Note: This page contains sample records for the topic na2o cao k2o from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: August 15, 2014.
1

Coarsening of needle-shaped apatite crystals in SiO2 • Al2O3 • Na2OK2OCaO • P2O5 • F glass  

Microsoft Academic Search

Coarsening of needle-shaped apatite crystals was studied in a SiO2 • Al2O3 • Na2OK2OCaO • P2O5 • F glass. Crystal numbers and size distributions were measured by image analysis of electron micrographs obtained from slightly etched fractures of powder compacts sintered from differently annealed glass powders. Results indicate that the growth of apatite needles is controlled

R. Müller; L. A. Abu-Hilal; S. Reinsch; W. Höland

1999-01-01

2

Melt densities for leucogranites and granitic pegmatites: Partial molar volumes for SiO 2, Al 2O 3, Na 2O, K 2O, Li 2O, Rb 2O, Cs 2O, MgO, CaO, SrO, BaO, B 2O 3, P 2O 5, F 2O -1, TiO 2, Nb 2O 5, Ta 2O 5, and WO 3  

NASA Astrophysics Data System (ADS)

The densities and thermal expansivities of thirty-eight haplogranitic silicate melts have been experimentally determined. The compositions represent the additions of approximately 5, 10, and 20 wt% of selected oxide components Al 2O 3, Na 2O, K 2O, Li 2O, Rb 2O, Cs 2O, MgO, CaO, SrO, BaO, TiO 2, Nb 2O 5, Ta 2O 5, and WO 3 to a base melt of haplogranitic (HPG8) composition. The densities of melts have been obtained by a combination of scanning dilatometry and room temperature Archimedean density determinations together with scanning calorimetry. The thermal expansivities were obtained by a combination of scanning calorimetry and scanning dilatometry. The results of the density and expansivity determinations for the melts are fit to a multicomponent linear least squares regression of molar volume vs. molar composition. The resulting partial molar volumes of the molten oxides are reported for a reference temperature of 750°C. The multicomponent linear least squares regression yields a description of the database with a root mean squared deviation of 0.3%. The fit to these new partial molar volume data includes our previous data for B 2O 3, P 2O 5, and F 2O -1-bearing haplogranitic melts. The partial molar volumes of the oxides vary from 10.53 ± 0.29 cm 3 mole -1 for MgO to 69.09 ± 1.82 cm 3 mol -1 for P 2O 5. Compared on the basis of one oxygen per mole they range from 10.53 ± 0.29 cm 3 mol -1 (MgO) to 55.38 ± 1.69 cm 3 mol -1 (Cs 2O). The present data, taken together with an estimate of the partial molar volume of water in these melts (13.1 ± 1.3 cm 3 mol -1) are recommended to be used to calculate the low pressure densities of leucogranitic and pegmatitic melts.

Knoche, R.; Dingwell, D. B.; Webb, S. L.

1995-11-01

3

Mixed-Alkali Effect in Li2O-Na2O-K2O-B2O3 Glasses: Infrared and Optical Absorption Studies  

NASA Astrophysics Data System (ADS)

The mixed-alkali effect (MAE) has been investigated in the glass system (40 - x)Li2O- xNa2O-10K2O-50B2O3 (0 mol% ? x ? 40 mol%) through density, modulated differential scanning calorimetry (DSC), and optical absorption studies. From the absorption studies, the values of the optical band gap ( E opt) for direct transition and Urbach energy (? E) have been evaluated. The values of E opt and ? E show nonlinear behavior with the compositional parameter. The density and glass-transition temperature of the present glasses also show nonlinear variation, supporting the existence of MAE. The infrared (IR) spectra of the glasses reveal the presence of three- and four-coordinated boron atoms. The specific vibrations of Li-O, Na-O, and K-O bonds were observed in the present IR study.

Samee, M. A.; Edukondalu, A.; Ahmmad, Shaik Kareem; Taqiullah, Sair Md.; Rahman, Syed

2013-08-01

4

EPR and optical absorption by Cu2+ ions in ZnO-Li2O-Na2O-K2O-B2O3 glasses  

NASA Astrophysics Data System (ADS)

Electron Paramagnetic Resonance (EPR) studies at room temperature in the x-band frequencies on xZnO-10Li2O-10Na2O-10K2O-(69-x)B2O3-1CuO (x=0,2,4,6 and 8 mole%) glass systems were reported. The non-linear variation of spin-Hamiltonian parameters with ZnO content indicated the change in the ligand field strength around Cu2+ ions in the host glass. The ground state of Cu2+ ions in the glass is designated as dx2-y2 orbital (2B1g) while the observed symmetry around it is tetragonally distorted octahedral. The molecular orbital coefficients ?2, ?2 and ?12 are evaluated for Cu2+ doped samples. The non-linear variation in the values of parameters indicated mixed alkali effect in the glasses.

Hameed, Abdul; Ramadevudu, G.; Shareefuddin, Md.; Chary, M. Narasimha

2014-04-01

5

First Measurements of Time-Dependent Nucleation as a Function of Composition in Na2O.2CaO.3SiO2 Glasses  

NASA Technical Reports Server (NTRS)

The first measurements in any system of the composition dependence of the time-dependent nucleation rate are presented Nucleation rates of the stoichiometric crystalline phase, Na2O.2CaO.3SiO2, from quenched glasses made with different SiO2 concentrations were determined as a function of temperature and glass composition. A strong compositional dependence of the nucleation rates and a weak dependence for the induction times are observed. Using measured values of the liquidus temperatures and growth velocities as a function of glass composition, these data are shown to be consistent with predictions from the classical theory of nucleation, assuming a composition-dependent interfacial energy.

Kelton, K. F.; Narayan, K. Lakshmi

1996-01-01

6

The effects of K2O on the compositions of near-solidus melts of garnet peridotite at 3 GPa and the origin of basalts from enriched mantle  

NASA Astrophysics Data System (ADS)

Enrichment in K2O in oceanic island basalts (OIB) is correlated with high SiO2, low CaO/Al2O3, and radiogenic isotopic signatures indicative of enriched mantle sources (EM1 and EM2). These are also chemical characteristics of the petit-spot lavas, which are highly enriched in K2O (3-4 wt%) compared to other primitive oceanic basalts. We present experimentally derived liquids with varying concentrations of K2O in equilibrium with a garnet lherzolite residue at 3 GPa to test the hypothesis that the major element characteristics of EM-type basalts are related to their enrichment in K2O. SiO2 is known to increase with K2O at pressures less than 3 GPa, but it was previously unknown if this effect was significant at the high pressures associated with partial melting at the base of the lithosphere. We find that at 3 GPa for each 1 wt% increase in the K2O content of a garnet lherzolite saturated melt, SiO2 increases by ~0.5 wt% and CaO decreases by ~0.5 wt%. MgO and each decrease slightly with K2O concentration, as do Na2O and Cr2O3. The effect of K2O alone is not strong enough to account for the SiO2 and CaO signatures associated with high-K2O OIB. The SiO2, CaO, and K2O concentrations of experimentally derived partial melts presented here resemble those of petit-spot lavas, but the Al2O3 concentrations from the experimental melts are greater. Partitioning of K2O between peridotite and melt suggests that petit spots, previously considered to sample ambient asthenosphere, require a source more enriched in K2O than the MORB source.

Davis, Fred A.; Hirschmann, Marc M.

2013-10-01

7

Enhanced osteocalcin expression by osteoblast-like cells (MC3T3-E1) exposed to bioactive coating glass (SiO2-CaO-P2O5-MgO-K2O-Na2O system) ions.  

PubMed

This study tested the hypothesis that bioactive coating glass (SiO(2)-CaO-P(2)O(5)-MgO-K(2)O-Na(2)O system), used for implant coatings, enhanced the induction of collagen type 1 synthesis and in turn enhanced the expression of downstream markers alkaline phosphatase, Runx2 and osteocalcin during osteoblast differentiation. The ions from experimental bioactive glass (6P53-b) and commercial Bioglass(TM) (45S5) were added to osteoblast-like MC3T3-E1 subclone 4 cultures as a supplemented ion extract (glass conditioned medium (GCM)). Ion extracts contained significantly higher concentrations of Si and Ca (Si, 47.9+/-10.4 ppm; Ca, 69.8+/-14.0 for 45S5; Si, 33.4+/-3.8 ppm; Ca, 57.1+/-2.8 ppm for 6P53-b) compared with the control extract (Si<0.1 ppm, Ca 49.0 ppm in alpha-MEM) (ANOVA, p<0.05). Cell proliferation rate was enhanced (1.5x control) within the first 3 days after adding 45S5 and 6P53-b GCM. MC3T3-E1 subclone 4 cultures were then studied for their response to the addition of test media (GCM and control medium along with ascorbic acid (AA; 50 ppm)). Each GCM+AA treatment enhanced collagen type 1 synthesis as observed in both gene expression results (day 1, Col1alpha1, 45S5 GCM+AA: 3x control+AA; 6P53-b GCM+AA: 4x control+AA; day 5, Col1alpha2, 45S5 GCM+AA: 3.15x control+AA; 6P53-b GCM+AA: 2.35x control+AA) and in histological studies (Picrosirius stain) throughout the time course of early differentiation. Continued addition of each GCM and AA treatment led to enhanced expression of alkaline phosphatase (1.4x control+AA after 5 days, 2x control+AA after 10 days), Runx2 (2x control+AA after 7 days) and osteocalcin gene (day 3, 45S5 GCM+AA: 14x control+AA; day 5, 6P53-b GCM+AA: 19x control+AA) and protein expression (40x-70x control+AA after 6 days). These results indicated the enhanced effect of bioactive glass ions on key osteogenic markers important for the bone healing process. PMID:19497391

Varanasi, V G; Saiz, E; Loomer, P M; Ancheta, B; Uritani, N; Ho, S P; Tomsia, A P; Marshall, S J; Marshall, G W

2009-11-01

8

The Meaning of High K2O Volcanism In the U.S. Cordillera  

NASA Astrophysics Data System (ADS)

K2O contents provide a highly effective discriminant between volcanic rocks erupted in the Cascades and Basin-and Range-provinces, with Cascades volcanics having lower K2O contents at a given SiO2. To differentiate these suites, we use a K-index, where K-index = K2Oobserved - 0.12[SiO2] + 5.1 (oxides in wt. %). In the Sierra Nevada, regional K2O contents are not controlled by wall-rock assimilation. In addition, none are candidates for K-metasomatism, and none are likely to be derived by partial melting of a K-metasomatized source. As to the latter issue, even volcanic rocks with the highest K2O in the Sierra Nevada have K2O/Na2O <5, and most such ratios are <3. In contrast, K-metasomatized rocks have K2O/Na2O >5, and as high as 30-40 (Brooks and Snee (1996). Also, Sierra-wide K2O variations are not connected to indices of subduction-related mantle enrichments (such as La/Nb, Ba/Nb or Sr/P2O5), and so K2O is unconnected to regional variations in source composition. K2O contents are instead controlled by the degree of partial melting (F) in the mantle source and fractional crystallization. Putirka and Busby (2007) show that maximum K2O in the Sierra increases with increasing crust thickness, and this relationship also holds across the U.S. the Cordillera (at 39oN latitude). This relationship implies that low F magmas more easily transit thick, low-density upper crust (Putirka and Busby, 2007), which is a consequence of the fact that low F melts are enriched not just in K2O, but also in H2O, which greatly lowers magma density (Ochs and Lange, 1999). This model can explain the contrast in Cascade and Basin-and-Range K2O contents: the modern Cascades are built on the thinner crust of accreted terranes, while typical Basin-and-Range volcanics are erupted on older, and thicker, cratonized crust. Mean crust density, however, cannot be the only explanation of high K2O. In the central Sierra Nevada, the Colorado River Extensional Corridor, and at the Lunar Crater/Nevada Test site area of NV, eruptions of high K2O magmas (K-index>1.65) coincide in time and space with episodes of high extensional strain, as determined by field relationships. One possible explanation for this coincidence is provided by Takada (1994), who shows that under conditions of high differential stress, small, deep-seated dikes are less likely to coalesce; small degree partial melts contained in such are thus more likely to erupt. In summary, we conclude that mean crust density and differential stress are the two most important controls on K2O. The southern Sierra Nevada provides a good example; there, a very thick low-density granitoid batholith generally prohibits the eruption of basaltic magmas, unless the lithosphere experiences a high differential stress state, at which point small amounts of low density, low F melts are able to erupt. Pulses of high K-index volcanism are thus not monitors of discrete delamination events, but are indicators of extensional strain. In the Sierra Nevada, these pulses occur at 10-9 Ma and 3-3.5 Ma, perhaps signaling episodes of range uplift.

Putirka, K. D.; Busby, C.

2010-12-01

9

Thermodynamic behavior of Na2O-B2O3 melt  

NASA Astrophysics Data System (ADS)

The activity of Na2O in a Na2O-B2O3 melt was measured at 1373 K by a chemical equilibration technique to understand the thermodynamic behavior of this slag system. Also, the activity coefficient of Na in Ag was preliminarily measured as fundamental thermodynamic data, to estimate the activity of Na2O in the slag. Sodium in the silver melt, within the present concentration range, exhibits the Henrian behavior, and the Henrian activity coefficient of Na in Ag (? 0 Na) is estimated to be 37.5 at 1373 K, indicating a positive deviation from ideality. The activity of Na2O in the slag varies from 1.86×10-6 to 4.99×10-4 when its content is increased from 11.0 to 64.9 mol pct; this indicates a significant negative deviation from ideality. The excess stability does not exhibit any pronounced peak, despite being drastically changed at specific slag compositions. Comparing the molar Gibbs free energy of mixing in various binary slags, Na2O was considered to be more basic than BaO (CaO) was, followed next by MgO; also, P2O5 would be significantly more acidic than SiO2 would be, followed next by B2O3. Comparing the heats of formation of solid compounds in binary slags, the larger the differences in the electronegativity values between slag components, the more the relative ionic characters of the melts seemed to be.

Park, Joo Hyun; Min, Dong Joon

2001-04-01

10

Fluorescence and Judd–Ofelt analysis of Nd 3+ doped P 2O 5–Na 2O–K 2O glass  

Microsoft Academic Search

Sodium potassium phosphate glass consisting different Nd2O3 concentrations have been prepared to study the effect of Nd3+ concentration on optical absorption and fluorescence properties. From the absorption spectra, Racah (E1, E2, E3), spin-orbit (?4f) and configuration interaction (?) parameters are calculated and reported for all the Nd3+ doped glasses. Judd–Ofelt intensity parameters (?2, ?4, ?6) are evaluated and these parameters

G. N. Hemantha Kumar; J. L. Rao; K. Ravindra Prasad; Y. C. Ratnakaram

2009-01-01

11

Distribution of anomalously high K2O volcanic rocks in Arizona: metasomatism at the Picacho Peak detachment fault.  

USGS Publications Warehouse

Metasomatized Tertiary lavas with anomalously high K2O and lower Na2O content are distributed within the NW-trending extensional terrain of SW Arizona. These rocks are common near core-complex-related detachment faults at Picacho Peak and the Harcuvar Mountains and in listric-faulted terrain at the Vulture Mountains. These rocks are also enriched in Zr but depleted in MgO. Fine-grained, euhedral orthoclase (adularia) is the dominant K-mineral; other secondary introduced minerals are quartz and calcite. Spatial association of metasomatism with the detachment faults suggests that detachment provided a conduit for hydrothermal fluids that altered the initial chemistry of the Tertiary volcanics and charged the upper plate rocks with mineralizing fluids that carried Zr and Ba, along with Au, Ag and Cu during detachment 17-18 m.y. ago.-L.C.H.

Brooks, W. E.

1986-01-01

12

Mixed alkali effect in quaternary K 2O-Li 2O-BaO-B 2O 3 glasses containing V 2O 5  

NASA Astrophysics Data System (ADS)

DC conductivity and density measurements have been carried out for xK 2O-( 25-x)Li 2O-10BaO-20V 2O 5-45B 2O 3 glasses and compared with K 2O-Li 2O-Fe 2O 3-B 2O 3 and K 2O-Na 2O-Fe 2O 3-P 2O 5 glasses. The results showed a pronounced mixed alkali effect (MAE) although polaronic conduction was observed in these glasses. There is a deviation from linearity in ln ?-1/T plots at a certain temperature ( Td) at which the transition from polaronic to ionic conduction occurs. The derivative ?T/?X(X=O/(KOO)) shows a dramatic change at nearly equal concentrations of alkali oxides and can be taken as a characteristic feature of MAE in these glasses. The type and concentration of both the transition metal and alkali ions as well as the host glass matrix govern how the relative mobilities of alkali ions and polarons suppress one another. Both density and molar volume change linearly with composition in opposite directions.

Mansour, E.

2005-05-01

13

Effects of Na2O on the Thermal Shock Resistance of Aluminosilicate Refractory Ceramics  

Microsoft Academic Search

This report presents the results of an experimental study of the effects of Na2O on the thermal shock resistance (number of cold shock cycles to failure) of aluminosilicate refractory ceramics. The addition of 4–6% mole is shown to improve the thermal shock resistance, which is characterized by the number of shock cycles to failure. The Na2O changes the viscosity-temperature characteristics,

W. O. Soboyejo; E. T. Akpan; I. B. Bashir; J. Zimba; N. Hosannah; S. Allameh

2007-01-01

14

Structure of Na2O·MO·SiO2·CaF2 (M=Mg, Ca) oxyfluoride glasses  

NASA Astrophysics Data System (ADS)

(9-x)CaO·xMgO·15Na2O·60SiO2·16CaF2(x=0, 2, 4, 6, and 9) oxyfluoride glasses were prepared. Utilizing the Raman scattering technique together with 29Si and 19F MAS NMR, the effect of alkaline metal oxides on the Q species of glass was characterized. Raman results show that as magnesia is added at the expense of calcium oxide, the disproportional reaction Q3?Q4+Q2 (Qn is a SiO4 tetrahedron with n bridging oxygens) prompted due to the high ionic field strength of magnesia, magnesium oxide entered into the silicate network as tetrahedral MgO4, and removed other modifying ions for charge compensation. This reaction was confirmed by 29Si MAS NMR. 19F MAS NMR results show that fluorine exists in the form of mixed calcium sodium fluoride species in all glasses and no Si-F bonds were formed. As CaO is gradually replaced by MgO (x=6, 9), a proportion of the magnesium ions combines with fluorine to form the MgF+ species. Meanwhile, some part of Na+ ions complex F- in the form of F-Na(6).

Cheng, Jin-shu; Deng, Wei; Wang, Mi-tang

2012-07-01

15

In vitro evaluation of bioactivity of CaO-SiO 2-P 2O 5-Na 2O-Fe 2O 3 glasses  

NASA Astrophysics Data System (ADS)

Glasses with compositions 41CaO(52 - x)SiO 24P 2O 5· xFe 2O 33Na 2O (2 ? x ? 10 mol.%) were prepared by melt quenching method. Bioactivity of the different glass compositions was studied in vitro by treating them with simulated body fluid (SBF). The glasses treated for various time periods in SBF were evaluated by examining apatite formation on their surface using grazing incidence X-ray diffraction, Fourier transform infrared reflection spectroscopy, scanning electron microscopy and energy dispersive spectroscopy techniques. Increase in bioactivity with increasing iron oxide content was observed. The results have been used to understand the evolution of the apatite surface layer as a function of immersion time in SBF and glass composition.

Singh, Rajendra Kumar; Kothiyal, G. P.; Srinivasan, A.

2009-05-01

16

Solute Distribution in the Na2o-B2O3-Nacl System. Iv. Polyborate Structures and Equilibria.  

National Technical Information Service (NTIS)

Analysis of the conjugate liquid phases in the immiscibility region of the Na2O-B2O3-NaCl system at 830C reveals discontinuities in the trends of solubility of each phase in the other. The discontinuities occur when the proportions of Na2O and B2O3 in the...

M. H. Rowell

1967-01-01

17

Determination of Na 2O from sodium aluminate NaAlO 2  

Microsoft Academic Search

The aim of the work was to find a suitable method and conditions for determining Na2O wt.% from NaAlO2. Problems were encountered while titrating NaAlO2 with hydrochloric acid. The problematic area was the pH range 4–10 where aluminum precipitates as hydroxides. The different species of the aluminate solution were determined using potentiometric and complexometric titrations. The equivalent point of the

Teemu Näykki; Anttila Raimo; Perämäki Paavo; Kurikka Antero; Nikula Päivi

2000-01-01

18

Na 2O solubility in CaO–MgO–SiO 2 melts  

Microsoft Academic Search

The sodium solubility in silicate melts in the CaO–MgO–SiO2 (CMS) system at 1400°C has been measured by using a closed thermochemical reactor designed to control alkali metal activity. In this reactor, Na(g) evaporation from a Na2O–xSiO2 melt imposes an alkali metal vapor pressure in equilibrium with the molten silicate samples. Because of equilibrium conditions in the reactor, the activity of

R. Mathieu; G. Libourel; E. Deloule; L. Tissandier; C. Rapin; R. Podor

2011-01-01

19

Flower-like Na2O nanotip synthesis via femtosecond laser ablation of glass  

PubMed Central

The current state-of-the-art in nanotip synthesis relies on techniques that utilize elaborate precursor chemicals, catalysts, or vacuum conditions, and any combination thereof. To realize their ultimate potential, synthesized nanotips require simpler fabrication techniques that allow for control over their final nano-morphology. We present a unique, dry, catalyst-free, and ambient condition method for creating densely clustered, flower-like, sodium oxide (Na2O) nanotips with controllable tip widths. Femtosecond laser ablation of a soda-lime glass substrate at a megahertz repetition rate, with nitrogen flow, was employed to generate nanotips with base and head widths as small as 100 and 20?nm respectively, and lengths as long as 10??m. Control of the nanotip widths was demonstrated via laser dwell time with longer dwell times producing denser clusters of thinner nanotips. Energy dispersive X-ray analysis reveals that nanotip composition is Na2O. A new formation mechanism is proposed, involving an electrostatic effect between ionized nitrogen and polar Na2O. The synthesized nanotips may potentially be used in antibacterial and hydrogen storage applications.

2012-01-01

20

Pyrolysis of Waste Polystyrene to Recover Styrene over Alkaline Mesoporous Molecular Sieve K2O-BaO\\/MCM-41  

Microsoft Academic Search

Mesoporous molecular sieve BaO\\/MCM-41 catalyst was synthesized under hydrothermal conditions and K2O-BaO\\/MCM-41 molecular sieve was prepared by impregnating BaO\\/MCM-41 with KNO3. The obtained K2O-BaO\\/ MCM-41 was used in catalytic pyrolysis of polystyrene(PS). The effects of catalyst kind, content of K2O, reaction temperature, pressure and time on pyrolysis results of PS were examined. The results showed that K2O-BaO\\/MCM-41 had better catalytic

Li Jianfeng; Liu Fusheng; Yu Shitao; Ge Xiaoping; Zhai Xin

2010-01-01

21

Raman spectroscopy of glasses and melts of the Na2O-GeO2 system  

NASA Astrophysics Data System (ADS)

Glasses and melts of the system X mol % Na2O · GeO2 ( X = 0, 10, 20, 30) are investigated using high-temperature Raman spectroscopy. Addition of an oxide modifier is shown to bring about an increase in the coordination number of central germanium atoms along with the depolarization of the three-dimensional GeO2 network. The glass-melt transition in germanate systems with a low oxide-modifier content is accompanied by the transition of six-coordinated germanium atoms into four-coordinated (with oxygen) ones and a simultaneous formation of nonbridge oxygen atoms.

Ivanova, T. N.; Bykov, V. N.

2010-08-01

22

Compositional and microstructural design of highly bioactive P2O5-Na2O-CaO-SiO2 glass-ceramics.  

PubMed

Bioactive glasses having chemical compositions between 1Na(2)O-2CaO-3SiO(2) (1N2C3S) and 1.5Na(2)O-1.5CaO-3SiO(2) (1N1C2S) containing 0, 4 and 6 wt.% P(2)O(5) were crystallized through two stage thermal treatments. By carefully controlling these treatments we separately studied the effects on the mechanical properties of two important microstructural features not studied before, crystallized volume fraction and crystal size. Fracture strength, elastic modulus and indentation fracture toughness were measured as a function of crystallized volume fraction for a constant crystal size. Glass-ceramics with a crystalline volume fraction between 34% and 60% exhibited a three-fold improvement in fracture strength and an increase of 40% in indentation fracture toughness compared with the parent glass. For the optimal crystalline concentration (34% and 60%) these mechanical properties were then measured for different grain sizes, from 5 to 21 ?m. The glass-ceramic with the highest fracture strength and indentation fracture toughness was that with 34% crystallized volume fracture and 13 ?m crystals. Compared with the parent glass, the average fracture strength of this glass-ceramic was increased from 80 to 210 MPa, and the fracture toughness from 0.60 to 0.95 MPa.m(1/2). The increase in indentation fracture toughness was analyzed using different theoretical models, which demonstrated that it is due to crack deflection. Fortunately, the elastic modulus E increased only slightly; from 60 to 70 GPa (the elastic modulus of biomaterials should be as close as possible to that of cortical bone). In summary, the flexural strength of our best material (215 MPa) is significantly greater than that of cortical bone and comparable with that of apatite-wollastonite (A/W) bioglass ceramics, with the advantage that it shows a much lower elastic modulus. These results thus provide a relevant guide for the design of bioactive glass-ceramics with improved microstructure. PMID:22032913

Peitl, Oscar; Zanotto, Edgar D; Serbena, Francisco C; Hench, Larry L

2012-01-01

23

Thermal and elastic characterization of Sb2O3-Na2O-ZnO glasses  

NASA Astrophysics Data System (ADS)

New glasses were investigated in the ternary system Sb2O3-Na2O-ZnO. The glass transition temperature, Tg, and the onset of the crystallization Tx range from 278 to 304 °C and from 370 to 450 °C, respectively. The thermal stability factor (Tx-Tg) lies between 109 and 155 °C. Ultrasonic velocities were measured by using the pulse echo method to determine the elastic parameters (E, G, K and L) and other related parameters (Poisson's ratio, acoustic impedance and Debye temperature). Other physical properties were also measured, such as density and microhardness. The different measured properties are analyzed in the light of the structural role of ZnO in these glasses.

Hamzaoui, M.; Azri, S.; Soltani, M. T.; Lebullenger, R.; Poulain, M.

2013-11-01

24

Determination of Na(2)O from sodium aluminate NaAlO(2).  

PubMed

The aim of the work was to find a suitable method and conditions for determining Na(2)O wt.% from NaAlO(2). Problems were encountered while titrating NaAlO(2) with hydrochloric acid. The problematic area was the pH range 4-10 where aluminum precipitates as hydroxides. The different species of the aluminate solution were determined using potentiometric and complexometric titrations. The equivalent point of the potentiometric titration was detected using Gran's plotting method. Precipitation of aluminum hydroxides did not interfere with titrations, because in potentiometric titrations the pH value was over 10 and in complexometric titrations the pH was 4. The results were accurate and determinations were easy to carry out. Sodium was also determined by DCP-AES. PMID:18968035

Näykki, T; Raimo, A; Paavo, P; Antero, K; Päivi, N

2000-07-31

25

Evaluation of CaO-SiO2-P2O5-Na2O-Fe2O3 bioglass-ceramics for hyperthermia application.  

PubMed

Magnetic bioglass ceramics (MBC) are being considered for use as thermoseeds in hyperthermia treatment of cancer. While the bioactivity in MBCs is attributed to the formation of the bone minerals such as crystalline apatite, wollastonite, etc. in a physiological environment, the magnetic property arises from the magnetite [Fe3O4] present in these implant materials. A new set of bioglasses with compositions 41CaO x (52-x)SiO2 x 4P2O5 x xFe2O3 x 3Na2O (2 < or = x < or = 10 mol% Fe2O3) have been prepared by melt quenching method. The as-quenched glasses were then heat treated at 1050 degrees C for 3 h to obtain the glass-ceramics. The structure and microstructure of the samples were characterized using X-ray diffraction and microscopy techniques. X-ray diffraction data revealed the presence of magnetite in the heat treated samples with x > or = 2 mol% Fe2O3. Room temperature magnetic property of the heat treated samples was investigated using a Vibrating Sample Magnetometer. Field scans up to 20 kOe revealed that the glass ceramic samples had a high saturation magnetization and low coercivity. Room temperature hysteresis cycles were also recorded at 500 Oe to ascertain the magnetic properties at clinically amenable field strengths. The area under the magnetic hysteresis loop is a measure of the heat generated by the MBC. The coercivity of the samples is another important factor for hyperthermia applications. The area under the loop increases with an increase in Fe2O3 molar concentration and the. coercivity decreases with an increase in Fe2O3 molar concentration The evolution of magnetic properties in these MBCs as a function of Fe2O3 molar concentration is discussed and correlated with the amount of magnetite present in them. PMID:18560766

Singh, Rajendra Kumar; Srinivasan, A; Kothiyal, G P

2009-12-01

26

Infrared studies of na 2O-B 2O 3-SiO 2 and al 2O 3-Na 2O-B 2O 3-SiO 2 glasses  

NASA Astrophysics Data System (ADS)

Infrared spectra of Na 2O-B 2O 3-SiO 2 and Al 2O 3-Na 2O-B 2O 3-SiO 2 glasses (with intermediate SiO 2 contents) have been analyzed to calculate the fraction N 4 of four coordinated borons. A reasonable agreement between the N 4 values calculated from IR spectra and those determined from NMR spectroscopy (or using literature models) could be attained under certain condition. It has been proposed that the absorption bands in the region 1000-1120 cm -1 arise from contributions of SiO 2 and B 2O 3 vibrations. The contribution of an oxide is proportional to its concentration. Heat treatment of Na 2O-B 2O 3-SiO 2 glasses does not change the value of N 4 and this indicates that the structure of alkali borate phase is the same in the glass obtained from melt and in the heat-treated one.

El-Egili, K.

2003-01-01

27

Effect of Na2O on the Reduction of Fe2O3 Compacts with CO/CO2  

NASA Astrophysics Data System (ADS)

Compacts of Fe2O3 and Fe2O3 doped with varying amounts of Na2O were isothermally reduced at several temperatures, using CO/CO2 mixed gas in a vertical resistance furnace. To determine the effect of Na2O on the reduction of Fe2O3 compacts, the mass loss due to oxygen removal was continuously recorded, from which the reduction rate and rate constant were obtained. Na2O was found to retard the reduction of Fe2O3 compacts. The apparent activation energy ( E a) of reaction and the mathematical relationship for pore gas diffusion suggested that the reduction behavior at the initial stages was controlled by a combination of pore gas diffusion and interfacial chemical reaction. At the intermediate and late stages of reduction, pore gas diffusion was the sole contributing factor. Morphological examination of the reduced compacts showed the formation of a liquid phase during the reduction process, which appeared to lower the rate of reaction.

Pan, Wen; Ma, Ze Jun; Zhao, Zhi Xing; Kim, Wan Ho; Min, Dong Joon

2012-12-01

28

FTIR and Raman spectra of the Na 2O–CuO–Bi 2O 3–P 2O 5 glasses  

Microsoft Academic Search

The structure and properties were investigated for (50?y)Na2O–yCuO–10Bi2O3–40P2O5 (0?y?25 mol%) glasses. Substitution of Bi2O3 for Na2O in the binary 60Na2O–40P2O5 glass decreases the molar volume (?Vm=2.97 cm3\\/mol) and increases further the glass transition temperature (?Tg=52 °C). FTIR and Raman spectra reveal the formation of P?O?Bi and P?O?Cu bonds in these glasses and indicate that Bi2O3 behaves as a network former

A Chahine; M Et-tabirou; J. L Pascal

2004-01-01

29

Non-Potassic Melts In CMAS-CO2-H2O-K2O Model Peridotite  

NASA Astrophysics Data System (ADS)

Volatile mediated model systems have been fundamental in shaping our knowledge about the way we view melting phase relations of peridotite at various depths in the Earth. Volatiles not only affect the melting temperatures, but the resulting liquids are, in some case, dramatically different than those witnessed in melting of dry peridotite. For example, the influence of CO2 and H2O on the melting phase relations of model peridotite shows a remarkable decrease in the solidus temperatures when compared to the dry peridotite (Gudfinnsson and Presnall, 2005). These model systems illustrate a gradational change above the solidus from carbonatites to kimberlites over several hundreds of degrees. Group-II kimberlites are ultrapotassic rocks with high water content where the mineral phlogopite is abundant. To get a better understanding of the melting phase relations related to carbonatitic and kimberlitic magmas, K2O was added to the system CMAS-CO2-H2O. In these systems, fluid and melt can co-exist in P-T space. However, from past studies, it is also known that in hydrous systems, both the fluid and melt will become indistinguishable from one another creating a singularity (second critical endpoint). Starting from the solidus located in six components (Keshav and Gudfinnsson, AGU abstract, 2009), with seven phases, melting phase relations in CMAS-CO2-H2O-K2O involving, fo-opx-cpx-garnet-carbonate-melt-fluid, are divariant. Fluid was recognized with the observation of large cavities seen in exposed capsules. Moreover, the presence of bright, needle-like grains found in large cavities in backscattered images implies the presence of solute in the fluid phase. Significantly, liquids on this divariant region have about 1000 ppm K2O, and so is the case with accompanying cpx. Hence, with this non-interesting amount of K2O in the mentioned phases, fluid must have all the potassium. At 30 kbar/1100C, with fo-opx-cpx-garnet-carbonate-phlogopite-melt-fluid, the melting phase relations become isobarically invariant. In contrast, the solidus in CMAS-CO2-H2O at 30 kbar is at 1000C. Above 1100C, phlogopite is no longer in equilibrium with the phase assemblage. In all the experimental charges, capsules were pierced, and a hydrous solution was seen escaping. When tested with litmus paper, in all cases at 25-50 kbar, this solution was determined to be highly basic (pH>10). Upon evaporation of the hydrous solution, a white precipitate was left behind around the piercing on the capsule wall. In CMAS-CO2-H2O, the fluid was found to be almost neutral (pH 7-8). The melt present in our experiments is carbonatitic in nature and does not contain any significant amounts of K2O. This contradicts a recent study on K2O in a natural composition (Foley et al, 2009) where carbonatitic melt had up to 13 wt% of K2O. Significantly, since K2O is perhaps all in the fluid, source regions for potassic magmas in the Earth’s mantle could not be created by metasomatism of alkali-rich, carbonatitic melts.

Buisman, I.; Walter, M. J.; Keshav, S.

2009-12-01

30

Ultrasonic studies on network structure of ternary TeO 2-WO 3-K 2O glass system  

NASA Astrophysics Data System (ADS)

Longitudinal and shear ultrasonic velocities were measured in different compositions of the glass system (TeO 2) 80-(WO 3) (20- x) -(K 2O) x using pulse echo technique. Measurements were carried out at 6 MHz frequency and at room temperature. Elastic moduli and some other physical parameters such as, glass transition temperature, Debye temperature, softening temperature, and fugacity have been calculated. Results indicated that these parameters depend upon the alkali oxide modifier (K 2O) content i.e., glass composition. Quantitative analysis has been carried out, in order to obtain more informations about the structure of these glasses, based on bond compression model, and ring deformation model, i.e., the cation-anion bond of each oxide.

Sidkey, M. A.; Gaafar, M. S.

2004-05-01

31

Synthesis and structural characterization of P 2O 5–CaO–Na 2O sol–gel materials  

Microsoft Academic Search

Ternary phosphate-based glasses in the system P2O5–CaO–Na2O were synthesized using the sol–gel approach. Glasses in this system have the potential for use as bioactive materials. A mixture of mono- and dialkyl phosphate PO(OH)3?x(OC2H5)x (x=1,2) and alkoxides of sodium and calcium in an ethylene glycol solution were used as precursors. One of the compositions has also been synthesized by sonocatalysis (application

Daniela Carta; Jonathan C. Knowles; Mark E. Smith; Robert J. Newport

2007-01-01

32

Lateral variation of H2O/K2O ratios in Quaternary Magma of the Northeastern Japan arc  

NASA Astrophysics Data System (ADS)

Water plays a fundamental role in the magma genesis beneath subduction zones. In order to estimate a spatial distribution of the density of water flux in the wedge mantle of the Northeastern Japan arc, this study examines a lateral variation of pre-eruptive bulk rock H2O/K2O contents among volcanoes located both in the frontal and in back arc settings. The analytical targets are the frontal volcanoes Nigorikawa (N42.12 E140.45), Zenikame (N41.74 E140.85), Adachi (N38.22 E140.65), and Nanashigure (N40.07 E141.11), and the back arc ones Hijiori (N38.61 E140.17) and Kanpu (N39.93 E139.88). The bulk magmatic H2O content (TH2O) is calculated from a mass balance of hydrogen isotopic ratios among three phases in a batch of magma; dissolved water in melt, excess H2O vapor, and hydrous phenocrysts such as amphiboles (Miyagi and Matsubaya, 2003). Since the amount of H2O in hydrous phenocryst is negligible, the bulk magmatic H2O content can be written as TH2O = (30 XD CD) / (15 - dT + dMW), where dMW is the measured hydrogen isotopic ratio of hydrous phenocrysts, XD is a melt fraction of magma, CD is a water concentration of the melt, and dT is hydrogen isotopic ratios of a bulk magma (assumed to be -50 per-mil). Both XD and CD are estimated from bulk rock chemistry of the sample using the MELTS program (Ghiorso and Sack, 1995). Hydrogen isotopic fractionation factors are assumed to be -15 and -30 per-mil for vapor and hydrous mineral, and vapor and silicate melt, respectively. There observed a clear difference among the H2O/K2O ratios of bulk magmas from the frontal and back arc volcanoes. For instance higher H2O/K2O wt ratios was observed in the frontal volcanoes (Nigorikawa 5.3, Zenikame 11-12, Adachi 8-10, and Nanashigure 4-18), while lower H2O/K2O wt ratios was observed in the back arc ones (Kanpu 0-2.5 and Hijiori 1.4). The lateral variation of H2O/K2O ratios infer the higher water flux through the frontal side of wedge mantle, which can be a potential cause of the larger quantity of volcanic products along the frontal side of the NE Japan arc. This research project has been conducted under the research contract with Nuclear and Industrial Safety Agency (NISA). I thank Drs. H. Kawaraya, D. Ishiyama, and O. Matsubaya at Akita univ. for their help in the analysis of hydrogen isotopic ratios.

Miyagi, I.

2012-12-01

33

Optical Properties on Li2O-K2O-WO3-B2O3 Glass System  

NASA Astrophysics Data System (ADS)

Mixed alkali tungsten borate glasses xLi2O-(30-x) K2O-10WO3-60B2O3 (0 < x < 30) were prepared from the melts. These glasses were characterized using X-ray diffraction, differential scanning calorimetry and density measurements. Optical absorption studies were carried out as a function of alkali content to look for mixed alkali effect (MAE) on the spectral properties of these glasses. From the study of ultraviolet absorption edge, the optical band gap energies and Urbach energies were evaluated. The average electronic polarizability of the oxide ion, optical basicity and the interaction parameters were also evaluated for all the glasses. Many of these parameters vary non-linearly exhibiting a minima or maxima with increasing alkali concentration, indicating the mixed alkali effect. An attempt is made to interpret MAE in this glass system in terms of its glass structure.

Edukondalu, A.; Samee, M. A.; Ahmmad, Shaikh Kareem; Taqiullah, Sair Md.; Rahman, Syed; Siva Kumar, K.

34

Metamorphic evolution of eclogites at Qinglongshan: modeling in system Na2O-CaO-K2O-FeO-MgO-Al2O3-SiO2-H2O-TiO2-Fe2O3  

NASA Astrophysics Data System (ADS)

Eclogite at Qinglongshan in NE Jiangsu province is one of the research objects which are investigated frequently and products are remarkable in ultra-high pressure (UHP) metamorphic petrology and geochemistry nearly twenty years. Though scholars in China and abroad have made abundant petrological work, there are opposite perspectives to some important petrological questions such as peak assemblage, crystalization time and condition of epidote porphyroblasts which contain coesite, peak assemblage contains talc or not, lawsonite has occurred in the rock or not. This paper choose eclogites in Qinglongshan. Besides traditional petrological work, we applied phase diagram modeling to mineral assemblage and chemical composition, quantitatively investigating the change with temperature and pressure. With the help of petrographic observation the petrological questiones can be solved. Eclogites in Qinglongshan can be divided into three categories: porphyroblastic foliated eclogites, granular massive eclogites and banded eclogites. The peak assemblage in three kinds of eclogites is garnet + omphacite + phengite + kyanite +rutile + coesite. The minerals in the peak assemblage show shape preferred orientation defining the rock foliation in porphyroblastic eclogites. The peak assemblage defined by garnet compositional isopleths in the calculated phase diagram is garnet +omphacite + phengite + kyanite + rutile + coesite + lawsonite + talc in porphyroblastic eclogites, and is garnet + omphacite + phengite + kyanite + rutile +coesite + lawsonite in banded eclogites, both inconsistent with the petrographic observation. This discrepancy probably resulted from the assumption of pure water as the ultrahigh-pressure (UHP) fluid phase. Three stages of metamorphism are established for Qinglongshan eclogites. Prograde inclusions such as amphibole, epidote, plagioclase, chlorite, muscovite, paragonite and albite coexist in the area of < 0.8GPa and < 575. It can infer from mineral assemblage that peak temperature and pressure are higher than 710 and 2.9GPa in porphyroblastic eclogites and >620 and 2.9GPa in banded eclogites. Both petrography and phase diagram modelling demonstrate a crystallization sequence of kyanite-epidote-talc, with the first two having begun to crystallize at UHP condition and hence including coesite. The mode of epidote increases dramatically at < 2 GPa resulting in the formation of large porphyroblasts. The randomly oriented porphyroblasts overprint the rock foliation, implying that they crystallized later than the peak assemblage under a weak shear stress field. Kyanite begun to crystallize at early retrogression in banded eclogites. Epidote begun to develop at low pressure, so there is no coesite in banded eclogites. Symplectite is the product of late retrograde metamorphism. The P-T paths of porphyroblastic eclogites and banded eclogites defined by the mineral assemblages are both typically the hair-pin type. The amounts of hydrous minerals increased during retrogression, implying continuous ingress of fluids into the rock.

Yan, R.; Yang, J.; Zhang, Z.

2011-12-01

35

Temperature programmed reduction studies on phase reconstruction of Na 2 O?MnO x -catalysts for the oxidative dehydrodimerization of methane  

Microsoft Academic Search

The change in phase composition and integral oxidation state of Na2O?MnOx-catalysts caused by simultaneous air and methane interaction was studied using Temperature Programmed Reduction. Sodium manganates (III, IV) continue to exist during catalytic reaction whereas sodium manganate (V) decomposes.

Dorit Wolf; Gerhard Wendt

1991-01-01

36

Phosphate capacity of CaO-AI2O3 slags containing CaF2, BaO, Li2O, or Na2O  

NASA Astrophysics Data System (ADS)

Phosphorus partition ratios between CaO-Al2O3 and CaO-Al2O3-CaF2 fluxes and Fe-Csat-P alloys have been measured as a function of slag composition at 1500 °C. The effects of additions of BaO, Li2O, and Na2O to the CaO-Al2O3-CaF2 system on the phosphorus partition ratios at 1400 °C and 1300 °C have been measured. From the partition ratio, and assuming that the oxygen potential is controlled by C-CO equilibrium, the phosphate capacities of the fluxes were calculated. Also, the activities of Li2O and Na2O were measured as a function of slag composition at 1300 °C by equilibrating the flux and the metal with Pb-Li or Pb-Na alloy and CO in a graphite crucible. The results indicate that phosphorus partition ratios with carbon-saturated iron and the phosphate capacities for additions of more basic oxides decrease in the following order: Na2O?;Li2O?;BaO. The activities of Li2O and Na2O in calcium aluminate fluxes have large negative deviations from ideal behavior; the activity coefficients at infinite dilution are on the order of 0.05 and 10-5, respectively.

Nassaralla, C.; Fruehan, R. J.

1992-03-01

37

Self induced gratings in ternary SiO2:SnO2:Na2O bulk glasses by UV light seeding  

NASA Astrophysics Data System (ADS)

The diffraction efficiency of gratings written in ternary SnO2:SiO2:Na2O bulk glasses rises dramatically with time after the occultation of the cw 244nm light used to write the thick hologram. This self-induced behavior lasts for several hours and ultimately leads to refractive index changes as high as 3 10-3.

Lancry, M.; Douay, M.; Niay, P.; Beclin, F.; Menke, Y.; Milanese, D.; Ferraris, M.; Poumellec, B.

2005-09-01

38

Phase equilibria in the oxide system Nd 2O 3-K 2O-P 2O 5  

NASA Astrophysics Data System (ADS)

A phase equilibria diagram of the partial system NdPO 4-K 3PO 4-KPO 3 has been developed as part of the research aimed at determining the phase equilibrium relationships in the oxide system Nd 2O 3-K 2O-P 2O 5. The investigations were conducted using thermoanalytical techniques, X-ray powder diffraction analysis and reflected-light microscopy. Three isopleths existing between: K 3Nd(PO 4) 2-K 4P 2O 7, NdPO 4-K 5P 3O 10 and NdPO 4-K 4P 2O 7 have been identified in the partial NdPO 4-K 3PO 4-KPO 3 system. Previously unknown potassium-neodymium phosphate "K 4Nd 2P 4O 15" has been discovered in the latter isopleth section. This phosphate exists in the solid phase up to a temperature of 890 °C at which it decomposes into the parent phosphates NdPO 4 and K 4P 2O 7. Four invariant points: two quasi-ternary eutectics, E 1 (1057 °C) and E 2 (580 °C) and two quasi-ternary peritectics, P 1 (1078 °C) and P 2 (610 °C), occur in the NdPO 4-K 3PO 4-KPO 3 region.

Szczygie?, Irena; Znamierowska, Teresa; Mizer, Dagmara

2010-07-01

39

Electrosynthesis, structural transitions and characterization of the new 10H-Ba 5Ru 3Na 2O 14  

NASA Astrophysics Data System (ADS)

The electrosynthesis in molten NaOH was successfully used in the Ba?Ru?Na?O system, leading to the preparation of the new Ba 5Ru 3Na 2O 14 oxide. This compound contains both isolated Ru 6+ and dimers of Ru 5+ cations. Because of anions deficient layers and vacancies ordering versus the temperature, the crystal structure was refined at three strategic temperatures from single crystal data. It adopts a 10H-perovskite related structure in which the central cubic block reorganizes itself with the temperature modifying Na + and Ru 6+ environments. At 100 K, the crystal symmetry is orthorhombic (pseudo-hexagonal), a=5.845(1) Å, b=10.145(2) Å, c=24.163(5) Å, space group C222 1, R1=4.45% and wR2=9.31%. The stacking sequence is (c'chcc') 2 where c and h stand for cubic and hexagonal BaO 3 layers, respectively, and c' stands for BaO 2.5? 0.5 layers. At 298 K, a=5.8146(4) Å, b=10.2812(7) Å, c=24.173(2) Å, the space group is Cmc2 1, and the stacking sequence is (cchcc?) 2 where c? stands for cubic BaO 2?, R1=4.18% and wR2=11.08%. Two anomalies measured on ?AC versus T at 265 and 214 K, respectively, suggest that the C222 1? Cmc2 1 transition would occur at one of these two temperatures. An order/disorder transition is then observed by XRD at 723 K assorted with an orthorhombic to hexagonal symmetry increasing. The 823 K crystal structure has been refined in the P 6¯2c space group and the sequence is (c?chcc?) 2 where c? stands for cubic Ba(O 5/6? 1/6) 3, a=5.9261(8) Å, c=24.400(5) Å, R1=6.45%, wR2=13.40%. Ru 5+2O 9 dimers are likely antiferromagnetically coupled from room temperature and the strong phenomenon observed at 29 K on ?AC= f( T) is possibly related to Ru 6+?Ru 5+2O 9 indirect magnetic exchanges. It is accompanied by a brutal increase of the resistivity.

Quarez, Eric; Mentré, Olivier

2003-08-01

40

Ionic conductivity of alkaline (Li 2O, Na 2O) and alkaline-earth (BaO) borates in crystallization (vitrification) region  

NASA Astrophysics Data System (ADS)

In this paper we report the existence of abnormal behavior of electric properties of alkaline (Li 2O,Na 2O) and alkaline-earth (BaO) borate in the melt—a crystal (glass) transition region. Results of measurement of conductivity in the mentioned interval evidence the existence of a strong variation of electric properties depending on the concentration of alkaline and alkaline-earth ions. The reasons of such behavior are discussed.

Solntsev, V. P.; Davydov, A. V.

2011-11-01

41

Effect of SiO2/Na2O mole ratio on the properties of foam geopolymers fabricated from circulating fluidized bed fly ash  

NASA Astrophysics Data System (ADS)

Geopolymers are three-dimensional aluminosilicates formed in a short time at low temperature by geopolymerization. In this paper, alkali-activated foam geopolymers were fabricated from circulating fluidized bed fly ash (CFA), and the effect of SiO2/Na2O mole ratio (0.91-1.68) on their properties was studied. Geopolymerization products were characterized by mechanical testing, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). The results show that SiO2/Na2O mole ratio plays an important role in the mechanical and morphological characteristics of geopolymers. Foam samples prepared in 28 d with a SiO2/Na2O mole ratio of 1.42 exhibit the greatest compressive strength of 2.52 MPa. Morphological analysis reveals that these foam geopolymers appear the relatively optimized pore structure and distribution, which are beneficial to the structure stability. Moreover, a combination of the Si/Al atomic ratio ranging between 1.47 and 1.94 with the Na/Al atomic ratio of about 1 produces the samples with high strength.

Liu, Ze; Shao, Ning-ning; Huang, Tian-yong; Qin, Jun-feng; Wang, Dong-min; Yang, Yu

2014-06-01

42

Effect of Na2O and B2O3 on the Crystallization Behavior of Low Fluorine Mold Fluxes for Casting Medium Carbon Steels  

NASA Astrophysics Data System (ADS)

An investigation has been conducted to study the effect of Na2O and B2O3 on the crystallization behavior of low fluorine (F) mold powders for casting medium carbon (MC) steels in this article. The results of this study indicated that B2O3 tends to lower the crystallization temperature and increase crystallization incubation time of the low F powders; however, Na2O plays an opposite role compared with that of B2O3. The crystalline phase of Ca11Si4B2O22 was formed in Sample D2 [F = 3 pct, Na2O = 10 pct, B2O3 = 8 pct (in wt pct)], which exhibited the most similar crystallization behavior to that of cuspidine, such that Sample D2 showed closest crystallization kinetics to that of a conventional high-F mold slag for casting MC steels. The precipitated crystalline phases for all the samples have been analyzed and discussed in the article.

Wei, Juan; Wang, Wanlin; Zhou, Lejun; Huang, Daoyuan; Zhao, Huan; Ma, Fanjun

2014-04-01

43

Lightweight geopolymer made of highly porous siliceous materials with various Na 2O\\/Al 2O 3 and SiO 2\\/Al 2O 3 ratios  

Microsoft Academic Search

The syntheses of lightweight geopolymeric materials from highly porous siliceous materials viz. diatomaceous earth (DE) and rice husk ash (RHA) with high starting SiO2\\/Al2O3 ratios of 13.0–33.5 and Na2O\\/Al2O3 ratios of 0.66–3.0 were studied. The effects of fineness and calcination temperature of DE, concentrations of NaOH and KOH, DE to RHA ratio; curing temperature and time on the mechanical properties

K. Pimraksa; P. Chindaprasirt; A. Rungchet; K. Sagoe-Crentsil; T. Sato

2011-01-01

44

The mixed network former effect in glasses: solid state NMR and XPS structural studies of the glass system (Na2O)(x)(BPO4)(1-x).  

PubMed

The structural organization of sodium borophosphate glasses with composition (Na(2)O)(x)(BPO(4))(1-x) (0.25 ?x? 0.55) has been investigated by differential scanning calorimetry, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), as well as single- and double resonance (11)B and (31)P magic-angle spinning (MAS) NMR. (11)B MAS-NMR data indicate the dominance of anionic four-coordinated boron units, and (31)P MAS NMR reveals the successive transformation of neutral P(3) into singly charged P(2) units and their further transformation into doubly charged P(1) units at high Na(2)O contents. The quantification of these units provides detailed insight into the competition of the network formers borate and phosphate for the network modifier oxide. At low modifier content (x < 0.35), the anionic species are almost exclusively borate (B(4)) units, whereas at higher sodium concentrations, large numbers of anionic phosphate (P(2) and P(1)) species are formed. O-1s XPS data provide a quantitative distinction between B-O-B, B-O-P, and P-O-P linkages as well as non-bridging oxygen atoms, and comparable numbers can be extracted from (11)B and (31)P MAS-NMR experiments. Both XPS as well as (31)P{(11)B} and (11)B{(31)P} rotational echo double resonance (REDOR) NMR results reveal strong interactions between the two network formers boron oxide and phosphorus oxide, resulting in a preferred formation of B-O-P linkages. For higher Na(2)O contents, however, the successive network modification diminishes this preference, resulting in close-to-statistical network connectivities. Compositional trends of T(g) in the Na(2)O-B(2)O(3)-P(2)O(5) glass forming system can be correlated with the overall network connectedness, expressed by the total number of bridging oxygen atoms per network former species. However, separate linear correlations are observed for different compositional lines, indicating also the relevance of the type of network former linkages present. PMID:21380468

Rinke, Matthias T; Eckert, Hellmut

2011-04-14

45

Gamma ray irradiation effects on the optical properties of BaO–Na2O–B2O3–SiO2 glasses  

NASA Astrophysics Data System (ADS)

This paper reports the effect of gamma radiation on the optical absorption spectra of xBaO–Na2O–(70?x) B2O3–SiO2 glass system with x = 0, 5, 10, 15, 20, 25 (mol%) recorded in spectral range from 200 to 900 nm at room temperature. The optical absorption edge, optical band gap and Urbach energy were determined from the absorption spectra before and after irradiation. Changes occurring in the optical parameters of these glasses have been associated with radiation induced structural defects and compositional changes.

Kaur, Ravneet; Singh, Surinder; Pandey, O. P.

2013-09-01

46

Investigation of phase equilibria and growth of BBO (?-BaB 2O 4) crystals in BaO-B 2O 3-Na 2O ternary system  

NASA Astrophysics Data System (ADS)

The BaO-B 2O 3-Na 2O ternary system is of great importance for growing crystals of low-temperature modification of barium borate (?-BaB 2O 4). A new solid-state triangulation scheme was suggested based on the existence of NaBaBO 3 compound. Primary crystallization areas of NaBaBO 3 and two new compounds—NaBa 4(BO 3) 3 and Ba 5B 4O 11—were determined. It was shown that crystals grown from depleted sodium system BaB 2O 4-NaBaBO 3 have great advantage concerning the quality.

Fedorov, P. P.; Kokh, A. E.; Kononova, N. G.; Bekker, T. B.

2008-04-01

47

Silicate liquid immiscibility in magmas and in the system K2O-FeO-AI2O3-SiO2: an example of serendipity  

USGS Publications Warehouse

The concept of silicate liquid immiscibility was invoked early in the history of petrology to explain certain pairs of compositionally divergent rocks, but. as a result of papers by Greig (Am. J. Sci. 13, 1-44, 133-154) and Bowen (The Evolution of the Igneous Rocks), it fell into disfavor for many years. The discovery of immiscibility in geologically reasonable temperature ranges and compositions in experimental work on the system K2O-FeO-Al2O3-SiO2, and of evidence for immiscibility in a variety of lunar and terrestrial rocks, has reinstated the process. Phase equilibria in the high-silica corner of the tetrahedron representing the system K2O- FeO-Al2O3-SiO2 are presented, in the form of constant FeO sections through the tetrahedron, at 10% increments. Those sections, showing the tentative relationships of the primary phase volumes, are based on 5631 quenching runs on 519 compositions, made in metallic iron containers in pure nitrogen. Thirteen crystalline compounds are involved, of which at least six show two or more crystal modifica-tions. Two separate phase volumes, in each of which two immiscible liquids, one iron-rich and the other iron-poor, are present at the liquidus. One of these volumes is entirely within the quaternary system, astride the 1:1 K2O:Al2O3 plane. No quaternary compounds as such have been found, but evidence does point toward at least partial quaternary solid solution, with rapidly lowering liquidus temperatures, from K2O??Al2O3?? 2SiO2 ('potash nepheline', kalsilite. kaliophilite) to the isostructural compound K2O??FeO??3SiO2, and from K2O??Al2O3??4SiO2 (leucite) to the isostructural compound K2O??FeO??5SiO2, Both of these series apparently involve substitution, in tetrahedral coordination. of a ferrous iron and a silicon ion for two aluminum ions. Some of the 'impurities' found in analyses of the natural phases may reflect these substitutions. As a result of the geometry of the immiscibility volume located entirely within the quaternary system, compositions near it show a number of phase changes and large amounts of crystallization with small temperature changes, generally in the range 1100-1150 C. Similar low-temperature, high-alkali immiscibility was discovered in a few exploratory runs in the equivalent systems with Rb or Cs substituting for K. But not in those with Li or Na. A review of the compositions and general behavior of systems involving immiscibility, both stable and metastable, and of the evidence for natural immiscibility. indicates that it may be a much more common feature than generally thought. Several examples of natural immiscibility are detailed; most yield a felsic. alkali-aluminosilicate melt and a mafic melt. from a wide variety of generally basaltic parental magmas, both under- and over saturated. Unfortunately, the best line of evidence for immiscibility in terrestrial rocks, a sharply defined meniscus between two compositionally disparate glasses, is by its very nature self-destructing, since it is effectively eliminated by either crystallization or gravitative separation and coalescence into separate magmas. Verification of operation of the exosolutionor 'splitting' process on a large scale will probably require careful study of isotopic and trace element partitioning in both laboratory and field. ?? 1978.

Roedder, E.

1978-01-01

48

Effect of glass composition on the properties of Er/Yb-doped SiO2-GeO2-B2O3-Na2O glasses for active waveguide application  

NASA Astrophysics Data System (ADS)

Er/Yb-doped multicomponent SiO2-GeO2-B2O3-Na2O glasses with different GeO2, B2O3 and Na2O contents were studied. The effect of glass component on the properties of Er ions in terms of absorption cross-section, fluorescence lifetime ?m and quantum efficiency was investigated with the aim of obtaining efficient active waveguide.

Ferraris, Monica; Chen, Qiuping; Milanese, Daniel; Righini, Giancarlo C.

2003-11-01

49

Effects of Li2O and Na2O on the Crystallization Behavior of Lime-Alumina-Based Mold Flux for Casting High-Al Steels  

NASA Astrophysics Data System (ADS)

With the development of advanced high strength steel (AHSS), a large amount of aluminum was added into steels. The reaction between aluminum in the molten steel and silica based mold flux in the continuous-casting process would tend to cause a series of problems and influence the quality of slabs. To solve the above problems caused by the slag-steel reaction, nonreactive lime-alumina-based mold flux system has been proposed. In this article, the effect of Li2O and Na2O on the crystallization behavior of the lime-alumina-silica-based mold flux has been studied by using the single hot thermocouple technology (SHTT) and double hot thermocouple technology (DHTT). The results indicated that Li2O and Na2O in the above mold flux system play different roles as they behaved in traditional lime-silica based mold flux, which would tend to inhibit general mold flux crystallization by lowering the initial crystallization temperature and increasing incubation time, especially in the high-temperature region. However, when their content exceeds a critical value, the crystallization process of mold fluxes in low temperature zone would be greatly accelerated by the new phase formation of LiAlO2 and Na x Al y Si z O4 crystals, respectively. The crystalline phases precipitated in all samples during the experiments are discussed in the article.

Lu, Boxun; Chen, Kun; Wang, Wanlin; Jiang, Binbin

2014-04-01

50

YAG laser-induced structural modification in transition metal ion containing 40K 2O–40Nb 2O 5–20SiO 2 glasses  

Microsoft Academic Search

Glasses with the compositions of 40K2O–40Nb2O5–20SiO2 (in mol%) containing different concentrations (0.01, 1 and 2mol%) of NiO were prepared by a melt quenching technique. The glasses were irradiated with a continuous wave Nd:YAG laser with a wavelength of 1064nm, and a metastable crystalline phase of KNbO3 was obtained. In 2mol% NiO-doped glass, lines with a width of ?10?m are successfully

B. Harihara Venkataraman; Takayuki Komatsu

2008-01-01

51

Structural variation in gamma ray irradiated PbO-Na2O-B2O3-SiO2 glasses  

NASA Astrophysics Data System (ADS)

Glasses with compositions xPbO-15Na2O-(70-x) B2O3-15SiO2 where x=5, 10, 15, 20 and 25 (mol%) have been prepared using the melt quenching technique. The structural properties of these glasses have been investigated using the FTIR spectroscopy. The effect of the presence of modifier PbO on the glass system is also studied. The FT-IR spectral investigation of these glasses exhibits characteristic vibrations of BO4 and BO3 units together with SiO4 as well as PbOn (n=4,6) groups. The gamma ray interaction of the present glass system in the dose range 0.1-60 kGy is investigated. The results indicate that gamma rays result in the structural rearrangements in glass affecting the bridging and non bridging oxygens.

Kaur, Ravneet; Singh, Surinder; Pandey, O. P.

2014-06-01

52

Visible and far-infrared spectroscopic studies of Co-doped (80-x)Sb2O3-20Na2O-xWO3 glasses  

NASA Astrophysics Data System (ADS)

We investigate the absorption of the glasses (80-x)Sb2O3-20Na2O-xWO3 (x mol% of WO3) in the spectral regions 12?500-28?571 and 2000-7800?cm-1. The samples are doped with 0.01, 0.03 or 0.05?mol% of Co3O4 and x=30%. The observed absorption band is due to the Co impurity in the visible spectral region. This absorption band of glasses does not contain information on the exact energy position of the Co levels. Therefore, we have calculated the second derivative of absorption. It has been established that Co2+ ions are surrounded by distorted octahedral coordination in the investigated glasses. The energy level structure of the Co2+ ion in the samples is also presented. We have calculated the crystal field parameter Dq and the Racah parameters B and C.

Petkova, P.; Soltani, M. T.; Petkov, S.; Tacheva, J.; Nedkov, V.

2012-05-01

53

Upconversion and fluorescence spectral studies of Er3+/Yb3+-codoped Bi2Q3-GeO2-Ga2Q3-Na2O glasses.  

PubMed

The absorption spectra and upconversion fluorescence spectra of Er3+/Yb3+-codoped natrium-gallium-germanium-bismuth glasses are measured and investigated. The intense green (533 and 549 nm) and red (672 nm) emission bands were simultaneously observed at room temperature. The quadratic dependence of the green and red emission on excitation power indicates that the two-photon absorption processes occur. The influence of Ga2C3 on upconversion intensity is investigated. The intensity of green emissions increases slowly with increasing Ga2O3 content, while the intensity of red emission increases significantly. The possible upconversion mechanisms for these glasses have also been discussed. The maximum phonon energy of the glasses determined based on the infrared (IR) spectral analysis is as low as 740 cm-1. The studies indicate that Bi2O3-GeO2-Ga2O3-Na2O glasses may be potential materials for developing upconversion optical devices. PMID:16843049

Nie, Qiuhua; Jiang, Cheng; Wang, Xunsi; Xu, Tiefeng; Li, Haoquan

2007-02-01

54

Influence of chromium ions on dielectric and spectroscopic properties of Na2O-PbO-B2O3 glass system  

NASA Astrophysics Data System (ADS)

Na2O-PbO-B2O3 glasses doped with Cr2O3 by varying its concentration relative to borate (in the range of 0 to 0.2 mol% in steps of 0.05 mol %) are prepared. Dielectric studies (dielectric constant epsilon', loss tan ?, conductivity ?ac etc in the frequency range 103 to 106 Hz and in the temperature range 30 to 250 °C) and spectroscopic properties like IR & ESR etc. were carried out on these samples. From these studies it was noticed that chromium with Cr6+ ions exist in network forming positions at low concentration i.e., at 0.05 mol% beyond which Cr6+ ions gradually get converted into Cr3+ ions, there by act as network modifiers and decrease the rigidity of the glass network.

Brahmaiah, A.; Krishna, S. Bala Murali; Kondaiah, M.; Bala Narendra Prasad, T.; Krishna Rao, D.

2009-07-01

55

FTIR structural investigation of gamma irradiated BaO-Na2O-B2O3-SiO2 glasses  

NASA Astrophysics Data System (ADS)

Fourier transform infrared (FT-IR) spectra of xBaO-15Na2O-(70-x)B2O3-15SiO2 glass system with x=0, 5, 10, 15 and 20 (mol%) has been measured in the spectral range 400-4000 cm-1 at room temperature in order to understand the characteristic frequencies of the chemical bonds and bonding mechanisms, which are susceptible to the structural and spectral changes. The effect of gamma irradiation in the dose range 0.1 kGy-60 kGy on the infrared absorption spectra of these glasses is also reported. The change in the glass structure due to the effect of composition is also discussed. It has been observed that irradiation of the glasses with the gamma rays increases the BO3 groups and the non bridging oxygens which make the network loose.

Kaur, Ravneet; Singh, Surinder; Pandey, Om Prakash

2012-12-01

56

Gels and gel-derived glasses in the system Na2O-B2O3-SiO2  

NASA Technical Reports Server (NTRS)

The containerless melting of high-purity multicomponent homogeneous gels and gel monoliths offers a unique approach to making ultrapure multicomponent optical glasses in the reduced gravity environment of space. Procedures for preparing and characterizing gels and gel-derived glasses in the system Na2O-B2O3-SiO2 are described. Preparation is based on the polymerization reactions of alkoxysilane with trimethyl borate or boric acid and a suitable sodium compound. The chemistry of the gelling process is discussed in terms of process parameters and the gel compositions. The physicochemical nature of gels prepared by three different procedures was found to be significantly different. Infrared absorption spectra indicate finite differences in the molecular structures of the different gels. The melting of the gel powders and the transformation of porous gel monoliths to transparent 'glass' without melting are described.

Mukherjee, S. P.

1983-01-01

57

Gels and gel-derived glasses in the Na2O-B2O3-SiO2 system. [containerless melting in space  

NASA Technical Reports Server (NTRS)

The containerless melting of high-purity multicomponent homogeneous gels and gel-monoliths offers a unique approach to making ultrapure multicomponent optical glasses in the reduced gravity environment of space. Procedures for preparing and characterizing gels and gel-derived glasses in the Na2O-B2O3-SiO2 system are described. Preparation is based on the polymerization reactions of alkoxysilane with trimethyl borate or boric acid and a suitable sodium compound. The chemistry of the gelling process is discussed in terms of process parameters and the gel compositions. The physicochemical nature of gels prepared by three different procedures were found to be significantly different. IR absorption spectra indicate finite differences in the molecular structures of the different gels. The melting of the gel powders and the transformation of porous gel-monoliths to transparent 'glass' without melting are described.

Mukherjee, S. P.

1982-01-01

58

Spectroscopic properties of Sm3+ and V4+ ions in Na2O-SiO2-ZrO2 glasses  

NASA Astrophysics Data System (ADS)

Na2O-SiO2-ZrO2 glasses of Sm3+ ions with and without V2O5 are characterized by spectroscopic and optical properties. The XRD and EDS spectra of the glass samples reveal an amorphous nature with different compositions within the glass matrix. The Infrared and Raman spectral studies are carried out and the existence of conventional structural units are analyzed in the glass network. The ESR spectra of the glass samples have indicating that a considerable proportion of vanadium ion exists in V4+ state. The optical absorption spectra of these glasses are recorded at room temperature, from the measured intensities of various absorption bands the Judd-Ofelt parameters ?2, ?4 and ?6 are calculated. The photo-luminescence spectra recorded with excited wavelength 400 nm, five emission bands are observed; in this the energy transfer probability takes place between Sm3+ and V4+ ions.

Neeraja, K.; Rao, T. G. V. M.; Kumar, A. Rupesh; Uma Lakshmi, V.; Veeraiah, N.; Rami Reddy, M.

2013-12-01

59

Accurate Procedure for Calibrating the CAO Optical Hygrometer.  

National Technical Information Service (NTIS)

Two hygrometers of the Central Aerological Observatory (CAO) (Russia) were calibrated with respect to the partial pressure of water vapor. Optical hygrometers from the CAO are designed for measuring water vapor at heights above 10 km. They use the fluores...

J. Gumbel U. Waelchli M. Kretova

1992-01-01

60

Optical absorption and emission of Ni-doped (80-x)Sb2O3-20K2O-xMoO3 glasses  

NASA Astrophysics Data System (ADS)

New antimony oxide glasses were synthesized by the conventional method in the ternary system (80-x)Sb2O3-20K2O-xMoO3 (x = 30 and 40 mol%) doped with 0.1 mol% of NiO. The optical absorption spectra of Ni-doped glasses in the spectral range 750-900 nm consist of two maxima around 780 and 850 nm that are related to Ni2+ in the octahedral environment. The maxima intensity decreases with increasing Sb2O3 and decreasing MoO3. The Condon-Shortley parameters F0, F2 and F4 have been used to determine the crystal field parameters of Ni2+ in these glasses. Racah's parameters have also been calculated. Visible emission at 560 nm has been obtained at room temperature.

Petkova, P.; Houhou, S.; Soltani, M. T.

2013-11-01

61

Physical and optical absorption studies on xNa2O-(40-x)Bi2O3-20CdO-40B2O3 glasses  

NASA Astrophysics Data System (ADS)

Glasses with composition xNa2O-(40-x)Bi2O3-20CdO-40B2O3 where (0 ? x ? 40) have been prepared using melt quench technique. Optical absorption spectra of the pure glasses reveled that the cutoff wave length decreases and optical band gap (Eopt) increases where as Urbach energy (?E) decreases with increase in Na2O content. The Eopt values of these glasses are found to be in the range 2.818-3.217 eV where as the values of ?E are in the range 0.23-0.35 eV.

Kumar, R. Vijaya; Reddy, V. Rajashekar; Naik, S. Srinu; Kumar, K. Siva

2014-04-01

62

Role of B2O3 on the Viscosity and Structure in the CaO-Al2O3-Na2O-Based System  

NASA Astrophysics Data System (ADS)

The effect of B2O3 on the viscosity and structure in the calcium-aluminate melt flux system containing Na2O was studied. An increase in the B2O3 content at fixed CaO/Al2O3 ratio lowered the viscosity. Higher CaO/Al2O3 ratio at fixed B2O3 content also decreased the viscosity. The alumino-borate structures were confirmed through Fourier transformed infrared (FTIR) and Raman spectroscopy and consisted of [AlO4]-tetrahedral structural units, [BO3]-triangular structural units, and [BO4]-tetrahedral structural units, which could be correlated to the viscosity. At fixed CaO/Al2O3 ratio, B2O3 additions decreased the [AlO4]-tetrahedral structural units and transformed the 3-D network structures such as pentaborate and tetraborate into 2-D network structures of boroxol and boroxyl rings by breaking the bridged oxygen atoms (O0) to produce non-bridged oxygen atoms (O-) leading to a decrease in the molten flux viscosity. At fixed B2O3 contents and higher CaO/Al2O3 ratio, 3-D complex network structures become 3-D simple and 2-D isolated network structures, resulting in lower viscosities. The apparent activation energy for viscous flow varied from 132 to 249 kJ/mol according to the composition of B2O3 and CaO/Al2O3 ratio.

Kim, Gi Hyun; Sohn, Il

2013-10-01

63

State-selective energy transfer from Er3+ to Eu3+ in Bi2O3-GeO2-Ga2O3-Na2O glasses.  

PubMed

The Eu(3+) ion was introduced into Er(3+) doped Bi(2)O(3)-GeO(2)-Ga(2)O(3)-Na(2)O (BGGN) glasses to improve the 1.5 microm band emission. As a function of Eu(2)O(3) doped content, we observed the increase in non-radiative decay rate of Er(3+) not only (4)I(11/2) energy level but also (4)I(13/2) energy level, while the lifetime of Er(3+):(4)I(11/2) and (4)I(13/2) levels were shortened from 607 to 241 micros and from 3.37 to 1.88 ms, respectively. Accordingly, the upconversion fluorescence (green and red) was quenched. The total quantum efficiency of the Er(3+):(4)I(13/2) increased with the Eu(2)O(3) content increasing up to 0.2 mol% due to the state-selective energy transfer from Er(3+) to Eu(3+). PMID:19010716

Wang, Jun; Zhou, Yaxun; Dai, Shixun; Xu, Tiefeng; Nie, Qiuhua

2009-02-01

64

Emission analysis of Dy 3+ and Pr 3+:Bi 2O 3-ZnF 2-B 2O 3-Li 2O-Na 2O glasses  

NASA Astrophysics Data System (ADS)

In this paper, we present the spectral results of Dy 3+ and Pr 3+ (1.0 mol%) ions doped Bi 2O 3-ZnF 2-B 2O 3-Li 2O-Na 2O glasses. Measurements of X-ray diffraction (XRD), differential scanning calorimetry (DSC) profiles of these rare-earth ions doped glasses have been carried out. From the DSC thermograms, glass transition ( Tg), crystallization ( Tc) and melting ( Tm) temperatures have been evaluated. The direct and indirect optical band gaps have been calculated based on the glasses UV absorption spectra. The emission spectrum of Dy 3+:glass has shown two emission transitions 4F 7/2? 6H 15/2 (482 nm) and 4F 7/2? 6H 13/2 (576 nm) with an excitation at 390 nm wavelength and Pr 3+:glass has shown a strong emission transition 1D 2? 3H 4 (610 nm) with an excitation at 445 nm. Upon exposure to UV radiation, Dy 3+ and Pr 3+ glasses have shown bright yellow and reddish colors, respectively, from their surfaces.

Lakshminarayana, G.; Vidya Sagar, R.; Buddhudu, S.

2008-01-01

65

Comparative effects of thermal quenching and ballistic collisions in SiO2–B2O3–Na2O glass  

NASA Astrophysics Data System (ADS)

The differences between the effects of irradiation and thermal quenching were studied in SiO2–B2O3–Na2O glass by molecular dynamics. Classical molecular dynamics simulations reproduced quenching rates between 2 × 1012 K/s and instantaneous quenching. Each configuration was then subjected to a series of displacement cascades. An acceleration of the quenching rate and the accumulation of ballistic collisions result in qualitatively similar effects: swelling, increasing disorder, depolymerization of the glassy network, a decrease in the mean coordination number of B atoms. Nevertheless, ballistic processes induce specific effects that are not reproduced by accelerated quenching: an even larger degree of disorder, higher potential energy, greater depolymerization around B sites and different free volume distribution. The memory of the initial quenching rate is largely lost following an accumulation of displacement cascades, and the structure of the irradiated glasses adopts a final configuration weakly dependant on the initial state. This study shows that comparing the structure of the initial glass prepared at different quenching rates with the structure of irradiated glasses makes it possible to discriminate between thermal quenching and ballistic effects.

Delaye, J.-M.; Peuget, S.; Calas, G.; Galoisy, L.

2014-05-01

66

High energy ion beam studies of ion exchange in a Na2O-Al2O3-SiO2 glass  

NASA Astrophysics Data System (ADS)

As part of understanding the processes leading to sodium release and ion exchange, the surface and near surface reaction regions on several specimens of a Na2O-Al2O3-SiO2 glass have been examined after exposures to isotopically labeled aqueous solutions. The majority of the analyses described here have been carried out using energetic ion beam analysis. Rutherford backscattering spectrometry (RBS) has been used to measure the overall glass composition and to determine the profiles and amounts of Na released from the surface. An important part of the ion exchange process is the uptake and incorporation of hydrogen and oxygen in the glass from the solution. To facilitate this analysis, the glasses were exposed to a solution containing 18O and D and analyzed by accelerator based nuclear reaction analysis. To confirm some of the RBS depth profile data very near the surface, x-ray photoelectron spectroscopy depth profiles were collected on some samples. Although the Na concentration is decreased in the near surface region, it is not totally removed from the outer surface. In this same region, there is also a significant amount of 18O incorporated demonstrating considerable interaction between the water and the glass. Deeper into the material the amounts of D and 18O are more consistent with water or D3O+ diffusion. These results suggest that there exist an outer reaction layer and an inner ion-exchange layer in the surface region of the reacted glass.

Shutthanandan, V.; Baer, D. R.; Thevuthasan, S.; Adams, E. M.; Maheswaran, S.; Engelhard, M. H.; Icenhower, J. P.; McGrail, B. P.

2002-02-01

67

Influence of fluoride additions on biological and mechanical properties of Na2O-CaO-SiO2-P2O5 glass-ceramics.  

PubMed

Two series of Na2O-CaO-SiO2-P2O5 glass-ceramics doped with NH4HF2 (G-NH4HF2) or CaF2 (G-CaF2) have been prepared by sol-gel method. The glass-ceramic phase composition and morphology were characterized by X-ray diffraction (XRD) and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS). The mechanical properties and thermal expansion coefficient were measured by a microhardness tester, an electronic tensile machine and a thermal expansion coefficient tester. The structure difference between these two glass-ceramics was investigated by Fourier transform infrared spectroscopy (FTIR), and the in vitro bioactivity of the glass-ceramics was determined by in vitro simulated body fluid (SBF) immersion test. The hemolysis test, in vitro cytotoxicity test, systemic toxicity test and the implanted experiment in animals were used to evaluate the biocompatibility of the glass-ceramics. The mechanical properties of sample G-NH4HF2 are lower than that of sample G-CaF2, and the bioactivity of sample G-NH4HF2 is better than that of sample G-CaF2. The thermal expansion coefficients of these two glass-ceramics are all closer to that of Ti6Al4V. After 7 days of SBF immersion, apatites were induced on glass-ceramic surface, indicating that the glass-ceramics have bioactivity. The hemolysis test, in vitro cytotoxicity test and systemic toxicity test demonstrate that the glass-ceramics do not cause hemolysis reaction, and have no toxicity to cell and living animal. The implanted experiment in animals shows that bone tissue can form a good osseointegration with the implant after implantation for two months, indicating that the glass-ceramics are safe to serve as implants. PMID:24411365

Li, H C; Wang, D G; Hu, J H; Chen, C Z

2014-02-01

68

SiO2-CaO-K2O coatings on alumina and Ti6Al4V substrates for biomedical applications.  

PubMed

Alumina and Ti6Al4V alloys are widely used for orthopedics and dental applications due to their good mechanical properties and biocompatibility. Unfortunately they can not provide a satisfactory osteointegration when implanted. In fact, both alumina and Ti6Al4V are not bioactive and thus they can only guarantee a morphological fixation with the surrounding tissues without a suitable chemical anchorage. Aiming to impart bioactive properties to these materials a coating can be proposed. At this purpose, a bioactive glass belonging to the SiO2-CaO-K2O system was selected and prepared. This glass, named SCK, possess a thermal expansion coefficient matching with the alumina (8.5x 10(- 6)/ degrees C) and Ti6Al4V (9 x 10(- 6)/ degrees C) ones and thus is a good candidate to produce coatings on both of them. Simple and low-cost enameling and glazing techniques were used to realize the coatings. Structural, morphological and compositional characterizations of the coatings were carried out by means of X-ray diffraction, optical and scanning microscopy and compositional analyses. The in vitro properties of the coatings were investigated by soaking them in a simulated body fluid (SBF) in order to study the precipitation, on their surfaces, of a biologically active layer of hydroxylapatite (HAp). PMID:16167116

Vitale-Brovarone, C; Verné, E

2005-09-01

69

Melting and subsolidus reactions in the system K2O-CaO-Al2O3-SiO2-H2O  

NASA Astrophysics Data System (ADS)

Beginning of melting and subsolidus relationships in the system K2O-CaO-Al2O3-SiO2-H2O have been experimentally investigated at pressures up to 20 kbars. The equilibria discussed involve the phases anorthite, sanidine, zoisite, muscovite, quartz, kyanite, gas, and melt and two invariant points: Point [Ky] with the phases An, Or, Zo, Ms, Qz, Vapor, and Melt; point [Or] with An, Zo, Ms, Ky, Qz, Vapor, and Melt. The invariant point [Ky] at 675° C and 8.7 kbars marks the lowest solidus temperature of the system investigated. At pressures above this point the hydrated phases zoisite and muscovite are liquidus phases and the solidus temperatures increase with increasing pressure. At 20 kbars beginning of melting occurs at 740 °C. The solidus temperatures of the quinary system K2O-CaO-Al2O3-SiO2-H2O are almost 60° C (at 20 kbars) and 170° C (at 2kbars) below those of the limiting quaternary system CaO-Al2O3-SiO2-H2O. The maximum water pressure at which anorthite is stable is lowered from 14 to 8.7 kbars in the presence of sanidine. The stability limits of anorthite+ vapor and anorthite+sanidine+vapor at temperatures below 700° C are almost parallel and do not intersect. In the wide temperature — pressure range at pressures above the reaction An+Or+Vapor = Zo+Ms+Qz and temperatures below the melting curve of Zo+Ms+Ky+Qz+Vapor, the feldspar assemblage anorthite+sanidine is replaced by the hydrated phases zoisite and muscovite plus quartz. CaO-Al2O3-SiO2-H2O. Knowledge of the melting relationships involving the minerals zoisite and muscovite contributes to our understanding of the melting processes occuring in the deeper parts of the crust. Beginning of melting in granites and granodiorites depends on the composition of plagioclase. The solidus temperatures of all granites and granodiorites containing plagioclases of intermediate composition are higher than those of the Ca-free alkali feldspar granite system and below those of the Na-free system discussed in this paper. The investigated system also provides information about the width of the P-T field in which zoisite can be stable together with an Al2SiO5 polymorph plus quartz and in which zoisite plus muscovite and quartz can be formed at the expense of anorthite and potassium feldspar. Addition of sodium will shift the boundaries of these fields to higher pressures (at given temperatures), because the pressure stability of albite is almost 10kbars above that of anorthite. Assemblages with zoisite+muscovite or zoisite+kyanite are often considered to be products of secondary or retrograde reactions. The P-T range in which hydration of granitic compositions may occur in nature is of special interest. The present paper documents the highest temperatures at which this hydration can occur in the earth's crust.

Johannes, Wilhelm

1980-09-01

70

Thermodynamic modeling of melts in the system Na 2O-NaAlO 2-SiO 2-F 2O -1  

NASA Astrophysics Data System (ADS)

Fluorine is a common volatile element in magmatic-hydrothermal systems, but its solution mechanisms and thermodynamic description in highly polymerized silicate melts are poorly known. We have developed a thermodynamic model for fluorosilicate liquids that links experimentally determined phase equilibria and spectroscopic information on melt structure. The model is applicable to crystallization of fluoride minerals, fluoride-silicate immiscibility in natural felsic melts, and metallurgical processes. Configurational properties of fluorosilicate melts are described by mixing on three site levels (sublattices): (1) alkali fluoride, polyhedral aluminofluoride and silicofluoride species and nonbridging terminations of the aluminosilicate network, (2) alkali-aluminate and silicate tetrahedra within the network and (3) bridging oxygen, nonbridging oxygen and terminal fluorine atoms on tetrahedral apices of the network. Abundances of individual chemical species are described by a homogeneous equilibrium representing melt depolymerization: F - (free) + O 0 (bridging) = F 0 (terminal) + O - (nonbridging) which corresponds to a replacement of an oxygen bridging two tetrahedra by a pair of terminations, one with F and the other with an O and a charge-balancing Na. In cryolite-bearing systems two additional interaction mechanisms occur: (1) the self-dissociation of octahedral aluminofluoride complexes: [AlF 6] = [AlF 4] + 2 [F], and (2) the short-range order between (O,F)-corners and (Si,NaAl)-centers of tetrahedra: Si-O-Si + 2 [NaAl]-F = [NaAl]-O-[NaAl] + 2 Si-F. Portrayal of these equilibria in ternary Thompson reaction space allows for the decrease in the number of interaction mechanisms by linearly combining melt depolymerization with tetrahedral short-range order. In this formulation, the nonideal thermodynamic properties are represented by reaction energies of homogeneous equilibria, thus defining directly individual chemical species concentrations and configurational properties. Thermodynamic expressions for the activity-composition relationships are simplified if all entities are expressed using symbolic molecular notation (e.g., SiO 2, SiF 4, [NaAl]O 2, [NaAl]F 4, NaF etc.) with corresponding nonfractional site multiplicities (1, 2 or 4). The model has been applied to three subsystems of the Na 2O-NaAlO 2-SiO 2-F 2O -1 compositional space. Activity-composition relationships in the villiaumite-sodium silicate binaries require clustering of silicate tetrahedra and only negligible interaction between fluoride species and silicate polymer. Phase equilibria in the cryolite-albite system with a large depression of albite liquidus are interpreted via complete substitution of O 0 by O - and F 0 in the silicate framework. With increasing fluorine content, initial Al-F and Si-O short-range order evolves into the partial O-F disorder. The present model provides a useful relationship between experimental equilibria, macroscopic thermodynamics and melt speciation, thus it facilitates comparisons with, and interpretations of, spectroscopic and molecular simulation data.

Dolejš, David; Baker, Don R.

2005-12-01

71

Formation of hydroxyapatite onto glasses of the CaO-MgO-SiO2 system with B2O3, Na2O, CaF2 and P2O5 additives.  

PubMed

New bioactive glasses with compositions based on the CaO-MgO-SiO(2) system and additives of B(2)O(3), P(2)O(5), Na(2)O, and CaF(2) were prepared. The in vitro mineralization behaviour was tested by immersion of powders or bulk glasses in simulated body fluid (SBF). Monitoring of ionic concentrations in SBF and scanning electron microscopy (SEM) observations at the surface of the glasses were conducted over immersion time. Raman and infrared (IR) spectroscopy shed light on the structural evolution occurring at the surface of the glasses that leads to formation of hydroxyapatite. PMID:16309741

Agathopoulos, S; Tulyaganov, D U; Ventura, J M G; Kannan, S; Karakassides, M A; Ferreira, J M F

2006-03-01

72

Mössbauer and optical spectroscopic study of temperature and redox effects on iron local environments in a Fe-doped (0.5 mol% Fe 2O 3) 18Na 2O–72SiO 2 glass  

Microsoft Academic Search

Local environments of ferric and ferrous irons were systematically studied with Mössbauer (at liquid helium temperature) and ultraviolet–visible–near infrared spectroscopic methods for various 18Na2O–72SiO2 glasses doped with 0.5 mol% Fe2O3. These were prepared at temperatures of 1300–1600 °C in ambient air or at 1500 °C under reducing conditions with oxygen partial pressures from 12.3 to 0.27×10?7 atmospheres. The Mössbauer spectroscopic

Ravi K. Kukkadapu; Hong Li; Gary Lynn L. Smith; Jarrod V. Crum; Jun-Sik Jeoung; W. Howard Poisl; Michael C. Weinberg

2003-01-01

73

In vitro bioactivity and crystallization behavior of bioactive glass in the system SiO 2 -CaO-Al 2 O 3 -P 2 O 5 Na 2 O-MgO-CaF 2  

Microsoft Academic Search

In this study, bioactivity of glass in the system SiO2-CaO-Al2O3-P2O5-Na2O-MgO-CaF2 was investigated. For this purpose, a glass sample was prepared by the traditional melting method. Crystallization behavior\\u000a of bioactive glass was also investigated using differential thermal analyses. The Avrami constant of bioactive glass sample\\u000a calculated according to the Ozawa equation was 3.72 ± 0.4, which indicates bulk crystallization. Using the

Melek Erol

2010-01-01

74

Effects of CaO/P2O5 ratio on the structure and elastic properties of SiO2-CaO-Na2O-P2O5 bioglasses.  

PubMed

The evolution of elastic properties and structure upon the change of CaO/P(2)O(5) ratio in SiO(2)-CaO-Na(2)O-P(2)O(5) glasses (45S5-derived and 55S4-derived) at ambient conditions has been studied by using both Brillouin and Raman spectroscopy coupled with X-ray diffraction. Under the same SiO(2)/Na(2)O ratio, it is found that a decrease in CaO/P(2)O(5) molar ratio has caused a more-polymerized silicate network via a net consumption of Q(0), Q(1), and Q(2) species yet enriching in Q(3) and Q(4) species. Brillouin experiments revealed that all the bulk, shear and Young's moduli of the glasses studied increases with the increase of CaO/P(2)O(5) molar ratio. The unexpected variation trend in shear modulus can be correlated to the contribution from cohesion, the less-polymerized phosphate Q species, and density. Compared to the 45S5-derived, the more-polymerized 55S4-deived glass has a lower bulk but slightly higher shear modulus at the given CaO/P(2)O(5) ratio. PMID:22109904

Lin, Chung-Cherng; Chen, Shih-Fan; Leung, Kak Si; Shen, Pouyan

2012-02-01

75

Approche thermodynamique de la corrosion des refractaires aluminosiliceux par le bain cryolithique : modelisation thermodynamique du systeme quaternaire reciproque AlF3-NaF-SiF 4-Al2O3-Na2O-SiO2  

NASA Astrophysics Data System (ADS)

The main objective of this thesis is the thermodynamic modeling of liquid and solid solutions, the stoichiometric compounds and the gaseous phase of the chemical system which represent the species involved in the corrosion of the refractory lining of the electrolysis cell. This chemical system is the quaternary reciprocal system AlF3-NaF-SiF4-Al 2O3-Na2O-SiO2 with aluminum and carbon. The modeling of the entire reciprocal system has never been realized before and is very challenging due to the nature of the oxyfluoride solution. The thermodynamic modeling is based on Gibbs free energy functions coming from the theory of solutions. The central hypothesis of this project is that, if it is possible to reproduce the strong short-range ordering observed between the ions of the liquid solution, then reasonable results will be obtained for the phase equilibria involved in this chemical system. The thermodynamic model used in this thesis is the Modified Quasichemical Model in the Quadruplet Approximation (MQMQA) which takes into account the short-range ordering between first- and also second-nearest-neighbors, and is the best suited to model the oxyfluoride liquid solution. First, the reciprocal system with the most negative Gibbs free energy change for the exchange reaction between the end-members, NaF-SiF4-Na 2O-SiO2, was modeled, allowing thus the validation of the recent modifications of the MQMQA aimed at improving the modeling of the thermodynamic properties of reciprocal solutions presenting a strong short-range order among first-nearest neighbors as well as second-nearest neighbors. In order to model this system, an estimate of the thermodynamic properties of the hypothetical SiF4 liquid was necessary. The experimental data in the binary systems NaF-SiF4 and Na2O-SiO2 are reproduced within the experimental error limits. In the reciprocal system, a group of data in conflict with all others could not be reproduced. The data considered reliable are well reproduced. A unique set of parameters was used to reproduce all the reciprocal sections and extrapolations outside these sections should be satisfactory. The ternary system Al2O3-Na2O-SiO 2 and the ternary reciprocal system AlF3-NaF-Al2O 3-Na2O have been treated jointly due to the fact that compromises were necessary for the optimization of the system common to the two systems, Al2O3-Na2O, in particular for the ?-alumina solid solution. The numerous experimental data relative to the thermodynamic properties of the stoichiometric or the solid solutions in the ternary system have been taken into account for the modeling of NaAlSiO4 and NaAlSi 3O8. Furthermore, the cation NaAl4+, used in the modeling to reproduce the charge compensation effect (substitution of Si4+ by Al3+ coupled to Na+ in the SiO2-rich region of the ternary oxide system), is present in both of these systems and the properties of the end-members related to it (NaAlF4 and NaAlO2) have been adjusted to reproduce the thermodynamic properties of the liquid phase. The absence or lack of experimental data in specific composition regions, in particular in the Na2O-rich region in the oxide system or in the oxide-rich region of the reciprocal system, makes the optimization of these two systems difficult. The modeling of the quaternary reciprocal system Al, Na, Si // F, O has been performed mainly by taking into account the experimental data available in the isoplethal sections NaF-NaAlSiO4, NaF-NaAlSi3O 8, Na3AlF6-NaAlSiO4 and Na3AlF 6-NaAlSi3O8 and by using the model parameters allowing the adjustment of the thermodynamic properties of the liquid solution in the composition region under consideration. The few available data and the conflict among them, undoubtedly related to the experimental difficulties, make the modeling of the quaternary reciprocal system complex. (Abstract shortened by UMI.).

Lambotte, Guillaume

76

In vitro cellular adhesion and antimicrobial property of SiO 2 –MgO–Al 2 O 3 –K 2 O–B 2 O 3 –F glass ceramic  

Microsoft Academic Search

The aim of the present study was to examine the cellular functionality and antimicrobial properties of SiO2–MgO–Al2O3–K2O–B2O3–F glass ceramics (GC) containing fluorophlogopite as major crystalline phase. The cellular morphology and cell adhesion study\\u000a using human osteoblast-like Saos-2 cells and mouse fibroblast L929 cells reveals good in vitro cytocompatibility of GC. The\\u000a potential use of the GC for biomedical application was

Sushma Kalmodia; Atiar Rahaman Molla; Bikramjit Basu

2010-01-01

77

Influence of the Ca\\/P ratio on the morphology of fluorapatite crystals in SiO 2–Al 2O 3–CaO–P 2O 5–K 2O–F ? glass-ceramics  

Microsoft Academic Search

The formation of fluorapatite crystals with needle-like morphology was studied in glass-ceramics (GCs) of the system SiO2–Al2O3–CaO–P2O5–K2O–F?. X-ray diffraction (XRD), 31P and 27Al nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), temperature-dependent electric conductance measurements, and transmission electron microscopy (TEM) with energy dispersive X-ray analysis were used to study the influence of the Ca\\/P ratio of the starting glass composition

C. Moisescu; T. Höche; G. Carl; R. Keding; C. Rüssel; W. D. Heerdegen

2001-01-01

78

Control of spectroscopic fluorescence parameters of Nd 3+ ions as a function of concentration in a SiO 2-Na 2O-Al 2O 3-B 2O 3 glass system  

NASA Astrophysics Data System (ADS)

Experimental evidence of spectroscopic parameter control was observed in Nd 3+ ions embedded in a SiO 2-Na 2O-Al 2O 3-B 2O 3 glass system. The parameters ?2,4,6 and others were determined by the Judd-Ofelt theory. It was found that these parameters were strongly dependent on Nd 3+ concentration, indicating a ligand field change. This Letter will present and discuss possible mechanisms responsible for changes in the Judd-Ofelt parameters. Furthermore, non-radiative energy transfer mechanisms such as energy migration, cross relaxation and losses from networked phonons and OH - radicals, will be proposed to explain the observed decrease in 4F 3/2 ? 4I 11/2 transition lifetime of Nd 3+.

Serqueira, E. O.; Dantas, N. O.; Bell, M. J. V.

2011-05-01

79

Effect of Fe 2O 3 concentration on the structure of the SiO 2-Na 2O-Al 2O 3-B 2O 3 glass system  

NASA Astrophysics Data System (ADS)

The structural properties of the glass matrix 40SiO 2·30Na 2O·1Al 2O 3·(29 - x)B 2O 3· xFe 2O 3 (mol%), 0.0 ? x ? 29.0 were studied by X-ray diffraction (XRD), differential thermal analysis (DTA) and Raman and infrared spectroscopy (FT-IR). XRD demonstrated Fe 3O 4 crystal formation for Fe 2O 3 concentrations of 29.0 mol%. DTA showed that glass transition and crystallization temperatures changed as a function of Fe 2O 3 concentration and that these alterations were related to structural change in the glass system. Interesting aspects of Raman and FT-IR spectra were found, and this gives information about of the structure changes in Si-O-Si units of these glasses as a function of Fe 2O 3 concentration.

Dantas, Noelio O.; Ayta, Walter E. F.; Silva, Anielle C. A.; Cano, Nilo F.; Silva, Sebastião W.; Morais, Paulo C.

2011-10-01

80

Synthesis, bioactivity and preliminary biocompatibility studies of glasses in the system CaO-MgO-SiO2-Na2O-P2O5-CaF2.  

PubMed

New compositions of bioactive glasses are proposed in the CaO-MgO-SiO(2)-Na(2)O-P(2)O(5)-CaF(2) system. Mineralization tests with immersion of the investigated glasses in simulated body fluid (SBF) at 37°C showed that the glasses favour the surface formation of hydroxyapatite (HA) from the early stages of the experiments. In the case of daily renewable SBF, monetite (CaHPO(4)) formation competed with the formation of HA. The influence of structural features of the glasses on their mineralization (bioactivity) performance is discussed. Preliminary in vitro experiments with osteoblasts' cell-cultures showed that the glasses are biocompatible and there is no evidence of toxicity. Sintering and devitrification studies of glass powder compacts were also performed. Glass-ceramics with attractive properties were obtained after heat treatment of the glasses at relatively low temperatures (up to 850°C). PMID:21188484

Tulyaganov, D U; Agathopoulos, S; Valerio, P; Balamurugan, A; Saranti, A; Karakassides, M A; Ferreira, J M F

2011-02-01

81

Caos en el mercado cambiario mexicano. Aplicación de la teoría del caos en los tipos de cambio  

Microsoft Academic Search

El presente trabajo estudia la dinámica cambiaria en México bajo el enfoque de una metodología poco conocida: la Teoría del Caos o, en términos de nuestra ciencia, la Economía Dinámica Caótica. Dado lo relativamente reciente de esta metodología, se presentará de manera clara y lo más rigurosamente posible sus bases teóricas, metodologías y campos de aplicación reciente; lo cual permitirá

Julián Ibarra Onofre

2004-01-01

82

CaO dispersed on carbon as an SO 2 sorbent  

Microsoft Academic Search

Calcium-containing carbons were tested as low-temperature sorbents for SO2. CaO particles dispersed on carbon were prepared by thermal decomposition of calcium acetate. Samples with calcium contents ranging from 1.5 to 8.0 wt% were analysed. CO2 chemisorption was used to characterize the area of the CaO particles available to interact with and retain SO2. CaO surface areas confirm that CaO dispersed

Marcia J. Muñoz-Guillena; M. C. Macías-Pérez; Angel Linares-Solano; Concepción Salinas-Martínez de Lecea

1997-01-01

83

Luminescence properties of deformed CaO crystals  

NASA Astrophysics Data System (ADS)

In deformed CaO crystals, the predominant optical-absorption band at 270 nm and the corresponding luminescence band at 450 nm have been investigated. The absorption coefficient increases linearly with deformation up to ~5% whereas the luminescence intensity saturates earlier. Thermal annealing indicates that appreciable decrease in the absorption begins at ~600 K. In contrast, the luminescence intensity diminishes very rapidly at temperatures not much above room temperature. Time-resolved luminescence indicates that the 450-nm band is composed of two bands: a 475-nm band with lifetimes of <3 ns and ~10 ?s, and a 440-nm band with a lifetime of ~1 ms at room temperature. In a test for laser action no optical gain was observed in a deformed CaO crystal.

Gonzalez, R.; Chen, Y.; Ballesteros, C.; Liu, Hanli; Williams, G. P., Jr.; Rosenblatt, G. H.; Williams, R. T.; Gellermann, W.

1993-03-01

84

Investigating the effect of SiO2-TiO 2-CaO-Na 2O-ZnO bioactive glass doped hydroxyapatite: characterisation and structural evaluation.  

PubMed

The effects of increasing bioactive glass additions, SiO2-TiO2-CaO-Na2O-ZnO up to 25 wt% in increments of 5 wt%, on the physical and mechanical properties of hydroxyapatite (HA) sintered at 900, 1000, 1100 and 1200 °C for 2 h was investigated. Increasing both the glass content and the temperature resulted in increased HA decomposition. This resulted in the formation of a number of bioactive phases. However the presence of the liquidus glass phase did not result in increased densification levels. At 1000 and 1100 °C the additions of 5 wt% glass resulted in a decrease in density which never recovered with increasing glass content. At 1200 °C a cyclic pattern resulted from increasing glass content. There was no direct relationship between strength and density with all samples experiencing no change or a decrease in strength with increasing glass content. Weibull statistics displayed no pattern with increasing glass content. PMID:24748516

Yatongchai, Chokchai; Wren, Anthony W; Curran, Declan J; Hampshire, Stuart; Towler, Mark R

2014-07-01

85

Investigating the surface reactivity of SiO2-TiO 2-CaO-Na 2O/SrO bioceramics as a function of structure and incubation time in simulated body fluid.  

PubMed

This study focuses on evaluating the biocompatibility of a SiO2-TiO2-CaO-Na2O/SrO glass and glass-ceramic series. Glass and ceramic samples were synthesized and characterized using X-ray diffraction. Each material was subject to maturation in simulated body fluid over 1, 7 and 30 days to describe any changes in surface morphology. Calcium phosphate (CaP) deposition was observed predominantly on the Na(+) containing amorphous and crystalline materials, with plate-like morphology. The precipitated surface layer was also observed to crystallize with respect to maturation, which was most evident in the amorphous Na(+) containing glasses, Ly-N and Ly-C. The addition of Sr(2+) greatly reduced the solubility of all samples, with limited CaP precipitation on the amorphous samples and no deposition on the crystalline materials. The morphology of the samples was also different, presenting irregular plate-like structures (Ly-N), needle-like deposits (Ly-C) and globular-like structures (Ly-S). Cell culture analysis presented a significant increase in cell viability with the Na(+) materials, 134 %, while the Sr(2+) containing glasses, 60-80 % and ceramics, 60-85 % presented a general reduction in cell viability, however these reductions were not significant. PMID:24796627

Li, Y; Coughlan, A; Wren, Anthony W

2014-08-01

86

Intense 2.7 µm emission and structural origin in Er3+-doped bismuthate (Bi2O3-GeO2-Ga2O3-Na2O) glass.  

PubMed

The 2.7 ?m emission properties in Er3+-doped bismuthate (Bi2O3-GeO2-Ga2O3-Na2O) glass were investigated in the present Letter. An intense 2.7 ?m emission in Er3+-doped bismuthate glass was observed. It is found that Er3+-doped bismuthate glass possesses high spontaneous transition probability A (65.26 s(-1)) and large 2.7 ?m emission cross section ?(em) (9.53×10(-21) cm2) corresponding to the stimulated emission of Er3+:4I11/2?4I13/2 transition. The emission characteristic and energy transfer process upon excitation of a conventional 980 nm laser diode in bismuthate glass were analyzed. Additionally, the structure of bismuthate glass was analyzed by the Raman spectrum. The advantageous spectroscopic characteristics of Er3+ single-doped bismuthate glass together with the prominent thermal property indicate that bismuthate glass might become an attractive host for developing solid-state lasers around 2.7 ?m. PMID:22854489

Guo, Yanyan; Li, Ming; Hu, Lili; Zhang, Junjie

2012-01-15

87

Structural and magnetic properties of SiO2-CaO-Na2O-P2O5 containing BaO-Fe2O3 glass-ceramics  

NASA Astrophysics Data System (ADS)

The incorporation method was employed to produce bioactive glass-ceramics from the BaFe12O19-SiO2-CaO-Na2O-P2O5 glass system. The ferrimagnetic BaFe12O19 was first prepared using a simple mixed oxide method, where the oxide precursors of 45S5 bioglass were initially mixed and then melted to form glass. The devitrification of Na3Ca6(PO4)5 and Fe3O4 was observed in all of the quenched glass samples. The glass samples were then subjected to a heat treatment schedule for further crystallization. It was found that the small traces of BaFe12O19 phases started to crystallize in high BF content samples of 20 and 40 wt%. These samples also exhibited good magnetic properties comparable to that of other magnetic glass-ceramics. The bioactivity of the BF glass-ceramics improved with increasing BF content as was evident by the formation of bone-like apatite layers on the surface of all of the glass-ceramics after soaking in SBF for 14 days. The results support the use of these bioactive glass-ceramics for hyperthermia treatment within the human body.

Leenakul, W.; Kantha, P.; Pisitpipathsin, N.; Rujijanagul, G.; Eitssayeam, S.; Pengpat, K.

2013-01-01

88

The Oxygenase CAO-1 of Neurospora crassa Is a Resveratrol Cleavage Enzyme  

PubMed Central

The genome of the ascomycete Neurospora crassa encodes CAO-1 and CAO-2, two members of the carotenoid cleavage oxygenase family that target double bonds in different substrates. Previous studies demonstrated the role of CAO-2 in cleaving the C40 carotene torulene, a key step in the synthesis of the C35 apocarotenoid pigment neurosporaxanthin. In this work, we investigated the activity of CAO-1, assuming that it may provide retinal, the chromophore of the NOP-1 rhodopsin, by cleaving ?-carotene. For this purpose, we tested CAO-1 activity with carotenoid substrates that were, however, not converted. In contrast and consistent with its sequence similarity to family members that act on stilbenes, CAO-1 cleaved the interphenyl C?-C? double bond of resveratrol and its derivative piceatannol. CAO-1 did not convert five other similar stilbenes, indicating a requirement for a minimal number of unmodified hydroxyl groups in the stilbene background. Confirming its biological function in converting stilbenes, adding resveratrol led to a pronounced increase in cao-1 mRNA levels, while light, a key regulator of carotenoid metabolism, did not alter them. Targeted ?cao-1 mutants were not impaired by the presence of resveratrol, a phytoalexin active against different fungi, which did not significantly affect the growth and development of wild-type Neurospora. However, under partial sorbose toxicity, the ?cao-1 colonies exhibited faster radial growth than control strains in the presence of resveratrol, suggesting a moderate toxic effect of resveratrol cleavage products.

Diaz-Sanchez, Violeta; F. Estrada, Alejandro; Limon, M. Carmen; Al-Babili, Salim

2013-01-01

89

The oxygenase CAO-1 of Neurospora crassa is a resveratrol cleavage enzyme.  

PubMed

The genome of the ascomycete Neurospora crassa encodes CAO-1 and CAO-2, two members of the carotenoid cleavage oxygenase family that target double bonds in different substrates. Previous studies demonstrated the role of CAO-2 in cleaving the C40 carotene torulene, a key step in the synthesis of the C35 apocarotenoid pigment neurosporaxanthin. In this work, we investigated the activity of CAO-1, assuming that it may provide retinal, the chromophore of the NOP-1 rhodopsin, by cleaving ?-carotene. For this purpose, we tested CAO-1 activity with carotenoid substrates that were, however, not converted. In contrast and consistent with its sequence similarity to family members that act on stilbenes, CAO-1 cleaved the interphenyl C?-C? double bond of resveratrol and its derivative piceatannol. CAO-1 did not convert five other similar stilbenes, indicating a requirement for a minimal number of unmodified hydroxyl groups in the stilbene background. Confirming its biological function in converting stilbenes, adding resveratrol led to a pronounced increase in cao-1 mRNA levels, while light, a key regulator of carotenoid metabolism, did not alter them. Targeted ?cao-1 mutants were not impaired by the presence of resveratrol, a phytoalexin active against different fungi, which did not significantly affect the growth and development of wild-type Neurospora. However, under partial sorbose toxicity, the ?cao-1 colonies exhibited faster radial growth than control strains in the presence of resveratrol, suggesting a moderate toxic effect of resveratrol cleavage products. PMID:23893079

Díaz-Sánchez, Violeta; Estrada, Alejandro F; Limón, M Carmen; Al-Babili, Salim; Avalos, Javier

2013-09-01

90

Studies on some ternary oxyborates of the Na 2O- Me2O 3-B 2O 3 ( Me=rare earth or aluminum) systems: Synthesis, structure and crystal growth  

NASA Astrophysics Data System (ADS)

Sodium rare-earth oxyborates Na 2RE2O(BO 3) 2 ( RE=Y, Nd, Er) were prepared for the first time in the present study. They were found to be isostructural with phases of the same composition containing Sm, Eu or Gd and reported by Corbel et al. [J. Solid State Chem.144 (1999) 35-44]. It was shown that the yttrium and erbium compounds could be synthesized at 900-1000 °C by a solid-state reaction between oxides in an equimolecular ratio. With both oxyborates melting led to decomposition into a mixture of Y(Er)BO 3, Y 2(Er 2)O 3 and Na 2B 4O 7. Just the opposite was observed during thermal treatment of the oxide mixture containing Nd 2O 3, from which a practically pure phase of Na 2Nd 2O(BO 3) 2 was only obtained after melting. The attempts to synthesize the oxyborate Na 2La 2O(BO 3) 2 showed it to be unstable, this leading to the formation of a mixture containing, in addition to Na 2La 2O(BO 3) 2, also other already known stable phases of the system Na 2O-La 2O 3-B 2O 3 along with an unknown ternary oxide phase. This phase was found to represent a new oxyborate of sodium and lanthanum with the formula Na 3La 9O 3(BO 3) 8, whose single crystals were obtained by flux growth. It was established that synthesis of a polycrystalline material with the same composition was also possible using solid-state interaction between Na 2CO 3, La 2O 3 and H 3BO 3 at 1000-1100 °C. X-ray diffraction experiments on single crystals were used to solve the structure of Na 3La 9O 3(BO 3) 8. The unit cell was found to be hexagonal, space group P62 m (No. 189) with Z=1. The compound can be regarded as the forefather of a second group of oxyborates representing a new family of isostructural compounds, Na 3RE9O 3(BO 3) 8. Such phases were obtained with RE=Nd, Sm and Eu whereas with RE=Y and Gd, the synthesis experiments failed. The concentration and temperature regions of crystallization of the double-oxyborate Na 2Al 2O(BO 3) 2 in the ternary system Na 2O-Al 2O 3-B 2O 3 were determined. This compound was shown to melt incongruently at 970±3 °C, which made high-temperature solution growth most appropriate for obtaining its single crystals with NaBO 2 as the best solvent. On the basis of the data obtained, a composition of the initial solution was proposed, the validity of the choice being demonstrated by the growth of Na 2Al 2O(BO 3) 2 single crystals on a seed using the top-seeded solution growth (TSSG) technique and slow cooling of the solution.

Peshev, P.; Pechev, S.; Nikolov, V.; Gravereau, P.; Chaminade, J.-P.; Binev, D.; Ivanova, D.

2006-09-01

91

The Structure of Na2O-Al2O3-SiO2 Glass: Impact on Sodium Ion Exchange in H2O and D2O  

SciTech Connect

The kinetics of matrix dissolution and alkali-exchange for a series of sodium aluminosilicate glass compositions was determined at constant temperature and solution pH(D) under conditions of silica-saturation. Steady state release rate for sodium was 10 to 50 times faster than the rate of matrix dissolution, demonstrating that alkali exchange is an important long-term reaction mechanism that must be considered when modeling systems near saturation with respect to dissolved glass components. Sodium release rates were 30% slower in D2O compared to rates in H2O; but matrix dissolution rates were unaffected. These results are consistent with rupture of the O-H bond as the rate-limiting reaction in Na+-H+ exchange whereas matrix dissolution is controlled by OH- or H2O catalyzed hydrolysis of Si-O-Si and Si-O-Al bonds. Changes in Na exchange rate with increasing Al2O3 content could not be reconciled with changes in the number of non-bridging oxygen (NBO) sites in the glass alone. A simple model was used to estimate a structural energy barrier for alkali ion exchange using Na-O bond length and coordination as measured by Na K-edge XANES spectroscopy, and binding energy shifts for Si-O-Na sites measured by XPS. The energy barrier was calculated to increase from 34 kJ/mol for Na2O?2SiO2 glass to 50 kJ/mol for a glass containing 15 mol% Al2O3, consistent with stronger bonding of Na on NBO sites and increasing mechanical stiffness of the glass network with increasing Al content. The calculated ion-exchange enthalpies were then used to calculate Na ion exchange rates as a function of glass composition. Agreement between the calculated and measured Na ion exchange rates was excellent.

McGrail, B PETER.; Icenhower, Jonathan P.; Shuh, D K.; Liu, P; Darab, John G.; Baer, Donald R.; Thevuthasan, Suntharampillai; Shutthanandan, V; Engelhard, Mark H.; Booth, C H.; Nachimuthu, P

2001-10-28

92

Fluorine speciation as a function of composition in peralkaline and peraluminous Na2O–CaO–Al2O3–SiO2 glasses: A multinuclear NMR study  

NASA Astrophysics Data System (ADS)

The incorporation mechanisms of fluorine (F) into peralkaline and peraluminous Na2O–CaO aluminosilicate glasses with ˜65 mol% SiO2 (model system for phonolites) were investigated by magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. In 19F MAS NMR spectra of the fluorine-bearing peralkaline glasses at least five F sites could be distinguished, while only three of these sites could be found in the corresponding peraluminous glasses, which shows that there are more F incorporation mechanisms in peralkaline than in peraluminous glasses. In the peralkaline glasses containing up to 6.2 mol% F the following F environments were identified: F–Ca(n) at ˜?113 ppm, Si–F–Na(n) or Al–F–Ca(n) at ˜?146 ppm, Al–F–Al at ˜?168 ppm, Al–F–Na(n) at ˜?188 ppm and F–Na(n) at ˜?225 ppm ("n" indicates that the number of atoms is variable or uncertain). F–Ca(n) is the most abundant site which is surprising as Ca is the least common cation in the glasses. The fraction of F–Ca(n) sites increases from 42% to 53% as the F content increases from 1.2 to 6.2 mol%. The addition of up to 16.5 mol% (5.3 wt%) water strongly affects F speciation in peralkaline glasses and results in a decrease in the fraction of F–Al sites compared to F–Ca(n) sites. It seems that hydroxyl groups (OH) and F occupy similar Al environments and that F cannot compete with OH.

Baasner, A.; Schmidt, B. C.; Dupree, R.; Webb, S. L.

2014-05-01

93

Magnetic and optical investigation of 40SiO2·30Na2O·1Al2O3·(29 - x)B2O3·xFe2O3 glass matrix  

NASA Astrophysics Data System (ADS)

Samples of 40SiO2·30Na2O·1Al2O3·(29 - x)B2O3·xFe2O3 (mol%), with 0.0 ? x ? 17.5, were prepared by the fusion method and investigated by electron paramagnetic resonance (EPR), optical absorption (OA) and Mössbauer spectroscopy (MS). The EPR spectra of the as-synthesized samples exhibit two well-defined EPR signals around g = 4.27 and g = 2.01 and a visible EPR shoulder around g = 6.4, assigned to isolated Fe3+ ion complexes (g = 4.27 and g = 6.4) and Fe3+-based clusters (g = 2.01). Analyses of both EPR line intensity and line width support the model picture of Fe3+-based clusters built in from two sources of isolated ions, namely Fe2+ and Fe3+; the ferrous ion being used to build in iron-based clusters at lower x-content (below about x = 2.5%) whereas the ferric ion is used to build in iron-based clusters at higher x-content (above about x = 2.5%). The presence of Fe2+ ions incorporated within the glass template is supported by OA data with a strong band around 1100 nm due to the spin-allowed 5Eg-5T2g transition in an octahedral coordination with oxygen. Additionally, Mössbauer data (isomer shift and quadrupole splitting) confirm incorporation of both Fe2+ and Fe3+ ions within the template, more likely in tetrahedral-like environments. We hypothesize that ferrous ions are incorporated within the glass template as FeO4 complex resulting from replacing silicon in non-bridging oxygen (SiO3O-) sites whereas ferric ions are incorporated as FeO4 complex resulting from replacing silicon in bridging-like oxygen silicate groups (SiO4).

Dantas, Noelio O.; Ayta, Walter E. F.; Silva, Anielle C. A.; Cano, Nilo F.; Rodriguez, Anselmo F. R.; Oliveira, Aderbal C.; Garg, Vijayendra K.; Morais, Paulo C.

2012-08-01

94

Silicate speciation in H2O-Na2O-SiO2 fluids from 3 to 40 mol% SiO2, to 600 °C and 2 GPa  

NASA Astrophysics Data System (ADS)

The silicate speciation in H2O-Na2O-SiO2 fluids was studied in situ up to 600 °C and 2.0 GPa using Raman spectroscopy and a Bassett-type hydrothermal diamond-anvil cell. Fluid compositions ranged from 3 to 40 mol% SiO2, with various Na/Si ratios. The main trends observed in Raman spectra of fluids with increasing SiO2 concentration include (1) decrease in the intensity of the ?770 cm-1 band (monomer, Q0, symmetric stretch); (2) increase in the intensity of the ?1050 cm-1 band (bridging oxygen Si-O-Si antisymmetric stretch) and the bands at ?450-600 cm-1 (bridging oxygen Si-O-Si bending modes); and (3) increase in spectral contributions at ?800-1000 cm-1 from stretching vibrations of Q1, Q2 and Q3 species. These trends are interpreted to represent decrease in the proportion of Q0 monomers, and increase in the proportions of Q1 and Q2 (±Q3) species, with increasing silicate concentration in the fluid up to 40 mol% SiO2. Raman spectra in the range of tetrahedral Si-O stretching vibrations (700-1200 cm-1) exhibit little discernable difference with changing Na/Si ratio, when compared at constant molar concentration of SiO2. Particularly at lower Na/Si ratio, increasing silicate concentration also results in increasing relative intensity of the Raman signal of O-H stretching vibrations at about 3300 cm-1, suggesting increased intermolecular hydrogen bonding between H2O molecules and/or oxygen atoms belonging to silicate species. These results suggest that silicate in hydrous fluids in the deep Earth remains occurs predominately as partly polymerized, Q1 and Q2 species up to high silicate concentrations, providing an opportune medium for mobilizing high field-strength and other elements in the lithosphere.

Steele-MacInnis, Matthew; Schmidt, Christian

2014-07-01

95

Optical characterization of Mn2+: Li2O-K2O-CdO-B2O3 glass system: Absorption edge, optical band gap, optical polarizability and optical basicity  

NASA Astrophysics Data System (ADS)

Mixed alkali borate glasses (30-x)Li2O-xK2O-10CdO-59B2O3 (0 <= × <= 30) implanted with 1mol% manganese ions (LKCBM) were prepared from the melts. These glasses were characterized using X-ray diffraction (XRD), differential scanning calorimetry (DSC) and density measurements. Optical absorption studies were carried out as a function of alkali content to look for `Mixed Alkali Effect' (MAE) on the spectral properties of these glasses. The optical absorption spectra of LKCBM exhibit a broad band around 21000 cm-1 which has been assigned to the transition 6A1g(S) ? 4T1g(G). From the study of ultraviolet absorption edge, the optical band gap energies and Urbach energies were evaluated. The average electronic polarizability of the oxide ion (?o2-), Optical basicity (wedge) and Yamasita-Kurosawas's interaction parameter (A) were also evaluated for all the glasses. In the present investigation many of the physical parameters like glass transition temperature, density, optical band gap and optical basicity vary non-linearly with alkali concentration (x) indicating MAE.

Padmaja, G.; Kistaiah, P.

2009-07-01

96

Optical absorption and EPR spectroscopic studies of (30 - x)Li 2O- xK 2O-10CdO-59B 2O 3-1Fe 2O 3: An evidence for mixed alkali effect  

NASA Astrophysics Data System (ADS)

Optical absorption and EPR spectroscopic studies were carried on (30 - x)Li 2O- xK 2O-10CdO-59B 2O 3-1Fe 2O 3 ( x = 0-30) glass system to understand the effect of progressive doping of Li + ion with K + ion. Optical absorption results show typical spectra of Fe 3+ ions and the various optical parameters such as, optical band gap, Urbach energy, oxide ion polarizability, optical basicity and interaction parameter were evaluated from the experimental data. The observed optical band gap and Urbach energy values show large deviation from the linearity where as the other parameters show small deviation from the linearity with the progressive substitution of Li + ions with K + ions. The observed EPR spectra are representative of Fe 3+ ion in octahedral and axial fields in the glass network. The number of paramagnetic centers and paramagnetic susceptibility values were evaluated at different resonance lines for all the specimens and these parameters show non-additive nature with the progressive substitution of Li + ions with K + ions in the glass network. This is first ever observation of mixed alkali effect (MAE) in EPR and optical parameters of mixed alkali borate glasses.

Padmaja, G.; Kistaiah, P.

2010-12-01

97

Mixed alkali effect in Mn2+ doped 20ZnO+xLi2O+(30-x)K2O+50B2O3(5?x?25) glasses.  

PubMed

Divalent Mn2+ ions containing 20ZnO+xLi2O+(30-x)K2O+50B2O3(5?x?25) mol% glasses are prepared by using melt quench technique and are characterized by several spectroscopic techniques. Various physical parameters are evaluated from the measured values of density and refractive index for the observation of mixed alkali effect. Structural changes of Mn2+ doped ZLKB glasses are investigated by Powder XRD, UV-VIS absorption, Electron Paramagnetic Resonance and FT-IR spectroscopic studies. The XRD pattern indicates the amorphous nature of prepared glasses. FT-IR measurements of all glasses revealed that the network structure of glass system are mainly based on BO3 and BO4 units placed in different structural groups in which the BO3 units being dominant. The EPR spectra of Mn2+ ions doped glasses exhibited a characteristic hyperfine sextet around g=2.0. The spectroscopic analyses of the obtained results confirmed near octahedral site symmetry for the Mn2+ impurity ions. Crystal field and Racah parameters are evaluated from optical absorption spectra. The optical band gap and Urbach energies are determined which exhibited the mixed alkali effect. PMID:23099172

Kumari, G Krishna; Krishna, Ch Rama; Begum, Sk Muntaz; Manjari, V Pushpa; Murthy, P N; Ravikumar, R V S S N

2013-01-15

98

Optical and fluorescence spectroscopy of Eu2O3-doped P2O5–K2O–KF–MO–Al2O3 (M = Mg, Sr and Ba) glasses  

NASA Astrophysics Data System (ADS)

Fluorophosphate glasses of composition, P2O5 + K2O + KF + MO + Al2O3 + xEu2O3 (M = Mg, Sr and Ba; x = 0.01, 0.05, 0.1, 1.0, 2.0, 4.0 and 6.0 mol%) were prepared and characterized their optical properties. Crystal-field (CF) analysis revealed a relatively weak CF strength around Eu3+ ions in the Ba based fluorophosphate glasses. The Judd-Ofelt parameters have been estimated from the oscillator strengths of 7F0 ? 5D2, 7F0 ? 5D4 and 7F0 ? 5L6 absorption transitions of Eu3+ ions and were used to evaluate the radiative properties of the 5D0 ? 7FJ (J = 0–4) transitions. Considerable variation has been observed in the relative intensity ratio of 5D0 ? 7F2 to 5D0 ? 7F1 transitions of Eu3+ ions due to change in the alkaline earth metal ions. The decay of the 5D0 level shows single exponential and less sensitive to Eu3+ ions concentration as well as MgO/SrO/BaO modifiers.

Kumar, K. Upendra; Babu, S. Surendra; Rao, Ch. Srinivasa; Jayasankar, C. K.

2011-06-01

99

Evidence for low-temperature ultrapotassic siliceous fluids in subduction zone environments from experiments in the system K 2O?MgO?Al 2O 3?SiO 2?H 2O (KMASH)  

NASA Astrophysics Data System (ADS)

Experiments in the system K 2O?MgO?Al 2O 3?SiO 2?H 2O (KMASH) were undertaken with the piston-cylinder-apparatus to study the reactions: 1) phengite±quartz+K,Mg-rich siliceous fluid=feldspar+phologopite+H 2O 2) phengite+talc+K,Mg-rich siliceous fluid=phlogopite+quartz/coesite+H 2O at temperatures between 400 and 700°C. The ultrapotassic fluid appearing at pressures above 15 kbar on the low-temperature sides of the corresponding reaction curves, which show positive d P/d T slopes, is probably supercritical. The P- T positions of the reactions are compatible with KMASH mineral reactions studied previously and with melting investigations in the KMASH system undertaken at temperatures higher than 700°C. It is possible that natural rocks, chiefly K-rich metasediments subducted as minor portions of the oceanic crust, could give rise to low-temperature ultrapotassic fluids, mainly at temperatures between 300° to 600°C and pressures between 15 and 30 kbar. The ascending K-rich fluids would penetrate the overlying mantle to metasomatize it. After termination of the subduction process, heating of this mantle material, previously cooled by the subducted lithosphere, could lead to the formation of high-temperature K-rich magmas.

Massonne, Hans-Joachim

1992-11-01

100

The Role of CaO in the Ziegler–Natta Catalyst for Propylene Polymerization  

Microsoft Academic Search

A certain amount of CaO enhanced the activity of Ziegler–Natta catalyst during propylene polymerization, but decreased isotacticity.\\u000a The results indicated that CaO accelerated the initial polymerization rates and improved catalyst against deactivation without\\u000a effects on melting point, crystallinity and morphology of polypropylene. The electron spin resonance (ESR) results revealed\\u000a that CaO facilitated the reduction of Ti4+ species.

Kitti Tangjituabun; Bunjerd Jongsomjit; Piyasan Praserthdam

2006-01-01

101

Optical Properties and Photoactivity of The Pigmentary TiO2 Doped with P2O5, K2O, Al2O3 and Sb2O3  

NASA Astrophysics Data System (ADS)

The influence of the increasing content of antimony calculated to Sb2O3 (0.08-0.57 mol%) with the constant amount of the other additives (calculated to P2O5, K2O, Al2O3) on the optical properties and photostability of doped rutile has been investigated. The properties of the obtained TiO2-PKAlSb samples were compared to the commercial TiO2-PKAl composition. The starting material was the concentrated suspension of technical-grade hydrated titanium dioxide (HTD). The dopant agents' solutions were introduced to HTD. Prepared samples were calcined with gradually increasing process temperature. The XRD analysis was used to determine the rutile content in the TiO2 samples. Optical properties of modified titanium dioxide have been determined spectrophotometrically by measuring the colour in the white (brightness, white tone) and grey system (relative lightening power, grey tone). Photostability was characterized by the white lead-glycerin test with UV-Vis light. It was observed that with the increasing content of antimony in rutile TiO2, doped with phosphates, potassium and aluminium, the brightness and grey tone were increasing but white tone decreased. The changes of the relative lightening power values were insignificant. Comparing the samples of TiO2-PKAlSb with the TiO2-PKAl composition it was observed that titanium dioxide doped with antimony had better white and grey tone. The increasing Sb2O3 content in the TiO2 caused the improvement of the photostability.

Gle?, M.; Grzmil, B.

2011-05-01

102

Effect of Bi2O3 addition on electron paramagnetic resonance, optical absorption, and conductivity in vanadyl-doped Li2O-K2O-Bi2O3-B2O3 glasses.  

PubMed

Glasses with composition 15Li(2)O-15K(2)O-xBi(2)O(3)-(65 - x)-B(2)O(3)/5V(2)O(5) (3 ? x ? 15) have been prepared by the conventional melt quench technique. The electron paramagnetic resonance spectra of VO(2+) in these glasses have been recorded in the X-band frequency (?9.3 GHz) at room temperature. The spin Hamiltonian parameters and covalency rates were evaluated. It was found that the V(4+) ions exist as vanadyl (VO(2+)) ions and are in an octahedral coordination with a tetragonal compression. The covalency rates (1 - ?(2)) and (1 - ?(2)) indicate moderate covalency for the ?- and ?-bonds. It was observed that the spin-Hamiltonian parameters depend slightly on the relative concentration of Bi(2)O(3). The optical properties of this glass system are studied from the optical absorption spectra recorded in the wavelength range 200-800 nm. The fundamental absorption edge has been identified from the optical absorption spectra. The values of optical band gap for indirect allowed transitions have been determined using available theories. The direct current electrical conductivity, ?, has been measured in the temperature range 373-573 K. The conductivity decreases with the increase in Bi(2)O(3) concentration. This has been discussed in terms of the decrease in the number of mobile ions and their mobility. An attempt is made to correlate the EPR, optical, and electrical results and to find the effect of Bi(2)O(3) content on these parameters. PMID:21247083

Subhadra, M; Kistaiah, P

2011-02-17

103

Experimental study of subsolidus phase relations and mixing properties of pyroxene and plagioclase in the system Na2O-CaO-Al2O3-SiO2  

NASA Astrophysics Data System (ADS)

In the system Na2O-CaO-Al2O3-SiO2 (NCAS), the equilibrium compositions of pyroxene coexisting with grossular and corundum were experimentally determined at 40 different P-T conditions (1,100 1,400° C and 20.5 38 kbar). Mixing properties of the Ca-Tschermak — Jadeite pyroxene inferred from the data are (J, K): 410_2004_Article_BF00381556_TeX2GIFE1.gif begin{gathered} G_{Px}^{xs} = X_{{text{CaTs}}} X_{{text{Jd}}} [14,810 - 7.15T - 5,070(X_{{text{CaTs}}} - X_{{text{Jd}}} ) \\ {text{ }} - 3,350(X_{{text{CaTs}}} - X_{{text{Jd}}} )^2 ] \\ The excess entropy is consistent with a complete disorder of cations in the M2 and the T site. Compositions of coexisting pyroxene and plagioclase were obtained in 11 experiments at 1,190 1,300° C/25 kbar. The data were used to infer an entropy difference between low and high anorthite at 1,200° C, corresponding to the enthalpy difference of 9.6 kJ/mol associated with the Cbar 1=Ibar 1 transition in anorthite as given by Carpenter and McConnell (1984). The resulting entropy difference of 5.0 J/ mol · K places the transition at 1,647° C. Plagioclase is modeled as ideal solutions, Cbar 1 and Ibar 1, with a non-first order transition between them approximated by an empirical expression (J, bar, K): 410_2004_Article_BF00381556_TeX2GIFE2.gif ? G_T = ? G_{1,473} left[ {1 - 3X_{Ab} tfrac{{T^4 - 1,473^4 }}{{left( {1,920 - 0.004P} right)^4 - 1,473^4 }}} right], where 410_2004_Article_BF00381556_TeX2GIFE3.gif ? G_{1,473} = 9,600 - 5.0T - 0.02P The derived mixing properties of the pyroxene and plagioclase solutions, combined with the thermodynamic properties of other phases, were used to calculate phase relations in the NCAS system. Equilibria involving pyroxene+plagioclase +grossular+corundum and pyroxene+plagioclase +grossular+kyani te are suitable for thermobarometry. Albite is the most stable plagioclase.

Gasparik, Tibor

1985-05-01

104

Temperature-dependent luminescence and temperature-stimulated NIR-to-VIS up-conversion in Nd3+-doped La2O3-Na2O-ZnO-TeO2 glasses  

NASA Astrophysics Data System (ADS)

Telluride glasses of the composition xNd2O3-(7-x)La2O3-3Na2O-25ZnO-65TeO2, where (0?x?7) were prepared by the melt quench technique. Some physical and optical properties of the glasses were evaluated. The thermal behavior i.e. glass transition and crystallization temperatures were studied by using TGA-DTA technique. Optical properties of Nd3+-doped telluride glasses were investigated between 298 and 700 K. Basing on the obtained values of J-O parameter values (×10-20 cm2: ?2=4.49±0.84, ?4=5.03±0.61, ?6=4.31±0.73), the radiative transition probabilities (AT), radiative lifetimes (?R), fluorescence branching ratios (?) and emission cross-sections (?em) were calculated for the 4F3/2?4IJ/2 (where J=9, 11 and 13) transitions of Nd3+ ions. The ?R value of the 4F3/2 level amount to 164 ?s and is slightly higher than the measured decay time of 162 ?s. With the increasing of Nd2O3 concentration from 0.5 to 7.0 mol% the experimental lifetime of the fluorescent level decreases from 162 to 5.6 ?s. The estimated quantum efficiency amount to 100%, based on a comparison of ?R and the experimental decay time of a slightly doped Nd3+ telluride glass. An analysis of the non-radiative decay was based on the cross-relaxation mechanisms. The 4F3/2?4I9/2 and 4F5/2?4I9/2 transitions were analyzed with respect to the fluorescence intensity ratio (FIR) and were found to be temperature dependent. Infrared-to-visible up-conversion emissions with a maximum at 603.0 and 635.3 nm were observed at high temperatures using the 804 nm excitation and are due to the 4G5/2?4I9/2 and 4G5/2?4I11/2 transitions of Nd3+ ions, respectively. The near quadratic dependence of fluorescence on excitation laser power confirms that two photons contribute to up-conversion of the orange emissions. The temperature-stimulated up-conversion excitation processes have been analyzed in detail. The optical results indicate that the investigated glasses are potentially applicable as a 1063 nm laser host as well as an optical sensor for temperature measurements.

Sobczyk, Marcin

2013-04-01

105

Electronic Energy Transfer on CaO Surfaces  

SciTech Connect

We excite low-coordinated surface sites of nanostructured CaO samples using tunable UV laser pulses and observe hyperthermal O-atom emission indicative of an electronic excited-state desorption mechanism. The O-atom yield increases dramatically with photon energy, between 3.75 and 5.4 eV, below the bulk absorption threshold. The peak of the kinetic energy distribution does not increase with photon energy in the range 3.9 to 5.15 eV. These results are analyzed in the context of a laser desorption model developed previously for nanostructured MgO samples. The data are consistent with desorption induced by exciton localization at corner-hole trapped surface sites following either direct corner excitation or diffusion and localization of excitons from higher coordinated surface sites.

Joly, Alan G.; Beck, Kenneth M.; Hess, Wayne P.

2008-09-28

106

Effects of Sm 3+/Yb 3+ co-doping and temperature on the Raman, IR spectra and structure of [TeO 2-GeO 2-K 2O-Sm 2O 3/Yb 2O 3] glasses  

NASA Astrophysics Data System (ADS)

Effects of Sm 3+/Yb 3+ co-doping on Raman scattering, IR absorption, temperature dependence of the Raman spectra up to 210 °C and the structure of two glass systems of the composition (80TeO 2-10GeO 2-8K 2O-2Sm 2O 3/Yb 2O 3) is discussed. It was found that the addition of Yb 3+ to the glass very strongly enhances the intensities of the antistokes’ Raman bands at 155, 375, 557 and 828 cm -1 and quenches both the intensities of the stokes’ vibration modes of the TeO 4 units in the range of 120-770 cm -1 and the intensities of the OH - stretching vibration modes in the range of 2600-3300 cm -1. Sm 2O 3/Yb 2O 3 rare earth co-doping has a great influence on removing and/or changing the nature of the OH - groups. The appearance and splitting of the stretching vibration modes of the OH - groups at lower frequencies (2770, 2970 cm -1) for the Sm +3 singly doped glass sample, compared to the band at ?3200 cm -1 for the Sm 3+/Yb 3+ co-doped glass sample, suggested that the OH - groups are more strongly bonded and incorporated with the glass matrix for the singly doped glass. Heating the sample up continuously weakens the hydrogen bonding of the OH - groups to the glass matrix leading to creation of NBO and breakdown of the connectivity of the OH - groups to the TeO 4, TeO 3+1 and TeO 3 structural units. Raman bands at 286, 477, 666 and 769 cm -1 were assigned to its respective vibrations of Te 2O 7, TeO 4-4 species, the (Te-O-Te) bending vibrations of the TeO 4 triagonal bipyramids (tbps), the axial symmetric stretching vibration modes (Te ax-O) s with bridging oxygen BO atoms and to the (Te-O) nbo non-bridging stretching vibration modes of the TeO 3+1 and/or TeO 3 pyramids.

Shaltout, I.; Badr, Y.

2006-05-01

107

Thermal reactions of aromatics with CaO. Technical progress report, September 1, 1981April 30, 1982  

Microsoft Academic Search

Research in this period focussed on understanding the calcination chemistry of CaO and its relation to the activity of CaO for pyrolysis of aromatic compounds. The main objectives are to arrive at a set of optimal calcination conditions under which to prepare CaO samples for systematic studies of the thermal reactions of aromatics with CaO, and to relate the chemical

J. P. Longwell; C. K. Lai; G. C. Williams; W. A. Peters

1982-01-01

108

CaO interaction in the staged combustion of coal  

SciTech Connect

The LIMB (limestone injection multi-stage burner) process offers special potential for reducing NO/sub x/ and SO/sub x/ by at least 50 percent in coal combustion. This is to be accomplished by adding limestone with fuel and/or air in a low NO/sub x/ burner. This program has been directed to defining the chemistry and kinetics necessary to optimize sulfur capture in LIMB combustion. More specifically, this program has attempted to clarify the role of calcium sulfide in LIMB chemistry. When limestone is added in a staged burner, there is a strong possibility that under certain circumstances CaS is produced in the reducing (fuel-rich) zone of the burner. Since CaS is more stable than CaSO/sub 4/, this affords the opportunity to (1) operate the burner at a higher temperature, 2200 to 2500 F, (2) pass the CaS rapidly through the high temperature zone (before dissociation), and (3) complete the combustion in a lean (air-rich) region where the sulfur is finally retained in CaSO/sub 4/. For these reasons this program has concentrated on the high temperature chemistry and kinetics of CaS. To achieve the program objective, the program was divided into three tasks. These involved (1) a study of CaS formation, (2) a brief examination of CaS oxidation, and (3) a laboratory examination of the combustion of coal in the presence of CaO under first stage, fuel-rich conditions. In the most general sense, the study has shown that the formation of CaS in the reducing zones of the burner may be restricted by competing kinetics and thermodynamics. The addition of lime in LIMB will require special care to optimize the ability to capture sulfur. 36 references, 44 figures, 10 tables.

Levy, A.; Merryman, E.L.; Rising, B.W.

1983-12-19

109

Nonisothermal Thermogravimetric Analysis of Thai Lignite with High CaO Content  

PubMed Central

Thermal behaviors and combustion kinetics of Thai lignite with different SO3-free CaO contents were investigated. Nonisothermal thermogravimetric method was carried out under oxygen environment at heating rates of 10, 30, and 50°C min?1 from ambient up to 1300°C. Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) methods were adopted to estimate the apparent activation energy (E) for the thermal decomposition of these coals. Different thermal degradation behaviors were observed in lignites with low (14%) and high (42%) CaO content. Activation energy of the lignite combustion was found to vary with the conversion fraction. In comparison with the KAS method, higher E values were obtained by the FWO method for all conversions considered. High CaO lignite was observed to have higher activation energy than the low CaO coal.

Pintana, Pakamon

2013-01-01

110

Catalytic reduction of nitric oxide by methane over CaO catalyst  

Microsoft Academic Search

The selective catalytic reduction of nitric oxide by methane was studied over CaO catalyst in a bubbling fluidized bed in\\u000a the temperature range of 800–900 °C, in which NO cannot be reduced by CH4 without CaO catalyst. The nitric oxide conversion was found to depend on oxygen and CH4 feed concentration, and also on temperature. In addition, the presence of

Wei Xu; Huiling Tong; Changhe Chen; Xuchang Xu

2008-01-01

111

Rapid simultaneous multi-element determination of soils and environmental samples with polarizing energy dispersive X-ray fluorescence (EDXRF) spectrometry using pressed powder pellets  

Microsoft Academic Search

A rapid simultaneous multi-element analysis method for soils and environmental samples has been established using polarizing energy dispersive X-ray fluorescence (EDXRF) spectrometry. The pressed powder pellet technique was adopted because it is simple and requires no specialized skills for sample preparation. The analytes examined were: Na2O, MgO, Al2O3, SiO2, P2O5, K2O, CaO, TiO2, MnO, Fe2O3, V, Cr, Co, Ni, Cu,

Hisaya Matsunami; Kenji Matsuda; Shin-ichi Yamasaki; Kazuhiko Kimura; Yasumasa Ogawa; Yoshinori Miura; Isao Yamaji; Noriyoshi Tsuchiya

2010-01-01

112

Composite Films of Gelatin and Hydroxyapatite\\/Bioactive Glass for Tissue-Engineering Applications  

Microsoft Academic Search

Cross-linked gelatin\\/hydroxyapatite\\/bioactive glass (G\\/HA\\/CEL2) films with different compositions (100:0:0 (G1); 30:70:0 (G2); 30:0:70 (G3); 30:35:35 (G4) (%, w\\/w\\/w)) were prepared as scaffold materials for tissue-engineering applications, particularly in the field of bone repair. A bioactive glass with 45% SiO2, 3% P2O5, 26% CaO, 7% MgO, 15% Na2O and 4% K2O molar composition was selected (CEL2). Genipin was used as a

Piergiorgio Gentile; Valeria Chiono; Francesca Boccafoschi; Francesco Baino; Chiara Vitale-Brovarone; Enrica Vernè; Niccoletta Barbani; Gianluca Ciardelli

2010-01-01

113

Evaluation of distribution, mobility and binding behaviour of heavy metals in surficial sediments of Louro River (Galicia, Spain) using chemometric analysis: a case study  

Microsoft Academic Search

Contents of total and extractable heavy metals, carbonates, MnO and Fe2O3, organic matter, and matrix components such as SiO2, Al2O3, CaO, Na2O, MgO, TiO2, K2O and P2O5 are used along with principal component analysis (PCA) for studying distribution, mobility and binding behaviour of Cd, Cr, Cu, Ni and Pb in the Louro River (Galicia, Spain). Eleven surficial sediment samples were

A. V. Filgueiras; I. Lavilla; C. Bendicho

2004-01-01

114

Thermodynamic analysis on solid-state reduction of CaO particles dispersed in Mg–Al alloy  

Microsoft Academic Search

AZ61B alloy powder composite with Al2Ca fine dispersoids was developed by using CaO additive particles as raw materials. For synthesis of Al2Ca in the matrix, CaO particles were elementally and uniformly mixed with AZ61B alloy chips via ECABMA process. The mechanism in formation of Al2Ca intermetallics was investigated by XRD and SEM–EDS analysis when AZ61B alloy green compacts containing CaO

Katsuyoshi Kondoh; Junji Fujita; Junko Umeda; Hisashi Imai; Keitaro Enami; Masaki Ohara; Takanori Igarashi

2011-01-01

115

The Cracking Experiment Research of Tar by CaO Catalyst  

NASA Astrophysics Data System (ADS)

The tar from rice husk gasification for power generation was taken as an example to be catalytically cracked by CaO catalyst. The experimental results showed the cracking efficiency of tar greatly increased from 28.66% by thermal cracking to 65.6% by catalytic cracking, the gas compositions from tar being cracked were H2, CO, CH4, and CO2, and the H2 was a majority of them. The DSC and XRT analysis revealed that the deposit carbon could be found after tar was catalytically cracked and the deposit carbon efficiency could reach 30.51%. The SEM photographs of CaO catalyst used as catalyst showed that the CaO catalyst was enwrapped by the deposit carbon and decreased its catalytic activity, at the same time, the pressure drop of gas passing through catalyst bed increased because of the deposit carbon, it was different for us to operate the cracking reactor of tar and CaO catalyst in the cracking reactor must be regenerated for its stable operation.

Lit, X. H.; Mi, T.; We, Z. S.; Chen, Y. F.; Wu, Q. X.

116

An analysis of the effect of carbonation conditions on CaO deactivation curves  

Microsoft Academic Search

There is a growing interest in developing high temperature CO2 capture looping systems using CaO as a regenerable sorbent. The evolution of the sorbent properties with the number of cycles plays an important role in the design of these systems. One of the key variables to be determined is the sorbent's CO2 carrying capacity at the end of the so

B. Arias; J. C. Abanades; G. S. Grasa

2011-01-01

117

The Cao Method for Determining the Minimum Embedding Dimension of Sea Clutter  

Microsoft Academic Search

To verify whether sea clutter has chaotic character or not, the minimum embedding dimension and time delay in phase space reconstruction are needed. This paper discusses two defects of false nearest neighbors (FNN) for calculating embedding dimension: noise sensitivity and effect of subjective parameter. It was confirmed that Cao method could overcome these limitations and settle on a suitable embedding

Xiaoke Xu; Xiaoming Liu; Xiaonan Chen

2006-01-01

118

Highly basic CaO nanoparticles in mesoporous carbon materials and their excellent catalytic activity.  

PubMed

Highly basic CaO nanoparticles immobilized mesoporous carbon materials (CaO-CMK-3) with different pore diameters have been successfully prepared by using wet-impregnation method. The prepared materials were subjected to extensive characterization studies using sophisticated techniques such as XRD, nitrogen adsorption, HRSEM-EDX, HRTEM and temperature programmed desorption of CO2 (TPD of CO2). The physico-chemical characterization results revealed that these materials possess highly dispersed CaO nanoparticles, excellent nanopores with well-ordered structure, high specific surface area, large specific pore volume, pore diameter and very high basicity. We have also demonstrated that the basicity of the CaO-CMK-3 samples can be controlled by simply varying the amount of CaO loading and pore diameter of the carbon support. The basic catalytic performance of the samples was investigated in the base-catalyzed transesterification of ethylacetoacetate by aryl, aliphatic and cyclic primary alcohols. CMK-3 catalyst with higher CaO loading and larger pore diameter was found to be highly active with higher conversion within a very short reaction time. The activity of 30% CaO-CMK3-150 catalyst for transesterification of ethylacetoacetate using different alcohols increases in the following order: octanol > butanol > cyclohexanol > benzyl alcohol > furfuryl alcohol. PMID:22905508

Raja, Pradeep Kumar; Chokkalingam, Anand; Priya, Subramaniam V; Balasubramanian, Veerappan V; Benziger, Mercy R; Aldeyab, Salem S; Jayavell, Ramasamy; Ariga, Katsukiho; Vinu, Ajayan

2012-06-01

119

Effect of specific surface area on the reactivity of CaO with SOâ  

Microsoft Academic Search

The rate of reaction of calcined limestone with SOâ and Oâ was measured at conditions that eliminate all resistances not associated with the CaO grain surface. Reactivity increased with the square of the BET surface area when grain size was varied as an experimental parameter. The observed effects of surface area and temperature account for the SOâ capture reported for

R. H. Borgwardt; K. R. Bruce

1986-01-01

120

CO 2 chemisorption at Ca and CaO surfaces: a study with MIES, UPS(HeI) and XPS  

NASA Astrophysics Data System (ADS)

Metastable impact electron spectroscopy (MIES) in combination with UPS(HeI) and X-ray photoelectron spectroscopy was applied to study chemisorption of CO 2 on Ca and CaO films at room temperature. Ca surfaces were prepared by evaporating Ca films (ca 20 nm thickness) on a clean Si(111) surface; information on the topological structure of the Ca film was obtained with scanning tunneling microscopy (STM). CaO films were produced by exposing Ca films to O 2 or N 2O. Ca surfaces exposed to CO 2 become terminated by carbonate complexes (CO 2-3) while features typical for (Ca-O) bonds are detected underneath the surface. A closed carbonate layer forms also when a CaO film is exposed to CO 2. The strong reactivity of the CaO surface against CO 2 is in agreement with recent results of cluster calculations.

Ochs, D.; Braun, B.; Maus-Friedrichs, W.; Kempter, V.

1998-11-01

121

Materials compatibility during the chlorination of molten CaCl/sub 2/. CaO salts. [CaCl/sub 2/. CaO salt  

SciTech Connect

As part of our effort to develop a semicontinuous PuO/sub 2/ reduction process, we are investigating promising materials for containing a 900/sup 0/C molten CaCl/sub 2/ . CaO chlorination reaction. We want the material to contain this reaction and to be reusable. We tested candidate materials in a simulated salt (no plutonium) using anhydrous HCl as the chlorinating agent. Data are presented on the performance of 36 metals and alloys, 9 ceramics, and 3 coatings.

Rense, C.E.C.; Fife, K.W.; Bowersox, D.F.; Ferran, M.D.

1987-01-01

122

[Determination of major elements in superphosphate by X-ray fluorescence spectrometry].  

PubMed

Phosphate fertilizer is one of the most important fertilizers. The authors determined nine kinds of major elements in superphosphate, the most important phosphate fertilizer, by X-ray fluorescence spectrometry. The detection range of SiO2, Al2O3, TFe2O3, MnO, MgO, CaO, Na2O, K2O and P2O5 is 15.0%-90.0%, 0.20%-25.0%, 0.20%-25.0%, 0.01%-0.35%, 0.20%-40.0%, 0.10%-35.0%, 0.10%-7.50%, 0.05%-7.50% and 1.00%-100.00% respectively, and the precision of the method for SiO2, Al2O3, TFe2O3, MnO, MgO, CaO, Na2O, K2O and P2O5 range from 0.20% to 0.005%, so the method of X-ray fluorescence spectrometry is a fast and effectual method for detecting the composition of phosphate fertilizer. The contents of the above elements showed (1) the detected superphosphate content is 18.101% of P2O5, which is accordant to the labeled level (> or = 16%); (2) the detected superphosphate contains much SiO2, TFe2O3, MgO, CaO and K2O, which are necessary for plant growth and the content of which is 16.954%, 1.495%, 1.580%, 21.428% and 1.585% respectively. These data showed that phosphate fertilizer sometimes can supply some trace elements for plants, but we should eliminate the interference effect of these elements when we research the role of phosphorus; (3) superphosphate contains 3.225% of Al2O3, so the authors should attention to the aluminium poison when superphosphate is used chronically. PMID:19271522

Rui, Yu-Kui; Li, He; Shen, Jian-Bo; Zhang, Fu-Suo

2008-11-01

123

Thermal diffusivity of sintered 12CaO×7Al2O3  

NASA Astrophysics Data System (ADS)

The thermal diffusivity and free carrier diffusion coefficient of 12CaO× 7 Al{2}O{3} (C12A7) sintered for different times in air or hydrogen followed by treatment with UV light were determined from photoacoustic phase and amplitude spectra obtained using the photoacoustic method with a transmission detection configuration. The influence of the sintering time on the values of the obtained parameters was analyzed and also the different sintering procedures.

Nikoli?, P. M.; Lukovi?, D. T.; Savi?, S. M.; Milovanovi?, A. M.; Uki?, S. R.; Nikoli?, M. V.; Stamenovi?, B.

2008-01-01

124

Characteristics of HCN removal using CaO at high temperatures  

SciTech Connect

Experimental investigation on the removal of hydrogen cyanide (HCN) using calcium oxide (CaO) was carried out in a fixed bed reactor at temperature ranging from 300 to 1173 K, and the original HCN was produced during the pyrolysis of pyridine. Effects of temperature, volume space velocity, and initial HCN concentration on HCN removal were discussed. The results of temperature-programmed experiments show that temperature is the main factor affecting HCN removal. With the formation of CO, HCN starts to decrease from 473 K, and remains unchanged from 673 to 873 K. At 873 K, there is a further decrease in HCN without CO formation, and when temperature is higher than 1023 K, HCN is removed completely. In the isothermal experiments, CaCN{sub 2} was detected at 723 K, but at higher temperatures of 923 and 1123 K, there was no CaCN{sub 2} in the solid residues, and the nitrogen in the removed HCN was equal to that in the formed N{sub 2}. This indicates that at a lower temperature CaO is consumed to remove HCN, CaO + 2HCN {yields} CaCN{sub 2} + CO + H{sub 2}; but at a higher temperature, CaO acts as a catalyst for HCN removal, 2C{sub i}H{sub j} + 2HCN {yields} N{sub 2} + (j + 1 - k)H{sub 2} + 2C{sub I} + 1H{sub k}. The investigation on the removal efficiency shows that there is a critical temperature and a critical volume space velocity at which the HCN removal efficiency is able to reach up to 100%. 41 refs., 9 figs., 2 tabs.

Houzhang Tan; Xuebin Wang; Congling Wang; Tongmo Xu [Xi'an Jiaotong University, Shaanxi (China). State Key Laboratory of Multiphase Flow in Power Engineering

2009-03-15

125

Development of new CaO based sorbent materials for CO 2 removal at high temperature  

Microsoft Academic Search

This study focuses on developing a CO2 sorbent with high sorption capacity (higher than 6mol\\/kg of sorbent) and long life-time. The target value of the sorption capacity was attained by screening and testing two different microporous CaO precursors, Ca(OH)2 and Ca(CH3COO)2. Between them, calcined calcium acetate showed the highest CO2 uptake ability, 50% increase of the weight of the sorbent

Christina S. Martavaltzi; Angeliki A. Lemonidou

2008-01-01

126

Porous carbon material containing CaO for acidic gas capture: preparation and properties.  

PubMed

A one-step process for the preparation of CaO-containing porous carbons is described. Mixtures of poly(ethylene terephthalate) with natural limestone were pyrolyzed and thus hybrid sorbents could be easily obtained. The polymeric material and the mineral served as a carbon precursor and CaO delivering agent, respectively. We discuss effects of the preparation conditions and the relative amounts of the raw materials used for the preparations on the porosity of the hybrid products. The micropore areas and volumes of the obtained products tended to decrease with increasing CaO contents. Increase in the preparation temperature entailed a decrease in the micropore volume, whereas the mesopore volume increased. The pore creation mechanism is proposed on the basis of thermogravimetric and temperature-programmed desorption measurements. The prepared CaO-containing porous carbons efficiently captured SO2 and CO2 from air. Washing out of CaO from the hybrid materials was confirmed as a suitable method to obtain highly porous carbon materials. PMID:23743266

Przepiórski, Jacek; Czy?ewski, Adam; Pietrzak, Robert; Toyoda, Masahiro; Morawski, Antoni W

2013-12-15

127

The adsorption of oxygen and water on Ca and CaO films studied with MIES, UPS and XPS  

NASA Astrophysics Data System (ADS)

Metastable induced electron spectroscopy (MIES), Ultraviolet photoelectron spectroscopy (UPS), and X-ray photoelectron spectroscopy (XPS) are employed to study the adsorption of water on Ca and CaO films as well as the adsorption of oxygen on Ca films. Ca films are prepared by evaporation of Ca onto clean Si(1 0 0) substrates. CaO films are produced by Ca evaporation in an oxygen atmosphere at a substrate temperature of 400 °C. Gas adsorption on the Ca films at room temperature, both for oxygen and water, is initiated by complete dissociation of the impinging molecules leading to the formation of Ca-O bonds. Exposure to water furthermore leads to the formation of hydroxyl groups via hydrogen abstraction from water forming a complete surface layer. Hydroxyl groups are also formed upon exposure of CaO films to water, but to a significantly smaller amount compared to Ca films exposed to water.

Bebensee, F.; Voigts, F.; Maus-Friedrichs, W.

2008-05-01

128

Pool-Frenkel effect and high frequency dielectric constant determination of semiconducting P2O5-Li2MoO4-Li2O and P2O5-Na2MoO4-Na2O bulk glasses  

NASA Astrophysics Data System (ADS)

The ternary 70P2O5-10Li2MoO4-20Li2O and 70P2O5-10Na2MoO4-20Na2O glasses, prepared by the press-melt quenching technique, were studied at temperatures between 298 and 418 K for their high dc electric field properties. For the above purpose, the effect of a strong electric field on the dc conduction of these amorphous bulk samples was investigated using the gap-type electrode configuration. At low electric fields, the current-voltage ( I — V) characteristics have a linear shape, while at high electric fields (> 103 V/cm), bulk samples show nonlinear effects (nonohmic conduction). Current-voltage curves show increasing departure from Ohm’s law with increasing current density, leading to critical phenomena at a maximum voltage (threshold voltage), known as switching (switch from a low-conduction state to a higher-conduction state at threshold voltage). The Pool-Frenkel high-field effect was observed at electrical fields of about 103 104 V/cm; then the lowering factor of the potential barrier, the high frequency dielectric constant, and the refractive index of these glasses were determined.

Souri, Dariush; Elahi, Mohammad; Yazdanpanah, Mohammad S.

2008-06-01

129

Self-healing of defects in CaO coatings on V-5%Cr5%Ti in liquid lithium  

Microsoft Academic Search

In-situ electrical resistance of CaO coatings produced on V-5%Cr-5%Ti by exposure of the alloy to liquid Li that contained 0.5-85 wt % dissolved Ca was measured as a function of time at temperatures between 250 and 600°C. Examination of the specimens after cooling to room temperature revealed no spallation, but homogeneous crazing cracks were present in the CaO coating. Additional

J. H. Park; T. F. Kassner

1994-01-01

130

The adsorption of oxygen and water on Ca and CaO films studied with MIES, UPS and XPS  

Microsoft Academic Search

Metastable induced electron spectroscopy (MIES), Ultraviolet photoelectron spectroscopy (UPS), and X-ray photoelectron spectroscopy (XPS) are employed to study the adsorption of water on Ca and CaO films as well as the adsorption of oxygen on Ca films. Ca films are prepared by evaporation of Ca onto clean Si(100) substrates. CaO films are produced by Ca evaporation in an oxygen atmosphere

F. Bebensee; F. Voigts; W. Maus-Friedrichs

2008-01-01

131

Correlations for the combustible sulfur contents of Turkish coals from sulfur forms and CaO analyses  

Microsoft Academic Search

Total and combustible sulfur, CaO, ash and sulfur forms in 19 selected Turkish coals with widely varying characteristics (from bituminous coal to low-grade lignite) were determined according to ASTM standards. The total sulfur, combustible sulfur and CaO contents (wt% db) varied over wide ranges: 0.5–12.9, 0.25–12.8 and 0.4–14.1 respectively. Correlations based on the pyritic, organic and sulfate sulfur forms gave

Davut Uzun; Sibel Özdo?an

1997-01-01

132

Modification of CaO by organic alumina precursor for enhancing cyclic capture of CO{sub 2} greenhouse gas  

SciTech Connect

The modification of CaO sorbent with organic alumina precursor to enhance the sorption capacity during cyclic capture is demonstrated in this study. The results indicate that during the 10 min sorption time for each cycle, the CO{sub 2} sorption capacity of original CaO sorbent is significantly decreased from 0.27 to 0.19 and 0.12 g CO{sub 2}/g sorbent after 5 and 60 cycles, respectively. On the other hand, the organic alumina modified CaO has a fresh capacity of 0.22 g CO{sub 2}/g sorbent, it increases to 0.24 g CO{sub 2}/g sorbent after 5 cycles, and then decreases to around 0.15 g CO{sub 2}/g sorbent after 60 cycles. When increasing the sorption time to 60 min at the 66th cycle, the sorption capacity of original CaO is 0.2, whereas it is 0.26 g CO{sub 2}/g sorbent for organic alumina modified CaO. The results demonstrate that by adding only 5% by weight of Ca{sub 12}Al{sub 14}O{sub 3}3 species into the CaO sorbent, the CO{sub 2} sorption capacity can be enhanced up to similar to 27% by weight.

Chen, Y.T.; Karthik, M.; Bai, H. [National Chiao Tung University, Hsinchu (Taiwan). Inst. of Environmental Engineering

2009-06-15

133

The adsorption of CO 2 and CO on Ca and CaO films studied with MIES, UPS and XPS  

NASA Astrophysics Data System (ADS)

Metastable Induced Electron Spectroscopy (MIES), Ultraviolet Photoelectron Spectroscopy (UPS), and X-ray Photoelectron Spectroscopy (XPS) are employed to study the adsorption of CO 2 and CO on Ca and CaO films. Ca films are prepared by evaporation of Ca onto clean Si(1 0 0) substrates. CaO films are produced by Ca evaporation in an oxygen atmosphere at a substrate temperature of 670 K. CO 2 interaction with the Ca films is initiated by dissociation of the impinging molecules leading to the formation of Ca-O bonds. These Ca-O bonds are subsequently consumed in the formation of a closed CaCO 3 layer on top of the surface. CO interaction with the Ca surfaces also leads to the dissociation of the molecule and the formation of Ca-O bonds. We find evidence for the subsequent formation of CO32- complexes on top of the surface. On CaO surfaces, both CO 2 and CO lead to the formation of a closed CaCO 3 top layer, though displaying very different reaction rates.

Voigts, F.; Bebensee, F.; Dahle, S.; Volgmann, K.; Maus-Friedrichs, W.

2009-01-01

134

Evolutionary Changes in Chlorophyllide a Oxygenase (CAO) Structure Contribute to the Acquisition of a New Light-harvesting Complex in Micromonas*?  

PubMed Central

Chlorophyll b is found in photosynthetic prokaryotes and primary and secondary endosymbionts, although their light-harvesting systems are quite different. Chlorophyll b is synthesized from chlorophyll a by chlorophyllide a oxygenase (CAO), which is a Rieske-mononuclear iron oxygenase. Comparison of the amino acid sequences of CAO among photosynthetic organisms elucidated changes in the domain structures of CAO during evolution. However, the evolutionary relationship between the light-harvesting system and the domain structure of CAO remains unclear. To elucidate this relationship, we investigated the CAO structure and the pigment composition of chlorophyll-protein complexes in the prasinophyte Micromonas. The Micromonas CAO is composed of two genes, MpCAO1 and MpCAO2, that possess Rieske and mononuclear iron-binding motifs, respectively. Only when both genes were introduced into the chlorophyll b-less Arabidopsis mutant (ch1-1) was chlorophyll b accumulated, indicating that cooperation between the two subunits is required to synthesize chlorophyll b. Although Micromonas has a characteristic light-harvesting system in which chlorophyll b is incorporated into the core antennas of reaction centers, chlorophyll b was also incorporated into the core antennas of reaction centers of the Arabidopsis transformants that contained the two Micromonas CAO proteins. Based on these results, we discuss the evolutionary relationship between the structures of CAO and light-harvesting systems.

Kunugi, Motoshi; Takabayashi, Atsushi; Tanaka, Ayumi

2013-01-01

135

Microporous crystal 12CaO x 7Al(2)O(3) encaging abundant O(-) radicals.  

PubMed

Extremely high concentrations (>1020 cm-3) of active oxygenic radicals, O- and O2-, have been created in the zeolitic crystal, 12CaO.7Al2O3 (C12A7), which can accommodate anions in its cavities. An increase in oxygen pressure and a decrease in water vapor pressure at high temperature enhance the formation of the radicals. The oxidation of Pt is observed on the surface of the material as a result of reaction with the active oxygens. PMID:11817934

Hayashi, Katsuro; Hirano, Masahiro; Matsuishi, Satoru; Hosono, Hideo

2002-02-01

136

Adsorption and dissociation kinetics of alkanes on CaO(100)  

NASA Astrophysics Data System (ADS)

The adsorption kinetics of ethane, butane, pentane, and hexane on CaO(100) have been studied by multi-mass thermal desorption (TDS) spectroscopy. The sample cleanliness was checked by Auger electron spectroscopy. A molecular and dissociative adsorption pathway was evident for the alkanes, except for ethane, which does not undergo bond activation. Two TDS peaks appeared when recording the parent mass, which are assigned to different adsorption sites/configurations of the molecularly adsorbed alkanes. Bond activation leads to desorption of hydrogen and several alkane fragments assigned to methane and ethylene formation. Only one TDS feature is seen in this case. Formation of carbon residuals was absent.

Chakradhar, A.; Liu, Y.; Schmidt, J.; Kadossov, E.; Burghaus, U.

2011-08-01

137

MAGNETIC BEHAVIOR OF IRON IONS IN THE P2O5·CaO GLASS MATRIX  

NASA Astrophysics Data System (ADS)

The temperature dependence of the magnetic susceptibility of xFe2O3·(100-x)-[P2O5·CaO] glasses with 0CaO glass matrix, the Fe2+ ion content is higher than that of the Fe3+ ions for glasses with x?10 mol%. For the glasses with x>35 mol%, the evaluated values of the ?eff indicate either the presence of Fe+ ions or the coordination influence on the magnetic moment of iron ions, but the presence of small quantities of the antiferromagnetic or ferrimagnetic interactions between iron ions in studied temperature range cannot be excluded. The high temperature susceptibility results indicate that the iron ions are isolated or participate in dipole-dipole interactions for glasses with x?35 mol% and are antiferromagnetically coupled for higher contents of Fe2O3.

ARDELEAN, I.; ANDRONACHE, C.; P??CU??, P.

138

Exciton-driven highly hyperthermal O-atom desorption from nanostructured CaO  

SciTech Connect

We report qualitatively new highly-hyperthermal (HHT) oxygen atom emission from nanostructured CaO excited by 6.4 eV nanosecond laser pulses. The kinetic energy distribution of emitted O-atoms peaks at 0.7 eV, which is over four times greater than previously observed. Excitation of MgO and CaO nanostructures with UV laser pulses is known to result in thermal and hyperthermal emission of oxygen atoms when photons with energies below and above the band gap, respectively, are used. The highly energetic atomic desorption we observe, following bulk excitation, challenges the conventional view that bulk excitation can only induce thermal desorption. Using density functional theory and an embedded cluster method, we propose a mechanism for this HHT feature based on the interaction of surface holes with bulk excitons. These experimental and theoretical results suggest that specific atomic desorption mechanisms in wide-bandgap materials can be controlled by selective electronic excitation of not only the surface but also the bulk of these materials

Sushko, Petr V.; Shluger, Alexander L.; Joly, Alan G.; Beck, Kenneth M.; Hess, Wayne P.

2011-01-27

139

Nb-doped CaO: an efficient electron donor system.  

PubMed

Transition metal atoms incorporated into insulating materials (oxides in particular) can deeply modify their adsorption properties. In particular, charge transfer to adsorbed species can be induced by the presence of substitutional dopants, which introduce new electronic states in the band gap of the host crystal. Here we show, by means of density functional theory calculations, that Nb represents an excellent dopant to turn the rather inactive CaO(100) surface into an electron-rich support. The charge transfer ability of the doped material is shown by comparing the adsorption properties of the electronegative Au atoms on pure and Nb-doped CaO. While in the first case the CaO-Au bonding is relatively weak and the Au atom is essentially neutral, in the Nb-doped system a much stronger adhesion is found due to a net charge transfer from the Nb dopant and to the formation of a gold anion. This mechanism occurs also for Nb in high oxidation states. Nb is thus an excellent modifier of the calcium oxide properties. PMID:24935643

Prada, Stefano; Giordano, Livia; Pacchioni, Gianfranco

2014-08-01

140

Ab initio study of CaO. The importance of atomic correlation and a bondlength question  

NASA Astrophysics Data System (ADS)

Extensively correlated ab initio potential energy and dipole moment curves are calculated for the X 1? +, a 3?, A 1? +, and 3? + states of CaO over the range 3.0 au ? R ? 6.0 au. The calculations are the first which correctly predict that X 1? + is the ground state of CaO. Vertical spectra, adiabatic spectra, spectroscopic constants, curve crossings, and dipole moments are determined. The 3? + results are apparently the first accurate values available. The dipole moment function is a linear function of bondlength for the ? states and 3? +. Two extrema occur in the dipole moment function of X 1? +. Combined with experimental results, this suggests that ?(X 1? +) exhibits a maximum near Re in the heavy alkaline earth monoxides. The ?(A 1? +) increases sharply near Re. The X 1? + calculations require special attention near Re: Localized ionic entities are involved which have different MO configurations and different correlation requirements. A second-order theory which correctly describes atomic correlation is necessary. The ab initio bondlengths are systematically larger than the experimental bondlengths by amounts that are greater than the expected accuracy limits of the calculations. This overestimation is also observed in KF, KCl and KOH, but ab initio bondlengths of the lighter metal alkali halides and alkaline earth monoxides agree closely with experiment. It appears that the core electrons must be responsible, possibly because of explicit core correlation requirements and/or relativistic corrections.

England, Walter B.

1980-11-01

141

Calcium precursors for the production of CaO sorbents for multicycle CO2 capture.  

PubMed

A screening of potential calcium precursors for the production of CaO sorbents for CO(2) capture at high temperature was conducted in this work. The precursors studied include microsized calcium carbonate (CC-CaO), calcium hydroxide (CH-CaO), nanosized (<70 nm) calcium carbonate (CC70 nm-CaO), nanosized (<160 nm) calcium oxide (CaO160 nm-CaO), calcium acetate hydrate (CA-CaO), calcium l-lactate hydrate (CL-CaO), calcium formate (CF-CaO), calcium citrate tetrahydrate (CCi-CaO), and calcium d-gluconate monohydrate (CG-CaO). The capture capability of these sorbents was investigated using a thermogravimetric analyzer (TGA) for multiple capture cycles. CG-CaO exhibited the best capacity for capturing CO(2) with a 1-min conversion of 65.9% and a 30-min conversion of 83.8% at the ninth cycle. Subsequently, a further parametric study was conducted to examine the effect of reaction conditions such as reaction temperature (550-750 degrees C) and CO(2) gas concentration (1-15%) on the capture capacity of CG-CaO. The sorbent CG-CaO also showed a much lower decomposition temperature and higher predicted residual conversion after prolonged cycles, compared with CC-CaO. PMID:20030311

Liu, Wenqiang; Low, Nathanael W L; Feng, Bo; Wang, Guoxiong; Diniz da Costa, João C

2010-01-15

142

Artificial total disc replacement versus fusion lumber degenerative disc disease: meta-analysis randomized controlled trials Review published: 2014. Bibliographic details: Rayo MJ Cao SS  

EPA Pesticide Factsheets

Did you mean: Artificial total disc replacement versus fusion lumber degenerative disc disease: meta-analysis randomized controlled trials Review published: 2014. Bibliographic details: Rayo MJ Cao SS ?

143

A conception of formation and operation of CaO coating in regime of self-healing  

NASA Astrophysics Data System (ADS)

Based on analysis of test results and literature data, a phenomenological model of components interaction in Li[Ca]-V[O] system is proposed. The model demonstrates a cyclic process. Each cycle consists of: I - oxygen transfer from vanadium into lithium; II - CaO layer grows and simultaneously titanium oxides dissolve and oxygen and titanium spreading into solid solution; III - liquid metal penetration into solid metal according to the mechanism of reactionary diffusion accompanied by triple oxide formation; IV - decay of a meta-stable triple oxide and recovering of CaO layer. Within the framework of the proposed model the possible behavior of a CaO coating under isothermal condition is considered.

Yeliseyeva, O. I.; Chernov, V. M.; Potapenko, M. M.; Tsaran, T. V.

2004-08-01

144

Self-healing of defects in CaO coatings on V-5%Cr-5%Ti in liquid lithium  

SciTech Connect

In-situ electrical resistance of CaO coatings produced on V-5%Cr-5%Ti by exposure of the alloy to liquid Li that contained 0.5-85 wt % dissolved Ca was measured as a function of time at temperatures between 250 and 600{degrees}C. Examination of the specimens after cooling to room temperature revealed no spallation, but homogeneous crazing cracks were present in the CaO coating. Additional tests to investigate the in-situ self-healing behavior of the cracks indicated that rapid healing occurred at >360{degrees}C.

Park, J.H.; Kassner, T.F.

1994-11-01

145

Corundum, rutile, periclase, and CaO in Ca,Al-rich inclusions from carbonaceous chondrites.  

PubMed

Four calcium,aluminum-rich inclusions from four carbonaceous chondrites-Allende, Acfer 082, Acfer 086, and Acfer 094-were studied by transmission electron microscopy. All inclusions contained at least two of the oxides periclase (MgO), rutile (TiO2), calcium oxide (CaO), and corundum (Al2O3). The oxides (50 to 200 nanometers in size) were found inside and at grain boundaries of the constituent minerals of the inclusions. Determining how these oxides formed may provide insight about condensation processes in the early solar nebula and the origin of refractory inclusions in chondrites. Formation of these oxides by exsolution is considered unlikely. An origin by kinetically controlled condensation appears more probable. PMID:8662462

Greshake, A; Bischoff, A; Putnis, A; Palme H

1996-05-31

146

Anti-inflammatory and hepatoprotective activity of peh-hue-juwa-chi-cao in male rats.  

PubMed

Peh-hue-juwa-chi-cao (PHJCC) is a common commercial name for the herbal extract of either Hedyotis diffusa (HD), H. corymbosa (HC), or Mollugo pentaphylla (MP). The present study was carried out to investigate the anti-inflammatory and hepatoprotective effects of these three extracts in rats. The results indicated that extracts of HC, HD and MP possess anti-inflammatory activity, and that MP has the greatest inhibition against carrageenan-induced paw edema. In the hepatoprotective study, results indicated that the three plant extracts significantly reduced the acute elevation of serum glutamate oxalate transaminase (sGOT) and serum glutamate pyruvate transaminase (sGPT) concentration, and alleviated the degree of liver damage 24 hours after the intraperitoneal administration of hepatotoxins. PMID:12230011

Lin, Chun-Ching; Ng, Lean-Teik; Yang, Jenq-Jer; Hsu, Yu-Fang

2002-01-01

147

Effect of the substitution of M2O3 (M = La, Y, In, Ga, Al) for CaO on the bioactivity of 2.5CaO x 2SiO2 glass.  

PubMed

Glasses were prepared whose compositions are defined by the following general formula: (2.5 - x)CaO x x/3M2O3 x 2SiO2 (0 < or = x < or = 0.6) (M = Ga, Al, In). Their bioactivity was studied "in vitro" by soaking the glasses in a simulated body fluid (SBF). The consequent formation of calcium phosphate layer was studied by means of electron microscopy (EM) equipped with an energy-dispersive system (EDS) for elemental analysis and Infrared (IR) spectroscopy. The results are compared to the literature relative to the substitution of La2O3 and Y2O3 for CaO. It is observed that, in general, the substitution of M2O3 for CaO in the binary CaO-SiO2 glass composition progressively reduces the ability to form a calcium phosphate layer on the surfaces exposed to simulated body fluid (SBF). The composition limit can be related to the ionic field strength of the substituting cation and to the CaO content of the base glass. According to the mechanism reported in the literature a silica gel-like surface layer initially forms on the surfaces exposed to SBF. The observed results can be attributed to the effect of the substitution of M2O3 for CaO on the acidic properties of the silanolic groups. PMID:11771691

Branda, F; Arcobello-Varlese, F; Costantini, A; Luciani, G

2002-02-01

148

Cathodic behavior of molten CaCl2-CaO and CaCl2-NaCl-CaO  

NASA Astrophysics Data System (ADS)

The cathodic behavior of molten CaCl2, CaCl2-CaO and equimolar CaCl2-NaCl-CaO was studied by cyclic voltammograms and constant potential polarization at temperatures of 1123 to 1173 K on molybdenum and titanium electrodes. The diffusion coefficient of Ca2+ (CaO) in molten CaCl2-CaO was calculated from the linear relationship between the square root of scan rate and the peak current density. The deposition potentials and the potential temperature coefficient of CaO in molten CaCl2-0.5mol%CaO and CaCl2-NaCl-0.5mol%CaO were also obtained from their cyclic voltammograms. The result shows that CaO is more easily reduced than CaCl2. The addition of NaCl in molten CaCl2-CaO induces the underpotential electrodeposition of CaO.

Wang, Shu-Lan; Wang, Wei; Li, Shi-Chao; Cao, Shan-Hui

2010-12-01

149

Heavy doping of H - ion in 12CaO·7Al 2O 3  

NASA Astrophysics Data System (ADS)

12CaO·7Al 2O 3 (C12A7, mayenite), which has a nanoscale porous structure that can accommodate extraframework species such as hydride (H -), oxide (O 2-), hydroxide (OH -) ions, and electrons, has been doped with H - ions to investigate its effects as dominant extraframework species. Chemical doping with CaH 2 enables the concentration of H - ions to reach almost the theoretical maximum. The concentration of H - ions is characterized by optical absorption intensity ascribed to photoionization of H - ions, and 1H magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. Persistent electron generation, which is accompanied by the formation of an F+ absorption band and electrical conductivity, by irradiation with ultraviolet light at room temperature increases as the H - ion doping increases until it reaches half the theoretical maximum and then decreases as the H - ion concentration increases further. This dependence indicates that both H - and O 2- ions are necessary for the generation of persistent electrons.

Hayashi, Katsuro

2011-06-01

150

Chemical analysis of the Chinese herbal medicine Gan-Cao (licorice).  

PubMed

Gan-Cao, or licorice, is a popular Chinese herbal medicine derived from the dried roots and rhizomes of Glycyrrhiza uralensis, G. glabra, and G. inflata. The main bioactive constituents of licorice are triterpene saponins and various types of flavonoids. The contents of these compounds may vary in different licorice batches and thus affect the therapeutic effects. In order to ensure its efficacy and safety, sensitive and accurate methods for the qualitative and quantitative analyses of saponins and flavonoids are of significance for the comprehensive quality control of licorice. This review describes the progress in chemical analysis of licorice and its preparations since 2000. Newly established methods are summarized, including spectroscopy, thin-layer chromatography, gas chromatography, high-performance liquid chromatography (HPLC), liquid chromatography/mass spectrometry (LC/MS), capillary electrophoresis, high-speed counter-current chromatography (HSCCC), electrochemistry, and immunoassay. The sensitivity, selectivity and powerful separation capability of HPLC and CE allows the simultaneous detection of multiple compounds in licorice. LC/MS provides characteristic fragmentations for the rapid structural identification of licorice saponins and flavonoids. The combination of HPLC and LC/MS is currently the most powerful technique for the quality control of licorice. PMID:18703197

Zhang, Qingying; Ye, Min

2009-03-13

151

Antioxidant activity of extracts of peh-hue-juwa-chi-cao in a cell free system.  

PubMed

In traditional Chinese medicine preparations, Hedyotis diffusa (HD), Hedyotis corymbosa (HC) and Mollugo pentaphylla (MP) are often used interchangeably under the name of "Peh-Hue-Juwa-Chi-Cao (PHJCC)." Although studies have been conducted to characterize the therapeutic activities of these different plant species, their antioxidant activity has never been investigated. In this study, our aim was to evaluate the antioxidant and free radical scavenging activities of these three different plant materials. At a concentration of 10 mg/ml, results showed that HD possesses the strongest inhibition on the FeCl2-ascorbic acid induced lipid peroxidation in rat liver homogenate, followed by HC and MP. MP showed a weak anti-lipid peroxidation activity at 1 and 3 mg/ml. Using Electron Spin Resonance (ESR) analysis, the order of superoxide anion scavenging activity was HC > HD > MP. However, MP was found to have the greatest hydroxyl radical scavenging activity compared to HC and HD. In conclusion, all three species used as PHJCC in Taiwan exhibited different antioxidant and free radical scavenging activities; these differences could explain, at least in part, the variation in therapeutic properties of PHJCC products in the market. PMID:15344417

Lin, Chun-Ching; Ng, Lean-Teik; Yang, Jenq-Jer

2004-01-01

152

Bulk Chemical Fractionation Between Basalt, Impact-Melts and Spherules of Lonar Impact Crater, India  

NASA Astrophysics Data System (ADS)

The ~50,000 year old Lonar Crater, India, is one of the two known continental impact craters that were excavated on basalt. In-situ impact-melts from within ejecta from the SE crater rim are associated with splash form impact-spherules of two types: mm-size non-magnetic spherules, also found in other parts of the ejecta, and slightly smaller magnetic spherules with smoother surfaces. Both impact-melts and the two types of spherules have homogeneous compositions, though minor systematic variations exist in impact melts. Compared to unaltered target basalt, average impact-melt characteristically shows ~21-22% depletion in Na2O and ~44-61% enrichment in K2O, while impact-spherules show more depletion in Na2O (~41-42%) and less enrichment in K2O (~21-29%). Additionally average magnetic spherules are enriched in MgO (~22%) and depleted in CaO (~9%) and Fe2O3}T (~7%), while non-magnetic spherules are depleted in MgO (~11%) and enriched in CaO (~13%) and Fe2O3T (~2%) over target-basalt. #Mg for impact-melts and non-magnetic spherules have restricted and overlapping values between ~0.35 and 0.43, but for magnetic spherules it varies between 0.38 and 0.56. The small variation in mobile CaO (~3.4 wt%), Na2O (~2.4 wt%) and K2O (~0.8 wt%) of target-rock and impactites suggest limited weathering of the samples. Lonar impactites were formed by plagioclase- dominated partial melting of target-basalt, which caused enrichment of K2O in impactites and Rb, Cs, Ba, La, Ce, Nd and Th in impact-melts and non-magnetic spherules, while another important target- rock constituent, augite, was variably mixed with plagioclase-melt only in the highest stage of shock metamorphism. Depletion of Na2O in impactites occurred due to limited separation of xenocrystic augite (Na2O ~0.23 and 0.26 wt%) from these molten impactites. Mixing models suggest proportions of plagioclase melt and augite in average impact-melts and non-magnetic spherules is close to ~1:0.4, in magnetic spherules it varies between 1:0.4 and 1:2.3. Proportions of ulvöspinel, a minor component of target-basalt, varied between 1:0.3 and 1:0.2. Volatile phases active during solidification of impactites were mainly H2O and Br. H2O was derived from target-basalt during impact, but depleted by a factor of ~9 times in average impact-melt. Inter-trappean ground water or pre-impact altered basalt flows was possible sources for Br. Enrichment of Br in average impact-melts and non-magnetic spherules (~3-4 times) over target-basalt suggests entrapment of this volatile inside impactites during their formation. The magnetic nature of high #Mg spherules is not clearly understood, may be due to a lower proportion of magnetite within these spherules. Studies of Lonar Crater ejecta have clear application to the nature of impact deposits on Mars being studied by MER rovers and in Columbia Hills.

Misra, S.; Prasad, M.; Saha, D.; Sengupta, D.; Khedekar, V. D.; Dube, A.; Newsom, H. E.

2005-12-01

153

Mechanism of expansion of concrete due to the presence of dead-burnt CaO and MgO  

Microsoft Academic Search

A new mechanism has been proposed to explain the delayed expansions, due to the presence of dead-burnt CaO or MgO, of Portland cement based materials. The mechanism is based on the crystal growth pressure, the solubility of hydroxide crystals, their growth habits and diffusion of Ca2+ and Mg2+ through the electrical double layer which forms round cement hydration products. In

S. Chatterji

1995-01-01

154

Electronic conductivities of commercial ZrO 2 + 3 to 4 wt pct CaO electrolytes  

Microsoft Academic Search

Potentiostatic electrochemical experiments with liquid metal electrodes have been analyzed to provide values for the mixed\\u000a electrical conduction parameters (PMion, o?o, Oo , Po,P\\u000a o, and E O,C.) associated with commercial-grade ZrO2 + 3 to 4 wt pct CaO electrolytes. Good agreement between experimental and calculated values for the open-circuit cell voltage,E o. c., for relatively high oxygen concentrations in

Lawrence M. Friedman; Karl E. Oberg; William M. Boorstein; Robert A. Rapp

1973-01-01

155

Optical design of CAOS: a high-resolution spectropolarimeter for the Catania Astrophysical Observatory 0.91-m telescope  

Microsoft Academic Search

CAOS (Catania Astrophysical Observatory Spectrograph) is a high-resolution (R~60,000), fiber fed, bench-mounted, prism cross-dispersed, white-pupil R-4 echelle spectrograph with polarimetric capabilities, for the 0.91m telescope on Mt. Etna. Wavelengths from 390 to 710 nm are covered in one-shot with a 2Kx2K 13.5 micron CCD. Inherent high efficiency of the spectrograph and optimum matching between fibers and spectrograph will allow high

Paolo Spano; F. Leone; Salvatore Scuderi; Santo Catalano; Filippo M. Zerbi

2004-01-01

156

CaO insulator coatings and self-healing of defects on V-Cr-Ti alloys in liquid lithium  

Microsoft Academic Search

Electrically insulating and corrosion-resistant coatings are required at the liquid metal\\/structural interface in fusion first-wall\\/blanket applications. The electrical resistance of CaO coatings produced on V-5%Cr-5%Ti by exposure of the alloy to liquid Li that contained 0.5--85 wt.% dissolved Ca was measured as a function of time at temperatures between 250 and 600°C. The solute element, Ca in liquid Li, reacted

J. H. Park; T. F. Kassner

1996-01-01

157

Theory of F centers in the alkaline-earth oxides MgO and CaO  

Microsoft Academic Search

We present results of a theoretical study of the electronic structure of isolated anion vacancies (F-center-like defects) in the alkaline-earth oxides MgO and CaO using the multiple-scattering-theory-based muffin-tin Green's-function method. These ab initio calculations are valence-charge self-consistent for the vacancy and first shell of cation neighbors but, at present, do not include effects due to atomic relaxation around the vacancy

Barry M. Klein; Warren E. Pickett; Larry L. Boyer; R. Zeller

1987-01-01

158

Identification of CaSO sub 4 formed by reaction of CaO and SO sub 2  

Microsoft Academic Search

The injection of calcium-based sorbents into coal-fired boilers for reaction with, and reduction in the levels of, sulfur dioxide (SOâ) in the flue gas has undergone considerable research and development. Significant effort has also been made in developing models for the overall reaction CaO + SOâ + 1\\/2 Oâ â CaSoâ in order to better predict the effects of system

B. K. Gullett; K. R. Bruce

1989-01-01

159

Experimental Investigation on the Effects of CaO on Coal-Ash Slagging on Refractory Boards  

Microsoft Academic Search

For that current power plants mainly use low-quality coal as fuel, Lengshui river coal ash as base-ash, separately make up ash-sample with CaO content of 10%, 20%, 30% or 40%, then measure the DT, ST, HT and FT of ash-sample by placing them at SDAF2000b ash melting point tester; spread ash upon SiC and aluminum refractory, calcined for 20 hrs

Yuan Jun; Chen Donglin; Tao Hualong; Pei Xiaochong

2009-01-01

160

Crossover from two- to three-dimensional gold particle shapes on CaO films of different thicknesses  

NASA Astrophysics Data System (ADS)

The growth of Au particles on Mo(001)-supported CaO films has been investigated as a function of film thickness by means of scanning tunneling microscopy and spectroscopy. Whereas, monolayer Au islands develop in the low-thickness regime [1-25 monolayers (ML)], formation of three-dimensional (3D) deposits is revealed above 40-ML film thickness. The two-dimensional (2D) growth morphology is ascribed to a charge transfer out of the CaO/Mo support into the adparticles, resulting in a reinforcement of the Au-CaO interface interaction and a strong preference for a wetting growth of gold. In the limit of ultrathin films, this charge transfer is governed by electron tunneling from the Mo substrate into the Au islands and is driven by the different Fermi levels of both systems. Although tunneling transport breaks down beyond 5-10-ML film thickness, the signature of charge-mediated Au growth remains detectable for even thicker films. This finding suggests the presence of intrinsic charge centers in the CaO film that are able to donate electrons to the gold. We relate these donor centers to Mo ions that spontaneously have diffused from the Mo support into the CaO lattice during growth. Given the low mobility of Mo in the oxide matrix, the donor concentration diminishes with film thickness and, hence, the ability of the CaO to transfer electrons into the Au deposits. Consequently, the 2D growth behavior of Au changes into the 3D regime that is characteristic for metals on inert oxide surfaces. Spectroscopic characterization of the Au particles revealed pronounced electron quantization and Coulomb charging effects due to the reduced island size.

Shao, Xiang; Nilius, Niklas; Freund, Hans-Joachim

2012-03-01

161

Individuality and Stability in Male Songs of Cao Vit Gibbons (Nomascus nasutus) with Potential to Monitor Population Dynamics.  

PubMed

Vocal individuality and stability has been used to conduct population surveys, monitor population dynamics, and detect dispersal patterns in avian studies. To our knowledge, it has never been used in these kinds of studies among primates. The cao vit gibbon is a critically endangered species with only one small population living in a karst forest along China-Vietnam border. Due to the difficult karst terrain, an international border, long life history, and similarity in male morphology, detailed monitoring of population dynamics and dispersal patterns are not possible using traditional observation methods. In this paper, we test individuality and stability in male songs of cao vit gibbons. We then discuss the possibility of using vocal individuality for population surveys and monitoring population dynamics and dispersal patterns. Significant individuality of vocalization was detected in all 9 males, and the correct rate of individual identification yielded by discriminant function analysis using a subset of variables was satisfactory (>90%). Vocal stability over 2-6 years was also documented in 4 males. Several characters of cao vit gibbons allowed long-term population monitoring using vocal recordings in both China and Vietnam: 1) regular loud calls, 2) strong individuality and stability in male songs, 3) stable territories, and 4) long male tenure. During the course of this research, we also observed one male replacement (confirmed by vocal analysis). This time- and labor-saving method might be the most effective way to detect dispersal patterns in this transboundary population. PMID:24788306

Feng, Jun-Juan; Cui, Liang-Wei; Ma, Chang-Yong; Fei, Han-Lan; Fan, Peng-Fei

2014-01-01

162

Individuality and Stability in Male Songs of Cao Vit Gibbons (Nomascus nasutus) with Potential to Monitor Population Dynamics  

PubMed Central

Vocal individuality and stability has been used to conduct population surveys, monitor population dynamics, and detect dispersal patterns in avian studies. To our knowledge, it has never been used in these kinds of studies among primates. The cao vit gibbon is a critically endangered species with only one small population living in a karst forest along China-Vietnam border. Due to the difficult karst terrain, an international border, long life history, and similarity in male morphology, detailed monitoring of population dynamics and dispersal patterns are not possible using traditional observation methods. In this paper, we test individuality and stability in male songs of cao vit gibbons. We then discuss the possibility of using vocal individuality for population surveys and monitoring population dynamics and dispersal patterns. Significant individuality of vocalization was detected in all 9 males, and the correct rate of individual identification yielded by discriminant function analysis using a subset of variables was satisfactory (>90%). Vocal stability over 2–6 years was also documented in 4 males. Several characters of cao vit gibbons allowed long-term population monitoring using vocal recordings in both China and Vietnam: 1) regular loud calls, 2) strong individuality and stability in male songs, 3) stable territories, and 4) long male tenure. During the course of this research, we also observed one male replacement (confirmed by vocal analysis). This time- and labor-saving method might be the most effective way to detect dispersal patterns in this transboundary population.

Ma, Chang-Yong; Fei, Han-Lan; Fan, Peng-Fei

2014-01-01

163

CaO insulator coatings and self-healing of defects on V-Cr-Ti alloys in liquid lithium  

SciTech Connect

Electrically insulating and corrosion-resistant coatings are required at the liquid metal/structural interface in fusion first-wall/blanket applications. The electrical resistance of CaO coatings produced on V-5%Cr-5%Ti by exposure of the alloy to liquid Li that contained 0.5--85 wt.% dissolved Ca was measured as a function of time at temperatures between 250 and 600{degrees}C. The solute element, Ca in liquid Li, reacted with the alloy substrate at 400--420{degrees}C to produce a CaO coating. Resistance of the coating layer measured in-situ in liquid Li was {approx}10{sup 6} {Omega} at 400{degrees}C. Thermal cycling between 300 and 700{degrees}C changed the coating layer resistance. which followed insulator behavior. These results suggest that thin homogeneous coatings can be produced on variously shaped surfaces by controlling the exposure time, temperature, and composition of the liquid metal. The technique can be applied to various shapes(e.g., inside/outside of tubes, complex geometrical shapes) because the coating is formed by liquid-phase reaction. Examination of the specimens after cooling to room temperature revealed no spallation, but homogeneous crazing cracks were present in the CaO coating. Additional tests to investigate the in-situ self-healing behavior of the cracks indicated that rapid healing occurred at {ge}360{degrees}C.

Park, J.H.; Kassner, T.F.

1996-02-01

164

Effect of FeO and CaO on the Sulfide Capacity of the Ferronickel Smelting Slag  

NASA Astrophysics Data System (ADS)

The effect of FeO and CaO on the sulfide capacity in MgO-SiO2-FeO based slags equilibrating with Fe-Ni alloys at 1773 K and 1873 K (1500 °C and 1600 °C) was investigated. The sulfide capacity in the MgO-SiO2-FeO and MgO-SiO2-CaO-FeO slags increased with higher FeO content and higher temperatures due to an increase in the activity of O2- and a decrease in the activity coefficient of sulfide ion in slag. The sulfide capacity of the MgO-SiO2-CaO-FeO slag also increased with an increase in the CaO content due largely to the increase in the activity of O2-. Furthermore, CaO and FeO seem to be more effective than MgO in increasing the sulfide capacity in the MgO-SiO2-CaO-FeO slag system. In addition, the comparison of the experimental results with the theoretical estimate using the modified empirical optical basicity showed relatively good linear agreement.

Kim, Ki Deok; Huh, Wan Wook; Min, Dong Joon

2014-06-01

165

Canopy spectral and chemical diversity from lowland to tree line in the Western Amazon using CAO-VSWIR  

NASA Astrophysics Data System (ADS)

Canopy chemistry and spectroscopy offer insight into community assembly and ecosystem processes in high-diversity tropical forests. Results from one lowland site in the Peruvian Amazon suggests both an environmental and an evolutionary component of canopy trait development however, the degree to which larger environmental differences influence diversity in canopy traits and their respective spectroscopic signatures across remains poorly understood. The spectranomics approach explicitly connects phylogenetic, chemical and spectral patterns in tropical canopies providing the basis for analysis, while high-fidelity, airborne remote sensing measurements extend plot-level data to landscape-scale, achieving a comprehensive view of the region. In 2011, the Carnegie Airborne Observatory (CAO) was used to sample a large region of the Western Amazon Basin in southeastern Peru, extending from lowlands to tree line in the Andean mountains. The CAO Visible-Shortwave Imaging Spectrometer (VSWIR) collected 480-band high-fidelity imaging spectroscopy data of the forest canopy, while its high-resolution LiDAR captured information on canopy structure and the underlying terrain. The data were used to quantify relationships between environmental gradients and canopy chemical and spectral diversity. Results suggest strong environmental control with additional phylogenetic influence over canopy spectral and chemical properties, particularly those related to structure, defense and metabolic function. Data from CAO-VSWIR extends the large range in canopy chemical and spectral diversity related to environmental factors across the Western Amazon Basin.

Martin, R. E.; Asner, G. P.

2012-12-01

166

Biodiesel production from transesterification of palm oil with methanol over CaO supported on bimodal meso-macroporous silica catalyst.  

PubMed

Calcium oxide-loaded porous materials have shown promise as catalysts in transesterification. However, the slow diffusion of bulky triglycerides through the pores limited the activity of calcium oxide (CaO). In this work, bimodal meso-macroporous silica was used as a support to enhance the accessibility of the CaO dispersed inside the pores. Unimodal porous silica having the identical mesopore diameter was employed for the purpose of comparison. Effects of CaO content and catalyst pellet size on the yield of fatty acid methyl esters (FAME) were investigated. The basic strength was found to increase with increasing the CaO content. The CaO-loaded bimodal porous silica catalyst with the pellet size of 325?m achieved a high %FAME of 94.15 in the first cycle, and retained an excellent %FAME of 88.87 after five consecutive cycles. PMID:24525218

Witoon, Thongthai; Bumrungsalee, Sittisut; Vathavanichkul, Peerawut; Palitsakun, Supaphorn; Saisriyoot, Maythee; Faungnawakij, Kajornsak

2014-03-01

167

Dip coated 12CaO·7Al 2O 3 thin films through sol–gel process using metal alkoxide  

Microsoft Academic Search

Transparent nanostructured 12CaO·7Al2O3 thin films with cubic structure have been prepared on soda lime glass substrates via the sol–gel dip coating using the precursor sol solution at low temperature. The structural, compositional, morphological and optical properties of the 12CaO·7Al2O3 films and powder were studied using X-ray diffractometry (XRD), X-ray photoelectron spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy. Optical

P. M. Chavhan; Anubha Sharma; R. K. Sharma; Gurmeet Singh; N. K. Kaushik

2010-01-01

168

Major and trace elements in igneous rocks from Apollo 15.  

NASA Technical Reports Server (NTRS)

The concentrations of major and trace elements have been determined in igneous rocks from Apollo 15. All materials analyzed have typical depletions of Eu except for minerals separated from sample 15085. Four samples have concentrations of trace elements that are similar to those of KREEP. The samples of mare basalt from Apollo 15 have higher concentrations of FeO, MgO, Mn, and Cr and lower concentrations of CaO, Na2O, K2O, and rare-earth elements (REE) as compared to the samples of mare basalt from Apollos 11, 12, and 14. The samples can be divided into two groups on the basis of their normative compositions. One group is quartz normative and has low concentrations of FeO while the other is olivine normative and has high concentrations of FeO. The trace element data indicate that the samples of olivine normative basalt could be from different portions of a single lava flow.

Helmke, P. A.; Blanchard, D. P.; Haskin, L. A.; Telander, K.; Weiss, C.; Jacobs, J. W.

1973-01-01

169

Antibacterial glass-composite coatings for protection of special purpose steel panels  

NASA Astrophysics Data System (ADS)

It has been established that the most informative and universal method for determination of biocide properties of vitreous coatings is qualitative method that takes into account the growth level of biotest microorganisms inoculated into liquid nutrient media. It is shown, that biocidity of glass-composite coatings on the basis of glasses of Na2O - K2O - CaO - ZrO2 - TiO2 - Al2O3 - P2O5 - B2O3 - SiO2 system is determined by the presence of calcium phosphates in them and depends on the type of bactericide filler. The most effective ones by the action on Pseudomonas aeruginosa bacterium and Aspergillus niger and Candida albicans fungi are zinc titanate and Ag+, to Escherichia coli- only zinc phosphate.

Savvova, O.; Bragina, L.; Babich, E.

2011-12-01

170

Volatile fractionation and tektite source material  

NASA Technical Reports Server (NTRS)

The arguments used by Love and Woronow (1988) to assess the role played in the origin of bediasites by extensive volatile fractionation are critically examined. Using the ratios of 'refractory' oxides, CaO, Al2O3, and MgO, to the 'volatile' oxides, Na2O and K2O, these authors concluded that vapor fractionation did not play a significant role. In this paper, experimental evidence is presented that shows that the assumption of volatility for the alkali elements (as least with respect to silica) to be not valid under the conditions under which tektites formed. It is shown that the results of vapor fractionation in experiments on glasses of tektite composition are approximately parallel the trends seen in bediasite analysis.

Walter, Louis S.

1989-01-01

171

[Determination of 12 elements in coal ash by x-ray fluorescence spectrometry].  

PubMed

A method for the determination of SiO2, Al2O3, Fe2O3, CaO, SO3, TiO2, K2O, Na2O, P2O5, MgO, MnO and BaO in coal ash by X-ray fluorescence spectrometry with melt sample preparation was developed. This method solved the problems of determination accuracy of S by using the 12:22 mix flux and oxide to lower the melt temperature. Using the soil standard sample and mixing the soil standard sample and coal ash standard sample solved the problem that there are not enough standard samples for coal ash analysis by XRF. The accuracy and precision of this method are acceptable, and the results are comparable to the those obtained by wet chemical method. PMID:18800742

Song, Yi; Guo, Fen; Gu, Song-hai

2008-06-01

172

Volatile fractionation and tektite source material  

NASA Astrophysics Data System (ADS)

The arguments used by Love and Woronow (1988) to assess the role played in the origin of bediasites by extensive volatile fractionation are critically examined. Using the ratios of 'refractory' oxides, CaO, Al2O3, and MgO, to the 'volatile' oxides, Na2O and K2O, these authors concluded that vapor fractionation did not play a significant role. In this paper, experimental evidence is presented that shows that the assumption of volatility for the alkali elements (as least with respect to silica) to be not valid under the conditions under which tektites formed. It is shown that the results of vapor fractionation in experiments on glasses of tektite composition are approximately parallel the trends seen in bediasite analysis.

Walter, L. S.

1989-09-01

173

CO2 and potassium in the mantle: carbonaceous pelite melts from the trailing edge of a detached slab hybridizing in the mantle to ultrapotassic kamafugite  

NASA Astrophysics Data System (ADS)

The ultrapotassic magmas from the Intra-Apennine and Roman provinces constitute worldwide endmembers in terms of K2O/Na2O, K2O content and CO2 degassing, and are associated with carbonatites. Group II kimberlites, which are geochemically similar but less extreme, occur on cratons stable since several 100 Ma. This geotectonic situation appears in strong contrast to the subduction setting of central Italy, where plate convergence has slowed down to less than a few mm/a, the slab now tearing off leading hot asthenospheric mantle to flow in between the trailing slab and the crust. A successful recipe for ultrapotassic magmas requires K/Na fractionation at some previous stage. Melts from fluid-absent melting of carbonaceous pelites at >3 GPa are ultrapottasic phonolites (SiO2 ~64 wt%) and have K2O/Na2O up to 9 because of residual cpx with jadeite80. The effect of CO2 is to stabilize residual jadeite, to lower SiO2, and to increase K2O/Na2O ratios (as compared to CO2 free melts with K2O/Na2O of 1-3 and SiO2 = 73-77 wt%). The carbonaceous pelite melts were equilibrated with fertile, refractory but cpx bearing mantle, and wherlite. At sufficient pressures (3.5 GPa) and XCO2 in the volatile component, hybridization of the carbonaceous pelite melts produces highly subsilicic kamafugites, with K2O/Na2O only slightly lowered, and XMg's >0.70 as characteristic of primitive melts. The essential role of CO2 is to reduce the olivine saturation volume and to shift the olivine-cpx-opx cotectic to lower SiO2. The Italian kamafugites are ultracalcic (CaO/Al2O3 = 1.2-1.4), and although carbonaceous pelite melts have little CaO and 20 wt% Al2O3, the assimilation of cpx and production of aluminous opx leads to ultracalcic compositions when equilibrated with refractory peridotite or wherlite. Temperatures necessary for the fluid absent carbonaceous pelite melting are 1050-1150 °C, far above any reasonable subduction geotherm. Hybridization in the mantle requires 1320-1400 °C (at 3.0-3.5 GPa). The proposition is, that the carbonaceous pelite melts only form in thermally relaxing slabs typical for an ending subduction. Slab break off causes inflow of hot asthenospheric mantle, which further heats the trailing edge of the slab. Normally, subduction ends through continental collision at the surface, and the melts from the trailing edge appear to freeze in the relatively cool mantle below the orogen and await the next thermal event in order to form group II kimberlites. In the particular Italian situation, where large scale plate tectonic movements changed the convergence into a strike slip, temperatures of the trailing slab edge and the asthenosphere are apparently sufficient to keep the carbonaceaous slab melts liquid during hydridization in the mantle, leading to the surface kamafugites. The short longevity of the ultrapotassic magmatism (800 ka) collaborates the concept of a one-time event, i.e. the one-time melting of the trailing slab edge during it's break-off.

Schmidt, M. W.

2007-12-01

174

Micelle-Assisted Synthesis of Al2O3·CaO Nanocatalyst: Optical Properties and Their Applications in Photodegradation of 2,4,6-Trinitrophenol  

PubMed Central

Calcium oxide (CaO) nanoparticles are known to exhibit unique property due to their high adsorption capacity and good catalytic activity. In this work the CaO nanocatalysts were prepared by hydrothermal method using anionic surfactant, sodium dodecyl sulphate (SDS), as a templating agent. The as-synthesized nanocatalysts were further used as substrate for the synthesis of alumina doped calcium oxide (Al2O3·CaO) nanocatalysts via deposition-precipitation method at the isoelectric point of CaO. The Al2O3·CaO nanocatalysts were characterized by FTIR, XRD, TGA, TEM, and FESEM techniques. The catalytic efficiencies of these nanocatalysts were studied for the photodegradation of 2,4,6-trinitrophenol (2,4,6-TNP), which is an industrial pollutant, spectrophotometrically. The effect of surfactant and temperature on size of nanocatalysts was also studied. The smallest particle size and highest percentage of degradation were observed at critical micelle concentration of the surfactant. The direct optical band gap of the Al2O3·CaO nanocatalyst was found as 3.3?eV.

Imtiaz, Ayesha; Khaleeq-ur-rahman, Muhammad; Adnan, Rohana

2013-01-01

175

Micelle-assisted synthesis of Al2O3·CaO nanocatalyst: optical properties and their applications in photodegradation of 2,4,6-trinitrophenol.  

PubMed

Calcium oxide (CaO) nanoparticles are known to exhibit unique property due to their high adsorption capacity and good catalytic activity. In this work the CaO nanocatalysts were prepared by hydrothermal method using anionic surfactant, sodium dodecyl sulphate (SDS), as a templating agent. The as-synthesized nanocatalysts were further used as substrate for the synthesis of alumina doped calcium oxide (Al2O3·CaO) nanocatalysts via deposition-precipitation method at the isoelectric point of CaO. The Al2O3·CaO nanocatalysts were characterized by FTIR, XRD, TGA, TEM, and FESEM techniques. The catalytic efficiencies of these nanocatalysts were studied for the photodegradation of 2,4,6-trinitrophenol (2,4,6-TNP), which is an industrial pollutant, spectrophotometrically. The effect of surfactant and temperature on size of nanocatalysts was also studied. The smallest particle size and highest percentage of degradation were observed at critical micelle concentration of the surfactant. The direct optical band gap of the Al2O3·CaO nanocatalyst was found as 3.3?eV. PMID:24311980

Imtiaz, Ayesha; Farrukh, Muhammad Akhyar; Khaleeq-ur-rahman, Muhammad; Adnan, Rohana

2013-01-01

176

Biomineral nanostructures of manganese oxides in oceanic ferromanganese nodules  

NASA Astrophysics Data System (ADS)

Manganese oxides, which are widespread and of great practical importance, are formed and transformed by the active role of microorganisms. Manganese aggregates occur as both crystallized varieties and disordered fine-grained phases with significant ore grade and up to 50-60 vol % of X-ray amorphous components. X-ray amorphous nanosized Mn oxides in Fe-Mn nodules from the Pacific Ocean floor were examined from the standpoint of their biogenic origin. SEM examination showed abundant mineralized biofilms on the studied samples. The chemical composition of bacterial mass is as follows (wt %): 28.34 MnO, 17.14 Fe2O3, 7.11 SiO2, 2.41 CaO, 17.90 TiO2, 1.74 Na2O, 1.73 Al2O3, 1.30 MgO, 1.25 P2O5, 1.25 SO3, 0.68 CoO, 0.54 CuO, 0.53 NiO, and 0.50 K2O. The chemical composition of fossilized cyanobacterial mats within the interlayer space of nodulesis as follows (wt %): 48.35 MnO, 6.23 Fe2O3, 8.76 MgO, 5.05 Al2O3, 4.45 SiO2, 3.63 NiO, 2.30 Na2O, 2.19 CuO, 1.31 CaO, and 0.68 K2O is direct evidence for participation of bacteria in Mn oxide formation. This phase consists of mineralized glycocalix consisting of nanosized flakes of todorokite. Native metals (Cu, Fe, and Zn) as inclusions 10-20 ?m in size were identified in ferromanganese nodules as well. The formation of nativemetals can be explained by their crystallization at highly reducing conditions maintained by organic matter.

Lysyuk, G. N.

2008-12-01

177

Age, origin, and tectonic implications of Palaeozoic rapakivi granites in the North Qaidam orogen, Northwest China  

NASA Astrophysics Data System (ADS)

Palaeozoic rapakivi granites occur in the western segment of the China Central Orogenic System. Exhibiting typical rapakivi texture (Fig. 1), these granites contain magmatic microgranular enclaves of intermediate compositions. SHRIMP zircon U-Pb ages for the granites and enclaves are 433 × 5 Ma and 433 × 3 Ma, respectively. The rapakivi granites are magnesian to ferroan, calc-alkalic to alkalic, and are characterized by high FeOt/(FeOt + MgO) (0.74-0.91) and Ga/Al ratios, and SiO2, Na2O + K2O and rare earth element (apart from Eu) contents, but low CaO, Ba, and Sr contents. These are typical A-type granite geochemical features. The granites and enclaves exhibit a uniform decrease in TiO2,CaO, Na2O, K2O, FeO, and MgO with increasing SiO2, and both lithologies have similar trace element patterns. Whole-rock ?Nd(t) values vary from -9.2 to -8.7 for the granites and from -9.0 to -8.4 for the enclaves, but zircon ?Hf(t) values vary more widely from -5.8 to -0.2 and -4.6 to +5.1, respectively. Our data suggest that the granites and enclaves have crystallized from different magmas. The granites appear to have been derived from old continental crust, whereas the enclaves required a source having a juvenile component. The spherical shape and undeformed nature of the granites and their geochemical characteristics, coupled with the (ultra)-high pressure metamorphism (494 to 460Ma) and evolution of Palaeozoic granitoid magmatism in the North Qaidam orogen, indicate that the rapakivi granites were generated in a post-collisional setting. These rocks are therefore an example of Palaeozoic rapakivi granites emplaced in a post-collisional, extensional orogenic setting.

Wang, X.; Hu, N.; Castro, A.; Wang, T.; Lu, X.

2013-12-01

178

Achondrite ALHA77005 - Alteration of chromite and olivine  

NASA Technical Reports Server (NTRS)

The olivine crystals of the 77005 achondrite are brown except for colorless shock lamellae, mottled patches, and grains adjacent to pools of impact melt. Sporadic dark alteration patches in brown olivine and Cr-rich spinel gave the following average electron-microprobe analyses: (olivine) P2O5 0.9, SiO2 57.9, TiO2 0, Al2O3 0.7, Cr2O3 0.4, V2O3 0, Fe2O3 (assumed oxidation state) 17.0, MgO 1.6, CaO 0.2, Na2O 0, K2O 1.8, SO3 (assumed oxidation state) 9.2, Cl 0.1, sum 89.8 wt pct; (spinel) P2O5 3.5, SiO2 2.1, TiO2 2.2, Al2O3 2.1, Cr2O3 13.4, V2O3 0.8, Fe2O3 40.7, MgO 0.9, CaO 0.1, Na2O 0, K2O 2.0, SO3 11.1, Cl 0.1, sum 79.0 wt pct. Ion-microprobe analyses revealed H in both. Rare orange patches in brown olivine from another area gave SiO2 33-35, FeO 30-28, MgO 28-32, sum 93 wt pct. Thermal metamorphism under dry oxidizing conditions is discussed as a possible alternative to shock-induced oxidation for generation of the brown olivine (McSween and Stoeffler, 1980). Because alteration patches transgress shock lamellae, and because sulfatic alteration occurs in fusion crusts of Antarctic meteorites (Gibson et al., 1983), alteration of the 77005 achondrite at the Antarctic surface is preferred to a complex series of processes needed for preterrestrial alteration.

Smith, J. V.; Steele, I. M.

1984-01-01

179

Comparison between the in vitro surface transformations of AP40 and RKKP bioactive glasses.  

PubMed

Two bioactive silica-phosphate glasses, AP40 and RKKP, were compared in their behaviour in simulated biological environment. Their chemical composition is practically identical, except that RKKP contains small amounts of amphoteric network-former oxides Ta2O5 and La2O3 (composition in wt% for AP40: beta-Ca3(PO4)2 24.50, SiO2 44.30, CaO 18.60, Na2O 4.60, K2O 0.19, MgO 2.82, CaF2 4.99; RKKP: beta-Ca3(PO4)2 24.23, SiO2 43.82, CaO 18.40, Na2O 4.55, K2O 0.19, MgO 2.79, CaF2 4.94, Ta2O5 0.99, La2O3 0.09). Previous investigations showed a better performance in osteopenic bone for RKKP. To gain more insight into these differences in biological behaviour, the in vitro bioactivity of the glasses was studied by treatment with a continuously replenished Hanks' Balanced Salt Solution (HBSS). The glasses were examined before and after HBSS treatment for 20 and 40 days by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), X-ray Energy Dispersion (EDX), Raman and IR vibrational spectroscopies. Some slight but notable differences between the two glasses were observed after HBSS treatment. IR and EDX analyses showed that deposits formed on both glasses were composed of a calcium deficient carbonate-apatite; however, the layer formed on RKKP glass was found to be slightly more calcium deficient and thinner. EDX analysis evidenced the presence of a small percentage of F- ions only in the layers formed on the RKKP samples. The differences disclosed, although slight, can contribute to the understanding of the different biological behaviour previously observed. PMID:15744599

Krajewski, A; Ravaglioli, A; Tinti, A; Taddei, P; Mazzocchi, M; Martinetti, R; Fagnano, C; Fini, M

2005-02-01

180

Achondrite ALHA77005 - Alteration of chromite and olivine  

NASA Astrophysics Data System (ADS)

The olivine crystals of the 77005 achondrite are brown except for colorless shock lamellae, mottled patches, and grains adjacent to pools of impact melt. Sporadic dark alteration patches in brown olivine and Cr-rich spinel gave the following average electron-microprobe analyses: (olivine) P2O5 0.9, SiO2 57.9, TiO2 0, Al2O3 0.7, Cr2O3 0.4, V2O3 0, Fe2O3 (assumed oxidation state) 17.0, MgO 1.6, CaO 0.2, Na2O 0, K2O 1.8, SO3 (assumed oxidation state) 9.2, Cl 0.1, sum 89.8 wt pct; (spinel) P2O5 3.5, SiO2 2.1, TiO2 2.2, Al2O3 2.1, Cr2O3 13.4, V2O3 0.8, Fe2O3 40.7, MgO 0.9, CaO 0.1, Na2O 0, K2O 2.0, SO3 11.1, Cl 0.1, sum 79.0 wt pct. Ion-microprobe analyses revealed H in both. Rare orange patches in brown olivine from another area gave SiO2 33-35, FeO 30-28, MgO 28-32, sum 93 wt pct. Thermal metamorphism under dry oxidizing conditions is discussed as a possible alternative to shock-induced oxidation for generation of the brown olivine (McSween and Stoeffler, 1980). Because alteration patches transgress shock lamellae, and because sulfatic alteration occurs in fusion crusts of Antarctic meteorites (Gibson et al., 1983), alteration of the 77005 achondrite at the Antarctic surface is preferred to a complex series of processes needed for preterrestrial alteration.

Smith, J. V.; Steele, I. M.

1984-09-01

181

GEMAS: Distribution of major elements in Polish agricultural soil  

NASA Astrophysics Data System (ADS)

Amount and quality of produced food is highly dependent on soil chemical properties and composition. The GEMAS project (Geochemical Mapping of Agricultural and Grazing Land Soil of Europe) has provided new homogeneous geochemical data for Polish agricultural soils. This study presents the distribution of common major elements such as CaO, MgO, Fe2O3, Al2O3, K2O, Na2O, SiO2, determined in 129 samples of agricultural soil of Poland. The total element concentrations obtained by X-ray fluorescence spectroscopy (XRF) were compared with the results from aqua regia acid digestion determined by ICP-MS. The distribution patterns of selected major elements reveal two major geochemical provinces - the northern province and the southern province, distinguished with respect to the natural geochemical background and resulting from the geological evolution of the region. The soil of the northern province (Polish Lowland), dominated by glacial deposits, show low contents of CaO, MgO, Fe2O3, Al2O3, K2O, Na2O, and high contents of SiO2. High silica content reflects the presence of sand-rich deposits which belong to the larger European feature with cover sands and loess of mainly Weichselian age and stretching from Ukraine to western Germany and Denmark. The southern province is characterised by high concentrations of almost all major elements (except SiO2). Soils in the Sudetes, Upper Silesia and the Carpathian Mountains developed in majority on pre-Quaternary rocks. In the Sudetes, soil formed on magmatic and metamorphic rocks of Paleozoic age. In the Carpathians and Upper Silesia, the flysch and molasse formations containing various material of magmatic and sedimentary origin constitute the immediate substratum of soil.

Dusza-Dobek, Aleksandra; Pasieczna, Anna; Kwecko, Pawe?

2014-05-01

182

Influence of high-temperature steam on the reactivity of CaO sorbent for CO? capture.  

PubMed

Calcium looping is a high-temperature CO(2) capture technology applicable to the postcombustion capture of CO(2) from power station flue gas, or integrated with fuel conversion in precombustion CO(2) capture schemes. The capture technology uses solid CaO sorbent derived from natural limestone and takes advantage of the reversible reaction between CaO and CO(2) to form CaCO(3); that is, to achieve the separation of CO(2) from flue or fuel gas, and produce a pure stream of CO(2) suitable for geological storage. An important characteristic of the sorbent, affecting the cost-efficiency of this technology, is the decay in reactivity of the sorbent over multiple CO(2) capture-and-release cycles. This work reports on the influence of high-temperature steam, which will be present in flue (about 5-10%) and fuel (?20%) gases, on the reactivity of CaO sorbent derived from four natural limestones. A significant increase in the reactivity of these sorbents was found for 30 cycles in the presence of steam (from 1-20%). Steam influences the sorbent reactivity in two ways. Steam present during calcination promotes sintering that produces a sorbent morphology with most of the pore volume associated with larger pores of ?50 nm in diameter, and which appears to be relatively more stable than the pore structure that evolves when no steam is present. The presence of steam during carbonation reduces the diffusion resistance during carbonation. We observed a synergistic effect, i.e., the highest reactivity was observed when steam was present for both calcination and carbonation. PMID:22191682

Donat, Felix; Florin, Nicholas H; Anthony, Edward J; Fennell, Paul S

2012-01-17

183

Steam-Coal Gasification Using CaO and KOH for in Situ Carbon and Sulfur Capture  

SciTech Connect

We present experimental results of coal gasification with and without the addition of calcium oxide and potassium hydroxide as dual-functioning catalyst–capture agents. Using two different coal types and temperatures between 700 and 900 °C, we studied the effect of these catalyst–capture agents on (1) the syngas composition, (2) CO{sub 2} and H{sub 2}S capture, and (3) the steam–coal gasification kinetic rate. The syngas composition from the gasifier was roughly 20% methane, 70% hydrogen, and 10% other species when a CaO/C molar ratio of 0.5 was added. We demonstrated significantly enhanced steam–coal gasification kinetic rates when adding small amounts of potassium hydroxide to coal when operating a CaO–CaCO{sub 3} chemical looping gasification reactor. For example, the steam–coal gasification kinetic rate increased 250% when dry mixing calcium oxide at a Ca/C molar ratio of 0.5 with a sub-bituminous coal, and the kinetic rate increased 1000% when aqueously mixing calcium oxide at a Ca/C molar ratio of 0.5 along with potassium hydroxide at a K/C molar ratio of 0.06. In addition, we conducted multi-cycle studies in which CaCO{sub 3} was calcined by heating to 900 °C to regenerate the CaO, which was then reused in repeated CaO–CaCO{sub 3} cycles. The increased steam–coal gasification kinetics rates for both CaO and CaO + KOH persisted even when the material was reused in six cycles of gasification and calcination. The ability of CaO to capture carbon dioxide decreased roughly 2–4% per CaO–CaCO{sub 3} cycle. We also discuss an important application of this combined gasifier–calciner to electricity generation and selling the purge stream as a precalcined feedstock to a cement kiln. In this scenario, the amount of purge stream required is fixed not by the degradation in the capture ability but rather by the requirements at the cement kiln on the amount of CaSO{sub 4} and ash in the precalcined feedstock.

Siefert, Nicholas S.; Shekhawat, Dushyant; Litster, Shawn; Berry, David, A

2013-08-01

184

Synthesis, characterization and crystal structures of three dinuclear diperoxo complexes of Mo(VI): K 2{O[MoO(O 2) 2H 2O] 2}·2H 2O, (C 6H 8N,NH 4){O[MoO(O 2) 2H 2O] 2} and (C 6H 8N,Na){O[MoO(O 2) 2H 2O] 2}  

Microsoft Academic Search

The crystal structures of three dinuclear diperoxo compounds have been determined from single-crystal X-ray diffraction data. All title compounds crystallize as yellow needle-shaped crystals in the triclinic space group P1¯(2). (1) K2{O[MoO(O2)2H2O]2}·2H2O crystallizes with a=6.2745(2), b=9.7279(3), c=11.2976(3)Å, ?=78.743(1), ?=80.190(1), ?=73.130(1)°, Z=2. (2) (2-MepyH,NH4){O[MoO(O2)2H2O]2}, where 2-MepyH denotes 2-methylopyridine, crystallize with a=6.733(5), b=8.364(5), c=13.984(5)Å, ?=73.702(5), ?=87.647(5), ?=85.216(5)°, Z=2. (3) (2-MepyH,Na){O[MoO(O2)2H2O]2} crystallize with

M. Grzywa; W. Nitek; W. ?asocha

2008-01-01

185

Thermal conductivity and Seebeck coefficient of 12CaO?7Al2O3 electride with a cage structure  

NASA Astrophysics Data System (ADS)

Thermal conductivity (?) and Seebeck coefficient (?) of electron-doped light-metal oxide 12CaO?7Al2O3 (C12A7 electride) with a subnanometer-sized cage structure are reported on single crystals with various electron concentrations (Ne) . The semiconducting C12A7 electride exhibits n -type conduction with the highest ? value of -100?VK-1 at 300 K. The ? exhibits an amorphouslike T2 dependence at low temperatures and varies between 2.3 and 4.5Wm-1K-1 at 300 K. This is an order-of-magnitude lower than that of the constituents, CaO (15Wm-1K-1) and Al2O3 (30Wm-1K-1) . These properties are attributed to the cage structure, suggesting that the semiconducting electride should be regarded as a phonon glass and electron crystal material. The thermoelectric performance of electrides evaluated by a dimensionless figure of merit (ZT) shows an optimized value of 2×10-3 at 300 K for the semiconducting electride with Ne of 5×1020cm-3 .

Kim, Sung Wng; Tarumi, Ryuichi; Iwasaki, Hideo; Ohta, Hiromichi; Hirano, Masahiro; Hosono, Hideo

2009-08-01

186

First-principles calculations of water-based surfactant-assisted growth of polar CaO(111) oxide film  

NASA Astrophysics Data System (ADS)

Despite many attempts to grow rocksalt (111) oxide surfaces, the growth of an atomically flat polar oxide film with an arbitrary thickness still remains challenging because of surface roughening during the growth process, such as faceting into neutral 100surface planes. This seemingly unavoidable behavior leads to a grainy morphology and diminished functionality. Here, we present a first-principles investigation of the surfactant-assisted growth of polar CaO(111) film in the presence of a water-based surfactant, both from thermodynamic and kinetic points of view. We show that water molecules not only supply a surfactant by depositing hydrogen on the surface throughout the growth process, but also supply oxygen atoms as an elemental constituent in the film growth, i.e. water oxygen atoms are easily inserted into the top surface layer of the growing film. We suggest that adding water surfactants to conventional synthesis techniques leads to the continuous presence of hydrogen atoms in the surface region during the growth process, which efficiently quenches polarity and dynamically stabilizes the growth of the polar surface, and thus facilitates the growth of defect-free CaO(111) films with arbitrary thickness.

Tan, Xin; Zapol, Peter

2013-03-01

187

Calorimetric determination of energetics of solid solutions of UO 2+ x with CaO and Y 2O 3  

NASA Astrophysics Data System (ADS)

Quantitative study of thermodynamic properties of solid solutions of UO 2+ x with divalent and trivalent oxides is important for predicting the behavior of oxide fuel. Although early literature work measured vapor pressure in some of these solid solutions, direct calorimetric measurements of enthalpies of formation have been hampered by the refractory nature of such oxides. First measurements of the enthalpies of formation in the systems UO 2+ x-CaO and UO 2+ x-YO 1.5, obtained by high-temperature oxide melt solution calorimetry, are reported. Both systems show significantly negative (exothermic) heats of formation from binary oxides (UO 2, plus O 2 and CaO or YO 1.5, as well as from UO 2 plus UO 3 and CaO or YO 1.5), consistent with reported free energy measurements in the urania-yttria system. The energetic contributions of oxygen content (oxidation of U 4+) and of charge balanced ionic substitution as well as defect clustering are discussed. Behavior of urania-yttria is compared to that of corresponding systems in which the tetravalent ion is Ce, Zr, or Hf. The substantial additional stability in the solid solutions compared to pure UO 2+ x may retard, in both thermodynamic and kinetic sense, the oxidation and leaching of spent fuel to form aqueous U 6+ and solid uranyl phases.

Mazeina, Lena; Navrotsky, Alexandra; Greenblatt, Martha

2008-02-01

188

Generation of hydrogen from polyvinyl chloride by milling and heating with CaO and Ni(OH)2.  

PubMed

This work discusses an alternative process option for the treatment of polyvinyl chloride (PVC) by producing hydrogen (H(2)) gas, at the same time fixing chlorine for proper environmental control. In the first-stage, a milling operation is performed in a planetary ball mill to obtain a mixture of PVC sample with CaO and Ni(OH)(2) to be used as feed in the second-step, involving heating of the milled product. Analyses by thermogravimetry-mass spectroscopy (TG-MS) and gas chromatography (GC) showed H(2), CH(4), CO and CO(2) as main constituents. The results clearly show that addition of Ni(OH)(2) to provide nickel as catalyst and CaO as adsorbent to fix CO(2) and HCl gases generated during heating, assisted in clean H(2) generation with concentration near 90% at temperatures between 450 and 550 degrees C. Analyses of solids after heating by X-ray diffraction and TG-DTA techniques showed both CaOHCl and CaCO(3) as main phases in the product. This process could be developed to treat PVC wastes together with other polymers and/or plastic wastes for production of H(2) gas. PMID:19231073

Tongamp, William; Zhang, Qiwu; Shoko, Miyagi; Saito, Fumio

2009-08-15

189

Charge competition with oxygen molecules determines the growth of gold particles on doped CaO films.  

PubMed

The influence of gas-phase oxygen on the growth of Au nanoparticles on Mo-doped CaO films has been investigated by means of low temperature scanning tunnelling microscopy and X-ray photoelectron spectroscopy. Whereas at ideal vacuum conditions, only 2D Au islands develop on the oxide surface, the fraction of 3D deposits increases with increasing O2 pressure until they become the dominant species in 106 mbar oxygen. The morphology crossover arises from changes in the interfacial electron flow between Mo donors in the CaO lattice and different ad-species on the oxide surface. In the absence of 02 molecules, the donor electrons are predominately transferred to the Au ad-atoms, which consequently experience enhanced binding to the oxide surface and agglomerate into 2D islands. In an oxygen atmosphere, on the other hand, a substantial fraction of the excess electrons is trapped by adsorbed O2 molecules, while the Au atoms remain neutral and assemble into tall 3D particles that are typical for non-doped oxides. Our experiments demonstrate how the competition for charge between different adsorbates governs the physical and chemical properties of doped oxides, so widely used in heterogeneous catalysis. PMID:24015581

Cui, Yi; Huang, Kai; Nilius, Niklas; Freund, Hans-Joachim

2013-01-01

190

Geochemical Distribution in the Surficial Sediments of Periyar River and Cochin Estuary on the South West Coast of India  

NASA Astrophysics Data System (ADS)

Geochemical study of bed sediments of Periyar river and Cochin estuary was carried out to understand the distribution, sources and possible factors responsible for the enrichment and depletion of various major and trace elements in the sediments. The river sediments are coarse to medium sand and estuarine sediments are sandy to clayey silt. The spatial distribution pattern of elements indicate that the sediment grain size is the major controlling factor in this estuarine-river system. The fine-grained sediments of the estuary are rich in MgO, CaO, Al2O3, TiO2, Fe2O3, Na2O, P2O5, MnO, Li, Sc, V, Cr, Co, Ni, Cu, Zn, As, Rb, Ta, Zr, Nb, Cd, Pb, LOI and poor in SiO2 and Ba. The organic rich sediments exhibit a similar distribution of Fe2O3, Al2O3, MgO and P2O5, Cu, Ni, Co, Cr and V. Factor analysis of the geochemical data gave four important factors which control the sediment chemistry. The first prominent factor (ca. 58 percent of variance) is characterised by high statistical loadings on most of the elements analysed except TiO2, CaO, K2O, Mo, Ag, Hf, Bi and Th. It is interpreted as a combined fine-grained alumino-silicate and organic matter factor. The second factor (13 percent of total variance) shows high loadings on the technogenic elements like Pb, Zn, Cd, Bi and also on Th. This is identified as an anthropogenic and industrial pollution factor. Factor 3, (11 percent variance) is characterised by high loadings on CaO, Sr and Ba and also on Na2O and K2O and can be interpreted as a biological contribution factor. The higher loadings on TiO2, MnO, Zr, Hf and Th in factor 4 (4 percent of variance) clearly represent the heavy minerals present in the study area. The factor scores point out that the fine-grained estuarine sediments mainly contribute towards the first factor whereas both estuarine and river sediments contribute to all other factors. The higher concentration of Fe2O3, K2O, MgO, P2O5, Zn, Ba, Pb, Cd, Bi, As, Cr, Ni and Sr in comparison with other Indian rivers suggest that the Periyar river and Cochin estuary is showing heavy anthropogenic contamination. Key words: Bottom sediments; Sediment chemistry; Factor analysis; Cochin estuary; Periyar river.

Paul, S. K.; Watanabe, Y.

2001-05-01

191

Solution of MgO, CaO, and TiO[sub 2] in [alpha]-Al[sub 2]O[sub 3  

SciTech Connect

Atomistic simulation methods are used to predict the preferred solution mechanisms and their associated energies. Both full- and partial-charge models are discussed. It was found that defect clustering always results in a significant lowering of the solution energies but does not change the preferred solution reaction of any of the oxides. The large size of the Ca[sup 2+] ion results not only in a higher solution energy (lower solubility) for CaO compared to MgO but also to a different preferred compensation mechanism. The predicted energy for the cosolution of MgO and TiO[sub 2] is dramatically smaller than for either oxide separately. Conversely, whereas solution of TiO[sub 2] aids the solution of CaO, additions of CaO do not support TiO[sub 2] solution.

Grimes, R.W. (Royal Institution of Great Britain, London (United Kingdom). Davy Faraday Research Lab.)

1994-02-01

192

The rates of desulfurization of liquid iron by solid CaO and CaO-saturated liquid iron oxide at 1600‡c  

Microsoft Academic Search

The rates of desulfurization of Fe-O-S melts by CaO crucibles and by CaO-saturated liquid iron oxide have been measured at\\u000a 1600 ‡C. It was found that irons containing 1.62 wt pct and 0.64 wt pct sulfur and 0.070 wt pct oxygen are desulfurized by\\u000a a reaction with the containing CaO crucible which does not involve the formation of a CaS

A. Saelim; D. R. Gaskell

1983-01-01

193

Mechanisms of oxygen ion diffusion in a nanoporous complex oxide 12CaO•7 Al2 O3  

NASA Astrophysics Data System (ADS)

We performed a theoretical analysis of O2- diffusion mechanisms in a nanoporous complex oxide 12CaO•7Al2O3 (C12A7). This material can be viewed as a positively charged framework, arranged in subnanometer sized cages, hosting extra-framework O2- ions occupying one in six cages. Using both classical molecular-dynamics simulations and ab initio calculations we demonstrate that the diffusion of O2- species is dominated by the exchange of framework and extra-framework O2- ions rather than by an interstitial diffusion mechanism. The results allow us to rationalize the origins of the experimentally observed high oxide ion conductivity of C12A7 and the stability of its lattice under positive ion-beam irradiation.

Sushko, Peter V.; Shluger, Alexander L.; Hayashi, Katsuro; Hirano, Masahiro; Hosono, Hideo

2006-01-01

194

Growth of shaped 12CaO×7Al 2O 3 crystals by the micro-pulling down method  

NASA Astrophysics Data System (ADS)

12CaO×7Al 2O 3 (C12A7) single crystals have been successfully grown by the micro-pulling down method for the first time. Single and transparent C12A7 crystal was obtained with radio-frequency heating ?-PD system. Phase stability is discussed as a function of oxygen concentration in the growth atmosphere. A minimum 1.0 Vol% O 2 with nitrogen atmosphere yields C12A7 phase. The distribution of Ca, Al and O elements at cross-section part was investigated by the electron probe microanalysis. The crystal composition deviation could be controlled by reducing O 2 gas concentration to 1.0 Vol%.

Liu, Lijuan; Kagamitani, Yuji; Ehrentraut, Dirk; Yokoyama, Chiaki; Fukuda, Tsuguo

2009-01-01

195

High electron doping to a wide band gap semiconductor 12CaO.7Al2O3 thin film  

NASA Astrophysics Data System (ADS)

High-density electrons (~1.9×1021 cm-3) were doped into a polycrystalline film of a wide band gap (~7 eV) semiconductor 12CaO.7Al2O3 (C12A7) by an in situ postdeposition reduction treatment using an oxygen-deficient C12A7 overlayer. The resultant film exhibits metallic conduction with a Hall mobility of ~2.5 cm2 V-1 s-1 and a conductivity of ~800 S cm-1. Optical analyses indicate that most of the doped electrons behave as free carriers with an effective mass of 0.82me and the estimated in-grain mobility is 5.2 cm2 V-1 s-1, which agrees reasonably with the value obtained for high-quality single crystals.

Miyakawa, Masashi; Hirano, Masahiro; Kamiya, Toshio; Hosono, Hideo

2007-04-01

196

Periodic Hartree-Fock study of B1 ? B2 reactions: phase transition in CaO  

NASA Astrophysics Data System (ADS)

The periodic Hartree-Fock method has been used to sample the potential energy hypersurface of CaO to determine a collective reaction pathway between the low-pressure (NaCl) and high-pressure (CsCl) phases. The predicted transition pressure, 68 GPa, is in good agreement with both experimental data and previous theoretical studies. At low pressure the enthalpy ( E + PV) surface presents only one minimum corresponding to the B1 (NaCl) structure. A second minimum appears at the B2 (CsCl) geometry when the pressure is increased. The transformation kinetics is estimated using the Johnson-Mehl model coupled to random nucleation and interface-controlled growth. Independently of the interfacial energy, the kinetics is highly pressure dependent. A pressure hysteresis loop is predicted. The results presented are in qualitative agreement with available data.

D'Arco, Philippe; Jolly, Luc-Henri; Silvi, Bernard

1992-08-01

197

Dry mechanochemical synthesis of hydroxyapatites from DCPD and CaO: influence of instrumental parameters on the reaction kinetics.  

PubMed

Mechanochemistry is a possible route to synthesize calcium deficient hydroxyapatite (CDHA) with an expected molar calcium-to-phosphate (Ca/P) ratio +/-0.01. To optimize the experimental conditions of CDHA preparation from dicalcium phosphate dihydrate (DCPD) and calcium oxide by dry mechanosynthesis reaction, we performed the kinetic study varying some experimental parameters. This kinetic study was carried out with two different planetary ball mills (Retsch or Fritsch Instuments). Results obtained with the two mills led to the same conclusions although the values of the rate constants of DCPD disappearance and times for complete reaction were very different. Certainly, the origin of these differences was from the mills used, thus we investigated the influence of instrumental parameters such as the mass and the surface area of the balls or the rotation velocity on the mechanochemical reaction kinetics of DCPD with CaO. Results show that the DCPD reaction rate constant and the inverse of the time for complete disappearance of CaO both vary linearly with (i) the square of the rotation velocity, (ii) the square of eccentricity of the vial on the rotating disc and (iii) the product of the mass by the surface area of the balls. These observations comply with theoretical models developed for mechanical alloying. The consideration of these four parameters allows the transposition of experimental conditions from one mill to another or the comparison between results obtained with different planetary ball mills. These instrumental parameters have to be well described in papers concerning mechanochemistry or when grinding is an important stage in a process. PMID:14643588

Mochales, Carolina; El Briak-BenAbdeslam, Hassane; Ginebra, Maria Pau; Terol, Alain; Planell, Josep A; Boudeville, Philippe

2004-01-01

198

FOURIER TRANSFORM INFRARED PHOTOACOUSTIC SPECTROSCOPY CHARACTERIZATION OF SULFUR-OXYGEN SPECIES RESULTING FROM THE REACTION OF SO2 WITH CAO AND CACO3  

EPA Science Inventory

Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS) has been used to investigate the reaction of SO2 in He with CaO and CaCO3 particles at temperatures between 25 and 900 C. SO2 reacts with CaC at 25 C, while the reaction of Ca-CO3 with SO2 is first evident at 550 C ...

199

Use of CaO as an activator for producing a price-competitive non-cement structural binder using ground granulated blast furnace slag  

SciTech Connect

The use of calcium oxide (CaO) demonstrates a superior potential for the activation of ground granulated blast furnace slag (GGBFS), and it produces a higher mechanical strength than calcium hydroxide [Ca(OH){sub 2}]. The mechanical strength differences between CaO- and Ca(OH){sub 2}-activated GGBFS binders are explored using isothermal calorimetry, powder X-ray diffraction, thermogravimetric and differential thermal analysis (TGA and DTA) as well as compressive strength testing. Calcium silicate hydrate (C–S–H), Ca(OH){sub 2} and a hydrotalcite-like phase are found as reaction products in all samples. The TGA and DTA results indicate that the use of CaO produces more C–S–H, although this is not likely to be the primary cause of higher strength development in the CaO-activated GGBFS. Rather, other factors such as porosity may govern the strength at a higher order of magnitude. Significant reduction of Ca(OH){sub 2} occurs only with the use of Ca(OH){sub 2}, followed by the formation of carbonate (CaCO{sub 3}), indicating carbonation. -- Highlights: •CaO showed a better potential for the activation of GGBFS than Ca(OH){sub 2}. •Strength test, XRD, TGA/DTA and isothermal calorimetry are used. •C-S-H, Ca(OH){sub 2}, and a hydrotalcite-like phase are found in all samples. •The use of Ca(OH){sub 2} causes some degree of carbonation.

Kim, Min Sik; Jun, Yubin; Lee, Changha, E-mail: clee@unist.ac.kr; Oh, Jae Eun, E-mail: ohjaeeun@unist.ac.kr

2013-12-15

200

Chlorophyll antenna size adjustments by irradiance in Dunaliella salina involve coordinate regulation of chlorophyll a oxygenase ( CAO ) and Lhcb gene expression  

Microsoft Academic Search

To elucidate the mechanism of irradiance-dependent adjustments in the chlorophyll antenna size of photosynthesis, we addressed the regulation of expression of genes encoding a variety of chlorophyll biosynthesis enzymes and that of the Lhcb genes in the model organism Dunaliella salina. Among the chlorophyll biosynthesis enzymes tested, only the chlorophyll a oxygenase (CAO) gene responded to changes in the level

Tatsuru Masuda; Ayumi Tanaka; Anastasios Melis

2003-01-01

201

A Systematic Review of the Mysterious Caterpillar Fungus Ophiocordyceps sinensis in Dong-ChongXiaCao ( D?ng Chóng Xià C?o) and Related Bioactive Ingredients.  

PubMed

The caterpillar fungus Ophiocordyceps sinensis (syn.Cordyceps sinensis), which was originally used in traditional Tibetan and Chinese medicine, is called either "yartsa gunbu" or "DongChongXiaCao ( D?ng Chóng Xià C?o)" ("winter worm-summer grass"), respectively. The extremely high price of DongChongXiaCao, approximately USD $20,000 to 40,000 per kg, has led to it being regarded as "soft gold" in China. The multi-fungi hypothesis has been proposed for DongChongXiaCao; however, Hirsutella sinensis is the anamorph of O. sinensis. In Chinese, the meaning of "DongChongXiaCao" is different for O. sinensis, Cordyceps spp., and Cordyceps sp. Over 30 bioactivities, such as immunomodulatory, antitumor, anti-inflammatory, and antioxidant activities, have been reported for wild DongChongXiaCao and for the mycelia and culture supernatants of O. sinensis. These bioactivities derive from over 20 bioactive ingredients, mainly extracellular polysaccharides, intracellular polysaccharides, cordycepin, adenosine, mannitol, and sterols. Other bioactive components have been found as well, including two peptides (cordymin and myriocin), melanin, lovastatin, ?-aminobutyric acid, and cordysinins. Recently, the bioactivities of O. sinensis were described, and they include antiarteriosclerosis, antidepression, and antiosteoporosis activities, photoprotection, prevention and treatment of bowel injury, promotion of endurance capacity, and learning-memory improvement. H. sinensis has the ability to accelerate leukocyte recovery, stimulate lymphocyte proliferation, antidiabetes, and improve kidney injury. Starting January 1(st), 2013, regulation will dictate that one fungus can only have one name, which will end the system of using separate names for anamorphs. The anamorph name "H. sinensis" has changed by the International Code of Nomenclature for algae, fungi, and plants to O. sinensis. PMID:24716152

Lo, Hui-Chen; Hsieh, Chienyan; Lin, Fang-Yi; Hsu, Tai-Hao

2013-01-01

202

Petrogenesis and metallogenic setting of the Habo porphyry Cu-(Mo-Au) deposit, Yunnan, China  

NASA Astrophysics Data System (ADS)

Although most porphyry-type deposits are associated with subduction-related magmas within magmatic arc settings, recent research has identified a number of porphyry-type deposits that formed in post-subduction tectonic settings. The newly discovered Habo porphyry Cu-(Mo-Au) deposit in Yunnan, China, formed in a post-subduction tectonic setting and is located in the southwest of the Cenozoic Ailao Shan-Red River continental collision zone. The deposit is associated with the Habo South granite pluton, which consists of three mineralization-related quartz monzonite porphyries and a post-mineralization diorite porphyry. Zircons from the Habo South granite and quartz monzonite porphyries were analyzed by in situ U-Pb LA-ICP-MS, yielding a similiar age of 36 Ma, with molybdenite Re-Os isotope dating indicating that the Habo porphyry deposit formed at 35.5 Ma. Both magmatism and the associated mineralization at Habo are coeval with porphyry copper deposits in the Yulong metallogenic belt of Eastern Tibet. The Habo South granite and porphyries have SiO2 concentrations of 67.28-73.44 wt.%, MgO concentrations of <1.5 wt.%, Al2O3 concentrations around 15 wt.%, Al2O3/(CaO + Na2O + K2O) (A/CNK) ratios of >1.1, K2O + Na2O concentrations generally between 7 and 9 wt.%, and K2O/Na2O ratios of >1.4, showing indicative of high-K magmas. The Habo South granite and quartz monzonite porphyries are enriched in light rare earth elements (LREE) and large ion lithophile elements (LILE), and depleted in heavy rare earth elements (HREE) and high field strength elements (HFSE), with high Sr and low Y concentrations. They have initial 87Sr/86Sr values of 0.7071-0.7083, with ?Nd(t) values from -5.3 to -3.7. These features are indicative of lower-crust derived adakitic magmas, and are similar to those of mineralized porphyries in the Yulong copper belt in Eastern Tibet. This mineralogical, geochemical, and isotope evidence strongly suggests that the magmas that formed both porphyries and the Habo South granite were derived by partial melting of a region of thickened lower crust, with assimilation of components generated from a region of phlogopite-bearing lithospheric mantle involved during intrusion. The Habo porphyry deposit represents an extension of the Yulong metallogenic belt and formed in response to regional tectonic activity in Eastern Tibet.

Zhu, Xiangping; Mo, Xuanxue; White, Noel C.; Zhang, Bo; Sun, Mingxiang; Wang, Shuxian; Zhao, Sili; Yang, Yong

2013-04-01

203

Lithogenic concentrations of trace metals in soils and saprolites over crystalline basement rocks: A case study from SW Nigeria  

NASA Astrophysics Data System (ADS)

In this study, an assessment of the lithogenic concentrations of trace metals in soils and saprolite over basement rock units in Ibadan, SW-Nigeria is presented in respect of bedrock types and geochemical controls on the weathering-associated release of trace metals. Consequently, soil, weathered and fresh rock samples from the Precambrian Basement of SW Nigeria were collected from three different bedrock units within Ibadan metropolis and subjected to mineralogical and geochemical analyses. The analytical results revealed major proportions of oxides in the range of 18-20% Al 2O 3, 2-6% Na 2O and 1-6% K 2O for weathered profiles over granite-gneiss and pegmatite units, compared to 2-3% Al 2O 3, <0.5% Na 2O and <1.0% K 2O over schist-quartzite. For the trace elements, weathered profiles on granite-gneiss and schist-quartzite settings exhibit similar enrichment trends (enrichment factor, EF ?l) for most of the trace elements, unlike the pegmatite bedrock. However, enrichments are relatively greater in the top soil unit compared to the intermediate saprolite unit, especially for Pb, Ni, Zn, Cr, Co, Rb, Sr and Ba, a situation attributed to leaching and redistribution within the weathered profiles through pedogenetic process and percolating groundwater. Furthermore, the estimated weathering indices using Ruxton Ratio (RR = {SiO 2/Al 2O 3}) and Chemical Index of Alteration (CIA = 100{Al 2O 3/[Al 2O 3 + CaO + Na 2O + K 2O]}) revealed RR of 2.9-3.7 and CIA of 54-73% for granite-gneiss and pegmatite units, implying medium levels of weathering, compared to RR of 30.8-35.5 and CIA of >60% for schist-quartzite units, which suggest weak chemical weathering. Also, the estimated high percentage loss, especially for Pb, Rb, Sr, Ba relative to the bedrocks, shows that the trace elements can be mobilized within the weathering profiles even at a low degree of chemical weathering. Such weathering-induced release of trace metals is of environmental significance as natural lithogenic input sources and as background reference for future monitoring of possible human/anthropogenic impacts.

Tijani, Moshood N.; Okunlola, Olugbenga A.; Abimbola, Akinlolu F.

2006-12-01

204

Selective catalytic reduction of nitric oxide by methane in the presence of oxygen over CaO catalyst  

SciTech Connect

The selective catalytic reduction of nitric oxide by methane in the presence of oxygen was studied over CaO catalyst in the temperature range 550--850 C. The nitric oxide conversion-versus-temperature profile was found to depend on oxygen feed concentration, while the selectivity to N{sub 2} formation was found to be 100% and independent of oxygen feed concentration in the range 1--10 mol%. The kinetic study has shown that the reaction order with respect to NO and CH{sub 4} is 1.0 and 0.5, respectively. On the other hand, the reaction order with respect to O{sub 2} was found to be slightly positive for O{sub 2} feed concentrations up to 1 mol% and slightly negative at higher concentrations. The apparent activation energy of the reaction in the presence of oxygen was found to be 14.6 kcal/mol. The addition of 2.5 mol% CO{sub 2} and 5 mol% H{sub 2}O in the feed stream had a considerable inhibiting effect on NO conversion in the range 550--650 C, while a small inhibiting effect of CO{sub 2} and a positive effect of H{sub 2}O were observed in the range 700--850 C. Temperature-programmed desorption (TPD) of NO revealed the presence of two well-resolved NO peaks in the temperature range 250--650 C, a behavior also observed during a temperature-programmed oxidation experiment under O{sub 2}/He flow. However, during temperature-programmed surface reaction under CH{sub 4}/He flow the NO desorption spectrum showed a significant shift of the stronger adsorbed NO species toward lower temperatures. Preadsorbed CO{sub 2} on the CaO surface was found to largely affect the chemisorption of NO and its desorption kinetics during TPD. The amount of deposited carbon-containing species on the catalyst surface during reaction was determined with transient titration experiments and it was found to be small.

Fliatoura, K.D.; Verykios, X.E. [Univ. of Patras (Greece). Dept. of Chemical Engineering] [Univ. of Patras (Greece). Dept. of Chemical Engineering; Costa, C.N.; Efstathiou, A.M. [Univ. of Cyprus, Nicosia (Cyprus). Dept. of Natural Sciences] [Univ. of Cyprus, Nicosia (Cyprus). Dept. of Natural Sciences

1999-04-25

205

Agglomeration characteristics of river sand and wheat stalk ash mixture at high temperatures  

NASA Astrophysics Data System (ADS)

The agglomeration characteristics of river sand and wheat stalk ash mixture at various temperatures are investigated using a muffle furnace. The surface structural changes, as well as the elemental makeup of the surface and cross-section of the agglomerates, are analyzed by polarized light microscopy, scanning electron microscopy (SEM), and energy dispersive X-ray (EDX). Multi-phase equilibrium calculation is performed with FactSage in identifying the melting behavior of the river sand-wheat stalk ash mixture at high temperatures. No indication of agglomeration is detected below 850°C. At a temperature of 900-1000°C, however, obvious agglomeration is observed and the agglomerates solidify further as temperature increases. The presence of potassium and calcium enrichment causes the formation of a sticky sand surface that induces agglomeration. The main component of the agglomerate surface is K2O-CaO-SiO2, which melts at low temperatures. The formation of molten silicates causes particle cohesion. The main ingredient of the binding phase in the cross-section is K2O-SiO2-Na2O-Al2O3-CaO; the agglomeration is not the result of the melting behavior of wheat stalk ash itself but the comprehensive results of chemical reaction and the melting behavior at high temperatures. The multi-phase equilibrium calculations agree well with the experimental results.

Shang, Linlin; Li, Shiyuan; Lu, Qinggang

2013-02-01

206

Strong enhancement of superconductivity in inorganic electride 12CaO·7Al2O3:e- under high pressure  

NASA Astrophysics Data System (ADS)

We present the results of the pressure dependence of the superconductivity of the inorganic electride 12CaO·7Al2O3:e- (C12A7:e-) single crystal through the ac-susceptibility measurement under high pressure. C12A7:e- has the cage structure and the density of states derived from the cages may play an important role in the superconductivity. The superconducting transition temperature ( T c) is ˜ 0.2 K at ambient pressure and monotonically increases up to 1.79 K at 4.7 GPa. The upper critical field H c2 and - dH c2/ dT at T c, in proportion to the density of states (DOS) at Fermi energy becomes larger under high pressure. The superconductivity in C12A7:e- is mediated by the electron-phonon interaction, and the increase of Tc with pressure may arise from a peak structure of the DOS of cage conduction band.

Tanaka, Shigeki; Kato, Tomoki; Miyake, Atsushi; Kagayama, Tomoko; Shimizu, Katsuya; Kim, Sung Wng; Matsuishi, Satoru; Hosono, Hideo

2013-08-01

207

From insulator to electride: a theoretical model of nanoporous oxide 12CaO.7Al2O3.  

PubMed

Recently, a novel inorganic electride stable at room temperatures has been obtained by reducing a complex nanoporous oxide 12CaO.7Al2O3 (C12A7) in a Ca atmosphere (Matsuishi, S.; Toda, Y.; Miyakawa, M.; Hayashi, K.; Kamiya, T.; Hirano, M.; Tanaka, I.; Hosono, H. Science 2003, 301, 626). In this system, up to 2.3 x 1021/cm3 electrons can be accommodated in a three-dimensional network of cages formed by a positively charged oxide framework. We demonstrate theoretically that at all concentrations, ne, the electrons are neither associated with specific atoms nor fully delocalized. At low ne, the electrons are isolated from each other and resemble the color centers in insulating materials. They are well localized in some of the lattice cages and yield strong inhomogeneous lattice distortions that provide polaron-type cage-to-cage electron hopping. As ne increases, the electrons form a denser electron gas and become more evenly spread over all available lattice cages. At sufficiently high ne, the system becomes metallic but still retains partially localized character of the conducting electrons. We describe the nature of the electronic states at the Fermi level and predict the changes in the optical and magnetic properties of this system as a function of ne. PMID:17243831

Sushko, Peter V; Shluger, Alexander L; Hirano, Masahiro; Hosono, Hideo

2007-01-31

208

Features and mechanism of H- anion emission from 12 CaO x 7 Al2O3 surface.  

PubMed

The hydrogen anion (H-) and other anionic species (O-, OH-, e-) in the gas phase, emitted from the synthesized crystal surface of 12 CaO x 7 Al2O3-H- (C12A7-H-), have been observed. The emission intensity of all the anionic species strongly depends on the sample surface temperature and the extraction field. H- has the highest emission branch ratio, and the extraction field can reduce its apparent activation energy. H- emission current at a microA/cm2-level has been achieved, which is about 4 orders of magnitude higher than that obtained from the thermal desorption process of CaH2. The observed anions of H- and OH- are attributed to their migration from the C12A7-H- cages onto the surface [i.e., Y-(cages) --> Y-(surface) --> Y-(gas phase) (Y = H, OH)]. The weak O- and electron emission would both arise from the dissociation of O2-: O2-(surface) --> O-(surface) + e-(surface) --> O-(gas phase) + e-(space). PMID:16852484

Huang, Fan; Li, Jiang; Wang, Lian; Dong, Ting; Tu, Jing; Torimoto, Yoshifumi; Sadakata, Masayoshi; Li, Quanxin

2005-06-23

209

Spectroscopic characterization of a multiband complex oxide: Insulating and conducting cement 12CaO·7Al2O3  

NASA Astrophysics Data System (ADS)

Natural 12CaO·7Al2O3 (C12A7) is a wide band gap insulator, but conductivity can be realized by introducing oxygen deficiency. Currently, there are two competing models explaining conductivity in oxygen-deficient C12A7, one involving the electron transfer via a “cage conduction band” inside the nominal band gap, the other involving electron hopping along framework lattice sites. To help resolve this debate, we probe insulating and conducting C12A7 with x-ray emission, x-ray absorption, and x-ray photoemission spectroscopy, which provide a full picture of both the valence and conduction band edges in these materials. These measurements suggest the existence of a narrow conduction band between the main conduction and valence bands common in both conducting and insulating C12A7 and support the theory that free electrons in oxygen-deficient C12A7 occupy the low-energy states of this narrow band. Our measurements are corroborated with density functional theory calculations.

McLeod, J. A.; Buling, A.; Kurmaev, E. Z.; Sushko, P. V.; Neumann, M.; Finkelstein, L. D.; Kim, S.-W.; Hosono, H.; Moewes, A.

2012-01-01

210

Insulator -- polaron conductor -- metal transitions in a complex oxide 12CaO.7Al2O3.  

NASA Astrophysics Data System (ADS)

Recent experiments have demonstrated that a complex nano-porous oxide 12CaO.7Al2O3 (C12A7) built of positively charged sub-nanometer cages can be converted from a transparent insulator to a transparent conductor by H2 doping followed by UV-light irradiation with 4--4.5 eV photons [1]. This irradiation induces optical absorption bands with maxima at 0.4 eV and 2.8 eV and high concentrations of unpaired electrons. We use ab initio calculations to reveal the mechanism of photo-induced insulator--conductor transition and the role of H atoms in this process and to elucidate the transport properties of the electrons in this system as a function of electron concentration. Our theoretical modeling suggests that at concentration below 10^20 cm-3 electrons are responsible for the polaron type electrical conductivity with the activation energy close to 0.1 eV as well as for the optical absorption at 0.4 eV and 2.8 eV [2]. We demonstrate that, as the electron concentration exceeds 10^20 cm-3, the character of electronic conductivity changes from polaron type to metallic. [1] K. Hayashi et al., Nature 419, 462 (2002). [2] P.V. Sushko, et al., Phys. Rev. Lett. 91, 126401 (2003); P.V. Sushko et al., Appl. Phys. Lett. 86, 092101 (2005).

Sushko, P.; Shluger, A.; Stoneham, A.; Hayashi, K.; Matsuishi, S.; Hirano, M.; Hosono, H.

2006-03-01

211

Preparation and visible emission of Er-doped 12CaO x 7Al2O3 powder.  

PubMed

Er(3+)-doped 12CaO x 7Al2O3 (C12A7:Er3+) powders were prepared using the sol-gel method. X-ray diffraction, micro-Raman spectra and absorption spectra showed that C12A7:Er3+ powder had been obtained. Sharp and intense Er(3+)-related emission from C12A7:Er3+ powder with different Er3+ concentrations in the visible region at room temperature was investigated by analyzing the local structure of Ca atoms in C12A7, and it revealed that cation sites with low symmetry of the host were beneficial to the photoluminescence of Er3+ ions. The emission lines were attributed to two types of Er3+ centers, isolated Er3+ ions and complex centers formed by aggregation of Er3+ ions. The PL intensity might be affected by free oxygen species relative to Er3+ ions formed by charge compensation. The inverse temperature dependent luminescence from the upper level of 2H11/2 state and that from the lower level of 4S3/2 state implied that the thermalization or thermal equilibrium of electrons between the two closely emission states occurred. PMID:18468174

Wang, D; Liu, Y X; Liu, Y C; Xu, C S; Shao, C L; Li, X H

2008-03-01

212

Characterization and luminescence of Eu3+ ions doped 12CaO 7Al2O3 nanopowders.  

PubMed

Eu3+ ions doped 12CaO 7Al2O3 (C12A7) powders with different Eu3+ concentrations were prepared by sol-gel combined with solid state reaction method. The results of XRD and Raman spectra showed that single cubic phase polycrystalline C12A7:Eu3+ powders were prepared. The absorption peaks attributed to f-f transition of Eu3+ ion can be observed, indicating that Eu3+ had been incorporated into C12A7 lattice site. Visible PL peaks around 578, 588, 614 nm were ascribed to 5D0 --> 7FJ (J = 0, 1, 2) transitions of Eu3+ under the excitation of 488 nm line. The PL of C12A7:Eu3+ showed the strongest emission intensity at Eu3+ concentration of 0.5 at%. Two different types of Eu3+ centers were identified by the two lines from 5D0 --> 7F0 transition emission. The doping mechanism of C12A7:Eu3+ might be attributed to Eu3+ ions substitution for two types of Ca2+ lattice sites in C12A7. The temperature dependent PL spectra of Eu-doped C12A7 were measured in the range from 100 to 300 K under the excitation of 488 nm laser line. The PL intensities as a function of temperature were well fitted by using a unified theoretical model, considering thermal activation and nonradiative energy transfer processes. PMID:22413328

Liu, C G; Liu, Y X; Wang, D; Yan, D T; Xu, C S

2011-11-01

213

Thermodynamics and kinetics of hydroxide ion formation in 12 CaO x 7 Al2O3.  

PubMed

We have examined the thermodynamics and kinetics of hydroxide (OH-) ions that formed in cages of 12 CaO x 7 Al2O3 (C12A7) with nanoporous structures. It is confirmed using thermogravimetric-evolved gas analyses (TG-EGA) that hydration in C12A7 is mediated by a reaction between an oxide (O2-) ion in the cage and an H2O molecule in the atmosphere to form two OH- ions in the cages. To simply and exactly quantify the OH- content from infrared absorption measurements of OH-stretching band, we propose a method combined with a thermodynamic analysis, allowing the simultaneous determination of the molar extinction coefficient of the OH-band, enthalpy, and entropy for the hydration. Hydration enthalpy in C12A7 is extremely high compared with other oxides and was enhanced by the marked instability of O2- ion in the cage. Consequently, high solubility of OH- ion is retained up to unusually high temperatures. Furthermore, we determined diffusion coefficients of species relevant to the hydration process and demonstrated that inward diffusion of OH- ions is the rate-determining process. PMID:16852465

Hayashi, Katsuro; Hirano, Masahiro; Hosono, Hideo

2005-06-23

214

Photoluminescence from Au ion-implanted nanoporous single-crystal 12CaO•7Al2O3  

NASA Astrophysics Data System (ADS)

Implantation of Au+ ions into a single crystalline 12CaO•7Al2O3 (C12A7) was performed at high temperatures with fluences from 1×1014 to 3×1016cm-2 . This material is composed of positively charged sub-nanometer-sized cages compensated by extra-framework negatively charged species. The depth profile of concentrations of Au species was analyzed using Rutherford backscattering spectrometry. The measured optical spectra and ab initio embedded cluster calculations show that the implanted Au species are stabilized in the form of negative Au- ions below the fluences of ˜1×1016cm-2 (Au volume concentration of ˜2×1021cm-3 ). These ions are trapped in the cages and exhibit photoluminescence (PL) bands peaking at 3.05 and 2.34eV at temperatures below 150K . At fluences exceeding ˜3×1016cm-2 , the implanted Au atoms form nano-sized clusters. This is manifested in quenching of the PL bands and creation of an optical absorption band at 2.43eV due to the surface plasmon of free carriers in the cluster. The PL bands are attributed to the charge transfer transitions (Au0+e-?Au-) due to recombination of photo-excited electrons (e-) , transiently transferred by ultraviolet excitation into a nearby cages, with Au0 atoms.

Miyakawa, Masashi; Kamioka, Hayato; Hirano, Masahiro; Kamiya, Toshio; Sushko, Peter V.; Shluger, Alexander L.; Matsunami, Noriaki; Hosono, Hideo

2006-05-01

215

Characterization and optical transition in tb-doped 12CaO x 7Al2O3 powders.  

PubMed

Tb-doped 12CaO x 7Al2O3 (C12A7:Tb3+) powders with strong green emission were prepared using the sol-gel method. X-ray diffraction, micro-Raman spectra, scanning electron microscopy and absorption spectra showed that C12A7:Tb3+ powders with grain size of 200-300 nm were synthesized. Porous powders could be formed as the concentration of Tb3+ was 5 at%. The absorption band around 209 nm was attributed to the host lattice absorption, and the bands around 255 nm and 274 nm were related to the 4f-5d transitions of Tb3+. The absorption intensity of the visible region was enhanced due to the presence of one 100 nm-diameter hole in every grain of C12A7:Tb3+ powders. The emission spectra showed noticeable influence of Tb-Tb cross relaxation, which favored the green photoluminescence (PL) over the blue PL. The study on the concentration quenching indicated that the energy transfers depopulating the 5D3 and 5D4 levels were assigned to the mechanisms of electric dipole-dipole and exchange interaction, respectively. PMID:20355639

Xue, L L; Liu, Y X; Xu, C S; Liu, Y C; Zhao, C J; Zhang, X T

2010-03-01

216

Photoluminescence of Au - formed in 12CaO · 7Al 2O 3 single crystal by Au +-implantation  

NASA Astrophysics Data System (ADS)

Au + ion implantation with fluences from 1 × 10 14 to 3 × 10 16 cm -2 into 12CaO · 7Al 2O 3 (C12A7) single crystals was carried out at a sample temperature of 600 °C. The implanted sample with the fluence of 1 × 10 15 cm -2 exhibited photoluminescence (PL) bands peaking at ˜3.1 and ˜2.3 eV at ?150 K when excited by He-Cd laser (325 nm). This was the first observation of PL from C12A7. These two PL bands are possibly due to intra-ionic transitions of an Au - ion having the electronic configuration of 6 s2, judged from their similarities to those reported on Au - ions in alkali halides. However, when the concentration of the implanted Au ions exceeded the theoretical maximum value of anions encaged in C12A7 (˜2.3 × 10 21 cm -3), surface plasmon absorption appeared in the optical absorption spectrum, suggesting Au colloids were formed at such high fluences. These observations indicate that negative gold ions are formed in the cages of C12A7 by the Au + implantation if an appropriate fluence is chosen.

Miyakawa, M.; Kamioka, H.; Hirano, M.; Kamiya, T.; Hosono, H.

2006-09-01

217

Role of MgO and CaO promoters in Ni-catalyzed hydrogenation reactions of CO and carbon  

SciTech Connect

The roles of Mg and Ca promoters in Ni-catalyzed hydrogasification of carbon were investigated with emphasis on nickel dispersion and nickel-carbon interactions during gasification. The dispersion of nickel on carbon, which was estimated by means of XRD, H{sub 2}-TPD, and CO methanation test, was (Ni + Mg){much gt}(Ni + Ca)>Ni. The increased dispersions of nickel by the Mg and Ca added were found to result in the enhanced Ni-C interaction, which was monitored through the desorption of CO from oxygen remaining on carbon, and, therefore, in the promotions of Ni-catalyzed lower-temperature gasification at 400-700 C. The Ca promoter was likely to give surface CaO(COO) species upon heating up to 550 C and release CO{sub 2} above {approximately} 650 C. The CO{sub 2} released is efficiently converted by the nickel adjacent to CaO into CO to create Ni-(O)-C species above 700 C, resulting in acceleration of Ni-catalyzed gasification above 700 C. In situ oxygen transfer to Ni/C during reaction is the most important role played by the Ca promoter.

Haga, Tetsuya; Ozaki, Junichi; Suzuki, Kyosuke; Nishiyama, Yoshiyuki ( Tohoku Univ., Sendai (Japan))

1992-03-01

218

CO{sub 2} capture capacity of CaO in long series of carbonation/calcination cycles  

SciTech Connect

Calcium oxide can be an effective sorbent to separate CO{sub 2} at high temperatures. When coupled with a calcination step to produce pure CO{sub 2}, the carbonation reaction is the basis for several high-temperature CO{sub 2} capture systems. The evolution with cycling of the capture capacity of CaO derived from natural limestones is experimentally investigated in this work. Long series of carbonation/calcination cycles (up to 500) varying different variables affecting sorbent capacity have been tested in a thermogravimetric apparatus. Calcination temperatures above T > 950{sup o}C and very long calcination times accelerate the decay in sorption capacity, while other variables have a comparatively modest effect on the overall sorbent performance. A residual conversion of about 7-8% that remains constant after many hundreds of cycles and that seems insensitive to process conditions has been found. This residual conversion makes very attractive the carbonation/calcination cycle, by reducing (or even eliminating) sorbent purge rates in the system. A semiempirical equation has been proposed to describe sorbent conversion with the number of cycles based on these new long data series.

Grasa, G.S.; Abanades, J.C. [CSIC, Zaragoza (Spain)

2006-12-20

219

Dielectric properties of (CuO, CaO2, and BaO)y/CuTl-1223 composites  

NASA Astrophysics Data System (ADS)

We synthesized (CuO, CaO2, and BaO)y/Cu0.5Tl0.5Ba2Ca2Cu3O10-? (y = 0, 5%, 10%, 15%) composites by solid-state reaction and characterized them by x-ray diffraction, scanning electron microscopy, dc-resistivity, and Fourier transform infrared spectroscopy. Frequency and temperature dependent dielectric properties, such as real and imaginary parts of the dielectric constant, dielectric loss, and ac-conductivity of these composites were studied by capacitance and conductance measurements as a function of frequency (10 kHz to 10 MHz) and temperature (78 to 300 K). X-ray diffraction analysis reveals that the characteristic behavior of the superconductor phase and the structure of Cu0.5Tl0.5Ba2Ca2Cu3O10-? are nearly undisturbed by doping with nanoparticles. Scanning electron microscopy images show the improvement in the intergranular linking between the superconducting grains occurring with increasing nanoparticle concentration. Microcracks are healed up with these nanoparticles, and superconducting volume fraction is also increased. Dielectric properties of these composites strongly depend on the frequency and temperature. Zero resistivity critical temperature and dielectric properties show opposite trends with the addition of nanoparticles to the Cu0.5Tl0.5Ba2Ca2Cu3O10-? superconductor matrix.

Mumtaz, M.; Kamran, M.; Nadeem, K.; Jabbar, Abdul; Khan, Nawazish A.; Saleem, Abida; Tajammul Hussain, S.; Kamran, M.

2013-07-01

220

Spectroscopic Characterization of a Multiband Complex Oxide: Insulating and Conducting Cement 12CaO·7Al?O?  

SciTech Connect

Natural 12CaO·7Al?O? (C12A7) is a wide band gap insulator, but conductivity can be realized by introducing oxygen deficiency. Currently, there are two competing models explaining conductivity in oxygen-deficient C12A7, one involving the electron transfer via a “cage conduction band” inside the nominal band gap, the other involving electron hopping along framework lattice sites. To help resolve this debate, we probe insulating and conducting C12A7 with x-ray emission, x-ray absorption, and x-ray photoemission spectroscopy, which provide a full picture of both the valence and conduction band edges in these materials. Thesemeasurements suggest the existence of a narrow conduction band between themain conduction and valence bands common in both conducting and insulating C12A7 and support the theory that free electrons in oxygen-deficient C12A7 occupy the low-energy states of this narrow band. Our measurements are corroborated with density functional theory calculations.

McLeod, John A.; Buling, A.; Kurmaev, Ernst Z.; Sushko, Petr V.; Neumann, N.; Finkelstein, L. D.; Kim, S. W.; Hosono, H.; Moewes, Alexander

2012-01-13

221

The effect of Al2O3, CaO, Cr2O3 and MgO on devitrification of silica  

NASA Technical Reports Server (NTRS)

The effect of doping on devitrification of vitreous silica was studied at 1100, 1200, and 1300 C. Dispersion of dopants on a molecular scale was accomplished via a sol-gel technique. All dopants accelerated the devitrification of silica but to different degrees. The most active was CaO followed by MgO, Al2O3, and Cr2O3. Pure silica and silica containing Cr2O3 and Al2O3 devitrified to alpha-cristobalite only, whereas silica doped with CaO and MgO produced alpha-quartz and alpha-cristobalite. It appears that prolonged heat treatment would cause alpha-quartz to transform to alpha-cristobalite.

Zaplatynsky, Isidor

1988-01-01

222

Preparation of CaO as OLED getter material through control of crystal growth of CaCO{sub 3} by block copolymers in aqueous solution  

SciTech Connect

As the starting materials of organic light-emitting diode (OLED) getter, calcium carbonate (CaCO{sub 3}) particles with various shapes and crystal structures have been successfully prepared with additives (L64 or PEGPG), which contain blocks of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO). These CaCO{sub 3} particles were calcinated into highly crystalline calcium oxide (CaO) nanoparticles with high capacity of water adsorption up to 14.23 wt.%. The CaCO{sub 3} and CaO particles prepared at various conditions were characterized using the field emission scanning electron microscopy (FE-SEM), Fourier transform infrared microscopy (FT-IR), X-ray powder diffraction (XRD), and dynamic vapor sorption (DVS) method.

Park, Jae-Hyung [Department of Chemical Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Oh, Seong-Geun [Department of Chemical Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of)], E-mail: seongoh@hanyang.ac.kr

2009-01-08

223

First-principles calculations of surfactant-assisted growth of polar CaO(111) oxide film: The case of water-based surfactant  

NASA Astrophysics Data System (ADS)

Surfactant-assisted growth of polar CaO(111) oxide film in the presence of water-based surfactant is studied by first-principles calculations both from thermodynamic and kinetic points of view. We show that the water molecules not only supply a surfactant by depositing hydrogen on the surface throughout the growth process, but also supply oxygen atoms as an elemental constituent in the film growth with rather small energy barriers, i.e. water oxygen atoms are easily inserted in the top surface layer of the growth film during the wet oxidation process. Adding the water surfactants to conventional synthesis techniques leads to the continuous presence of hydrogen atoms in the surface region during the growth process, which efficiently quenches polarity and dynamically stabilizes the growth of the polar surface, and thus facilitates the growth of defect-free CaO(111) films with arbitrary thickness.

Tan, Xin; Zapol, Peter

2012-07-01

224

The Vibrational Frequencies of CaO2, ScO2, and TiO2: A Comparison of Theoretical Methods  

NASA Technical Reports Server (NTRS)

The vibrational frequencies of several states of CaO2, ScO2, and TiO2 are computed at using density functional theory (DFT), the Hatree-Fock approach, second order Moller-Plesset perturbation theory (MP2), and the complete-active-space self-consistent-field theory. Three different functionals are used in the DFT calculations, including two hybrid functionals. The coupled cluster singles and doubles approach including the effect of unlinked triples, determined using perturbation theory, is applied to selected states. The Becke-Perdew 86 functional appears to be the cost effective method of choice, although even this functional does not perform well for one state of CaO2. The MP2 approach is significantly inferior to the DFT approaches.

Rosi, Marzio; Bauschlicher, Charles W., Jr.; Chertihin, George V.; Andrews, Lester; Arnold, James O. (Technical Monitor)

1997-01-01

225

Comparison of phosgene, chlorine, and hydrogen chloride as reagents for converting molten CaO. CaCl/sub 2/ to CaCl/sub 2/  

SciTech Connect

One method at Los Alamos for preparing impure plutonium metal from the impure oxide is by batch reduction with calcium metal at 850/sup 0/C in a CaCl/sub 2/ solvent. The solvent salt from this reduction is currently discarded as low-level radioactivity waste only because it is saturated with the CaO byproduct. We have demonstrated a pyrochemical technique for converting the CaO to CaCl/sub 2/ thereby incorporating solvent recycling into the batch reduction process. We will discuss the effectiveness of HCl, Cl/sub 2/, and COCl/sub 2/ as chlorinating agents and recycling actual spent process solvent salts. 6 refs., 8 figs.

Fife, K.W.

1985-01-01

226

Role of Y2O3, CaO, MgO additives on structural and microstructural behavior of zirconia/mullite aggregates  

NASA Astrophysics Data System (ADS)

Zirconia mullite (MUZ), Y2O3-MUZ, CaO-MUZ and MgO-MUZ composites, synthesized through plasma fusion technique, are becoming important due to their commercial scale of production within five minutes of plasma treatment from sillimanite, zircon and alumina mixture. The X-ray diffraction studies reveal the monoclinic zirconia phase in MUZ composite whereas mixed monoclinic, tetragonal and cubic phases of zirconia have been observed in Y2O3, CaO, MgO added MUZ composites. The Y2O3, CaO and MgO additives act as sintering aids to favour the transformation and stabilisation of tetragonal and cubic zirconia phases at room temperature. These additives also play a key role in the development of various forms of microstructure to achieve dense MUZ composites.

Mishra, D. K.; Prusty, Sasmita; Mohapatra, B. K.; Singh, S. K.; Behera, S. N.

2012-07-01

227

Comparison of phosgene, chlorine, and hydrogen chloride as reagents for converting molten CaO. CaCl/sub 2/ to CaCl/sub 2/  

SciTech Connect

One method used at Los Alamos for preparing impure plutonium metal from the impure oxide is batch reduction with calcium metal at 850/sup 0/C in a CaCl/sub 2/ solvent. The solvent salt from this reduction is currently discarded as low-level radioactive waste only because it is saturated with the CaO by-product. We have demonstrated a pyrochemical technique for converting the CaO to CaCl/sub 2/, thereby incorporating solvent recycle into the batch reduction process. We discuss the effectiveness of HCl, Cl/sub 2/, and COCl/sub 2/ as chlorinating agents and present initial data on regenerating and recycling actual, spent-solvent salts. 6 refs., 8 figs., 1 tab.

Fife, K.W.; Bowersox, D.F.; McCormick, E.D.

1985-09-01

228

Pure CaO, MgO (Periclase), TiO2 (Rutile), and Al2O3 (Corundum) in Ca,Al-rich Inclusions from Carbonaceous Chondrites  

NASA Astrophysics Data System (ADS)

Transmission electron microscopy (TEM) studies were performed on four Ca,Al-rich inclusions (two Type A, one Type B, and a spinel-perovskite spherule) from the carbonaceous chondrites Allende (CV3), Acfer 082 (CV3), Acfer 086 (CV3), and Acfer 094 (unique). Two Type A and one Type B inclusion contain the pure oxide phases rutile (TiO2) and CaO. Within a spinel-perovskite spherule from Acfer 094 periclase (MgO) and corundum (Al2O3) were found coexisting with rutile and CaO. The oxides were found as tiny single grains (50-200 nm) of rounded morphologies inside and at grain boundaries of constituent minerals of the CAIs. We suggest that these oxides are primary condensation products which did not react during the condensation process with the remaining nebular gas to form other oxides or silicates.

Greshake, A.; Bischoff, A.; Putnis, A.

1996-03-01

229

Biomass gasification with steam in fluidized bed: Effectiveness of CaO, MgO, and CaO-MgO for hot raw gas cleaning  

Microsoft Academic Search

The upgrading of the raw hot gas from a bubbling fluidized bed biomass gasifier is studied using cheap calcined minerals or rocks downstream from the gasifier. Biomass gasification is made with steam (not air) at 750--780 C and about 0.5--1.0 kg of biomass\\/h. Calcined solids used are dolomite (MgO-CaO), pure calcite (CaO), and pure magnesite (MgO). Variables studied have been

Jesús Delgado; María P. Aznar; José Corella

1997-01-01

230

A chromodomain protein encoded by the arabidopsis CAO gene is a plant-specific component of the chloroplast signal recognition particle pathway that is involved in LHCP targeting.  

PubMed Central

A recessive mutation in Arabidopsis, named chaos (for chlorophyll a/b binding protein harvesting-organelle specific; designated gene symbol CAO), was isolated by using transposon tagging. Characterization of the phenotype of the chaos mutant revealed a specific reduction of pigment binding antenna proteins in the thylakoid membrane. These nuclear-encoded proteins utilize a chloroplast signal recognition particle (cpSRP) system to reach the thylakoid membrane. Both prokaryotes and eukaryotes possess a cytoplasmic SRP containing a 54-kD protein (SRP54) and an RNA. In chloroplasts, the homolog of SRP54 was found to bind a 43-kD protein (cpSRP43) rather than to an RNA. We cloned the CAO gene, which encodes a protein identified as Arabidopsis cpSRP43. The product of the CAO gene does not resemble any protein in the databases, although it contains motifs that are known to mediate protein-protein interactions. These motifs include ankyrin repeats and chromodomains. Therefore, CAO encodes an SRP component that is unique to plants. Surprisingly, the phenotype of the cpSRP43 mutant (i.e., chaos) differs from that of the Arabidopsis cpSRP54 mutant, suggesting that the functions of the two proteins do not strictly overlap. This difference also suggests that the function of cpSRP43 is most likely restricted to protein targeting into the thylakoid membrane, whereas cpSRP54 may be involved in an additional process(es), such as chloroplast biogenesis, perhaps through chloroplast-ribosomal association with chloroplast ribosomes.

Klimyuk, V I; Persello-Cartieaux, F; Havaux, M; Contard-David, P; Schuenemann, D; Meiherhoff, K; Gouet, P; Jones, J D; Hoffman, N E; Nussaume, L

1999-01-01

231

CaO insulator coatings and self-healing of defects on V-Cr-Ti alloys in liquid lithium system  

Microsoft Academic Search

Electrically insulating and corrosion-resistant coatings are required at the liquid metal\\/structural interface in fusion first-wall\\/blanket applications. Electrical resistance of CaO coatings that were produced on V-5%Cr-5%Ti by exposure of the alloy to liquid Li containing 0.5-85 wt.% dissolved Ca was measured as a function of time at temperatures between 250 and 600°C. The solute element, Ca in liquid Li, reacted

J. H. Park; T. F. Kassner

1995-01-01

232

CaO insulator coatings and self-healing of defects on V?Cr?Ti alloys in liquid lithium system  

Microsoft Academic Search

Electrically insulating and corrosion-resistant coatings are required at the liquid metal\\/structural interface in fusion first-wall\\/blanket applications. The electrical resistance of CaO coatings produced on V?5%Cr?5%Ti by exposure of the alloy to liquid Li that contained 0.5–85 wt% dissolved Ca was measured as a function of time at temperatures between 250 and 600°C. The solute element, Ca in liquid Li, reacted

J.-H. Park; T. F. Kassner

1996-01-01

233

Kinetics of SO{sub 2} sorption from air by Al{sub 2}O{sub 3} and CaO  

SciTech Connect

Removal of sulfur dioxide from gases, which is an important problem, can be accomplished by various methods, in particular, by low-temperature adsorption and high-temperature chemical uptake. This communication presents data on the kinetics of sorption of sulfur dioxide from air by alumina and calcium oxide. Sorption and chemical uptake of SO{sub 2} from air by Al{sub 2}O{sub 3} and CaO have been studied.

Vitvitskii, A.I.; Voronina, E.V. [Russian Scientific Center, St. Petersburg (Russian Federation)

1995-01-20

234

Solution derived 12CaO·7Al 2O 3 thin films on MgO(1 0 0) substrate  

Microsoft Academic Search

12CaO·7Al2O3 (C12A7) is known as a component of alumina cement and shows various remarkable properties: generation of high oxidizing power using oxygen radical O?, high electric conductivity (?1500Scm?1) for the electron clathrated one, etc. Most of the C12A7 thin film fabrication processes reported have been based on PLD method so far, which require high vacuum level and high energy consumption.

Naonori Sakamoto; Yuki Matsuyama; Masahito Hori; Naoki Wakiya; Hisao Suzuki

2010-01-01

235

Synthesis of Calcium Phosphates by PO(OH) x (OBut) 3?x and CaO 2 C 2 H 4  

Microsoft Academic Search

In this work, an alkoxide solution route to synthesize Ca phosphates was developed. For the precursors, a CaO2C2H4 solution was prepared by dissolving Ca metal powder into ethylene glycol, and a PO(OH)x(OBut)3-x solution was prepared by dissolving P2O5 inton -butanol under reflux conditions. In order to obtain a mixed solution of the two precursors, acetic acid was used as an

Wenjian Weng; J. L. Baptista

1997-01-01

236

Quantitative evaluation of antibacterial activities of metallic oxide powders (ZnO, MgO and CaO) by conductimetric assay  

Microsoft Academic Search

Antibacterial activities of metallic oxide (ZnO, MgO and CaO) powders against Staphylococcus aureus and Escherichia coli were quantitatively evaluated by measuring the change in electrical conductivity of the growth medium caused by bacterial metabolism (conductimetric assay). The obtained conductivity curves were analyzed using the growth inhibition kinetic model proposed by Takahashi for calorimetric evaluation, and the metallic oxides were determined

J. Sawai

2003-01-01

237

Identification of CaSO sub 4 formed by reaction of CaO and SO sub 2 (journal article). Report for October 1988March 1989  

Microsoft Academic Search

The injection of calcium-based sorbents into coal-fired boilers for reaction with, and reduction in the levels of, sulfur dioxide (SOâ) in the flue gas has undergone considerable research and development. Significant effort has also been made in developing models for the overall reaction CaO + SOâ + 1\\/2 Oâ <-> CaSOâ in order to better predict the effects of system

B. K. Gullett; K. R. Bruce

1989-01-01

238

CaO insulator coatings and self-healing of defects on V?Cr?Ti alloys in liquid lithium system  

NASA Astrophysics Data System (ADS)

Electrically insulating and corrosion-resistant coatings are required at the liquid metal/structural interface in fusion first-wall/blanket applications. The electrical resistance of CaO coatings produced on V?5%Cr?5%Ti by exposure of the alloy to liquid Li that contained 0.5-85 wt% dissolved Ca was measured as a function of time at temperatures between 250 and 600°C. The solute element, Ca in liquid Li, reacted with the alloy substrate at 400-420°C to produce a CaO coating. Resistance of the coating layer measured in-situ in liquid Li was ? 10 6 ? at 400°C. Thermal cycling between 300 and 700°C changed the coating layer resistance, which followed insulator behavior. These results suggest that thin homogeneous coatings can be produced on variously shaped surfaces by controlling the exposure time, temperature, and composition of the liquid metal. The technique can be applied to various shapes (e.g., inside/outside of tubes, complex geometrical shapes) because the coating is formed by liquid-phase reaction. Examination of the specimens after cooling to room temperature revealed no spallation, but homogeneous crazing cracks were present in the CaO coating. Additional tests to investigate the in-situ self-healing behavior of the cracks indicated that rapid healing occurred at ? 360°C.

Park, J.-H.; Kassner, T. F.

1996-10-01

239

CaO insulator coatings and self-healing of defects on V-Cr-Ti alloys in liquid lithium system  

SciTech Connect

Electrically insulating and corrosion-resistant coatings are required at the liquid metal/structural interface in fusion first-wall/blanket applications. Electrical resistance of CaO coatings that were produced on V-5%Cr-5%Ti by exposure of the alloy to liquid Li containing 0.5-85 wt.% dissolved Ca was measured as a function of time at temperatures between 250 and 600{degrees}C. The solute element, Ca in liquid Li, reacted with the alloy substrate at 400-420{degrees}C to produce a CaO coating. Resistance of the coating layer measured in-situ in liquid Li was {approx}10{sup 6} {Omega} at 400{degrees}C. Thermal cycling between 300 and 700{degrees}C changed the coating layer resistance, which followed insulator behavior. These results suggest that thin homogeneous coatings can be produced on variously shaped surfaces by controlling the exposure time, temperature, and composition of the liquid metal. The technique can be applied to various shapes (e.g., inside/outside of tubes, complex geometrical shapes) because the coating is formed by liquid-phase reaction. Examination of the specimens after cooling to room temperature revealed no spallation, but homogeneous crazing cracks were present in the CaO coating. Additional tests to investigate the in-situ self-healing behavior of the cracks indicated that rapid healing occurred at {>=}360{degrees}C.

Park, J.H.; Kassner, T.F.

1995-09-01

240

Oxidation Studies of SiAlON/MgAlON Ceramics with Fe2O3 and CaO Impurities, Part I: Kinetics  

NASA Astrophysics Data System (ADS)

T he oxidation behaviors of composites SiAlON/MgAlON phases (?-SiAlON, 15R-SiAlON and MgAlON) synthesized from the residue during the leaching treatment of salt cake and corresponding synthetic samples were investigated in air by thermogravimetric measurements. Combined kinetics, viz. linear law + arctan law + parabolic law, are used to describe the kinetics of oxidation in isothermal mode. The oxidation studies reveal the effects of impurities, namely, Fe2O3 and CaO, present in the salt cake residue. The addition of Fe2O3 results in a lower activation energy and more aggressive oxidation. The addition of CaO caused the shrinkage during the synthesis and liquid formation during the oxidation above 1673 K (1400 °C). The impurities of CaO and Fe2O3 in the leaching residue can result in an aggressive oxidation at low temperature and a protective oxidation at temperatures above the eutectic point.

Li, Peng; Zhang, Mei; Teng, Lidong; Seetharaman, Seshadri

2013-02-01

241

The rates of desulfurization of liquid iron by solid CaO and CaO-saturated liquid iron oxide at 1600‡c  

NASA Astrophysics Data System (ADS)

The rates of desulfurization of Fe-O-S melts by CaO crucibles and by CaO-saturated liquid iron oxide have been measured at 1600 ‡C. It was found that irons containing 1.62 wt pct and 0.64 wt pct sulfur and 0.070 wt pct oxygen are desulfurized by a reaction with the containing CaO crucible which does not involve the formation of a CaS product layer. The rate of desulfurization reaction is controlled by diffusion of sulfur in the iron melt, and a value of 6.7 ±1.7 × 10-5 cm2 per second was obtained for the diffusion coefficient of sulfur in liquid iron. Iron containing 0.088 wt pct sulfur and 0.070 wt pct oxygen is not desulfurized by solid CaO. The rate of desulfurization of liquid iron containing 0.088 wt pct sulfur and 0.070 wt pct oxygen by CaO-saturated liquid iron oxide is significantly greater than that calculated on the assumption of diffusion control in the metal phase, and evidence is presented in support of speculation that the reaction rate is enhanced by Marangoni turbulence at the slag-metal interface. The addition of 4 wt pct CaF2 to the CaO-saturated liquid iron oxide has no influence on the rate of desulfurization of the melt.

Saelim, A.; Gaskell, D. R.

1983-06-01

242

Tephra record from the Sea of Marmara for the last 70 ka and its paleoceanographic implications  

NASA Astrophysics Data System (ADS)

Sea of Marmara (SoM) is a gateway between the Mediterraean and Black seas, and a tectonically active basin located on a transform plate boundary. Tephra record in the SoM is therefore very important for dating palaeoceanographic, paleoclimatic and tectonic events. We report three tephra units in cores from the SoM extending back to ca 70 ka BP and including an upper marine and a lower lacustrine units separated by a 12 ka (uncalib.) boundary. The uppermost tephra unit is up to 8 mm thick layer in the marine unit. It is heterogenous phonolitic with high total alkali content of 12.4-15.7 wt % and K2O/Na2O of 0.9 to 1.2. The middle and lower tephra layers occur in the lacustrine unit in ca 29 m-long Core MD-01-2430. The middle tephra (MT-1) is a 70 mm-thick homogeneously rhyolitic layer. The lower tephra (MT-2) is 140 mm thick and has a phonolitic-trachytic composition with CaO content of 1.7-1.9 wt % and bimodal K2O/Na2O of 1.0-1.4. Using their geochemical composition and stratigraphic analysis, we assign the tephra units, from top to bottom, to Vesuvius AP2 Pumice, Santorini Cape Riva and Campanian Ignimbrite, which have been previously dated at 3.5 ka BP, 21.95 ka BP, and 39.3 ka BP (all calender ka). The continuous sedimentary record in the Core MD-01-2430 covering the last ca 70 ka indicates that the SoM was lacustrine, disconnected from the Mediterraean Sea during MIS4, MIS3 and most of MIS2. This implies that the sill depth of the Çanakkale Strait (Dardanelles) was shallower than the present-day -65 m sill depth during MIS3 and MIS4. Figure 1: Morphotectonic map of the Sea of Marmara showing location of the studied cores (red stars). Figure 2: Geochemical biplots of tephra glass composition. a) Total alkali silica diagram b) FeO versus total alkalies for allocating cryptotephras from core MNTKS34 and ML01 to the AP2 tephra from Vesuvius. c) FeO versus CaO for correlating tephra MT1 with the Y-2 tephra from Santorini. d) SiO2 versus CaO for discriminating the MT2 tephra (Campanian Ignimbrite).

Cagatay, M.; Wulf, S.; Guichard, F.; Ozmaral, A.; Sancar; Akçer-Ön, S.; Henry, P.; Gasperini, L.

2013-12-01

243

Conversion of melt-derived microfibrous borate (13-93B3) and silicate (45S5) bioactive glass in a simulated body fluid.  

PubMed

Microfibrous bioactive glasses are showing a considerable capacity to heal soft tissue wounds, but little information is available on the mechanism of healing. In the present study, the conversion of microfibrous borate bioactive glass (diameter = 0.2-5 ?m) with the composition designated 13-93B3 (5.5 Na2O, 11.1 K2O, 4.6 MgO, 18.5 CaO, 3.7 P2O5, 56.6 B2O3 wt%) was evaluated in vitro as a function of immersion time in a simulated body fluid (SBF) at 37 °C using structural and chemical techniques. Silicate 45S5glass microfibers (45 SiO2, 24.5 Na2O, 24.5 CaO, 6 P2O5 wt%) were also studied for comparison. Microfibrous 13-93B3 glass degraded almost completely and converted to a calcium phosphate material within 7-14 days in SBF, whereas >85 % of the silica remained in the 45S5 microfibers, forming a silica gel phase. An amorphous calcium phosphate (ACP) product that formed on the 13-93B3 microfibers crystallized at a slower rate to hydroxyapatite (HA) when compared to the ACP that formed on the 45S5 fibers. For immersion times >3 days, the 13-93B3 fibers released a higher concentration of Ca into the SBF than the 45S5 fibers. The fast and more complete degradation, slow crystallization of the ACP product, and higher concentration of dissolved Ca in SBF could contribute to the capacity of the microfibrous borate 13-93B3 glass to heal soft tissue wounds. PMID:23233025

Liu, Xin; Rahaman, Mohamed N; Day, Delbert E

2013-03-01

244

Pan-African alkali granites and syenites of Kerala as imprints of taphrogenic magmatism in the South Indian shield  

NASA Technical Reports Server (NTRS)

Granite and syenite plutons with alkaline affinities ranging in age from 550 to 750 Ma sporadically puncture the Precambrian granulites of the Kerala region. All the bodies are small (20 to 60 sq km), E-W to NW-SE elongated elliptical intrusives with sharp contacts and lie on or close to major late Proterozoic lineaments. Geochemical plots of A-F-M and An-Ab-Or relations show an apparent alkali enrichment trend on the former, but the plutons define relatively distinct fields on the latter. Most of the plutons are adamellitic to granitic by chemistry. The variations of SiO2 with log sub 10 K2O/MgO (1) brings out the distinct alkaline nature of the plutons. Some of the granites are extremely potassic, like the Peralimala pluton, which shows up to 11.8 percent K2O. On a SiO2-Al2O3-Na2O+K2O (mol percent) plot, the plutons vary from peraluminous to peralkaline, but none are nepheline normative. Low MgO, low to moderate CaO and high Fe2O3/FeO values are other common characteristics. Among trace elements, depletion of Ba, Sr and Rb with high K/Ba and K/Rb values are typical. Overall, the plutons show a trend of decreasing K/Rb ratio with increasing K content. Individual plutons show more clearly defined trends similar to those from granitic masses characterized by plagioclase fractionation.

Santosh, M.; Drury, S. A.; Iyer, S. S.

1988-01-01

245

High-intensity atomic oxygen radical anion emission mechanism from 12CaO·7Al 2O 3 crystal surface  

NASA Astrophysics Data System (ADS)

12CaO · 7Al 2O 3 (C12A7) crystal is an interesting material where a large amount of O -(c) and O 2-(c) can be formed and trapped in the cages when it is sintered in dry oxygen. The emissive features of this material including the emission species, temperature dependence, field dependence, emission branch ratio, emission stability, the effects of water on the emission intensity, have been investigated. The temperature and oxygen pressure dependences of the electrical conductivity have also been measured. The mechanisms of the O - emission have been discussed based on the investigations of the emission and electrical conductivity features.

Li, Quanxin; Hosono, Hideo; Hirano, Masahiro; Hayashi, Katsuro; Nishioka, Masateru; Kashiwagi, Hideo; Torimoto, Yoshifumi; Sadakata, Masayoshi

2003-03-01

246

Thermal reactions of aromatics with CaO. Technical progress report, September 1, 1980-April 30, 1981. [Compounds tested -1-methylnaphthalene, toulene, benzene, n-heptane  

SciTech Connect

Experiments were performed near atmospheric pressure for the temperature range 550 to 950/sup 0/C. Helium carrier gas containing 3 mole % of the vapor phase reactant was passed through approximately 5.5-cm-deep, 0.7-cm-ID packed beds containing calcium oxide or quartz (for comparison studies). Contact times were approximately 2 s and around 5 mg of pure compound were fed in each run. Reaction products and unreacted feed were collected and analyzed. Carbon balances were performed on selected runs. The effects of CaO source and the method of CaO preparation were also investigated. Extents of conversion, and product distributions for n-heptane cracking were similar for calcium oxide and for quartz. However, the temperature for removal of aromatic hydrocarbons from the helium hydrocarbon mixtures in the presence of calcium oxide was reduced 140 to 180/sup 0/C from that with quartz. The temperature required for 20% conversion of each compound in the presence of calcium oxide and quartz respectively were: 1 - methylnaphthalene - 570 and 750/sup 0/C; toluene - 685 and 825/sup 0/C; benzene 750 and 890/sup 0/C; and n-heptane 585 and 610/sup 0/C. The reactivity of the aromatics increased with addition of a methyl group or a second aromatic ring to the molecule. Coke is the major product from the reaction of each aromatic. Methane yields from 1-methylnaphthalene and toluene were lower in the reactions over calcium oxide. On a unit weight basis calcium oxide obtained by calcining calcium hydroxide at final reaction temperatures was more active for benzene cracking than CaO obtained by calcining limestone. Calcium oxide cracking activity declines as coke is deposited on its surface but may be at least partially regenerated by burning off the coke. Apparent activation energies obtained by fitting a single reaction first order decomposition model to the data were lower for aromatics cracking over CaO compared to quartz but the opposite effect was found for n-heptane.

Longwell, J.P.; Ellig, D.L.; Krasniak, S.; Lai, S.C.K.; Williams, G.C.; Peters, W.A.

1981-07-01

247

Sol–gel derived 6CaO·6SrO·7Al 2O 3 thin films using metal alkoxides  

Microsoft Academic Search

The novel 6CaO·6SrO·7Al2O3 (C6S6A7) thin films were deposited onto soda lime glass substrate using calcium, strontium, aluminium isopropoxide and 2-methoxy ethanol as starting materials via sol–gel dip coating technique. The electrical and optical properties of C6S6A7 films were investigated for films sample annealed at 450°C for 2h in air and hydrogen (H2) atmosphere, respectively. X-ray diffraction pattern and Fourier transformed

P. M. Chavhan; Anubha Sharma; R. K. Sharma; CheolGi Kim; N. K. Kaushik

2011-01-01

248

The effects of Mn2+ doping on the luminescence properties of 12CaO 7Al2O:Eu2+ nanocrystal phosphor.  

PubMed

The long lasting blue phosphorescence (LLP) and photostimulated luminescence (PSL) after ultraviolet light irradiation at room temperature in 12CaO 7Al2O3:xEu2+, yMn2+ (x = 0, 0.001; y = 0, 0.01) prepared by the chemical co-precipitation method were observed. It was shown that novel oxide 12CaO 7Al2O3:Eu2+, Mn2+ (C12A7:Eu2+, Mn2+) with unique nanocage structure can store energy when irradiated with 365 nm photons. And photon energy can be subsequently released by exposed to 980 nm light. The codopant Mn2+ enhances the intensity of the persistent phosphorescence and PSL due to the existence of more shallow and new deeper electron traps in C12A7: Eu2+, Mn2+. A model for energy storing and recovering and the detailed mechanism of PSL are presented through comparing with the luminescence properties of the co-doped C12A7:Eu2+, Mn2+ and C12A7:Eu2+. PMID:22413331

Yan, X L; Liu, Y X; Yan, D T; Zhu, H C; Liu, C G; Xu, C S

2011-11-01

249

Surface defects and their impact on the electronic structure of Mo-doped CaO films: an STM and DFT study.  

PubMed

The functionality of doped oxides sensitively depends on the spatial distribution of the impurity ions and their interplay with compensating defects in the lattice. In our combined scanning tunneling microscopy (STM) and density functional theory (DFT) study, we analyze defects occurring in Mo-doped CaO(001) films at the atomic scale. By means of topographic imaging, we identify common point and line defect in the doped oxide, in particular Mo donors and compensating Ca vacancies. The influence of charged defects on the oxide electronic structure is analyzed by STM conductance spectroscopy. The experimentally observed defect features are connected to typical point defects in the CaO lattice by means of DFT calculations. Apart from the identification of individual defects, our study reveals a pronounced inhomogeneity of the oxide electronic structure, reflecting the uneven spatial distribution of dopants in the lattice. Our results provide the basis for a better understanding of adsorption and reaction patterns on doped oxides, as widely used in heterogeneous catalysis. PMID:24837555

Cui, Yi; Shao, Xiang; Prada, Stefano; Giordano, Livia; Pacchioni, Gianfranco; Freund, Hans-Joachim; Nilius, Niklas

2014-06-01

250

Phase equilibria in the system HfO[sub 2]-Y[sub 2]O[sub 3]-CaO  

SciTech Connect

This paper reports on phase equilibria in the system HfO[sub 2]-Y[sub 2]O[sub 3]-CaO which were studied in the temperature range 1250[degrees] to 2850[degrees]C by both experimental methods (X-ray phase analysis at 20[degrees] to 2000[degrees]C, petrography, annealing and quenching, differential thermal analysis in He at temperatures to 2500[degrees]C, thermal analysis in air using a solar furnace at temperatures to 3000[degrees]C, and electron microprobe X-ray analysis) and theoretical means (development of a mathematical model for the liquidus surface by means of the reduced polynomial method). Phase equilibria were determined by the structure of the restricting binary systems. No ternary compounds were found. The liquidus was characterized by the presence of six four-phase, invariant equilibria. Solid solutions were based on monoclinic (M), tetragonal (T), and cubic (F) modifications of HfO[sub 2]; C and H forms of Y[sub 2]O[sub 3]; CaO; and CaHfO[sub 3] that crystallized in two polymorphous modifications, namely, the cubic and rhombic perovskite-type structure.

Andrievskaya, E.R.; Lopato, L.M. (Inst. of Materials Science Problems, 252142 Kiev, Ukraine (USSR))

1992-11-01

251

Interaction of granitic and basic magmas: experimental observations on contamination processes at 10 kbar with H2O  

NASA Astrophysics Data System (ADS)

Experiments designed to simulate the interaction of juxtaposed rhyolitic and basic magmas were conducted at 10 kbar with H2O, using reaction-couples consisting of Westerly granite (WG) against basalt (DW-1) and WG against a synthetic mafic glass (SMG, enriched in MgO and Na2O relative to DW-1). Each couple was run with ˜5 and ˜10 wt% H2O corresponding respectively to H2O-undersaturated and H2O-oversaturated conditions. Experiments were run for 42 44 h at 920° C, above the liquidus of WG and within the melting intervals of DW-1 and SMG. WG was run above the basic material in all but one experiment. The composition of the granitic melt was altered only through material exchange with the adjacent basic melts, whereas that of the basic melts also changed (relative to the bulk basic composition) due to partial crystallization. Some crystallization also occurred within the zone of interaction. For control, the basic compositions were also run alone under the same conditions as the reaction-couple experiments. The crystalline phase assemblages in the basic ends of the coupled experiments differed from those produced from the basic materials alone, demonstrating interaction with the granite melt. Moreover, compositional gradients within the basic ends of coupled experiments are indicated by changes in phase assemblage and compositions with distance from the interface with WG. Microprobe analyses of glass collected along the length of the capsules confirm published observations that alkali diffusion is very fast: K2O and Na2O homogenized throughout the capsules in less than the two-day run times. This, coupled with the fact that introduction of K2O into SMG stabilized biotite, produced the result that after interaction the bulk basic material (melt+crystals) contained more K2O than the coexisting felsic melt. Only very gentle gradients for CaO, FeO, and MgO are preserved in our experiments, in contrast with published anhydrous results, suggesting that the difference in activity coefficients for these components between basic and felsic melts is reduced by the introduction of H2O. Gradients for SiO2 and Al2O3 are of comparable length to those of the divalent cations, confirming earlier results that the diffusivities of the network-formers limit the rate of diffusion of Ca, Fe, and Mg.

Johnston, A. Dana; Wyllie, Peter J.

1988-03-01

252

Reconnaissance study of the Taylor Mountains pluton, southwestern Alaska  

USGS Publications Warehouse

The Taylor Mountains pluton is a Late Cretaceous to early Tertiary (median age 65 + or ? 2 Ma) epizonal, composite biotite granite stock located about 235 km (145 mi) northeast of Dillingham in southwestern Alaska. This 30 km2 (12 mi2) pluton has sharp and discordant contacts with hornfels that developed in Upper Cretaceous clastic sedimentary rocks of the Kuskokwim Group. The three intrusive phases in the Taylor Mountains pluton, in order of emplacement, are (1) porphyritic granite containing large K-feldspar phenocrysts in a coarse-grained groundmass, (2) porphyritic granite containing large K-feldspar and smaller, but still coarse, plagioclase, quartz, and biotite phenocrysts in a fine-grained groundmass, and (3) fine-grained, leucocratic, equigranular granite. The porphyritic granites have different emplacement histories, but similar compositions; averages are 69.43 percent SiO2, 1.62 percent CaO, 5.23 percent FeO+MgO, 3.11 percent Na2O, and 4.50 percent K2O. The fine-grained, equigranular granite is distinctly felsic compared to porphyritic granite; it averages 75.3 percent SiO2, 0.49 percent CaO, 1.52 percent FeO+MgO, 3.31 percent Na2O, and 4.87 percent K2O. Many trace elements including Ni, Cr, Sc, V, Ba, Sr, Zr, Y, Nb, La, Ce, Th, and Nd are strongly depleted in fine-grained equigranular granite. Trace elements are not highly enriched in any of the granites. Known hydrothermal alteration is limited to one tourmaline-quartz replacement zone in porphyritic granite. Mineral deposits in the Taylor Mountains area are primarily placer gold (plus wolframite, cassiterite, and cinnabar); sources for these likely include scattered veins in hornfels peripheral to the Taylor Mountain pluton. The granite magmas that formed the Taylor Mountains pluton are thought to represent melted continental crust that possibly formed in response to high heat flow in the waning stage of Late Cretaceous subduction beneath interior Alaska.

Hudson, Travis L.; Miller, Marti L.; Klimasauskas, Edward P.; Layer, Paul W.

2010-01-01

253

Generation of negative ions in the gas phase from a 12CaO.7Al2O3 membrane-coated ceramic heater under atmospheric pressure  

NASA Astrophysics Data System (ADS)

12CaO.7Al2O3 (C12A7) crystal is able to generate strong and high purity oxygen anion (O-) beam under reduced pressure. However, the emission of O- or related species under atmospheric pressure has not been evaluated. In this study, the characteristics of negative ion species emissions from the C12A7 membrane-coated ceramic heater under atmospheric pressure were investigated by quadrupole mass spectrometer. Negative ion species were confirmed to be emitted even under atmospheric pressure. It was supposed that the detected negative ion clusters, such as O-(H2O)n, O2-(H2O)n, and CO4-(H2O)n, were generated by the reaction of negative ions emitted from the heater with impurities in He gas.

Yamamoto, Mitsuo; Shima, Akio; Nishioka, Masateru; Sadakata, Masayoshi

2008-12-01

254

Electronic insulator-conductor conversion in hydride ion-doped 12CaO.7Al2O3 by electron-beam irradiation  

NASA Astrophysics Data System (ADS)

We report formation of persistent carrier electrons in hydride ion (H-)-incorporated 12CaO.7Al2O3 (C12A7) by electron-beam irradiation. The electrical conductivity of H--doped C12A7 single crystals increases with the electron-beam irradiation dose, accompanied with a green coloration attributable to a carrier electron formation. A 25 keV electron beam with a dose of ~500 ?C cm-2 fully converts the conductivity in surface layers to the depth of ~4 ?m. Carrier electron formation is most likely due to electron-hole pairs generated in the electron excitation volume and subsequent energy transfer to the H- ions. The estimated carrier formation yield per an incident electron is ~30. These findings may enable a fine patterning of the conductive area without photomasks and photoresists.

Hayashi, Katsuro; Toda, Yoshitake; Kamiya, Toshio; Hirano, Masahiro; Yamanaka, Minako; Tanaka, Isao; Yamamoto, Takahisa; Hosono, Hideo

2005-01-01

255

Evidence for Bardeen-Cooper-Schrieffer-type superconducting behavior in the electride (CaO)12(Al2O3)7:e- from heat capacity measurements  

NASA Astrophysics Data System (ADS)

The heat capacity of the single crystalline electride of (CaO)12(Al2O3)7:e- (C12A7:e-) with Tc=0.2K was larger than that of electron-undoped C12A7 in the temperature range 0.085-5K , reflecting the metallic nature of the electride. A superconducting transition was detected as a heat capacity jump ?Cp=3.4mJmol-1K-1 , and the profile and magnitude of ?Cp agreed well with those expected from the BCS theory. The electron-phonon coupling constant (?˜0.46) and Debye temperature (?D˜630K) were much larger than those for alkali metals having s -like conduction electrons as in the present electride, suggesting that electrides having a rigid structure will be a class of BCS superconductors.

Kohama, Yoshimitsu; Kim, Sung Wng; Tojo, Takeo; Kawaji, Hitoshi; Atake, Tooru; Matsuishi, Satoru; Hosono, Hideo

2008-03-01

256

Effect of H2O on NO Reduction over NSR Catalyst 12CaO·7Al2O3/10%K  

NASA Astrophysics Data System (ADS)

A novel NOx storage/reduction catalyst 12CaO·7Al2O3/10%K, defined as C12A7/K, was prepared, which possesses good NOx storage/reduction ability with a high sulfur-tolerance. The effect of H2O on the NO reduction features over the C12A7/K catalyst was investigated. The NO conversion and the N2 selectivity were measured as a function of temperature and H2O concentration. In the presence of 1.2% H2O, both the NO conversion and the N2 selectivity significantly decrease at lower temperature region (< 500°C). At temperatures over 500°C, however, the NO reduction is only slightly influenced by H2O. The species of NO3-/NO2- are confirmed as main storage components in the C12A7/K catalyst, which are further reduced into N2 by H2 under the reduction conditions.

Gao, Ai-mei; Wang, Hua-jing; Tu, Jing; Li, Quan-xin

2006-12-01

257

Photoinduced generation of electron anions in H-doped nanoporous oxide 12CaO.7Al2O3: Toward an optically controlled formation of electrides  

NASA Astrophysics Data System (ADS)

We suggest, on the basis of detailed ab initio calculations of both ground and photoexcited states of H-doped 12CaO.7Al2O3 (C12A7:H), that stable high-conductivity regions can be optically generated in this insulating system. Each H- ion in C12A7:H can, under photoirradiation at 3.8-4.5 eV, produce up to two electrons and a proton that binds to the lattice network and forms OH-. Mobile electrons play a role of anions in this system. They move over subnanosized cages of the C12A7 lattice via polaron hopping. The insulating state is reversibly restored upon heating to 300 °C.

Sushko, Peter V.; Shluger, Alexander L.; Hayashi, Katsuro; Hirano, Masahiro; Hosono, Hideo

2005-02-01

258

Nanoblock coupling effect in iodine intercalated [Bi(0.82)CaO(2)](2)[CoO(2)](1.69) layered cobaltite.  

PubMed

We report on the structural, microstructural, and electronic properties of iodine intercalated [Bi0.82CaO2]2[CoO2]1.69 misfit cobaltite. We first prove through a detailed and careful structural study that the block layer structure can be modified in the desired way. Iodine enters the material between the [BiO] double layers, and the c-cell parameter of the pristine compound is elongated by 3.6 Angstrom. On the basis of this result, we point out the coupling between the block-layer structure and the transport properties. Additionally, we provide in-depth commentary and discussion of some extra results, clarifying some doping effects in the quasi-2D studied phase. Finally, we also propose some expressions that might be useful to material scientists for the tuning of the properties of such compounds. PMID:17323941

Guilmeau, E; Pollet, M; Grebille, D; Hervieu, M; Muguerra, H; Cloots, R; Mikami, M; Funahashi, R

2007-03-19

259

Performance of CaO and MgO for the hot gas clean up in gasification of a chlorine-containing (RDF) feedstock.  

PubMed

Calcined limestone (CaO) and calcined dolomite (CaO.MgO) were tested at bench scale to study their usefulness in cleaning hot raw gas from a fluidized bed gasifier of a synthetic or simulated refuse-derived fuel (RDF) with a high (3 wt%) content in chlorine. In the gas cleaning reactor two main reactions occurred simultaneously: the elimination of HCl and the elimination of tar by steam reforming. The elimination of HCl formed CaCl2 and MgCl2 with melting points below the high (above 800 degrees C) temperatures required for the simultaneous tar elimination reaction. So, the CaO-based particles progressively melted and the catalytic gas cleaning reactor became a compact, agglomerated or glued, cake. Therefore, the life and usefulness of the CaO-based solids used was very low. Nevertheless, and to further avoid these problems, some positive guidelines for future research are proposed here. PMID:18372172

Corella, José; Toledo, José M; Molina, Gregorio

2008-11-01

260

On the magnetic and spectroscopic properties of high-valent Mn3CaO4 cubanes as structural units of natural and artificial water-oxidizing catalysts.  

PubMed

The Mn(IV)3CaO4 cubane is a structural motif present in the oxygen-evolving complex (OEC) of photosystem II and in water-oxidizing Mn/Ca layered oxides. This work investigates the magnetic and spectroscopic properties of two recently synthesized complexes and a series of idealized models that incorporate this structural unit. Magnetic interactions, accessible spin states, and (55)Mn isotropic hyperfine couplings are computed with quantum chemical methods and form the basis for structure-property correlations. Additionally, the effects of oxo-bridge protonation and one-electron reduction are examined. The calculated properties are found to be in excellent agreement with available experimental data. It is established that all synthetic and model Mn(IV)3CaO4 cubane complexes have the same high-spin S = (9)/2 ground state. The magnetic coupling conditions under which different ground spin states can be accessed are determined. Substitution of Mn(IV) magnetic centers by diamagnetic ions [e.g., Ge(IV)] allows one to "switch off" specific spin sites in order to examine the magnetic orbitals along individual Mn-Mn exchange pathways, which confirms the predominance of ferromagnetic interactions within the cubane framework. The span of the Heisenberg spin ladder is found to correlate inversely with the number of protonated oxo bridges. Energetic comparisons for protonated models show that the tris-?-oxo bridge connecting only Mn ions in the cubane has the lowest proton affinity and that the average relaxation energy per additional proton is on the order of 18 kcal·mol(-1), thus making access to ground states other than the high-spin S = (9)/2 state in these cubanes unlikely. The relevance of these cubanes for the OEC and synthetic oxides is discussed. PMID:23527603

Krewald, Vera; Neese, Frank; Pantazis, Dimitrios A

2013-04-17

261

Phase equilibria and crystal chemistry of the CaO-1/2 >Nd2O3-CoOz system at 885 °C in air  

NASA Astrophysics Data System (ADS)

The phase diagram of the CaO-1/2 >Nd2O3-CoOz system at 885 °C in air has been determined. The system consists of two calcium cobaltate compounds that have promising thermoelectric properties, namely, the 2D thermoelectric oxide solid solution, (Ca3-xNdx)Co4O9-z (0?x?0.5), which has a misfit layered structure, and Ca3Co2O6 which consists of 1D chains of alternating CoO6 trigonal prisms and CoO6 octahedra. Ca3Co2O6 was found to be a point compound without the substitution of Nd on the Ca site. The reported Nd2CoO4 phase was not observed at 885 °C. A ternary (Ca1-xNd1+x)CoO4-z (x=0) phase, or (CaNdCo)O4-z, was found to be stable at this temperature. A solid solution region of distorted perovskite (Nd1-xCax)CoO3-z (0?x?0.25, space group Pnma) was established. In the peripheral binary systems, while a solid solution region was identified for (Nd1-xCax)2O3-z (0?x?0.2), Nd was not found to substitute in the Ca site of CaO. Six solid solution tie-line regions and six three-phase regions were determined in the CaO-Nd2O3-CoOz system in air.

Wong-Ng, W.; Laws, W.; Talley, K. R.; Huang, Q.; Yan, Y.; Martin, J.; Kaduk, J. A.

2014-07-01

262

Synthesis of SiO2 and CaO rich calcium silicate systems via sol-gel process: Bioactivity, biocompatibility, and drug delivery tests.  

PubMed

Silica and calcium silicate amorphous materials, mixed with sodium ampicillin, a broad-spectrum antibiotic, have been synthesized by sol-gel method. The amorphous nature of the gels was ascertained by X-ray diffraction analysis. The bioactivity of the synthesized materials has been put into evidence by the appearance of a crystal of hydroxyapatite on the surface of the samples soaked in a fluid simulating the composition of the human blood plasma, as detected through FTIR measurements and SEM micrographs. The present work refers to a series of in-vitro biocompatibility tests, which has been performed on silicate and CaO rich calcium silicate gel-glasses, to study the cell behavior when seeded on 1 cm(2) material fragments, introduced into an in-vitro culture system. 3T3 cell lines have been used and the viability has been evaluated by WST-8 test. The composition of the adopted glasses can be expressed by the following general formula: x CaO• (1?-?x) SiO2 with x?=?0.00; 0.30; 0.40; 0.50; 0.60. Subsequently, release kinetics in a simulate body fluid (SBF) has been investigated. The amount of sodium ampicillin released has been detected by UV-Vis spectroscopy. The release kinetics has appeared to occur in more than one stage. All data have shown that those materials could be used as drug delivery bioactive systems. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 3087-3092, 2014. PMID:24123774

Catauro, M; Papale, F; Roviello, G; Ferone, C; Bollino, F; Trifuoggi, M; Aurilio, C

2014-09-01

263

Petrological and experimental phase equilibria constraints on magma storage conditions beneath Cerro Uturuncu, Bolivia  

NASA Astrophysics Data System (ADS)

Volcanic unrest manifest as surface deformation detected with InSAR recently drew attention to Cerro Uturuncu, a dormant dacitic stratovolcano in the Bolivian altiplano that last erupted 271 ka. Magma intrusion in the mid to upper crust is thought to be responsible for the deformation calculated as 1-2 cm/yr central uplift rate between 1992 and 2006. Using petrological and experimental phase equilibrium experiments designed to replicate natural mineral assemblages, phase proportions and phase compositions, we aim to constrain the pre-eruptive pressure, temperature, fO2 and fH2O storage conditions of Uturuncu magmas. Plagioclase, orthopyroxene, biotite, titaniferous magnetite, ilmenite, apatite and a rhyolitic glassy matrix are ubiquitous in all 50 thin sections of Uturuncu lava samples studied. All of the lavas are porphyritic with examples of normal and reverse zoning in plagioclase and orthopyroxene phenocrysts. Biotite commonly has dehydration reaction rims. Magmatic temperatures of ~870°C and fO2s around NNO+1.3 have been estimated from coexisting Fe-Ti oxides. A water content of 3.6 wt%, similar to those calculated in melt inclusions using the by-difference method, was estimated using plagioclase-melt equilibria and, assuming the magma was water saturated, VolatileCalc indicates a magma storage pressure of at least 91 MPa. Several previous studies have experimentally investigated phase equilibria of silicic magmatic systems including Volcan San Pedro (Chile), Mount Unzen (Japan), and Fish Canyon and Mount St. Helens (USA). Compared to these systems, Uturuncu lavas have higher SiO2 by 1.0-4.2 wt%; higher K2O by 0.5-3.3 wt%; and Na2O lower by 1.9-2.8 wt%, and are unique in crystallising biotite in the absence of hornblende. Crystallisation experiments are being performed in cold-seal hydrothermal pressure apparatuses with two synthetic starting materials that replicate the bulk dacite and rhyolite glass chemistry of a glassy lava sample with a relatively low microlite content and a total crystallinity of 36 vol%. The dacite composition is SiO2 67.0 wt%, Al2O3 15.9 wt%, K2O 4.5 wt%, FeO 4.0 wt%, CaO 3.6 wt%, Na2O 2.1 wt%, MgO 1.5 wt%; the rhyolitic composition is SiO2 75.1 wt%, Al2O3 13.4 wt%, K2O 6.7 wt%, FeO 1.1 wt%, CaO 0.8 wt%, Na2O 2.2 wt%, MgO 0.2 wt%. Experiments are being conducted at temperatures between 800-900°C and pressures between 50-300 MPa at water saturated conditions. The results will be compared to natural samples to assess storage conditions of the 890-271 ka eruptions at Uturuncu, and the storage depths inferred today from geophysical data.

Muir, D. D.; Blundy, J. D.; Rust, A.; Brooker, R.

2011-12-01

264

A Systematic Review of the Mysterious Caterpillar Fungus Ophiocordyceps sinensis in Dong-ChongXiaCao (???? D?ng Ch?ng Xi? C?o) and Related Bioactive Ingredients  

PubMed Central

The caterpillar fungus Ophiocordyceps sinensis (syn.† Cordyceps sinensis), which was originally used in traditional Tibetan and Chinese medicine, is called either “yartsa gunbu” or “DongChongXiaCao (???? D?ng Chóng Xià C?o)” (“winter worm-summer grass”), respectively. The extremely high price of DongChongXiaCao, approximately USD $20,000 to 40,000 per kg, has led to it being regarded as “soft gold” in China. The multi-fungi hypothesis has been proposed for DongChongXiaCao; however, Hirsutella sinensis is the anamorph of O. sinensis. In Chinese, the meaning of “DongChongXiaCao” is different for O. sinensis, Cordyceps spp.,‡ and Cordyceps spƒ. Over 30 bioactivities, such as immunomodulatory, antitumor, anti-inflammatory, and antioxidant activities, have been reported for wild DongChongXiaCao and for the mycelia and culture supernatants of O. sinensis. These bioactivities derive from over 20 bioactive ingredients, mainly extracellular polysaccharides, intracellular polysaccharides, cordycepin, adenosine, mannitol, and sterols. Other bioactive components have been found as well, including two peptides (cordymin and myriocin), melanin, lovastatin, ?-aminobutyric acid, and cordysinins. Recently, the bioactivities of O. sinensis were described, and they include antiarteriosclerosis, antidepression, and antiosteoporosis activities, photoprotection, prevention and treatment of bowel injury, promotion of endurance capacity, and learning-memory improvement. H. sinensis has the ability to accelerate leukocyte recovery, stimulate lymphocyte proliferation, antidiabetes, and improve kidney injury. Starting January 1st, 2013, regulation will dictate that one fungus can only have one name, which will end the system of using separate names for anamorphs. The anamorph name “H. sinensis” has changed by the International Code of Nomenclature for algae, fungi, and plants to O. sinensis.

Lo, Hui-Chen; Hsieh, Chienyan; Lin, Fang-Yi; Hsu, Tai-Hao

2013-01-01

265

Provenance of loess deposits in the Eastern Qinling Mountains (central China) and their implications for the paleoenvironment  

NASA Astrophysics Data System (ADS)

Loess deposits in the Eastern Qinling Mountains (central China) provide a detailed archive for reconstructing the paleoenvironment during early hominin occupation. The study of the loess deposits also provides a unique opportunity to understand Pleistocene atmospheric circulation in this transitional climatic zone. However, the provenance and formation of the loess deposits were not well understood until now. In this paper, we report on new geomorphologic investigations and depositional analyses of the loess deposits. The results suggest that Gobi deserts and drylands in northern and northwestern China were one of the dust sources. These loess deposits show similar geochemical composition as the average upper crust (UCC), and may indicate that they experienced multiple sedimentary processes, with the dust being well mixed before deposition. However, the higher 87Sr/86Sr ratios (between 0.719650 and 0.721043) and extremely low ?Nd(0) values (between -11.98 and -18.97), which are different from the typical loess of the Chinese Loess Plateau, demonstrate that proximal clastic sediments that were apparently derived from the weathered Qinling orogen bedrocks, form the other important source for the loess deposits. The chemical Index of Alteration [CIA = Al2O3/(Al2O3 + CaO* + Na2O + K2O) × 100] and Chemical Proxy of Alteration [CPA = 100 × Al2O3/(Al2O3 + Na2O)], both in molar proportions show that the loess has experienced intense pedogenesis. We conclude that the loess deposit has a mixed provenance. The palaeoclimate in the Eastern Qinling Mountains remained mild in the glacial periods due to the topography and unique geographic locations, providing a suitable place for hominine occupation.

Zhang, Hongyan; Lu, Huayu; Jiang, Shao-Yong; Vandenberghe, Jef; Wang, Shejiang; Cosgrove, Richard

2012-06-01

266

X-ray fluorescence analysis with micro glass beads using milligram-scale siliceous samples for archeology and geochemistry  

NASA Astrophysics Data System (ADS)

A micro glass bead technique was developed to assay precious siliceous samples for geochemical and archeological analyses. The micro-sized (approximately 3.5 mm in diameter and 0.8 mm in height) glass beads were prepared by mixing and fusing 1.1 mg of the powdered sample and 11.0 mg of the alkali lithium tetraborate flux for wavelength-dispersive X-ray fluorescence determination of major oxides (Na2O, MgO, Al2O3, SiO2, P2O5, K2O, CaO, TiO2, MnO, and total Fe2O3). The preparation parameters, including temperature and agitation during the fusing process, were optimized for the use of a commercial platinum crucible rather than a custom-made crucible. The procedure allows preparation of minute sample amounts of siliceous samples using conventional fusing equipment. Synthetic calibration standards were prepared by compounding chemical reagents such as oxides, carbonates, and diphosphates. Calibration curves showed good linearity with r values > 0.997, and the lower limits of detection were in the 10s to 100s of ?g g- 1 range (e.g., 140 ?g g- 1 for Na2O, 31 ?g g- 1 for Al2O3, and 8.9 ?g g- 1 for MnO). Using the present method, we determined ten major oxides in igneous rocks, stream sediments, ancient potteries, and obsidian. This was applicable to siliceous samples with various compositions, because of the excellent agreement between the analytical and recommended values of six geochemical references. This minimal-scale analysis may be available for precious and limited siliceous samples (e.g., rock, sand, soil, sediment, clay, and archeological ceramics) in many fields such as archeology and geochemistry.

Ichikawa, Shintaro; Nakamura, Toshihiro

2014-06-01

267

Mineralogy, conditions of crystallization and melt generation of epidote-bearing porphyries from the Middle Urals, Russian federation  

NASA Astrophysics Data System (ADS)

Epidote-bearing porphyritic dikes (whole rock analysis: SiO2 = 55-65 wt. %, MgO <2.1 wt. %, K2O <2.5 wt. %, Al2O3 >17 wt. %, Na2O + K2O = 5.7-9.4 wt. %) situated in the continental margin zone, the Middle Urals, Russian Federation have been dated using SHRIMP U-Pb zircon techniques and give a Middle Devonian age of 388 ± 2 Ma and 389 ± 6 Ma. The porphyries contain phenocrysts of magmatic epidote ( Ps = 17-25 %), Ca- and Mn-rich (CaO >9 wt. %; MnO >6 wt. %) almandine garnet, Al-rich (Al2O3 = 12-16 wt. %) amphibole, titanite, plagioclase, biotite, muscovite, apatite, and quartz. 60 to 70 % groundmass of the porphyritic dikes consists of fine-grained albite, quartz, and K-feldspar. A variety of thermobarometric estimations, plus comparison with published experimental data indicate that the phenocryst assemblage was stable between 5 and 11 kbar and 690 to 800 °C. Oxygen fugacity was close to or greater than log fo2 = Ni-NiO + 1. Later stage formation of the quartz-feldspar groundmass took place at hypabyssal conditions, corresponding to 1 to 2 kbar and 660 to 690 °C. The porphyritic dikes are metaluminous to slightly peraluminous (ACNK = 0.7-1.17). They are enriched in REE and depleted Nb and Ti. They show features typical of subduction-related magmas. Chemical composition and isotopic ratios of 86Sr/87Sri = 0.709-0.720 suggest that both mantle- and deep crustal-derived materials were involved in their petrogenesis.

Pribavkin, Sergey V.; Avdonina, Irina S.; Zamyatin, Dmitry A.

2013-02-01

268

The Neoproterozoic Hongliujing A-type granite in Central Tianshan (NW China): LA-ICP-MS zircon U-Pb geochronology, geochemistry, Nd-Hf isotope and tectonic significance  

NASA Astrophysics Data System (ADS)

Located between the Turpan-Hami, Junggar and Tarim blocks, the Central Tianshan zone is an important component of the Central Asian Orogenic Belt (CAOB) and crucial linkage between the Siberian, Kazakhstan, Junggar, Turpan-Hami and Tarim blocks. The Hongliujing granite associated with Nb-Ta mineralization in the Central Tianshan zone, dated at ca. 740 Ma using zircon LA-ICP-MS dating, is the first reported Neoproterozoic intrusion with a reliable and precise age in the Chinese Central Tianshan. The Hongliujing granite shares all the characteristics of A-type granites. It contains predominant alkali feldspar, and is characterized by high contents of SiO2, Na2O + K2O, K2O and high field strength elements (such as Nb, Ta, Zr, Ga and Y), and low contents of CaO, MgO, Ba and Sr, with high FeOt/(FeOt + MgO) and Ga/Al ratios typical of A-type granites. Based on the geochemistry and zircon Hf isotope data, we propose that the Hongliujing granite was most likely produced by partial melting of basic rocks in the lower crust which may have been derived from mantle magmas. The Hongliujing granite belongs to A1-type granites, which indicate a rifting formation environment, suggesting that like the Tarim Block, the Central Tianshan zone recorded Neoproterozoic rift-related igneous events related to the breakup of the Rodinia supercontinent. Our study verifies that not only the Tarim Block is related to the breakup of the Rodinia supercontinent, but also it is true for some key blocks in CAOB such as the Central Tianshan. Our new geochemical and geochronologic data also support and strengthen the notion that the Central Tianshan zone may be a part of the Tarim Block.

Lei, Ru-Xiong; Wu, Chang-Zhi; Chi, Guo-Xiang; Gu, Lian-Xing; Dong, Lian-Hui; Qu, Xun; Jiang, Yao-Hui; Jiang, Shao-Yong

2013-09-01

269

Straczekite, a new calcium barium potassium vanadate mineral from Wilson Springs, Arkansas.  

USGS Publications Warehouse

Straczekite occurs as a rare secondary mineral in fibrous seams, along with other V minerals (A.M. 64-713), in ore from the vanadium mine in Wilson Springs (formerly Potash Sulfur Springs), Garland County, Arkansas. It forms soft, thin laths of dark greenish black crystals up to 0.5 mm in length. Indexed XRD data are tabulated; strongest lines 3.486(100), 10.449(50), 1.8306(50), 1.9437(15) A; a 11.679, b 3.6608, c 10.636 A, beta 100.53o; space group C2/m, C2 or Cm. Chemical analysis gave V2O5 66.4, V2O4 15.3, Fe2O3 0.9, Na2O 0.4, K2O 1.8, CaO 2.5, BaO 5.5, H2O 7.2, = 100.0, leading to the formula (Ca0.39Ba0.31K0.33Na0.11)- 196(V4+1.59V5+6.31Fe3+0.10)O20.02(H2O)2.9; Dcalc. 3.21 g/cm3. A possible layer structure is discussed. The name is for J. A. Straczek, Chief Geologist at Union Carbide Corp.-R.A.H.

Evans, Jr, H. T.; Nord, G.; Marinenko, J.; Milton, C.

1984-01-01

270

Vanadium chlorite from a sandstone-hosted vanadium-uranium deposit, Henry basin, Utah.  

USGS Publications Warehouse

This ore deposit formed by reduction and precipitation of U and V in the presence of organic matter at the interface between a stagnant brine and overlying circulating meteoric water. Some samples of the vanadium chlorite (heated before analysis) contain = or >10% V2O5; in fresh samples most of the V is in the V3+ state. XRD data suggest that Fe and V are concentrated preferentially in the interlayer hydroxide sheets of the chlorite. A d060 value of 1.52 A indicates that the chlorite probably has a dioctahedral structure distended by the presence of octahedral Fe and V; it is a IIb polytype. The V ore zone is flanked by peripheral zones with perfectly ordered chlorite/smectite containing much less V than the pure chlorite. Chemical analysis of a sample heated to 900oC before analysis gave SiO2 44.89, Al2O3 25.14, TiO2 0.35, Fe2O3 8.29, MgO 8.47, CaO 0.84, Na2O 0.27, K2O 2.18, Li2O 0.16, UO3 0.92, V2O5 9.14, = 100.65, together with Cr 10, Mn 200, Co 150, Ni 5.8, Cu 10, Zn 140 ppm; XRD, DTG, TG and IR curves are presented. -R.A.H.

Whitney, G.; Northrop, H. R.

1986-01-01

271

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

NASA Technical Reports Server (NTRS)

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).

Righter, K.; Ghiorso, M.

2009-01-01

272

Mineralogy, major and trace element geochemistry of riverbed sediments in the headwaters of the Yangtze, Tongtian River and Jinsha River  

NASA Astrophysics Data System (ADS)

We collected riverbed sediments of the headwaters of the Yangtze River (Chumaer River, Tuotuo River, Gaerqu River and Buqu River), Tongtian River and Jinsha River (HTJR) flowing on the eastern Tibetan Plateau and analyzed their mineralogical features, major and trace element contents. The results show: (i) very poor correlations of Na 2O, K 2O, CaO, Ba, and Sr to SiO 2, LREE to Th, HREE to Hf, and Ta/La to Ti, and characteristics of Eu anomaly (the ratios of (Eu/Eu *) N range from 0.60 to 0.83 with an average value of 0.71) all indicate that the Jinsha River sediments have not undergone much mineralogical sorting; (ii) illite and chlorite are predominant clay minerals, and quartz, calcite, dolomite, albite, and K-feldspar are prevailing non-clay minerals. The characteristics of mineral assemblage indicate relatively weak chemical weathering degree in these river basins; (iii) very high contents of Fe 2O 3, MgO, TiO 2, Sc, V, Cr, Co, and Ni at Panzhihua mainly result from the huge-sized V-Ti magnetite deposits occurred in layered gabbroic intrusion; and (iv) the chemical alteration index (CIA) in the HTJR ranges from 46.5 to 69.2 and with an average value of 60.5 which indicates relatively weak weathering degree.

Wu, Weihua; Xu, Shijun; Lu, Huayu; Yang, Jiedong; Yin, Hongwei; Liu, Wen

2011-01-01

273

Novel systems for tailored neurotrophic factor release based on hydrogel and resorbable glass hollow fibers.  

PubMed

A novel system for the release of neurotrophic factor into a nerve guidance channel (NGC) based on resorbable phosphate glass hollow fibers (50P2O5-30CaO-9Na2O-3SiO2-3MgO-2.5K2O-2.5TiO2 mol%) in combination with a genipin-crosslinked agar/gelatin hydrogel (A/G_GP) is proposed. No negative effect on the growth of neonatal olfactory bulb ensheathing cell line (NOBEC) as well as on the expression of pro- and anti-apoptotic proteins was measured in vitro in the presence of fiber dissolution products in the culture medium. For the release studies, fluorescein isothiocyanate-dextran (FD-20), taken as growth factor model molecule, was solubilized in different media and introduced into the fiber lumen exploiting the capillary action. The fibers were filled with i) FD-20/phosphate buffered saline (PBS) solution, ii) FD-20/hydrogel solution before gelation and iii) hydrogel before gelation, subsequently lyophilized and then filled with the FD-20/PBS solution. The different strategies used for the loading of the FD-20 into the fibers resulted in different release kinetics. A slower release was observed with the use of A/G_GP hydrogel. At last, poly(?-caprolactone) (PCL) nerve guides containing the hollow fibers and the hydrogel have been fabricated. PMID:24433883

Novajra, G; Tonda-Turo, C; Vitale-Brovarone, C; Ciardelli, G; Geuna, S; Raimondo, S

2014-03-01

274

Nyerereite from calcite carbonatite at the Kerimasi Volcano, Northern Tanzania  

NASA Astrophysics Data System (ADS)

The extinct Quaternary Kerimasi volcano located in the southern part of the Gregory Rift, northern Tanzania, contains both intrusive and extrusive calciocarbonatites. One carbonate mineral with a high content of Na and Ca has been found in a sample of volcanic carbonatite, which is probably a cumulate rock. On the basis of Raman spectroscopy and SEM/EDS, this mineral was identified as nyerereite, ideally Na2Ca(CO3)2. It occurs as solid inclusions up to 300 × 200 ?m in size in magnetite and contains (wt. %) 25.4-27.4 Na2O, 26.0-26.8 CaO, 1.6-1.9 K2O, 0.6-1.8 FeO, 0.3-0.6 SrO, <0.4 BaO, 1.4-2.3 SO3, and 0.6-0.9 P2O5. The average mineral formula is (Na1.84K0.08)?1.92(Ca1.00Fe0.03Sr0.01)?1.04[(CO3)1.91(SO4)0.05(PO4)0.02]?1.98. A few inclusions in magnetite also contain calcite, which is considered here to be a late-stage, subsolidus mineral. The occurrence of nyerereite in carbonatite supports Hay's (1983) idea that some of the extrusive carbonatites at the Kerimasi volcano were originally alkaline rich and contained both calcite and nyerereite as primary minerals.

Zaitsev, A. N.

2010-12-01

275

Phosphate glass fibres and their role in neuronal polarization and axonal growth direction.  

PubMed

Phosphate glass fibres with composition 50P(2)O(5)-30CaO-9Na(2)O-3SiO(2)-3MgO-(5-x)K(2)O-xTiO(2)mol.% (x=0, 2.5, 5, respectively coded as TiPS(0), TiPS(2.5) and TiPS(5)) were drawn following the preform drawing approach. A 20-day solubility test in bi-distilled water was carried out on glass fibres with different compositions and diameters ranging between 25 and 82 ?m. The results show that the glass composition, the initial fibre diameter and the thermal treatment are the main factors influencing the dissolution kinetics and that the fibres maintain their structural integrity and composition during dissolution. Biological tests were carried out on aligned TiPS(2.5) glass fibres using Neonatal Olfactory Bulb Ensheathing Cell Line (NOBEC) and Dorsal Root Ganglia (DRG) neurons. The fibres showed to be permissive substrates for cell adhesion and proliferation. The aligned configuration of the fibres seemed to provide a directional cue for growing axons of DRG neurons, which showed to sprout and grow long neurites along the fibre axis direction. These promising findings encourages further studies to evaluate the potential use of resorbable glass fibres (e.g.in combination with a nerve guidance tube) for the enhancement of the peripheral nerve healing with the role of supporting and guiding the cells involved in the nerve regeneration. PMID:22134161

Vitale-Brovarone, C; Novajra, G; Lousteau, J; Milanese, D; Raimondo, S; Fornaro, M

2012-03-01

276

Heavy metal contamination of the Sacca di Goro lagoon area (Po River Delta, Northern Italy)  

NASA Astrophysics Data System (ADS)

The lagoon area of the Sacca di Goro, within the Po River delta, is ca. 20 km2 wide, with a mean depth of 1.5 m and a mean salinity of 29%o. It holds a major naturalistic interest as well as an economic one due to the aquaculture activities (mussels and clams). In this lagoon system, the quality of the sea-bottom sediments is crucial not only for the cultivated species, but also for the potential bio-accumulation problems in heavy metals. The definition of the qualitative status of the lagoon sediments is crucial for adopting the best management strategies and the protection of the environmental conditions. We determined the concentration in SiO2, TiO2, Al2O3, Fe2O3, MgO, MnO, CaO, Na2O, K2O, P2O5, Ba, Ce, Co, Cr, La, Nb, Ni, Pb, Rb, Sr, Th, V, Y, Zn, Cu, Ga, Nd, S and Sr, of 31 samples homogeneously collected over the lagoon area. This large dataset allowed i) to define the environmental quality of the sediments, ii) to recognise the areas with the higher contamination risk; and iii) to emphasise the local occurrence of polluting phenomena associated to chromium, nickel, vanadium, cobalt, lead, zinc and copper.

Rapti-Caputo, Dimitra

2010-05-01

277

Melt-derived bioactive glass scaffolds produced by a gel-cast foaming technique.  

PubMed

Porous melt-derived bioactive glass scaffolds with interconnected pore networks suitable for bone regeneration were produced without the glass crystallizing. ICIE 16 (49.46% SiO(2), 36.27% CaO, 6.6% Na(2)O, 1.07% P(2)O(5) and 6.6% K(2)O, in mol.%) was used as it is a composition designed not to crystallize during sintering. Glass powder was made into porous scaffolds by using the gel-cast foaming technique. All variables in the process were investigated systematically to devise an optimal process. Interconnect size was quantified using mercury porosimetry and X-ray microtomography (?CT). The reagents, their relative quantities and thermal processing protocols were all critical to obtain a successful scaffold. Particularly important were particle size (a modal size of 8 ?m was optimal); water and catalyst content; initiator vitality and content; as well as the thermal processing protocol. Once an optimal process was chosen, the scaffolds were tested in simulated body fluid (SBF) solution. Amorphous calcium phosphate formed in 8h and crystallized hydroxycarbonate apatite (HCA) formed in 3 days. The compressive strength was approximately 2 MPa for a mean interconnect size of 140 ?m between the pores with a mean diameter of 379 ?m, which is thought to be a suitable porous network for vascularized bone regeneration. This material has the potential to bond to bone more rapidly and stimulate more bone growth than current porous artificial bone grafts. PMID:21130188

Wu, Zoe Y; Hill, Robert G; Yue, Sheng; Nightingale, Donovan; Lee, Peter D; Jones, Julian R

2011-04-01

278

Evaluation of distribution, mobility and binding behaviour of heavy metals in surficial sediments of Louro River (Galicia, Spain) using chemometric analysis: a case study.  

PubMed

Contents of total and extractable heavy metals, carbonates, MnO and Fe2O3, organic matter, and matrix components such as SiO2, Al2O3, CaO, Na2O, MgO, TiO2, K2O and P2O5 are used along with principal component analysis (PCA) for studying distribution, mobility and binding behaviour of Cd, Cr, Cu, Ni and Pb in the Louro River (Galicia, Spain). Eleven surficial sediment samples were taken along the beds of the river course. Total metal concentrations were obtained after microwave-assisted digestion whilst extractable metal contents were obtained following a three-stage sequential extraction scheme (i.e. soluble, reducible and oxidisable fractions). Loading plots of heavy metals bound to carbonates, Fe-Mn oxides, organic matter and aluminosilicates allowed determination of binding behaviour. Correlations found indicate that Pb and Cu are mainly discharged from urban wastes, whereas Cr and Ni are from electroplating and galvanizing industries. The occurrence of diffuse pollution sources along the river can account for the binding behaviour of Cd. Metal mobility decreased in the order: Cd > Pb > Cu > Ni > Cr. Despite total contents indicating moderate-to-high heavy metal pollution in this river, metals are mostly distributed in the residual fraction, hence showing a low risk of mobility. PMID:15325163

Filgueiras, A V; Lavilla, I; Bendicho, C

2004-09-01

279

The Oro Grande, New Mexico, chondrite and its lithic inclusion.  

NASA Technical Reports Server (NTRS)

The Oro Grande, New Mexico, U.S.A., chondrite was found in 1971. Electron microprobe analyses and microscopic examination show the following mineralogy: olivine (Fa 19.3 mole %), orthopyroxene (Fs 16.2 mole %), diopside, feldspar (An 13.6 mole %), chlorapatite, whitlockite, kamacite, taenite, troilite, chromite, and an iron-bearing terrestrial weathering product. A bulk chemical analysis of the meteorite shows the following results (weight %): Fe 0.84, Ni 1.46, Co 0.07, FeS 3.62, SiO2 34.18, TiO2 0.14, Al2O3 1.83, Cr2O3 0.55, Fe2O3 21.25, FeO 9.13, MnO 0.31, MgO 21.52, CaO 1.72, Na2O 0.70, K2O 0.08, P2O5 0.25, H2O(+) 2.14, H2O(-) 0.40, C 0.22, sum 100.41. On the basis of composition and texture the Oro Grande meteorite is classified as an H5 chondrite.

Fodor, R. V.; Keil, K.; Jarosewich, E.

1972-01-01

280

[Determination of major elements in soil from cancer village by X-ray fluorescence spectrometry].  

PubMed

Many social problems arise from environmental pollution, cancer village is one of the many important problems caused by pollution. The authors selected a typical cancer village where 80-100 people died of cancer in the last five years, but there are only a total of 1 200 people in this village. The authors sampled soils from crops-planted areas and detected the major elements by X-ray fluorescence spectrometry. The results showed that the contents of SiO2, TiO2, Al2O3, Fe2O3, MnO, MgO, CaO, Na2O, K2O and P2O5 in soil of this village were 66.05%, 0.66%, 11.37%, 3.93%, 0.075%, 1.97%, 5.47%, 1.90%, 2.11% and 0.20% respectively; with the precision being +/- 0.20%, +/- 0.005%, +/- 0.10%, +/- 0.10%, +/- 0.005%, +/- 0.05%, +/- 0.04%, +/- 0.08%, +/- 0.02% and +/- 0.005% respectively, which showed that X-ray fluorescence spectrometry is a good method. PMID:19271523

Wei, Zhen-Lin; Li, He; Rui, Yu-Kui

2008-11-01

281

Reactions of yttria-stabilized zirconia with oxides and sulfates of various elements  

NASA Technical Reports Server (NTRS)

The reactions between partially stabilized zirconia, containing 8 weight-percent yttria, and oxides and sulfates of various elements were studied at 1200, 1300, and 1400 C for times to 800, 400, and 200 hours, respectively. These oxides and sulfates represent impurities and additives potentially present in gas turbine fuels or impurities in the turbine combustion air as well as the elements of the substrate alloys in contact with zirconia. Based on the results, these compounds can be classified in four groups: (1) compounds which did not react with zirconia (Na2SO4, K2SO4, Cr2O3, Al2O3 and NiO); (2) compounds that reached completely with both zirconia phases (CaO, BaO, and BaSO4); (3) compounds that reacted preferentially with monoclinic zirconia (Na2O, K2O, CoO, Fe2O3, MgO, SiO2, and ZnO); and (4) compounds that reacted preferentially with cubic zirconia (V2O5, P2O5).

Zaplatynsky, I.

1978-01-01

282

High-silica glass inclusions in olivine of Luna-24 samples  

NASA Technical Reports Server (NTRS)

Optical examination of nine polished grain mounts of Luna-24 drill-core material (0.09-0.50 mm size) revealed melt inclusions in olivine crystals. Two inclusions consist of clear glass with exceptionally high Si, yet contain no visible daughter minerals and have had no reaction effects with the olivine walls. Their compositions (one has SiO2 93.8, Al2O3 1.51, FeO 2.32, MgO 1.61, CaO 0.06, Na2O less than 0.05, K2O 0.11, total 99.41%; the other is similar) are unique and quite unlike the high-Si high-K melt of granitic composition that is found as inclusions in late-stage minerals of these (and the Apollo) samples, from silicate liquid immiscibility. The host olivines are Fo73 and Fo51. The origin of the melt in the inclusions and the lack of reaction effects are perplexing unsolved problems.

Roedder, E.; Weiblen, P. W.

1977-01-01

283

Petrology and oxygen isotope geochemistry of a fossil seawater hydrothermal system within the Solea graben, northern Troodos ophiolite, Cyprus  

NASA Astrophysics Data System (ADS)

Hydrothermal mineral zonations and O isotope patterns of the northern Troodos complex do not parallel the ophiolite pseudostratigraphy, but reflect the convective geometry of an Upper Cretaceous seawater hydrothermal system. Large areas of the sheeted intrusive complex (SIC), including the subaxial region of the Solea graben, are composed of 18O-rich, subgreenschist mineral assemblages and may represent regions of diffuse seawater recharge. Other areas of the SIC are recrystallized to distinctive epidosite rocks: granular, high-variance assemblages of epidote + quartz ± chlorite that are depleted in 18O, Al2O3, Na2O, K2O, Zr, Cu, and Zn and are enriched in CaO and Sr compared with other mafic volcanic and dike rocks of the Solea graben. Epidosite alteration occurred at temperatures of ˜310-370°C and involved fluids with ?18O values and salinities similar to those of Upper Cretaceous seawater. The epidosite zones are discordant with earlier, mineral/O isotope zonations and with the axis of spreading in the Solea graben, suggesting a postspreading, off-axis origin. The seawater hydrothermal system responsible for Solea graben massive sulfide deposits was probably driven by hypabyssal intrusions (not exposed), emplaced in a terminal, failed spreading episode. The geometries of O isotope surfaces within the Solea graben imply that the epidosites formed in fossil upflow and deep recharge conduits. Depletions in base metals show that epidosite alteration liberated Cu and Zn to mineralizing fluids within the fossil upflow zone.

Schiffman, Peter; Smith, Brian M.

1988-05-01

284

Petrogenesis of selected A-type granitic intrusions from Central Eastern Desert of Egypt  

NASA Astrophysics Data System (ADS)

The Pan-African orogeny in the Arabian-Nubian Shield was terminated by intrusion of A-type granites (~ 595 Ma; Greenberg, 1981) and its volcanic equivalents. Subsequent to the intrusions of these granitic bodies the shield was exhumed. Eroded A-type granite pebbles were found in the molasse sediments that were deposited in intermountain basins. Therefore the A-type granites provide information about the last stage of the Pan-African geochemical system. Preliminary whole-rock geochemical data of three granitic intrusions (Kadabora, Um Naggat and El shiekh Salem) from the Central Eastern Desert of Egypt; indicate that all of them are peraluminous and with A-type characteristics. These intrusions show low CaO content (average 0.43 %wt), high FeOT/MgO ratio (10.46-121.88), high Na2O+K2O (average 8.04 %wt), marked enrichment of high field strength elements (Y, Nb and Ga except Zr), depletion in MgO (0.01-0.11 %wt) and with low concentration of Sr and Ba. The studied granitoids were emplaced in within plate tectonic regime. References: Greenberg, J.K. (1981): Characteristic and origin of Egyptian younger granites. Bull. Geol. Soc. Am. Part 1, v.92: 224-232.

Hassan, Tharwat; Asran, Asran; Amron, Taha; Hauzenberger, Christoph

2014-05-01

285

A Structurally Based Viscosity Model for Oxide Melts  

NASA Astrophysics Data System (ADS)

A structurally based viscosity model is proposed to represent the viscosity of oxide melts as functions of both temperature and composition; The oxide melts cover the following constituents: Li2O, Na2O, K2O, MgO, CaO, SrO, BaO, FeO, MnO, Al2O3, SiO2, CaF2, TiO2, Fe2O3, and P2O5. The model describes the slag structure in terms of the various forms of oxygen ions which are classified according to the metal cations they bond with. Approximate methods for calculating the concentrations of these oxygen ions are proposed and are then used to describe the effect of melt structure on viscosity. The model provides a good description of the variations in viscosity with composition and temperature. The measured viscosities were compared with values calculated with the model, and the current model was found to provide reliable estimates of viscosities of slags used in various industrial processes ( e.g., blast furnace, basic oxygen steelmaking, ladle refining, continuous casting of steel, coal gasification, and electroslag remelting).

Zhang, Guo-Hua; Chou, Kuo-Chih; Mills, Ken

2014-04-01

286

Luminescence and energy transfer characteristics of Ce3+- and Tb3+-codoped nanoporous 12CaO 7Al2O3 phosphors.  

PubMed

The novel green-emitting phosphors of 12CaO 7Al2O3:Ce3+ , Tb3+ (C12A7:Ce3+, Tb3+) were synthesized by a solid-state reaction. Upon the excitation of Ce3+ at 350 nm, the C12A7:Ce3+, Tb3+ phosphor shows intense green emissions located at 543 nm assigning to 5D4-7F5 transitions of Tb3+ ions, and weak blue emissions centered at 434 nm due to the transitions of Ce3+ 5d-4f. The photoluminescence (PL) intensity of Ce3+ decrease with increasing Tb3+ concentration, indicating the effective energy transfer (ET) occurred from Ce3+ to Tb3+ in C12A7:Ce3+, Tb3+. The ET efficiency between Ce3+ and Tb3+ in the optimum composition reaches to 99%. Based on Dexter's ET theory, we have demonstrated that the efficient ET is a resonant type via dipole-dipole mechanism with an energy transfer critical distance of 4.02 A. Our results suggested that C12A7:Ce3+, Tb3+ phosphor would be a promising green-emitting phosphor for UV-converting white light-emitting diodes. PMID:22413329

Liu, X L; Liu, Y X; Yan, D T; Zhu, H C; Liu, C G; Xu, C S

2011-11-01

287

Synthesis and luminescence properties of Ce 3+ doped nanoporous 12CaO·7Al 2O 3 powders and ceramics  

NASA Astrophysics Data System (ADS)

Ce 3+ doped nanoporous 12CaO·7Al 2O 3 (C12A7) was synthesized using the self-propagating combustion method and solid state reaction. Ceramics of high density were produced using the melt-solidification process in a carbon crucible. The obtained samples were characterized using XRD and SEM methods and studied by means of low temperature time resolved luminescence under laser and synchrotron radiation excitation. It was shown that the Ce 3+ ion in C12A7 emits broad-band 5d-4f luminescence peaked at ˜3.0 eV. The decay curves of Ce 3+ emission in the studied samples have complicated nature depending on the excitation energy with the main decay component of 20-30 ns life time, typical for parity and spin allowed transitions of Ce 3+. The emission of Ce 3+ ions is efficiently excited through the intra-centre as well as in the intrinsic absorption region of C12A7.

Tõldsepp, E.; Avarmaa, T.; Denks, V.; Feldbach, E.; Kirm, M.; Maaroos, A.; Mändar, H.; Vielhauer, S.

2010-06-01

288

Nanoporous crystal 12CaO.7Al2O3: a playground for studies of ultraviolet optical absorption of negative ions.  

PubMed

A novel nanoporous material 12CaO.7Al2O3 (C12A7) offers a possibility of incorporating large concentrations (>1021 cm-3) of a wide range of extraframework anions inside its nanopores. We have investigated, both experimentally and theoretically, optical absorption associated with several types of such anions, including F-, OH-, O-, O2-, O2-, and O22-, and assigned their optical absorption bands. It is demonstrated that the chemical identity and concentration of extraframework anions can be controlled by an appropriate treatment of "as grown" C12A7. We also show that the position of the adsorption edge is, in turn, determined by the chemical identity of the extraframework species and can be varied in the range of approximately 4-6 eV. We suggest that C12A7 is a unique host material, which can be used as a playground for studying negatively charged species that are unstable in other environments. PMID:17269815

Hayashi, Katsuro; Sushko, Peter V; Ramo, David Muñoz; Shluger, Alexander L; Watauchi, Satoshi; Tanaka, Isao; Matsuishi, Satoru; Hirano, Masahiro; Hosono, Hideo

2007-03-01

289

Ab initio study of the positronation of the CaO and SrO molecules including calculation of annihilation rates.  

PubMed

Ab initio multireference single- and double-excitation configuration interaction calculations have been performed to compute potential curves for ground and excited states of the CaO and SrO molecules and their positronic complexes, e(+)CaO, and e(+)SrO. The adiabatic dissociation limit for the (2)?(+) lowest states of the latter systems consists of the positive metal ion ground state (M(+)) and the OPs complex (e(+)O(-)), although the lowest energy limit is thought to be e(+)M + O. Good agreement is found between the calculated and experimental spectroscopic constants for the neutral diatomics wherever available. The positron affinity of the closed-shell X (1)?(+) ground states of both systems is found to lie in the 0.16-0.19 eV range, less than half the corresponding values for the lighter members of the alkaline earth monoxide series, BeO and MgO. Annihilation rates (ARs) have been calculated for all four positronated systems for the first time. The variation with bond distance is generally similar to what has been found earlier for the alkali monoxide series of positronic complexes, falling off gradually from the OPs AR value at their respective dissociation limits. The e(+)SrO system shows some exceptional behavior, however, with its AR value reaching a minimum at a relatively large bond distance and then rising to more than twice the OPs value close to its equilibrium distance. PMID:22522712

Buenker, Robert J; Liebermann, Heinz-Peter

2012-07-15

290

The adsorption of mercury-species on relaxed and rumpled CaO (0 0 1) surfaces investigated by density functional theory.  

PubMed

This research examines the importance of several computational choices in modeling mercury species adsorption on calcium oxide surfaces and is the second in a series of papers. The importance of surface relaxation was tested and it was found that adsorption energies changed for HgCl(2), moving adsorption from being at the borderline of physisorption and chemisorption to being strongly chemisorbed. Results for Hg and HgCl were unaffected. A second computational choice, that of the cluster or periodic model size was tested in both the plane of the model (4 × 4 or 5 × 5 model sizes) and for the depth (two or three layers). It was found that the minimum cluster size for handling mercury adsorption was 5 × 5 and that only two layers of depth were needed. The energetic results show that rumpled CaO surfaces will only weakly physisorb elemental mercury, but could be used to capture HgCl(2) from coal combustion flue gases, which is in agreement with limited experimental data. PMID:20505965

Blowers, Paul; Kim, Bo Gyeong

2011-03-01

291

NOx uptake on alkaline earth oxides (BaO, MgO, CaO and SrO) supported on ?-Al2O3  

SciTech Connect

NOx uptake experiments were performed on a series of alkaline earth oxide (AEO) (MgO, CaO, SrO, BaO) on ?-alumina materials. Temperature Programmed Desorption (TPD) conducted on He flow revealed the presence of two kinds of nitrate species: i.e. bulk and surface nitrates. The ratio of these two types of nitrate species strongly depends on the nature of the alkaline earth oxide. The amount of bulk nitrate species increases with the basicity of the alkaline earth oxide. This conclusion was supported by the results of infrared and 15N solid state NMR studies of NO2 adsorption. Due to the low melting point of the precursor used for the preparation of MgO/Al2O3 material (Mg(NO3)2), a significant amount of Mg was lost during sample activation (high temperature annealing) resulting in a material with properties were very similar to that of the ?-Al2O3 support. The effect of water on the NOx species formed in the exposure of the AEO-s to NO2 was also investigated. In agreement with our previous findings for the BaO/?-Al2O3 system, an increase of the bulk nitrate species and the simultaneous decrease of the surface nitrate phase were observed for all of these materials.

Verrier, Christelle LM; Kwak, Ja Hun; Kim, Do Heui; Peden, Charles HF; Szanyi, Janos

2008-07-15

292

Comparison of CaO's effect on the fate of heavy metals during thermal treatment of two typical types of MSWI fly ashes in China.  

PubMed

Both grate and fluidized bed incinerators are widely used for MSW incineration in China. CaO addition for removing hazardous emissions from MSWI flue gas changes the characteristics of fly ash and affects the thermal behavior of heavy metals when the ash is reheated. In the present work, two types of MSWI fly ashes, sampled from both grate and fluidized bed incinerators respectively, were thermal treated at 1023-1323 K and the fate of heavy metals was observed. The results show that both of the fly ashes were rich in Ca and Ca-compounds were the main alkaline matter which strongly affected the leaching behavior of heavy metals. Ca was mostly in the forms of Ca(OH)2 and CaCO3 in the fly ash from grate incinerator in which nascent fly ash particles were covered by Ca-compounds. In contrast, the content of Ca was lower in the fly ash from fluidized bed incinerator and Ca was mostly in the form of CaSO4. Chemical reactions among Ca-compounds caused particle agglomeration in thermal treated fly ash from grate incinerator, restraining the heavy metals volatilization. In thermal treated fly ash from fluidized bed incinerator, Ca was converted into aluminosilicates especially at 1323 K which enhanced heavy metals immobilization, decreasing their volatile fractions as well as leaching concentrations. Particle agglomeration hardly affected the leaching behavior of heavy metals. However, it suppressed the leachable-CaCrO4 formation and lowered Cr leaching concentration. PMID:23800595

Hu, Hong-Yun; Liu, Huan; Shen, Wen-Qing; Luo, Guang-Qian; Li, Ai-Jun; Lu, Zhao-Ling; Yao, Hong

2013-10-01

293

Synthesis and characterization of phosphates in molten systems Cs 2O-P 2O 5-CaO- MIII2O 3 ( MIII—Al, Fe, Cr)  

NASA Astrophysics Data System (ADS)

The crystallization of complex phosphates from the melts of Cs 2O-P 2O 5-CaO- MIII2O 3 ( MIII—Al, Fe, Cr) systems have been investigated at fixed value Cs/P molar ratios equal to 0.7, 1.0 and 1.3 and ??/?=0.2 and Ca/ ?III=1. The fields of crystallization of CsCaP 3O 9, ?-Ca 2P 2O 7, Cs 2CaP 2O 7, Cs 3CaFe(P 2O 7) 2, Ca 9MIII(PO 4) 7 ( MIII—Fe, Cr), Cs 0.63Ca 9.63Fe 0.37(PO 4) 7 and CsCa 10(PO 4) 7 were determined. Obtained phosphates were investigated using powder X-ray diffraction and FTIR spectroscopy. Novel whitlockite-related phases CsCa 10(PO 4) 7 and Cs 0.63Ca 9.63Fe 0.37(PO 4) 7 have been characterized by single crystal X-ray diffraction: space group R3c, a=10.5536(5) and 10.5221(4) Å, ?=37.2283(19) and 37.2405(17) Å, respectively.

Zatovsky, Igor V.; Strutynska, Nataliya Yu.; Baumer, Vyacheslav N.; Slobodyanik, Nikolay S.; Ogorodnyk, Ivan V.; Shishkin, Oleg V.

2011-03-01

294

Complex Band Structure of MgO, CaO, SrO, BaO insulators: DFT-LDA vs. QSGW theory  

NASA Astrophysics Data System (ADS)

The recent discovery of a very large magneto-resistance in highly crystalline tunnel junctions with MgO barrier triggered extensive experimental research in the field. The complex band structure of the barrier material is an important property of corresponding MTJs [1]. This property have been studied theoretically on the basis of the density functional theory within the local density functional approximation (DFT-LDA) [1,2]. In this work we compare DFT-LDA and QSGW theory results for lowest evanescent states decay constants for a number of oxides MgO, CaO, SrO, BaO. We employ recently developed QSGW theory [3] to calculate electronic band structure. Then the attenuation constant for evanescent states in the band gap have been calculated by interpolating electron dispersion relation using polynomial fit, procedure analogous to one suggested and tested in [1]. We find that attenuation constant for evanescent states does not simply scales with the value of band gap. [1]. W. H. Butler, X.-G. Zhang, and T. C. Schulthess, and J. M. MacLarenm, Phys. Rev. B 63, 054416 (2001) [2]. K. D. Belashchenko, J. Velev, and E. Y. Tsymbal, Phys. Rev. B 72, 140404(R) (2005) [3] M. van Schilfgaarde, T. Kotani, and S. V. Faleev, Phys. Rev. Lett. 96, 226402 (2006);

Mryasov, Oleg; Faleev, Sergey

2010-03-01

295

Transesterification of sunflower oil on single step sol-gel made Al2O3 supported CaO catalysts: effect of basic strength and basicity on turnover frequency.  

PubMed

The activities of single step sol-gel made calcium oxide on alumina catalysts were studied as a function of CaO loading, methanol/oil molar ratio and the amount of the catalyst in the transesterification of sunflower oil at 50°C. Also, the turnover frequency (TOF) of the catalysts was calculated to better understand the relationship between the basicity/basic strength and the catalytic activity. From volcano curve (TOF vs. basic strength), it was found that under 50°C and methanol/oil molar ratio of 9, 60% CaO/Al(2)O(3) had the highest turnover frequency, 0.028s(-1), whereas 85% CaO/Al(2)O(3) showed the highest biodiesel yield, ?96.6%, but TOF obtained on it was 0.012s(-1). It seemed that 60% CaO catalyst had the proper basic strength to obtain the highest TOF. PMID:22197075

Umdu, Emin Selahattin; Seker, Erol

2012-02-01

296

Investigation of the influence of CaS, CaO and CaF 2 fillers on the transfer and wear of nylon by microscopy and XPS analysis  

Microsoft Academic Search

The effect of CaS, CaO and CaF2 fillers on the transfer, friction and wear behaviors of nylon was studied. Sliding was performed in ambient atmosphere at a speed of 1.0 m s?1 and a load of 19.6 N, and a pin-on-disk configuration was used. The filler content in nylon was fixed at 35% by volume. The counterface disk was made

S. Bahadur; Deli Gong; James Anderegg

1996-01-01

297

Effect of CaO on retention of S, Cl, Br, As, Mn, V, Cr, Ni, Cu, Zn, W and Pb in bottom ashes from fluidized-bed coal combustion power station.  

PubMed

This work was conducted to evaluate whether Ca-bearing additives used during coal combustion can also help with the retention of some other elements. This work was focused on the evaluation of bottom ashes collected during four full-scale combustion tests at an operating thermal fluidized-bed power station. Bottom ashes were preferred to fly ashes for the study to avoid interference from condensation processes usually occurring in the post-combustion zone. This work focused on the behaviors of S, Cl, Br, As, Mn, V, Cr, Ni, Cu, Zn, W, and Pb. Strong positive correlations with CaO content in bottom ashes were observed (for all four combustion tests) for S, As, Cl and Br (R=0.917-0.999). Strong inverse proportionality was calculated between the contents of Pb, Zn, Ni, Cr and Mn and CaO, so these elements showed association to materials other than Ca-bearing compounds (e.g., to aluminosilicates, organic matter, etc.). Somewhat unclear behaviors were observed for W, Cu, and V. Their correlation coefficients were evaluated as statistically "not significant", i.e., these elements were not thought to be significantly associated with CaO. It was also discovered that major enrichment of CaO in the finest bottom ash fractions could be advantageously used for simple separation of elements strongly associated with these fractions, mainly S and As, but also Cl or Br. Removal of 5% of the finest ash particles brings about a decrease in As concentration down to 77%-80% of its original bulk ash content, which can be conveniently used e.g., when high As content complicates further ash utilization. PMID:25079991

Barto?ová, Lucie; Klika, Zden?k

2014-07-01

298

Large enhancement in methane-to-syngas conversion activity of supported Ni catalysts due to precoating of catalyst supports with MgO, CaO or rare-earth oxide  

Microsoft Academic Search

Supported nickel catalysts prepared using commercial sintered low surface area porous catalyst carriers (containing SiO2 and\\/or Al2O3) precoated with MgO, CaO or rare-earth oxide show very much higher activity, selectivity and productivity in methane-to-syngas conversion reactions, than the catalysts prepared using catalyst carriers without any precoating. Among the precoating metal oxides, the best performance is observed for MgO.

V. R. Choudhary; B. S. Uphade; A. S. Mamman

1995-01-01

299

Non-linear properties of supercooled liquids in the system Na2O?SiO2  

Microsoft Academic Search

The physical properties, viscosity, density, heat capacity and thermal expansivity, of relaxed supercooled liquids in the temperature range just above the glass transition have been determined for ten compositions along the compositional binary Na20-SiO2, in the range of 2-45 mole% Na20, by a combination of scanning calorimetry, dilatometry and micropenetration viscometry. The viscosity, density, heat capacity and thermal expansivity in

R. Knoche; D. B. Dingwell; F. A. Seifert; S. L. Webb

1994-01-01

300

Elevation of liquidus temperature in a gel-derived Na2O-SiO2 glass  

NASA Technical Reports Server (NTRS)

The liquidus temperatures of a 19 wt% soda-silica glass prepared by gel and conventional techniques were determined. X-ray diffraction measurements of the glasses which were heat-treated at several temperatures were used to experimentally determine the liquidus temperatures. It was found that the gel-derived glass has an elevated liquidus. This result is discussed in relation to the previous discovery that the immiscibility temperature of this gel-derived glass is elevated

Weinberg, M. C.; Neilson, G. F.

1983-01-01

301

Geochronology and geochemistry of the Early Cretaceous Jigongshan and Qijianfeng batholiths in the Tongbai orogen, central China: implications for lower crustal delamination  

NASA Astrophysics Data System (ADS)

The Jigongshan and Qijianfeng batholiths in the Tongbai orogen consist mainly of porphyritic hornblende-biotite monzogranite, biotite monzogranite, and biotite syenogranite, which are variably intruded by lamprophyre, diorite, and syenogranite dykes. Mafic microgranular enclaves commonly occur in the hornblende-biotite monzogranite, whereas surmicaceous enclaves are found in the biotite monzogranite. Both batholiths have zircon U-Pb ages ranging from ca. 139 to 120 Ma, indicating their emplacement in the Early Cretaceous. The hornblende-biotite monzogranite has an adakitic affinity marked by relatively high Sr/Y and (La/Yb) N ratios, lack of Eu anomalies, low MgO and Ni contents, and Na2O > K2O. Its chemical compositions, combined with enriched Sr-Nd isotopic signatures, suggest formation by dehydration melting of mafic rocks in a thickened lower crust. This thickened crust resulted from the Permo-Triassic subduction-collision between the North China and South China blocks and persisted until the Early Cretaceous. The biotite monzogranite and biotite syenogranite have low Al2O3, CaO, and Sr contents, low Rb/Sr, FeOt/MgO, and (Na2O + K2O)/CaO ratios, and flat HREE patterns with moderate to weak Eu anomalies. They were produced by partial melting of crustal materials under relatively low pressure. Partial melting at different crustal levels could have significantly contributed to mechanical weakening of the crust. The diorite and lamprophyre dykes show linear trends between SiO2 and major or trace elements on Harker diagrams, with two lamprophyre samples containing normative nepheline and olivine. These rocks have high La/Yb and Dy/Yb ratios, both displaying co-variation with contents of Yb. They were originated from relatively deep lithospheric mantle followed by fractionation of olivine + clinopyroxene + apatite + Fe-Ti oxides. Extensive partial melting in the lithospheric mantle indicates relatively high temperatures at this level. We suggest that the presence of adakitic magmas, thickened but weakened crust and high temperatures in the lithosphere mantle point to lower crustal delamination in the Early Cretaceous in the Tongbai orogen.

Zhang, Jinyang; Ma, Changqian; Li, Jianwei; She, Zhenbing; Zhang, Chao

2013-06-01

302

Preparation and Characterization of Storage and Emission Functional Material of Cs2O-doped 12CaO·7Al2O3  

NASA Astrophysics Data System (ADS)

We provides a novel approach to generate low-temperature atomic oxygen anions (O-) emission using the cesium oxide-doped 12CaO·7Al2O3 (Cs2O-doped C12A7). The maximal emission intensity of O- from the Cs2O-doped C12A7 at 700 °C and 800 V/cm reached about 0.54 ?A/cm2, which was about two times as strong as that from the un-doped C12A7 (0.23 ?A/cm2) under the same condition. The initiative temperature of the O- emission from the Cs2O-doped C12A7 was about 500 °C, which was also much lower than the initiative temperature from the un-doped C12A7 (570 °C) in the given field of 800 V/cm. High pure O- emission close to 100% could be obtained from the Cs2O-doped C12A7 under the lower temperature (<550°C). The emission features of the Cs2O-doped C12A7, including the emission distribution, temperature effect, and emission branching ratio have been investigated in detail and compared with the un-doped C12A7. The structure and storage characteristics of the resulting material were also investigated via X-ray diffraction and electron paramagnetic resonance. It was found that doping Cs2O to C12A7 will lower the initiative emission temperature and enhance the emission intensity.

Ning, Shen; Shen, Jing; Li, Xing-long; Li, Quan-xin

2011-06-01

303

Hydride ion as a two-electron donor in a nanoporous crystalline semiconductor 12CaO.7Al2O3.  

PubMed

The 12CaO.7Al2O3 (C12A7) crystal with a nanoporous lattice framework exhibits high electrical conductivity with an activation energy of approximately 1.5 eV when equilibrated in a hydrogen atmosphere above approximately 800 degrees C. The high conductivity is preserved in a quenched state below approximately 600 degrees C with a reduced activation energy of approximately 0.8 eV. Such complex behavior in electrical conductivity is associated with incorporation of hydride ions (H-) in cages of the lattice framework. Electromotive force measurements reveal that the major carrier for the conductivity is electron with a small contribution by proton (H+), ruling out the possibility of direct intercage migration of the H- ion. A combination of these observations with the ab initio calculations leads to the conclusion that the electrons are thermally generated from the H- ion by the dissociation into two electrons and an proton, which is further converted to an OH- ion via reaction with an extraframework oxide ion (O2-). The energy difference between the initial (H- + O2-) and the final (2e- + OH-) states as evaluated by the theoretical calculation is as small as approximately 1 eV, which agrees well with an experimentally obtained enthalpy change, approximately 1.4 eV. Thus, internal equilibration between the extraframework hydrogen and the oxygen species is responsible for the thermal generation of the carrier electron. It is also suggested that the same conductive (2e- + OH-) state is reached by the photoirradiation of H- -containing C12A7. In this case the photoionization of H- forms an electron and an Ho atom, which then forms an OH- ion and another electron with thermal assistance. The persistence of photoinduced conductivity is explained by the slow kinetics of the reverse process at room temperature. PMID:16375369

Hayashi, Katsuro; Sushko, Peter V; Shluger, Alexander L; Hirano, Masahiro; Hosono, Hideo

2005-12-22

304

Oxidation Studies of SiAlON/MgAlON Ceramics with Fe2O3 and CaO Impurities, Part II: Phase Evolution  

NASA Astrophysics Data System (ADS)

The oxidation behavior of composite SiAlON/MgAlON phases, synthesized from the leaching residue after the aqueous treatment of salt cake from aluminum remelting, is compared with the oxidation of corresponding synthetic samples. The samples were subjected to oxidation under air as the oxidant atmosphere in the temperature range of 1373 K to 1773 K (1100 °C to 1500 °C). The phases present were analyzed by scanning electron microscopy (SEM)-electron-dispersive spectroscopy (EDS) and X-ray diffraction (XRD) to arrive at the evolution of the various phases formed during oxidation. From the experimental results, especially by the characterization of the oxidation products, the mechanism of the oxidation reaction was deduced as follows: With the progress of oxidation, the composition of the material being oxidized moved toward the Al2O3-rich corner of MgO-Al2O3-SiO2 and CaO-MgO-Al2O3-SiO2 phase diagrams relevant to the SiAlON/MgAlON composite. At lower temperatures, the addition of Fe2O3 and CaO facilitated the formation of cordierite and anorthite, respectively. With increasing temperature, islands of silicate melt were formed dissolving these oxides, with the liquidus temperature getting lowered as a consequence. The liquid phase formed engulfed the adjacent solid phases providing strong mobility for the cations and enabling the crystal growth. As a result, intermediate products, i.e., cordierite, anorthite, and spinel, which were formed earlier during oxidation, are found to get dissolved in the liquid phase.

Li, Peng; Zhang, Mei; Teng, Lidong; Seetharaman, Seshadri

2013-02-01

305

A Statistical Framework for Calculating and Assessing Compositional Linear Trends Within Fault Zones: A Case Study of the NE Block of the Clark Segment, San Jacinto Fault, California, USA  

NASA Astrophysics Data System (ADS)

Utilizing chemical data derived from the various fault zone architectural components of the Clark strand of the San Jacinto fault, southern California, USA, we apply for the first time non-central principal component analysis to calculate a compositional linear trend within molar A-CN-K space. In this procedure A-CN-K are calculated as the molar proportions of Al2O3 (A), CaO* + Na2O (CN), and K2O (K) in the sum of molar Al2O3, Na2O, CaO*, and K2O. CaO* is the molar CaO after correction for apatite. We then derive translational invariant chemical alteration intensity factors, t, for each architectural component through orthogonal projection of analyzed samples onto the compositional linear trend. The chemical alteration intensity factor t determines the relative change in composition compared to the original state (i.e., the composition of the altered wall rocks). It is dependent on the degree of intensity to which the process or processes responsible for the change in composition of each architectural component has been active. These processes include shearing, fragmentation, fluid flow, and generation of frictional heat. Non-central principal component analysis indicates that principal component 1 explains 99.7 % of the spread of A-CN-K data about the calculated compositional linear trend (i.e., the variance). The significance level for the overall one-way analysis of variance (ANOVA) is 0.0001. Such a result indicates that at least one significant difference across the group of means of t values is different at the 95 % confidence level. Following completion of the overall one-way ANOVA, the difference in means t test indicated that the mean of the t values for the fault core are different than the means obtained from the transition and damage zones. In contrast, at the 95 % confidence level, the means of the t values for the transition and damage zones are not statistically distinguishable. The results of XRD work completed during this study revealed that the <2 µm fraction is composed primarily of illite/smectite with ~15 % illite in the damage zone, of illite/smectite with ~30 % illite in the transition zone, and of discreet illite with very minor smectite in the fault core. These changes parallel the increasing values of the chemical alteration intensity factors (i.e., t). Based on the above results, it is speculated that when fault zones are derived from tonalitic wall rocks at depths of ~400 ± 100 m, the onset of the illite/smectite to illite conversion will occur when t values exceed 0.20 ± 0.12, the average chemical alteration intensity factor calculated for the transition zone. Under such conditions during repeated rupturing events, frictional heat is produced and acidic fluids with elevated temperatures (? ~125 °C) are flushed through the fault core. Over time, the combination of shearing, fragmentation, and frictionally elevated temperatures eventually overcomes the kinetic barrier for the illite/smectite to illite transition. Such settings and processes are unique to fault zones, and as a result, they represent an underappreciated setting for the development of illite from illite/smectite. The success of non-central principal component analysis in this environment offers the first statistically rigorous methodology for establishing the existence of compositional linear trends in fault zones. This method also derives quantifiable alteration intensity factors that could potentially be used to compare the intensity of alteration at different segments of a fault, as well as offer a foundation to interpret the potential driving forces for said alteration and differences therein.

Rockwell, Brian G.; Girty, Gary H.; Rockwell, Thomas K.

2014-05-01

306

[Influence of cations on the laser Raman spectra of silicate glasses].  

PubMed

Na2O(K2O)-CaO(MgO)-SiO2, Na2O(K2O)-Al2O3-SiO2, Na2O(K2O)-B2O3-SiO2, Na2O(K2O)-PbO-SiO2 and PbO-BaO-SiO2 glass systems were investigated using laser Raman spectroscopic technique. The modification of short-range structure of glass caused by network modifier cations will influence Raman signature. Alkali and alkali-earth ions can weaken the bridging oxygen bond, thus lower the frequency of Si-O(b)-Si anti-symmetric stretching vibration. When coordina ted by oxygen ions, B3+ can form [BO4] tetrahedron and enter the silicon-oxygen network, but this effect had little impact on the frequency of Raman peaks located in the high-frequency region. Al3+ can also be coordinated by oxygen ions to form [AlO4] tetrahedron. [AlO4] will increase the disorder degree of network while entering network. Ba2+ can increase the density of electron cloud along the Si-O(nb) bond when it bonds with non-bridging oxygen, which will lead to a higher peak intensity of O-Si-O stretching vibration. The Raman peaks of alkli- and alkali-earth silicate glasses are mainly distributed in the region of 400 - 1 200 cm(-1), while in the spectrum of Na2O(K2O)-PbO-SiO2 glass system a 131 cm(-1) peak existed. The authors assigned it to the Pb-O symmetric stretching vibration. Some of the samples were produced in the laboratory according to the average compositions of ancient glasses, so this research is very significant to discriminating ancient silicate glasses of different systems by Laser Raman spectroscopic technique. PMID:22715771

Xiong, Yi; Zhao, Hong-xia; Gan, Fu-xi

2012-04-01

307

Compact Adaptive Optics Systems (CAOS).  

National Technical Information Service (NTIS)

As feasibility study has been conducted to investigate whether compact adaptive optical (AO) systems based on the use of transparent wavefront modulators are viable. The results presented here consider the generic properties of suitable wavefront sensor t...

A. H. Greenway

2002-01-01

308

Cuprian fraipontite and sauconite from the Defiance-Silver Bill mines, Gleeson, Arizona.  

USGS Publications Warehouse

XRD studies have shown the fine-grained, light blue-green mineral previously identified as turquoise or chrysocolla to be the rare species fraipontite + or - admixed sauconite. Composite microprobe and XRF analyses gave SiO2 24.8, Al2O3 17.3, CaO 0.34, CuO 5.2, ZnO 40.95, H2O (ign. loss, 900oC) 12.8, = 101.39, yielding the formula (Zn1.84Al0.77Cu0.24box 0.13- Ca0.02)3.00(Si1.51Al0.49)2.00O5(OH)4. Semiquantitative emission spectrographic analysis showed Fe 0.007, Mg 0.01, Ca 0.07, Si 10, Al major, Na 0.015, Zn major, Cu 5%; Mn 15, B 150, Be 7, Ni 50, Pb 15, Sc 15, Ga 70 and Ag 1 ppm. It has a 5.331(8), b 9.23(1), c 7.275(6) A, beta 104.15o; H. 3.5-4; Dcalc 3.44, Dobs. 3.08- 3.10; mean refr. ind. approx 1.61. Much of the fraipontite is admixed with sauconite, which may be forming from the fraipontite. XRF analysis of this material gave SiO2 32.8, Al2O3 10.9, MgO < 0.1, CaO 1.51, Na2O < 0.2, K2O < 0.02, TiO2 < 0.02, P2O5 < 0.02, MnO < 0.02, CuO 4.65, ZnO 39.9, ign. loss 13.9, = 103.7.-G.W.R.

Foord, E. E.; Taggart, J. E.; Conklin, N. M.

1983-01-01

309

Geochemistry of Mesoproterozoic sedimentary rocks of upper Vindhyan Group, southeastern Rajasthan and implications for weathering history, composition and tectonic setting of continental crust in the northern part of Indian shield  

NASA Astrophysics Data System (ADS)

The upper Vindhyan succession of southeastern Rajasthan is divisible into Kaimur, Rewa and Bhander Groups. The major and trace element (including rare earth elements) data of the upper Vindhyan shales and sandstones are investigated to determine the weathering history, composition, and tectonic setting of Mesoproterozoic continental crust. CIA (chemical index of alteration) values, A-CN-K plot (A = Al2O3, CN = CaO* + Na2O, K = K2O) and depletion in U, Na2O, CaO, Sr and Ba suggest that the source area experienced moderate to high degree of chemical weathering under warm and humid conditions. Provenance modeling indicates that the Kaimur sandstones are best modeled with a mixture having 40% granitic gneiss, 20% Tonalite-Trondhjemite-Granodiorite (TTG), 20% mafic enclaves and 20% Berach Granite of the Banded Gneissic Complex (BGC). A mixture of 60% granitic gneiss, 20% mafic enclaves and 20% Berach Granite of the BGC can model the Rewa and Bhander Groups. It is suggested that the upper Vindhyan sedimentation commenced at the time of Delhi-Sausar orogeny at about 1100-1000 Ma. The orogenic movements uplifted the parts of old continental crust in the BGC terrain creating positive areas, which exposed older crustal blocks containing TTG as important component. The debris of Kaimur sandstone probably derived from these uplifted blocks. As indicated by Palaeocurrent data, the Rewa and Bhander formations were derived from Bundelkhand Granitic Gneiss Complex (BGGC) occurring to the north of the basin and/or the Chotanagpur Granitic Gneiss Complex (CGGC) of eastern Indian shield. The derivation of Lower and upper groups of Vindhyan succession from different source terrains of identical composition suggests that at the time of Vindhyan sedimentation, the BGC of Rajasthan, the BGGC of Central India and the CGGC of eastern India had similar lithological composition. This implies that well before the origin of the Vindhyan basin these discrete terrains evolved as a single unit that existed as a Mesoarchaean nucleus in the northern part of the Indian shield.

Raza, Mahshar; Khan, Abdullah; Bhardwaj, V. R.; Rais, Sarwar

2012-04-01

310

Effects of CaF2 vis-a-vis TiO2 as nucleating agent in SiO2-Al2O3-CaO glass-ceramics  

NASA Astrophysics Data System (ADS)

The independent effects of CaF2 and TiO2 on the glass-ceramics based on SiO2-Al2O3-CaO system have been investigated. The crystallization behavior, microstructure, mechanical properties and chemical resistance of the glass-ceramics were studied by Differential Thermal Analysis (DTA), Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), FTIR, mechanical and chemical resistance measurements. The CaF2 containing glass ceramics are found to be much superior to that of TiO2 containing glass ceramics on the basis of sintering strength, mechanical and chemical properties.

Mukherjee, Debasis Pradip; Datta, Tanmoy; Das, Sudip Kumar

2013-06-01

311

Conditions of crystallization of the Ural platinum-bearing ultrabasic massifs: evidence from melt inclusions  

NASA Astrophysics Data System (ADS)

Conditions of the Ural platinum-bearing ultramafic massifs formation attract attention of numerous researchers. A most important peculiarity of such plutons is their dunite cores, to which commercial Pt deposits are related. There are a different opinions about genesis of these massifs and usual methods not always can solve this question. As a result of melt inclusions study in the Cr-spinel the new data on physical and chemical parameters of dunite crystallization of the Nizhnii Tagil platinum-bearing ulrabasic massif (Ural) was obtained. The comparative analysis of Cr-spinels, containing melt inclusions, has shown essential differences of these minerals from chromites of the ultrabasic ophiolite complexes and of modern oceanic crust. Contents of major chemical components in the heated and quenched melt inclusions are close to those in the picrite and this testifies dunite crystallization from ultrabasic (to 24 wt.% MgO) magma. On the variation diagrams for inclusions in Cr-spinel the following changes of chemical compositions are established: during SiO2 growth there is falling of FeO, MgO, and increase of CaO, Na2O contents. Values of TiO2, Al2O3, K2O and P2O5 remain as a whole constant. Comparing to the data on the melt inclusions in Cr-spinel from the Konder massif, we see that values of the most part of chemical components (SiO2, TiO2, K2O, P2O5) are actually overlapped. At the same time, for the Nizhnii Tagil platinum-bearing massif the big maintenances of FeO and CaO in inclusions are marked. Distinct dependence of the majority of components from the MgO content in inclusions is observed: values TiO2, Al2O3 FeO, CaO and Na2O fall at transition to more magnesia melts. On the peculiarities of distribution of petrochemical characteristics melt inclusions in considered Cr-spinels are co-ordinated with the data on evolution of compositions of melts and rocks of model stratified ultramafic plutons during their crystallization in the magmatic chambers. On the diagrams an association of melt inclusions with the data on inclusions in Cr-spinels from the Konder platinum-bearing and Karashat ophiolite massifs is clearly visible. Our computer simulations on the basis of melt inclusion compositions by the PETROLOG program package (Danyushevsky, Plechov, 2011) allowed to evaluate the crystallization temperature of dunites of the Nizhnii Tagil platinum-bearing massif in the intrusive chamber. The most part of olivine was formed from 1430 to 1360°C and continued to crystallize until to 1280°C. Cr-spinel crystallized from melts in the range of temperatures from 1345 to 1310°C. The investigations were supported by the Russian Foundation for Basic Research (project No 12-05-00959) and by Projects N 2.1 and N 50.

Simonov, Vladimir; Puchkov, Victor; Prikhod'ko, Vladimir; Stupakov, Sergey; Kotlyarov, Alexey

2013-04-01

312

Surface and chemical study of SiO{sub 2} {center_dot} P{sub 2}O{sub 5} {center_dot} CaO {center_dot} (MgO) bioactive glasses  

SciTech Connect

Glasses in SiO{sub 2} {center_dot} CaO {center_dot} P{sub 2}O{sub 5} and SiO{sub 2} {center_dot} CaO {center_dot} P{sub 2}O{sub 5} {center_dot} MgO systems have been prepared by a sol-gel synthesis procedure. The calcined glasses have been characterized by XRD, N{sub 2} adsorption, Hg porosimetry, XPS and TEM have been also subjected to in vitro tests (immersion in a simulated body fluid) to evaluate their bioactivity. The presence of magnesium in the glasses increases the surface area and porosity, but is retards the formation of an apatite layer on the surface of glasses in the in vitro test. The XPS reveals that the surfaces of the glasses are richer in phosphorus and poorer in calcium than the bulk, whereas the magnesium, if present, associates preferentially to phosphorus at the glass surface. The TEM shows the presence of apatite-like calcium phosphate domains in the magnesium -free glasses, which are barely detected in the glasses, which contain this element. These apatitic domains are proposed to be the nucleation centers for the crystallization of apatite in the in vitro tests.

Perez-Pariente, J.; Balas, F.; Vallet-Regi, M.

2000-03-01

313

Evidence from FTIR difference spectroscopy that D1-Asp61 influences the water reactions of the oxygen-evolving Mn4CaO5 cluster of photosystem II.  

PubMed

Understanding the mechanism of photosynthetic water oxidation requires characterizing the reactions of the water molecules that serve as substrate or that otherwise interact with the oxygen-evolving Mn4CaO5 cluster. FTIR difference spectroscopy is a powerful tool for studying the structural changes of hydrogen bonded water molecules. For example, the O-H stretching mode of water molecules having relatively weak hydrogen bonds can be monitored near 3600 cm(-1), the D-O-D bending mode can be monitored near 1210 cm(-1), and highly polarizable networks of hydrogen bonds can be monitored as broad features between 3000 and 2000 cm(-1). The two former regions are practically devoid of overlapping vibrational modes from the protein. In Photosystem II, water oxidation requires a precisely choreographed sequence of proton and electron transfer steps in which proton release is required to prevent the redox potential of the Mn4CaO5 cluster from rising to levels that would prevent its subsequent oxidation. Proton release takes place via one or more proton egress pathways leading from the Mn4CaO5 cluster to the thylakoid lumen. There is growing evidence that D1-D61 is the initial residue of one dominant proton egress pathway. This residue interacts directly with water molecules in the first and second coordination spheres of the Mn4CaO5 cluster. In this study, we explore the influence of D1-D61 on the water reactions accompanying oxygen production by characterizing the FTIR properties of the D1-D61A mutant of the cyanobacterium, Synechocystis sp. PCC 6803. On the basis of mutation-induced changes to the carbonyl stretching region near 1747 cm(-1), we conclude that D1-D61 participates in the same extensive networks of hydrogen bonds that have been identified previously by FTIR studies. On the basis of mutation-induced changes to the weakly hydrogen-bonded O-H stretching region, we conclude that D1-D61 interacts with water molecules that are located near the Cl(-)(1) ion and that deprotonate or participate in stronger hydrogen bonds as a result of the S1 to S2 and S2 to S3 transitions. On the basis of the elimination of a broad feature between 3100 and 2600 cm(-1), we conclude that the highly polarizable network of hydrogen bonds whose polarizability or protonation state increases during the S1 to S2 transition involves D1-D61. On the basis of the elimination of features in the D-O-D bending region, we conclude that D1-D61 forms a hydrogen bond to one of the H2O molecules whose H-O-H bending mode changes in response to the S1 to S2 transition. The elimination of this H2O molecule in the D1-D61A mutant provides one rationale for the decreased efficiency of water oxidation in this mutant. Finally, we discuss reasons why the recent conclusion that a substrate-containing cluster of five water molecules accepts a proton from the Mn4CaO5 cluster during the S1 to S2 transition and deprotonates during subsequent S state transitions should be reassessed. PMID:24730551

Debus, Richard J

2014-05-13

314

Novel Application of Alkali Oxides in Basic Tundish Fluxes for Enhancing Inclusion Removal in 321 Stainless Steels  

NASA Astrophysics Data System (ADS)

Fundamental work on the effect of alkali oxides including Li2O, Na2O, and K2O on the absorption ability of inclusions in a typical basic tundish flux for 321 stainless steels has been studied. The effects on the absorption ability are dependent on the type of alkali oxides and the amount composed within the tundish flux. Results from kinetics studies using an induction furnace at 1823 K (1550 °C) on the reaction of tundish fluxes containing alkali oxides with 321 stainless steels suggest minimal improvement with Li2O and Na2O additions and in some cases hindered inclusion removal, but K2O additions seems to significantly improve the cleanliness in the as-quenched 321 stainless steel melts compared to preexisting tundish flux compositions. Both Li2O and Na2O significantly lower the viscosity of the melt, while K2O increases the viscosity. Although alkali oxides have a propensity to enhance the cohesion of aluminate melts due to the ionic compensation effect in [AlO4]5--tetrahedral structural units, this effect was not pronounced for Li2O and Na2O compared to K2O additions, which may be due to the large ionic radius size of potassium. An automated SEM-EDS analysis was utilized to identify the inclusion morphology and abundance within the steel. Fourier transform infrared spectroscopy was used to identify the effects of alkali oxides on the tundish flux structure for improved absorption capability and described the characteristic effect of K2O on increasing the asymmetric stretching vibrations of [AlO4]5--tetrahedral structural units and Si-O-Al bonding within the flux, thus polymerizing the flux and selectively absorbing inclusions.

Yu, Jong Yeong; Kang, Youngjo; Sohn, Il

2014-01-01

315

Antibacterial glass films prepared on metal surfaces by sol–gel method  

Microsoft Academic Search

This paper describes the preparation and characterization of glass films consisting of SiO2, Li2O, Na2O, K2O or MgO in varying compositions on stainless steel and aluminum substrates by sol–gel method. Silver phosphate or silver\\u000a incorporated zeolite was also introduced into the sols for obtaining antibacterial effect. The SiO2\\/Li2O\\/Na2O system having the composition of 85:5:10 wt% was found as the optimum

Nadir Kiraz; Ömer Kesmez; Esin Burunkaya; Leyla Budama; Burçin Acar; Meltem Asiltürk; H. Erdem Çamurlu; Ertu?rul Arpaç

2010-01-01

316

Disorder of O 2- ion and incorporation of O - and O2- radicals in nanoporous crystal 12CaO · 7Al 2O 3 studied by low-temperature heat capacity measurements  

NASA Astrophysics Data System (ADS)

Heat capacity of nanoporous crystal, 12CaO · 7Al 2O 3 (C12A7), was measured between 85 mK and 5 K under magnetic field up to 9 T. The heat capacity under zero magnetic field did not fit to the T3 law; the deviation was discussed in terms of the disorder of the O 2- ions in the subnanometer-sized cages in C12A7 lattice. Under magnetic field, the heat capacity showed a Schottky-type anomaly due to the Zeeman splitting of O - and O2- radicals ( S = 1/2) incorporated in the cages. The total concentration of O - and O2- radicals in the crystal was estimated to be 4.4 × 10 18 cm -3 (2.3 × 10 21 mol -1, 3.8 × 10 -3 mol mol -1).

Kohama, Yoshimitsu; Tojo, Takeo; Kawaji, Hitoshi; Atake, Tooru; Matsuishi, Satoru; Hosono, Hideo

2006-04-01

317

Characterization of 12CaO x 7Al2O3 doped indium tin oxide films for transparent cathode in top-emission organic light-emitting diodes.  

PubMed

12CaO x 7Al2O3, insulator (C12A7) doped indium tin oxide (ITO) (ITO:C12A7) films were fabricated using a radio frequency magnetron co-sputtering system with ITO and C12A7 targets. The qualitative and quantitative properties of ITO:C12A7 films, as a function of C12A7 concentration, were examined via X-ray photoemission spectroscopy and synchrotron X-ray scattering as well as by conducting atomic force microscopy. The work function of ITO:C12A7 (1.3%) films of approximately 2.8 eV obtained by high resolution photoemission spectroscopy measurements make them a reasonable cathode for top-emission organic light-emitting diodes. PMID:24245291

Jung, Chul Ho; Hwang, In Rok; Park, Bae Ho; Yoon, Dae Ho

2013-11-01

318

Enhanced stability of CaO and/or La2O3 promoted Pd/Al2O3 egg-shell catalysts in partial oxidation of methane to syngas.  

PubMed

An egg-shell Pd/Al2O3 catalyst showed higher activity than a regular Pd/Al2O3 catalyst in the partial oxidation of methane to syngas, but a common problem of this reaction is the catalyst deactivation on stream. We attempted to modify the egg-shell catalyst via impregnation with some metal oxide additives. Although the addition of MgO did not show any beneficial effect, the addition of CaO and/or La2O3 significantly improved the stability due to the suppression of carbon deposition and phase transformation of the Al2O3 support. The catalysts were characterized by X-ray diffraction (XRD), N2 adsorption-desorption, and thermogravimetric analysis (TGA). PMID:23860276

Wang, Jinlong; Yu, Hongbo; Ma, Zhen; Zhou, Shenghu

2013-01-01

319

The high-temperature thermal expansion of BiPbSrCaCuO superconductor and the oxide components (Bi2O3, PbO, CaO, CuO)  

Microsoft Academic Search

The thermal expansion of superconducting Bi1.6Pb0.4Sr2Ca2Cu3Ox (BiPbSrCaCuO) and its oxide components Bi2O3, PbO, CaO and CuO have been studied by high-temperature dilatometric measurements (30–800°C). The thermal expansion coefficient for the BiPbSrCaCuO superconductor in the range 150–830°C is a=6.4×10-6K-1. The temperature dependences of ?L\\/L of pressed Bi2O3 reveals sharp changes of length on heating (T1=712°C), and on cooling (T2=637°C and T3=577°C),

T. D. Dzhafarov; M. Altunbas; O. Görür

1996-01-01

320

Substitution of CaO by BaO to improve the microwave dielectric properties of CaO–Li 2O–Sm 2O 3–TiO 2 ceramics  

Microsoft Academic Search

Sintered CaO–Li2O3–Sm2O3–TiO2(16:9:12:63) composition (CLST) at 1325°C shows microwave dielectric properties: ?r=104.1, Q?f value=4320 GHz, and ?f=13.2 ppm\\/°C. When BaO is used to substitute CaO in the CLST composition to form CaO–BaO–Li2O–Sm2O3–TiO2=16?x:x:9:12:63 (x=2 and 4 for CBLST2 and CBLST4), the sintered CBLST2 and CBLST4 ceramics show coexistence of two phases, the perovskite CaO–Li2O3–Sm2O3–TiO2 (CLST) phase and BaSm2Ti4O12 (BST). As the BaO

Ying-Chung Chen; Ping-Shou Cheng; Cheng-Fu Yang; Wen-Cheng Tzou

2001-01-01

321

Fabrication and electron transport properties of epitaxial films of electron-doped 12CaO.7Al{sub 2}O{sub 3} and 12SrO.7Al{sub 2}O{sub 3}  

SciTech Connect

Epitaxial growth and electron doping of 12CaO.7Al{sub 2}O{sub 3} (C12A7) and 12SrO.7Al{sub 2}O{sub 3} (S12A7) are reported. The C12A7 films were prepared on Y{sub 3}Al{sub 5}O{sub 12} (YAG) single-crystal substrates by pulsed laser deposition at room temperature and subsequent thermal crystallization. X-ray diffraction patterns revealed the films were grown epitaxially with the orientation relationship of (001)[100] C12A7 || (001)[100] YAG. For S12A7, pseudo-homoepitaxial growth was attained on the C12A7 epitaxial layer. Upon electron doping, metallic conduction was achieved in the C12A7 film and the S12A7/C12A7 double-layered films. Analyses of optical absorption spectra for the S12A7/C12A7 films provided the densities of free electrons in each layer separately. Hall measurements exhibited larger electron mobility in the S12A7/C12A7 film than those in C12A7 and S12A7 films, suggesting free electrons may be accumulated at the S12A7/C12A7 interface due presumably to a discontinuity of the cage conduction bands. - Graphical abstract: Reciprocal space maps around the 408 and the 709 diffractions show the films were grown epitaxially with the orientation relationship of (001)[100] 12SrO.7Al{sub 2}O{sub 3} || (001)[100] 12CaO.7Al{sub 2}O{sub 3} || (001)[100] Y{sub 3}Al{sub 5}O{sub 12}.

Miyakawa, Masashi, E-mail: m-miyakawa@lucid.msl.titech.ac.j [Frontier Research Center, Tokyo Institute of Technology, Mail Box S2-13, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan); Hiramatsu, Hidenori [Frontier Research Center, Tokyo Institute of Technology, Mail Box S2-13, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan); Kamiya, Toshio [Materials and Structures Laboratory, Tokyo Institute of Technology, Mail Box R3-1, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan); Hirano, Masahiro [Frontier Research Center, Tokyo Institute of Technology, Mail Box S2-13, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan); Hosono, Hideo [Frontier Research Center, Tokyo Institute of Technology, Mail Box S2-13, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan); Materials and Structures Laboratory, Tokyo Institute of Technology, Mail Box R3-1, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan)

2010-02-15

322

Age and origin of high Ba–Sr appinite–granites at the northwestern margin of the Tibet Plateau: Implications for early Paleozoic tectonic evolution of the Western Kunlun orogenic belt  

Microsoft Academic Search

The Buya appinite–granite is a typical high Ba–Sr granite emplaced at the northern West Kunlun orogenic belt along the northwestern margin of the Tibetan Plateau. The granite is dated at ca. 430 Ma using the SHRIMP U–Pb zircon method. It consists of alkaline feldspar granites with coeval appinite enclaves. The granite possesses high SiO2 (69.77–72.69%), K2O (4.44–5.10%) and total alkalinity (K2O+Na2O=8.80–9.92%),

Hai-Min Ye; Xian-Hua Li; Zheng-Xiang Li; Chuan-Lin Zhang

2008-01-01

323

Geochemistry and petrogenesis of Mashhad granitoids: An insight into the geodynamic history of the Paleo-Tethys in northeast of Iran  

NASA Astrophysics Data System (ADS)

Mashhad granitoids in northeast Iran are part of the so-called Silk Road arc that extended for 8300 km along the entire southern margin of Eurasia from North China to Europe and formed as the result of a north-dipping subduction of the Paleo-Tethys. The exact timing of the final coalescence of the Iran and Turan plates in the Silk Road arc is poorly constrained and thus the study of the Mashhad granitoids provides valuable information on the geodynamic history of the Paleo-Tethys. Three distinct granitoid suites are developed in space and time (ca. 217-200 Ma) during evolution of the Paleo-Tethys in the Mashhad area. They are: 1) the quartz diorite-tonalite-granodiorite, 2) the granodiorite, and 3) the monzogranite. Quartz diorite-tonalite-granodiorite stock from Dehnow-Vakilabad (217 ± 4-215 ± 4 Ma) intruded the pre-Late Triassic metamorphosed rocks. Large granodiorite and monzogranite intrusions, comprising the Mashhad batholith, were emplaced at 212 ± 5.2 Ma and 199.8 ± 3.7 Ma, respectively. The high initial 87Sr/86Sr ratios (0.708042-0.708368), low initial 143Nd/144Nd ratios (0.512044-0.51078) and low ?Nd(t) values (- 5.5 to - 6.1) of quartz diorite-tonalite-granodiorite stock along with its metaluminous to mildly peraluminous character (Al2O3/(CaO + Na2O + K2O) Mol. = 0.94-1.15) is consistent with geochemical features of I-type granitoid magma. This magma was derived from a mafic mantle source that was enriched by subducted slab materials. The granodiorite suite has low contents of Y (? 18 ppm) and heavy REE (HREE) (Yb < 1.53 ppm) and high contents of Sr (> 594 ppm) and high ratio of Sr/Y (> 35) that resemble geochemical characteristics of adakite intrusions. The metaluminous to mildly peraluminous nature of granodiorite from Mashhad batholiths as well as its initial 87Sr/86Sr ratios (0.705469-0.706356), initial 143Nd/144Nd ratios (0.512204-0.512225) and ?Nd(t) values (- 2.7 to - 3.2) are typical of adakitic magmas generated by partial melting of a subducted slab. These magmas were then hybridized in the mantle wedge with peridotite melt. The quartz diorite-tonalite-granodiorite stock and granodiorite batholith could be considered as arc-related granitoid intrusions, which were emplaced during the northward subduction of Paleo-Tethys Ocean crust beneath the Turan micro-continent. The monzogranite is strongly peraluminous (Al2O3/(CaO + Na2O + K2O) Mol. = 1.07-1.17), alkali-rich with normative corundum ranging between 1.19% and 2.37%, has high initial 87Sr/86Sr ratios (0.707457-0.709710) and low initial 143Nd/144Nd ratios (0.512042-0.512111) and ?Nd(t) values (- 5.3 to - 6.6) that substantiate with geochemical attributes of S-type granites formed by dehydration-melting of heterogeneous metasedimentary assemblages in thickened lower continental crust. The monzogranite was emplaced as a consequence of high-temperature metamorphism during the final integration of Turan and Iran plates. The ages found in the Mashhad granites show that the subduction of Paleo-Tethys under the Turan plate that led to the generation of arc-related Mashhad granites in late-Triassic, finally ceased due to the collision of Iran and Turan micro-plates in early Jurassic.

Mirnejad, H.; Lalonde, A. E.; Obeid, M.; Hassanzadeh, J.

2013-06-01

324

Geochemistry and origin of the early Mesoproterozoic mangerite-charnockite-rapakivi granite association of the Serra da Providência suite and associated gabbros, central-eastern Rondônia, SW Amazonian Craton, Brazil  

NASA Astrophysics Data System (ADS)

The Serra da Providência suite (SPS) is constituted of quartz mangerite-charnockite-rapakivi granite and coeval mafic rocks, intruded during the 1.60-1.53 Ga interval into Paleoproterozoic metamorphic basement (Jamari Complex) in the Juruena-Rondônia geochronologic province, SW Amazonian Craton. In this region the Serra da Providência suite consists of two batholiths and several small plutons represented by syeno-monzogranites and igneous quartz mangerite and charnockites. The Serra da Providência granites are ferroan, calc-alkalic to alkali-calcic and characterized by high Na2O + K2O, Rb, Zr, Y, Nb, Ta, Ce, Zn, Ga, and REE (except for Eu), moderate Ba, and low Sr, MgO, and CaO. Ga/Al, Y/Nb, FeOT/(FeOT + MgO) and K2O/Na2O ratios are high and Sr/Ba and Rb/Ba are low and are geochemically similar to typical A2-subtype granites. The SPS charnockites and quartz mangerites display values of FeOT, MgO, CaO, Ba, Rb, Sr, Nb/Ta and Zr/Hf similar to the SPS A-type granites. The occurrence of magnetite as an accessory phase and the high FeOT/(FeOT + MgO) in granites, charnockites and quartz mangerites suggest crystallization from a relatively oxidized magma and also explain the occurrence of titanite as a primary phase in these granites, similar to those reported in several localities of the Amazonian Craton. The parental magma of the mafic rocks of the SPS probably had mainly enriched sources and resulted from melting of heterogeneous mantle reservoirs with coherent chemical characteristics. Trace elements data indicate subduction-modified mantle sources for the mafic rocks that are in agreement with the post-collisional character of this magmatism. A large set of whole-rock Sm-Nd isotope data (Bettencourt et al., 1999; Scandolara, 2006; Santos et al., 2008 and this work) demonstrate that granites, charnockites and quartz mangerites of the study area are the product of magmas derived from interaction between enriched mantle derived magmas (in very subordinate proportions) and recycled crust in larger proportion. The source region is dominated by Paleoproterozoic material, but several samples yield Archaean model ages that are the first evidence for such ancient source materials in the SW Amazonian Craton. The Serra da Providência suite was emplaced during the post-collisional stage of the Juruena-Jamari arc and Madeirinha orogeny (Scandolara et al., 2011), and post-dates the collision between the Tapajós (Tapajós-Parima geochronological province, Pará, Brazil) and Bolívia (palaeocontinent which precedes Sunsás geochronological province) blocks. Its geochemical and structural features are coincident with those recognized in post-collisional granitoids. Geochemical data suggest that complex processes which involved crustal melting, fractional crystallization, magma mixing and, in some extent, crustal assimilation were responsible for the magmatism of the Serra da Providência suite. The magmas that constitute the Serra da Providência suite resulted from varying degrees of partial melting of a compositionally heterogeneous source. The nature of the source and the degree of melting exerted a significant control over compositional variation in some of the parental magmas which were also affected by subsequent fractional crystallization and mingling processes. Internal variations in composition observed in several bodies can be the result of incremental amalgamation of different magma pulses that varied mainly in the degree of partial melting.

Scandolara, Jaime E.; Fuck, Reinhardt A.; Dall'Agnol, Roberto; Dantas, Elton L.

2013-08-01

325

Growth of Megaspherulites In a Rhyolitic Vitrophyre  

NASA Technical Reports Server (NTRS)

Megaspherulites occur in the middle zone of a thick sequence of rhyolitic vitrophyre that occupies a small, late Eocene to early Oligocene volcanic-tectonic basin near Silver Cliff, Custer County, Colorado. Diameters of the megaspherulites range from 0.3 m to over 3.66 m, including a clay envelope. The megaspherulites are compound spherulites. consisting of an extremely large number (3.8 x 10(exp 9) to 9.9 x 10(exp 9)) of individual growth cones averaging 3 mm long by 1.25 mm wide at their termination. They are holocrystalline, very fine- to fine-grained, composed of disordered to ordered sanidine (orthoclase) and quartz, and surrounded by a thin K-feldspar, quartz rich rind, an inner clay layer with mordenite, and an outer clay layer composed wholly of 15 A montmorillonite. Whole rock analyses of the megaspherulites show a restricted composition from their core to their outer edge, with an average analyses of 76.3% SiO2, 0.34% CaO, 2.17% Na2O, 6.92% K2O, 0.83% H2O+ compared to the rhyolitic vitrophyre from which they crystallize with 71.07% SiO2, 0.57% CaO, 4.06% Na2O,4.l0% K2O, and 6.40% H2O+. The remaining oxides of Fe2O3 (total Fe), A12O3, MnO,MgO, TiO2, P2O5, Cr2O3, and trace elements show uniform distribution between the megaspherulites and the rhyolitic vitrophyre. Megaspherulite crystallization began soon after the rhyolitic lava ceased to flow as the result of sparse heterogeneous nucleation, under nonequilibrium conditions, due to a high degree of undercooling, delta T. The crystals grow with a fibrous habit which is favored by a large delta T ranging between 245 C and 295 C, despite lowered viscosity, and enhanced diffusion due to the high H2O content, ranging between 5% and 7%. Therefore, megaspherulite growth proceeded in a diffusion controlled manner, where the diffusion, rate lags behind the crystal growth rate at the crystal-liquid interface, restricting fibril lengths and diameters to the 10 micron to 15 micron and 3 micron and 8 micron ranges respectively. Once diffusion reestablishes itself at the crystallization front, a new nucleation event occurs at the terminated tips of the fibril cones and a new cone begins to develop with a similar orientation (small angle branching) to the earlier cones. During crystallization, these fibril cones impinge upon each other, resulting in fibril cone-free areas. These cone-free areas consist of coarser, fine-grained phases, dominated by quartz, which crystallized from the melt as it accumulated between the crystallizing K-feldspar fibrils of the cones. The anhydrous nature of the disordered to ordered sanidine (orthoclase) and quartz, suggests that water in the vitrophyre moved ahead of the crystallization front, resulting in a water rich fluid being enriched in Si, K, Na, Mg, Ca, Sr, Ba, and Y. The clay layers associated with the megaspherulites are therefore, the result of the deuteric alteration between the fractionated water and the vitrophyre, as indicated by the presence of the minerals mordenite and montmorillonite. This silica rich fluid also resulted in the total silicification of the megaspherulites within the upper 3 m of the vitrophyre.

Smith, Robert K.; Tremallo, Robin L.; Lofgren, Gary E.

2000-01-01

326

Major Elements Budget Between Abyssal Peridotite And Seawater During The Serpentinization  

NASA Astrophysics Data System (ADS)

Water-Rock Interaction is one of the most hot-debated issues among geologists, geophysicists, as well as geochemists. Abyssal peridotites recovered from the seafloor are often greatly affected or alterated by seawater in the form of serpentinization. The alteration to the peridotites makes it difficult to do the straightforward analysis for its primary composition as it was settled in the upper mantle, which confine the usage of these rare direct samples from the mantle in the scientific study, such as mantle dynamics, mantle composition and crust-mantle interaction. Besides, It was revealed recently that the serpentinization of abyssal peridotites may give birth to the hydrothermal activity. The elements migration during the serpentinization may perform a great role on the chemical composition of the hydrothermal fluid, which can support a hidden chemosynthetic ecosystem in the abyssal seabed. The research work focused on the major elements behavior during the serpentinization by studying the partially serpentinized samples of abyssal peridotite from Southwest Indian Ridge. The primary mineral assemblage of peridotite is olivine (Mg2SiO4), orthopyroxene (Mg2Si2O6), clinopyroxene (CaMgSi2O6) and spinel ((Mg,Fe)(Al,Cr)2O4). The major chemical composition are usually as SiO2 (30~45wt.%), MgO (20~45 wt.%), FeO and Fe2O3 (total 5~15 wt.%). Besides there are very few MnO, CaO, Al2O3, Cr2O3, NiO, Na2O, K2O and H2O. While on the other hand the serpentinized peridotite shows a more complicated mineral assemblage, besides the primary minerals there are more alteration minerals, such as serpentine (Mg3[Si2O5](OH)4), magnetite (Fe3O4), talc (Mg3[Si4O10](OH)2), brucite (Mg(OH)2), tremolite (Ca2Mg5[Si8O22](OH)2), chromite (FeCr2O4), chlorite ((Mg,Fe)6[(Si,Al)4O10](OH)8), and other accessary minerals like native metals, sulfides, clay minerals and hornblende. According to the EMPA analysis, the serpentinized sample shows the chemical composition as SiO2(~40 wt.%), MgO(~30 wt.%), total FeO(~7 wt.%), Al2O3(~1 wt.%), MnO(~0.4 wt.%), Cr2O3(~0.3 wt.%), NiO(~0.2 wt.%), CaO(~0.2 wt.%), and very few TiO2, Na2O and K2O. The overall percentages for all the elements mentioned above are usually around 80wt.%, about 20% less than full percent, which indicates the volatile matters in the altered samples. Based on the preliminary study, we get the general picture for the major elements behavior during the alteration. Taking the abyssal peridotite for example, it gains large quantities of H and O in the form of H2O, and other volatile elements like F, Cl, B from the seawater during serpentinization. It may also get additional Na, K, Mg from the seawater as shown from the standardized concentration in primary minerals as well as altered minerals. It loses Fe, Al, Ca, Si during the serpentinization seen from the EMPA mapping results. The element Mn, Cr and Ni are relatively immobile during the alteration. To get more precise deduction as to the element budget during the alteration process, much more sensitive analytical instruments like LA-ICP-MS are needed. And more work need to be done to get the quantitive estimation for transferring rate of each element.

Yu, X.; Dong, Y.; Li, X.; Chu, F.

2012-12-01

327

Petrography and Geochemistry of the Zamora Batholith in the south of the sub-Andean zone (Ecuador)  

NASA Astrophysics Data System (ADS)

The Zamora Batholith is an intrusive complex that is located in the extreme south-east of Ecuador. It has dimensions of 200 x 50 km approximately. It is mainly located in the Zamora Chinchipe province from which it takes its name. This study consisted in the petrographic and geochemical characterization of the Zamora Batholith in the area covered by 1: 50,000 geological maps of Centro Shaime, Guayzimi, Paquisha, Los Encuentros and El Pangui. Fieldwork was done by the "Proyecto Mapeo Geológico escala 1:50.000 (zonas prospectivas mineras)" of the Instituto Nacional de Investigación Geológico, Minero, Metalúrgico of Ecuador. This research was performed with 59 thin sections and 10 whole - rock chemical analysis done in the C.I.C of the Granada University. The Zamora Batholith intrudes Triassic to Jurassic volcanic rocks. It is overlaid by sandstones of the Hollin Formation of the Upper Aptian age and shale and limestone from the Napo Formation. Post-cretaceous deposits of ash and lava flows of andesitic to rhyolitic compositions cover the batholith. The petrography of the Zamora Batholith ranges from tonalite to monzogranite with the same qualitative mineralogy. The rocks are composed by different proportions of plagioclase, amphibole, feldspar K, quartz, biotite, opaque, pyroxene and epidote, as accessory minerals has zircon, sphene and apatite. To the south of the Conguime and Guayzimi towns, the dominant petrography is medium to coarse grained amphibole granodiorite with tonalitic and monzogranitic subordinates. To the north monzogranites are dominant rocks and subordinate granodiorites. To the East of Santa Elena the sienogranites are associated with El Hito porphyritic granite that intrudes to Zamora Batholith. Frequently the batholith has propylitic alteration; which produces a primary association of chlorite, epidote, calcite and pyrite. The granitoids have dioritic to granitic compositions (60.09 to 73.6 wt.% SiO2) and are I - type, medium to high-K calc-alkaline. They have affinities slightly peraluminous (ASI = 1,00 to 1,16). CaO is moderate to high (CaO ? 3.58), the alkalis have averaged of Na2O?3,09 and K2O?3,28. The concentrations of Na2O/K2O are moderate ranging between 0.7 and 1.7, with an average value of 1.04. The contents of Ba and Sr are moderate. The content of Zr is low (61 to 161 ppm). The multi-element diagrams normalized to chondritic values and to primitive mantle show Nb and Ta negative anomaly. Considering the multi-element diagrams, the rocks are slightly enriched in LILE (Large Ion-Lithophile-elements) mainly in Rb, Cs and Ba and slight positive anomalies in K and Sr, other incompatible elements have negative anomalies such as HFSE ( High Field Strength Elements) Ti, Nb, Ta. The values of (Eu/Eu*)N are in the range of 0.54 to 1.03. (Eu* = (SmN*GdN)1/2). Correlations between major element and silica, and relationships between trace elements indicate that fractional crystallization is a dominant process in the magma evolution. Most granitoids are also slightly peraluminous; but we believe this characteristic is due to rock alteration. The Zamora Batolith is a plutonic complex generated within a magmatic arc in normal conditions of maturity.

Villares, F. M.

2013-05-01

328

Primitive, high-Mg basaltic andesites: direct melts of the shallow, hot, wet mantle  

NASA Astrophysics Data System (ADS)

Direct mantle melts are rare in subduction zone settings. Such melts are identified by Mg #s (Mg # = Mg / (Mg+Fe)) greater than ~0.73, indicating chemical equilibrium with Fo90 mantle olivine. Most of these primitive arc melts are basaltic, characterized by SiO2 contents of ~48-50 wt % and MgO contents ranging from 8-10 wt %. However, primitive basaltic andesites with mantle-equilibrated Mg #s have also been found at subduction zones worldwide. These basaltic andesites have higher SiO2 contents (53-58 wt %) than typical primitive basalts as well as high MgO (8-10 wt %). Because these rocks have high SiO2 contents and yet retain evidence for chemical equilibrium with the mantle (Mg #s), their petrogenesis has sparked intense debate as researchers have tried to discern how these samples fit into the paradigm of mantle melting at subduction zones. Through an understanding of the conditions and processes that produce the SiO2 enrichment in these rocks, we also aim to understand the role of these melts in producing the observed andesitic compositional characteristics of the continental crust. To understand the petrogenesis of primitive, high-Mg basaltic andesites, this study investigates the experimental melts of undepleted mantle peridotite plus a slab component (Na-2O + K2O) from 1,205-1,470°C at 1.0-2.0 GPa under water-undersaturated conditions (0-5 wt % H2O). At 1.0 and 1.2 GPa, the experimental melts reproduce the compositions of natural primitive, high-Mg basaltic andesites in all major elements (SiO2, TiO2, Al2O3, FeO, MnO, MgO, and Na2O+K2O) except CaO. CaO contents are higher than the range of the natural samples by ~2 wt % at the highest silica contents of the experiments (54-56 wt% SiO2). This suggests that at 1.0-1.2 GPa, a higher percent of melting (30-35 %) with 3-5 wt % H2O is required to drive the chemical compositions of the experiments toward the representative compositions of the natural rocks. The experimental melts also show that mantle-wall rock reaction is a feasible mechanism for producing the SiO2 enrichment of the natural samples. We calculate reaction coefficients to determine the amount of mantle-wall rock reaction necessary to change the experimental compositions into natural primitive, high-Mg basaltic andesites. In the reaction (orthopyroxene ? olivine + liquid), orthopyroxene dissolves to produce liquid and olivine. We use experimentally determined phase boundaries to show that at a given pressure, less hydrous experimental melts require more reaction to reach a representative primitive, high-Mg basaltic andesite than more hydrous melts.

Andrews, A.; Grove, T. L.

2013-12-01

329

Reaction between Metapelite-derived Hydrous Partial Melt and Subsolidus Fertile Peridotite at 2-3 GPa - Generation of High-K Magmas in Subduction Zones  

NASA Astrophysics Data System (ADS)

Trace compositions of arc magmas display signatures of recycled sediments [1] and thermal and geodynamic models of subduction zones suggest that sediment contribution to sub-arc mantle occurs in the form of hydrous melts generated at the slab-mantle interface by fluid-present melting [2, 3] or in the mantle wedge by diapiric rise of downgoing sediments [4]. Partial melts of hydrous pelitic sediments are rhyolitic in P-T conditions of the mantle wedge and are out of equilibrium with the surrounding peridotite, which implies inevitable reaction between such melt and overlying peridotite. However, partial melting in the mantle wedge with slab input has mostly been studied in peridotite+H2O systems [e.g. 5] and experimental constraints on sediment-peridotite hybrid remain limited [6]. In this study, we explore the phase equilibria of a sediment melt-fluxed fertile peridotite with the aim of understanding genesis of high-K arc magmas. Experiments were performed in AuPd capsules using a piston cylinder, on a 1:3 mixture of rhyolitic melt with 7.3 wt.% H2O [3] and fertile peridotite from 1150-1350 °C at 2-3 GPa. Interstitial melt/fluid is present at 1150 °C, 2 GPa and 1150-1200 °C, 3 GPa. While residual opx+cpx+biotite are present at both pressures, olivine is present from 1200-1300 °C, 2 GPa and garnet from 1150-1300 °C, 3 GPa. Cpx and biotite disappear at 1200-1250 °C, 2 GPa and 1350 °C, 3 GPa. At 2 GPa, from 1200-1300 °C, the melt composition (on a volatile-free basis), shows an increase in SiO2 (50-51 wt.%), MgO (10-14 wt.%) and decrease in Al2O3 (16-14 wt.%), CaO (10-7 wt.%), Na2O (3-2 wt.%) and H2O (13-8 wt.%.). K2O increases from 5 to 7 wt.% till 1250 °C followed by a decrease to 5 wt.%, at 1300 °C. FeO* varies between 6 and 5 wt.%. At 3 GPa, from 1225-1350 °C, the reacted melt displays an increase in SiO2 (47-49 wt.%), FeO* (4.2-5.4 wt.%), MgO (11-14 wt.%), and decrease in Al2O3 (15-14 wt.%), CaO (12-7 wt.%), Na2O (4-3 wt.%) and H2O (16-11 wt.%). K2O displays an increase from 7 to 8 wt.%, till 1300 °C, followed by a decrease to 7 wt.%, after the disappearance of biotite. Our study demonstrates that shoshonitic melt can be generated from partial reactive crystallization of sediment-derived hydrous rhyolite in a fertile peridotite matrix at high melt:rock ratio. Thus, we propose that such a melt-rock reaction can produce high-K arc magmas with trace element signatures of recycled sediments. Also, the phlogopite-bearing websterite produced as a residue of reaction in our study, upon survival in the wedge, can produce post-collisional high K-magmas by later tectonic perturbation and rifting-induced decompression. [1] Plank & Langmuir (1993) Nature 362, 739-743. [2] Syracuse & Abers (2010) PEPI 183, 73-90. [3] Hermann & Spandler (2008) JPet 49, 717-740. [4] Behn et al. (2011) NatGeoSci 4, 641-646. [5] Grove et al. (2006) EPSL 249, 74-89. [6] Sekine & Wyllie (1982) CMP 81, 190-202.

Nelson, J. M.; Mallik, A.; Dasgupta, R.

2013-12-01

330

Comparing results from two continental geochemical surveys to world soil composition and deriving Predicted Empirical Global Soil (PEGS2) reference values  

NASA Astrophysics Data System (ADS)

Analytical data for 10 major oxides (Al2O3, CaO, Fe2O3, K2O, MgO, MnO, Na2O, P2O5, SiO2 and TiO2), 16 total trace elements (As, Ba, Ce, Co, Cr, Ga, Nb, Ni, Pb, Rb, Sr, Th, V, Y, Zn and Zr), 14 aqua regia extracted elements (Ag, As, Bi, Cd, Ce, Co, Cs, Cu, Fe, La, Li, Mn, Mo and Pb), Loss On Ignition (LOI) and pH from 3526 soil samples from two continents (Australia and Europe) are presented and compared to (1) the composition of the upper continental crust, (2) published world soil average values, and (3) data from other continental-scale soil surveys. It can be demonstrated that average upper continental crust values do not provide reliable estimates for natural concentrations of elements in soils. For many elements there exist substantial differences between published world soil averages and the median concentrations observed on two continents. Direct comparison with other continental datasets is hampered by the fact that often mean, instead of the statistically more robust median, is reported. Using a database of the worldwide distribution of lithological units, it can be demonstrated that lithology is a poor predictor of soil chemistry. Climate-related processes such as glaciation and weathering are strong modifiers of the geochemical signature inherited from bedrock during pedogenesis. To overcome existing shortcomings of predicted global or world soil geochemical reference values, we propose Preliminary Empirical Global Soil reference values based on analytical results of a representative number of soil samples from two continents (PEGS2).

de Caritat, Patrice; Reimann, Clemens; Bastrakov, E.; Bowbridge, D.; Boyle, P.; Briggs, S.; Brown, D.; Brown, M.; Brownlie, K.; Burrows, P.; Burton, G.; Byass, J.; de Caritat, P.; Chanthapanya, N.; Cooper, M.; Cranfield, L.; Curtis, S.; Denaro, T.; Dhnaram, C.; Dhu, T.; Diprose, G.; Fabris, A.; Fairclough, M.; Fanning, S.; Fidler, R.; Fitzell, M.; Flitcroft, P.; Fricke, C.; Fulton, D.; Furlonger, J.; Gordon, G.; Green, A.; Green, G.; Greenfield, J.; Harley, J.; Heawood, S.; Hegvold, T.; Henderson, K.; House, E.; Husain, Z.; Krsteska, B.; Lam, J.; Langford, R.; Lavigne, T.; Linehan, B.; Livingstone, M.; Lukss, A.; Maier, R.; Makuei, A.; McCabe, L.; McDonald, P.; McIlroy, D.; McIntyre, D.; Morris, P.; O'Connell, G.; Pappas, B.; Parsons, J.; Petrick, C.; Poignand, B.; Roberts, R.; Ryle, J.; Seymon, A.; Sherry, K.; Skinner, J.; Smith, M.; Strickland, C.; Sutton, S.; Swindell, R.; Tait, H.; Tang, J.; Thomson, A.; Thun, C.; Uppill, B.; Wall, K.; Watkins, J.; Watson, T.; Webber, L.; Whiting, A.; Wilford, J.; Wilson, T.; Wygralak, A.; Albanese, S.; Andersson, M.; Arnoldussen, A.; Baritz, R.; Batista, M. J.; Bel-lan, A.; Birke, M.; Cicchella, C.; Demetriades, A.; Dinelli, E.; De Vivo, B.; De Vos, W.; Duris, M.; Dusza-Dobek, A.; Eggen, O. A.; Eklund, M.; Ernstsen, V.; Filzmoser, P.; Finne, T. E.; Flight, D.; Forrester, S.; Fuchs, M.; Fugedi, U.; Gilucis, A.; Gosar, M.; Gregorauskiene, V.; Gulan, A.; Halami?, J.; Haslinger, E.; Hayoz, P.; Hobiger, G.; Hoffmann, R.; Hoogewerff, J.; Hrvatovic, H.; Husnjak, S.; Janik, L.; Johnson, C. C.; Jordan, G.; Kirby, J.; Kivisilla, J.; Klos, V.; Krone, F.; Kwecko, P.; Kuti, L.; Ladenberger, A.; Lima, A.; Locutura, J.; Lucivjansky, P.; Mackovych, D.; Malyuk, B. I.; Maquil, R.; McLaughlin, M.; Meuli, R. G.; Miosic, N.; Mol, G.; Négrel, P.; O'Connor, P.; Oorts, K.; Ottesen, R. T.; Pasieczna, A.; Petersell, V.; Pfleiderer, S.; Po?avi?, M.; Prazeres, C.; Rauch, U.; Reimann, C.; Salpeteur, I.; Schedl, A.; Scheib, A.; Schoeters, I.; Sefcik, P.; Sellersjö, E.; Skopljak, F.; Slaninka, I.; Šorša, A.; Srvkota, R.; Stafilov, T.; Tarvainen, T.; Trendavilov, V.; Valera, P.; Verougstraete, V.; Vidojevi?, D.; Zissimos, A. M.; Zomeni, Z.

2012-02-01

331

Mineralogical, geochemical and radiological characterisation of Selmo Formation in Batman area, Turkey.  

PubMed

This work deals with the mineralogical, geochemical and radiological characterisations of Selmo Formation in Batman neighbourhood. The upper Miocene-Pliocene Selmo Formation is common in the centre of Batman and composed of carbonated sandy claystones and silty-sandy stone lenses. The common whole minerals of the samples are quartz, feldspars, calcite and dolomite. The clay minerals are smectite, illite, chlorite and mixed-layer clay (chlorite-smectite). The geochemical mean values of the samples are 51.7% SiO(2); 12.6% Al(2)O(3); 6.2% Fe(2)O(3); 3.6% MgO; 6.3% CaO; 1.1% Na(2)O; 1.7% K(2)O; 0.8% TiO(2); 0.2% P(2)O(5); 0.1% MnO; and 0.03% Cr(2)O(3). In addition, baseline maps for the concentrations of each radionuclide, the radium equivalent activity and the outdoor gamma dose rate distributions have been plotted for the study area. The mean activity concentrations of (226)Ra, (232)Th, (40)K and (137)Cs were determined to be 32, 24, 210 and 9 Bq kg(-1), respectively. The assessments of the radiological hazard indices, such as radium equivalent activity, absorbed dose rate in air, annual effective dose equivalent, excess lifetime cancer risk, external hazard index and internal hazard index, were calculated and compared with the internationally accepted reference values. This study shows that the concentrations of radioactivities in the measured samples were within the recommended safety limits and did not pose to be any significant source of radiation hazard. PMID:22316137

Isik, Umit; Damla, Nevzat; Akkoca, Dicle Bal; Cevik, U?ur

2012-06-01

332

Application of chemical, physical and chemometric analytical techniques to the study of ancient ceramic oil lamps.  

PubMed

A chemical, mineralogical and morphological characterization of 54 fragments of oil lamps found in two Spanish archaeological sites (Cordoba and Herrera de Pisuerga (Palencia)) has been performed. Flame atomic absorption and emission spectrometry were used for the determination of Al(2)O(3), CaO, Fe(2)O(3), K(2)O, MgO, MnO, Na(2)O and TiO(2) as major constituents and Cu, Cr, Ni, Pb and Zn as minor and trace selected elements. Physical, mineralogical and morphological analyses were made by using dilatometry at constant heating rate for the thermal behaviour, X-ray diffraction spectrometry for the mineralogical composition and, in a group of selected samples, scanning electron microscopy and polarizing petrographic microscopy for the observation of thin layers and mineral identification. Separations of light and heavy minerals were carried out with bromoform and X-ray diffraction analysis was applied to both fractions. Multivariate statistical analysis was used to establish correlations between variables and to deduce factors which allow the gathering of oil lamp samples in groups as a function of their composition. The results of these analyses allow the comparison among pieces and the establishment of conclusions about several aspects of their manufacture, the origin of the raw materials and the provenance of the oil lamps (local or imported). They provide information supporting certain archaeological hypothesis. For example, some oil lamps found in Herrera de Pisuerga showed a clearly different physicochemical composition. They were probably brought from Italy by the Roman Legions together with their initial furniture household. PMID:18970455

García Giménez, R; Vigil de la Villa, R; Petit Domínguez, M D; Rucandio, M I

2006-02-15

333

Chemical modifications accompanying blueschist facies metamorphism of Franciscan conglomerates, Diablo Range, California  

USGS Publications Warehouse

As part of an investigation of blueschist-facies mineral parageneses in pebbles and matrix of some Franciscan metaconglomerates of the Diablo Range, California, textural and major-element chemical analyses were conducted on a number of igneous pebbles that comprise a range of rock types from granite and dacite to gabbro and basalt. Compositions of the igneous pebbles differ significantly from common igneous rocks, particularly with respect to Ca, K, Na, Si and H2O. The SiO2 and H2O contents are characteristically high and the K2O contents low. The CaO and Na2O contents may be relatively enriched or reduced in different pebbles. The igneous pebbles show little evidence of alteration prior to their incorporation into the Franciscan conglomerates, and the chemical modifications are considered to have been produced during metamorphism of the conglomerates to (lawsonite + albite + aragonite ?? jadeite)-bearing assemblages. The observed variations in the pebbles are shown to be functions of: (1) bulk chemistry; (2) the igneous mineral assemblage; (3) the stable metamorphic mineral assemblage; and (4) the composition of pore fluids in the conglomerates. The relative proportions of Mg and Fe in most of the pebbles apparently have been unaffected by the metamorphism, and these parameters, along with other textural and chemical factors, were used to determine the petrogenetic affinities of the igneous pebbles. The plutonic and most of the volcanic pebbles correspond to calc-alkaline rock series, whereas a few volcanic pebbles show apparent Fe-enrichment characteristic of tholeiitic rocks. A continental margin arc-batholith complex would be the best source for these igneous detrital assemblages. Conglomerates in local areas differ in igneous lithologies from conglomerates in other areas and probably differ somewhat in age, perhaps reflecting varying degrees of unroofing of such a complex during deposition of Franciscan sediments. ?? 1981.

Moore, D. E.; Liou, J. G.; King, B. -S.

1981-01-01

334

Inorganic geochemistry data from Lake El'gygytgyn sediments: marine isotope stages 6-11  

NASA Astrophysics Data System (ADS)

Geochemical analyses were performed on sediments recovered by deep drilling at Lake El'gygytgyn in central Chukotka, northeastern Russia (67°30' N; 172°05' E). Major and rare element concentrations were determined using X-ray fluorescence spectroscopy (XRF) on the < 250 ?m fraction from 617 samples dated to ca. 440 and 125 ka, which approximates marine isotope stages (MIS) 11 to 6. The inorganic geochemistry indicates significant variations in elemental composition between glaciations and interglaciations. Interglacial sediments are characterized by high contents of SiO2, Na2O, CaO, K2O, and Sr and are depleted in Al2O3, Fe2O3, TiO2, and MgO. An extreme SiO2 enrichment during MIS 11.3 and 9.3 was caused by an enhanced flux of biogenic silica (BSi). The geochemical structure of MIS 11 shows similar characteristics as seen in MIS 11 records from Lake Baikal (southeastern Siberia) and Antarctic ice cores, thereby arguing for the influence of global forcings on these records. High sediment content of TiO2, Fe2O3, MgO, Al2O3, LOI, Ni, Cr, and Zr typifies glacial stages, with the most marked increases during MIS 7.4 and 6.6. Reducing conditions during glacial times are indicated by peaks in the Fe2O3 content and coinciding low Fe2O3/MnO ratios. This conclusion also is supported by P2O5 and MnO enrichment, indicating an increased abundance of authigenic, fine-grained vivianite. Elemental ratios (CIA, CIW, PIA, and Rb/Sr) indicate that glacial sediments are depleted in mobile elements, like Na, Ca, K and Sr. This depletion was caused by changes in the sedimentation regime and thus reflects environmental changes.

Minyuk, P. S.; Borkhodoev, V. Y.; Wennrich, V.

2014-03-01

335

Inorganic data from El'gygytgyn Lake sediments: stages 6-11  

NASA Astrophysics Data System (ADS)

Geochemical study was performed on sediment of deep drilling core from El'gygytgyn Lake, located in central Chukotka, northeastern Russia (67°30' N; 172°05' E). Major and rare elements were determined by X-ray fluorescence spectroscopy (XRF) on 600 samples covering the timeframe between ca. 450 and 125 ka corresponding to Marine Isotope Stages (MIS) 11 to 6. Inorganic geochemistry data indicates significant variations in the elemental compositions corresponding to the glacials and interglacials periods. Interglacial sediments are characterized by high contents of SiO2, Na2O, CaO, K2O, Sr and are depleted in Al2O3, Fe2O3, TiO2, MgO. Extreme enrichments in SiO2 during MIS 11.3 and 9.3 are caused by an enhanced flux of biogenic silica (BSi). Geochemical structure of stage 11 shows very similar peculiarities to features of stage 11 from records of Lake Baikal/SE Siberia and Antarctic ice cores. High contents of TiO2, Fe2O3, MgO, Al2O3, LOI, Ni, Cr and Zr are typical for sediments of glacial stages, among those MIS 7.4 and 6.6 are the most marked. Peaks in the Fe2O3 content and coinciding low Fe2O3/MnO ratios during glacials indicate reducing condition in the sediments. This is also supported by enrichments in P2O5 and MnO, indicating an increased abundance of authigenic fine grained vivianite. Some elemental ratios indicate an enhanced alteration of glacial sediments accompanied by a loss of mobile elements, like Na, Ca, K and Sr. The higher alteration of sediments can presumably be traced back to changes in the sedimentation regime and diagenetic processes, and thus, reflects environmental changes.

Minyuk, P. S.; Borkhodoev, V. Ya.; Wennrich, V.

2013-01-01

336

Petrography and geochemistry of lower carboniferous greywacke and mudstones in Northeast Junggar, China: Implications for provenance, source weathering, and tectonic setting  

NASA Astrophysics Data System (ADS)

Northeast Junggar occupies an important position that links East Junggar and Chinese Altai. Numerous magmatic and sedimentary rocks of the Paleozoic in this area recorded the final amalgamation processes of East Junggar and Chinese Altai. This study analyzes the petrological and geochemical characteristics of sandstones and mudstones from the Early Carboniferous Nanmingshui formation in Northeast Junggar. The provenance and tectonic setting of these clastic rocks are discussed. Petrography indicates that the composition and texture maturity of the sandstones are low. The components of the sandstones are mainly volcanic fragments (61-87%), feldspars (9-30%), and monocrystalline quartz (2-18%), with a few polycrystalline quartz and other minerals. Slice observation indicates that the majority of the volcanic fragments of sandstones are basic-intermediate volcanic rocks with a few dacite and felsic plutonic fragments. The detrital modes of the sandstones reflect that these sandstones are derived from undissected arcs. A low to moderate chemical index of alteration and the Al2O3-CaO* + Na2O-K2O diagram reflect a low to moderate weathering degree in the source area. Trace and rare earth element (e.g., La, Th, Hf, Sc, Cr, Co, and Eu) contents and their ratios suggest that the source rocks of the clastic rocks are intermediate-basic rocks with some felsic rocks. Compared with sandstones, the source rocks for mudstones are more felsic. The petrography and geochemistry characteristics of the clastic rocks suggest that the proximal Dulate arc should be the primary source area. Mixing calculations based on REE data suggest that approximately two-thirds of the sandstone fragments are intermediate-basic volcanic rocks. The contents of the major and trace elements, as well as the stratum features, of the clastic rocks manifest that these clastic rocks resemble sedimentary rocks in a back-arc basin. The formation of this back-arc basin is caused by the southward subduction of the Zaysan-Erqis Ocean.

Tao, Huifei; Sun, Shu; Wang, Qingchen; Yang, Xiaofa; Jiang, Lin

2014-06-01

337

[Study on the determination of trace composition and impurity elements in kaolin with ICP-MS].  

PubMed

The direct determination method of trace composition, Fe2O3, TiO2, MnO, K2O, Na2O, CaO and MgO, and impurity elements, Pb, Cr, Cd, Cu and As, in kaolin was studied by using inductive coupled plasma mass spectrometry (ICP-MS). After the samples were dissolved completely in HF-HNO3 at low temperature, silicon was volatilized in the form of SiF4 and separated from the solution. Then the solution was continually evaporated to dry to get the solid substance which was dissolved by the nitric acid (1+3). The internal elements 45Sc, 115In and 205Tl were added on line and the effect of matrix, interface and fluctuation of instrument was overcome effectively by using internal standard calibration method. By choosing the optional operating parameters and appropriate isotopes of element to be detected, the influence of mass spectrometry interference was conquered effectively. The effect of temperature in samples preparation on the determination of arsenic was tested. The recovery for spiking sample is in the range from 95.0% to 101.0% and the relative standard deviation is in the range from 1.1% to 2.01%. In order to check the accuracy of the method, the kaolin standard reference material GBW03122 was also analyzed, and the analytical values conformed to standard values. This method has the characteristics of being simple, rapid and accurate, and can be used in the testing of trace composition and impurity elements in kaolin and ceramic product. PMID:19445238

Huang, Dong-Gen; Zhou, Wen-Bin; Liu, Lei; Quan, Shui-Qing; He, Zong-Jian; Wan, Jin-Bao

2009-02-01

338

Oriented bioactive glass (13-93) scaffolds with controllable pore size by unidirectional freezing of camphene-based suspensions: microstructure and mechanical response  

PubMed Central

Scaffolds of 13-93 bioactive glass (composition 6Na2O, 8K2O, 8MgO, 22CaO, 2P2O5, 54SiO2; mol %), containing oriented pores with controllable diameter, were prepared by unidirectional freezing of camphene-based suspensions (10 vol% particles) on a cold substrate (?196°C or 3°C). By varying the annealing time (0–72 h) to coarsen the camphene phase, constructs with the same porosity (86 ± 1%) but with controllable pore diameters (15–160 ?m) were obtained after sublimation of the camphene. The pore diameters had a self-similar distribution that could be fitted by a diffusion-controlled coalescence model. Sintering (1 h at 690°C) was accompanied by a decrease in the porosity and pore diameter, the magnitude of which depended on the pore size of the green constructs, giving scaffolds with a porosity of 20–60% and average pore diameter of 6–120 ?m. The compressive stress vs. deformation response of the sintered scaffolds in the orientation direction was linear, followed by failure. The compressive strength and elastic modulus in the orientation direction varied from 180 MPa and 25 GPa, respectively, (porosity = 20%) to 16 MPa and 4 GPa, respectively, (porosity = 60%), which were 2–3 times larger than the values in the direction perpendicular to the orientation. The potential use of these 13-93 bioactive glass scaffolds for the repair of large defects in load-bearing bones, such as segmental defects in long bones, is discussed.

Liu, Xin; Rahaman, Mohamed N.; Fu, Qiang

2010-01-01

339

Geochemistry of rock units at the potential repository level, Yucca Mountain, Nevada  

USGS Publications Warehouse

The compositional variability of the phenocryst-poor member of the 12.8 Ma Topopah Spring Tuff at the potential repository level was assessed by duplicate analysis of 20 core samples from the cross drift at Yucca Mountain, Nevada. Previous analyses of outcrop and core samples of the Topopah Spring Tuff showed that the phenocryst-poor rhyolite, which includes both lithophysal and nonlithophysal zones, is relatively uniform in composition. Analyses of rock samples from the cross drift, the first from the actual potential repository block, also indicate the chemical homogeneity of this unit excluding localized deposits of vapor-phase minerals and low-temperature calcite and opal in fractures, cavities, and faults. The possible influence of vapor-phase minerals and calcite and opal coatings on rock composition at a scale sufficiently large to incorporate these heterogeneously distributed deposits was evaluated and is considered to be relatively minor. Therefore, the composition of the phenocryst-poor member of the Topopah Spring Tuff is considered to be adequately represented by the analyses of samples from the cross drift. The mean composition as represented by the 10 most abundant oxides in wt. % or g/100 g is: SiO2, 76.29; Al2O3, 12.55; FeO, 0.14; Fe2O3, 0.97; MgO, 0.13; CaO, 0.50; Na2O, 3.52; K2O, 4.83; TiO2, 0.11; and MnO, 0.07. ?? 2002 Published by Elsevier Science Ltd.

Peterman, Z. E.; Cloke, P. L.

2002-01-01

340

Tertiary epizonal plutonic rocks of the Selway-Bitterroot Wilderness, Idaho County, Idaho  

SciTech Connect

Geologic mapping in the Selway-Bitterroot Wilderness identified approximately 731 kmS of epizonal plutonic granitic rocks within the Bitterroot lobe of the Idaho batholith. From north to south, the intrusions are the Rock Lake Creek stock and the Whistling Pig, Running Creek, Bad Luck and Painted Rocks plutons. The stock and plutons consist of medium- to coarse-grained biotite and hornblende-biotite syenorgranite to monzogranite and quartz syenite capped by fine-grained biotite leucogranite. These rocks are intruded by late-synplutonic leucogranite dikes and post plutonic porphyritic rhyolite to rhyodacite and basalt dikes. The medium-grained granitic rocks are high in SiO2, K2O, Na2O, Ga, Th, U, W and Zr, but low in Al7O3, CaO, MgO, Cr, Ni, Co and V. Most of the granites are peraluminous. Rare-earth element (REE) plots (rock sample/chondrite) show enrichment in light REE over heavy REE with strong EU depletions. K-Ar biotite radiometric age determinations for medium-grained granites in all of the plutons range from approximately 51 Ma (Whistling Pig pluton) to 43.7 Ma (Painted Rocks pluton). Petrogenetic studies suggest that the plutons were rapidly emplaced to within 3.0 km of the paleosurface. The types, textures and color of the rocks result from devolatilization of the crystallizing melt and very low-grade hydrothermal alteration. The fluorine-rich melts are the fractionated with accumulate residue; they are considered to be anorogenic (A-type) granites intruded into the center of a metamorphic core complex.

Motzer, W.E.

1996-01-01

341

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

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

342

The role of magma mixing in the petrogenesis of mafic alkaline lavas, Rockeskyllerkopf Volcanic Complex, West Eifel, Germany  

NASA Astrophysics Data System (ADS)

The quaternary Rockeskyllerkopf Volcanic Complex (RVC) comprises three spatially and temporally distinct volcanic centers that can also be distinguished on the basis of their geochemical signatures. All the volcanic products in the complex are olivine basanites whose major and trace element compositions span almost the entire range defined for the West Eifel field as a whole. The RVC lavas have lower Al2O3, Na2O and Y contents and higher TiO2, CaO, K2O, Sc, V, Co, Rb, and Ba than the Tertiary lavas in nearby Hocheifel volcanic field. Within the complex, the oldest South East Lammersdorf Center (SEL) comprises primitive lavas with an average MgO content of ˜11 wt.% and LaN/YbN of 29 ± 2. The second center, Mäuseberg, has similar MgO to SEL but is distinct in its much higher LaN/YbN of 42 ± 2. The Rockeskyllerkopf Center, which was erupted after a break in activity, comprises lavas similar in composition to the SEL Center but with distinctly higher Al2O3 and lower MgO contents. Given the lack of evidence for significant fractionation or assimilation in the RVC lavas, we attribute the compositional variations within and between the centers of the RVC to be due to variations in the composition of the source region in combination with magma mixing. Our preferred model involves 1-5% partial melting of LREE-enriched mantle in the garnet stability field, likely within the thermal boundary layer at the base of the lithospheric mantle. These melts mixed to variable degrees with 2-4% partial melts of phlogopite-spinel peridotite formed at higher levels in the modally metasomatised lithospheric mantle.

Shaw, Cliff S. J.; Woodland, Alan B.

2012-03-01

343

Petrography and geochemistry of intraclastic manganese carbonates from the ˜2.2 Ga Nsuta deposit of Ghana: Significance for manganese sedimentation in the Palaeoproterozoic of West Africa  

NASA Astrophysics Data System (ADS)

Intraclastic Mn carbonate rocks occur in the marginal areas of the manganese-carbonate orebody (manganesestone) of the Palaeoproterozoic Nsuta deposit in the Birimian of Ghana. Macroscopically the intraclastic rocks display graded bedding and are typified by a matrix-supported fabric with subangular to subrounded particles less than a millimetre to ˜1.5 × 0.5 cm. Both clasts and matrix consist mainly of varying proportions of microcrystalline and microconcretionary carbonates, quartz, muscovite and subordinate pyrite. Within individual intraclasts, carbonate minerals (including distinctly zoned microconcretions) are essentially Mg kutnahorite and Mg-Ca rhodochrosite, similar to the carbonate minerals in the manganesestone. Whole rock chemistry of the intraclastic carbonates shows significant variability in the amounts of SiO 2, Al 2O 3, MnO, MgO, CaO, Na 2O and, to a lesser extent, K 2O. Major element contents of the manganesestone similarly vary widely, except that these have, in particular, comparably higher MnO but less SiO 2 and Al 2O 3 than the intraclastic carbonates and host rock Mn phyllite. Rare earth element (REE) concentrations in the intraclastic carbonates are approximately an order of magnitude higher than in the manganesestone. Whereas both rocks exhibit positive Eu anomalies, only the manganesestone shows a discernibly negative Ce anomaly. Petrographic and geochemical features suggest that the intraclasts are fragments of reworked Mn carbonate sediments derived from intraformational erosion and subsequent (mass flow) deposition as carbonate "turbidite" mud. Processes such as submarine slumping, sliding and other sediment gravity flows may have likely interrupted Mn sedimentation and transported partially consolidated manganiferous sediments down slopes into the early Birimian ocean.

Nyame, F. K.

2008-02-01

344

Genesis of the Yuanlingzhai porphyry molybdenum deposit, Jiangxi province, South China: Constraints from petrochemistry and geochronology  

NASA Astrophysics Data System (ADS)

The newly discovered Yuanlingzhai porphyry molybdenum (Mo) deposit in southern Jiangxi province belongs to the group of Mo-only deposits in the Nanling region. The mineralization developed at contact zones between the Yuanlingzhai granite porphyry and Neoproterozoic metamorphic rocks of the Xunwu Formation. Precise LA-MC-ICPMS zircon U-Pb dating of the Yuanlingzhai porphyry, as well as the adjacent western Keshubei and eastern Keshubei granites, yielded ages of 165.49 ± 0.59 Ma, 159.68 ± 0.43 Ma, and 185.13 ± 0.52-195.14 ± 0.63 Ma, respectively. Molybdenite Re-Os isochron ages of the ores are 160 ± 1-162.7 ± 1.1 Ma, which is consistent with the age of large-scale W-Sn deposits in South China. The Yuanlingzhai porphyry is characterized by high K2O, P2O5, and A/CNK (1.33-1.59), and low CaO and Na2O. The rock shows relatively enriched LREE without significant Eu anomalies (Eu/Eu* = 0.80-0.90). Geochemical and mineralogical characteristics indicate that the ore-hosting porphyry is a typical S-type granite generated from the partial melting of crustal material with only minor mantle contribution. Both Harker and evolutionary discrimination diagrams indicate that the Yuanlangzhai and western Keshubei granites are not products of co-magmatic evolution. The Keshubei granites and Xunwu Formation were not significant sources for the components in the porphyry mineralization, but the Yuanlangzhai granite may have supplied some ore-forming material. However, the main ore-forming material was carried by fluids from deep sources, as demonstrated by fluid inclusion and stable isotope data from the molybdenum deposit. The Mo porphyry deposit formed in an extensional setting, and was possibly associated with Jurassic subduction of the Izanagi Plate.

Huang, Fan; Wang, Denghong; Santosh, M.; Wang, Chenghui; Zeng, Zailin; Liu, Shanbao; Wang, Liqiang; Zhang, Yongzhong

2014-01-01

345

(210)Pb and composition data of near-surface sediments and interstitial waters evidencing anthropogenic inputs in Amazon River mouth, Macapá, Brazil.  

PubMed

Activity profiles of excess (210)Pb determined in three sediment cores from Amazon River mouth, Macapá city, Brazil, provided the evaluation of sedimentation rates, contributing to a better knowledge of the hydrological conditions in the site that is the capital of Amapá State and is drained by the waters of the huge Amazon River. Chemical data were also determined in the sediments, allowing identify signatures coupled to anthropogenic inputs held in the past in Amapá State. Significant direct relationships between LOI (loss on ignition) and organic matter were found for all sediments profiles. Silica was found to be inversely related to organic matter in the three profiles; its decrease accompanied an increase on the specific surface of the sediments. This relationship was confirmed by a great number of inverse significant correlations among silica and oxides Na(2)O, K(2)O, CaO, MgO, Al(2)O(3), P(2)O(5), Fe(2)O(3) and MnO. It was possible to identify the role of organic matter on adsorption of several oxides in the core sediments profiles. Apparent sediment mass accumulation rates corresponding to values between 450 and 2510 mg cm(-2)yr(-1) were obtained, and are compatible with the results of others studies. The (210)Pb activities in one sampling point suggested the occurrence of anthropogenic inputs related to the initial period of the mining activities conducted in Serra do Navio, Amapá State, for the commercialization of Mn ores. This was reinforced by the abrupt fluctuations in chemical data obtained for the sediments and composition of the interstitial waters occurring there. The Atlantic hurricane activity also appeared to affect the sedimentation rates in the area, as two different values were recorded in each profile. PMID:21353731

Nery, José Reinaldo Cardoso; Bonotto, Daniel Marcos

2011-04-01

346

Silicate globules in kyanite from grospydites of the Zagadochnaya kimberlite pipe, Yakutia: The problem of the origin  

NASA Astrophysics Data System (ADS)

The results of complex study of silicate globules and ?-quartz paramorphs after coesite in kyanite from grospydites from the Zagadochnaya kimberlite pipe, Yakutia, using optical and scanning electron spectroscopy, electron and ion microprobes, LA ICP MS and Raman spectroscopy, are presented. The existence of radial fractures diverging from silicate globules into the matrix (kyanite) attests to the fact that the content of the globules is extremely condensed. A zonal structure is usually typical for globules: a coat and a core, which can be explicitly distinguished under the electron microscope, can be differentiated in them. Compositionally, the coat of the globule corresponds to potassium feldspar (wt %: 66.4 SiO2; 16.9 Al2O3; 0.4 FeO; 0.1 CaO; 0.2 Na2O; 14.7 K2O). The globules were also detected in which along with K, a high content of Na and Ca was also ascertained in the silicate coat. The globule coat is considerably enriched with Ba, La, Ce, Nb, and a number of other noncompatible elements as compared with xenolith minerals. The water content in globules is ˜0.6 wt %. As compared with the host mineral (kyanite), the core part of the globules is also enriched with Co, Ni, Zn, and Cu; their content in kyanite is negligibly low. The entire data collection attests to the fact that the formation of silicate globules could have been caused by interaction of the conservated fluid and/or water-silicate melt with the host mineral and crystalline inclusions of clinopyroxene and garnet with decreasing pressure during the transportation of grospydite xenoliths by the kimberlite melt to the Earth's surface.

Tomilenko, A. A.; Kovyazin, S. V.; Pokhilenko, L. N.; Sobolev, N. V.

2011-01-01

347

Experiments on liquid immiscibility along tholeiitic liquid lines of descent  

NASA Astrophysics Data System (ADS)

Crystallization experiments have been conducted on compositions along tholeiitic liquid lines of descent to define the compositional space for the development of silicate liquid immiscibility. Starting materials have 46-56 wt% SiO2, 11.7-17.7 wt% FeOtot, and Mg-number between 0.29 and 0.36. These melts fall on the basaltic trends relevant for Mull, Iceland, Snake River Plain lavas and for the Sept Iles layered intrusion, where large-scale liquid immiscibility has been recognized. At one atmosphere under anhydrous conditions, immiscibility develops below 1,000-1,020°C in all of these compositionally diverse lavas. Extreme iron enrichment is not necessary; immiscibility also develops during iron depletion and silica enrichment. Variations in melt composition control the development of silicate liquid immiscibility along the tholeiitic trend. Elevation of Na2O + K2O + P2O5 + TiO2 promotes the development of two immiscible liquids. Increasing melt CaO and Al2O3 stabilizes a single-liquid field. New data and published phase equilibria show that anhydrous, low-pressure fractional crystallization is the most favorable condition for unmixing during differentiation. Pressure inhibits immiscibility because it expands the stability field of high-Ca clinopyroxene, which reduces the proportion of plagioclase in the crystallizing assemblage, thus enhancing early iron depletion. Magma mixing between primitive basalt and Fe-Ti-P-rich ferrobasalts can serve to elevate phosphorous and alkali contents and thereby promote unmixing. Water might decrease the temperature and size of the two-liquid field, potentially shifting the binodal (solvus) below the liquidus, leading the system to evolve as a single-melt phase.

Charlier, Bernard; Grove, Timothy L.

2012-07-01

348

X-ray fluorescence analysis of rare earth elements in rocks using low dilution glass beads.  

PubMed

Major and trace elements (Na, Mg, Al, Si, P, K, Ca, Ti, Mn, Fe, Rb, Sr, Y, Zr, La, Ce, Pr, Nd, Sm, Gd, Dy, Th and U) in igneous rocks were assayed with fused lithium borate glass beads using X-ray fluorescence spectrometry. Low dilution glass beads, which had a 1:1 sample-to-flux ratio, were prepared for determination of rare earth elements. Complete vitrification of 1:1 mixture required heating twice at 1200 degrees C with agitation. Extra pure reagents containing determinants were used for calibrating standards instead of the rock standard. The calibration curves of the 23 elements showed good linearity. Furthermore, the lower limits of detection corresponding to three times the standard deviation for blank measurements were 26 mass ppm for Na2O, 6.7 for MgO, 4.5 for Al2O3, 4.5 for SiO2, 18 for P2O5, 1.1 for K2O, 4.0 for CaO, 3.9 for TiO2, 1.6 for MnO, 0.8 for Fe2O3, 0.5 for Rb, 0.2 for Sr, 0.4 for Y, 0.5 for Zr, 3.3 for La, 6.5 for Ce, 2.7 for Pr, 2.1 for Nd, 1.7 for Sm, 0.7 for Gd, 2.7 for Dy, 0.5 for Th, and 0.6 for U. Using the present method, we determined the contents of these 23 elements in four rhyolitic and granitic rocks from Japan. PMID:16038502

Nakayama, Kenichi; Nakamura, Toshihiro

2005-07-01

349

Petrological and geochemical comparition between the upper and lower rhyolite of the Binchuan basaltic profile,Emeishan LIP succession  

NASA Astrophysics Data System (ADS)

Emeishan basalt is well known worldwide,and it has been well tested from the geochemistry and petrology.However,the eruptional rock sequences is rare reported. Some former work reported that on the top of Emeishan basalt,there is always sit with rhyolite(or felsic-composition,mainly are rhyolite and trachyte ).This work is focusing on newly found rhyolite and trachyte succession at the bottom of Binchuan basalt pofile,and the comparition between the bottom and top felsic-composition of the Binchuan pofile basaltic related succession from petrological and geochemistry points. The bottom rhyolite is lack of phenocryst,and the filling of blowhole is observed quartz only. Otherwise,the phenocryst of the top rhyolite is mainly alkaline-feldspar. The upper layered rhyolite is less sillical rich than the lower part with the content of SiO2 65-70,68-74 respectively. Additionally,the content of TiO2 (0.82-0.87,0.57-0.70),Total Fe2O3(5.15-5.87,2.89-4.88),MgO(2.13-2.64,0.19-0.48),CaO(1.18-1.49,0.13-0.42), P2O5(0.18-0.25,0.02-0.25) of the upper layered rhyolite is more abundant than the lower layer. However,the amount of the Na2O,K2O of both upper and lower rhyolite can not be distinguished clearly as weathering effect suspectively. This may note that the two kinds of rhyolite are formed from different geological process. The upper may due to the crystallization differentiation of the mafic magmas ,while the lower is formed in the result of crust remelting.

Huixin, H.; Yu, W.

2013-12-01

350

Composite films of gelatin and hydroxyapatite/bioactive glass for tissue-engineering applications.  

PubMed

Cross-linked gelatin/hydroxyapatite/bioactive glass (G/HA/CEL2) films with different compositions (100:0:0 (G1); 30:70:0 (G2); 30:0:70 (G3); 30:35:35 (G4) (%, w/w/w)) were prepared as scaffold materials for tissue-engineering applications, particularly in the field of bone repair. A bioactive glass with 45% SiO2, 3% P2O5, 26% CaO, 7% MgO, 15% Na2O and 4% K2O molar composition was selected (CEL2). Genipin was used as a cross-linker for the gelatin component. Samples were characterized in terms of their bioactivity, thermal properties, mechanical behaviour and cell compatibility. After only 3 days of incubation in simulated body fluid (SBF) at 37 degrees C, calcium phosphate crystals precipitated on G3 and G4 surfaces, due to the high CEL2 bioactivity. Cross-linking increased the thermal stability of the gelatine component as indicated by thermal analysis (denaturation temperature was 92.3 degrees C and 97.6 degrees C for not cross-linked and cross-linked gelatin, respectively). Furthermore, tensile modulus of samples increased with increasing the inorganic phase amount (from 4.72 +/- 0.23 MPa for G1 to 6.46 +/- 0.05 MPa for G4). The adhesion and proliferation of human primary osteoblasts on composite films was evaluated. Cell viability was high with respect to the control for all samples and the presence of hydroxyapatite exerted an important role in the ability of mineralization. PMID:20507716

Gentile, Piergiorgio; Chiono, Valeria; Boccafoschi, Francesca; Baino, Francesco; Vitale-Brovarone, Chiara; Vernè, Enrica; Barbani, Niccoletta; Ciardelli, Gianluca

2010-01-01

351

Differentiation in the cumulates from a Mauna Loa, Hawaii magma chamber  

SciTech Connect

The interstitial glass in cognate nodules from Mauna Loa, has by chemical diffusion or convective fluid transport, remained in equilibrium with the overlying magma. The glass bearing nodules were collected from Damona Cone on the southwest rift zone of Mauna Loas. The nodules have approximately 15% olivine, 40% orthopyroxene plus clinopyroxene (3-20%), and 85% plagioclase plus vescicular glass (2-25%). Olivine norites have anhedral olivine mantled with anhedral orthopyroxene, subhedral to euhedral pyroxene, anhedral plagioclase, and 20 to 25% glass. Olivine gabbros have anhedral olivine, subequant, anhedral to subhedral pyroxene and plagioclase and less than 10% glass. The bulk composition of greater than 15%, MgO, with the textures, indicate the nodules are an accumulative origin. Thus these nodules are partially solidified pieces of crystal/liquid accumulative mush. The compositions of the olivines are Fa 18 to 25 mole percent, of the plagioclases are An 70 to 80 mole percent. The composition of the orthopyroxene is En76 Fs19 Wo5, and of the clinopyroxene is En50 Fall Wo30. The composition of the interstitial glasses is: SiO2 52.54, TiO2 2.04, Al2O3 14.39, FeO 11.47, MgO 7.15, CaO 10.28, Na20 1.42, K2O 0.39, P2O5 0.21. The low Na2O is from two nodules that may have experienced high temperature alteration. The uniformity of the glass composition, in contrast to its large variation in the mode, suggests the interstitial liquid in the mush has remained in equilibrium with some large reservoir of MgO rich liquid, such as the magma above the mush. Two possible mechanisms of cation exchange between the magma and the interstitial liquid of the mush are chemical diffusion and convective fluid transport.

Schwindinger, K.R.; Anderson, A.F.

1985-01-01

352

A lower crustal mafic source for the ca. 2550 Ma Qôrqut Granite Complex in southern West Greenland  

NASA Astrophysics Data System (ADS)

The late Neoarchaean Qôrqut Granite Complex is the youngest large igneous intrusion in the Nuuk region in southern West Greenland, where basement is primarily of Eoarchaean and Mesoarchaean age with a tonalite–trondhjemite–granodiorite (TTG) composition. The Qôrqut granite is generally undeformed and it intruded during a prolonged period, starting at ca. 2730 Ma, characterised by crustal reworking, possibly related to syn- or post accretion tectonics or continental collision. We present major and trace element whole rock chemistry and combined U/Pb, Hf and O isotope data from zircon. We obtained a mean zircon U/Pb age of 2547 ± 4 Ma (MSWD = 0.63). Initial ?Hf values range from ? 12 to ? 18 requiring a long residence time and a rather homogeneous source. Sample averaged zircon ?18O values range from 6.1 ± 0.2‰ to 6.5 ± 0.3/0.7‰ best interpreted with a source region of mainly unweathered mantle derived igneous rocks. Compared to the regional TTG basement, the QGC is characterised by low CaO and Na2O and high K2O, LREE and Rb contents, and a stronger fractionated REE pattern with a negative Eu anomaly. We show that the homogeneous Hf isotope signature of the granite together with its low epsilon value and its pristine oxygen isotope composition are best explained with an Eoarchaean mafic source with a 176Lu/176Hf around 0.015–0.019. Trace element modelling confirms that a mafic source in REE and with an eclogitic residue and with plagioclase as a fractionating phase would generate appropriate melt compositions. Modelling requires residual rutile in the source which constrain the pressures to > ca. 13–18 kbar. Zirconium saturation temperatures suggest magma temperatures in the range 750–850 °C. The obtained P–T conditions suggest a lower crustal source region in a thickened crustal unit consistent with a post or late continental collisional setting.

Næraa, T.; Kemp, A. I. S.; Scherstén, A.; Rehnström, E. F.; Rosing, M. T.; Whitehouse, M. J.

2014-04-01

353

Reactivity of clay minerals with acids and alkalies  

USGS Publications Warehouse

One-g samples of a montmorillonite, a metabentonite, an illite, two kaolinites, and three halloysites were treated with 50 ml of hydrochloric acid (6??45 N, 1:1), acetic acid (4??5 N, 1:3), sodium hydroxide (2??8 N), sodium chloride solution (pH 6??10; Na = 35???; Cl = 21??5???), and natural sea water (pH 7??85; Na = 35??5???; Cl = 21??5???) for a 10-day period in stoppered plastic vials. The supernatant solutions were removed from the clay minerals and analyzed for SiO2, Al2O3, CaO, MgO, Na2O, and K2O. All the solutions removed some SiO2, Al2O3, and Fe2O3 from the samples, but the quantities were small. Sodium hydroxide attacked the kaolin group minerals more strongly than it did montmorillonite, metabentonite, or illite. Halloysite was more strongly attacked by hydrochloric acid than was any of the other experimental minerals. Hydrochloric acid removed iron oxide coatings from soil clay minerals, but acetic acid did not remove them completely. The samples most strongly attacked by HCl and NaOH were examined by X-ray diffraction. Acid treatment did not destroy the structure of the clays, but the halloysite structure was partially destroyed. Sodium hydroxide attacked the halloysite structure, as shown by chemical analysis and X-ray diffraction. These experiments show that treatment in dilute acids has no harmful effect in the preparation of clays for X-ray diffraction. Acetic acid is preferred to hydrochloric acid for this purpose. Hydrochloric acid cleans clay minerals by removing free iron oxide from the surface; acetic acid is less effective. ?? 1971.

Carroll, D.; Starkey, H. C.

1971-01-01

354

Paleoenvironmental History of the Retezat Mountains (Southern Carpathians) Inferred from Geochemical Data  

NASA Astrophysics Data System (ADS)

This study applied lake sediment geochemistry to reconstruct climate changes in the Southern Carpathians within the frame of PROLONG (Providing long environmental records of Late Quaternary climatic oscillations in the Retezat Mountains) project. The main aim of this project is to reconstruct the changes during the Lateglacial and the Early Holocene period in the Retezat Mountains, Southern Carpathians. After retreat of the last major glaciers numerous glacial lakes leaving behind with sediments dating back to ca. 16,000 cal. yr BP. In 2007 and 2008 continuous undisturbed sediment cores were obtained from four glacial lakes (Brazi, Gales, Lia, Bukura) in the Retezat Mts. (Southern Carpathians, Romania) with Livingstone and modified Kullenberg corers. Two of the studied lakes are located on the southern slope (Bukura, Lia) of the mountain, while the Brazi and Gales are situated on the northern slope. After the drillings, the sediment cores were sliced into 1 cm wide subsamples. High-resolution geochemical analysis was done to study soil development an in-lake processes in response to high-frequency and high-amplitude climatic changes within the Lateglacial and Early Holocene. Loss-on-ignition was used to determining the sediment organic matter content. Total element concentrations were measured using an Inductive Coupled Plasma Optical Emission Spectrometer (ICP-OES) and Microwave Plasma Atomic Emission Spectrometer (MP-AES). Concentration of major elements by means of bulk analysis were determined and calculated in oxide forms (Al2O3, SiO2, TiO2, CaO, MgO, K2O, Na2O, Fe2O3, MnO, SO3). Multivariate statistical analyses (PCA, LDA) and cluster analysis were performed on geochemical records. The sediments deposited during the cold and warm period of Lateglacial and Early Holocene showed significantly different chemical compositions. The results indicate that the detailed geochemical analysis on the sediment has the potential to reflect past climatic conditions.

Hubay, Katalin; Braun, Mihály; Harangi, Sándor; Magyari, Enik?

2014-05-01

355

Authenticity and provenance studies of copper-bearing andesines using Cu isotope ratios and element analysis by fs-LA-MC-ICPMS and ns-LA-ICPMS.  

PubMed

Whereas colored andesine/labradorite had been thought unique to the North American continent, red andesine supposedly coming from the Democratic Republic of the Congo (DR Congo), Mongolia, and Tibet has been on the market for the last 10 years. After red Mongolian andesine was proven to be Cu-diffused by heat treatment from colorless andesine starting material, efforts were taken to distinguish minerals sold as Tibetan and Mongolian andesine. Using nanosecond laser ablation-inductively coupled plasma mass spectrometry (ICPMS), the main and trace element composition of andesines from different origins was determined. Mexican, Oregon, and Asian samples were clearly distinguishable by their main element content (CaO, SiO(2) Na(2)O, and K(2)O), whereas the composition of Mongolian, Tibetan, and DR Congo material was within the same range. Since the Li concentration was shown to be correlated with the Cu concentration, the formerly proposed differentiation by the Ba/Sr vs. Ba/Li ratio does not distinguish between samples from Tibet and Mongolia, but only between red and colorless material. Using femtosecond laser ablation multi-collector ICPMS in high-resolution mode, laboratory diffused samples showed variations up to 3‰ for (65)Cu/(63)Cu within one mineral due to the diffusion process. Ar isotope ratio measurements proved that heat treatment will reduce the amount of radiogenic (40)Ar in the samples significantly. Only low levels of radiogenic Ar were found in samples collected on-site in both mine locations in Tibet. Together with a high intra-sample variability of the Cu isotope ratio, andesine samples labeled as coming from Tibet are most probably Cu-diffused, using initially colorless Mongolian andesines as starting material. Therefore, at the moment, the only reliable source of colored andesine/labradorite remains the state of Oregon. PMID:20967428

Fontaine, Gisela H; Hametner, Kathrin; Peretti, Adolf; Günther, Detlef

2010-12-01

356

Geochemical trends in the Jos-Bukuru granites of central Nigeria: magmatic and metallogenic implications  

NASA Astrophysics Data System (ADS)

The Jos-Bukuru Complex is the largest individual ring complex in the Nigerian province occupying an area of approximately 430 km 2. The Complex is composed of fayalite granite and porphyrites, hastingsite granites and biotite granites. The biotite granites play host to both disseminated and vein controlled mineralization. Columbite - Cassiterite deposits occur in the Rayfield (Centre and Southern eastern parts of the Complex) and Cassiterite-wolframite bearing quartz-topaz-greisens are found as veins in the Southwestern and Northwestern (Sabon Gida and Ngell phases) parts of the Complex. Geochemical evidence suggest that the fayalite granites and hastingsite biotite granites are metaluminous, while the biotite granites are generally peraluminous. Their sum characteristics point to an A-type classification with high SiO 2, K 2O and Na 2O, low CaO and MgO. Although the major element characteristics are comparatively similar, the trace elements show strong variations. Generally the high concentrations of Rb, Li, F, Nb, Sn, Th, Y and low contents of Ba and Sr compared with low-Ca granites indicate a high degree of fractionation of magma prior to emplacement. However the element enrichment and depletion trends in the biotite granites supports a model of liquid - state diffusion and or convective fractionation analogous to those observed for chemically zoned high silica magma chamber. It is suggested that such processes have been instrumental to the formationof tin and associated mineral deposits in the complex. Thus extreme enrichment of the large ion lithophile elements and depletion of Ba and Sr are useful indicators of mineralizing processes and ore bearing plutons.

Imeokparia, E. G.

357

Chemical composition of phosphorites of the Phosphoria Formation  

USGS Publications Warehouse

The chemical composition, both major and minor constituents, of 60 samples of phosphorite from the Phosphoria Formation was determined. Major constituents of the average phosphorite are, by weight per cent: SiO2, 11??9; Al2O3, 1??7; Fe2O3,1??1; MgO, 0??3; CaO, 44??0; Na2O, 0??6; K2O, 0??5; total H2O, 2??2; H2O-, 0??6; TiO2, 0??1; P2O5, 30??5; CO2, 2??2; SO3, 1??8; F, 3??1; organic matter, 2??1; and oil, 0??2. Uranium averages 0??009 per cent. The phosphate mineral is basically apatite, Ca5(PO4)3F, with small but significant and variable substitutions-Na, Sr, U and Th for Ca, and CO3 and SO4 for PO4. Rare metals not associated with apatite are associated principally with the organic-matter component of the rocks. This group includes As, Ag, Cd, Cr, Cu, Mo, Ni, Sb, Se, V and Zn. Chromium is the most abundant, having a modal abundance of 0??1 per cent and a maximum concentration of 0??3 per cent. The average phosphorite is composed of approximately 80 per cent apatite, 10 per cent quartz, 5 per cent muscovite-illite, 2 per cent organic matter, 1 per cent dolomite-calcite, 1 per cent iron oxide, and 1 per cent other components. It is texturally a medium-grained pellet phosphorite. ?? 1966.

Gulbrandsen, R. A.

1966-01-01

358

Experimental constraints on the destabilization of basalt + calcite + anhydrite at high pressure-high temperature and implications for meteoroid impact modeling  

NASA Astrophysics Data System (ADS)

Calcite CaCO3 and anhydrite CaSO4 are two sedimentary components or alteration products of basalts on the Earth, Venus, and Mars. The fate of anhydrite-, calcite-bearing crust during a meteoroid impact must be addressed in order to evaluate: (1) the potential S- and C-gas release to the atmosphere, (2) the formation of S- and C-rich melts, and (3) the crystallization of S- and C-rich minerals which may be recognized by spectral analyses of planetary surfaces. We performed piston-cylinder experiments at 1 GPa, between 1200 and 1750 °C, on a mixture of 70 wt.% tholeiitic basalt + 15 wt.% anhydrite + 15 wt.% calcite. Up to ~ 1440 °C, an ultracalcic (CaO > 19.8 wt.%; CaO/Al2O3 > 1 wt.%) picrobasaltic (SiO2 ~ 39-43 wt.%; Na2O + K2O < 2 wt.%) melt containing up to 5.7 wt.% SO3 and up to 5.1 wt.% CO2 + H2O (calculated by difference) is present in equilibrium with fassaitic clinopyroxene, anhydrite, scapolite, chromian spinel and a gas composed mainly of CO and, occasionally, aliphatic thiols like CH3(CH2)3SH. Hydrogen was incorporated either by contact between the starting material and air or by diffusion through the capsule during the experiments. Above ~ 1440 °C, a CaO-rich (~ 35 wt.%) sulfate-carbonate (SC) melt which contains 41-47 wt.% SO3, 7-12 wt.% CO2 + H2O and a few percent of Na2O, forms in equilibrium with the picrobasaltic melt. This study shows that a meteoroid impact onto an anhydrite- and calcite-bearing basaltic crust is likely to release CO gas to the atmosphere, while S is trapped in solid or liquid phases. Under hydrous conditions, however, the S/C in the gas may increase. The importance of the temperature parameter on the impact phase relations is also demonstrated. In particular, SC melt may form by meteoroid impact, and flow rapidly on a planetary surface. Physical modeling must therefore be combined with high P-high T phase diagrams of complex assemblages similar to planetary lithologies in order to evaluate the effects of a meteoroid impact.

Martin, A. M.; Righter, K.; Treiman, A. H.

2012-05-01

359

Immobilization of High-Level Wastes into Sintered Glass: 1. Hot Pressing Process.  

National Technical Information Service (NTIS)

In order to immobilize the high-level radioactive wastes from the reprocessing, fuel elements borosilicate glass was adopted. Sintering experiments are described with the variety VG 98/12 (SiO2, TiO2, Al2O3, B2O3, MgO, CaO and Na2O) (which does not presen...

D. O. Russo N. Messi de Bernasconi M. A. Audero

1987-01-01

360

Bioactive borate glass scaffolds: in vitro and in vivo evaluation for use as a drug delivery system in the treatment of bone infection  

Microsoft Academic Search

The objective of this work was to evaluate borate bioactive glass scaffolds (with a composition in the system Na2O–K2O–MgO–CaO–B2O3–P2O5) as devices for the release of the drug Vancomycin in the treatment of bone infection. A solution of ammonium phosphate,\\u000a with or without dissolved Vancomycin, was used to bond borate glass particles into the shape of pellets. The in vitro degradation

Xin Liu; Zongping Xie; Changqing Zhang; Haobo Pan; Mohamed N. Rahaman; Xin Zhang; Qiang Fu; Wenhai Huang

2010-01-01

361

Loess geochemistry and its implications for particle origin and composition of the upper continental crust  

Microsoft Academic Search

Chemical and NdSr isotopic compositions of loess samples from Argentina, Europe and Spitsbergen were analyzed to examine the nature of source terrains, the origin of silt-size particles and the suitability of using loess as starting material for estimating the average chemical composition of the upper continental crust. From the relations between Na2O\\/Al2O3 and K\\/2O\\/Al2O3 ratios and CIA values (chemical index

Sylvain Gallet; Bor-Ming Jahn; Brigitte Van Vliet Lanoë; Aline Dia; Eduardo Rossello

1998-01-01

362

Improvement of the chemical composition and founding technology of high-lead glass in a high-efficiency furnace  

Microsoft Academic Search

A new composition for electrovacuum lead glass with a 20 wt. % PbO has been synthesized. The system of loading the charge and glass scrap into a furnace and a new system of tube shaping are described. The effect of the moisture content of the charge and the temperature on volatilization of PbO, Na2O, and K2O is investigated. It is

A. P. Sivko; V. V. Lityushkin; V. I. Uvarov; A. I. Zyuzin; M. V. Yakovleva

1995-01-01

363

Solvent free synthesis of chalcone and flavanone over zinc oxide supported metal oxide catalysts  

Microsoft Academic Search

Liquid phase Claisen–Schmidt condensation between 2?-hydroxyacetophenone and benzaldehyde to form 2?-hydroxychalcone, followed by intramolecular cyclisation to form flavanone was carried out over zinc oxide supported metal oxide catalysts under solvent free condition. The reaction was carried out over ZnO supported MgO, BaO, K2O and Na2O catalysts with 0.2g of each catalyst at 140°C for 3h. Magnesium oxide impregnated zinc oxide

S. Saravanamurugan; M. Palanichamy; Banumathi Arabindoo; V. Murugesan

2005-01-01

364

Petrochemical variations among mildly peralkaline (comendite) obsidians from the oceans and continents  

Microsoft Academic Search

Eleven new analyses and modes of comendite obsidians are presented, and compared with all available data on similar rocks. Most specimens are aphyric or contain only sparse phenocrysts, most commonly alkali feldspar. The oxides SiO2, Al2O3, Na2O and K2O total over ninety percent by weight in all analyses. Iron, as FeO, is the only other constituent rising above one percent

D. K. Bailey; R. MacDonald

1970-01-01

365

Effect of surface morphology of macro-scale perlite particles on adsorption process of Malachite Green dye  

Microsoft Academic Search

Perlite is a mineral compound. It is a mixture of SiO2, Al2O3, Na2O, K2O, Fe2O3 and so on. Its high porosity and low density cause that it is being used as an adsorbent to remove organic and inorganic pollutants from wastewater in many researches. But its capacity depends on its structure as an adsorbent. In this research, the effect of

Khashayar Badii; Farrokh-Legha Amini; Soodeh-Sadat Rasoli Ahari

2011-01-01

366

Method of preventing oxidation of graphite fireproof material  

NASA Technical Reports Server (NTRS)

A method of preventing oxidation of graphite fireproof material is given. A blend of 1 to 33 weight parts alumina and 3 to 19 parts of K2O + Na2O in 100 parts of SiO2 is pulverized followed by addition of 5 to 160 parts of silicon carbide powder in 100 parts of the mixture. This is thoroughly blended and coated on the surface of graphite fireproof material.

Yamauchi, S.; Suzuki, H.

1981-01-01

367

Geochemical and isotopic composition and inherited zircon ages as evidence for lower crustal origin of two Variscan S-type granites in the NW Bohemian massif  

Microsoft Academic Search

Geochemical and Nd-Sr isotopic compositions and U-Pb zircon ages of two Variscan granites (Neunburg and Oberviechtach) from southern Oberpfalz, NW Bohemian massif, have been investigated in order to place constraints on their formation and on the crustal reworking. Both granites exhibit similar mineralogical, chemical and isotopic characteristics. They have peraluminous compositions (A\\/CNK ratios 1.2-1.3) and display high K2O\\/Na2O ratios of

F. Chen; W. Siebel; M. Satir

2003-01-01

368

Evolution of the trachydacite and pantellerite magmas of the bimodal volcanic association of Dzarta-Khuduk (Central Mongolia): evidence from melt inclusions  

NASA Astrophysics Data System (ADS)

Using various methods of melt inclusion investigation, including electron and ion microprobe techniques, we estimated the composition, evolution, and formation conditions of melts producing the trachydacites and pantellerites of the Late Paleozoic bimodal volcanic association of Dzarta-Khuduk, CentralMongolia. Dzarta Huduk paleovolcano occupies an area of more than 120 square kilometers. A sequence of felsic agpaitic volcanics rests on subalkali basalts and consists of intercalating alkaline trachydacites, pantellerites, and comendites. Their mineralogical and chemicall characteristics correspond to silicic peralkaline rocks of the K-Na series with an agpaitic index of >1 and high contents of F, Zr, Li, Rb, and REE. Primary crystalline and melt inclusions were detected in anorthoclase from trachydacites and quartz from pantellerites and pantelleritic tuffs. Among the crystalline inclusions, we identified hedenbergite, fluorapatite, and pyrrhotite in the trachydacites and F-arfvedsonite, fluorite, ilmenite, and the rare REE diorthosilicate chevkinite in the pantellerites. Melt inclusions in anorthoclase from the trachydacites are composed of glass, a gas phase, and daughter minerals (F-arfvedsonite, fluorite, villiaumite, and anorthoclase rim on the inclusion wall). Melt inclusions in quartz from the pantellerites are composed of glass, a gas phase, and a fine-grained salt aggregate consisting of Li, Na, and Ca fluorides (griceite, villiaumite, and fluorite). Melt inclusions in quartz crystalloclasts from the pantelleritic tuffs are composed of homogeneous silicate glasses. The phenocrysts of the trachydacites and pantellerites crystallized at temperatures of 1060-1000°C. During thermometric experiments with quartz-hosted melt inclusions from the pantellerites, the formation of immiscible silicate and salt (fluoride) melts was observed at a temperature of 800°C. Homogeneous melt inclusions in anorthoclase from the trachydacites have both trachydacite and rhyolite compositions (wt %):68-70 SiO2, 12-13 Al2O3, 0.34-0.74 TiO2, 5-7 FeO, 0.4-0.9 CaO, and 9-12 Na2O + K2O. The agpaitic index ranges from 0.92 to 1.24. The glasses of homogenized melt inclusions in quartz from the pantellerites and pantelleritic tuffs have rhyolitic compositions. Compared with the homogeneous glasses trapped in anorthoclase of the trachydacites, quartz-hosted inclusions from the pantellerites show higher SiO2 (72-78 wt %) and lower Al2O3 contents (7.8-10.0 wt %). They also contain 0.14-0.26 wt % TiO2, 2.5-4.9 wt % FeO, 9 -11 wt % Na2O + K2O, and 0.9-0.15 wt % CaO and show an agpaitic index of 1.2-2.05. Homogeneous melt inclusions in quartz from the pantelleritic tuffs contain 69-72 wt % SiO2. The contents of other major components, including TiO2, Al2O3, FeO, and CaO, are close to those in the homogeneous glasses of quartz-hosted melt inclusions in the pantellerites. The contents of Na2O + K2O are 4-10 wt %, and the agpaitic index is 1.0-1.6. The glasses of melt inclusions from each rock group show distinctive volatile compositions. The H2O content is up to 0.08 wt % in anorthoclase of the trachydacites, 0.4-1.4 wt % in quartz of the pantellerites, and up to 5 wt % in quartz of the pantelleritic tuffs. The content of F in the glasses of melt inclusions in the phenocrysts of the trachydacites is no higher than 0.67 wt %, and up to 1.4-2.8 wt % in quartz from the pantellerites. The Cl content is up to 0.2 wt % in the glasses of melt inclusions in the minerals of the trachydacites and up to 0.5 wt % in the glasses of quartz-hosted melt inclusions from the pantellerites. The investigation of trace elements in the homogenized glasses of melt inclusions in minerals showed that the trachydacites and pantellerites were formed from strongly evolved rare-metal alkaline silicate melts with high contents of Li, Zr, Rb, Y, Hf, Th, U, and REE. The analysis of the composition of homogeneous melt inclusions in the minerals of the above rocks allowed us to distinguish magmatic processes resulting in the enrichment of these rocks in trace and rare earth element

Andreeva, I.

2012-04-01

369

A multiphase strategy for realizing green cathodoluminescence in 12CaO·7Al2O3-CaCeAl3O7:Ce3+,Tb3+ conductive phosphor.  

PubMed

A multiphase strategy is proposed and successfully applied to make the insulating green phosphor CaCeAl3O7:Tb(3+) conductive in the form of 12CaO·7Al2O3-CaCeAl3O7:Ce(3+),Tb(3+). The phosphor shows bright green-light emission with a short lifetime (2.51 ms) under low-voltage electron beam excitation (3 kV). The green photo- and cathodoluminescence from (5)D4-(7)F(J) (J = 6, 5, 4, 3) transitions of Tb(3+) are significantly enhanced in comparison with pure C12A7:Tb(3+). It was confirmed that this enhancement is the consequence of the joint effects of energy transfer from Ce(3+) to Tb(3+) and broadening of the absorption spectrum of Ce(3+) due to the existence of multiple phases. In particular, under 800 V electron beam excitation, cathodoluminescence is improved by the modified electrical conductivity of the phosphor. When compared to the commercial Zn2SiO4:Mn(2+) with a long luminescence lifetime of 11.9 ms, this conductive green phosphor has greater advantage for fast displays. PMID:24061503

Liu, Xiuling; Liu, Yuxue; Yan, Duanting; Zhu, Hancheng; Liu, Chunguang; Liu, Weizhen; Xu, Changshan; Liu, Yichun; Zhang, Hong; Wang, Xiaojun

2013-12-14

370

Large conductivity enhancement in polycrystalline 12CaO · 7Al 2O 3 thin films induced by extrusion of clathrated O 2- ions by hot Au + implantation and ultraviolet light illumination  

NASA Astrophysics Data System (ADS)

Large enhancement in electrical conductivity from <10 -10 S cm -1 to ˜4 × 10 -2 S cm -1 was achieved in polycrystalline 12CaO · 7Al 2O 3 (p-C12A7) thin films by hot Au + implantation at 600 °C and subsequent ultraviolet (UV) light illumination. Although the as-implanted films were transparent and insulating, the subsequent UV-light illumination induced persistent electronic conduction and coloration. A good correlation was found between the concentration of photo-induced F +-like centers (a cage trapping an electron) and calculated displacements per atom, indicating that the hot Au + implantation extruded free O 2- ions from the cages in the p-C12A7 films by kick-out effects and left electrons in the cages. These results suggest that H - ions are formed by the Au + implantation through the decomposition of preexisting OH - ions. Subsequent UV-light illumination produced F +-like centers via photoionization of the H - ions, which leads to the electronic conduction and coloration.

Miyakawa, M.; Hirano, M.; Kamiya, T.; Hosono, H.

2006-09-01

371

Fabrication and electron transport properties of epitaxial films of electron-doped 12CaO·7Al 2O 3 and 12SrO·7Al 2O 3  

NASA Astrophysics Data System (ADS)

Epitaxial growth and electron doping of 12CaO·7Al 2O 3 (C12A7) and 12SrO·7Al 2O 3 (S12A7) are reported. The C12A7 films were prepared on Y 3Al 5O 12 (YAG) single-crystal substrates by pulsed laser deposition at room temperature and subsequent thermal crystallization. X-ray diffraction patterns revealed the films were grown epitaxially with the orientation relationship of (001)[100] C12A7 || (001)[100] YAG. For S12A7, pseudo-homoepitaxial growth was attained on the C12A7 epitaxial layer. Upon electron doping, metallic conduction was achieved in the C12A7 film and the S12A7/C12A7 double-layered films. Analyses of optical absorption spectra for the S12A7/C12A7 films provided the densities of free electrons in each layer separately. Hall measurements exhibited larger electron mobility in the S12A7/C12A7 film than those in C12A7 and S12A7 films, suggesting free electrons may be accumulated at the S12A7/C12A7 interface due presumably to a discontinuity of the cage conduction bands.

Miyakawa, Masashi; Hiramatsu, Hidenori; Kamiya, Toshio; Hirano, Masahiro; Hosono, Hideo

2010-02-01

372

Kinetics of Reduction of SiO2 in SiO2-Al2O3-CaO Slags by Al in Fe-Al(-Si) Melts  

NASA Astrophysics Data System (ADS)

Kinetic models considering mass transport in, (i) metal phase only and (ii) both metal and slag phases (mixed control or two-phase mass transfer) were developed for the reduction of SiO2 in a SiO2-Al2O3-CaO slag by Al in an Al-Fe melt. The models were validated with experiments of the reaction with Fe-Al melt and SiO2-Al2O3-CaO-MgOsat slags at 1873 K (1600 °C). The models predict that the rate of reaction is slower in the mixed control model because of the added resistance of slag phase mass transport. The mixed control becomes applicable when the slag contains low amounts of SiO2. In this case, when the initial Al content in the metal increases, the normalized rate of reaction decreases. The increased Al content in the metal retards the reaction due to the limited SiO2 provided to the reaction interface in the mixed control model. Sensitivity analyses were done using the models for the ratios of mass transfer coefficients of Si to Al, and Al2O3 to Si, along with slag density, which did not impose a significant effect.

Park, Jiwon; Sridhar, Seetharaman; Fruehan, Richard J.

2014-05-01

373

Spectroscopic CW-EPR and HYSCORE investigations of Cu(2+) and O(2)(-) species in copper doped nanoporous calcium aluminate (12CaO.7Al(2)O(3)).  

PubMed

Continuous wave (CW) and pulse electron paramagnetic resonance in a variant of hyperfine sublevel correlation spectroscopy (HYSCORE) were used for obtaining structural information concerning speciation and local environment of alien Cu(2+) and native O(2)(-) ions encaged in copper doped nanoporous 12CaO.7Al(2)O(3) (mayenite). The samples were prepared by a solid-state reaction and characterized by means of XRD, SEM, and Raman techniques. X-Band CW-EPR spectra showed that three different Cu(2+) species together with paramagnetic extraframework O(2)(-) anions were present in the mayenite sample, whereas extraframework OH(-) anions were revealed by Raman spectroscopy. (27)Al HYSCORE provided evidence for the interaction of Cu(2+) ions with the mayenite framework. Superhyperfine interaction of the Cu(2+) ions with proximal (d(Cu-OH) = 2.4 A) and distal (d(Cu-OH) = 5.0 A) OH(-) anions, located in the same and the nearby cage, respectively, was resolved by means of (1)H HYSCORE spectra. A different situation held for the encaged O(2)(-) radicals found to be sitting on the Ca(2+) ions. They exhibited only a weak superhyperfine interaction of 1 MHz with the (27)Al(3+) framework ions. PMID:20657948

Maurelli, Sara; Ruszak, Monika; Witkowski, Stefan; Pietrzyk, Piotr; Chiesa, Mario; Sojka, Zbigniew

2010-09-28

374

The Iceland Deep Drilling Project (IDDP): (2) Petrology and geochemistry of rhyolitic melts drilled at Krafla  

NASA Astrophysics Data System (ADS)

The Iceland Deep Drilling Project (IDDP) in the Krafla Geothermal Field was intended to investigate the feasibility of producing energy from geothermal systems at supercritical conditions. Drilling was stopped at 2104 meter when a rhyolitic melt was intersected. Sporadic cuttings included abundant dark brown, sparsely phyric obsidian. Most fragments were poorly vesiculated, but white frothy pumice, some with highly stretched bubbles, sere also present. The dense obsidian and highly vesiculated samples have identical phenocryst assemblages, major element compositions, and volatile contents. The glass is a high silica (75.0 wt %) rhyolite with low TiO2 (0.3 wt %) and 3.7 and 3.0 wt % Na2O and K2O, respectively. Phenocrysts include titanomagnetite, plagioclase, augite and pigeonite, with minor amounts of apatite, rare zircon crystals and pyrrhotite, which occurs as rounded droplets of an immiscible sulfide liquid. Augite and pigeonite each contain abundant exsolution lamellae of the complimentary phase. Plagioclase shows some compositional zoning, but mostly is in the range from An45-An48. The low water contents (1.75 wt %) are consistent with the absence of hydrous phenocrysts, and together with the CO2 content (75 ppm) indicate relatively shallow (<4 km) degassing. Stable isotope compositions (?18O = 3.2‰, ?D = -118‰) indicate an origin by partial melting of hydrothermally altered crustal rock, as do chondrite-normalized rare earth element patterns, that are enriched in light elements and relatively flat for middle and heavy elements. Fragments of a partially crystallized granite intrusion with areas of interstitial melt quenched to glass by the drilling fluids also are present in the drill cuttings from the bottom of the hole. The granite is composed of alkali feldspar, plagioclase, quartz, augite and titanomagnetite. The interstitial glass has a silica content (75.6 wt. %) similar to the rhyolite melt, but is easily distinguished from it by higher K2O and lower CaO contents. REE elements are strongly enriched in the interstitial glass, relative to the rhyolite, but show similar chondrite-normalized patterns. Some glass-rich fragments are crowded with crystals and glomerocrysts typical of the granite intrusion, except that alkali feldspar only occurs as remnants of resorbed crystals. The glass in these fragments plots on mixing/assimilation curves between the interstitial granite melt and the rhyolite melt and clearly indicate emplacement of a separate melt into the zone occupied by the still crystallizing rhyolitic intrusion.

Zierenberg, R. A.; Elders, W. A.; Fridleifsson, G. O.; Schiffman, P.; Marks, N. E.; Lesher, C. E.; Lowenstern, J. B.; Pope, E. C.; Bird, D. K.; Mortensen, A.; Gudmundsson

2009-12-01

375

The significance of mafic microgranular enclaves in the petrogenesis of the Dehno Complex, Sanandaj-Sirjan belt, Iran  

NASA Astrophysics Data System (ADS)

Quartz-monzodioritic and granodioritic enclaves occur in the Upper Cretaceous-Paleocene Dehno Complex, NW of Isfahan, Iran. They are hosted by hornblende-granodiorite and granodiorite-monzogranite, respectively. The presence of xenocrystic plagioclase, biotite, quartz, magnesio-hornblende, occasionally with relics of clinopyroxene (in quartz-monzodiorites), minor K-feldspar and the lack of peraluminous minerals dominate the mineralogy of these rocks and suggest a metaluminous source. The plagioclase in the quartz-monzodioritic enclaves has higher An-content than that of the respective plagioclase of their host (hornblende-granodiorite) indicating crystallization from more mafic magma. The quartz-monzodioritic enclaves generally contain higher values of Fe 2O 3, MgO, CaO, MnO, Na 2O, transition elements (Ni, Cr, Co, V), REE and lower values of SiO 2, K 2O, P 2O 5 and Zr than their host which are in consistent with occurrence of abundant ferromagnesian minerals in these rocks. Compare to their host, the granodioritic enclaves have higher amount of Fe 2O 3, MgO, MnO, TiO 2, P 2O 5, Rb, Zr, Y, Ni, Cr, Co and lower concentration of SiO 2, K 2O and Ba. Aside from hornblende-granodiorite and granodiorite-monzogranite, the Dehno Complex comprises leucogranodiorite and tourmaline-leuco granites. Geochemically, the rocks of the Complex are metaluminous to strongly peraluminous and are enriched in LILE (e.g. Rb, K, Sr, Ba) and depleted in HFSE (e.g. Nb, Ta, P, Ti, Zr, Hf) with medium to high-K calc-alkaline nature. These geochemical features are proposed for the volcanic arc granites emplaced in an active continental margin. Whole-rock and quartz ?18O values for all rocks are high (9.7-14.4‰ and 10.1-14.9‰, respectively), suggesting the interaction of magma with crustal-derived components. The strongly peraluminous composition can be interpreted in terms of this hypothesis. All these mineralogical and geochemical features support the idea that the granitoid rocks of the Dehno Complex developed through variable degrees of mixing/mingling between a basic magma and a supracrustal melt during subduction of the Neotethys oceanic crust beneath Central Iranian microcontenent. The quartz-monzodioritic enclaves most likely represent the nearest composition to the original more mafic magma. The granodioritic enclaves result from the mixing/mingling of globules basic magma with host granitic magma.

Rajaieh, M.; Khalili, M.; Richards, I.

2010-07-01

376

Heterogeneous reactions of volatile organic compounds on oxide particles of the most abundant crustal elements: Surface reactions of acetaldehyde, acetone, and propionaldehyde on SiO2, Al2O3, Fe2O3, TiO2, and CaO [SiO2 Al2O3 Fe2O3 TiO2  

Microsoft Academic Search

The heterogeneous reactivity of volatile organic compounds (VOCs) on oxide particles has been investigated. Oxide particles composed of the most abundant elements present in the Earth's crust were used to identify potentially important reactions of VOCs on mineral dust. In particular, heterogeneous reactions of acetaldehyde, acetone, and propionaldehyde on alpha-Al2O3, alpha-Fe2O3, TiO2, CaO, and SiO2 particle surfaces have been investigated.

P. Li; K. A. Perreau; E. Covington; C. H. Song; G. R. Carmichael; V. H. Grassian

2001-01-01

377

Moessbauer Effect Study of Bi2O3. Na2O. B2O3. Fe2O3 Glass System  

SciTech Connect

Sodium-tetra-borate host glass containing both bismuth and iron cations were prepared obeying the composition (Na2B4O7)0.75 (Fe2O3)0.25-x (Bi2O3)x [where x = 0.0, 0.05, 0.10, 0.15, 0.20, and 0.25 mol.%]. X-ray diffraction indicated that all samples were in a homogeneous glassy phase. Moessbauer effect results showed that all iron ions appeared as Fe3+ ions occupying tetrahedral coordination state. The covalency of the Fe-O bond increased as bismuth oxide was gradually increased. IR measurements indicated the presence of some non-bridging oxygens and confirmed that iron ions occupy the tetrahedral coordination state. It was found also that, as Bi2O3 was gradually increased both magnetic susceptibility and specific volume decreased, while both density and molar volume increased.

Salah, S.H.; Kashif, I.; Salem, S.M.; Mostafa, A.G.; El-Manakhly, K.A. [Physics and Chemistry Dept., Faculty of Science, Al-Azhar Univ., Cairo (11884) (Egypt)

2005-04-26

378

The effect of light rare earths on the chemical durability and weathering of Na 2O–CaO–SiO 2 glasses  

Microsoft Academic Search

In this paper, the investigation on chemical durability and weathering of soda–lime–silicate glasses containing light rare earths (La, Ce and Nd) prepared with traditional melt-quenching methods was carried out by ICP-AES, optical microscopy, SEM and EDS. The weight losses of different glasses in different attacking media were measured, and the normalized releases were calculated. The results showed that the presence

Mitang Wang; Jinshu Cheng; Qiming Liu; Peijing Tian; Mei Li

2010-01-01

379

Tm 3+ doped Bi 2O 3-GeO 2-Na 2O glasses for 1.8 ?m fluorescence  

NASA Astrophysics Data System (ADS)

53.3BiO 1.5-33.3GeO 2-13.4NaO 0.5 (cation%) glasses with various Tm 3+ concentration were prepared by melt-quenching method. These glasses show high density, high refractive index, low phonon energy and good stability against crystallization. Absorption spectra of Tm 3+-doped bismuthate glass were measured to obtain the radiative lifetimes by Judd-Ofelt theory. The absorption (4.5 × 10 -21 cm 2) and emission (6.7 × 10 -21 cm 2) cross-sections were calculated by Beer-Lambert and McCumber theory. The results show that the Tm 3+ ( 3F 4 ? 3H 6) in these glasses have high spontaneous radiative transition probabilities and large stimulated emission cross-section. Then the fluorescence emission spectra were measured under 808 nm excitation and the maximum emission intensity at 1.8 ?m is obtained at 0.9 mol% Tm 2O 3 in the glasses.

Fan, Huiyan; Gao, Guojun; Wang, Guonian; Hu, Junjiang; Hu, Lili

2010-03-01

380

An XRD study of the effect of the SiO 2\\/Na 2O ratio on the alkali activation of fly ash  

Microsoft Academic Search

Soluble silica has a very significant effect on the microstructural and mechanical development of the cementitious materials produced as a result of the alkali activation of fly ash. In this study, four different alkaline solutions with different soluble silica contents were used to activate fly ash. The primary reaction product was a sodium aluminosilicate gel, while different types of zeolites

M. Criado; A. Fernández-Jiménez; A. G. de la Torre; M. A. G. Aranda; A. Palomo

2007-01-01

381

Boson mode, Medium Range Structure and Intermediate Phase (IP) in (Na2O)x(B2O3)1-x glasses  

NASA Astrophysics Data System (ADS)

Raman scattering of titled glasses are examined using a T64000 Dispersive system. Scattering strengths of the Boson mode (40 cm-1, 70 cm-1) and the Boroxyl ring (BR) mode (808 cm-1) are found to decrease with increasing x at the same rate in the 0 < x < 20% soda range. Apparently, the 2D character of BRs embedded in a 3D network gives rise to the Boson mode.ootnotetextM. Flores-Ruiz and G. Naumis, PRB, 2011. 83: p. 184204 The triad of modes (705, 740, 770 cm-1) near the 808 cm-1 mode are found to display a maximum in scattering strength near x = 37% (705 cm-1), 33% (740 cm-1) and 25% (770 cm-1), suggesting that these are also ring modes of Na-tripentaborate (STPB), Na-diborate (SDB) and Na-triborate (STB) super-structures. Variations in Raman scattering strengths also suggest that STB percolate near x = 20%, the stress transition, while the STPB and SDTB percolate near x = 40%, the rigidity transition. These transitions were inferred from m-DSC experiments that show an intermediate phase in the 20% < x < 40% range in dry and homogeneous glasses.

Vignarooban, K.; Boolchand, P.; Micoulaut, M.; Malki, M.

2012-02-01

382

Effect of crucible material on optical bandgap and activation energy of Na 2 O-CdO-P 2 O 5 glasses  

Microsoft Academic Search

In the sodium cadmium phosphate glasses, the effect of diffused alumina from alumina crucible has been assessed by measuring various properties such as mass density, refractive index, optical bandgap and dc conductivity. The results of measurements corresponding to glasses prepared in alumina crucible have been compared with those of glasses prepared in platinum crucible with and without adding Al2O3. The

M. Altaf; M. A. Chaudhry

2005-01-01

383

O(-) identified at high temperatures in CaO-based catalysts for oxidative methane dimerization  

NASA Technical Reports Server (NTRS)

A technique called charge-distribution analysis (CDA) is employed to study mobile charge carriers in the oxidation catalysts CaO, CaO with 11 percent Na2O, and CaO with 10 percent La2O3. A threshold temperature of about 550-600 C is identified at which highly mobile charge carriers are present, and the CDA studies show that they are O(-) states. The present investigation indicates the usefulness of CDA in catalysis research with pressed powder samples and gas/solid reactions.

Freund, F.; Maiti, G. C.; Batllo, F.; Baerns, M.

1990-01-01

384

Simulations with CAO-3D model of photochemical response caused by precipitating electrons and solar protons at both polar regions during geomagnetic storms in October-November 2003 (preliminary comparison with MIPAS data)  

NASA Astrophysics Data System (ADS)

Relativistic electrons precipitating from radiation belts and solar protons can penetrate below 100 km into the polar atmosphere sometimes reaching the stratospheric levels wasting its energy and causing the ionization. It leads to additional production of NOx and HOx chemical com-pounds which destroy ozone in the chemical catalytic cycles. One of the strongest geomagnetic storms accompained by a strong Solar Proton Eevent (SPE) occured in October-November 2003. This period was covered also by observations with MIPAS instrument placed on board of ENVISAT satellite. The response of atmospheric chemical composition in both polar regions was studied with CAO-3D photochemical-transport model. In order to calculate ionization rates induced by precipitating electrons and solar protons during late October and November 2003, corresponding proton and electron fluxes in different energetic channels from GOES-10 and POES-15/16 have been used. The Atmospheric Ionization Module Osnabruck -AIMOS /Wissing and Kallenrode, 2009/ was used to calculate 3D fields of ionization rates separately by electrons and protons. Photochemical simulations showed that Northern and Southern po-lar regions had different photochemical response. Such difference mostly is the result of the two factors: polar cap expansion during the geomagnetic storm and the effect of horizontal transport. The calculated members of NOy, HOx, Cly families were preliminary compared with corresponding observed data measured by MIPAS and showed a general agreement. The sensitivity of calculated chemical response to the efficiencies of NOx and HOx production by en-ergetic particles have been studied also. This work was supported by Russian Science Foudation for Basic Research (grant 09-05-009949) and by contract 1-6-08 under Russian Sub-Program "Reseach and Investigation of Antarctica".

Krivolutsky, Alexei A.; Banin, Max; Maik Wissing, Jan; Vyushkova, Tatyana

385

Removal of Cd2+ from water by Friedel's salt (FS: 3CaO x A12O3 x CaCI2 x 10H2O): sorption characteristics and mechanisms.  

PubMed

The development of low-cost and efficient new mineral adsorbents has been a hot topic in recent years. In this study, Friedel's salt (FS: 3CaO x A12O3 x CaCl2 x10H2O), a hexagonal layered inorganic absorbent, was synthesized to remove Cd2+ from water. The adsorption process was simulated by Langmuir and Freundlich models. The adsorption mechanism was further analyzed with TEM, XRD, FT-IR analysis and monitoring of metal cations released and solution pH variation. The results indicated the adsorbent FS had an outstanding ability for Cd(II) adsorption. The maximum adsorption capacity of the FS for Cd(II) removal can reach up to 671.14 mg/g. The nearly equal numbers of Cd2+ adsorbed and Ca2+ released demonstrated that ion-exchange (both surface and inner) of the FS for Cd(II) played an important role during the adsorption process. Furthermore, the surface of the FS after adsorption was microscopically disintegrated while the inner lamellar structure was almost unchanged. The behavior of Cd(II) adsorption by FS was significantly affected by surface reactions. The mechanisms of Cd2+ adsorption by the FS mainly included surface complexation and surface precipitation. In the present study, the adsorption process was fitted better by the Langmuir isotherm model (R2 = 0.9999) than the Freundlich isotherm model (R2 = 0.8122). Finally, due to the high capacity for ion-exchange on the FS surface, FS is a promising layered inorganic adsorbent for the removal of Cd(II) from water. PMID:24520713

Zhang, Juanjuan; Zhao, He; Cao, Hongbin; Li, Heping; Li, Zhibao

2013-09-01

386

CaO X 1 ? + Calcium oxide  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume A1 'Diamagnetic Diatomic Molecules. Part 1' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

Hüttner, W.

387

Physico-chemical conditions of crystallization of the Guli ulrabasic massif (North Part of the Siberian Platform): evidence from melt inclusions  

NASA Astrophysics Data System (ADS)

Conditions of formation of the Guli ultrabasic massif (Maimecha Kotui Province in the North Part of the Siberian Platform) attract attention of numerous researchers. For the solution of genetic problems of various rocks from this ultramafic complex the data on melt inclusions in minerals has been earlier used (Sokolov et al., 1999; Rass, Plechov, 2000; Sokolov, 2003; Panina, 2006). At the same time, formation of dunites, occupying the main volume of the Guli massif, remain almost not considered by means of thermobarogeochemical methods and the role of magmatic processes in this case is not ascertained. As a result of melt inclusions study in the Cr-spinel the new data on physical and chemical parameters of dunite crystallization in the Guli ulrabasic massif was obtained. On the ratio (Na2O + K2O) - SiO2 the majority of analyses of glasses and calculated compositions of inclusions settle down in the field of subalkaline series. On the diagram MgO - SiO2 bulk chemical compositions of inclusions (with the magnesium content of 19-28 wt. %) correspond to picrites and picrite-basalts. They are in close association with the data on inclusions in the Cr-spinel from dunites of Konder (Siberian Platform) and Nizhnii Tagil (Ural Mountains) platinum-bearing ultrabasic massifs and also are situated near to the field of inclusions in the olivine phenocrysts from meimechites (Maimecha Kotui Province in the North Part of the Siberian Platform). Similarity of melt inclusions in the Cr-spinel from the dunite of the Guli massif and in the olivine from meimechites is established on the variety of petrochemical components - Al2O3, CaO, Na2O, K2O. The calculated compositions of inclusions from dunites coincide mostly with the data on inclusions from meimechites, while glasses of inclusions from Cr-spinel contain less titan and magnesium. As a whole for the melts of the Maimecha Kotui Province (that form both dunites of the Guli massif and meimechites) much higher contents of TiO2 (from above 2.7 wt. %) are characteristic in comparison with magmatic systems of the platinum-bearing ultrabasic massifs of Ural and Siberia. Our computer simulations on the basis of melt inclusion compositions by the PETROLOG program package (Danyushevsky, Plechov, 2011) show the high crystallization temperature of olivines from dunites of the Guli massif in the intrusive chamber - 1590-1415 °C. Formation of the Cr-spinels occurred also at high parameters - 1405-1365 °C. These temperatures correspond to established earlier temperature interval of crystallization of olivines from meimechites - 1600-1420 °C (Sobolev et al., 1999, 2009). As a whole, the melt inclusions study in the Cr-spinel directly testify to formation of dunites from the Guli massif from high magnesia melt, relative on its petrochemical composition and high-temperature characteristics to meimechite magma. Consecutive evolution of composition of magmatic systems is established during intra-chamber crystallization of dunites from picrite-meimechite to picrite-basalt and basalt melts. The investigations were supported by the Project N VIII.66.1.1 and by the Russian Foundation for Basic Research (Project N 12-05-00959).

Simonov, Vladimir; Vasiliev, Yuri; Kotlyarov, Alexey; Stupakov, Sergey

2014-05-01

388

The origin of intraplate volcanism associated with cross grain gravity lineations: geochemical constraints in the GLIMPSE region  

NASA Astrophysics Data System (ADS)

Intraplate volcanism that is apparently unrelated to deep mantle plumes is common in the Pacific Ocean. Some of this volcanism is found in near-axis seamounts, but several localities with large scale volcanic edifices or magmatic ridges require substantially greater melt production. The GLIMPSE region and the Pukapuka Ridge represent such large scale intraplate volcanism in the South Pacific. The origin of these features must be linked to their association with cross grain gravity lineations. Three models have been proposed to explain their origin: 1. Mini-hot spot, 2. Lithospheric boudinage, 3 Secondary convection caused by shearing of the plate over the mantle. By comparing the chemistry of these lavas to on-axis volcanism, the possible models can be investigated. Full quantitative tests await the synthesis of geochemistry, seismic and geophysical data and dating. The GLIMPSE samples are offset from East Pacific Rise (EPR) samples in major element compositions. For a given MgO, GLIMPSE samples have lower SiO_2, CaO and higher Al_2O_3, Na_2O, and K_2O with MgO concentrations ranging from greater than 9 to less than 1 wt% . Average Na_2O concentrations for the same MgO are higher by 0.6 wt% . The highly incompatible element abundances and ratios show that the mean source is significantly more enriched than what appears at the EPR. The Pukapuka samples measured by Janney et al. (2000) show similar offsets in major and trace element abundances. The lower SiO_2 contents suggest higher average pressures of melting than EPR basalts. At the same time the trace elements show little evidence of high pressure melting in the presence of ga