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

PubMed

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

2015-07-02

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

Multimodal emissions from Tb{sup 3+}/Yb{sup 3+} co-doped lithium borate glass: Upconversion, downshifting and quantum cutting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bahadur, A.; Yadav, R.S.; Yadav, R.V.

This paper reports the optical properties of Tb{sup 3+}/Yb{sup 3+} co-doped lithium borate (LB) glass prepared by melt quench method. The absorption spectrum of the Yb{sup 3+} doped LB glass contains intense NIR band centered at 976 nm due to {sup 2}F{sub 7/2}→{sup 2}F{sub 5/2} transition. The emission spectra of the prepared glasses have been monitored on excitation with 266, 355 and 976 nm. The Yb{sup 3+} doped glass emits a broad NIR band centered at 976 nm whereas the Tb{sup 3+} doped glass gives off visible bands on excitations with 266 and 355 nm. When the Tb{sup 3+} andmore » Yb{sup 3+} ions are co-doped together, the emission intensity in the visible region decreases whereas it increases in the NIR region significantly. The increase in the emission intensity in the NIR region is due to efficient cooperative energy transfer (CET) from Tb{sup 3+} to Yb{sup 3+} ions. The quantum cutting efficiency for Tb{sup 3+}/Yb{sup 3+} co-doped glass has been calculated and compared for 266 and 355 nm excitations. The quantum cutting efficiency is larger for 355 nm excitation (137%). The Tb{sup 3+}/Yb{sup 3+} co-doped LB glass also emits upconverted visible bands on excitation with 976 nm. The mechanisms involved in the energy transfer have been discussed using schematic energy level diagram. The Tb{sup 3+}/Yb{sup 3+} co-doped LB glass may be used in the optical devices and in solar cell for solar spectral conversion and behaves as a multi-modal photo-luminescent material. - Graphical abstract: The Tb{sup 3+}/Yb{sup 3+} co-doped lithium borate (LB) glass prepared by melt quench method emits upconverted visible emissions through upconversion CET from Yb{sup 3+} to Tb{sup 3+} ions and quantum cutting emissions through downconversion CET from Tb{sup 3+} to Yb{sup 3+} ions. Therefore, the Tb{sup 3+}/Yb{sup 3+} co-doped LB glass may find applications in optical devices and solar cell and behaves as a multi-modal photo-luminescent material. - Highlights: • The Tb{sup 3

Redox equilibria of multivalent ions in silicate glasses

NASA Technical Reports Server (NTRS)

Lauer, H. V., Jr.; Morris, R. V.

1977-01-01

Experimental studies were made on the compositional dependence of the redox equilibrium of Eu in synthetic silicate liquids, together with an empirical model describing the observed compositional dependence. Electron paramagnetic resonance (EPR) was used to measure the concentration ratio of Eu(2+) to Eu(3+) in various glasses formed by rapidly quenching silicate liquids. The compositional field studied comprised mixtures of SiO2, TiO2, Al2O3, CaO, MgO, and Na2O. The proposed model describes the Eu(2+)/Eu(3+) ratio over the entire compositional field in terms of parameters easily related to each glass composition. The general applicability and utility of the model is further demonstrated by its application to the Fe(2+)-Fe(3+), Ce(3+)-Ce(4+), and Cr(3+)-Cr(6+) redox reactions in binary alkali oxide silicate glasses of Li, Na, and K.

Role of electron transfer in Ce{sup 3+} sensitized Yb{sup 3+} luminescence in borate glass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sontakke, Atul D., E-mail: sontakke.atul.55a@st.kyoto-u.ac.jp; Katayama, Yumiko; Zhuang, Yixi

2015-01-07

In a Ce{sup 3+}-Yb{sup 3+} system, two mechanisms are proposed so far namely, the quantum cutting mechanism and the electron transfer mechanism explaining Yb{sup 3+} infrared luminescence under Ce{sup 3+} excitation. Among them, the quantum cutting mechanism, where one Ce{sup 3+} photon (ultraviolet/blue) gives rise to two Yb{sup 3+} photons (near infrared) is widely sought for because of its huge potential in enhancing the solar cell efficiency. In present study on Ce{sup 3+}-Yb{sup 3+} codoped borate glasses, Ce{sup 3+} sensitized Yb{sup 3+} luminescence at ∼1 μm have been observed on Ce{sup 3+} 5d state excitation. However, the intensity of sensitized Yb{supmore » 3+} luminescence is found to be very weak compared to the strong quenching occurred in Ce{sup 3+} luminescence in Yb{sup 3+} codoped glasses. Moreover, the absolute luminescence quantum yield also showed a decreasing trend with Yb{sup 3+} codoping in the glasses. The overall behavior of the luminescence properties and the quantum yield is strongly contradicting with the quantum cutting phenomenon. The results are attributed to the energetically favorable electron transfer interactions followed by Ce{sup 3+}-Yb{sup 3+} ⇌ Ce{sup 4+}-Yb{sup 2+} inter-valence charge transfer and successfully explained using the absolute electron binding energies of dopant ions in the studied borate glass. Finally, an attempt has been presented to generalize the electron transfer mechanism among opposite oxidation/reduction property dopant ions using the vacuum referred electron binding energy (VRBE) scheme for lanthanide series.« less

Transparent Oxyfluoride Nano-Glass-Ceramics Doped with Pr3+ and Pr3+-Yb3+ for NIR Emission

NASA Astrophysics Data System (ADS)

Gorni, Giulio; Cosci, Alessandro; Pelli, Stefano; Pascual, Laura; Durán, Alicia; Pascual, M. J.

2016-12-01

Pr3+-Yb3+ co-doped oxyfluoride glasses and glass-ceramics (GC) containing LaF3 nanocrystals have been prepared to obtain NIR emission of Yb3+ ions upon Pr3+ excitation in the blue region of the visible spectrum. Two different compositions have been tested 0.1-0.5 Pr-Yb and 0.5-1 Pr-Yb, in addition to Pr3+ singly doped samples. The crystallization mechanism of the nano-glass-ceramics was studied by DTA revealing that it occurs from a constant number of nuclei, the crystal growth being limited by diffusion. HR-TEM demonstrated that phase separation acts as precursor for LaF3 crystallization and a detailed analysis of the chemical composition (EDXS) revealed the enrichment in RE3+ ions inside the initial phase separated droplets, from which the LaF3 crystals are formed. The RE3+ ions incorporation inside LaF3 crystals was also proved by photoluminescence measurements showing Stark splitting of the RE3+ ions energy levels in the glass-ceramic samples. Lifetimes measurements showed the existence of a better energy transfer process between Pr3+ and Yb3+ ions in the glass-ceramics compared to the as made glass, and the highest value of energy transfer efficiency is 59% and the highest theoretical quantum efficiency is 159%, obtained for glass-ceramics GC0.1-0.5 Pr-Yb treated at 620 ºC-40 h.

Tetrahedrally Coordinated Fe3+ in Silicate Glasses: A Mossbauer, Iron K-edge XANES and Raman Spectroscopies Study

NASA Astrophysics Data System (ADS)

Cochain, B.; Neuville, D. R.; McCammon, C.; Henderson, G. S.; de Ligny, D.; Pinet, O.; Richet, P.

2009-05-01

In natural or industrial glasses, iron is the most abundant transition metal. A good knowledge of its redox equilibrium is important to better understand the chemical and structural evolution of magmas (crystallization, viscosity), and also to optimize vitrification processes and properties of iron-bearing glasses. To study the role of iron in silicate glasses and melts, we have used in a consistent manner the Mössbauer, iron K-edge XANES and Raman spectroscopies to investigate several series of silicate glasses as a function of redox state. The samples were selected to cover a wide composition range and to investigate the interactions of iron with two network forming cations, namely, Al3+ and B3+. The glasses investigated were synthesized at high temperature under various conditions of oxygen fugacity to achieve different redox ratios for each composition. Therefore, the iron redox state was varied from the most oxidized to the most reduced. Iron redox ratios were first determined by wet chemical analysis and in some cases by room temperature Mossbauer spectroscopy. This experimental method was also used to determine the local structure of iron of some of the investigated glasses. These results where compared to iron K-edge XANES/EXAFS spectroscopy results, which lead to the iron redox state and indicate that Fe2+ is in octahedral coordination whereas Fe3+ is in tetrahedral coordination. In addition, Raman spectroscopy gave us information on the network polymerization of glasses. Clearly changes in Raman spectra are visible with the evolution of iron redox ratio. For a given composition, we observed systematically, in the 800-1200 cm-1 envelope, which is sensitive to the environment of tetrahedrally coordinated cations, the growth of a band with the iron content and the oxidation state of the sample. The peak area of this band, which we attribute to vibrational modes involving tetrahedrally coordinated Fe3+, increases with the oxidation of the sample. This

Fluorescence properties of Yb3+-Er3+ co-doped phosphate glasses containing silver nanoparticles

NASA Astrophysics Data System (ADS)

Martínez Gámez, Ma A.; Vallejo H, Miguel A.; Kiryanov, A. V.; Licea-Jiménez, L.; Lucio M, J. L.; Pérez-García, S. A.

2018-04-01

Er3+-Yb3+ co-doped phosphate glasses containing silver nitrate (SN), were fabricated. Transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy (XPS) analyses were used to evidence the nucleation and presence of silver nanoparticles (SNP). The basic parameters of the glasses were inspected by means of absorption and fluorescence spectra, and fluorescence lifetimes under excitation at 916 nm (in-band of Yb3+), and at 406 nm (in-band of surface plasmon resonance given by the presence of SNP). The spectra as well as estimates for the basic parameters defining the lasing/amplifying potential of the glasses were studied as a function of SN concentration. The experimental results indicate that by increasing the SN content an enhancement of Er3+/Yb3+ fluorescence takes place.

Silicate release from glass for pharmaceutical preparations.

PubMed

Bohrer, Denise; Bortoluzzi, Fabiana; Nascimento, Paulo Cícero; Carvalho, Leandro Machado; Ramirez, Adrian Gustavo

2008-05-01

Glass is made of polymeric silica and other minor components, which are necessary for turning the silica into a material more easily moldable and resistant to temperature changes. Glass containers for pharmaceutical usage are classified according to their resistance to a chemical attack, a test carried out in the presence of water and heat. The test is designed to show the released alkalinity, a variable dependent on the amount of sodium oxide, one of the minor components added to the glass mass. In this work, the release of silica from glass by action of constituents from pharmaceutical formulations was investigated. The study included products used in large volumes and usually stored in glass containers. Solutions of amino acids, electrolytes, glucose, oligoelements and others such as heparin and sodium bicarbonate were individually stored in glass containers and heated at 121 degrees C for 30min, as in the water attack test. The test was also carried out only with water, where the pH varied from 2 to 12. The released silicate was measured either by photometry or atomic absorption spectrometry, depending on the nature of the sample. The results showed that silicate is released during the heating cycle even if the contact is with pure water only. The pH exerts a considerable influence on the release, being that the higher the pH, the higher the silica dissolved. An elevated pH, however, is not the only factor responsible for silica dissolution. While in the solutions of NaCl, KCl, Mg Cl2 and ZnSO4 and in most of the amino acids, the concentration of silicate was as high as in pure water (0.1-1.0mg Si/L). In the solutions of sodium acetate, bicarbonate and gluconate, its concentration was much higher, over 30mg Si/L. These results were confirmed by the analysis of commercial products, where in solutions of amino acids the level of silicate ranged from 0.14 to 0.19mg Si/L. On the other hand, calcium gluconate, sodium bicarbonate and potassium phosphate presented

Nd3+, Yb3+ and Ho3+ Codoped Oxyfluoride Glass Ceramics with High Efficient Green Upconversion Luminescence

NASA Astrophysics Data System (ADS)

Zhang, Jun-Jie; Kawamoto, Yoji; Dai, Shi-Xun; Zhang, Li-Yan; Hu, Li-Li

2004-06-01

New oxyfluoride glasses and glass ceramic codoped with Nd3+, Yb3+ and Ho3+ were prepared. The x-ray diffraction analysis revealed that the heat treatments of the oxyfluoride glasses could cause the precipitation of (Nd3+, Yb3+, Ho3+)-doped fluorite-type crystals. Very strong green up-conversion luminescence due to the Ho3+: (5F4, 5S2)rightarrow5I8 transition under 800-nm excitation was observed in these transparent glass ceramics. The intensity of the green up-conversion luminescence in a 1-mol% YbF3-containing glass ceramic was found to be about 120 times stronger than that in the precursor oxyfluoride glass. The reason for the highly efficient Ho3+ up-conversion luminescence in the oxyfluoride glass ceramics is discussed.

Lattice thermal conductivity of silicate glasses at high pressures

NASA Astrophysics Data System (ADS)

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

2016-12-01

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

Mechanical properties of zirconia reinforced lithium silicate glass-ceramic.

PubMed

Elsaka, Shaymaa E; Elnaghy, Amr M

2016-07-01

The aim of this study was to assess the mechanical properties of recently introduced zirconia reinforced lithium silicate glass-ceramic. Two types of CAD/CAM glass-ceramics (Vita Suprinity (VS); zirconia reinforced lithium silicate and IPS e.max CAD (IC); lithium disilicate) were used. Fracture toughness, flexural strength, elastic modulus, hardness, brittleness index, and microstructures were evaluated. Data were analyzed using independent t tests. Weibull analysis of flexural strength data was also performed. VS had significantly higher fracture toughness (2.31±0.17MPam(0.5)), flexural strength (443.63±38.90MPa), elastic modulus (70.44±1.97GPa), and hardness (6.53±0.49GPa) than IC (P<0.001). On the other hand, VS glass-ceramic revealed significantly a higher brittleness index (2.84±0.26μm(-1/2)) (lower machinability) than IC glass-ceramic (P<0.05). VS demonstrated a homogeneous fine crystalline structure while, IC revealed a structure with needle-shaped fine-grained crystals embedded in a glassy matrix. The VS glass-ceramic revealed a lower probability of failure and a higher strength than IC glass-ceramic according to Weibull analysis. The VS zirconia reinforced lithium silicate glass-ceramic revealed higher mechanical properties compared with IC lithium disilicate glass-ceramic. Copyright © 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

A-thermal elastic behavior of silicate glasses.

PubMed

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

2016-02-24

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

Glass formation, properties, and structure of soda-yttria-silicate glasses

NASA Technical Reports Server (NTRS)

Angel, Paul W.; Hann, Raiford E.

1991-01-01

The glass formation region of the soda yttria silicate system was determined. The glasses within this region were measured to have a density of 2.4 to 3.1 g/cu cm, a refractive index of 1.50 to 1.60, a coefficient of thermal expansion of 7 x 10(exp -6)/C, softening temperatures between 500 and 780 C, and Vickers hardness values of 3.7 to 5.8 GPa. Aqueous chemical durability measurements were made on select glass compositions while infrared transmission spectra were used to study the glass structure and its effect on glass properties. A compositional region was identified which exhibited high thermal expansion, high softening temperatures, and good chemical durability.

Efficient Nd3+→Yb3+ energy transfer processes in high phonon energy phosphate glasses for 1.0 μm Yb3+ laser

NASA Astrophysics Data System (ADS)

Rivera-López, F.; Babu, P.; Basavapoornima, Ch.; Jayasankar, C. K.; Lavín, V.

2011-06-01

Efficient Nd3+→Yb3+ resonant and phonon-assisted energy transfer processes have been observed in phosphate glasses and have been studied using steady-state and time-resolved optical spectroscopies. Results indicate that the energy transfer occurs via nonradiative electric dipole-dipole processes and is enhanced with the concentration of Yb3+ acceptor ions, having an efficiency higher than 75% for the glass doped with 1 mol% of Nd2O3 and 4 mol% of Yb2O3. The luminescence decay curves show a nonexponential character and the energy transfer microscopic parameter calculated with the Inokuti-Hirayama model gives a value of 240 × 10-40 cm6 s-1, being one of the highest reported in the literature for Nd3+-Yb3+ co-doped matrices. From the steady-state experimental absorption and emission cross-sections, a general expression for estimating the microscopic energy transfer parameter is proposed based upon the theoretical methods developed by Miyakawa and Dexter and Tarelho et al. This expression takes into account all the resonant mechanisms involved in an energy transfer processes together with other phonon-assisted nonvanishing overlaps. The value of the Nd3+→Yb3+ energy transfer microscopic parameter has been calculated to be 200 × 10-40 cm6 s-1, which is in good agreement with that obtained from the Inokuti-Hirayama fitting. These results show the importance of the nonresonant phonon-assisted Nd3+→Yb3+ energy transfer processes and the great potential of these glasses as active matrices in the development of multiple-pump-channel Yb3+ lasers.

Synchrotron X-ray spectroscopic investigations of an Nb-bearing silicate melt in contact with an aqueous fluid

NASA Astrophysics Data System (ADS)

Mayanovic, R. A.; Anderson, A. J.; Bassett, W. A.; Chou, I.

2006-05-01

Understanding the structural properties of trace elements in hydrous silicate melts in contact with a hydrothermal fluid is fundamentally important for a better assessment of the role of such elements in silicate melts being subjected to hydrothermal processes. We describe the use of synchrotron x-ray microprobe techniques and the modified hydrothermal diamond-anvil cell for in-situ spectroscopic analysis of individual phases of a silicate-melt/fluid system. Synchrotron X-ray fluorescence (XRF) and Nb K-edge X-ray absorption fine structure (XAFS) measurements were made on sectors ID20 and ID13 at the Advanced Photon Source, at the Argonne National Laboratory, on a Nb-bearing granitic glass in H2O and separately in a 1 M Na2CO3 aqueous solution at temperatures ranging from 25 to 880 °C and at up to 700 MPa of pressure. Individual phases of the Nb-glass/fluid system (at low temperatures) or the hydrous-silicate-melt/fluid system (at elevated temperatures) were probed using an X-ray beam focused to a diameter of 5 μm at the location of the sample. XRF analysis shows that the Nb partitions selectively from the hydrous silicate melt into the aqueous fluid at high temperatures in the Nb-glass/Na2CO3/H2O system but not so in the Nb-glass/H2O system. Analysis of XAFS spectra measured from the hydrous silicate melt phase of the Nb-glass/H2O sample in the 450 to 700 °C range shows that the first shell contains six oxygen atoms at a distance of ~1.98 Å. Our results suggest that reorganization of the silicate structure surrounding Nb occurs in the melt when compared to that of the starting glass. The X-ray absorption near edge structure (XANES) spectra show a pre-edge peak feature located at ~18995 eV that exhibits sharpening and becomes more intensified in the 450 to 700 °C range. Fitting of the Nb K-edge XANES spectra measured from the melt is accomplished using FEFF8.28 and an atomic model NbSi4O6-4(Na, K). The model is based on the structure of fresnoite (Ba2TiSi2O8

Enhanced frequency upconversion in Er3+-Yb3+ codoped heavy metal oxides based tellurite glasses.

PubMed

Azam, Mohd; Rai, Vineet Kumar

2018-01-24

The spectroscopic investigations on the Er 3+ /Yb 3+ ions doped/codoped TeO 2 -ZnO (TZ), TeO 2 -ZnO-WO 3 (TZW) and TeO 2 -ZnO-WO 3 -TiO 2 (TZWTi) heavy metal oxide (HMO) glasses have been made. The absorption, photoluminescence, decay curve and Judd-Ofelt analysis have been performed to optimise the optical properties of the Er 3+ /Yb 3+ ions. The effect of incorporation of HMOs like WO 3 and TiO 2 in the Er 3+ /Yb 3+ doped/codoped TZ glass on its optical properties have been investigated. The enhancement in upconversion emission intensity has been explained on the basis of efficient energy transfer and inhomogeneous local field generation around the rare earth ions. The spectroscopic quality factor, absorption and stimulated emission cross-sections, optical gain, quantum efficiency (∼17.53%), energy transfer efficiency (∼61.64%), colour purity (∼94.7%) and ionic nature of the bonding have been determined. The Er 3+ -Yb 3+ -TZWTi glass can be used in visible lasers, yellowish green optical devices and home appliances.

Interaction of water vapor with silicate glass surfaces: Mass-spectrometric investigations

NASA Astrophysics Data System (ADS)

Kudriavtsev, Yu.; Asomoza-Palacio, R.; Manzanilla-Naim, L.

2017-05-01

The secondary ion mass-spectroscopy technique was used to study the results of hydration of borosilicate, aluminosilicate, and soda-lime silicate glasses in 1H2 18O water vapor containing 97% of the isotope 18O. It is shown that hydration of the surface of the soda-lime silicate glass occurs as a result of the ion-exchange reaction with alkali metals. In the case of borosilicate and aluminosilicate glasses, water molecules decompose on the glass surface, with the observed formation of hydrogenated layer in the glass being the result of a solid-state chemical reaction—presumably, with the formation of hydroxides from aluminum and boron oxides.

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

NASA Astrophysics Data System (ADS)

Mastalska-Popiawska, J.; Izak, P.

2017-01-01

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

Spin-Glass Ground State in a Triangular-Lattice Compound YbZnGaO4

NASA Astrophysics Data System (ADS)

Ma, Zhen; Wang, Jinghui; Dong, Zhao-Yang; Zhang, Jun; Li, Shichao; Zheng, Shu-Han; Yu, Yunjie; Wang, Wei; Che, Liqiang; Ran, Kejing; Bao, Song; Cai, Zhengwei; Čermák, P.; Schneidewind, A.; Yano, S.; Gardner, J. S.; Lu, Xin; Yu, Shun-Li; Liu, Jun-Ming; Li, Shiyan; Li, Jian-Xin; Wen, Jinsheng

2018-02-01

We report on comprehensive results identifying the ground state of a triangular-lattice structured YbZnGaO4 as a spin glass, including no long-range magnetic order, prominent broad excitation continua, and the absence of magnetic thermal conductivity. More crucially, from the ultralow-temperature ac susceptibility measurements, we unambiguously observe frequency-dependent peaks around 0.1 K, indicating the spin-glass ground state. We suggest this conclusion holds also for its sister compound YbMgGaO4 , which is confirmed by the observation of spin freezing at low temperatures. We consider disorder and frustration to be the main driving force for the spin-glass phase.

Influence of F- on stark splitting of Yb3+ and the thermal expansion of silica glass

NASA Astrophysics Data System (ADS)

Cao, Yabin; Chen, Si; Shao, Chongyun; Yu, Chunlei

2018-06-01

A local phosphate/fluoride environment of Yb3+ was created in silica glass using a multi-step method. The influence of F- on the Stark splitting of Yb3+ in Al3+/P5+/F- co-doped silica glass was studied at room-temperature, in addition to its effect on the thermal expansion performance of the glass matrix. The results indicate that Yb3+ ions in Al3+/P5+/F- co-doped silica glass have a larger Stark splitting energy of 2F7/2 compared to Al3+/P5+ co-doped silica glass. Moreover, a larger integrated absorption cross-section (34.58 pm2 × nm), stimulated emission cross-section (0.63 pm2), and better thermal expansion performance (1.3062 × 10-6 K- at 100 °C) are achieved in Al3+/P5+/F- co-doped silica glass. Finally, different function mechanisms of F- in silica and phosphate glasses were analyzed and the F-Si bond was used to explain the results in silica glass. The combination of low refractive index, large Stark splitting energy of 2F7/2, and small thermal expansion makes Al3+/P5+/F- co-doped silica glass a preferred material for large mode area fibers for high-power laser applications.

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

PubMed Central

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

2015-01-01

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

Structure-Dependent Spectroscopic Properties of Yb3+-Doped Phosphosilicate Glasses Modified by SiO₂.

PubMed

Wang, Ling; Zeng, Huidan; Yang, Bin; Ye, Feng; Chen, Jianding; Chen, Guorong; Smith, Andew T; Sun, Luyi

2017-02-28

Yb 3+ -doped phosphate glasses containing different amounts of SiO₂ were successfully synthesized by the conventional melt-quenching method. The influence mechanism of SiO₂ on the structural and spectroscopic properties was investigated systematically using the micro-Raman technique. It was worth noting that the glass with 26.7 mol % SiO₂ possessed the longest fluorescence lifetime (1.51 ms), the highest gain coefficient (1.10 ms·pm²), the maximum Stark splitting manifold of ²F 7/2 level (781 cm -1 ), and the largest scalar crystal-field N J and Yb 3+ asymmetry degree. Micro-Raman spectra revealed that introducing SiO₂ promoted the formation of P=O linkages, but broke the P=O linkages when the SiO₂ content was greater than 26.7 mol %. Based on the previous 29 Si MAS NMR experimental results, these findings further demonstrated that the formation of [SiO₆] may significantly affect the formation of P=O linkages, and thus influences the spectroscopic properties of the glass. These results indicate that phosphosilicate glasses may have potential applications as a Yb 3+ -doped gain medium for solid-state lasers and optical fiber amplifiers.

Upconversion properties of Er3+/Yb3+ co-doped TeO2-TiO2-K2O glasses.

PubMed

Su, Fangning; Deng, Zaide

2006-01-01

The Er3+/Yb3+ co-doped TeO2-TiO2-K2O glasses were prepared by conventional melting procedures, and their upconversion spectra were performed. The dependence of luminescence intensity on the ratio of Yb3+/Er3+ was studied, and the relationship between green upconversion luminescence intensity and Er3+ concentration is discussed in detail. The 546 nm green upconversion luminescence intensity is optimised in the studied glasses either when the Yb3+/Er3+ ratio is 25/1 and Er3+ concentration is 0.1 mol%, or when the Yb3+/Er3+ ratio is 10/1 and Er3+ concentration is 0.15 mol%. These glasses could be one of the potential candidates for LD pumping microchip solid-state lasers.

Photoluminescence properties of Mn2+/Yb3+ co-doped oxyfluoride glasses for solar cells application

NASA Astrophysics Data System (ADS)

Yan, Ying; Chen, Zeng; Jia, Xiyang; Li, Shengjun

2018-01-01

Mn2+/Yb3+ co-doped oxyfluoride glasses were facilely synthesized in the SiO2-Al2O3-Na2O-CaF2 system. Partial crystallization processed during the preparation of the glasses, by which small amounts of CaF2 nano-crystals were formed. Under ultraviolet and blue (370-500 nm) light excitation, an efficient down-conversion involving the emission of near-infrared is realized in the Mn2+/Yb3+ co-doped oxyfluoride glasses. The near-infrared emission peaks mainly at 976 nm and secondarily at 1020 nm, which is a comfortable match with the band gap of c-Si. The variation in visible and near-infrared spectra and the decay curves of Mn2+:4T1 → 6A1 emission have been investigated to verify the possible energy transfer from Mn2+ ions to Yb3+ ions. On analyzing the energy transfer processes theoretically and experimentally, we propose that quantum cutting and down-shifting processes may occur simultaneously in the samples. We suggest that the Mn2+-Yb3+ co-doped materials can provide a novel direction to realize UV-Vis to NIR down-conversion for Si solar cells.

LOW VELOCITY SHPERE IMPACT OF SODA LIME SILICATE GLASS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morrissey, Timothy G; Fox, Ethan E; Wereszczak, Andrew A

2012-01-01

This report summarizes TARDEC-sponsored work at Oak Ridge National Laboratory (ORNL) during the FY11 involving low velocity ( 30 m/s or 65 mph) ball impact testing of Starphire soda lime silicate glass. The intent was to better understand low velocity impact response in the Starphire for sphere densities that bracketed that of rock. Five sphere materials were used: borosilicate glass, soda-lime silicate glass, steel, silicon nitride, and alumina. A gas gun was fabricated to produce controlled velocity delivery of the spheres against Starphire tile targets. Minimum impact velocities to initiate fracture in the Starphire were measured and interpreted in contextmore » to the kinetic energy of impact and the elastic property mismatch between the any of the five sphere-Starphire-target combinations.« less

Size determination of gold nanoparticles in silicate glasses by UV-Vis spectroscopy

NASA Astrophysics Data System (ADS)

Ali, Shahid; Khan, Younas; Iqbal, Yaseen; Hayat, Khizar; Ali, Muhammad

2017-01-01

A relatively easier and more accurate method for the determination of average size of metal nanoparticles/aggregates in silicate glasses based on ultraviolet visible (UV-Vis) spectra fitted with the Mie and Mie-Gans models was reported. Gold ions were diffused into sodalime silicate and borosilicate glasses by field-assisted solid-state ion-exchange technique using the same experimental parameters for both glasses. Transmission electron microscopy was performed to directly investigate the morphology and distribution of the dopant nanoparticles. UV-Vis spectra of the doped glasses showed broad surface plasmon resonance peaks in their fingerprint regions, i.e., at 525 and 500 nm for sodalime silicate and borosilicate glass matrices, respectively. These spectra were fitted with the Mie model for spherical nanoparticles and the Mie-Gans model for spheroidal nanoparticles. Although both the models were developed for colloidal nanoparticles, the size of the nanoparticles/aggregates calculated was accurate to within ˜10% in both the glass matrices in comparison to the size measured directly from the transmission electron microscope images.

Chromium speciation in oxide-type compounds: application to minerals, gems, aqueous solutions and silicate glasses

NASA Astrophysics Data System (ADS)

Farges, François

2009-09-01

Cr K-edge XANES spectra were obtained for a variety of Cr-bearing model compounds containing Cr(II), Cr(III), Cr(IV), Cr(V) and Cr(VI), in which the Cr-site symmetry is D4h, Oh and Td. The centroid position of the pre-edge feature is a better indicator of the Cr valence than the edge position. In Cr-rich oxides, higher-energy transitions must be excluded in order to refine a robust valence for Cr. The pre-edge for chromates is not unique and varies as a function of the CrO4 2- moiety distortion, which is often related to Cr-polymerization (monochromate vs. dichromate). Both the analogy with the Mn K-pre-edge information and ab initio FEFF calculations of the pre-edge feature for Cr(III) and Cr(VI) confirm the experimental trends. This methodology is applied to the Cr K-edge pre-edge feature collected in gems (emerald, spinel and ruby), the layered minerals fuchsite and kämmererite, two Cr-bearing aqueous solutions and a set of sodo-calcic silicate glasses used for bottling sparkling white wine. In emerald and fuchsite, the Cr-site is differently distorted than its ruby or spinel counterpart. In a Cr(III)-bearing aqueous solution and sodo-calcic glass, no evidence for Cr(III) with Td and C3v symmetry is detected. However, minor amounts of chromate moieties (most likely monomeric) are detected in a glass synthesized in air. Preliminary spectra for the wine bottle glass suggest that only trace amounts of chromates might possibly be present in these glasses.

Investigation of Tm3+/Yb3+ co-doped germanate-tellurite glasses for efficient 2 µm mid-infrared laser materials

NASA Astrophysics Data System (ADS)

Dou, Aoju; Shen, Lingling; Wang, Ning; Cai, Yangjian; Cai, Muzhi; Guo, Yanyan; Huang, Feifei; Tian, Ying; Xu, Shiqing; Zhang, Junjie

2018-05-01

The Tm3+/Yb3+ co-doped germanate-tellurite glasses with good thermal properties were prepared. Based on the absorption spectra and the Judd-Ofelt theory, the J-O intensity parameters (Ω t ), radiative transition probability (276.78 s- 1), fluorescence lifetime (3.89 ms), absorption and emission cross sections ({σ e} = 1.35 × 10- 20 cm2) were calculated. The 2 µm mid-infrared emission resulting from the 3F4→3H6 transition of Tm3+ sensitized by Yb3+ was observed pumped by 980 nm LD. Besides, the energy transfer mechanism between Yb3+ and Tm3+ was thoroughly discussed. The measured 2 µm emission lifetime of Tm3+/Yb3+ co-doped glass can reach as high as 2.38 ms. The above results showed that Tm3+/Yb3+ co-doping glass could be expected to be a promising material to achieve high efficient 2 µm lasing with a 980 nm LD pumping.

Conduction mechanism in bismuth silicate glasses containing titanium

NASA Astrophysics Data System (ADS)

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

2014-11-01

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

Optical waveguides in fluoride lead silicate glasses fabricated by carbon ion implantation

NASA Astrophysics Data System (ADS)

Shen, Xiao-liang; Wang, Yue; Zhu, Qi-feng; Lü, Peng; Li, Wei-nan; Liu, Chun-xiao

2018-03-01

The carbon ion implantation with energy of 4.0 MeV and a dose of 4.0×1014 ions/cm2 is employed for fabricating the optical waveguide in fluoride lead silicate glasses. The optical modes as well as the effective refractive indices are measured by the prism coupling method. The refractive index distribution in the fluoride lead silicate glass waveguide is simulated by the reflectivity calculation method (RCM). The light intensity profile and the energy losses are calculated by the finite-difference beam propagation method (FD-BPM) and the program of stopping and range of ions in matter (SRIM), respectively. The propagation properties indicate that the C2+ ion-implanted fluoride lead silicate glass waveguide is a candidate for fabricating optical devices.

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

NASA Astrophysics Data System (ADS)

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

2016-12-01

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

Enhanced NIR downconversion luminescence by precipitating nano Ca5(PO4)3F crystals in Eu2+-Yb3+ co-doped glass

NASA Astrophysics Data System (ADS)

Li, Chen; Song, Zhiguo; Li, Yongjin; Lou, Kai; Qiu, Jianbei; Yang, Zhengwen; Yin, Zhaoyi; Wang, Xue; Wang, Qi; Wan, Ronghua

2013-10-01

Eu2+-Yb3+ co-doped transparent glass-ceramic containing nano-Ca5(PO4)3F (FAP) was prepared in reducing atmosphere. XRD and TEM analysis indicated that nano-FAP about 40 nm precipitated homogeneously in glass matrix after heat treatment. Confirmed by spectroscopy measurements, the crystal-like absorption and emission of Eu2+ indicated the partition of Eu2+ into FAP nanocrystals in glass ceramic. NIR emission due to the transition 2F→2F of Yb3+ ions (about 980-1100 nm) was observed from glasses under ultraviolet excitation, ascribed to downconversion from Eu2+ to Yb3+, which can be enhanced by precipitating nano-FAP crystals. The results indicated that Eu2+-Yb3+ co-doped glass-ceramic embedding with nano-FAP is a promising candidate as downconversion materials for enhancing conversion efficiency of solar cells.

Enhanced frequency upconversion study in Er3+/Yb3+ doped/codoped TWTi glasses

NASA Astrophysics Data System (ADS)

Azam, Mohd; Rai, Vineet Kumar

2018-04-01

Er3+/Yb3+ doped/codoped TeO2-WO3-TiO2 (TWTi) glasses have been prepared by using the melt-quenching technique. The upconversion (UC) emission spectra of the developed glasses have been recorded upon 980 nm laser excitation. Three intense UC emission bands have been observed within the green and red region centered at ˜532 nm, ˜553 nm and ˜669 nm corresponding to the 2H11/2→4I15/2, 4S3/2→4I15/2 and 4F9/2→4I15/2 transitions respectively in the singly Er3+ doped glass. On introducing Yb3+ ions in the singly Er3+ doped glass, an enhancement of about ˜ 12 times and ˜50 times in the green and red bands respectively have been observed even at low pump power ˜ 364 mW followed by two photon absorption process. Colour tunability from yellowish green to pure green colour region has been observed on varying the pump power. The prepared glass can be used to produce NIR to green upconverter and colour tunable display devices.

Water speciation in sodium silicate glasses (quenched melts): A comprehensive NMR study

NASA Astrophysics Data System (ADS)

Xue, X.; Kanzaki, M.; Eguchi, J.

2012-12-01

Dissolution mechanism of water is an important factor governing how the dissolved water affects the physical and thermodynamic properties of silicate melts and glasses. Our previous studies have demonstrated that 1H MAS NMR in combination with 29Si-1H and 27Al-1H double-resonance NMR experiments is an effective approach for unambiguously differentiating and quantifying different water species in quenched silicate melts (glasses). Several contrasting dissolution mechanisms have been revealed depending on the melt composition: for relatively polymerized melts, the formation of SiOH/AlOH species (plus molecular H2O) and depolymerization of the network structure dominate; whereas for depolymerized Ca-Mg silicate melts, free OH (e.g. MgOH) become increasingly important (cf. [1]). The proportion of free OH species has been shown to decrease with both increasing melt polymerization (silica content) and decreasing field strength of the network modifying cations (from Mg to Ca). Our previous 1H and 29Si MAS NMR results for hydrous Na silicate glasses of limited compositions (Na2Si4O9 and Na2Si2O5) were consistent with negligible free OH (NaOH) species and depolymerizing effect of water dissolution [2]. On the other hand, there were also other studies that proposed the presence of significant NaOH species in hydrous glasses near the Na2Si2O5 composition. The purpose of this study is apply the approach of combined 1H MAS NMR and double-resonance (29Si-1H and 23Na-1H) NMR to gain unambiguous evidence for the OH speciation in Na silicate glasses (melts) as a function of composition. Hydrous Na silicate glasses containing mostly ≤ 1 wt% H2O for a range of Na/Si ratios from 0.33 to 1.33 have been synthesized by rapidly quenching melts either at 0.2 GPa using an internally heated gas pressure vessel or at 1 GPa using a piston cylinder high-pressure apparatus. NMR spectra have been acquired using a 9.4 T Varian Unity-Inova spectrometer. The 29Si and 1H chemical shifts are

Fluorescence investigation of Ho3+ in Yb3+ sensitized mixed-alkali bismuth gallate glasses.

PubMed

Lin, H; Zhang, Y Y; Pun, E Y B

2008-12-15

Efficient 2.0 microm infrared and visible upconversion emissions have been observed in Ho3+/Yb3+ co-doped mixed-alkali bismuth gallate (LKBBG) glasses having a maximum-phonon energy of 673 cm(-1). The Judd-Ofelt parameters Omega2, Omega4 and Omega6 of Ho3+ indicate that there is a high asymmetry and strong covalent environment in LKBBG glasses. The large absorption and emission cross-sections of Yb3+ confirm that it is a suitable sensitizer for capturing and transferring pump energy to Ho3+. The emission cross-section profile for the 5I7-->5I8 transition is derived using the reciprocity method and the peak value is 5.54 x 10(-21)cm2, which is much larger than the value in fluorozircoaluminate glasses. LKBBG glasses exhibit low maximum-phonon energy and large refractive index, and it is possible to achieve an effective 1.66 microm U-band emission of Ho3+ under 900 nm laser radiation.

Calcium titanium silicate based glass-ceramic for nuclear waste immobilisation

NASA Astrophysics Data System (ADS)

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

2018-04-01

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

Structure-Dependent Spectroscopic Properties of Yb3+-Doped Phosphosilicate Glasses Modified by SiO2

PubMed Central

Wang, Ling; Zeng, Huidan; Yang, Bin; Ye, Feng; Chen, Jianding; Chen, Guorong; Smith, Andew T.; Sun, Luyi

2017-01-01

Yb3+-doped phosphate glasses containing different amounts of SiO2 were successfully synthesized by the conventional melt-quenching method. The influence mechanism of SiO2 on the structural and spectroscopic properties was investigated systematically using the micro-Raman technique. It was worth noting that the glass with 26.7 mol % SiO2 possessed the longest fluorescence lifetime (1.51 ms), the highest gain coefficient (1.10 ms·pm2), the maximum Stark splitting manifold of 2F7/2 level (781 cm−1), and the largest scalar crystal-field NJ and Yb3+ asymmetry degree. Micro-Raman spectra revealed that introducing SiO2 promoted the formation of P=O linkages, but broke the P=O linkages when the SiO2 content was greater than 26.7 mol %. Based on the previous 29Si MAS NMR experimental results, these findings further demonstrated that the formation of [SiO6] may significantly affect the formation of P=O linkages, and thus influences the spectroscopic properties of the glass. These results indicate that phosphosilicate glasses may have potential applications as a Yb3+-doped gain medium for solid-state lasers and optical fiber amplifiers. PMID:28772601

Ag-doped Lithium alumino silicate photostructurable glass for microdevice fabrication

NASA Astrophysics Data System (ADS)

Mishra, Richa; Goswami, Madhumita; Krishnan, Madangopal

2018-04-01

Ag-doped LAS glass of composition (wt.%):74SiO2-6Al2O3-15Li2O-5X (X=other additives) were prepared by melt-quench technique and characterized for thermal and optical properties using DTA and UV-Visible spectrometer. XRD technique was used for phase identification in the heat treated glasses. Glass samples were exposed to UV-light for conversion of Ce3+ to Ce4+ state and Ag+ into Ago metallic state. DTA shows a lower crystallization temperature (Tp) at around 605°C for exposed samples as compared to unexposed base glass which is at around 625°C. UV-Visible spectra shows a broad band at around 305nm which indicates Ce3+ in base glass whereas in case of UV-exposed sample the reduced peak intensity indicates conversion of Ce3+ to Ce4+ ions, which also confirm formation of Ago in glass samples. Ag agglomeration was also confirmed from the band position at 430nm in heat treated sample, found responsible for early growth of meta-silicate phase in exposed sample. The meta-silicate phase was selectively etched for fabrication of micro-devices.

Effect of cryogenic temperature on spectroscopic and laser properties of Er, Yb-doped potassium-lanthanum phosphate glass

NASA Astrophysics Data System (ADS)

Švejkar, Richard; Šulc, Jan; Němec, Michal; Jelínková, Helena; Nitsch, Karel; Cihlář, Antonín.; Král, Robert; Nejezchleb, Karel; Nikl, Martin

2017-05-01

Glass matrix doped with rare-earth ions is a promising laser active medium for high power laser systems. Due to amorphous structure of glasses the absorption and emission spectra lines are broader in comparison with crystalline materials thus pumping radiation can be absorbed efficiently, moreover much broader gain bandwidth is suitable for generation of ultra-short pulses. Another advantage of the glass matrix is the possibility to fabricate large volume ingots and simultaneously preservation of sufficient optical quality. The lower thermal conductivity of glasses can be compensated by geometry of the active medium for instance shaped into fibres or discs. We present temperature dependence of spectroscopic and laser properties of newly developed Er, Yb - doped potassium-lanthanum phosphate glass, which is appropriate for generation of radiation at 1.53 μm. The sample of Er,Yb:KLaP glassy mixture was cut into disc shape with dimensions of 2.5 mm (thickness) and 5 mm (diameter) and its faces were polished plan-parallelly without being anti-reflection coated. The temperature dependence of the transmission and emission spectra Er,Yb:KLaP together with the fluorescence decay time were measured the temperature range from 80 to 400 K. The fluorescence lifetime of manifold 4I13/2 (upper laser level) prolonged and the intensity of up-conversion radiation decreased with decreasing temperature. The longitudinal excitation of Er,Yb:KLaP was carried out by a fibre-coupled laser diode (pulse duration 2 ms, repetition rate 10 Hz, pump wavelength 969 nm). Laser resonator was hemispherical, with flat pumping mirror (HR @ 1.5 μm) and spherical output coupler (R = 98 % @ 1.5 - 1.6 μm). The Er,Yb:KLaP glass laser properties were investigated in the temperature range 80 - 300 K. The highest slope efficiency with respect to absorbed pumped power was 6.1 % at 80 K. The maximum output of peak amplitude power was 0.71 W at 80 K, i.e. 1.2 times higher than at 300 K. Tunability of laser

Mechanisms and concentrations dependence of up-conversion luminescence in Tm^3^+/Yb^3^+ codoped oxyfluoride glass-ceramics [rapid communication

NASA Astrophysics Data System (ADS)

Zhang, Junjie; He, Dongbing; Duan, Zhongchao; Zhang, Liyan; Dai, Shixun; Hu, Lili

2005-04-01

The up-conversion properties of Tm3+/Yb3+ codoped oxyfluoride glass-ceramics under 980 nm excitation were investigated. Intense blue up-conversion luminescence due to the Tm3+: 1G4 → 3H6 transition was observed in the glass-ceramics. The intensity of the blue up-conversion luminescence in a 1 mol% YbF3-containing glass-ceramic was found to be about 40 times stronger than that in the precursor oxyfluoride glass. The up-conversion mechanism is proposed. The reason for the intense Tm3+ up-conversion luminescence in the oxyfluoride glass-ceramics and the concentrations dependence of upconversion luminescence are also discussed.

Water-bearing, high-pressure Ca-silicates

NASA Astrophysics Data System (ADS)

Németh, Péter; Leinenweber, Kurt; Ohfuji, Hiroaki; Groy, Thomas; Domanik, Kenneth J.; Kovács, István J.; Kovács, Judit S.; Buseck, Peter R.

2017-07-01

Water-bearing minerals provide fundamental knowledge regarding the water budget of the mantle and are geophysically significant through their influence on the rheological and seismic properties of Earth's interior. Here we investigate the CaO-SiO2-H2O system at 17 GPa and 1773 K, corresponding to mantle transition-zone condition, report new high-pressure (HP) water-bearing Ca-silicates and reveal the structural complexity of these phases. We document the HP polymorph of hartrurite (Ca3SiO5), post-hartrurite, which is tetragonal with space group P4/ncc, a = 6.820 (5), c = 10.243 (8) Å, V = 476.4 (8) Å3, and Z = 4, and is isostructural with Sr3SiO5. Post-hartrurite occurs in hydrous and anhydrous forms and coexists with larnite (Ca2SiO4), which we find also has a hydrous counterpart. Si is 4-coordinated in both post-hartrurite and larnite. In their hydrous forms, H substitutes for Si (4H for each Si; hydrogrossular substitution). Fourier transform infrared (FTIR) spectroscopy shows broad hydroxyl absorption bands at ∼3550 cm-1 and at 3500-3550 cm-1 for hydrous post-hartrurite and hydrous larnite, respectively. Hydrous post-hartrurite has a defect composition of Ca2.663Si0.826O5H1.370 (5.84 weight % H2O) according to electron-probe microanalysis (EPMA), and the Si deficiency relative to Ca is also observed in the single-crystal data. Hydrous larnite has average composition of Ca1.924Si0.851O4H0.748 (4.06 weight % H2O) according to EPMA, and it is in agreement with the Si occupancy obtained using X-ray data collected on a single crystal. Superlattice reflections occur in electron-diffraction patterns of the hydrous larnite and could indicate crystallographic ordering of the hydroxyl groups and their associated cation defects. Although textural and EPMA-based compositional evidence suggests that hydrous perovskite may occur in high-Ca-containing (or low silica-activity) systems, the FTIR measurement does not show a well-defined hydroxyl absorption band for this

Survey and research on up-conversion emission character and energy transition of Yb3+/Er3+/Tm3+ co-doped phosphate glass and glass ceramic

NASA Astrophysics Data System (ADS)

Yu, Yin; Song, Feng; Ming, Chengguo; Liu, Jiadong; Li, Wei; Liu, Yanling; Zhao, Hongyan

2012-11-01

By conventional high-temperature melting method, Yb3+/Er3+/Tm3+ co-doped phosphate glass was synthesized. After annealing the precursor glass, the phosphate glass ceramic (GC) was obtained. By measuring the X-ray diffraction (XRD) spectrum, it is proved that the LiYbP4O12 and Li6P6O18 nano-crystals have existed in the phosphate GC. The up-conversion (UC) emission intensity of the GC is obvious stronger compared to that of the glass. The reason is that the shorter distance between rare earth ions in the glass ceramic increases the energy transitions from the sensitized ions (Yb3+) to the luminous ions (Er3+ and Tm3+). By studying the dependence of UC emissions on the pump power, the 523 and 546 nm green emissions of Er3+ ions in the glass are two-photon processes. But in the glass ceramic, they are two/three-photon processes. The phenomenon implies that a three-photon process has participated in the population of the two green emissions. Using Dexter theory, we discuss the energy transitions of Er3+ and Tm3+. The results indicate the energy transition of Tm3+ to Er3+ is very strong in the GC, which changes the population mechanism of UC emissions of Er3+.

Influence of Thermal Annealing and a Glass Coating on the Strength of Soda-Lime-Silicate Glass

DTIC Science & Technology

2017-11-01

ARL-TN-0858 ● NOV 2017 US Army Research Laboratory Influence of Thermal Annealing and a Glass Coating on the Strength of Soda...NOV 2017 US Army Research Laboratory Influence of Thermal Annealing and a Glass Coating on the Strength of Soda-Lime-Silicate Glass... Research Directorate, ARL Approved for public release; distribution is unlimited. ii REPORT DOCUMENTATION PAGE Form Approved OMB

Dynamic Fatigue of a Titanium Silicate Glass

NASA Technical Reports Server (NTRS)

Tucker, Dennis S.; Nettles, Alan T.; Cagle, Holly A.; Smith, W. Scott (Technical Monitor)

2002-01-01

A dynamic fatigue study was performed on a Titanium Silicate Glass in order to assess its susceptibility to delayed failure. Fracture mechanics techniques were used to analyze the results for the purpose of making lifetime predictions for optical elements made from this material. The material has reasonably good resistance (N=23 to stress corrosion in ambient conditions).

NIR luminescence studies on Er{sup 3+}:Yb{sup 3+} co-doped sodium telluroborate glasses for lasers and optical amplifer applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Annapoorani, K.; Marimuthu, K., E-mail: mari-ram2000@yahoo.com; Murthy, N. Suriya

2016-05-23

Er{sup 3+}:Yb{sup 3+} co-doped Sodium telluroborate glasses were prepared with the chemical composition (49.5–x)B{sub 2}O{sub 3}+25TeO{sub 2}+5Li{sub 2}CO{sub 3}+10ZnO+10NaF+0.5Er{sub 2}O{sub 3}+xYb{sub 2}O{sub 3} (where x= 0.1, 0.5, 1.0 and 2.0 in mol %) following the melt quenching technique. With the addition of Yb{sup 3+} ions into Er{sup 3+} ions in the prepared glasses, the absorption cross-section values were found to increase due to the effective energy transfer from {sup 2}F{sub 5/2} level of Yb{sup 3+} ions to the {sup 4}I{sub 11/2} level of Er{sup 3+} ions. The fluorescence around 1550 nm correspond to the {sup 4}I{sub 13/2}→{sup 4}I{sub 15/2} transition wasmore » observed under 980 nm pumping. Among the present glasses, integrated intensity was found to be higher for 1.0 mol% Yb{sup 3+} ion glass. The parameters such as stimulated emission cross- section, Gain bandwidth and quantum efficiency of the {sup 4}I{sub 13/2}→{sup 4}I{sub 15/2} transition was found to be higher for the NTBE1.0Y glass and the same is suggested for potential NIR lasers and optical amplifier applications.« less

Research on up- and down-conversion emissions of Er3+/Yb3+ co-doped phosphate glass ceramic

NASA Astrophysics Data System (ADS)

Ming, Chengguo; Song, Feng; An, Liqun; Ren, Xiaobin; Yuan, Yize; Cao, Yang; Wang, Gangzhi

2012-12-01

By high-temperature melting method and thermal treatment technology, Er3+/Yb3+ co-doped phosphate glass and glass ceramic samples were prepared. The luminescence spectra of the glass and glass ceramic samples were studied under 975 nm excitation. In visible and near-infrared bands, the emission intensity of the glass ceramic is stronger than that of the glass. The glass ceramic can comprehensively improve the luminous characters of the precursor glass. The phosphate glass ceramic will be valuable luminescence materials.

Strong emission in Yb3+/Er3+ co-doped phosphate glass ceramics

NASA Astrophysics Data System (ADS)

Liu, Yanling; Song, Feng; Jia, Guozhi; Zhang, Yanbang; Tang, Yi

Yb3+/Er3+ co-doped phosphate glass and glass ceramics were prepared by high-temperature melting method. The X-ray diffraction, transmission electron micrographs, up-conversion and infrared emissions, photothermal conversion properties of the samples have been measured. The results showed the annealing time had a great impact on the microstructure and luminous performance of the phosphate glass. At the beginning of annealing, the metaphosphate crystals were firstly dissolved out. The metaphosphate crystals gradually turned into the orthophosphate with the increasing of annealing time. The emission intensity of the sample was obviously improved after the precursor glass was annealed. The up-conversion and infrared emissions of the sample annealed at 600 °C for 24 h, reached the maximum intensity. Compared with the photothermal properties of glass, the lower photothermal conversion efficiency of the glass ceramics testified the strong emission.

Intense blue up-conversion luminescence in Tm 3+/Yb 3+ codoped oxyfluoride glass-ceramics containing β-PbF 2 nanocrystals

NASA Astrophysics Data System (ADS)

Zhang, Junjie; Duan, Zhongchao; He, Dongbing; Dai, Shixun; Zhang, Liyan; Hu, Lili

2005-12-01

Up-conversion luminescence properties of a Tm 3+/Yb 3+ codoped oxyfluoride glass-ceramics under 980 nm excitation are investigated. Intense blue emission centered at 476 nm, corresponding to 1G 4 → 3H 6 transitions of Tm 3+ was simultaneously observed in the transparent oxyfluoride glass ceramics at room temperature. The intensity of the blue up-conversion luminescence in a 1 mol% YbF 3-containing glass-ceramic was found to be about 40 times stronger than that in the precursor oxyfluoride glass. The reason for the intense Tm 3+ up-conversion luminescence in the oxyfluoride glass-ceramics is discussed. The dependence of up-conversion intensities on excitation power and possible up-conversion mechanism are also evaluated.

Intense blue up-conversion luminescence in Tm3+/Yb3+ codoped oxyfluoride glass-ceramics containing beta-PbF2 nanocrystals.

PubMed

Zhang, Junjie; Duan, Zhongchao; He, Dongbing; Dai, Shixun; Zhang, Liyan; Hu, Lili

2005-12-01

Up-conversion luminescence properties of a Tm3+/Yb3+ codoped oxyfluoride glass-ceramics under 980 nm excitation are investigated. Intense blue emission centered at 476 nm, corresponding to 1G4-->3H6 transitions of Tm3+ was simultaneously observed in the transparent oxyfluoride glass ceramics at room temperature. The intensity of the blue up-conversion luminescence in a 1 mol% YbF3-containing glass-ceramic was found to be about 40 times stronger than that in the precursor oxyfluoride glass. The reason for the intense Tm3+ up-conversion luminescence in the oxyfluoride glass-ceramics is discussed. The dependence of up-conversion intensities on excitation power and possible up-conversion mechanism are also evaluated.

Yb3+-Er3+-Tm3+ co-doped nano-glass-ceramics tuneable up-conversion phosphor

NASA Astrophysics Data System (ADS)

Méndez-Ramos, J.; Rodriguez, V. D.; Tikhomirov, V. K.; Del-Castillo, J.; Yanes, A. C.

2008-08-01

Transparent Yb3+-Er3+-Tm3+ co-doped nano-glass-ceramics have been prepared, 32(SiO{2}) 9(AlO{1.5}) 31.5(CdF{2}) 18.5(PbF{2}) 5.5(ZnF{2}): 3.5(Yb-Er-TmF{3}) mol%, where the co-dopants partition mostly to the fluoride PbF{2}-based nano-crystals. A comparative study of the up-conversion luminescence in nano-glass-ceramics and its precursor glass indicates that these materials can be used as blue/green/red tuneable up-conversion phosphor, in particular for white light generation. A ratio between blue, green and red emission bands of the Tm3+ and Er3+ can be widely varied with nano-ceramming of the precursor glass and with changing a pump power of luminescence. The change in the ratio between the blue, green and red emission bands is explained to be due to substantial lowering phonon energy and shortening of inter-dopant distances with nano-ceramming of the precursor glass and due to change in the ratio of 2- and 3-photon up-conversion processes with pump power.

The influence of SrO and CaO in silicate and phosphate bioactive glasses on human gingival fibroblasts.

PubMed

Massera, J; Kokkari, A; Närhi, T; Hupa, L

2015-06-01

In this paper, we investigate the effect of substituting SrO for CaO in silicate and phosphate bioactive glasses on the human gingival fibroblast activity. In both materials the presence of SrO led to the formation of a CaP layer with partial Sr substitution for Ca. The layer at the surface of the silicate glass consisted of HAP whereas at the phosphate glasses it was close to the DCPD composition. In silicate glasses, SrO gave a faster initial dissolution and a thinner reaction layer probably allowing for a continuous ion release into the solution. In phosphate glasses, SrO decreased the dissolution process and gave a more strongly bonded reaction layer. Overall, the SrO-containing silicate glass led to a slight enhancement in the activity of the gingival fibroblasts cells when compared to the SrO-free reference glass, S53P4. The cell activity decreased up to 3 days of culturing for all phosphate glasses containing SrO. Whereas culturing together with the SrO-free phosphate glass led to complete cell death at 7 days. The glasses containing SrO showed rapid cell proliferation and growth between 7 and 14 days, reaching similar activity than glass S53P4. The addition of SrO in both silicate and phosphate glasses was assumed beneficial for proliferation and growth of human gingival fibroblasts due to Sr incorporation in the reaction layer at the glass surface and released in the cell culture medium.

Interactions of silicate glasses with aqueous environments under conditions of prolonged contact and flow

NASA Technical Reports Server (NTRS)

Barkatt, Aaron; Saad, E. E.; Adiga, R. B.; Sousanpour, W.; Barkatt, AL.; Feng, X.; O'Keefe, J. A.; Alterescu, S.

1988-01-01

This paper discusses mechanisms involving saturation and reactions that lead to the formation of altered phases in silicate glasses considered for use in geologic repositories for nuclear waste. It is shown that the rate of dissolution of silicate glasses exposed to a broad range of contact times, leachant compositions, and surface-to-volume ratios is strongly affected by the presence of reactive species such as Al, Mg, and Fe. The reactive materials may originate in the leachant or, under conditions of high surface-to-volume ratio, in the glass itself. The effects of glass composition on the course of the corrosion process can be viewed in terms of the formation of a surface layer on the leached glass; the type, composition, and structure of this layer control the dissolution behavior of the glass.

Study of upconversion fluorescence property of novel Er3+/Yb3+ co-doped tellurite glasses.

PubMed

Xu, Tie-Feng; Li, Guang-Po; Nie, Qiu-Hua; Shen, Xiang

2006-06-01

Er3+/Yb3+ co-doped TeO2-B2O3-Nb2O5-ZnO (TBN) glasses were prepared. The absorption spectra and upconversion luminescence spectra of TBN glasses were measured and analyzed. The upconversion emission bands centered at 530, 546 and 658 nm were observed under the excitation at 975 nm, corresponding to the transitions of 2H11/2-->4I15/2, 4S3/2-->4I15/2 and 4F9/2-->4I15/2 respectively. The ratio of red emission to green emission increases with an increasing of Yb3+ ions concentration. According to the quadratic dependence on excitation power, the possible upconversion mechanisms and processes were discussed.

Spectral properties of Er3+/Yb3+ codoped tungsten-tellurite glasses.

PubMed

Shen, Xiang; Nie, QiuHua; Xu, TieFeng; Gao, Yuan

2005-07-01

The spectral properties of Er3+/Yb3+ codoped tungsten-tellurite (WT) glasses have been investigated. The measured absorption spectra are analyzed by Judd-Ofelt theory. The compositional change of intensity parameter omega2 is attributed to the change in the covalency between the Er3+ and oxygen ions, the asymmetry in the local structures around the Er3+ ions can be neglected. The lifetimes of 4I(13/2) level of Er3+ in WT glasses are measured and comparable with other TeO2-based glasses. The stimulated emission cross-section is calculated based on McCumber theory. The fluorescence full width at half maximum (FWHM) and the emission cross-section (sigma(peak)) of the 4I(13/2) --> 4I(15/2) transition of Er3+ in different glass hosts have been compared. The suitability of such WT glasses as host materials for 1.5 microm broadband amplification is discussed.

Optical transitions of Ho(3+) in oxyfluoride glasses and upconversion luminescence of Ho(3+)/Yb(3+)-codoped oxyfluoride glasses.

PubMed

Feng, Li; Wu, Yinsu

2015-05-05

Optical properties of Ho(3+)-doped SiO2-BaF2-ZnF2 glasses have been investigated on the basis of the Judd-Ofelt theory. Judd-Ofelt intensity parameters, radiative transition probabilities, fluorescence branching ratios and radiative lifetimes have been calculated for different glass compositions. Upconversion emissions were observed in Ho(3+)/Yb(3+)-codoped SiO2-BaF2-ZnF2 glasses under 980nm excitation. The effects of composition, concentration of the doping ions, and excitation pump power on the upconversion emissions were also systematically studied. Copyright © 2015 Elsevier B.V. All rights reserved.

Compositional investigation of ∼2 μm luminescence of Ho{sup 3+}-doped lead silicate glass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Xueqiang; Huang, Feifei; Gao, Song

2015-11-15

Graphical abstract: Ho{sup 3+}-doped lead silicate glass with lowest maximum phonon energy possesses highest ∼2 μm luminescence intensity. - Highlights: • With increment of lead oxide, maximum phonon energy in lead silicate glass decreased. • ∼2 μm luminescent intensity of Ho{sup 3+} increased with increment of lead oxide. • Lowest lead oxide content glass possesses highest quantum efficiency due to low maximum phonon energy. - Abstract: Lead silicate glass samples with varying lead oxide content were prepared in this study, and their luminescent properties were examined and analyzed. It was found that with increasing lead oxide content, the maximum phononmore » energies of the glass samples decreased, while their spontaneous transition probabilities first increased and then decreased. The influence of the spontaneous transition rate, A{sub 10}, and the multi-phonon relaxation rate, W{sub 10}, on the sample luminescent properties was analyzed using rate equations. As a result, it was found that with increasing lead oxide content, W{sub 10}/A{sub 10} decreased, while the quantum efficiency increased. Thus, the luminescent intensity at ∼2 μm increased in the glass samples with increased lead oxide content. The high luminescent intensity and long lifetime indicate that silicate glasses containing high levels of lead oxide could potentially be used in ∼2 μm lasers.« less

Optically active Er-Yb doped glass films prepared by pulsed laser deposition

NASA Astrophysics Data System (ADS)

Serna, R.; Ballesteros, J. M.; Jiménez de Castro, M.; Solis, J.; Afonso, C. N.

1998-08-01

Active rare-earth Er3+-Yb3+ co-doped phosphate glass films are produced in a single step by pulsed laser deposition. The films are multimode waveguides and exhibit the highest refractive index, optical density and 1.54 μm photoluminescence intensity and lifetime when deposited at low oxygen pressure (Pox⩽4×10-5 Torr). The density of the films obtained under these conditions is higher than that of the target material as a consequence of the high kinetic energy of the species generated during ablation. Luminescent emission can be excited by optical pumping the Er3+ ions either directly or through cross-relaxation of the Yb3+. Post-deposition annealing allows us to improve the luminescence performance.

Broadband ∼3 μm mid-infrared emission in Dy3+/Yb3+ co-doped germanate glasses

NASA Astrophysics Data System (ADS)

Shen, Lingling; Wang, Ning; Dou, Aoju; Cai, Yangjian; Tian, Ying; Huang, Feifei; Xu, Shiqing; Zhang, Junjie

2018-01-01

The Dy3+/Yb3+ co-doped germanate glasses with good thermal stability have been prepared by the conventional melt quenching method. The J-O intensity parameters and radiative properties such as spontaneous transition probilities (Arad), fluorescence branching ratios (β) and radiative lifetimes (τrad) were investigated according to the absorption spectrum based on Judd-Ofelt theory. An intense emission around ∼3 μm with the FWHM reaching to 322 nm was obtained in present glasses excited by 980 nm LD. The high spontaneous transition probability (63.94 s-1), large emission cross section (6.0 × 10-21 cm2) and superior gain performance corresponding to the Dy3+: 6H13/2 → 6H15/2 transition were obtained. Moreover, the energy transfer mechanism was analyzed qualitatively, and it was found that the energy transfer from Yb3+: 2F5/2 to Dy3+: 6H5/2 level could be quite efficient. Hence, the results indicated that the prepared Dy3+/Yb3+ co-doped germanate glass could be a potential candidate for ∼3 μm mid-infrared solid state lasers.

Nonlinear dynamics and instability of aqueous dissolution of silicate glasses and minerals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Yifeng; Jove-Colon, Carlos F.; Kuhlman, Kristopher L.

2016-07-22

Aqueous dissolution of silicate glasses and minerals plays a critical role in global biogeochemical cycles and climate evolution. The reactivity of these materials is also important to numerous engineering applications including nuclear waste disposal. The dissolution process has long been considered to be controlled by a leached surface layer in which cations in the silicate framework are gradually leached out and replaced by protons from the solution. This view has recently been challenged by observations of extremely sharp corrosion fronts and oscillatory zonings in altered rims of the materials, suggesting that corrosion of these materials may proceed directly through congruentmore » dissolution followed by secondary mineral precipitation. Here we show that complex silicate material dissolution behaviors can emerge from a simple positive feedback between dissolution-induced cation release and cation-enhanced dissolution kinetics. This self-accelerating mechanism enables a systematic prediction of the occurrence of sharp dissolution fronts (vs. leached surface layers), oscillatory dissolution behaviors and multiple stages of glass dissolution (in particular the alteration resumption at a late stage of a corrosion process). In conclusion, our work provides a new perspective for predicting long-term silicate weathering rates in actual geochemical systems and developing durable silicate materials for various engineering applications.« less

Highly efficient green up-conversion luminescence of Nd3+-Yb3+-Ho3+ codoped fluorite-type nanocrystals in transparent glass ceramics

NASA Astrophysics Data System (ADS)

Qiu, Jianbei; Kawamoto, Yoji; Zhang, Junjie

2002-11-01

Oxyfluoride glasses were developed with composition 30SiO2[middle dot]15AlO1.5[middle dot]28PbF2[middle dot]22CdF2[middle dot](4.8-x)GdF3[middle dot]0.1NdF3[middle dot]0.1HoF3[middle dot]xYbF3 (x=0, 0.1, 0.2, 0.5, 1, 2, 3, 4, and 4.8) in mole percent. Powder x-ray diffraction analysis revealed that the heat treatments of the oxyfluoride glasses at 450 degC for 0.5 h cause the precipitation of Nd3+-Yb3+-Ho3+ codoped fluorite-type nanocrystals of about 16.3 nm in diameter in the glass matrix. These transparent glass ceramics exhibited very strong green up-conversion luminescence due to the Ho3+: (5F4, 5S2)[right arrow]5I8 transition under 800 nm excitation. The intensity of the green up-conversion luminescence in a 1 mol % YbF3-containing glass ceramic was found to be about 120 times stronger than that in the precursor oxyfluoride glass. The reason for the highly efficient Ho3+ up-conversion luminescence in the oxyfluoride glass ceramics is discussed. An up-conversion mechanism is also proposed.

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

NASA Astrophysics Data System (ADS)

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

2016-01-01

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

2.7 μm emission properties of Er3+ doped tungsten-tellurite glass sensitized by Yb3+ ions.

PubMed

Guo, Yanyan; Ma, Yaoyao; Huang, Feifei; Peng, Yapei; Zhang, Liyan; Zhang, Junjie

2013-07-01

With a 980 nm laser diode (LD) pumped, the sensitized effect of Yb(3+) ions on 2.7 μm emission properties and energy transfer mechanism in Yb(3+)/Er(3+) co-doped tungsten-tellurite glass were investigated in present paper. Based on absorption spectra, Judd-Ofelt parameters and radiative transition probabilities were calculated and analyzed. The emission spectra were tested and the optimized concentration ratio of Yb(3+) to Er(3+) ions was found to be 3:0.5 with a largest calculated emission cross-section (6.05×10(-21) cm(2)) corresponding to Er(3+):(4)I11/2→(4)I13/2 transition. When the concentration ratio of Yb(3+) to Er(3+) ions was 4:0.5, 1.5 μm and 2.7 μm emission decreased while up-conversion increased. The decreased 1.5 μm and 2.7 μm emission were induced by the saturation of Er(3+):(4)I13/2 level. In brief, the advantageous spectroscopic characteristics indicated that Yb(3+)/Er(3+) co-doped tungsten-tellurite glass may be a promising candidate for application of 2.7 μm emission. Copyright © 2013 Elsevier B.V. All rights reserved.

Blue upconversion in Yb3+/Tm3+ co-doped silica fiber based on glass phase-separation technology

NASA Astrophysics Data System (ADS)

Yang, Yu; Chu, Yingbo; Chen, Zhangru; Xing, Yingbin; Hu, Xionwei; Li, Haiqing; Peng, Jinggang; Dai, Nengli; Li, Jinyan; Yang, Luyun

2018-02-01

Yb3+/Tm3+ co-doped silica fiber was prepared successfully by glass phase-separation technology. The measured refractive index profile indicated that the active fiber core had an excellent uniformity. The highest emission intensity was obtained in a sample with a Yb3+ concentration of 0.3 mol/L and a Tm3+ concentration of 0.1 mol/L. Under the excitation at 976 nm, intense blue upconversion emission of Tm3+ at 474 nm was observed due to energy transfer from Yb3+ to Tm3+. A three-photon process was responsible for the blue emission. Due to re-absorption resulted from the Tm3+:3H6→1G4 transition, the blue emission peak was red-shifted. It is suggested that the fiber preparation technology based on glass phase-separation technology can be a potential candidate for preparing active fibers with large core or complex fiber structure.

Tm3+/Yb3+ co-doped tellurite glass with silver nanoparticles for 1.85 μm band laser material

NASA Astrophysics Data System (ADS)

Huang, Bo; Zhou, Yaxun; Cheng, Pan; Zhou, Zizhong; Li, Jun; Jin, Wei

2016-10-01

Tm3+/Yb3+ co-doped tellurite glasses with different silver nanoparticles (Ag NPs) concentrations were prepared using the conventional melt-quenching technique and characterized by the UV/Vis/NIR absorption spectra, 1.85 μm band fluorescence emission spectra, transmission electron microscopy (TEM) images, differential scanning calorimeter (DSC) curves and X-ray diffraction (XRD) patterns to investigate the effects of Ag NPs on the 1.85 μm band spectroscopic properties of Tm3+ ions, thermal stability and structural nature of glass hosts. Under the excitation of 980 nm laser diode (LD), the 1.85 μm band fluorescence emission of Tm3+ ions enhances significantly in the presence of Ag NPs with average diameter of ∼8 nm and local surface Plasmon resonance (LSPR) band of ∼590 nm, which is mainly attributed to the increased local electric field induced by Ag NPs at the proximity of doped rare-earth ions on the basis of energy transfer from Yb3+ to Tm3+ ions. An improvement by about 110% of fluorescence intensity is observed in the Tm3+/Yb3+ co-doped tellurite glass containing 0.5 mol% amount of AgNO3 while the prepared glass samples possess good thermal stability and amorphous structural nature. Meanwhile, the Judd-Ofelt intensity parameters Ωt (t = 2,4,6), spontaneous radiative transition probabilities, fluorescence branching ratios and radiative lifetimes of relevant excited levels of Tm3+ ions were determined based on the Judd-Ofelt theory to reveal the enhanced effects of Ag NPs on the 1.85 μm band spectroscopic properties, and the energy transfer micro-parameters and phonon contribution ratios were calculated based on the non-resonant energy transfer theory to elucidate the energy transfer mechanism between Yb3+ and Tm3+ ions. The present results indicate that the prepared Tm3+/Yb3+ co-doped tellurite glass with an appropriate amount of Ag NPs is a promising lasing media applied for 1.85 μm band solid-state lasers and amplifiers.

Role of Yb3+ ions on enhanced ~2.9 μm emission from Ho3+ ions in low phonon oxide glass system

PubMed Central

Balaji, Sathravada; Gupta, Gaurav; Biswas, Kaushik; Ghosh, Debarati; Annapurna, Kalyandurg

2016-01-01

The foremost limitation of an oxide based crystal or glass host to demonstrate mid- infrared emissions is its high phonon energy. It is very difficult to obtain radiative mid-infrared emissions from these hosts which normally relax non-radiatively between closely spaced energy levels of dopant rare earth ions. In this study, an intense mid-infrared emission around 2.9 μm has been perceived from Ho3+ ions in Yb3+/Ho3+ co-doped oxide based tellurite glass system. This emission intensity has increased many folds upon Yb3+: 985 nm excitation compared to direct Ho3+ excitations due to efficient excited state resonant energy transfer through Yb3+: 2F5/2 → Ho3+: 5I5 levels. The effective bandwidth (FWHM) and cross-section (σem) of measured emission at 2.9 μm are assessed to be 180 nm and 9.1 × 10−21 cm2 respectively which are comparable to other crystal/glass hosts and even better than ZBLAN fluoride glass host. Hence, this Ho3+/Yb3+ co-doped oxide glass system has immense potential for the development of solid state mid-infrared laser sources operating at 2.9 μm region. PMID:27374129

Effect of silver nanoparticles on the 1.53 μm fluorescence in Er3+/Yb3+ codoped tellurite glasses

NASA Astrophysics Data System (ADS)

Wu, Libo; Zhou, Yaxun; Zhou, Zizhong; Cheng, Pan; Huang, Bo; Yang, Fengjing; Li, Jun

2016-07-01

Improving the spectroscopic properties of rare earth (RE) doped glass materials is a challenging task. In the present work the metallic silver nanoparticles (Ag NPs) were embedded into Er3+/Yb3+ codoped tellurite glasses with composition TeO2-Bi2O3-TiO2, prepared using melt-quenching and subsequent heat-treated techniques, and the improved effect of Ag NPs on the 1.53 μm band fluorescence of Er3+ ions was investigated. About 24 h heat-treatment of Er3+/Yb3+ codoped tellurite glass containing 1 mol % amount of AgNO3 at the temperature 370 °C yielded the well-dispersed and near-spherical Ag NPs with ∼11.4 nm average diameter as evidenced by transmission electron microscopy (TEM) image. The intense 1.53 μm band fluorescence was observed in the prepared Er3+/Yb3+ codoped tellurite glasses under the excitation of 980 nm and was further improved with the presence of Ag NPs in the glass matrix, which is attributed to the enhanced local electric field around doped RE ions induced by Ag NPs and the possible energy transfer from Ag NPs to Er3+ ions. The enhanced local electric field was well demonstrated by comparing the variation of emission spectra of hypersensitive probe Eu3+ ions in tellurite glasses with and without Ag NPs. From the Judd-Ofelt analysis, it was also found that the value of Ω6 intensity parameter increased slightly with the increase of Ag NPs concentration in a certain range, also confirming the possibility of realizing strong fluorescence emission. In addition, the amorphous structural nature was demonstrated by the measured X-ray diffraction (XRD) patterns with no sharp diffraction peak. The enhanced 1.53 μm band fluorescence indicates that the Er3+/Yb3+ codoped tellurite glass with an appropriate amount of Ag NPs is a promising candidate for the development of Er3+-doped fiber amplifiers (EDFAs) applied in the WDM systems.

Sintering and foaming of barium silicate glass powder compacts

NASA Astrophysics Data System (ADS)

Mueller, Ralf; Reinsch, Stefan; Agea-Blanco, Boris

2016-10-01

The manufacture of sintered glasses and glass-ceramics, glass matrix composites and glass-bounded ceramics or pastes is often affected by gas bubble formation. Against this background, we studied sintering and foaming of barium silicate glass powders used as SOFC sealants using different powder milling procedures. Sintering was measured by means of heating microscopy backed up by XPD, DTA, Vacuum Hot Extraction (VHE) and optical and electron microscopy. Foaming increased significantly as milling progressed. For moderately milled glass powders, subsequent storage in air could also promote foaming. Although the powder compacts were uniaxially pressed and sintered in air, the milling atmosphere sig¬ni¬ficantly affected foaming. The strength of this effect increased in the order Ar ? N2 < air < CO2. Conformingly, VHE studies revealed that the pores of foamed samples predominantly encapsulated CO2, even for powders milled in Ar and N2. Results of this study thus indicate that foaming is caused by carbonaceous species trapped on the glass powder surface. Foaming could be substantially reduced by milling in water and 10 wt% HCl.

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

NASA Technical Reports Server (NTRS)

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

2000-01-01

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

In-situ determination of the oxidation state of iron in Fe-bearing silicate melts

NASA Astrophysics Data System (ADS)

Courtial, P.; Wilke, M.; Potuzak, M.; Dingwell, D. B.

2005-12-01

Terrestrial lavas commonly contain up to 10 wt% of iron. Furthermore, rocks returned from the Moon indicate lunar lava containing up to 25 wt% of iron and planetary scientists estimated that the martian mantle has about 18 wt% of iron. An experimental challenge in dealing with Fe-bearing silicate melts is that the oxidation state, controlling the proportions of ferric and ferrous iron, is a function of composition, oxygen fugacity and temperature and may vary significantly. Further complications concerning iron originate from its potential to be either four-, six- or even five-fold coordinated in both valence states. Therefore, the oxidation state of iron was determined in air for various Fe-bearing silicate melts. Investigated samples were Na-disilicate (NS), one atmosphere anorthite-diopside eutectic (AD) and haplogranitic (HPG8) melts containing up to 20, 20 and 10 wt% of iron, respectively. XANES spectra at the Fe K-edge were collected for all the melts at beamline A1, HASYLAB, Hamburg, using a Si(111) 4-crystal monochromator. Spectra were collected for temperatures up to 1573 K using a Pt-Rh loop as heating device. The Fe oxidation state was determined from the centroid position of the pre-edge feature using the calibration of Wilke et al. (2004). XANES results suggest that oxidation state of iron does not change within error for NS melts with addition of Fe, while AD and HPG8 melts become more oxidised with increasing iron content. Furthermore, NS melts are well more oxidised than AD and HPG8 melts that exhibit relatively similar oxidation states for identical iron contents. The oxidation state of iron for NS melts appears to be slightly temperature-dependent within the temperature range investigated (1073-1573 K). However, this trend is stronger for AD and HPG8 melts. Assuming that glass reflects a picture of the homogeneous equilibria of the melt, the present in-situ Fe-oxidation states determined for these melts were compared to those obtained on quenched

UV irradiation-induced Raman spectra changes in lead silicate glasses

NASA Astrophysics Data System (ADS)

Jia, Hongzhi; Chen, Guanghui; Wang, Wencheng

2006-12-01

The Raman spectra for a series of lead silicate glasses with different PbO content before and after irradiation with different energy density by the frequency-quadrupled output of a Q-switched YAG laser (266 nm, 10 Hz repetition rate) were measured. The intensity of Pb-O band near 140 cm -1 in the Raman spectra decreases after UV irradiation and no new band appears in the Raman spectra. Exposed to the UV beam with high energy density (150 mJ/cm 2), although the total dose is smaller than the dose with low energy density (50 mJ/cm 2), the intensity of the 140 cm -1 band drops heavilier than exposed to the UV beam with low energy density. This shows that the UV irradiation can cause the broken of Pb-O bond in lead silicate glasses and the broken of Pb-O bond is related to the energy density of UV beam.

Mineral stimulation of subsurface microorganisms: release of limiting nutrients from silicates

USGS Publications Warehouse

Roger, Jennifer Roberts; Bennett, Philip C.

2004-01-01

Microorganisms play an important role in the weathering of silicate minerals in many subsurface environments, but an unanswered question is whether the mineral plays an important role in the microbial ecology. Silicate minerals often contain nutrients necessary for microbial growth, but whether the microbial community benefits from their release during weathering is unclear. In this study, we used field and laboratory approaches to investigate microbial interactions with minerals and glasses containing beneficial nutrients and metals. Field experiments from a petroleum-contaminated aquifer, where silicate weathering is substantially accelerated in the contaminated zone, revealed that phosphorus (P) and iron (Fe)-bearing silicate glasses were preferentially colonized and weathered, while glasses without these elements were typically barren of colonizing microorganisms, corroborating previous studies using feldspars. In laboratory studies, we investigated microbial weathering of silicates and the release of nutrients using a model ligand-promoted pathway. A metal-chelating organic ligand 3,4 dihydroxybenzoic acid (3,4 DHBA) was used as a source of chelated ferric iron, and a carbon source, to investigate mineral weathering rate and microbial metabolism.In the investigated aquifer, we hypothesize that microbes produce organic ligands to chelate metals, particularly Fe, for metabolic processes and also form stable complexes with Al and occasionally with Si. Further, the concentration of these ligands is apparently sufficient near an attached microorganism to destroy the silicate framework while releasing the nutrient of interest. In microcosms containing silicates and glasses with trace phosphate mineral inclusions, microbial biomass increased, indicating that the microbial community can use silicate-bound phosphate inclusions. The addition of a native microbial consortium to microcosms containing silicates or glasses with iron oxide inclusions correlated to

Cooperative infrared to visible upconversion and visible to near-infrared quantum cutting in Tb and Yb co-doped glass containing Ag nanoparticles

NASA Astrophysics Data System (ADS)

Pan, Z.; Sekar, G.; Akrobetu, R.; Mu, R.; Morgan, S. H.

2011-10-01

Tb, Yb, and Ag co-doped glass nano-composites were synthesized in a lithium-lanthanum-aluminosilicate glass matrix (LLAS) by a melt-quench technique. Ag nanoparticles (NPs) were formed in the glass matrix and confirmed by optical absorption and transmission electron microscopy (TEM). Plasmon enhanced luminescence was observed. Cooperative infrared to visible upconversion and visible to near-infrared quantum cutting were studied for samples with different thermal annealing times. Because the Yb3+ emission at 940 - 1020 nm is matched well with the band gap of crystalline Si, the quantum cutting effect may have its potential application in silicon-based solar cells.

Contact fatigue mechanisms as a function of crystal aspect ratio in baria-silicate glass ceramics

NASA Astrophysics Data System (ADS)

Suputtamongkol, Kallaya

2003-10-01

Ceramic materials are potentially useful for dental applications because of their esthetic potential and biocompatibility. However, the existence of fatigue damage in ceramics raises considerable concern regarding its effect on the life prediction of dental prostheses. During normal mastication, dental restorations are subjected to repeated loading more than a thousand times per day and relatively high clinical failure rates for ceramic prostheses have been reported. To simulate the intraoral loads, Hertzian indentation loading was used in this study to characterize the fatigue failure mechanisms of ceramic materials using clinically relevant parameters. The baria-silicate system was chosen because of the nearly identical composition between the crystal and the glass matrix. Little or no residual stress is expected from the elastic modulus and thermal expansion mismatches between the two phases. Crystallites with different aspect ratios can also be produced by controlled heat treatment schedules. The objective of this study was to characterize the effect of crystal morphology on the fatigue mechanisms of bariasilicate glass-ceramics under clinically relevant conditions. The results show that the failure of materials with a low toughness such as baria-silicate glass (0.7 MPa•m1/2) and glass-ceramic with an aspect ratio of 3/1 (1.3 MPa•m1/2) initiated from a cone crack developed during cyclic loading for 103 to 105 cycles. The mean strength values of baria-silicate glass and glass-ceramic with an aspect ratio of 3/1 decreased significantly as a result of the presence of a cone crack. Failure of baria-silicate glass-ceramics with an aspect ratio of 8/1 (Kc = 2.1 MPa•m1/2) was initiated from surface flaws caused by either polishing or cyclic loading. The gradual decrease of fracture stress was observed in specimens with an aspect ratio of 8/1 after loading in air for 103 to 10 5 cycles. A reduction of approximately 50% in fracture stress levels was found for

Spectral chemistry of green glass-bearing 15426 regolith

NASA Technical Reports Server (NTRS)

Burns, R. G.; Dyar, M. D.

1983-01-01

The detection of appreciable concentrations of ferric iron in a synthetic green glass equilibrated at an oxygen fugacity of 10 to the -11th atm prompted a Moessbauer spectral study of pristine emerald-green glass spherules carefully handpicked from regolith sample 15426. No Fe(3+) ions were detected in this lunar sample or in a synthetic green glass simulant equilibrated at fO2 = 10 to the -14th atm, suggesting that the green glass clods in rock 15426 formed under conditions of correspondingly low oxygen fugacities. The Moessbauer spectra indicated the presence of olivine crystallites in the lunar emerald green glass spherules. Measurements of homogeneous and partially devitrified synthetic silicate glasses revealed that significant changes of coordination environment about Fe(2+) ions in the glass structure occur during crystallization of olivine crystals from the melt.

White light upconversion emission in Yb3+/ Er3+/ Tm3+ codoped oxy-fluoride lithium tungsten tellurite glass ceramics

NASA Astrophysics Data System (ADS)

Ansari, Ghizal F.; Mahajan, S. K.

2012-02-01

The bright white upconversion emission ( tri-colour UC) is generated in Er/Tm/Yb tri -doped oxy-fluoride lithium tungsten tellurite (TWLOF)glass ceramics containing crystalline phase LiYbF4 under the excitation of 980nm laser diode. The most appropriate combination of rare-earth ions (2mol% YbF3 1mol% ErF3 and 1mol%TmF3 )of glass ceramic sample has been determined to tune the primary colour (RGB and generate white light emission. By varying the pump power, intense and weak blue (487nm, 437nm), green (525nm and 545nm) and red (662nm) emission are simultaneously observed at room temperature. The dependence of upconversion emission intensity suggest that a theephoton process is responsible for the blue emission of Tm3+ ions and red emission due to both Tm3+ and Er3+ ions , while green emission originated from two photon processes in Er3+ ions. Also tri colour upconvesion and energy transfer in this glass ceramics sample were studied under 808nm laser diode excitation. The Upconversion mechanisms and Tm3+ ions plays role of both emitter and activator (transfer energy to Er) were discussed.

Evaluation of TeO2 content on the optical and spectroscopic properties of Yb3+-doped calcium borotellurite glasses.

PubMed

Lima, A M O; Gomes, J F; Hegeto, F L; Medina, A N; Steimacher, A; Barboza, M J

2018-03-15

This paper reports the synthesis and the characterization of Yb 3+ -doped calcium borotellurite (CaBTeX) glasses with composition 10CaF 2 -(29.5-0.4x)CaO-(60-0.6x)B 2 O 3 -xTeO 2 -0.5Yb 2 O 3 (x=10, 16, 22, 31 and 54mol%). The results of XRD confirm the amorphous character of all the samples. The density, molar volume, refractive index and electronic polarizability values show an increase with TeO 2 content. Otherwise, the optical band gap energy shows a decrease with the increase of TeO 2 content. The replacement of CaO and B 2 O 3 by TeO 2 changes the glass structure, which decreases the excited Yb 3+ /cm 3 and, consequently, the luminescence intensity. The temperature dependence of luminescence was studied for all the samples up to 420K. The fluorescence lifetime does not change significantly due to TeO 2 addition. In addition, absorption and emission cross section were calculated and present high values as compared to other tellurite and phosphate glasses. Copyright © 2017 Elsevier B.V. All rights reserved.

Evaluation of TeO2 content on the optical and spectroscopic properties of Yb3 +-doped calcium borotellurite glasses

NASA Astrophysics Data System (ADS)

Lima, A. M. O.; Gomes, J. F.; Hegeto, F. L.; Medina, A. N.; Steimacher, A.; Barboza, M. J.

2018-03-01

This paper reports the synthesis and the characterization of Yb3 +-doped calcium borotellurite (CaBTeX) glasses with composition 10CaF2-(29.5 - 0.4x)CaO-(60 - 0.6x)B2O3-xTeO2-0.5Yb2O3 (x = 10, 16, 22, 31 and 54 mol%). The results of XRD confirm the amorphous character of all the samples. The density, molar volume, refractive index and electronic polarizability values show an increase with TeO2 content. Otherwise, the optical band gap energy shows a decrease with the increase of TeO2 content. The replacement of CaO and B2O3 by TeO2 changes the glass structure, which decreases the excited Yb3 +/cm3 and, consequently, the luminescence intensity. The temperature dependence of luminescence was studied for all the samples up to 420 K. The fluorescence lifetime does not change significantly due to TeO2 addition. In addition, absorption and emission cross section were calculated and present high values as compared to other tellurite and phosphate glasses.

Quantitative analysis of major elements in silicate minerals and glasses by micro-PIXE

USGS Publications Warehouse

Campbell, J.L.; Czamanske, G.K.; MacDonald, L.; Teesdale, W.J.

1997-01-01

The Guelph micro-PIXE facility has been modified to accommodate a second Si(Li) X-ray detector which records the spectrum due to light major elements (11 ??? Z ??? 20) with no deleterious effects from scattered 3 MeV protons. Spectra have been recorded from 30 well-characterized materials, including a broad range of silicate minerals and both natural and synthetic glasses. Sodium is mobile in some of the glasses, but not in the studied mineral lattices. The mean value of the instrumental constant H for each of the elements Mg, Al, and Si in these materials is systematically 6-8% lower than the H-value measured for the pure metals. Normalization factors are derived which permit the matrix corrections requisite for trace-element measurements in silicates to be based upon pure metal standards for Mg, Al and Si, supplemented by well-established, silicate mineral standards for the elements Na, K and Ca. Rigorous comparisons of electron microprobe and micro-PIXE analyses for the entire, 30-sample suite demonstrate the ability of micro-PIXE to produce accurate analysis for the light major elements in silicates. ?? 1997 Elsevier Science B.V.

Experimental and theoretical investigation of the elastic moduli of silicate glasses and crystals

NASA Astrophysics Data System (ADS)

Philipps, Katharina; Stoffel, Ralf Peter; Dronskowski, Richard; Conradt, Reinhard

2017-02-01

A combined quantum-mechanical and thermodynamic approach to the mechanical properties of multicomponent silicate glasses is presented. Quantum chemical calculations based on density-functional theory (DFT) on various silicate systems were performed to explore the crystalline polymorphs existing for a given chemical composition. These calculations reproduced the properties of known polymorphs even in systems with extensive polymorphism, like MgSiO3. Properties resting on the atomic and electronic structure, i.e., molar volumes (densities) and bulk moduli were predicted correctly. The theoretical data (molar equilibrium volumes, bulk moduli) were then used to complement the available experimental data. In a phenomenological evaluation, experimental data of bulk moduli, a macroscopic property resting on phononic structure, were found to linearly scale with the ratios of atomic space demand to actual molar volume in a universal way. Silicates ranging from high-pressure polymorphs to glasses were represented by a single master line. This suggests that above the Debye limit (in practice: above room temperature), the elastic waves probe the short range order coordination polyhedra and their next-neighbor linkage only, while the presence or absence of an extended translational symmetry is irrelevant. As a result, glasses can be treated - with respect to the properties investigated - as commensurable members of polymorphic series. Binary glasses fit the very same line as their one-component end-members, again both in the crystalline and glassy state. Finally, it is shown that the macroscopic properties of multicomponent glasses also are linear superpositions of the properties of their constitutional phases (as determined from phase diagrams or by thermochemical calculations) taken in their respective glassy states. This is verified experimentally for heat capacities and Young’s moduli of industrial glass compositions. It can be concluded, that the combined quantum

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

NASA Astrophysics Data System (ADS)

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

2018-03-01

Despite the pioneering efforts to explore the nature of carbon in carbon-bearing silicate melts under compression, experimental data for the speciation and the solubility of carbon in silicate melts above 4 GPa have not been reported. Here, we explore the speciation of carbon and pressure-induced changes in network structures of carbon-bearing silicate (Na2O-3SiO2, NS3) and sodium aluminosilicate (NaAlSi3O8, albite) glasses quenched from melts at high pressure up to 8 GPa using multi-nuclear solid-state NMR. The 27Al triple quantum (3Q) MAS NMR spectra for carbon-bearing albite melts revealed the pressure-induced increase in the topological disorder around 4 coordinated Al ([4]Al) without forming [5,6]Al. These structural changes are similar to those in volatile-free albite melts at high pressure, indicating that the addition of CO2 in silicate melts may not induce any additional increase in the topological disorder around Al at high pressure. 13C MAS NMR spectra for carbon-bearing albite melts show multiple carbonate species, including [4]Si(CO3)[4]Si, [4]Si(CO3)[4]Al, [4]Al(CO3)[4]Al, and free CO32-. The fraction of [4]Si(CO3)[4]Al increases with increasing pressure, while those of other bridging carbonate species decrease, indicating that the addition of CO2 may enhance mixing of Si and Al at high pressure. A noticeable change is not observed for 29Si NMR spectra for the carbon-bearing albite glasses with varying pressure at 1.5-6 GPa. These NMR results confirm that the densification mechanisms established for fluid-free, polymerized aluminosilicate melts can be applied to the carbon-bearing albite melts at high pressure. In contrast, the 29Si MAS NMR spectra for partially depolymerized, carbon-bearing NS3 glasses show that the fraction of [5,6]Si increases with increasing pressure at the expense of Q3 species ([4]Si species with one non-bridging oxygen as the nearest neighbor). The pressure-induced increase in topological disorder around Si is evident from an

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

NASA Astrophysics Data System (ADS)

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

2009-11-01

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

Origin of near to middle infrared luminescence and energy transfer process of Er(3+)/Yb(3+)co-doped fluorotellurite glasses under different excitations.

PubMed

Huang, Feifei; Liu, Xueqiang; Ma, Yaoyao; Kang, Shuai; Hu, Lili; Chen, Danping

2015-02-04

We report the near to middle infrared luminescence and energy transfer process of Er(3+)/Yb(3+) co-doped fluorotellurite glasses under 980, 1550 and 800 nm excitations, respectively. Using a 980 nm laser diode pump, enhanced 1.5 and 2.7 μm emissions from Er(3+):I13/2→(4)I15/2 and I11/2→(4)I13/2 transitions are observed, in which Yb(3+) ions can increase pumping efficiency and be used as energy transfer donors. Meanwhile, Yb(3+) can also be used as an acceptor and intensive upconversion luminescence of around 1000 nm is achieved from Er(3+):I11/2→(4)I15/2 and Yb(3+): F5/2→(4)F7/2 transitions using 1550 nm excitation. In addition, the luminescence properties and variation trendency by 800 nm excitation is similar to that using 1550 nm excitation. The optimum Er(3+) and Yb(3+) ion ratio is 1:1.5 and excess Yb(3+) ions decrease energy transfer efficiency under the two pumpings. These results indicate that Er(3+)/Yb(3+) co-doped fluorotellurite glasses are potential middle- infrared laser materials and may be used to increase the efficiency of the silicon solar cells.

Time Evolution of Radiation-Induced Luminescence in Terbium-Doped Silicate Glass

NASA Technical Reports Server (NTRS)

West, Michael S.; Winfree, William P.

1996-01-01

A study was made on two commercially available terbium-doped silicate glasses. There is an increased interest in silicate glasses doped with rare-earth ions for use in high-energy particle detection and radiographic applications. These glasses are of interest due to the fact that they can be formed into small fiber sensors; a property that can be used to increase the spatial resolution of a detection system. Following absorption of radiation, the terbium ions become excited and then emit photons via 4f-4f electronic transitions as they relax back to the ground state. The lifetime of these transitions is on the order of milliseconds. A longer decay component lasting on the order of minutes has also been observed. While radiative transitions in the 4f shell of rare-earth ions are generally well understood by the Judd-Olfelt theory, the pr'esence of a longer luminescence decay component is not. Experimental evidence that the long decay component is due, in part, to the thermal release of trapped charge carriers will be presented. In addition, a theoretical model describing the time evolution of the radiation-induced luminescence will be presented.

Analysis on energy transfer process of Ho3+ doped fluoroaluminate glass sensitized by Yb3+ for mid-infrared 2.85 μm emission

NASA Astrophysics Data System (ADS)

Zhou, Beier; Wei, Tao; Cai, Muzhi; Tian, Ying; Zhou, Jiajia; Deng, Degang; Xu, Shiqing; Zhang, Junjie

2014-12-01

This work reports the mid-infrared emission properties around 2.85 μm in a Yb3+/Ho3+ codoped fluoroaluminate glass. This fluoroaluminate glass shows a good thermal stability and high transmittance around 3 μm. The mid-infrared emission characteristics and energy transfer mechanism upon the excitation of the conventional 980 nm laser diode have been investigated. The prepared glass possesses higher spontaneous transition probability (31.77 s-1) along with the larger calculated emission cross section (1.91×10-20 cm2) corresponding to the laser transition of Ho3+:5I6→5I7. Besides, the upconversion, 1.2 μm and 2 μm fluorescence spectra were measured to understand mid-infrared emission behavior together with decay curves of Ho3+:5I6 level. Moreover, energy transfer microparameters between Yb3+ and Ho3+ were calculated and discussed based on Dexter's model. Hence, the advantageous spectroscopic characteristics of Yb3+/Ho3+ codoped fluoroaluminate glass as well as the good thermal property indicate that this kind of glass is an attractive host for developing mid-infrared solid state laser.

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

NASA Astrophysics Data System (ADS)

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

2013-06-01

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

Synthesis, characterization of CaF2 doped silicate glass-ceramics.

PubMed

Riaz, Madeeha; Zia, Rehana; Mirza, Ambreen; Hussain, Tousif; Bashir, Farooq; Anjum, Safia

2017-06-01

This paper reports the fabrication and characterization of silicate glass-ceramics doped with (0-12mol%) CaF 2 . TGA-DSC analysis was carried out to determine the crystallization temperature and stability of glass measured by two glass parameters; Hruby parameter K H =(T x -T g )/(T L -T x ) and Weinberg parameter K W =(T c -T g )/T L . It was found that with CaF 2 doping improved sinterability at low temperature and provided stability to the glass. The XRD pattern exhibits a single phase of combeite and doping of CaF 2 cause increase in crystallite size. Microstructure of samples was also improved with CaF 2 addition, pores were significantly reduced. After 15days immersion in simulated body fluid all samples developed apatite layer onto its surface. Hence, the addition of CaF 2 provided bioactive glass-ceramic material having a low processing temperature. Copyright © 2017 Elsevier B.V. All rights reserved.

Bifunction in Er{sup 3+}/Yb{sup 3+} co-doped BaTi{sub 2}O{sub 5}–Gd{sub 2}O{sub 3} glasses prepared by aerodynamic levitation method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Minghui; University of Chinese Academy of Sciences, Beijing 100039; Yu, Jianding

2013-11-15

Graphical abstract: - Highlights: • Novel BaTi{sub 2}O{sub 5}–Gd{sub 2}O{sub 3} based glasses have been prepared by aerodynamic levitation. • The obtained glasses show high thermal stability with T{sub g} = 763.3 °C. • Er{sup 3+}/Yb{sup 3+} co-doped glasses show strong upconversion based on a two-photon process. • Red emission is stronger than green emissions for EBT by high Yb{sup 3+} concentration. • Magnetic ions are paramagnetic and the distribution is homogeneous in the glasses. - Abstract: Novel Er{sup 3+}/Yb{sup 3+} co-doped BaTi{sub 2}O{sub 5}–Gd{sub 2}O{sub 3} spherical glasses have been fabricated by aerodynamic levitation method. The thermal stability, upconversionmore » luminescence, and magnetic properties of the present glass have been studied. The glasses show high thermal stability with 763.3 °C of the onset temperature of the glass transition. Red and green emissions centered at 671 nm, 548 nm and 535 nm are obtained at 980 nm excitation. The upconversion is based on a two-photon process by energy transfer, excited-state absorption, and energy back transfer. Yb{sup 3+} ions are more than Er{sup 3+} ions in the glass, resulting in efficient energy back transfer from Er{sup 3+} to Yb{sup 3+}. So the red emission is stronger than the green emissions. Magnetization curves indicate that magnetic rare earth ions are paramagnetic and the distribution is homogeneous and random in the glass matrix. Aerodynamic levitation method is an efficient way to prepare glasses with homogeneous rare earth ions.« less

Origin of near to middle infrared luminescence and energy transfer process of Er3+/Yb3+co-doped fluorotellurite glasses under different excitations

PubMed Central

Huang, Feifei; Liu, Xueqiang; Ma, Yaoyao; Kang, Shuai; Hu, Lili; Chen, Danping

2015-01-01

We report the near to middle infrared luminescence and energy transfer process of Er3+/Yb3+ co-doped fluorotellurite glasses under 980, 1550 and 800 nm excitations, respectively. Using a 980 nm laser diode pump, enhanced 1.5 and 2.7 μm emissions from Er3+:I13/2→4I15/2 and I11/2→4I13/2 transitions are observed, in which Yb3+ ions can increase pumping efficiency and be used as energy transfer donors. Meanwhile, Yb3+ can also be used as an acceptor and intensive upconversion luminescence of around 1000 nm is achieved from Er3+:I11/2→4I15/2 and Yb3+: F5/2→4F7/2 transitions using 1550 nm excitation. In addition, the luminescence properties and variation trendency by 800 nm excitation is similar to that using 1550 nm excitation. The optimum Er3+ and Yb3+ ion ratio is 1:1.5 and excess Yb3+ ions decrease energy transfer efficiency under the two pumpings. These results indicate that Er3+/Yb3+ co-doped fluorotellurite glasses are potential middle- infrared laser materials and may be used to increase the efficiency of the silicon solar cells. PMID:25648651

Silicate glasses and sulfide melts in the ICDP-USGS Eyreville B core, Chesapeake Bay impact structure, Virginia, USA

USGS Publications Warehouse

Belkin, H.E.; Horton, J. Wright

2009-01-01

Optical and electron-beam petrography of melt-rich suevite and melt-rock clasts from selected samples from the Eyreville B core, Chesapeake Bay impact structure, reveal a variety of silicate glasses and coexisting sulfur-rich melts, now quenched to various sulfi de minerals (??iron). The glasses show a wide variety of textures, fl ow banding, compositions, devitrifi cation, and hydration states. Electron-microprobe analyses yield a compositional range of glasses from high SiO2 (>90 wt%) through a range of lower SiO2 (55-75 wt%) with no relationship to depth of sample. Some samples show spherical globules of different composition with sharp menisci, suggesting immiscibility at the time of quenching. Isotropic globules of higher interfacial tension glass (64 wt% SiO2) are in sharp contact with lower-surface-tension, high-silica glass (95 wt% SiO2). Immiscible glass-pair composition relationships show that the immiscibility is not stable and probably represents incomplete mixing. Devitrifi cation varies and some low-silica, high-iron glasses appear to have formed Fe-rich smectite; other glass compositions have formed rapid quench textures of corundum, orthopyroxene, clinopyroxene, magnetite, K-feldspar, plagioclase, chrome-spinel, and hercynite. Hydration (H2O by difference) varies from ~10 wt% to essentially anhydrous; high-SiO2 glasses tend to contain less H2O. Petrographic relationships show decomposition of pyrite and melting of pyrrhotite through the transformation series; pyrite? pyrrhotite? troilite??? iron. Spheres (~1 to ~50 ??m) of quenched immiscible sulfi de melt in silicate glass show a range of compositions and include phases such as pentlandite, chalcopyrite, Ni-As, monosulfi de solid solution, troilite, and rare Ni-Fe. Other sulfi de spheres contain small blebs of pure iron and exhibit a continuum with increasing iron content to spheres that consist of pure iron with small, remnant blebs of Fe-sulfi de. The Ni-rich sulfi de phases can be explained by

Preparations of PbSe quantum dots in silicate glasses by a melt-annealing technique

NASA Astrophysics Data System (ADS)

Ma, D. W.; Cheng, C.; Zhang, Y. N.; Xu, Z. S.

2014-11-01

Silicate glass containing PbSe quantum dots (QDs) has important prospective applications in near infra-red optoelectronic devices. In this study, single-stage and double-stage heat-treatment methods were used respectively to prepare PbSe QDs in silicate glasses. Investigation results show that the double-stage heat-treatment is a favorable method to synthesize PbSe QDs with strong photoluminescence (PL) intensity and narrow full weight at half maximum (FWHM) in PL peak. Therefore, the method to prepare PbSe QDs was emphasized on the double-stage heat-treatment. Transmission electron microscopy measurements show that the standard deviations of the average QD sizes from the samples heat-treated at the development temperature of 550 °C fluctuate slightly in the range of 0.6-0.8 nm, while this deviation increases up to 1.2 nm for the sample with the development temperature of 600 °C. In addition, the linear relationship between the QD size and holding time indicates that the crystallization behavior of PbSe QDs in silicate glasses is interface-controlled growth in early stage of crystallization. The growth rates of PbSe QDs are determined to be 0.24 nm/h at 550 °C and 0.72 nm/h at 600 °C. In short, the double-stage heat-treatment at 450 °C for 20 h followed by heat-treatment at 550 °C for 5 h is a preferred process for the crystallization of PbSe QDs in silicate glass. Through this treatment, PbSe QDs with a narrow size dispersion of 5.0 ± 0.6 nm can be obtained, the PL peak from this sample is highest in intensity and narrowest in FWHM among all samples, and the peak is centered on 1575 nm, very close to the most common wavelength of 1550 nm in fiber-optic communication systems.

[Influence of cations on the laser Raman spectra of silicate glasses].

PubMed

Xiong, Yi; Zhao, Hong-xia; Gan, Fu-xi

2012-04-01

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.

Reductive surface synthesis of gold nanoparticles on silicate glass and their biochemical sensor applicationsa

PubMed Central

Li, M.; Kim, D.-P.; Jeong, G.-Y.; Seo, D.-K.; Park, C.-P.

2012-01-01

Gold nanoparticles (Au NPs) were directly synthesized on the surface of polyvinylsilazane (PVSZ, -[(vinyl)SiH-NH2]-) without use of extra reductive additives. The reductive Si-H functional groups on the surface of cured PVSZ acted as surface bound reducing agents to form gold metal when contacted with an aqueous Au precursor (HAuCl4) solution, leading to formation of Au NPs adhered to silicate glass surface. The Au NPs-silicate platforms were preliminarily tested to detect Rhodamine B (1 μM) by surface enhanced Raman scattering. Furthermore, gold microelectrode obtained by post-chemical plating was used as an integrated amperometric detection element in the polydimethylsilane-glass hybrid microfluidic chip. PMID:24324531

Insights into Silicate and Oxide Melt Structure from Amorphous, Non-Glass-Forming Materials

NASA Astrophysics Data System (ADS)

Stebbins, J. F.

2015-12-01

Many silicate and oxide liquids of interest in the Earth sciences and in technology cannot readily be quenched to glasses, either because of low silica contents (and hence low viscosity at the melting point and accompanying liquid 'fragility') or because of liquid-liquid unmixing at high temperature. Although in-situ, high temperature structural tools have been in use for decades and are rapidly developing, many methods are still most informative for glass samples quenched to ambient pressure and temperature, e.g. high-resolution solid-state NMR. Amorphous oxides, including alumina and silicate compositions, have widespread technological applications. These are generally deposited by a variety of high-energy sputtering methods, as films of thicknesses of 10's to 100's of nm. Using Al-27, Si-29, and O-17 NMR, we have recently shown that for such films, very similar short-range structure is seen in materials made by very different kinetic pathways, such as sol-gel synthesis vs. ion-beam sputtering. This path-independent structure suggests that these materials pass through transient equilibrium states during their formation, probably that of deeply supercooled liquids just above glass transition temperatures. In the HfO2-SiO2 and ZrO2-SiO2 systems, for example, samples have well-resolved O-17 NMR spectra, allowing quantitation of O sites with only Hf(Zr) neighbors (so-called "free" oxide ions), with mixed Hf(Zr) and Si neighbors, and Si only. The observed oxygen speciation agrees well with a simple thermodynamic model of one of the most fundamental equilibria in silicate systems, namely the reaction of bridging (Si-O-Si) and "free" (e.g. OHf3 and OHf4) oxide ions to produce "non-bridging" oxygens (e.g. Si-OHf2). This new approach to sampling such structural equilibria in compositions far outside the range of normal glass-forming liquids may provide new insights into more geological compositions as well, as well as in more general models of silicate melt chemistry.

Optical transitions of Tm3+ in oxyfluoride glasses and compositional and thermal effect on upconversion luminescence of Tm3+/Yb3+-codoped oxyfluoride glasses.

PubMed

Feng, Li; Wu, Yinsu; Liu, Zhuo; Guo, Tao

2014-01-24

Optical properties of Tm(3+)-doped SiO2-BaF2-ZnF2 glasses have been investigated on the basis of the Judd-Ofelt theory. Judd-Ofelt intensity parameters, radiative transition probabilities, fluorescence branching ratios and radiative lifetimes have been calculated for different glass compositions. Upconversion emissions were observed in Tm(3+)/Yb(3+)-codoped SiO2-BaF2-ZnF2 glasses under 980 nm excitation. The effects of composition, concentration of the doping ions, temperature, and excitation pump power on the upconversion emissions were also systematically studied. Copyright © 2013 Elsevier B.V. All rights reserved.

Multicolor upconversion emission from Tm3++Ho3++Yb3+ codoped tellurite glass on NIR excitations

NASA Astrophysics Data System (ADS)

Giri, N. K.; Rai, D. K.; Rai, S. B.

2008-06-01

Multicolor emission has been produced using 798 nm and 980 nm laser excitation in a Tm3++Ho3++Yb3+ codoped tellurite based glass. This glass generates simultaneously red, green and blue (RGB) emission on 798 nm excitation. Multicolor emission thus obtained was tuned to white luminescence by adjusting the Ho3+ ion concentration. There is a close match between the calculated color coordinate for the white luminescence obtained here and the point of equal energy which represents white in the 1931 CIE chromaticity diagram. The 980 nm excitation of the same sample on the other hand gives intense green and red emission and the glass appears greenish.

5  W output power from a double-clad hybrid fiber with Yb-doped phosphate core and silicate cladding.

PubMed

Wang, Longfei; He, Dongbing; Zhang, Lei; Yu, Chunlei; Feng, Suya; Wang, Meng; Chen, Danping; Hu, Lili

2017-08-01

For the first time, to the best of our knowledge, we report on the realization of a laser from a Yb-doped phosphate core/silicate cladding double-clad hybrid fiber. 5 W output power was extracted with 14.6% slope efficiency and a laser spectrum of a 1027 nm central wavelength from a 20 cm long single-mode fiber with a ∼10  μm core diameter in a 20%-4% laser cavity. The laser efficiency can be significantly enhanced by correspondingly adjusting and optimizing the laser oscillator.

Universal calibration of Raman spectroscopy for the analysis of volatiles in glasses of variable composition

NASA Astrophysics Data System (ADS)

Schiavi, Federica; Bolfan-Casanova, Nathalie

2017-04-01

The amount and distribution of volatiles (water, carbon dioxide …) in magmas represent key parameters for the understanding of magma processes and dynamics within volcanic plumbing systems. Micro-Raman spectroscopy is an excellent technique for accurate determination of volatile contents in magmas, as it combines several advantages. The technique is non-destructive and requires minimal sample preparation before the analysis. Its high lateral and in-depth spatial resolution is crucial for the study of small objects and samples that are chemically and texturally heterogeneous at the small scale (microns). Moreover, the high confocality allows analysis of sample regions not exposed to the surface and 3D mapping. We present a universal calibration of Raman spectroscopy for quantification of volatiles in silicate glasses. The proposed method is based on internal calibration, i.e., on the correlation between the glass water content and the ratio between the areas of the water and silicate Raman bands. Synthetic glasses with variable major element compositions (basaltic, andesitic, rhyolitic, dacitic ..) bearing different H2O (up to 7 wt%) and CO2 contents are used as standard glasses. Natural silicate glasses, mainly in the form of melt inclusions, are used to test the goodness of the proposed method. In addition to quantification of volatiles in glass, in bubble-bearing melt inclusions we perform micro-Raman spectroscopy investigation of gas-bearing bubbles for accurate determination of total volatile contents in melt inclusions.

The electronic structure of iron in rhyolitic and basaltic glasses at high pressure

NASA Astrophysics Data System (ADS)

Solomatova, N. V.; Jackson, J. M.; Sturhahn, W.; Roskosz, M.

2016-12-01

The physical properties of silicate melts within the Earth's mantle affect the chemical and thermal evolution of the Earth's interior. To understand melting processes within the Earth, it is imperative to determine the structure of silicate melts at high pressure. It has been proposed that iron-bearing silicate melts may exist in the lower mantle just above the core-mantle boundary [1]. The behavior of iron in mantle melts is poorly understood, but can be experimentally approximated by iron-bearing silicate glasses. Previous studies have conflicting conclusions on whether iron in lower mantle silicate melts goes through a high-spin to low-spin transition [2-4]. Additionally, the average coordination environment of iron in glasses is poorly constrained. XANES experiments on basaltic glasses have demonstrated that both four and six-fold coordinated iron may exist in significant amounts regardless of oxidation state [5] while conventional Mössbauer experiments have observed five-fold coordinated Fe2+ with small amounts of four and six-fold coordinated Fe2+ [6]. In an attempt to resolve these discrepancies, we have measured the hyperfine parameters of iron-bearing rhyolitic glass up to 115 GPa and basaltic glass up to 92 GPa in a neon pressure medium using time-resolved synchrotron Mössbauer spectroscopy at the Advanced Photon Source (Argonne National Laboratory, IL). We observed changes in the hyperfine parameters likely due to coordination changes as a result of increasing pressure. Our results indicate that iron does not undergo a high-spin to low-spin transition within the pressure range investigated. Changes in the electronic configuration, such as the spin state of iron affects the compressibility and thermal properties of melts. With the assumption that silica glasses can be used to model structural behavior in silicate melts, our study predicts that iron in chemically-complex silica-rich melts in the lower mantle likely exists in a high-spin state. Select

Plasmon-photon conversion to near-infrared emission from Yb(3+): (Au/Ag-nanoparticles) in tungsten-tellurite glasses.

PubMed

Rivera, V A G; Ledemi, Yannick; Pereira-da-Silva, Marcelo A; Messaddeq, Younes; Marega, Euclydes

2016-01-04

This manuscript reports on the interaction between (2)F5/2→(2)F7/2 radiative transition from Yb(3+) ions and localized surface plasmon resonance (from gold/silver nanoparticles) in a tungsten-tellurite glass. Such an interaction, similar to the down-conversion process, results in the Yb(3+) emission in the near-infrared region via resonant and non-resonant energy transfers. We associated such effects with the dynamic coupling described by the variations generated by the Hamiltonian HDC in either the oscillator strength, or the local crystal field, i.e. the line shape changes in the emission band. Here, the Yb(3+) ions emission is achieved through plasmon-photon coupling, observable as an enhancement or quenching in the luminescence spectra. Metallic nanoparticles have light-collecting capability in the visible spectrum and can accumulate almost all the photon energy on a nanoscale, which enable the excitation and emission of the Yb(3+) ions in the near-infrared region. This plasmon-photon conversion was evaluated from the cavity's quality factor (Q) and the coupling (g) between the nanoparticles and the Yb(3+) ions. We have found samples of low-quality cavities and strong coupling between the nanoparticles and the Yb(3+) ions. Our research can be extended towards the understanding of new plasmon-photon converters obtained from interactions between rare-earth ions and localized surface plasmon resonance.

Plasmon-photon conversion to near-infrared emission from Yb3+: (Au/Ag-nanoparticles) in tungsten-tellurite glasses

PubMed Central

Rivera, V. A. G.; Ledemi, Yannick; Pereira-da-Silva, Marcelo A.; Messaddeq, Younes; Marega Jr, Euclydes

2016-01-01

This manuscript reports on the interaction between 2F5/2→2F7/2 radiative transition from Yb3+ ions and localized surface plasmon resonance (from gold/silver nanoparticles) in a tungsten-tellurite glass. Such an interaction, similar to the down-conversion process, results in the Yb3+ emission in the near-infrared region via resonant and non-resonant energy transfers. We associated such effects with the dynamic coupling described by the variations generated by the Hamiltonian HDC in either the oscillator strength, or the local crystal field, i.e. the line shape changes in the emission band. Here, the Yb3+ ions emission is achieved through plasmon-photon coupling, observable as an enhancement or quenching in the luminescence spectra. Metallic nanoparticles have light-collecting capability in the visible spectrum and can accumulate almost all the photon energy on a nanoscale, which enable the excitation and emission of the Yb3+ ions in the near-infrared region. This plasmon-photon conversion was evaluated from the cavity’s quality factor (Q) and the coupling (g) between the nanoparticles and the Yb3+ ions. We have found samples of low-quality cavities and strong coupling between the nanoparticles and the Yb3+ ions. Our research can be extended towards the understanding of new plasmon-photon converters obtained from interactions between rare-earth ions and localized surface plasmon resonance. PMID:26725938

Elaboration And Characterization Of Foam Glass Based On Cullet With Addition Of Soluble Silicates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ayadi, A.; Stiti, N.; Benhaoua, F.

2011-01-17

The politics of the energy saving and of the acoustic comfort buildings is at the heart of the research of new compounds permitting to improve the materials performance actually commercialised. With this aim in view, we'll purpose to elaborate a porous material (foam glass) with addition of soluble silicates (up to 40%) of which the principal material is the waste glass in order to recycle it and improving the present laws about the waste products in closed circuit: (Finished products (leftarrow) waste products (leftarrow) finished products). The investigations have shown that grinding waste glass to particle size less than 0.1more » mm and adding 1% of Ca CO{sub 3} content provide production of material with the following properties: particle density 0,5 g/cm{sup 3}, strength 17,50 MPa and water adsorption 95%, the temperature for foaming ranges were determined at 850 deg. C. The microstructures are homogenous, with pore sizes up to 2 mm. The addition of soluble silicates (up to 40%) has resulted in the foam glass of very high porosity. The foam glass is counted among the new glass products meeting certain requirements sought comfort in the building industry in particular (thermal and acoustic insulation). The product obtained present of excellent properties thermal ({lambda} = 0,031 W/m deg. C) and acoustic (R = 15 dB).« less

Elaboration And Characterization Of Foam Glass Based On Cullet With Addition Of Soluble Silicates

NASA Astrophysics Data System (ADS)

Ayadi, A.; Stiti, N.; Benhaoua, F.; Boumchedda, K.; Lerari, Y.

2011-01-01

The politics of the energy saving and of the acoustic comfort buildings is at the heart of the research of new compounds permitting to improve the materials performance actually commercialised. With this aim in view, we'll purpose to elaborate a porous material (foam glass) with addition of soluble silicates (up to 40%) of which the principal material is the waste glass in order to recycle it and improving the present laws about the waste products in closed circuit: (Finished products ← waste products← finished products). The investigations have shown that grinding waste glass to particle size less than 0.1 mm and adding 1% of Ca CO3 content provide production of material with the following properties: particle density 0,5 g/cm3, strength 17,50 MPa and water adsorption 95%, the temperature for foaming ranges were determined at 850° C. The microstructures are homogenous, with pore sizes up to 2 mm. The addition of soluble silicates (up to 40%) has resulted in the foam glass of very high porosity. The foam glass is counted among the new glass products meeting certain requirements sought comfort in the building industry in particular (thermal and acoustic insulation). The product obtained present of excellent properties thermal (λ = 0,031 W/m° C) and acoustic (R = 15 dB).

Lifetime Predictions of a Titanium Silicate Glass with Machined Flaws

NASA Technical Reports Server (NTRS)

Tucker, Dennis S.; Nettles, Alan T.; Cagle, Holly

2003-01-01

A dynamic fatigue study was performed on a Titanium Silicate glass to assess its susceptibility to delayed failure and to compare the results with those of a previous study. Fracture mechanics techniques were used to analyze the results for the purpose of making lifetime predictions. The material strength and lifetime was seen to increase due to the removal of residual stress through grinding and polishing. Influence on time-to-failure is addressed for the case with and without residual stress present. Titanium silicate glass otherwise known as ultra-low expansion (ULE)* glass is a candidate for use in applications requiring low thermal expansion characteristics such as telescope mirrors. The Hubble Space Telescope s primary mirror was manufactured from ULE glass. ULE contains 7.5% titanium dioxide which in combination with silica results in a homogenous glass with a linear expansion coefficient near zero. delayed failure . This previous study was based on a 230/270 grit surface. The grinding and polishing process reduces the surface flaw size and subsurface damage, and relieves residual stress by removing the material with successively smaller grinding media. This results in an increase in strength of the optic during the grinding and polishing sequence. Thus, a second study was undertaken using samples with a surface finish typically achieved for mirror elements, to observe the effects of surface finishing on the time-to-failure predictions. An allowable stress can be calculated for this material based upon modulus of rupture data; however, this does not take into account the problem of delayed failure, most likely due to stress corrosion, which can significantly shorten lifetime. Fortunately, a theory based on fracture mechanics has been developed enabling lifetime predictions to be made for brittle materials susceptible to delayed failure. Knowledge of the factors governing the rate of subcritical flaw growth in a given environment enables the development of

Predicting the dissolution kinetics of silicate glasses using machine learning

NASA Astrophysics Data System (ADS)

Anoop Krishnan, N. M.; Mangalathu, Sujith; Smedskjaer, Morten M.; Tandia, Adama; Burton, Henry; Bauchy, Mathieu

2018-05-01

Predicting the dissolution rates of silicate glasses in aqueous conditions is a complex task as the underlying mechanism(s) remain poorly understood and the dissolution kinetics can depend on a large number of intrinsic and extrinsic factors. Here, we assess the potential of data-driven models based on machine learning to predict the dissolution rates of various aluminosilicate glasses exposed to a wide range of solution pH values, from acidic to caustic conditions. Four classes of machine learning methods are investigated, namely, linear regression, support vector machine regression, random forest, and artificial neural network. We observe that, although linear methods all fail to describe the dissolution kinetics, the artificial neural network approach offers excellent predictions, thanks to its inherent ability to handle non-linear data. Overall, we suggest that a more extensive use of machine learning approaches could significantly accelerate the design of novel glasses with tailored properties.

Effect of iron particle size and volume fraction on the magnetic properties of Fe/silicate glass soft magnetic composites

NASA Astrophysics Data System (ADS)

Ding, Wei; Jiang, Longtao; Liao, Yaqin; Song, Jiabin; Li, Bingqing; Wu, Gaohui

2015-03-01

Fe/silicate glass soft magnetic composites (SMC) were fabricated by powder metallurgy with 1000 MPa pressure at room temperature, and then annealed at 700 °C for 90 min. The iron particles distributed uniformly in the composites, and have been separated from each other by a continuous silicate glass insulating layer. Fe/glass interface was well bonded and a quasi-continuous layer Fe3O4 and FeO exited. Very fine crystalline phases Na12Ca3Fe2(Si6O18)2 were formed in silicate glass. Composite containing 57 vol% 75 μm iron particles demonstrated highest resistivity of 7.8×10-3 Ω m. The μm, Bs and Bt increased while Hc of Fe/silicate glass composites decreased with the increase of average size of iron particles. The composite with highest amount (82 vol%) and largest average size (140 μm) of iron particles demonstrated best μm, Bs and Bt and Hc, which were 622, 1.57 T, 1.43 T, 278 A/m, respectively. The composite containing 57 vol% 75 μm iron particles demonstrated minimum core loss of 3.5 W/kg at 50 Hz and 28.1 W/kg at 400 Hz, while the composite containing 82 vol% 140 μm iron particles exhibited maximum core loss of 5.2 W/kg at 50 Hz and 67.7 W/kg at 400 Hz.

Energy transfer and optical gain properties of P{sub 2}O{sub 5}-ZnO-LiF: (Yb{sup 3+}, Er{sup 3+}) glasses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reddy, C. Parthasaradhi, E-mail: cgparthasaradhi@gmail.com, E-mail: ktrkreddy@gmail.com; Naresh, V.; Reddy, K. T. Ramakrishna, E-mail: cgparthasaradhi@gmail.com, E-mail: ktrkreddy@gmail.com

2015-06-24

The present paper reports on the results pertaining to the emission properties of 0.5 mol% Er{sup 3+} and together (0.5 Yb{sup 3+} /0.5 Er{sup 3+}) doped PZL (P{sub 2}O{sub 5}-ZnO-LiF) glasses prepared by a melt quenching method. From the optical absorption data, absorption and stimulated emission cross-sections have been evaluated using McCumber’s theory and further cross-sectional gain has also been computed for Yb{sup 3+}/Er{sup 3+} doped glass. On exciting the single (Er{sup 3+}) and dual rare earth ions (Yb{sup 3+}/Er{sup 3+}) doped glass sample at λ{sub exci} = 379 nm, three emission bands in the visible region {sup 2}H{sub 11/2}→{sup 4}I{sub 15/2}more » (526 nm), {sup 4}S{sub 3/2}→{sup 4}I{sub 15/2} (549 nm) and {sup 4}F{sub 9/2}→{sup 4}I{sub 15/2} (664 nm) are observed and while at λ{sub exci} = 980 nm (Laser Diode) excitation a broad emission at 1530 nm attributed to {sup 4}H{sub 13/2}→{sup 4}I{sub 15/2} is observed in the NIR region. The enhancement in visible and NIR emission intensities with the addition of Yb{sup 3+} to Er{sup 3+} due to an energy transfer process from Yb{sup 3+} to Er{sup 3+} has been explained in terms of an energy level diagram.« less

High Pressure Response of Siliceous Materials

DTIC Science & Technology

2013-02-01

quartz, Starphire soda lime silicate glass, hydrated Starphire, BOROFLOAT borosilicate glass, an iron-containing soda lime silicate glass, opal (a hydrated... Opal (hydrated amorphous silica). .............................................................................. 10 2.7. ROBAX glass ceramic...spectrum as a function of stress for BOROFLOAT borosilicate glass. .......... 29 4.8. Raman spectrum as a function of stress for opal (hydrated

Dehydroxylated clay silicates on Mars: Riddles about the Martian regolith solved with ferrian saponites

NASA Technical Reports Server (NTRS)

Burns, Roger G.

1992-01-01

Clay silicates, resulting from the chemical weathering of volcanic glasses and basaltic rocks of Mars, are generally believed to be major constituents of the martian regolith and atmospheric dust. Because little attention has been given to the role, if any, of Mg-bearing clay silicates on the martian surface, the crystal chemistry, stability, and reactivity of Mg-Fe smectites are examined. Partially dehydroxylated ferrian saponites are suggested to be major constituents of the surface of Mars, regulating several properties of the regolith.

Gallium-containing phospho-silicate glasses: synthesis and in vitro bioactivity.

PubMed

Franchini, Mirco; Lusvardi, Gigliola; Malavasi, Gianluca; Menabue, Ledi

2012-08-01

A series of Ga-containing phospho-silicate glasses based on Bioglass 45S5, having molar formula 46.2SiO2·24.3Na2O·26.9CaO·2.6P2O5·xGa2O3 (x=1.0, 1.6, 3.5), were prepared by fusion method. The reference Bioglass 45S5 without gallium was also prepared. The synthesized glasses were immersed in simulated body fluid (SBF) for 30 days in order to observe ion release and hydroxyapatite (HA) formation. All Ga-containing glasses maintain the ability of HA formation as indicated by main X-ray diffractometric peaks and/or electronic scanning microscopy results. HA layer was formed after 1 day of SBF soaking in 45S5 glass containing up to 1.6% Ga2O3 content. Moreover, gallium released by the glasses was found to be partially precipitated on the glass surface as gallium phosphate. Further increase in gallium content reduced the ion release in SBF. The maximum of Ga(3+) concentration measured in solution is ~6 ppm determined for 3.5% Ga2O3 content. This amount is about half of the toxic level (14 ppm) of gallium and the glasses release gallium till 30 days of immersion in SBF. Considering the above results, the studied materials can be proposed as bioactive glasses with additional antimicrobial effect of gallium having no toxic outcome. Copyright © 2012 Elsevier B.V. All rights reserved.

Raman study of potassium silicate glasses containing Rb +, Sr 2+, Y 3+ and Zr 4+: Implications for cation solution mechanisms in multicomponent silicate liquids

NASA Astrophysics Data System (ADS)

Ellison, Adam J. G.; Hess, Paul C.

1994-04-01

The parallel- and perpendicular-polarized Raman spectra of (1 - x)K 2O · xM 2/zz+O · 4SiO 2e glasses are presented, where M is one of the Period V cations Rb +, Sr 2+, Y 3+ or Zr 4+. These compositions represent the equal-oxygen substitution of a Period V cation for K +, which preserves the ratio of non-bridging oxygen (NBO) to Si atoms but not, in general, the ratio of all oxygen to all cations. Rb + and K + occupy very similar sites and appear to share the same NBO with virtually no energetic penalty. As the valence of the Period V cation increases, so does the tendency of the cation to form silicate species that are depolymerized relative to the species dominating the structure of the bulk glass. The tendency to form regions comparatively rich in Si-O-Si bonds increases in the same sense. The dominant silicate species are those with 0 or 1 NBO in all glasses. The spectra indicate that K+ shares NBO with Rb + or Sr 2+, that there is relatively little sharing of NBO by K + and Y 3+, and that K + and Zr 4+ share the same NBO in what appears to be a nearly fixed bulk stoichiometric K:Zr ratio of 2:1. The latter provides a mechanism for the substantial increase in ZrO 2 solubility seen in peralkaline liquids. A novel means of expressing homogeneous equilibria in silicate liquids is presented, whereby it is possible to make concrete predictions about the coordination numbers of cations in silicate liquids and to predict how they might be affected by the presence of other cations.

Mineralogical Characterization of Fe-Bearing AGB and Supernova Silicate Grains From the Queen Alexandra Range 99177 Meteorite

NASA Technical Reports Server (NTRS)

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

2017-01-01

Spectroscopic observations of the circumstellar envelopes of evolved O-rich stars indicate the dust is mostly amorphous silicate with olivine-like compositions. Spectral modeling suggests these grains are Fe-rich [Mg/(Mg+Fe) 0.5], but it is not known whether the Fe is distributed within the silicate matrix or exists as metal inclusions. In contrast, the crystalline silicates are inferred to be extremely Mg-rich [Mg/(Mg+Fe) > 0.95]. The mineralogies and chemical compositions of dust in supernova (SN) remnants are not as well constrained, but abundant silicates of olivine-like and enstatite-like compositions have been fit to the infrared emission features. Silicates in the interstellar medium (ISM) are >99% amor-phous and Fe-bearing. The dearth of crystalline silicates in the ISM requires that some amorphization or destruction mechanisms process these grains.

A fruitful demonstration in sensors based on upconversion luminescence of Yb3+/Er3+codoped Sb2O3-WO3-Li2O (SWL) glass-ceramic

NASA Astrophysics Data System (ADS)

Prasad Sukul, Prasenjit; Kumar, Kaushal

2016-07-01

In this article, erbium and ytterbium doped lithium tungsten antimonate (Yb3+/Er3+:Sb2O3-WO3-Li2O) glass-ceramics (GC) is synthesized and its novel applications in temperature sensing and detection of latent fingerprints is studied. It is also estimated that this material could be useful as a solar cell concentrator. The upconversion emission studies on Yb3+/Er3+:SWL glass-ceramics have shown intense green emission at 525 nm (2H11/2 → 4I15/2) & 545 nm (4s3/2 → 4I15/2). The variation of UC intensities with external temperature have shown a well-fashioned pattern, which suggests that the 2H11/2 and 4S3/2 levels of Er3+ ion are thermally coupled and can act as a temperature sensor in the 300-500 K temperature range. Dry powder of Yb3+/Er3+:SWL glass-ceramic is used to develop latent fingerprint with high contrast in green color on glass slide.

Properties of New Glass Ionomer Restorative Materials Marketed for Stress Bearing Areas

DTIC Science & Technology

2018-03-22

REPORT TYPE 22/03/2018 Poster 4. TITLE AND SUBTITLE Prope1iies of New Glass-Ionomer Restorative Materials Marketed for Stress -Bearing Areas 6...Adobe Professional 7 .0 INTRODUCTION Equia Forte is a new GIC which is marketed for posterior stress bearing restorations due to its newer...research on this and other newer glass ionomer systems being indicated for use in class II posterior stress - bearing preparations. OBJECTIVE The

Ho3+-Yb3+ codoped tellurite based glasses in visible lasers and optical devices: Judd-Ofelt analysis and frequency upconversion

NASA Astrophysics Data System (ADS)

Azam, Mohd; Rai, Vineet Kumar

2017-04-01

The optical absorption and frequency upconversion emission in the Ho3+/Yb3+ codoped TeO2-ZnO (TZ), TeO2-ZnO-WO3 (TZW) and TeO2-ZnO-WO3-TiO2 (TZWTi) glasses prepared by melting and quenching method has been studied. Judd-Ofelt theory has been used to calculate the Judd-Ofelt intensity parameters (Ω2, Ω4 and Ω6), transition probabilities, radiative lifetimes, absorption cross sections and the branching ratios. Upconversion (UC) emission bands centered at ∼ 549 nm, ∼658 nm and ∼754 nm are observed upon 980 nm excitation. On codoping with the Yb3+ ions at 3.0 mol% the upconversion emission intensity enhancement of about ∼57 times, ∼342 times and ∼480 times for the green band whereas for the red band arising from the Ho3+ ions it is about ∼71 times, ∼438 times and ∼707 times respectively have been observed. The enhancement observed in the UC emission intensity is explained on the basis of efficient energy transfer from Yb3+ to Ho3+, larger absorption cross section, larger oscillator strengths and increase in the local field corrections factor. The spectroscopic quality factor Ω4/Ω6 has been calculated to get the information about the developed materials for laser applications. The upconversion emission cross section determined on the basis of Judd-Ofelt analysis is found to be maximum for Ho-Yb-TZWTi glass. The nephelauxetic ratio, bonding and covalency parameters have been calculated to know the nature of bonding between the rare earth ions and neighbouring oxygen atoms. The high color purity 83.8% has been reported in the codoped glasses at ∼81.2 W/cm2 pump power density.

Trends in Effective Diffusion Coefficients for Ion-exchange Strengthening of Soda Lime Silicate Glasses

NASA Astrophysics Data System (ADS)

Karlsson, Stefan; Wondraczek, Lothar; Ali, Sharafat; Jonson, Bo

2017-04-01

Monovalent cations enable efficient ion exchange processes due to their high mobility in silicate glasses. Numerous properties can be modified in this way, e.g., mechanical, optical, electrical or chemical performance. In particular, alkali cation exchange has received significant attention, primarily with respect to introducing compressive stress into the surface region of a glass, which increases mechanical durability. However, most of the present applications rely on specifically tailored matrix compositions in which the cation mobility is enhanced. This largely excludes the major area of soda lime silicates (SLS) such as are commodity in almost all large-scale applications of glasses. Basic understanding of the relations between structural parameters and the effective diffusion coefficients may help to improve ion-exchanged SLS glass products, on the one hand in terms of obtainable strength and on the other in terms of cost. In the present paper, we discuss the trends in the effective diffusion coefficients when exchanging Na+ for various monovalent cations (K+, Cu+, Ag+, Rb+ and Cs+) by drawing relations to physico-chemical properties. Correlations of effective diffusion coefficients were found for the bond dissociation energy and the electronic cation polarizability, indicating that localization and rupture of bonds are of importance for the ion exchange rate.

The stability of hibonite and other aluminous phases in silicate melts: Implications for the origin of hibonite-bearing inclusions

NASA Technical Reports Server (NTRS)

Beckett, J. R.; Stolper, E.

1993-01-01

Phase fields in which hibonite (Hib) and silicate melt coexist with spinel (Sp), CaAl4O7 (CA2), gehlenitic melilite (Mel), anorthite (An), or corundum (Cor) in the system CaO-MgO-Al203-SiO2-TiO2 (CMAST) were determined and activity models developed for Mel and Hib solid solutions. Experimentally determined partition coefficients for Ti between Hib and coexisting melt, D sub t, vary from 0.8 to 2.1 and generally decrease with increasing TiO2 content in the liquid (L). Based on Ti partioning between Hib and melt, bulk inclusion compositions and Hib-saturated liquid use phase diagrams, the Hib in Fluffy Type A inclusions (FTA's) from Allende and at least some of the Hib from Hib-rich inclusions is relict; much of the Hib from Hib-glass spherules probably crystallized from a melt under nonequilibrium conditions. Bulk compositions for all of these Ca-Al-rich inclusions (CAI's) are consistent with an origin as Mel + Hib + Sp + perovskite (Pv) proto-inclusions in which Mel was partially altered. In some cases, the proto-inclusion was partially or completely melted with vaporization occurring over a period of time sufficient to remove any Na introduced by the alteration process but frequently insufficient to dissolve all of the original hibonite. If equilibration temperatures based on Hib-bearing CAI's reflect condensation in a cooling gas of solar composition, then Hib + Cor condensed at approximately 1260 C (referenced to 10 exp -3 atm) and Hib + Sp + Mel at approximately 1215 +/- 10 C. Simple thermochemical models for the substitution of trace elements into the Ca-site of meteoritic Hib suggest that virtually all Eu is divalent in early condensate Hibs but that Eu(2+)/Eu(3+) decreases by a factor of 20 or more during the course of condensation, primarily because the ratio is proportional to the partial pressure of Al, which decreases dramatically as aluminous phases condense. The relative sizes of Eu and Yb anomalies in meteoritic Hibs and CAI's may be influenced by

Low Velocity Sphere Impact of a Soda Lime Silicate Glass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wereszczak, Andrew A; Fox, Ethan E; Morrissey, Timothy G

2011-10-01

This report summarizes TARDEC-sponsored work at Oak Ridge National Laboratory (ORNL) during the FY11 involving low velocity (< 30 m/s or < 65 mph) ball impact testing of Starphire soda lime silicate glass. The intent was to better understand low velocity impact response in the Starphire for sphere densities that bracketed that of rock. Five sphere materials were used: borosilicate glass, soda-lime silicate glass, steel, silicon nitride, and alumina. A gas gun was fabricated to produce controlled velocity delivery of the spheres against Starphire tile targets. Minimum impact velocities to initiate fracture in the Starphire were measured and interpreted inmore » context to the kinetic energy of impact and the elastic property mismatch between the any of the five sphere-Starphire-target combinations. The primary observations from this low velocity (< 30 m/s or < 65 mph) testing were: (1) Frictional effects contribute to fracture initiation. (2) Spheres with a lower elastic modulus require less force to initiate fracture in the Starphire than spheres with a higher elastic modulus. (3) Contact-induced fracture did not initiate in the Starphire SLS for impact kinetic energies < 150 mJ. Fracture sometimes initiated or kinetic energies between {approx} 150-1100 mJ; however, it tended to occur when lower elastic modulus spheres were impacting it. Contact-induced fracture would always occur for impact energies > 1100 mJ. (4) The force necessary to initiate contact-induced fracture is higher under dynamic or impact conditions than it is under quasi-static indentation conditions. (5) Among the five used sphere materials, silicon nitride was the closest match to 'rock' in terms of both density and (probably) elastic modulus.« less

Monolithic thermally bonded Er3+, Yb3+:glass/Co2+:MgAl2O4 microchip lasers

NASA Astrophysics Data System (ADS)

Mlynczak, Jaroslaw; Belghachem, Nabil

2015-12-01

The highest ever reported 10 kW peak power in monolithic thermally bonded Er3+, Yb3+:glass/Co2+:MgAl2O4 microchip laser was achieved. To show the superiority of monolithic microchip lasers over those with external mirrors the laser generation characteristics of the same samples in both cases were compared.

High Pressure Response of Siliceous Materials

DTIC Science & Technology

2013-02-01

iron-containing soda lime silicate glass, opal (a hydrated silicate glass), ROBAX glass ceramic, and others were single crystal (α-quartz) and...10 2.6. Opal (hydrated amorphous silica...Raman spectrum as a function of stress for opal (hydrated silica) glass. ................... 29 4.9. Raman spectrum as a function of stress for

Development of dense glass-ceramic from recycled soda-lime-silicate glass and fly ash for tiling

NASA Astrophysics Data System (ADS)

Mustaffar, Mohd Idham; Mahmud, Mohamad Haniza; Hassan, Mahadi Abu

2017-12-01

Dense glass-ceramics were prepared by sinter-crystallization process from a combination of soda-lime-silicate glass waste and fly ash. Bentonite clay that acted as a binder was also added in a prepared formulation. The powder mixture of soda-lime glass, fly ash and bentonite clay were compacted by using uniaxial hydraulic press machine and sintered at six (6) various temperatures namely 750, 800, 850, 900, 950 and 1000 °C. The heating rate and sintering time were set at 5 °C/min and 30 minutes respectively. The results revealed that modulus of rupture (MOR), density and linear shrinkage increase first from 750 to 800 °C but decrease later after 800 to 1000 °C. In the meantime, water absorption was showing completely an opposite trend. The glass-ceramic sintered at 800 °C was found to have the best combination of physical-mechanical properties and has the potential to be applied in the construction industry particularly as floor and wall tiles because of the simple manufacturing process at low temperature.

Structural and optical study on antimony-silicate glasses doped with thulium ions.

PubMed

Dorosz, D; Zmojda, J; Kochanowicz, M; Miluski, P; Jelen, P; Sitarz, M

2015-01-05

Structural, spectroscopic and thermal properties of SiO₂-Al₂O₃-Sb₂O₃-Na₂O glass system doped with 0.2 mol% Tm₂O₃ have been presented. Synthesis of antimony-silicate glasses with relatively low phonon energy (600 cm(-1), which implicates a small non-radiative decay rate) was performed by conventional high-temperature melt-quenching methods. The effect of SiO₂/Sb₂O₃ ratio in fabricated Tm(3+) doped glass on thermal, structural and luminescence properties was investigated. On the basis of structural investigations decomposition of absorption bands in the infrared FTIR region was performed, thus determining that antimony ions are the only glass-forming ions, setting up the lattice of fabricated glasses. Luminescence band at the wavelength of 1.8 μm corresponding to (3)F₄→(3)H₆ transition in thulium ions was obtained under 795 nm laser pumping. It was observed that combination of relatively low phonon energy and greater separation of optically active centers in the fabricated glasses influenced in decreasing the luminescence intensity at 1800 nm. Copyright © 2014 Elsevier B.V. All rights reserved.

Preparation and laser properties of Yb3+-doped microstructure fiber based on hydrolysis-melting technique

NASA Astrophysics Data System (ADS)

Wang, Chao

2017-01-01

The Yb3+-doped silica glass was prepared by the SiCl4 hydrolysis doping and powder melting technology based on high frequency plasma. The absorption and emission characteristics of the Yb3+-doped silica glass are studied at room temperature. The integrated absorption cross section, stimulated emission cross section and fluorescence lifetime are calculated to be 8.56×104 pm3, 1.39 pm2 and 0.56 ms, respectively. The Yb3+-doped microstructure fiber (MSF) was also fabricated by using the Yb3+-doped silica glass as fiber core. What's more, the laser properties of the Yb3+-doped MSF are studied.

Tin Valence and Local Environments in Silicate Glasses as Determined From X-ray Absorption Spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

McKeown,D.; Buechele, A.; Gan, H.

2008-01-01

X-ray absorption spectroscopy (XAS) was used to characterize the tin (Sn) environments in four borosilicate glass nuclear waste formulations, two silicate float glasses, and three potassium aluminosilicate glasses. Sn K-edge XAS data of most glasses investigated indicate Sn4+O6 units with average Sn-O distances near 2.03 Angstroms. XAS data for a float glass fabricated under reducing conditions show a mixture of Sn4+O6 and Sn2+O4 sites. XAS data for three glasses indicate Sn-Sn distances ranging from 3.43 to 3.53 Angstroms, that suggest Sn4+O6 units linking with each other, while the 4.96 Angstroms Sn-Sn distance for one waste glass suggests clustering of unlinkedmore » Sn4+O6 units.« less

Structure and up-conversion luminescence in sol-gel derived Er 3+-Yb 3+ co-doped SiO 2:PbF 2 nano-glass-ceramics

NASA Astrophysics Data System (ADS)

del-Castillo, J.; Yanes, A. C.; Méndez-Ramos, J.; Tikhomirov, V. K.; Rodríguez, V. D.

2009-11-01

Transparent oxyfluoride nano-glass-ceramics 90(SiO 2)10(PbF 2) co-doped with 0.3 Yb 3+ and 0.1 Er 3+ (mol%) have been prepared by thermal treatment of precursor sol-gel glasses. X-ray diffraction and high resolution transmission electron microscopy analysis pointed out a precipitation of cubic β-PbF 2 nanocrystals of certain diameter in nano-glass-ceramics varying from 10 to 20 nm depending on heat treatment conditions. The incorporation of Yb 3+ and Er 3+ dopants in these nanocrystals has been confirmed by signatures of luminescence spectroscopy. Up-conversion luminescence pumped at 980 nm has been detected. Colour tuneability of up-conversion luminescence varying pump power has been analyzed in terms of standard chromaticity diagram. This tuneability opens applications for up-conversion phosphors and three-dimensional optical recording.

1.5-μm high-average power laser amplifier using a Er,Yb:glass planar waveguide for coherent Doppler lidar

NASA Astrophysics Data System (ADS)

Sakimura, Takeshi; Watanabe, Yojiro; Ando, Toshiyuki; Kameyama, Shumpei; Asaka, Kimio; Tanaka, Hisamichi; Yanagisawa, Takayuki; Hirano, Yoshihito; Inokuchi, Hamaki

2012-11-01

We have developed a 1.5-μm eye-safe wavelength high average power laser amplifier using an Er,Yb:glass planar waveguide for coherent Doppler LIDAR. Large cooling surface of the planar waveguide enabled high average power pumping for Er,Yb:glass which has low thermal fracture limit. Nonlinear effects are suppressed by the large beam size which is designed by the waveguide thickness and the beam width of the planar direction. Multi-bounce optical path configuration and high-intensity pumping provide high-gain and high-efficient operation using three-level laser material. With pulsed operation, the maximum pulse energy of 1.9 mJ was achieved at the repetition rate of 4 kHz. Output average power of the amplified signal was 7.6W with the amplified gain of more than 20dB. This amplifier is suitable for coherent Doppler LIDAR to enhance the measurable range.

Comparative analysis of luminescent properties of germanate glass and double-clad optical fibers co-doped with Yb3+/Ho3+ ions

NASA Astrophysics Data System (ADS)

Pietrzycki, Marcin; Kochanowicz, Marcin; Romańczuk, Patryk; Żmojda, Jacek; Miluski, Piotr; Ragiń, Tomasz; Jeleń, Piotr; Sitarz, Maciej; Dorosz, Dominik

2016-09-01

The 2 μm and visible emission of low phonon (805 cm-1) germanate glasses and double - clad optical fiber co-doped with 0.7Yb2O3/(0.07-0.7)Ho2O3 ions have been investigated. Luminescence at 2 μm corresponding to Ho3+: 5I7 → 5I8 as well as upconversion luminescence in the visible spectral range corresponding to the Ho3+: 5S2(5F4)→5I8 (545 nm), and Ho3+: 5F5→5I8 (655 nm) transition, respectively were obtained. The optimization of the acceptor content and donor-acceptor ratio were conducted with the purpose of maximizing the luminescence intensity. The highest luminescence intensity in both spectral range was obtained in glass co-doped with 0.7Yb2O3/0.15 Ho2O3. Despite relatively small effective absorption coefficient of the optical fiber comparative analysis of luminescent properties of fabricated glasses (further core) and double - clad optical fiber showed significant contribution of reabsorption process of emitted ASE signal.

Dispersion and thermal properties of lithium aluminum silicate glasses doped with Cr3+ ions

NASA Astrophysics Data System (ADS)

El-Diasty, Fouad; Abdel-Baki, Manal; Abdel Wahab, Fathy A.; Darwish, Hussein

2006-10-01

A series of new lithium aluminum silicate (LAS) glass systems doped with chromium ion is prepared. The reflectance and transmittance of the glass slabs are recorded. By means of an iteration procedure, the glass refractive index n and the extinction coefficient k and their dispersions are obtained. Across a wide spectral range of 0.2-1.6 μm, the dispersion curves are used to determine the atomic and quantum constants of the prepared glasses. These findings provide the average oscillator wavelength, the average oscillator strength, oscillator energy, dispersion energy, lattice energy, and material dispersion of the glass materials to be calculated. For optical waveguide applications, the wavelength for zero material dispersion is obtained. Dilatometric measurements are performed and the thermal expansion coefficient is calculated to throw some light on the thermo-optical properties of the present glasses correlating them with their structure and the presence of nonbridging oxygen ions.

High-Temperature Thermal Diffusivity Measurements of Silicate Glasses

NASA Astrophysics Data System (ADS)

Pertermann, M.; Hofmeister, A. M.; Whittington, A. G.; Spera, F. J.; Zayac, J.

2005-12-01

Transport of heat in geologically relevant materials is of great interest because of its key role in heat transport, magmatism and volcanic activity on Earth. To better understand the thermal properties of magmatic materials at high temperatures, we measured the thermal diffusivity of four synthetic end-member silicate glasses with the following compositions: albite (NaAlSi3O8), orthoclase (KAlSi3O8), anorthite (CaAl2Si2O8), and diopside (CaMgSi2O6). Thermal diffusivity measurements were conducted with the laser-flash technique and data were acquired from room temperature to a maximum temperature near 1100°C, depending on the glass transition temperature. The presence of sub-mm sized bubbles in one of the orthoclase samples had no discernable effect on measured diffusivities. At room temperature, the three feldspar-type glasses have thermal diffusivity (D) values of 0.58-0.61 mm2/s, whereas the diopside glass has 0.52 mm2/s. With increasing temperature, D decreases by 5-10% (relative) for all samples and becomes virtually constant at intermediate temperatures. At higher temperatures, the anorthite and diopside glasses exhibit significant drops in thermal diffusivity over a 50-100°C interval, correlating with previously published heat capacity changes near the glass transition for these compositions. For anorthite, D (in mm2/s) decreases from 0.48 at 750-860°C to 0.36 at 975-1075°C; for diopside, D changes from 0.42 at 630-750°C to 0.30 at 850-910°C, corresponding to relative drops of 24 and 29%, respectively. Albite and orthoclase glasses do not exhibit this change and also lack significant changes in heat capacity near the glass transition. Instead, D is constant at 400-800°C for albite, and for orthoclase values go through a minimum at 500-600°C before increasing slightly towards 1100°C but it never exceeds the room temperature D. Our data on thermal diffusivity correlate closely with other thermophysical properties. Thus, at least in case of simple

Enhanced 3  μm luminescence properties based on effective energy transfer Yb3+ : 2F5/2→Dy3+ : 6H5/2 in fluoaluminate glass modified by TeO2.

PubMed

Qi, Fangwei; Huang, Feifei; Wang, Tao; Tian, Ying; Lei, Ruoshan; Ye, Renguang; Zhang, Junjie; Zhang, Long; Xu, Shiqing

2017-11-01

Enhanced 3 μm luminescence of Dy 3+ based on the effective process of Yb 3+ :F 5/2 2→Dy 3+ :H 5/2 6 with a higher energy transfer coefficient of 7.36×10 -39   cm 6 /s in fluoaluminate glass modified by TeO 2 was obtained. The energy transfer efficiency from Yb 3+ to Dy 3+ in Dy 3+ /Yb 3+ codoped glass was as high as 80%, indicating the effective energy transfer of Yb 3+ . The higher temperature of the glass transition (T g ) and larger characteristic temperatures (ΔT,K gl ) revealed better thermal properties of the prepared glasses compared with the traditional fluoaluminate glasses, which is of great benefit to fiber drawing. The lower hydroxyl content (15.7 ppm) indicated better fluorescence properties of the glass. It was noted that the longer lifetime of 572 μs and higher emission cross section of 5.22×10 -21   cm 2 along with the bandwidth of 245 nm around 3 μm proved potential applications in mid-IR laser materials of the present glass.

Multicolor up conversion emission and color tunability in Yb 3+/Tm 3+/Ho 3+ triply doped heavy metal oxide glasses

NASA Astrophysics Data System (ADS)

Ledemi, Yannick; Manzani, Danilo; Ribeiro, Sidney J. L.; Messaddeq, Younes

2011-10-01

Multicolor and white light emissions have been achieved in Yb 3+, Tm 3+ and Ho 3+ triply doped heavy metal oxide glasses upon laser excitation at 980 nm. The red (660 nm), green (547 nm) and blue (478 nm) up conversion emissions of the rare earth (RE) ions triply doped TeO 2-GeO 2-Bi 2O 3-K 2O glass (TGBK) have been investigated as a function of the RE concentration and excitation power of the 980 nm laser diode. The most appropriate combination of RE in the TGBK glass host (1.6 wt% Yb 2O 3, 0.6 wt% Tm 2O 3 and 0.1 wt% Ho 2O 3) has been determined with the purpose to tune the primary colors (RGB) respective emissions and generate white light emission by varying the pump power. The involved infrared to visible up conversion mechanisms mainly consist in a three-photon blue up conversion of Tm 3+ ions and a two-photon green and red up conversions of Ho 3+ ions. The resulting multicolor emissions have been described according to the CIE-1931 standards.

Violet-green excitation for NIR luminescence of Yb3+ ions in Bi2O3-B2O3-SiO2-Ga2O3 glasses.

PubMed

Li, Weiwei; Cheng, Jimeng; Zhao, Guoying; Chen, Wei; Hu, Lili; Guzik, Malgorzata; Boulon, Georges

2014-04-21

60Bi(2)O(3)-20B(2)O(3)-10SiO(2)-10Ga(2)O(3) glasses doped with 1-9 mol% Yb(2)O(3) were prepared and investigated mainly on their violet-green excitation for the typical NIR emission of Yb(3+), generally excited in the NIR. Two violet excitation bands at 365 nm and 405 nm are related to Yb(2+) and Bi(3+). 465 nm excitation band and 480 nm absorption band in the blue-green are assigned to Bi(0) metal nanoparticles/grains. Yb-content-dependence of the excitation and absorption means that Bi(0) is the reduced product of Bi(3+), but greatly competed by the redox reaction of Yb(2+) ↔ Yb(3+). It is proved that the violet-green excitations result in the NIR emission of Yb(3+). On the energy transfer, the virtual level of Yb(3+)-Yb(3+) as well as Bi(0) dimers probably plays an important role. An effective and controllable way is suggested to achieve nano-optical applications by Bi(0) metal nanoparticles/grains and Yb(3+).

Effects of alteration product precipitation on glass dissolution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Strachan, Denis M.; Neeway, James J.

2014-06-01

Understanding the mechanisms that control the durability of nuclear waste glass is paramount if reliable models are to be constructed so that the glass dissolution rate in a given geological repository can be calculated. Presently, it is agreed that (boro)silicate glasses dissolve in water at a rate dependent on the solution concentration of orthosilicic acid (H 4SiO 4) with higher [H 4SiO 4] leading to lower dissolution rates. Once the reaction has slowed as a result of the buildup of H 4SiO 4, another increase in the rate has been observed that corresponds to the precipitation of certain silica-bearing alterationmore » products. However, it has also been observed that the concentration of silica-bearing solution species does not significantly decrease, indicating saturation, while other glass tracer elements concentrations continue to increase, indicating that the glass is still dissolving. In this study, we have used the Geochemist’s Workbench code to investigate the relationship between glass dissolution rates and the precipitation rate of a representative zeolitic silica-bearing alteration product, analcime [Na(AlSi 2O 6)∙H 2O]. To simplify the calculations, we suppressed all alteration products except analcime, gibbsite (Al(OH) 3), and amorphous silica. The pseudo-equilibrium-constant matrix for amorphous silica was substituted for the glass pseudo-equilibrium-constant matrix because it has been shown that silicate glasses act as a silica-only solid with respect to kinetic considerations. In this article, we present the results of our calculations of the glass dissolution rate at different values for the analcime precipitation rate constant and the effects of varying the glass dissolution rate constant at a constant analcime precipitation rate constant. From the simulations we conclude, firstly, that the rate of glass dissolution is dependent on the kinetics of formation of the zeolitic phase. Therefore, the kinetics of secondary phase formation is an

Ab Initio Modeling of Structure and Properties of Single and Mixed Alkali Silicate Glasses.

PubMed

Baral, Khagendra; Li, Aize; Ching, Wai-Yim

2017-10-12

A density functional theory (DFT)-based ab initio molecular dynamics (AIMD) has been applied to simulate models of single and mixed alkali silicate glasses with two different molar concentrations of alkali oxides. The structural environments and spatial distributions of alkali ions in the 10 simulated models with 20% and 30% of Li, Na, K and equal proportions of Li-Na and Na-K are studied in detail for subtle variations among the models. Quantum mechanical calculations of electronic structures, interatomic bonding, and mechanical and optical properties are carried out for each of the models, and the results are compared with available experimental observation and other simulations. The calculated results are in good agreement with the experimental data. We have used the novel concept of using the total bond order density (TBOD), a quantum mechanical metric, to characterize internal cohesion in these glass models. The mixed alkali effect (MAE) is visible in the bulk mechanical properties but not obvious in other physical properties studied in this paper. We show that Li doping deviates from expected trend due to the much stronger Li-O bonding than those of Na and K doping. The approach used in this study is in contrast with current studies in alkali-doped silicate glasses based only on geometric characterizations.

Coordination of Fe, Ga and Ge in high pressure glasses by Moessbauer, Raman and X-ray absorption spectroscopy, and geological implications

NASA Technical Reports Server (NTRS)

Fleet, M. E.; Henderson, G. S.; Herzberg, C. T.; Crozier, E. D.; Osborne, M. D.; Scarfe, C. M.

1984-01-01

For some time, it has been recognized that the structure of silicate liquids has a great bearing on such magma properties as viscosity, diffusivity, and thermal expansion and on the extrapolation of thermodynamic quantities outside of the experimentally measurable range. In this connection it is vital to know if pressure imposes changes in melt structure similar to the pressure-induced reconstructive transformations in crystals. In the present study on 1 bar and high pressure glasses, an investigation is conducted regarding the coordination of Fe(3+) in Fe silicate glasses by Moessbauer spectroscopy. Raman spectroscopy is employed to explore the coordinations of Ge(4+) in GeO2 glasses and of Ga(3+) in NaGa silicate glasses, while the coordination of Ga(3+) in NaGaSiO4 glasses is studied with the aid of methods of X-ray absorption spectroscopy.

Coordination of Fe, Ga and Ge in high pressure glasses by Moessbauer, Raman and X-ray absorption spectroscopy, and geological implications

NASA Astrophysics Data System (ADS)

Fleet, M. E.; Herzberg, C. T.; Henderson, G. S.; Crozier, E. D.; Osborne, M. D.; Scarfe, C. M.

1984-07-01

For some time, it has been recognized that the structure of silicate liquids has a great bearing on such magma properties as viscosity, diffusivity, and thermal expansion and on the extrapolation of thermodynamic quantities outside of the experimentally measurable range. In this connection it is vital to know if pressure imposes changes in melt structure similar to the pressure-induced reconstructive transformations in crystals. In the present study on 1 bar and high pressure glasses, an investigation is conducted regarding the coordination of Fe(3+) in Fe silicate glasses by Moessbauer spectroscopy. Raman spectroscopy is employed to explore the coordinations of Ge(4+) in GeO2 glasses and of Ga(3+) in NaGa silicate glasses, while the coordination of Ga(3+) in NaGaSiO4 glasses is studied with the aid of methods of X-ray absorption spectroscopy.

Spectroscopy and enhanced frequency upconversion in Nd3+-Yb3+ codoped TPO glasses: energy transfer and NIR to visible upconverter.

PubMed

Azam, Mohd; Rai, Vineet Kumar; Mohanty, Deepak Kumar

2017-09-22

TeO 2 -Pb 3 O 4 (TPO) glasses codoped with Nd 3+ and Yb 3+ ions have been fabricated by conventional melting technique. The absorption, emission and excitation spectra of the samples have been recorded. The optical band gap in both the doped/codoped glasses is found to be ∼3.31 eV. Judd-Ofelt analysis has been carried out by using the absorption spectrum of 0.8 mol% Nd 3+ doped glass to determine the radiative properties viz radiative transition probabilities, branching ratios, radiative lifetimes, quality factor and emission cross sections of some emitting levels for Nd 3+ ions. The radiative transition probability for the 4 G 7/2  →  4 I 9/2 transition (∼1926 Hz) is found to be maximum compared to other 4 G 5/2  →  4 I 9/2 (∼1622 Hz) and 4 F 5/2  →  4 I 9/2 (∼865 Hz) transitions. Upconversion (UC) luminescence of the samples has been examined by the 980 nm CW diode laser excitation. Effect of addition of Yb 3+ ions in the Nd 3+ doped glasses on UC emission intensity has been discussed. The UC emission intensity corresponding to the green, red and NIR bands in the codoped glass has been enhanced by ∼17, ∼12 and ∼42 times as compared to that of the Nd 3+ singly doped glass. The quantum efficiency for the 4 G 7/2 level is found to be ∼32%. The nephelauxetic ratio, bonding parameter and covalency of Nd 3+ ions have been found positive which represents the covalent bonding between Nd 3+ ion and oxygen atom. The colour tunability from yellowish-green to dominant green region has been obtained in the optimized codoped TPO glass.

Spectroscopy and enhanced frequency upconversion in Nd3+-Yb3+ codoped TPO glasses: energy transfer and NIR to visible upconverter

NASA Astrophysics Data System (ADS)

Azam, Mohd; Rai, Vineet Kumar; Mohanty, Deepak Kumar

2017-09-01

TeO2-Pb3O4 (TPO) glasses codoped with Nd3+ and Yb3+ ions have been fabricated by conventional melting technique. The absorption, emission and excitation spectra of the samples have been recorded. The optical band gap in both the doped/codoped glasses is found to be ˜3.31 eV. Judd-Ofelt analysis has been carried out by using the absorption spectrum of 0.8 mol% Nd3+ doped glass to determine the radiative properties viz radiative transition probabilities, branching ratios, radiative lifetimes, quality factor and emission cross sections of some emitting levels for Nd3+ ions. The radiative transition probability for the 4G7/2 → 4I9/2 transition (˜1926 Hz) is found to be maximum compared to other 4G5/2 → 4I9/2 (˜1622 Hz) and 4F5/2 → 4I9/2 (˜865 Hz) transitions. Upconversion (UC) luminescence of the samples has been examined by the 980 nm CW diode laser excitation. Effect of addition of Yb3+ ions in the Nd3+ doped glasses on UC emission intensity has been discussed. The UC emission intensity corresponding to the green, red and NIR bands in the codoped glass has been enhanced by ˜17, ˜12 and ˜42 times as compared to that of the Nd3+ singly doped glass. The quantum efficiency for the 4G7/2 level is found to be ˜32%. The nephelauxetic ratio, bonding parameter and covalency of Nd3+ ions have been found positive which represents the covalent bonding between Nd3+ ion and oxygen atom. The colour tunability from yellowish-green to dominant green region has been obtained in the optimized codoped TPO glass.

Spectroscopy and visible frequency upconversion in Er3+-Yb3+: TeO2-ZnO glass.

PubMed

Mohanty, Deepak Kumar; Rai, Vineet Kumar

2014-01-01

The UV-Vis-NIR absorption studies of the Er(3+)/Er(3+)-Yb(3+) doped/codoped TeO2-ZnO (TZO) glasses fabricated by the melting and quenching method has been performed. The spectroscopic radiative parameters viz. radiative transition probabilities, branching ratios and lifetimes have been determined from the absorption spectrum by using Judd-Ofelt theory. The near infrared (NIR) to visible frequency upconversion (UC) have been monitored by using an excitation of 976 nm wavelength radiation from a CW diode laser. The effect of codoping with Yb(3+) ions on the intensity of the UC emission bands from the Er(3+) ions throughout visible region has been studied. The mechanism responsible for the observed upconversion emissions in the prepared samples have been explained on the basis of excited state absorption and efficient energy transfer processes. Copyright © 2013 Elsevier B.V. All rights reserved.

∼2 μm fluorescence radiative dynamics and energy transfer between Er{sup 3+} and Tm{sup 3+} ions in silicate glass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Ming; Liu, Xueqiang; Graduate School of Chinese Academy of Sciences, Beijing 100039

2014-03-01

Graphical abstract: - Highlights: • A Er{sup 3+}/Tm{sup 3+} co-doped silicate glass with good thermal stability (k{sub gl} = 0.402 for STE glass) is prepared. • Efficient ∼2 μm emission is observed under 808 nm and 980 nm laser excitation. • The glass structure and spectroscopic properties are confirmed by optical absorption, IR transmission, Raman and fluorescence studies. • The content of OH groups deceases efficiently after fluorine ions are introduced. • The energy transfer coefficient from Er{sup 3+} to Tm{sup 3+} in STFE glass is 13.39 × 10{sup −40} cm{sup 6}/s. - Abstract: A Er{sup 3+}/Tm{sup 3+} co-doped silicatemore » glass with good thermal stability is prepared by melt-quenching method. An efficient emission of ∼2 μm is observed under different selective laser excitations. The optical absorption and transmission spectra, Raman spectra, and emission spectra are tested to characterize ∼2 μm emission properties of Er{sup 3+}/Tm{sup 3+} co-doped silicate glasses and a reasonable energy transfer mechanism of ∼2 μm emission between Er{sup 3+} and Tm{sup 3+} ions is proposed. Based on the optical absorption spectra, the Judd–Ofelt parameters and radiative properties were calculated. Intense ∼2 μm emission is obtained from Er{sup 3+}/Tm{sup 3+} co-doped silicate glasses due to the efficient energy transfer from Er{sup 3+} to Tm{sup 3+} ions. The energy transfer coefficient from Er{sup 3+} to Tm{sup 3+} ions can reach as high as 13.39 × 10{sup −40} cm{sup 6}/s. In addition, the population of the OH groups is decreased and the ∼2 μm emission is effectively enhanced with fluoride introduction. The emission property, together with good thermal property, indicates that Er{sup 3+}/Tm{sup 3+} co-doped silicate glass is a potential kind of laser glass for efficient ∼2 μm laser.« less

Bent channel design in buried Er3+/Yb3+ codoped phosphate glass waveguide fabricated by field-assisted annealing

NASA Astrophysics Data System (ADS)

Zhao, Ruitu; Wang, Mu; Chen, Baojie; Liu, Ke; Pun, Edwin Yue-Bun; Lin, Hai

2011-04-01

Bent waveguide structures (S-, U-, and F-bend) based on buried Er3+/Yb3+ codoped phosphate glass waveguide channel fabricated by field-assisted annealing have been designed to achieve high-gain C-band integrated amplification. Using a simulated-bend method, the optimal radius for the curved structure is derived to be 0.90 cm with loss coefficient of 0.02 dB/cm, as the substrate size is schemed to be 4×3 cm2. In the wavelength range of 1520 to 1575 nm, obvious gain enhancement for the bent structure waveguides is anticipated, and for the F-bend waveguide, the internal gain at 1534-nm wavelength is derived to be 41.61 dB, which is much higher than the value of 26.22 and 13.81 dB in the U- and S-bend waveguides, respectively, and over three times higher than that of the straight one. The simulation results indicate that the bent structure design is beneficial in obtaining high signal gain in buried Er3+/Yb3+ codoped phosphate glass waveguides, which lays the foundation for further design and fabrication of integrated devices.

Analysis of H2O in silicate glass using attenuated total reflectance (ATR) micro-FTIR spectroscopy

USGS Publications Warehouse

Lowenstern, Jacob B.; Pitcher, Bradley W.

2013-01-01

We present a calibration for attenuated total reflectance (ATR) micro-FTIR for analysis of H2O in hydrous glass. A Ge ATR accessory was used to measure evanescent wave absorption by H2O within hydrous rhyolite and other standards. Absorbance at 3450 cm−1 (representing total H2O or H2Ot) and 1630 cm−1 (molecular H2O or H2Om) showed high correlation with measured H2O in the glasses as determined by transmission FTIR spectroscopy and manometry. For rhyolite, wt%H2O=245(±9)×A3450-0.22(±0.03) and wt%H2Om=235(±11)×A1630-0.20(±0.03) where A3450 and A1630 represent the ATR absorption at the relevant infrared wavelengths. The calibration permits determination of volatiles in singly polished glass samples with spot size down to ~5 μm (for H2O-rich samples) and detection limits of ~0.1 wt% H2O. Basaltic, basaltic andesite and dacitic glasses of known H2O concentrations fall along a density-adjusted calibration, indicating that ATR is relatively insensitive to glass composition, at least for calc-alkaline glasses. The following equation allows quantification of H2O in silicate glasses that range in composition from basalt to rhyolite: wt%H2O=(ω×A3450/ρ)+b where ω = 550 ± 21, b = −0.19 ± 0.03, ρ = density, in g/cm3, and A3450 is the ATR absorbance at 3450 cm−1. The ATR micro-FTIR technique is less sensitive than transmission FTIR, but requires only a singly polished sample for quantitative results, thus minimizing time for sample preparation. Compared with specular reflectance, it is more sensitive and better suited for imaging of H2O variations in heterogeneous samples such as melt inclusions. One drawback is that the technique can damage fragile samples and we therefore recommend mounting of unknowns in epoxy prior to polishing. Our calibration should hold for any Ge ATR crystals with the same incident angle (31°). Use of a different crystal type or geometry would require measurement of several H2O-bearing standards to provide a crystal

The dissolution mechanisms of silicate and glass-ionomer dental cements.

PubMed

Kuhn, A T; Wilson, A D

1985-11-01

The mechanism of dissolution of two dental cements of the acid-base setting types (silicate and glass-ionomer) is considered. Dissolution is incongruent, probably because most of the leached species can derive both from the matrix (polysalt gel) and the partly reacted glass particles. The release occurs by means of three discrete mechanisms, surface wash-off, diffusion through pores and cracks or diffusion through the bulk. Such behaviour is shown to be capable of being modelled with extremely high goodness-of-fit values, using equations such as y = const + at1/2 + bt. Analogies with research from the fields of geochemistry and nuclear fuel storage are made and these systems obey similar relationships. The dental cement systems differ, however, in that their dissolution is to some extent reversible. This is explained in terms of formation of insoluble complexes, either by reaction of the constituent ions, or by replacement of OH-, for example, with F-.

Paleomagnetism and Mineralogy of Unusual Silicate Glasses and Baked Soils on the Surface of the Atacama Desert of Northern Chile: A Major Airburst Impact ~12ka ago?.

NASA Astrophysics Data System (ADS)

Roperch, P. J.; Blanco, N.; Valenzuela, M.; Gattacceca, J.; Devouard, B.; Lorand, J. P.; Tomlinson, A. J.; Arriagada, C.; Rochette, P.

2015-12-01

Unusual silicate glasses were found in northern Chile in one of the driest place on earth, the Atacama Desert. The scoria-type melted rocks are littered on the ground at several localities distributed along a longitudinal band of about 50km. The silicate glasses have a stable natural remanent magnetization carried by fine-grained magnetite and acquired during cooling. At one locality, fine-grained overbank sediments were heated to form a 10 to 20 cm-thick layer of brick-type samples. Magnetic experiments on oriented samples demonstrate that the baked clays record a thermoremanent magnetization acquired in situ above 600°C down to more than 10cm depth and cooled under a normal polarity geomagnetic field with a paleointensity of 40μT. In some samples of the silicate glass, large grains of iron sulphides (troilite) are found in the glass matrix with numerous droplets of native iron, iron sulphides and iron phosphides indicating high temperature and strong redox conditions during melting. The paleomagnetic record of the baked clays and the unusual mineralogy of the silicate glasses indicate a formation mainly by in situ high temperature radiation. Paleomagnetic experiments and chemical analyses indicate that the silicate glasses are not fulgurite type rocks due to lightning events, nor volcanic glasses or even metallurgical slags related to mining activity. The existence of a well-developped baked clay layer indicates that the silicate glasses are not impact-related ejectas. The field, paleomagnetic and mineralogical observations support evidence for a thermal event likely related to a major airburst. The youngest calibrated 14C age on a charcoal sample closely associated with the glass indicates that the thermal event occurred around 12 to 13 ka BP. The good conservation of the surface effects of this thermal event in the Atacama Desert could provide a good opportunity to further estimate the threats posed by large asteroid airbursts.

Investigation of thermal stability and spectroscopic properties in Er3+/Yb3+-codoped TeO2-Li2O-B2O3-GeO2 glasses.

PubMed

Nie, Qiu-Hua; Gao, Yuan; Xu, Tie-Feng; Shen, Xiang

2005-06-01

The new Er3+/Yb3+ co-doped 70TeO2-5Li2O-(25-x)B2O3-xGeO2 (x = 0, 5, 10, 15 fand 20 mol.%) glasses were prepared. The thermal stability, absorption spectra, emission spectra and lifetime of the 4I(13/2) level of Er3+ ions were measured and studied. The FT-IR spectra were carried out in order to investigate the structure of local arrangements in glasses. It is found that the thermal stability, absorption cross-section of Yb3+, emission intensity and lifetime of the 4I(13/2) level of Er3+ increase with increasing GeO2 content in the glass composition, while the fluorescence width at half maximum (FWHM) at 1.5 um of Er3+ is about 70 nm. The obtained data suggest that this system glass can be used as a candidate host material for potential broadband optical amplifiers.

Sol-Gel Derived Active Material for Yb Thin-Disk Lasers

PubMed Central

Almeida, Rui M.; Ribeiro, Tiago

2017-01-01

A ytterbium doped active material for thin-disk laser was developed based on aluminosilicate and phosphosilicate glass matrices containing up to 30 mol% YbO1.5. Thick films and bulk samples were prepared by sol-gel processing. The structural nature of the base material was assessed by X-ray diffraction and Raman spectroscopy and the film morphology was evidenced by scanning electron microscopy. The photoluminescence (PL) properties of different compositions, including emission spectra and lifetimes, were also studied. Er3+ was used as an internal reference to compare the intensities of the Yb3+ PL peaks at ~ 1020 nm. The Yb3+ PL lifetimes were found to vary between 1.0 and 0.5 ms when the Yb concentration increased from 3 to 30 mol%. Based on a figure of merit, the best active material selected was the aluminosilicate glass composition 71 SiO2-14 AlO1.5-15 YbO1.5 (in mol%). An active disk, ~ 36 μm thick, consisting of a Bragg mirror, an aluminosilicate layer doped with 15 mol% Yb and an anti-reflective coating, was fabricated. PMID:28869488

On the origin of the low-temperature band in depolarization current spectra of poled multicomponent silicate glasses

NASA Astrophysics Data System (ADS)

Brunkov, P. N.; Kaasik, V. P.; Lipovskii, A. A.; Tagantsev, D. K.

2018-04-01

Thermally stimulated depolarization current spectra of poled silicate multicomponent glasses in the vicinity of room temperature (220-320 K) have been recorded and two bands, typical for such glasses, have been observed. It was shown that the high-temperature band (at about 290 K) is related to the relaxation of poled glass structure in the bulk, while the low-temperature band (at about 230-270 K) should be attributed to the surface phenomenon—absorption/desorption of positive species of ambient atmosphere, supposedly, water cluster ions H+(H2O)n.

A medium range order structural connection to the configurational heat capacity of borate-silicate mixed glasses.

PubMed

Liu, Hao; Smedskjaer, Morten M; Tao, Haizheng; Jensen, Lars R; Zhao, Xiujian; Yue, Yuanzheng

2016-04-28

It has been reported that the configurational heat capacity (C(p,conf)) first increases and then becomes saturated with increasing B2O3/SiO2 ratio in borate-silicate mixed glasses. Through Raman spectroscopy measurements, we have, in this work, found an implication for the intermediate range order (IRO) structural connection to the composition dependence of the C(p,conf) of borate-silicate mixed glasses. In the silica-rich compositions, the C(p,conf) rapidly increases with increasing B2O3 content. This is attributed to the increase of the content of the B-O-Si network units ([B2Si2O8](2-)) and 6-membered borate rings with 1 or 2 B(4). In the boron-rich compositions, the C(p,conf) is almost constant, independent of the increase in the B2O3/SiO2 ratio. This is likely attributed to the counteraction between the decrease of the fraction of two types of metaborate groups and the increase of the fraction of other borate superstructural units (particularly 6-membered borate rings). The overall results suggest that the glasses containing more types of superstructural units have a larger C(p,conf).

Velocity of a freely rising gas bubble in a soda-lime silicate glass melt

NASA Technical Reports Server (NTRS)

Hornyak, E. J.; Weinberg, M. C.

1984-01-01

A comparison is conducted between measured velocities for the buoyant rise of single bubbles of varying size and composition, in a soda-lime silicate glass melt, with the steady state velocities predicted by the Stokes and Hadamard-Rybczynski formulas. In all cases, the data are noted to fit the Hadamard-Rybczynski expression for steady state rise speed considerably better than the Stokes formula.

Bioactive glass/polymer composites for bone and nerve repair and regeneration

NASA Astrophysics Data System (ADS)

Mohammadkhah, Ali

Bioactive glasses have several attractive properties in hard and soft tissue repair but their brittleness limited their use, as scaffolding materials, for applications in load-bearing hard tissue repair. At the same time, because of their bioactive properties, they are being studied more often for soft tissue repair. In the present work, a new glass/polymer composite scaffold was developed for the repair of load-bearing bones with high flexural strength and without brittle behavior. The new composites have 2.5 times higher flexural strength and ˜100 times higher work of fracture (without catastrophic failure) compared to a similar bare glass scaffold. Also the use of two known bioactive glasses (13-93-B3 and 45S5) was investigated in developing glass/Poly(epsilon-caprolactone) (PCL) composite films for peripheral nerve repair. It was found that a layer of globular hydroxyapatite (HA) formed on both sides of the composites. The borate glass in the composites was fully reacted in SBF and different ions were released into the solution. The addition of bioactive glass particles to the PCL lowered its elastic modulus and yield strength, but the composites remained intact after the 14 day period in SBF at 37°C. Finally, in an effort to design a better bioactive glass, new borosilicate glass compositions were developed that possess advantages of borate and silicate bioactive glasses at the same time. It was found that replacing small amounts of B2O3 with SiO2 improved glass formation, resistance to nucleation and crystallization, and increased the release rate of boron and silicon in vitro. This new borosilicate glass could be a good alternative to existing silicate and borate bioactive glasses.

Bone regeneration in rat calvarial defects implanted with fibrous scaffolds composed of a mixture of silicate and borate bioactive glasses.

PubMed

Gu, Yifei; Huang, Wenhai; Rahaman, Mohamed N; Day, Delbert E

2013-11-01

Previous studies have evaluated the capacity of porous scaffolds composed of a single bioactive glass to regenerate bone. In the present study, scaffolds composed of a mixture of two different bioactive glasses (silicate 13-93 and borate 13-93B3) were created and evaluated for their response to osteogenic MLO-A5 cells in vitro and their capacity to regenerate bone in rat calvarial defects in vivo. The scaffolds, which have similar microstructures (porosity=58-67%) and contain 0, 25, 50 and 100 wt.% 13-93B3 glass, were fabricated by thermally bonding randomly oriented short fibers. The silicate 13-93 scaffolds showed a better capacity to support cell proliferation and alkaline phosphatase activity than the scaffolds containing borate 13-93B3 fibers. The amount of new bone formed in the defects implanted with the 13-93 scaffolds at 12 weeks was 31%, compared to values of 25, 17 and 20%, respectively, for the scaffolds containing 25, 50 and 100% 13-93B3 glass. The amount of new bone formed in the 13-93 scaffolds was significantly higher than in the scaffolds containing 50 and 100% 13-93B3 glass. While the 13-93 fibers were only partially converted to hydroxyapatite at 12 weeks, the 13-93B3 fibers were fully converted and formed a tubular morphology. Scaffolds composed of an optimized mixture of silicate and borate bioactive glasses could provide the requisite architecture to guide bone regeneration combined with a controllable degradation rate that could be beneficial for bone and tissue healing. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Alteration layer formation of Ca- and Zn-oxide bearing alkali borosilicate glasses for immobilisation of UK high level waste: A vapour hydration study

NASA Astrophysics Data System (ADS)

Cassingham, N. J.; Corkhill, C. L.; Stennett, M. C.; Hand, R. J.; Hyatt, N. C.

2016-10-01

The UK high level nuclear waste glass modified with CaO/ZnO was investigated using the vapour phase hydration test, performed at 200 °C, with the aim of understanding the impact of the modification on the chemical composition and microstructure of the alteration layer. Experiments were undertaken on non-modified and CaO/ZnO-modified base glass, with or without 25 wt% of simulant Magnox waste calcine. The modification resulted in a dramatic reduction in gel layer thickness and also a reduction in the reaction rate, from 3.4 ± 0.3 g m-2 d-1 without CaO/ZnO modification to 0.9 ± 0.1 g m-2 d-1 with CaO/ZnO. The precipitated phase assemblage for the CaO/ZnO-modified compositions was identified as hydrated Ca- and Zn-bearing silicate phases, which were absent from the non-modified counterpart. These results are in agreement with other recent studies showing the beneficial effects of ZnO additions on glass durability.

MAS-NMR investigations of the crystallization behaviour of lithium aluminum silicate (LAS) glasses containing P 2O 5 and TiO 2 nucleants

NASA Astrophysics Data System (ADS)

Ananthanarayanan, A.; Kothiyal, G. P.; Montagne, L.; Revel, B.

2010-06-01

Lithium aluminum silicate (LAS) glass of composition (mol%) 20.4Li 2O-4.0Al 2O 3-68.6SiO 2-3.0K 2O-2.6B 2O 3-0.5P 2O 5-0.9TiO 2 was prepared by melt quenching. The glass was then nucleated and crystallized based on differential thermal analysis (DTA) data and was characterized by 29Si, 31P, 11B and 27Al MAS-NMR. XRD and 29Si NMR showed that lithium metasilicate (Li 2SiO 3) is the first phase to c form followed by cristobalite (SiO 2) and lithium disilicate (Li 2Si 2O 5). 29Si MAS-NMR revealed a change in the network structure already for the glasses nucleated at 550 °C. Since crystalline Li 3PO 4, as observed by 31P MAS-NMR, forms concurrently with the silicate phases, we conclude that crystalline Li 3PO 4 does not act as a nucleating agent for lithium silicate phases. Moreover, 31P NMR indicates the formation of M-PO 4 ( M=B, Al or Ti) complexes. The presence of BO 3 and BO 4 structural units in all the glass/glass-ceramic samples is revealed through 11B MAS-NMR. B remains in the residual glass and the crystallization of silicate phases causes a reduction in the number of alkali ions available for charge compensation. As a result, the number of trigonally coordinated B (BO 3) increases at the expense of tetrahedrally coordinated B (BO 4). The 27Al MAS-NMR spectra indicate the presence of tetrahedrally coordinated Al species, which are only slightly perturbed by the crystallization.

High-efficiency ytterbium-free erbium-doped all-glass double cladding silicate glass fiber for resonantly-pumped fiber lasers.

PubMed

Qiang, Zexuan; Geng, Jihong; Luo, Tao; Zhang, Jun; Jiang, Shibin

2014-02-01

A highly efficient ytterbium-free erbium-doped silicate glass fiber has been developed for high-power fiber laser applications at an eye-safe wavelength near 1.55 μm. Our preliminary experiments show that high laser efficiency can be obtained from a relatively short length of the gain fiber when resonantly pumped at 1535 nm in both core- and cladding-pumping configurations. With a core-pumping configuration as high as 75%, optical-to-optical efficiency and 4 W output power were obtained at 1560 nm from a 1 m long gain fiber. When using a cladding-pumping configuration, approximately 13 W output power with 67.7% slope efficiency was demonstrated from a piece of 2 m long fiber. The lengths of silicate-based gain fiber are much shorter than their silica-based counterparts used in other experiments, which is significantly important for high-power narrow-band and/or pulsed laser applications.

Yb:YAG ceramic-based laser driver for Inertial Fusion Energy (IFE)

NASA Astrophysics Data System (ADS)

Vetrovec, John; Copeland, Drew A.; Litt, Amardeep S.

2016-03-01

We report on a new class of laser amplifiers for inertial confinement fusion (ICF) drivers based on a Yb:YAG ceramic disk in an edge-pumped configuration and cooled by a high-velocity gas flow. The Yb lasant offers very high efficiency and low waste heat. The ceramic host material has a thermal conductivity nearly 15-times higher than the traditionally used glass and it is producible in sizes suitable for a typical 10- to 20-kJ driver beam line. The combination of high lasant efficiency, low waste heat, edge-pumping, and excellent thermal conductivity of the host, enable operation at 10 to 20 Hz at over 20% wall plug efficiency while being comparably smaller and less costly than recently considered face-pumped alternative drivers using Nd:glass, Yb:S-FAP, and cryogenic Yb:YAG. Scalability of the laser driver over a broad range of sizes is presented.

Spectroscopic investigation of zinc tellurite glasses doped with Yb3 + and Er3 + ions

NASA Astrophysics Data System (ADS)

Bilir, Gökhan; Kaya, Ayfer; Cinkaya, Hatun; Eryürek, Gönül

2016-08-01

This paper presents a detailed spectroscopic investigation of zinc tellurite glasses with the compositions (0.80 - x - y) TeO2 + (0.20) ZnO + xEr2O3 + yYb2O3 (x = 0, y = 0; x = 0.004, y = 0; x = 0, y = 0.05 and x = 0.004, y = 0.05 per moles). The samples were synthesized by the conventional melt quenching method. The optical absorption and emission measurements were conducted at room temperature to determine the spectral properties of lanthanides doped zinc tellurite glasses and, to study the energy transfer processes between dopant lanthanide ions. The band gap energies for both direct and indirect possible transitions and the Urbach energies were measured from the absorption spectra. The absorption spectra of the samples were analyzed by using the Judd-Ofelt approach. The effect of the ytterbium ions on the emission properties of erbium ions was investigated and the energy transfer processes between dopant ions were studied by measuring the up-conversion emission properties of the materials. The color quality parameters of obtained visible up-conversion emission were also determined as well as possibility of using the Er3 + glasses as erbium doped fiber amplifiers at 1.55 μm in infrared emission region.

Polysilicate binding for silicate paints

NASA Astrophysics Data System (ADS)

Ivanovna, Loganina Valentina; Nikolaevna, Kislitsyna Svetlana; Bisengalievich, Mazhitov Yerkebulan

2018-06-01

It was suggested, that the polysilicate solutions obtained by mixing liquid glass and silicic acid sol as a binder in the manufacture of silicate paints. Information is provided on the structure and a property of the sodium polysilicate binder is presented. It has been found that the addition of silica powder to a liquid glass causes gelling in the course of time. It has been established that the introduction of the sol (increasing the silicate module) contributes to an increase in the fraction of high-polymer fractions of silicic anion, with the increase in the sol content of the polymer form of silica increasing. The research results the structure of sols and polysilicate solutions by the method of violation of total internal reflection. By the method of IR spectroscopy, the molybdate method established the presence of silica in the polysilicate binder polymeric varieties, which provides an increase in the stability of silicate coatings.

Heisenberg spin-glass behaviour in Ga0.99Yb0.01FeO3

NASA Astrophysics Data System (ADS)

Neacsa, Daniela Maria; Gruener, Gisèle; Hebert, Sylvie; Soret, Jean-Claude

2017-06-01

The dynamic and static magnetic properties of Ga0.99Yb0.01FeO3 are studied in detail using ac susceptibility and dc magnetization measurements. The study shows that the compound undergoes a spin-glass freezing at Tg ≈ 213 K . The dynamic scaling analysis of ac susceptibility data reveals typical features characteristic of canonical spin-glasses, i.e., relaxation time τ∗ ∼10-14 s , critical exponent νz = 4.1 ± 0.2 , and frequency sensitivity parameter δf ∼10-3 within three frequency decades. The analysis of the critical behaviour of the static nonlinear susceptibility yields the critical exponents γ = 4.3 ± 0.1, β = 1.0 ± 0.1 , and δ = 5.5 ± 0.5 , which lie between those typical of three-dimensional (3D) weakly anisotropic Heisenberg and Ising spin glasses. The analysis of the field-cooled and zero-field-cooled magnetization data allows to define two characteristic temperatures depending on the applied magnetic field. The upper one, Tirr(H) , is the threshold temperature corresponding to the appearance of weak irreversibility, whereas the lower one, Ts(H) , marks the onset of strong irreversibility. The resulting field-temperature phase diagram turns out to be in good quantitative agreement with the mean-field predictions for 3D Heisenberg spin-glass with random magnetic anisotropy, and appears consistent with the chiral driven freezing scenario.

Molar volume, excess enthalpy, and Prigogine-Defay ratio of some silicate glasses with different (P,T) histories.

PubMed

Wondraczek, Lothar; Behrens, Harald

2007-10-21

Structural relaxation in silicate glasses with different (p,T) histories was experimentally examined by differential scanning calorimetry and measurements of molar volume under ambient pressure. Temperature and pressure-dependent rates of changes in molar volume and generation of excess enthalpy were determined for sodium trisilicate, soda lime silicate, and sodium borosilicate (NBS) compositions. From the derived data, Prigogine-Defay ratios are calculated and discussed. Changes of excess enthalpy are governed mainly by changes in short-range structure, as is shown for NBS where boron coordination is highly sensitive to pressure. For all three glasses, it is shown how the relaxation functions that underlie volume, enthalpy, and structural relaxation decouple for changes in cooling rates and pressure of freezing, respectively. The magnitude of the divergence between enthalpy and volume may be related to differences in structural sensitivity to changes in the (p,V,T,t) space on different length scales. The findings suggest that the Prigogine-Defay ratio is related to the magnitude of the discussed decoupling effect.

Manufacture of ultra high precision aerostatic bearings based on glass guide

NASA Astrophysics Data System (ADS)

Guo, Meng; Dai, Yifan; Peng, Xiaoqiang; Tie, Guipeng; Lai, Tao

2017-10-01

The aerostatic guide in the traditional three-coordinate measuring machine and profilometer generally use metal or ceramics material. Limited by the guide processing precision, the measurement accuracy of these traditional instruments is around micro-meter level. By selection of optical materials as guide material, optical processing method and laser interference measurement can be introduced to the traditional aerostatic bearings manufacturing field. By using the large aperture wave-front interference measuring equipment , the shape and position error of the glass guide can be obtained in high accuracy and then it can be processed to 0.1μm or even better with the aid of Magnetorheological Finishing(MRF) and Computer Controlled Optical Surfacing (CCOS) process and other modern optical processing method, so the accuracy of aerostatic bearings can be fundamentally improved and ultra high precision coordinate measuring can be achieved. This paper introduces the fabrication and measurement process of the glass guide by K9 with 300mm measuring range, and its working surface accuracy is up to 0.1μm PV, the verticality and parallelism error between the two guide rail face is better than 2μm, and the straightness of the aerostatic bearings by this K9 glass guide is up to 40nm after error compensation.

Irradiation-induced Ag nanocluster nucleation in silicate glasses: Analogy with photography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Espiau de Lamaestre, R.; Fontainebleau Research Center, Corning SA, 77210 Avon; Bea, H.

2007-11-15

The synthesis of Ag nanoclusters in soda lime silicate glasses and silica was studied by optical absorption and electron spin resonance experiments under both low (gamma ray) and high (MeV ion) deposited energy density irradiation conditions. Both types of irradiation create electrons and holes whose density and thermal evolution--notably via their interaction with defects--are shown to determine the clustering and growth rates of Ag nanocrystals. We thus establish the influence of redox interactions of defects and silver (poly)ions. The mechanisms are similar to the latent image formation in photography: Irradiation-induced photoelectrons are trapped within the glass matrix, notably on dissolvedmore » noble metal ions and defects, which are thus neutralized (reverse oxidation reactions are also shown to exist). Annealing promotes metal atom diffusion, which, in turn, leads to cluster nuclei formation. The cluster density depends not only on the irradiation fluence but also--and primarily--on the density of deposited energy and the redox properties of the glass. Ion irradiation (i.e., large deposited energy density) is far more effective in cluster formation, despite its lower neutralization efficiency (from Ag{sup +} to Ag{sup 0}) as compared to gamma photon irradiation.« less

Entropy and structure of silicate glasses and melts

USGS Publications Warehouse

Richet, P.; Robie, R.A.; Hemingway, B.S.

1993-01-01

Low-temperature adiabatic Cp measurements have been made on NaAlSi2O6, MgSiO3, Ca3Al2Si3O12 and Ca1.5Mg1.5Al2Si3O12 glasses. Above about 50 K, these and previous data show that the heat capacity is an additive function of composition to within ??1% throughout the investigated glassforming part of the system CaO-MgO-Al2O3-SiO2. In view of the determining role of oxygen coordination polyhedra on the low-temperature entropy, this is interpreted as indicating that Si and Al are tetrahedrally coordinated in all these glasses, in agreement with structural data; whereas Ca and Mg remain octahedrally coordinated. In contrast, heat capacities and entropies are not additive functions of composition for alkali aluminosilicates, indicating increases in the coordination numbers of alkali elements from about six to nine when alumina is introduced. A thermochemical consequence of additivity of vibrational entropies of glasses is that entropies of mixing are essentially configurational for calcium and magnesium aluminosilicate melts. For alkali-bearing liquids, it is probable that vibrational entropies contribute significantly to entropies of mixing. At very low temperatures, the additive nature of the heat capacity with composition is less well followed, likely as a result of specific differences in medium-range order. ?? 1993.

Optical band gap studies on lithium aluminum silicate glasses doped with Cr3+ ions

NASA Astrophysics Data System (ADS)

El-Diasty, Fouad; Abdel Wahab, Fathy A.; Abdel-Baki, Manal

2006-11-01

Lithium aluminum silicate glass system (LAS) implanted with chromium ions is prepared. The reflectance and transmittance measurements are used to determine the dispersion of absorption coefficient. The optical data are explained in terms of the different oxidation states adopted by the chromium ions into the glass network. It is found that the oxidation state of the chromium depends on its concentration. Across a wide spectral range, 0.2-1.6μm, analysis of the fundamental absorption edge provides values for the average energy band gaps for allowed direct and indirect transitions. The optical absorption coefficient just below the absorption edge varies exponentially with photon energy indicating the presence of Urbach's tail. Such tail is decreased with the increase of the chromium dopant. From the analysis of the optical absorption data, the absorption peak at ground state exciton energy, the absorption at band gap, and the free exciton binding energy are determined. The extinction coefficient data are used to determine the Fermi energy level of the studied glasses. The metallization criterion is obtained and discussed exploring the nature of the glasses. The measured IR spectra of the different glasses are used to throw some light on the optical properties of the present glasses correlating them with their structure and composition.

Thermal analysis of a diffusion bonded Er3+,Yb3+:glass/Co2+: MgAl2O4 microchip lasers

NASA Astrophysics Data System (ADS)

Belghachem, Nabil; Mlynczak, Jaroslaw; Kopczynski, krzysztof; Mierczyk, Zygmunt; Gawron, Michal

2016-10-01

The analysis of thermal effects in a diffusion bonded Er3+,Yb3+:glass/Co2+:MgAl2O4 microchip laser is presented. The analysis is performed for both wavelengths at 940 nm and at 975 nm as well as for two different sides of pumping, glass side and saturable absorber side. The heat sink effect of Co2+:MgAl2O4, as well as the impact of the thermal expansion and induced stress on the diffusion bonding are emphasised. The best configurations for reducing the temperature peaks, the Von Mises stresses on the diffusion bonding, and the thermal lensing are determined.

Effect of γ-radiation on the optical properties of soda-lime-silicate glasses

NASA Astrophysics Data System (ADS)

Vanina, E. A.; Chibisova, M. A.; Chibisov, A. N.

2007-11-01

We have studied the effect of γ-radiation on the optical constants of soda-lime-silicate glasses. As the irradiation dose grows in the interval from 3.7 to 3.7 × 101 Gy, the refractive index n increases, while the optical bandgap width decreases (from 3.13 to 3.05 3.09 eV); upon irradiation to a dose of 3.7 × 102 Gy, the refractive index n drops, while the optical bandgap width E g increases up to 3.23 eV.

Brillouin-scattering studies of a sodium silicate glass in solid and melt conditions at temperatures up to 1000 °C

NASA Astrophysics Data System (ADS)

Xu, Ji-An; Manghnani, Murli H.

1992-01-01

By using the sapphire-glass-sapphire sandwich-glass-assemblage Brillouin-scattering technique, the velocities of shear and longitudinal modes of a sodium silicate glass have been measured as a function of temperature up to 1000 °C. A turning point was found at the strain point (494 °C) but not at the softening point (720 °C). Combined with the results of the 90°- and 180°-scattering-geometry measurements, the refractive index (n) of the glass as a function of temperature was also determined. As a result, independent criteria for both the strain and softening points are suggested.

White light upconversion emissions in Er3+/Tm3+/Yb3+ tridoped oxyfluoride glass

NASA Astrophysics Data System (ADS)

Guan, Xiaoping; Xu, Wei; Zhu, Shuang; Song, Qiutong; Wu, Xijun; Liu, Hailong

2015-10-01

Rare earth ions doped glasses producing visible upconversion emissions are of great interest due to their potential applications in the photonics filed. In fact, practical application of upconversion emissions has been used to obtain color image displays and white light sources. However, there are few reports on the thermal effect on tuning the emission color of the RE doped materials. In this work, the Er3+/Tm3+/Yb3+ tridoped oxyfluoride glasses were prepared through high temperature solid-state method. Under a 980 nm diode laser excitation, the upconversion emissions from the samples were studied. At room-temperature, bright white luminescence, whose CIE chromaticity coordinate was about (0.28, 0.31), can be obtained when the excitation power was 120 mW. The emission color was changed by varying the intensity ratios between RGB bands, which are strongly dependent on the rare earth ions concentration. The temperature dependent color emissions were also investigated. As temperature increased, the intensities for the emission bands presented different decay rates, finally resulting in the changing of the CIE coordinate. When the temperature was 573 K, white light with color coordinate of (0.31, 0.33) was achieved, which matches well with the white reference (0.33, 0.33). The color tunability, high quality of white light and intense emission intensity make the transparent oxyfluoride glasses excellent candidates for applications in solid-state lighting.

Spectroscopic investigation of zinc tellurite glasses doped with Yb(3+) and Er(3+) ions.

PubMed

Bilir, Gökhan; Kaya, Ayfer; Cinkaya, Hatun; Eryürek, Gönül

2016-08-05

This paper presents a detailed spectroscopic investigation of zinc tellurite glasses with the compositions (0.80-x-y) TeO2+(0.20) ZnO+xEr2O3+yYb2O3 (x=0, y=0; x=0.004, y=0; x=0, y=0.05 and x=0.004, y=0.05 per moles). The samples were synthesized by the conventional melt quenching method. The optical absorption and emission measurements were conducted at room temperature to determine the spectral properties of lanthanides doped zinc tellurite glasses and, to study the energy transfer processes between dopant lanthanide ions. The band gap energies for both direct and indirect possible transitions and the Urbach energies were measured from the absorption spectra. The absorption spectra of the samples were analyzed by using the Judd-Ofelt approach. The effect of the ytterbium ions on the emission properties of erbium ions was investigated and the energy transfer processes between dopant ions were studied by measuring the up-conversion emission properties of the materials. The color quality parameters of obtained visible up-conversion emission were also determined as well as possibility of using the Er(3+) glasses as erbium doped fiber amplifiers at 1.55μm in infrared emission region. Copyright © 2016 Elsevier B.V. All rights reserved.

Silicate and borate glasses as composite fillers: a bioactivity and biocompatibility study.

PubMed

Lopes, P P; Ferreira, B J M Leite; Gomes, P S; Correia, R N; Fernandes, M H; Fernandes, M H V

2011-06-01

Composites filled with a silicate glass (CSi) and a new borate glass (CB) were developed and compared in terms of their in vitro behaviour both in acellular and cellular media. Acellular tests were carried out in SBF and the composites were characterized by SEM-EDS, XRD and ICP. Biocompatibility studies were investigated by in vitro cell culture with MG-63 osteoblast-like and human bone marrow cells. The growth of spherical calcium phosphate aggregates was observed in acellular medium on all composite surfaces indicating that these materials became potentially bioactive. The biological assessment resulted in a dissimilar behavior of the composites. The CSi demonstrated an inductive effect on the proliferation of cells. The cells showed a normal morphology and high growth rate when compared to standard culture plates. Contrarily, inhibition of cell proliferation occurred in the CB probably due to its high degradation rate, leading to high B and Mg ionic concentration in the cell culture medium.

Fluorosilicate and fluorophosphate superfluorescent multicore optical fibers co-doped with Nd3+/Yb3+

NASA Astrophysics Data System (ADS)

Kochanowicz, M.; Zmojda, J.; Dorosz, D.

2014-06-01

In the paper spectroscopic properties of two fluorosilicate and fluorophosphate glass systems co-doped with Nd3+/Yb3+ ions are investigated. As a result of optical excitation at the wavelength of 808 nm strong and wide emission in the 1 μm region corresponding to the superposition of optical transitions 4F3/2 → 4I11/2 (Nd3+) and 2F5/2 → 2F7/2 (Yb3+) can be observed. The optimization of Nd3+ → Yb3+ energy transfer in both glasses allows to manufacture multicore optical fibers with narrowing and red-shifting of amplified spontaneous emission (ASE) at 1.1 μm.

L-Edge Xanes Measurements of the Oxidation State of Tungsten in Iron Bearing and Iron Free Silicate Glasses

NASA Technical Reports Server (NTRS)

Danielson, L. R.; Righter, K.; Sutton, S.; Newville, M.

2008-01-01

Tungsten is important in constraining core formation of the Earth because this element is a moderately siderophile element (depleted 10 relative to chondrites) and, as a member of the Hf-W isotopic system, it is useful in constraining the timing of core formation. A number of previous experimental studies have been carried out to determine the silicate solubility and metal-silicate partitioning behavior of W, including its concomitant oxidation state. However, results of previous studies are inconsistent on whether W occurs as W(4+) or W(6+). It is assumed that W(4+) is the cation valence relevant to core formation. Given the sensitivity to silicate composition of high valence cations, knowledge of the oxidation state of W over a wide range of fO2 is critical to understanding the oxidation state of the mantle and core formation processes. This study seeks to measure the W valence and change in valence state over the range of fO2 most relevant to core formation, around IW-2.

Kinetics and mechanisms of the conversion of silicate (45S5), borate, and borosilicate glasses to hydroxyapatite in dilute phosphate solutions.

PubMed

Huang, Wenhai; Day, Delbert E; Kittiratanapiboon, Kanisa; Rahaman, Mohamed N

2006-07-01

Bioactive glasses with controllable conversion rates to hydroxyapatite (HA) may provide a novel class of scaffold materials for bone tissue engineering. The objective of the present work was to comprehensively characterize the conversion of a silicate bioactive glass (45S5), a borate glass, and two intermediate borosilicate glass compositions to HA in a dilute phosphate solution at 37 degrees Celsius. The borate glass and the borosilicate glasses were derived from the 45S5 glass by fully or partially replacing the SiO(2) with B(2)O(3). Higher B(2)O(3) content produced a more rapid conversion of the glass to HA and a lower pH value of the phosphate solution. Whereas the borate glass was fully converted to HA in less than 4 days, the silicate (45S5) and borosilicate compositions were only partially converted even after 70 days, and contained residual SiO(2) in a Na-depleted core. The concentration of Na(+) in the phosphate solution increased with reaction time whereas the PO(4) (3-) concentration decreased, both reaching final limiting values at a rate that increased with the B(2)O(3) content of the glass. However, the Ca(2+) concentration in the solution remained low, below the detection limit of atomic absorption, throughout the reaction. Immersion of the glasses in a mixed solution of K(2)HPO(4) and K(2)CO(3) produced a carbonate-substituted HA but the presence of the K(2)CO(3) had little effect on the kinetics of conversion to HA. The kinetics and mechanisms of the conversion process of the four glasses to HA are compared and used to develop a model for the process.

Na/Ca Intermixing around Silicate and Phosphate Groups in Bioactive Phosphosilicate Glasses Revealed by Heteronuclear Solid-State NMR and Molecular Dynamics Simulations.

PubMed

Mathew, Renny; Stevensson, Baltzar; Edén, Mattias

2015-04-30

We characterize the intermixing of network-modifying Na(+)/Ca(2+) ions around the silicate (QSi(n)) and phosphate (QP(n)) tetrahedra in a series of 16 Na2O–CaO–SiO2–P2O5 glasses, whose P content and silicate network connectivity were varied independently. The set includes both bioactive and bioinactive compositions and also encompasses two soda-lime-silicate members devoid of P, as well as two CaO–SiO2 glasses and one Na2O–SiO2–P2O5 glass. The various Si/P↔Na/Ca contacts were probed by molecular dynamics (MD) simulations together with heteronuclear magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) experimentation utilizing (23)Na{(31)P} and (23)Na{(29)Si} REDOR, as well as (31)P{ (23)Na} and (29)Si{(23)Na} REAPDOR. We introduce an approach for quantifying the extent of Na(+)/Ca(2+) ordering around a given QP(n) or QSi(n) group, encoded by the preference factor 0⩽ PM ⩽ 1 conveying the relative weights of a random cation intermixing (PM = 0) and complete preference/ordering (PM = 1) for one of the species M, which represents either Na(+) or Ca(2+). The MD-derived preference factors reveal phosphate and silicate species surrounded by Na(+)/Ca(2+) ions intermixed nearly randomly (PM ≲ 0.15), except for the QSi(4) and QSi(1) groups, which manifest more significant cation ordering with preference for Na+ and Ca2+, respectively. The overall weak preferences are essentially independent of the Si and P contents of the glass, whereas PM primarily correlates with the total amount of network modifiers: as the latter is increased, the Na/Ca distribution around the {QP(0), QSi(1), QSi(2)} groups with preference for Ca2(+ )tend to randomize (i.e., PCa decreases), while the PNa-values grow slightly for the {QP(1), QSi(3), QSi(4)} species already preferring coordination of Na. The set of experimental preference factors {PCa} for the orthophosphate (QP(0)) groups extracted from (31)P{(23)Na} REAPDOR NMR-derived M2(P–Na) dipolar second moments agrees

Optical thermometry based on green upconversion emission in Er3+/Yb3+ codoped BaGdF5 glass ceramics

NASA Astrophysics Data System (ADS)

Wu, Ting; Zhao, Shilong; Lei, Ruoshan; Huang, Lihui; Xu, Shiqing

2018-02-01

Er3+/Yb3+ codoped BaGdF5 glass ceramics have been prepared and used to develop a portable all-fiber temperature sensor based on fluorescence intensity ratio technique. XRD and TEM results affirm the generation of BaGdF5 nanocrystals in the borosilicate glass. Eu3+ ions are used as spectral probe to investigate external environment around rare earth (RE) ions. Intense green upconversion emissions from Er3+ ions are detected in the BaGdF5 glass ceramics and their intensity are enhanced about three orders of magnitude after heat treatment, which is attributed to the enrichment of RE ions in the BaGdF5 phase. Based on green upconversion emission from Er3+ ions, the temperature sensing property of the portable all-fiber temperature sensor is studied. The maximum absolute sensitivity is 15.5 × 10-4 K-1 at 567 K and the relative sensitivity is 1.28% K-1 at 298 K, respectively.

Ytterbium-doped glass-ceramics for optical refrigeration.

PubMed

Filho, Elton Soares de Lima; Krishnaiah, Kummara Venkata; Ledemi, Yannick; Yu, Ye-Jin; Messaddeq, Younes; Nemova, Galina; Kashyap, Raman

2015-02-23

We report for the first time the characterization of glass-ceramics for optical refrigeration. Ytterbium-doped nanocrystallites were grown in an oxyfluoride glass matrix of composition 2YbF(3):30SiO(2)-15Al(2)O(3)-25CdF(2)-22PbF(2)-4YF(3), forming bulk glass-ceramics at three different crystalisation levels. The samples are compared with a corresponding uncrystalised (glass) sample, as well as a Yb:YAG sample which has presented optical cooling. The measured X-ray diffraction spectra, and thermal capacities of the samples are reported. We also report for the first time the use of Yb:YAG as a reference for absolute photometric quantum efficiency measurement, and use the same setup to characterize the glass and glass-ceramic samples. The cooling figure-of-merit was measured by optical calorimetry using a fiber Bragg grating and found to depend on the level of crystallization of the sample, and that samples with nanocrystallites result in higher quantum efficiency and lower background absorption than the pure-glass sample. In addition to laser-induced cooling, the glass-ceramics have the potential to serve as a reference for quantum efficiency measurements.

Laboratory synthesis of silicate glass spherules: Application to impact ejecta

NASA Astrophysics Data System (ADS)

Stoddard, P. S.; Pahlevan, K.; Tumber, S.; Weber, R.; Lee, K. K.

2012-12-01

To investigate the process by which molten droplets of impact ejecta solidify into glassy spherule tektites, we employed laser levitation experiments to recreate the hot temperatures of falling molten rock. Following models for Earth composition based on enstatite chondrites, we levitated mixtures of oxide powders in a stream of gas and melted them with a laser, producing silicate glass beads. After quenching, we polished the ~1 mm diameter samples in cross-section and analyzed with electron probe microanalysis (EPMA). Fine and coarsely-spaced EPMA transects across each bead displayed diffusion profiles at their edges, particularly in their SiO2 and MgO content. Heating altered the beads' bulk composition as well; all of the glassy spherules were compositionally different from the initial combination of powders. By comparing these changes to the environmental factors acting on the bead (e.g., temperature, type of levitation gas, duration of heating and amount of rotation), we produced a model for how molten ejecta change chemically and physically as they solidify into a glass. We find that high temperatures likely generated on impact have a strong effect on the composition of tektites; therefore, attempts to correlate tektites to their parent rocks should correct for this effect.

Pressure-induced nano-crystallization of silicate garnets from glass

PubMed Central

Irifune, T.; Kawakami, K.; Arimoto, T.; Ohfuji, H.; Kunimoto, T.; Shinmei, T.

2016-01-01

Transparent ceramics are important for scientific and industrial applications because of the superior optical and mechanical properties. It has been suggested that optical transparency and mechanical strength are substantially enhanced if transparent ceramics with nano-crystals are available. However, synthesis of the highly transparent nano-crystalline ceramics has been difficult using conventional sintering techniques at relatively low pressures. Here we show direct conversion from bulk glass starting material in mutianvil high-pressure apparatus leads to pore-free nano-polycrystalline silicate garnet at pressures above ∼10 GPa in a limited temperature range around 1,400 °C. The synthesized nano-polycrystalline garnet is optically as transparent as the single crystal for almost the entire visible light range and harder than the single crystal by ∼30%. The ultrahigh-pressure conversion technique should provide novel functional ceramics having various crystal structures, including those of high-pressure phases, as well as ideal specimens for some mineral physics applications. PMID:27924866

Addition of a Fluoride-containing Radiopacifier Improves Micromechanical and Biological Characteristics of Modified Calcium Silicate Cements.

PubMed

Antonijevic, Djordje; Jeschke, Anke; Colovic, Bozana; Milovanovic, Petar; Jevremovic, Danimir; Kisic, Danilo; vom Scheidt, Annika; Hahn, Michael; Amling, Michael; Jokanovic, Vukoman; Busse, Björn; Djuric, Marija

2015-12-01

Calcium silicate cements (CSCs) with the addition of nanohydroxyapatite and calcium carbonate play a critical role in dental applications. To further improve their properties, particularly radiopacity and biointeractivity, the fluoride-containing radiopacifier ytterbium trifluoride (YbF3) was added to their composition, and biological and mechanical characteristics were evaluated. YbF3 was added to 3 different CSCs: cement I (CSC + calcium carbonate), cement II (CSC + nanohydroxyapatite), and Portland cement. Material characterization encompassed measurements of pH, calcium, ytterbium, and fluoride ion release; radiopacity; setting time; porosity; microindentation properties; wettability; and Fourier transform infrared spectroscopic, x-ray diffraction, and scanning electron microscopic analyses. Osteoblast- and osteoclast-like cells were grown on the materials' surface to evaluate their adherence. The addition of calcium carbonate, nanohydroxyapatite, and 30 wt% of YbF3 improved radiopacity and the setting time of experimental cements. The pH values did not differ among the groups. The greatest ytterbium and fluoride releases occurred in the Portland cement + YbF3 group. Combined x-ray diffraction and Fourier transform infrared spectroscopic analysis showed the presence of calcium hydroxide and calcium silicate hydrates. In addition, the presence of calcium ytterbium fluoride and ytterbium oxide proved that YbF3 reacted with cement compounds. Wettability of cement I + YbF3 was superior to other formulations, but its porosity and microindentation properties were weaker than in the Portland cement + YbF3 mixture. Cement II + YbF3 presented micromechanical indentation and porosity characteristics similar to the Portland-based cement formulation. Osteoclast- and osteoblast-like cells adhered to the cements' surfaces without alteration of the cell structural integrity. YbF3-containing CSCs with nanostructured hydroxyapatite and calcium carbonate are well suited for

Strength improvement and purification of Yb 2Si 2O 7-SiC nanocomposites by surface oxidation treatment

DOE PAGES

Nguyen, Son T.; Nakayama, Tadachika; Suematsu, Hisayuki; ...

2017-04-03

A two-step processing was developed to prepare Yb 2Si 2O 7-SiC nanocomposites. Yb 2Si 2O 7-Yb 2SiO 5-SiC composites were first fabricated by a solid state reaction/hot-pressing method. The composites were then annealed at 1250°C in air for 2 h to activate the oxidation of SiC, which effectively transformed the Yb 2SiO 5 into Yb 2Si 2O 7. The surface cracks purposely induced can be fully healed during the oxidation treatment. The treated composites have improved flexural strength compared to their pristine composites. As a result, the mechanism for crack-healing and silicate transformation have been proposed and discussed in detail.

Effect of ZnO on the Physical Properties and Optical Band Gap of Soda Lime Silicate Glass

PubMed Central

Zaid, Mohd Hafiz Mohd; Matori, Khamirul Amin; Aziz, Sidek Hj. Abdul; Zakaria, Azmi; Ghazali, Mohd Sabri Mohd

2012-01-01

This manuscript reports on the physical properties and optical band gap of five samples of soda lime silicate (SLS) glass combined with zinc oxide (ZnO) that were prepared by a melting and quenching process. To understand the role of ZnO in this glass structure, the density, molar volume and optical band gaps were investigated. The density and absorption spectra in the Ultra-Violet-Visible (UV-Visible) region were recorded at room temperature. The results show that the densities of the glass samples increased as the ZnO weight percentage increased. The molar volume of the glasses shows the same trend as the density: the molar volume increased as the ZnO content increased. The optical band gaps were calculated from the absorption edge, and it was found that the optical band gap decreased from 3.20 to 2.32 eV as the ZnO concentration increased. PMID:22837711

Tm3+-doped lead silicate glass sensitized by Er3+ for efficient 2 μm mid-infrared laser material

NASA Astrophysics Data System (ADS)

Zhang, Junjie; Wang, Ning; Guo, Yanyan; Cai, Muzhi; Tian, Ying; Huang, Feifei; Xu, Shiqing

2018-06-01

Er3+/Tm3+ co-doped lead silicate glasses with low phonon (953 cm-1) and good thermal stability were synthesized. The 2 μm mid-infrared emission resulting from the 3F4 → 3H6 transition of Tm3+ sensitized by Er3+ has been observed by 808 nm LD pumping. The optimal luminescence intensity was obtained in the sample with 1Tm2O3/2.5Er2O3 co-doped. Moreover, the energy transfer mechanism from Er3+ to Tm3+ ion was analyzed. Absorption and emission cross section have been calculated. The calculated maximum emission cross section of Tm3+ is 2.689 × 10-21 cm2 at 1863 nm. Microparameters of energy transfer between Er3+ and Tm3+ ions have also been analyzed. These results ensure that the prepared Er3+/Tm3+ co-doped lead silicate glasses have excellent spectroscopic properties in mid-infrared region and provide a beneficial guide for mid-infrared laser material.

Kinetic D/H fractionation during hydration and dehydration of silicate glasses, melts and nominally anhydrous minerals

NASA Astrophysics Data System (ADS)

Roskosz, M.; Deloule, E.; Ingrin, J.; Depecker, C.; Laporte, D.; Merkel, S.; Remusat, L.; Leroux, H.

2018-07-01

The distribution of hydrogen isotopes during diffusion-driven aqueous processes in silicate glasses, melts and crystals was investigated. Hydration/dehydration experiments were performed on silica glasses at 1000 °C and 1 bar total pressure. Dehydration triggered by decompression-driven bubble nucleation and growth was performed on rhyolitic melts at 800 °C and a few hundred MPa. Hydrogen extraction from a nominally anhydrous mineral (grossular) single crystal was carried out at 800 °C and ambient pressure. After these three series of experiments, pronounced water (sensu lato) concentration profiles were observed in all recovered samples. In the grossular single-crystal, a large spatial variation in H isotopes (δD variation > 550‰) was measured across the sample. This isotopic distribution correlates with the hydrogen extraction profile. The fit to the data suggests an extreme decoupling between hydrogen and deuterium diffusion coefficients (DH and DD respectively), akin to the decoupling expected in a dilute ideal gas (DH/DD ≈ 1.41). Conversely, no measurable spatially- and time-resolved isotopic variations were measured in silicate glasses and melts. This contrasted behavior of hydrogen isotopes likely stands in the different water speciation and solution mechanisms in the three different materials. Glasses and melts contain essentially hydroxyl and molecular water groups but the mobile species is molecular water in both cases. Protonated defects make up most of the water accommodated in grossular and other nominally anhydrous minerals (NAM). These defects are also the mobile species that diffuse against polarons. These results are crucial to accurately model the degassing behavior of terrestrial and lunar magmas and to derive the initial D/H of water trapped in fluid inclusions commonly analyzed in mantle NAMs, which suffered complex geological histories.

MAS-NMR studies of lithium aluminum silicate (LAS) glasses and glass-ceramics having different Li 2O/Al 2O 3 ratio

NASA Astrophysics Data System (ADS)

Ananthanarayanan, A.; Kothiyal, G. P.; Montagne, L.; Revel, B.

2010-01-01

Emergence of phases in lithium aluminum silicate (LAS) glasses of composition (wt%) xLi 2O-71.7SiO 2-(17.7- x)Al 2O 3-4.9K 2O-3.2B 2O 3-2.5P 2O 5 (5.1≤ x≤12.6) upon heat treatment were studied. 29Si, 27Al, 31P and 11B MAS-NMR were employed for structural characterization of both LAS glasses and glass-ceramics. In glass samples, Al is found in tetrahedral coordination, while P exists mainly in the form of orthophosphate units. B exists as BO 3 and BO 4 units. 27Al NMR spectra show no change with crystallization, ruling out the presence of any Al containing phase. Contrary to X-ray diffraction studies carried out, 11B (high field 18.8 T) and 29Si NMR spectra clearly indicate the unexpected crystallization of a borosilicate phase (Li,K)BSi 2O 6, whose structure is similar to the aluminosilicate virgilite. Also, lithium disilicate (Li 2Si 2O 5), lithium metasilicate (Li 2SiO 3) and quartz (SiO 2) were identified in the 29Si NMR spectra of the glass-ceramics. 31P NMR spectra of the glass-ceramics revealed the presence of Li 3PO 4 and a mixed phase (Li,K) 3PO 4 at low alkali concentrations.

Trace element studies of silicate-rich inclusions in the Guin (UNGR) and Kodaikanal (IIE) iron meteorites

NASA Astrophysics Data System (ADS)

Kurat, Gero; Zinner, Ernst; Varela, Maria Eugenia

2007-08-01

A devitrified glass inclusion from the Guin (UNGR) iron consists of cryptocrystalline feldspars, pyroxenes, and silica and is rich in SiO2, Al2O3, and Na2O. It contains a rutile grain and is in contact with a large Cl apatite. The latter is very rich in rare earth elements (REEs) (˜80 × CI), which display a flat abundance pattern, except for Eu and Yb, which are underabundant. The devitrified glass is very poor in REEs (<0.1 × CI), except for Eu and Yb, which have positive abundance anomalies. Devitrified glass and Cl apatite are out of chemical equilibrium and their complementary REE patterns indicate a genesis via condensation under reducing conditions. Inclusion 1 in the Kodaikanal (IIE) iron consists of glass only, whereas inclusion 2 consists of clinopyroxene, which is partly overgrown by low-Ca pyroxene, and apatite embedded in devitrified glass. All minerals are euhedral or have skeletal habits indicating crystallization from the liquid precursor of the glass. Pyroxenes and the apatite are rich in trace elements, indicating crystallization from a liquid that had 10-50 × CI abundances of REEs and refractory lithophile elements (RLEs). The co-existing glass is poor in REEs (˜0.1-1 × CI) and, consequently, a liquid of such chemical composition cannot have crystallized the phenocrysts. Glasses have variable chemical compositions but are rich in SiO2, Al2O3, Na2O, and K2O as well as in HFSEs, Be, B, and Rb. The REE abundance patterns are mostly flat, except for the glass-only inclusion, which has heavy rare earth elements (HREEs) > light rare earth elements (LREEs) and deficits in Eu and Yb—an ultrarefractory pattern. The genetic models suggested so far cannot explain what is observed and, consequently, we offer a new model for silicate inclusion formation in IIE and related irons. Nebular processes and a relationship with E meteorites (Guin) or Ca-Al-rich inclusions (CAIs) (Kodaikanal) are indicated. A sequence of condensation (CaS, TiN or refractory

Present and future of glass-ionomers and calcium-silicate cements as bioactive materials in dentistry: Biophotonics-based interfacial analyses in health and disease

PubMed Central

Watson, Timothy F.; Atmeh, Amre R.; Sajini, Shara; Cook, Richard J.; Festy, Frederic

2014-01-01

Objective Since their introduction, calcium silicate cements have primarily found use as endodontic sealers, due to long setting times. While similar in chemistry, recent variations such as constituent proportions, purities and manufacturing processes mandate a critical understanding of service behavior differences of the new coronal restorative material variants. Of particular relevance to minimally invasive philosophies is the potential for ion supply, from initial hydration to mature set in dental cements. They may be capable of supporting repair and remineralization of dentin left after decay and cavity preparation, following the concepts of ion exchange from glass ionomers. Methods This paper reviews the underlying chemistry and interactions of glass ionomer and calcium silicate cements, with dental tissues, concentrating on dentin–restoration interface reactions. We additionally demonstrate a new optical technique, based around high resolution deep tissue, two-photon fluorescence and lifetime imaging, which allows monitoring of undisturbed cement–dentin interface samples behavior over time. Results The local bioactivity of the calcium-silicate based materials has been shown to produce mineralization within the subjacent dentin substrate, extending deep within the tissues. This suggests that the local ion-rich alkaline environment may be more favorable to mineral repair and re-construction, compared with the acidic environs of comparable glass ionomer based materials. Significance The advantages of this potential re-mineralization phenomenon for minimally invasive management of carious dentin are self-evident. There is a clear need to improve the bioactivity of restorative dental materials and these calcium silicate cement systems offer exciting possibilities in realizing this goal. PMID:24113131

Present and future of glass-ionomers and calcium-silicate cements as bioactive materials in dentistry: biophotonics-based interfacial analyses in health and disease.

PubMed

Watson, Timothy F; Atmeh, Amre R; Sajini, Shara; Cook, Richard J; Festy, Frederic

2014-01-01

Since their introduction, calcium silicate cements have primarily found use as endodontic sealers, due to long setting times. While similar in chemistry, recent variations such as constituent proportions, purities and manufacturing processes mandate a critical understanding of service behavior differences of the new coronal restorative material variants. Of particular relevance to minimally invasive philosophies is the potential for ion supply, from initial hydration to mature set in dental cements. They may be capable of supporting repair and remineralization of dentin left after decay and cavity preparation, following the concepts of ion exchange from glass ionomers. This paper reviews the underlying chemistry and interactions of glass ionomer and calcium silicate cements, with dental tissues, concentrating on dentin-restoration interface reactions. We additionally demonstrate a new optical technique, based around high resolution deep tissue, two-photon fluorescence and lifetime imaging, which allows monitoring of undisturbed cement-dentin interface samples behavior over time. The local bioactivity of the calcium-silicate based materials has been shown to produce mineralization within the subjacent dentin substrate, extending deep within the tissues. This suggests that the local ion-rich alkaline environment may be more favorable to mineral repair and re-construction, compared with the acidic environs of comparable glass ionomer based materials. The advantages of this potential re-mineralization phenomenon for minimally invasive management of carious dentin are self-evident. There is a clear need to improve the bioactivity of restorative dental materials and these calcium silicate cement systems offer exciting possibilities in realizing this goal. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Carbonate-silicate liquid immiscibility upon impact melting, Ries Crater, Germany

NASA Astrophysics Data System (ADS)

Graup, Guenther

1999-05-01

The 24-km-diameter Ries impact crater in southern Germany is one of the most studied impact structures on Earth. The Ries impactor struck a Triassic to Upper Jurassic sedimentary sequence overlying Hercynian crystalline basement. At the time of impact (14.87 +/- 0.36 Ma; Storzer et al., 1995), the 350 m thick Malm limestone was present only to the S and E of the impact site. To the N and W, the Malm had been eroded away, exposing the underlying Dogger and Lias. The largest proportion of shocked target material is in the impact melt-bearing breccia suevite. The suevite had been believed to be derived entirely from the crystalline basement. Calcite in the suevite has been interpreted as a post-impact hydrothermal deposit. From optical inspection of 540 thin sections of suevite from 32 sites, I find that calcite in the suevite shows textural evidence of liquid immiscibility with the silicate impact melt. Textural evidence of liquid immiscibility between silicate and carbonate melt in the Ries suevite includes: carbonate globules within silicate glass, silicate globules embedded in carbonate, deformable and coalescing carbonate spheres within silicate glass, sharp menisci or cusps and budding between silicate and carbonate melt, fluidal textures and gas vesicles in carbonate schlieren, a quench crystallization sequence of the carbonate, spinifex textured quenched carbonate, separate carbonate spherules in the suevite mineral-fragment-matrix, and inclusions of mineral fragments suspended in carbonate blebs. Given this evidence of liquid immiscibility, the carbonate in the suevite has, therefore, like the silicate melt a primary origin by impact shock melting. Evidence of carbonate-silicate liquid immiscibility is abundant in the suevites to the SW to E of the Ries crater. The rarer suevites to the W to NE of the crater are nearly devoid of carbonate melts. This correspondence between the occurrence of outcropping limestones at the target surface and the formation of

Ce3+/Yb3+/Er3+ triply doped bismuth borosilicate glass: a potential fiber material for broadband near-infrared fiber amplifiers

PubMed Central

Chu, Yushi; Ren, Jing; Zhang, Jianzhong; Peng, Gangding; Yang, Jun; Wang, Pengfei; Yuan, Libo

2016-01-01

Erbium doped bismuth borosilicate (BBS) glasses, possessing the broadest 1.55 μm near infrared (NIR) emission band among oxide glasses, stand out as excellent fiber material for optical fiber amplifiers. In this work, we demonstrate that both broadened and enhanced NIR emission of Er3+ can be obtained by sensibly combining the effects such as mixed glass former effect, phonon-assisted energy transfer (PAET) and de-excitation effect induced by codopant. Specially, by codoping CeO2 in a controlled manner, it leads to not only much improved optical quality of the glasses, enhanced NIR emission, but also significantly suppressed energy transfer up-conversion (ETU) luminescence which is detrimental to the NIR emission. Cerium incorporated in the glasses exists overwhelmingly as the trivalent oxidation state Ce3+ and its effects on the luminescence properties of Er3+ are discussed. Judd-Ofelt analysis is used to evaluate gain amplification of the glasses. The result indicates that Ce3+/Yb3+/Er3+ triply doped BBS glasses are promising candidate for erbium doped fiber amplifiers. The strategy described here can be readily extended to other rare-earth ions (REs) to improve the performance of REs doped fiber lasers and amplifiers. PMID:27646191

Thermochemistry of Silicates

NASA Technical Reports Server (NTRS)

Costa, Gustavo; Jacobson, Nathan

2015-01-01

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

Large-mode-area single-mode-output Neodymium-doped silicate glass all-solid photonic crystal fiber

PubMed Central

Li, Wentao; Chen, Danping; Qinling, Zhou; Hu, Lili

2015-01-01

We have demonstrated a 45 μm core diameter Neodymium-doped all-solid silicate glass photonic crystal fiber laser with a single mode laser output. The structure parameters and modes information of the fiber are both demonstrated by theoretical calculations using Finite Difference Time Domain (FDTD) method and experimental measurements. Maximum 0.8 W output power limited by launched pump power has been generated in 1064 nm with laser beam quality factor M2 1.18. PMID:26205850

Inhibition and enhancement of microbial surface colonization: the role of silicate composition

USGS Publications Warehouse

Roberts, Jennifer A.

2004-01-01

Classical treatment of cell attachment by models of filtration or coulombic attraction assumes that attachment of cells to mineral surfaces would be controlled by factors such as response to predation, collision efficiency, or coulombic attraction between the charged groups at the mineral and cell surfaces. In the study reported here, the passive model of attachment was investigated using a native microbial consortium and a variety of Al- and Fe-bearing silicates and oxides to determine if other controls, such as mineral composition, also influence the interaction between cells and surfaces. Results from in situ colonization studies in an anaerobic groundwater at pH 6.8 combined with most probable number analyses (MPN) of surface-adherent cells demonstrate that electrostatic effects dominate microbial colonization on positively charged oxide surfaces regardless of mineral composition. In contrast, on negatively charged silicate minerals and glasses, the solid phase composition is a factor in determining the extent of microbial colonization, as well as the diversity of the attached community. In particular, silicates containing more than 1.2% Al exhibit less biomass than Al-poor silicates and MPN suggests a shift in community diversity, possibly indicating Al toxicity on these surfaces. When Fe is present in the silicate, however, this trend is reversed and abundant colonization of the surface is observed. Here, microorganisms preferentially colonize those silicate surfaces that offer beneficial nutrients and avoid those that contain potentially toxic elements.

Structural environments of incompatible elements in silicate glass/melt systems: I. Zirconium at trace levels

NASA Astrophysics Data System (ADS)

Farges, Franã§Ois; Ponader, Carl W.; Brown, Gordon E., Jr.

1991-06-01

The structural environments of trace levels (2˜000 ppm) of Zr 4+ in several silicate glasses were examined as a function of melt composition and polymerization using Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. Glass compositions investigated were albite (NaAlSi 3O 8: AB) and a peralkaline composition (Na 3.3AlSi 7O 17: PR)- Zirconium was added to the oxide-carbonate mix prior to melting in the form of ZrO 2 (baddeleyite). A second set of Zr-silicate glasses containing 2000 ppm Zr and 1.0 to 2.4 wt% halogens (F as NaF and Cl as NaCl) was also synthesized. These included the Zr-AB and Zr-PR base-glass compositions as well as Zr-sodium trisilicate composition (Na2Si 3O 7: TS). In all glasses studied, Zr is mainly 6-coordinated by oxygen atoms ( d[Zr-O] ˜2.07 ± 0.01 Å). In the most polymerized glass (AB), a small but significant amount of Zr was also found to occur in 8-coordinated sites ( d[Zr-O] ˜2.22 Å). No clear evidence for F or Cl complexes of Zr was observed in any of the halogen-containing glasses. The regularity of the Zr site increases in the series AB < TS ˜PR. We attribute this change to an increase in the number of non-bridging oxygens in the first-coordination sphere of Zr related to the depolymerizing effects of halogens and/or sodium. Minor but significant interactions of Zr with the tetrahedral network were observed ( d[Zr-{Si, Al}] ˜3.65-3.71 Å ± 0.03 Å), which are consistent with Zr-O-{Si, Al} angles close to 160-170°, as in catapleiite (Na 2ZrSi 3O 9 · 2H 2O). Intermediaterange order, as reflected by the presence and number of second-neighbor {Si, Al} around Zr, increases significantly with increasing melt polymerization. The local environment around Zr is more strongly influenced by bonding requirements than by the network topology of the melt. Stabilization of zirconium in 6-coordinated sites in relatively depolymerized melts should act to decrease the crystal-melt partition coefficients of Zr and may explain the

Spectroscopic study of biologically active glasses

NASA Astrophysics Data System (ADS)

Szumera, M.; Wacławska, I.; Mozgawa, W.; Sitarz, M.

2005-06-01

It is known that the chemical activity phenomenon is characteristic for some inorganic glasses and they are able to participate in biological processes of living organisms (plants, animals and human bodies). An example here is the selective removal of silicate-phosphate glass components under the influence of biological solutions, which has been applied in designing glasses acting as ecological fertilizers of controlled release rate of the nutrients for plants. The structure of model silicate-phosphate glasses containing the different amounts of the glass network formers, i.e. Ca 2+ and Mg 2+, as a binding components were studied. These elements besides other are indispensable of the normal growth of plants. In order to establish the function and position occupied by the particular components in the glass structure, the glasses were examined by FTIR spectroscopy (with spectra decomposition) and XRD methods. It has been found that the increasing amount of MgO in the structure of silicate-phosphate glasses causes the formation of domains the structure of which changes systematically from a structure of the cristobalite type to a structure corresponding to forsterite type. Whilst the increasing content of CaO in the structure of silicate-phosphate glasses causes the formation of domains the structure of which changes from a structure typical for cristobalite through one similar to the structure of calcium orthophosphate, to a structure corresponding to calcium silicates. The changing character of domains structure is the reason of different chemical activity of glasses.

Development of ytterbium-doped oxyfluoride glasses for laser cooling applications.

PubMed

Krishnaiah, Kummara Venkata; de Lima Filho, Elton Soares; Ledemi, Yannick; Nemova, Galina; Messaddeq, Younes; Kashyap, Raman

2016-02-26

Oxyfluoride glasses doped with 2, 5, 8, 12, 16 and 20 mol% of ytterbium (Yb(3+)) ions have been prepared by the conventional melt-quenching technique. Their optical, thermal and thermo-mechanical properties were characterized. Luminescence intensity at 1020 nm under laser excitation at 920 nm decreases with increasing Yb(3+) concentration, suggesting a decrease in the photoluminescence quantum yield (PLQY). The PLQY of the samples was measured with an integrating sphere using an absolute method. The highest PLQY was found to be 0.99(11) for the 2 mol% Yb(3+): glass and decreases with increasing Yb(3+) concentration. The mean fluorescence wavelength and background absorption of the samples were also evaluated. Upconversion luminescence under 975 nm laser excitation was observed and attributed to the presence of Tm(3+) and Er(3+) ions which exist as impurity traces with YbF3 starting powder. Decay curves for the Yb(3+): (2)F5/2 → (2)F7/2 transition exhibit single exponential behavior for all the samples, although lifetime decrease was observed for the excited level of Yb(3+) with increasing Yb(3+) concentration. Also observed are an increase in the PLQY and a slight decrease in lifetime with increasing the pump power. Finally, the potential of these oxyfluoride glasses with high PLQY and low background absorption for laser cooling applications is discussed.

Modeling the Onset of Phase Separation in CaO-SiO2-CaCl2 Chlorine-Containing Silicate Glasses.

PubMed

Swansbury, Laura A; Mountjoy, Gavin; Chen, Xiaojing; Karpukhina, Natalia; Hill, Robert

2017-06-08

The addition of chlorine into a bioactive glass composition is expected to reduce its abrasiveness and increase its bioactivity, which is important for dental applications such as toothpastes. There is a lack of information and understanding regarding the structural role of chlorine in chlorine-containing bioactive silicate glasses. This has prompted classical core-shell model molecular dynamics simulations of (50 - x/2)CaO-(50 - x/2)SiO 2 -xCaCl 2 glasses to be performed, where x ranges from x = 0.0 to 43.1 mol % CaCl 2 . These ternary glasses are advantageous for a fundamental study because they do not have additional network formers (e.g., phosphorus pentoxide) or modifiers (e.g., sodium) typically found in bioactive glass compositions. The (50 - x/2)CaO-(50 - x/2)SiO 2 -xCaCl 2 glasses were seen to become phase-separated around the x = 16.1 mol % CaCl 2 composition, and chlorine predominantly coordinated with calcium. These findings provide a solid foundation for further computational modeling work on more complex chlorine-containing bioactive glass compositions.

Spectroscopy `outside the box': Towards wider application of NMR to minerals and glasses with abundant paramagnetic cations - Fe, Ni, Co, and Cu silicates

NASA Astrophysics Data System (ADS)

Stebbins, J. F.

2017-12-01

Since the early applications of solid-state NMR (Nuclear Magnetic Resonance) to silicates in the early 1980's, this powerful method has been widely applied to problems of short- to medium-range structure, particularly for materials in which order/disorder is critical, such as crystalline solid solutions, glasses, and even melts. However, almost all such work has been on materials with low (< a few %) contents of ions with unpaired electron spins. Such spins interact strongly with NMR-observed nuclear spins, and can cause severe line broadening and loss of information, in some cases making spectra nearly unobservable. Many groups of minerals with abundant, paramagnetic transition metals (notably Fe2+) and rare earth cations, as well as wide, petrologically important ranges of glass composition have thus been excluded. Inspired by in-depth NMR studies of 31P, 7Li, and other nuclides in lithium-transition metal oxide and phosphate battery materials (C. Grey and others), and with some serendipitous discovery plus persistence to look far outside of "normal" parameter space, we have recently shown that high resolution, structurally informative spectra can actually be obtained for silicate, oxide, and phosphate solid solutions with moderate (0.1 up to 10%) contents of paramagnetic cations such as Fe2+, Ni2+, Co2+ and REE3+. Very recently we have extended this to observe some of the first quantitative NMR spectra of silicate minerals in which a paramagnetic transition metal is the major cation, obtaining useful data for a series of Cu2+ silicates, fayalite (Fe2SiO4) and Ni- and Co- equivalents of diopside (CaMSi2O6). New data for glasses of the latter compositions may be the first such accurate results for any transition metal-rich glass. Although we are still far from a detailed theoretical understanding of these data, the spectra for the glasses are quite different from those of the crystals, suggesting the possibility of medium-range ordering and clustering of NiO and

Cooling rate effects in sodium silicate glasses: Bridging the gap between molecular dynamics simulations and experiments

NASA Astrophysics Data System (ADS)

Li, Xin; Song, Weiying; Yang, Kai; Krishnan, N. M. Anoop; Wang, Bu; Smedskjaer, Morten M.; Mauro, John C.; Sant, Gaurav; Balonis, Magdalena; Bauchy, Mathieu

2017-08-01

Although molecular dynamics (MD) simulations are commonly used to predict the structure and properties of glasses, they are intrinsically limited to short time scales, necessitating the use of fast cooling rates. It is therefore challenging to compare results from MD simulations to experimental results for glasses cooled on typical laboratory time scales. Based on MD simulations of a sodium silicate glass with varying cooling rate (from 0.01 to 100 K/ps), here we show that thermal history primarily affects the medium-range order structure, while the short-range order is largely unaffected over the range of cooling rates simulated. This results in a decoupling between the enthalpy and volume relaxation functions, where the enthalpy quickly plateaus as the cooling rate decreases, whereas density exhibits a slower relaxation. Finally, we show that, using the proper extrapolation method, the outcomes of MD simulations can be meaningfully compared to experimental values when extrapolated to slower cooling rates.

Photoluminescence of transparent glass-ceramics based on ZnO nanocrystals and co-doped with Eu3+, Yb3+ ions

NASA Astrophysics Data System (ADS)

Arzumanyan, Grigory M.; Kuznetsov, Evgeny A.; Zhilin, Aleksandr A.; Dymshits, Olga S.; Shemchuk, Daria V.; Alekseeva, Irina P.; Mudryi, Alexandr V.; Zhivulko, Vadim D.; Borodavchenko, Olga M.

2016-12-01

Glasses of the K2Osbnd ZnOsbnd Al2O3sbnd SiO2 system co-doped with Eu2O3 and Yb2O3 were prepared by the melt-quenching technique. Transparent zincite (ZnO) glass-ceramics were obtained by secondary heat-treatments at 680-860 °C. At 860 °C, traces of Eu oxyapatite appeared in addition to ZnO nanocrystals. The average crystal size obtained from the X-ray diffraction data was found to range between 14 and 35 nm. Absorption spectra of the initial glasses are composed of an absorption edge and absorption bands due to electronic transitions of Eu3+ ions. With heat-treatment, the absorption edge pronouncedly shifts to the visible spectral range. The luminescence properties of the glass and glass-ceramics were studied by measuring their excitation and emission spectra at 300, 78, and 4.2 K. Strong red emission of Eu3+ ions dominated by the 5D0-7F2 (612 nm) electric dipole transition was detected. Changes in the luminescence properties of the Eu3+-related excitation and emission bands were observed after heat-treatments at 680 °C and 860 °C. The ZnO nanocrystals showed both broad luminescence (400-850 nm) and free-exciton emission near 3.3 eV at room temperature. The upconversion luminescence spectrum of the initial glass was obtained under excitation of the 976 nm laser source.

Energy transfer characteristics of silicate glass doped with Er3+, Tm3+, and Ho3+ for ˜2 μm emission

NASA Astrophysics Data System (ADS)

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

2013-12-01

A Er3+/Tm3+/Ho3+ tri-doped silicate glass with good thermal stability is prepared by melt-quenching method. Efficient ˜2 μm emission is observed under 808 nm laser excitation. It is found that the 2.0 μm emission of Ho3+ can be enhanced under the excitation at 808 nm by incorporating Er3+ and Tm3+. Based on the measurement of absorption spectra, the Judd-Ofelt intensity parameters, radiation emission probability, and branching ratio are calculated to evaluate the spectroscopic properties simultaneously. The maximum value of emission cross section of Ho3+ is 3.54 × 10-21 cm2 at 2008 nm. Additionally, the phonon assistance and the micro-parameters in the energy transfer process are quantitatively analyzed by using Dexter model. The energy transfer coefficient from Tm3+ to Ho3+ can reach as high as 21.44 × 10-40 cm6/s, respectively. The emission property together with good thermal property indicates that Er3+/Tm3+/Ho3+ tri-doped silicate glass is a potential kind of laser glass for efficient 2 μm laser.

Effect of natural and synthetic iron corrosion products on silicate glass alteration processes

NASA Astrophysics Data System (ADS)

Dillmann, Philippe; Gin, Stéphane; Neff, Delphine; Gentaz, Lucile; Rebiscoul, Diane

2016-01-01

Glass long term alteration in the context of high-level radioactive waste (HLW) storage is influenced by near-field materials and environmental context. As previous studies have shown, the extent of glass alteration is strongly related to the presence of iron in the system, mainly provided by the steel overpack around surrounding the HLW glass package. A key to understanding what will happen to the glass-borne elements in the geological disposal lies in the relationship between the iron-bearing phases and the glass alteration products formed. In this study, we focus on the influence of the formation conditions (synthetized or in-situ) and the age of different iron corrosion products on SON68 glass alteration. Corrosion products obtained from archaeological iron artifacts are considered here to be true analogues of the corrosion products in a waste disposal system due to the similarities in formation conditions and physical properties. These representative corrosion products (RCP) are used in the experiment along with synthetized iron anoxic corrosion products and pristine metallic iron. The model-cracks of SON68 glass were altered in cell reactors, with one of the different iron-sources inserted in the crack each time. The study was successful in reproducing most of the processes observed in the long term archaeological system. Between the different systems, alteration variations were noted both in nature and intensity, confirming the influence of the iron-source on glass alteration. Results seem to point to a lesser effect of long term iron corrosion products (RCP) on the glass alteration than that of the more recent products (SCP), both in terms of general glass alteration and of iron transport.

Modifier cation effects on 29Si nuclear shielding anisotropies in silicate glasses

NASA Astrophysics Data System (ADS)

Baltisberger, Jay H.; Florian, Pierre; Keeler, Eric G.; Phyo, Pyae A.; Sanders, Kevin J.; Grandinetti, Philip J.

2016-07-01

We have examined variations in the 29Si nuclear shielding tensor parameters of SiO4 tetrahedra in a series of seven alkali and alkaline earth silicate glass compositions, Cs2O · 4.81 SiO2, Rb2O · 3.96 SiO2, Rb2O · 2.25 SiO2, K2O · 4.48 SiO2, Na2O · 4.74 SiO2, BaO · 2.64 SiO2, and SrO · 2.36 SiO2, using natural abundance 29Si two-dimensional magic-angle flipping (MAF) experiments. Our analyses of these 2D spectra reveal a linear dependence of the 29Si nuclear shielding anisotropy of Q(3) sites on the Si-non-bridging oxygen bond length, which in turn depends on the cation potential and coordination of modifier cations to the non-bridging oxygen. We also demonstrate how a combination of Cu2+ as a paramagnetic dopant combined with echo train acquisition can reduce the total experiment time of 29Si 2D NMR measurements by two orders of magnitude, enabling higher throughput 2D NMR studies of glass structure.

Modifier cation effects on (29)Si nuclear shielding anisotropies in silicate glasses.

PubMed

Baltisberger, Jay H; Florian, Pierre; Keeler, Eric G; Phyo, Pyae A; Sanders, Kevin J; Grandinetti, Philip J

2016-07-01

We have examined variations in the (29)Si nuclear shielding tensor parameters of SiO4 tetrahedra in a series of seven alkali and alkaline earth silicate glass compositions, Cs2O·4.81 SiO2, Rb2O·3.96 SiO2, Rb2O·2.25 SiO2, K2O·4.48 SiO2, Na2O·4.74 SiO2, BaO·2.64 SiO2, and SrO·2.36 SiO2, using natural abundance (29)Si two-dimensional magic-angle flipping (MAF) experiments. Our analyses of these 2D spectra reveal a linear dependence of the (29)Si nuclear shielding anisotropy of Q((3)) sites on the Si-non-bridging oxygen bond length, which in turn depends on the cation potential and coordination of modifier cations to the non-bridging oxygen. We also demonstrate how a combination of Cu(2+) as a paramagnetic dopant combined with echo train acquisition can reduce the total experiment time of (29)Si 2D NMR measurements by two orders of magnitude, enabling higher throughput 2D NMR studies of glass structure. Copyright © 2016 Elsevier Inc. All rights reserved.

Thermal history effects on electrical relaxation and conductivity for potassium silicate glass with low alkali concentrations

NASA Technical Reports Server (NTRS)

Angel, Paul W.; Hann, Raiford E.; Cooper, Alfred R.

1993-01-01

Electrical response measurements from 10 Hz to 100 kHz between 120 and 540 C were made on potassium-silicate glasses with alkali oxide contents of 2, 3, 5 and 10 mol percent. Low alkali content glasses were chosen in order to try to reduce the Coulombic interactions between alkali ions to the point that frozen structural effects from the glass could be observed. Conductivity and electrical relaxation responses for both annealed and quenched glasses of the same composition were compared. Lower DC conductivity (sigma(sub DC)) activation energies were measured for the quenched compared to the annealed glasses. The two glasses with the lowest alkali contents exhibited a non-Arrhenius concave up curvature in the log(sigma(sub DC)) against 1/T plots, which decreased upon quenching. A sharp decrease in sigma(sub DC) was observed for glasses containing K2O concentrations of 5 mol percent or less. The log modulus loss peak (M'') maximum frequency plots against 1/T all showed Arrhenius behavior for both annealed and quenched samples. The activation energies for these plots closely agreed with the sigma(sub DC) activation energies. A sharp increase in activation energy was observed for both series as the potassium oxide concentration decreased. Changes in the electrical response are attributed to structural effects due to different alkali concentrations. Differences between the annealed and quenched response are linked to a change in the distribution of activation energies (DAE).

Investigation of gold and bimetallic gold/silver nanoparticles in soda-lime-silicate glasses formed by means of excimer laser irradiation

NASA Astrophysics Data System (ADS)

Heinz, M.; Dubiel, M.; Meinertz, J.; Ihlemann, J.; Hoell, A.

2017-02-01

In this study, plasmonic Au and Au/Ag nanostructures in soda-lime-silicate glasses have been generated by means of ArF-excimer laser irradiation (193 nm) below the ablation threshold of the glass. For this purpose pure and silver/sodium ion-exchanged float glasses have been coated by gold and then irradiated by the laser. The formation of Au and Au/Ag nanoparticles could be verified by the surface plasmon resonances between 420 and 620 nm, which were obtained by optical spectroscopy. Both, pure Au and Ag particles as well as bimetallic Au/Ag nanoparticles, could be observed by means of small angle X-ray scattering experiments. These results demonstrate that such procedures enable the spaceselected generation of plasmonic nanostructures in glass surfaces by excimer laser irradiation.

Pulse energy dependence of refractive index change in lithium niobium silicate glass during femtosecond laser direct writing.

PubMed

Cao, Jing; Poumellec, Bertrand; Brisset, François; Lancry, Matthieu

2018-03-19

Femtosecond laser-induced refractive index changes in lithium niobium silicate glass were explored at high repetition rate (300 fs, 500 kHz) by polarized light microscopy, full-wave retardation plate, quantitative birefringence microscopy, and digital holographic microscopy. We found three regimes on energy increase. The first one corresponds to isotropic negative refractive index change (for pulse energy ranging 0.4-0.8 μJ/pulse, 0.6 NA, 5μm/s, 650μm focusing depth in the glass). The second one (0.8-1.2 μJ/pulse) corresponds to birefringence with well-defined slow axis orientation. The third one (above 1.2 μJ/pulse) is related to birefringence direction fluctuation. Interestingly, these regimes are consistent with crystallization ones. In addition, an asymmetric orientational writing effect has been detected on birefringence. These topics extend the possibility of controlling refractive index change in multi-component glasses.

Optical band gap and spectroscopic study of lithium alumino silicate glass containing Y 3+ ions

NASA Astrophysics Data System (ADS)

Shakeri, M. S.; Rezvani, M.

2011-09-01

The effect of different amounts of Y 2O 3 dopant on lithium alumino silicate (LAS) glass has been studied in this work. Glasses having 14.8Li 2O-20Al 2O 3-65.2SiO 2 (wt%) composition accompanied with Y 2O 3 dopant were prepared by normal melting process. In order to calculate the absorption coefficient of samples, transmittance and reflectance spectra of polished samples were measured in the room temperature. Optical properties i.e. Fermi energy level, direct and indirect optical band gaps and Urbach energy were calculated using functionality of extinction coefficient from Fermi-Dirac distribution function, Tauc's plot and the exponential part of absorption coefficient diagram, respectively. It has been clarified that variation in mentioned optical parameters is associated with the changes in physical properties of samples i.e. density or molar mass. On the other hand, increasing of Y 3+ ions in the glassy microstructure of samples provides a semiconducting character to LAS glass by reducing the direct and indirect optical band gaps of glass samples from 1.97 to 1.67 and 3.46 to 2.1 (eV), respectively. These changes could be attributed to the role of Y 3+ ions as the network former in the track of SiO 4 tetrahedrals.

Development of ytterbium-doped oxyfluoride glasses for laser cooling applications

PubMed Central

Krishnaiah, Kummara Venkata; Soares de Lima Filho, Elton; Ledemi, Yannick; Nemova, Galina; Messaddeq, Younes; Kashyap, Raman

2016-01-01

Oxyfluoride glasses doped with 2, 5, 8, 12, 16 and 20 mol% of ytterbium (Yb3+) ions have been prepared by the conventional melt-quenching technique. Their optical, thermal and thermo-mechanical properties were characterized. Luminescence intensity at 1020 nm under laser excitation at 920 nm decreases with increasing Yb3+ concentration, suggesting a decrease in the photoluminescence quantum yield (PLQY). The PLQY of the samples was measured with an integrating sphere using an absolute method. The highest PLQY was found to be 0.99(11) for the 2 mol% Yb3+: glass and decreases with increasing Yb3+ concentration. The mean fluorescence wavelength and background absorption of the samples were also evaluated. Upconversion luminescence under 975 nm laser excitation was observed and attributed to the presence of Tm3+ and Er3+ ions which exist as impurity traces with YbF3 starting powder. Decay curves for the Yb3+: 2F5/2 → 2F7/2 transition exhibit single exponential behavior for all the samples, although lifetime decrease was observed for the excited level of Yb3+ with increasing Yb3+ concentration. Also observed are an increase in the PLQY and a slight decrease in lifetime with increasing the pump power. Finally, the potential of these oxyfluoride glasses with high PLQY and low background absorption for laser cooling applications is discussed. PMID:26915817

Ultrasonic characterization of silicate glasses, polymer composites and hydrogels

NASA Astrophysics Data System (ADS)

Lee, Wan Jae

In many applications of material designing and engineering, high-frequency linear viscoelastic properties of materials are essential. Traditionally, the high-frequency properties are estimated through the time-temperature superposition (WLF equation) of low-frequency data, which are questionable because the existence of multi-phase in elastomer compounds. Moreover, no reliable data at high frequencies over MHz have been available thus far. Ultrasound testing is cost-effective for measuring high-frequency properties. Although both ultrasonic longitudinal and shear properties are necessary in order to fully characterize high-frequency mechanical properties of materials, longitudinal properties will be extensively explored in this thesis. Ultrasonic pulse echo method measures longitudinal properties. A precision ultrasonic measurement system has been developed in our laboratory, which allows us to monitor the in-situ bulk and/or surface properties of silicate glasses, polymer composites and even hydrogels. The system consists of a pulse-echo unit and an impedance measurement unit. A pulse echo unit is explored mainly. First, a systematic procedure was developed to obtain precise water wavespeed value. A calibration curve of water wavespeed as a function of temperature has been established, and water wavespeed at 23°C serves as a yardstick to tell whether or not a setup is properly aligned. Second, a sound protocol in calculating attenuation coefficient and beam divergence effects was explored using three kinds of silicate glass of different thicknesses. Then the system was applied to four composite slabs, two slabs for each type of fiberglass reinforced plastics, phenolic and polyester manufactured under different processing conditions: one was made by the normal procedures and the other with deliberate flaws such as voids, tapes and/or prepared at improper operation temperature and pressure. The experiment was conducted under the double blind test protocol. After

The Oxidation State of Tungsten in Iron Bearing and Iron Free Silicate Glasses: Results from W L-Edge Xanes Measurements

NASA Technical Reports Server (NTRS)

Danielson, Lisa R.; Righter, K.; Sutton S.; Newville, M.; Le, L.

2007-01-01

Tungsten is important in constraining core formation of the Earth because this element is a moderately siderophile element (depleted approx. 10 relative to chondrites) and, as a member of the Hf-W isotopic system, it is useful in constraining the timing of core formation. A number of previous experimental studies have been carried out to determine the silicate solubility and metal-silicate partitioning behavior of W, including its concomitant oxidation state. However, results of previous studies (figure 1) are inconsistent on whether W occurs as W(4+) or W(6+).

Ultralow-threshold Yb(3+):SiO(2) glass laser fabricated by the solgel process.

PubMed

Ostby, Eric P; Yang, Lan; Vahala, Kerry J

2007-09-15

A Yb-doped silica microcavity laser on a silicon chip is fabricated from a solgel thin film. The high-Q micro-toroid cavity, which has a finesse of 10,000, is evanescently coupled to an optical fiber taper. We report a threshold of 1.8 microW absorbed power that is, to the best of our knowledge, the lowest published threshold to date for any Yb-doped laser. The effect of Yb(3+) concentration on laser threshold is experimentally quantified.

Light induced dielectric constant of Alumina doped lead silicate glass based on silica sands

NASA Astrophysics Data System (ADS)

Diantoro, Markus; Natalia, Desi Ayu; Mufti, Nandang; Hidayat, Arif

2016-04-01

Numerous studies on glass ceramic compounds have been conducted intensively. Two major problems to be solved are to simplify the fabrication process by reducing melting temperature as well as improving various properties for various fields of technological application. To control the dielectric constant, the researchers generally use a specific dopant. So far there is no comprehensive study to control the dielectric constant driven by both of dopant and light intensity. In this study it is used Al2O3 dopant to increase the light induced dielectric constant of the glass. The source of silica was taken from local silica sands of Bancar Tuban. The sands were firstly leached using hydrochloric acid to improve the purity of silica which was investigated by means of XRF. Fabricating the glass samples were performed by using melting-glass method. Silica powder was mixed with various ratio of SiO2:Na2CO3:PbO:Al2O3. Subsequently, a mixture of various Al2O3 doped lead silicate glasses were melted at 970°C and directy continued by annealed at 300°C. The samples were investigated by XRD, FTIR, SEM-EDX and measuring dielectric constant was done using dc-capacitance meter with various light intensities. The investigation result of XRD patterns showed that the crystal structures of the samples are amorphous state. The introduction of Al2O3 does not alter the crystal structure, but significantly change the structure of the functional glass bonding PbO-SiO2 which was shown by the FTIR spectra. It was noted that some new peak peaks were exist in the doped samples. Measuring result of dielectricity shows that the dielectric constant of glass increases with the addition of Al2O3. Increasing the light intensity gives rise to increase their dielectric constant in general. A detail observation of the dielectric seen that there are discontinuous step-like of dielectric. Most likely a specific quantization mechanism occurs when glass exposed under light.

Femtosecond laser-induced refractive index modification in multicomponent glasses

NASA Astrophysics Data System (ADS)

Bhardwaj, V. R.; Simova, E.; Corkum, P. B.; Rayner, D. M.; Hnatovsky, C.; Taylor, R. S.; Schreder, B.; Kluge, M.; Zimmer, J.

2005-04-01

We present a comprehensive study on femtosecond laser-induced refractive index modification in a wide variety of multicomponent glasses grouped as borosilicate, aluminum-silicate, and heavy-metal oxide glasses along with lanthanum-borate and sodium-phosphate glasses. By using high-spatial resolution refractive index profiling techniques, we demonstrate that under a wide range of writing conditions the refractive index modification in multicomponent glasses can be positive, negative, or nonuniform, and exhibits a strong dependence on the glass composition. With the exception of some aluminum-silicate glasses all other glasses exhibited a negative/nonuniform index change. We also demonstrate direct writing of waveguides in photosensitive Foturan® glass with a femtosecond laser without initiating crystallization by thermal treatment. Upon ceramization of lithium-aluminum-silicate glasses such as Foturan®, Zerodur®, and Robax® we observe switching of laser-induced refractive index change from being positive to negative. The measured transmission losses in the waveguides at 1550nm agree with the index profile measurements in alkali-free aluminum-silicate glasses.

A Multi-spectroscopic Investigation of Sulphur Speciation in Silicate Glasses and Slags

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bingham, P.; Connelly, A; Hand, R

2010-01-01

Sulphur K-edge x-ray absorption near-edge structure (XANES), sulphur K{sub {alpha}} and K{sub {beta}} high resolution x-ray emission spectroscopies (XES), electron paramagnetic resonance (EPR) and optical absorption spectroscopies have been used to study the speciation of sulphur in a range of soda-lime-silica glasses and silicate slags. Several inorganic standards with known sulphur oxidation states and structural environments have also been analysed. Results confirm that the average oxidation state of sulphur in glasses decreases, as expected, in the order (colourless>light olive>dark olive>light amber>dark amber). This behaviour is consistent with decreasing S{sup 6+}/{Sigma}S ratio, which has been quantified by linear combination fitting ofmore » XES S K{alpha} spectra, and with analysed sulphur contents which exhibit a characteristic relationship with oxygen partial pressure, pO{sub 2}. A combination of S{sup 6+}, S{sup 5+}, S{sup 4+} and more reduced sulphur species has been detected in olive and amber glasses. The S{sup 4+} and S{sup 5+} species are most evident in olive-coloured glasses produced under moderately reducing conditions that coincide with minimum sulphur solubilities. The reduced form of sulphur, present in all reduced glasses, is interpreted as being present as S{sup 2-} on the basis of XANES, XES, EPR and optical measurements. An alternative interpretation of the data is that there is a continuum of less strongly reduced species, primarily S{sup +} and S{sup 2+}; this interpretation has less merit. In this paper we show that the established relationship that describes sulphur redox only in terms of S{sup 6+} and S{sup 2-}, and which states that only these two species co-exist over a narrow, moderately reducing range of pO{sub 2}, does not fully describe the behaviour of S in the industrial, non-equilibrated glasses studied. Hence this relationship requires slight modification for non-equilibrated systems to explain the existence of

Intense upconversion luminescence and effect of local environment for Tm3+/Yb3+ co-doped novel TeO2-BiCl3 glass system.

PubMed

Wang, Guonian; Dai, Shixun; Zhang, Junjie; Wen, Lei; Yang, Jianhu; Jiang, Zhonghong

2006-05-15

We present the results of a study that uses theoretical and experimental methods to investigate the characteristics of the upconversion luminescence of Tm3+/Yb3+ codoped TeO2-BiCl3 glass system as a function of the BiCl3 fraction. These glasses are potentially important in the design of upconversion fiber lasers. Effect of local environment around Tm3+ on upconversion fluorescence intensity was analyzed by theoretical calculations. The structure and spectroscopic properties were investigated in the experiments by measuring the Raman spectra, IR transmission spectra, and absorption and fluorescence intensities at room temperature. The results indicate that blue luminescence quantum efficiency increases with increasing BiCl3 content from 10 to 60 mol%, which were interpreted by the increase of asymmetry of glass structure, decrease of phonon energy and removing of OH- groups.

Tuning into single-band red upconversion luminescence in Yb(3+)/Ho(3+) activated nano-glass-ceramics through Ce(3+) doping.

PubMed

Chen, Daqin; Zhou, Yang; Wan, Zhongyi; Ji, Zhenguo; Huang, Ping

2015-03-28

Yb(3+)/Ho(3+) activated glass ceramics containing β-YF3 nanocrystals were successfully fabricated. The green ((5)S2/(5)F4→(5)I8) upconversion emission is dominant in the glass ceramics and is about 160 times stronger than that of the precursor glass, resulting from the partition of lanthanide activators into a low-phonon-energy crystalline lattice and the subsequent low probability of multi-phonon nonradiative relaxation from the (5)S2/(5)F4 and (5)I6 states to the lower ones. Upon the introduction of Ce(3+) ions into nano-glass-ceramics, two efficient cross-relaxation processes between Ho(3+) and Ce(3+), i.e., Ho(3+):(5)S2/(5)F4 + Ce(3+):(2)F5/2→Ho(3+):(5)F5 + Ce(3+):(2)F7/2 and Ho(3+):(5)I6 + Ce(3+):(2)F5/2→Ho(3+):(5)I7 + Ce(3+):(2)F7/2, are demonstrated to greatly suppress the population of the green-emitting (5)S2/(5)F4 state and to enhance the population of the red-emitting (5)F5 one, leading to the intense single-band red UC radiation of Ho(3+).

Crystallization kinetics of Mg–Cu–Yb–Ca–Ag metallic glasses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsarkov, Andrey A., E-mail: tsarkov@misis.ru; WPI Advanced Institute for Materials Research, Tohoku University, Katahira 2-1-1, Aoba-Ku, Sendai 980-8577; Zanaeva, Erzhena N.

The paper presents research into a Mg–Cu–Yb system based metallic glassy alloys. Metallic glasses were prepared using induction melting and further injection on a spinning copper wheel. The effect of alloying by Ag and Ca on the glass forming ability and the kinetics of crystallization of Mg–Cu–Yb system based alloys were studied. The differential scanning calorimeter and X-ray diffractometer were used to investigate the kinetics of crystallization and the phase composition of the samples. An indicator of glass forming ability, effective activation energy of crystallization, and enthalpy of mixing were calculated. An increase of the Ca and Ag content hasmore » a positive effect on the glass forming ability, the effective activation energy of crystallization, and the enthalpy of mixing. The highest indicators of the glass forming ability and the thermal stability were found for alloys that contain both alloying elements. The Ag addition suppresses precipitation of the Mg{sub 2}Cu phase during crystallization. A dual-phase glassy-nanocrystalline Mg structure was obtained in Mg{sub 65}Cu{sub 25}Yb{sub 10} and Mg{sub 59.5}Cu{sub 22.9}Yb{sub 11}Ag{sub 6.6} alloys after annealing. Bulk samples with a composite glassy-crystalline structure were obtained in Mg{sub 59.5}Cu{sub 22.9}Yb{sub 11}Ag{sub 6.6} and Mg{sub 64}Cu{sub 21}Yb{sub 9.5}Ag{sub 5.5} alloys. A thermodynamic database for the Mg–Cu–Yb–Ca–Ag system was created to compare the process of crystallization of alloys with polythermal sections of the Mg–Cu–Yb–Ca–Ag phase diagram. - Highlights: • New alloy compositions based on Mg–Cu–Yb system were developed and investigated. • Increasing content of Ag and Ca leads to improving GFA. • Bulk samples with a composite glassy-crystalline structure were obtained. • Thermodynamic database for Mg–Cu–Yb–Ca–Ag system was created.« less

The effects of RF plasma ashing on zinc orthotitanate/potassium silicate thermal control coatings

NASA Technical Reports Server (NTRS)

Dever, Joyce A.; Bruckner, Eric J.

1992-01-01

Samples of YB-71, a white thermal control coating composed of zinc orthotitanate pigment in a potassium silicate binder, were exposed in air plasma and in oxygen plasma to determine optical property and surface chemistry changes. Results show that YB-71 undergoes a significant reflectance decrease upon exposure to the simulated LEO atomic oxygen environment provided by an air plasma asher. YB-71 samples exposed to the same effective fluence in oxygen plasma, or in a UV screening Faraday cage in air or oxygen, do not undergo as severe reflectance decreases as the samples exposed in the air plasma asher environment. The UV and VUV radiation present in the plasma ashers affects the YB-71 degradation. It is noted that, when using plasma ashers to determine LEO degradation, it is necessary to take into account the sensitivity of the material to the synergistic effects of atomic oxygen and accelerated UV radiation.

Optical band gap and spectroscopic study of lithium alumino silicate glass containing Y3+ ions.

PubMed

Shakeri, M S; Rezvani, M

2011-09-01

The effect of different amounts of Y2O3 dopant on lithium alumino silicate (LAS) glass has been studied in this work. Glasses having 14.8Li2O-20Al2O3-65.2SiO2 (wt%) composition accompanied with Y2O3 dopant were prepared by normal melting process. In order to calculate the absorption coefficient of samples, transmittance and reflectance spectra of polished samples were measured in the room temperature. Optical properties i.e. Fermi energy level, direct and indirect optical band gaps and Urbach energy were calculated using functionality of extinction coefficient from Fermi-Dirac distribution function, Tauc's plot and the exponential part of absorption coefficient diagram, respectively. It has been clarified that variation in mentioned optical parameters is associated with the changes in physical properties of samples i.e. density or molar mass. On the other hand, increasing of Y3+ ions in the glassy microstructure of samples provides a semiconducting character to LAS glass by reducing the direct and indirect optical band gaps of glass samples from 1.97 to 1.67 and 3.46 to 2.1 (eV), respectively. These changes could be attributed to the role of Y3+ ions as the network former in the track of SiO4 tetrahedrals. Copyright © 2011 Elsevier B.V. All rights reserved.

Loss of halogens from crystallized and glassy silicic volcanic rocks

USGS Publications Warehouse

Noble, D.C.; Smith, V.C.; Peck, L.C.

1967-01-01

One hundred and sixty-four F and Cl analyses of silicic welded tuffs and lavas and glass separates are presented. Comparison of the F and Cl contents of crystallized rocks with those of nonhydrated glass and hydrated glassy rocks from the same rock units shows that most of the halogens originally present were lost on crystallization. An average of about half of the F and four-fifths of the Cl originally present was lost. Analyses of hydrated natural glasses and of glassy rocks indicate that in some cases significant amounts of halogens may be removed from or added to hydrated glass through prolonged contact with ground water. The data show that the original halogen contents of the groundmass of a silicic volcanic rock can be reliably determined only from nonhydrated glass. ?? 1967.

Regularities in Low-Temperature Phosphatization of Silicates

NASA Astrophysics Data System (ADS)

Savenko, A. V.

2018-01-01

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

Ho3+/Yb3+ co-doped TeO2-BaF2-Y2O3 glasses for ∼1.2 μm laser applications

NASA Astrophysics Data System (ADS)

Wang, Shunbin; Li, Chengzhi; Yao, Chuanfei; Jia, Shijie; Jia, Zhixu; Qin, Guanshi; Qin, Weiping

2017-02-01

Intense ∼1.2 μm fluorescence is observed in Ho3+/Yb3+ co-doped TeO2-BaF2-Y2O3 glasses under 915 nm laser diode excitation. The 1.2 μm emission can be ascribed to the transition 5I6→5I8 of Ho3+. With the introducing of BaF2, the content of OH in the glasses drops markedly, and the 1.2 μm emission intensity increases gradually as increasing the concentration percentage of BaF2. Furthermore, microstructured fibers based on the TeO2-BaF2-Y2O3 glasses are fabricated by using a rod-in-tube method, and a relative positive gain of ∼9.42 dB at 1175.3 nm is obtained in a 5 cm long fiber.

Preparation of high density heavy metal fluoride glasses with extended ultraviolet and infra red ranges, and such high density heavy metal fluoride glasses

NASA Technical Reports Server (NTRS)

Martin, Steven W. (Inventor); Huebsch, Jesse (Inventor)

2001-01-01

A heavy metal fluoride glass composition range (in mol percent) consisting essentially of: (16-30)BaF.sub.2.(8-26)HfF.sub.4.(6-24)InF.sub.3 or GaF.sub.3.(4-16)CdF.sub.2.(6-24)YbF.sub.3.(4-22)ZnF.sub.2. In an alternative embodiment, a heavy metal fluoride glass composition range (in mol percent) comprises (16-30)BaF.sub.2.(8-26)HfF.sub.4.(6-24) of (0-24)InF.sub.3, (0-24)GaF.sub.3 and (0-19)AlF.sub.3.(1-16)CdF.sub.2.(6-24)YbF.sub.3.(4-26)ZnF.sub.2. A preferred heavy metal fluoride glass produced in accordance with the present invention comprises a composition (in mol %) and comprises about 26BaF.sub.2.18HfF.sub.4.7InF.sub.3.5GaF.sub.3.10CdF.sub.2.18YbF.sub.3. 16ZnF.sub.2. A preferred heavy metal fluoride glass has maximum thickness of most preferably about 3 mm. Another preferred heavy metal fluoride glass comprises a composition (in mol %) and comprises about 26BaF.sub.2.18HfF.sub.4.12AlF.sub.3.10CdF.sub.2.18YbF.sub.3.16ZnF.sub.2.

Silicate, borosilicate, and borate bioactive glass scaffolds with controllable degradation rate for bone tissue engineering applications. I. Preparation and in vitro degradation.

PubMed

Fu, Qiang; Rahaman, Mohamed N; Fu, Hailuo; Liu, Xin

2010-10-01

Bioactive glass scaffolds with a microstructure similar to that of dry human trabecular bone but with three different compositions were evaluated for potential applications in bone repair. The preparation of the scaffolds and the effect of the glass composition on the degradation and conversion of the scaffolds to a hydroxyapatite (HA)-type material in a simulated body fluid (SBF) are reported here (Part I). The in vitro response of osteogenic cells to the scaffolds and the in vivo evaluation of the scaffolds in a rat subcutaneous implantation model are described in Part II. Scaffolds (porosity = 78-82%; pore size = 100-500 microm) were prepared using a polymer foam replication technique. The glasses consisted of a silicate (13-93) composition, a borosilicate composition (designated 13-93B1), and a borate composition (13-93B3), in which one-third or all of the SiO2 content of 13-93 was replaced by B2O3, respectively. The conversion rate of the scaffolds to HA in the SBF increased markedly with the B2O3 content of the glass. Concurrently, the pH of the SBF also increased with the B2O3 content of the scaffolds. The compressive strengths of the as-prepared scaffolds (5-11 MPa) were in the upper range of values reported for trabecular bone, but they decreased markedly with immersion time in the SBF and with increasing B2O3 content of the glass. The results show that scaffolds with a wide range of bioactivity and degradation rate can be achieved by replacing varying amounts of SiO(2) in silicate bioactive glass with B2O3. Copyright 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2010.

Water in silicate melts

NASA Astrophysics Data System (ADS)

McMillan, Paul; Stolper, Edward

Water is one of the more important volatile species in magmas, both in terms of its abundance and its influence on the properties of a given magma. Many workers in the geological sciences have measured, modeled, and speculated on the interaction of water with silicate melts as a function of pressure. At the same time, glass and materials scientists have collected a considerable body of data on the effect of water on the properties of liquid and glassy silicates at 1 atmosphere (1.01325×105 N m-2) and below. A special session on “Solubility and Transport Properties of Water in Silicate Melts” was held during the 1983 AGU Spring Meeting, May 30-June 3, in Baltimore. The session had three main objectives: (1) review the present data base and discuss the status of current models in order to identify areas where further work is needed; (2) introduce interested geologists to the large body of work being carried out in the glass and materials sciences; and (3) consider static properties, such as thermodynamic relations, structure of hydrous melts, and dynamic properties including diffusion and viscosity. This report summarizes the major topics discussed. More detailed information may be found in the published abstracts (Eos, May 3, 1983, pp. 338-343).

Thermochemistry of Rare Earth Silicates for Environmental Barrier Coatings

NASA Technical Reports Server (NTRS)

Costa, Gustavo; Jacobson, Nathan

2015-01-01

Rare earth silicates are promising candidates as environmental protective coatings (EBCs) for silica-forming ceramics and composites in combustion environments since they are predicted to have lower reactivity with the water vapor combustion products. The reactivity of rare earth silicates is assessed by the thermodynamic activity of the silica component which is best measured by Knudsen effusion mass spectrometry (KEMS). Here, we discuss a novel method based on a reducing agent to increase the partial pressure of SiO(g) which is then used to calculate thermodynamic activity of silica in Y2O3-SiO2 and Yb2O3-SiO2 systems. After the KEMS measurements, samples were probed by X-ray diffraction and their phase content was calculated from Rietveld refinement.

Accurate predictions of iron redox state in silicate glasses: A multivariate approach using X-ray absorption spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dyar, M. Darby; McCanta, Molly; Breves, Elly

2016-03-01

Pre-edge features in the K absorption edge of X-ray absorption spectra are commonly used to predict Fe3+ valence state in silicate glasses. However, this study shows that using the entire spectral region from the pre-edge into the extended X-ray absorption fine-structure region provides more accurate results when combined with multivariate analysis techniques. The least absolute shrinkage and selection operator (lasso) regression technique yields %Fe3+ values that are accurate to ±3.6% absolute when the full spectral region is employed. This method can be used across a broad range of glass compositions, is easily automated, and is demonstrated to yield accurate resultsmore » from different synchrotrons. It will enable future studies involving X-ray mapping of redox gradients on standard thin sections at 1 × 1 μm pixel sizes.« less

Accurate predictions of iron redox state in silicate glasses: A multivariate approach using X-ray absorption spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dyar, M. Darby; McCanta, Molly; Breves, Elly

2016-03-01

Pre-edge features in the K absorption edge of X-ray absorption spectra are commonly used to predict Fe 3+ valence state in silicate glasses. However, this study shows that using the entire spectral region from the pre-edge into the extended X-ray absorption fine-structure region provides more accurate results when combined with multivariate analysis techniques. The least absolute shrinkage and selection operator (lasso) regression technique yields %Fe 3+ values that are accurate to ±3.6% absolute when the full spectral region is employed. This method can be used across a broad range of glass compositions, is easily automated, and is demonstrated to yieldmore » accurate results from different synchrotrons. It will enable future studies involving X-ray mapping of redox gradients on standard thin sections at 1 × 1 μm pixel sizes.« less

X-Ray Absorption Spectroscopy Studies of the Atomic Structure of Zirconium-Doped Lithium Silicate Glasses and Glass-Ceramics, Zirconium-Doped Lithium Borate Glasses, and Vitreous Rare-Earth Phosphates

NASA Astrophysics Data System (ADS)

Yoo, Changhyeon

In the first part of this work, the atomic-scale structure around rare-earth (RE = Pr, Nd, Eu, Dy, and Er) cations (RE3+) in rare-earth sodium ultraphosphate (REUP) glasses were investigated using RE LIII -edge (RE = Nd, Er, Dy, and Eu) and K-edge (RE = Pr and Dy) Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. (RE2O 3)x(Na2O)y(P2O5) 1-x-y glasses in the compositional range 0 ≤ x ≤ 0.14 and 0.3 ≤ x + y ≤ 0.4 were studied. For the nearest oxygen shell, the RE-oxygen (RE-O) coordination number decreases from 10.8 to 6.5 with increasing RE content for Pr-, Nd-, Dy-, and Er-doped sodium ultraphosphate glasses. For Eu-doped samples, the Eu-O coordination number was between 7.5 and 8.8. Also, the RE-O mean distance ranges were between 2.43-2.45 A, 2.40-2.43 A, 2.36-2.38 A, 2.30-2.35 A, and 2.28-2.30 A for Pr-, Nd-, Eu-, Dy-, and Er-doped samples, respectively. In the second part, a series of Zr-doped (3-10 mol%) lithium silicate (ZRLS) glass-ceramics and their parent glasses and a series of Zr-doped (2-6 mol% ZrO2) lithium borate (ZRLB) glasses were investigated using Zr K-edge EXAFS and X-ray Absorption Near Edge Structure (XANES) spectroscopy. Immediate coordination environments of all ZRLS glasses are remarkably similar for different compositions. For the nearest oxygen shell, the Zr-O coordination number ranges were between 6.1 and 6.3 for nucleated and crystallized samples, respectively. Also, the Zr-O mean distance remains similar around 2.10 A. For these glasses, the composition dependence of structural parameters was small. Small changes in the coordination environment were observed for ZRLS glass-ceramics after thermal treatments. In contrast, Zr coordination environment in ZRLB glasses appear to depend appreciably on the Zr concentration. For the nearest oxygen shell, the Zr-O coordination number increased from 6.1 to 6.8 and the Zr-O distance decreased from 2.18 A to 2.14 A with decreasing ZrO2 content.

Sensitivity of novel silicate and borate-based glass structures on in vitro bioactivity and degradation behaviour.

PubMed

Mancuso, Elena; Bretcanu, Oana; Marshall, Martyn; Dalgarno, Kenneth W

2017-10-15

Three novel glass compositions, identified as NCL2 (SiO 2 -based), NCL4 (B 2 O 3 -based) and NCL7 (SiO 2 -based), along with apatite-wollastonite (AW) were processed to form sintered dense pellets, and subsequently evaluated for their in vitro bioactive potential, resulting physico-chemical properties and degradation rate. Microstructural analysis showed the carbonated hydroxyapatite (HCA) precipitate morphology following SBF testing to be composition-dependent. AW and the NCL7 formulation exhibited greater HCA precursor formation than the NCL2 and NCL4-derived pellets. Moreover, the NCL4 borate-based samples showed the highest biodegradation rate; with silicate-derived structures displaying the lowest weight loss after SBF immersion. The results of this study suggested that glass composition has significant influence on apatite-forming ability and also degradation rate, indicating the possibility to customise the properties of this class of materials towards the bone repair and regeneration process.

Equilibrium Tin Isotope Fractionation during Metal-Sulfide-Silicate Differentiation: A Nuclear Resonant Inelastic X-ray Scattering Approach

NASA Astrophysics Data System (ADS)

Roskosz, M.; Amet, Q.; Fitoussi, C.; Laporte, D.; Hu, M. Y.; Alp, E. E.

2016-12-01

Metal-silicate differentiation was recently addressed through the insight of the isotopic composition of siderophile elements (mainly Fe, Si and Cr isotopes) of planetary and extraterrestrial bodies. A key limitation of this approach is however the knowledge of equilibrium fractionation factors between coexisting phases (metal alloys, silicates and sulfides) used to interpret data on natural samples. These properties are difficult to determine experimentally. In this context, tin is generally classified as a chalcophile element but it is also siderophile and volatile. We applied a synchrotron-based method to circumvent difficulties related to determination of equilibrium isotope fractionation. The nuclear resonant inelastic x-ray scattering (NRIXS) was used to measure the phonon excitation spectrum and then to derive the force constant and finally the fractionation factors of Sn-bearing geomaterials. Spectroscopic measurements were carried out at room pressure at Sector 30-ID (APS, USA). A range of Fe-Ni alloys, rhyolitic and basaltic glasses and iron sulfides containing isotopically enriched 119Sn were synthesized. The tin content and the redox conditions prevailing during the synthesis were varied. The data evaluation was carried out using PHOENIX and SciPhon programs. A strong effect of both the redox state and the tin content was measured. In addition, the composition of the silicate glasses was found to be another important factor determining the tin isotope metal-silicate-sulfide fractionation factors. Our results are consistent with trends previously observed in the case of iron isotopes [1,2]. We will discuss the implications of our experimental results in terms of tin isotope planetary signatures. References: [1] Dauphas et al. (2014), EPSL, 398, 127-140; [2] Roskosz et al. (2015), GCA, 169, 184-199.

Fluoride glass compositions

DOE Office of Scientific and Technical Information (OSTI.GOV)

El-Bayoumi, O.

1983-08-09

This invention relates to Fluoride-based glasses that exhibit a high degree of transparency throughout the near ultraviolet visible and mid infrared portions of the spectrum. The glasses are composed of MgF2 and ZnF2 as essential compositional ingredients together with at least two other metallic fluorides from the group of YbF3, ThF4, PbF2, A1F3 and MnF2.

The effect of micro-structure on upconversion luminescence of Nd3+/Yb3+ co-doped La2O3-TiO2-ZrO2 glass-ceramics

NASA Astrophysics Data System (ADS)

Zhang, Minghui; Wen, Haiqin; Pan, Xiuhong; Yu, Jianding; Jiang, Meng; Yu, Huimei; Tang, Meibo; Gai, Lijun; Ai, Fei

2018-03-01

Nd3+/Yb3+ co-doped La2O3-TiO2-ZrO2 glasses have been prepared by aerodynamic levitation method. The glasses show high refractive index of 2.28 and Abbe number of 18.3. Glass-ceramics heated at 880 °C for 50 min perform the strongest upconversion luminescence. X-ray diffraction patterns of glass-ceramics with different depths indicate that rare earth ions restrain crystallization. Body crystallization mechanism mixed with surface crystallization is confirmed in the heat treatment. Surface crystals achieve priority to grow, resulting in important effects on upconversion luminescence. The results of atomic force microscope and scanning electron microscope indicate that crystal particles with uniform size distribute densely and homogenously on the surface and large amount of glass matrix exists in the glass ceramics heated at 880 °C for 50 min. Crystals in the glass-ceramics present dense structure and strong boundaries, which can reduce the mutual nonradiative relaxation rate among rare earth ions and then improve upconversion luminescence effectively. Based on micro-structural study, the mechanism that upconversion luminescence can be improved by heat treatment has been revealed. The results of micro-structural analysis agree well with the spectra.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ishizuka, Shinnosuke; Kimura, Yuki; Sakon, Itsuki

2015-04-20

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

Silicate, borosilicate, and borate bioactive glass scaffolds with controllable degradation rate for bone tissue engineering applications. II. In vitro and in vivo biological evaluation.

PubMed

Fu, Qiang; Rahaman, Mohamed N; Bal, B Sonny; Bonewald, Lynda F; Kuroki, Keiichi; Brown, Roger F

2010-10-01

In Part I, the in vitro degradation of bioactivAR52115e glass scaffolds with a microstructure similar to that of human trabecular bone, but with three different compositions, was investigated as a function of immersion time in a simulated body fluid. The glasses consisted of a silicate (13-93) composition, a borosilicate composition (designated 13-93B1), and a borate composition (13-93B3), in which one-third or all of the SiO2 content of 13-93 was replaced by B2O3, respectively. This work is an extension of Part I, to investigate the effect of the glass composition on the in vitro response of osteogenic MLO-A5 cells to these scaffolds, and on the ability of the scaffolds to support tissue infiltration in a rat subcutaneous implantation model. The results of assays for cell viability and alkaline phosphatase activity showed that the slower degrading silicate 13-93 and borosilicate 13-93B1 scaffolds were far better than the borate 13-93B3 scaffolds in supporting cell proliferation and function. However, all three groups of scaffolds showed the ability to support tissue infiltration in vivo after implantation for 6 weeks. The results indicate that the required bioactivity and degradation rate may be achieved by substituting an appropriate amount of SiO2 in 13-93 glass with B2O3, and that these trabecular glass scaffolds could serve as substrates for the repair and regeneration of contained bone defects. Copyright 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2010.

White light generation via up-conversion and blue tone in Er3+/Tm3+/Yb3+-doped zinc-tellurite glasses

NASA Astrophysics Data System (ADS)

Rivera, V. A. G.; Ferri, F. A.; Nunes, L. A. O.; Marega, E.

2017-05-01

Yb3+, Er3+ and Tm3+ triply doped zinc-tellurite glass have been prepared containing up to 3.23 wt% of rare-earth ion oxides, were characterized by absorption spectroscopy, excitation, emission and up-conversion spectra. Transparent and homogeneous glasses have been produced, managing the red, green and blue emission bands, in order to generate white light considering the human eye perception. The energy transfer (resonant or non-resonant) between those rare-earth ions provides a color balancing mechanism that maintains the operating point in the white region, generating warm white light, cool white light and artificial daylight through the increase of the 976/980 nm diode laser excitation power from 4 to 470 mW. A light source at 4000 K is obtained under the excitation at 980 nm with 15 mW, providing a white light environment that is comfortable to the human eye vision. The spectroscopic study presented in this work describes the white light generation by the triply-doped zinc-tellurite glass, ranging from blue, green and red, by controlling the laser excitation power and wavelength at 976/980 nm. Such white tuning provokes healthy effects on human health throughout the day, especially the circadian system.

Chemical Behavior of Sulfur in Minerals and Silicate Glasses Studied Using Inner Shell Spectroscopy

NASA Astrophysics Data System (ADS)

Alonso Mori, R.; Paris, E.; Glatzel, P.; Giuli, G.; Scaillet, B.

2008-12-01

Understanding the chemical behaviour of sulfur is of fundamental importance in explaining different geological mechanisms ranging from volcano-climatic interactions to the genesis of ore deposits. Understanding how sulphur behaves is also of great economic importance in industrial activities including glass-forming processes and the treatment of vitreous waste material from refuse incineration. The chemical behaviour of sulfur in minerals and glasses has been widely studied via X-ray absorption near edge structure (XANES) spectroscopy, which probes the unoccupied density of states and thus provides information on the oxidation state and local structure of the species under study. However, the XANES spectral shape is influenced by various effects, namely the local symmetry, the ligand type, even up to high coordination spheres, and the valence electron occupation, making it difficult to systematically analyze the different spectral contributions. We use X-ray emission spectroscopy (XES) as a complementary technique to avoid some of the inherent difficulties of XANES analysis, and to extract additional information on the electronic structure. The Kb lines, close to the K-edge, directly yield the p-density of occupied valence states, giving valuable information on the local coordination. We have compared XANES and Kb XES experimental data on sulfur- bearing minerals with ab initio quantum-chemical calculations based on density functional theory (DFT), in order to visualize the molecular orbitals and to extract information about the chemical bonding in these compounds. The S Ka emission lines, which arise from 2p to 1s transitions, are expected to be mostly free from chemical bond effects except for small energy shifts that reflect the valence orbital electron population via screening effects. S Ka shifts can be readily used to determine the speciation of sulfur in silicate glasses. The electronic configuration of the sulfur atoms is obtained by calculating the

Dissolution of lanthanide alumino-silicate oxynitride glasses

NASA Astrophysics Data System (ADS)

Bois, L.; Barré, N.; Guillopé, S.; Guittet, M. J.; Gautier-Soyer, M.; Duraud, J. P.; Trocellier, P.; Verdier, P.; Laurent, Y.

2000-01-01

The aqueous corrosion behavior of lanthanide aluminosilicate glasses has been studied under static conditions ( T=96°C, duration=1 and 3 months, glass surface area/leachate volume, S/ V=0.3 cm -1) by means of solution and solid analyses. It was found that these glasses exhibit a high chemical durability. The influence of yttrium, magnesium and nitrogen, which are supposed to improve the mechanical properties, on the chemical durability, has been investigated. After a one-month experiment, lanthanum and yttrium releases were found to be about 10 -7 mol l -1, while silicon and aluminum releases were about 10 -5 mol l -1. Yttrium seems to improve the chemical durability. The presence of nitrogen does not seem to modify the glass constituents releases, but seems to improve the surface state of the altered glass. XPS experiments reveal that lanthanum and yttrium are more concentrated near the surface (20-30 Å) of the glass after the leaching test.

Cluster formation of network-modifier cations in cesium silicate glasses

NASA Astrophysics Data System (ADS)

Jardón-Álvarez, Daniel; Sanders, Kevin J.; Phyo, Pyae; Baltisberger, Jay H.; Grandinetti, Philip J.

2018-03-01

Natural abundance 29Si two-dimensional magic-angle flipping (2D MAF) NMR spectra were measured in a series of ten cesium silicate glass compositions xCs2O.(1 - x)SiO2, where x is 0.067, 0.113, 0.175, 0.179, 0.218, 0.234, 0.263, 0.298, 0.31, and 0.36. The Q3 shielding anisotropy decreases with increasing Cs content—interpreted as an increase in the non-bridging oxygen (NBO) bond length from increasing Cs coordination (clustering) around the NBO. The 29Si 2D MAF spectra for four glass compositions x = 0.218, 0.234, 0.263, 0.298 exhibit a second co-existing and distinctly smaller shielding anisotropy corresponding to a significantly longer Si-NBO length arising from a higher degree of Cs clustering around the NBO. This second Q3 site appears at a Cs2O mole fraction close to the critical mole fraction of x = 0.24 associated with the percolation threshold of non-bridging oxygen in random close packing of oxygen, thus suggesting that the longer Si-NBO length is associated with an infinite size spanning cluster while the sites with larger anisotropies are associated with shorter Si-NBO lengths and belong to finite size clusters. The equilibrium constant of the Q3 disproportionation reaction was determined as k3 = 0.005, indicating a Qn anionic species distribution close to a binary model as expected for a low field strength modifier such as cesium. It is also found that evolution of the isotropic Q4 and line shapes with increasing Cs content are consistent with a random connectivity model between Qn of differing number of bridging oxygen, n.

The stability of hibonite, melilite and other aluminous phases in silicate melts: Implications for the origin of hibonite-bearing inclusions from carbonaceous chondrites

NASA Technical Reports Server (NTRS)

Beckett, J. R.; Stolper, E.

1994-01-01

Phase fields in which hibonite and silicate melt coexist with spinel CaAl4O7, gehlenitic melilite, anorthite or corundum at 1 bar in the system CaO-MgO-Al2O3-SiO2-TiO2 were determined. The hibonites contain up to 1.7 wt% SiO2. For TiO2, the experimentally determined partition coefficients between hibonite and coexisting melt D(sub i)(sup Hib/L), vary from 0.8 to 2.1 and generally decrease with increasing TiO2 in the liquid. Based on Ti partitioning between hibonite and melt, bulk inclusion compositions and hibonite-saturated liquidus phase diagrams, the hibonite in hibonite-poor fluffy Type A inclusions from Allende and at least some hibonite from hibonite-rich inclusions is relict, although much of the hibonite from hibonite-glass spherules probably crystallized metasably from a melt. Bulk compositions for all of these CAIs are consistent with an origin as melite + hibonite + spinel + perovskite phase assembalges that were partially altered and in some cases partially or completely melted. The duration of the melting event was sufficient to remove any Na introduced by the alteration process but frequently insufficient to dissolve all of the original hibonite. Simple thermochemical models developed for meteoritic melilite and hibonite solid solutions were used to obtain equilibration temperatures of hibonite-bearing phase assemblages with vapor. Referenced to 10(exp -3) atm, hibonite + corundum + vapor equilibrated at approximately 1260 C and hibonite + spinel +/- melilite + vapor at 1215 +/- 10 C. If these temperatures reflect condensation in a cooling gas of solar composition, then hibonite +/- corundum condensed first, followed by spinel and then melilite. The position of perovskite within this sequence is uncertain, but it probably began to condense before spinel. This sequence of phase appearances and relative temperatures is generally consistent with observed textures but differs from expectations based on classical condensation calculations in that

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

PubMed

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

2017-09-01

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

Approximate chemical analysis of volcanic glasses using Raman spectroscopy

PubMed Central

Morgavi, Daniele; Hess, Kai‐Uwe; Neuville, Daniel R.; Borovkov, Nikita; Perugini, Diego; Dingwell, Donald B.

2015-01-01

The effect of chemical composition on the Raman spectra of a series of natural calcalkaline silicate glasses has been quantified by performing electron microprobe analyses and obtaining Raman spectra on glassy filaments (~450 µm) derived from a magma mingling experiment. The results provide a robust compositionally‐dependent database for the Raman spectra of natural silicate glasses along the calcalkaline series. An empirical model based on both the acquired Raman spectra and an ideal mixing equation between calcalkaline basaltic and rhyolitic end‐members is constructed enabling the estimation of the chemical composition and degree of polymerization of silicate glasses using Raman spectra. The model is relatively insensitive to acquisition conditions and has been validated using the MPI‐DING geochemical standard glasses1 as well as further samples. The methods and model developed here offer several advantages compared with other analytical and spectroscopic methods such as infrared spectroscopy, X‐ray fluorescence spectroscopy, electron and ion microprobe analyses, inasmuch as Raman spectroscopy can be performed with a high spatial resolution (1 µm2) without the need for any sample preparation as a nondestructive technique. This study represents an advance in efforts to provide the first database of Raman spectra for natural silicate glasses and yields a new approach for the treatment of Raman spectra, which allows us to extract approximate information about the chemical composition of natural silicate glasses using Raman spectroscopy. We anticipate its application in handheld in situ terrestrial field studies of silicate glasses under extreme conditions (e.g. extraterrestrial and submarine environments). © 2015 The Authors Journal of Raman Spectroscopy Published by John Wiley & Sons Ltd PMID:27656038

Glasses, ceramics, and composites from lunar materials

NASA Technical Reports Server (NTRS)

Beall, George H.

1992-01-01

A variety of useful silicate materials can be synthesized from lunar rocks and soils. The simplest to manufacture are glasses and glass-ceramics. Glass fibers can be drawn from a variety of basaltic glasses. Glass articles formed from titania-rich basalts are capable of fine-grained internal crystallization, with resulting strength and abrasion resistance allowing their wide application in construction. Specialty glass-ceramics and fiber-reinforced composites would rely on chemical separation of magnesium silicates and aluminosilicates as well as oxides titania and alumina. Polycrystalline enstatite with induced lamellar twinning has high fracture toughness, while cordierite glass-ceramics combine excellent thermal shock resistance with high flexural strengths. If sapphire or rutile whiskers can be made, composites of even better mechanical properties are envisioned.

Glass-on-Glass Fabrication of Bottle-Shaped Tunable Microlasers and their Applications

PubMed Central

Ward, Jonathan M.; Yang, Yong; Nic Chormaic, Síle

2016-01-01

We describe a novel method for making microbottle-shaped lasers by using a CO2 laser to melt Er:Yb glass onto silica microcapillaries or fibres. This is realised by the fact that the two glasses have different melting points. The CO2 laser power is controlled to flow the doped glass around the silica cylinder. In the case of a capillary, the resulting geometry is a hollow, microbottle-shaped resonator. This is a simple method for fabricating a number of glass whispering gallery mode (WGM) lasers with a wide range of sizes on a single, micron-scale structure. The Er:Yb doped glass outer layer is pumped at 980 nm via a tapered optical fibre and WGM lasing is recorded around 1535 nm. This structure facilitates a new way to thermo-optically tune the microlaser modes by passing gas through the capillary. The cooling effect of the gas flow shifts the WGMs towards shorter wavelengths and thermal tuning of the lasing modes over 70 GHz is achieved. Results are fitted using the theory of hot wire anemometry, allowing the flow rate to be calibrated with a flow sensitivity as high as 72 GHz/sccm. Strain tuning of the microlaser modes by up to 60 GHz is also demonstrated. PMID:27121151

Micro-PIXE analysis of silicate reference standards

USGS Publications Warehouse

Czamanske, G.K.; Sisson, T.W.; Campbell, J.L.; Teesdale, W.J.

1993-01-01

The accuracy and precision of the University of Guelph proton microprobe have been evaluated through trace-element analysis of well-characterized silicate glasses and minerals, including BHVO-1 glass, Kakanui augite and hornblende, and ten other natural samples of volcanic glass, amphibole, pyroxene, and garnet. Using the 2.39 wt% Mo in a NIST steel as the standard, excellent precision and agreement between reported and analyzed abundances were obtained for Fe, Ni, Cu, Zn, Ga, Rb, Sr, Y, Zr, and Nb. -from Authors

Ionic conductivity of sodium silicate glasses grown within confined volume of mesoporous silica template

NASA Astrophysics Data System (ADS)

Chatterjee, Soumi; Saha, Shyamal Kumar; Chakravorty, Dipankar

2018-04-01

Nanodimensional sodium silicate glasses of composition 30Na2O.70SiO2 has been prepared within the pores of 5.5 nm of mesoporous silica as a template using the surfactant P123. The nanocomposite was characterized by X-ray diffraction, transmission electron microscope, and X-ray photoelectron spectroscopy. Electrical conductivity of the sample was studied by ac impedance spectroscopy. The activation energy for ionic conduction was found to be 0.13 eV with dc conductivity at room temperature of 10-6 S-cm-1. This is attributed to the creation of oxygen ion vacancies at the interface of mesoporous silica and nanoglass arising out of the presence of Si2+ species in the system. These nanocomposites are expected to be useful for applications in sodiumion battery for storage of renewable energy.

Ytterbium-Phosphate Glass for Microstructured Fiber Laser

PubMed Central

Stępień, Ryszard; Franczyk, Marcin; Pysz, Dariusz; Kujawa, Ireneusz; Klimczak, Mariusz; Buczyński, Ryszard

2014-01-01

In the paper, we report on the development of a synthesis and melting method of phosphate glasses designed for active microstructured fiber manufacturing. Non-doped glass synthesized in a P2O5-Al2O3-BaO-ZnO-MgO-Na2O oxide system served as the matrix material; meanwhile, the glass was doped with 6 mol% (18 wt%) of Yb2O3, as fiber core. The glasses were well-fitted in relation to optical (refractive index) and thermal proprieties (thermal expansion coefficient, rheology). The fiber with the Yb3+-doped core, with a wide internal photonic microstructure for a laser pump, as well as with a high relative hole size in the photonic outer air-cladding, was produced. The laser built on the basis of this fiber enabled achieving 8.07 W of output power with 20.5% slope efficiency against the launched pump power, in single-mode operation M2 = 1.59, from a 53 cm-long cavity. PMID:28788702

Metal-silicate interaction in quenched shock-induced melt of the Tenham L6-chondrite

NASA Astrophysics Data System (ADS)

Leroux, Hugues; Doukhan, Jean-Claude; Guyot, François

2000-07-01

The metal-silicate microstructures in the shock-induced melt pockets of the Tenham (L6) chondrite have been investigated by analytical transmission electron microscopy. The melt areas, formed under high-pressure, high-temperature dynamic shock conditions, consist of spherical Fe-Ni metal/iron sulfide globules embedded in a silicate glass matrix, showing that the melt was quenched at high cooling rate. The Fe-Ni fraction in the globules is two-phase, composed of a bcc phase (˜5 wt% Ni) and an fcc phase (˜49 wt% Ni), indicating that fractional crystallisation of the metal occurred during the fast cooling. The metal fraction also contains appreciable amounts of non-siderophile elements (mostly Si, Mg and O) suggesting that these elements were trapped in the metal, either as alloying components or as tiny silicate or oxide inclusions. In the iron sulfide fraction, the Na content is high (>3 wt%), suggesting chalcophile behaviour for Na during the shock event. The composition of the silicate glass reflects non-equilibrium melting of several silicate phases (olivine, pyroxene and plagioclase). Moreover, the FeO content is high compared to the FeO contents of the unmelted silicates. Some Fe redistribution took place between metal and silicate liquids during the shock event. The silicate glass also contains tiny iron sulfide precipitates which most probably originated by exsolution during quench, suggesting that the molten silicate retained significant amounts of S, dissolved at high temperature and high pressure. Based on these observations, we suggest that non-equilibrium phenomena may be important in determining the compositions of metal and silicate reservoirs during their differentiation.

The Load-Bearing Capacity of Timber-Glass Composite I-Beams Made with Polyurethane Adhesives

NASA Astrophysics Data System (ADS)

Rodacki, Konrad

2017-12-01

This article discusses the issue of composite timber-glass I-beams, which are an interesting alternative for load-bearing beams of ceilings and roofs. The reasoning behind the use of timber-glass I-beams is the combination of the best features of both materials - this enables the creation of particularly safe beams with regard to structural stability and post-breakage load capacity. Due to the significant differences between the bonding surfaces of timber and glass, a study on the adhesion of various adhesives to both surfaces is presented at the beginning of the paper. After examination, two adhesives were selected for offering the best performance when used with composite beams. The beams were investigated using a four-point bending test under quasi-static loading.

Intrinsic Nano-Ductility of Glasses: The Critical Role of Composition

NASA Astrophysics Data System (ADS)

Wang, Bu; Yu, Yingtian; Lee, Young; Bauchy, Mathieu

2015-02-01

Understanding, predicting and eventually improving the resistance to fracture for silicate materials is of primary importance to design tougher new glasses suitable for advanced applications. However, the fracture mechanism at the atomic level in amorphous silicate materials is still a topic of debate. In particular, there are some controversies about the existence of ductility at the nanoscale during crack propagation. Here, we present simulations of fracture of three archetypical silicate glasses, using molecular dynamics. The simulations clearly show that, depending on their composition, silicate glasses can exhibit different degrees of ductility at the nanoscale. Additionally, we show that the methodology used in the present work can provide realistic predictions of fracture energy and toughness.

A compact high power Er:Yb:glass eyesafe laser for infrared remote sensing applications

NASA Astrophysics Data System (ADS)

Vitiello, Marco; Pizzarulli, Andrea; Ruffini, Andrea

2010-10-01

The key features and performances of a compact, lightweight, high power Er3+:Yb3+ glass laser transmitter are reported on. The theory employed to get an optimal design of the device is also described. In free running regime high energies of about 15mJ in 3ms long pulses were obtained, with an optical efficiency close to 85%. When q-switched by a Co: MALO crystal of carefully selected initial transmittivity, a high peak power in excess of 500 kW was obtained in about 9ns pulse duration, with an optical efficiency of 60%. The laser was successfully run with no significant power losses at repetition rates up to 5Hz due to a carefully designed heat sink which allowed an efficient conduction cooling of both the diode bars and the phosphate glass. The transmitter emits at a wavelength of 1535nm in the so-called "eyesafe" region of the light spectrum thus being highly attractive for any application involving the risk of human injury as is typically the case in remote sensing activities. Moreover, the spectral band around 1,5mm corresponds to a peak in the athmospheric transmittance thus being more effective in adverse weather conditions with respect to other wavelengths. Actually, the device has been successfully integrated into a rangefinder system allowing a reliable and precise detection of small targets at distances up to 20Km. Moreover, the transmitter capabilities were used into a state of the art infrared laser illuminator for night vision allowing even the recognition of a human being at distances in excess of 5Km.

Characterizing Amorphous Silicates in Extraterrestrial Materials

NASA Astrophysics Data System (ADS)

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

2015-12-01

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

Low Velocity Sphere Impact of a Borosilicate Glass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morrissey, Timothy G; Ferber, Mattison K; Wereszczak, Andrew A

2012-05-01

This report summarizes US Army TARDEC sponsored work at Oak Ridge National Laboratory (ORNL) involving low velocity (< 30 m/s or < 65 mph) ball impact testing of Borofloat borosilicate glass, and is a follow-up to a similar study completed by the authors on Starphire soda-lime silicate glass last year. The response of the borosilicate glass to impact testing at different angles was also studied. The Borofloat glass was supplied by the US Army Research Laboratory and its tin-side was impacted or indented. The intent was to better understand low velocity impact response in the Borofloat. Seven sphere materials weremore » used whose densities bracket that of rock: borosilicate glass, soda-lime silicate glass, silicon nitride, aluminum oxide, zirconium oxide, carbon steel, and a chrome steel. A gas gun or a ball-drop test setup was used to produce controlled velocity delivery of the spheres against the glass tile targets. Minimum impact velocities to initiate fracture in the Borofloat were measured and interpreted in context to the kinetic energy of impact and the elastic property mismatch between the seven sphere-Borofloat-target combinations. The primary observations from this low velocity (< 30 m/s or < 65 mph) testing were: (1) BS glass responded similarly to soda-lime silicate glass when spherically indented but quite differently under sphere impact conditions; (2) Frictional effects contributed to fracture initiation in BS glass when it spherically indented. This effect was also observed with soda-lime silicate glass; (3) The force necessary to initiate fracture in BS glass under spherical impact decreases with increasing elastic modulus of the sphere material. This trend is opposite to what was observed with soda-lime silicate glass. Friction cannot explain this trend and the authors do not have a legitimate explanation for it yet; (4) The force necessary to initiate contact-induced fracture is higher under dynamic conditions than under quasi-static conditions

Ion transport mechanism in glasses: non-Arrhenius conductivity and nonuniversal features.

PubMed

Murugavel, S; Vaid, C; Bhadram, V S; Narayana, C

2010-10-28

In this article, we report non-Arrhenius behavior in the temperature-dependent dc conductivity of alkali ion conducting silicate glasses well below their glass transition temperature. In contrast to the several fast ion-conducting and binary potassium silicate glasses, these glasses show a positive deviation in the Arrhenius plot. The observed non-Arrhenius behavior is completely reproducible in nature even after prolonged annealing close to the glass transition temperature of the respective glass sample. These results are the manifestation of local structural changes of the silicate network with temperature and give rise to different local environments into which the alkali ions hop, revealed by in situ high-temperature Raman spectroscopy. Furthermore, the present study provides new insights into the strong link between the dynamics of the alkali ions and different sites associated with it in the glasses.

Lithium conductivity in an Li-bearing double-ring silicate mineral, sogdianite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, S.-H.; Hoelzel, M.; Forschungsneutronenquelle Heinz Maier-Leibnitz

The crystal structure of an Li-bearing double-ring silicate mineral, sogdianite ((Zr{sub 1.18}Fe{sup 3+} {sub 0.55}Ti{sub 0.24}Al{sub 0.03})(Y {sub 1.64},Na{sub 0.36})K{sub 0.85}[Li{sub 3}Si{sub 12}O{sub 30}], P6/mcc, a{approx}10.06 A, c{approx}14.30 A, Z=2), was investigated by neutron powder diffraction from 300 up to 1273 K. Rietveld refinements of displacement parameters revealed high anisotropic Li motions perpendicular to the crystallographic c-axis, indicating an exchange process between tetrahedral T2 and octahedral A sites. AC impedance spectra of a sogdianite single crystal (0.04x0.09x0.25 cm{sup 3}) show that the material is an ionic conductor with conductivity values of {sigma}=4.1x10{sup -5} S cm{sup -1} at 923 K andmore » 1.2x10{sup -3} S cm{sup -1} at 1219 K perpendicular to the c-axis, involving two relaxation processes with activation energies of 1.26(3) and 1.08(3) eV, respectively. - Graphical abstract: Structure of sogdianite with atomic displacement parameter (ADP) ellipsoids at 1273 K.« less

Laser characteristics at 1535 nm and thermal effects of an Er:Yb phosphate glass microchip pumped by Ti:sapphire laser

NASA Astrophysics Data System (ADS)

Cai, Zhiping; Chardon, Alain; Xu, Huiying; Féron, Patrice; Michel Stéphan, Guy

2002-03-01

An Er:Yb codoped phosphate glass microchip laser has been studied under pumping with a Ti:sapphire laser ranging from 945 to 990 nm. The characteristics (threshold, slope efficiency) are first described for an optimized laser. The gain spectrum is calculated for the transition 4I13/2→ 4I15/2 around 1535 nm from fundamental spectroscopic data and from experimental results. Red-shift effect on the frequency of a single mode is experimentally observed when the pump power is increased, originating from thermal effects. Temperature inside the microchip cavity and thermal expansion coefficient were determined by employing the intensity ratio of two green upconversion emission line centered at 530 and 554 nm, respectively, which quantitatively explain this red shift.

High slope efficiency and high refractive index change in direct-written Yb-doped waveguide lasers with depressed claddings.

PubMed

Palmer, Guido; Gross, Simon; Fuerbach, Alexander; Lancaster, David G; Withford, Michael J

2013-07-15

We report the first Yb:ZBLAN and Yb:IOG10 waveguide lasers fabricated by the fs-laser direct-writing technique. Pulses from a Titanium-Sapphire laser oscillator with 5.1 MHz repetition rate were utilized to generate negative refractive index modifications in both glasses. Multiple modifications were aligned in a depressed cladding geometry to create a waveguide. For Yb:ZBLAN we demonstrate high laser slope efficiency of 84% with a maximum output power of 170 mW. By using Yb:IOG10 a laser performance of 25% slope efficiency and 72 mW output power was achieved and we measured a remarkably high refractive index change exceeding Δn = 2.3 × 10(-2).

Gain and noise figure enhancement of Er+3/Yb+3 co-doped fiber/Raman hybrid amplifier

NASA Astrophysics Data System (ADS)

Mahran, O.

2016-02-01

An Er/Yb co-doped fiber/Raman hybrid amplifier (HA) is proposed and studied theoretically and analytically to improve the gain and noise figure of optical amplifiers. The calculations are performed under a uniform dopant and steady-state conditions. The initial energy transfer efficiency for Er/Yb co-doped fiber amplifier (EYDFA) is introduced, while the amplified spontaneous emission (ASE) is neglected. The glass fiber used for both Er/Yb and Raman amplifiers is phosphate. Different pump powers are used for both EYDFA and RA with 1 μW input signal power, 1 m length of Er/Yb amplifier and 25 km length of Raman amplifier (RA). The proposed model is validated for Er/Yb co-doped amplifier and Raman amplifier separately by comparing the calculating results with the experimental data. A high gain and low noise figure at 200 mW Raman pump power and 500 mW Er/Yb pump power are obtained for the proposed HA as compared with the experimental results of EYDFA, Raman amplifier and the EDFA/Raman hybrid amplifier.

Characterization by combined optical and FT infrared spectra of 3d-transition metal ions doped-bismuth silicate glasses and effects of gamma irradiation.

PubMed

ElBatal, F H; Abdelghany, A M; ElBatal, H A

2014-03-25

Optical and infrared absorption spectral measurements were carried out for binary bismuth silicate glass and other derived prepared samples with the same composition and containing additional 0.2% of one of 3d transition metal oxides. The same combined spectroscopic properties were also measured after subjecting the prepared glasses to a gamma dose of 8 Mrad. The experimental optical spectra reveal strong UV-near visible absorption bands from the base and extended to all TMs-doped samples and these specific extended and strong UV-near visible absorption bands are related to the contributions of absorption from both trace iron (Fe(3+)) ions present as contaminated impurities within the raw materials and from absorption of main constituent trivalent bismuth (Bi(3+)) ions. The strong UV-near visible absorption bands are observed to suppress any further UV bands from TM ions. The studied glasses show obvious resistant to gamma irradiation and only small changes are observed upon gamma irradiation. This observed shielding behavior is related to the presence of high Bi(3+) ions with heavy mass causing the observed stability of the optical absorption. Infrared absorption spectra of the studied glasses reveal characteristic vibrational bands due to both modes from silicate network and the sharing of Bi-O linkages and the presence of TMs in the doping level (0.2%) causes no distinct changes within the number or position of the vibrational modes. The presence of high Bi2O3 content (70 mol%) appears to cause stability of the structural building units towards gamma irradiation as revealed by FTIR measurements. Copyright © 2013 Elsevier B.V. All rights reserved.

Compositional dependent partial molar volume and compressibility of CO2 in rhyolite, phonolite and basalt glasses

NASA Astrophysics Data System (ADS)

Lerch, P.; Seifert, R.; Malfait, W. J.; Sanchez-Valle, C.

2012-12-01

Carbon dioxide is the second most abundant volatile in magmatic systems and plays an important role in many magmatic processes, e.g. partial melting, volatile saturation, outgassing. Despite this relevance, the volumetric properties of carbon-bearing silicates at relevant pressure and temperature conditions remain largely unknown because of considerable experimental difficulties associated with in situ measurements. Density and elasticity measurements on quenched glasses can provide an alternative source of information. For dissolved water, such measurements indicate that the partial molar volume is independent of compositions at ambient pressure [1], but the partial molar compressibility is not [2, 3]. Thus the partial molar volume of water may depend on melt composition at elevated pressure. For dissolved CO2, no such data is available. In order to constrain the effect of magma composition on the partial molar volume and compressibility of dissolved carbon, we determined the density and elasticity for three series of carbon-bearing basalt, phonolite and rhyolite glasses, quenched from 3.5 GPa and relaxed at ambient pressure. The CO2 content varies between 0 to 3.90 wt% depending on the glass composition. Glass densities were determined using the sink/float method in a diiodomethane (CH2I2) - acetone mixture. Brillouin measurements were conducted on relaxed and unrelaxed silicate glasses in platelet geometry to determine the compressional (VP) and shear (VS) wave velocities and elastic moduli. The partial molar volume of CO2 in rhyolite, phonolite and basalt glasses is 25.4 ± 0.9, 22.1 ± 0.6 and 26.6 ±1.8 cm3/mol, respectively. Thus, unlike for dissolved water, the partial molar volume of CO2 displays a resolvable compositional effect. Although the composition and CO2/carbonate speciation of the phonolite glasses is intermediate between that of the rhyolite and basalt glasses, the molar volume is not. Similar to dissolved water, the partial molar bulk modulus

Electrophoretic deposition of mesoporous bioactive glass on glass-ceramic foam scaffolds for bone tissue engineering.

PubMed

Fiorilli, Sonia; Baino, Francesco; Cauda, Valentina; Crepaldi, Marco; Vitale-Brovarone, Chiara; Demarchi, Danilo; Onida, Barbara

2015-01-01

In this work, the coating of 3-D foam-like glass-ceramic scaffolds with a bioactive mesoporous glass (MBG) was investigated. The starting scaffolds, based on a non-commercial silicate glass, were fabricated by the polymer sponge replica technique followed by sintering; then, electrophoretic deposition (EPD) was applied to deposit a MBG layer on the scaffold struts. EPD was also compared with other techniques (dipping and direct in situ gelation) and it was shown to lead to the most promising results. The scaffold pore structure was maintained after the MBG coating by EPD, as assessed by SEM and micro-CT. In vitro bioactivity of the scaffolds was assessed by immersion in simulated body fluid and subsequent evaluation of hydroxyapatite (HA) formation. The deposition of a MBG coating can be a smart strategy to impart bioactive properties to the scaffold, allowing the formation of nano-structured HA agglomerates within 48 h from immersion, which does not occur on uncoated scaffold surfaces. The mechanical properties of the scaffold do not vary after the EPD (compressive strength ~19 MPa, fracture energy ~1.2 × 10(6) J m(-3)) and suggest the suitability of the prepared highly bioactive constructs as bone tissue engineering implants for load-bearing applications.

Feasibility study of CaSO4:Tb,Yb as a thermoluminescent dosimeter

NASA Astrophysics Data System (ADS)

Junot, Danilo O.; Santos, Max A.; Chagas, Marcos A. P.; Couto dos Santos, Marcos A.; Nunes, Luiz A. O.; Souza, Divanizia N.

2014-02-01

A new composite based on CaSO4, using terbium as dopant and ytterbium as co-dopant (CaSO4:Tb,Yb), was developed for employment as a thermoluminescent (TL) dosimeter. The crystals used in this work were grown using a production route based on the Yamashita method (Yamashita et al., 1968). Crystal powder was calcined at 600 °C for 1 h. Pellets were made by adding commercial and colorless glass to improve physical resistance and sintered at 700 °C for 6 h. All samples were irradiated by a beta source (90Sr/90Y) and received doses from 1 Gy to 5 Gy. TL analyses have been performed and characteristics such as sensitivity, reproducibility, linearity, and fading have been studied. The CaSO4:Tb,Yb pellets glow curves presented two peaks, the first at around 115 °C, and the second at around 200 °C. The highest intensity was shown for CaSO4:Tb,Yb with a concentration of 0.1 mol% of Tb and Yb together. In all the samples the TL response was proportional to the absorbed dose. Therefore, the CaSO4:Tb,Yb has potential to be used as a thermoluminescent dosimeter.

High temperature crystal field spectra of transition metal-bearing minerals - Relevance to remote-sensed spectra of planetary surfaces

NASA Technical Reports Server (NTRS)

Parkin, K. M.; Burns, R. G.

1980-01-01

It is pointed out that transition metal ions in silicate minerals, glasses, and crystalline and amorphous oxyhydroxides and salts contribute to the visible-near infrared spectral profiles of planetary surfaces. Investigations are conducted to obtain spectral information which might be helpful in the interpretation of the remote-sensed spectra of planetary surfaces. A description is presented of the results of high temperature crystal field spectral measurements of a variety of heated minerals containing Cr(3+), Fe(3+), Fe(++), and Mn(++) ions in different coordination symmetries, taking into account a correlation of the temperature-induced variations with those previously observed for octahedrally coordinated Fe(++)-bearing silicates. The employed experimental methods are also discussed, giving attention to the preparation of the samples, the determination of the absorption spectra, electron microprobe analyses, and the curve fitting procedure.

Framework influence of erbium doped oxyfluoride glasses on their optical properties

NASA Astrophysics Data System (ADS)

Środa, Marcin; Cholewa-Kowalska, Katarzyna; Różański, Marek; Nocuń, Marek

2011-01-01

Glasses of different matrix (phosphate, borate, silicate and lead-silicate) were studied for their optical properties. The effect of Er dopant on transmittance and luminescence properties was presented. The significant “red shift” and “blue shift” of UV edge absorption were discussed based on the changes in the framework of the borate and phosphate glasses, respectively. It was showed that the integral intensity of the two main optical absorption transitions monotonically increases with the order: phosphate < borate < silicate < lead-silicate. Ellipsometric measurement was applied to obtain the refractive index of the glasses. The correlation between the shift of edge absorption and the change of refractive index was presented. Effect of glassy matrix on luminescence of Er3+ was discussed.

Pump-induced phase aberrations in Yb3+-doped materials(Conference Presentation)

NASA Astrophysics Data System (ADS)

Keppler, Sebastian; Tamer, Issa; Hornung, Marco; Körner, Jörg; Liebetrau, Hartmut; Hein, Joachim; Kaluza, Malte C.

2017-05-01

the cooling period between subsequent pump pulses. We found that both phase effects significantly contribute to the overall phase distortions. Since the temporal characteristic of the electronic phase depends on the fluorescence lifetime and the thermal phase on the thermal diffusivity, both phase effects could be distinguished by their different lifetimes. The measurements were carried out for Yb:YAG, Yb:CaF2 and Yb:glass, and are in excellent agreement to our detailed, COMSOL-based, spatio-temporal phase simulations. Since Yb:CaF2 and Yb:glass provide a negative dn/dT, the electronic phase change becomes even more important and, in case of Yb:CaF2, almost completely compensates the thermal phase imprint of a pump pulse during the time frame of laser pulse amplification.

Al Speciation in Silicate Melts: AlV a new Network Former?

NASA Astrophysics Data System (ADS)

Neuville, D. R.; Florian, P.; de Ligny, D.; Montouillout, V.; Massiot, D.

2009-05-01

The first human glasses were made 3500 BC. It was essentially sodo-lime silicate glass. To improve the chemical resistance, the thermal properties and increase the viscosity it is interesting to add aluminum in these silicates. But what is the speciation of the aluminum and how it varies according to the chemical composition and to the temperature? The aluminum appears essentially in four or five fold coordination in glasses and melts melted. The proportion of [5]Al varies according to the alkaline or to the earth-alkaline content and to the temperature. We shall present in a first part the influence of the network-modifier on the proportion of [5]Al and then we shall present some new results of absorption of high-temperature using NMR and XANES spectroscopy at the Al K-edge. Finally, from glass transition temperature measurements we propose to explain that [5]Al can be a new network former.

YB-1 regulates tiRNA-induced Stress Granule formation but not translational repression

PubMed Central

Lyons, Shawn M.; Achorn, Chris; Kedersha, Nancy L.; Anderson, Paul J.; Ivanov, Pavel

2016-01-01

Stress-induced angiogenin (ANG)-mediated tRNA cleavage promotes a cascade of cellular events that starts with production of tRNA-derived stress-induced RNAs (tiRNAs) and culminates with enhanced cell survival. This stress response program relies on a subset tiRNAs that inhibit translation initiation and induce the assembly of stress granules (SGs), cytoplasmic ribonucleoprotein complexes with cytoprotective and pro-survival properties. SG-promoting tiRNAs bear oligoguanine motifs at their 5′-ends, assemble G-quadruplex-like structures and interact with the translational silencer YB-1. We used CRISPR/Cas9-based genetic manipulations and biochemical approaches to examine the role of YB-1 in tiRNA-mediated translational repression and SG assembly. We found that YB-1 directly binds to tiRNAs via its cold shock domain. This interaction is required for packaging of tiRNA-repressed mRNAs into SGs but is dispensable for tiRNA-mediated translational repression. Our studies reveal the functional role of YB-1 in the ANG-mediated stress response program. PMID:27174937

Dissolution of glass wool, rock wool and alkaline earth silicate wool: morphological and chemical changes in fibers.

PubMed

Campopiano, Antonella; Cannizzaro, Annapaola; Angelosanto, Federica; Astolfi, Maria Luisa; Ramires, Deborah; Olori, Angelo; Canepari, Silvia; Iavicoli, Sergio

2014-10-01

The behavior of alkaline earth silicate (AES) wool and of other biosoluble wools in saline solution simulating physiological fluids was compared with that of a traditional wool belonging to synthetic vitreous fibers. Morphological and size changes of fibers were studied by scanning electron microscopy (SEM). The elements extracted from fibers were analyzed by inductively coupled plasma atomic emission spectrometry. SEM analysis showed a larger reduction of length-weighted geometric mean fiber diameter at 4.5 pH than at 7.4 pH. At the 7.4 pH, AES wool showed a higher dissolution rate and a dissolution time less than a few days. Their dissolution was highly non-congruent with rapid leaching of calcium. Unlike rock wool, glass wool dissolved more rapidly at physiological pH than at acid pH. Dissolution of AES and biosoluble rock wool is accompanied by a noticeable change in morphology while by no change for glass wool. Biosoluble rock wool developed a leached surface with porous honeycomb structure. SEM analysis showed the dissolution for glass wool is mainly due to breakage transverse of fiber at pH 7.4. AES dissolution constant (Kdis) was the highest at pH 7.4, while at pH 4.5 only biosoluble rockwool 1 showed a higher Kdis. Copyright © 2014 Elsevier Inc. All rights reserved.

Studies and testing of antireflective (AR) coatings for soda-lime glass

NASA Technical Reports Server (NTRS)

Pastirik, E. M.; Sparks, T. G.; Coleman, M. G.

1978-01-01

Processes for producing antireflection films on glass are concentrated in three areas: acid etching of glass, plasma etching of glass, and acid development of sodium silicate films on glass. The best transmission was achieved through the acid etching technique, while the most durable films were produced from development of sodium silicate films. Control of the acid etching technique is presently inadequate for production implementation. While films having excellent antireflective properties were fabricated by plasma etching techniques, all were water soluble.

Computational modelling of large deformations in layered-silicate/PET nanocomposites near the glass transition

NASA Astrophysics Data System (ADS)

Figiel, Łukasz; Dunne, Fionn P. E.; Buckley, C. Paul

2010-01-01

Layered-silicate nanoparticles offer a cost-effective reinforcement for thermoplastics. Computational modelling has been employed to study large deformations in layered-silicate/poly(ethylene terephthalate) (PET) nanocomposites near the glass transition, as would be experienced during industrial forming processes such as thermoforming or injection stretch blow moulding. Non-linear numerical modelling was applied, to predict the macroscopic large deformation behaviour, with morphology evolution and deformation occurring at the microscopic level, using the representative volume element (RVE) approach. A physically based elasto-viscoplastic constitutive model, describing the behaviour of the PET matrix within the RVE, was numerically implemented into a finite element solver (ABAQUS) using an UMAT subroutine. The implementation was designed to be robust, for accommodating large rotations and stretches of the matrix local to, and between, the nanoparticles. The nanocomposite morphology was reconstructed at the RVE level using a Monte-Carlo-based algorithm that placed straight, high-aspect ratio particles according to the specified orientation and volume fraction, with the assumption of periodicity. Computational experiments using this methodology enabled prediction of the strain-stiffening behaviour of the nanocomposite, observed experimentally, as functions of strain, strain rate, temperature and particle volume fraction. These results revealed the probable origins of the enhanced strain stiffening observed: (a) evolution of the morphology (through particle re-orientation) and (b) early onset of stress-induced pre-crystallization (and hence lock-up of viscous flow), triggered by the presence of particles. The computational model enabled prediction of the effects of process parameters (strain rate, temperature) on evolution of the morphology, and hence on the end-use properties.

Fatigue failure load of two resin-bonded zirconia-reinforced lithium silicate glass-ceramics: Effect of ceramic thickness.

PubMed

Monteiro, Jaiane Bandoli; Riquieri, Hilton; Prochnow, Catina; Guilardi, Luís Felipe; Pereira, Gabriel Kalil Rocha; Borges, Alexandre Luiz Souto; de Melo, Renata Marques; Valandro, Luiz Felipe

2018-06-01

To evaluate the effect of ceramic thickness on the fatigue failure load of two zirconia-reinforced lithium silicate (ZLS) glass-ceramics, adhesively cemented to a dentin analogue material. Disc-shaped specimens were allocated into 8 groups (n=25) considering two study factors: ZLS ceramic type (Vita Suprinity - VS; and Celtra Duo - CD), and ceramic thickness (1.0; 1.5; 2.0; and 2.5mm). A trilayer assembly (ϕ=10mm; thickness=3.5mm) was designed to mimic a bonded monolithic restoration. The ceramic discs were etched, silanized and luted (Variolink N) into a dentin analogue material. Fatigue failure load was determined using the Staircase method (100,000 cycles at 20Hz; initial fatigue load ∼60% of the mean monotonic load-to-failure; step size ∼5% of the initial fatigue load). A stainless-steel piston (ϕ=40mm) applied the load into the center of the specimens submerged in water. Fractographic analysis and Finite Element Analysis (FEA) were also performed. The ceramic thickness influenced the fatigue failure load for both ZLS materials: Suprinity (716N up to 1119N); Celtra (404N up to 1126N). FEA showed that decreasing ceramic thickness led to higher stress concentration on the cementing interface. Different ZLS glass-ceramic thicknesses influenced the fatigue failure load of the bonded system (i.e. the thicker the glass ceramic is, the higher the fatigue failure load will be). Different microstructures of the ZLS glass-ceramics might affect the fatigue behavior. FEA showed that the thicker the glass ceramic is, the lower the stress concentration at the tensile surface will be. Copyright © 2018 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.

Phosphate-core silica-clad Er/Yb-doped optical fiber and cladding pumped laser.

PubMed

Egorova, O N; Semjonov, S L; Velmiskin, V V; Yatsenko, Yu P; Sverchkov, S E; Galagan, B I; Denker, B I; Dianov, E M

2014-04-07

We present a composite optical fiber with a Er/Yb co-doped phosphate-glass core in a silica glass cladding as well as cladding pumped laser. The fabrication process, optical properties, and lasing parameters are described. The slope efficiency under 980 nm cladding pumping reached 39% with respect to the absorbed pump power and 28% with respect to the coupled pump power. Due to high doping level of the phosphate core optimal length was several times shorter than that of silica core fibers.

Additivity of the coefficient of thermal expansion in silicate optical fibers.

PubMed

Cavillon, M; Dragic, P D; Ballato, J

2017-09-15

A model that predicts the material additivity of the thermal expansion coefficient in the binary silicate glasses most commonly used for present (GeO 2 -SiO 2 , P 2 O 5 -SiO 2 , B 2 O 3 -SiO 2 , and Al 2 O 3 -SiO 2 ) and emerging (BaO-SiO 2 ) optical fibers is proposed. This model is based on a derivation of the expression for the coefficient of thermal expansion in isotropic solids, and gives direct insight on the parameters that govern its additivity in silicate glasses. Furthermore, a consideration of the local structural environment of the glass system is necessary to fully describe its additivity behavior in the investigated systems. This Letter is important for better characterizing and understanding of the impact of temperature and internal stresses on the behavior of optical fibers.

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

NASA Astrophysics Data System (ADS)

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

2018-01-01

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

The Brittle-Ductile Transition in Crystal and Bubble-bearing Magmas

NASA Astrophysics Data System (ADS)

Caricchi, L.; Pistone, M.; Cordonnier, B.; Tripoli, B.; Ulmer, P.; Reusser, E.; Marone, F.; Burlini, L.

2011-12-01

The strain response of magma is critically dependent upon its viscosity, the magnitude of the applied stress and the experimental time-scale. The brittle-ductile transition in pure silicate melts is expected for an applied stress approaching 108±0.5 Pa (Dingwell, 1997). However, magmas are mostly mixture of crystal and bubble-bearing silicate melts. To date, there are no data to constrain the ductile-brittle transition for three-phase magmas. Thus, we conducted consistent torsion experiments at high temperature (673-973 K) and high pressure (200 MPa), in the strain rate range 1*10-5-4*10-3 s-1, using a HT-HP internally-heated Paterson-type rock deformation apparatus. The samples are composed of hydrous haplogranitic glass, quartz crystals (24-65 vol%) and CO2-rich gas-pressurized bubbles (9-12 vol%). The applied strain rate was increased until brittle failure occurred; micro-fracturing and healing processes commonly occurred before sample macroscopic fracturing. The experimental results highlight a clear relationship between the effective viscosity of the three-phase magmas, strain rate, temperature and the onset of brittle-ductile behavior. Crystal- and bubble-free melts at high viscosity (1011-1011.6 Pa*s at 673 K) show brittle behavior in the strain rate range between 1*10-4 and 5*10-4 s-1. For comparable viscosities crystal and bubble-bearing magmas show a transition to brittle behavior at lower strain rates. Synchrotron-based 3D imaging of fractured samples, show the presence of fractures with an antithetic trend with respect to shear strain directions. The law found in this study expresses the transition from ductile to brittle behavior for real magmas and could significantly improve our understanding of the control of brittle processes on extrusion of high-viscosity magmas and degassing at silicic volcanoes.

Electronic structure of ferromagnetic heavy fermion, YbPdSi, YbPdGe, and YbPtGe studied by photoelectron spectroscopy, x-ray emission spectroscopy, and DFT + DMFT calculations

DOE PAGES

Yamaoka, Hitoshi; Thunstrom, Patrik; Tsujii, Naohito; ...

2017-11-02

Here, the electronic structures of ferromagnetic heavy fermion Yb compounds of YbPdSi, YbPdGe, and YbPtGe are studied by photoelectron spectroscopy around the Yb 4d–4f resonance, resonant x-ray emission spectroscopy at the Yb L 3 absorption edge, and density functional theory combined with dynamical mean field theory calculations. These compounds all have a temperature-independent intermediate Yb valence with largemore » $${\\rm Yb}^{3+}$$ and small $${\\rm Yb}^{2+}$$ components. The magnitude of the Yb valence is evaluated to be YbPtGe $<$ YbPdGe $$\\lesssim $$ YbPdSi, suggesting that YbPtGe is the closest to the quantum critical point among the three Yb compounds. Our results support the scenario of the coexistence of heavy fermion behavior and ferromagnetic ordering which is described by a magnetically-ordered Kondo lattice where the magnitude of the Kondo effect and the RKKY interaction are comparable.« less

Electronic structure of ferromagnetic heavy fermion, YbPdSi, YbPdGe, and YbPtGe studied by photoelectron spectroscopy, x-ray emission spectroscopy, and DFT + DMFT calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yamaoka, Hitoshi; Thunstrom, Patrik; Tsujii, Naohito

Here, the electronic structures of ferromagnetic heavy fermion Yb compounds of YbPdSi, YbPdGe, and YbPtGe are studied by photoelectron spectroscopy around the Yb 4d–4f resonance, resonant x-ray emission spectroscopy at the Yb L 3 absorption edge, and density functional theory combined with dynamical mean field theory calculations. These compounds all have a temperature-independent intermediate Yb valence with largemore » $${\\rm Yb}^{3+}$$ and small $${\\rm Yb}^{2+}$$ components. The magnitude of the Yb valence is evaluated to be YbPtGe $<$ YbPdGe $$\\lesssim $$ YbPdSi, suggesting that YbPtGe is the closest to the quantum critical point among the three Yb compounds. Our results support the scenario of the coexistence of heavy fermion behavior and ferromagnetic ordering which is described by a magnetically-ordered Kondo lattice where the magnitude of the Kondo effect and the RKKY interaction are comparable.« less

Near-infrared luminescent and antireflective in SiO2/YVO4:Yb3+ bilayer films for c-Si solar cells

NASA Astrophysics Data System (ADS)

Peng, Yingjie; Liu, Jie; Zhang, Kun; Luo, Hui; Li, Jihong; Xu, Bo; Han, Lixian; Li, Xiaojuan; Yu, Xibin

2011-09-01

We demonstrate a facile approach for the architecture of a multifunctional bilayer thin films which show both antireflection and near-infrared (NIR) luminescence. NIR luminescence YVO4:Yb3+ transparent film and nanoporous SiO2 film were successively built on slide glass. Intense NIR emission around 900-1100 nm has been obtained, which is assigned to the electronic transition 2F7/2→2F5/2 of Yb3+, meanwhile, the maximum transmittance reached as high as ˜95%, whereas that of the glass substrate is ˜91%. It is the sought candidate material for c-Si solar cell by downconversion of UV light to NIR photons and increasing photon transmission.

Polymeric, Metallic, and Other Glasses in Introductory Chemistry

ERIC Educational Resources Information Center

Hawkes, Stephen J.

2008-01-01

Non-ceramic glasses are not adequately discussed in introductory chemistry. Such glasses include polycarbonate, which many corrective lenses are made of, amber, enamel, gelatin, hard candy, coal, refrigerated glycerol, and metallic glasses that have been marketed in recent decades. What is usually discussed in elementary texts is siliceous glass,…

Glass-silicon column

DOEpatents

Yu, Conrad M.

2003-12-30

A glass-silicon column that can operate in temperature variations between room temperature and about 450.degree. C. The glass-silicon column includes large area glass, such as a thin Corning 7740 boron-silicate glass bonded to a silicon wafer, with an electrode embedded in or mounted on glass of the column, and with a self alignment silicon post/glass hole structure. The glass/silicon components are bonded, for example be anodic bonding. In one embodiment, the column includes two outer layers of silicon each bonded to an inner layer of glass, with an electrode imbedded between the layers of glass, and with at least one self alignment hole and post arrangement. The electrode functions as a column heater, and one glass/silicon component is provided with a number of flow channels adjacent the bonded surfaces.

Demonstration of passively cooled high-power Yb fiber amplifier

NASA Astrophysics Data System (ADS)

Bradford, Joshua; Cook, Justin; Antonio-Lopez, Jose Enrique; Shah, Larry; Amezcua Correa, Rodrigo; Richardson, Martin

2018-02-01

This work investigates the feasibility of passive cooling in high-power Yb amplifiers. Experimentally, an all-glass airclad step-index (ACSI) amplifier is diode-pumped with 400W and provides 200W power levels. With only natural convection to extract heat, core temperatures are estimated near 130°C with no degradation of performance relative to cooled architectures. Further, advanced analysis techniques allow for core temperature determination using thermal interferometry without the need for complicated stabilization or calibration.

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

NASA Astrophysics Data System (ADS)

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

2001-12-01

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

Enhancement stability and catalytic activity of immobilized α-amylase using bioactive phospho-silicate glass as a novel inorganic support.

PubMed

Ahmed, Samia A; Mostafa, Faten A; Ouis, Mona A

2018-06-01

α-Amylase enzyme was immobilized on bioactive phospho-silicate glass (PS-glass) as a novel inorganic support by physical adsorption and covalent binding methods using glutaraldehyde and poly glutaraldehyde as a spacer. Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) studies confirmed the glass-enzyme linkage. Dissolution of PS-glass in acidic and neutral pH is higher than that of alkaline pH. Some immobilization variables were optimized using statistical factorial design (Central Composite Design). Optimized immobilization variables enhanced the immobilization yield (IY) from 27.9 to 79.9% (2.9-fold). It was found that the immobilized enzyme had higher optimum temperature, higher half-life time (t 1/2 ), lower activation energy (E a ), lower deactivation constant rate (k d ) and higher decimal reduction time (D-values) within the temperature range of 40-60°C. Differential scanning calorimetry analysis (DSC) confirmed the thermalstability of the immobilized enzyme. The immobilized enzyme was stable at a wide pH range (5.0-8.0). Kinetic studies of starch hydrolysis demonstrated that immobilized enzyme had lower Michaelis constant (K m ), maximum velocity (V max ) and catalytic efficiency (V max /K m ) values. The storage stability and reusability of the immobilized enzyme were found to be about 74.7 and 62.5% of its initial activity after 28days and 11cycles, respectively. Enhanced α-amylase stabilities upon immobilization make it suitable for industrial application. Copyright © 2018 Elsevier B.V. All rights reserved.

Cesium titanium silicate and method of making

DOEpatents

Balmer, Mari L.

1997-01-01

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

Cesium titanium silicate and method of making

DOEpatents

Balmer, M.L.

1997-01-07

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

An evaluation of the processing conditions, structure, and properties (biaxial flexural strength and antibacterial efficacy) of sintered strontium-zinc-silicate glass ceramics.

PubMed

Looney, Mark; Shea, Helen O'; Gunn, Lynda; Crowley, Dolores; Boyd, Daniel

2013-05-01

The use of artificial bone grafts has increased in order to satisfy a growing demand for bone replacement materials. Initial mechanical stability of synthetic bone grafts is very advantageous for certain clinical applications. Coupled with the advantage of mechanical strength, a material with inherent antibacterial properties would be very beneficial. A series of strontium-doped zinc silicate (Ca-Sr-Na-Zn-Si) glass ceramics have been characterized in terms of their crystalline structure, biaxial flexural strength and antibacterial efficacy based on the identification of optimum sintering conditions. All three glass ceramics, namely, BT110, BT111, and BT112 were found to be fully crystalline, with BT111 and BT112 comprising of biocompatible crystalline phases. The biaxial flexural strengths of the three glass ceramics ranged from 70 to 149 MPa and were shown to be superior to those of clinically established ceramics in dry conditions and following incubation in simulated physiological conditions. The bacteriostatic effect for each glass ceramic was also established, where BT112 showed an inhibitory effect against three of the most common bacteria found at implantation sites, namely, Enterococcus faecalis, methicillin-resistant Staphylococcus aureus (MRSA), and Pseudomonas aeruginosa. The results of the evaluation suggest that the materials studied offer advantages over current clinical materials and indicate the potential suitability of the glass ceramics as therapeutic bone grafts.

Enhanced performance of Cr,Yb:YAG microchip laser by bonding Yb:YAG crystal.

PubMed

Cheng, Ying; Dong, Jun; Ren, Yingying

2012-10-22

Highly efficient, laser-diode pumped Yb:YAG/Cr,Yb:YAG self-Q-switched microchip lasers by bonding Yb:YAG crystal have been demonstrated for the first time to our best knowledge. The effect of transmission of output coupler (T(oc)) on the enhanced performance of Yb:YAG/Cr,Yb:YAG microchip lasers has been investigated and found that the best laser performance was achieved with T(oc) = 50%. Slope efficiency of over 38% was achieved. Average output power of 0.8 W was obtained at absorbed pump power of 2.5 W; corresponding optical-to-optical efficiency of 32% was obtained. Laser pulses with pulse width of 1.68 ns, pulse energy of 12.4 μJ, and peak power of 7.4 kW were obtained. The lasers oscillated in multi-longitudinal modes. The wide separation of longitudinal modes was attributed to the mode selection by combined etalon effect of Cr,Yb:YAG, Yb:YAG thin plates and output coupler. Stable periodical pulse trains at different pump power levels have been observed owing to the longitudinal modes coupling and competition.

Nickel-iron spherules from aouelloul glass

USGS Publications Warehouse

Chao, E.C.T.; Dwornik, E.J.; Merrill, C.W.

1966-01-01

Nickel-iron spherules, ranging from less than 0.2 to 50 microns in diameter and containing 1.7 to 9.0 percent Ni by weight, occur in glass associated with the Aouelloul crater. They occur in discrete bands of siliceous glass enriched in dissolved iron. Their discovery is significant tangible evidence that both crater and glass originated from terrestrial impact.

Thermophysical and structural studies on some glass-ceramics and role of nano size crystallites

NASA Astrophysics Data System (ADS)

Kothiyal, G. P.; Arvind, A.; Kumar, Rakesh; Dixit, Anupam; Sharma, Kuldeep; Goswami, Madhumita

2009-07-01

In this paper, we present some studies on structure and thermophysical properties of glass and glass-ceramics with possible bio-medical and sealing applications. The glass-ceramics prepared for bio-medical applications include phosphate as well as silico-phosphate compositions. In vitro bio-compatibility/activity of these materials is discussed. The glass-ceramics used for the sealing application are lithium aluminium silicate (LAS) and lithium zinc silicate (LZS). The phase formation and some aspects of thermophysical properties and sealing are discussed.

Proof Test Diagrams for a Lithia-Alumina-Silica Glass-Ceramic

NASA Technical Reports Server (NTRS)

Tucker, Dennis S.

2003-01-01

The glass-ceramic (Zerodur, Schott Glaswerke, Mainz, Germany) contains 70% to 78% by weight crystalline phase of high-quartz structure with a mean crystal size of 50-55 nm. The vitreous phase has a positive thermal expansion coefficient which is practically balanced by the negative coefficient of the crystalline phase. This results in a material which can maintain longitudinal stability during thermal cycling. This was one of the reasons for its choice as the material for the grazing incidence mirrors for the Chandra X-Ray Facility. Brittle materials such as glass and glass-ceramics which exhibit slow crack growth and subsequent fast fracture to failure exhibit a time dependence in strength. The decrease in strength for a constant applied load is known as static fatigue. In many cases, environment plays a major role in the material lifetime. It has been shown for silicate glasses that crack velocity will increase as the amount of water vapor in the environment surface finish and rate of loading. A rough surface finish leads to a lower tensile strength than for an optically polished surface. The strength of glass is observed in general to increase with increasing load rate. This phenomena is known as dynamic fatigue. This was observed for Zerodur by Tucker and Gent and Tucker in previous dynamic fatigue studies, in which lifetimes were obtained. All of the above named factors need to be considered when glass is to be used in load bearing applications.

Genesis of recent silicic magmatism in the Medicine Lake Highland, California - Evidence from cognate inclusions found at Little Glass Mountain

NASA Technical Reports Server (NTRS)

Mertzman, S. A.; Williams, R. J.

1981-01-01

Sparse, granular inclusions of early-formed minerals found within the Little Glass Mountain rhyolite flows in northern California are shown to provide a means of characterizing the physical conditions, at depth, beneath the Medicine Lake Highland during the latest phase of volcanic activity. Mineral compositions, in combination with thermodynamic calculations and experiments, suggest crystalization at a pressure of 5,200 bars within a 966-836 C temperature range; implying that mineral segregation and equilibration occurred at a depth of 15-18 km beneath the surface. In addition, mass balance calculations indicate that the Medicine Lake flow is a close approximation to the parental magma for the latest silicic lavas.

Structure-composition trends in multicomponent borosilicate-based glasses deduced from molecular dynamics simulations with improved B-O and P-O force fields.

PubMed

Stevensson, Baltzar; Yu, Yang; Edén, Mattias

2018-03-28

We present a comprehensive molecular dynamics (MD) simulation study of composition-structure trends in a set of 25 glasses of widely spanning compositions from the following four systems of increasing complexity: Na 2 O-B 2 O 3 , Na 2 O-B 2 O 3 -SiO 2 , Na 2 O-CaO-SiO 2 -P 2 O 5 , and Na 2 O-CaO-B 2 O 3 -SiO 2 -P 2 O 5 . The simulations involved new B-O and P-O potential parameters developed within the polarizable shell-model framework, thereby combining the beneficial features of an overall high accuracy and excellent transferability among different glass systems and compositions: this was confirmed by the good accordance with experimental data on the relative BO 3 /BO 4 populations in borate and boro(phospho)silicate networks, as well as with the orthophosphate fractions in bioactive (boro)phosphosilicate glasses, which is believed to strongly influence their bone-bonding properties. The bearing of the simulated melt-cooling rate on the borate/phosphate speciations is discussed. Each local {BO 3 , BO 4 , SiO 4 , PO 4 } coordination environment remained independent of the precise set of co-existing network formers, while all trends observed in bond-lengths/angles mainly reflected the glass-network polymerization, i.e., the relative amounts of bridging oxygen (BO) and non-bridging oxygen (NBO) species. The structural roles of the Na + /Ca 2+ cations were also probed, targeting their local coordination environments and their relative preferences to associate with the various borate, silicate, and phosphate moieties. We evaluate and discuss the common classification of alkali/alkaline-earth metal ions as charge-compensators of either BO 4 tetrahedra or NBO anions in borosilicate glasses, also encompassing the less explored NBO-rich regime: the Na + /Ca 2+ cations mainly associate with BO/NBO species of SiO 4 /BO 3 groups, with significant relative Na-BO 4 contacts only observed in B-rich glass networks devoid of NBO species, whereas NBO-rich glass networks also

Sound velocity of 23 Å phase (a new Al-bearing hydrous Mg-silicate) to 14 GPa

NASA Astrophysics Data System (ADS)

Cai, N.; Chen, T.; Qi, X.; Inoue, T.; Li, B.

2016-12-01

Dense hydrous phases are believed to play an important role in transporting water back into the deep interior of the Earth. Recently, a new Al-bearing hydrous Mg-silicate named 23 Å phase (ideal composition Mg11Al2Si4O16(OH)12) was reported (Cai et al., 2015), which could be a very important hydrous phase in subducting slab. Here for the first time we measured the compressional and shear wave velocities of this new hydrous phase under mantle pressures. The sample was synthesized at 10 GPa and 1000 ºC using the chemical mixture of stoichiometric as starting materials. The recovered sample was then crushed into fine powder and hot pressed at 10 GPa and 900 ºC for 3 hours. X-ray diffraction, density measurement, and SEM characterization indicated that the specimen is nearly a pure phase, 20 µm in grain size, with a bulk density of 3.004 g/cm3. The acoustic measurements were conducted in a 1000-ton uniaxial split-cylinder multi-anvil apparatus using ultrasonic interferometry techniques (Li et al., 1996) up to 14 GPa at room temperature. The pressures were determined in situ by using alumina buffer rod as a pressure marker (Wang et al., 2015). A dual-mode piezoelectric transducer enables us to measure P and S wave travel times simultaneously, which in turn allows for a precise determination of the sound velocities and elastic bulk and shear moduli at high pressures. Preliminary results suggest that the velocities, (especially for S wave) of this 23 Å phase are slower than that of phase A and most of the mantle minerals. These results may have important implications for understanding some localized low velocity zones in subduction zones. Cai, N., T. Inoue, K. Fujino, H. Ohfuji and H. Yurimoto (2015) A Possible New Al-bearing Hydrous Mg-silicate (23 Å phase) in the Deep Upper Mantle. Am Mineral. 100: 2330-2335. Li, B., I. Jackson, T. Gasparik, and R. C. Liebermann (1996), Elastic wave velocity measurement in multianvil apparatus to 10 GPa using ultrasonic

Growth and luminescent properties of Yb:YAG and Ca co-doped Yb:YAG ultrafast scintillation crystals

NASA Astrophysics Data System (ADS)

Zhu, Maodong; Qi, Hongji; Pan, Mingyan; Hou, Qing; Jiang, Benxue; Jin, Yaxue; Han, Hetong; Song, Zhaohui; Zhang, Hui

2018-05-01

In this work, Yb-doped Y3Al5O12 [yttrium aluminum garnet (YAG)] crystals and Ca co-doped Yb:YAG crystals were grown by the Czochralski (CZ) method. The chemical formulas of the two crystals are (Yb0.1Y0.9)3Al5O12 and (Ca0.001Yb0.1Y0.899)3Al5O12, respectively. The structural, optical and luminescent properties of the Yb:YAG and Ca, Yb:YAG crystals were investigated by X-ray rocking curve, X-ray diffraction, Raman spectra, UV-Visble-NIR absorption spectra and X-ray fluorescence. X-ray fluorescence spectrum with two emission peaks at 330 nm and 490 nm were observed in the two kinds of crystals, which would increase slightly after the annealing. Comparing to the Yb:YAG crystal, Ca co-doped Yb:YAG crystal behaved the better luminescent intensity without changing the crystal structure and vibrational modes. This indicates that by doping Ca2+ in Yb:YAG crystal may be an appropriate way to enhance the luminescent property of the scintillation crystal.

Boson peak of alkali and alkaline earth silicate glasses: influence of the nature and size of the network-modifying cation.

PubMed

Richet, Nicolas F

2012-01-21

The influence of the size of the alkaline earth cation on the boson peak of binary metasilicate glasses, MSiO(3) (M = Mg, Ca, Sr, Ba), has been investigated from vibrational densities of states determined by inversion of low-temperature heat capacities. As given both by C(p)/T(3) and g(ω)/ω(2), the intensity of the boson peak undergoes a 7-fold increase from Mg to Ba, whereas its temperature and frequency correlatively decrease from 18 to 10 K and from 100 to 20 cm(-1), respectively. The boson peak results from a combination of librations of SiO(4) tetrahedra and localized vibrations of network-modifying cations with non-bridging oxygens whose contribution increases markedly with the ionic radius of the alkaline earth. As a function of ionic radii, the intensity for Sr and Ba varies in the same way as previously found for alkali metasilicate glasses. The localized vibrations involving alkali and heavy alkaline earth cations appear to be insensitive to the overall glass structure. Although the new data are coherent with an almost linear relationship between the temperature of the boson peak and transverse sound velocity, pure SiO(2) and SiO(2)-rich glasses make marked exceptions to this trend because of the weak transverse character of SiO(4) librations. Finally, the universality of the calorimetric boson peak is again borne out because all data for silicate glasses collapse on the same master curve when plotted in a reduced form (C(P)∕/T(3))/(C(P)/T(3))(b) vs. T/T(b). © 2012 American Institute of Physics

Chondrule-like objects and brown glasses in howardites

NASA Technical Reports Server (NTRS)

Olsen, Edward J.; Fredriksson, Kurt; Rajan, Sundar; Noonan, Albert

1990-01-01

Chondrulelike objects and brown glasses were analyzed in the howardites, Bununu, Malvern, Monticello, Pavlovka, and Yamato 7308. The objects are very similar to chondrules in ordinary and carbonaceous chondrites. Like the brown glasses, the chondrulelike objects could have been produced by impact melting that left some crystalline nuclei, followed by a slower cooling rate than for the glasses. Alternatively, these objects are chondrules implanted from chondrite impactors. They are, however, without rims or any adhering matrix. The brown glasses appear to represent melting of average regolithic surface material, except for Monticello and Y7308, both of which have some siliceous glasses. The siliceous glasses could not have been produced by vapor fractionation but by melting of differentiated lithologies such as fayalitic granites. Impact mechanics indicates that howardites with abundant brown glasses came from an asteroid larger than Vesta (greater than 400 km radius), upon which impacts occurred at relative velocities of up to 5 km/s. Howardites with little or no brown glasses came from a smaller parent body. It is concluded that at least two parent bodies are likely sources for the basaltic achondrites.

Glass corrosion in natural environment

NASA Technical Reports Server (NTRS)

Thorpe, Arthur N.

1989-01-01

A series of studies of the effects of solutes which appear in natural aqueous environments, specifically Mg and Al, under controlled conditions, permit characterization of the retardation of silicate glass leaching in water containing such solutes. In the case of Mg the interaction with the glass appears to consist of exchange with alkali ions present in the glass to a depth of several microns. The effect of Al can be observed at much lower levels, indicating that the mechanism in the case of Al involves irreversible formation of aluminosilicate species at the glass surface.

Evaluation of reformulated thermal control coatings in a simulated space environment. Part 1: YB-71

NASA Technical Reports Server (NTRS)

Cerbus, Clifford A.; Carlin, Patrick S.

1994-01-01

The Air Force Space and Missile Systems Center and Wright Laboratory Materials Directorate (WL/ML) have sponsored and effort to effort to reformulate and qualify Illinois Institute of Technology Research Institute (IITRI) spacecraft thermal control coatings. S13G/LO-1, Z93, and YB-71 coatings were reformulated because the potassium silicate binder, Sylvania PS-7, used in the coatings is no longer manufactured. Coatings utilizing the binder's replacement candidate, Kasil 2130, manufactured by The Philadelphia Quartz (PQ) Corporation, Baltimore, Maryland, and undergoing testing at the Materials Directorate's Space Combined Effects Primary Test and Research Equipment (SCEPTRE) Facility operated by the University of Dayton Research Institute (UDRI). The simulated space environment consists of combined ultraviolet (UV) and electron exposure with in site specimen reflectance measurements. A brief description of the effort at IITRI, results and discussion from testing the reformulated YB-71 coating in SCEPTRE, and plans for further testing of reformulated Z93 and S13G/LO-1 are presented.

Relationship between topological order and glass forming ability in densely packed enstatite and forsterite composition glasses

PubMed Central

Kohara, S.; Akola, J.; Morita, H.; Suzuya, K.; Weber, J. K. R.; Wilding, M. C.; Benmore, C. J.

2011-01-01

The atomic structures of magnesium silicate melts are key to understanding processes related to the evolution of the Earth’s mantle and represent precursors to the formation of most igneous rocks. Magnesium silicate compositions also represent a major component of many glass ceramics, and depending on their composition can span the entire fragility range of glass formation. The silica rich enstatite (MgSiO3) composition is a good glass former, whereas the forsterite (Mg2SiO4) composition is at the limit of glass formation. Here, the structure of MgSiO3 and Mg2SiO4 composition glasses obtained from levitated liquids have been modeled using Reverse Monte Carlo fits to diffraction data and by density functional theory. A ring statistics analysis suggests that the lower glass forming ability of the Mg2SiO4 glass is associated with a topologically ordered and very narrow ring distribution. The MgOx polyhedra have a variety of irregular shapes in MgSiO3 and Mg2SiO4 glasses and a cavity analysis demonstrates that both glasses have almost no free volume due to a large contribution from edge sharing of MgOx-MgOx polyhedra. It is found that while the atomic volume of Mg cations in the glasses increases compared to that of the crystalline phases, the number of Mg-O contacts is reduced, although the effective chemical interaction of Mg2+ remains similar. This unusual structure-property relation of Mg2SiO4 glass demonstrates that by using containerless processing it may be possible to synthesize new families of dense glasses and glass ceramics with zero porosity. PMID:21873237

Copper solubility in a basaltic melt and sulfide liquid/silicate melt partition coefficients of Cu and Fe

NASA Astrophysics Data System (ADS)

Ripley, Edward M.; Brophy, James G.; Li, Chusi

2002-09-01

The solubility of copper in a sulfur-saturated basaltic melt has been determined at 1245°C as a function of fO 2 and fS 2. Copper solubilities at log fO 2 values between -8 and -11 fall into two distinct populations as a function of fS 2. At log fS 2 values < -1.65, sulfide liquid that coexists with the basaltic glass quenches to sulfur-poor bornite solid solution. At log fS 2 values in excess of -1.65, the sulfide liquid quenches to a complex intergrowth of sulfur-rich bornite and intermediate solid solution. Copper solubilities in the low-fS 2 population range from 594 to 1550 ppm, whereas those in the high-fS 2 population range from 80 to 768 ppm. Sulfide liquid/silicate liquid partition coefficients (D) for Cu and Fe range from 480 to 1303 and 0.7 to 13.6, respectively. Metal-sulfur complexing in the silicate liquid is shown to be insignificant relative to metal-oxide complexing for Fe but permissible for Cu at high fS 2 values. On log D Fe (sulfide-silicate) and log D Cu (sulfide-silicate) vs. 1/2 (log fS 2 - log fO 2) diagrams, both fS 2 populations show distinct but parallel trends. The observation of two D values for any fS 2/fO 2 ratio indicates nonideal mixing of species involved in the exchange reaction. The two distinct trends observed for both Cu and Fe are thought to be due to variations in activity coefficient ratios (e.g., γ FeO/γ FeS and γ CuO 0.5/γ CuS 0.5). Results of the experiments suggest that accurate assessments of fS 2/fO 2 ratios are required for the successful numerical modeling of processes such as the partial melting of sulfide-bearing mantle and the crystallization of sulfide-bearing magmas, as well as the interpretation of sulfide mineralogical zoning. In addition, the experiments provide evidence for oxide or oxy-sulfide complexing for Cu in silicate magmas and suggest that the introduction of externally derived sulfur to mafic magma may be an important process for the formation of Cu-rich disseminated magmatic sulfide ore

Direct ink writing of highly porous and strong glass scaffolds for load-bearing bone defects repair and regeneration.

PubMed

Fu, Qiang; Saiz, Eduardo; Tomsia, Antoni P

2011-10-01

The quest for synthetic materials to repair load-bearing bone lost because of trauma, cancer, or congenital bone defects requires the development of porous, high-performance scaffolds with exceptional mechanical strength. However, the low mechanical strength of porous bioactive ceramic and glass scaffolds, compared with that of human cortical bone, has limited their use for these applications. In the present work bioactive 6P53B glass scaffolds with superior mechanical strength were fabricated using a direct ink writing technique. The rheological properties of Pluronic® F-127 (referred to hereafter simply as F-127) hydrogel-based inks were optimized for the printing of features as fine as 30 μm and of three-dimensional scaffolds. The mechanical strength and in vitro degradation of the scaffolds were assessed in a simulated body fluid (SBF). The sintered glass scaffolds showed a compressive strength (136 ± 22 MPa) comparable with that of human cortical bone (100-150 MPa), while the porosity (60%) was in the range of that of trabecular bone (50-90%). The strength is ~100-times that of polymer scaffolds and 4-5-times that of ceramic and glass scaffolds with comparable porosities. Despite the strength decrease resulting from weight loss during immersion in SBF, the value (77 MPa) is still far above that of trabecular bone after 3 weeks. The ability to create both porous and strong structures opens a new avenue for fabricating scaffolds for load-bearing bone defect repair and regeneration. Published by Elsevier Ltd.

Direct Ink Writing of Highly Porous and Strong Glass Scaffolds for Load-bearing Bone Defects Repair and Regeneration

PubMed Central

Fu, Qiang; Saiz, Eduardo; Tomsia, Antoni P.

2011-01-01

The quest for synthetic materials to repair load-bearing bone lost because of trauma, cancer, or congenital bone defects requires development of porous and high-performance scaffolds with exceptional mechanical strength. However, the low mechanical strength of porous bioactive ceramic and glass scaffolds, compared with that of human cortical bone, has limited their use for these applications. In the present work, bioactive 6P53B glass scaffolds with superior mechanical strength were fabricated using a direct ink writing technique. The rheological properties of Pluronic® F-127 (referred to hereafter simply as F-127) hydrogel-based inkswere optimized for the printing of features as fine as 30 μm and of the three-dimensional scaffolds. The mechanical strength and in vitro degradation of the scaffolds were assessed in a simulated body fluid (SBF). The sintered glass scaffolds show a compressive strength (136 ± 22 MPa) comparable to that of human cortical bone (100-150 MPa), while the porosity (60%) is in the range of that of trabecular bone (50-90%).The strength is ~100 times that of polymer scaffolds and 4–5 times that of ceramic and glass scaffolds with comparable porosities. Despite the strength decrease resulting from weight loss during immersion in an SBF, the value (77 MPa) is still far above that of trabecular bone after three weeks. The ability to create both porous and strong structures opens a new avenue for fabricating scaffolds for load-bearing bone defect repair and regeneration. PMID:21745606

Glass-ceramic nuclear waste forms obtained by crystallization of SiO 2-Al 2O 3-CaO-ZrO 2-TiO 2 glasses containing lanthanides (Ce, Nd, Eu, Gd, Yb) and actinides (Th): Study of the crystallization from the surface

NASA Astrophysics Data System (ADS)

Loiseau, P.; Caurant, D.

2010-07-01

Glass-ceramic materials containing zirconolite (nominally CaZrTi 2O 7) crystals in their bulk can be envisaged as potential waste forms for minor actinides (Np, Am, Cm) and Pu immobilization. In this study such matrices are synthesized by crystallization of SiO 2-Al 2O 3-CaO-ZrO 2-TiO 2 glasses containing lanthanides (Ce, Nd, Eu, Gd, Yb) and actinides (Th) as surrogates. A thin partially crystallized layer containing titanite and anorthite (nominally CaTiSiO 5 and CaAl 2Si 2O 8, respectively) growing from glass surface is also observed. The effect of the nature and concentration of surrogates on the structure, the microstructure and the composition of the crystals formed in the surface layer is presented in this paper. Titanite is the only crystalline phase able to significantly incorporate trivalent lanthanides whereas ThO 2 precipitates in the layer. The crystal growth thermal treatment duration (2-300 h) at high temperature (1050-1200 °C) is shown to strongly affect glass-ceramics microstructure. For the system studied in this paper, it appears that zirconolite is not thermodynamically stable in comparison with titanite growing form glass surface. Nevertheless, for kinetic reasons, such transformation (i.e. zirconolite disappearance to the benefit of titanite) is not expected to occur during interim storage and disposal of the glass-ceramic waste forms because their temperature will never exceed a few hundred degrees.

Glass formation and crystallization in high-temperature glass-ceramics and Si3N4

NASA Technical Reports Server (NTRS)

Drummond, Charles H., III

1991-01-01

The softening of glassy grain boundaries in ceramic matrix composites and Si3N4 at high temperatures reduces mechanical strength and the upper-use temperature. By crystallizing this glass to a more refractory crystalline phase, a material which performs at higher temperatures may result. Three systems were examined: a cordierite composition with ZrO2 as a nucleating agent; celsian compositions; and yttrium silicate glasses both in bulk and intergranular in Si3N4. For the cordierite compositions, a series of metastable phases was obtained. The crystallization of these compositions was summarized in terms of metastable ternary isothermal sections. Zircon formed at the expense of ZrO2 and spinel. In SiC composites, the transformations were slower. In celsian, two polymorphs were crystallized. One phase, hexacelsian, which always crystallized, even when metastable, had an undesirable volume change. The other phase, celsian, was very difficult to crystallize. In yttrium silicate bulk glasses, similar in composition to the intergranular glass in Si3N4, a number of polymorphs of Y2Si2O7 were crystallized. The conditions under which these polymorphs formed are compared with crystallization in Si3N4.

Initial Examination of Low Velocity Sphere Impact of Glass Ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morrissey, Timothy G; Fox, Ethan E; Wereszczak, Andrew A

This report summarizes US Army TARDEC sponsored work at Oak Ridge National Laboratory (ORNL) involving low velocity (< 30 m/s or < 65 mph) sphere impact testing of two materials from the lithium aluminosilicate family reinforced with different amounts of ceramic particulate, i.e., glass-ceramic materials, SCHOTT Resistan{trademark}-G1 and SCHOTT Resistan{trademark}-L. Both materials are provided by SCHOTT Glass (Duryea, PA). This work is a follow-up to similar sphere impact studies completed by the authors on PPG's Starphire{reg_sign} soda-lime silicate glass and SCHOTT BOROFLOAT{reg_sign} borosilicate glass. A gas gun or a sphere-drop test setup was used to produce controlled velocity delivery ofmore » silicon nitride (Si{sub 3}N{sub 4}) spheres against the glass ceramic tile targets. Minimum impact velocities to initiate fracture in the glass-ceramics were measured and interpreted in context to the kinetic energy of impact and the elastic property mismatch between sphere and target material. Quasistatic spherical indentation was also performed on both glass ceramics and their contact damage responses were compared to those of soda-lime silicate and borosilicate glasses. Lastly, variability of contact damage response was assessed by performing spherical indentation testing across the area of an entire glass ceramic tile. The primary observations from this low velocity (< 30 m/s or < 65 mph) testing were: (1) Resistan{trademark}-L glass ceramic required the highest velocity of sphere impact for damage to initiate. Starphire{reg_sign} soda-lime silicate glass was second best, then Resistan{trademark}-G1 glass ceramic, and then BOROFLOAT{reg_sign} borosilicate glass. (2) Glass-ceramic Resistan{trademark}-L also required the largest force to initiate ring crack from quasi-static indentation. That ranking was followed, in descending order, by Starphire{reg_sign} soda-lime silicate glass, Resistan{trademark}-G1 glass ceramic, and BOROFLOAT{reg_sign} borosilicate glass

Effect of nano-scale morphology on micro-channel wall surface and electrical characterization in lead silicate glass micro-channel plate

NASA Astrophysics Data System (ADS)

Cai, Hua; Li, Fangjun; Xu, Yanglei; Bo, Tiezhu; Zhou, Dongzhan; Lian, Jiao; Li, Qing; Cao, Zhenbo; Xu, Tao; Wang, Caili; Liu, Hui; Li, Guoen; Jia, Jinsheng

2017-10-01

Micro-channel plate (MCP) is a two dimensional arrays of microscopic channel charge particle multiplier. Silicate composition and hydrogen reduction are keys to determine surface morphology of micro-channel wall in MCP. In this paper, lead silicate glass micro-channel plates in two different cesium contents (0at%, 0.5at%) and two different hydrogen reduction temperatures (400°C,450°C) were present. The nano-scale morphology, elements content and chemical states of microporous wall surface treated under different alkaline compositions and reduction conditions was investigated by Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS), respectively. Meanwhile, the electrical characterizations of MCP, including the bulk resistance, electron gain and the density of dark current, were measured in a Vacuum Photoelectron Imaging Test Facility (VPIT).The results indicated that the granular phase occurred on the surface of microporous wall and diffuses in bulk glass is an aggregate of Pb atom derived from the reduction of Pb2+. In micro-channel plate, the electron gain and bulk resistance were mainly correlated to particle size and distribution, the density of dark current (DDC) went up with the increasing root-mean-square roughness (RMS) on the microporous wall surface. Adding cesiums improved the size of Pb atomic aggregation, lowered the relative concentration of [Pb] reduced from Pb2+ and decreased the total roughness of micro-channel wall surface, leading a higher bulk resistance, a lower electron gain and a less dark current. Increasing hydrogen reduction temperature also improved the size of Pb atomic aggregation, but enhanced the relative concentration of [Pb] and enlarged the total roughness of micro-channel wall surface, leading a higher bulk resistance, a lower electron gain and a larger dark current. The reasons for the difference of electrical characteristics were discussed.

Deformation, Stress Relaxation, and Crystallization of Lithium Silicate Glass Fibers Below the Glass Transition Temperature

NASA Technical Reports Server (NTRS)

Ray, Chandra S.; Brow, Richard K.; Kim, Cheol W.; Reis, Signo T.

2004-01-01

The deformation and crystallization of Li(sub 2)O (center dot) 2SiO2 and Li(sub 2)O (center dot) 1.6SiO2 glass fibers subjected to a bending stress were measured as a function of time over the temperature range -50 to -150 C below the glass transition temperature (Tg). The glass fibers can be permanently deformed at temperatures about 100 C below T (sub)g, and they crystallize significantly at temperatures close to, but below T,, about 150 C lower than the onset temperature for crystallization for these glasses in the no-stress condition. The crystallization was found to occur only on the surface of the glass fibers with no detectable difference in the extent of crystallization in tensile and compressive stress regions. The relaxation mechanism for fiber deformation can be best described by a stretched exponential (Kohlrausch-Williams-Watt (KWW) approximation), rather than a single exponential model.The activation energy for stress relaxation, Es, for the glass fibers ranges between 175 and 195 kJ/mol, which is considerably smaller than the activation energy for viscous flow, E, (about 400 kJ/mol) near T, for these glasses at normal, stress-free condition. It is suspected that a viscosity relaxation mechanism could be responsible for permanent deformation and crystallization of the glass fibers below T,

Optical ridge waveguides in Er3+/Yb3+ co-doped phosphate glass produced by ion irradiation combined with femtosecond laser ablation for guided-wave green and red upconversion emissions

NASA Astrophysics Data System (ADS)

Chen, Chen; He, Ruiyun; Tan, Yang; Wang, Biao; Akhmadaliev, Shavkat; Zhou, Shengqiang; de Aldana, Javier R. Vázquez; Hu, Lili; Chen, Feng

2016-01-01

This work reports on the fabrication of ridge waveguides in Er3+/Yb3+ co-doped phosphate glass by the combination of femtosecond laser ablation and following swift carbon ion irradiation. The guiding properties of waveguides have been investigated at 633 and 1064 nm through end face coupling arrangement. The refractive index profile on the cross section of the waveguide has been constructed. The propagation losses can be reduced considerably after annealing treatment. Under the optical pump laser at 980 nm, the upconversion emission of both green and red fluorescence has been realized through the ridge waveguide structures.

Reversible redox and clusterization of silver in glasses by X-ray irradiation and heat treatment: Mechanism of photochromic behavior of halogen-free silver-doped glass

NASA Astrophysics Data System (ADS)

Isaji, Tomoya; Wakasugi, Takashi; Fukumi, Kohei; Kadono, Kohei

2012-01-01

We investigated photochromic behavior, i.e. X-ray irradiation and post-heat-treatment-induced reversible redox and clusterization reactions of silver, in soda-lime silicate (74SiO2·16Na2O·8CaO·2Al2O3) and aluminosilicate ((75 - x)SiO2·25Na2O·xAl2O3 (x = 5-25)) glasses. Generation and annihilation of silver nanoparticles were observed for soda-lime silicate and x = 5 aluminosilicate glasses doped with 0.05 wt.% or less of Ag while no nanoparticles were formed for x = 15-25 aluminosilicate glasses even doped with 0.5 wt.% of Ag. These results were analyzed from the viewpoints of the reaction kinetics and network structures of the glasses.

Bioactive Glass and Glass-Ceramic Scaffolds for Bone Tissue Engineering

PubMed Central

Gerhardt, Lutz-Christian; Boccaccini, Aldo R.

2010-01-01

Traditionally, bioactive glasses have been used to fill and restore bone defects. More recently, this category of biomaterials has become an emerging research field for bone tissue engineering applications. Here, we review and discuss current knowledge on porous bone tissue engineering scaffolds on the basis of melt-derived bioactive silicate glass compositions and relevant composite structures. Starting with an excerpt on the history of bioactive glasses, as well as on fundamental requirements for bone tissue engineering scaffolds, a detailed overview on recent developments of bioactive glass and glass-ceramic scaffolds will be given, including a summary of common fabrication methods and a discussion on the microstructural-mechanical properties of scaffolds in relation to human bone (structure-property and structure-function relationship). In addition, ion release effects of bioactive glasses concerning osteogenic and angiogenic responses are addressed. Finally, areas of future research are highlighted in this review. PMID:28883315

Glass viscosity calculation based on a global statistical modelling approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fluegel, Alex

2007-02-01

A global statistical glass viscosity model was developed for predicting the complete viscosity curve, based on more than 2200 composition-property data of silicate glasses from the scientific literature, including soda-lime-silica container and float glasses, TV panel glasses, borosilicate fiber wool and E type glasses, low expansion borosilicate glasses, glasses for nuclear waste vitrification, lead crystal glasses, binary alkali silicates, and various further compositions from over half a century. It is shown that within a measurement series from a specific laboratory the reported viscosity values are often over-estimated at higher temperatures due to alkali and boron oxide evaporation during the measurementmore » and glass preparation, including data by Lakatos et al. (1972) and the recently published High temperature glass melt property database for process modeling by Seward et al. (2005). Similarly, in the glass transition range many experimental data of borosilicate glasses are reported too high due to phase separation effects. The developed global model corrects those errors. The model standard error was 9-17°C, with R^2 = 0.985-0.989. The prediction 95% confidence interval for glass in mass production largely depends on the glass composition of interest, the composition uncertainty, and the viscosity level. New insights in the mixed-alkali effect are provided.« less

Optimized design of Yb3+/Er3+-codoped cross-coupled integrated microring resonator arrays

NASA Astrophysics Data System (ADS)

Gǎlǎtus, Ramona; Vallés, Juan A.

2014-09-01

In this work the analytical model of the scattering response of a highly Yb3+/Er3+-codoped phosphate glass microring resonator array is developed. The microscopic statistical formalism is used to simulate its performance as a wavelengthselective amplifier. The performance of the integrated add-drop filter was investigated based on the signal transfer functions for Through and Drop ports, correlated the with gain coefficient and its dependence on pump power, signal power and Yb3+/Er3+- dopants concentration. In consequence, microring arrays with gain operating in the near infrared spectral range and, in particular, in the 1.5-mm wavelength band (emission band of Er-doped fiber amplifiers and lasers, already used in several bio/chemical sensing tasks) are highly attractive.

Latent fingermark detection for NaYF4:Er3+/Yb3+ upconversion phosphor synthesized by thermal decomposition route

NASA Astrophysics Data System (ADS)

Maurya, S. K.; Tiwari, S. P.; Kumar, A.; Kumar, K.

2018-04-01

The synthesis and spectroscopy of the upconverting nanoparticles, cubic NaYF4:Er3+/Yb3+ phosphor is developed for latent fingermark detection. The cubic phase of NaYF4: Er3+/Yb3+ phosphor is synthesized by thermal decomposition method using trifluoroacetate precursor with coordinating ligand octadecene and oleic acid in a mixture of technical grade. The synthesized samples showed intense green emission using 976 nm diode laser as an excitation source. Because of excellent property of luminescence in green regime the sample is used to detect the latent fingermark on a porous glass surface.

Glass corrosion in natural environments

NASA Technical Reports Server (NTRS)

Thorpe, Arthur N.; Barkatt, Aaron

1992-01-01

Experiments carried out during the progress period are summarized. Experiments carried out involving glass samples exposed to solutions of Tris have shown the appearance of 'spikes' upon monitoring glass dissolution as a function of time. The periodic 'spikes' observed in Tris-based media were interpreted in terms of cracking due to excessive stress in the surface region of the glass. Studies of the interactions of silicate glasses with metal ions in buffered media were extended to systems containing Al. Caps buffer was used to establish the pH. The procedures used are described and the results are given. Preliminary studies were initiated as to the feasibility of adding a slowly dissolving solid compound of the additive to the glass-water system to maintain a supply of dissolved additive. It appears that several magnesium compounds have a suitable combination of solubility and affinity towards silicate glass surfaces to have a pronounced retarding effect on the extraction of uranium from the glass. These preliminary findings raise the possibility that introducing a magnesium source into geologic repositories for nuclear waste glass in the form of a sparingly soluble Mg-based backfill material may cause a substantial reduction in the extent of long-term glass corrosion. The studies described also provide mechanistic understanding of the roles of various metal solutes in the leachant. Such understanding forms the basis for developing long-term predictions of nuclear waste glass durability under repository conditions. From what is known about natural highly reduced glasses such as tektites, it is clear that iron is dissolved as ferrous iron with little or no ferric iron. The reducing conditions were high enough to cause metallic iron to exsolve out of the glass in the form of submicroscopic spherules. As the nuclear waste glass is much less reduced, a study was initiated on other natural glasses in addition to the nuclear waste glass. Extensive measurements were

Electron-band theory inspired design of magnesium-precious metal bulk metallic glasses with high thermal stability and extended ductility.

PubMed

Laws, Kevin J; Shamlaye, Karl F; Granata, Davide; Koloadin, Leah S; Löffler, Jörg F

2017-06-13

Magnesium-based bulk metallic glasses (BMGs) exhibit high specific strengths and excellent glass-forming ability compared to other metallic systems, making them suitable candidates for next-generation materials. However, current Mg-based BMGs tend to exhibit low thermal stability and are prone to structural relaxation and brittle failure. This study presents a range of new magnesium-precious metal-based BMGs from the ternary Mg-Ag-Ca, Mg-Ag-Yb, Mg-Pd-Ca and Mg-Pd-Yb alloy systems with Mg content greater than 67 at.%. These alloys were designed for high ductility by utilising atomic bond-band theory and a topological efficient atomic packing model. BMGs from the Mg-Pd-Ca alloy system exhibit high glass-forming ability with critical casting sizes of up to 3 mm in diameter, the highest glass transition temperatures (>200 °C) of any reported Mg-based BMG to date, and sustained compressive ductility. Alloys from the Mg-Pd-Yb family exhibit critical casting sizes of up to 4 mm in diameter, and the highest compressive plastic (1.59%) and total (3.78%) strain to failure of any so far reported Mg-based glass. The methods and theoretical approaches presented here demonstrate a significant step forward in the ongoing development of this extraordinary class of materials.

Alkali Silicate Glass Coatings for Mitigating the Risks of Tin Whiskers

NASA Astrophysics Data System (ADS)

Hillman, Dave; Wilcoxon, Ross; Lower, Nate; Grossman, Dan

2015-12-01

Alkali silicate glass (ASG) coatings were investigated as a possible method for inhibiting tin whisker initiation and growth. The aqueous-based ASG formulations used in this study were deposited with equipment and conditions that are typical of those used to apply conventional conformal coatings. Processes for controlling ASG coating properties were developed, and a number of ASG-based coating combinations were applied to test components with pure tin surfaces. Coatings were applied both in a laboratory environment at Rockwell Collins and in a manufacturing environment at Plasma Ruggedized Solutions. Testing in elevated humidity/temperature environments and subsequent inspection of the test articles identified coating combinations that inhibited tin whisker growth as well as other material combinations that actually accelerated tin whisker growth. None of the coatings evaluated in this study, including conventional acrylic and Parylene conformal coatings, completely prevented the formation of tin whiskers. Two of the coatings were particularly effective at reducing the risks of whisker growth, albeit through different mechanisms. Parylene conformal coating almost, but not completely, eliminated whisker formation, and only a few tin whiskers were found on these surfaces during the study. A composite of ASG and alumina nanoparticles inhibited whisker formation to a lesser degree than Parylene, but did disrupt whisker growth mechanisms so as to inhibit the formation of long, and more dangerous, tin whiskers. Additional testing also demonstrated that the conformal coatings had relatively little effect on the dielectric loss of a stripline test structure operating at frequencies over 30 GHz.

Yb:S-FAP Lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schaffers, K I

It has recently been reported that several high power, diode-pumped laser systems have been developed based on crystals of Yb:S-FAP [Yb{sup 3+}:Sr{sub 5}(PO{sub 4}){sub 3}F]. The Mercury Laser, at Lawrence Livermore National Laboratory, is the most prominent system using Yb:S-FAP and is currently producing 23J at 5 Hz in a 15 nsec pulse, based on partial activation of the system. In addition, a regenerative amplifier is being developed at Waseda University in Japan and has produced greater than 12 mJ with high beam quality at 50Hz repetition rate. Q-peak has demonstrated 16 mJ of maximum energy/output pulse in a multi-pass,more » diode side-pumped amplifier and ELSA in France is implementing Yb:S-FAP in a 985 nm pump for an EDFA, producing 250 mW. Growth of high optical quality crystals of Yb:S-FAP is a challenge due to multiple crystalline defects. However, at this time, a growth process has been developed to produce high quality 3.5 cm diameter Yb:S-FAP crystals and a process is under development for producing 6.5 cm diameter crystals.« less

Lattice instability and enhancement of superconductivity in YB6

NASA Astrophysics Data System (ADS)

Sluchanko, N.; Glushkov, V.; Demishev, S.; Azarevich, A.; Anisimov, M.; Bogach, A.; Voronov, V.; Gavrilkin, S.; Mitsen, K.; Kuznetsov, A.; Sannikov, I.; Shitsevalova, N.; Filipov, V.; Kondrin, M.; Gabáni, S.; Flachbart, K.

2017-10-01

The superconducting and normal state characteristics of yttrium hexaboride (YB6) have been investigated for the single crystals with a transition temperatures Tc ranging between 4.2 K and 7.6 K. The extracted set of microscopic parameters [the coherence length ξ (0 )˜320 -340 Å , the penetration depth λ (0 )˜1100 -3250 Å and the mean free path of charge carriers l =11 -58 Å , the Ginzburg-Landau-Maki parameters κ1 ,2(0 ) ˜3.3 -9.5, and the superconducting gap Δ (0 )˜6.2 -14.8 K] confirms the type II superconductivity in "dirty limit" (ξ ≫l ) with a medium to strong electron-phonon interaction (the electron-phonon interaction constant λe -ph=0.32 -0.96 ) and s -type pairing of charge carriers in this compound [2 Δ (0 ) /kBTc≈3 -4]. The comparative analysis of charge transport (resistivity, Hall and Seebeck coefficients) and thermodynamic (heat capacity, magnetization) properties in the normal state in YB6 allowed to assume a transition into the cage-glass state at T*˜50 K with a static disorder in the arrangement of the Y3 + ions. We argue that the significant Tc variations in YB6 single crystals are determined by two main factors: (i) the superconductivity enhancement is related with the increase of the number of vacancies, both at yttrium and boron sites, leading to nonstoichiometric composition, which is accompanied by the enhancement of electron-phonon interaction in the hexaboride lattice; (ii) stronger Tc depression is observed in near stoichiometric and more dense crystals and it is induced by the development of bcc lattice instability producing strong distortion, disordering, and formation of defect complexes in the matrix of YB6.

Photoluminescence properties of LiF bismuth silicate glass

NASA Astrophysics Data System (ADS)

Krishnan, M. Laya; Kumar, V. V. Ravi Kanth

2018-04-01

The sample (60-X) Bi2O3-30SiO2-XLiF where X=10, 15, 25 were prepared by conventional melt quenching method. X-ray diffraction pattern conformed the amorphous nature of the prepared sample and a broad peak at 2θ=30°. The Raman spectra confirmed that the Bi can exist both network former (BiO3 pyramidal) and network modifier (BiO6 octahedral)in the glass matrix. The samples showing broad absorption at 470nm is due to the presence of Bi2+ ions, because of increasing optical basicity the absorption edge of the sample is blue shifted. The photoluminescence spectra of the glass under 350nm excitation are showing two main peaks at 430nm and 630 nm due to Bi3+ and Bi2+ respectively and 25 LBS glass showing yellow, 15LBS showing near bluish white and 10LBS showing blue luminescence. The color purity and correlated color temperature are also calculated.

Precipitation of Secondary Phases from the Dissolution of Silicate Glasses

NASA Technical Reports Server (NTRS)

Ming, Douglas W.; Golden, D. C.

2004-01-01

Basaltic and anorthositic glasses were subjected to aqueous weathering conditions in the laboratory where the variables were pH, temperature, glass composition, solution composition, and time. Leached layers formed at the surfaces of glasses followed by the precipitation of X-ray amorphous iron and titanium oxides in acidic and neutral solutions at 25 C over time. Glass under oxidative hydrothermal treatments at 150 C yielded a three-layered surface; which included an outer smectite layer, a Fe-Ti oxide layer and an innermost thin leached layer. The introduction of Mg into solutions facilitated the formation of phyllosilicates. Aqueous hydrothermal treatment of anorthositic glasses (high Ca, low Ti) at 200 C readily formed smectite, whereas, the basaltic glasses (high Ti) were more resistant to alteration and smectite was not observed. Alkaline hydrothermal treatment at 2000e produced zeolites and smectites; only smectites formed at 200 C in neutral solutions. These mineralogical changes, although observed under controlled conditions, have direct applications in interpreting planetary (e.g., meteorite parent bodies) and terrestrial aqueous alteration processes.

Model for the interpretation of nuclear magnetic resonance relaxometry of hydrated porous silicate materials

NASA Astrophysics Data System (ADS)

Faux, D. A.; Cachia, S.-H. P.; McDonald, P. J.; Bhatt, J. S.; Howlett, N. C.; Churakov, S. V.

2015-03-01

Nuclear magnetic resonance (NMR) relaxation experimentation is an effective technique for probing the dynamics of proton spins in porous media, but interpretation requires the application of appropriate spin-diffusion models. Molecular dynamics (MD) simulations of porous silicate-based systems containing a quasi-two-dimensional water-filled pore are presented. The MD simulations suggest that the residency time of the water on the pore surface is in the range 0.03-12 ns, typically 2-5 orders of magnitude less than values determined from fits to experimental NMR measurements using the established surface-layer (SL) diffusion models of Korb and co-workers [Phys. Rev. E 56, 1934 (1997), 10.1103/PhysRevE.56.1934]. Instead, MD identifies four distinct water layers in a tobermorite-based pore containing surface Ca2 + ions. Three highly structured water layers exist within 1 nm of the surface and the central region of the pore contains a homogeneous region of bulklike water. These regions are referred to as layer 1 and 2 (L1, L2), transition layer (TL), and bulk (B), respectively. Guided by the MD simulations, a two-layer (2L) spin-diffusion NMR relaxation model is proposed comprising two two-dimensional layers of slow- and fast-moving water associated with L2 and layers TL+B, respectively. The 2L model provides an improved fit to NMR relaxation times obtained from cementitious material compared to the SL model, yields diffusion correlation times in the range 18-75 ns and 28-40 ps in good agreement with MD, and resolves the surface residency time discrepancy. The 2L model, coupled with NMR relaxation experimentation, provides a simple yet powerful method of characterizing the dynamical properties of proton-bearing porous silicate-based systems such as porous glasses, cementitious materials, and oil-bearing rocks.

(Energetics of silicate melts from thermal diffusion studies)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1989-01-01

Research during the past year has been concentrated in four major areas. We are continuing work initiated during the first two years on modelling thermal diffusion on multicomponent silicate liquids. We have derived appropriate relations for ternary and quaternary systems and reanalyzed experimental thermal diffusion data for the ternary system fayalite-leucite-silica. In our manuscript entitled Thermal Diffusion in Petrology'', to be published in Adv. in Phy. Geochem., we show that these model results independently recover the compositional extent and temperature of liquid immiscibility in this system. Such retrieval provides a rigorous test of our theoretical predictions and simplified treatment ofmore » complex silicate liquids reported in Geochimica Cosmochimica Acta in 1986. The usefulness of our Soret research in providing mixing energies of silicate liquids has been recently confirmed by Ghiorso (1987, Cont. Min. Pet.). This demonstration provides a strategy for incorporating Soret data into the calibration of phase equilibrium-based solution models such as the one developed by Ghiorso. During the past year we also have resumed our studies of thermal diffusion in borosilicate glasses which also exhibit liquid immiscibility. Our objectives in studying these systems are (1) to further test of our multicomponent thermal diffusion model and (2) to provide quantitative constraints on the mixing properties of these glass-forming systems which are important for evaluating their suitability for storage of high-level nuclear waste. 16 refs.« less

Wastewater reuse in liquid sodium silicate manufacturing in alexandria, egypt.

PubMed

Ismail, Gaber A; Abd El-Salam, Magda M; Arafa, Anwar K

2009-01-01

Soluble sodium silicates (waterglass) are liquids containing dissolved glass which have some water like properties. They are widely used in industry as sealants, binders, deflocculants, emulsifiers and buffers. Their most common applications in Egypt are in the pulp and paper industry (where they improve the brightness and efficiency of peroxide bleaching) and the detergent industry, in which they improve the action of the detergent and lower the viscosity of liquid soaps. The survey results showed that the production was carried out batch-wise, in an autoclave (dissolver). Sodium silicate in the state of crushed glass was charged in an autoclave (dissolver) with sodium hydroxide and water. The product is filtered through a press. The left over sludge (mud and silicates impurities) is emptied into the local sewer system. Also, sludge (silica gel) was discharged from the neutralization process of the generated alkaline wastewater and consequently clogging the sewerage system. So this study was carried out to modify the current wastewater management system which eliminates sludge formation, the discharge of higher pH wastewater to the sewer system, and to assess its environmental and economic benefits. To assess the characteristics of wastewater to be reused, physico-chemical parameters of 12 samples were tested using standard methods. The survey results showed that a total capacity of the selected enterprise was 540 tons of liquid sodium silicates monthly. The total amount of wastewater being discharged was 335 m3/month. Reusing of wastewater as feed autoclave water reduced water consumption of 32.1% and reduced wastewater discharge/month that constitutes 89.6% as well as saving in final product of 6 ton/month. It was concluded that reusing of wastewater generated from liquid sodium silicate manufacturing process resulted in cheaper and environmental-friendly product.

Overexpression of YB1 C-terminal domain inhibits proliferation, angiogenesis and tumorigenicity in a SK-BR-3 breast cancer xenograft mouse model.

PubMed

Shi, Jian-Hong; Cui, Nai-Peng; Wang, Shuo; Zhao, Ming-Zhi; Wang, Bing; Wang, Ya-Nan; Chen, Bao-Ping

2016-01-01

Y-box-binding protein 1 (YB1) is a multifunctional transcription factor with vital roles in proliferation, differentiation and apoptosis. In this study, we have examined the role of its C-terminal domain (YB1 CTD) in proliferation, angiogenesis and tumorigenicity in breast cancer. Breast cancer cell line SK-BR-3 was infected with GFP-tagged YB1 CTD adenovirus expression vector. An 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) proliferation assay showed that YB1 CTD decreased SK-BR-3 cell proliferation, and down-regulated cyclin B1 and up-regulated p21 levels in SK-BR-3 cells. YB1 CTD overexpression changed the cytoskeletal organization and slightly inhibited the migration of SK-BR-3 cells. YB1 CTD also inhibited secreted VEGF expression in SK-BR-3 cells, which decreased SK-BR-3-induced EA.hy926 endothelial cell angiogenesis in vitro. YB1 CTD overexpression attenuated the ability of SK-BR-3 cells to form tumours in nude mice, and decreased in vivo VEGF levels and angiogenesis in the xenografts in SK-BR-3 tumour-bearing mice. Taken together, our findings demonstrate the vital role of YB1 CTD overexpression in inhibiting proliferation, angiogenesis and tumorigenicity of breast cancer cell line SK-BR-3.

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

PubMed

Murakami, Motohiko; Bass, Jay D

2011-10-18

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

The 3D Distribution of Magma Bodies that Fed the Paraná Silicic Volcanics, Brazil: A Combination of Field Evidence, Textural Analysis, and Geothermobarometry

NASA Astrophysics Data System (ADS)

Harmon, L.; Gualda, G. A. R.; Gravley, D. M.

2016-12-01

The Paraná Silicic Volcanics include some of the largest eruptive deposits known in the geological record. However, we know very little about the magma bodies that fed these eruptions. Combining physical volcanology, geochemistry, and geothermobarometry techniques, we aim to find the sources of extinct magma bodies to build a 3D view of the magma structure at the time by discovering storage conditions, eruption styles, and post-eruption alteration. The approach elucidates temporal and spatial eruption styles and sequences of the silicic units that make up the Palmas unit of the Serra Geral formation, Brazil. We use field investigations to determine the history of volcanic deposits, domes, and changes in eruptive style; we map and characterize volcanic deposits based on thickness (thicker is proximal to source) and distribution of effusive (proximal to source) and explosive deposits. We focus on several exposed canyons that exhibit either exclusively explosive or effusive, or a clear progression from explosive to effusive deposits. The progression from explosive to effusive indicates a system change from explosively energetic to effusively waning. Additionally, observation of pervasive flow banding in both effusive and explosive deposits indicates rheomorphic flow through many portions of the field area, an indicator of hot emplacement. Geochemical work focuses on the pre-eruptive magma conditions to determine the depth of magma bodies. We utilize glass bearing samples of both the explosively deposited juvenile blob-like structures and obsidian samples to determine crystallization depth. The glass is variably altered, via silicification and devitrification processes, with the blobs more greatly silicified than the obsidian. We use rhyolite-MELTS geothermobarometry when pristine glass can be found. Initial results indicate shallow ( 80 MPa) storage conditions for the explosively erupted blobs. The combination of techniques builds a 3D understanding of extinct super

Paleomagnetic Evidence for Partial Differentiation of the Silicate-Bearing IIE Iron Meteorite Parent Body

NASA Astrophysics Data System (ADS)

Maurel, C.; Bryson, J. F. J.; Weiss, B. P.; Scholl, A.

2016-12-01

The identification of dozens of petrologically diverse chondritic and achondritic meteoritic groups indicates that a diversity of planetesimals formed in the early solar system. It is commonly thought that planetesimals formed as either unmelted or else fully differentiated bodies, implying that chondrites and achondrites cannot have originated on a single body. However, it has been suggested that partially melted bodies with chondritic crusts and achondritic interiors may also have formed. This alternative proposal is supported by the recent identification of post-accretional remanent magnetization in CV, H chondrites, and also possibly in CM chondrites, which has been interpreted as possible evidence for a core dynamo on their parent bodies. Other piece of evidence suggesting the existence of partially differentiated bodies is the existence of the silicate-bearing IIE iron meteorites. The IIEs are composed of a Fe-Ni alloy matrix containing a mixture of chondritic, primitive achondritic, and chondritic silicate inclusions that likely formed on a single parent body. Therefore, IIEs may sample all three putative layers of a layered, partially differentiated body. On the other hand, the siderophile element compositions of the matrix metal demonstrate that it is not the product of fractional crystallization of a molten core. This suggests that the matrix metal is derived from isolated reservoirs of metal in the mantle and/or crust. It is unknown whether a large-scale metallic core, not represented by known meteorite samples, also formed on the same parent planetesimal. We can search for evidence of a molten, advecting core by assessing whether IIE irons contain remanent magnetization produced by a core dynamo. With this goal, we studied the paleomagnetism of a cloudy zone (CZ) interface in the Fe-Ni matrix of the IIE iron Colomera using X-ray photoelectron emission microscopy (XPEEM). Our initial results suggest that a steady, intense magnetic field was present

Paleomagnetic Evidence for Partial Differentiation of the Silicate-Bearing IIE Iron Meteorite Parent Body

NASA Astrophysics Data System (ADS)

Maurel, C.; Bryson, J. F. J.; Weiss, B. P.; Scholl, A.

2017-12-01

The identification of dozens of petrologically diverse chondritic and achondritic meteoritic groups indicates that a diversity of planetesimals formed in the early solar system. It is commonly thought that planetesimals formed as either unmelted or else fully differentiated bodies, implying that chondrites and achondrites cannot have originated on a single body. However, it has been suggested that partially melted bodies with chondritic crusts and achondritic interiors may also have formed. This alternative proposal is supported by the recent identification of post-accretional remanent magnetization in CV, H chondrites, and also possibly in CM chondrites, which has been interpreted as possible evidence for a core dynamo on their parent bodies. Other piece of evidence suggesting the existence of partially differentiated bodies is the existence of the silicate-bearing IIE iron meteorites. The IIEs are composed of a Fe-Ni alloy matrix containing a mixture of chondritic, primitive achondritic, and chondritic silicate inclusions that likely formed on a single parent body. Therefore, IIEs may sample all three putative layers of a layered, partially differentiated body. On the other hand, the siderophile element compositions of the matrix metal demonstrate that it is not the product of fractional crystallization of a molten core. This suggests that the matrix metal is derived from isolated reservoirs of metal in the mantle and/or crust. It is unknown whether a large-scale metallic core, not represented by known meteorite samples, also formed on the same parent planetesimal. We can search for evidence of a molten, advecting core by assessing whether IIE irons contain remanent magnetization produced by a core dynamo. With this goal, we studied the paleomagnetism of a cloudy zone (CZ) interface in the Fe-Ni matrix of the IIE iron Colomera using X-ray photoelectron emission microscopy (XPEEM). Our initial results suggest that a steady, intense magnetic field was present

Enamel and Dentin Surface Finishing Influence on the Roughness and Microshear Bond Strength of a Lithium Silicate Glass-Ceramic for Laminate Veneers.

PubMed

Gonzaga, Carla Castiglia; Bravo, Ruth Peggy; Pavelski, Thiago Vinícius; Garcia, Paula Pontes; Correr, Gisele Maria; Leonardi, Denise Piotto; da Cunha, Leonardo Fernandes; Furuse, Adilson Yoshio

2015-01-01

Objectives. This study evaluated the influence of cavity surface finishing with diamond burs of different grit mounted on high-speed turbine and ultrasound on the roughness and microshear bond strength (MBS) of a lithium silicate glass-ceramic to enamel and dentin. Methods. Enamel and dentin specimens were divided into seven groups, according to the type of surface finishing: 1200-grit sandpaper (control), two different brands of medium-grit and fine-grit diamond burs in a high-speed turbine; medium-grit and fine-grit CVD (chemical vapor deposition) tips in an ultrasonic device. Roughness parameters (n = 5) and MSBS to a glass-ceramic (n = 10) were determined. Data were analyzed using ANOVA and Tukey's test (α = 5%). Results. Control group showed lower mean roughness readings and groups that used medium-grit diamond burs showed the highest mean roughness values. Regarding MSBS, there was no statistical difference when comparing the groups gritted with the same brand of medium- and fine-grit burs and tips. Conclusions. Cavity surface finishing influenced the roughness parameters and MSBS of a glass-ceramic to enamel and dentin. Medium-grit diamond burs in high-speed turbine showed the highest mean roughness values. Fine-grit CVD tips in ultrasound presented the highest MSBS values for both enamel and dentin.

Enamel and Dentin Surface Finishing Influence on the Roughness and Microshear Bond Strength of a Lithium Silicate Glass-Ceramic for Laminate Veneers

PubMed Central

Gonzaga, Carla Castiglia; Bravo, Ruth Peggy; Pavelski, Thiago Vinícius; Garcia, Paula Pontes; Correr, Gisele Maria; Leonardi, Denise Piotto; da Cunha, Leonardo Fernandes; Furuse, Adilson Yoshio

2015-01-01

Objectives. This study evaluated the influence of cavity surface finishing with diamond burs of different grit mounted on high-speed turbine and ultrasound on the roughness and microshear bond strength (MBS) of a lithium silicate glass-ceramic to enamel and dentin. Methods. Enamel and dentin specimens were divided into seven groups, according to the type of surface finishing: 1200-grit sandpaper (control), two different brands of medium-grit and fine-grit diamond burs in a high-speed turbine; medium-grit and fine-grit CVD (chemical vapor deposition) tips in an ultrasonic device. Roughness parameters (n = 5) and MSBS to a glass-ceramic (n = 10) were determined. Data were analyzed using ANOVA and Tukey's test (α = 5%). Results. Control group showed lower mean roughness readings and groups that used medium-grit diamond burs showed the highest mean roughness values. Regarding MSBS, there was no statistical difference when comparing the groups gritted with the same brand of medium- and fine-grit burs and tips. Conclusions. Cavity surface finishing influenced the roughness parameters and MSBS of a glass-ceramic to enamel and dentin. Medium-grit diamond burs in high-speed turbine showed the highest mean roughness values. Fine-grit CVD tips in ultrasound presented the highest MSBS values for both enamel and dentin. PMID:27347507

Genesis of IIICD Iron Meteorites: Evidence From Silicate Inclusions

NASA Astrophysics Data System (ADS)

McCoy, T. J.; Keil, K.; Scott, E. R. D.; Haack, H.

1992-07-01

The IAB and IIICD iron meteorite groups exhibit much larger ranges in siderophile concentrations than other groups and commonly contain silicate inclusions. Extensive studies of metal in both groups and silicates in IAB irons have led to a variety of ideas to explain the genesis of these groups. Wasson et al. (1980) envision each meteorite forming in a separate impact melt pool. Kracher (1982, 1985) suggested that the siderophile trends might result from fractional crystallization of both metal and troilite in a S-saturated magma. A role for oxidation-reduction in these groups has been proposed by Scott and Bild (1974). Similarities in siderophile elemental trends indicate that IIICD metal has a similar origin, although data on silicate inclusions in IIICD irons are scarce (Ramdohr, 1973; Scott and Bild, 1974; Kracher and Kurat, 1977; Prinz et al., 1982; Clayton et al., 1983). We report the first detailed study of silicate inclusions in IIICD iron meteorites in an attempt to elucidate their history. We have studied the only silicate-bearing IIICD irons - Carlton, Dayton, and the recently reported Maltahohe. Silicate-graphite-phosphate inclusions comprise at most a few percent of the bulk meteorite, and silicates comprise <25 vol% of the inclusion. Silicate mineralogy and chemistry vary systematically with increasing M content of the metal. Maltahohe (10.7 wt% Ni) and Carlton (13.0%) contain olivine, pyroxene, and plagioclase, whereas Dayton (17.0%) contains pyroxene, plagioclase, and SiO2. Pyroxene becomes more FeO-rich from Maltahohe (FS(sub)7.8) to Carlton (Fs(sub)9.7) to Dayton (Fs(sub)11.6). Inverse FeO zoning in silicates and lower Fa than Fs indicate reduction in all three meteorites. Plagioclase compositions in IIICD (An(sub)1.1-4.9) are lower than IAB (An(sub)9.2-2l.5) and uncorrelated with Ni content. The abundances of associated phases also vary. Graphite comprises ~25 vol% of Maltahohe silicate inclusions, but only a few percent in Carlton, and is absent

SnO-containing oxide glasses emitting in 1.0–2.0 µm spectral range

NASA Astrophysics Data System (ADS)

Denker, B. I.; Galagan, B. I.; Sverchkov, S. E.; Dianov, E. M.

2018-06-01

Different SnO-containing oxide glasses with various net formers (silicate, phosphate, germanate, borate, and a number of mixed compositions) were investigated for the presence of near-infrared photoluminescence. It was found that SnO-containing silicate and germanate, and also a plurality of mixed glass compositions, exhibit wideband photoluminescence peaking at 1.5–1.6 µm and with lifetimes in the order of 100 µs. These glasses are interesting as promising active materials for widely tunable fiber lasers and wideband amplifiers.

Solubility of copper in silicate melts as function of oxygen and sulfur fugacities, temperature, and silicate composition

NASA Astrophysics Data System (ADS)

Holzheid, A.; Lodders, K.

2001-06-01

The solubility of Cu in silicate melts coexisting with liquid Cu(Fe) metal and liquid Cu(Fe) sulfide was determined experimentally at oxygen fugacities ranging from 10 -9.1 to 10 -13.6 bar and sulfur fugacities ranging from 10 -2.5 to 10 -6.3 bar at 1300°C. An iron oxide-free silicate of anorthite-diopside eutectic composition and a synthetic MgO-rich basaltic silicate (FeO-bearing) were used in the partitioning experiments. In S-containing systems, some of the metal reacted to metal sulfide. The silicates in the four systems investigated (Fe-free and S-free; Fe-containing and S-free; Fe-free and S-containing; Fe-containing and S-containing) had different colors depending on the dissolved Cu species and the presence of iron and/or sulfur. Irrespective of the presence of sulfur, the solubility of Cu in the silicate increases with increasing oxygen fugacity and metal/silicate partition coefficients for Cu decrease. Increasing the temperature from 1300°C to 1514°C increases the Cu solubility (decreases the metal/silicate partition coefficient) at an oxygen fugacity 0.5 log units below the iron-wüstite (IW) equilibrium in the Fe-free, S-free and Fe-containing, S-free systems. We infer the presence of monovalent Cu + ("CuO 0.5") in the silicate melt on the basis of the solubility of Cu as function of oxygen fugacity. Experiments containing iron yield a formal valence of ˜0.5 for Cu at very low oxygen fugacities, which is not observed in Fe-free systems. The low formal valence is explained by redox reactions between iron and copper in the silicate melts. There is no evidence for sulfidic dissolution of Cu in the silicates but sulfur has indirect effects on Cu partitioning. Iron metal/silicate partition coefficients depend on oxygen fugacity and on sulfur fugacity. Sulfidic dissolution of iron and oxide-sulfide exchange reactions with Cu cause a small increase in Cu metal/silicate partition coefficients. We derive an activity coefficient (γ CuO 0.5) of 10 ± 1 for

Crystal field excitations from Yb3 + ions at defective sites in highly stuffed Yb2Ti2O7

NASA Astrophysics Data System (ADS)

Sala, G.; Maharaj, D. D.; Stone, M. B.; Dabkowska, H. A.; Gaulin, B. D.

2018-06-01

The pyrochlore magnet Yb2Ti2O7 has been proposed as a quantum spin ice candidate, a spin liquid state expected to display emergent quantum electrodynamics with gauge photons among its elementary excitations. However, Yb2Ti2O7 's ground state is known to be very sensitive to its precise stoichiometry. Powder samples, produced by solid-state synthesis at relatively low temperatures, tend to be stoichiometric, while single crystals grown from the melt tend to display weak "stuffing" wherein ˜2 % of the Yb3 +, normally at the A site of the A2B2O7 pyrochlore structure, reside as well at the B site. In such samples Yb3 + ions should exist in defective environments at low levels and be subjected to crystalline electric fields very different from those at the stoichiometric A sites. Neutron scattering measurements of Yb3 + in four compositions of Yb2 +xTi2 -xO7 -y show the spectroscopic signatures for these defective Yb3 + ions and explicitly demonstrate that the spin anisotropy of the Yb3 + moment changes from X Y -like for stoichiometric Yb3 + to Ising-like for "stuffed" B site Yb3 + or for A site Yb3 + in the presence of oxygen vacancies.

Spectroscopic properties of Er(3+)/Yb(3+) co-doped Bi(2)O(3)-B(2)O(3)-GeO(2) glasses.

PubMed

Zhang, Xudong; Xu, Tiefeng; Nie, Qiuhua; Dai, Shixun; Shen, Xiang; Zhang, Xianghua

2007-05-01

Er(3+)/Yb(3+) co-doped 60Bi(2)O(3)-(40 - x)B(2)O(3)-xGeO(2) (BBG; x=0, 5, 10, 15 mol%) glasses that are suitable for fiber lasers, amplifiers have been fabricated and characterized. The absorption spectra, emission spectra, and lifetime of the (4)I(13/2) level and quantum efficiency of Er(3+):(4)I(13/2) --> (4)I(15/2) transition were measured and calculated. With the substitution of GeO(2) for B(2)O(3), both Delta lambda(eff) and sigma(e) decrease from 75 to 71 nm and 9.88 to 8.12 x 10(-21) cm(2), respectively. The measured lifetime of the (4)I(13/2) level and quantum efficiency of Er(3+):(4)I(13/2) --> (4)I(15/2) transition increase from 1.18 to 1.5 ms and 36.2% to 43.2%, respectively. The emission spectra of Er(3+):(4)I(13/2) --> (4)I(15/2) transition was also analyzed using a peak-fit routine, and an equivalent four-level system was proposed to estimate the stark splitting for the (4)I(15/2) and (4)I(13/2) levels of Er(3+) in the BBG glasses. The results indicate that the (4)I(13/2) --> (4)I(15/2) emission of Er(3+) can be exhibit a considerable broadening due to a significant enhance the peak A, and D emission.

Petrography of impact glasses and melt breccias from the El'gygytgyn impact structure, Russia

NASA Astrophysics Data System (ADS)

Pittarello, Lidia; Koeberl, Christian

2013-07-01

The El'gygytgyn impact structure, 18 km in diameter and 3.6 Ma old, in Arctic Siberia, Russia, is the only impact structure on Earth mostly excavated in acidic volcanic rocks. The Late Cretaceous volcanic target includes lavas, tuffs, and ignimbrites of rhyolitic, dacitic, and andesitic composition, and local occurrence of basalt. Although the ejecta blanket around the crater is nearly completely eroded, bomb-shaped impact glasses, redeposited after the impact event, occur in lacustrine terraces within the crater. Here we present detailed petrographic descriptions of newly collected impact glass-bearing samples. The observed features contribute to constrain the formation of the melt and its cooling history within the framework of the impact process. The collected samples can be grouped into two types, characterized by specific features: (1) "pure" glasses, containing very few clasts or new crystals and which were likely formed during the early stages of cratering and (2) a second type, which represents composite samples with impact melt breccia lenses embedded in silicate glass. These mixed samples probably resulted from inclusion of unmelted impact debris during ejection and deposition. After deposition the glassy portions continued to deform, whereas the impact melt breccia inclusions that probably had already cooled down behaved as rigid bodies in the flow.

The structural influence of aluminium ions on emission characteristics of Sm{sup 3+} ions in lead aluminium silicate glass system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhargavi, K.; Srinivasa Reddy, M.; Raghava Rao, P.

Graphical abstract: The optical absorption and photoluminescence spectra of Sm ions in PbO-Al{sub 2}O{sub 3}-SiO{sub 2} glasses mixed with different concentrations of Al{sub 2}O{sub 3} have been investigated. From these spectra, the emission probabilities and also fluorescence lifetime principal transition viz., {sup 4}G{sub 5/2} {yields} {sup 6}H{sub 7/2} of Sm{sup 3+} ions of has been evaluated. The analysis of results of these studies has indicated that there is a less radiative trapping and enhanced fluorescence lifetime and high quantum efficiency in the glasses mixed with 8.0 mol% of Al{sub 2}O{sub 3}. Highlights: Black-Right-Pointing-Pointer Glasses of the composition (40 - x)PbO-(5more » + x)Al{sub 2}O{sub 3}-54SiO{sub 2}:1.0Sm{sub 2}O{sub 3} with x = 5-10 mol% were prepared. Black-Right-Pointing-Pointer Spectroscopic properties (OA, PL and IR) were investigated. Black-Right-Pointing-Pointer Emission probability, lifetime, branching ratio of {sup 4}G{sub 5/2} {yields} {sup 6}H{sub 7/2} transition of Sm{sup 3+} have been evaluated. Black-Right-Pointing-Pointer Analysis of the results indicated that glass mixed with 8.0 mol% exhibits high luminescence efficiency. -- Abstract: Optical absorption and photoluminescence characteristics of Sm{sup 3+} ions in lead silicate glasses mixed with different concentrations of Al{sub 2}O{sub 3} (5-10 mol%) have been investigated. From these studies, the radiative properties viz., spontaneous emission probability A, the total emission probability, the radiative lifetime {tau}{sub R}, the fluorescent branching ratio {beta} of emission transition of {sup 4}G{sub 5/2} {yields} {sup 6}H{sub 7/2} along with other transitions for Sm{sup 3+} have been evaluated and found to be the highest for the glass mixed with 8.0 mol% of Al{sub 2}O{sub 3}.The IR spectral studies have indicated that Al{sup 3+} ions do participate in the glass network with AlO{sub 4} and AlO{sub 6} structural units and further revealed that the concentration

Role of magnesium oxide and strontium oxide as modifiers in silicate-based bioactive glasses: Effects on thermal behaviour, mechanical properties and in-vitro bioactivity.

PubMed

Bellucci, Devis; Sola, Antonella; Salvatori, Roberta; Anesi, Alexandre; Chiarini, Luigi; Cannillo, Valeria

2017-03-01

The composition of a CaO-rich silicate bioglass (BG_Ca-Mix, in mol%: 2.3 Na 2 O; 2.3 K 2 O; 45.6 CaO; 2.6 P 2 O 5 ; 47.2 SiO 2 ) was modified by replacing a fixed 10mol% of CaO with MgO or SrO or fifty-fifty MgO-SrO. The thermal behaviour of the modified glasses was accurately evaluated via differential thermal analysis (DTA), heating microscopy and direct sintering tests. The presence of MgO and/or SrO didn't interfere with the thermal stability of the parent glass, since all the new glasses remained completely amorphous after sintering (treatment performed at 753°C for the glass with MgO; at 750°C with SrO; at 759°C with MgO and SrO). The sintered samples achieved good mechanical properties, with a Young's modulus ranging between 57.9±6.7 for the MgO-SrO modified composition and 112.6±8.0GPa for the MgO-modified one. If immersed in a simulated body fluid (SBF), the modified glasses after sintering retained the strong apatite forming ability of the parent glass, in spite of the presence of MgO and/or SrO. Moreover, the sintered glasses, tested with MLO-Y4 osteocytes by means of a multi-parametrical approach, showed a good bioactivity in vitro, since neither the glasses nor their extracts caused any negative effect on cell viability or any inhibition on cell growth. The best results were achieved by the MgO-modified glasses, both BGMIX_Mg and BGMIX_MgSr, which were able to exert a strong stimulating effect on the cell growth, thus confirming the beneficial effect of MgO on the glass bioactivity. Copyright © 2016 Elsevier B.V. All rights reserved.

Yb7Ni4InGe12: a quaternary compound having mixed valent Yb atoms grown from indium flux.

PubMed

Subbarao, Udumula; Jana, Rajkumar; Chondroudi, Maria; Balasubramanian, Mahalingam; Kanatzidis, Mercouri G; Peter, Sebastian C

2015-03-28

The new intermetallic compound Yb7Ni4InGe12 was obtained as large silver needle shaped single crystals from reactive indium flux. Single crystal X-ray diffraction suggests that Yb7Ni4InGe12 crystallizes in the Yb7Co4InGe12 structure type, and tetragonal space group P4/m and lattice constants are a = b = 10.291(2) Å and c = 4.1460(8) Å. The crystal structure of Yb7Ni4InGe12 consists of columnar units of three different types of channels filled with the Yb atoms. The crystal structure of Yb7Ni4InGe12 is closely related to Yb5Ni4Ge10. The effective magnetic moment obtained from the magnetic susceptibility measurements in the temperature range 200-300 K is 3.66μB/Yb suggests mixed/intermediate valence behavior of ytterbium atoms. X-ray absorption near edge spectroscopy (XANES) confirms that Yb7Ni4InGe12 exhibits mixed valence.

Impact Experiments into Borosilicate Glass at Three Scale Sizes

DTIC Science & Technology

2009-11-01

DEDF and soda - lime glass during rod impact. Shock Compression in Condensed Matter–2005 (Furnish MD, Elert M, Russell TP, and White CT, Eds.) AIP Conf...in a float soda - lime silicate glass . Int. J. Appl. Glass Sci., to be submitted (2009). 18. Chocron S, Dannemann KA, Nicholls AE, and Anderson CE Jr...UNCLASSIFIED UNCLASSIFIED Impact Experiments into Borosilicate Glass at Three Scale Sizes Charles E. Anderson, Jr. Carl E. Weiss Sidney Chocron

Laser-diode-excited blue upconversion in Tm3+/Yb3+ -codoped TeO2-Ga2O3-R2O (R=Li, Na, K) glasses.

PubMed

Zhao, Chun; Zhang, Qinyuan; Yang, Gangfeng; Jiang, Zhonghong

2008-01-01

This paper reports on intense blue upconversion in Tm(3+)/Yb(3+) codoped TeO(2)-Ga(2)O(3)-R(2)O(R=Li, Na, K) glasses upon excitation with commercial available laser diode (LD). Effects of alkali ions on the Raman spectra, thermal stability and spectroscopic properties of the tellurite-gallium glasses have also been investigated. Energy transfer and the involved upconversion mechanisms have been discussed. Intense blue upconversion emission centered at 476 nm along with a weak red emission at 650 nm has been observed upon excitation of 977 nm LD, assigned to the transitions of 1G4-->3H6, and 1G4-->3H4 and/or 3F(2,3)-->3H6 of Tm(3+), respectively. The blue upconversion intensity has a cubelike dependence on incident pump laser power, indicating a three-photon process. However, a quadratic dependence of the 476 nm upconversion intensity on the incident pump laser power has been observed when samples under excitation of 808 nm LD due to a two-photon absorption process. Enhanced upconversion luminescence have been observed with replacing K(+) for Na(+) and Li(+).

Functional conservation of rice OsNF-YB/YC and Arabidopsis AtNF-YB/YC proteins in the regulation of flowering time.

PubMed

Hwang, Yoon-Hyung; Kim, Soon-Kap; Lee, Keh Chien; Chung, Young Soo; Lee, Jeong Hwan; Kim, Jeong-Kook

2016-04-01

Rice Os NF - YB and Os NF - YC complement the late flowering phenotype of Arabidopsis nf - yb double and nf - yc triple mutants, respectively. In addition, OsNF-YB and OsNF-YC interact with AtNF-YC and AtNF-YB, respectively. Plant NUCLEAR FACTOR Y (NF-Y) transcription factors play important roles in plant development and abiotic stress. In Arabidopsis thaliana, two NF-YB (AtNF-YB2 and AtNF-YB3) and five NF-YC (AtNF-YC1, AtNF-YC2, AtNF-YC3, AtNF-YC4, and AtNF-YC9) genes regulate photoperiodic flowering by interacting with other AtNF-Y subunit proteins. Three rice NF-YB (OsNF-YB8, OsNF-YB10, and OsNF-YB11) and five rice OsNF-YC (OsNF-YC1, OsNF-YC2, OsNF-YC4, OsNF-YC6, and OsNF-YC7) genes are clustered with two AtNF-YB and five AtNF-YC genes, respectively. To investigate the functional conservation of these NF-YB and NF-YC genes in rice and Arabidopsis, we analyzed the flowering phenotypes of transgenic plants overexpressing the respective OsNF-YB and OsNF-YC genes in Arabidopsis mutants. Overexpression of OsNF-YB8/10/11 and OsNF-YC2 complemented the late flowering phenotype of Arabidopsis nf-yb2 nf-yb3 and nf-yc3 nf-yc4 nf-yc9 mutants, respectively. The rescued phenotype of 35S::OsNF-YC2 nf-yc3 nf-yc4 nf-yc9 plants was attributed to the upregulation of FLOWERING LOCUS T (FT) and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1). In vitro and in planta protein-protein analyses revealed that OsNF-YB8/10/11 and OsNF-YC1/2/4/6/7 interact with AtNF-YC3/4/9 and AtNF-YB2/3, respectively. Our data indicate that some OsNF-YB and OsNF-YC genes are functional equivalents of AtNF-YB2/3 and AtNF-YC3/4/9 genes, respectively, and suggest functional conservation of Arabidopsis and rice NF-Y genes in the control of flowering time.

Glass binder development for a glass-bonded sodalite ceramic waste form

DOE Office of Scientific and Technical Information (OSTI.GOV)

Riley, Brian J.; Vienna, John D.; Frank, Steven M.

This paper discusses work to develop Na2O-B2O3-SiO2 glass binders for immobilizing LiCl-KCl eutectic salt waste in a glass-bonded sodalite waste form following electrochemical reprocessing of used metallic nuclear fuel. Here, five new glasses with high Na2O contents were designed to generate waste forms having higher sodalite contents and fewer stress fractures. The structural, mechanical, and thermal properties of the new glasses were measured using variety of analytical techniques. The glasses were then used to produce ceramic waste forms with surrogate salt waste. The materials made using the glasses developed during this study were formulated to generate more sodalite than materialsmore » made with previous baseline glasses used. The coefficients of thermal expansion for the glass phase in the glass-bonded sodalite waste forms made with the new binder glasses were closer to the sodalite phase in the critical temperature region near and below the glass transition temperature. These improvements should result in lower probability of cracking in the full-scale monolithic ceramic waste form, leading to better long-term chemical durability. Additionally, a model generated during this study for predicting softening temperature of silicate binder glasses is presented.« less

PRIMARY MINERALIZATION OF URANIUM-BEARING "SILICEOUS REEF" VEINS IN THE BOULDER BATHOLITH, MONTANA. PART I. THE HOST ROCKS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wright, H.D.; Bieler, B.H.

1960-01-01

Between 1952 and 1956 a study was made of some of the uranium-bearing hydrothermal veins in the northern part of the Boulder batholith, Montana. Three mines, the W. Wilson, G. Washington, and Free Enterprise, were investigated in detail. The veins are characterized by a microcrystalline quartz gangue containing sparsely scattered, very fine-grained sulfide minerals and uraninite. Above the present water table, secondary uranium minerals are abundant locally. Throughout the area the veins --called "siliceous reefs"--strike east to northeast, are of steep dip, and vary in thickness from a fraction of an inch to several feet. The country rock is granodioritemore » containing, in order of abundance, plagioclase (An/sub 30/ to An/sub 36/), quartz, orthoclase, biotite, and hornblende, with apatite, zircon, and sphene. Small bodies of aplite, pegmatite, and alaskite occur along some veins. The granodiorite adjacent to the veins is rather strongly altered. The alteration is similar throughout all of the deposits studied, in barren and orebearing portions alike. The essential minerals show a characteristic sequence of alteration, in the order hornblende, andesine, biotite, orthoclase, and quartz. Successive zones of alteration are characterized, from the vein outward, by maximum development of sericite (muscovite polytype 1M, in part), kaolinite, and montmorillonite. Other alteration products are quartz, pyrite, calcite, leucoxene, and chlorite. The alteration resulted in an increase in silica and ferric iron, a decrease in alumina, total iron, ferrous iron, lime, soda, and magnesia, and little change in potash, titania, phosphorus, carbon dioxide, and sulfur. Consideration of the stability fields of the sheet structure silicate minerals indicates little basis for interpretation of the temperatures prevailing during mineralization. (auth)« less

Co-settling of Chromite and Sulfide Melt Droplets and Trace Element Partitioning between Sulfide and Silicate Melts

NASA Astrophysics Data System (ADS)

Manoochehri, S.; Schmidt, M. W.; Guenther, D.

2013-12-01

Gravitational settling of immiscible, dense sulfide melt droplets together with other cumulate phases such as chromite, combined with downward percolation of these droplets through a cumulate pile, is thought to be one of the possible processes leading to the formation of PGE rich sulfide deposits in layered mafic intrusions. Furthermore some chromitite seams in the Merensky Reef (Bushveld Complex) are considered to be acting as a filter or barrier for further downward percolation of sulfide melts into footwall layers. To investigate the feasibility of such mechanical processes and to study the partitioning behavior of 50 elements including transition metals and REEs (but not PGEs) between a silicate and a sulfide melt, two separate series of high temperature (1250-1380 °C) centrifuge-assisted experiments at 1000 g, 0.4-0.6 GPa were conducted. A synthetic silicate glass with a composition representative of the parental magma of the Bushveld Complex (~ 55 wt% SiO2) was mixed with pure FeS powder. For the first series of experiments, 15 or 25 wt% natural chromite with average grain sizes of ~ 5 or 31 μm were added to a mixture of silicate glass and FeS (10 wt%) adding 1 wt% water. For the second series, a mixture of the same glass and FeS was doped with 50 trace elements. These mixtures were first statically equilibrated and then centrifuged. In the first experimental series, sulfide melt droplets settled together with, but did not segregate from chromite grains even after centrifugation at 1000 g for 12 hours. A change in initial chromite grain size and proportions didn't have any effect on segregation. Without chromite, the starting mixture resulted in the formation of large sulfide melt pools together with finer droplets still disseminated through the silicate glass and both at the bottom of the capsule. The incomplete segregation of sulfide melt is interpreted as being due to high interfacial energies between sulfide and silicate melts/crystals which hinder

PMR-15/Layered Silicate Nanocomposites For Improved Thermal Stability And Mechanical Properties

NASA Technical Reports Server (NTRS)

Campbell, Sandi; Scheiman, Daniel; Faile, Michael; Papadopoulos, Demetrios; Gray, Hugh R. (Technical Monitor)

2002-01-01

Montmorillonite clay was organically modified by co-exchange of an aromatic diamine and a primary alkyl amine. The clay was dispersed into a PMR (Polymerization of Monomer Reactants)-15 matrix and the glass transition temperature and thermal oxidative stability of the resulting nanocomposites were evaluated. PMR-15/ silicate nanocomposites were also investigated as a matrix material for carbon fabric reinforced composites. Dispersion of the organically modified silicate into the PMR-15 matrix enhanced the thermal oxidative stability, the flexural strength, flexural modulus, and interlaminar shear strength of the polymer matrix composite.

White phosphor using Yb3+-sensitized Er3+-and Tm3+-doped sol-gel derived lead-fluorosilicate transparent glass ceramic excited at 980 nm

NASA Astrophysics Data System (ADS)

Tavares, M. C. P.; da Costa, E. B.; Bueno, L. A.; Gouveia-Neto, A. S.

2018-01-01

Generation of primary colors and white light through frequency upconversion using sol-gel derived 80SiO2:20PbF2 vitroceramic phosphors doped with Er3+, Er3+/Yb3+, Tm3+/Yb3+, and Er3+/Tm3+/Yb3+ excited at 980 nm is demonstrated. For Er3+ and Er3+/Yb3+ doped samples emissions were obtained in the blue (410 nm), green (530, and 550 nm) and red (670 nm) regions, corresponding to the 2H9/2 → 4I15/2,2H11/2 → 4I15/2, 4S3/2 → 4I152 and 4F9/2 → 4I15/2 transitions of Er3+, respectively. The codoping with Yb3+ ions altered the spectral profile of most of the emissions compared to the single doped samples, resulting in changes in the emitted color, in addition to a significant increase in the emission intensity. In Tm3+/Yb3+ co-doped samples visible emissions in the blue (480 nm), and red (650 nm), corresponding to transitions 1G4 → 3H6 and 1G4 → 3F4 of Tm3+, respectively, were obtained. The emission intensity around 480 nm overcome the red emission, and luminescence showed a predominantly blue tone. White light with CIE-1931 coordinates (0.36; 0.34) was produced by homogeneously mixing up powders of heat treated at 400 °C co-doped samples 5.0Er3+/5.0Yb3+ and 0.5Tm3+/2.5Yb3+ in the mass ratio of 13%, and 87%, respectively. The measured emission spectrum for a sample resulting from the mixture showed a profile with very good agreement with the spectrum found from the superimposition of the spectra of the co-doped samples.

Hall and transverse even effects in the vicinity of a quantum critical point in Tm{sub 1-x}Yb{sub x}B{sub 12}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sluchanko, N. E., E-mail: nes@lt.gpi.ru; Azarevich, A. N.; Bogach, A. V.

2012-09-15

The angular, temperature, and magnetic field dependences of the resistance recorded in the Hall effect geometry are studied for the rare-earth dodecaboride Tm{sub 1-x}Yb{sub x}B{sub 12} solid solutions where the metal-insulator and antiferromagnetic-paramagnetic phase transitions are observed in the vicinity of the quantum critical point x{sub c} Almost-Equal-To 0.3. The measurements performed on high-quality single crystals in the temperature range 1.9-300 K for the first time have revealed the appearance of the second harmonic contribution, a transverse even effect in these fcc compounds near the quantum critical point. This contribution a is found to increase drastically both under the Tm-to-ytterbiummore » substitution in the range x > x{sub c} and with an increase in the external magnetic field. Moreover, as the Yb concentration x increases, a negative peak of a significant amplitude appears on the temperature dependences of the Hall coefficient R{sub H}(T) for the Tm{sup 1-x}Yb{sub x}B{sub 12} compounds, in contrast to the invariable behavior R{sub H}(T) Almost-Equal-To const found for TmB{sub 12}. The complicated activation-type behavior of the Hall coefficient is observed at intermediate temperatures for x {>=} 0.5 with activation energies E{sub g}/k{sub B} Almost-Equal-To 200 K and E{sub a}/k{sub B} 55-75 K, and the sign inversion of R{sub H}(T) is detected at liquid-helium temperatures in the coherent regime. Renormalization effects in the electron density of states induced by variation of the Yb concentration are analyzed. The anomalies of the charge transport in Tm{sub 1-x}Yb{sub x}B{sub 12} solid solutions in various regimes (charge gap formation, intra-gap many-body resonance, and coherent regime) are discussed in detail and the results are interpreted in terms of the electron phase separation effects in combination with the formation of nanosize clusters of rare earth ions in the cage-glass state of the studied dodecaborides. The data obtained

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

PubMed

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

2013-03-01

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 μm) 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.

Formation and Properties of Laser-Induced Periodic Surface Structures on Different Glasses.

PubMed

Gräf, Stephan; Kunz, Clemens; Müller, Frank A

2017-08-10

The formation and properties of laser-induced periodic surface structures (LIPSS) was investigated on different technically relevant glasses including fused silica, borosilicate glass, and soda-lime-silicate glass under irradiation of fs-laser pulses characterized by a pulse duration τ = 300 fs and a laser wavelength λ = 1025 nm. For this purpose, LIPSS were fabricated in an air environment at normal incidence with different laser peak fluence, pulse number, and repetition frequency. The generated structures were characterized by using optical microscopy, scanning electron microscopy, focused ion beam preparation and Fast-Fourier transformation. The results reveal the formation of LIPSS on all investigated glasses. LIPSS formation on soda-lime-silicate glass is determined by remarkable melt-formation as an intra-pulse effect. Differences between the different glasses concerning the appearing structures, their spatial period and their morphology were discussed based on the non-linear absorption behavior and the temperature-dependent viscosity. The findings facilitate the fabrication of tailored LIPSS-based surface structures on different technically relevant glasses that could be of particular interest for various applications.

Formation and Properties of Laser-Induced Periodic Surface Structures on Different Glasses

PubMed Central

Kunz, Clemens; Müller, Frank A.

2017-01-01

The formation and properties of laser-induced periodic surface structures (LIPSS) was investigated on different technically relevant glasses including fused silica, borosilicate glass, and soda-lime-silicate glass under irradiation of fs-laser pulses characterized by a pulse duration τ = 300 fs and a laser wavelength λ = 1025 nm. For this purpose, LIPSS were fabricated in an air environment at normal incidence with different laser peak fluence, pulse number, and repetition frequency. The generated structures were characterized by using optical microscopy, scanning electron microscopy, focused ion beam preparation and Fast-Fourier transformation. The results reveal the formation of LIPSS on all investigated glasses. LIPSS formation on soda-lime-silicate glass is determined by remarkable melt-formation as an intra-pulse effect. Differences between the different glasses concerning the appearing structures, their spatial period and their morphology were discussed based on the non-linear absorption behavior and the temperature-dependent viscosity. The findings facilitate the fabrication of tailored LIPSS-based surface structures on different technically relevant glasses that could be of particular interest for various applications. PMID:28796180

Structural and magnetic properties of two branches of the tripod-kagome-lattice family A2R3Sb3O14 (A = Mg, Zn; R = Pr, Nd, Gd, Tb, Dy, Ho, Er, Yb)

NASA Astrophysics Data System (ADS)

Dun, Z. L.; Trinh, J.; Lee, M.; Choi, E. S.; Li, K.; Hu, Y. F.; Wang, Y. X.; Blanc, N.; Ramirez, A. P.; Zhou, H. D.

2017-03-01

We present a systematic study of the structural and magnetic properties of two branches of the rare-earth tripod-kagome-lattice (TKL) family A2R3Sb3O14 (A = Mg, Zn; R = Pr, Nd, Gd, Tb, Dy, Ho, Er, Yb; here, we use abbreviation A-R, as in MgPr for Mg2Pr3Sb3O14 ), which complements our previously reported work on MgDy, MgGd, and MgEr [Z. L. Dun et al., Phys. Rev. Lett. 116, 157201 (2016), 10.1103/PhysRevLett.116.157201]. The present susceptibility (χdc, χac) and specific-heat measurements reveal various magnetic ground states, including the nonmagnetic singlet state for MgPr, ZnPr; long-range orderings (LROs) for MgGd, ZnGd, MgNd, ZnNd, and MgYb; a long-range magnetic charge ordered state for MgDy, ZnDy, and potentially for MgHo; possible spin-glass states for ZnEr, ZnHo; the absence of spin ordering down to 80 mK for MgEr, MgTb, ZnTb, and ZnYb compounds. The ground states observed here bear both similarities as well as striking differences from the states found in the parent pyrochlore systems. In particular, while the TKLs display a greater tendency towards LRO, the lack of LRO in MgHo, MgTb, and ZnTb can be viewed from the standpoint of a balance among spin-spin interactions, anisotropies, and non-Kramers nature of single-ion state. While substituting Zn for Mg changes the chemical pressure, and subtly modifies the interaction energies for compounds with larger R ions, this substitution introduces structural disorder and modifies the ground states for compounds with smaller R ions (Ho, Er, Yb).

Luminescence of Er/Yb and Tm/Yb doped FAp nanoparticles and ceramics

NASA Astrophysics Data System (ADS)

Grigorjeva, L.; Smits, K.; Millers, D.; Jankoviča, Dz

2015-03-01

The nanoparticles of hydroxiapatite and fluorapatite doped with Er/Yb and Tm/Yb were synthesized and characterized by FTIR, XRD, SEM and TEM methods. The results of up-conversion luminescence studies were presented for the samples as prepared, annealed at 500°C and at 900-1000 °C. At annealing above 800°C the ceramic state was formed. It is shown that fluorapatite host is more appropriate than hydroxiapatite host for rare ions luminescence and up-conversion processes. The post preparing annealing of nanarticles significantly enhanced the luminescence intensity. The Tm/Yb doped fluorapatite shows intense up-conversion luminescence in 790-800 nm spectral region and is potentially useful for biomedical applications.

Four nucleocytoplasmic-shuttling proteins and p53 interact specifically with the YB-NLS and are involved in anticancer reagent-induced nuclear localization of YB-1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tanaka, Toru; Ohashi, Sachiyo; Kobayashi, Shunsuke

In cancer cells, anticancer reagents often trigger nuclear accumulation of YB-1, which participates in the progression of cancer malignancy. YB-1 has a non-canonical nuclear localization signal (YB-NLS). Here we found that four nucleocytoplasmic-shuttling RNA-binding proteins and p53 interact specifically with the YB-NLS and co-accumulate with YB-1 in the nucleus of actinomycin D-treated cells. To elucidate the roles of these YB-NLS-binding proteins, we performed a dominant-negative experiment in which a large excess of YB-NLS interacts with the YB-NLS-binding proteins, and showed inhibitory effects on actinomycin D-induced nuclear transport of endogenous YB-1 and subsequent MDR1 gene expression. Furthermore, the YB-NLS-expressing cells weremore » also found to show increased drug sensitivity. Our results suggest that these YB-NLS-associating proteins are key factors for nuclear translocation/accumulation of YB-1 in cancer cells. - Highlights: • Four nucleocytoplasmic-shuttling proteins and p53 associate with YB-NLS. • They showed nuclear co-accumulation with YB-1 in actinomycin D-treated cells. • Overexpression of YB-NLS was carried out to take YB-NLS-binding proteins from YB-1. • YB-NLS inhibited actinomycin D-induced nuclear localization of endogenous YB-1. • YB-NLS suppressed actinomycin D-induced expression of MDR1.« less

Cell adhesion to borate glasses by colloidal probe microscopy.

PubMed

Wiederhorn, Sheldon M; Chae, Young-Hun; Simon, Carl G; Cahn, Jackson; Deng, Yan; Day, Delbert

2011-05-01

The adhesion of osteoblast-like cells to silicate and borate glasses was measured in cell growth medium using colloidal probe microscopy. The probes consisted of silicate and borate glass spheres, 25-50 μm in diameter, attached to atomic force microscope cantilevers. Variables of the study included glass composition and time of contact of the cell to the glasses. Increasing the time of contact from 15 to 900 s increased the force of adhesion. The data could be plotted linearly on a log-log plot of adhesive force versus time. Of the seven glasses tested, five had slopes close to 0.5, suggesting a square root dependence of the adhesive force on the contact time. Such behavior can be interpreted as a diffusion limited process occurring during the early stages of cell attachment. We suggest that the rate limiting step in the adhesion process is the diffusion of integrins resident in the cell membrane to the area of cell attachment. Data presented in this paper support the hypothesis of Hench et al. that strong adhesion depends on the formation of a calcium phosphate reaction layer on the surfaces of the glass. Glasses that did not form a calcium phosphate layer exhibited a weaker adhesive force relative to those glasses that did form a calcium phosphate layer. Published by Elsevier Ltd.

Pressure-induced Ge coordination change in SiO2-GeO2 glasses

NASA Astrophysics Data System (ADS)

Majérus, O.; Cormier, L.; Itié, J.-P.; Calas, G.

2003-04-01

Among the parameters controlling igneous processes in Earth, the density and transport properties of silicate melts are playing a major role. These properties are strongly dependent upon pressure, in a way that can significantly differ from the crystalline phases. The study of the pressure-induced structural changes can give a further understanding of the peculiar microscopic origins of these properties in molten phases. As in silicate minerals, the coordination change IVSi towards VISi is expected to be the major transformation occurring in melts at mantle conditions, yielding amorphous phases with properties distinct to those corresponding to a tetrahedral framework. This change is predicted by molecular dynamics simulations, but experimental evidences are scarce because of difficult technical constraints. The binary SiO_2-GeO_2 system allows a further insight into the compression mechanism of a tetrahedral framework glass structure. The Ge coordination change and its composition dependence can be assessed by using XAS spectroscopy at Ge K-edge with a diamond anvil cell. In this study, we report an in situ investigation carried out on well characterized glasses of the SiO_2-GeO_2 system. Experiments were preformed on the D11 beamline which is a unique dispersive experimental setup developed at the Laboratoire pour l’Utilisation du Rayonnement Magnétique (LURE, Orsay, France). Pressures up to 25 GPa have been obtained. With increasing SiO_2 content, both Ge-O distances extracted from EXAFS data and XANES features indicate the regular increase of the pressure threshold for the Ge coordination change (from 4 in pure GeO_2 to 12 Gpa in 80 mol% SiO_2-bearing glass), which corresponds to the end of the elastic compression regime, and the achievement of the transformation on a broader pressure range as predicted in pure SiO_2. These data are compared to results on slightly depolymerised glasses of Na_2O-GeO_2 composition, where a greater variety of compression

Effect of clayey groundwater on the dissolution rate of SON68 simulated nuclear waste glass at 70 °C

NASA Astrophysics Data System (ADS)

De Echave, T.; Tribet, M.; Jollivet, P.; Marques, C.; Gin, S.; Jégou, C.

2018-05-01

To predict the long-term behavior of high-level radioactive waste glass, it is necessary to study aqueous dissolution of the glass matrix under geological repository conditions. The present article focuses on SON68 (an inactive surrogate of the R7T7 glass) glass alteration in synthetic clayey groundwater at 70 °C. Experiments in deionized water as reference were also performed in the same conditions. Results are in agreement with those of previous studies showing that magnesium present in the solution is responsible for higher glass alteration. This effect is transient and pH-dependent: Once all the magnesium is consumed, the glass alteration rate diminishes. Precipitation of magnesium silicate of the smectite group seems to be the main factor for the increased glass alteration. A pH threshold of 7.5-7.8 was found, above which precipitation of these magnesium silicates at 70 °C is possible. TEM observations reveal that magnesium silicates grow at the expense of the passivating gel, which partly dissolves, forming large pores which increase mass transfer between the reacting glass surface and the bulk solution.

The fate of silicon during glass corrosion under alkaline conditions: A mechanistic and kinetic study with the International Simple Glass

NASA Astrophysics Data System (ADS)

Gin, Stéphane; Jollivet, Patrick; Fournier, Maxime; Berthon, Claude; Wang, Zhaoying; Mitroshkov, Alexandre; Zhu, Zihua; Ryan, Joseph V.

2015-02-01

International Simple Glass - a six oxide borosilicate glass selected by the international nuclear glass community to improve the understanding of glass corrosion mechanisms and kinetics - was altered at 90 °C in a solution initially saturated with respect to amorphous 29SiO2. The pH90°C, was fixed at 9 at the start of the experiment and raised to 11.5 after 209 d by the addition of KOH. Isotope sensitive analytical techniques were used to analyze the solution and altered glass samples, helping to understand the driving forces and rate limiting processes controlling long-term glass alteration. At pH 9, the corrosion rate continuously drops and the glass slowly transforms into a uniform, homogeneous amorphous alteration layer. The mechanisms responsible for this transformation are water penetration through the growing alteration layer and ion exchange. We demonstrate that this amorphous alteration layer is not a precipitate resulting from the hydrolysis of the silicate network; it is mostly inherited from the glass structure from which the most weakly bonded cations (Na, Ca and B) have been released. At pH 11.5, the alteration process is very different: the high solubility of glass network formers (Si, Al, Zr) triggers the rapid and complete dissolution of the glass (dissolution becomes congruent) and precipitation of amorphous and crystalline phases. Unlike at pH 9 where glass corrosion rate decreased by 3 orders of magnitude likely due to the retroaction of the alteration layer on water dynamics/reactivity at the reaction front, the rate at pH 11.5 is maintained at a value close to the forward rate due to both the hydrolysis of the silicate network promoted by OH- and the precipitation of CSH and zeolites. This study provides key information for a unified model for glass dissolution.

Three-dimensional culture of dental pulp stem cells in direct contact to tricalcium silicate cements.

PubMed

Widbiller, M; Lindner, S R; Buchalla, W; Eidt, A; Hiller, K-A; Schmalz, G; Galler, K M

2016-03-01

Calcium silicate cements are biocompatible dental materials applicable in contact with vital tissue. The novel tricalcium silicate cement Biodentine™ offers properties superior to commonly used mineral trioxide aggregate (MTA). Objective of this study was to evaluate its cytocompatibility and ability to induce differentiation and mineralization in three-dimensional cultures of dental pulp stem cells after direct contact with the material. Test materials included a new tricalcium silicate (Biodentine™, Septodont, Saint-Maur-des-Fossés, France), MTA (ProRoot® MTA, DENSPLY Tulsa Dental Specialities, Johnson City, TN, USA), glass ionomer (Ketac™ Molar Aplicap™, 3M ESPE, Seefeld, Germany), human dentin disks and polystyrene. Magnetic activated cell sorting for to the surface antigen STRO-1 was performed to gain a fraction enriched with mesenchymal stem cells. Samples were allowed to set and dental pulp stem cells in collagen carriers were placed on top. Scanning electron microscopy of tricalcium silicate cement surfaces with and without cells was conducted. Cell viability was measured for 14 days by MTT assay. Alkaline phosphatase activity was evaluated (days 3, 7, and 14) and expression of mineralization-associated genes (COL1A1, ALP, DSPP, and RUNX2) was quantified by real-time quantitative PCR. Nonparametric statistical analysis for cell viability and alkaline phosphatase data was performed to compare different materials as well as time points (Mann-Whitney U test, α = 0.05). Cell viability was highest on tricalcium silicate cement, followed by MTA. Viability on glass ionomer cement and dentin disks was significantly lower. Alkaline phosphatase activity was lower in cells on new tricalcium silicate cement compared to MTA, whereas expression patterns of marker genes were alike. Increased cell viability and similar levels of mineralization-associated gene expression in three-dimensional cell cultures on the novel tricalcium silicate cement and mineral

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

NASA Astrophysics Data System (ADS)

Sanchez-Valle, Carmen; Malfait, Wim J.

2016-04-01

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

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

PubMed Central

Murakami, Motohiko; Bass, Jay D.

2011-01-01

Ultralow velocity zones are the largest seismic anomalies in the mantle, with 10–30% seismic velocity reduction observed in thin layers less than 20–40 km thick, just above the Earth’s core-mantle boundary (CMB). The presence of silicate melts, possibly a remnant of a deep magma ocean in the early Earth, have been proposed to explain ultralow velocity zones. It is, however, still an open question as to whether such silicate melts are gravitationally stable at the pressure conditions above the CMB. Fe enrichment is usually invoked to explain why melts would remain at the CMB, but this has not been substantiated experimentally. Here we report in situ high-pressure acoustic velocity measurements that suggest a new transformation to a denser structure of MgSiO3 glass at pressures close to those of the CMB. The result suggests that MgSiO3 melt is likely to become denser than crystalline MgSiO3 above the CMB. The presence of negatively buoyant and gravitationally stable silicate melts at the bottom of the mantle, would provide a mechanism for observed ultralow seismic velocities above the CMB without enrichment of Fe in the melt. An ultradense melt phase and its geochemical inventory would be isolated from overlying convective flow over geologic time. PMID:21969547

Glass microsphere lubrication

NASA Technical Reports Server (NTRS)

Geiger, Michelle; Goode, Henry; Ohanlon, Sean; Pieloch, Stuart; Sorrells, Cindy; Willette, Chris

1991-01-01

The harsh lunar environment eliminated the consideration of most lubricants used on earth. Considering that the majority of the surface of the moon consists of sand, the elements that make up this mixture were analyzed. According to previous space missions, a large portion of the moon's surface is made up of fine grained crystalline rock, about 0.02 to 0.05 mm in size. These fine grained particles can be divided into four groups: lunar rock fragments, glasses, agglutinates (rock particles, crystals, or glasses), and fragments of meteorite material (rare). Analysis of the soil obtained from the missions has given chemical compositions of its materials. It is about 53 to 63 percent oxygen, 16 to 22 percent silicon, 10 to 16 percent sulfur, 5 to 9 percent aluminum, and has lesser amounts of magnesium, carbon, and sodium. To be self-supporting, the lubricant must utilize one or more of the above elements. Considering that the element must be easy to extract and readily manipulated, silicon or glass was the most logical choice. Being a ceramic, glass has a high strength and excellent resistance to temperature. The glass would also not contaminate the environment as it comes directly from it. If sand entered a bearing lubricated with grease, the lubricant would eventually fail and the shaft would bind, causing damage to the system. In a bearing lubricated with a solid glass lubricant, sand would be ground up and have little effect on the system. The next issue was what shape to form the glass in. Solid glass spheres was the only logical choice. The strength of the glass and its endurance would be optimal in this form. To behave as an effective lubricant, the diameter of the spheres would have to be very small, on the order of hundreds of microns or less. This would allow smaller clearances between the bearing and the shaft, and less material would be needed. The production of glass microspheres was divided into two parts, production and sorting. Production includes the

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

PubMed Central

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

2017-01-01

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

Brillouin-scattering studies of K2Si4O9 glass and melt up to 1000 °C

NASA Astrophysics Data System (ADS)

Xu, Ji-An; Manghnani, Murli H.; Richet, Pascal

1992-10-01

The Brillouin-scattering technique has been used with glass plate samples and with glass sandwich assemblies to measure the acoustic velocities of K2Si4O9 glass as a function of temperature up to 1000 °C. Results differ from those of the sodium silicate glass reported earlier in that the turning points of the velocity versus temperature curves for the potassium silicate glass are found not only at the strain point (466 °C) but also at the softening point (720 °C). Combined with the results of the 90° platelet- and 180° back-scattering geometry measurements, the refractive index n and equation of state of the glass and melt as a function of temperature were also determined.

Crystal structure of YbCu6In6 and mixed valence behavior of Yb in YbCu(6-x)In(6+x) (x = 0, 1, and 2) solid solution.

PubMed

Subbarao, Udumula; Peter, Sebastian C

2012-06-04

High quality single crystals of YbCu(6)In(6) have been grown using the flux method and characterized by means of single crystal X-ray diffraction data. YbCu(6)In(6) crystallizes in the CeMn(4)Al(8) structure type, tetragonal space group I4/mmm, and the lattice constants are a = b = 9.2200(13) Å and c = 5.3976(11) Å. The crystal structure of YbCu(6)In(6) is composed of pseudo-Frank-Kasper cages filled with one ytterbium atom in each ring. The neighboring cages share corners along [100] and [010] to build the three-dimensional network. YbCu(6-x)In(6+x) (x = 0, 1, and 2) solid solution compounds were obtained from high frequency induction heating and characterized using powder X-ray diffraction. The magnetic susceptibilities of YbCu(6-x)In(6+x) (x = 0, 1, and 2) were investigated in the temperature range 2-300 K and showed Curie-Weiss law behavior above 50 K, and the experimentally measured magnetic moment indicates mixed valent ytterbium. A deviation in inverse susceptibility data at 200 K suggests a valence transition from Yb(2+) to Yb(3+) as the temperature decreases. An increase in doping of Cu at the Al2 position enhances the disorder in the system and enhancement in the trivalent nature of Yb. Electrical conductivity measurements show that all compounds are of a metallic nature.

Multiple visible emissions by means of up-conversion process in a microstructured tellurite glass optical fiber.

PubMed

Boetti, Nadia G; Lousteau, Joris; Negro, Davide; Mura, Emanuele; Scarpignato, Gerardo; Abrate, Silvio; Milanese, Daniel

2012-02-27

We present a microstructured fiber whose 9 µm diameter core consists in three concentric rings made of three active glasses having different rare earth oxide dopants, Yb3+/Er3+, Yb3+/Tm3+ and Yb3+/Pr3+, respectively. Morphological and optical characterization of the optical fiber are presented. The photoluminescence spectrum is investigated for different pumping conditions using a commercial 980 nm laser diode. Tuning of the RGB (or white light) emission is demonstrated not only by adjusting the pump power but also by using an optical iris as spatial filter which, thanks to the microstructured core, also acts as a spectral filter.

Effects of rare-earth doping on femtosecond laser waveguide writing in zinc polyphosphate glass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fletcher, Luke B.; Witcher, Jon J.; Troy, Neil

We have investigated waveguide writing in Er-Yb doped zinc polyphosphate glass using a femtosecond laser with a repetition rate of 1 KHz. We find that fabrication of good waveguides requires a glass composition with an O/P ratio of 3.25. The dependence on laser writing parameters including laser fluence, focusing conditions, and scan speed is reported. Waveguide properties together with absorption and emission data indicate that these glasses can be used for the fabrication of compact, high gain amplifying devices.

Polymer/Silicate Nanocomposites Developed for Improved Thermal Stability and Barrier Properties

NASA Technical Reports Server (NTRS)

Campbell, Sandi G.

2001-01-01

The nanoscale reinforcement of polymers is becoming an attractive means of improving the properties and stability of polymers. Polymer-silicate nanocomposites are a relatively new class of materials with phase dimensions typically on the order of a few nanometers. Because of their nanometer-size features, nanocomposites possess unique properties typically not shared by more conventional composites. Polymer-layered silicate nanocomposites can attain a certain degree of stiffness, strength, and barrier properties with far less ceramic content than comparable glass- or mineral-reinforced polymers. Reinforcement of existing and new polyimides by this method offers an opportunity to greatly improve existing polymer properties without altering current synthetic or processing procedures.

Galactic Hearts of Glass

NASA Technical Reports Server (NTRS)

2006-01-01

[figure removed for brevity, see original site] Click on image for larger graph

This artist's concept shows delicate greenish crystals sprinkled throughout the violent core of a pair of colliding galaxies. The white spots represent a thriving population of stars of all sizes and ages. NASA's Spitzer Space Telescope detected more than 20 bright and dusty galactic mergers like the one depicted here, all teeming with the tiny gem-like crystals.

When galaxies collide, they trigger the birth of large numbers of massive stars. Astronomers believe these blazing hot stars act like furnaces to produce silicate crystals in the same way that glass is made from sand. The stars probably shed the crystals as they age, and as they blow apart in supernovae explosions.

At the same time the crystals are being churned out, they are also being destroyed. Fast-moving particles from supernova blasts easily convert silicates crystals back to their amorphous, or shapeless, form.

How is Spitzer seeing the crystals if they are rapidly disappearing? Astronomers say that, for a short period of time at the beginning of galactic mergers, massive stars might be producing silicate crystals faster than they are eliminating them. When our own galaxy merges with the Andromeda galaxy in a few billion years, a similar burst of massive stars and silicate crystals might occur.

Crystal Storm in Distant Galaxy The graph (see inset above) of infrared data from NASA's Spitzer Space Telescope tells astronomers that a distant galaxy called IRAS 08752+3915 is experiencing a storm of tiny crystals made up of silicates. The crystals are similar to the glass-like grains of sand found on Earth's many beaches.

The data were taken by Spitzer's infrared spectrograph, which splits light open to reveal its rainbow-like components. The resulting spectrum shown here reveals the signatures of both crystalline (green) and non-crystalline (brown) silicates.

Spitzer detected the same

Phase-equilibrium geobarometers for silicic rocks based on rhyolite-MELTS. Part 4: Plagioclase, orthopyroxene, clinopyroxene, glass geobarometer, and application to Mt. Ruapehu, New Zealand

NASA Astrophysics Data System (ADS)

Harmon, Lydia J.; Cowlyn, James; Gualda, Guilherme A. R.; Ghiorso, Mark S.

2018-01-01

A new phase equilibria geobarometer determines magmatic storage and crystallization conditions, including pressure, temperature, oxygen fugacity ({f_{{{o}_2}}}), and the presence of a fluid phase for glass-bearing rocks containing the assemblage plagioclase + pyroxene(s). This newly developed geobarometer can better constrain crystallization conditions of shallow (< 500 MPa; < 20 km), glass-bearing andesites to dacites. The geobarometer utilizes rhyolite-MELTS to determine crystallization conditions in natural pumice and scoria samples. The validity of the geobarometer is tested by comparing it to results from experiments. Uncertainties are assessed using Monte Carlo simulations. We apply the geobarometer to the plag + opx + cpx-bearing system of Mt. Ruapehu, in the southern Taupo Volcanic Zone, New Zealand. The samples from Mt. Ruapehu are tested from 5 to 400 MPa and from super-liquidus to 90% crystalline ( 1200 to 700 °C). Mt. Ruapehu serves as a methodological testing ground for the geobarometer, and results from our geobarometer agree with recent Mt. Ruapehu studies. Results show a distribution of crystallization pressures ranging from 50 to 150 MPa ( 2.0 to 5.9 km) for different eruptions, with modes of 110 MPa ( 4.3 km) and 130 MPa ( 5.1 km). These are consistent with field interpretations of different eruptive styles based on juvenile clast textures and previous knowledge of the magma plumbing system. Mt. Ruapehu magmas are fluid saturated, with {f_{{{o}_2}}} of ΔQFM + 1 (NNO).

Reduction of iron-bearing lunar minerals for the production of oxygen

NASA Technical Reports Server (NTRS)

Massieon, Charles; Cutler, Andrew; Shadman, Farhang

1992-01-01

The kinetics and mechanism of the reduction of simulants of the iron-bearing lunar minerals olivine ((Fe,Mg)2SiO4), pyroxene ((Fe,Mg,Ca)SiO3), and ilmenite (FeTiO3) are investigated, extending previous work with ilmenite. Fayalite is reduced by H2 at 1070 K to 1480 K. A layer of mixed silica glass and iron forms around an unreacted core. Reaction kinetics are influenced by permeation of hydrogen through this layer and a reaction step involving dissociated hydrogen. Reaction mechanisms are independent of Mg content. Augite, hypersthene, and hedenbergite are reduced in H2 at the same temperatures. The products are iron metal and lower iron silicates mixed throughout the mineral. Activation energy rises with calcium content. Ilmenite and fayalite are reduced with carbon deposited on partially reduced minerals via the CO disproportionation reaction. Reduction with carbon is rapid, showing the carbothermal reduction of lunar minerals is possible.

Highly evolved rhyolitic glass compositions from the Toba Caldera, Sumatra

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chesner, C.A.

1985-01-01

The quartz latite to rhyolitic ash flow tuffs erupted form the Toba Caldera, perhaps the largest caldera on earth (100 by 30 kms), provide the unique opportunity to study a highly differentiated liquid in equilibrium with numerous mineral phases. Not only are the rocks very crystal rich (30-50%), but at present a minimum of 15 co-existing mineral phases have been identified. Both whole-rock and glass analyses were made by XRF techniques providing data on both major and trace elements. Whole rock chemistry of individual pumices from the youngest eruption at Toba (75,000 years ago), are suggestive of the eruption ofmore » two magma compositions across a boundary layer in the magma chamber. Glass chemistry of the pumices also show two distinct liquid compositions. The more silicic pumices, which have the most evolved glass compositions, are similar to the whole rock chemistry of the few aplitic pumices and cognate granitic xenoliths that were collected. This highly evolved composition resulted from the removal of up to 15 mineral phases and may be a fractionation buffered, univariant composition. The glasses from the less silicic pumices are similar to the whole rock chemistry of the more silicic pumice, thus falling nicely on a fractionation trend towards the univariant composition for these rocks. This set of glass compositions allows an independent test for the origin of distal ashes thought to have erupted from Toba and deposited in Malaysia, the Indian Ocean, and as far away as India.« less

Evolution of trees and mycorrhizal fungi intensifies silicate mineral weathering

PubMed Central

Quirk, Joe; Beerling, David J.; Banwart, Steve A.; Kakonyi, Gabriella; Romero-Gonzalez, Maria E.; Leake, Jonathan R.

2012-01-01

Forested ecosystems diversified more than 350 Ma to become major engines of continental silicate weathering, regulating the Earth's atmospheric carbon dioxide concentration by driving calcium export into ocean carbonates. Our field experiments with mature trees demonstrate intensification of this weathering engine as tree lineages diversified in concert with their symbiotic mycorrhizal fungi. Preferential hyphal colonization of the calcium silicate-bearing rock, basalt, progressively increased with advancement from arbuscular mycorrhizal (AM) to later, independently evolved ectomycorrhizal (EM) fungi, and from gymnosperm to angiosperm hosts with both fungal groups. This led to ‘trenching’ of silicate mineral surfaces by AM and EM fungi, with EM gymnosperms and angiosperms releasing calcium from basalt at twice the rate of AM gymnosperms. Our findings indicate mycorrhiza-driven weathering may have originated hundreds of millions of years earlier than previously recognized and subsequently intensified with the evolution of trees and mycorrhizas to affect the Earth's long-term CO2 and climate history. PMID:22859556

Evolution of trees and mycorrhizal fungi intensifies silicate mineral weathering.

PubMed

Quirk, Joe; Beerling, David J; Banwart, Steve A; Kakonyi, Gabriella; Romero-Gonzalez, Maria E; Leake, Jonathan R

2012-12-23

Forested ecosystems diversified more than 350 Ma to become major engines of continental silicate weathering, regulating the Earth's atmospheric carbon dioxide concentration by driving calcium export into ocean carbonates. Our field experiments with mature trees demonstrate intensification of this weathering engine as tree lineages diversified in concert with their symbiotic mycorrhizal fungi. Preferential hyphal colonization of the calcium silicate-bearing rock, basalt, progressively increased with advancement from arbuscular mycorrhizal (AM) to later, independently evolved ectomycorrhizal (EM) fungi, and from gymnosperm to angiosperm hosts with both fungal groups. This led to 'trenching' of silicate mineral surfaces by AM and EM fungi, with EM gymnosperms and angiosperms releasing calcium from basalt at twice the rate of AM gymnosperms. Our findings indicate mycorrhiza-driven weathering may have originated hundreds of millions of years earlier than previously recognized and subsequently intensified with the evolution of trees and mycorrhizas to affect the Earth's long-term CO(2) and climate history.

Structure and intense UV up-conversion emissions in RE3+-doped sol-gel glass-ceramics containing KYF4 nanocrystals

NASA Astrophysics Data System (ADS)

Yanes, A. C.; Santana-Alonso, A.; Méndez-Ramos, J.; del-Castillo, J.

2013-12-01

Transparent nano-glass-ceramics containing KYF4 nanocrystals were successfully obtained by the sol-gel method, doped with Eu3+ and co-doped with Yb3+ and Tm3+ ions. Precipitation of cubic KYF4 nanocrystals was confirmed by X-ray diffraction and high-resolution transmission electron microscope images. Excitation and emission spectra let us to discern between ions into KYF4 nanocrystals and those remaining in a glassy environment, supplemented with time-resolved photoluminescence decays, that also clearly reveal differences between local environments. Unusual high-energy up-conversion emissions in the UV range were obtained in Yb3+-Tm3+ co-doped samples, and involved mechanisms were discussed. The intensity of these high-energy emissions was analyzed as a function of Yb3+ concentration, heat treatment temperature of precursor sol-gel glasses and pump power, determining the optimum values for potential optical applications as highly efficient UV up-conversion materials in UV solid-state lasers.

The formation of cobalt-bearing ferromanganese crusts under fluid destruction of silicate matter

NASA Astrophysics Data System (ADS)

Maksimov, S. O.; Safronov, P. P.

2016-02-01

The processes of fluid destruction of various silicate rocks under diffusion of flows of compressed gases (mainly carbonaceous) were studied. The gas condensate nature was ascertained for the forming alumoslilicate and ore (cobalt-iron-manganese hydroxide) substances produced under this fluid destruction in the forms of microcrusts and microconcretions. The ore condensates contained in high concentrations the typomorphic elements of oceanic ferromanganese formations (Mn, Co, Ni, Cu, Pb, Ce, and Pt). The elemental composition of the ore oxide substance formed under the destruction of various silicate matrices exhibits a definite degree of endemism with prevalence of the Co-Mn association. The pronounced concentration of barium is related to the substantially carbonaceous composition of the fluid systems. A cerium paradox is revealed: Ce3+ is oxidized into Ce4+ and absorbed by ferromanganese hydrogel and the minimum of cerium appears in rare-earth phosphates.

Giant siliceous spicules from the deep-sea glass sponge Monorhaphis chuni.

PubMed

Wang, Xiaohong; Schröder, Heinz C; Müller, Werner E G

2009-01-01

Only 13 years after realizing, during a repair of a telegraph cable pulled out from the deep sea, that the depth of the ocean is plentifully populated with a highly diverse fauna and flora, the Challenger expedition (1873-1876) treasured up a rich collection of vitreous sponges (Hexactinellida). They had been described by Schulze and represent the phylogenetically oldest class of siliceous sponges (phylum Porifera); they are eye-catching because of their distinct body plan, which relies on a filigree skeleton. It is constructed by an array of morphologically determined elements, the spicules. Soon after, during the German Deep Sea Expedition "Valdivia" (1898-1899), Schulze could describe the largest siliceous hexactinellid sponge on Earth, the up to 3-m high Monorhaphis chuni, which develops the equally largest bio-silica structure, the giant basal spicules (3 mx10 mm). Using these spicules as a model, basic knowledge on the morphology, formation, and development of the skeletal elements could be achieved. They are formed by a proteinaceous scaffold (composed of a 27-kDa protein), which mediates the formation of the siliceous lamellae, into which the proteins are encased. The high number of 800 of 5-10 microm thick lamellae is concentrically arranged around the axial canal. The silica matrix is composed of almost pure silicon oxide, providing it with unusually optophysical properties, which are superior to those of man-made waveguides. Experiments might suggest that the spicules function in vivo as a nonocular photoreception system. In addition, the spicules have exceptional mechanical properties, combining mechanical stability with strength and stiffness. Like demosponges, also the hexactinellids synthesize their silica enzymatically, via the enzyme silicatein (27-kDa protein). It is suggested that these basic insights will surely contribute to a further applied utilization and exploration of silica in bio-material/biomedical science.

Sol-Gel Glasses

NASA Technical Reports Server (NTRS)

Mukherjee, S. P.

1985-01-01

Multicomponent homogeneous, ultrapure noncrystalline gels/gel derived glasses are promising batch materials for the containerless glass melting experiments in microgravity. Hence, ultrapure, homogeneous gel precursors could be used to: (1) investigate the effect of the container induced nucleation on the glass forming ability of marginally glass forming compositions; and (2) investigate the influence of gravity on the phase separation and coarsening behavior of gel derived glasses in the liquid-liquid immiscibility zone of the nonsilicate systems having a high density phase. The structure and crystallization behavior of gels in the SiO2-GeO2 as a function of gel chemistry and thermal treatment were investigated. As are the chemical principles involved in the distribution of a second network former in silica gel matrix being investigated. The procedures for synthesizing noncrystalline gels/gel-monoliths in the SiO2-GeO2, GeO2-PbO systems were developed. Preliminary investigations on the levitation and thermal treatment of germania silicate gel-monoliths in the Pressure Facility Acoustic Levitator were done.

The Role of Gas-Silicate Chemisorption Reactions in Modifying Planetary Crusts and Surfaces

NASA Astrophysics Data System (ADS)

King, P. L.; Henley, R. W.; Wykes, J. L.; Renggli, C.; Troitzsch, U.; Clark, D.; O'Neill, H. S.

2014-12-01

Evidence for gas-solid reactions is found throughout the solar system: for example, sulfidation reactions in some meteorites and secondary phases coating lunar pyroclastic glasses. On Earth, the products of gas-solid reactions are documented in volcanic systems, metalliferous mineral deposits, impact craters, and on dust or meteorites after passage through the atmosphere - such reactions are also likely on the surfaces of Mars and Venus. To understand the chemical dynamics of such gas-solid reactions, we are undertaking systematic experiments and thermochemical modelling. Experiments were conducted in a vertical gas-mixing furnace at 600 - 800 °C and 1 bar, using SO2and a range of Ca-bearing materials: labradorite, feldspar glass and anorthosite (rock). In each case, anhydrite formed rapidly. In shorter experiments with labradorite, isolated anhydrite is observed surrounded by 'moats' of Ca-depleted silicate. In longer experiments, anhydrite is found as clusters of crystals that, in some cases, extend from the substrate forming precarious 'towers' (Figure). Anhydrite fills cracks in porous samples. We propose that the nucleation and rapid growth of anhydrite on the surface of these Ca-rich phases occurs by chemisorption of SO2(g) molecules with slightly negatively charged oxygen onto available near-surface calcium with slight positive charge. Anhydrite growth is sustained by SO2(g) chemisorption and Ca migration through the reacting silicate lattice, accelerated by increased bond lengths at high temperature. Significantly, the chemisorption reaction indicates that SO2 disproportionates to form both oxidized sulfur (as anhydrite) and a reduced sulfur species (e.g., an S* radical ion). On Earth, in the presence of H2O, the predominant reduced sulfur species is H2S, through an overall reaction: 3CaAl2Si2O8 + 4 SO2(g)+ H2O(g) → 3CaSO4 + 3Al2SiO5 + 3SiO2 + H2S(g)The reduced sulfur may react with gas phase Fe, Ni, Zn and Cu cluster compounds to form metal sulfides

Yb:YAG disc for high energy laser systems

NASA Astrophysics Data System (ADS)

Nejezchleb, Karel; Kubát, Jan; Å ulc, Jan; Jelínková, Helena

2017-02-01

Large Yb:YAG crystals were grown using of new improved technology enabling to produce YAG crystals without central growth defect. The crystals diameter reached 115-120mm and their central part was used for manufacturing of discs with the diameter larger than 55 mm. Both sides of this discs were polished and coated. Doping concentration of Yb3+ ions in Yb:YAG crystals was measured using of X-ray fluorescence spectrometry. Absorption coefficient of Yb:YAG was measured for different doping concentration of Yb3+ ions. Fluorescence decay time of Yb:YAG was measured at temperatures of 300K and 80 K. We found the fluorescence decay time of the values of 0.95-1 ms at both temperatures stable and independent on the Yb3+ doping concentration in the range of 1-10 at.% Yb/Y demonstrating high chemical purity of grown crystals. Optical homogeneity as measured using of Fizeau double pass interferometer at 633nm resulted with PV values lower than 0.15 λ on clear aperture of 35 mm. Polished surfaces were ideally parallel with the wedge lower than 2 arcsec. Uniformity of laser properties of Yb:YAG was verified by scanning of the disc as active media in plan-convex pulsed laser resonator pumped by semiconductor diode (wavelength 969 nm, pumping beam diameter 100 μm). It was confirmed, that newly developed technology allows to manufacture very large high quality Yb:YAG discs suitable for high power lasers and amplifiers.

Sol-gel synthesis and in vitro bioactivity of copper and zinc-doped silicate bioactive glasses and glass-ceramics.

PubMed

Bejarano, Julian; Caviedes, Pablo; Palza, Humberto

2015-03-11

Metal doping of bioactive glasses based on ternary 60SiO2-36CaO-4P2O5 (58S) and quaternary 60SiO2-25CaO-11Na2O-4P2O5 (NaBG) mol% compositions synthesized using a sol-gel process was analyzed. In particular, the effect of incorporating 1, 5 and 10 mol% of CuO and ZnO (replacing equivalent quantities of CaO) on the texture, in vitro bioactivity, and cytocompatibility of these materials was evaluated. Our results showed that the addition of metal ions can modulate the textural property of the matrix and its crystal structure. Regarding the bioactivity, after soaking in simulated body fluid (SBF) undoped 58S and NaBG glasses developed an apatite surface layer that was reduced in the doped glasses depending on the type of metal and its concentration with Zn displaying the largest inhibitions. Both the ion release from samples and the ion adsorption from the medium depended on the type of matrix with 58S glasses showing the highest values. Pure NaBG glass was more cytocompatible to osteoblast-like cells (SaOS-2) than pure 58S glass as tested by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. The incorporation of metal ions decreased the cytocompatibility of the glasses depending on their concentration and on the glass matrix doped. Our results show that by changing the glass composition and by adding Cu or Zn, bioactive materials with different textures, bioactivity and cytocompatibility can be synthesized.

Soda-Lime-Silicate Float Glass: A Property Comparison

DTIC Science & Technology

2017-10-01

transparent armor systems. Thus, it is necessary to measure and compare the chemical composition as well as the physical and mechanical properties of...this study show that all 3 SLS glasses have essentially the same chemical composition and the same physical and mechanical properties, indicating they

Nucleation and Crystallization as Induced by Bending Stress in Lithium Silicate Glass Fibers