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Sample records for anhydrous silicate melt

  1. Trace element partitioning between ilmenite, armalcolite and anhydrous silicate melt: Implications for the formation of lunar high-Ti mare basalts

    NARCIS (Netherlands)

    Kan Parker, M. van; Mason, P.R.D.; Westrenen, W. van

    2011-01-01

    We performed a series of experiments at high pressures and temperatures to determine the partitioning of a wide range of trace elements between ilmenite (Ilm), armalcolite (Arm) and anhydrous lunar silicate melt, to constrain geochemical models of the formation of titanium-rich melts in the Moon. Ex

  2. Compressibility of hydrated and anhydrous sodium silicate-based liquids and glasses, as analogues for natural silicate melts, by Brillouin scattering spectroscopy

    Science.gov (United States)

    Tkachev, Sergey Nikolayevich

    A mathematical formalism was tested on compressibility studies of water, before applying it to the high pressure-temperature compressibility studies of hydrated and anhydrous sodium silicate-based liquids and glasses. The hypersonic sound velocity, refractive index and attenuation coefficient obtained using Brillouin light scattering spectroscopy technique were in agreement with literature data. From the measured sound velocities, the pressure dependence of the bulk moduli and density of liquid water were calculated, using Vinet equation of state. The formalism was extended to the Brillouin scattering studies of the elastic properties of alkaline-calcium silica hydrogels and float glass, which exhibits a dramatic increase in the pressure dependence of longitudinal velocity and a discontinuity in the compressibility at about 6 GPa. It is demonstrated that an apparent second-order transition to a new amorphous phase can form via the abrupt onset of a new compressional mechanism, which may be triggered by a shift in polymerization of the glass or an onset of a change in coordination of silicon. Brillouin scattering measurements were carried out on an aqueous solution of Na2O-2SiO2 and anhydrous Na2O-2SiO 2 glass and liquid at high P-T conditions. The "modified" platelet scattering geometry has allowed a determination of the longitudinal velocity independently from refractive index, and hence the adiabatic compressibility and density of liquids as a function of pressure and temperature. The observed increase in density of the melt and glass phases formed at high P-T conditions is likely associated with structural effects. The large values of KS' of the liquid phase illustrate that the means of compaction of the liquid differs substantially from that of the glass, and that the liquid is able to access a wider range of compaction mechanisms. The measured bulk modulus of Na2O-2SiO2 aqueous solution is closer to values of silicate melts than to that of end-member water at

  3. Experimental study of trace element partitioning between lunar orthopyroxene and anhydrous silicate melt: Effects of lithium and iron

    NARCIS (Netherlands)

    Kan Parker, M. van; Mason, P.R.D.; Westrenen, W. van

    2011-01-01

    Orthopyroxene (Opx) was present during a significant portion of crystallisation of the lunar magma ocean, but its influence on co-existing melt trace element contents is not well quantified. We performed highpressure (P, 1.1 to 3.2 GPa), high-temperature (T, 1400 to 1600 °C) experiments on synthetic

  4. Volatile diffusion in silicate melts and its effects on melt inclusions

    Directory of Open Access Journals (Sweden)

    P. Scarlato

    2005-06-01

    Full Text Available A compendium of diffusion measurements and their Arrhenius equations for water, carbon dioxide, sulfur, fluorine, and chlorine in silicate melts similar in composition to natural igneous rocks is presented. Water diffusion in silicic melts is well studied and understood, however little data exists for melts of intermediate to basic compositions. The data demonstrate that both the water concentration and the anhydrous melt composition affect the diffusion coefficient of water. Carbon dioxide diffusion appears only weakly dependent, at most, on the volatilefree melt composition and no effect of carbon dioxide concentration has been observed, although few experiments have been performed. Based upon one study, the addition of water to rhyolitic melts increases carbon dioxide diffusion by orders of magnitude to values similar to that of 6 wt% water. Sulfur diffusion in intermediate to silicic melts depends upon the anhydrous melt composition and the water concentration. In water-bearing silicic melts sulfur diffuses 2 to 3 orders of magnitude slower than water. Chlorine diffusion is affected by both water concentration and anhydrous melt composition; its values are typically between those of water and sulfur. Information on fluorine diffusion is rare, but the volatile-free melt composition exerts a strong control on its diffusion. At the present time the diffusion of water, carbon dioxide, sulfur and chlorine can be estimated in silicic melts at magmatic temperatures. The diffusion of water and carbon dioxide in basic to intermediate melts is only known at a limited set of temperatures and compositions. The diffusion data for rhyolitic melts at 800°C together with a standard model for the enrichment of incompatible elements in front of growing crystals demonstrate that rapid crystal growth, greater than 10-10 ms-1, can significantly increase the volatile concentrations at the crystal-melt interface and that any of that melt trapped

  5. Structural chemistry of anhydrous sodium silicates - a review.

    Science.gov (United States)

    Kahlenberg, Volker

    2010-01-01

    Sodium silicates are of considerable importance for many fields of inorganic chemistry and applied mineralogy, being either raw materials for synthesis or already finished products. In addition to their industrial relevance they have also been studied intensively because of their interesting physico-chemical properties including high ion-exchange capacity and selectivity or two-dimensional sodium diffusion and conductivity. Furthermore, the structural chemistry of crystalline sodium silicates offers the crystallographer challenging tasks such as polytypism, polymorphism, temperature and/or pressure-dependent phase transitions, pseudo-symmetry, complex twinning phenomena as well as incommensurately modulated structures. Many of these structural problems have been solved only recently, although in some cases they have been known for several decades. This article will provide an overview on the structurally characterized sodium silicates and their fascinating crystallochemical characteristics.

  6. Stability of foams in silicate melts

    Science.gov (United States)

    Proussevitch, Alexander A.; Sahagian, Dork L.; Kutolin, Vladislav A.

    1993-12-01

    Bubble coalescence and the spontaneous disruption of high-porosity foams in silicate melts are the result of physical expulsion of interpore melt (syneresis) leading to bubble coalescence, and diffusive gas exchange between bubbles. Melt expulsion can be achieved either along films between pairs of bubbles, or along Plateau borders which represent the contacts between 3 or more bubbles. Theoretical evaluation of these mechanisms is confirmed by experimental results, enabling us to quantify the relevant parameters and determine stable bubble size and critical film thickness in a foam as a function of melt viscosity, surface tension, and time. Foam stability is controlled primarily by melt viscosity and time. Melt transport leading to coalescence of bubbles proceeds along inter-bubble films for smaller bubbles, and along Plateau borders for larger bubbles. Thus the average bubble size accelerates with time. In silicate melts, the diffusive gas expulsion out of a region of foam is effective only for water (and even then, only at small length scales), as the diffusion of CO 2 is negligible. The results of our analyses are applicable to studies of vesicularity of lavas, melt degassing, and eruption mechanisms.

  7. Partitioning coefficients between olivine and silicate melts

    Science.gov (United States)

    Bédard, J. H.

    2005-08-01

    Variation of Nernst partition coefficients ( D) between olivine and silicate melts cannot be neglected when modeling partial melting and fractional crystallization. Published natural and experimental olivine/liquidD data were examined for covariation with pressure, temperature, olivine forsterite content, and melt SiO 2, H 2O, MgO and MgO/MgO + FeO total. Values of olivine/liquidD generally increase with decreasing temperature and melt MgO content, and with increasing melt SiO 2 content, but generally show poor correlations with other variables. Multi-element olivine/liquidD profiles calculated from regressions of D REE-Sc-Y vs. melt MgO content are compared to results of the Lattice Strain Model to link melt MgO and: D0 (the strain compensated partition coefficient), EM3+ (Young's Modulus), and r0 (the size of the M site). Ln D0 varies linearly with Ln MgO in the melt; EM3+ varies linearly with melt MgO, with a dog-leg at ca. 1.5% MgO; and r0 remains constant at 0.807 Å. These equations are then used to calculate olivine/liquidD for these elements using the Lattice Strain Model. These empirical parameterizations of olivine/liquidD variations yield results comparable to experimental or natural partitioning data, and can easily be integrated into existing trace element modeling algorithms. The olivine/liquidD data suggest that basaltic melts in equilibrium with pure olivine may acquire small negative Ta-Hf-Zr-Ti anomalies, but that negative Nb anomalies are unlikely to develop. Misfits between results of the Lattice Strain Model and most light rare earth and large ion lithophile partitioning data suggest that kinetic effects may limit the lower value of D for extremely incompatible elements in natural situations characterized by high cooling/crystallization rates.

  8. Structural study and crystallography of the major compound of anhydrous cement: tri-calcium silicate; Etude structurale et cristallographie du compose majoritaire du ciment anhydre: le silicate tricalcique

    Energy Technology Data Exchange (ETDEWEB)

    Noirfontaine, M.N. de

    2000-01-01

    Anhydrous (Portland) cement is mainly composed of a synthetic material, the clinker, whose major compound is tri-calcium silicate (Ca{sub 3}SiO{sub 5}), often referred as C{sub 3}S with the compact oxides notations, C = CaO et S = SiO{sub 2}. The polymorphism of C{sub 3}S, still not well known, is the main subject of the thesis. Various crystal structures (rhombohedral R, monoclinic M1, M2, M3 and triclinic T1, T2, T3) can be found, depending on temperature and impurities. The only known structures are T1, M1 and M3, involving large unit cells with an orientational disorder of silicate tetrahedra. The single crystal studies exhibit no clear relation between the various polymorphs. Starting from known results from literature single crystal experiments, we establish the metric and structural relations between the different structures. Averaged structures for the T1, M1 and M3 polymorphs are proposed, together with all the matrices of transformation between the unit cells. We also introduce new 1-D, 2-D, and 3-D structural units, which make easier the understanding of the structures of C{sub 3}S, with the result of a better description of the orientational disorder. The effects of impurities on the structure are discussed. In industrial clinkers, impurities stabilize mainly M1 and M3 monoclinic forms. We propose a space group (Pc) and two structural models (a superstructure and an approximate averaged structure) for the M1 form. All the models are validated on synthetic compounds (M3, M2, M1 et T1) and industrial clinkers analysed by X-Ray powder diffraction with Rietveld analysis. (author)

  9. Electrical conductivity measurements on silicate melts using the loop technique

    Science.gov (United States)

    Waff, H. S.

    1976-01-01

    A new method is described for measurement of the electrical conductivity of silicate melts under controlled oxygen partial pressure at temperatures to 1550 C. The melt samples are suspended as droplets on platinum-rhodium loops, minimizing iron loss from the melt due to alloying with platinum, and providing maximum surface exposure of the melt to the oxygen-buffering gas atmosphere. The latter provides extremely rapid equilibration of the melt with the imposed oxygen partial pressure. The loop technique involves a minimum of setup time and cost, provides reproducible results to within + or - 5% and is well suited to electrical conductivity studies on silicate melts containing redox cations.

  10. Silicic Arc Magmas And Silicic Slab Melts: The Melt-Rock Reaction Link

    Science.gov (United States)

    Straub, S. M.; Gomez-Tuena, A.; Bolge, L. L.; Espinasa-Perena, R.; Bindeman, I. N.; Stuart, F. M.; Zellmer, G. F.

    2013-12-01

    While a genetic link between silicic arc magmas and silicic melts from the subducted slab has long been proposed, this hypothesis is commonly refuted because most arc magmas lack a 'garnet-signature' which such slab melts must have. A comprehensive geochemical study of high-Mg# arc magmas from the Quaternary central Mexican Volcanic Belt (MVB), however, shows that this conflict can be reconciled if melt-rock reaction processes in the mantle wedge were essential to arc magma formation. In the central MVB, monogenetic and composite volcanoes erupt high-Mg# basalts to andesites with highly variable trace element patterns. These magmas contain high-Ni olivines (olivine Ni higher than permissible for olivines in partial peridotite melts) with high 3He/4He = 7-8 Ra that provide strong evidence for silicic slab components that infiltrate the subarc mantle to produce olivine-free segregations of 'reaction pyroxenite' in the sources of individual volcanoes. Melting of silica-excess and silica-deficient reaction pyroxenites can then produce high-Mg# basaltic and dacitic primary melts that mix during ascent through mantle and crust to form high-Mg# andesites. Mass balance requires that reaction pyroxenites contain at least >15-18 wt%, and likely more, of slab component. However, because the HREE of the slab component are efficiently retained in the eclogitic slab, elements Ho to Lu in partial melts from reaction pyroxenites remain controlled by the mantle and maintain MORB-normalized Ho/Lun ˜1.15 close to unity. In contrast, the MREE to LREE and fluid mobile LILE of the arc magmas are either controlled, or strongly influenced, by slab-contributions. The origin from hybrid sources also shows in the major elements that are blends of mantle-derived elements (Mg, Ca, Mn, Fe, Ti) and elements augmented by slab contributions (Si, Na, K, P, and possibly Al). Moreover, strong correlations between bulk rock SiO2, 87Sr/86Sr and δ18O (olivines) can be interpreted as mixtures of subarc

  11. Viscosity model for fully liquid silicate melt

    Directory of Open Access Journals (Sweden)

    Zhang Guo-Hua

    2012-01-01

    Full Text Available A model for estimating the viscosity of silicate melt as derived in our previous paper is extended to the system containing MgO, CaO, SrO, BaO, Li2O, Na2O, K2O, which can express the nonlinear variation of activation energy of viscosity with the composition. It is found that the optimized parameters of model which characterize the deforming ability of bonds around non-bridging oxygen decrease with increasing the bond strength of M-O bond expressed by I=2Q/RMz+ + rO2-2 (where Q is the valence of cation M; r is the radius. It is pointed out that viscosity is not only determined by the bond strength, but also by the radius of cation which is defined as the size effect. The radius of cation plays paradox roles in the two factors: smaller radius leads to a stronger bond, thus a higher viscosity; while cations with smaller radius are easier to diffuse when neglecting the interaction force, thus a lower viscosity will be.

  12. Melt-processed anhydrous proton exchange membranes for fuel cell applications

    Energy Technology Data Exchange (ETDEWEB)

    Mokrini, A.; Siu, A.; Diaz, G.; Crites, C.; Robitaille, L. [National Research Council of Canada, Boucherville, PQ (Canada). Industrial Materials Inst.

    2009-07-01

    The current benchmark materials for proton exchange membrane (PEM) fuel cells are perfluorosulfonic acid resins (PFSA) because of their excellent stability and proton conductivity of 0.1 s/cm at 80 degrees C when fully humidified. However their performance decreases significantly at higher temperatures and low humidity. This paper presented the properties of nanocomposite PEMs incorporating a series of anhydrous charge carriers that are viable candidates for making water-free membranes that can operate at temperatures above 120 degrees C. However, the volatility or leaching of these anhydrous charge carriers could prevent them from being successfully used in open electrochemical systems. Therefore, in this study, the anhydrous charge carriers were immobilized on inorganic nanoparticles and incorporated into PEMs formulations. Nanoparticles with diameters ranging from 50-200 nm were synthesized via a sol-gel process and the desired anhydrous charge carriers immobilized on their surfaces. Nanocomposite PEMs were prepared using melt-processing technologies, by blending the grafted nanoparticles and fluorinated polymers such as poly (vinylidene fluoride) (PVDF) and ionomers such as Nafion. This paper presented the properties of the PEMs developed as a function of nanoparticles size and content, as well as the proton conductivity at controlled temperature and RH.

  13. Nitrogen distribution between aqueous fluids and silicate melts

    Science.gov (United States)

    Li, Yuan; Huang, Ruifang; Wiedenbeck, Michael; Keppler, Hans

    2015-02-01

    The partitioning of nitrogen between hydrous fluids and haplogranitic, basaltic, or albitic melts was studied at 1-15 kbar, 800-1200 °C, and oxygen fugacities (fO2) ranging from the Fe-FeO buffer to 3log units above the Ni-NiO buffer. The nitrogen contents in quenched glasses were analyzed either by electron microprobe or by secondary ion mass spectrometry (SIMS), whereas the nitrogen contents in fluids were determined by mass balance. The results show that the nitrogen content in silicate melt increases with increasing nitrogen content in the coexisting fluid at given temperature, pressure, and fO2. Raman spectra of the silicate glasses suggest that nitrogen species change from molecular N2 in oxidized silicate melt to molecular ammonia (NH3) or the ammonium ion (NH4+) in reduced silicate melt, and the normalized Raman band intensities of the nitrogen species linearly correlate with the measured nitrogen content in silicate melt. Elevated nitrogen contents in silicate melts are observed at reduced conditions and are attributed to the dissolution of NH3/NH4+. Measured fluid/melt partition coefficients for nitrogen (DNfluid/ melt) range from 60 for reduced haplogranitic melts to about 10 000 for oxidized basaltic melts, with fO2 and to a lesser extent melt composition being the most important parameters controlling the partitioning of nitrogen. Pressure appears to have only a minor effect on DNfluid/ melt in the range of conditions studied. Our data imply that degassing of nitrogen from both mid-ocean ridge basalts and arc magmas is very efficient, and predicted nitrogen abundances in volcanic gases match well with observations. Our data also confirm that nitrogen degassing at present magma production rates is insufficient to accumulate the atmosphere. Most of the nitrogen in the atmosphere must have degassed very early in Earth's history and degassing was probably enhanced by the oxidation of the mantle.

  14. The Reaction of Carbonates in Contact with Superheated Silicate Melts: New Insights from MEMIN Laser Melting Experiments

    Science.gov (United States)

    Hamann, C.; Hecht, L.; Schäffer, S.; Deutsch, A.; Lexow, B.

    2016-08-01

    The reaction of carbonates in contact with silicate impact melts is discussed quite controversially in the impact community. Here, we discuss four MEMIN laser melting experiments involving carbonates in contact with superheated silicate melts.

  15. Behaviour of Silicate Melts in Respect of Volume

    Institute of Scientific and Technical Information of China (English)

    张金民; 叶大年

    1989-01-01

    The volumes per oxygen of some silicate melts have been calculated and then compared with those of silicate glasses.It is suggested that the volume of a silicate melt can be divided into two parts.One is contri buted by the silicon-oxygen network and the other by the “oxides”.Variation patterns of VPOs suggest that the volume of the Si-O network generally remains unchanged and the expansion of the melt is caused mainly by the locat expansion of the “oxides”.It is further proposed that the radius of O2- shows little variation,in striking contrast to the radius of cations.The mechanism governing the expansion is discussed in detail.

  16. Mathematical Viscosity Models for Ternary Metallic and Silicate Melts

    Institute of Scientific and Technical Information of China (English)

    FU Yuan-kun; MENG Xian-min; GUO Han-jie

    2004-01-01

    The mathematical viscosity models for metallic melts were discussed. The experimental data of Ag-Au-Cu systems were used to verify the models based on Chou's general geometric thermodynamic model and the calculated results are consistent with the reported experimental data. A new model predicting the viscosity of multi-component silicate melts was established. The CaO-MnO-SiO2, CaO-FeO-SiO2 and FeO-MnO-SiO2 silicate slag systems were used to verify the model.

  17. The Partitioning of Tungsten bwtween Aqueous Fluids and Silicate Melts

    Institute of Scientific and Technical Information of China (English)

    许永胜; 张本仁; 等

    1993-01-01

    An experimental study has been carried out to determine the partition coefficients of tungsten between aqueous fluids and granitic melts at 800℃ and 1.5kb with natural granite as the starting material,The effects of the solution on the partition coefficients of tungsten show a wequence of P>co32->B>H2O.The effects are limited(generally KD<0.3)and the tungsten shows a preferential trend toward the melt over the aqueous fiuid.The value of KD increases with increasing concentration of phosphorus;the KD increases first and then reduces with the concentration of CO32-;when temperature decreases,the KD between the solution of CO32- and the silicate melt increases,and that between the solution of B4O72- and the silicate melt decreases.The partition coefficients of phosphorus and sodium between fluids and silicate melts have been calculated from the concentrations of the elements in the melts.The KD value for phosphorus is 0.38 and that for sodium is 0.56.Evidence shows that the elements tend to become richer and richer in the melts.

  18. Modeling the viscosity of silicate melts containing manganese oxide

    Directory of Open Access Journals (Sweden)

    Kim Wan-Yi

    2013-01-01

    Full Text Available Our recently developed model for the viscosity of silicate melts is applied to describe and predict the viscosities of oxide melts containing manganese oxide. The model requires three pairs of adjustable parameters that describe the viscosities in three systems: pure MnO, MnO-SiO2 and MnO-Al2O3-SiO2. The viscosity of other ternary and multicomponent silicate melts containing MnO is then predicted by the model without any additional adjustable model parameters. Experimental viscosity data are reviewed for melts formed by MnO with SiO2, Al2O3, CaO, MgO, PbO, Na2O and K2O. The deviation of the available experimental data from the viscosities predicted by the model is shown to be within experimental error limits.

  19. Taste Masking of Griseofulvin and Caffeine Anhydrous Using Kleptose Linecaps DE17 by Hot Melt Extrusion.

    Science.gov (United States)

    Juluri, Abhishek; Popescu, Carmen; Zhou, Leon; Murthy, Reena N; Gowda, Vanaja K; Chetan Kumar, P; Pimparade, Manjeet B; Repka, Michael A; Murthy, S Narasimha

    2016-02-01

    The objective of this project was to investigate the potential of Kleptose Linecaps DE17 (KLD) in masking the unpleasant/bitter taste of therapeutic agents by hot melt extrusion (HME). Griseofulvin (GRI) and caffeine anhydrous (CA) were used as a bitter active pharmaceutical ingredient (API) model drugs. Thermogravimetric studies confirmed the stability of GRI, CA, and KLD at the employed extrusion temperatures. The differential scanning calorimetry (DSC) studies revealed a characteristic melting endotherm of GRI at 218-220°C and CA at 230-232°C in the physical mixtures as well as in all extrudates over the period of study, indicating the crystalline nature of drug. HME of KLD was achieved only in the presence of plasticizer. Among the several plasticizers investigated, xylitol showed improved processability of KLD at 15% w/w concentration. Dissolution studies of HME extrudates using simulated salivary medium exhibited ∼threefold less release compared to physical mixture at the end of 5 min (the lesser drug release, better the taste masking efficiency). Furthermore, the results from the sensory evaluation of products in human panel demonstrated strong bitter taste in the case of physical mixture compared to the HME formulation, suggesting the potential of Kleptose Linecaps DE17 as taste masking polymer in melt extruded form.

  20. Sulfur Solubility In Silicate Melts: A Thermochemical Model

    Science.gov (United States)

    Moretti, R.; Ottonello, G.

    A termochemical model for calculating sulfur solubility of simple and complex silicate melts has been developed in the framework of the Toop-Samis polymeric approach combined with a Flood - Grjotheim theoretical treatment of silicate slags [1,2]. The model allows one to compute sulfide and sulfate content of silicate melts whenever fugacity of gaseous sulphur is provided. "Electrically equivalent ion fractions" are needed to weigh the contribution of the various disproportion reactions of the type: MOmelt + 1/2S2 ,gas MSmelt+1/2O2 ,gas (1) MOmelt + 1/2S2 ,gas + 3/2O2 ,gas MSO4 ,melt (2) Eqs. 1 and 2 account for the oxide-sulfide and the oxide-sulfate disproportiona- tion in silicate melt. Electrically equivalent ion fractions are computed, in a fused salt Temkin notation, over the appropriate matrixes (anionic and cationic). The extension of such matrixes is calculated in the framework of a polymeric model previously developed [1,2,3] and based on a parameterization of acid-base properties of melts. No adjustable parameters are used and model activities follow the raoultian behavior implicit in the ion matrix solution of the Temkin notation. The model is based on a huge amount of data available in literature and displays a high heuristic capability with virtually no compositional limits, as long as the structural role assigned to each oxide holds. REFERENCES: [1] Ottonello G., Moretti R., Marini L. and Vetuschi Zuccolini M. (2001), Chem. Geol., 174, 157-179. [2] Moretti R. (2002) PhD Thesis, University of Pisa. [3] Ottonello G. (2001) J. Non-Cryst. Solids, 282, 72-85.

  1. Quantitative determination of amorphous nicardipine hydrochloride in long acting formula (NIC-LA) using light anhydrous silicic acid.

    Science.gov (United States)

    Kohinata, Takeru; Fujii, Mitsuo; Nakamura, Souichiro; Hamada, Noritaka; Yonemochi, Etsuo; Terada, Katsuhide

    2004-12-01

    We investigated a method to quantitatively determine amorphous nicardipine hydrochloride (NIC) in the NIC-long acting formula (LA) model formulas prepared using NIC, light anhydrous silicic acid (LASA) and carboxymethylethylcellulose (CMEC). Consequently, since the quantity of total NIC in the formula can be determined by means of HPLC and crystal NIC can be determined by the differential scanning calorimetry (DSC) method because the heat of fusion (85.08 J/g) of NIC is constant and unaffected by excipients, we developed the HPLC-DSC method by which the quantity of amorphous NIC is calculated as the difference between the quantity of total NIC determined by HPLC and the quantity of crystal NIC determined by DSC. This practical HPLC-DSC method was confirmed to have good accuracy and reproducibility.

  2. Mg-perovskite/silicate melt and magnesiowuestite/silicate melt partition coefficients for KLB-1 at 250 Kbars

    Science.gov (United States)

    Drake, Michael J.; Rubie, David C.; Mcfarlane, Elisabeth A.

    1992-01-01

    The partitioning of elements amongst lower mantle phases and silicate melts is of interest in unraveling the early thermal history of the Earth. Because of the technical difficulty in carrying out such measurements, only one direct set of measurements was reported previously, and these results as well as interpretations based on them have generated controversy. Here we report what are to our knowledge only the second set of directly measured trace element partition coefficients for a natural system (KLB-1).

  3. Investigating sulfur partitioning between nominally volatile-free minerals and silicate melts

    Science.gov (United States)

    Marzoli, A.; Callegaro, S.; Baker, D. R.; Geraki, K.; Maneta, V.

    2015-12-01

    Despite the key role played by volatile species in magmatic systems, it is still challenging to quantify their concentrations in ancient melts. We suggested a quantitative approach for estimating S contents in basaltic melts (Callegaro et al., 2014), based on direct measurement of S on clinopyroxene and calculation of its concentration in the melt through an experimentally determined partition coefficient (KD). We further investigated the partitioning of sulfur between silicate melts and nominally volatile-free minerals (olivine, orthopyroxene, clinopyroxene, and plagioclase), as well as between melt and amphibole. Partitioning experiments were performed with basaltic, andesitic and dacitic bulk compositions, at hydrous and anhydrous conditions, and at high and low oxygen fugacities (fO2), where sulfur in the melt is dominantly present as an S6+ or S2- species, respectively (Wilke et al., 2011). Sulfur concentrations in melts were measured by electron microprobe and in crystals by synchrotron X-ray fluorescence. At low fO2 the average crystal/liquid KDs for sulfur vary from 0.0004 (at a maximum) for olivine, to 0.003 (another maximum) for orthopyroxene, to 0.03 for clinopyroxene, and to 0.07 for plagioclase. The KDs correlate positively with the cation-oxygen bond lengths in the crystals. At high fO2 the KDs drop to approximately one-third of those observed at low fO2. These observations suggest that S2- replaces oxygen in the crystal structure. Water has no measureable influence on the crystal/melt partitioning of sulfur. Clinopyroxene/melt KDs are correlated with the Mg/(Mg+Fe) ratio of the crystal, but appear insensitive to the IVAl in the structure. Plagioclase/melt S partitioning appears unaffected by anorthite content and iron concentration in the crystal. These new KDs allow the determination of sulfur concentration in the igneous melts co-existing with these crystals and provide insights into the volatile concentrations of ancient magmas and their possible

  4. S-Isotope Fractionation between Fluid and Silicate Melts

    Science.gov (United States)

    Fiege, A.; Holtz, F.; Shimizu, N.; Behrens, H.; Mandeville, C. W.; Simon, A. C.

    2013-12-01

    Large amounts of sulfur (S) can be released from silicate melts during volcanic eruption. Degassing of magma can lead to S-isotope fractionation between fluid and melt. However, experimental data on fluid-melt S-isotope fractionation are scarce and no data exist for silicate melts at temperatures (T) > 1000°C. Recent advances in in situ S-isotope analyses using secondary ion mass spectroscopy (SIMS) enable determinations of the isotopic composition in silicate glasses with low S content [1] and allow us to investigate experimentally fluid-melt S-isotope fractionation effects in magmatic systems. Isothermal decompression experiments were conducted in internally heated pressure vessels (IHPV). Volatile-bearing (~3 to ~8 wt% H2O, 140 to 2700 ppm S, 0 to 1000 ppm Cl) andesitic and basaltic glasses were synthesized at ~1040°C, ~500 MPa and log(fO2) = QFM to QFM+4 (QFM: quartz-magnetite-fayalite buffer). The decompression experiments were carried out at T = 1030 to 1200°C and similar fO2. Pressure (P) was released continuously from ~400 MPa to 150, 100 or 70 MPa with rates (r) ranging from 0.001 to 0.2 MPa/s. The samples were either rapidly quenched after decompression or annealed for various times (tA) at final conditions (1 to 72 h) before quenching. The volatile-bearing starting glasses and the partially degassed experimental glasses were analyzed by electron microprobe (e.g. Cl-, S-content), IR-spectroscopy (H2O content) and SIMS (δ34S). The gas-melt isotope fractionation factors (αg-m) were estimated following Holloway and Blank [2] and utilizing mass balance calculations. The results show that αg-m remains constant within error over the investigated range of r and tA, reflecting fluid-melt equilibrium fractionation of S isotopes for given T and fO2. Data obtained for oxidizing conditions (~QFM+4) are in agreement with observations in arc magmas [3] and close to what is predicted by previous theoretical and experimental data [4; 5; 6]; e.g. a α(SO2 gas - SO42

  5. Melting Phase Relation of Nominally Anhydrous, Carbonated Pelite at Sub-arc Depths and Cycling of Sedimentary Carbon in Subduction Zones

    Science.gov (United States)

    Tsuno, K.; Dasgupta, R.

    2009-12-01

    An important mass transfer process for subduction zone magmatism is the cycling of C-O-H volatiles from subducting slab to arc volcanoes. However, CO2 is known to remain stable in subducting lithologies in the form crystalline carbonates. Mass balance of chemical tracers between slab input and arc output1 and stable isotopic compositions of arc fluids2, on the other hand, suggest that subducting sediments contribute to arc volcanism and arc-flux of CO2 derives primarily from subducting sediments. Therefore, it is important to explore the possible link between sediment contributions to arc volcanism and CO2 release from subducting sediments to mantle wedge. We have investigated, using an end-loaded piston cylinder device, melting relation of a carbonate-bearing, nominally anhydrous pelagic sediment composition at a single pressure of 3 GPa and at temperatures of 900-1350 °C. The starting material (HPLC1) has ~5 wt.% CO2 and corresponds (in H2O-free basis) to a mixture of 10 wt.% pelagic carbonate unit and 90 wt.% overlying hemipelagic mud unit that enter the Central American trench3. The subsolidus assemblage at 900 °C consists of garnet+cpx+K-feldspar+coesite+rutile+ankeritess, whereas just above the solidus (900-1000 °C), carbonatitic melt appears and ankeritess disappears (1000-1100 °C). The appearance of CO2-bearing silicate melt at 1100 °C coincides with the disappearance of K-feldspar and rutile, and the melt coexists with garnet+cpx+coesite/quartz from 1100 to 1300 °C. The liquidus is located >1350 °C, and the sole liquidus phase is quartz. Silicate melt composition evolves systematically from 1100 to 1350 °C with a decrease in SiO2 (65.7 to 59.1 wt.%), Al2O3 (13.5 to 12.4 wt.%), K2O (~5.5 to 2.1 wt.%), and CO2 (~8.5 to 5.2 wt.%), whereas MgO, FeO*, and CaO contents of the melt increase from 0.4 to 2.6 wt.%, 1.5 to 6.7 wt.%, and 2.4 to 8.7 wt.%, respectively. The Na2O content increases from 2.3 to 3.6 wt.% between 1100 and 1200 °C and decreases to 2

  6. Studying regimes of convective heat transfer in the production of high-temperature silicate melts

    Science.gov (United States)

    Volokitin, O. G.; Sheremet, M. A.; Shekhovtsov, V. V.; Bondareva, N. S.; Kuzmin, V. I.

    2016-09-01

    The article presents the results of theoretical and experimental studies of the production of high-temperature silicate melts using the energy of low-temperature plasma in a conceptually new setup. A mathematical model of unsteady regimes of convective heat and mass transfer is developed and numerically implemented under the assumption of non-Newtonian nature of flow in the melting furnace with plasma-chemical synthesis of high-temperature silicate melts. Experiments on melting silicate containing materials were carried out using the energy of low-temperature plasma. The dependence of dynamic viscosity of various silicate materials (basalt, ash, waste of oil shale) was found experimentally.

  7. Reinterpretation of reduction potential measurements done by linear sweep voltammetry in silicate melts

    Science.gov (United States)

    Colson, R. O.; Haskin, L. A.; Keedy, C. R.

    1991-01-01

    The equilibrium concentrations of Ni between silicate melt and Pt were determined experimentally as a function of oxygen fugacity. The results demonstrate that metallic species derived in linear sweep voltammetry experiments in silicate melts are diffusing into Pt electrodes and not into the melt, as was concluded by previoius studies. This requires reinterpretation of previous linear sweep voltammetry results and recalculation and correction of reported reduction potentials. This paper reports these corrected reduction potentials. Also reported are the activity coefficients for Ni in synthetic basalt and diopsidic melts and for Co in diopsidic melt.

  8. Chemical interactions and configurational disorder in silicate melts

    Directory of Open Access Journals (Sweden)

    G. Ottonello

    2005-06-01

    Full Text Available The Thermodynamics of quasi-chemical and polymeric models are briefly reviewed. It is shown that the two classes are mutually consistent, and that opportune conversion of the existing quasi-chemical parameterization of binary interactions in MO-SiO2 joins to polymeric models may be afforded without substantial loss of precision. It is then shown that polymeric models are extremely useful in deciphering the structural and reactive properties of silicate melts and glasses. They not only allow the Lux-Flood character of the dissolved oxides to be established, but also discriminate subordinate strain energy contributions to the Gibbs free energy of mixing from the dominant chemical interaction terms. This discrimination means that important information on the short-, medium- and long-range periodicity of this class of substances can be retrieved from thermodynamic analysis. Lastly, it is suggested that an important step forward in deciphering the complex topology of the inhomogeneity ranges observed at high SiO2 content can be performed by applying SCMF theory and, particularly, Matsen-Schick spectral analysis, hitherto applied only to rubberlike materials.

  9. A sample holding technique for study of crystal growth in silicate melts

    Science.gov (United States)

    Donaldson, C. H.; Williams, R. J.; Lofgren, G.

    1975-01-01

    A thin platinum wire loop is an effective way to hold silicate melts during experimentation in a gas-mixing furnace. This method results in a minimum of physical and chemical interaction between the sample and container but maximum interaction between sample and gas mixture. However, volatilization of sodium occurs while the silicate is molten. By minimizing the chance of heterogeneous nucleation, the method is ideal for experimental investigation of the origin of rock textures.

  10. Termochemical Models For Slags and Silicate Melts, Review and Perspectives

    Science.gov (United States)

    Ottonello, G.

    Thermochemical models devoted to the comprehension of reactive and mixing properties of silicate melts and slags may be roughly grouped into four main classes: 1) fictive chemical; 2) quasi chemical; 3) fictive structural; 4) polymeric. In the first class we may group the fictive regular mixture approach of Ghiorso and Carmichael [1,2]and its extensions [3-5]and the subregular model of Berman and Brown [6]. To the second class belong the modified quasi chemical approach of Pelton and coworkers [7,8] , and the Kapoor - Froberg cellular model and its extensions [9-11]. The third class has much to share with the second one (and indeed the cellular model could be ascribed to this class as well). To this class belong the "central surround model" of Sastri and Lahiri [12] , the associated solution models of Bjorkman [13], Hastie and coworkers [14]and Goel and coworkers [15], the two sublattice model of Hillert and coworkers [16]and the polynomial expansions of Hoch and Arpshofen [17] . The fourth class encompasses the models of Masson[18-20] , Toop-Samis [21,22]and its extensions [23-25] . The phylosophy beyond each one of the four classes is basically different. Benefits and drawbacks are present in any of them, and applications are often limited to simple systems (or to sufficiently complex systems, in the case of arbitrary deconvolutions of type 1) and to limited P-T ranges. The crucial aspects of the various models will be outlined to some extent. It will be shown that, often, model conflictuality is only appartent and that, in some cases, model failure is unperceived by acritical utilizers. New perspectives in the future research devoted to the comprehension of melt reactivity in compositionally complex systems, with special enphasis on the solubility of gaseous components and unmixing, will be finally discussed. References: [1] Ghiorso M.S. and Carmichael I.S.E. (1980) Contrib. Mineral. Petrol., 71, 323-342. [2] Ghiorso M.S., Carmichael I.S.E., Rivers M.L. and Sack

  11. Energetics of silicate melts from thermal diffusion studies

    Energy Technology Data Exchange (ETDEWEB)

    Walker, D.

    1992-07-01

    Efforts are reported in the following areas: laboratory equipment (multianvils for high P/T work, pressure media, SERC/DL sychrotron), liquid-state thermal diffusion (silicate liquids, O isotopic fractionation, volatiles, tektites, polymetallic sulfide liquids, carbonate liquids, aqueous sulfate solutions), and liquid-state isothermal diffusion (self-diffusion, basalt-rhyolite interdiffusion, selective contamination, chemical diffusion).

  12. Pt, Au, Pd and Ru Partitioning Between Mineral and Silicate Melts: The Role of Metal Nanonuggets

    Science.gov (United States)

    Malavergne, V.; Charon, E.; Jones, J.; Agranier, A.; Campbell, A.

    2012-01-01

    The partition coefficients of Pt and other Pt Group Elements (PGE) between metal and silicate D(sub Metal-Silicate) and also between silicate minerals and silicate melts D(sub Metal-Silicate) are among the most challenging coefficients to obtain precisely. The PGE are highly siderophile elements (HSE) with D(sub Metal-Silicate) >10(exp 3) due to the fact that their concentrations in silicates are very low (ppb to ppt range). Therefore, the analytical difficulty is increased by the possible presence of HSE-rich-nuggets in reduced silicate melts during experiments). These tiny HSE nuggets complicate the interpretation of measured HSE concentrations. If the HSE micro-nuggets are just sample artifacts, then their contributions should be removed before calculations of the final concentration. On the other hand, if they are produced during the quench, then they should be included in the analysis. We still don't understand the mechanism of nugget formation well. Are they formed during the quench by precipitation from precursor species dissolved homogeneously in the melts, or are they precipitated in situ at high temperature due to oversaturation? As these elements are important tracers of early planetary processes such as core formation, it is important to take up this analytical and experimental challenge. In the case of the Earth for example, chondritic relative abundances of the HSE in some mantle xenoliths have led to the concept of the "late veneer" as a source of volatiles (such as water) and siderophiles in the silicate Earth. Silicate crystal/liquid fractionation is responsible for most, if not all, the HSE variation in the martian meteorite suites (SNC) and Pt is the element least affected by these fractionations. Therefore, in terms of reconstructing mantle HSE abundances for Mars, Pt becomes a very important player. In the present study, we have performed high temperature experiments under various redox conditions in order to determine the abundances of Pt, Au

  13. Chemistry of Impact-Generated Silicate Melt-Vapor Debris Disks

    CERN Document Server

    Visscher, Channon

    2013-01-01

    In the giant impact theory for lunar origin, the Moon forms from material ejected by the impact into an Earth-orbiting disk. Here we report the initial results from a silicate melt-vapor equilibrium chemistry model for such impact-generated planetary debris disks. In order to simulate the chemical behavior of a two-phase (melt+vapor) disk, we calculate the temperature-dependent pressure and chemical composition of vapor in equilibrium with molten silicate from 2000 to 4000 K. We consider the elements O, Na, K, Fe, Si, Mg, Ca, Al, Ti, and Zn for a range of bulk silicate compositions (Earth, Moon, Mars, eucrite parent body, angrites, and ureilites). In general, the disk atmosphere is dominated by Na, Zn, and O2 at lower temperatures (< 3000 K) and SiO, O2, and O at higher temperatures. The high-temperature chemistry is consistent for any silicate melt composition, and we thus expect abundant SiO, O2, and O to be a common feature of hot, impact-generated debris disks. In addition, the saturated silicate vapor...

  14. Ionic-polymeric models and the amphoteric behavior of water in silicate melts

    Science.gov (United States)

    Moretti, R.

    2012-04-01

    In silicate melts it is almost impossible to readily distinguish solute and solvent like in aqueous solutions. The anionic framework of silicate melts, in fact, makes solute and solvents so intimately related that one cannot identify a solvation shell and identify directly, from structural studies, the complexes needed to define acid-base reactions. Therefore, the distinction between solute and solvent becomes blurred in systems such as silicate melts, because speciation is not only complex but changes with the marked depolymerization of the silicate framework that obtains from pure SiO2 to metal-oxide rich compositions. These features do not allow proper understanding of the actual physico-chemical role of many species detected by conventional techniques, a fact which can lead to confusing notation. However, these may not be serious limits to account correctly for the acid-base reactions that take place in every kind of magmatic setting, provided a 'syntax' describing the effective interactions among significative cationic and anionic entities. In particular, the syntax for acid-base exchanges is needed such that constituting oxides (i.e. chemical components) can be treated independently of (but not necessarily extraneous to) structural features in defining such entities. So-called ionic-polymeric models highlight the mutual correspondence between polymerization and acid-base properties of dissolved oxides through the Lux-Flood formalism for molten oxides. They thus provide the syntax to write chemical exchanges, but have no pretension to structural description. In fact the concept of melt polymerization is used to identify basic anions and cations that can be used, along with their formal charge, to describe effectively acid-base interactions taking place in melts. In this respect, an example is given by the description of the amphoteric behavior of water dissolved on melts, hence water autoprotolysis. Although it exerts a profound influence on properties of

  15. Melt inclusion record of immiscibility between silicate, hydrosaline, and carbonate melts: Applications to skarn genesis at Mount Vesuvius

    Science.gov (United States)

    Fulignati, Paolo; Kamenetsky, Vadim S.; Marianelli, Paola; Sbrana, Alessandro; Mernagh, Terrence P.

    2001-11-01

    Foid-bearing syenites and endoskarn xenoliths of the A.D. 472 Vesuvius eruption represent the magma chamber carbonate wall-rock interface. Melt inclusions hosted in crystals from these rocks offer a rare opportunity to depict the formation and the composition of metasomatic skarn-forming fluids at the peripheral part of a growing K-alkaline magma chamber disrupted by an explosive eruption. Four principal types of melt inclusions represent highly differentiated phonolite (type 1), hydrosaline melt (type 3), unmixed silicate salt melts (type 2), and a complex chloride-carbonate melt with minor sulfates (type 4). The high-temperature (700 800 °C) magmatic-derived hydrosaline melt is considered to be the main metasomatic agent for the skarn-forming reactions. The interaction between this melt (fluid) and carbonate wall rocks produces a Na-K-Ca carbonate-chloride melt that shows immiscibility between carbonate and chloride constituents at ˜700 °C in 1 atm experiments. This unmixing can be viewed as a possible mechanism for the origin of carbonatites associated with intrusion-related skarn systems.

  16. H2O-rich melt inclusions in fayalitic olivine from Hekla volcano: Implications for phase relationships in silicic systems and driving forces of explosive volcanism on Iceland

    Science.gov (United States)

    Portnyagin, Maxim; Hoernle, Kaj; Storm, Sonja; Mironov, Nikita; van den Bogaard, Christel; Botcharnikov, Roman

    2012-12-01

    Silicic Icelandic magmas are widely believed to contain low to moderate H2O content prior to degassing, and that their high explosivity mostly results from the interaction of the magmas with ice or meteoric water. Here we report the compositions of glass inclusions (SiO2=57-72 wt%, K2O=1.3-2.6 wt%) in Fe-rich olivines (Fo2-42) from the largest Holocene eruptions of Hekla volcano (H3 and H4) on Iceland, which preserved quenched melts with very high primary H2O contents (3.3-6.2 wt%). The silicic Hekla melts originate primarily by extensive (˜90%) crystal fractionation of H2O-poor (˜0.6 wt%) basalts and represent an end member in the systematics of terrestrial magmas because they originate at low fO2 (ΔQFM ˜-0.1 to -0.4) and have as high H2O contents as significantly more oxidized island-arc magmas (ΔQFM≥1). This demonstrates that H2O and ΔQFM do not correlate in silicic magmas from different tectonic settings, and that fO2, not H2O content, shows a major difference between silicic ocean-island (e.g., Icelandic) and island-arc magmas. Analysis of available experimental data suggests that high H2O activity and low fO2 expand the field of olivine stability in silicic melts. Low fO2 and low MgO content could also suppress crystallization of amphibole. On the basis of these results we propose that an anhydrous mineral assemblage bearing Fe-rich olivine in evolved volcanic and Skaergaard-type intrusive rocks does not imply low H2O in magmas prior to degassing but, in contrast to the commonly held view, is an indicator of H2O-rich silicic parental magmas crystallized at low fO2. Finally, the high H2O content in magma was a major driving force of the largest explosive eruptions of Hekla volcano and must be at least as important for driving silicic explosive volcanism on Iceland as magma-ice interaction.

  17. Trace element geochemistry of Amba Dongar carbonatite complex, India: Evidence for fractional crystallization and silicate-carbonate melt immiscibility

    Indian Academy of Sciences (India)

    Jyotiranjan S Ray; P N Shukla

    2004-12-01

    Carbonatites are believed to have crystallized either from mantle-derived primary carbonate magmas or from secondary melts derived from carbonated silicate magmas through liquid immiscibility or from residual melts of fractional crystallization of silicate magmas. Although the observed coexistence of carbonatites and alkaline silicate rocks in most complexes, their coeval emplacement in many, and overlapping initial 87Sr/86Sr and 143Nd/144Nd ratios are supportive of their cogenesis; there have been few efforts to devise a quantitative method to identify the magmatic processes. In the present study we have made an attempt to accomplish this by modeling the trace element contents of carbonatites and coeval alkaline silicate rocks of Amba Dongar complex, India. Trace element data suggest that the carbonatites and alkaline silicate rocks of this complex are products of fractional crystallization of two separate parental melts. Using the available silicate melt-carbonate melt partition coefficients for various trace elements, and the observed data from carbonatites, we have tried to simulate trace element distribution pattern for the parental silicate melt. The results of the modeling not only support the hypothesis of silicate-carbonate melt immiscibility for the evolution of Amba Dongar but also establish a procedure to test the above hypothesis in such complexes.

  18. Silicate melts density, buoyancy relations and the dynamics of magmatic processes in the upper mantle

    Science.gov (United States)

    Sanchez-Valle, Carmen; Malfait, Wim J.

    2016-04-01

    Although silicate melts comprise only a minor volume fraction of the present day Earth, they play a critical role on the Earth's geochemical and geodynamical evolution. Their physical properties, namely the density, are a key control on many magmatic processes, including magma chamber dynamics and volcanic eruptions, melt extraction from residual rocks during partial melting, as well as crystal settling and melt migration. However, the quantitative modeling of these processes has been long limited by the scarcity of data on the density and compressibility of volatile-bearing silicate melts at relevant pressure and temperature conditions. In the last decade, new experimental designs namely combining large volume presses and synchrotron-based techniques have opened the possibility for determining in situ the density of a wide range of dry and volatile-bearing (H2O and CO2) silicate melt compositions at high pressure-high temperature conditions. In this contribution we will illustrate some of these progresses with focus on recent results on the density of dry and hydrous felsic and intermediate melt compositions (rhyolite, phonolite and andesite melts) at crustal and upper mantle conditions (up to 4 GPa and 2000 K). The new data on felsic-intermediate melts has been combined with in situ data on (ultra)mafic systems and ambient pressure dilatometry and sound velocity data to calibrate a continuous, predictive density model for hydrous and CO2-bearing silicate melts with applications to magmatic processes down to the conditions of the mantle transition zone (up to 2773 K and 22 GPa). The calibration dataset consist of more than 370 density measurements on high-pressure and/or water-and CO2-bearing melts and it is formulated in terms of the partial molar properties of the oxide components. The model predicts the density of volatile-bearing liquids to within 42 kg/m3 in the calibration interval and the model extrapolations up to 3000 K and 100 GPa are in good agreement

  19. Vanadium magnetite-melt oxybarometry of natural, silicic magmas: a comparison of various oxybarometers and thermometers

    Science.gov (United States)

    Arató, Róbert; Audétat, Andreas

    2017-07-01

    To test a recently developed oxybarometer for silicic magmas based on partitioning of vanadium between magnetite and silicate melt, a comprehensive oxybarometry and thermometry study on 22 natural rhyolites to dacites was conducted. Investigated samples were either vitrophyres or holocrystalline rocks in which part of the mineral and melt assemblage was preserved only as inclusions within phenocrysts. Utilized methods include vanadium magnetite-melt oxybarometry, Fe-Ti oxide thermometry and -oxybarometry, zircon saturation thermometry, and two-feldspar thermometry, with all analyses conducted by laser-ablation ICP-MS. Based on the number of analyses, the reproducibility of the results and the certainty of contemporaneity of the analyzed minerals and silicate melts the samples were grouped into three classes of reliability. In the most reliable ( n = 5) and medium reliable ( n = 10) samples, all fO2 values determined via vanadium magnetite-melt oxybarometry agree within 0.5 log units with the fO2 values determined via Fe-Ti oxide oxybarometry, except for two samples of the medium reliable group. In the least reliable samples ( n = 7), most of which show evidence for magma mixing, calculated fO2 values agree within 0.75 log units. Comparison of three different thermometers reveals that temperatures obtained via zircon saturation thermometry agree within the limits of uncertainty with those obtained via two-feldspar thermometry in most cases, whereas temperatures obtained via Fe-Ti oxide thermometry commonly deviate by ≥50 °C due to large uncertainties associated with the Fe-Ti oxide model at T- fO2 conditions typical of most silicic magmas. Another outcome of this study is that magma mixing is a common but easily overlooked phenomenon in silicic volcanic rocks, which means that great care has to be taken in the application and interpretation of thermometers and oxybarometers.

  20. Development of a new laboratory technique for high-temperature thermal emission spectroscopy of silicate melts

    Science.gov (United States)

    Lee, Rachel J.; Ramsey, Michael S.; King, Penelope L.

    2013-05-01

    the prevalence of glass and molten silicates in volcanic environments, and the important role of surface emissivity in thermal infrared (TIR) measurements, it is imperative to characterize accurately the spectral features associated with silicate glasses and melts. A microfurnace has been developed specifically for use with a laboratory Fourier transform infrared (FTIR) spectrometer to collect the first in situ TIR emission spectra of actively melting and cooling silicate glasses. The construction, implementation, and calibration of the microfurnace spectrometer system are presented here. Initial testing of the microfurnace is also discussed, which includes acquisition of thermal emission spectra of a quartz powder (unmelted), a melted and cooled oligoclase feldspar, and glassy melt of rhyolitic composition. Unlike a solid material, which may only have bending and stretching vibrations within its molecular structure, a fully molten material will exhibit several more degrees of freedom in structural movement, thus changing its spectral character. Differences in spectral behavior and morphology are observed between a glass in a solid state and its molten counterpart, confirming previous field measurements of lower emissivity upon melting. This laboratory microfurnace system has been designed to quantify the TIR emission spectral behavior of glassy materials in various physical states. Ultimately, it is hoped that the microfurnace data will help improve the ability of field-based, airborne, and spaceborne TIR data to characterize glassy volcanic terranes.

  1. Effect of melting conditions on striae in iron-bearing silicate melts

    DEFF Research Database (Denmark)

    Jensen, Martin; Yue, Yuanzheng

    2012-01-01

    Chemical striae are present in a broad range of glass products, but due to their negative impact on e.g., the optical and mechanical properties, elimination of striae from melts is a key issue in glass technology. By varying melting temperatures, retentions times and redox conditions of an iron......-bearing calciumaluminosilicate melt, we quantify the effect of each of the three melting parameters on the stria content in the melt. The quantification of the stria content in the melt is conducted by means of image analysis on casted melt samples. We find that in comparison to an extension of retention time an increase...... factors such as compositional fluctuation of melts and bubbling due to iron reduction on the stria content. During the melting process, striae with a chemical gradient in a more mobile species equilibrate faster than striae caused by a chemical gradient in a less mobile species. The temperature and time...

  2. A study of redox kinetic in silicate melt; Etude cinetique des reactions d'oxydoreduction dans les silicates

    Energy Technology Data Exchange (ETDEWEB)

    Magnien, V

    2005-12-15

    The aim of this thesis is to understand better iron redox reactions and mechanisms in silicate glasses and melts. Particular interest has been paid to the influence of temperature and chemical composition. For this purpose, the influence of alkali element content, iron content and network formers on the kinetics of redox reactions has been determined through XANES and Raman spectroscopy experiments performed either near the glass transition or above the liquidus temperature. As a complement, electrical conductivity and RBS spectroscopy experiments have been made to characterize the diffusivity of the species that transport electrical charges and the reaction morphology, respectively. Temperature and composition variations can induce changes in the dominating redox mechanism. At a given temperature, the parameters that exert the strongest influence on redox mechanisms are the presence or lack of divalent cations and the existing decoupling between the mobility of network former and modifier elements. Near Tg, the diffusion of divalent cations, when present in the melt, controls the kinetics of iron redox reactions along with a flux of electron holes. Composition, through the degree of polymerization and the silicate network structure, influences the kinetics and the nature of the involved cations, but not the mechanisms of the reaction. Without alkaline earth elements, the kinetics of redox reactions are controlled by the diffusion of oxygen species. With increasing temperatures, the diffusivities of all ionic species tend to become similar. The decoupling between ionic fluxes then is reduced so that several mechanisms become kinetically equivalent and can thus coexist. (author)

  3. Redox Equilibria of Chromium in Calcium Silicate Base Melts

    Science.gov (United States)

    Mirzayousef-Jadid, A.-M.; Schwerdtfeger, Klaus

    2009-08-01

    The oxidation state of chromium has been determined at 1600 °C in CaO-SiO2-CrO x melts with CaO/SiO2 ratios (mass pct) of 0.66, 0.93, and 1.10, and 0.15 to 3.00 pct Cr2O3 (initial). A few experiments were also carried out with CaO-SiO2-Al2O3-CrO x melts at 1430 °C. The slag samples were equilibrated with gas phases of controlled oxygen pressure. Two techniques were applied to determine the oxidation state: thermogravimetry and quenching of the samples with subsequent wet chemical analysis. In the low-oxygen pressure range, the chromium is mainly divalent. In the high-oxygen pressure range, it is trivalent and hexavalent. It was found that the Cr3+/Cr2+ and Cr6+/Cr3+ ratios depend on oxygen pressure at a constant CaO/SiO2 ratio and a constant content of total chromium, according to the ideal law of mass action. According to the respective chemical reactions, these ratios change proportional to p_{{{text{O}}2 }}{}^{1/4} or p_{{{text{O}}_{ 2} }}{}^{3/4}, respectively. They also increase with increasing basicity. The data are used to compute the fractions of the different ions in the melt. There is a certain range of oxygen pressure in which all three valence states, Cr2+, Cr3+, and Cr6+, coexist. The color of the solidified slag samples is described and is explained with the help of transmission spectra.

  4. The effect of sulfide dissolved in silicate melts on enhancing the solubility of the Highly Siderophile Elements

    Science.gov (United States)

    O'Neill, H. S.

    2015-12-01

    There are large inconsistencies among experimental studies of Highly Siderophile Element (HSE) partitioning relations between silicates and metal or sulfide phases, which has usually been attributed to "micronuggets", a general term for sub-optical (approximately HSE sulfide-melt/silicate-melt partition coefficients, where results range over several orders of magnitude. Moreover, nearly all the reported results of directly determined sulfide-melt/silicate-melt partition coefficients are considerably lower than values calculated by combining metal/silicate-melt with metal/sulfide-melt partition coefficients. This discrepancy has been attributed to large effects of S dissolved as sulfide in the silicate melts on HSE solubilities. As such large effects are not expected from the thermodynamic modeling of sulfide solubilities in silicate melts, it has been proposed that HSEs dissolve in sulfide-containing silicate melts by forming HSE-S complexes. This idea has been tested by experiments that compare the solubilities of Ir, Re and Ru in a high-TiO2 silicate melt both with and without dissolved sulfide at 1400 to 1600ºC at atmospheric pressure. The high TiO2 suppresses micronuggets. Experiments were analysed by LA-ICP-MS, with detection limits approaching 2 ppb. For Ir, the results show that at fO2 low enough to enable measurable sulfide in the melt, the presence of the sulfide just raises the level of dissolved Ir above detection limits. These results suggest a fairly large influence of the sulfide, but are not quantitative. By contrast, the experiments on Ru and Re clearly show only a modest effect of dissolved sulfide.

  5. Partitioning of protactinium, uranium, thorium and other trace elements between columbite and hydrous silicate melt

    Science.gov (United States)

    Huang, F.; Schmidt, M. W.; Günther, D.; Eikenberg, J.

    2009-12-01

    U-series disequilibria are a unique powerful tool to constrain the time-scales and processes of magmatism in mid-ocean ridge, intra-plate, and convergent margin settings. 235U-231Pa is one of the important parent-daughter pairs (231Pa half life = 33 kyr) because protactinium is normally much more incompatible than U during magmatism and thus the ubiquitously observed 231Pa excess in young igneous rocks most likely reflects melting processes. However, because of the extreme incompatibility of protactinium in most silicate minerals (mineral/meltDPa determined at the permissible Pa doping level of 10 ppm (bulk). Experiments were run in a piston cylinder apparatus at 0.5 GPa and 1115 oC using Pt double capsules with NNO or FMQ as external fO2 buffers. The starting material is a hydrous per-aluminous granitic composition, doped with Pa solution in the Paul Scherrer Institute and also contains other trace elements including U, Th, REE, Zr, Hf, W, Mo, Ti, V, Ge, P, and Sn. Experiments employing an oscillating rather than constant temperature have produced columbite crystals up to 30 μm and large areas of crystal-free water-saturated silicate melts. Columbite/silicate melt partition coefficients of non-radioactive trace elements are presently measured by LA-ICP-MS, and Pa will be added as a next stage. The result will give the oxidation state of Pa at oxygen fugacities of the mantle and crust, and have important implications for the partitioning of Pa between silicate minerals and melt and on our understanding of 231Pa-235U disequilibrium in natural magmatic systems.

  6. Redox Equilibrium of Niobium in Calcium Silicate Base Melts

    Science.gov (United States)

    Mirzayousef-Jadid, A.-M.; Schwerdtfeger, Klaus

    2010-10-01

    The oxidation state of niobium has been determined at 1873 K (1600 °C) in CaO-SiO2-NbO x melts with CaO/SiO2 ratios (mass pct) of 0.66, 0.93 and 1.10, and 5.72 to 11.44 pct Nb2O5 (initial). The slag samples were equilibrated with gas phases of controlled oxygen pressure, then quenched to room temperature and analyzed chemically. The niobium is mainly pentavalent with small amounts in the tetravalent state. It was found that the Nb5+/Nb4+ ratio increases with oxygen pressure at a constant CaO/SiO2 ratio and constant content of total niobium, closely according to the ideal law of mass action, which is proportional to {text{p}}_{{{text{O}}2 }}^{1/4} . The ratio also increases with total niobium content, and it seems to have a maximum at a basicity of about 0.93. The color of the solidified slag samples is described and is explained with the help of transmission spectra.

  7. Silicate melt inclusions and glasses in lunar soil fragments from the Luna 16 core sample

    Science.gov (United States)

    Roedder, E.; Weiblen, P.W.

    1972-01-01

    More than 2000 fragments were studied microscopically, and electron microprobe analyses were made of 39 selected areas, from a few square mm of polished surface, through 75- to 425-??m fragments of lunar soil from two samples of the Luna 16 core. The silicate melt inclusions and glasses differ in important details from those observed earlier in the Apollo samples. Melt inclusions in olivine contain epitaxially oriented daughter crystals, but also show a similar epitaxy around the outside of the crystals not observed in previous lunar samples. Melt inclusions in ilmenite suggest trapping at successive stages in a differentiation sequence. There is abundant evidence for late-stage silicate liquid immiscibility, with melt compositions similar but not identical to those from Apollo 11 and 12. A comparison of the alkali ratio of any given bulk rock analysis with that of its late-stage, high-silica melt shows gross differences for different rocks. This is pertinent to understanding late-stage differentiation processes. Glass fragments and spherules exhibit a wide range of crystallization textures, reflecting their wide range of compositions and cooling histories. No significant differences were found between the two portions of core examined (Zones A and D). ?? 1972.

  8. Experimental investigations of influence of pressure on the solubility of sulfur in silicate melts.

    Science.gov (United States)

    Kostyuk, Anastasia; Gorbachev, Nikolay

    2010-05-01

    Sulfide-silicate demixing of silicate melts on immiscible silicate and sulfide liquids occurs at magma sulfur saturation. This type of liquation plays an important role in geochemistry of mantle magmas, in processes of magmatic differentiation, and in ore deposit formation. The major parameter defining sulfide-silicate stratification of silicate melts is solubility of sulfur in magmas. It is considered that «solubility of sulfur» is concentration of sulfur in silicate melts. The previous researches have established positive dependence of solubility of sulphur on temperature [1, 2], melt composition [3, 4], oxidation-reduction conditions [5, 6] and our experimental data confirm it. However, available data does not give a simple answer about dependence of solubility of sulfur from pressure in modelling and natural "dry" sulfide-saturated silicate melts. The reason of difference in experiments remains not clear and further work is needed on this topic. In this paper, we report our findings on the influence of pressure on the solubility of sulfur in hydrous magnesian melts. This melts are represent by olivine basalt - picrite, coexisting with Fe-Cu-Ni sulfide melt and harzburgite (Ol+Opx) and it was investigated in a temperature range from 1200 to 1350°С and a pressure range from 0.2 to 2.5 GPa. Experiments were carried out on the piston-cylinder at Р=1-2.5GPa and in an internal-heated pressure vessels at P=0.2-0.6 GPa by a quenching technique. Our findings disagree with all previous studies demonstrating the positive [7] or negative [8, 9] influence of pressure on the solubility of sulfur in silicate melts. Our researches have shown complicated influence of pressure. Concentration of sulfur in glasses increases with increase in pressure from 0.2 to 0.6 GPa in experiments where andesite was used as a starting material. The sulfur concentration increases from 0.09 wt.% at 0.2 GPa to 0.4 wt.% at 0.6 GPa and Т=1200°С. In hydrous magnesian basalts (12-18 % MgO), we

  9. Evolution of melt-vapor surface tension in silicic volcanic systems: Experiments with hydrous melts

    Science.gov (United States)

    Mangan, M.; Sisson, T.

    2005-01-01

    We evaluate the melt-vapor surface tension (??) of natural, water-saturated dacite melt at 200 MPa, 950-1055??C, and 4.8-5.7 wt % H2O. We experimentally determine the critical supersaturation pressure for bubble nucleation as a function of dissolved water and then solve for ?? at those conditions using classical nucleation theory. The solutions obtained give dacite melt-vapor surface tensions that vary inversely with dissolved water from 0.042 (??0.003) J m-2 at 5.7 wt% H2O to 0.060 (??0.007) J m-2 at 5.2 wt% H2O to 0.073 (??0.003) J m-2 at 4.8 wt% H2O. Combining our dacite results with data from published hydrous haplogranite and high-silica rhyolite experiments reveals that melt-vapor surface tension also varies inversely with the concentration of mafic melt components (e.g., CaO, FeOtotal, MgO). We develop a thermodynamic context for these observations in which melt-vapor surface tension is represented by a balance of work terms controlled by melt structure. Overall, our results suggest that cooling, crystallization, and vapor exsolution cause systematic changes in ?? that should be considered in dynamic modeling of magmatic processes.

  10. Structure and Viscosity of Carbonate-Silicate Melts Using in situ Techniques

    Science.gov (United States)

    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.

  11. Trace element partitioning between aqueous fluids and silicate melts measured with a proton microprobe

    Energy Technology Data Exchange (ETDEWEB)

    Adam, J.; Green, T.H. [Macquarie Univ., North Ryde, NSW (Australia). School of Earth Sciences; Sie, S.H. [Commonwealth Scientific and Industrial Research Organisation (CSIRO), North Ryde, NSW (Australia). Div. of Exploration Geoscience

    1996-12-31

    A series of experiments were performed to examine the capacity of H{sub 2}O-fluids to concentrate and transport incompatible elements through peridotitic mantle and metamorphosed (eclogitic) ocean crust. Two naturally occurring rock compositions, trondhjemitic and basanitic, were used in experiments. The proton microprobe was used to determine the trace element concentrations in the solutes from H{sub 2}O-fluids equilibrated at 900-1100 degree C, 2.0 GPa with water saturated melts of trondhjemitic and basanitic compositions. Partitioning data for H{sub 2}O-fluids and silicate melts show that H{sub 2}O-fluids equilibrated with mantle peridotites will not be strongly enriched in trace elements relative to their wallrocks, and thus they melts do not strongly concentrate alkaline earths Th and U, relative to high-field strength elements. 3 refs., 1 tab., 2 figs.

  12. Zircon saturation in silicate melts: a new and improved model for aluminous and alkaline melts

    Science.gov (United States)

    Gervasoni, Fernanda; Klemme, Stephan; Rocha-Júnior, Eduardo R. V.; Berndt, Jasper

    2016-03-01

    The importance of zircon in geochemical and geochronological studies, and its presence not only in aluminous but also in alkaline rocks, prompted us to think about a new zircon saturation model that can be applied in a wide range of compositions. Therefore, we performed zircon crystallization experiments in a range of compositions and at high temperatures, extending the original zircon saturation model proposed by Watson and Harrison (Earth Planet Sci Lett 64:295-304, 1983) and Boehnke et al. (Chem Geol 351:324-334, 2013). We used our new data and the data from previous studies in peraluminous melts, to describe the solubility of zircon in alkaline and aluminous melts. To this effect, we devised a new compositional parameter called G [ {( {3 \\cdot {{Al}}2 {{O}}3 + {{SiO}}2 )/({{Na}}2 {{O}} + {{K}}2 {{O}} + {{CaO}} + {{MgO}} + {{FeO}}} )} ] (molar proportions), which enables to describe the zircon saturation behaviour in a wide range of rock compositions. Furthermore, we propose a new zircon saturation model, which depends basically on temperature and melt composition, given by (with 1σ errors): ln [ {{Zr}} ] = ( {4.29 ± 0.34} ) - ( {1.35 ± 0.10} ) \\cdot ln G + ( {0.0056 ± 0.0002} ) \\cdot T( °C ) where [Zr] is the Zr concentration of the melt in µg/g, G is the new parameter representing melt composition and T is the temperature in degrees Celsius. The advantages of the new model are its straightforward use, with the G parameter being calculated directly from the molar proportions converted from electron microprobe measurements, the temperature calculated given in degrees Celsius and its applicability in a wider range of rocks compositions. Our results confirm the high zircon solubility in peralkaline rocks and its dependence on composition and temperature. Our new model may be applied in all intermediate to felsic melts from peraluminous to peralkaline compositions.

  13. Effect of water on the fluorine and chlorine partitioning behavior between olivine and silicate melt

    Science.gov (United States)

    Joachim, Bastian; Stechern, André; Ludwig, Thomas; Konzett, Jürgen; Pawley, Alison; Ruzié-Hamilton, Lorraine; Clay, Patricia L.; Burgess, Ray; Ballentine, Christopher J.

    2017-04-01

    Halogens show a range from moderate (F) to highly (Cl, Br, I) volatile and incompatible behavior, which makes them excellent tracers for volatile transport processes in the Earth's mantle. Experimentally determined fluorine and chlorine partitioning data between mantle minerals and silicate melt enable us to estimate Mid Ocean Ridge Basalt (MORB) and Ocean Island Basalt (OIB) source region concentrations for these elements. This study investigates the effect of varying small amounts of water on the fluorine and chlorine partitioning behavior at 1280 °C and 0.3 GPa between olivine and silicate melt in the Fe-free CMAS+F-Cl-Br-I-H2O model system. Results show that, within the uncertainty of the analyses, water has no effect on the chlorine partitioning behavior for bulk water contents ranging from 0.03 (2) wt% H2O (DCl ol/melt = 1.6 ± 0.9 × 10-4) to 0.33 (6) wt% H2O (DCl ol/melt = 2.2 ± 1.1 × 10-4). Consequently, with the effect of pressure being negligible in the uppermost mantle (Joachim et al. Chem Geol 416:65-78, 2015), temperature is the only parameter that needs to be considered for the determination of chlorine partition coefficients between olivine and melt at least in the simplified iron-free CMAS+F-Cl-Br-I-H2O system. In contrast, the fluorine partition coefficient increases linearly in this range and may be described at 1280 °C and 0.3 GPa with ( R 2 = 0.99): DF^{ol/melt} = 3.6± 0.4 × 10^{-3} × X_{H}_{2O}( wt %) + 6 ± 0.4× 10^{-4}. The observed fluorine partitioning behavior supports the theory suggested by Crépisson et al. (Earth Planet Sci Lett 390:287-295, 2014) that fluorine and water are incorporated as clumped OH/F defects in the olivine structure. Results of this study further suggest that fluorine concentration estimates in OIB source regions are at least 10% lower than previously expected (Joachim et al. Chem Geol 416:65-78, 2015), implying that consideration of the effect of water on the fluorine partitioning behavior between Earth

  14. [A study of phonon vibration like modes for aggregation structure in silicate melts by high temperature Raman spectrum].

    Science.gov (United States)

    Xu, Pei-Cang; Li, Ru-Bi; Shang, Tong-Ming; Zhou, Jian; Sun, Jian-Hua; You, Jing-Lin

    2010-05-01

    Silicate melts are special fractal dimension system that is metastable state of near-way order and far-way disorder. In this paper, the size of nanometer aggregation structure and the frequences of phonon vibration like mode in the low dimension silicate series (CaO-Al2O3-SiO2 and Na2-Al2O3-SiO2 series) synthesized via high temperature melting and sol gel methods were measured by means of small-angle X-ray scattering (SAXS), low wavenumber Raman spectrum (LWRS) and high temperature Raman spectrum (HTRS in situ measuring). The nanometer self-similarity aggregation structure(it's size is about a few nm to a few tens nm) and phonic phonon vibration like modes of low temperature silicate gel, high temperature silicate melts and it's quenching glasses phases were obtained. So a quantitative method by HTRS for measuring the aggregation size in the high temperature melts was established. The results showed that the aggregation size of the silicate melts is smaller at high temperature than at room temperature and the number of bridge oxygen in one Si-O tetrahedron in network structure units is decreasing at high temperature. This study work provides important theory and information for deliberating geochemistry characteristic, crystallization & evolution of natural magma and enhancing performance of low dimension silicate matelials.

  15. High-temperature apparatus for chaotic mixing of natural silicate melts

    Energy Technology Data Exchange (ETDEWEB)

    Morgavi, D.; Petrelli, M.; Vetere, F. P.; González-García, D.; Perugini, D., E-mail: diego.perugini@unipg.it [Department of Physics and Geology, Petro-Volcanology Research Group (PVRG), University of Perugia, Piazza Università, Perugia 06100 (Italy)

    2015-10-15

    A unique high-temperature apparatus was developed to trigger chaotic mixing at high-temperature (up to 1800 °C). This new apparatus, which we term Chaotic Magma Mixing Apparatus (COMMA), is designed to carry out experiments with high-temperature and high-viscosity (up to 10{sup 6} Pa s) natural silicate melts. This instrument allows us to follow in time and space the evolution of the mixing process and the associated modulation of chemical composition. This is essential to understand the dynamics of magma mixing and related chemical exchanges. The COMMA device is tested by mixing natural melts from Aeolian Islands (Italy). The experiment was performed at 1180 °C using shoshonite and rhyolite melts, resulting in a viscosity ratio of more than three orders of magnitude. This viscosity ratio is close to the maximum possible ratio of viscosity between high-temperature natural silicate melts. Results indicate that the generated mixing structures are topologically identical to those observed in natural volcanic rocks highlighting the enormous potential of the COMMA to replicate, as a first approximation, the same mixing patterns observed in the natural environment. COMMA can be used to investigate in detail the space and time development of magma mixing providing information about this fundamental petrological and volcanological process that would be impossible to investigate by direct observations. Among the potentials of this new experimental device is the construction of empirical relationships relating the mixing time, obtained through experimental time series, and chemical exchanges between the melts to constrain the mixing-to-eruption time of volcanic systems, a fundamental topic in volcanic hazard assessment.

  16. The formation of nuggets of highly siderophile elements in quenched silicate melts at high temperatures: Before or during the silicate quench?

    Science.gov (United States)

    Malavergne, V.; Charon, E.; Jones, J.; Cordier, P.; Righter, K.; Deldicque, D.; Hennet, L.

    2016-01-01

    The Highly Siderophile Elements (HSE) are powerful tracers of planetary differentiation. Despite the importance of their partitioning between silicate and metal for the understanding of planetary core formation, especially for the Earth and Mars, there is still a huge discrepancy between conclusions based on different high temperature (HT) experimental studies. These disagreements may be due to the presence of HSE micro and nanonuggets in HT experiments. The formation of these nuggets is still interpreted in different ways. One hypothesis is that these HSE nuggets formed during the quench of the silicate melt, while another hypothesis supposes that these nuggets formed before the quench and represented artefacts of HT experiments. The goal of this work is to clarify whether the presence of HSE nuggets in silicate melts is linked to a quench effect or not. Understanding the formation of these HSE nuggets represents thus a necessary step towards the resolution of the Earth's core formation scenarios. We performed new HT experiments (1275-2000 °C) at different oxygen fugacities (fO2), between ambient air up to ∼5 log units below the Iron-Wüstite buffer [IW-5], for two different silicate compositions (synthetic martian and terrestrial basalts) mixed with a metallic mixture of Pt-Au-Pd-Ru. Our 1275-1600 °C experiments were contained in either olivine, diopside or graphite crucible; experiments at 2000 °C were performed using a levitation method, so no capsule was necessary. Our samples contained quenched silicate melts, minerals (olivine, pyroxene, spinel depending on the run), a two-phase metallic bead and nano and micro-nuggets of HSE. Our samples underwent fine textural, structural and analytical characterizations. The distribution of the nuggets was not homogeneous throughout the quenched silicate melt. HSE nuggets were present within crystals. Dendritic textures from the quenched silicate melt formed around HSE nuggets, which could be crystallized, showing

  17. Silicate melt structure at high temperatures and pressures: concepts and questions

    Science.gov (United States)

    Stebbins, J. F.

    2016-12-01

    A great deal is now known about the structure of glass-forming silicate (and other oxide) liquids, from decades of research on quenched glasses of interest to the geosciences and technology. However, specific structural information and derived general concepts from such studies are only the starting point for thinking about melts at temperatures far above the glass transition, and for high pressures and compositions that do not result in quenchable glasses. This talk will attempt to briefly summarize what we know about temperature and pressure effects on melt structure, emphasizing questions yet to be clearly answered. As examples of the latter, we are yet to have a quantitative structural explanation of the all-important configurational entropy and enthalpy of even simple silicate compositions, suggesting that short-lived and possibly ill-defined defect structures account for much of the non-vibrational energy taken up on heating to liquidus temperatures. At least in the pressure range before major increases in silicon coordination (which probably includes the upper mantle source regions for most modern mafic magmas), known changes in cation coordination are not enough to account for known changes in density, either at high T/P or in quenched and decompressed glasses. And even the basic concepts of silicate melt structure, such as `network formers' and `network modifiers' are inadequate in a high pressure liquid comprised primarily of cations with 6, 7 or 8-fold coordination. Such kinds of questions pose important and intriguing challenges for structural thinking based on improved computational models and rapid advances in in-situ, high P/T structural measurements.

  18. Partitioning of potassium between silicates and sulphide melts - Experiments relevant to the earth's core.

    Science.gov (United States)

    Goettel, K. A.

    1972-01-01

    The partitioning of potassium between roedderite, K2Mg5Si12O30 and an Fe-FeS melt was investigated at temperatures about 40 C above the Fe-FeS eutectic. Roedderite was considered a prime candidate for one of the potassium-bearing phases in the primitive earth because roedderite and merrihueite are the only two silicates containing essential potassium which have been identified in stony meteorites. Application of the results to a primitive chondritic earth is discussed, and it is concluded that extraction of most of the earth's potassium into the Fe-FeS core would occur under the conditions in the early earth.-

  19. Viscosity of Carbonate-Silicate Melts Using Ultra-High Resolution Falling Sphere Viscometry

    Science.gov (United States)

    Hummer, D. R.; Kavner, A.; Manning, C. E.; Park, C.; Kono, Y.; Kenney-Benson, C.

    2014-12-01

    Carbonatites are carbon-rich magmas that participate in the deep-Earth carbon cycle, and may be precursors to many types of terrestrial magmatism. [1] Viscosity is a crucial parameter in determining migration rates and behavior of melts from the upper mantle to Earth's surface, but very little is known about the viscosity of carbonate-silicate liquids at conditions relevant to Earth's interior. To examine the viscosity of carbonate-silicate liquids as a function of composition, we performed in situ falling sphere viscosity experiments using a high speed X-ray camera and Paris-Edinburgh press at the HPCAT beamline (Advanced Photon Source, Argonne National Laboratory). Mixtures from the CaCO3-CaSiO3 (calcite-wollastonite) binary system were used to simulate mantle silicate carbonatites. Samples were loaded using the experimental setup of Yamada et al [2], held at 3 GPa, and heated until the sample was fully molten (between 1350-1650 oC). The high speed camera recorded the falling rate of a platinum sphere placed near the top of the sample chamber, enabling the calculation of terminal velocity and hence viscosity. Results indicate that pure CaCO3 at upper mantle conditions has a very low viscosity of ~0.006 Pa-s, only a little higher than that of water. This viscosity is 2-6 times lower than that of potassium carbonates at similar pressures (2.5-4.0 GPa) but at somewhat lower temperatures (800-1200 oC). [3] Our measured viscosity as a function of increasing silicate content increases along a log-linear trend, reaching 0.256 Pa-s for CaSiO3 liquid. This heavy dependence of viscosity on composition has implications for melt migration processes at different depths, suggesting either viscosity-driven or porosity-driven migration depending on both extent of melting and carbonate content. [1] Dasgupta, R. et al. (2013) Nature 493, 211-215. [2] Yamada, A. et al. (2011) Rev. Sci. Instr. 82, 015103. [3] Dobson, D. et al. (1996) Earth Plan. Sci. Lett. 143, 207-215.

  20. VOLATILECALC: A silicate melt-H2O-CO2 solution model written in Visual Basic for excel

    Science.gov (United States)

    Newman, S.; Lowenstern, J. B.

    2002-01-01

    We present solution models for the rhyolite-H2O-CO2 and basalt-H2O-CO2 systems at magmatic temperatures and pressures below ~ 5000 bar. The models are coded as macros written in Visual Basic for Applications, for use within MicrosoftR Excel (Office'98 and 2000). The series of macros, entitled VOLATILECALC, can calculate the following: (1) Saturation pressures for silicate melt of known dissolved H2O and CO2 concentrations and the corresponding equilibrium vapor composition; (2) open- and closed-system degassing paths (melt and vapor composition) for depressurizing rhyolitic and basaltic melts; (3) isobaric solubility curves for rhyolitic and basaltic melts; (4) isoplethic solubility curves (constant vapor composition) for rhyolitic and basaltic melts; (5) polybaric solubility curves for the two end members and (6) end member fugacities of H2O and CO2 vapors at magmatic temperatures. The basalt-H2O-CO2 macros in VOLATILECALC are capable of calculating melt-vapor solubility over a range of silicate-melt compositions by using the relationships provided by Dixon (American Mineralogist 82 (1997) 368). The output agrees well with the published solution models and experimental data for silicate melt-vapor systems for pressures below 5000 bar. ?? 2002 Elsevier Science Ltd. All rights reserved.

  1. Reaction rim growth on olivine in silicic melts: Implications for magma mixing

    Science.gov (United States)

    Coombs, Michelle L.; Gardner, James E.

    2004-01-01

    Finely crystalline amphibole or pyroxene rims that form during reaction between silicic host melt and cognate olivine xenocrysts, newly introduced during magma mixing events, can provide information about the timing between mixing and volcanic eruptions. We investigated rim growth experimentally by placing forsteritic olivine in rhyolitic and rhyodacitic melts for times between 25 and 622 h at 50 and 150 MPa, H2O-saturated, at the Ni-NiO buffer. Rims of orthopyroxene microlites formed from high-silica rhyolite and rhyodacite melts at 885°C and 50 MPa, and in the rhyolite at 150 MPa and 885°C. Rims of amphibole with lesser orthopyroxene formed in the rhyolite at 150 MPa and 800°C and in the rhyodacite at 150 MPa and 885°C. Irregular, convolute olivine edges and mass balance between olivine, melt, and rim phases show that olivine partly dissolved at all conditions. Iron-rich zones at the exteriors of olivines, which increased in width parabolically with time, show that Fe-Mg interdiffusion occurring in olivines was not outpaced by olivine dissolution. Linear increases of the square of rim widths with time suggest that diffusion within the melt is the rate-controlling process for olivine dissolution and rim growth. Rims grew one-half to one order-of-magnitude faster when melt water contents were doubled, unless conditions were far above the liquidus. Rim growth rate in rhyolite increases from 0.055 ± 0.01 µm2/h at 885°C and 50 MPa to 0.64 ± 0.13 µm2/h at 800°C and 150 MPa. Melt composition has a lesser effect on rim growth rates, with growth rate increasing as melt SiO2 content decreases. Pyroxene rims on olivines in andesite erupted from Arenal volcano (Costa Rica) grew at a rate of 3.0 ± 0.2 µm2/h over an eleven-year period. This rate is faster than those of the experiments due to lower melt viscosity and higher temperatures, and suggests that a magma mixing event preceded the start of the eruption by days.

  2. Occurrence of silicate melt, carbonate-rich melt and fluid during medium pressure anatexis of metapelitic gneisses (Oberpfalz, Bavaria) revealed by melt and fluid inclusions study

    Science.gov (United States)

    Ferrero, Silvio; O'Brien, Patrick; Hecht, Lutz; Wunder, Bernd

    2014-05-01

    of a silicate melt and a carbonate-rich melt during anatexis at relatively shallow crustal levels, but this hypothesis needs to be further tested through re-homogenization experiments by piston cylinder means. References Bartoli, O., Cesare, B., Poli, S., Bodnar, R.J., Acosta-Vigil, A., Frezzotti, M.L. & Meli, S., 2013. Recovering the composition of melt and the fluid regime at the onset of crustal anatexis and S-type granite formation. Geology, 41, 115-118. Cesare, B., Ferrero, S., Salvioli-Mariani, E., Pedron, D. & Cavallo, A., 2009. Nanogranite and glassy inclusions: the anatectic melt in migmatites and granulites. Geology, 37, 627-630. Ferrero, S., Bartoli, O., Cesare, B., Salvioli Mariani, E., Acosta-Vigil, A., Cavallo, A., Groppo, C. & Battiston, S., 2012. Microstructures of melt inclusions in anatectic metasedimentary rocks. Journal of Metamorphic Geology, 30, 303-322. Ferrero, S., Braga, R., Berkesi, M., Cesare, B. & Laridhi Ouazaa, N., 2014. Production of Metaluminous melt during fluid-present anatexis: an example from the Maghrebian basement, La Galite Archipelago, central Mediterranean. Journal of Metamorphic Geology, DOI:10.1111/jmg.12068. Tanner, D.C. & Behrmann, J.H., 1995. The Variscan tectonics of the Moldanubian gneisses, Oberpfalzer Wald: a compressional history. Neues Jahrbuch fur Geologie und Palaontologie. Abhandlungen, 197, 331-355. Touret, J.L.R., 2009. Mantle to lower-crust fluid/melt transfer through granulite metamorphism. Russian Geology and Geophysics, 50, 1052-1062.

  3. Microstructure and mechanical properties of stainless steel/calcium silicate composites manufactured by selective laser melting.

    Science.gov (United States)

    Zheng, Zeng; Wang, Lianfeng; Jia, Min; Cheng, Lingyu; Yan, Biao

    2017-02-01

    Selective laser melting (SLM) is raised as one kind of additive manufacturing (AM) which is based on the discrete-stacking concept. This technique can fabricate advanced composites with desirable properties directly from 3D CAD data. In this research, 316L stainless steel (316L SS) and different fractions of calcium silicate (CaSiO3) composites (weight fractions of calcium silicate are 0%, 5%,10% and 15%, respectively) were prepared by SLM technique with a purpose to develop biomedical metallic materials. The relative density, tensile, microhardness and elastic modulus of the composites were tested, their microstructures and fracture morphologies were observed using optical microscope (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). It was found that the addition of CaSiO3 particles influenced the microstructure and mechanical properties of specimens significantly. The CaSiO3 precipitates from the overlap of adjacent tracks and became the origin of the defects. The tensile strength of specimens range 320-722MPa. The microhardness and elastic modulus are around 250HV and 215GPa respectively. These composites were ductile materials and the fracture mode of the composites was mixed mode of ductile and brittle fracture. The 316L SS/CaSiO3 composites can be a potential biomedical metallic materials in the medical field.

  4. Immiscible silicate liquid partition coefficients: implications for crystal-melt element partitioning and basalt petrogenesis

    Science.gov (United States)

    Veksler, Ilya V.; Dorfman, Alexander M.; Danyushevsky, Leonid V.; Jakobsen, Jakob K.; Dingwell, Donald B.

    2006-12-01

    This study investigates partitioning of elements between immiscible aluminosilicate and borosilicate liquids using three synthetic mixtures doped with 32 trace elements. In order to get a good spatial separation of immiscible liquids, we employed a high-temperature centrifuge. Experiments were performed at 1,050-1,150°C, 1 atm, in sealed Fe and Pt containers. Quenched products were analysed by electron microprobe and LA ICP-MS. Nernst partition coefficients ( D’s) between the Fe-rich and Si-rich aluminosilicate immiscible liquids are the highest for Zn (3.3) and Fe (2.6) and the lowest for Rb and K (0.4-0.5). The plots of D values against ionic potential Z/r in all the compositions show a convex upward trend, which is typical also for element partitioning between immiscible silicate and salt melts. The results bear upon the speciation and structural position of elements in multicomponent silicate liquids. The ferrobasalt-rhyolite liquid immiscibility is observed in evolved basaltic magmas, and may play an important role in large gabbroic intrusions, such as Skaergaard, and during the generation of unusual lavas, such as ferropicrites.

  5. Immiscible silicate liquids at high pressure: the influence of melt structure on elemental partitioning

    Energy Technology Data Exchange (ETDEWEB)

    Vicenzi, E. [Princeton Materials Laboratory, Princeton, NJ (United States); Green, T.H. [Macquarie Univ., North Ryde, NSW (Australia); Sie, S.H. [Commonwealth Scientific and Industrial Research Organisation (CSIRO), North Ryde, NSW (Australia). Div. of Exploration Geoscience

    1993-12-31

    Micro-PIXE analyses have been applied to study partitioning of trace elements between immiscible silicate melts stabilised at 0.5 and 1.0 GPa over a temperature range of 1160-1240 deg C in the system SiO{sub 2}-FeO-Al{sub 2}0{sub 3}-K{sub 2}0 (+P{sub 2}0{sub 5}). The system was doped with a suite of trace elements of geochemical interest: Rb, Ba, Pb, Sr, La, Ce, Sm, Ho, Y, Lu, Th, U, Zr, Hf, Nb and Ta at approximately 200 ppm level for all elements except for the REE`s, Ba and Ta (600-1200 ppm). Trace element partitioning was found to be a complex function of cation field strength (charge/radius{sup 2}). Although field strength is important in determining the nature and degree of partitioning, the authors emphasised that it is only one component of the underlying mechanism for the way in which elements distribute themselves between two silicate liquids. 8 refs., 2 figs.

  6. A theoretical model of isotopic fractionation by thermal diffusion and its implementation on silicate melts

    Science.gov (United States)

    Xuefang, L.; Liu, Y.

    2015-12-01

    Huang et al (2010) found that Fe, Ca and Mg isotope fractionations of high-temperature silicate melts are only associated with the temperature gradients in thermal diffusion processes and are independent of compositions and mean temperatures [1]. Richter et al (2010) doubted that the existing data are sufficient to obtain such conclusion [2]. A few theoretical models have been proposed for explaining isotopic fractionations in these processes under high temperatures [3, 4]. However, molecular-level mechanisms and theoretical treatments of these processes are still under debating. Here we provide a unified theory based on the local thermodynamic equilibrium treatment (LTE) of statistical mechanics for evaluating thermal isotopic fractionations under a wide range of temperatures. Under high temperatures, our theory however can be reasonably approximated to this equation: where A and B are constants which are related to specific isotope systems and chemical compositions of silicate melts. If the thermal gradient is not very large and the mean temperature is high, the second part of the above equation can be safely neglected and obtain an extremely simple equation which is linearly depended on temperatures, agreeing with what Huang et al (2010) concluded. Based on this terse equation, we can not only easily provide isotope fractionation data for almost all kinds of isotope systems, but also can provide the mechanisms of isotope fractionation in thermal diffusion processes. [1] Huang et al (2010) Nature 464, 396-400. [2] Richter et al (2010) Nature 472, E1-E1. [3] Dominguez et al (2011) Nature 473, 70-73.

  7. Determination Of Partial Molar Volumes Of Iron Species In Silicate Melts

    Science.gov (United States)

    Dwyer, C. A.; Kress, V. C.

    2009-12-01

    One of the major questions of planetary geology is the composition and conditions of the Earth interior. Magmas are among our most important windows into the interior. Iron, being a major element with multiple valence states, is an important influence on redox state. One way to investigate redox state is via a volume equation of state. Density data are used in computing partial molar volumes, which may then be used to construct a volume equation of state. We have devised an apparatus which permits high-quality density measurements in silicate melts at high temperatures (up to ≈1500 °C) and reduced oxygen fugacity at atmospheric pressure using the Archimedean single-bob method. With this apparatus, we have collected the first high-quality density data of iron-bearing silicate melts which had their iron predominately as ferrous. We measured the density of Columbia River Basalt (approximate temperature range: 1250 °C -- 1450 °C) and an artificial composition in the FeO-FeO1.5-CaO-SiO2 system (≈1460 °C) at the oxygen fugacity corresponding to the Iron-Wüstite buffer. We used these data in conjunction with literature density data gathered at thermodynamic equilibrium to calculate the partial molar volume of the iron species as a function of temperature at standard pressure. We speciated iron according to: 0.4 FeO + 0.6 FeO1.5 ↔ FeO1.3 The partial molar volumes of FeO, FeO1.5, and FeO1.3 were fit well with no compositional dependence, despite the wide range of compositions included in this study. To the extent that melt structure can be inferred from partial molar volumes, this result suggests that there is no compositional dependency to the structure of any of these iron species. Our partial molar volumes of FeO and FeO1.5 are consistent within one standard error of those found by Lange & Carmichael (1987) and Ghiorso & Kress (2004). However, our partial molar volume for FeO1.3 at reference temperature was one-third that of Ghiorso & Kress (2004) (Lange

  8. Melt fracturing and healing: A mechanism for degassing and origin of silicic obsidian

    Science.gov (United States)

    Cabrera, A.; Weinberg, R.F.; Wright, H.M.N.; Zlotnik, S.; Cas, Ray A.F.

    2011-01-01

    We present water content transects across a healed fault in pyroclastic obsidian from Lami pumice cone, Lipari, Italy, using synchrotron Fourier transform infrared spectroscopy. Results indicate that rhyolite melt degassed through the fault surface. Transects define a trough of low water content coincident with the fault trace, surrounded on either side by high-water-content plateaus. Plateaus indicate that obsidian on either side of the fault equilibrated at different pressure-temperature (P-T) conditions before being juxtaposed. The curves into the troughs indicate disequilibrium and water loss through diffusion. If we assume constant T, melt equilibrated at pressures differing by 0.74 MPa before juxtaposition, and the fault acted as a low-P permeable path for H2O that diffused from the glass within time scales of 10 and 30 min. Assuming constant P instead, melt on either side could have equilibrated at temperatures differing by as much as 100 ??C, before being brought together. Water content on the fault trace is particularly sensitive to post-healing diffusion. Its preserved value indicates either higher temperature or lower pressure than the surroundings, indicative of shear heating and dynamic decompression. Our results reveal that water contents of obsidian on either side of the faults equilibrated under different P-T conditions and were out of equilibrium with each other when they were juxtaposed due to faulting immediately before the system was quenched. Degassing due to faulting could be linked to cyclical seismic activity and general degassing during silicic volcanic activity, and could be an efficient mechanism of producing low-water-content obsidian. ?? 2011 Geological Society of America.

  9. An experimental study on the effect of temperature and melt composition on the partitioning of nickel between olivine and silicate melt

    Energy Technology Data Exchange (ETDEWEB)

    Kinzler, R.J.; Grove, T.L.; Recca, S.I. (Massachusetts Institute of Technology, Cambridge (USA))

    1990-05-01

    Experiments in the simple system CaO-MgO-Al{sub 2}O{sub 3}-SiO{sub 2}Na{sub 2}O-FeO were carried out to investigate the control of temperature and melt composition on the partitioning of nickel between olivine and silicate melt (D{sup oliv/liq}{sub Ni}). Eleven experiments determine the influence of changing forsterite (Of) content on D{sup oliv/liq}{sub Ni} in this simple system. The equation of Hart and Davis (1978) that accounts for the variation of D{sup oliv/liq}{sub Ni} in terms of MgO content of the silicate liquid is tested using experimental data from iron-bearing simple and natural systems and found to be inadequate to explain the observed variation of D{sup oliv/liq}{sub Ni}. Two different equations are formulated to describe the partitioning behavior of Ni between olivine and silicate melt. The first is similar to that of Hart and Davis (1978) and uses an expression for Ni-Mg exchange between olivine and silicate melt. The second uses an expression for the Ni-olivine formation reaction. The Ni-Mg exchange equation for D{sup oliv/liq}{sub Ni} depends on the forsterite content of the olivine and the mole fraction MgO{sup liq}, and predicts the experimentally determined values within {plus minus}13% relative average error. The Ni-olivine formation reaction equation for D{sup oliv/liq}{sub Ni} depends on temperature, mole fraction SiO{sup liq}{sub 2}, and melt compositional terms that arise from a symmetric, binary, Margules formulation of the activity coefficients for NiO{sup liq} and SiO{sup liq}{sub 2}. This equation predicts the experimentally determined values within {plus minus}9% relative average error.

  10. Sulfur solubility in reduced mafic silicate melts: Implications for the speciation and distribution of sulfur on Mercury

    Science.gov (United States)

    Namur, Olivier; Charlier, Bernard; Holtz, Francois; Cartier, Camille; McCammon, Catherine

    2016-08-01

    Chemical data from the MESSENGER spacecraft revealed that surface rocks on Mercury are unusually enriched in sulfur compared to samples from other terrestrial planets. In order to understand the speciation and distribution of sulfur on Mercury, we performed high temperature (1200-1750 °C), low- to high-pressure (1 bar to 4 GPa) experiments on compositions representative of Mercurian lavas and on the silicate composition of an enstatite chondrite. We equilibrated silicate melts with sulfide and metallic melts under highly reducing conditions (IW-1.5 to IW-9.4; IW = iron-wüstite oxygen fugacity buffer). Under these oxygen fugacity conditions, sulfur dissolves in the silicate melt as S2- and forms complexes with Fe2+, Mg2+ and Ca2+. The sulfur concentration in silicate melts at sulfide saturation (SCSS) increases with increasing reducing conditions (from 10 wt.% S at IW-8) and with increasing temperature. Metallic melts have a low sulfur content which decreases from 3 wt.% at IW-2 to 0 wt.% at IW-9. We developed an empirical parameterization to predict SCSS in Mercurian magmas as a function of oxygen fugacity (fO2), temperature, pressure and silicate melt composition. SCSS being not strictly a redox reaction, our expression is fully valid for magmatic systems containing a metal phase. Using physical constraints of the Mercurian mantle and magmas as well as our experimental results, we suggest that basalts on Mercury were free of sulfide globules when they erupted. The high sulfur contents revealed by MESSENGER result from the high sulfur solubility in silicate melt at reducing conditions. We make the realistic assumption that the oxygen fugacity of mantle rocks was set during equilibration of the magma ocean with the core and/or that the mantle contains a minor metal phase and combine our parameterization of SCSS with chemical data from MESSENGER to constrain the oxygen fugacity of Mercury's interior to IW- 5.4 ± 0.4. We also calculate that the mantle of Mercury

  11. Anionic Pt in Silicate Melts at Low Oxygen Fugacity: Speciation, Partitioning and Implications for Core Formation Processes on Asteroids

    Science.gov (United States)

    Medard, E.; Martin, A. M.; Righter, K.; Malouta, A.; Lee, C.-T.

    2017-01-01

    Most siderophile element concentrations in planetary mantles can be explained by metal/ silicate equilibration at high temperature and pressure during core formation. Highly siderophile elements (HSE = Au, Re, and the Pt-group elements), however, usually have higher mantle abundances than predicted by partitioning models, suggesting that their concentrations have been set by late accretion of material that did not equilibrate with the core. The partitioning of HSE at the low oxygen fugacities relevant for core formation is however poorly constrained due to the lack of sufficient experimental constraints to describe the variations of partitioning with key variables like temperature, pressure, and oxygen fugacity. To better understand the relative roles of metal/silicate partitioning and late accretion, we performed a self-consistent set of experiments that parameterizes the influence of oxygen fugacity, temperature and melt composition on the partitioning of Pt, one of the HSE, between metal and silicate melts. The major outcome of this project is the fact that Pt dissolves in an anionic form in silicate melts, causing a dependence of partitioning on oxygen fugacity opposite to that reported in previous studies.

  12. XANES evidence for sulphur speciation in Mn-, Ni- and W-bearing silicate melts

    Science.gov (United States)

    Evans, K. A.; O'Neill, H. St. C.; Mavrogenes, J. A.; Keller, N. S.; Jang, L.-Y.; Lee, J.-F.

    2009-11-01

    S K-edge XANES and Mn-, W- and Ni-XANES and EXAFS spectra of silicate glasses synthesised at 1400 °C and 1 bar with compositions in the CaO-MgO-Al 2O 3-SiO 2-S plus MnO, NiO, or WO 3 systems were used to investigate sulphur speciation in silicate glasses. S K-edge spectra comprised a composite peak with an edge between 2470 and 2471.4 eV, which was attributed to S 2-, and a peak of variable height with an edge at 2480.2-2480.8 eV, which is consistent with the presence of S 6+. The latter peak was attributed to sample oxidation during sample storage. W-rich samples produced an additional lower energy peak at 2469.8 eV that is tentatively attributed to the existence of S 3p orbitals hybridised with the W 5d states. Deconvolution of the composite peak reveals that the composite peak for Mn-bearing samples fits well to a model that combines three Lorentzians at 2473.1, 2474.9 and 2476.2 eV with an arctan edge step. The composite peak for W-bearing samples fits well to the same combination plus an additional Lorentzian at 2469.8 eV. The ratio of the proportions of the signal accounted for by peaks at 2473.1 and 2476.2 eV correlates with Mn:Ca molar ratios, but not with W:Ca ratios. Spectra from Ni-bearing samples were qualitatively similar but S levels were too low to allow robust quantification of peak components. Some part of the signal accounted for by the 2473.1 eV peak was therefore taken to record the formation of Mn-S melt species, while the 2469.8 peak is interpreted to record the formation of W-S melt species. The 2474.9 and 2476.2 eV peaks were taken to be dominated by Ca-S and Mg-S interactions. However, a 1:1 relationship between peak components and specific energy transitions is not proposed. This interpretation is consistent with known features of the lower parts of the conduction band in monosulphide minerals and indicates a similarity between sulphur species in the melts and the monosulphides. S-XANES spectra cannot be reproduced by a combination of the

  13. Partitioning of Moderately Siderophile Elements Among Olivine, Silicate Melt, and Sulfide Melt: Constraints on Core Formation in the Earth and Mars

    Science.gov (United States)

    Gaetani, Glenn A.; Grove, Timothy L.

    1997-01-01

    This study investigates the effects of Variations in the fugacities of oxygen and sulfur on the partitioning of first series transition metals (V, Cr, Mn, Fe, Co, Ni. and Cu) and W among coexisting sulfide melt, silicate melt, and olivine. Experiments were performed at 1 atm pressure, 1350 C, with the fugacities of oxygen and sulfur controlled by mixing CO2, CO, and SO2 gases. Starting compositions consisted of a CaO-MgO-Al2O3-SiO2-FeO-Na2O analog for a barred olivine chondrule from an ordinary chondrite and a synthetic komatiite. The f(sub O2)/f(sub S2), conditions ranged from log of f(sub O2) = -7.9 to - 10.6, with log of f(sub S2) values ranging from - 1.0 to -2.5. Our experimental results demonstrate that the f(sub O2)/f(sub S2) dependencies of sulfide melt/silicate melt partition coefficients for the first series transition metals arc proportional to their valence states. The f(sub O2)/f(sub S2) dependencies for the partitioning of Fe, Co, Ni, and Cu are weaker than predicted on the basis of their valence states. Variations in conditions have no significant effect on olivine/melt partitioning other than those resulting from f(sub O2)-induced changes in the valence state of a given element. The strong f(sub O2)/f(sub S2) dependence for the olivine/silicate melt partitioning of V is attributable to a change of valence state, from 4+ to 3+, with decreasing f(sub O2). Our experimentally determined partition coefficients are used to develop models for the segregation of sulfide and metal from the silicate portion of the early Earth and the Shergottite parent body (Mars). We find that the influence of S is not sufficient to explain the overabundance of siderophile and chalcophile elements that remained in the mantle of the Earth following core formation. Important constraints on core formation in Mars are provided by our experimental determination of the partitioning of Cu between silicate and sulfide melts. When combined with existing estimates for siderophile

  14. Late Neoproterozoic to Carboniferous genesis of A-type magmas in Avalonia of northern Nova Scotia: repeated partial melting of anhydrous lower crust in contrasting tectonic environments

    Science.gov (United States)

    Murphy, J. Brendan; Shellnutt, J. Gregory; Collins, William J.

    2017-07-01

    Avalonian rocks in northern mainland Nova Scotia are characterized by voluminous 640-600 Ma calc-alkalic to tholeiitic mafic to felsic magmas produced in a volcanic arc. However, after the cessation of arc activity, repeated episodes of felsic magmatism between ca. 580 Ma and 350 Ma are dominated by A-type geochemical characteristics. Sm-Nd isotopic data, combined with zircon saturation temperature estimates, indicate that these magmas were formed by high temperature (800-1050 °C) melting of the same anhydrous crustal source. Regional tectonic considerations indicate that A-type felsic magmatism was produced (1) at 580 Ma in a San Andreas-type strike slip setting, (2) at 495 Ma as Avalonia rifted off Gondwana, (3) at 465 and 455 in an ensialic island arc environment and (4) at 360-350 Ma during post-collisional, intra-continental strike-slip activity as Avalonia was translated dextrally along the Laurentian margin. These results attest to the importance of crustal source, rather than tectonic setting, in the generation of these A-type magmas and are an example of how additional insights are provided by comparing the geochemical and isotopic characteristics of igneous suites of different ages within the same terrane. They also suggest that the shallow crustal rocks in northern mainland Nova Scotia were not significantly detached from their lower crustal source between ca. 620 Ma and 350 Ma, a time interval that includes the separation of Avalonia from Gondwana, its drift and accretion to Laurentia as well as post-accretionary strike-slip displacement.

  15. Chemical compositions of aqueous fluid, silicate melt, and supercritical fluid in the vicinity of the second critical endpoint in the system peridotite-H2O

    Science.gov (United States)

    Mibe, K.; Kawamoto, T.; Ono, S.

    2012-12-01

    Knowing the chemical compositions of fluid and melt is fundamental in understanding the magma genesis and chemical differentiation in the Earth's interior. We investigated the stability fields of aqueous fluid, silicate melt, and supercritical fluid magma using in-situ x-ray radiography and the second critical endpoint in the system peridotite-H2O was determined to be around 3.8 GPa (Mibe et al., 2007, JGR). Using the quenched recovered samples obtained by Mibe et al. (2007), we determined the chemical compositions of aqueous fluid, silicate melt, and supercritical fluid in the vicinity of the second critical endpoint in the system peridotite-H2O by EPMA analyses. A 10- to 30-μm diameter electron beam was used to obtain the composition of quenched materials from aqueous fluid, silicate melt, and supercritical fluid. The compositions of coexisting aqueous fluid and silicate melt were determined at 3.3 GPa and 3.6 GPa and 1180°C. In both samples, olivine coexists with aqueous fluid and silicate melt. In the run at 3.3 GPa, the composition of aqueous fluid was high-Mg dacitic, whereas the composition of silicate melt was hydrous peridotite. In the run at 3.6 GPa, the composition of aqueous fluid was high-Mg andesitic, whereas the composition of silicate melt was hydrous komatiitic. Although aqueous fluids in both runs are high-Mg, both MgO and FeO preferentially enters into silicate melt compared to aqueous fluid.

  16. Coordinated Hard Sphere Mixture (CHaSM): A fast approximate model for oxide and silicate melts at extreme conditions

    Science.gov (United States)

    Wolf, A. S.; Asimow, P. D.; Stevenson, D. J.

    2015-12-01

    Recent first-principles calculations (e.g. Stixrude, 2009; de Koker, 2013), shock-wave experiments (Mosenfelder, 2009), and diamond-anvil cell investigations (Sanloup, 2013) indicate that silicate melts undergo complex structural evolution at high pressure. The observed increase in cation-coordination (e.g. Karki, 2006; 2007) induces higher compressibilities and lower adiabatic thermal gradients in melts as compared with their solid counterparts. These properties are crucial for understanding the evolution of impact-generated magma oceans, which are dominated by the poorly understood behavior of silicates at mantle pressures and temperatures (e.g. Stixrude et al. 2009). Probing these conditions is difficult for both theory and experiment, especially given the large compositional space (MgO-SiO2-FeO-Al2O3-etc). We develop a new model to understand and predict the behavior of oxide and silicate melts at extreme P-T conditions (Wolf et al., 2015). The Coordinated Hard Sphere Mixture (CHaSM) extends the Hard Sphere mixture model, accounting for the range of coordination states for each cation in the liquid. Using approximate analytic expressions for the hard sphere model, this fast statistical method compliments classical and first-principles methods, providing accurate thermodynamic and structural property predictions for melts. This framework is applied to the MgO system, where model parameters are trained on a collection of crystal polymorphs, producing realistic predictions of coordination evolution and the equation of state of MgO melt over a wide P-T range. Typical Mg-coordination numbers are predicted to evolve continuously from 5.25 (0 GPa) to 8.5 (250 GPa), comparing favorably with first-principles Molecular Dynamics (MD) simulations. We begin extending the model to a simplified mantle chemistry using empirical potentials (generally accurate over moderate pressure ranges, compression.

  17. Transient High-Temperature Processing of Silicates in Fulgurites as Analogues for Meteorite and Impact Melts

    Science.gov (United States)

    Parnell, J.; Thackrey, S.; Muirhead, D. K.; Wright, A. J.

    2008-03-01

    A fulgurite from the Sahara yielded petrographic data valuable as an analogue for highly reduced meteorite and impact melts, including iron silicide formation, devolatilization features, zircon melting and extreme melt heterogeneity.

  18. Comparison of element and isotope diffusion of K and Ca in multicomponent silicate melts

    Science.gov (United States)

    van der Laan, Sieger; Zhang, Youxue; Kennedy, Allen K.; Wyllie, Peter J.

    1994-05-01

    Recent experimental work has shown that the homogenization of elemental concentrations can be much slower than that of isotopic ratios when there are strong concentration gradients in SiO 2 and Al 2O 3. The ramifications of this result for magma homogenization and other petrological problems related to diffusion are significant. We report here a comparison of experimental profiles of elemental concentrations and isotopic fractions of K and Ca in rhyolite-andesite (large concentration gradients) and rhyolite-rhyolite (small concentration gradients) melt couples. When the concentration profile and the isotopic profile of the same element in a single couple are compared, the former is much shorter than the latter in the rhyolite-andesite couple, consistent with other recent studies. However, the lengths of both concentration and isotopic profiles are similar in the rhyolite-rhyolite couple. Therefore, diffusion of an element or oxide may be decoupled from or coupled with isotopic 'diffusion', depending on whether large concentration gradients of major components are present. When the two couples are compared, the intrinsic effective binary diffusivities obtained from isotopic profiles are similar for each element in the two couples, whereas the effective binary diffusivity of K obtained from the concentration profile in the rhyolite-rhyolite couple is 37 times that in the rhyolite-andesite couple. Therefore, isotopic homogenization is roughly independent of elemental homogenization and the presence of SiO 2, Al 2O 3, and other concentration gradients, whereas elemental homogenization is strongly affected by concentration gradients. Our experimental data (isotopic and concentration profiles including uphill diffusion profiles) can be modeled quantitatively to a good approximation using a modified effective binary diffusion model in which the flux of a component is assumed to be proportional to its activity gradient instead of its concentration gradient. Therefore, the

  19. Crystal-chemical controls on the partitioning of Sr and Ba between plagioclase feldspar, silicate melts, and hydrothermal solutions

    Energy Technology Data Exchange (ETDEWEB)

    Blundy, J.D.; Wood, B.J. (Bristol Univ. (England))

    1991-01-01

    The aim of this paper is to evaluate the factors which control the partitioning of alkaline earth elements (Ba and Sr) between plagioclase feldspar and silicate melts, specifically the respective role of crystal chemistry, melt chemistry, and temperature. We have selected plagioclase because of the wealth of volcanic and experimental data, the compositional simplicity of plagioclase, and its relevance to many petrological problems. We begin our study by examining experimental data on Sr partitioning between plagioclase and hydrothermal solutions in an attempt to constrain the role of crystal chemistry. We establish a simple thermodynamic model for trace element partitioning between plagioclase and hydrothermal solutions. This treatment is then extended to the plagioclase-melt system using available data from both experimental and volcanic systems in order to derive a general equation for Sr and Ba partitioning. Finally we consider the geochemical applications and implications of our findings.

  20. The effect of liquid composition on the partitioning of Ni between olivine and silicate melt

    Science.gov (United States)

    Matzen, Andrew K.; Baker, Michael B.; Beckett, John R.; Wood, Bernard J.; Stolper, Edward M.

    2017-01-01

    We report the results of experiments designed to separate the effects of temperature and pressure from liquid composition on the partitioning of Ni between olivine and liquid, D_{{Ni}}^{{ol/liq}}. Experiments were performed from 1300 to 1600 °C and 1 atm to 3.0 GPa, using mid-ocean ridge basalt (MORB) glass surrounded by powdered olivine in graphite-Pt double capsules at high pressure and powdered MORB in crucibles fabricated from single crystals of San Carlos olivine at one atmosphere. In these experiments, pressure and temperature were varied in such a way that we produced a series of liquids, each with an approximately constant composition ( 12, 15, and 21 wt% MgO). Previously, we used a similar approach to show that D_{{Ni}}^{{ol/liq}} for a liquid with 18 wt% MgO is a strong function of temperature. Combining the new data presented here with our previous results allows us to separate the effects of temperature from composition. We fit our data based on a Ni-Mg exchange reaction, which yields ln ( {D_{{Ni}}^{{molar}} } ) = { -Δ _{r(1)} H_{{T_{{ref}} ,P_{{ref}} }}°}/RT + {Δ _{r(1)} S_{{T_{{ref}} ,P_{{ref}} }}°}/R - ln ( {{X_{{MgO}}^{{liq}} }/{X_{{{{MgSi}_{ 0. 5} {{O}}_{ 2} }}^{{ol}} }}} ). Each subset of constant composition experiments displays roughly the same temperature dependence of D_{{Ni}}^{{ol/liq}} (i.e.,-Δ _{r(1)} H_{{T_{{ref}} ,P_{{ref}} }}°/R) as previously reported for liquids with 18 wt% MgO. Fitting new data presented here (15 experiments) in conjunction with our 13 previously published experiments (those with 18 wt% MgO in the silicate liquid) to the above expression gives -Δ _{r(1)} H_{{T_{{ref}} ,P_{{ref}} }}°/R = 3641 ± 396 (K) and Δ _{r(1)} S_{{T_{{ref}} ,P_{{ref}} }}° /R = - 1.597 ± 0.229. Adding data from the literature yields -Δ _{r(1)} H_{{T_{{ref}} ,P_{{ref}} }}° /R = 4505 ± 196 (K) and Δ _{r(1)} S_{{T_{{ref}} ,P_{{ref}} }}° /R = - 2.075 ± 0.120, a set of coefficients that leads to a predictive equation for D

  1. Tysnes Island - An unusual clast composed of solidified, immiscible, Fe-FeS and silicate melts. [in meteorite

    Science.gov (United States)

    Wilkening, L. L.

    1978-01-01

    An inclusion found in the Tysnes Island gas-rich H4 chondrite is described. The clast consists of two distinct portions, separated by a smooth boundary; the portions are a tear-drop shaped Fe-FeS eutecticlike intergrowth (0.5 cm greatest dimension) and a silicate consisting primarily of olivine in glass. Nickel enrichment is found in the metal at the metal-sulfide boundaries and in nodules within the metal. It is thought that the portions separated from one another as immiscible liquids and that the modal composition of each portion agrees with the compositions predicted for a total melt of an H-group chondrite. The inclusion is discussed in terms of the process of metal-silicate fractionation suggested by Fodor and Keil (1976).

  2. Eclogite-associated potassic silicate melts and chloride-rich fluids in the mantle: a possible connection

    Science.gov (United States)

    Safonov, O.; Butvina, V.

    2009-04-01

    Relics of potassium-rich (4-14 wt. % of K2O and K2O/Na2O > 1.0) melts are a specific features of some partially molten diamondiferous eclogite xenoliths in kimberlites worldwide [1, 2]. In addition, potassic silicic melt inclusions with up to 16 wt. % of K2O are associated with eclogite phases in kimberlitic diamonds (O. Navon, pers. comm.). According to available experimental data, no such potassium contents can be reached by "dry" and hydrous melting of eclogite. These data point to close connection between infiltration of essentially potassic fluids, partial melting and diamond formation in mantle eclogites [2]. Among specific components of these fluids, alkali chlorides, apparently, play an important role. This conclusion follows from assemblages of the melt relics with chlorine-bearing phases in eclogite xenoliths [1], findings of KCl-rich inclusions in diamonds from the xenoliths [3], and concentration of Cl up to 0.5-1.5 wt. % in the melt inclusions in diamonds. In this presentation, we review our experimental data on reactions of KCl melts and KCl-bearing fluids with model and natural eclogite-related minerals and assemblages. Experiments in the model system jadeite(±diopside)-KCl(±H2O) at 4-7 GPa showed that, being immiscible, chloride liquids provoke a strong K-Na exchange with silicates (jadeite). As a result, low-temperature ultrapotassic chlorine-bearing (up to 3 wt. % of Cl) aluminosilicate melts form. These melts is able to produce sanidine, which is characteristic phase in some partially molten eclogites. In addition, in presence of water Si-rich Cl-bearing mica (Al-celadonite-phlogopite) crystallizes in equilibrium with sanidine and/or potassic melt and immiscible chloride liquid. This mica is similar to that observed in some eclogitic diamonds bearing chloride-rich fluid inclusions [4], as well as in diamonds in partially molten eclogites [2]. Interaction of KCl melt with pyrope garnet also produce potassic aluminosilicate melt because of high

  3. A micro-scale investigation of melt production and extraction in the upper mantle based on silicate melt pockets in ultramafic xenoliths from the Bakony-Balaton Highland Volcanic Field (Western Hungary)

    DEFF Research Database (Denmark)

    Bali, Eniko; Zanetti, A.; Szabo, C.;

    2008-01-01

    Mantle xenoliths in Neogene alkali basalts of the Bakony-Balaton Highland Volcanic Field (Western Hungary) frequently have melt pockets that contain silicate minerals, glass, and often carbonate globules. Textural, geochemical and thermobarometric data indicate that the melt pockets formed at rel...

  4. Experimental, in-situ carbon solution mechanisms and isotope fractionation in and between (C-O-H)-saturated silicate melt and silicate-saturated (C-O-H) fluid to upper mantle temperatures and pressures

    Science.gov (United States)

    Mysen, Bjorn

    2017-02-01

    Our understanding of materials transport processes in the Earth relies on characterizing the behavior of fluid and melt in silicate-(C-O-H) systems at high temperature and pressure. Here, Raman spectroscopy was employed to determine structure of and carbon isotope partitioning between melts and fluids in alkali aluminosilicate-C-O-H systems. The experimental data were recorded in-situ while the samples were at equilibrium in a hydrothermal diamond anvil cell at temperatures and pressures to 825 °C and >1300 MPa, respectively. The carbon solution equilibrium in both (C-O-H)-saturated melt and coexisting, silicate-saturated (C-O-H) fluid is 2CO3 + H2O + 2Qn + 1 = 2HCO3 + 2Qn. In the Qn-notation, the superscript, n, is the number of bridging oxygen in silicate structural units. At least one oxygen in CO3 and HCO3 groups likely is shared with silicate tetrahedra. The structural behavior of volatile components described with this equilibrium governs carbon isotope fractionation factors between melt and fluid. For example, the ΔH equals 3.2 ± 0.7 kJ/mol for the bulk 13C/12C exchange equilibrium between fluid and melt. From these experimental data, it is suggested that at deep crustal and upper mantle temperatures and pressures, the δ13C-differences between coexisting silicate-saturated (C-O-H) fluid and (C-O-H)-saturated silicate melts may change by more than 100‰ as a function of temperature in the range of magmatic processes. Absent information on temperature and pressure, the use of carbon isotopes of mantle-derived magma to derive isotopic composition of magma source regions in the Earth's interior, therefore, should be exercised with care.

  5. The incorporation of an organically modified layered silicate in monolithic polymeric matrices produced using hot melt extrusion

    Energy Technology Data Exchange (ETDEWEB)

    Lyons, John G. [Centre for Biopolymer and Biomolecular Research, Athlone Institute of Technology, Dublin Road, Athlone, Co. Westmeath (Ireland)]. E-mail: slyons@ait.ie; Holehonnur, Harshad [Centre for Biopolymer and Biomolecular Research, Athlone Institute of Technology, Dublin Road, Athlone, Co. Westmeath (Ireland)]. E-mail: hholehonnur@ait.ie; Devine, Declan M. [Centre for Biopolymer and Biomolecular Research, Athlone Institute of Technology, Dublin Road, Athlone, Co. Westmeath (Ireland)]. E-mail: ddevine@ait.ie; Kennedy, James E. [Centre for Biopolymer and Biomolecular Research, Athlone Institute of Technology, Dublin Road, Athlone, Co. Westmeath (Ireland)]. E-mail: jkennedy@ait.ie; Geever, Luke M. [Centre for Biopolymer and Biomolecular Research, Athlone Institute of Technology, Dublin Road, Athlone, Co. Westmeath (Ireland)]. E-mail: lgeever@ait.ie; Blackie, Paul [Centre for Biopolymer and Biomolecular Research, Athlone Institute of Technology, Dublin Road, Athlone, Co. Westmeath (Ireland)]. E-mail: pblackie@ait.ie; Higginbotham, Clement L. [Centre for Biopolymer and Biomolecular Research, Athlone Institute of Technology, Dublin Road, Athlone, Co. Westmeath (Ireland)]. E-mail: chigginbotham@ait.ie

    2007-06-15

    The body of work described in this research paper outlines the use of nanoclay particles as a novel filler material in a hot melt extruded monolithic polymer matrix for oral drug delivery. Several batches of matrix material were prepared with Carvedilol used as the active pharmaceutical ingredient. An organically modified layered silicate was used as the filler material at various levels of inclusion. The resultant matrices were characterised using steady state parallel plate rheometry, differential scanning calorimetry (DSC), atomic force microscopy (AFM), mechanical testing, and dissolution testing. The mechanical analysis indicated that the nanoclay filler incorporation resulted in an increase in all of the mechanical properties of the matrix. Dissolution analysis showed that the presence of the filler particles resulted in a slower release rate of API than for the matrix alone. The results detailed within this paper indicate that nanoclay materials are an interesting prospect for use as filler materials for extended release hot melt produced dosage forms.

  6. Coordinated Hard Sphere Mixture (CHaSM): A simplified model for oxide and silicate melts at mantle pressures and temperatures

    Science.gov (United States)

    Wolf, Aaron S.; Asimow, Paul D.; Stevenson, David J.

    2015-08-01

    We develop a new model to understand and predict the behavior of oxide and silicate melts at extreme temperatures and pressures, including deep mantle conditions like those in the early Earth magma ocean. The Coordinated Hard Sphere Mixture (CHaSM) is based on an extension of the hard sphere mixture model, accounting for the range of coordination states available to each cation in the liquid. By utilizing approximate analytic expressions for the hard sphere model, this method is capable of predicting complex liquid structure and thermodynamics while remaining computationally efficient, requiring only minutes of calculation time on standard desktop computers. This modeling framework is applied to the MgO system, where model parameters are trained on a collection of crystal polymorphs, producing realistic predictions of coordination evolution and the equation of state of MgO melt over a wide range of pressures and temperatures. We find that the typical coordination number of the Mg cation evolves continuously upward from 5.25 at 0 GPa to 8.5 at 250 GPa. The results produced by CHaSM are evaluated by comparison with predictions from published first-principles molecular dynamics calculations, indicating that CHaSM is accurately capturing the dominant physics controlling the behavior of oxide melts at high pressure. Finally, we present a simple quantitative model to explain the universality of the increasing Grüneisen parameter trend for liquids, which directly reflects their progressive evolution toward more compact solid-like structures upon compression. This general behavior is opposite that of solid materials, and produces steep adiabatic thermal profiles for silicate melts, thus playing a crucial role in magma ocean evolution.

  7. V OLATILEC ALC: a silicate melt-H 2O-CO 2 solution model written in Visual Basic for excel

    Science.gov (United States)

    Newman, Sally; Lowenstern, Jacob B.

    2002-06-01

    We present solution models for the rhyolite-H 2O-CO 2 and basalt-H 2O-CO 2 systems at magmatic temperatures and pressures below ˜5000 bar. The models are coded as macros written in Visual Basic for Applications, for use within Microsoft ® Excel (Office'98 and 2000). The series of macros, entitled V OLATILEC ALC, can calculate the following: (1) Saturation pressures for silicate melt of known dissolved H 2O and CO 2 concentrations and the corresponding equilibrium vapor composition; (2) open- and closed-system degassing paths (melt and vapor composition) for depressurizing rhyolitic and basaltic melts; (3) isobaric solubility curves for rhyolitic and basaltic melts; (4) isoplethic solubility curves (constant vapor composition) for rhyolitic and basaltic melts; (5) polybaric solubility curves for the two end members and (6) end member fugacities of H 2O and CO 2 vapors at magmatic temperatures. The basalt-H 2O-CO 2 macros in V OLATILEC ALC are capable of calculating melt-vapor solubility over a range of silicate-melt compositions by using the relationships provided by Dixon (American Mineralogist 82 (1997) 368). The output agrees well with the published solution models and experimental data for silicate melt-vapor systems for pressures below 5000 bar.

  8. Redox dynamics in multicomponent, iron-bearing silicate melts and glasses: Application to the float-glass processing of high-temperature silicate glassmelts

    Science.gov (United States)

    Cook, Glen Bennett

    Processing high-strain-point glasses by the float process is challenged by the relative thermochemical properties of glassmelts and the liquid-metal float medium. As the chemical reaction between the glassmelt and the float metal involves dynamic reduction of the glassmelt, this research has examined the constraints on high-temperature float processing of glassmelts by combining metal-alloy/oxide reaction thermodynamics and Wagnerian kinetic models for redox reactions in silicate melts. The dynamic response of Fe-bearing, p-type (polaronic) semiconducting amorphous silicates to a chemical potential gradient of oxygen has been shown to be rate-limited by the chemical diffusion of network-modifying cations. The persistence of this mechanism to very low Fe concentrations in Fe-doped magnesium aluminosilicate glasses was proven with Rutherford backscattering spectroscopy. Three glasses, with 0.1, 0.5, and 1.25 mol. % FeO were reacted with air at temperatures from 710-845sp°C. For all compositions and temperatures, oxidation was dominated by network modifier diffusion; an activation energy of 475 kJ*molsp{-1} characterized the process. Chemical dynamics in a high-temperature float environment were characterized on liquid-liquid reaction couples between two low-Fe sodium-aluminoborosilicate (NABS) glassmelts (0.01 and 0.08 mol. % FeO) and Au-30Sn and Au-28Ge (atomic basis) alloys. Experiments were performed in the temperature range 1250-1450sp°C for 30 min; wavelength-dispersive and Rutherford backscattering spectroscopies were employed. These exothermic liquid-metal alloys display large negative deviations from ideal solution behavior, with significantly depressed chemical activities. Diffusion of Sn or Ge in the NABS glassmelts (depth and concentration) was limited at all temperatures to levels comparable to conventional soda-lime (NCS) float glass (˜2 min on pure Sn at 1100sp°C). Incorporation of Sn or Ge was reduced significantly in the higher-Fe-content NABS

  9. Energetics of silicate melts from thermal diffusion studies. Annual progress report

    Energy Technology Data Exchange (ETDEWEB)

    Walker, D.

    1992-07-01

    Efforts are reported in the following areas: laboratory equipment (multianvils for high P/T work, pressure media, SERC/DL sychrotron), liquid-state thermal diffusion (silicate liquids, O isotopic fractionation, volatiles, tektites, polymetallic sulfide liquids, carbonate liquids, aqueous sulfate solutions), and liquid-state isothermal diffusion (self-diffusion, basalt-rhyolite interdiffusion, selective contamination, chemical diffusion).

  10. The Effect of Composition and Pressure on the Structure of Carbonate-Silicate Melts Using in situ X-ray Diffuse Scattering

    Science.gov (United States)

    Hummer, D. R.; Kavner, A.; Manning, C. E.

    2013-12-01

    Carbonatites are carbon-rich magmas that make up a crucial portion of the deep-Earth carbon cycle. During transport from the site of melting, reaction with surrounding mantle and crust can cause significant changes in their carbonate-silicate ratio. However, very little is known about the structure of carbonate-silicate liquids at the high pressures and temperatures where melts originate and metasomatism occurs. To examine how the melt structure of carbonate-silicate binary systems evolves as a function of pressure and composition, we performed in situ X-ray scattering experiments in the Paris-Edinburgh press at HPCAT (Advanced Photon Source). Mixtures from the CaCO3-CaSiO3 and CaCO3-Mg2SiO4 binary systems were used to simulate mantle carbonatites with differing Si:O ratio. Samples were loaded using the experimental setup of Yamada et al [1], and held at 1800 oC and a pressure of either 3 or 6 GPa while energy dispersive X-ray scattering spectra were recorded. Spectra were collected at nine different scattering angles to achieve coverage in reciprocal space up to q = 20 Å-1. Pair distribution functions for pure calcite confirm that carbonates form a simple ionic liquid, as found by previous investigators. [2,3] The silicate portion of carbonate-silicate melts, however, is extensively chain polymerized. This polymerization occurs even in melts containing Mg2SiO4, in which the solid is completely unpolymerized. However, analysis of Si-Si distances reveals that Mg2SiO4-bearing melts likely contain shorter, more distorted chains, while CaSiO3-bearing melts form extended chains with a Si-O-Si angles close to 180o. For silicate-rich mixtures in both systems, the extent of silica polymerization (as measured by the amount of scattering at the Si-Si pair distance of 3.3 Å) moderately increases with increasing carbonate content. Comparing pair distribution functions calculated from 3 and 6 GPa data reveal that pressure moderately increases the degree of polymerization of

  11. Carbonate-silicate melt immiscibility, REE mineralising fluids, and the evolution of the Lofdal Intrusive Suite, Namibia

    Science.gov (United States)

    Bodeving, Sarah; Williams-Jones, Anthony E.; Swinden, Scott

    2017-01-01

    The Lofdal Intrusive Suite, Namibia, consists of calcio-carbonatite and silica-undersaturated alkaline intrusive rocks ranging in composition from phono-tephrite to phonolite (and nepheline syenite). The most primitive of these rocks is the phono-tephrite, which, on the basis of its Y/Ho and Nb/Ta ratios, is interpreted to have formed by partial melting of the mantle. Roughly linear trends in major and trace element contents from phono-tephrite to phonolite and nepheline syenite indicate that the latter two rock types evolved from the phono-tephrite by fractional crystallisation. The nepheline syenite, however, has a lower rare earth element (REE) content than the phonolite. The carbonatite has a primitive mantle-normalised REE profile roughly parallel to that of the silica-undersaturated alkaline igneous rocks, although the absolute REE concentrations are higher. Like the phono-tephrite, it also has a mantle Y/Ho ratio. However, the Nb/Ta and Zr/Hf ratios are significantly higher. Moreover, the carbonatite displays strong negative Ta, Zr and Hf anomalies on spidergrams, whereas the silicate rocks display positive anomalies for these elements. Significantly, this behaviour is predicted by the corresponding carbonatite-silicate melt partition coefficients, as is the behaviour of the REE. Based on these observations, we interpret the carbonatite to represent an immiscible liquid that exsolved from the phono-tephrite or possibly the phonolite melt. The result was a calcio-carbonatite that is enriched in the heavy REE (HREE) relative to most other carbonatites. Fluids released from the corresponding magma are interpreted to have been the source of the REE mineralisation that is currently the target of exploration.

  12. An experimental study of the partitioning of trace elements between rutile and silicate melt as a function of oxygen fugacity

    Directory of Open Access Journals (Sweden)

    GUILHERME MALLMANN

    2014-12-01

    Full Text Available Subduction zone or arc magmas are known to display a characteristic depletion of High Field Strength Elements (HFSE relative to other similarly incompatible elements, which can be attributed to the presence of the accessory mineral rutile (TiO2 in the residual slab. Here we show that the partitioning behavior of vanadium between rutile and silicate melt varies from incompatible (∼0.1 to compatible (∼18 as a function of oxygen fugacity. We also confirm that the HFSE are compatible in rutile, with D(Ta> D(Nb>> (D(Hf>/∼ D(Zr, but that the level of compatibility is strongly dependent on melt composition, with partition coefficients increasing about one order of magnitude with increasing melt polymerization (or decreasing basicity. Our partitioning results also indicate that residual rutile may fractionate U from Th due to the contrasting (over 2 orders of magnitude partitioning between these two elements. We confirm that, in addition to the HFSE, Cr, Cu, Zn and W are compatible in rutile at all oxygen fugacity conditions.

  13. A thermodynamical model for the surface tension of silicate melts in contact with H2O gas

    Science.gov (United States)

    Colucci, Simone; Battaglia, Maurizio; Trigila, Raffaello

    2016-01-01

    Surface tension plays an important role in the nucleation of H2O gas bubbles in magmatic melts and in the time-dependent rheology of bubble-bearing magmas. Despite several experimental studies, a physics based model of the surface tension of magmatic melts in contact with H2O is lacking. This paper employs gradient theory to develop a thermodynamical model of equilibrium surface tension of silicate melts in contact with H2O gas at low to moderate pressures. In the last decades, this approach has been successfully applied in studies of industrial mixtures but never to magmatic systems. We calibrate and verify the model against literature experimental data, obtained by the pendant drop method, and by inverting bubble nucleation experiments using the Classical Nucleation Theory (CNT). Our model reproduces the systematic decrease in surface tension with increased H2O pressure observed in the experiments. On the other hand, the effect of temperature is confirmed by the experiments only at high pressure. At atmospheric pressure, the model shows a decrease of surface tension with temperature. This is in contrast with a number of experimental observations and could be related to microstructural effects that cannot be reproduced by our model. Finally, our analysis indicates that the surface tension measured inverting the CNT may be lower than the value measured by the pendant drop method, most likely because of changes in surface tension controlled by the supersaturation.

  14. The solvation radius of silicate melts based on the solubility of noble gases and scaled particle theory

    Energy Technology Data Exchange (ETDEWEB)

    Ottonello, Giulio, E-mail: giotto@dipteris.unige.it [DISTAV, Università di Genova, Corso Europa 26, 16132 Genova (Italy); Richet, Pascal [Institut de Physique du Globe, Rue Jussieu 2, 75005 Paris (France)

    2014-01-28

    The existing solubility data on noble gases in high-temperature silicate melts have been analyzed in terms of Scaling Particle Theory coupled with an ab initio assessment of the electronic, dispersive, and repulsive energy terms based on the Polarized Continuum Model (PCM). After a preliminary analysis of the role of the contracted Gaussian basis sets and theory level in reproducing appropriate static dipole polarizabilities in a vacuum, we have shown that the procedure returns Henry's law constants consistent with the values experimentally observed in water and benzene at T = 25 °C and P = 1 bar for the first four elements of the series. The static dielectric constant (ε) of the investigated silicate melts and its optical counterpart (ε{sup ∞}) were then resolved through the application of a modified form of the Clausius-Mossotti relation. Argon has been adopted as a probe to depict its high-T solubility in melts through an appropriate choice of the solvent diameter σ{sub s}, along the guidelines already used in the past for simple media such as water or benzene. The σ{sub s} obtained was consistent with a simple functional form based on the molecular volume of the solvent. The solubility calculations were then extended to He, Ne, and Kr, whose dispersive and repulsive coefficients are available from theory and we have shown that their ab initio Henry's constants at high T reproduce the observed increase with the static polarizability of the series element with reasonable accuracy. At room temperature (T = 25 °C) the calculated Henry's constants of He, Ne, Ar, and Kr in the various silicate media predict higher solubilities than simple extrapolations (i.e., Arrhenius plots) based on high-T experiments and give rise to smooth trends not appreciably affected by the static polarizabilities of the solutes. The present investigation opens new perspectives on a wider application of PCM theory which can be extended to materials of great

  15. Noble gas solubility in silicate melts:a review of experimentation and theory, and implications regarding magma degassing processes

    Directory of Open Access Journals (Sweden)

    A. Paonita

    2005-06-01

    Full Text Available Noble gas solubility in silicate melts and glasses has gained a crucial role in Earth Sciences investigations and in the studies of non-crystalline materials on a micro to a macro-scale. Due to their special geochemical features, noble gases are in fact ideal tracers of magma degassing. Their inert nature also allows them to be used to probe the structure of silicate melts. Owing to the development of modern high pressure and temperature technologies, a large number of experimental investigations have been performed on this subject in recent times. This paper reviews the related literature, and tries to define our present state of knowledge, the problems encountered in the experimental procedures and the theoretical questions which remain unresolved. Throughout the manuscript I will also try to show how the thermodynamic and structural interpretations of the growing experimental dataset are greatly improving our understanding of the dissolution mechanisms, although there are still several points under discussion. Our improved capability of predicting noble gas solubilities in conditions closer to those found in magma has allowed scientists to develop quantitative models of magma degassing, which provide constraints on a number of questions of geological impact. Despite these recent improvements, noble gas solubility in more complex systems involving the main volatiles in magmas, is poorly known and a lot of work must be done. Expertise from other fields would be extremely valuable to upcoming research, thus focus should be placed on the structural aspects and the practical and commercial interests of the study of noble gas solubility.

  16. Diffusion of major and trace elements in natural silicate melts as a tool to investigate timescales in magma mixing

    Science.gov (United States)

    González-García, Diego; Zezza, Angela; Behrens, Harald; Vetere, Francesco; Petrelli, Maurizio; Morgavi, Daniele; Perugini, Diego

    2016-04-01

    New melt injection into a shallow magma chamber is regarded as one of the potential triggers for explosive volcanic eruptions. Chemical diffusion occurring between the two mixing melts is a time-dependent process, and thus has the potential to shed light on the timescales involved in magma mixing events leading to an eruption. In order to achieve this, a complete database of diffusion coefficients in natural melts is a necessary prerequisite. We have carried out a set of 12 diffusion couple experiments in order to determine diffusion coefficients (D) of major and trace elements in two natural silicate melts. Two end-members from the Vulcano island (Aeolian archipelago, Italy) have been chosen for the experiments: a shoshonite (Vulcanello lava platform) and a rhyolitic obsidian (Pietre Cotte lava flow, La Fossa cone). Glasses from each end-member with added water contents of 0 wt%, 1 wt% and 2 wt% were produced in an Internally Heated Pressure Vessel (IHPV). Two glass cylinders with similar water content but different base composition are inserted in Au-Pd capsules and experiments are run in the IHPV at 1200° C with pressure from 0.5 to 3 kbar. Experiment capsules are rapidly quenched and analyzed by FTIR, EPMA and LA-ICP-MS for H2O, major and trace elements, respectively, along 2 mm linear profiles extending across the interface. A Boltzmann-Matano approach is used to obtain concentration-dependent diffusivities. The obtained concentration-distance profiles are asymmetric and extend deeper into the shoshonite relative to the rhyolite, indicating that diffusion is slower in the latter. Results show that diffusivities are notably accelerated by the presence of H2O in the melt. Experiments performed by using water-free glass show diffusivities one order of magnitude lower compared to glasses containing up to 2 wt% H2O. The effect of pressure, in the investigated range, is negligible and falls within measurement error. Among major elements, Si and Ti are the slowest

  17. Mg-perovskite/silicate melt partition coefficients in the CMS system at 2430 C and 226 Kbars

    Science.gov (United States)

    Mcfarlane, Elisabeth A.; Drake, Michael J.; Gasparik, Tibor

    1992-01-01

    The partitioning of elements among lower mantle phases and silicate melts is of interest in unraveling the early thermal history of the Earth. Because of the technical difficulty in carrying out such measurements, only one direct set of measurements has been reported, and these results as well as interpretations based on them have generated controversy. The first set of direct measurements on a synthetic system in the CaO-MgO-SiO2 (CMS) is reported. An experiment was conducted at Stony Brook, using the USSA-2000 split sphere anvil apparatus. An experiment in the CMS system doped with oxides of Al, Ti, Sc, and Sm and run at a nominal temperature of 2380 C and pressure of 226 kbars is reported. Nominal temperatures were measured with a W 3 percent Re/W 25 percent Re thermocouple. The hot spot temperature, where the liquidus is located, is estimated to be at 2430 C. A 10 mm MgO octahedron was used in concert with 4 mm truncation edge lengths on the WC cubes. The sample was contained in a Re capsule which was inserted into a LaCrO3 furnace. Pressure was calibrated at 2000 C. Run duration was approximately 3 minutes. The charge was mounted in epoxy and analyzed using a CAMECA SX-50 electron microprobe. Standard operating conditions were employed, although counting time for the less abundant elements was increased to improved counting statistics. The melt is unquenchable, and forms a dendritic intergrowth of quench crystals and residual melt. It was analyzed using a 30 micron raster. The structural identity of the Mg-perovskite phase was confirmed using x ray microdiffractometry. The results of the investigation are presented.

  18. Melt-rich segregations in the Skaergaard Marginal Border Series: Tearing of a vertical silicate mush

    Science.gov (United States)

    Humphreys, M. C. S.; Holness, M. B.

    2010-10-01

    The Marginal Border Series (MBS) of the Skaergaard Intrusion crystallised on the steeply dipping sidewalls of the magma chamber. Melt-rich segregations, previously described as the 'wavy pyroxene rock' are a key feature of the otherwise homogeneous outermost parts of the MBS. The lens-shaped segregations consistently strike parallel to the chamber wall and have a moderate dip towards it. The shape, size, grain size and mineralogy of the segregations evolve systematically away from the chamber wall. The segregations become bigger, more widely spaced, chemically more evolved and more irregular in shape with increasing distance from the margin. The segregations were previously interpreted as a nucleation effect parallel to the thermal gradient. However, they dip toward the margin, not parallel to it. We offer a new interpretation: that the segregations represent tearing of poorly consolidated crystal mush during localised sagging of the vertical solidification front. The tears form during a process analogous to 'hot tearing' of metal alloys, although the driving force for tearing is probably gravitational collapse of the vertical solidification front, or perhaps contemporaneous faulting during chamber filling. Small, regular tears formed in the thinner, more rapidly cooled outer parts of the MBS, while the larger, irregular tears formed in the coarser grained, inner parts. Movement of interstitial liquid fed the cracks after tearing, and the liquid crystallised as relatively evolved, coarse-grained segregations. The mineral chemistry and texture of the segregations suggest that the tearing occurs relatively early in the crystallisation history.

  19. Experimental partial melting of the Allende (CV) and Murchison (CM) chondrites and the origin of asteroidal basalt

    Science.gov (United States)

    Jurewicz, A. J. G.; Mittlefehldt, D. W.; Jones, J. H.

    1993-05-01

    Following the investigation of Jurewicz et al. (1991) on the composition of partial melts of eucrites and angrites, this study investigates partial melts of the Allende and Murchison chondrites and details the anhydrous phase relations of both chondrites at 1 atm, under temperatures and oxygen fugacities plausigle for the formation of basaltic meteorites. It was found that, in general, ambient oxygen fugacity exerts a strong influence on the compositions of partial melts of chondrites by controlling the amount of FeO available to the silicate system. At high f(O2), angritic magmas are produced, whereas eucritic melts are produced at low levels of f(O2).

  20. The formation of the Yichun Ta-Nb deposit, South China, through fractional crystallization of magma indicated by fluid and silicate melt inclusions

    Science.gov (United States)

    Li, Shenghu; Li, Jiankang; Chou, I.-Ming; Jiang, Lei; Ding, Xin

    2017-04-01

    The Yichun Ta-Nb deposit, which is located in Jiangxi Province, South China, can be divided into four lithological zones (from bottom upward): two-mica granite, muscovite granite, albite granite, and lepidolite-albite granite zones. It remains controversial whether these distinct vertical zones were formed through late magmatic-hydrothermal metasomatic alteration or fractional crystallization of magma. To investigate the evolution mechanism of rock- and ore-forming fluid in this deposit, we studied fluid and melt inclusions in quartz and lepidolite in these four granite zones. These fluid inclusions are mainly composed of H2O-NaCl, and have homogenization temperatures ranging from 160 °C to 240 °C, with densities between 0.86 and 0.94 g/cm3 and salinities between 0.5 and 6.5 wt% NaCl equivalent. Raman spectroscopic analyses showed that the daughter minerals contained in silicate melt inclusions are mainly quartz, lepidolite, albite, muscovite, microcline, topaz, and sassolite. From the lower to upper granite zones, the albite contents in silicate melt inclusions increase, while the muscovite contents decrease gradually until muscovite is substituted by lepidolite in the lepidolite-albite granite zone. Additionally, the calculated densities of the silicate melt inclusions exhibit decreasing trends from bottom upward. The total homogenization temperatures of silicate melt inclusions, which were observed under external pressures created in the sample chamber of a hydrothermal diamond-anvil cell, decreased from 860 °C in the lower lithological zone to 776 °C in the upper lithological zone, and the initial melting temperatures of solid phases were 570-710 °C. The calculated initial H2O contents of granitic magma showed an increasing trend from the lower (∼2 wt% in the two-mica granite zone) to the upper granitic zones (∼3 wt% in the albite granite zone). All of these features illustrate that the vertical granite zones in the Yichun Ta-Nb deposit formed through

  1. Trace element composition of silicate inclusions in sub-lithospheric diamonds from the Juina-5 kimberlite: Evidence for diamond growth from slab melts

    Science.gov (United States)

    Thomson, A. R.; Kohn, S. C.; Bulanova, G. P.; Smith, C. B.; Araujo, D.; Walter, M. J.

    2016-11-01

    The trace element compositions of inclusions in sub-lithospheric diamonds from the Juina-5 kimberlite, Brazil, are presented. Literature data for mineral/melt partition coefficients were collated, refitted and employed to interpret inclusion compositions. As part of this process an updated empirical model for predicting the partitioning behaviour of trivalent cations for garnet-melt equilibrium calibrated using data from 73 garnet-melt pairs is presented. High levels of trace element enrichment in inclusions interpreted as former calcium silicate perovskite and majoritic garnet preclude their origin as fragments of an ambient deep mantle assemblage. Inclusions believed to represent former bridgmanite minerals also display a modest degree of enrichment relative to mantle phases. The trace element compositions of 'NAL' and 'CF phase' minerals are also reported. Negative Eu, Ce, and Y/Ho anomalies alongside depletions of Sr, Hf and Zr in many inclusions are suggestive of formation from a low-degree carbonatitic melt of subducted oceanic crust. Observed enrichments in garnet and 'calcium perovskite' inclusions limit depths of melting to less than 600 km, prior to calcium perovskite saturation in subducting assemblages. Less enriched inclusions in sub-lithospheric diamonds from other global localities may represent deeper diamond formation. Modelled source rock compositions that are capable of producing melts in equilibrium with Juina-5 'calcium perovskite' and majorite inclusions are consistent with subducted MORB. Global majorite inclusion compositions suggest a common process is responsible for the formation of many superdeep diamonds, irrespective of geographic locality. Global transition zone inclusion compositions are reproduced by fractional crystallisation from a single parent melt, suggesting that they record the crystallisation sequence and melt evolution during this interaction of slab melts with ambient mantle. All observations are consistent with the

  2. An element with a liquid, anhydrous electrolyte

    Energy Technology Data Exchange (ETDEWEB)

    Nankay, S.; Indzima, T.; Toyeguti, Y.

    1982-09-01

    A liquid anhydrous element and a heat treated Mn0/sub 2/ cathode, to which sodium silicate in the form of Na/sub 2/0 with 5/2Si0/sub 2/ liquid glass is added in a volume of 3 grams per 100 grams of Mn0/sub 2/ is used in the element with a light metal, lithium type anode. Moreover 4.5 grams of acetylene soot is added to the active cathode mass. A fluorine bearing resin is used as the binder. The cathode stores well.

  3. Experimental observations on noble metal nanonuggets and Fe-Ti oxides, and the transport of platinum group elements in silicate melts

    Science.gov (United States)

    Anenburg, Michael; Mavrogenes, John A.

    2016-11-01

    Platinum group element (PGE) nanonuggets are a nuisance in experimental studies designed to measure solubility or partitioning of noble metals in silicate melts. Instead of treating nanonuggets as experimental artifacts, we studied their behaviour motivated by recent discoveries of PGE nanonuggets in a variety of natural settings. We used an experimental setup consisting of AgPd, Pt or AuPd capsules and Fe(-Ti) oxide-saturated hydrous peralkaline silicate melts to maximise nanonugget production. TABS (Te, As, Bi, Sb, Sn) commonly occur in PGM (platinum group minerals), prompting addition of Bi to our experiments to investigate its properties as well. Three-dimensional optical examination by 100× objective and immersion oil reveals variable colour which correlates with nanonugget size and shape due to plasmon resonance effects. We observe two textural types: (1) intermediate-sized nanonuggets dispersed in the glass and adhering to oxides, and (2) abundant fine nanonuggets dispersed in the glass with coarse euhedral crystals in contact with oxides. Slow cooling removes dispersed nanonuggets and greatly coarsens existing oxide-associated metal crystals. Nanonugget-free halos are commonly observed around oxide grains. All metal phases are composed of major (Ag, Pd) and trace (Pt, Ir, Au) capsule material. Our results show reduction processes, imposed by growing oxides, causing local metal saturation in the oxide rich zones with preferential nucleation on smaller oxide grains. The redox gradient then blocks additional metals from diffusing into oxide rich zones, forming halos. As the entire experimental charge is reduced throughout the run, nanonuggets form in the distal glass. Bismuth contents of metal phases do not depend on Bi2O3 amounts dissolved in the melt. Further PGM crystallisation consumes nanonuggets as feedstock. We conclude that the appearance of metallic PGE phases happens in two stages: first as nanonuggets and then as larger PGM. Once formed

  4. Solidus and liquidus temperatures and mineralogies for anhydrous garnet-lherzolite to 15 GPa

    Science.gov (United States)

    Herzberg, C. T.

    1983-01-01

    Strong convergence is noted, in experimental data for systems pertaining to anhydrous fertile garnet-lherzolite in the 6.5-15 GPa range, either to a common temperature or to temperatures differing by only about 100 C. The major element composition of magmas generated by even minor degrees of partial melting may be similar to the composition of the primordial, bulk silicate earth in an upper mantle stratigraphic column more than 160 km deep. Whether or not the solidus and liquidus intersect, the liquidus mineralogy for undepleted garnet-lherzolite compositions is found to change from olivine, at low pressures, to pyroxene, garnet, or a solid solution of both, at pressures greater than 10-15 GPa.

  5. On the Chemical Evolution of Upper Mantle of the Early Earth—An Experimental Study on Melting of the Silicate Phase in Jilin Chondrite at High Pressures

    Institute of Scientific and Technical Information of China (English)

    谢鸿森; 方虹; 等

    1989-01-01

    Relatively old ages of chondrites(normally around 4.5Ga)suggest that their parent bodies did not experience any mely-fractionation under high temperature and high pressure conditions pertaining to the interior of terrestrial plaets.Therefore,it is reasonable to take chondrites as starting materials in the study of the chemical evolution of the early earth.The sillicate phase in the Jilin chondrite (H5)was chosen for this purpose because it possesses a chemical composition similar to that of the primitive mantle.The melting experiment was carried out at 20-30 k bar and has rsulted in a product which contains1-5% melts in addition to solid cryustal phase.The chemical composition of the melt phases and the partitioning of various elements between the coexisting silicate melts are geochemically similar to those of anatectic rocks on the earth.This can thus serve as the basis for discussing the chemical evolution of the early upper mantle.

  6. Structure and disorder in iron-bearing sodium silicate glasses and melts: High-resolution 29Si and 17O solid-state NMR study

    Science.gov (United States)

    Kim, H.; Lee, S.

    2012-12-01

    Understanding of the effect of iron content on the structure (Si coordination environment and the degree of polymerization) of iron-bearing silicate melts and glasses is essential for studying their macroscopic properties and diverse geological processes in Earth's interior. Although the recent advances in high-resolution solid-state NMR techniques provide detailed structural information of a diverse iron-free oxide glasses with varying composition (e.g., Lee, P. Natl. Acad. Sci. USA., 2011, 108, 6847; Lee and Sung, Chem. Geol., 2008, 256, 326; Park and Lee, Geochim. Cosmochim. Acta, 2012, 80, 125; Lee et al., Phys. Rev., 103, 095501, 2009), their application to iron-bearing silicate glasses has a limited usefulness in resolving atomic configurations due to the effect of paramagnetic cation (i.e., Fe) on the NMR spectra. Here, we report the first ^{29}Si and ^{17}O NMR spectra for sodium-iron silicate glasses with varying iron content (Na_{2}O-Fe_{2}O_{3}-SiO_{2} glasses, up to 34.60 wt% Fe_{2}O_{3}), revealing previously unknown details of iron-induced changes in structure and disorder. While signal intensity decreases and peak width increases exponentially with increasing iron content [=Fe_{2}O_{3}/(Na_{2}O+Fe_{2}O_{3})], ^{29}Si MAS NMR spectra for sodium-iron silicate glasses present the slight peak shift and an asymmetrical peak broadening toward higher Q^{n} species with increasing iron content. This result implies an increase in the degree of polymerization with increasing iron content. Additionally, ^{29}Si spin-relaxation time (T_{1}) for the glasses decreases with increasing of iron content by several orders of magnitude. ^{17}O 3QMAS NMR spectra for the glasses show well-resolved non-bridging oxygen (NBO, Na-O-Si) and bridging oxygen (BO, Si-O-Si) even at relatively high iron content, providing the first direct experimental estimation of the degree of polymerization. In sodium-iron silicate glasses, the fraction of NBO decreases with increasing iron

  7. A Tale of Two Melt Rocks: Equilibration and Metal/Sulfide-Silicate Segregation in the L7 Chondrites PAT 91501 and LEW 88663

    Science.gov (United States)

    Harvey, R. P.

    1993-07-01

    Type 7 ordinary chondrites have experienced temperatures near or beyond those necessary for partial melting. Two recently collected Antarctic specimens, PAT91501 (PAT) and LEW88663 (LEW), have been tentatively identified as L7 chondrites based on mineral and oxygen isotope compositions [1,2]. The petrology and mineralogy of these meteorites suggests that they have undergone significant metal/sulfide-silicate segregation, with implications for meteorite parent bodies. PAT consists of an equigranular contact-framework of nearly euhedral olivine grains, with interstitial spaces filled by plagioclase, pyroxenes, and several minor phases. Ortho- and clinopyroxene occur in an exsolution relationship. Olivine and pyroxene are highly equilibrated, varying PAT using the methods of [3] are self-consistent at about 1180 degrees C. In thin section, PAT contains only traces of metal, as tiny isolated blebs in sulfide grains; large (>1 cm) globular sulfide inclusions are seen in hand-sample [1], but are not present in the section examined. LEW was originally classified as an achondrite with olivine and pyroxene compositions similar to those in L chondrites [2]. Metal is absent in LEW, although the specimen is small and heavily rusted, making it impossible to gauge the original metal content. Olivine grains are commonly rounded in shape and seldom in contact with more than a few other grains. LEW olivine and pyroxene are also highly equilibrated. Veins of Ni-bearing metal oxides and sulfides are common. Both low- and high-Ca pyroxene occur as discrete grains, orthopyroxene often poikilitically enclosing olivine. Pyroxene equilibration temperatures for LEW are more variable than those for PAT and consistently lower, with an average around 900 degrees C. The various textural and compositional characteristics of PAT and LEW suggest they have experienced partial melting to varying degrees. Both visually resemble charges from experimental melting of ordinary chondrites [4-6]. The

  8. Clinopyroxene-melt element partitioning during interaction between trachybasaltic magma and siliceous crust: Clues from quartzite enclaves at Mt. Etna volcano

    Science.gov (United States)

    Mollo, S.; Blundy, J. D.; Giacomoni, P.; Nazzari, M.; Scarlato, P.; Coltorti, M.; Langone, A.; Andronico, D.

    2017-07-01

    A peculiar characteristic of the paroxysmal sequence that occurred on March 16, 2013 at the New South East Crater of Mt. Etna volcano (eastern Sicily, Italy) was the eruption of siliceous crustal xenoliths representative of the sedimentary basement beneath the volcanic edifice. These xenoliths are quartzites that occur as subspherical bombs enclosed in a thin trachybasaltic lava envelope. At the quartzite-magma interface a reaction corona develops due to the interaction between the Etnean trachybasaltic magma and the partially melted quartzite. Three distinct domains are observed: (i) the trachybasaltic lava itself (Zone 1), including Al-rich clinopyroxene phenocrysts dispersed in a matrix glass, (ii) the hybrid melt (Zone 2), developing at the quartzite-magma interface and feeding the growth of newly-formed Al-poor clinopyroxenes, and (iii) the partially melted quartzite (Zone 3), producing abundant siliceous melt. These features makes it possible to quantify the effect of magma contamination by siliceous crust in terms of clinopyroxene-melt element partitioning. Major and trace element partition coefficients have been calculated using the compositions of clinopyroxene rims and glasses next to the crystal surface. Zone 1 and Zone 2 partition coefficients correspond to, respectively, the chemical analyses of Al-rich phenocrysts and matrix glasses, and the chemical analyses of newly-formed Al-poor crystals and hybrid glasses. For clinopyroxenes from both the hybrid layer and the lava flow expected relationships are observed between the partition coefficient, the valence of the element, and the ionic radius. However, with respect to Zone 1 partition coefficients, values of Zone 2 partition coefficients show a net decrease for transition metals (TE), high-field strength elements (HFSE) and rare earth elements including yttrium (REE + Y), and an increase for large ion lithophile elements (LILE). This variation is associated with coupled substitutions on the M1, M2 and

  9. New approach on volatile contents determination in silicate melt inclusions: A coupling X-ray microtomography and geochemical approach in Los Humeros caldera complex (Eastern Mexican Volcanic Belt)

    Science.gov (United States)

    Creon, L.; Levresse, G.; Carrasco Nuñez, G.

    2016-12-01

    Volatile contents and magma degassing behavior are known to affect the style, frequency, and intensity of near-surface magmatic processes. For this reason, much effort have been devoted to characterize the volatile evolution of shallow magmatic systems to better constrain volcanic history. Silicate melt inclusions (SMI) represent samples of melt that were isolated from the bulk magma at depth, thus preserving the PTX conditions of the pre-eruptive material. SMI are often affected by the formation of a bubble after trapping; this is a natural consequence of the PVTX properties of crystal-melt-volatile systems. Previous workers have recognized that bubble formation is an obstacle, which affects the interpretation of SMI trapping conditions based only on analysis of the glass phase. Indeed, they explained that bubbles can contain a significant percentage of the volatiles, particularly for those with low solubility in the melt (e.g. CO2). In this study, we propose to define the pre-eruptive PTX conditions of Los Humeros magma chamber using SMI from the various eruption events within 460 and 30 Ka. An innovative analytical coupling has been used in order to determine: (1) the volume of the SMI glass and bubble, using high resolution 3D X-ray microtomography; (2) the density and composition of the bubbles, using Raman spectroscopy; (3) the volatile element contents in glass, using NanoSIMS; and, (4) the major elements composition of the glass, using EPMA. The recalculated volatile concentrations of the total SMI (glass + bubble), illustrate clearly that the volatile content determinations using only the glass phase, underestimate drastically the total volatile content and therefore induce significant error on the determination of the pre-eruptive volcanic budget and on the constrain on the volcanic and thermal history. This study had moreover highlighted the complex evolution of Los Humeros composite magma chamber and, gave constrains for geothermal exploration purpose.

  10. Degassing-induced crystallization in silicate melt inclusion: evaluating the role of post-entrapment changes in melt inclusion from the SW volcanic flows of Deccan Large Igneous Province (Deccan LIP) lava.

    Science.gov (United States)

    Rani Choudhary, Babita

    2017-04-01

    Melt inclusions represent sampling of magma during their growth in magma chambers and during ascent to the surface. Several studies of melt inclusions in Large Igneous Provinces (LIPs) in different parts of the world have been documented in the literature (Sobolev et al. 2011; Kamenetsky et al. 2012). Melt inclusions study from Deccan LIP can provide new insights into the physio-chemical conditions and evolution of this important LIP. The Deccan LIP was fissure eruption mainly emplaced over a very short duration at 66 Ma (Schoene et al. 2015). To better characterize and explain the diversity in geochemical composition, petrogenesis and volatile degassing, melt inclusions studies have been carried out in clinopyroxene and plagioclase feldspar from a suite of samples in the Western Ghats section. Samples were obtained from the upper three formations (the Wai subgroup). The inclusions are primary and range in shape and size varies from a few microns, up to 100 microns. The inclusions are crystalline, and contain daughter phases. Some are glassy, with or without a shrinkage bubble. The melt inclusions show substantial variations in major element composition. Inclusions are significantly enriched in TiO2 (3.68 to 0.08 wt%) and FeO (18.3 to 2.63 wt%). SiO2 ranges from 43.4-66.8 wt% and classification diagrams of total alkali (Na2O+K2O) Vs. silica melt inclusions show that most inclusions are of sub-alkaline to mildly alkaline composition. Al2O3 ranges from 9.7- 22.4wt % and MgO 18.3-1.6. EPMA measurements demonstrated the presence of daughter crystals, such as magnetite and titanomagnetite, and high FeO, TiO2 and CaO within melt inclusions among the silicate daughter crystal clusters. Volatiles are determined have wide range in composition in both plagioclase- and pyroxene-hosted melt inclusions by using FTIR technique, values up to 2wt% H2Ototal and 1808 ppm CO2. Moreover the variability in composition and volatiles the melt from the samples in a single flow suggests

  11. Wüstite stability in the presence of a CO2-fluid and a carbonate-silicate melt: Implications for the graphite/diamond formation and generation of Fe-rich mantle metasomatic agents

    Science.gov (United States)

    Bataleva, Yuliya V.; Palyanov, Yuri N.; Sokol, Alexander G.; Borzdov, Yuri M.; Bayukov, Oleg A.

    2016-02-01

    Experimental simulation of the interaction of wüstite with a CO2-rich fluid and a carbonate-silicate melt was performed using a multianvil high-pressure split-sphere apparatus in the FeO-MgO-CaO-SiO2-Al2O3-CO2 system at a pressure of 6.3 GPa and temperatures in the range of 1150 °C-1650 °C and with run time of 20 h. At relatively low temperatures, decarbonation reactions occur in the system to form iron-rich garnet (Alm75Prp17Grs8), magnesiowüstite (Mg# ≤ 0.13), and CO2-rich fluid. Under these conditions, magnesiowüstite was found to be capable of partial reducing CO2 to C0 that leads to the formation of Fe3+-bearing magnesiowüstite, crystallization of magnetite and metastable graphite, and initial growth of diamond seeds. At T ≥ 1450 °C, an iron-rich carbonate-silicate melt (FeO ~ 56 wt.%, SiO2 ~ 12 wt.%) forms in the system. Interaction between (Fe,Mg)O, SiO2, fluid and melt leads to oxidation of magnesiowüstite and crystallization of fayalite-magnetite spinel solid solution (1450 °C) as well as to complete dissolution of magnesiowüstite in the carbonate-silicate melt (1550 °C-1650 °C). In the presence of both carbonate-silicate melt and CO2-rich fluid, dissolution (oxidation) of diamond and metastable graphite was found to occur. The study results demonstrate that under pressures of the lithospheric mantle in the presence of a CO2-rich fluid, wüstite/magnesiowüstite is stable only at relatively low temperatures when it is in the absolute excess relative to CO2-rich fluid. In this case, the redox reactions, which produce metastable graphite and diamond with concomitant partial oxidation of wüstite to magnetite, occur. Wüstite is unstable under high concentrations of a CO2-rich fluid as well as in the presence of a carbonate-silicate melt: it is either completely oxidized or dissolves in the melt or fluid phase, leading to the formation of Fe2 +- and Fe3 +-enriched carbonate-silicate melts, which are potential metasomatic agents in the

  12. The Extent of Disorder among Charge-balancing Cations in Silicate Glasses and Melts: Spectroscopic Analysis and ab initio Molecular Orbital Calculations

    Science.gov (United States)

    Lee, S.; Doyle, C. S.; Stebbins, J. F.

    2001-12-01

    Aluminosilicate melts are one of the dominant components in upper mantle and crust. Essential to the thermodynamic and transport properties of these systems is the full understanding on the atomic arrangements and the extent of disorder. Recent quantification of the extent of disorder among 'framework cations' in silicate melts using NMR provided improved prospects on the atomic structure of the glasses and melt and their corresponding properties and allowed the degree of randomness to be evaluated in terms of the degree of Al-avoidance (Q) and degree of phase separations (P) (Lee and Stebbins, J. Phys. Chem. B 104, 4091; Lee and Stebbins, GCA in press). Quantitative estimation of the extent of disorder among 'charge-balancing cations' including Na in aluminosilicate glasses, however, has remained an unsolved problem and these cations have often been assumed to be randomly distributed. Here, we explore the intermediate range order around Na in charge-balanced aluminosilicate glasses using Na-23 NMR and Near-edge X-ray absorption fine structure (NEXAFS) with full multiple scattering (FMS) simulations combined with ab initio molecular orbital calculations. We also quantify the extent of disorder in charge balancing cations as a function of Na-O bond length (d(Na-O)) distribution with composition and present a structural model favoring ordered Na distributions. Peak position in Na-23 magic angle spinning (MAS) spectra of aluminosilicate glasses with varying R (Si/Al) at 14.1 T varies from -10.28 ppm (R = 0.7) to -19.98 ppm (R = 6). These results suggest that average d(Na-O) increases with increasing R, which is confirmed by Na-23 multiple quantum MAS spectra where the chemical shift moves toward lower frequency with increasing Si and shows the individual Gaussian components of Na-O distributions such as Na-(Al-O-Al), Na-(Si-O-Al) and Na-(Si-O-Si). Calculated d(Na-(Al-O-Al)) of 2.57 Å is shorter than d(Na-(Si-O-Si)) of 2.88 Å. Strong compositional dependence is

  13. The effects of dissolved CO 2 on the density and viscosity of silicate melts: a preliminary study

    Science.gov (United States)

    Bourgue, Emmanuelle; Richet, Pascal

    2001-11-01

    A potassium silicate liquid with 56.9 mol% SiO 2 (KS 1.3) has been used as a model system to determine at 1 bar the influence of carbon dioxide on the viscosity and density of magma. For the maximum concentration of 3.5 wt% that could be dissolved, the viscosity decreases by two orders of magnitude near the glass transition at around 750 K. For 1 wt% CO 2, the decrease is 1 and only 0.04 log unit at 750 and 1500 K, respectively. Dissolved CO 2 has a composition independent partial molar volume of 25.6±0.8 cm 3/mol in glasses at room temperature, and does not affect the thermal expansion coefficient of the supercooled liquid which is (12.3±0.3)×10 -5 K -1 for CO 2 contents varying from 0.6 to 2.2 wt%. Qualitatively, these effects are similar to those of water. However, the density of dissolved CO 2 varies from about 1.7 to 1.5 g/cm 3 in a 700 K interval above the glass transition, and lowers the density of the glass less than water whose density decreases from 1.5 to 1.2 g/cm 3 under the same conditions. The relevance of these results to natural magma is finally pointed out.

  14. Liquid immiscibility recorded in melt inclusions within corundum from alkaline basalt, Changle area,Shandong province, Eastern China%中国山东昌乐地区碱性玄武岩刚玉中记录的岩浆不混溶作用

    Institute of Scientific and Technical Information of China (English)

    刘吉强; 倪培; 沈昆; 丁俊英

    2007-01-01

    Abundant melt- and fluid inclusions occur in corundum megacrysts of alkaline basalt from the Changle area, Shandong province, eastern China. One type of melt inclusions, i.e. multiphase melt inclusions ( glass + bubbles + daughter minerals) were identified ,which occur along growth zones of host corundum megacrysts. Microthermometry and laser Raman microprobe analysis were performed on the melt inclusions. The bubbles within the melt inclusions are confirmed to be CO2-rich phase and the daughter minerals are probably silicates, such as augite and okenite. The results of high temperature homogenization experiment strongly suggest that two immiscible melts, i.e. a H2O- and CO2-rich melt and an anhydrous and CO2-poor melt were trapped by melt inclusions in corundum megacryst.

  15. Hydrogen Isotopic Systematics of Nominally Anhydrous Phases in Martian Meteorites

    Science.gov (United States)

    Tucker, Kera

    Hydrogen isotope compositions of the martian atmosphere and crustal materials can provide unique insights into the hydrological and geological evolution of Mars. While the present-day deuterium-to-hydrogen ratio (D/H) of the Mars atmosphere is well constrained (~6 times that of terrestrial ocean water), that of its deep silicate interior (specifically, the mantle) is less so. In fact, the hydrogen isotope composition of the primordial martian mantle is of great interest since it has implications for the origin and abundance of water on that planet. Martian meteorites could provide key constraints in this regard, since they crystallized from melts originating from the martian mantle and contain phases that potentially record the evolution of the H 2O content and isotopic composition of the interior of the planet over time. Examined here are the hydrogen isotopic compositions of Nominally Anhydrous Phases (NAPs) in eight martian meteorites (five shergottites and three nakhlites) using Secondary Ion Mass Spectrometry (SIMS). This study presents a total of 113 individual analyses of H2O contents and hydrogen isotopic compositions of NAPs in the shergottites Zagami, Los Angeles, QUE 94201, SaU 005, and Tissint, and the nakhlites Nakhla, Lafayette, and Yamato 000593. The hydrogen isotopic variation between and within meteorites may be due to one or more processes including: interaction with the martian atmosphere, magmatic degassing, subsolidus alteration (including shock), and/or terrestrial contamination. Taking into consideration the effects of these processes, the hydrogen isotope composition of the martian mantle may be similar to that of the Earth. Additionally, this study calculated upper limits on the H2O contents of the shergottite and nakhlite parent melts based on the measured minimum H2O abundances in their maskelynites and pyroxenes, respectively. These calculations, along with some petrogenetic assumptions based on previous studies, were subsequently used

  16. Multidiffusion mechanisms for noble gases (He, Ne, Ar) in silicate glasses and melts in the transition temperature domain: Implications for glass polymerization

    Science.gov (United States)

    Amalberti, Julien; Burnard, Pete; Laporte, Didier; Tissandier, Laurent; Neuville, Daniel R.

    2016-01-01

    Noble gases are ideal probes to study the structure of silicate glasses and melts as the modifications of the silicate network induced by the incorporation of noble gases are negligible. In addition, there are systematic variations in noble gas atomic radii and several noble gas isotopes with which the influence of the network itself on diffusion may be investigated. Noble gases are therefore ideally suited to constrain the time scales of magma degassing and cooling. In order to document noble gas diffusion behavior in silicate glass, we measured the diffusivities of three noble gases (4He, 20Ne and 40Ar) and the isotopic diffusivities of two Ar isotopes (36Ar and 40Ar) in two synthetic basaltic glasses (G1 and G2; 20Ne and 36Ar were only measured in sample G1). These new diffusion results are used to re-interpret time scales of the acquisition of fractionated atmospheric noble gas signatures in pumices. The noble gas bearing glasses were synthesized by exposing the liquids to high noble gas partial pressures at high temperature and pressure (1750-1770 K and 1.2 GPa) in a piston-cylinder apparatus. Diffusivities were measured by step heating the glasses between 423 and 1198 K and measuring the fraction of gas released at each temperature step by noble gas mass spectrometry. In addition we measured the viscosity of G1 between 996 and 1072 K in order to determine the precise glass transition temperature and to estimate network relaxation time scales. The results indicate that, to a first order, that the smaller the size of the diffusing atom, the greater its diffusivity at a given temperature: D(He) > D(Ne) > D(Ar) at constant T. Significantly, the diffusivities of the noble gases in the glasses investigated do not display simple Arrhenian behavior: there are well-defined departures from Arrhenian behavior which occur at lower temperatures for He than for Ne or Ar. We propose that the non-Arrhenian behavior of noble gases can be explained by structural modifications

  17. Low-(18)O Silicic Magmas: Why Are They So Rare?

    Energy Technology Data Exchange (ETDEWEB)

    Balsley, S.D.; Gregory, R.T.

    1998-10-15

    LOW-180 silicic magmas are reported from only a small number of localities (e.g., Yellowstone and Iceland), yet petrologic evidence points to upper crustal assimilation coupled with fractional crystallization (AFC) during magma genesis for nearly all silicic magmas. The rarity of 10W-l `O magmas in intracontinental caldera settings is remarkable given the evidence of intense 10W-l*O meteoric hydrothermal alteration in the subvolcanic remnants of larger caldera systems. In the Platoro caldera complex, regional ignimbrites (150-1000 km3) have plagioclase 6180 values of 6.8 + 0.1%., whereas the Middle Tuff, a small-volume (est. 50-100 km3) post-caldera collapse pyroclastic sequence, has plagioclase 8]80 values between 5.5 and 6.8%o. On average, the plagioclase phenocrysts from the Middle Tuff are depleted by only 0.3%0 relative to those in the regional tuffs. At Yellowstone, small-volume post-caldera collapse intracaldera rhyolites are up to 5.5%o depleted relative to the regional ignimbrites. Two important differences between the Middle Tuff and the Yellowstone 10W-180 rhyolites elucidate the problem. Middle Tuff magmas reached water saturation and erupted explosively, whereas most of the 10W-l 80 Yellowstone rhyolites erupted effusively as domes or flows, and are nearly devoid of hydrous phenocrysts. Comparing the two eruptive types indicates that assimilation of 10W-180 material, combined with fractional crystallization, drives silicic melts to water oversaturation. Water saturated magmas either erupt explosively or quench as subsurface porphyrins bejiire the magmatic 180 can be dramatically lowered. Partial melting of low- 180 subvolcanic rocks by near-anhydrous magmas at Yellowstone produced small- volume, 10W-180 magmas directly, thereby circumventing the water saturation barrier encountered through normal AFC processes.

  18. Thermodynamic models and experimental petrology: the case of the anhydrous melting of the Ollo de Sapo gneiss; Modelos termodinamicos y petrologia experimental: el caso de la fusion anhidra del gneis Ollo de Sapo

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Arias, M.; Corretge, L. G.

    2010-07-01

    During the last years, a couple of software to model the behaviour of a rock under P-T-X changes using thermodynamic databases have been developed. The result of such models is a pseudo section or projection in the P-T plane of a phase diagram of a system at a fixed composition, i.e. a phase diagram section. Although its usefulness has been well demonstrated, a comparison between theoretical and experimental data is advisable to see the degree of approximation of the theoretical model to the reality but also to consider the kinetic effects in experiments. In this paper, theoretical and experimental results of the melting of the Ollo de Sapo Gneiss are compared. (Author) 32 refs.

  19. The formation and chemistry of low degree hydrous partial melt on top of the transition zone

    Science.gov (United States)

    Frost, Daniel J.; Mookherjee, Mainak

    2010-05-01

    There is some geophysical evidence for the presence of silicate melt on top of the 410 km seismic discontinuity. It has also been argued that the difference in the water storage capacity of upper mantle versus transition zone minerals may cause dehydration melting as material up-wells across the 410. Studies have proposed that hydrous partial melts may be neutrally buoyant in the mantle at these conditions. In order to assess these possibilities it is important to determine the likely composition of small degree hydrous melts at these conditions and to measure the H2O contents of mantle minerals coexisting with this melt phase. The composition of a hydrous melt in equilibrium with a mantle peridotite composition has been determined at conditions of the 410 and 1450°C. Sandwich experiments were performed where an 'initial-guess' hydrous melt composition was equilibrated with 50% anhydrous peridotite. The resulting melt composition was used to assemble a further melt, which was then equilibrated in the same way. After several iterations it was possible to derive a melt composition, which was in equilibrium with a mineral assemblage identical to that observed for an anhydrous peridotite composition at the same conditions. We assess whether this melt composition could be neutrally buoyant at 410km. The 410 km discontinuity may also correspond to a transition in redox state in the mantle from a reducing transition zone to a less reduced upper mantle. Volatiles may also collect and induce melting at this horizon due to the oxidation of a rising mobile reduced fluid phase containing CH4. Minerals in mantle upwelling out of a hydrous melt layer would be expected to have H2O contents close to saturation; however, this may not be the case if the melt layer also contains other volatile components such as CO2 or CH4, which further lower the H2O activity in the melt. We assess ranges of melt compositions that may be in equilibrium with minerals containing relatively low H2O

  20. Si isotope fractionation between Si-poor metal and silicate melt at pressure-temperature conditions relevant to metal segregation in small planetary bodies

    Science.gov (United States)

    Kempl, J.; Vroon, P. Z.; Zinngrebe, E.; van Westrenen, W.

    2013-04-01

    Experimental investigations of Si isotope fractionation between Si-bearing metal alloy and silicate phases have to date been limited to high pressure (1-7 GPa) and high temperature (1800-2200 °C) conditions at highly reducing conditions, to optimize applicability of results to early core formation processes in the Earth. Here, we assess the extent and mechanism of Si isotopic fractionation at conditions relevant to metal segregation in small (km-scale) planetary bodies, using samples obtained from an industrial-scale blast furnace of Tata Steel (IJmuiden, the Netherlands). During the low-pressure, high-temperature process of steelmaking inhomogeneous blast furnace burden consisting of pre- and untreated iron ore, iron silicates and coke is reduced to oxygen fugacities near the C-CO buffer, resulting in the segregation of a metal phase containing only ∼0.3 wt% Si. Seven sample sets, each comprising a metal alloy and a silicate slag, were taken during tapping of the blast furnace at tapping temperatures between 1400 °C and 1600 °C. We find large isotopic mass fractionation between metal and silicate, with Δ30Sisilicate-metal varying between 0.7‰ and 1.6‰, values that are as high as previously obtained in high-pressure, highly reduced experiments. A model for metal-silicate Si isotope fractionation in blast furnaces can explain both the sense and magnitude of fractionation, if the presence of SiO-bearing vapour is explicitly taken into account. Our data indicate that significant Si isotope fractionation can occur between metal and silicate at low-pressure, high-temperature and only mildly reducing conditions for which Si solubility in molten Fe-rich metal is low. This suggests an important role for SiO at low confining pressures. Our data can be applied to models of aubrite meteorite formation through high-temperature differentiation of an enstatite chondrite parent body. Our calculations suggest a far larger degree of rehomogenisation during differentiation

  1. Stardust silicates from primitive meteorites.

    Science.gov (United States)

    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.

  2. Anhydrous Taphole Mix for Blast Furnace

    Institute of Scientific and Technical Information of China (English)

    Yu Lingyan

    2010-01-01

    @@ 1 Scope This standard specifies the term,definition,brand,label,technical requirements,test methods,quality appraisal procedures,packing,marking,transportation,storage,and quality certificate of anhydrous taphole mix for blast furnace.

  3. 21 CFR 573.180 - Anhydrous ammonia.

    Science.gov (United States)

    2010-04-01

    ... silage. (2)(i) The food additive anhydrous ammonia is applied directly to corn plant material for use in... to corn plant material containing 28 to 38 percent dry matter. (iv) The silage treated with...

  4. 7 CFR 58.325 - Anhydrous milkfat.

    Science.gov (United States)

    2010-01-01

    ... eligible for official certification, the anhydrous milkfat shall be made by a continuous separation process directly from milk or cream. The cream used shall be comparable to the flavor quality specified above for...

  5. Initiation of large-volume silicic centers in the Yellowstone hotspot track: insights from H2O- and F-rich quartz-hosted rhyolitic melt inclusions in the Arbon Valley Tuff of the Snake River Plain

    Science.gov (United States)

    Drew, Dana L.; Bindeman, Ilya N.; Loewen, Matthew W.; Wallace, Paul J.

    2016-01-01

    During the onset of caldera cluster volcanism at a new location in the Snake River Plain (SRP), there is an increase in basalt fluxing into the crust and diverse silicic volcanic products are generated. The SRP contains abundant and compositionally diverse hot, dry, and often low-δ18O silicic volcanic rocks produced through time during the formation of individual caldera clusters, but more H2O-rich eruptive products are rare. We report analyses of quartz-hosted melt inclusions from pumice clasts from the upper and lower Arbon Valley Tuff (AVT) to gain insight into the initiation of caldera cluster volcanism. The AVT, a voluminous, caldera-forming rhyolite, represents the commencement of volcanism (10.44 Ma) at the Picabo volcanic field of the Yellowstone hotspot track. This is a normal δ18O rhyolite consisting of early and late erupted members (lower and upper AVT, respectively) with extremely radiogenic Sr isotopes and unradiogenic Nd isotopes, requiring that ~50 % of the mass of these elements is derived from melts of Archean upper crust. Our data reveal distinctive features of the early erupted lower AVT melt including: variable F concentrations up to 1.4 wt%, homogenous and low Cl concentrations (~0.08 wt%), H2O contents ranging from 2.3 to 6.4 wt%, CO2 contents ranging from 79 to 410 ppm, and enrichment of incompatible elements compared to the late erupted AVT, subsequent Picabo rhyolites, SRP rhyolites, and melt inclusions from other metaluminous rhyolites (e.g., Bishop Tuff, Mesa Falls Tuff). We couple melt inclusion data with Ti measurements and cathodoluminescence (CL) imaging of the host quartz phenocrysts to elucidate the petrogenetic evolution of the AVT rhyolitic magma. We observe complex and multistage CL zoning patterns, the most critical being multiple truncations indicative of several dissolution-reprecipitation episodes with bright CL cores (higher Ti) and occasional bright CL rims (higher Ti). We interpret the high H2O, F, F/Cl, and

  6. Y2O3掺杂对硅酸盐玻璃结构及其熔体黏度的影响%Effect of Y2O3 Dopant on Structure and Viscosity of Silicate Glass and Melt

    Institute of Scientific and Technical Information of China (English)

    王觅堂; 程金树; 李梅; 何峰

    2013-01-01

    Silicate glasses and melts, soda lime silicate glass frits with various contents of Y2O3 were prepared via melting-quenching in water The effect of Y2O3 on the structure and viscosity was investigated. The samples were characterized by Raman spectrometer and viscometer, respectively. The melting temperature was obtained based on the Arrhenius equation. Some expressions for the glass structure (i.e., fraction of non-bridging oxygen, average number of non-bridging oxygen per tetrahedron, average number of oxygen pre tetrahedron and average number of bridging comers per tetrahedron) were proposed. The results show that Y2O3 doped into soda lime silicate glass can change the [SiO4] tetrahedron structural unit, and the average number of non-bridging oxygen per tetrahedron and the average number of oxygen pre tetrahedron both increase and the average number of bridging corners per tetrahedron decreases with increasing the content of Y2O3. In addition, the incorporation of Y2O3 also decreases the viscosity and melting temperature of soda lime silicate glass.%为了探索稀土氧化物Y2O3掺杂对硅酸盐玻璃结构及其高温熔体黏度的影响,用熔融-水淬法制得了掺杂不同含量Y2O3的Na2O-CaO-SiO2系玻璃料,采用激光共聚焦Raman光谱仪和高温旋转黏度计分别对玻璃料进行了Raman光谱和黏度的测试,根据Arrhenius方程推算了玻璃的熔制温度,同时给出了计算玻璃结构中每个四面体中的氧数、非桥氧数、平均桥数及非桥氧比例的公式.结果表明:Y2O3的掺杂使得Na2O-CaO-SiO2系玻璃中,具有不同非桥氧的结构单元之间发生了一定转化.随着Y2O3掺杂量的增加,玻璃中每个四面体中的氧数和非桥氧数都逐渐增大,玻璃中每个四面体中的连接数降低.此外Y2O3的掺杂降低了Na2O-CaO-SiO2系玻璃的高温黏度与熔制温度,且与玻璃结构的变化规律相一致.

  7. Experimental study on preparation of sodium silicate by purification of gangue and alkali melting activation%煤矸石除杂及碱融活化制取硅酸钠的实验研究

    Institute of Scientific and Technical Information of China (English)

    孔德顺; 吴红

    2013-01-01

    研究利用煤矸石中的硅元素制取硅酸钠,先将煤矸石粉在750℃下煅烧2h,除去有机质并破坏了煤矸石中的高岭石等矿物的晶型结构,再将煅烧过的煤矸石粉在95℃、液固比(mL/g)为8:1、质量分数为40%的硫酸中酸浸5h,煤矸石煅烧粉中的铁和铝等金属杂质离子的总去除率为86.93%;还研究了碱融活化条件对硅元素溶出率的影响,获得了适宜的碱融活化条件:m(酸浸粉):m(碳酸钠)=1:1.5、碱融温度为800 ℃、碱融时间为2h.在此条件下,硅元素溶出率大于75%,最终获得了硅酸钠溶液.%In order to utilize silicon in the coal gangue to prepare sodium silicate,the gangue powder was calcined at 750 ℃for 2 h firstly,then the organic matters were removed and the crystal structures of the minerals,such as kaolin in the gangue were destroyed.The calcined gangue powder was leached in sulfuric acid with mass fraction of 40% and liquid to solid ratio of 8:l at 95 ℃ for 5 h.The total removal ratio of impurity metal ions,such as iron and aluminum was 86.93%;the influences of the alkali melting activation conditions on the dissolution ratios of silicon element were investigated,then the suitable activation conditions were obtained:the mass ratio of acid leaching powder to sodium carbonate was 1:1.5,the alkali melting temperature was 800 ℃,and the alkali melting time was 2 h.Under these conditions silicon element dissolution ratio was more than 75% and the sodium silicate solution was obtained finally.

  8. Argon Diffusion Measured in Rhyolite Melt at 100 MPa

    Science.gov (United States)

    Weldon, N.; Edwards, P. M.; Watkins, J. M.; Lesher, C. E.

    2016-12-01

    Argon diffusivity (D_{Ar} ) controls the rate and length scale of argon exchange between melt and gas phases and is used as a parameter to model noble gas fractionation during magma degassing. D_{Ar} may also be useful in geochronology to estimate the distribution of excess (non-radiogenic) atmospheric argon in lavas. Our measurements of D_{Ar} in molten anhydrous rhyolite near 1000 °C and 100 MPa add to the existing dataset. Using a rapid-quench cold seal pressure apparatus we exposed cylindrical charges drilled from a Miocene rhyolite flow near Buck Mtn., CA to a pure argon atmosphere resulting in a gradually lengthening argon concentration gradient between the saturated surface and the argon poor interior. Argon concentration was measured by electron microprobe along radial transects from the center to the surface of bisected samples. D_{Ar} was calculated for each transect by fitting relative argon concentration (as a function of distance from the surface) to Green's function (given each experiment's specific temperature, pressure and runtime). Variability (σ = 1.202{μm }^{2} /s) was smaller than in previous studies, but still greater than what is likely due to analytical or experimental uncertainty. We observed a symmetric geometric bias in the distribution of argon in our samples, possibly related to advective redistribution of argon accompanying the deformation of cylindrical charges into spheroids driven by surface tension. Average diffusivity, D_{Ar} = 4.791{μm }^{2} /s, is close to the predicted value, D_{Ar} = {μm }^{2} /s ( σ_{ \\bar{x} } = 1.576 {μm }^{2} /s), suggesting that Behrens and Zhang's (2001) empirical model is valid for anhydrous rhyolite melts to relatively higher temperatures and lower pressures. Behrens, H. and Y. Zhang (2001). "Ar diffusion in hydrous silicic melts: implications for volatile diffusion mechanisms and fractionation." Earth and Planetary Science Letters 192: 363-376.

  9. Silicate melt inclusion evidence for extreme pre-eruptive enrichment and post-eruptive depletion of lithium in silicic volcanic rocks of the western United States: implications for the origin of lithium-rich brines

    Science.gov (United States)

    Hofstra, Albert H.; Todorov, T.I.; Mercer, C.N.; Adams, D.T.; Marsh, E.E.

    2013-01-01

    To evaluate whether anatectic and/or highly fractionated lithophile element-enriched rhyolite tuffs deposited in arid lacustrine basins lose enough lithium during eruption, lithification, and weathering to generate significant Li brine resources, pre-eruptive melt compositions, preserved in inclusions, and the magnitude of post-eruptive Li depletions, evident in host rhyolites, were documented at six sites in the western United States. Each rhyolite is a member of the bimodal basalt-rhyolite assemblage associated with extensional tectonics that produced the Basin and Range province and Rio Grande rift, an evolving pattern of closed drainage basins, and geothermal energy or mineral resources. Results from the 0.8 Ma Bishop tuff (geothermal) in California, 1.3 to 1.6 Ma Cerro Toledo and Upper Bandelier tephra (geothermal) and 27.9 Ma Taylor Creek rhyolite (Sn) in New Mexico, 21.7 Ma Spor Mountain tuff (Be, U, F) and 24.6 Ma Pine Grove tuff (Mo) in Utah, and 27.6 Ma Hideaway Park tuff (Mo) in Colorado support the following conclusions. Melt inclusions in quartz phenocrysts from rhyolite tuffs associated with hydrothermal deposits of Sn, Mo, and Be are extremely enriched in Li (1,000s of ppm); those from Spor Mountain have the highest Li abundance yet recorded (max 5,200 ppm, median 3,750 ppm). Forty-five to 98% of the Li present in pre-eruptive magma was lost to the environment from these rhyolite tuffs. The amount of Li lost from the small volumes (1–10 km3) of Li-enriched rhyolite deposited in closed basins is sufficient to produce world-class Li brine resources. After each eruption, meteoric water leaches Li from tuff, which drains into playas, where it is concentrated by evaporation. The localized occurrence of Li-enriched rhyolites may explain why brines in arid lacustrine basins seldom have economic concentrations of Li. Considering that hydrothermal deposits of Sn, Mo, Be, U, and F may indicate potential for Li brines in nearby basins, we surmise that the

  10. The viscosity of planetary tholeiitic melts: A configurational entropy model

    Science.gov (United States)

    Sehlke, Alexander; Whittington, Alan G.

    2016-10-01

    The viscosity (η) of silicate melts is a fundamental physical property controlling mass transfer in magmatic systems. Viscosity can span many orders of magnitude, strongly depending on temperature and composition. Several models are available that describe this dependency for terrestrial melts quite well. Planetary basaltic lavas however are distinctly different in composition, being dominantly alkali-poor, iron-rich and/or highly magnesian. We measured the viscosity of 20 anhydrous tholeiitic melts, of which 15 represent known or estimated surface compositions of Mars, Mercury, the Moon, Io and Vesta, by concentric cylinder and parallel plate viscometry. The planetary basalts span a viscosity range of 2 orders of magnitude at liquidus temperatures and 4 orders of magnitude near the glass transition, and can be more or less viscous than terrestrial lavas. We find that current models under- and overestimate superliquidus viscosities by up to 2 orders of magnitude for these compositions, and deviate even more strongly from measured viscosities toward the glass transition. We used the Adam-Gibbs theory (A-G) to relate viscosity (η) to absolute temperature (T) and the configurational entropy of the system at that temperature (Sconf), which is in the form of log η =Ae +Be /TSconf . Heat capacities (CP) for glasses and liquids of our investigated compositions were calculated via available literature models. We show that the A-G theory is applicable to model the viscosity of individual complex tholeiitic melts containing 10 or more major oxides as well or better than the commonly used empirical equations. We successfully modeled the global viscosity data set using a constant Ae of -3.34 ± 0.22 log units and 12 adjustable sub-parameters, which capture the compositional and temperature dependence on melt viscosity. Seven sub-parameters account for the compositional dependence of Be and 5 for Sconf. Our model reproduces the 496 measured viscosity data points with a 1

  11. Assessment of mass fraction and melting temperature for the application of limestone concrete and siliceous concrete to nuclear reactor basemat considering molten core-concrete interaction

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ho Jae; Kim, Do Gyeum [Korea Institute of Civil Engineering and Building Technology, Goyang (Korea, Republic of); Cho, Jae Leon [Korea Hydro and Nuclear Power Co., Ulsan (Korea, Republic of); Yoon, Eui Sik [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of); Cho, Myung Suk [Korea Hydro and Nuclear Power Co., Central Research Institute, Daejeon (Korea, Republic of)

    2016-04-15

    Severe accident scenarios in nuclear reactors, such as nuclear meltdown, reveal that an extremely hot molten core may fall into the nuclear reactor cavity and seriously affect the safety of the nuclear containment vessel due to the chain reaction caused by the reaction between the molten core and concrete. This paper reports on research focused on the type and amount of vapor produced during the reaction between a high-temperature molten core and concrete, as well as on the erosion rate of concrete and the heat transfer characteristics at its vicinity. This study identifies the mass fraction and melting temperature as the most influential properties of concrete necessary for a safety analysis conducted in relation to the thermal interaction between the molten core and the basemat concrete. The types of concrete that are actually used in nuclear reactor cavities were investigated. The H2O content in concrete required for the computation of the relative amount of gases generated by the chemical reaction of the vapor, the quantity of CO2 necessary for computing the cooling speed of the molten core, and the melting temperature of concrete are evaluated experimentally for the molten core-concrete interaction analysis.

  12. Origin of silicic volcanic rocks in Central Costa Rica: a study of a chemically variable ash-flow sheet in the Tiribí Tuff

    Science.gov (United States)

    Hannah, Rachel; Vogel, Thomas; Patino, Lina; Alvarado, Guillermo; Pérez, Wendy; Smith, Diane

    2002-01-01

    Chemical heterogeneities of pumice clasts in an ash-flow sheet can be used to determine processes that occur in the magma chamber because they represent samples of magma that were erupted at the same time. The dominant ash-flow sheet in the Tiribí Tuff contains pumice clasts that range in composition from 55.1 to 69.2 wt% SiO2. It covers about 820 km2 and has a volume of about 25 km3 dense-rock equivalent (DRE). Based on pumice clast compositions, the sheet can be divided into three distinct chemical groupings: a low-silica group (55.1-65.6 wt% SiO2), a silicic group (66.2-69.2 wt% SiO2), and a mingled group (58.6-67.7 wt% SiO2; all compositions calculated 100% anhydrous). Major and trace element modeling indicates that the low-silica magma represents a mantle melt that has undergone fractional crystallization, creating a continuous range of silica content from 55.1-65.6 wt% SiO2. Eu/Eu*, MREE, and HREE differences between the two groups are not consistent with crystal fractionation of the low-silica magma to produce the silicic magma. The low-silica group and the silicic group represent two distinct magmas, which did not evolve in the same magma chamber. We suggest that the silicic melts resulted from partial melting of relatively hot, evolved calc-alkaline rocks that were previously emplaced and ponded at the base of an over-thickened basaltic crust. The mingled group represents mingling of the two magmas shortly before eruption. Electronic supplementary material to this paper can be obtained by using the Springer LINK server located at http://dx.doi.org/10.1007/s00445-001-0188-8.

  13. Experimental determination of carbon partitioning between upper mantle minerals and silicate melts: initial results and comparison to trace element partitioning (Nb, Rb, Ba, U, Th, K)

    Science.gov (United States)

    Rosenthal, A.; Hauri, E. H.; Hirschmann, M. M.; Davis, F. A.; Withers, A. C.; Fogel, M. L.

    2012-12-01

    Inventories of C in the mantle and magmatic fluxes of C between the mantle and the Earth's outer envelopes are poorly constrained in part owing to challenges in determining undegassed C concentrations of pristine basalts. Saal et al. [1] proposed that the behavior of Nb could be used as a proxy for C, owing to apparently similar behavior of the two elements in Siqueiros Transform MORB, but higher C/Nb ratios in popping rocks [2] call into question the applicability of the C/Nb proxy. Here, we present experimentally determined carbon partition coefficients (D's) between nominally volatile-free mantle minerals (olivine, OL; orthopyroxene, OPX; clinopyroxene, CPX; garnet, GA) and melts at 0.8-3 GPa, and 1250-1500°C. We conducted piston-cylinder experiments using an olivine-tholeiite + 4 wt% CO2, doped with Nb, Rb, U, Th, and 13C to enhance detection limits. To promote growth of crystals big enough for SIMS analyses, experiments were either long (D12C, but a few have the opposite. Continuous exchange of the liquid (initially rich in 13C) with the graphite capsules (rich in 12C) may yield D's with 13C>12C. D's with 12C>13C are likely owing to either low count rates or comparatively high analytical contamination. Concentrations in minerals vary from 0.20-3.46 ppm for C, 25-176 ppm for H2O, and 0.05-1.21 ppm for F, whereas liquids tend to much higher values (C≤0.9 wt%; H2O≤1.5 wt%; F≤34 ppm; P≤0.25 wt%; S≤43 ppm; Cl≤77 ppm). Resulting D's indicate that C is highly incompatible in all major mantle mineral phases, with D's for OL, OPX and CPX of close to 5x10-4, and for GA ~2.2x10-4. D's for H2O (2x10-4 to ~3x10-2) and F (~2.3x10-3 to ~5.8x10-2) are comparable to those found in previous studies. Trace element partition determinations are in progress, but comparison to previous studies indicates that carbon is significantly more incompatible during mantle melting than Nb, U, or Th, and has behavior approximately similar to Ba. We therefore suggest that

  14. Synchrotron x-ray spectroscopy of EuHN O3 aqueous solutions at high temperatures and pressures and Nb-bearing silicate melt phases coexisting with hydrothermal fluids using a modified hydrothermal diamond anvil cell and rail assembly

    Science.gov (United States)

    Mayanovic, Robert A.; Anderson, Alan J.; Bassett, William A.; Chou, I.-Ming

    2007-01-01

    A modified hydrothermal diamond anvil cell (HDAC) rail assembly has been constructed for making synchrotron x-ray absorption spectroscopy, x-ray fluorescence, and x-ray mapping measurements on fluids or solid phases in contact with hydrothermal fluids up to ???900??C and 700 MPa. The diamond anvils of the HDAC are modified by laser milling grooves or holes, for the reduction of attenuation of incident and fluorescent x rays and sample cavities. The modified HDAC rail assembly has flexibility in design for measurement of light elements at low concentrations or heavy elements at trace levels in the sample and the capability to probe minute individual phases of a multiphase fluid-based system using focused x-ray microbeam. The supporting rail allows for uniform translation of the HDAC, rotation and tilt stages, and a focusing mirror, which is used to illuminate the sample for visual observation using a microscope, relative to the direction of the incident x-ray beam. A structure study of Eu(III) aqua ion behavior in high-temperature aqueous solutions and a study of Nb partitioning and coordination in a silicate melt in contact with a hydrothermal fluid are described as applications utilizing the modified HDAC rail assembly. ?? 2007 American Institute of Physics.

  15. 铂铑合金在硅酸盐熔体中铂和铑损失的研究%Study on the Loss of Platinum and Rhodium in Silicate Melts of Platinum-Rhodium Alloy

    Institute of Scientific and Technical Information of China (English)

    金英杰; 李树屏; 杨志先

    2015-01-01

    Study of the loss of platinum and rhodium in silicate melts of platinum-rhodium alloy. At a certain temperature, platinum and rhodium were lose, and the loss of rhodium was 3.6~5 times of the amount of platium. And qualitative analysis the change of the section rhodium content of PtRh20 in long term use. As a result, the rhodium content was falled 30% to 50%.%研究了铂铑制品中铂和铑在硅酸恿熔体中的损失。发现了在一定温度下,铂和铑在硅酸恿熔体的作用下均会损失,其中铑损失量是铂损失量的3.6~5倍。并定性研究了PtRh20制品在长期使用后厚度方向上铑含量的变化,发现在使用18个月后PtRh20制品铑含量降低了30%~50%。

  16. NQR frequencies of anhydrous carbamazepine polymorphic phases

    CERN Document Server

    Bonin, C J; Pusiol, D J

    2010-01-01

    In this work we propose the Nuclear Quadrupole Resonance (NQR) technique as an analytical method suitable for polymorphism detection in active parts (or active principles) of pharmaceuticals with high pharmacological risk. Samples of powder carbamazepine (5H-dibenz(b,f)-azepine-5-carboxamide) are studied. In its anhydrous state, this compound presents at least three different polymorphic forms: form III, the commercial one, form II, and form I. Of these, only form III possesses desirable therapeutic effects. By using the NQR technique, it was possible to characterize two of the three polymorphic phases (I and III) for anhydrous carbamazepine in few minutes at room temperature, detecting the characteristic frequencies of 14N nuclei (I=1) present in their chemical composition and in the frequency range 2.820-3.935 MHz. For form II, characteristic lines were not detected within this range of frequencies. The lines detected for form III are centered at the frequencies \

  17. Million-year melt-presence in monotonous intermediate magma for a volcanic-plutonic assemblage in the Central Andes: Contrasting histories of crystal-rich and crystal-poor super-sized silicic magmas

    Science.gov (United States)

    Kaiser, Jason F.; de Silva, Shanaka; Schmitt, Axel K.; Economos, Rita; Sunagua, Mayel

    2017-01-01

    crystallized as a granodiorite pluton which was sampled as xenoliths in much later volcanic events. Over the ∼1.1 Ma zircon crystallization history for the PGI, postcaldera lavas and xenoliths, the melt remained in an ∼100-150 °C temperature window as indicated by Ti-in-zircon thermometry. Although chemical trends are consistent with zircon crystallization at variable temperatures, there is no secular cooling, but rather a thermal rejuvenation following the 2.89 Ma PGI eruption. As such these data provide a "low and slow" temporal constraint for models for the pre-eruptive lifetimes of mushy magma in contrast to the "rapid" mobilization of crystal-poor silicic magmas, consistent with a model where the latter are incubated within the former and extracted rapidly prior to eruption. The thermal and chemical monotony of crystal-rich dacites throughout a caldera cycle connotes conditions where near-eutectic melt can be maintained in near-surface magma reservoirs for an extended period of time if the subvolcanic magma reservoir is sufficiently large so that hotter and initially zircon-undersaturated magma can replenish shallow magma vented in a supereruption.

  18. Demethylation of Quinine Using Anhydrous Aluminium Trichloride

    OpenAIRE

    Aiyi Asnawi; As’ari Nawawi; Rahmana Emran Kartasasmita; Slamet Ibrahim3)

    2011-01-01

    Quinine is a natural alkaloid having a methoxy group bound to quinoline ring and an allyl group bound to quinuclidine ring. Demethylation of quinine applying strong acid such as HBr or HI at high temperature was unsuccessful. The aim of this research was to obtain demethylated quinine by means of mild and selective demethylation procedure to prevent the addition reaction of allyl group. Selective demethylation of quinine has been carried out using anhydrous aluminium trichloride as reagent. T...

  19. The use of anhydrous ammonia for bioventing

    Energy Technology Data Exchange (ETDEWEB)

    Zytner, R.G.; Hallman, M.; Gimenez, B.F.; Jennings, R.; Leek, K. [Guelph Univ., ON (Canada). Faculty of Graduate Studies

    2002-07-01

    Soils contaminated with hydrocarbons can be effectively treated using bioventing remediation technology, an ideal method for removing residual contamination left by soil vapour extraction (SVE). Bioventing uses low or intermitted air flow rates to produce oxygen-rich conditions in the vadose zone, thereby promoting the formation of micro-organisms that can mineralize the hydrocarbons if enough nutrients are present. There is concern regarding the use of nutrients (the addition of nitrogen) to the subsurface because current applications methods cannot uniformly disperse nitrogen throughout the entire subsurface. Two research studies are being conducted using gasoline contaminated soil to address this concern. The first phase of the study focuses on how to best deliver nitrogen to the subsurface. Injecting anhydrous ammonia into the contaminated surface was one suggestion for stimulating the growth of hydrocarbon degraders. SVE extraction well models indicated this was an effective and safe way to disperse nitrogen. The second phase of the study involved the use of respirometers to compare total petroleum hydrocarbon (TPH) degradation with nitrogen additions in the form of NH{sub 4}Cl or anhydrous ammonia. The respirometers were run for about 1 month after which time it was determined that the use of anhydrous ammonia is an effective method to promote bioventing.

  20. Low to Extremely Low Water Abundances Measured in Nominally Anhydrous Minerals in Mafic to Granitic Apollo Rock Clasts

    Science.gov (United States)

    Simon, J. I.; Christoffersen, R.; Wang, J.; Alexander, C. M. O'D.; Mills, R. D.; Hauri, E. H.

    2017-01-01

    Lunar sample-based volatile studies have focused on assessing the inventory and distribution of water in the Moon. Some have focused on the relatively young mare basalts and pyroclastic glasses, which result from partial melting of the relatively young lunar mantle. Less certain is the water inventory for the oldest materials available, which have the greater potential to record the earliest history of volatiles in the Moon (and thus provide evidence for the "wet" vs. "dry" accretion hypotheses of the Earth-Moon system. Studies of volatiles in ancient lunar rocks have largely focused on apatite. One recent FTIR (Fourier Transform Infrared Radiometer) study of plagioclase reported a relatively "wet" (approximately 320 parts per million) magma for primordial ferroan anorthosites (FANs). Another, a NanoSIMS study of alkali feldspar, reported a "wet" (approximately 1 weight percentage) felsic magma, but due to the differentiation processes required for silicic magmatism in the lunar crust, predicted an essentially "dry" (less than 100 parts per million) bulk Moon. Thus, despite evidence that appears to complicate the early "dry" Moon paradigm, there is no apparent unanimity among the measurements, even those on apatite. This disparity is clearly seen by the order of magnitude different water estimates for lunar "alkali-rich suite rocks" (Fig. 1). Some of the apparent differences may be explained by recent improvements in the apatite-based water estimates that better account for relative compatibilities of OH-, Cl, and F. In the present work, we seek to expand our understanding of the volatile abundances in early formed lunar magmas, their source reservoirs, and to address the potential role that felsic magmas play on the lunar hydrogen budget over time by employing NanoSIMS analysis of nominally anhydrous minerals.

  1. Water in Nominally Anhydrous Minerals from Nakhlites and Shergottites

    Science.gov (United States)

    Peslier, Anne H.

    2013-01-01

    Estimating the amount of water in the interior of terrestrial planets has tremendous implications on our understanding of solar nebula evolution, planet formation and geological history, and extraterrestrial volcanism. Mars has been a recent focus of such enquiry with complementary datasets from spacecrafts, rovers and martian meteorite studies. In planetary interiors, water can be dissolved in fluids or melts and hydrous phases, but can also be locked as protons attached to structural oxygen in lattice defects in nominally anhydrous minerals (NAM) such as olivine, pyroxene, or feldspar [1-3]. Measuring water in Martian meteorite NAM is challenging because the minerals are fragile and riddled with fractures from impact processes that makes them break apart during sample processing. Moreover, curing the sample in epoxy causes problems for the two main water analysis techniques, Fourier transform infrared spectrometry (FTIR) and secondary ionization mass spectrometry (SIMS). Measurements to date have resulted in a heated debate on how much water the mantle of Mars contains. SIMS studies of NAM [4], amphiboles [5], and apatites [6-8] from Martian meteorites report finding enough water in these phases to infer that the martian mantle is as hydrous as that of the Earth. On the other hand, a SIMS study of glass in olivine melt inclusions from shergottites concludes that the Martian mantle is much drier [9]. The latter interpretation is also supported by the fact that most martian hydrous minerals generally have the relevant sites filled with Cl and F instead of H [10,11]. As for experimental results, martian basalt compositions can be reproduced using water as well as Cl in the parent melts [12,13]. Here FTIR is used to measure water in martian meteorite minerals in order to constrain the origin of the distribution of water in martian meteorite phases.

  2. Heat Capacity of Hydrous Silicate Melts

    Science.gov (United States)

    Robert, G.; Whittington, A. G.; Stechern, A.; Behrens, H.

    2015-12-01

    We determined the heat capacities of four series of glasses and liquids of basaltic and basaltic andesite compositions including two natural remelts from Fuego volcano, Guatemala, and two Fe-free analogs. The samples are low-alkali, Ca- and Mg-rich aluminosilicates with non-bridging oxygen to tetrahedrally-coordinated cation ratios (NBO/T) ranging between 0.33 and 0.67. Differential scanning calorimetry measurements were performed at atmospheric pressure between room temperature and ≈100 K above the glass transition for hydrous samples and up to ≈1800 K for dry samples. The water contents investigated range up to 5.34 wt.% (16.4 mol%). Water does not measurably affect the heat capacity of glasses (T

  3. Cumulate Fragments in Silicic Ignimbrites

    Science.gov (United States)

    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.

  4. The distribution of chromium among orthopyroxene, spinel and silicate liquid at atmospheric pressure

    Science.gov (United States)

    Barnes, S. J.

    1986-01-01

    The Cr distributions for a synthetic silicate melt equilibrated with bronzitic orthopyroxene and chromite spinel between 1334 and 1151 C over a range of oxygen fugacities between the nickel-nickel oxide and iron-wuestite buffers are studied. The occurrence, chemical composition, and structure of the orthopyroxene-silicate melt and the spinel-silicate melt are described. It is observed that the Cr content between bronzite and the melt increases with falling temperature along a given oxygen buffer and decreases with falling oxygen fugacity at a given temperature; however, the Cr content of the melt in equilibrium with spinel decreases with falling temperature and increases with lower oxygen fugacity.

  5. Adsorption of dimeric surfactants in lamellar silicates

    Energy Technology Data Exchange (ETDEWEB)

    Balcerzak, Mateusz; Pietralik, Zuzanna [Department of Macromolecular Physics, Faculty of Physics, A. Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland); Domka, Ludwik [Department of Metalorganic Chemistry, Faculty of Chemistry, A. Mickiewicz University, Grunwaldzka 6, 60-780 Poznań (Poland); Skrzypczak, Andrzej [Institute of Chemical Technology, Poznań University of Technology, Berdychowo 4, 60-965 Poznań (Poland); Kozak, Maciej, E-mail: mkozak@amu.edu.pl [Department of Macromolecular Physics, Faculty of Physics, A. Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland)

    2015-12-01

    Highlights: • The intercalation of dimeric surfactants changed the morphology of MMT samples. • XRD indicated structures formed by surfactant molecules in interlayer space. • The four-step thermal decomposition of dimeric surfactant, confirms intercalation. - Abstract: The adsorption of different types of cationic surfactants in lamellar silicates changes their surface character from hydrophilic to hydrophobic. This study was undertaken to obtain lamellar silicates modified by a series of novel dimeric (gemini) surfactants of different length alkyl chains and to characterise these organophilised materials. Synthetic sodium montmorillonite SOMASIF® ME 100 (M) and enriched bentonite of natural origin (Nanoclay – hydrophilic bentonite®) were organophilised with dimeric (gemini) surfactants (1,1′-(1,4-butanediyl)bis(alkoxymethyl)imidazolium dichlorides). As a result of surfactant molecule adsorption in interlamellar space, the d-spacing (d{sub 001}) increased from 0.97 nm (for the anhydrous structure) to 2.04 nm. A Fourier transform infrared spectroscopy (FTIR) analysis of the modified systems reveals bands assigned to the stretching vibrations of the CH{sub 2} and CH{sub 3} groups and the scissoring vibrations of the NH group from the structure of the dimeric surfactants. Thermogravimetric (TG) and derivative thermogravimetric (DTG) studies imply a four-stage process of surfactant decomposition. Scanning electron microscopy (SEM) images provide information on the influence of dimeric surfactant intercalation into the silicate structures. Particles of the modified systems show a tendency toward the formation of irregularly shaped agglomerates.

  6. Sodium Picosulfate, Magnesium Oxide, and Anhydrous Citric Acid

    Science.gov (United States)

    Sodium picosulfate, magnesium oxide, and anhydrous citric acid combination powder is used to empty the colon (large ... clear view of the walls of the colon. Sodium picosulfate is in a class of medications called ...

  7. Mass transfer in the lower crust: Evidence for incipient melt assisted flow along grain boundaries in the deep arc granulites of Fiordland, New Zealand

    Science.gov (United States)

    Stuart, Catherine A.; Piazolo, Sandra; Daczko, Nathan R.

    2016-09-01

    Knowledge of mass transfer is critical in improving our understanding of crustal evolution, however mass transfer mechanisms are debated, especially in arc environments. The Pembroke Granulite is a gabbroic gneiss, passively exhumed from depths of >45 km from the arc root of Fiordland, New Zealand. Here, enstatite and diopside grains are replaced by coronas of pargasite and quartz, which may be asymmetric, recording hydration of the gabbroic gneiss. The coronas contain microstructures indicative of the former presence of melt, supported by pseudosection modeling consistent with the reaction having occurred near the solidus of the rock (630-710°C, 8.8-12.4 kbar). Homogeneous mineral chemistry in reaction products indicates an open system, despite limited metasomatism at the hand sample scale. We propose the partial replacement microstructures are a result of a reaction involving an externally derived hydrous, silicate melt and the relatively anhydrous, high-grade assemblage. Trace element mapping reveals a correlation between reaction microstructure development and bands of high-Sr plagioclase, recording pathways of the reactant melt along grain boundaries. Replacement microstructures record pathways of diffuse porous melt flow at a kilometer scale within the lower crust, which was assisted by small proportions of incipient melt providing a permeable network. This work recognizes melt flux through the lower crust in the absence of significant metasomatism, which may be more common than is currently recognized. As similar microstructures are found elsewhere within the exposed Fiordland lower crustal arc rocks, mass transfer of melt by diffuse porous flow may have fluxed an area >10,000 km2.

  8. CO2-SO3-rich (carbonate-sulfate) melt/fluids in the lithosphere beneath El Hierro, Canary Islands.

    Science.gov (United States)

    Oglialoro, E.; Ferrando, S.; Malaspina, N.; Villa, I. M.; Frezzotti, M. L.

    2015-12-01

    Mantle xenoliths from the island of El Hierro, the youngest of the Canary Islands, have been studied to characterize fluxes of carbon in the lithosphere of an OIB volcanism region. Fifteen xenoliths (4-10 cm in diameter) were collected in a rift lava flow (15-41 ka) at a new xenolith locality in El Julan cliff (S-SW of the island). Peridotites consist of protogranular to porphyroblastic spinel harzburgites, lherzolites, and subordinate dunites. One spinel clinopyroxenite, and one olivine-websterite were also analyzed. Ultramafic xenoliths were classified as HEXO (harzburgite and dunite with exsolved orthopyroxene), HLCO (harzburgite and lherzolite containing orthopyroxene without visible exsolution lamellae), and HTR (transitional harzburgite with exsolved orthopyroxene porphyroclasts, and poikilitic orthopyroxene) following [1]. While HLCO and HTR peridotites contain mostly CO2 fluid inclusions, HEXO peridotites preserve an early association of melt/fluid inclusions containing dominantly carbonate/sulfate/silicate glass, evolving to carbonate/sulfate/phosphate/spinel aggregates, with exsolved CO2 (± carbonates, anhydrite and H2O). Chemical and Raman analyses identify dolomite, Mg-calcite, anhydrite, sulfohalite [Na6(SO4)2FCl] (± other anhydrous and hydrous alkali-sulfates), apatite, and Cr-spinel in the inclusions. Sulfides are noticeably absent. The microstructure and chemical composition of the metasomatic fluids indicate that the peridotites were infiltrated by a carbonate-sulfate-silicate melt/fluid enriched in CO2, H2O, and P. A mantle origin for this fluid is supported by high densities of CO2inclusions (> 1g/cm3), determined by Raman microspectroscopy and cross-checked by microthermometry. Consequently, El Julan peridotites provide the first evidence for liberating oxidized C and S fluxes from the Earth lithosphere in an OIB source region, and suggest that oxidation of sulfide to sulfate can occur during small-degree partial melting of the upper mantle

  9. Cooling rate calculations for silicate glasses.

    Science.gov (United States)

    Birnie, D. P., III; Dyar, M. D.

    1986-03-01

    Series solution calculations of cooling rates are applied to a variety of samples with different thermal properties, including an analog of an Apollo 15 green glass and a hypothetical silicate melt. Cooling rates for the well-studied green glass and a generalized silicate melt are tabulated for different sample sizes, equilibration temperatures and quench media. Results suggest that cooling rates are heavily dependent on sample size and quench medium and are less dependent on values of physical properties. Thus cooling histories for glasses from planetary surfaces can be estimated on the basis of size distributions alone. In addition, the variation of cooling rate with sample size and quench medium can be used to control quench rate.

  10. Preparation of anhydrous lanthanum bromide for scintillation crystal growth

    Institute of Scientific and Technical Information of China (English)

    ZHANG Tong; LI Hongwei; ZHAO Chunlei; YU Jinqiu; HU Yunsheng; CUI Lei; HE Huaqiang

    2012-01-01

    This paper reported an efficient and economical method for preparation of anhydrous LaBr3 for scintillation crystal growth.High purity anhydrous LaBr3 powders in large quantities were successfully obtained by stepped dehydration of LaBr3·7H2O using NH4Br as additive.Experiments revealed that adding proper amount of NH4Br could effectively restrain the hydrolysis of LaBr3 during dehydration and thus decreased the yield of deleterious impurity of LaOBr.Optimum preparation conditions,including the amount of NH4Br in use,the dehydration temperature and atmosphere,were investigated by DTA/TG and water/oxygen analysis.The Raman characterization of the as-prepared anhydrous LaBr3 was also presented.

  11. Crystallization behavior of anhydrous milk fat-sunflower oil wax blends.

    Science.gov (United States)

    Kerr, Rebekah M; Tombokan, Xenia; Ghosh, Supriyo; Martini, Silvana

    2011-03-23

    This research evaluates the effect of sunflower oil wax (SFOw) addition on the crystallization behavior and functional properties of anhydrous milk fat (AMF). Induction times of nucleation, melting behavior, microstructure of crystals, and hardness were evaluated for samples of pure AMF and AMF with 0.1 and 0.25% SFOw. Results from this research show that the addition of waxes induced the onset of crystallization of AMF by inducing its nucleation, as evidenced by decreased induction times of nucleation and the formation of smaller crystals. Crystal growth after tempering was also promoted by waxes, and significantly harder lipid networks were obtained. Results presented in this paper suggest that SFOw can be used as an additive to alter the physiochemical properties of low trans-fatty acid lipids.

  12. Trondhjemitic melts produced by in-situ differentiation of a tholeiitic lava flow, Reykjanes Peninsula, Iceland.

    Science.gov (United States)

    Martin, E.; Sigmarsson, O.

    2006-12-01

    How the continental crust began to form early in Earth's history is unconstrained. However, it is reasonable to presume that higher heat flow in the past, resulted in more frequent interaction of mantle plumes and mid- oceanic ridges. If true, then Iceland could be a good analogue for processes occurring on Earth at its youth stage. This is supported by the relatively high abundance of silicic rocks in Iceland but their rarity on other oceanic hot spots. The origin of Icelandic silicic rocks has been a subject of a lively debate but has been shown to be principally formed by partial melting of hydrothermally altered basaltic crust. However, in rare cases, their origin by fractional crystallization from mantle derived basalts is suggested. Segregation veins in lava flows frequently contain interstitial glasses of silicic compositions. Moreover, they allow an exceptional overview of the fractional crystallization mechanism. These veins form by gas filter pressing during cooling and degassing of solidifying lava flows, after approximately 50% fractional crystallization of anhydrous minerals. Pairs of samples, host lava and associated segregation veins, from Reykjanes Peninsula (Iceland), Lanzarote (Canary Island) and Masaya's volcano (Nicaragua), allow the assessment of a near-complete fractional crystallization of olivine tholeiitic basalt at pressure close to one atmosphere. Interstitial glass patches in segregation veins represent the final product of this process (80 97 % of fractional crystallization). These ultimate liquids are of granitic composition in the case of Lanzarote and Masaya but overwhelmingly trondhjemitic at Reykjanes. It appears that the initial K2O/Na2O of the basaltic liquid controls the evolution path of the residual liquid composition produced at pressure close to 0.1 MPa (1 bar). Granitic liquids are generated from basalts of high initial K2O/Na2O whereas low initial K2O/Na2O leads to trondhjemitic compositions. The trondhjemitic composition

  13. Solid Phase Synthesis of Anhydrous Zinc Borate from Zinc and Boron Oxide and Utilization as a Flame Retardant in Dye and Textile

    OpenAIRE

    AYAR, Barış; GÜRÜ, Metin; ÇAKANYILDIRIM, Çetin

    2014-01-01

    Durability of materials to flame and stability at high temperatures are very important in order to increase the field of use. Non-flammability is not the only requirement materials should not have toxic gas products during the burning, also. Anhydrous zinc borate was chosen as flame retardant due to its advantages, such as; light weight, high melting point, low thermal expansion, and intrinsic smoke suppressant and corrosion resistance properties. For the synthesis, metallic zinc and anhydrou...

  14. Nanostructured silicate polymer concrete

    Directory of Open Access Journals (Sweden)

    Figovskiy Oleg L'vovich

    2014-03-01

    Full Text Available It has been known that acid-resistant concretes on the liquid glass basis have high porosity (up to 18~20 %, low strength and insufficient water resistance. Significant increasing of silicate matrix strength and density was carried out by incorporation of special liquid organic alkali-soluble silicate additives, which block superficial pores and reduce concrete shrinkage deformation. It was demonstrated that introduction of tetrafurfuryloxisilane additive sharply increases strength, durability and shock resistance of silicate polymer concrete in aggressive media. The experiments showed, that the strength and density of silicate polymer concrete increase in case of decreasing liquid glass content. The authors obtained optimal content of silicate polymer concrete, which possesses increased strength, durability, density and crack-resistance. Diffusive permeability of concrete and its chemical resistance has been investigated in various corroding media.

  15. Compact anhydrous HCl to aqueous HCl conversion system

    Science.gov (United States)

    Grossman, M.W.; Speer, R.

    1993-06-01

    The present invention is directed to an inexpensive and compact apparatus adapted for use with a [sup 196]Hg isotope separation process and the conversion of anhydrous HCl to aqueous HCl without the use of air flow to carry the HCl vapor into the converter system.

  16. Process for the production of sodium carbonate anhydrate

    NARCIS (Netherlands)

    Oosterhof, H.; Van Rosmalen, G.M.; Witkamp, G.J.; De Graauw, J.

    2000-01-01

    The invention is directed to a process for the production of sodium carbonate-anhydrate having a bulk density of at least 800 kg/m<3>, said process comprising: providing a suspension of solid sodium carbonate and/or solid sodium bicarbonate and/or solid double salts at least comprising one of

  17. Solid state interconversion between anhydrous norfloxacin and its hydrates.

    Science.gov (United States)

    Chongcharoen, Wanchai; Byrn, Stephen R; Sutanthavibul, Narueporn

    2008-01-01

    This work is focused on characterizing and evaluating the solid state interconversion of norfloxacin (NF) hydrates. Four stoichiometric NF hydrates, dihydrate, hemipentahydrate, trihydrate, pentahydrate and a disordered NF state, were generated by various methods and characterized by X-ray powder diffractometry (XRPD), thermal analysis and Karl Fisher titrimetry. XRPD patterns of all NF hydrates exhibited crystalline structures. NF hydrate conversion was studied with respect to mild elevated temperature and various degrees of moisture levels. NF hydrates transformed to anhydrous NF Form A after gentle heating at 60 degrees C for 48 h except dihydrate and trihydrate where mixture in XRPD patterns between anhydrous NF Form A and former structures existed. Desiccation of NF hydrates at 0% RH for 7 days resulted in only partial removal of water molecules from the hydrated structures. The hydrated transitional phase and the disordered NF state were obtained from the incomplete dehydration of NF hydrates after thermal treatment and pentahydrate NF after desiccation, respectively. Anhydrous NF Form A and NF hydrates transformed to pentahydrate NF when exposed to high moisture environment except dihydrate. In conclusion, surrounding moisture levels, temperatures and the duration of exposure strongly influenced the interconversion pathways and stoichiometry of anhydrous NF and its hydrates. (c) 2007 Wiley-Liss, Inc.

  18. Chronology and shock history of the Bencubbin meteorite: A nitrogen, noble gas, and Ar-Ar investigation of silicates, metal and fluid inclusions

    Science.gov (United States)

    Marty, Bernard; Kelley, Simon; Turner, Grenville

    2010-11-01

    We have investigated the distribution and isotopic composition of nitrogen and noble gases, and the Ar-Ar chronology of the Bencubbin meteorite. Gases were extracted from different lithologies by both stepwise heating and vacuum crushing. Significant amounts of gases were found to be trapped within vesicles present in silicate clasts. Results indicate a global redistribution of volatile elements during a shock event caused by an impactor that collided with a planetary regolith. A transient atmosphere was created that interacted with partially or totally melted silicates and metal clasts. This atmosphere contained 15N-rich nitrogen with a pressure ⩾3 × 10 5 hPa, noble gases, and probably, although not analyzed here, other volatile species. Nitrogen and noble gases were re-distributed among bubbles, metal, and partly or totally melted silicates, according to their partition coefficients among these different phases. The occurrence of N 2 trapped in vesicles and dissolved in silicates indicates that the oxygen fugacity ( fO2) was greater than the iron-wüstite buffer during the shock event. Ar-Ar dating of Bencubbin glass gives an age of 4.20 ± 0.05 Ga, which probably dates this impact event. The cosmic-ray exposure age is estimated at ˜40 Ma with two different methods. Noble gases present isotopic signatures similar to those of "phase Q" (the major host of noble gases trapped in chondrites) but elemental patterns enriched in light noble gases (He, Ne and Ar) relative to Kr and Xe, normalized to the phase Q composition. Nitrogen isotopic data together with 40Ar/ 36Ar ratios indicate mixing between a 15N-rich component (δ 15N = +1000‰), terrestrial N, and an isotopically normal, chondritic N. Bencubbin and related 15N-rich meteorites of the CR clan do not show stable isotope (H and C) anomalies, precluding contribution of a nucleosynthetic component as the source of 15N enrichments. This leaves two possibilities, trapping of an ancient, highly fractionated

  19. Theoretical Prediction of Melting Relations in the Deep Mantle: the Phase Diagram Approach

    Science.gov (United States)

    Belmonte, D.; Ottonello, G. A.; Vetuschi Zuccolini, M.; Attene, M.

    2016-12-01

    Despite the outstanding progress in computer technology and experimental facilities, understanding melting phase relations in the deep mantle is still an open challenge. In this work a novel computational scheme to predict melting relations at HP-HT by a combination of first principles DFT calculations, polymer chemistry and equilibrium thermodynamics is presented and discussed. The adopted theoretical framework is physically-consistent and allows to compute multi-component phase diagrams relevant to Earth's deep interior in a broad range of P-T conditions by a convex-hull algorithm for Gibbs free energy minimisation purposely developed for high-rank simplexes. The calculated phase diagrams are in turn used as a source of information to gain new insights on the P-T-X evolution of magmas in the deep mantle, providing some thermodynamic constraints to both present-day and early Earth melting processes. High-pressure melting curves of mantle silicates are also obtained as by-product of phase diagram calculation. Application of the above method to the MgO-Al2O3-SiO2 (MAS) ternary system highlights as pressure effects are not only able to change the nature of melting of some minerals (like olivine and pyroxene) from eutectic to peritectic (and vice versa), but also simplify melting relations by drastically reducing the number of phases with a primary phase field at HP-HT conditions. It turns out that mineral phases like Majorite-Pyrope garnet and Anhydrous Phase B (Mg14Si5O24), which are often disregarded in modelling melting processes of mantle assemblages, are stable phases at solidus or liquidus conditions in a P-T range compatible with the mantle transition zone (i.e. P = 16 - 23 GPa and T = 2200 - 2700 °C) when their thermodynamic and thermophysical properties are properly assessed. Financial support to the Senior Author (D.B.) during his stay as Invited Scientist at the Institut de Physique du Globe de Paris (IPGP, Paris) is warmly acknowledged.

  20. 49 CFR 173.195 - Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution).

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Hydrogen cyanide, anhydrous, stabilized... Hazardous Materials Other Than Class 1 and Class 7 § 173.195 Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution). (a) Hydrogen cyanide, anhydrous, stabilized, must be packed in...

  1. 7 CFR 51.1178 - Maximum anhydrous citric acid permissible for corresponding total soluble solids.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Maximum anhydrous citric acid permissible for... Sinensis (l) Osbeck) § 51.1178 Maximum anhydrous citric acid permissible for corresponding total soluble solids. For determining the grade of juice, the maximum permissible anhydrous citric acid content...

  2. Melting carbonated epidote eclogites: carbonatites from subducting slabs

    Science.gov (United States)

    Poli, Stefano

    2016-12-01

    Current knowledge on the solidus temperature for carbonated eclogites suggests that carbonatitic liquids should not form from a subducted oceanic lithosphere at sub-arc depth. However, the oceanic crust includes a range of gabbroic rocks, altered on rifts and transforms, with large amounts of anorthite-rich plagioclase forming epidote on metamorphism. Epidote disappearance with pressure depends on the normative anorthite content of the bulk composition; we therefore expect that altered gabbros might display a much wider pressure range where epidote persists, potentially affecting the solidus relationships. A set of experimental data up to 4.6 GPa, and 1000 °C, including new syntheses on mafic eclogites with 36.8 % normative anorthite, is discussed to unravel the effect of variable bulk and volatile compositions in model eclogites, enriched in the normative anorthite component ( An 37 and An 45). Experiments are performed in piston cylinder and multianvil machines. Garnet, clinopyroxene, and coesite form in all syntheses. Lawsonite was found to persist at 3.7 GPa, 750 °C, with both dolomite and magnesite; at 3.8 GPa, 775-800 °C, fluid-saturated conditions, epidote coexists with kyanite, dolomite, and magnesite. The anhydrous assemblage garnet, omphacite, aragonite, and kyanite is found at 4.2 GPa, 850 °C. At 900 °C, a silicate glass of granitoid composition, a carbonatitic precipitate, and Na-carbonate are observed. Precipitates are interpreted as evidence of hydrous carbonatitic liquids at run conditions; these liquids produced are richer in Ca compared to experimental carbonatites from anhydrous experiments, consistently with the dramatic role of H2O in depressing the solidus temperature for CaCO3. The fluid-absent melting of the assemblage epidote + dolomite, enlarged in its pressure stability for An-rich gabbros, is expected to promote the generation of carbonatitic liquids. The subsolidus breakdown of epidote in the presence of carbonates at depths

  3. Polymer-Layer Silicate Nanocomposites

    DEFF Research Database (Denmark)

    Potarniche, Catalina-Gabriela

    Nowadays, some of the material challenges arise from a performance point of view as well as from recycling and biodegradability. Concerning these aspects, the development of polymer layered silicate nanocomposites can provide possible solutions. This study investigates how to obtain polymer layered...... silicate nanocomposites and their structure-properties relationship. In the first part of the thesis, thermoplastic layered silicates were obtained by extrusion. Different modification methods were tested to observe the intercalation treatment effect on the silicate-modifier interactions. The silicate...

  4. Method of synthesis of anhydrous thorium(IV) complexes

    Science.gov (United States)

    Kiplinger, Jaqueline L; Cantat, Thibault

    2013-04-30

    Method of producing anhydrous thorium(IV) tetrahalide complexes, utilizing Th(NO.sub.3).sub.4(H.sub.2O).sub.x, where x is at least 4, as a reagent; method of producing thorium-containing complexes utilizing ThCl.sub.4(DME).sub.2 as a precursor; method of producing purified ThCl.sub.4(ligand).sub.x compounds, where x is from 2 to 9; and novel compounds having the structures: ##STR00001##

  5. Silicic Large Igneous Provinces

    Institute of Scientific and Technical Information of China (English)

    Scott Bryan

    2007-01-01

    @@ Large Igneous Provinces (LIPs) are the end-product of huge additions of magma to the continental crust both at the surface and at depth. Since the first categorisation of LIPs by Coffin & Eldholm (1994), it has been recognised that LIPs are more varied inform, age and character, and this includes the recognition of Silicic LIPs. Silicic LIPs are the largest accumulations of primary volcaniclastic rocks at the Earth's surface with areal extents >0.1 Mkm2 and extrusive and subvolcanic intrusive volumes >0.25 Mkm3. The Late Palaeozoic to Cenozoic Silicic LIP events are the best recognised and are similar in terms of their dimension, crustal setting, volcanic architecture and geochemistry.

  6. Formulation and in vitro evaluation of theophylline anhydrous bioadhesive tablets

    Directory of Open Access Journals (Sweden)

    Deshmukh V

    2009-01-01

    Full Text Available The aim of the current study was to design oral controlled release (CR theophylline anhydrous bioadhesive tablets and to optimize the drug release profile and in vitro bioadhesion strength. Different types of natural hydrophilic polymers such as xanthun gum, locust bean gum, guar gum, karaya gum, and their combinations were used to formulate matrix tablets. Tablets of anhydrous theophylline were prepared by the direct compression method and were subjected to in vitro drug dissolution for 12 hours using the USP dissolution apparatus basket type at a speed of 100 rpm and temperature of 37 ± 0.5°C using gastric fluid (pH 1.2. The bioadhesive strength of the tablets was measured as the force of detachment against the porcine gastric mucosa. The in vitro release study as well as the retention time of the bioadhesive tablets on the mucous membrane were investigated to develop a bioadhesive polymer-based CR delivery system and to evaluate the performance of such a delivery device. The combination of karaya gum:guar gum (6:4 tablet showed a greater bioadhesive strength as compared with a single gum and other gum combination tablets. Karaya gum:guar gum-loaded tablets were not discharged from the mucous membrane and were dissolved in the gastric fluid. An increase in the gum concentration increases the drug release profile beyond 12 hours whereas there is no significant effect of gum concentration on the bioadhesive strength of the tablet.

  7. A New Thickener for CO2 Anhydrous Fracturing Fluid

    Directory of Open Access Journals (Sweden)

    Zhang Jian

    2015-01-01

    Full Text Available CO2 dry fracturing technology is well-known for its advantages. Little water is used in this technology, which is able to ease the pressure of consumption on water resources. Many abroad theoretical researches, laboratory experiments and field tests have been taken to explore the yield mechanism, the adaptability and the technology of pure liquid CO2 fracturing. These achievements have been applied to a variety of reservoirs transformation and improven the effectiveness of stimulation treatment in a degree. The researches and studies in the domestic didn’t get popular until recent years. Thus, this article firstly introduces the main development and application about pure CO2 anhydrous fracturing technology, and sums up the effect and evaluation of its fluid through application examples both in the domestic and abroad. However, although this technology has many excellent qualities, but systematic studies indicate that its proppant-carrying capacity is less competitive because of the low viscosity of pure CO2 liquid and other reasons. In a consequence, it is necessary to develop an appropriate thickener for CO2 anhydrous fracturing fluid to improve its carrying capacity. Then this article describes some studies of previous scholars about CO2 thickener. Then we put forward our own research ideas and transform it into actual experiments. Thanks to the valid performances of these tests, we successfully develop a thickener X and cosolvent B.

  8. Anhydrous crystals of DNA bases are wide gap semiconductors.

    Science.gov (United States)

    Maia, F F; Freire, V N; Caetano, E W S; Azevedo, D L; Sales, F A M; Albuquerque, E L

    2011-05-07

    We present the structural, electronic, and optical properties of anhydrous crystals of DNA nucleobases (guanine, adenine, cytosine, and thymine) found after DFT (Density Functional Theory) calculations within the local density approximation, as well as experimental measurements of optical absorption for powders of these crystals. Guanine and cytosine (adenine and thymine) anhydrous crystals are predicted from the DFT simulations to be direct (indirect) band gap semiconductors, with values 2.68 eV and 3.30 eV (2.83 eV and 3.22 eV), respectively, while the experimentally estimated band gaps we have measured are 3.83 eV and 3.84 eV (3.89 eV and 4.07 eV), in the same order. The electronic effective masses we have obtained at band extremes show that, at low temperatures, these crystals behave like wide gap semiconductors for electrons moving along the nucleobases stacking direction, while the hole transport are somewhat limited. Lastly, the calculated electronic dielectric functions of DNA nucleobases crystals in the parallel and perpendicular directions to the stacking planes exhibit a high degree of anisotropy (except cytosine), in agreement with published experimental results.

  9. Impact-induced melting during accretion of the Earth

    CERN Document Server

    de Vries, Jellie; Melosh, H Jay; Jacobson, Seth A; Morbidelli, Alessandro; Rubie, David C

    2016-01-01

    Because of the high energies involved, giant impacts that occur during planetary accretion cause large degrees of melting. The depth of melting in the target body after each collision determines the pressure and temperature conditions of metal-silicate equilibration and thus geochemical fractionation that results from core-mantle differentiation. The accretional collisions involved in forming the terrestrial planets of the inner Solar System have been calculated by previous studies using N-body accretion simulations. Here we use the output from such simulations to determine the volumes of melt produced and thus the pressure and temperature conditions of metal-silicate equilibration, after each impact, as Earth-like planets accrete. For these calculations a parametrised melting model is used that takes impact velocity, impact angle and the respective masses of the impacting bodies into account. The evolution of metal-silicate equilibration pressures (as defined by evolving magma ocean depths) during Earth's ac...

  10. Free fatty acids and their esters modulate isothermal crystallization of anhydrous milk fat.

    Science.gov (United States)

    Bayard, Mathilde; Leal-Calderon, Fernando; Cansell, Maud

    2017-03-01

    The effect of free fatty acids with different chain lengths or unsaturation degree on anhydrous milk fat (AMF) crystallization was evaluated. The impact of esterification was also studied using three triglycerides. Melted blends containing the additives at concentrations lower than 12wt.% were quenched at 25°C and isothermal crystallization was monitored by pulsed low-resolution nuclear magnetic resonance. In parallel, polarized light microscopy was used to observe the microstructure. Compounds based on long chain saturated fatty acids, i.e. palmitic, stearic, eicosanoic acids, tripalmitin and tristearin accelerated crystallization. Conversely, propanoic, hexanoic and oleic acids slowed down the process, while triacetin had no impact. Interestingly, above a critical concentration, the addition of palmitic, stearic or eicosanoic acids caused a transition from a one-step to two-step process. Gompertz model was used to fit the experimental data and to assess the influence of the molecular properties of the additives on the kinetic parameters. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. Experimental studies of crystal-melt differentiation in planetary basalt compositions

    Science.gov (United States)

    Grove, T. L.

    1987-01-01

    An important process that controls the evolution of magmas on and within planetary bodies is crystal-melt differentiation. Experimental studies of silicate melt solidification were performed on several planetary and terrestrial melt compositions, and experiments on one of these compositions in the microgravity environment of the space station would provide an opportunity to understand the factors that control crystal growth and crystal-melt exchange processes at crystal-melt interfaces during solidification. Experimental requirements are presented.

  12. Evolution of silicic volcanism following the transition to the modern High Cascades, Deschutes Formation, central Oregon

    Science.gov (United States)

    Eungard, D.; Kent, A. J.; Grunder, A.

    2012-12-01

    An understanding of the controls on silicic volcanism within convergent margin environments has important implications for crustal growth and modification during subduction. In the central Oregon Cascade range silicic volcanism has generally decreased in both size and frequency of eruptions over the last ~40 million years. Despite the general decrease, an increased abundance of silicic volcanism is observed from 5-8 Ma, corresponding to the transition from the Western Cascades to High Cascades volcanic regime. In order to constrain the processes that lead to formation of silicic magmas at this time we have studied the petrogenesis of two extensive and well-preserved ash-flow tuffs from this time period hosted within the Deschutes Formation of central Oregon. The Lower Bridge (LBT) and McKenzie Canyon Tuffs (MCT) produced ~5 km3 each of magma of predominantly rhyolitic and basaltic andesite composition. Both include large volumes of rhyolite, although the MCT also contains a significant mafic component. Both tuffs are normally zoned with mafic ejecta concentrated upsection. Geothermometry also shows that the rhyolitic component in both magmas was relatively hot (~830 degrees C). Distribution, thickness, welding facies, and paleoflow indications from imbricated pumice suggest that both eruptions derive from the same source region, probably near the present day Three Sisters complex, and were likely produced from the same magmatic system. Variations in major and trace element geochemistry also indicate that the magmas involved in both eruptions were produced through fractionation and mixing of mantle melts with a silicic partial melt derived from melting of mafic crust. Production of these voluminous silicic magmas required both crystal fractionation of incoming melts from the mantle, together with mixing with silicic partial melts derived from relatively hot mafic crust. This observation provides a potential explanation for the decrease in silicic melt production

  13. Silicates in Alien Asteroids

    Science.gov (United States)

    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.

  14. Silicates in Alien Asteroids

    Science.gov (United States)

    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.

  15. Melts of garnet lherzolite: experiments, models and comparison to melts of pyroxenite and carbonated lherzolite

    Science.gov (United States)

    Grove, Timothy L.; Holbig, Eva S.; Barr, Jay A.; Till, Christy B.; Krawczynski, Michael J.

    2013-01-01

    Phase equilibrium experiments on a compositionally modified olivine leucitite from the Tibetan plateau have been carried out from 2.2 to 2.8 GPa and 1,380–1,480 °C. The experiments-produced liquids multiply saturated with spinel and garnet lherzolite phase assemblages (olivine, orthopyroxene, clinopyroxene and spinel ± garnet) under nominally anhydrous conditions. These SiO2-undersaturated liquids and published experimental data are utilized to develop a predictive model for garnet lherzolite melting of compositionally variable mantle under anhydrous conditions over the pressure range of 1.9–6 GPa. The model estimates the major element compositions of garnet-saturated melts for a range of mantle lherzolite compositions and predicts the conditions of the spinel to garnet lherzolite phase transition for natural peridotite compositions at above-solidus temperatures and pressures. We compare our predicted garnet lherzolite melts to those of pyroxenite and carbonated lherzolite and develop criteria for distinguishing among melts of these different source types. We also use the model in conjunction with a published predictive model for plagioclase and spinel lherzolite to characterize the differences in major element composition for melts in the plagioclase, spinel and garnet facies and develop tests to distinguish between melts of these three lherzolite facies based on major elements. The model is applied to understand the source materials and conditions of melting for high-K lavas erupted in the Tibetan plateau, basanite–nephelinite lavas erupted early in the evolution of Kilauea volcano, Hawaii, as well as younger tholeiitic to alkali lavas from Kilauea.

  16. Thermochemistry of Silicates

    Science.gov (United States)

    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).

  17. Characterizing Amorphous Silicates in Extraterrestrial Materials

    Science.gov (United States)

    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

  18. 7 CFR 58.715 - Cream, plastic cream and anhydrous milkfat.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 3 2010-01-01 2010-01-01 false Cream, plastic cream and anhydrous milkfat. 58.715 Section 58.715 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING... Service 1 Quality Specifications for Raw Material § 58.715 Cream, plastic cream and anhydrous...

  19. Impact melting of the largest known enstatite meteorite: Al Haggounia 001, a fossil EL chondrite

    Science.gov (United States)

    Rubin, Alan E.

    2016-09-01

    Al Haggounia 001 and paired specimens (including Northwest Africa [NWA] 2828 and 7401) are part of a vesicular, incompletely melted, EL chondrite impact melt rock with a mass of ~3 metric tons. The meteorite exhibits numerous shock effects including (1) development of undulose to weak mosaic extinction in low-Ca pyroxene; (2) dispersion of metal-sulfide blebs within silicates causing "darkening"; (3) incomplete impact melting wherein some relict chondrules survived; (4) vaporization of troilite, resulting in S2 bubbles that infused the melt; (5) formation of immiscible silicate and metal-sulfide melts; (6) shock-induced transportation of the metal-sulfide melt to distances >10 cm (7) partial resorption of relict chondrules and coarse silicate grains by the surrounding silicate melt; (8) crystallization of enstatite in the matrix and as overgrowths on relict silicate grains and relict chondrules; (9) crystallization of plagioclase from the melt; and (10) quenching of the vesicular silicate melt. The vesicular samples lost almost all of their metal during the shock event and were less susceptible to terrestrial weathering; in contrast, the samples in which the metal melt accumulated became severely weathered. Literature data indicate the meteorite fell ~23,000 yr ago; numerous secondary phases formed during weathering. Both impact melting and weathering altered the meteorite's bulk chemical composition: e.g., impact melting and loss of a metal-sulfide melt from NWA 2828 is responsible for bulk depletions in common siderophile elements and in Mn (from alabandite); weathering of oldhamite caused depletions in many rare earth elements; the growth of secondary phases caused enrichments in alkalis, Ga, As, Se, and Au.

  20. Diapiric ascent of silicic magma beneath the Bolivian Altiplano

    OpenAIRE

    Del Potro, R.; M. Díez; Blundy, J.; Camacho, Antonio G.; Gottsmann, Joachim

    2013-01-01

    The vertical transport of large volumes of silicic magma, which drives volcanic eruptions and the long-term compositional evolution of the continental crust, is a highly debated problem. In recent years, dyking has been favored as the main ascent mechanism, but the structural connection between a distributed configuration of melt-filled pores in the source region and shallow magma reservoirs remains unsolved. In the Central Andes, inversion of a new high-resolution Bouguer anomaly data over t...

  1. Core Formation on Asteroid 4 Vesta: Iron Rain in a Silicate Magma Ocean

    Science.gov (United States)

    Kiefer, Walter S.; Mittlefehldt, David W.

    2017-01-01

    Geochemical observations of the eucrite and diogenite meteorites, together with observations made by NASA's Dawn spacecraft, suggest that Vesta resembles H chondrites in bulk chemical composition, possibly with about 25% of a CM-chondrite like composition added in. For this model, the core is 15% by mass (or 8 volume %) of the asteroid. The abundances of moderately siderophile elements (Ni, Co, Mo, W, and P) in eucrites require that essentially all of the metallic phase in Vesta segregated to form a core prior to eucrite solidification. Melting in the Fe-Ni-S system begins at a cotectic temperature of 940 deg. C. Only about 40% of the total metal phase, or 3-4 volume % of Vesta, melts prior to the onset of silicate melting. Liquid iron in solid silicate initially forms isolated pockets of melt; connected melt channels, which are necessary if the metal is to segregate from the silicate, are only possible when the metal phase exceeds about 5 volume %. Thus, metal segregation to form a core does not occur prior to the onset of silicate melting.

  2. Investigation of synthesized Be-bearing silicate glass as laboratory reference sample at X-ray electron probe microanalysis of silicates

    Science.gov (United States)

    Belozerova, Olga Yu.; Mikhailov, Mikhail A.; Demina, Tamara V.

    2017-01-01

    The article discusses estimates of the stability and homogeneity in Be-Mg-Al-silicate glass produced by the authors and its applicability as a laboratory reference sample for X-ray electron probe microanalysis (EPMA) of Be-bearing silicate matters: crystals and quenching melt (glasses), silicates and oxides. The results were obtained using Superprobe-733 and Superprobe JXA-8200 (JEOL Ltd, Japan) devices. The sample homogeneity was studied on macro (10-100 μm) and micro (1-10 μm) levels and was evaluated by the scheme of dispersion analysis. The applicability of Be-bearing silicate glass as a reference sample for Mg, Al, Si determinations was tested on the international certified reference glasses and laboratory reference samples of minerals with a known composition. The obtained experimental metrological characteristics correspond to the "applied geochemistry" type of analysis (second category) and suggest that Be-bearing silicate glass is appropriate as a laboratory reference sample for EPMA of Be-bearing silicate matters, silicates and oxides. Using Be-Mg-Al-silicate glass as a reference sample we obtained satisfactory data on the composition of both some minerals including cordierite and beryllium cordierite, beryllium indialite, beryl and metastable phases (chrysoberyl, compounds with structure of β-quartz and petalite).

  3. Relationships between Basic and Silicic Magmatism in Continental Rift Settings: A Petrogeochemical Study of Carboniferous Post-collisional Rift Silicic Volcanics in Tianshan, NW China

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Petrogeochemical data are reported for silicic volcanic rocks from the Tianshan Carboniferous rift, with the aim of discussing the petrogenesis of silicic magmas. Incompatible element vs. incompatible element diagrams display smooth positive trends for the Tianshan Carboniferous rift-related volcanic rocks; the isotope ratios of the silicic lavas [87Sr/86Sr(t)=0.69988-0.70532; εNd(t)=4.76-8.00; 206Pb/204Pb(t)=17.435-18.017; 207Pb/204Pb(t)=15.438-15.509; 208Pb/204Pb(t) = 37.075-37.723] encompass those of the basic lavas. These data suggest a genetic link between rhyolites and basalts, but are not definitive in establishing whether silicic rocks are related to basalts through fractional crystallization or partial melting. Geochemical modeling of incompatible vs. compatible elements excludes the possibility that silicic melts are generated by the melting of basaltic rocks, and indicates a derivation by fractional crystallization plus moderate assimilation of wall rocks (AFC) starting from intermediate rocks to silicic rocks. Continuous AFC from basalt to rhyolite,with small rates of crustal assimilation, best explains the geochemical data. The presence or absence of bimodal volcanism (the "Daly Gap") might be related to cooling rates of magma chambers. In central and eastern Tianshan, the crust was thinner and the cooling rates of the magma chamber within the crust were greater. These conditions resulted in a rapid fall in temperature within the magma reservoir and caused a narrow temperature interval over which intermediate melts formed, effectively reducing the volume of the intermediate melts.

  4. Silicate mineralogy at the surface of Mercury

    Science.gov (United States)

    Namur, Olivier; Charlier, Bernard

    2017-01-01

    NASA's MESSENGER spacecraft has revealed geochemical diversity across Mercury's volcanic crust. Near-infrared to ultraviolet spectra and images have provided evidence for the Fe2+-poor nature of silicate minerals, magnesium sulfide minerals in hollows and a darkening component attributed to graphite, but existing spectral data is insufficient to build a mineralogical map for the planet. Here we investigate the mineralogical variability of silicates in Mercury's crust using crystallization experiments on magmas with compositions and under reducing conditions expected for Mercury. We find a common crystallization sequence consisting of olivine, plagioclase, pyroxenes and tridymite for all magmas tested. Depending on the cooling rate, we suggest that lavas on Mercury are either fully crystallized or made of a glassy matrix with phenocrysts. Combining the experimental results with geochemical mapping, we can identify several mineralogical provinces: the Northern Volcanic Plains and Smooth Plains, dominated by plagioclase, the High-Mg province, strongly dominated by forsterite, and the Intermediate Plains, comprised of forsterite, plagioclase and enstatite. This implies a temporal evolution of the mineralogy from the oldest lavas, dominated by mafic minerals, to the youngest lavas, dominated by plagioclase, consistent with progressive shallowing and decreasing degree of mantle melting over time.

  5. Fluorescent Er2O3 doped lead silicate glass for optical amplifiers

    OpenAIRE

    Mennig, Martin; Niegisch, Nico; Kalleder, Axel; Schmidt, Helmut K.; Graf, Jürgen; Sautter, Helmut

    1999-01-01

    A hot-pressing method is investigated for the fabrication of a planar optical waveguide amplifier. Therefore commercially available LaSFN15 produced by Schott is used as substrate and cladding material in combination with Er2O3 doped lead silicate glass as core material, synthesised by a hybrid sol-gel melting technique. The lead silicate glass is selected for its low melting temperature required for the waveguide processing. The core glass is adapted to the LaSFN15 with respect to the therma...

  6. Mbosi: An anomalous iron with unique silicate inclusions

    Science.gov (United States)

    Olsen, Edward J.; Clayton, Robert N.; Mayeda, Toshiko K.; Davis, Andrew M.; Clarke, Roy S., Jr.; Wasson, John T.

    1996-09-01

    The Mbosi iron meteorite contains millimeter size silicate inclusions. Mbosi is an ungrouped iron meteorite with a Ge/Ga ratio >10, which is an anomalous property shared with the five-member IIF iron group, the Eagle Station pallasites and four other ungrouped irons. Neither the IIF group nor the four other ungrouped irons are known to have silicate inclusions. Chips from three Mbosi inclusions were studied, but most of the work concentrated on a whole 3.1 mm circular inclusion. This inclusion consists of a mantle and a central core of different mineralogies. The mantle is partially devitrified quartz-normative glass, consisting of microscopic crystallites of two pyroxenes and plagioclase, which are crystalline enough to give an x-ray powder diffraction pattern but not coarse enough to permit analyses of individual minerals. The core consists of silica. The bulk composition does not match any known meteorite type, although there is a similarity in mode of occurrence to quartz-normative silicate inclusions in some HE irons. Mbosi silicate appears to be unique. The bulk rare earth element (REE) pattern of the mantle is flat at ≅ 7×C1; the core is depleted in REE but shows a small positive Eu anomaly. The O-isotope composition of bulk silicate lies on a unit slope mixing line (parallel and close to the C3 mixing line) that includes the Eagle Station pallasites and the iron Bocaiuva (related to the IIF irons); all of these share the property of having Ge/Ga ratios >10. It is concluded that Mbosi silicate represents a silica-bearing source rock that was melted and injected into metal. Melting occurred early in the history of the parent body because the metal now shows a normal Widmanstätten structure with only minor distortion that was caused when the parent body broke up and released meteorites into interplanetary space. The cause of Ge/Ga ratios being >10 in these irons is unknown. The fact that silicates in Mbosi, Bocaiuva (related to IIF irons) and the Eagle

  7. Final report on the safety assessment of aluminum silicate, calcium silicate, magnesium aluminum silicate, magnesium silicate, magnesium trisilicate, sodium magnesium silicate, zirconium silicate, attapulgite, bentonite, Fuller's earth, hectorite, kaolin, lithium magnesium silicate, lithium magnesium sodium silicate, montmorillonite, pyrophyllite, and zeolite.

    Science.gov (United States)

    Elmore, Amy R

    2003-01-01

    This report reviews the safety of Aluminum, Calcium, Lithium Magnesium, Lithium Magnesium Sodium, Magnesium Aluminum, Magnesium, Sodium Magnesium, and Zirconium Silicates, Magnesium Trisilicate, Attapulgite, Bentonite, Fuller's Earth, Hectorite, Kaolin, Montmorillonite, Pyrophyllite, and Zeolite as used in cosmetic formulations. The common aspect of all these claylike ingredients is that they contain silicon, oxygen, and one or more metals. Many silicates occur naturally and are mined; yet others are produced synthetically. Typical cosmetic uses of silicates include abrasive, opacifying agent, viscosity-increasing agent, anticaking agent, emulsion stabilizer, binder, and suspending agent. Clay silicates (silicates containing water in their structure) primarily function as adsorbents, opacifiers, and viscosity-increasing agents. Pyrophyllite is also used as a colorant. The International Agency for Research on Cancer has ruled Attapulgite fibers >5 microm as possibly carcinogenic to humans, but fibers mining and processing of Aluminum Silicate, Calcium Silicate, Zirconium Silicate, Fuller's Earth, Kaolin, Montmorillonite, Pyrophyllite, and Zeolite. The Cosmetic Ingredient Review (CIR. The Cosmetic Ingredient Review (CIR) Expert Panel concluded that the extensive pulmonary damage in humans was the result of direct occupational inhalation of the dusts and noted that lesions seen in animals were affected by particle size, fiber length, and concentration. The Panel considers that most of the formulations are not respirable and of the preparations that are respirable, the concentration of the ingredient is very low. Even so, the Panel considered that any spray containing these solids should be formulated to minimize their inhalation. With this admonition to the cosmetics industry, the CIR Expert Panel concluded that these ingredients are safe as currently used in cosmetic formulations. The Panel did note that the cosmetic ingredient, Talc, is a hydrated magnesium silicate

  8. Periodic quantum chemical studies on anhydrous and hydrated acid clinoptilolite.

    Science.gov (United States)

    Valdiviés Cruz, Karell; Lam, Anabel; Zicovich-Wilson, Claudio M

    2014-08-07

    Periodic quantum chemistry methods as implemented in the crystal09 code were considered to study acid clinoptilolite (HEU framework type), both anhydrous and hydrated. The most probable location of acid sites and water molecules together with other structural details has been the object of particular attention. Calculations were performed at hybrid and pristine DFT levels of theory with a VDZP quality basis set in order to compare performances. It arises that PBE0 provides the best agreement with experimental data as concerns structural features and the most stable Al distribution in the framework. The role of the water molecule distribution in the stability of the systems, the most probable structure that they induce in the material, and their eventual influence on further chemical modification processes, such as dealumination, are discussed in detail. Results show that, apart from the usually considered interactions of water molecules with the zeolite framework, that is, a H-bond with Brönsted acid sites and coordination with framework Al as Lewis ones, it is necessary to consider cooperation of other weaker effects so as to fully understand the hydration effect in this kind of materials.

  9. Laryngeal sequelae due to accidental inhalation of anhydrous ammonia

    Directory of Open Access Journals (Sweden)

    Cruz, Walter Paiva

    2009-03-01

    Full Text Available Introduction: Anhydrous Ammonia (AA is a caustic compound commonly used in the industry that can cause burns, even with brief contact. As with other alkali burns, the early washing to remove the AA from burnt areas is crucial to limit tissue damage. The concentration of toxic agent and duration of its contact determine the degree of skin and mucosa destruction. A tanker truck carrying AA (NH3 fell off a highway, and released a dense cloud of AA gas. Fifty-four people inhaled the gas and after ninety days, three people were still experiencing hoarseness and were examined. Case Report: We assessed three patients with laryngeal sequelae due to AA inhalation burn. We found a case of hyperemia and edema, one case of granuloma of the posterior third portion of the left vocal cord, and one case of vocal cord adhesion. Necropsy findings are commented both macroscopically and microscopically. The sequelae and the best treatments for them are discussed herein.

  10. Novel anhydrous emulsions: formulation as controlled release vehicles.

    Science.gov (United States)

    Suitthimeathegorn, Orawan; Jaitely, Vikas; Florence, Alexander T

    2005-07-25

    Novel anhydrous emulsions, which may offer some advantages as depot or reservoir vehicles for lipophilic drugs in controlled delivery systems, were formulated using castor oil as the disperse phase and dimethicone or cyclopentasiloxane as the continuous phase. Among the emulsifiers studied only silicone surfactants (cyclomethicone/dimethicone copolyols) which were miscible in silicone oil stabilized the emulsions. Cyclomethicone/PEG/PPG-18/18 Dimethicone and Cyclopentasiloxane/PEG/PPG-18/18 Dimethicone were more effective in lowering the interfacial tension between castor oil and both dimethicone and cyclopentasiloxane. Emulsions formulated using either of these two surfactants were found to be stable against phase separation and exhibited least globule growth over 168 h. The average particle size was found to be 2-6 microm in these systems formed by probe sonication. Slow release patterns of 3H-dehydroepiandrosterone (DHEA) and 3H-dexamethasone solubilized in the disperse castor oil phase into an aqueous dialyzing medium were observed over 48 h.

  11. Detection of structural heterogeneity of glass melts

    DEFF Research Database (Denmark)

    Yue, Yuanzheng

    2004-01-01

    The structural heterogeneity of both supercooled liquid and molten states of silicate has been studied using calorimetric method. The objects of this study are basaltic glasses and liquids. Two experimental approaches are taken to detect the structural heterogeneity of the liquids. One is the hyp......The structural heterogeneity of both supercooled liquid and molten states of silicate has been studied using calorimetric method. The objects of this study are basaltic glasses and liquids. Two experimental approaches are taken to detect the structural heterogeneity of the liquids. One...... is discussed. The ordered structure of glass melts above the liquidus temperature is indirectly characterized by use of X-ray diffraction method. The new approaches are of importance for monitoring the glass melting and forming process and for improving the physical properties of glasses and glass fibers....

  12. Using microkinetic analysis to search for novel anhydrous formaldehyde production catalysts

    DEFF Research Database (Denmark)

    Li, Han-Jung; Lausche, Adam C.; Peterson, Andrew A.

    2015-01-01

    Abstract Direct dehydrogenation of methanol to produce anhydrous formaldehyde is investigated using periodic density functional theory (DFT) and combining the microkinetic model to estimate rates and selectivities on stepped (211) surfaces under a desired reaction condition. Binding energies...

  13. Activation of Anhydrate Phosphogypsmn by K2SO4 and Hemihydrate Gypsum

    Institute of Scientific and Technical Information of China (English)

    YANG Min; QIAN Jueshi

    2011-01-01

    Lime pretreated phosphogypsum(PG) was calcined at 500 ℃ to produce anhydrate gypsum cement.Due to the slow hydration of anhydrate gypsum,additives,K2SO4 and hemihydrate gypsum were selected to accelerate the hydration of anhydrate.The hydration characteristics,the resistance to hydrodynamic water,and the mineralogical studies were investigated.The experimental results suggest that activated by K2SO4 and hemihydrate,anhydrate PG hydrates much more rapidly than that in the presence of only K2SO4 or in the absence of additives.The binder has proper setting time,good strength development,and relatively better resistance to water.The hardened binder has hydrated products of rod or stick like shaped dihydrate gypsum crystals.

  14. Study on the Stability of DeoxyArbutin in an Anhydrous Emulsion System

    OpenAIRE

    Chiu-Wen Chen; Shu-Mei Lee; Yi-Shyan Chen; Pey-Shiuan Wu; Nai-Fang Chang; Chao-Hsun Yang; Chih-Chien Lin

    2011-01-01

    The skin-whitening agent, deoxyArbutin, is a potent tyrosinase inhibitor that is safer than hydroquinone and arbutin. However, it is thermolabile in aqueous solutions, where it decomposes to hydroquinone. Pharmaceutical and cosmetic emulsions are normally oil-in-water (o/w) or water-in-oil (w/o) systems; however, emulsions can be formulated with no aqueous phase to produce an anhydrous emulsion system. An anhydrous emulsion system could offer a stable vehicle for compounds that are sensitive ...

  15. Material transport in laser-heated diamond anvil cell melting experiments

    Science.gov (United States)

    Campbell, Andrew J.; Heinz, Dion L.; Davis, Andrew M.

    1992-01-01

    A previously undocumented effect in the laser-heated diamond anvil cell, namely, the transport of molten species through the sample chamber, over distances large compared to the laser beam diameter, is presented. This effect is exploited to determine the melting behavior of high-pressure silicate assemblages of olivine composition. At pressures where beta-spinel is the phase melted, relative strengths of partitioning can be estimated for the incompatible elements studied. Iron was found to partition into the melt from beta-spinel less strongly than calcium, and slightly more strongly than manganese. At higher pressures, where a silicate perovskite/magnesiowuestite assemblage is melted, it is determined that silicate perovskite is the liquidus phase, with iron-rich magnesiowuestite accumulating at the end of the laser-melted stripe.

  16. Potassium Silicate Foliar Fertilizer Grade from Geothermal Sludge and Pyrophyllite

    Directory of Open Access Journals (Sweden)

    Muljani Srie

    2016-01-01

    Full Text Available Potassium silicate fertilizer grade were successfully produced by direct fusion of silica (SiO2 and potasium (KOH and K2CO3 in furnaces at temperatures up to melting point of mixture. The geothermal sludge (98% SiO2 and the pyrophyllite (95% SiO2 were used as silica sources. The purposes of the study was to synthesise potassium silicate fertilizer grade having solids concentrations in the range of 31-37% K2O, and silica in the range of 48-54% SiO2. The weight ratio of silicon dioxide/potasium solid being 1:1 to 5:1. Silica from geothermal sludge is amorphous, whereas pyrophylite is crystalline phase. The results showed that the amount of raw materials needed to get the appropriate molar ratio of potassium silicate fertilizer grade are different, as well as the fusion temperature of the furnace. Potassium silicate prepared from potassium hydroxide and geothermal sludge produced a low molar ratio (2.5: 1 to 3: 1. The potassium required quite small (4:1 in weight ratio, and on a fusion temperature of about 900 °C. Meanwhile, the potassium silicate prepared from pyrophyllite produced a high molar ratio (1.4 - 9.4 and on a fusion temperature of about 1350 °C, so that potassium needed large enough to meet the required molar ratio for the fertilizer grade. The product potassium silicate solid is amorphous with a little trace of crystalline.

  17. Relations between aliphatics and silicate components in 12 stratospheric particles deduced from vibrational spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Merouane, S.; Djouadi, Z.; Le Sergeant d' Hendecourt, L., E-mail: sihane.merouane@ias.u-psud.fr [Institut d' Astrophysique Spatiale, CNRS, UMR-8617, Université Paris Sud, Bâtiment 121, F-91405 Orsay Cedex (France)

    2014-01-10

    Interplanetary dust particles (IDPs) are among the most pristine extraterrestrial samples available in the laboratory for analyses with moderate to high spatial- and spectral-resolution spectroscopic techniques. Their composition can provide precious information on the early stages of the solar nebula as well as on the processes on the surfaces of different small bodies in the solar system from which IDPs originate. In this work, we have analyzed six anhydrous IDPs and six stratospheric particles possibly of cosmic origin through infrared (IR) and Raman micro-spectroscopy to study and investigate their silicate and organic components. We find that the length/ramification of the aliphatic organics given by the CH{sub 2}/CH{sub 3} ratios in the IDPs is closely linked to the silicate family (pyroxene or olivine) present in the samples. Both IR and Raman data suggest that this relation is not correlated with either aqueous (as evidenced by the absence of aqueous related minerals) or thermal processes (as deduced from Raman measurements). Therefore, this observation might be related to the initial path of formation of the organics on the silicate surfaces, thus tracing a possible catalytic role that silicates would play in the formation and/or ramification of organic matter in the primitive nebula.

  18. Core formation in silicate bodies

    Science.gov (United States)

    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

  19. Environmental silicate nano-biocomposites

    CERN Document Server

    Pollet, Eric

    2012-01-01

    Environmental Silicate Nano-Biocomposites focuses on nano-biocomposites, which are obtained by the association of silicates such as bioclays with biopolymers. By highlighting recent developments and findings, green and biodegradable nano-composites from both renewable and biodegradable polymers are explored. This includes coverage of potential markets such as packaging, agricultures, leisure and the fast food industry. The knowledge and experience of more than twenty international experts in diverse fields, from chemical and biochemical engineering to applications, is brought together in four different sections covering: Biodegradable polymers and Silicates, Clay/Polyesters Nano-biocomposites, Clay/Agropolymers Nano-biocomposites, and Applications and biodegradation of Nano-biocomposites. By exploring the relationships between the biopolymer structures, the processes, and the final properties Environmental Silicate Nano-Biocomposites explains how to design nano-materials to develop new, valuable, environmenta...

  20. The maximum water storage capacities in nominally anhydrous minerals in the mantle transition zone and lower mantle

    Science.gov (United States)

    Inoue, T.; Yurimoto, H.

    2012-12-01

    Water is the most important volatile component in the Earth, and affects the physicochemical properties of mantle minerals, e.g. density, elastic property, electrical conductivity, thermal conductivity, rheological property, melting temperature, melt composition, element partitioning, etc. So many high pressure experiments have been conducted so far to determine the effect of water on mantle minerals. To clarify the maximum water storage capacity in nominally anhydrous mantle minerals in the mantle transition zone and lower mantle is an important issue to discuss the possibility of the existence of water reservoir in the Earth mantle. So we have been clarifying the maximum water storage capacity in mantle minerals using MA-8 type (KAWAI-type) high pressure apparatus and SIMS (secondary ion mass spectroscopy). Upper mantle mineral, olivine can contain ~0.9 wt% H2O in the condition just above 410 km discontinuity in maximum (e.g. Chen et al., 2002; Smyth et al., 2006). On the other hand, mantle transition zone mineral, wadsleyite and ringwoodite can contain significant amount (about 2-3 wt.%) of H2O (e.g. Inoue et al., 1995, 1998, 2010; Kawamoto et al., 1996; Ohtani et al., 2000). But the lower mantle mineral, perovskite can not contain significant amount of H2O, less than ~0.1 wt% (e.g. Murakami et al., 2002; Inoue et al., 2010). In addition, garnet and stishovite also can not contain significant amount of H2O (e.g. Katayama et al., 2003; Mookherjee and Karato, 2010; Litasov et al., 2007). On the other hand, the water storage capacities of mantle minerals are supposed to be significantly coupled with Al by a substitution with Mg2+, Si4+ or Mg2+ + Si4+, because Al3+ is the trivalent cation, and H+ is the monovalent cation. To clarify the degree of the substitution, the water contents and the chemical compositions of Al-bearing minerals in the mantle transition zone and the lower mantle were also determined in the Al-bearing systems with H2O. We will introduce the

  1. Determining the Metal/Silicate Partition Coefficient of Germanium: Implications for Core and Mantle Differentiation.

    Science.gov (United States)

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

    2010-01-01

    Currently there are several hypotheses for the thermal state of the early Earth. Some hypothesize a shallow magma ocean, or deep magma ocean, or heterogeneous accretion which requires no magma ocean at all. Previous models are unable to account for Ge depletion in Earth's mantle relative to CI chondrites. In this study, the element Ge is used to observe the way siderophile elements partition into the metallic core. The purpose of this research is to provide new data for Ge and to further test these models for Earth's early stages. The partition coefficients (D(sub Ge) = c(sub metal)/c(sub silicate), where D = partition coefficient of Ge and c = concentration of Ge in the metal and silicate, respectively) of siderophile elements were studied by performing series of high pressure, high temperature experiments. They are also dependent on oxygen fugacity, and metal and silicate composition. Ge is a moderately siderophile element found in both the mantle and core, and has yet to be studied systematically at high temperatures. Moreover, previous work has been limited by the low solubility of Ge in silicate melts (less than 100 ppm and close to detection limits for electron microprobe analysis). Reported here are results from 14 experiments studying the partitioning of Ge between silicate and metallic liquids. The Ge concentrations were then analyzed using Laser Ablation Inductively Coupled Mass Spectrometry (LA-ICP-MS) which is sensitive enough to detect ppm levels of Ge in the silicate melt.

  2. Immiscible silicate liquids and phosphoran olivine in Netschaëvo IIE silicate: Analogue for planetesimal core-mantle boundaries

    Science.gov (United States)

    Van Roosbroek, Nadia; Hamann, Christopher; McKibbin, Seann; Greshake, Ansgar; Wirth, Richard; Pittarello, Lidia; Hecht, Lutz; Claeys, Philippe; Debaille, Vinciane

    2017-01-01

    We have investigated a piece of the Netschaëvo IIE iron meteorite containing a silicate inclusion by means of electron microprobe analysis (EMPA) and transmission electron microscopy (TEM). Netschaëvo contains chondrule-bearing clasts and impact melt rock clasts were also recently found. The examined inclusion belongs to the latter and is characterized by a porphyritic texture dominated by clusters of coarse-grained olivine and pyroxene, set in a fine-grained groundmass that consists of new crystals of olivine and a hyaline matrix. This matrix material has a quasi-basaltic composition in the inner part of the inclusion, whereas the edge of the inclusion has a lower SiO2 concentration and is enriched in MgO, P2O5, CaO, and FeO. Close to the metal host, the inclusion also contains euhedral Mg-chromite crystals and small (olivine crystallites containing up to 14 wt% P2O5, amorphous material, and interstitial Cl-apatite crystals. The Si-rich silicate glass globules show a second population of Fe-rich silicate glass droplets, indicating they formed by silicate liquid immiscibility. Together with the presence of phosphoran olivine and quenched Cl-apatite, these textures suggest rapid cooling and quenching as a consequence of an impact event. Moreover, the enrichment of phosphorus in the silicate inclusion close to the metal host (phosphoran olivine and Cl-apatite) indicates that phosphorus re-partitioned from the metal into the silicate phase upon cooling. This probably also took place in pallasite meteorites that contain late-crystallizing phases rich in phosphorus. Accordingly, our findings suggest that oxidation of phosphorus might be a general process in core-mantle environments, bearing on our understanding of planetesimal evolution. Thus, the Netschaëvo sample serves as a natural planetesimal core-mantle boundary experiment and based on our temperature estimates, the following sequence of events takes place: (i) precipitation of olivine (1400-1360 °C), (ii) re

  3. How to identify garnet lherzolite melts and distinguish them from pyroxenite melts

    Science.gov (United States)

    Grove, T. L.; Holbig, E.; Barr, J. A.; Till, C.; Krawczynski, M. J.

    2013-12-01

    Liquids form in equilibrium with garnet lherzolite sources when the Earth's mantle melts at depths of greater than ~ 60 km. We present a phase equilibrium investigation of Tibetan plateau olivine leucitites from 2.2 to 2.8 GPa and 1380 to 1480 °C. The resulting liquids were multiply saturated with spinel and garnet lherzolite assemblages (olivine, orthopyroxene, clinopyroxene and spinel +/-garnet) under nominally anhydrous conditions. These SiO2-undersaturated liquids and published experimental data have been used to develop a new model that parameterizes the major element compositions of garnet lherzolite partial melts, allowing the prediction of melt compositions from depleted to metasomatically enriched peridotite. The model is calibrated over the pressure range of 1.9 to 6 GPa. The model also predicts the suprasolidus pressure and temperature of the spinel to garnet lherzolite phase transition for natural peridotite compositions. Combined with the recent parameterization of melting in the plagioclase- and spinel- lherzolite facies (Till et al., 2012, JGR, 117, B06206), the new model distinguishes between melts of garnet vs. spinel vs. plagioclase lherzolites, but can also be used to distinguish between melts of lherzolitic vs. pyroxenitic source regions, allowing source lithology to be uniquely identified. Pyroxenite melts fall into two compositionally distinct groups; an olivine-normative, SiO2-undersaturated group and quartz-normative, SiO2-oversaturated group. Melts of plagioclase, spinel, and garnet lherzolite plot between these two types of pyroxenitic melts in mineral normative composition space. When our model is applied to high-K lavas erupted in the Tibetan plateau, we find that these magmas are derived from both pyroxenite and lherzolite source regions. Distinctive enrichments in compatible trace elements (Ni, Cr) are observed in the lherzolite-derived magmas. Applied to Hawaiian basalts, our model suggests the transitional and weakly alkaline pre

  4. Effect of cooling rate on crystallization in an aluminophosphosilicate melt

    DEFF Research Database (Denmark)

    Liu, S. J.; Zhang, Yanfei; Yue, Yuanzheng

    2011-01-01

    The effect of cooling rate on spontaneous crystallization behavior of an alumino-phospho-silicate melt is studied by means of differential scanning calorimetry, X-ray diffraction, scanning electron microscopy and viscometry. The cooling rates of 160, 2100 and 12000 K/s are attained by subjecting...

  5. Effect of cooling rate on crystallization in an aluminophosphosilicate melt

    DEFF Research Database (Denmark)

    Liu, S. J.; Zhang, Yanfei; Yue, Yuanzheng

    2011-01-01

    The effect of cooling rate on spontaneous crystallization behavior of an alumino-phospho-silicate melt is studied by means of differential scanning calorimetry, X-ray diffraction, scanning electron microscopy and viscometry. The cooling rates of 160, 2100 and 12000 K/s are attained by subjecting...

  6. Study on the Stability of DeoxyArbutin in an Anhydrous Emulsion Systemy

    Directory of Open Access Journals (Sweden)

    Chiu-Wen Chen

    2011-09-01

    Full Text Available The skin-whitening agent, deoxyArbutin, is a potent tyrosinase inhibitor that is safer than hydroquinone and arbutin. However, it is thermolabile in aqueous solutions, where it decomposes to hydroquinone. Pharmaceutical and cosmetic emulsions are normally oil-in-water (o/w or water-in-oil (w/o systems; however, emulsions can be formulated with no aqueous phase to produce an anhydrous emulsion system. An anhydrous emulsion system could offer a stable vehicle for compounds that are sensitive to hydrolysis or oxidation. Therefore, to enhance the stability of deoxyArbutin in formulations, we chose the polyol-in-silicone, anhydrous emulsion system as the basic formulation for investigation. The quantity of deoxyArbutin and the accumulation of hydroquinone in both hydrous and anhydrous emulsions at various temperatures were analyzed through an established high performance liquid chromatographic (HPLC method. The results indicated that water increased the decomposition of deoxyArbutin in the formulations and that the polyol-in-silicone, oil-based, anhydrous emulsion system provided a relatively stable surrounding for the deoxyArbutin that delayed its degradation at 25 °C and 45 °C. Moreover, the composition of the inner hydrophilic phase, containing different amounts of glycerin and propylene glycol, affected the stability of deoxyArbutin. Thus, these results will be beneficial when using deoxyArbutin in cosmetics and medicines in the future.

  7. NON-AUTOCLAVE SILICATE BRICK

    Directory of Open Access Journals (Sweden)

    V. N. Yaglov

    2015-01-01

    Full Text Available The paper proposes a technology for obtaining bricks on the basis of lime-silica mixtures where chemical interactions are practically completely realized in dispersive state at the stage of preparation of binding contact maturing and raw mixture as a whole. The role of forming operation (moulding is changed in principle because in this case conversion of dispersive system into a rock-like solid occurs and due to this the solid obtains complete water-resistance in contact with water immediately after forming operation. Theoretical basis for the developed technology is capability of silicate dispersive substances (hydrated calcium silicate to transit in non-stable state, to form a rock-like water-resistant solid in the moment of mechanical load application during forming process. Specific feature of the proposed method is an exclusion of additional operations for autoclaving of products from the process of obtaining a silicate brick.Synthetic hydrated calcium silicate in contrast to natural ones are more uniform in composition and structure, they contain less impurities and they are characterized by dispersive composition and due to the mentioned advantages they find wider practical application. Contact-condensation binders permit to manipulate product properties on their basis and ensure maximum correspondence to the requirements of the concrete application. Raw material sources for obtaining synthetic hydrated calcium silicates are practically un-limited because calcium-silicon containing substances are found as in various technogenic wastes so in natural compounds as well. So the problem for obtaining hydrated calcium silicates having contact-condensation ability for structure formation becomes more and more actual one. This transition is considered as dependent principally on arrangement rate of substance particles which determined the level of its instability.

  8. Interaction between SiO2 and a KF-KCl-K2SiF6 Melt.

    Science.gov (United States)

    Zaykov, Yurii P; Isakov, Andrey V; Zakiryanova, Irina D; Reznitskikh, Olga G; Chemezov, Oleg V; Redkin, Alexander A

    2014-02-13

    The solubility mechanism of silica in a fluoride-chloride melt has been determined in situ using Raman spectroscopy. The spectroscopy data revealed that the silica solubility process involved Si-O bond breakage and Si-F bond formation. The process results in the formation of silicate complexes, fluorine-bearing silicate complexes, and silicon tetrafluoride in the melt. Mass spectrometry of the vapor phase over the KF-KCl-K2SiF6 and KF-KCl-K2SiF6-SiO2 melts and differential scanning calorimetry coupled with thermal gravimetric analysis of these melts were performed to verify the silica solubility mechanism.

  9. Effect of nitrapyrin on emission of nitrous oxide from soil fertilized with anhydrous ammonia

    Science.gov (United States)

    Bremner, J. M.; Breitenbeck, G. A.; Blackmer, A. M.

    1981-04-01

    Field studies using a chamber technique to measure emissions of nitrous oxide (N2O) showed that the N2O emissions induced by fertilization of soil with anhydrous ammonia (180 kg N ha-1) were markedly reduced by addition of nitrapyrin [2-chloro-6-(trichloromethyl)-pyridine] to this fertilizer. The emission of N2O induced by application of anhydrous ammonia in the fall was reduced 63% by addition of nitrapyrin at the rate of 0.56 kg ha-1. The corresponding reduction when nitrapyrin was added to anhydrous ammonia applied in the spring was 87%. These observations indicate that nitrapyrin has potential value for reduction of the N2O emissions induced by nitrogen fertilization of soils and the possible adverse effects of these emissions on our climate.

  10. Pretreatment of corn stover using low-moisture anhydrous ammonia (LMAA) process.

    Science.gov (United States)

    Yoo, Chang Geun; Nghiem, Nhuan P; Hicks, Kevin B; Kim, Tae Hyun

    2011-11-01

    A simple pretreatment method using anhydrous ammonia was developed to minimize water and ammonia inputs for cellulosic ethanol production, termed the low moisture anhydrous ammonia (LMAA) pretreatment. In this method, corn stover with 30-70% moisture was contacted with anhydrous ammonia in a reactor under nearly ambient conditions. After the ammoniation step, biomass was subjected to a simple pretreatment step at moderate temperatures (40-120°C) for 48-144 h. Pretreated biomass was saccharified and fermented without an additional washing step. With 3% glucan loading of LMAA-treated corn stover under best treatment conditions (0.1g-ammonia+1.0 g-water per g biomass, 80°C, and 84 h), simultaneous saccharification and cofermentation test resulted in 24.9 g/l (89% of theoretical ethanol yield based on glucan+xylan in corn stover). Copyright © 2011 Elsevier Ltd. All rights reserved.

  11. Infrared Spectroscopy and Stable Isotope Geochemistry of Hydrous Silicate Glasses

    Energy Technology Data Exchange (ETDEWEB)

    Stolper, Edward

    2007-03-05

    The focus of this DOE-funded project has been the study of volatile components in magmas and the atmosphere. Over the twenty-one year period of this project, we have used experimental petrology and stable isotope geochemistry to study the behavior and properties of volatile components dissolved in silicate minerals and melts and glasses. More recently, we have also studied the concentration and isotopic composition of CO2 in the atmosphere, especially in relation to air quality issues in the Los Angeles basin.

  12. Concentration Quenching in Erbium Doped Bismuth Silicate Glasses

    Institute of Scientific and Technical Information of China (English)

    DAI Shi-Xun; XU Tie-Feng; NIE Qiu-Hua; SHEN Xiang; WANG Xun-Si

    2006-01-01

    @@ Er2 O3-doped bismuth silicate glasses are prepared by the conventional melt-quenching method, and the Er3+ : 4 I13/2 → 4I15/2 fluorescence properties are studied for different Er3+ concentrations. Infrared spectra are measured to estimate the exact content of OH- groups in the samples. Based on the electric dipole-dipole interaction theory,the interaction parameter CEr,Er for the migration rate of Er3+ :4 I13/2 → 4 I13/2 in proposed glasses is calculated.

  13. Impact-melt origin for the Simondium, Pinnaroo, and Hainholz mesosiderites: implicatiions for impact processes beyond the Earth--Moon system

    Energy Technology Data Exchange (ETDEWEB)

    Floran, R J; Caulfield, J B.D.; Harlow, G E; Prinz, M

    1978-05-01

    The Simondium, Pinnaroo, and Hainholz mesosiderites are interpreted to be clast-laden impact melts that crystallized from immiscible silicate, metallic (Fe-FeS) liquids. The existence of silicate melts is shown by intergranular basaltic textures. Metallic melts are inferred on the basis of smooth boundaries between metal and troilite and the occurrence of troilite as anastomosing areas that radiate outward into the silicate fractions. These relations suggest that troilite crystallized after silicates, concentrating as a late-stage residuum. Evidence for impact melting includes: diversity and abundance of clast types (mineral, metal, lithic) in various stages of recrystallization and assimilation; differences in mineral chemistries between clasts and igneous-textured matrix silicates; unusual metal plus silicate bulk composition. Silicate clasts consist primarily of orthopyroxene and minor olivine with a range of Fe/Fe + Mg ratios, anorthitic plagioclase, and rare orthopyroxenite (diogenite) fragments. Substantial amounts of Fe-Ni metal were melted during the impact events and minor amounts were incorporated into the melts as clasts. The clast populations suggest that at least four rock types were melted and mixed: (a) diogenite, (b) a plagioclase-rich source, possibly cumulate eucrite, (c) dunite, and (d) metal. Most orthopyroxene appears to have been derived from fragmentation of diogenites. Orthopyroxene (En/sub 82-61/) and olivine (Fo/sub 86-67/) clasts include much material unsampled as individual meteorites and probably represent a variety of source rocks.

  14. An unrealistic drift in assay on anhydrous basis towards content limit

    Directory of Open Access Journals (Sweden)

    Shivram K

    2009-01-01

    Full Text Available The assay on anhydrous basis is a mathematically derived value from an experimental results of assay and water content tests. The results of assay and water content tests are determined, separately, on as-is basis. The industry-accepted formula for assay on anhydrous basis = (assay on as-is basis×100/(100-%water. Statistically, the two variables involved in accepted formula are assay on as-is basis and water to obtain assay on anhydrous basis. The experimental errors associated with these two variables propagate in assay on anhydrous basis. The error propagates either in constructive or destructive mode. The constructive mode of error propagation is combination of positive error of assay on as-is basis and positive error of water or negative error of assay on as-is basis and negative error of water. The constructive mode of error propagation has more impact on assay on anhydrous basis values and its confidence interval. The destructive mode of error propagation is combination of a positive error of assay on as-is basis and a negative error of water or vice versa. The destructive mode of error propagation has lesser impact on assay on anhydrous basis values and its confidence interval in comparison to the constructive mode of error propagation. In accepted formula said above, the constructive or destructive error propagation causes unrealistic drift of assay on anhydrous basis towards either lower or higher side of content limit of substance. The risk of rejection of pharmaceutical use substance is higher based on assay test results that results are calculated from industry-accepted formula. The purpose of the study is to propose an alternative formula to overcome limitations of accepted formula and justify the propagation of errors in realistic way. We have given three examples of pharmaceutical use substances to emphasise the above proposition. The proposed formula for assay on anhydrous basis= (assay on as-is basis×F/(F-%water in which F is

  15. 21 CFR 872.6670 - Silicate protector.

    Science.gov (United States)

    2010-04-01

    ... DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6670 Silicate protector. (a) Identification. A silicate protector is a device made of silicone intended to be applied with an absorbent tipped applicator to...

  16. Primary carbonatite melt from deeply subducted oceanic crust

    Energy Technology Data Exchange (ETDEWEB)

    Walter, M.J.; Bulanova, G.P.; Armstrong, L.S.; Keshav, S.; Blundy, J.D.; Gudfinnesson, G.; Lord, O.T.; Lennie, A.R.; Clark, S.M.; Smith, C.B.; Gobbo, L.

    2008-07-01

    Partial melting in the Earth's mantle plays an important part in generating the geochemical and isotopic diversity observed in volcanic rocks at the surface. Identifying the composition of these primary melts in the mantle is crucial for establishing links between mantle geochemical 'reservoirs' and fundamental geodynamic processes. Mineral inclusions in natural diamonds have provided a unique window into such deep mantle processes. Here they provide exper8imental and geochemical evidence that silicate mineral inclusions in diamonds from Juina, Brazil, crystallized from primary and evolved carbonatite melts in the mantle transition zone and deep upper mantle. The incompatible trace element abundances calculated for a melt coexisting with a calcium-titanium-silicate perovskite inclusion indicate deep melting of carbonated oceanic crust, probably at transition-zone depths. Further to perovskite, calcic-majorite garnet inclusions record crystallization in the deep upper mantle from an evolved melt that closely resembles estimates of primitive carbonatite on the basis of volcanic rocks. Small-degree melts of subducted crust can be viewed as agents of chemical mass-transfer in the upper mantle and transition zone, leaving a chemical imprint of ocean crust that can possibly endure for billions of years.

  17. Antibacterial Activity of Silicate Bioceramics

    Institute of Scientific and Technical Information of China (English)

    HU Sheng; NING Congqin; ZHOU Yue; CHEN Lei; LIN Kaili; CHANG Jiang

    2011-01-01

    Four kinds of pure silicate ceramic particles, CaSiO3, Ca3SiO5, bredigite and akermanite were prepared and their bactericidal effects were systematically investigated. The phase compositions of these silicate ceramics were characterized by XRD. The ionic concentration meas urement revealed that the Calcium (Ca) ion concentration were relatively higher in Ca3SiO5 and bredigite, and much lower in CaSiO3 and akermanite. Accordingly, the pH values of the four silicate ceramics extracts showed a positive correlation with the particle concentrations. Meanwhile, by decreasing the particle size, higher Ca ion concentrations can be achieved, leading to the increase of aqueous pH value as well. In summary, all of the four silicate ceramics tested in our study showed antibacterial effect in a dose-dependent manner. Generally, the order of their antibacterial activity against E.coli from strong to weak is Ca3SiO5, bredigite, CaSiO3 and akermanite.

  18. Amended Silicated for Mercury Control

    Energy Technology Data Exchange (ETDEWEB)

    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

  19. Influence of amorphous content on compaction behaviour of anhydrous alpha-lactose.

    Science.gov (United States)

    Ziffels, S; Steckel, H

    2010-03-15

    Modified lactoses are widely used as filler-binders in direct compression of tablets. Until today, little about the compaction behaviour of anhydrous alpha-lactose is known. In this study, a new method to prepare anhydrous alpha-lactose from alpha-lactose monohydrate by desiccation with heated ethanol was evaluated and the influence of amorphous content in the lactose powder prior to modification on powder properties, compaction behaviour and storage stability was determined. The modification process led to anhydrous alpha-lactose with decreased bulk and tapped density, increased flow rate and significantly higher specific surface area. Due to the higher specific surface area, the compaction behaviour of the anhydrous alpha-lactose was found to be significantly better than the compaction behaviour of powder blends consisting of alpha-lactose monohydrate and amorphous lactose. An influence of the amorphous content prior to modification could be observed only at higher compaction forces. In general, tablets of modified powders needed longer time to disintegrate directly after compression. However, the storage stability of modified tablets was found to be better compared to the amorphous-crystalline tablets which were influenced by storage conditions, initial crushing strength as well as amorphous content due to the re-crystallization of amorphous lactose during storage. 2009 Elsevier B.V. All rights reserved.

  20. Effects of ionization on silicate glasses. [Silicate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Primak, W.

    1982-02-01

    This evaluation of radiation effects in silicate glasses caused by ionization is based on our own investigations, on material collected in our files (reports, articles, and notes), and on a computer literature search through recent issues of Physics Abstracts and Chemical Abstracts (and the apparently pertinent references which appeared). Some of our recent results, available heretofore only in internal correspondence, are presented in some detail. It is concluded that research into the behavior of silicate glasses generally will be required before the specific effects in the radioactive waste storage glasses can be properly understood and evaluated. Two particular neglected areas of investigation are targeted for immediate concern: a kinetic analysis of annealing data and the acquisition of data on effects of irradiation at controlled elevated temperatures.

  1. Corn yield and nitrate loss in subsurface drainage affected by timing of anhydrous ammonia application

    Science.gov (United States)

    Surprisingly little research has examined the corn yield, N use efficiency, and water quality implications of N fertilizer timing. We applied anhydrous ammonia either in the fall after harvest (F) at 196 kg ha-1, or in the spring before planting (PP) or as an early sidedress (SD) at rates of 168 kg ...

  2. Removal of lead from cathode ray tube funnel glass by generating the sodium silicate.

    Science.gov (United States)

    Hu, Biao; Zhao, Shuangshuang; Zhang, Shuhao

    2015-01-01

    In the disposal of electronic waste, cathode ray tube (CRT) funnel glass is an environmental problem of old television sets. Removal of the lead from CRT funnel glass can prevent its release into the environment and allow its reuse. In this research, we reference the dry progress productive technology of sodium silicate, the waste CRT glass was dealt with sodium silicate frit melted and sodium silicate frit dissolved. Adding a certain amount of Na ₂CO₃to the waste CRT glass bases on the material composition and content of it, then the specific modulus of sodium silicate frit is obtained by melting progress. The silicon, potassium and sodium compounds of the sodium silicate frit are dissolved under the conditions of high temperature and pressure by using water as solvent, which shows the tendency that different temperature, pressure, liquid-solid ratio and dissolving time have effect on the result of dissolving. At 175°C(0.75MPa), liquid-solid ratio is 1.5:1, the dissolving time is 1h, the dissolution rate of sodium silicate frit is 44.725%. By using sodium sulfide to separate hydrolysis solution and to collect lead compounds in the solution, the recovery rate of lead in dissolving reached 100% and we can get clean sodium silicate and high purity of lead compounds. The method presented in this research can recycle not only the lead but also the sodium, potassium and other inorganic minerals in CRT glass and can obtain the comprehensive utilization of leaded glass.

  3. First finding of burkeite in melt inclusions in olivine from sheared lherzolite xenoliths.

    Science.gov (United States)

    Korsakov, Andrey V; Golovin, Alexander V; De Gussem, Kris; Sharygin, Igor S; Vandenabeele, Peter

    2009-08-01

    For the first time burkeite was observed as a daughter phase in the melt inclusions in olivine by Raman spectroscopy. The olivine comes from sheared lherzolite xenoliths from the Udachnaya-East kimberlite pipe (Yakutia, Russia). This anhydrous sulfate-carbonate mineral (Na(6)(CO(3))(SO(4))(2)) is generally considered to be a characteristic mineral in saline soils or in continental lacustrine evaporite deposits. Recently, however, this mineral was identified in hydrothermal fluids. Our observations indicate that burkeite can also be formed from a mantle-derived melt.

  4. Silicate Composition of the Interstellar Medium

    CERN Document Server

    Fogerty, Shane; Watson, Dan M; Sargent, Benjamin A; Koch, Ingrid

    2016-01-01

    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. Analysis of the well-known 9.7{\\mu}m 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 modelled 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. Modelling the optical depth along lines of sight toward the extinguished objects Cyg OB2 No. 12 and {\\zeta} 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 Trapez...

  5. Surface characterization of silicate bioceramics.

    Science.gov (United States)

    Cerruti, Marta

    2012-03-28

    The success of an implanted prosthetic material is determined by the early events occurring at the interface between the material and the body. These events depend on many surface properties, with the main ones including the surface's composition, porosity, roughness, topography, charge, functional groups and exposed area. This review will portray how our understanding of the surface reactivity of silicate bioceramics has emerged and evolved in the past four decades, owing to the adoption of many complementary surface characterization tools. The review is organized in sections dedicated to a specific surface property, each describing how the property influences the body's response to the material, and the tools that have been adopted to analyse it. The final section introduces the techniques that have yet to be applied extensively to silicate bioceramics, and the information that they could provide.

  6. Hydrothermal Synthesis of Metal Silicates

    Institute of Scientific and Technical Information of China (English)

    Lii Kwang-Hwa

    2004-01-01

    Organically templated metal phosphates have been extensively studied because of interesting structural chemistry and potential applications in catalysis. However, in most cases the organic templates cannot be removed without collapse of the frameworks. This is in contrast to the high thermal stability and extensive applications of zeolites in refinery and petrochemical processes.Therefore, studies have been directed to the synthesis of transition metal silicates to produce more stable frameworks. Our synthetic methods are twofold, namely mild hydrothermal reactions in Teflon-lined autoclaves at 100-200 ℃ using organic amines as templates and high-temperature,high-pressure hydrothermal reactions in gold ampoules contained in a high-pressure reaction vessel at ca. 550 ℃ and 150 Mpa using alkali metal cations as templates. In this presentation I will report the high-temperature, high-pressure hydrothermal synthesis, crystal structures, and solid-state NMR spectroscopy of a number of new silicates of indium, uranium, and transition metals.

  7. Biogenic silicate accumulation in sediments, Jiaozhou Bay

    Institute of Scientific and Technical Information of China (English)

    LI Xuegang; SONG Jinming; DAI Jicui; YUAN Huamao; LI Ning; LI Fengye; SUN Song

    2006-01-01

    It has been widely recognized that low silicate content in seawater is a major limiting factor to phytoplankton primary production in Jiaozhou Bay. However the reason of Si-limitation remains poorly understood. In the present study we measured the biogenic silicate content and discussed the accumulation of silicate in Jiaozhou Bay sediment. The results show that the biogenic silica content in the sediment of the Jiaozhou Bay is obviously much higher than those in the Yellow Sea and the Bohai Sea. The BSi:TN ratios and BSi:16P ratios in the sediment are > 1 and the OC:BSi ratio in sediment is lower than these of Redfield ratio (106:16), indicating that the decomposition rate of OC is much higher than that for BSi in similar conditions. Therefore, the majority of the biogenic silicate was buried and thus did not participate in silicate recycling. Silicate accumulation in sediment may explain why Si limits the phytoplankton growth in the Jiaozhou Bay. Comparing the flux of biogenic silicate from sediments with primary production rate, it can be concluded that only 15.5% of biogenic silicate is hydrolyzed during the journey from surface to bottom in seawater, thus approximate 84.5% of biogenic silicate could reach the bottom. The silicate releasing rate from the sediment to seawater is considerably lower than that of sedimentation of biogenic silicate, indicating silicate accumulation in sediment too. In a word, the silicate accumulation in sediment is the key reason of silicate limiting to phytoplankton growth in Jiaozhou Bay.

  8. Longevity of silicate ceramic restorations.

    Science.gov (United States)

    Beier, Ulrike Stephanie; Dumfahrt, Herbert

    2014-09-01

    The demand for esthetic restorations has resulted in an increased use of dental ceramics as a biocompatible and functionally sufficient alternative to conventional restorative materials. Silicate ceramic restorations are widely used for veneers, inlays, onlays, and crowns in dentistry. Long-term data are of crucial importance to optimize clinical practice. The purpose of the present article is to summarize data of the Innsbruck ceramic evaluation up to 261 months with the focus on longevity and failure characteristics.

  9. Energetics of melts from thermal diffusion studies. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Lesher, C.E.

    1998-12-01

    Most processes in geology are a consequence at some level of the flow of energy or mass. Heat conduction and chemical diffusion are examples of two of these sorts of flows which are driven by temperature and chemical potential imbalances, respectively. In the general case these flows may be coupled so that, for instance, a temperature gradient may result in a flow of mass as well as heat. This effect in liquids was demonstrated by Soret (1879) and bears his name. In gases or solids the phenomenon is given the general name thermal diffusion. It was the purpose of this research program to examine the Soret effect in molten silicates under laboratory conditions. Results of these experiments are used to evaluate the form and quantitative values of many thermodynamic and kinetic properties of silicate melts over a range of temperature, pressure, and bulk composition. The author published a comprehensive review and synthesis with a microscopic theoretical explanation for the effect at low pressure in silicate liquids of geological interest. He conducted experimental investigations of molecular diffusion in the absence of a thermal gradient through experiments involving dissolution of solid silicates in molten silicate and interdiffusion of species between miscible silicate liquids. Collectively these results enable the author to construct a more comprehensive model of molecular diffusion in magmatic liquids. He has applied this model to problems of magma mixing and crustal assimilation.

  10. Impact-induced melting during accretion of the Earth

    Science.gov (United States)

    de Vries, Jellie; Nimmo, Francis; Melosh, H. Jay; Jacobson, Seth A.; Morbidelli, Alessandro; Rubie, David C.

    2016-12-01

    Because of the high energies involved, giant impacts that occur during planetary accretion cause large degrees of melting. The depth of melting in the target body after each collision determines the pressure and temperature conditions of metal-silicate equilibration and thus geochemical fractionation that results from core-mantle differentiation. The accretional collisions involved in forming the terrestrial planets of the inner Solar System have been calculated by previous studies using N-body accretion simulations. Here we use the output from such simulations to determine the volumes of melt produced and thus the pressure and temperature conditions of metal-silicate equilibration, after each impact, as Earth-like planets accrete. For these calculations a parameterised melting model is used that takes impact velocity, impact angle and the respective masses of the impacting bodies into account. The evolution of metal-silicate equilibration pressures (as defined by evolving magma ocean depths) during Earth's accretion depends strongly on the lifetime of impact-generated magma oceans compared to the time interval between large impacts. In addition, such results depend on starting parameters in the N-body simulations, such as the number and initial mass of embryos. Thus, there is the potential for combining the results, such as those presented here, with multistage core formation models to better constrain the accretional history of the Earth.

  11. Concentrations and behavior of oxygen and oxide ion in melts of composition CaO.MgO.xSiO2

    Science.gov (United States)

    Semkow, K. W.; Haskin, L. A.

    1985-01-01

    The behavior of oxygen and oxide ion in silicate melts was investigated through their electrochemical reactions at a platinum electrode. Values are given for the diffusion coefficient for molecular oxygen in diopside melt and the activation energy of diffusion. It is shown that molecular oxygen dissociates prior to undergoing reduction and that oxide ion reacts quickly with silicate polymers when it is produced. The concentration of oxide ion is kept low by a buffering effect of the silicate, the exact level being dependent on the silicate composition. Data on the kinetics of reaction of the dissociation of molecular oxygen and on the buffering reactions are provided. It is demonstrated that the data on oxygen in these silicate melts are consistent with those for solid buffers.

  12. A Disequilibrium Melting Spectrum: Partially Melted Crustal Xenoliths from the Wudalianchi Volcanic Field, NE China.

    Science.gov (United States)

    McLeod, C. L.; McGee, L. E.

    2015-12-01

    Disequilibrium melting has been established as a common process occurring during crustal anatexis and thus demonstrates that crustal assimilation by ascending mantle-derived magmas is likley not a closed system. Observations of extreme compositional heterogeneity within partial melts derived from crustal xenoliths have been documented in several recent examples, however, the retention or transfer of elements to and from residues and glasses, and their relative contributions to potential crustal contaminants warrants further investigation. Sampled lavas from the Huoshaoshan volcano in the Holocene Wudalianchi volcanic field of Northeast China contain crustal xenoliths which preserve a spectrum of partial melting both petrographically and geochemically, thus providing an excellent, natural example of crustal anatexis. Correlations exist between the volume of silicic glass preserved within the xenoliths and bulk rock SiO2 (70-83 wt%), Al2O3 (16-8 wt%), glass 87Sr/86Sr (0.715-0.908), abundances of elements common in feldspars and micas (Sr, Ba, Rb) and elements common in accessory minerals (Y, Zr, Nb). These correlations are likely associated with the consumption of feldspars and micas and the varying retention of accessory phases during partial melting. The xenoliths which contain the greater volumes of silicic glass and residual quartz (interpreted as being the most melted) were found within pahoehoe lava, whilst the least melted xenoliths were found within scoria of the summit cone of Huoshaoshan; thus it is interpreted that the extent of melting is linked to the immersion time in the lava. Small-scale (mm) mingling and transfer of material from the enclosing lava to the xenolith is observed, however, modelling of potential contaminant compositions is inconsistent with crustal contamination during lava petrogenesis. It is inferred that crustal contamination in sampled lavas is localized within the open magmatic system and most likely occurs at the contact zone

  13. Chemical Zoning of Feldspars in Lunar Granitoids: Implications for the Origins of Lunar Silicic Magmas

    Science.gov (United States)

    Mills, R. D; Simon, J. I.; Alexander, C.M. O'D.; Wang, J.; Christoffersen, R.; Rahman, Z..

    2014-01-01

    Fine-scale chemical and textural measurements of alkali and plagioclase feldspars in the Apollo granitoids (ex. Fig. 1) can be used to address their petrologic origin(s). Recent findings suggest that these granitoids may hold clues of global importance, rather than of only local significance for small-scale fractionation. Observations of morphological features that resemble silicic domes on the unsampled portion of the Moon suggest that local, sizable net-works of high-silica melt (>65 wt % SiO2) were present during crust-formation. Remote sensing data from these regions suggest high concentrations of Si and heat-producing elements (K, U, and Th). To help under-stand the role of high-silica melts in the chemical differentiation of the Moon, three questions must be answered: (1) when were these magmas generated?, (2) what was the source material?, and (3) were these magmas produced from internal differentiation. or impact melting and crystallization? Here we focus on #3. It is difficult to produce high-silica melts solely by fractional crystallization. Partial melting of preexisting crust may therefore also have been important and pos-sibly the primary mechanism that produced the silicic magmas on the Moon. Experimental studies demonstrate that partial melting of gabbroic rock under mildly hydrated conditions can produce high-silica compositions and it has been suggested by that partial melting by basaltic underplating is the mechanism by which high-silica melts were produced on the Moon. TEM and SIMS analyses, coordinated with isotopic dating and tracer studies, can help test whether the minerals in the Apollo granitoids formed in a plutonic setting or were the result of impact-induced partial melting. We analyzed granitoid clasts from 3 Apollo samples: polymict breccia 12013,141, crystalline-matrix breccia 14303,353, and breccia 15405,78

  14. The stable Cr isotopic compositions of chondrites and silicate planetary reservoirs

    Science.gov (United States)

    Schoenberg, Ronny; Merdian, Alexandra; Holmden, Chris; Kleinhanns, Ilka C.; Haßler, Kathrin; Wille, Martin; Reitter, Elmar

    2016-06-01

    The depletion of chromium in Earth's mantle (∼2700 ppm) in comparison to chondrites (∼4400 ppm) indicates significant incorporation of chromium into the core during our planet's metal-silicate differentiation, assuming that there was no significant escape of the moderately volatile element chromium during the accretionary phase of Earth. Stable Cr isotope compositions - expressed as the ‰-difference in 53Cr/52Cr from the terrestrial reference material SRM979 (δ53/52CrSRM979 values) - of planetary silicate reservoirs might thus yield information about the conditions of planetary metal segregation processes when compared to chondrites. The stable Cr isotopic compositions of 7 carbonaceous chondrites, 11 ordinary chondrites, 5 HED achondrites and 2 martian meteorites determined by a double spike MC-ICP-MS method are within uncertainties indistinguishable from each other and from the previously determined δ53/52CrSRM979 value of -0.124 ± 0.101‰ for the igneous silicate Earth. Extensive quality tests support the accuracy of the stable Cr isotope determinations of various meteorites and terrestrial silicates reported here. The uniformity in stable Cr isotope compositions of samples from planetary silicate mantles and undifferentiated meteorites indicates that metal-silicate differentiation of Earth, Mars and the HED parent body did not cause measurable stable Cr isotope fractionation between these two reservoirs. Our results also imply that the accretionary disc, at least in the inner solar system, was homogeneous in its stable Cr isotopic composition and that potential volatility loss of chromium during accretion of the terrestrial planets was not accompanied by measurable stable isotopic fractionation. Small but reproducible variations in δ53/52CrSRM979 values of terrestrial magmatic rocks point to natural stable Cr isotope variations within Earth's silicate reservoirs. Further and more detailed studies are required to investigate whether silicate

  15. Evidences of Cold-Melting Mechanism and Cold-Dissolving-Melting Mechanism for Low-heating Solid-state Reaction%低热固相反应冷融熔机理和冷溶熔机理的证据

    Institute of Scientific and Technical Information of China (English)

    唐新村; 黄伯云; 贺跃辉

    2005-01-01

    The cold-melting mechanism and the cold-dissolving-melting mechanism were further studied by TG/DTA and in situ micro-photographs techniques with the mixture of dimethylglyoxime and Ni(Ac)2·4H2O, and the mixture of dimethylglyoxime and anhydrous Ni(Ac)2 as the modeled reactive examples. The endothermic peaks on the DTA curves at about 38℃ revealed the formation process of the cold-melting layer and cold-dissolving-melting layer on the surface of reactant particles. Further, the cold-melting state and the cold-dissolving-melting state were observed by the micrographs. These results provided the direct evidences for the theories of cold-melting mechanism and the cold-dissolving-melting mechanism.

  16. Li+ alumino-silicate ion source development for the Neutralized Drift Compression Experiment (NDCX)

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-10-01

    We report results on lithium alumino-silicate ion source development in preparation for warmdense-matter heating experiments on the new Neutralized Drift Compression Experiment (NDCXII). The practical limit to the current density for a lithium alumino-silicate source is determined by the maximum operating temperature that the ion source can withstand before running into problems of heat transfer, melting of the alumino-silicate material, and emission lifetime. Using small prototype emitters, at a temperature of ~;;1275 oC, a space-charge-limited Li+ beam current density of J ~;;1 mA/cm2 was obtained. The lifetime of the ion source was ~;;50 hours while pulsing at a rate of 0.033 Hz with a pulse duration of 5-6 mu s.

  17. Partial melting of apatite-bearing charnockite, granulite, and diorite: Melt compositions, restite mineralogy, and petrologic implications

    Science.gov (United States)

    Beard, James S.; Lofgren, Gary E.; Sinha, A. Krishna; Tollo, Richard P.

    1994-01-01

    Melting experiments (P = 6.9 kbar, T = 850-950 deg C, NNO is less than fO2 is less than HM) were done on mafic to felsic charnockites, a dioritic gneiss, and a felsic garnet granulite, all common rock types in the Grenville basement of eastern North America. A graphite-bearing granulite gneiss did not melt. Water (H2O(+) = 0.60 to 2.0 wt %) is bound in low-grade, retrograde metamorphic minerals and is consumed during the earliest stages of melting. Most melts are water-undersaturated. Melt compositions range from metaluminous, silicic granodiorite (diorite starting composition) to peraluminous or weakly metaluminous granites (all others). In general, liquids become more feldspathic, less silicic, and less peraluminous and are enriched in FeO, MgO, and TiO2 with increasing temperature. Residual feldspar mineralogy controls the CaO, K2O, and Na2O contents of the partial melts and the behavior of these elements can be used, particularly if the degree of source melting can be ascertained, to infer some aspects of the feldspar mineralogy of the source. K-feldspar, a common restite phase in the charnockite and granulite (but not the diorite) should control the behavior of Ba and, possibly, Eu in these systems and yield signatures of these elements that can distinguish source regions and, in some cases, bulk versus melt assimilation. Apatite, a common restite phase, is enriched in rare earth elements (REE), especially middle REE. Retention of apatite in the restite will result in steep, light REE-enriched patterns for melts derived from the diorite and charnockites.

  18. Float processing of high-temperature complex silicate glasses and float baths used for same

    Science.gov (United States)

    Cooper, Reid Franklin (Inventor); Cook, Glen Bennett (Inventor)

    2000-01-01

    A float glass process for production of high melting temperature glasses utilizes a binary metal alloy bath having the combined properties of a low melting point, low reactivity with oxygen, low vapor pressure, and minimal reactivity with the silicate glasses being formed. The metal alloy of the float medium is exothermic with a solvent metal that does not readily form an oxide. The vapor pressure of both components in the alloy is low enough to prevent deleterious vapor deposition, and there is minimal chemical and interdiffusive interaction of either component with silicate glasses under the float processing conditions. Alloys having the desired combination of properties include compositions in which gold, silver or copper is the solvent metal and silicon, germanium or tin is the solute, preferably in eutectic or near-eutectic compositions.

  19. Electroenzymatic Reactions With Oxygen on Laccase-Modified Electrodes in Anhydrous (Pure) Organic Solvent

    DEFF Research Database (Denmark)

    Yarapolov, A.; Shleev, S.; Zaitseva, E.

    2007-01-01

    The electroenzymatic reactions of Trametes hirsuta laccase in the pure organic solvent dimethyl sulfoxide (DMSO) have been investigated within the framework for potential use as a catalytic reaction scheme for oxygen reduction. The bioelectrochemical characteristics of laccase were investigated...... in two different ways: (i) by studying the electroreduction of oxygen in anhydrous DMSO via a direct electron transfer mechanism without proton donors and (ii) by doing the same experiments in the presence of laccase substrates, which display in pure organic solvents both the properties of electron...... donors as well as the properties of weak acids. The results obtained with laccase in anhydrous DMSO were compared with those obtained previously in aqueous buffer. It was shown that in the absence of proton donors under oxygenated conditions, formation of superoxide anion radicals is prevented at bare...

  20. Method of Preparation for High-Purity Nanocrystalline Anhydrous Cesium Perrhenate

    Directory of Open Access Journals (Sweden)

    Katarzyna Leszczyńska-Sejda

    2017-03-01

    Full Text Available This paper is devoted to the preparation of high-purity anhydrous nanocrystalline cesium perrhenate, which is applied in catalyst preparation. It was found that anhydrous cesium perrhenate with a crystal size <45 nm can be obtained using cesium ion sorption and elution using aqueous solutions of perrhenic acid with subsequent crystallisation, purification, and drying. The following composition of the as-obtained product was reported: 34.7% Cs; 48.6% Re and <2 ppm Bi; <3 ppm Zn; <2 ppm As; <10 ppm Ni; < 3 ppm Mg; <5 ppm Cu; <5 ppm Mo; <5 ppm Pb; <10 ppm K; <2 ppm Na; <5 ppm Ca; <3 ppm Fe.

  1. Ab initio and DFT studies of the structure and vibrational spectra of anhydrous caffeine.

    Science.gov (United States)

    Srivastava, Santosh K; Singh, Vipin B

    2013-11-01

    Vibrational spectra and molecular structure of anhydrous caffeine have been systematically investigated by second order Moller-Plesset (MP2) perturbation theory and density functional theory (DFT) calculations. Vibrational assignments have been made and many previous ambiguous assignments in IR and Raman spectra are amended. The calculated DFT frequencies and intensities at B3LYP/6-311++G(2d,2p) level, were found to be in better agreement with the experimental values. It was found that DFT with B3LYP functional predicts harmonic vibrational wave numbers more close to experimentally observed value when it was performed on MP2 optimized geometry rather than DFT geometry. The calculated TD-DFT vertical excitation electronic energies of the valence excited states of anhydrous caffeine are found to be in consonance to the experimental absorption peaks.

  2. Structural basis for the transformation pathways of the sodium naproxen anhydrate-hydrate system

    DEFF Research Database (Denmark)

    Bond, Andrew; Cornett, Claus; Larsen, Flemming Hofmann

    2014-01-01

    Crystal structures are presented for two dihydrate polymorphs (DH-I and DH-II) of the non-steroidal anti-inflammatory drug sodium (S)-naproxen. The structure of DH-I is determined from twinned single crystals obtained by solution crystallization. DH-II is obtained by solid-state routes, and its...... structure is derived using powder X-ray diffraction, solid-state (13)C and (23)Na MAS NMR, and molecular modelling. The validity of both structures is supported by dispersion-corrected density functional theory (DFT-D) calculations. The structures of DH-I and DH-II, and in particular their relationships...... to the monohydrate (MH) and anhydrate (AH) structures, provide a basis to rationalize the observed transformation pathways in the sodium (S)-naproxen anhydrate-hydrate system. All structures contain Na(+)/carboxylate/H2O sections, alternating with sections containing the naproxen molecules. The structure of DH...

  3. Ab initio and DFT studies of the structure and vibrational spectra of anhydrous caffeine

    Science.gov (United States)

    Srivastava, Santosh K.; Singh, Vipin B.

    2013-11-01

    Vibrational spectra and molecular structure of anhydrous caffeine have been systematically investigated by second order Moller-Plesset (MP2) perturbation theory and density functional theory (DFT) calculations. Vibrational assignments have been made and many previous ambiguous assignments in IR and Raman spectra are amended. The calculated DFT frequencies and intensities at B3LYP/6-311++G(2d,2p) level, were found to be in better agreement with the experimental values. It was found that DFT with B3LYP functional predicts harmonic vibrational wave numbers more close to experimentally observed value when it was performed on MP2 optimized geometry rather than DFT geometry. The calculated TD-DFT vertical excitation electronic energies of the valence excited states of anhydrous caffeine are found to be in consonance to the experimental absorption peaks.

  4. Melting of Transition Metals

    Energy Technology Data Exchange (ETDEWEB)

    Ross, M; Japel, S; Boehler, R

    2005-04-11

    We review the transition melting studies carried out at Mainz, and describe a recently developed model used to explain that the relatively low melting slopes are due to the partially filled d-bands, and the persistence of the pressure induced s-d transition. The basic tenets of the model have now been reconfirmed by new measurements for Cu and Ni. The measurements show that Cu which has a filled 3d-band, has a melt slope that is about 2.5 greater than its neighbor Ni. In the case of Mo, the apparent discrepancy of DAC melting measurements with shock melting can be explained by accounting for the change in melt slope due to the bcc-cp transition observed in the shock studies. The Fe melt curve is revisited. The possible relevance of the Jahn-Teller effect and recently observed transition metal melts with Icosahedral Short-Range Order (ISRO) is discussed.

  5. The Global Array of Primitve Arc Melts

    Science.gov (United States)

    Schmidt, M. W.; Jagoutz, O. E.

    2015-12-01

    A longstanding question concerns the nature of the melts forming in the subarc mantle and giving rise to arc magmatism. The global array of primitive arc melts (1180 volcanic rocks in 25 arcs extracted from the georoc database, calculated to be in equilibrium with mantle olivine) yields five principal melt types: calc-alkaline basalts and high-Mg andesites, tholeiitic basalts and high-Mg andesites, and shoshonitic or alkaline arc melts; many arcs have more than one type. Primitive calc-alkaline basalts occur in 11 arcs but most strikingly, 8 continental arcs (incl. Aleutians, Cascades, Japan, Mexico, Kamtschatka) have a continuous range of calc-alkaline basalts to high-Mg andesites with mostly 48-58 wt% SiO2. In each arc, these are spatially congruent, trace element patterns overlap, and major elements form a continuum. Their Ca-Mg-Si systematics suggests saturation in olivine+opx+cpx. We hence interpret the large majority of high-Mg andesites as derived from primitive calc-alkaline basalts through fractionation and reaction in the shallower mantle. Removal of anhydrous mantle phases at lower pressures increases SiO2 and H2O-contents while Mg# and Ni remain buffered to mantle values. Primitive tholeiitic basalts (Cascades, Kermadec, Marianas, Izu-Bonin, Japan, Palau, Sunda) have a much lesser subduction signal (e.g. in LILE) than the calc-alkaline suite. These tholeiites have been interpreted to form through decompression melting, but also characterize young intraoceanic arcs. In the two continental arcs with both tholeiitic and calc-alkaline primitive basalts (clearly distinct in trace patterns), there is no clear spatial segregation (Casacades, Japan). Three intraoceanic arcs (Marianas, Izu-Bonin, Tonga) have primitive tholeiitic, highly depleted high-Mg andesites (boninites) with HFSE and HREE slightly above primitive mantle values. These deviate in majors from the array formed by the basalts and calc-alkaline andesites suggesting that only these formed from a

  6. Neutron diffraction analysis of residual stresses near unannealed welds in anhydrous ammonia nurse tanks.

    Science.gov (United States)

    Becker, A T; Chumbley, L S; Goettee, D; Russell, A M

    2014-01-01

    Neutron diffraction analysis was employed to measure residual stresses near welds in used anhydrous ammonia nurse tanks. Tensile residual stresses contribute to stress corrosion cracking of nurse tanks, which can cause tanks to release toxic ammonia vapor. The analysis showed that tensile residual stresses were present in the tanks measured, and the magnitudes of these stresses approached the yield strength of the steel. Implications for agricultural safety and health are discussed.

  7. Mössbauer study on the gamma radiolysis of anhydrous cesium tris (oxalato) ferrate(III)

    Science.gov (United States)

    Ladriere, J.; Senterre, V.; Apers, D.

    1992-04-01

    The final product of the gamma radiolysis of anhydrous cesium tris(oxalato) ferrate(III) has been identified by Mössbauer spectroscopy as Cs2Fe(ox)2. The radiolytic decomposition proceeds as a first-order process due to the original compound depletion and to the radiolytic stability of the ferrous compound. Lamb-Mössbauer factors measurements indicate that the recoilless fractions of the iron species are practically unaffected by the radiolysis.

  8. THE PRODUCTION OF PURE ABSOLUTE ALCOHOL WITH CALCIUM CARBIDE AND ANHYDROUS COPPER SULPHATE.

    Science.gov (United States)

    Lyons, R E; Smith, L T

    1925-09-01

    (1) The above is recommended as an economical, convenient and quick method for producing absolute alcohol on a laboratory scale. If the distillation is executed with free flame, excessive or careless heating must be avoided near the end of the operation because of the copper acetylide in the residue. (2) Calcium carbide is recommended over potassium permanganate or anhydrous copper sulphate as a qualitative reagent in detecting traces of water in alcohol.

  9. Electrical conductivity and viscosity of borosilicate glasses and melts

    DEFF Research Database (Denmark)

    Ehrt, Doris; Keding, Ralf

    2009-01-01

    , 0 to 62·5 mol% B2O3, and 25 to 85 mol% SiO2. The glass samples were characterised by different methods. Refractive indices, density and thermal expansion were measured. Phase separation effects were investigated by electron microscopy. The electrical conductivity of glasses and melts were determined...... by impedance measurements in a wide temperature range (250 to 1450°C). The activation energies were calculated by Arrhenius plots in various temperature regions: below the glass transition temperature, Tg, above the melting point, Tl, and between Tg and Tl. Viscosity measurements were carried out...... with different methods from Tg to the melt. The measured data were fitted and the activation energies calculated. Simple exponential behaviour was found only in very narrow temperature ranges. The effect of B2O3 in sodium borosilicate glasses and melts is discussed in comparison with sodium silicate glasses...

  10. Sb/Mn co-doped oxyfluoride silicate glasses for potential applications in photosynthesis

    OpenAIRE

    Zhu, Chaofeng; ZHANG, XIANGHUA; Ma, Hongli

    2016-01-01

    International audience; A series of Sb/Mn co-doped oxyfluoride silicate glasses were prepared via the melt-quenching method to explore red luminescent materials for potential applications in photosynthesis of green plants, and these glasses are investigated by means of luminescence decay curves, absorption, emission, and excitation spectra. We find that the as-prepared glasses are transparent in the visible region and can emit strong red light under ultraviolet, purple, and green light excita...

  11. Preparation of anhydrous magnesium chloride in a gas-solid reaction with ammonium carnallite

    Institute of Scientific and Technical Information of China (English)

    Zhou Ningbo; Chen Baizhen; He Xinkuai; Li Yibing

    2006-01-01

    Dehydrated ammonium carnallite was synthesized with bischofite from salt lake and ammonium chloride solution in a 1:1 molar ratio of MgCl2:NH4Cl,dehydrated at 160℃ for about 4 h.The yield was above 85%.The product was then mixed with solid-state ammonium chloride with a 1:4 mass ratio for the further dehydration at 410℃.The decomposition of NH4Cl made a pressure of NH3 at 30.5 kPa to prevent the hydrolysis of ammonium carnallite.The anhydration of magnesium chloride was achieved at 700℃.The results showed that anhydrous magnesium chloride contains magnesium oxide in an amount that was less than 0.1% by weight.XRD pattern and SEM micrograph showed a good dispersion of ammonium carnallite and anhydrous magnesium chloride crystals with well-distributed big grains,just enough to meet the need for the production of magnesium metal in the electrolysis process.

  12. Preparation and characteristic research of anhydrous magnesium chloride with dehydrated ammonium carnallite

    Institute of Scientific and Technical Information of China (English)

    ZHOU Ning-bo; CHEN Bai-zhen; HE Xin-kuai; LI Yi-bing

    2006-01-01

    Taking the saline lake bischofite and NH4Cl that was removed with the ammonia method and continuwas synthesized. And then the ammonium carnallite was dehydrated to some extent at 160℃ for 4 h. Ammonium carnallite reacted with ammonia at 240℃ for 150 min and the ammonation ammonium carnallite was produced. Finally, the ammonation ammonium carnallite was calcined at 750℃ into anhydrous magnesium chloride containing only 0.1% (mass fraction) of MgO. On the other hand, dehydrated ammonium carnallite was mixed with the solid ammonium chloride at mass ratio 1:4 at high temperature and with the differential pressure of HN3 above 30.5 kPa. The dehydrated ammonium carnallite of mixture was dehydrated at 410℃, and then calcined at 700℃ into anhydrous magnesium chloride with only 0. 087% (mass fraction) of MgO. X-ray diffraction and electron microscopy analysis results prove that anhydrous magnesium chloride obtained by both methods hasn't mixed phases, the particle is large and even has good dispersion, which is suitable for preparation of metal magnesium in the electrolysis.

  13. Anhydrous proton conducting membranes for PEM fuel cells based on Nafion/Azole composites

    Energy Technology Data Exchange (ETDEWEB)

    Sen, Unal; Ata, Ali [Gebze Institute of Technology, Materials Science and Engineering, Gebze, Kocaeli (Turkey); Uenueguer Celik, Sevim; Bozkurt, Ayhan [Department of Chemistry, Fatih University, 34500, Buyukcekmece, Istanbul (Turkey)

    2008-06-15

    Proton conducting membranes are the most crucial part of energy generating electrochemical systems such as polymer electrolyte membrane fuel cells (PEMFCs). In this work, Nafion based proton conducting anhydrous composite membranes were prepared via two different approaches. In the first, commercial Nafion115 and Nafion112 were swelled in the concentrated solution of azoles such as 1H-1,2,4-triazole (Tri), 3-amino-1,2,4-triazole (ATri) and 5-aminotetrazole (ATet) as heterocyclic protogenic solvents. In the second, the proton conducting films were cast from the Nafion/Azole solutions. The partial protonation of azoles in the anhydrous membranes were studied by Fourier transform infrared (FT-IR) spectroscopy. Thermal properties were investigated via thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). TGA results showed that Nafion/ATri and Nafion/ATet electrolytes are thermally stable at least up to 200 C. Methanol permeability measurements showed that the composite membranes have lower methanol permeability compared to Nafion112. Nafion115/ATri system has better conductivity at 180 C, exceeding 10{sup -3} S/cm compared to other Nafion/heterocycle systems under anhydrous conditions. (author)

  14. Use of lycopene as a natural antioxidant in extending the shelf-life of anhydrous cow milk fat.

    Science.gov (United States)

    Siwach, Ruby; Tokas, Jayanti; Seth, Raman

    2016-05-15

    Oxidative rancidity in anhydrous cow milk fat leads to reduction in its shelf life. Use of synthetic antioxidants is prevalent in dairy industry to prevent the development of rancidity. Keeping in view the increasing demand for natural additives, the present study was carried out to explore the potential of lycopene as a natural antioxidant in anhydrous cow milk fat. Lycopene at five different levels (30, 60, 90, 120 and 150 ppm) and butylated hydroxyl anisole (200 ppm), were incorporated in anhydrous cow milk fat. Potential of lycopene extract to enhance the shelf life of anhydrous cow milk fat was evaluated by measuring Free Fatty Acids, peroxide value, Thiobarbituric Acid value and color value during 12 months of storage at ambient conditions (30°C). Lycopene significantly (pLycopene containing samples scored significantly higher in terms of sensory attributes as compared to control.

  15. Nanoscale zinc silicate from phytoliths

    Science.gov (United States)

    Qadri, S. B.; Gorzkowski, E. P.; Rath, B. B.; Feng, C. R.; Amarasinghe, R.; Freitas, J. A.; Culbertson, J. C.; Wollmershauser, J. A.

    2017-10-01

    We report a faster, less expensive method of producing zinc silicate nanoparticles. Such particles are used in high volume to make phosphors and anti-corrosion coatings. The approach makes use of phytoliths (plant rocks), which are microscopic, amorphous, and largely silicate particles embedded in plants, that lend themselves to being easily broken down into nanoparticles. Nanoparticles of Zn2SiO4 were produced in a two stage process. In the refinement stage, plant residue, mixed with an appropriate amount of ZnO, was heated in an argon atmosphere to a temperature exceeding 1400 °C for four to six hours and then heated in air at 650 °C to remove excess carbon. TEM shows 50-100 nm nanoparticles. Raman scattering indicates that only the -Zn2SiO4 crystalline phase was present. X-ray analysis indicated pure rhombohedral R 3 bar phase results from using rice/wheat husks. Both samples luminesced predominantly at 523 nm when illuminated with X-rays or UV laser light.

  16. Silicate condensation in Mira variables

    CERN Document Server

    Gail, Hans-Peter; Pucci, Annemarie

    2016-01-01

    We study whether the condensation of silicate dust in Mira envelopes could be caused by cluster formation by the abundant SiO molecules. For a simplified model of the pulsational motions of matter in the the outer layers of a Mira variable which is guided by a numerical model for Mira pulsations, the equations of dust nucleation and growth are solved in the co-moving frame of a fixed mass element. It is assumed that seed particles form by clustering of SiO molecules. The calculation of the nucleation rate is based on the experimental data of Nuth and Donn (1982). The quantity of dust formed is calculated by a moment method and the calculation of radiation pressure on the dusty gas is based on a dirty silicate model. 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 while subsequent dust growth occurs during the descending part of the motion and continues after the next shock reversed motion. It is found tha...

  17. Differentiation of Asteroid 4 Vesta: Core Formation by Iron Rain in a Silicate Magma Ocean

    Science.gov (United States)

    Kiefer, Walter S.; Mittlefehldt, David W.

    2017-01-01

    Geochemical observations of the eucrite and diogenite meteorites, together with observations made by NASA's Dawn spacecraft while orbiting asteroid 4 Vesta, suggest that Vesta resembles H chondrites in bulk chemical composition, possible with about 25 percent of a CM-chondrite like composition added in. For this model, the core is 15 percent by mass (or 8 percent by volume) of the asteroid, with a composition of 73.7 percent by weight Fe, 16.0 percent by weight S, and 10.3 percent by weight Ni. The abundances of moderately siderophile elements (Ni, Co, Mo, W, and P) in eucrites require that essentially all of the metallic phase in Vesta segregated to form a core prior to eucrite solidification. The combination of the melting phase relationships for the silicate and metal phases, together with the moderately siderophile element concentrations together require that complete melting of the metal phase occurred (temperature is greater than1350 degrees Centigrade), along with substantial (greater than 40 percent) melting of the silicate material. Thus, core formation on Vesta occurs as iron rain sinking through a silicate magma ocean.

  18. Lipase-catalyzed process in an anhydrous medium with enzyme reutilization to produce biodiesel with low acid value.

    Science.gov (United States)

    Azócar, Laura; Ciudad, Gustavo; Heipieper, Hermann J; Muñoz, Robinson; Navia, Rodrigo

    2011-12-01

    One major problem in the lipase-catalyzed production of biodiesel or fatty acid methyl esters (FAME) is the high acidity of the product, mainly caused by water presence, which produces parallel hydrolysis and esterification reactions instead of transesterification to FAME. Therefore, the use of reaction medium in absence of water (anhydrous medium) was investigated in a lipase-catalyzed process to improve FAME yield and final product quality. FAME production catalyzed by Novozym 435 was carried out using waste frying oil (WFO) as raw material, methanol as acyl acceptor, and 3Å molecular sieves to extract the water. The anhydrous conditions allowed the esterification of free fatty acids (FFA) from feedstock at the initial reaction time. However, after the initial esterification process, water absence avoided the consecutives reactions of hydrolysis and esterification, producing FAME mainly by transesterification. Using this anhydrous medium, a decreasing in both the acid value and the diglycerides content in the product were observed, simultaneously improving FAME yield. Enzyme reuse in the anhydrous medium was also studied. The use of the moderate polar solvent tert-butanol as a co-solvent led to a stable catalysis using Novozym 435 even after 17 successive cycles of FAME production under anhydrous conditions. These results indicate that a lipase-catalyzed process in an anhydrous medium coupled with enzyme reuse would be suitable for biodiesel production, promoting the use of oils of different origin as raw materials.

  19. Formation of Cosmic Crystals in Highly-Supersaturated Silicate Vapor Produced by Planetesimal Bow Shocks

    CERN Document Server

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

    2010-01-01

    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 evaporated 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; the cooling rate is estimated, for instance, to be as high as 2000 K s$^{-1}$ 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 muc...

  20. Silicates materials of high vacuum technology

    CERN Document Server

    Espe, Werner

    2013-01-01

    Materials of High Vacuum Technology, Volume 2: Silicates covers silicate insulators of special importance to vacuum technology. The book discusses the manufacture, composition, and physical and chemical properties of technical glasses, quartz glass, quartzware, vycor glass, ceramic materials, mica, and asbestos.

  1. Conduction mechanism in bismuth silicate glasses containing titanium

    Science.gov (United States)

    Dult, Meenakshi; Kundu, R. S.; Murugavel, S.; Punia, R.; Kishore, N.

    2014-11-01

    Bismuth silicate glasses mixed with different concentrations of titanium dioxide having compositions xTiO2-(60-x)Bi2O3-40SiO2 with x=0, 5, 10, 15 and 20 were prepared by the normal melt quench technique. The frequency dependence of the ac electrical conductivity of different compositions of titanium bismuth silicate glasses has been studied in the frequency range 10-1 Hz to 10 MHz and in the temperature range 623-703 K. The temperature and frequency dependent conductivity is found to obey Jonscher's universal power law for all the compositions of titanium bismuth silicate glass system. The dc conductivity (σdc), so called crossover frequency (ωH), and frequency exponent (s) have been estimated from the fitting of experimental data of ac conductivity with Jonscher's universal power law. Enthalpy to dissociate the cation from its original site next to a charge compensating center (Hf) and enthalpy of migration (Hm) have also been estimated. The conductivity data have been analyzed in terms of different theoretical models to determine the possible conduction mechanism. Analysis of the conductivity data and the frequency exponent shows that the correlated barrier hopping of electrons between Ti3+ and Ti4+ ions in the glasses is the most favorable mechanism for ac conduction. The temperature dependent dc conductivity has been analyzed in the framework of theoretical variable range hopping model (VRH) proposed by Mott which describe the hopping conduction in disordered semiconducting systems. The various polaron hopping parameters have also been deduced. Mott's VRH model is found to be in good agreement with experimental data and the values of inverse localization length of s-like wave function (α) obtained by this model with modifications suggested by Punia et al. are close to the ones reported for a number of oxide glasses.

  2. Mesoporous Silicate Materials in Sensing

    Directory of Open Access Journals (Sweden)

    Paul T. Charles

    2008-08-01

    Full Text Available 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 cocondensation 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.

  3. Channelling of Melt Above Plumes and Beneath MORs

    Science.gov (United States)

    Mueller, K.; Schmeling, H.

    2003-12-01

    We investigate melt transportation in partially molten rocks under different stress fields above the head of a mantle plume or beneath a spreading mid-oceanic ridge under hydrous and anhydrous conditions. We model such aggregates with the 2D-FD code FDCON [1] by means of a porous deformable matrix with melt under the influence of a given stress field to clarify the following key questions: Could channeling occur in a matrix containing a random melt distribution under a given stress field? Which orientation does it take? Is it possible to achieve a focusing of melt towards a MOR (dykes)? Does applying simple or pure shear to the matrix result in a difference in the formation and orientation of channels? How does the channel instability evolve during finite simple shear? In a deforming partially molten aggregate, weakening of the solid matrix due to the presence of melt creates an instability in which melt is localized by the following mechanism: regions of initially high melt fraction are areas of low viscosity and pressure, so that melt is drawn into these regions from higher pressure surroundings. This further enhances the melt weakening, producing a self-excited localization mechanism [2]. The channeling developing in models with a random melt distribution of 3.5 +/- 0.5% shows that melt is accumulated preferably in inclined channels. For both, simple as well as pure shear, the growth rate is highest for an orientation parallel to the direction of the maximum compressive stress and proportional to applied stress and the reverse of the Melt Retention Number. This also confirms the theoretical growth rate found by Stevenson [2]. In our isothermal models we found that the influence of water reduces the growth rate, in contrast to non-isothermal models of Hall [3]. Under simple shear melt channels evolve from an irregular melt distribution at angles of 45 degrees to the direction of shear. Upon further straining they rotate out of the orientation of maximum growth

  4. Dihedral angle of carbonatite melts in mantle residue near the upper mantle and transition zone

    Science.gov (United States)

    Ghosh, S. K.; Rohrbach, A.; Schmidt, M. W.

    2015-12-01

    Carbonate melts are thought to be ideal metasomatic agents in the deep upper mantle (Green & Wallace, 1988) and these melts are low in viscosities (10-1-10-3 Pa·s) compared to primitive basalt (101-102 Pa·s), furthermore the ability to form an interconnected grain-edge melt network at low melt fractions (3 GPa (Dasgupta et al. 2006, Ghosh et al., 2009), dissolve a number of geochemically incompatible elements much better than silicate melts (Blundy and Dalton, 2000). Previous studies of carbonate melt dihedral angles in olivine-dominated matrices yielded 25-30oat 1-3 GPa, relatively independent of melt composition (Watson et al., 1990) and temperature (Hunter and McKenzie, 1989). Dihedral angles of carbonate melts in contact with deep mantle silicate phases (e.g. garnet, wadsleyite, and ringwoodite) which constitute more than 70 % of the deep upper mantle and transition zone have not been studied yet. We have performed multi-anvil experiments on carbonate-bearing peridotites with 5.0 wt% CO2 from 13.5 to 20 GPa 1550 oC to investigate the dihedral angle of magnesio-carbonatite melts in equilibrium with garnet, olivine (and its high-pressure polymorphs), and clinoenstatite. The dihedral angle of carbonate melts in the deep upper mantle and transition zone is ~30° for majorite garnet and olivine (and its polymorphs) dominated matrices. It does not change with increasing pressure in the range 13.5-20 GPa. Our results suggest that very low melt fractions of carbonatite melt forming in the deep upper mantle and transition zone are interconnected at melt fractions less than 0.01. Consistent with geophysical observations, this could possibly explain low velocity regions in the deep mantle and transition zone.

  5. Silicate sulfidation and chemical differences between enstatite chondrites and Earth

    Science.gov (United States)

    Lehner, S. W.; Petaev, M. I.; Buseck, P. R.

    2013-12-01

    -sensitive material and contains minor elements such as Na, Ca, Mg, or Fe, which also occur in the adjacent minerals. Its high S content and vesicular nature point to formation by quenching of a high-temperature melt saturated with a gaseous phase. The porous silica occurs in ~50% of chondrules [12], metal-sulfide nodules, and as inter-chondrule clasts, suggesting it is a good tracer of silicate sulfidation. Refs: [1] Javoy M. (1995) GRL 22: 2219-2222. [2] Javoy M. et al. (2010) EPSL 293: 259-268. [3] Kaminski E. & Javoy M. (2013) EPSL 365: 97-107. [4] Jacobsen S.B. et al. (2013) LPSC 44: #2344. [5] Weisberg M.K. et al. (2011) GCA 75: 6556-6569. [6] Lehner S.W. et al. (2013) GCA 101: 34-56. [7] Simon S.B. et al. (2013) LPSC 44: #2270. [8] Lehner S.W. et al. (2012) LPSC 43: #2252. [9] Shahar A. et al. (2011) GCA 75: 7688-7697. [10] Kempl J. et al. (2013) EPSL 368: 61-68. [11] Fitoussi C. & Bourdon B. (2012) Science 335: 1477-1480. [12] Piani L. et al. (2013) MetSoc 76: # 5178.

  6. Melt-intercalation studies of polystyrene ionomers in pristine montmorillonite

    Science.gov (United States)

    Bhiwankar, Nikhil N.

    The main objective of this study was to examine the use of ionomers, specifically alkylamine-neutralized sulfonated polystyrene (SPS) for promoting intercalation into unmodified sodium montmorillonite clay and its use as a compatabilizer for intercalating another polymer into unmodified silicate clay. The processing parameters and chemical structure of polymers which led to the formation of partially intercalated/exfoliated morphologies were investigated. Melt-intercalated polymer layered silicate nanocomposites (PLSNs) are made by mixing polymers and organically modified silicates by the application of shear forces. However, the thermal decomposition temperatures of the organic modifications are usually comparable to the processing temperatures of most of the polymers. Hence, in this work modification of the polymer, rather than the clay, for promoting melt intercalation, specifically the introduction of alkyl ammonium salt groups along the polymer chain was considered. In this study the effects of viscosity, shear rates and mixing times on the morphology of nanocomposites were investigated. The effect of ionic content in the polymer chain of SPS in the batch mixtures of SPS and PS was researched. We also compared the effect on the extent of intercalation in these silicate clay galleries as a function of size of the counter-ions by varying the alkyl chain length and as a function of basicity of these counter-ions by varying the number of alkyl substituents that are attached on the N of the amine. The melt mixing of pristine Na-Mmt with alkyl ammonium and quaternary ammonium salts of SPS ionomers, resulted in an increase in the silicate gallery spacing consistent with intercalation. Mixtures of the ionomer with PS exhibited similar gallery spacing increases, indicating that the ionomer is an effective compatibilizing agent for the melt-intercalation of hydrophobic polymers into the clay. The extent of intercalation was independent of the melt processing conditions

  7. Residual stresses and phase transformations in Ytterbium silicate environmental barrier coatings

    Science.gov (United States)

    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.

  8. Thermometry of the magma ocean: Controls on the metal-silicate partitioning of gold

    Science.gov (United States)

    Bennett, N. R.; Brenan, J. M.; Fei, Y.

    2016-07-01

    We have performed experiments to investigate the solubility and metal-silicate partitioning of gold as a function of metal sulphur content (XS), silicate melt polymerization (NBO/T) and pressure (P). These experiments show that Au becomes less siderophile both with increasing pressure and as the metal phase becomes more sulphur-rich. For the studied range of compositions, melt polymerization has no effect on the solubility of Au. The reduction in the siderophile tendency of gold with increasing metal sulphur content is greater than expected on the basis of activity-composition relationships in the metal phase. This suggests a significant role for complexing between Au and S in the silicate melt. Our new experimental results are combined with literature data to yield a parameterisation for the exchange coefficient of Au (KdAuMet/Sil) as a function of P, T and XS: Using this relationship, alongside similar parameterisations for Ni and Co selected from the literature, we performed continuous accretion models to delineate regions of parameter space in which Au and moderately siderophile element (MSE) abundances in the primitive upper mantle (PUM) could be reproduced. These models suggest that for metal-silicate equilibrium at very high pressures, Au will be overabundant in the PUM if equilibrium also occurs at extreme temperatures. Instead, most successful models are found when equilibrium occurs at high pressure but sub-liquidus temperatures. This result is in keeping with the physical conditions expected for a scenario where core-forming metal ponds and equilibrates at the rheological base of a magma ocean (e.g. Wade and Wood, 2005).

  9. Transition-metal-free hydration of nitriles using potassium tert-butoxide under anhydrous conditions.

    Science.gov (United States)

    Midya, Ganesh Chandra; Kapat, Ajoy; Maiti, Subhadip; Dash, Jyotirmayee

    2015-04-17

    Potassium tert-butoxide acts as a nucleophilic oxygen source during the hydration of nitriles to give the corresponding amides under anhydrous conditions. The reaction proceeds smoothly for a broad range of substrates under mild conditions, providing an efficient and economically affordable synthetic route to the amides in excellent yields. This protocol does not need any transition-metal catalyst or any special experimental setup and is easily scalable to bulk scale synthesis. A single-electron-transfer radical mechanism as well as an ionic mechanism have been proposed for the hydration process.

  10. The Cl Isotope Composition of the Moon as evidence for an Anhydrous Mantle (Invited)

    Science.gov (United States)

    Sharp, Z. D.; Shearer, C., Jr.; McKeegan, K. D.; Barnes, J.; Wang, Y.

    2010-12-01

    The chlorine isotope composition of primitive terrestrial basalts and carbonaceous chondrites cover a narrow range centered around 0‰ with a total variation of ± 0.5‰. In contrast, the chlorine isotope composition of bulk samples and in situ ion microprobe analyses of lunar basalts and glasses cover a range of 25‰. Three possibilities were considered to explain the large spread: 1) initial isotopic heterogeneities, 2) devolatilization from solar wind/micrometeorite bombardment, 3) degassing under anhydrous conditions. The first of these possibilities is rejected because the Moon went through an magma ocean stage which would have homogenized any isotopic heterogeneities. To examine surface effects, we chose samples that have extremely different degrees of surface exposure. We find no correlation between the Cl isotope composition and surface exposure. We also conducted a laboratory experiment in which a thin film of NaCl was bombarded with a proton source for 24 hours with no change in Cl isotope composition. The third possibility is that the fractionation is explained by the anhydrous character of the Moon. On Earth, the volatiling Cl species is HCl. HCl is known to preferentially incorporate 37Cl relative to 35Cl due to the high bond strength of the molecule. This is offset by the higher translational velocity of H35Cl, so that overall, there is very little Cl isotope fractionation during degassing. We propose that lunar basalts were anhydrous and the volatile Cl species were metal chlorides, such as ZnCl2, NaCl, FeCl2, etc. The bond strength of metal chlorides and Cl dissolved in a basalt are similar, so that fractionation is caused mainly by volatilization, with the light isotopologue preferentially lost to the vapor phase. This idea is supported by the consistent lower Cl isotope ratios of water soluble salt fraction (~10 ‰ lower) and the lowest lunar Cl isotope values close to those of bulk Earth. The H content of lunar magmas must have been lower

  11. Melting the hydrous, subarc mantle: the origin of primitive andesites

    Science.gov (United States)

    Mitchell, Alexandra L.; Grove, Timothy L.

    2015-08-01

    of mantle lherzolite under anhydrous conditions. This study shows that experimental melts of a FM peridotite plus the addition of alkalis reproduce the compositions of natural PAs in SiO2, Al2O3, TiO2, Cr2O3, MgO, and Na2O at 1.0-1.2 GPa and H2O contents of 0-7 wt%. Our results also suggest that PAs form under a maximum range of extents of melting from F = 0.2-0.3. The CaO contents of the melts produced are 1-5 wt% higher than the natural samples. This is not a result of a depleted source composition or of extremely high extents of melt but is potentially caused by a very low CaO content contribution from deeper in the mantle wedge.

  12. Composition dependence of spontaneous crystallization of phosphosilicate glass melts during cooling

    DEFF Research Database (Denmark)

    Liu, S.J.; Zhu, C.F.; Zhang, Y.F.

    2012-01-01

    Crystallization behavior of alumino-phospho-silicate melts during cooling is studied by means of the differential scanning calorimetry, X-ray diffractometry and viscometry. The results show a pronounced impact of alkaline earth oxide, alkali oxide and fluoride on the crystal type...

  13. Fourier transform infrared spectroscopy for the analysis of neutralizer-carbomer and surfactant-carbomer interactions in aqueous, hydroalcoholic, and anhydrous gel formulations

    National Research Council Canada - National Science Library

    Islam, Mohammad T; Rodríguez-Hornedo, Naír; Ciotti, Susan; Ackermann, Chrisita

    2004-01-01

    .... Comparisons of the spectra of Carbopol dispersions in aqueous, anhydrous, and hydroalcoholic systems, performed for the first time, show Carbopol-neutralizer and Carbopol-surfactant interactions vary...

  14. Evidence for pressure-release melting beneath magmatic arcs from basalt at Galunggung, Indonesia

    Science.gov (United States)

    Sisson, T.W.; Bronto, S.

    1998-01-01

    The melting of peridotite in the mantle wedge above subduction zones is generally believed to involve hydrous fluids derived from the subducting slab. But if mantle peridotite is upwelling within the wedge, melting due to pressure release could also contribute to magma production. Here we present measurements of the volatile content of primitive magmas from Galunggung volcano in the Indonesian are which indicate that these magmas were derived from the pressure-release melting of hot mantle peridotite. The samples that we have analysed consist of mafic glass inclusions in high-magnesium basalts. The inclusions contain uniformly low H2O concentrations (0.21-0.38 wt%), yet relatively high levels of CO2 (up to 750 p.p.m.) indicating that the low H2O concentrations are primary and not due to degassing of the magma. Results from previous anhydrous melting experiments on a chemically similar Aleutian basalts indicate that the Galunggung high-magnesium basalts were last in equilibrium with peridotite at ~1,320 ??C and 1.2 GPa. These high temperatures at shallow sub-crustal levels (about 300-600 ??C hotter than predicted by geodynamic models), combined with the production of nearly H2O- free basaltic melts, provide strong evidence that pressure-release melting due to upwelling in the sub-are mantle has taken place. Regional low- potassium and low-H2O (ref. 5) basalts found in the Cascade are indicate that such upwelling-induced melting can be widespread.

  15. Carbon Monoxide Silicate Reduction System Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The Carbon Monoxide Silicate Reduction System (COSRS) is a novel technology for producing large quantities of oxygen on the Moon. Oxygen yields of 15 kilograms per...

  16. Carbon Monoxide Silicate Reduction System Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The Carbon Monoxide Silicate Reduction System (COSRS) is an innovative method that for the first time uses the strong reductant carbon monoxide to both reduce iron...

  17. Characterization of silicate/Si(001) interfaces

    Science.gov (United States)

    Copel, M.; Cartier, E.; Narayanan, V.; Reuter, M. C.; Guha, S.; Bojarczuk, N.

    2002-11-01

    Many of the proposed high permittivity gate dielectrics for silicon-based microelectronics rely on a stack configuration, with an SiO2 buffer layer to provide an interface. We describe a means for creating gate dielectrics with a direct yttrium silicate-silicon interface through the solid-state reaction of yttria and silicon oxynitride, avoiding the preparation of an oxide-free silicon surface. Characterization by medium-energy ion scattering indicates complete consumption of the underlying oxide through silicate formation during high-temperature annealing. Furthermore, the silicate dielectric exhibits small flat-band voltage shifts, indicating low quantities of charge, without passivation steps. Creation of a silicate-silicon interfaces by a simple route may enable the study of an alternate class of dielectrics.

  18. Effects of water, depth and temperature on partial melting of mantle-wedge fluxed by hydrous sediment-melt in subduction zones

    Science.gov (United States)

    Mallik, Ananya; Dasgupta, Rajdeep; Tsuno, Kyusei; Nelson, Jared

    2016-12-01

    This study investigates the partial melting of variable bulk H2O-bearing parcels of mantle-wedge hybridized by partial melt derived from subducted metapelites, at pressure-temperature (P-T) conditions applicable to the hotter core of the mantle beneath volcanic arcs. Experiments are performed on mixtures of 25% sediment-melt and 75% fertile peridotite, from 1200 to 1300 °C, at 2 and 3 GPa, with bulk H2O concentrations of 4 and 6 wt.%. Combining the results from these experiments with previous experiments containing 2 wt.% bulk H2O (Mallik et al., 2015), it is observed that all melt compositions, except those produced in the lowest bulk H2O experiments at 3 GPa, are saturated with olivine and orthopyroxene. Also, higher bulk H2O concentration increases melt fraction at the same P-T condition, and causes exhaustion of garnet, phlogopite and clinopyroxene at lower temperatures, for a given pressure. The activity coefficient of silica (ϒSiO2) for olivine-orthopyroxene saturated melt compositions (where the activity of silica, aSiO2 , is buffered by the reaction olivine + SiO2 = orthopyroxene) from this study and from mantle melting studies in the literature are calculated. In melt compositions generated at 2 GPa or shallower, with increasing H2O concentration, ϒSiO2 increases from transition from non-ideal mixing as OH- in the melt (ϒSiO2 2 GPa, ϒSiO2 >1 at higher H2O concentrations in the melt, indicate requirement of excess energy to incorporate molecular H2O in the silicate melt structure, along with a preference for bridging species and polyhedral edge decorations. With vapor saturation in the presence of melt, ϒSiO2 decreases indicating approach towards ideal mixing of H2O in silicate melt. For similar H2O concentrations in the melt, ϒSiO2 for olivine-orthopyroxene saturated melts at 3 GPa is higher than melts at 2 GPa or shallower. This results in melts generated at 3 GPa being more silica-poor than melts at 2 GPa. Thus, variable bulk H2O and pressure of

  19. Anhydrous proton conducting materials based on sulfonated dimethylphenethylchlorosilane grafted mesoporous silica/ionic liquid composite.

    Science.gov (United States)

    Amiinu, Ibrahim Saana; Liang, Xinmiao; Tu, Zhengkai; Zhang, Haining; Feng, Jiwen; Wan, Zhongmin; Pan, Mu

    2013-11-27

    Efficient membrane proton conductivity at elevated temperatures (>100 °C) and reduced humidification conditions is a critical issue hindering fuel cell commercialization. Herein, proton conducting materials consisting of high surface area acid catalyzed mesoporous silica functionalized with sulfonated dimethylphenethylchlorosilane was investigated under anhydrous conditions. The organic moiety covalently bonded to the silica substrate via active hydroxyl groups on the silica pore surface. The structure and dynamic phases of the attached organic molecule were characterized and qualitatively determined by XRD, TEM, FT-IR, and solid state NMR. The amount of grafted organic molecules was estimated to be 2.45 μmol m(-2) by carbon elemental analysis. The so-formed composite materials showed adequate thermal stability up to 300 °C as determined by TGA. Under anhydrous conditions, ionic conductivity of the composite material upon ionic liquid impregnation reaches a peak value of 1.14 × 10(-2) S cm(-1) at 160 °C associated with the activation energy of 9.24 kJ mol(-1) for proton transport.

  20. Anhydrous ethanol production in sugar mills; Produccion de etanol anhidro en ingenios azucareros

    Energy Technology Data Exchange (ETDEWEB)

    Enriquez Poy, Manuel. E-mail:poymanuel@prodigy.net.mx

    2007-04-15

    The anhydrous ethanol production is recent and limited, because the disadvantage of the renewable energies is the economic impossibility of the projects. Nevertheless, there are aspects to consider to achieve the anhydrous ethanol production, among which are: the cost of the raw material, the self-sufficiency of energy from the sugar cane bagasse without the need of oil burning, the larger size of the distilleries, incorporation of the Cogeneration with delivery of electricity to the public network in the sugar mill facilities, the introduction of the biotechnology to improve the processes of fermentation and subsidies to agriculture. [Spanish] La produccion de etanol anhidro es reciente y limitada, debido a que la desventaja de las energias renovables es la inviabilidad economica de los proyectos. Sin embargo hay aspectos a considerar para lograr la produccion de etanol anhidro, entre los cuales estan: el costo de la materia prima, la autosuficiencia energetica a partir del bagazo de la cana sin necesidad de petroleo, mayor tamano de las destilerias, incorporacion de la Cogeneracion con entrega de electricidad a la red publica en el ingenio, la introduccion de la biotecnologia para mejorar los procesos de fermentacion y subsidios a la agricultura.

  1. Structural and Theoretical Investigation of Anhydrous 3,4,5-Triacetoxybenzoic Acid.

    Directory of Open Access Journals (Sweden)

    Paulo S Carvalho

    Full Text Available A comprehensive investigation of anhydrous form of 3,4,5-Triacetoxybenzoic acid (TABA is reported. Single crystal X-ray diffraction, Thermal analysis, Fourier Transform Infrared spectroscopy (FTIR and DFT calculations were applied for TABA characterization. This anhydrous phase crystallizes in the triclinic [Formula: see text] space group (Z' = 1 and its packing shows a supramolecular motif in a classical [Formula: see text] ring formed by acid-acid groups association. The phase stability is accounted in terms of supramolecular architecture and its thermal behaviour. Conformation search at B3LYP/6-311++G(2d,p level of theory shows the existence of three stable conformers and the most stable conformation was found experimentally. The reactivity of TABA was investigated using the molecular orbital theory and molecular electrostatic potential. The calculation results were used to simulate the infrared spectrum. There is a good agreement between calculated and experimental IR spectrum, which allowed the assignment of the normal vibrational modes.

  2. A kinetic study of non-isothermal decomposition process of anhydrous nickel nitrate under air atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Jankovic, B., E-mail: bojanjan@ffh.bg.ac.r [Faculty of Physical Chemistry, University of Belgrade, Studentski Trg 12-16, P. O. Box 137, 11001 Belgrade (Serbia); Mentus, S. [Faculty of Physical Chemistry, University of Belgrade, Studentski Trg 12-16, P. O. Box 137, 11001 Belgrade (Serbia); Jelic, D. [Faculty of Medicine, University of Banja Luka, 78000 Banja Luka (Bosnia and Herzegowina)

    2009-08-01

    The non-isothermal decomposition process of anhydrous nickel nitrate under air atmosphere was investigated. The kinetic analysis of decomposition process was performed using Friedman (FR), Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) isoconversional methods. The kinetic model was determined by the Malek's method. The composite differential method I was used for checking the established reaction model. It was found that the value of E{sub a} calculated by composite differential method (E{sub a}=147.1 kJ mol{sup -1}) represents the medium value between the values of the apparent activation energy calculated by FR (E{sub a,FR}=152.8 kJ mol{sup -1}) and FWO (E{sub a,FWO}=143.1 kJ mol{sup -1}) methods. Using two special functions (y(alpha) and z(alpha)), it was found that the two-parameter autocatalytic model (Sestak-Berggren (SB) kinetic model) with kinetic exponents M=0.23 and N=1.14 is the most adequate one to describe the decomposition kinetics of the studied system at various heating rates. The obtained non-isothermal differential conversion curves from the experimental data show the results being accordant with those theoretically calculated. It was concluded that the SB kinetic model can be used for a quantitative description of non-isothermal decomposition process of anhydrous nickel nitrate which involves the partially overlapping nucleation and growth phases.

  3. Polyelectrolyte microcapsules as ionic liquid reservoirs within ionomer membrane to confer high anhydrous proton conductivity

    Science.gov (United States)

    Zhang, Haoqin; Wu, Wenjia; Li, Yifan; Liu, Yong; Wang, Jingtao; Zhang, Bing; Liu, Jindun

    2015-04-01

    Herein, novel composite membranes are prepared by embedding methacrylic acid polyelectrolyte microcapsules (PMCs) into sulfonated poly(ether ether ketone) (SPEEK) matrix, followed by impregnating imidazole-type ionic liquids (ILs). Within the composite membrane, the lumens of PMCs act as IL reservoirs, which provide large space for IL storage and thus significantly elevate the IL uptake. The IL leaching measurement suggests that the cross-linked shells of PMCs manipulate the IL release, endowing the composite membrane with high IL retention. Moreover, the high IL retention renders the composite membrane more anhydrous hopping sites (e.g., the imidazole groups on IL and the acid-base pairs between imidazole and sulfonic acid groups), imparting a facilitated proton conduction via Grotthuss mechanism. In particular, the composite membrane containing 12% PMCs achieves a high anhydrous proton conductivity of 33.7 mS cm-1 at 150 °C. The same membrane also exhibits a surprising steady-state IL retention of 36.9% after leaching in liquid water.

  4. Intrinsic luminescence of alkali silicate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Arbuzov, V.I.; Grabovskis, V.Y.; Tolstoi, M.N.; Vitol, I.K.

    1986-09-01

    This study obtains additional information on L centers and their role in electron excitation and intrinsic luminescence of a whole series. (Li, Na, K, Rb, and Cs) of alkali silicate glasses. The authors compare the features of the interaction with radiation of specimens of glass and crystal of a similar chemical composition, since silicates of alkali metals can be obtained in both the glassy and crystalline states.

  5. Experimental Determination of Spinel/Melt, Olivine/Melt, and Pyroxene/Melt Partition Coefficients for Re, Ru, Pd, Au, and Pt

    Science.gov (United States)

    Righter, K.; Campbell, A. J.; Humayun, M.

    2003-01-01

    Experimental studies have identified spinels as important hosts phases for many of the highly siderophile elements (HSE). Yet experimental studies involving chromite or Cr-rich spinel have been lacking. Experimental studies of partitioning of HSEs between silicate, oxides and silicate melt are plagued by low solubilities and the presence of small metallic nuggets at oxygen fugacities relevant to magmas, which interfere with analysis of the phases of interest. We have circumvented these problems in two ways: 1) performing experiments at oxidized conditions, which are still relevant to natural systems but in which nuggets are not observed, and 2) analysis of run products with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), allowing a combination of high sensitivity and good spatial resolution.

  6. Structural characterization of anhydrous naloxone- and naltrexone hydrochloride by high resolution laboratory X-ray powder diffraction and thermal analysis.

    Science.gov (United States)

    Sugimoto, Kunihisa; Dinnebier, Robert E; Zakrzewski, Marek

    2007-12-01

    The crystal structures of the analgesic compounds anhydrous naloxone and naltrexone hydrochloride were determined ab initio from high resolution laboratory X-ray powder diffraction data. Both compounds crystallize in the orthorhombic space group P2(1)2(1)2(1) with lattice parameters of a = 14.6588(10) A, b = 17.4363(9) A, c = 7.96200(22) A, and V = 2035.06(23) A(3) for naloxone hydrochloride and a = 15.4560(5) A, b = 14.9809(4) A, c = 7.84121(18) A, and V = 1815.58(11) A(3) for naltrexone hydrochloride. The crystal structure of anhydrous naloxone hydrochloride forms one-dimensional chains through hydrogen bonds. In the crystal structure of anhydrous naltrexone hydrochloride, two-dimensional sheets are formed by hydrogen bonds. The dehydration processes of naloxone hydrochloride dehydrate and naltrexone hydrochloride tetrahydrate was analyzed by DTA, DSC, TG, and MG.

  7. Thermodynamics and Kinetics of Silicate Vaporization

    Science.gov (United States)

    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.

  8. Determination of Reactive Surface Area of Melt Glass

    Energy Technology Data Exchange (ETDEWEB)

    Bourcier,W.L.; Roberts, S.; Smith, D.K.; Hulsey, S.; Newton,L.; Sawvel, A.; Bruton, C.; Papelis, C.; Um, W.; Russell, C. E.; Chapman,J.

    2000-10-01

    A comprehensive investigation of natural and manmade silicate glasses, and nuclear melt glass was undertaken in order to derive an estimate of glass reactive surface area. Reactive surface area is needed to model release rates of radionuclides from nuclear melt glass in the subsurface. Because of the limited availability of nuclear melt glasses, natural volcanic glass samples were collected which had similar textures and compositions as those of melt glass. A flow-through reactor was used to measure the reactive surface area of the analog glasses in the presence of simplified NTS site ground waters. A measure of the physical surface area of these glasses was obtained using the BET gas-adsorption method. The studies on analog glasses were supplemented by measurement of the surface areas of pieces of actual melt glass using the BET method. The variability of the results reflect the sample preparation and measurement techniques used, as well as textural heterogeneity inherent to these samples. Based on measurements of analog and actual samples, it is recommended that the hydraulic source term calculations employ a range of 0.001 to 0.01 m{sup 2}/g for the reactive surface area of nuclear melt glass.

  9. Optical absorption and fluorescent behaviour of titanium ions in silicate glasses

    Indian Academy of Sciences (India)

    Manoj Kumar; Aman Uniyal; A P S Chauhan; S P Singh

    2003-04-01

    Titanium in normal melting conditions in air atmosphere present as Ti4+ ion in basic silicate glasses exhibited an ultra-violet cut-off in silicate glasses, viz. soda–magnesia–silica, soda–magnesia–lime–silica and soda–lime–silica glasses. This indicates that Ti4+ ion can be a good replacement for Ce4+ ion in producing UV-absorbing silicate glasses for commercial applications. The wavelength maxima at which the infinite absorption takes place in glasses was found to be around 310 nm against Ti-free blank glass in UV-region. The mechanism of electronic transition from O2- ligands to Ti4+ ion was suggested as L $\\rightarrow$ M charge transfer. The low energy tails of the ultra-violet cut-off were found to obey Urbach’s rule in the optical range 360–500 nm. The fluorescence spectra of these glasses were also studied and based on the radiative fluorescent properties it was suggested that the soda–lime–silica glass containing Ti4+ ion with greater emission crosssection would emit a better fluorescence than the corresponding soda–magnesia–lime–silica and soda–magnesia–silica glasses. The shift of emission wavelengths maxima towards longer wavelength in titania introduced silicate glasses was observed on replacement of MgO by CaO which may be attributed due to an increase in basicity of the glass system.

  10. Raman spectra and structure study of silicate glasses and their liquids

    Institute of Scientific and Technical Information of China (English)

    YOU Jinglin; JIANG Guochang; CHEN Hui; XU Kuangdi

    2006-01-01

    Stress index of tetrahedron (SIT) was defined to describe the topological connectivities among various silicon-oxygen tetrahedra (SiOT) in anionic clusters of binary silicate crystals, glasses, and melts. It was found that the value of SIT was well correlated with the wavenumber of Raman active symmetric stretching vibration of non-bridging oxygen of SiOT. The spatial fractional dimension of hyperfine structure was introduced while comparative analysis was made with the value of SIT. It can be concluded that the concepts of SIT, vibrational wavenumber, and spatial fractional dimension were inherently and holographically correlated and exhibit isomorphic representations of complex structure of binary silicates.Experimental Raman spectra of binary silicates with different alkali cations were investigated. It was demonstrated that alkali cations have little effect on the vibrational wavenumber of symmetric stretching of non-bridging oxygen (NBO) of SiOT, but remarkably affect its Raman active optical cross section, as was consensus resulted from ab initio calculation. It can also be concluded that the spatial fractional dimension of binary silicate is predominantly determined by the hyperfine structure of the anionic clusters and little affected by alkali cations, although the species of anionic clusters and their distributions were originally assigned by the content of alkali oxides. And Raman optical activity extinct effect of isolated SiOT at high basicity should be considered while being applied to quantitatively analysis.

  11. (2) H/(1) H measurements of amphiboles and nominally anhydrous minerals (clinopyroxene, garnetand diamond)usinghigh-temperatureCF-EA-PY-IRMS.

    Science.gov (United States)

    Fourel, François; Lécuyer, Christophe; Demeny, Attila; Boulvais, Philippe; Lange, Lutz; Jacob, Dorrit E; Kovacs, Istvan

    2017-09-20

    We have used ahigh-precision, high efficiency method for themeasurementof the(2) H/(1) H ratios of hydrous silicates (amphiboles) and nominally anhydrous minerals (NAM) such as clinopyroxene, garnet and diamond, which are usually extremely resistant to pyrolysis. This opens up new fields of investigation to better understand the conditionsof formation fordeep-Earth minerals. The technique described hereinvolvesIsotopic Ratio Mass Spectrometry (IRMS) online in continuous flow mode with an Elemental Analyzer (EA) using"purge and trap" technology rather than conventional packed column-GC gas separation. The system is equipped with a special high temperature furnace reaching 1500°C, with a longer hot zone and improved temperature stability. Emphasis is put on the efficiency of the system to reliably pyrolyserefractory minerals difficult to analyse with other conventional systems. While conventional systems usually fail to generate hydrogen suitable for isotopic analyses, with the technique presented here we were able to measure (2) H/(1) H ratios from 4diamond samples (δ(2) H= -60, -77, -84 and -79‰ V-SMOW; average SD =4.5‰; n=2),3 garnet samples (δ(2) Hfrom -70 to -63‰), and 9 clinopyroxenes (δ(2) H from -92 to -58‰) associated with7 amphiboles (δ(2) Hfrom -76 to -27‰) from single mantle rock. The possibility of using such a system to reliably measure (2) H/(1) H ratios from refractory minerals, which are usually extremely difficult to analyse, offers a new tool of investigation for giving us unrivaled clues to study the Earth's deep interiors. This article is protected by copyright. All rights reserved.

  12. Characteristics of melt inclusions in skarn minerals from Fe,Cu(Au) and Au(Cu) ore deposits in the region from Daye to Jiujiang

    Institute of Scientific and Technical Information of China (English)

    赵斌; 赵劲松; 李兆麟; 张重泽; 彭卓伦

    2003-01-01

    A vast amount of the melt inclusions and fluid-melt inclusions have been found in skarn minerals from Fe, Cu(Au) and Au(Cu) ore deposits distributed from Daye to Jiujiang along the Yangtze River besides vapor-liquid inclusions. The melt inclusions are many and varied in shape. They mainly consist of crystallized silicate phases (CSi), iron phases (Fe), amorphous silicate phases (ASi) and vapor (V) with different volume percentages, and some of them contain several crystallized silicate phases. These melt inclusion sizes are commonly (10-46)×(6-15) μm2. A difference between the fluid-melt inclusions and melt inclusions is that the liquid phase appears in the former and their homogenization temperatures are lower than the latter. We measured the homogenization temperatures of the melt inclusions, fluid-melt inclusions and fluid inclusions in ten thin sections from eight ore deposits on Leitz microscope heating stage 1350 which was made in Germany. Forty-eight homogenization temperature values have been obtained. Among them, thirty-nine values are homogenization temperatures of the melt inclusions in garnet and pyroxene from skarns, two values are homogenization temperatures of fluid-melt inclusions, others belong to the fluid inclusions. Melt inclusions in garnet and pyroxene have homogenization temperatures of 890-1115℃. Fluid-melt inclusions have homogenization temperatures of 745-750℃. Homogenization temperatures of fluid inclusions are between 580℃ and 675℃. The average of thirty- nine homogenization temperatures for the melt inclusions is 1029.9℃. Wethink studied skarns to be magmatic genesis on the basis of available data relative to the characteristic features of phase states within the melt inclusions and the fluid melt inclusions and their homogenization temperatures.

  13. Signatures of nonthermal melting

    Directory of Open Access Journals (Sweden)

    Tobias Zier

    2015-09-01

    Full Text Available Intense ultrashort laser pulses can melt crystals in less than a picosecond but, in spite of over thirty years of active research, for many materials it is not known to what extent thermal and nonthermal microscopic processes cause this ultrafast phenomenon. Here, we perform ab-initio molecular-dynamics simulations of silicon on a laser-excited potential-energy surface, exclusively revealing nonthermal signatures of laser-induced melting. From our simulated atomic trajectories, we compute the decay of five structure factors and the time-dependent structure function. We demonstrate how these quantities provide criteria to distinguish predominantly nonthermal from thermal melting.

  14. Ion Probe Study of Silicate Inclusions from Colomera (IIE) Iron Meteorite:the Rare Earth Element Perspective

    Institute of Scientific and Technical Information of China (English)

    HSU Weibiao

    2004-01-01

    Coupled with a petrographical study, I carried out an ion probe study of rare earth element microdistributions in mineral phases of silicate inclusions from the Colomera IIE iron meteorite. Most mineral grains have homogeneous REEs, but show considerable inter-grain variations by a factor of 2 to 100. The whole rock REE abundances for Colomera,estimated by combining REE data with modal abundances, are relatively LREE-enriched with REEs of ~10'CI, which suggest that Colomera silicates were highly differentiated and might represent a low degree partial melt (~10%) of a chondritic source. REE geochemistry of Colomera silicate inclusions points to an origin that involves differentiation,dynamic mixing, remelting, reduction, recrystallization, and subsequent rapid cooling near the surface of a planetary body.

  15. EFFECT OF AMPHIPHILIC POLY (STYRENE-B-ETHYLENE OXIDE) DIBLOCK COPOLYMER INTERCALATED LAYERED SILICATE AS FILLER ON ACRYLONITRILE-BUTADIENE-STYRENE RESIN

    Institute of Scientific and Technical Information of China (English)

    Guo Tianying; Zhang Jie; Hao Guangjie; Song Moudao; Zhang Banghua

    2003-01-01

    The diblock copolymers intercalated layered silicate was prepared via a melt dispersion technique. Then the effect of intercalated hybrid as filler on acrylonitrile- butadiene-styrene resin was characterized by X-ray diffraction, transmission electron microscopy, stress-strain measurements in elongation.

  16. Influence of silicate anions structure on desilication in silicate-bearing sodium aluminate solution

    Institute of Scientific and Technical Information of China (English)

    刘桂华; 张闻; 齐天贵; 彭志宏; 周秋生; 李小斌

    2016-01-01

    The structural changes of silicate anions in the desilication process with the addition of calcium hydrate alumino-carbonate were studied by measuring Raman spectra, infrared spectra and corresponding second derivative spectra. The results show that the desilication ratio in the solution prepared by the addition of sodium silicate (solution-SS) is much greater than that in the solution by the addition of green liquor (solution-GL), and low alumina concentration in the sodium aluminate solutions facilitates the desilication process. It is also shown that alumino-silicate anions in the solution-GL, and Q3 polymeric silicate anions in solution-SS are predominant, respectively. In addition, increasing the concentration of silica favors respectively the formation of the alumino-silicate or the Q3 silicate anions in the solution-GL or the solution-SS. Therefore, it can be inferred that the low desilication ratio in the silicate-bearing aluminate solution is mainly attributed to the existence of alumino-silicate anions.

  17. Seebeck effect influence on joule heat evolution in electrically conductive silicate materials

    Science.gov (United States)

    Fiala, Lukáš; Medved, Igor; Maděra, Jiří; Černý, Robert

    2016-07-01

    In general, silicate building materials are non-conductive matters that are not able to evolve heat when they are subjected to an external voltage. However, the electrical conductivity can be increased by addition of electrically conductive admixtures in appropriate amount which leads to generation of conductive paths in materials matrix. Such enhanced materials can evolve Joule heat and are utilizable as a core of self-heating or snow-melting systems. In this paper, Joule heat evolution together with Seebeck effect in electrically conductive silicate materials was taken into consideration and the model based on heat equation with included influence of DC electric field was proposed. Besides, a modeling example of heating element was carried out on FEM basis and time development of temperature in chosen surface points was expressed in order to declare ability of such system to be applicable.

  18. Ion-exchanged waveguide lasers in Er3+/Yb3+ codoped silicate glass.

    Science.gov (United States)

    Peters, P M; Funk, D S; Peskin, A P; Veasey, D L; Sanford, N A; Houde-Walter, S N; Hayden, J S

    1999-11-20

    We investigated an Er(3+)/Yb(3+) codoped silicate glass as a host material for waveguide lasers operating near 1.5 microm. Spectroscopic properties of the glass are reported. Waveguide lasers were fabricated by K(+)-ion exchange from a nitrate melt. The waveguides support a single transverse mode at 1.5 microm. An investigation of the laser performance as a function of the Yb:Er ratio was performed, indicating an optimal ratio of approximately 5:1. Slope efficiencies of as great as 6.5% and output powers as high as 19.6 mW at 1.54 microm were realized. The experimental results are compared with a waveguide laser model that is used to extract the Er(3+) upconversion coefficients and the Yb(3+)-Er(3+) cross-relaxation coefficients. The results indicate the possibility of obtaining high-performance waveguide lasers from a durable silicate host glass.

  19. Effect of Fe2O3 on the physical and structural properties of bismuth silicate glasses

    Science.gov (United States)

    Parmar, Rajesh; Kundu, R. S.; Punia, R.; Aghamkar, P.; Kishore, N.

    2013-06-01

    Iron containing bismuth silicate glasses with compositions 70SiO2ṡ(100-x)Bi2O3ṡxFe2O3 have been prepared using conventional melt-quenching method and their amorphous nature has been investigated using XRD. Density has been measured using Archimedes' principle and molar volume (Vm) have also been estimated. With increase in Fe2O3 content, there is a decrease in density and molar volume of the glass samples. The glass transition temperature (Tg) have been determined using Differential Scanning Calorimetry (DSC) and are observed to increase with increase in Fe2O3 content. In the present glass system bismuth and iron plays the role of network modifier and the symmetry of silicate network goes on increasing with Fe2O3 content and it modifies the physical and structural properties of these glasses.

  20. A Study of Ca-Mg Silicate Crystalline Glazes--An Analysis on Forms of Crystals

    Institute of Scientific and Technical Information of China (English)

    LIU Pei-de; YU Ping-li; WU Ji-huai

    2004-01-01

    In the study on Ca-Mg silicate crystalline glazes, we found some disequilibrated crystallization phenomena,such as non-crystallographic small angle forking and spheroidal growth, parasitism and wedging-form of crystals, dendritic growth, secondary nucleation, etc. Those phenomena possibly resulted from two factors:(1) partial temperature gradient, which is caused by heat asymmetry in the electrical resistance furnace,when crystals crystalize from silicate melt ; (2) constitutional supercooling near the surface of crystals. The disparity of disequilibrated crystallization phenomena in different main crystalline phases causes various morphological features of the crystal aggregates. At the same time, disequilibrated crystallization causes great stress retained in the crystals, which results in cracks in glazes when the temperature drops. According to the results, the authors analyzed those phenomena and displayed correlative figures and data.

  1. Multiphase solid inclusions in ultrahigh-pressure metamorphic rocks: A snapshot of anatectic melts during continental collision

    Science.gov (United States)

    Gao, Xiao-Ying; Chen, Yi-Xiang; Zhang, Qiang-Qiang

    2017-09-01

    Partial melting of crustal rocks may take place during continental collision, giving rise to anatectic melts. Their composition and evolution are major concerns in the chemical geodynamics of continental subduction zones. They are often recorded by multiphase solid (MS) inclusions enclosed by peritectic minerals in ultrahigh-pressure (UHP) metamorphic terranes inside collisional orogens. These MS inclusions generally show negative crystal shapes with the wedge-shaped off-shoot structure in garnet, omphacite and kyanite. They contain a number of silicate, carbonate and sulfate minerals such as K-feldspar, plagioclase, quartz, epidote, calcite and barite, with occasional occurrences of magnetite, zircon and pyrite. An integrated study of petrology, mineralogy and geochemistry indicates that the MS inclusions are the primary crystallization product of former silicate and carbonate melts. The silicate melts were derived from dehydration melting of hydrous minerals such as phengite and paragonite in UHP metamorphic rocks, and the carbonate melts were produced by partial melting of subducted carbonate minerals. Some MS inclusions show remarkably high Na contents, suggesting their derivation from dehydration melting of paragonite. In contrast, K-bearing MS inclusions are produced by dehydration melting of K-bearing hydrous minerals like phengite. Many studies have been devoted to the mineralogical and geochemical compositions of MS inclusions in UHP metamorphic rocks, with the aim to determine the time and mechanism of crustal anataxis during collisional orogeny. Various analytical methods were used to characterize the morphology, texture, mineral chemistry and trace element composition of MS inclusions. The results provide insights into the physicochemical properties of anatectic melts in continental subduction zones. The partial melting of deeply subducted crustal rocks would lead to their significant differentiation in lithochemistry and geochemistry. This process has

  2. Siderophile elements in the upper mantle of the Earth: New clues from metal-silicate partition coefficients

    Science.gov (United States)

    Holzheid, A.; Borisov, A.; Palme, H.

    1993-01-01

    New, precise data on the solubilities of Ni, Co, and Mo in silicate melts at 1400 C and fO2 from IW to IW-2 are presented. The results suggest NiO, CoO as stable species in the melt. No evidence for metallic Ni or Co was found. Equilibrium was ensured by reversals with initially high Ni and Co in the glass. Mo appears to change oxidation state at IW-1, from MoO3 to MoO2. Metal-silicate partition coefficients calculated from these data and recent data on Pd indicate similar partition coefficients for Pd and Mo at the conditions of core formation. This unexpected result constrains models of core formation in the Earth.

  3. Melt Cast High Explosives

    Directory of Open Access Journals (Sweden)

    Stanisław Cudziło

    2014-12-01

    Full Text Available [b]Abstract[/b]. This paper reviews the current state and future developments of melt-cast high explosives. First the compositions, properties and methods of preparation of trinitrotoluene based (TNT conventional mixtures with aluminum, hexogen (RDX or octogen (HMX are described. In the newer, less sensitive explosive formulations, TNT is replaced with dinitroanisole (DNANDNANDNAN and nitrotriazolone (NTONTONTO, nitroguanidine (NG or ammonium perchlorate (AP are the replacement for RDRDX and HMX. Plasticized wax or polymer-based binder systems for melt castable explosives are also included. Hydroxyl terminated polybutadiene (HPTB is the binder of choice, but polyethylene glycol, and polycaprolactone with energetic plasticizers are also used. The most advanced melt-cast explosives are compositions containing energetic thermoplastic elastomers and novel highly energetic compounds (including nitrogen rich molecules in whose particles are nanosized and practically defect-less.[b]Keywords[/b]: melt-cast explosives, detonation parameters

  4. Melting of sodium clusters

    CERN Document Server

    Reyes-Nava, J A; Beltran, M R; Michaelian, K

    2002-01-01

    Thermal stability properties and the melting-like transition of Na_n, n=13-147, clusters are studied through microcanonical molecular dynamics simulations. The metallic bonding in the sodium clusters is mimicked by a many-body Gupta potential based on the second moment approximation of a tight-binding Hamiltonian. The characteristics of the solid-to-liquid transition in the sodium clusters are analyzed by calculating physical quantities like caloric curves, heat capacities, and root-mean-square bond length fluctuations using simulation times of several nanoseconds. Distinct melting mechanisms are obtained for the sodium clusters in the size range investigated. The calculated melting temperatures show an irregular variation with the cluster size, in qualitative agreement with recent experimental results. However, the calculated melting point for the Na_55 cluster is about 40 % lower than the experimental value.

  5. Force induced DNA melting

    Energy Technology Data Exchange (ETDEWEB)

    Santosh, Mogurampelly; Maiti, Prabal K [Center for Condensed Matter Theory, Department of Physics, Indian Institute of Science, Bangalore-12 (India)], E-mail: santosh@physics.iisc.ernet.in, E-mail: maiti@physics.iisc.ernet.in

    2009-01-21

    When pulled along the axis, double-strand DNA undergoes a large conformational change and elongates by roughly twice its initial contour length at a pulling force of about 70 pN. The transition to this highly overstretched form of DNA is very cooperative. Applying a force perpendicular to the DNA axis (unzipping), double-strand DNA can also be separated into two single-stranded DNA, this being a fundamental process in DNA replication. We study the DNA overstretching and unzipping transition using fully atomistic molecular dynamics (MD) simulations and argue that the conformational changes of double-strand DNA associated with either of the above mentioned processes can be viewed as force induced DNA melting. As the force at one end of the DNA is increased the DNA starts melting abruptly/smoothly above a critical force depending on the pulling direction. The critical force f{sub m}, at which DNA melts completely decreases as the temperature of the system is increased. The melting force in the case of unzipping is smaller compared to the melting force when the DNA is pulled along the helical axis. In the case of melting through unzipping, the double-strand separation has jumps which correspond to the different energy minima arising due to sequence of different base pairs. The fraction of Watson-Crick base pair hydrogen bond breaking as a function of force does not show smooth and continuous behavior and consists of plateaus followed by sharp jumps.

  6. Infrared spectroscopy and hydrogen isotope geochemistry of hydrous silicate glasses. Progress report, June 1, 1996--May 31, 1999

    Energy Technology Data Exchange (ETDEWEB)

    Epstein, S.; Stolper, E.

    1998-06-01

    This DOE-funded project (DE-FG03-ER13445, 6/1/96-5/31/99) emphasizes study of the behavior of volatiles in magmatic systems. The project is explicitly focused on the combined application of IR spectroscopy, experimental petrology, and stable isotope geochemistry to understanding the behavior and properties of the volatile components dissolved in silicate melts and glasses, although in recent years, our emphasis has broadened to include non-volatile aspects of stable isotope geochemistry. Results obtained during the current grant and previous grant periods confirm that when applied to study of well-chosen synthetic and natural systems, the combination of these approaches and techniques can yield insights of general petrological and volcanological value and of practical value to DOE. In particular, the results of our DOE-funded work has led to a deeper understanding of the physical chemistry of silicate melts as well as specific constraints on the thermal and chemical evolution of high-level magmatic systems of the sort being evaluated as potential geothermal and magmathermal energy sources. Moreover, our work has also contributed to understanding the behavior of H-, C-, and O-bearing species in amorphous and crystalline silicates, including the kinetics of their interactions; we believe these results will contribute to efforts to use silicates in the development of nuclear waste disposal strategies.

  7. Highly Efficient and Versatile Synthesis of Some Important Precursors from 1,6-Anhydrous-β-D-glucopyranose as a Green Starting Material

    Institute of Scientific and Technical Information of China (English)

    WEI Guohua; CAI Chao; DU Yuguo

    2009-01-01

    Some important precursors (1,6-anhydrous-2-deoxy-2-azido-β-D-glucopyranose (3),1,6-anhydrous-2-deoxy-2-azido-3,4-di-O-benzyl-β-D-mannopyranose (5), 1,6:2,3-dianhydrouso-β-D-glucopyranose (6), 1,6-anhydrous-3-deoxy-3-azido-β-D-glucopyranose (10) and 1,6-anhydrous-2,4-di-O-benzoyl-β-D-glucopyranose (11)) for complex oligosaccharide synthesis were readily prepared from a green starting material 1,6-anhydrous-β-D-glucopyranose in one or two steps with moderate to high yields.These improved methods established herein will greatly facilitate the assembly of some complex oligosaccharides for the biological study.

  8. Detection of anhydrous hydrochloric acid, HCl, in IRC+10216 with the Herschel SPIRE and PACS spectrometers

    CERN Document Server

    Cernicharo, J; Barlow, M J; Agundez, M; Royer, P; Vandenbussche, B; Wesson, R; Polehampton, E T; De Beck, E; Blommaert, J A D L; Daniel, F; De Meester, W; Exter, K M; Feuchtgruber, H; Gear, W K; Goicoechea, J R; Gomez, H L; Groenewegen, M A T; Hargrave, P C; Huygen, R; Imhof, P; Ivison, R J; Jean, C; Kerschbaum, F; Leeks, S J; Lim, T L; Matsuura, M; Olofsson, G; Posch, T; Regibo, S; Savini, G; Sibthorpe, B; Swinyard, B M; Vandenbussche, B; Waelkens, C

    2010-01-01

    We report on the detection of anhydrous hydrochloric acid (hydrogen chlorine, HCl) in the carbon-rich star IRC+10216 using the spectroscopic facilities onboard the Herschel satellite. Lines from J=1-0 up to J=7-6 have been detected. From the observed intensities, we conclude that HCl is produced in the innermost layers of the circumstellar envelope with an abundance relative to H2 of 5x10^-8 and extends until the molecules reach its photodissociation zone. Upper limits to the column densities of AlH, MgH, CaH, CuH, KH, NaH, FeH, and other diatomic hydrides have also been obtained.

  9. SIMULATION OF THE DISTILLATION BY PRESSURE REDUCTION TO OBTAIN ANHYDROUS ETHANOL

    Directory of Open Access Journals (Sweden)

    Yeney Lauzurique Guerra

    2016-10-01

    Full Text Available In this work the distillation by pressure reduction was evaluated through the HYSYS v3.2 process simulator. Due to the lack of data in the consulted bibliography to perform the simulation, the STATGRAPHICS Centurion XVI software was used to obtain a response surface that would define optimal operating conditions. The property package selected to work was based on the Margules model. An anhydrous ethanol molar composition of 0.9917 was obtained. Temperature profiles were analyzed as well as liquid and vapor molar flows and dehydration column composition profiles. The influence of operating parameters on the efficiency of simulated technology was determined by analyzing one case study. According to economic evaluation, the implementation of this technology is not economically profitable; taking into account current prices and costs mostly due to high energy consumption and construction costs of the tower. This result contributes to the pursuit of other profitable technologies from the economic point of view.

  10. Correlated Nitrogen And Carbon Anomalies In An Anhydrous Interplanetary Dust Particles

    Energy Technology Data Exchange (ETDEWEB)

    Floss, C; Stadermann, F J; Bradley, J; Dai, Z; Graham, G

    2003-10-31

    Given the ubiquitous presence of H and N isotopic anomalies in interplanetary dust particles (IDPs) and their probable association with carbonaceous material, the lack of similar isotopic anomalies in C has been a major conundrum. We report here the first observation of correlated N and C isotopic anomalies in organic matter from an anhydrous non-cluster IDP. The {sup 15}N composition of the anomalous region is the highest seen to date in an IDP and is accompanied by a moderate depletion in {sup 13}C. Theoretical models suggest that low temperature formation of organic compounds in cold interstellar molecular clouds does produce C and N fractionations, but it remains to be seen if these models can reproduce the specific effects we observe here.

  11. Distribution and recovery of nitrogen-15-labeled liquid anhydrous ammonia among various soil fractions

    Energy Technology Data Exchange (ETDEWEB)

    Norman, R.J.; Kurtz, L.T.; Stevenson, F.J.

    Since liquid anhydrous ammonia (LAA) is a major N fertilizer, information was sought about the proportions of LAA that enter into various combinations in soils. Liquid anhydrous NH/sub 3/, labeled with /sup 15/N was injected into three soils (Drummer, Typic Haplaquoll; Blount, Aeric Ochraqualf; Cisne, Mollic Albaqualf) in the laboratory at a rate equivalent to a field application of 206 kg N ha /sup 1/ in 76.2 cm knife-spacings. At 1, 7, 14, 28, 56, and 112 d after application, fertilizer N present in different soil fractions was determined in five concentric zones with radii of 0 to 1.5, 1.5 to 3.0, 3.0 to 4.5, 4.5 to 6.0, and 6.0 to 7.0 cm around the point of application. Depending on the soil, from 68 to 83% of the applied /sup 15/N was accounted for as (exchangeable NH/sub 4//sup +/ + NO/sub 3//sup -/ + NO/sub 2//sup -/)-N by the 112th day following application, the remainder being accounted for as clay-fixed NH/sub 4//sup +/ (1.9-4.9%), organic matter-fixed NH/sub 3/ (4.0-6.0%), and biologically immobilized organic N (3.9-9.3%). From 50 to 70% of the organic matter-fixed NH/sub 3/-N was released by hydrolysis with dilute KOH solution as compared to 10 to 15% for the immobilized N. Total recovery of /sup 15/N at 112 d ranged from 77% for the Cisne soil to about 97% for the Drummer and Blount soils. Lateral distributions and transformations of NH/sub 4//sup +/ and NO/sub 3//sup -/ and pH trends after LAA applications were similar to those reported by previous investigators.

  12. Effects of coffee and caffeine anhydrous on strength and sprint performance.

    Science.gov (United States)

    Trexler, Eric T; Smith-Ryan, Abbie E; Roelofs, Erica J; Hirsch, Katie R; Mock, Meredith G

    2016-09-01

    Caffeine and coffee are widely used among active individuals to enhance performance. The purpose of the current study was to compare the effects of acute coffee (COF) and caffeine anhydrous (CAF) intake on strength and sprint performance. Fifty-four resistance-trained males completed strength testing, consisting of one-rep max (1RM) and repetitions to fatigue (RTF) at 80% of 1RM for leg press (LP) and bench press (BP). Participants then completed five, 10-second cycle ergometer sprints separated by one minute of rest. Peak power (PP) and total work (TW) were recorded for each sprint. At least 48 hours later, participants returned and ingested a beverage containing CAF (300 mg flat dose; yielding 3-5 mg/kg bodyweight), COF (8.9 g; 303 mg caffeine), or placebo (PLA; 3.8 g non-caloric flavouring) 30 minutes before testing. LP 1RM was improved more by COF than CAF (p = .04), but not PLA (p = .99). Significant interactions were not observed for BP 1RM, BP RTF, or LP RTF (p > .05). There were no sprint × treatment interactions for PP or TW (p > .05). 95% confidence intervals revealed a significant improvement in sprint 1 TW for CAF, but not COF or PLA. For PLA, significant reductions were observed in sprint 4 PP, sprint 2 TW, sprint 4 TW, and average TW; significant reductions were not observed with CAF or COF. Neither COF nor CAF improved strength outcomes more than PLA, while both groups attenuated sprint power reductions to a similar degree. Coffee and caffeine anhydrous may be considered suitable pre-exercise caffeine sources for high-intensity exercise.

  13. Composite polymer electrolyte containing ionic liquid and functionalized polyhedral oligomeric silsesquioxanes for anhydrous PEM applications.

    Science.gov (United States)

    Subianto, Surya; Mistry, Mayur K; Choudhury, Namita Roy; Dutta, Naba K; Knott, Robert

    2009-06-01

    A new type of supported liquid membrane was made by combining an ionic liquid (IL) with a Nafion membrane reinforced with multifunctional polyhedral oligomeric silsesquioxanes (POSSs) using a layer-by-layer strategy for anhydrous proton-exchange membrane (PEM) application. The POSS was functionalized by direct sulfonation, and the sulfonated POSS (S-POSS) was incorporated into Nafion 117 membranes by the infiltration method. The resultant hybrid membrane shows strong ionic interaction between the Nafion matrix and the multifunctional POSS, resulting in increased glass transition temperature and thermal stability at very low loadings of S-POSS (1%). The presence of S-POSS has also improved the proton conductivity especially at low humidities, where it shows a marked increase due to its confinement in the ionic domains and promotes water uptake by capillary condensation. In order to achieve anhydrous conductivity, the IL 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMI-BTSI) was incorporated into these membranes to provide proton conduction in the absence of water. Although the incorporation of an IL shows a plasticizing effect on the Nafion membrane, the S-POSS composite membrane with an IL shows a higher modulus at high temperatures compared to Nafion 117 and a Nafion-IL membrane, with significantly higher proton conductivity (5 mS/cm at 150 degrees C with 20% IL). This shows the ability of the multifunctional POSS and IL to work symbiotically to achieve the desirable proton conductivity and mechanical properties of such membranes by enhancing the ionic interaction within the material.

  14. Crystal structure of aspartame anhydrate from powder diffraction data. Structural aspects of the dehydration process of aspartame

    NARCIS (Netherlands)

    Guguta, C.; Meekes, H.L.M.; Gelder, R. de

    2006-01-01

    Aspartame has three pseudo-polymorphic forms, two hydrates and a hemi-hydrate, for which crystal structures were determined from single-crystal diffraction data. This paper presents the crystal structure of the anhydrate, which was obtained by dehydrating the hemi-hydrate. The crystal structure of a

  15. Anhydrous ZnCl2: A Highly Efficient Reagent for Facile and Regioselective Conversion of Epoxides to β-Chlorohydrins

    Directory of Open Access Journals (Sweden)

    Ronak Eisavi

    2016-01-01

    Full Text Available Facile conversion of structurally different epoxides to the corresponding β-chlorohydrins was carried out successfully with anhydrous ZnCl2 in CH3CN. The reactions were carried out within 10-50 min to give β-chlorohydrins with perfect regioselectivity and high yields (80-97%.

  16. Biomarker generation from Type II-S kerogens in claystone and limestone during hydrous and anhydrous pyrolysis

    NARCIS (Netherlands)

    Sinninghe Damsté, J.S.; Koopmans, M.P.; Carson, F.C.; Lewan, M.D.

    1998-01-01

    A claystone and a limestone containing immature Type II-S kerogen were thermally matured in the presence and absence of water, to study the influence of water and clay minerals on the generation of biomarkers. In contrast to hydrous pyrolysis, anhydrous pyrolysis of the claystone did not generate bi

  17. 75 FR 70687 - Storage and Handling of Anhydrous Ammonia Standard; Extension of the Office of Management and...

    Science.gov (United States)

    2010-11-18

    ... containers and systems to store and transfer anhydrous ammonia in the workplace. DATES: Comments must be... INFORMATION.'' Docket: To read or download comments or other material in the docket, go to http://www....g., copyrighted material) is not publicly available to read or download through the Web site....

  18. TEM and NanoSIMS Study of Hydrated/Anhydrous Phase Mixed IDPs: Cometary or Asteroidal Origin?

    Science.gov (United States)

    Nakamura, K.; Messenger, S.; Keller, L. P.

    2005-01-01

    Chondritic interplanetary dust particles (IDPs) are subdivided into (1) particles that form highly porous aggregates (chondritic porous "CP" IDPs), and (2) smooth particles ("CS" IDPs). Infrared (IR) spectroscopy has been a valuable tool for non-destructively determining the bulk mineralogy of IDPs. Most IDPs fall within three distinct IR groups: (1) olivine-rich particles, (2) pyroxene-rich particles, and (3) phyllosilicate-rich particles. From the IR studies, IDPs dominated by anhydrous minerals tend to be fine grained (CP), while phyllosilicate-rich IDPs are mostly CS. CP IDPs have been linked to cometary sources based on their compositions, spectral properties, and atmospheric entry velocities. Since no spectral signatures of hydrated minerals have been detected in comets, CS IDPs are thought to derive from primitive asteroids. Transmission electron microscopy (TEM) studies have revealed that the mineralogical distinctions between CP and CS IDPs are not always clear. Previous investigators have reported trace amounts of hydrous minerals in dominantly anhydrous particles. A better understanding of these particles will help to elucidate whether there is a genetic relationship between anhydrous and hydrated IDPs, provide insight into the earliest stages of aqueous alteration of primitive materials, and may help to determine whether comets have experienced any aqueous processing. Here we report a combined TEM and isotopic imaging study of an unusual anhydrous IDP with hydrated phases. Additional information is included in the original extended abstract.

  19. Zn isotopic heterogeneity in the mantle: A melting control?

    Science.gov (United States)

    Doucet, Luc S.; Mattielli, Nadine; Ionov, Dmitri A.; Debouge, Wendy; Golovin, Alexander V.

    2016-10-01

    We present new Zn elemental and isotope data on seventeen fertile and refractory mantle peridotite xenoliths. Eleven fertile peridotites are garnet and spinel lherzolites from Vitim and Tariat (Siberia and Mongolia) and represent some of the most pristine fertile peridotites available. Six refractory peridotites are spinel harzburgites from the Udachnaya kimberlite (Siberian craton) that are nearly pristine residues of high-degree polybaric melting at high pressure (7-4 GPa). Geochemical data suggest that Zn isotopic compositions in the peridotites have not been affected by post-melting processes such as metasomatism, contamination by the host-magmas or alteration. The fertile peridotites have uniform Zn concentrations (59 ± 2 ppm) and Zn isotopic compositions with δ66Zn (relative to JMC-Lyon-03-0749l) = +0.30 ± 0.03‰ consistent with the Bulk Silicate Earth estimates of δ66Zn = +0.28 ± 0.05‰ (Chen et al., 2013). The refractory peridotites have Zn concentrations ranging from 30 to 48 ppm and δ66Zn from + 0.10 ± 0.01 ‰ to + 0.18 ± 0.01 ‰ with an average of + 0.14 ± 0.03 ‰. Our data suggest that the lithospheric mantle has a heterogeneous Zn isotopic composition. Modeling of Zn isotope partitioning during partial melting of fertile mantle suggests that high degrees of melt extraction (>30%) may significantly fractionate Zn isotopes (up to 0.16‰) and that during mantle melting, Zn concentrations and isotopic compositions are mainly controlled by the stability of clinopyroxene and garnet within the melting residue. Because the stability of clinopyroxene and garnet is mainly pressure dependent we suggest that both the depth and the degrees of melt extraction may control Zn isotope fractionation during mantle melting.

  20. Self consistent model of core formation and the effective metal-silicate partitioning

    Science.gov (United States)

    Ichikawa, H.; Labrosse, S.; Kameyama, M.

    2010-12-01

    numerical simulation is impossible. In this study, we made 1D numerical simulations of the whole magma ocean incorporating a parameterization based on direct numerical simulation results of a 10cm-scale emulsion of liquid iron in liquid silicates. We computed the evolution of the thermal and chemical structure during the separation of iron phase. The maximum temperature, which exceeds peridotite melting temperature for several thousands Kelvin, is obtained at the boundary between the metal ponds (or the core if the whole planet is liquid) and the silicate layer. We have found effective P-T conditions for chemical equilibrium in the magma ocean, which is the P-T condition estimated from the resulting partitioning of elements, is not on the melting curve of silicate.

  1. Petrogenesis and geodynamic significance of silicic volcanism in the western Trans-Mexican Volcanic Belt

    Science.gov (United States)

    Petrone, C. M.; Ferrari, L.; Orozco, M. A.; Lopez Martinez, M.

    2012-04-01

    Silicic volcanism in the western Trans-Mexican Volcanic Belt (WTMVB) was defined a Pliocene ignimbrite flare-up associated with the rifting of the Jalisco block from mainland Mexico (Frey et al., 2007; GSAB). With the integration of new and published geochronologic, geochemical, and isotope data we revise this interpretation and propose a new petrogenetic model. The oldest silicic volcanism consists of large silicic domes and minor pyroclastic flows (~370 km3) emplaced to the north of Guadalajara above a thick succession of ~11 to 8.7 Ma basaltic lavas, which yielded Ar-Ar and obsidian FT ages of ~7.5 to 5 Ma. Shortly after (4.9 to 2.9 Ma) large amount of rhyolitic lavas and ash flow tuffs (~500 km3) were emplaced in a WNW-ESE trending belt from Guadalajara to Compostela. Rhyolitic domes and flows (~430 km3) were emplaced also in the Pleistocene mostly between Tequila and Guadalajara with the late Pleistocene La Primavera caldera (~35 km3) as the sole explosive volcanic episodes. As a whole, silicic volcanism occurred from Late Miocene to the Pleistocene, and was dominated by dome and lava flows. Most rhyolites have high LILE/HFSE values and negative spikes at Nb, P and Ti. They also show the same Ba/Nb and K/Rb values and slightly higher Rb/Sr ratios as the 11-8 Ma basalts. Rhyolite Sr isotope data (87Sr/86Sr init = 0.70371 - 070598) are only slightly more radiogenic than the 11-8 basalts (87Sr/86Sr init = 0.70349-0.70410), whereas Nd isotope ratios are indistinguishable from them. Sr and Nd isotope ratios of the rhyolites are also similar to the crust nearby, indicating that they can be compatible either with fractional crystallization (FC) of basalts or with crust assimilation/melting. However REE contents are too low to be the result of basalt FC. Isotope and REE data can be successfully modelled with an initial crustal melt which subsequently undergone fractional crystallization of feldspar and quartz. Late Miocene slab detachment and subsequent slab rollback

  2. MELTED BUTTER TECHNOLOGY DEVELOPMENT

    Directory of Open Access Journals (Sweden)

    L. V. Golubeva

    2014-01-01

    Full Text Available Summary. Melted butter is made from dairy butter by rendering the fat phase. It has specific taste and aroma, high-calorie content and good assimilability. Defects of butter which appeared during the storage causes by the development of microbiological processes or by the chemical oxidation. On the development of these processes influence quality and composition of fresh butter, its physical structure, content of the increased amount of gas phase and content of heavy metals, storage conditions. Microbiological spoilage of butter occurs generally due to damage of plasma which is good environment for the development of microorganisms. Defects of microbiological origin include: unclean, sour, moldy, yeasty, cheesy, bitter taste. Defects of test and smell chemical origin are formed due to hydrolytic digestion of lipids. It's prevailed at long storage of butter in the conditions of freezing temperatures. It's picked out the following main processes of spoiling: souring, acidifying and sallowness. Often these processes take place simultaneously.It has been investigated melted butter with lactated additive. The latter improves the microbiological and toxicological safety, prolongs the storage condition of the products. Technological efficiency of the additives is achieved by a multilayer products formation from the inactive bound water, preventing microorganisms growth and by the barrier layer with lactate inhibiting hydrolytic reactions. Oil samples were obtained with the batch-type butter maker application, then they were melted and after that lactated additive were supplemented. It has been studied organoleptic and physico-chemical indices of the melted butter samples. The fatty-acid composition of melted butter were studied. Comparative analysis of fatty-acid composition of cow's milk fat and produced melted butter has shown their similarity. Also in the last sample there is increased weight fraction of linoleic and linolenic acids. The obtained

  3. Carbonatitic and granitic melts produced under conditions of primary immiscibility during anatexis in the lower crust

    Science.gov (United States)

    Ferrero, Silvio; Wunder, Bernd; Ziemann, Martin A.; Wälle, Markus; O'Brien, Patrick J.

    2016-11-01

    Carbonatites are peculiar magmatic rocks with mantle-related genesis, commonly interpreted as the products of melting of CO2-bearing peridotites, or resulting from the chemical evolution of mantle-derived magmas, either through extreme differentiation or secondary immiscibility. Here we report the first finding of anatectic carbonatites of crustal origin, preserved as calcite-rich polycrystalline inclusions in garnet from low-to-medium pressure migmatites of the Oberpfalz area, SW Bohemian Massif (Central Europe). These inclusions originally trapped a melt of calciocarbonatitic composition with a characteristic enrichment in Ba, Sr and LREE. This interpretation is supported by the results of a detailed microstructural and microchemical investigation, as well as re-melting experiments using a piston cylinder apparatus. Carbonatitic inclusions coexist in the same cluster with crystallized silicate melt inclusions (nanogranites) and COH fluid inclusions, suggesting conditions of primary immiscibility between two melts and a fluid during anatexis. The production of both carbonatitic and granitic melts during the same anatectic event requires a suitable heterogeneous protolith. This may be represented by a sedimentary sequence containing marble lenses of limited extension, similar to the one still visible in the adjacent central Moldanubian Zone. The presence of CO2-rich fluid inclusions suggests furthermore that high CO2 activity during anatexis may be required to stabilize a carbonate-rich melt in a silica-dominated system. This natural occurrence displays a remarkable similarity with experiments on carbonate-silicate melt immiscibility, where CO2 saturation is a condition commonly imposed. In conclusion, this study shows how the investigation of partial melting through melt inclusion studies may unveil unexpected processes whose evidence, while preserved in stiff minerals such as garnet, is completely obliterated in the rest of the rock due to metamorphic re

  4. Crust behavior and erosion rate prediction of EPR sacrificial material impinged by core melt jet

    Energy Technology Data Exchange (ETDEWEB)

    Li, Gen; Liu, Ming, E-mail: ming.liu@mail.xjtu.edu.cn; Wang, Jinshi; Chong, Daotong; Yan, Junjie

    2017-04-01

    Highlights: • A numerical code was developed to analyze melt jet-concrete interaction in the frame of MPS method. • Crust and ablated concrete layer at UO{sub 2}-ZrO{sub 2} melt and concrete interface periodically developed and collapsed. • Concrete surface temperature fluctuated around a low temperature and ablation temperature. • Concrete erosion by Fe-Zr melt jet was significantly faster than that by UO{sub 2}-ZrO{sub 2} melt jet. - Abstract: Sacrificial material is a special ferro-siliceous concrete, designed in the ex-vessel core melt stabilization system of European Pressurized water Reactor (EPR). Given a localized break of RPV lower head, the melt directly impinges onto the dry concrete in form of compact jet. The concrete erosion behavior influences the failure of melt plug, and further affects melt spreading. In this study, a numerical code was developed in the frame of Moving Particle Semi-implicit (MPS) method, to analyze the crust behavior and erosion rate of sacrificial concrete, impinged by prototypic melt jet. In validation of numerical modeling, the time-dependent erosion depth and erosion configuration matched well with the experimental data. Sensitivity study of sacrificial concrete erosion indicates that the crust and ablated concrete layer presented at UO{sub 2}-ZrO{sub 2} melt and concrete interface, whereas no crust could be found in the interaction of Fe-Zr melt with concrete. The crust went through stabilization-fracture-reformation periodic process, accompanied with accumulating and collapsing of molten concrete layer. The concrete surface temperature fluctuated around a low temperature and ablation temperature. It increased as the concrete surface layer was heated to melting, and dropped down when the cold concrete was revealed. The erosion progression was fast in the conditions of small jet diameter and large concrete inclination angle, and it was significantly faster in the erosion by metallic melt jet than by oxidic melt jet.

  5. Absorption of light by lead silicate borate glasses containing gadolinium tellurite

    Energy Technology Data Exchange (ETDEWEB)

    Ivanchenko, L.A.; Obolonchik, V.A.; Ovcharenko, N.V.; Frankfurt, V.M.; Serdyuk, V.A.; Zaletilo, L.S.

    1987-03-01

    The authors investigate how the properties of lead silicate borate glasses change when rare-earth tellurites are added to them. The choice of glasses based on PbO was prompted by the fact that they are low-melting and will dissolve large amounts of compounds of type Ln/sub 2/Te/sub 3/O/sub 9/. The compositions of the resultant glasses are shown. The refractive indices and absorption edge in the visible region of the spectrum is also presented. The dependences of the absorptive index of glasses in both visible and in IR regions are shown, as is the reflection spectra in the IR.

  6. Nanostructure of Calcium Silicate Hydrates in Cements

    KAUST Repository

    Skinner, L. B.

    2010-05-11

    Calcium silicate hydrate (CSH) is the major volume phase in the matrix of Portland cement concrete. Total x-ray scattering measurements with synchrotron x rays on synthetic CSH(I) shows nanocrystalline ordering with a particle diameter of 3.5(5) nm, similar to a size-broadened 1.1 nm tobermorite crystal structure. The CSH component in hydrated tricalcium silicate is found to be similar to CSH(I). Only a slight bend and additional disorder within the CaO sheets is required to explain its nanocrystalline structure. © 2010 The American Physical Society.

  7. Differentiation of Planetesimals and the Thermal Consequences of Melt Migration

    CERN Document Server

    Moskovitz, Nicholas

    2011-01-01

    We model the heating of a primordial planetesimal by decay of the short-lived radionuclides Al-26 and Fe-60 to determine (i) the timescale on which melting will occur; (ii) the minimum size of a body that will produce silicate melt and differentiate; (iii) the migration rate of molten material within the interior; and (iv) the thermal consequences of the transport of Al-26 in partial melt. Our models incorporate results from previous studies of planetary differentiation and are constrained by petrologic (i.e. grain size distributions), isotopic (e.g. Pb-Pb and Hf-W ages) and mineralogical properties of differentiated achondrites. We show that formation of a basaltic crust via melt percolation was limited by the formation time of the body, matrix grain size and viscosity of the melt. We show that low viscosity (100 km in size. Differentiation would be mos t likely for planetesimals larger than 20 km in diameter that accreted within ~2.7 Myr of CAI formation.

  8. Petrogenesis of Miller Range 07273, a new type of anomalous melt breccia: Implications for impact effects on the H chondrite asteroid

    Science.gov (United States)

    Ruzicka, Alex M.; Hutson, Melinda; Friedrich, Jon M.; Rivers, Mark L.; Weisberg, Michael K.; Ebel, Denton S.; Ziegler, Karen; Rumble, Douglas; Dolan, Alyssa A.

    2017-09-01

    Miller Range 07273 is a chondritic melt breccia that contains clasts of equilibrated ordinary chondrite set in a fine-grained (pressure, a sudden pressure drop, and a slower drop in temperature. Olivine and orthopyroxene in chondrule clasts were the least melted and the most deformed, whereas matrix and troilite melted completely and crystallized to nearly strain-free minerals. Coarse metal was largely but incompletely liquefied, and matrix silicates formed by the breakdown during melting of albitic feldspar and some olivine to form pyroxene at high pressure (>3 GPa, possibly to 15-19 GPa) and temperature (>1350 °C, possibly to ≥2000 °C). The higher pressures and temperatures would have involved back-reaction of high-pressure polymorphs to pyroxene and olivine upon cooling. Silicates outside of melt matrix have compositions that were relatively unchanged owing to brief heating duration.

  9. Effect of Sulfur on Siderophile Element Partitioning Between Olivine and Martian Primary Melt

    Science.gov (United States)

    Usui, T.; Shearer, C. K.; Righter, K.; Jones, J. H.

    2011-01-01

    Since olivine is a common early crystallizing phase in basaltic magmas that have produced planetary and asteroidal crusts, a number of experimental studies have investigated elemental partitioning between olivine and silicate melt [e.g., 1, 2, 3]. In particular, olivine/melt partition coefficients of Ni and Co (DNi and DCo) have been intensively studied because these elements are preferentially partitioned into olivine and thus provide a uniquely useful insight into the basalt petrogenesis [e.g., 4, 5]. However, none of these experimental studies are consistent with incompatible signatures of Co [e.g., 6, 7, 8] and Ni [7] in olivines from Martian meteorites. Chemical analyses of undegassed MORB samples suggest that S dissolved in silicate melts can reduce DNi up to 50 % compared to S-free experimental systems [9]. High S solubility (up to 4000 ppm) for primitive shergottite melts [10] implies that S might have significantly influenced the Ni and Co partitioning into shergottite olivines. This study conducts melting experiments on Martian magmatic conditions to investigate the effect of S on the partitioning of siderophile elements between olivine and Martian primary melt.

  10. The Role of Hydrogen Bonding on Laminar Burning Velocity of Hydrous and Anhydrous Ethanol Fuel with Small Addition of n-Heptane

    Directory of Open Access Journals (Sweden)

    I Made Suarta

    2016-01-01

    Full Text Available The molecular structure of mixed hydrous and anhydrous ethanol with up to 10% v n-heptane had been studied. The burning velocity was examined in a cylindrical explosion combustion chamber. The result showed that the burning velocity of hydrous ethanol is higher than anhydrous ethanol and n-heptane at stoichiometric, rich, and very rich mixtures. The burning velocity of hydrous ethanol with n-heptane drops drastically compared to the burning velocity of anhydrous ethanol with n-heptane. It is caused by two reasons. Firstly, there was a composition change of azeotropic hydrous ethanol molecules within the mixture of fuel. Secondly, at the same volume the number of ethanol molecules in hydrous ethanol was less than in anhydrous ethanol at the same composition of the n-heptane in the mixture. At the mixture of anhydrous ethanol with n-heptane, the burning velocity decreases proportionally to the addition of the n-heptane composition. The burning velocity is between the velocities of anhydrous ethanol and n-heptane. It shows that the burning velocity of anhydrous ethanol mixed with n-heptane is only influenced by the mixture composition.

  11. Hydrolytic Stability of 3-Aminopropylsilane Coupling Agent on Silica and Silicate Surfaces at Elevated Temperatures

    DEFF Research Database (Denmark)

    Okhrimenko, Denis; Budi, Akin; Ceccato, Marcel

    2017-01-01

    in coupling efficiency, thus decreasing the product quality and the mechanical strength of the polymer-inorganic material interface. Therefore, a better understanding of the chemical state and stability of APS on inorganic surfaces is needed. In this work, we investigated APS adhesion on silica wafers...... and compared its properties with those on complex silicate surfaces such as those used by industry (mineral fibers and fiber melt wafers). The APS was deposited from aqueous and organic (toluene) solutions and studied with surface sensitive techniques, including X-ray photoelectron spectroscopy (XPS), atomic...... and substrate roughness influence the amount of deposited APS. More APS was deposited and its layers were more stable on fiber melt than on silica wafers. The changes in the amount of adsorbed APS can be successfully monitored by streaming potential. These results will aid in improving industrial...

  12. 21 CFR 172.410 - Calcium silicate.

    Science.gov (United States)

    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...

  13. Stability of calcium silicate in basic solution

    Institute of Scientific and Technical Information of China (English)

    刘桂华; 李小斌; 彭志宏; 周秋生

    2003-01-01

    Mixture of CaO and SiO2 was sintered at 1 200 or 1 400 ℃ according to the mole ratio of CaO/SiO2 of 1 or 2, and then calcium silicate was leached in pure caustic or soda solution. The results indicated that calcium silicate exists much more stably in caustic solution than that in soda solution, and CaO*SiO2 is more stable than β-2CaO*SiO2 whether in caustic solution or in soda solution. The increase of sintering temperature favored the stability of calcium silicate in the leaching process. When β-2CaO*SiO2 was leached in soda solution, the increase of leaching temperature and time resulted in decomposing of more calcium silicate. And when β-2CaO*SiO2 was leached in caustic solution at high temperature, much 2CaO*SiO2*H2O but little CaO*SiO2*H2O appeared in slag.

  14. Making Earth's earliest continental crust - an analogue from voluminous Neogene silicic volcanism in NE-Iceland

    Science.gov (United States)

    Berg, Sylvia E.; Troll, Valentin R.; Burchardt, Steffi; Riishuus, Morten S.; Deegan, Frances M.; Harris, Chris; Whitehouse, Martin J.; Gústafsson, Ludvik E.

    2014-05-01

    Borgarfjörður Eystri in NE-Iceland represents the second-most voluminous exposure of silicic eruptive rocks in Iceland and is a superb example of bimodal volcanism (Bunsen-Daly gap), which represents a long-standing controversy that touches on the problem of crustal growth in early Earth. The silicic rocks in NE-Iceland approach 25 % of the exposed rock mass in the region (Gústafsson et al., 1989), thus they significantly exceed the usual ≤ 12 % in Iceland as a whole (e.g. Walker, 1966; Jonasson, 2007). The origin, significance, and duration of the voluminous (> 300 km3) and dominantly explosive silicic activity in Borgarfjörður Eystri is not yet constrained (c.f. Gústafsson, 1992), leaving us unclear as to what causes silicic volcanism in otherwise basaltic provinces. Here we report SIMS zircon U-Pb ages and δ18O values from the region, which record the commencement of silicic igneous activity with rhyolite lavas at 13.5 to 12.8 Ma, closely followed by large caldera-forming ignimbrite eruptions from the Breiðavik and Dyrfjöll central volcanoes (12.4 Ma). Silicic activity ended abruptly with dacite lava at 12.1 Ma, defining a ≤ 1 Myr long window of silicic volcanism. Magma δ18O values estimated from zircon range from 3.1 to 5.5 (± 0.3; n = 170) and indicate up to 45 % assimilation of a low-δ18O component (e.g. typically δ18O = 0 ‰, Bindeman et al., 2012). A Neogene rift relocation (Martin et al., 2011) or the birth of an off-rift zone to the east of the mature rift associated with a thermal/chemical pulse in the Iceland plume (Óskarsson & Riishuus, 2013), likely brought mantle-derived magma into contact with fertile hydrothermally-altered basaltic crust. The resulting interaction triggered large-scale crustal melting and generated mixed-origin silicic melts. Such rapid formation of silicic magmas from sustained basaltic volcanism may serve as an analogue for generating continental crust in a subduction-free early Earth (e.g. ≥ 3 Ga, Kamber et

  15. COMPARISON OF SOL-GEL SILICATE COATINGS ON Ti SUBSTRATE

    OpenAIRE

    2012-01-01

    The objective of the submitted work was to prepare and to characterize two types of silicate coatings prepared by the sol-gel method using the dip-coating technique on a titanium substrate. Efforts have been made to use mechanical properties of bio-inert titanium and bioactive properties of a silicate layer enriched with an admixture of compounds identified below. The first group consisted of silicate coatings containing silver, brushite and monetite. The other group of silicate coatings cont...

  16. Laser Irradiated Impact Experiments Show that Nanophase Iron Particles Formed by Shock-Induced Melting Rather than Vapor Deposition

    Science.gov (United States)

    Li, Y.; Li, S. J.; Xie, Z. D.; Li, X. Y.

    2016-08-01

    As the laser irradiated results of chondrite, Impact melting fractionation of ferromagnesian silicates induced by meteorites may be the major origin of np-Fe0, rather than vapour deposition origin only, especially for np-Fe0 in agglutinatic glasses.

  17. OXYGEN BUBBLE DEVELOPMENT ON A PLATINUM ELECTRODE IN BOROSILICATE GLASS MELT BY THE EFFECT OF ALTERNATING CURRENT

    Directory of Open Access Journals (Sweden)

    Jiri Matej

    2014-10-01

    or on alternating reduction and re-forming of oxidic layer on the electrode in the transition range, has been suggested. Start of bubble evolution at low alternating current density has also been observed in simple sodium-calcium-silicate glass melt. A relation between bubble release and platinum corrosion caused by reduced silicon has been suggested

  18. Heterogeneously entrapped, vapor-rich melt inclusions record pre-eruptive magmatic volatile contents

    Science.gov (United States)

    Steele-MacInnis, Matthew; Esposito, Rosario; Moore, Lowell R.; Hartley, Margaret E.

    2017-04-01

    Silicate melt inclusions (MI) commonly provide the best record of pre-eruptive H2O and CO2 contents of subvolcanic melts, but the concentrations of CO2 and H2O in the melt (glass) phase within MI can be modified by partitioning into a vapor bubble after trapping. Melt inclusions may also enclose vapor bubbles together with the melt (i.e., heterogeneous entrapment), affecting the bulk volatile composition of the MI, and its post-entrapment evolution. In this study, we use numerical modeling to examine the systematics of post-entrapment volatile evolution within MI containing various proportions of trapped vapor from zero to 95 volume percent. Modeling indicates that inclusions that trap only a vapor-saturated melt exhibit significant decrease in CO2 and moderate increase in H2O concentrations in the melt upon nucleation and growth of a vapor bubble. In contrast, inclusions that trap melt plus vapor exhibit subdued CO2 depletion at equivalent conditions. In the extreme case of inclusions that trap mostly the vapor phase (i.e., CO2-H2O fluid inclusions containing trapped melt), degassing of CO2 from the melt is negligible. In the latter scenario, the large fraction of vapor enclosed in the MI during trapping essentially serves as a buffer, preventing post-entrapment modification of volatile concentrations in the melt. Hence, the glass phase within such heterogeneously entrapped, vapor-rich MI records the volatile concentrations of the melt at the time of trapping. These numerical modeling results suggest that heterogeneously entrapped MI containing large vapor bubbles represent amenable samples for constraining pre-eruptive volatile concentrations of subvolcanic melts.

  19. On edge melting under the Colorado Plateau margin

    Science.gov (United States)

    Rudzitis, Sean; Reid, Mary R.; Blichert-Toft, Janne

    2016-07-01

    Asthenosphere beneath the relatively thin lithosphere of the Basin and Range province appears to be juxtaposed in step-like fashion against the Colorado Plateau's thick lithospheric keel. Primary to near-primary basalts are found above this edge, in the San Francisco-Morman Mountain volcanic fields, north central Arizona, western USA. We show that at least two distinct peridotite-dominated mantle end-members contributed to the origin of the basalts. One has paired Nd and Hf isotopic characteristics that cluster near the mantle array and trace element patterns as expected for melts generated in the asthenosphere, possibly in the presence of garnet. The second has isotopic compositions displaced above the ɛHf - ɛNd mantle array which, together with its particular trace element characteristics, indicate contributions from hydrogenous sediments and/or melt (carbonatite or silicate)-related metasomatism. Melt equilibration temperatures obtained from Si- and Mg-thermobarometry are mostly 1340-1425°C and account for the effects of water (assumed to be 2 wt.%) and estimated CO2 (variable). Melt equilibration depths cluster at the inferred location of the lithosphere-asthenosphere boundary at ˜70-75 km beneath the southwestern margin of the Colorado Plateau but scatter to somewhat greater values (˜100 km). Melt generation may have initiated in or below the garnet-spinel facies transition zone by edge-driven convection and continued as mantle and/or melts upwelled, assimilating and sometimes equilibrating with shallower contaminated mantle, until melts were finally extracted.

  20. GLASS MELTING PHENOMENA, THEIR ORDERING AND MELTING SPACE UTILISATION

    Directory of Open Access Journals (Sweden)

    Němec L.

    2013-12-01

    Full Text Available Four aspects of effective glass melting have been defined – namely the fast kinetics of partial melting phenomena, a consideration of the melting phenomena ordering, high utilisation of the melting space, and effective utilisation of the supplied energy. The relations were defined for the specific melting performance and specific energy consumption of the glass melting process which involve the four mentioned aspects of the process and indicate the potentials of effective melting. The quantity “space utilisation” has been treated in more detail as an aspect not considered in practice till this time. The space utilisation was quantitatively defined and its values have been determined for the industrial melting facility by mathematical modelling. The definitions of the specific melting performance and specific energy consumption have been used for assessment of the potential impact of a controlled melt flow and high space utilisation on the melting process efficiency on the industrial scale. The results have shown that even the partial control of the melt flow, leading to the partial increase of the space utilisation, may considerably increase the melting performance, whereas a decrease of the specific energy consumption was determined to be between 10 - 15 %.

  1. The fatty acids and alkanes of Satureja adamovicii Silic and Satureja fukarekii Silic (NOTE

    Directory of Open Access Journals (Sweden)

    DUSANKA KITIC

    1999-05-01

    Full Text Available The content and composition of fatty acids and alkanes of Satureja adamovicii Silic and Satureja fukarekii Silic were analized by GC. It was found that unsaturated acids prevailed and that the major components were palmitic, oleic, linoleic and linolenic acids. The hydrocarbon fractions of pentane extracts were shown to consist of the alkane homologues (C17 to C34 with nonacosane and hentriacontane being prevailing compounds.

  2. 40 CFR 721.9513 - Modified magnesium silicate polymer (generic).

    Science.gov (United States)

    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 for...

  3. Intra-cratonic melting as a result of delamination of mantle lithosphere - insight from numerical modelling

    Science.gov (United States)

    Gorczyk, W.; Vogt, K.; Gerya, T.; Hobbs, B. E.

    2012-12-01

    It is becoming increasingly apparent that intense deformation, metamorphism and metasomatism occur within continental cratonic blocks far removed form subducting margins Such changes may occur intra-cratonically arising from lithospheric thickening and the development of gravitational instabilities, but mostly occur at the boundary of cratonic blocks. The contact of two cratons is characterized by rheological lateral variations within mantle-lithosphere and overlying crust. Tectonic stresses acting on craton/craton boundaries may lead to thinning or thickening due to delamination of the mantle lithosphere. This is reflected in tectonic deformation, topography evolution, melting and crustal metamorphism. To understand the controls on these processes a number of 2D, coupled petrological thermo-mechanical numerical experiments has been performed to test the response of a laterally weakened zone to a compressional regime. The results indicate that the presence of water-bearing minerals in the lithosphere and lower crust is essential to initiate melting, which in the later stages may expand to dry melting of crust and mantle. In the case of anhydrous crust and lithosphere, no melting occurs. Thus a variety of instabilities, melting behaviour and topographic responses occurs at the base of the lithosphere as well as intensive faulting and buckling in the crust dependent on the strength and "water" content of the lithosphere.

  4. Preparation and Characterization of Anhydrous Magnesium Chloride in Organic Solvent%有机溶剂法无水氯化镁的制备与表征

    Institute of Scientific and Technical Information of China (English)

    周宁波; 陈白珍; 何新快; 李义兵

    2005-01-01

    Ammonium carnallite was synthesized by hydrated magnesium chloride in salt lake and ammonium chloride solution. Dehydrated ammonium carnallite was dissolved in methanol under low temperature by feeding ammonia, to prepare anhydrous magnesium chloride. The results show that anhydrous magnesium chloride contains magnesium oxide in an amount less than 0.1% by weight, the yield of magnesium chloride was above 99.5%. Ammonium carnallite, ammoniation magnesium chloride and anhydrous magnesium chloride were characterized by thermoanalysis, X-ray powder diffraction and scanning electron microscopy.

  5. Melting of the Primitive Mercurian Mantle, Insights into the Origin of Its Surface Composition

    Science.gov (United States)

    Boujibar, A.; Righter, K.; Rapp, J. F.; Ross, D. K.; Pando, K. M.; Danielson, L. R.; Fontaine, E.

    2016-01-01

    Recent findings of the MESSENGER mission on Mercury have brought new evidence for its reducing nature, widespread volcanism and surface compositional heteregeneity. MESSENGER also provided major elemental ratios of its surface that can be used to infer large-scale differentiation processes and the thermal history of the planet. Mercury is known as being very reduced, with very low Fe-content and high S and alkali contents on its surface. Its bulk composition is therefore likely close to EH enstatite chondrites. In order to elucidate the origin of the chemical diversity of Mercury's surface, we determined the melting properties of EH enstatite chondrites, at pressures between 1 bar and 3 GPa and oxygen fugacity of IW-3 to IW-5, using piston-cylinder experiments, combined with a previous study on EH4 melting at 1 bar. We found that the presence of Ca-rich sulfide melts induces significant decrease of Ca-content in silicate melts at low pressure and low degree of melting (F). Also at pressures lower than 3 GPa, the SiO2-content decreases with F, while it increases at 3 GPa. This is likely due to the chemical composition of the bulk silicate which has a (Mg+Fe+Ca)/Si ratio very close to 1 and to the change from incongruent to congruent melting of enstatite. We then tested whether the various chemical compositions of Mercury's surface can result from mixing between two melting products of EH chondrites. We found that the majority of the geochemical provinces of Mercury's surface can be explained by mixing of two melts, with the exception of the High-Al plains that require an Al-rich source. Our findings indicate that Mercury's surface could have been produced by polybaric melting of a relatively primitive mantle.

  6. Vibrational spectroscopy to support the link between rheology and continuous twin-screw melt granulation on molecular level: A case study.

    Science.gov (United States)

    Monteyne, Tinne; Heeze, Liza; Oldörp, Klaus; Vervaet, Chris; Remon, Jean-Paul; De Beer, Thomas

    2016-06-01

    Twin screw hot melt granulation (TSHMG) is an innovative and continuous drug formulation process allowing granulation of moisture sensitive drugs. However, due to the lack of experience and in-depth process understanding, this technique is not yet widely used. During the TSHMG process, the microstructure of the granules is generated and modified and strongly depends on the flow behavior of the material. Hence, rheology might be a suitable tool to simulate and examine this process. However, chemical interactions of the material are influencing the physical properties leading to the microstructure. In this research project it is spectroscopically investigated whether the heat applied in a rheometer induces the same molecular effects as these occurring during TSHMG of the model formulation caffeine anhydrous/Soluplus®. Hence, it is evaluated whether rheology can be used as a simulation tool to improve the understanding of the material behavior at molecular level during continuous melt granulation. Therefore, in-line Raman spectroscopy is executed during TSHMG and in situ Fourier Transform Infra-red (FTIR) during oscillatory rheological experiments. The results from the in-line Raman monitoring revealed polymorph transition of caffeine anhydrous during twin screw melt granulation with Soluplus® which is stimulated depending on the binder concentration and/or granulation temperature. A correlation was seen between the FTIR spectra obtained during the rheological temperature ramp and the in-line collected Raman spectra during the melt granulation runs. The polymorphic conversion of caffeine anhydrous could be detected in the same temperature range with both techniques, proving the comparability of plate-plate rheometry and hot melt granulation (HMG) for this case with the used parameter settings. Process simulation using rheology combined with in situ FTIR seems a promising approach to increase process understanding and to facilitate binder and parameter selection for

  7. Viscosity Measurement for Tellurium Melt

    Science.gov (United States)

    Lin, Bochuan; Li, Chao; Ban, Heng; Scripa, Rosalia N.; Su, Ching-Hua; Lehoczky, Sandor L.

    2006-01-01

    The viscosity of high temperature Te melt was measured using a new technique in which a rotating magnetic field was applied to the melt sealed in a suspended ampoule, and the torque exerted by rotating melt flow on the ampoule wall was measured. Governing equations for the coupled melt flow and ampoule torsional oscillation were solved, and the viscosity was extracted from the experimental data by numerical fitting. The computational result showed good agreement with experimental data. The melt velocity transient initiated by the rotating magnetic field reached a stable condition quickly, allowing the viscosity and electrical conductivity of the melt to be determined in a short period.

  8. Optical analysis of samarium doped sodium bismuth silicate glass

    Science.gov (United States)

    Thomas, V.; Sofin, R. G. S.; Allen, M.; Thomas, H.; Biju, P. R.; Jose, G.; Unnikrishnan, N. V.

    2017-01-01

    Samarium doped sodium bismuth silicate glass was synthesized using the melt quenching method. Detailed optical spectroscopic studies of the glassy material were carried out in the UV-Vis-NIR spectral range. Using the optical absorption spectra Judd-Ofelt (JO) parameters are derived. The calculated values of the JO parameters are utilized in evaluating the various radiative parameters such as electric dipole line strengths (Sed), radiative transition probabilities (Arad), radiative lifetimes (τrad), fluorescence branching ratios (β) and the integrated absorption cross- sections (σa) for stimulated emission from various excited states of Sm3 +‡ ion. The principal fluorescence transitions are identified by recording the fluorescence spectrum. Our analysis revealed that the novel glassy system has the optimum values for the key parameters viz. spectroscopic quality factor, optical gain, stimulated emission cross section and quantum efficiency, which are required for a high performance optical amplifier. Calculated chromaticity co-ordinates (0.61, 0.38) also confirm its application potential in display devices.

  9. Thermoacoustic Streaming and Ultrasonic Processing of Low Melting Melts

    Science.gov (United States)

    Trinh, E. H.

    1997-01-01

    Ultrasonic levitation allows the processing of low melting materials both in 1 G as well as in microgravity. The free suspension of the melts also facilitates undercooling, permitting the measurements of the physical properties of the metastable liquids.

  10. MELTS_Excel: A Microsoft Excel-based MELTS interface for research and teaching of magma properties and evolution

    Science.gov (United States)

    Gualda, Guilherme A. R.; Ghiorso, Mark S.

    2015-01-01

    thermodynamic modeling software MELTS is a powerful tool for investigating crystallization and melting in natural magmatic systems. Rhyolite-MELTS is a recalibration of MELTS that better captures the evolution of silicic magmas in the upper crust. The current interface of rhyolite-MELTS, while flexible, can be somewhat cumbersome for the novice. We present a new interface that uses web services consumed by a VBA backend in Microsoft Excel©. The interface is contained within a macro-enabled workbook, where the user can insert the model input information and initiate computations that are executed on a central server at OFM Research. Results of simple calculations are shown immediately within the interface itself. It is also possible to combine a sequence of calculations into an evolutionary path; the user can input starting and ending temperatures and pressures, temperature and pressure steps, and the prevailing oxidation conditions. The program shows partial updates at every step of the computations; at the conclusion of the calculations, a series of data sheets and diagrams are created in a separate workbook, which can be saved independently of the interface. Additionally, the user can specify a grid of temperatures and pressures and calculate a phase diagram showing the conditions at which different phases are present. The interface can be used to apply the rhyolite-MELTS geobarometer. We demonstrate applications of the interface using an example early-erupted Bishop Tuff composition. The interface is simple to use and flexible, but it requires an internet connection. The interface is distributed for free from http://melts.ofm-research.org.

  11. Interpreting the I-Xe system in individual silicate grains from Toluca IAB

    Science.gov (United States)

    Pravdivtseva, O. V.; Meshik, A. P.; Hohenberg, C. M.; Petaev, M.

    2009-12-01

    Detailed isotopic and mineralogical studies of silicate inclusions separated from a troilite nodule of the Toluca IAB iron meteorite reveal the presence of radiogenic 129Xe in chlorapatite, plagioclase, perryite, and pyroxene grains. Subsequent I-Xe studies of 32 neutron-irradiated pyroxene grains indicate that high-Mg and low-Mg pyroxenes have distinctive I-Xe signatures. The I-Xe system in high-Mg pyroxenes closed at 4560.5 ± 2.4 Ma, probably reflecting exsolution of silicates from the melt, while the low-Mg pyroxenes closed at 4552.0 ± 3.7 Ma, 8.5 Ma later, providing a means for determining the cooling rate at the time of exsolution. If the host Toluca graphite-troiliterich inclusion formed after the breakup and reassembly of the IAB parent body as has been suggested, the I-Xe ages of the high-Mg pyroxenes separated from this inclusions indicate that this catastrophic impact occurred not later than 4560.5 Ma, 6.7 Ma after formation of CAIs. The cooling rate at the time of silicates exsolution in Toluca is 14.5 ± 10.0 °C/Ma.

  12. Melt production and magma emplacement: What use are they?

    Science.gov (United States)

    Nimmo, F.

    2003-04-01

    I will review the processes of melt production and magma emplacement and address two questions: how do these processes affect planetary evolution?; and what can we learn from observing them, both now and in the future? Melt production is primarily controlled by the temperature of the planetary interior. The extraction of melt from silicate mantles has a number of effects. Firstly, it advects heat (e.g. Io, Venus?). Secondly, it segregates radiogenic materials into the crust, thus cooling the mantle (e.g. Mars, Earth). Thirdly, it removes volatiles from the interior (e.g. Venus, Mars). Recognition that melting is occurring gives us information about likely conditions inside the planet. Models of melt generation by convective upwelling have been used to constrain the interior properties of the Earth, Venus and Mars. Melting during tidal heating (Io) or accretion is less well understood. Magma emplacement is primarily controlled by the density of the magma and the surrounding material. Extrusive activity is likely for high volatile concentrations or low crustal densities. Water is particularly difficult to erupt, since (unlike silicates) the melt is denser than the solid. Different styles of magma emplacement are observed: voluminous surface flows and volcanic edifices of various kinds (ubiquitous); giant radiating dyke swarms (Earth, Venus, Mars); intrusive sills and diapirs (Earth, Venus?, Mars?, Europa?). The extrusive emplacement of magma will cause resurfacing, and is thus easily detected. The release of volatiles during emplacement may have local (e.g. Laki) or global (Venus? Mars?) effects on climate and atmosphere. Intrusive emplacement is harder to detect, but may interact with local volatiles to create unusual landforms (Earth, Mars). The style and volume of emplacement is a useful diagnostic tool. The morphology of lava flows gives information about the rheology and composition of the flow material (e.g. Venus, Miranda). Observations of dykes may be used to

  13. Structure, Solubility and Stability of Orbifloxacin Crystal Forms: Hemihydrate versus Anhydrate.

    Science.gov (United States)

    Santos, Olimpia Maria Martins; Freitas, Jennifer Tavares Jacon; Cazedey, Edith Cristina Laignier; de Araújo, Magali Benjamim; Doriguetto, Antonio Carlos

    2016-03-09

    Orbifloxacin (ORBI) is a widely used antimicrobial drug of the fluoroquinolone class. In the official pharmaceutical compendia the existence of polymorphism in this active pharmaceutical ingredient (API) is reported. No crystal structure has been reported for this API and as described in the literature, its solubility is very controversial. Considering that different solid forms of the same API may have different physicochemical properties, these different solubilities may have resulted from analyses inadvertently carried out on different polymorphs. The solubility is the most critical property because it can affect the bioavailability and may compromise the quality of a drug product. The crystalline structure of ORBI determined by SCXRD is reported here for the first time. The structural analysis reveals that the ORBI molecule is zwitterionic and hemihydrated. ORBI hemihydrated form was characterized by the following techniques: TG/DTA, FTIR-ATR, and PXRD. A second crystalline ORBI form is also reported: the ORBI anhydrous form was obtained by heating the hemihydrate. These ORBI solid forms were isomorphous, since no significant change in unit cell and space group symmetry were observed. The solid-state phase transformation between these forms is discussed and the equilibrium solubility data were examined in order to check the impact of the differences observed in their crystalline structures.

  14. Structure, Solubility and Stability of Orbifloxacin Crystal Forms: Hemihydrate versus Anhydrate

    Directory of Open Access Journals (Sweden)

    Olimpia Maria Martins Santos

    2016-03-01

    Full Text Available Orbifloxacin (ORBI is a widely used antimicrobial drug of the fluoroquinolone class. In the official pharmaceutical compendia the existence of polymorphism in this active pharmaceutical ingredient (API is reported. No crystal structure has been reported for this API and as described in the literature, its solubility is very controversial. Considering that different solid forms of the same API may have different physicochemical properties, these different solubilities may have resulted from analyses inadvertently carried out on different polymorphs. The solubility is the most critical property because it can affect the bioavailability and may compromise the quality of a drug product. The crystalline structure of ORBI determined by SCXRD is reported here for the first time. The structural analysis reveals that the ORBI molecule is zwitterionic and hemihydrated. ORBI hemihydrated form was characterized by the following techniques: TG/DTA, FTIR-ATR, and PXRD. A second crystalline ORBI form is also reported: the ORBI anhydrous form was obtained by heating the hemihydrate. These ORBI solid forms were isomorphous, since no significant change in unit cell and space group symmetry were observed. The solid-state phase transformation between these forms is discussed and the equilibrium solubility data were examined in order to check the impact of the differences observed in their crystalline structures.

  15. Laboratory-Scale Membrane Reactor for the Generation of Anhydrous Diazomethane.

    Science.gov (United States)

    Dallinger, Doris; Pinho, Vagner D; Gutmann, Bernhard; Kappe, C Oliver

    2016-07-15

    A configurationally simple and robust semibatch apparatus for the in situ on-demand generation of anhydrous solutions of diazomethane (CH2N2) avoiding distillation methods is presented. Diazomethane is produced by base-mediated decomposition of commercially available Diazald within a semipermeable Teflon AF-2400 tubing and subsequently selectively separated from the tubing into a solvent- and substrate-filled flask (tube-in-flask reactor). Reactions with CH2N2 can therefore be performed directly in the flask without dangerous and labor-intensive purification operations or exposure of the operator to CH2N2. The reactor has been employed for the methylation of carboxylic acids, the synthesis of α-chloro ketones and pyrazoles, and palladium-catalyzed cyclopropanation reactions on laboratory scale. The implementation of in-line FTIR technology allowed monitoring of the CH2N2 generation and its consumption. In addition, larger scales (1.8 g diazomethane per hour) could be obtained via parallelization (numbering up) by simply wrapping several membrane tubings into the flask.

  16. Vibrational Spectroscopy and Phonon-Related Properties of the L-Aspartic Acid Anhydrous Monoclinic Crystal.

    Science.gov (United States)

    Silva, A M; Costa, S N; Sales, F A M; Freire, V N; Bezerra, E M; Santos, R P; Fulco, U L; Albuquerque, E L; Caetano, E W S

    2015-12-10

    The infrared absorption and Raman scattering spectra of the monoclinic P21 l-aspartic acid anhydrous crystal were recorded and interpreted with the help of density functional theory (DFT) calculations. The effect of dispersive forces was taken into account, and the optimized unit cells allowed us to obtain the vibrational normal modes. The computed data exhibits good agreement with the measurements for low wavenumbers, allowing for a very good assignment of the infrared and Raman spectral features. The vibrational spectra of the two lowest energy conformers of the l-aspartic molecule were also evaluated using the hybrid B3LYP functional for the sake of comparison, showing that the molecular calculations give a limited description of the measured IR and Raman spectra of the l-aspartic acid crystal for wavenumbers below 1000 cm(-1). The results obtained reinforce the need to use solid-state calculations to describe the vibrational properties of molecular crystals instead of calculations for a single isolated molecule picture even for wavenumbers beyond the range usually associated with lattice modes (200 cm(-1) < ω < 1000 cm(-1)).

  17. Investigation of the Dermal Absorption and Irritation Potential of Sertaconazole Nitrate Anhydrous Gel

    Directory of Open Access Journals (Sweden)

    Mahima Manian

    2016-07-01

    Full Text Available Effective topical therapy of cutaneous fungal diseases requires the delivery of the active agent to the target site in adequate concentrations to produce a pharmacological effect and inhibit the growth of the pathogen. In addition, it is important to determine the concentration of the drug in the skin in order to evaluate the subsequent efficacy and potential toxicity for topical formulations. For this purpose, an anhydrous gel containing sertaconazole nitrate as a model drug was formulated and the amount of the drug in the skin was determined by in vitro tape stripping. The apparent diffusivity and partition coefficients were then calculated by a mathematical model describing the dermal absorption as passive diffusion through a pseudo-homogenous membrane. The skin irritation potential of the formulation was also assessed by using the in vitro Epiderm™ model. An estimation of the dermal absorption parameters allowed us to evaluate drug transport across the stratum corneum following topical application. The estimated concentration for the formulation was found to be higher than the MIC100 at the target site which suggested its potential efficacy for treating fungal infections. The skin irritation test showed the formulation to be non-irritating in nature. Thus, in vitro techniques can be used for laying the groundwork in developing efficient and non-toxic topical products.

  18. IR and Raman spectroscopic studies of sol–gel derived alkaline-earth silicate glasses

    Indian Academy of Sciences (India)

    Angelos G Kalampounias

    2011-04-01

    IR and Raman spectroscopies have been utilized to study the structure and vibrational modes of sol–gel-derived binary silicate glasses. The present study is motivated by the immense geological significance and focuses on the MO–SiO2 (M = Ca, Mg) binary systems in an effort to unveil the role of the CaO and MgO modifiers when incorporated to the 3D silica structure. Glasses in the composition range = 0, 0.1, 0.2, 0.3 and 0.4 prepared by the sol–gel method were compared with the corresponding glasses formed by appropriate mixing of SiO2 and MO powders through melting and fast cooling. The vibrational spectra of the sol–gel-derived glasses have revealed considerable changes in relative intensities as a function of the MO mole fraction. These changes signify structural modifications on the silica network. The population of the 3 species was found to increase for both modified silicate systems. The rate of increase is more pronounced in the CaO–SiO2 glasses. The extent of network depolymerization in the porous glass is higher at the same content of alkaline earth oxide compared to the bulk glass. The results are indicative of a more `defective’ nature of the sol–gel glasses compared to the corresponding melt-quenched ones.

  19. Immiscible iron- and silica-rich melts in basalt petrogenesis documented in the Skaergaard intrusion

    Science.gov (United States)

    Jakobsen, J. K.; Veksler, I. V.; Tegner, C.; Brooks, C. K.

    2005-11-01

    Silicate liquid immiscibility in basalt petrogenesis is a contentious issue. Immiscible iron- and silica-rich liquids were reported in melt inclusions of lunar basalt and in groundmass glasses of terrestrial volcanics. In fully crystallized plutonic rocks, however, silicate liquid immiscibility has yet to be proven. Here we report the first finding of natural, immiscible iron- and silica-rich melts in a plutonic environment documented in the Skaergaard intrusion, East Greenland. Primary melt inclusions (now finely crystallized) in apatite are either dark or light colored. The predominant dark colored type contains 30.9 ± 4.2 wt% FeOt and 40.7 ± 3.6 wt% SiO2, whereas the light colored type contains 8.6 ± 5.9 wt% FeOt and 65.6 ± 7.3 wt% SiO2. Similar light colored melt inclusions in olivine and fine-grained dark and light colored interstitial pockets also give evidence of crystallization from emulsion of silica and iron-rich liquids. On the outcrop scale, silica-rich (melanogranophyre) pods and layers in iron-rich ferrodiorite of the Upper Zone of the Skaergaard intrusion witness segregation of the two liquids. These findings demand that silicate immiscibility is considered in basalt petrogenesis. Some granitic rocks may represent unmixed silica-rich melt, whereas the dense, iron-rich melt is likely to sink in the crust and could mix with hot mantle-derived magma to form unusual rocks, like ferropicrites, otherwise interpreted as products of heterogeneous mantle sources.

  20. Production of High-Purity Anhydrous Nickel(II Perrhenate for Tungsten-Based Sintered Heavy Alloys

    Directory of Open Access Journals (Sweden)

    Katarzyna Leszczyńska-Sejda

    2017-04-01

    Full Text Available This paper presents a method for the production of high-purity anhydrous nickel(II perrhenate. The method comprises sorption of nickel(II ions from aqueous nickel(II nitrate solutions, using strongly acidic C160 cation exchange resin, and subsequent elution of sorbed nickel(II ions using concentrated perrhenic acid solutions. After the neutralization of the resulting rhenium-nickel solutions, hydrated nickel(II perrhenate is then separated and then dried at 160 °C to obtain the anhydrous form. The resulting compound is reduced in an atmosphere of dissociated ammonia in order to produce a Re-Ni alloy powder. This study provides information on the selected properties of the resulting Re-Ni powder. This powder was used as a starting material for the production of 77W-20Re-3Ni heavy alloys. Microstructure examination results and selected properties of the produced sintered heavy alloys were compared to sintered alloys produced using elemental W, Re, and Ni powders. This study showed that the application of anhydrous nickel(II perrhenate in the production of 77W-20Re-3Ni results in better properties of the sintered alloys compared to those made from elemental powders.

  1. Thermodynamics of Oligonucleotide Duplex Melting

    Science.gov (United States)

    Schreiber-Gosche, Sherrie; Edwards, Robert A.

    2009-01-01

    Melting temperatures of oligonucleotides are useful for a number of molecular biology applications, such as the polymerase chain reaction (PCR). Although melting temperatures are often calculated with simplistic empirical equations, application of thermodynamics provides more accurate melting temperatures and an opportunity for students to apply…

  2. Melting of polydisperse hard disks

    NARCIS (Netherlands)

    Pronk, S.; Frenkel, D.

    2004-01-01

    The melting of a polydisperse hard-disk system is investigated by Monte Carlo simulations in the semigrand canonical ensemble. This is done in the context of possible continuous melting by a dislocation-unbinding mechanism, as an extension of the two-dimensional hard-disk melting problem. We find

  3. Melting of polydisperse hard disks

    NARCIS (Netherlands)

    Pronk, S.; Frenkel, D.

    2004-01-01

    The melting of a polydisperse hard-disk system is investigated by Monte Carlo simulations in the semigrand canonical ensemble. This is done in the context of possible continuous melting by a dislocation-unbinding mechanism, as an extension of the two-dimensional hard-disk melting problem. We find th

  4. DSC study of phase transition of anhydrous phospholipid DHPC and influence of water content

    Institute of Scientific and Technical Information of China (English)

    王邦宁; 谈夫

    1997-01-01

    The phase transition behavior of 1,2-di-n-heptadecanoyl phosphatidylcholme (DHPC)with and without water has been studied by use of differential scanning calorimetry It was found by experiment that the glass transition occurred at first during the first heating of a sample of DHPC without water and then the sample underwent melting as an ordinary crystal.Therefore the sample of DHPC without water was a glassy crystal However,the DHPC sample crystallizing from melt was an ordinary crystal From the relationship between the total melting enthalpy Qf of freezable water and the water content h,it was concluded that the water contained in the DHPC samples might exist in three states recognizable thermodynamically.The water in the first state was an unfreezable water It was the water bound directly with the head groups of the phospholipid,i.e.the primary hydration water Every head group might bind seven such molecules of water.The water in the second state was the secondary hydration water,us melt ing point was

  5. Tracking bubble evolution inside a silicic dike

    Science.gov (United States)

    Álvarez-Valero, Antonio M.; Okumura, Satoshi; Arzilli, Fabio; Borrajo, Javier; Recio, Clemente; Ban, Masao; Gonzalo, Juan C.; Benítez, José M.; Douglas, Madison; Sasaki, Osamu; Franco, Piedad; Gómez-Barreiro, Juan; Carnicero, Asunción

    2016-10-01

    Pressure estimates from rapidly erupted crustal xenoliths constrain the depth of intrusion of the silicic lavas hosting them. This represents an opportunity for tracking magmatic bubble's evolution and quantifying the variation in bubble volume during rapid magma ascent through a volcanic dike just prior to eruption. The petrology, stable-isotope geochemistry and X-ray micro-tomography of dacites containing crustal xenoliths, erupted from a Neogene volcano in SE Spain, showed an increase in porosity from ~ 1.7 to 6.4% from ~ 19 to 13 km depth, at nearly constant groundmass and crystal volumes. This result provides additional constraints for experimental and numerical simulations of subvolcanic magma-crust degassing processes in silicic systems, and may allow the characterization of volcanic eruptive styles based on volatile content.

  6. Recycle of silicate waste into mesoporous materials.

    Science.gov (United States)

    Kim, Jung Ho; Kim, Minwoo; Yu, Jong-Sung

    2011-04-15

    Template synthesis of porous carbon materials usually requires selective removal of template silica from the carbon/silica composites. It not only involves waste of valuable chemicals, but also poses significant environmental concerns including high waste treatment cost. Recycling of silicates released from such nanocasting methods is successfully performed for the first time to regenerate valuable mesoporous MCM and SBA type silica materials, which will not only help in saving valuable chemicals, but also in decreasing chemical waste, contributing in improvement of our environmental standards. This approach can thus improve cost effectiveness for the mass production of nanostructured carbon and others utilizing silica directed nanocasting method by recycling otherwise silicate waste into highly desirable valuable mesoporous silica.

  7. Pavement Snow Melting

    Energy Technology Data Exchange (ETDEWEB)

    Lund, John W.

    2005-01-01

    The design of pavement snow melting systems is presented based on criteria established by ASHRAE. The heating requirements depends on rate of snow fall, air temperature, relative humidity and wind velocity. Piping materials are either metal or plastic, however, due to corrosion problems, cross-linked polyethylene pipe is now generally used instead of iron. Geothermal energy is supplied to systems through the use of heat pipes, directly from circulating pipes, through a heat exchanger or by allowing water to flow directly over the pavement, by using solar thermal storage. Examples of systems in New Jersey, Wyoming, Virginia, Japan, Argentina, Switzerland and Oregon are presented. Key words: pavement snow melting, geothermal heating, heat pipes, solar storage, Wyoming, Virginia, Japan, Argentina, Klamath Falls.

  8. Six White Dwarfs with Circumstellar Silicates

    CERN Document Server

    Jura, M; Zuckerman, B

    2008-01-01

    Spitzer Space Telescope spectra reveal 10 micron silicate emission from circumstellar dust orbiting six externally-polluted white dwarfs. Micron-size glasses with an olivine stoichiometry can account for the distinctively broad wings that extend to 12 microns; these particles likely are produced by tidal-disruption of asteroids. The absence of infrared PAH features is consistent with a scenario where extrasolar rocky planets are assembled from carbon-poor solids.

  9. Highly CO2-supersaturated melts in the Pannonian lithospheric mantle - A transient carbon reservoir?

    Science.gov (United States)

    Créon, Laura; Rouchon, Virgile; Youssef, Souhail; Rosenberg, Elisabeth; Delpech, Guillaume; Szabó, Csaba; Remusat, Laurent; Mostefaoui, Smail; Asimow, Paul D.; Antoshechkina, Paula M.; Ghiorso, Mark S.; Boller, Elodie; Guyot, François

    2017-08-01

    Subduction of carbonated crust is widely believed to generate a flux of carbon into the base of the continental lithospheric mantle, which in turn is the likely source of widespread volcanic and non-volcanic CO2 degassing in active tectonic intracontinental settings such as rifts, continental margin arcs and back-arc domains. However, the magnitude of the carbon flux through the lithosphere and the budget of stored carbon held within the lithospheric reservoir are both poorly known. We provide new constraints on the CO2 budget of the lithospheric mantle below the Pannonian Basin (Central Europe) through the study of a suite of xenoliths from the Bakony-Balaton Highland Volcanic Field. Trails of secondary fluid inclusions, silicate melt inclusions, networks of melt veins, and melt pockets with large and abundant vesicles provide numerous lines of evidence that mantle metasomatism affected the lithosphere beneath this region. We obtain a quantitative estimate of the CO2 budget of the mantle below the Pannonian Basin using a combination of innovative analytical and modeling approaches: (1) synchrotron X-ray microtomography, (2) NanoSIMS, Raman spectroscopy and microthermometry, and (3) thermodynamic models (Rhyolite-MELTS). The three-dimensional volumes reconstructed from synchrotron X-ray microtomography allow us to quantify the proportions of all petrographic phases in the samples and to visualize their textural relationships. The concentration of CO2 in glass veins and pockets ranges from 0.27 to 0.96 wt.%, higher than in typical arc magmas (0-0.25 wt.% CO2), whereas the H2O concentration ranges from 0.54 to 4.25 wt.%, on the low end for estimated primitive arc magmas (1.9-6.3 wt.% H2O). Trapping pressures for vesicles were determined by comparing CO2 concentrations in glass to CO2 saturation as a function of pressure in silicate melts, suggesting pressures between 0.69 to 1.78 GPa. These values are generally higher than trapping pressures for fluid inclusions

  10. Hard X-ray irradiation of cosmic silicate analogs: structural evolution and astrophysical implications

    Science.gov (United States)

    Gavilan, L.; Jäger, C.; Simionovici, A.; Lemaire, J. L.; Sabri, T.; Foy, E.; Yagoubi, S.; Henning, T.; Salomon, D.; Martinez-Criado, G.

    2016-03-01

    Context. Protoplanetary disks, interstellar clouds, and active galactic nuclei contain X-ray-dominated regions. X-rays interact with the dust and gas present in such environments. While a few laboratory X-ray irradiation experiments have been performed on ices, X-ray irradiation experiments on bare cosmic dust analogs have been scarce up to now. Aims: Our goal is to study the effects of hard X-rays on cosmic dust analogs via in situ X-ray diffraction. By using a hard X-ray synchrotron nanobeam, we seek to simulate cumulative X-ray exposure on dust grains during their lifetime in these astrophysical environments and provide an upper limit on the effect of hard X-rays on dust grain structure. Methods: We prepared enstatite (MgSiO3) nanograins, which are analogs to cosmic silicates, via the melting-quenching technique. These amorphous grains were then annealed to obtain polycrystalline grains. These were characterized via scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) before irradiation. Powder samples were prepared in X-ray transparent substrates and were irradiated with hard X-rays nanobeams (29.4 keV) provided by beamline ID16B of the European Synchrotron Radiation Facility (Grenoble). X-ray diffraction images were recorded in transmission mode, and the ensuing diffractograms were analyzed as a function of the total X-ray exposure time. Results: We detected the amorphization of polycrystalline silicates embedded in an organic matrix after an accumulated X-ray exposure of 6.4 × 1027 eV cm-2. Pure crystalline silicate grains (without resin) do not exhibit amorphization. None of the amorphous silicate samples (pure and embedded in resin) underwent crystallization. We analyze the evolution of the polycrystalline sample embedded in an organic matrix as a function of X-ray exposure. Conclusions: Loss of diffraction peak intensity, peak broadening, and the disappearance of discrete spots and arcs reveal the amorphization

  11. Experimental determination of Fe isotope fractionation between liquid metal, silicate and sulfide at high pressures and temperatures

    Science.gov (United States)

    Williams, H. M.; Wood, B. J.; Halliday, A. N.

    2007-12-01

    There is evidence for significant equilibrium Fe isotope fractionation (≤0.26‰/amu) between metal and troilite (FeS) in iron meteorites (Williams et al., EPSL (250) 2006) and a smaller fractionation (Gessmann and Wood, EPSL (200) 2002; Wood et al., EPSL (in revision) 2007). Metal, sulfide and silicate fractions were separated from mounted and sectioned experimental charges using a computer-controlled micromill (New Wave-Merchantek). Sample dissolution, Fe purification and isotopic analysis followed established procedures (Williams et al., EPSL (235) 2005). In agreement with another preliminary high-pressure experimental study (Poitrasson and Roskosz, LPSC XXXVIII 2007) we find no appreciable fractionation between liquid iron metal and basaltic melt. However, there is a resolvable Fe isotope fractionation between silicate melt and Fe-S alloy which ranges from 0.12±0.04 to 0.15±0.04‰/amu for separate experiments (errors are propagated based on the 2 SD errors of replicate analyses). The Fe isotope compositions of coexisting phases from these experiments define a positive linear relationship with a slope that is, within error, equal to unity, implying isotopic equilibrium. No relationship between apparent fractionation factor and pressure or temperature is detectable within the range covered by the experiments. The fractionation factors determined from our experiments overlap with the average equilibrium fractionation factor obtained between silicate melt and pyrrhotite (Fe1-xS) of 0.18±0.02‰/amu at 0.5GPa and 1114-1274K (Schuessler et al., GCA (71) 2007) and are also broadly consistent with silicate-FeS fractionation factors inferred indirectly from iron meteorites and pallasites which range from ~0.16 to 0.24‰/amu. Taken together these observations suggest that resolvable stable isotope fractionation between Fe-S alloys and silicate melts can take place at extreme pressure and temperature conditions and that isotopically light Fe can be sequestered into

  12. Optical absorption and DFT calculations in L-aspartic acid anhydrous crystals: Charge carrier effective masses point to semiconducting behavior

    Science.gov (United States)

    Silva, A. M.; Silva, B. P.; Sales, F. A. M.; Freire, V. N.; Moreira, E.; Fulco, U. L.; Albuquerque, E. L.; Maia, F. F., Jr.; Caetano, E. W. S.

    2012-11-01

    Density functional theory (DFT) computations within the local-density approximation and generalized gradient approximation in pure form and with dispersion correction (GGA+D) were carried out to investigate the structural, electronic, and optical properties of L-aspartic acid anhydrous crystals. The electronic (band structure and density of states) and optical absorption properties were used to interpret the light absorption measurements we have performed in L-aspartic acid anhydrous crystalline powder at room temperature. We show the important role of the layered spatial disposition of L-aspartic acid molecules in anhydrous L-aspartic crystals to explain the observed electronic and optical properties. There is good agreement between the GGA+D calculated and experimental lattice parameters, with (Δa, Δb, Δc) deviations of (0.029,-0.023,-0.024) (units in Å). Mulliken [J. Chem. Phys.JCPSA60021-960610.1063/1.1740588 23, 1833 (1955)] and Hirshfeld [Theor. Chim. ActaTCHAAM0040-574410.1007/BF00549096 44, 129 (1977)] population analyses were also performed to assess the degree of charge polarization in the zwitterion state of the L-aspartic acid molecules in the DFT converged crystal. The lowest-energy optical absorption peaks related to transitions between the top of the valence band and the bottom of the conduction band involve O 2p valence states and C 1p and O 2p conduction states, with the carboxyl and COOH lateral chain group contributing significantly to the energy band gap. Among the calculated band gaps, the lowest GGA+D (4.49-eV) gap is smaller than the experimental estimate of 5.02 eV, as obtained by optical absorption. Such a wide-band-gap energy together with the small carrier effective masses estimated from band curvatures allows us to suggest that an L-aspartic acid anhydrous crystal can behave as a wide-gap semiconductor. A comparison of effective masses among directions parallel and perpendicular to the L-aspartic molecules layers reveals that charge

  13. Crystallisation mechanism of a multicomponent lithium alumino-silicate glass

    Energy Technology Data Exchange (ETDEWEB)

    Wurth, R. [Otto-Schott-Institut, Jena University, Fraunhoferstr. 6, 07743 Jena (Germany); Pascual, M.J., E-mail: mpascual@icv.csic.es [Instituto de Ceramica y Vidrio, CSIC, Kelsen 5, 28049 Madrid (Spain); Mather, G.C.; Pablos-Martin, A.; Munoz, F.; Duran, A. [Instituto de Ceramica y Vidrio, CSIC, Kelsen 5, 28049 Madrid (Spain); Cuello, G.J. [Institut Laue-Langevin, Boite Postale 156, 38042 Grenoble Cedex 9 (France); Ruessel, C. [Otto-Schott-Institut, Jena University, Fraunhoferstr. 6, 07743 Jena (Germany)

    2012-06-15

    A base glass of composition 3.5 Li{sub 2}O Bullet-Operator 0.15 Na{sub 2}O Bullet-Operator 0.2 K{sub 2}O Bullet-Operator 1.15 MgO Bullet-Operator 0.8 BaO Bullet-Operator 1.5 ZnO Bullet-Operator 20 Al{sub 2}O{sub 3} Bullet-Operator 67.2 SiO{sub 2} Bullet-Operator 2.6 TiO{sub 2} Bullet-Operator 1.7 ZrO{sub 2} Bullet-Operator 1.2 As{sub 2}O{sub 3} (in wt.%), melted and provided by SCHOTT AG (Mainz), was used to study the crystallisation mechanism of lithium alumino-silicate glass employing X-ray diffraction combined with neutron diffraction and non-isothermal differential scanning calorimetry (DSC). A high-quartz solid solution of LiAlSi{sub 2}O{sub 6} with nanoscaled crystals forms at 750 Degree-Sign C. Quantitative Rietveld refinement of samples annealed at 750 Degree-Sign C for 8 h determined a crystallised fraction of around 59 wt.%. The room temperature crystallised phase adopts an ordered, {beta}-eucryptite-like structure (2 Multiplication-Sign 2 Multiplication-Sign 2 cell) with Li ordered in the structural channels. The Avrami parameter (n {approx} 4), calculated from DSC data using different theoretical approaches, indicates that bulk crystallisation occurs and that the number of nuclei increases during annealing. The activation energy of the crystallisation is 531 {+-} 20 kJ mol{sup -1}. - Highlights: Black-Right-Pointing-Pointer Nanoscaled high-quartz crystals from a multicomponent lithium alumino-silicate glass. Black-Right-Pointing-Pointer Combined X-ray and neutron diffraction structural refinement. Black-Right-Pointing-Pointer {beta}-Eucryptite-like structure (2 Multiplication-Sign 2 Multiplication-Sign 2 cell) with Li ordered in the structural channels. Black-Right-Pointing-Pointer 3-Dimensional bulk crystallisation mechanism with an increasing number of nuclei. Black-Right-Pointing-Pointer Usage and validation of an alternative approach to calculate the Avrami parameter.

  14. Anhydrous octyl-glucoside phase transition from lamellar to isotropic induced by electric and magnetic fields.

    Science.gov (United States)

    Hashim, Rauzah; Sugimura, Akihiko; Nguan, Hock-Seng; Rahman, Matiur; Zimmermann, Herbert

    2017-02-28

    A static deuterium nuclear magnetic resonance ((2)HNMR) technique (magnetic field, B = 7.05 T) was employed to monitor the thermotropic lamellar phase of the anhydrous 1:1 mixture sample of octyl-b-D-glucoside (βOG) and that of partially deuterium labelled at the alpha position on the chain, i.e.,βOG-d2 In the absence of an electric field, the (2)H NMR spectrum of the mixture gives a typical quadrupolar doublet representing the aligned lamellar phase. Upon heating to beyond the clearing temperature at 112 °C, this splitting converts to a single line expected for an isotropic phase. Simultaneous application of magnetic and electric fields (E = 0.4 MV/m) at 85 °C in the lamellar phase, whose direction was set to be parallel or perpendicular to the magnetic field, resulted in the change of the doublet into a single line and this recovers to the initial doublet with time for both experimental geometries. This implies E- and B-field-induced phase transitions from the lamellar to an isotropic phase and a recovery to the lamellar phase again with time. Moreover, these phase transformations are accompanied by a transient current. A similar observation was made in a computational study when an electric field was applied to a water cluster system. Increasing the field strength distorts the water cluster and weakens its hydrogen bonds leading to a structural breakdown beyond a threshold field-strength. Therefore, we suggest the observed field-induced transition is likely due to a structure change of the βOG lamellar assembly caused by the field effect and not due to Joule heating.

  15. Deep Martian Mantle Melting and Implications for the Source Regions of Martian Basalts

    Science.gov (United States)

    Liebske, C.

    2016-12-01

    The chemical compositions of Martian SNC meteorites (Shergotty, Nakhla and Chassigny types) show significant variations in major and trace element contents, suggesting that parental magmas originate from different geochemical reservoirs. Radiogenic isotope systematics further indicate that some reservoirs were strongly influenced by silicate differentiation processes about 4.5 Gyr ago, placing such events in tight vicinity to core formation, and therefore favour magma ocean crystallisation and differentiation as a plausible mechanism for generating a diversity of sources. However, any predictions of geochemical signatures resulting from large scale magma ocean differentiation require precise knowledge of melting relations of a primordial bulk silicate Mars composition to be known. The aim of this study is to investigate solidus and liquids temperatures, mineral modes and melt fractions for the bulk silicate Mars (BSM) composition proposed by Taylor (2013, Chemie der Erde 73, 401-420) in a self consistent set of experiments from ambient to core-mantle boundary (estimated at around 20 GPa) pressures. Specific emphasis is put on the presure range greater than 10 GPa to more rigorously investigate the potential role of majoritic garnet during magma ocean differentiation. The new results, combined with data from previous studies on phase relations and mineral-melt element partitioning, are being used to derive time-integrated geochemical models to discuss fractionation mechanisms that could lead to the distinct chemical signatures of source regions proposed for martian meteorites.

  16. Effect of silicate solutions on metakaolinite based cementitious material

    Institute of Scientific and Technical Information of China (English)

    XIAO Xue-jun; LI Hua-jian; SUN Heng-hu

    2006-01-01

    High performance metakaolinite based cementitious materials were prepared with metakaolinite as main component, and the different modules of Na and Na-K silicate solutions as diagenetic agent. The results show that the mechanical properties are affected by different silicate solutions, compressive strengths of pastes hydrated for 3 d and 28 d with Na-K silicate solution (The modulus is 1) are about 43.68 and 78.52 MPa respectively. By analyzing the mechanical properties of Metakaolinite based cementitious materials, the diagenetic effect of lower module is better than higher module, and Na-K silicate solution is better than Na silicate solution. The structure of the Na and Na-K silicate solutions is studied with IR and 29Si NMR, the reason of the lower module and Na-K silicate solution improving the mechanical properties is that the low module silicate solution has lower polymeric degree of silicon dioxide, and the higher polymeric degree of silicon oxide tetrahedron(Q4) in Na-K silicate solution is less than Na silicate solution.

  17. Diseases associated with exposure to silica and nonfibrous silicate minerals. Silicosis and Silicate Disease Committee

    Energy Technology Data Exchange (ETDEWEB)

    1988-07-01

    Silicosis, a disease of historical importance, continues to occur cryptically today. Its pathogenesis is under ongoing study as new concepts of pathobiology evolve. In this article, the gross and microscopic features of the disease in the lungs and the lesions in lymph nodes and other viscera are described. These tissue changes are then discussed in the context of clinical disease and other possible or established complications of silica exposure (ie, scleroderma and rheumatoid arthritis, glomerulonephritis, and bronchogenic carcinoma). Silicates are members of a large family of common minerals, some of which have commercial importance. Silicates are less fibrogenic than silica when inhaled into the lungs, but cause characteristic lesions after heavy prolonged exposure. The features of these disease conditions are described herein. Various aspects of the mineralogy and tissue diagnosis of silicosis and lung disease due to silicates are reviewed. An overview of contemporary regulatory considerations is provided.204 references.

  18. Silicate Based Glass Formulations for Immobilization of U.S. Defense Wastes Using Cold Crucible Induction Melters

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Gary L.; Kim, Dong-Sang; Schweiger, Michael J.; Marra, James C.; Lang, Jesse B.; Crum, Jarrod V.; Crawford, Charles L.; Vienna, John D.

    2014-05-22

    The cold crucible induction melter (CCIM) is an alternative technology to the currently deployed liquid-fed, ceramic-lined, Joule-heated melter for immobilizing of U.S. tank waste generated from defense related reprocessing. In order to accurately evaluate the potential benefits of deploying a CCIM, glasses must be developed specifically for that melting technology. Related glass formulation efforts have been conducted since the 1990s including a recent study that is first documented in this report. The purpose of this report is to summarize the silicate base glass formulation efforts for CCIM testing of U.S. tank wastes. Summaries of phosphate based glass formulation and phosphate and silicate based CCIM demonstration tests are reported separately (Day and Ray 2013 and Marra 2013, respectively). Combined these three reports summarize the current state of knowledge related to waste form development and process testing of CCIM technology for U.S. tank wastes.

  19. Paleomagnetism and Mineralogy of Unusual Silicate Glasses and Baked Soils on the Surface of the Atacama Desert of Northern Chile: A Major Airburst Impact ~12ka ago?.

    Science.gov (United States)

    Roperch, P. J.; Blanco, N.; Valenzuela, M.; Gattacceca, J.; Devouard, B.; Lorand, J. P.; Tomlinson, A. J.; Arriagada, C.; Rochette, P.

    2015-12-01

    Unusual silicate glasses were found in northern Chile in one of the driest place on earth, the Atacama Desert. The scoria-type melted rocks are littered on the ground at several localities distributed along a longitudinal band of about 50km. The silicate glasses have a stable natural remanent magnetization carried by fine-grained magnetite and acquired during cooling. At one locality, fine-grained overbank sediments were heated to form a 10 to 20 cm-thick layer of brick-type samples. Magnetic experiments on oriented samples demonstrate that the baked clays record a thermoremanent magnetization acquired in situ above 600°C down to more than 10cm depth and cooled under a normal polarity geomagnetic field with a paleointensity of 40μT. In some samples of the silicate glass, large grains of iron sulphides (troilite) are found in the glass matrix with numerous droplets of native iron, iron sulphides and iron phosphides indicating high temperature and strong redox conditions during melting. The paleomagnetic record of the baked clays and the unusual mineralogy of the silicate glasses indicate a formation mainly by in situ high temperature radiation. Paleomagnetic experiments and chemical analyses indicate that the silicate glasses are not fulgurite type rocks due to lightning events, nor volcanic glasses or even metallurgical slags related to mining activity. The existence of a well-developped baked clay layer indicates that the silicate glasses are not impact-related ejectas. The field, paleomagnetic and mineralogical observations support evidence for a thermal event likely related to a major airburst. The youngest calibrated 14C age on a charcoal sample closely associated with the glass indicates that the thermal event occurred around 12 to 13 ka BP. The good conservation of the surface effects of this thermal event in the Atacama Desert could provide a good opportunity to further estimate the threats posed by large asteroid airbursts.

  20. Mantle Origin of Silicic Calc-alkaline Basalts to Andesites in the Central Mexican Volcanic Belt

    Science.gov (United States)

    Straub, S. M.; Zellmer, G. F.; Gómez-Tuena, A.; Stuart, F.; Espinasa-Perena, R.; Cai, Y.

    2011-12-01

    The Quaternary central Mexican Volcanic Belt, constructed on ~50 km thick continental crust, erupts a broad spectrum of basaltic to dacitic calc-alkaline magmas with the arc-typical high ratios of large-ion lithophile to high-field strength elements. In order to understand their genesis, we investigated high-Mg# olivine-phyric calc-alkaline basalts to andesites from Holocene monogenetic volcanoes Tuxtepec (50.2 wt% SiO2; 9.7 wt% MgO), Yecahuazac (53.1;8.0), Suchiooc Cone (53.2;9.2), Guespalapa (54.4-61.2;5.3-7.9) and Cuatepel (55.6-58.9;5.4-7.5), and as well as one basaltic andesite from composite volcano Popocateptl (56.7;6.9). The high 3He/4He (7.3 ± 0.3 Ra; n=16) of olivine phenocrysts that crystallize at upper crustal levels, and the limited range of Sr-Nd-Hf isotope ratios preclude any significant crustal contamination of these magmas. Moreover, small, but significant differences in Sr-Nd-Hf isotope ratios and the variations of olivine phenocrysts in the Fo-Ni space conclusively rule out that these magmas were related through fractional crystallization. Consequently, the basaltic to andesitic magmas must originate from the sub-arc mantle. Building on the high-Ni content of the olivines that by far exceed Ni abundances of olivines in partial melts of peridotite, we propose that the subarc MVB mantle contains segregations of silica-excess and silica-deficient 'reaction pyroxenites' that formed through infiltration of highly reactive silicic fluids or melts from slab. Upon melting, the pyroxenites produce dacitic and basaltic initial melts, respectively, that mix in variable proportions during ascent through mantle and crust. This genetic model links the silica enrichment of the arc magmas directly to the silica flux from slab, with no requirement for any significant melt silica increase in the overlying crust.

  1. Rejuvenation of shallow-crustal silicic magma bodies at Augustine and Hayes volcanoes, Alaska

    Science.gov (United States)

    Coombs, M. L.; Vazquez, J. A.; Hayden, L. A.; Calvert, A. T.; Lidzbarski, M. I.; Andersen, N. L.; Till, C. B.

    2015-12-01

    Rejuvenation of crystal-rich magma bodies leading to eruption can occur on a variety of scales and in varied tectonic settings. Two examples from the Aleutian arc highlight 1) segregation of silicic melt from an intermediate mush, and 2) "defrosting" of a shallowly emplaced intrusion. Augustine Volcano erupted a late Pleistocene rhyolite pumice fall that we link through zircon geochronology to cumulate dioritic blocks, ripped from Augustine's shallow magmatic plumbing system and ejected during the 2006 eruption. Unpolished zircon rims from the rhyolite yield a U-Th age of ~25 ka, and interiors yield a dominant age population of ~26 ka. Zircons from diorites have interior ages and compositions indistinguishable from those of the rhyolite. The diorites, rhyolite, and early Holocene dacites define whole-rock linear unmixing trends consistent with melt (rhyolite) extraction from a mush (dacites), leaving behind a cumulate residue (diorites). A volatile-rich basalt erupted just prior to the rhyolite likely facilitated melt extraction from the mush. The rhyolitic Hayes River ignimbrite, erupted from Hayes volcano, contains dense porphyry blocks that match pumices in composition and phenocryst content and are samples of a shallow intrusion. Autocrystic monazite accommodated up to several weight % Th and significantly affected the U-Th ratio of the magma during differentiation. An isochron for early melt and low-U monazites yields an age of ~67 ka, whereas one for late melt and high-U monazites yields ~42 ka. This younger age is indistinguishable from the laser single crystal Ar-Ar age for sanidine of 41±2 ka (1 sigma). We interpret the apparent ~25 k.y. crystallization interval to represent the assembly and differentiation timescale associated with the Hayes magma body. Sharp reverse zoning in sanidine from pumice (but not porphyry) records a thermal pulse not seen in the more slowly reacting phases, suggesting that a rejuvenation event occurred just prior to eruption.

  2. Determination of chlorine in silicate rocks

    Science.gov (United States)

    Peck, L.C.

    1959-01-01

    In a rapid accurate method for the determination of chlorine in silicate rocks, the rock powder is sintered with a sodium carbonate flux containing zinc oxide and magnesium carbonate. The sinter cake is leached with water, the resulting solution is filtered, and the filtrate is acidified with nitric acid. Chlorine is determined by titrating this solution with mercuric nitrate solution using sodium nitroprusside as the indicator. The titration is made in the dark with a beam of light shining through the solution. The end point of the titration is found by visually comparing the intensity of this beam of light with that of a similar beam of light in a reference solution.

  3. Nitridosilicates - a significant extension of silicate chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Schnick, W.; Huppertz, H. [Bayreuth Univ. (Germany). Lab. fuer Anorganische Chemie

    1997-05-01

    A new dimension in silicate chemistry becomes accessible through substitution of oxygen by nitrogen. Multinary nitridosilicates, such as Ln{sub 3}Si{sub 6}N{sub 11} (Ln = La, Ce, Pr, Nd, Sm) shown on the right, are built up from SiN{sub 4} tetrahedra into network structures. Owing to the stability of the covalent Si-N bonds and the high degree of condensation, the nitridosilicates show remarkable chemical and thermal stabilities, similar to Si{sub 3}N{sub 4}. (orig.) 22 refs.

  4. Microbial dissolution of silicate materials. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Schwartzman, D. [Howard Univ., Washington, DC (United States). Dept. of Biology

    1996-03-26

    The objective of this research was to better understand the role of selected thermophilic bacteria in the colonization and dissolution of silicate minerals, with potential applications to the HDR Project. The demonstration of enhanced dissolution from microbial effects is critically dependent on providing a mineral bait within a media deficient in the critical nutrient found in the mineral (e.g., Fe). Reproducible experimental conditions in batch experiments require agitation to expose mineral powders, as well as nearly similar initial conditions for both inoculated cultures and controls. It is difficult, but not impossible to ensure reproducible conditions with microbes favoring filamentous growth habits.

  5. LABORATORY INVESTIGATIONS OF SILICATE MUD CONTAMINATION WITH CALCIUM

    Directory of Open Access Journals (Sweden)

    Nediljka Gaurina-Međimurec

    2004-12-01

    Full Text Available The silicate-based drilling fluid is a low solids KCl/polymer system with the addition of soluble sodium or potassium silicate to enhance inhibition and wellbore stability. Silicate-based drilling fluids exhibit remarkable shale and chalk stabilizing properties, resulting in gauge hole and the formation of firm cuttings when drilling reactive shales and soft chalks. Silicates protect shales by in-situ gellation when exposed to the neutral pore fluid and precipitation, which occurs on contact with divalent ions present at the surface of the shale. Also, silicates prevent the dispersion and washouts when drilling soft chalk by reacting with the Ca2+ ions present on chalk surfaces of cutting and wellbore to form a protective film. The silicate-based drilling fluid can be used during drilling hole section through shale interbeded anhydrite formations because of its superior shale stabilizing characteristics. However, drilling through the anhydrite can decrease the silicate concentration and change rheological and filtration fluid properties. So, the critical concentration of calcium ions should be investigated by lab tests. This paper details the mechanism of shale inhibition using silicate-based drilling fluid, and presents results of lab tests conducted to ascertain the effect of Ca2+ ions on silicate level in the fluid and the fluid properties.

  6. Melting of Ice under Pressure

    Energy Technology Data Exchange (ETDEWEB)

    Schwegler, E; Sharma, M; Gygi, F; Galli, G

    2008-07-31

    The melting of ice under pressure is investigated with a series of first principles molecular dynamics simulations. In particular, a two-phase approach is used to determine the melting temperature of the ice-VII phase in the range of 10 to 50 GPa. Our computed melting temperatures are consistent with existing diamond anvil cell experiments. We find that for pressures between 10 to 40 GPa, ice melts as a molecular solid. For pressures above {approx}45 GPa there is a sharp increase in the slope of the melting curve due to the presence of molecular dissociation and proton diffusion in the solid, prior to melting. The onset of significant proton diffusion in ice-VII as a function of increasing temperature is found to be gradual and bears many similarities to that of a type-II superionic solid.

  7. In vitro study on the interaction of ketotifen fumarate with anhydrous theophylline

    Directory of Open Access Journals (Sweden)

    Mohammed Aktar Sayeed

    2012-06-01

    Full Text Available The purpose of the present study was to investigate the interaction between ketotifen fumarate and anhydrous theophylline in aqueous media of various pH (1.2 and 6.8. Using Job's continuous-variation analysis and Ardon's spectrophotomeric measurement methods, the values of the stability constants of theophylline with ketotifen were determined at a fixed temperature (37 ºC at various pH. The stability constants, ranging between 5.66 and 9.92, were derived from Ardon's plot, indicating that comparatively stable complexes had formed as a result of an interaction between the drugs. However, following the interaction of theophylline with ketotifen, stability constants were O objetivo do presente estudo foi investigar a interação entre o fumarato de cetotifeno e a teofilina anidra em meios aquosos com vários pH (1,2 e 6,8. Utilizando a análise da variação contínua de Job e os métodos de medida espectrofotométrica de Ardon, os valores das constantes de estabilidade da teofilina com o cetotifeno foram determinados em temperatura fixa (37 oC em vários pH. As constantes de estabilidade, variando entre 5,66 e 9,92 derivaram-se a partir do delineamento de Ardon, indicando, comparativamente, que complexos estáveis se formaram como resultado da interação entre os fármacos. Entretanto, seguindo a interação da teofilina com o cetotifeno, as constantes de estabilidade foram <1, em pH gástrico (1,2 e intestinal (8,8. A administração concomitante de cetotifeno e teofilina poderia resultar na formação de complexo estável, o que reduz a atividade terapêutica de ambos os fármacos.

  8. A Clinopyroxene-Plagioclase Geobarometer for A-type Silicic Volcanic Rocks

    Science.gov (United States)

    Wolff, J.; Iveson, A. A.; Davis, K.; Johnson, T. A.; Gahagan, S.; Ellis, B. S.

    2015-12-01

    Constraining the crustal storage depths of magmas is important in understanding volcanism. The reaction: anorthite (pl) = Ca-Tschermak's (cpx) + silica (Q or liq) has a large volume change and hence offers potential as a geobarometer, but has not been extensively exploited as such. One of the chief barriers to its wide application is consistent estimation of melt silica activity for assemblages that lack quartz. We have skirted this problem by confining attention to metaluminous silicic compositions (SiO2 > 60% by weight), for which silica activity during crystallization is presumed to be close to 1, and calibrated the barometer for the range 0 - 2 GPa using the LEPR database and additional experiments from the literature. Additional improvement is obtained by excluding hydrous phase-bearing assemblages. Despite the analytical uncertainties present in older experimental investigations, with knowledge of temperature, and clinopyroxene, plagioclase and host melt compositions, pressures for amphibole- and biotite-free dacites and rhyolites can be estimated to ±0.17 GPa (1 sigma). The limitations of the barometer render it most applicable to intraplate, A-type rhyolites. Application to one such system, the Snake River Plain rhyolites, indicate that both melt-hosted phenocrysts and clinopyroxene-plagioclase aggregate grains found in these rhyolites formed at low pressures, <0.5 GPa. This is consistent with isotopic evidence for a shallow crustal origin for Snake River Plain rhyolites.

  9. Special topical approach to the treatment of acne. Suppression of sweating with aluminum chloride in an anhydrous formulation.

    Science.gov (United States)

    Hurley, H J; Shelley, W B

    1978-12-01

    A new topical approach to acne treatment--the use of aluminum chloride hexahydrate in anhydrous ethanol (ACAE)--was studied in 141 patients. Using sequential treatment schedules, paired comparison techniques, and various concentrations of ACAE, we established maximal efficacy with minimal local irritation for the 6.25% strength solution. Clinical efficacy and lack of toxicity of this formulation were confirmed by the additional clinical study of 65 patients. The antiperspirant and antibacterial actions of 6.25% ACAE solution were then verified on acne skin areas. It is postulated that the clinical improvement in acne that follows the topical use of ACAE results from one or both of these actions.

  10. A Safe and Brief Way for Preparing Anhydrous LnCl3 (Ln=Sc, Y, La to Lu)

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Anhydrous lanthanide chlorides LnCl3 (Ln=Sc, Y, La to Lu except for Pm), which are difficult to prepare in other ways, were prepared by chemical vapor transport (CVT) process. Rare earth oxide reacted with Al2Cl6 at 300℃ to produce LnCl3, which was then separated from other solids by means of CVT at a temperature gradient from 400 to 180℃. Residual Al2Cl6 (g) was removed by carrier of dry N2 gas at 200℃. The yielding rates were >90%, and the purity of products was >99.5%.

  11. Improved quantification of alite and belite in anhydrous Portland cements by 29Si MAS NMR: Effects of paramagnetic ions

    DEFF Research Database (Denmark)

    Poulsen, Søren Lundsted; Kocaba, Vanessa; Le Saoût, Gwenn;

    2009-01-01

    The applicability, reliability, and repeatability of 29Si MAS NMR for determination of the quantities of alite (Ca3SiO5) and belite (Ca2SiO4) in anhydrous Portland cement was investigated in detail for 11 commercial Portland cements and the results compared with phase quantifications based...... on powder X-ray diffraction combined with Rietveld analysis and with Taylor-Bogue calculations. The effects from paramagnetic ions (Fe3+) on the spinning sideband intensities, originating from dipolar couplings between 29Si and the spins of the paramagnetic electrons, were considered and analyzed in spectra...

  12. MULTIPLE MELTING IN NYLON 1010

    Institute of Scientific and Technical Information of China (English)

    FU Shuren; CHEN Taoyung

    1983-01-01

    Multiple melting behavior of nylon 1010 has been investigated by using DSC instrument. Effects of partial scanning, partial scanning and annealing, heating rate, cooling rate and stepwise annealing on the melting curve were studied. Experimental results indicate that the sample undergoes a process of continuous melting and recrystallization during DSC scanning. Nylon 1010 contains a distribution of crystallites of different degrees of perfection which is strongly dependent on its previous thermal history. From the structural reorganization point of view, the origin of double and multiple peaks of the melting curve is explained.

  13. Argon Partitioning Between Metal and Silicate Liquids in the Laser-Heated DAC to 25 GPa

    Science.gov (United States)

    Bouhifd, M. A.; Jephcoat, A. P.

    2003-12-01

    The accretion of the Earth from primordial material and its subsequent segregation into core and mantle are fundamental problems in terrestrial and solar system science. Many of the questions about the process, although well developed as model scenarios over the last few decades, are still open and much debated, and include, for example, whether the core is, or was, a reservoir for the noble (rare) gases. In the present study we use for the first time the laser-heated diamond-anvil cell (LHDAC) to study the Ar partitioning at high-pressure and temperature between metal and silicate liquids. Little work has been reported on noble gas partitioning at pressure since a single multi-anvil experiment to 10 GPa (Matsuda et al., 1993). We used either compacted glass powders simulating that of a model C1 chondrite and iron metal, or pure metal alloys (pure Fe, FeNiCo alloy, FeSi). Thermal insulation from the diamonds was achieved with solid argon as pressure medium. The samples were heated by a multimode YAG laser for an average of 15 minutes and temperatures were determined spectro-radiometrically with a fit to a grey-body Planck function. Samples recovered after the runs were analysed by electron microprobe with spatial resolution near 1 μ m. The argon melts by conductive heating from the molten sample dissolving into the metal/silicate melt. Preliminary results on Ar solubility at lower pressures show good agreement with data reported by White et al. (1986) for Ar solubility in sanidine (KAlSi3O8). With sanidine melt, Ar solubility increases up to around 5-6 GPa where it reaches about 2.5 wt%, and remains roughly constant to higher pressures, suggesting that a threshold concentration is reached. Similar behavior is observed for a mix of C1-chondrite composition and iron and the results imply that the solubility of Ar is intimately related to liquid structure at high pressure. We also present results on Ar solubility into pure silicate liquids of varying composition in

  14. Microstructural development of melt-grown mullite fibrils

    Science.gov (United States)

    Baer, Amanda

    The crystallization behavior of mullite growing from the melt within a siliceous glassy phase has been investigated. Initial studies examined single crystal, nominally continuous mullite fibers grown in bundles by directional solidification using a modified version of the Edge-Defined Film-Fed Growth (EFG) process (GE-AE/Saphikon, Inc.). These fibers are intended to be recovered by dissolution of the glass matrix and used as reinforcements of ceramic matrix composites. Subsequent experiments employed small-scale crucible-based solidification experiments conducted at the UCSB Materials Processing Lab. The EFG approach yielded ribbons containing bundles of aligned single-crystal mullite with relatively small diameters embedded in a silicate glass matrix. Because of interactions between the growing crystals, however, the fibers recovered are actually discontinous crystals and hence termed "fibrils." Ribbons were produced from SiOsb2-Alsb2Osb3-MgO melts at solidification rates ranging from 2.5 to 61 cm/h. Typically, mullite fibers grew in the (001) direction and had distinct facets on the \\{110)-type planes. The mullite fibrils exhibited a variety of cross-sectional profiles-including various forms of glass-filled hollows, internal splintering, and lateral dendritic growth-which resulted largely from morphological instability during growth, and thus depended on the alloy composition and solidification parameters. Morphological instabilities became more pronounced with increasing growth velocity. Increasing the MgO content or the Alsb2Osb3/SiOsb2 ratio reduced these instabilities, indicating the role of alloy chemistry in modifying the transport properties in the melt, and hence the ease of solute redistribution. The crucible experiments examined the role of melt chemistry further, paying particular attention to the effects of various modifying additions to the SiOsb2-Alsb2Osb3 melt (MgO, BaO, Nasb2O, and Ksb2O). The choice of modifying oxide had a significant effect

  15. Research drilling in young silicic volcanoes

    Energy Technology Data Exchange (ETDEWEB)

    Eichelberger, J.C.

    1989-06-30

    Magmatic activity, and particularly silicic magmatic activity, is the fundamental process by which continental crust forms and evolves. The transport of magma from deep crustal reservoirs to the surface is a neglected but important aspect of magmatic phenomena. It encompasses problems of eruptive behavior, hydrothermal circulation, and ore deposition, and must be understood in order to properly interpret deeper processes. Drilling provides a means for determining the relationship of shallow intrusive processes to eruption processes at young volcanoes where eruptions are best understood. Drilling also provides a means for directly observing the processes of heat and mass transfer by which recently emplaced intrusions approach equilibrium with their new environment. Drilling in the Inyo Chain, a 600-year-old chain of volcanic vents in California, has shown the close relationship of silicic eruption to shallow dike emplacement, the control of eruptive style by shallow porous-flow degassing, the origin of obsidian by welding, the development of igneous zonation by viscosity segregation, and the character and size of conduits in relation to well-understood magmatic and phreatic eruptions. 36 refs., 9 figs.

  16. Stability constants for silicate adsorbed to ferrihydrite

    DEFF Research Database (Denmark)

    Hansen, Hans Christian Bruun; Wetche, T.P.; Raulund-Rasmussen, Karsten

    1994-01-01

    experiments in 0.01 m NaNO3 electrolyte (pH 3-6). The surface equilibrium constants were calculated according to the two-layer model by Dzombak & Morel (1990). Near equilibrium between protons/hydroxyls in solution and the ferrihydrite surface was obtained within minutes while equilibration with silicate...... required days-weeks, both reactions probably being diffusion controlled. Applying the values for specific surface area and site densities for ferrihydrite used by Dzombak & Morel (1990) (600 m2 g-1, 3.4 mumole m-2) the constants pK(al)intr 6.93 +/- 0.12, pK(a2)intr = 8.72 +/- 0.17 and log K(Si) = 3.62 were...... calculated by using the FITEQL optimization routine. Use of the specific surface area actually measured (269 m2 g-1) gave a poorer fit of the experimental data. Due to the slow adsorption of silicate and hence long shaking times, changes in the surface characteristics of the ferrihydrite seem to take place...

  17. Melt pool dynamics during selective electron beam melting

    Science.gov (United States)

    Scharowsky, T.; Osmanlic, F.; Singer, R. F.; Körner, C.

    2014-03-01

    Electron beam melting is a promising additive manufacturing technique for metal parts. Nevertheless, the process is still poorly understood making further investigations indispensable to allow a prediction of the part's quality. To improve the understanding of the process especially the beam powder interaction, process observation at the relevant time scale is necessary. Due to the difficult accessibility of the building area, the high temperatures, radiation and the very high scanning speeds during the melting process the observation requires an augmented effort in the observation equipment. A high speed camera in combination with an illumination laser, band pass filter and mirror system is suitable for the observation of the electron beam melting process. The equipment allows to observe the melting process with a high spatial and temporal resolution. In this paper the adjustment of the equipment and results of the lifetime and the oscillation frequencies of the melt pool for a simple geometry are presented.

  18. Experimental investigation of the partitioning of phosphorus between metal and silicate phases - Implications for the earth, moon and eucrite parent body

    Science.gov (United States)

    Newsom, H. E.; Drake, M. J.

    1983-01-01

    An experimental study is reported of the partitioning of Phosphorus between solid metal and basaltic silicate liquid as a function of temperature and oxygen fugacity and of the implications for the earth, moon and eucrite parent body (EPB). The relationship established between the partition coefficient and the fugacity is given at 1190 C by log D(P) = -1.12 log fO2 - 15.95 and by log D(P) = -1.53 log fO2 17.73 at 1300 C. The partition coefficient D(P) was determined, and it is found to be consistent with a valence state of 5 for P in the molten silicate. Using the determined coefficient the low P/La ratios of the earth, moon, and eucrites relative to C1 chondrites can be explained. The lowering of the P/La ratio in the eucrites relative to Cl chondrite by a factor of 40 can be explained by partitioning P into 20-25 wt% sulfur-bearing metallic liquid corresponding to 5-25% of the total metal plus silicate system. The low P/La and W/La ratios in the moon may be explained by the partitioning of P and W into metal during formation of a small core by separation of liquid metal from silicate at low degrees of partial melting of the silicates. These observations are consistent with independent formation of the moon and the earth.

  19. Convective melting in a magma chamber: theory and numerical experiment.

    Science.gov (United States)

    Simakin, A.

    2012-04-01

    We present results of the numerical modeling of convective melting in a magma chamber in 2D. Model was pointed on the silicic system approximated with Qz-Fsp binary undersaturated with water. Viscosity was calculated as a function of the melt composition, temperature and crystal content and comprises for the pure melt 104.5-105.5 Pas. Lower boundary was taken thermally insulated in majority of the runs. Size of FEM (bilinear elements) grid for velocity is 25x25 cm and for the integration of the density term 8x8 cm. Melting of the chamber roof proceeds with the heat supply due to the chaotic thermo-compositional convection and conductive heat loose into melted substrate. We compare our numerical data with existing semi-analytical models. Theoretical studies of the assimilation rates in the magma chambers usually use theoretical semi-analytical model by Huppert and Sparks (1988) (e.g., Snyder, 2000). We find that this model has strong points: 1) Independence of the melting rate on the sill thickness (Ra>>Rac) 2) Independence of the convective heat transfer on the roof temperature 3) Determination of the exponential thermal boundary layer ahead of the melting front and weak points: 1) Ignoring the possibility of the crystallization without melting regime for narrow sills and dykes. 2)Neglecting of two-phase character of convection. 3)Ignoring of the strong viscosity variation near the melting front. Independence of convective flux from the sill size (at Ra>>Rac) allows reducing of computational domain to the geologically small size (10-15 m). Concept of exponential thermal boundary layer is also rather important. Length scale (L0) of this layer is related to the melting rate and thermal diffusivity coefficient kT as L0=kT/um and at the melting rate 10 m/yr becomes about 2 m. Such small scale implies that convective melting is very effective (small conductive heat loss) and part of the numerical domain filled with roof rocks can be taken small. In the H&S model

  20. Beyond the Melting Pot Reconsidered.

    Science.gov (United States)

    Anderson, Elijah

    2000-01-01

    Discusses the 1963 book, "Beyond the Melting Pot," which suggested that eventually the problem of different ethnicities in the U.S. would be resolved and society would become one melting pot. Examines how changes in immigration and economic structures have affected the issue, noting the devastating effect of the dominant culture's…

  1. Petrophysical Analysis of Siliceous Ooze Sediments, Ormen Lange Field, Norway

    DEFF Research Database (Denmark)

    Awedalkarim, Ahmed; Fabricius, Ida Lykke

    Skeletal remains of siliceous algae form biogenic fine grained highly porous pelagic siliceous ooze sediments that were found above the reservoir of the Ormen Lange gas field which is located in the southern part of the Norwegian Sea (Figure 1a). The Palaeocene sandstone of the “Egga” Formation i...

  2. Silicate Adsorption in Paddy Soils of Guangdong Province, China

    Institute of Scientific and Technical Information of China (English)

    HUANG Li-Yuan; LI Hua-Xing; ZHANG Xin-Ming; LU Wei-Sheng; LIU Yuan-Jin

    2006-01-01

    Silicate adsorption in eight paddy soils developed from four different parent materials in Guangdong Province, China was examined to obtain fundamental knowledge of silicate adsorption to improve the efficacy of silicate fertilizer use in these areas. A correlation analysis showed that silicate adsorption did not obey the Langmuir equation (r = -0.664-0.301) but did obey the Freundlich and Temkin equations (P ≤ 0.01, r = 0.885-0.990). When the equilibrium silicate concentration (Ci) was less than 45 mg SiO2 kg-1, the adsorption capacity was in the following decreasing order of paddy soils: basalt-derived > Pearl River Delta sediment-derived > granite-derived > sand-shale-derived. Stepwise regression and path analysis showed that for the investigated paddy soils amorphous MnO and Al2O3 were the two most important materials that affected silicate adsorption. Moreover, as Ci increased, amorphous Al2O3 tended to play a more important role in silicate adsorption, while the effects of amorphous MnO on silicate adsorption tended to decrease.

  3. Crystalline silicates in AGB and post-AGB stars

    NARCIS (Netherlands)

    Waters, LBFM; Molster, FJ; LeBertre, T; Lebre, A; Waelkens, C

    1999-01-01

    We discuss ISO spectroscopy of oxygen-rich dust shells surrounding evolved stars. The dust that condenses in the outflows of stars on the Asymptotic Giant Branch consists mainly of amorphous silicates and simple oxides. For high mass loss rates, crystalline silicates begin to appear at modest abunda

  4. The shape and composition of interstellar silicate grains

    NARCIS (Netherlands)

    Min, M.; Waters, L.B.F.M.; de Koter, A.; Hovenier, J.W.; Keller, L.P.; Markwick-Kemper, F.

    2007-01-01

    We investigate the composition and shape distribution of silicate dust grains in the interstellar medium. The effects of the amount of magnesium and iron in the silicate lattice are studied in detail. We fit the spectral shape of the interstellar 10 mu m extinction feature as observed towards the ga

  5. The shape and composition of interstellar silicate grains

    NARCIS (Netherlands)

    Min, M.; Waters, L.B.F.M.; de Koter, A.; Hovenier, J.W.; Keller, L.P.; Markwick-Kemper, F.

    2007-01-01

    We investigate the composition and shape distribution of silicate dust grains in the interstellar medium. The effects of the amount of magnesium and iron in the silicate lattice are studied in detail. We fit the spectral shape of the interstellar 10 mu m extinction feature as observed towards the

  6. Ionic-liquid-based proton conducting membranes for anhydrous H2/Cl2 fuel-cell applications.

    Science.gov (United States)

    Liu, Sa; Zhou, Li; Wang, Pengjie; Zhang, Fangfang; Yu, Shuchun; Shao, Zhigang; Yi, Baolian

    2014-03-12

    An ionic-liquid-doped poly(benzimidazole) (PBI) proton-conducting membrane for an anhydrous H2/Cl2 fuel cell has been proposed. Compared with other ionic liquids, such as imidazole-type ionic liquids, diethylmethylammonium trifluoromethanesulfonate ([dema][TfO]) showed better electrode reaction kinetics (H2 oxidation and Cl2 reduction reaction at platinum) and was more suitable for a H2/Cl2 fuel cell. PBI polymer and [dema][TfO] were compatible with each other, and the hybrid membranes exhibited high stability and good ionic conductivity, reaching 20.73 mS cm(-1) at 160 °C. We also analyzed the proton-transfer mechanism in this ionic-liquid-based membrane and considered that both proton-hopping and diffusion mechanisms existed. In addition, this composite electrolyte worked well in a H2/Cl2 fuel cell under non-water conditions. This work would give a good path to study the novel membranes for anhydrous H2/Cl2 fuel-cell application.

  7. Measurement of bonding energy in an anhydrous nitrogen atmosphere and its application to silicon direct bonding technology

    Science.gov (United States)

    Fournel, F.; Continni, L.; Morales, C.; Da Fonseca, J.; Moriceau, H.; Rieutord, F.; Barthelemy, A.; Radu, I.

    2012-05-01

    Bonding energy represents an important parameter for direct bonding applications as well as for the elaboration of physical mechanisms at bonding interfaces. Measurement of bonding energy using double cantilever beam (DCB) under prescribed displacement is the most used technique thanks to its simplicity. The measurements are typically done in standard atmosphere with relative humidity above 30%. Therefore, the obtained bonding energies are strongly impacted by the water stress corrosion at the bonding interfaces. This paper presents measurements of bonding energies of directly bonded silicon wafers under anhydrous nitrogen conditions in order to prevent the water stress corrosion effect. It is shown that the measurements under anhydrous nitrogen conditions (less than 0.2 ppm of water in nitrogen) lead to high stable debonding lengths under static load and to higher bonding energies compared to the values measured under standard ambient conditions. Moreover, the bonding energies of Si/SiO2 or SiO2/SiO2 bonding interfaces are measured overall the classical post bond annealing temperature range. These new results allow to revisit the reported bonding mechanisms and to highlight physical and chemical phenomena in the absence of stress corrosion effect.

  8. Noble metal nanoclusters and nanoparticles precede mineral formation in magmatic sulphide melts.

    Science.gov (United States)

    Helmy, Hassan M; Ballhaus, Chris; Fonseca, Raúl O C; Wirth, Richard; Nagel, Thorsten; Tredoux, Marian

    2013-01-01

    In low temperature aqueous solutions, it has long been recognized by in situ experiments that many minerals are preceded by crystalline nanometre-sized particles and non-crystalline nanophases. For magmatic systems, nanometre-sized precursors have not yet been demonstrated to exist, although the suggestion has been around for some time. Here we demonstrate by high temperature quench experiments that platinum and arsenic self-organize to nanoparticles, well before the melt has reached a Pt-As concentration at which discrete Pt arsenide minerals become stable phases. If all highly siderophile elements associate to nanophases in undersaturated melts, the distribution of the noble metals between silicate, sulphide and metal melts will be controlled by the surface properties of nano-associations, more so than by the chemical properties of the elements.

  9. A geochemical study of the winonaites: Evidence for limited partial melting and constraints on the precursor composition

    Science.gov (United States)

    Hunt, Alison C.; Benedix, Gretchen K.; Hammond, Samantha J.; Bland, Philip A.; Rehkämper, Mark; Kreissig, Katharina; Strekopytov, Stanislav

    2017-02-01

    The winonaites are primitive achondrites which are associated with the IAB iron meteorites. Textural evidence implies heating to at least the Fe, Ni-FeS cotectic, but previous geochemical studies are ambiguous about the extent of silicate melting in these samples. Oxygen isotope evidence indicates that the precursor material may be related to the carbonaceous chondrites. Here we analysed a suite of winonaites for modal mineralogy and bulk major- and trace-element chemistry in order to assess the extent of thermal processing as well as constrain the precursor composition of the winonaite-IAB parent asteroid. Modal mineralogy and geochemical data are presented for eight winonaites. Textural analysis reveals that, for our sub-set of samples, all except the most primitive winonaite (Northwest Africa 1463) reached the Fe, Ni-FeS cotectic. However, only one (Tierra Blanca) shows geochemical evidence for silicate melting processes. Tierra Blanca is interpreted as a residue of small-degree silicate melting. Our sample of Winona shows geochemical evidence for extensive terrestrial weathering. All other winonaites studied here (Fortuna, Queen Alexander Range 94535, Hammadah al Hamra 193, Pontlyfni and NWA 1463) have chondritic major-element ratios and flat CI-normalised bulk rare-earth element patterns, suggesting that most of the winonaites did not reach the silicate melting temperature. The majority of winonaites were therefore heated to a narrow temperature range of between ∼1220 (the Fe, Ni-FeS cotectic temperature) and ∼1370 K (the basaltic partial melting temperature). Silicate inclusions in the IAB irons demonstrate partial melting did occur in some parts of the parent body (Ruzicka and Hutson, 2010), thereby implying heterogeneous heat distribution within this asteroid. Together, this indicates that melting was the result of internal heating by short-lived radionuclides. The brecciated nature of the winonaites suggests that the parent body was later disrupted by

  10. Chemical and mineralogical size segregation in the impact disruption of anhydrous stone meteorites

    Energy Technology Data Exchange (ETDEWEB)

    Flynn, G.J.; Durda, D.D. (SUNYP); (SW Research Institute)

    2005-02-02

    We performed impact disruption experiments on pieces from eight different anhydrous chondritic meteorites - four weathered ordinary chondrite finds from North Africa (NWA791, NWA620, NWA869 and MOR001), three almost unweathered ordinary chondrite falls (Mbale, Gao, and Saratov), and an almost unweathered carbonaceous chondrite fall (Allende). In each case the impactor was a small (1/8 or 1/4 in) aluminum sphere fired at the meteorite target at {approx} 5 km/s, comparable to the mean collision speed in the main-belt. Some of the {approx}5 to {approx} 150 {micro}m debris from each disruption was collected in aerogel capture cells, and the captured particles were analyzed by in situ synchrotron-based X-ray fluorescence. For each meteorite, many of the smallest particles (< 10 {micro}m up to 35 {micro}m in size, depending on the meteorite) exhibit very high Ni/Fe ratios compared to the Ni/Fe ratios measured in the larger particles (> 45 {micro}m), a composition consistent with the smallest debris being dominated by matrix material while the larger debris is dominated by fragments from olivine chondrules. These results may explain why the {approx} 10 {micro}m interplanetary dust particles (IDPs) collected from the Earth's stratosphere are C-rich and volatile-rich compared to the presumed solar nebula composition. The {approx} 10 {micro}m IDPs may simply sample the matrix of an inhomogeneous parent body, structurally and mineralogically similar to the chondritic meteorites, which are inhomogeneous assemblages of compact, strong, C- and volatile-poor chondrules that are distributed in a more porous, C- and volatile-rich matrix. In addition, these results may explain why the micrometeorites, which are {approx} 50 {micro}m to millimeters in size, recovered from the polar ices are Ni- and S-poor compared to chondritic meteorites, since these polar micrometeorites may preferentially sample fragments from the Ni- and S-poor olivine chondrules. These results indicate that

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

    Science.gov (United States)

    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.

  12. Fault rheology beyond frictional melting.

    Science.gov (United States)

    Lavallée, Yan; Hirose, Takehiro; Kendrick, Jackie E; Hess, Kai-Uwe; Dingwell, Donald B

    2015-07-28

    During earthquakes, comminution and frictional heating both contribute to the dissipation of stored energy. With sufficient dissipative heating, melting processes can ensue, yielding the production of frictional melts or "pseudotachylytes." It is commonly assumed that the Newtonian viscosities of such melts control subsequent fault slip resistance. Rock melts, however, are viscoelastic bodies, and, at high strain rates, they exhibit evidence of a glass transition. Here, we present the results of high-velocity friction experiments on a well-characterized melt that demonstrate how slip in melt-bearing faults can be governed by brittle fragmentation phenomena encountered at the glass transition. Slip analysis using models that incorporate viscoelastic responses indicates that even in the presence of melt, slip persists in the solid state until sufficient heat is generated to reduce the viscosity and allow remobilization in the liquid state. Where a rock is present next to the melt, we note that wear of the crystalline wall rock by liquid fragmentation and agglutination also contributes to the brittle component of these experimentally generated pseudotachylytes. We conclude that in the case of pseudotachylyte generation during an earthquake, slip even beyond the onset of frictional melting is not controlled merely by viscosity but rather by an interplay of viscoelastic forces around the glass transition, which involves a response in the brittle/solid regime of these rock melts. We warn of the inadequacy of simple Newtonian viscous analyses and call for the application of more realistic rheological interpretation of pseudotachylyte-bearing fault systems in the evaluation and prediction of their slip dynamics.

  13. Analysis of the surface of tricalcium silicate during the induction period by X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Bellmann, F., E-mail: frank.bellmann@uni-weimar.de [Institute for Building Materials Science, Bauhaus University Weimar, 99423 Weimar (Germany); Sowoidnich, T.; Ludwig, H.-M. [Institute for Building Materials Science, Bauhaus University Weimar, 99423 Weimar (Germany); Damidot, D. [Ecole des Mines de Douai, Civil and Environmental Engineering Department, 941 rue Charles Bourseul, BP 10838, 59508 Doua cedex (France)

    2012-09-15

    X-ray photoelectron spectroscopy allows the analysis of surface layers with a thickness of a few nanometers. The method is sensitive to the chemical environment of the atoms since the binding energy of the electrons depends on the chemical bonds to neighboring atoms. It has been applied to the hydration of tricalcium silicate (Ca{sub 3}SiO{sub 5}, C{sub 3}S) by analyzing a sample after 30 min of hydration. Also two references have been investigated namely anhydrous C{sub 3}S and intermediate phase in order to enable a quantitative evaluation of the experimental data. In the hydrated C{sub 3}S sample, the analyzed volume (0.2 mm{sup 2} surface by 13 nm depth) contained approximately 44 wt.% of C{sub 3}S and 56 wt.% of intermediate phase whereas C-S-H was not detected. Scanning Electron Microscopy data and geometric considerations indicate that the intermediate phase forms a thin layer having a thickness of approximately 2 nm and covers the complete surface instead of forming isolated clusters.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  15. Multiple ways of producing intermediate and silicic rocks within Thingmúli and other Icelandic volcanoes

    DEFF Research Database (Denmark)

    Charreteur, Gilles; Tegner, Christian; Haase, Karsten

    2013-01-01

    of the LFe trend do not reach iron-rich end members. The HFe trend is interpreted as a result of fractional crystallization; numerical modelling using the MELTS algorithm suggests that crystallization took place under redox conditions constrained to one-log unit below the fayalite-magnetite-quartz oxygen....... A high-iron trend (HFe) contains 6-14 wt% total FeO in silicic rocks with c. 1 wt% MgO, as well as sodic plagioclase and hedenbergite phenocrysts. A low-iron trend (LFe) contains 3-5 wt% FeO at c. 1 wt% MgO, which is typical of Iceland but higher than MORB compositions. The most evolved phenocrysts...

  16. Organic modification of layered silicates. Structural and thermal characterizations

    Energy Technology Data Exchange (ETDEWEB)

    Prado, L.A.S. de A.; Schulte, K. [Polymer Composites, Denickstrasse 15, TU Hamburg-Harburg, D-21073 Hamburg (Germany); Karthikeyan, C.S.; Nunes, S.P. [Institute of Chemistry, GKSS Research Centre, Max-Planck Strasse 1, D-21502 Geesthacht (Germany); De Torriani, Iris L. [Instituto de Fisica Gleb Wataghin, Universidade Estadual de Campinas, Cidade Universitaria Zeferino Vaz, CEP 13083-970, Campinas-SP (Brazil)

    2005-05-01

    Organic modification of natural and synthetic layered silicates namely montmorillonite and laponite is reported in this work. The modified silicates are being subsequently used in the preparation of nano-composite membranes based on ionomers for fuel cells application. Laponite, an entirely synthetic silicate, was modified using organosiloxanes containing imidazole groups. Two different strategies were adopted for modification: (a) swelling of the silicate in 2-butanone followed by functionalization using the siloxane at room temperature, (b) direct reaction between laponite and the organosiloxane in xylene at 120{sup o}C. Montmorillonite, a natural silicate, was supplied in the alkyl-ammonium form containing -OH groups. The modification of this silicate was conducted following the procedure (b). The structures of both plain and modified silicates were investigated by XRD showing that the interlayer distance (around 17A) was not affected during the functionalization of laponite. However, a noticeable increase in the interlayer distance from 18.0A to 24.5A was observed for the modified montmorillonite. This clearly shows the presence of polysiloxane chains in between the silicate layers. Further characterization showed that the modification of these silicates was in the range between 16% and 23% (molar percentage). TGA was done between 25 and 300{sup o}C in order to study the thermal degradation pattern of the silicates. The amount of adsorbed water could be determined from the results. The functionalization reduced the adsorption of water from 13.5% to 6.8% for laponite and from 8.5% to 4% for montmorillonite.

  17. The origin of crystalline residues in Stardust Al foils: Surviving cometary dust or crystallized impact melts?

    Science.gov (United States)

    Wozniakiewicz, Penelope J.; Kearsley, Anton T.; Ishii, Hope A.; Burchell, Mark J.; Bradley, John P.; Teslich, Nick; Cole, Mike J.; Price, Mark C.

    2012-04-01

    Samples returned by the Stardust mission from comet 81P/Wild 2 provide an unequaled opportunity to investigate cometary formation and evolution. Crystalline silicates have been identified in impact craters in Stardust Al foil, yet their origin is ambiguous. They may be original cometary components, or they may have grown from melt generated by impact. We have now studied experimental impacts of the calcium silicate mineral wollastonite, using scanning and transmission electron microscopy to document the relationship between impact feature shape and crystal lattice orientation in impact residue. Wollastonite can have a characteristic acicular habit, forming crater shapes that indicate crystal orientation upon impact. From extracted impact residue, we determined the lattice orientation of crystalline material for comparison with the whole particle orientation. We assume that crystallization from melt, without surviving seed nuclei, should result in randomly oriented crystallite growth, with no preferred direction for individual crystals. However, we find that the majority of crystalline material in the residue retains b-axis orientation parallel to the long axis of the crater form. This, together with impact parameter calculations and lack of Al incorporation by the residue (suggesting melting did not occur), indicates that these crystals and, by analogy, the majority of Al-free crystalline silicates in Stardust foil, are surviving remnants of the impactor. Furthermore, amorphous wollastonite residue probably did not form via melting and subsequent quenching, but instead by high-pressure amorphization or degradation of unquenchable phases. Finally, one crystal studied appears to be a new high-pressure/temperature polymorph of CaSiO3, indicating that such polymorphs may be observed in Stardust residues in craters.

  18. Disordered Silicates in Space: a Study of Laboratory Spectra of "Amorphous" Silicates

    CERN Document Server

    Speck, Angela K; Hofmeister, Anne M

    2011-01-01

    We present a laboratory study of silicate glasses of astrophysically relevant compositions including olivines, pyroxenes and melilites. With emphasis on the classic Si-O stretching feature near 10 microns, we compare infrared spectra of our new samples with laboratory spectra on ostensibly similar compositions, and also with synthetic silicate spectral data commonly used in dust modeling. Several different factors affect spectral features including sample chemistry (e.g., polymerization, Mg/Fe ratio, oxidation state and Al-content) and different sample preparation techniques lead to variations in porosity, density and water content. The convolution of chemical and physical effects makes it difficult to attribute changes in spectral parameters to any given variable. It is important that detailed chemical and structural characterization be provided along with laboratory spectra. In addition to composition and density, we measured the glass transition temperatures for the samples which place upper limits on the ...

  19. Isotopic constraints of mantle derived carbonatitic melts from Calatrava, Spain

    Science.gov (United States)

    Humphreys, E. R.; Bailey, K.; Hawkesworth, C. J.; Wall, F.; Avanzinelli, R.

    2010-12-01

    asthenospheric mantle; we therefore infer that metasomatism has resulted in the thickening and enriching of the lithosphere. Carbonatitic and silicate metasomatism is reported from the mantle in this region and the presence of abundant igneous carbonate associated with other alkaline volcanic rocks in the province, leads us to conclude that the presence of CO2 in the mantle and the resulting carbonatitic melts may play a crucial role in the genesis of many intraplate alkaline volcanic rocks. Humphreys, E.R., Bailey, K., Hawkesworth, C.J., Wall, F., Najorka, J. & Rankin, A. (2010). Aragonite in olivine from Calatrava, Spain: Evidence for mantle carbonatitic melts from >100km depth. Geology, 38, 911-914. Woolley, A.R. & Church, A.A. (2005). Extrusive carbonatites: A brief review. Lithos, 85, 1-14.

  20. ER3+-DOPED SODA-LIME SILICATE GLASS: ARTIFICIAL PINK GEMSTONE

    Directory of Open Access Journals (Sweden)

    Weeranut Kaewwiset

    2012-01-01

    Full Text Available Er3+-doped soda-lime silicate glasses of the composition (in mol% (65-xSiO2:25Na2O:10CaO:xEr2O3 (where x = 0, 1, 2, 3, 4 and 5 were fabricated by conventional melt quenching technique. The physical and optical properties were measured and investigated. The erbium oxide enters the glass network as a modifier by occupying the interstitial space in the network and generating the NBOs to the structure. The molar volume increases with an increase in Er2O3 content, which is attributed to the increase in the number of Non-Bridging Oxygen (NBOs. The increase of NBOs in the structure generally leads to an increase in average atomic separation. The density, molar volume and refractive index of glasses increased linearly with increasing Er2O3 concentration. The color of glasses was changed from light pink to intense pink as the Er2O3 concentration was increased from 1 to 5 mol%. The Vickers hardness of Er3+-doped glasses was found to be in the range of 450-500 HV. In this study, it can be concluded that the soda-lime silicate glasses doped with high Er2O3 concentration has intense pink color and high value of hardness which is suitable to be cut as gems.

  1. Fe2O3 Modified Physical, Structural and Optical Properties of Bismuth Silicate Glasses

    Directory of Open Access Journals (Sweden)

    Rajesh Parmar

    2013-01-01

    Full Text Available Iron-containing bismuth silicate glasses with compositions 60SiO2·(100−xBi2O3·xFe2O3 have been prepared by conventional melt-quenching technique. The amorphous nature of the glass samples has been ascertained by the X-ray diffraction. The density (d has been measured using Archimedes principle, molar volume (Vm has also been estimated, and both are observed to decrease with the increase in iron content. The glass transition temperature (Tg of these iron bismuth silicate glasses has been determined using differential scanning calorimetry (DSC technique, and it increases with the increase in Fe2O3 content. The IR spectra of these glasses consist mainly of [BiO6], [BiO3], and [SiO4] structural units. The optical properties are measured using UV-VIS spectroscopy. The optical bandgap energy (Eop is observed to decrease with the increase in Fe2O3 content, whereas reverse trend is observed for refractive index.

  2. Metal-silicate Partitioning and Its Role in Core Formation and Composition on Super-Earths

    Science.gov (United States)

    Schaefer, Laura; Jacobsen, Stein B.; Remo, John L.; Petaev, M. I.; Sasselov, Dimitar D.

    2017-02-01

    We use a thermodynamic framework for silicate-metal partitioning to determine the possible compositions of metallic cores on super-Earths. We compare results using literature values of the partition coefficients of Si and Ni, as well as new partition coefficients calculated using results from laser shock-induced melting of powdered metal-dunite targets at pressures up to 276 GPa, which approaches those found within the deep mantles of super-Earths. We find that larger planets may have little to no light elements in their cores because the Si partition coefficient decreases at high pressures. The planet mass at which this occurs will depend on the metal-silicate equilibration depth. We also extrapolate the equations of state (EOS) of FeO and FeSi alloys to high pressures, and present mass–radius diagrams using self-consistent planet compositions assuming equilibrated mantles and cores. We confirm the results of previous studies that the distribution of elements between mantle and core will not be detectable from mass and radius measurements alone. While observations may be insensitive to interior structure, further modeling is sensitive to compositionally dependent properties, such as mantle viscosity and core freeze-out properties. We therefore emphasize the need for additional high pressure measurements of partitioning as well as EOSs, and highlight the utility of the Sandia Z-facilities for this type of work.

  3. Oxygen isotopes of some trondhjemites, siliceous gneisses, and associated mafic rocks

    Science.gov (United States)

    Barker, F.; Friedman, I.; Hunter, D.R.; Gleason, J.D.

    1976-01-01

    Analyses of oxygen isotopes in whole-rock samples of 58 Precambrian and Phanerozoic trondhjemites and siliceous gneisses and of 28 cogenetic mafic to intermediate rocks from North America, Fennoscandia, and southern Africa give the following results: 1. (1) 47 trondhjemites, tonalites, and mostly Archean acidic gneisses that apparently are not isotopically disturbed show an overage ?? 15O of +7.3??? and a range of 5.2-8.9???; 11 other samples are slightly to moderately disturbed and show higher values; and 2. (2) the mafic rocks show a wide range of ??-values, from about 0-9??? but the undisturbed ones give an average ?? 18O of 5.2???. The ?? 18O values of the trondhjemitic intrusives and siliceous gneisses of similar composition are lower than those of most granitic rocks and support models for derivation of these rocks from basaltic parents. This approach, however, cannot be used to determine if individual bodies formed by differentiation or by partial melting. ?? 1976.

  4. Monazite and xenotime solubility in granitic melts and the origin of the lanthanide tetrad effect

    Science.gov (United States)

    Duc-Tin, Quach; Keppler, Hans

    2015-01-01

    monazite and xenotime fractionation. The solubility of monazite and xenotime in silicate melt probably shows the tetrad effect, because of the very unusual coordination of the rare earth elements in these phosphate minerals, which is different from the coordination of the melt and therefore causes different crystal field interactions with the partially filled f orbitals of the rare earths. The tetrad effect in granites cannot be used as an indicator of fluid/rock or fluid/melt interaction, since it can be experimentally reproduced in the absence of any fluids.

  5. An Overview of the Origin of A-type Silicic Magmatism Along the Snake River Plain-Yellowstone Hotspot Track

    Science.gov (United States)

    Christiansen, E. H.; Bindeman, I. N.; Leishman, J. R.

    2015-12-01

    Disparate models have been proposed for the origin of A-type rhyolites--a volumetrically minor part of modern terrestrial magmatism. But understanding the origin of A-type granites and rhyolites has significance for understanding the formation of the Earth's first silicic crust and for planetary magmatism--small volumes of such granitic materials have been found in lunar rocks, martian and asteroidal meteorites, and have been speculated to have formed on Venus. On other planets, vertical tectonics and plume-like mantle convection dominate, not the recycling of wet, oxidized plates of lithosphere as on Earth. Thus, understanding the origins of A-type silicic magma is important on multiple levels. Voluminous A-type rhyolite were produced on the Snake River Plain-Yellowstone hotspot track and provide the opportunity to better understand these important silicic magmas. Detailed petrologic studies suggest that most Snake River Plain rhyolites ultimately formed by partially melting of previously emplaced basaltic intrusions rather than by fractional crystallization of basalt or melting of Archean crust. This hypothesis is favored because of the bimodal association of rhyolite and basalt without linking intermediate compositions. In addition, incompatible element ratios (e.g., La/Nb, Pb/Ce), a lack of old zircon antecrysts, low-U inherited zircon, high ɛNd and ɛHf values, high eruption temperatures (1050°C to 850°C), low fO2 (near QFM), and H2O (as low as 1.5%), link the rhyolites to a plume-derived basaltic parent through partial melting with lesser incorporation of the Archean to Mesozoic crust that underlies the plain. Moreover, the contrast with wetter, lower temperature rhyolites that must have formed by direct crustal melting (e.g., Arbon Valley Tuff) strengthens this interpretation. Many of the rhyolites also have low δ18O values that must be produced in two stages: first by partial melting of already hydrothermally altered basalt, and subsequently in single

  6. Origins of ultralow velocity zones through slab-derived metallic melt.

    Science.gov (United States)

    Liu, Jiachao; Li, Jie; Hrubiak, Rostislav; Smith, Jesse S

    2016-05-17

    Understanding the ultralow velocity zones (ULVZs) places constraints on the chemical composition and thermal structure of deep Earth and provides critical information on the dynamics of large-scale mantle convection, but their origin has remained enigmatic for decades. Recent studies suggest that metallic iron and carbon are produced in subducted slabs when they sink beyond a depth of 250 km. Here we show that the eutectic melting curve of the iron-carbon system crosses the current geotherm near Earth's core-mantle boundary, suggesting that dense metallic melt may form in the lowermost mantle. If concentrated into isolated patches, such melt could produce the seismically observed density and velocity features of ULVZs. Depending on the wetting behavior of the metallic melt, the resultant ULVZs may be short-lived domains that are replenished or regenerated through subduction, or long-lasting regions containing both metallic and silicate melts. Slab-derived metallic melt may produce another type of ULVZ that escapes core sequestration by reacting with the mantle to form iron-rich postbridgmanite or ferropericlase. The hypotheses connect peculiar features near Earth's core-mantle boundary to subduction of the oceanic lithosphere through the deep carbon cycle.

  7. The theoretical plausibility of central pit crater formation via melt drainage

    Science.gov (United States)

    Elder, Catherine M.; Bray, Veronica J.; Melosh, H. Jay

    2012-11-01

    Central pit craters are seen in large craters on some icy satellites and on Mars. We investigate the hypothesis that central pits form when impact melt drains into fractures beneath the impact crater. For this process to occur, the volume of melt generated during the impact, the volume of void space in fractures beneath the impact crater, and the volume of melt able to drain before the fractures freeze shut all must exceed the volume of the observed central pits. We estimate the volume of melt generated using results from previous numerical modeling studies. The fracture volume is estimated using gravity anomalies over terrestrial craters. To estimate the amount of melt able to drain before freezing, we consider flow through plane parallel fractures. These calculations all suggest that enough liquid water could drain into fractured ice beneath a crater on Ganymede to form a central pit. On Earth and the Moon, silicate impact melt will freeze before a large volume is able to drain, so we do not expect to see central pits in impact craters in targets with no ice. In summary, we find our calculations are consistent with observed central pits in craters on Ganymede and the lack of central pits in craters on Earth and the Moon.

  8. Interstellar Silicate Dust in the z=0.89 Absorber Towards PKS 1830-211: Crystalline Silicates at High Redshift?

    CERN Document Server

    Aller, Monique C; York, Donald G; Vladilo, Giovanni; Welty, Daniel E; Som, Debopam

    2012-01-01

    We present evidence of a >10-sigma detection of the 10 micron 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_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 wit...

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

    Energy Technology Data Exchange (ETDEWEB)

    Aller, Monique C.; Kulkarni, Varsha P.; Som, Debopam [Department of Physics and Astronomy, University of South Carolina, 712 Main Street, Columbia, SC 29208 (United States); York, Donald G.; Welty, Daniel E. [Department of Astronomy and Astrophysics, University of Chicago, 5640 S. Ellis Ave., Chicago, IL 60637 (United States); Vladilo, Giovanni, E-mail: ALLERM@mailbox.sc.edu [Osservatorio Astonomico di Trieste, Via Tiepolo 11, 34143 Trieste (Italy)

    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.

  10. Volatile-rich Melts in the Earth's Upper Mantle (AGU Kuno Medal)

    Science.gov (United States)

    Dasgupta, Rajdeep

    2013-04-01

    The onset of silicate magma generation in the Earth's upper mantle influences the thermal evolution of the planet, fluxes of key volatiles to the exosphere, and geochemical and geophysical properties of the mantle. Although carbonatitic fluid with variable water content could be stable ≤250 km beneath mid oceanic ridges [1-3], owing to the small fraction (oxygen fugacity of the mantle in the garnet peridotite field [2, 3], we suggest that on a global scale, carbonated silicate melt generation at ~250-180 km deep redox solidus, with destabilization of metal and majorite in the upwelling mantle, explains oceanic low-velocity zone and electrical conductivity structure of the mantle. In locally oxidized domains (i.e., higher than average Fe3+/Fetotal), deeper carbonated silicate melt may contribute to the X-discontinuity. Furthermore, the new experimental results along with the electrical conductivity of molten carbonated peridotite [8] and that of the oceanic upper mantle [6] suggest that if CO2-rich melt is the only possible agent to explain the high electrical conductivity of the asthenospheric mantle then the mantle at depth is CO2-rich but H2O-poor; higher H2O content in the mantle enhances melting, lowers the CO2 content and likely the conductivity of such melts. Finally, carbonated silicate melts restrict the stability of carbonatite in the Earth's deep oceanic upper mantle and the inventory of carbon, water, and other highly incompatible elements at ridges becomes controlled by flux of the former [7]. Although the stability of carbonatitic melt may be eliminated beneath oceanic ridges at all depths, beneath continents stability of carbonatitic melt is expected. Archean cratonic mantle (geotherms corresponding to surface heat flux of 40-50 mW m-2) crosses the carbonated peridotite solidus, at a depth of ~100-220 km [9]; thus considering the oxygen fugacity profile for cratons [3], carbonatitic melt is expected to be stable at 100-180 km depths, at a narrow

  11. Si- and alkali-rich melt inclusions in minerals of mantle peridotites from eastern China: Implication for lithospheric evolution

    Institute of Scientific and Technical Information of China (English)

    FAN; Qicheng; SUI; Jianli; XU; Ping; LI; Ni; SUN; Qian; WANG; Tuanhua

    2006-01-01

    Minerals of spinel- and garnet-facies mantle xenoliths entrained in Cenozoic basalts from eastern China (North China, Northeastern China and Southeastern China coastal area) contains lots of melt inclusions. Studies on these melt inclusions show that the glass inclusions are rich in SiO2 (60%―68%) and alkalis (K2O+Na2O=5%―11%, especially for K2O) as well as volatiles such as H2O and CO2 (2%―7%), which belong to dacites and andesites of the high-K calcic alkali series rocks with few shoshonites. High Al and Ca diopside in melt inclusion is the product of melt crystallization at high temperature and pressure, rather than the product of devitrification. Results show that these K-rich (in general K2O>3%) intermediate-acidic silicate melt inclusions have characteristics of continent without a genetical link to host basalts and their phenocrystic minerals. Thus, these trapped melt inclusions represent melts of Mesozoic lithospheric mantle-crust interaction and imply that the continental lithospheric mantle beneath eastern China had undergone fragmentation and recreation processes during the Mesozoic and Cenozoic periods. This result undoubtly provides important implication for the evolution of sub-continental lithosphere beneath eastern China. We propose that these Si- and alkalis-rich melts should be responsible for the mantle chemical heterogeneity underneath eastern China.

  12. Electrical Conductivity of Cryolite Melts

    Science.gov (United States)

    Fellner, P.; Grjotheim, K.; Kvande, H.

    1985-11-01

    This paper proposes an equation for the electrical conductivity of multicomponent cryolite-based mixtures. The equation is based on a physical model which assumes that the conductivity is proportional to the number density of the effective electric charges in the melt. The various authors in the available literature show a great discrepancy in conductivity data of cryolite-based melts. The equation based on the physical model enables determination of which set of data is preferable. Special consideration in this respect is given to the influence of magnesium flouride and lithium flouride additions to the melt.

  13. Characterization of mesostasis regions in lunar basalts: Understanding late-stage melt evolution and its influence on apatite formation

    Science.gov (United States)

    Potts, Nicola J.; TartèSe, Romain; Anand, Mahesh; Westrenen, Wim; Griffiths, Alexandra A.; Barrett, Thomas J.; Franchi, Ian A.

    2016-09-01

    Recent studies geared toward understanding the volatile abundances of the lunar interior have focused on the volatile-bearing accessory mineral apatite. Translating measurements of volatile abundances in lunar apatite into the volatile inventory of the silicate melts from which they crystallized, and ultimately of the mantle source regions of lunar magmas, however, has proved more difficult than initially thought. In this contribution, we report a detailed characterization of mesostasis regions in four Apollo mare basalts (10044, 12064, 15058, and 70035) in order to ascertain the compositions of the melts from which apatite crystallized. The texture, modal mineralogy, and reconstructed bulk composition of these mesostasis regions vary greatly within and between samples. There is no clear relationship between bulk-rock basaltic composition and that of bulk-mesostasis regions, indicating that bulk-rock composition may have little influence on mesostasis compositions. The development of individual melt pockets, combined with the occurrence of silicate liquid immiscibility, exerts greater control on the composition and texture of mesostasis regions. In general, the reconstructed late-stage lunar melts have roughly andesitic to dacitic compositions with low alkali contents, displaying much higher SiO2 abundances than the bulk compositions of their host magmatic rocks. Relevant partition coefficients for apatite-melt volatile partitioning under lunar conditions should, therefore, be derived from experiments conducted using intermediate compositions instead of compositions representing mare basalts.

  14. In situ XRD Study of Ca2+ Saturated Montmorillonite (STX-1) Exposed to Anhydrous and Wet Supercritical Carbon Dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Schaef, Herbert T.; Ilton, Eugene S.; Qafoku, Odeta; Martin, Paul F.; Felmy, Andrew R.; Rosso, Kevin M.

    2012-01-09

    Reactions involving scCO2 and a calcium saturated dioctahedral smectite (Ca-STX-1) were examined by in situ high-pressure x-ray diffraction over a range of temperatures (50° to 100°C) and pressures (90, 125, and 180 bar) relevant to long term geologic storage of CO2. Exposure of Ca-STX-1 containing one water of hydration (1W) to anhydrous scCO2 at 50°C and 90 bar produced an immediate increase of ~0.8 Å in the d001 basal reflection that was sustained for the length of the experiment (~44 hours). Higher ordered basal reflections displayed similar shifts. Following depressurization, positions of basal reflections and FWHM values (d001) returned to initial values, with no measurable modification to the clay structure or water content. Similar results were obtained for tests conducted at 50°C and higher pressures (125 and 180 bar). Exposure of Ca-STX-1 containing two waters of hydration (2W) to scCO2 resulted in a decrease in the d001 reflection from 14.48 Å to 12.52 Å, after pressurization, indicating a partial loss of interlayer water. In addition, the hydration state of the clay became more homogeneous during contact with anhydrous scCO2 and after depressurization. In the presence of scCO2 and water, the clay achieved a 3W hydration state, based on a d001 spacing of 18.8 Å. In contrast to scCO2, comparable testing with N2 gas indicated trivial changes in the d001 series regardless of hydration state (1W or 2W). In the presence of free water and N2, the basal spacing for the Ca-STX-1 expanded slightly, but remained in the 2W hydration state. These experiments indicate that scCO2 can intercalate hydrated clays, where the 1W hydrate state is stable when exposed to anhydrous scCO2 under conditions proposed for geologic storage of CO2. Consequently, clays can act as secondary CO2 traps where potential collapse or expansion of the interlayer spacing depends on the initial hydration state of the clay and scCO2.

  15. Behavior of calcium silicate hydrate in aluminate solution

    Institute of Scientific and Technical Information of China (English)

    LI Xiao-bin; ZHAO Zhuo; LIU Gui-hua; ZHOU Qiu-sheng; PENG Zhi-hong

    2005-01-01

    Using calcium hydroxide and sodium silicate as starting materials, two kinds of calcium silicate hydrates, CaO · SiO2 · H2O and 2CaO · SiO2 · 1.17H2O, were hydro-thermally synthesized at 120 ℃. The reaction rule of calcium silicate hydrate in aluminate solution was investigated. The result shows that CaO · SiO2 · H2O is more stable than 2CaO · SiO2 · 1.17H2 O in aluminate solution and its stability increases with the increase of reaction temperature but decreases with the increase of caustic concentration. The reaction between calcium silicate hydrate and aluminate solution is mainly through two routes. In the first case, Al replaces partial Si in calcium silicate hydrate, meanwhile 3CaO · Al2 O3 · xSiO2 · (6-2x) H2 O (hydro-garnet) is formed and some SiO2 enters the solution. In the second case, calcium silicate hydrate can react directly with aluminate solution, forming hydro-garnet and Na2O · Al2O3 · 2SiO2 · nH2O (DSP). The desilication reaction of aluminate solution containing silicate could contribute partially to forming DSP.

  16. Deep ocean biogeochemistry of silicic acid and nitrate

    Science.gov (United States)

    Sarmiento, J. L.; Simeon, J.; Gnanadesikan, A.; Gruber, N.; Key, R. M.; Schlitzer, R.

    2007-03-01

    Observations of silicic acid and nitrate along the lower branch of the global conveyor belt circulation show that silicic acid accumulation by diatom opal dissolution occurs at 6.4 times the rate of nitrate addition by organic matter remineralization. The export of opal and organic matter from the surface ocean occurs at a Si:N mole ratio that is much smaller than this almost everywhere (cf. Sarmiento et al., 2004). The preferential increase of silicic acid over nitrate as the deep circulation progresses from the North Atlantic to the North Pacific is generally interpreted as requiring deep dissolution of opal together with shallow remineralization of organic matter (Broecker, 1991). However, Sarmiento et al. (2004) showed that the primary reason for the low silicic acid concentration of the upper ocean is that the waters feeding the main thermocline from the surface Southern Ocean are depleted in silicic acid relative to nitrate. By implication, the same Southern Ocean processes that deplete the silicic acid in the surface Southern Ocean must also be responsible for the enhanced silicic acid concentration of the deep ocean. We use observations and results from an updated version of the adjoint model of Schlitzer (2000) to confirm that this indeed the case.

  17. The shape and composition of interstellar silicate grains

    CERN Document Server

    Min, M; De Koter, A; Hovenier, J W; Keller, L P; Markwick-Kemper, F

    2006-01-01

    We investigate the composition and shape distribution of silicate dust grains in the interstellar medium. The effect of the amount of magnesium in the silicate lattice is studied. We fit the spectral shape of the interstellar 10 mu extinction feature as observed towards the galactic center. We use very irregularly shaped coated and non-coated porous Gaussian Random Field particles as well as a statistical approach to model shape effects. For the dust materials we use amorphous and crystalline silicates with various composition and SiC. The results of our analysis of the 10 mu feature are used to compute the shape of the 20 mu silicate feature and to compare this with observations. By using realistic particle shapes we are, for the first time, able to derive the magnesium fraction in interstellar silicates. We find that the interstellar silicates are highly magnesium rich (Mg/(Fe+Mg)>0.9) and that the stoichiometry lies between pyroxene and olivine type silicates. This composition is not consistent with that o...

  18. Reagentless and calibrationless silicate measurement in oceanic waters.

    Science.gov (United States)

    Giraud, William; Lesven, Ludovic; Jońca, Justyna; Barus, Carole; Gourdal, Margaux; Thouron, Danièle; Garçon, Véronique; Comtat, Maurice

    2012-08-15

    Determination of silicate concentration in seawater without addition of liquid reagents was the key prerequisite for developing an autonomous in situ electrochemical silicate sensor (Lacombe et al., 2007) [11]. The present challenge is to address the issue of calibrationless determination. To achieve such an objective, we chose chronoamperometry performed successively on planar microelectrode (ME) and ultramicroelectrode (UME) among the various possibilities. This analytical method allows estimating simultaneously the diffusion coefficient and the concentration of the studied species. Results obtained with ferrocyanide are in excellent agreement with values of the imposed concentration and diffusion coefficient found in the literature. For the silicate reagentless method, successive chronoamperometric measurements have been performed using a pair of gold disk electrodes for both UME and ME. Our calibrationless method was tested with different concentrations of silicate in artificial seawater from 55 to 140×10(-6) mol L(-1). The average value obtained for the diffusion coefficient of the silicomolybdic complex is 2.2±0.4×10(-6) cm(2) s(-1), consistent with diffusion coefficient values of molecules in liquid media. Good results were observed when comparing known concentration of silicate with experimentally derived ones. Further work is underway to explore silicate determination within the lower range of oceanic silicate concentration, down to 0.1×10(-6) mol L(-1). Copyright © 2012 Elsevier B.V. All rights reserved.

  19. Silicate-Iron partitioning of Palladium and Ruthemium up to 110 GPa using nano-X-Ray Fluorescence imaging

    Science.gov (United States)

    Petitgirard, S.; Andrault, D.; Borchert, M.; Appel, K.; Deguen, R.; Mezouar, M.; Villanova, J.

    2012-12-01

    Metal-silicate partitioning of Highly Siderophile Elements (HSE) are a key to understand the accretion of the earth and the formation of its core from a silicate magma ocean. So far, all the metal-silicate partitioning studies make use of 'classical' HP-HT techniques, e.g., multi-anvil press, and therefore are limited to PT conditions of the Earth s mantle (max. 25 GPa/2200°C). There is urgent need for experiments at much higher pressures and temperatures (e.g., to simulate conditions of core-mantle boundary) because it remains unclear if determined metal-silicate partition coefficients of HSE can simply be extrapolated to much higher pressures and temperatures. Here, we present first preliminary data on metal-silicate trace element partitioning from a new experimental approach to obtain information at ultra high pressures and temperatures. Synthesis of high pressure melting were performed at beamline ID27 (ESRF, Grenoble, France) using double-side laser-heated diamond-anvil cells (DAC) up to ~110 GPa and 4200 K. Samples are analysed after laser heating by nano-X-Ray Fluorescence at the nano-probe end-station ID22NI (ESRF, France). Samples consist of a CI-mantle glass synthesized using a levitation set-up and contain 1wt % of Pd and Ru. The sample chamber, drilled in a Re gasket, is loaded with a chip of the dopped glass overlapped by a trace element free metal foil (Fe0.9Ni0.1). NaCl is used as a thermal insulator and pressure media, and a ruby sphere is used to measure the pressure. Laser heating was performed at the interface of the chondrite glass and metallic foil until complete melting is observed. Samples were removed of the gasket by dissolving the NaCl medium and placed on a mylar foil for analysis at ID22NI. Very fine map were performed using the 100 x 90 nanometres beam that offers a very high flux of 10e11 photons/s with excitation energy of 29.6 KeV. Quantitative data analysis is currently in progress and other techniques will be used to complement

  20. Temporal magma dynamics during solidification of the mafic-silicic complex of Isle au Haut, Maine

    Science.gov (United States)

    Patwardhan, Kaustubh

    The Isle au Haut Igneous Complex provides a unique opportunity to examine in detail the in situ physical and chemical interactions between contemporaneously emplaced mafic and silicic magmas. The complex contains a 600 m thick sequence of 11 alternating layers of gabbro and diorite (typically 15--40 m thick). Purely on the basis of density contrasts (2.65 g/cm 3 gabbro vs. 2.55 g/cm3 diorite), the entire system should have undergone wholesale instability and mixing; it is instead arrested in a grossly unstable state of interaction while molten. Chilled margins along the lower contacts of the gabbros and structural integrity of the diorite layers indicate that near liquidus gabbroic magma invaded partly crystalline, cooler diorite. Mineral assemblages, chemical analyses, and phase equilibria calculations indicate initial temperatures during emplacement of ˜1180°C (gabbro) and ˜1000°C (diorite). Conductive thermal models yield solidification timescales of 15--60 years for individual gabbro layers and about a thousand years for the entire complex. There is ample evidence for two phases of small-scale interfacial Rayleigh-Taylor type instabilities of dioritic melt into the gabbros. Phase I occurred immediately upon gabbro emplacement whereas evenly spaced, slender more silicic pipes represent a much later stage (Phase II). Pipe geometry and spacing, estimated viscosities of the gabbroic magma and silicic melt, and the sudden increase in silica near the upper contact of the diorite, all indicate a thin (˜18--53 cm) buoyant layer at the upper contact of the diorite as the source of the pipes. Compaction of the diorite produced this layer over a period of about ten years. Simultaneous solidification along the lower contact of the overlying gabbro, thickening inwards, increased viscosity enough to arrest pipe ascent after a few meters. Crystal size distribution (CSD) analyses of the gabbro layers yield crystal growth rates (G0 = 2--4 x 10-10 cm/s) and nucleation rates

  1. Study on the Physical and Chemical Conditions of Ore Formation of Hetai Ductile Shear Zone—Hosted Gold Deposit and Discovery of Melt Inclusions

    Institute of Scientific and Technical Information of China (English)

    李兆麟; 翟伟; 等

    2002-01-01

    The Hetai ductile shear zone-hosted gold deposit occurs in the deep-seated falut mylonite zone of the Sinian-Silurian metamorphic rock series.In this study there have been discovered melt inclusions,fluid-melt inclusions and organic inclusions in ore-bearing ruartz veins of the ore deposit and mylonite for the first time.The homogenization temperatures of the various types of inclusions are 160℃,180-350℃,530℃and 870℃ for organic inclusions,liquid inclsions two-phase immiscible liquid inclusions and melt inclusion,respectively,Ore fluid is categoriezed as the neutral to basic K+-Ca2+-Mg2+-Na+-SO42--HCO3-Cl- system.The contents of trace gases follow a descending order of H2O>CO2>CH4>(orCO>C2H2>C2H6>O2>N2.The concentrations of K+,Ca2+,SO42-,HCO3-,Cl-,H2O and C2H2 in fluid inclusions are related to the contents of gold and the Au/Ag ratios in from different levels of the gold deposit.This is significant for deep ore prospecting in the region.Daughter minerals in melt inclusions were analyzed using SEM.Quartz,orthoclase,wollastonite and other silicate minerals were identified.They were formed in different mineral assemblages.This analysis further proves the existence of melt inclusions in ore veins.Sedimentary metamophic rocks could form silicate melts during metamorphic anatexis and dynamic metamorphism,which possess melt-soulution characteristics.Ore formation is related to the multi-stage forming process of silicate melt and fluid.

  2. Study on the Physical and Chemical Conditions of Ore Formation of Hetai Ductile Shear Zone-Hosted Gold Deposit and Discovery of Melt Inclusions

    Institute of Scientific and Technical Information of China (English)

    李兆麟; 翟伟; 李文; 石贵勇; 文拥军

    2002-01-01

    The Hetai ductile shear zone-hosted gold deposit occurs in the deep-seated fault mylonite zone of the Sinian-Silurian metamorphic rock series. In this study there have been discovered melt inclusions, fluid-melt inclusions and organic inclusions in ore-bearing quartz veins of the ore deposit and mylonite for the first time. The homogenization temperatures of the various types of inclusions are 160℃, 180 - 350℃, 530℃ and 870℃ for organic inclusions, liquid inclusions, two-phase immiscible liquid inclusions and melt inclusions, respectively. Ore fluid is categorized as the neutral to basic K+ -Ca2+ -Mg2+ -Na+ - SO2- 4-HCO3-Cl- system. The contents of trace gases follow a descending order of H2O>CO2>CH4>(or < ) H2>CO>C2H2>C2I-I6>O2>N2.The concentrations of K , Ca2 + ,SO2-4,HCO3-,Cl- H2O and C2H2 in fluid inclusions are related to the contents of gold and the Au/Ag ratios in ores from different levels of the gold deposit. This is significant for deep ore prospecting in the region. Daughter minerals in melt inclusions were analyzed using SEM. Quartz, orthoclase, wollastonite and other silicate minerals were identified. They were formed in different mineral assemblages.This analysis further proves the existence of melt inclusions in ore veins. Sedimentary metamorphic rocks could form silicate melts during metamorphic anatexis and dynamic metamorphism, which possess melt-solution characteristics. Ore formation is related to the multi-stage forming process of silicate melt and fluid.

  3. Effect of melt composition on crustal carbonate assimilation: Implications for the transition from calcite consumption to skarnification and associated CO2 degassing

    Science.gov (United States)

    Carter, Laura B.; Dasgupta, Rajdeep

    2016-10-01

    Skarns are residue of relatively low-temperature magma-induced decarbonation in the crust largely associated with silicic plutons. Mafic magmatic intrusions are also capable of releasing excess CO2 due to carbonate assimilation. However, the effect of mafic to silicic melt evolution on the decarbonation processes, in addition to temperature controls on carbonate-intrusive magmatic systems, particularly at continental arcs, remains unclear. In this study, experiments performed in a piston cylinder apparatus at midcrustal depth (0.5 GPa) at supersolidus temperatures (900-1200°C) document calcite interaction with andesite and dacite melts at equilibrium under closed-system conditions at calcite saturation in a 1:1 melt-calcite ratio by weight. With increasing silica content in the starting melt, at similar melt fractions and identical pressure, assimilation decreases drastically (≤65% andesite-calcite to ≤18% dacite-calcite). In conjunction, the CaO/SiO2 ratio in melts resulting from calcite assimilation in andesitic starting material is >1, but ≤0.3 in those formed from dacite-calcite interaction. With increasing silica-content in the starting melt skarn mineralogy, particularly wollastonite, increases in modal abundance while diopsidic clinopyroxene decreases slightly. More CO2 is released with andesite-calcite reaction (≤2.9 × 1011 g/y) than with more skarn-like dacite-calcite interaction (≤8.1 × 1010 g/y, at one volcano assuming respective calcite-free-superliquidus conditions and a magma flux of 1012 g/y). Our experimental results thus suggest that calcite assimilation in more mafic magmas may have first degassed a significant amount of crustal carbon before the melt evolves to more silicic compositions, producing skarn. Crustal decarbonation in long-lived magmatic systems may hence deliver significant albeit diminishing amounts of carbon to the atmosphere and contribute to long-term climate change.

  4. Functional substitution of coordination polyhedron in crystal structure of silicates

    Institute of Scientific and Technical Information of China (English)

    叶大年; 马哲生; 赫伟; 李哲; 施倪承; D.Pushcharovsky

    2002-01-01

    On the bases of the study of comparative crystal chemistry of silicates it has been concluded that the octahedra and square pyramids of Ti-0 and Zr-O play functional role of tetrahedra of Si-O in the construction of crystal structures. Therefore, those silicates may be named titano-and zircono-silicates. Because of the functional similarity of coordination polyhedra, the structures of cristobalite and feldspar have been compared with those of perovskite and garnet, respectively. As a new concept, the functional replacement of tetrahedra by octahedra and/or pyramids is defined by the authors of this paper for favorable comparison of relative crystal structures.

  5. Sensitized photoluminescence of erbium silicate synthesized on porous silicon framework

    Science.gov (United States)

    Shen, Hao; Xu, Lingbo; Li, Dongsheng; Yang, Deren

    2017-09-01

    Er silicate/porous silicon (PS) composites with effective sensitized erbium emission at 1.53 μm have been synthesized on the PS framework. Cross-sectional scanning electron microscopy and X-ray diffraction reveal that the PS is coated by Er silicate in composites. Indirect excitation of Er3+ ion luminescence via energy transfer from PS is confirmed. The temperature dependence of Er-related photoluminescence intensity and lifetime is investigated, which concludes a phonon-mediated energy transfer process. The combination of the PS framework and Er silicate provides a possible strategy for practical silicon-based light sources.

  6. Fire Resistance of Wood Impregnated with Soluble Alkaline Silicates

    Directory of Open Access Journals (Sweden)

    Carlos Alberto Giudice

    2007-01-01

    Full Text Available The aim of this paper is to determine the fire performance of wood panels (Araucaria angustifolia impregnated with soluble alkaline silicates. Commercial silicates based on sodium and potassium with 2.5/1.0 and 3.0/1.0 silica/alkali molar ratios were selected; solutions and glasses were previously characterized. Experimental panels were tested in a limiting oxygen chamber and in a two-foot tunnel. Results displayed a high fire-retardant efficiency using some soluble silicates.

  7. Journal of the Chinese Silicate Society (Selected Articles).

    Science.gov (United States)

    2014-09-26

    A-A157 497 JOURNAL OF THE CHINESE SILICATE SOCIETY (SELECTED i/i ARTICLES)(U) FOREIGN TECHNOLOGY DIV IWRIGHT-PRT RSON U CLSS..AFE OH 11 JUN 85...7 V- V 17 -, 7Z I T7. k. V.-.’.~. W ~ . FTD-ID(RS)T-0160-85 FOREIGN TECHNOLOGY DIVISION JOURNAL OF THE CHINESE SILICATE SOCIETY... JOURNAL OF THE CHINESE SILICATE SOCIETY D- At"Ibutilonf (Selected Articles) Availability Cadm English pages: 28 Dist ’Avail ald/zr Source: Guisuanyan

  8. Nitrogen Control in VIM Melts

    Science.gov (United States)

    Jablonski, P. D.; Hawk, J. A.

    NETL has developed a design and control philosophy for the addition of nitrogen to austenitic and ferritic steels. The design approach uses CALPHAD as the centerpiece to predict the level to which nitrogen is soluble in both the melt and the solid. Applications of this technique have revealed regions of "exclusion" in which the alloy, while within specification limits of prescribed, cannot be made by conventional melt processing. Furthermore, other investigations have found that substantial retrograde solubility of nitrogen exists, which can become problematic during subsequent melt processing and/or other finishing operations such as welding. Additionally, the CALPHAD method has been used to adjust primary melt conditions. To that end, nitrogen additions have been made using chrome nitride, silicon nitride, high-nitrogen ferrochrome as well as nitrogen gas. The advantages and disadvantages of each approach will be discussed and NETL experience in this area will be summarized with respect to steel structure.

  9. Digging into Augustine Volcano's Silicic Past

    Science.gov (United States)

    Nadeau, P. A.; Webster, J. D.; Goldoff, B. A.

    2014-12-01

    Activity at Augustine Volcano, Alaska, has been marked by intermediate composition domes, flows, and tephras during the Holocene. Erosive lahars associated with the 2006 eruption exposed voluminous rhyolite pumice fall beneath glacial tills. The rhyolite is both petrologically and mineralogically different from more recent eruptions, with abundant amphibole (both calcium-amphiboles and cummingtonite) and quartz, both rare in more recent products. Three distinct lithologies are present, with textural and chemical variations between the three. Fe-Ti oxide equilibria indicate temperatures of ~765°C and oxygen fugacities of NNO +1.5. Melt inclusions indicate that the stratigraphically lowest lithology began crystallizing isobarically at ~260 MPa with the contemporary mixed H2O-CO2 fluid phase becoming progressively H2O-rich. The other lithologies were likely crystallized under more H2O-dominated conditions, as indicated by the presence of cummingtonite. Apatites and melt inclusions have generally lower chlorine contents than more recently erupted material, which is typically high in chlorine. Xenocrysts of olivine and clinopyroxene in two of the three lithologies contain mafic (basalt to basaltic andesite) melt inclusions that indicate the likelihood of mixing and/or mingling of magmas as an eruption trigger. We interpret the three lithologies as representative of a smaller pumiceous rhyolite eruption, with subsequent extrusion of a rhyodacite banded lava dome or flow. This was followed by a large-scale rhyolitic pumice eruption that entrained portions of the banded flow as lithic inclusions. The unique qualities of this pre-glacial rhyolite and the potential hazards of a similarly large eruption in modern times indicate that further study is warranted.

  10. Submarine silicic volcanism: Processes and products

    Digital Repository Service at National Institute of Oceanography (India)

    Kalangutkar, N.G.; Iyer, S.D.

    of producing a natural Icelandic granite from an evolved Kilauea-type basalt under low ƒo2, P fluid=1 to 2 kb, and P H2 O

    melts generated by anatexis of gabbros which have initial low TiO 2 contents due to their depleted nature of typical cumulate formed in the oceanic crust, whereas TiO 2...

  11. Thermal Decomposition of Anhydrous Alkali Metal Dodecaborates M2B12H12 (M = Li, Na, K

    Directory of Open Access Journals (Sweden)

    Liqing He

    2015-11-01

    Full Text Available Metal dodecaborates M2/nB12H12 are regarded as the dehydrogenation intermediates of metal borohydrides M(BH4n that are expected to be high density hydrogen storage materials. In this work, thermal decomposition processes of anhydrous alkali metal dodecaborates M2B12H12 (M = Li, Na, K synthesized by sintering of MBH4 (M = Li, Na, K and B10H14 have been systematically investigated in order to understand its role in the dehydrogenation of M(BH4n. Thermal decomposition of M2B12H12 indicates multistep pathways accompanying the formation of H-deficient monomers M2B12H12−x containing the icosahedral B12 skeletons and is followed by the formation of (M2B12Hzn polymers. The decomposition behaviors are different with the in situ formed M2B12H12 during the dehydrogenation of metal borohydrides.

  12. Kinetic analysis for non-isothermal decomposition of un-irradiated and gamma-irradiated anhydrous cadmium nitrate

    Energy Technology Data Exchange (ETDEWEB)

    Culas, S.; Samuel, J. [Mar Ivanios College, Kerala (India). Dept. of Chemistry

    2014-04-01

    The thermal decomposition of untreated and γ-irradiated samples of anhydrous cadmium nitrate was performed under non-isothermal conditions at different heating rates (5, 10, 15 and 20 C min{sup -1}). The results showed that the decomposition proceeds in one major step with the formation of cadmium oxide as solid residue. The data were analysed by using both isoconversional and non-isoconversional methods. The activation energy was calculated by various model-free isoconversional methods: Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS) and Friedman (FR) methods. Irradiation enhances the decomposition and the effect increases with the irradiation dose. The activation energy decreases on irradiation. The appropriate conversion model for the thermal decomposition process selected by means of the master-plot method agrees with phase boundary reaction with spherical symmetry (R3 mechanism) for both untreated and irradiated salts at all heating rates. (orig.)

  13. Electrical conduction and glass relaxation in alkali- silicate glasses

    Science.gov (United States)

    Angel, Paul William

    Electrical response measurements from 1 Hz to 1 MHz between 50o and 540oC were made on potassium, sodium and lithium-silicate glasses with low alkali oxide contents. Conductivity and electrical relaxation responses for both annealed and air quenched glasses of the same composition were compared. Quenching was found to lower the dc conductivity, σdc, and activation energy as well as increase the pre-exponential term when compared to the corresponding annealed glass of the same composition. All of the glasses exhibited Arrhenius behavior in the log σdc against 1/T plots. A sharp decrease in σdc was observed for glasses containing alkali concentrations of 7 mol% or less. The σdc activation energy exhibited similar behavior when plotted as a function of alkali composition and was explained in terms of a mixture of the weak and strong electrolyte models. The depression angle for fits to the complex impedance data were also measured as a function of thermal history, alkali concentration and alkali species. These results were interpreted in terms of changes in the distribution of relaxation times. Annealed samples from a single melt of a 10 mol% K2O-90SiO2 glass were reheated to temperatures ranging from 450o to 800oC, held isothermally for 20 min, and then quenched in either air or silicon oil. The complex impedance of both an annealed and the quenched samples were then measured as a function of temperature from 120o to 250oC. The σdc was found to be remain unaffected by heat treatments below 450oC, to increase rapidly over an approximate 200oC range of temperatures that was dependent on cooling rate and to be constant for heat treatments above this range. This behavior is interpreted in terms of the mean structural relaxation time as a function of temperature and cooling rate near the glass transition temperature and glass transformation ranges. A more detailed definition for the transition and transformation temperatures and ranges was also provided.

  14. Subglacial Silicic Eruptions: Wet Cavities and Moist Cavities.

    Science.gov (United States)

    Stevenson, J. A.; McGarvie, D. W.; Gilbert, J. S.; Smellie, J. L.

    2007-05-01

    Comparing the deposits of subglacial eruptions with those of subaerial and subaqueous eruptions enables the influence of magma-water-ice interactions to be explored. In this presentation, the Icelandic subglacial rhyolite tuyas of Kerlingarfjöll and Prestahnúkur are compared with subaerial and subaqueous rhyolite formations at Sierra La Primavera, México. Prestahnúkur formed by the subglacial lava effusion and thick lava flows with steep termini are products of confinement by ice walls. Basal deposits of perlitised obsidian lobes suggest a water-saturated environment, and the extremely abundant microvesicular lava blocks surrounding these lobes and throughout the edifice are broadly similar to the carapaces of silicic lava domes at La Primavera known to have a subaqueous origin. Although bedded and sorted deposits are present at Prestahnúkur, they are trivial compared to the thick and extensive caldera-lake deposits of La Primavera, which even contain a "giant pumice" marker bed formed by the lake-wide deposition of once-bouyant blocks. The Kerlingarfjöll rhyolite tuyas formed during explosive subglacial eruptions. The first-erupted material forms structureless beds of phreatomagmatically-fragmented ash; ash from subaqueous eruptions at La Primavera is similarly fine grained, but in contrast is well-bedded (due to lacustrine deposition). Later-erupted material at Kerlingarfjöll typically consists of massive unconsolidated lapilli-tuffs. The lapilli themselves are similar to those within the well-sorted subaerially-formed pumice cones La Primavera, however Kerlingarfjöll's lapilli- tuffs have grain-size characteristics of proximal pyroclastic flows. These observations suggest that although similar fragmentation mechanisms operated in both locations, transport and consequent sorting was limited at Kerlingarfjöll. The different products of the two Icelandic subglacial tuyas are related to their different eruption rates and magma volatile contents. Melting of

  15. Silicic magma differentiation in ascent conduits. Experimental constraints

    Science.gov (United States)

    Rodríguez, Carmen; Castro, Antonio

    2017-02-01

    Crystallization of water-bearing silicic magmas in a dynamic thermal boundary layer is reproduced experimentally by using the intrinsic thermal gradient of piston-cylinder assemblies. The standard AGV2 andesite under water-undersaturated conditions is set to crystallize in a dynamic thermal gradient of about 35 °C/mm in 10 mm length capsules. In the hotter area of the capsule, the temperature is initially set at 1200 °C and decreases by programmed cooling at two distinct rates of 0.6 and 9.6 °C/h. Experiments are conducted in horizontally arranged assemblies in a piston cylinder apparatus to avoid any effect of gravity settling and compaction of crystals in long duration runs. The results are conclusive about the effect of water-rich fluids that are expelled out the crystal-rich zone (mush), where water saturation is reached by second boiling in the interstitial liquid. Expelled fluids migrate to the magma ahead of the solidification front contributing to a progressive enrichment in the fluxed components SiO2, K2O and H2O. The composition of water-rich fluids is modelled by mass balance using the chemical composition of glasses (quenched melt). The results are the basis for a model of granite magma differentiation in thermally-zoned conduits with application of in-situ crystallization equations. The intriguing textural and compositional features of the typical autoliths, accompanying granodiorite-tonalite batholiths, can be explained following the results of this study, by critical phenomena leading to splitting of an initially homogeneous magma into two magma systems with sharp boundaries. Magma splitting in thermal boundary layers, formed at the margins of ascent conduits, may operate for several km distances during magma transport from deep sources at the lower crust or upper mantle. Accordingly, conduits may work as chromatographic columns contributing to increase the silica content of ascending magmas and, at the same time, leave behind residual mushes that

  16. Laser melting of uranium carbides

    Science.gov (United States)

    Utton, C. A.; De Bruycker, F.; Boboridis, K.; Jardin, R.; Noel, H.; Guéneau, C.; Manara, D.

    2009-03-01

    In the context of the material research aimed at supporting the development of nuclear plants of the fourth Generation, renewed interest has recently arisen in carbide fuels. A profound understanding of the behaviour of nuclear materials in extreme conditions is of prime importance for the analysis of the operation limits of nuclear fuels, and prediction of possible nuclear reactor accidents. In this context, the main goal of the present paper is to demonstrate the feasibility of laser induced melting experiments on stoichiometric uranium carbides; UC, UC1.5 and UC2. Measurements were performed, at temperatures around 3000 K, under a few bars of inert gas in order to minimise vaporisation and oxidation effects, which may occur at these temperatures. Moreover, a recently developed investigation method has been employed, based on in situ analysis of the sample surface reflectivity evolution during melting. Current results, 2781 K for the melting point of UC, 2665 K for the solidus and 2681 K for the liquidus of U2C3, 2754 K for the solidus and 2770 K for the liquidus of UC2, are in fair agreement with early publications where the melting behaviour of uranium carbides was investigated by traditional furnace melting methods. Further information has been obtained in the current research about the non-congruent (solidus-liquidus) melting of certain carbides, which suggest that a solidus-liquidus scheme is followed by higher ratio carbides, possibly even for UC2.

  17. Scaleable Clean Aluminum Melting Systems

    Energy Technology Data Exchange (ETDEWEB)

    Han, Q.; Das, S.K. (Secat, Inc.)

    2008-02-15

    The project entitled 'Scaleable Clean Aluminum Melting Systems' was a Cooperative Research and Development Agreements (CRADAs) between Oak Ridge National Laboratory (ORNL) and Secat Inc. The three-year project was initially funded for the first year and was then canceled due to funding cuts at the DOE headquarters. The limited funds allowed the research team to visit industrial sites and investigate the status of using immersion heaters for aluminum melting applications. Primary concepts were proposed on the design of furnaces using immersion heaters for melting. The proposed project can continue if the funding agency resumes the funds to this research. The objective of this project was to develop and demonstrate integrated, retrofitable technologies for clean melting systems for aluminum in both the Metal Casting and integrated aluminum processing industries. The scope focused on immersion heating coupled with metal circulation systems that provide significant opportunity for energy savings as well as reduction of melt loss in the form of dross. The project aimed at the development and integration of technologies that would enable significant reduction in the energy consumption and environmental impacts of melting aluminum through substitution of immersion heating for the conventional radiant burner methods used in reverberatory furnaces. Specifically, the program would couple heater improvements with furnace modeling that would enable cost-effective retrofits to a range of existing furnace sizes, reducing the economic barrier to application.

  18. Crystalline anhydrous {alpha},{alpha}-trehalose (polymorph {beta}) and crystalline dihydrate {alpha},{alpha}-trehalose: A calorimetric study

    Energy Technology Data Exchange (ETDEWEB)

    Pinto, Susana S. [Centro de Quimica Estrutural, Complexo Interdisciplinar, Instituto Superior Tecnico, 1049-001 Lisbon (Portugal)]. E-mail: susanapinto@ist.utl.pt; Diogo, Herminio P. [Centro de Quimica Estrutural, Complexo Interdisciplinar, Instituto Superior Tecnico, 1049-001 Lisbon (Portugal)]. E-mail: hdiogo@ist.utl.pt; Moura-Ramos, Joaquim J. [Centro de Quimica-Fisica Molecular, Complexo Interdisciplinar, Instituto Superior Tecnico, 1049-001 Lisbon (Portugal)]. E-mail: mouraramos@ist.utl.pt

    2006-09-15

    The mean values of the standard massic energy of combustion of crystalline anhydrous {alpha},{alpha}-trehalose (C{sub 12}H{sub 22}O{sub 11}, polymorph {beta}) and crystalline dihydrate {alpha},{alpha}-trehalose (C{sub 12}H{sub 26}O{sub 13}) measured by static-bomb combustion calorimetry in oxygen, at the temperature T=298.15K, are {delta}{sub c}u{sup o}=-(16434.05+/-4.50)J.g{sup -1} and {delta}{sub c}u{sup o}=-(14816.05+/-3.52)J.g{sup -1}, respectively. The standard (p{sup o}=0.1MPa) molar enthalpy of formation of these compounds were derived from the corresponding standard molar enthalpies of combustion, respectively, {delta}{sub f}H{sub m}{sup o} (C{sub 12}H{sub 22}O{sub 11},cr)=-(2240.9+/-3.9)kJ.mol{sup -1}, and {delta}{sub f}H{sub m}{sup o} (C{sub 12}H{sub 26}O{sub 13},cr)=-(2832.6+/-3.6)kJ.mol{sup -1}. The values of the standard enthalpies of formation obtained in this work, together with data on enthalpies of solution at infinite dilution ({delta}{sub sol}H{sup {approx}}) for crystalline dihydrate and amorphous anhydrous trehalose, allow a better insight on the thermodynamic description of the trehalose system which can provide, together with the future research on the subject, a contribution for understanding the metabolism in several organisms, as well as the phase transition between the different polymorphs.

  19. Recent Advances in Anhydrous Solvents for CO2 Capture: Ionic Liquids, Switchable Solvents, and Nanoparticle Organic Hybrid Materials

    Directory of Open Access Journals (Sweden)

    YOUNGJUNE ePARK

    2015-10-01

    Full Text Available CO2 capture by amine scrubbing, which has a high CO2 capture capacity and a rapid reaction rate, is the most employed and investigated approach to date. There are a number of recent large-scale demonstrations including the Boundary Dam Carbon Capture Project by SaskPower in Canada that have reported successful implementations of aqueous amine solvent in CO2 capture from flue gases. The findings from these demonstrations will significantly advance the field of CO2 capture in the coming years. While the latest efforts in aqueous amine solvents are exciting and promising, there are still several drawbacks to amine-based CO2 capture solvents including high volatility and corrosiveness of the amine solutions, as well as the high parasitic energy penalty during the solvent regeneration step. Thus, in a parallel effort, alternative CO2 capture solvents, which are often anhydrous, have been developed as the third-generation CO2 capture solvents. These novel classes of liquid materials include: Ionic Liquids (ILs, CO2-triggered switchable solvents (i.e., CO2 Binding Organic Liquids (CO2BOLs, Reversible Ionic Liquids (RevILs, and Nanoparticle Organic Hybrid Materials (NOHMs. This paper provides a review of these various anhydrous solvents and their potential for CO2 capture. Particular attention is given to the mechanisms of CO2 absorption in these solvents, their regeneration and their processability – especially taking into account their viscosity. While not intended to provide a complete coverage of the existing literature, this review aims at pointing the major findings reported for these new classes of CO2 capture media.

  20. Fluid-melt partitioning of sulfur in differentiated arc magmas and the sulfur yield of explosive volcanic eruptions

    Science.gov (United States)

    Masotta, M.; Keppler, H.; Chaudhari, A.

    2016-03-01

    The fluid-melt partitioning of sulfur (DSfluid/melt) in differentiated arc magmas has been experimentally investigated under oxidizing conditions (Re-ReO2 buffer) from 800 to 950 °C at 200 MPa. The starting glasses ranged in composition from trachyte to rhyolite and were synthesized targeting the composition of the residual melt formed after 10-60% crystallization of originally trachy-andesitic, dacitic and rhyodacitic magmas (Masotta and Keppler, 2015). Fluid compositions were determined both by mass balance and by Raman spectroscopy of fluid inclusions. DSfluid/melt increases exponentially with increasing melt differentiation, ranging from 2 to 15 in the trachytic melt, from 20 to 100 in the dacitic and rhyodacitic melts and from 100 to 120 in the rhyolitic melt. The variation of the DSfluid/melt is entirely controlled by the compositional variation of the silicate melt, with temperature having at most a minor effect within the range investigated. Experiments from this study were used together with data from the literature to calibrate the following model that allows predicting DSfluid/melt for oxidized arc magmas: where nbo/t is the non-bridging oxygen atoms per tetrahedron, ASI is the alumina saturation index, Al# and Ca# are two empirical compositional parameters calculated in molar units (Al # = XAl2O3/XSiO2 +XTiO2 +XAl2O3 and Ca # = XCaO/XNa2O +XK2O). The interplay between fluid-melt partitioning and anhydrite solubility determines the sulfur distribution among anhydrite, melt and fluid. At increasing melt polymerization, the exponential increase of the partition coefficient and the decrease of anhydrite solubility favor the accumulation of sulfur either in the fluid phase or as anhydrite. On the other hand, the higher anhydrite solubility and lower partition coefficient for less polymerized melts favor the retention of sulfur in the melt. At equilibrium conditions, these effects yield a maximum of the sulfur fraction in the fluid phase for slightly

  1. Pretreatment of corn stover by low moisture anhydrous ammonia (LMMA) in a pilot-scale reactor and bioconversion to fuel ethanol and industrial chemicals

    Science.gov (United States)

    Corn stover (CS) adjusted to 50%, 66% and 70% moisture was pretreated by the low moisture anhydrous ammonia (LMAA) process in a pilot-scale ammoniation reactor. After ammoniation, the 70% moisture CS was treated at 90 degree C and 100 degree C whereas the others were treated at 90 degree C only. The...

  2. Control of powdery mildew on glasshouse-grown roses and tomatoes in the Netherlands using anhydrous milk fat and soybean oil emulsions

    NARCIS (Netherlands)

    Wurms, K.V.; Hofland-Zijlstra, Jantineke

    2015-01-01

    Powdery mildew (PM) is a very serious disease affecting glasshouse-grown roses and tomatoes in the Netherlands. Control is limited because of resistance to existing fungicides. Anhydrous milk fat (AMF) and soybean oil (SBO) emulsions were evaluated for control of PM in roses and tomatoes. Both AM

  3. Origin of mantle peridotite: Constraints from melting experiments to 16.5 GPa

    Science.gov (United States)

    Herzberg, Claude; Gasparik, Tibor; Sawamoto, Hiroshi

    1990-09-01

    Experimental data are reported for the melting of komatiite, peridotite, and chondrite compositions in the pressure range 5-16.5 GPa. All experiments were run using the multiple-anvil apparatus facilities at Nagoya and Stony Brook. Equilibrium between coexisting crystals and liquid is demonstrated to occur in less than 3 min in the 2100°C range. The anhydrous solidus in CaO-MgO-Al2O3-SiO2 has been calibrated and is shown to be about 100° higher than that for naturally occurring peridotite (KLB1). All melting curves have positive dT/dP. The effect of pressure is to expand the crystallization field of garnet at the expense of all other phases, resulting in a change in the liquidus phase from olivine to garnet at high pressures. The melting of rocks which contain the four crystalline phases olivine, orthopyroxene, clinopyroxene, and garnet is restricted to enstatite-rich compositions such as chondrite. For these it is demonstrated that melting is peritectic, rather than eutectic, and takes the form L+Opx = Ol+Cpx+Gt. Partial melting yields liquids with the following properties: 5 GPa for komatiite; and 10-15 GPa for liquid peridotite with about 40% MgO, but one that is unlike mantle peridotite in that it is distinctly enriched in silica. These results provide a test and refutation of the model that upper mantle peridotite originated by direct initial melting of a chondritic mantle (Herzberg and O'Hara, 1985). Unlike chondrite, partial melting of peridotite does not usually involve orthopyroxene. Instead, it occurs by the generation of ultrabasic liquids along a cotectic involving L+Ol+Cpx+Gt. Although the thermal and compositional characteristics of this cotectic have not been fully calibrated, it is very likely that it will degenerate into a thermal minimum (L+Ol+Cpx+Gt), compositionally similar to komatiite at 5 GPa and mantle peridotite at 10-15 GPa. Peridotite liquids that occupy a thermal minimum can be derived from those formed from the melting of chondrite by

  4. Nanostructure of Er3+ doped silicates.

    Science.gov (United States)

    Yao, Nan; Hou, Kirk; Haines, Christopher D; Etessami, Nathan; Ranganathan, Varadh; Halpern, Susan B; Kear, Bernard H; Klein, Lisa C; Sigel, George H

    2005-06-01

    We demonstrate nanostructural evolution resulting in highly increased photoluminescence in silicates doped with Er3+ ions. High-resolution transmission electron microscopy (HRTEM) imaging, nano-energy dispersed X-ray (NEDX) spectroscopy, X-ray diffraction (XRD) and photoluminescence analysis confirm the local composition and structure changes of the Er3+ ions upon thermal annealing. We studied two types of amorphous nanopowder: the first is of the composition SiO2/18Al2O3/2Er2O3 (SAE), synthesized by combustion flame-chemical vapor condensation, and the second is with a composition of SiO2/8Y2O3/2Er2O3 (SYE), synthesized by sol-gel synthesis (composition in mol%). Electron diffraction and HRTEM imaging clearly show the formation of nanocrystallites with an average diameter of approximately 8 nm in SAE samples annealed at 1000 degrees C and SYE samples annealed at 1200 degrees C. The volume fraction of the nanocrystalline phase increased with each heat treatment, eventually leading to complete devitrification at 1400 degrees C. Further XRD and NEDX analysis indicates that the nanocrystalline phase has the pyrochlore structure with the formula Er(x)Al(2-x)Si2O7 or Er(x)Y(2-x)Si2O7 and a surrounding silica matrix.

  5. Silicate Urolithiasis during Long-Term Treatment with Zonisamide

    Directory of Open Access Journals (Sweden)

    Satoru Taguchi

    2013-01-01

    Full Text Available Silicate urinary calculi are rare in humans, with an incidence of 0.2% of all urinary calculi. Most cases were related to excess ingestion of silicate, typically by taking magnesium trisilicate as an antacid for peptic ulcers over a long period of time; however, there also existed unrelated cases, whose mechanism of development remains unclear. On the other hand, zonisamide, a newer antiepileptic drug, is one of the important causing agents of iatrogenic urinary stones in patients with epilepsy. The supposed mechanism is that zonisamide induces urine alkalinization and then promotes crystallization of urine components such as calcium phosphate by inhibition of carbonate dehydratase in renal tubular epithelial cells. Here, we report a case of silicate urolithiasis during long-term treatment with zonisamide without magnesium trisilicate intake and discuss the etiology of the disease by examining the silicate concentration in his urine.

  6. Properties of sodium silicate bonded sand hardened by microwave heating

    Institute of Scientific and Technical Information of China (English)

    Wang Jina; Fan Zitian; Zan Xiaolei; Pan Di

    2009-01-01

    The sodium silicate bonded sand hardened by microwave heating has many advantages,such as low sodium silicate adding quantity,fast hardening speed,high room temperature strength,good collapsibility and certain surface stability. However,it has big moisture absorbability in the air,which would lead to the compression strength and the surface stability of the sand molds being sharply reduced. In this study,the moisture absorbability of the sodium silicate bonded sand hardened by microwave heating in different humidity conditions and the effect factors were investigated. Meanwhile,the reasons for the big moisture absorbability of the sand were analyzed.Some measures to overcome the problems of high moisture absorbability,bad surface stability and sharply reducing strength in the air were discussed. The results of this study establish the foundation of green and clean foundry technology based on the microwave heating hardening sodium silicate sand process.

  7. Polymer/layered silicates nanocomposites for barrier technology

    CSIR Research Space (South Africa)

    Labuschagne, Philip W

    2012-02-01

    Full Text Available -1 Intelligent Nanomaterials: Processes, Properties, and Applications February 2012/Chapter 13 Polymer/layered silicates nanocomposites for barrier technology Labuschagne, PW, Moolman, S and Maity, A. Corresponding author: PLabusch...

  8. Characterization of iron-phosphate-silicate chemical garden structures.

    Science.gov (United States)

    Barge, Laura M; Doloboff, Ivria J; White, Lauren M; Stucky, Galen D; Russell, Michael J; Kanik, Isik

    2012-02-28

    Chemical gardens form when ferrous chloride hydrate seed crystals are added or concentrated solutions are injected into solutions of sodium silicate and potassium phosphate. Various precipitation morphologies are observed depending on silicate and phosphate concentrations, including hollow plumes, bulbs, and tubes. The growth of precipitates is controlled by the internal osmotic pressure, fluid buoyancy, and membrane strength. Additionally, rapid bubble-led growth is observed when silicate concentrations are high. ESEM/EDX analysis confirms compositional gradients within the membranes, and voltage measurements across the membranes during growth show a final potential of around 150-200 mV, indicating that electrochemical gradients are maintained across the membranes as growth proceeds. The characterization of chemical gardens formed with iron, silicate, and phosphate, three important components of an early earth prebiotic hydrothermal system, can help us understand the properties of analogous structures that likely formed at submarine alkaline hydrothermal vents in the Hadean-structures offering themselves as the hatchery of life.

  9. The crystalline fraction of interstellar silicates in starburst galaxies

    CERN Document Server

    Kemper, F; Woods, Paul M

    2010-01-01

    We present a model using the evolution of the stellar population in a starburst galaxy to predict the crystallinity of the silicates in the interstellar medium of this galaxy. We take into account dust production in stellar ejecta, and amorphisation and destruction in the interstellar medium and find that a detectable amount of crystalline silicates may be formed, particularly at high star formation rates, and in case supernovae are efficient dust producers. We discuss the effect of dust destruction and amorphisation by supernovae, and the effect of a low dust-production efficiency by supernovae, and find that when taking this into account, crystallinity in the interstellar medium becomes hard to detect. Levels of 6.5-13% crystallinity in the interstellar medium of starburst galaxies have been observed and thus we conclude that not all these crystalline silicates can be of stellar origin, and an additional source of crystalline silicates associated with the Active Galactic Nucleus must be present.

  10. Spinning dust emission from ultrasmall silicates: emissivity and polarization spectrum

    CERN Document Server

    Hoang, Thiem; Lan, Nguyen Quynh

    2016-01-01

    Anomalous microwave emission (AME) is an important Galactic foreground of Cosmic Microwave Background (CMB) radiation. It is believed that the AME arises from rotational emission by spinning polycyclic aromatic hydrocarbons (PAHs) in the interstellar medium (ISM). In this paper, we assume that a population of ultrasmall silicate grains may exist in the ISM, and quantify rotational emissivity from these tiny particles and its polarization spectrum. We found that spinning silicate nanoparticles can produce strong rotational emission when those small grains follow a log-normal size distribution. The polarization fraction of spinning dust emission from tiny silicates increases with decreasing the dipole moment per atom ($\\beta$) and can reach $P\\sim 20\\%$ for $\\beta\\sim 0.1$D at grain temperature of 60 K. We identify a parameter space $(\\beta,Y_{Si})$ for silicate nanoparticles in which its rotational emission can adequately reproduce both the observed AME and the polarization of the AME, without violating the ob...

  11. Quantifying melting and mobilistaion of interstitial melts in crystal mushes

    Science.gov (United States)

    Veksler, Ilya; Dobson, Katherine; Hess, Kai-Uwe; Ertel-Ingrisch, Werner; Humphreys, Madeleine

    2015-04-01

    The deformation of crystals mushes and separation of melts and crystals in is critical to understanding the development of physical and chemical heterogeneity in magma chambers and has been invoked as an eruption trigger mechanism. Here we investigate the behaviour of the melt in the well characterised, classic crystal mush system of the Skaergaard intrusion by combining experimental petrology and the non-destructive 3D imaging methods. Starting materials for partial melting experiments were four samples from the upper Middle Zone of the Layered Series. Cylinders, 15 mm in diameter and 20 mm in length, were drilled out of the rock samples, placed in alumina crucibles and held for 5 days in electric furnaces at atmospheric pressure and 1050-1100 °C. Redox conditions set by the CO-CO2 gas mixture were kept close to those of the FMQ buffer. We then use spatially registered 3D x-ray computed tomography images, collected before and after the experiment, to determine the volume and distribution of the crystal framework and interstitial phases, and the volume, distribution and connectivity the interstitial phases that undergo melting and extraction while at elevated temperature. Image analysis has allowed us to quantify these physical changes with high spatial resolution. Our work is a first step towards quantitative understanding of the melt mobilisation and migration processes operating in notionally locked crystal rich magmatic systems.

  12. MAS-NMR study of lithium zinc silicate glasses and glass-ceramics with various ZnO content

    Science.gov (United States)

    Goswami, Madhumita; Kothiyal, Govind P.; Montagne, Lionel; Delevoye, Laurent

    2008-02-01

    Lithium zinc silicate glasses of composition (mol%): 17.5Li 2O-(72- x)SiO 2- xZnO-5.1Na 2O-1.3P 2O 5-4.1B 2O 3, 5.5⩽ x⩽17.7, were prepared by conventional melt-quenched technique and converted to glass-ceramic by controlled crystallization process. 29Si and 31P MAS-NMR was used to characterize the structure of both glass and glass-ceramic samples. Despite the complex glass composition, Q2, Q3 and Q4 sites are identified from 29Si MAS-NMR, which relative intensities are found to vary with the ZnO content, indicating a network depolymerization by ZnO. Moreover, well separated Q3 and Q4 resonances for low ZnO content indicates the occurrence of phase separation. From 31P MAS-NMR, it is seen that phosphorus is mainly present in the form of ortho-( Q0) and pyro-phosphate ( Q1) structural units and variation of ZnO content did not have much effect on these resonances, which provides an additional evidence for phase separation in the glass. On conversion to glass-ceramics, lithium disilicate (Li 2Si 2O 5), lithium zinc ortho-silicate (Li 3Zn 0.5SiO 4), tridymite (SiO 2) and cristobalite (SiO 2) were identified as major silicate crystalline phases. Using 29Si MAS-NMR, quantification of these silicate crystalline phases is carried out and correlated with the ZnO content in the glass-ceramics samples. In addition, 31P spectra unambiguously revealed the presence of crystalline Li 3PO 4 and (Na,Li) 3PO 4 in the glass-ceramics.

  13. Methods for Melting Temperature Calculation

    Science.gov (United States)

    Hong, Qi-Jun

    Melting temperature calculation has important applications in the theoretical study of phase diagrams and computational materials screenings. In this thesis, we present two new methods, i.e., the improved Widom's particle insertion method and the small-cell coexistence method, which we developed in order to capture melting temperatures both accurately and quickly. We propose a scheme that drastically improves the efficiency of Widom's particle insertion method by efficiently sampling cavities while calculating the integrals providing the chemical potentials of a physical system. This idea enables us to calculate chemical potentials of liquids directly from first-principles without the help of any reference system, which is necessary in the commonly used thermodynamic integration method. As an example, we apply our scheme, combined with the density functional formalism, to the calculation of the chemical potential of liquid copper. The calculated chemical potential is further used to locate the melting temperature. The calculated results closely agree with experiments. We propose the small-cell coexistence method based on the statistical analysis of small-size coexistence MD simulations. It eliminates the risk of a metastable superheated solid in the fast-heating method, while also significantly reducing the computer cost relative to the traditional large-scale coexistence method. Using empirical potentials, we validate the method and systematically study the finite-size effect on the calculated melting points. The method converges to the exact result in the limit of a large system size. An accuracy within 100 K in melting temperature is usually achieved when the simulation contains more than 100 atoms. DFT examples of Tantalum, high-pressure Sodium, and ionic material NaCl are shown to demonstrate the accuracy and flexibility of the method in its practical applications. The method serves as a promising approach for large-scale automated material screening in which

  14. Anhydrate to hydrate solid-state transformations of carbamazepine and nitrofurantoin in biorelevant media studied in situ using time-resolved synchrotron X-ray diffraction.

    Science.gov (United States)

    Boetker, Johan P; Rantanen, Jukka; Arnfast, Lærke; Doreth, Maria; Raijada, Dhara; Loebmann, Korbinian; Madsen, Cecilie; Khan, Jamal; Rades, Thomas; Müllertz, Anette; Hawley, Adrian; Thomas, Diana; Boyd, Ben J

    2016-03-01

    Transformation of the solid-state form of a drug compound in the lumen of the gastrointestinal tract may alter the drug bioavailability and in extreme cases result in patient fatalities. The solution-mediated anhydrate-to-hydrate phase transformation was examined using an in vitro model with different biorelevant media, simulated fasted and fed state intestinal fluids containing bile salt and dioleoylphosphatidylcholine (DOPC) micelles, DOPC/sodium dodecyl sulfate (SDS) mixture, bile salt solution and water. Two anhydrate compounds (carbamazepine, CBZ and nitrofurantoin, NF) with different overall transformation time into hydrate form were used as model compounds. The transformations were monitored using direct structural information from time-resolved synchrotron X-ray diffraction. The kinetics of these transformations were estimated using multivariate data analysis (principal component analysis, PCA) and compared to those for nitrofurantoin (NF). The study showed that the solution-mediated phase transformation of CBZ anhydrate was remarkably faster in the DOPC/SDS medium compared to transformation in all the other aqueous dispersion media. The conversion time for CBZ anhydrate in water was shorter than for DOPC/SDS but still faster than the conversion seen in fed and fasted state micellar media. The conversion of CBZ anhydrate to hydrate was the slowest in the solution containing bile salt alone. In contrast, the solution-mediated phase transformations of NF did only show limited kinetic dependence on the dispersion media used, indicating the complexity of the nucleation process. Furthermore, when the CBZ and NF material was compacted into tablets the transformation times were remarkably slower. Results suggest that variations in the composition of the contents of the stomach/gut may affect the recrystallization kinetics, especially when investigating compounds with relatively fast overall transformation time, such as CBZ.

  15. Trace element composition and U-Pb age of zircons from Estherville: Constraints on the timing of the metal-silicate mixing event on the mesosiderite parent body

    Science.gov (United States)

    Haba, Makiko K.; Yamaguchi, Akira; Kagi, Hiroyuki; Nagao, Keisuke; Hidaka, Hiroshi

    2017-10-01

    Mesosiderites are a group of stony-iron meteorites, which are thought to be the result of mixing of silicates with Fe-Ni metal. In this study, we combined textural observations with geochemical and chronological studies of two zircon grains found in the Estherville mesosiderite. One of the zircons (Zrc1) occurs with pyroxene, plagioclase, troilite, and silica, and the other (Zrc2) is located at a boundary between Fe-Ni metal and a silicate part mainly composed of pyroxene and plagioclase. The textural observations demonstrate that Zrc1 is relatively homogenous, whereas Zrc2 is composed of at least two chemically distinct domains. Trace element analyses of Zrc2 resolve large concentration gradients within this single grain with variations that are an order of magnitude for rare earth elements (REE) and two orders of magnitude for U and Th. The lowest trace element concentration in Zrc2 is more than an order of magnitude lower than those of lunar and eucritic zircons. However, it is similar to those of Zrc1 and a zircon from the Vaca Muerta mesosiderite. The calculated REE composition of the melt in equilibrium with Zrc2 shows that Zrc2 and perhaps also Zrc1 did not crystallize from a melt that was produced by fractional crystallization of the primary magmatic mineral assemblages. The zircons with low REE, U, and Th concentrations can be interpreted to have formed in a residual melt after incorporation of large amounts of REE, U, and Th into secondary phosphate minerals, which formed during the metal-silicate mixing event. The large concentration gradients observed in Zrc2 suggest significant heterogeneities in the melt from which the zircon crystallized. Alternatively, either mixing or diffusion between a relict zircon and a newly formed zircon could explain the observed concentration gradients. However, the REE patterns of Zrc2 cannot be explained by mixing or diffusion between the two distinct generations of zircons. These considerations suggest that Zrc1 and Zrc2

  16. Determination of reactivity rates of silicate particle-size fractions

    OpenAIRE

    Angélica Cristina Fernandes Deus; Leonardo Theodoro Büll; Juliano Corulli Corrêa; Roberto Lyra Villas Boas

    2014-01-01

    The efficiency of sources used for soil acidity correction depends on reactivity rate (RR) and neutralization power (NP), indicated by effective calcium carbonate (ECC). Few studies establish relative efficiency of reactivity (RER) for silicate particle-size fractions, therefore, the RER applied for lime are used. This study aimed to evaluate the reactivity of silicate materials affected by particle size throughout incubation periods in comparison to lime, and to calculate the RER for silicat...

  17. Metal-silicate partitioning of U: Implications for the heat budget of the core and evidence for reduced U in the mantle

    Science.gov (United States)

    Chidester, Bethany A.; Rahman, Zia; Righter, Kevin; Campbell, Andrew J.

    2017-02-01

    Earth's core might require an internal heat source, such as radioactive decay, to explain the presence of the magnetic field through geologic time. To investigate whether U would be an important heat source in the core, we performed metal-silicate partitioning experiments of U at P-T (up to 67 GPa and 5400 K) conditions more relevant to a magma ocean scenario than has previously been reported. This study finds the partitioning of U to be strongly dependent on ƒO2, temperature, the S content of the metal and the SiO2 content of the silicate during core-mantle differentiation. Differentiation at mean conditions of 42-58 GPa and 3900-4200 K would put 1.4-3.5 ppb U (2-8 wt% S) in the core, amounting to a maximum of 1.4 (+1/-0.7) TW of heat 4.5 billion years ago. This is likely not enough heat to mitigate early widespread mantle melting. It was also found that U likely exists in the 2+ oxidation state in silicate melts in the deep Earth, a state which has not been previously observed in nature.

  18. Friction and Wear Behaviors of Nano-Silicates in Water

    Institute of Scientific and Technical Information of China (English)

    Chen Boshui; Lou Fang; Fang Jianhua; Wang Jiu; Li Jia

    2009-01-01

    Nano-metric magnesium silicate and zinc silicate with particle size of about 50--70nm were prepared in water by the method of chemical deposition. The antiwear and friction reducing abilities of the nano-silicates, as well as their compos-ites with oleie acid tri-ethanolamine (OATEA), were evaluated on a four-ball friction tester. The topographies and tribochemical features of the worn surfaces were analyzed by scanning electron microscope (SEM) and X-ray photoelectron spectroscope (XPS). Results show that nano-silicates alone provide poor antiwear and friction reducing abilities in water, but exhibits excellent synergism with OATEA in reducing friction and wear. The synergism in reducing friction and wear between naao-silicates and OATEA does exist almost regardless of particle sizes and species, and may be attributed, on one hand, to the formation of an adsorption film of OATEA, and, on the other hand, to the formation oftdbochemical species of silicon dioxide and iron oxides on the friction surfaces. Tribo-reactions and tribo-adsorptions of nano-silicates and OATEA would produce hereby an effective composite boondary lubrication film, which could efficiently enhance the anti-wear and friction-reducing abilities of water.

  19. High Pressure/Temperature Metal Silicate Partitioning of Tungsten

    Science.gov (United States)

    Shofner, G. A.; Danielson, L.; Righter, K.; Campbell, A. J.

    2010-01-01

    The behavior of chemical elements during metal/silicate segregation and their resulting distribution in Earth's mantle and core provide insight into core formation processes. Experimental determination of partition coefficients allows calculations of element distributions that can be compared to accepted values of element abundances in the silicate (mantle) and metallic (core) portions of the Earth. Tungsten (W) is a moderately siderophile element and thus preferentially partitions into metal versus silicate under many planetary conditions. The partitioning behavior has been shown to vary with temperature, silicate composition, oxygen fugacity, and pressure. Most of the previous work on W partitioning has been conducted at 1-bar conditions or at relatively low pressures, i.e. <10 GPa, and in two cases at or near 20 GPa. According to those data, the stronger influences on the distribution coefficient of W are temperature, composition, and oxygen fugacity with a relatively slight influence in pressure. Predictions based on extrapolation of existing data and parameterizations suggest an increased pressured dependence on metal/ silicate partitioning of W at higher pressures 5. However, the dependence on pressure is not as well constrained as T, fO2, and silicate composition. This poses a problem because proposed equilibration pressures for core formation range from 27 to 50 GPa, falling well outside the experimental range, therefore requiring exptrapolation of a parametereized model. Higher pressure data are needed to improve our understanding of W partitioning at these more extreme conditions.

  20. The Origin of the Compositional Diversity of Mercury's Surface Constrained From Experimental Melting of Enstatite Chondrites

    Science.gov (United States)

    Boujibar, A.; Righter, K.; Pando, K.; Danielson, L.

    2015-01-01

    Mercury is known as an endmember planet as it is the most reduced terrestrial planet with the highest core/mantle ratio. MESSENGER spacecraft has shown that its surface is FeO-poor (2-4 wt%) and Srich (up to 6-7 wt%), which confirms the reducing nature of its silicate mantle. Moreover, high resolution images revealed large volcanic plains and abundant pyroclastic deposits, suggesting important melting stages of the Mercurian mantle. This interpretation was confirmed by the high crustal thickness (up to 100 km) derived from Mercury's gravity field. This is also corroborated by a recent experimental result that showed that Mercurian partial melts are expected to be highly buoyant within the Mercurian mantle and could have risen from depths as high as the core-mantle boundary. In addition MESSENGER spacecraft provided relatively precise data on major elemental compositions of Mercury's surface. These results revealed important chemical and mineralogical heterogeneities that suggested several stages of differentiation and re-melting processes. However, the extent and nature of compositional variations produced by partial melting remains poorly constrained for the particular compositions of Mercury (very reducing conditions, low FeO-contents and high sulfur-contents). Therefore, in this study, we investigated the processes that lead to the various compositions of Mercury's surface. Melting experiments with bulk Mercury-analogue compositions were performed and compared to the compositions measured by MESSENGER.

  1. Water- and Boron-Rich Melt Inclusions in Quartz from the Malkhan Pegmatite, Transbaikalia, Russia

    Directory of Open Access Journals (Sweden)

    Elena Badanina

    2012-11-01

    Full Text Available In this paper we show that the pegmatite-forming processes responsible for the formation of the Malkhan pegmatites started at magmatic temperatures around 720 °C. The primary melts or supercritical fluids were very water- and boron-rich (maximum values of about 10% (g/g B2O3 and over the temperature interval from 720 to 600 °C formed a pseudobinary solvus, indicated by the coexistence of two types of primary melt inclusions (type-A and type-B representing a pair of conjugate melts. Due to the high water and boron concentration the pegmatite-forming melts are metastable and can be characterized either as genuine melts or silicate-rich fluids. This statement is underscored by Raman spectroscopic studies. This study suggested that the gel state proposed by some authors cannot represent the main stage of the pegmatite-forming processes in the Malkhan pegmatites, and probably in all others. However there are points in the evolution of the pegmatites where the gel- or gel-like state has left traces in form of real gel inclusions in some mineral in the Malkhan pegmatite, however only in a late, fluid dominated stage.

  2. Melting of superheated molecular crystals

    Science.gov (United States)

    Cubeta, Ulyana; Bhattacharya, Deepanjan; Sadtchenko, Vlad

    2017-07-01

    Melting dynamics of micrometer scale, polycrystalline samples of isobutane, dimethyl ether, methyl benzene, and 2-propanol were investigated by fast scanning calorimetry. When films are superheated with rates in excess of 105 K s-1, the melting process follows zero-order, Arrhenius-like kinetics until approximately half of the sample has transformed. Such kinetics strongly imply that melting progresses into the bulk via a rapidly moving solid-liquid interface that is likely to originate at the sample's surface. Remarkably, the apparent activation energies for the phase transformation are large; all exceed the enthalpy of vaporization of each compound and some exceed it by an order of magnitude. In fact, we find that the crystalline melting kinetics are comparable to the kinetics of dielectric α-relaxation in deeply supercooled liquids. Based on these observations, we conclude that the rate of non-isothermal melting for superheated, low-molecular-weight crystals is limited by constituent diffusion into an abnormally dense, glass-like, non-crystalline phase.

  3. Potassium silicate and calcium silicate on the resistance of soybean to Phakopsora pachyrhizi infection

    Directory of Open Access Journals (Sweden)

    Maria Fernanda Cruz

    2013-01-01

    Full Text Available The control of Asian Soybean Rust (ASR, caused by Phakopsora pachyrhizi, has been difficult due to the aggressiveness of the pathogen and the lack of resistant cultivars. The objective of this study was to evaluate the effects of spray of potassium silicate (PS and soil amendment with calcium silicate (CS on soybean resistance to ASR. The PS solution was sprayed to leaves 24 hours prior to fungal inoculation while CS was amended to the soil at thirty-five days before sowing. The infection process of P. pachyrhizi was investigated by scanning electron microscopy. The uredia on leaves of plants sprayed with PS were smaller and more compact than those observed on the leaves of plants grown in soil amended with CS or in soil non-amended with CS (control treatment. On leaves of plants from the control treatment, uredia produced many urediniospores at 9 days after inoculation, and the ASR severity was 15, 8 and 9%, respectively, for plants from control, PS and CS treatments. In conclusion, the spray of PS contributed to reduce the number of uredia per cm² of leaf area and both PS spray and CS resulted in lower ASR symptoms.

  4. Durability of Silicate Glasses: An Historical Approach

    Energy Technology Data Exchange (ETDEWEB)

    Farges, Francois; /Museum Natl. Hist. Natur. /Stanford U., Geo. Environ. Sci.; Etcheverry, Marie-Pierre; /Marne la Vallee U.; Haddi, Amine; /Marne la Valle U.; Trocellier,; /Saclay; Curti, Enzo; /PSI, Villigen; Brown, Gordon E., Jr.; /SLAC, SSRL

    2007-01-02

    We present a short review of current theories of glass weathering, including glass dissolution, and hydrolysis of nuclear waste glasses, and leaching of historical glasses from an XAFS perspective. The results of various laboratory leaching experiments at different timescales (30 days to 12 years) are compared with results for historical glasses that were weathered by atmospheric gases and soil waters over 500 to 3000 years. Good agreement is found between laboratory experiments and slowly leached historical glasses, with a strong enrichment of metals at the water/gel interface. Depending on the nature of the transition elements originally dissolved in the melt, increasing elemen