from different structural groups, i.e. chabazite, mordenite, ferrierite and clinoptilolite. The Na-forms of sorbents were exchanged with hexadecyltrimethylammonium cations (HDTMA(+)) and organo-zeolites were obtained. External cation exchange capacities (ECEC) of organo-zeolites were measured. Their values are 17mmol/100g for chabazite, 4mmol/100g for mordenite and ferrierite and 10mmol/100g for clinoptilolite. The used initial inputs of HDTMA correspond to 100% and 200% ECEC of the minerals. Organo-modificated sorbents were subsequently used for immobilization of mentioned anions. It was proven that aforementioned anions' sorption causes changes in IR spectra of the HDTMA-zeolites. These alterations are dependent on the kind of anions that were sorbed. In all cases, variations are due to bands corresponding to the characteristic Si-O(Si,Al) vibrations (occurring in alumino- and silicooxygen tetrahedra building spatial framework of zeolites). Alkylammonium surfactant vibrations have also been observed. Systematic changes in the spectra connected with the anion concentration in the initial solution have been revealed. The amounts of sorbed CrO4(2-), AsO4(3-) and PO4(3-) ions were calculated from the difference between their concentrations in solutions before (initial concentration) and after (equilibrium concentration) sorption experiments. Concentrations of anions were determined by spectrophotometric method.

  2. Silicate Glass Corrosion Mechanism revisited

    NASA Astrophysics Data System (ADS)

    Geisler, Thorsten; Lenting, Christoph; Dohmen, Lars

    2015-04-01

    Understanding the mechanism(s) of aqueous corrosion of nuclear waste borosilicate glasses is essential to predict their long-term aqueous durability in a geologic repository. Several observations have been made with compositionally different silicate glasses that cannot be explained by any of the established glass corrosion models. These models are based on diffusion-controlled ion exchange and subsequent structural reorganisation of a leached, hydrated residual glass, leaving behind a so-called gel layer. In fact, the common observation of lamellar to more complex pattern formation observed in experiment and nature, the porous structure of the corrosion layer, an atomically sharp boundary between the corrosion zone and the underlying pristine glass, as well as results of novel isotope tracer and in situ, real time experiments rather support an interface-coupled glass dissolution-silica reprecipitation model. In this model, the congruent dissolution of the glass is coupled in space and time to the precipitation and growth of amorphous silica at an inwardly moving reaction front. We suggest that these coupled processes have to be considered to realistically model the long-term performance of silicate glasses in aqueous environments.

  3. Natural zeolite reactivity towards ozone: the role of compensating cations.

    PubMed

    Valdés, Héctor; Alejandro, Serguei; Zaror, Claudio A

    2012-08-15

    Among indoor pollutants, ozone is recognised to pose a threat to human health. Recently, low cost natural zeolites have been applied as alternative materials for ozone abatement. In this work, the effect of compensating cation content of natural zeolite on ozone removal is studied. A Chilean natural zeolite is used here as starting material. The amount of compensating cations in the zeolite framework was modified by ion exchange using an ammonium sulphate solution (0.1 mol L(-1)). Characterisation of natural and modified zeolites were performed by X-ray powder diffraction (XRD), nitrogen adsorption at 77K, elemental analysis, X-ray fluorescence (XRF), thermogravimetric analysis coupled with mass spectroscopy (TGA-MS), and temperature-programmed desorption of ammonia (NH(3)-TPD). Ozone adsorption and/or decomposition on natural and modified zeolites were studied by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Results show that the zeolite compensating cation content affects ozone interaction with zeolite active sites. Ammonium ion-exchange treatments followed by thermal out-gassing at 823 K, reduces ozone diffusion resistance inside the zeolite framework, increasing ozone abatement on zeolite surface active sites. Weak and strong Lewis acid sites of zeolite surface are identified here as the main active sites responsible of ozone removal.

  4. Phonolite-hosted zeolite deposits in the Kaiserstuhl Volcanic Complex, Germany

    NASA Astrophysics Data System (ADS)

    Weisenberger, Tobias; Spürgin, Simon

    2014-05-01

    intrusions and through time. Zeolites formed during sub-solidus hydrothermal alteration under alkaline conditions and completely replace feldspathoid minerals in the matrix of the rock. A sequence of Ca-Na dominated zeolite species (gonnardite, thomsonite, mesolite) is followed by pure sodium endmember species (analcime, natrolite). These sequence reflects an increase in log[aNa+)/(aH+)] of the precipitating fluid. In contrast to the Fohberg phonolitc the Endhale phonolite contains analcime in addition to natrolite as pure Na zeolite species. The appearance of analcime is caused by higher silica activity during fluid rock interaction, which favors the formation of analcime over natrolite. The Fohberg phonolite is cut by fractures, which are totally or partially sealed with secondary minerals. Secondary minerals contain zeolites, followed by calcite and a variety of other silicates, carbonates, and sulphates as younger generations. Stable isotope analyses of late fracture calcite indicate the late circulation of meteoric fluids and mobilization of organic matter from surrounding sedimentary units.

  5. Photostable Solid Dispersion of Nifedipine by Porous Calcium Silicate.

    PubMed

    Fujimoto, Yumi; Hirai, Nobuaki; Takatani-Nakase, Tomoka; Takahashi, Koichi

    2016-01-01

    Nifedipine (NIF) is a typical light-sensitive drug requiring protection from light during manufacture, storage, and handling of its dosage forms. The purpose of this study was to evaluate the utility of porous calcium silicate (PCS) for maintaining the photostability of NIF in a solid dispersion formulation. Adsorption solid dispersion (ASD) prepared using NIF and PCS as an amorphous formulation was more stable to light irradiation than a physical mixture of NIF and microcrystalline cellulose (a control physical mixture) as a crystalline formulation. In addition, PCS in physical mixtures with NIF adequately protected NIF from photodegradation, suggesting that this protective effect could be because of some screening effect by the porous structure of PCS blocking the passage of light reaching NIF in pores of PCS. These findings suggest that PCS is useful for improving the solubility and photostability of NIF in solid dispersion formulation.

  6. Photostable Solid Dispersion of Nifedipine by Porous Calcium Silicate.

    PubMed

    Fujimoto, Yumi; Hirai, Nobuaki; Takatani-Nakase, Tomoka; Takahashi, Koichi

    2016-01-01

    Nifedipine (NIF) is a typical light-sensitive drug requiring protection from light during manufacture, storage, and handling of its dosage forms. The purpose of this study was to evaluate the utility of porous calcium silicate (PCS) for maintaining the photostability of NIF in a solid dispersion formulation. Adsorption solid dispersion (ASD) prepared using NIF and PCS as an amorphous formulation was more stable to light irradiation than a physical mixture of NIF and microcrystalline cellulose (a control physical mixture) as a crystalline formulation. In addition, PCS in physical mixtures with NIF adequately protected NIF from photodegradation, suggesting that this protective effect could be because of some screening effect by the porous structure of PCS blocking the passage of light reaching NIF in pores of PCS. These findings suggest that PCS is useful for improving the solubility and photostability of NIF in solid dispersion formulation. PMID:27477662

  7. Photocatalytic activity of undoped and Ag-doped TiO{sub 2}-supported zeolite for humic acid degradation and mineralization

    SciTech Connect

    Lazau, C.; Ratiu, C.; Orha, C.; Pode, R.; Manea, F.

    2011-11-15

    Highlights: {yields} Hybrid materials based on natural zeolite and TiO{sub 2} obtained by solid-state reaction. {yields} XRD proved the presence of anatase form of undoped and Ag-doped TiO{sub 2} onto zeolite. {yields} FT-IR spectra evidenced the presence on TiO{sub 2} bounded at the zeolite network. {yields} Ag-doped TiO{sub 2} onto zeolitic matrix exhibited an enhanced photocatalytic activity. -- Abstract: The hybrid materials based on natural zeolite and undoped and Ag-doped TiO{sub 2}, i.e., Z-Na-TiO{sub 2} and Z-Na-TiO{sub 2}-Ag, were successfully synthesized by solid-state reaction in microwave-assisted hydrothermal conditions. Undoped TiO{sub 2} and Ag-doped TiO{sub 2} nanocrystals were previously synthesized by sol-gel method. The surface characterization of undoped TiO{sub 2}/Ag-doped TiO{sub 2} and natural zeolite hybrid materials has been investigated by X-ray diffraction, DRUV-VIS spectroscopy, FT-IR spectroscopy, BET analysis, SEM microscopy and EDX analysis. The results indicated that anatase TiO{sub 2} is the dominant crystalline type as spherical form onto zeolitic matrix. The presence of Ag into Z-Na-TiO{sub 2}-Ag was confirmed by EDX analysis. The DRUV-VIS spectra showed that Z-Na-TiO{sub 2}-Ag exhibited absorption within the range of 400-500 nm in comparison with Z-Na-TiO{sub 2} catalyst. The enhanced photocatalytic activity of Z-Na-TiO{sub 2}-Ag catalyst is proved through the degradation and mineralization of humic acid under ultraviolet and visible irradiation.

  8. Dynamic crystallization of silicate melts

    NASA Technical Reports Server (NTRS)

    Russell, W. J.

    1984-01-01

    Two types of furnaces with differing temperature range capabilities were used to provide variations in melt temperatures and cooling rates in a study of the effects of heterogeneous nucleation on crystallization. Materials of chondrule composition were used to further understanding of how the disequilibrium features displayed by minerals in rocks are formed. Results show that the textures of natural chondrules were duplicated. It is concluded that the melt history is dominant over cooling rate and composition in controlling texture. The importance of nuclei, which are most readily derived from preexisting crystalline material, support an origin for natural chondrules based on remelting of crystalline material. This would be compatible with a simple, uniform chondrule forming process having only slight variations in thermal histories resulting in the wide range of textures.

  9. Humidity sensing by nanocomposites of silver in silicate glass ceramics

    NASA Astrophysics Data System (ADS)

    Pal, B. N.; Kundu, T. K.; Banerjee, S.; Chakravorty, D.

    2003-04-01

    Silver nanoparticles of diameters in the range 3.4 to 13.2 nm were grown within a silicate glass ceramics containing barium titanate phase. The glass ceramics were filled with silver particles by subjecting the former to a Na+-Ag+ ion exchange process followed by a reduction treatment in hydrogen. Silver particles were formed at the interfaces of the silicate glass and the barium titanate phases, respectively. The silver particle sizes could be varied by controlling the fractal structure of the crystalline phase by prior heat treatment. Electrical resistivity measurements were carried out on cold-pressed specimens of nanocomposite powders prepared as just stated. A five order of magnitude resistivity change was recorded in the case of nanocomposite specimen with a silver particle diameter of 10.1 nm in the relative humidity range of 25% to 85%. The resistivity of the nanocomposites was found to be controlled by a variable range hopping conduction. It is believed that the silver nanoparticles provide sites where physisorption of water molecules takes place which increases the number of localized states near the Fermi level.

  10. Carbon substitution for oxygen in silicates in planetary interiors

    PubMed Central

    Sen, Sabyasachi; Widgeon, Scarlett J.; Navrotsky, Alexandra; Mera, Gabriela; Tavakoli, Amir; Ionescu, Emanuel; Riedel, Ralf

    2013-01-01

    Amorphous silicon oxycarbide polymer-derived ceramics (PDCs), synthesized from organometallic precursors, contain carbon- and silica-rich nanodomains, the latter with extensive substitution of carbon for oxygen, linking Si-centered SiOxC4-x tetrahedra. Calorimetric studies demonstrated these PDCs to be thermodynamically more stable than a mixture of SiO2, C, and silicon carbide. Here, we show by multinuclear NMR spectroscopy that substitution of C for O is also attained in PDCs with depolymerized silica-rich domains containing lithium, associated with SiOxC4-x tetrahedra with nonbridging oxygen. We suggest that significant (several percent) substitution of C for O could occur in more complex geological silicate melts/glasses in contact with graphite at moderate pressure and high temperature and may be thermodynamically far more accessible than C for Si substitution. Carbon incorporation will change the local structure and may affect physical properties, such as viscosity. Analogous carbon substitution at grain boundaries, at defect sites, or as equilibrium states in nominally acarbonaceous crystalline silicates, even if present at levels at 10–100 ppm, might form an extensive and hitherto hidden reservoir of carbon in the lower crust and mantle. PMID:24043830

  11. 21 CFR 182.2437 - Magnesium silicate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Magnesium silicate. 182.2437 Section 182.2437 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) SUBSTANCES GENERALLY RECOGNIZED AS SAFE Anticaking Agents § 182.2437 Magnesium silicate. (a) Product....

  12. Silicate minerals and the interferon system

    SciTech Connect

    Hahon, N.; Booth, J.A.

    1987-08-01

    Natural-occurring minerals representative of six silicate classes were examined for their influence on interferon induction by influenza virus in Rhesus monkey kidney (LLC-MK/sub 2/) cell monolayers. Minerals within the classes nesosilicate, sorosilicate, cyclosilicate, and inosilicate exhibited either little or marked (50% or greater) inhibition of interferon induction. Within the inosilicate class, however, minerals of the pyroxenoid group (wollastonite, pectolite, and rhodonite) all significantly showed a two- to threefold increase in interferon production. Silicate materials in the phyllosilicate and tectosilicate classes all showed inhibitory activity for the induction process. When silicate minerals were coated with the polymer poly(4-vinylpyridine-N-oxide), the inhibitory activity of silicates on viral interferon induction was counteracted. Of nine randomly selected silicate minerals, which inhibited viral interferon induction, none adversely affected the ability of exogenous interferon to confer antiviral cellular resistance. Increased levels of influenza virus multiplication concomitant with decreased levels of interferon occurred in cell monolayers pretreated with silicates. The findings of this study demonstrate the diverse effects of minerals representative of different silicate classes on the interferon system and indicate that certain silicates in comprising the viral interferon induction process may increase susceptibility to viral infection.

  13. 21 CFR 182.2227 - Calcium silicate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Calcium silicate. 182.2227 Section 182.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) SUBSTANCES GENERALLY RECOGNIZED AS SAFE Anticaking Agents § 182.2227 Calcium silicate. (a) Product. Calcium...

  14. Catalytic Fast Pyrolysis of Cellulose Using Nano Zeolite and Zeolite/Matrix Catalysts in a GC/Micro-Pyrolyzer.

    PubMed

    Lee, Kyong-Hwan

    2016-05-01

    Cellulose, as a model compound of biomass, was catalyzed over zeolite (HY,.HZSM-5) and zeolite/matrix (HY/Clay, HM/Clay) in a GC/micro-pyrolyzer at 500 degrees C, to produce the valuable products. The catalysts used were pure zeolite and zeolite/matrix including 20 wt% matrix content, which were prepared into different particle sizes (average size; 0.1 mm, 1.6 mm) to study the effect of the particle size of the catalyst for the distribution of product yields. Catalytic pyrolysis had much more volatile products as light components and less content of sugars than pyrolysis only. This phenomenon was strongly influenced by the particle size of the catalyst in catalytic fast pyrolysis. Also, in zeolite and zeolite/matrix catalysts the zeolite type gave the dominant impact on the distribution of product yields. PMID:27483802

  15. Catalytic Fast Pyrolysis of Cellulose Using Nano Zeolite and Zeolite/Matrix Catalysts in a GC/Micro-Pyrolyzer.

    PubMed

    Lee, Kyong-Hwan

    2016-05-01

    Cellulose, as a model compound of biomass, was catalyzed over zeolite (HY,.HZSM-5) and zeolite/matrix (HY/Clay, HM/Clay) in a GC/micro-pyrolyzer at 500 degrees C, to produce the valuable products. The catalysts used were pure zeolite and zeolite/matrix including 20 wt% matrix content, which were prepared into different particle sizes (average size; 0.1 mm, 1.6 mm) to study the effect of the particle size of the catalyst for the distribution of product yields. Catalytic pyrolysis had much more volatile products as light components and less content of sugars than pyrolysis only. This phenomenon was strongly influenced by the particle size of the catalyst in catalytic fast pyrolysis. Also, in zeolite and zeolite/matrix catalysts the zeolite type gave the dominant impact on the distribution of product yields.

  16. Epitaxial Growth of ZSM-5@Silicalite-1: A Core-Shell Zeolite Designed with Passivated Surface Acidity.

    PubMed

    Ghorbanpour, Arian; Gumidyala, Abhishek; Grabow, Lars C; Crossley, Steven P; Rimer, Jeffrey D

    2015-04-28

    The design of materials with spatially controlled chemical composition has potential advantages for wide-reaching applications that span energy to medicine. Here, we present a method for preparing a core-shell aluminosilicate zeolite with continuous translational symmetry of nanopores and an epitaxial shell of tunable thickness that passivates Brønsted acid sites associated with framework Al on exterior surfaces. For this study, we selected the commercially relevant MFI framework type and prepared core-shell particles consisting of an aluminosilicate core (ZSM-5) and a siliceous shell (silicalite-1). Transmission electron microscopy and gas adsorption studies confirmed that silicalite-1 forms an epitaxial layer on ZSM-5 crystals without blocking pore openings. Scanning electron microscopy and dynamic light scattering were used in combination to confirm that the shell thickness can be tailored with nanometer resolution (e.g., 5-20 nm). X-ray photoelectron spectroscopy and temperature-programmed desorption measurements revealed the presence of a siliceous shell, while probe reactions using molecules that were either too large or adequately sized to access MFI pores confirmed the uniform shell coverage. The synthesis of ZSM-5@silicalite-1 offers a pathway for tailoring the physicochemical properties of MFI-type materials, notably in the area of catalysis, where surface passivation can enhance product selectivity without sacrificing catalyst activity. The method described herein may prove to be a general platform for zeolite core-shell design with potentially broader applicability to other porous materials.

  17. Decomposition of NO over [Co]-ZSM-5 zeolite: Effect of co-adsorbed O{sub 2}

    SciTech Connect

    Chang, Y.; McCarty, J.G.

    1998-09-10

    The decomposition of NO over four Co-containing ZSM-5 zeolites and Pr, Ga-, and Cu-exchanged ZSM-5 zeolites was investigated using the isotope labeled {sup 15}N{sup 18}O and a temperature-programmed desorption (TPD) technique. The authors found that [Co]-ZSM-5 that contains Co in the framework had the highest activity for NO decomposition, almost an order of magnitude greater than that previously reported for a zeolite catalyst, namely Cu-ZSM-5 obtained under steady-state conditions. The phenomenally high activity of [Co]-ZSM-5 is due to the unique incorporation of Co{sup 2+} in the siliceous MFI structure. For all the catalysts investigated, co-adsorption of NO and O{sub 2} led to a substantial increase in the amount of NO{sub x} adsorbed. However, the adsorbed species were not necessarily NO{sub 2} as reported by others. The authors believe that the interaction between adsorbed NO{sub x} species and O{sub 2} is responsible for enhancing the rate of NO{sub x} decomposition. It is obvious that the framework Co{sup 2+} behaves very differently from Co{sup 2+} in the countercation position and from extra-framework CoO such as that supported on or dispersed on the surface of silicalite also having the same MFI structure.

  18. One-pot synthesis of MWW zeolite nanosheets using a rationally designed organic structure-directing agent

    PubMed Central

    Luo, Helen Y.; Michaelis, Vladimir K.; Hodges, Sydney; Griffin, Robert G.

    2015-01-01

    A new material MIT-1 comprised of delaminated MWW zeolite nanosheets is synthesized in one-pot using a rationally designed organic structure-directing agent (OSDA). The OSDA is comprised of a hydrophilic head segment that resembles the OSDA used to synthesize the zeolite precursor MCM22(P), a hydrophobic tail segment that resembles the swelling agent used to swell MCM22(P), and a di-quaternary ammonium linker that connects both segments. MIT-1 features high crystallinity and surface areas exceeding 500 m2g−1, and can be synthesized over a wide synthesis window that includes Si/Al ratios ranging from 13 to 67. Characterization data reveal high mesoporosity and acid strength with no detectable amorphous silica phases. Compared to MCM-22 and MCM-56, MIT-1 shows a three-fold increase in catalytic activity for the Friedel-Crafts alkylation of benzene with benzyl alcohol. PMID:26478803

  19. The 8-13 micron spectra of comets and the composition of silicate grains

    NASA Technical Reports Server (NTRS)

    Hanner, Martha S.; Lynch, David K.; Russell, Ray W.

    1994-01-01

    We have analyzed the existing spectra of seven comets which show an emission feature at 7.8-13 micrometers. Most have been converted to a common calibration, taking into account the SiO feature in late-type standard stars. The spectra are compared with spectra of the Trapezium, interplanetary dust particles (IDPs), laboratory mineral samples, and small particle emission models. The emission spectra show a variety of shapes; there is no unique 'cometary silicate'. A peak at 11.20-11.25 micrometers, indicative of small crystalline olivine particles, is seen in only three comets of this sample, P/Halley, Bradfield 1987 XXIX, and Levy 1990 XX. The widths of the emission features range from 2.6 to 4.1 micrometers (FWHM). To explain the differing widths and the broad 9.8 micrometers maximum, glassy silicate particles, including both pyroxene and olivine compositions, are the most plausible candidates. Calculations of emission models confirm that small grains of glassy silicate well mixed with carbonaceous material are plausible cometary constituents. No single class of chondritic aggregate IDPs exhibits spectra closely matching the comet spectra. A mixture of IDP spectra, particularly the glass-rich aggregates, approximately matches the spectra of comets P/Halley, Levy, and Bradfield 1987 XXIX. Yet, if comets are simply a mix of IDP types, it is puzzling that the classes of IDPs are so distinct. None of the comet spectra match the spectrum of the Trapezium. Thus, the mineralogy of the cometary silicates is not the same as that of the interstellar medium. The presence of a component of crystalline silicates in comets may be evidence of mixing between high- and low-temperature regions in the solar nebula.

  20. Liquid crystalline composites containing phyllosilicates

    DOEpatents

    Chaiko; David J.

    2007-05-08

    The present invention provides barrier films having reduced gas permeability for use in packaging and coating applications. The barrier films comprise an anisotropic liquid crystalline composite layer formed from phyllosilicate-polymer compositions. Phyllosilicate-polymer liquid crystalline compositions of the present invention can contain a high percentage of phyllosilicate while remaining transparent. Because of the ordering of the particles in the liquid crystalline composite, barrier films comprising liquid crystalline composites are particularly useful as barriers to gas transport.

  1. Biochemical evolution. I. Polymerization on internal, organophilic silica surfaces of dealuminated zeolites and feldspars

    PubMed Central

    Smith, Joseph V.

    1998-01-01

    Catalysis at mineral surfaces might generate replicating biopolymers from simple chemicals supplied by meteorites, volcanic gases, and photochemical gas reactions. Many ideas are implausible in detail because the proposed mineral surfaces strongly prefer water and other ionic species to organic ones. The molecular sieve silicalite (Union Carbide; = Al-free Mobil ZSM-5 zeolite) has a three-dimensional, 10-ring channel system whose electrically neutral Si-O surface strongly adsorbs organic species over water. Three -O-Si tetrahedral bonds lie in the surface, and the fourth Si-O points inwards. In contrast, the outward Si-OH of simple quartz and feldspar crystals generates their ionic organophobicity. The ZSM-5-type zeolite mutinaite occurs in Antarctica with boggsite and tschernichite (Al-analog of Mobil Beta). Archean mutinaite might have become de-aluminated toward silicalite during hot/cold/wet/dry cycles. Catalytic activity of silicalite increases linearly with Al-OH substitution for Si, and Al atoms tend to avoid each other. Adjacent organophilic and catalytic Al-OH regions in nanometer channels might have scavenged organic species for catalytic assembly into specific polymers protected from prompt photochemical destruction. Polymer migration along weathered silicic surfaces of micrometer-wide channels of feldspars might have led to assembly of replicating catalytic biomolecules and perhaps primitive cellular organisms. Silica-rich volcanic glasses should have been abundant on the early Earth, ready for crystallization into zeolites and feldspars, as in present continental basins. Abundant chert from weakly metamorphosed Archaean rocks might retain microscopic clues to the proposed mineral adsorbent/catalysts. Other framework silicas are possible, including ones with laevo/dextro one-dimensional channels. Organic molecules, transition-metal ions, and P occur inside modern feldspars. PMID:9520372

  2. IMPROVED CATALYSTS FOR HEAVY OIL UPGRADING BASED ON ZEOLITE Y NANOPARTICLES ENCAPSULATED IN STABLE NANOPOROUS HOST

    SciTech Connect

    Conrad Ingram; Mark Mitchell

    2005-11-15

    Composite materials of SBA-15/zeolite Y were synthesized from zeolite Y precursor and a synthesis mixture of mesoporous silicate SBA-15 via a hydrothermal process in the presence of a slightly acidic media of pH 4-6 with 2M H{sub 2}SO{sub 4}. The SBA-15/ZY composites showed Type IV adsorption isotherms, narrow BJH average pore size distribution of 4.9 nm, surface areas up to 800 m{sup 2}2/g and pore volumes 1.03 cm{sup 3}, all comparable to pure SBA-15 synthesized under similar conditions. Chemical analysis revealed Si/Al ratio down to 8.5 in the most aluminated sample, and {sup 27}AlSS MAS NMR confirmed aluminum was in tetrahedral coordination. This method of introduction of Al in pure T{sub d} coordination is effective in comparison to other direct and post synthesis alumination methods. Bronsted acid sites were evident from a pyridinium peak at 1544 cm-1 in the FTIR spectrum after pyridine adsorption, and from NH{sub 3} -TPD experiments. SBA-15/ZY composites showed significant catalytic activities for the dealkylation of isopropylbenzene to benzene and propene, similar to those of commercial zeolite Y. It was observed that higher conversion for catalysts synthesized with high amount of ZY precursor mixture added to the SBA-15. Over all the composites has shown good catalytic activity. Further studies will be focused on gaining a better understand the nature of the precursor, and to characterize and to locate the acid sites in the composite material. The composite will also be evaluated for heavy oil conversion to naphtha and middle distillates.

  3. Mesoporous Silicate Materials in Sensing

    PubMed Central

    Melde, Brian J.; Johnson, Brandy J.; Charles, Paul T.

    2008-01-01

    Mesoporous silicas, especially those exhibiting ordered pore systems and uniform pore diameters, have shown great potential for sensing applications in recent years. Morphological control grants them versatility in the method of deployment whether as bulk powders, monoliths, thin films, or embedded in coatings. High surface areas and pore sizes greater than 2 nm make them effective as adsorbent coatings for humidity sensors. The pore networks also provide the potential for immobilization of enzymes within the materials. Functionalization of materials by silane grafting or through co-condensation of silicate precursors can be used to provide mesoporous materials with a variety of fluorescent probes as well as surface properties that aid in selective detection of specific analytes. This review will illustrate how mesoporous silicas have been applied to sensing changes in relative humidity, changes in pH, metal cations, toxic industrial compounds, volatile organic compounds, small molecules and ions, nitroenergetic compounds, and biologically relevant molecules.

  4. Multicomponent liquid ion exchange with chabazite zeolites

    SciTech Connect

    Robinson, S.M.; Arnold, W.D. Jr.; Byers, C.W.

    1993-10-01

    In spite of the increasing commercial use of zeolites for binary and multicomponent sorption, the understanding of the basic mass-transfer processes associated with multicomponent zeolite ion-exchange systems is quite limited. This study was undertaken to evaluate Na-Ca-Mg-Cs-Sr ion exchange from an aqueous solution using a chabazite zeolite. Mass-transfer coefficients and equilibrium equations were determined from experimental batch-reactor data for single and multicomponent systems. The Langmuir isotherm was used to represent the equilibrium relationship for binary systems, and a modified Dubinin-Polyani model was used for the multicomponent systems. The experimental data indicate that diffusion through the microporous zeolite crystals is the primary diffusional resistance. Macropore diffusion also significantly contributes to the mass-transfer resistance. Various mass-transfer models were compared to the experimental data to determine mass-transfer coefficients. Effective diffusivities were obtained which accurately predicted experimental data using a variety of models. Only the model which accounts for micropore and macropore diffusion occurring in series accurately predicted multicomponent data using single-component diffusivities. Liquid and surface diffusion both contribute to macropore diffusion. Surface and micropore diffusivities were determined to be concentration dependent.

  5. MERCURY SEPARATION FROM POLLUTANT WATER USING ZEOLITES

    EPA Science Inventory

    Arsenic is known to be a hazardous contaminant in drinking water that causes arsenical dermatitis and skin cancer. In the present work, the potential use of a variety of synthetic zeolites for removal of arsenic from water has been examined at room temperature. Experiments have...

  6. Dispersion enhanced metal/zeolite catalysts

    DOEpatents

    Sachtler, Wolfgang M. H.; Tzou, Ming-Shin; Jiang, Hui-Jong

    1987-01-01

    Dispersion stabilized zeolite supported metal catalysts are provided as bimetallic catalyst combinations. The catalyst metal is in a reduced zero valent form while the dispersion stabilizer metal is in an unreduced ionic form. Representative catalysts are prepared from platinum or nickel as the catalyst metal and iron or chromium dispersion stabilizer.

  7. Dispersion enhanced metal/zeolite catalysts

    DOEpatents

    Sachtler, W.M.H.; Tzou, M.S.; Jiang, H.J.

    1987-03-31

    Dispersion stabilized zeolite supported metal catalysts are provided as bimetallic catalyst combinations. The catalyst metal is in a reduced zero valent form while the dispersion stabilizer metal is in an unreduced ionic form. Representative catalysts are prepared from platinum or nickel as the catalyst metal and iron or chromium dispersion stabilizer.

  8. Zeolite 5A Catalyzed Etherification of Diphenylmethanol

    ERIC Educational Resources Information Center

    Cooke, Jason; Henderson, Eric J.; Lightbody, Owen C.

    2009-01-01

    An experiment for the synthetic undergraduate laboratory is described in which zeolite 5A catalyzes the room temperature dehydration of diphenylmethanol, (C[subscript 6]H[subscript 5])[subscript 2]CHOH, producing 1,1,1',1'-tetraphenyldimethyl ether, (C[subscript 6]H[subscript 5])[subscript 2]CHOCH(C[subscript 6]H[subscript 5])[subscript 2]. The…

  9. Chemical interactions in multimetal/zeolite catalysts

    SciTech Connect

    Sachtler, W.M.H.

    1992-02-07

    Mechanistic explanations have been found for the migration of atoms and ions through the zeolite channels leading to specific distribution of ions and the metal clusters. In this report, we summarize the state of understanding attained on a number of topics in the area of mono- and multimetal/zeolite systems, to which our recent research has made significant contributions. The following topics are discussed: (1) Formation of isolated metal atoms in sodalite cages; (2) differences of metal/zeolite systems prepared by ion reduction in channels or via isolated atoms; (3) rejuvenation of Pd/NaY and Pd/HY catalysts by oxidative redispersion of the metal; (4) formation of mono- or bimetal particles in zeolites by programmed reductive decomposition of volatile metal complexes; (5) cation-cation interaction as a cause of enhanced reducibility; (6) formation of palladium carbonyl clusters in supercages; (7) enhanced catalytic activity of metal particle-proton complexes for hydrocarbon conversion reactions; (8) stereoselectivity of catalytic reactions due to geometric constraints of particles in cages.

  10. Crystalline titanate catalyst supports

    DOEpatents

    Anthony, Rayford G.; Dosch, Robert G.

    1993-01-01

    A series of new crystalline titanates (CT) are shown to have considerable potential as catalyst supports. For Pd supported catalyst, the catalytic activity for pyrene hydrogenation was substantially different depending on the type of CT, and one was substantially more active than Pd on hydrous titanium oxide (HTO). For 1-hexene hydrogenation the activities of the new CTs were approximately the same as for the hydrous metal oxide supports.

  11. Crystalline titanate catalyst supports

    DOEpatents

    Anthony, R.G.; Dosch, R.G.

    1993-01-05

    A series of new crystalline titanates (CT) are shown to have considerable potential as catalyst supports. For Pd supported catalyst, the catalytic activity for pyrene hydrogenation was substantially different depending on the type of CT, and one was substantially more active than Pd on hydrous titanium oxide (HTO). For 1-hexene hydrogenation the activities of the new CTs were approximately the same as for the hydrous metal oxide supports.

  12. Zeolite based microconcentrators for volatile organic compounds sensing at trace-level: fabrication and performance

    NASA Astrophysics Data System (ADS)

    Almazán, Fernando; Pellejero, Ismael; Morales, Alberto; Urbiztondo, Miguel A.; Sesé, Javier; Pina, M. Pilar; Santamaría, Jesús

    2016-08-01

    A novel 6-step microfabrication process is proposed in this work to prepare microfluidic devices with integrated zeolite layers. In particular, microfabricated preconcentrators designed for volatile organic compounds (VOC) sensing applications are fully described. The main novelty of this work is the integration of the pure siliceous MFI type zeolite (silicalite-1) polycrystalline layer, i.e. 4.0  ±  0.5 μm thick, as active phase, within the microfabrication process just before the anodic bonding step. Following this new procedure, Si microdevices with an excellent distribution of the adsorbent material, integrated resistive heaters and Pyrex caps have been obtained. Firstly, the microconcentrator performance has been assessed by means of the normal hexane breakthrough curves as a function of sampling and desorption flowrates, temperature and micropreconcentrator design. In a step further, the best preconcentrator device has been tested in combination with downstream Si based microcantilevers deployed as VOC detectors. Thus, a preliminar evaluation of the improvement on detection sensitivity by silicalite-1 based microconcentrators is presented.

  13. Intrinsic flexibility of porous materials; theory, modelling and the flexibility window of the EMT zeolite framework

    PubMed Central

    Fletcher, Rachel E.; Wells, Stephen A.; Leung, Ka Ming; Edwards, Peter P.; Sartbaeva, Asel

    2015-01-01

    Framework materials have structures containing strongly bonded polyhedral groups of atoms connected through their vertices. Typically the energy cost for variations of the inter-polyhedral geometry is much less than the cost of distortions of the polyhedra themselves – as in the case of silicates, where the geometry of the SiO4 tetrahedral group is much more strongly constrained than the Si—O—Si bridging angle. As a result, framework materials frequently display intrinsic flexibility, and their dynamic and static properties are strongly influenced by low-energy collective motions of the polyhedra. Insight into these motions can be obtained in reciprocal space through the ‘rigid unit mode’ (RUM) model, and in real-space through template-based geometric simulations. We briefly review the framework flexibility phenomena in energy-relevant materials, including ionic conductors, perovskites and zeolites. In particular we examine the ‘flexibility window’ phenomenon in zeolites and present novel results on the flexibility window of the EMT framework, which shed light on the role of structure-directing agents. Our key finding is that the crown ether, despite its steric bulk, does not limit the geometric flexibility of the framework. PMID:26634720

  14. Intrinsic flexibility of porous materials; theory, modelling and the flexibility window of the EMT zeolite framework.

    PubMed

    Fletcher, Rachel E; Wells, Stephen A; Leung, Ka Ming; Edwards, Peter P; Sartbaeva, Asel

    2015-12-01

    Framework materials have structures containing strongly bonded polyhedral groups of atoms connected through their vertices. Typically the energy cost for variations of the inter-polyhedral geometry is much less than the cost of distortions of the polyhedra themselves - as in the case of silicates, where the geometry of the SiO4 tetrahedral group is much more strongly constrained than the Si-O-Si bridging angle. As a result, framework materials frequently display intrinsic flexibility, and their dynamic and static properties are strongly influenced by low-energy collective motions of the polyhedra. Insight into these motions can be obtained in reciprocal space through the `rigid unit mode' (RUM) model, and in real-space through template-based geometric simulations. We briefly review the framework flexibility phenomena in energy-relevant materials, including ionic conductors, perovskites and zeolites. In particular we examine the `flexibility window' phenomenon in zeolites and present novel results on the flexibility window of the EMT framework, which shed light on the role of structure-directing agents. Our key finding is that the crown ether, despite its steric bulk, does not limit the geometric flexibility of the framework.

  15. Elastic properties of silicate melts at high pressure and implications for low velocity anomalies in the crust and mantle

    NASA Astrophysics Data System (ADS)

    Clark, A. N.; Lesher, C. E.

    2015-12-01

    Regions of low seismic velocities in the mantle and crust are commonly attributed to the presence of silicate melt or aqueous fluid. The elastic properties of silicate melts are typically modeled at high pressure using equations of state developed for crystalline materials. However, amorphous silicates spanning a wide range of composition and structure, i.e. SiO2 to MgSiO3, and including naturally occurring basalt compositions, exhibit a weak dependence of P-wave velocity on density in clear violation of Birch's law, which governs the behavior of crystalline materials. This anomalous behavior is attributed to the high degree of flexibility of the silicate network on loading that may be a general property of naturally occurring silicate melts at crustal and upper mantle conditions. If this is the case, P-wave velocities for silicate melts will be significantly less pressure dependent than previously assumed, which in turn will enhance the effects of melt fraction on lowering aggregate mantle seismic velocities. Here we present VP calculated for partially molten mantle up to 20 GPa showing that melt fractions purported to explain VP reductions associated with the lithosphere-asthenosphere boundary may be overestimated by 15%, while those reported for the transition zone may be overestimated to an even greater extent. Moreover, we predict that d lnVS/d lnVP (RSP) should vary little across low velocities regions within the upper mantle due solely to the presence of melt, but will be strongly influenced by how melt is distributed, consistent the work of [1]. Finally, RSP is found to be relatively insensitive to type of fluid present, contrary to conventional wisdom, and thus caution is warranted in attributing changes in RSP to either silicate melt or aqueous fluids. The implications of these findings for interpreting low velocity anomalies beneath hotspots and arcs (e.g. Iceland and Japan) will be discussed. [1] Takei, Y. (2002) JGR vol. 107

  16. Ni(2+)-zeolite/ferrosphere and Ni(2+)-silica/ferrosphere beads for magnetic affinity separation of histidine-tagged proteins.

    PubMed

    Vereshchagina, T A; Fedorchak, M A; Sharonova, O M; Fomenko, E V; Shishkina, N N; Zhizhaev, A M; Kudryavtsev, A N; Frank, L A; Anshits, A G

    2016-01-28

    Magnetic Ni(2+)-zeolite/ferrosphere and Ni(2+)-silica/ferrosphere beads (Ni-ferrosphere beads - NFB) of a core-shell structure were synthesized starting from coal fly ash ferrospheres having diameters in the range of 0.063-0.050 mm. The strategy of NFB fabrication is an oriented chemical modification of the outer surface preserving the magnetic core of parent beads with the formation of micro-mesoporous coverings. Two routes of ferrosphere modification were realized, such as (i) hydrothermal treatment in an alkaline medium resulting in a NaP zeolite layer and (ii) synthesis of micro-mesoporous silica on the glass surface using conventional methods. Immobilization of Ni(2+) ions in the siliceous porous shell of the magnetic beads was carried out via (i) the ion exchange of Na(+) for Ni(2+) in the zeolite layer or (ii) deposition of NiO clusters in the zeolite and silica pores. The final NFB were tested for affinity in magnetic separation of the histidine-tagged green fluorescent protein (GFP) directly from a cell lysate. Results pointed to the high affinity of the magnetic beads towards the protein in the presence of 10 mM EDTA. The sorption capacity of the ferrosphere-based Ni-beads with respect to GFP was in the range 1.5-5.7 mg cm(-3). PMID:26688000

  17. Activity of double wash-coat monolith catalyst with noble metals and zeolites in selective catalytic reduction of NO(x) with C3H6.

    PubMed

    Lee, Jung-Dae; Kim, Ki-Joong; Kim, Yong-Hwa; Jeon, Gyung-Soo; Choi, Young-Key; Ahn, Ho-Geun

    2008-10-01

    The selective catalytic reduction (SCR) of NO(x) with C3H6 was studied in the presence of oxygen. The double wash-coat monolith catalysts for SCR comprised a lower layer of Au (or Pt)/Al2O3 and a upper layer of zeolites. The catalytic performance of the double wash-coated catalyst was remarkably improved to broaden the temperature window. The Au and Pt particles were dispersed uniformly on the monolith with particle sizes range of 3 approximately 5 nm and 5 approximately 10 nm, respectively. The catalyst binders used were colloidal silica, potassium silicate and tetraethyl orthosilicate, and the best catalyst activity was achieved with using colloidal silica as a binder. The zeolites used for the catalyst upper layer were MCM-41, FER, Y5.3-Zeolite and ZSM5, among which the NH4-ZSM5-coated catalyst showed the highest activity. The experimental results confirmed the promising potential of the double wash-coat, monolith catalyst for SCR of NO(x) with C3H6 due to the effective combination of noble metal monolith catalyst with zeolite for the removal of NO(x) by SCR with hydrocarbons.

  18. Ni(2+)-zeolite/ferrosphere and Ni(2+)-silica/ferrosphere beads for magnetic affinity separation of histidine-tagged proteins.

    PubMed

    Vereshchagina, T A; Fedorchak, M A; Sharonova, O M; Fomenko, E V; Shishkina, N N; Zhizhaev, A M; Kudryavtsev, A N; Frank, L A; Anshits, A G

    2016-01-28

    Magnetic Ni(2+)-zeolite/ferrosphere and Ni(2+)-silica/ferrosphere beads (Ni-ferrosphere beads - NFB) of a core-shell structure were synthesized starting from coal fly ash ferrospheres having diameters in the range of 0.063-0.050 mm. The strategy of NFB fabrication is an oriented chemical modification of the outer surface preserving the magnetic core of parent beads with the formation of micro-mesoporous coverings. Two routes of ferrosphere modification were realized, such as (i) hydrothermal treatment in an alkaline medium resulting in a NaP zeolite layer and (ii) synthesis of micro-mesoporous silica on the glass surface using conventional methods. Immobilization of Ni(2+) ions in the siliceous porous shell of the magnetic beads was carried out via (i) the ion exchange of Na(+) for Ni(2+) in the zeolite layer or (ii) deposition of NiO clusters in the zeolite and silica pores. The final NFB were tested for affinity in magnetic separation of the histidine-tagged green fluorescent protein (GFP) directly from a cell lysate. Results pointed to the high affinity of the magnetic beads towards the protein in the presence of 10 mM EDTA. The sorption capacity of the ferrosphere-based Ni-beads with respect to GFP was in the range 1.5-5.7 mg cm(-3).

  19. Conversion of Ethanol to Hydrocarbons on Hierarchical HZSM-5 Zeolites

    SciTech Connect

    Ramasamy, Karthikeyan K.; Zhang, He; Sun, Junming; Wang, Yong

    2014-02-22

    This study reports synthesis, characterization, and catalytic activity of the nano-size hierarchical HZSM-5 zeolite with high mesoporosity produced via a solvent evaporation procedure. Further, this study compares hierarchical zeolites with conventional HZSM-5 zeolite with similar Si/Al ratios for the ethanol-to-hydrocarbon conversion process. The catalytic performance of the hierarchical and conventional zeolites was evaluated using a fixed-bed reactor at 360 °C, 300 psig, and a weight hourly space velocity of 7.9 h-1. For the low Si/Al ratio zeolite (~40), the catalytic life-time for the hierarchical HZSM-5 was approximately 2 times greater than the conventional HZSM-5 despite its coking amount deposited 1.6 times higher than conventional HZSM-5. For the high Si/Al ratio zeolite (~140), the catalytic life-time for the hierarchical zeolite was approximately 5 times greater than the conventional zeolite and the amount of coking deposited was 2.1 times higher. Correlation was observed between catalyst life time, porosity, and the crystal size of the zeolite. The nano-size hierarchical HZSM-5 zeolites containing mesoporosity demonstrated improved catalyst life-time compared to the conventional catalyst due to faster removal of products, shorter diffusion path length, and the migration of the coke deposits to the external surface from the pore structure.

  20. Energetics of sodium-calcium exchanged zeolite A.

    PubMed

    Sun, H; Wu, D; Guo, X; Shen, B; Navrotsky, A

    2015-05-01

    A series of calcium-exchanged zeolite A samples with different degrees of exchange were prepared. They were characterized by powder X-ray diffraction (XRD) and differential scanning calorimetry (DSC). High temperature oxide melt drop solution calorimetry measured the formation enthalpies of hydrated zeolites CaNa-A from constituent oxides. The water content is a linear function of the degree of exchange, ranging from 20.54% for Na-A to 23.77% for 97.9% CaNa-A. The enthalpies of formation (from oxides) at 25 °C are -74.50 ± 1.21 kJ mol(-1) TO2 for hydrated zeolite Na-A and -30.79 ± 1.64 kJ mol(-1) TO2 for hydrated zeolite 97.9% CaNa-A. Dehydration enthalpies obtained from differential scanning calorimetry are 32.0 kJ mol(-1) H2O for hydrated zeolite Na-A and 20.5 kJ mol(-1) H2O for hydrated zeolite 97.9% CaNa-A. Enthalpies of formation of Ca-exchanged zeolites A are less exothermic than for zeolite Na-A. A linear relationship between the formation enthalpy and the extent of calcium substitution was observed. The energetic effect of Ca-exchange on zeolite A is discussed with an emphasis on the complex interactions between the zeolite framework, cations, and water.

  1. Zeolite Nanoparticles for Selective Sorption of Plasma Proteins

    PubMed Central

    Rahimi, M.; Ng, E.-P.; Bakhtiari, K.; Vinciguerra, M.; Ahmad, H. Ali; Awala, H.; Mintova, S.; Daghighi, M.; Bakhshandeh Rostami, F.; de Vries, M.; Motazacker, M. M.; Peppelenbosch, M. P.; Mahmoudi, M.; Rezaee, F.

    2015-01-01

    The affinity of zeolite nanoparticles (diameter of 8–12 nm) possessing high surface area and high pore volume towards human plasma proteins has been investigated. The protein composition (corona) of zeolite nanoparticles has been shown to be more dependent on the plasma protein concentrations and the type of zeolites than zeolite nanoparticles concentration. The number of proteins present in the corona of zeolite nanoparticles at 100% plasma (in vivo state) is less than with 10% plasma exposure. This could be due to a competition between the proteins to occupy the corona of the zeolite nanoparticles. Moreover, a high selective adsorption for apolipoprotein C-III (APOC-III) and fibrinogen on the zeolite nanoparticles at high plasma concentration (100%) was observed. While the zeolite nanoparticles exposed to low plasma concentration (10%) exhibited a high selective adsorption for immunoglobulin gamma (i.e. IGHG1, IGHG2 and IGHG4) proteins. The zeolite nanoparticles can potentially be used for selectively capture of APOC-III in order to reduce the activation of lipoprotein lipase inhibition during hypertriglyceridemia treatment. The zeolite nanoparticles can be adapted to hemophilic patients (hemophilia A (F-VIII deficient) and hemophilia B (F-IX deficient)) with a risk of bleeding, and thus might be potentially used in combination with the existing therapy. PMID:26616161

  2. Zeolite Nanoparticles for Selective Sorption of Plasma Proteins.

    PubMed

    Rahimi, M; Ng, E-P; Bakhtiari, K; Vinciguerra, M; Ali Ahmad, H; Awala, H; Mintova, S; Daghighi, M; Bakhshandeh Rostami, F; de Vries, M; Motazacker, M M; Peppelenbosch, M P; Mahmoudi, M; Rezaee, F

    2015-01-01

    The affinity of zeolite nanoparticles (diameter of 8-12 nm) possessing high surface area and high pore volume towards human plasma proteins has been investigated. The protein composition (corona) of zeolite nanoparticles has been shown to be more dependent on the plasma protein concentrations and the type of zeolites than zeolite nanoparticles concentration. The number of proteins present in the corona of zeolite nanoparticles at 100% plasma (in vivo state) is less than with 10% plasma exposure. This could be due to a competition between the proteins to occupy the corona of the zeolite nanoparticles. Moreover, a high selective adsorption for apolipoprotein C-III (APOC-III) and fibrinogen on the zeolite nanoparticles at high plasma concentration (100%) was observed. While the zeolite nanoparticles exposed to low plasma concentration (10%) exhibited a high selective adsorption for immunoglobulin gamma (i.e. IGHG1, IGHG2 and IGHG4) proteins. The zeolite nanoparticles can potentially be used for selectively capture of APOC-III in order to reduce the activation of lipoprotein lipase inhibition during hypertriglyceridemia treatment. The zeolite nanoparticles can be adapted to hemophilic patients (hemophilia A (F-VIII deficient) and hemophilia B (F-IX deficient)) with a risk of bleeding, and thus might be potentially used in combination with the existing therapy. PMID:26616161

  3. Zeolite Nanoparticles for Selective Sorption of Plasma Proteins

    NASA Astrophysics Data System (ADS)

    Rahimi, M.; Ng, E.-P.; Bakhtiari, K.; Vinciguerra, M.; Ahmad, H. Ali; Awala, H.; Mintova, S.; Daghighi, M.; Bakhshandeh Rostami, F.; de Vries, M.; Motazacker, M. M.; Peppelenbosch, M. P.; Mahmoudi, M.; Rezaee, F.

    2015-11-01

    The affinity of zeolite nanoparticles (diameter of 8-12 nm) possessing high surface area and high pore volume towards human plasma proteins has been investigated. The protein composition (corona) of zeolite nanoparticles has been shown to be more dependent on the plasma protein concentrations and the type of zeolites than zeolite nanoparticles concentration. The number of proteins present in the corona of zeolite nanoparticles at 100% plasma (in vivo state) is less than with 10% plasma exposure. This could be due to a competition between the proteins to occupy the corona of the zeolite nanoparticles. Moreover, a high selective adsorption for apolipoprotein C-III (APOC-III) and fibrinogen on the zeolite nanoparticles at high plasma concentration (100%) was observed. While the zeolite nanoparticles exposed to low plasma concentration (10%) exhibited a high selective adsorption for immunoglobulin gamma (i.e. IGHG1, IGHG2 and IGHG4) proteins. The zeolite nanoparticles can potentially be used for selectively capture of APOC-III in order to reduce the activation of lipoprotein lipase inhibition during hypertriglyceridemia treatment. The zeolite nanoparticles can be adapted to hemophilic patients (hemophilia A (F-VIII deficient) and hemophilia B (F-IX deficient)) with a risk of bleeding, and thus might be potentially used in combination with the existing therapy.

  4. UTILITY OF ZEOLITES IN REMOVAL OF INORGANIC AND ORGANIC WATER POLLUTANTS

    EPA Science Inventory

    Zeolites are well known for their ion exchange, adsorption and acid catalysis properties. Different inorganic and organic pollutants have been removed from water at room temperature using various zeolites. Synthetic zeolite Faujasite Y has been used to remove inorganic pollutants...

  5. Study on the order degree and geochemical characteristics of major elements of siliceous rock in eastern Qinling area, China.

    PubMed

    Ming, Lü; Li, Hong-Zhong; Zhao, Ming-zhen; Ma, Ming-wu; Yang, Zhi-Jun; Liang, Jin

    2014-11-01

    Siliceous rocks were extensively distributed in the marine volcanic sedimentary formation of Erlangping Group in the Early Paleozoic in eastern Qinling area. These siliceous rocks formed in the same age, but had differences in the degree of crystallization and order because of the late diagenetic evolution. In the present study, the major elements and order degree of the siliceous rocks were studied, which were from the Erlangping Group in Xixia area, Songxian area and Nanzhao area of eartern Qinling orogenic belt. As shown in the results, the siliceous rocks contained SiO2 with percentage between 84.75% and 94.12% and average of 89.09%. The SiO2/(K2O+Na2O) values were from 26.69 to 114.78 with 65.67 as its average, and the values of SiO2/Al2O3 were from 10.48 to 61.52 with average of 30.58. These above characteristics excellently agreed with the geochemical characteristics of hydrothermal siliceous rocks, which deposited in the continental margin environment. In the Raman analytical results, the quartz contributed to the characteristic Raman shifts at 394, 464, 465 and 467 cm(-1). In the results of Gaussian fitting the degrees of order increased with the order of siliceous rocks of Songxian area, Nanzhao area and Xixia area, which were witnessed by the descending in FWHM values of quartz in the siliceous rocks of Songxian area, Nanzhao area and Xixia area orderly. Disagreeing with the FWHM values of Gaussian fitting, the silica contents of the siliceous rocks had a rising trend of Songxian (87.36%), Nanzhao (89.57%), Xixia area (90.35%), which meant a descending in impurity elements with the order of Songxian area, Nanzhao area and Xixia areas. According to this, there was high agreement between lower crystallinity degree and higher purity of silica, and this denoted that the rising in order degree of silica would result in lower impurity in siliceous rocks. Although the crystallinity degrees could change with the influences of temperature, pressure and its

  6. Study on the order degree and geochemical characteristics of major elements of siliceous rock in eastern Qinling area, China.

    PubMed

    Ming, Lü; Li, Hong-Zhong; Zhao, Ming-zhen; Ma, Ming-wu; Yang, Zhi-Jun; Liang, Jin

    2014-11-01

    Siliceous rocks were extensively distributed in the marine volcanic sedimentary formation of Erlangping Group in the Early Paleozoic in eastern Qinling area. These siliceous rocks formed in the same age, but had differences in the degree of crystallization and order because of the late diagenetic evolution. In the present study, the major elements and order degree of the siliceous rocks were studied, which were from the Erlangping Group in Xixia area, Songxian area and Nanzhao area of eartern Qinling orogenic belt. As shown in the results, the siliceous rocks contained SiO2 with percentage between 84.75% and 94.12% and average of 89.09%. The SiO2/(K2O+Na2O) values were from 26.69 to 114.78 with 65.67 as its average, and the values of SiO2/Al2O3 were from 10.48 to 61.52 with average of 30.58. These above characteristics excellently agreed with the geochemical characteristics of hydrothermal siliceous rocks, which deposited in the continental margin environment. In the Raman analytical results, the quartz contributed to the characteristic Raman shifts at 394, 464, 465 and 467 cm(-1). In the results of Gaussian fitting the degrees of order increased with the order of siliceous rocks of Songxian area, Nanzhao area and Xixia area, which were witnessed by the descending in FWHM values of quartz in the siliceous rocks of Songxian area, Nanzhao area and Xixia area orderly. Disagreeing with the FWHM values of Gaussian fitting, the silica contents of the siliceous rocks had a rising trend of Songxian (87.36%), Nanzhao (89.57%), Xixia area (90.35%), which meant a descending in impurity elements with the order of Songxian area, Nanzhao area and Xixia areas. According to this, there was high agreement between lower crystallinity degree and higher purity of silica, and this denoted that the rising in order degree of silica would result in lower impurity in siliceous rocks. Although the crystallinity degrees could change with the influences of temperature, pressure and its

  7. CO2 SEPARATIONS USING ZEOLITE MEMBRANES

    SciTech Connect

    Richard D. Noble; John L. Falconer

    2001-06-30

    Zeolite and other inorganic molecular sieve membranes have shown potential for separations based on molecular size and shape because of their small pore sized, typically less than 1 nm, and their narrow pore size distribution. The high thermal and chemical stability of these inorganic crystals make them ideal materials for use in high temperature applications such as catalytic membrane reactors. Most of the progress with zeolite membranes has been with MFI zeolites prepared on porous disks and tubes. The MFI zeolite is a medium pore size structure having nearly circular pores with diameters between .53 and .56 nm. Separation experiments through MFI membranes indicate that competitive adsorption separates light gas mixtures. Light gas selectivities are typically small, however, owing to small differences in adsorption strengths and their small sizes relative to the MFI pore opening. Furthermore, competitive adsorption does not work well at high temperature where zeolite membranes are stable and have potential application. Separation by differences in size has a greater potential to work at high temperature than competitive adsorption, but pores smaller than those in MFI zeolites are required. Therefore, some studies focused on the synthesis of a small, 8-membered-pore structures such as zeolite A (0.41-nm pore diameter) and SAPO-34, a chabazite (about .4-nm pore diameter with about 1.4 nm cages) analog. The small pore size of the zeolite A and SAPO-34 structures made the separation of smaller molecules by differences in size possible. Zeolite MFI and SAPO-34 membranes were prepared on the inside surface of porous alumina tubes by hydrothermal synthesis, and single gas and binary mixture permeances were measured to characterize the membrane's performance. A mathematical diffusion model was developed to determine the relative quantities of zeolite and non-zeolite pores in different membranes by modeling the permeation date of CO{sub 2}. This model expresses the total

  8. Silicate Composition of the Interstellar Medium

    NASA Astrophysics Data System (ADS)

    Fogerty, S.; Forrest, W.; Watson, D. M.; Sargent, B. A.; Koch, I.

    2016-10-01

    The composition of silicate dust in the diffuse interstellar medium and in protoplanetary disks around young stars informs our understanding of the processing and evolution of the dust grains leading up to planet formation. An analysis of the well-known 9.7 μm feature indicates that small amorphous silicate grains represent a significant fraction of interstellar dust and are also major components of protoplanetary disks. However, this feature is typically modeled assuming amorphous silicate dust of olivine and pyroxene stoichiometries. Here, we analyze interstellar dust with models of silicate dust that include non-stoichiometric amorphous silicate grains. Modeling the optical depth along lines of sight toward the extinguished objects Cyg OB2 No. 12 and ζ Ophiuchi, we find evidence for interstellar amorphous silicate dust with stoichiometry intermediate between olivine and pyroxene, which we simply refer to as “polivene.” Finally, we compare these results to models of silicate emission from the Trapezium and protoplanetary disks in Taurus.

  9. Polyamide 6/Layered Silicate Nanocomposites

    NASA Astrophysics Data System (ADS)

    Dębowska, M.; Rudzińska-Girulska, J.; Pigłowski, J.; Dołęga, J.

    2008-05-01

    Polyamide 6 (PA6) and its two exfoliated nanocomposites (PA6/Nf919 and PA6/BZ-COCO), with bentonite (2.5 wt.%) organophilically treated with different cations, were studied. Improved mechanical properties, changes in crystallinity and morphology as well as higher glass transition temperature values were observed for the nanocomposites in comparison to the neat PA6. For the nanocomposite PA6/BZ-COCO, of better surface modification of platelets and better interaction between the polymeric matrix and the organobentonite, higher values of Young's modulus and yielding point together with higher contribution of larger free volume holes to free volume distributions occurred.

  10. Identifying the Crystal Graveyards Remaining After Large Silicic Eruptions

    NASA Astrophysics Data System (ADS)

    Gelman, S. E.; Deering, C. D.; Bachmann, O.; Huber, C.; Gutiérrez, F. J.

    2014-12-01

    The accumulation of voluminous crystal-poor rhyolites from an upper crustal mush environment inherently necessitates the complementary formation of unerupted silicic cumulates. However, identification of such frozen cumulates remains controversial. This has motivated us to develop of a new geochemical model aimed at better constraining the behavior of trace elements in a magma reservoir concurrently tracking crystallization and imperfect segregation of melt. We use a numerical method to solve our model equations rather than seek analytical solutions, thereby relieving overly simplistic assumptions for the dependencies between partition coefficient or melt segregation rate as functions of crystallinity. Our model allows partition coefficient to vary depending on the crystallinizing mineralogy at any particular stage in magma cooling, as well as the ability to test different rates and efficiencies of crystal-melt segregation. We apply our model first to the Searchlight Pluton as a well-constrained case study, which allows us to quantitatively test existing interpretations of that pluton. Building on this, we broaden our model to better understand the relationship between volcanic and plutonic rocks utilizing the NAVDAT database. Our results produce unambiguous fractionation signatures for segregated melts, while those signatures are muted for their cumulate counterparts. These models suggest that some large granitiods may represent accumulations of crystals, having lost melt in some cases to volcanic eruptions or to higher level evolved plutonic units, although the trace element signature of this process is expected to be subtle.

  11. 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.

  12. Preparation of Robust, Thin Zeolite Membrane Sheet for Molecular Separation

    SciTech Connect

    Liu, Wei; Zhang, Jian; Canfield, Nathan L.; Saraf, Laxmikant V.

    2011-10-19

    This paper reports a feasibility study on the preparation of zeolite membrane films on a thin, porous metal support sheet (50-{micro}m thick). Zeolite sodium A (NaA) and silicalite zeolite frameworks are chosen to represent synthesis of respective hydrophilic-type and hydrophobic-type zeolite membranes on this new support. It is found that a dense, continuous inter-grown zeolite crystal layer at a thickness less than 2 {micro}m can be directly deposited on such a support by using direct and secondary growth techniques. The resulting membrane shows excellent adhesion on the metal sheet. Molecular-sieving functions of the prepared membranes are characterized with ethanol/water separation, CO2 separation, and air dehumidification. The results show great potential to make flexible metal-foil-like zeolite membranes for a range of energy conversion and environmental applications.

  13. Atomic sites and stability of Cs+ captured within zeolitic nanocavities.

    PubMed

    Yoshida, Kaname; Toyoura, Kazuaki; Matsunaga, Katsuyuki; Nakahira, Atsushi; Kurata, Hiroki; Ikuhara, Yumi H; Sasaki, Yukichi

    2013-01-01

    Zeolites have potential application as ion-exchangers, catalysts and molecular sieves. Zeolites are once again drawing attention in Japan as stable adsorbents and solidification materials of fission products, such as (137)Cs(+) from damaged nuclear-power plants. Although there is a long history of scientific studies on the crystal structures and ion-exchange properties of zeolites for practical application, there are still open questions, at the atomic-level, on the physical and chemical origins of selective ion-exchange abilities of different cations and detailed atomic structures of exchanged cations inside the nanoscale cavities of zeolites. Here, the precise locations of Cs(+) ions captured within A-type zeolite were analyzed using high-resolution electron microscopy. Together with theoretical calculations, the stable positions of absorbed Cs(+) ions in the nanocavities are identified, and the bonding environment within the zeolitic framework is revealed to be a key factor that influences the locations of absorbed cations.

  14. Atomic sites and stability of Cs+ captured within zeolitic nanocavities

    NASA Astrophysics Data System (ADS)

    Yoshida, Kaname; Toyoura, Kazuaki; Matsunaga, Katsuyuki; Nakahira, Atsushi; Kurata, Hiroki; Ikuhara, Yumi H.; Sasaki, Yukichi

    2013-08-01

    Zeolites have potential application as ion-exchangers, catalysts and molecular sieves. Zeolites are once again drawing attention in Japan as stable adsorbents and solidification materials of fission products, such as 137Cs+ from damaged nuclear-power plants. Although there is a long history of scientific studies on the crystal structures and ion-exchange properties of zeolites for practical application, there are still open questions, at the atomic-level, on the physical and chemical origins of selective ion-exchange abilities of different cations and detailed atomic structures of exchanged cations inside the nanoscale cavities of zeolites. Here, the precise locations of Cs+ ions captured within A-type zeolite were analyzed using high-resolution electron microscopy. Together with theoretical calculations, the stable positions of absorbed Cs+ ions in the nanocavities are identified, and the bonding environment within the zeolitic framework is revealed to be a key factor that influences the locations of absorbed cations.

  15. Zeolite catalysis in conversion of cellulosics. Annual report

    SciTech Connect

    Tsao, G.T.

    1994-02-01

    The authors have studied the kinetics of oxylose/xylulose isomerization in significant detail over a variety of zeolites and obtained the pseudo-first order reaction rate constants. The authors have found that HY zeolite is still the best material and zeolites are more selective than homogeneous acid catalysts where decomposition of the sugar compounds is much faster. They have completed, as described in the Year 2 Work Plan, the study of cellobiose hydrolysis with an ion exchange resin. The kinetics of the solid-catalyzed reaction is qualitatively similar to that for catalysis by homogeneous acids. The planned program of NMR studies has revealed the dynamics of sugar molecules within the zeolite cavities. Two chemisorbed and a physisorbed state have been identified in HY zeolite. A new state, accounting for as much as a half of the sugar, has been found in ZSM-5 zeolite.

  16. Zeolite and swine inoculum effect on poultry manure biomethanation

    NASA Astrophysics Data System (ADS)

    Kougias, P. G.; Fotidis, I. A.; Zaganas, I. D.; Kotsopoulos, T. A.; Martzopoulos, G. G.

    2013-03-01

    Poultry manure is an ammonia-rich substrate that inhibits methanogenesis, causing severe problems to the anaerobic digestion process. In this study, the effect of different natural zeolite concentrations on the mesophilic anaerobic digestion of poultry waste inoculated with well-digested swine manure was investigated. A significant increase in methane production was observed in treatments where zeolite was added, compared to the treatment without zeolite.Methane production in the treatment with 10 g dm-3 of natural zeolite was found to be 109.75% higher compared to the treatment without zeolite addition. The results appear to be influenced by the addition of zeolite, which reduces ammonia toxicity in anaerobic digestion and by the ammonia-tolerant swine inoculum.

  17. Silicate mineralogy of martian meteorites

    NASA Astrophysics Data System (ADS)

    Papike, J. J.; Karner, J. M.; Shearer, C. K.; Burger, P. V.

    2009-12-01

    Basalts and basaltic cumulates from Mars (delivered to Earth as meteorites) carry a record of the history of that planet - from accretion to initial differentiation and subsequent volcanism, up to recent times. We provide new microprobe data for plagioclase, olivine, and pyroxene from 19 of the martian meteorites that are representative of the six types of martian rocks. We also provide a comprehensive WDS map dataset for each sample studied, collected at a common magnification for easy comparison of composition and texture. The silicate data shows that plagioclase from each of the rock types shares similar trends in Ca-Na-K, and that K 2O/Na 2O wt% of plagioclase multiplied by the Al content of the bulk rock can be used to determine whether a rock is "enriched" or "depleted" in nature. Olivine data show that meteorite Y 980459 is a primitive melt from the martian mantle as its olivine crystals are in equilibrium with its bulk rock composition; all other olivine-bearing Shergottites have been affected by fractional crystallization. Pyroxene quadrilateral compositions can be used to isolate the type of melt from which the grains crystallized, and minor element concentrations in pyroxene can lend insight into parent melt compositions. In a comparative planetary mineralogy context, plagioclase from Mars is richer in Na than terrestrial and lunar plagioclase. The two most important factors contributing to this are the low activity of Al in martian melts and the resulting delayed nucleation of plagioclase in the crystallizing rock. Olivine from martian rocks shows distinct trends in Ni-Co and Cr systematics compared with olivine from Earth and Moon. The trends are due to several factors including oxygen fugacity, melt compositions and melt structures, properties which show variability among the planets. Finally, Fe-Mn ratios in both olivine and pyroxene can be used as a fingerprint of planetary parentage, where minerals show distinct planetary trends that may have been

  18. Asymmetric printing of molecules and zeolites on self assembled monolayers.

    PubMed

    Kehr, Nermin Seda; Schäfer, Andreas; Ravoo, Bart Jan; De Cola, Luisa

    2010-04-01

    Microcontact printing (mCP) is used to immobilize dyes and peptides asymmetrically, by a "peptide coupling" reaction, on monolayers of zeolite L crystals in the contact area between the stamp and the surface of the monolayer. Chemically patterned surfaces of monolayers of zeolite L crystals are obtained by using patterned stamps with different ink solutions. Additional printing of functionalized nano-objects on SAMs of zeolite L crystals is demonstrated.

  19. Large zeolites - Why and how to grow in space

    NASA Technical Reports Server (NTRS)

    Sacco, Albert, Jr.

    1991-01-01

    The growth of zeolite crystals which are considered to be the most valuable catalytic and adsorbent materials of the chemical processing industry are discussed. It is proposed to use triethanolamine as a nucleation control agent to control the time release of Al in a zeolite A solution and to increase the average and maximum crystal size by 25-50 times. Large zeolites could be utilized to make membranes for reactors/separators which will substantially increase their efficiency.

  20. Fluoride-assisted synthesis of bimodal microporous SSZ-13 zeolite.

    PubMed

    Zhu, Xiaochun; Kosinov, Nikolay; Hofmann, Jan P; Mezari, Brahim; Qian, Qingyun; Rohling, Roderigh; Weckhuysen, Bert M; Ruiz-Martínez, Javier; Hensen, Emiel J M

    2016-02-21

    The presence of small amount of fluoride in alkaline hydrothermal synthesis of SSZ-13 zeolite yields bimodal microporous particles with substantially improved performance in the methanol-to-olefins (MTO) reaction. Hydrocarbon uptake measurements and fluorescence microspectroscopy of spent catalysts demonstrate enhanced diffusion through micropores at the grain boundaries of nanocrystals running through the zeolite particles. Fluoride-assisted SSZ-13 synthesis is a cheap and scalable approach to optimize the performance of MTO zeolite catalysts. PMID:26810114

  1. Peculiarities of the dielectric response of natural zeolite composites prepared by using zeolite and silicon powders

    NASA Astrophysics Data System (ADS)

    Ozturk Koc, S.; Orbukh, V. I.; Eyvazova, G. M.; Lebedeva, N. N.; Salamov, B. G.

    2016-03-01

    We present the real and imaginary part of the dielectric permittivity of natural zeolite composites prepared by using zeolite and silicon powders. The dielectric response (DR) dependences on the frequency (3-300 GHz) of electric field and different Si concentrations (5-33%) are non-monotonic and a maximum peak is observed. This peak position is practically independent on the frequency and its maximum is observed in zeolite composites which included 9% of the Si-powder. Also the maximum peak is decreased by about an order of magnitude when frequency increases from 500 Hz to 5 kHz. Addition of the conductive Si-particles to zeolite-powder leads to two opposite effects. Firstly, the movement of electrons in the Si-particles provides increase of DR. Secondly, cations which leaving from zeolite pores can be neutralized by the particles of Si in the intercrystalline-space. Such a peculiar mechanism for recombination of Si electrons and cations from pores leads to a reduction of DR for large silicon concentrations. Due to the fact that the contribution of free carriers in the decreasing of the DR as the frequency increases, it is consistent with the suggestion that the maximum peak decreases with increasing frequency.

  2. Redox Processes in Silicate Melts

    NASA Astrophysics Data System (ADS)

    Cicconi, M. R.; de Ligny, D.

    2015-12-01

    Studies into the redox state of magmas provide important constrains on the formation and evolution of planetary bodies Indeed, oxygen fugacity is a key parameter in controlling the physical and chemical properties of melts and therefore it determine the possible interactions between reservoirs within the mantle and between the mantle and surface. It follows that redox mechanisms play a key role in determining the dynamics of the (inner and outer) terrestrial planets. The redox conditions that have accompanied basalt evolution on planetary bodies are known to be different, albeit with some similarities. The strongly reducing environments of the moon and meteorites have led to significant reduced mineralogical assemblages, whereas analogous terrestrial materials predominantly contain the corresponding oxidized compounds. Important geochemical elements such as Fe, Cr, V, Ce and Eu, exist in magmatic systems with different valences and coordination geometries, and the key subjects which need to be understood are: factors influencing redox mechanisms, and the effect on mineral assemblage, element partitioning, mass transfers processes and rheology of the melts. Examples on the study of Ce, Eu and Fe in silicate glasses/melts and on the parameters influencing their oxidation states will be provided.

  3. Large zeolites: why and how to grow in space

    NASA Astrophysics Data System (ADS)

    Sacco, Albert, Jr.

    1991-12-01

    Zeolite crystals are one of the Chemical Process Industry's most valuable catalytic and adsorbent materials. Large, essentially defect-free zeolite crystals could be used to better understand zeolite catalysis mechanisms, and could help in designing better zeolite adsorption systems. In addition, if zeolites could be made large enough, they could be used to make zeolite membranes; these could be used as reactors/separators, resulting in highly improved efficiency. Space provides a unique environment to grow large zeolites by allowing them to continue to grow suspended in their nutrient field. In order to better utilize this microgravity environment, it is necessary to control the nucleation event. Triethanolamine (TEA) can be used to control the time release of aluminum in a zeolite A solution. In a 1 g environment, the use of TEA resulted in a 25 - 50X increase in average and maximum crystal size. It is proposed that if fluid motion can be controlled and the rate of nutrient transport increased, substantially larger zeolite crystals can be formed in microgravity, using such nucleation control agents.

  4. Zeolite Crystal Growth in Microgravity and on Earth

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The Center for Advanced Microgravity Materials Processing (CAMMP), a NASA-sponsored Research Partnership Center, is working to improve zeolite materials for storing hydrogen fuel. CAMMP is also applying zeolites to detergents, optical cables, gas and vapor detection for environmental monitoring and control, and chemical production techniques that significantly reduce by-products that are hazardous to the environment. Shown here are zeolite crystals (top) grown in a ground control experiment and grown in microgravity on the USML-2 mission (bottom). Zeolite experiments have also been conducted aboard the International Space Station.

  5. Method for the recovery of silver from silver zeolite

    DOEpatents

    Reimann, George A.

    1986-01-01

    High purity silver is recovered from silver exchanged zeolite used to capture radioactive iodine from nuclear reactor and nuclear fuel reprocessing environments. The silver exchanged zeolite is heated with slag formers to melt and fluidize the zeolite and release the silver, the radioactivity removing with the slag. The silver containing metallic impurities is remelted and treated with oxygen and a flux to remove the metal impurities. About 98% of the silver in the silver exchanged zeolite having a purity of 99% or better is recoverable by the method.

  6. Method for the recovery of silver from silver zeolite

    DOEpatents

    Reimann, G.A.

    1985-03-05

    High purity silver is recovered from silver exchanged zeolite used to capture radioactive iodine from nuclear reactor and nuclear fuel reprocessing environments. The silver exchanged zeolite is heated with slag formers to melt and fluidize the zeolite and release the silver, the radioactivity removing with the slag. The silver containing metallic impurities is remelted and treated with oxygen and a flux to remove the metal impurities. About 98% of the silver in the silver exchanged zeolite having a purity of 99% or better is recoverable by the method.

  7. Dry method for recycling iodine-loaded silver zeolite

    DOEpatents

    Thomas, Thomas R.; Staples, Bruce A.; Murphy, Llewellyn P.

    1978-05-09

    Fission product iodine is removed from a waste gas stream and stored by passing the gas stream through a bed of silver-exchanged zeolite until the zeolite is loaded with iodine, passing dry hydrogen gas through the bed to remove the iodine and regenerate the bed, and passing the hydrogen stream containing the hydrogen iodide thus formed through a lead-exchanged zeolite which adsorbs the radioactive iodine from the gas stream and permanently storing the lead-exchanged zeolite loaded with radioactive iodine.

  8. Ion exchange properties of Japanese natural zeolites in seawater.

    PubMed

    Wajima, Takaaki

    2013-01-01

    Ion exchange properties of five different Japanese natural zeolites in seawater were examined. Sodium ions could be reduced by all zeolites, although anions, Cl(-) and SO(4)(2-), in seawater showed barely changes. Natural zeolite desalination treatment mainly depends on the ion exchange between Na(+), K(+) and Mg(2+) in seawater and Ca(2+) in natural zeolite. This study found that mordenite is superior to clinoptilolite for use in Na(+) reduction. Mordenite with high cation exchange capacity containing Ca(2+) resulted in the highest Na(+) reduction from seawater.

  9. Highly silicic compositions on the Moon.

    PubMed

    Glotch, Timothy D; Lucey, Paul G; Bandfield, Joshua L; Greenhagen, Benjamin T; Thomas, Ian R; Elphic, Richard C; Bowles, Neil; Wyatt, Michael B; Allen, Carlton C; Donaldson Hanna, Kerri; Paige, David A

    2010-09-17

    Using data from the Diviner Lunar Radiometer Experiment, we show that four regions of the Moon previously described as "red spots" exhibit mid-infrared spectra best explained by quartz, silica-rich glass, or alkali feldspar. These lithologies are consistent with evolved rocks similar to lunar granites in the Apollo samples. The spectral character of these spots is distinct from surrounding mare and highlands material and from regions composed of pure plagioclase feldspar. The variety of landforms associated with the silicic spectral character suggests that both extrusive and intrusive silicic magmatism occurred on the Moon. Basaltic underplating is the preferred mechanism for silicic magma generation, leading to the formation of extrusive landforms. This mechanism or silicate liquid immiscibility could lead to the formation of intrusive bodies.

  10. Magnesium silicates adsorbents of organic compounds

    NASA Astrophysics Data System (ADS)

    Ciesielczyk, Filip; Krysztafkiewicz, Andrzej; Jesionowski, Teofil

    2007-08-01

    Studies were presented on production of highly dispersed magnesium silicate at a pilote scale. The process of silicate adsorbent production involved precipitation reaction using water glass (sodium metasilicate) solution and appropriate magnesium salt, preceded by an appropriate optimization stage. Samples of best physicochemical parameters were in addition modified (in order to introduce to silica surface of several functional groups) using the dry technique and various amounts of 3-isocyanatepropyltrimethoxysilane, 3-thiocyanatepropyltrimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane. The so prepared samples were subjected to a comprehensive physicochemical analysis. At the terminal stage of studies attempts were made to adsorb phenol from its aqueous solutions on the surface of unmodified and modified magnesium silicates. Particle size distributions were determined using the ZetaSizer Nano ZS apparatus. In order to define adsorptive properties of studied magnesium silicates isotherms of nitrogen adsorption/desorption on their surfaces were established. Efficiency of phenol adsorption was tested employing analysis of post-adsorption solution.

  11. Highly silicic compositions on the Moon.

    PubMed

    Glotch, Timothy D; Lucey, Paul G; Bandfield, Joshua L; Greenhagen, Benjamin T; Thomas, Ian R; Elphic, Richard C; Bowles, Neil; Wyatt, Michael B; Allen, Carlton C; Donaldson Hanna, Kerri; Paige, David A

    2010-09-17

    Using data from the Diviner Lunar Radiometer Experiment, we show that four regions of the Moon previously described as "red spots" exhibit mid-infrared spectra best explained by quartz, silica-rich glass, or alkali feldspar. These lithologies are consistent with evolved rocks similar to lunar granites in the Apollo samples. The spectral character of these spots is distinct from surrounding mare and highlands material and from regions composed of pure plagioclase feldspar. The variety of landforms associated with the silicic spectral character suggests that both extrusive and intrusive silicic magmatism occurred on the Moon. Basaltic underplating is the preferred mechanism for silicic magma generation, leading to the formation of extrusive landforms. This mechanism or silicate liquid immiscibility could lead to the formation of intrusive bodies. PMID:20847267

  12. Oxidation of the Ru(0001) surface covered by weakly bound, ultrathin silicate films

    NASA Astrophysics Data System (ADS)

    Emmez, Emre; Anibal Boscoboinik, J.; Tenney, Samuel; Sutter, Peter; Shaikhutdinov, Shamil; Freund, Hans-Joachim

    2016-04-01

    Bilayer silicate films grown on metal substrates are weakly bound to the metal surfaces, which allows ambient gas molecules to intercalate the oxide/metal interface. In this work, we studied the interaction of oxygen with Ru(0001) supported ultrathin silicate and aluminosilicate films at elevated O2 pressures (10- 5-10 mbar) and temperatures (450-923 K). The results show that the silicate films stay essentially intact under these conditions, and oxygen in the film does not exchange with oxygen in the ambient. O2 molecules readily penetrate the film and dissociate on the underlying Ru surface underneath. The silicate layer does however strongly passivate the Ru surface towards RuO2(110) oxide formation that readily occurs on bare Ru(0001) under the same conditions. The results indicate considerable spatial effects for oxidation reactions on metal surfaces in the confined space at the interface. Moreover, the aluminosilicate films completely suppress the Ru oxidation, providing some rationale for using crystalline aluminosilicates in anti-corrosion coatings.

  13. Influence of Silicate Melt Composition on Metal/Silicate Partitioning of W, Ge, Ga and Ni

    NASA Technical Reports Server (NTRS)

    Singletary, S. J.; Domanik, K.; Drake, M. J.

    2005-01-01

    The depletion of the siderophile elements in the Earth's upper mantle relative to the chondritic meteorites is a geochemical imprint of core segregation. Therefore, metal/silicate partition coefficients (Dm/s) for siderophile elements are essential to investigations of core formation when used in conjunction with the pattern of elemental abundances in the Earth's mantle. The partitioning of siderophile elements is controlled by temperature, pressure, oxygen fugacity, and by the compositions of the metal and silicate phases. Several recent studies have shown the importance of silicate melt composition on the partitioning of siderophile elements between silicate and metallic liquids. It has been demonstrated that many elements display increased solubility in less polymerized (mafic) melts. However, the importance of silicate melt composition was believed to be minor compared to the influence of oxygen fugacity until studies showed that melt composition is an important factor at high pressures and temperatures. It was found that melt composition is also important for partitioning of high valency siderophile elements. Atmospheric experiments were conducted, varying only silicate melt composition, to assess the importance of silicate melt composition for the partitioning of W, Co and Ga and found that the valence of the dissolving species plays an important role in determining the effect of composition on solubility. In this study, we extend the data set to higher pressures and investigate the role of silicate melt composition on the partitioning of the siderophile elements W, Ge, Ga and Ni between metallic and silicate liquid.

  14. Fracture of Silicate Glasses: Ductile or Brittle?

    NASA Astrophysics Data System (ADS)

    Guin, Jean-Pierre; Wiederhorn, Sheldon M.

    2004-05-01

    Atomic force microscopy is used to investigate the possibility of cavity formation during crack growth in silicate glasses. Matching areas on both fracture surfaces were mapped and then compared. For silica glass, and soda-lime-silicate glass, the fracture surfaces matched to a resolution of better than 0.3 nm normal to the surface and 5 nm parallel to the surface. We could find no evidence for cavity formation in our study and suggest that completely brittle fracture occurs in glass.

  15. Pf/Zeolite Catalyst for Tritium Stripping

    SciTech Connect

    Hsu, R.H.

    2001-03-26

    This report described promising hydrogen (protium and tritium) stripping results obtained with a Pd/zeolite catalyst at ambient temperature. Preliminary results show 90-99+ percent tritium stripping efficiency may be obtained, with even better performance expected as bed configuration and operating conditions are optimized. These results suggest that portable units with single beds of the Pd/zeolite catalyst may be utilized as ''catalytic absorbers'' to clean up both tritium gas and tritiated water. A cart-mounted prototype stripper utilizing this catalyst has been constructed for testing. This portable stripper has potential applications in maintenance-type jobs such as tritium line breaks. This catalyst can also potentially be utilized in an emergency stripper for the Replacement Tritium Facility.

  16. Bis-GMA/TEGDMA Dental Composites Reinforced with Electrospun Nylon 6 Nanocomposite Nanofibers Containing Highly Aligned Fibrillar Silicate Single Crystals.

    PubMed

    Tian, Ming; Gao, Yi; Liu, Yi; Liao, Yiliang; Xu, Riwei; Hedin, Nyle E; Fong, Hao

    2007-04-24

    The objective of this research was to study the reinforcement of electrospun nylon 6/fibrillar silicate nanocomposite nanofibers on Bis-GMA/TEGDMA dental composites. The hypothesis was that the uniform distribution of nano-scaled and highly aligned fibrillar silicate single crystals into electrospun nylon 6 nanofibers would improve the mechanical properties of the resulting nanocomposite nanofibers, and would lead to the effective reinforcement of dental composites. The nylon 6/fibrillar silicate nanocomposite nanofibers were crystalline, structurally oriented and had an average diameter of approximately 250 nm. To relatively well distribute nanofibers in dental composites, the nanofiber containing composite powders with a particle structure similar to that in interpenetration networks were prepared first, and then used to make the dental composites. The results indicated that small mass fractions (1 % and 2 %) of nanofiber impregnation improved the mechanical properties substantially, while larger mass factions (4 % and 8 %) of nanofiber impregnation resulted in less desired mechanical properties.

  17. Thermodynamics and Kinetics of Silicate Vaporization

    NASA Technical Reports Server (NTRS)

    Jacobson, Nathan S.; Costa, Gustavo C. C.

    2015-01-01

    Silicates are a common class of materials that are often exposed to high temperatures. The behavior of these materials needs to be understood for applications as high temperature coatings in material science as well as the constituents of lava for geological considerations. The vaporization behavior of these materials is an important aspect of their high temperature behavior and it also provides fundamental thermodynamic data. The application of Knudsen effusion mass spectrometry (KEMS) to silicates is discussed. There are several special considerations for silicates. The first is selection of an appropriate cell material, which is either nearly inert or has well-understood interactions with the silicate. The second consideration is proper measurement of the low vapor pressures. This can be circumvented by using a reducing agent to boost the vapor pressure without changing the solid composition or by working at very high temperatures. The third consideration deals with kinetic barriers to vaporization. The measurement of these barriers, as encompassed in a vaporization coefficient, is discussed. Current measured data of rare earth silicates for high temperature coating applications are discussed. In addition, data on magnesium-iron-silicates (olivine) are presented and discussed.

  18. Crystallization of neodymium-rich phases in silicate glasses developed for nuclear waste immobilization

    NASA Astrophysics Data System (ADS)

    Caurant, D.; Majerus, O.; Loiseau, P.; Bardez, I.; Baffier, N.; Dussossoy, J. L.

    2006-08-01

    Glass-ceramics containing neodymium-rich crystalline phases can be obtained by crystallization of silicate glasses (nucleation + crystal growth heat treatments) or by controlled cooling of melts. Such materials could be envisaged as durable matrices for conditioning minor actinides- and Pu-rich nuclear wastes if the partitioning ratio of the wastes between crystalline phase and residual glass is high (principle of double containment barrier). In radioactive waste forms, Nd would be partially substituted by actinides and neutron absorbers (Gd). In this work, two silicate glass compositions leading to efficient nucleation and crystallization of either zirconolite (Ca 1- xNd xZrTi 2- xAl xO 7, x < 1) or apatite (Ca 2Nd 8Si 6O 26) in their bulk were studied as potential waste forms. The effect of the method used to prepare glass-ceramics (controlled cooling from the melt or nucleation + crystal growth from the glass) on both the microstructure and the structure of the neodymium-rich crystalline phase was studied. The highest number of zirconolite or apatite crystals in the bulk was obtained using the nucleation + crystal growth method. However, the percentage of neodymium incorporated in zirconolite crystals remained too small to make realistic the use of such materials for the conditioning of actinides in comparison with more durable bulk ceramics.

  19. Structural and diffusion characterizations of steam-stable mesostructured zeolitic UL-ZSM-5 materials.

    PubMed

    Vinh-Thang, Hoang; Huang, Qinglin; Ungureanu, Adrian; Eić, Mladen; Trong-On, Do; Kaliaguine, Serge

    2006-05-01

    A series of mesoporous UL-ZSM-5 materials (Si/Al = 50) with different micro- and mesoporosity as well as crystallinity was prepared following the procedure proposed in one of our recent studies (Trong-On, D.; Kaliaguine, S. Angew. Chem. Int. Ed. 2001, 40, 3248-3251. Trong-On, D.; Kaliaguine, S. U.S. Patent 6,669,924, B1, 2003). These materials have zeolitic structure in the form of nanoparticles intergrown in the walls of the amorphous wormhole-like aluminosilicate mesopores of Al-Meso-50, which was used as a precursor in the synthesis. The structure, crystallinity, and textural properties of the synthesized materials, as well as a reference ZSM-5 zeolite sample, were determined by X-ray diffraction (XRD), transmission electron microscopy (TEM)/scanning electron microscoy (SEM) analyses, Fourier transform infrared spectroscopy (FTIR), 27Al magic angle spinning (MAS) nuclear magnetic resonance (NMR), and nitrogen adsorption/desorption techniques. The acid properties were examined by FTIR of adsorbed pyridine. UL-ZSM-5 materials were shown to be highly hydrothermally stable. The diffusion of two C7 hydrocarbons, i.e., n-heptane and toluene, in four UL-ZSM-5 materials with different microporosities, related acidities, and crystallinities were investigated using the zero-length column (ZLC) method. Furthermore, the wormhole-like mesostructured aluminosilicate precursor (Al-Meso-50) and a reference MFI zeolite sample were also investigated using the same technique. A theoretical model considering a combination of mesopore diffusion (with surface slip in the main channels) with an activated, mainly surface diffusion mechanism in the intrawall biporous structure, was proposed and employed to interpret the experimental ZLC results. A classical Knudsen type of diffusion was replaced by an activated surface slip type of diffusion mechanism in the mesopores. The transport of n-heptane in UL-ZSM-5 materials was found to be mainly controlled by mesopore diffusion in the main

  20. Characterization of active sites in zeolite catalysts

    SciTech Connect

    Eckert, J.; Bug, A.; Nicol, J.M.

    1997-11-01

    This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Atomic-level details of the interaction of adsorbed molecules with active sites in catalysts are urgently needed to facilitate development of more effective and/or environmentally benign catalysts. To this end the authors have carried out neutron scattering studies combined with theoretical calculations of the dynamics of small molecules inside the cavities of zeolite catalysts. The authors have developed the use of H{sub 2} as a probe of adsorption sites by observing the hindered rotations of the adsorbed H{sub 2} molecule, and they were able to show that an area near the four-rings is the most likely adsorption site for H{sub 2} in zeolite A while adsorption of H{sub 2} near cations located on six-ring sites decreases in strength as Ni {approximately} Co > Ca > Zn {approximately} Na. Vibrational and rotational motions of ethylene and cyclopropane adsorption complexes were used as a measure for zeolite-adsorbate interactions. Preliminary studies of the binding of water, ammonia, and methylamines were carried out in a number of related guest-host materials.

  1. Modelling of the prebiotic synthesis of oligopeptides: silicate catalysts help to overcome the critical stage

    NASA Astrophysics Data System (ADS)

    Zamaraev, Kirill I.; Romannikov, Vyacheslav N.; Salganik, Rudolph I.; Wlassoff, Wjatschesslaw A.; Khramtsov, Valeriy V.

    1997-08-01

    On the basis of experimental studies of the initial stages of glycine oligomerization in aqueous suspension of zeolite and kaolinite catalysts, a model is suggested for the prebiotic synthesis of oligopeptides from α-amino acids. The formation of linear dipeptides by hydrolysis of one amide bond in the cyclic piperazinedione intermediate (formed from glycine spontaneously) is found to be the critical stage of the reaction. This stage is base catalyzed and its rate increases when pH of the medium goes up. The linear glycyl-glycine yield rises under effect of hydroxyl anions generated from different sources including insoluble silicates and soluble sodium bicarbonate. During prebiotic evolution silicates capable of cation-exchange can serve as local sources of the hydroxyl anions which dramatically accelerate formation of linear dipeptides from cyclic ones. Oligopeptides of higher molecular weight are then easily formed from the linear dipeptides at neutral pH, even in the absence of catalysts or sources of energy (e.g. such as light). The described catalytic synthesis could occur in the proximity of submarine hydrothermal vents.

  2. Liquid Crystalline Microemulsions

    NASA Astrophysics Data System (ADS)

    Huang, Chien-Yueh; Petschek, Rolfe G.

    2000-03-01

    If an isotropic component of an emulsion is replaced by one having liquid crystalline (e.g. nematic) order the equilibrium behavior can change dramatically. There are long range enthalpic effects which can result in either repulsive or attractive interactions between the surfaces of an emulsion and entropic effects which generally result in an attractive interaction between these surfaces. We review briefly the possibility of stable blue-phase like microemulsions in mixtures of chiral nematics, appropriate surfactants and an incompatible isotropic solvent. We discuss the entropic effects in a lamellar phase, including the effects of changes in elastic constants and surface-nematic coupling. The effects of fluctuations on blue phases will be briefly discussed.

  3. Liquid crystalline polymers

    NASA Technical Reports Server (NTRS)

    1990-01-01

    The remarkable mechanical properties and thermal stability of fibers fabricated from liquid crystalline polymers (LCPs) have led to the use of these materials in structural applications where weight savings are critical. Advances in processing of LCPs could permit the incorporation of these polymers into other than uniaxial designs and extend their utility into new areas such as nonlinear optical devices. However, the unique feature of LCPs (intrinsic orientation order) is itself problematic, and current understanding of processing with control of orientation falls short of allowing manipulation of macroscopic orientation (except for the case of uniaxial fibers). The current and desirable characteristics of LCPs are reviewed and specific problems are identified along with issues that must be addressed so that advances in the use of these unique polymers can be expedited.

  4. The effect of sulphur in silicate melt on partitioning of Ni and other trace elements

    NASA Astrophysics Data System (ADS)

    Wood, Bernard; Kiseeva, Ekaterina; Wohlers, Anke

    2016-04-01

    It has been suggested that variations in the sulphur contents of silicate melts affect the partitioning of trace chalcophile elements, particularly Ni, between silicate melt and crystalline phases such as olivine [1]. The general idea is that Ni (and other elements) complex with sulphur dissolved in the melt, thereby stabilising Ni in the melt and reducing the olivine-melt partition coefficient DNi. More recent experiments lead to the assertion that any sulphur effect, if present is small and can be ignored [2]. Experiments aimed at addressing this problem have, however, struggled with the difficulty that the maximum S contents of olivine- precipitating melts do not exceed ~0.5% even at sulphide saturation. Any effect is therefore difficult to establish unequivocally. Here we have taken advantage of the fact that experiments under strongly reducing conditions, where FeO activity in the silicate melt is very low lead to much higher concentrations of S than those associated with olivine precipitation. We have therefore investigated partitioning between sulphide melts and haplobasaltic silicate melt at concentrations of FeO between 0.3 and 10 weight% in order to investigate the "sulphur-effect" on partitioning. At the lowest FeO contents we are able to drive the S content of the melt to 10 weight% enabling the effects to be unequivocally established. We find that partitioning of strongly lithophile elements Nb, Ta, U, REE partition more strongly out of silicate melt as its S content increases. The effect is, surprisingly, predominantly due to the effect of S on the activity coefficient of FeO in the melt. In contrast strongly chalcophile Ni, Cu, Ag partition more strongly into the melt as its S content increases. This is due to a dramatic lowering of the activity coefficients of these elements in the silicate as S increases. Elements which show little effect of S include Pb, Co and In. The results enable us to predict the effects of sulphur on olivine-melt and

  5. Structure and Viscosity of Carbonate-Silicate Melts Using in situ Techniques

    NASA Astrophysics Data System (ADS)

    Hummer, D. R.; Manning, C. E.; Kavner, A.; Kono, Y.; Park, C.; Kenney-Benson, C.

    2015-12-01

    The chemical properties of carbon-rich magmas at high pressures and temperatures are a major factor controlling the deep-Earth carbon cycle, and may play a crucial role in global magmatism at depth. We have measured the structure of carbonate-silicate liquids as a function of carbon content along the calcite-wollastonite (CaCO3-CaSiO3) and calcite-forsterite (CaCO3-Mg2SiO3) compositional joins at ~1800 oC, and 3 or 6 GPa in a Paris-Edinburgh press using X-ray diffuse scattering. Pair distribution functions calculated from the scattering data confirm that CaCO3 behaves as an ionic liquid, while compositions with 40-100 wt% wollastonite contain polymerized silicate with an average connectivity (Qn) of at least two bridging O per Si (Q2). Even liquid compositions with as little as 35 wt% forsterite component contain silicate polymers, despite the absence of bridging O in the crystalline orthosilicate. As the carbonate content of the melt is increased, the average connectivity of SiO4 units linearly increases from ~Q2 for pure wollastonite liquid to >Q3 for 40 wt% wollastonite, even though less silicate is present. Analysis of Ca-Ca and Ca-Si pair correlations, as well as Ca-O bond distances, indicate that Ca2+ bonds more strongly to the silicate framework as carbonate content increases. Increasing pressure from 3 to 6 GPa at constant composition causes Qn to fall near Q0. The trends in local atomic structure with composition and pressure explain falling sphere viscometry measurements in carbonate-silicate liquids at upper mantle conditions. These viscosities are as low as 6x10-3 Pa-s for pure CaCO3, only half a log unit higher than that of water, and span ~1.6 log units between the carbonate and silicate end-members. Structural and viscosity trends taken together indicate carbonate-rich, depolymerized and highly mobile liquid at depth which transitions into silicate-rich, polymerized and much less mobile liquid as the melt ascends into the crust.

  6. The formation of molecular hydrogen on silicate dust analogs: The rotational distribution

    SciTech Connect

    Gavilan, L.; Lemaire, J. L.; Vidali, G.; Sabri, T.; Jæger, C.

    2014-02-01

    Our laboratory experiments continue to explore how the formation of molecular hydrogen is influenced by dust and how dust thereby affects hydrogen molecules adsorbed on its surface. In Sabri et al., we present the preparation of nanometer-sized silicate grain analogs via laser ablation. These analogs illustrate extremes in structure (fully crystalline or fully amorphous grains), and stoichiometry (the forsterite and fayalite end-members of the olivine family). These were inserted in FORMOLISM, an ultra-high vacuum setup where they can be cooled down to ∼5 K. Atomic beams are directed at these surfaces and the formation of new molecules is studied via REMPI(2+1) spectroscopy. We explored the rotational distribution (0 ≤ J'' ≤ 5) of v'' = 0 of the ground electronic state of H{sub 2}. The results of these measurements are reported here. Surprisingly, molecules formed and ejected from crystalline silicates have a cold (T {sub rot} ∼ 120 K) rotational energy distribution, while for molecules formed on and ejected from amorphous silicate films, the rotational temperature is ∼310 K. These results are compared to previous experiments on metallic surfaces and theoretical simulations. Solid-state surface analysis suggests that flatter grains could hinder the 'cartwheel' rotation mode. A search for hot hydrogen, predicted as a result of H{sub 2} formation, hints at its production. For the first time, the rotational distribution of hydrogen molecules formed on silicate dust is reported. These results are essential to understanding the chemistry of astrophysical media containing bare dust grains.

  7. Preparation and screening of crystalline zeolite and hydrothermally-synthesized materials

    DOEpatents

    Schultz, Peter G.; Xiang, Xiaodong; Goldwasser, Isy; Briceno, Gabriel; Sun, Xiao-Dong; Wang, Kai-An

    2005-03-08

    Methods and apparatus for the preparation and use of a substrate having an array of diverse materials in predefined regions thereon. A substrate having an array of diverse materials thereon is generally prepared by delivering components of materials to predefined regions on a substrate, and simultaneously reacting the components to form at least two materials. Materials which can be prepared using the methods and apparatus of the present invention include, for example, covalent network solids, ionic solids and molecular solids. More particularly, materials which can be prepared using the methods and apparatus of the present invention include, for example, inorganic materials, intermetallic materials, metal alloys, ceramic materials, organic materials, organometallic materials, non-biological organic polymers, composite materials (e.g., inorganic composites, organic composites, or combinations thereof), etc. Once prepared, these materials can be screened for useful properties including, for example, electrical, thermal, mechanical, morphological, optical, magnetic, chemical, or other properties. Thus, the present invention provides methods for the parallel synthesis and analysis of novel materials having useful properties.

  8. Characterization and antibacterial activity of silver exchanged regenerated NaY zeolite from surfactant-modified NaY zeolite.

    PubMed

    Salim, Mashitah Mad; Malek, Nik Ahmad Nizam Nik

    2016-02-01

    The antibacterial activity of regenerated NaY zeolite (thermal treatment from cetyltrimethyl ammonium bromide (CTAB)-modified NaY zeolite and pretreatment with Na ions) loaded with silver ions were examined using the broth dilution minimum inhibitory concentration (MIC) method against Escherichia coli (E. coli ATCC 11229) and Staphylococcus aureus (S. aureus ATCC 6538). X-ray diffraction (XRD), attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) and chemical elemental analyses were used to characterize the regenerated NaY and AgY zeolites. The XRD patterns indicated that the calcination and addition of silver ions on regenerated NaY zeolite did not affect the structure of the regenerated NaY zeolite as the characteristic peaks of the NaY zeolite were retained, and no new peaks were observed. The regenerated AgY zeolite showed good antibacterial activity against both bacteria strains in distilled water, and the antibacterial activity of the samples increased with increasing Ag loaded on the regenerated AgY zeolite; the regenerated AgY zeolite was more effective against E. coli than S. aureus. However, the antibacterial activity of the regenerated AgY was not effective in saline solution for both bacteria. The study showed that CTAB-modified NaY zeolite materials could be regenerated to NaY zeolite using thermal treatment (550°C, 5h) and this material has excellent performance as an antibacterial agent after silver ions loading. PMID:26652350

  9. Characterization and antibacterial activity of silver exchanged regenerated NaY zeolite from surfactant-modified NaY zeolite.

    PubMed

    Salim, Mashitah Mad; Malek, Nik Ahmad Nizam Nik

    2016-02-01

    The antibacterial activity of regenerated NaY zeolite (thermal treatment from cetyltrimethyl ammonium bromide (CTAB)-modified NaY zeolite and pretreatment with Na ions) loaded with silver ions were examined using the broth dilution minimum inhibitory concentration (MIC) method against Escherichia coli (E. coli ATCC 11229) and Staphylococcus aureus (S. aureus ATCC 6538). X-ray diffraction (XRD), attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) and chemical elemental analyses were used to characterize the regenerated NaY and AgY zeolites. The XRD patterns indicated that the calcination and addition of silver ions on regenerated NaY zeolite did not affect the structure of the regenerated NaY zeolite as the characteristic peaks of the NaY zeolite were retained, and no new peaks were observed. The regenerated AgY zeolite showed good antibacterial activity against both bacteria strains in distilled water, and the antibacterial activity of the samples increased with increasing Ag loaded on the regenerated AgY zeolite; the regenerated AgY zeolite was more effective against E. coli than S. aureus. However, the antibacterial activity of the regenerated AgY was not effective in saline solution for both bacteria. The study showed that CTAB-modified NaY zeolite materials could be regenerated to NaY zeolite using thermal treatment (550°C, 5h) and this material has excellent performance as an antibacterial agent after silver ions loading.

  10. The catalytic diversity of zeolites: confinement and solvation effects within voids of molecular dimensions.

    PubMed

    Gounder, Rajamani; Iglesia, Enrique

    2013-05-01

    The ability of molecular sieves to control the access and egress of certain reactants and products and to preferentially contain certain transition states while excluding others based on size were captured as shape selectivity concepts early in the history of zeolite catalysis. The marked consequences for reactivity and selectivity, specifically in acid catalysis, have since inspired and sustained many discoveries of novel silicate frameworks and driven the engineering of hierarchical structures and void size to influence catalysis. The catalytic diversity of microporous voids is explored and extended here in the context of their solvating environments, wherein voids act as hosts and stabilize guests, whether reactive intermediates or transition states, by van der Waals forces. We use specific examples from acid catalysis, including activation of C-C and C-H bonds in alkanes, alkylation and hydrogenation of alkenes, carbonylation of dimethyl ether, and elimination and homologation reactions of alkanols and ethers, which involve transition states and adsorbed precursors of varying size and composition. Mechanistic interpretations of measured turnover rates enable us to assign precise chemical origins to kinetic and thermodynamic constants in rate equations and, in turn, to identify specific steps and intermediates that determine the free energy differences responsible for chemical reactivity and selectivity. These free energy differences reflect the stabilization of transition states and their relevant precursors via electrostatic interactions that depend on acid strength and van der Waals interactions that depend on confinement within voids. Their respective contributions to activation free energies are examined by Born-Haber thermochemical cycles by considering plausible transition states and the relevant precursors. These examples show that zeolite voids solvate transition states and precursors differently, and markedly so for guest moieties of different size and

  11. Compositional effects on Si–OH bond length in hydrous silicates with implications for trends in the SiOH acidity

    SciTech Connect

    Zarubin, Dmitri P.

    2014-04-01

    Theoretical calculations of the structure and Brønsted acidity of SiOH groups in silica clusters have never addressed the question if these vary with the degree of SiOH deprotonation. In this connection, a statistical analysis is presented of Si–OH bond lengths in crystalline hydrogen silicates with well-determined structures with a special emphasis placed on effects of the silicate composition. It is found that among hydrogen silicates of large cations with low charges the Si–OH bonds are always longer than terminal Si–O bonds in the same anion and correlate in length with the anionic charge per tetrahedron. The findings are explained by steric limitations on charge balancing at oxygen atoms by hydrogen bonds and/or cations. It is suggested that similar limitations and imbalances may underlie the well-known trends in the Brønsted acidity of silicic acids and silicas in aqueous media: decreased acidity with increased SiOH deprotonation and increased acidity with increased tetrahedra connectivity. - Graphical abstract: Si–OH bonds in crystalline silicates lengthen with the anionic charge per tetrahedron, which is in parallel with the well-known trend of decreased acidity of silicic acids and silicas in solution with increased degree of deprotonation. - Highlights: • Si–OH bonds in alkali hydrogen silicates are always longer than terminal Si–O bonds. • Si–OH bonds in silicates lengthen with the anionic charge per tetrahedron. • The Si–OH bond elongation results from inherent underbonding of terminal O atoms. • The longer the Si–OH bond, the less acidic the OH group is.

  12. Antimony and silicon environments in antimony silicate glasses

    SciTech Connect

    Mee, M.; Davies, B.C.; Orman, R.G.; Thomas, M.F.; Holland, D.

    2010-09-15

    Antimony silicate glasses, of general formula xSb{sub 2}O{sub 3}.(1-x)SiO{sub 2} (0.1{<=}x{<=}0.78), have been prepared by melt-quenching and their structures studied using {sup 29}Si MAS NMR spectroscopy, {sup 121}Sb Moessbauer spectroscopy and Raman spectroscopy. Oxidation during melting gives rise to Sb{sup 5+} in concentrations, which increase linearly with x to give a value of {approx}10% when x=0.78. {sup 121}Sb Moessbauer spectra show Moessbauer shifts and quadrupole splittings consistent with Sb{sup 3+} in a [:SbO{sub 3}] trigonal pyramid, similar to that in crystalline Sb{sub 2}O{sub 3}. A broad band in the Raman spectrum at {approx}410 cm{sup -1} is due to the vibrations of such a unit. The dependence of the silicon Q{sup n} speciation on x can be interpreted by the formation of Sb-O-Sb links possibly to form rings of 4 [:SbO{sub 3}] units such as are found in valentinite. - Graphical abstract: Antimony silicate glasses have been shown to contain Sb{sup 3+} in [:SbO{sub 3}] trigonal pyramid units using {sup 121}Sb Moessbauer spectroscopy and Raman spectroscopy. {sup 29}Si magic-angle-spinning NMR has shown silicon Q{sup n} speciation which can be interpreted as formation of rings of 4 [:SbO{sub 3}] units such as are found in valentinite.

  13. Selective thermal and photooxidation of hydrocarbons in zeolites by oxygen

    DOEpatents

    Frei, H.; Blatter, F.; Sun, H.

    1999-06-22

    A process is described for selective thermal oxidation or photooxidation of hydrocarbons adsorbed onto zeolite matrices. A highly selective thermal oxidation and photooxidation of unsubstituted or alkyl substituted alkanes, alkenes, aromatics and cycloalkyls in solvent free zeolites under dark thermal conditions or under irradiation with visible light. The process oxidizes hydrocarbons almost completely selectively without substantial production of byproducts. 19 figs.

  14. Selective thermal and photooxidation of hydrocarbons in zeolites by oxygen

    DOEpatents

    Frei, Heinz; Blatter, Fritz; Sun, Hai

    2001-01-01

    A process for a combined selective thermal oxidation and photooxidation of hydrocarbons adsorbed onto zeolite matrices. A highly combined selective thermal oxidation and photooxidation of unsubstituted or alkyl substituted alkanes, alkenes, aromatics and cycloalkyls in solvent free zeolites under dark thermal conditions or under irradiation with visible light. The process oxidizes hydrocarbons almost completely selectively without substantial production of byproducts.

  15. Selective thermal oxidation of hydrocarbons in zeolites by oxygen

    DOEpatents

    Frei, Heinz; Blatter, Fritz; Sun, Hai

    2000-01-01

    A process for selective thermal oxidation of hydrocarbons adsorbed onto zeolite matrices. A highly selective thermal oxidation of unsubstituted or alkyl substituted alkanes, alkenes, aromatics and cycloalkyls is carried out in solvent free zeolites under dark thermal conditions. The process oxidizes hydrocarbons almost completely selectively without substantial production of byproducts.

  16. Selective thermal and photooxidation of hydrocarbons in zeolites by oxygen

    DOEpatents

    Frei, Heinz; Blatter, Fritz; Sun, Hai

    1999-01-01

    A process for selective thermal oxidation or photooxidation of hydrocarbons adsorbed onto zeolite matrices. A highly selective thermal oxidation and photooxidation of unsubstituted or alkyl substituted alkanes, alkenes, aromatics and cycloalkyls in solvent free zeolites under dark thermal conditions or under irradiation with visible light. The process oxidizes hydrocarbons almost completely selectively without substantial production of byproducts.

  17. FUNDAMENTALS AND APPLICATIONS OF PERVAPORATION THROUGH ZEOLITE MEMBRANES

    EPA Science Inventory

    Zeolite membranes are well suited for separating liquid-phase mixtures by pervaporation because of their molecular-sized pores and their hydrophilic/hydrophobic nature, and the first commercial application of zeolite membranes has been for dehydrating organics [1]. Because of ...

  18. Crewmember working on the mid deck Zeolite Crystal Growth experiment.

    NASA Technical Reports Server (NTRS)

    1992-01-01

    View showing Payload Specialist Bonnie Dunbar, in the mid deck, conducting the Zeolite Crystal Growth (ZCG) Experiment in the mid deck stowage locker work area. View shows assembly of zeolite sample in the metal autoclave cylinders prior to insertion into the furnace.

  19. Zeolites in the Pine Ridge Indian Reservation, South Dakota

    USGS Publications Warehouse

    Raymond, William H.; Bush, Alfred L.; Gude, Arthur J.

    1982-01-01

    Zeolites of possible commercial value occur in the Brule Formation of Oligocene age and the Sharps Formation (Harksen, 1961) of Miocene age which crop out in a wide area in the northern part of the Pine Ridge Indian Reservation. The thickness of the zeolite-bearing Interval and the extent of areas within the Interval which contain significant amounts of zeolites are far greater than was expected prior to this investigation. The shape of the zeolite-bearing Interval is tabular and the dimensions of Its exposure are roughly 10 ml x 200 mi x 150 ft (16 km x 160 km x 45 m) thick. Within the study area, there are tracts in which the zeolite resource potential is significant (see pl. 2). This report is intended to inform the Oglala Sioux Tribe of some of the most promising zeolite occurrences. Initial steps can then be taken by the Tribe toward possible development of the resources, should they wish to do so. The data contained herein identify areas of high zeolite potential, but are not adequate to establish economic value for the deposits. If development is recommended by the tribal government, we suggest that the tribal government contact companies involved in research and production of natural zeolites and provide them with the data in this report.

  20. Applications of two-dimensional solid state nuclear magnetic resonance in silicates

    NASA Astrophysics Data System (ADS)

    Xu, Zhi

    1998-10-01

    Nuclear magnetic resonance (NMR) is a powerful technique and has been routinely applied in many fields. In this study, we have used high resolution two-dimensional (2D) solid state NMR techniques to study the dynamic process of Li diffusion, the kinetic process of oxygen isotope exchange, and the structural characterization of hydrous and anhydrous silicate glasses at atomic level. In the Li diffusion study, we first established the correlation between the sp6Li chemical shifts and the lithium coordination environments in lithium containing silicates. Then, we assigned the sp6Li magic angle spinning (MAS) spectrum and applied 1D, 2D variable temperature exchange NMR to observe Lisp+ diffusion in lithium orthosilicate. For the first time, our result revealed a detailed picture of the hopping rates of Lisp+ ions among structurally distinct sites and helped to define the diffusion pathway. We have shown that Lisp+ ions hopping rates and activation energies depend on site geometry. NMR measurements on Li ionic hopping frequencies was used to accurately predict the bulk conductivity. In the site-specific oxygen isotope exchange study, we first developed a method to obtain quantitative sp{17}O NMR spectra. Then, we applied the method to stilbite, a natural zeolite. We have shown for the first time that framework oxygens in Al-O-Si sites react faster with oxygens in the channel water than oxygens in Si-O-Si sites. Such an observation has partially proved the quantum ab initio calculation on water adsorption onto silicates. Our measured kinetics results agreed well with bulk isotopic measurements. Water dissolution mechanism in silicates glasses, especially aluminosilicate glasses, has been a long-standing controversy. We have used the sp{17}O spectra for hydrous and anhydrous sodium tetrasilicate glasses and albite glasses to study the structural role of hydrogen-containing species. For the first time, we have observed the oxygen peak for SiOH in hydrous sodium

  1. The interaction of aluminum with silicic acid in dilute solution and its biological relevance

    SciTech Connect

    Chappell, J.S.; Birchall, J.D. )

    1988-09-01

    The affinity of silicic acid, Si(OH){sub 4}, for aluminum is a unique one in chemistry, owing to ionic size, charge, and coordination geometry of the species involved. The chemistry of aluminosilicates generally has been concerned with the solid state (minerals such as clays, feldspars and zeolites), and relatively little attention has been given to the species which exist in solution since aluminosilicates are highly insoluble near neutral pH. However, under dilute conditions the kinetics of colloid formation can be quite slow and the soluble precursors to a solid phase may be reasonably metastable. When equilibrium is approached, the solubility levels are typically 0.05-0.28 {mu}mol/L Al and 18-210 {mu}mol/L Si. These soluble species are usually regarded as simple hydroxyaluminum ions and silicic acid, although it remains arguable as to whether these species may be associated with each other. The formation of a stable soluble specie would allow for molecular aluminosilicates to exist at below saturation levels. So at concentrations above saturation stable aluminosilicates do form (as a part of an insoluble phase), and they may possibly exist at below saturation (as a stable soluble specie). This interaction is then relevant to biology, where human plasma levels (0.06-0.54 {mu}mol/L Al, 14-39 {mu}mol/L Si) (6,7) fall among saturation values. There is a growing concern over the toxic effects of aluminum, but its chemistry with silicic acid has not been addressed. This chemistry is the topic of this study.

  2. Monoethanol amine modified zeolite 13X for CO{sub 2} adsorption at different temperatures

    SciTech Connect

    P.D. Jadhav; R.V. Chatti; R.B. Biniwale; N.K. Labhsetwar; S. Devotta; S.S. Rayalu . s_rayalu@neeri.res.in

    2007-12-15

    Zeolite 13X has been modified with monoethanol amine (MEA). MEA loadings of 0.5-25 wt % have been achieved using the impregnation method in different solvents. The mode of incorporation based on methanol with stirring at room temperature appears to be the most feasible. The adsorbent has been characterized for crystallinity, surface area, pore volume, and pore size. The thermal stability of the adsorbent is studied using a thermal analyzer. The CO{sub 2} adsorption capacity of adsorbents is evaluated using the breakthrough adsorption method with a packed column on a 10 g scale. The adsorption capacities of adsorbents are estimated in the temperature range 30-120{sup o}C. The adsorbents show improvement in CO{sub 2} adsorption capacity over the unmodified zeolite by a factor of ca. 1.6 at 30{sup o}C, whereas at 120{sup o}C the efficiency improved by a factor of 3.5. For adsorption at these temperatures, different MEA loading levels were found to be suitable as per the governing adsorption phenomena, that is, physical or chemical. The adsorbent is also studied for CO{sub 2} selectivity over N{sub 2} at 75{sup o}C. The MEA-modified adsorbent shows better CO{sub 2} selectivity, which was improved further in the presence of moisture. 25 refs., 6 figs., 3t abs.

  3. Some observations on the synthesis of fully-dispersible nanocrystalline zeolite ZSM-5.

    PubMed

    Selvin, Rosilda; Chiang, Anthony S T

    2014-09-01

    A facile method for the rapid synthesis of fully-dispersible ZSM-5 (Si/Al = 100) of about 30 nm size in high yield (about 91%) is described. The method comprises three steps, viz., concentration of an initial clear solution, low-temperature (80 degrees C) ageing of concentrated sol, and high-temperature (175 degrees C) hydrothermal treatment or microwave heating (175 degrees C) of aged concentrated sol. A simple vacuum-concentration method was used for the extraction of pure NPs of ZSM-5 in solution. XRD, FT-IR, TGA and ASAP characterizations showed that the NPs were partially crystalline. The concentration step accelerated the aggregation of primary units, which helps in the production of a large number of nucleation centers protected by TPA+ ions against aggregation. During low-temperature ageing, the number of critical sized nuclei increases, growing into zeolite. The high-temperature heating results in the complete growth of unreacted silica, giving high yields. A key factor for generating small non-aggregated zeolite crystals is the amount of water in the synthesis sol. The three-step method presented here produces a target material of small and uniform sized, non-aggregated ZSM-5 of about 30 nm in a short reaction time. The results are significant, as the synthesis method adopted here produces much uniform, non-aggregated nanocrystalline ZSM-5 in a shorter time with high yield.

  4. The characterisation by luminescence spectroscopy of uranium(VI) incorporated into zeolites and aluminas

    NASA Astrophysics Data System (ADS)

    Azenha, M. E. D. G.; da Graça Miguel, M.; Formosinho, S. J.; Burrows, H. D.

    2001-05-01

    Luminescence spectroscopy of solids at 77 K has been used to characterise the uranium(VI) species incorporated into α-alumina, γ-alumina and zeolites Y and ZSM-20 by adsorption from solution and into ZSM-5 by chemical synthesis. With uranyl adsorbed from nitrate solutions onto α- and γ-aluminas, the luminescence measurements show the dominant uranium species is schoepite, UO 3· xH 2O, in agreement with results from X-ray diffraction and Raman spectroscopy. With uranyl acetate, there are indications that a crystalline acetate species is also present. With zeolite-Y and ZSM-20, the main species is a dimer. In addition, some monomeric [UO 2(H 2O) 5] 2+ is also present. With ZSM-5, although this is not observed in X-ray diffraction, the luminescence spectrum shows the presence of a species, similar to the schoepite seen with the aluminas. It is suggested that this may be due both to closely related polymeric species, and to uranyl anions, such as [UO 2(OH) 4] 2- and [UO 2(OH) 3] -.

  5. Zeolites in Eocene basaltic pillow lavas of the Siletz River Volcanics, Central Coast Range, Oregon.

    USGS Publications Warehouse

    Keith, T.E.C.; Staples, L.W.

    1985-01-01

    Zeolites and associated minerals occur in a tholeiitic basaltic pillow lava sequence. Although the zeolite assemblages are similar to those found in other major zeolite occurrences in basaltic pillow lavas, regional zoning of the zeolite assemblages is not apparent. The formation of the different assemblages is discussed.-D.F.B.

  6. Silicate liquid immiscibility in lunar magmas, evidenced by melt inclusions in lunar rocks.

    PubMed

    Roedder, E; Weiblen, P W

    1970-01-30

    Examination of multiphase melt inclusions in 91 sections of 26 lunar rocks revealed abundant evidence of late-stage immiscibility in all crystalline rock sections and in soil fragments and most breccias. The two individual immiscible silicate melts (now glasses) vary in composition, but are essentially potassic granite and pyroxenite. This immiscibility may be important in the formation of the lunar highlands and tektites. Other inclusions yield the following temperatures at which the several minerals first appear on cooling the original magma: ilmenite (?) liquidus, 1210 degrees C; pyroxene, 1140 degrees C; plagioclase, 1105 degrees C; solidus, 1075 degrees C. The glasses also place some limitations on maximum and minimum cooling rates.

  7. An Observational Test for Shock-induced Crystallization of Cometary Silicates

    NASA Technical Reports Server (NTRS)

    Nuth, J. A.; Johnson, N. M.

    2003-01-01

    Crystalline silicates have been observed in comets and in protostellar nebulae, and there are currently at least two explanations for their formation: thermal annealing in the inner nebula, followed by transport to the regions of cometary formation and in-situ shock processing of amorphous grains at 5 - 10 AU in the Solar Nebula. The tests suggested to date to validate these models have not yet been carried out: some of these tests require a longterm commitment to observe both the dust and gas compositions in a large number of comets. Here we suggest a simpler test.

  8. Formation of Silicate Grains in Circumstellar Environments: Experiment, Theory and Observations

    NASA Technical Reports Server (NTRS)

    Castleman, A., Jr.; Reber, A.; Clayborne, P.; Reveles, J.; Khanna, S.; Ali, A.

    2006-01-01

    Amongst chemical reactions (1) in the molecular universe (2), condensation reaction is probably the most poorly understood. The condensation of a solid from its components in the gas phase occurs in many parts of our galaxy such as stellar mass outflows, the terrestrial region of protoplanetary disks and in primordial solar nebula (3). But how does the transition occur from molecules to intermediate clusters to macroscopic grains? The major focus of the present work is the identification of chemical condensation reaction pathways that lead to the formation of stoichiometry, composition and crystallinity of cosmic silicates from vapor phase species.

  9. Fly ash based zeolitic pigments for application in anticorrosive paints

    NASA Astrophysics Data System (ADS)

    Shaw, Ruchi; Tiwari, Sangeeta

    2016-04-01

    The purpose of this work is to evaluate the utilization of waste fly ash in anticorrosive paints. Zeolite NaY was synthesized from waste fly ash and subsequently modified by exchanging its nominal cation Na+ with Mg2+ and Ca2+ ions. The metal ion exchanged zeolite was then used as anticorrosive zeolitic pigments in paints. The prepared zeolite NaY was characterized using X-Ray diffraction technique and Scanning electron microscopy. The size, shape and density of the prepared fly ash based pigments were determined by various techniques. The paints were prepared by using fly ash based zeolitic pigments in epoxy resin and the percentages of pigments used in paints were 2% and 5%. These paints were applied to the mild steel panels and the anticorrosive properties of the pigments were assessed by the electrochemical spectroscopy technique (EIS).

  10. Potential and actual uses of zeolites in crop protection.

    PubMed

    De Smedt, Caroline; Someus, Edward; Spanoghe, Pieter

    2015-10-01

    In this review, it is demonstrated that zeolites have a potential to be used as crop protection agents. Similarly to kaolin, zeolites can be applied as particle films against pests and diseases. Their honeycomb framework, together with their carbon dioxide sorption capacity and their heat stress reduction capacity, makes them suitable as a leaf coating product. Furthermore, their water sorption capacity and their smaller particle sizes make them effective against fungal diseases and insect pests. Finally, these properties also ensure that zeolites can act as carriers of different active substances, which makes it possible to use zeolites for slow-release applications. Based on the literature, a general overview is provided of the different basic properties of zeolites as promising products in crop protection.

  11. Preparation of a Versatile Bifunctional Zeolite for Targeted Imaging Applications

    PubMed Central

    Ndiege, Nicholas; Raidoo, Renugan; Schultz, Michael K.; Larsen, Sarah

    2011-01-01

    Bifunctional zeolite Y was prepared for use in targeted in vivo molecular imaging applications. The strategy involved functionalization of the external surface of zeolite Y with chloropropyltriethoxysilane followed by reaction with sodium azide to form azide-functionalized NaY, which is amenable to copper(1) catalyzed click chemistry. In this study, a model alkyne (4-pentyn-1-ol) was attached to the azide-terminated surface via click chemistry to demonstrate feasibility for attachment of molecular targeting vectors (e.g., peptides, aptamers) to the zeolite surface. The modified particle efficiently incorporates the imaging radioisotope gallium-68 (68Ga) into the pores of the azide-functionalized NaY zeolite to form a stable bifunctional molecular targeting vector. The result is a versatile “clickable” zeolite platform that can be tailored for future in vivo molecular targeting and imaging modalities. PMID:21306141

  12. Mineral resource of the month: natural and synthetic zeolites

    USGS Publications Warehouse

    Virta, R.

    2008-01-01

    Robert Virta, mineral commodity specialist for the U.S. Geological Survey, prepared the following information about the zeolite industry. Volcanic rocks containing natural zeolites — hydrated aluminosilicate minerals that contain alkaline and alkaline-earth metals — have been mined worldwide for more than 1,000 years for use as cements and building stone. For centuries, people thought natural zeolites occurred only in small amounts inside cavities of volcanic rock. But in the 1950s and early 1960s, large zeolite deposits were discovered in volcanic tuffs in the western United States and in marine tuffs in Italy and Japan. And since then, similar deposits have been found around the world, from Hungary to Cuba to New Zealand. The discovery of these larger deposits made commercial mining of natural zeolite possible.

  13. Design of composite photocatalyst of TiO2 and Y-zeolite for degradation of 2-propanol in the gas phase under UV and visible light irradiation.

    PubMed

    Kamegawa, Takashi; Ishiguro, Yasushi; Kido, Ryota; Yamashita, Hiromi

    2014-10-13

    Hydrophobic Y-zeolite (SiO2/Al2O3 = 810) and TiO2 composite photocatalysts were designed by using two different types of TiO2 precursors, i.e., titanium ammonium oxalate and ammonium hexafluorotitanate. The porous structure, surface property and state of TiO2 were investigated by various characterization techniques. By using an ammonium hexafluorotitanate as a precursor, hydrophobic modification of the Y-zeolite surface and realizing visible light sensitivity was successfully achieved at the same time after calcination at 773 K in the air. The prepared sample still maintained the porous structure of Y-zeolite and a large surface area. Highly crystalline anatase TiO2 was also formed on the Y-zeolite surface by the role of fluorine in the precursor. The usages of ammonium hexafluorotitanate were effective for the improvement of the photocatalytic performance of the composite in the degradation of 2-propanol in the gas phase under UV and visible light (λ > 420 nm) irradiation.

  14. Influence of NaA Zeolite Crystal Expansion/Contraction on Zeolite Membrane Separations

    SciTech Connect

    Sorenson, Stephanie G; Payzant, E Andrew; Gibbons, Will T; Soydas, Belma; Kita, Hidetoshi; Noble, Richard D; Falconer, John L.

    2011-01-01

    In-situ powder XRD measurements showed that the NaA zeolite unit cell contracts and expands upon adsorption, and these changes in zeolite crystal size correlate with permeation changes through NaA zeolite membranes. These membranes had high pervaporation selectivities, even though gas permeation was mainly through defects, as indicated by Knudsen selectivities for gases. At 300 K and a thermodynamic activity of 0.03, water contracted the NaA crystals by 0.22 vol%, and this contraction increased the helium flux through two NaA membranes by approximately 80%. Crystal contraction also increased the fluxes of i-butane during vapor permeation and i-propanol (IPA) during pervaporation (~ 0.03 wt% water). At activities above 0.07, water expanded NaA crystals and correspondingly decreased the membrane fluxes of helium, i-butane, and IPA. Similarly, methanol contracted NaA crystals by 0.05 vol% at an activity of 0.02, and this contraction slightly increased the helium and i-butane fluxes through a NaA membrane. Above an activity of 0.06, methanol expanded the crystals, and the fluxes of helium and i-butane through a NaA membrane decreased. The adsorbate-induced changes explain some pervaporation behavior reported by others, and they indicate that crystal expansion and contraction may increase or decrease zeolite NaA membrane selectivity by changing the defect sizes.

  15. Residual stresses and phase transformations in Ytterbium silicate environmental barrier coatings

    NASA Astrophysics Data System (ADS)

    Stolzenburg, Fabian

    Due to their high melting temperature, low density, and good thermomechanical stability, silicon-based ceramics (SiC, Si3N4) are some of the most promising materials systems for high temperature structural applications in gas turbine engines. However, their silica surface layer reacts with water vapor contained in combustion environments. The resulting hydroxide layer volatilizes, leading to component recession. Environmental barrier coatings (EBCs) have been developed to shield the substrate from degradation. Next generation coatings for silicon-based ceramics based on ytterbium silicates have shown a promising combination of very low and good thermomechanical properties. The focus of this thesis is threefold: In the first part, phase transformations in plasma sprayed ytterbium silicates were investigated. Plasma sprayed materials are known to contain large amounts of amorphous material. Phase changes during the conversion from amorphous to crystalline materials were investigated as they have been known to lead to failure in many coatings. The second part of this work focused on measuring residual stresses in multilayer EBCs using synchrotron X-ray diffraction (XRD). Strains were resolved spatially, with probe sizes as small as 20 um. Stresses were calculated using mechanical properties of ytterbium silicates, determined with in-situ loading and heating experiments. In-situ and ex-situ heating experiments allowed for the study of changes in stress states that occur in these EBC materials during heating and cooling cycles. Lastly, the interaction of ytterbium silicates with low-melting environmental calcium-magnesium-aluminosilicate (CMAS) glasses was studied. Synchrotron XRD was used to study the influence of CMAS on the stress state in the coating, X-ray computed tomography was used to provide 3D images of coatings, and EDS and TEM analysis were used to study the interactions at the CMAS/ytterbium silicate interface in detail.

  16. Radiation-induced silver agglomeration in molecular sieves: A comparison between A and X zeolites

    NASA Astrophysics Data System (ADS)

    Sadło, Jarosław; Waşowicz, Tomasz; Michalik, Jacek

    1995-06-01

    The stabilization conditions of silver atoms and clusters in hydrated and dehydrated AgNa-A and AgNa-X zeolites γ-irradiated at 77 K have been studied by ESR. It was found that silver agglomeration mechanisms in hydrated A and X zeolites are very similar and are controlled by the migration of silver atoms into the α-cages. In dehydrated zeolites agglomeration leads to completely different silver clusters in A and X zeolites. Small cationic clusters are stabilized in A zeolites and metallic clusters in X zeolites. Various factors affecting the agglomeration process in A and X zeolites are discussed.

  17. Nanocomposites of Poly(vinylidene Fluoride) with Organically Modified Silicate

    SciTech Connect

    Buckley,J.; Cebe, P.; Cherdack, D.; Crawford, J.; Ince, B.; Jenkins, M.; Pan, J.; Reveley, M.; Washington, N.; Wolchover, N.

    2006-01-01

    We report a study of the impact of cold crystallization on the structure of nanocomposites comprising poly(vinylidene fluoride) (PVDF) and Lucentite STN{trademark} organically modified silicate (OMS). Nanocomposites were prepared from solution over a very wide composition range, from 0.01 to 20% OMS by weight. Thermal preparation involved cold crystallization at 145 degC of quenched, compression-molded plaques. Static and real-time wide and small angle X-ray scattering (WAXS, SAXS), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC) were used to investigate the crystalline phase of PVDF. For OMS content greater than 0.50 wt%, WAXS studies show that that the silicate gallery spacing increases modestly in the nanocomposites compared to neat OMS film, indicating a level of polymer intercalation. Using Gaussian peak fitting of WAXS profiles, we determine that the composition range can be divided into three parts. First, for OMS greater than 0.5 wt%, alpha phase fraction, {phi}{sub {alpha}}, is insignificant ({phi}{sub {alpha}}{approx}0-0.01). Second, at the intermediate range, for OMS between 0.5 wt% down to 0.025 wt%, beta phase dominates and the beta fraction,{phi}{sub {beta}}, is related to alpha by {phi}{sub {beta}}>{phi}{sub {alpha}}. Third, below 0.025 wt% OMS, alpha dominates and {phi}{sub {alpha}}>{phi}{sub {beta}}. The ability of small amounts of OMS ({le}0.025 wt%) to cause beta crystal domination is remarkable. Overall, crystallinity index (from the ratio of WAXS crystal peak area to total area) ranges from about 0.36 to 0.51 after cold crystallization. Real-time WAXS studies during heating of initially cold crystallized nanocomposites show that there is no inter-conversion between the alpha and beta phase PVDF crystals, where these crystals coexist at room temperature. While all samples showed a strong SAXS Bragg peak, indicating existence of two-phase lamellar stacks, the sample containing predominantly beta phase

  18. [Infrared Spectra Characteristics of the Silicate Nickel Ores: A Comparison Study on Different Ore Samples from Indonesia and China].

    PubMed

    Yang, Meng-li; Fu, Wei; Wang, Bao-hua; Zhang, Ya-qian; Huang, Xiao-rong; Niu, Hu-jie

    2015-03-01

    The silicate nickel ores developed in the lateritic nickel deposit, from Kolonodale, Sulawesi Island, Indonesia, and Yuanjiang, Yunnan province, China, were selected for the present study. The X-ray diffraction and Fourier infrared spectra were used to analyze the mineralogical attribute of laterite nickel ores from two different places. The results show that these two different silicate nickel ores have unique infrared spectra characteristics individually, which contributes to the ore classification. The silicate nickel ores from Kolonodale deposit, Indonesia, can be classified as the serpentine type, the montmorillonite + serpentine type, and the garnierite type. While, the silicate nickel ores from Yuanjiang deposit, China, can be classified as the serpentine type and the talc + serpentine type. Moreover, the mineral crystallinity of Yuanjiang nickel ores is generally better than Kolonodale nickel ores. According to the advantage of infrared absorption spectra in distinguishing mineral polytypes, it can be determined that lizardite is the main mineral type in the silicate nickel ores of the two deposits, and there is no obvious evidence of chrysotile and antigorite's existence. The characteristic of infrared absorption spectra also shows that frequency change of OH libration indicates Ni (Fe) replacing Mg in the serpentine type nickel-bearing mineral, that is, OH libration of serpentine moves to higher frequency, with the proportion of Ni (Fe) replacing Mg increasing. PMID:26117869

  19. [Infrared Spectra Characteristics of the Silicate Nickel Ores: A Comparison Study on Different Ore Samples from Indonesia and China].

    PubMed

    Yang, Meng-li; Fu, Wei; Wang, Bao-hua; Zhang, Ya-qian; Huang, Xiao-rong; Niu, Hu-jie

    2015-03-01

    The silicate nickel ores developed in the lateritic nickel deposit, from Kolonodale, Sulawesi Island, Indonesia, and Yuanjiang, Yunnan province, China, were selected for the present study. The X-ray diffraction and Fourier infrared spectra were used to analyze the mineralogical attribute of laterite nickel ores from two different places. The results show that these two different silicate nickel ores have unique infrared spectra characteristics individually, which contributes to the ore classification. The silicate nickel ores from Kolonodale deposit, Indonesia, can be classified as the serpentine type, the montmorillonite + serpentine type, and the garnierite type. While, the silicate nickel ores from Yuanjiang deposit, China, can be classified as the serpentine type and the talc + serpentine type. Moreover, the mineral crystallinity of Yuanjiang nickel ores is generally better than Kolonodale nickel ores. According to the advantage of infrared absorption spectra in distinguishing mineral polytypes, it can be determined that lizardite is the main mineral type in the silicate nickel ores of the two deposits, and there is no obvious evidence of chrysotile and antigorite's existence. The characteristic of infrared absorption spectra also shows that frequency change of OH libration indicates Ni (Fe) replacing Mg in the serpentine type nickel-bearing mineral, that is, OH libration of serpentine moves to higher frequency, with the proportion of Ni (Fe) replacing Mg increasing.

  20. Oxidative regeneration of toluene-saturated natural zeolite by gaseous ozone: the influence of zeolite chemical surface characteristics.

    PubMed

    Alejandro, Serguei; Valdés, Héctor; Manéro, Marie-Hélène; Zaror, Claudio A

    2014-06-15

    In this study, the effect of zeolite chemical surface characteristics on the oxidative regeneration of toluene saturated-zeolite samples is investigated. A Chilean natural zeolite (53% clinoptilolite, 40% mordenite and 7% quartz) was chemically modified by acid treatment with hydrochloric acid and by ion-exchange with ammonium sulphate. Thermal pre-treatments at 623 and 823K were applied and six zeolite samples with different chemical surface characteristics were generated. Chemical modification of natural zeolite followed by thermal out-gassing allows distinguishing the role of acidic surface sites on the regeneration of exhausted zeolites. An increase in Brønsted acid sites on zeolite surface is observed as a result of ammonium-exchange treatment followed by thermal treatment at 623K, thus increasing the adsorption capacity toward toluene. High ozone consumption could be associated to a high content of Lewis acid sites, since these could decompose ozone into atomic active oxygen species. Then, surface oxidation reactions could take part among adsorbed toluene at Brønsted acid sites and surface atomic oxygen species, reducing the amount of adsorbed toluene after the regenerative oxidation with ozone. Experimental results show that the presence of adsorbed oxidation by-products has a negative impact on the recovery of zeolite adsorption capacity.

  1. The crystalline revolution :ISO's finding opens a new research field, "astro-mineralogy"

    NASA Astrophysics Data System (ADS)

    2000-02-01

    Silicate minerals were known to be a main component of dust in space, but detecting them in a crystallised state has been a surprise. It allows the identification of precise silicates in astronomical objects, which will open "a totally new field in astronomy: astro-mineralogy. This is the crystalline revolution", said the author, Dutch astronomer Rens Waters of Amsterdam university. "It's really fantastic, this possibility of identifying the silicates. Before ISO everybody thought that all silicates in space were amorphous, without a well-ordered internal structure; that means you cannot differentiate among the many different silicates existing. Now we can try to identify them and track their presence in different regions. A whole new research field is starting", said Rens Waters, who brought to the press conference samples of several terrestrial crystalline silicates: olivine and pyroxene, the most common silicates on Earth. Crystals give key clues about the physical conditions and evolutionary history of crystal-bearing objects. The precise mechanisms for crystal-making are now being researched now very actively in the laboratories, although some working-hypotheses are already being used. For instance, crystals can be made by heating the material to temperatures above 1 300 degrees Centigrade and then cooling it down slowly. Those found so far by ISO are at -170 degrees Centigrade, both in stellar envelopes and in protoplanetary discs. In the case of the old stars -red giant stars, where crystals are found to account for as much as 20% of all the surrounding dust, astronomers think that that the high temperatures near the star triggered the crystallisation of the silicates. In the protoplanetary discs some experts postulate that electric shocks - like lightning flashes - heated the dust, which cooled afterwards. "The crystals detected by ISO in these discs have a size of about a thousandth of a millimetre. They collide with each other, forming bigger and bigger

  2. Investigation on the effect of zeolite precursor on the formation process of MCM-41 containing zeolite Y building units

    NASA Astrophysics Data System (ADS)

    Li, Peng; Xiong, Guang; Liu, Liping; Wang, Longlong

    2013-04-01

    The formation process of MCM-41 containing zeolite Y building units has been investigated by UV Raman spectroscopy, 29Si and 27Al MAS NMR spectroscopy, X-ray diffraction (XRD), N2 adsorption and electron microscopy (SEM and TEM). It is found that the precursor containing zeolite Y secondary building units promotes the formation of a metastable mesopore structure just after mixing the zeolite precursors with CTAB. In contrast, the low-polymerized aluminosilicates and well-crystallized zeolite crystals cannot be assembled with CTAB at this stage. The result supports that the zeolite secondary building units should promote to the formation of the mesopore wall. This has been ascribed to its high anionic charge density as well as the appropriate multidentate coordination. Lowering down the pH value to 9.3 facilitates the further polymerization of the aluminosilicate species to build up a stable mesoporous phase.

  3. Molybdenum Valence in Basaltic Silicate Melts

    NASA Technical Reports Server (NTRS)

    Danielson, L. R.; Righter, K.; Newville, M.; Sutton, S.; Pando, K.

    2010-01-01

    The moderately siderophile element molybdenum has been used as an indicator in planetary differentiation processes, and is particularly relevant to core formation [for example, 1-6]. However, models that apply experimental data to an equilibrium differentiation scenario infer the oxidation state of molybdenum from solubility data or from multivariable coefficients from metal-silicate partitioning data [1,3,7]. Partitioning behavior of molybdenum, a multivalent element with a transition near the J02 of interest for core formation (IW-2) will be sensitive to changes in JO2 of the system and silicate melt structure. In a silicate melt, Mo can occur in either 4+ or 6+ valence state, and Mo6+ can be either octahedrally or tetrahedrally coordinated. Here we present first XANES measurements of Mo valence in basaltic run products at a range of P, T, and JO2 and further quantify the valence transition of Mo.

  4. Core formation in silicate bodies

    NASA Astrophysics Data System (ADS)

    Nimmo, F.; O'Brien, D. P.; Kleine, T.

    2008-12-01

    Differentiation of a body into a metallic core and silicate mantle occurs most efficiently if temperatures are high enough to allow at least the metal to melt [1], and is enhanced if matrix deformation occurs [2]. Elevated temperatures may occur due to either decay of short-lived radio-isotopes, or gravitational energy release during accretion [3]. For bodies smaller than the Moon, core formation happens primarily due to radioactive decay. The Hf-W isotopic system may be used to date core formation; cores in some iron meteorites and the eucrite parent body (probably Vesta) formed within 1 My and 1-4~My of solar system formation, respectively [4]. These formation times are early enough to ensure widespread melting and differentiation by 26Al decay. Incorporation of Fe60 into the core, together with rapid early mantle solidification and cooling, may have driven early dynamo activity on some bodies [5]. Iron meteorites are typically depleted in sulphur relative to chondrites, for unknown reasons [6]. This depletion contrasts with the apparently higher sulphur contents of cores in larger planetary bodies, such as Mars [7], and also has a significant effect on the timing of core solidification. For bodies of Moon-size and larger, gravitational energy released during accretion is probably the primary cause of core formation [3]. The final stages of accretion involve large, stochastic collisions [8] between objects which are already differentiated. During each collision, the metallic cores of the colliding objects merge on timescales of a few hours [9]. Each collision will reset the Hf-W isotopic signature of both mantle and core, depending on the degree to which the impactor core re-equilibrates with the mantle of the target [10]. The re-equilibration efficiency depends mainly on the degree to which the impactor emulsifies [11], which is very uncertain. Results from N-body simulations [8,12] suggest that significant degrees of re- equilibration are required [4,10]. Re

  5. [Zeolite catalysis in conversion of cellulosics

    SciTech Connect

    Tsao, G.T.

    1992-01-01

    To transform biomass into fermentable substrate for yeast, we are using zeolites instead of enzymes to catalyze the two bottleneck reactions in biomass conversion, xylose isomerization and ceuobiose hydrolysis. The experimental results on these reactions carried out over various zeolites and other catalysts are presented herein. The advantages and disadvantages of using these catalysts over enzymes are also discussed. Heterogeneous solid catalysts other than zeolites has been employed for cellobiose-to-glucose hydrolysis. The size and shape selectivity that makes zeoutes unique for some reactions can add diffusional hindrance. We have spent some time screening various known solid acidic catalysts. We report that a class of cationic ion exchange resins in the acidified form (e.g. Amberlite) has worked well as an acidic catalyst in hydrolyzing cellobiose to glucose. Our experimental results, together with those obtained from a homogeneous acid catalyst (e.g. sulfuric acid) for comparison are provided. Having succeeded in finding an alternative solid acid catalyst for hydrolysis, we explored other solid resin or other homogeneous but non-enzyme catalyst to carry out the xylose-to-xylulose isomerization. A fairly extensive search has been made. We explored the use of sodium aluminates in the homogeneous phase isomerization of glucose to fructose and obtained a very high conversion of glucose to fructose with the final mixture containing 85% of fructose instead of the common 45%. Fructose apparently complexes with aluminates, and its equilibrium concentration is shifted to considerably higher values than permitted by simple glucose/fructose equilibrium. We have recently found a number of catalysts capable of promoting isomerization between aldoses and ketoses. One solid resin, known as polyvinyl pyridine (PVP), is able to convert xylose to xylulose at a pH below 7. Our usage of alternative isomerization catalysts, including PVP, are described.

  6. [Zeolite catalysis in conversion of cellulosics

    SciTech Connect

    Tsao, G.T.

    1992-12-31

    To transform biomass into fermentable substrate for yeast, we are using zeolites instead of enzymes to catalyze the two bottleneck reactions in biomass conversion, xylose isomerization and ceuobiose hydrolysis. The experimental results on these reactions carried out over various zeolites and other catalysts are presented herein. The advantages and disadvantages of using these catalysts over enzymes are also discussed. Heterogeneous solid catalysts other than zeolites has been employed for cellobiose-to-glucose hydrolysis. The size and shape selectivity that makes zeoutes unique for some reactions can add diffusional hindrance. We have spent some time screening various known solid acidic catalysts. We report that a class of cationic ion exchange resins in the acidified form (e.g. Amberlite) has worked well as an acidic catalyst in hydrolyzing cellobiose to glucose. Our experimental results, together with those obtained from a homogeneous acid catalyst (e.g. sulfuric acid) for comparison are provided. Having succeeded in finding an alternative solid acid catalyst for hydrolysis, we explored other solid resin or other homogeneous but non-enzyme catalyst to carry out the xylose-to-xylulose isomerization. A fairly extensive search has been made. We explored the use of sodium aluminates in the homogeneous phase isomerization of glucose to fructose and obtained a very high conversion of glucose to fructose with the final mixture containing 85% of fructose instead of the common 45%. Fructose apparently complexes with aluminates, and its equilibrium concentration is shifted to considerably higher values than permitted by simple glucose/fructose equilibrium. We have recently found a number of catalysts capable of promoting isomerization between aldoses and ketoses. One solid resin, known as polyvinyl pyridine (PVP), is able to convert xylose to xylulose at a pH below 7. Our usage of alternative isomerization catalysts, including PVP, are described.

  7. Characteristics of Lead Sorption by Zeolite Minerals

    NASA Astrophysics Data System (ADS)

    Al-Sewailem, M. S.

    Lead adsorption behavior was investigated using four Zeolite minerals (clinoptilolite, analcime, phillipsite and chabazite). The used Pb2+ concentrations were 0, 0.1, 0.5, 1.0, 2.0, 3.0 and 5 µmol mL-1. Results indicated that Pb2+ sorption followed the Langmuir adsorption isotherm, but over limited concentration ranges for clinoptilolite and analcime. The bindg energy (Kd) reached, 2.400 and 0.875 g L-1 for phillipsite and chabazite, respectively. The maximum adsorption capacity for such minerals reached 208.33 and 204.08 mg g-1 with correlation coefficient (R2) reached, 0.997 and 0.995, respectively. Meanwhile, two stages for Pb2+adsorption were observed with clinoptilolite and analcime in the low and high concentrations of the applied Pb2+. Data also was applicable to the Freundlich adsorption isotherm over the used entire Pb2+ concentration ranges. The binding energy (n) reached, 1.014, 1.005, 1.001 and 1.001 g L-1 for clinoptilolite, analcime, phillipsite and chabazite, respectively. However, the b values (maximum adsorption capacity) reached 202.582, 201.651, 207.062 and 206.871 mg g-1 with correlation coefficient (R2) nearly one for all studying minerals, respectively. Desorption data indicated that most of the sorbed Pb2+ was extractedin the 1st extraction following the adsorption experiment. The ability of the used zeolite minerals to retain Pb2+ was high and there were differences between the studied minerals in sorption of Pb2+. In conclusion, data eliminated that, zeolite minerals especially, philipsite and chabazite, could be successfully used as packing material in subsurface reactive barriers intercepting ground water plumes and for fixed bed reactors designed to remove Pb2+ from industrial wastewater.

  8. Statistics of silicate units in binary glasses

    NASA Astrophysics Data System (ADS)

    Gaddam, Anuraag; Montagne, Lionel; Ferreira, José M. F.

    2016-09-01

    In this paper, we derive a new model to determine the distribution of silicate units in binary glasses (or liquids). The model is based on statistical mechanics and assumes grand canonical ensemble of silicate units which exchange energy and network modifiers from the reservoir. This model complements experimental techniques, which measure short range order in glasses such as nuclear magnetic resonance (NMR) spectroscopy. The model has potential in calculating the amounts of liquid-liquid phase segregation and crystal nucleation, and it can be easily extended to more complicated compositions. The structural relaxation of the glass as probed by NMR spectroscopy is also reported, where the model could find its usefulness.

  9. Imperfect wetting of hydrogen in zeolite

    SciTech Connect

    Sullivan, N.S.; Rall, M.

    1995-11-01

    We have considered the theoretical dependencies of the amount of supercooling of liquid hydrogen as a function of pore size for constrained geometries in order to compare the different mechanisms for supercooling that can be observed: notably the inhibition of nucleation in small geometries and the use of surfaces for which there is imperfect wetting. Analysis of the dependence of the observed supercooling reported elsewhere for molecular hydrogen and hydrogen deuteride on the pore size in zeolites supports the view that imperfect wetting occurs for small pores that have rough surfaces and dimension less than approximately 10{angstrom}.

  10. Design and characterization of chitosan/zeolite composite films--Effect of zeolite type and zeolite dose on the film properties.

    PubMed

    Barbosa, Gustavo P; Debone, Henrique S; Severino, Patrícia; Souto, Eliana B; da Silva, Classius F

    2016-03-01

    Chitosan films can be used as wound dressings for the treatment of chronic wounds and severe burns. The antimicrobial properties of these films may be enhanced by the addition of silver. Despite the antimicrobial activity of silver, several studies have reported the cytotoxicity as a factor limiting its biomedical applications. This problem may, however, be circumvented by the provision of sustained release of silver. Silver zeolites can be used as drug delivery platforms to extend the release of silver. The objective of this study was to evaluate the addition of clinoptilolite and A-type zeolites in chitosan films. Sodium zeolites were initially subjected to ion-exchange in a batch reactor. Films were prepared by casting technique using a 2% w/w chitosan solution and two zeolite doses (0.1 or 0.2% w/w). Films were characterized by thermal analysis, color analysis, scanning electron microscopy, X-ray diffraction, and water vapor permeation. The results showed that films present potential for application as dressing. The water vapor permeability is one of the main properties in wound dressings, the best results were obtained for A-type zeolite/chitosan films, which presented a brief reduction of this property in relation to zeolite-free chitosan film. On the other hand, the films containing clinoptilolite showed lower water vapor permeation, which may be also explained by the best distribution of the particles into the polymer which also promoted greater thermal resistance.

  11. Role of subcolloidal (nanosized) precursor species in the early stage of the crystallization of zeolites in heterogeneous systems.

    PubMed

    Ren, Nan; Bosnar, Sanja; Bronić, Josip; Dutour Sikirić, Maja; Mišić, Tea; Svetličić, Vesna; Mao, Jian-Jiang; Antonić Jelić, Tatjana; Hadžija, Mirko; Subotić, Boris

    2014-07-22

    A critical analysis was carried out for the purpose of understanding the role of subcolloidal (nanosized) (alumino)silicate precursor species in the early stage of crystallization of zeolites in heterogeneous systems (hydrogels). The formation and evolution of these subcolloidal species in both the solid and the liquid phases were investigated by various experimental methods such a scanning electron microscopy (SEM, FE-SEM), transmission electron microscopy, atomic force microscopy, particle size analysis, pH measurement, atomic absorption spectroscopy, and dynamic light scattering, after careful separation of intermediates from reaction mixture by two-step centrifugation treatment. The results revealed that a chain of processes (i) the formation of low-molecular-weight (LMW) silicate species, by dissolution of Al-enriched amorphous silica, and their aggregation into about 3 nm sized primary precursor species (PPSs), (ii) the formation of larger (∼3 to ∼15 nm sized) silicate precursor species (LSPSs) by a rapid aggregation/coalescence of PPSs, (iii) the formation of "gel" (primary amorphous precursor) by a random aggregation of LSPSs at room temperature, and (iv) the formation of the worm-like particles (secondary amorphous precursor) occurred in the solid phase during heating of the reaction mixture (hydrogel) from room temperature to 170 °C. It is interesting that almost the same processes occur in the liquid phase but with decreased rate according to the relative low concentration of LMW silicate species. With the above described findings, it is highly expected that the manipulation of crystallization pathway through controlling the formation/evolution of precursor species in the initial stage of the process can be achieved. PMID:24960175

  12. Microcalorimetric study of silica- and zeolite-supported platinum catalysts

    SciTech Connect

    Sharma, S.B.; Dumesic, J.A. ); Miller, J.T. )

    1994-07-01

    Microcalorimetric measurements of the differential heats of hydrogen and carbon monoxide adsorption versus adsorbate coverate were made at 403 K for platinum supported on silica, magnesia/alumina, L-zeolite, Y-zeolite, and ZSM-5. The differential heats at zero coverage for hydrogen and carbon monoxide adsorption were 90 and 140 kJ/mol, respectively, for platinum supported on silica and nonacidic zeolites. The differential heats were large by approximately 20 kJ/mol for hydrogen and carbon monoxide adsorption on platinum particles supported on basis supports such as potassium/silica, magnesia/alumina, and zeolites containing basic cations (K[sup +], Ba[sup 2+]) exchanged in excess of the zeolite framework aluminum content. The microcalorimetric results suggest that the high paraffin aromatization activity and selectivity observed for L-zeolite-supported platinum catalysts do not appear to be caused solely by changes in the adsorptive properties of the cluster-size platinum particles located within the zeolite. 35 refs., 10 figs., 2 tabs.

  13. Zeolite Crystal Growth (ZCG) Flight on USML-2

    NASA Technical Reports Server (NTRS)

    Sacco, Albert, Jr.; Bac, Nurcan; Warzywoda, Juliusz; Guray, Ipek; Marceau, Michelle; Sacco, Teran L.; Whalen, Leah M.

    1997-01-01

    The extensive use of zeolites and their impact on the world's economy has resulted in many efforts to characterize their structure, and improve the knowledge base for nucleation and growth of these crystals. The zeolite crystal growth (ZCG) experiment on USML-2 aimed to enhance the understanding of nucleation and growth of zeolite crystals, while attempting to provide a means of controlling the defect concentration in microgravity. Zeolites A, X, Beta, and Silicalite were grown during the 16 day - USML-2 mission. The solutions where the nucleation event was controlled yielded larger and more uniform crystals of better morphology and purity than their terrestrial/control counterparts. The external surfaces of zeolite A, X, and Silicalite crystals grown in microgravity were smoother (lower surface roughness) than their terrestrial controls. Catalytic studies with zeolite Beta indicate that crystals grown in space exhibit a lower number of Lewis acid sites located in micropores. This suggests fewer structural defects for crystals grown in microgravity. Transmission electron micrographs (TEM) of zeolite Beta crystals also show that crystals grown in microgravity were free of line defects while terrestrial/controls had substantial defects.

  14. Distribution of metal and adsorbed guest species in zeolites

    SciTech Connect

    Chmelka, B.F.

    1989-12-01

    Because of their high internal surface areas and molecular-size cavity dimensions, zeolites are used widely as catalysts, shape- selective supports, or adsorbents in a variety of important chemical processes. For metal-catalyzed reactions, active metal species must be dispersed to sites within the zeolite pores that are accessible to diffusing reactant molecules. The distribution of the metal, together with transport and adsorption of reactant molecules in zeolite powders, are crucial to ultimate catalyst performance. The nature of the metal or adsorbed guest distribution is known, however, to be dramatically dependent upon preparatory conditions. Our objective is to understand, at the molecular level, how preparatory treatments influence the distribution of guest species in zeolites, in order that macroscopic adsorption and reaction properties of these materials may be better understood. The sensitivity of xenon to its adsorption environment makes {sup 129}Xe NMR spectroscopy an important diagnostic probe of metal clustering and adsorbate distribution processes in zeolites. The utility of {sup 129}Xe NMR depends on the mobility of the xenon atoms within the zeolite-guest system, together with the length scale of the sample heterogeneity being studied. In large pore zeolites containing dispersed guest species, such as Pt--NaY, {sup 129}Xe NMR is insensitive to fine structural details at room temperature.

  15. Copper cation removal in an electrokinetic cell containing zeolite.

    PubMed

    Elsayed-Ali, Omar H; Abdel-Fattah, Tarek; Elsayed-Ali, Hani E

    2011-01-30

    Zeolites are used in environmental remediation of soil or water to immobilize or remove toxic materials by cation exchange. An experiment was conducted to test the use a low electric field to direct the toxic cations towards the zeolite. An electrokinetic cell was constructed using carbon electrodes. Synthetic Linde Type A (LTA) zeolite was placed in the cell. Copper(II) chloride dissolved in water was used as a contaminant. The Cu(2+) concentration was measured for ten hours with and without an applied electric field. The removal of the Cu(2+) ions was accelerated by the applied field in the first two hours. For longer time, the electric field did not improve the removal rate of the Cu(2+) ions. The presence of zeolite and applied electric field complicates the chemistry near the cathode and causes precipitation of Cu(2+) ions as copper oxide on the surface of the zeolite. With increased electric field the zeolite farther away from the cathode had little cation exchange due to the higher drift velocity of the Cu(2+) ions. The results also show that, in the LTA Zeolite A pellets, the cation exchange of Cu is limited to a shell of several tens of micrometers. PMID:21109348

  16. Microfabrics in Siliceous Hotsprings: Yellowstone National Park, Wyoming

    NASA Technical Reports Server (NTRS)

    Guidry, S. A.; Chafetz, H. S.; Westall, F.

    2001-01-01

    Microfabrics shed light on the mechanisms governing siliceous sinter precipitation, the profound effects of microorganisms, as well as a conventional facies model for siliceous hotsprings. Additional information is contained in the original extended abstract.

  17. Reactive oxygen species mediated DNA damage in human lung alveolar epithelial (A549) cells from exposure to non-cytotoxic MFI-type zeolite nanoparticles.

    PubMed

    Bhattacharya, Kunal; Naha, Pratap C; Naydenova, Izabela; Mintova, Svetlana; Byrne, Hugh J

    2012-12-17

    Increasing utilization of engineered nanoparticles in the field of electronics and biomedical applications demands an assessment of risk associated with deliberate or accidental exposure. Metal based nanoparticles are potentially most important of all the nanoparticles in terms of health risks. Microporous alumino-silicates and pure silicates named as zeolites and zeo-type materials with variety of structures, chemical compositions, particle sizes and morphologies have a significant number of industrial uses such as in catalysis, sorption and ion-exchange processes. In particular, the nanosized particles due to their unique properties are used in hybrid organic-inorganic materials for photography, photonics, electronics, labeling, imaging, and sensing. The aim of the current study is to investigate pure silica MFI-type zeolites nanoparticles with sizes of 50nm and 100nm (samples MFI-50 and MFI-100) under suspended conditions and their toxicological effects on human lung alveolar (A549) cells under in vitro conditions. Live cell imaging showed that the nanoparticles precipitated from the colloidal suspension of cell culture media as large agglomerates, coming in contact with the cell surface through sedimentation. A cellular proliferative capacity test showed the zeolite nanoparticles to exhibit no significant cytotoxicity below a concentration of 100μg/ml. However, both the MFI-50 and MFI-100 nanoparticles induced high intracellular reactive oxygen species (ROS) generation and elevated mitochondrial membrane potential in the A549 cells over the measured time period of 12h and at concentrations up to ≤50μg/ml. DNA fragmentation analysis using the comet assay showed that the MFI-50 and MFI-100 nanoparticles cause genotoxicity in a concentration dependent manner. Furthermore, the rate at which maximum genomic damage was caused by MFI-100 nanoparticles in the A549 cells was found to be high as compared to the MFI-50 nanoparticles. However, the damage caused by the

  18. Thermal conductivity of pure silica MEL and MFI zeolite thin films

    NASA Astrophysics Data System (ADS)

    Coquil, Thomas; Lew, Christopher M.; Yan, Yushan; Pilon, Laurent

    2010-08-01

    This paper reports the room temperature cross-plane thermal conductivity of pure silica zeolite (PSZ) MEL and MFI thin films. PSZ MEL thin films were prepared by spin coating a suspension of MEL nanoparticles in 1-butanol solution onto silicon substrates followed by calcination and vapor-phase silylation with trimethylchlorosilane. The mass fraction of nanoparticles within the suspension varied from 16% to 55%. This was achieved by varying the crystallization time of the suspension. The thin films consisted of crystalline MEL nanoparticles embedded in a nonuniform and highly porous silica matrix. They featured porosity, relative crystallinity, and MEL nanoparticles size ranging from 40% to 59%, 23% to 47% and 55 nm to 80 nm, respectively. PSZ MFI thin films were made by in situ crystallization, were b-oriented, fully crystalline, and had a 33% porosity. Thermal conductivity of these PSZ thin films was measured at room temperature using the 3ω method. The cross-plane thermal conductivity of the MEL thin films remained nearly unchanged around 1.02±0.10 W m-1 K-1 despite increases in (i) relative crystallinity, (ii) MEL nanoparticle size, and (iii) yield caused by longer nanoparticle crystallization time. Indeed, the effects of these parameters on the thermal conductivity were compensated by the simultaneous increase in porosity. PSZ MFI thin films were found to have similar thermal conductivity as MEL thin films even though they had smaller porosity. Finally, the average thermal conductivity of the PSZ films was three to five times larger than that reported for amorphous sol-gel mesoporous silica thin films with similar porosity and dielectric constant.

  19. Europium-doped yttrium silicate nanophosphors prepared by flame synthesis

    SciTech Connect

    Qin Xiao . E-mail: xqin@princeton.edu; Ju Yiguang; Bernhard, Stefan; Yao Nan

    2007-08-07

    Europium-doped yttrium silicate (Y{sub 2}SiO{sub 5}:Eu{sup 3+}) nanophosphors were successfully synthesized by flame spray pyrolysis method. The effect of silicon concentration on the crystal structure and morphology of the Y{sub 2}SiO{sub 5}:Eu{sup 3+} phosphors were investigated. As-prepared phosphor consists of spherical nanoparticles with filled morphology, high crystallinity, narrow size distribution, and intense photoluminescence. The crystal structure and photoluminescence intensity of Y{sub 2}SiO{sub 5}:Eu{sup 3+} nanophosphors are strongly affected by the ratio of silicon to yttrium in the precursor solution, and the maximum photoluminescence intensity is obtained from particles prepared from the silicon to yttrium ratio of 1.25. A concentration quenching limit is observed at 30 mol% Eu of yttrium. The photoluminescence intensity also increases with the increase of the concentration of precursor solution. This work demonstrates the advantages of flame spray pyrolysis method for the preparation of multi-component nanophosphor, which can be found potential application in lamp and display industries.

  20. Mechanical behavior of a composite interface: Calcium-silicate-hydrates

    NASA Astrophysics Data System (ADS)

    Palkovic, Steven D.; Moeini, Sina; Yip, Sidney; Büyüköztürk, Oral

    2015-07-01

    The generalized stacking fault (GSF) is a conceptual procedure historically used to assess shear behavior of defect-free crystalline structures through molecular dynamics or density functional theory simulations. We apply the GSF technique to the spatially and chemically complex quasi-layered structure of calcium-silicate-hydrates (C-S-H), the fundamental nanoscale binder within cementitious materials. A failure plane is enforced to calculate the shear traction-displacement response along a composite interface containing highly confined water molecules, hydroxyl groups, and calcium ions. GSF simulations are compared with affine (homogeneous) shear simulations, which allow strain to localize naturally in response to the local atomic environment. Comparison of strength and deformation behavior for the two loading methods shows the composite interface controls bulk shear deformation. Both models indicate the maximum shear strength of C-S-H exhibits a normal-stress dependency typical of cohesive-frictional materials. These findings suggest the applicability of GSF techniques to inhomogeneous structures and bonding environments, including other layered systems such as biological materials containing organic and inorganic interfaces.

  1. Mechanical behavior of a composite interface: Calcium-silicate-hydrates

    SciTech Connect

    Palkovic, Steven D.; Moeini, Sina; Büyüköztürk, Oral; Yip, Sidney

    2015-07-21

    The generalized stacking fault (GSF) is a conceptual procedure historically used to assess shear behavior of defect-free crystalline structures through molecular dynamics or density functional theory simulations. We apply the GSF technique to the spatially and chemically complex quasi-layered structure of calcium-silicate-hydrates (C-S-H), the fundamental nanoscale binder within cementitious materials. A failure plane is enforced to calculate the shear traction-displacement response along a composite interface containing highly confined water molecules, hydroxyl groups, and calcium ions. GSF simulations are compared with affine (homogeneous) shear simulations, which allow strain to localize naturally in response to the local atomic environment. Comparison of strength and deformation behavior for the two loading methods shows the composite interface controls bulk shear deformation. Both models indicate the maximum shear strength of C-S-H exhibits a normal-stress dependency typical of cohesive-frictional materials. These findings suggest the applicability of GSF techniques to inhomogeneous structures and bonding environments, including other layered systems such as biological materials containing organic and inorganic interfaces.

  2. Dynamic Fatigue of a Titanium Silicate Glass

    NASA Technical Reports Server (NTRS)

    Tucker, Dennis S.; Nettles, Alan T.; Cagle, Holly A.; Smith, W. Scott (Technical Monitor)

    2002-01-01

    A dynamic fatigue study was performed on a Titanium Silicate Glass in order to assess its susceptibility to delayed failure. Fracture mechanics techniques were used to analyze the results for the purpose of making lifetime predictions for optical elements made from this material. The material has reasonably good resistance (N=23 to stress corrosion in ambient conditions).

  3. 21 CFR 172.410 - Calcium silicate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... CONSUMPTION (CONTINUED) FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Anticaking... agent in food in an amount not in excess of that reasonably required to produce its intended effect. (b... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Calcium silicate. 172.410 Section 172.410 Food...

  4. 21 CFR 573.260 - Calcium silicate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Calcium silicate. 573.260 Section 573.260 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS FOOD ADDITIVES PERMITTED IN FEED AND DRINKING WATER OF ANIMALS Food...

  5. 21 CFR 573.260 - Calcium silicate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Calcium silicate. 573.260 Section 573.260 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS FOOD ADDITIVES PERMITTED IN FEED AND DRINKING WATER OF ANIMALS Food...

  6. 21 CFR 573.260 - Calcium silicate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Calcium silicate. 573.260 Section 573.260 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS FOOD ADDITIVES PERMITTED IN FEED AND DRINKING WATER OF ANIMALS Food...

  7. 21 CFR 573.260 - Calcium silicate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Calcium silicate. 573.260 Section 573.260 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS FOOD ADDITIVES PERMITTED IN FEED AND DRINKING WATER OF ANIMALS Food...

  8. 21 CFR 573.260 - Calcium silicate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Calcium silicate. 573.260 Section 573.260 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS FOOD ADDITIVES PERMITTED IN FEED AND DRINKING WATER OF ANIMALS Food...

  9. Chemically bonded phospho-silicate ceramics

    DOEpatents

    Wagh, Arun S.; Jeong, Seung Y.; Lohan, Dirk; Elizabeth, Anne

    2003-01-01

    A chemically bonded phospho-silicate ceramic formed by chemically reacting a monovalent alkali metal phosphate (or ammonium hydrogen phosphate) and a sparsely soluble oxide, with a sparsely soluble silicate in an aqueous solution. The monovalent alkali metal phosphate (or ammonium hydrogen phosphate) and sparsely soluble oxide are both in powder form and combined in a stochiometric molar ratio range of (0.5-1.5):1 to form a binder powder. Similarly, the sparsely soluble silicate is also in powder form and mixed with the binder powder to form a mixture. Water is added to the mixture to form a slurry. The water comprises 50% by weight of the powder mixture in said slurry. The slurry is allowed to harden. The resulting chemically bonded phospho-silicate ceramic exhibits high flexural strength, high compression strength, low porosity and permeability to water, has a definable and bio-compatible chemical composition, and is readily and easily colored to almost any desired shade or hue.

  10. Structure and properties of metal-exchanged zeolites studied using gradient-corrected and hybrid functionals. I. Structure and energetics

    NASA Astrophysics Data System (ADS)

    Göltl, Florian; Hafner, Jürgen

    2012-02-01

    The structural and energetic properties of purely siliceous, proton-, and Cu- and Co-exchanged chabazite have been studied using periodic density-functional (DFT) calculations with both conventional gradient-corrected exchange-correlation functionals and hybrid functionals mixing exact (i.e., Hartree-Fock) and DFT exchange. Spin-polarized and fixed-moment calculations have been performed to determine the equilibrium and excited spin-configurations of the metal-exchanged chabazites. For the purely siliceous chabazite, hybrid functionals predict a slightly more accurate cell volume and lattice geometry. For isolated Al/Si substitution sites, gradient-corrected functionals predict that the lattice distortion induced by the substitution preserves the local tetrahedral symmetry, whereas hybrid functionals lead to a distorted Al coordination with two short and two long Al-O bonds. Hybrid functionals yield a stronger cation-framework binding that conventional functionals in metal-exchanged zeolites, they favor shorter cation-oxygen bonds and eventually also a higher coordination of the cation. Both types of functionals predict the same spin in the ground-state. The structural optimization of the excited spin-states shows that the formation of a high-spin configuration leads to a strong lattice relaxation and a weaker cation-framework bonding. For both Cu- and Co-exchanged chabazite, the prediction of a preferred location of the cation in a six-membered ring of the zeolite agrees with experiment, but the energy differences between possible cation locations and the lattice distortion induced by the Al/Si substitution and the bonding of the cation depends quite significantly on the choice of the functional. All functionals predict similar energy differences for excited spin states. Spin-excitations are shown to be accompanied by significant changes in the cation coordination, which are more pronounced with hybrid functionals. The consequences of electronic spectra and

  11. 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.

  12. 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.

  13. Gallium Zeolites for Light Paraffin Aromatization

    SciTech Connect

    Price, G.L.; Dooley, K.M.

    1999-02-10

    The primary original goal of this project was to investigate the active state of gallium-containing MFI catalysts for light paraffin aromatization, in particular the state of gallium in the active material. Our original hypothesis was that the most active and selective materials were those which contained gallium zeolitic cations, and that previously reported conditions for the activation of gallium-containing catalysts served to create these active centers. We believed that in high silica materials such as MFI, ion-exchange is most effectively accomplished with metals in their 1+ oxidation state, both because of the sparsity of the anionic ion-exchange sites associated with the zeolite, and because the large hydration shells associated with aqueous 3+ cations hinder transport. Metals such as Ga which commonly exist in higher oxidation states need to be reduced to promote ion-exchange and this is the reason that reduction of gallium-containing catalysts for light paraffin aromatization often yields a dramatic enhancement in catalytic activity. We have effectively combined reduction with ion-exchange and we term this combined process ''reductive solid-state ion-exchange''. Our hypothesis has largely been proven true, and a number of the papers we have published directly address this hypothesis.

  14. Quantitatively Probing the Al Distribution in Zeolites

    SciTech Connect

    Vjunov, Aleksei; Fulton, John L.; Huthwelker, Thomas; Pin, Sonia; Mei, Donghai; Schenter, Gregory K.; Govind, Niranjan; Camaioni, Donald M.; Hu, Jian Z.; Lercher, Johannes A.

    2014-06-11

    The degree of substitution of Si4+ by Al3+ in the oxygen-terminated tetrahedra (Al T-sites) of zeolites determines the concentration of ion-exchange and Brønsted acid sites. As the location of the tetrahedra and the associated subtle variations in bond angles influence the acid strength, quantitative information about Al T-sites in the framework is critical to rationalize catalytic properties and to design new catalysts. A quantitative analysis is reported that uses a combination of extended X-ray absorption fine structure (EXAFS) analysis and 27Al MAS NMR spectroscopy supported by DFT-based molecular dynamics simulations. To discriminate individual Al atoms, sets of ab initio EXAFS spectra for various T-sites are generated from DFT-based molecular dynamics simulations allowing quantitative treatment of the EXAFS single- and multiple-photoelectron scattering processes out to 3-4 atom shells surrounding the Al absorption center. It is observed that identical zeolite types show dramatically different Al-distributions. A preference of Al for T-sites that are part of one or more 4-member rings in the framework over those T-sites that are part of only 5- and 6-member rings in the HBEA150 sample has been determined from a combination of these methods. This work was supported by the U. S. Department of Energy (DOE), Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences.

  15. Multinuclear MAS NMR investigation of zeolites reacted with chlorofluorocarbons

    NASA Astrophysics Data System (ADS)

    Hannus, I.; Kónya, Z.; Lentz, P.; Nagy, J. B.; Kiricsi, I.

    1999-05-01

    Multinuclear ( 23Na, 27Al, 29Si, 13C) MAS NMR techniques were used for investigation of surface reaction of Y-type zeolites with CFCs (CCl 4, CCl 3F, CCl 2F 2, CClF 3, CF 4) and HCFC (CHClF 2). The hydrogen containing derivative reacts slowly. Those possessing more than 2 F atoms can be regarded as stable unreactive materials. CCl 4, CCl 3F, CCl 2F 2 react strongly with the zeolites. The reaction of HCFC with zeolites has a different mechanism to the other CFCs tested. On the basis of multinuclear NMR results a mechanism is given for the decomposition of HCFC.

  16. Accelerated crystallization of zeolites via hydroxyl free radicals.

    PubMed

    Feng, Guodong; Cheng, Peng; Yan, Wenfu; Boronat, Mercedes; Li, Xu; Su, Ji-Hu; Wang, Jianyu; Li, Yi; Corma, Avelino; Xu, Ruren; Yu, Jihong

    2016-03-11

    In the hydrothermal crystallization of zeolites from basic media, hydroxide ions (OH(-)) catalyze the depolymerization of the aluminosilicate gel by breaking the Si,Al-O-Si,Al bonds and catalyze the polymerization of the aluminosilicate anions around the hydrated cation species by remaking the Si,Al-O-Si,Al bonds. We report that hydroxyl free radicals (•OH) are involved in the zeolite crystallization under hydrothermal conditions. The crystallization processes of zeolites-such as Na-A, Na-X, NaZ-21, and silicalite-1-can be accelerated with hydroxyl free radicals generated by ultraviolet irradiation or Fenton's reagent.

  17. Method of preparing sodalite from chloride salt occluded zeolite

    DOEpatents

    Lewis, M.A.; Pereira, C.

    1997-03-18

    A method is described for immobilizing waste chloride salts containing radionuclides and hazardous nuclear material for permanent disposal starting with a substantially dry zeolite and sufficient glass to form leach resistant sodalite with occluded radionuclides and hazardous nuclear material. The zeolite and glass are heated to a temperature up to about 1000 K to convert the zeolite to sodalite and thereafter maintained at a pressure and temperature sufficient to form a sodalite product near theoretical density. Pressure is used on the formed sodalite to produce the required density.

  18. Method of preparing sodalite from chloride salt occluded zeolite

    DOEpatents

    Lewis, Michele A.; Pereira, Candido

    1997-01-01

    A method for immobilizing waste chloride salts containing radionuclides and hazardous nuclear material for permanent disposal starting with a substantially dry zeolite and sufficient glass to form leach resistant sodalite with occluded radionuclides and hazardous nuclear material. The zeolite and glass are heated to a temperature up to about 1000.degree. K. to convert the zeolite to sodalite and thereafter maintained at a pressure and temperature sufficient to form a sodalite product near theoretical density. Pressure is used on the formed sodalite to produce the required density.

  19. Zeolite crystal growth in space - What has been learned

    NASA Technical Reports Server (NTRS)

    Sacco, A., Jr.; Thompson, R. W.; Dixon, A. G.

    1993-01-01

    Three zeolite crystal growth experiments developed at WPI have been performed in space in last twelve months. One experiment, GAS-1, illustrated that to grow large, crystallographically uniform crystals in space, the precursor solutions should be mixed in microgravity. Another experiment evaluated the optimum mixing protocol for solutions that chemically interact ('gel') on contact. These results were utilized in setting the protocol for mixing nineteen zeolite solutions that were then processed and yielded zeolites A, X and mordenite. All solutions in which the nucleation event was influenced produced larger, more 'uniform' crystals than did identical solutions processed on earth.

  20. Thermoset polymer-layered silicic acid nanocomposites

    NASA Astrophysics Data System (ADS)

    Wang, Zhen

    Nanocomposites are formed when phase mixing occurs on a nanometer length scale. Due to the improved phase morphology and interfacial properties, nanocomposites exhibit mechanical properties superior to conventional composites. Toyota researchers first demonstrated that organoclay could be exfoliated in a nylon-6 matrix to greatly improve the thermal and mechanical properties of the polymer, which has resulted in a practical application in the automobile industry. A great deal of research has been conducted on organic-inorganic hybrid composites in which smectite clays are used as reinforcement agents. However, little work has been devoted to derivatives of other layered inorganic solids. In the present work, the first examples of organic polymer-layered silicic acid nanocomposites have been prepared by formation of a cured epoxy polymer network in the presence of organo cation exchange forms of magadiite. The exfoliation of silicate nanolayers in the epoxy matrix was achieved by in-situ intragallery polymerization during the thermosetting process. In general, the tensile properties, solvent resistance, barrier properties and chemical stability of the polymer matrix are greatly improved by the embedded silicate nanolayers when the matrix is flexible (sub-ambient Tg). The improvement of properties are dependent on the silicate loading, the degree of nanolayer separation and interfacial properties. Interestingly, the exfoliation also affects the polymer elasticity in a favorable way. The mechanism leading to nanocomposite formation is proposed. One exfoliated epoxy-magadiite nanocomposite/composition possessed unique transparent optical properties. The exfoliation chemistry was successfully extended to the other members of the layered silicic acid family. A new approach also was developed to prepare thermoset epoxy polymer-layered silicate nanocomposites in which curing agents can be directly intercalated into the intragallery without the need for alkylammonium ions

  1. Adsorptive Separation of 1-Butanol from Aqueous Solutions Using MFI- and FER-Type Zeolite Frameworks: A Monte Carlo Study.

    PubMed

    DeJaco, Robert F; Bai, Peng; Tsapatsis, Michael; Siepmann, J Ilja

    2016-03-01

    Anaerobic fermentation can transform carbohydrates to yield a multicomponent mixture comprising mainly of acetone, 1-butanol, and ethanol (ABE) in a typical weight ratio of 3:6:1. Compared to ethanol, 1-butanol, the main product of ABE fermentation, offers significant advantages as a biofuel or a fuel additive. However, the toxicity of 1-butanol for cell cultures requires broth concentrations to be low in 1-butanol (≈1-2 wt %). An energy-efficient recovery method that performs well even at low 1-butanol concentrations is therefore necessary to ensure economic feasibility of the ABE fermentation process. In this work, configurational-bias Monte Carlo simulations in the Gibbs ensemble are performed to probe the adsorption of 1-butanol/water solutions onto all-siliceous zeolites with the framework types MFI and FER. At low solution concentration, the selectivity and capacity for 1-butanol in MFI are larger than those in FER, while the opposite is true for concentrations at or above those of ABE broths. Structural analysis at various loadings sheds light on the different sorbate-sorbate and sorbate-sorbent interactions that govern trends in adsorption in each zeolite.

  2. The evolution of strength and crystalline phases for alkali-activated ground blast furnace slag and fly ash-based geopolymers

    SciTech Connect

    Oh, Jae Eun; Monteiro, Paulo J.M.; Jun, Ssang Sun; Choi, Sejin; Clark, Simon M.

    2010-02-15

    The increase in strength and evolution of crystalline phases in inorganic polymer cement, made by the alkali activation of slag, Class C and Class F fly ashes, was followed using compressive strength test and synchrotron X-ray diffraction. In order to increase the crystallinity of the product the reactions were carried out at 80 deg. C. We found that hydrotalcite formed in both the alkali-activated slag cements and the fly ash-based geopolymers. Hydroxycancrinite, one member of the ABC-6 family of zeolites, was found only in the fly ash geopolymers. Assuming that the predominantly amorphous geopolymer formed under ambient conditions relates to the crystalline phases found when the mixture is cured at high temperature, we propose that the structure of this zeolitic precursor formed in Na-based high alkaline environment can be regarded as a disordered form of the basic building unit of the ABC-6 group of zeolites which includes poly-types such as hydroxycancrinite, hydroxysodalite and chabazite-Na.

  3. In Situ Crystallization of Al-Containing Silicate Nanosheets on Monodisperse Amorphous Silica Microspheres.

    PubMed

    Okada, Tomohiko; Sueyoshi, Mai; Minamisawa, Hikari M

    2015-12-29

    The fine crystals of an Al-containing layered silicate, whose negative layer charge is generated by an isomorphous substitution in the tetrahedral SiO4 framework, successfully grew on monodisperse amorphous silica microspheres with diameters of 1.0 and 2.6 μm. The fine, plate-like crystals were observed to thoroughly cover the surface of the silica spheres, irrespective of their size, by the hydrothermal reactions of the silica powder in aqueous alkali solution containing Al and Mg ions in a rotating Teflon-lined autoclave. The crystal size increased when the concentration of the precursors was low. The presence of fluorine in the reaction media enlarged the crystalline phase in the direction of the layer stacking while reducing the plate size. The difference in the crystal size affected the kinetics on the hinokitiol desorption in n-hexane from the layered silicates modified with organoammonium ions. The organically modified layered silicate behaved as an exfoliated nanosheet in the nonpolar solvent. The less harmful elements in this hybrid suggest that it can be used in cosmetic and pharmaceutical applications as a drug support, without flaking off the fine layers on the microspherical substrates. PMID:26639090

  4. Solubility of Zinc Silicate and Zinc Ferrite in Aqueous Solution to High Temperatures

    SciTech Connect

    Palmer, Donald; Anovitz, Lawrence {Larry} M

    2009-07-01

    Crystalline zinc silicate, Zn{sub 2}SiO{sub 4}, and zinc ferrite, ZnFe{sub 2}O{sub 4}, were prepared and characterized. The solubilities of these phases were measured using flow-through apparatus from 50 to 350 C in 100 C intervals over a wide range of pH. Both solid phases dissolve incongruently, presumably to form ZnO(s) and Fe{sub 2}O{sub 3}(s) (or the corresponding hydroxide phases at low temperature), respectively. The respective concentrations of zinc(II) and iron(III) matched those of ZnO(cr) and Fe{sub 2}O{sub 3}(s) ({ge}150 C) reported in the literature, whereas the corresponding Si(IV) and Zn(II) concentrations were at least an order of magnitude below the solubility limits for their pure oxide phases. Therefore, the solubility constants for zinc silicate and ferrite were determined with respect to the known solubility constants for ZnO(cr) and Fe{sub 2}O{sub 3}(s) ({ge}150 C), respectively, and the corresponding concentrations of Si(IV) and Zn(II) measured in this study. The results of independent experiments, as well as those reported in the literature provide insights into the mechanism(s) of formation of zinc silicate and ferrite in the primary circuits of nuclear reactors.

  5. 40 CFR 721.9513 - Modified magnesium silicate polymer (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Modified magnesium silicate polymer... Specific Chemical Substances § 721.9513 Modified magnesium silicate polymer (generic). (a) Chemical... as modified magnesium silicate polymer (PMN P-98-604) is subject to reporting under this section...

  6. 40 CFR 721.9513 - Modified magnesium silicate polymer (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Modified magnesium silicate polymer... Specific Chemical Substances § 721.9513 Modified magnesium silicate polymer (generic). (a) Chemical... as modified magnesium silicate polymer (PMN P-98-604) is subject to reporting under this section...

  7. 40 CFR 721.9513 - Modified magnesium silicate polymer (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Modified magnesium silicate polymer... Specific Chemical Substances § 721.9513 Modified magnesium silicate polymer (generic). (a) Chemical... as modified magnesium silicate polymer (PMN P-98-604) is subject to reporting under this section...

  8. 21 CFR 182.2122 - Aluminum calcium silicate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Aluminum calcium silicate. 182.2122 Section 182...) SUBSTANCES GENERALLY RECOGNIZED AS SAFE Anticaking Agents § 182.2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent. (c) Limitations, restrictions, or explanation....

  9. 21 CFR 182.2122 - Aluminum calcium silicate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Aluminum calcium silicate. 182.2122 Section 182.2122 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent....

  10. 21 CFR 582.2122 - Aluminum calcium silicate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Aluminum calcium silicate. 582.2122 Section 582.2122 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent....

  11. 21 CFR 582.2122 - Aluminum calcium silicate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Aluminum calcium silicate. 582.2122 Section 582.2122 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent....

  12. 21 CFR 182.2122 - Aluminum calcium silicate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Aluminum calcium silicate. 182.2122 Section 182.2122 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent....

  13. 21 CFR 582.2122 - Aluminum calcium silicate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Aluminum calcium silicate. 582.2122 Section 582.2122 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent....

  14. 21 CFR 182.2122 - Aluminum calcium silicate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Aluminum calcium silicate. 182.2122 Section 182.2122 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent....

  15. 21 CFR 582.2122 - Aluminum calcium silicate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Aluminum calcium silicate. 582.2122 Section 582.2122 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent....

  16. 21 CFR 582.2122 - Aluminum calcium silicate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Aluminum calcium silicate. 582.2122 Section 582.2122 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent....

  17. 21 CFR 182.2122 - Aluminum calcium silicate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Aluminum calcium silicate. 182.2122 Section 182.2122 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent....

  18. 40 CFR 721.10495 - Metal silicate (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Metal silicate (generic). 721.10495... Substances § 721.10495 Metal silicate (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as metal silicate (PMN P-05-634) is subject...

  19. 40 CFR 721.10495 - Metal silicate (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Metal silicate (generic). 721.10495... Substances § 721.10495 Metal silicate (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as metal silicate (PMN P-05-634) is subject...

  20. 40 CFR 721.9513 - Modified magnesium silicate polymer (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Modified magnesium silicate polymer... Specific Chemical Substances § 721.9513 Modified magnesium silicate polymer (generic). (a) Chemical... as modified magnesium silicate polymer (PMN P-98-604) is subject to reporting under this section...

  1. 40 CFR 721.9513 - Modified magnesium silicate polymer (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Modified magnesium silicate polymer... Specific Chemical Substances § 721.9513 Modified magnesium silicate polymer (generic). (a) Chemical... as modified magnesium silicate polymer (PMN P-98-604) is subject to reporting under this section...

  2. Optical and crystallization studies of titanium dioxide doped sodium and potassium silicate glasses

    NASA Astrophysics Data System (ADS)

    ElBatal, F. H.; Marzouk, M. A.; ElBatal, H. A.

    2016-10-01

    Combined optical and FTIR spectral analysis were used to investigate prepared invert two alkali silicate glasses (Na2O·SiO2sbnd K2O·SiO2) containing high titanium oxide content. Glass ceramic derivatives were prepared through thermal two step regime of the parent glasses and they were characterized by FTIR and X-ray diffraction measurements. Experimental optical spectra indicate the appearance of an additional UV band due to absorption of tetravalent titanium ions beside the UV bands due to trace ferric ions impurities. FT infrared absorption spectra reveal composite vibrational bands due to vibrational modes of both silicate groups and TiO4 or Sisbnd Osbnd Ti units. Such tetravalent groupings of titanium ions confirm the stability of such invert glasses containing as such two main glass forming oxides. FTIR spectra of the glass - ceramic derivatives show nearly the same IR vibrational modes as their parent glasses. X-ray diffraction analysis show the separation of crystalline sodium or potassium titanate phases beside a minor form of silica and the results confirm that TiO2 acts mainly as network forming units leading to the formation of crystalline titanate phases.

  3. Thermal conductivity, bulk properties, and thermal stratigraphy of silicic tuffs from the upper portion of hole USW-G1, Yucca Mountain, Nye County, Nevada

    SciTech Connect

    Lappin, A.R.; VanBuskirk, R.G.; Enniss, D.O.; Buters, S.W.; Prater, F.M.; Muller, C.B.; Bergosh, J.L.

    1982-03-01

    Thermal-conductivity and bulk-property measurements were made on welded and nonwelded silicic tuffs from the upper portion of Hole USW-G1, located near the southwestern margin of the Nevada Test Site. Bulk-property measurements were made by standard techniques. Thermal conductivities were measured at temperatures as high as 280{sup 0}C, confining pressures to 10 MPa, and pore pressures to 1.5 MPa. Extrapolation of measured saturated conductivities to zero porosity suggests that matrix conductivity of both zeolitized and devitrified tuffs is independent of stratigraphic position, depth, and probably location. This fact allows development of a thermal-conductivity stratigraphy for the upper portion of Hole G1. Estimates of saturated conductivities of zeolitized nonwelded tuffs and devitrified tuffs below the water table appear most reliable. Estimated conductivities of saturated densely welded devitrified tuffs above the water table are less reliable, due to both internal complexity and limited data presently available. Estimation of conductivity of dewatered tuffs requires use of different air thermal conductivities in devitrified and zeolitized samples. Estimated effects of in-situ fracturing generally appear negligible.

  4. Dry plasma processing for industrial crystalline silicon solar cell production

    NASA Astrophysics Data System (ADS)

    Hofmann, M.; Rentsch, J.; Preu, R.

    2010-10-01

    This paper gives an overview on the standard crystalline silicon solar cell manufacturing processes typically applied in industry. Main focus has been put on plasma processes which can replace existing, mainly wet chemical processes within the standard process flow. Finally, additional plasma processes are presented which are suited for higher-efficient solar cells, i.e. for the “passivated emitter and rear cell” concept (PERC) or the “heterojunction with intrinsic thin layer” approach (HIT). Plasma processes for the deposition of thin dielectric or semiconducting layers for surface passivation, emitter deposition or anti-reflective coating purposes are presented. Plasma etching processes for the removal of phosphorus silicate glass or parasitic emitters, for wafer cleaning and masked and mask-free surface texturisation are discussed.

  5. Magnesia-alumina-aluminum phosphate-zeolite catalyst

    SciTech Connect

    Reynolds, E.H.; Stanulonis, J.J.; Swift, H.E.

    1980-09-16

    A catalyst for cracking gasoline feedstock with superior selectivity to gasoline production and greater metals tolerance comprises a magnesia-alumina-aluminum phosphate matrix composited with a zeolite having cracking activity.

  6. [Zeolite-containing tripoli powder in experimental hepatology].

    PubMed

    Kolotilova, M L; Ivanov, L N

    2005-01-01

    Biological activity of zeolite-containing tripoli powder was studied in rats. Biochemical, enzymatic and lipid peroxidation indices were assessed. The results of the study confirm enterosorption and detoxication activity of the powder.

  7. Characterization of a zeolite membrane for catalytic membrane reactor application

    SciTech Connect

    Giroir-Fendler, A.; Peureux, J.; Mozzanega, H.; Dalmon, J.A.

    1996-12-31

    This paper describes the morphological and transport properties of a composite zeolite (silicalite) - alumina membrane. Some advantages obtained in combining the membrane with a conventional fixed-bed catalyst are also reported.

  8. 12. INTERIOR OF BUILDING 2, ORIGINAL ZEOLITE PLANT, AT WEYMOUTH ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    12. INTERIOR OF BUILDING 2, ORIGINAL ZEOLITE PLANT, AT WEYMOUTH LOOKING WEST TO FOUNTAIN. STAIRWAY RUNS DOWN TO FILTRATION BAYS. - F. E. Weymouth Filtration Plant, 700 North Moreno Avenue, La Verne, Los Angeles County, CA

  9. The stability of copper oxo species in zeolite frameworks

    DOE PAGES

    Vilella, Laia; Studt, Felix

    2016-03-07

    Cu-exchanged zeolites are promising heterogeneous catalysts, as they provide a confined environment to carry out highly selective reactions. Furthermore, the knowledge of how the zeolite framework and the location of Al atoms therein affect the adsorption of copper species is still not well understood. In this work, DFT was used to investigate the adsorption of potential Cu oxo active species suggested in the literature [Cu(η2-O2), Cu(µ-O)Cu, and Cu2O2] into zeolites with different pore sizes and shapes (AFI, CHA, TON, MOR, and MFI). The calculations revealed that both monomeric and dimeric Cu oxo species bind strongly to the O atoms ofmore » the lattice. For the monometallic species similar adsorption energies are obtained with the different zeolite frameworks, whereas an optimum Al–Al distance is required for the dimeric species.« less

  10. Zeolite - A Natural Filter Material for Lead Polluted Water

    NASA Astrophysics Data System (ADS)

    Neamţu, Corina Ioana; Pică, Elena Maria; Rusu, Tiberiu

    2014-11-01

    Reducing the concentration of lead ions in a wastewater using zeolite has proven to be a successful water treatement method, all over the world. Putting the two media (solid and liquid) in contact in static conditions had good results regarding the concentration of the filtered solution, the pH and the electric conductivity, depending on the values of certain parameters such as the amount of the zeolite, volume of the solution or interaction time. The present study highlights the zeolite ability to retain the lead ions from a solution, in dynamic interaction conditions between the two environments, in a short interaction time. The results confirmed the effectiveness of ion exchange water treatment method in the conditions set, emphasizing once again the properties of the filter material - the zeolite

  11. CO2 capture using zeolite 13X prepared from bentonite

    NASA Astrophysics Data System (ADS)

    Chen, Chao; Park, Dong-Wha; Ahn, Wha-Seung

    2014-02-01

    Zeolite 13X was prepared using bentonite as the raw material by alkaline fusion followed by a hydrothermal treatment without adding any extra silica or alumina sources. The prepared zeolite 13X was characterized by X-ray powder diffraction, N2-adsorption-desorption measurements, and scanning electron microscopy. The CO2 capture performance of the prepared zeolite 13X was examined under both static and flow conditions. The prepared zeolite 13X showed a high BET surface area of 688 m2/g with a high micropore volume (0.30 cm3/g), and exhibited high CO2 capture capacity (211 mg/g) and selectivity to N2 (CO2/N2 = 37) at 25 °C and 1 bar. In addition, the material showed fast adsorption kinetics, and stable CO2 adsorption-desorption recycling performance at both 25 and 200 °C.

  12. Hierarchical zeolites overcome all obstacles: next stop industrial implementation.

    PubMed

    Verboekend, Danny; Mitchell, Sharon; Pérez-Ramírez, Javier

    2013-01-01

    This review emphasizes key recent accomplishments towards the industrial exploitation of hierarchically structured zeolites in catalytic processes. A major milestone comprises the demonstration that affordable post-synthetic modifications enable the transformation of any conventional zeolite into hierarchical analogues with tunable porosity and functionality. Through specific examples, belonging to the transformation of fossil fuel and renewable feedstocks, we quantitatively illustrate the spectacular benefits attained upon application of hierarchical zeolite catalysts due to improved accessibility or modification of the type and distribution of active sites. A crucial step for these exciting lab-designed materials to be implemented in industrial processes is to shape them into technical forms. Accordingly, we studied the synthesis, characterization, and catalytic evaluation of millimeter-sized hierarchical zeolite bodies, enriching the fundamental understanding on scale-up and representing an additional solid step towards the commercial application of these materials.

  13. Amorphous Silicates in Primitive Meteoritic Materials: Acfer 094 and IDPs

    NASA Technical Reports Server (NTRS)

    Keller, L. P.; Nakamura-Messenger, K.; Messenger, S.; Walker, Robert M.

    2009-01-01

    The abundance of presolar grains is one measure of the primitive nature of meteoritic materials. Presolar silicates are abundant in meteorites whose matrices are dominated by amorphous silicates such as the unique carbonaceous chondrite Acfer 094. Presolar silicates are even more abundant in chondritic-porous interplanetary dust particles (CP-IDPs). Amorphous silicates in the form of GEMS (glass with embedded metal and sulfides) grains are a major component of CP IDPs. We are studying amorphous silicates in Acfer 094 matrix in order to determine whether they are related to the GEMS grains in CPIDPs

  14. Workshop on hydrology of crystalline basement rocks

    SciTech Connect

    Davis, S.N.

    1981-08-01

    This workshop covered the following subjects: measurements in relatively shallow boreholes; measurement and interpretation of data from deep boreholes; hydrologic properties of crystalline rocks as interpreted by geophysics and field geology; rock mechanics related to hydrology of crystalline rocks; the possible contributions of modeling to the understanding of the hydrology of crystalline rocks; and geochemical interpretations of the hydrology of crystalline rocks. (MHR)

  15. In-situ growth of porous alumino-silicates and fabrication of nano-porous membranes

    NASA Astrophysics Data System (ADS)

    Kodumuri, Pradeep

    2009-12-01

    Feasibility of depositing continuous films of nano-porous alumino-silicates, primarily zeolites and MCM-41, on metallic and non-metallic substrates was examined with an aim to develop membranes for separation of gaseous mixtures and also for application as hydrogen storage material. Mesoporous silica was deposited in-side the pores of these nano-porous disks with an aim to develop membranes for selective separations. Our study involves supported zeolite film growth on substrates using in-situ hydrothermal synthesis. Faujasite, Silicalite and Mesoporous silica have been grown on various metallic and non-metallic supports. Metallic substrates used for film growth included anodized titanium, sodium hydroxide treated Titanium, Anodized aluminum, and sintered copper. A non-metallic substrate used was nano-porous aluminum oxide. Zeolite film growth was characterized using Scanning Electron Microscope (AMRAY 1820) and High Resolution Transmission electron microscope. Silicalite was found to grow uniformly on all the substrates to form a uniform and closely packed film. Faujasite tends to grow in the form of individual particles which do not inter-grow like silicalite to form a continuous film. Mesoporous silica was found to grow uniformly on anodized aluminum compared to growth on sintered copper and anodized titanium. Mesoporous silica growth on AnodiscRTM was found to cover more than half the surface of the substrate. Commercially obtained AnodiscRTM was found to have cylindrical channels of the pore branching into each other and since we needed pore channels of uniform dimension for Mesoporous silica growth, we have fabricated nano-porous alumina with uniform pore channels. Nano-porous alumina membranes containing uniform distribution of through thickness cylindrical pore channels were fabricated using anodization of aluminum disks. Free-standing nano-porous alumina membranes were used as templates for electro-deposition in order to fabricate nickel and palladium nano

  16. Preparation and characterization of TiO2/silicate hierarchical coating on titanium surface for biomedical applications.

    PubMed

    Huang, Qianli; Liu, Xujie; Elkhooly, Tarek A; Zhang, Ranran; Yang, Xing; Shen, Zhijian; Feng, Qingling

    2016-03-01

    In the current work, TiO2/silicate hierarchical coatings with various nanostructure morphologies were successfully prepared on titanium substrates through micro-arc oxidation (MAO) and subsequent hydrothermal treatment (HT). Moreover, the nucleation mechanism and growth behavior of the nanostructures, hydrophilicity, protein adsorption and apatite-inducing ability of various coatings were also explored. The novel TiO2/silicate hierarchical coatings comprised calcium silicate hydrate (CSH) as an outer-layer and TiO2 matrix as an inner-layer. According to the morphological features, the nanostructures were classified as nanorod, nanoplate and nanoleaf. The morphology, degree of crystallinity and crystalline phases of CSH nanostructures could be controlled by optimizing the HT conditions. The nucleation of CSH nanostructures is caused by release and re-precipitation mechanism. The TiO2/CSH hierarchical coatings exhibited some enhanced physical and biological performances compared to MAO-fabricated coating. The improvement of the hydrophilicity, fibronectin adsorption and apatite-inducing ability was found to be morphological dependent according to the following trend: nanoleaf coating>nanoplate coating>nanorod coating>MAO coating. The results indicate that the tuning of physical and morphological properties of nanostructures coated on biomaterial surface could significantly influence the hydrophilicity, protein adsorption and in vitro bioactivity of biomaterial.

  17. Self-construction of core-shell and hollow zeolite analcime icositetrahedra: a reversed crystal growth process via oriented aggregation of nanocrystallites and recrystallization from surface to core.

    PubMed

    Chen, Xueying; Qiao, Minghua; Xie, Songhai; Fan, Kangnian; Zhou, Wuzong; He, Heyong

    2007-10-31

    Zeolite analcime with a core-shell and hollow icositetrahedron architecture was prepared by a one-pot hydrothermal route in the presence of ethylamine and Raney Ni. Detailed investigations on samples at different preparation stages revealed that the growth of the complex single crystalline geometrical structure did not follow the classic crystal growth route, i.e., a crystal with a highly symmetric morphology (such as polyhedra) is normally developed by attachment of atoms or ions to a nucleus. A reversed crystal growth process through oriented aggregation of nanocrystallites and surface recrystallization was observed. The whole process can be described by the following four successive steps. (1) Primary analcime nanoplatelets undergo oriented aggregation to yield discus-shaped particles. (2) These disci further assemble into polycrystalline microspheres. (3) The relatively large platelets grow into nanorods by consuming the smaller ones, and meanwhile, the surface of the microspheres recrystallizes into a thin single crystalline icositetrahedral shell via Ostwald ripening. (4) Recrystallization continues from the surface to the core at the expense of the nanorods, and the thickness of the monocrystalline shell keeps on increasing until all the nanorods are consumed, leading to hollow single crystalline analcime icositetrahedra. The present work adds new useful information for the understanding of the principles of zeolite growth.

  18. Commander Bowersox Tends to Zeolite Crystal Samples Aboard Space Station

    NASA Technical Reports Server (NTRS)

    2003-01-01

    Expedition Six Commander Ken Bowersox spins Zeolite Crystal Growth sample tubes to eliminate bubbles that could affect crystal formation in preparation of a 15 day experiment aboard the International Space Station (ISS). Zeolites are hard as rock, yet are able to absorb liquids and gases like a sponge. By using the ISS microgravity environment to grow better, larger crystals, NASA and its commercial partners hope to improve petroleum manufacturing and other processes.

  19. Metal Oxide/Zeolite Combination Absorbs H2S

    NASA Technical Reports Server (NTRS)

    Voecks, Gerald E.; Sharma, Pramod K.

    1989-01-01

    Mixed copper and molybdenum oxides supported in pores of zeolite found to remove H2S from mixture of gases rich in hydrogen and steam, at temperatures from 256 to 538 degree C. Absorber of H2S needed to clean up gas streams from fuel processors that incorporate high-temperature steam reformers or hydrodesulfurizing units. Zeolites chosen as supporting materials because of their high porosity, rigidity, alumina content, and variety of both composition and form.

  20. Nanostructures having crystalline and amorphous phases

    DOEpatents

    Mao, Samuel S; Chen, Xiaobo

    2015-04-28

    The present invention includes a nanostructure, a method of making thereof, and a method of photocatalysis. In one embodiment, the nanostructure includes a crystalline phase and an amorphous phase in contact with the crystalline phase. Each of the crystalline and amorphous phases has at least one dimension on a nanometer scale. In another embodiment, the nanostructure includes a nanoparticle comprising a crystalline phase and an amorphous phase. The amorphous phase is in a selected amount. In another embodiment, the nanostructure includes crystalline titanium dioxide and amorphous titanium dioxide in contact with the crystalline titanium dioxide. Each of the crystalline and amorphous titanium dioxide has at least one dimension on a nanometer scale.