High-temperature apparatus for chaotic mixing of natural silicate melts

Energy Technology Data Exchange (ETDEWEB)

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

2015-10-15

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

High-temperature apparatus for chaotic mixing of natural silicate melts

International Nuclear Information System (INIS)

Morgavi, D.; Petrelli, M.; Vetere, F. P.; González-García, D.; Perugini, D.

2015-01-01

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

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)

Olivine/melt transition metal partitioning, melt composition, and melt structure—Melt polymerization and Qn-speciation in alkaline earth silicate systems

Science.gov (United States)

Mysen, Bjorn O.

2008-10-01

govern their solubility behavior in silicate melts.

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)

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

Energy Technology Data Exchange (ETDEWEB)

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

1997-12-31

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

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

Energy Technology Data Exchange (ETDEWEB)

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

1996-12-31

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

Composition dependence of spontaneous crystallization of phosphosilicate glass melts during cooling

DEFF Research Database (Denmark)

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

2012-01-01

Crystallization behavior of alumino-phospho-silicate melts during cooling is studied by means of the differential scanning calorimetry, X-ray diffractometry and viscometry. The results show a pronounced impact of alkaline earth oxide, alkali oxide and fluoride on the crystal type and crystallizat......Crystallization behavior of alumino-phospho-silicate melts during cooling is studied by means of the differential scanning calorimetry, X-ray diffractometry and viscometry. The results show a pronounced impact of alkaline earth oxide, alkali oxide and fluoride on the crystal type...... and crystallization degree. It is found that adding NaF into the studied compositions slightly decreases melt fragility and improves both the glass-forming ability and melt workability. This effect is associated with the unique structural role of NaF compared to the other modifier oxides. It is also found...

Lattice thermal conductivity of silicate glasses at high pressures

Science.gov (United States)

Chang, Y. Y.; Hsieh, W. P.

2016-12-01

Knowledge of the thermodynamic and transport properties of magma holds the key to understanding the thermal evolution and chemical differentiation of Earth. The discovery of the remnant of a deep magma ocean above the core mantle boundary (CMB) from seismic observations suggest that the CMB heat flux would strongly depend on the thermal conductivity, including lattice (klat) and radiative (krad) components, of dense silicate melts and major constituent minerals around the region. Recent measurements on the krad of dense silicate glasses and lower-mantle minerals show that krad of dense silicate glasses could be significantly smaller than krad of the surrounding solid mantle phases, and therefore the dense silicate melts would act as a thermal insulator in deep lower mantle. This conclusion, however, remains uncertain due to the lack of direct measurements on the lattice thermal conductivity of silicate melts under relevant pressure-temperature conditions. Besides the CMB, magmas exist in different circumstances beneath the surface of the Earth. Chemical compositions of silicate melts vary with geological and geodynamic settings of the melts and have strong influences on their thermal properties. In order to have a better view of heat transport within the Earth, it is important to study compositional and pressure dependences of thermal properties of silicate melts. Here we report experimental results on lattice thermal conductivities of silicate glasses with basaltic and rhyolitic compositions up to Earth's lower mantle pressures using time-domain thermoreflectance coupled with diamond-anvil cell techniques. This study not only provides new data for the thermal conductivity of silicate melts in the Earth's deep interior, but is crucial for further understanding of the evolution of Earth's complex internal structure.

Sulfur concentration at sulfide saturation (SCSS) in magmatic silicate melts

Science.gov (United States)

Liu, Yanan; Samaha, Naji-Tom; Baker, Don R.

2007-04-01

The sulfur concentration in silicate melts at sulfide saturation (SCSS) was experimentally investigated in a temperature range from 1150 to 1450 °C and a pressure range from 500 MPa to 1 GPa in a piston-cylinder apparatus. The investigated melt compositions varied from rhyolitic to basaltic and water concentrations varied from 0 to ˜9 wt%. All experiments were saturated with FeS melt or pyrrhotite crystals. Temperature was confirmed to have a positive effect on the SCSS. Experimental oxygen fugacities were either near the carbon-carbon monoxide buffer or one log unit above the nickel-nickel oxide buffer, and found to positively affect the SCSS. Combining our results with data from the literature we constructed a model to predict the SCSS in melts ranging in composition from komatiitic to rhyolitic, with water concentrations from 0 to 9 wt%, at pressures from 1 bar to 9 GPa and oxygen fugacities between ˜2 log units below the fayalite-magnetite-quartz buffer to ˜2 log units above it. The coefficients were obtained by multiple linear regression of experimental data and the best model found for the prediction of the SCSS is: ln(Sinppm)=11.35251-{4454.6}/{T}-0.03190{P}/{T}+0.71006ln(MFM)-1.98063[(MFM)(XO)]+0.21867ln(XO)+0.36192lnX where P is in bar, T is in K, MFM is a compositional parameter describing the melt based upon cation mole fractions: MFM={Na+K+2(Ca+Mg+Fe)}/{Si×(Al+Fe)}, XO is the mole fraction of water in the melt, and X is the mole fraction of FeO in the melt. This model was independently tested against experiments performed on anhydrous and hydrous melts in the temperature range from 800 to 1800 °C and 1-9 GPa. The model typically predicts the measured values of the natural log of the SCSS (in ppm) for komatiitic to rhyolitic (˜42 to ˜74 wt% SiO 2) melts to within 5% relative, but is less accurate for high-silica (>76 wt% SiO 2) rhyolites, especially those with molar ratios of iron to sulfur below 2. We demonstrate how this model can be used with

Generation of Silicic Melts in the Early Izu-Bonin Arc Recorded by Detrital Zircons in Proximal Arc Volcaniclastic Rocks From the Philippine Sea

Science.gov (United States)

Barth, A. P.; Tani, K.; Meffre, S.; Wooden, J. L.; Coble, M. A.; Arculus, R. J.; Ishizuka, O.; Shukle, J. T.

2017-10-01

A 1.2 km thick Paleogene volcaniclastic section at International Ocean Discovery Program Site 351-U1438 preserves the deep-marine, proximal record of Izu-Bonin oceanic arc initiation, and volcano evolution along the Kyushu-Palau Ridge (KPR). Pb/U ages and trace element compositions of zircons recovered from volcaniclastic sandstones preserve a remarkable temporal record of juvenile island arc evolution. Pb/U ages ranging from 43 to 27 Ma are compatible with provenance in one or more active arc edifices of the northern KPR. The abundances of selected trace elements with high concentrations provide insight into the genesis of U1438 detrital zircon host melts, and represent useful indicators of both short and long-term variations in melt compositions in arc settings. The Site U1438 zircons span the compositional range between zircons from mid-ocean ridge gabbros and zircons from relatively enriched continental arcs, as predicted for melts in a primitive oceanic arc setting derived from a highly depleted mantle source. Melt zircon saturation temperatures and Ti-in-zircon thermometry suggest a provenance in relatively cool and silicic melts that evolved toward more Th and U-rich compositions with time. Th, U, and light rare earth element enrichments beginning about 35 Ma are consistent with detrital zircons recording development of regional arc asymmetry and selective trace element-enriched rear arc silicic melts as the juvenile Izu-Bonin arc evolved.

The partitioning of barium and lead between silicate melts and aqueous fluids at high pressures and temperatures

International Nuclear Information System (INIS)

Bureau, Helene; Menez, Benedicte; Khodja, Hicham; Daudin, Laurent; Gallien, Jean-Paul; Massare, Dominique; Shaw, Cliff; Metrich, Nicole

2003-01-01

The origin of subduction-related magmas is still a matter of debate in the Earth Sciences. These magmas are characterised by their distinctive trace element compositions compared to magmas from other tectonic settings, e.g. mid-ocean ridges or rifts. The distinct trace element composition of these magmas is generally attributed to alteration of the source region by a contaminating agent: either a silicate melt or a hydrous fluid, possibly chlorine-enriched. In this study, we have used μPIXE (proton induced X-ray emission) to analyse synthetic samples obtained from a micro-experimental petrology study that aims to determine the partitioning behaviour of two key elements, Ba and Pb, between silicate melt and both pure water and saline fluids. Our experiments were performed at high-pressure (>0.34-1.53 GPa) and high-temperature (697-1082 deg. C) in a hydrothermal diamond anvil cell, that was used as a transparent rapid quench autoclave. We observed that at high pressure and temperature, in the presence of pure water, Ba and Pb are not strongly fractionated into one phase or the other. The partition coefficient of Pb is ranging from 0.46 to 1.28. Results from one experiment performed at 0.83 GPa and 847 deg. C, in the presence of a saline fluid indicate that the presence of Cl induces strong fractionation of Pb and moderate fractionation of Ba both into the silicate melt. In addition, our data indicate that Cl is strongly partitioned into the fluid phase

Redox equilibria and the structural role of iron in alumino-silicate melts

Science.gov (United States)

Dickenson, M. P.; Hess, P. C.

1982-01-01

The relationship between the redox ratio Fe+2/(Fe+2+Fe+3) and the K2O/(K2O + Al2O3) ratio (K2O*) were experimentally investigated in silicate melts with 78 mol% SiO2 in the system SiO2-Al2O3-K2O-FeO-Fe2O3, in air at 1,400° C. Quenched glass compositions were analyzed by electron microprobe and wet chemical microtitration techniques. Minimum values of the redox ratio were obtained at K2O*≈0.5. The redox ratio in peralkaline melts (K2O*>0.5) increases slightly with K2O* whereas this ratio increases dramatically in peraluminous melts (K2O*<0.5) as K2O is replaced by Al2O3. These data indicate that all Fe+3 (and Al+3) occur as tetrahedral species charge balanced with K+ in peralkaline melts. In peraluminous melts, Fe+3 (and Al+3) probably occur as both tetrahedral species using Fe+2 as a charge-balancing cation and as network-modifying cations associated with non-bridging oxygen.

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

Origin of silicic magmas along the Central American volcanic front: Genetic relationship to mafic melts

Science.gov (United States)

Vogel, Thomas A.; Patino, Lina C.; Eaton, Jonathon K.; Valley, John W.; Rose, William I.; Alvarado, Guillermo E.; Viray, Ela L.

2006-09-01

Silicic pyroclastic flows and related deposits are abundant along the Central American volcanic front. These silicic magmas erupted through both the non-continental Chorotega block to the southeast and the Paleozoic continental Chortis block to the northwest. The along-arc variations of the silicic deposits with respect to diagnostic trace element ratios (Ba/La, U/Th, Ce/Pb), oxygen isotopes, Nd and Sr isotope ratios mimic the along-arc variation in the basaltic and andesitic lavas. This variation in the lavas has been interpreted to indicate relative contributions from the slab and asthenosphere to the basaltic magmas [Carr, M.J., Feigenson, M.D., Bennett, E.A., 1990. Incompatible element and isotopic evidence for tectonic control of source mixing and melt extraction along the Central American arc. Contributions to Mineralogy and Petrology, 105, 369-380.; Patino, L.C., Carr, M.J. and Feigenson, M.D., 2000. Local and regional variations in Central American arc lavas controlled by variations in subducted sediment input. Contributions to Mineralogy and Petrology, 138 (3), 265-283.]. With respect to along-arc trends in basaltic lavas the largest contribution of slab fluids is in Nicaragua and the smallest input from the slab is in central Costa Rica — similar trends are observed in the silicic pyroclastic deposits. Data from melting experiments of primitive basalts and basaltic andesites demonstrate that it is difficult to produce high K 2O/Na 2O silicic magmas by fractional crystallization or partial melting of low-K 2O/Na 2O sources. However fractional crystallization or partial melting of medium- to high-K basalts can produce these silicic magmas. We interpret that the high-silica magmas associated Central America volcanic front are partial melts of penecontemporaneous, mantle-derived, evolved magmas that have ponded and crystallized in the mid-crust — or are melts extracted from these nearly completely crystallized magmas.

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

Science.gov (United States)

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

2016-01-01

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

Wear and chemistry of zirconium-silicate, aluminium-silicate and zirconium-aluminium-silicate glasses in alkaline medium

International Nuclear Information System (INIS)

Rouse, C.G.; Lemos Guenaga, C.M. de

1984-01-01

A study of the chemical durability, in alkaline solutions, of zirconium silicate, aluminium silicate, zirconium/aluminium silicate glasses as a function of glass composition is carried out. The glasses were tested using standard DIN-52322 method, where the glass samples are prepared in small polished pieces and attacked for 3 hours in a 800 ml solution of 1N (NaOH + NA 2 CO 3 ) at 97 0 C. The results show that the presence of ZrO 2 in the glass composition increases its chemical durability to alkaline attack. Glasses of the aluminium/zirconium silicate series were melted with and without TiO 2 . It was shown experimentally that for this series of glasses, the presence of both TiO 2 and ZrO 2 gave better chemical durability results. However, the best overall results were obtained from the simpler zirconium silicate glasses, where it was possible to make glasses with higher values of ZrO 2 . (Author) [pt

The structural role and homogeneous redox equilibria of iron in peraluminous, metaluminous and peralkaline silicate melts

Science.gov (United States)

Dickenson, M. P.; Hess, P. C.

1986-02-01

The compositional dependence of the redox ratio (FeO/FeO1.5) has been experimentally determined in K2O-Al2O3-SiO2-Fe2O3-FeO (KASFF) and K2O-CaO-Al2O3-SiO2-Fe2O3-FeO (KCASFF) silicate melts. Compositions were equilibrated at 1,450° C in air, with 78 mol % SiO2. KASFF melts have from 1 to 5 mol % Fe2O3 and include both peraluminous (K2OAl2O3) compositions. KCASFF melts have 1 mol % Fe2O3 encompassing peraluminous, metaluminous (CaO+K2O>Al2O3) and peralkaline compositions. Peralkaline KASFF melts with 1 mol % Fe2O3 have low and constant values for the redox ratio, whereas in peraluminous melts the redox ratio increases with increasing (K2O/Al2O3). Increasing total iron concentration increases the redox ratio in peraluminous melts and slightly decreases the redox ratio in peralkaline melts. Substituting CaO for K2O at fixed total iron (1 mol %) increases the redox ratio in both peraluminous and metaluminous KCASFF melts; however, the redox ratio in peralkaline KCASFF melts is not affected by this exchange. These data indicate that Fe3+ is in four-fold coordination, with K+ or Ca2+ providing local charge balance. The tetrahedral ferric species is most stable in peralkaline melts and least stable in peraluminous melts, due to the competition between Al3+ and Fe3+ for charge balancing cations in the latter melt. Tetrahedral Fe3+ is also less stable when Ca2+ provides local charge balance. The data are consistent with a network modifying role for Fe2+ in the melt. The data are interpreted to reflect the effects of melt composition on the partitioning of K+ and Ca2+ and Fe3+ and Al3+ between various species in the melt. These relationships are discussed in terms of homogeneous equilibria between various iron-bearing and iron-free melt species. The results also reflect the effect of liquid composition on the exchange potentials μFe3+ Al-1 and μCa0.5K-1. The exchange potentials are relatively constant in peralkaline melts, but decrease in metaluminous and peraluminous

Experimental Partitioning of Chalcophile Elements between Mantle Silicate Minerals and Basaltic Melt at High Pressures and Temperatures - Implications for Sulfur Geochemistry of Mantle and Crust

Science.gov (United States)

Dasgupta, R.; Jego, S.; Ding, S.; Li, Y.; Lee, C. T.

2015-12-01

The behavior of chalcophile elements during mantle melting, melt extraction, and basalt differentiation is critical for formation of ore deposits and geochemical model and evolution of crust-mantle system. While chalcophile elements are strongly partitioned into sulfides, their behavior with different extent of melting, in particular, in the absence of sulfides, can only be modeled with complete knowledge of the partitioning behavior of these elements between dominant mantle minerals and basaltic melt with or without dissolved sulfide (S2-). However, experimental data on mineral-melt partitioning are lacking for many chalcophile elements. Crystallization experiments were conducted at 3 GPa and 1450-1600 °C using a piston cylinder and synthetic silicate melt compositions similar to low-degree partial melt of peridotite. Starting silicate mixes doped with 100-300 ppm of each of various chalcophile elements were loaded into Pt/graphite double capsules. To test the effect of dissolved sulfur in silicate melt on mineral-melt partitioning of chalcophile elements, experiments were conducted on both sulfur-free and sulfur-bearing (1100-1400 ppm S in melt) systems. Experimental phases were analyzed by EPMA (for major elements and S) and LA-ICP-MS (for trace elements). All experiments produced an assemblage of cpx + melt ± garnet ± olivine ± spinel and yielded new partition coefficients (D) for Sn, Zn, Mo, Sb, Bi, Pb, and Se for cpx/melt, olivine/melt, and garnet/melt pairs. Derived Ds (mineral/basalt) reveal little effect of S2- in the melt on mineral-melt partition coefficients of the measured chalcophile elements, with Ds for Zn, Mo, Bi, Pb decreasing by less than a factor of 2 from S-free to S-bearing melt systems or remaining similar, within error, between S-free and S-bearing melt systems. By combining our data with existing partitioning data between sulfide phases and silicate melt we model the fractionation of these elements during mantle melting and basalt

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

Science.gov (United States)

Kiefer, Walter S.; Mittlefehldt, David W.

2017-01-01

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

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.

Derivation of intermediate to silicic magma from the basalt analyzed at the Vega 2 landing site, Venus.

Science.gov (United States)

Shellnutt, J Gregory

2018-01-01

Geochemical modeling using the basalt composition analyzed at the Vega 2 landing site indicates that intermediate to silicic liquids can be generated by fractional crystallization and equilibrium partial melting. Fractional crystallization modeling using variable pressures (0.01 GPa to 0.5 GPa) and relative oxidation states (FMQ 0 and FMQ -1) of either a wet (H2O = 0.5 wt%) or dry (H2O = 0 wt%) parental magma can yield silicic (SiO2 > 60 wt%) compositions that are similar to terrestrial ferroan rhyolite. Hydrous (H2O = 0.5 wt%) partial melting can yield intermediate (trachyandesite to andesite) to silicic (trachydacite) compositions at all pressures but requires relatively high temperatures (≥ 950°C) to generate the initial melt at intermediate to low pressure whereas at high pressure (0.5 GPa) the first melts will be generated at much lower temperatures (< 800°C). Anhydrous partial melt modeling yielded mafic (basaltic andesite) and alkaline compositions (trachybasalt) but the temperature required to produce the first liquid is very high (≥ 1130°C). Consequently, anhydrous partial melting is an unlikely process to generate derivative liquids. The modeling results indicate that, under certain conditions, the Vega 2 composition can generate silicic liquids that produce granitic and rhyolitic rocks. The implication is that silicic igneous rocks may form a small but important component of the northeast Aphrodite Terra.

Form-stable LiNO_3–NaNO_3–KNO_3–Ca(NO_3)_2/calcium silicate composite phase change material (PCM) for mid-low temperature thermal energy storage

International Nuclear Information System (INIS)

Jiang, Zhu; Leng, Guanghui; Ye, Feng; Ge, Zhiwei; Liu, Chuanping; Wang, Li; Huang, Yun; Ding, Yulong

2015-01-01

Graphical abstract: The figure (a) displays the microstructure of calcium silicate and the inset figure is the LiNO_3–NaNO_3–KNO_3–Ca(NO_3)_2/calcium silicate composite PCM. Calcium silicate is used as a porous skeleton material which could absorb large amounts of the nitrate PCM in voids and prevent the PCM from leakage during phase change process. Figure (b) shows the heat capacity of the composite PCM and the inset figure is the DSC curve of the composite. It indicates that this composite has a low melting point (103.5 °C) and good energy storage property. Based on the novel LiNO_3–NaNO_3–KNO_3–Ca(NO_3)_2/calcium silicate composite PCM, this work involves fabrication process, thermal and microstructural characterization, and chemical and physical stability measurements. - Highlights: • A novel LiNO_3–NaNO_3–KNO_3–Ca(NO_3)_2/calcium silicate composite PCM was prepared. • It has a low melting point (103.5 °C) and could remain stable until 585.5 °C. • It could keep form-stable without leakage during phase change process. • Thermal conductivity of the composite PCM reaches up to 1.177 W m"−"1 K"−"1. • It shows good thermal reliability after 1000 times heating and cooling cycling. - Abstract: In this paper, a novel form-stable LiNO_3–NaNO_3–KNO_3–Ca(NO_3)_2/calcium silicate composite PCM was developed by cold compression and sintering. The eutectic quaternary nitrate is used as PCM, while calcium silicate is used as structural supporting material. X-ray Diffraction (XRD) shows the PCM and the supporting material have good chemical compatibility. This composite PCM has a low melting point (103.5 °C) and remain stable without decomposition until 585.5 °C. Moreover, this composite shows excellent long term stability after 1000 melting and freezing cycles. Thermal conductivity of the composite was measured to be 1.177 W m"−"1 K"−"1, and that could be increased by adding thermal conductivity enhancers into the composite

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

Science.gov (United States)

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

2015-12-01

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

Evidence for a sulfur-undersaturated lunar interior from the solubility of sulfur in lunar melts and sulfide-silicate partitioning of siderophile elements

Science.gov (United States)

Steenstra, E. S.; Seegers, A. X.; Eising, J.; Tomassen, B. G. J.; Webers, F. P. F.; Berndt, J.; Klemme, S.; Matveev, S.; van Westrenen, W.

2018-06-01

Sulfur concentrations at sulfide saturation (SCSS) were determined for a range of low- to high-Ti lunar melt compositions (synthetic equivalents of Apollo 14 black and yellow glass, Apollo 15 green glass, Apollo 17 orange glass and a late-stage lunar magma ocean melt, containing between 0.2 and 25 wt.% TiO2) as a function of pressure (1-2.5 GPa) and temperature (1683-1883 K). For the same experiments, sulfide-silicate partition coefficients were derived for elements V, Cr, Mn, Co, Cu, Zn, Ga, Ge, As, Se, Mo, Sn, Sb, Te, W and Pb. The SCSS is a strong function of silicate melt composition, most notably FeO content. An increase in temperature increases the SCSS and an increase in pressure decreases the SCSS, both in agreement with previous work on terrestrial, lunar and martian compositions. Previously reported SCSS values for high-FeO melts were combined with the experimental data reported here to obtain a new predictive equation to calculate the SCSS for high-FeO lunar melt compositions. Calculated SCSS values, combined with previously estimated S contents of lunar low-Ti basalts and primitive pyroclastic glasses, suggest their source regions were not sulfide saturated. Even when correcting for the currently inferred maximum extent of S degassing during or after eruption, sample S abundances are still > 700 ppm lower than the calculated SCSS values for these compositions. To achieve sulfide saturation in the source regions of low-Ti basalts and lunar pyroclastic glasses, the extent of degassing of S in lunar magma would have to be orders of magnitude higher than currently thought, inconsistent with S isotopic and core-to-rim S diffusion profile data. The only lunar samples that could have experienced sulfide saturation are some of the more evolved A17 high-Ti basalts, if sulfides are Ni- and/or Cu rich. Sulfide saturation in the source regions of lunar melts is also inconsistent with the sulfide-silicate partitioning systematics of Ni, Co and Cu. Segregation of

Silicate enamel for alloyed steel

International Nuclear Information System (INIS)

Ket'ko, K.K.

1976-01-01

The use of silicate enamels in the metallurgical industry is discussed. Presented are the composition and the physico-chemical properties of the silicate enamel developed at the factory 'Krasnyj Oktyabr'. This enamel can be used in the working conditions both in the liquid and the solid state. In so doing the enamel is melted at 1250 to 1300 deg C, granulated and then reduced to a fraction of 0.3 to 0.5 mm. The greatest homogeneity is afforded by a granulated enamel. The trials have shown that the conversion of the test ingots melted under a layer of enamel leads to the smaller number of the ingots rejected for surface defect reasons and the lower metal consumption for slab cleaning. The cost of the silicate enamel is somewhat higher than that of synthetic slags but its application to the melting of stainless steels is still economically beneficial and technologically reasonable. Preliminary calculations only for steel EhI4IEh have revealed that the use of this enamel saves annually over 360000 roubles [ru

Kinetics of iron redox reaction in silicate melts: A high temperature Xanes study on an alkali basalt

Energy Technology Data Exchange (ETDEWEB)

Cochain, B; Neuville, D R; Roux, J; Strukelj, E; Richet, P [Physique des Mineraux et Magmas, Geochimie-Cosmochimie, CNRS-IPGP, 4 place Jussieu, 75005 Paris (France); Ligny, D de [Universite Claude Bernard Lyon 1, LPCML, F-69622 Villeurbanne (France); Baudelet, F, E-mail: cochain@ipgp.jussieu.f [Synchrotron SOLEIL, L' Orme des Merisiers, Saint Aubin (France)

2009-11-15

In Earth and Materials sciences, iron is the most important transition element. Glass and melt properties are strongly affected by iron content and redox state with the consequence that some properties (i.e. viscosity, heat capacity, crystallization...) depend not only on the amounts of Fe{sup 2+} and Fe{sup 3+}, but also on the coordination state of these ions. In this work we investigate iron redox reactions through XANES experiments at the K-edge of iron. Using a high-temperature heating device, pre-edge of XANES spectra exhibits definite advantages to make in-situ measurements and to determine the evolution of redox state with time, temperature and composition of synthetic silicate melts. In this study, new kinetics measurements are presented for a basalt melt from the 31,000-BC eruption of the Puy de Lemptegy Volcano in France. These measurements have been made between 773 K and at superliquidus temperatures up to 1923 K.

Kinetics of iron redox reaction in silicate melts: A high temperature Xanes study on an alkali basalt

International Nuclear Information System (INIS)

Cochain, B; Neuville, D R; Roux, J; Strukelj, E; Richet, P; Ligny, D de; Baudelet, F

2009-01-01

In Earth and Materials sciences, iron is the most important transition element. Glass and melt properties are strongly affected by iron content and redox state with the consequence that some properties (i.e. viscosity, heat capacity, crystallization...) depend not only on the amounts of Fe 2+ and Fe 3+ , but also on the coordination state of these ions. In this work we investigate iron redox reactions through XANES experiments at the K-edge of iron. Using a high-temperature heating device, pre-edge of XANES spectra exhibits definite advantages to make in-situ measurements and to determine the evolution of redox state with time, temperature and composition of synthetic silicate melts. In this study, new kinetics measurements are presented for a basalt melt from the 31,000-BC eruption of the Puy de Lemptegy Volcano in France. These measurements have been made between 773 K and at superliquidus temperatures up to 1923 K.

Silicate Inclusions in IAB Irons: Correlations Between Metal Composition and Inclusion Properties, and Inferences for Their Origin

Science.gov (United States)

Benedix, G. K.; McCoy, T. J.; Keil, K.

1995-09-01

IAB irons are the largest group of iron meteorites, exhibit a large range of siderophile element concentrations in their metal, and commonly contain silicate inclusions with roughly chondritic composition. They are closely related to IIICD irons [1,2] and their inclusions resemble winonaites [3]. It has been suggested that IAB's and IIICD's formed in individual impact melt pools [4,2] on a common parent body. However, it has also been suggested that fractional crystallization [5,6] of a S-saturated core could produce the observed siderophile element trends. Metal composition is correlated with silicate inclusion mineralogy in IIICD's [1], indicating reactions between solid silicates and the metallic magma in a core. These trends observed in IIICD's differ from those in IAB's, suggesting different parent bodies. A bi-modal grouping, based primarily on mineralogy and mineral abundances, was suggested for IAB inclusions [7]. However, recent recoveries of several new silicate-bearing IAB's, along with the emergence of new ideas on their origins, prompted a comprehensive study to document more fully the range of inclusions within IAB irons, to examine possible correlations between the compositions of the metallic host and the silicate inclusions, and to elucidate the origin of IAB irons. We are studying troilite-graphite-silicate inclusions in 24 IAB irons with Ni concentrations ranging from 6.6-25.0%. These include Odessa and Copiapo types [7], newly recovered meteorites (e.g., Lueders [8]) and meteorites with extreme Ni contents (e.g., Jenny's Creek, 6.8%; San Cristobal, 25.0% [9]). The inclusions exhibit a range of textures from recrystallized to partial melts (e.g., Caddo County [10]). Rigorous classification [7] is hampered by heterogeneities between group meteorites, between different samples of distinct meteorites, and within individual inclusions. While intergroup heterogeneities make comparisons between the suite of IAB's somewhat difficult, some general trends

The Origin of Silicic Arc Crust - Insights from the Northern Pacific Volcanic Arcs through Space and Time

Science.gov (United States)

Straub, S. M.; Kelemen, P. B.

2016-12-01

The remarkable compositional similarities of andesitic crust at modern convergent margins and the continental crust has long evoked the hypothesis of similar origins. Key to understanding either genesis is understanding the mode of silica enrichment. Silicic crust cannot be directly extracted from the upper mantle. Hence, in modern arcs, numerous studies - observant of the pervasive and irrefutable evidence of melt mixing - proposed that arc andesites formed by mixing of mantle-derived basaltic melts and fusible silicic material from the overlying crust. Mass balance requires the amount of silicic crust in such hybrid andesites to be on the order to tens of percent, implying that their composition to be perceptibly influenced by the various crustal basements. In order to test this hypothesis, major and trace element compositions of mafic and silicic arc magmas with arc-typical low Ce/PbMexico) were combined with Pb isotope ratios. Pb isotope ratios are considered highly sensitive to crustal contamination, and hence should reflect the variable composition of the oceanic and continental basement on which these arcs are constructed. In particular, in thick-crust continental arcs where the basement is isotopically different from the mantle and crustal assimilation thought to be most prevalent, silicic magmas must be expected to be distinct from those of the associated mafic melts. However, in a given arc, the Pb isotope ratios are constant with increasing melt silica regardless of the nature of the basement. This observation argues against a melt origin of silicic melts from the crustal basement and suggest them to be controlled by the same slab flux as their co-eval mafic counterparts. This inference is validated by the spatial and temporal pattern of arc Pb isotope ratios along the Northern Pacific margins and throughout the 50 million years of Cenozoic evolution of the Izu Bonin Mariana arc/trench system that are can be related to with systematic, `real

SILICATE COMPOSITION OF THE INTERSTELLAR MEDIUM

International Nuclear Information System (INIS)

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

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. An analysis of the well-known 9.7 μ 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 modeled assuming amorphous silicate dust of olivine and pyroxene stoichiometries. Here, we analyze interstellar dust with models of silicate dust that include non-stoichiometric amorphous silicate grains. Modeling the optical depth along lines of sight toward the extinguished objects Cyg OB2 No. 12 and ζ Ophiuchi, we find evidence for interstellar amorphous silicate dust with stoichiometry intermediate between olivine and pyroxene, which we simply refer to as “polivene.” Finally, we compare these results to models of silicate emission from the Trapezium and protoplanetary disks in Taurus.

SILICATE COMPOSITION OF THE INTERSTELLAR MEDIUM

Energy Technology Data Exchange (ETDEWEB)

Fogerty, S.; Forrest, W.; Watson, D. M.; Koch, I. [Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 (United States); Sargent, B. A., E-mail: sfogerty@pas.rochester.edu [Center for Imaging Science and Laboratory for Multiwavelength Astrophysics, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623 (United States)

2016-10-20

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

On determination of melt composition by liquidus curves for a number of oxide systems for crystal formation

International Nuclear Information System (INIS)

Soboleva, L.V.

1991-01-01

Consideration is given to liquidus curves in 31 phase diagrams of a series of borate, aluminate, silicate, germanate, titanate and other systems with unlimited mutual solubility in liquid state. Proposed optimal compositions of melts for preparation of crystals of compounds, forming in these systems, were calculated

Evidence for the presence of carbonate melt during the formation of cumulates in the Colli Albani Volcanic District, Italy

Science.gov (United States)

Shaw, Cliff S. J.

2018-06-01

Fergusite and syenite xenoliths and mafic lapilli from two locations in the Villa Senni ignimbrite of the Colli Albani Volcanic District show evidence for fractionation of a silicate magma that led to exsolution of an immiscible carbonate melt. The fergusite xenoliths are divided into two groups on the basis of their clinopyroxene compositions. Group 1 clinopyroxene records the crystallisation of a silicate melt and enrichment of the melt in Al, Ti and Mn and depletion in Si as well as enrichment in incompatible trace elements. The second group of clinopyroxene compositions (group 2) comes mainly from Ba-F-phlogopite- and Ti-andradite-bearing fergusites. They have significantly higher Si and lower Al and Ti and, like the coexisting phlogopite and garnet are strongly enriched in Mn. The minerals in the fergusites containing group 2 clinopyroxene are enriched in Ba, Sr, Cs, V and Li all of which are expected to partition strongly into a carbonate melt phase relative to the coexisting silicate melt. The compositional data suggest that the group 1 fergusites record sidewall crystallisation of CO2-rich silicate melt and that once the melt reached a critical degree of fractionation, carbonate melt exsolved. The group 2 fergusites record continued crystallisation in this heterogeneous silicate - carbonate melt system. Composite xenoliths of fergusite and thermometamorphic skarn record contact times of hundreds to a few thousand years indicating that fractionation and assimilation was relatively rapid.

The Origin of the Compositional Diversity of Mercury's Surface Constrained From Experimental Melting of Enstatite Chondrites

Science.gov (United States)

Boujibar, A.; Righter, K.; Pando, K.; Danielson, L.

2015-01-01

Mercury is known as an endmember planet as it is the most reduced terrestrial planet with the highest core/mantle ratio. MESSENGER spacecraft has shown that its surface is FeO-poor (2-4 wt%) and Srich (up to 6-7 wt%), which confirms the reducing nature of its silicate mantle. Moreover, high resolution images revealed large volcanic plains and abundant pyroclastic deposits, suggesting important melting stages of the Mercurian mantle. This interpretation was confirmed by the high crustal thickness (up to 100 km) derived from Mercury's gravity field. This is also corroborated by a recent experimental result that showed that Mercurian partial melts are expected to be highly buoyant within the Mercurian mantle and could have risen from depths as high as the core-mantle boundary. In addition MESSENGER spacecraft provided relatively precise data on major elemental compositions of Mercury's surface. These results revealed important chemical and mineralogical heterogeneities that suggested several stages of differentiation and re-melting processes. However, the extent and nature of compositional variations produced by partial melting remains poorly constrained for the particular compositions of Mercury (very reducing conditions, low FeO-contents and high sulfur-contents). Therefore, in this study, we investigated the processes that lead to the various compositions of Mercury's surface. Melting experiments with bulk Mercury-analogue compositions were performed and compared to the compositions measured by MESSENGER.

Calcium Isotopic Composition of Bulk Silicate Earth

Science.gov (United States)

Kang, J.; Ionov, D. A.; Liu, F.; Zhang, C.; Zhang, Z.; Huang, F.

2016-12-01

Ca isotopes are used to study the accretion history of the Earth and terrestrial planets, but, Ca isotopic composition of the Bulk Silicate Earth (BSE) remains poorly constrained [1]. To better understand the Ca isotopic composition of BSE, we analyzed 22 well studied peridotite xenoliths from Tariat (Mongolia), Vitim (southern Siberia) and Udachnaya (Siberian Craton). These samples include both fertile and highly depleted garnet and spinel peridotites that show no or only minor post-melting metasomatism or alteration. Ca isotope measurements were done on a Triton-TIMS using double spike method at the Guangzhou Institute of Geochemistry, CAS. The data are reported as δ44/40Ca (relative to NIST SRM 915a). Results for geostandards are consistent with those from other laboratories. 2 standard deviations of SRM 915a analyses are 0.13‰ (n=48). δ44/40Ca of both and fertile and refractory peridotites range from 0.79 to 1.07‰ producing an average of 0.93±0.12‰ (2SD). This value defines the Ca isotopic composition of the BSE, which is consistent with the average δ44/40Ca of oceanic basalts ( 0.90‰)[2,3]. [1] Huang et al (2010) EPSL 292; [2] Valdes et al (2014) EPSL 394; [3]DePaolo (2004) RMG 55.

Apatite-Melt Partitioning at 1 Bar: An Assessment of Apatite-Melt Exchange Equilibria Resulting from Non-Ideal Mixing of F and Cl in Apatite

Science.gov (United States)

McCubbin, F. M.; Ustunisik, G.; Vander Kaaden, K. E.

2016-01-01

The mineral apatite [Ca5(PO4)3(F,Cl,OH)] is present in a wide range of planetary materials. Due to the presence of volatiles within its crystal structure (X-site), many recent studies have attempted to use apatite to constrain the volatile contents of planetary magmas and mantle sources. In order to use the volatile contents of apatite to precisely determine the abundances of volatiles in coexisting silicate melt or fluids, thermodynamic models for the apatite solid solution and for the apatite components in multi-component silicate melts and fluids are required. Although some thermodynamic models for apatite have been developed, they are incomplete. Furthermore, no mixing model is available for all of the apatite components in silicate melts or fluids, especially for F and Cl components. Several experimental studies have investigated the apatite-melt and apatite-fluid partitioning behavior of F, Cl, and OH in terrestrial and planetary systems, which have determined that apatite-melt partitioning of volatiles are best described as exchange equilibria similar to Fe-Mg partitioning between olivine and silicate melt. However, McCubbin et al. recently reported that the exchange coefficients may vary in portions of apatite compositional space where F, Cl, and OH do not mix ideally in apatite. In particular, solution calorimetry data of apatite compositions along the F-Cl join exhibit substantial excess enthalpies of mixing. In the present study, we conducted apatite-melt partitioning experiments in evacuated, sealed silica-glass tubes at approximately 1 bar and 950-1050 degrees Centigrade on a synthetic Martian basalt composition equivalent to the basaltic shergottite Queen Alexandria Range (QUE) 94201. These experiments were conducted dry, at low pressure, to assess the effects of temperature and apatite composition on the partitioning behavior of F and Cl between apatite and basaltic melt along the F-Cl apatite binary join, where there is non-ideal mixing of F and Cl

Multiple ways of producing intermediate and silicic rocks within Thingmúli and other Icelandic volcanoes

DEFF Research Database (Denmark)

Charreteur, Gilles; Tegner, Christian; Haase, Karsten

2013-01-01

Major and trace element compositions of rocks and coexisting phenocrysts of the ThingmA(0)li volcano suggest a revision of the existing models for the formation of intermediate and silicic melts in Iceland. The new data define two compositional tholeiitic trends with a significant gap between the...... between the compositions of intermediate and silicic rocks and plate tectonic setting, therefore, should be avoided....

Silicic magma generation at Askja volcano, Iceland

Science.gov (United States)

Sigmarsson, O.

2009-04-01

Rate of magma differentiation is an important parameter for hazard assessment at active volcanoes. However, estimates of these rates depend on proper understanding of the underlying magmatic processes and magma generation. Differences in isotope ratios of O, Th and B between silicic and in contemporaneous basaltic magmas have been used to emphasize their origin by partial melting of hydrothermally altered metabasaltic crust in the rift-zones favoured by a strong geothermal gradient. An alternative model for the origin of silicic magmas in the Iceland has been proposed based on U-series results. Young mantle-derived mafic protolith is thought to be metasomatized and partially melted to form the silicic end-member. However, this model underestimates the compositional variations of the hydrothermally-altered basaltic crust. New data on U-Th disequilibria and O-isotopes in basalts and dacites from Askja volcano reveal a strong correlation between (230Th/232Th) and delta 18O. The 1875 AD dacite has the lowest Th- and O isotope ratios (0.94 and -0.24 per mille, respectively) whereas tephra of evolved basaltic composition, erupted 2 months earlier, has significantly higher values (1.03 and 2.8 per mille, respectively). Highest values are observed in the most recent basalts (erupted in 1920 and 1961) inside the Askja caldera complex and out on the associated fissure swarm (Sveinagja basalt). This correlation also holds for older magma such as an early Holocene dacites, which eruption may have been provoked by rapid glacier thinning. Silicic magmas at Askja volcano thus bear geochemical signatures that are best explained by partial melting of extensively hydrothermally altered crust and that the silicic magma source has remained constant during the Holocene at least. Once these silicic magmas are formed they appear to erupt rapidly rather than mixing and mingling with the incoming basalt heat-source that explains lack of icelandites and the bi-modal volcanism at Askja

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

Science.gov (United States)

Kiefer, Walter S.; Mittlefehldt, David W.

2017-01-01

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

Silicic melt evolution in the early Izu-Bonin arc recorded in detrital zircons: Zircon U-Pb geochronology and trace element geochemistry for Site U1438, Amami Sankaku Basin

Science.gov (United States)

Barth, A. P.; Tani, K.; Meffre, S.; Wooden, J. L.; Coble, M. A.

2016-12-01

Understanding the petrologic evolution of oceanic arc magmas through time is important because these arcs reveal the processes of formation and the early evolution of juvenile continental crust. The Izu-Bonin (IB) arc system has been targeted because it is one of several western Pacific intraoceanic arcs initiated at 50 Ma and because of its prominent spatial asymmetry, with widespread development of relatively enriched rear arc lavas. We examined Pb/U and trace element compositions in zircons recovered at IODP Site 351-U1438 and compared them to regional and global zircon suites. These new arc zircon data indicate that detrital zircons will yield new insights into the generation of IB silicic melts and form a set of useful geochemical proxies for interpreting ancient arc detrital zircon provenance. Project IBM drilling target IBM1 was explored by Expedition 351 at Site U1438, located in the proximal back-arc of the northern Kyushu-Palau Ridge (KPR) at 27.3°N. A 1.2 km thick section of Paleogene volcaniclastic rocks, increasingly lithified and hydrothermally altered with depth, constitutes a proximal rear arc sedimentary record of IB arc initiation and early arc evolution. The ages and compositions of U1438 zircons are compatible with provenance in one or more edifices of the northern KPR and are incompatible with drilling contamination. Melt zircon saturation temperatures and Ti-in-zircon thermometry suggest a provenance in relatively cool and silicic KPR melts. The abundances of selected trace elements with high native concentrations provide insight into the petrogenesis of U1438 detrital zircon host melts, and may be useful indicators of both short and long-term variations in melt compositions in arc settings. The U1438 zircons are slightly enriched in U and LREE and are depleted in Nb compared to zircons from mid-ocean ridges and the Parece-Vela Basin, as predicted for melts in a primitive oceanic arc setting with magmas derived from a highly depleted mantle

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

DEFF Research Database (Denmark)

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

2008-01-01

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

Planetesimal core formation with partial silicate melting using in-situ high P, high T, deformation x-ray microtomography

Science.gov (United States)

Anzures, B. A.; Watson, H. C.; Yu, T.; Wang, Y.

2017-12-01

Differentiation is a defining moment in formation of terrestrial planets and asteroids. Smaller planetesimals likely didn't reach high enough temperatures for widescale melting. However, we infer that core formation must have occurred within a few million years from Hf-W dating. In lieu of a global magma ocean, planetesimals likely formed through inefficient percolation. Here, we used in-situ high temperature, high pressure, x-ray microtomography to track the 3-D evolution of the sample at mantle conditions as it underwent shear deformation. Lattice-Boltzmann simulations for permeability were used to characterize the efficiency of melt percolation. Mixtures of KLB1 peridotite plus 6.0 to 12.0 vol% FeS were pre-sintered to achieve an initial equilibrium microstructure, and then imaged through several consecutive cycles of heating and deformation. The maximum calculated melt segregation velocity was found to be 0.37 cm/yr for 6 vol.% FeS and 0.61 cm/year for 12 vol.% FeS, both below the minimum velocity of 3.3 cm/year required for a 100km planetesimal to fully differentiate within 3 million years. However, permeability is also a function of grain size and thus the samples having smaller grains than predicted for small planetesimals could have contributed to low permeability and also low migration velocity. The two-phase (sulfide melt and silicate melt) flow at higher melt fractions (6 vol.% and 12 vol.% FeS) was an extension of a similar study1 containing only sulfide melt at lower melt fraction (4.5 vol.% FeS). Contrary to the previous study, deformation did result in increased permeability until the sample was sheared by twisting the opposing Drickamer anvils by 360 degrees. Also, the presence of silicate melt caused the FeS melt to coalesce into less connected pathways as the experiment with 6 vol.% FeS was found to be less permeable than the one with 4.5 vol.% FeS but without any partial melt. The preliminary data from this study suggests that impacts as well as

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

NARCIS (Netherlands)

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

2011-01-01

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

Metal-silicate Partitioning and Its Role in Core Formation and Composition on Super-Earths

Energy Technology Data Exchange (ETDEWEB)

Schaefer, Laura; Petaev, M. I.; Sasselov, Dimitar D. [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States); Jacobsen, Stein B.; Remo, John L., E-mail: lschaefer@asu.edu [Harvard University, Department of Earth and Planetary Sciences, 20 Oxford St., Cambridge, MA 02138 (United States)

2017-02-01

We use a thermodynamic framework for silicate-metal partitioning to determine the possible compositions of metallic cores on super-Earths. We compare results using literature values of the partition coefficients of Si and Ni, as well as new partition coefficients calculated using results from laser shock-induced melting of powdered metal-dunite targets at pressures up to 276 GPa, which approaches those found within the deep mantles of super-Earths. We find that larger planets may have little to no light elements in their cores because the Si partition coefficient decreases at high pressures. The planet mass at which this occurs will depend on the metal-silicate equilibration depth. We also extrapolate the equations of state (EOS) of FeO and FeSi alloys to high pressures, and present mass–radius diagrams using self-consistent planet compositions assuming equilibrated mantles and cores. We confirm the results of previous studies that the distribution of elements between mantle and core will not be detectable from mass and radius measurements alone. While observations may be insensitive to interior structure, further modeling is sensitive to compositionally dependent properties, such as mantle viscosity and core freeze-out properties. We therefore emphasize the need for additional high pressure measurements of partitioning as well as EOSs, and highlight the utility of the Sandia Z-facilities for this type of work.

Partial reactive crystallization of variable CO2-bearing siliceous MORB-eclogite-derived melt in fertile peridotite and genesis of alkalic basalts with signatures of crustal recycling

Science.gov (United States)

Mallik, A.; Dasgupta, R.

2013-12-01

The presence of heterogeneity in the form of recycled altered oceanic crust (MORB-eclogite) has been proposed in the source of HIMU ocean island basalts (OIBs) [1]. Partial melts of recycled oceanic crust, however, are siliceous and Mg-poor and thus do not resemble the major element compositions of alkalic OIBs that are silica-poor and Mg-rich. In an upwelling heterogenous mantle, MORB-eclogite undergoes melting deeper than volatile-free peridotite, hence, andesitic partial melt derived from eclogite will react with subsolidus peridotite. We have examined the effect of such a melt-rock reaction under volatile-free conditions at 1375 °C, 3 GPa by varying the melt-rock ratio from 8 to 50 wt.% [2]. We concluded that the reacted melts reproduce certain major element characteristics of oceanic basanites, but not nephelinites. Also, the melt-rock reaction produces olivine and garnet-bearing websteritic residue. Because presence of CO2 has been invoked in the source of many HIMU ocean islands, the effect of CO2 on such a melt-rock reaction needs to be evaluated. Accordingly, we performed reaction experiments on mixtures of 25% and 33% CO2-bearing andesitic partial melt and peridotite at 1375 °C, 3 GPa by varying the dissolved CO2 content of the reacting melts from 1 to 5 wt.% (bulk CO2 from 0.25 to 1.6 wt.%) [3, this study]. Owing to melt-rock reaction, with increasing CO2 in the bulk mixture, (a) modes of olivine and cpx decrease while melt, opx and garnet increase, (b) reacted melts evolve to greater degree of Si-undersaturation (from andesite through basanite to nephelinite), (c) enhanced crystallization of garnet take place with higher CO2 in the melt, reducing alumina content of the reacted melts, and (d) CaO and MgO content of the reacted melts increase, without affecting FeO* and Na2O contents (indicating greater propensity of Ca2+ and Mg2+ over Fe2+ and Na+ to enter silicate melt as carbonate). For a given melt-MgO, the CO2-bearing reacted melts are a better

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

Science.gov (United States)

Safonov, O.; Butvina, V.

2009-04-01

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

Evidence of denser MgSiO3 glass above 133 gigapascal (GPa) and implications for remnants of ultradense silicate melt from a deep magma ocean.

Science.gov (United States)

Murakami, Motohiko; Bass, Jay D

2011-10-18

Ultralow velocity zones are the largest seismic anomalies in the mantle, with 10-30% seismic velocity reduction observed in thin layers less than 20-40 km thick, just above the Earth's core-mantle boundary (CMB). The presence of silicate melts, possibly a remnant of a deep magma ocean in the early Earth, have been proposed to explain ultralow velocity zones. It is, however, still an open question as to whether such silicate melts are gravitationally stable at the pressure conditions above the CMB. Fe enrichment is usually invoked to explain why melts would remain at the CMB, but this has not been substantiated experimentally. Here we report in situ high-pressure acoustic velocity measurements that suggest a new transformation to a denser structure of MgSiO(3) glass at pressures close to those of the CMB. The result suggests that MgSiO(3) melt is likely to become denser than crystalline MgSiO(3) above the CMB. The presence of negatively buoyant and gravitationally stable silicate melts at the bottom of the mantle, would provide a mechanism for observed ultralow seismic velocities above the CMB without enrichment of Fe in the melt. An ultradense melt phase and its geochemical inventory would be isolated from overlying convective flow over geologic time.

Redox Reaction in Silicate Melts Monitored by ''Static'' In-Situ Fe K-Edge XANES up to 1180 deg. C

International Nuclear Information System (INIS)

Wilke, Max; Partzsch, Georg M.; Welter, Edmund; Farges, Francois

2007-01-01

A new experimental setup to measure in-situ kinetics of redox reactions in silicate melts is presented. To study the progress of the Fe-redox reaction, the variation of the signal is recorded at an energy, where the difference between the spectra of the oxidized and reduced Fe in the melt is largest (''static XANES''). To control the redox conditions, the gas atmosphere could be changed between to types of gases using computer-controlled valves (N2:H2 and air, respectively). In this way, a number of reduction/oxidation cycles can be monitored in-situ and continuously. Applied at the Fe K-edge in molten silicates, we obtained a set of high quality data, which includes the very first steps of the redox reaction. An Avrami-type equation is used to investigate rate-controlling parameters for the iron oxidation/reduction kinetics for two melts (basaltic and Na trisilicate) for temperatures up to 1180 deg. C

Making mushy magma chambers in the lower continental crust: Cold storage and compositional bimodality

Science.gov (United States)

Jackson, Matthew; Blundy, Jon; Sparks, Steve

2017-04-01

Increasing geological and geophysical evidence suggests that crustal magma reservoirs are normally low melt fraction 'mushes' rather than high melt fraction 'magma chambers'. Yet high melt fractions must form within these mush reservoirs to explain the observed flow and eruption of low crystallinity magmas. In many models, crystallinity is linked directly to temperature, with higher temperature corresponding to lower crystallinity (higher melt fraction). However, increasing temperature yields less evolved (silicic) melt composition for a given starting material. If mobile, low crystallinity magmas require high temperature, it is difficult to explain how they can have evolved composition. Here we use numerical modelling to show that reactive melt flow in a porous and permeable mush reservoir formed by the intrusion of numerous basaltic sills into the lower continental crust produces magma in high melt fraction (> 0.5) layers akin to conventional magma chambers. These magma-chamber-like layers contain evolved (silicic) melt compositions and form at low (close to solidus) temperatures near the top of the mush reservoir. Evolved magma is therefore kept in 'cold storage' at low temperature, but also at low crystallinity so the magma is mobile and can leave the mush reservoir. Buoyancy-driven reactive flow and accumulation of melt in the mush reservoir controls the temperature and composition of magma that can leave the reservoir. The modelling also shows that processes in lower crustal mush reservoirs produce mobile magmas that contain melt of either silicic or mafic composition. Intermediate melt compositions are present but are not within mobile magmas. Silicic melt compositions are found at high melt fraction within the magma-chamber like layers near the top of the mush reservoir. Mafic melt compositions are found at high melt fraction within the cooling sills. Melt elsewhere in the reservoir has intermediate composition, but remains trapped in the reservoir because

Micro-XANES measurements on experimental spinels and the oxidation state of vanadium in coexisting spinel and silicate melt

International Nuclear Information System (INIS)

Righter, K.; Sutton, S.R.; Newville, M.; Le, L.; Schwandt, C.S.

2006-01-01

We show that experimental spinels coexisting with silicate melt always have lower valence vanadium, and that spinels typically have 3+, whereas the coexisting melt has 4+ or 5+. Implications of these results for planetary basalts will be discussed. Spinel can be a significant host phase for V which has multiple oxidation states V 2+ , V 3+ , V 4+ or V 5+ at oxygen fugacities relevant to natural systems. The magnitude of D(V) spinel/melt is known to be a function of composition, temperature and fO 2 , but the uncertainty of the oxidation state under the range of natural conditions has made elusive a thorough understanding of D(V) spinel/melt. For example, V 3+ is likely to be stable in spinels, based on exchange with Al in experiments in the CaO-MgO-Al 2 O 3 -SiO 2 system. On the other hand, it has been argued that V 4+ will be stable across the range of natural oxygen fugacities in nature. In order to build on our previous work in more oxidized systems, we have carried out experiments at relatively reducing conditions from the FMQ buffer to 2 log fO 2 units below the IW buffer. These spinel-melt pairs, where V is present in the spinel at natural levels (∼300 ppm V), were analyzed using an electron microprobe at NASA-JSC and mi-cro-XANES at the Advanced Photon Source at Argonne National Laboratory. The new results will be used together with previous results to understand the valence of V in spinel-melt systems across 12 orders of magnitude of oxygen fugacity, and with application to natural systems.

The same features of interaction of UO2 nuclear fuel with silicate melts

International Nuclear Information System (INIS)

Ipatov, A.P.; Bel'skaya, Eh.A.; Kerko, P.F.; Pavlyukovich, P.A.; Rytvinskaya, Eh.V.; Kopets, Z.V.

1997-01-01

Summarized results of the experimental investigations of interaction between uranium dioxide and silicate melts of multicomponent oxide systems SiO 2 -CaO-Al 2 O 3 -Na 2 O in a wide range of basicity (0,47-1,2) at constant mass content of Al 2 O 3 -Na 2 O in each experiment. Used form of combined data processing in non dimensional coordinates permitted to get generalized curve of the studied dependence with maximum at 0,6-0,7 basicity

Metal/sulfide-silicate intergrowth textures in EL3 meteorites: Origin by impact melting on the EL parent body

Science.gov (United States)

van Niekerk, Deon; Keil, Klaus

2011-10-01

We document the petrographic setting and textures of Fe,Ni metal, the mineralogy of metallic assemblages, and the modal mineral abundances in the EL3 meteorites Asuka (A-) 881314, A-882067, Allan Hills 85119, Elephant Moraine (EET) 90299/EET 90992, LaPaz Icefield 03930, MacAlpine Hills (MAC) 02635, MAC 02837/MAC 02839, MAC 88136, Northwest Africa (NWA) 3132, Pecora Escarpment 91020, Queen Alexandra Range (QUE) 93351/QUE 94321, QUE 94594, and higher petrologic type ELs Dar al Gani 1031 (EL4), Sayh al Uhaymir 188 (EL4), MAC 02747 (EL4), QUE 94368 (EL4), and NWA 1222 (EL5). Large metal assemblages (often containing schreibersite and graphite) only occur outside chondrules and are usually intergrown with silicate minerals (euhedral to subhedral enstatite, silica, and feldspar). Sulfides (troilite, daubréelite, and keilite) are also sometimes intergrown with silicates. Numerous authors have shown that metal in enstatite chondrites that are interpreted to have been impact melted contains euhedral crystals of enstatite. We argue that the metal/sulfide-silicate intergrowths in the ELs we studied were also formed during impact melting and that metal in EL3s thus does not retain primitive (i.e., nebular) textures. Likewise, the EL4s are also impact-melt breccias. Modal abundances of metal in the EL3s and EL4s range from approximately 7 to 30 wt%. These abundances overlap or exceed those of EL6s, and this is consistent either with pre-existing heterogeneity in the parent body or with redistribution of metal during impact processes.

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

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...... 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...

Energetics of silicate melts from thermal diffusion studies. Final report

International Nuclear Information System (INIS)

Walker, D.

1997-01-01

Initially this project was directed towards exploiting Soret diffusion of silicate liquids to learn about the internal energetics of the constituents of the liquids. During the course of this project this goal was realized at the same time a series of intellectual and technical developments expanded the scope of the undertaking. Briefly recapping some of the highlights, the project was initiated after the discovery that silicate liquids were strongly Soret-active. It was possible to observe the development of strong diffusive gradients in silicate liquid composition in response to laboratory-imposed thermal gradients. The character of the chemical separations was a direct window into the internal speciation of the liquids; the rise time of the separation was a useful entree to quantitatively measuring chemical diffusivity; and the steady state magnitude of the separation proved to be an excellent determinant of the constituents' mixing energies. A comprehensive program was initiated to measure the separations, rise times, and mixing energies of a range of geologically and technically interesting silicate liquids. An additional track of activities in the DOE project has run in parallel to the Soret investigation of single-phase liquids in a thermal gradient. This additional track is the study of liquid-plus-crystal systems in a thermal gradient. In these studies solubility-driven diffusion introduced many useful effects, some quite surprising. In partially molten silicate liquids the authors applied their experiments to understanding magmatic cumulate rocks. They have also applied their understanding of these systems to aspects of evaporite deposits in the geological record. They also undertook studies of this sort in systems with retrograde solubility in order to form the basis for understanding remediation for brine migration problems in evaporite-hosted nuclear waste repositories such as the WIPP

The solubility of Pd and Au in hydrous intermediate silicate melts: The effect of oxygen fugacity and the addition of Cl and S

Science.gov (United States)

Sullivan, Neal A.; Zajacz, Zoltan; Brenan, James M.

2018-06-01

The solubilities of Pd and Au in a hydrous trachyandesitic melt were experimentally determined at 1000 °C and 200 MPa at oxygen fugacity (ƒO2) from 0.45 log units below to 6.55 log units above the Ni-NiO buffer (NNO). The effect of adding metal-binding ligands (i.e. Cl and S) to the silicate melt was also studied. The solubility of Au increases from 0.15 ± 0.1 to 3.85 ± 1.48 ppm in Cl- and S-free melts with ƒO2 increasing from NNO-0.45 to NNO+6.55 with a slope that suggests that it is present in 1+ oxidation state over the entire studied ƒO2 range. On the other hand, Pd solubility, shows a more moderate increase with ƒO2, especially in the lower half of the studied range, increasing from 2.66 ± 0.25 ppm at NNO-0.45 to only 3.62 ± 0.38 ppm at NNO+1.72 in Cl- and S-free melts. Overall, the variation in Pd solubility as a function of ƒO2 indicates Pd being dissolved in the silicate melt in both zero and 1+ oxidation state, with the former being dominant below NNO+4.5. At NNO-0.45 to +3.48, the addition of 3170-4060 ppm Cl to the silicate melt increased the solubility of Au by an average factor of 1.5, in comparison to Cl-free melts. However, at NNO+6.55, Au solubility increased by a factor of 2.5. The addition of Cl had a negligible effect on the solubility of Pd except for a large increase (factor of 2.4) at NNO+6.55. At reducing conditions (NNO-0.45), the addition of 170 ppm S to the silicate melt increased the solubility of Au by a factor of ∼4 but did not change the solubility of Pd in comparison to S-free melts. The observation that Pd is dominantly present as Pd0 at NNO one may expect similar behavior in fluids degassing from magmas at depth, the lack of oxidized Pd species could be an important factor behind the scarcity of economically viable Pd-rich magmatic-hydrothermal deposits observed in nature.

In situ study at high pressure and temperature of the environment of water in hydrous Na and Ca aluminosilicate melts and coexisting aqueous fluids

Science.gov (United States)

Le Losq, Charles; Dalou, Célia; Mysen, Bjorn O.

2017-07-01

The bonding and speciation of water dissolved in Na silicate and Na and Ca aluminosilicate melts were inferred from in situ Raman spectroscopy of the samples, in hydrothermal diamond anvil cells, while at crustal temperature and pressure conditions. Raman data were also acquired on Na silicate and Na and Ca aluminosilicate glasses, quenched from hydrous melts equilibrated at high temperature and pressure in a piston cylinder apparatus. In the hydrous melts, temperature strongly influences O-H stretching ν(O-H) signals, reflecting its control on the bonding of protons between different molecular complexes. Pressure and melt composition effects are much smaller and difficult to discriminate with the present data. However, the chemical composition of the melt + fluid system influences the differences between the ν(O-H) signals from the melts and the fluids and, hence, between their hydrogen partition functions. Quenching modifies the O-H stretching signals: strong hydrogen bonds form in the glasses below the glass transition temperature Tg, and this phenomenon depends on glass composition. Therefore, glasses do not necessarily record the O-H stretching signal shape in melts near Tg. The melt hydrogen partition function thus cannot be assessed with certainty using O-H stretching vibration data from glasses. From the present results, the ratio of the hydrogen partition functions of hydrous silicate melts and aqueous fluids mostly depends on temperature and the bulk melt + fluid system chemical composition. This implies that the fractionation of hydrogen isotopes between magmas and aqueous fluids in water-saturated magmatic systems with differences in temperature and bulk chemical composition will be different.

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.

DEPENDENCY OF SULFATE SOLUBILITY ON MELT COMPOSITION AND MELT POLYMERIZATION

International Nuclear Information System (INIS)

JANTZEN, CAROL M.

2004-01-01

Sulfate and sulfate salts are not very soluble in borosilicate waste glass. When sulfate is present in excess it can form water soluble secondary phases and/or a molten salt layer (gall) on the melt pool surface which is purported to cause steam explosions in slurry fed melters. Therefore, sulfate can impact glass durability while formation of a molten salt layer on the melt pool can impact processing. Sulfate solubility has been shown to be compositionally dependent in various studies, (e.g. , B2O3, Li2O, CaO, MgO, Na2O, and Fe2O3 were shown to increase sulfate solubility while Al2O3 and SiO2 decreased sulfate solubility). This compositional dependency is shown to be related to the calculated melt viscosity at various temperatures and hence the melt polymerization

Tin isotope fractionation during magmatic processes and the isotope composition of the bulk silicate Earth

Science.gov (United States)

Wang, Xueying; Amet, Quentin; Fitoussi, Caroline; Bourdon, Bernard

2018-05-01

Tin is a moderately volatile element whose isotope composition can be used to investigate Earth and planet differentiation and the early history of the Solar System. Although the Sn stable isotope composition of several geological and archaeological samples has been reported, there is currently scarce information about the effect of igneous processes on Sn isotopes. In this study, high-precision Sn isotope measurements of peridotites and basalts were obtained by MC-ICP-MS with a double-spike technique. The basalt samples display small variations in δ124/116Sn ranging from -0.01 ± 0.11 to 0.27 ± 0.11‰ (2 s.d.) relative to NIST SRM 3161a standard solution, while peridotites have more dispersed and more negative δ124Sn values ranging from -1.04 ± 0.11 to -0.07 ± 0.11‰ (2 s.d.). Overall, basalts are enriched in heavy Sn isotopes relative to peridotites. In addition, δ124Sn in peridotites become more negative with increasing degrees of melt depletion. These results can be explained by different partitioning behavior of Sn4+ and Sn2+ during partial melting. Sn4+ is overall more incompatible than Sn2+ during partial melting, resulting in Sn4+-rich silicate melt and Sn2+-rich residue. As Sn4+ has been shown experimentally to be enriched in heavy isotopes relative to Sn2+, the effect of melting is to enrich residual peridotites in relatively more compatible Sn2+, which results in isotopically lighter peridotites and isotopically heavier mantle-derived melts. This picture can be disturbed partly by the effect of refertilization. Similarly, the presence of enriched components such as recycled oceanic crust or sediments could explain part of the variations in Sn isotopes in oceanic basalts. The most primitive peridotite analyzed in this study was used for estimating the Sn isotope composition of the BSE, with δ124Sn = -0.08 ± 0.11‰ (2 s.d.) relative to the Sn NIST SRM 3161a standard solution. Altogether, this suggests that Sn isotopes may be a powerful probe of

Measurements of the Activity of dissolved H2O in an Andesite Melt

Science.gov (United States)

Moore, G. M.; Touran, J. P.; Pu, X.; Kelley, K. A.; Cottrell, E.; Ghiorso, M. S.

2016-12-01

The large effect of dissolved H2O on the physical and chemical nature of silicate melts, and its role in driving volcanism, is well known and underscores the importance of this volatile component. A complete understanding of the chemical behavior of dissolved H2O in silicate melts requires the quantification of its thermodynamic activity as a function of pressure, temperature, and melt composition, particularly at low H2O contents (i.e. at under-saturated conditions). Knowledge of the activity of H2O in silicate melts at H2O-undersaturated conditions will improve our understanding of hydrous phase equilibria, as well as our models of physical melt properties. Measurement of the activity of any silicate melt component, much less that of a volatile component such as H2O, is a difficult experimental task however. By using a modified double capsule design (Matjuschkin et al, 2015) to control oxygen fugacity in piston cylinder experiments, along with high precision X-ray absorption techniques (XANES) to measure iron oxidation state in silicate glasses (Cottrell et al, 2009), we are able to constrain the H2O activity in silicate melts at under-saturated conditions. Preliminary results on an andesite melt with low H2O content (3 wt%) have been shown (Moore et al, 2016) to match predicted H2O activity values calculated using the H2O equation of state of Duan and Zhang (1996) and the H2O solubility model of Ghiorso and Gualda (2015). More recent results on the same andesite melt containing approximately 5 wt% H2O however show a large negative deviation from the predicted values. Reversal experiments involving an oxidized starting material are ongoing, as well as further characterization of the samples to detect the presence of possible contaminants that would induce reduction of the melt beyond that related to the H2O activity (e.g. graphite contamination).

The density, compressibility and seismic velocity of hydrous melts at crustal and upper mantle conditions

Science.gov (United States)

Ueki, K.; Iwamori, H.

2015-12-01

Various processes of subduction zone magmatism, such as upward migration of partial melts and fractional crystallization depend on the density of the hydrous silicate melt. The density and the compressibility of the hydrous melt are key factors for the thermodynamic calculation of phase relation of the hydrous melt, and the geophysical inversion to predict physicochemical conditions of the melting region based on the seismic velocity. This study presents a new model for the calculations of the density of the hydrous silicate melts as a function of T, P, H2O content and melt composition. The Birch-Murnaghan equation is used for the equation of state. We compile the experimentally determined densities of various hydrous melts, and optimize the partial molar volume, compressibility, thermal expansibility and its pressure derivative, and K' of the H2O component in the silicate melt. P-T ranges of the calibration database are 0.48-4.29 GPa and 1033-2073 K. As such, this model covers the P-T ranges of the entire melting region of the subduction zone. Parameter set provided by Lange and Carmichael [1990] is used for the partial molar volume and KT value of the anhydrous silicate melt. K' of anhydrous melt is newly parameterized as a function of SiO2 content. The new model accurately reproduces the experimentally determined density variations of various hydrous melts from basalt to rhyolite. Our result shows that the hydrous melt is more compressive and less dense than the anhydrous melt; with the 5 wt% of H2O in melt, density and KT decrease by ~10% and ~30% from those of the anhydrous melt, respectively. For the application of the model, we calculated the P-wave velocity of the hydrous melt. With the 5 wt% of H2O, P-wave velocity of the silicate melt decreases by >10%. Based on the melt P-wave velocity, we demonstrate the effect of the melt H2O content on the seismic velocity of the partially molten zone of the subduction zone.

Melt inclusions: Chapter 6

Science.gov (United States)

,; Lowenstern, J. B.

2014-01-01

Melt inclusions are small droplets of silicate melt that are trapped in minerals during their growth in a magma. Once formed, they commonly retain much of their initial composition (with some exceptions) unless they are re-opened at some later stage. Melt inclusions thus offer several key advantages over whole rock samples: (i) they record pristine concentrations of volatiles and metals that are usually lost during magma solidification and degassing, (ii) they are snapshots in time whereas whole rocks are the time-integrated end products, thus allowing a more detailed, time-resolved view into magmatic processes (iii) they are largely unaffected by subsolidus alteration. Due to these characteristics, melt inclusions are an ideal tool to study the evolution of mineralized magma systems. This chapter first discusses general aspects of melt inclusions formation and methods for their investigation, before reviewing studies performed on mineralized magma systems.

Effect of layered silicates and reactive compatibilization on structure and properties of melt-drawn HDPE/PA6 microfibrillar composites

Czech Academy of Sciences Publication Activity Database

Kelnar, Ivan; Kaprálková, Ludmila; Kratochvíl, Jaroslav; Padovec, Z.; Růžička, M.; Hromádková, Jiřina

2016-01-01

Roč. 73, č. 6 (2016), s. 1673-1688 ISSN 0170-0839 R&D Projects: GA ČR(CZ) GA13-15255S Institutional support: RVO:61389013 Keywords : nanocomposite * blend * melt drawing Subject RIV: JI - Composite Materials Impact factor: 1.430, year: 2016

The role of liquid-liquid immiscibility and crystal fractionation in the genesis of carbonatite magmas: insights from Kerimasi melt inclusions

Science.gov (United States)

Guzmics, Tibor; Zajacz, Zoltán; Mitchell, Roger H.; Szabó, Csaba; Wälle, Markus

2015-02-01

We have reconstructed the compositional evolution of the silicate and carbonate melt, and various crystalline phases in the subvolcanic reservoir of Kerimasi Volcano in the East African Rift. Trace element concentrations of silicate and carbonate melt inclusions trapped in nepheline, apatite and magnetite from plutonic afrikandite (clinopyroxene-nepheline-perovskite-magnetite-melilite rock) and calciocarbonatite (calcite-apatite-magnetite-perovskite-monticellite-phlogopite rock) show that liquid immiscibility occurred during the generation of carbonatite magmas from a CO2-rich melilite-nephelinite magma formed at relatively high temperatures (1,100 °C). This carbonatite magma is notably more calcic and less alkaline than that occurring at Oldoinyo Lengai. The CaO-rich (32-41 wt%) nature and alkali-"poor" (at least 7-10 wt% Na2O + K2O) nature of these high-temperature (>1,000 °C) carbonate melts result from strong partitioning of Ca (relative to Mg, Fe and Mn) in the immiscible carbonate and the CaO-rich nature (12-17 wt%) of its silicate parent (e.g., melilite-nephelinite). Evolution of the Kerimasi carbonate magma can result in the formation of natrocarbonatite melts with similar composition to those of Oldoinyo Lengai, but with pronounced depletion in REE and HFSE elements. We suggest that this compositional difference results from the different initial parental magmas, e.g., melilite-nephelinite at Kerimasi and a nephelinite at Oldoinyo Lengai. The difference in parental magma composition led to a significant difference in the fractionating mineral phase assemblage and the element partitioning systematics upon silicate-carbonate melt immiscibility. LA-ICP-MS analysis of coeval silicate and carbonate melt inclusions provides an opportunity to infer carbonate melt/silicate melt partition coefficients for a wide range of elements. These data show that Li, Na, Pb, Ca, Sr, Ba, B, all REE (except Sc), U, V, Nb, Ta, P, Mo, W and S are partitioned into the carbonate

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

Energy Technology Data Exchange (ETDEWEB)

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

1994-12-31

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

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

Energy Technology Data Exchange (ETDEWEB)

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

1993-12-31

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

Tin in granitic melts: The role of melting temperature and protolith composition

Science.gov (United States)

Wolf, Mathias; Romer, Rolf L.; Franz, Leander; López-Moro, Francisco Javier

2018-06-01

Granite bound tin mineralization typically is seen as the result of extreme magmatic fractionation and late exsolution of magmatic fluids. Mineralization, however, also could be obtained at considerably less fractionation if initial melts already had enhanced Sn contents. We present chemical data and results from phase diagram modeling that illustrate the dominant roles of protolith composition, melting conditions, and melt extraction/evolution for the distribution of Sn between melt and restite and, thus, the Sn content of melts. We compare the element partitioning between leucosome and restite of low-temperature and high-temperature migmatites. During low-temperature melting, trace elements partition preferentially into the restite with the possible exception of Sr, Cd, Bi, and Pb, that may be enriched in the melt. In high-temperature melts, Ga, Y, Cd, Sn, REE, Pb, Bi, and U partition preferentially into the melt whereas Sc, V, Cr, Co, Ni, Mo, and Ba stay in the restite. This contrasting behavior is attributed to the stability of trace element sequestering minerals during melt generation. In particular muscovite, biotite, titanite, and rutile act as host phases for Sn and, therefore prevent Sn enrichment in the melt as long as they are stable phases in the restite. As protolith composition controls both the mineral assemblage and modal contents of the various minerals, protolith composition eventually also controls the fertility of a rock during anatexis, restite mineralogy, and partitioning behavior of trace metals. If a particular trace element is sequestered in a phase that is stable during partial melting, the resulting melt is depleted in this element whereas the restite becomes enriched. Melt generation at high temperature may release Sn when Sn-hosts become unstable. If melt has not been lost before the breakdown of Sn-hosts, Sn contents in the melt will increase but never will be high. In contrast, if melt has been lost before the decomposition of Sn

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.

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

Energy Technology Data Exchange (ETDEWEB)

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

2014-01-28

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

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

Science.gov (United States)

Ottonello, Giulio; Richet, Pascal

2014-01-28

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

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

International Nuclear Information System (INIS)

Ottonello, Giulio; Richet, Pascal

2014-01-01

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

Structure and properties of alumino-boro-silicate glasses and melts

Science.gov (United States)

neuville, D. R.; Florian, P.; Cadars, S.; Massiot, D.

2012-12-01

The relationship between physical properties and structure of glasses and melts in the system MO-T2O3-SiO2 (with M= Na2, Ca and T= Al, B) are technologically and geologically important, in particular to understand the microscopic origin of the configurational thermodynamic properties. The connection of these network former is fundamental to understand the physical properties of magmatic liquids. The configurational properties of melts and glasses provide fundamental information needed to characterize magmatic processes. A principal difficulty, however is to link the "macroscopic" configurational entropy with the structure of melts. This has been done by combining viscometry with Raman and NMR spectroscopy studies. From the viscosity measurements at low and high temperatures, we have obtained the configurational entropy, Sconf (log η = Ae + Be/TSconf, were η is the viscosity, T the temperature and Ae, Be two constants). Silicon, aluminum, and boron are 3 network formers playing different role on the silicate network, whereas Si is the strongest network former in coordination 4, 5 or 6 as a function of T, P; Al can play different function as a network former in 4- or 5-fold coordination and probably as a network modifier in 6 fold coordination. Boron observed in 3 or 4 fold coordination is always a network former but for very "fragile" glasses. For the glass the Al/B substitution produce a small decrease of the molar volume while this substitution produced a strong decrease of viscosity and glass transition temperature while the fragility of the network is less affected by this chemical change. Raman spectra show significant change in the D1 and D2 bands. NMR spectroscopies show also significant change as a function of chemical change and temperature. All this observations will be discussed and interpreted in order to link microscopic versus macroscopic changes.

Investigating Planetesimal Evolution by Experiments with Fe-Ni Metallic Melts: Light Element Composition Effects on Trace Element Partitioning Behavior

Science.gov (United States)

Chabot, N. L.

2017-12-01

As planetesimals were heated up in the early Solar System, the formation of Fe-Ni metallic melts was a common occurrence. During planetesimal differentiation, the denser Fe-Ni metallic melts separated from the less dense silicate components, though some meteorites suggest that their parent bodies only experienced partial differentiation. If the Fe-Ni metallic melts did form a central metallic core, the core eventually crystallized to a solid, some of which we sample as iron meteorites. In all of these planetesimal evolution processes, the composition of the Fe-Ni metallic melt influenced the process and the resulting trace element chemical signatures. In particular, the metallic melt's "light element" composition, those elements present in the metallic melt in a significant concentration but with lower atomic masses than Fe, can strongly affect trace element partitioning. Experimental studies have provided critical data to determine the effects of light elements in Fe-Ni metallic melts on trace element partitioning behavior. Here I focus on combining numerous experimental results to identify trace elements that provide unique insight into constraining the light element composition of early Solar System Fe-Ni metallic melts. Experimental studies have been conducted at 1 atm in a variety of Fe-Ni systems to investigate the effects of light elements on trace element partitioning behavior. A frequent experimental examination of the effects of light elements in metallic systems involves producing run products with coexisting solid metal and liquid metal phases. Such solid-metal-liquid-metal experiments have been conducted in the Fe-Ni binary system as well as Fe-Ni systems with S, P, and C. Experiments with O-bearing or Si-bearing Fe-Ni metallic melts do not lend themselves to experiments with coexisting solid metal and liquid metal phases, due to the phase diagrams of these elements, but experiments with two immiscible Fe-Ni metallic melts have provided insight into

The Effect of fO2 on Partition Coefficients of U and Th between Garnet and Silicate Melt

Science.gov (United States)

Huang, F.; He, Z.; Schmidt, M. W.; Li, Q.

2014-12-01

Garnet is one of the most important minerals controlling partitioning of U and Th in the upper mantle. U is redox sensitive, while Th is tetra-valent at redox conditions of the silicate Earth. U-series disequilibria have provided a unique tool to constrain the time-scales and processes of magmatism at convergent margins. Variation of garnet/meltDU/Th with fO2 is critical to understand U-series disequilibria in arc lavas. However, there is still no systematic experimental study about the effect of fO2 on partitioning of U and Th between garnet and melt. Here we present experiments on partitioning of U, Th, Zr, Hf, Nb, Ta, and REE between garnet and silicate melts at various fO2. The starting material was hydrous haplo-basalt. The piston cylinder experiments were performed with Pt double capsules with C-CO, MnO-Mn3O4 (MM), and hematite-magnetite (HM) buffers at 3 GPa and 1185-1230 oC. The experiments produced garnets with diameters > 50μm and quenched melt. Major elements were measured by EMPA at ETH Zurich. Trace elements were determined using LA-ICP-MS at Northwestern University (Xi'an, China) and SIMS (Cameca1280 at the Institute of Geology and Geophysics, Beijing, China), producing consistent partition coefficient data for U and Th. With fO2 increasing from CCO to MM and HM, garnet/meltDU decreases from 0.041 to 0.005, while garnet/meltDTh ranges from 0.003 to 0.007 without correlation with fO2. Notably, garnet/meltDTh/U increases from 0.136 at CCO to 0.41 at HM. Our results indicate that U is still more compatible than Th in garnet even at the highest fO2 considered for the subarc mantle wedge (~NNO). Therefore, we predict that if garnet is the dominant phase controlling U-Th partitioning during melting of the mantle wedge, melts would still have 230Th excess over 238U. This explains why most young continental arc lavas have 230Th excess. If clinopyroxene is the dominant residual phase during mantle melting, U could be more incompatible than Th at high fO2

Vapor pressure and vapor fractionation of silicate melts of tektite composition

Science.gov (United States)

Walter, Louis S.; Carron, M.K.

1964-01-01

The total vapor pressure of Philippine tektite melts of approximately 70 per cent silica has been determined at temperatures ranging from 1500 to 2100??C. This pressure is 190 ?? 40 mm Hg at 1500??C, 450 ?? 50 mm at 1800??C and 850 ?? 70 mm at 2100?? C. Determinations were made by visually observing the temperature at which bubbles began to form at a constant low ambient pressure. By varying the ambient pressure, a boiling point curve was constructed. This curve differs from the equilibrium vapor pressure curve due to surface tension effects. This difference was evaluated by determining the equilibrium bubble size in the melt and calculating the pressure due to surface tension, assuming the latter to be 380 dyn/cm. The relative volatility from tektite melts of the oxides of Na, K, Fe, Al and Si has been determined as a function of temperature, total pressure arid roughly, of oxygen fugacity. The volatility of SiO2 is decreased and that of Na2O and K2O is increased in an oxygen-poor environment. Preliminary results indicate that volatilization at 2100??C under atmospheric pressure caused little or no change in the percentage Na2O and K2O. The ratio Fe3 Fe2 of the tektite is increased in ambient air at a pressure of 9 ?? 10-4 mm Hg (= 106.5 atm O2, partial pressure) at 2000??C. This suggests that tektites were formed either at lower oxygen pressures or that they are a product of incomplete oxidation of parent material with a still lower ferricferrous ratio. ?? 1964.

Carbonatite and silicate melt metasomatism of the mantle surrounding the Hawaiian plume: Evidence from volatiles, trace elements, and radiogenic isotopes in rejuvenated-stage lavas from Niihau, Hawaii

Science.gov (United States)

Dixon, Jacqueline; Clague, David A.; Cousens, Brian; Monsalve, Maria Luisa; Uhl, Jessika

2008-09-01

We present new volatile, trace element, and radiogenic isotopic compositions for rejuvenated-stage lavas erupted on Niihau and its submarine northwest flank. Niihau rejuvenated-stage Kiekie Basalt lavas are mildly alkalic and are isotopically similar to, though shifted to higher 87Sr/86Sr and lower 206Pb/204Pb than, rejuvenated-stage lavas erupted on other islands and marginal seafloor settings. Kiekie lavas display trace element heterogeneity greater than that of other rejuvenated-stage lavas, with enrichments in Ba, Sr, and light-rare earth elements resulting in high and highly variable Ba/Th and Sr/Ce. The high Ba/Th lavas are among the least silica-undersaturated of the rejuvenated-stage suite, implying that the greatest enrichments are associated with the largest extents of melting. Kiekie lavas also have high and variable H2O/Ce and Cl/La, up to 620 and 39, respectively. We model the trace element concentrations of most rejuvenated-stage lavas by small degrees (˜1% to 9%) of melting of depleted peridotite recently metasomatized by a few percent of an enriched incipient melt (0.5% melting) of the Hawaiian plume. Kiekie lavas are best explained by 4% to 13% partial melting of a peridotite source metasomatized by up to 0.2% carbonatite, similar in composition to oceanic carbonatites from the Canary and Cape Verde Islands, with lower proportion of incipient melt than that for other rejuvenated-stage lavas. Primary H2O and Cl of the carbonatite component must be high, but variability in the volatile data may be caused by heterogeneity in the carbonatite composition and/or interaction with seawater. Our model is consistent with predictions based on carbonated eclogite and peridotite melting experiments in which (1) carbonated eclogite and peridotite within the Hawaiian plume are the first to melt during plume ascent; (2) carbonatite melt metasomatizes plume and surrounding depleted peridotite; (3) as the plume rises, silica-undersaturated silicate melts are also

Deep-Earth Equilibration between Molten Iron and Solid Silicates

Science.gov (United States)

Brennan, M.; Zurkowski, C. C.; Chidester, B.; Campbell, A.

2017-12-01

Elemental partitioning between iron-rich metals and silicate minerals influences the properties of Earth's deep interior, and is ultimately responsible for the nature of the core-mantle boundary. These interactions between molten iron and solid silicates were influential during planetary accretion, and persist today between the mantle and liquid outer core. Here we report the results of diamond anvil cell experiments at lower mantle conditions (40 GPa, >2500 K) aimed at examining systems containing a mixture of metals (iron or Fe-16Si alloy) and silicates (peridotite). The experiments were conducted at pressure-temperature conditions above the metallic liquidus but below the silicate solidus, and the recovered samples were analyzed by FIB/SEM with EDS to record the compositions of the coexisting phases. Each sample formed a three-phase equilibrium between bridgmanite, Fe-rich metallic melt, and an oxide. In one experiment, using pure Fe, the quenched metal contained 6 weight percent O, and the coexisting oxide was ferropericlase. The second experiment, using Fe-Si alloy, was highly reducing; its metal contained 10 wt% Si, and the coexisting mineral was stishovite. The distinct mineralogies of the two experiments derived from their different starting metals. These results imply that metallic composition is an important factor in determining the products of mixed phase iron-silicate reactions. The properties of deep-Earth interfaces such as the core-mantle boundary could be strongly affected by their metallic components.

Ar and K partitioning between clinopyroxene and silicate melt to 8 GPa

Science.gov (United States)

Chamorro, E. M.; Brooker, R. A.; Wartho, J.-A.; Wood, B. J.; Kelley, S. P.; Blundy, J. D.

2002-02-01

The relative incompatibility of Ar and K are fundamental parameters in understanding the degassing history of the mantle. Clinopyroxene is the main host for K in most of the upper mantle, playing an important role in controlling the K/Ar ratio of residual mantle and the subsequent time-integrated evolution of 40Ar/36Ar ratios. Clinopyroxene also contributes to the bulk Ar partition coefficient that controls the Ar degassing rate during mantle melting. The partitioning of Ar and K between clinopyroxene and quenched silicate melt has been experimentally determined from 1 to 8 GPa for the bulk compositions Ab80Di20 (80 mol% albite-20 mol% diopside) and Ab20Di80 with an ultraviolet laser ablation microprobe (UVLAMP) technique for Ar analysis and the ion microprobe for K. Data for Kr (UVLAMP) and Rb (ion probe) have also been determined to evaluate the role of crystal lattice sites in controlling partitioning. By excluding crystal analyses that show evidence of glass contamination, we find relatively constant Ar partition coefficients (DAr) of 2.6 × 10-4 to 3.9 × 10-4 for the Ab80Di20 system at pressures from 2 to 8 GPa. In the Ab20Di80 system, DAr shows similar low values of 7.0 × 10-5 and 3.0 × 10-4 at 1 to 3 GPa. All these values are several orders of magnitude lower than previous measurements on separated crystal-glass pairs. DK is 10 to 50 times greater than DRb for all experiments, and both elements follow parallel trends with increasing pressure, although these trends are significantly different in each system studied. The DK values for clinopyroxene are at least an order of magnitude greater than DAr under all conditions investigated here, but DAr appears to show more consistent behavior between the two systems than K or Rb. The partitioning behavior of K and Rb can be explained in terms of combined pressure, temperature, and crystal chemistry effects that result in changes for the size of the clinopyroxene M2 site. In the Ab20Di80 system, where

I-Xe dating of silicate and troilite from IAB iron meteorites

International Nuclear Information System (INIS)

Niemeyer, S.

1978-01-01

The IAB iron meteorites may be related to the chondrites; siderophile elements in the metal matrix have chondritic abundances, and the abundant silicate inclusions are chondritic both in mineralogy and in chemical composition. Silicate and troilite (FeS) and IAB irons were analyzed by the I-Xe technique. Four IAB silicate samples gave well-defined I-Xe ages [in millions of years relative to Bjurboele; the monitor error (+-2.5 m.y.) is not included]: -3.7 +- 0.3 for Woodbine, -0.7 +- 0.6 for Mundrabilla, +1.4 +- 0.7 for Copiapo, and +2.6 +- 0.6 for Landes. The ( 129 Xe/ 132 Xe)/sub trapped/ ratios are consistent with previous values for chondrites, with the exception of Landes which has an extraordinary trapped ratio of 3.5 +- 0.2. Both analyses of silicate from Pitts gave anomalous I-Xe patterns: intermediate-temperature points defined good correlations but higher-temperature (greater than or equal to 1400 0 C) points lay above (extra 129 Xe) these lines. The two correlations have different slopes, so it cannot be assigned a definite I-Xe age to Pitts silicate. Troilite samples from Mundrabilla and Pitts were also analyzed: Pitts troilite gave a complex I-Xe pattern, which suggests an age of +17 m.y.; Mundrabilla troilite defined a good I-Xe correlation, which after correction for neutron capture on 128 Te an age of -10.8 +- 0.7 m.y. Thus, surprisingly, low-melting troilite substantially predates high-melting silicate in Mundrabilla. Abundances of Ga, Ge, and Ni in metal from these meteorites are correlated with I-Xe ages of the silicate (referred to henceforth as the metal-silicate correlation). After exploring possible relationships between the I-Xe ages and other properties of the IAB group, it was concluded that the metal-silicate correlation, the old Mundrabilla troilite, and other results favor a nebular formation model (e.g. Wasson, 1970a)

Iron metal production in silicate melts through the direct reduction of Fe/II/ by Ti/III/, Cr/II/, and Eu/II/. [in lunar basalts

Science.gov (United States)

Schreiber, H. D.; Balazs, G. B.; Shaffer, A. P.; Jamison, P. L.

1982-01-01

The production of metallic iron in silicate melts by chemical reactions of Ti(3+), Cr(2+), and Eu(2+) with Fe(2+) is demonstrated under experimental conditions in a simplified basaltic liquid. These reactions form a basis for interpreting the role of isochemical valency exchange models in explanations for the reduced nature of lunar basalts. The redox couples are individually investigated in the silicate melt to ascertain reference redox ratios that are independent of mutual interactions. These studies also provide calibrations of spectral absorptions of the Fe(2+) and Ti(2+) species in these glasses. Subsequent spectrophotometric analyses of Fe(2+) and Ti(2+) in glasses doped with both iron and titanium and of Fe(2+) in glasses doped with either iron and chromium or iron and europium ascertain the degree of mutual interactions in these dual-doped glasses.

Effect of pressure on the short-range structure and speciation of carbon in alkali silicate and aluminosilicate glasses and melts at high pressure up to 8 GPa: 13C, 27Al, 17O and 29Si solid-state NMR study

Science.gov (United States)

Kim, Eun Jeong; Fei, Yingwei; Lee, Sung Keun

2018-03-01

increase in peak width of [4]Si with pressure. 17O NMR spectrum shows that the fraction of Na⋯Osbnd [5]Si in carbon-bearing NS3 glasses is less than that of carbon-free NS3 glasses at 6 GPa potentially due to the formation of bridging carbonate species. While its presence is not evident from the 17O NMR spectrum primarily due to low carbon concentration, 13C MAS NMR results imply the formation of bridging carbonates, [4]Si(CO3)[4]Si, above 6 GPa. The spin-lattice relaxation time (T1) of CO2 in albite melts increases with increasing pressure from 42 s (at 1.5 GPa) to 149 s (at 6 GPa). Taking the pressure-induced change in T1 of carbon species into consideration, total carbon content in carbon-bearing albite melts increases with pressure from ∼1 wt% at 1.5 GPa to ∼4.1 wt% at 6 GPa. The results also reveal a noticeable drop in the peak intensity of free carbonates in carbon-bearing NS3 melts at 6 GPa, implying a potential non-linear change in the carbon solubility with pressure. The current results of carbon speciation in the silicate melts above 4 GPa provide an improved link among the atomic configurations around carbon species, their carbon contents, and isotope composition of carbon-bearing melts in the upper mantle.

Contribution of early impact events to metal-silicate separation, thermal annealing, and volatile redistribution: Evidence in the Pułtusk H chondrite

Science.gov (United States)

Krzesińska, Agata M.

2017-11-01

Three-dimensional X-ray tomographic reconstructions and petrologic studies reveal voluminous accumulations of metal in Pułtusk H chondrite. At the contact of these accumulations, the chondritic rock is enriched in troilite. The rock contains plagioclase-rich bands, with textures suggesting crystallization from melt. Unusually large phosphates are associated with the plagioclase and consist of assemblages of merrillite, and fluorapatite and chlorapatite. The metal accumulations were formed by impact melting, rapid segregation of metal-sulfide melt and the incorporation of this melt into the fractured crater basement. The impact most likely occurred in the early evolution of the H chondrite parent body, when post-impact heat overlapped with radiogenic heat. This enabled slow cooling and separation of the metallic melt into metal-rich and sulfide-rich fractions. This led to recrystallization of chondritic rock in contact with the metal accumulations and the crystallization of shock melts. Phosphorus was liberated from the metal and subsumed by the silicate shock melt, owing to oxidative conditions upon slow cooling. The melt was also a host for volatiles. Upon further cooling, phosphorus reacted with silicates leading to the formation of merrillite, while volatiles partitioned into the residual halogen-rich, dry fluid. In the late stages, the fluid altered merrillite to patchy Cl/F-apatite. The above sequence of alterations demonstrates that impact during the early evolution of chondritic parent bodies might have contributed to local metal segregation and silicate melting. In addition, postshock conditions supported secondary processes: compositional/textural equilibration, redistribution of volatiles, and fluid alterations.

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.

Experimental and geochemical evidence for derivation of the El Capitan Granite, California, by partial melting of hydrous gabbroic lower crust

Science.gov (United States)

Ratajeski, K.; Sisson, T.W.; Glazner, A.F.

2005-01-01

Partial melting of mafic intrusions recently emplaced into the lower crust can produce voluminous silicic magmas with isotopic ratios similar to their mafic sources. Low-temperature (825 and 850??C) partial melts synthesized at 700 MPa in biotite-hornblende gabbros from the central Sierra Nevada batholith (Sisson et al. in Contrib Mineral Petrol 148:635-661, 2005) have major-element and modeled trace-element (REE, Rb, Ba, Sr, Th, U) compositions matching those of the Cretaceous El Capitan Granite, a prominent granite and silicic granodiorite pluton in the central part of the Sierra Nevada batholith (Yosemite, CA, USA) locally mingled with coeval, isotopically similar quartz diorite through gabbro intrusions (Ratajeski et al. in Geol Soc Am Bull 113:1486-1502, 2001). These results are evidence that the El Capitan Granite, and perhaps similar intrusions in the Sierra Nevada batholith with lithospheric-mantle-like isotopic values, were extracted from LILE-enriched, hydrous (hornblende-bearing) gabbroic rocks in the Sierran lower crust. Granitic partial melts derived by this process may also be silicic end members for mixing events leading to large-volume intermediate composition Sierran plutons such as the Cretaceous Lamarck Granodiorite. Voluminous gabbroic residues of partial melting may be lost to the mantle by their conversion to garnet-pyroxene assemblages during batholithic magmatic crustal thickening. ?? Springer-Verlag 2005.

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

Science.gov (United States)

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

2011-01-01

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

In vitro degradation and surface bioactivity of iron-matrix composites containing silicate-based bioceramic

NARCIS (Netherlands)

Wang, S; Xu, Y; Zhou, J.; Li, H; Chang, Jiang; Huan, Z

2017-01-01

Iron-matrix composites with calcium silicate (CS) bioceramic as the reinforcing phase were fabricated through powder metallurgy processes. The microstructures, mechanical properties, apatite deposition and biodegradation behavior of the Fe-CS composites, as well as cell attachment and proliferation

Reworking of Archean mantle in the NE Siberian craton by carbonatite and silicate melt metasomatism: Evidence from a carbonate-bearing, dunite-to-websterite xenolith suite from the Obnazhennaya kimberlite

Science.gov (United States)

Ionov, Dmitri A.; Doucet, Luc S.; Xu, Yigang; Golovin, Alexander V.; Oleinikov, Oleg B.

2018-03-01

The Obnazhennaya kimberlite in the NE Siberian craton hosts a most unusual cratonic xenolith suite, with common rocks rich in pyroxenes and garnet, and no sheared peridotites. We report petrographic and chemical data for whole rocks (WR) and minerals of 20 spinel and garnet peridotites from Obnazhennaya with Re-depletion Os isotope ages of 1.8-2.9 Ga (Ionov et al., 2015a) as well as 2 pyroxenites. The garnet-bearing rocks equilibrated at 1.6-2.8 GPa and 710-1050 °C. Some xenoliths contain vermicular spinel-pyroxene aggregates with REE patterns in clinopyroxene mimicking those of garnet. The peridotites show significant scatter of Mg# (0.888-0.924), Cr2O3 (0.2-1.4 wt.%) and high NiO (0.3-0.4 wt.%). None are pristine melting residues. Low-CaO-Al2O3 (≤0.9 wt.%) dunites and harzburgites are melt-channel materials. Peridotites with low to moderate Al2O3 (0.4-1.8 wt.%) usually have CaO > Al2O3, and some have pockets of calcite texturally equilibrated with olivine and garnet. Such carbonates, exceptional in mantle xenoliths and reported here for the first time for the Siberian mantle, provide direct evidence for modal makeover and Ca and LREE enrichments by ephemeral carbonate-rich melts. Peridotites rich in CaO and Al2O3 (2.7-8.0 wt.%) formed by reaction with silicate melts. We infer that the mantle lithosphere beneath Obnazhennaya, initially formed in the Mesoarchean, has been profoundly modified. Pervasive inter-granular percolation of highly mobile and reactive carbonate-rich liquids may have reduced the strength of the mantle lithosphere leading the way for reworking by silicate melts. The latest events before the kimberlite eruption were the formation of the carbonate-phlogopite pockets, fine-grained pyroxenite veins and spinel-pyroxene symplectites. The reworked lithospheric sections are preserved at Obnazhennaya, but similar processes could erode lithospheric roots in the SE Siberian craton (Tok) and the North China craton, where ancient melting residues and

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

A new approach to reconstructing the composition and evolution of kimberlite melts: A case study of the archetypal Bultfontein kimberlite (Kimberley, South Africa)

Science.gov (United States)

Soltys, Ashton; Giuliani, Andrea; Phillips, David

2018-04-01

The compositions of kimberlite melts at depth and upon emplacement in the upper crust remain elusive. This can be attributed to the unquantified effects of multiple processes, such as alteration, assimilation, xenocryst contamination, and fractional crystallisation. The inability to accurately constrain the composition and physical properties of kimberlite melts prevents a comprehensive understanding of their petrogenesis. To improve constraints on the compositions of kimberlite melts, we have combined modal analysis including the discrimination of xenocrystic from magmatic phases, with mineral chemistry determinations to reconstruct a whole-rock composition. We apply this approach to a sample of "fresh" macrocrystic hypabyssal kimberlite (sample BK-1) from the Bultfontein mine (Kimberley, South Africa). The accuracy of this whole-rock reconstruction method is validated by the similarity between reconstructed and measured whole-rock compositions. A series of corrections are then applied to account for the effects of post-emplacement serpentinisation, pre-emplacement olivine crystallisation, and the inclusion and assimilation of mantle material. This approach permits discernment of melt compositions at different stages of kimberlite evolution. The primitive melt parental to the Bultfontein kimberlite is estimated to contain 17.4-19.0 wt% SiO2, 20.2-22.8 wt% MgO, 20.9-21.9 wt% CaO, 2.1-2.3 wt% P2O5, 1.2-1.4 wt% TiO2, 0.9-1.1 wt% Al2O3, and 0.6-0.7 wt% K2O, and has a Mg# of 83.4-84.4. Primary volatile contents (i.e., after an attempt to account for volatile loss) are tentatively estimated at 2.1-2.2 wt% H2O and 22.9-25.4 wt% CO2. This composition is deficient in SiO2, MgO and H2O, but enriched in CaO and CO2 compared with most previous estimates of primitive kimberlite melts. We suggest that the primitive melt parental to the Bultfontein kimberlite was a transitional silicate-carbonate melt, which was progressively enriched in SiO2, MgO, Al2O3, Cr2O3, and Na2O through

Evolution of Shock Melt Compositions in Lunar Agglutinates

Science.gov (United States)

Vance, A. M.; Christoffersen, R.; Keller, L. P.

2015-01-01

Lunar agglutinates are aggregates of regolith grains fused together in a glassy matrix of shock melt produced during smaller-scale (mostly micrometeorite) impacts. Agglutinate formation is a key space weathering process under which the optically-active component of nanophase metallic Fe (npFe(sup 0)) is added to the lunar regolith. Here we have used energy-dispersive X-ray (EDX) compositional spectrum imaging in the SEM to quantify the chemical homogeneity of agglutinitic glass, correlate its homogeneity to its parent soil maturity, and identify the principle chemical components contributing to the shock melt compositional variations.

Effect of natural fiber types and sodium silicate coated on natural fiber mat/PLA composites: Tensile properties and rate of fire propagation

Science.gov (United States)

Thongpin, C.; Srimuk, J.; hipkam, N.; Wachirapong, P.

2015-07-01

In this study, 3 types of natural fibres, i.e. jute, sisal and abaca, were plain weaved to fibre mat. Before weaving, the fibres were treated with 5% NaOH to remove hemi cellulose and lignin. The weaving was performed by hand using square wooden block fit with nails for weaving using one and two types of natural fibres as weft and warp fibre to produce natural fibre mat. The fibre mat was also impregnated in sodium silicate solution extracted from rich husk ash. The pH of the solution was adjusted to pH 7 using H2SO4 before impregnation. After predetermined time, sodium silicate was gelled and deposited on the mat. The fabric mat and sodium silicate coated mat were then impregnated with PLA solution to produce prepreg. Dried pepreg was laminated with PLA sheet using compressing moulding machine to obtain natural fibre mat/PLA composite. The composite containing abaca aligned in longitudinal direction with respect to tension force enhanced Young's modulus more than 300%. Fibre mat composites with abaca aligned in longitudinal direction also showed tensile strength enhancement nearly 400% higher than neat PLA. After coating with sodium silicate, the tensile modulus of the composites was found slightly increased. The silicate coating was disadvantage on tensile strength of the composite due to the effect of sodium hydroxide solution that was used as solvent for silicate extraction from rice husk ash. However, sodium silicate could retard rate of fire propagation about 50%compare to neat PLA and about 10% reduction compared to fibre mat composites without sodium silicate coated fibre mat.

Effect of natural fiber types and sodium silicate coated on natural fiber mat/PLA composites: Tensile properties and rate of fire propagation

International Nuclear Information System (INIS)

Thongpin, C; Srimuk, J; Hipkam, N; Wachirapong, P

2015-01-01

In this study, 3 types of natural fibres, i.e. jute, sisal and abaca, were plain weaved to fibre mat. Before weaving, the fibres were treated with 5% NaOH to remove hemi cellulose and lignin. The weaving was performed by hand using square wooden block fit with nails for weaving using one and two types of natural fibres as weft and warp fibre to produce natural fibre mat. The fibre mat was also impregnated in sodium silicate solution extracted from rich husk ash. The pH of the solution was adjusted to pH 7 using H 2 SO 4 before impregnation. After predetermined time, sodium silicate was gelled and deposited on the mat. The fabric mat and sodium silicate coated mat were then impregnated with PLA solution to produce prepreg. Dried pepreg was laminated with PLA sheet using compressing moulding machine to obtain natural fibre mat/PLA composite. The composite containing abaca aligned in longitudinal direction with respect to tension force enhanced Young's modulus more than 300%. Fibre mat composites with abaca aligned in longitudinal direction also showed tensile strength enhancement nearly 400% higher than neat PLA. After coating with sodium silicate, the tensile modulus of the composites was found slightly increased. The silicate coating was disadvantage on tensile strength of the composite due to the effect of sodium hydroxide solution that was used as solvent for silicate extraction from rice husk ash. However, sodium silicate could retard rate of fire propagation about 50%compare to neat PLA and about 10% reduction compared to fibre mat composites without sodium silicate coated fibre mat. (paper)

Study of the electroplating mechanism and physicochemical proprieties of deposited Ni-W-Silicate composite alloy

International Nuclear Information System (INIS)

Sassi, W.; Dhouibi, L.; Berçot, P.; Rezrazi, M.; Triki, E.

2014-01-01

In this work, layers based on Nickel-Tungsten (Ni-W) were electroplated from citrate-ammonia bath with and without silicate addition. Firstly, Electrochemical Quartz Crystal Microbalance (EQCM) and Global Discharge Optical Emission Spectroscopy (GDOES) were used to investigate the electroplating mechanism of both coatings. The gain mass was 14 and 4.13 μg cm −2 for Ni-W-Sil and Ni-W coatings, respectively. Secondly, the morphology of the composite alloy shows a smooth and homogenous surface with compact cauliflower like-structure identified as silicate incorporation. Finally, after a long immersion into chloride solution, Ni-W-Sil composite film showed a good surface stability and a remarkable mechanical hardness. These proprieties enhanced the electrochemical behavior of the composite alloy

A dearth of intermediate melts at subduction zone volcanoes and the petrogenesis of arc andesites.

Science.gov (United States)

Reubi, Olivier; Blundy, Jon

2009-10-29

Andesites represent a large proportion of the magmas erupted at continental arc volcanoes and are regarded as a major component in the formation of continental crust. Andesite petrogenesis is therefore fundamental in terms of both volcanic hazard and differentiation of the Earth. Andesites typically contain a significant proportion of crystals showing disequilibrium petrographic characteristics indicative of mixing or mingling between silicic and mafic magmas, which fuels a long-standing debate regarding the significance of these processes in andesite petrogenesis and ultimately questions the abundance of true liquids with andesitic composition. Central to this debate is the distinction between liquids (or melts) and magmas, mixtures of liquids with crystals, which may or may not be co-genetic. With this distinction comes the realization that bulk-rock chemical analyses of petrologically complex andesites can lead to a blurred picture of the fundamental processes behind arc magmatism. Here we present an alternative view of andesite petrogenesis, based on a review of quenched glassy melt inclusions trapped in phenocrysts, whole-rock chemistry, and high-pressure and high-temperature experiments. We argue that true liquids of intermediate composition (59 to 66 wt% SiO(2)) are far less common in the sub-volcanic reservoirs of arc volcanoes than is suggested by the abundance of erupted magma within this compositional range. Effective mingling within upper crustal magmatic reservoirs obscures a compositional bimodality of melts ascending from the lower crust, and masks the fundamental role of silicic melts (>/=66 wt% SiO(2)) beneath intermediate arc volcanoes. This alternative view resolves several puzzling aspects of arc volcanism and provides important clues to the integration of plutonic and volcanic records.

Compositions of melts for growth of functional single crystals of complex oxides and other compounds

Science.gov (United States)

Soboleva, L. V.

2008-12-01

The melt compositions ( M c) are calculated for growing crystals with valuable physical properties. The calculation is based on the compositions of the invariant points of the liquidus curves for 33 congruently and 12 incongruently melting solid phases of 42 fusibility diagrams of binary systems. These systems include Na, Ca, Ba, Mg, and Y aluminates; Bi and Pb germanates; Li, K, Ba, and Bi borates; Ba, Fe, Sr, and Bi titanates; Li, K, Cs, Ba, Zn, Ca niobates; Li, Pb, and Gd molibdates; Pb and Nd tungstates; etc. More than 60 studies with data on the experimentally found melt compositions ( M e) for growing the noted crystals are analyzed. It is shown that the melt compositions M c and M e for growth of congruently and incongruently melting crystals are similar. Large-size stoichiometric crystals of high optical quality are grown using these melt compositions. Nonstoichiometric crystals of low structural quality are grown from melt compositions either corresponding to the stoichiometric ratio of the components ( M s) or similar to the compositions at invariant points ( M i). In these cases, a large difference is observed between the melt compositions M c, M s, and M e.

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

Directory of Open Access Journals (Sweden)

A. Paonita

2005-06-01

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

Evolution of Shock Melt Compositions in Lunar Regoliths

Science.gov (United States)

Vance, A. M.; Christoffersen, R.; Keller, L. P.; Berger, E. L.; Noble, S. K.

2016-01-01

Space weathering processes - driven primarily by solar wind ion and micrometeorite bombardment, are constantly changing the surface regoliths of airless bodies, such as the Moon. It is essential to study lunar soils in order to fully under-stand the processes of space weathering, and how they alter the optical reflectance spectral properties of the lunar surface relative to bedrock. Lunar agglutinates are aggregates of regolith grains fused together in a glassy matrix of shock melt produced during micrometeorite impacts into the lunar regolith. The formation of the shock melt component in agglutinates involves reduction of Fe in the target material to generate nm-scale spherules of metallic Fe (nanophase Fe0 or npFe0). The ratio of elemental Fe, in the form of npFe0, to FeO in a given bulk soil indicates its maturity, which increases with length of surface exposure as well as being typically higher in the finer-size fraction of soils. The melting and mixing process in agglutinate formation remain poorly understood. This includes incomplete knowledge regarding how the homogeneity and overall compositional trends of the agglutinate glass portions (agglutinitic glass) evolve with maturity. The aim of this study is to use sub-micrometer scale X-ray compositional mapping and image analysis to quantify the chemical homogeneity of agglutinitic glass, correlate its homogeneity to its parent soil maturity, and identify the principal chemical components contributing to the shock melt composition variations. An additional focus is to see if agglutinitic glass contains anomalously high Fe sub-micron scale compositional domains similar to those recently reported in glassy patina coatings on lunar rocks.

Thermogravimetric analysis of phase transitions in cement compositions mixed by sodium silicate solution

Directory of Open Access Journals (Sweden)

Fedosov Sergey Viktorovich

2014-01-01

Full Text Available This paper presents a study of the capability to modify cement by mechanical activation of sodium silicate water solution. Admixtures or blends of binding agents were employed for modifying concrete properties. The liquid glass is applied to protect from chemically or physically unfavorable environmental impacts, such as acidic medium and high temperature. The sodium silicate is a high-capacity setting accelerator. The increasing of the liquid glass proportion in the mix leads to the degradation of the cement paste plasticity and for this reason it is necessary to reduce the amount of liquid glass in the cement paste. The activation of dilute water solution of sodium silicate into rotary pulsating apparatus directly before tempering of the cement paste is an effective way to decrease mass fraction of liquid glass in the cement paste. The results of the combined influence of liquid glass and mechanical activation on physicochemical processes taking place in cement stone are represented in this research. Thermogravimetric analysis was used in order to study cement blends. Thermogravimetric analysis of modified cement stone assays was performed by thermo analyzer SETARAM TGA 92-24. The results of the analysis of phase transition taking place under high-temperature heating of cement stone modified by the mechanical activation of the water solution of the sodium silicate were introduced. Thermograms of cement stone assays were obtained at different hardening age. The comparison of these thermograms allows us to come to a conclusion on the formation and the retention during long time of a more dense structure of the composite matrix mixed by the mechanical activation of sodium silicate water solution. The relation between the concrete composition and its strength properties was stated. Perhaps, the capability of modified concrete to keep calcium ions in sparingly soluble hydrosilicates leads to the increase in its durability and corrosion resistance.

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

Composite nanoparticles: A new way to siliceous materials and a model of biosilica synthesis

International Nuclear Information System (INIS)

Annenkov, Vadim V.; Pal'shin, Viktor A.; Verkhozina, Olga N.; Larina, Lyudmila I.; Danilovtseva, Elena N.

2015-01-01

A new polyampholyte based on poly (acrylic acid) which bears pendant polyamine oligomeric chains (average number of the nitrogen atoms is 11.2) is obtained. This polymer is a model of silaffins – proteins playing important role in formation of siliceous structures in diatom algae and sponges. The polymer catalyses condensation of silicic acid. The obtained solutions contain oligosilicates coordinated with the polymer chains. The action of 50,000 g gravity on this solution results in concentrating-induced condensation of the pre-condensed siliceous oligomers. The obtained solid silica contains 4% admixture of the organic polymer which is close to the silica from diatom frustules. These results confirm the hypothesis about formation of biosilica under the action of desiccation agent, e.g. aquaporins. The formation of solid substances during centrifugation of solutions containing soluble oligomers is a new promising approach to inorganic and composite materials which allows to work in aqueous medium and to reuse the organic polymer. - Highlights: • A polyampholyte with pendant polyamine chains is obtained. • The polymer catalyses condensation of silicic acid giving stable solutions. • Gravity-induced (50,000 g) formation of solid silica was observed in these solutions. • The obtained silica is close to biosilica from diatom frustules. • A new approach to inorganic and composite materials is proposed.

Composite nanoparticles: A new way to siliceous materials and a model of biosilica synthesis

Energy Technology Data Exchange (ETDEWEB)

Annenkov, Vadim V., E-mail: annenkov@lin.irk.ru [Limnological Institute, Siberian Branch of the Russian Academy of Sciences, Irkutsk 664033 (Russian Federation); Pal' shin, Viktor A.; Verkhozina, Olga N. [Limnological Institute, Siberian Branch of the Russian Academy of Sciences, Irkutsk 664033 (Russian Federation); Larina, Lyudmila I. [A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, Irkutsk 664033 (Russian Federation); Danilovtseva, Elena N. [Limnological Institute, Siberian Branch of the Russian Academy of Sciences, Irkutsk 664033 (Russian Federation)

2015-09-01

A new polyampholyte based on poly (acrylic acid) which bears pendant polyamine oligomeric chains (average number of the nitrogen atoms is 11.2) is obtained. This polymer is a model of silaffins – proteins playing important role in formation of siliceous structures in diatom algae and sponges. The polymer catalyses condensation of silicic acid. The obtained solutions contain oligosilicates coordinated with the polymer chains. The action of 50,000 g gravity on this solution results in concentrating-induced condensation of the pre-condensed siliceous oligomers. The obtained solid silica contains 4% admixture of the organic polymer which is close to the silica from diatom frustules. These results confirm the hypothesis about formation of biosilica under the action of desiccation agent, e.g. aquaporins. The formation of solid substances during centrifugation of solutions containing soluble oligomers is a new promising approach to inorganic and composite materials which allows to work in aqueous medium and to reuse the organic polymer. - Highlights: • A polyampholyte with pendant polyamine chains is obtained. • The polymer catalyses condensation of silicic acid giving stable solutions. • Gravity-induced (50,000 g) formation of solid silica was observed in these solutions. • The obtained silica is close to biosilica from diatom frustules. • A new approach to inorganic and composite materials is proposed.

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

Science.gov (United States)

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

2014-01-01

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

Polymer/Layered Silicate Nano composites

International Nuclear Information System (INIS)

Bakhit, M.E.E.H.

2012-01-01

Polymer–clay nano composites have attracted the attention of many researchers and experimental results are presented in a large number of recent papers and patents because of the outstanding mechanical properties and low gas permeabilities that are achieved in many cases. Polymer-clay nano composites are a new class of mineral-field polymer that contain relatively small amounts (<10%) of nanometer-sized clay particles. Polymer/clay nano composites have their origin in the pioneering research conducted at Toyota Central Research Laboratories and the first historical record goes back to 1987. The matrix was nylon-6 and the filler MMT. Because of its many advantages such as high mechanical properties, good gas barrier, flame retardation, etc. polymer/clay nano composites have been intensely investigated and is currently the subject of many research programs. Nano composite materials are commercially important and several types of products with different shapes and applications including food packaging films and containers, engine parts, dental materials, etc. are now available in markets. A number of synthesis routes have been developed in the recent years to prepare these materials, which include intercalation of polymers or prepolymers from solution, in-situ polymerization, melt intercalation etc. In this study, new nano composite materials were produced from the components of rubber (Nbr, SBR and EPDM) as the polymeric matrix and organically modified quaternary alkylammonium montmorillonite in different contents (3, 5, 7, and 10 phr) as the filler by using an extruder then, the rubber nano composite sheets were irradiated at a dose of 0, 50, 75, 100 and 150 KGy using Electron beam Irradiation technique as a crosslinking agent. These new materials can be characterized by using various analytical techniques including X-ray diffractometer XRD, Thermogravimetric analyzer TGA, scanning electron microscope (SEM), transmission electron microscope (TEM),Fourier transform

The Effect of Pressure on Iron Speciation in Silicate Melts at a Fixed Oxygen Fugacity: The Possibility of a Redox Profile Through a Terrestrial Magma Ocean

Science.gov (United States)

Armstrong, K.; Frost, D. J.; McCammon, C. A.; Rubie, D. C.; Boffa Ballaran, T.

2017-12-01

As terrestrial planets accreted, mantle silicates equilibrated with core-forming metallic iron, which would have imposed a mantle oxygen fugacity below the iron-wüstite oxygen buffer. Throughout Earth's history, however, the oxygen fugacity of at least the accessible portions of the upper mantle has been 4-5 orders of magnitude higher. The process that caused the rapid increase in the redox state of the mantle soon after core formation is unclear. Here we test the possibility that pressure stabilises ferric iron in silicate melts, as has been observed in silicate minerals. A deep magma ocean, which would have likely existed towards the end of accretion, could then develop a gradient in oxygen fugacity for a fixed ferric-ferrous ratio as a result of pressure. We have equilibrated an andesitic melt with a Ru-RuO2 buffer in a multianvil press between 5 and 24 GPa. Further experiments were performed on the same melt in equilibrium with iron metal. The recovered melts were then analysed using Mössbauer spectroscopy to determine the ferric/ferrous ratio. The results show that for the Ru-RuO2 buffer at lower pressures, the ferric iron content decreases with pressure, due to a positive volume change of the reaction FeO + 1/4O2 = FeO1.5. Ferric iron content also appears to be sensitive to water content at lower pressures. However, above 15 GPa this trend apparently reverses and the ferric iron content increases with pressure. This reversal in pressure dependence would drive the oxygen fugacity of a deep magma ocean with a fixed ferric/ferrous ratio down with increasing depth. This would create a redox gradient, where the magma ocean could potentially be in equilibrium with metallic iron at its base but more oxidised in its shallower regions. Crystallisation of this magma ocean could render an upper mantle oxygen fugacity similar to that in the Earth's accessible mantle today.

Developing a novel magnesium glycerophosphate/silicate-based organic-inorganic composite cement for bone repair.

Science.gov (United States)

Ding, Zhengwen; Li, Hong; Wei, Jie; Li, Ruijiang; Yan, Yonggang

2018-06-01

Considering that the phospholipids and glycerophosphoric acid are the basic materials throughout the metabolism of the whole life period and the bone is composed of organic polymer collagen and inorganic mineral apatite, a novel self-setting composite of magnesium glycerophosphate (MG) and di-calcium silicate(C2S)/tri-calcium silicate(C3S) was developed as bio-cement for bone repair, reconstruction and regeneration. The composite was prepared by mixing the MG, C2S and C3S with the certain ratios, and using the deionized water and phosphoric acid solution as mixed liquid. The combination and formation of the composites was characterized by FTIR, XPS and XRD. The physicochemical properties were studied by setting time, compressive strength, pH value, weight loss in the PBS and surface change by SEM-EDX. The biocompatibility was evaluated by cell culture in the leaching solution of the composites. The preliminary results showed that when di- and tri-calcium silicate contact with water, there are lots of Ca(OH) 2 generated making the pH value of solution is higher than 9 which is helpful for the formation of hydroxyapatite(HA) that is the main bone material. The new organic-inorganic self-setting bio-cements showed initial setting time is ranged from 20 min to 85 min and the compressive strength reached 30 MPa on the 7th days, suitable as the bone fillers. The weight loss was 20% in the first week, and 25% in the 4th week. Meanwhile, the new HA precipitated on the composite surface during the incubation in the SBF showed bioactivity. The cell cultured in the leaching liquid of the composite showed high proliferation inferring the new bio-cement has good biocompatibility to the cells. Copyright © 2018 Elsevier B.V. All rights reserved.

Synthesis, mechanical properties, and in vitro biocompatibility with osteoblasts of calcium silicate-reduced graphene oxide composites.

Science.gov (United States)

Mehrali, Mehdi; Moghaddam, Ehsan; Shirazi, Seyed Farid Seyed; Baradaran, Saeid; Mehrali, Mohammad; Latibari, Sara Tahan; Metselaar, Hendrik Simon Cornelis; Kadri, Nahrizul Adib; Zandi, Keivan; Osman, Noor Azuan Abu

2014-03-26

Calcium silicate (CaSiO3, CS) ceramics are promising bioactive materials for bone tissue engineering, particularly for bone repair. However, the low toughness of CS limits its application in load-bearing conditions. Recent findings indicating the promising biocompatibility of graphene imply that graphene can be used as an additive to improve the mechanical properties of composites. Here, we report a simple method for the synthesis of calcium silicate/reduced graphene oxide (CS/rGO) composites using a hydrothermal approach followed by hot isostatic pressing (HIP). Adding rGO to pure CS increased the hardness of the material by ∼40%, the elastic modulus by ∼52%, and the fracture toughness by ∼123%. Different toughening mechanisms were observed including crack bridging, crack branching, crack deflection, and rGO pull-out, thus increasing the resistance to crack propagation and leading to a considerable improvement in the fracture toughness of the composites. The formation of bone-like apatite on a range of CS/rGO composites with rGO weight percentages ranging from 0 to 1.5 has been investigated in simulated body fluid (SBF). The presence of a bone-like apatite layer on the composite surface after soaking in SBF was demonstrated by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The biocompatibility of the CS/rGO composites was characterized using methyl thiazole tetrazolium (MTT) assays in vitro. The cell adhesion results showed that human osteoblast cells (hFOB) can adhere to and develop on the CS/rGO composites. In addition, the proliferation rate and alkaline phosphatase (ALP) activity of cells on the CS/rGO composites were improved compared with the pure CS ceramics. These results suggest that calcium silicate/reduced graphene oxide composites are promising materials for biomedical applications.

Bioactivity of thermal plasma synthesized bovine hydroxyapatite/glass ceramic composites

International Nuclear Information System (INIS)

Yoganand, C P; Selvarajan, V; Rouabhia, Mahmoud; Cannillo, Valeria; Sola, Antonella

2010-01-01

Bone injuries and failures often require the inception of implant biomaterials. Research in this area is receiving increasing attention worldwide. A variety of artificial bone materials, such as metals, polymeric materials, composites and ceramics, are being explored to replace diseased bones. Calcium phosphate ceramics are currently used as biomaterials for many applications in both dentistry and orthopedics. Bioactive silicate-based glasses show a higher bioactive behaviour than calcium phosphate materials. It is very interesting to study the mixtures of HA and silicate-based glasses. In the present study; natural bovine hydroxyapatite / SiO 2 -CaO-MgO glass composites were produced using the Transferred arc plasma (TAP) melting method. TAP melting route is a brisk process of preparation of glass-ceramics in which the raw materials are melted in the plasma and crystallization of the melt occurs while cooling down at a much faster rate in relatively short processing times compared to the conventional methods of manufacture of glass ceramics/composites. It is well known that; one essential step to the understanding of the biological events occurring at the bone tissue/material interface is the biological investigation by in vitro tests. Cell lines are commonly used for biocompatibility tests, and are very efficient because of their reproducibility and culture facility. In this study, we report the results of a study on the response of primary cultures of human fibroblast cells to TAP melted bioactive glass ceramics.

Electrical conductivity and viscosity of borosilicate glasses and melts

DEFF Research Database (Denmark)

Ehrt, Doris; Keding, Ralf

2009-01-01

, 0 to 62·5 mol% B2O3, and 25 to 85 mol% SiO2. The glass samples were characterised by different methods. Refractive indices, density and thermal expansion were measured. Phase separation effects were investigated by electron microscopy. The electrical conductivity of glasses and melts were determined......Simple sodium borosilicate and silicate glasses were melted on a very large scale (35 l Pt crucible) to prepare model glasses of optical quality in order to investigate various properties depending on their structure. The composition of the glass samples varied in a wide range: 3 to 33·3 mol% Na2O...... by impedance measurements in a wide temperature range (250 to 1450°C). The activation energies were calculated by Arrhenius plots in various temperature regions: below the glass transition temperature, Tg, above the melting point, Tl, and between Tg and Tl. Viscosity measurements were carried out...

The neodymium stable isotope composition of the silicate Earth and chondrites

Science.gov (United States)

McCoy-West, Alex J.; Millet, Marc-Alban; Burton, Kevin W.

2017-12-01

The non-chondritic neodymium (Nd) 142Nd/144Nd ratio of the silicate Earth potentially provides a key constraint on the accretion and early evolution of the Earth. Yet, it is debated whether this offset is due to the Earth being formed from material enriched in s-process Nd isotopes or results from an early differentiation process such as the segregation of a late sulfide matte during core formation, collisional erosion or a some combination of these processes. Neodymium stable isotopes are potentially sensitive to early sulfide segregation into Earth's core, a process that cannot be resolved using their radiogenic counterparts. This study presents the first comprehensive Nd stable isotope data for chondritic meteorites and terrestrial rocks. Stable Nd measurements were made using a double spike technique coupled with thermal ionisation mass spectrometry. All three of the major classes of chondritic meteorites, carbonaceous, enstatite and ordinary chondrites have broadly similar isotopic compositions allowing calculation of a chondritic mean of δ146/144Nd = -0.025 ± 0.025‰ (±2 s.d.; n = 39). Enstatite chondrites yield the most uniform stable isotope composition (Δ146/144Nd = 26 ppm), with considerably more variability observed within ordinary (Δ146/144Nd = 72 ppm) and carbonaceous meteorites (Δ146/144Nd = 143 ppm). Terrestrial weathering, nucleosynthetic variations and parent body thermal metamorphism appear to have little measurable effect on δ146/144Nd in chondrites. The small variations observed between ordinary chondrite groups most likely reflect inherited compositional differences between parent bodies, with the larger variations observed in carbonaceous chondrites being linked to varying modal proportions of calcium-aluminium rich inclusions. The terrestrial samples analysed here include rocks ranging from basaltic to rhyolitic in composition, MORB glasses and residual mantle lithologies. All of these terrestrial rocks possess a broadly similar Nd

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

Science.gov (United States)

Colucci, Simone; Battaglia, Maurizio; Trigila, Raffaello

2016-01-01

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

Effect of magnesium aluminum silicate glass on the thermal shock resistance of BN matrix composite ceramics

NARCIS (Netherlands)

Cai, Delong; Jia, Dechang; Yang, Zhihua; Zhu, Qishuai; Ocelik, Vaclav; Vainchtein, Ilia D.; De Hosson, Jeff Th M.; Zhou, Yu

The effects of magnesium aluminum silicate (MAS) glass on the thermal shock resistance and the oxidation behavior of h-BN matrix composites were systematically investigated at temperature differences from 600 degrees C up to 1400 degrees C. The retained strength rate of the composites rose with the

Melting in super-earths.

Science.gov (United States)

Stixrude, Lars

2014-04-28

We examine the possible extent of melting in rock-iron super-earths, focusing on those in the habitable zone. We consider the energetics of accretion and core formation, the timescale of cooling and its dependence on viscosity and partial melting, thermal regulation via the temperature dependence of viscosity, and the melting curves of rock and iron components at the ultra-high pressures characteristic of super-earths. We find that the efficiency of kinetic energy deposition during accretion increases with planetary mass; considering the likely role of giant impacts and core formation, we find that super-earths probably complete their accretionary phase in an entirely molten state. Considerations of thermal regulation lead us to propose model temperature profiles of super-earths that are controlled by silicate melting. We estimate melting curves of iron and rock components up to the extreme pressures characteristic of super-earth interiors based on existing experimental and ab initio results and scaling laws. We construct super-earth thermal models by solving the equations of mass conservation and hydrostatic equilibrium, together with equations of state of rock and iron components. We set the potential temperature at the core-mantle boundary and at the surface to the local silicate melting temperature. We find that ancient (∼4 Gyr) super-earths may be partially molten at the top and bottom of their mantles, and that mantle convection is sufficiently vigorous to sustain dynamo action over the whole range of super-earth masses.

REDOX BEHAVIOR AND DIFFUSIVITY OF ANTIMONY AND CERIUM ION IN ALKALI ALKALINE EARTH SILICATE GLASS MELTS

Directory of Open Access Journals (Sweden)

K. D. Kim

2010-03-01

Full Text Available Redox behavior and diffusivity of antimony and cerium ion in alkali alkaline earth silicate CRT (Cathode Ray Tube model glass melts were studied by means of square wave voltammetry under the frequency range of 5-1000 Hz and in the temperature range of 800-1400°C. According to voltammogram, peaks due to Sb³⁺/Sb⁰ were positioned in the negative potential region while peaks due to Sb⁵⁺/Sb³⁺ and Ce⁴⁺/Ce³⁺ were found in the positive potential region. By using some equations, correlation for peak potential versus temperature and peak current versus reciprocal frequency was examined, respectively. Their correlation showed a linear relation in the applied temperature and frequency range. Based on the linear relationship, thermodynamic and kinetic properties for each redox reaction were suggested.

Laser ablation of silicate glasses doped with transuranic actinides

International Nuclear Information System (INIS)

Gibson, J.K.; Haire, R.G.

1998-01-01

Direct sampling laser ablation plasma mass spectrometry (DS-LAMS) was applied to silica glasses doped with 237 Np, 242 Pu or 241 Am using a unique instrument recently installed into a transuranic glovebox. The primary goal was to assess the utility of mass spectrometry of directly ablated ions for facile evaluation of actinide (An) constituents of silicate glass immobilization matrices used for encapsulation of radionuclides. The instrument and general procedures have been described elsewhere. Three high-purity silicate glasses prepared by a sol-gel process (SG) and one conventional high-temperature (HT; melting point ∼ 1,450 C) borosilicate glass were studied. These glasses comprised the following constituents, with compositions expressed in mass percentages: Np-HT ∼ 30% SiO 2 + 6% B 2 O 3 + 3% BaO + 13% Al 2 O 3 + 10% PbO + 30% La 2 O 3 + 8% 237 NpO 2 ; Np-SG ∼ 70% SiO 2 + 30% 237 NpO 2 ; Pu-SG ∼ 70% SiO 2 + 30% 242 PuO 2 ; Am-SG ∼ 85% SiO 2 + 15% 241 AmO 2

Calcium titanium silicate based glass-ceramic for nuclear waste immobilisation

Science.gov (United States)

Sharma, K.; Srivastav, A. P.; Goswami, M.; Krishnan, Madangopal

2018-04-01

Titanate based ceramics (synroc) have been studied for immobilisation of nuclear wastes due to their high radiation and thermal stability. The aim of this study is to synthesis glass-ceramic with stable phases from alumino silicate glass composition and study the loading behavior of actinides in glass-ceramics. The effects of CaO and TiO2 addition on phase evolution and structural properties of alumino silicate based glasses with nominal composition x(10CaO-9TiO2)-y(10Na2O-5 Al2O3-56SiO2-10B2O3); where z = x/y = 1.4-1.8 are reported. The glasses are prepared by melt-quench technique and characterized for thermal and structural properties using DTA and Raman Spectroscopy. Glass transition and peak crystallization temperatures decrease with increase of CaO and TiO2 content, which implies the weakening of glass network and increased tendency of glasses towards crystallization. Sphene (CaTiSiO5) and perovskite (CaTiO3) crystalline phases are confirmed from XRD which are well known stable phase for conditioning of actinides. The microsturcture and elemental analysis indicate the presence of actinide in stable crystalline phases.

Viscosity and electrical conductivity of glass melts as a function of waste composition

International Nuclear Information System (INIS)

Plodinec, M.J.; Wiley, J.R.

1979-01-01

Radioactive waste at the Savannah River Plant contains high concentrations of nonradioactive compounds of iron and aluminum. Simulated waste compositions containing varying ratios of iron to aluminum were added to glass melts to determine the effect on the melt properties. Waste containing high-aluminum increased the melt viscosity, but waste containing high-iron reduced the melt viscosity. Aluminum and iron both reduced the melt conductivity

Conduction mechanism in bismuth silicate glasses containing titanium

International Nuclear Information System (INIS)

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

2014-01-01

Bismuth silicate glasses mixed with different concentrations of titanium dioxide having compositions xTiO 2 –(60−x)Bi 2 O 3 –40SiO 2 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 (σ dc ), so called crossover frequency (ω H ), 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 (H f ) and enthalpy of migration (H m ) 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 Ti 3+ and Ti 4+ 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

Water-fluxed melting of the continental crust: A review

Czech Academy of Sciences Publication Activity Database

Weinberg, R. F.; Hasalová, Pavlína

212-215, January (2015), s. 158-188 ISSN 0024-4937 Institutional support: RVO:67985530 Keywords : aqueous fluids * crustal anatexis * granites * silicate melts * water-fluxed melting Subject RIV: DB - Geology ; Mineralogy Impact factor: 3.723, year: 2015

Stable chromium isotopic composition of meteorites and metal-silicate experiments: Implications for fractionation during core formation

Science.gov (United States)

Bonnand, P.; Williams, H. M.; Parkinson, I. J.; Wood, B. J.; Halliday, A. N.

2016-02-01

We present new mass independent and mass dependent Cr isotope compositions for meteorites measured by double spike thermal ionisation mass spectrometry. Small differences in both mass independent 53Cr and 54Cr relative to the Bulk Silicate Earth are reported and are very similar to previously published values. Carbonaceous chondrites are characterised by an excess in 54Cr compared to ordinary and enstatite chondrites which make mass independent Cr isotopes a useful tool for distinguishing between meteoritic groups. Mass dependent stable Cr isotope compositions for the same samples are also reported. Carbonaceous and ordinary chondrites are identical within uncertainty with average δ53 Cr values of - 0.118 ± 0.040 ‰ and - 0.143 ± 0.074 ‰ respectively. The heaviest isotope compositions are recorded by an enstatite chondrite and a CO carbonaceous chondrite, both of which have relatively reduced chemical compositions implying some stable Cr isotope fractionation related to redox processes in the circumstellar disk. The average δ53 Cr values for chondrites are within error of the estimate for the Bulk Silicate Earth (BSE) also determined by double spiking. The lack of isotopic difference between chondritic material and the BSE provides evidence that Cr isotopes were not fractionated during core formation on Earth. A series of high-pressure experiments was also carried out to investigate stable Cr isotope fractionation between metal and silicate and no demonstrable fractionation was observed, consistent with our meteorites data. Mass dependent Cr isotope data for achondrites suggest that Cr isotopes are fractionated during magmatic differentiation and therefore further work is required to constrain the Cr isotopic compositions of the mantles of Vesta and Mars.

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

Science.gov (United States)

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

2015-01-01

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

The study of thermal interaction and microstructure of sodium silicate/bentonite composite under microwave radiation

Energy Technology Data Exchange (ETDEWEB)

Subannajui, Kittitat, E-mail: kittitat.sub@mahidol.ac.th [Faculty of Science, Mahidol University, 272 Rama VI Road, Ratchathewi District, Bangkok 10400 (Thailand); Center of Nanoscience and Nanotechnology Research Unit, Mahidol University, 272 Rama VI Road, Ratchathewi District, Bangkok 10400 (Thailand)

2016-12-01

The commercial heating oven usually consumes the power around 2500–3000 Watt and the temperature inside the oven is still below 350 °C. If we need to increase a temperature above 500 °C, a special heating setup with a higher power furnace is required. However, in this work, we propose a composite material that interacts with 2.45 GHz 500 Watt microwave and rapidly redeems the thermal energy with the temperature around 600–900 °C. The composite amorphous material easily forms liquid ceramics phase with a high temperature output and responds to the microwave radiation better than that of the solid phase. During the heating process, phase transformation occurs. This method is very effective and can be used to drastically reduce the power consumption of any heating process. - Highlights: • Amorphous phase transforms to liquid phase by microwave radiation. • Pure sodium silicate and pure bentonite cannot show temperature overshoot. • Silicate-bentonite composite shows a high temperature overshoot above 700 °C. • A rapid heating crucible for the annealing application is fabricated.

Redox dependent behaviour of molybdenum during magmatic processes in the terrestrial and lunar mantle: Implications for the Mo/W of the bulk silicate Moon

Science.gov (United States)

Leitzke, F. P.; Fonseca, R. O. C.; Sprung, P.; Mallmann, G.; Lagos, M.; Michely, L. T.; Münker, C.

2017-09-01

We present results of high-temperature olivine-melt, pyroxene-melt and plagioclase-melt partitioning experiments aimed at investigating the redox transition of Mo in silicate systems. Data for a series of other minor and trace elements (Sc, Ba, Sr, Cr, REE, Y, HFSE, U, Th and W) were also acquired to constrain the incorporation of Mo in silicate minerals. All experiments were carried out in vertical tube furnaces at 1 bar and temperatures ranging from ca. 1220 to 1300 °C. Oxygen fugacity was controlled via CO-CO2 gas mixtures and varied systematically from 5.5 log units below to 1.9 log units above the fayalite-magnetite-quartz (FMQ) redox buffer thereby covering the range in oxygen fugacities of terrestrial and lunar basalt genesis. Molybdenum is shown to be volatile at oxygen fugacities above FMQ and that its compatibility in pyroxene and olivine increases three orders of magnitude towards the more reducing conditions covered in this study. The partitioning results show that Mo is dominantly tetravalent at redox conditions below FMQ-4 and dominantly hexavalent at redox conditions above FMQ. Given the differences in oxidation states of the terrestrial (oxidized) and lunar (reduced) mantles, molybdenum will behave significantly differently during basalt genesis in the Earth (i.e. highly incompatible; average DMoperidotite/melt ∼ 0.008) and Moon (i.e. moderately incompatible/compatible; average DMoperidotite/melt ∼ 0.6). Thus, it is expected that Mo will strongly fractionate from W during partial melting in the lunar mantle, given that W is broadly incompatible at FMQ-5. Moreover, the depletion of Mo and the Mo/W range in lunar samples can be reproduced by simply assuming a primitive Earth-like Mo/W for the bulk silicate Moon. Such a lunar composition is in striking agreement with the Moon being derived from the primitive terrestrial mantle after core formation on Earth.

I-Xe dating of silicate and troilite from IAB iron meteorites

International Nuclear Information System (INIS)

Niemeyer, S.

1979-01-01

Silicate and troilite (FeS) from IAB irons were analyzed by the I-Xe technique. Four IAB silicate samples gave well-defined I-Xe ages [in millions of years relative to Bjurbole: - 3.7 +- 0.3 for Woodbine, -0.7 +- 0.6 for Mundrabilla, + 1.4 +- 0.7 for Copiapo, and +2.6 +- 0.6 for Landes. The ( 129 Xe/ 132 Xe)sub(trapped) ratios are consistent with previous values for chondrites, with the exception of Landes which has an extraordinary trapped ratio of 3.5 +- 0.2. Both analyses of silicate from Pitts gave anomalous I-Xe patterns. Troilite samples were also analyzed: Pitts troilite gave a complex I-Xe pattern, which suggests an age of +17 Myr; Mundrabilla troilite defined a good I-Xe correlation, which after correction for neutron capture on 128 Te gave an age of -10.8 +- 0.7 Myr. Thus, low-melting troilite predates high-melting silicate in Mundrabilla. Abundances of Ga, Ge, and Ni in metal from these meteorites are correlated with I-Xe ages of the silicate; meteorites with older silicates have greater Ni contents. No model easily accounts for this result as well as other properties of IAB irons; nevertheless, these results, taken at face value, favour a nebular formation model. The great age of troilite from Mundrabilla suggests that this troilite formed in a different nebular region from the silicate and metal, and was later mechanically mixed with these other phases. The correlation between the trace elements in the metal and the I-Xe ages of the silicate provides one of the first known instances in which another well-defined meteoritic property correlates with I-Xe ages. In addition, almost all the 129 Xe in Mundrabilla silicate (etched in acid) was correlated with 128 Xe. These two results further support the validity of the I-Xe dating method. (author)

A volatile-rich Earth's core inferred from melting temperature of core materials

Science.gov (United States)

Morard, G.; Andrault, D.; Antonangeli, D.; Nakajima, Y.; Auzende, A. L.; Boulard, E.; Clark, A. N.; Lord, O. T.; Cervera, S.; Siebert, J.; Garbarino, G.; Svitlyk, V.; Mezouar, M.

2016-12-01

Planetary cores are mainly constituted of iron and nickel, alloyed with lighter elements (Si, O, C, S or H). Understanding how these elements affect the physical and chemical properties of solid and liquid iron provides stringent constraints on the composition of the Earth's core. In particular, melting curves of iron alloys are key parameter to establish the temperature profile in the Earth's core, and to asses the potential occurrence of partial melting at the Core-Mantle Boundary. Core formation models based on metal-silicate equilibration suggest that Si and O are the major light element components1-4, while the abundance of other elements such as S, C and H is constrained by arguments based on their volatility during planetary accretion5,6. Each compositional model implies a specific thermal state for the core, due to the different effect that light elements have on the melting behaviour of Fe. We recently measured melting temperatures in Fe-C and Fe-O systems at high pressures, which complete the data sets available both for pure Fe7 and other binary alloys8. Compositional models with an O- and Si-rich outer core are suggested to be compatible with seismological constraints on density and sound velocity9. However, their crystallization temperatures of 3650-4050 K at the CMB pressure of 136 GPa are very close to, if not higher than the melting temperature of the silicate mantle and yet mantle melting above the CMB is not a ubiquitous feature. This observation requires significant amounts of volatile elements (S, C or H) in the outer core to further reduce the crystallisation temperature of the core alloy below that of the lower mantle. References 1. Wood, B. J., et al Nature 441, 825-833 (2006). 2. Siebert, J., et al Science 339, 1194-7 (2013). 3. Corgne, A., et al Earth Planet. Sc. Lett. 288, 108-114 (2009). 4. Fischer, R. a. et al. Geochim. Cosmochim. Acta 167, 177-194 (2015). 5. Dreibus, G. & Palme, H. Geochim. Cosmochim. Acta 60, 1125-1130 (1995). 6. Mc

Shock compression behavior of bi-material powder composites with disparate melting temperatures

International Nuclear Information System (INIS)

Sullivan, Kyle T.; Swift, Damian; Barham, Matthew; Stölken, James; Kuntz, Joshua; Kumar, Mukul

2014-01-01

Laser driven experiments were used to investigate the shock compression behavior of powder processed Bismuth/Tungsten (Bi/W) composite samples. The constituents provide different functionality to the composite behavior as Bi could be shock melted at the pressures attained in this work, while the W could not. Samples were prepared by uniaxial pressing, and the relative density was measured as a function of particle size, applied pressure, and composition for both hot and cold pressing conditions. This resulted in sample densities between 73% and 99% of the theoretical maximum density, and also noticeable differences in microstructure in the hot and cold pressed samples. The compression waves were generated with a 1.3 × 1.3 mm square spot directly onto the surface of the sample, using irradiances between 10 12 and 10 13  W/cm 2 , which resulted in calculated peak pressures between 50 and 150 GPa within a few micrometers. Sample recovery and post-mortem analysis revealed the formation of a crater on the laser drive surface, and the depth of this crater corresponded to the depth to which the Bi had been melted. The melt depth was found to be primarily a function of residual porosity and composition, and ranged from 167 to 528 μm. In general, a higher porosity led to a larger melt depth. Direct numerical simulations were performed, and indicated that the observed increase in melt depth for low-porosity samples could be largely attributed to increased heating associated with work done for pore collapse. However, the relative scaling was sensitive to composition, with low volume fraction Bi samples exhibiting a much stronger dependence on porosity than high Bi content samples. Select samples were repeated using an Al foil ablator, but there were no noticeable differences ensuring that the observed melting was indeed pressure-driven and was not a result of direct laser heating. The resultant microstructures and damage near the spall surface were also investigated

Calculation of Oxygen Fugacity in High Pressure Metal-Silicate Experiments and Comparison to Standard Approaches

Science.gov (United States)

Righter, K.; Ghiorso, M.

2009-01-01

Calculation of oxygen fugacity in high pressure and temperature experiments in metal-silicate systems is usually approximated by the ratio of Fe in the metal and FeO in the silicate melt: (Delta)IW=2*log(X(sub Fe)/X(sub FeO)), where IW is the iron-wustite reference oxygen buffer. Although this is a quick and easy calculation to make, it has been applied to a huge variety of metallic (Fe- Ni-S-C-O-Si systems) and silicate liquids (SiO2, Al2O3, TiO2, FeO, MgO, CaO, Na2O, K2O systems). This approach has surely led to values that have little meaning, yet are applied with great confidence, for example, to a terrestrial mantle at "IW-2". Although fO2 can be circumvented in some cases by consideration of Fe-M distribution coefficient, these do not eliminate the effects of alloy or silicate liquid compositional variation, or the specific chemical effects of S in the silicate liquid, for example. In order to address the issue of what the actual value of fO2 is in any given experiment, we have calculated fO2 from the equilibria 2Fe (metal) + SiO2 (liq) + O2 = Fe2SiO4 (liq).

A model of sulphur solubility for hydrous mafic melts: application to the determination of magmatic fluid compositions of Italian volcanoes

Directory of Open Access Journals (Sweden)

M. Pichavant

2005-06-01

Full Text Available We present an empirical model of sulphur solubility that allows us to calculate f S2 if P, T, fO2 and the melt composition, including H2O and S, are known. The model is calibrated against three main experimental data bases consisting in both dry and hydrous silicate melts. Its prime goal is to calculate the f S2 of hydrous basalts that currently lack experimental constraints of their sulphur solubility behaviour. Application of the model to Stromboli, Vesuvius, Vulcano and Etna eruptive products shows that the primitive magmas found at these volcanoes record f S2 in the range 0.1-1 bar. In contrast, at all volcanoes the magmatic evolution is marked by dramatic variations in f S2 that spreads over up to 9 orders of magnitude. The f S2 can either increase during differentiation or decrease during decompression to shallow reservoirs, and seems to be related to closed versus open conduit conditions, respectively. The calculated f S2 shows that the Italian magmas are undersaturated in a FeS melt, except during closed conduit conditions, in which case differentiation may eventually reach conditions of sulphide melt saturation. The knowledge of f S2, fO2 and fH2O allows us to calculate the fluid phase composition coexisting with magmas at depth in the C-O-H-S system. Calculated fluids show a wide range in composition, with CO2 mole fractions of up to 0.97. Except at shallow levels, the fluid phase is generally dominated by CO2 and H2O species, the mole fractions of SO2 and H2S rarely exceeding 0.05 each. The comparison between calculated fluid compositions and volcanic gases shows that such an approach should provide constraints on both the depth and mode of degassing, as well as on the amount of free fluid in magma reservoirs. Under the assumption of a single step separation of the gas phase in a closed-system condition, the application to Stromboli and Etna suggests that the main reservoirs feeding the eruptions and persistent

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.

Low melting high lithia glass compositions and methods

Science.gov (United States)

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

2000-01-01

The invention relates to methods of vitrifying waste and for lowering the melting point of glass forming systems by including lithia formers in the glass forming composition in significant amounts, typically from about 0.16 wt % to about 11 wt %, based on the total glass forming oxides. The lithia is typically included as a replacement for alkali oxide glass formers that would normally be present in a particular glass forming system. Replacement can occur on a mole percent or weight percent basis, and typically results in a composition wherein lithia forms about 10 wt % to about 100 wt % of the alkali oxide glass formers present in the composition. The present invention also relates to the high lithia glass compositions formed by these methods. The invention is useful for stabilization of numerous types of waste materials, including aqueous waste streams, sludge solids, mixtures of aqueous supernate and sludge solids, combinations of spent filter aids from waste water treatment and waste sludges, supernate alone, incinerator ash, incinerator offgas blowdown, or combinations thereof, geological mine tailings and sludges, asbestos, inorganic filter media, cement waste forms in need of remediation, spent or partially spent ion exchange resins or zeolites, contaminated soils, lead paint, etc. The decrease in melting point achieved by the present invention desirably prevents volatilization of hazardous or radioactive species during vitrification.

Solvent free low-melt viscosity imide oligomers and thermosetting polymide composites

Science.gov (United States)

Chuang, Chun-Hua (Inventor)

2012-01-01

.[.This invention relates to the composition and a solvent-free process for preparing novel imide oligomers and polymers specifically formulated with effective amounts of a dianhydride such as 2,3,3',4-biphenyltetra carboxylic dianydride (a-BPDA), at least one aromatic diamine and an endcapped of 4-phenylethynylphthalic anhydride (PEPA) or nadic anhydride to produce imide oligomers that possess a low-melt viscosity of 1-60 poise at 260-280.degree. C. When the imide oligomer melt is cured at about 371.degree. C. in a press or autoclave under 100-500 psi, the melt resulted in a thermoset polyimide having a glass transition temperature (T.sub.g) equal to and above 310.degree. C. A novel feature of this process is that the monomers; namely the dianhydrides, diamines and the endcaps, are melt processable to form imide oligomers at temperatures ranging between 232-280.degree. C. (450-535.degree. F.) without any solvent. These low-melt imide oligomers can be easily processed by resin transfer molding (RTM), vacuum-assisted resin transfer molding (VARTM) or the resin infusion process with fiber preforms e.g. carbon, glass or quartz preforms to produce polyimide matrix composites with 288-343.degree. C. (550-650.degree. F.) high temperature performance capability..]. .Iadd.This invention relates to compositions and a solvent-free reaction process for preparing imide oligomers and polymers specifically derived from effective amounts of dianhydrides such as 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA), at least one aromatic polyamine and an end-cap such as 4-phenylethynyphthalic anhydride (PEPA) or nadic anhydride to produce imide oligomers that possess a low-melt viscosity of 1-60 poise at 260.degree. C.-280.degree. C..Iaddend.

The preparation and mechanical properties of carbon–carbon/lithium–aluminum–silicate composite joints

International Nuclear Information System (INIS)

Li, Ke-zhi; Wang, Jie; Ren, Xiao-bin; Li, He-jun; Li, Wei; Li, Zhao-qian

2013-01-01

Highlights: ► First study to join carbon cloth laminated C–C composites to LAS glass–ceramics. ► First study on the flexural property of C–C/LAS joints at different temperatures. ► The joint flexural strength at 800 °C can increase 14.1% than at room temperature. ► A quasi-ductile fracture behavior can be found in the C–C/LAS joints. -- Abstract: Silica carbide modified carbon cloth laminated C–C composites have been successfully joined to lithium–aluminum–silicate (LAS) glass–ceramics using magnesium–aluminum–silicate (MAS) glass–ceramics as interlayer by vacuum hot-press technique. The microstructure, mechanical properties and fracture mechanism of C–C/LAS composite joints were investigated. SiC coating modified the wettability between C–C composites and LAS glass–ceramics. Three continuous and homogenous interfaces (i.e. C–C/SiC, SiC/MAS and MAS/LAS) were formed by element interdiffusions and chemical reactions, which lead to a smooth transition from C–C composites to LAS glass–ceramics. The C–C/LAS joints have superior flexural property with a quasi-ductile behavior. The average flexural strength of C–C/LAS joints can be up to 140.26 MPa and 160.02 MPa at 25 °C and 800 °C, respectively. The average shear strength of C–C/LAS joints achieves 21.01 MPa and the joints are apt to fracture along the SiC/MAS interface. The high retention of mechanical properties at 800 °C makes the joints to be potentially used in a broad temperature range as structural components.

Mechanical and microstructure of reinforced hydroxyapatite/calcium silicate nano-composites materials

International Nuclear Information System (INIS)

Beheri, Hanan H.; Mohamed, Khaled R.; El-Bassyouni, Gehan T.

2013-01-01

Highlights: ► Nano sized of HA and CS powders were prepared. ► Mechanical of HACS composites enhanced with content of CS. ► The apatite formation onto the composites is proved. -- Abstract: In this study, the nano sized hydroxyapatite (HA) and calcium silicate (CS) powders prepared by both chemical precipitation and sol–gel methods respectively. Biphasic nano-composites materials containing different ratios of HA and CS were fabricated and assessed using X-ray diffraction (XRD), Fourier transmission infrared reflectance (FT-IR), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) techniques. The effect of variation of ratios between HA and CS on mechanical properties, microstructure and in vitro study was studied. The results proved that the mechanical properties were enhanced with increasing the CS ratio in the composite. In vitro study proved the formation and nucleation of apatite onto composites surfaces which contain low content of CS after one week of immersion. Finally, it is concluded that the HACS composites containing high HA content at the expense of CS content will be promising for bone substitute’s applications, especially in load bearing sites.

Solvent Free Low-Melt Viscosity Imide Oligomers And Thermosetting Polyimide Composites

Science.gov (United States)

Chuang, CHun-Hua (Inventor)

2006-01-01

This invention relates to the composition and a solvent-free process for preparing novel imide oligomers and polymers specifically formulated with effective amounts of a dianhydride such as 2,3,3',4-biphenyltetra carboxylic dianydride (a-BPDA), at least one aromatic diamine' and an endcapped of 4-phenylethynylphthalic anhydride (PEPA) or nadic anhydride to produce imide oligomers that possess a low-melt viscosity of 1-60 poise at 260-280" C. When the imide oligomer melt is cured at about 371 C. in a press or autoclave under 100-500 psi, the melt resulted in a thermoset polyimide having a glass transition temperature (T(sub g)) equal to and above 310 C. A novel feature of this process is that the monomers; namely the dianhydrides, diamines and the endcaps, are melt processable to form imide oligomers at temperatures ranging between 232-280 C. (450-535 F) without any solvent. These low-melt imide oligomers can be easily processed by resin transfer molding (RTM), vacuum-assisted resin transfer molding (VARTM) or the resin infusion process with fiber preforms e.g. carbon, glass or quartz preforms to produce polyimide matrix composites with 288-343C (550-650 F) high temperature performance capability.

Composition and origin of rhyolite melt intersected by drilling in the Krafla geothermal field, Iceland

Science.gov (United States)

Zierenberg, R.A.; Schiffman, P.; Barfod, G.H.; Lesher, C.E.; Marks, N.E.; Lowenstern, Jacob B.; Mortensen, A.K.; Pope, E.C.; Bird, D.K.; Reed, M.H.; Friðleifsson, G.O.; Elders, W.A.

2013-01-01

The Iceland Deep Drilling Project Well 1 was designed as a 4- to 5-km-deep exploration well with the goal of intercepting supercritical hydrothermal fluids in the Krafla geothermal field, Iceland. The well unexpectedly drilled into a high-silica (76.5 % SiO2) rhyolite melt at approximately 2.1 km. Some of the melt vesiculated while extruding into the drill hole, but most of the recovered cuttings are quenched sparsely phyric, vesicle-poor glass. The phenocryst assemblage is comprised of titanomagnetite, plagioclase, augite, and pigeonite. Compositional zoning in plagioclase and exsolution lamellae in augite and pigeonite record changing crystallization conditions as the melt migrated to its present depth of emplacement. The in situ temperature of the melt is estimated to be between 850 and 920 °C based on two-pyroxene geothermometry and modeling of the crystallization sequence. Volatile content of the glass indicated partial degassing at an in situ pressure that is above hydrostatic (~16 MPa) and below lithostatic (~55 MPa). The major element and minor element composition of the melt are consistent with an origin by partial melting of hydrothermally altered basaltic crust at depth, similar to rhyolite erupted within the Krafla Caldera. Chondrite-normalized REE concentrations show strong light REE enrichment and relative flat patterns with negative Eu anomaly. Strontium isotope values (0.70328) are consistent with mantle-derived melt, but oxygen and hydrogen isotope values are depleted (3.1 and −118 ‰, respectively) relative to mantle values. The hydrogen isotope values overlap those of hydrothermal epidote from rocks altered by the meteoric-water-recharged Krafla geothermal system. The rhyolite melt was emplaced into and has reacted with a felsic intrusive suite that has nearly identical composition. The felsite is composed of quartz, alkali feldspar, plagioclase, titanomagnetite, and augite. Emplacement of the rhyolite magma has resulted in partial melting of

Evolution of silicic magmas in the Kos-Nisyros volcanic center: cycles associated with caldera collapse

Science.gov (United States)

Ruprecht, J. S.; Bachmann, O.; Deering, C. D.; Huber, C.; Skopelitis, A.; Schnyder, C.

2010-12-01

Multiple eruptions of silicic magma (dacite and rhyolites) occurred over the last ~ 3 My in the Kos-Nisyros volcanic center (eastern Aegean sea). Over the course of this period, magmas have changed from hornblende-biotite rich units with low eruption temperatures (≤750-800 °C; Kefalos and Kos units) to hotter (>800-850 °C), pyroxene-bearing units (Nisyros units) and are transitioning back to colder magmas (Yali units). Using bulk-rock compositions, mineral chemistry, and zircon Hf isotopes, we show that the two different types of silicic magmas followed the same differentiation trend; they all evolved by crystal fractionation (and minor assimilation) from parents with intermediate compositions characterized by high Sr/Y and low Nb content, following a wet, high oxygen fugacity liquid line of descent typical of subduction zones. As the transition between the Kos-Kefalos and Nisyros-type magmas occurred immediately and abruptly after the major caldera collapse in the area (the 161 ky Kos Plateau Tuff; KPT), we suggest that the efficient emptying of the magma chamber during the KPT drew most of the eruptible magma out and partly froze the silicic magma source zone in the upper crust due to rapid unloading, decompression and resulting crystallization. Therefore, the system had to reinstate a shallow silicic production zone from more mafic parents, recharged at temperatures typically around 850-900 °C from the mid to lower crust. The first silicic eruptions evolving from these parents after the caldera collapse (Nisyros units) were thus slightly hotter and less evolved than the Kefalos-Kos package. However, with time, the upper crustal intermediate mush grew and cooled, leading to interstitial melt compositions reaching again the highly-evolved, cold state that prevailed prior to the Kefalos-Kos. The recent (albeit not precisely dated) eruption of the high-SiO2 rhyolite of Yali suggests that another large, potentially explosive magma chamber is presently building

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...

Synthesis of non-siliceous mesoporous oxides.

Science.gov (United States)

Gu, Dong; Schüth, Ferdi

2014-01-07

Mesoporous non-siliceous oxides have attracted great interest due to their unique properties and potential applications. Since the discovery of mesoporous silicates in 1990s, organic-inorganic assembly processes by using surfactants or block copolymers as soft templates have been considered as a feasible path for creating mesopores in metal oxides. However, the harsh sol-gel conditions and low thermal stabilities have limited the expansion of this method to various metal oxide species. Nanocasting, using ordered mesoporous silica or carbon as a hard template, has provided possibilities for preparing novel mesoporous materials with new structures, compositions and high thermal stabilities. This review concerns the synthesis, composition, and parameter control of mesoporous non-siliceous oxides. Four synthesis routes, i.e. soft-templating (surfactants or block copolymers as templates), hard-templating (mesoporous silicas or carbons as sacrificial templates), colloidal crystal templating (3-D ordered colloidal particles as a template), and super lattice routes, are summarized in this review. Mesoporous metal oxides with different compositions have different properties. Non-siliceous mesoporous oxides are comprehensively described, including a discussion of constituting elements, synthesis, and structures. General aspects concerning pore size control, atomic scale crystallinity, and phase control are also reviewed.

Metal/silicate partitioning of Pt and the origin of the "late veneer"

Science.gov (United States)

Ertel, W.; Walter, M. J.; Drake, M. J.; Sylvester, P. J.

2002-12-01

Highly siderophile elements (HSEs) are perfect tools for investigating core forming processes in planetary bodies due to their Fe-loving (siderophile) geochemical behavior. Tremendous scientific effort was invested into this field during the past 10 years - mostly in 1 atm experiments. However, little is known about their high-pressure geochemistry and partitioning behavior between core and mantle forming phases. This knowledge is essential to distinguish between equilibrium (Magma Ocean) and non-equilibrium (heterogeneous accretion, late veneer) models for the accretion history for the early Earth. We therefore chose to investigate the partitioning behavior of Pt up to pressures of 140 kbar (14 GPa) and temperatures of 1950°C. The used melt composition - identical to melt systems used in 1 atm experiments - is the eutectic composition of Anorthite-Diopside (AnDi), a pseudo-basalt. A series of runs were performed which were internaly buffered by the piston cylinder apparatus, and were followed by duplicate experiments buffered in the AnDi-C-CO2 system. These experiments constitute reversals since they approach equilibrium from an initially higher and lower Pt solubility (8 ppm in the non-buffered runs, and essentially Pt free in the buffered runs). Experimental charges were encapsulated in Pt capsules which served as source for Pt. Experiments up to 20 kbar were performed in a Quickpress piston cylinder apparatus, while experiments at higher pressures were performed in a Walker-type (Tucson, AZ) and a Kawai-type (Misasa, Japan) multi anvil apparatus. Time series experiments were performed in piston-cylinder runs to determine minimum run durations for the achievement of equilibrium, and to guarantee high-quality partitioning data. 6 hours was found to be sufficient to obtain equilibrium. In practice, all experiments exceeded 12 hours to assure equilibrium. In a second set of runs the temperature dependence of the partitioning behavior of Pt was investigated between

Mantle melting and melt refertilization beneath the Southwest Indian Ridge: Mineral composition of abyssal peridotites

Science.gov (United States)

Chen, Ling; Zhu, Jihao; Chu, Fengyou; Dong, Yan-hui; Liu, Jiqiang; Li, Zhenggang; Zhu, Zhimin; Tang, Limei

2017-04-01

As one of the slowest spreading ridges of the global ocean ridge system, the Southwest Indian Ridge (SWIR) is characterized by discontinued magmatism. The 53°E segment between the Gallieni fracture zone (FZ) (52°20'E) and the Gazelle FZ (53°30'E) is a typical amagmatic segment (crustal thickness 1cm) Opx, and Mg-rich mineral compositions akin to harzburgite xenoliths that sample old continental lithospheric mantle (Kelemen et al., 1998). Melt refertilization model shows that Group 2 peridotites were affected by an enriched low-degree partial melt from the garnet stability field. These results indicate that depleted mantle which experiences ancient melting event are more sensitive to melt refertilization, thus may reduce the melt flux, leading to extremely thin crust at 53°E segment. This research was granted by the National Basic Research Programme of China (973 programme) (grant No. 2013CB429705) and the Fundamental Research Funds of Second Institute of Oceanography, State Oceanic Administration (JG1603, SZ1507). References: Johnson K T M, Dick H J B, Shimizu N. Melting in the oceanic upper mantle: An ion microprobe study of diopsides in abyssal peridotites[J]. Journal of Geophysical Research, 1990, 95(B3):2661-2678. Kelemen P B, Hart S R, Bernstein S. Silica enrichment in the continental upper mantle via melt/rock reaction[J]. Earth & Planetary Science Letters, 1998, 164(1-2):387-406. Zhou H, Dick H J. Thin crust as evidence for depleted mantle supporting the Marion Rise.[J]. Nature, 2013, 494(7436):195-200.

Petrological Geodynamics of Mantle Melting I. AlphaMELTS + Multiphase Flow: Dynamic Equilibrium Melting, Method and Results

Directory of Open Access Journals (Sweden)

Massimiliano Tirone

2017-10-01

Full Text Available The complex process of melting in the Earth's interior is studied by combining a multiphase numerical flow model with the program AlphaMELTS which provides a petrological description based on thermodynamic principles. The objective is to address the fundamental question of the effect of the mantle and melt dynamics on the composition and abundance of the melt and the residual solid. The conceptual idea is based on a 1-D description of the melting process that develops along an ideal vertical column where local chemical equilibrium is assumed to apply at some level in space and time. By coupling together the transport model and the chemical thermodynamic model, the evolution of the melting process can be described in terms of melt distribution, temperature, pressure and solid and melt velocities but also variation of melt and residual solid composition and mineralogical abundance at any depth over time. In this first installment of a series of three contributions, a two-phase flow model (melt and solid assemblage is developed under the assumption of complete local equilibrium between melt and a peridotitic mantle (dynamic equilibrium melting, DEM. The solid mantle is also assumed to be completely dry. The present study addresses some but not all the potential factors affecting the melting process. The influence of permeability and viscosity of the solid matrix are considered in some detail. The essential features of the dynamic model and how it is interfaced with AlphaMELTS are clearly outlined. A detailed and explicit description of the numerical procedure should make this type of numerical models less obscure. The general observation that can be made from the outcome of several simulations carried out for this work is that the melt composition varies with depth, however the melt abundance not necessarily always increases moving upwards. When a quasi-steady state condition is achieved, that is when melt abundance does not varies significantly

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.

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

Energy Technology Data Exchange (ETDEWEB)

Sabri, T.; Jäger, C. [Laboratory Astrophysics Group of the Max Planck Institute for Astronomy at the Friedrich Schiller University Jena Institute of Solid State Physics, Helmholtzweg 3, D-07743 Jena (Germany); Gavilan, L.; Lemaire, J. L.; Vidali, G. [Observatoire de Paris/Université de Cergy-Pontoise, 5 mail Gay Lussac, F-95000 Cergy-Pontoise (France); Mutschke, H. [Laboratory Astrophysics Group of the Astrophysical Institute and University Observatory, Friedrich Schiller University Jena Schillergässchen 3, D-07743 Jena (Germany); Henning, T., E-mail: tolou.sabri@uni-jena.de [Max Planck Institute for Astronomy Königstuhl 17, D-69117 Heidelberg (Germany)

2014-01-10

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

VIBROCASTING CRUCIBLES OF DIFFERENT COMPOSITION FOR FRYING INDUCTION MELTING ALLOYS

OpenAIRE

V. V. Primachenko; V. V. Martynenko; I. G. Szulik; S. V. Chaplyanko; L. V. Gritsyuk; L. P. Tkachenko

2012-01-01

It is shown that PSC «UKRNIIO them. A.S.Berezhnogo  has developed technologies for a wide range of induction melting temperature alloys and started commercial production of crucibles of different composition.

Structure and properties of polymer-silicate nanocomposites based on polytetrafluoroethylene

Energy Technology Data Exchange (ETDEWEB)

Sleptsova, Sardana A.; Okhlopkova, Aitalina A. [North-Eastern Federal University, Yakutsk (Russian Federation)

2011-07-01

The results of physicomechanical, tribological , and structural investigation of polytetrafluoroethylene based polymers and natural layered silicates are reported. It is shown that the tribological behaviour of the composites can be significantly improved by introducing a small amount of activated silicates. The results of structural examination of the composite friction surfaces by scanning-probe microscopy and IR spectroscopy are discussed. Key words: polytetrafluoroethylene, layered silicates, wear resistance, friction coefficient, structure, IR-spectrum.

Compressive strength and magnetic properties of calcium silicate-zirconia-iron (III) oxide composite cements

Science.gov (United States)

Ridzwan, Hendrie Johann Muhamad; Shamsudin, Roslinda; Ismail, Hamisah; Yusof, Mohd Reusmaazran; Hamid, Muhammad Azmi Abdul; Awang, Rozidawati Binti

2018-04-01

In this study, ZrO2 microparticles and γ-Fe2O3 nanoparticles have been added into calcium silicate based cements. The purpose of this experiment was to investigate the compressive strength and magnetic properties of the prepared composite cement. Calcium silicate (CAS) powder was prepared by hydrothermal method. SiO2 and CaO obtained from rice husk ash and limestone respectively were autoclaved at 135 °C for 8 h and sintered at 950°C to obtain CAS powder. SiO2:CaO ratio was set at 45:55. CAS/ZrO2 sample were prepared with varying ZrO2 microparticles concentrations by 0-40 wt. %. Compressive strength value of CAS/ZrO2 cements range from 1.44 to 2.44 MPa. CAS/ZrO2/γ-Fe2O3 sample with 40 wt. % ZrO2 were prepared with varying γ-Fe2O3 nanoparticles concentrations (1-5 wt. %). The additions of γ-Fe2O3 nanoparticles showed up to twofold increase in the compressive strength of the cement. X-Ray diffraction (XRD) results confirm the formation of mixed phases in the produced composite cements. Vibrating sample magnetometer (VSM) analysis revealed that the ferromagnetic behaviour has been observed in CAS/ZrO2/γ-Fe2O3 composite cements.

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.

The application of silicon and silicates in dentistry: a review.

Science.gov (United States)

Lührs, A-K; Geurtsen, Werner

2009-01-01

Silicates and silicate-based compounds are frequently used materials in dentistry. One of their major applications is their use as fillers in different dental filling materials such as glass-ionomer cements, compomers, composites, and adhesive systems. In these materials, the fillers react with acids during the setting process or they improve the mechanical properties by increasing physical resistance, thermal expansion coefficient and radiopacity in acrylic filling materials. They also reduce polymerization shrinkage, and increase esthetics as well as handling properties. Furthermore, silicates are used for the tribochemical silication of different surfaces such as ceramics or alloys. The silicate layer formed in this process is the chemical basis for silanes that form a bond between this layer and the organic composite matrix. It also provides a micromechanical bond between the surface of the material and the composite matrix. Silicates are also a component of dental ceramics, which are frequently used in dentistry, for instance for veneers, inlays, and onlays, for denture teeth, and for full-ceramic crowns or as crown veneering materials.

Detection of structural heterogeneity of glass melts

DEFF Research Database (Denmark)

Yue, Yuanzheng

2004-01-01

The structural heterogeneity of both supercooled liquid and molten states of silicate has been studied using calorimetric method. The objects of this study are basaltic glasses and liquids. Two experimental approaches are taken to detect the structural heterogeneity of the liquids. One is the hyp......The structural heterogeneity of both supercooled liquid and molten states of silicate has been studied using calorimetric method. The objects of this study are basaltic glasses and liquids. Two experimental approaches are taken to detect the structural heterogeneity of the liquids. One...... is the hyperquench-anneal-calorimetric scan approach, by which the structural information of a basaltic supercooled liquid and three binary silicate liquids is acquired. Another is the calorimetrically repeated up- and downscanning approach, by which the structural heterogeneity, the intermediate range order...... is discussed. The ordered structure of glass melts above the liquidus temperature is indirectly characterized by use of X-ray diffraction method. The new approaches are of importance for monitoring the glass melting and forming process and for improving the physical properties of glasses and glass fibers....

Shock melting and vaporization of lunar rocks and minerals.

Science.gov (United States)

Ahrens, T. J.; O'Keefe, J. D.

1972-01-01

The entropy associated with the thermodynamic states produced by hypervelocity meteoroid impacts at various velocities are calculated for a series of lunar rocks and minerals and compared with the entropy values required for melting and vaporization. Taking into account shock-induced phase changes in the silicates, we calculate that iron meteorites impacting at speeds varying from 4 to 6 km/sec will produce shock melting in quartz, plagioclase, olivine, and pyroxene. Although calculated with less certainty, impact speeds required for incipient vaporization vary from 7 to 11 km/sec for the range of minerals going from quartz to periclase for aluminum (silicate-like) projectiles. The impact velocities, which are required to induce melting in a soil, are calculated to be in the range of 3 to 4 km/sec, provided thermal equilibrium is achieved in the shock state.

Eruption style at Kīlauea Volcano in Hawai‘i linked to primary melt composition

Science.gov (United States)

Sides. I.R.,; Edmonds, M.; Maclennan, J.; Swanson, Don; Houghton, Bruce F.

2014-01-01

Explosive eruptions at basaltic volcanoes have been linked to gas segregation from magmas at shallow depths in the crust. The composition of primary melts formed at greater depths was thought to have little influence on eruptive style. Ocean island basaltic volcanoes are the product of melting of a geochemically heterogeneous mantle plume and are expected to give rise to heterogeneous primary melts. This range in primary melt composition, particularly with respect to the volatile components, will profoundly influence magma buoyancy, storage and eruption style. Here we analyse the geochemistry of a suite of melt inclusions from 25 historical eruptions at the ocean island volcano of Kīlauea, Hawai‘i, over the past 600 years. We find that more explosive styles of eruption at Kīlauea Volcano are associated statistically with more geochemically enriched primary melts that have higher volatile concentrations. These enriched melts ascend faster and retain their primary nature, undergoing little interaction with the magma reservoir at the volcano’s summit. We conclude that the eruption style and magma-supply rate at Kīlauea are fundamentally linked to the geochemistry of the primary melts formed deep below the volcano. Magmas might therefore be predisposed towards explosivity right at the point of formation in their mantle source region.

Melt compositions and processes in the kimberlite provience of southern West Greenland

DEFF Research Database (Denmark)

Pilbeam, Llewellyn; Nielsen, Troels; Waight, Tod Earle

2011-01-01

] whilst the silica content and H2O/CO2 ratio of the bulk rocks increases towards Sisimuit [2, 3]. A common carbonatite rich end-member is implicated [2]. This is in contrast to the prevailing dogma of a continuum from carbonatite though aillikite to kimberlite with increasing melting degree [4......]. The authors have demonstrated that a process of DFC (digestion fractional crystallisation) whereby the cognate olivine crystallisation is coupled to entrained xenocrystic orthopyroxene assimilation is a key process during the formation of the Majugaa occurrence of the Manitsoq region [5]. Mass balance...... considerations are here applied to the Majuagaa bulk rock in term of the DFC mechanism obtaining an estimate of parental melt and magma composition for the Majuagaa kimberlite. We use bulk rock major and trace element geochemistry together with mineral chemistry to investigate the range of melt compositions...

VIBROCASTING CRUCIBLES OF DIFFERENT COMPOSITION FOR FRYING INDUCTION MELTING ALLOYS

Directory of Open Access Journals (Sweden)

V. V. Primachenko

2012-01-01

Full Text Available It is shown that PSC «UKRNIIO them. A.S.Berezhnogo  has developed technologies for a wide range of induction melting temperature alloys and started commercial production of crucibles of different composition.

The partitioning of sulfur between multicomponent aqueous fluids and felsic melts

Science.gov (United States)

Binder, Bernd; Wenzel, Thomas; Keppler, Hans

2018-02-01

Sulfur partitioning between melt and fluid phase largely controls the environmental impact of volcanic eruptions. Fluid/melt partitioning data also provide the physical basis for interpreting changes in volcanic gas compositions that are used in eruption forecasts. To better constrain some variables that control the behavior of sulfur in felsic systems, in particular the interaction between different volatiles, we studied the partitioning of sulfur between aqueous fluids and haplogranitic melts at 200 MPa and 750-850 °C as a function of oxygen fugacity (Ni-NiO or Re-ReO2 buffer), melt composition (Al/(Na + K) ratio), and fluid composition (NaCl and CO2 content). The data confirm a first-order influence of oxygen fugacity on the partitioning of sulfur. Under "reducing conditions" (Ni-NiO buffer), D fluid/melt is nearly one order of magnitude larger (323 ± 14 for a metaluminous melt) than under "oxidizing conditions" (Re-ReO2 buffer; 74 ± 5 for a metaluminous melt). This effect is likely related to a major change in sulfur speciation in both melt and fluid. Raman spectra of the quenched fluids show the presence of H2S and HS- under reducing conditions and of SO4 2- and HSO4 - under oxidizing conditions, while SO2 is undetectable. The latter observation suggests that already at the Re-ReO2 buffer, sulfur in the fluid is almost completely in the S6+ state and, therefore, more oxidized than expected according to current models. CO2 in the fluid (up to x CO2 = 0.3) has no effect on the fluid/melt partitioning of sulfur, neither under oxidizing nor under reducing conditions. However, the effect of NaCl depends on redox state. While at oxidizing conditions, D fluid/melt is independent of x NaCl, the fluid/melt partition coefficient strongly decreases with NaCl content under reducing conditions, probably due to a change from H2S to NaSH as dominant sulfur species in the fluid. A decrease of D fluid/melt with alkali content in the melt is observed over the entire

Crystallization and melting behavior of multi-walled carbon nanotube-reinforced nylon-6 composites

NARCIS (Netherlands)

Phang, In Yee; Ma, Jianhua; Shen, Lu; Liu, Tianxi; Zhang, Wei-De

2006-01-01

The crystallization and melting behavior of neat nylon-6 (PA6) and multi-walled carbon nanotubes (MWNTs)/PA6 composites prepared by simple melt-compounding was comparatively studied. Differential scanning calorimetry (DSC) results show two crystallization exotherms (TCC, 1 and TCC, 2) for PA6/MWNTs

Melt-processable, radiation cross-linkable E--CTFE copolymer compositions

International Nuclear Information System (INIS)

Robertson, A.B.; Schaffhauser, R.J.

1976-01-01

Melt-processable, radiation cross-linkable ethylene/chlorotrifluoroethylene copolymer compositions are provided which contain about 0.1 to 5 percent by weight of the copolymer of a radiation cross-linking promoter, about 0.01 to 5 percent by weight of an anti-oxidant and about 0.1 to 30 precent by weight of an acid scavenger. Such compositions do not give off odors when irradiated to cross-link the copolymer and do not develop bubbles after irradiation. 15 claims, no drawings

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.

Regularities in Low-Temperature Phosphatization of Silicates

Science.gov (United States)

Savenko, A. V.

2018-01-01

The regularities in low-temperature phosphatization of silicates are defined from long-term experiments on the interaction between different silicate minerals and phosphate-bearing solutions in a wide range of medium acidity. It is shown that the parameters of the reaction of phosphatization of hornblende, orthoclase, and labradorite have the same values as for clayey minerals (kaolinite and montmorillonite). This effect may appear, if phosphotization proceeds, not after silicate minerals with a different structure and composition, but after a secondary silicate phase formed upon interaction between silicates and water and stable in a certain pH range. Variation in the parameters of the reaction of phosphatization at pH ≈ 1.8 is due to the stability of the silicate phase different from that at higher pH values.

Thirteen million years of silicic magma production in Iceland: Links between petrogenesis and tectonic settings

Science.gov (United States)

Martin, E.; Sigmarsson, O.

2010-04-01

The origin of the Quaternary silicic rocks in Iceland is thought to be linked to the thermal state of the crust, which in turn depends on the regional tectonic settings. This simple model is tested here on rocks from the Miocene to present, both to suggest an internally consistent model for silicic magma formation in Iceland and to constrain the link between tectonic settings and silicic magma petrogenesis. New major and trace-element compositions together with O-, Sr- and Nd-isotope ratios have been obtained on silicic rocks from 19 volcanic systems ranging in age from 13 Ma to present. This allows us to trace the spatial and temporal evolution of both magma generation and the corresponding sources. Low δ18O (geothermal gradient. But later than 5.5 Ma they were produced in a flank zone environment by fractional crystallisation alone, probably due to decreasing geothermal gradient, of basalts derived from a mantle source with lower 143Nd/ 144Nd. This is in agreement with an eastwards rift-jump, from Snæfellsnes towards the present Reykjanes Rift Zone, between 7 and 5.5 Ma. In the South Iceland Volcanic Zone (SIVZ), the intermediate Nd-signature observed in silicic rocks from the Torfajökull central volcano reflects the transitional character of the basalts erupted at this propagating rift segment. Therefore, the abundant evolved rocks at this major silicic complex result from partial melting of the transitional alkaline basaltic crust (Iceland can, therefore, be used for deciphering past geodynamic settings characterized by rift- and off-rift zones resulting from interaction of a mantle plume and divergent plate boundaries.

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

Directory of Open Access Journals (Sweden)

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.

Chemistry of the subalkalic silicic obsidians

Science.gov (United States)

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

1992-01-01

liquid-state differentiation mechanisms, or in other words a complex interaction of petrogenetic processes (CIPP types). Such rocks may also form by volatile-fluxed partial melting of the wallrocks, and subsequent mixing into the magma reservoir. Compositional ranges and averages for CLPD and CIPP obsidians are given. It is shown by analogy with well-documented, zoned ash-flow ruffs that obsidians fractionated by CIPP have very low Mg, P, Ba, and Sr contents, flat rare-earth-element patterns with extensive Eu anomalies, low K/Rb and Zr/Nb ratios, and relatively high Na2O/K2O ratios. There is, however, considerable compositional overlap between CLPD and CIPP obsidians. The effects of magma mixing, assimilation, and vapor-phase transport in producing compositional variations in the obsidians are briefly assessed. The geochemistry of the subalkalic silicic obsidians is described on an element-by-element basis, in order to provide a database for silicic magma compositions that will hopefully contribute to studies of granitic rocks. Attempts are also made to isolate the geochemical effects of tectonic environment and genetic mechanism for each element, by comparison with data from crystal-liquid equilibria-controlled systems, from ash-flow sheets zoned by CIPP, and from mixed-magma series. A final tabulation relates the complexities of obsidian geochemistry to all the tectonic and genetic variables.

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

Science.gov (United States)

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

2003-01-01

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

Preparation of TiC/Ni3Al Composites by Upward Melt Infiltration

Institute of Scientific and Technical Information of China (English)

无

2000-01-01

TiC/Ni3Al composites have been prepared using upward infiltration method. The densificstion was performed by both Ni3Al melt filling and TiC sintering during the infiltration. The dissolution of TiC in liquid Ni3Al has been evidenced by finding Ni3(Al,Ti)C after fast cooling in the TiC/Ni3Al composites. The dissolution may be responsible for the infiltration and sintering. Compared with downward infiltration, the upward infiltration brought about higher strength and fracture toughness and shorter infiltration time. TiC/20 vol. pct Ni3Al composite processed by upward infiltration had a flexural strength of 1476 Mpa with a statistic Weibull modulus of 20.2 and a fracture toughness of 20.4 Mpa(m). Better mechanical properties may be attributed to melt unidirectional movement in upward infiltration.

Dependence of Hardness of Silicate Glasses on Composition and Thermal History

DEFF Research Database (Denmark)

Jensen, Martin; Smedskjær, Morten Mattrup; Yue, Yuanzheng

composition on hardness of silicate glasses. E-glasses of different compositions are subjected to various degrees of annealing to obtain various fictive temperatures in the glasses. It is found that hardness decreases with the fictive temperature. Addition of Na2O to a SiO2-Al2O3-Na2O glass system causes......The prediction of hardness is possible for crystalline materials, but so far not possible for glasses. In this work, several important factors that should be used for predicting the hardness of glasses are discussed. To do so, we have studied the influences of thermal history and chemical...... a decrease in hardness. However, hardness cannot solely be determined from the degree of polymerisation of the glass network. It is also determined by the effect of ionic radius on hardness. However, this effect has opposite trend for alkali and alkaline earth ions. The hardness increases with ionic radius...

Bismuth silicate glass containing heavy metal oxide as a promising radiation shielding material

Science.gov (United States)

Elalaily, Nagia A.; Abou-Hussien, Eman M.; Saad, Ebtisam A.

2016-12-01

Optical and FTIR spectroscopic measurements and electron paramagnetic resonance (EPR) properties have been utilized to investigate and characterize the given compositions of binary bismuth silicate glasses. In this work, it is aimed to study the possibility of using the prepared bismuth silicate glasses as a good shielding material for γ-rays in which adding bismuth oxide to silicate glasses causes distinguish increase in its density by an order of magnitude ranging from one to two more than mono divalent oxides. The good thermal stability and high density of the bismuth-based silicate glass encourage many studies to be undertaken to understand its radiation shielding efficiency. For this purpose a glass containing 20% bismuth oxide and 80% SiO2 was prepared using the melting-annealing technique. In addition the effects of adding some alkali heavy metal oxides to this glass, such as PbO, BaO or SrO, were also studied. EPR measurements show that the prepared glasses have good stability when exposed to γ-irradiation. The changes in the FTIR spectra due to the presence of metal oxides were referred to the different housing positions and physical properties of the respective divalent Sr2+, Ba2+ and Pb2+ ions. Calculations of optical band gap energies were presented for some selected glasses from the UV data to support the probability of using these glasses as a gamma radiation shielding material. The results showed stability of both optical and magnetic spectra of the studied glasses toward gamma irradiation, which validates their irradiation shielding behavior and suitability as the radiation shielding candidate materials.

An Interconnected Network of Core-Forming Melts Produced by Shear Deformation

Science.gov (United States)

Bruhn, D.; Groebner, N.; Kohlstedt, D. L.

2000-01-01

The formation mechanism of terrestrial planetary is still poorly understood, and has been the subject of numerous experimental studies. Several mechanisms have been proposed by which metal-mainly iron with some nickel-could have been extracted from a silicate mantle to form the core. Most recent models involve gravitational sinking of molten metal or metal sulphide through a partially or fully molten mantle that is often referred to as a'magma ocean. Alternative models invoke percolation of molten metal along an interconnected network (that is, porous flow) through a solid silicate matrix. But experimental studies performed at high pressures have shown that, under hydrostatic conditions, these melts do not form an interconnected network, leading to the widespread assumption that formation of metallic cores requires a magma ocean. In contrast, here we present experiments which demonstrate that shear deformation to large strains can interconnect a significant fraction of initially isolated pockets of metal and metal sulphide melts in a solid matrix of polycrystalline olivine. Therefore, in a dynamic (nonhydrostatic) environment, percolation remains a viable mechanism for the segregation and migration of core-forming melts in a solid silicate mantle.

High Pressure/Temperature Metal Silicate Partitioning of Tungsten

Science.gov (United States)

Shofner, G. A.; Danielson, L.; Righter, K.; Campbell, A. J.

2010-01-01

The behavior of chemical elements during metal/silicate segregation and their resulting distribution in Earth's mantle and core provide insight into core formation processes. Experimental determination of partition coefficients allows calculations of element distributions that can be compared to accepted values of element abundances in the silicate (mantle) and metallic (core) portions of the Earth. Tungsten (W) is a moderately siderophile element and thus preferentially partitions into metal versus silicate under many planetary conditions. The partitioning behavior has been shown to vary with temperature, silicate composition, oxygen fugacity, and pressure. Most of the previous work on W partitioning has been conducted at 1-bar conditions or at relatively low pressures, i.e. pressure. Predictions based on extrapolation of existing data and parameterizations suggest an increased pressured dependence on metal/ silicate partitioning of W at higher pressures 5. However, the dependence on pressure is not as well constrained as T, fO2, and silicate composition. This poses a problem because proposed equilibration pressures for core formation range from 27 to 50 GPa, falling well outside the experimental range, therefore requiring exptrapolation of a parametereized model. Higher pressure data are needed to improve our understanding of W partitioning at these more extreme conditions.

[Isotope tracer studies of diffusion in silicates and of geological transport processes using actinide elements

International Nuclear Information System (INIS)

Wasserburg, G.J.

1991-01-01

This report consists of sections entitled resonance ionization mass spectrometry of Os, Mg self-diffusion in spinel and silicate melts, neotectonics: U-Th ages of solitary corals from the California coast, uranium-series evidence on diagenesis and hydrology of carbonates of Barbados, diffusion of H 2 O molecules in silicate glasses, and development of an extremely high abundance sensitivity mass spectrometer

Aluminum deoxidation equilibria and inclusion modification mechanism by calcium treatment of stainless steel melts

International Nuclear Information System (INIS)

Park, Joo Hyun; Kim, Dong Sik; Kim, Yong Hwan; Lee, Sang Beom

2005-01-01

A thermodynamic equilibrium between aluminum and oxygen along with the inclusion morphology in Fe-16%Cr stainless steel was investigated to understand the fundamentals of aluminum deoxidation technology for ferritic stainless steels. Further, the effects of calcium addition on the changes in chemistry and morphology of inclusions were discussed. The measured results for aluminum-oxygen equilibria exhibit relatively good agreement with the calculated values, indicating that the introduction of the first- and second-order interaction parameters, recently reported, is reasonable to numerically express aluminum deoxidation equilibrium in a ferritic stainless steel. In the composition of dissolved aluminum content greater than about 60 ppm, pure alumina particles were observed, while the alumino-manganese silicates containing Cr 2 O 3 were appeared at less than 20 mass ppm of dissolved aluminum. The formation of calcium aluminate inclusions after Ca treatment could be discussed based on the thermodynamic equilibrium with calcium, aluminum, and oxygen in the steel melts. In the composition of steel melt with relatively high content of calcium and low aluminum, the log(X CaO /X Al 2 O 3 ) of inclusions linearly increases with increasing the log [a Ca /a Al 2 ·a O 2 ] with the slope close to unity. However, the slope of the line is significantly lower than the expected value in the composition of steel melt with relatively low calcium and high aluminum contents

Pore solution in alkali-activated slag cement pastes. Relation to the composition and structure of calcium silicate hydrate

International Nuclear Information System (INIS)

Puertas, F.; Fernandez-Jimenez, A.; Blanco-Varela, M.T.

2004-01-01

In this work, the relationship between the composition of pore solution in alkali-activated slag cement (AAS) pastes activated with different alkaline activator, and the composition and structure of the main reaction products, has been studied. Pore solution was extracted from hardened AAS pastes. The analysis of the liquids was performed through different techniques: Na, Mg and Al by atomic absorption (AA), Ca ions by ionic chromatography (IC) and Si by colorimetry; pH was also determined. The solid phases were analysed by XRD, FTIR, solid-state 29 Si and 27 Al NMR and BSE/EDX. The most significant changes in the ionic composition of the pore solution of the AAS pastes activated with waterglass take place between 3 and 24 h of reaction. These changes are due to the decrease of the Na content and mainly to the Si content. Results of 29 Si MAS NMR and FTIR confirm that the activation process takes place with more intensity after 3 h (although at this age, Q 2 units already exist). The pore solution of the AAS pastes activated with NaOH shows a different evolution to this of pastes activated with waterglass. The decrease of Na and Si contents progresses with time. The nature of the alkaline activator influences the structure and composition of the calcium silicate hydrate formed as a consequence of the alkaline activation of the slag. The characteristic of calcium silicate hydrate in AAS pastes activated with waterglass is characterised by a low structural order with a low Ca/Si ratio. Besides, in this paste, Q 3 units are detected. The calcium silicate hydrate formed in the pastes activated with NaOH has a higher structural order (higher crystallinity) and contains more Al in its structure and a higher Ca/Si ratio than those obtained with waterglass

Effects of ZrB{sub 2} on substructure and wear properties of laser melted in situ ZrB{sub 2p}/6061Al composites

Energy Technology Data Exchange (ETDEWEB)

Zeng, Yida [School of Material Science and Engineering, Tianjin University, Tianjin 300072 (China); State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001 (China); Chao, Yuhjin [School of Material Science and Engineering, Tianjin University, Tianjin 300072 (China); Department of Mechanical Engineering, University of South Carolina, Columbia, SC 29208 (United States); Luo, Zhen, E-mail: lz@tju.edu.cn [School of Material Science and Engineering, Tianjin University, Tianjin 300072 (China); State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001 (China); Cai, Yangchuan [School of Material Science and Engineering, Tianjin University, Tianjin 300072 (China); State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001 (China); Huang, Yongxian [State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001 (China)

2016-03-01

Graphical abstract: - Highlights: • Laser beam partly disperses ZrB{sub 2} particle clusters and showing dispersed particles state after matrix solidification. • Laser melting process narrower cellular spacing in composites than AA6061 matrix. • Compared with matrix alloy, crystal orientation near melted layer edge of the composites is almost random duo to heterogeneous nucleation in melt and pinning effect of laser dispersed ZrB{sub 2} nanoparticles at solidification front. • Laser melted layer shows better wear properties than matrix and composite without laser melting. - Abstract: Aluminum matrix composites reinforced by in situ ZrB{sub 2} particles were successfully fabricated from an Al-KBF{sub 4}-K{sub 2}ZrF{sub 6} system via a direct melt reaction. A laser surface melting strategy is used to improve the surface strength of the in situ ZrB{sub 2p}/6061Al composite, which includes a series of laser-melted composites with different laser power processed by a 2 kW YAG laser generator. XRD and EDS results demonstrated the existence of ZrB{sub 2} nanoparticles in the composite. After laser melting, the penetration depth of the molten pool increases with increasing power density. OM and SEM analysis indicate that the laser melting process yields narrower cellular spacing of the matrix and partly disperses the ZrB{sub 2} particle clusters. Compared with laser-melted matrix alloys, the crystal orientations near the melted layers edge of the composite are almost random due to heterogeneous nucleation in the melt and the pinning effect of laser-dispersed ZrB{sub 2} nanoparticles at the solidification front. Wear test results show that the laser melted layer performs better at wear resistance than both the substrate and the matrix AA6061 by measuring wear mass loss. Compared with composite samples prepared without laser melting, the wear mass loss of the laser melted composites decreased from 61 to 56 mg under a load of 98 N for 60 min.

Molten (Mg0.88Fe0.12)2SiO4 at lower mantle conditions - Melting products and structure of quenched glasses

Science.gov (United States)

Williams, Quentin

1990-01-01

Infrared spectra of quenched magnesium silicate glasses synthesized by fusing olivine at pressures in excess of 50 GPa and temperatures greater than 2500 K demonstrate that silicon is dominantly present in four-fold coordination with respect to oxygen within these quenched glasses. This low coordination is attributed, by analogy with the structural behavior of glasses compressed at 300 K, to the instability of higher coordinations in glasses of these compositions on decompression. Spectra of glasses formed in a hydrous environment document that water is extensively soluble in melts at these high pressures and temperatures. Also, these results are consistent with the melting of (Mg0.88Fe0.12)2SiO4 compositions to liquids near pyroxene in stoichiometry under these conditions, with iron-rich magnesiowuestite being the liquidus phase.

Primary magmas and mantle sources of Emeishan basalts constrained from major element, trace element and Pb isotope compositions of olivine-hosted melt inclusions

Science.gov (United States)

Ren, Zhong-Yuan; Wu, Ya-Dong; Zhang, Le; Nichols, Alexander R. L.; Hong, Lu-Bing; Zhang, Yin-Hui; Zhang, Yan; Liu, Jian-Qiang; Xu, Yi-Gang

2017-07-01

Olivine-hosted melt inclusions within lava retain important information regarding the lava's primary magma compositions and mantle sources. Thus, they can be used to infer the nature of the mantle sources of large igneous provinces, which is still not well known and of the subject of debate. We have analysed the chemical compositions and Pb isotopic ratios of olivine-hosted melt inclusions in the Dali picrites, Emeishan Large Igneous Province (LIP), SW China. These are the first in-situ Pb isotope data measured for melt inclusions found in the Emeishan picrites and allow new constraints to be placed on the source lithology of the Emeishan LIP. The melt inclusions show chemical compositional variations, spanning low-, intermediate- and high-Ti compositions, while their host whole rocks are restricted to the intermediate-Ti compositions. Together with the relatively constant Pb isotope ratios of the melt inclusions, the compositional variations suggest that the low-, intermediate- and high-Ti melts were derived from compositionally similar sources. The geochemical characteristics of melt inclusions, their host olivines, and whole-rocks from the Emeishan LIP indicate that Ca, Al, Mn, Yb, and Lu behave compatibly, and Ti, Rb, Sr, Zr, and Nb behave incompatibly during partial melting, requiring a pyroxenite source for the Emeishin LIP. The wide range of Ti contents in the melt inclusions and whole-rocks of the Emeishan basalts reflects different degrees of partial melting in the pyroxenite source at different depths in the melting column. The Pb isotope compositions of the melt inclusions and the OIB-like trace element compositions of the Emeishan basalts imply that mixing of a recycled ancient oceanic crust (EM1-like) component with a peridotite component from the lower mantle (FOZO-like component) could have underwent solid-state reaction, producing a secondary pyroxenite source that was subsequently partially melted to form the basalts. This new model of pyroxenite

Effect of moisture and chitosan layered silicate on morphology and properties of chitosan/layered silicates films

International Nuclear Information System (INIS)

Silva, J.R.M.B. da; Santos, B.F.F. dos; Leite, I.F.

2014-01-01

Thin chitosan films have been for some time an object of practical assessments. However, to obtain biopolymers capable of competing with common polymers a significant improvement in their properties is required. Currently, the technology of obtaining polymer/layered silicates nanocomposites has proven to be a good alternative. This work aims to evaluate the effect of chitosan content (CS) and layered silicates (AN) on the morphology and properties of chitosan/ layered silicate films. CS/AN bionanocomposites were prepared by the intercalation by solution in the proportion 1:1 and 5:1. Then were characterized by infrared spectroscopy (FTIR), diffraction (XRD) and X-ray thermogravimetry (TG). It is expected from the acquisition of films, based on different levels of chitosan and layered silicates, choose the best composition to serve as a matrix for packaging drugs and thus be used for future research. (author)

Highly CO2-supersaturated melts in the Pannonian lithospheric mantle - A transient carbon reservoir?

Science.gov (United States)

Créon, Laura; Rouchon, Virgile; Youssef, Souhail; Rosenberg, Elisabeth; Delpech, Guillaume; Szabó, Csaba; Remusat, Laurent; Mostefaoui, Smail; Asimow, Paul D.; Antoshechkina, Paula M.; Ghiorso, Mark S.; Boller, Elodie; Guyot, François

2017-08-01

Subduction of carbonated crust is widely believed to generate a flux of carbon into the base of the continental lithospheric mantle, which in turn is the likely source of widespread volcanic and non-volcanic CO2 degassing in active tectonic intracontinental settings such as rifts, continental margin arcs and back-arc domains. However, the magnitude of the carbon flux through the lithosphere and the budget of stored carbon held within the lithospheric reservoir are both poorly known. We provide new constraints on the CO2 budget of the lithospheric mantle below the Pannonian Basin (Central Europe) through the study of a suite of xenoliths from the Bakony-Balaton Highland Volcanic Field. Trails of secondary fluid inclusions, silicate melt inclusions, networks of melt veins, and melt pockets with large and abundant vesicles provide numerous lines of evidence that mantle metasomatism affected the lithosphere beneath this region. We obtain a quantitative estimate of the CO2 budget of the mantle below the Pannonian Basin using a combination of innovative analytical and modeling approaches: (1) synchrotron X-ray microtomography, (2) NanoSIMS, Raman spectroscopy and microthermometry, and (3) thermodynamic models (Rhyolite-MELTS). The three-dimensional volumes reconstructed from synchrotron X-ray microtomography allow us to quantify the proportions of all petrographic phases in the samples and to visualize their textural relationships. The concentration of CO2 in glass veins and pockets ranges from 0.27 to 0.96 wt.%, higher than in typical arc magmas (0-0.25 wt.% CO2), whereas the H2O concentration ranges from 0.54 to 4.25 wt.%, on the low end for estimated primitive arc magmas (1.9-6.3 wt.% H2O). Trapping pressures for vesicles were determined by comparing CO2 concentrations in glass to CO2 saturation as a function of pressure in silicate melts, suggesting pressures between 0.69 to 1.78 GPa. These values are generally higher than trapping pressures for fluid inclusions

Synthesis of yttrium silicate luminescent materials by sol-gel method

International Nuclear Information System (INIS)

Arkhipov, D.V.; Vasina, O.Yu.; Popovich, N.V.; Galaktionov, S.S.; Soshchin, N.P.

1996-01-01

Several yttrium-silicate composition with Y 2 O 3 content within 44-56% have been synthesized. it is ascertained that employment of sol-gel technique permits preparation of luminescent materials on yttrium silicate basis, which compare favourably with bath-produced specimens. The influence of phase composition of sol-gel phosphors on basic performance indices: intensity and luminescence spectrum, has been analyzed

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.

X-ray Raman scattering study of MgSiO₃ glass at high pressure: Implication for triclustered MgSiO₃ melt in Earth's mantle

Energy Technology Data Exchange (ETDEWEB)

Lee, Sung Keun; Lin, Jung-Fu; Cai, Yong Q.; Hiraoka, Nozomu; Eng, Peter J.; Okuchi, Takuo; Mao, Ho-kwang; Meng, Yue; Hu, Michael Y.; Chow, Paul; Shu, Jinfu; Li, Baosheng; Fukui, Hiroshi; Lee, Bum Han; Kim, Hyun Na; Yoo, Choong-Shik [SNU; (LLNL); (NSRRC); (Okayama); (UC); (CIW); (Wash State U); (Nagoya); (SBU)

2015-02-09

Silicate melts at the top of the transition zone and the core-mantle boundary have significant influences on the dynamics and properties of Earth's interior. MgSiO₃-rich silicate melts were among the primary components of the magma ocean and thus played essential roles in the chemical differentiation of the early Earth. Diverse macroscopic properties of silicate melts in Earth's interior, such as density, viscosity, and crystal-melt partitioning, depend on their electronic and short-range local structures at high pressures and temperatures. Despite essential roles of silicate melts in many geophysical and geodynamic problems, little is known about their nature under the conditions of Earth's interior, including the densification mechanisms and the atomistic origins of the macroscopic properties at high pressures. Here, we have probed local electronic structures of MgSiO₃ glass (as a precursor to Mg-silicate melts), using high-pressure x-ray Raman spectroscopy up to 39 GPa, in which high-pressure oxygen K-edge features suggest the formation of tricluster oxygens (oxygen coordinated with three Si frameworks; ^[3]O) between 12 and 20 GPa. Our results indicate that the densification in MgSiO₃ melt is thus likely to be accompanied with the formation of triculster, in addition to a reduction in nonbridging oxygens. The pressure-induced increase in the fraction of oxygen triclusters >20 GPa would result in enhanced density, viscosity, and crystal-melt partitioning, and reduced element diffusivity in the MgSiO₃ melt toward deeper part of the Earth's lower mantle.

Coating and melt induced agglomeration in a poultry litter fired fluidized bed combustor

International Nuclear Information System (INIS)

Billen, Pieter; Creemers, Benji; Costa, José; Van Caneghem, Jo; Vandecasteele, Carlo

2014-01-01

The combustion of poultry litter, which is rich in phosphorus, in a fluidized bed combustor (FBC) is associated with agglomeration problems, which can lead to bed defluidization and consequent shutdown of the installation. Whereas earlier research indicated coating induced agglomeration as the dominant mechanism for bed material agglomeration, it is shown experimentally in this paper that both coating and melt induced agglomeration occur. Coating induced agglomeration mainly takes place at the walls of the FBC, in the freeboard above the fluidized bed, where at the prevailing temperature the bed particles are partially molten and hence agglomerate. In the ash, P 2 O 5 forms together with CaO thermodynamically stable Ca 3 (PO 4 ) 2 , thus reducing the amount of calcium silicates in the ash. This results in K/Ca silicate mixtures with lower melting points. On the other hand, in-bed agglomeration is caused by thermodynamically unstable, low melting HPO 4 2− and H 2 PO 4 − salts present in the fuel. In the hot FBC these salts may melt, may cause bed particles to stick together and may subsequently react with Ca salts from the bed ash, forming a solid bridge of the stable Ca 3 (PO 4 ) 2 between multiple particles. - Highlights: • Coating induced agglomeration not due to K phosphates, but due to K silicates. • Melt induced agglomeration due to H 2 PO 4 − and HPO 4 2− salts in the fuel. • Wall agglomeration corresponds to coating induced mechanism. • In-bed agglomeration corresponds to melt induced mechanism

High-Resolution Melt Analysis for Rapid Comparison of Bacterial Community Compositions

DEFF Research Database (Denmark)

Hjelmsø, Mathis Hjort; Hansen, Lars Hestbjerg; Bælum, Jacob

2014-01-01

In the study of bacterial community composition, 16S rRNA gene amplicon sequencing is today among the preferred methods of analysis. The cost of nucleotide sequence analysis, including requisite computational and bioinformatic steps, however, takes up a large part of many research budgets. High......-resolution melt (HRM) analysis is the study of the melt behavior of specific PCR products. Here we describe a novel high-throughput approach in which we used HRM analysis targeting the 16S rRNA gene to rapidly screen multiple complex samples for differences in bacterial community composition. We hypothesized...... that HRM analysis of amplified 16S rRNA genes from a soil ecosystem could be used as a screening tool to identify changes in bacterial community structure. This hypothesis was tested using a soil microcosm setup exposed to a total of six treatments representing different combinations of pesticide...

Effect of re-melting on particle distribution and interface formation in SiC reinforced 2124Al matrix composite

Energy Technology Data Exchange (ETDEWEB)

Mandal, Durbadal, E-mail: durbadal73@yahoo.co.in [MEF Division, CSIR-National Metallurgical Laboratory, Jamshedpur 831007 (India); Viswanathan, Srinath [Dept of Metallurgical and Materials Engineering, University of Alabama, Tuscaloosa, AL (United States)

2013-12-15

The interface between metal matrix and ceramic reinforcement particles plays an important role in improving properties of the metal matrix composites. Hence, it is important to find out the interface structure of composite after re-melting. In the present investigation, the 2124Al matrix with 10 wt.% SiC particle reinforced composite was re-melted at 800 °C and 900 °C for 10 min followed by pouring into a permanent mould. The microstructures reveal that the SiC particles are distributed throughout the Al-matrix. The volume fraction of SiC particles varies from top to bottom of the composite plate and the difference increases with the decrease of re-melting temperature. The interfacial structure of re-melted 2124Al–10 wt.%SiC composite was investigated using scanning electron microscopy, an electron probe micro-analyzer, a scanning transmission electron detector fitted with scanning electron microscopy and an X-ray energy dispersive spectrometer. It is found that a thick layer of reaction product is formed at the interface of composite after re-melting. The experimental results show that the reaction products at the interface are associated with high concentration of Cu, Mg, Si and C. At re-melting temperature, liquid Al reacts with SiC to form Al{sub 4}C{sub 3} and Al–Si eutectic phase or elemental Si at the interface. High concentration of Si at the interface indicates that SiC is dissociated during re-melting. The X-ray energy dispersive spectrometer analyses confirm that Mg- and Cu-enrich phases are formed at the interface region. The Mg is segregated at the interface region and formed MgAl{sub 2}O{sub 4} in the presence of oxygen. The several elements identified at the interface region indicate that different types of interfaces are formed in between Al matrix and SiC particles. The Al–Si eutectic phase is formed around SiC particles during re-melting which restricts the SiC dissolution. - Highlights: • Re-melted composite shows homogeneous particle

SLUDGE MASS REDUCTION: PRIMARY COMPOSITIONAL FACTORS THAT INFLUENCE MELT RATE FOR FUTURE SLUDGE BATCH PROJECTIONS

International Nuclear Information System (INIS)

Newell, J; Miller, D; Stone, M; Pickenheim, B

2008-01-01

The Savannah River National Laboratory (SRNL) was tasked to provide an assessment of the downstream impacts to the Defense Waste Processing Facility (DWPF) of decisions regarding the implementation of Al-dissolution to support sludge mass reduction and processing. Based on future sludge batch compositional projections from the Liquid Waste Organization's (LWO) sludge batch plan, assessments have been made with respect to the ability to maintain comparable projected operating windows for sludges with and without Al-dissolution. As part of that previous assessment, candidate frits were identified to provide insight into melt rate for average sludge batches representing with and without Al-dissolution flowsheets. Initial melt rate studies using the melt rate furnace (MRF) were performed using five frits each for Cluster 2 and Cluster 4 compositions representing average without and with Al-dissolution. It was determined, however, that the REDOX endpoint (Fe 2+ /ΣFe for the glass) for Clusters 2 and 4 resulted in an overly oxidized feed which negatively affected the initial melt rate tests. After the sludge was adjusted to a more reduced state, additional testing was performed with frits that contained both high and low concentrations of sodium and boron oxides. These frits were selected strictly based on the ability to ascertain compositional trends in melt rate and did not necessarily apply to any acceptability criteria for DWPF processing. The melt rate data are in general agreement with historical trends observed at SRNL and during processing of SB3 (Sludge Batch 3)and SB4 in DWPF. When MAR acceptability criteria were applied, Frit 510 was seen to have the highest melt rate at 0.67 in/hr for Cluster 2 (without Al-dissolution), which is compositionally similar to SB4. For Cluster 4 (with Al-dissolution), which is compositionally similar to SB3, Frit 418 had the highest melt rate at 0.63 in/hr. Based on this data, there appears to be a slight advantage of the Frit

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.

Effects of slag composition and process variables on decontamination of metallic wastes by melt refining

International Nuclear Information System (INIS)

Heshmatpour, B.; Copeland, G.L.

1981-01-01

Melt refining has been suggested as an alternative for decontamination and volume reduction of low-level-contaminated metallic wastes. Knowledge of metallurgical and thermochemical aspects of the process is essential for effective treatment of various metals. Variables such as slag type and composition, melting technique, and refractory materials need to be identified for each metal or alloy. Samples of contaminated metals were melted with fluxes by resistance furnace or induction heating. The resulting ingots as well as the slags were analyzed for their nuclide contents, and the corresponding partition ratios were calculated. Compatibility of slags and refractories was also investigated, and proper refractory materials were identified. Resistance furnace melting appeared to be a better melting technique for nonferrous scrap, while induction melting was more suitable for ferrous metals. In general uranium contents of the metals, except for aluminum, could be reduced to as low as 0.01 to 0.1 ppM by melt refining. Aluminum could be decontaminated to about 1 to 2 ppM U when certain fluoride slags were used. The extent of decontamination was not very sensitive to slag type and composition. However, borosilicate and basic oxidizing slags were more effective on ferrous metals and Cu; NaNO 3 -NaCl-NaOH type fluxes were desirable for Zn, Pb, and Sn; and fluoride type slags were effective for decontamination of Al. Recrystallized alumina proved to be the most compatible refractory for melt refining both ferrous and nonferrous metals, while graphite was suitable for nonferrous metal processing. In conclusion, melt refining is an effective technique for volume reduction ad decontamination of contaminated metal scrap when proper slags, melting technique, and refractories are used

Sources and mobility of carbonate melts beneath cratons, with implications for deep carbon cycling, metasomatism and rift initiation

Science.gov (United States)

Tappe, Sebastian; Romer, Rolf L.; Stracke, Andreas; Steenfelt, Agnete; Smart, Katie A.; Muehlenbachs, Karlis; Torsvik, Trond H.

2017-05-01

Kimberlite and carbonatite magmas that intrude cratonic lithosphere are among the deepest probes of the terrestrial carbon cycle. Their co-existence on thick continental shields is commonly attributed to continuous partial melting sequences of carbonated peridotite at >150 km depths, possibly as deep as the mantle transition zone. At Tikiusaaq on the North Atlantic craton in West Greenland, approximately 160 Ma old ultrafresh kimberlite dykes and carbonatite sheets provide a rare opportunity to study the origin and evolution of carbonate-rich melts beneath cratons. Although their Sr-Nd-Hf-Pb-Li isotopic compositions suggest a common convecting upper mantle source that includes depleted and recycled oceanic crust components (e.g., negative ΔεHf coupled with > + 5 ‰ δ7Li), incompatible trace element modelling identifies only the kimberlites as near-primary low-degree partial melts (0.05-3%) of carbonated peridotite. In contrast, the trace element systematics of the carbonatites are difficult to reproduce by partial melting of carbonated peridotite, and the heavy carbon isotopic signatures (-3.6 to - 2.4 ‰ δ13C for carbonatites versus -5.7 to - 3.6 ‰ δ13C for kimberlites) require open-system fractionation at magmatic temperatures. Given that the oxidation state of Earth's mantle at >150 km depth is too reduced to enable larger volumes of 'pure' carbonate melt to migrate, it is reasonable to speculate that percolating near-solidus melts of carbonated peridotite must be silicate-dominated with only dilute carbonate contents, similar to the Tikiusaaq kimberlite compositions (e.g., 16-33 wt.% SiO2). This concept is supported by our findings from the North Atlantic craton where kimberlite and other deeply derived carbonated silicate melts, such as aillikites, exsolve their carbonate components within the shallow lithosphere en route to the Earth's surface, thereby producing carbonatite magmas. The relative abundances of trace elements of such highly

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

International Nuclear Information System (INIS)

Schneider, E.

1985-11-01

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

High porosity harzburgite and dunite channels for the transport of compositionally heterogeneous melts in the mantle: II. Geochemical consequences

Science.gov (United States)

Liang, Y.; Schiemenz, A.; Xia, Y.; Parmentier, E.

2009-12-01

In a companion numerical study [1], we explored the spatial distribution of high porosity harzburgite and dunite channels produced by reactive dissolution of orthopyroxene (opx) in an upwelling mantle column and identified a number of new features. In this study, we examine the geochemical consequences of channelized melt flow under the settings outlined in [1] with special attention to the transport of compositionally heterogeneous melts and their interactions with the surrounding peridotite matrix during melt migration in the mantle. Time-dependent transport equations for a trace element in the interstitial melt and solids that include advection, dispersion, and melt-rock reaction were solved in a 2-D upwelling column using the high-order numerical methods outlined in [1]. The melt and solid velocities were taken from the steady state or quasi-steady state solutions of [1]. In terms of trace element fractionation, the simulation domain can be divided into 4 distinct regions: (a) high porosity harzburgite channel, overlain by; (b) high porosity dunite channel; (c) low porosity compacting boundary layer surrounding the melt channels; and (d) inter-channel regions outside (c). In the limit of local chemical equilibrium, melting in region (d) is equivalent to batch melting, whereas melting and melt extraction in (c) is more close to fractional melting with the melt suction rate first increase from the bottom of the melting column to a maximum near the bottom of the dunite channel and then decrease upward in the compacting boundary layer. The melt composition in the high porosity harzburgite channel is similar to that produced by high-degree batch melting (up to opx exhaustion), whereas the melt composition in the dunite is a weighted average of the ultra-depleted melt from the harzburgite channel below, the expelled melt from the compacting boundary layer, and melt produced by opx dissolution along the sidewalls of the dunite channel. Compaction within the dunite

Kinetics and mechanisms of iron redox reactions in silicate melts: The effects of temperature and alkali cations

Energy Technology Data Exchange (ETDEWEB)

Magnien, V.; Pinet, O. [CEA VALRHO, SCDV/LEBV, F-30207 Bagnols Sur Ceze, (France); Magnien, V.; Neuville, D. R.; Roux, J.; Richet, P. [IPGP, CNRS, Physique des Mineraux et Magmas, F-75252 Paris 05, (France); Cormier, L. [Univ Paris 06, IMPMC, F-75015 Paris, (France); Hazemann, J. L. [CNRS, Inst Neel, F-38043 Grenoble, (France); De Ligny, D. [Univ Lyon 1, LMLC, CNRS, UMR 5620, F-69622 Villeurbanne, (France); Pascarelli, S. [European Synchrotron Radiat Facil, F-38043 Grenoble, (France); Vickridge, I. [Univ Paris 06, INSP, F-75015 Paris, (France)

2008-07-01

The kinetics and the mechanisms of iron redox reactions in molten Fe-bearing pyroxene compositions have been investigated by Raman spectroscopy and X-ray absorption Near Edge Structure (XANES) experiments at the iron K-edge. The former experiments have been made only near the glass transition whereas the latter have also been performed from about 1300 to 2100 K. The same kinetics are observed with both techniques. They are described by characteristic times that depend primarily on temperature and not on the initial redox state. At high temperatures, where both kinds of reactions could be investigated, these times are similar for oxidation and reduction. From these characteristic times we have calculated as a function of temperature and composition a parameter termed effective redox diffusivity. For a given melt, the diffusivities follow two distinct Arrhenius laws, which indicate that the mechanisms of the redox reaction are not the same near the glass transition and at high temperatures. As is now well established, diffusion of divalent cations is the dominant mechanism at low temperatures but the enhanced kinetics observed for alkali-bearing melts indicate that Li{sup +} and Na{sup +} also participate in ionic transport. At super-liquidus temperatures, in contrast, diffusion of oxygen represents the dominant mechanism. (authors)

Methods of vitrifying waste with low melting high lithia glass compositions

Science.gov (United States)

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

2001-01-01

The invention relates to methods of vitrifying waste and for lowering the melting point of glass forming systems by including lithia formers in the glass forming composition in significant amounts, typically from about 0.16 wt % to about 11 wt %, based on the total glass forming oxides. The lithia is typically included as a replacement for alkali oxide glass formers that would normally be present in a particular glass forming system. Replacement can occur on a mole percent or weight percent basis, and typically results in a composition wherein lithia forms about 10 wt % to about 100 wt % of the alkali oxide glass formers present in the composition. The present invention also relates to the high lithia glass compositions formed by these methods. The invention is useful for stabilization of numerous types of waste materials, including aqueous waste streams, sludge solids, mixtures of aqueous supernate and sludge solids, combinations of spent filter aids from waste water treatment and waste sludges, supernate alone, incinerator ash, incinerator offgas blowdown, or combinations thereof, geological mine tailings and sludges, asbestos, inorganic filter media, cement waste forms in need of remediation, spent or partially spent ion exchange resins or zeolites, contaminated soils, lead paint, etc. The decrease in melting point achieved by the present invention desirably prevents volatilization of hazardous or radioactive species during vitrification.

Melt density and the average composition of basalt

Science.gov (United States)

Stolper, E.; Walker, D.

1980-01-01

Densities of residual liquids produced by low pressure fractionation of olivine-rich melts pass through a minimum when pyroxene and plagioclase joint the crystallization sequence. The observation that erupted basalt compositions cluster around the degree of fractionation from picritic liquids corresponding to the density minimum in the liquid line of descent may thus suggest that the earth's crust imposes a density fiber on the liquids that pass through it, favoring the eruption of the light liquids at the density minimum over the eruption of denser more fractionated and less fractionated liquids.

Effect of organo clay addition on thermal properties of poly lactide/ polycaprolactone (PLA/ PCL) nano composites

International Nuclear Information System (INIS)

Siti Zulaiha Hairaldin; Wan Md Zin Wan Yunus; Norazoma Ibrahim

2010-01-01

In this study, melt blending technique was applied to prepare poly lactide/polycaprolactone (PLA/ PCL) nano composites with various blends. Montmorillonite (MMT) was used as an addition to the matrix. In this study, melt blending technique was applied to prepare poly lactide/polycaprolactone (PLA/ PCL) nano composites. Montmorillonite (MMT) was used as an addition to the matrix with various percentages. The other one is modified clay prepared by modifying the nature of montmorillonite with octadecylamine (ODA) to improve the characteristic of PLA/ PCL blends. X-ray diffraction (XRD) results indicated intercalation of the PLA/ PCL into silicate nano size interlayers galleries of the nano composites. The presence of modified clays in nano composite was confirmed by FTIR spectrum. TGA and DTG results show addition of MMT and modified clay ODA-MMT improved the thermal stability of the PLA/ PCL blends. (author)

Nanoporous Calcium Silicate and PLGA Bio composite for Bone Repair

International Nuclear Information System (INIS)

Su, J.; Wang, Z.; Wu, Y.; Cao, L.; Ma, Y.; Yu, B.; Li, M.; Yan, Y.

2010-01-01

Nanoporous calcium silicate (n-CS) with high surface area was synthesized using the mixed surfactants of EO20PO70EO20 (polyethylene oxide)20(polypropylene oxide)70(polyethylene oxide)20, P123) and hexadecyltrimethyl ammonium bromide (CTAB) as templates, and its composite with poly(lactic acid-co-glycolic acid) (PLGA) were fabricated. The results showed that the n-CS/PLGA composite (n-CPC) with 20 wt% n-CS could induce a dense and continuous layer of apatite on its surface after soaking in simulated body fluid (SBF) for 1 week, suggesting the excellent in vitro bioactivity. The n-CPC could promote cell attachment on its surfaces. In addition, the proliferation ratio of MG63 cells on n-CPC was significantly higher than PLGA; the results demonstrated that n-CPC had excellent cytocompatibility. We prepared n-CPC scaffolds that contained open and interconnected macroporous ranging in size from 200 to 500 μ m. The n-CPC scaffolds were implanted in femur bone defect of rabbits, and the in vivo biocompatibility and osteogenicity of the scaffolds were investigated. The results indicated that n-CPC scaffolds exhibited good biocompatibility, degradability, and osteogenesis in vivo. Collectively, these results suggested that the incorporation of n-CS in PLGA produced biocomposites with improved bioactivity and biocompatibility.

Novel powder/solid composites possessing low Young’s modulus and tunable energy absorption capacity, fabricated by electron beam melting, for biomedical applications

International Nuclear Information System (INIS)

Ikeo, Naoko; Ishimoto, Takuya; Nakano, Takayoshi

2015-01-01

Highlights: • We fabricated novel porous composites by electron beam melting. • The composites consist of necked powder and melted solid framework. • Unmelted powder that is usually discarded was mechanically functionalized by necking. • The composites possess controllably low Young’s modulus and excellent toughness. • The composites would be promising for utilization in biomedical applications. - Abstract: A novel, hierarchical, porous composite from a single material composed of necked powder and melted solid, with tunable mechanical properties, is fabricated by electron beam melting and subsequent heat treatment. The composite demonstrates low Young’s modulus (⩽31 GPa) and excellent energy absorption capacity, both of which are necessary for use in orthopedic applications. To the best of our knowledge, this is the first report on the synthesis of a material combining controllably low Young’s modulus and excellent toughness

Transparent phosphosilicate glasses containing crystals formed during cooling of melts

DEFF Research Database (Denmark)

Liu, S. J.; Zhang, Yanfei; He, W.

2011-01-01

The effect of P2O5-SiO2 substitution on spontaneous crystallization of SiO2-Al2O3-P2O5- Na2O-MgO melts during cooling was studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and rotation viscometry. Results show that addition of P2O5 leads...... to amorphous phase separation (APS), i.e., phosphate- and silicate-rich phases. It is due to the tendency of Mg2+ to form [MgO4] linking with [SiO4]. Molar substitution of P2O5 for SiO2 enhances the network polymerization of silicate-rich phase in the melts, and thereby the spontaneous crystallization of cubic...... Na2MgSiO4 is also enhanced during cooling of the melts. In addition, the sizes of the local crystalline and separated glassy domains are smaller than the wavelength of the visible light, and this leads to the transparency of the obtained glasses containing crystals....

Wind-eroded silicate as a source of hydrogen peroxide on Mars

DEFF Research Database (Denmark)

Bak, Ebbe Norskov; Merrison, Jonathan P.; Jensen, Svend Knak

-sists of silicates [4] that due to wind erosion has a very fine grained texture. Based on the composition of the surface material and investigations showing that crushing of silicates can give rise to reactive oxygen species [5], we hypothesized that wind erosion of silicates can explain the reactivity of Martian...... soil. Wind-erosion of silicate could thus be one of several causes of the soil’s reactivity. As our experiments show, the globally distributed wind eroded silicate dust can lead to the production of hydrogen peroxide which might explain the reactivity of the Martian soil. The reactivity of eroded...

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

Energy Technology Data Exchange (ETDEWEB)

Schneider, E.

1985-11-01

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

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.

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

International Nuclear Information System (INIS)

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

2010-01-01

We report results on lithium alumino-silicate ion source development in preparation for warm-dense-matter heating experiments on the new Neutralized Drift Compression Experiment (NDCX-II). 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 C, a space-charge-limited Li + beam current density of J ∼1 mA/cm 2 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 (micro) s.

Study the Properties of Sodium Silicate Composite as a Barrier Separating Between the Internal Oil Distillation Towers and Chemical Fumes of Crude Oil

Directory of Open Access Journals (Sweden)

سلام حسين علي

2016-07-01

Full Text Available The study of surface hardness, wear resistance, adhesion strength, electrochemical corrosion resistance and thermal conductivity of coatings composed from sodium silicate was prepared using graphite micro-size particles and carbon nano particles as fillers respectively of concentration of (1-5%, for the purpose of covering and protecting the oil distillation towers. The results showed that the sodium silicate coating reinforced with carbon nano-powder has higher resistance to stitches, mechanical wear, adhesive and thermal conductivity than graphite/sodium silicate composite especially when the ratio 5% and 1%, the electrochemical corrosion test confirmed that the coating process of stainless steel 304 lead to increasing the corrosion resistance, where the reinforcing of sodium silicate lead to a significant improvement in the corrosion resistance, the corrosion resistance behavior change depending on the type of reinforcement material, this is consistent with the field test results.

Immiscible iron- and silica-rich melt in basalt petrogenesis documented in the Skaergaard intrusion

DEFF Research Database (Denmark)

Jakobsen, Jakob Kløve; Veksler, Ilya; Tegner, Christian

2005-01-01

colored type contains 30.9 6 4.2 wt% FeOt and 40.7 6 3.6 wt% SiO2, whereas the light colored type contains 8.6 6 5.9 wt% FeOt and 65.6 6 7.3 wt% SiO2. Similar light colored melt inclusions in olivine and fine grained dark and light colored interstitial pockets also give evidence of crystallization from......Silicate liquid immiscibility in basalt petrogenesis is a contentious issue. Immiscible iron and silica-rich liquids were reported in melt inclusions of lunar basalt and in groundmass glasses of terrestrial volcanics. In fully crystallized plutonic rocks, however, silicate liquid immiscibility has...

Deformation, static recrystallization, and reactive melt transport in shallow subcontinental mantle xenoliths (Tok Cenozoic volcanic field, SE Siberia)

Science.gov (United States)

Tommasi, Andréa; Vauchez, Alain; Ionov, Dmitri A.

2008-07-01

Partial melting and reactive melt transport may change the composition, microstructures, and physical properties of mantle rocks. Here we explore the relations between deformation and reactive melt transport through detailed microstructural analysis and crystallographic orientation measurements in spinel peridotite xenoliths that sample the shallow lithospheric mantle beneath the southeastern rim of the Siberian craton. These xenoliths have coarse-grained, annealed microstructures and show petrographic and chemical evidence for variable degrees of reaction with silicate melts and fluids, notably Fe-enrichment and crystallization of metasomatic clinopyroxene (cpx). Olivine crystal preferred orientations (CPO) range from strong to weak. [010]-fiber patterns, characterized by a point concentration of [010] normal to the foliation and by dispersion of [100] in the foliation plane with a weak maximum parallel to the lineation, predominate relative to the [100]-fiber patterns usually observed in lithospheric mantle xenoliths and peridotite massifs. Variations in olivine CPO patterns or intensity are not correlated with modal and chemical compositions. This, together with the analysis of microstructures, suggests that reactive melt percolation postdated both deformation and static recrystallization. Preferential crystallization of metasomatic cpx along (010) olivine grain boundaries points to an influence of the preexisting deformation fabrics on melt transport, with higher permeability along the foliation. Similarity between orthopyroxene (opx) and cpx CPO suggests that cpx orientations may be inherited from those of opx during melt-rock reaction. As observed in previous studies, reactive melt transport does not weaken olivine CPO and seismic anisotropy in the upper mantle, except in melt accumulation domains. In contrast, recovery and selective grain growth during static recrystallization may lead to development of [010]-fiber olivine CPO and, if foliations are

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.

Mechanical and physical properties of calcium silicate/alumina composite for biomedical engineering applications.

Science.gov (United States)

Shirazi, F S; Mehrali, M; Oshkour, A A; Metselaar, H S C; Kadri, N A; Abu Osman, N A

2014-02-01

The focus of this study is to investigate the effect of Al2O3 on α-calcium silicate (α-CaSiO3) ceramic. α-CaSiO3 was synthesized from CaO and SiO2 using mechanochemical method followed by calcinations at 1000°C. α-CaSiO3 and alumina were grinded using ball mill to create mixtures, containing 0-50w% of Al2O3 loadings. The powders were uniaxially pressed and followed by cold isostatic pressing (CIP) in order to achieve greater uniformity of compaction and to increase the shape capability. Afterward, the compaction was sintered in a resistive element furnace at both 1150°C and 1250°C with a 5h holding time. It was found that alumina reacted with α-CaSiO3 and formed alumina-rich calcium aluminates after sintering. An addition of 15wt% of Al2O3 powder at 1250°C were found to improve the hardness and fracture toughness of the calcium silicate. It was also observed that the average grain sizes of α-CaSiO3 /Al2O3 composite were maintained 500-700nm after sintering process. © 2013 Published by Elsevier Ltd.

Application of siliceous metal product for preliminary deoxidizing of metal in open-hearth furnaces

International Nuclear Information System (INIS)

Luk'yanenko, A.A.; Evdokimov, A.V.; Kornilov, V.N.; Il'in, V.I.; Kuleshov, Yu.V.

1995-01-01

Metal wastes of abrasive processes-concomitant product of synthetic corundum production containing approximately 10 % Si - were tested for preliminary deoxidizing of metal in furnace to reduce manganese loss in burning and to increase the steel deoxidizing. The technology of preliminary deoxidizing of metal by siliceous metal product was mastered in the course of low carbon steel melting (st3sp, st4sp). The results of the study has shown that the use of siliceous metal product permits reducing the consumption of manganese-containing ferroalloys. 1 tab

Evidence for large compositional ranges in coeval melts erupted from Kīlauea's summit reservoir: Chapter 7

Science.gov (United States)

Helz, Rosalind T.; Clague, David A.; Mastin, Larry G.; Rose, Timothy R.; Carey, Rebecca; Cayol, Valérie; Poland, Michael P.; Weis, Dominique

2015-01-01

Petrologic observations on Kīlauea's lavas include abundant microprobe analyses of glasses, which show the range of melts available in Kīlauea's summit reservoir over time. During the past two centuries, compositions of melts erupted within the caldera have been limited to MgO = 6.3–7.5 wt%. Extracaldera lavas of the 1959, 1971, and 1974 eruptions contain melts with up to 10.2, 8.9, and 9.2 wt% MgO, respectively, and the 1924 tephra contains juvenile Pele's tears with up to 9.1 wt% MgO. Melt compositions from explosive deposits at Kīlauea, including the Keanakāko‘i (A.D. 1500–1800), Kulanaokuaiki (A.D. 400–1000), and Pāhala (10–25 ka) tephra units, show large ranges of MgO contents. The range of melt MgO is 6.5–11.0 wt% for the Keanakāko‘i; the Kulanaokuaiki extends to 12.5% MgO and the Pāhala Ash includes rare shards with 13–14.5% MgO. The frequency distributions for MgO in the Keanakāko‘i and Kulanaokuaiki glasses are bimodal, suggesting preferential magma storage at two different depths. Kīlauea's summit reservoir contains melts ranging from 6.5 to at least 11.0 wt% MgO, and such melts were available for sampling near instantaneously and repeatedly over centuries. More magnesian melts are inferred to have risen directly from greater depth.

Determination of enthalpy–temperature–composition relations in incongruent-melting phase change materials

International Nuclear Information System (INIS)

Desgrosseilliers, Louis; Allred, Paul; Groulx, Dominic; White, Mary Anne

2013-01-01

This paper demonstrates that liquidus line (T-x) data can be obtained from calorimetric determinations of phase transition enthalpy profiles (H-T) for incongruent-melting phase change materials (PCMs) more efficiently than using traditional cooling curves. An accurate and reliable equilibrium mixture enthalpy model bridges the H-T and T-x gap to provide a full suite of high density H-T-x data to assist latent heat energy storage researchers to evaluate composition-dependent two-phase equilibrium processes. The proposed method is validated for T-history method H-T determinations of 1:1 diluted sodium acetate trihydrate in water, and can also be used with other laboratory calorimetric techniques used to determine the phase transition enthalpy profiles of incongruent-melting compounds. -- Highlights: • H-T data can also be used to obtain valuable liquidus region T-x data. • Applies to all incongruent-melting compounds with known thermodynamic properties. • Reduces the effort and cost of assessing full suite H-T-x data for PCMs. • Uses existing T-x or H-T data of incongruent-melting PCMs to determine the other

Q-Speciation and Network Structure Evolution in Invert Calcium Silicate Glasses.

Science.gov (United States)

Kaseman, Derrick C; Retsinas, A; Kalampounias, A G; Papatheodorou, G N; Sen, S

2015-07-02

Binary silicate glasses in the system CaO-SiO2 are synthesized over an extended composition range (42 mol % ≤ CaO ≤ 61 mol %), using container-less aerodynamic levitation techniques and CO2-laser heating. The compositional evolution of Q speciation in these glasses is quantified using (29)Si and (17)O magic angle spinning nuclear magnetic resonance spectroscopy. The results indicate progressive depolymerization of the silicate network upon addition of CaO and significant deviation of the Q speciation from the binary model. The equilibrium constants for the various Q species disproportionation reactions for these glasses are found to be similar to (much smaller than) those characteristic of Li (Mg)-silicate glasses, consistent with the corresponding trends in the field strengths of these modifier cations. Increasing CaO concentration results in an increase in the packing density and structural rigidity of these glasses and consequently in their glass transition temperature Tg. This apparent role reversal of conventional network-modifying cations in invert alkaline-earth silicate glasses are compared and contrasted with that in their alkali silicate counterparts.

Decomposition of pre calcined aluminium silicate ores of Afghanistan by hydrochloric acid

International Nuclear Information System (INIS)

Khomidi, A.K.; Mamatov, E.D.

2015-01-01

Present article is devoted to decomposition of pre calcined aluminium silicate ores of Afghanistan by hydrochloric acid. The physicochemical properties of initial aluminium silicate ores were studied by means of X-ray phase, differential thermal and silicate analysis. The chemical composition of aluminium containing ores was determined. The optimal conditions of interaction of initial and pre calcined siallites with hydrochloric acid were defined. The kinetics of acid decomposition of aluminium silicate ores was studied as well.

Aluminum Silicate Nanotube Coating of Siloxane-Poly(lactic acid-Vaterite Composite Fibermats for Bone Regeneration

Directory of Open Access Journals (Sweden)

Shuji Yamazaki

2012-01-01

Full Text Available In our earlier work, a flexible fibermat consisting of a biodegradable composite with soluble silicate species, which has been reported to enhance bone formation, was prepared successfully using poly(L-lactic acid and siloxane-containing calcium carbonate particles by electrospinning. The fibermat showed enhanced bone formation in an in vivo test. In the present work, to improve the hydrophilicity of skeletal fibers in a fibermat, they were coated with nanotubular aluminum silicate crystals, which have a hydrophilic surface that has excellent affinity to body fluids and a high surface area advantageous for pronounced protein adsorption. The nanotubes were coated easily on the fiber surface using an electrophoretic method. In a conventional contact angle test, a drop of water rapidly penetrated into the nanotube-coated fibermat. The culture test using murine osteoblast-like cells (MC3T3-E1 showed that the cell attachment to the nanotube-coated fibermat at an early stage after seeding was enhanced in comparison with that to the noncoated one. This approach may provide a new method of improving the surface of polymer-based biomaterials.

Property-Composition-Temperature Modeling of Waste Glass Melt Data Subject to a Randomization Restriction

International Nuclear Information System (INIS)

Piepel, Gregory F.; Heredia-Langner, Alejandro; Cooley, Scott K.

2008-01-01

Properties such as viscosity and electrical conductivity of glass melts are functions of melt temperature as well as glass composition. When measuring such a property for several glasses, the property is typically measured at several temperatures for one glass, then at several temperatures for the next glass, and so on. This data-collection process involves a restriction on randomization, which is referred to as split-plot experiment. The split-plot data structure must be accounted for in developing property-composition-temperature models and the corresponding uncertainty equations for model predictions. Instead of ordinary least squares (OLS) regression methods, generalized least squares (GLS) regression methods using restricted maximum likelihood (REML) estimation must be used. This article describes the methodology for developing property-composition-temperature models and corresponding prediction uncertainty equations using the GLS/REML regression approach. Viscosity data collected on 197 simulated nuclear waste glasses are used to illustrate the GLS/REML methods for developing a viscosity-composition-temperature model and corresponding equations for model prediction uncertainties. The correct results using GLS/REML regression are compared to the incorrect results obtained using OLS regression

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

Science.gov (United States)

Cooper, R. F.

2010-12-01

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

Phase composition and microstructure of WC-Co alloys obtained by selective laser melting

Science.gov (United States)

Khmyrov, Roman S.; Shevchukov, Alexandr P.; Gusarov, Andrey V.; Tarasova, Tatyana V.

2018-03-01

Phase composition and microstructure of initial WC, BK8 (powder alloy 92 wt.% WC-8 wt.% Co), Co powders, ball-milled powders with four different compositions (1) 25 wt.% WC-75 wt.% Co, (2) 30 wt.% BK8-70 wt.% Co, (3) 50 wt.% WC-50 wt.% Co, (4) 94 wt.% WC-6 wt.% Co, and bulk alloys obtained by selective laser melting (SLM) from as-milled powders in as-melted state and after heat treatment were investigated by scanning electron microscopy and X-ray diffraction analysis. Initial and ball-milled powders consist of WC, hexagonal α-Co and face-centered cubic β-Co. The SLM leads to the formation of major new phases W3Co3C, W4Co2C and face-centered cubic β-Co-based solid solution. During the heat treatment, there occurs partial decomposition of the face-centered cubic β-Co-based solid solution with the formation of W2C and hexagonal α-Co solid solution. The microstructure of obtained bulk samples, in general, corresponds to the observed phase composition.

Calc-silicate mineralization in active geothermal systems

Energy Technology Data Exchange (ETDEWEB)

Bird, D.K.; Schiffman, P.; Elders, W.A.; Williams, A.E.; McDowell, S.D.

1983-01-01

The detailed study of calc-silicate mineral zones and coexisting phase relations in the Cerro Prieto geothermal system were used as examples for thermodynamic evaluation of phase relations among minerals of variable composition and to calculate the chemical characteristics of hydrothermal solutions compatible with the observed calc-silicate assemblages. In general there is a close correlation between calculated and observed fluid compositions. Calculated fugacities of O{sub 2} at about 320{degrees}C in the Cerro Prieto geothermal system are about five orders of magnitude less than that at the nearby Salton Sea geothermal system. This observation is consistent with the occurrence of Fe{sup 3+} rich epidotes in the latter system and the presence of prehnite at Cerro Prieto.

An Iron-Rain Model for Core Formation on Asteroid 4 Vesta

Science.gov (United States)

Kiefer, Walter S.; Mittlefehldt, David W.

2016-01-01

Asteroid 4 Vesta is differentiated into a crust, mantle, and core, as demonstrated by studies of the eucrite and diogenite meteorites and by data from NASA's Dawn spacecraft. Most models for the differentiation and thermal evolution of Vesta assume that the metal phase completely melts within 20 degrees of the eutectic temperature, well before the onset of silicate melting. In such a model, core formation initially happens by Darcy flow, but this is an inefficient process for liquid metal and solid silicate. However, the likely chemical composition of Vesta, similar to H chondrites with perhaps some CM or CV chondrite, has 13-16 weight percent S. For such compositions, metal-sulfide melting will not be complete until a temperature of at least 1350 degrees Centigrade. The silicate solidus for Vesta's composition is between 1100 and 1150 degrees Centigrade, and thus metal and silicate melting must have substantially overlapped in time on Vesta. In this chemically and physically more likely view of Vesta's evolution, metal sulfide drops will sink by Stokes flow through the partially molten silicate magma ocean in a process that can be envisioned as "iron rain". Measurements of eucrites show that moderately siderophile elements such as Ni, Mo, and W reached chemical equilibrium between the metal and silicate phases, which is an important test for any Vesta differentiation model. The equilibration time is a function of the initial metal grain size, which we take to be 25-45 microns based on recent measurements of H6 chondrites. For these sizes and reasonable silicate magma viscosities, equilibration occurs after a fall distance of just a few meters through the magma ocean. Although metal drops may grow in size by merger with other drops, which increases their settling velocities and decreases the total core formation time, the short equilibration distance ensures that the moderately siderophile elements will reach chemical equilibrium between metal and silicate before

Hadean silicate differentiation revealed by anomalous 142Nd in the Réunion hotspot source

Science.gov (United States)

Peters, B. J.; Carlson, R.; Day, J. M.; Horan, M.

2017-12-01

Geochemical and geophysical data show that volcanic hotspots can tap ancient domains sequestered in Earth's deep mantle. Evidence from stable and long-lived radiogenic isotope systems has demonstrated that many of these domains result from tectonic and differentiation processes that occurred more than two billion years ago. Recent advances in the analysis of short-lived radiogenic isotopes have further shown that some hotspot sources preserve evidence for metal-silicate differentiation occurring within the first one percent of Earth's history. Despite these discoveries, efforts to detect variability in the lithophile 146Sm-142Nd (t1/2 = 103 Ma) system in Phanerozoic hotspot lavas have not yet detected significant global variation. We report 142Nd/144Nd ratios in Réunion Island basalts that are statistically distinct from the terrestrial Nd standard ranging to both higher and lower 142Nd/144Nd. Variations in 142Nd/144Nd, which total nearly 15 ppm on Réunion, are correlated with 3He/4He among both anomalous and non-anomalous samples. Such behavior implies that there were analogous changes in Sm/Nd and (U+Th)/3He that occurred during a Hadean silicate differentiation event and were not completely overprinted by the depleted mantle. Variations in the 142Nd-143Nd compositions of Réunion basalts can be explained by a single Hadean melting event producing enriched and depleted domains that partially re-mixed after 146Sm was no longer extant. Assuming differentiation occurred at pressures where perovskite is stable, anomalies of the magnitude observed in Réunion basalts require melting of at least 50% across a wide depth range, and up to 90% for melting at pressures near those of the deepest mantle. Models with best fits to Nd isotope data suggest this differentiation occurred around 4.40 Ga and mixing occurred after 4 Ga. This two-stage differentiation process nearly erased the ancient, anomalous 142Nd composition of the Réunion source and produced the relatively

Thermal behavior and densification mechanism during selective laser melting of copper matrix composites: Simulation and experiments

International Nuclear Information System (INIS)

Dai, Donghua; Gu, Dongdong

2014-01-01

Highlights: • Thermal behavior and densification activity during SLM of composites are simulated. • Temperature distributions and melt pool dimensions during SLM are disclosed. • Motion behaviors of gaseous bubbles in laser induced melt pool are elucidated. • Simulation results show good agreement with the obtained experimental results. - Abstract: Simulation of temperature distribution and densification process of selective laser melting (SLM) WC/Cu composite powder system has been performed, using a finite volume method (FVM). The transition from powder to solid, the surface tension induced by temperature gradient, and the movement of laser beam power with a Gaussian energy distribution are taken into account in the physical model. The effect of the applied linear energy density (LED) on the temperature distribution, melt pool dimensions, behaviors of gaseous bubbles and resultant densification activity has been investigated. It shows that the temperature distribution is asymmetric with respect to the laser beam scanning area. The center of the melt pool does not locate at the center of the laser beam but slightly shifts towards the side of the decreasing X-axis. The dimensions of the melt pool are in sizes of hundreds of micrometers and increase with the applied LED. For an optimized LED of 17.5 kJ/m, an enhanced efficiency of gas removal from the melt pool is realized, and the maximum relative density of laser processed powder reaches 96%. As the applied LED surpasses 20 kJ/m, Marangoni flow tends to retain the entrapped gas bubbles. The flow pattern has a tendency to deposit the gas bubbles at the melt pool bottom or to agglomerate gas bubbles by the rotating flow in the melt pool, resulting in a higher porosity in laser processed powder. The relative density and corresponding pore size and morphology are experimentally acquired, which are in a good agreement with the results predicted by simulation

Infrared Spectroscopic Study For Structural Investigation Of Lithium Lead Silicate Glasses

International Nuclear Information System (INIS)

Ahlawat, Navneet; Aghamkar, Praveen; Ahlawat, Neetu; Agarwal, Ashish; Monica

2011-01-01

Lithium lead silicate glasses with composition 30Li 2 O·(70-x)PbO·xSiO 2 (where, x = 10, 20, 30, 40, 50 mol %)(LPS glasses) were prepared by normal melt quench technique at 1373 K for half an hour in air to understand their structure. Compositional dependence of density, molar volume and glass transition temperature of these glasses indicates more compactness of the glass structure with increasing SiO 2 content. Fourier transform infrared (FTIR) spectroscopic data obtained for these glasses was used to investigate the changes induced in the local structure of samples as the ratio between PbO and SiO 2 content changes from 6.0 to 0.4. The observed absorption band around 450-510 cm -1 in IR spectra of these glasses indicates the presence of network forming PbO 4 tetrahedral units in glass structure. The increase in intensity with increasing SiO 2 content (upto x = 30 mol %) suggests superposition of Pb-O and Si-O bond vibrations in absorption band around 450-510 cm -1 . The values of optical basicity in these glasses were found to be dependent directly on PbO/SiO 2 ratio.

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.

Intraplate mantle oxidation by volatile-rich silicic magmas

Energy Technology Data Exchange (ETDEWEB)

Martin, Audrey M.; Médard, Etienne; Righter, Kevin; Lanzirotti, Antonio

2017-11-01

The upper subcontinental lithospheric mantle below the French Massif Central is more oxidized than the average continental lithosphere, although the origin of this anomaly remains unknown. Using iron oxidation analysis in clinopyroxene, oxybarometry, and melt inclusions in mantle xenoliths, we show that widespread infiltration of volatile (HCSO)-rich silicic melts played a major role in this oxidation. We propose the first comprehensive model of magmatism and mantle oxidation at an intraplate setting. Two oxidizing events occurred: (1) a 365–286 Ma old magmatic episode that produced alkaline vaugnerites, potassic lamprophyres, and K-rich calc-alkaline granitoids, related to the N–S Rhenohercynian subduction, and (2) < 30 Ma old magmatism related to W–E extension, producing carbonatites and hydrous potassic trachytes. These melts were capable of locally increasing the subcontinental lithospheric mantle fO2 to FMQ + 2.4. Both events originate from the melting of a metasomatized lithosphere containing carbonate + phlogopite ± amphibole. The persistence of this volatile-rich lithospheric source implies the potential for new episodes of volatile-rich magmatism. Similarities with worldwide magmatism also show that the importance of volatiles and the oxidation of the mantle in intraplate regions is underestimated.

Effect of silicate module of water glass on rheological parameters of poly(sodium acrylate)/sodium silicate hydrogels

Science.gov (United States)

Mastalska-Popiawska, J.; Izak, P.

2017-01-01

The poly(sodium acrylate)/sodium silicate hydrogels were synthesized in the presence of sodium thiosulphate and potassium persulphate as the redox initiators and N,N’-methylene-bisacrylamide as the cross-linking monomer. 20 wt% aqueous solution of sodium acrylate was polymerized together with water glass with different silicate modules (M) from 1.74 to 2.29, in three mass ratio of the monomer solution to the water glass 2:1, 1:1 and 1:2. Such obtained hybrid composites were rheologically tested using the oscillation method. It allowed to designate the crossover point during polymerization, as well as to define the viscoelastic properties of the casted hydrogel samples one week after the reaction. The obtained results of the oscillation measurements showed that cross-linking reaction proceeds very quickly and the lower the silicate module is, the process starts faster. After the completion of the reaction the silicate-polymer hydrogels are strongly elastic materials and the highest elasticity characterizes systems with the mass ratio 1:2, i.e. with the highest water glass content.

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

Science.gov (United States)

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

2013-01-01

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

Fabrication of WCp/NiBSi metal matrix composite by electron beam melting

Energy Technology Data Exchange (ETDEWEB)

Peng, Hui, E-mail: penghui@buaa.edu.cn [School of Materials Science and Engineering, Beihang University (BUAA), No. 37 Xueyuan Road, Beijing 100191 (China); Beijing Key Laboratory for Advanced Functional Material and Thin Film Technology, Beihang University, No. 37 Xueyuan Road, Beijing 100191 (China); Key Laboratory of Aerospace Materials & Performance (Ministry of Education), Beihang University, No. 37 Xueyuan Road, Beijing 100191 (China); Liu, Chang [School of Materials Science and Engineering, Beihang University (BUAA), No. 37 Xueyuan Road, Beijing 100191 (China); Guo, Hongbo, E-mail: guo.hongbo@buaa.edu.cn [School of Materials Science and Engineering, Beihang University (BUAA), No. 37 Xueyuan Road, Beijing 100191 (China); Beijing Key Laboratory for Advanced Functional Material and Thin Film Technology, Beihang University, No. 37 Xueyuan Road, Beijing 100191 (China); Key Laboratory of Aerospace Materials & Performance (Ministry of Education), Beihang University, No. 37 Xueyuan Road, Beijing 100191 (China); Yuan, Yuan [Zhuzhou Seed Cemented Carbide Technology Co. Ltd, No. 1099 Xiangda Road, Zhuzhou, Hunan 412000 (China); Gong, Shengkai; Xu, Huibin [School of Materials Science and Engineering, Beihang University (BUAA), No. 37 Xueyuan Road, Beijing 100191 (China); Beijing Key Laboratory for Advanced Functional Material and Thin Film Technology, Beihang University, No. 37 Xueyuan Road, Beijing 100191 (China); Key Laboratory of Aerospace Materials & Performance (Ministry of Education), Beihang University, No. 37 Xueyuan Road, Beijing 100191 (China)

2016-06-01

A blend of NiBSi and WC powders was used as raw material for fabricating a metal matrix composite (MMC) by electron beam melting (EBM). Dense and crack-free microstructure was produced with evenly distributed WC reinforcements. Mechanical properties, including macro- and micro-hardness, flexural strength, impact toughness and compressive strength, were investigated.

Fabrication of WCp/NiBSi metal matrix composite by electron beam melting

International Nuclear Information System (INIS)

Peng, Hui; Liu, Chang; Guo, Hongbo; Yuan, Yuan; Gong, Shengkai; Xu, Huibin

2016-01-01

A blend of NiBSi and WC powders was used as raw material for fabricating a metal matrix composite (MMC) by electron beam melting (EBM). Dense and crack-free microstructure was produced with evenly distributed WC reinforcements. Mechanical properties, including macro- and micro-hardness, flexural strength, impact toughness and compressive strength, were investigated.

Formation and Evolution of the Continental Lithospheric Mantle: Perspectives From Radiogenic Isotopes of Silicate and Sulfide Inclusions in Macrodiamonds

Science.gov (United States)

Shirey, S. B.; Richardson, S. H.

2007-12-01

initial Os isotopic compositions in 3.5 Ga Slave (Panda) and 2.9 Ga Kaapvaal (Kimberley) sulfides, the low Sm/Nd and elevated initial Sr isotopic compositions of 3.4 Ga Kaapvaal (Kimberley) harzburgitic garnets, the preponderance of 2.9 Ga eclogitic sulfides in every western Kaapvaal craton locality, and the occurrence of surficial, volcanogenic S in Kaapvaal (Orapa) sulfides. The continental lithosphere was accessible to melts and fluids from the asthenosphere throughout the Proterozoic as evident from silicate and sulfide inclusion suites of 0.9 to 2.0 Ga age in every locality studied in the Kaapvaal craton. The correspondence of silicate inclusion type with current seismic velocity structure of the Kaapvaal mantle keel shows that its structure is at least Bushveld age (2 Ga) and due to compositional differences. Seismic velocity structures of continental mantle keels may be more a function of their geologic history than current temperature distribution.

Physicochemical Study of Irradiated polypropylene/Organo :Modified Montmorillonite Composites by Using Electron Beam Irradiation Technique

International Nuclear Information System (INIS)

Hassan, M.S.

2008-01-01

Polypropylene/ Organo modified montmorillonite composites (PP/ OMMT) were prepared by melt blending with a twin screw extruder. The thermal properties by thermo gravimetric analysis (TGA), the dispersion of OMMT of macromolecules by X-ray diffraction (XRD), mechanical properties and the morphology by scanning electron microscopy (SEM) were investigated. The effect of electron beam irradiation on these properties was also studied. The results showed an intercalation between the silicate layers and the PP polymer matrix. The (PP/ OMMT) composites exhibit higher thermal stability and lower mechanical properties than pure polypropylene

Temperature Effects on Aluminoborosilicate Glass and Melt Structure

Science.gov (United States)

Wu, J.; Stebbins, J. F.

2008-12-01

Quantitative determination of the atomic-scale structure of multi-component oxide melts, and the effects of temperature on them, is a complex problem. Ca- and Na- aluminoborosilicates are especially interesting, not only because of their major role in widespread technical applications (flat-panel computer displays, fiber composites, etc.), but because the coordination environments of two of their main network cations (Al3+ and B3+) change markedly with composition and temperature is ways that may in part be analogous to processes in silicate melts at high pressures in the Earth. Here we examine a series of such glasses with different cooling rates, chosen to evaluate the role modifier cation field strength (Ca2+ vs. Na+) and of non-bridging oxygen (NBO) content. To explore the effects of fictive temperature, fast quenched and annealed samples were compared. We have used B-11 and Al-27 MAS NMR to measure the different B and Al coordinations and calculated the contents of non-bridging oxygens (NBO). Lower cooling rates increase the fraction of [4]B species in all compositions. The conversion of [3]B to [4]B is also expected to convert NBO to bridging oxygens, which should affect thermodynamic properties such as configurational entropy and configurational heat capacity. For four compositions with widely varying compositions and initial NBO contents, analysis of the speciation changes with the same, simple reaction [3]B = [4]B + NBO yields similar enthalpy values of 25±7 kJ/mol. B-11 triple quantum MAS NMR allows as well the proportions of [3]B boroxol ring and non-ring sites to be determined, and reveals more [3]B boroxol ring structures present in annealed (lower temperature) glasses. In situ, high-temperature MAS NMR spectra have been collected on one of the Na-aluminoborosilicate and on a sodium borate glass at 14.1 T. The exchange of boron between the 3- and 4-coordinated sites is clearly observed well above the glass transition temperatures, confirming the

Melting of corrosion-resistant steel of martensite class with given phase composition

International Nuclear Information System (INIS)

Grashchenkov, P.M.; Kachanov, E.B.; Stetsenko, N.V.; Moshkevich, E.I.; Bunina, T.I.

1979-01-01

Introduced is a melting procedure for the EhP410U (vacuum arc remelted) and VNC-2M (electroslag remelted) stainless steels with carbon (carbon ferrochrome) and nickel additions to ensure a present phase composition. Magnetizability of cold specimens of the EhP410U steel should be within the limits 17.0-19.5 mV by a special device. During melting of the second steel controlled are not only cold specimens magnetizability of which should be not less than 16 mV, but hot as well (at 25O-400 deg C) by the level of magnetizability not higher than 0.5 mV. During vacuum arc remelting nitrogen content reduces in general by 0.014% and manganese content - by 0.23%; correspondingly the magnetizability of specimens insceases approximately by 1 mV. During electroslag remelting chemical and phase composition practically are not changed. Total and diffusible hydrogen contents in the vacuum remelted steel is rather low (1-5 and 0.03-0.35 cm 3 /100 gs), which provides increased reliability of the articles

Melt Inclusion Analysis of RBT 04262 with Relationship to Shergottites and Mars Surface Compositions

Science.gov (United States)

Potter, S. A.; Brandon, A. D.; Peslier, A. H.

2015-01-01

Martian meteorite RBT 04262 is in the shergottite class. It displays the two lithologies typically found in "lherzolitic shergottites": one with a poikilitic texture of large pyroxene enclosing olivine and another with non-poikilitic texture. In the case of RBT 04262, the latter strongly ressembles an olivine- phyric shergottite which led the initial classification of this meteorite in that class. RBT 04262 has been studied with regards to its petrology, geochemistry and cosmic ray exposure and belongs to the enriched oxidized end-member of the shergottites. Studies on RBT 04262 have primarily focused on the bulk rock composition or each of the lithologies independently. To further elucidate RBT 04262's petrology and use it to better understand Martian geologic history, an in-depth study of its melt inclusions (MI) is being conducted. The MI chosen for this study are found within olivine grains. MI are thought to be trapped melts of the crystallizing magma preserved by the encapsulating olivine and offer snapshots of the composition of the magma as it evolves. Some MI, in the most Mg-rich part of the olivine of olivine-pyric shergottites, may even be representative of the meteorite parent melt.

PYROXENITE VEINS WITHIN SSZ PERIDOTITES – EVIDENCE OF MELT-ROCK INTERACTION (EGIINGOL MASSIF), MAJOR AND TRACE ELEMENT COMPOSITION OF MINERALS

OpenAIRE

A. A. Karimov; M A. Gornova; V. A. Belyaev

2017-01-01

Evidence of melt-rock reaction between suprasubduction zone (SSZ) peridotites and island arc boninititc and tholeiitic melts are identified. This process is the cause of replacive dunites and pyroxenite veins forming, which are represent the ways of island-arc melts migration. The peridotite-melt interaction is confirmed by compositional features of rocks and minerals. Influence of boninitic melt in peridotites of South Sandwich island arc leads to increasing of TiO2 and Cr-number (Cr#) in sp...

Selective silicate-directed motility in diatoms

DEFF Research Database (Denmark)

Bondoc, Karen Grace V.; Heuschele, Jan; Gillard, Jeroen

2016-01-01

the major sink in the global Si cycle. Dissolved silicic acid (dSi) availability frequently limits diatom productivity and influences species composition of communities. We show that benthic diatoms selectively perceive and behaviourally react to gradients of dSi. Cell speed increases under d...

Conversion of rice hull ash into soluble sodium silicate

Directory of Open Access Journals (Sweden)

Edson Luiz Foletto

2006-09-01

Full Text Available Sodium silicate is used as raw material for several purposes: silica gel production, preparation of catalysts, inks, load for medicines, concrete hardening accelerator, component of detergents and soaps, refractory constituent and deflocculant in clay slurries. In this work sodium silicate was produced by reacting rice hull ash (RHA and aqueous sodium hydroxide, in open and closed reaction systems. The studied process variables were time, temperature of reaction and composition of the reaction mixture (expressed in terms of molar ratios NaOH/SiO2 and H2O/SiO2. About 90% silica conversion contained in the RHA into sodium silicate was achieved in closed system at 200 °C. The results showed that sodium silicate production from RHA can generate aggregate value to this residue.

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.

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

DEFF Research Database (Denmark)

Okhrimenko, Denis; Budi, Akin; Ceccato, Marcel

2017-01-01

and compared its properties with those on complex silicate surfaces such as those used by industry (mineral fibers and fiber melt wafers). The APS was deposited from aqueous and organic (toluene) solutions and studied with surface sensitive techniques, including X-ray photoelectron spectroscopy (XPS), atomic...

Comparison of physical, chemical and cellular responses to nano- and micro-sized calcium silicate/poly(epsilon-caprolactone) bioactive composites.

Science.gov (United States)

Wei, Jie; Heo, S J; Kim, D H; Kim, S E; Hyun, Y T; Shin, Jung-Woog

2008-06-06

In this study, we fabricated nano-sized calcium silicate/poly(epsilon-caprolactone) composite (n-CPC) and micro-sized calcium silicate/poly(epsilon-caprolactone) composite (m-CPC). The composition, mechanical properties, hydrophilicity and degradability of both n-CPC and m-CPC were determined, and in vitro bioactivity was evaluated by investigating apatite forming on their surfaces in simulated body fluid (SBF). In addition, cell responses to the two kinds of composites were comparably investigated. The results indicated that n-CPC has superior hydrophilicity, compressive strength and elastic modulus properties compared with m-CPC. Both n-CPC and m-CPC exhibited good in vitro bioactivity, with different morphologies of apatite formation on their surfaces. The apatite layer on n-CPC was more homogeneous and compact than on m-CPC, due to the elevated levels of calcium and silicon concentrations in SBF from n-CPC throughout the 14-day soaking period. Significantly higher levels of attachment and proliferation of MG63 cells were observed on n-CPC than on m-CPC, and significantly higher levels of alkaline phosphatase activity were observed in human mesenchymal stem cells (hMSCs) on n-CPC than on m-CPC after 7 days. Scanning electron microscopy observations revealed that hMSCs were in intimate contact with both n-CPC and m-CPC surfaces, and significantly cell adhesion, spread and growth were observed on n-CPC and m-CPC. These results indicated that both n-CPC and m-CPC have the ability to support cell attachment, growth, proliferation and differentiation, and also yield good bioactivity and biocompatibility.

Melting Behavior and Thermolysis of NaBH4−Mg(BH42 and NaBH4−Ca(BH42 Composites

Directory of Open Access Journals (Sweden)

Morten B. Ley

2015-04-01

Full Text Available The physical properties and the hydrogen release of NaBH4–Mg(BH42 and NaBH4−Ca(BH42 composites are investigated using in situ synchrotron radiation powder X-ray diffraction, thermal analysis and temperature programmed photographic analysis. The composite, xNaBH4–(1 − xMg(BH42, x = 0.4 to 0.5, shows melting/frothing between 205 and 220 °C. However, the sample does not become a transparent molten phase. This behavior is similar to other alkali-alkaline earth metal borohydride composites. In the xNaBH4–(1 − xCa(BH42 system, eutectic melting is not observed. Interestingly, eutectic melting in metal borohydrides systems leads to partial thermolysis and hydrogen release at lower temperatures and the control of sample melting may open new routes for obtaining high-capacity hydrogen storage materials.

KINETICS OF A SILICATE COMPOSITION GELATION IN PRESENCE OF REACTION RATE REGULATING COMPOUNDS

Directory of Open Access Journals (Sweden)

Olga Titova

2013-12-01

Full Text Available The influence of organic and inorganic additions on the formation rate of the silicate gels standard systems – sodium silicate solution in model fresh water was studied. As a result of the experiments were selected optimum concentrations of additives - gelation time regulators

Coordinated HArd Sphere Model (CHASM): A Simplified Model for Silicate and Oxide Liquids at Mantle Conditions

Science.gov (United States)

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

2013-12-01

Recent first-principles theoretical calculations (Stixrude 2009) and experimental shock-wave investigations (Mosenfelder 2009) indicate that melting perovskite requires significantly less energy than previously thought, supporting the idea of a deep-mantle magma ocean early in Earth's history. The modern-day solid Earth is thus likely the result of crystallization from an early predominantly molten state, a process that is primarily controlled by the poorly understood behavior of silicate melts at extreme pressures and temperatures. Probing liquid thermodynamics at mantle conditions is difficult for both theory and experiment, and further challenges are posed by the large relevant compositional space including at least MgO, SiO2, and FeO. First-principles molecular dynamics has been used with great success to determine the high P-T properties of a small set of fixed composition silicate-oxide liquids including MgO (Karki 2006), SiO2 (Karki 2007), Mg2SiO4 (de Koker 2008), MgSiO3 (Stixrude 2005), and Fe2SiO4 (Ramo 2012). While extremely powerful, this approach has limitations including high computational cost, lower bounds on temperature due to relaxation constraints, as well as restrictions to length scales and time scales that are many orders of magnitude smaller than those relevant to the Earth or experimental methods. As a compliment to accurate first-principles calculations, we have developed the Coordinated HArd Sphere Model (CHASM). We extend the standard hard sphere mixture model, recently applied to silicate liquids by Jing (2011), by accounting for the range of oxygen coordination states available to liquid cations. Utilizing approximate analytic expressions for the hard sphere model, the method can predict complex liquid structure and thermodynamics while remaining computationally efficient. Requiring only minutes on standard desktop computers rather than months on supercomputers, the CHASM approach is well-suited to providing an approximate thermodynamic

Bursting the bubble of melt inclusions

Science.gov (United States)

Lowenstern, Jacob B.

2015-01-01

Most silicate melt inclusions (MI) contain bubbles, whose significance has been alternately calculated, pondered, and ignored, but rarely if ever directly explored. Moore et al. (2015) analyze the bubbles, as well as their host glasses, and conclude that they often hold the preponderance of CO2 in the MI. Their findings entreat future researchers to account for the presence of bubbles in MI when calculating volatile budgets, saturation pressures, and eruptive flux.

Melting and Sintering of Ashes

DEFF Research Database (Denmark)

Hansen, Lone Aslaug

1997-01-01

-1300°C, and a trend of higher fusion temperatures with increasing contents of Al-silicates and quartz was found.c) Fly ashes, bottom ashes and deposits from coal/straw co-firing were all found to consist mainly of metal-alumina and alumina-silicates. These ashes all melt in the temperature range 1000......The thesis contains an experimental study of the fusion and sintering of ashes collected during straw and coal/straw co-firing.A laboratory technique for quantitative determination of ash fusion has been developed based on Simultaneous Thermal Analysis (STA). By means of this method the fraction......, the biggest deviations being found for salt rich (i.e. straw derived) ashes.A simple model assuming proportionality between fly ash fusion and deposit formation was found to be capable of ranking deposition rates for the different straw derived fly ashes, whereas for the fly ashes from coal/straw co-firing...

Mechanical properties of polymer-infiltrated-ceramic (sodium aluminum silicate) composites for dental restoration.

Science.gov (United States)

Cui, Bencang; Li, Jing; Wang, Huining; Lin, Yuanhua; Shen, Yang; Li, Ming; Deng, Xuliang; Nan, Cewen

2017-07-01

To fabricate indirect restorative composites for CAD/CAM applications and evaluate the mechanical properties. Polymer-infiltrated-ceramic composites were prepared through infiltrating polymer into partially sintered sodium aluminum silicate ceramic blocks and curing. The corresponding samples were fabricated according to standard ISO-4049 using for mechanical properties measurement. The flexural strength and fracture toughness were measured using a mechanical property testing machine. The Vickers hardness and elastic modulus were calculated from the results of nano-indentation. The microstructures were investigated using secondary electron detector. The density of the porous ceramic blocks was obtained through TG-DTA. The conversion degrees were calculated from the results of mid-infrared spectroscopy. The obtained polymer infiltrated composites have a maximum flexural strength value of 214±6.5MPa, Vickers hardness of 1.76-2.30GPa, elastic modulus of 22.63-27.31GPa, fracture toughness of 1.76-2.35MPam 1/2 and brittleness index of 0.75-1.32μm -1/2 . These results were compared with those of commercial CAD/CAM blocks. Our results suggest that these materials with good mechanical properties are comparable to two commercial CAD/CAM blocks. The sintering temperature could dramatically influence the mechanical properties. Restorative composites with superior mechanical properties were produced. These materials mimic the properties of natural dentin and could be a promising candidate for CAD/CAM applications. Copyright © 2017 Elsevier Ltd. All rights reserved.

Simulation experiment on the flooding behaviour of core melts: KATS-9

International Nuclear Information System (INIS)

Fieg, G.; Massier, H.; Schuetz, W.; Stegmaier, U.; Stern, G.

2000-11-01

For future Light Water Reactors special devices (core catchers) are being developed to prevent containment failure by basement erosion after reactor pressure vessel meltthrough during a core meltdown accident. Quick freezing of the molten core masses is desirable to reduce release of radioactivity. Several concepts of core catcher devices have been proposed based on the spreading of corium melt onto flat surfaces with subsequent water cooling. A KATS-experiment has been performed to investigate the flooding behaviour of high temperature melts using alumina-iron thermite melts as a simulant. The oxidic thermite melt is conditioned by adding other oxides to simulate a realistic corium melt as close as possible in terms of liquidus and solidus temperatures. Before flooding with water, spreading of the separate oxidic and metallic melts has been done in one-dimensional channels with a silicate concrete as the substrate. The flooding rate was, in relation to the melt surface, identical to the flooding rate in EPR. (orig.) [de

Experimental determination of trace-element partitioning between pargasite and a synthetic hydrous andesitic melt

Science.gov (United States)

Brenan, J. M.; Shaw, H. F.; Ryerson, F. J.; Phinney, D. L.

1995-10-01

In order to more fully establish a basis for quantifying the role of amphibole in trace-element fractionation processes, we have measured pargasite/silicate melt partitioning of a variety of trace elements (Rb, Ba, Nb, Ta, Hf, Zr, Ce, Nd, Sm, Yb), including the first published values for U, Th and Pb. Experiments conducted at 1000°C and 1.5 GPa yielded large crystals free of compositional zoning. Partition coefficients were found to be constant at total concentrations ranging from ˜ 1 to > 100 ppm, indicating Henry's Law is oparative over this interval. Comparison of partition coefficients measured in this study with previous determinations yields good agreement for similar compositions at comparable pressure and temperature. The compatibility of U, Th and Pb in amphibole decreases in the order Pb > Th > U. Partial melting or fractional crystallization of amphibole-bearing assemblages will therefore result in the generation of excesses in 238U activity relative to 230Th, similar in magnitude to that produced by clinopyroxene. The compatibility of Pb in amphibole relative to U or Th indicates that melt generation in the presence of residual amphibole will result in the long-term enrichment in Pb relative to U or Th in the residue. This process is therefore incapable of producing the depletion in Pb relative to U or Th inferred from the Pb isotopic composition of MORB and OIB. Comparison of partition coefficients measured in this study with previous values for clinopyroxene allows some distinction to be made between expected trace-element fractionations produced during dry (cpx present) and wet (cpx + amphibole present) melting. Rb, Ba, Nb and Ta are dramatically less compatible in clinopyroxene than in amphibole, whereas Th, U, Hf and Zr have similar compatibilities in both phases. Interelement fractionations, such as DNb/DBa are also different for clinopyroxene and amphibole. Changes in certain ratios, such as Ba/Nb, Ba/Th, and Nb/Th within comagmatic suites may

Dynamic observations of vesiculation reveal the role of silicate crystals in bubble nucleation and growth in andesitic magmas

Energy Technology Data Exchange (ETDEWEB)

Pleše, P.; Higgins, M. D.; Mancini, L.; Lanzafame, G.; Brun, F.; Fife, J. L.; Casselman, J.; Baker, D. R.

2018-01-01

Bubble nucleation and growth control the explosivity of volcanic eruptions, and the kinetics of these processes are generally determined from examinations of natural samples and quenched experimental run products. These samples, however, only provide a view of the final state, from which the initial conditions of a time-evolving magmatic system are then inferred. The interpretations that follow are inexact due to the inability of determining the exact conditions of nucleation and the potential detachment of bubbles from their nucleation sites, an uncertainty that can obscure their nucleation location – either homogeneously within the melt or heterogeneously at the interface between crystals and melts. We present results of a series of dynamic, real-time 4D X-ray tomographic microscopy experiments where we observed the development of bubbles in crystal bearing silicate magmas. Experimentally synthesized andesitic glasses with 0.25–0.5 wt% H2O and seed silicate crystals were heated at 1 atm to induce bubble nucleation and track bubble growth and movement. In contrast to previous studies on natural and experimentally produced samples, we found that bubbles readily nucleated on plagioclase and clinopyroxene crystals, that their contact angle changes during growth and that they can grow to sizes many times that of the silicate on whose surface they originated. The rapid heterogeneous nucleation of bubbles at low degrees of supersaturation in the presence of silicate crystals demonstrates that silicates can affect when vesiculation ensues, influencing subsequent permeability development and effusive vs. explosive transition in volcanic eruptions.

Dynamic observations of vesiculation reveal the role of silicate crystals in bubble nucleation and growth in andesitic magmas

Science.gov (United States)

Pleše, P.; Higgins, M. D.; Mancini, L.; Lanzafame, G.; Brun, F.; Fife, J. L.; Casselman, J.; Baker, D. R.

2018-01-01

Bubble nucleation and growth control the explosivity of volcanic eruptions, and the kinetics of these processes are generally determined from examinations of natural samples and quenched experimental run products. These samples, however, only provide a view of the final state, from which the initial conditions of a time-evolving magmatic system are then inferred. The interpretations that follow are inexact due to the inability of determining the exact conditions of nucleation and the potential detachment of bubbles from their nucleation sites, an uncertainty that can obscure their nucleation location - either homogeneously within the melt or heterogeneously at the interface between crystals and melts. We present results of a series of dynamic, real-time 4D X-ray tomographic microscopy experiments where we observed the development of bubbles in crystal bearing silicate magmas. Experimentally synthesized andesitic glasses with 0.25-0.5 wt% H2O and seed silicate crystals were heated at 1 atm to induce bubble nucleation and track bubble growth and movement. In contrast to previous studies on natural and experimentally produced samples, we found that bubbles readily nucleated on plagioclase and clinopyroxene crystals, that their contact angle changes during growth and that they can grow to sizes many times that of the silicate on whose surface they originated. The rapid heterogeneous nucleation of bubbles at low degrees of supersaturation in the presence of silicate crystals demonstrates that silicates can affect when vesiculation ensues, influencing subsequent permeability development and effusive vs. explosive transition in volcanic eruptions.

Phase relations in the Cabeza de Araya cordierite monzogranite, Iberian Massif: implications for the formation of cordierite in a crystal mush

Energy Technology Data Exchange (ETDEWEB)

García Moreno, O.; Corretgé, L.G.; Holtz, F.; García-Arias, M.; Rodriguez, C.

2017-07-01

Experimental investigations and thermodynamic calculations of the phase relations of a cordierite-rich monzogranite from the Cabeza de Araya batholith (Cáceres, Spain) have been performed to understand the formation of cordierite. The experiments failed to crystallize cordierite in the pressure range 200-600MPa, in the temperature range 700-975ºC and for different water activities (melt water contents between 2 and 6 wt.%). In contrast, clinopyroxene and orthopyroxene (absent in the natural mineral rock assemblage), together with biotite, were observed as ferromagnesian assemblage in a wide range of experimental conditions. Thermodynamic calculations, using the software PERPLE{sub X}, describe the formation of cordierite only at 200 and 400MPa and very low water contents, and the amount of cordierite formed in the models is always below 3.5 vol.%. The results indicate that cordierite is not in equilibrium with the bulk rock compositions. The most probable explanation was that cordierite nucleated and crystallized from a melt that is not in equilibrium with part of the mineral assemblage present in the magma. This “non-reactive” mineral assemblage was mainly composed of plagioclase. The silicate melts from which cordierite crystallized was more Al-rich and K-rich than the silicate melt composition in equilibrium with the bulk composition. One possible process for the high Al content of the silicate melt is related to assimilation and partial melting of Al-rich metasediments. An exo-perictetic reaction is assumed to account for both textural and geochemical observations. On the other hand, hybridization processes typical for calc-alkaline series can also explain the high proportions of “non-reactive” minerals observed in relatively high temperature magmas. This study clearly demonstrates that silicate melts in a crystal mush can depart significantly from the composition of melt that should be in equilibrium with the bulk solid assemblage.

Experimental Behavior of Sulfur Under Primitive Planetary Differentiation Processes, the Sulfide Formations in Enstatite Meteorites and Implications for Mercury.

Science.gov (United States)

Malavergne, V.; Brunet, F.; Righter, K.; Zanda, B.; Avril, C.; Borensztajn, S.; Berthet, S.

2012-01-01

Enstatite meteorites are the most reduced naturally-occuring materials of the solar system. The cubic monosulfide series with the general formula (Mg,Mn,Ca,Fe)S are common phases in these meteorite groups. The importance of such minerals, their formation, composition and textural relationships for understanding the genesis of enstatite chondrites (EC) and aubrites, has long been recognized (e.g. [1]). However, the mechanisms of formation of these sulfides is still not well constrained certainly because of possible multiple ways to produce them. We propose to simulate different models of formation in order to check their mineralogical, chemical and textural relevancies. The solubility of sulfur in silicate melts is of primary interest for planetary mantles, particularly for the Earth and Mercury. Indeed, these two planets could have formed, at least partly, from EC materials (e.g. [2, 3, 4]). The sulfur content in silicate melts depends on the melt composition but also on pressure (P), temperature (T) and oxygen fugacity fO2. Unfortunately, there is no model of general validity in a wide range of P-T-fO2-composition which describes precisely the evolution of sulfur content in silicate melts, even if the main trends are now known. The second goal of this study is to constrain the sulfur content in silicate melts under reducing conditions and different temperatures.

Facile synthesis of three-dimensional diatomite/manganese silicate nanosheet composites for enhanced Fenton-like catalytic degradation of malachite green dye

Science.gov (United States)

Jiang, De Bin; Yuan, Yunsong; Zhao, Deqiang; Tao, Kaiming; Xu, Xuan; Zhang, Yu Xin

2018-05-01

In this work, we demonstrate a novel and simple approach for fabrication of the complex three-dimensional (3D) diatomite/manganese silicate nanosheet composite (DMSNs). The manganese silicate nanosheets are uniformly grown on the inner and outer surface of diatomite with controllable morphology using a hydrothermal method. Such structural features enlarged the specific surface area, resulting in more catalytic active sites. In the heterogeneous Fenton-like reaction, the DMSNs exhibited excellent catalytic capability for the degradation of malachite green (MG). Under optimum condition, 500 mg/L MG solution was nearly 93% decolorized at 70 min in the reaction. The presented results show an enhanced catalytic behavior of the DMSNs prepared by the low-cost natural diatomite material and simple controllable process, which indicates their potential for environmental remediation applications. [Figure not available: see fulltext.

Experimental evidence for Mo isotope fractionation between metal and silicate liquids

Science.gov (United States)

Hin, Remco C.; Burkhardt, Christoph; Schmidt, Max W.; Bourdon, Bernard; Kleine, Thorsten

2013-10-01

Stable isotope fractionation of siderophile elements may inform on the conditions and chemical consequences of core-mantle differentiation in planetary objects. The extent to which Mo isotopes fractionate during such metal-silicate segregation, however, is so far unexplored. We have therefore investigated equilibrium fractionation of Mo isotopes between liquid metal and liquid silicate to evaluate the potential of Mo isotopes as a new tool to study core formation. We have performed experiments at 1400 and 1600 °C in a centrifuging piston cylinder. Tin was used to lower the melting temperature of the Fe-based metal alloys to double spike technique. In experiments performed at 1400 °C, the 98Mo/95Mo ratio of silicate is 0.19±0.03‰ (95% confidence interval) heavier than that of metal. This fractionation is not significantly affected by the presence or absence of carbon. Molybdenum isotope fractionation is furthermore independent of oxygen fugacity in the range IW -1.79 to IW +0.47, which are plausible values for core formation. Experiments at 1600 °C show that, at equilibrium, the 98Mo/95Mo ratio of silicate is 0.12±0.02‰ heavier than that of metal and that the presence or absence of Sn does not affect this fractionation. Equilibrium Mo isotope fractionation between liquid metal and liquid silicate as a function of temperature can therefore be described as ΔMoMetal-Silicate98/95=-4.70(±0.59)×105/T2. Our experiments show that Mo isotope fractionation may be resolvable up to metal-silicate equilibration temperatures of about 2500 °C, rendering Mo isotopes a novel tool to investigate the conditions of core formation in objects ranging from planetesimals to Earth sized bodies.

Crystallisation mechanism of a multicomponent lithium alumino-silicate glass

International Nuclear Information System (INIS)

Wurth, R.; Pascual, M.J.; Mather, G.C.; Pablos-Martín, A.; Muñoz, F.; Durán, A.; Cuello, G.J.; Rüssel, C.

2012-01-01

A base glass of composition 3.5 Li 2 O∙0.15 Na 2 O∙0.2 K 2 O∙1.15 MgO∙0.8 BaO∙1.5 ZnO∙20 Al 2 O 3 ∙67.2 SiO 2 ∙2.6 TiO 2 ∙1.7 ZrO 2 ∙1.2 As 2 O 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 2 O 6 with nanoscaled crystals forms at 750 °C. Quantitative Rietveld refinement of samples annealed at 750 °C for 8 h determined a crystallised fraction of around 59 wt.%. The room temperature crystallised phase adopts an ordered, β-eucryptite-like structure (2 × 2 × 2 cell) with Li ordered in the structural channels. The Avrami parameter (n ∼ 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 −1 . - Highlights: ► Nanoscaled high-quartz crystals from a multicomponent lithium alumino-silicate glass. ► Combined X-ray and neutron diffraction structural refinement. ► β-Eucryptite-like structure (2 × 2×2 cell) with Li ordered in the structural channels. ► 3-Dimensional bulk crystallisation mechanism with an increasing number of nuclei. ► Usage and validation of an alternative approach to calculate the Avrami parameter.

Evaluation of a Melt Infiltrated SiC/SiC Ceramic Matrix Composite

Science.gov (United States)

2017-12-20

temperature performance of a state- of-the-art CMC provides evidence that this new class of materials can, or perhaps cannot, meet the harsh...and elevated temperature . This report describes tensile, creep, and fatigue testing procedures and presents the results. 15. SUBJECT TERMS ceramic...matrix composites, creep, dwell fatigue, fatigue, high temperature , melt infiltrated, SiC/SiC 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF

Identification of an Extremely 180-Rich Presolar Silicate Grain in Acfer 094

Science.gov (United States)

Nguyen, A. N.; Messenger, S.

2009-01-01

Presolar silicate grains have been abundantly identified since their first discovery less than a decade ago [1,2,3]. The O isotopic compositions of both silicate and oxide stardust indicate the vast majority (>90%) condensed around Orich asymptotic giant branch (AGB) stars. Though both presolar phases have average sizes of 300 nm, grains larger than 1 m are extremely uncommon for presolar silicates. Thus, while numerous isotopic systems have been measured in presolar oxide grains [4], very few isotopic analyses for presolar silicates exist outside of O and Si [2,5]. And still, these measurements suffer from isotopic dilution with surrounding matrix material [6]. We conduct a search for presolar silicates in the primitive carbonaceous chondrite Acfer 094 and in some cases obtain high spatial resolution, high precision isotopic ratios.

Carbonate formation in non-aqueous environments by solid-gas carbonation of silicates

Science.gov (United States)

Day, S. J.; Thompson, S. P.; Evans, A.; Parker, J. E.

2012-02-01

We have produced synthetic analogues of cosmic silicates using the Sol Gel method, producing amorphous silicates of composition Mg(x)Ca(1-x)SiO3. Using synchrotron X-ray powder diffraction on Beamline I11 at the Diamond Light Source, together with a newly-commissioned gas cell, real-time powder diffraction scans have been taken of a range of silicates exposed to CO2 under non-ambient conditions. The SXPD is complemented by other techniques including Raman and Infrared Spectroscopy and SEM imaging.

Fabrication of fiber composites with a MAX phase matrix by reactive melt infiltration

International Nuclear Information System (INIS)

Lenz, F; Krenkel, W

2011-01-01

Due to the inherent brittleness of ceramics it is very desirable to increase the damage tolerance of ceramics. The ternary MAX phases are a promising group of materials with high fracture toughness. The topic of this study is the development of ceramic matrix composites (CMCs) with a matrix containing MAX phases, to achieve a damage tolerant structural composite material. For this purpose carbon fiber reinforced preforms with a carbon-titanium carbide matrix (C/C-TiC) were developed and infiltrated with silicon by a pressureless reactive melt infiltration. Finally liquid silicon caused the formation of SiC, TiSi 2 and Ti 3 SiC 2 in the matrix of the composite.

Discovery of Ni-smectite-rich saprolite at Loma Ortega, Falcondo mining district (Dominican Republic): geochemistry and mineralogy of an unusual case of "hybrid hydrous Mg silicate - clay silicate" type Ni-laterite

Science.gov (United States)

Tauler, Esperança; Lewis, John F.; Villanova-de-Benavent, Cristina; Aiglsperger, Thomas; Proenza, Joaquín A.; Domènech, Cristina; Gallardo, Tamara; Longo, Francisco; Galí, Salvador

2017-10-01

Hydrous Mg silicate-type Ni-laterite deposits, like those in the Falcondo district, Dominican Republic, are dominated by Ni-enriched serpentine and garnierite. Recently, abundant Ni-smectite in the saprolite zone have been discovered in Loma Ortega, one of the nine Ni-laterite deposits in Falcondo. A first detailed study on these Ni-smectites has been performed (μXRD, SEM, EPMA), in addition to a geochemical and mineralogical characterisation of the Loma Ortega profile (XRF, ICP-MS, XRD). Unlike other smectite occurrences in laterite profiles worldwide, the Loma Ortega smectites are trioctahedral and exhibit high Ni contents never reported before. These Ni-smectites may be formed from weathering of pyroxene and olivine, and their composition can be explained by the mineralogy and the composition of the Al-depleted, olivine-rich parent ultramafic rock. Our study shows that Ni-laterites are mineralogically complex, and that a hydrous Mg silicate ore and a clay silicate ore can be confined to the same horizon in the weathering profile, which has significant implications from a recovery perspective. In accordance, the classification of "hybrid hydrous Mg silicate - clay silicate" type Ni-laterite deposit for Loma Ortega would be more appropriate.

Preparation of β-belite using liquid alkali silicates

International Nuclear Information System (INIS)

Koutník, P.

2017-01-01

The aim of this study is the preparation of β-belite by a solid-state reaction using powdered limestone, amorphous silica and liquid alkali silicates. The raw materials were blended, the mixtures were agglomerated and then burnt. The resulting samples were characterized by X-ray diffraction analysis and scanning electron microscopy. Free lime content in the β-belite samples was also determined. The effects of CaO/SiO2 ratio (1.6–2.1), burning temperature (800–1400 °C), utilization of different raw materials (silica fume, synthetic silica, potassium silicate, sodium silicate, potassium hydroxide) and burning time (0.5–16 h) on free lime content and mineralogical composition were investigated. The purest ?-belite samples were prepared from a mixture of powdered limestone, silica fume and liquid potassium silicate with a ratio CaO/SiO2 = 2 by burning at temperatures between 1100 and 1300 °C for more than 2 h. Decreasing of the CaO/SiO2 ratio led to rankinite formation and lower a burning temperature led to the formation of wollastonite. [es

Draft paper: On the analysis of diffusive mass transfer in ex-vessel corium pools

International Nuclear Information System (INIS)

Frolov, Kyrill N.

2003-01-01

In case of a severe accident at a nuclear power plant (NPP) involving the reactor pressure vessel (RPV) melt-through, confident solidification of ex-vessel corium is the imperative condition of its safe retention within the plant containment. The rate-determining process for solidification of ex-vessel coriums in the long-term is the chemical diffusion in the liquid phase at the solid-liquid interface. The process of chemical diffusion in the diffusive boundary layer can evolve taking on different rates, depending on the boundary conditions and the melt composition. Nonetheless, the chemical diffusion rates would entwine the self-diffusivities of corium constituents, which in turn would depend on the melt chemical composition. This work looks at some aspects of analytical and experimental determination of self-diffusivities of corium constituents. Following the corium-concrete interaction, an ex-vessel corium melt would contain several chemical components, including a fraction of silica. Accordingly, ex-vessel corium is considered in this paper as a silicate melts. In the realm of the geological and glass sciences, where silicate melts are most often discussed, the diffusive transport and viscous flow are conceived interrelated from a phenomenological point of view. Though the viscous and diffusive mass transfer mechanisms are not identical for different species even in the same melt, a combination of semi-empirical models can still provide an estimation of the diffusion thresholds in ex-vessel corium melts. Thus, the first part of this paper presents an analysis of the applicability of such empirical models for simple silicate melts based on the published data. This is followed by an estimation of diffusivities in melt compositions typical of ex-vessel coriums. Alternatively, although the general trend towards a coupled description of the viscous flow and diffusion for ex-vessel corium melts seems promising, it is limited to published data on self-diffusivities of

Application of Sodium Silicate Enhances Cucumber Resistance to Fusarium Wilt and Alters Soil Microbial Communities

Directory of Open Access Journals (Sweden)

Xingang Zhou

2018-05-01

Full Text Available Exogenous silicates can enhance plant resistance to pathogens and change soil microbial communities. However, the relationship between changes in soil microbial communities and enhanced plant resistance remains unclear. Here, effects of exogenous sodium silicate on cucumber (Cucumis sativus L. seedling resistance to Fusarium wilt caused by the soil-borne pathogen Fusarium oxysporum f.sp. cucumerinum Owen (FOC were investigated by drenching soil with 2 mM sodium silicate. Soil bacterial and fungal community abundances and compositions were estimated by real-time PCR and high-throughput amplicon sequencing; then, feedback effects of changes in soil biota on cucumber seedling resistance to FOC were assessed. Moreover, effects of sodium silicate on the growth of FOC and Streptomyces DHV3-2, an antagonistic bacterium to FOC, were investigated both in vitro and in the soil environment. Results showed that exogenous sodium silicate enhanced cucumber seedling growth and resistance to FOC. In bare soil, sodium silicate increased bacterial and fungal community abundances and diversities. In cucumber-cultivated soil, sodium silicate increased bacterial community abundances, but decreased fungal community abundances and diversities. Sodium silicate also changed soil bacterial and fungal communality compositions, and especially, decreased the relative abundances of microbial taxa containing plant pathogens but increased these with plant-beneficial potentials. Moreover, sodium silicate increased the abundance of Streptomyces DHV3-2 in soil. Soil biota from cucumber-cultivated soil treated with sodium silicate decreased cucumber seedling Fusarium wilt disease index, and enhanced cucumber seedling growth and defense-related enzyme activities in roots. Sodium silicate at pH 9.85 inhibited FOC abundance in vitro, but did not affect FOC abundance in soil. Overall, our results suggested that, in cucumber-cultivated soil, sodium silicate increased cucumber seedling

Polymer-layered silicate nano composite by UV-radiation curing: an original synthesis

International Nuclear Information System (INIS)

Keller, L.; Decker, C.; Zahouily, K.; Miehe-Brendle, J.; Le Meins, J.M.

2004-01-01

Full text.Because of the many hopes which they raise, the nano composite materials are the subject of an increasing number of scientific publications. Indeed, the intimate association of a polymer matrix and silicate nano-platelets leads to the formation of materials having mechanical and barriers properties improved (fire, gas, humidity...). A literature survey shows that these materials are generally produced by a thermal polymerization, which presents two major disadvantages: the use of organic solvents and a great consumption of energy. To overcome such limitations, photo initiated polymerization was chosen to synthesize nano composite materials. By this technology, called UV radiation curing, a solvent-free resin is transformed within seconds into a solid polymer upon exposure to UV-radiation at ambient temperature. The principal objective of this study was to develop photopolymerizable systems with clay particles having a layer structure (phyllosilicates). The clay mineral was made organophilic by treatment with an alkylammonium salt to allow the acrylate resin to penetrate into the expanded galleries. A morphological characterization of the materials obtained was carried out by X-rays diffraction and electronic microscopy transmission. The polymerization of the various resins under the UV exposure was followed in situ by using the real-time infrared spectroscopy (RT-FTIR) and attenuated total reflection (ATR). The results obtained show that the presence of the organo clay does not modify much the polymerization kinetics. The nano composite material thus obtained is transparent, insoluble in the organic solvents and presents improved mechanical properties, compared to the neat resin and the micro composite, for a load factor ranging between 2 and 5%wt. The addition of nanoparticles also makes it possible to reduce efficiently the brightness of coatings UV and finally confers to this material barriers properties higher than that of the photo crosslinked

SOFT X-RAY IRRADIATION OF SILICATES: IMPLICATIONS FOR DUST EVOLUTION IN PROTOPLANETARY DISKS

Energy Technology Data Exchange (ETDEWEB)

Ciaravella, A.; Cecchi-Pestellini, C.; Jiménez-Escobar, A. [INAF—Osservatorio Astronomico di Palermo, P.za Parlamento 1, I-90134 Palermo (Italy); Chen, Y.-J.; Huang, C.-H. [Department of Physics, National Central University, Jhongli City, Taoyuan County 32054, Taiwan (China); Muñoz Caro, G. M. [Centro de Astrobiología (INTA-CSIC), Carretera de Ajalvir, km 4, Torrejón de Ardoz, E-28850 Madrid (Spain); Venezia, A. M., E-mail: aciaravella@astropa.unipa.it [ISMN—CNR, Via Ugo La Malfa 153, I-90146 Palermo (Italy)

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 Mg{sub 2}SiO{sub 4} 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.

Spectroscopic properties of 1.8 μm emission in Tm3+ doped bismuth silicate glass

International Nuclear Information System (INIS)

Zhao, Guoying; Tian, Ying; Wang, Xin; Fan, Huiyan; Hu, Lili

2013-01-01

The emission properties around 1.8 μm in Tm 3+ doped bismuth silicate glass have been investigated. Based on the obtained Raman spectroscopy and differential scanning calorimetry curves, it is found the introduced Bi 2 O 3 can efficiently reduce the phonon energy of silicate glass to 926 cm −1 . The energy gap between glass transition temperature and onset temperature of crystallization is 169 °C. The OH − content maintains lower in glass by bubbling dry O 2 during the melting process. The cut-off wavelength in mid-infrared range is as long as 5 μm. Bismuth silicate glass has high radiative transition probability of 238.80 s −1 corresponding to the Tm 3+ : 3 F 4 → 3 H 6 transition compared with conventional silicate glasses. The strongest emission at 1.8 μm with a large full width at half-maximum of 238 nm is achieved from this bismuth silicate glass doped with 0.9 mol% Tm 2 O 3 . Its fluorescence lifetime at 1.8 μm is 640 μs. - Highlights: ► The 1.8 μm fluorescence of Tm 3+ -doped bismuth silicate glass is investigated. ► The prepared glass has lower phonon energy than other typical silicate glasses. ► A broadband 1.8 μm emission with the FWHM of 238 nm is observed. ► The fluorescence lifetime of Tm 3+ : 3 F 4 level reaches 640 μs.

Petrological Geodynamics of Mantle Melting II. AlphaMELTS + Multiphase Flow: Dynamic Fractional Melting

Science.gov (United States)

Tirone, Massimiliano

2018-03-01

In this second installment of a series that aims to investigate the dynamic interaction between the composition and abundance of the solid mantle and its melt products, the classic interpretation of fractional melting is extended to account for the dynamic nature of the process. A multiphase numerical flow model is coupled with the program AlphaMELTS, which provides at the moment possibly the most accurate petrological description of melting based on thermodynamic principles. The conceptual idea of this study is based on a description of the melting process taking place along a 1-D vertical ideal column where chemical equilibrium is assumed to apply in two local sub-systems separately on some spatial and temporal scale. The solid mantle belongs to a local sub-system (ss1) that does not interact chemically with the melt reservoir which forms a second sub-system (ss2). The local melt products are transferred in the melt sub-system ss2 where the melt phase eventually can also crystallize into a different solid assemblage and will evolve dynamically. The main difference with the usual interpretation of fractional melting is that melt is not arbitrarily and instantaneously extracted from the mantle, but instead remains a dynamic component of the model, hence the process is named dynamic fractional melting (DFM). Some of the conditions that may affect the DFM model are investigated in this study, in particular the effect of temperature, mantle velocity at the boundary of the mantle column. A comparison is made with the dynamic equilibrium melting (DEM) model discussed in the first installment. The implications of assuming passive flow or active flow are also considered to some extent. Complete data files of most of the DFM simulations, four animations and two new DEM simulations (passive/active flow) are available following the instructions in the supplementary material.

PYROXENITE VEINS WITHIN SSZ PERIDOTITES – EVIDENCE OF MELT-ROCK INTERACTION (EGIINGOL MASSIF, MAJOR AND TRACE ELEMENT COMPOSITION OF MINERALS

Directory of Open Access Journals (Sweden)

A. A. Karimov

2017-01-01

Full Text Available Evidence of melt-rock reaction between suprasubduction zone (SSZ peridotites and island arc boninititc and tholeiitic melts are identified. This process is the cause of replacive dunites and pyroxenite veins forming, which are represent the ways of island-arc melts migration. The peridotite-melt interaction is confirmed by compositional features of rocks and minerals. Influence of boninitic melt in peridotites of South Sandwich island arc leads to increasing of TiO2 and Cr-number (Cr# in spinels [Pearce et al., 2000] e.g. REE patterns of clinopyroxene from Voykar are equilibrium to boninitic melts [Belousov et al., 2009]. We show that pyroxenites are formed sequential, orthopyroxenites are originated firstly, websterites – after, and the main forming process is interaction of SSZ peridotites with percolating boninite-like melts.

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

Science.gov (United States)

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

2015-12-01

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

Temperature Dependence of Electrical Resistance of Woven Melt-Infiltrated SiCf/SiC Ceramic Matrix Composites

Science.gov (United States)

Appleby, Matthew P.; Morscher, Gregory N.; Zhu, Dongming

2016-01-01

Recent studies have successfully shown the use of electrical resistance (ER)measurements to monitor room temperature damage accumulation in SiC fiber reinforced SiC matrix composites (SiCf/SiC) Ceramic Matrix Composites (CMCs). In order to determine the feasibility of resistance monitoring at elevated temperatures, the present work investigates the temperature dependent electrical response of various MI (Melt Infiltrated)-CVI (Chemical Vapor Infiltrated) SiC/SiC composites containing Hi-Nicalon Type S, Tyranno ZMI and SA reinforcing fibers. Test were conducted using a commercially available isothermal testing apparatus as well as a novel, laser-based heating approach developed to more accurately simulate thermomechanical testing of CMCs. Secondly, a post-test inspection technique is demonstrated to show the effect of high-temperature exposure on electrical properties. Analysis was performed to determine the respective contribution of the fiber and matrix to the overall composite conductivity at elevated temperatures. It was concluded that because the silicon-rich matrix material dominates the electrical response at high temperature, ER monitoring would continue to be a feasible method for monitoring stress dependent matrix cracking of melt-infiltrated SiC/SiC composites under high temperature mechanical testing conditions. Finally, the effect of thermal gradients generated during localized heating of tensile coupons on overall electrical response of the composite is determined.

Nanoparticle dispersion effect of laser-surface melting in ZrB{sub 2p}/6061Al composites

Energy Technology Data Exchange (ETDEWEB)

Zeng, Yida; Chao, Yuhjin; Luo, Zhen, E-mail: lz-tju@163.com [Tianjin University, School of Material Science and Engineering (China); Huang, Yongxian [State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology (China)

2017-04-15

Zirconium diboride (ZrB{sub 2p}, 15 vol%)/6061 aluminum (Al) composites were fabricated via in situ reaction. The existence, morphologies, and dispersion degree of the in situ ZrB{sub 2} particles with size from tens to hundreds of nanometers were studied by X-ray diffractometry, energy-dispersive X-ray spectroscopy, field-emission scanning electron microscopy, and high-resolution transmission electron microscopy. As the particle-settlement effect becomes dominant during the composite fabrication process, ZrB{sub 2} nanoparticles agglomerate to a certain extent in some areas of the as-cast composites. A laser-surface melting (LSM) strategy was applied to disperse agglomerated ZrB{sub 2} nanoparticles in as-cast composites, and the ZrB{sub 2} nanoparticle dispersion is affected visibly by LSM. After LSM, nanoparticles tend to distribute along the grain boundary. Particle clusters were dispersed in an explosive orientation and the particle diffusion distance varied in terms of its radius and melt-viscosity vicinity. High-resolution transmission electron microscopy showed the existence of a subgrain structure near the ZrB{sub 2}–Al interface after LSM. This may increase the yield strength when a dislocation tangle forms.

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

Energy Technology Data Exchange (ETDEWEB)

Zhu, Chaofeng [Key Laboratory of Processing and Testing Technology of Glass & Functional Ceramics of Shandong Province, Qilu University of Technology, Jinan 250353 (China); Laboratoire des Verres et Céramiques, UMR-CNRS 6226, Université de Rennes 1, Rennes 35042 (France); Zhang, Xianghua, E-mail: xiang-hua.zhang@univ-rennes1.fr [Laboratoire des Verres et Céramiques, UMR-CNRS 6226, Université de Rennes 1, Rennes 35042 (France); Ma, Hongli [Laboratoire des Verres et Céramiques, UMR-CNRS 6226, Université de Rennes 1, Rennes 35042 (France)

2016-03-15

A series of Sb/Mn co-doped oxyfluoride silicate glasses were prepared via the melt-quenching method to explore red luminescent materials for potential applications in photosynthesis of green plants, and these glasses are investigated by means of luminescence decay curves, absorption, emission, and excitation spectra. We find that the as-prepared glasses are transparent in the visible region and can emit strong red light under ultraviolet, purple, and green light excitations. Furthermore, energy transfer from Sb{sup 3+} to Mn{sup 2+} ions occurs in Sb/Mn co-doped glasses. The results demonstrate that the as-prepared Sb/Mn co-doped oxyfluoride silicate glasses may serve as a potential candidate for developing glass greenhouse, which can enhance the utilization of solar energy for the photosynthesis of the green plants.

High-level radioactive waste isolation by incorporation in silicate rock

International Nuclear Information System (INIS)

Schwartz, L.L.; Cohen, J.J.; Lewis, A.E.; Braun, R.L.

1978-01-01

A number of technical possibilities for isolating high-level radioactive materials have been theoretically investigated at various times and places. Isolating such wastes deep underground to ensure long term removal from the biosphere is one such possibility. The present concept involves as a first step creating the necessary void space at considerable depth, say 2 to 5 km, in a very-low-permeability silicate medium such as shale. Waste in dry, calcined or vitrified form is then lowered into the void space, and the access hole or shaft sealed. Energy released by the radioactive decay raises the temperature to a point where the surrounding rock begins to melt. The waste is then dissolved in it. The extent of this melt region grows until the heat generated is balanced by conduction away from the molten zone. Resolidification then begins, and ends when the radioactive decay has progressed to the point that the temperature falls below the melting point of the rock-waste solution. Calculations are presented showing the growth and resolidification process. A nuclear explosion is one way of creating the void space. (author)

Fluctuation-induced conductivity in melt-textured Pr-doped YBa2Cu3O7-δ composite superconductor

DEFF Research Database (Denmark)

Opata, Yuri Aparecido; Monteiro, João Frederico Haas Leandro; Siqueira, Ezequiel Costa

2018-01-01

In this study, the effects of thermal fluctuations on the electrical conductivity in melt-textured YBa2Cu3O7-δ, Y0.95Pr0.05Ba2Cu3O7-δ and (YBa2Cu3O7-δ)0.95–(PrBa2Cu3O7-δ)0.05 composite superconductor were considered. The composite superconductor samples were prepared through the top seeding method...... using melt-textured NdBa2Cu3O7-d seeds. The resistivity measurements were performed with a low-frequency, low-current AC technique in order to extract the temperature derivative and analyze the influence of the praseodymium ion on the normal superconductor transition and consequently on the fluctuation...

Constraining the Volatile Regime of Primitive Somma-Vesuvius Magmas Based on the Compositions of Phenocrysts and Melt Inclusions

Science.gov (United States)

Danyushevsky, L. V.; Esposito, R.; De Vivo, B.; Redi, D.; Lima, A.; Bodnar, R. J.; Gurenko, A.

2017-12-01

The volcanic complex of Mt. Somma-Vesuvius is located in the Campanian Plain on east of Naples. We present the results of a mineralogical and melt inclusion studies of primitive volcanic products erupted during the last 2 magmatic cycles of Soma-Vesuvius, aimed at better understanding the volatile fluxes and eruptive behaviour of the volcano. Our results suggest that despite large differences in the compositions of the erupted magmas (from olivine-bearing basaltic lavas to leucite-bearing phonolites) and the eruption style (from plinian to strombolian), there was very little change in the nature of the parental magmas. Melt inclusions in olivine phenocrysts in all volcanic products and styles reveal the highest volatile contents in the most magnesian, early formed crystals (Fo90; H2O 4-5 wt%; CO2 3,000-4,000 ppm), decreasing to near 0 levels of concentrations in olivine Fo70. Major and trace element compositions of the clinopyroxene phenocrysts (Mg#92-70) also suggest a similar parental magma composition and similar liquid lines of decent for all Somma-Vesuvius eruptions. Our results are best explained by a model which relates the eruption style to the intensity of melt supply under the volcano. High intensity plinian eruptions occur after a prolonged repose time, whereas strombolian eruptions occur during periods of more frequent volcanic activity [1]. We will also discuss possible implications for the role of carbonate assimilation during magma evolution of Somma-Vesuvius and for total volatile budget of the SOmma-Vesuvius eruptions. [1] [42] Lima, A., Danyushevsky, L.V., De Vivo, B. and Fedele, L. 2003: A model for the evolution of the Mt. Somma-Vesuvius magmatic system based on fluid and melt inclusion investigations. In: Melt Inclusions in volcanic systems: Methods, applications and Problems (B. De Vivo & R.J. Bodnar, Eds), Series: Developments in Volcanology. No. 5 Elsevier, Amsterdam, 227-251

XANES analysis of calcium and sodium phosphates and silicates and hydroxyapatite-Bioglass (registered) 45S5 co-sintered bioceramics

International Nuclear Information System (INIS)

Demirkiran, Hande; Hu Yongfeng; Zuin, Lucia; Appathurai, Narayana; Aswath, Pranesh B.

2011-01-01

Bioglass (registered) 45S5 was co-sintered with hydroxyapatite at 1200 deg. C. When small amounts ( 5 (PO 4 ) 2 SiO 4 and Na 3 Ca 6 (PO 4 ) 5 in an amorphous silicate matrix respectively. These chemistries show improved bioactivity compared to hydroxyapatite and are the subject of this study. The structure of several crystalline calcium and sodium phosphates and silicates as well as the co-sintered hydroxyapatite-Bioglass (registered) 45S5 bioceramics were examined using XANES spectroscopy. The nature of the crystalline and amorphous phases were studied using silicon (Si) and phosphorus (P) K- and L 2,3 -edge and calcium (Ca) K-edge XANES. Si L 2,3 -edge spectra of sintered bioceramic compositions indicates that the primary silicates present in these compositions are sodium silicates in the amorphous state. From Si K-edge spectra, it is shown that the silicates are in a similar structural environment in all the sintered bioceramic compositions with 4-fold coordination. Using P L 2,3 -edge it is clearly shown that there is no evidence of sodium phosphate present in the sintered bioceramic compositions. In the P K-edge spectra, the post-edge shoulder peak at around 2155 eV indicates that this shoulder to be more defined for calcium phosphate compounds with decreasing solubility and increasing thermodynamic stability. This shoulder peak is more noticeable in hydroxyapatite and β-TCP indicating greater stability of the phosphate phase. The only spectra that does not show a noticeable peak is the composition with Na 3 Ca 6 (PO 4 ) 5 in a silicate matrix indicating that it is more soluble compared to the other compositions.

Experimental testing of a small sorption air cooler using composite material made from natural siliceous shale and chloride

International Nuclear Information System (INIS)

Liu, Hongzhi; Nagano, Katsunori; Morita, Atsushi; Togawa, Junya; Nakamura, Makoto

2015-01-01

A sorption air cooler experimental setup including a reactor and fin tube condenser/evaporator was built. The reactor was developed with inner copper fins and dual layers of curing copper meshes. Composite material made by impregnating LiCl into the mesopores of Wakkanai Siliceous Shale (WSS) micropowders was packed between the intervals of two fins. Heat transfer was enhanced by the attached fins, and the dual layers of curing meshes installed between each interval of two fins were designed to improve the sorbate mass transfer. On the other hand, the fin-tube evaporator/condenser with fins outside is valuable for improving the convective heat transfer between the functional water inside the evaporator/condenser and the flowing outside heat transfer medium, air. The sorption capacity of the composite material increased dramatically after being impregnated with LiCl. Among the four tested samples, WSS + 40 wt% LiCl exhibits the best performance. A regeneration temperature of 80 °C appears to be optimal for obtaining both a high COP and high specific cooling power. A lower condensation temperature can increase the cooling power. The sorption and desorption times of 60 min yield a reasonable compromise between cooling COP and mass specific cooling powers. The developed sorption air cooler system using WSS + 40 wt% LiCl can store heat at temperatures below 100 °C and produce cooling energy with a cooling coefficient of performance (COP) of approximately 0.3. - Highlights: • Mesoporous composite material was developed using natural siliceous shale and LiCl. • Properties of the developed material were measured. • A sorption air cooler experimental setup including an inner-fin reactor and a fin tube condenser/evaporator was built. • The performance of the composite material in the sorption air cooler was examined. • The sorption air cooler system can produce cooling energy with a cooling COP around 0.3

The system analysis of temperature and melting enthalpy of intermetallic compounds of antimony-lanthanoids system of Sb Ln, Sb2Ln composition

International Nuclear Information System (INIS)

Badalova, M.A.; Chamanova, M.; Dodkhoev, E.S.; Badalov, A.; Abdusalyamova, M.N.

2015-01-01

Present article is devoted to system analysis of temperature and melting enthalpy of intermetallic compounds of antimony-lanthanoids system of Sb Ln, Sb 2 Ln composition. The melting enthalpy was estimated. The temperature value was determined.

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

Science.gov (United States)

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

2014-05-01

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

Hadean silicate differentiation preserved by anomalous 142Nd/144Nd ratios in the Réunion hotspot source

Science.gov (United States)

Peters, Bradley J.; Carlson, Richard W.; Day, James M. D.; Horan, Mary F.

2018-03-01

Active volcanic hotspots can tap into domains in Earth’s deep interior that were formed more than two billion years ago. High-precision data on variability in tungsten isotopes have shown that some of these domains resulted from differentiation events that occurred within the first fifty million years of Earth history. However, it has not proved easy to resolve analogous variability in neodymium isotope compositions that would track regions of Earth’s interior whose composition was established by events occurring within roughly the first five hundred million years of Earth history. Here we report 142Nd/144Nd ratios for Réunion Island igneous rocks, some of which are resolvably either higher or lower than the ratios in modern upper-mantle domains. We also find that Réunion 142Nd/144Nd ratios correlate with helium-isotope ratios (3He/4He), suggesting parallel behaviour of these isotopic systems during very early silicate differentiation, perhaps as early as 4.39 billion years ago. The range of 142Nd/144Nd ratios in Réunion basalts is inconsistent with a single-stage differentiation process, and instead requires mixing of a conjugate melt and residue formed in at least one melting event during the Hadean eon, 4.56 billion to 4 billion years ago. Efficient post-Hadean mixing nearly erased the ancient, anomalous 142Nd/144Nd signatures, and produced the relatively homogeneous 143Nd/144Nd composition that is characteristic of Réunion basalts. Our results show that Réunion magmas tap into a particularly ancient, primitive source compared with other volcanic hotspots, offering insight into the formation and preservation of ancient heterogeneities in Earth’s interior.

Effect of antimony-oxide on the shielding properties of some sodium-boro-silicate glasses.

Science.gov (United States)

Zoulfakar, A M; Abdel-Ghany, A M; Abou-Elnasr, T Z; Mostafa, A G; Salem, S M; El-Bahnaswy, H H

2017-09-01

Some sodium-silicate-boro-antimonate glasses having the molecular composition [(20) Na 2 O - (20) SiO 2 - (60-x) B 2 O 3 - (x) Sb 2 O 3 (where x takes the values 0, 5 … or 20)] have been prepared by the melt quenching method. The melting and annealing temperatures were 1500 and 650K respectively. The amorphous nature of the prepared samples was confirmed by using X-ray diffraction analysis. Both the experimental and empirical density and molar volume values showed gradual increase with increasing Sb 2 O 3 content. The empirical densities showed higher values than those obtained experimentally, while the empirical molar volume values appeared lower than those obtained experimentally, which confirm the amorphous nature and randomness character of the studied samples. The experimentally obtained shielding parameters were approximately coincident with those obtained theoretically by applying WinXCom program. At low gamma-ray energies (0.356 and 0.662MeV) Sb 2 O 3 has approximately no effect on the total Mass Attenuation Coefficient, while at high energies it acts to increase the total Mass Attenuation Coefficient gradually. The obtained Half Value Layer and Mean Free Path values showed gradual decrease as Sb 2 O 3 was gradually increased. Also, the Total Mass Attenuation Coefficient values obtained between about 0.8 and 3.0MeV gamma-ray energy showed a slight decrease, as gamma-ray photon energy increased. This may be due to the differences between the Attenuation Coefficients of both antimony and boron oxides at various gamma-ray photon energies. However, it can be stated that the addition of Sb 2 O 3 into sodium-boro-silicate glasses increases the gamma-ray Attenuation Coefficient and the best sample is that contains 20 mol% of Sb 2 O 3 , which is operating well at 0.356 and 0.662MeV gamma-ray. Copyright © 2017 Elsevier Ltd. All rights reserved.

Vibrational investigation of calcium-silicate cements for endodontics in simulated body fluids

Science.gov (United States)

Taddei, Paola; Modena, Enrico; Tinti, Anna; Siboni, Francesco; Prati, Carlo; Gandolfi, Maria Giovanna

2011-05-01

Calcium-silicate MTA (Mineral Trioxide Aggregate) cements have been recently developed for oral and endodontic surgery. This study was aimed at investigating commercial (White ProRoot MTA, White and Grey MTA-Angelus) and experimental (wTC-Bi) accelerated calcium-silicate cements with regards to composition, hydration products and bioactivity upon incubation for 1-28 days at 37 °C, in Dulbecco's Phosphate Buffered Saline (DPBS). Deposits on the surface of the cements and the composition changes during incubation were investigated by micro-Raman and ATR/FT-IR spectroscopy, and pH measurements. Vibrational techniques disclosed significant differences in composition among the unhydrated cements, which significantly affected the bioactivity as well as pH, and hydration products of the cements. After one day in DPBS, all the cements were covered by a more or less homogeneous layer of B-type carbonated apatite. The experimental cement maintained a high bioactivity, only slightly lower than the other cements and appears a valid alternative to commercial cements, in view of its adequate setting time properties. The bioactivity represents an essential property to favour bone healing and makes the calcium-silicate cements the gold standard materials for root-apical endodontic surgery.

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.

Silicate Veining Above an Ascending Mantle Plume - Evidence from New Ethiopian Xenolith Localities

Science.gov (United States)

Rooney, T. O.; Furman, T.; Ayalew, D.; Yirgu, G.

2004-12-01

Quaternary basaltic eruptions in the Debre Zeyit (Bishoftu) and Butajira regions of the Main Ethiopian Rift host Al-augite, norite and rare lherzolite xenoliths, xenocrysts and megacrysts. These explosive basaltic eruptions are located 20 km to the west of the main rift axis and are characterized by cinder cones and maars. The host basalt was generated as a small degree partial melt of fertile peridotite between 15 and 25 kb and host abundant Al-augite (Type II) xenoliths derived from pressures up to 10 kb. The central Main Ethiopian Rift lies in a transitional zone between the continental rifting of East Africa and the sea floor spreading associated with the Red Sea. Lithospheric and sub-lithospheric processes that occur during the transition from continental to oceanic magmatism may be investigated using these xenolith-bearing basalts. Neither carbonatitic nor hydrous (amphibole + phlogopite) metasomatism is evident in either the xenoliths or host basalts, suggesting that infiltration of silicate melts that produced Al-augite veining dominates the regional lower crust and lithospheric mantle. These veins are significantly hotter (200 - 300 ° C) than the lherzolite wall rock they intrude suggesting the thermal influence of the Afar plume. Recent geophysical tomography indicates that this veining is pervasive and segmented, supporting the association of these Al-augite veins with the formation of a proto-ridge axis. Al-augite xenoliths and megacrysts have been observed in other continental rift settings such as Durango (Luhr, 2001) and Lake Baikal (Litasov, 2000), indicating Al-augite silicate melt metasomatism is a fundamental process associated with continental rift development.

PGE mineralization and melt composition of chromitites in Proterozoic ophiolite complexes of Eastern Sayan, Southern Siberia

Directory of Open Access Journals (Sweden)

O. Kiseleva

2017-07-01

Full Text Available The Ospino-Kitoi and Kharanur ultrabasic massifs represent the northern and southern ophiolite branches respectively of the Upper Onot ophiolitic nappe and they are located in the southeastern part of the Eastern Sayan (SEPES ophiolites. Podiform chromitites with PGE mineralization occur as lensoid pods within dunites and rarely in harzburgites or serpentinized peridotites. The chromitites are classified into type I and type II based on their Cr#. Type I (Cr# = 59–85 occurs in both northern and southern branches, whereas type II (Cr# = 76–90 occurs only in the northern branch. PGE contents range from ∑PGE 88–1189 ppb, Pt/Ir 0.04–0.42 to ∑PGE 250–1700 ppb, Pt/Ir 0.03–0.25 for type I chromitites of the northern and southern branches respectively. The type II chromitites of the northern branch have ∑PGE contents higher than that of type I (468–8617 ppb, Pt/Ir 0.1–0.33. Parental melt compositions, in equilibrium with podiform chromitites, are in the range of boninitic melts and vary in Al2O3, TiO2 and FeO/MgO contents from those of type I and type II chromitites. Calculated melt compositions for type I chromitites are (Al2O3melt = 10.6–13.5 wt.%, (TiO2melt = 0.01–0.44 wt.%, (Fe/Mgmelt = 0.42–1.81; those for type II chromitites are: (Al2O3melt = 7.8–10.5 wt.%, (TiO2melt = 0.01–0.25 wt.%, (Fe/Mgmelt = 0.5–2.4. Chromitites are further divided into Os-Ir-Ru (I and Pt-Pd (II based on their PGE patterns. The type I chromitites show only the Os-Ir-Ru pattern whereas type II shows both Os-Ir-Ru and Pt-Pd patterns. PGE mineralization in type I chromitites is represented by the Os-Ir-Ru system, whereas in type II it is represented by the Os-Ir-Ru-Rh-Pt system. These results indicate that chromitites and PGE mineralization in the northern branch formed in a suprasubduction setting from a fluid-rich boninitic melt during active subduction. However, the chromitites and PGE mineralization of the southern

Petrogenesis of siliceous high-Mg series rocks as exemplified by the Early Paleoproterozoic mafic volcanic rocks of the Eastern Baltic Shield: enriched mantle versus crustal contamination

Science.gov (United States)

Bogina, Maria; Zlobin, Valeriy; Sharkov, Evgenii; Chistyakov, Alexeii

2015-04-01

The Early Paleoproterozoic stage in the Earth's evolution was marked by the initiation of global rift systems, the tectonic nature of which was determined by plume geodynamics. These processes caused the voluminous emplacement of mantle melts with the formation of dike swarms, mafic-ultramafic layered intrusions, and volcanic rocks. All these rocks are usually considered as derivatives of SHMS (siliceous high-magnesian series). Within the Eastern Baltic Shield, the SHMS volcanic rocks are localized in the domains with different crustal history: in the Vodlozero block of the Karelian craton with the oldest (Middle Archean) crust, in the Central Block of the same craton with the Neoarchean crust, and in the Kola Craton with a heterogeneous crust. At the same time, these rocks are characterized by sufficiently close geochemical characteristics: high REE fractionation ((La/Yb)N = 4.9-11.7, (La/Sm)N=2.3-3.6, (Gd/Yb)N =1.66-2.74)), LILE enrichment, negative Nb anomaly, low to moderate Ti content, and sufficiently narrow variations in Nd isotope composition from -2.0 to -0.4 epsilon units. The tectonomagmatic interpretation of these rocks was ambiguous, because such characteristics may be produced by both crustal contamination of depleted mantle melts, and by generation from a mantle source metasomatized during previous subduction event. Similar REE patterns and overlapping Nd isotope compositions indicate that the studied basaltic rocks were formed from similar sources. If crustal contamination en route to the surface would play a significant role in the formation of the studied basalts, then almost equal amounts of contaminant of similar composition are required to produce the mafic rocks with similar geochemical signatures and close Nd isotopic compositions, which is hardly possible for the rocks spaced far apart in a heterogeneous crust. This conclusion is consistent with analysis of some relations between incompatible elements and their ratios. In particular, the

Effect of layered silicate content on the morphology and thermal properties of Poly(vinyl alcohol) films

International Nuclear Information System (INIS)

Silva, Jessica R.M.B. da; Santos, Barbara F.F. dos; Leite, Itamara F.

2015-01-01

This study aims to evaluate the effect of layered silicate content on the morphology and thermal properties of PVA films. The PVA/layered silicate (AN) films were prepared by intercalation solution, using 1 to 2% of bentonite with respect to the PVA total weight. Then the films were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetry (TG) and differential scanning calorimetry (DSC). Results of the FTIR revealed interaction between the functional groups of the PVA and the layered silicate. The XRD analysis showed that nanocomposites with intercalated and partially exfoliated morphology were obtained. The results of TG showed that the nanocomposite PVA/2%AN showed higher thermal stability compared to PVA/1%AN. The DSC results showed that the addition of AN to the PVA did not affect crystallization rate, as well as promoted a reduction in glass transition temperature and melting of the PVA. (author)

Joining of SiCf/SiC composites for thermonuclear fusion reactors

International Nuclear Information System (INIS)

Ferraris, M.; Badini, C.; Montorsi, M.; Appendino, P.; Scholz, H.W.

1994-01-01

Due to their favourable radiological behaviour, SiC f /SiC composites are promising structural materials for future use in fusion reactors. A problem to cope with is the joining of the ceramic composite material (CMC) to itself for more complex structures. Maintenance concepts for a reactor made of SiC f /SiC will demand a method of joining. The joining agents should comply with the low-activation approach of the base material. With the acceptable elements Si and Mg, sandwich structures of composite/metal/composite were prepared in Ar atmosphere at temperatures just above the melting points of the metals. Another promising route is the use of joining agents of boro-silicate glasses: their composition can be tailored to obtain softening temperatures of interest for fusion applications. The glassy joint can be easily ceramised to improve thermomechanical properties. The joining interfaces were investigated by SEM-EDS, XRD and mechanical tests. ((orig.))

Utilization of poly(methyl methacrylate – carbon nanotube and polystyrene – carbon nanotube in situ polymerized composites as masterbatches for melt mixing

Directory of Open Access Journals (Sweden)

M. Lahelin

2012-10-01

Full Text Available Carbon nanotubes (CNTs were melt mixed directly or by using an in situ polymerized masterbatch into a matrix polymer, polystyrene (PS or poly(methyl methacrylate (PMMA. The mechanical properties of the composites were mostly determined by the amount of CNTs, and not by the use of directly melt mixed CNTs or the use of the masterbatch. In contrast, the electrical resistivity of the composites was dependent on the manner in which the CNTs were added to the matrix polymer. When there was increased interfacial adhesion between the components, as for PS and the CNTs, the use of directly melt mixed CNTs gave better resistivity results. Without strong interactions between the CNTs and the matrix, as with PMMA and CNTs, the use of a tailored masterbatch had a significant effect on properties of the final composites. The molecular weight and viscosity of masterbatches can be varied and when the PMMA-masterbatch had optimized viscosity with respect to the PMMA matrix, electrical resistivity of the final composites decreased noticeably.

Insight into highly efficient removal of cadmium and methylene blue by eco-friendly magnesium silicate-hydrothermal carbon composite

Science.gov (United States)

Xiong, Ting; Yuan, Xingzhong; Chen, Xiaohong; Wu, Zhibin; Wang, Hou; Leng, Lijian; Wang, Hui; Jiang, Longbo; Zeng, Guangming

2018-01-01

Water pollution is one of the forefront environmental problems. Due to the simplification, flexibility and low cost, the adsorption becomes one of the most fashionable technology and the exploitation of adsorbents has drawn greatly attention. In this study, a novel magnesium silicate-hydrothermal carbon composite (MS-C) was synthesized by facile hydrothermal carbonization and used to remove the cadmium (Cd(II)) and methylene blue (MB) from wastewater. It was shown that the porous and lump-like magnesium silicate (MS) was decorated with multiple hydrothermal carbon (HC) via the Csbnd Osbnd Si covalent bonding. Further, the adsorption behavior of Cd(II) and MB based on the MS, HC, and MS-C were systematically investigated. The equilibrium data of both Cd(II) and MB were fitted well with Langmuir model. Compared to pure MS and HC, the adsorption capacity of composite was significantly improved, accompanied by the maximum adsorption capacity of 108 mg/g for Cd(II) and 418 mg/g for MB, respectively. In the Cd(II)-MB binary system, the adsorption of Cd(II) was favored in comparison with that of MB. The removal of Cd(II) was mainly ascribed to electrostatic attraction and the ion exchange interaction. Meanwhile, the adsorption of MB onto adsorbent was driven by the electrostatic attraction, π-π interaction and hydrogen bond. In view of these empirical results and real water treatment, the environmental friendly and low-cost MS-C holds a potential for separate or simultaneous removal of Cd(II) and MB in practical applications.

Lithium concentration dependence of implanted helium retention in lithium silicates

Energy Technology Data Exchange (ETDEWEB)

Szocs, D.E., E-mail: szocsd@rmki.kfki.h [KFKI Research Institute for Particle and Nuclear Physics, H-1525 Budapest, P.O. Box 49 (Hungary); Szilagyi, E.; Bogdan, Cs.; Kotai, E. [KFKI Research Institute for Particle and Nuclear Physics, H-1525 Budapest, P.O. Box 49 (Hungary); Horvath, Z.E. [Research Institute for Technical Physics and Materials Science, H-1525 Budapest, P.O. Box 49 (Hungary)

2010-06-15

Helium ions of 500 keV were implanted with a fluence of 1.4 x 10{sup 17} ion/cm{sup 2} into various lithium silicates to investigate whether a threshold level of helium retention exists in Li-containing silicate ceramics similar to that found in SiO{sub x} in previous work. The composition and phases of the as prepared lithium silicates were determined by proton backscattering spectrometry (p-BS) and X-ray diffraction (XRD) methods with an average error of {+-}10%. Electrostatic charging of the samples was successfully eliminated by wrapping the samples in Al foil. The amounts of the retained helium within the samples were determined by subtracting the non-implanted spectra from the implanted ones. The experimental results show a threshold in helium retention depending on the Li concentration. Under 20 at.% all He is able to escape from the material; at around 30 at.% nearly half of the He, while over 65 at.% all implanted He is retained. With compositions expressed in SiO{sub 2} volume percentages, a trend similar to those reported of SiO{sub x} previously is found.

Tip-induced nanoreactor for silicate

Science.gov (United States)

Gao, Ming; Ma, Liran; Liang, Yong; Gao, Yuan; Luo, Jianbin

2015-09-01

Nanoscale scientific issues have attracted an increasing amount of research interest due to their specific size-effect and novel structure-property. From macro to nano, materials present some unique chemical reactivity that bulk materials do not own. Here we introduce a facile method to generate silicate with nanoscale control based on the establishment of a confined space between a meso/nanoscale tungsten tip and a smooth silica/silicon substrate. During the process, local water-like droplets deposition can be obviously observed in the confinement between the Si/SiO2 surfaces and the KOH-modified tungsten tip. By the combination of in-situ optical microscopy and Raman spectroscopy, we were able to take a deep insight of both the product composition and the underlying mechanism of such phenomena. It was indicated that such nanoreactor for silicate could be quite efficient as a result of the local capillarity and electric field effect, with implications at both nano and meso scales.

Zoning and exsolution in cumulate alkali feldspars from the eruption (12.9 Ka) of Laacher see volcano (Western Germany) as an indicator of time-scales and dynamics of carbonate-silicate unmixing

Science.gov (United States)

Sourav Rout, Smruti; Wörner, Gerhard

2017-04-01

Time-scales extracted from the detailed analysis of chemically zoned minerals provide insights into crystal ages, magma storage and compositional evolution, including mixing and unmixing events. This allows having a better understanding of pre-eruptive history of large and potentially dangerous magma chambers. We present a comprehensive study of chemical diffusion across zoning and exsolution patterns of alkali feldspars in carbonatite-bearing cognate syenites from the 6.3 km3 (D.R.E) phonolitic Laacher See Tephra (LST) eruption 12.9 ka ago. The Laacher See volcano is located in the Quaternary East Eifel volcanic field of the Paleozoic Rhenish Massif in Western Germany and has produced a compositionally variable sequence in a single eruption from a magma chamber that was zoned from mafic phonolite at the base to highly evolved, actively degassing phonolite magma at the top. Diffusion chronometry is applied to major and trace element compositions obtained on alkali feldspars from carbonate-bearing syenitic cumulates. Methods used were laser ablation inductively coupled plasma mass spectrometry (LA ICP-MS) in combination with energy-dispersive and wavelength-dispersive electron microprobe analyses (EDS & WDS-EMPA). The grey scale values extracted from multiple accumulations of back-scattered electron images represent the K/Na ratio owing to the extremely low concentrations of Ba and Sr (transition and phase separation). A distinctive uphill diffusive analysis is used specifically for the phase separation in the case of exsolution features (comprising of albite- and orthoclase-rich phases) in sanidines. The error values are aggregates of propagated error through calculations and the uncertainty in temperature values. Trace element compositional data of distinct feldspar compositions that are assumed to have grown before and after silicate-carbonate unmixing are used to estimate partition coefficients between carbonate and silicate melt. The resulting values correlate

Preparation of new series of poly(amide-imide) reinforced layer silicate nano composite containing N-trimellitimide-L-alanine

International Nuclear Information System (INIS)

Faghihi, K.; Soleimani, M.; Shabanian, M.

2011-01-01

A new poly(amide-imide)-montmorillonite series were generated through solution intercalation technique. Cloisite 20A was used as a modified montmorillonite for ample compatibility with the poly(amide-imide) (PAI) matrix. The PAI 5 chains were synthesized by the direct polycondensation reaction of N-trimellitylimido-L-alanine (3) with 4,4'-diamino diphenyl ether (4) in the presence of tryphenyl phosphites (TPP), CaCl 2 , pyridine and N-methyl-2-pyrrolidone (NMP). Morphology and structure of the resulting PAI-nano composite films 5a-5d with (5-20 Wt%) silicate particles were characterized by Ftir spectroscopy, X-ray diffraction and scanning electron microscopy. The effect of clay dispersion and the interaction between clay and polymeric chains on the properties of nano composites films were investigated by using UV-Vis spectroscopy, thermogravimetric analysis and water uptake measurements. (Author)

Preparation of new series of poly(amide-imide) reinforced layer silicate nano composite containing N-trimellitimide-L-alanine

Energy Technology Data Exchange (ETDEWEB)

Faghihi, K.; Soleimani, M. [Polymer Research Laboratory, Department of Chemistry, Faculty of Science, Islamic Azad University, Arak Branch, Arak (Iran, Islamic Republic of); Shabanian, M., E-mail: k-faghihi@araku.ac.ir [Young Researches Club, Islamic Azad University, Arak Branch, Arak (Iran, Islamic Republic of)

2011-07-01

A new poly(amide-imide)-montmorillonite series were generated through solution intercalation technique. Cloisite 20A was used as a modified montmorillonite for ample compatibility with the poly(amide-imide) (PAI) matrix. The PAI 5 chains were synthesized by the direct polycondensation reaction of N-trimellitylimido-L-alanine (3) with 4,4'-diamino diphenyl ether (4) in the presence of tryphenyl phosphites (TPP), CaCl{sub 2}, pyridine and N-methyl-2-pyrrolidone (NMP). Morphology and structure of the resulting PAI-nano composite films 5a-5d with (5-20 Wt%) silicate particles were characterized by Ftir spectroscopy, X-ray diffraction and scanning electron microscopy. The effect of clay dispersion and the interaction between clay and polymeric chains on the properties of nano composites films were investigated by using UV-Vis spectroscopy, thermogravimetric analysis and water uptake measurements. (Author)

Extensive young silicic volcanism produces large deep submarine lava flows in the NE Lau Basin

Science.gov (United States)

Embley, Robert W.; Rubin, Kenneth H.

2018-04-01

New field observations reveal that extensive (up to 402 km2) aphyric, glassy dacite lavas were erupted at multiple sites in the recent past in the NE Lau basin, located about 200 km southwest of Samoa. This discovery of volumetrically significant and widespread submarine dacite lava flows extends the domain for siliceous effusive volcanism into the deep seafloor. Although several lava flow fields were discovered on the flank of a large silicic seamount, Niuatahi, two of the largest lava fields and several smaller ones ("northern lava flow fields") were found well north of the seamount. The most distal portion of the northernmost of these fields is 60 km north of the center of Niuatahi caldera. We estimate that lava flow lengths from probable eruptive vents to the distal ends of flows range from a few km to more than 10 km. Camera tows on the shallower, near-vent areas show complex lava morphology that includes anastomosing tube-like pillow flows and ropey surfaces, endogenous domes and/or ridges, some with "crease-like" extrusion ridges, and inflated lobes with extrusion structures. A 2 × 1.5 km, 30-m deep depression could be an eruption center for one of the lava flow fields. The Lau lava flow fields appear to have erupted at presumptive high effusion rates and possibly reduced viscosity induced by presumptive high magmatic water content and/or a high eruption temperature, consistent with both erupted composition ( 66% SiO2) and glassy low crystallinity groundmass textures. The large areal extent (236 km2) and relatively small range of compositional variation ( σ = 0.60 for wt% Si02%) within the northern lava flow fields imply the existence of large, eruptible batches of differentiated melt in the upper mantle or lower crust of the NE Lau basin. At this site, the volcanism could be controlled by deep crustal fractures caused by the long-term extension in this rear-arc region. Submarine dacite flows exhibiting similar morphology have been described in ancient

Universality of the high-temperature viscosity limit of silicate liquids

DEFF Research Database (Denmark)

Zheng, Qiuju; Mauro, John C.; Ellison, Adam J.

2011-01-01

We investigate the high-temperature limit of liquid viscosity by analyzing measured viscosity curves for 946 silicate liquids and 31 other liquids including metallic, molecular, and ionic systems. Our results show no systematic dependence of the high-temperature viscosity limit on chemical...... composition for the studied liquids. Based on theMauro-Yue-Ellison-Gupta-Allan (MYEGA) model of liquid viscosity, the high-temperature viscosity limit of silicate liquids is 10−2.93 Pa·s. Having established this value, there are only two independent parameters governing the viscosity-temperature relation...

Utilization of poly(methyl methacrylate) – carbon nanotube and polystyrene – carbon nanotube in situ polymerized composites as masterbatches for melt mixing

OpenAIRE

M. Lahelin; M. Annala; J. Seppala

2012-01-01

Carbon nanotubes (CNTs) were melt mixed directly or by using an in situ polymerized masterbatch into a matrix polymer, polystyrene (PS) or poly(methyl methacrylate) (PMMA). The mechanical properties of the composites were mostly determined by the amount of CNTs, and not by the use of directly melt mixed CNTs or the use of the masterbatch. In contrast, the electrical resistivity of the composites was dependent on the manner in which the CNTs were added to the matrix polymer. When there was inc...

Calcium-Magnesium-Alumino-Silicates (CMAS) Reaction Mechanisms and Resistance of Advanced Turbine Environmental Barrier Coatings for SiC/SiC Ceramic Matrix Composites

Science.gov (United States)

Zhu, Dongming; Costa, Gustavo; Harder, Bryan J.; Wiesner, Valerie L.; Hurst, Janet B.; Puleo, Bernadette J.

2017-01-01

Environmental barrier coatings (EBCs) and SiC/SiC ceramic matrix composites (CMCs) systems will play a crucial role in future turbine engines for hot-section component applications because of their ability to significantly increase engine operating temperatures, reduce engine weight and cooling requirements. The development of prime-reliant environmental barrier coatings is an essential requirement to enable the applications of the 2700-3000 F EBC - CMC systems. This presentation primarily focuses on the reaction mechanisms of advanced NASA environmental barrier coating systems, when in contact with Calcium-Magnesium Alumino-Silicates (CMAS) at high temperatures. Advanced oxide-silicate defect cluster environmental barrier coatings are being designed for ultimate balanced controls of the EBC temperature capability and CMAS reactivity, thus improving the CMAS resistance. Further CMAS mitigation strategies are also discussed.

Melt Infiltrated Ceramic Composites (Hipercomp) for Gas Turbine Engine Applications

Energy Technology Data Exchange (ETDEWEB)

Gregory Corman; Krishan Luthra

2005-09-30

This report covers work performed under the Continuous Fiber Ceramic Composites (CFCC) program by GE Global Research and its partners from 1994 through 2005. The processing of prepreg-derived, melt infiltrated (MI) composite systems based on monofilament and multifilament tow SiC fibers is described. Extensive mechanical and environmental exposure characterizations were performed on these systems, as well as on competing Ceramic Matrix Composite (CMC) systems. Although current monofilament SiC fibers have inherent oxidative stability limitations due to their carbon surface coatings, the MI CMC system based on multifilament tow (Hi-Nicalon ) proved to have excellent mechanical, thermal and time-dependent properties. The materials database generated from the material testing was used to design turbine hot gas path components, namely the shroud and combustor liner, utilizing the CMC materials. The feasibility of using such MI CMC materials in gas turbine engines was demonstrated via combustion rig testing of turbine shrouds and combustor liners, and through field engine tests of shrouds in a 2MW engine for >1000 hours. A unique combustion test facility was also developed that allowed coupons of the CMC materials to be exposed to high-pressure, high-velocity combustion gas environments for times up to {approx}4000 hours.

Controlled structure and properties of silicate nanoparticle networks for incorporation of biosystem components

International Nuclear Information System (INIS)

Sakai-Kato, Kumiko; Kawanishi, Toru; Hasegawa, Toshiaki; Takaoka, Akio; Kato, Masaru; Toyo'oka, Toshimasa; Utsunomiya-Tate, Naoko

2011-01-01

Inorganic nanoparticles are of technological interest in many fields. We created silicate nanoparticle hydrogels that effectively incorporated biomolecules that are unstable and involved in complicated reactions. The size of the silicate nanoparticles strongly affected both the physical characteristics of the resulting hydrogel and the activity of biomolecules incorporated within the hydrogel. We used high-resolution transmission electron microscopy (TEM) to analyze in detail the hydrogel network patterns formed by the silicate nanoparticles. We obtained clear nanostructured images of biomolecule-nanoparticle composite hydrogels. The TEM images also showed that larger silicate nanoparticles (22 nm) formed more loosely associated silicate networks than did smaller silicate nanoparticles (7 nm). The loosely associated networks formed from larger silicate nanoparticles might facilitate substrate diffusion through the network, thus promoting the observed increased activity of the entrapped biomolecules. This doubled the activity of the incorporated biosystems compared with that of biosystems prepared by our own previously reported method. We propose a reaction scheme to explain the formation of the silicate nanoparticle networks. The successful incorporation of biomolecules into the nanoparticle hydrogels, along with the high level of activity exhibited by the biomolecules required for complicated reaction within the gels, demonstrates the nanocomposites' potential for use in medical applications.

Magnetic susceptibility of semiconductor melts

International Nuclear Information System (INIS)

Kutvitskij, V.A.; Shurygin, P.M.

1975-01-01

The temperature dependences chi of various alloys confirm the existence of cluster formations in molten semiconductors, the stability of these formations in melts being considerably affected by the anion nature. The concentrational dependences of the magnetic susceptibility for all the investigated systems exhibit the diamagnetism maxima corresponding to the compound compositions. Heating the melt causes ''smearing'' the maxima, which is related with the cluster structure dissociation. The existence of the maxima concentrational dependence chi corresponding to BiTe and BiSe is found in the isotherms. The non-linear dependence of chi on the composition shows the absence of a single-valued relation between the phase diagram and the chi-diagram for melts

Microstructure of reaction zone in WCp/duplex stainless steels matrix composites processing by laser melt injection

NARCIS (Netherlands)

Do Nascimento, A. M.; Ocelik, V.; Ierardi, M. C. F.; De Hosson, J. Th. M.

2008-01-01

The laser melt injection (LMI) process has been used to create a metal matrix composite consisting of 80gm sized multi-grain WC particles embedded in three cast duplex stainless steels. The microstruture was investigated by scanning electron microscopy with integrated EDS and electron back-scatter

NVP melt/magma viscosity: insight on Mercury lava flows

Science.gov (United States)

Rossi, Stefano; Morgavi, Daniele; Namur, Olivier; Vetere, Francesco; Perugini, Diego; Mancinelli, Paolo; Pauselli, Cristina

2016-04-01

After more than four years of orbiting Mercury, NASA's MESSENGER spacecraft came to an end in late April 2015. MESSENGER has provided many new and surprising results. This session will again highlight the latest results on Mercury based on MESSENGER observations or updated modelling. The session will further address instrument calibration and science performance both retrospective on MESSENGER and on the ESA/JAXA BepiColombo mission. Papers covering additional themes related to Mercury are also welcomed. Please be aware that this session will be held as a PICO session. This will allow an intensive exchange of expertise and experience between the individual instruments and mission. NVP melt/magma viscosity: insight on Mercury lava flows S. Rossi1, D. Morgavi1, O. Namur2, D. Perugini1, F.Vetere1, P. Mancinelli1 and C. Pauselli1 1 Dipartimento di Fisica e Geologia, Università di Perugia, piazza Università 1, 06123 Perugia, Italy 2 Uni Hannover Institut für Mineralogie, Leibniz Universität Hannover, Callinstraβe 3, 30167 Hannover, Germany In this contribution we report new measurements of viscosity of synthetic komatitic melts, used the behaviour of silicate melts erupted at the surface of Mercury. Composition of Mercurian surface magmas was calculated using the most recent maps produced from MESSENGER XRS data (Weider et al., 2015). We focused on the northern hemisphere (Northern Volcanic Province, NVP, the largest lava flow on Mercury and possibly in the Solar System) for which the spatial resolution of MESSENGER measurements is high and individual maps of Mg/Si, Ca/Si, Al/Si and S/Si were combined. The experimental starting material contains high Na2O content (≈7 wt.%) that strongly influences viscosity. High temperature viscosity measurements were carried out at 1 atm using a concentric cylinder apparatus equipped with an Anton Paar RheolabQC viscometer head at the Department of Physics and Geology (PVRG_lab) at the University of Perugia (Perugia, Italy

Sulfur isotope fractionation between fluid and andesitic melt: An experimental study

Science.gov (United States)

Fiege, Adrian; Holtz, François; Shimizu, Nobumichi; Mandeville, Charles W.; Behrens, Harald; Knipping, Jaayke L.

2014-01-01

Glasses produced from decompression experiments conducted by Fiege et al. (2014a) were used to investigate the fractionation of sulfur isotopes between fluid and andesitic melt upon magma degassing. Starting materials were synthetic glasses with a composition close to a Krakatau dacitic andesite. The glasses contained 4.55–7.95 wt% H2O, ∼140 to 2700 ppm sulfur (S), and 0–1000 ppm chlorine (Cl). The experiments were carried out in internally heated pressure vessels (IHPV) at 1030 °C and oxygen fugacities (fO2) ranging from QFM+0.8 log units up to QFM+4.2 log units (QFM: quartz–fayalite–magnetite buffer). The decompression experiments were conducted by releasing pressure (P) continuously from ∼400 MPa to final P of 150, 100, 70 and 30 MPa. The decompression rate (r) ranged from 0.01 to 0.17 MPa/s. The samples were annealed for 0–72 h (annealing time, tA) at the final P and quenched rapidly from 1030 °C to room temperature (T).The decompression led to the formation of a S-bearing aqueous fluid phase due to the relatively large fluid–melt partitioning coefficients of S. Secondary ion mass spectrometry (SIMS) was used to determine the isotopic composition of the glasses before and after decompression. Mass balance calculations were applied to estimate the gas–melt S isotope fractionation factor αg-m.No detectable effect of r and tA on αg-m was observed. However, SIMS data revealed a remarkable increase of αg-m from ∼0.9985 ± 0.0007 at >QFM+3 to ∼1.0042 ± 0.0042 at ∼QFM+1. Noteworthy, the isotopic fractionation at reducing conditions was about an order of magnitude larger than predicted by previous works. Based on our experimental results and on previous findings for S speciation in fluid and silicate melt a new model predicting the effect of fO2 on αg-m (or Δ34Sg–m) in andesitic systems at 1030 °C is proposed. Our experimental results as well as our modeling are of high importance for the interpretation of S isotope

Solidification observations and sliding wear behavior of vacuum arc melting processed Ni–Al–TiC composites

International Nuclear Information System (INIS)

Karantzalis, A.E.; Lekatou, A.; Tsirka, K.

2012-01-01

Monolithic Ni 3 Al and Ni–25 at.%Al intermetallic matrix TiC-reinforced composites were successfully produced by vacuum arc melting. TiC crystals were formed through a dissolution–reprecipitation mechanism and their final morphology is explained by means of a) Jackson's classical nucleation and growth phenomena and b) solidification rate considerations. The TiC presence altered the matrix microconstituents most likely due to specific melt–particle interactions and crystal plane epitaxial matching. TiC particles caused a significant decrease on the specific wear rate of the monolithic Ni 3 Al alloy and the possible wear mechanisms are approached by means of a) surface oxidation, b) crack/flaws formation, c) material detachment and d) debris–counter surfaces interactions. - Highlights: ► Vacuum arc melting (VAM) of Ni-Al based intermetallic matrix composite materials. ► Solidification phenomena examination. ► TiC crystal formation and growth mechanisms. ► Sliding wear examination.

A conceptual model for the asthenosphere: redox melting in the C-O-H-bearing mantle vs. geophysical observations

Science.gov (United States)

Gaillard, Fabrice; Tarits, Pascal; Massuyeau, Malcolm; David, Sifre; Leila, Hashim; Emmanuel, Gardes

2013-04-01

pump results in an increasingly reduced mantle with depth. Recent surveys have calibrated the carbon-carbonate redox transition at mantle pressure and have located its depth around 180-250 km (depth of redox melting); Deeper, only diamond is stable; Shallower, carbonates, mostly in its molten state, are expected. This petrological model is confronted to the most recent geophysical observations. Such observations indicate that melting must occur at depth down to 400 km, which conflict with the concept of redox melting. What is the composition of the melt? Hydrous silicate melt or hydrous carbonated melt? What does it mean in terms of deep upper mantle redox state?

Ferric iron partitioning between pyroxene and melt during partial melting of the Earth's upper mantle

Science.gov (United States)

Rudra, A.; Hirschmann, M. M.

2017-12-01

The oxidation state of the Earth's mantle influences melt production, volatile behavior, partitioning of key trace elements and possible saturation of alloy at depth. Average Fe3+/FeT ratios in MORBs indicate oxygen fugacitiy of the source regions is close to QFM, in contrast to a 3 log unit variation of fO2 recorded by abyssal peridotites. Quantification of the relationship between basalt and source Fe3+/FeT, oxygen fugacity, and melting requires constraints on Fe3+ partitioning between melt and mantle minerals and in particular the principal Fe3+ host, pyroxene. McCanta et al. (2004) investigated valence dependent partitioning of Fe between Martian ferroan pigeonites and melt, but behavior in terrestrial pyroxene compositions relevant to MORB petrogenesis has not been investigated. We are conducting 1 atm controlled fO2 experiments over 4 log unit variation of fO2 between ΔQFM = 2.5 to -1.5 to grow pyroxenes of variable tetrahedral and octahedral cationic population from andesitic melts of varying Mg#, alumina and alkali content. Dynamic crystallization technique facilitates growth of pyroxene crystals (100-200 um) that EPMA analyses show to be compositionally homogeneous and in equilibrium with the melt. Fe3+/FeT ratio of the synthetic pyroxenes have been analyzed by XAFS spectroscopy at the APS (GSECARS) synchrotron. To quantify the x-ray anisotropy in pyroxenes, we collected Fe K-edge XAFS spectra of oriented natural single crystals for a wide range compositions whose Fe3+/FeT ratios we determined by Mossbauer spectroscopy. We have collected both XANES and EXAFS spectral regions spanning from 7020-7220 eV to explore predictive capabilities of different spectral regions about ferric iron concentration and site occupancy. Our results will document the Fe3+ compatibility in pyroxenes of different compositions under a variety of fO2 conditions, which in turn will better constrain the interrelationship between mantle redox and melting.

Differences between silica and limestone concretes that may affect their interaction with corium

International Nuclear Information System (INIS)

Journeau, C.; Haquet, J. F.; Piluso, P.; Bonnet, J. M.

2008-01-01

Recent Molten Core Concrete Interaction tests performed at Argonne National Laboratory and at CEA Cadarache have shown that, whereas the ablation of limestone-rich concretes is almost isotropic, the ablation of silica-rich concretes is much faster towards the sides than towards the bottom of the cavity. The following differences exists between limestone-rich and silica-rich concretes: limestone concretes liberate about twice as much gas, at a given ablation rate than siliceous concretes (more than 50% more at constant heat flux) and this can affect pool hydraulics and crust stability: limestone concrete has a higher liquidus temperature than siliceous concrete and molten limestone concrete has a larger diffusion coefficient and can more easily dissolve a corium crust than siliceous melt; limestone aggregates are destroyed by de-carbonation at around 1000 K while silica aggregates melt only above 2000 K, so that floating silica aggregates can form cold spots increasing corium solidification near the interface; de-carbonation of limestone leads to a significant shrinkage of concrete melt volume compared to the cold solid that hampers the mechanical stability of overlying crusts; the chemical composition of molten mortar (sand + cement) and concrete (sand + gravel + cement) is close for limestone-rich concretes while it is different for siliceous concretes, so that the melt composition may vary significantly in case of non-simultaneous melting of the siliceous concrete constituents; molten silicates have a large viscosity, so that transport properties are different for the two types of concretes. The small range of plant concrete compositions that have been considered for MCCI experiments has not yet been found sufficient to determine which of the above-mentioned differences is paramount to explain the observed difference in ablation patterns. Separate Effect Tests using specially-designed 'artificial concretes' and prototypic corium would provide the necessary

EXPERIMENTAL INVESTIGATION OF IRRADIATION-DRIVEN HYDROGEN ISOTOPE FRACTIONATION IN ANALOGS OF PROTOPLANETARY HYDROUS SILICATE DUST

Energy Technology Data Exchange (ETDEWEB)

Roskosz, Mathieu; Remusat, Laurent [IMPMC, CNRS UMR 7590, Sorbonne Universités, Université Pierre et Marie Curie, IRD, Muséum National d’Histoire Naturelle, CP 52, 57 rue Cuvier, Paris F-75231 (France); Laurent, Boris; Leroux, Hugues, E-mail: mathieu.roskosz@mnhn.fr [Unité Matériaux et Transformations, Université Lille 1, CNRS UMR 8207, Bâtiment C6, F-59655 Villeneuve d’Ascq (France)

2016-11-20

The origin of hydrogen in chondritic components is poorly understood. Their isotopic composition is heavier than the solar nebula gas. In addition, in most meteorites, hydrous silicates are found to be lighter than the coexisting organic matter. Ionizing irradiation recently emerged as an efficient hydrogen fractionating process in organics, but its effect on H-bearing silicates remains essentially unknown. We report the evolution of the D/H of hydrous silicates experimentally irradiated by electrons. Thin films of amorphous silica, amorphous “serpentine,” and pellets of crystalline muscovite were irradiated at 4 and 30 keV. For all samples, irradiation leads to a large hydrogen loss correlated with a moderate deuterium enrichment of the solid residue. The entire data set can be described by a Rayleigh distillation. The calculated fractionation factor is consistent with a kinetically controlled fractionation during the loss of hydrogen. Furthermore, for a given ionizing condition, the deuteration of the silicate residues is much lower than the deuteration measured on irradiated organic macromolecules. These results provide firm evidence of the limitations of ionizing irradiation as a driving mechanism for D-enrichment of silicate materials. The isotopic composition of the silicate dust cannot rise from a protosolar to a chondritic signature during solar irradiations. More importantly, these results imply that irradiation of the disk naturally induces a strong decoupling of the isotopic signatures of coexisting organics and silicates. This decoupling is consistent with the systematic difference observed between the heavy organic matter and the lighter water typically associated with minerals in the matrix of most carbonaceous chondrites.

Kinetics of mineral condensation in the solar nebula

International Nuclear Information System (INIS)

Grove, T.L.

1987-01-01

A natural extension of the type of gas-mineral-melt condensation experiments is to study the gas-mineral-melt reaction process by controlling the reaction times of appropriate gas compositions with silicate materials. In a condensing and vaporizing gas-solid system, important processes that could influence the composition of and speciation in the gas phase are the kinetics of vaporization of components from silicate crystals and melts. The high vacuum attainable in the space station would provide an environment for studying these processes at gas pressures much lower than those obtainable in experimental devices operated at terrestrial conditions in which the gas phase and mineral or melt would be allowed to come to exchange equilibrium. Further experiments would be performed at variable gas flow rates to simulate disequilibrium vapor fractionation. In this type of experiment it is desirable to analyze directly the species in the gas phase in equilibrium with the condensed silicate material. This analytical method would provide a direct determination of the species present in the gas phase. Currently, the notion of gas speciation is based on calculations from thermodynamic data. The proposed experiments require similar furnace designs and use similar experimental starting compositions, pressures, and temperatures as those described by Mysen

Effects of chemical composition of fly ash on efficiency of metal separation in ash-melting of municipal solid waste

Energy Technology Data Exchange (ETDEWEB)

Okada, Takashi, E-mail: t-okada@u-fukui.ac.jp [Laboratory of Solid Waste Disposal Engineering, Graduate School of Engineering, Hokkaido University, Kita 13 Nishi 8, Kita-ku, Sapporo 060-8628 (Japan); Tomikawa, Hiroki [Laboratory of Solid Waste Disposal Engineering, Graduate School of Engineering, Hokkaido University, Kita 13 Nishi 8, Kita-ku, Sapporo 060-8628 (Japan)

2013-03-15

Highlights: ► Separation of Pb and Zn from Fe and Cu in ash-melting of municipal solid waste. ► Molar ratio of Cl to Na and K in fly ash affected the metal-separation efficiency. ► The low molar ratio and a non-oxidative atmosphere were better for the separation. - Abstract: In the process of metal separation by ash-melting, Fe and Cu in the incineration residue remain in the melting furnace as molten metal, whereas Pb and Zn in the residue are volatilized. This study investigated the effects of the chemical composition of incineration fly ash on the metal-separation efficiency of the ash-melting process. Incineration fly ash with different chemical compositions was melted with bottom ash in a lab-scale reactor, and the efficiency with which Pb and Zn were volatilized preventing the volatilization of Fe and Cu was evaluated. In addition, the behavior of these metals was simulated by thermodynamic equilibrium calculations. Depending on the exhaust gas treatment system used in the incinerator, the relationships among Na, K, and Cl concentrations in the incineration fly ash differed, which affected the efficiency of the metal separation. The amounts of Fe and Cu volatilized decreased by the decrease in the molar ratio of Cl to Na and K in the ash, promoting metal separation. The thermodynamic simulation predicted that the chlorination volatilization of Fe and Cu was prevented by the decrease in the molar ratio, as mentioned before. By melting incineration fly ash with the low molar ratio in a non-oxidative atmosphere, most of the Pb and Zn in the ash were volatilized leaving behind Fe and Cu.

Analyses and predictions of the thermodynamic properties and phase diagrams of silicate systems

Energy Technology Data Exchange (ETDEWEB)

Blander, M. (Argonne National Lab., IL (United States)); Pelton, A.; Eriksson, G. (Ecole Polytechnique, Montreal, PQ (Canada). Dept. of Metallurgy and Materials Engineering)

1992-01-01

Molten silicates are ordered solutions which can not be well represented by the usual polynomial representation of deviations from ideal solution behavior (i.e. excess free energies of mixing). An adaptation of quasichemical theory which is capable of describing the properties of ordered solutions represents the measured properties of binary silicates over broad ranges of composition and temperature. For simple silicates such as the MgO-FeO-SiO{sub 2} ternary system, in which silica is the only acid component, a combining rule generally leads to good predictions of ternary solutions from those of the binaries. In basic solutions, these predictions are consistent with those of the conformal ionic solution theory. Our results indicate that our approach could provide a potentially powerful tool for representing and predicting the properties of multicomponent molten silicates.

Analyses and predictions of the thermodynamic properties and phase diagrams of silicate systems

Energy Technology Data Exchange (ETDEWEB)

Blander, M. [Argonne National Lab., IL (United States); Pelton, A.; Eriksson, G. [Ecole Polytechnique, Montreal, PQ (Canada). Dept. of Metallurgy and Materials Engineering

1992-07-01

Molten silicates are ordered solutions which can not be well represented by the usual polynomial representation of deviations from ideal solution behavior (i.e. excess free energies of mixing). An adaptation of quasichemical theory which is capable of describing the properties of ordered solutions represents the measured properties of binary silicates over broad ranges of composition and temperature. For simple silicates such as the MgO-FeO-SiO{sub 2} ternary system, in which silica is the only acid component, a combining rule generally leads to good predictions of ternary solutions from those of the binaries. In basic solutions, these predictions are consistent with those of the conformal ionic solution theory. Our results indicate that our approach could provide a potentially powerful tool for representing and predicting the properties of multicomponent molten silicates.

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

Magma storage constrains by compositional zoning of plagioclase from dacites of the caldera forming eruptions of Vetrovoy Isthmus and Lvinaya Past’ Bay (Iturup Island, Kurile Islands)

Science.gov (United States)

Maksimovich, I. A.; Smirnov, S. Z.; Kotov, A. A.; Timina, T. Yu; Shevko, A. V.

2017-12-01

The Vetrovoy Isthmus and the Lvinaya Past’ Bay on the Iturup island (Kuril island arc) are the results of large Plinian eruptions of compositionally similar dacitic magmas. This study is devoted to a comparative analysis of the storage and crystallization conditions for magma reservoirs, which were a source of large-scale explosive eruptions. The plagioclase is most informative mineral in studying of the melt evolution. The studied plagioclases possess a complex zoning patterns, which are not typical for silicic rocks in island-arc systems. It was shown that increase of Ca in the plagioclase up to unusually high An95 is related to increase of H2O pressure in both volcanic magma chambers. The study revealed that minerals of the Vetrovoy Isthmus and Lvinaya Past’ crystallized from compositionally similar melts. Despite the compositional similarity of the melts, the phenocryst assemblage of the Lvinaya Past’ differs from the Vetrovoy Isthmus by the presence of the amphibole, which indicates that the pressure in the magmatic chamber exceeded 1-2 kbar at a 4-6 wt. % of H2O in the melt. The rocks of the Vetrovoy Isthmus do not contain amphibole phenocrysts, but melt and fluid inclusions assemblages in plagioclase demonstrate that the magma degassed in the course of evolution. This is an indication that the pressure did not exceed significantly 1-2 kbar.

Recognizing subtle evidence for silicic magma derivation from petrochemically-similar arc crust: Isotopic and chemical evidence for the bimodal volcanic series of Gorely Volcanic Center, Kamchatka, Russia

Science.gov (United States)

Seligman, A. N.; Bindeman, I. N.; Ellis, B. S.; Ponomareva, V.; Leonov, V.

2012-12-01

The Kamchatka Peninsula is home to some of the most prolific subduction related volcanic activity in the world. Gorely caldera and its central volcano are located in the rear of its currently active Eastern Volcanic Front. Recent work determined the presence of explosive ignimbrite eruptions sourced from Gorely volcano during the Pleistocene. We studied 32 eruptive units, including tephrochronologically-dated Holocene tephra, stratigraphically-arranged ignimbrites, as well as pre- and post-caldera lavas. We analyzed oxygen isotope ratios of pyroxene and plagioclase grains by laser fluorination, and major and trace element compositions of whole rocks. In addition, we determined 87Sr/86Sr and 143Nd/144Nd ratios of caldera-forming ignimbrite eruptions. Chemical compositions show that Gorely eruptive units range from basalt to basaltic andesite in the "Pra-Gorely" stages prior to caldera formation and the modern Gorely stages forming its current edifice. In contrast, eruptive material from earlier ignimbrites exposed at Opasny Ravine consists primarily of dacite. Whole rock analyses for Gorely indicate that silicic rocks and ignimbrites volumetrically dominate all other products, forming separate bimodal peaks in our SiO2-frequency diagram. In addition, trace element concentrations and ratios define two trends, one for more silicic and another for more mafic material. δ18Omelt values range from a low of 4.85 up to 6.22‰, where the lowest value was found in the last caldera forming eruption, suggesting incorporation of hydrothermally-altered material from earlier eruptions. 87Sr/86Sr and 143Nd/144Nd ratios range from 0.70328 to 0.70351 and from 0.51303 to 0.51309 respectively, with higher and more diverse values being characteristic of earlier ignimbrite units; again suggesting incorporation of surrounding crustal material. In contrast to these results, MELTS modeling using a variety of likely primitive basalts from Gorely shows it is possible to obtain silicic

Wear resistance of WCp/Duplex Stainless Steel metal matrix composite layers prepared by laser melt injection

NARCIS (Netherlands)

Do Nascimento, A. M.; Ocelik, V.; Ierardi, M. C. F.; De Hosson, J. Th. M.

2008-01-01

Laser Melt Injection (LMI) was used to prepare metal matrix composite layers with a thickness of about 0.7 mm and approximately 10% volume fraction of WC particles in three kinds of Cast Duplex Stainless Steels (CDSSs). WC particles were injected into the molten surface layer using Nd:YAG high power

Encapsulation of TRISO particle fuel in durable soda-lime-silicate glasses

International Nuclear Information System (INIS)

Heath, Paul G.; Corkhill, Claire L.; Stennett, Martin C.; Hand, Russell J.; Meyer, Willem C.H.M.; Hyatt, Neil C.

2013-01-01

Tri-Structural Isotropic (TRISO) coated particle-fuel is a key component in designs for future high temperature nuclear reactors. This study investigated the suitability of three soda lime silicate glass compositions, for the encapsulation of simulant TRISO particle fuel. A cold press and sinter (CPS) methodology was employed to produce TRISO particle–glass composites. Composites produced were determined to have an aqueous durability, fracture toughness and Vickers’ hardness comparable to glasses currently employed for the disposal of high level nuclear wastes. Sintering at 700 °C for 30 min was found to remove all interconnected porosity from the composite bodies and oxidation of the outer pyrolytic carbon layer during sintering was prevented by processing under a 5% H 2 /N 2 atmosphere. However, the outer pyrolytic carbon layer was not effectively wetted by the encapsulating glass matrix. The aqueous durability of the TRISO particle–glass composites was investigated using PCT and MCC-1 tests combined with geochemical modelling. It was found that durability was dependent on silicate and calcium solution saturation. This study provides significant advancements in the preparation of TRISO particle encapsulant waste forms. The potential for the use of non-borosilicate sintered glass composites for TRISO particle encapsulation has been confirmed, although further refinements are required

Encapsulation of TRISO particle fuel in durable soda-lime-silicate glasses

Energy Technology Data Exchange (ETDEWEB)

Heath, Paul G.; Corkhill, Claire L.; Stennett, Martin C.; Hand, Russell J. [Immobilisation Science Laboratory, Department of Materials Science and Engineering, Robert Hadfield Building, University of Sheffield, Sheffield S1 3JD (United Kingdom); Meyer, Willem C.H.M. [Necsa, South African Nuclear Energy Corporation, PO Box 582, Pretoria, Gauteng (South Africa); Hyatt, Neil C., E-mail: n.c.hyatt@sheffield.ac.uk [Immobilisation Science Laboratory, Department of Materials Science and Engineering, Robert Hadfield Building, University of Sheffield, Sheffield S1 3JD (United Kingdom)

2013-05-15

Tri-Structural Isotropic (TRISO) coated particle-fuel is a key component in designs for future high temperature nuclear reactors. This study investigated the suitability of three soda lime silicate glass compositions, for the encapsulation of simulant TRISO particle fuel. A cold press and sinter (CPS) methodology was employed to produce TRISO particle–glass composites. Composites produced were determined to have an aqueous durability, fracture toughness and Vickers’ hardness comparable to glasses currently employed for the disposal of high level nuclear wastes. Sintering at 700 °C for 30 min was found to remove all interconnected porosity from the composite bodies and oxidation of the outer pyrolytic carbon layer during sintering was prevented by processing under a 5% H{sub 2}/N{sub 2} atmosphere. However, the outer pyrolytic carbon layer was not effectively wetted by the encapsulating glass matrix. The aqueous durability of the TRISO particle–glass composites was investigated using PCT and MCC-1 tests combined with geochemical modelling. It was found that durability was dependent on silicate and calcium solution saturation. This study provides significant advancements in the preparation of TRISO particle encapsulant waste forms. The potential for the use of non-borosilicate sintered glass composites for TRISO particle encapsulation has been confirmed, although further refinements are required.

XANES analysis of calcium and sodium phosphates and silicates and hydroxyapatite-Bioglass (registered) 45S5 co-sintered bioceramics

Energy Technology Data Exchange (ETDEWEB)

Demirkiran, Hande [Graduate Student, Materials Science and Engineering Department, University of Texas at Arlington, Arlington, TX (United States); Hu Yongfeng; Zuin, Lucia [Beamline Scientist, Canadian Light Source, Saskatoon, SK (Canada); Appathurai, Narayana [Beamline Scientist, Synchrotron Radiation Center, Madison, WI (United States); Aswath, Pranesh B., E-mail: aswath@uta.edu [Materials Science and Engineering Department, University of Texas at Arlington, Arlington, TX (United States)

2011-03-12

Bioglass (registered) 45S5 was co-sintered with hydroxyapatite at 1200 deg. C. When small amounts (< 5 wt.%) of Bioglass (registered) 45S5 was added it behaved as a sintering aid and also enhanced the decomposition of hydroxyapatite to {beta}-tricalcium phosphate. However when 10 wt.% and 25 wt.% Bioglass (registered) 45S5 was used it resulted in the formation of Ca{sub 5}(PO{sub 4}){sub 2}SiO{sub 4} and Na{sub 3}Ca{sub 6}(PO{sub 4}){sub 5} in an amorphous silicate matrix respectively. These chemistries show improved bioactivity compared to hydroxyapatite and are the subject of this study. The structure of several crystalline calcium and sodium phosphates and silicates as well as the co-sintered hydroxyapatite-Bioglass (registered) 45S5 bioceramics were examined using XANES spectroscopy. The nature of the crystalline and amorphous phases were studied using silicon (Si) and phosphorus (P) K- and L{sub 2,3}-edge and calcium (Ca) K-edge XANES. Si L{sub 2,3}-edge spectra of sintered bioceramic compositions indicates that the primary silicates present in these compositions are sodium silicates in the amorphous state. From Si K-edge spectra, it is shown that the silicates are in a similar structural environment in all the sintered bioceramic compositions with 4-fold coordination. Using P L{sub 2,3}-edge it is clearly shown that there is no evidence of sodium phosphate present in the sintered bioceramic compositions. In the P K-edge spectra, the post-edge shoulder peak at around 2155 eV indicates that this shoulder to be more defined for calcium phosphate compounds with decreasing solubility and increasing thermodynamic stability. This shoulder peak is more noticeable in hydroxyapatite and {beta}-TCP indicating greater stability of the phosphate phase. The only spectra that does not show a noticeable peak is the composition with Na{sub 3}Ca{sub 6}(PO{sub 4}){sub 5} in a silicate matrix indicating that it is more soluble compared to the other compositions.

The Okhansk Meteorite: Specifics of Composition, Structure, and Genesis

Directory of Open Access Journals (Sweden)

A.I. Bakhtin

2016-12-01

Full Text Available The Okhansk meteorite fell on August 18, 1887 near the village of Tabor, about 15 km away from the town of Okhansk in Perm province and weighed 186.5 kg (the total weight of collected fragments, according to P.I. Krotov, was more than 245 kg. The shock wave from the meteorite entry knocked down animals and riders on horses. Despite the fact that it was significantly stronger than that caused by the Chelyabinsk meteorite of 2013, all information about this meteorite has completely erased from people's memory. It has been shown that the meteorite is an ordinary olivine-bronzite chondrite. Its main silicate minerals are olivine, bronzite, plagioclase, and diopside. The main ore minerals are kamacite and troilite. The meteorite contains silicate glass in large amounts. The analysis of the composition and structure of the Okhansk meteorite has demonstrated that it was formed at the early stages of accretion of the melted substance of the protosolar nebula without undergoing endogenous, temperature, or pressure changes.

USE OF LOCAL NATURAL SILICEOUS RAW MATERIAL AND WASTES FOR PRODUCTION OF HEAT-INSULATING FOAMCONCRETE

Directory of Open Access Journals (Sweden)

V. U. Matsapulin

2015-01-01

Full Text Available The article analyzes the resource base, reserves and the use of siliceous rocks, their economic feasibility of the use for production of building materials of new generation with low-energy and other costs. Presented are the results of laboratory research and testing technology of production of insulating foam from a composition based on an aqueous solution of sodium silicate obtained from the local siliceous rocks (diatomite and the liquid alkali component - soapstock, hardener from ferrochrome slag and waste carbonate rock able to harden at a low temperature processing ( 100-110 ° C.

Composition characteristics and regularities of dissolving of hydroxyapatite materials obtained in water solutions with varied content of silicate ions

Science.gov (United States)

Solonenko, A. P.

2018-01-01

Research aimed at developing new bioactive materials for the repair of defects in bone tissues, do not lose relevance due to the strengthening of the regenerative approach in medicine. From this point of view, materials based on calcium phosphates, including silicate ions, consider as one of the most promising group of substances. Methods of synthesis and properties of hydroxyapatite doped with various amounts of SiO4 4- ions are described in literature. In the present work synthesis of a solid phase in the systems Ca(NO3)2 - (NH4)2HPO4 - Na2SiO3 - NH4OH - H2O (Cca/CP = 1.70) performed with a wide range of sodium silicate additive concentration (y = CSi/CP = 0 ÷ 5). It is established that under the studied conditions at y ≥ 0.3 highly dispersed poorly crystallized apatite containing isomorphic impurities of CO3 2- and SiO4 4- precipitates in a mixture with calcium hydrosilicate and SiO2. It is shown that the resulting composites can gradually dissolve in physiological solution and initiate passive formation of the mineral component of hard tissues.

Chitosan-magnesium aluminum silicate composite dispersions: characterization of rheology, flocculate size and zeta potential.

Science.gov (United States)

Khunawattanakul, Wanwisa; Puttipipatkhachorn, Satit; Rades, Thomas; Pongjanyakul, Thaned

2008-03-03

Composite dispersions of chitosan (CS), a positively charged polymer, and magnesium aluminum silicate (MAS), a negatively charged clay, were prepared and rheology, flocculate size and zeta potential of the CS-MAS dispersions were investigated. High and low molecular weights of CS (HCS and LCS, respectively) were used in this study. Moreover, the effects of heat treatment at 60 degrees C on the characteristics of the CS-MAS dispersions and the zeta potential of MAS upon addition of CS at different pHs were examined. Incorporation of MAS into CS dispersions caused an increase in viscosity and a shift of CS flow type from Newtonian to pseudoplastic flow with thixotropic properties. Heat treatment brought about a significant decrease in viscosity and hysteresis area of the composite dispersions. Microscopic studies showed that flocculation of MAS occurred after mixing with CS. The size and polydispersity index of the HCS-MAS flocculate were greater than those of the LCS-MAS flocculate. However, a narrower size distribution and the smaller size of the HCS-MAS flocculate were found after heating at 60 degrees C. Zeta potentials of the CS-MAS flocculates were positive and slightly increased with increasing MAS content. In the zeta potential studies, the negative charge of the MAS could be neutralized by the addition of CS. Increasing the pH and molecular weight of CS resulted in higher CS concentrations required to neutralize the charge of MAS. These findings suggest that the electrostatic interaction between CS and MAS caused a change in flow behavior and flocculation of the composite dispersions, depending on the molecular weight of CS. Heat treatment affected the rheological properties and the flocculate size of the composite dispersions. Moreover, pH of medium and molecular weight of CS influence the zeta potential of MAS.

Composite Biomaterials Based on Sol-Gel Mesoporous Silicate Glasses: A Review

Science.gov (United States)

Baino, Francesco; Fiorilli, Sonia; Vitale-Brovarone, Chiara

2017-01-01

Bioactive glasses are able to bond to bone and stimulate the growth of new tissue while dissolving over time, which makes them ideal materials for regenerative medicine. The advent of mesoporous glasses, which are typically synthesized via sol-gel routes, allowed researchers to develop a broad and versatile class of novel biomaterials that combine superior bone regenerative potential (compared to traditional melt-derived glasses) with the ability of incorporating drugs and various biomolecules for targeted therapy in situ. Mesoporous glass particles can be directly embedded as a bioactive phase within a non-porous (e.g., microspheres), porous (3D scaffolds) or injectable matrix, or be processed to manufacture a surface coating on inorganic or organic (macro)porous substrates, thereby obtaining hierarchical structures with multiscale porosity. This review provides a picture of composite systems and coatings based on mesoporous glasses and highlights the challenges for the future, including the great potential of inorganic–organic hybrid sol-gel biomaterials. PMID:28952496

SILICATE EVOLUTION IN BROWN DWARF DISKS

International Nuclear Information System (INIS)

Riaz, B.

2009-01-01

We present a compositional analysis of the 10 μm silicate spectra for brown dwarf disks in the Taurus and Upper Scorpius (UppSco) star-forming regions, using archival Spitzer/Infrared Spectrograph observations. A variety in the silicate features is observed, ranging from a narrow profile with a peak at 9.8 μm, to nearly flat, low-contrast features. For most objects, we find nearly equal fractions for the large-grain and crystalline mass fractions, indicating both processes to be active in these disks. The median crystalline mass fraction for the Taurus brown dwarfs is found to be 20%, a factor of ∼2 higher than the median reported for the higher mass stars in Taurus. The large-grain mass fractions are found to increase with an increasing strength in the X-ray emission, while the opposite trend is observed for the crystalline mass fractions. A small 5% of the Taurus brown dwarfs are still found to be dominated by pristine interstellar medium-like dust, with an amorphous submicron grain mass fraction of ∼87%. For 15% of the objects, we find a negligible large-grain mass fraction, but a >60% small amorphous silicate fraction. These may be the cases where substantial grain growth and dust sedimentation have occurred in the disks, resulting in a high fraction of amorphous submicron grains in the disk surface. Among the UppSco brown dwarfs, only usd161939 has a signal-to-noise ratio high enough to properly model its silicate spectrum. We find a 74% small amorphous grain and a ∼26% crystalline mass fraction for this object.

Melting point of yttria

International Nuclear Information System (INIS)

Skaggs, S.R.

1977-06-01

Fourteen samples of 99.999 percent Y 2 O 3 were melted near the focus of a 250-W CO 2 laser. The average value of the observed melting point along the solid-liquid interface was 2462 +- 19 0 C. Several of these same samples were then melted in ultrahigh-purity oxygen, nitrogen, helium, or argon and in water vapor. No change in the observed temperature was detected, with the exception of a 20 0 C increase in temperature from air to helium gas. Post test examination of the sample characteristics, clarity, sphericity, and density is presented, along with composition. It is suggested that yttria is superior to alumina as a secondary melting-point standard

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

International Nuclear Information System (INIS)

Smits, G.

1987-01-01

(U,Th)-silicates form two complete series of anhydrous and hydrated species with general formulae (U,Th)SiO 4 and (U,Th)SiO 4 .nH 2 O 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

Effect of composition in the development of carbamazepine hot-melt extruded solid dispersions by application of mixture experimental design.

Science.gov (United States)

Djuris, Jelena; Ioannis, Nikolakakis; Ibric, Svetlana; Djuric, Zorica; Kachrimanis, Kyriakos

2014-02-01

This study investigates the application of hot-melt extrusion for the formulation of carbamazepine (CBZ) solid dispersions, using polyethyleneglycol-polyvinyl caprolactam-polyvinyl acetate grafted copolymer (Soluplus, BASF, Germany) and polyoxyethylene-polyoxypropylene block copolymer (Poloxamer 407). In agreement with the current Quality by Design principle, formulations of solid dispersions were prepared according to a D-optimal mixture experimental design, and the influence of formulation composition on the properties of the dispersions (CBZ heat of fusion and release rate) was estimated. Prepared solid dispersions were characterized using differential scanning calorimetry, attenuated total reflectance infrared spectroscopy and hot stage microscopy, as well as by determination of the dissolution rate of CBZ from the hot-melt extrudates. Solid dispersions of CBZ can be successfully prepared using the novel copolymer Soluplus. Inclusion of Poloxamer 407 as a plasticizer facilitated the processing and decreased the hardness of hot-melt extrudates. Regardless of their composition, all hot-melt extrudates displayed an improvement in the release rate compared to the pure CBZ, with formulations having the ratio of CBZ : Poloxamer 407 = 1 : 1 showing the highest increase in CBZ release rate. Interactions between the mixture components (CBZ and polymers), or quadratic effects of the components, play a significant role in overall influence on the CBZ release rate. © 2013 Royal Pharmaceutical Society.

Cubic zirconia in >2370 °C impact melt records Earth's hottest crust

Science.gov (United States)

Timms, Nicholas E.; Erickson, Timmons M.; Zanetti, Michael R.; Pearce, Mark A.; Cayron, Cyril; Cavosie, Aaron J.; Reddy, Steven M.; Wittmann, Axel; Carpenter, Paul K.

2017-11-01

Bolide impacts influence primordial evolution of planetary bodies because they can cause instantaneous melting and vaporization of both crust and impactors. Temperatures reached by impact-generated silicate melts are unknown because meteorite impacts are ephemeral, and established mineral and rock thermometers have limited temperature ranges. Consequently, impact melt temperatures in global bombardment models of the early Earth and Moon are poorly constrained, and may not accurately predict the survival, stabilization, geochemical evolution and cooling of early crustal materials. Here we show geological evidence for the transformation of zircon to cubic zirconia plus silica in impact melt from the 28 km diameter Mistastin Lake crater, Canada, which requires super-heating in excess of 2370 °C. This new temperature determination is the highest recorded from any crustal rock. Our phase heritage approach extends the thermometry range for impact melts by several hundred degrees, more closely bridging the gap between nature and theory. Profusion of >2370 °C superheated impact melt during high intensity bombardment of Hadean Earth likely facilitated consumption of early-formed crustal rocks and minerals, widespread volatilization of various species, including hydrates, and formation of dry, rigid, refractory crust.

Surface charges and Np(V) sorption on amorphous Al- and Fe- silicates

International Nuclear Information System (INIS)

Del Nero, M.; Assada, A.; Barillon, R.; Duplatre, G.; Made, B.

2005-01-01

complex function of silicate bulk chemistry and solution chemistry, i.e. of pH and aqueous Si concentrations. Simple conceptual models of the surface chemistry of the Al- and Fe-silicates are developed here, based on the wealth of experimental data of silicate surface charges. The surface complexation models predict reasonably the effect of solution chemistry on the sorption of neptunyl ions on poorly ordered silicates of various compositions, and can thus be useful in extrapolating neptunyl mobility in many geochemical systems. (authors)

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.

Crystallization and mechanical properties of reinforced PHBV composites using melt compounding: Effect of CNCs and CNFs.

Science.gov (United States)

Jun, Du; Guomin, Zhao; Mingzhu, Pan; Leilei, Zhuang; Dagang, Li; Rui, Zhang

2017-07-15

Nanocellulose reinforced poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) composites were prepared using melt compounding. The effects of nanocellulose types (CNCs and CNFs) and nanocellulose content (1, 2, 3, 4, 5, 6 and 7wt%) on the crystallization, thermal and mechanical properties of PHBV composites were systematically compared in this study. The thermal stability of PHBV composites was improved by both CNCs and CNFs. CNFs with a higher thermal stability leaded to a higher thermal stability of PHBV composites. Both CNCs and CNFs induced a reduction in the crystalline size of PHBV spherulites. Furthermore, CNCs could act as a better nucleating agent for PHBV than did CNFs. CNCs and CNFs showed reinforcing effects in PHBV composites. At the equivalent content of nanocellulose, CNCs led to a higher tensile modulus of PHBV composites than did CNFs. 1wt% CNCs/PHBV composites exhibited the most optimum mechanical properties. Copyright © 2017 Elsevier Ltd. All rights reserved.

Final report on the safety assessment of potassium silicate, sodium metasilicate, and sodium silicate.

Science.gov (United States)

Elmore, Amy R

2005-01-01

Potassium Silicate, Sodium Metasilicate, and Sodium Silicate combine metal cations with silica to form inorganic salts used as corrosion inhibitors in cosmetics. Sodium Metasilicate also functions as a chelating agent and Sodium Silicate as a buffering and pH adjuster. Sodium Metasilicate is currently used in 168 formulations at concentrations ranging from 13% to 18%. Sodium Silicate is currently used in 24 formulations at concentrations ranging from 0.3% to 55%. Potassium Silicate and Sodium Silicate have been reported as being used in industrial cleaners and detergents. Sodium Metasilicate is a GRAS (generally regarded as safe) food ingredient. Aqueous solutions of Sodium Silicate species are a part of a chemical continuum of silicates based on an equilibrium of alkali, water, and silica. pH determines the solubility of silica and, together with concentration, determines the degree of polymerization. Sodium Silicate administered orally is readily absorbed from the alimentary canal and excreted in the urine. The toxicity of these silicates has been related to the molar ratio of SiO2/Na2O and the concentration being used. The Sodium Metasilicate acute oral LD50 ranged from 847 mg/kg in male rats to 1349.3 mg/kg in female rats and from 770 mg/kg in female mice to 820 mg/kg in male mice. Gross lesions of variable severity were found in the oral cavity, pharynx, esophagus, stomach, larynx, lungs, and kidneys of dogs receiving 0.25 g/kg or more of a commercial detergent containing Sodium Metasilicate; similar lesions were also seen in pigs administered the same detergent and dose. Male rats orally administered 464 mg/kg of a 20% solution containing either 2.0 or 2.4 to 1.0 ratio of sodium oxide showed no signs of toxicity, whereas doses of 1000 and 2150 mg/kg produced gasping, dypsnea, and acute depression. Dogs fed 2.4 g/kg/day of Sodium Silicate for 4 weeks had gross renal lesions but no impairment of renal function. Dermal irritation of Potassium Silicate, Sodium

Crustal thermal state and origin of silicic magma in Iceland: the case of Torfajökull, Ljósufjöll and Snæfellsjökull volcanoes

Science.gov (United States)

Martin, E.; Sigmarsson, O.

2007-05-01

Pleistocene and Holocene peralkaline rhyolites from Torfajökull (South Iceland Volcanic Zone) and Ljósufjöll central volcanoes and trachytes from Snæfellsjökull (Snæfellsnes Volcanic Zone) allow the assessment of the mechanism for silicic magma genesis as a function of geographical location and crustal geothermal gradient. The low δ18O (2.4‰) and low Sr concentration (12.2 ppm) measured in Torfajökull rhyolites are best explained by partial melting of hydrated metabasaltic crust followed by major fractionation of feldspar. In contrast, very high 87Sr/86Sr (0.70473) and low Ba (8.7 ppm) and Sr (1.2 ppm) concentrations measured in Ljósufjöll silicic lavas are best explained by fractional crystallisation and subsequent 87Rb decay. Snæfellsjökull trachytes are also generated by fractional crystallisation, with less than 10% crustal assimilation, as inferred from their δ18O. The fact that silicic magmas within, or close to, the rift zone are principally generated by crustal melting whereas those from off-rift zones are better explained by fractional crystallisation clearly illustrates the controlling influence of the thermal state of the crust on silicic magma genesis in Iceland.

Material properties influence on steam explosion efficiency. Prototypic versus simulant melts, eutectic versus non-eutectic melts

International Nuclear Information System (INIS)

Leskovar, M.; Mavko, B.

2006-01-01

A steam explosion may occur during a severe nuclear reactor accident if the molten core comes into contact with the coolant water. A strong enough steam explosion in a nuclear power plant could jeopardize the containment integrity and so lead to a direct release of radioactive material to the environment. Details of processes taking place prior and during the steam explosion have been experimentally studied for a number of years with adjunct efforts in modelling these processes to address the scaling of these experiments. Steam explosion experiments have shown that there are important differences of behaviour between simulant and prototypical melts, and that also at prototypical melts the fuel coolant interactions depend on the composition of the corium. In experiments with prototypic materials no spontaneous steam explosions occurred (except with an eutectic composition), whereas with simulant materials the steam explosions were triggered spontaneously. The energy conversion ratio of steam explosions with prototypic melts is at least one order of magnitude lower than the energy conversion ratio of steam explosions with simulant melts. Although the different behaviour of prototypic and simulant melts has been known for a number of years, there is no reliable explanation for these differences. Consequently it is not possible to reliably estimate whether corium would behave so non-explosive also in reactor conditions, where the mass of poured melt is nearly three orders of magnitude larger than in experimental conditions. An even more fascinating material effect was observed recently at corium experiments with eutectic and non-eutectic compositions. It turned out that eutectic corium always exploded spontaneously, whereas non-eutectic corium never exploded spontaneously. In the paper, a possible explanation of both material effects (prototypic/simulant melts, eutectic/non-eutectic corium) on the steam explosion is provided. A model for the calculation of the

Electrochemistry of lunar rocks

Science.gov (United States)

Lindstrom, D. J.; Haskin, L. A.

1979-01-01

Electrolysis of silicate melts has been shown to be an effective means of producing metals from common silicate materials. No fluxing agents need be added to the melts. From solution in melts of diopside (CaMgSi2O6) composition, the elements Si, Ti, Ni, and Fe have been reduced to their metallic states. Platinum is a satisfactory anode material, but other cathode materials are needed. Electrolysis of compositional analogs of lunar rocks initially produces iron metal at the cathode and oxygen gas at the anode. Utilizing mainly heat and electricity which are readily available from sunlight, direct electrolysis is capable of producing useful metals from common feedstocks without the need for expendable chemicals. This simple process and the products obtained from it deserve further study for use in materials processing in space.

Nanostructured silicate polymer concrete

Directory of Open Access Journals (Sweden)

Figovskiy Oleg L'vovich

2014-03-01

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

Glass science tutorial: Lecture number-sign 2, Operating electric glass melters. James N. Edmonson, Lecturer

International Nuclear Information System (INIS)

Kruger, A.A.

1994-10-01

This report contains basic information on electric furnaces used for glass melting and on the properties of glass useful for the stabilization of radioactive wastes. Furnace nomenclature, furnace types, typical silicate glass composition and properties, thermal conductivity information, kinetics of the melting process, glass furnace refractory materials composition and thermal conductivity, and equations required for the operation of glass melters are included

Silicic magma differentiation in ascent conduits. Experimental constraints

Science.gov (United States)

Rodríguez, Carmen; Castro, Antonio

2017-02-01

Crystallization of water-bearing silicic magmas in a dynamic thermal boundary layer is reproduced experimentally by using the intrinsic thermal gradient of piston-cylinder assemblies. The standard AGV2 andesite under water-undersaturated conditions is set to crystallize in a dynamic thermal gradient of about 35 °C/mm in 10 mm length capsules. In the hotter area of the capsule, the temperature is initially set at 1200 °C and decreases by programmed cooling at two distinct rates of 0.6 and 9.6 °C/h. Experiments are conducted in horizontally arranged assemblies in a piston cylinder apparatus to avoid any effect of gravity settling and compaction of crystals in long duration runs. The results are conclusive about the effect of water-rich fluids that are expelled out the crystal-rich zone (mush), where water saturation is reached by second boiling in the interstitial liquid. Expelled fluids migrate to the magma ahead of the solidification front contributing to a progressive enrichment in the fluxed components SiO2, K2O and H2O. The composition of water-rich fluids is modelled by mass balance using the chemical composition of glasses (quenched melt). The results are the basis for a model of granite magma differentiation in thermally-zoned conduits with application of in-situ crystallization equations. The intriguing textural and compositional features of the typical autoliths, accompanying granodiorite-tonalite batholiths, can be explained following the results of this study, by critical phenomena leading to splitting of an initially homogeneous magma into two magma systems with sharp boundaries. Magma splitting in thermal boundary layers, formed at the margins of ascent conduits, may operate for several km distances during magma transport from deep sources at the lower crust or upper mantle. Accordingly, conduits may work as chromatographic columns contributing to increase the silica content of ascending magmas and, at the same time, leave behind residual mushes that

Compositional Evolution of Calcium Silicate Hydrate (C-S-H) Structures by Total X-Ray Scattering

KAUST Repository

Soyer-Uzun, Sezen; Chae, Sejung Rosie; Benmore, Chris J.; Wenk, Hans-Rudolf; Monteiro, Paulo J. M.

2011-01-01

High-energy X-ray diffraction was employed to study the structural characteristics of a set of C-S-H samples with 0.6 ≤ C/S a;circ 1.75. It has been observed that Si is tetrahedrally coordinated to O for all samples irrespective of chemical composition and the Ca-O coordination number gradually decreases from ∼7 to ∼6 with increasing C/S ratio. This suggests that the C-S-H structure evolves from a tobermorite-like structure into a jennite-like structure as a function of increasing C/S ratio as the interlayer space decreases from ∼1.3 to ∼1 nm. Evolution of these short- and medium-range order structural characteristics in the C-S-H system is associated with the alteration of the Ca-O layers and silicate depolymerization with increasing C/S. © 2011 The American Ceramic Society.

Compositional Evolution of Calcium Silicate Hydrate (C-S-H) Structures by Total X-Ray Scattering

KAUST Repository

Soyer-Uzun, Sezen

2011-12-09

High-energy X-ray diffraction was employed to study the structural characteristics of a set of C-S-H samples with 0.6 ≤ C/S a;circ 1.75. It has been observed that Si is tetrahedrally coordinated to O for all samples irrespective of chemical composition and the Ca-O coordination number gradually decreases from ∼7 to ∼6 with increasing C/S ratio. This suggests that the C-S-H structure evolves from a tobermorite-like structure into a jennite-like structure as a function of increasing C/S ratio as the interlayer space decreases from ∼1.3 to ∼1 nm. Evolution of these short- and medium-range order structural characteristics in the C-S-H system is associated with the alteration of the Ca-O layers and silicate depolymerization with increasing C/S. © 2011 The American Ceramic Society.

X-ray absorption study of Ti-bearing silicate glasses

OpenAIRE

Dingwell, Donald B.; Paris, Eleonora; Seifert, Friedrich; Mottana, Annibale; Romano, Claudia

1994-01-01

Ti K-edge XANES spectra have been collected on a series of Ti-bearing silicate glasses with metasilicate and tetrasilicate compositions. The intensity of the preedge feature in these spectra has been found to change with glass composition and varies from 29 to 58% (normalized intensity) suggesting a variation in structural environent around the absorbing atom. The pre-edge peak intensity increases for the alkali titanium tetrasilicate glasses from 35% to 58% in the order Li < Na < K < Rb, Cs ...

Cumulates, Dykes and Pressure Solution in the Ice-Salt Mantle of Europa: Geological Consequences of Pressure Dependent Liquid Compositions and Volume Changes During Ice-Salt Melting Reactions.

Science.gov (United States)

Day, S.; Asphaug, E.; Bruesch, L.

2002-12-01

Water-salt analogue experiments used to investigate cumulate processes in silicate magmas, along with observations of sea ice and ice shelf behaviour, indicate that crystal-melt separation in water-salt systems is a rapid and efficient process even on scales of millimetres and minutes. Squeezing-out of residual melts by matrix compaction is also predicted to be rapid on geological timescales. We predict that the ice-salt mantle of Europa is likely to be strongly stratified, with a layered structure predictable from density and phase relationships between ice polymorphs, aqueous saline solutions and crystalline salts such as hydrated magnesium sulphates (determined experimentally by, inter alia, Hogenboom et al). A surface layer of water ice flotation cumulate will be separated from denser salt cumulates by a cotectic horizon. This cotectic horizon will be both the site of subsequent lowest-temperature melting and a level of neutral buoyancy for the saline melts produced. Initial melting will be in a narrow depth range owing to increasing melting temperature with decreasing pressure: the phase relations argue against direct melt-though to the surface unless vesiculation occurs. Overpressuring of dense melts due to volume expansion on cotectic melting is predicted to lead to lateral dyke emplacement and extension above the dyke tips. Once the liquid leaves the cotectic, melting of water ice will involve negative volume change. Impact-generated melts will drain downwards through the fractured zones beneath crater floors. A feature in the complex crater Mannan'an, with elliptical ring fractures around a conical depression with a central pit, bears a close resemblance to Icelandic glacier collapse cauldrons produced by subglacial eruptions. Other structures resembling Icelandic cauldrons occur along Europan banded structures, while resurgence of ice rubble within collapse structures may produce certain types of chaos region. More general contraction of the ice mantle

Anti-carburizing Coating for Resin Sand Casting of Low Carbon Steel Based on Composite Silicate Powder Containing Zirconium

Directory of Open Access Journals (Sweden)

Zhan Chunyi

2018-01-01

Full Text Available This paper studied the structure and properties of anticarburizing coating based on composite silicate powder containing zirconium by X-ray diffraction analyzer, thermal expansion tester, digital microscope and other equipment. It is introduced that the application example of the coating in the resin-sand casting of ZG1Cr18Ni9Ti stainless steel impeller. The anti-carburizing effect of the coating on the surface layer of the cast is studied by using direct reading spectrometer and spectrum analyzer. The change of the micro-structure of the coating after casting and cooling is observed by scanning electron microscope. The analysis of anti-carburizing mechanism of the coating is presented. The results indicate that the coating possesses excellent suspension property, brush ability, permeability, levelling property and crackresistance. The coating exhibits high strength and low gas evolution. Most of the coating could be automatically stripped off flakily when the casting was shaken out. The casting possesses excellent surface finish and antimetal penetration effect. The carburizing layer thickness of the stainless steel impeller casting with respect to allowable upper limit of carbon content is about 1mm and maximum carburizing rate is 23.6%. The anticarburizing effect of casting surface is greatly improved than that of zircon powder coating whose maximum carburizing rate is 67.9% and the carburizing layer thickness with respect to allowable upper limit of carbon content is greater than 2mm. The composite silicate powder containing zirconium coating substantially reduces the zircon powder which is expensive and radioactive and mainly dependent on imports. The coating can be used instead of pure zircon powder coating to effectively prevent metal-penetration and carburizing of resin-sand-casting surface of low carbon steel, significantly improve the foundry production environment and reduce the production costs.

Early planetesimal melting from an age of 4.5662 Gyr for differentiated meteorites

DEFF Research Database (Denmark)

Baker, J.; Bizzarro, Martin; Wittig, N.

2005-01-01

for these meteorites, however, are typically younger than age constraints for planetesimal differentiation. Such young ages indicate that the energy required to melt their parent bodies could not have come from the most likely heat source-radioactive decay of short-lived nuclides (Al and Fe) injected from a nearby...... decay could have triggered planetesimal melting. Small Mg excesses in bulk angrite samples confirm that Al decay contributed to the melting of their parent body. These results indicate that the accretion of differentiated planetesimals pre-dated that of undifferentiated planetesimals, and reveals......Long- and short-lived radioactive isotopes and their daughter products in meteorites are chronometers that can test models for Solar System formation. Differentiated meteorites come from parent bodies that were once molten and separated into metal cores and silicate mantles. Mineral ages...

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 not...

An experimental study of Fe-Ni exchange between sulfide melt and olivine at upper mantle conditions: implications for mantle sulfide compositions and phase equilibria

Science.gov (United States)

Zhang, Zhou; von der Handt, Anette; Hirschmann, Marc M.

2018-03-01

The behavior of nickel in the Earth's mantle is controlled by sulfide melt-olivine reaction. Prior to this study, experiments were carried out at low pressures with narrow range of Ni/Fe in sulfide melt. As the mantle becomes more reduced with depth, experiments at comparable conditions provide an assessment of the effect of pressure at low-oxygen fugacity conditions. In this study, we constrain the Fe-Ni composition of molten sulfide in the Earth's upper mantle via sulfide melt-olivine reaction experiments at 2 GPa, 1200 and 1400 °C, with sulfide melt X_{{{Ni}}}^{{{Sulfide}}}={{Ni}}/{{Ni+{Fe}}} (atomic ratio) ranging from 0 to 0.94. To verify the approach to equilibrium and to explore the effect of {f_{{{O}2}}} on Fe-Ni exchange between phases, four different suites of experiments were conducted, varying in their experimental geometry and initial composition. Effects of Ni secondary fluorescence on olivine analyses were corrected using the PENELOPE algorithm (Baró et al., Nucl Instrum Methods Phys Res B 100:31-46, 1995), "zero time" experiments, and measurements before and after dissolution of surrounding sulfides. Oxygen fugacities in the experiments, estimated from the measured O contents of sulfide melts and from the compositions of coexisting olivines, were 3.0 ± 1.0 log units more reduced than the fayalite-magnetite-quartz (FMQ) buffer (suite 1, 2 and 3), and FMQ - 1 or more oxidized (suite 4). For the reduced (suites 1-3) experiments, Fe-Ni distribution coefficients K_{{D}}{}={(X_{{{Ni}}}^{{{sulfide}}}/X_{{{Fe}}}^{{{sulfide}}})}/{(X_{{{Ni}}^{{{olivine}}}/X_{{{Fe}}}^{{{olivine}}})}} are small, averaging 10.0 ± 5.7, with little variation as a function of total Ni content. More oxidized experiments (suite 4) give larger values of K D (21.1-25.2). Compared to previous determinations at 100 kPa, values of K D from this study are chiefly lower, in large part owing to the more reduced conditions of the experiments. The observed difference does not seem

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

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......, 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...

Rapid timescales for accretion and melting of differentiated planetesimals inferred from Al-Mg chronometry

DEFF Research Database (Denmark)

Bizzarro, Martin; Haack, H.; Baker, J.A.

2005-01-01

. Initial Al/Al values range from (1.26 ± 0.37) × 10 to (5.12 ± 0.81) × 10 at the time of magmatism on the EPB and MPB, and are among the highest Al abundances reported for igneous meteorites. These results indicate that widespread silicate melting and differentiation of rocky bodies occurred within 3...

Reduction experiment of FeO-bearing amorphous silicate: application to origin of metallic iron in GEMS

Energy Technology Data Exchange (ETDEWEB)

Matsuno, Junya; Tsuchiyama, Akira; Miyake, Akira [Department of Geology and Mineralogy, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwake, Sakyo-ku, Kyoto 606-8502 (Japan); Noguchi, Ryo [Department of Earth and Space Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043 (Japan); Ichikawa, Satoshi, E-mail: jmatsuno@kueps.kyoto-u.ac.jp [Institute for Nano-science Design, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531 (Japan)

2014-09-10

Glass with embedded metal and sulfides (GEMS) are amorphous silicates included in anhydrous interplanetary dust particles (IDPs) and can provide information about material evolution in our early solar system. Several formation processes for GEMS have been proposed so far, but these theories are still being debated. To investigate a possible GEMS origin by reduction of interstellar silicates, we synthesized amorphous silicates with a mean GEMS composition and performed heating experiments in a reducing atmosphere. FeO-bearing amorphous silicates were heated at 923 K and 973 K for 3 hr, and at 1023 K for 1-48 hr at ambient pressure in a reducing atmosphere. Fe grains formed at the interface between the silicate and the reducing gas through a reduction. In contrast, TEM observations of natural GEMS show that metallic grains are uniformly embedded in amorphous silicates. Therefore, the present study suggests that metallic inclusions in GEMS could not form as reduction products and that other formation process such as condensation or irradiation are more likely.

Selective laser melting of carbon/AlSi10Mg composites: Microstructure, mechanical and electronical properties

Energy Technology Data Exchange (ETDEWEB)

Zhao, Xiao; Song, Bo, E-mail: bosong@hust.edu.cn; Fan, Wenrui; Zhang, Yuanjie; Shi, Yusheng

2016-04-25

Carbon nanotubes/AlSi10Mg composites has drawn lots of attention in structural engineering and functional device applications due to its extraordinary high elastic modulus and mechanical strength as well as excellent electrical and thermal conductivities. In this study, the CNTs/AlSi10Mg composites was firstly prepared and then processed by selective laser melting. The powder preparation, SLM process, and microstructure evolution, properties were clarified. The results showed that CNTs were decomposed due to the direct interaction with the laser beam. The SLMed composites displayed a similar microstructure to that of SLMed AlSi10Mg. The common brittleness phase Al{sub 4}C{sub 3} didn't form, and the carbon dispersion strengthening was observed. The electrical resistivity of the composites was reduced significantly and the hardness was improved. - Highlights: • Carbon nanotubes/AlSi10Mg powder were prepared by slurry ball milling process. • Carbon nanotubes/AlSi10Mg composites were firstly prepared by SLM. • The electrical resistivity of the composites was significantly reduced and hardness was improved.

VARIATIONS OF THE 10 μm SILICATE FEATURES IN THE ACTIVELY ACCRETING T TAURI STARS: DG Tau AND XZ Tau

International Nuclear Information System (INIS)

Bary, Jeffrey S.; Leisenring, Jarron M.; Skrutskie, Michael F.

2009-01-01

Using the Infrared Spectrograph aboard the Spitzer Space Telescope, we observed multiple epochs of 11 actively accreting T Tauri stars in the nearby Taurus-Auriga star-forming region. In total, 88 low-resolution mid-infrared spectra were collected over 1.5 years in Cycles 2 and 3. The results of this multi-epoch survey show that the 10 μm silicate complex in the spectra of two sources-DG Tau and XZ Tau-undergoes significant variations with the silicate feature growing both weaker and stronger over month- and year-long timescales. Shorter timescale variations on day- to week-long timescales were not detected within the measured flux errors. The time resolution coverage of this data set is inadequate for determining if the variations are periodic. Pure emission compositional models of the silicate complex in each epoch of the DG Tau and XZ Tau spectra provide poor fits to the observed silicate features. These results agree with those of previous groups that attempted to fit only single-epoch observations of these sources. Simple two-temperature, two-slab models with similar compositions successfully reproduce the observed variations in the silicate features. These models hint at a self-absorption origin of the diminution of the silicate complex instead of a compositional change in the population of emitting dust grains. We discuss several scenarios for producing such variability including disk shadowing, vertical mixing, variations in disk heating, and disk wind events associated with accretion outbursts.

Confined Water in Layered Silicates: The Origin of Anomalous Thermal Expansion Behavior in Calcium-Silicate-Hydrates

International Nuclear Information System (INIS)

Krishnan, N. M. Anoop; Wang, Bu; Falzone, Gabriel; Le Pape, Yann; Neithalath, Narayanan

2016-01-01

Water, under conditions of nanoscale confinement, exhibits anomalous dynamics, and enhanced thermal deformations, which may be further enhanced when such water is in contact with hydrophilic surfaces. Such heightened thermal deformations of water could control the volume stability of hydrated materials containing nanoconfined structural water. Understanding and predicting the thermal deformation coefficient (TDC, often referred to as the CTE, coefficient of thermal expansion), which represents volume changes induced in materials under conditions of changing temperature, is of critical importance for hydrated solids including: hydrogels, biological tissues, and calcium silicate hydrates, as changes in their volume can result in stress development, and cracking. By pioneering atomistic simulations, we examine the physical origin of thermal expansion in calcium-silicate-hydrates (C–S–H), the binding agent in concrete that is formed by the reaction of cement with water. We report that the TDC of C–S–H shows a sudden increase when the CaO/SiO_2 (molar ratio; abbreviated as Ca/Si) exceeds 1.5. This anomalous behavior arises from a notable increase in the confinement of water contained in the C–S–H’s nanostructure. We identify that confinement is dictated by the topology of the C–S–H’s atomic network. Altogether, the results suggest that thermal deformations of hydrated silicates can be altered by inducing compositional changes, which in turn alter the atomic topology and the resultant volume stability of the solids.

Confined Water in Layered Silicates: The Origin of Anomalous Thermal Expansion Behavior in Calcium-Silicate-Hydrates.

Science.gov (United States)

Krishnan, N M Anoop; Wang, Bu; Falzone, Gabriel; Le Pape, Yann; Neithalath, Narayanan; Pilon, Laurent; Bauchy, Mathieu; Sant, Gaurav

2016-12-28

Water, under conditions of nanoscale confinement, exhibits anomalous dynamics, and enhanced thermal deformations, which may be further enhanced when such water is in contact with hydrophilic surfaces. Such heightened thermal deformations of water could control the volume stability of hydrated materials containing nanoconfined structural water. Understanding and predicting the thermal deformation coefficient (TDC, often referred to as the CTE, coefficient of thermal expansion), which represents volume changes induced in materials under conditions of changing temperature, is of critical importance for hydrated solids including: hydrogels, biological tissues, and calcium silicate hydrates, as changes in their volume can result in stress development, and cracking. By pioneering atomistic simulations, we examine the physical origin of thermal expansion in calcium-silicate-hydrates (C-S-H), the binding agent in concrete that is formed by the reaction of cement with water. We report that the TDC of C-S-H shows a sudden increase when the CaO/SiO 2 (molar ratio; abbreviated as Ca/Si) exceeds 1.5. This anomalous behavior arises from a notable increase in the confinement of water contained in the C-S-H's nanostructure. We identify that confinement is dictated by the topology of the C-S-H's atomic network. Taken together, the results suggest that thermal deformations of hydrated silicates can be altered by inducing compositional changes, which in turn alter the atomic topology and the resultant volume stability of the solids.

Nanoporous layered silicate AMH-3/cellulose acetate nanocomposite membranes for gas separations

KAUST Repository

Kim, Wun-gwi; Lee, Jong Suk; Bucknall, David G.; Koros, William J.; Nair, Sankar

2013-01-01

Nanoporous layered silicate/polymer composite membranes are of interest because they can exploit the high aspect ratio of exfoliated selective flakes/layers to enhance molecular sieving and create a highly tortuous transport path for the slower

Comparative study on the change in index of refraction in ion-exchange interdiffusion in alkali-silicate glasses containing calcium, strontium, barium and titanium oxides

International Nuclear Information System (INIS)

Livshits, V.Ya.; Marchuk, E.A.

1993-01-01

Different ability to ion exchange from the salts of lithium-sodium-silicate glass melt containing calcium (or strontium, or barium) and titanium oxides in addition has been shown. CaO, SrO and BaO have negative effect, but TiO 2 -positive one on the fullness of ion exchange of lithium-sodium and on the rate of interdiffusion in alkali-silicate glass. The value of change in index of refraction of glass with TiO 2 is twice higher than glass with calcium oxide (or strontium, or barium) as the fourth component

Hydrologic controls on radiogenic Sr in meltwater from an alpine glacier system: Athabasca Glacier, Canada

International Nuclear Information System (INIS)

Arendt, C.A.; Stevenson, E.I.; Aciego, S.M.

2016-01-01

Filtered subglacial meltwater samples were collected daily during the onset of melt (May) and peak melt (July) over the 2011 melt season at the Athabasca Glacier (Alberta, Canada) and analyzed for strontium-87/strontium-86 ("8"7Sr/"8"6Sr) isotopic composition to infer the evolution of subglacial weathering processes. Both the underlying bedrock composition and subglacial water–rock interaction time are the primary influences on meltwater "8"7Sr/"8"6Sr. The Athabasca Glacier is situated atop Middle Cambrian carbonate bedrock that also contains silicate minerals. The length of time that subglacial meltwater interacts with the underlying bedrock and substrate is a predominant determining factor in solute concentration. Over the course of the melt season, increasing trends in Ca/K and Ca/Mg correspond to overall decreasing trends in "8"7Sr/"8"6Sr, which indicate a shift in weathering processes from the presence of silicate weathering to primarily carbonate weathering. Early in the melt season, rates of carbonate dissolution slow as meltwater approaches saturation with respect to calcite and dolomite, corresponding to an increase in silicate weathering that includes Sr-rich silicate minerals, and an increase in meltwater "8"7Sr/"8"6Sr. However, carbonate minerals are preferentially weathered in unsaturated waters. During the warmest part of a melt season the discharged meltwater is under saturated, causing an increase in carbonate weathering and a decrease in the radiogenic Sr signal. Likewise, larger fraction contributions of meltwater from glacial ice corresponds to lower "8"7Sr/"8"6Sr values, as the meltwater has lower water–rock interaction times in the subglacial system. These results indicate that although weathering of Sr-containing silicate minerals occurs in carbonate dominated glaciated terrains, the continual contribution of new meltwater permits the carbonate weathering signal to dominate. - Highlights: • Glacial meltwater "8"7Sr/"8"6Sr used to

Low-Li2O Frits: Selecting Glasses that Support the Melt Rate Studies and Challenge the Current Durability Model

International Nuclear Information System (INIS)

Peeler, D. K.; Edwards, T. B.

2005-01-01

During the progressive development of the cold cap model (as it applies to a potential melt rate predictive tool), the formation of an Al-Li-silicate phase was identified as an intermediate reaction phase that could possibly hinder melt rate for SB4. To test this theory, six glasses were designed (using Frit 320's composition as the baseline) to maintain a constant 20 wt% sum of alkali content (in frit) by varying Na 2 O to Li 2 O ratios. The Li 2 O concentration ranged from 8 wt% down to 0% in either 2% or 1% increments with the differences being accounted for by an increase in Na 2 O concentration. Although the primary objective of the ''lower Li 2 O'' frits was to evaluate the potential for melt rate improvements, assessments of durability (as measured by the Product Consistency Test (PCT)) were also performed. The results suggest that durable glasses can be produced with these ''lower Li 2 O'' frits should it be necessary to pursue this option for improving melt rate. In addition to the series of glasses to support melt rate assessments, a series of frits were also developed to challenge the current durability model based on the limits proposed by Edwards et al. (2004). Although the ''new'' limits allow access into compositional regions of interest (i.e., higher alkali systems) which can improve melt rate and/or waste loading, there may still be ''additional'' conservatism. In this report, two series of glasses were developed to challenge the ''new'' durability limits for the SB4 system. In the first series, the total alkali of the Frit 320-based glasses (designed to support the melt rate program) was increased from 20 wt% to 21 wt% (in the frit), but the series also evaluated the possible impact of various Na 2 O and Li 2 O mass ratio differences. The second series pushed the alkali limit in the frit even further with frits containing either 22 or 24 wt% total alkali as well as various Na 2 O and Li 2 O mass ratios. The results of the PCT evaluation indicated

Synthesis and crystal structures of a novel layered silicate SSA-1 and its microporous derivatives by topotactic transformation.

Science.gov (United States)

Takahashi, S; Kurita, Y; Ikeda, T; Miyamoto, M; Uemiya, S; Oumi, Y

2016-10-18

The synthesis of a novel layered silicate SSA-1 (SSA: silicate synthesized with a quaternary amine) was achieved in the SiO 2 -H 2 O-TEAOH (TEAOH: tetraethylammonium hydroxide - as an organic structural directing agent) system. The crystal structure of SSA-1 involved two silicate layers composed of bre [10T]-type CBU (Composite Building Unit) and TEAOH in interlayers. The topotactic transformation of SSA-1 by calcination was examined, resulting in a porous material (PML-1: porous material transformed from a layered silicate) with a 108 m 2 g -1 BET surface area and 0.035 cm 3 g -1 pore volume. PML-1 is a siliceous microporous material with silanols in the framework and possesses unique properties, such as hydrophilicity, in spite of all its silica composition. The most reasonable crystal structure of PML-1 was successfully determined on the basis of the crystal structure of SSA-1 by a combination of manual modelling, PXRD pattern simulation, DFT optimization and Rietveld analysis. Additionally, an interlayer expanded siliceous zeolite SSA-1 (IEZ-SSA-1) was also successfully prepared by silylation using trichloro(methyl)silane under acidic conditions. IEZ-SSA-1 showed hydrophilicity or hydrophobicity properties by changing the functional group of the pillar part in the interlayer. Additionally, IEZ-SSA-1 showed a large gas adsorption property (537 m 2 g -1 and 0.21 cm 3 g -1 ).

Wear and Reactivity Studies of Melt infiltrated Ceramic Matrix Composite

Science.gov (United States)

Jarmon, David C.; Ojard, Greg; Brewer, David N.

2013-01-01

As interest grows in the use of ceramic matrix composites (CMCs) for critical gas turbine engine components, the effects of the CMCs interaction with the adjoining structure needs to be understood. A series of CMC/material couples were wear tested in a custom elevated temperature test rig and tested as diffusion couples, to identify interactions. Specifically, melt infiltrated silicon carbide/silicon carbide (MI SiC/SiC) CMC was tested in combination with a nickel-based super alloy, Waspaloy, a thermal barrier coating, Yttria Stabilized Zirconia (YSZ), and a monolithic ceramic, silicon nitride (Si3N4). To make the tests more representative of actual hardware, the surface of the CMC was kept in the as-received state (not machined) with the full surface features/roughness present. Test results include: scanning electron microscope characterization of the surfaces, micro-structural characterization, and microprobe analysis.

The evolution of grain mantles and silicate dust growth at high redshift

Science.gov (United States)

Ceccarelli, Cecilia; Viti, Serena; Balucani, Nadia; Taquet, Vianney

2018-05-01

In dense molecular clouds, interstellar grains are covered by mantles of iced molecules. The formation of the grain mantles has two important consequences: it removes species from the gas phase and promotes the synthesis of new molecules on the grain surfaces. The composition of the mantle is a strong function of the environment that the cloud belongs to. Therefore, clouds in high-zeta galaxies, where conditions - like temperature, metallicity, and cosmic ray flux - are different from those in the Milky Way, will have different grain mantles. In the last years, several authors have suggested that silicate grains might grow by accretion of silicon-bearing species on smaller seeds. This would occur simultaneously with the formation of the iced mantles and be greatly affected by its composition as a function of time. In this work, we present a numerical study of the grain mantle formation in high-zeta galaxies, and we quantitatively address the possibility of silicate growth. We find that the mantle thickness decreases with increasing redshift, from about 120 to 20 layers for z varying from 0 to 8. Furthermore, the mantle composition is also a strong function of the cloud redshift, with the relative importance of CO, CO2, ammonia, methane, and methanol highly varying with z. Finally, being Si-bearing species always a very minor component of the mantle, the formation of silicates in molecular clouds is practically impossible.

Crystallization and melting behavior of isotactic polypropylene composites filled by zeolite supported β-nucleator

International Nuclear Information System (INIS)

Jiang, Juan; Li, Gu; Tan, Nanshu; Ding, Qian; Mai, Kancheng

2012-01-01

Highlights: ► The supported calcium pimelate β-zeolite was prepared. ► The β-nucleation of zeolite was enhanced dramatically through reaction. ► High β-phase content iPP composites were obtained by introducing the β-zeolite into iPP. - Abstract: In order to prepare the zeolite filled β-iPP composites, the calcium pimelate as β-nucleator supported on the surface of zeolite (β-zeolite) was prepared by the interaction between calcified zeolite and pimelic acid. The β-nucleation, crystallization behavior and melting characteristic of zeolite, calcified zeolite and β-zeolite filled iPP composites were investigated by differential scanning calorimetry and wide-angle X-ray diffractometer. The results indicated that addition of the zeolite and calcified zeolite as well as β-zeolite increased the crystallization temperature of iPP. The zeolite and calcified zeolite filled iPP composites mainly crystallized in the α-crystal form and the strong β-heterogeneous nucleation of β-zeolite results in the formation of only β-crystal in β-zeolite filled iPP composites. The zeolite filled β-iPP composites with high β-crystal contents (above 0.90) can be easily obtained by adding β-zeolite into iPP matrix.

Silicate bonded ceramics of laterites

International Nuclear Information System (INIS)

Wagh, A.S.; Douse, V.

1989-05-01

Sodium silicate is vacuum impregnated in bauxite waste (red mud) at room temperature to develop ceramics of mechanical properties comparable to the sintered ceramics. For a concentration up to 10% the fracture toughness increases from 0.12 MNm -3/2 to 0.9 MNm -3/2 , and the compressive strength from 7 MNm -2 to 30 MNm -2 . The mechanical properties do not deteriorate, when soaked in water for an entire week. The viscosity and the concentration of the silicate solution are crucial, both for the success of the fabrication and the economics of the process. Similar successful results have been obtained for bauxite and lime stone, even though the latter has poor weathering properties. With scanning electron microscopy and energy dispersive analysis, an attempt is made to identify the crystals formed in the composite, which are responsible for the strength. The process is an economic alternative to the sintered ceramics in the construction industry in the tropical countries, rich in lateritic soils and poor in energy. Also the process has all the potential for further development in arid regions abundant in limestone. (author). 6 refs, 20 figs, 3 tabs

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.

A Physical Model for Three-Phase Compaction in Silicic Magma Reservoirs

Science.gov (United States)

Huber, Christian; Parmigiani, Andrea

2018-04-01

We develop a model for phase separation in magma reservoirs containing a mixture of silicate melt, crystals, and fluids (exsolved volatiles). The interplay between the three phases controls the dynamics of phase separation and consequently the chemical and physical evolution of magma reservoirs. The model we propose is based on the two-phase damage theory approach of Bercovici et al. (2001, https://doi.org/10.1029/2000JB900430) and Bercovici and Ricard (2003, https://doi.org/10.1046/j.1365-246X.2003.01854.x) because it offers the leverage of considering interface (in the macroscopic limit) between phases that can deform depending on the mechanical work and phase changes taking place locally in the magma. Damage models also offer the advantage that pressure is defined uniquely to each phase and does not need to be equal among phases, which will enable us to consider, in future studies, the large capillary pressure at which fluids are mobilized in mature, crystal-rich, magma bodies. In this first analysis of three-phase compaction, we solve the three-phase compaction equations numerically for a simple 1-D problem where we focus on the effect of fluids on the efficiency of melt-crystal separation considering the competition between viscous and buoyancy stresses only. We contrast three sets of simulations to explore the behavior of three-phase compaction, a melt-crystal reference compaction scenario (two-phase compaction), a three-phase scenario without phase changes, and finally a three-phase scenario with a parameterized second boiling (crystallization-induced exsolution). The simulations show a dramatic difference between two-phase (melt crystals) and three-phase (melt-crystals-exsolved volatiles) compaction-driven phase separation. We find that the presence of a lighter, significantly less viscous fluid hinders melt-crystal separation.

Laser-induced breakdown spectroscopy analysis of minerals: Carbonates and silicates

International Nuclear Information System (INIS)

McMillan, Nancy J.; Harmon, Russell S.; De Lucia, Frank C.; Miziolek, Andrzej M.

2007-01-01

Laser-induced breakdown spectroscopy (LIBS) provides an alternative chemical analytical technique that obviates the issues of sample preparation and sample destruction common to most laboratory-based analytical methods. This contribution explores the capability of LIBS analysis to identify carbonate and silicate minerals rapidly and accurately. Fifty-two mineral samples (18 carbonates, 9 pyroxenes and pyroxenoids, 6 amphiboles, 8 phyllosilicates, and 11 feldspars) were analyzed by LIBS. Two composite broadband spectra (averages of 10 shots each) were calculated for each sample to produce two databases each containing the composite LIBS spectra for the same 52 mineral samples. By using correlation coefficients resulting from the regression of the intensities of pairs of LIBS spectra, all 52 minerals were correctly identified in the database. If the LIBS spectra of each sample were compared to a database containing the other 51 minerals, 65% were identified as a mineral of similar composition from the same mineral family. The remaining minerals were misidentified for two reasons: 1) the mineral had high concentrations of an element not present in the database; and 2) the mineral was identified as a mineral with similar elemental composition from a different family. For instance, the Ca-Mg carbonate dolomite was misidentified as the Ca-Mg silicate diopside. This pilot study suggests that LIBS has promise in mineral identification and in situ analysis of minerals that record geological processes

Les silicates alcalins, matière de base des mousses minérales isolantes. Etude bibliographique Alkaline Silicates, As a Basic Material for Insulating Mineral Foams. Bibliographie Study

Directory of Open Access Journals (Sweden)

Lesage J.

2006-11-01

Full Text Available Dans cette étude bibliographique, on décrit les méthodes d'obtention des silicates alcalins ainsi que leurs propriétés et les propriétés de leurs polymères en insistant sur l'influence du pH, de la concentration et de la température sur la polymérisation et les caractéristiques des polymères obtenus. On présente ensuite le mode d'obtention des mousses à partir de solutions aqueuses de silicates, ainsi que leurs propriétés et l'influence de divers additifs tels que les agents tensioactifs, moussants, gélifiants ou les agents de durcissement sur les propriétés des mousses. II ressort de cette bibliographie que des mousses polysilicates solubles peuvent être obtenues à partir de solutions de silicates à faible rapport molaire SiO2/Na2O. Par ailleurs, en faisant varier la composition des solutions de silicates alcalins et par l'emploi d'additifs, il est possible de produire une gamme très variée de mousses polysilicates dont les propriétés d'isolation, de solubilité et de résistance mécanique, voire de perméabilité, sont très variées, ce qui leur ouvre la voie à de nombreuses possibilités de débouchés industriels. This article gives a bibliographic description of methods for obtaining alkaline silicates as well as their properties and the properties of their polymers. Emphasis is placed on the influence of the pH, and on the influence of the concentration and temperature on the polymerization and the characteristics of the polymers obtained. Then a method is recommended for obtaining foams from aqueous silicate solutions together with the properties of such foams and the influence of different additives such as surfactants, foaming agents, gelling agents and hardening agents on the properties of foams. This bibliographic study shows that soluble polysilicate foams may be obtained from silicate solutions with a low SiO2/Na2O molar ratio. Furthermore, by varying the composition of alkaline silicate solutions and by

Nuclear waste management by in-situ melting

International Nuclear Information System (INIS)

Angelo, J.A. Jr.

1976-01-01

A systematic assessment of the in-situ melting concept as an ultimate waste disposal option shows that the placement of solidifed, high-level radioactive wastes in an in-situ melting cavity with a crushed rock backfill not only eliminates the major deficiencies inherent in other in-situ melting schemes, but also satisfies reasonable criteria for ultimate disposal. In-situ melting reduces the waste isolation time requirements to several hundred years. Calculated spent fuel and processing waste afterheat values assess the role of actinide and cladding material nuclides in creating the total afterheat and provide quantitative variation with time for these values for contamporary and advanced-design fission reactors. The dominant roles of 134 Cs in thermal spectrum reactor afterheats during the first decade of cooling of the actinide nuclides in all typical waste after-heats following a century or two of cooling are identified. The spatial and temporal behavior of a spherically symmetric waste repository experiencing in-situ melting in an equal density, homogeneous medium for silicate rock and salt is controlled primarily by the overall volumetric thermal source strength, the time-dependent characteristics of the high-level wastes, and the thermophysical properties of the surrounding rock environment. Calculations were verified by experimental data. The hazard index for typical high-level wastes is dominated by the fission product nuclides for the first three centuries of decay. It is then controlled by the actinides, especially americium, which dominates for 10,000 years. With in-situ melting, the hazard index for the re-solidifed rock/waste matrix deepunderground falls below the hazard index of naturally occurring uranium ore bodies within a few hundred years, whether or not the more hazardous actinide nuclides are selectively removed from the wastes prior to storage

A new viscosity model for waste glass formulations

International Nuclear Information System (INIS)

Sadler, A.L.K.

1996-01-01

Waste glass formulation requires prediction, with reasonable accuracy, of properties over much wider ranges of composition than are typically encountered in any single industrial application. Melt viscosity is one such property whose behavior must be predicted in formulating new waste glasses. A model was developed for silicate glasses which relates the Arrhenius activation energy for flow to an open-quotes effectiveclose quotes measure of non-bridging oxygen content in the melt, NBO eff . The NBO eff parameter incorporates the differing effects of modifying cations on the depolymerization of the silicate network. The activation energy-composition relationship implied by the model is in accordance with experimental behavior. The model was validated against two different databases, with satisfactory results

Ca/Al of plagioclase-hosted melt inclusions as an indicator for post-entrapment processes at mid-ocean ridges?

Energy Technology Data Exchange (ETDEWEB)

Zhang, H.T.; Yang, Y.M.; Yan, Q.S.; Shi, Z.F.; Zhu, Z.W.; Su, W.C.; Qin, C.J.; Ye, J.

2016-07-01

The composition of melt inclusions in basalts erupted at mid-ocean ridges may be modified by post-entrapment processes, so the present composition of melt inclusions may not represent their original composition at the time of entrapment. By combining the melt inclusion composition in samples from the South Mid-Atlantic Ridge at 19°S analyzed in this study, and from the Petrological Database, we found that post-entrapment crystallization processes resulted in higher Ca/Al, Mg#[100×atomic Mg2+/(Mg2++Fe2+)], MgO and FeO contents, and lower CaO and Al2O3 contents of plagioclase-hosted melt inclusions relative to those hosted in olivine. In addition, melt inclusions hosted in plagioclase with anorthite content larger than 80mol.% had been modified more readily than others. By discussing the relationships between Ca/Al and fractional crystallization, post-entrapment crystallization, and the original melt composition, we propose that Ca/Al can be regarded as an indicator of the effect of post-entrapment processes on melt inclusion composition. Specifically, i) when Ca/Al<0.78, melt inclusion compositions corrected for fractional crystallization to Mg#=72 can represent the primary magma at mid-ocean ridges; ii) when 0.78melt inclusions are mainly modified by post-entrapment crystallization effects, and can reveal the original melt composition after correcting for these effects; iii) when Ca/Al>1.0, the compositions of melt inclusions do not reflect the original melt composition nor preserve information about the mantle source. According to these criteria, plagioclase-hosted melt inclusions with Ca/Al>1.0 in basalts from the South Mid-Atlantic Ridge at19°S cannot represent the composition of the melt at the moment of their entrapment. (Author)

High through-plane thermal conduction of graphene nanoflake filled polymer composites melt-processed in an L-shape kinked tube.

Science.gov (United States)

Jung, Haejong; Yu, Seunggun; Bae, Nam-Seok; Cho, Suk Man; Kim, Richard Hahnkee; Cho, Sung Hwan; Hwang, Ihn; Jeong, Beomjin; Ryu, Ji Su; Hwang, Junyeon; Hong, Soon Man; Koo, Chong Min; Park, Cheolmin

2015-07-22

Design of materials to be heat-conductive in a preferred direction is a crucial issue for efficient heat dissipation in systems using stacked devices. Here, we demonstrate a facile route to fabricate polymer composites with directional thermal conduction. Our method is based on control of the orientation of fillers with anisotropic heat conduction. Melt-compression of solution-cast poly(vinylidene fluoride) (PVDF) and graphene nanoflake (GNF) films in an L-shape kinked tube yielded a lightweight polymer composite with the surface normal of GNF preferentially aligned perpendicular to the melt-flow direction, giving rise to a directional thermal conductivity of approximately 10 W/mK at 25 vol % with an anisotropic thermal conduction ratio greater than six. The high directional thermal conduction was attributed to the two-dimensional planar shape of GNFs readily adaptable to the molten polymer flow, compared with highly entangled carbon nanotubes and three-dimensional graphite fillers. Furthermore, our composite with its density of approximately 1.5 g/cm(3) was mechanically stable, and its thermal performance was successfully preserved above 100 °C even after multiple heating and cooling cycles. The results indicate that the methodology using an L-shape kinked tube is a new way to achieve polymer composites with highly anisotropic thermal conduction.

Drivers of plant species composition in siliceous spring ecosystems: groundwater chemistry, catchment traits or spatial factors?

Directory of Open Access Journals (Sweden)

Carl BEIERKUHNLEIN

2009-08-01

Full Text Available Spring water reflects the hydrochemistry of the aquifer in the associated catchments. On dense siliceous bedrock, the nearsurface groundwater flow is expected to be closely related to the biogeochemical processes of forest ecosystems, where the impact of land use is also low. We hypothesize that the plant species composition of springs mainly reflects hydrochemical conditions. Therefore, springs may serve as indicator systems for biogeochemical processes in complex forest ecosystems. To test this hypothesis, we investigate the influence of spring water chemical properties, catchment traits, and spatial position on plant species composition for 73 springs in forested catchments in central Germany, using non-metric multidimensional scaling (NMDS, Mantel tests, and path analyses. Partial Mantel tests and path analyses reveal that vegetation is more greatly influenced by spring water chemistry than by catchment traits. Consequently, the catchment's influence on vegetation is effective in an indirect way, via spring water. When considering spatial aspects (in particular altitude in addition, the explanatory power of catchment traits for spring water properties is reduced almost to zero. As vegetation shows the highest correlation with the acidity gradient, we assume that altitude acts as a sum parameter that incorporates various acidifying processes in the catchment. These processes are particularly related to altitude – through bedrock, climatic parameters and forest vegetation. The species composition of undisturbed springs is very sensitive in reflecting such conditions and may serve as an integrative tool for detecting complex ecological processes.

Melting technique for vanadium containing steels

Energy Technology Data Exchange (ETDEWEB)

Grishanov, M P; Gutovskij, I B; Vakhrushev, A S

1980-04-28

To descrease cost price of high-quality vanadium steels a method of their melting in open-hearth furnaces with acid lining using slag-metal fraction of vanadium, which is loaded in the content of 2.1-4.7% of melting mass, is suggested. Introduction of slag-metal fraction of vanadium ensures the formation of slag with composition that guarantees the necessary content of vanadium in steel and does not require introduction of expensive vanadium-containing ferroalloys into the melt.

21 CFR 172.410 - Calcium silicate.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Calcium silicate. 172.410 Section 172.410 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Agents § 172.410 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be safely...

Structure of aluminosilicate melts produced from granite rocks for the manufacturing of petrurgical glass-ceramics construction materials

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Simakin, A. G.

2001-12-01

Full Text Available The aluminosilicate melt is a partly ordered phase and is the origin of glass for producing glassceramics and petrurgical materials. They are well extended used as construction materials for pavings and coatings. Its structure can be described in the terms of the aluminosilica tetrahedras coordination so-called Q speciation. The proportions of tetrahedra with different degree of connectivity with others (from totally connected to free has been studied by NMR and IR methods for sodium-silicate melts. Medium range structure can be characterized by the sizes of irreducible rings composed of the aluminosilica tetrahedra. Systematic increase of the four member rings proportion in the sequence of the Ab-An glasses were observed. The water dissolution in sodium-silicate glass affects the Q speciation. Cations network-modifiers positions in the melt structure are important to know since these cations stabilize particular structure configurations. Modification of the distribution of Na coordination in the sodium-silicate glass at water dissolution was determined by NMR spectroscopy. The observed modification of the hydrous aluminosilicate melt structure resulted in the shift of the eutectic composition in the granite system with decreasing of the crystallization field of feldspars. The feldspar growth rates show practically no dependence on the water content in the concentration range 2-4 wt.%. Likewise, the solved water has a little influence on the crystal growth rate of the lithium silicate phase in lithium containing glasses in accordance with estimated enhancing of the diffusion transport.

Los fundidos de alumino-silicato son una fase parcialmente ordenada. Su estructura puede ser descrita en términos de la coordinación de tetraedros de alúmina-sílice también denominados especies Q. La proporción de tetraedros con diferente grado de conectividad entre si se ha investigado por espectroscopias de RMN e IR en fundidos de silicatos

Presolar silicates in the matrix and fine-grained rims around chondrules in primitive CO3.0 chondrites: Evidence for pre-accretionary aqueous alteration of the rims in the solar nebula

Science.gov (United States)

Haenecour, Pierre; Floss, Christine; Zega, Thomas J.; Croat, Thomas K.; Wang, Alian; Jolliff, Bradley L.; Carpenter, Paul

2018-01-01

To investigate the origin of fine-grained rims around chondrules (FGRs), we compared presolar grain abundances, elemental compositions and mineralogies in fine-grained interstitial matrix material and individual FGRs in the primitive CO3.0 chondrites Allan Hills A77307, LaPaz Icefield 031117 and Dominion Range 08006. The observation of similar overall O-anomalous (∼155 ppm) and C-anomalous grain abundances (∼40 ppm) in all three CO3.0 chondrites suggests that they all accreted from a nebular reservoir with similar presolar grain abundances. The presence of presolar silicate grains in FGRs combined with the observation of similar estimated porosity between interstitial matrix regions and FGRs in LAP 031117 and ALHA77307, as well as the identification of a composite FGR (a small rimmed chondrule within a larger chondrule rim) in ALHA77307, all provide evidence for a formation of FGRs by accretion of dust grains onto freely-floating chondrules in the solar nebula before their aggregation into their parent body asteroids. Our study also shows systematically lower abundances of presolar silicate grains in the FGRs than in the matrix regions of CO3 chondrites, while the abundances of SiC grains are the same in all areas, within errors. This trend differs from CR2 chondrites in which the presolar silicate abundances are higher in the FGRs than in the matrix, but similar to each other within 2σ errors. This observation combined with the identification of localized (micrometer-scaled) aqueous alteration in a FGR of LAP 031117 suggests that the lower abundance of presolar silicates in FGRs reflects pre-accretionary aqueous alteration of the fine-grained material in the FGRs. This pre-accretionary alteration could be due to either hydration and heating of freely floating rimmed chondrules in icy regions of the solar nebula or melted water ice associated with 26Al-related heating inside precursor planetesimals, followed by aggregation of FGRs into the CO chondrite parent-body.

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.

Diagenetic and compositional controls of wettability in siliceous sedimentary rocks, Monterey Formation, California

Science.gov (United States)

Hill, Kristina M.