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Sample records for acid silicates

  1. Process for acidizing hot siliceous material

    Energy Technology Data Exchange (ETDEWEB)

    Scheuerman, R. F.; Silverman, S. A.

    1985-10-22

    The dissolving of siliceous material in an environment containing corrodable metal and having a temperature exceeding about 300/sup 0/ F. is improved by using an aqueous solution containing an amount of ammonium fluoride equivalent to that in a 2-3 molar solution of hydrogen fluoride and enough weak acid and weak acid salt to provide a pH of near to but less than 7.

  2. 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.

  3. Leaf application of silicic acid to upland rice and corn

    Directory of Open Access Journals (Sweden)

    Carlos Alexandre Costa Crusciol

    2013-12-01

    Full Text Available This study aimed to evaluate the effect of Si (stabilized silicic acid, Silamol® leaf application on mineral nutrition and yield in upland rice and corn crops. The treatments were the control (without Si and Si foliar split spraying using 2 L ha-1 of the Silamol® commercial product, with 0.8% soluble Si as concentrated stabilized silicic acid. Silicon leaf application increased the concentrations of K, Ca and Si in rice and corn leaves, the number of panicles per m2 of rice and the number of grains per ear of corn; accordingly, the Si leaf application provided a higher grain yield in both crops.

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

    Directory of Open Access Journals (Sweden)

    Jurkić Lela Munjas

    2013-01-01

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

  5. Competitive Adsorption of Arsenite and Silicic Acid on Goethite

    OpenAIRE

    Luxton, Todd Peter

    2002-01-01

    The adsorption behavior of silicic acid and arsenite alone and competitively on goethite over a broad pH range (3-11) at environmentally relevant concentrations was investigated utilizing pH adsorption data and zeta potential measurements. Both addition scenarios (Si before As(III) and As(III) before Si) were examined. The results of the adsorption experiments and zeta potential measurements were then used to model the single ion and competitive ion adsorption on goethite with the CD-MUSIC ...

  6. Precipitation of silicic acid from geothermal water by addition of cetyl-trimethyl-ammonium bromide

    Energy Technology Data Exchange (ETDEWEB)

    Kitsuki, Harumi; Yokoyama, Takushi; Shimada, Kanichi; Yamanaka, Chiho; Nishu, Keisuke; Shimizu, Shin; Tarutani, Toshikazu

    1986-01-25

    Cetyl-trimethyl-ammonium bromide (CTAB) was added to sodium silicate solution and geothermal hot water (Ohtake Geothermal Power Plant and Hatchobaru Geo-thermal Power Plant) to precipitate silica. 1) CTA ions do not react with monosilicic acid, but only the polymerization among the polysilicic acids proceeds and causes silica to precipitate. Optimum pH for the silica precipitation is 6 - 7 and the higher concentration of polysilicic acid will cause more precipitation. 2) When added to geothermal hot water, the silica precipita-tion increases with the increase of CTAB concentration within the range of 10/sup -7/ - 10/sup -4/ mol dm/sup 3/ concentration. Almost all poly-silicic acid precipitated at 10/sup -4/ mol dm/sup 3/ when measured for silica precipitation after 5 minutes. Total concentration of silicic acid was higher in the Hatchobaru geothermal water than that of the Ohtake geothermal water. (10 figs, 14 refs)

  7. Use of mesoporous silicate nanoparticles as drug carrier for mefenamic acid

    Science.gov (United States)

    Mustafa, F. M.; Hodali, H. A.

    2015-10-01

    The aim of the study is to evaluate the use of mesoporous silicate nanoparticles for the loading and release of the non-steroidal anti-inflammatory drug, mefenamic acid. Nanoparticles of the mesoporous silicate materials, MCM-41 and SBA-16 were synthesized and characterized by XRD, SEM, FT-IR, TGA and BET surface area techniques. Both silicate systems were loaded with mefenamic acid with loading capacities of 18.6% and 11.6%, respectively. The in vitro release of mefenamic acid into simulated body fluid (pH = 7.4) at 37°C was investigated. The percent release was nonlinearly regressed against time (t) according to the first order kinetic release model; Higuchi's first burst model and Kopcha's empirical model. The overall %release was obtained for both silicate systems and was found to be about 60%. Analysis of results show the rate of drug release is more rapid from SBA-16 (the more interconnected porous network) than from MCM-41. It also show that drug release from either mesoporous silicate is a diffusion controlled process.

  8. Deglacial diatom production in the tropical North Atlantic driven by enhanced silicic acid supply

    Science.gov (United States)

    Hendry, Katharine R.; Gong, Xun; Knorr, Gregor; Pike, Jennifer; Hall, Ian R.

    2016-03-01

    Major shifts in ocean circulation are thought to be responsible for abrupt changes in temperature and atmospheric CO2 during the last deglaciation, linked to variability in meridional heat transport and deep ocean carbon storage. There is also widespread evidence for shifts in biological production during these times of deglacial CO2 rise, including enhanced diatom production in regions such as the tropical Atlantic. However, it remains unclear as to whether this diatom production was driven by enhanced wind-driven upwelling or density-driven vertical mixing, or by elevated thermocline concentrations of silicic acid supplied to the surface at a constant rate. Here, we demonstrate that silicic acid supply at depth in the NE Atlantic was enhanced during the abrupt climate events of the deglaciation. We use marine sediment archives to show that an increase in diatom production during abrupt climate shifts could only occur in regions of the NE Atlantic where the deep supply of silicic acid could reach the surface. The associated changes are indicative of enhanced regional wind-driven upwelling and/or weakened stratification due to circulation changes during phases of weakened Atlantic meridional overturning. Globally near-synchronous pulses of diatom production and enhanced thermocline concentrations of silicic acid suggest that widespread deglacial surface-driven breakdown of stratification, linked to changes in atmospheric circulation, had major consequences for biological productivity and carbon cycling.

  9. Alleviating aluminium toxicity on an acid sulphate soils in Peninsular Malaysia with application of calcium silicate

    OpenAIRE

    A. A. Elisa; Ninomiya, S.; J. Shamshuddin; Roslan, I.

    2015-01-01

    A study was conducted to alleviate Al toxicity of an acid sulphate soils collected from paddy cultivation area in Kedah, Peninsular Malaysia. For this purpose, the collected acid sulphate soils were treated with calcium silicate. The treated soils were incubated for 120 days in submerged condition in a glasshouse. Subsamples were collected every 30 days throughout the incubation period. Soil pH and exchangeable Al showed positive effect; soil pH increased from ...

  10. Characterization of modified calcium-silicate cements exposed to acidic environment

    Energy Technology Data Exchange (ETDEWEB)

    Camilleri, Josette, E-mail: josette.camilleri@um.edu.mt

    2011-01-15

    Portland cement which is used as a binder in concrete in the construction industry has been developed into a biomaterial. It is marketed as mineral trioxide aggregate and is used in dentistry. This material has been reported to be very biocompatible and thus its use has diversified. The extended use of this material has led to developments of newer versions with improved physical properties. The aim of this study was to evaluate the effect of acidic environments found in the oral cavity on fast setting calcium silicate cements with improved physical properties using a combination of techniques. Two fast setting calcium silicate cements (CSA and CFA) and two cement composites (CSAG and CFAG) were assessed by subjecting the materials to lactic acid/sodium lactate buffer gel for a period of 28 days. At weekly intervals the materials were viewed under the tandem scanning confocal microscope (TSM), and scanning electron microscope (SEM). The two prototype cements exhibited changes in their internal chemistry with no changes in surface characteristics. Since the changes observed were mostly sub-surface evaluation of surface characteristics of cement may not be sufficient in the determination of chemical changes occurring. - Research Highlights: {yields} An acidic environment affects modified fast setting calcium silicate-based cements. {yields} No surface changes are observed in acidic environment. {yields} An acidic environment causes sub-surface changes in the material chemistry which are only visible in fractured specimens. {yields} A combination of techniques is necessary in order to evaluate the chemical changes occurring.

  11. Characterization of modified calcium-silicate cements exposed to acidic environment

    International Nuclear Information System (INIS)

    Portland cement which is used as a binder in concrete in the construction industry has been developed into a biomaterial. It is marketed as mineral trioxide aggregate and is used in dentistry. This material has been reported to be very biocompatible and thus its use has diversified. The extended use of this material has led to developments of newer versions with improved physical properties. The aim of this study was to evaluate the effect of acidic environments found in the oral cavity on fast setting calcium silicate cements with improved physical properties using a combination of techniques. Two fast setting calcium silicate cements (CSA and CFA) and two cement composites (CSAG and CFAG) were assessed by subjecting the materials to lactic acid/sodium lactate buffer gel for a period of 28 days. At weekly intervals the materials were viewed under the tandem scanning confocal microscope (TSM), and scanning electron microscope (SEM). The two prototype cements exhibited changes in their internal chemistry with no changes in surface characteristics. Since the changes observed were mostly sub-surface evaluation of surface characteristics of cement may not be sufficient in the determination of chemical changes occurring. - Research Highlights: → An acidic environment affects modified fast setting calcium silicate-based cements. → No surface changes are observed in acidic environment. → An acidic environment causes sub-surface changes in the material chemistry which are only visible in fractured specimens. → A combination of techniques is necessary in order to evaluate the chemical changes occurring.

  12. Determination of silica in silicates by differential spectrophotometry as α-molybdosilicic acid

    International Nuclear Information System (INIS)

    A method for determining silica in silicates by differential spectrophotometry, using β-molybdosilic acid, is described. The sample is attacked by a mixture of boron trioxide and lithium carbonate (10:1). α-molydbosilicic acid is developed in a buffered solution (pH approximatelly 3.9) containing acetic acid and sodium acetate. The analytical procedure involves a series of preliminary steps which were previously elaborated for the gravimetric determination of silica as oxine molybdosilicate and which account for the removal of phosphorus, titanium and zirconium through ion exchange resins. (C.L.B.)

  13. Effects of Calcium Lignosulfonate and Silicic Acid on Ammonium Nitrate Degradation

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    Ahmet Ozan Gezerman

    2014-01-01

    Full Text Available Ammonium nitrate salts are the most commonly used nitrogenous fertilizers in industry. However, storage of ammonium nitrate is problematic, since its initial properties can decline because of environmental factors, leading to large economic losses. In this study, in order to prevent the caking and degradation of ammonium nitrate, an alternative composition with additional calcium lignosulfonate and silicic acid was studied. The resulting fertilizer was analyzed by screening analysis, ion chromatography, and electron microscopy methods.

  14. Sustainable activity of hydrothermally synthesized mesoporous silicates in acetic acid esterification

    OpenAIRE

    ŞİMŞEK, VELİ; DEĞİRMENCİ, LEVENT; MÜRTEZAOĞLU, KIRALİ

    2015-01-01

    A hydrothermal method was applied in the synthesis of mesoporous silicates containing silicotungstic acid (STA). The synthesis procedures were developed by modification of procedures previously applied in the synthesis of MCM-41 and SBA-15. The synthesized catalysts were named MCM-41-S and SBA-15-S based on MCM-41 and SBA-15. Their activities were investigated in ethyl acetate production, which was selected as the model reaction. The results indicated that the activity of SBA-15-S catalysts i...

  15. Alleviating aluminum toxicity in an acid sulfate soil from Peninsular Malaysia by calcium silicate application

    OpenAIRE

    A. A. Elisa; Ninomiya, S.; J. Shamshuddin; Roslan, I.

    2016-01-01

    In response to human population increase, the utilization of acid sulfate soils for rice cultivation is one option for increasing production. The main problems associated with such soils are their low pH values and their associated high content of exchangeable Al, which could be detrimental to crop growth. The application of soil amendments is one approach for mitigating this problem, and calcium silicate is an alternative soil amendment that could be used. Therefore, the ma...

  16. Method of gradual acid leaching of uranium ores of silicate and aluminosilicate nature

    International Nuclear Information System (INIS)

    Leaching uranium ore pulp is divided into two stages. The first stage takes place without any addition of a leaching agent at elevated pressure and temperature. In the second stage, sulfuric acid is added to the pulp (50 to 1000 kg per tonne of ore) or an oxidation agent. Leaching then proceeds according to routine procedures. The procedure is used to advantage for silicate or aluminosilicate ores which contain uranium minerals which are difficult to leach, pyrite and reducing substances. The two stage leaching allows to use the technology of pressure leaching, reduces consumption of sulfuric acid and oxidation agents and still achieves the required reduction oxidation potential. (E.S.)

  17. Estimates of late Quaternary mode and intermediate water silicic acid concentration in the Pacific Southern Ocean

    Science.gov (United States)

    Rousseau, Jonathon; Ellwood, Michael J.; Bostock, Helen; Neil, Helen

    2016-04-01

    The Southern Ocean plays a critical role in the exchange of carbon between the ocean and atmosphere over glacial-interglacial timescales. Hypotheses used to explain late Quaternary variations in atmospheric carbon dioxide (CO2) implicate changes in the nutrient dynamics and circulation of the Southern Ocean. Here we present silicon isotope (δ30Si) records of late Quaternary sponges and diatoms from the NZ-sector of the Southern Ocean. Analysis of our sponge δ30Si records strongly suggests that the silicic acid concentration at mode and intermediate depths was higher during the LGM and the deglacial period compared to the present day. Our diatom δ30Si record suggests biological productivity near of the Polar Front was greater during the deglacial period, but not significantly different during the LGM compared to the present day. Taking our dataset in context with other regional paleoceanographic records, we interpret the predicted elevation in LGM and deglacial silicic acid concentration to reflect a shoaling of water masses during the LGM and 'leakage' of excess Southern Ocean dissolved silicon during the deglacial period.

  18. Process for the conversion of sugars to lactic acid and 2-hydroxy-3-butenoic acid or esters thereof comprising a metallo-silicate material and a metal ion

    DEFF Research Database (Denmark)

    2015-01-01

    A process for the preparation of lactic acid and 2-hydroxy- 3-butenoic acid or esters thereof from a sugar in the presence of a metallo-silicate material, a metal ion and a solvent, wherein the metal ion is selected from one or more of the group consisting of potassium ions, sodium ions, lithium...... ions, rubidium ions and caesium ions....

  19. Water-Dispersible Silica-Polyelectrolyte Nanocomposites Prepared via Acid-Triggered Polycondensation of Silicic Acid and Directed by Polycations

    Directory of Open Access Journals (Sweden)

    Philip Overton

    2016-03-01

    Full Text Available The present work describes the acid-triggered condensation of silicic acid, Si(OH4, as directed by selected polycations in aqueous solution in the pH range of 6.5–8.0 at room temperature, without the use of additional solvents or surfactants. This process results in the formation of silica-polyelectrolyte (S-PE nanocomposites in the form of precipitate or water-dispersible particles. The mean hydrodynamic diameter (dh of size distributions of the prepared water-dispersible S-PE composites is presented as a function of the solution pH at which the composite formation was achieved. Poly(2-(dimethylaminoethyl methacrylate (PDMAEMA and block copolymers of DMAEMA and oligo(ethylene glycol methyl ether methacrylate (OEGMA were used as weak polyelectrolytes in S-PE composite formation. The activity of the strong polyelectrolytes poly(methacryloxyethyl trimethylammonium iodide (PMOTAI and PMOTAI-b-POEGMA in S-PE formation is also examined. The effect of polyelectrolyte strength and the OEGMA block on the formation of the S-PE composites is assessed with respect to the S-PE composites prepared using the PDMAEMA homopolymer. In the presence of the PDMAEMA60 homopolymer (Mw = 9400 g/mol, the size of the dispersible S-PE composites increases with solution pH in the range pH 6.6–8.1, from dh = 30 nm to dh = 800 nm. S-PDMAEMA60 prepared at pH 7.8 contained 66% silica by mass (TGA. The increase in dispersible S-PE particle size is diminished when directed by PDMAEMA300 (Mw = 47,000 g/mol, reaching a maximum of dh = 75 nm. S-PE composites formed using PDMAEMA-b-POEGMA remain in the range dh = 20–30 nm across this same pH regime. Precipitated S-PE composites were obtained as spheres of up to 200 nm in diameter (SEM and up to 65% mass content of silica (TGA. The conditions of pH for the preparation of dispersible and precipitate S-PE nanocomposites, as directed by the five selected polyelectrolytes PDMAEMA60, PDMAEMA300, PMOTAI60, PDMAEMA60-b-POEGMA38 and

  20. Inorganic polymers from laterite using activation with phosphoric acid and alkaline sodium silicate solution: Mechanical and microstructural properties

    Energy Technology Data Exchange (ETDEWEB)

    Lassinantti Gualtieri, Magdalena, E-mail: magdalena.gualtieri@unimore.it [Dipartimento di Ingegneria " Enzo Ferrari" , Università degli studi di Modena e Reggio Emilia, Via Vignolese 905/a, I-41125 Modena (Italy); Romagnoli, Marcello [Dipartimento di Ingegneria " Enzo Ferrari" , Università degli studi di Modena e Reggio Emilia, Via Vignolese 905/a, I-41125 Modena (Italy); Pollastri, Simone; Gualtieri, Alessandro F. [Dipartimento di Scienze Chimiche e Geologiche, Università degli studi di Modena e Reggio Emilia, Via S. Eufemia 19I, I-41121 Modena (Italy)

    2015-01-15

    Geopolymers from laterite, an iron-rich soil available in developing countries, have great potential as building materials. In this work, laterite from Togo (Africa) was used to prepare geopolymers using both phosphoric acid and alkaline sodium silicate solution. Microstructural properties were investigated by scanning electron microscopy, X-ray powder diffraction and mercury porosimetry, whereas thermal properties were evaluated by thermal analyses. The local environment of iron was studied by X-ray Absorption Spectroscopy (XANES region). The mechanical properties were determined. Modulus of Rupture and Young's modulus fell in the ranges 3.3–4.5 MPa and 12–33 GPa, respectively, rendering the materials good candidates for construction purposes. Heating above 900 °C results in weight-gain, presumably due to iron redox reactions. X-ray Absorption Spectroscopy data evidence changes in the chemical and structural environments of iron following thermal treatment of geopolymers. These changes indicate interaction between the geopolymer structure and iron during heating, possibly leading to redox properties. -- Highlights: •Geopolymerization of laterite is promising for fabrication of building materials. •Both phosphoric acid and alkaline sodium silicate solution can be used for activation. •Thermally activated redox properties of the inorganic polymers were observed.

  1. Synthesis and Characterization of Modified Epoxy Resins by Silicic Acid Tetraethyl Ester and Nano-SiO2

    Institute of Scientific and Technical Information of China (English)

    李海燕; 张之圣

    2004-01-01

    A kind of modified epoxy resins was obtained by condensation of epoxy resin with silicic acid tetraethyl ester(TEOS) and nano-SiO2. The reactions were performed with hydrochloric acid as a catalyst at 63 °C.The structure, thermal stability and morphological characteristics of the modified epoxy resins were studied through infrared spectra(FT-IR) analysis, thermogravimetric (TG) analysis and scanning electron microscopy respectively. It has been found from the IR and TG study that modified epoxy resins have greater thermal stability than epoxy resins, and its thermal stability has been improved by the formation of inter-crosslinked network structure. The modified epoxy resins exhibit heterogeneous morphology and heterogeneity increases with more TEOS feeding, which in turn confirms the formation of inter-crosslinked network structure in modified epoxy resins.

  2. Microwave-Assisted Conversion of Levulinic Acid to γ-Valerolactone Using Low-Loaded Supported Iron Oxide Nanoparticles on Porous Silicates

    Directory of Open Access Journals (Sweden)

    Alfonso Yepez

    2015-09-01

    Full Text Available The microwave-assisted conversion of levulinic acid (LA has been studied using low-loaded supported Fe-based catalysts on porous silicates. A very simple, productive, and highly reproducible continuous flow method has been used for the homogeneous deposition of metal oxide nanoparticles on the silicate supports. Formic acid was used as a hydrogen donating agent for the hydrogenation of LA to effectively replace high pressure H2 mostly reported for LA conversion. Moderate LA conversion was achieved in the case of non-noble metal-based iron oxide catalysts, with a significant potential for further improvements to compete with noble metal-based catalysts.

  3. Micronutrients Status of Bio fuel Plant (Moringa Irrigated By Diluted Seawater As Affected By Silicate And Salicylic Acid

    Directory of Open Access Journals (Sweden)

    Hussein M.M

    2014-12-01

    Full Text Available A pot experiment was conducted in the greenhouse of the National Research Centre to evaluate the effect of salt stress and foliar amendments on mineral status of moringa plants. The treatments of salinity were irrigated by diluted seawater with 2000 and 4000 ppm salts and tap water (285 ppm as a control. The treatments of silicate treatments were 300 ppm SiO2 as potassium silicate and 300 ppm salicylic acid + 300 ppm SiO2 more than distilled water as a control. Significant responses were detected in Zn, Mn and Cu ppm as a result of salt stress but Fe ppm without significant responds to this treatment. The depression effect in nutrients of plants received Si+SA exceeded those induced by Si alone. Generally, the all calculated ratios (Mn with N, P, K and Na lowered by the high salinity level and the reverse were true by the lesser level of salinity. The ratios of macronutrients and micronutrients as affected by salinity, foliar application as well as the interactive effect between them were included.

  4. Aluminum Silicate Nanotube Modification of Cotton-Like Siloxane-poly(L-lactic acid-vaterite Composites

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    Daiheon Lee

    2013-01-01

    Full Text Available In our earlier work, a cotton-like biodegradable composite, consisting of poly(L-lactic acid with siloxane-containing vaterite, has been prepared by electrospinning. In the present work, the fibers skeleton of the cotton-like composites was modified successfully with imogolite, which is hydrophilic and biocompatible, via a dip process using ethanol diluted solution to improve the cellular initial attachment. Almost no change in the fiber morphology after the surface modification was observed. The surface-modified composite showed the similar calcium and silicate ions releasabilities, for activating the osteoblasts, as an unmodified one. Cell culture tests showed that the initial adhesion of murine osteoblast-like cells on the surface of the fibers was enhanced by surface modification.

  5. Study and make sulfur dioxide treatment equipment for degradation process of fine silicate zircon ore by sulfuric acid

    International Nuclear Information System (INIS)

    The against absorbent method was researched by research group to solve the above issue. This method was carried out by adsorbent lime-milk agent on the buffer of porous material with diameter D=9 cm and height H=1.2 m. The main parameters were gained: absorbent effect reached 98% with lime-milk concentration of 14% in water, against air flow speed of 0.7 m/s and lime-milk output of 0.45 liter/minute. Base on the above main researched parameter, the SO2 treatment equipment system by sulfuric acid was worked out with the scale of 0.5 ton/batch/day; absorbent tower diameter D=0.47 m, buffer height H=3.5 m and expenditure of 33.2 kg CaO/ton of zircon silicate. (author)

  6. 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.

  7. EFFECT OF QUARTZ/MULLITE BLEND CERAMIC ADDITIVE ON IMPROVING RESISTANCE TO ACID OF SODIUM SILICATE-ACTIVATED SLAG CEMENT. CELCIUS BRINE.

    Energy Technology Data Exchange (ETDEWEB)

    SUGAMA, T.; BROTHERS, L.E.; VAN DE PUTTE, T.R.

    2006-06-01

    We evaluated the usefulness of manufactured quartz/mullite blend (MQMB) ceramic powder in increasing the resistance to acid of sodium silicate-activated slag (SSAS) cementitious material for geothermal wells. A 15-day exposure to 90{sup o} CO{sub 2}-laden H{sub 2}SO{sub 4} revealed that the MQMB had high potential as an acid-resistant additive for SSAS cement. Two factors, the appropriate ratio of slag/MQMB and the autoclave temperature, contributed to better performance of MQMB-modified SSAS cement in abating its acid erosion. The most effective slag/MQMB ratio in minimizing the loss in weight by acid erosion was 70/30 by weight. For autoclave temperature, the loss in weight of 100 C autoclaved cement was a less than 2%, but at 300 C it was even lower. Before exposure to acid, the cement autoclaved at 100 C was essentially amorphous; increasing the temperature to 200 C led to the formation of crystalline analcime in the zeolitic mineral family during reactions between the mullite in MQMB and the Na from sodium silicate. In addition, at 300 C, crystal of calcium silicate hydrate (1) (CSH) was generated in reactions between the quartz in MQMB and the activated slag. These two crystalline phases (CSH and analcime) were responsible for densifying the autoclaved cement, conveying improved compressive strength and minimizing water permeability. The CSH was susceptible to reactions with H{sub 2}SO{sub 4}, forming two corrosion products, bassanite and ionized monosilicic acid. However, the uptake of ionized monosilicic acid by Mg dissociated from the activated slag resulted in the formation of lizardite as magnesium silicate hydrate. On the other hand, the analcime was barely susceptible to acid if at all. Thus, the excellent acid resistance of MQMB-modified SSAS cement was due to the combined phases of lizardite and analcime.

  8. Influence of Bath Composition at Acidic pH on Electrodeposition of Nickel-Layered Silicate Nanocomposites for Corrosion Protection

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    Jeerapan Tientong

    2013-01-01

    Full Text Available Nickel-layered silicates were electrochemically deposited from acidic bath solutions. Citrate was used as a ligand to stabilize nickel (II ions in the plating solution. The silicate, montmorillonite, was exfoliated by stirring in aqueous solution over 24 hours. The plating solutions were analyzed for zeta-potential, particle size, viscosity, and conductivity to investigate the effects of the composition at various pHs. The solution particles at pH 2.5 (−22.2 mV and pH 3.0 (−21.9 mV were more stable than at pH 1.6 (−10.1 mV as shown by zeta-potential analysis of the nickel-citrate-montmorillonite plating solution. Ecorr for the films ranged from −0.32 to −0.39 V with varying pH from 1.6 to 3.0. The films were immersed in 3.5% NaCl and the open circuit potential monitored for one month. The coatings deposited at pH 3.0 were stable 13 days longer in the salt solution than the other coatings. X-ray diffraction showed a change in the (111/(200 ratio for the coatings at the various pHs. The scanning electron microscopy and hardness results also support that the electrodeposition of nickel-montmorillonite at pH 3.0 (234 GPa had improved hardness and morphology compared to pH 2.5 (174 GPa and pH 1.6 (147 GPa.

  9. Determination of Iron in Layered Crystal Sodium Disilicate and Sodium Silicate by Flame Atomic Absorption Spectrometry with Boric Acid as a Matrix Modifier

    Institute of Scientific and Technical Information of China (English)

    Zhi Hua WANG; Min CAI; Shu Jun WANG

    2006-01-01

    The effects of matrix silicate and experimental conditions on the determination of iron in flame atomic absorption spectrometry (FAAS) were investigated. It was found that boric acid as a matrix modifier obviously eliminated silicate interference. Under the optimum operating conditions, the determination results of iron in layered crystal sodium disilicate and sodium silicate samples by FAAS were satisfactory. The linear range of calibration curve is 0-10.5 μg.mL-1, the relative standard deviation of method is 1.2%-2.2%, the recovery of added iron is 96.0%-101%, the of iron of the standard curve method, standard addition calibration and colorimetry method was the same, but the first has the merits of rapid sample preparation, reduced contamination risks and fast analysis.

  10. Synthesis and Characterization of Silicate Ester Prodrugs and Poly(ethylene glycol)-b-poly(lactic-co-glycolic acid) Block Copolymers for Formulation into Prodrug-Loaded Nanoparticles

    Science.gov (United States)

    Wohl, Adam Richard

    Fine control of the physical and chemical properties of customized materials is a field that is rapidly advancing. This is especially critical in pursuits to develop and optimize novel nanoparticle drug delivery. Specifically, I aim to apply chemistry concepts to test the hypothesis "Silicate ester prodrugs of paclitaxel, customized to have the proper hydrophobicity and hydrolytic lability, can be formulated with well-defined, biocompatible, amphiphilic block copolymers into nanoparticles that are effective drugs." Chapter 1 briefly describes the context and motivation of the scientific pursuits described in this thesis. In Chapter 2, a family of model silicate esters is synthesized, the hydrolysis rate of each compound is benchmarked, and trends are established based upon the steric bulk and leaving group ability of the silicate substituents. These trends are then applied to the synthesis of labile silicate ester prodrugs in Chapter 3. The bulk of this chapter focuses on the synthesis, hydrolysis, and cytotoxicity of prodrugs based on paclitaxel, a widely used chemotherapeutic agent. In Chapter 4, a new methodology for the synthesis of narrowly dispersed, "random" poly(lactic-co-glycolic acid) polymers by a constant infusion of the glycolide monomer is detailed. Using poly(ethylene glycol) as a macroinitiator, amphiphilic block copolymers were synthesized. Co-formulating a paclitaxel silicate and an amphiphilic block copolymer via flash nanoprecipitation led to highly prodrug-loaded, kinetically trapped nanoparticles. Studies to determine the structure, morphology, behavior, and efficacy of these nanoparticles are described in Chapter 5. Efforts to develop a general strategy for the selective end-functionalization of the polyether block of these amphiphilic block copolymers are discussed in Chapter 6. Examples of this strategy include functionalization of the polyether with an azide or a maleimide. Finally, Chapter 7 provides an outlook for future development of

  11. Sorption of uranyl(VI) cations on suspended silicate: effects of N-donor ligands, carboxylic acids, organic cosolvents, and metal ions

    Energy Technology Data Exchange (ETDEWEB)

    Pathak, P.N.; Choppin, G.R. [Florida State Univ., Tallahassee, FL (United States). Dept. of Chemistry and Biochemistry

    2007-07-01

    Sorption of uranyl ion, UO{sub 2}{sup 2+}, on silicate particles (3.00g/L) was studied in sodium perchlorate solution as a function of pcH and ionic strength at 298 K. The effects of different ligands (e.g., N-donors, carboxylic acids) on the uranyl sorption were investigated. At I = 0.20 M (NaClO{sub 4}), uranyl sorption on silicate increased from ca. 6% (pcH 3.0) to ca. 99% (at pcH 6.5), above which a small decrease was observed. A synergistic enhancement in uranyl sorption was observed in the presence of N-donor ligands such as 1,10-phenanthroline and ethylenediamine in the pcH range 3 to 4.5 as compared to that in the absence of ligands. Carboxylic acids inhibited the sorption in the order: citric acid > malonic acid > nitrilotriacetic acid > iminodiacetic acid > sulfosalicylic acid > succinic acid > glycolic acid. The presence of organic cosolvents such as dimethylsulfoxide, glycerol and tetrahydrofuran had no significant influence on the uranyl sorption profile. Uranyl sorption decreased marginally in the presence of 1.00 x 10{sup -3} M Eu(III). (orig.)

  12. MODIFICATION OF PRECIPITATED CALCIUM CARBONATE FILLER USING SODIUM SILICATE/ZINC CHLORIDE BASED MODIFIERS TO IMPROVE ACID-RESISTANCE AND USE OF THE MODIFIED FILLER IN PAPERMAKING

    Directory of Open Access Journals (Sweden)

    Jing Shen

    2009-11-01

    Full Text Available In order to improve the acid-resistant property of papermaking grade precipitated calcium carbonate filler and to obtain modified filler in powder form, sodium silicate/zinc chloride based modifiers were used in filler modification, and the use of modified filler in papermaking of deinked pulp derived from recycled newspaper was also preliminarily investigated. Under the preliminarily optimized experimental conditions, when sodium silicate, zinc chloride, sodium hexametaphosphate, and phosphoric acid with dosages of 10 wt%, 3 wt%, 1 wt% and 0.2 wt%, respectively, were used as modifiers, and when the temperature, aging time, and PCC concentration during the filler modification process was 70 oC, 7 h and 9.1 wt%, respectively, the acid-resistant property of filler was significantly improved after modification, as evaluated using alum consumption and pH methods. The use of modified precipitated calcium carbonate filler prepared under the optimized conditions provided considerably more brightness and light scattering improvement in comparison to unmodified filler, and filler modification was found to have only negligible influence on tensile and burst strength of the paper, air permeability of the paper, and retention performance of the filler. Surface analysis of the modified filler using XPS and SEM confirmed the occurring of surface encapsulation and modification of precipitated calcium carbonate filler when the relevant modifiers were used in filler modification. The encapsulating effect of modifiers on filler was thought to be favorable to improvement in acid-resistant property, and optical properties of the filled paper.

  13. Oxygen and silicon stable isotopes of diatom silica. Reconstructing changes in surface water hydrography and silicic acid utilization in the late Pleistocene subarctic Pacific

    International Nuclear Information System (INIS)

    Deglacial variations in upper ocean nutrient dynamics and stratification in high latitudes, as well as associated changes in thermohaline overturning circulation, are thought to have played a key role in changing atmospheric CO2 concentrations. This thesis examines the relationship between past changes in subarctic Pacific upper ocean stratification and nutrient (silicic acid) utilization, using oxygen and silicon stable isotopes of diatom silica, for the first time at millennial-scale resolution and analyzed with a new and efficient instrumentation set-up. The isotopic data, presented in three manuscripts, show a consistent picture of millennial-scale variability in upper ocean stratification and silicic acid utilization during the last ∝50 ka BP, e.g. indicating that the subarctic Pacific was a source region for atmospheric CO2 during the last deglaciation (late Heinrich Stadial 1 and the Boelling/Alleroed). The presented results demonstrate the high potential of combined diatom oxygen and silicon stable isotope analysis especially for, but not restricted to, marine regions characterized by a low biogenic carbonate content like the subarctic Pacific and the Southern Ocean.

  14. Oxygen and silicon stable isotopes of diatom silica. Reconstructing changes in surface water hydrography and silicic acid utilization in the late Pleistocene subarctic Pacific

    Energy Technology Data Exchange (ETDEWEB)

    Maier, Edith

    2014-03-05

    Deglacial variations in upper ocean nutrient dynamics and stratification in high latitudes, as well as associated changes in thermohaline overturning circulation, are thought to have played a key role in changing atmospheric CO{sub 2} concentrations. This thesis examines the relationship between past changes in subarctic Pacific upper ocean stratification and nutrient (silicic acid) utilization, using oxygen and silicon stable isotopes of diatom silica, for the first time at millennial-scale resolution and analyzed with a new and efficient instrumentation set-up. The isotopic data, presented in three manuscripts, show a consistent picture of millennial-scale variability in upper ocean stratification and silicic acid utilization during the last ∝50 ka BP, e.g. indicating that the subarctic Pacific was a source region for atmospheric CO{sub 2} during the last deglaciation (late Heinrich Stadial 1 and the Boelling/Alleroed). The presented results demonstrate the high potential of combined diatom oxygen and silicon stable isotope analysis especially for, but not restricted to, marine regions characterized by a low biogenic carbonate content like the subarctic Pacific and the Southern Ocean.

  15. Electrospun nanofibrous scaffolds of poly (L-lactic acid)-dicalcium silicate composite via ultrasonic-aging technique for bone regeneration

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Shengjie [Department of Orthopaedics, The First Affiliated Hospital of Soochow University, 188 Shizi St, Suzhou, Jiangsu 215006 (China); Sun, Junying, E-mail: wodaoshi@sohu.com [Department of Orthopaedics, The First Affiliated Hospital of Soochow University, 188 Shizi St, Suzhou, Jiangsu 215006 (China); Li, Yadong [College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, Jiangsu 215123 (China); Li, Jun [Department of Orthopaedics, The First Affiliated Hospital of Soochow University, 188 Shizi St, Suzhou, Jiangsu 215006 (China); Cui, Wenguo [Orthopedic Institute, Soochow University, 708 Renmin Rd, Suzhou, Jiangsu 215007 (China); Li, Bin, E-mail: binli@suda.edu.cn [Department of Orthopaedics, The First Affiliated Hospital of Soochow University, 188 Shizi St, Suzhou, Jiangsu 215006 (China)

    2014-02-01

    Polymeric nanofibrous composite scaffolds incorporating bioglass and bioceramics have been increasingly promising for bone tissue engineering. In the present study, electrospun poly (L-lactic acid) (PLLA) scaffolds containing dicalcium silicate (C{sub 2}S) nanoparticles (approximately 300 nm) were fabricated. Using a novel ultrasonic dispersion and aging method, uniform C{sub 2}S nanoparticles were prepared and they were homogenously distributed in the PLLA nanofibers upon electrospinning. In vitro, the PLLA-C{sub 2}S fibers induced the formation of HAp on the surface when immersed in simulated body fluid (SBF). During culture, the osteoblastic MC3T3-E1 cells adhered well on PLLA-C{sub 2}S scaffolds, as evidenced by the well-defined actin stress fibers and well-spreading morphology. Further, compared to pure PLLA scaffolds without C{sub 2}S, PLLA-C{sub 2}S scaffolds markedly promoted the proliferation of MC3T3-E1 cells as well as their osteogenic differentiation, which was characterized by the enhanced alkaline phosphatase (ALP) activity. Together, findings from this study clearly demonstrated that PLLA-C{sub 2}S composite scaffold may function as an ideal candidate for bone tissue engineering. - Highlights: • Dicalcium silicate (C{sub 2}S) nanoparticles were prepared via a sol–gel process. • C{sub 2}S nanoparticles were stabilized using ultrasonic-aging technique. • PLLA-C{sub 2}S composite nanofibers were fabricated through electrospinning technique. • C{sub 2}S nanoparticles could be homogenously distributed in nanofibers. • The composite scaffolds enhanced proliferation and differentiation of osteoblasts.

  16. Preparation and characterization of new poly(amide–imide reinforced layer silicate nanocomposite containing N,N′-pyrromellitoyl-bis-l-phenyl acetic acid

    Directory of Open Access Journals (Sweden)

    Khalil Faghihi

    2014-12-01

    Full Text Available Two new samples of poly(amide–imide/montmorillonite reinforced nanocomposites containing N,N′-pyrromellitoyl-bis-l-phenyl acetic acid moiety in the main chain were synthesized by a convenient solution intercalation technique. Poly(amide–imide (PAI 3 as a source of polymer matrix was synthesized by the direct polycondensation reaction of N,N′-pyrromelitoyl-bis-l-phenyl acetic acid 1 with 4,4′-diamino diphenyl ether 2 in the presence of triphenyl phosphite (TPP, CaCl2, pyridine and N-methyl-2-pyrrolidone (NMP. Morphology and structure of the resulting PAI-nanocomposite films 4a and 4b with 10% and 20% silicate particles were characterized by FTIR spectroscopy, X-ray diffraction (XRD and scanning electron microscopy (SEM. The effect of clay dispersion and the interaction between clay and polymeric chains on the properties of nanocomposite films were investigated by using UV–vis spectroscopy, thermogravimetric analysis (TGA and water uptake measurements.

  17. Aluminum Silicate Nanotube Modification of Cotton-Like Siloxane-poly(L-lactic acid)-vaterite Composites

    OpenAIRE

    Daiheon Lee; Hirotaka Maeda; Akiko Obata; Keiichi Inukai; Katsuya Kato; Toshihiro Kasuga

    2013-01-01

    In our earlier work, a cotton-like biodegradable composite, consisting of poly(L-lactic acid) with siloxane-containing vaterite, has been prepared by electrospinning. In the present work, the fibers skeleton of the cotton-like composites was modified successfully with imogolite, which is hydrophilic and biocompatible, via a dip process using ethanol diluted solution to improve the cellular initial attachment. Almost no change in the fiber morphology after the surface modification was observed...

  18. Profiling fatty acids in vegetable oils by reactive pyrolysis-gas chromatography with dimethyl carbonate and titanium silicate.

    Science.gov (United States)

    Fabbri, Daniele; Baravelli, Valentina; Chiavari, Giuseppe; Prati, Silvia

    2005-12-30

    A novel methodology in on-line pyrolysis-gas chromatography (Py-GC) for the fast analysis of fatty acids in vegetable oils with minimal sample treatment and the use of non-toxic reagents is described. Pyrolysis at 500 degrees C for 10 s of sub-microgram quantity of vegetable oil dissolved in dimethyl carbonate (DMC) and in the presence of nanopowder titanium silicon oxide resulted in the production of fatty acid methyl esters (FAMEs) as unique products. Pyrolysis performed by means of a resistively heated filament pyrolyser interfaced to a GC-MS apparatus enabled the direct analysis of evolved FAMEs. The DMC/Py-GC-MS analysis was tested on soybean, coconut, linseed, walnut and olive oil and the results compared to the classical BF(3)-methanol as reference methodology. The DMC method exhibited a lower precision and was biased towards lower levels of polyunsaturated fatty acids (PUFA) in comparison to the BF(3)-methanol method, but was more advantageous in terms of reduced sample treatment, waste generation and risk factors of employed chemicals.

  19. Profiling fatty acids in vegetable oils by reactive pyrolysis-gas chromatography with dimethyl carbonate and titanium silicate.

    Science.gov (United States)

    Fabbri, Daniele; Baravelli, Valentina; Chiavari, Giuseppe; Prati, Silvia

    2005-12-30

    A novel methodology in on-line pyrolysis-gas chromatography (Py-GC) for the fast analysis of fatty acids in vegetable oils with minimal sample treatment and the use of non-toxic reagents is described. Pyrolysis at 500 degrees C for 10 s of sub-microgram quantity of vegetable oil dissolved in dimethyl carbonate (DMC) and in the presence of nanopowder titanium silicon oxide resulted in the production of fatty acid methyl esters (FAMEs) as unique products. Pyrolysis performed by means of a resistively heated filament pyrolyser interfaced to a GC-MS apparatus enabled the direct analysis of evolved FAMEs. The DMC/Py-GC-MS analysis was tested on soybean, coconut, linseed, walnut and olive oil and the results compared to the classical BF(3)-methanol as reference methodology. The DMC method exhibited a lower precision and was biased towards lower levels of polyunsaturated fatty acids (PUFA) in comparison to the BF(3)-methanol method, but was more advantageous in terms of reduced sample treatment, waste generation and risk factors of employed chemicals. PMID:16216255

  20. Evidence for Siliceous Deposits Formed by Acid-Sulfate Alteration at Home Plate in Gusev Crater, Mars

    Science.gov (United States)

    Morris, R. V.; Ming, D. W.; Gellert, R.; Yen, A. S.; Clark, B. C.; Ruff, S. W.; Graff, T. G.; Arvidson, R. E.; Squyres, S. W.; Science Teams, T.

    2007-12-01

    The Alpha Particle X-ray Spectrometer (APXS) instrument on the Mars Exploration Rover (MER) Spirit measured three targets on or adjacent to Home Plate in Gusev Crater that have unusually high SiO2 concentrations (68 to 91%), unusually low FeO concentrations (1 to 7%, with total Fe as FeO), and unusually high TiO2/FeO ratios (0.2 to 1.2 by weight). Two targets are high albedo soil (Gertrude Weise) exposed by the rover wheels (Kenosha Comets and Lefty Ganote), and one target is a rock (Fuzzy Smith). Kenosha Comets has the highest SiO2 concentration, lowest FeO concentration, and highest TiO2/FeO ratio. Mineralogical evidence from the MER Miniature Thermal Emission Spectrometer (Mini-TES) suggests that high proportions of amorphous (non- crystalline) SiO2 account for the high SiO2 concentration of Gertrude Weise. Mini-TES data were not acquired for Fuzzy Smith. The spectral evidence for amorphous SiO2 includes deep emissivity minima near 9 and 21 microns. Amorphous SiO2 is typically characterized by a shoulder near 8 microns, but the Gertrude Weise spectra are instead characterized by a well-defined emissivity minimum. The difference is attributed to scattering and/or geometric effects. The chemistry of Gertrude Weise and Fuzzy Smith is very similar to that for a tholeiitic basaltic rock altered under acid-sulfate conditions in a fumarolic (hydrothermal) environment on Kilauea Volcano (Hawaii). The terrestrial acid sulfate alteration resulted in compositions having about 62 to 91% SiO2, 1 to 8% FeO, and 0.3 to 5 TiO2/FeO. The SiO2 and TiO2 are passively enriched while all other major elements are removed by leaching. XRD analysis shows that SiO2 and TiO2 are present as amorphous SiO2 (opal-A) and anatase, respectively. Alunite is also present. Thermal emission spectra of the Kilauea rock obtained from its exterior surface and from 500-1000 micron and grinding and sieving are all characterized by the emissivity features at 8, 9, and 21 micron for opal-A. The features

  1. Siliceous microfossil extraction from altered Monterey rocks

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, C.O.; Casey, R.E.

    1986-04-01

    Samples of altered Monterey rocks of differing lithologies were processed by various methods to develop new techniques for extracting siliceous microfossils. The preliminary use of thin sections made from the same rocks reduced the number of probable samples (samples worth further processing) by about one-third. Most of the siliceous microfossils contained in altered Monterey rocks appear to be highly recrystallized and are extremely fragile; however, some contained silicified and silica-infilled radiolarians and planktonic and benthonic foraminifera, which are very tough. In general the most useful techniques were gently hydrochloric acid, hydrogen peroxide, formic acid, monosodium glutamate, and regular siliceous microfossil extraction techniques. Unsuccessful techniques and a new siliceous microfossil flotation technique are also documented.

  2. Heavy silicon isotopic composition of silicic acid and biogenic silica in Arctic waters over the Beaufort shelf and the Canada Basin

    Science.gov (United States)

    Varela, D. E.; Brzezinski, M. A.; Beucher, C. P.; Jones, J. L.; Giesbrecht, K. E.; Lansard, B.; Mucci, A.

    2016-06-01

    The silicon isotopic composition of silicic acid (δ30Si(OH)4) and biogenic silica (δ30Si-bSiO2) were measured for the first time in marine Arctic waters from the Mackenzie River delta to the deep Canada Basin in the late summer of 2009. In the upper 100 m of the water column, δ30Si(OH)4 signals (+1.82‰ to +3.08‰) were negatively correlated with the relative contribution of Mackenzie River water. The biogenic Si isotope fractionation factor estimated using an open system model, 30ɛ = -0.97 ± 0.17‰, agrees well with laboratory and global-ocean estimates. Nevertheless, the δ30Si dynamics of this region may be better represented by closed system isotope models that yield lower values of 30ɛ, between -0.33‰ and -0.41‰, depending on how the contribution of sea-ice diatoms is incorporated. In the upper 400 m, δ30Si-bSiO2 values were among the heaviest ever measured in marine suspended bSiO2 (+2.03‰ to +3.51‰). A positive correlation between δ30Si-bSiO2 and sea-ice cover implies that heavy signals can result from isotopically heavy sea-ice diatoms introduced to pelagic assemblages. Below the surface bSiO2 production zone, the δ30Si(OH)4 distribution followed that of major water masses. Vertical δ30Si(OH)4 profiles showed a minimum (average of +1.84 ± 0.10‰) in the upper halocline (125-200 m) composed of modified Pacific water and heavier average values (+2.04 ± 0.11‰) in Atlantic water (300-500 m deep). In the Canada Basin Deep Water (below 2000 m), δ30Si(OH)4 averaged +1.88 ± 0.12‰, which represents the most positive value ever measured anywhere in the deep ocean. Since most Si(OH)4 enters the Arctic from shallow depths in the Atlantic Ocean, heavy deep Arctic δ30Si(OH)4 signals likely reflect the influx of relatively heavy intermediate Atlantic waters. A box model simulation of the global marine δ30Si(OH)4 distribution successfully reproduced the observed patterns, with the δ30Si(OH)4 of the simulated deep Arctic Ocean being the

  3. Evaluation of cyclonic ash, commercial Na-silicates, lime and phosphoric acid for metal immobilisation purposes in contaminated soils in Flanders (Belgium)

    Energy Technology Data Exchange (ETDEWEB)

    Geebelen, Wouter [Hasselt University, Centre for Environmental Sciences, Environmental Biology, Agoralaan - Gebouw D, B-3590 Diepenbeek (Belgium)]. E-mail: wouter.geebelen@uhasselt.be; Sappin-Didier, Valerie [UMR TCEM, INRA, Centre de recherche Bordeaux - Aquitaine, BP 81, 33883 Villenave d' Ornon cedex (France)]. E-mail: didier@bordeaux.inra.fr; Ruttens, Ann [Hasselt University, Centre for Environmental Sciences, Environmental Biology, Agoralaan - Gebouw D, B-3590 Diepenbeek (Belgium); Carleer, Robert [Hasselt University, Centre for Environmental Sciences, Applied Chemistry, Agoralaan - Gebouw D, B-3590 Diepenbeek (Belgium)]. E-mail: robert.carleer@uhasselt.be; Yperman, Jan [Hasselt University, Centre for Environmental Sciences, Applied Chemistry, Agoralaan - Gebouw D, B-3590 Diepenbeek (Belgium)]. E-mail: jan.yperman@uhasselt.be; Bongue-Boma, Kwele [UMR TCEM, INRA, Centre de recherche Bordeaux - Aquitaine, BP 81, 33883 Villenave d' Ornon cedex (France); Mench, Michel [UMR BIOGECO INRA, Ecology of Communities, Bordeaux 1 University, Bat B8 RdC Est, av. des Facultes, F-33405 Talence (France)]. E-mail: mench@bordeaux.inra.fr; Lelie, Niels van der [Brookhaven National Laboratory, Biology Department, Bldg. 463, New York, NY 11973-5000 (United States)]. E-mail: vdlelied@bnl.gov; Vangronsveld, Jaco [Hasselt University, Centre for Environmental Sciences, Environmental Biology, Agoralaan - Gebouw D, B-3590 Diepenbeek (Belgium)]. E-mail: jaco.vangronsveld@uhasselt.be

    2006-11-15

    In order to reduce the health risks associated with historically enriched metal smelting sites in Flanders (Belgium), the capacities of a non-beringite cyclonic ash and commercial Na-silicates to fix metals and create conditions to restore vegetation cover were evaluated and compared to lime and H{sub 3}PO{sub 4}. All tested amendments reduced Ca(NO{sub 3}){sub 2}-extractable soil metal concentrations and reduced metal uptake in Agrostis capillaris seedlings. Sodium released by Na-silicates was possibly toxic to bean plants while an isotopic dilution technique revealed that metals were only weakly sorbed by silicates (i.e. reversible sorption). Cyclonic ash appeared more efficient than lime in both reducing oxidative stress in beans and Zn, Cu and Pb uptake in grasses. The metal fixing mechanism for both amendments appeared similar (i.e. irreversible fixation at constant pH), in contrast to H{sub 3}PO{sub 4} where at least part of the immobilised Cd was irreversibly fixed across a range of pH. - Metal immobilising capacities of Na-silicates are weak, while the active mechanism of cyclonic ash is the same as lime.

  4. 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.

  5. Research Progress in Poly(lactic acid ) /Layered Silicate Nanocomposites%聚乳酸/层状硅酸盐纳米复合材料研究进展

    Institute of Scientific and Technical Information of China (English)

    张玉霞; 刘学; 刘本刚; 王向东

    2012-01-01

    介绍了聚乳酸/层状硅酸盐纳米复合材料研究进展,阐述了其制备方法如原位聚合插层法、溶液插层法、熔融插层法等,详述了聚乳酸添加纳米层状硅酸盐后结构与性能的变化,包括复合材料的微观结构、结晶性能、热性能、力学性能、流变性能、加工性能、阻隔性能、阻燃性能的变化。研究表明,采用不同的制备方法如原位聚合插层法、溶液插层法、熔融插层法等能制得插层型、剥离型以及插层与剥离混合型聚乳酸/层状硅酸盐纳米复合材料;添加纳米层状硅酸盐后,得到的聚乳酸/层状硅酸盐纳米复合材料结晶速率提高,结晶度增加,说明层状硅酸盐起到了成核剂的作用;热稳定性、拉伸模量和冲击强度、阻透性能和阻燃性能都有不同程度提高;流变性能也得到改善。%Research advances in the preparation and properties of poiy (lactic acid ) /layered silicate nanocomposites were introduced. Details on preparation technologies of poly(lactic acid) /layered silicate nanocomposites such as intercalation from solution, in-situ intercalative polymerization, melt intercalation technique, and their properties such as morphologies, crystallization behavior, thermal performance, mechanical properties, rheological behavior, processing ability, barrier performance and flame retardance, etc. It was shown that poly(lactie acid)/layered silicate nanocomposites with interealative or/and exfoliated structure by the three preparation processes were made respectively. Their properties, including crystallization rate and degree, thermal stability, tensile modulus and impact strength, gas barrier and flame retardance, as well as rheological behavior were improved.

  6. 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.

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

    OpenAIRE

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

    2016-01-01

    Silicate hydration is prevalent in natural and technological processes, such as, mineral weathering, glass alteration, zeolite syntheses and cement hydration. Tricalcium silicate (Ca3SiO5), the main constituent of Portland cement, is amongst the most reactive silicates in water. Despite its widespread industrial use, the reaction of Ca3SiO5 with water to form calcium-silicate-hydrates (C-S-H) still hosts many open questions. Here, we show that solid-state nuclear magnetic resonance measuremen...

  8. Acid-resistant calcium silicate-based composite implants with high-strength as load-bearing bone graft substitutes and fracture fixation devices.

    Science.gov (United States)

    Wei, Chung-Kai; Ding, Shinn-Jyh

    2016-09-01

    To achieve the excellent mechanical properties of biodegradable materials used for cortical bone graft substitutes and fracture fixation devices remains a challenge. To this end, the biomimetic calcium silicate/gelatin/chitosan oligosaccharide composite implants were developed, with an aim of achieving high strength, controlled degradation, and superior osteogenic activity. The work focused on the effect of gelatin on mechanical properties of the composites under four different kinds of mechanical stresses including compression, tensile, bending, and impact. The evaluation of in vitro degradability and fatigue at two simulated body fluid (SBF) of pH 7.4 and 5.0 was also performed, in which the pH 5.0 condition simulated clinical conditions caused by bacterial induced local metabolic acidosis or tissue inflammation. In addition, human mesenchymal stem cells (hMSCs) were sued to examine osteogenic activity. Experimental results showed that the appropriate amount of gelatin positively contributed to failure enhancement in compressive and impact modes. The 10wt% gelatin-containing composite exhibits the maximum value of the compressive strength (166.1MPa), which is within the reported compressive strength for cortical bone. The stability of the bone implants was apparently affected by the in vitro fatigue, but not by the initial pH environments (7.4 or 5.0). The gelatin not only greatly enhanced the degradation of the composite when soaked in the dynamic SBF solution, but effectively promoted attachment, proliferation, differentiation, and formation of mineralization of hMSCs. The 10wt%-gelatin composite with high initial strength may be a potential implant candidate for cortical bone repair and fracture fixation applications. PMID:27254281

  9. 21 CFR 573.260 - Calcium silicate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Calcium silicate. 573.260 Section 573.260 Food and... Listing § 573.260 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be safely used as an anticaking agent in animal feed, provided that the amount of calcium silicate does...

  10. 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.

  11. 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.

  12. 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...

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

    Science.gov (United States)

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

    2016-01-01

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

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

    Science.gov (United States)

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

    2016-03-01

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

  15. Stability constants for silicate adsorbed to ferrihydrite

    DEFF Research Database (Denmark)

    Hansen, Hans Christian Bruun; Wetche, T.P.; Raulund-Rasmussen, Karsten;

    1994-01-01

    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......Intrinsic surface acidity constants (K(a1)intr, K(a2)intr) and surface complexation constant for adsorption of orthosilicate onto synthetic ferrihydrite (K(Si) for the complex = FeOSi(OH)3) have been determined from acid/base titrations in 0.001-0.1 m NaClO4 electrolytes and silicate adsorption...

  16. Tin-containing silicates

    DEFF Research Database (Denmark)

    Osmundsen, Christian M.; Holm, Martin Spangsberg; Dahl, Søren;

    2012-01-01

    stannosilicates have been investigated: Sn-BEA, Sn-MFI, Sn-MCM-41 and Sn-SBA-15. When comparing the properties of tin sites in the structures, substantial differences are observed. Sn-beta displays the highest Lewis acid strength, as measured by probe molecule studies using infrared spectroscopy, which gives......The selective conversion of biomass-derived substrates is one of the major challenges facing the chemical industry. Recently, stannosilicates have been employed as highly active and selective Lewis acid catalysts for a number of industrially relevant reactions. In the present work, four different...... it a significantly higher activity at low temperatures than the other structures investigated. Furthermore, the increased acid strength translates into large differences in selectivity between the catalysts, thus demonstrating the influence of the structure on the active site, and pointing the way forward...

  17. 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.

  18. Interaction of silicic acid with goethite

    NARCIS (Netherlands)

    Hiemstra, T.; Barnett, M.O.; Riemsdijk, van W.H.

    2007-01-01

    The adsorption of Si on goethite (¿-FeOOH) has been studied in batch experiments that cover the natural range of Si concentrations as found in the environment. The results have been interpreted and quantified with the charge distribution (CD) and multi-site surface complexation (MUSIC) model in comb

  19. Rubber curing chemistry governing the orientation of layered silicate

    Directory of Open Access Journals (Sweden)

    2007-11-01

    Full Text Available The effect of curing systems on the orientation and the dispersion of the layered silicates in acrylonitrile butadiene rubber nanocomposite is reported. Significant differences in X-ray diffraction pattern between peroxide curing and sulfur curing was observed. Intense X-ray scattering values in the XRD experiments from peroxide cured vulcanizates indicate an orientation of the layers in a preferred direction as evinced by transmission electron micrographs. However, sulfur cured vulcanizates show no preferential orientation of the silicate particles. Nevertheless, a closer inspection of transmission electron microscopy (TEM images of peroxide and sulfur cured samples shows exfoliated silicate layers in the acrylonitrile butadiene rubber (NBR matrix. It was revealed in the prevailing study that the use of an excess amount of stearic acid in the formulation of the sulfur curing package leads to almost exfoliated type X-ray scattering pattern.

  20. 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.

  1. Oligo-lysine Induced Formation of Silica Particles in Neutral Silicate Solution

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Oligo-(lysine)n (n = 1-4) containing different numbers of lysine residues was used to induce the condensation of silicic acid to form silica particles in neutral silicate solution. It was found that the condensation rate and the formation of silica particles are dependent on the number of lysine residues in an oligo-lysine. Oligo-lysine with more lysine residues can link more silicic acid together to form a matrix that promotes the effective aggregation of the condensed silica pieces to form large silica particles.

  2. Square-wave anodic-stripping voltammetric determination of Cd, Pb, and Cu in a hydrofluoric acid solution of siliceous spicules of marine sponges (from the Ligurian Sea, Italy, and the Ross Sea, Antarctica)

    Energy Technology Data Exchange (ETDEWEB)

    Truzzi, C.; Annibaldi, A.; Illuminati, S.; Bassotti, E.; Scarponi, G. [Polytechnic University of Marche, Ancona (Italy). Department of Marine Science

    2008-09-15

    Square-wave anodic-stripping voltammetry (SWASV) was set up and optimized for simultaneous determination of cadmium, lead, and copper in siliceous spicules of marine sponges, directly in the hydrofluoric acid solution ({proportional_to}0.55 mol L{sup -1} HF, pH {proportional_to}1.9). A thin mercury-film electrode (TMFE) plated on to an HF-resistant epoxy-impregnated graphite rotating-disc support was used. The optimum experimental conditions, evaluated also in terms of the signal-to-noise ratio, were as follows: deposition potential -1100 mV vs. Ag/AgCl, KCl 3 mol L{sup -1}, deposition time 3-10 min, electrode rotation 3000 rpm, SW scan from -1100 mV to +100 mV, SW pulse amplitude 25 mV, frequency 100 Hz, {delta}E{sub step} 8 mV, t{sub step} 100 ms, t{sub wait} 60 ms, t{sub delay} 2 ms, t{sub meas} 3 ms. Under these conditions the metal peak potentials were Cd -654{+-}1 mV, Pb -458 {+-} 1 mV, Cu -198{+-}1 mV. The electrochemical behaviour was reversible for Pb, quasi-reversible for Cd, and kinetically controlled (possibly following chemical reaction) for Cu. The linearity of the response with concentration was verified up to {proportional_to}4 {mu}g L{sup -1} for Cd and Pb and {proportional_to}20 {mu}g L{sup -1} for Cu. The detection limits were 5.8 ng L{sup -1}, 3.6 ng L{sup -1}, and 4.3 ng L{sup -1} for Cd, Pb, and Cu, respectively, with t{sub d}=5 min. The method was applied for determination of the metals in spicules of two specimens of marine sponges (Demosponges) from the Portofino natural reserve (Ligurian Sea, Italy, Petrosia ficiformis) and Terra Nova Bay (Ross Sea, Antarctica, Sphaerotylus antarcticus). The metal contents varied from tens of ng g{sup -1} to {proportional_to}1 {mu}g g{sup -1}, depending on the metal considered and with significant differences between the two sponge species. (orig.)

  3. Square-wave anodic-stripping voltammetric determination of Cd, Pb, and Cu in a hydrofluoric acid solution of siliceous spicules of marine sponges (from the Ligurian Sea, Italy, and the Ross Sea, Antarctica).

    Science.gov (United States)

    Truzzi, C; Annibaldi, A; Illuminati, S; Bassotti, E; Scarponi, G

    2008-09-01

    Square-wave anodic-stripping voltammetry (SWASV) was set up and optimized for simultaneous determination of cadmium, lead, and copper in siliceous spicules of marine sponges, directly in the hydrofluoric acid solution (approximately 0.55 mol L(-1) HF, pH approximately 1.9). A thin mercury-film electrode (TMFE) plated on to an HF-resistant epoxy-impregnated graphite rotating-disc support was used. The optimum experimental conditions, evaluated also in terms of the signal-to-noise ratio, were as follows: deposition potential -1100 mV vs. Ag/AgCl, KCl 3 mol L(-1), deposition time 3-10 min, electrode rotation 3000 rpm, SW scan from -1100 mV to +100 mV, SW pulse amplitude 25 mV, frequency 100 Hz, DeltaE(step) 8 mV, t(step) 100 ms, t(wait) 60 ms, t(delay) 2 ms, t(meas) 3 ms. Under these conditions the metal peak potentials were Cd -654 +/- 1 mV, Pb -458 +/- 1 mV, Cu -198 +/- 1 mV. The electrochemical behaviour was reversible for Pb, quasi-reversible for Cd, and kinetically controlled (possibly following chemical reaction) for Cu. The linearity of the response with concentration was verified up to approximately 4 microg L(-1) for Cd and Pb and approximately 20 microg L(-1) for Cu. The detection limits were 5.8 ng L(-1), 3.6 ng L(-1), and 4.3 ng L(-1) for Cd, Pb, and Cu, respectively, with t(d) = 5 min. The method was applied for determination of the metals in spicules of two specimens of marine sponges (Demosponges) from the Portofino natural reserve (Ligurian Sea, Italy, Petrosia ficiformis) and Terra Nova Bay (Ross Sea, Antarctica, Sphaerotylus antarcticus). The metal contents varied from tens of ng g(-1) to approximately 1 microg g(-1), depending on the metal considered and with significant differences between the two sponge species. PMID:18642105

  4. Development of Silicate Polymers

    DEFF Research Database (Denmark)

    Søgaard, Erik Gydesen; Simonsen, Morten Enggrob

      The development of inorganic polymers is a new promising technology that may be used in many applications. The syntheses of inorganic polymers are normally carried out either by mixing an amorphous material for example silicium dioxide with a mineral base or dissolving metal oxids or metal...... hydroxide in acid and increase pH to saturation of the metal hydroxide. It is assumed that the syntheses of the inorganic polymer are carried out through polymerisation of oligomers (dimer, trimer) which provide the actual unit structures of the three dimensional macromolecular structure. In this work...

  5. 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.

  6. 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

  7. 21 CFR 182.2227 - Calcium silicate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Calcium silicate. 182.2227 Section 182.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) SUBSTANCES GENERALLY RECOGNIZED AS SAFE Anticaking Agents § 182.2227 Calcium silicate. (a) Product. Calcium silicate....

  8. 21 CFR 582.2227 - Calcium silicate.

    Science.gov (United States)

    2010-04-01

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

  9. Determination of reactivity rates of silicate particle-size fractions

    Directory of Open Access Journals (Sweden)

    Angélica Cristina Fernandes Deus

    2014-04-01

    Full Text Available 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 silicate particle-size fractions. Six correction sources were evaluated: three slags from distinct origins, dolomitic and calcitic lime separated into four particle-size fractions (2, 0.84, 0.30 and <0.30-mm sieves, and wollastonite, as an additional treatment. The treatments were applied to three soils with different texture classes. The dose of neutralizing material (calcium and magnesium oxides was applied at equal quantities, and the only variation was the particle-size material. After a 90-day incubation period, the RER was calculated for each particle-size fraction, as well as the RR and ECC of each source. The neutralization of soil acidity of the same particle-size fraction for different sources showed distinct solubility and a distinct reaction between silicates and lime. The RER for slag were higher than the limits established by Brazilian legislation, indicating that the method used for limes should not be used for the slags studied here.

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

    Science.gov (United States)

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

    2003-01-01

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

  11. 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.

  12. 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...

  13. Polymer-Layer Silicate Nanocomposites

    DEFF Research Database (Denmark)

    Potarniche, Catalina-Gabriela

    with a spectacular improvement up to 300 % in impact strength were obtained. In the second part of this study, layered silicate bio-nanomaterials were obtained starting from natural compounds and taking into consideration their biocompatibility properties. These new materials may be used for drug delivery systems......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...... toughness-stiffness requirements. The new compatibilizer system used to obtain nanocomposites, presented an improvement of 8-20 % in tensile strength, 15-34 % in Young’s modulus, 23-34 % in fatigue tests and 20-58% in degree of crystalline phase. By introducing a rubbery phase as modifier, nanocomposites...

  14. 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.

  15. 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.

  16. Modifying Silicates for Better Dispersion in Nanocomposites

    Science.gov (United States)

    Campbell, Sandi

    2005-01-01

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

  17. Process and self-acidifying liquid system for dissolving a siliceous material in a remote location

    Energy Technology Data Exchange (ETDEWEB)

    Lybarger, J.H.; Templeton, C.C.; Richardson, E.A.; Scheuerman, R.F.

    1980-12-02

    A process is provided for dissolving a siliceous material in a remote location into which a fluid can be flowed. The process comprises the following: 1) mixing at least one aqueous liquid, at least one water-soluble fluoride salt, and at least one relatively slowly reactive acid-yielding material that yeilds an acid capable of converting an aqueous solution of the fluoride salt to an aqueous solution of hydrofluoric acid, to form a substantially homogeneous liquid system in which the components interact to provide an aqueous solution that contains enough hydrofluoric acid to dissolve bentonite while having a pH of at least approx. 2; 2) flowing the liquid system into contact with siliceous material to be dissolved; and 3) adjusting the composition of the liquid system and the rate of flowing it so that the siliceous material is contacted by the system while the bentonite-dissolving proportion of hydrofluoric acid is present in the aqueous solution. 5 claims.

  18. Effect of silicate fertilization on soil and on palisade grass plants under grazing intensities

    OpenAIRE

    Pedro Henrique de Cerqueira Luz; Letícia de Abreu Faria; Felipe Barros Macedo; Valdo Rodrigues Herling; Antonio Batista Sanches; Rosane Cláudia Rodrigues

    2011-01-01

    Application of calcium silicate (SiCa) as soil acidity corrective was evaluated in a Rhodic Hapludox soil with palisade grass conducted under pasture rotation system with different grazing intensities. Experimental design was complete randomized blocks with four grazing intensities - grazing intensities were imposed by forage supply (50, 100, 150 and 200 kg t-1 of DM per LW) - in experimental plots with four replicates and, in the subplots, with seven doses of calcium silicate combined with l...

  19. Bioactivity studies of calcium magnesium silicate prepared from eggshell waste by sol–gel combustion synthesis

    OpenAIRE

    Rajan Choudhary; Sivasankar Koppala; Sasikumar Swamiappan

    2015-01-01

    The present study focused on the synthesis of calcium magnesium silicate (akermanite, Ca2MgSi2O7) using eggshell biowaste (as calcium source), magnesium nitrate and tetraethyl orthosilicate (TEOS) as starting materials. Sol–gel combustion method was adopted to obtain calcium magnesium silicate. Citric acid was used as a fuel (reducing agent) and nitrate ions present in the metal nitrates acts as an oxidizing agent during combustion process. The characterization of synthesized calcium magnesiu...

  20. Synthesis and optical features of an europium organic-inorganic silicate hybrid

    Energy Technology Data Exchange (ETDEWEB)

    Franville, A.C.; Zambon, D.; Mahiou, R.; Chou, S.; Cousseins, J.C. [Universite Blaise Pascal, Aubiere (France). Lab. des Materiaux Inorganiques; Troin, Y. [Laboratoire de Chimie des Heterocycles et des Glucides, EA 987, Universite Blaise-Pascal and ENSCCF, F-63177 Aubiere Cedex (France)

    1998-07-24

    A europium organic-inorganic silicate hybrid was synthesized by grafting a coordinative group (dipicolinic acid) to a silicate network precursor (3-aminopropyltriethoxysilane) via a covalent bonding. Sol-gel process and complexation were performed using different experimental conditions. The hybrid materials, in particular the Eu{sup 3+} coordination mode, were characterized by infrared and luminescence spectroscopies. Morphology of the materials and TG analysis showed that grafted silica enhanced thermal and mechanical resistances of the organic part. (orig.) 7 refs.

  1. Effect of silicate-based corrosion inhibitor from rice husk ash on aluminum alloy in 0.5M HCl

    Science.gov (United States)

    Othman, N. K.; Mohamad, N.; Zulkafli, R.; Jalar, A.

    2013-05-01

    Silicate-based corrosion inhibitor prepared by treating silica powder extracted from rice husk ash with concentrated alkaline. The electrochemical behavior of the Al 6061 immersed in 0.5 M hydrochloric acid (HCl) has been studied using the measurements of weight loss, potentiodynamic polarization and optical or scanning electron microscopy (SEM). It was found that, the optimum concentration of silicate-based corrosion inhibitor was prominent at 5 ppm. The small addition of silicate-based corrosion inhibitor was exhibited the decreasing of the weight loss of Al 6061 in acidic medium. SEM micrograph proved that the morphology of untreated Al 6061 with silicate-base corrosion inhibitor contributes more corrosion attack on sample compared to that treated Al 6061. The purpose of this research is to understand the effect of silicate-based corrosion inhibitor concentration yielded from rice husk ash on aluminum alloy.

  2. 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.

  3. 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...

  4. Carbonate verse silicate Sr isotope in lake sediments and its response to Little Ice Age

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The 87Sr/86Sr ratios of silicate (acid-insoluble, AI) and carbonate (acid-soluble, AS) of the lake sediments from the Daihai Lake, Inner Mongolia, since the last 500 years are measured respectively, indicating that chemical weathering of silicate minerals was in an early stage since the Little Ice Age within the Daihai watershed by combination with mineral constitute, Rb/Sr ratio and CaCO3 content in the sediments. During the Little Ice Age maximum, an evident peak in the 87Sr/86Sr ratios of both silicate and carbonate in sediments suggests that a cold climate condition is unfavorable to dissolving radiogenic strontium from silicate minerals. Meanwhile, the variation of 87Sr/86Sr ratios of silicate and carbonate also reflects a projected warming climate favorable to intensifying chemical weathering after the Little Ice Age. Consequently, the 87Sr/86Sr ratio of both silicate and carbonate in inland lake sediments can be used as an effective proxy of the past climate in single watershed.

  5. 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.

  6. Determination of silicon dioxide in siliceous refractory materials by potassium fluosilicate precipitation-acid base titration method%氟硅酸钾沉淀-酸碱滴定法测定硅质耐火材科料中二氧化硅

    Institute of Scientific and Technical Information of China (English)

    李环亭; 董艳艳; 刘晓毅; 孙晓红; 赵维平

    2011-01-01

    提出一种不用铂金坩埚和不需要用氢氟酸挥硅的氟硅酸钾沉淀-酸碱滴定法测定硅质耐火材料中SiO2含量方法,考察了检测的准确度和精确度,探讨了影响检测的干扰因素和可能的干扰机理.试样在银或者镍坩埚中,用氢氧化钠熔融,二氧化硅转化为硅酸钠,在有过量氯化钾存在的强酸性溶液中加入氟化钾溶液,生成氟硅酸钾沉淀,经过滤、洗涤后溶于沸水中,以酚酞为指示剂,NaOH标准溶液滴定水解后生成的氢氟酸.试样中SiO2的质量分数与Al2O3的质量分数比值大于或等于3.5时Al2O3对测定没有影响.应用本法检测硅质砂岩、硅砖等硅质耐火材料样品中的SiO2含量,测定值与认定值相符,且重复性较好.%A determination method of silicon dioxide in siliceous refractory materials by potassium fluosilicate precipitation-acid-base titration method was established. Neither a platinum crucible nor the volatilization of silicon by hydrofluoric acid was needed. The determination accuracy and precision were investigated. The interference factors and possible interference mechanism were discussed. The samples were melted in a silver or nickel crucible with sodium hydroxide, during which the silicon dioxide in sample was converted into sodium silicate. Then, potassium fluoride solution was added into strong acid solution containing excessive potassium chloride to form potassium fluosilicate precipitation. After filtration and washing, the precipitates were dissolved in boiling water. The generated hydrofluoric acid through hydrolysis was titrated with standard sodium hydroxide solution using phenolphthalein as indicator. It was generally considered that. when the ratio between mass fraction of silicon dioxide and aluminum oxide in sample was higher or equal to 3. 5, the aluminum oxide had no influence on the determination. This method has been applied to the determination of silicon dioxide in siliceous refractory materials

  7. 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.

  8. Pre-hydrolysed ethyl silicate as an alternative precursor for SiO{sub 2}-coated carbon nanofibers

    Energy Technology Data Exchange (ETDEWEB)

    Barrena, M.I., E-mail: ibarrena@quim.ucm.es [Departamento de Ciencia de los Materiales e Ingenieria Metalurgica, Facultad de Ciencias Quimicas, Universidad Complutense de Madrid, Av. Complutense s/n, 28040 Madrid (Spain); Gomez de Salazar, J.M.; Soria, A.; Matesanz, L. [Departamento de Ciencia de los Materiales e Ingenieria Metalurgica, Facultad de Ciencias Quimicas, Universidad Complutense de Madrid, Av. Complutense s/n, 28040 Madrid (Spain)

    2011-11-15

    This work reported basically aims at understanding the extent of SiO{sub 2}-coated carbon nanofibers using two different sol-gel precursors for the silicate glass. The silicate precursors employed were tetraethoxysilane (TEOS) and pre-hydrolysed ethyl silicate. The first route consisted in an acid hydrolysis and polycondensation of the TEOS and the second one in a polycondensation of the pre-hydrolysed ethyl silicate. The techniques of Fourier Infra Red spectroscopy, thermogravimetric analysis, scanning electron microscopy and X-ray diffraction were used to characterize the materials obtained. Both kinds of SiO{sub 2} precursor can coat the CNF effectively. However, the use of pre-hydrolysed ethyl silicate (faster gelation times and higher surface areas) can be considered a low-cost and facile alternative with respect to the use of TEOS, to obtain industrially silica-coated carbon nanofibers.

  9. Heavy ion bombardment of silicates and nitrides

    International Nuclear Information System (INIS)

    Several silicates, including α-quartz, zirconium silicate, thorium silicate, LiAlSiO4, a silicate glass and several nitrides, α and β Si3N4, AlN, ZrN as well as Si2N2O and ThO2, have been irradiated by 1019 to 1021 Krypton (3 MeV) ions/m2. The damaged powders of original particle size less than 5 μm, have been examined by x-ray diffraction and electron microscope methods. The silicates and Si2N2O become non-crystalline by 10 x 1019 ions/m2. The particles change shape, extending and bloating under prolonged irradiations of the order of 100 x 1019 ions/m2. Silicate glass also undergoes this irradiation creep process. The nitrides and ThO2 behave quite differently and even at fluences of 200 x 1019 x ions/m-2 the powders remain crystalline, retaining relatively sharp edges to the particles without exhibiting irradiation creep. This difference in behavior can be related to the nature of the framework crystal structures, flexible for the silicates with variable bond angles, rigid for the nitrides with fixed bond angles. This may explain the behavior of radioactive minerals not found in a metamict condition. (author)

  10. The role of nitrification in silicate hydrolysis in soils near Santa Cruz, CA

    Science.gov (United States)

    Kyker-Snowman, E.; White, A.; Lawrence, C. R.; Schulz, M. S.

    2013-12-01

    In some ecosystems, nitrification (microbial conversion of ammonium to nitrate) may supplant carbonic acid as a source of acidity and drive silicate weathering. Recent studies have explored the impact that ammonium fertilizer addition to soils has on weathering of various mineral types (Pacheco et al. 2013) and demonstrated directly that ammonium addition to soils can increase carbonate weathering (Gandois et al. 2011). Some evidence points to a role for nitrification in silicate weathering at a series of coastal grassland terraces near Santa Cruz, CA. Weathering rates in these soils have been estimated using the byproducts of silicate hydrolysis (Cl--adjusted Na+ and other cations). If carbonic acid from dissolved CO2 is the source of acidity in silicate hydrolysis, bicarbonate should balance the cations produced during weathering. However, in the Santa Cruz soils nitrate is the dominant anion balancing cation concentrations. High concentrations of CO2 (>1%) at depths greater than 1m may provide additional support for nitrification-based silicate hydrolysis at Santa Cruz. We evaluate the role of nitrification in silicate weathering for soils from the Santa Cruz Marine Terrace Chronosequence using a column ammonium-addition experiment and a basic weathering model. The column experiment uses ammonium inputs in excess of natural inputs and measures weathering products in eluted fluids over time. The model incorporates more realistic estimates of ammonium input and explores whether the observed concentrations of cations, nitrate and CO2 seen at Santa Cruz can be explained by nitrification-driven acidity or if other inputs need to be considered. Gandois, L, Perrin, A-S, and Probst, A. 2011. Impact of nitrogenous fertiliser-induced proton release on cultivated soils with contrasting carbonate contents: A column experiment. Geochimica et Cosmochimica Acta 75 pp. 1185-1198. Pacheco, F, Landim, P, and Szocs, T. 2013. Anthropogenic impacts on mineral weathering: A

  11. 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.

  12. 双极性膜电渗析技术在硅溶胶生产中的应用%Application of bipolar membrane electrodialysis in production of silicic acid

    Institute of Scientific and Technical Information of China (English)

    林爱光

    2001-01-01

    报道了双极性膜电渗析取代现行工艺中泡花碱转化成硅溶胶的酸化过程的研究.转化得到的硅溶胶中SiO2含量达到6%~10%,pH值在3以下,平均电流效率在55%~75%范围内,平均耗电低于1 kW*h/kg(每千克硅溶胶),制得的硅溶胶产品符合工业要求.%A new technology, bipolar membrane electrodialysis(BME), was developed to convert sodium silicate(Na2SO3) into silicasol (H2SO3). By optimizing the operation condition, one can easily obtain the product with desired SiO2 content about 6%~10% and pH value about 3. In this new process, the average efficiency of electric current is 55%~75% and the power cost is less than 1 kW*h/(kg silicasol). So it provides a attractive method for the production of silicasol.

  13. Uranium-thorium silicates, with specific reference to the species in the Witwatersrand reefs

    International Nuclear Information System (INIS)

    (U,Th)-silicates form two complete series of anhydrous and hydrated species with general formulae (U,Th)SiO4 and (U,Th)SiO4.nH2O respectively. The end-members of the anhydrous series are anhydrous coffinite and thorite, and those of the hydrated series, coffinite and thorogummite. Although the silicates are relatively rare in nature, coffinite is a common ore mineral in uranium deposits of the sandstone type. In the Witwatersrand reefs, (U,Th)-silicates are extremely rare in most reefs, except for the Elsburg Reefs on the West Rand Goldfield and the Dominion Reef. In these reefs detrital uraninite has been partly or entirely transformed to (U,Th)-silicates of coffinite composition, but thorite and thorogummite of detrital origin are also found in the Dominion Reef. In leaching tests on polished sections of rock samples containing (U,Th)-silicates, a dilute sulphuric acid solution, to which ferric iron had been added, was used as the lixiviant. It appeared that the dissolution of coffinite is less rapid than that of uraninite and uraniferous leucoxene. However, the reaction of silicates of high thorium content is much slower, and was not completed during the tests

  14. Magnetic properties of sheet silicates

    International Nuclear Information System (INIS)

    Susceptibility, magnetisation and Moessbauer measurements are reported for a representative selection of 2:1 layer phyllosilicates. Eight samples from the mica, vermiculite and smectite groups include examples diluted in iron which are paramagnetic at all temperatures, as well as iron-rich silicates which order magnetically below 10 K. Anisotropic susceptibility of crystals of muscovite, biotite and vermiculite is quantitatively explained with a model where the Fe2+ ions lie in sites of effective trigonal symmetry, the trigonal axis lying normal to the sheets. The ferrous ground state is an orbital singlet. Ferric iron gives an isotropic contribution to the susceptibility. Fe2+-Fe2+ exchange interactions are ferromagnetic with Gapprox. equal to2 K, whereas Fe3+-Fe3+ coupling is antiferromagnetic in the purely ferric minerals. A positive paramagnetic Curie temperature for glauconite may be attributable to Fe2+ → Fe3+ charge transfer. Magnetic order was found to set in inhomogeneously for glauconite at 1-7 K. One biotite sample showed an antiferromagnetic transition at Tsub(N) = 7 K marked by a well-defined susceptibility maximum. Its magnetic structure, consisting of ferromagnetic sheets with moments in their planes coupled antiferromagnetically by other, weak interactions, resembles that found earlier for the 1:1 mineral greenalite. (orig.)

  15. 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...

  16. Geo-neutrinos and Silicate Earth Enrichment

    CERN Document Server

    Dye, Steve

    2010-01-01

    The terrestrial distribution of U, Th, and K abundances governs the thermal evolution, traces the differentiation, and reflects the bulk composition of the earth. Comparing the bulk earth composition to chondritic meteorites estimates the net amounts of these radiogenic heat-producing elements available for partitioning to the crust, mantle, and core. Core formation enriches the abundances of refractory lithophile elements, including U and Th, in the silicate earth by ~1.5. Global removal of volatile elements potentially increases this enrichment to ~2.8. The K content of the silicate earth follows from the ratio of K to U. Variable enrichment produces a range of possible heat-producing element abundances in the silicate earth. A model assesses the essentially fixed amounts of U, Th, and K in the approximately closed crust reservoir. Subtracting these sequestered crustal amounts from the variable amounts in the silicate earth results in a range of possible mantle allocations, leaving global dynamics and therm...

  17. Silicate production and availability for mineral carbonation.

    Science.gov (United States)

    Renforth, P; Washbourne, C-L; Taylder, J; Manning, D A C

    2011-03-15

    Atmospheric carbon dioxide sequestered as carbonates through the accelerated weathering of silicate minerals is proposed as a climate change mitigation technology with the potential to capture billions of tonnes of carbon per year. Although these materials can be mined expressly for carbonation, they are also produced by human activities (cement, iron and steel making, coal combustion, etc.). Despite their potential, there is poor global accounting of silicates produced in this way. This paper presents production estimates (by proxy) of various silicate materials including aggregate and mine waste, cement kiln dust, construction and demolition waste, iron and steel slag, and fuel ash. Approximately 7-17 billion tonnes are produced globally each year with an approximate annual sequestration potential of 190-332 million tonnes C. These estimates provide justification for additional research to accurately quantify the contemporary production of silicate minerals and to determine the location and carbon capture potential of historic material accumulations. PMID:21332128

  18. 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...

  19. 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.

  20. Geoengineering potential of artificially enhanced silicate weathering of olivine.

    Science.gov (United States)

    Köhler, Peter; Hartmann, Jens; Wolf-Gladrow, Dieter A

    2010-11-23

    Geoengineering is a proposed action to manipulate Earth's climate in order to counteract global warming from anthropogenic greenhouse gas emissions. We investigate the potential of a specific geoengineering technique, carbon sequestration by artificially enhanced silicate weathering via the dissolution of olivine. This approach would not only operate against rising temperatures but would also oppose ocean acidification, because it influences the global climate via the carbon cycle. If important details of the marine chemistry are taken into consideration, a new mass ratio of CO(2) sequestration per olivine dissolution of about 1 is achieved, 20% smaller than previously assumed. We calculate that this approach has the potential to sequestrate up to 1 Pg of C per year directly, if olivine is distributed as fine powder over land areas of the humid tropics, but this rate is limited by the saturation concentration of silicic acid. In our calculations for the Amazon and Congo river catchments, a maximum annual dissolution of 1.8 and 0.4 Pg of olivine seems possible, corresponding to the sequestration of 0.5 and 0.1 Pg of C per year, but these upper limit sequestration rates come at the environmental cost of pH values in the rivers rising to 8.2. Open water dissolution of fine-grained olivine and an enhancement of the biological pump by the rising riverine input of silicic acid might increase our estimate of the carbon sequestration, but additional research is needed here. We finally calculate with a carbon cycle model the consequences of sequestration rates of 1-5 Pg of C per year for the 21st century by this technique.

  1. Compositional dependence of in vitro response to commercial silicate glasses

    Science.gov (United States)

    Jedlicka, Amy B.

    Materials are often incorporated into the human body, interacting with surrounding fluids, cells and tissues. The reactions that occur between a material and this surrounding biological system are not fundamentally understood. Basic knowledge of material biocompatibility and the controlling processes is lacking. This thesis examines material biocompatibility of a series of silicate-based glasses on a primary level determining cell response to material composition and durability. The silicate glass system studied included two BioglassRTM compositions with known biologically favorable response, two fiberglass compositions, with demonstrated 'not-unfavorable' in vitro response, a ternary soda-lime-silicate glass, a binary alkali silicate glass, and pure silica. Chemical durability was analyzed in three different fluids through solution analysis and material characterization. In vitro response to the substrates was observed. Cell behavior was then directly correlated to the material behavior in cell culture medium under the same conditions as the in vitro test, yet in the absence of cells. The effect of several physical and chemical surface treatments on substrates with predetermined biocompatible behavior was subsequently determined. The chemically durable glasses with no added B2O3 elicited similar cell response as the control polystyrene substrate. The addition of B2O3 resulted in polygonal cell shape and restricted cell proliferation. The non-durable glasses presented a dynamic surface to the cells, which did not adversely affect in vitro response. Extreme dissolution of the binary alkali silicate glass in conjunction with increased pH resulted in unfavorable cell response. Reaction of the Bioglass RTM compositions, producing a biologically favorable calcium-phosphate surface film, caused enhanced cell attachment and spreading. Surface energy increase due to sterilization procedures did not alter cellular response. Surface treatment procedures influencing substrate

  2. 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.

  3. Enhanced bioactivity of glass ionomer cement by incorporating calcium silicates.

    Science.gov (United States)

    Chen, Song; Cai, Yixiao; Engqvist, Håkan; Xia, Wei

    2016-01-01

    Glass ionomer cements (GIC) are known as a non-bioactive dental cement. During setting the GIC have an acidic pH, driven by the acrylic acid component. It is a challenge to make GIC alkaline without disturbing its mechanical properties. One strategy was to add slowly reacting systems with an alkaline pH. The aim of the present study is to investigate the possibility of forming a bioactive dental material based on the combination of glass ionomer cement and calcium silicates. Two types of GIC were used as control. Wollastonite (CS also denoted β-CaSiO3) or Mineral Trioxide Aggregate (MTA) was incorporated into the 2 types of GIC. The material formulations' setting time, compressive strength, pH and bioactivity were compared between modified GIC and GIC control. Apatite crystals were found on the surfaces of the modified cements but not on the control GIC. The compressive strength of the cement remained with the addition of 20% calcium silicate or 20% MTA after one day immersion. In addition, the compressive strength of GIC modified with 20% MTA had been increased during the 14 d immersion (p < 0 .05). PMID:26787304

  4. Porous Silicates Modified with Zirconium Oxide and Sulfate Ions for Alcohol Dehydration Reactions

    Directory of Open Access Journals (Sweden)

    Heriberto Esteban Benito

    2015-01-01

    Full Text Available Porous silicates were synthesized by a nonhydrothermal method, using sodium silicate as a source of silica and cetyltrimethylammonium bromide as a template agent. Catalysts were characterized using thermogravimetric analysis, N2 physisorption, X-ray diffraction, FTIR spectroscopy, pyridine adsorption, potentiometric titration with n-butylamine, scanning electronic microscopy, and transmission electronic microscopy. The surface area of the materials synthesized was greater than 800 m2/g. The introduction of zirconium atoms within the porous silicates increased their acid strength from −42 to 115 mV, while the addition of sulfate ions raised this value to 470 mV. The catalytic activity for the dehydration of alcohols yields conversions of up to 70% for ethanol and 30% for methanol.

  5. 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

  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. Simultaneous spectrophotometric determination of phosphate and silicate ions in river water by using ion-exclusion chromatographic separation and post-column derivatization

    OpenAIRE

    Nakatani, Nobutake; Kozaki, Daisuke; Masuda, Wakako; Nakagoshi, Nobukazu; Hasebe, Kiyoshi; Mori, Masanobu; Tanaka, Kazuhiko

    2008-01-01

    The simultaneous spectrophotometric determination of phosphate and silicate ions in river water was examined by using ion-exclusion chromatography and post-column derivatization. Phosphate and silicate ions were separated by the ion-exclusion column packed with a polymethacrylate-based weakly acidic cation-exchange resin in the H+-form (TSKgel Super IC-A/C) by using ultra pure water as an eluent. After the postcolumn derivatization with molybdate and ascorbic acid, so-called molybdenum-blue, ...

  8. Effects of surface application of dolomitic limestone and calcium-magnesium silicate on soybean and maize in rotation with green manure in a tropical region

    Directory of Open Access Journals (Sweden)

    Gustavo Spadotti Amaral Castro

    2015-01-01

    Full Text Available Although lime is currently the material most frequently used to ameliorate soil acidity in Brazil, silicate could efficiently replace this source because of its greater solubility and its greater silicon content, which are beneficial for plant development. This study aimed to evaluate the effects of superficial lime and silicate application on soil chemical attributes as well as on soybean and maize nutrition and grain yields when these crops are grown in rotation with green manure. The experimental design was a complete randomized block with sixteen replicates. Plots were treated with one of two materials for acidity correction (dolomitic lime and calcium/magnesium silicate or with no soil correction, as a control. Silicate corrected soil acidity and increased exchangeable base levels in soil at greater depths faster than does liming. The application of both acidity-correcting materials increased N, Ca and Mg leaf concentrations, and all yield components and grain yield in soybean; but in maize, just silicate also increased N and Si when compared with lime, whereas both acidity-correcting increased just two yield components: grains per ear and mass of 100 grains, resulting in highest grain yield. The application of both acidity-correcting materials increased dry matter production of green manures, but for pigeon pea the silicate provided the best result in this dry-winter region.

  9. Silicate Inclusions in the Kodaikanal IIE Iron Meteorite

    Science.gov (United States)

    Kurat, G.; Varela, M. E.; Zinner, E.

    2005-03-01

    II-E iron meteorites are particularly interesting because they contain an exotic zoo of silicate inclusions including some chemically strongly fractionated ones. Here we present preliminary findings in our study of Kodaikanal silicate inclusions.

  10. 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.

  11. 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...

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

    OpenAIRE

    DIANA HORKAVCOVÁ; TEREZA BĚLOUBKOVÁ; ZUZANA MIZEROVÁ; LUDVÍK ŠANDA; ZUZANA CÍLOVÁ; MARKÉTA ČASTORÁLOVÁ; ALEŠ HELEBRANT

    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...

  13. LABORATORY INVESTIGATIONS OF SILICATE MUD CONTAMINATION WITH CALCIUM

    OpenAIRE

    Nediljka Gaurina-Međimurec; Katarina Simon; Davorin Matanović

    2004-01-01

    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 ...

  14. The role of water in silicate oligomerization reaction

    NARCIS (Netherlands)

    T.T. Trinh; A.P.J. Jansen; R.A. Santen; E.J. Meijer

    2009-01-01

    The silicate oligomerization reaction is key to sol-gel chemistry and zeolite synthesis. Numerous experimental and theoretical studies have been devoted to investigating the physical chemistry of silicate oligomers in the prenucleation stage of siliceous zeolite formation. Most of the previous quant

  15. 21 CFR 182.2122 - Aluminum calcium silicate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Aluminum calcium silicate. 182.2122 Section 182.2122 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent....

  16. 21 CFR 582.2122 - Aluminum calcium silicate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Aluminum calcium silicate. 582.2122 Section 582.2122 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent....

  17. 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...

  18. The importance of the Maillard-metal complexes and their silicates in astrobiology

    Science.gov (United States)

    Liesch, Patrick J.; Kolb, Vera M.

    2007-09-01

    The Maillard reaction occurs when sugars and amino acids are mixed together in the solid state or in the aqueous solution. Since both amino acids and sugar-like compounds are found on meteorites, we hypothesized that they would also undergo the Maillard reaction. Our recent work supports this idea. We have shown previously that the water-insoluble Maillard products have substantial similarities with the insoluble organic materials from the meteorites. The Maillard organic materials are also part of the desert varnish on Earth, which is a dark, shiny, hard rock coating that contains iron and manganese and is glazed in silicate. Rocks that are similar in appearance to the desert varnish have been observed on the Martian surface. They may also contain the organic materials. We have undertaken study of the interactions between the Maillard products, iron and other metals, and silicates, to elucidate the role of the Maillard products in the chemistry of desert varnish and meteorites. Specifically, we have synthesized a series of the Maillard-metal complexes, and have tested their reactivity towards silicates. We have studied the properties of these Maillard-metal-silicate products by the IR spectroscopy. The astrobiological potential of the Maillard-metal complexes is assessed.

  19. Silicate fertilization of tropical soils: silicon availability and recovery index of sugarcane

    Directory of Open Access Journals (Sweden)

    Mônica Sartori de Camargo

    2013-10-01

    Full Text Available Sugarcane is considered a Si-accumulating plant, but in Brazil, where several soil types are used for cultivation, there is little information about silicon (Si fertilization. The objectives of this study were to evaluate the silicon availability, uptake and recovery index of Si from the applied silicate on tropical soils with and without silicate fertilization, in three crops. The experiments in pots (100 L were performed with specific Si rates (0, 185, 370 and 555 kg ha-1 Si, three soils (Quartzipsamment-Q, 6 % clay; Rhodic Hapludox-RH, 22 % clay; and Rhodic Acrudox-RA, 68 % clay, with four replications. The silicon source was Ca-Mg silicate. The same Ca and Mg quantities were applied to all pots, with lime and/or MgCl2, when necessary. Sugarcane was harvested in the plant cane and first- and second-ratoon crops. The silicon rates increased soil Si availability and Si uptake by sugarcane and had a strong residual effect. The contents of soluble Si were reduced by harvesting and increased with silicate application in the following decreasing order: Q>RH>RA. The silicate rates promoted an increase in soluble Si-acetic acid at harvest for all crops and in all soils, except RA. The amounts of Si-CaCl2 were not influenced by silicate in the ratoon crops. The plant Si uptake increased according to the Si rates and was highest in RA at all harvests. The recovery index of applied Si (RI of sugarcane increased over time, and was highest in RA.

  20. 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

  1. 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.

  2. 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.

  3. Aggregation of Calcium Silicate Hydrate Nanoplatelets.

    Science.gov (United States)

    Delhorme, Maxime; Labbez, Christophe; Turesson, Martin; Lesniewska, Eric; Woodward, Cliff E; Jönsson, Bo

    2016-03-01

    We study the aggregation of calcium silicate hydrate nanoplatelets on a surface by means of Monte Carlo and molecular dynamics simulations at thermodynamic equilibrium. Calcium silicate hydrate (C-S-H) is the main component formed in cement and is responsible for the strength of the material. The hydrate is formed in early cement paste and grows to form platelets on the nanoscale, which aggregate either on dissolving cement particles or on auxiliary particles. The general result is that the experimentally observed variations in these dynamic processes generically called growth can be rationalized from interaction free energies, that is, from pure thermodynamic arguments. We further show that the surface charge density of the particles determines the aggregate structures formed by C-S-H and thus their growth modes. PMID:26859614

  4. Effects of ionization on silicate glasses

    International Nuclear Information System (INIS)

    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

  5. 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.

  6. Submarine silicic volcanism: Processes and products

    Digital Repository Service at National Institute of Oceanography (India)

    Kalangutkar, N.G.; Iyer, S.D.

    and these are supported by several experimental studies (Annen et al., 2006). A silicic calc-alkalic magma can form by differentiation from a more mafic parent magma and by crustal anatexis. Several evidences show the origin of some rhyolitic and andesitic magma... to be related due to similar tectonic settings. Fractional crystallisation: This process produces a series of residual liquids of variable compositions as compared to their parental magmas and is best explained by the Bowen’s reaction principle (Bowen, 1922...

  7. Polymorphism in silicate-postperovskite reviewed (Invited)

    Science.gov (United States)

    Tschauner, O. D.

    2010-12-01

    Early on in the examination of postperovskite(ppv)-type magnesium metasilicate it had been debated if this potential deep mantle mineral can be subject to further structural transformation as function of composition, pressure, and temperature within the range of conditions in the lower mantle. MgSiO3-perovskite accommodates minor elements through local lattice distortions by tilt of the corner-sharing octahedral framework. The CaIrO3-type ppv structure does not seem to possess a similar mechanism of local relaxation of lattice strain. Instead minor elements may rather be accommodated by periodic kinks in this layered structure (1). This kinking-mechanism allows for generating a plethora of polymorphs similar in structure and free energy (1,2). However, the elastic properties of ppv may be strongly affected by this type of structural modification. While structural analogues of silicate-ppv exhibit this type of polymorphism (3,4) previous attempts to examine polymorphism in silicate-ppv remained suggestive (2,5). This is mostly owed to the severe constraints imposed on powder diffraction studies conducted under the extreme conditions of stability of MgSiO3-ppv. Here I present new results on silicate-ppv based on different experimental strategies which shed more light on this complex yet important issue of structural modifications in minor-element bearing silicate-ppv. (1) Oganov et al. Nature 438, 1142 (2005);(2) Tschauner et al. Am. Min. 93, 533 (2008); (3) Shirako et al. Phys. Chem. Min. 36, 455 (2009); Yakovlev et al. J. Sol. Stat. Chem. 182, 1545 (2009) Work supported through NNSA Cooperative Agreement DOE-FC88-01NV14049

  8. Premixed calcium silicate cement for endodontic applications

    OpenAIRE

    Persson, Cecilia; Engqvist, Håkan

    2011-01-01

    Calcium silicate-based materials (also called MTA) are increasingly being used in endodontic applications. However, the handling properties of MTA are not optimal when it comes to injectability and cohesion. Premixing the cements using glycerol avoids these issues. However, there is a lack of data on the effect of common cement variables on important properties of premixed cements for endodontic applications. In this study, the effects of liquid-to-powder ratio, amount of radiopacifier and am...

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

    Science.gov (United States)

    Marler, Bernd; Müller, Melanie; Gies, Hermann

    2016-06-21

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

  10. Volume of ionic sites in silicate glasses

    International Nuclear Information System (INIS)

    Molar volume data of alkali and alkaline earth silicate glasses have been used to calculate the free volume associated with the bridging and nonbridging oxygen and modifier ions. The free volume associated with the bridging oxygen is constant (15.39 x 10-24 cm3) for all modifier ions up to 33.3 mol% modifier oxide. It decreases (in alkali or alkaline earth silicate glasses) with increasing number of nonbridging oxygen ions per structural unit and/or radius of the modifier ion. The nonbridging oxygen ion is associated with a constant free volume (6.50 x 10-24 cm3) in all cases. Modifier ions are associated with free volume that increases with increasing number of nonbridging oxygen ions per structural unit and/or radius of the modifier ion. The used model explores the change in the free volume due to changing the concentration of alkali oxides in mixed alkali silicate glasses. The results show that, in such glasses, the free volume related to a certain type of alkali oxide increases with increasing content

  11. Synthesis and characterization of functional copolymer/organo-silicate nanoarchitectures through interlamellar complex-radical (coterpolymerization

    Directory of Open Access Journals (Sweden)

    2008-09-01

    Full Text Available The functional copolymers, having a combination of rigid/flexible linkages and an ability of complex-formation with interlayered surface of organo-silicate, and their nanocomposites have been synthesized by interlamellar complex-radical (coterpolymerization of intercalated monomer complexes of maleic anhydride (MA and itaconic acid (IA with dimethyl dodecylamine surface modified montmorillonite (organo-MMT (MA…DMDA-MMT and IA…DMDA-MMT n-butyl methacrylate (BMA and/or BMA/styrene monomer mixtures. The results of nanocomposite structure–composition– property relationship studies indicate that interlamellar complex-formation between anhydride/acid units and surface alkyl amine and rigid/flexible linkage balance in polymer chains are important factors providing the effective intercalation/ exfoliation of the polymer chains into the silicate galleries, the formation of nanostructural hybrids with higher thermal stability, dynamic mechanical behaviour and well dispersed morphology.

  12. Sorption of uranium(VI) from aqueous solution onto magnesium silicate hollow spheres

    International Nuclear Information System (INIS)

    The sorption of uranium(VI) from aqueous solutions was investigated using synthesized magnesium silicate hollow spheres as a novel adsorbent. Batch experiments were conducted to study the effects of initial pH, amount of adsorbent, contact time and initial U(VI) concentrations on uranium sorption efficiency. The desorbing of U(VI) and the effect of coexisting ions were also investigated. Kinetic studies showed that the sorption followed a pseudo-second-order kinetic model. The Langmuir sorption isotherm model correlates well with the uranium sorption equilibrium data for the concentration range of 25-400 mg/L. The maximum uranium sorption capacity onto magnesium silicate hollow spheres was estimated to be about 107 mg/g under the experimental conditions. Desorption of uranium was achieved using inorganic acid as the desorbing agent. The practical utility of magnesium silicate hollow spheres for U(VI) uptake was investigated with high salt concentration of intercrystalline brine. This work suggests that magnesium silicate hollow spheres can be used as a highly efficient adsorbent for removal of uranium from aqueous solutions. (author)

  13. 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.

  14. An Evaluation of Ethyl Silicate-Based Grouts for Weathered Silicate Stones

    Science.gov (United States)

    Dolph, Brittany Helen

    Culturally significant monuments made of weathered siliceous stone often display sub-surface condition issues such as cracks and voids. These issues require grouts that are ideally compatible with the composition and properties of the substrate. Based on the successful application of ethyl silicates as consolidants in recent literature, this study examines possible formulation pathways for the development of a grout incorporating ethyl silicate. Tetraethylorthosilicate (TEOS), dibutyltin dilaurate (DBTL) as a catalyst, silicone oil (PDMS), various grades of ground quartz, sepiolite, and hollow glass spheres were used in differing concentrations to create samples. These were visually and physically assessed on workability, separation, shrinkage, cracking, strength, and flexibility. Quantitative analysis was performed on selected formulations using UV-Vis-NIR reflectance spectroscopy in coordination with a weight loss experiment to investigate kinetics, dynamic mechanical analysis (DMA), and scanning electron microscopy (SEM). Successful formulations tended to include oligomeric TEOS, crushed quartz of mixed grades, sepiolite powder, and PDMS, and show promise for future investigations.

  15. Effects of surface application of dolomitic limestone and calcium-magnesium silicate on soybean and maize in rotation with green manure in a tropical region

    OpenAIRE

    2015-01-01

    Although lime is currently the material most frequently used to ameliorate soil acidity in Brazil, silicate could efficiently replace this source because of its greater solubility and its greater silicon content, which are beneficial for plant development. This study aimed to evaluate the effects of superficial lime and silicate application on soil chemical attributes as well as on soybean and maize nutrition and grain yields when these crops are grown in rotation with green manure. The exper...

  16. Potassium silicate and calcium silicate on the resistance of soybean to Phakopsora pachyrhizi infection

    OpenAIRE

    Maria Fernanda Cruz; Fabrício Ávila Rodrigues; Ana Paula Cardoso Diniz; Maurilio Alves Moreira; Everaldo Gonçalves de Barros

    2013-01-01

    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 ...

  17. 77 FR 21676 - Silicic Acid, Sodium Salt etc.; Tolerance Exemption

    Science.gov (United States)

    2012-04-11

    ... inert ingredient in a pesticide chemical formulation. Dow Corning Corporation submitted a petition to..., reaction with poly(oxypropylene)-poly(oxyethylene) glycol on food or feed commodities. DATES: This... limited to: Crop production (NAICS code 111). Animal production (NAICS code 112). Food...

  18. Redox control of sulfur degassing in silicic magmas

    OpenAIRE

    Scaillet, Bruno; Clémente, Béatrice; Evans, Bernard W.; Pichavant, Michel

    1998-01-01

    International audience Explosive eruptions involve mainly silicic magmas in which sulfur solubility and diffusivity are low. This inhibits sulfur exsolution during magma uprise as compared to more mafic magmas such as basalts. Silicic magmas can nevertheless liberate large quantities of sulfur as shown by the monitoring of SO2 in recent explosive silicic eruptions in arc settings, which invariably have displayed an excess of sulfur relative to that calculated from melt degassing. If this e...

  19. NMR study of hydrated calcium silicates

    International Nuclear Information System (INIS)

    Radioactive wastes storage methods are developed by the CEA. As cements are important materials as well for hours living radioisotopes than for years living radioisotopes, a better knowledge of this material will allow to anticipate its behaviour and to obtain safer storage methods. The structure of calcium silicates (C-S-H) (main constituent of cements) have then been determined in this thesis by nuclear magnetic resonance. This method has allow to explain in structural terms, the different calcium rates that can be measured in the C-S-H too. (O.M.)

  20. EXAFS studies of silicate glasses containing uranium

    International Nuclear Information System (INIS)

    Sodium silicate glasses containing hexavalent uranium ions have been studied using the EXAFS technique. The U6+ ions appear in the uranyl configuration with two oxygen atoms at 1.85 A and four to five at 2.2-2.3 A. In the glasses (0.25Na2O.0.75SiO2)sub(1-x)(UO3)sub(x) with x = 0.02 to x = 0.1, planar (or nearly planar) uranium containing clusters, with U-U distances of 3.3 A, are observed. A layered model is proposed to describe these glasses. (Auth.)

  1. 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.

  2. Mechanical loss associated with silicate bonding of fused silica

    International Nuclear Information System (INIS)

    We report on mechanical loss associated with hydroxy-catalysis (or 'silicate') bonding between fused silica substrates in the presence of potassium hydroxide or sodium silicate. We measured the mechanical quality factor of three fused silica samples, each composed of two half-rods bonded together on their flat surfaces and compared them to that of an unbonded half-rod. The measurements show a significant reduction of quality factor due to mechanical loss associated with the silicate bonds. We calculate the loss factor of the bonded region φbond and estimate that the effect of silicate bonding on thermal noise in the Advanced LIGO interferometers will be small

  3. 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.

  4. SPM nanolithography of hydroxy-silicates

    International Nuclear Information System (INIS)

    Bio-nanopatterning of surfaces is becoming a crucial technique with applications ranging from molecular and cell biology to medicine. Scanning probe microscopy (SPM) is one of the most useful tools for nanopatterning of flat surfaces. However, these patterns are usually built on homogeneous surfaces and require chemical functionalization to ensure specific affinity. Layered magnesium–aluminum hydroxide–silicates have already shown unique self-assembly properties on DNA molecules, due to their peculiar crystal chemistry based on alternating positive and negative crystal layers. However, patterns on these surfaces tend to be randomly organized. Here we show etching and oxidation at the nanometer scale of magnesium–aluminum hydroxide–silicates using the same SPM probe for the creation of organized nanopatterns. In particular, it is possible to produce three-dimensional structures in a reproducible way, with a depth resolution of 0.4 nm, lateral resolution of tens of nm, and a speed of about 10 μm s−1. We report, as an example, the construction of an atomically flat charged pattern, designed to guide DNA deposition along predetermined directions without the need of any chemical functionalization of the surface. (paper)

  5. Carbon Mineralization Using Phosphate and Silicate Ions

    Science.gov (United States)

    Gokturk, H.

    2013-12-01

    Carbon dioxide (CO2) reduction from combustion of fossil fuels has become an urgent concern for the society due to marked increase in weather related natural disasters and other negative consequences of global warming. CO2 is a highly stable molecule which does not readily interact with other neutral molecules. However it is more responsive to ions due to charge versus quadrupole interaction [1-2]. Ions can be created by dissolving a salt in water and then aerosolizing the solution. This approach gives CO2 molecules a chance to interact with the hydrated salt ions over the large surface area of the aerosol. Ion containing aerosols exist in nature, an example being sea spray particles generated by breaking waves. Such particles contain singly and doubly charged salt ions including Na+, Cl-, Mg++ and SO4--. Depending on the proximity of CO2 to the ion, interaction energy can be significantly higher than the thermal energy of the aerosol. For example, an interaction energy of 0.6 eV is obtained with the sulfate (SO4--) ion when CO2 is the nearest neighbor [2]. In this research interaction between CO2 and ions which carry higher charges are investigated. The molecules selected for the study are triply charged phosphate (PO4---) ions and quadruply charged silicate (SiO4----) ions. Examples of salts which contain such molecules are potassium phosphate (K3PO4) and sodium orthosilicate (Na4SiO4). The research has been carried out with first principle quantum mechanical calculations using the Density Functional Theory method with B3LYP functional and Pople type basis sets augmented with polarization and diffuse functions. Atomic models consist of the selected ions surrounded by water and CO2 molecules. Similar to the results obtained with singly and doubly charged ions [1-2], phosphate and silicate ions attract CO2 molecules. Energy of interaction between the ion and CO2 is 1.6 eV for the phosphate ion and 3.3 eV for the silicate ion. Hence one can expect that the selected

  6. Simple preparation and initial characterization of semi-amorphous hollow calcium silicate hydrate nanoparticles by ammonia-hydrothermal-template techniques

    International Nuclear Information System (INIS)

    Semi-amorphous hollow calcium silicate hydrate nanoparticles (CS10d120Hac) were successfully synthesized via simple ammonia-hydrothermal-template approach (AHT) followed by acid treatment. Results revealed that the newly synthesized samples had homogenous hollow nano-interior wherein the shell wall contained semi-amorphous calcium silicate hydrate. The AHT intensified the formation of a stronger electrostatic interaction (Si–O–Ca) from the weaker electrostatic contact composed of silicate wall-calcium hydroxide interaction (Si–OH–Ca) forming a thin semi-amorphous calcium silicate hydrate shell wall. This is also a convenient way for structural stability of the hollow CS10d120Hac. The CS10d120Hac showed a relatively higher surface area, which is uniquely rare especially if compared with bulk calcium silicate particles. This CS10d120Hac can be selectively functionalized with multiple organic and inorganic groups. Hence, this work may open a new route for the formation of hybrid hollow bio-active particles.

  7. TECHNOLOGICAL OPTIONS FOR ACID RAIN CONTROL

    Science.gov (United States)

    Discussed are acid rain control options available to the electric utility industry. They include coal switching, flue gas desulfurization, and such emerging lower cost technologies as Limestone Injection Multistage Burners (LIMB) and Advanced Silicate (ADVACATE), both developed ...

  8. Self-assembly of natural light-harvesting bacteriochlorophylls of green sulfur photosynthetic bacteria in silicate capsules as stable models of chlorosomes.

    Science.gov (United States)

    Saga, Yoshitaka; Akai, Sho; Miyatake, Tomohiro; Tamiaki, Hitoshi

    2006-01-01

    Naturally occurring bacteriochlorophyll(BChl)s-c, -d, and -e from green sulfur photosynthetic bacteria were self-assembled in an aqueous solution in the presence of octadecyltriethoxysilane and tetraethoxysilane, followed by polycondensation of the alkoxysilanes by incubation for 50 h at 25 degrees C. The resulting BChl self-assemblies in silicate capsules exhibited visible absorption and circular dichroism spectra similar to the corresponding natural light-harvesting systems (chlorosomes) of green sulfur bacteria. Dynamic light scattering measurements indicated that the silicate capsules had an average hydrodynamic diameter of several hundred nanometers. BChl self-aggregates in silicate capsules were significantly stable to a nonionic surfactant Triton X-100, which was apt to decompose the BChl aggregates to their monomeric form, compared with conventional micelle systems. BChls in silicate capsules were more tolerant to demetalation of the central magnesium under acidic conditions than the natural systems. PMID:16848406

  9. 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.

  10. Spectral properties of porphyrins in the systems with layered silicates

    International Nuclear Information System (INIS)

    This work is focused on investigation of hybrid materials based on layered silicates, representing host inorganic component, and porphyrin dyes as organic guest. Aqueous colloidal dispersions, as well as thin solid films of layered silicate/porphyrin systems were studied. Modification of photophysical properties, such as absorption and fluorescence of molecules, adsorbed or incorporated in layered silicate hosts, were studied mainly to spread the knowledge about the environments suitable for incorporating aromatic compounds, providing photoactive properties of potential technological interest. TMPyP cations interact with the surfaces of layered silicates via electrostatic interactions. The extent of dye adsorption on colloidal particles of the silicates is influenced by the CEC values and swelling ability of silicates. Interaction of porphyrins with layered silicate hosts leads to significant changes of dye spectral properties. One of the key parameters that has a crucial impact on this interaction is the layer charge of silicate template. Other factors influence the resulting spectral properties of hybrid systems, such as the method of hybrid material preparation, the material's type (colloid, film), and the modification of the silicate host. Molecular orientation studies using linearly-polarized spectroscopies in VIS and IR regions revealed that TMPyP molecules were oriented in almost parallel fashion with respect to the silicate surface plane. Slightly higher values of the orientation angle of TMPyP transition moment were observed for the TMPyP/FHT system. Thus, flattening of the guest TMPyP molecules is the next important factor (mainly in the systems with lower layer charge), influencing its spectral properties upon the interaction with layered silicates. Fluorescence was effectively quenched in the systems based on solid films prepared from the high concentration of the dye (10-3 mol.dm-3). The quenching is most probably related to the structure of the

  11. Petrophysical Analysis of Siliceous Ooze Sediments, Ormen Lange Field, Norway

    DEFF Research Database (Denmark)

    Awedalkarim, Ahmed; Fabricius, Ida Lykke

    is the main gas reservoir (NDP). In this study, we are interested in the siliceous ooze intervals only. A possible hydrocarbon prospect of siliceous ooze is proposed, but siliceous ooze is significantly different in structure from most commonly known hydrocarbon reservoir rocks. For instance, the pore...... and to a lesser extent upon other elements. It is normally assumed that the contribution to the neutron porosity measurement comes entirely from the hydrogen in fluids fully occupying the pore space. But, elements other than hydrogen that exist in the rock matrix do contribute to the signal; and hydrogen is also...... to analyse and interpret logging data acquired through siliceous ooze sediments. Our main objectives were to characterize and evaluate the petrophysics of siliceous ooze and to find the true porosity and water saturation to test its hydrocarbon reservoir potential. We used and integrated core analysis data...

  12. Thermal Ablation Modeling for Silicate Materials

    Science.gov (United States)

    Chen, Yih-Kanq

    2016-01-01

    A thermal ablation model for silicates is proposed. The model includes the mass losses through the balance between evaporation and condensation, and through the moving molten layer driven by surface shear force and pressure gradient. This model can be applied in ablation simulations of the meteoroid or glassy Thermal Protection Systems for spacecraft. Time-dependent axi-symmetric computations are performed by coupling the fluid dynamics code, Data-Parallel Line Relaxation program, with the material response code, Two-dimensional Implicit Thermal Ablation simulation program, to predict the mass lost rates and shape change. For model validation, the surface recession of fused amorphous quartz rod is computed, and the recession predictions reasonably agree with available data. The present parametric studies for two groups of meteoroid earth entry conditions indicate that the mass loss through moving molten layer is negligibly small for heat-flux conditions at around 1 MW/cm(exp. 2).

  13. Radiation effects on lead silicate glass surfaces

    International Nuclear Information System (INIS)

    Radiation-induced changes in the microstructure of lead silicate glass were investigated in situ under Mg Kα irradiation in an ultra-high vacuum (UHV) environment by X-ray photoelectron spectroscopy (XPS). Lead-oxygen bond breaking resulting in the formation of pure lead was observed. The segregation, growth kinetics and the structural relaxation of the lead, with corresponding changes in the oxygen and silicon on the glass surfaces were studied by measuring the time-dependent changes in concentration, binding energy shifts, and the full width at half maximum. A bimodal distribution of the oxygen XPS signal, caused by bridging and non-bridging oxygens, was found during the relaxation process. All experimental data indicate a reduction of the oxygen concentration, a phase separation of the lead from the glass matrix, and the metallization of the lead occurred during and after the X-ray irradiation. (author)

  14. Redox kinetics and mechanism in silicate melts

    International Nuclear Information System (INIS)

    This work contributes to better understand iron redox reactions and mechanisms in silicate melts. It was conducted on compositions in both Na2O-B2O3-SiO2-FeO and Na2O-Al2O3-SiO2-FeO systems. The influence of boron-sodium and aluminum-sodium substitutions and iron content on properties and structure of glasses and on the iron redox kinetics has been studied by Raman, Moessbauer and XANES spectroscopies at the B and Fe K-edges. In borosilicate glasses, an increase in iron content or in the Fe3+/ΣFe redox state implies a structural rearrangement of the BO4 species in the glass network whereas the BO3 and BO4 relative proportions remain nearly constant. In all studied glasses and melts, Fe3+ is a network former in tetrahedral coordination, unless for aluminosilicates of ratio Al/Na≥1 where Fe3+ is a network modifier in five-fold coordination. Near Tg, diffusion of network modifying cations controls the iron redox kinetics along with a flux of electron holes. At liquidus temperatures, oxygen diffusion is considered to be the mechanism that governs redox reactions. This study shows the role played by the silicate network polymerization on the redox kinetics. In borosilicate melts, iron redox kinetics depends on the boron speciation between BO3 and BO4 that depends itself on the sodium content. Furthermore, an increase in the network-former/network-modifier ratio implies a decrease in oxygen diffusion that results in a slowing down of the redox kinetics. The obtained results allow a description of the iron redox kinetics for more complex compositions as natural lavas or nuclear waste model glasses. (author)

  15. Imaging of drug loading distributions in individual microspheres of calcium silicate hydrate - an X-ray spectromicroscopy study

    Science.gov (United States)

    Guo, Xiaoxuan; Wang, Zhiqiang; Wu, Jin; Wang, Jian; Zhu, Ying-Jie; Sham, Tsun-Kong

    2015-04-01

    Imaging is one of the most direct and ideal ways to track drug loading distributions in drug carriers on the molecular level, which will facilitate the optimization of drug carriers and drug loading capacities. Herein, we report the mapping of an individual mesoporous calcium silicate hydrate (CSH) microsphere before and after the loading of ibuprofen (IBU) and the interactions between drug carriers and drug molecules simultaneously by scanning transmission X-ray microscopy (STXM). Nanoscaled X-ray absorption near edge structure (XANES) spectroscopy clearly indicates that IBU is bonded to calcium and silicate sites via carboxylic acid groups. More importantly, STXM has been successfully used to determine the absolute thickness of IBU, revealing its distribution in the CSH microsphere.Imaging is one of the most direct and ideal ways to track drug loading distributions in drug carriers on the molecular level, which will facilitate the optimization of drug carriers and drug loading capacities. Herein, we report the mapping of an individual mesoporous calcium silicate hydrate (CSH) microsphere before and after the loading of ibuprofen (IBU) and the interactions between drug carriers and drug molecules simultaneously by scanning transmission X-ray microscopy (STXM). Nanoscaled X-ray absorption near edge structure (XANES) spectroscopy clearly indicates that IBU is bonded to calcium and silicate sites via carboxylic acid groups. More importantly, STXM has been successfully used to determine the absolute thickness of IBU, revealing its distribution in the CSH microsphere. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr07471h

  16. High CO2 and silicate limitation synergistically increase the toxicity of Pseudo-nitzschia fraudulenta.

    Directory of Open Access Journals (Sweden)

    Avery O Tatters

    Full Text Available Anthropogenic CO(2 is progressively acidifying the ocean, but the responses of harmful algal bloom species that produce toxins that can bioaccumulate remain virtually unknown. The neurotoxin domoic acid is produced by the globally-distributed diatom genus Pseudo-nitzschia. This toxin is responsible for amnesic shellfish poisoning, which can result in illness or death in humans and regularly causes mass mortalities of marine mammals and birds. Domoic acid production by Pseudo-nitzschia cells is known to be regulated by nutrient availability, but potential interactions with increasing seawater CO(2 concentrations are poorly understood. Here we present experiments measuring domoic acid production by acclimatized cultures of Pseudo-nitzschia fraudulenta that demonstrate a strong synergism between projected future CO(2 levels (765 ppm and silicate-limited growth, which greatly increases cellular toxicity relative to growth under modern atmospheric (360 ppm or pre-industrial (200 ppm CO(2 conditions. Cellular Si:C ratios decrease with increasing CO(2, in a trend opposite to that seen for domoic acid production. The coastal California upwelling system where this species was isolated currently exhibits rapidly increasing levels of anthropogenic acidification, as well as widespread episodic silicate limitation of diatom growth. Our results suggest that the current ecosystem and human health impacts of toxic Pseudo-nitzschia blooms could be greatly exacerbated by future ocean acidification and 'carbon fertilization' of the coastal ocean.

  17. Argillization by descending acid at Steamboat Springs, Nevada

    Science.gov (United States)

    Schoen, R.; White, D.E.; Hemley, J.J.

    1974-01-01

    Steamboat Springs, Nevada, an area of present-day hot springs, clearly illustrates the genetic dependence of some kaolin deposits on hot-spring activity. Andesite, granodiorite and arkosic sediments are locally altered at the land surface to siliceous residues consisting of primary quartz and anatase, plus opal from primary silicates. These siliceous residues commonly exhibit the textural and structural features of their unaltered equivalents. Beneath the siliceous residues, kaolin and alunite replace primary silicates and fill open spaces, forming a blanketlike deposit. Beneath the kaolin-alunite zone, montmorillonite, commonly accompanied by pyrite, replaces the primary silicates. On the ground surface, the same alteration mineral zones can he traced outward from the siliceous residue; however, hematite rather than pyrite accompanies montmorillonite. Chemical analysis indicates that sulfuric acid is the active altering agent. The acid forms from hydrogen sulfide that exsolves from deep thermal water, rises above the water table and is oxidized by sulfur-oxidizing bacteria living near the ground surface. This acid dissolves in precipitation or condensed water vapor and percolates downward destroying most of the primary minerals producing a siliceous residue. Coincidence of the water table with the downward transition from siliceous residue to kaolin alunite signifies decreasing hydrogen metasomatism because of dilution of descending acid by ground water. In hot-spring areas, beds of siliceous sinter deposited at the surface by hypogene thermal water look, superficially, like areas of surficial acid alteration. Features diagnostic of a surficial alteration are the relict rock structures of a siliceous residue and a kaolin-alunite zone immediately beneath. ?? 1974.

  18. 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.

  19. 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...

  20. 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.

  1. 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.

  2. Chemistry of the subalkalic silicic obsidians

    Science.gov (United States)

    MacDonald, Ray; Smith, Robert L.; Thomas, John E.

    1992-01-01

    Nonhydrated obsidians are quenched magmatic liquids that record in their chemical compositions details of the tectonic environment of formation and of the differentiation mechanisms that affected their subsequent evolution. This study attempts to analyze, in terms of geologic processes, the compositional variations in the subalkalic silicic obsidians (Si02≥70 percent by weight, molecular (Na2O+K20)>Al2O3). New major- and trace-element determinations of 241 samples and a compilation of 130 published major-element analyses are reported and interpreted. Obsidians from five different tectonic settings are recognized: (1) primitive island arcs, (2) mature island arcs, (3) continental margins, (4) continental interiors, and (5) oceanic extensional zones. Tectonomagmatic discrimination between these groups is successfully made on Nb-Ta, Nb-FeOt and Th-Hf-Ta plots, and compositional ranges and averages for each group are presented. The chemical differences between groups are related to the type of crust in which magmas were generated. With increasingly sialic (continental type) crust, the obsidians show overall enrichment in F, Be, Li, Mo, Nb, Rb, Sn, Ta, U, W, Zn, and the rare-earth elements, and depletion in Mg, Ca, Ba, Co, Sc, Sr, and Zr. They become more potassic, have higher Fe/Mg and F/Cl ratios, and lower Zr/Hf, Nb/Ta, and Th/U ratios. Higher values of total rare-earth elements are accompanied by light rare-earth-element enrichment and pronounced negative Eu anomalies. An attempt is made to link obsidian chemistry to genetic mechanlism. Two broad groups of rocks are distinguished: one generated where crystal-liquid processes dominated (CLPD types), which are the products of crustal anatexis, possibly under conditions of low halogen fugacity, ± crystal fractionation ± magma mixing; and a second group represented by rocks formed in the upper parts of large magma chambers by interplays of crystal fractionation, volatile transfer, magma mixing, and possibly various

  3. Phosphorus availability in oxidic soils treated with lime and silicate applications

    Directory of Open Access Journals (Sweden)

    Aline da Silva Sandim

    2014-08-01

    Full Text Available Based on the assumption that silicate application can raise soil P availability for crops, the aim of this research was to compare the effect of silicate application on soil P desorption with that of liming, in evaluations based on two extractors and plant growth. The experiment was carried out in randomized blocks with four replications, in a 3 × 3 × 5 factorial design, in which three soil types, three P rates, and four soil acidity correctives were evaluated in 180 experimental plots. Trials were performed in a greenhouse using corn plants in 20-dm³ pots. Three P rates (0, 50 and 150 mg dm-3 were applied in the form of powder triple superphosphate and the soil was incubated for 90 days. After this period, soil samples were collected for routine chemical analysis and P content determination by the extraction methods resin, Mehlich-1 and remaining P. Based on the results, acidity correctives were applied at rates calculated for base saturation increased to 70 %, with subsequent incubation for 60 more days, when P content was determined again. The acidity correctives consisted of: dolomitic lime, steelmaking slag, ladle furnace slag, and wollastonite. Therefore, our results showed that slags raised the soil P content more than lime, suggesting a positive correlation between P and Si in soil. Silicon did not affect the extractor choice since both Mehlich-1 and resin had the same behavior regarding extracted P when silicon was applied to the soil. For all evaluated plant parameters, there was significant interaction between P rates and correctives; highest values were obtained with silicate.

  4. OPTIMAL METHOD FOR PREPARATION OF SILICATE ROCK SAMPLES FOR ANALYTICAL PURPOSES

    Directory of Open Access Journals (Sweden)

    Maja Vrkljan

    2004-12-01

    Full Text Available The purpose of this study was to determine an optimal dissolution method for silicate rock samples for further analytical purposes. Analytical FAAS method of determining cobalt, chromium, copper, nickel, lead and zinc content in gabbro sample and geochemical standard AGV-1 has been applied for verification. Dissolution in mixtures of various inorganic acids has been tested, as well as Na2CO3 fusion technique. The results obtained by different methods have been compared and dissolution in the mixture of HNO3 + HF has been recommended as optimal.

  5. The di- and tricalcium silicate dissolutions

    International Nuclear Information System (INIS)

    In this study, a specially designed reactor connected to an ICP spectrometer enabled the careful determination of the dissolution rates of C3S, C2S and CaO, respectively, over a broad range of concentration of calcium and silicates under conditions devoid of C–S–H. The kinetic laws, bridging the dissolution rates and the undersaturations, were obtained after extrapolation of rate zero allowing the estimation of the true experimental solubility products of C3S (Ksp = 9.6 · 10−23), C2S (Ksp = 4.3 · 10−18) and CaO (Ksp = 9.17 · 10−6). The latter are then compared to the solubilities calculated from the enthalpies of formation. We propose that the observed deviations result from the protonation of the unsaturated oxygen atoms present at the surface of these minerals. Hydration rates measured in cement pastes or in C3S pastes are in excellent agreement with the kinetic law found in this study for C3S under conditions undersaturated with respect to C–S–H

  6. 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.

  7. 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.

  8. 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.

  9. 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...

  10. 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.

  11. Characterization of the Aqueous Uranyl-Silicate Complex Using X-Ray Absorption Spectroscopy and Ab Initio Modeling

    Science.gov (United States)

    Vu, M.; Massey, M.; Huang, P.

    2015-12-01

    The speciation of aqueous uranium ions is an important factor in predicting its mobility and fate in the environment. Two major controls on speciation are pH and the presence of complexing ligands. For the case of aqueous uranyl, UO22+(aq), some common complexes include uranyl-hydroxy, uranyl-carbonato, and uranyl-calcium-carbonato complexes, all of which differ in chemical reactivity and mobility. Uranyl-silicate complexes are also known but remain poorly characterized. In this work, we studied uranyl speciation in a series of aqueous solutions of 0.1 mM uranyl and 2 mM silicate with pH ranging from 4 to 7. Extended X-Ray Absorption Fine Structure (EXAFS) spectra of these samples were recorded at the Stanford Synchrotron Radiation Lightsource (SLAC National Accelerator Laboratory). Of particular note are the uranyl and silicate concentrations employed in our experiments, which are lower than conditions in previously reported EXAFS studies and approach conditions in natural groundwater systems. Preliminary analyses of EXAFS data indicate that uranyl speciation changes across the pH range, consistent with published thermodynamic data that suggest uranyl-silicate complexes may be important for pH ~ 5 and below, while uranyl-carbonato complexes become dominant at circumneutral pH. To guide the interpretation of the EXAFS data, molecular-scale simulations were carried out using density functional theory. We considered two classes of models: (i) hydrated clusters, and (ii) ab initio molecular dynamics simulations of 3D-periodic models involving uranyl and silicate in water. These calculations reveal that at pH ~ 5, the uranyl speciation is the [UO2(H2O)4H3SiO4]+ complex formed by the substitution of an equatorial uranyl water with a monodentate silicate ligand. The evidence from experiments and simulations provide a consistent picture for the uranyl-silicate complex, which may be important in the transport of uranyl in acidic, silicate-rich waters.

  12. History of Nebular Processing Traced by Silicate Stardust in IDPS

    Science.gov (United States)

    Messenger, Scott R.; Keller, L. P.; Nakamura-Messenger, K.

    2010-01-01

    Chondritic porous interplanetary dust particles (CP-IDPs) may be the best preserved remnants of primordial solar system materials, in part because they were not affected by parent body hydrothermal alteration. Their primitive characteristics include fine grained, unequilibrated, anhydrous mineralogy, enrichment in volatile elements, and abundant molecular cloud material and silicate stardust. However, while the majority of CP-IDP materials likely derived from the Solar System, their formation processes and provenance are poorly constrained. Stardust abundances provide a relative measure of the extent of processing that the Solar System starting materials has undergone in primitive materials. For example, among primitive meteorites silicate stardust abundances vary by over two orders of magnitude (less than 10-200 ppm). This range of abundances is ascribed to varying extents of aqueous processing in the meteorite parent bodies. The higher average silicate stardust abundances among CP-IDPs (greater than 375 ppm) are thus attributable to the lack of aqueous processing of these materials. Yet, silicate stardust abundances in IDPs also vary considerably. While the silicate stardust abundance in IDPs having anomalous N isotopic compositions was reported to be 375 ppm, the abundance in IDPs lacking N anomalies is less than 10 ppm. Furthermore, these values are significantly eclipsed among some IDPs with abundances ranging from 2,000 ppm to 10,000 ppm. Given that CP-IDPs have not been significantly affected by parent body processes, the difference in silicate stardust abundances among these IDPs must reflect varying extents of nebular processing. Here we present recent results of a systematic coordinated mineralogical/isotopic study of large cluster IDPs aimed at (1) characterizing the mineralogy of presolar silicates and (2) delineating the mineralogical and petrographic characteristics of IDPs with differing silicate stardust abundances. One of the goals of this study is

  13. Evolution of trees and mycorrhizal fungi intensifies silicate mineral weathering

    OpenAIRE

    Quirk, J; D. J. Beerling; S. A. Banwart; Kakonyi, G.; Romero-Gonzalez, M. E.; Leake, J.R.

    2012-01-01

    Forested ecosystems diversified more than 350 Ma to become major engines of continental silicate weathering, regulating the Earth's atmospheric carbon dioxide concentration by driving calcium export into ocean carbonates. Our field experiments with mature trees demonstrate intensification of this weathering engine as tree lineages diversified in concert with their symbiotic mycorrhizal fungi. Preferential hyphal colonization of the calcium silicate-bearing rock, basalt, progressively increase...

  14. Silicate Urolithiasis during Long-Term Treatment with Zonisamide

    OpenAIRE

    Yukio Homma; Akira Ishikawa; Kanami Takaya; Teruaki Kobayashi; Yorito Nose; Toshikazu Sato; Satoru Taguchi

    2013-01-01

    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 epilep...

  15. Influence of PC superplasticizers on tricalcium silicate hydration.

    OpenAIRE

    Pourchet, S.; Comparet, C.; Nicoleau, L.; Nonat, A.

    2007-01-01

    The influence of polycarboxylate superplasticizers with variations of content of anionic groups was studied on pure tricalcium silicate hydration. The hydration in diluted suspension has been investigated by conductimetry, calorimetry, and ionic and total organic carbon analysis of the liquid phase. The tricalcium silicate hydration is always delayed in presence of polycarboxylate superplasticizer. Moreover, the delay can be correlated with the number of carboxylate groups which are on the ad...

  16. Effects of silicate application on soil fertility and wheat yield

    OpenAIRE

    Marcos Vinícius Mansano Sarto; Maria do Carmo Lana; Leandro Rampim; Jean Sérgio Rosset; Jaqueline Rocha Wobeto

    2015-01-01

    An improvement in soil chemical properties and crop development with silicate application has been confirmed in several plant species. The effects of silicate application on soil chemical properties and wheat growth were investigated in the present study. The experiment was carried out in 8-L plastic pots in a greenhouse. Treatments were arranged in a randomized block design in a 3 × 5 factorial: three soils [Rhodic Acrudox (Ox1), Rhodic Hapludox (Ox2) and Arenic Hapludult (Ult)] and five sil...

  17. Silicate fertilizer and irrigation depth in corn production

    OpenAIRE

    Edvaldo Eloy Dantas Júnior; Lucia Helena Garófala Chaves; Fernando Antônio Melo da Costa; Hans Raj Gheyi

    2013-01-01

    Calcium-magnesium silicates improve the soil physicochemical properties and provide benefits to plant nutrition, since they are sources of silica, calcium and magnesium. The objective of this study was to evaluate the grain yield of irrigated corn fertilized with calcium-magnesium silicate. The experiment was carried out in a greenhouse in Campina Grande - PB, Brazil, using plastic pots containing 80 kg of soil. The treatments consisted of the combination of four irrigation depths, related to...

  18. Mineralogy and chemical compositions of Colomera (IIE) silicate inclusions

    OpenAIRE

    Hsu, W.; H. Takeda; Huss, G. R.; Wasserburg, G. J.

    1997-01-01

    Irons of groups lAB and IIE contain silicate inclusions. In IAB irons, these inclusions are basically chondritic, but in IIE they vary from chondritic to highly differentiated [1,2]. In this work, we present detailed studies of mineralogy and trace-element geochemistry of eight silicate inclusions from Colomera with the goal of better understanding early planetary differentiation and possible genetic relationships between iron and stony meteorites.

  19. Spinning dust emission from ultrasmall silicates: emissivity and polarization spectrum

    OpenAIRE

    Hoang, Thiem; Vinh, Nguyen Anh; 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...

  20. H-Bond interactions between silicates and water during zeolite pre-nucleation.

    Science.gov (United States)

    Mora-Fonz, Miguel J; Catlow, C Richard A; Lewis, Dewi W

    2008-11-21

    The relative strength of water-water, water-silicate and silicate-silicate interactions are studied, in order to explain the low solubility of the monomer (Si(OH)(4)), and determine the degree of dispersion of silicate clusters in solution during the hydrothermal synthesis of zeolites. We will show how the hydrogen bond interactions between water and monomeric silicate species are similar to that in pure water, whilst monomer-monomer interactions are stronger. However, when larger silicate species are also considered we find the relative hydrogen-bonding strength to follow: water-water silicate-water silicate-silicate. The effects of pH are also considered. The implications of the relative strength of these interactions on the formation of larger silicate species, leading to zeolite pre-nucleation, are discussed. PMID:18979042

  1. 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.

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

    Directory of Open Access Journals (Sweden)

    DIANA HORKAVCOVÁ

    2012-12-01

    Full Text Available 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 contained calcium nitrate and triethyl phosphate. Mechanically and chemically treated titanium substrates were dipped into sols and dried and fired. Silicate coatings from the first group were also chemically treated in 10 mol.l-1 solution of sodium hydroxide. All coatings were measured to determine their adhesive and bioactive properties and furthermore the antibacterial properties were tested in the case of first group. Surfaces of the coated substrates were investigated after the firing and after the individual tests with optical and electron microscopy and X-ray microdiffraction. A tape test demonstrated excellent adhesive property of all coatings to the substrate, classified with degree 5. A static in vitro test demonstrated bioactivity of nearly all the coatings. The basic silicate coating from the first group and one type of coating from the second group were identified as inert. Antibacterial properties of silicate coatings containing silver showed to be different when tested against Escherichia coli bacteria. A complete inhibition of the growth of bacteria under our experimental conditions was observed for the coating containing silver and monetite and a partial inhibition of the growth of bacteria for coatings containing silver and silver in combination with brushite.

  3. 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

  4. Heterogeneous nucleation of protein crystals on fluorinated layered silicate.

    Directory of Open Access Journals (Sweden)

    Keita Ino

    Full Text Available Here, we describe an improved system for protein crystallization based on heterogeneous nucleation using fluorinated layered silicate. In addition, we also investigated the mechanism of nucleation on the silicate surface. Crystallization of lysozyme using silicates with different chemical compositions indicated that fluorosilicates promoted nucleation whereas the silicates without fluorine did not. The use of synthesized saponites for lysozyme crystallization confirmed that the substitution of hydroxyl groups contained in the lamellae structure for fluorine atoms is responsible for the nucleation-inducing property of the nucleant. Crystallization of twelve proteins with a wide range of pI values revealed that the nucleation promoting effect of the saponites tended to increase with increased substitution rate. Furthermore, the saponite with the highest fluorine content promoted nucleation in all the test proteins regardless of their overall net charge. Adsorption experiments of proteins on the saponites confirmed that the density of adsorbed molecules increased according to the substitution rate, thereby explaining the heterogeneous nucleation on the silicate surface.

  5. Silicate fertilizer and irrigation depth in corn production

    Directory of Open Access Journals (Sweden)

    Edvaldo Eloy Dantas Júnior

    2013-08-01

    Full Text Available Calcium-magnesium silicates improve the soil physicochemical properties and provide benefits to plant nutrition, since they are sources of silica, calcium and magnesium. The objective of this study was to evaluate the grain yield of irrigated corn fertilized with calcium-magnesium silicate. The experiment was carried out in a greenhouse in Campina Grande - PB, Brazil, using plastic pots containing 80 kg of soil. The treatments consisted of the combination of four irrigation depths, related to water replacement of 50, 75, 100 and 125% of the crop evapotranspiration, with fertilizer levels of 0, 82, 164 and 246 g of calcium-magnesium silicate, with three replications. The experimental design was in randomized blocks, with the irrigation depths distributed in bands while the silicon levels constituted the subplots. Corn yield was influenced by calcium-magnesium silicate and by irrigation depth, obtaining the greatest grain yield with the dose of 164 g pot-1 irrigated at the highest water level. The water-use efficiency of in corn production tended to decrease when the irrigation depth was increased. The best water-use efficiency was observed when the irrigation level was between 87 and 174 mm, and the dose of silicate was 164 g pot-1.

  6. Silicate Dust in Evolved Protoplanetary Disks: Growth, Sedimentation, and Accretion

    CERN Document Server

    Sicilia-Aguilar, Aurora; Watson, Dan; Bohac, Chris; Henning, Thomas; Bouwman, Jeroen; 10.1086/512121

    2009-01-01

    We present the Spitzer IRS spectra for 33 young stars in Tr 37 and NGC 7160. The sample includes the high- and intermediate-mass stars with MIPS 24 microns excess, the only known active accretor in the 12 Myr-old cluster NGC 7160, and 19 low-mass stars with disks in the 4 Myr-old cluster Tr 37. We examine the 10 microns silicate feature, present in the whole sample of low-mass star and in 3 of the high- and intermediate-mass targets, and we find that PAH emission is detectable only in the Herbig Be star. We analyze the composition and size of the warm photospheric silicate grains by fitting the 10 microns silicate feature, and study the possible correlations between the silicate characteristics and the stellar and disk properties (age, SED slope, accretion rate, spectral type). We find indications of dust settling with age and of the effect of turbulent enrichment of the disk atmosphere with large grains. Crystalline grains are only small contributors to the total silicate mass in all disks, and do not seem t...

  7. 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.

  8. Effect of Minor Elements on Silicate Cement Clinker

    Institute of Scientific and Technical Information of China (English)

    HUANG Congyun; ZHANG Mingfei; ZHANG Meixiang; LONG Shizong; CHEN Yuankui; MA Baoguo

    2005-01-01

    The effect of rare-earth and HX addition agent on the burn-ability of silicate cement clinker was investigated by orthogonal experiment. The result shows, compared with blank sample, f- CaO of the samples added with rare-earth and HX agent drops by 84.95% , its 3d and 28d compressive strength enhances by 24.40%and 16.90%, respectively. It was discovered by means of X-ray diffraction and high temperature microscope analysis that sintering temperature of the sample added with rare-earth and HX addition agent is about 1320℃. At the same time, the burning temperature of tricalcium silicate desends and its crystal growth forming-rate increases.Tricalcium silicate content in burning clinker is higher and its crystal is larger.

  9. Functional substitution of coordination polyhedron in crystal structure of silicates

    Institute of Scientific and Technical Information of China (English)

    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-O 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.

  10. Electric field-induced softening of alkali silicate glasses

    Energy Technology Data Exchange (ETDEWEB)

    McLaren, C.; Heffner, W.; Jain, H. [Department of Materials Science and Engineering, Lehigh University, Bethlehem, Pennsylvania 18015 (United States); Tessarollo, R.; Raj, R. [Department of Mechanical Engineering, University of Colorado at Boulder, Boulder, Colorado 80309 (United States)

    2015-11-02

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

  11. Calcined sodium silicate as solid base catalyst for biodiesel production

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Feng; Peng, Zhen-Gang; Dai, Jian-Ying; Xiu, Zhi-Long [Department of Bioscience and Biotechnology, School of Environmental and Biological Science and Technology, Dalian University of Technology, Dalian 116024 (China)

    2010-03-15

    This paper examined the use of calcined sodium silicate as a novel solid base catalyst in the transesterification of soybean oil with methanol. The calcined sodium silicate was characterized by DTA-TG, Hammett indicator method, XRD, SEM, BET, IR and FT-IR. It catalyzed the transesterification of soybean oil to biodiesel with a yield of almost 100% under the following conditions: sodium silicate of 3.0 wt.%, a molar ratio of methanol/oil of 7.5:1, reaction time of 60 min, reaction temperature of 60 C, and stirring rate of 250 rpm. The oil containing 4.0 wt.% water or 2.5 wt.% FFA could also be transesterified by using this catalyst. The catalyst can be reused for at least 5 cycles without loss of activity. (author)

  12. Formation of Magnesium Silicates is Limited around Evolved Stars

    Science.gov (United States)

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

    2009-05-01

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

  13. 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.

  14. 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.

  15. Mantle Mineral/Silicate Melt Partitioning

    Science.gov (United States)

    McFarlane, E. A.; Drake, M. J.

    1992-07-01

    Introduction: The partitioning of elements among mantle phases and silicate melts is of interest in unraveling the early thermal history of the Earth. It has been proposed that the elevated Mg/Si ratio of the upper mantle of the Earth is a consequence of the flotation of olivine into the upper mantle (Agee and Walker, 1988). Agee and Walker (1988) have generated a model via mass balance by assuming average mineral compositions to generate upper mantle peridotite. This model determines that upper mantle peridotite could result from the addition of 32.7% olivine and 0.9% majorite garnet into the upper mantle, and subtraction of 27.6% perovskite from the upper mantle (Agee and Walker, 1988). The present contribution uses experimental data to examine the consequences of such multiple phase fractionations enabling an independent evaluation of the above mentioned model. Here we use Mg-perovskite/melt partition coefficients from both a synthetic and a natural system (KLB-1) obtained from this laboratory. Also used are partition coefficient values for majorite garnet/melt, beta spinel/melt and olivine/melt partitioning (McFarlane et al., 1991b; McFarlane et al., 1992). Multiple phase fractionations are examined using the equilibrium crystallization equation and partition coefficient values. The mineral proportions determined by Agee and Walker (1988) are converted into weight fractions and used to compute a bulk partition coefficient value. Discussion: There has been a significant debate concerning whether measured values of trace element partition coefficients permit large-scale fractionation of liquidus phases from an early terrestrial magma ocean (Kato et al., 1988a,b; Walker and Agee, 1989; Drake, 1989; Drake et al., 1991; McFarlane et al., 1990, 1991). It should be noted that it is unclear which, if any, numerical values of partition coefficients are appropriate for examining this question, and certainly the assumptions for the current model must be more fully

  16. Imaging of drug loading distributions in individual microspheres of calcium silicate hydrate--an X-ray spectromicroscopy study.

    Science.gov (United States)

    Guo, Xiaoxuan; Wang, Zhiqiang; Wu, Jin; Wang, Jian; Zhu, Ying-Jie; Sham, Tsun-Kong

    2015-04-21

    Imaging is one of the most direct and ideal ways to track drug loading distributions in drug carriers on the molecular level, which will facilitate the optimization of drug carriers and drug loading capacities. Herein, we report the mapping of an individual mesoporous calcium silicate hydrate (CSH) microsphere before and after the loading of ibuprofen (IBU) and the interactions between drug carriers and drug molecules simultaneously by scanning transmission X-ray microscopy (STXM). Nanoscaled X-ray absorption near edge structure (XANES) spectroscopy clearly indicates that IBU is bonded to calcium and silicate sites via carboxylic acid groups. More importantly, STXM has been successfully used to determine the absolute thickness of IBU, revealing its distribution in the CSH microsphere.

  17. 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.

  18. Discovery of ancient silicate stardust in a meteorite.

    Science.gov (United States)

    Nguyen, Ann N; Zinner, Ernst

    2004-03-01

    We have discovered nine presolar silicate grains from the carbonaceous chondrite Acfer 094. Their anomalous oxygen isotopic compositions indicate formation in the atmospheres of evolved stars. Two grains are identified as pyroxene, two as olivine, one as a glass with embedded metal and sulfides (GEMS), and one as an Al-rich silicate. One grain is enriched in 26Mg, which is attributed to the radioactive decay of 26Al and provides information about mixing processes in the parent star. This discovery opens new means for studying stellar processes and conditions in various solar system environments.

  19. 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.

  20. Aluminum-silicates flotation with quaternary ammonium salts

    Institute of Scientific and Technical Information of China (English)

    王毓华; 胡岳华; 陈湘清

    2003-01-01

    The zeta potential measurements show that the flotation separation of diaspore from kaolinite, illite and pyrophyllite could be achieved in the range of pH 46.5 with cationic collectors. A special quaternary ammonium salts(DTAL) shows better selectivity than that the dodecyl amine(DDA) does for the flotation of three silicates. The closed-circuit flotation results show that the reverse flotation de-silicate can be achieved with DTAL as collector, a new inorganic reagent(SFL) as depressant and MIBC as frother to obtain a bauxite concentrate m(Al2O3)/m(SiO2)>10, Al2O3 recovery>86%).

  1. High-Q bismuth silicate nonlinear glass microsphere resonators

    OpenAIRE

    Wang, Pengfei; Murugan, Ganapathy; Lee, Timothy; Ding, Ming; Brambilla, Gilberto; Semenova, Yuliya; Wu, Qiang; Koizumi,Fumihito; Farrell, Gerald

    2012-01-01

    The fabrication and characterization of a bismuth-silicate glass microsphere resonator has been demonstrated. At wavelengths near 1550 nm, high-modes can be efficiently excited in a 179-μm diameter bismuth-silicate glass microsphere via evanescent coupling using a tapered silica fiber with a waist diameter of circa 2 μm. Resonances with Q-factors as high as were observed. The dependence of the spectral response on variations in the input power level was studied in detail to gain an insight in...

  2. Lead Silicate Glass Microsphere Resonators With Absorption-Limited Q

    OpenAIRE

    Wang, Pengfei; Murugan, Genapathy; Lee, Timothy; Feng, Xian; Semenova, Yuliya; Wu, Qiang; Loh, Wei; Brambilla, Gilberto; Wilkinson, James; Farrell, Gerald

    2011-01-01

    We report the fabrication and characterization of a lead-silicate glass microsphere resonator. We show that at the wavelengths near 1555 nm high Q modes can be efficiently excited from a 109 μm diameter lead-silicate glass microsphere via evanescent coupling using a tapered silica fiber with a waist diameter of 2 μm. Resonances with Q-factors as high as 0.9×107 were observed. This is very close to the theoretical material-limited Q-factor and is the highest Q-factor reported so far from a non...

  3. Nicotine–magnesium aluminum silicate microparticle surface modified with chitosan for mucosal delivery

    Energy Technology Data Exchange (ETDEWEB)

    Kanjanakawinkul, Watchara [Faculty of Pharmaceutical Sciences, Khon Kaen University, Khon Kaen 40002 (Thailand); Rades, Thomas [School of Pharmacy, University of Otago, Dunedin 9054 (New Zealand); Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, DK-2100 Copenhagen (Denmark); Puttipipatkhachorn, Satit [Department of Manufacturing Pharmacy, Faculty of Pharmacy, Mahidol University, Bangkok 10400 (Thailand); Pongjanyakul, Thaned, E-mail: thaned@kku.ac.th [Faculty of Pharmaceutical Sciences, Khon Kaen University, Khon Kaen 40002 (Thailand)

    2013-04-01

    Magnesium aluminum silicate (MAS), a negatively charged clay, and nicotine (NCT), a basic drug, can interact electrostatically to form microparticles. Chitosan (CS) was used for the surface modification of the microparticles, and a lyophilization method was used to preserve the original particle morphology. The microparticles were characterized in terms of their physicochemical properties, NCT content, mucoadhesive properties, and release and permeation across porcine esophageal mucosa. The results showed that the microparticles formed via electrostatic interaction between MAS and protonated NCT had an irregular shape and that their NCT content increased with increasing NCT ratios in the microparticle preparation solution. High molecular weight CS (800 kDa) adsorbed to the microparticle surface and induced a positive surface charge. CS molecules intercalated into the MAS silicate layers and decreased the crystallinity of the microparticles, leading to an increase in the release rate and diffusion coefficient of NCT from the microparticles. Moreover, the microparticle surface modified with CS was found to have higher NCT permeation fluxes and mucoadhesive properties, which indicated the significant role of CS for NCT mucosal delivery. However, the enhancement of NCT permeation and of mucoadhesive properties depended on the molecular weight and concentration of CS. These findings suggest that NCT-MAS microparticle surface modified with CS represents a promising mucosal delivery system for NCT. Highlights: ► Nicotine–magnesium aluminum silicate microparticles were prepared using electrostatic interaction. ► Lyophilization was used for drying and maintaining an original morphology of the microparticles. ► Chitosan (CS) was used for surface modification of the microparticles at acidic pH. ► Surface modification using CS caused an increase in release and permeation of nicotine. ► Microparticle surface-modified with CS presented better mucoadhesive properties.

  4. Core Formation Timescale, Silicate-Metal Equilibration, and W Diffusivity

    Science.gov (United States)

    Yin, Q.; Jacobsen, B.; Tinker, D.; Lesher, C.

    2004-12-01

    The extent to which material accreted to the proto-Earth and segregated to form the core was chemically and isotopically equilibrated with the silicate mantle is an outstanding problem in planetary science. This is particularly important when attempting to assign a meaningful age for planetary accretion and core formation based on Hf-W isotope systematics. The Earth and other terrestrial planets likely formed by accretion of previously differentiated planetesimals. For the planetesimals themselves the most important energy source for metal-silicate differentiation is the combined radioactive heating due to decay of 26Al (half-life 0.7 Ma) and 60Fe (half-life 1.5 Ma). It is expected that the fractionation of Hf and W during planetesimal core formation will lead to a divergence in the W isotopic compositions of the core and silicate portions of these bodies. This expectation is supported by the enormously radiogenic 182W signatures reported for basaltic eucrites. The observation that the W isotopic compositions of the silicate portions of Earth, Moon and Mars are similar and markedly less radiogenic than eucrites suggests that during planet accretion the pre-differentiated metallic core material containing low 182W must have equilibrated extensively with the more radiogenic (high 182W) silicate material to subdue the ingrowth of 182W in the silicate mantle of the planets. The standard theory of planet formation predicts that after runaway and oligarchic growth, the late stage of planet formation is characterized by impact and merging of Mars-sized objects. This is a tremendously energetic process estimated to raise the temperature of the proto-Earth to about 7000K (a temperature equivalent to a mass spectrometer's plasma source, which indiscriminately ionizes all incoming elements). After the giant impacts, the proto-Earth had a luminosity and surface temperature close to a low mass star for a brief period of time. Stevenson (1990) argued that emulsification caused

  5. Non-conservative controls on distribution of dissolved silicate in Cochin Backwaters

    Digital Repository Service at National Institute of Oceanography (India)

    Balachandran, K.K.; Sankaranarayanan, V.N.; Joseph, T.; Nair, M.

    Cochin backwater system was studied with regard to dissolved silicate (DSi) to understand its seasonal distribution and behaviour during estuarine mixing. Silicate had a linear relationship with salinity during the high river discharge period...

  6. 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.

  7. Modelling of the prebiotic synthesis of oligopeptides: silicate catalysts help to overcome the critical stage

    Science.gov (United States)

    Zamaraev, Kirill I.; Romannikov, Vyacheslav N.; Salganik, Rudolph I.; Wlassoff, Wjatschesslaw A.; Khramtsov, Valeriy V.

    1997-08-01

    On the basis of experimental studies of the initial stages of glycine oligomerization in aqueous suspension of zeolite and kaolinite catalysts, a model is suggested for the prebiotic synthesis of oligopeptides from α-amino acids. The formation of linear dipeptides by hydrolysis of one amide bond in the cyclic piperazinedione intermediate (formed from glycine spontaneously) is found to be the critical stage of the reaction. This stage is base catalyzed and its rate increases when pH of the medium goes up. The linear glycyl-glycine yield rises under effect of hydroxyl anions generated from different sources including insoluble silicates and soluble sodium bicarbonate. During prebiotic evolution silicates capable of cation-exchange can serve as local sources of the hydroxyl anions which dramatically accelerate formation of linear dipeptides from cyclic ones. Oligopeptides of higher molecular weight are then easily formed from the linear dipeptides at neutral pH, even in the absence of catalysts or sources of energy (e.g. such as light). The described catalytic synthesis could occur in the proximity of submarine hydrothermal vents.

  8. 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).

  9. Calorimetric signature of structural heterogeneity in a ternary silicate glass

    DEFF Research Database (Denmark)

    Zhang, Yanfei; Yang, G.; Yue, Yuanzheng

    2013-01-01

    We investigate the structural heterogeneity in a silicate glass by hyperquenching–annealing–calorimetry approach. The results show a striking phenomenon: two separated sub-Tg relaxation peaks appear on the calorimetric curve of the hyperquenched CaO–MgO–SiO2 glass, implying the existence of two...

  10. Annealing of Silicate Dust by Nebular Shocks at 10 AU

    Science.gov (United States)

    Harker, David E.; Desch, Steven J.; DeVincenzi, D. (Technical Monitor)

    2001-01-01

    Silicate dust grains in the interstellar medium are known to be mostly amorphous, yet crystalline silicate grains have been observed in many long-period comets and in protoplanetary disks. Annealing of amorphous silicate grains into crystalline grains requires temperatures greater than or approximately equal to 1000 K, but exposure of dust grains in comets to such high temperatures is apparently incompatible with the generally low temperatures experienced by comets. This has led to the proposal of models in which dust grains were thermally processed near the protoSun, then underwent considerable radial transport until they reached the gas giant planet region where the long-period comets originated. We hypothesize instead that silicate dust grains were annealed in situ, by shock waves triggered by gravitational instabilities. We assume a shock speed of 5 km/s, a plausible value for shocks driven by gravitational instabilities. We calculate the peak temperatures of pyroxene grains under conditions typical in protoplanetary disks at 5-10 AU. We show that in situ annealing of micron-sized dust grains can occur, obviating the need for large-scale radial transport.

  11. On the Dissolution Behavior of Sulfur in Ternary Silicate Slags

    Science.gov (United States)

    Kang, Youn-Bae; Park, Joo Hyun

    2011-12-01

    Sulfur dissolution behavior, in terms of sulfide capacity ( C S), in ternary silicate slags (molten oxide slags composed of MO - NO - SiO2, where M and N are Ca, Mn, Fe, and Mg), is discussed based on available experimental data. Composition dependence of the sulfur dissolution, at least in the dilute region of sulfur, may be explained by taking into account the cation-anion first-nearest-neighbor (FNN) interaction (stability of sulfide) and the cation-cation second-nearest-neighbor (SNN) interaction over O anion (oxygen proportions in silicate slags). When the Gibbs energy of a reciprocal reaction MO + NS = MS + NO is positive, the sulfide capacity of slags with virtually no SiO2 or low SiO2 concentration decreases as the concentration of MO increases. However, in some slags, as SiO2 concentration increases, replacing NO by MO at a constant SiO2 concentration may increase sulfide capacity when the basicity of NO is less than that of MO. This phenomenon is observed as rotation of iso- C S lines in ternary silicate slags, and it is explained by simultaneous consideration of the stability of sulfide and oxygen proportions in the silicate slags. It is suggested that a solution model for the prediction of sulfide capacity should be based on the actual dissolution mechanism of sulfur rather than on the simple empirical correlation.

  12. Small angle X-ray scattering from hydrating tricalcium silicate

    International Nuclear Information System (INIS)

    The small-angle X-ray scattering technique was used to study the structural evolution of hydrated tricalcium silicate at room temperature. The changes in specific area of the associated porosity and the evolution of density fluctuations in the solid hydrated phase were deduced from the scattering data. A correlation of these variations with the hydration mechanism is tried. (Author)

  13. Thermal conductivity and dielectric constant of silicate materials

    Science.gov (United States)

    Simon, I.; Wechsler, A. E.

    1968-01-01

    Report on the thermal conductivity and dielectric constant of nonmetallic materials evaluates the mechanisms of heat transfer in evacuated silicate powders and establishes the complex dielectric constant of these materials. Experimental measurements and results are related to postulated lunar surface materials.

  14. In vitro macrophage cytotoxicity of five calcium silicates.

    OpenAIRE

    Skaug, V; Davies, R.; Gylseth, B

    1984-01-01

    Five calcium silicate minerals (two naturally occurring and three synthetic compounds) with defined morphology and chemical composition were compared for their cytotoxic and lysosomal enzyme releasing effects on unstimulated mouse peritoneal macrophages in vitro. One synthetic material, a fibrous tobermorite, was cytotoxic towards the cells, and two naturally occurring wollastonites induced selective release of beta-glucuronidase from the cells.

  15. SINTERING AND SULFATION OF CALCIUM SILICATE-ALUMINATE

    Science.gov (United States)

    The effect of sintering on the reactivity of solids at high temperature was studied. The nature of the interaction was studied with calcium silicate-aluminate reacting with SO2 between 665 and 800 C. The kinetics of the sintering and sulfation processes were measured independentl...

  16. Silicate karst associated with lateritic formations (examples from eastern Niger)

    OpenAIRE

    Sponholz, Barbara

    2011-01-01

    Silicate and iron crust karst pits and sinkholes in eastern Niger are filled with reworked lateritic sediments or with unconsolidated palaeosoils and aeolian deposits. The fillings facies depend on the environmental conditions during deposition. Geomorphological and sedimentological studies on the karst fillings and the interpretation of various karst/filling associations allow an approach to the chronology of landscape development in eastern Niger plateaus.

  17. Determination of boron in silicates after ion exchange separation

    Science.gov (United States)

    Kramer, H.

    1955-01-01

    Existing methods for the determination of boron in silicates are not entirely satisfactory. Separation as the methyl ester is lengthy and frequently erratic. An accurate and rapid method applicable to glass, mineral, ore, and water samples uses ion exchange to remove interfering cations, and boron is determined titrimetrically in the presence of mannitol, using a pH meter to indicate the end point.

  18. Thermodynamic consistencies and anomalies among end-member silicate garnets.

    Science.gov (United States)

    Glasser, Leslie

    2014-09-01

    Materials with the garnet crystal structure include silicate minerals of importance both in geology, on account of their use in geothermobarometry, and industrially as abrasives. As a consequence of the former, there is considerable published thermodynamic information concerning them. We here examine this thermodynamic information for end-member silicate garnets (some of which are synthetic since not all occur in nature) for consistencies and anomalies, using thermodynamic relations between thermodynamic properties that we have established over recent years. The principal properties of interest are formula volume, heat capacity, entropy, formation enthalpy (from which the Gibbs energy may be obtained), and isothermal compressibility. A significant observation is that the ambient-temperature heat capacities of the silicate garnets are rather similar, whereas their ambient-temperature entropies are roughly proportional to their formula volumes. Evaluation of their Debye temperatures implies that their vibrational contributions to heat capacity are fully excited at ambient temperatures. The relatively small isothermal compressibilities of these garnets is related to the rigidity of their constituent silicate tetrahedra. We here establish additive single-ion values for each of the thermodynamic properties, which may be applied in estimating corresponding values for related materials.

  19. Nd3+ Doped Silicate Glass Photonic Crystal Fibres

    Institute of Scientific and Technical Information of China (English)

    YANG Lu-Yun; CHEN Dan-Ping; XIA Jin-An; WANG Chen; JIANG Xiong-Wei; ZHU Cong-Shan; QIU Jian-Rong

    2005-01-01

    @@ We report on the fabrication of two kinds of large core area Nd3+ doped silicate glass photonic crystal fibres, and demonstration of the fibre waveguiding properties. The measured minimum loss of one kind ofibres is 2.5 db/m at 660nm. The fibres sustain only a single mode at least over the wavelength range from 660nm to 980nm.

  20. 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. PMID:22035594

  1. Estimation of high temperature metal-silicate partition coefficients

    Science.gov (United States)

    Jones, John H.; Capobianco, Christopher J.; Drake, Michael J.

    1992-01-01

    It has been known for some time that abundances of siderophile elements in the upper mantle of the Earth are far in excess of those expected from equilibrium between metal and silicate at low pressures and temperatures. Murthy (1991) has re-examined this excess of siderophile element problem by estimating liquid metal/liquid silicate partition coefficients reduces from their measured values at a lower temperature, implying that siderophile elements become much less siderophilic at high temperatures. Murthy then draws the important conclusion that metal/silicate equilibrium at high temperatures can account for the abundances of siderophile elements in the Earth's mantle. Of course, his conclusion is critically dependent on the small values of the partition coefficients he calculates. Because the numerical values of most experimentally-determined partition coefficients increase with increasing temperature at both constant oxygen fugacity and at constant redox buffer, we think it is important to try an alternative extrapolation for comparison. We have computed high temperature metal/silicate partition coefficients under a different set of assumptions and show that such long temperature extrapolations yield values which are critically dependent upon the presumed chemical behavior of the siderophile elements in the system.

  2. Electron stimulated hydroxylation of a metal supported silicate film.

    Science.gov (United States)

    Yu, Xin; Emmez, Emre; Pan, Qiushi; Yang, Bing; Pomp, Sascha; Kaden, William E; Sterrer, Martin; Shaikhutdinov, Shamil; Freund, Hans-Joachim; Goikoetxea, Itziar; Wlodarczyk, Radoslaw; Sauer, Joachim

    2016-02-01

    Water adsorption on a double-layer silicate film was studied by using infrared reflection-absorption spectroscopy, thermal desorption spectroscopy and scanning tunneling microscopy. Under vacuum conditions, small amounts of silanols (Si-OH) could only be formed upon deposition of an ice-like (amorphous solid water, ASW) film and subsequent heating to room temperature. Silanol coverage is considerably enhanced by low-energy electron irradiation of an ASW pre-covered silicate film. The degree of hydroxylation can be tuned by the irradiation parameters (beam energy, exposure) and the ASW film thickness. The results are consistent with a generally accepted picture that hydroxylation occurs through hydrolysis of siloxane (Si-O-Si) bonds in the silica network. Calculations using density functional theory show that this may happen on Si-O-Si bonds, which are either parallel (i.e., in the topmost silicate layer) or vertical to the film surface (i.e., connecting two silicate layers). In the latter case, the mechanism may additionally involve the reaction with a metal support underneath. The observed vibrational spectra are dominated by terminal silanol groups (ν(OD) band at 2763 cm(-1)) formed by hydrolysis of vertical Si-O-Si linkages. Film dehydroxylation fully occurs only upon heating to very high temperatures (∼ 1200 K) and is accompanied by substantial film restructuring, and even film dewetting upon cycling hydroxylation/dehydroxylation treatment.

  3. Silicate Dispersion and Mechanical Reinforcement in Polysiloxane/Layered Silicate Nanocomposites

    KAUST Repository

    Schmidt, Daniel F.

    2010-01-12

    We report the first in-depth comparison of the mechanical properties and equilibrium solvent uptake of a range of polysiloxane nanocomposites based on treated and untreated montmorillonite and fumed silica nanofillers. We demonstrate the ability of equilibrium solvent uptake data (and, thus, overall physical and chemical cross-link density) to serve as a proxy for modulus (combining rubber elasticity and Flory-Rehner theory), hardness (via the theory of Boussinesq), and elongation at break, despite the nonideal nature of these networks. In contrast, we find that tensile and tear strength are not well-correlated with solvent uptake. Interfacial strength seems to dominate equilibrium solvent uptake and the mechanical properties it predicts. In the montmorillonite systems in particular, this results in the surprising consequence that equilibrium solvent uptake and mechanical properties are independent of dispersion state. We conclude that edge interactions play a more significant role than degree of exfoliation, a result unique in the field of polymer nanocomposites. This demonstrates that even a combination of polymer/nanofiller compatibility and thermodynamically stable nanofiller dispersion levels may not give rise to reinforcement. These findings provide an important caveat when attempting to connect structure and properties in polymer nanocomposites, and useful guidance in the design of optimized polymer/layered silicate nanocomposites in particular. © 2009 American Chemical Society.

  4. Silicate anion structural change in calcium silicate hydrate gel on dissolution of hydrated cement

    International Nuclear Information System (INIS)

    High pH conditions of aqueous solutions in a radioactive waste repository can be brought about by dissolution of cementitious materials. In order to clarify the mechanisms involved in maintaining this high pH for long time, we investigated the dissolution phenomena of OPC hydrate. In the present research, leaching tests on powdered cement hydrates were conducted by changing the ratio of mass of leaching water to mass of OPC hydrate (liquid/solid ratio) from 10 - 2,000 (wt/wt). Ordinary Portland Cement hydrate was contacted with deionized water and placed in a sealed bottle. After a predetermined period, the solid was separated from the solution. From the results of XRD analysis on the solid phase and the Ca concentration in the aqueous phase, it was confirmed that Ca(OH)2 was preferentially dissolved when the liquid/solid ratio was 10 or 100 (wt/wt), and that C-S-H gel as well as Ca(OH)2 were dissolved when the liquid/solid ratio was 500 (wt/wt) or larger. 29Si-NMR results showed that the silicate anion chain of the C-S-H gel became longer when the liquid/solid ratio was 500 (wt/wt) or greater. This indicates that leaching of OPC hydrate results in a structural change of C-S-H gel. (author)

  5. PREFACE: 5th Baltic Conference on Silicate Materials

    Science.gov (United States)

    Mezinskis, G.; Bragina, L.; Colombo, P.; Frischat, G. H.; Grabis, J.; Greil, P.; Deja, J.; Kaminskas, R.; Kliava, J.; Medvids, A.; Nowak, I.; Siauciunas, R.; Valancius, Z.; Zalite, I.

    2011-12-01

    Logo This Volume of IOP Conference Series: Materials Science and Engineering presents a selection of the contributions to the 5th Baltic Conference on Silicate Materials (BaltSilica2011) held at Riga Technical University, Riga, Latvia from 23-25 May 2011. The conference was organized by Riga Technical University (Latvia) and Kaunas University of Technology (Lithuania). The series of Baltic conferences on silicate materials was started since 2004: the first conference was held in Riga, Latvia, 2004; the second conference was held in Kaunas, Lithuania 2005; the third was held again in Riga, Latvia, 2007, and the fourth was held in Kaunas, Lithuania 2009. BaltSilica 2011 was attended by around 50 participants from Latvia, Lithuania, Estonia, Germany, Poland, Italy, France, Ukraine and Russia. In comparison with previous silicate materials conferences, the broadening of participating countries is an indication of the interest of scientists, engineers and students to exchange research ideas, latest results, and to find new research topics for cooperation in the fields of silicate, high temperature materials, and inorganic nanomaterials. The scientific programme included 8 invited plenary lectures 23 oral presentations and 25 posters [1]. Scientific themes covered in the conference and in this special issue: Natural and Artificial Stone Materials; Traditional and New Ceramic and Glass-Like Materials; Nanoparticles and Nanomaterials. This volume consists of 23 selected proceeding papers. The Editor of this special issue is grateful to all the contributors to BaltSilica 2011. I am also very grateful to the scientific committee, the local organizing committee, the session chairs, the referees who refereed the submitted articles to this issue, and to students from the Department of Silicate, High Temperature and Inorganic Nanomaterials Technology of the Riga Technical University who ensured the smooth running of the conference. Particular thanks goes to eight plenary

  6. Laboratory Analysis of Silicate Stardust Grains of Diverse Stellar Origins

    Science.gov (United States)

    Nguyen, Ann N.; Keller, Lindsay P.; Nakamura-Messenger, Keiko

    2016-01-01

    Silicate dust is ubiquitous in a multitude of environments across the cosmos, including evolved oxygen-rich stars, interstellar space, protoplanetary disks, comets, and asteroids. The identification of bona fide silicate stardust grains in meteorites, interplanetary dust particles, micrometeorites, and dust returned from comet Wild 2 by the Stardust spacecraft has revolutionized the study of stars, interstellar space, and the history of dust in the Galaxy. These stardust grains have exotic isotopic compositions that are records of nucleosynthetic processes that occurred in the depths of their now extinct parent stars. Moreover, the chemical compositions and mineralogies of silicate stardust are consequences of the physical and chemical nature of the stellar condensation environment, as well as secondary alteration processes that can occur in interstellar space, the solar nebula, and on the asteroid or comet parent body in which they were incorporated. In this talk I will discuss our use of advanced nano-scale instrumentation in the laboratory to conduct coordinated isotopic, chemical, and mineralogical analyses of silicate stardust grains from AGB stars, supernovae, and novae. By analyzing the isotopic compositions of multiple elements in individual grains, we have been able to constrain their stellar sources, explore stellar nucleosynthetic and mixing processes, and Galactic chemical evolution. Through our mineralogical studies, we have found these presolar silicate grains to have wide-ranging chemical and mineral characteristics. This diversity is the result of primary condensation characteristics and in some cases secondary features imparted by alteration in space and in our Solar System. The laboratory analysis of actual samples of stars directly complements astronomical observations and astrophysical models and offers an unprecedented level of detail into the lifecycles of dust in the Galaxy.

  7. Petrophysical Analysis of Siliceous-Ooze Sediments, More Basin, Norwegian Sea

    DEFF Research Database (Denmark)

    Awedalkarim, Ahmed; Sørensen, Morten Kanne; Fabricius, Ida Lykke

    2014-01-01

    Pelagic siliceous-ooze sediments occur above the hydrocarbon reservoir of the Ormen Lange gas field in More Basin, Norwegian Sea. A possible hydrocarbon prospect of siliceous ooze was proposed, but siliceous ooze is significantly different in texture from most commonly known reservoir rocks...

  8. Experimental weathering rates of aluminium silicates

    International Nuclear Information System (INIS)

    The chemical weathering of primary rocks and minerals in natural systems has a major impact on soil development and its composition. Chemical weathering is driven to a large extent by mineral dissolution. Through mineral dissolution, elements are released into groundwater and can readily react to precipitate secondary minerals such as clays, zeolites, and carbonates. Carbonates form from divalent cations (e.g. Ca, Fe and Mg) and CO2, and kaolin clay and gibbsite formation is attributed to the weathering of aluminium-rich minerals, most notably the feldspars. The CarbFix Project in Hellisheidi (SW-Iceland) aims to use natural weathering processes to form carbonate minerals by the re-injection of CO2 from a geothermal power plant back into surrounding basaltic rocks. This process is driven by the dissolution of basaltic rocks, rich in divalent cations, which can combine with injected CO2 to form and precipitate carbonates. This thesis focuses on the dissolution behaviour of Stapafell crystalline basalt, which consists of three major phases (plagioclase, pyroxene, and olivine) and is rich in divalent cations. Steady-state element release rates from crystalline basalt at far-from-equilibrium conditions were measured at pH from 2 to 11 and temperatures from 5 to 75 C in mixed-flow reactors. Steady-state Si and Ca release rates exhibit a U-shaped variation with pH, where rates decrease with increasing pH at acid condition but increase with increasing pH at alkaline conditions. Silicon release rates from crystalline basalt are comparable to Si release rates from basaltic glass of the same chemical composition at low pH and temperatures ≥25 C but slower at alkaline pH and temperatures ≥50 C. In contrast, Mg and Fe release rates decrease continuously with increasing pH at all temperatures. This behaviour is interpreted to stem from the contrasting dissolution behaviours of the three major minerals comprising the basalt: plagioclase, pyroxene, and olivine. Element

  9. Effects of surface application of calcium-magnesium silicate and gypsum on soil fertility and sugarcane yield

    Directory of Open Access Journals (Sweden)

    Carlos Alexandre Costa Crusciol

    2014-12-01

    Full Text Available Lime application recommendations for amendment of soil acidity in sugarcane were developed with a burnt cane harvesting system in mind. Sugarcane is now harvested in most areas without burning, and lime application for amendment of soil acidity in this system in which the sugarcane crop residue remains on the ground has been carried out without a scientific basis. The aim of this study was to evaluate the changes in soil acidity and stalk and sugar yield with different rates of surface application of calcium, magnesium silicate, and gypsum in ratoon cane. The experiment was performed after the 3rd harvest of the variety SP 81-3250 in a commercial green sugarcane plantation of the São Luiz Sugar Mill (47º 25' 33" W; 21º 59' 46" S, located in Pirassununga, São Paulo, in southeast Brazil. A factorial arrangement of four Ca-Mg silicate rates (0, 850, 1700, and 3400 kg ha-1 and two gypsum rates (0 and 1700 kg ha-1 was used in the experiment. After 12 months, the experiment was harvested and technological measurements of stalk and sugar yield were made. After harvest, soil samples were taken at the depths of 0.00-0.05, 0.05-0.10, 0.10-0.20, 0.20-0.40, and 0.40-0.60 m in all plots, and the following determinations were made: soil pH in CaCl2, organic matter, P, S, K, Ca, Mg, H+Al, Al, Si, and base saturation. The results show that the application of gypsum reduced the exchangeable Al3+ content and Al saturation below 0.05 m, and increased the Ca2+ concentration in the whole profile, the Mg2+ content below 0.10 m, K+ below 0.4 m, and base saturation below 0.20 m. This contributed to the effect of surface application of silicate on amendment of soil acidity reaching deeper layers. From the results of this study, it may be concluded that the silicate rate recommended may be too low, since the greater rates used in this experiment showed greater reduction in soil acidity, higher levels of nutrients at greater depths and an increase in stalk and sugar

  10. The determination of calcium in phosphate, carbonate, and silicate rocks by flame photometer

    Science.gov (United States)

    Kramer, Henry

    1956-01-01

    A method has been developed for the determination of calcium in phosphate, carbonate, and silicate rocks using the Beckman flame photometer, with photomultiplier attachement. The sample is dissolved in hydrofluoric, nitric, and perchloric acids, the hydrofluoric and nitric acids are expelled, a radiation buffer consisting of aluminum, magnesium, iron, sodium, potassium, phosphoric acid, and nitric acid is added, and the solution is atomized in an oxy-hydrogen flame with an instrument setting of 554 mµ. Measurements are made by comparison against calcium standards, prepared in the same manner, in the 0 to 50 ppm range. The suppression of calcium emission by aluminum and phosphate was overcome by the addition of a large excess of magnesium. This addition almost completely restores the standard curve obtained from a solution of calcium nitrate. Interference was noted when the iron concentration in the aspirated solution (including the iron from the buffer) exceeded 100 ppm iron. Other common rock-forming elements did not interfere. The results obtained by this procedure are within ± 2 percent of the calcium oxide values obtained by other methods in the range 1 to 95 percent calcium oxide. In the 0 to 1 percent calcium oxide range the method compares favorably with standard methods.

  11. Effect of sodium silicate modification on selected properties of loose self-setting sands

    Directory of Open Access Journals (Sweden)

    D.Drożyński

    2010-10-01

    Full Text Available The paper presents the results of the tensile tests Rmu carried out on sands with sodium silicate, modified with SiO2, Al2O3 and ZnO in the form of aqueous colloidal solution or powder.It has been proved that the improvement of sand properties depends on:modifier type, chemical reaction of the modifier (acid-base reaction,method by which the modifier is introduced to binder,modifier content. It has been observed that among the tested modifiers, SiO2 and Al2O3 have stronger effect on the sand strength improvement than ZnO. Great degree of Rmu improvement has been obtained by introducing to the binder either SiO2 (Rmu improved by 30% or Al2O3 (Rmu improved by 50%, both in the form of powders.

  12. Electrokinetic characteristic and coagulation behavior of flocculant polyaluminum silicate chloride (PASiC)

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The electrokinetic characteristics and coagulation behaviors of polyaluminum silicate chloride (PASiC) and polyaluminum chloride (PAC) were studied and compared by streaming current (SC) measurement and jar test method. The experimental results showed that the interaction between polysilicic acid characterized negative charge and hydrolyzed aluminum species result in a decrease of the charge-neutralizing ability of PAiSC, compared to PAC. The decrease has a close relationship with the basicity (B) and Al/Si molar ratio in PASiC. The less the B value and the Al/Si molar ratio, the lower the charge-neutralizing ability of PASiC is. In contrast, the preparation technique for PASiC affects the charge-neutralization of PASiC to a smaller extent. In addition, compared with PAC, PASiC may enhance aggregating efficiency and give better coagulating effects.

  13. Characterization of a calcium phospho-silicated apatite with iron oxide inclusions

    Science.gov (United States)

    Desport, Barthélémy; Carpena, Joëlle; Lacout, Jean-Louis; Borschneck, Daniel; Gattacceca, Jérôme

    2011-02-01

    An iron oxide containing calcium phosphate-silicate hydroxyapatite was synthesized by calcination at 900 °C of a sample obtained by precipitation in basic aqueous solution of Ca, P, Si, Fe and Mg containing acidic solution made from dissolution of natural minerals. XRD and FTIR were used for crystallographic characterization of the main apatitic phase. Its composition was determined using ICP-AES. EDX coupled with SEM and TEM evidenced the heterogeneity of this compound and the existence of iron-magnesium oxide. Magnetic analyses highlighted that this phase was non-stoichiometric magnesioferrite (Mg 1.2Fe 1.8O 3.9) spherical nanoparticles. Those analyses also put into evidence the role of calcination in synthesis. Carbonates detected by FTIR and estimated by SEM-EDX in non-calcinated sample were removed from apatitic structure, and crystallization of apatite was enhanced during heating. Moreover, there was phase segregation that led to magnesioferrite formation.

  14. X-ray scattering on layered silicates in polymeric matrices

    International Nuclear Information System (INIS)

    Nanocomposites based on polymeric matrices have been studied via small angle X-ray scattering with respect to the dispersion and the orientation of filler particles. Both natural and synthetic layered silicates were used as filler particles. For this purpose, a software was developed which allows to determine the size and the size distribution of nanoparticles with various geometries by analyzing small angle X-ray scattering data. In contrast to conventional software, the one developed and used here is based on free distribution functions, e.g. no particular size distribution is pre-supposed. By example of three different reference systems it could be shown that the software works reliably and accurately. Using the computer-based evaluation of scattering data, significantly more information can be obtained about the samples compared to classical analytical and numerical evaluation schemes. By means of this software, the inner structure of the microgel PVCUAAEM (Poly(N-Vinylcaprolactam- co-acetoacetoxyethylmethacrylat)) filled with a synthetic layered silicate was investigated as a function of temperature. For this temperature-sensitive microgelnanocomposite, the dispersion of the silicate layers was determined and a structural model was developed. It could be shown that with increasing temperature, the layers move closer together and, depending on the amount of filler content, the filler particles drift to the surface of the nanocomposites. Additionally, for higher filler contents the charged layered silicate prevents the typical reduction of the particle radius, which is otherwise observed with increasing temperature. For polyethylene filled with natural layered silicate, it could be shown that small angle X-ray scattering allows the quantitative evaluation of the orientation of platelet-shaped nanoparticles in a polymeric matrix. Based on spatially resolved measurements of injection-molded tensile bars, the degree of orientation could be determined quantitatively

  15. Polymerisation, basicity, oxidation state and their role in ionic modelling of silicate melts

    Directory of Open Access Journals (Sweden)

    R. Moretti

    2005-06-01

    Full Text Available In order to describe and quantify the reactivity of silicate melts, the ionic notation provided by the Temkin formalism has been historically accepted, giving rise to the study of melt chemical equilibria in terms of completely dissociated ionic species. Indeed, ionic modelling of melts works properly as long as the true extension of the anionic matrix is known. This information may be attained in the framework of the Toop-Samis (1962a,b model, through a parameterisation of the acid-base properties of the dissolved oxides. Moreover, by combining the polymeric model of Toop and Samis with the «group basicity» concept of Duffy and Ingram (1973, 1974a,b, 1976 the bulk optical basicity (Duffy and Ingram, 1971; Duffy, 1992 of molten silicates and glasses can be split into two distinct contributions, i.e. the basicity of the dissolved basic oxides and the basicity of the polymeric units. Application to practical cases, such as the assessment of the oxidation state of iron, require bridging of the energetic gap between the standard state of completely dissociated component (Temkin standard state and the standard state of pure melt component at P and T of interest. On this basis it is possible to set up a preliminary model for iron speciation in both anhydrous and hydrous aluminosilicate melts. In the case of hydrous melts, I introduce both acidic and basic dissociation of the water component, requiring the combined occurrence of H+ cations, OH- free anions and, to a very minor extent, of T-OH groups. The amphoteric behaviour of water revealed by this study is therefore in line with the earlier prediction of Fraser (1975.

  16. Removal of Cadmium Ions from Aqueous Solution by Silicate-incorporated Hydroxyapatite

    Institute of Scientific and Technical Information of China (English)

    SHI Hebin; ZHONG Hong; LIU Yu; DENG Jinyang

    2007-01-01

    This article reports a preliminary research on silicate-incorporated hydroxyapatite as a new environmental mineral used to remove cadmium ions from aqueous solutions. The silicate-incorporated hydroxyapatite was prepared by coprecipitation and calcining, and silicate was incorporated into the crystal lattice of hydroxyapatite by partial substitution of phosphate. The amount of cadmium ions removed by silicate-incorporated hydroxyapatite was significantly elevated, which was 76% higher than that of pure hydroxyapatite. But the sorption behavior of cadmium ions on silicate-incorporated hydroxyapatite was similar to that of pure hydroxyapatite. Morphological study revealed that silicate incorporation confined the crystal growth and increased the specific surface area of hydroxyapatite,which were in favor of enhancing the cadmium ion sorpfion capacity of the samples. Incorporation of silicate into hydroxyapatite seems to be an effective approach to improve the environmental property of hydroxyapatite on removal of aqueous cadmium ions.

  17. Synthesis and characterization of Si/Ga Eni Carbon Silicates

    Institute of Scientific and Technical Information of China (English)

    Giuseppe Bellussi; Angela Carati; Stefania Guidetti; Caterina Rizzo; Roberto Millini; Stefano Zanardi; Erica Montanari; Wallace O’Neil Parker Jr.; Michela Bellettato

    2015-01-01

    Phenylene-gallosilicates were prepared with the same crystalline structure as their aluminum ana-logues. The new Ga-Eni Carbon Silicates (Ga-ECS) phases were investigated by X-ray diffraction, scanning electron microscopy, nuclear magnetic resonance and thermogravimetric analysis, which demonstrated that gallium isomorphously replaced aluminum in the framework of the organ-ic-inorganic hybrids similar to the case of classical zeolites. Hybrid ECS materials were obtained with different types of bridged silsesquioxane precursors that maintained the aluminum-silicate nature of the inorganic moiety. This work confirms a new level of crystal chemistry versatility for this class of materials, and demonstrates the possibility to tailor also the inorganic part of the framework by changing the nature of the trivalent heteroatom.

  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. In vitro bioactivity of a tricalcium silicate cement

    International Nuclear Information System (INIS)

    Tricalcium silicate is the major constituent of Portland cement and the responsible for their mechanical strength at early stages. In order to be used as and additive of conventional calcium phosphate cement (CPC), in vitro bioactivity of a calcium silicate cement (CSC) after soaking in simulated body fluid (SBF) for 14 days was study. The cement was obtained by mixing Ca3SiO5, obtained by sol-gel process, and a Na2HPO4 solution. The morphological and structural changes of the material before and after soaking were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed the formation of a layer of a Hydroxyapatite (HA) onto the CSC cement after soaking for 1h in SBF that became denser with the increase of soaking time. The study suggests that Ca3SiO5 would be an effective additive to improve the bioactivity and long term strength of conventional CPC. (author)

  20. Silicates in D-type symbiotic stars: an ISO overview

    CERN Document Server

    Angeloni, R; Ciroi, S; Rafanelli, P

    2007-01-01

    We investigate the IR spectral features of a sample of D-type symbiotic stars. Analyzing unexploited ISO-SWS data, deriving the basic observational parameters of dust bands and comparing them with respect to those observed in other astronomical sources, we try to highlight the effect of environment on grain chemistry and physic. We find strong amorphous silicate emission bands at 10 micron and 18 micron in a large fraction of the sample. The analysis of the 10 micron band, along with a direct comparison with several astronomical sources, reveals that silicate dust in symbiotic stars shows features between the characteristic circumstellar environments and the interstellar medium. This indicates an increasing reprocessing of grains in relation to specific symbiotic behavior of the objects. A correlation between the central wavelength of the 10 and 18 micron dust bands is found. By the modeling of IR spectral lines we investigate also dust grains conditions within the shocked nebulae. Both the unusual depletion ...

  1. Dry reusing and wet reclaiming of used sodium silicate sand

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Based on the characteristics of used sodium silicate sand and the different use requirements for recycled sand, "dry reusing and wet reclaiming of used sodium silicate sand" is considered as the most suitable technique for the used sand. When the recycled sand is used as support sand, the used sand is only reused by dry process including breaking, screening, dust-removal, etc., and it is not necessary that the used sand is reclaimed with strongly rubbing and scraping method, but when the recycled sand is used as facing sand (or single sand), the used sand must be reclaimed by wet method for higher removal rate of the residual binders. The characteristics and the properties of the dry reused sand are compared with the wet reclaimed sand after combining the different use requirements of support sand and facing sand (or single sand), and above the most adaptive scheme has also been validated.

  2. Xe and Kr analyses of silicate inclusions from iron meteorites.

    Science.gov (United States)

    Bogard, D. D.; Huneke, J. C.; Burnett, D. S.; Wasserburg, G. J.

    1971-01-01

    Measurements have been conducted of the amounts and isotopic composition of Xe and Kr in silicate inclusions of several iron meteorites. It is shown that the Xe and Kr contents are comparable to chondritic values. The isotopic compositions show trapped gas of both chondritic and atmospheric composition. Large spallation effects occur in some of the meteorites; the spallation spectra in some instances differ from those reported for stone meteorites. In several meteorites, very large neutron capture effects on Br and I occur. All samples have pronounced Xe129 excesses which apparently indicate differences in the formation times from chondrites of less than about 100 million years; however, the presence of trapped Xe132 in silicates which were enclosed in molten Fe-Ni and cooled slowly proves that they were not entirely outgassed, so that some of the Xe129 excess may also be trapped.

  3. EXAFS studies of sodium silicate glasses containing dissolved actinides

    International Nuclear Information System (INIS)

    Sodium silicate glasses containing dissolved Th, U, Np, and Pu have been studied using the EXAFS technique. Th4+, U4+, Np4+, and Pu4+ ions in the silicate glasses are 8-fold coordinated to oxygen neighbors. The higher valent U6+ and Np5+ ions have complex local symmetries. The U6+ ions appear in a uranyl configuration with 2 oxygen atoms at 1.85A and 4 at 2.25A from the U ion. The Np5+ local symmetry is more complex and difficult to determine uniquely. The U6+ glasses show substantial clustering of the uranium atoms. A structural model, with nearly planar uranyl sheets sandwiched between alkali and silica layers, is used to explain the U6+ EXAFS data. This model allows us to understand why U6+ ions are much more soluble in the glasses than the actinide 4+ ions. 4 references, 2 figures

  4. Effective elastic moduli of polymer-layered silicate nanocomposites

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Polymer-layered silicate (PLS) nanocomposites exhibit some mechanical properties that are much better than conventional polymer filled composites. A relatively low content of layered silicate yields a significant enhancement of material performance. After the volume fraction of clay reaches a relatively low "critical value"; however, further increasing does not show a greater stiffening effect. This phenomenon is contrary to previous micromechanical pre-dictions and is not understood well. Based on the analysis on the microstructures of PLS nanocomposites, the present note provides an insight into the physical micromechanisms of the above unexpected phenomenon. The Mori-Tanaka scheme and a numerical method are employed to estimate the effec-tive elastic moduli of such a composite.

  5. Fabrication of unique hollow silicate nanoparticles with hierarchically micro/mesoporous shell structure by a simple double template approach.

    Science.gov (United States)

    Rivera-Virtudazo, R V; Fuji, M; Takai, C; Shirai, T

    2012-12-01

    An innovative type of hollow silicate nanoparticle with a micro/mesoporous shell wall (NSHPMS) was synthesized at room temperature via an eco-friendly double template approach, followed by simple acid reflux. TEM observations of NSHPMSs showed hollow interior nanoparticles (wormhole-like shell structure. The nitrogen gas (N(2)) adsorption/desorption isotherm exhibited a unique two-step pattern: the first step (0.2 wormhole mesoporous shell wall provided sufficient spaces that contribute to high adsorption capacities and faster adsorption rates. One can envision that larger quantities of framework composition can be obtained using our NSHPMSs. PMID:23138674

  6. Analysis of silicate rocks by x-ray fluorescence spectrometry

    International Nuclear Information System (INIS)

    This study aims at developing an all-purpose method for the determination of various elements in silicate rocks, by means of X-ray fluorescence spectrometry. The sample is prepared by borax fusion, in the presence of cobalt oxide acting as an inner standard meant for eliminating certain errors. Contents are computed in comparison with outer standards having a chemical composition akin to that of the rock sample under analysis. (authors)

  7. Scenario of Growing Crops on Silicates in Lunar Gargens

    Science.gov (United States)

    Kozyrovska, N.; Kovalchuk, M.; Negutska, V.; Lar, O.; Korniichuk, O.; Alpatov, A.; Rogutskiy, I.; Kordyum, V.; Foing, B.

    Self-perpetuating gardens will be a practical necessity for humans, living in permanently manned lunar bases. A lunar garden has to supplement less appetizing packaged food brought from the Earth, and the ornamental plants have to serve as valuable means for emotional relaxation of crews in a hostile lunar environment. The plants are less prone to the inevitable pests and diseases when they are in optimum condition, however, in lunar greenhouses there is a threat for plants to be hosts for pests and predators. Although the lunar rocks are microorganism free, there will be a problem with the acquired infection (pathogens brought from the Earth) in the substrate used for the plant growing. On the Moon pests can be removed by total fumigation, including seed fumigation. However, such a treatment is not required when probiotics (biocontrol bacteria) for seed inoculation are used. A consortium of bacteria, controlling plant diseases, provides the production of an acceptable harvest under growth limiting factors and a threatening infection. To model lunar conditions we have used terrestrial alumino-silicate mineral anorthosite (Malyn, Ukraine) which served us as a lunar mineral analog for a substrate composition. With the idea to provide a plant with some essential growth elements siliceous bacterium Paenibacillus sp. has been isolated from alumino-silicate mineral, and a mineral leaching has been simulated in laboratory condition. The combination of mineral anorthosite and siliceous bacteria, on one hand, and a consortium of beneficial bacteria for biocontrol of plant diseases, on the other hand, are currently used in model experiments to examine the wheat and potato growth and production in cultivating chambers under controlled conditions.

  8. Dentin-cement Interfacial Interaction: Calcium Silicates and Polyalkenoates

    OpenAIRE

    Atmeh, A.R.; Chong, E. Z.; Richard, G; Festy, F.; Watson, T.F.

    2012-01-01

    The interfacial properties of a new calcium-silicate-based coronal restorative material (Biodentine™) and a glass-ionomer cement (GIC) with dentin have been studied by confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), micro-Raman spectroscopy, and two-photon auto-fluorescence and second-harmonic-generation (SHG) imaging. Results indicate the formation of tag-like structures alongside an interfacial layer called the “mineral infiltration zone”, where the alkaline c...

  9. Forming the Moon from terrestrial silicate-rich material

    OpenAIRE

    Meijer, R.J.; Anisichkin, V. F.; van Westrenen, W.

    2010-01-01

    Recent high-precision measurements of the isotopic composition of lunar rocks demonstrate that the bulk silicate Earth and the Moon show an unexpectedly high degree of similarity. This is inconsistent with one of the primary results of classic dynamical simulations of the widely accepted giant impact model for the formation of the Moon, namely that most of the mass of the Moon originates from the impactor, not Earth. Resolution of this discrepancy without changing the main premises of the gia...

  10. Strength and impermeability recovery of siliceous mudstone from complete failure

    International Nuclear Information System (INIS)

    Radionuclide migration can be undesirably increased by weakening the mechanical properties of a rock mass in the excavated disturbed zone (EDZ) around the tunnels of a geological disposal facility for high level radioactive waste. Laboratory testing of loading stress and loading time on failed siliceous mudstone specimens has identified the potential for the long-term recovery of the strength and impermeability of the rock mass in the EDZ. (author)

  11. Coloration processes in soda-lime silicate glasses

    International Nuclear Information System (INIS)

    The effect of mechanical stretching upon room temperature γ coloration of soda-lime silicate (SLS) glasses has been investigated. Optical absorption measurements were performed to follow the formation and thermal bleaching of the induced color centers. It has been shown that the mechanical deformation reduces the coloration effectivity and thermal stability of the created centers. It has been proposed that increase of the concentration of the non-bridging oxygens accelerate the bleaching processes

  12. Metabolic effects of a novel silicate inositol complex of the nitric oxide precursor arginine in the obese insulin-resistant JCR:LA-cp rat.

    Science.gov (United States)

    Proctor, Spencer D; Kelly, Sandra E; Vine, Donna F; Russell, James C

    2007-10-01

    . We conclude that the arginine silicate inositol complex is absorbed efficiently, raising plasma arginine levels, and is more biologically effective than the free amino acid hydrochloride. This has different beneficial metabolic effects in both sexes of an animal model of insulin resistance and cardiovascular disease, consistent with reduction in end-stage disease.

  13. 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.

  14. Electrochemical Studies on Silicate and Bicarbonate Ions for Corrosion Inhibitors

    Science.gov (United States)

    Mohorich, Michael E.; Lamb, Joshua; Chandra, Dhanesh; Daemen, Jaak; Rebak, Raul B.

    2010-10-01

    Several types of carbon and high-strength low-alloy (HSLA) steels are being considered for use in the underground reinforcement of the Yucca Mountain Nuclear Waste Repository. In this study, potentiodynamic polarization under reducing conditions was used to determine the corrosion rates (CRs) and passivity behavior of AISI 4340 steel using different combinations of sodium silicate (Na2SiO3) and sodium bicarbonate (NaHCO3), in both pure water (PW) and simulated seawater (SW, 3.5 pct NaCl). These experiments were carried out to examine the potential inhibiting properties of the silicate or bicarbonate ions on the surface of the steel. The addition of sodium silicate to solution reduced the observed CR at room temperature to 19 μm/y at 0.005 M concentration and 7 μm/y at 0.025 M concentration in PW. The addition of sodium bicarbonate increased the CR from 84 μm/y (C = 0.1 M) to 455 μm/y (C = 1 M). These same behaviors were also observed at higher temperatures.

  15. Electrical properties of iron doped apatite-type lanthanum silicates

    Institute of Scientific and Technical Information of China (English)

    SHI Qingle; ZHANG Hua

    2012-01-01

    The effect of Fe doping on the electrical properties of lanthanum silicates was investigated.The apatite-type lanthanum silicates La10Si6-xFexO27-x/2 (x=0.2,0.4,0.6,0.8,1.0) were synthesized via sol-gel process.The unit cell volume increased with Fe doping because the ionic radius of Fe3+ ion is larger than that of Si4+ ion.The conductivities of La10Si6-xFexO27 x/2 first increased and then decreased with the increasing of Fe content.The increase of the conductivity might be attributed to the distortion of the cell lattice,which assisted the migration of the interstitial oxygen ions.The decrease of the conductivity might be caused by the lower concentration of interstitial oxygen ions.The optimum Fe doping content in lanthanum silicates was 0.6.La10Si5.4Fe0.6O26.7 exhibited the highest ionic conductivity of 2.712× 10-2 S/cm at 800 ℃.The dependence of conductivity on oxygen partial pressure p(O2) suggested that the conductivity of La10Si6-xFexO27-x/2 was mainly contributed by ionic conductivity.

  16. A Review: Fundamental Aspects of Silicate Mesoporous Materials

    Directory of Open Access Journals (Sweden)

    Zeid A. ALOthman

    2012-12-01

    Full Text Available Silicate mesoporous materials have received widespread interest because of their potential applications as supports for catalysis, separation, selective adsorption, novel functional materials, and use as hosts to confine guest molecules, due to their extremely high surface areas combined with large and uniform pore sizes. Over time a constant demand has developed for larger pores with well-defined pore structures. Silicate materials, with well-defined pore sizes of about 2.0–10.0 nm, surpass the pore-size constraint (<2.0 nm of microporous zeolites. They also possess extremely high surface areas (>700 m2 g−1 and narrow pore size distributions. Instead of using small organic molecules as templating compounds, as in the case of zeolites, long chain surfactant molecules were employed as the structure-directing agent during the synthesis of these highly ordered materials. The structure, composition, and pore size of these materials can be tailored during synthesis by variation of the reactant stoichiometry, the nature of the surfactant molecule, the auxiliary chemicals, the reaction conditions, or by post-synthesis functionalization techniques. This review focuses mainly on a concise overview of silicate mesoporous materials together with their applications. Perusal of the review will enable researchers to obtain succinct information about microporous and mesoporous materials.

  17. Translational dynamics of water in a nanoporous layered silicate

    Science.gov (United States)

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

    2005-03-01

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

  18. Kinetics of structure formation in PP/layered silicate nanocomposites

    Directory of Open Access Journals (Sweden)

    2009-11-01

    Full Text Available Polypropylene (PP/organophilized montmorillonite (OMMT and polypropylene/organophilized montmorillonite/maleic anhydride grafted polypropylene (MAPP composites were prepared in an internal mixer under a wide range of processing conditions to study the kinetics of structure formation. Structure and properties were characterized by a variety of techniques. The gallery structure of the organophilic silicate changed in spite of the fact that no compatibilizer was added to PP/OMMT composites. Silicate reflection shifted towards smaller 2θangles, broadened and its intensity decreased indicating intercalation. Transmission electron microscopy (TEM micrographs even showed individual platelets at long mixing times. However, the extent and direction of changes in the gallery structure of the silicate did not justify those observed in properties. The analysis of the results and additional experiments proved that the degradation of the polymer also takes place during processing leading to the formation of carbonyl and/or carboxyl groups, as well as to the decrease of molecular weight. The modification of the chain structure of the polymer influences interfacial interactions and the intercalation process. Some properties are directly determined by molecular weight (rheological properties, elongation. Both the clay and the MAPP seem to accelerate degradation. Thermooxidative degradation must have disadvantageous effect during the application of PP nanocomposites and needs further study.

  19. 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).

  20. Influence of commercial and residual sorbents and silicates as additives on the stabilisation/solidification of organic and inorganic industrial waste.

    Science.gov (United States)

    Coz, A; Andrés, A; Soriano, S; Viguri, J R; Ruiz, M C; Irabien, J A

    2009-05-30

    An environmental problem of the foundry activities is the management of industrial waste generated in different processes. The foundry sludge from gas wet cleaning treatment that contains organic and inorganic compounds and a high content of water is an interesting example. Due to their characteristics, they can be managed using different stabilisation/solidification (S/S) technologies prior to land disposal. The purpose of this work is to study S/S formulations in order to improve the control of the mobility of the pollutants and the ecotoxicity of the samples. Different mixtures of cement or lime as binders and additives (foundry sand, silica fume, sodium silicate, silicic acid, activated carbon and black carbon) have been used in order to reduce the mobility of the chemical and ecotoxicological regulated parameters and to compare the results for commercial and residual additives. The best results have been obtained with sorbents (activated carbon and black carbon) or sodium silicate. The results of the foundry sand ash as additive can conclude that it can be used as replacement in the cement products. However, silica fume in the samples with lime and siliceous resin sand as additives gives products that do not fulfil the regulated limits. Finally, some linear expressions between the chemical parameters and the quantity of material used in the samples have been obtained. PMID:18835094

  1. 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

    Isotopic similarity between the Earth-Moon system and enstatite chondrites (ECs) led to the idea that ECs were Earth's building blocks [1-3]. However, compared to Earth's mantle, ECs have low Fe0/Fe ratios, are enriched in volatile elements, and depleted in refractory lithophile elements and Mg [4]. Therefore, deriving Earth composition from ECs requires a loss of volatiles during or prior to accretion and sequestering a large fraction of Si in the deep Earth. Alternatively, the isotopic similarity between the Earth and ECs is explained by their formation from a common precursor that experienced different evolutionary paths resulting in the chemical difference [4]. The vestiges of such a precursor are still present in the unequilibrated ECs as FeO-rich silicates with O isotopic compositions identical to bulk ECs and Earth [5]. Conversion of such a precursor into the characteristic EC mineral assemblage requires high-temperature processing in an H-poor environment with high fS2 and fO2 close to that of the classic solar nebula [6], consistent with redox conditions inferred from Ti4+/Ti3+ ratios in EC pyroxene [7]. Under such conditions reaction of FeO-rich silicates with S-rich gas results in their replacement by the assemblage of FeO-poor silicates; Fe, Mg, Ca sulfides; free silica; and Si-bearing Fe,Ni metal alloy. The progressive sulfidation of ferromagnesian silicates in chondrules results in loss of Mg and addition of Fe, Mn, S, Na, K and, perhaps, other volatiles [6]. At the advanced stages of silicate sulfidation recorded in the metal-sulfide nodules [8], a portion of Si is reduced and dissolved in the Fe,Ni metal. This process is known to fractionate Si isotopes [9,10] and would explain the differences between the ECs and Earth's mantle [11]. The sulfidation of silicates also produces porous S-rich silica, a peculiar phase observed so far only in the ECs. It consists of a sinewy SiO2-rich framework enclosing numerous vesicles filled with beam

  2. The effect of land plants on weathering rates of silicate minerals

    Science.gov (United States)

    Drever, James I.

    1994-05-01

    Land plants and their associated microbiota directly affect silicate mineral weathering in several ways: by generation of chelating ligands, by modifying pH through production of CO 2 or organic acids, and by altering the physical properties of a soil, particularly the exposed surface areas of minerals and the residence time of water. In laboratory experiments far from equilibrium, 1 mM oxalate (a strong chelator of Al) has a negligible effect on the dissolution rate of alkali feldspars, but some effect on calcic feldspars and olivine. By analogy to oxalate, the overall effect of organic ligands on the weathering rate of silicate minerals in nature is likely to be small, except perhaps in microenvironments adjacent to roots and fungal hyphae. The effect of pH on silicate mineral dissolution rate depends on pH: below pH 4-5, the rate increases with decreasing pH, in the circumneutral region the rate is pH-independent, and at pH values above around 8 the rate increases with increasing pH. Vegetation should thus cause an increase in weathering rate through the pH effect only where the pH is below 4-5. As an overall generalization, the effect of plants on weathering rate through changes in soil-solution chemistry is probably small for granitic rocks; it may be greater for more mafic rocks. It is the release of Ca and Mg from mafic rocks that has the greatest influence on the global CO 2 budget. The effect of changes in soil physical properties on weathering rate can be major. By binding fine particles, plants can greatly increase weathering rates in areas of high physical erosion. Where erosion rates are lower, the effect of plants is less clear. On long timescales plants may decrease chemical weathering by binding secondary products and isolating unweathered minerals from meteoric water. A major unknown in estimating the effect of the advent of land plants on weathering rates is the nature (thickness, particle size distribution, permeability) of the regolith on the

  3. Structure and Morphology of Si3N4 Powders Prepared by Carbon Thermal Reduction and Nitriding Method with Silicic Acid Gel%硅酸凝胶碳热还原氮化法制备氮化硅粉体的结构及形貌

    Institute of Scientific and Technical Information of China (English)

    姜坤; 郑治祥; 朱文振; 吕珺; 徐光青

    2012-01-01

    以水玻璃为硅源,炭黑为碳源,利用碳热还原氮化法制备了Si3N4粉体,研究了氮化温度、氮化时间和碳硅物质的量比对产物结构的影响,并对其形貌进行了观察。结果表明:氮化温度高于1400℃时,产物全部为Si3N4;氮化时间大于5h时,可以得到较纯的α-Si3N4;碳硅物质的量比为3:1时,产物全部为Si3N4;碳硅物质的量比为4:l的前躯体在1400℃氮化5h后得到的Si3N4粉体为不规则的、分散性良好的颗粒,颗粒尺寸为0.3~1μm;碳硅物质的量比为3:1的前躯体在1450℃氮化5h后得到的Si3N4粉体分散性良好,具有规则锤状形态。%Taking sodium silicate as silicon source and carbon black as carbon source, the Sia N, powders were prepared by carbon thermal reduction and nitriding method, and the effects of nitriding temperature, nitriding time and mole ratio of carbon to silicon on structure were studied, and the morphology was observed. The results show that all products were SiaN4 when nitriding temperature was over 1 400 ℃, the fairly pure α-SiaN4 could be obtained when nitriding time was more than 5 h, and all products were Si3N4 when the mole ratio of carbon to silicon was 3 : 1. The Si3N4 powders prepared by nitriding the precursor with mole ratio of carbon to silicon of 4 : 1 at 1 400 ℃for ,5 h had irregular particles and good dispersity, the particles size was 0. 3-1μm, and the Si3 N4 powders prepared by nitriding the prectlrsor with mole ratio of carbon to silicon of 3 : 1 at 1 450 ℃ for 5 h had good dispersity and appeared regular hammer-like.

  4. Fractionation and solubility of cadmium in paddy soils amended with porous hydrated calcium silicate

    Institute of Scientific and Technical Information of China (English)

    ZHAO Xiu-lan; Saigusa Masaihiko

    2007-01-01

    Previous studies have shown that porous hydrated calcium silicate(PS)is very effective in decreasing cadmium(Cd)content in brown rice.However,it is unclear whether me PS influences cadmium transformation in soil.The present study examined the effect of PS on pH,cadmium transformation and cadmium solubility in Andosol and Alluvial soil,and also compared its effects with CaCO3,acidic porous hydrated calcium silicate(APS)and silica gel.Soil cadmium was operationally fractionationed into exchangeable(Exch),bound to carbonates(Carb).bound to iron and manganese oxides(FeMnOx),bound to organic matters(OM)and residual(Res)fraction.ApplicatiOn of PS and CaCO3 at hig rates enhanced soil pH,while APS and silica gel did not obviously change soil pH.PS and CaCO3 also increased the FeMnOx-Cd in Andosol and Carb-Cd in Alluvial soil,thus reducing the Exch-Cd in me tested soils.However,PS was less effecfive than CaCO3 at the same application rate.Cadmium fractions in the two soils were not changed by the treatments of APS and silica gel.There were no obvious differences in the solubility of cadmium in soils treated with PS,APS,silica gel and CaCO3 except Andosol treated 2.0%CaCO3 at the same pH of soil-CaCl2 suspensions.These findings suggested that the decrease of cadmium availability in soil was mainly attributed to the increase of soil pH caused by PS.

  5. Preparation and fluorescence property of red-emitting Eu3+-activated amorphous calcium silicate phosphor

    International Nuclear Information System (INIS)

    This paper describes the energy efficient synthesis of a red-emitting Eu3+-activated amorphous calcium silicate phosphor produced by heating a Eu3+-activated calcium silicate hydrate phosphor. Concentration quenching of the Eu3+-activated calcium silicate hydrate phosphor was not observed and the emission intensity did not decrease up to a Eu/(Ca+Eu) atomic ratio of 0.46. Heating of the Eu3+-activated calcium silicate hydrate (Eu/(Ca+Eu) atomic ratio = 0.32) phosphor produced an amorphous Eu3+-activated calcium silicate phosphor, which had a maximum emission intensity at 870 oC and emitted in the red under near-ultraviolet irradiation (395 nm). The emission intensity of the Eu3+-activated amorphous calcium silicate phosphor was about half that of a commercial BaMgAl10O17:Eu2+ phosphor, and shows great potential for application in white light-emitting diodes.

  6. The silicate absorption profile in the ISM towards the heavily obscured nucleus of NGC 4418

    CERN Document Server

    Roche, P F; Gonzalez-Martin, O

    2015-01-01

    The 9.7-micron silicate absorption profile in the interstellar medium provides important information on the physical and chemical composition of interstellar dust grains. Measurements in the Milky Way have shown that the profile in the diffuse interstellar medium is very similar to the amorphous silicate profiles found in circumstellar dust shells around late M stars, and narrower than the silicate profile in denser star-forming regions. Here, we investigate the silicate absorption profile towards the very heavily obscured nucleus of NGC 4418, the galaxy with the deepest known silicate absorption feature, and compare it to the profiles seen in the Milky Way. Comparison between the 8-13 micron spectrum obtained with TReCS on Gemini and the larger aperture spectrum obtained from the Spitzer archive indicates that the former isolates the nuclear emission, while Spitzer detects low surface brightness circumnuclear diffuse emission in addition. The silicate absorption profile towards the nucleus is very similar to...

  7. Productivity and nutritive value of bluestem grass fertilized with calcium and magnesium silicate

    OpenAIRE

    Cinthya Souza Santana; Laura Souza Santos; Greiciele de Morais; Luiz Arnaldo Fernandes; Luciana Castro Geraseev

    2016-01-01

    This study evaluated the effect of application of calcium and magnesium silicate on the productivity, chemical composition and in situ ruminal degradation of bluestem grass (Andropogon gayanus Kunth, cv. Baeti; Embrapa 23) during the rainy and dry seasons. The design consisted of completely randomized blocks in a 6x2 factorial scheme (six silicate doses and two cutting seasons), arranged in plots subdivided over time. The plots were the calcium and magnesium silicate doses (0, 200, 400, 600, ...

  8. SILICATES ON IAPETUS FROM CASSINI’S COMPOSITE INFRARED SPECTROMETER

    Energy Technology Data Exchange (ETDEWEB)

    Young, Cindy L.; Wray, James J. [School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA (United States); Clark, Roger N. [Planetary Science Institute, Tucson, AZ (United States); Spencer, John R. [Southwest Research Institute, Boulder, CO (United States); Jennings, Donald E. [NASA Goddard Space Flight Center, Greenbelt, MD (United States); Hand, Kevin P.; Carlson, Robert W. [Jet Propulsion Laboratory, Pasadena, CA (United States); Poston, Michael J. [Caltech, Pasadena, CA (United States)

    2015-10-01

    We present the first spectral features obtained from Cassini’s Composite Infrared Spectrometer (CIRS) for any icy moon. The spectral region covered by CIRS focal planes (FP) 3 and 4 is rich in emissivity features, but previous studies at these wavelengths have been limited by low signal-to-noise ratios (S/Ns) for individual spectra. Our approach is to average CIRS FP3 spectra to increase the S/N and use emissivity spectra to constrain the composition of the dark material on Iapetus. We find an emissivity feature at ∼855 cm{sup −1} and a possible doublet at 660 and 690 cm{sup −1} that do not correspond to any known instrument artifacts. We attribute the 855 cm{sup −1} feature to fine-grained silicates, similar to those found in dust on Mars and in meteorites, which are nearly featureless at shorter wavelengths. Silicates on the dark terrains of Saturn’s icy moons have been suspected for decades, but there have been no definitive detections until now. Serpentines reported in the literature at ambient temperature and pressure have features near 855 and 660 cm{sup −1}. However, peaks can shift depending on temperature and pressure, so measurements at Iapetus-like conditions are necessary for more positive feature identifications. As a first investigation, we measured muscovite at 125 K in a vacuum and found that this spectrum does match the emissivity feature near 855 cm{sup −1} and the location of the doublet. Further measurements are needed to robustly identify a specific silicate, which would provide clues regarding the origin and implications of the dark material.

  9. 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.

  10. Sealing of cracks in cement using microencapsulated sodium silicate

    Science.gov (United States)

    Giannaros, P.; Kanellopoulos, A.; Al-Tabbaa, A.

    2016-08-01

    Cement-based materials possess an inherent autogenous self-healing capability allowing them to seal, and potentially heal, microcracks. This can be improved through the addition of microencapsulated healing agents for autonomic self-healing. The fundamental principle of this self-healing mechanism is that when cracks propagate in the cementitious matrix, they rupture the dispersed capsules and their content (cargo material) is released into the crack volume. Various healing agents have been explored in the literature for their efficacy to recover mechanical and durability properties in cementitious materials. In these materials, the healing agents are most commonly encapsulated in macrocontainers (e.g. glass tubes or capsules) and placed into the material. In this work, microencapsulated sodium silicate in both liquid and solid form was added to cement specimens. Sodium silicate reacts with the calcium hydroxide in hydrated cement paste to form calcium-silicate-hydrate gel that fills cracks. The effect of microcapsule addition on rheological and mechanical properties of cement is reported. It is observed that the microcapsule addition inhibits compressive strength development in cement and this is observed through a plateau in strength between 28 and 56 days. The improvement in crack-sealing for microcapsule-containing specimens is quantified through sorptivity measurements over a 28 day healing period. After just seven days, the addition of 4% microcapsules resulted in a reduction in sorptivity of up to 45% when compared to specimens without any microcapsule addition. A qualitative description of the reaction between the cargo material and the cementitious matrix is also provided using x-ray diffraction analysis.

  11. 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.

  12. Cracking phenomena in lithium-di-silicate glass ceramics

    Indian Academy of Sciences (India)

    Rajat Banerjee

    2001-04-01

    Lithium-di-silicate glass ceramic (Li2O, SiO2) with uniformly oriented crystals was placed on a Vickers indentation with extrusion axis horizontally parallel to the base axis. The material was rotated through 0°– 90° and at each angle a 20 N load was applied to ascertain the crack path. It was observed that the crack length decreases and the crack deviates from its original path with increasing angle. The deviation of the crack was correlated with the component of the crack driving force and the theoretical strength of the aligned crystals at different angles.

  13. 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.

  14. Microstructural study of an iron silicate catalyst by electron microscopy

    International Nuclear Information System (INIS)

    This paper reports the effects of various synthesis conditions on the structure of iron silicate analogs of zeolite ZSM-5 considered. Scanning electron microscopy and morphologies. Particle sizes vary from tenths of a micron to several microns, depending on degree of agitation during crystal growth, while morphology is additionally dependent on the concentration of iron in the gel during crystallization. Transmission electron microscopy (TEM) was used to determine the size and spatial distributions of iron-rich (as compared to the FeZSM-5 matrix) second phase particles within the ZSM-5 framework as a function of SiO2/Fe2O3-ratio, thermal and hydrothermal treatments

  15. 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.

  16. In vitro bioactivity and cytocompatibility of tricalcium silicate

    Indian Academy of Sciences (India)

    Xiaoming Liao; Hongyang Zhu; Guangfu Yin; Zhongbing Huang; Yadong Yao; Xianchun Chen

    2011-08-01

    The in vitro bioactivity of tricalcium silicate (Ca3SiO5) ceramics was investigated by the bone-like apatite-formation ability in simulated body fluid (SBF), and the cytocompatibility was evaluated through osteoblast adhesion and proliferation assay. The results show that the Ca3SiO5 ceramics possess bone-like apatite formation ability in SBF. In vitro cytocompatible evaluation reveals that osteoblasts adhere and spread well on the Ca3SiO5 ceramics, indicating good bioactivity and cytocompatibility.

  17. Tin in silicate glasses: structure, thermodynamics and kinetics

    International Nuclear Information System (INIS)

    In this work Moessbauer spectroscopy is used to investigate the oxidation states and structures of tin in silicate glasses. Thermal treatment of the glasses in atmospheres with varying oxygen partial pressure leads to the simultaneous appearance of reduction and diffusion. Experiments with varying treatment time give the opportunity to study diffusion and reduction processes in detail. Comparison of the hyperfine parameters of reference materials with measured parameter provides information about the local surroundings of the tin atoms. An octahedral surrounding for Sn4+ is presumed, while Sn2+ and three oxygen atoms form a tetrahedral coordination.

  18. Kinetics of Cyclohexanone Ammoximation over Titanium Silicate Molecular Sieves

    Institute of Scientific and Technical Information of China (English)

    李永祥; 吴巍; 闵恩泽

    2005-01-01

    An intrinsic kinetics of cyclohexanone ammoximation in the liquid phase over titanium silicate molecular sieves is investigated in an isothermal slurry reactor at different initial reactant concentrations, catalyst loading,and reaction temperature. The rate equations are developed by analyzing data of kinetic measurements. More than 10 side reactions were found. H202 decomposition reaction Inust be considered and other side reactions can be neglected in the kinetic modeling. The predicted values of reaction rates based on the kinetic models are almost consistent with experimental ones. The models have guidance to the selection of reactor types and they are useful to the design and operation of reactor used.

  19. Ladinian radiolarian fauna, siliceous rock from the Xianshuihe Belt, West Sichuan and their tectonic significance

    Institute of Scientific and Technical Information of China (English)

    LIANG Bin; FENG Qinglai; WANG Quanwei; GUO Jianqiu; ZHONG Changhong; LI Zhenjiang

    2005-01-01

    Ladinian radiolarian fauna, including Muelleritortis, Baumgartneria, Oertlispongus,Paroertlispongus, Pseudoertlispongus, etc., was discovered from the siliceous rock of the Runiange Formation in the Xianshuihe belt, West Sichuan Province. Geochemical test on five samples from the siliceous rock indicates that SiO2 content varies in 71.16%-90.06% and Si/Al ratio, in 49-71, which shows that the siliceous rock contains more terrigenous mud sediments.The siliceous rock is characterized by the large ratios of Al203/(Al203+Fe203) (0.63-0.81) and TiN (>26), the low ratio of V/Y (<2.8), and low vanadium content (<23 μg/g), which are similar to the geochemical characteristics of continental margin siliceous rock. The Ce/Ce* ratios of the four samples vary in 1.02-1.47 and the LaN/CeN ratio, in 0.75-1.07, which imply that the siliceous rock was deposited in the continental margin basin. But only one sample is similar to the oceanic siliceous rock in REE. Turbidite-siliceous rock bearing radiolarian-basalt assemblage and the geochemical characteristics of the siliceous rock indicate that the Xianshuihe belt is in the strong rift stage in the Ladinian age.

  20. Synthesis, characterization and modelling of zinc and silicate co-substituted hydroxyapatite

    OpenAIRE

    Friederichs, Robert J.; Chappell, Helen F.; Shepherd, David V.; Best, Serena M.

    2015-01-01

    Experimental chemistry and atomic modelling studies were performed here to investigate a novel ionic co-substitution in hydroxyapatite (HA). Zinc, silicate co-substituted HA (ZnSiHA) remained phase pure after heating to 1100°C with Zn and Si amounts of 0.6 wt% and 1.2 wt%, respectively. Unique lattice expansions in ZnSiHA, silicate Fourier transform infrared peaks and changes to the hydroxyl IR stretching region suggested Zn and silicate co-substitution in ZnSiHA. Zn and silicate insertion in...

  1. On the Anomalous Silicate Absorption Feature of the Prototypical Seyfert 2 Galaxy NGC 1068

    OpenAIRE

    Koehler, Melanie; Li, Aigen

    2012-01-01

    The first detection of the silicate absorption feature in AGNs was made at 9.7 micrometer for the prototypical Seyfert 2 galaxy NGC 1068 over 30 years ago, indicating the presence of a large column of silicate dust in the line-of-sight to the nucleus. It is now well recognized that type 2 AGNs exhibit prominent silicate absorption bands, while the silicate bands of type 1 AGNs appear in emission. More recently, using the Mid-Infrared Interferometric Instrument on the Very Large Telescope Inte...

  2. Nutrient accumulation and biomass production of alfafa after soil amendment with silicates

    Directory of Open Access Journals (Sweden)

    Angélica Cristina Fernandes Deus

    2014-06-01

    Full Text Available Studies on the use of silicate correctives in agriculture show that they have great potential to improve soil chemical characteristics, however, little information is available on the reactivity rates of their particle-size fractions. This study investigated whether the reactivity rates obtained experimentally could be considered in the calculation of ECC (effective calcium carbonate for soil liming, promoting adequate development of alfalfa plants. Six treatments were evaluated in the experiment, consisting of two slag types applied in two rates. The experimental ECC was used to calculate one of the rates and the ECC determined in the laboratory was used to calculate the other. Rates of limestone and wollastonite were based on the ECC determined in laboratory. The rates of each soil acidity corretive were calculated to increase the base saturation to 80%. The treatments were applied to a Rhodic Hapludox and an Alfisol Ferrudalfs. The methods for ECC determination established for lime can be applied to steel slag. The application of slag corrected soil acidity with consequent accumulation of Ca, P, and Si in alfalfa, favoring DM production.

  3. Identification and Practical Application of Silicate-dissolving Bacteria

    Institute of Scientific and Technical Information of China (English)

    LIN Qi-mei; RAO Zheng-hua; SUN Yan-xing; YAO Jun; XING Li-jun

    2002-01-01

    Slime-forming bacteria were isolated from soils, rock surface and earthworm intestine, and their effects on dissolving silicate minerals and tomato growth were examined. One of the bacteria, Bacillus mucilaginosus RGBc13, had particularly strong ability to form slime and dissolve silicates. RGBc13 could also colonize and develop in both non-rhizosphere and rhizosphere soil. Total number of slime-forming bacteria increased from 2.9 × 103 cfu·g- 1and 8.4 × 103 cfu·g-1 to 9.6 × 106 cfu·g-1 and 6.0 × 107 cfu·g-1 in the non-rhizosphere and rhizosphere soils respectively. Potassium and phosphorus nutritional conditions in the rhizosphere were markedly improved through inoculation of this bacterium. Available K and P respectively increased from 25.86 and 3.63mg· kg-1 in the non-rhizosphere soil to 91.23 and 5.74mg· kg-1 in the rhizosphere soil. Tomato biomass increased by 125%, K and P uptakes were more than 150%, greater than the non- inoculation. Thus, there is a potential in applying RGBc13 for improving plant K and P nutrition.

  4. Cobalt silicate hierarchical hollow spheres for lithium-ion batteries

    Science.gov (United States)

    Yang, Jun; Guo, Yuanyuan; Zhang, Yufei; Sun, Chencheng; Yan, Qingyu; Dong, Xiaochen

    2016-09-01

    In this paper, the synthesis of cobalt silicate novel hierarchical hollow spheres via a facile hydrothermal method is presented. With a unique hollow structure, the Co2SiO4 provides a large surface area, which can shorten the lithium ions diffusion length and effectively accommodate the volumetic variation during the lithiation/de-lithiation process. Serving as an anode material in lithium-ion battery application, the Co2SiO4 electrode demonstrates a high reversible specific capacity (first-cycle charge capacity of 948.6 mAh g-1 at 100 mA g-1), a cycling durability (specific capacity of 791.4 mAh g-1 after 100 cycles at 100 mA g-1), and a good rate capability (specific capacity of 349.4 mAh g-1 at 10 A g-1). The results indicate that the cobalt silicate hierarchical hollow sphere holds the potential applications in energy storage electrodes.

  5. A study of redox kinetic in silicate melt

    International Nuclear Information System (INIS)

    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)

  6. Silicates on Iapetus from Cassini's Composite Infrared Spectrometer

    CERN Document Server

    Young, Cindy L; Clark, Roger N; Spencer, John R; Jennings, Donald E; Hand, Kevin P; Poston, Michael J; Carlson, Robert W

    2015-01-01

    We present the first spectral features obtained from Cassini's Composite Infrared Spectrometer (CIRS) for any icy moon. The spectral region covered by CIRS focal planes (FP) 3 and 4 is rich in emissivity features, but previous studies at these wavelengths have been limited by low signal to noise ratios (S/Rs) for individual spectra. Our approach is to average CIRS FP3 spectra to increase the S/R and use emissivity spectra to constrain the composition of the dark material on Iapetus. We find an emissivity feature at ~855 cm-1 and a possible doublet at 660 and 690 cm-1 that do not correspond to any known instrument artifacts. We attribute the 855 cm-1 feature to fine-grained silicates, similar to those found in dust on Mars and in meteorites, which are nearly featureless at shorter wavelengths. Silicates on the dark terrains of Saturn's icy moons have been suspected for decades, but there have been no definitive detections until now. Serpentines reported in the literature at ambient temperature and pressure hav...

  7. The electrical conductivity of silicate liquids at extreme conditions

    Science.gov (United States)

    Scipioni, R.; Stixrude, L. P.

    2015-12-01

    Could the Earth have had a silicate dynamo early in its history? One requirement is that the electrical conductivity of silicate liquids be sufficiently high. However, very little is known about this property at the extreme conditions of pressure and temperature that prevailed in the magma ocean. We have computed from first principles molecular dynamics simulations the dc conductivity of liquid Silica SiO2 at pressure and temperature conditions spanning those of the magma ocean and super-Earth interiors. We find semi-metallic values of the conductivity at conditions typical of the putative basal magma ocean in the Early Earth. The variation of the conductivity with pressure and temperature displays interesting behavior that we rationalize on the basis of the closing the pseudo-gap at the Fermi level. For temperatures lower than T heat capacity, and reflectivity. The behavior of the heat capacity is different to that inferred from multiple Hugoniot experiments. These differences and the effect of including exact exchange on the calculations are discussed. Our results have important consequences for magnetic field generation in the early Earth and super-Earths.

  8. Santaclaraite, a new calcium-manganese silicate hydrate from California.

    Science.gov (United States)

    Erd, Richard C.; Ohashi, Y.

    1984-01-01

    Santaclaraite, ideally CaMn4(Si5O14(OH))(OH).H2O, occurs as pink and tan veins and masses in Franciscan chert in the Diablo Range, Santa Clara and Stanislaus counties, California. It is associated with four unidentified Mn silicates, Mn-howieite, quartz, braunite, calcite, rhodochrosite, kutnahorite, baryte, harmotome, chalcopyrite and native copper. Santaclaraite is triclinic, space group B1, a 15.633(1), b 7.603(1) , c 12.003(1) A, alpha 109.71(1)o, beta 88.61(1)o, gamma 99.95(1) o, V 1322.0(3) A3; Z = 4. The strongest lines of the X-ray pattern are 7.04(100), 3.003(84), 3.152(80), 7.69(63), 3.847(57) A. Crystals are lamellar to prismatic (flattened on (100)), with good cleavage on (100) and (010); H. 61/2 Dcalc. 3.398 g/cm3, Dmeas. 3.31 (+ or -0.01); optically biaxial negative, alpha 1.681, beta 1.696, gamma 1.708 (all + or - 0.002), 2Valpha 83 (+ or -1)o. Although chemically a hydrated rhodonite, santaclaraite dehydrates to Mn-bustamite at approx 550oC (in air) . Santaclaraite is a five-tetrahedral-repeat single-chain silicate and has structural affinities with rhodonite, nambulite, marsturite, babingtonite and inesite.-J.A.Z.

  9. A silicate disk in the heart of the Ant

    CERN Document Server

    Chesneau, Olivier; Balick, Bruce; Lagadec, Eric; Matsuura, Mikako; Smith, Nathan; Spang, Alain; Wolf, Sebastian; Zijlstra, Albert A

    2007-01-01

    We aim at getting high spatial resolution information on the dusty core of bipolar planetary nebulae to directly constrain the shaping process. Methods: We present observations of the dusty core of the extreme bipolar planetary nebula Menzel 3 (Mz 3, Hen 2-154, the Ant) taken with the mid-infrared interferometer MIDI/VLTI and the adaptive optics NACO/VLT. The core of Mz 3 is clearly resolved with MIDI in the interferometric mode, whereas it is unresolved from the Ks to the N bands with single dish 8.2 m observations on a scale ranging from 60 to 250 mas. A striking dependence of the dust core size with the PA angle of the baselines is observed, that is highly suggestive of an edge-on disk whose major axis is perpendicular to the axis of the bipolar lobes. The MIDI spectrum and the visibilities of Mz 3 exhibit a clear signature of amorphous silicate, in contrast to the signatures of crystalline silicates detected in binary post-AGB systems, suggesting that the disk might be relatively young. We used radiative-...

  10. Ion-specific effects influencing the dissolution of tricalcium silicate

    Energy Technology Data Exchange (ETDEWEB)

    Nicoleau, L. [BASF Research Construction Materials and Systems, BASF Construction Chemicals GmbH, 83308 Trostberg (Germany); Schreiner, E., E-mail: eduard.schreiner@basf.com [BASF Materials and Systems, BASF SE, 67056 Ludwigshafen (Germany); Nonat, A., E-mail: andre.nonat@u-bourgogne.fr [Institut Carnot de Bourgogne, UMR6303 CNRS, 9 avenue Alain Savary, BP 47870, 21078 Dijon Cedex (France)

    2014-05-01

    It has been recently demonstrated that the dissolution kinetics of tricalcium silicate (C{sub 3}S) is driven by the deviation from its solubility equilibrium. In this article, special attention is paid to ions relevant in cement chemistry likely to interact with C{sub 3}S. In order to determine whether specific effects occur at the interface C{sub 3}S–water, particular efforts have been made to model ion activities using Pitzer's model. It has been found that monovalent cations and monovalent anions interact very little with the surface of C{sub 3}S. On the other side, divalent anions like sulfate slow down the dissolution more strongly by modifying the surface charging of C{sub 3}S. Third, aluminate ions covalently bind to surface silicate monomers and inhibit the dissolution in mildly alkaline conditions. The formation and the breaking of these bonds depend on pH and on [Ca{sup 2+}]. Thermodynamic calculations performed using DFT combined with the COSMO-RS solvation method support the experimental findings.

  11. Cobalt silicate hierarchical hollow spheres for lithium-ion batteries

    Science.gov (United States)

    Yang, Jun; Guo, Yuanyuan; Zhang, Yufei; Sun, Chencheng; Yan, Qingyu; Dong, Xiaochen

    2016-09-01

    In this paper, the synthesis of cobalt silicate novel hierarchical hollow spheres via a facile hydrothermal method is presented. With a unique hollow structure, the Co2SiO4 provides a large surface area, which can shorten the lithium ions diffusion length and effectively accommodate the volumetic variation during the lithiation/de-lithiation process. Serving as an anode material in lithium-ion battery application, the Co2SiO4 electrode demonstrates a high reversible specific capacity (first-cycle charge capacity of 948.6 mAh g‑1 at 100 mA g‑1), a cycling durability (specific capacity of 791.4 mAh g‑1 after 100 cycles at 100 mA g‑1), and a good rate capability (specific capacity of 349.4 mAh g‑1 at 10 A g‑1). The results indicate that the cobalt silicate hierarchical hollow sphere holds the potential applications in energy storage electrodes.

  12. The structure of alkali silicate gel by total scattering methods

    KAUST Repository

    Benmore, C.J.

    2010-06-01

    The structure of the alkali silicate gel (ASR) collected from the galleries of Furnas Dam in Brazil was determined by a pair distribution function (PDF) analysis of high energy X-ray diffraction data. Since this method is relatively new to concrete structure analysis a detailed introduction on the PDF method is given for glassy SiO2. The bulk amorphous structure of the dam material is confirmed as no Bragg peaks are observed in the scattered intensity. The real space results show that the local structure of the amorphous material is similar to kanemite (KHSi2O5:3H2O) however the long range layer structure of the crystal is broken up in the amorphous state, so that ordering only persists of the length scale of a few polyhedra. The silicate layer structure is a much more disordered than predicted by molecular dynamics models. The X-ray results are consistent with the molecular dynamics model of Kirkpatrick et al. (2005) [1] which predicts that most of the water resides in pores within the amorphous network rather than in layers. The total scattering data provide a rigorous basis against which other models may also be tested. © 2010.

  13. Authigenic Mineralization of Silicates at the Organic-water Interface

    Science.gov (United States)

    McEvoy, B.; Wallace, A. F.

    2015-12-01

    It is relatively common for some fraction of organic material to be preserved in the sedimentary rock record as disseminated molecular fragments. The survival of wholly coherent tissues from primarily soft-bodied organisms is far more unusual. However, the literature is now well- populated with spectacular examples of soft-tissue preservation ranging from a 2,600 year old human brain to the tissues of the Ediacaran biota that have survived ~600 million years. Some of the most exceptional examples of soft tissue preservation are from the Proterozoic-Cambrian transition, however, nearly all modes of fossil preservation during this time are debated. Clay mineral templates have been implicated as playing a role in several types of soft tissue preservation, including Burgess Shale and Beecher's Trilobite-type preservation, and more recently, Bitter Springs-type silicification. Yet, there is still much debate over whether these clay mineral coatings form during early stage burial and diagenesis, or later stage metamorphism. This research addresses this question by using in situ fluid cell Atomic Force Microscopy (AFM) to investigate the nucleation and growth of silicate minerals on model biological surfaces. Herein we present preliminary results on the deposition of hydrous magnesium silicates on self-assembled monolayers (-OH, -COOH, -CH3, and -H2PO3 terminated surfaces) at ambient conditions.

  14. Polymer-Layered Silicate Nanocomposites for Cryotank Applications

    Science.gov (United States)

    Miller, Sandi G.; Meador, Michael A.

    2007-01-01

    Previous composite cryotank designs have relied on the use of conventional composite materials to reduce microcracking and permeability. However, revolutionary advances in nanotechnology derived materials may enable the production of ultra-lightweight cryotanks with significantly enhanced durability and damage tolerance, as well as reduced propellant permeability. Layered silicate nanocomposites are especially attractive in cryogenic storage tanks based on results that have been reported for epoxy nanocomposite systems. These materials often exhibit an order of magnitude reduction in gas permeability when compared to the base resin. In addition, polymer-silicate nanocomposites have been shown to yield improved dimensional stability, strength, and toughness. The enhancement in material performance of these systems occurs without property trade-offs which are often observed in conventionally filled polymer composites. Research efforts at NASA Glenn Research Center have led to the development of epoxy-clay nanocomposites with 70% lower hydrogen permeability than the base epoxy resin. Filament wound carbon fiber reinforced tanks made with this nanocomposite had a five-fold lower helium leak rate than the corresponding tanks made without clay. The pronounced reduction observed with the tank may be due to flow induced alignment of the clay layers during processing. Additionally, the nanocomposites showed CTE reductions of up to 30%, as well as a 100% increase in toughness.

  15. Lightning and Mass Independent Oxygen Isotopic Fractionation in Nebular Silicates

    Science.gov (United States)

    Nuth, Joseph A.

    2009-01-01

    Lightning has long been postulated as the agent of Chondru|e formation in the solar nebula, but it may have an additional role to play as well. Lightning bolts of almost any scale will both vaporize dust and liberate oxygen atoms that will then interact with both nebular gases as well as the refractory silicate vapor as it re-condenses. Such processes should result in the addition of the heavy oxygen isotopes to the growing silicate grains while the light oxygen-16 becomes part of the gas phase water. This process will proceed to some extent throughout the history of any turbulent nebula and will result in the gradual increase of O-16 in the gas phase and in a much larger relative increase in the O-17 and O-18 content of the nebular dust. Laboratory experiments have demonstrated the production of such "heavy oxygen enriched", non-mass-dependently-fractionated dust grains in a high voltage discharge in a hydrogen rich gas containing small quantities of silane, pentacarbonyl iron and oxygen.

  16. Potassium-silicate glass exposed to low energy H+ beam

    International Nuclear Information System (INIS)

    Highlights: ► Pristine potassium-silicate glass was irradiated with 5 keV protons. ► Surface relaxation increases amount of K and NBO in the surface layer. ► Enhanced bombardment leads to a continuous decrease of NBO and K. ► A constant surplus of K in elemental state was found on the glass surface. - Abstract: Pristine surface of binary potassium silicate glass 85SiO2·15K2O was prepared in vacuum and irradiated with a 5 keV proton beam within the range of 0.6–103 C/m2. The response of glass surface was monitored by XPS and the evolution of atomic concentrations divided it into two stages. During the first one, amounts of both potassium and non-bridging oxygen (NBO) increase in the surface layer and are governed by surface relaxation. The second stage is characterised by a continuous decrease of NBO and K. Comparison of K and NBO concentrations yielded a constant surplus of K proving the existence of potassium elemental state on the glass surface. Ratio of bridging oxygen (BO) and silicon is conserved during proton bombardment. The extrapolation of the glass response to the enhanced irradiation predicts a formation of substoichiometric SiOx with some elemental K on the topmost surface.

  17. Selective and simultaneous determination of phosphate and silicate ions in leaching process waters for ceramics glaze raw materials of narutal origin by ion-exclusion chromatography coupled with UV-detection after postcolumn derivatization.

    Science.gov (United States)

    Ikedo, Mikaru; Mori, Masanobu; Kurachi, Kazumasa; Hu, Wenzhi; Tanaka, Kazuhiko

    2006-01-01

    The selective and simultaneous ion-exclusion chromatography (IEC) with UV-detection on a weakly acidic cation-exchange resin column in the H+ -form (TSKgel Super IC-A/C) was developed and applied for the simultaneous determination of phosphate and silicate ions as the water quality parameters required for optimizing the water-leaching process for ceramics glaze raw materials of natural origin including feldspar, woods-ash, and straw-ash. Phosphate and silicate ions in these water-leaching process water samples were separated selectively from the coexisting anions such as sulfate, chloride, nitrate and carbonate ions, based on the ion-exclusion separation mechanism. They were detected selectively and simultaneously by a postcolumn derivatization with molybdenum-yellow using the UV-detector. Under the optimized separation and detection conditions (eluent, 0-1 mM sulfuric acid; reactant, 10 mM sodium molybdate-25 mM sulfuric acid; detector, UV at 370 nm; temperature, 45 degrees C), the linearity of calibration was in the range 0.1 - 10 ppm for both phosphate and silicate ions, and the detection limits at S/N = 3 were 2.58 ppb for silicate ions and 4.75 ppb for phosphate ions. The effectiveness of this method was demonstrated in practical applications to the water-leaching process for some ceramics glaze raw materials. PMID:16429785

  18. Interaction of dispersed polyvynil acetate with silicate in finishing materials

    Directory of Open Access Journals (Sweden)

    Runova, R. F.

    1996-12-01

    Full Text Available This article focuses on the processes of interaction between calcium silicate hydrates and dispersed polyvinyl acetate in tight films with the aim of developing compounds meant for restoration and finishing works. The basis of this development relies on the concept concerning the determining role of the crystal-chemical factor of the silicate phase in the formation of organic-mineral compounds of increased durability. The characteristics of dispersed calcium silicate hydrates are portrayed. The preparation conditions, accounting for the synthesis of the product of submicrocrystalline structure, conforming with the stoichiometry CaO∙SiO2 =0.8-2.0 have been determined. The interaction has been studied for compounds achieved by mixing ingredients in a rapid whirling mixer, and subjected to hardening at T=20+2 T. With the aid of XRD, DTA and Infra-Red Spectrometry methods the formation process of the sophisticated polymer silicate phase in the material was observed for a period of 90 days. The properties of the film were investigated and its high resistance against the influence of external factors was established. On this basis a conclusion concerning the quite high effectiveness of substituting portland cement with dispersed calcium silicate hydrate in polymer cement compounds has been made. White colour and other various special properties determine the suitability for repair and finishing works on facades of buildings.

    Este artículo está orientado a estudiar los procesos de interacción entre los silicatos cálcicos hidratados y el acetato de polivinilo disperso en capas impermeables, con el objeto de desarrollar compuestos destinados para la restauración. El fundamento de estos estudios es determinar el papel que los factores cristaloquímicos de las fases silicato tienen en la formación de compuestos órganominerales de elevada durabilidad. Se han descrito las características de los silicatos cálcicos hidratados

  19. Corrosion resistance of enamel coating modified by calcium silicate and sand particle for steel reinforcement in concrete

    Science.gov (United States)

    Tang, Fujian

    Porcelain enamel has stable chemical property in harsh environments such as high temperature, acid and alkaline, and it can also chemically react with substrate reinforcing steel resulting in improved adherence strength. In this study, the corrosion resistances of enamel coating modified by calcium silicate and sand particles, which are designed for improved bond strength with surrounding concrete, were investigated in 3.5 wt% NaCl solution. It consists of two papers that describe the results of the study. The first paper investigates the corrosion behavior of enamel coating modified by calcium silicate applied to reinforcing steel bar in 3.5 wt% NaCl solution by OCP, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. The coatings include a pure enamel, a mixed enamel that consists of 50% pure enamel and 50% calcium silicate by weight, and a double enamel that has an inner pure enamel layer and an outer mixed enamel layer. Electrochemical tests demonstrates that both pure and double enamel coatings can significantly improve corrosion resistance, while the mixed enamel coating offers very little protection due to connected channels. The second paper is focused on the electrochemical characteristics of enamel coating modified by sand particle applied to reinforcing steel bar in 3.5 wt% NaCl solution by EIS. Six percentages by weight are considered including 5%, 10%, 20%, 30%, 50%, and 70%. Results reveal that addition of sand particle does not affect its corrosion resistance significantly. Most of the sand particles can wet very well with enamel body, while some have a weak zone which is induced during the cooling stage due to different coefficient of thermal expansion. Therefore, quality control of sand particle is the key factor to improve its corrosion resistance.

  20. 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)

  1. Is Tridymite at Gale Crater Evidence for Silicic Volcanism on Mars?

    Science.gov (United States)

    Morris, Richard V.; Vaniman, David T.; Ming, Douglas W.; Graff, Trevor G.; Downs, Robert T.; Fendrich, Kim; Mertzman, Stanley A.

    2016-01-01

    The X-ray diffraction (XRD) instrument (CheMin) onboard the MSL rover Curiosity detected 17 wt% of the SiO2 polymorph tridymite (relative to bulk sample) for the Buckskin drill sample (73 wt% SiO2) obtained from sedimentary rock in the Murray formation at Gale Crater, Mars. Other detected crystalline materials are plagioclase, sanidine, cristobalite, cation-deficient magnetite, and anhydrite. XRD amorphous material constitutes approx. 60 wt% of bulk sample, and the position of its broad diffraction peak near approx. 26 deg. 2-theta is consistent with opal-A. Tridymite is a lowpressure, high-temperature mineral (approx. 870 to 1670 deg. C) whose XRD-identified occurrence on the Earth is usually associated with silicic (e.g., rhyolitic) volcanism. High SiO2 deposits have been detected at Gale crater by remote sensing from martian orbit and interpreted as opal-A on the basis H2O and Si-OH spectral features. Proposed opal-A formation pathways include precipitation of silica from lake waters and high-SiO2 residues of acid-sulfate leaching. Tridymite is nominally anhydrous and would not exhibit these spectral features. We have chemically and spectrally analyzed rhyolitic samples from New Mexico and Iwodake volcano (Japan). The glassy (by XRD) NM samples have H2O spectral features similar to opal-A. The Iwodake sample, which has been subjected to high-temperature acid sulfate leaching, also has H2O spectral features similar to opal-A. The Iwodake sample has approx. 98 wt% SiO2 and 1% wt% TiO2 (by XRF), tridymite (>80 wt.% of crystalline material without detectable quartz by XRD), and H2O and Si-OH spectral features. These results open the working hypothesis that the opal-A-like high-SiO2 deposits at Gale crater detected from martian orbit are products of alteration associated with silicic volcanism. The presence or absence of tridymite will depend on lava crystallization temperatures (NM) and post crystallization alteration temperatures (Iwodake).

  2. Examination of silicate limitation of primary production in Jiaozhou Bay, China. I. Silicate being a limiting factor of phytoplankton primary production

    Science.gov (United States)

    Yang, Dong-Fang; Zhang, Jing; Lu, Ji-Bin; Gao, Zhen-Hui; Chen, Yu

    2002-09-01

    Jiaozhou Bay data collected from May 1991 to February 1994, in 12 seasonal investigations, and provided the authors by the Ecological Station of Jiaozhou Bay, were analyzed to determine the spatiotemporal variations in temperature, light, nutrients (NO{3/-}-N, NO{2/-}-N, NH{4/+}-N, SiO{3/2-}-Si, PO{4/3-}-P), phytoplankton, and primary production in Jiaozhou Bay. The results indicated that only silicate correlated well in time and space with, and had important effects on, the characteristics, dynamic cycles and trends of, primary production in Jiaozhou Bay. The authors developed a corresponding dynamic model of primary production and silicate and water temperature. Eq. (1) of the model shows that the primary production variation is controlled by the nutrient Si and affected by water temperature; that the main factor controlling the primary production is Si; that water temperature affects the composition of the structure of phytoplankton assemblage; that the different populations of the phytoplankton assemblage occupy different ecological niches for C, the apparent ratio of conversion of silicate in seawater into phytoplankton biomas and D, the coefficient of water temperature's effect on phytoplankton biomass. The authors researched the silicon source of Jiaozhou Bay, the biogeochemical sediment process of the silicon, the phytoplankton predominant species and the phytoplankton structure. The authors considered silicate a limiting factor of primary production in Jiaozhou Bay, whose decreasing concentration of silicate from terrestrial source is supposedly due to dilution by current and uptake by phytoplankton; quantified the silicate assimilated by phytoplankton, the intrinsic ratio of conversion of silicon into phytoplankton biomass, the proportion of silicate uptaken by phytoplankton and diluted by current; and found that the primary production of the phytoplankton is determined by the quantity of the silicate assimilated by them. The phenomenon of apparently high

  3. EXAMINATION OF SILICATE LIMITATION OF PRIMARY PRODUCTION IN JIAOZHOU BAY, CHINA Ⅰ. SILICATE BEING A LIMITING FACTOR OF PHYTOPLANKTON PRIMARY PRODUCTION

    Institute of Scientific and Technical Information of China (English)

    杨东方; 张经; 吕吉斌; 高振会; 陈豫

    2002-01-01

    Jiaozhou Bay data collected from May 1991 to February 1994, in 12 seasonal investigations, and provided the authors by the Ecological Station of Jiaozhou B ay, were analyzed to determine the spatiotemporal variations in temperature, light, nutrients (NO-3-N, NO-2-N, NH+4-N, SiO2-3-Si, PO3-4-P), phytoplankton, and primary production in Jiaozhou Bay. The results indicated that only silicate correlated well in time and space with, and had important effects on, the characteristics, dynamic cycles and trends of, primary production in Jiaozhou Bay. The authors developed a corresponding dynamic model of primary production and silicate and water temperature. Eq.(1) of the model shows that the primary production variation is controlled by the nutrient Si and affected by water temp erature; that the main factor controlling the primary production is Si; that water temper ature affects the composition of the structure of phytoplankton assemblage; that the different populations of the phytoplankton assemblage occupy different ecologica l niches for C, the apparent ratio of conversion of silicate in seawater into phytoplankton biomas and D, the coefficient of water temperature's effect on phytoplankton biomass. The authors researched the silicon source of Jiaozhou Bay , the biogeochemical sediment process of the silicon, the phytoplankton predominan t species and the phytoplankton structure. The authors considered silicate a limit ing factor of primary production in Jiaozhou Bay, whose decreasing concentration of silicate from terrestrial source is supposedly due to dilution by current and up take by phytoplankton; quantified the silicate assimilated by phytoplankton, the intrins ic ratio of conversion of silicon into phytoplankton biomass, the proportion of silicate uptaken by phytoplankton and diluted by current; and found that the primary production of the phytoplankton is determined by the quantity of the silicate assimilated by them. The phenomenon of apparently high plant

  4. EXAMINATION OF SILICATE LIMITATION OF PRIMARY PRODUCTION IN JIAOZHOU BAY, CHINA——I. SILICATE BEING A LIMITING FACTOR OF PHYTOPLANKTON PRIMARY PRODUCTION

    Institute of Scientific and Technical Information of China (English)

    杨东方; 张经; 吕吉斌; 高振会; 陈豫

    2002-01-01

    Jiaozhou Bay data collected from May 1991 to February 1994, in 12 seasonal investigations, and provided the authors by the Ecological Station of Jiaozhou Bay, were analyzed to determine the spatiotemporal variations in temperature, light, nutrients (NO3--N, NO2--N, NH4+-N, SIO32--Si, PO43--P), phytoplankton, and primary production in Jiaozhou Bay. The results indicated that only silicate correlated well in time and space with, and had important effects on, the characteristics, dynamic cycles and trends of, primary production in Jiaozhou Bay. The authors developed a corresponding dynamic model of primary production and silicate and water temperature. Eq. ( 1 ) of the model shows that the primary production variation is controlled by the nutrient Si and affected by water temperature; that the main factor controlling the primary production is Si; that water temperature affects the composition of the structure of phytoplankton assemblage; that the different populations of the phytoplankton assemblage occupy different ecological niches for C, the apparent ratio of conversion of silicate in seawater into phytoplankton biomas and D, the coefficient of water temperature's effect on phytoplankton biomass. The authors researched the silicon source of Jiaozhou Bay, the biogeochemical sediment process of the silicon, the phytoplankton predominant species and the phytoplankton structure. The authors considered silicate a limiting factor of primary production in Jiaozhou Bay, whose decreasing concentration of silicate from terrestrial source is supposedly due to dilution by current and uptake by phytoplankton; quantified the silicate assimilated by phytoplankton, the intrinsic ratio of conversion of silicon into phytoplankton biomass, the proportion of silicate uptaken by phytoplankton and diluted by current; and found that the primary production of the phytoplankton is determined by the quantity of the silicate assimilated by them. The phenomenon of apparently high plant

  5. Mechanical and thermal properties of sodium silicate treated moso bamboo particles reinforced PVC composites

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The main objective of this research was to study the potential of sodium silicate modification on moso bamboo particles as reinforcements for thermoplastic. Moso bamboo particles were modified with sodium silicate aqueous solutions (of 0.5%, 1%, 2%, 5% and 10% concentrations). The mechanical properties of sodium silicate treated moso bamboo particles reinforced PVC composites (BPPC) were calculated and compared with raw bamboo particles filled samples. The thermal characteristics of the BPPC were studied to investigate the feasibility of sodium silicate treatment on moso bamboo particles. The particle morphology and BPPC microstructure were investigated by scanning electron microscopy. Results showed that the tensile strength and modulus of elasticity of the BPPC increased before the concentration of sodium silicate solution reached 5% and got their maximum values of 15.72 MPa and 2956.80 MPa, respectively at 5% concentration. The modulus of rupture obtained the maximum value of 27.73 MPa at 2% concentration. The mechanical curve decreased as the concentration of solution went higher. Differential scanning calorimetric analysis illustrated that the sodium silicate solution treated BPPC possesses a better compatibility. More uniform dispersion of moso bamboo particles in PVC matrix was obtained after the sodium silicate treatment. Hence, the sodium silicate was a feasible and competitive agent of creating moso bamboo particles reinforced PVC composites.

  6. Synthesis and reaction behavior of calcium silicate hydrate in basic system

    Institute of Scientific and Technical Information of China (English)

    刘桂华; 贺强; 李小斌; 彭志宏; 周秋生

    2004-01-01

    At the molar ratio of CaO to SiO2 of 1, with calcium hydroxide and sodium silicate, calcium silicate hydrate was synthesized at 50, 100, 170 ℃, respectively. The results show that temperature favors the formation of calcium silicate hydrate with perfect structure. When calcium silicate hydrate reacts with caustic solution, the decomposition rate of calcium silicate hydrate increases with the increasing caustic concentration and decreases with the raising synthesis temperature and the prolongation of reaction time. The decomposition rate is all less than 1.2 % in caustic solution, and XRD pattern of the residue after reaction with caustic solution is found as the same as that of original calcium silicate hydrate, which indicates the stable existence of calcium silicate hydrate in caustic solution.When reacted with soda solution, the decomposition rate increases with the increasing soda concentration and reaction time, while decreases with the synthesis temperature. The decomposition rate is more than 2% because CaO · SiO2 · H2O(CSH( Ⅰ )), except Ca5 (OH)2Si6O16 · 4H2O and Ca6Si6O17 (OH)2, is decomposed. So the synthesis temperature and soda concentration should be controlled in the process of transformation of sodium aluminosilicate hydrate into calcium silicate hydrate.

  7. FT-IR and 29 Si-NMR for evaluating aluminium silicate precursors for geopolymers

    NARCIS (Netherlands)

    Valcke, S.L.A.; Pipilikaki, P.; Fischer, H.R.; Verkuijlen, M.H.W.; Eck, E.R.H.

    2014-01-01

    Geopolymers are systems of inorganic binders that can be used for sustainable, cementless concrete and are formed by alkali activation of an aluminium–silicate precursor (often secondary resources like fly ash or slag). The type of aluminium– silicate precursor and its potential variations within on

  8. Annealing of Pre-Cometary Silicate Grains in Solar Nebula Shocks

    Science.gov (United States)

    Harker, D. E.; Desch, S. J.

    2002-01-01

    Comets contain crystalline silicate grains which could only have formed at high temperatures, not generally experienced by comets. We test the hypothesis that amorphous silicates were annealed by shock waves in the solar nebula. Additional information is contained in the original extended abstract.

  9. Microstructure engineering of Portland cement pastes and mortars through addition of ultrafine layer silicates

    DEFF Research Database (Denmark)

    Lindgreen, Holger; Geiker, Mette Rica; Krøyer, Hanne;

    2008-01-01

    Pozzolanic submicron-sized silica fume and the non-pozzolanic micron- and nano-sized layer silicates (clay minerals) kaolinite, smectite and palygorskite have been used as additives in Portland cement pastes and mortars. These layer silicates have different particle shape (needles and plates...

  10. Synthesis, structure peculiarities and electric conductivity of alkali metal-rare earth silicates (germanates)

    International Nuclear Information System (INIS)

    The process of obtaining of rare earth-alkali metal silicates (germanates) is studied. The analysis of possibilities of structural disordering of alkaline cations in these structures is given. The interaction of the structure of different by the composition alkali alkali metal - rare earth silicates with electric conductivity values is shown

  11. Sodium Silicate Behavior in Porous Media Applied for In-Depth Profile Modifications

    Directory of Open Access Journals (Sweden)

    Hossein A. Akhlaghi Amiri

    2014-03-01

    Full Text Available This paper addresses alkaline sodium silicate (Na-silicate behavior in porous media. One of the advantages of the Na-silicate system is its water-like injectivity during the placement stage. Mixing Na-silicate with saline water results in metal silicate precipitation as well as immediate gelation. This work demonstrated that low salinity water (LSW, sea water diluted 25 times could be used as a pre-flush in flooding operations. A water override phenomenon was observed during gel formation which is caused by gravity segregation. Dynamic adsorption tests in the sand-packed tubes showed inconsiderable adsorbed silicon density (about 8.5 × 10−10 kg/cm3 for a solution with 33 mg/L silicon content, which is less than the estimated mono-layer adsorption density of 1.4 × 10−8 kg/cm3. Na-silicate enhanced water sweep efficiency after application in a dual-permeability sand-pack system, without leak off into the oil-bearing low permeability (LP zone. Field-scale numerical sensitivity studies in a layered reservoir demonstrated that higher permeability and viscosity contrasts and lower vertical/horizontal permeability ratio result in lower Na-silicate leakoff into the matrix. The length of the mixing zone between reservoir water and the injected Na-silicate solution, which is formed by low salinity pre-flush, acts as a buffer zone.

  12. The interaction of components organic-silicate paintwork material with painted surface

    OpenAIRE

    Шолух, Н.Е.; Кудюков, Ю.П.; Ржецкий, Е.А.

    2010-01-01

    The interaction of components organic-silicate paintwork material with painted surface is studied. It is shown that coverings on a basis of organic-silicate composition that is putting on a surfaces of concrete, brick, plaster, asbestos cement and similar building materials, have good physical-mechanical indicators.

  13. Synthesis of magnesium silicate from wheat husk ash: Effects of parameters on structural and surface properties

    Directory of Open Access Journals (Sweden)

    Pinar Terzioglu

    2012-11-01

    Full Text Available In the present study, magnesium silicate was produced by using wheat husk ash. Wheat husk was burned at 600 °C to obtain an amorphous ash structure, and the ash was processed with sodium hydroxide solution with heat to extract silica. Sodium silicate solution and magnesium salts were used to synthesize magnesium silicate. The present study investigates effects of the feeding rate on magnesium silicate production (0.6 mL/min, 35 mL/min, 70 mL/min, the type of magnesium salt (MgSO4 • 7H2O or MgCl2 • 6H2O, temperature (25 °C or 50 °C, and the washing agent (water and acetone on the chemical composition and surface characteristics of magnesium silicate. The results demonstrated that all of the variables affected the surface characteristics of magnesium silicate, such as surface area, particle size, and pore volume. However, it was also observed that the studied parameters did not affect the chemical composition of magnesium silicate. The wheat husk ash-based magnesium silicates obtained in the experimental study had a BET surface area ranging from 79 to 91 m2/g and a particle size varying from 42 to 63 µm.

  14. Quantitative estimation of the reinforcing effect of layered silicates in PP nanocomposites

    NARCIS (Netherlands)

    Szazdi, Laszlo; Pukansky Jr, Bela; Vancso, G. Julius; Pukanszky, Bela

    2006-01-01

    Various polypropylene/layered silicate composites were prepared with different silicate contents. Montmorillonites with and without organophilization as well as three maleinated polypropylenes were used to change the extent of exfoliation and hence the properties of the composites. Structure was cha

  15. Nanoparticles Containing High Loads of Paclitaxel-Silicate Prodrugs: Formulation, Drug Release, and Anticancer Efficacy.

    Science.gov (United States)

    Han, Jing; Michel, Andrew R; Lee, Han Seung; Kalscheuer, Stephen; Wohl, Adam; Hoye, Thomas R; McCormick, Alon V; Panyam, Jayanth; Macosko, Christopher W

    2015-12-01

    We have investigated particle size, interior structure, drug release kinetics, and anticancer efficacy of PEG-b-PLGA-based nanoparticles loaded with a series of paclitaxel (PTX)-silicate prodrugs [PTX-Si(OR)3]. Silicate derivatization enabled us to adjust the hydrophobicity and hydrolytic lability of the prodrugs by the choice of the alkyl group (R) in the silicate derivatives. The greater hydrophobicity of these prodrugs allows for the preparation of nanoparticles that are stable in aqueous dispersion even when loaded with up to ca. 75 wt % of the prodrug. The hydrolytic lability of silicates allows for facile conversion of prodrugs back to the parent drug, PTX. A suite of eight PTX-silicate prodrugs was investigated; nanoparticles were made by flash nanoprecipitation (FNP) using a confined impingement jet mixer with a dilution step (CIJ-D). The resulting nanoparticles were 80-150 nm in size with a loading level of 47-74 wt % (wt %) of a PTX-silicate, which corresponds to 36-59 effective wt % of free PTX. Cryogenic transmission electron microscopy images show that particles are typically spherical with a core-shell structure. Prodrug/drug release profiles were measured. Release tended to be slower for prodrugs having greater hydrophobicity and slower hydrolysis rate. Nanoparticles loaded with PTX-silicate prodrugs that hydrolyze most rapidly showed in vitro cytotoxicity similar to that of the parent PTX. Nanoparticles loaded with more labile silicates also tended to show greater in vivo efficacy.

  16. Effect of silicate pretreatment, post-sealing and additives on corrosion resistance of phosphated galvanized steel

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Sodium silicate (water glass) pretreatment before phosphating, silicate post-sealing after phosphating and adding silicate to a traditional phosphating solution were respectively carried out to obtain the improved phosphate coatings with high corrosion resistance and coverage on hot-dip galvanized(HDG) steel. The corrosion resistance, morphology and chemical composition of the coatings were investigated using neutral salt spray(NSS) tests, scanning electron microscopy(SEM) and energy dispersive spectroscopy(EDS). The results show that pretreatment HDG steel with silicate solutions, phosphate coatings with finer crystals and higher coverage are formed and the corrosion resistance is enhanced. Adding silicate to a traditional phosphating solution, the surface morphology of the coatings is nearly unchanged. The corrosion resistance of the coatings is mainly dependent on phosphating time.Phosphating for a longer time (such as 5 min), the corrosion resistance, increasing with concentration of silicate, is improved significantly. Post-sealing the phosphated HDG steel with silicate solutions, the pores among the zinc phosphate crystals are sealed with the films containing Si, P, O and Zn and the continuous composite coatings are formed. The corrosion resistance of the composite coatings, related to the pH value, contents of hydrated gel of silica and Si2O52- and post-sealing time, is increased markedly. The improved coatings with optimal corrosion resistance are obtained for phosphating 5 min and post-sealing with 5 g/L silicate solution for 10 min.

  17. Dynamic Strengthening During High Velocity Shear Experiments with Siliceous Rocks

    Science.gov (United States)

    Liao, Z.; Chang, J. C.; Boneh, Y.; Chen, X.; Reches, Z.

    2011-12-01

    It is generally accepted that dynamic-weakening is essential for earthquake instability, and many experimental works have documented this weakening. Recent observations revealed also opposite trends of dynamic-strengthening in experiments (Reches & Lockner, 2010). We present here our experimental results of this dynamic-strengthening and discuss possible implications to earthquake behavior. We ran hundreds of experiments on experimental faults made of siliceous rock including granite, syenite, diorite, and quartzite. The experimental fault is comprised of two solid cylindrical blocks with a raised-ring contact of 7 cm diameter and 1 cm width. We recognized general, three regimes of strength-velocity relations: (I) Dynamic weakening (drop of 20-60% of static strength) as slip velocity increased from ~0.0003 m/s (lowest experimental velocity) to a critical velocity, Vc=0.008-0.16 m/s; (II) Abrupt transition to dynamic strengthening regime during which the fault strength almost regains its static strength; and (III) Quasi-constant strength with further possible drops as velocity approaches ~1 m/s. The critical velocity depends on the sample lithology: Vc is ~0.06 m/s for granite, ~0.008 m/s for syenite, ~0.01 m/s for diorite, and ~0.16 m/s for quartzite. The strengthening stage is associated with temperature increase, wear-rate increase, and the occurrence of intense, high frequency stick-slip events (Reches & Lockner, 2010). Sammis et al., (this meeting) attributed this strengthening to dehydration of the thin water layer that covers the gouge particles as the temperature increases. On the other hand, we note that tens of experiments with dolomite samples (non-siliceous), which were deformed under similar conditions, did not exhibit the velocity strengthening (unpublished). Based on the analyses by Andrews (2004, 2005), we speculate that velocity strengthening may bound the slip velocity. The numerical models of Andrews show that the slip velocity along a slip

  18. Soft X-ray Irradiation of Silicates: Implications on Dust Evolution in Protoplanetary Disks

    CERN Document Server

    Ciaravella, A; Chen, Y -J; Caro, G M Muñoz; Huang, C -H; Jiménez-Escobar, A; Venezia, A M

    2016-01-01

    The processing of energetic photons on bare silicate grains was simulated experimentally on silicate ?lms submitted to soft X-rays of energies up to 1.25 keV. The silicate material was prepared by means of a microwave assisted solgel technique. Its chemical composition reflects the Mg2SiO4 stoichiometry with residual impurities due to the synthesis method. The experiments were performed using the spherical grating monochromator beamline at the National Synchrotron Radiation Research Center in Taiwan. We found that soft X-ray irradiation induces structural changes that can be interpreted as an amorphization of the processed silicate material. The present results may have relevant implications in the evolution of silicate materials in X-ray irradiated protoplanetary disks.

  19. Preparation of TiO2 nanotubes/mesoporous calcium silicate composites with controllable drug release.

    Science.gov (United States)

    Xie, Chunling; Li, Ping; Liu, Yan; Luo, Fei; Xiao, Xiufeng

    2016-10-01

    Nanotube structures such as TiO2 nanotube (TNT) arrays produced by self-ordering electrochemical anodization have been extensively explored for drug delivery applications. In this study, we presented a new implantable drug delivery system that combined mesoporous calcium silicate coating with nanotube structures to achieve a controllable drug release of water soluble and antiphlogistic drug loxoprofen sodium. The results showed that the TiO2 nanotubes/mesoporous calcium silicate composites were successfully fabricated by a simple template method and the deposition of mesoporous calcium silicate increased with the soaking time. Moreover, the rate of deposition of biological mesoporous calcium silicate on amorphous TNTs was better than that on anatase TNTs. Further, zinc-incorporated mesoporous calcium silicate coating, produced by adding a certain concentration of zinc nitrate into the soaking system, displayed improved chemical stability. A significant improvement in the drug release characteristics with reduced burst release and sustained release was demonstrated. PMID:27287140

  20. Newly Identified Silicate Carbon Stars from IRAS Low-Resolution Spectra

    Institute of Scientific and Technical Information of China (English)

    Pei-Sheng Chen; Pin Zhang

    2006-01-01

    The discovery of silicate carbon star poses a challenge to the theory of stellar evolution in the late stage, hence it is important to look for more silicate carbon stars. To this end we have carried out cross-identifications between the new IRAS Low-Resolution Spectrum (LRS) database and the new carbon star catalog, CGCS3. We have found nine new silicate carbon stars with silicate features around 10μm and/or 18 μm. These newly identified stars are located in the Regions Ⅲa and Ⅶ in the IRAS two-color diagram, which means they indeed have typical far infrared colors of silicate carbon stars. The infrared properties of each of these sources are discussed.

  1. Soft X-Ray Irradiation of Silicates: Implications for Dust Evolution in Protoplanetary Disks

    Science.gov (United States)

    Ciaravella, A.; Cecchi-Pestellini, C.; Chen, Y.-J.; Muñoz Caro, G. M.; Huang, C.-H.; Jiménez-Escobar, A.; Venezia, A. M.

    2016-09-01

    The processing of energetic photons on bare silicate grains was simulated experimentally on silicate films submitted to soft X-rays of energies up to 1.25 keV. The silicate material was prepared by means of a microwave assisted sol-gel technique. Its chemical composition reflects the Mg2SiO4 stoichiometry with residual impurities due to the synthesis method. The experiments were performed using the spherical grating monochromator beamline at the National Synchrotron Radiation Research Center in Taiwan. We found that soft X-ray irradiation induces structural changes that can be interpreted as an amorphization of the processed silicate material. The present results may have relevant implications in the evolution of silicate materials in X-ray-irradiated protoplanetary disks.

  2. 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.

  3. Effects of solution pH and synthetic method on destabilization process of polytitanium-silicate-chloride.

    Science.gov (United States)

    Huang, Xin; Gao, Baoyu; Sun, Yangyang; Yue, Qinyan; Wang, Yan; Li, Qian

    2016-07-01

    Effect of solution pH on coagulation performance and flock properties of a novel inorganic polymer coagulant-polytitanium-silicate-chloride (PTSC) in humic acid-kaolin water treatment was investigated in this work. PTSC was synthesized by two approaches: composite and co-complexion, denoted as PTSCm and PTSCc respectively. The effect of the synthetic method was also considered. Results indicated that turbidity and DOM removal were improved by addition of polysilicic acid, especially under acidic condition. PTSCc achieved slightly better DOM removal than that of PTSCm. Flocks formed under acidic condition was smaller than those form under alkaline condition. In addition, flocks formed by PTSCc were larger than PTSCm flocks. Results also indicated that flock strength and recovery ability was slightly improved by the addition of PSiA. Moreover, under acidic condition, PTSC flocks had larger fractal dimension with more compact structure, especially for PTSCm flocks. In contrast, they were looser compared with PTC flock, especially for PTSCm flocks under neutral and alkaline conditions. PMID:26994354

  4. Geochemical modeling of the influence of silicate mineral alteration on alkalinity production and carbonate precipitation

    Science.gov (United States)

    Herda, Gerhard; Kraemer, Stephan M.; Gier, Susanne; Meister, Patrick

    2016-04-01

    High CO2 partial pressure (pCO2) in deep rock reservoirs causes acidification of the porefluid. Such conditions occur during injection and subsurface storage of CO2 (to prevent the release of greenhouse gas) but also naturally in zones of strong methanogenic microbial activity in organic matter-rich ocean margin sediments. The acidic fluids are corrosive to carbonates and bear the risk of leakage of CO2 gas to the surface. Porefluid acidification may be moderated by processes that increase the alkalinity, i.e. that produce weak acid anions capable of buffering the acidification imposed by the CO2. Often, alkalinity increases as a result of anaerobic microbial activity, such as anaerobic oxidation of methane. However, on a long term the alteration of silicates, in particular, clay minerals, may be a more efficient mechanism of alkalinity production. Under altered temperature, pressure and porefluid composition at depth, clay minerals may change to thermodynamically more stable states, thereby increasing the alkalinity of the porefluid by partial leaching of Mg-(OH)2 and Ca-(OH)2 (e.g. Wallmann et al., 2008; Mavromatis et al., 2014). This alteration may even be enhanced by a high pCO2. Thus, silicate alteration can be essential for a long-term stabilization of volatile CO2 in the form of bicarbonate or may even induce precipitation of carbonate minerals, but these processes are not fully understood yet. The goal of this study is to simulate the alkalinity effect of silicate alteration under diagenetic conditions and high pCO2 by geochemical modeling. We are using the program PHREEQC (Parkhurst and Appelo, 2013) to generate high rock/fluid ratio characteristics for deep subsurface rock reservoirs. Since we are interested in the long-term evolution of diagenetic processes, over millions of years, we do not consider kinetics but calculate the theoretically possible equilibrium conditions. In a first step we are calculating the saturation state of different clay minerals

  5. Effects of Silicate, Phosphate, and Calcium on the Stability of Aldopentoses

    Science.gov (United States)

    Nitta, Sakiko; Furukawa, Yoshihiro; Kakegawa, Takeshi

    2016-06-01

    Ribose is an important constituent of RNA: ribose connects RNA bases and forms a strand of sugar phosphates. Accumulation of ribose on prebiotic Earth was difficult because of its low stability. Improvement in the yield of ribose by the introduction of borate or silicate in a formose-like reaction has been proposed. The effects of borates have been further analyzed and confirmed in subsequent studies. Nonetheless, the effects of silicates and phosphates remain unclear. In the present study, we incubated aldopentoses in a highly alkaline aqueous solution at a moderate temperature to determine the effects of silicate or phosphate on the degradation rates of ribose and its isomeric aldopentoses. The formation of a complex of silicate (or phosphate) with ribose was also analyzed in experiments with 29Si and 31P nuclear magnetic resonance (NMR). We found that silicate or phosphate complexes of ribose were not detectable under our experimental conditions. The stability of ribose and lyxose improved after addition of 40-fold molar excess (relative to a pentose) of sodium silicate or sodium phosphate to the alkaline solution. The stability was not improved further when an 80-fold molar excess of sodium silicate or sodium phosphate was added. Calcium was removed from these solutions by precipitation of calcium salts. The drop in Ca2+ concentration might have improved the stability of ribose and lyxose, which are susceptible to aldol addition. The improvement of ribose stability by the removal of Ca2+ and by addition of silicate or phosphate was far smaller than the improvement by borate. Furthermore, all aldopentoses showed similar stability in silicate- and phosphate-containing solutions. These results clearly show that selective stabilization of ribose by borate cannot be replaced by the effects of silicate or phosphate; this finding points to the importance of borate in prebiotic RNA formation.

  6. High-performance polymer/layered silicate nanocomposites

    Science.gov (United States)

    Heidecker, Matthew J.

    High-performance layered-silicate nanocomposites of Polycarbonate (PC), poly(ethylene terephthalate) (PET), and their blends were produced via conventional melt-blending techniques. The focus of this thesis was on the fundamentals of dispersion, control of thermal stability, maintenance of melt-blending processing conditions, and on optimization of the composites' mechanical properties via the design of controlled and thermodynamically favorable nano-filler dispersions within the polymer matrices. PET and PC require high temperatures for melt-processing, rendering impractical the use of conventional/commercial organically-modified layered-silicates, since the thermal degradation temperatures of their ammonium surfactants lies below the typical processing temperatures. Thus, different surfactant chemistries must be employed in order to develop melt-processable nanocomposites, also accounting for polymer matrix degradation due to water (PET) or amine compounds (PC). Novel high thermal-stability surfactants were developed and employed in montmorillonite nanocomposites of PET, PC, and PC/PET blends, and were compared to the respective nanocomposites based on conventional quaternary-ammonium modified montmorillonites. Favorable dispersion was achieved in all cases, however, the overall material behavior -- i.e., the combination of crystallization, mechanical properties, and thermal degradation -- was better for the nanocomposites based on the thermally-stable surfactant fillers. Studies were also done to trace, and ultimately limit, the matrix degradation of Polycarbonate/montmorillonite nanocomposites, through varying the montmorillonite surfactant chemistry, processing conditions, and processing additives. Molecular weight degradation was, maybe surprisingly, better controlled in the conventional quaternary ammonium based nanocomposites -- even though the thermal stability of the organically modified montmorillonites was in most cases the lowest. Dependence of the

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

    Science.gov (United States)

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

    2016-01-01

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

  8. Reactivity, swelling and aggregation of mixed-size silicate nanoplatelets

    Science.gov (United States)

    Segad, M.; Cabane, B.; Jönsson, Bo

    2015-10-01

    Montmorillonite is a key ingredient in a number of technical applications. However, little is known regarding the microstructure and the forces between silicate platelets. The size of montmorillonite platelets from different natural sources can vary significantly. This has an influence on their swelling behavior in water as well as in salt solutions, particularly when tactoid formation occurs, that is when divalent counterions are present in the system. A tactoid consists of a limited number of platelets aggregated in a parallel arrangement with a constant separation. The tactoid size increases with platelet size and with very small nanoplatelets, ~30 nm, no tactoids are observed irrespectively of the platelet origin and concentration of divalent ions. The formation and dissociation of tactoids seem to be reversible processes. A large proportion of small nanoplatelets in a mixed-size system affects the tactoid formation, reduces the aggregation number and increases the extra-lamellar swelling in the system.

  9. Discrete element modeling of calcium-silicate-hydrate

    International Nuclear Information System (INIS)

    The discrete element method (DEM) was used to model calcium-silicate-hydrate (C-S-H) at the nanoscale. The C-S-H nanoparticles were modeled as spherical particles with diameters of approximately 5 nm. Interparticle forces included traditional mechanical contact forces, van der Waals forces and ionic correlation forces due to negatively charged C-S-H nanoparticles and ion species in the nanopores. Previous work by the authors demonstrated the DEM method was feasible in studying the properties of the C-S-H nanostructures. In this work, the simulations were performed to look into the effects of nanoparticle packing, nanoparticle morphology, interparticle forces and nanoparticle properties on the deformation mechanisms and mechanical properties of the C-S-H matrix. This work will provide insights into possible ways to improve the properties of the C-S-H matrix. (paper)

  10. Thermodynamics and kinetics of the sulfation of porous calcium silicate

    Science.gov (United States)

    Miller, R. A.; Kohl, F. J.

    1981-01-01

    The sulfation of plasma sprayed calcium silicate in flowing SO2/air mixtures at 900 and 1000 C was investigated thermogravimetrically. Reaction products were analyzed using electron microprobe and X-ray diffraction analysis techniques, and results were compared with thermodynamic predictions. The percentage, by volume, of SO2 in air was varied between 0.036 and 10 percent. At 10 percent SO2 the weight gain curve displays a concave downward shoulder early in the sulfation process. An analytical model was developed which treats the initial process as one which decays exponentially with increasing time and the subsequent process as one which decays exponentially with increasing weight gain. At lower SO2 levels the initial rate is controlled by the reactant flow rate. At 1100 C and 0.036 percent SO2 there is no reaction, in agreement with thermodynamic predictions.

  11. Chemistry of Silicate Atmospheres of Evaporating Super-Earths

    CERN Document Server

    Schaefer, Laura

    2009-01-01

    We model the formation of silicate atmospheres on hot volatile-free super-Earths. Our calculations assume that all volatile elements such as H, C, N, S, and Cl have been lost from the planet. We find that the atmospheres are composed primarily of Na, O2, O, and SiO gas, in order of decreasing abundance. The atmospheric composition may be altered by fractional vaporization, cloud condensation, photoionization, and reaction with any residual volatile elements remaining in the atmosphere. Cloud condensation reduces the abundance of all elements in the atmosphere except Na and K. We speculate that large Na and K clouds such as those observed around Mercury and Io may surround hot super-Earths. These clouds would occult much larger fractions of the parent star than a closely bound atmosphere, and may be observable through currently available methods.

  12. Shrinking core models applied to the sodium silicate production process

    Directory of Open Access Journals (Sweden)

    Stanković Mirjana S.

    2007-01-01

    Full Text Available The sodium silicate production process, with the molar ratio SiO2/Na2O = 2, for detergent zeolite 4A production, is based on quartz sand dissolving in NaOH aqueous solution, with a specific molality. It is a complex process performed at high temperature and pressure. It is of vital importance to develop adequate mathematical models, which are able to predict the dynamical response of the process parameters. A few kinetic models were developed within this study, which were adjusted and later compared to experimental results. It was assumed that SiO2 particles are smooth spheres, with uniform diameter. This diameter decreases during dissolving. The influence of particle diameter, working temperature and hydroxide ion molality on the dissolution kinetics was investigated. It was concluded that the developed models are sufficiently correct, in the engineering sense, and can be used for the dynamical prediction of process parameters.

  13. Photoluminescence in amorphous MgSiO_3 silicate

    CERN Document Server

    Thompson, S P; Day, S J; Connor, L D; Evans, A

    2013-01-01

    Samples of amorphous MgSiO_3 annealed at temperature steps leading up to their crystallisation temperature show a rise in photoluminescence activity, peaking at ~450C. The photoluminescence band has a main peak at 595nm and a weaker peak at 624nm. We present laboratory data to show that the maximum in photoluminescence activity is related to substantial structural reordering that occurs within a relatively narrow temperature range. We attribute the origin of the photoluminescence to non-bridging oxygen hole centre defects, which form around ordered nano-sized domain structures as a result of the breakup of tetrahedral connectivity in the disordered inter-domain network, aided by the loss of bonded OH. These defects are removed as crystallisation progresses, resulting in the decrease and eventual loss of photoluminescence. Thermally processed hydrogenated amorphous silicate grains could therefore represent a potential carrier of extended red emission.

  14. Stylolites, porosity, depositional texture, and silicates in chalk facies sediments

    DEFF Research Database (Denmark)

    Fabricius, Ida Lykke; Borre, Mai K.

    2007-01-01

    and sediments as counteracted by the pressure in the pore fluid, so the regional overpressure in the Central North Sea is one reason why the two localities have different relationships between temperature and effective burial stress. In the chalk of the Ontong Java Plateau the onset of calcite-silicate pressure......Comparison of chalk on the Ontong Java Plateau and chalk in the Central North Sea indicates that, whereas pressure dissolution is controlled by effective burial stress, pore-filling cementation is controlled by temperature. Effective burial stress is caused by the weight of all overlying water...... equilibrated to quartz before the onset of pressure dissolution and thus, in this case, dissolution and precipitation of calcite have no lag. This temperature versus effective burial stress induced difference in diagenetic history is of particular relevance when exploring for hydrocarbons in normally pressured...

  15. Structural changes between soda-lime silicate glass and melt

    International Nuclear Information System (INIS)

    Neutron diffraction has been used to study the structure of a glass and melt of composition 75SiO2-15Na2O-10CaO. RMC modeling of the neutron and X-ray diffraction data for the glass allowed the determination of the Na and Ca environment. The structure has been investigated at 300 K, just below the glass transition at 823 K and in the melt at 1273 K. The short range order does not present important modifications with temperature while significant reorganization appears at the medium range order. These latter changes can be associated with the Si and O pairs and indicate the relaxation of the silicate network. This indicates that the glass formation involved structural rearrangement during cooling. (authors)

  16. Femtosecond Laser Induced Rewritable Optical Memory in Silicate Glasses

    Institute of Scientific and Technical Information of China (English)

    JIANG Xiongwei; QIU Jianrong; ZHU Congshan; K.Hirao; GAN Fuxi

    2001-01-01

    A novel method for producing rewritable optical memory with ultra-high storage density and ultra-high recording and readout speed is presented. A 120 fs, 800 nm, 1 kHz laser focused by an objective lens is used to produce recording bits in glass with high transmittance contrast. These recording bits can be erased by heat-treatment. The mechanism has been discussed by means of the absorption and electron spin resonance(ESR) spectra of silicate glasses before and after irradiation by the laser. The absorption of glasses increases greatly after irradiation because of color-center generation through multi-photon absorption. ESR spectra shows that the color-center induced in the glass are hole-trapped defects. The color-center disappears when the glass heated because the holes and electrons at traps are released by thermal stimulation and recombine again.

  17. XPS study of CaO in sodium silicate glass

    International Nuclear Information System (INIS)

    This paper shows that CaO added to silicate glasses behaves much like Na2O in converting bridging oxygen sites to nonbridging sites. Good correspondence with model predictions was obtained but deviations were still sufficiently large to warrant attention. We speculate that some CaO may remain unreacted or that small-scale phase separation may occur. XPS core level shifts were monitored and possible charge-transfer effects were considered. Preliminary theoretical calculations utilizing a molecular-cluster approach were presented. XPS spectra for various glass compositions were simulated by appropriately combining local densities of state calculated for individual atoms. Dominant spectral features observed experimentally were found in the simulations. In conjunction with experiments, more carefully refined calculations will be subsequently examined. 7 figures

  18. The mechanisms of water diffusion in polymerized silicate melts

    Science.gov (United States)

    Behrens, Harald; Nowak, M.

    1997-02-01

    Diffusion of water was experimentally investigated for melts of albitic (Ab) and quartz-orthoclasic (Qz29Or71, in wt %) compositions with water contents in the range of 0 to 8.5 wt % at temperatures of 1100 to 1200 °C and at pressures of 1.0 and 5.0 kbar. Apparent chemical diffusion coefficients of water ( D water) were determined from concentration-distance profiles measured by FTIR microspectroscopy. Under the same P- T condition and water content the diffusivity of water in albitic, quartz-orthoclasic and haplogranitic (Qz28Ab38 Or34, Nowak and Behrens, this issue) melts is identical within experimental error. Comparison to data published in literature indicates that anhydrous composition only has little influence on the mobility of water in polymerized melts but that the degree of polymerization has a large effect. For instance, Dwater is almost identical for haplogranitic and rhyolitic melts with 0.5-3.5 wt % water at 850 °C but it is two orders of magnitude higher in basaltic than in haplogranitic melts with 0.2-0.5 wt % water at 1300 °C. Based on the new water diffusivity data, recently published in situ near-infrared spectroscopic data (Nowak 1995; Nowak and Behrens 1995), and viscosity data (Schulze et al. 1996) for hydrous haplogranitic melts current models for water diffusion in silicate melts are critically reviewed. The NIR spectroscopy has indicated isolated OH groups, pairs of OH groups and H2O molecules as hydrous species in polymerized silicate melts. A significant contribution of isolated OH groups to the transport of water is excluded for water contents above 10 ppm by comparison of viscosity and water diffusion data and by inspection of concentration profiles from trace water diffusion. Spectroscopic measurements have indicated that the interconversion of H2O molecules and OH pairs is relatively fast in silicate glasses and melts even at low temperature and it is inferred that this reaction is an active step for migration of water. However

  19. 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

  20. Hydrogen isotope investigation of amphibole and biotite phenocrysts in silicic magmas erupted at Lassen Volcanic Center, California

    Science.gov (United States)

    Underwood, S.J.; Feeley, T.C.; Clynne, M.A.

    2012-01-01

    prior to eruption, degassed vesiculated magma or lava had drained back down the volcanic conduit and mixed with less devolatilized magma. The vesiculated magma contained hydrous phenocrysts with lattice damage, which locally raised the effective H diffusion coefficient by ca 10–100 × and resulted in increased mineral dehydrogenation. Remobilization of dacite magma mush by relatively more reduced mafic magma appears to have generated further fO2 variations in May 1915 as oxidized magma from shallow levels circulated to depths where dehydrogenation of hydrous phenocrysts began. The δDMagmatic H2O expressed in LVC acid hot springs is likely a mixture derived from devolatilized ascending mafic magmas and crystallizing silicic magma mush.

  1. Preparation and characterization of bioactive and degradable composites containing ordered mesoporous calcium-magnesium silicate and poly(L-lactide)

    Energy Technology Data Exchange (ETDEWEB)

    Ji, Jiajin [Key Shanghai Key Laboratory of Advanced Polymeric Materials, East China University of Science and Technology, Shanghai 200237 (China); Dong, Xieping, E-mail: jxzhyxh@163.com [Department of Orthopaedic Surgery, Jiangxi People' s Hospital, Nanchang 330006 (China); Ma, Xuhui [Polymer Science (Shenzhen) New Materials Co., Ltd., Shenzhen 518101 (China); Tang, Songchao, E-mail: schtang@ecust.edu.cn [Key Shanghai Key Laboratory of Advanced Polymeric Materials, East China University of Science and Technology, Shanghai 200237 (China); Wu, Zhaoying; Xia, Ji; Wang, Quanxiang; Wang, Yutao; Wei, Jie [Key Shanghai Key Laboratory of Advanced Polymeric Materials, East China University of Science and Technology, Shanghai 200237 (China)

    2014-10-30

    Highlights: • Mesoporous calcium-magnesium silicate and poly(L-lactide) composite was fabricated. • The composite has good hydrophilicity, in vitro degradation and bioactivity. • The composite could support cell attachment, proliferation and differentiation. - Abstract: Polylactide (PLA) and its copolymers have been widely used for bone tissue regeneration. In this study, a bioactive composite of ordered mesoporous calcium–magnesium silicate (m-CMS) and poly(L-lactide) (PLLA) was fabricated by melt blending method. The results indicated that the m-CMS particles were entrapped by polymer phase, and crystallinity of PLLA significantly decreased while the thermal stability of the m-CMS/PLLA composites was not obviously affected by addition of the m-CMS into PLLA. In addition, compared to PLLA, incorporation of the m-CMS into PLLA significantly improved the hydrophilicity, in vitro degradability and bioactivity (apatite-formation ability) of the m-CMS/PLLA composite, which were m-CMS content dependent. Moreover, it was found that incorporation of the m-CMS into PLLA could neutralize the acidic degradation by-products and thus compensated for the decrease of pH value. In cell culture experiments, the results showed that the composite enhanced attachment, proliferation and alkaline phosphatase activity (ALP) of MC3T3-E1 cells, which were m-CMS content dependent. The results indicated that the addition of bioactive materials to PLLA could result in a composite with improved properties of hydrophilicity, degradability, bioactivity and cytocompatibility.

  2. Preparation and characterization of bioactive and degradable composites containing ordered mesoporous calcium-magnesium silicate and poly(L-lactide)

    International Nuclear Information System (INIS)

    Highlights: • Mesoporous calcium-magnesium silicate and poly(L-lactide) composite was fabricated. • The composite has good hydrophilicity, in vitro degradation and bioactivity. • The composite could support cell attachment, proliferation and differentiation. - Abstract: Polylactide (PLA) and its copolymers have been widely used for bone tissue regeneration. In this study, a bioactive composite of ordered mesoporous calcium–magnesium silicate (m-CMS) and poly(L-lactide) (PLLA) was fabricated by melt blending method. The results indicated that the m-CMS particles were entrapped by polymer phase, and crystallinity of PLLA significantly decreased while the thermal stability of the m-CMS/PLLA composites was not obviously affected by addition of the m-CMS into PLLA. In addition, compared to PLLA, incorporation of the m-CMS into PLLA significantly improved the hydrophilicity, in vitro degradability and bioactivity (apatite-formation ability) of the m-CMS/PLLA composite, which were m-CMS content dependent. Moreover, it was found that incorporation of the m-CMS into PLLA could neutralize the acidic degradation by-products and thus compensated for the decrease of pH value. In cell culture experiments, the results showed that the composite enhanced attachment, proliferation and alkaline phosphatase activity (ALP) of MC3T3-E1 cells, which were m-CMS content dependent. The results indicated that the addition of bioactive materials to PLLA could result in a composite with improved properties of hydrophilicity, degradability, bioactivity and cytocompatibility

  3. Physical properties of sodium silicate based silica aerogels prepared by single step sol-gel process dried at ambient pressure

    International Nuclear Information System (INIS)

    The experimental results on physical properties of water glass (sodium silicate) based silica aerogels prepared by single step sol-gel process, dried at atmospheric pressure are reported. The hydrolysis and condensation reactions of the sodium silicate precursor proceeded with tartaric acid as a catalyst. The hydrogel was vapour passed in order to remove sodium salt from the gel network. Solvent exchange was carried out using methanol and hexane as a solvents. Finally, surface chemical modification of the gel was done using trimethylchlorosilane (TMCS) followed by ambient pressure drying of the gel up to the temperature 200 deg. C. To get good quality aerogels various sol-gel parameters such as water vapour passing period varied from 0.5 to 2 h, gel aging from 1 to 4 h, Na2SiO3/H2O molar ratio from 3 x 10-3 to 1.5 x 10-2, tartaric acid/Na2SiO3 molar ratio from 0.3 to 1.9 and TMCS/Na2SiO3 molar ratio from 4.8 to 12. The aerogels were characterized by percentage of volume shrinkage, bulk density, porosity and hydrophobicity. The hydrophobicity of the aerogel was confirmed by Fourier Transform Infrared (FTIR) Spectroscopy and contact angle measurements. Microstructural studies have been carried out by Scanning Electron Microscopy (SEM) and nitrogen adsorption BET analysis. From the TGA-DTA studies of the aerogels, it was found that the aerogels were thermally stable up to 470 oC. Low density (∼0.066 g/cm3), high hydrophobicity (∼145 deg.), high porosity (∼97 %), high pore volume, surface area of 510 m2/g aerogels have been obtained for Na2SiO3:H2O:tartaric acid (C4H6O6):TMCS molar ratio at 1:166.6:2.5:12 respectively with half an hour water vapour passing.

  4. Synthesis and Characterization of Different Crystalline Calcium Silicate Hydrate: Application for the Removal of Aflatoxin B1 from Aqueous Solution

    OpenAIRE

    Lu Zeng; Ligang Yang; Shuping Wang; Kai Yang

    2014-01-01

    Different crystalline calcium silicate hydrates (CSH) were synthesized under specific hydrothermal conditions and several methods were used to analyze samples. Amorphous calcium silicate hydrates (ACSH) mainly consists of disordered calcium silicate hydrate gel (C-S-H gel) and crystalline calcium silicate hydrates (CCSH) consists of crystallized tobermorite. The adsorption of carcinogenic aflatoxin B1 (AFB1) onto ACSH and CCSH was investigated. The adsorption kinetics was studied using pseudo...

  5. Oxygen isotope and petrological study of silicate inclusions in IIE iron meteorites and their relationship with H chondrites

    OpenAIRE

    Mcdermott, Kathryn H.; Greenwood, Richard C.; Scott, Edward R. D.; Franchi, Ian A.; Anand, Mahesh

    2015-01-01

    The origin of silicate-bearing irons, especially those in groups IAB, IIICD, and IIE, is poorly understood as silicate should have separated rapidly from molten metal. Here we report the results of high precision oxygen isotope analysis of silicate inclusions in eleven group IIE meteorites and a petrological study of silicate inclusions in ten IIE irons including those in Garhi Yasin and Tarahumara, which have not been described in detail before. Oxygen isotopes have also been analysed in 20 ...

  6. A-thermal elastic behavior of silicate glasses.

    Science.gov (United States)

    Rabia, Mohammed Kamel; Degioanni, Simon; Martinet, Christine; Le Brusq, Jacques; Champagnon, Bernard; Vouagner, Dominique

    2016-02-24

    Depending on the composition of silicate glasses, their elastic moduli can increase or decrease as function of the temperature. Studying the Brillouin frequency shift of these glasses versus temperature allows the a-thermal composition corresponding to an intermediate glass to be determined. In an intermediate glass, the elastic moduli are independent of the temperature over a large temperature range. For sodium alumino-silicate glasses, the a-thermal composition is close to the albite glass (NaAlSi3O8). The structural origin of this property is studied by in situ high temperature Raman scattering. The structure of the intermediate albite glass and of silica are compared at different temperatures between room temperature and 600 °C. When the temperature increases, it is shown that the high frequency shift of the main band at 440 cm(-1) in silica is a consequence of the cristobalite-like alpha-beta transformation of 6-membered rings. This effect is stronger in silica than bond elongation (anharmonic effects). As a consequence, the elastic moduli of silica increase as the temperature increases. In the albite glass, the substitution of 25% of Si(4+) ions by Al(3+) and Na(+) ions decreases the proportion of SiO2 6-membered rings responsible for the silica anomaly. The effects of the silica anomaly balance the anharmonicity in albite glass and give rise to an intermediate a-thermal glass. Different networks, formers or modifiers, can be added to produce different a-thermal glasses with useful mechanical or chemical properties. PMID:26815634

  7. Evaluation of apatite silicates as solid oxide fuel cell electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Marrero-Lopez, D. [Dpto. de Fisica Aplicada I, Laboratorio de Materiales y Superficies (Unidad Asociada al C.S.I.C.), Universidad de Malaga, 29071 Malaga (Spain); Dpto. de Quimica Inorganica, Universidad de La Laguna, 38200 La Laguna, Tenerife (Spain); Martin-Sedeno, M.C.; Aranda, M.A.G. [Dpto. de Quimica Inorganica, Universidad Malaga, 29071 Malaga (Spain); Pena-Martinez, J. [Dpto. de Quimica Inorganica, Universidad de La Laguna, 38200 La Laguna, Tenerife (Spain); Instituto de Energias Renovables, Parque Tecnologico, Universidad de Castilla La Mancha, 02006 Albacete (Spain); Ruiz-Morales, J.C.; Nunez, P. [Dpto. de Quimica Inorganica, Universidad de La Laguna, 38200 La Laguna, Tenerife (Spain); Ramos-Barrado, J.R. [Dpto. de Fisica Aplicada I, Laboratorio de Materiales y Superficies (Unidad Asociada al C.S.I.C.), Universidad de Malaga, 29071 Malaga (Spain)

    2010-05-01

    Apatite-type silicates have been considered as promising electrolytes for Solid Oxide Fuel Cells (SOFC); however studies on the potential use of these materials in SOFC devices have received relatively little attention. The lanthanum silicate with composition La{sub 10}Si{sub 5.5}Al{sub 0.5}O{sub 26.75} has been evaluated as electrolyte with the electrode materials commonly used in SOFC, i.e. manganite, ferrite and cobaltite as cathode materials and NiO-CGO composite, chromium-manganite and Sr{sub 2}MgMoO{sub 6} as anode materials. Chemical compatibility, area-specific resistance and fuel cell studies have been performed. X-ray powder diffraction (XRPD) analysis did not reveal any trace of reaction products between the apatite electrolyte and most of the aforementioned electrode materials. However, the area-specific polarisation resistance (ASR) of these electrodes in contact with apatite electrolyte increased significantly with the sintering temperature, indicating reactivity at the electrolyte/electrode interface. On the other hand, the ASR values are significantly improved using a ceria buffer layer between the electrolyte and electrode materials to prevent reactivity. Maximum power densities of 195 and 65 mWcm{sup -2} were obtained at 850 and 700 C, respectively in H{sub 2} fuel, using an 1 mm-thick electrolyte, a NiO-Ce{sub 0.8}Gd{sub 0.2}O{sub 1.9} composite as anode and La{sub 0.6}Sr{sub 0.4}Co{sub 0.8}Fe{sub 0.2}O{sub 3-{delta}} as cathode materials. This fuel cell was tested for 100 h in 5%H{sub 2}-Ar atmosphere showing stable performance. (author)

  8. A Study of Siliceous Pneumoconiosis in a Desert Area of Sunan County,Gansu Province,China

    Institute of Scientific and Technical Information of China (English)

    1993-01-01

    Three hundred and ninety five residents in a desert area were examined with chest radiographs and 28 cases with siliceous pneumoconiosis were found.The prevalence of siliceous pneumoconiosis was 7.09%,and that over 40 years of age was 21%.The histological findings of lungs from a camel living in that area for 20 years also confirmed to have siliceous pneumoconiosis.

  9. Selective separation of silica from a siliceous-calcareous phosphate rock

    Institute of Scientific and Technical Information of China (English)

    Guo Fang; Li Jun

    2011-01-01

    Selective separation of silica from a siliceous-calcareous phosphate ore that had been sieved into different size fractions is investigated by a combination of chemical analysis, zeta potential measurement and FTIR and XPS techniques. Scrubbing is a better choice than flotation for removing silica from the coarse fractions. The P2O5 grade of the coarse fractions is increased to about 30% by scrubbing and the product yields are higher than those obtained by flotation. The silica in the fine fraction is separated by reverse flotation. An alkyl amine salt (DAH) is an effective collector and the P2Os grade of the fine fraction can be increased by 7% to beyond 30% under acidic conditions. The higher zeta potential obtained using DAH suggests that it is more strongly absorbed onto the ore panicles than the other cationic collectors.FTIR and XPS results confirm physical absorption of the cationic collector onto the ore surface. They also indicate that calcite is dissolved at low pH values, which increases the Si concentration on the ore surface.

  10. Selective separation and determination of isoproterenol on thin layers of bismuth silicate ion-exchanger

    Institute of Scientific and Technical Information of China (English)

    Vanik GHOULIPOUR; Zahra HASSANKHANI-MAJD

    2015-01-01

    A simple and sensitive method for the separation and determination of isoproterenol from other do-ping drugs has been developed on thin layers of bismuth silicate,a synthetic inorganic ion exchanger as adsor-bent in thin layer chromatography(TLC). A mixture of methanol and 0. 1 mol/L formic acid(3:7,v/v)was employed as the mobile phase. The development time was 32 min. The quantitative measurement were per-formed with a Camag TLC Scanner-3 at wavelength(λ)of 410 nm. The isoproterenol recovery in this procedure was 98. 9%. The linear correlation coefficient was greater than 0. 987 1 and the relative standard deviation (RSD)was less than 0.94. The limit of detection(LOD)and limit of quantification(LOQ)were 7.7×10-7 mol/L and 3. 85 ×10-6 mol/L,respectively. This method has been applied in the determination of isoproterenol in dosage forms and in biological fluids.

  11. Selective separation and determination of isoproterenol on thin layers of bismuth silicate ion-exchanger.

    Science.gov (United States)

    Ghoulipour Vanik; Hassankhani-Majd Zahra

    2015-06-01

    A simple and sensitive method for the separation and determination of isoproterenol from other doping drugs has been developed on thin layers of bismuth silicate, a synthetic inorganic ion exchanger as adsorbent in thin layer chromatography (TLC). A mixture of methanol and 0.1 mol/L formic acid (3:7, v/v) was employed as the mobile phase. The development time was 32 min. The quantitative measurement were performed with a Camag TLC Scanner-3 at wavelength (λ) of 410 nm. The isoproterenol recovery in this procedure was 98.9%. The linear correlation coefficient was greater than 0. 987 1 and the relative standard deviation (RSD) was less than 0.94. The limit of detection (LOD) and limit of quantification ( LOQ) were 7.7 x 10(-7) mol/L and 3.85 x 10(-6) mol/L, respectively. This method has been applied in the determination of isoproterenol in dosage forms and in biological fluids.

  12. Effect of silicate incorporation on in vivo responses of α-tricalcium phosphate ceramics.

    Science.gov (United States)

    Kamitakahara, Masanobu; Tatsukawa, Eri; Shibata, Yasuaki; Umemoto, Shota; Yokoi, Taishi; Ioku, Koji; Ikeda, Tohru

    2016-05-01

    In addition to calcium phosphate-based ceramics, glass-based materials have been utilized as bone substitutes, and silicate in these materials has been suggested to contribute to their ability to stimulate bone repair. In this study, a silicate-containing α-tricalcium phosphate (α-TCP) ceramic was prepared using a wet chemical process. Porous granules composed of silicate-containing α-TCP, for which the starting composition had a molar ratio of 0.05 for Si/(P + Si), and silicate-free α-TCP were prepared and evaluated in vivo. When implanted into bone defects that were created in rat femurs, α-TCP ceramics either with or without silicate were biodegraded, generating a hybrid tissue composed of residual ceramic granules and newly formed bone, which had a tissue architecture similar to physiological trabecular structures, and aided regeneration of the bone defects. Supplementation with silicate significantly promoted osteogenesis and delayed biodegradation of α-TCP. These results suggest that silicate-containing α-TCP is advantageous for initial skeletal fixation and wound regeneration in bone repair. PMID:27003839

  13. Valence determination of rare earth elements in lanthanide silicates by L 3-XANES spectroscopy

    Science.gov (United States)

    Kravtsova, Antonina N.; Guda, Alexander A.; Goettlicher, Joerg; Soldatov, Alexander V.; Taroev, Vladimir K.; Kashaev, Anvar A.; Suvorova, Lyudmila F.; Tauson, Vladimir L.

    2016-05-01

    Lanthanide silicates have been hydrothermally synthesized using Cu and Ni containers. Chemical formulae of the synthesized compounds correspond to K3Eu[Si6O15] 2H2O, HK6Eu[Si10O25], K7Sm3[Si12O32], K2Sm[AlSi4O12] 0.375H2O, K4Yb2[Si8O21], K4Ce2[Al2Si8O24]. The oxidation state of lanthanides (Eu, Ce, Tb, Sm, Yb) in these silicates has been determined using XANES spectroscopy at the Eu, Ce, Tb, Sm, Yb, L 3- edges. The experimental XANES spectra were recorded using the synchrotron radiation source ANKA (Karlsruhe Institute of Technology) and the X-ray laboratory spectrometer Rigaku R- XAS. By comparing the absorption edge energies and white line intensities of the silicates with the ones of reference spectra the oxidation state of lanthanides Eu, Ce, Tb, Sm, Yb has been found to be equal to +3 in all investigated silicates except of the Ce-containing silicate from the run in Cu container where the cerium oxidation state ranges from +3 (Ce in silicate apatite and in a KCe silicate with Si12O32 layers) to +4 (starting CeO2 or oxidized Ce2O3).

  14. Evaluation of the effect of sodium silicate addition to mine backfill, Gelfill − Part 1

    Directory of Open Access Journals (Sweden)

    M. Kermani

    2015-06-01

    Full Text Available In this paper, the mechanical properties of sodium silicate-fortified backfill, called Gelfill, were investigated by conducting a series of laboratory experiments. Two configurations were tested, i.e. Gelfill and cemented hydraulic fill (CHF. The Gelfill has an alkali activator such as sodium silicate in its materials in addition to primary materials of mine backfill which are tailings, water and binders. Large numbers of samples of Gelfill and CHF with various mixture designs were cast and cured for over 28 d. The mechanical properties of samples were investigated using uniaxial compression test, and the results were compared with those of reference samples made without sodium silicate. The test results indicated that the addition of an appropriate amount of an alkali activator such as sodium silicate can enhance the mechanical (uniaxial compressive strength and physical (water retention properties of backfill. The microstructure analysis conducted by mercury intrusion porosimetry (MIP revealed that the addition of sodium silicate can modify the pore size distribution and total porosity of Gelfill, which can contribute to the better mechanical properties of Gelfill. It was also shown that the time and rate of drainage in the Gelfill specimens are less than those in CHF specimens made without sodium silicate. Finally, the study showed that the addition of sodium silicate can reduce the required setting time of mine backfill, which can contribute to increase mine production in accordance with the mine safety.

  15. Evaluation of the effect of sodium silicate addition to mine backfill, Gelfill L Part 1

    Institute of Scientific and Technical Information of China (English)

    M. Kermani; F.P. Hassani; E. Aflaki; M. Benzaazoua; M. Nokken

    2015-01-01

    In this paper, the mechanical properties of sodium silicate-fortified backfill, called Gelfill, were investi-gated by conducting a series of laboratory experiments. Two configurations were tested, i.e. Gelfill and cemented hydraulic fill (CHF). The Gelfill has an alkali activator such as sodium silicate in its materials in addition to primary materials of mine backfill which are tailings, water and binders. Large numbers of samples of Gelfill and CHF with various mixture designs were cast and cured for over 28 d. The me-chanical properties of samples were investigated using uniaxial compression test, and the results were compared with those of reference samples made without sodium silicate. The test results indicated that the addition of an appropriate amount of an alkali activator such as sodium silicate can enhance the mechanical (uniaxial compressive strength) and physical (water retention) properties of backfill. The microstructure analysis conducted by mercury intrusion porosimetry (MIP) revealed that the addition of sodium silicate can modify the pore size distribution and total porosity of Gelfill, which can contribute to the better mechanical properties of Gelfill. It was also shown that the time and rate of drainage in the Gelfill specimens are less than those in CHF specimens made without sodium silicate. Finally, the study showed that the addition of sodium silicate can reduce the required setting time of mine backfill, which can contribute to increase mine production in accordance with the mine safety.

  16. On the Anomalous Silicate Absorption Feature of the Prototypical Seyfert 2 Galaxy NGC 1068

    CERN Document Server

    Koehler, Melanie

    2012-01-01

    The first detection of the silicate absorption feature in AGNs was made at 9.7 micrometer for the prototypical Seyfert 2 galaxy NGC 1068 over 30 years ago, indicating the presence of a large column of silicate dust in the line-of-sight to the nucleus. It is now well recognized that type 2 AGNs exhibit prominent silicate absorption bands, while the silicate bands of type 1 AGNs appear in emission. More recently, using the Mid-Infrared Interferometric Instrument on the Very Large Telescope Interferometer, Jaffe et al. (2004) by the first time spatially resolved the parsec-sized dust torus around NGC 1068 and found that the 10 micrometer silicate absorption feature of the innermost hot component exhibits an anomalous profile differing from that of the interstellar medium and that of common olivine-type silicate dust. While they ascribed the anomalous absorption profile to gehlenite (Ca_2Al_2SiO_7, a calcium aluminum silicate species), we propose a physical dust model and argue that, although the presence of gehl...

  17. The preparation of an elastomer/silicate layer nanocompound with an exfoliated structure and a strong ionic interfacial interaction by utilizing an elastomer latex containing pyridine groups

    Energy Technology Data Exchange (ETDEWEB)

    He Shaojian; Wang Yiqing; Feng Yiping; Liu Qingsheng; Zhang Liqun, E-mail: zhanglq@mail.buct.edu.cn [Key Laboratory for Nanomaterials, Ministry of Education, Beijing University of Chemical Technology, Beijing 100029 (China)

    2010-03-19

    A great variety of polymer/layered silicate (PLS) nanocomposites have been reported, however, there are few exfoliated PLS nanocomposites and their inorganic-organic interfaces are still a great problem, especially for the elastomers. In this research, a kind of exfoliated elastomer/silicate layer nanocompound was prepared and proved by XRD and TEM, in which 10 phr Na{sup +}-montmorillonite was dispersed in butadiene-styrene-vinyl pyridine rubber by latex compounding method with acidic flocculants. Moreover, a dynamic mechanical thermal analyzer (DMTA) suggested a strong interfacial interaction (interaction parameter B{sub H} = 4.91) between the silicate layers and macromolecules in addition to the weak inorganic-organic interfacial interaction, and solid state {sup 15}N NMR indicated the formation of a strong ionic interface through the acidifying pyridine. Subsequently, a remarkable improvement of the dispersing morphology, mechanical performance and gas barrier property appeared, compared to that using calcium ion flocculants. This supports the formation of an exfoliated structure and an improved interfacial interaction.

  18. The preparation of an elastomer/silicate layer nanocompound with an exfoliated structure and a strong ionic interfacial interaction by utilizing an elastomer latex containing pyridine groups.

    Science.gov (United States)

    He, Shao-jian; Wang, Yi-qing; Feng, Yi-ping; Liu, Qing-sheng; Zhang, Li-qun

    2010-03-19

    A great variety of polymer/layered silicate (PLS) nanocomposites have been reported, however, there are few exfoliated PLS nanocomposites and their inorganic-organic interfaces are still a great problem, especially for the elastomers. In this research, a kind of exfoliated elastomer/silicate layer nanocompound was prepared and proved by XRD and TEM, in which 10 phr Na(+)-montmorillonite was dispersed in butadiene-styrene-vinyl pyridine rubber by latex compounding method with acidic flocculants. Moreover, a dynamic mechanical thermal analyzer (DMTA) suggested a strong interfacial interaction (interaction parameter B(H) = 4.91) between the silicate layers and macromolecules in addition to the weak inorganic-organic interfacial interaction, and solid state (15)N NMR indicated the formation of a strong ionic interface through the acidifying pyridine. Subsequently, a remarkable improvement of the dispersing morphology, mechanical performance and gas barrier property appeared, compared to that using calcium ion flocculants. This supports the formation of an exfoliated structure and an improved interfacial interaction. PMID:20173242

  19. Use of silicate shells to prevent sintering during thermally induced chemical ordering of iron platinum nanoparticles

    Science.gov (United States)

    Reed, Dwayne Fitzgerald

    Its very high value of magnetocrystalline anisotropy makes the L1 0 phase of FePt a leading candidate for future high density magnetic recording systems. FePt nanoparticles can be prepared by a number of chemical methods. However, these particles have a face-centered cubic structure, with low anisotropy and are superparamagnetic. They must be heated to temperatures above 500 °C to obtain the chemically ordered L10 phase. However, during heating the particles coalesce to give twinned grains with large sizes (10-30 nm). Here we provide a solution to the sintering problem by developing a sol-gel procedure for coating the FePt particles with an amorphous silica shell. The silica shell prevents the FePt particles from agglomerating when heated to 700 °C to effect chemical ordering. FePt nanoparticles were prepared by the super-hydride reduction of platinum(II) acetylacetonate and iron(II) chloride in hot diphenyl ether in the presence of oleylamine and oleic acid capping ligands. The particles had an average diameter of 5-6 nm, a face-centered cubic structure and were superparamagnetic. The particles were coated using a microemulsion process producing a 6 nm silicon oxide shell with a single nanoparticle core-shell structure. The nanoparticles were heated to 700 °C for times of 30 min and 1hr to achieve L10 phase transformation. These samples were annealed in a tube furnace under 95% Ar/5% H2. Many procedures were found to be ineffective. They mostly consisted of biphasic reaction systems and several trials where reaction variables were altered in search of the appropriate conditions. This work has impacted the search for a higher density magnetic recording medium by allowing the study of FePt under a protected environment while achieving chemical ordering. If the L10 FePt nanoparticles will be used in magnetic recording, the particles will require a hard coating to prevent wear. In the course of the present work, it has been shown that the silicate shells

  20. Interannual variability in biochemistry of partially mixed estuaries: Dissolved silicate cycles in northern San Francisco Bay

    Science.gov (United States)

    Peterson, David H.; Cayan, Daniel R.; Festa, John F.

    1986-01-01

    Much of the interannual variability in partially mixed estuaries in dissolved inorganic nutrient and dissolved oxygen patterns results from an enhancement or reduction of their annual cycle (generally via climatic forcing). In northern San Francisco Bay estuary the annual cycle of dissolved silicate supply peaks in spring and the effect of phytoplankton removal peaks in fall. Because riverine silicate sources are enhanced in wet years and reduced in dry years, the annual silicate cycle is modified accordingly. Effects of phytoplankton removal are reduced and delayed in wet years and enhanced and advanced (seen earlier) in dry years. Similar reasoning can apply to interpreting and understanding other mechanisms and rates.

  1. Biocompatibility and bioactivity of calcium silicate-based endodontic sealers in human dental pulp cells

    OpenAIRE

    Leticia Boldrin MESTIERI; GOMES-CORNÉLIO, Ana Lívia; RODRIGUES, Elisandra Márcia; SALLES, Loise Pedrosa; BOSSO-MARTELO, Roberta; Juliane Maria GUERREIRO-TANOMARU; TANOMARU-FILHO, Mário

    2015-01-01

    Mineral Trioxide Aggregate (MTA) is a calcium silicate-based material. New sealers have been developed based on calcium silicate as MTA Fillapex and MTA Plus. Objective The aim of this study was to evaluate biocompatibility and bioactivity of these two calcium silicate-based sealers in culture of human dental pulp cells (hDPCs). Material and Methods The cells were isolated from third molars extracted from a 16-year-old patient. Pulp tissue was sectioned into fragments with approximately 1 mm3...

  2. Synthesis of pure zeolite P2 from calcium silicate hydrate; tobermorite

    OpenAIRE

    Nasser Y. Mostafa; Rasha A. Garib; Z. K. Heiba; Abd-Elkader, Omar H.; M. M. Al-Majthoub

    2015-01-01

    Calcium silicate hydrate phases offer the possibility to become potential zeolites precursors due to its high silica contents. Pure calcium silicate hydrate phase; tobermorite (Ca5Si6O16(OH)2·4H2O), was prepared by hydrothermal method at 175°C. Tobermorite was sucssefully converted to Zeolite P2 for the first time via refluxing in 3 M NaOH solution and in the presence of Al source. Sodium hydroxide removed calcium ions from the interlayers of calcium silicate phase and form mesoporous zeolite...

  3. The Dependence of the XRD Morphology of Some Bionanocomposites on the Silicate Treatment

    Directory of Open Access Journals (Sweden)

    Doina Dimonie

    2008-01-01

    Full Text Available The degree of intercalation of the polyvinyl alcohol-starch blend with the layered silicate is increased if the silicates is untreated or intercalated with ammonium ions that contain small radicals. If untreated silicate like NaMMT is used, it is possible to obtain exfoliated-intercalated nanocomposites. The materials based on PVOH, starch, and Nanocor I 28, Nanocor I 33, or Cloisite 15 A can be intercalated nanocomposites. If the blend of PVOH and starch is reinforced with Cloisite 93 A, microcomposites can result. The study will continue with the analysis of the new morphologies considering the transmission electron microscopy (TEM.

  4. Uniform upconversion in high-concentration Er3+-doped soda lime silicate and aluminosilicate glasses

    International Nuclear Information System (INIS)

    Uniform upconversion in erbium-doped silicate glasses is investigated as a function of glass composition, concentration, and fabrication method. Comparisons of upconversion coefficients are made among soda lime silicate and aluminosilicate bulk glasses and soda lime silicate waveguides. Comparisons are also made with studies performed by other researchers. The results indicate that both the composition and the preparation method of the glass affect the value of the upconversion coefficient, with as much as a factor-of-4 variation observed at fixed Er3+ concentration. Values of the upconversion coefficient are found to be consistent with the Foerster endash Dexter microscopic model. copyright 1997 Optical Society of America

  5. Structural study of nickel reduction in silicate melts

    Science.gov (United States)

    Marcq, B.; Galoisy, L.; Libourel, G.; Calas, G.

    2003-04-01

    Composition of the global Earth has been partially controlled by precursors chemical variability (chondrites) and by primitive earth differentiation processes. In the core, the segregation of a metallic phase (Fe, Ni) and the metal-silicate melt reactions are essential to understand primitive earth differenciation processes. From an industrial point of view, the segregation of a metallic phase from melts is widely used in metallurgy to obtain steel and cast in blast furnaces. Ni2+ bearing glasses, used as snapshot of the corresponding, melts have been synthesized under a controlled oxygen fugacity, in order to understand metal-silicate melts reduction mechanisms. The aim of this study is to follow Ni2+ environment, as a function of reduction. The methods used, optical absorption spectroscopy, EXAFS and XANES, precisely describe the sites occupied by Ni2+ in the glass. Reduction experiments were performed between 1350^oC and 1365^oC using a composition close to the anorthite-diopside system eutectic (49% SiO_2, 22% CaO, 19% Al_2O_3, 9% MgO in weight percent) with 1% NiO. A wide range of oxygen fugacities has been used, from 6.5 (Ni +1/2 O_2 NiO buffer value at 1350^oC, 1atm) to 13 (beyond Iron-Wustite buffer) with duration going from 15 min to 24 hours. Effect of Fe content and pressure are not taken into account in the present study, as it would result in a multiplication of parameters, making results more difficult to interpret. Optical spectroscopy shows that Ni2+, is mainly 5- and 4-coordinated in the initial composition (^5[Ni]/^4[Ni]=7,14). Optical spectra shows an important evolution with reduction, indicating that modifications occurs in the glass structure around Ni2+. ^5[Ni]/^4[Ni] ratio decrease with oxygen fugacity. The apparition of metallic Ni in the glass is not the only origin of the varitation of the optical spectra. EXAF and XANES data, showing a strong evolution with the glass reduction, will be also discussed.

  6. The limitations of melting on the reactivation of silicic mushes

    Science.gov (United States)

    Huber, Christian; Bachmann, Olivier; Dufek, Josef

    2010-08-01

    High crystallinity silicic ignimbrites (such as the Monotonous Intermediates) typically erupt magma with an average crystallinity ranging from 40 to 50%. This average crystallinity is believed to be just under the threshold at which magma behaves as a solid (50-60% crystals), i.e. the locking point crystallinity, where convection is suppressed and large eruptions are unlikely. These magmas often display textural features which suggest that their average crystallinity was once higher and decreased before the eruption as a result of reheating through the injection of new magma. In this study, we use a theoretical 1D heat conduction model with phase change to test the ability of different melting scenarios of crystal mushes to meet the 40 to 50% crystallinity constraint observed in the field. Our heat conduction and melting models allow us to derive analytical solutions for the average crystallinity in the magma body (initially a crystal mush). We focus on the propagation of the melting front coinciding with the locking point crystallinity for different crystallinity-temperature relationships and various choices of temperature boundary conditions. We develop another analytical model based on stagnant-lid convection scaling to assess the role of convection on the expected average crystallinity of the magma subjected to wholesale steady-state convection. We find that, for all realistic melting scenarios, the average crystallinity of a silicic magma body that passed through the rheological transition is always substantially lower than what is observed in the field. We further show with a simple energy balance that the thermal energy needed to unlock/remobilize these magma bodies requires the intrusion of about an order of magnitude of more magma than the mush. Based on these results we argue that, although melting is a key process in the thermal reactivation of high crystallinity magma bodies, another coupled process is required in order to reactivate large volumes of

  7. 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.

  8. Performance of Different Acids on Sandstone Formations

    Directory of Open Access Journals (Sweden)

    M. A. Zaman

    2013-12-01

    Full Text Available Stimulation of sandstone formations is a challenging task, which involves several chemicals and physical interactions of the acid with the formation. Some of these reactions may result in formation damage. Mud acid has been successfully used to stimulate sandstone reservoirs for a number of years. It is a mixture of hydrofluoric (HF and hydrochloric (HCl acids designed to dissolve clays and siliceous fines accumulated in the near-wellbore region. Matrix acidizing may also be used to increase formation permeability in undamaged wells. The change may be up to 50% to 100% with the mud acid. For any acidizing process, the selection of acid (Formulation and Concentration and the design (Pre-flush, Main Acid, After-flush is very important. Different researchers are using different combinations of acids with different concentrations to get the best results for acidization. Mainly the common practice is combination of Hydrochloric Acid – Hydrofluoric with Concentration (3% HF – 12% HCl. This paper presents the results of a laboratory investigation of Orthophosphoric acid instead of hydrochloric acid in one combination and the second combination is Fluoboric and formic acid and the third one is formic and hydrofluoric acid. The results are compared with the mud acid and the results calculated are porosity, permeability, and FESEM Analysis and Strength tests. All of these new combinations shows that these have the potential to be used as acidizing acids on sandstone formations.

  9. 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.

  10. Lunar highland melt rocks - Chemistry, petrology and silicate mineralogy

    Science.gov (United States)

    Vaniman, D. T.; Papike, J. J.

    1980-01-01

    A selected suite containing several of the largest samples of lunar highland melt rocks includes impact melt specimens (anorthositic gabbro, low-K Fra Mauro) and volcanic specimens (intermediate-K Fra Mauro). Although previous assumptions of LKFM volcanism have fallen into disfavor, no fatal arguments against this hypothesis have been presented, and the evidence of a possibly 'inherited igneous' olivine-plagioclase cosaturation provides cause for keeping a volcanic LKFM hypothesis viable. Comparisons of silicate mineralogy with melt rock compositions provide information on the specimen's composition and cooling history. Plagioclase-rock compositions can be matched to the experimentally determined equilibria for appropriate samples to identify melt rocks with refractory anorthitic clasts. Olivine-rock compositions indicate that melt rock vitrophyres precipitate anomalously Fe-rich olivine; the cause of this anomaly is not immediately evident. The Al-Ti and Ca-Fe-Mg zonation in pyroxene provide information on relative cooling rates of highland melt rocks, but Cr- and Al-content (where Al-rich low-Ca pyroxene cores are preserved in rapidly cooled samples) can be correlated with composition of the host rock.

  11. Structure characterization for the geopolymer of sodium silicate and metakaolin

    Institute of Scientific and Technical Information of China (English)

    CAO De-guang; SU Da-gen

    2005-01-01

    Geopolymers of metakaolin and sodium silicate were synthesized respectively with the ratios of the amount of SiO2 in the sodium silica solution to that of Al2O3 in metakaolinite equal to 1.0, and 0.66. The geopolymeric structures of the products were investigated by 27Al and 29Si solid-state nuclear magnetic resonances with magic-angle spinning (MAS NMR), Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), differential scanning colorimetry (DSC) and scanning electron microscopy (SEM). The reaction of the Al-O sheet in meakaolinite with low-order polymerized Si-O tetrahedral units such as monomer of SiO4 yields three-dimensional structures with the Q3 Si-O tetrahedral structure and the coordination of Al(IV) in the Al-O tetrahedral structure. The geopolymers are essentially X-ray amorphous. The assays by 27Al and 29Si NMR, FTIR confirm that the active structure in the metakaolinite is the sheet of Al-O with three coordination states.

  12. New electrorheological fluid obtained from mercaptosilsesquioxane-modified silicate suspensions.

    Science.gov (United States)

    Marins, Jéssica A; Dahmouche, Karim; Soares, Bluma G

    2013-01-01

    Ormosil based on mercaptosilsesquioxane-modified silicate (SiO2/SSQ-SH) particle was prepared by sol-gel process involving a co-condensation of the hydrolyzed 3-mercaptopropyl-trimethoxysilane (MPTMS) and tetraetoxysilane (TEOS). The resulting material was characterized by (29)Si solid nuclear magnetic resonance spectroscopy ((29)Si NMR), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy (FEG-SEM) and small angle X-ray scattering (SAXS). The (SiO2/SSQ-SH) particle presents a hierarchical structure, extending from micro to nanoscale and consisting of three structural levels. This SiO2/SSQ-SH particle was used for the first time as the dispersed phase in silicone oil suspension to develop a new electro-rheological fluid with a very good response under the action of electrical field from 1 to 4 kV/mm, whose values are comparable to those exhibited by other conventional ER fluids, under the influence of electric field. PMID:25428054

  13. Immobilisation of active concrete debris using soluble sodium silicates

    International Nuclear Information System (INIS)

    Demolition of concrete biological shields will generate large quantities of active demolition debris. The size distribution of such concrete may range from pieces of size less than one tonne down to dust. Handling and disposal methods for this material are still the subject of current research. Although the literature indicates that the mechanisms of silicate/concrete interaction are not well understood, successful setting of the smaller size fraction of concrete demolition debris can be achieved at laboratory scale. Hardened properties of the set slurry are also acceptable. A study of the full scale process has resulted in an outline design for a suitable on-site plant. Estimated capital costs of the equipment are of the order of pounds 1.1M. The project has shown that the material of less than 5mm particle size can be set by this technique. Whilst this meets the original objectives of immobilising dust, it had been hoped that the 10mm size material, (which will require removal from the larger debris before grouting can take place) could also be disposed of by the slurry setting technique. Co-disposal of slurry and large active items in the same container is unlikely to be worthwhile. 14 tabs., 5 figs., 30 refs

  14. Mechanical behavior of a composite interface: Calcium-silicate-hydrates

    Energy Technology Data Exchange (ETDEWEB)

    Palkovic, Steven D.; Moeini, Sina; Büyüköztürk, Oral, E-mail: obuyuk@mit.edu [Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Yip, Sidney [Department of Nuclear Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2015-07-21

    The generalized stacking fault (GSF) is a conceptual procedure historically used to assess shear behavior of defect-free crystalline structures through molecular dynamics or density functional theory simulations. We apply the GSF technique to the spatially and chemically complex quasi-layered structure of calcium-silicate-hydrates (C-S-H), the fundamental nanoscale binder within cementitious materials. A failure plane is enforced to calculate the shear traction-displacement response along a composite interface containing highly confined water molecules, hydroxyl groups, and calcium ions. GSF simulations are compared with affine (homogeneous) shear simulations, which allow strain to localize naturally in response to the local atomic environment. Comparison of strength and deformation behavior for the two loading methods shows the composite interface controls bulk shear deformation. Both models indicate the maximum shear strength of C-S-H exhibits a normal-stress dependency typical of cohesive-frictional materials. These findings suggest the applicability of GSF techniques to inhomogeneous structures and bonding environments, including other layered systems such as biological materials containing organic and inorganic interfaces.

  15. Calcium silicate hydrates: Solid and liquid phase composition

    International Nuclear Information System (INIS)

    This paper presents a review on the relationship between the composition, the structure and the solution in which calcium silicate hydrate (C–S–H) is equilibrated. The silica chain length in C–S–H increases with the silicon concentration and the calcium content in the interlayer space with the calcium concentrations. Sodium and potassium are taken up in the interlayer space, preferentially at low calcium concentrations and thus by low Ca/Si C–S–H. Aluminium uptake in C–S–H increases strongly at higher aluminium concentrations in the solution. At low Ca/Si, aluminium substitutes silica in the bridging position, at Ca/Si > 1 aluminium is bound in TAH. Recently developed thermodynamic models are closely related to the structure of C–S–H and tobermorite, and able to model not only the solubility and the chemical composition of the C–S–H, but also to predict the mean silica chain length and the uptake of aluminium

  16. Mechanical behavior of a composite interface: Calcium-silicate-hydrates

    International Nuclear Information System (INIS)

    The generalized stacking fault (GSF) is a conceptual procedure historically used to assess shear behavior of defect-free crystalline structures through molecular dynamics or density functional theory simulations. We apply the GSF technique to the spatially and chemically complex quasi-layered structure of calcium-silicate-hydrates (C-S-H), the fundamental nanoscale binder within cementitious materials. A failure plane is enforced to calculate the shear traction-displacement response along a composite interface containing highly confined water molecules, hydroxyl groups, and calcium ions. GSF simulations are compared with affine (homogeneous) shear simulations, which allow strain to localize naturally in response to the local atomic environment. Comparison of strength and deformation behavior for the two loading methods shows the composite interface controls bulk shear deformation. Both models indicate the maximum shear strength of C-S-H exhibits a normal-stress dependency typical of cohesive-frictional materials. These findings suggest the applicability of GSF techniques to inhomogeneous structures and bonding environments, including other layered systems such as biological materials containing organic and inorganic interfaces

  17. LABORATORY ANALYSIS OF PRESOLAR SILICATE STARDUST FROM A NOVA

    International Nuclear Information System (INIS)

    We report the major element as well as the oxygen, magnesium, and silicon isotope composition of a unique presolar silicate grain found in the fine-grained fraction of the Antarctic CR2 chondrite Graves Nunataks 95229. The grain is characterized by an extremely high 17O/16O ratio (6.3 ± 0.2 × 10–3) relative to solar values, whereas its 18O/16O ratio is solar within measurement uncertainty. It also shows enrichments in 25,26Mg and a significant excess in 30Si relative to solar system compositions, with δ25Mg = 79 ± 21 per mille , δ26Mg = 70 ± 20 per mille , and δ30Si = 379 ± 92 per mille . This isotopic composition is consistent with an origin in the ejecta of a ∼1.3-1.4 M☉ ONe nova with large contributions of material from a main-sequence companion star of roughly solar metallicity. However, many details of the stellar source remain undetermined, owing to the uncertainties of current nova nucleosynthesis models. Auger electron spectroscopic analyses identify O, Mg, Si, and Fe as the grain's major constituents. Its (Mg+Fe)/Si atomic ratios are lower than that of olivine and correspond on average to Fe-Mg-pyroxene. A complex texture and heterogeneous major element distribution within the grain attest to condensation under non-equilibrium conditions, which is consistent with the proposed nova origin.

  18. CO2 sequestration using calcium-silicate concrete

    International Nuclear Information System (INIS)

    This study examined the feasibility of sequestering carbon dioxide (CO2) using calcium silicate while developing a strong and durable concrete building product. In addition to offering a solution for a safe, environmentally sound manner to sequester carbon dioxide, the carbonation curing of concrete has the potential to provide a permanent storage for exhaust CO2. The calcium compounds in cement react with CO2 through the early-age carbonation curing, forming geologically stable calcium carbonates. In this study, both type 10 and type 30 Portland cements were used as CO2 binders in concretes with 0, 25, 50, and 75 per cent quartz aggregates and lightweight aggregates. The sequestration took place in a chamber under 0.5 MPa pressure at ambient temperature for a duration of 2 hours. The recovered CO2 from flue gas was simulated using a 100 per cent concentration of CO2. The CO2 uptake was quantified by direct mass gain and by an infrared-based carbon analyzer. The performance of the carbonated concrete was evaluated by its strength. In 2 hours, a CO2 uptake of 9 to 16 per cent by binder mass was achieved. The carbonation curing of concrete was found to provide better strength, stability, permeability and abrasion resistance in concrete products without steel reinforcement. 10 refs., 4 tabs., 10 figs

  19. Combustion synthesis and photoluminescence study of silicate biomaterials

    Indian Academy of Sciences (India)

    V B Bhatkar; N V Bhatkar

    2011-10-01

    Silicate based bioceramics are promising candidates as biomaterials for tissue engineering. The combustion synthesis method provides control on the morphology and particle size of the synthesized material. This paper discusses the combustion synthesis of akermanite (Ca2MgSi2O7 and Sr2MgSi2O7), which has been shown to have good in vitro and in vivo bioactivities by earlier studies. Both Ca2MgSi2O7 and Sr2MgSi2O7 have akermanite structure. Ca2MgSi2O7 and Sr2MgSi2O7 were prepared using urea and ammonium nitrate. The combustion synthesis using urea and ammonium nitrate was found to be cost effective and efficient method of synthesis. The photoluminescence study of Ca2MgSi2O7 : Eu2+ and Sr2MgSi2O7 :Eu2+ shows host specific intense emission of Eu2+.

  20. O-17 NMR studies of some silicate crystals and glasses

    CERN Document Server

    Yildirim, E K

    2000-01-01

    structure. Therefore some of the Sn has to be in three coordinated to oxygen for charge balancing. The sup 1 sup 7 O MAS NMR spectra of a partially crystallised sample showed three distinct sites which are assigned as Sn-O-Sn, Si-O-Sn, and Si-O-Si on the basis of their chemical shift. The C sub Q values obtained from the simulations of these peaks supports this assignment. The sup 2 sup 9 Si MAS NMR of the same sample showed two crystalline and a glassy peaks which are fitted to two crystalline and two glassy sites. The possible composition of this sample was calculated and found to be SiSn sub 8 O sub 1 sub 0. Crystalline and glassy silicates were investigated by means of sup 1 sup 7 O NMR. The dependence of the measured efg on the Si-O-AI bond angle was investigated in some crystalline aluminosilicate sodalites and kalsilite. The results show that C sub Q increases with increasing bond angle while eta decreases with increasing bond angle and they both follow a similar function to that found for the Si-O-Si ...

  1. Distribution of Water in Synthetic Calcium Silicate Hydrates.

    Science.gov (United States)

    Roosz, C; Gaboreau, S; Grangeon, S; Prêt, D; Montouillout, V; Maubec, N; Ory, S; Blanc, P; Vieillard, P; Henocq, P

    2016-07-12

    Understanding calcium silicate hydrates (CSHs) is of paramount importance for understanding the behavior of cement materials because they control most of the properties of these man-made materials. The atomic scale water content and structure have a major influence on their properties, as is analogous with clay minerals, and we should assess these. Here, we used a multiple analytical approach to quantify water distribution in CSH samples and to determine the relative proportions of water sorbed on external and internal (interlayer) surfaces. Water vapor isotherms were used to explain the water distribution in the CSH microstructure. As with many layered compounds, CSHs have external and internal (interlayer) surfaces displaying multilayer adsorption of water molecules on external surfaces owing to the hydrophilic surfaces. Interlayer water was also quantified from water vapor isotherm, X-ray diffraction (XRD), and thermal gravimetric analyses (TGA) data, displaying nonreversible swelling/shrinkage behavior in response to drying/rewetting cycles. From this quantification and balance of water distribution, we were able to explain most of the widely dispersed data already published according to the various relative humidity (RH) conditions and measurement techniques. Stoichiometric formulas were proposed for the different CSH samples analyzed (0.6 < Ca/Si < 1.6), considering the interlayer water contribution. PMID:27281114

  2. Fluorescence properties of Eu3+-doped alumino silicate glasses

    Science.gov (United States)

    Herrmann, Andreas; Kuhn, Stefan; Tiegel, Mirko; Rüssel, Christian

    2014-11-01

    Alumino silicate glasses of a very broad range of molar compositions doped with 1 ṡ 1020 Eu3+ cm-3 (about 0.2 mol% Eu2O3) were prepared. As network modifier oxides Li2O, Na2O, K2O, MgO, CaO, SrO, BaO, ZnO, PbO, Y2O3 and La2O3 have been used. All glasses show relatively broad fluorescence excitation and emission spectra. For most glasses only a weak effect of the glass composition on the excitation and emission spectra is observed. Although the glasses should be structurally similar, notable differences are found for the fluorescence lifetimes. These increase steadily with decreasing mean atomic weight, decreasing refractive index and decreasing optical basicity of the glasses, which may be explained by local field effects. An exception from this rule are the strontium, barium and potassium containing glasses, which show significantly increased fluorescence lifetimes despite of their high refractive index, optical basicity and molecular weight. The non mono-exponential fluorescence decay curves as well as the fluorescence spectra indicate a massive change in the local surroundings of the doped rare earth ions for these glasses.

  3. Praseodymium silicate high-k dielectrics on Si(001)

    International Nuclear Information System (INIS)

    Aggressive scaling of the complementary metal-oxide-semiconductor (CMOS) transistors resulted in the silicon dioxide (SiO2) gate dielectrics being as thin as 1.2 nm in the state-of-the-art high performance transistors. In consequence, the leakage current due to direct tunneling of electrons through the gate oxide increased significantly resulting in an unacceptably high level of power dissipation. For this reason, it is very desirable to replace the SiO2 gate dielectric with an insulator of a higher dielectric constant (high-k). The higher dielectric constant allows for the use of physically thicker dielectric layers with high capacitance densities but strongly reduced tunneling currents. This work focuses on the preparation and characterization of Praseodymium silicate high-k dielectric layers on Si(001) and evaluates the potential of this material to replace SiO2 as a gate dielectric in the state-of-the-art and future CMOS technology generations. (orig.)

  4. 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.

  5. Quantum-dot composite silicate glasses obtained by ion implantation

    International Nuclear Information System (INIS)

    Ion implantation is a useful technique to obtain composite materials such as nanocluster-containing silicate glasses. Depending on the choice of the pair 'implanted atom-dielectric host', ion implantation of metals in glass gives rise to the formation of new compounds and/or metallic nanoparticles. In spite of the great interest, processes governing the chemical and physical interaction between the implanted atoms and the atoms in the host matrix are not completely understood. In this paper, metal, alloy and binary compound nanocluster formation is studied after ion implantation in silica and soda-lime glass. Particular emphasis is given to the comparison among different existing approaches to the understanding of the chemical interactions in these systems. As the physical properties of these composites depend on the cluster structure, composition and size, it is important to set procedures for modifying these characteristics. Recent results indicate that thermal treatments in controlled atmosphere of gold + copper double-implanted silica favor the formation of either alloy nanoclusters or copper compounds, depending on the annealing atmosphere

  6. Calcium silicate hydrates: Solid and liquid phase composition

    Energy Technology Data Exchange (ETDEWEB)

    Lothenbach, Barbara, E-mail: Barbara.lothenbach@empa.ch [Laboratory Concrete & Construction Chemistry, Empa (Switzerland); Nonat, André [ICB, UMR CNRS 6303 CNRS-Université de Bourgogne, Faculté des Sciences et Techniques, BP47870, 21078 Dijon Cedex (France)

    2015-12-15

    This paper presents a review on the relationship between the composition, the structure and the solution in which calcium silicate hydrate (C–S–H) is equilibrated. The silica chain length in C–S–H increases with the silicon concentration and the calcium content in the interlayer space with the calcium concentrations. Sodium and potassium are taken up in the interlayer space, preferentially at low calcium concentrations and thus by low Ca/Si C–S–H. Aluminium uptake in C–S–H increases strongly at higher aluminium concentrations in the solution. At low Ca/Si, aluminium substitutes silica in the bridging position, at Ca/Si > 1 aluminium is bound in TAH. Recently developed thermodynamic models are closely related to the structure of C–S–H and tobermorite, and able to model not only the solubility and the chemical composition of the C–S–H, but also to predict the mean silica chain length and the uptake of aluminium.

  7. Preparation of calcium silicate absorbent from iron blast furnace slag.

    Science.gov (United States)

    Brodnax, L F; Rochelle, G T

    2000-09-01

    Calcium silicate hydrate (CSH) solids were prepared from hydrated lime and iron blast furnace slag in an aqueous agitated slurry at 92 degrees C. While it was hoped a minimal lime/slag ratio could be used to create near-amorphous CSH, the surface area of the product improved by increasing the lime/slag weight ratio to 2. The addition of gypsum to the lime/slag system dramatically improved the formation of surface area, creating solids with 139 m2/g after 30 hr of reaction when only a minimal amount of lime was present. The SO2 reactivity of solids prepared with gypsum greatly exceeded that of hydrated lime, achieving greater than 70-80% conversion of the alkalinity after 1 hr of reaction with SO2. The use of CaCl2 as an additive to the lime/slag system, in lieu of gypsum, also produced high-surface-area solids, 115 m2/g after 21 hr of reaction. However, the SO2 reactivity of these sorbents was relatively low given the high surface area. This emphasized that the correlation between surface area and SO2 reactivity was highly dependent on the solid phase, which was subsequently dependent on slurry composition. PMID:11055162

  8. Thermal properties of polyolefin composites with copper silicate

    Science.gov (United States)

    Klozinski, Arkadiusz; Jakubowska, Paulina; Ambrozewicz, Damian; Jesionowski, Teofil

    2015-05-01

    The aim of this work was to specify thermal properties of polyolefin composites with copper silicate. Low density polyethylene (LDPE) and polypropylene (PP) composites with 2, 4 and 8 wt % of the filler (CuO.SiO2) were analyzed. Characteristic temperatures of the polymer compositions, i.e. the melting (Tm) and crystallization temperatures (Tc), obtained by means of Differential Scanning Calorimetry (DSC), were determined. The impact of the applied additives on composites thermal stability was established using thermogravimetry measurements (TGA). Afterwards, the flammability test was performed. The measurement was complemented with the establishment of the maximum combustion temperature using infrared recording techniques and image analysis (infrared camera). One of the most important parameter of thermoplastics is the softening point which was also determined. The measurement was carried out using a Vicat apparatus. Thermal characteristic was also supplemented with an assessment of the thermal diffusivity (the parameter determining the cooling time in an injection mold). The tests were conducted using the modified Angstrom method and an infrared camera.

  9. Silicate grout curtains behaviour for the protection of coastal aquifers

    Energy Technology Data Exchange (ETDEWEB)

    Elektorowicz, M.; Chifrina, R.; Hesnawi, R. [Concordia Univ., Montreal, Quebec (Canada)

    1997-12-31

    Tests were performed to evaluate the behaviour of silicate grout with different reagents (ethylacetate - formamide SA and calcium chloride SC) in pure silica sand and natural soils from coastal areas containing organic matter, clayey soil and silica sand. The grouted specimens were tested with simulated fresh and salt water. The setting process during chemical grouting in the soil and sand was studied. The grouting of soil and sand with SA caused a transfer to the environment of some compounds: sodium formate, sodium acetate, ammonia and part of the initial ethylacetate and formamide. This process had a tendency to decrease for approximately 4 months. The stability of specimens was low. The grouting of soil and sand with SC caused no significant contamination of the environment. The increase of pH of environmental water was even less than with SA grouting. Also, the stability of specimens is higher in comparison with SA grouting. Salt water protected the specimens grouted with SA and SC from destruction and prevented contamination.

  10. Carbonation of metal silicates for long-term CO2 sequestration

    Science.gov (United States)

    Blencoe, James G; Palmer, Donald A; Anovitz, Lawrence M; Beard, James S

    2014-03-18

    In a preferred embodiment, the invention relates to a process of sequestering carbon dioxide. The process comprises the steps of: (a) reacting a metal silicate with a caustic alkali-metal hydroxide to produce a hydroxide of the metal formerly contained in the silicate; (b) reacting carbon dioxide with at least one of a caustic alkali-metal hydroxide and an alkali-metal silicate to produce at least one of an alkali-metal carbonate and an alkali-metal bicarbonate; and (c) reacting the metal hydroxide product of step (a) with at least one of the alkali-metal carbonate and the alkali-metal bicarbonate produced in step (b) to produce a carbonate of the metal formerly contained in the metal silicate of step (a).

  11. Turbulent metal-silicate mixing, fragmentation, and equilibration in magma oceans

    CERN Document Server

    Deguen, Renaud; Olson, Peter

    2014-01-01

    Much of the Earth was built by high-energy impacts of planetesimals and embryos, many of these impactors already differentiated, with metallic cores of their own. Geochemical data provide critical information on the timing of accretion and the prevailing physical conditions, but their interpretation depends critically on the degree of metal-silicate chemical equilibration during core-mantle differentiation, which is poorly constrained. Efficient equilibration requires that the large volumes of iron derived from impactor cores mix with molten silicates down to scales small enough to allow fast metal-silicate mass transfer. Here we use fluid dynamics experiments to show that large metal blobs falling in a magma ocean mix with the molten silicate through turbulent entrainment, with fragmentation into droplets eventually resulting from the entrainment process. In our experiments, fragmentation of the dense fluid occurs after falling a distance equal to 3-4 times its initial diameter, at which point a sizable volu...

  12. Polymer Derived Rare Earth Silicate Nanocomposite Protective Coatings for Nuclear Thermal Propulsion Systems Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The objective of this Phase I SBIR program is to develop polymer derived rare earth silicate nanocomposite environmental barrier coatings (EBC) for providing...

  13. THE ALUMINA-SILICATES IN STABILIZATION PROCESSES IN FLUIDIZED-BED ASH

    Directory of Open Access Journals (Sweden)

    IVANA PERNA

    2011-03-01

    Full Text Available Presented study of coal fluidized-bed ash solidification was accompanied with specific studies of alumino-silicates residues in ashes. The specific technology of fluid coal burning and its relatively low temperature combustion combines coal burning and decomposition of calcium carbonate added to the fluid layer in the main endeavor to capture all sulfur oxides. The burning temperature seems be decisive to the behavior of clayed residues and calcium carbonate decomposition in connection for the future solidification of fluidized bed ash. The calcareous substances in combination with alumino-silicate residues form solid bodies where silicates play decisive role of long-term stability and insolubility of obtained solids. The position of aluminum ions in clayed residues of burned coal were studied by MAS-NMR with attention on aluminum ion coordination to oxygen and formation of roentgen amorphous phase of poly-condensed calcium alumina-silicate.

  14. Cementing properties of steel slag activated by sodium silicates and sodium hydroxide

    Institute of Scientific and Technical Information of China (English)

    Wen Ni; En Wang; Jianping Li; Han Sun

    2005-01-01

    Steel slag which is mainly composed of γ-CasSiO4 and other silicates or alumino-silicates is activated by sodium silicates and sodium hydroxide. The powders of such steel slag are usually inert to hydrate and subsequently have very low ability of cementing. But when sodium silicates and sodium hydroxide are used as activators the steel slag shows very good properties of cementing. When activated with NaOH solution the hardened slurry of the steel slag has a compressive strength of 11.13 MPa after being cured for 28 days. When activated with Na2SiO3 solution the samples after being cured for 28 days have an average compressive strength of 40.23 MPa. While the steel slag slurry which is only mixed with water has a compressive of 0.88 MPa after being cured for 28 days.

  15. Some observations on use of siliceous mineral waters in reduction of corrosion in RCC structures

    Digital Repository Service at National Institute of Oceanography (India)

    Venugopal, C.

    The corrosion-resisting characteristics of reinforcement in cement blended with siliceous mineral wastes viz. gold tailing and flyash have been evaluated by using an accelerated corrosion technique. The additions of these mineral admixtures...

  16. Polymer Derived Rare Earth Silicate Nanocomposite Protective Coatings for Nuclear Thermal Propulsion Systems Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Leveraging a rapidly evolving state-of-the-art technical base empowered by Phase I NASA SBIR funding, NanoSonic's polymer derived rare earth silicate EBCs will...

  17. Geotechnical properties of two siliceous cores from the central Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Khadge, N.H.

    Physical properties of the siliceous sediments from the Central Indian Basin are measured on two short cores. The properties such as water content, Atterberg limits, porosity specific gravity, wet density show the medium to high plastic sediment...

  18. Viscosity and thermal expansion of rare earth containing soda-lime-silicate glass

    International Nuclear Information System (INIS)

    Viscosity, coefficient of thermal expansion, glass transition temperature and dilatometric softening temperature of soda-lime-silicate glass doped with rare earth oxides (La2O3, CeO2, Nd2O3) were investigated by the rotating crucible viscometer and dilatometry, the melting temperature and activation energy for viscous flow of the studied melt were derived on the basis of Arrhenius equation, in order to reveal the effects of rare earth elements on the behavior of soda-lime-silicate glass. The results show that introduction of rare earth oxides increases the coefficient of thermal expansion, decreases viscosity of soda-lime-silicate glass, and Nd2O3 is an exception in viscosity. The glass transition temperature, dilatometric softening temperature, melting temperature and activation energy for viscous flow of soda-lime-silicate glass doped with rare earth oxides increase with increasing cationic field strength of corresponding rare earth ions.

  19. Polymer Derived Yttrium Silicate Ablative TPS Materials for Next-Generation Exploration Missions Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Through the proposed NASA SBIR program, NanoSonic will optimize its HybridSil® derived yttrium silicates to serve as next-generation reinforcement for carbon...

  20. Comparative petrology of silicates in the Udei Station (IAB) and Miles (IIE) iron meteorites: Implications for the origin of silicate-bearing irons

    Science.gov (United States)

    Ruzicka, Alex; Hutson, Melinda

    2010-01-01

    The textures and mineral chemistries of silicate inclusions in the Udei Station (IAB) and Miles (fractionated IIE) iron meteorites were studied using optical and electron microscopy, SEM, EMPA, and LA-ICP-MS techniques to better understand the origin of silicate-bearing irons. Inclusions in Udei Station include near-chondritic, basaltic/gabbroic, feldspathic orthopyroxenitic, and harzburgitic lithologies. In Miles, most inclusions can be described as feldspathic pyroxenite or pyroxene-enriched basalt/gabbro. The trace-element compositions of both orthopyroxene and plagioclase grains are similar in different lithologies from Udei Station; whereas in different inclusions from Miles, the compositions of orthopyroxene grains are similar, while those of clinopyroxene, plagioclase, and especially Cl-apatite are variable. Orthopyroxene in Miles tends to be enriched in REE compared to that in Udei Station, but the reverse is true for plagioclase and clinopyroxene. The data can be explained by models involving partial melting of chondritic protoliths, silicate melt migration, and redox reactions between silicate and metal components to form phosphate. The extent of heating, melt migration, and phosphate formation were all greater in Miles. Silicates in Miles were formed from liquids produced by ˜30% partial melting of a chondritic precursor brought to a peak temperature of ˜1250 °C. This silicate melt crystallized in two stages. During Stage 1, crystallizing minerals (orthopyroxene, clinopyroxene, chromite, and olivine) were largely in equilibrium with an intercumulus melt that was evolving by igneous fractionation during slow cooling, with a residence time of ˜20 ka at ˜1150 °C. During Stage 2, following probable re-melting of feldspathic materials, and after the silicate "mush" was mixed with molten metal, plagioclase and phosphate fractionally crystallized together during more rapid cooling down to the solidus. In Udei Station, despite a lower peak temperature (IIE

  1. 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

  2. Observations on the morphological diversity and distribution of two siliceous nannoplankton genera, Hyalolithus and Petasaria

    DEFF Research Database (Denmark)

    Jordan, Richard W.; Abe, Kent; Cruz, Jarret;

    2016-01-01

    Scale-bearing siliceous nannoplankton are occasionally encountered in surface seawater samples, but are rarely identified or illustrated. In this study, the morphological diversity of the haptophyte Hyalolithus neolepis and the enigmatic Petasaria heterolepis are investigated in scanning and tran......Scale-bearing siliceous nannoplankton are occasionally encountered in surface seawater samples, but are rarely identified or illustrated. In this study, the morphological diversity of the haptophyte Hyalolithus neolepis and the enigmatic Petasaria heterolepis are investigated in scanning...

  3. Spectroscopic study of silicate glass structure. Application to the case of iron and magnesium

    International Nuclear Information System (INIS)

    During the last 10 years, I focused my research topics on silicate glass structure. More specifically I have been interested by two main components of natural and technological silicate glasses, Fe and Mg. Using solid state spectroscopic methods adapted to the disordered nature of glass coupled to molecular dynamics simulation and modeling or ab initio calculation, I have studied the environment of iron and magnesium and their impact on glass properties. Information on the distribution of environments in glasses have been extracted. (author)

  4. STUDY ON CORROSION RESISTANCE OF REBAR IN HYBRID GRINDING FLY ASH-LIME SILICATE CONCRETE

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    The corrosion resistance of rebar in fly ash-lime sili cate concrete as well as its marco properties and pore distribution is investiga ted.The results show that the fly ash is activated, the compressive strength of the silicate concrete is strengthened and its pore structure is modified after f ly ash and lime being hybrid ground.Also the corrosion resistance of rebar in the silicate concrete is improved.

  5. Creating of highly active calcium-silicate phases for application in endodontics

    OpenAIRE

    Čolović B.; Jokanović V.; Jović N.

    2013-01-01

    The synthesis of active silicate phases by combined sol gel and high-temperature selfpropagating wave method, is described in this paper. They show a significant decrease of setting time and good mechanical properties, which are very important for its potential application in endodontic practice. Particularly, process of hydration of calcium silicate phases is carefully analyzed, from the aspect of phase changes during their soaking in water for 1, 3, 7 and...

  6. Biocompatibility of a new nanomaterial based on calcium silicate implanted in subcutaneous connective tissue of rats

    OpenAIRE

    Petrović Violeta; Opačić-Galić Vanja; Jokanović V.; Jovanović M.; Basta-Jovanović Gordana; Živković S.

    2012-01-01

    The aim of the study was to investigate rat connective tissue response to a new calcium silicate system 7, 15, 30 and 60 days after implantation. Twenty Wistar albino male rats received two tubes half-filled with a new calcium silicate system (NCSS) or MTA in subcutaneous tissue. The empty half of the tubes served as controls. Five animals were sacrificed after 7, 15, 30 and 60 days and samples of the subcutaneous tissue around implanted material were submi...

  7. Use of Propranolol-Magnesium Aluminium Silicate Intercalated Complexes as Drug Reservoirs in Polymeric Matrix Tablets

    OpenAIRE

    T. Pongjanyakul; S Rojtanatanya

    2012-01-01

    The objective of the present study was to investigate the use of propranolol-magnesium aluminium silicate intercalated complexes as drug reservoirs in hydroxypropylmethylcellulose tablets. The matrix tablets containing the complexes were prepared and characterised with respect to propranolol release and were subsequently compared with those loading propranolol or a propranolol-magnesium aluminium silicate physical mixture. Additionally, the effects of varying viscosity grades of hydroxypropyl...

  8. Determine the Compressive Strength of Calcium Silicate Bricks by Combined Nondestructive Method

    OpenAIRE

    2014-01-01

    The paper deals with the application of combined nondestructive method for assessment of compressive strength of calcium silicate bricks. In this case, it is a combination of the rebound hammer method and ultrasonic pulse method. Calibration relationships for determining compressive strength of calcium silicate bricks obtained from nondestructive parameter testing for the combined method as well as for the L-type Schmidt rebound hammer and ultrasonic pulse method are quoted here. Calibration ...

  9. XRF analysis of major and trace elements for silicate rocks using low dilution ratio fused glass

    OpenAIRE

    Tanaka, Ryoji; ORIHASHI, Yuji

    1997-01-01

    An X-ray fluorescence spectrometry (XRF) method to determine 10 major and 18 trace elements in silicate rocks has been investigated. The analysis is carried out on fused glass beads, containing one part rock powder, two parts of lithium metaborate/tetraborate flux and 0.3 parts of lithium n itrate by weight. Calibration lines were established using international silicate rock reference materials. The low dilution fused glass technique effectively eliminates particle size effect...

  10. Evaluation of the mechanical properties of acetic-cure silicone with the addition of magnesium silicate

    OpenAIRE

    Ronald Vargas Orellana; Neide Pena Coto; Igor Studart Medeiros; Reinaldo Brito Dias

    2015-01-01

    Current study evaluates the mechanical properties (tensile and tear strength) of an acetic-cure silicone with the addition of 10 or 20% vol. magnesium silicate. Magnesium silicate was added to the silicone at concentrations of 10 (MS-10) and 20% (MS-20) volume, followed by the analysis of tensile strength, maximal elongation during tensile and tear strength. Results were compared to control group of silicone without additives (CG). Mean rates were determined and compared by analysis of v...

  11. The natural hydrous sodium silicates from the northern bank of Lake Chad : occurrence, petrology and genesis

    OpenAIRE

    Sebag, D.; Verrecchia, Eric P.; Lee, Seong-Joo; Durand, A

    2005-01-01

    Hydrous sodium silicates sometimes associated with zeolites, form in an alkaline environment, in which there is a high concentration of dissolved silica. Such an environment existed during the Holocene in N'Guigmi interdunal depressions (Lake Chad), which led to the precipitation of various types of hydrous sodium silicates, including magadiite, kenyaite, and zeolites. Scanning electron and optical microscope observations allow several microstructures to be distinguished. These microstructure...

  12. Silicate Esters of Paclitaxel and Docetaxel: Synthesis, Hydrophobicity, Hydrolytic Stability, Cytotoxicity, and Prodrug Potential

    OpenAIRE

    Wohl, Adam R.; Michel, Andrew R.; Kalscheuer, Stephen; Macosko, Christopher W.; Panyam, Jayanth; Hoye, Thomas R.

    2014-01-01

    We report here the synthesis and selected properties of various silicate ester derivatives (tetraalkoxysilanes) of the taxanes paclitaxel (PTX) and docetaxel (DTX) [i.e., PTX-OSi(OR)3 and DTX-OSi(OR)3]. Both the hydrophobicity and hydrolytic lability of these silicates can be (independently) controlled by choice of the alkyl group (R). The synthesis, structural characterization, hydrolytic reactivity, and in vitro cytotoxicity against the MDA-MB-231 breast cancer cell line of most of these de...

  13. A MODEL FOR THE DUST ENVELOPE OF THE SILICATE CARBON STAR IRAS 09425-6040

    Energy Technology Data Exchange (ETDEWEB)

    Suh, Kyung-Won, E-mail: kwsuh@chungbuk.ac.kr [Department of Astronomy and Space Science, Chungbuk National University, Cheongju-City, 28644 (Korea, Republic of)

    2016-03-01

    IRAS 09425-6040 (I09425) is a silicate carbon star with conspicuous crystalline silicate and water-ice features and emission excesses in the far-infrared and millimeter (mm) wavelength ranges. To understand properties of the dust envelope of I09425, we propose a physical model based on the observations and known properties of asymptotic giant branch stars and dust. We perform radiative transfer model calculations using multiple dust shells and disks with various dust species. We compare the model results with the observed spectral energy distribution (SED) acquired with different telescopes. We find that the physical model for I09425 using multiple shells of carbon and silicate dust and multiple disks of amorphous and crystalline silicates reproduces the observed SED fairly well. This object looks to have detached cold O-rich (silicate and water-ice) dust shells, which could be remnants of the recent chemical transition from O to C and an inner C-rich dust shell. A long-lived thin disk of very large silicate grains can reproduce the emission excess in the mm wavelength band and a recently formed thick disk of crystalline silicates can reproduce the prominent emission features in the spectral range 8–45 μm. The highly crystallized silicates could be recently formed by high temperature annealing due to the last O-rich superwind just before the chemical transition of the central star. I09425 could be a rare object that has the remnants of past O-rich stellar winds in the outer shells as well as in the circumbinary disks.

  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. Functional nanocomposites prepared by self-assembly and polymerization of diacetylene surfactants and silicic acid

    Science.gov (United States)

    Yang, Yi; Lu, Yunfeng; Lu, Mengcheng; Huang, Jinman; Haddad, Raid; Xomeritakis, George; Liu, Nanguo; Malanoski, Anthony P.; Sturmayr, Dietmar; Fan, Hongyou; Sasaki, Darryl Y.; Assink, Roger A.; Shelnutt, John A.; van Swol, Frank; Lopez, Gabriel P.; Burns, Alan R.; Brinker, C. Jeffrey

    2003-01-01

    Conjugated polymer/silica nanocomposites with hexagonal, cubic, or lamellar mesoscopic order were synthesized by self-assembly using polymerizable amphiphilic diacetylene molecules as both structure-directing agents and monomers. The self-assembly procedure is rapid and incorporates the organic monomers uniformly within a highly ordered, inorganic environment. By tailoring the size of the oligo(ethylene glycol) headgroup of the diacetylene-containing surfactant, we varied the resulting self-assembled mesophases of the composite material. The nanostructured inorganic host altered the diacetylene polymerization behavior, and the resulting nanocomposites show unique thermo-, mechano-, and solvatochromic properties. Polymerization of the incorporated surfactants resulted in polydiacetylene (PDA)/silica nanocomposites that were optically transparent and mechanically robust. Molecular modeling and quantum calculations and (13)C spin-lattice relaxation times (T(1)) of the PDA/silica nanocomposites indicated that the surfactant monomers can be uniformly organized into precise spatial arrangements prior to polymerization. Nanoindentation and gas transport experiments showed that these nanocomposite films have increased hardness and reduced permeability as compared to pure PDA. Our work demonstrates polymerizable surfactant/silica self-assembly to be an efficient, general approach to the formation of nanostructured conjugated polymers. The nanostructured inorganic framework serves to protect, stabilize, and orient the polymer, mediate its performance, and provide sufficient mechanical and chemical stability to enable integration of conjugated polymers into devices and microsystems.

  16. On the Anomalous Silicate Emission Features of AGNs: A Possible Interpretation Based on Porous Dust

    CERN Document Server

    Li, M P; Li, Aigen

    2008-01-01

    The recent Spitzer detections of the 9.7 micron Si--O silicate emission in type 1 AGNs provide support for the AGN unification scheme. The properties of the silicate dust are of key importance to understanding the physical, chemical and evolutionary properties of the obscuring dusty torus around AGNs. Compared to that of the Galactic interstellar medium (ISM), the 10 micron silicate emission profile of type 1 AGNs is broadened and has a clear shift of peak position to longer wavelengths. In literature this is generally interpreted as an indication of the deviations of the silicate composition, size, and degree of crystallization of AGNs from that of the Galactic ISM. In this Letter we show that the observed peak shift and profile broadening of the 9.7 micron silicate emission feature can be explained in terms of porous composite dust consisting of ordinary interstellar amorphous silicate, amorphous carbon and vacuum. Porous dust is naturally expected in the dense circumnuclear region around AGNs, as a consequ...

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

    Science.gov (United States)

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

    2016-04-01

    Calcium silicate slag is an alkali leaching waste generated during the process of extracting Al2O3 from high-alumina fly ash. In this research, a cementitious material composed of calcium silicate slag was developed, and its mechanical and physical properties, hydration characteristics and environmental friendly performance were investigated. The results show that an optimal design for the cementitious material composed of calcium silicate slag was determined by the specimen CFSC7 containing 30% calcium silicate slag, 5% high-alumina fly ash, 24% blast furnace slag, 35% clinker and 6% FGD gypsum. This blended system yields excellent physical and mechanical properties, confirming the usefulness of CFSC7. The hydration products of CFSC7 are mostly amorphous C-A-S-H gel, rod-like ettringite and hexagonal-sheet Ca(OH)2 with small amount of zeolite-like minerals such as CaAl2Si2O8·4H2O and Na2Al2Si2O8·H2O. As the predominant hydration products, rod-like ettringite and amorphous C-A-S-H gel play a positive role in promoting densification of the paste structure, resulting in strength development of CFSC7 in the early hydration process. The leaching toxicity and radioactivity tests results indicate that the developed cementitious material composed of calcium silicate slag is environmentally acceptable. This study points out a promising direction for the proper utilization of calcium silicate slag in large quantities. PMID:26691955

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

    Science.gov (United States)

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

    2016-04-01

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

  19. Growth of titanium silicate thin films by photo-induced chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Z.M.; Fang, Q.; Zhang, J.-Y.; Wu, J.X.; Di, Y.; Chen, W.; Chen, M.L.; Boyd, Ian W

    2004-04-01

    Titanium silicate thin films have been grown on Si substrates by photo-induced chemical vapor deposition using 222-nm ultraviolet excimer lamps. Titanium tetraisopropoxide (TTIP) and tetraethoxysilane (TEOS) were used as precursors. TTIP and TEOS were dissolved together in cyclohexane and introduced into the photochemical reaction chamber through a droplet injector vaporizer. The composition of the film was controlled by changing the ratio of TTIP to TEOS in the precursor solution. High quality titanium silicate films with various Ti/Si ratios and low carbon content have been achieved as revealed by X-ray photoelectron spectroscopy measurements. The atomic percentage of Ti content in the grown silicate films is significantly larger than that in the precursor solution. The films were measured to be 30-80 nm in thickness and 1.91-2.31 in refractive index by ellipsometry. Both the growth rate and refractive index increase with increasing Ti percentage in the silicate films. The evolution of Fourier transform infrared spectra of the silicate films with solution composition shows that the Ti-O-Si absorption at approximately 920 cm{sup -1} becomes stronger, while the Ti-O absorption at approximately 430 cm{sup -1} becomes weaker with decreasing Ti percentage in the solution. A small feature at {approx}1035 cm{sup -1} related to Si-O-Si bonds is also observed in the SiO{sub 2}-rich Ti silicate film.

  20. 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.

  1. SON68 glass dissolution driven by magnesium silicate precipitation

    Science.gov (United States)

    Fleury, Benjamin; Godon, Nicole; Ayral, André; Gin, Stéphane

    2013-11-01

    Experimental results are reported on the effect of magnesium silicate precipitation on the mechanisms and rate of borosilicate glass dissolution. Leaching experiments with SON68 glass, a borosilicate containing no Mg, were carried out in initially deionized water at 50 °C with a glass-surface-area-to-solution-volume ratio of 20,000 m-1. After 29 days of alteration the experimental conditions were modified by the addition of Mg to trigger the precipitation of Mg-silicate. Additional experiments were conducted to investigate the importance of other parameters such as pH or dissolved silica on the mechanisms of precipitation of Mg-silicates and their consequences on the glass dissolution rate. Mg-silicates precipitate immediately after Mg is added. The amount of altered glass increases with the quantity of added Mg, and is smaller when silicon is added in solution. A time lag is observed between the addition of magnesium and the resumption of glass alteration because silicon is first provided by partial dissolution of the previously formed alteration gel. It is shown that nucleation does not limit Mg-silicate precipitation. A pH above 8 is necessary for the phase to precipitate under the investigated experimental conditions. On the other hand the glass alteration kinetics limits the precipitation if the magnesium is supplied in solution at a non-limiting rate. The concentration of i in solution was analyzed as well as that of boron. The quantity of i released from the glass is estimated with the assumption that i and B are released congruently at the glass dissolution front. The remained quantity of the element i is then supposed to be in the gel or in the secondary phase. In this paper, we do not make a difference between gel and hydrated glass using the same word 'gel' whereas Gin et al. [40] makes this difference. Recent papers [40,41] discussed about different key issues related to the passivation properties of the alteration layer including the hydrated glass

  2. Application of reference point indentation for micro-mechanical surface characterization of calcium silicate based dental materials.

    Science.gov (United States)

    Antonijević, Djordje; Milovanović, Petar; Riedel, Christoph; Hahn, Michael; Amling, Michael; Busse, Björn; Djurić, Marija

    2016-04-01

    The objective of this study was to elucidate micromechanical properties of Biodentine and two experimental calcium silicate cements (CSCs) using Reference Point Indentation (RPI). Biomechanical characteristics of the cement type and the effects of a radiopacifier, liquid components, acid etching treatment and bioactivation in simulated body fluid (SBF) were investigated by measuring the microhardness, average unloading slope (Avg US) and indentation distance increase (IDI). Biodentine had a greater microhardness than the experimental CSCs, while the Avg US and IDI values were not significantly different among investigated materials. There was a statistically significant difference in microhardness and IDI values between pure CSCs and radiopacified cements (p < 0.05). Micromechanical properties were not affected by different liquid components used. Acid-etching treatment reduced Biodentine's microhardness while cements' immersion in SBF resulted in greater microhardness and higher IDI values compared to the control group. Clearly, the physiological environment and the cements' composition affect their surface micromechanical properties. The addition of calcium chloride and CSCs' immersion in SBF are beneficial for CSCs' micromechanical performance, while the addition of radiopacifiers and acid etching treatment weaken the CSCs' surface. Application of RPI aids with the characterization of micromechanical properties of synthetic materials' surfaces. PMID:26888441

  3. Sulphur dioxide removal using South African limestone/siliceous materials

    Energy Technology Data Exchange (ETDEWEB)

    D.O. Ogenga; M.M. Mbarawa; K.T. Lee; A.R. Mohamed; I. Dahlan [Tshwane University of Technology, Pretoria (South Africa)

    2010-09-15

    This study presents an investigation into the desulfurization effect of sorbent derived from South African calcined limestone conditioned with fly ash. The main aim was to examine the effect of chemical composition and structural properties of the sorbent with regard to SO{sub 2} removal in dry-type flue gas desulfurization (FGD) process. South African fly ash and CaO obtained from calcination of limestone in a laboratory kiln at a temperature of 900{sup o}C were used to synthesize CaO/ash sorbent by atmospheric hydration process. The sorbent was prepared under different hydration conditions: CaO/fly ash weight ratio, hydration temperature (55-75{sup o}C) and hydration period (4-10 h). Desulfurization experiments were done in the fixed bed reactor at 87{sup o}C and relative humidity of 50%. The chemical composition of both the fly ash and calcined limestone had relatively high Fe{sub 2}O{sub 3} and oxides of other transitional elements which provided catalytic ability during the sorbent sorption process. Generally the sorbents had higher SO{sub 2} absorption capacity in terms of mol of SO{sub 2} per mol of sorbent (0.1403-0.3336) compared to hydrated lime alone (maximum 0.1823). The sorbents were also found to consist of mesoporous structure with larger pore volume and BET specific surface area than both CaO and fly ash. X-ray diffraction (XRD) analysis showed the presence of complex compounds containing calcium silicate hydrate in the sorbents. 19 refs., 6 figs., 3 tabs.

  4. LABORATORY ANALYSIS OF PRESOLAR SILICATE STARDUST FROM A NOVA

    Energy Technology Data Exchange (ETDEWEB)

    Leitner, J.; Kodolanyi, J.; Hoppe, P. [Max Planck Institute for Chemistry, Particle Chemistry Department, Hahn-Meitner-Weg 1, D-55128 Mainz (Germany); Floss, C., E-mail: jan.leitner@mpic.de [Laboratory for Space Sciences and Physics Department, Washington University, One Brookings Drive, St. Louis, MO 63130 (United States)

    2012-08-01

    We report the major element as well as the oxygen, magnesium, and silicon isotope composition of a unique presolar silicate grain found in the fine-grained fraction of the Antarctic CR2 chondrite Graves Nunataks 95229. The grain is characterized by an extremely high {sup 17}O/{sup 16}O ratio (6.3 {+-} 0.2 Multiplication-Sign 10{sup -3}) relative to solar values, whereas its {sup 18}O/{sup 16}O ratio is solar within measurement uncertainty. It also shows enrichments in {sup 25,26}Mg and a significant excess in {sup 30}Si relative to solar system compositions, with {delta}{sup 25}Mg = 79 {+-} 21 per mille , {delta}{sup 26}Mg = 70 {+-} 20 per mille , and {delta}{sup 30}Si = 379 {+-} 92 per mille . This isotopic composition is consistent with an origin in the ejecta of a {approx}1.3-1.4 M{sub Sun} ONe nova with large contributions of material from a main-sequence companion star of roughly solar metallicity. However, many details of the stellar source remain undetermined, owing to the uncertainties of current nova nucleosynthesis models. Auger electron spectroscopic analyses identify O, Mg, Si, and Fe as the grain's major constituents. Its (Mg+Fe)/Si atomic ratios are lower than that of olivine and correspond on average to Fe-Mg-pyroxene. A complex texture and heterogeneous major element distribution within the grain attest to condensation under non-equilibrium conditions, which is consistent with the proposed nova origin.

  5. Sodium silicate solutions from dissolution of glasswastes. Statistical analysis

    Directory of Open Access Journals (Sweden)

    Torres-Carrasco, M.

    2014-05-01

    Full Text Available It has studied the solubility process of four different waste glasses (with different particle sizes, 125 µm in alkaline solutions (NaOH and NaOH/Na₂CO₃ and water as a reference and under different conditions of solubility (at room temperature, at 80°C and a mechano-chemical process. Have established the optimal conditions of solubility and generation of sodium silicates solutions, and these were: the smaller particle size (Se ha estudiado el proceso de solubilidad de cuatro diferentes residuos vítreos (con distintas granulometrías, 125 µm en disoluciones alcalinas de NaOH y NaOH/Na₂CO₃ y agua como medio de referencia y bajo distintas condiciones de solubilidad (a temperatura ambiente, a 80°C y con un proceso mecano-químico. Se han establecido las condiciones óptimas de solubilidad y generación de disoluciones de silicato sódico, y estas son: menor tamaño de partícula del residuo vítreo (inferior a 45 µm, con la disolución de NaOH/Na₂CO₃ y tratamiento térmico a 80°C durante 6 horas de agitación. El análisis estadístico realizado a los resultados obtenidos da importancia a las variables estudiadas y a las interacciones de las mismas. A través de ²⁹Si RMN MAS se ha confirmado la formación, tras los procesos de disolución, de un silicato monomérico, apto para su utilización como activador en la preparación de cementos y hormigones alcalinos.

  6. Rheological and thermal properties of polylactide/silicate nanocomposites films.

    Science.gov (United States)

    Ahmed, Jasim; Varshney, Sunil K; Auras, Rafeal

    2010-03-01

    Polylactide (DL)/polyethylene glycol/silicate nanocomposite blended biodegradable films have been prepared by solvent casting method. Rheological and thermal properties were investigated for both neat amorphous polylactide (PLA-DL form) and blend of montmorillonite (clay) and poly (ethylene glycol) (PEG). Melt rheology of the PLA individually and blends (PLA/clay; PLA/PEG; PLA/PEG/clay) were performed by small amplitude oscillation shear (SAOS) measurement. Individually, PLA showed an improvement in the viscoelastic properties in the temperature range from 180 to 190 degrees C. Incorporation of nanoclay (3% to 9% wt) was attributed by significant improvements in the elastic modulus (G') of PLA/clay blend due to intercalation at higher temperature. Both dynamic modulii of PLA/PEG blend were significantly reduced with addition of 10% PEG. Rheometric measurement could not be conducted while PLA/PEG blends containing 25% PEG. A blend of PLA/PEG/clay (68/23/9) showed liquid-like properties with excellent flexibility. Thermal analysis of different clay loading films indicated that the glass transition temperatures (T(g)) remained unaffected irrespective of clay concentration due to immobilization of polymer chain in the clay nanocomposite. PEG incorporation reduced the T(g) of the blend (PLA/PEG and PLA/PEG/clay) significantly. Both rheological and thermal analysis data supported plasticization and flexibility of the blended films. It is also interesting to study competition between PLA and PEG for the intercalation into the interlayer spacing of the clay. This study indicates that PLA/montmorillonite blend could serve as effective nano-composite for packaging and other applications. PMID:20492249

  7. Interstellar Extinction and Polarization by Graphite-Silicate Clusters

    Science.gov (United States)

    Johnson, E. T.; Draine, B. T.

    2004-12-01

    The geometry of interstellar dust continues to be uncertain. In some models, intertellar grains are assumed to homogeneous spheres, with a suitable mixture of sizes and compositions in order to reproduce observations of of absorption and scattering (e.g., Weingartner & Draine 2001, or Zubko et al. 2004). However, it is often thought that the larger interstellar grains may be formed by agglomeration of smaller particles, with the resulting ``cluster'' being of nonuniform composition and having a ``fluffy'' geometry. The optical properties of such ``fluffy'' grains have sometimes been estimated using ``effective medium theory'' or other approximations, but it is now possible to directly calculate scattering and absorption using the discrete dipole approximation (Draine & Flatau 1994). We construct candidate clusters by random ballistic agglomeration of small graphite and silicate spheres, and calculate their scattering and absorption cross sections using the discrete dipole approximation code DDSCAT 6.x (Draine & Flatau 2004). We consider a model for interstellar dust consisting of very small grains plus clusters built by ballistic agglomeration with a suitable size distribution, and we test the model by trying to reproduce the observed wavelength dependence of interstellar extinction and polarization. This research was supported in part by NSF grants AST-0216105 and AST-0406883. References: Draine, B.T., & Flatau, P.J. 1994, JOSA, A11, 1491l Draine, B.T., & Flatau, P.J. 2004, http://arxiv.org/abs/astro-ph/0409262l Weingartner, J.C., & Draine, B.T. 2001, ApJ, 548, 296l Zubko, V., Dwek, E., & Arendt, R.G. 2004, ApJS, 152, 211l

  8. Chalcophile element partitioning into magmatic sulphides: the effect of silicate melt composition

    Science.gov (United States)

    Kiseeva, Kate; Wood, Bernard

    2016-04-01

    Partitioning of many elements between sulphide and silicate melts is a function of the FeO content of the silicate liquid (Kiseeva and Wood, 2013). The theoretical relationship is a linear one between LogDM (DM=[M]sulph/[M]sil) and -log[FeO] with a slope of n/2, where n is the valency of trace element M. In practice we find that the slope deviates from the theoretical one because of the presence of oxygen in the sulphide. In our recent study we investigated the effects of sulphide composition and temperature on chalcophile element partitioning between sulphide and silicate liquids (Kiseeva and Wood, 2015). We have concluded that partitioning of most chalcophile elements is a strong function of the oxygen (or FeO) content of the sulphide. As expected, lithophile elements partition more strongly into sulphide as its oxygen content increases, while chalcophile elements enter sulphide less readily with increasing oxygen. The effect of Ni and Cu content of sulphide is significantly smaller than the effect of oxygen, while the effects of temperature are large only for a number of elements (such as Ni, Cu, Ag). In this study we show that in addition to the effect of sulphide composition, for certain elements the effect of silicate melt composition on sulphide/silicate partitioning can be quite large. For instance, within the range of NBO/T between 0.5 and 2 the DTlsulph/sil changes in order of magnitude. For the elements, like Pb, partition coefficient does not seem to change much with the silicate melt composition, while for Sb the effect of the silicate melt composition on D is a factor of 3. Partitioning of chalcophile elements into more evolved, alkali-rich and felsic magmas is estimated to be very different from the partitioning into basaltic melts, mainly due to the strong effects of temperature and alkali components. Although it is highly likely that sulphide is in solid form at liquidus temperatures for dacite and rhyolite and thus the partitioning of chalcophile

  9. Solidification/stabilization and leaching behavior of PbCl₂ in fly-ash hydrated silicate matrix and fly-ash geopolymer matrix.

    Science.gov (United States)

    Li, Yang; Gao, Xingbao; Wang, Qi; He, Jie; Yan, Dahai

    2015-05-01

    Fly ash (FA) for reuse as a construction material is activated using two methods, to produce hydrated silicate and geopolymer gels. We investigated the solidification/stabilization and leaching behavior of PbCl2 in a geopolymer matrix (GM) and hydrated silicate matrix (HSM), based on FA as the source material, to evaluate the environmental and health risks. The GM and HSM synthetic conditions were 60 °C, 20 % relative humidity (RH), and 12 wt% (6 mol/L) NaOH, and 20 ± 2 °C, ≥ 90 % RH, and 30 wt.%, respectively, based on their compressive strength performances. X-ray diffraction (XRD) showed that Pb participated in hydration and geopolymerization, and was incorporated in the structural components of the hydrated silicate and geopolymer. In leaching experiments, the solidification/stabilization effects of Pb and Cl in the HSM and GM improved with increasing curing time. After long-term curing (28 days), the immobility of Pb in the GM was better than that in the HSM. Sodalite improved the Cl-stabilizing ability of the GM compared with that of the HSM. In static monolithic leaching experiments, HSM and GM had the same Pb-leaching behaviors. Based on the changes in the location of the neutral sphere layer with decreasing acid-neutralizing capacity, Pb release was divided into alkaline-release, stagnation, and acid-release stages. The neutral sphere layer contained the highest Pb concentration during permeation toward the block center from the block edge. This behavior regulation could also apply to other amphoteric metals immobilized by GMs and HSMs.

  10. Carbon mineralization and pyrite oxidation in groundwater: Importance for silicate weathering in boreal forest soils and stream base-flow chemistry

    International Nuclear Information System (INIS)

    Research highlights: → Organic compounds is mineralized during later transport in deep groundwater aquifers. → Carbonic acid generated by this process stimulates dissolution of silicate minerals. → Protons derived from pyrite oxidation also affects weathering in deep groundwater. → The identified weathering mechanisms affect base-flow chemistry in boreal streams. - Abstract: What role does mineralized organic C and sulfide oxidation play in weathering of silicate minerals in deep groundwater aquifers? In this study, how H2CO3, produced as a result of mineralization of organic matter during groundwater transport, affects silicate weathering in the saturated zone of the mineral soil along a 70 m-long boreal hillslope is demonstrated. Stream water measurements of base cations and δ18O are included to determine the importance of the deep groundwater system for downstream surface water. The results suggest that H2CO3 generated from organic compounds being mineralized during the lateral transport stimulates weathering at depths between 0.5 and 3 m in the soil. This finding is indicated by progressively increasing concentrations of base cations-, silica- and inorganic C (IC) in the groundwater along the hillslope that co-occur with decreasing organic C (OC) concentrations. Protons derived from sulfide oxidation appear to be an additional driver of the weathering process as indicated by a build-up of SO42- in the groundwater during lateral transport and a δ34S per mille value of +0.26-3.76 per mille in the deep groundwater indicating S inputs from pyrite. The two identified active acids in the deep groundwater are likely to control the base-flow chemistry of streams draining larger catchments (>1 km2) as evident by δ18O signatures and base cation concentrations that overlap with that of the groundwater.

  11. Preparation of novel nanoporous layered silicates by swelling of AMH-3 and their use in nanocomposite membranes for gas separation

    Science.gov (United States)

    Choi, Sunho

    Nanoporous layered materials can be described as a class of lamellar solids that have an intermediate structure between layered materials (e.g., clays) and nanoporous frameworks (e.g., zeolites). Among these, nanoporous layered silicates have been studied for various industrial applications since the rich intercalation chemistry of clays can be applied to yield their swollen and exfoliated derivatives. Their pore connectivity in the direction perpendicular to the layers has been expected to provide an ability of molecular recognition based on the size of permeating species. These unique structural characteristics are important in the membrane industry because the molecular sieving of permeable nanolayers, if exfoliated and incorporated in polymers, is able to enhance the separation properties of polymeric membranes. AMH-3, a layered silicate built of nanoporous layers and interlayer space occupied by cations and water molecules, has been known to have a unique three-dimensional eight membered-ring (8 MR) pore system. Due to its unique porosity, it has been proposed to use exfoliated layers of AMH-3 as a selectivity-enhancing additive in polymers for small molecule separation. However, experimental procedures for the AMH-3 swelling, required for the nanocomposite demonstrated. This research reveals a novel process for AMH-3 swelling, involving the sequential intercalation of surfactant molecules following proton exchange of interlayer cations in the presence of amino acids. Structural information of swollen AMH-3 is investigated using various characterization techniques and the emergence of structural changes indicates that it should be considered as a new nanoporous layered silicate rather than a simple intercalated derivative. Consequently, polymeric nanocomposites incorporating the nanoparticles of swollen AMH-3 are fabricated by solution blending. These nanocomposite membranes present substantial improvements of the hydrogen/carbon dioxide ideal selectivity more

  12. Reduction in Acidity of RDX and its Compositions by Use of Suitable Additives

    Directory of Open Access Journals (Sweden)

    Harihar Singh

    1983-01-01

    Full Text Available Calcium Silicate and Zinc Stearate have been used as additives to reduce the acidity of RDX and RDX/TNT compositions. They have been found to be effective in reducing the acidity of RDX/TNT compositions but ineffective for RDX alone. An explanation to this effect has been provided.

  13. Directed osteogenic differentiation of human mesenchymal stem/precursor cells on silicate substituted calcium phosphate.

    Science.gov (United States)

    Cameron, Kate; Travers, Paul; Chander, Chaman; Buckland, Tom; Campion, Charlie; Noble, Brendon

    2013-01-01

    Insufficient, underactive, or inappropriate osteoblast function results in serious clinical conditions such as osteoporosis, osteogenesis imperfecta and fracture nonunion and therefore the control of osteogenesis is a medical priority. In vitro mesenchymal stem cells (MSCs) can be directed to form osteoblasts through the addition of soluble factors such as β-glycerophosphate, ascorbic acid, and dexamethasone; however this is unlikely to be practical in the clinical setting. An alternative approach would be to use a scaffold or matrix engineered to provide cues for differentiation without the need for soluble factors. Here we describe studies using Silicate-substituted calcium phosphate (Si-CaP) and unmodified hydroxyapatite (HA) to test whether these materials are capable of promoting osteogenic differentiation of MSCs in the absence of soluble factors. Si-CaP supported attachment and proliferation of MSCs and induced osteogenesis to a greater extent than HA, as evidenced through upregulation of the osteoblast-related genes: Runx2 (1.2 fold), Col1a1 (2 fold), Pth1r (1.5 fold), and Bglap (1.7 fold) Dmp1 (1.1 fold), respectively. Osteogenic-associated proteins, alkaline phosphatase (1.4 fold), RUNX2, COL1A1, and BGLAP, were also upregulated and there was an increased production of mineralized bone matrix (1.75 fold), as detected by the Von Kossa Assay. These data indicate that inorganic substrates are capable of directing the differentiation programme of stem cells in the absence of known chemical drivers and therefore may provide the basis for bone repair in the clinical setting.

  14. Development of an immobilization process for heavy metal containing galvanic solid wastes by use of sodium silicate and sodium tetraborate

    International Nuclear Information System (INIS)

    Highlights: • A new physico-chemical process below 1000 °C for immobilization of galvanic sludges. • Sodium tetraborate and sodium silicate have been used as additives. • A strategy for adjustment of solid waste/additive mixture composition is presented. • Strategy is valid for wastes of hydrometallurgical and electro-plating processes. • Lower energy consumption and treated waste volume, shorter process time are provided. - Abstract: Heavy metal containing sludges from wastewater treatment plants of electroplating industries are designated as hazardous waste since their improper disposal pose high risks to environment. In this research, heavy metal containing sludges of electroplating industries in an organized industrial zone of Istanbul/Turkey were used as real-sample model for development of an immobilization process with sodium tetraborate and sodium silicate as additives. The washed sludges have been precalcined in a rotary furnace at 900 °C and fritted at three different temperatures of 850 °C, 900 °C and 950 °C. The amounts of additives were adjusted to provide different acidic and basic oxide ratios in the precalcined sludge-additive mixtures. Leaching tests were conducted according to the toxicity characteristic leaching procedure Method 1311 of US-EPA. X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscope-energy dispersive spectrometer (SEM-EDS) and flame atomic absorption spectroscopy (FAAS) have been used to determine the physical and chemical changes in the products. Calculated oxide molar ratios in the precalcined sludge-additive mixtures and their leaching results have been used to optimize the stabilization process and to determine the intervals of the required oxide ratios which provide end-products resistant to leaching procedure of US-EPA. The developed immobilization-process provides lower energy consumption than sintering-vitrification processes of glass–ceramics

  15. Experimental calibration of a new oxybarometer for silicic magmas based on the partitioning of vanadium between magnetite and silicate melt

    Science.gov (United States)

    Arató, Róbert; Audétat, Andreas

    2016-04-01

    Oxygen fugacity is an important parameter in magmatic systems that affects the stability of mineral phases and fluid species. However, there is no well-established method to reconstruct the oxygen fugacity of slowly cooled magmas such as granite, for example, because existing oxybarometers (e.g., magnetite-ilmenite method) are susceptible to re-equilibration processes during slow cooling and thus lead to erroneous results when applied for granitic rocks. In this study, we aim at developing an oxybarometer that is based on the partitioning of vanadium (a redox-sensitive element) between magnetite inclusions and silicate melt inclusions preserved in quartz phenocrysts, where they were protected from subsolidus alteration and can be measured as entities by LA-ICP-MS. In the first - experimental - part of this study we investigated the effects of temperature (800-950 ° C), pressure (1-2 kbar), oxygen fugacity (from ΔFMQ+0.7 to ΔFMQ+4.0), magnetite composition, and melt composition on the partition coefficient of vanadium between magnetite and melt (DVmgt-melt). The experiments were carried out in cold-seal pressure vessels and the starting material was a mixture of V-doped haplogranite glasses or natural obsidian powder with variable aluminum saturation index (ASI), and synthetic, V-free magnetite of 10-20 μm grain size. The vanadium partition coefficient was found to depend strongly on oxygen fugacity, and to lesser (but still considerable) degrees on melt composition and temperature. A more than 1.5 log unit decrease in DVmgt-melt values with increasing oxygen fugacity can be explained by a change of the dominant valence state of V in the silicate melt. For a given oxygen fugacity buffer DVmgt-melt decreases with increasing temperature, but this reflects mostly the change in absolute fO2 values while the net temperature effect is in fact positive. DVmgt-melt depends significantly on melt composition, resulting in higher D-values with increasing aluminum

  16. Physical processes affecting availability of dissolved silicate for diatom production in the Arabian Sea

    Science.gov (United States)

    Young, David K.; Kindle, John C.

    1994-01-01

    A passive tracer to represent dissolved silicate concentrations, with biologically realistic uptake kinetics, is successfully incorporated into a three-dimensional, eddy-resolving, ocean circulation model of the Indian Ocean. Hypotheses are tested to evaluate physical processes which potentially affect the availability of silicate for diatom production in the Arabian Sea. An alternative mechanism is offered to the idea that open ocean upwelling is primarily responsible for the high, vertical nutrient flux and consequent large-scale phytoplankton bloom in the northwestern Arabian Sea during the southwest monsoon. Model results show that dissolved silicate in surface waters available for uptake by diatoms is primarily influenced by the intensity of nearshore upwelling from soutwest monsoonal wind forcing and by the offshore advective transport of surface waters. The upwelling, which in the model occurs within 200 +/- 50 km of the coast, appears to be a result of a combination of coastal upwelling, Elkman pumping, and divergence of the coastal flow as it turns offshore. Localized intensifications of silicate concentrations appear to be hydrodynamically driven and geographically correlated to coastal topographic features. The absence of diatoms in sediments of the eastern Arabian Basin is consistent with modeled distributional patterns of dissolved silicate resulting from limited westward advection of upwelled coastal waters from the western continental margin of India and rapid uptake of available silicate by diatoms. Concentrations of modeled silicate become sufficiently low to become unavailable for diatom production in the eastern Arabian Sea, a region between 61 deg E and 70 deg E at 8 deg N on the south, with the east and west boundaries converging on the north at approximately 67 deg E, 20 deg N.

  17. Polymer/Silicate Nanocomposites Used to Manufacture Gas Storage Tanks With Reduced Permeability

    Science.gov (United States)

    Campbell, Sandi G.; Johnston, Chris

    2004-01-01

    Over the past decade, there has been considerable research in the area of polymer-layered silicate nanocomposites. This research has shown that the dispersion of small amounts of an organically modified layered silicate improves the polymer strength, modulus, thermal stability, and barrier properties. There have been several reports on the dispersion of layered silicates in an epoxy matrix. Potential enhancements to the barrier properties of epoxy/silicate nanocomposites make this material attractive for low permeability tankage. Polymer matrix composites (PMCs) have several advantages for cryogenic storage tanks. They are lightweight, strong, and stiff; therefore, a smaller fraction of a vehicle's potential payload capacity is used for propellant storage. Unfortunately, the resins typically used to make PMC tanks have higher gas permeability than metals. This can lead to hydrogen loss through the body of the tank instead of just at welds and fittings. One approach to eliminate this problem is to build composite tanks with thin metal liners. However, although these tanks provide good permeability performance, they suffer from a substantial mismatch in the coefficient of thermal expansion, which can lead to failure of the bond between the liner and the body of the tank. Both problems could be addressed with polymersilicate nanocomposites, which exhibit reduced hydrogen permeability, making them potential candidates for linerless PMC tanks. Through collaboration with Northrop Grumman and Michigan State University, nanocomposite test tanks were manufactured for the NASA Glenn Research Center, and the helium permeability was measured. An organically modified silicate was prepared at Michigan State University and dispersed in an epoxy matrix (EPON 826/JeffamineD230). The epoxy/silicate nanocomposites contained either 0 or 5 wt% of the organically modified silicate. The tanks were made by filament winding carbon fibers with the nanocomposite resin. Helium permeability

  18. 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.

  19. CHEMISTRY OF IMPACT-GENERATED SILICATE MELT-VAPOR DEBRIS DISKS

    Energy Technology Data Exchange (ETDEWEB)

    Visscher, Channon [Department of Space Studies, Southwest Research Institute, Boulder, CO 80302 (United States); Fegley, Bruce Jr. [Planetary Chemistry Laboratory, Department of Earth and Planetary Sciences and McDonnell Center for Space Sciences, Washington University in St. Louis, St. Louis, MO 63130 (United States)

    2013-04-10

    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 O{sub 2} at lower temperatures (<3000 K) and SiO, O{sub 2}, and O at higher temperatures. The high-temperature chemistry is consistent for any silicate melt composition, and we thus expect abundant SiO, O{sub 2}, and O to be a common feature of hot, impact-generated debris disks. In addition, the saturated silicate vapor is highly oxidizing, with oxygen fugacity (f{sub O{sub 2}}) values (and hence H{sub 2}O/H{sub 2} and CO{sub 2}/CO ratios) several orders of magnitude higher than those in a solar-composition gas. High f{sub O{sub 2}} values in the disk atmosphere are found for any silicate composition because oxygen is the most abundant element in rock. We thus expect high oxygen fugacity to be a ubiquitous feature of any silicate melt-vapor disk produced via collisions between rocky planets.

  20. Effect of Silica Ratio on the Corrosion Behavior of Nano-silica Potassium Silicate Coatings on Aluminum Alloy 2024

    Science.gov (United States)

    Bahri, H.; Danaee, I.; Rashed, G. R.; Zaarei, D.

    2015-02-01

    Nano-silica modified potassium silicate conversion coating was deposited in different nano-silica/potassium silicate ratios on the surface of 2024 aluminum alloy. The corrosion behavior of coatings was studied by electrochemical impedance spectroscopy, current transient, potentiodynamic polarization, and surface techniques. The ratio of nano-silica/potassium silicate was optimized in order to obtain higher corrosion protection. The experimental results indicated that with increasing nano-silica/potassium silicate ratio, the corrosion resistance of aluminum increases. Furthermore, the pitting corrosion probability of potassium silicate conversion coating decreased with increasing silica ratio. This can be related to the size of nano-silica particles and the ability to fill the pores in potassium silicate coating and reinforce the created siloxane bridges.

  1. Physical characterization of magmatic liquids. [Ultrasonic and Brillouin Scattering Studies of Natural and Synthetic Silicates and Oxides

    Energy Technology Data Exchange (ETDEWEB)

    Manghnani, M.H.

    1992-06-05

    This report describes a research project that was conducted from August 15, 1985 to February 28, 1992. The project was based on the ultrasonic studies of natural and synthetic silicate melts, and the study of Brillouin scattering of synthetic silicates and oxides. Measurements of the compressional wave velocity and attenuation can be established using the ultrasonic methods. Temperature dependences of silicates can be established by the Brillouin scattering. (MB)

  2. Low-temperature fabrication of macroporous scaffolds through foaming and hydration of tricalcium silicate paste and their bioactivity

    OpenAIRE

    Huan, Z.; Chang, J.; Zhou, J.

    2009-01-01

    A low-temperature fabrication method for highly porous bioactive scaffolds was developed. The two-step method involved the foaming of tricalcium silicate cement paste and hydration to form calcium silicate hydrate and calcium hydroxide. Scaffolds with a combination of interconnected macro- and micro-sized pores were fabricated by making use of the decomposition of a hydrogen peroxide (H2O2) solution that acted as a foaming agent and through the hydration of tricalcium silicate cement. It was ...

  3. Outgassing of silicic magma through bubble and fracture networks (Invited)

    Science.gov (United States)

    Okumura, S.; Nakamura, M.; Uesugi, K.

    2013-12-01

    Outgassing of magma is a fundamental process that controls the style and explosivity of volcanic eruptions. Vesiculation during the ascent and decompression of magma results in the formation of bubble networks within the magma. The permeable gas escape through the bubble networks is an efficient way to induce the outgassing of silicic magma (Eichelberger et al., 1986). To understand magma ascent dynamics and predict the style and explosivity of eruptions, it is necessary to constrain the rate of magma outgassing as the magma ascends in a volcanic conduit. However, the gas permeability of natural samples should not be considered, because it reflects complicated processes involving vesiculation, deformation, outgassing, and compaction. Experimental studies have demonstrated that vesiculation and compaction processes show hysteresis behavior (Okumura et al., 2013). Thus, we have performed experiments to simulate magma decompression and the deformation of vesicular magmas (e.g., Okumura et al., 2009, 2012). A series of decompression and deformation experiments indicates that the gas permeability is less than the order of 10-15 m2 for isotropic vesiculation at vesicularity <60-80 vol%. When magma ascent is simulated with shear deformation, the gas permeability is much greater than that observed under isotropic conditions. Akin to bubble networks, permeable networks consisting of shear-induced brittle fractures are thought to be efficient outgassing pathways (Gonnermann and Manga, 2003). Our recent experiments demonstrated that fractured magma has a higher gas permeability than vesicular magma at least at vesicularities <~40 vol%. This indicates that fracture networks in magma become efficient parts for the outgassing. However, as shear fracturing results from high strain rates in highly viscous magma, outgassing via fracture networks can be enhanced in localized shear zones and shallow parts of the conduit. The permeable bubble and fracture networks are preferentially

  4. Development of novel mesoporous silicates for bioseparations and biocatalysis

    Science.gov (United States)

    Katiyar, Amit

    The recent growth of the biopharmaceutical industry is due to the discovery of monoclonal antibodies and recombinant DNA technologies. Large-scale production of therapeutic proteins and monoclonal antibodies requires efficient technologies to separate products from complex synthesis mixtures. Chromatography is widely used for this purpose at both the analytical and process scales. Research in the last three decades has provided an improved understanding of the thermodynamic and mass transfer effects underlying the chromatographic behavior of biomolecules, leading to improvements in chromatographic equipment, separation media, and operating procedures. This dissertation reports on the development of ordered mesoporous silica-based adsorbents for chromatographic protein separations. The synthesis of mesoporous materials with different structural properties is reported here. Protein adsorption and enzymatic catalysis studies were conducted to evaluate the chromatographic performance of these materials. Initial studies focused on small pore materials (MCM-41), which had high protein adsorption capacities. These high protein loadings were attributed to high external surface area (˜600 m 2/g), meaning that MCM-41 materials are of limited use for size-selective chromatographic protein separation. Synthesis strategies were developed to produce large pore fibrous and spherical SBA-15 particles. The effects of synthesis conditions on particle properties are presented. Large pore Spherical ordered SBA-15 materials were used to demonstrate for the first time the size-selective separation of proteins. BSA and lysozyme were tagged with fluorescent molecules, allowing direct visualization of the size selective separation of these proteins. Flow microcalorimetry (FMC) results were used to interpret the size-selective behavior of these materials. The potential of siliceous SBA-15 materials to serve as hosts for enzymes in biocatalytic transformations was also explored. Materials

  5. Are All Active Galactic Nuclei Born Equal? The Silicate Dust Mineralogy Perspective

    Science.gov (United States)

    Li, Aigen

    Dust is the cornerstone of the unification theory of active galactic nuclei (AGNs). This theory proposes that all AGNs are essentially the same object or "born equal" but viewed from different lines of sight; much of the observed diversity arises from different viewing angles toward the central engine and a dusty toroidal structure around it. When the dusty torus is viewed face-on, both the central engine and the broad-line regions can be seen directly causing objects to appear as type 1 AGNs; when the dusty torus is viewed edge- on, the anisotropic obscuration created by the torus causes objects to appear as type 2 AGNs. It is this crucial role played by dust in the unified model of AGNs that makes understanding dust properties very important in understanding AGNs. Little is known about the dust in the circumnuclear torus of AGNs. There is evidence suggesting that the size and composition of the dust in AGNs may differ substantially from that of the Galactic interstellar dust, as reflected by the flat or "gray" extinction, and the anomalous silicate emission or absorption features observed respectively in type 1 and type 2 AGNs. The silicate feature profiles of AGNs are rather diverse in peak wavelengths, widths, strengths, and band ratios of the 18 micrometer O--Si--O feature to the 9.7 micrometer Si--O feature, suggesting that the AGN silicate grains are diverse in composition and size (or probably not "born equal"). We propose a two-year project to study the size and composition of the dust in AGNs, with special attention paid to the silicate mineralogy. We will obtain constraints on the silicate composition and size by modeling the Spitzer IRS spectra of >100 AGNs of various types. We will examine whether (and how) the silicate composition and size properties vary with the properties of an AGN (e.g. type, luminosity). This research will improve our understanding of the physical properties of the dust torus and the origin of the observed silicate emission

  6. A cubic calcium oxynitrido-silicate, Ca2.89Si2N1.76O4.24

    OpenAIRE

    Ali Sharafat; Pedro Berastegui; Saeid Esmaeilzadeh; Lars Eriksson; Jekabs Grins

    2011-01-01

    The title compound, tricalcium oxynitride silicate, with composition Ca3-xSi2N2-2xO4+2x (x ≃ 0.12), is a perovskite-related calcium oxynitrido silicate containing isolated oxynitrido silicate 12-rings. The N atoms are statistically disordered with O atoms (occupancy ratio N:O = 0.88:0.12) and occupy the bridging positions in the 12 ring oxynitrido silicate anion, while the remaining O atoms are located at the terminal positions of the Si(O,N)4 tetrahedra. The majority of the Ca2+ ca...

  7. An improved sodium silicate binder modified by ultra-fine powder materials

    Institute of Scientific and Technical Information of China (English)

    WANG Ji-na; FAN Zi-tian; WANG Hua-fang; DONG Xuan-pu; HUANG Nai-yu

    2007-01-01

    This paper presents a new method of modifying sodium silicate binder with ultra-fine powders. The sodium silicate binder modified by ultra-fine powder A and the organic B can reduce the addition amount of the binder. The results indicate that the 24 h strength has increased by 39.9% at room temperature and the residual strength has decreased by 30.7% at 800℃, compared to the conventional sodium silicate. An available material to improve the moisture resistance was also found by adding about 2% more inorganic C, and it can increase the moist strength by 20%. In the end, the microanalyses are given to explain the modifying machanism, i. e., the ultra-fine powder A can refine the sodium silicate binder to avoid holes in the binder bond, which can increase the 24 h strength at room temperture, and can lead to more cracks in the bond after the molding sand is heated to 800℃. This is because of the stress caused by the new eutectic complex of modified sodium silicate binder.

  8. Factors Affecting Alkaline Sodium Silicate Gelation for In-Depth Reservoir Profile Modification

    Directory of Open Access Journals (Sweden)

    Aly A. Hamouda

    2014-01-01

    Full Text Available Alkaline sodium silicate (Na-silicate is environment-friendly and possesses water-like viscosity during the injection stage for in-depth reservoir treatment to enhance sweep efficiency. Gel setting time (tg and gel strength are interrelated. Factors that accelerate tg are Na-silicate content (wt%, low pH, presence of divalent ions and temperature. Pressure drop across the gel accelerates syneresis; however, the gel appeared to remain intact. Presence of Ca2+ and Mg2+ ions is shown to increase gel strength. With a Na-silicate content of 4.5 wt%, for example, at a pH of 10.3 and a temperature of 20 °C, gel strength almost tripled and was reached about eight times faster at the combined tested concentration of 0.009 M, based on the average effect from the coexistence of both ions. Low-salinity water (LSW has an ion composition of 25-fold diluted seawater, did not show precipitation, and could accordingly be a candidate for a pre-flush before the injection of a Na-silicate solution in the event of a field application. This is important since LSW for enhancing oil recovery is a popular method in oil industry. A suggested predictive tool (simple graphical method to estimate the effect of different factors on gelation time and gel strength is presented.

  9. Influence of dispersing agent in formation of B-dicalcium silicate from rice husk

    International Nuclear Information System (INIS)

    Present experimental work describes the synthesis of beta-dicalcium silicate from rice husk by using dispersing agent during formation of calcium hydro silicate (CSH) gel. The growth of CSH gel retards the impeller mixing phenomenon. This type of problem can be resolved by using dispersing agent. Amorphous silica was obtained from HCl treated rice husk. Calcination temperature of rice husk was maintained at 600 degree C for 90 minutes. In the presence of water, amorphous silica was treated with calcium oxide by using 0.2 % dispersing agent to develop CSH gel. The CSH gel was developed in oven for 12 hours at 90 degree C followed by drying at 105 degree C for 12 hours in an oven. Dried gels were heated up to 900 degree C to obtain beta form of dicalcium silicate. The CSH gel and beta-dicalcium silicate were examined by XRD, FTIR, SEM and TGA. It was observed that by using pretreated rice husk truly amorphous silica can be obtained. It was also observed that dispersing agent facilitated the formation of CSH gel. Observations further revealed that such amorphous CSH gel started converting into beta form of dicalcium silicate at 600 degree C. (author)

  10. Pilot study on binding of bovine salivary proteins to grit silicates and plant phytoliths

    Institute of Scientific and Technical Information of China (English)

    Marcus MAU; Thomas M.KAISER; Karl-Heinz S(U)DEKUM

    2013-01-01

    Mostly fed with grass in fresh or conserved form,cattle and other livestock have to cope with silicate defence bodies from plants (phytoliths) and environmental silicates (grit),which abrade tooth enamel and could additionally interact with various salivary proteins.To detect potential candidates for silicate-binding proteins,bovine whole saliva was incubated with grass-derived phytoliths and silicates.Interactions of salivary proteins with pulverized bovine dental enamel and dentine were additionally analysed.After intense washing,the powder fractions were loaded onto 1D-polyacrylamide gels,most prominent adhesive protein bands were cut out and proteins were identified by mass spectrometry within three independent replicates.All materials were mainly bound by bovine odorant-binding protein,bovine salivary protein 30× 103 and carbonic anhydrase VI.The phytolith/silicate fraction showed additional stronger interaction with haemoglobin β and lactoperoxidase.Conceivably,the binding of these proteins to the surfaces may contribute to biological processes occurring on them.

  11. Improved mechanical and corrosion properties of nickel composite coatings by incorporation of layered silicates

    Energy Technology Data Exchange (ETDEWEB)

    Tientong, J. [University of North Texas, Department of Chemistry, 1155 Union Circle #305070, Denton, TX 76203 (United States); Ahmad, Y.H. [Center for Advanced Materials, P.O. Box 2713, Qatar University, Doha (Qatar); Nar, M.; D' Souza, N. [University of North Texas, Department of Mechanical and Energy Engineering, Denton, TX 76207 (United States); Mohamed, A.M.A. [Center for Advanced Materials, P.O. Box 2713, Qatar University, Doha (Qatar); Golden, T.D., E-mail: tgolden@unt.edu [University of North Texas, Department of Chemistry, 1155 Union Circle #305070, Denton, TX 76203 (United States)

    2014-05-01

    Layered silicates as exfoliated montmorillonite are incorporated into nickel films by electrodeposition, enhancing both corrosion resistance and hardness. Films were deposited onto stainless steel from a plating solution adjusted to pH 9 containing nickel sulfate, sodium citrate, and various concentrations of exfoliated montmorillonite. The presence of the incorporated layered silicate was confirmed by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The composite films were also compact and smooth like the pure nickel films deposited under the same conditions as shown by scanning electron microscopy. X-ray diffraction results showed that incorporation of layered silicates into the film do not affect the nickel crystalline fcc structure. The nanocomposite films exhibited improved stability and adhesion. Pure nickel films cracked and peeled from the substrate when immersed in 3.5% NaCl solution within 5 days, while the nanocomposite films remained attached even after 25 days. The corrosion resistance of the nickel nanocomposites was also improved compared to nickel films. Nickel-layered silicate composites showed a 25% increase in Young's modulus and a 20% increase in hardness over pure nickel films. - Highlights: • 0.05–2% of layered silicates are incorporated into crystalline nickel films. • Resulting composite films had improved stability and adhesion. • Corrosion resistance improved for the composite films. • Hardness improved 20% and young's modulus improved 25% for the composite films.

  12. Structure and properties of soda lime silicate glass doped with rare earth

    International Nuclear Information System (INIS)

    Soda-lime-silicate glasses doped with different rare-earth oxides (La2O3, CeO2, Nd2O3, Gd2O3 and Y2O3) of 1 mol% content were prepared with the traditional melting-quenching methods. In order to reveal the effects of rare-earth elements on the behavior of soda-lime-silicate glass, the structure of soda-lime-silicate glasses doped with different rare-earth oxides were determined with Fourier transform infrared spectrometer using the KBr method, and viscosity of glass melts were measured by the rotating crucible viscometer, the melting temperature of the studied glasses were derived on the basis of Arrhenius Equation, moreover the density, bending strength and molar volume were measured and calculated. The effect of rare-earth dopants on the structure of soda-lime-silicate was analyzed by a shift of peak position and variation in the full-width at half-maximum. The effect of doping rare-earth oxides into glass on the viscosity, density and bending strength was interpreted by changing in structure of soda-lime-silicate glasses doped with rare-earth oxides.

  13. Nonlinear dynamics and instability of aqueous dissolution of silicate glasses and minerals

    Science.gov (United States)

    Wang, Yifeng; Jove-Colon, Carlos F.; Kuhlman, Kristopher L.

    2016-07-01

    Aqueous dissolution of silicate glasses and minerals plays a critical role in global biogeochemical cycles and climate evolution. The reactivity of these materials is also important to numerous engineering applications including nuclear waste disposal. The dissolution process has long been considered to be controlled by a leached surface layer in which cations in the silicate framework are gradually leached out and replaced by protons from the solution. This view has recently been challenged by observations of extremely sharp corrosion fronts and oscillatory zonings in altered rims of the materials, suggesting that corrosion of these materials may proceed directly through congruent dissolution followed by secondary mineral precipitation. Here we show that complex silicate material dissolution behaviors can emerge from a simple positive feedback between dissolution-induced cation release and cation-enhanced dissolution kinetics. This self-accelerating mechanism enables a systematic prediction of the occurrence of sharp dissolution fronts (vs. leached surface layers), oscillatory dissolution behaviors and multiple stages of glass dissolution (in particular the alteration resumption at a late stage of a corrosion process). Our work provides a new perspective for predicting long-term silicate weathering rates in actual geochemical systems and developing durable silicate materials for various engineering applications.

  14. Polymer/Silicate Nanocomposites Developed for Improved Strength and Thermal Stability

    Science.gov (United States)

    Campbell, Sandi G.

    2003-01-01

    Over the past decade, polymer-silicate nanocomposites have been attracting considerable attention as a method of enhancing polymer properties. The nanometer dimensions of the dispersed silicate reinforcement can greatly improve the mechanical, thermal, and gas barrier properties of a polymer matrix. In a study at the NASA Glenn Research Center, the dispersion of small amounts (less than 5 wt%) of an organically modified layered silicate (OLS) into the polymer matrix of a carbon-fiber-reinforced composite has improved the thermal stability of the composite. The enhanced barrier properties of the polymer-clay hybrid are believed to slow the diffusion of oxygen into the bulk polymer, thereby slowing oxidative degradation of the polymer. Electron-backscattering images show cracking of a nanocomposite matrix composite in comparison to a neat resin matrix composite. The images show that dispersion of an OLS into the matrix resin reduces polymer oxidation during aging and reduces the amount of cracking in the matrix significantly. Improvements in composite flexural strength, flexural modulus, and interlaminar shear strength were also obtained with the addition of OLS. An increase of up to 15 percent in these mechanical properties was observed in composites tested at room temperature and 288 C. The best properties were seen with low silicate levels, 1 to 3 wt%, because of the better dispersion of the silicate in the polymer matrix.

  15. On-line silicate analyzer%硅酸根在线分析仪

    Institute of Scientific and Technical Information of China (English)

    周娜

    2012-01-01

    Aiming at the effect of silicate in the steam-water system of coal generator on the safety of thermal power equipment,the importance of silicate monitoring is expounded. The chemical principles,measure process,operation procedure and performance parameters of the on-line silicate analyzer FIA -33M are introduced. By analysis and contrast,the data obtained from practical operation and laboratory manual determination in FIA-33M on-line silicate analyzer indicate that it can accomplish the monitoring task by silicate in the steam-water system of coal generator.%针对燃煤发电机组汽水系统中硅酸根对于热力设备安全的影响,阐述了硅酸根监测的重要性,着重介绍了FIA-33M型硅酸根在线分析仪的化学原理、测量流程、操作步骤、性能参数.通过分析对比FIA-33M型硅酸根在线分析仪在实际运行与实验室手动测定得出的数值,认为该仪器可以完成针对燃煤发电机组汽水系统中硅酸根在线监测任务.

  16. 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...

  17. Zirconium silicate assisted removal of residual proteins after organic solvent deproteinization of human plasma, enhancing the stability of the LC–ESI-MS response for the bioanalysis of small molecules

    Energy Technology Data Exchange (ETDEWEB)

    Hussain, Shah; Pezzei, Cornelia [Institute of Analytical Chemistry and Radiochemistry, CCB-Center for Chemistry and Biomedicine, Leopold-Franzens University, Innrain 80/82, 6020 Innsbruck (Austria); Güzel, Yüksel [Institute of Analytical Chemistry and Radiochemistry, CCB-Center for Chemistry and Biomedicine, Leopold-Franzens University, Innrain 80/82, 6020 Innsbruck (Austria); ADSI-Austrian Drug Screening Institute, Innrain 66a, 6020 Innsbruck (Austria); Rainer, Matthias [Institute of Analytical Chemistry and Radiochemistry, CCB-Center for Chemistry and Biomedicine, Leopold-Franzens University, Innrain 80/82, 6020 Innsbruck (Austria); Huck, Christian W., E-mail: Christian.W.Huck@uibk.ac.at [Institute of Analytical Chemistry and Radiochemistry, CCB-Center for Chemistry and Biomedicine, Leopold-Franzens University, Innrain 80/82, 6020 Innsbruck (Austria); Bonn, Günther K. [Institute of Analytical Chemistry and Radiochemistry, CCB-Center for Chemistry and Biomedicine, Leopold-Franzens University, Innrain 80/82, 6020 Innsbruck (Austria); ADSI-Austrian Drug Screening Institute, Innrain 66a, 6020 Innsbruck (Austria)

    2014-12-10

    Highlights: • A novel sample preparation technique for isolation of small molecules from human plasma. • Effectiveness of zirconium silicate for the removal of residual proteins after protein precipitation. • Abolishing the consumption of salts for the depletion of residual proteins after protein precipitation. • More than 99.6% removal of plasma proteins. - Abstract: An efficient blood plasma clean-up method was developed, where methanol protein precipitation was applied, followed by zirconium silicate assisted exclusion of residual proteins. A strong binding of zirconium (IV) silicate to the proteins enabled the elimination of remaining proteins after solvent deproteinization through a rapid solid-phase extraction (SPE) procedure. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI/TOF MS) was used for monitoring the proteins during clean-up practice applied to human plasma samples. The proteins were quantified by colorimetric detection using the bicinchoninic acid (BCA) assay. The presented analytical strategy resulted in the depletion of >99.6% proteins from human plasma samples. Furthermore, high-performance liquid chromatography hyphenated to diode-array and electrospray ionization mass spectrometric detection (HPLC–DAD/ESI MS) was applied for qualitative and quantitative analysis of the caffeoylquinic acids (CQAs) and their metabolites in human plasma. The procedure demonstrated high recoveries for the standard compounds spiked at different concentrations. Cynarin and chlorogenic acid were recovered in the range of 81–86% and 78–83%, respectively. Caffeic acid was extracted in the excess of 89–92%, while ferulic acid and dihydroxyhydrocinnamic acid showed a recovery of 87–91% and 92–95%, respectively. The method was partially validated in accordance with FDA-Industry Guidelines for Bioanalytical Method Validation (2001). The presented scheme improves the clean-up efficacy of the methanol deproteinization

  18. Zirconium silicate assisted removal of residual proteins after organic solvent deproteinization of human plasma, enhancing the stability of the LC–ESI-MS response for the bioanalysis of small molecules

    International Nuclear Information System (INIS)

    Highlights: • A novel sample preparation technique for isolation of small molecules from human plasma. • Effectiveness of zirconium silicate for the removal of residual proteins after protein precipitation. • Abolishing the consumption of salts for the depletion of residual proteins after protein precipitation. • More than 99.6% removal of plasma proteins. - Abstract: An efficient blood plasma clean-up method was developed, where methanol protein precipitation was applied, followed by zirconium silicate assisted exclusion of residual proteins. A strong binding of zirconium (IV) silicate to the proteins enabled the elimination of remaining proteins after solvent deproteinization through a rapid solid-phase extraction (SPE) procedure. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI/TOF MS) was used for monitoring the proteins during clean-up practice applied to human plasma samples. The proteins were quantified by colorimetric detection using the bicinchoninic acid (BCA) assay. The presented analytical strategy resulted in the depletion of >99.6% proteins from human plasma samples. Furthermore, high-performance liquid chromatography hyphenated to diode-array and electrospray ionization mass spectrometric detection (HPLC–DAD/ESI MS) was applied for qualitative and quantitative analysis of the caffeoylquinic acids (CQAs) and their metabolites in human plasma. The procedure demonstrated high recoveries for the standard compounds spiked at different concentrations. Cynarin and chlorogenic acid were recovered in the range of 81–86% and 78–83%, respectively. Caffeic acid was extracted in the excess of 89–92%, while ferulic acid and dihydroxyhydrocinnamic acid showed a recovery of 87–91% and 92–95%, respectively. The method was partially validated in accordance with FDA-Industry Guidelines for Bioanalytical Method Validation (2001). The presented scheme improves the clean-up efficacy of the methanol deproteinization

  19. Petrology of silicate inclusions in the Sombrerete ungrouped iron meteorite: Implications for the origins of IIE-type silicate-bearing irons

    Science.gov (United States)

    Ruzicka, Alex; Hutson, Melinda; Floss, Christine

    2006-11-01

    The petrography and mineral and bulk chemistries of silicate inclusions in Sombrerete, an ungrouped iron that is one of the most phosphate-rich meteorites known, was studied using optical, scanning electron microscopy (SEM), electron microprobe analysis (EMPA), and secondary ion mass spectrometry (SIMS) techniques. Inclusions contain variable proportions of alkalic siliceous glass (˜69 vol% of inclusions on average), aluminous orthopyroxene (˜9%, Wo1-4Fs25-35, up to ˜3 wt% Al), plagioclase (˜8%, mainly An70-92), Cl-apatite (˜7%), chromite (˜4%), yagiite (˜1%), phosphate-rich segregations (˜1%), ilmenite, and merrillite. Ytterbium and Sm anomalies are sometimes present in various phases (positive anomalies for phosphates, negative for glass and orthopyroxene), which possibly reflect phosphate-melt-gas partitioning under transient, reducing conditions at high temperatures. Phosphate-rich segregations and different alkalic glasses (K-rich and Na-rich) formed by two types of liquid immiscibility. Yagiite, a K-Mg silicate previously found in the Colomera (IIE) iron, appears to have formed as a late-stage crystallization product, possibly aided by Na-K liquid unmixing. Trace-element phase compositions reflect fractional crystallization of a single liquid composition that originated by low-degree (˜4-8%) equilibrium partial melting of a chondritic precursor. Compositional differences between inclusions appear to have originated as a result of a "filter-press differentiation" process, in which liquidus crystals of Cl-apatite and orthopyroxene were less able than silicate melt to flow through the metallic host between inclusions. This process enabled a phosphoran basaltic andesite precursor liquid to differentiate within the metallic host, yielding a dacite composition for some inclusions. Solidification was relatively rapid, but not so fast as to prevent flow and immiscibility phenomena. Sombrerete originated near a cooling surface in the parent body during rapid

  20. Immobilization of Zinc Phthalocyanines in Silicate Matrices and Investigation of Their Photobactericidal Effect on E.coli

    Directory of Open Access Journals (Sweden)

    Spas Artarsky

    2006-01-01

    Full Text Available The aim of the present investigation was to immobilize zinc phthalocyanines in a silicate matrix and to test the photobactericidal properties of the matrices so prepared toward Esherichia coli in model aqueous media. For the purpose, tetra tertiary butyl zinc phthalocyanine (TBZnPc and zinc phthalocyanine tetrasulfonic acid (ZnPcTS were used. The abilities of these two photosensitizers to generate singlet oxygen in solution were compared by following the rate of photobleaching of 1,3-diphenylisobenzofuran (DPBF at 430 nm in dimethylformamide (DMF.The results of this study show clearly that, under the conditions used here, the TBZnPc is the more effective generator of singlet oxygen; with it the DPBF was virtually completely photobleached in 4 min, while with the ZnPcTS under the same conditions, it took 12 min to reach this point. Glass conjugates with the two phthalocyanines were obtained by the sol-gel technique and were characterized by a well-defined color due to the phthalocyanine incorporated in the silicate matrix. Glasses with an intense, but inhomogeneous, green color were obtained when the tetrasulfonic derivative of the zinc phthalocyanine was used, while blue glasses of evenly distributed coloration were formed from the tetra tertiary butyl derivative.The ZnPcTS conjugate demonstrates more effective singlet oxygen evolution than is the case with the TBZnPc conjugate. These results are the opposite of those obtained for the free phthalocyanines in solution. The structural formulae of the compounds show that TBZnPc has a more pronounced hydrophobic character than the sulfonic derivative. In our view, the relative reactivities of the conjugates can be explained by the tetrasulfonic derivative being situated mainly in the surface parts of the glass matrix where the hydrophilic character is prevailing, while the tertiary butyl derivative is mainly present in the internal parts of the matrix as a result of which it is less accessible and

  1. Simultaneous spectrophotometric determination of orthophosphate and silicate ions in river water using ion-exclusion chromatography with an ascorbate solution as both eluent and reducing agent, followed by postcolumn derivatization with molybdate.

    Science.gov (United States)

    Nakatani, Nobutake; Masuda, Wakako; Kozaki, Daisuke; Goto, Ryozo; Nakagoshi, Nobukazu; Mori, Masanobu; Hasebe, Kiyoshi; Tanaka, Kazuhiko

    2009-03-01

    Ion-exclusion chromatography was examined for the simultaneous spectrophotometric determinations of orthophosphate and silicate ions in river water using an ascorbate solution as both an eluent and a reducing agent, followed by postcolumn derivatization using molybdate. The detector responses for both ions increased with increased ascorbic acid concentration in the eluent, but peak tailing was observed for the orthophosphate ion. This suggests that the amounts of undissociated orthophosphate ions increased with decreased eluent pH, resulting in the penetration of the phosphate to the Donnan's membrane formed on the resin surface. Using a neutral sodium ascorbate solution as an eluent, the peak shape was improved. With optimized separation and derivatization conditions (eluent, 20 mM sodium ascorbate; color-forming reagent, 10 mM sodium molybdate-60 mM sulfuric acid; flow rates of eluent and color-forming reagent, 0.4 and 0.2 mL min(-1); coil length, 6 m), the detection limits of orthophosphate and silicate ions were 0.9 and 1.0 microg L(-1), respectively. This method was successfully applied to the determination of orthophosphate and silicate ions in Kurose River water and the quantitative evaluations of the effects of water intake to a reservoir and discharge from a biological sewage treatment plant on the fluxes of these ions in the river. PMID:19276594

  2. Effect of Mineral Dusts on the Growth of Silicate Bacteria S35

    Institute of Scientific and Technical Information of China (English)

    DAI Qunwei; DONG Faqin; DENG Jianjun

    2008-01-01

    In order to compare the chemical compositions and physical properities of dusts on silicate bacteria S35, the chemical compositions of six kinds of mineral dusts have been analyzed and the changes of pH value, glucose (GLU), electrolyte and Mn, Si, Fe before and after the dusts reacted with silicate bacteria S35 have been measured. The SEM analysis has been used to study the bacterial form and interface action status in the course of reaction between dusts and bacteria. The results show that these mineral dusts have different effects on experiment bacteria. Therefore, it is concluded that the effect of mineral dusts on silicate bacteria has correlation with the chemical compositions and physical properities of dusts.

  3. The origin of GEMS in IDPs as deduced from microstructural evolution of amorphous silicates with annealing

    CERN Document Server

    Davoisne, C; Leroux, H; D'Hendecourt, L B; Jones, A; Deboffle, D

    2006-01-01

    We present laboratory studies of the micro-structural evolution of an amorphous ferro-magnesian silicate, of olivine composition, following thermal annealing under vacuum. Annealing under vacuum was performed at temperatures ranging from 870 to 1020 K. After annealing spheroidal metallic nano-particles (2-50 nm) are found within the silicate films. We interpret this microstructure in terms of a reduction of the initial amorphous silicate FeO component, because of the carbon-rich partial pressure in the furnace due to pumping mechanism. Annealing in a controlled oxygen-rich atmosphere confirms this interpretation. The observed microstructures closely resemble those of the GEMS (Glass with Embedded Metal and Sulphides) found in chondritic IDPs (Interplanetary Dust Particles). Since IDPs contain abundant carbonaceous matter, a solid-state reduction reaction may have occurred during heating in the hot inner regions of the proto-solar disc. Related to this, the presence of forsterite grains grown from the amorphou...

  4. Electrophoretic deposition of magnesium silicates on titanium implants: Ion migration and silicide interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Afshar-Mohajer, M. [Center for Advanced Manufacturing and Material Processing, Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur 50603 (Malaysia); Yaghoubi, A., E-mail: yaghoubi@siswa.um.edu.my [Center for High Impact Research, University of Malaya, Kuala Lumpur 50603 (Malaysia); Ramesh, S., E-mail: ramesh79@um.edu.my [Center for Advanced Manufacturing and Material Processing, Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur 50603 (Malaysia); Bushroa, A.R.; Chin, K.M.C.; Tin, C.C. [Center for Advanced Manufacturing and Material Processing, Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur 50603 (Malaysia); Chiu, W.S. [Low Dimensional Materials Research Center, Department of Physics, University of Malaya, Kuala Lumpur 50603 (Malaysia)

    2014-07-01

    Magnesium silicates (Mg{sub x}SiO{sub y}) and in particular forsterite (Mg{sub 2}SiO{sub 4}) owing to their low thermal expansion mismatch with metals are promising materials for bioactive coating of implants. Here, we report the electrophoretic deposition (EPD) of forsterite onto titanium substrates using different precursors. Unlike bulk samples which achieve full stoichiometry only beyond 1400 °C, non-stoichiometric magnesium silicate rapidly decomposes into magnesium oxide nanowires during sintering. Elemental mapping and X-ray diffraction suggest that oxygen diffusion followed by ion exchange near the substrate leads to formation of an interfacial Ti{sub 5}Si{sub 3} layer. Pre-annealed forsterite powder on the other hand shows a comparatively lower diffusion rate. Overall, magnesium silicate coatings do not exhibit thermally induced microcracks upon sintering as opposed to calcium phosphate bioceramics which are currently in use.

  5. Magnetic separation studies for a low grade siliceous iron ore sample

    Institute of Scientific and Technical Information of China (English)

    Dwari Ranjan Kumar; Rao Danda Srinivas; Reddy Palli Sita Ram

    2013-01-01

    Investigations were carried out,on a low grade siliceous iron ore sample by magnetic separation,to establish its amenability for physical beneficiation.Mineralogical studies revealed that the sample consists of magnetite,hematite and goethite as major opaque oxide minerals where as silicates as well as carbonates form the gangue minerals in the sample.Processes involving combination of classification,dry magnetic separation and wet magnetic separation were carried out to upgrade the low grade siliceous iron ore sample to make it suitable as a marketable product.The sample was first ground and each closed size sieve fractions were subjected to dry magnetic separation and it was observed that limited upgradation is possible.The ground sample was subjected to different finer sizes and separated by wet low intensity magnetic separator.It was possible to obtain a magnetic concentrate of 67% Fe by recovering 90% of iron values at below 200 μm size.

  6. 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.

  7. Electrophoretic deposition of magnesium silicates on titanium implants: Ion migration and silicide interfaces

    International Nuclear Information System (INIS)

    Magnesium silicates (MgxSiOy) and in particular forsterite (Mg2SiO4) owing to their low thermal expansion mismatch with metals are promising materials for bioactive coating of implants. Here, we report the electrophoretic deposition (EPD) of forsterite onto titanium substrates using different precursors. Unlike bulk samples which achieve full stoichiometry only beyond 1400 °C, non-stoichiometric magnesium silicate rapidly decomposes into magnesium oxide nanowires during sintering. Elemental mapping and X-ray diffraction suggest that oxygen diffusion followed by ion exchange near the substrate leads to formation of an interfacial Ti5Si3 layer. Pre-annealed forsterite powder on the other hand shows a comparatively lower diffusion rate. Overall, magnesium silicate coatings do not exhibit thermally induced microcracks upon sintering as opposed to calcium phosphate bioceramics which are currently in use.

  8. Flotation de-silicating from diasporic-bauxite with cetyl trimethylammonium bromide

    Institute of Scientific and Technical Information of China (English)

    王毓华; 胡岳华; 刘晓文

    2003-01-01

    Using cetyl trimethylammonium bromide (CTAB) as collector, the flotation de-silicating from diasporicbauxite was investigated. And the Zeta potentials and contact-angles of silicate minerals and diaspore were also stuite and illite become more positive, and the contact angles of these three silicates also increase evidently in the pH range of 2-8, but the Zeta potentials and contact angles of diaspore change little. So, the floatability of the four minerals is in the following order: pyrophyllite>kaolinite≈illite>diaspore. The open-circuit flotation results also show that a bauxite concentrate with m(Al2 O3 )/m(SiO2 ) over 9.3 and Al2 O3 recovery over 76% can be obtained from diasporic-bauxite ore. The result of XRD of the bauxite concentrate shows that pyrophyllite is easier to be removed from diasporic-bauxite than illite and kaolinite due to its better floatability.

  9. Metal-Silicate Partitioning of Tungsten from 10 to 50 GPa

    Science.gov (United States)

    Shofner, G. A.; Campbell, A. J.; Danielson, L.; Rahman, Z.; Righter, K.

    2014-01-01

    Geochemical models of core formation are commonly based on core and mantle abundances of siderophile elements that partitioned between silicate and metal in a magma ocean in the early Earth. Tungsten is a moderately siderophile element that may provide constraints on the pressure, temperature, composition, and oxygen fugacity conditions, and on the timing of core formation in the Earth. Previous experimental studies suggest that pressure exerts little to no influence over W metal-silicate partitioning up to 24 GPa, and indicate that the stronger influences are temperature, composition, and oxygen fugacity. However, core formation models based in part on W, predict metal-silicate equilibration pressures outside the available experimental pressure range, requiring extrapolation of parameterized models. Therefore, higher pressure experimental data on W were needed to constrain this important parameter.

  10. Extraction of Soluble Sodium Silicate using Corn Cob Ash as a Silica Source

    Directory of Open Access Journals (Sweden)

    B.A. Ajayi

    2015-09-01

    Full Text Available Extraction of soluble sodium silicate was carried out in this study using corn cob ash as silica source and alkali as soda source. Initially, received corn cob was burnt in open air to obtain the corn cob ash. The obtained corn cob ash was then placed inside refractory crucible and further heating was carried out inside muffle furnace at the temperature of 6000C for 5hrs. The thermally treated corn cob ash was mixed with 3M conc. NAOH and boiled with a constant stirring in a heating glass vessel placed inside a thermostatic water bath at 800C for 4hrs and 900C for 3hrs respectively. Various analyses such as PH value, specific gravity, electrical conductivity, viscosity were conducted on the produced sodium silicate and the results were compared with the reference sodium silicate sample.

  11. Kinetics and Mechanism of Adsorption of Phosphate on Fluorine-containing Calcium Silicate

    Institute of Scientific and Technical Information of China (English)

    ZHU Xinhua; ZHANG Zhao; SHEN Jun

    2016-01-01

    The nanowires-reticulated calcium silicate with a speciifc surface area more than 100 m2/g was prepared by a hydrothermal process using hydrated lime (Ca(OH)2, HL) and silica containing soluble lfuoride, which was a by-product of lfuorine industry, and the soluble lfuoride in raw silica was ifxed as CaSiF6 at the same time. The kinetic characteristics and mechanism of adsorbing phosphate by lfuorine-containing calcium silicate were investigated in the experiments of phosphorus (P) removal from aqueous solution. The results show that the prepared lfuorine-containing calcium silicate has excellent performance for adsorbing phosphate, the adsorption process appears to follow pseudo-second-order reaction kinetics and the process is mainly controlled by chemisorption. The product resulted from P adsorption is mainly composed of hydroxyapatite (HAP) and lfuorapatite (FAP), which are further used as adsorbents of heavy metal ion Cd2+ in aqueous solution and display excellent performance.

  12. Eu-, Tb-, and Dy-Doped Oxyfluoride Silicate Glasses for LED Applications

    DEFF Research Database (Denmark)

    Zhu, C.F.; Wang, J.; Zhang, M.M.;

    2014-01-01

    , and red-light wavelengths from Tb, Dy, and Eu ions. The optical performances can be tuned by varying the glass composition and excitation wavelength. Furthermore, we observed a remarkable emission spectral change for the Tb3+ single-doped oxyfluoride silicate glasses. The 5D3 emission of Tb3+ can......Luminescence glass is a potential candidate for the light-emitting diodes (LEDs) applications. Here, we study the structural and optical properties of the Eu-, Tb-, and Dy-doped oxyfluoride silicate glasses for LEDs by means of X-ray diffraction, photoluminescence spectra, Commission Internationale...... de L’Eclairage (CIE) chromaticity coordinates, and correlated color temperatures (CCTs). The results show that the white light emission can be achieved in Eu/Tb/Dy codoped oxyfluoride silicate glasses under excitation by near-ultraviolet light due to the simultaneous generation of blue, green, yellow...

  13. Uncertainty in silicate mineral weathering rate estimates: source partitioning and policy implications

    Science.gov (United States)

    Futter, M. N.; Klaminder, J.; Lucas, R. W.; Laudon, H.; Köhler, S. J.

    2012-06-01

    Precise and accurate estimates of silicate mineral weathering rates are crucial when setting policy targets for long-term forest sustainability, critical load calculations and assessing consequences of proposed geo-engineering solutions to climate change. In this paper, we scrutinize 394 individual silicate mineral weathering estimates from 82 sites on three continents. We show that within-site differences of several hundred per cent arise when different methods are used to estimate weathering rates, mainly as a result of uncertainties related to input data rather than conceptually different views of the weathering process. While different methods tend to rank sites congruently from high to low weathering rates, large within-site differences in estimated weathering rate suggest that policies relying on quantitative estimates based upon a single method may have undesirable outcomes. We recommend the use of at least three independent estimates when making management decisions related to silicate mineral weathering rates.

  14. Vesuvianite–wollastonite–grossular-bearing calc-silicate rock near Tatapani, Surguja district, Chhattisgarh

    Indian Academy of Sciences (India)

    S C Patel

    2007-04-01

    This paper reports the occurrence of vesuvianite + wollastonite + grossular + diopside + microcline + quartz assemblage in an enclave of calc-silicate rocks occurring within quartzofeldspathic gneiss near Tatapani in the western part of Chhotanagpur Gneissic Complex. The enclave contains phlogopite-absent and phlogopite-bearing calc-silicate rocks, the latter being much more abundant than the former. The above assemblage occurs in the phlogopite-absent rock. Phlogopite-bearing rock contains the assemblage phlogopite + salite + microcline + plagioclase + quartz. A strong schistosity is developed in both the calc-silicate rocks and the minerals are syntectonic with the major foliation-forming event in the area. The vesuvianite-bearing assemblage is formed by amphibolite facies regional metamorphism of a calcareous protolith at pressure > 4 kbar and XCO2 (fluid) > 0.15.

  15. Development of Biomedical Polymer-Silicate Nanocomposites: A Materials Science Perspective

    Directory of Open Access Journals (Sweden)

    Chia-Jung Wu

    2010-04-01

    Full Text Available Biomedical polymer-silicate nanocomposites have potential to become critically important to the development of biomedical applications, ranging from diagnostic and therapeutic devices, tissue regeneration and drug delivery matrixes to various bio-technologies that are inspired by biology but have only indirect biomedical relation. The fundamental understanding of polymer-nanoparticle interactions is absolutely necessary to control structure-property relationships of materials that need to work within the chemical, physical and biological constraints required by an application. This review summarizes the most recent published strategies to design and develop polymer-silicate nanocomposites (including clay based silicate nanoparticles and bioactive glass nanoparticles for a variety of biomedical applications. Emerging trends in bio-technological and biomedical nanocomposites are highlighted and potential new fields of applications are examined.

  16. The inhibitory effects of potassium chloride versus potassium silicate application on (137)Cs uptake by rice.

    Science.gov (United States)

    Fujimura, Shigeto; Yoshioka, Kunio; Ota, Takeshi; Ishikawa, Tetsuya; Sato, Makoto; Satou, Mutsuto

    2016-03-01

    After the accident at the Fukushima Dai-ichi Nuclear Power Plant owned by the Tokyo Electric Power Company on 11 March 2011, potassium fertilizer was applied to agricultural fields in the southern Tohoku and northern Kanto regions of Japan to reduce the uptake of radiocesium by crops. In this study, we examined the effects of two types of potassium fertilizers, potassium chloride (a readily available potassium fertilizer) and potassium silicate (a slow-release potassium fertilizer), as well as a split application of potassium, on the accumulation of (137)Cs by rice plants in two pot experiments. The (137)Cs concentrations in the brown rice and in the above-ground plants were significantly lower after potassium chloride application than after potassium silicate application. The potassium ion (K(+)) concentrations in soil solutions sampled 9 and 21 d after transplanting were significantly higher for the potassium chloride application than for the potassium silicate application. The K(+) concentrations in soil solutions observed in the application of potassium silicate were similar to those in the treatment when no potassium was applied. This finding indicates that the application of potassium silicate did not sufficiently increase the available K(+) for rice plants in the soil, which led to a greater uptake of (137)Cs after the potassium silicate application than after the application of potassium chloride. The (137)Cs concentration in brown rice was higher in the split application of potassium fertilizer with the second application at the full heading stage than that without split application and the split application with the second application before heading. PMID:26773513

  17. Carbonate-silicate liquid immiscibility in the mantle propels kimberlite magma ascent

    Science.gov (United States)

    Kamenetsky, Vadim S.; Yaxley, Gregory M.

    2015-06-01

    Kimberlite is a rare volcanic rock renowned as the major host of diamonds and originated at the base of the subcontinental lithospheric mantle. Although kimberlite magmas are dense in crystals and deeply-derived rock fragments, they ascend to the surface extremely rapidly, enabling diamonds to survive. The unique physical properties of kimberlite magmas depend on the specific compositions of their parental melts that, in absence of historical eruptions and due to pervasive alteration of kimberlite rocks, remain highly debatable. We explain exceptionally rapid ascent of kimberlite magma from mantle depths by combining empirical data on the essentially carbonatite composition of the kimberlite primary melts and experimental evidence on interaction of the carbonate liquids with mantle minerals. Our experimental study shows that orthopyroxene is completely dissolved in a Na2CO3 melt at 2.0-5.0 GPa and 1000-1200 °C. The dissolution of orthopyroxene results in homogeneous silicate-carbonate melt at 5.0 GPa and 1200 °C, and is followed by unmixing of carbonate and carbonated silicate melts and formation of stable magmatic emulsion at lower pressures and temperatures. The dispersed silicate melt has a significant capacity for storing a carbonate component in the deep mantle (13 wt% CO2 at 2.0 GPa). We envisage that this component reaches saturation and is gradually released as CO2 bubbles, as the silicate melt globules are transported upwards through the lithosphere by the carbonatite magma. The globules of unmixed, CO2-rich silicate melt are continuously produced upon further reaction between the natrocarbonatite melt and mantle peridotite. On decompression the dispersed silicate melt phase ensures a continuous supply of CO2 bubbles that decrease density and increase buoyancy and promote rapid ascent of the magmatic emulsion.

  18. Nanotubes within transition metal silicate hollow spheres: Facile preparation and superior lithium storage performances

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Fan; An, Yongling; Zhai, Wei; Gao, Xueping [Key Laboratory for Liquid–Solid Structural Evolution & Processing of Materials (Ministry of Education), Jinan 250100 (China); Feng, Jinkui, E-mail: jinkui@sdu.edu.cn [Key Laboratory for Liquid–Solid Structural Evolution & Processing of Materials (Ministry of Education), Jinan 250100 (China); Ci, Lijie [Key Laboratory for Liquid–Solid Structural Evolution & Processing of Materials (Ministry of Education), Jinan 250100 (China); Xiong, Shenglin [School of Materials Science and Engineering, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100 (China)

    2015-10-15

    Highlights: • The hollow Co{sub 2}SiO{sub 4}, MnSiO{sub 3} and CuSiO{sub 3} were successfully prepared by a facile hydrothermal method using SiO{sub 2} nanosphere. • The hollow Co{sub 2}SiO{sub 4}, MnSiO{sub 3} and CuSiO{sub 3} were tested as anode materials for lithium batteries. • The hollow Co{sub 2}SiO{sub 4}, MnSiO{sub 3} and CuSiO{sub 3} delivered superior electrochemical performance. • The lithium storage mechanism is probe via cyclic voltammetry and XPS. - Abstract: A series of transition metal silicate hollow spheres, including cobalt silicate (Co{sub 2}SiO{sub 4}), manganese silicate (MnSiO{sub 3}) and copper silicate (CuSiO{sub 3}.2H{sub 2}O, CuSiO{sub 3} as abbreviation in the text) were prepared via a simple and economic hydrothermal method by using silica spheres as chemical template. Time-dependent experiments confirmed that the resultants formed a novel type of hierarchical structure, hollow spheres assembled by numerous one-dimensional (1D) nanotubes building blocks. For the first time, the transition metal silicate hollow spheres were characterized as novel anode materials of Li-ion battery, which presented superior lithium storage capacities, cycle performance and rate performance. The 1D nanotubes assembly and hollow interior endow this kind of material facilitate fast lithium ion and electron transport and accommodate the big volume change during the conversion reactions. Our study shows that low-cost transition metal silicate with rationally designed nanostructures can be promising anode materials for high capacity lithium-ion battery.

  19. Effect of Laser Power on Atom Probe Tomography of Silicates

    Science.gov (United States)

    Parman, S. W.; Gorman, B.; Jackson, C.; Cooper, R. F.; Diercks, D.

    2011-12-01

    via surface diffusion and subsequently evaporated. Identifying clusters in the TOF data is problematic and may result in uncounted or misidentified ions. This problem appears to be exacerbated in high oxygen content materials like silicates due to the overlap of O+ and O2++. Both of these factors contributed to the high errors on the initial olivine APT analyses. Here, we report the results of using a laser with 100 times lower power than our previous analyses (500 pJ vs. 5 pJ). As expected, this yields a substantial improvement in both overheating and clustering, resulting in improved accuracy of the compositional analyses. In terms of mass resolution, the improvement is observable as a notable decrease in the full peak width at 1/10th peak maximum, from 5 ns to 0.4 ns.

  20. Corrosion of low Si-alloyed steels in aqueous solution at 90 deg. C. Inhibitive action of silicates; Corrosion d'aciers faiblement allies au silicium en solution aqueuse a 90 deg. C. Action inhibitrice des silicates

    Energy Technology Data Exchange (ETDEWEB)

    Giordana, S

    2002-02-01

    Low-Si alloyed steels, with Si content ranging from 0.25 to 3.2 wt%, as potential candidate materials for high-level nuclear waste disposal containers, have been studied four the point of view of their corrosion behaviour at 90 deg C in an aqueous solution simulating groundwater (0.1 M NaCl borate-buffered solution with a pH of 8.5) both in reducing and in aerated conditions. The influence of silicate addition to the solution is examined so as to represent the silicon of groundwater, coming from the clay dissolution. When no silicate was added to the solution, silicon as an alloying element was proved to degrade in the first moments the steel ability to passivate. For longer immersion times, protective effects developed most efficiently on the steel containing 3.2 wt% silicon both in reducing an in aerating conditions, Infrared spectroscopy, EDSX, XRD and Raman microprobe were applied to characterise the oxide layer composition, which was found to be a mixture of magnetite and maghemite. In the presence of silicate in the solution, clay-like iron silicates appeared in the corrosion layer. Electrochemical tests results show that adding silicate into solution resulted in increasing the steel ability to passivate. In the short term, the inhibiting effect of silicate was confirmed by mass loss tests, but the tendency was inverse in the long term. Silicate iron layers were eventually less protective than the magnetite layers formed in the absence of silicate. (author)

  1. Influence of Chemical Conditions on the Nanoporous Structure of Silicate Aerogels

    Directory of Open Access Journals (Sweden)

    Katalin Sinkó

    2010-01-01

    Full Text Available Silica or various silicate aerogels can be characterized by highly porous, open cell, low density structures. The synthesis parameters influence the three-dimensional porous structures by modifying the kinetics and mechanism of hydrolysis and condensation processes. Numerous investigations have shown that the structure of porous materials can be tailored by variations in synthesis conditions (e.g., the type of precursors, catalyst, and surfactants; the ratio of water/precursor; the concentrations; the medium pH; and the solvent. The objectives of this review are to summarize and elucidate the effects of chemical conditions on the nanoporous structure of sol-gel derived silicate aerogels.

  2. Influence of CeO_2 on scintillating properties of Tb~(3+)-doped silicate glasses

    Institute of Scientific and Technical Information of China (English)

    孙心瑗; 顾牡; 张敏; 黄世明

    2010-01-01

    A series of Tb3+-,Ce3+-doped,and Tb3+/Ce3+-codoped silicate glasses were synthesized by melt-quenching technique.Some properties of the investigated glasses were characterized by X-ray photoelectron spectroscopy(XPS),photoluminescence(PL),X-ray excited luminescence(XEL) and thermoluminescence(TL) spectra.The result of XPS revealed that both Ce3+ and Ce4+ ions coexisted in these silicate glasses,and energy transfer from Ce3+ to Tb3+ ions was observed under UV excitation.However,under X-ray excitation the XEL...

  3. 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.

  4. Prediction of Liquid Immiscibility in Silicate Melts in Special Reference to Their Free Energies

    Institute of Scientific and Technical Information of China (English)

    苏良赫; 段年高

    1990-01-01

    Currie proposed a cirterion for predicting liquid immiscibility in silicate melts with reference to their free energies efore and after crystal fractionization of a melt.The present authors have calculated the rock analysis data given by Philpotts and proved the validity of Currie's method.The authors are particularly interested in the study of immiscibility in the magma in relation with iron deposits.Therefore,they have also calculated the data for artificial silicate melts as well as the data from the famous Kirunavaara iron deposit.

  5. Microstructure engineering of Portland cement pastes and mortars through addition of ultrafine layer silicates

    DEFF Research Database (Denmark)

    Lindgreen, Holger; Geiker, Mette; Krøyer, Hanne;

    2008-01-01

    Pozzolanic submicron-sized silica fume and the non-pozzolanic micron- and nano-sized layer silicates (clay minerals) kaolinite, smectite and palygorskite have been used as additives in Portland cement pastes and mortars. These layer silicates have different particle shape (needles and plates......), surface charge, and size (micron and nano). The structure of the resulting cement pastes and mortars has been investigated by atomic force microscopy (AFM), helium porosimetry, nitrogen adsorption (specific surface area and porosity), low-temperature calorimetry (LTC) and thermal analysis. The main result...

  6. Sensitivity of Structural Results to Initial Configurations and Quench Algorithms of Lead Silicate Glass

    Energy Technology Data Exchange (ETDEWEB)

    Hemesath, Eric R.; Corrales, Louis R.

    2005-06-15

    The sensitivity of resulting structures to starting configurations and quench algorithms were characterized using molecular dynamics (MD) simulations. The classical potential model introduced by Damodaran, Rao, and Rao (DRR) Phys. Chem. Glasses 31, 212 (1990) for lead silicate glass was used. Glasses were prepared using five distinct initial configurations and four glass forming algorithms. In previous MD work of bulk lead silicate glasses the ability of this potential model to provide good structural results were established by comparing to experimental results. Here the sensitivity of the results to the simulation methodology and the persistence of clustering with attention to details of molecular structure are determined.

  7. Anthropogenic Origin of Siliceous Scoria Droplets from Pleistocene and Holocene Archeaological Sites in Northern Syria

    DEFF Research Database (Denmark)

    Thy, Peter; Willcox, George; Barfod, Gry;

    2015-01-01

    Siliceous scoria droplets, measuring from 1 to 10 mm, from one late Pleistocene and four early Holocene archaeological sites in northern Syria are compared to similar droplets previously suggested to be the result of a cosmic impact at the onset of the Younger Dryas global cooling event. The !ndi......Siliceous scoria droplets, measuring from 1 to 10 mm, from one late Pleistocene and four early Holocene archaeological sites in northern Syria are compared to similar droplets previously suggested to be the result of a cosmic impact at the onset of the Younger Dryas global cooling event...

  8. Attributes of the soil fertilized with sewage sludge and calcium and magnesium silicate

    OpenAIRE

    Geraldo R. Zuba Junio; Regynaldo A. Sampaio; Altina L. Nascimento; Luiz A. Fernandes; Natália N. de Lima; João P. Carneiro

    2015-01-01

    ABSTRACTThis study aimed to evaluate the chemical attributes of an Inceptisol cultivated with castor bean (Ricinus communis L.), variety ‘BRS Energia’, fertilized with sewage sludge compost and calcium (Ca) and magnesium (Mg) silicate. The experiment was conducted at the ICA/UFMG, in a randomized block design, using a 2 x 4 factorial scheme with three replicates, and the treatments consisted of two doses of Ca-Mg silicate (0 and 1 t ha-1) and four doses of sewage sludge compost (0, 23.81, 47....

  9. PMR-15/Layered Silicate Nanocomposites For Improved Thermal Stability And Mechanical Properties

    Science.gov (United States)

    Campbell, Sandi; Scheiman, Daniel; Faile, Michael; Papadopoulos, Demetrios; Gray, Hugh R. (Technical Monitor)

    2002-01-01

    Montmorillonite clay was organically modified by co-exchange of an aromatic diamine and a primary alkyl amine. The clay was dispersed into a PMR (Polymerization of Monomer Reactants)-15 matrix and the glass transition temperature and thermal oxidative stability of the resulting nanocomposites were evaluated. PMR-15/ silicate nanocomposites were also investigated as a matrix material for carbon fabric reinforced composites. Dispersion of the organically modified silicate into the PMR-15 matrix enhanced the thermal oxidative stability, the flexural strength, flexural modulus, and interlaminar shear strength of the polymer matrix composite.

  10. K8(K5F)U6Si8O40: An Intergrowth Uranyl Silicate.

    Science.gov (United States)

    Morrison, Gregory; Tran, T Thao; Halasyamani, P Shiv; Zur Loye, Hans-Conrad

    2016-04-01

    Single crystals of K8(K5F)U6Si8O40 were grown from a mixed alkali halide flux. K8(K5F)U6Si8O40 is the first intergrowth uranyl silicate, being composed of alternating slabs related to two previously reported uranyl silicates: Cs2USiO6 and [Na9F2][(UO2)(UO2)2(Si2O7)2]. It exhibits intense luminescence, which is influenced by the [(UO2)2O] dimers present in the structure. PMID:26974872

  11. Formation of apatite on the surface of plasma sprayed dicalcium silicate coating

    Institute of Scientific and Technical Information of China (English)

    LIU Xuan-yong; DING Chuan-xian

    2001-01-01

    @@ INTRODUCTION Since the discovery of Bioglass by Hench et al. in 1969, various kinds of glass and glass-ceramic have been found to bond to living bone. All those bioglass and glass-ceramic including CaO-SiO2 components contributed to the bioactivity of those materials. The polymorphism of dicalcium silicate (Ca2SiO4) has been well studied because of the considerable importance of this compound in the cement and refractories industries. Dicalcium silicate may be bioactive in human body because it is also composed of CaO-SiO2 components.

  12. A low-temperature sol-gel route for the synthesis of bioactive calcium silicates

    Institute of Scientific and Technical Information of China (English)

    Yong-Sen Sun; Ai-Ling Li; Fu-Jian Xu; Dong Qiu

    2013-01-01

    Sol-gel-derived bioactive calcium silicates,synthesized from calcium nitrate tetrahydrate and calcium 2-methoxyethoxide as calcium precursor respectively,were calcified under different temperatures.A series of techniques including SEM,TGA,solid 29Si NMR,nitrogen adsorption,and simulated body fluids (SBF) soaking were employed to study their textural features and in vitro bioactivity.It was confirmed that calcium 2-methoxyethoxide is a promising candidate of calcium precursor for bioactive calcium silicates stabilized under low temperatures.This has implications in fabrication of organic-inorganic hybrid composites.

  13. TEM studies of silver nanoparticles in phase-separated soda lime silicate glasses

    International Nuclear Information System (INIS)

    Transmission electron microscopy (TEM) was used to characterise the microstructure of a phase-separated soda lime silicate glass in which sodium was partially substituted by silver during the ion exchange process. To transform the dopant ions into nanosized particles of colloidal silver, high-temperature annealing (in air and hydrogen) and irradiation (γ-rays from a 60Co source) were used. It has been stated that both treatments affect not only the dopant ions but also the morphology of the matrix. A variety of the induced changes could be exploited for new applications of multicomponent soda lime silicate glasses

  14. The LithicUB project: A virtual lithotheque of siliceous rocks at the University of Barcelona

    Directory of Open Access Journals (Sweden)

    Marta Sánchez

    2014-03-01

    Full Text Available The LithicUB project began in 2009 with two main objectives. The first objective was to make available to the scientific community the description and classification of a set of siliceous rocks that had been recovered from different surveys. The second to make public the lithotheque as a useful tool for archaeological research, related to the procurement and management of lithic raw materials in Prehistory. Thanks to several research projects that have been carried out, the number of samples is steadily increasing and diversifying, including siliceous rocks collected in Spain, Portugal, France, Jordan and Israel.

  15. Polymer/Silicate Nanocomposites Developed for Improved Thermal Stability and Barrier Properties

    Science.gov (United States)

    Campbell, Sandi G.

    2001-01-01

    The nanoscale reinforcement of polymers is becoming an attractive means of improving the properties and stability of polymers. Polymer-silicate nanocomposites are a relatively new class of materials with phase dimensions typically on the order of a few nanometers. Because of their nanometer-size features, nanocomposites possess unique properties typically not shared by more conventional composites. Polymer-layered silicate nanocomposites can attain a certain degree of stiffness, strength, and barrier properties with far less ceramic content than comparable glass- or mineral-reinforced polymers. Reinforcement of existing and new polyimides by this method offers an opportunity to greatly improve existing polymer properties without altering current synthetic or processing procedures.

  16. The effect of sulphur in silicate melt on partitioning of Ni and other trace elements

    Science.gov (United States)

    Wood, Bernard; Kiseeva, Ekaterina; Wohlers, Anke

    2016-04-01

    It has been suggested that variations in the sulphur contents of silicate melts affect the partitioning of trace chalcophile elements, particularly Ni, between silicate melt and crystalline phases such as olivine [1]. The general idea is that Ni (and other elements) complex with sulphur dissolved in the melt, thereby stabilising Ni in the melt and reducing the olivine-melt partition coefficient DNi. More recent experiments lead to the assertion that any sulphur effect, if present is small and can be ignored [2]. Experiments aimed at addressing this problem have, however, struggled with the difficulty that the maximum S contents of olivine- precipitating melts do not exceed ~0.5% even at sulphide saturation. Any effect is therefore difficult to establish unequivocally. Here we have taken advantage of the fact that experiments under strongly reducing conditions, where FeO activity in the silicate melt is very low lead to much higher concentrations of S than those associated with olivine precipitation. We have therefore investigated partitioning between sulphide melts and haplobasaltic silicate melt at concentrations of FeO between 0.3 and 10 weight% in order to investigate the "sulphur-effect" on partitioning. At the lowest FeO contents we are able to drive the S content of the melt to 10 weight% enabling the effects to be unequivocally established. We find that partitioning of strongly lithophile elements Nb, Ta, U, REE partition more strongly out of silicate melt as its S content increases. The effect is, surprisingly, predominantly due to the effect of S on the activity coefficient of FeO in the melt. In contrast strongly chalcophile Ni, Cu, Ag partition more strongly into the melt as its S content increases. This is due to a dramatic lowering of the activity coefficients of these elements in the silicate as S increases. Elements which show little effect of S include Pb, Co and In. The results enable us to predict the effects of sulphur on olivine-melt and

  17. Electrophoretic deposition of calcium silicate-reduced graphene oxide composites on titanium substrate

    DEFF Research Database (Denmark)

    Mehrali, Mehdi; Akhiani, Amir Reza; Talebian, Sepehr;

    2016-01-01

    silicate-reduced graphene oxide (CS-rGO) composites were synthesized, using an in situ hydrothermal method. CS nanowires were uniformly decorated on the rGO, with an appropriate interfacial bonding. The CS-rGO composites behaved like hybrid composites when deposited on a titanium substrate by cathodic......Calcium silicate (CS)/graphene coatings have been used to improve the biological and mechanical fixation of metallic prosthesis. Among the extraordinary features of graphene is its very high mechanical strength, which makes it an attractive nanoreinforcement material for composites. Calcium...

  18. Mechanical Properties and Durability of Advanced Environmental Barrier Coatings in Calcium-Magnesium-Alumino-Silicate Environments

    Science.gov (United States)

    Miladinovich, Daniel S.; Zhu, Dongming

    2011-01-01

    Environmental barrier coatings are being developed and tested for use with SiC/SiC ceramic matrix composite (CMC) gas turbine engine components. Several oxide and silicate based compositons are being studied for use as top-coat and intermediate layers in a three or more layer environmental barrier coating system. Specifically, the room temperature Vickers-indentation-fracture-toughness testing and high-temperature stability reaction studies with Calcium Magnesium Alumino-Silicate (CMAS or "sand") are being conducted using advanced testing techniques such as high pressure burner rig tests as well as high heat flux laser tests.

  19. Nafion-layered silicate nanocomposite membrane for fuel cell application

    OpenAIRE

    Thomassin, Jean-Michel; Pagnoulle, Christophe; Bizzari, Didier; Caldarella, Giuseppe; Germain, Albert; Jérôme, Robert

    2004-01-01

    Direct methanol fuel cells (DMFCs) using a proton exchange membrane as electrolyte is an attractive option for electricity generation. The most widely used membrane in the DMFC system is based on a perfluorinated polymer bearing sulfonic acid functions like Nafion®. The latter combines chemical, mechanical and thermal stability and high protonic conductivity but shows elevated methanol permeability. We propose the preparation of a novel type of hybrid membranes to tentatively solve this probl...

  20. Corrosion of low Si-alloyed steels in aqueous solution at 90 deg. C. Inhibitive action of silicates

    International Nuclear Information System (INIS)

    Low-Si alloyed steels, with Si content ranging from 0.25 to 3.2 wt%, as potential candidate materials for high-level nuclear waste disposal containers, have been studied four the point of view of their corrosion behaviour at 90 deg C in an aqueous solution simulating groundwater (0.1 M NaCl borate-buffered solution with a pH of 8.5) both in reducing and in aerated conditions. The influence of silicate addition to the solution is examined so as to represent the silicon of groundwater, coming from the clay dissolution. When no silicate was added to the solution, silicon as an alloying element was proved to degrade in the first moments the steel ability to passivate. For longer immersion times, protective effects developed most efficiently on the steel containing 3.2 wt% silicon both in reducing an in aerating conditions, Infrared spectroscopy, EDSX, XRD and Raman microprobe were applied to characterise the oxide layer composition, which was found to be a mixture of magnetite and maghemite. In the presence of silicate in the solution, clay-like iron silicates appeared in the corrosion layer. Electrochemical tests results show that adding silicate into solution resulted in increasing the steel ability to passivate. In the short term, the inhibiting effect of silicate was confirmed by mass loss tests, but the tendency was inverse in the long term. Silicate iron layers were eventually less protective than the magnetite layers formed in the absence of silicate. (author)