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Sample records for high silica glasses

  1. Short-term stability of high-silica glasses

    NASA Technical Reports Server (NTRS)

    Leiser, D. B.

    1981-01-01

    The devitrification characteristics of high-silica (70-90%) glasses for use in potential higher temperature coatings on advanced insulation systems for space vehicles were determined at 1260 C after 24 h. These data indicate that additives can be used to maintain the stability of these coatings relative to cristobalite formation.

  2. Enhanced plasticity of silica glass at high pressure

    NASA Astrophysics Data System (ADS)

    Wakabayashi, Daisuke; Funamori, Nobumasa; Sato, Tomoko

    2015-01-01

    We have measured shear flow and residual structural anisotropy of Si O2 glass uniaxially compressed in a diamond-anvil cell at room temperature with in situ optical-microscope and ex situ x-ray diffraction techniques, respectively. Large shear flow began at 8 -10 GPa and continued at least up to 20 GPa, where the macroscopic differential strain reached 70%. Recovered samples after shear flow were in the fully densified state and showed a large microscopic differential strain of 3% only in the intermediate-range network structure. These phenomena may be attributable to the changes in the Si-O bond covalency and the Si-O-Si bond angle with pressure and stresses.

  3. High-silica /greater than 60%/ lunar glasses in an Apollo 14 soil sample - Evidence for silicic lunar volcanism

    NASA Technical Reports Server (NTRS)

    Glass, B. P.

    1976-01-01

    The major-element compositions of 93 low-specific-gravity (less than 2.60) high-silica (greater than 60%) glass particles from a sample of lunar fines (14259,20) were determined by electron microprobe analyses. The size, shape, abundance, mineralogy, and major-element composition of more than 60% of the high-silica glasses is consistent with their being fragments of interstitial glass from mare basalts. However, one group of 30 glasses with between 72% and 78% SiO2 and an average of approximately 2.6% FeO can be distinguished from other high-silica glasses both chemically and petrographically. Glass particles with this composition do not contain crystalline inclusions and are fairly homogeneous not only within a single particle but also from particle to particle. The chemistry and petrology of these glasses suggest that they are not fragments of interstitial glass or shock-melted particles from a 'granitic' source rock. Rather, the homogeneity and lack of crystalline inclusions suggest that this group of high-silica glasses was the product of lunar acidic volcanism.

  4. Blue emission from Eu2+-doped high silica glass by near-infrared femtosecond laser irradiation

    NASA Astrophysics Data System (ADS)

    Qiao, Yanbo; Chen, Danping; Ren, Jinjun; Wu, Botao; Qiu, Jianrong; Akai, Tomoko

    2008-01-01

    Eu2+-doped high silica glass (HSG) is fabricated by sintering porous glass which is impregnated with europium ions. Eu2+-doped HSG is revealed to yield intense blue emission excited by ultraviolet (UV) light and near-infrared femtosecond laser. The emission profile obtained by UV excitation can be well traced by near-infrared femtosecond laser. The upconversion emission excited by 800 nm femtosecond laser is considered to be related to a two-photon absorption process from the relationship between the integrated intensity and the pump power. A tentative scheme of upconverted blue emission from Eu2+-doped HSG was also proposed. The HSG materials presented herein are expected to find applications in high density optical storage and three-dimensional color displays.

  5. Generation of multiple stress waves in silica glass in high fluence femtosecond laser ablation

    SciTech Connect

    Hu Haofeng; Wang Xiaolei; Zhai Hongchen; Zhang Nan; Wang Pan

    2010-08-09

    Shadowgraphs of dynamic processes outside and inside transparent target during the intense femtosecond laser ablation of silica glass are recorded. Two material ejections outside the target and two corresponding stress waves inside the target are observed at different energy fluences. In particular, a third stress wave can be observed at energy fluence as high as 40 J/cm{sup 2}. The first wave is a thermoelastic wave, while the second and the third may be generated subsequently by the mechanical expansions. In addition, the magnitudes of the three stress waves decrease sequentially based on our analysis.

  6. High-pressure infrared sepctra of alpha-quartz, coesite, stishovite and silica glass

    NASA Technical Reports Server (NTRS)

    Williams, Q.; Hemley, R. J.; Kruger, M. B.; Jeanloz, R.

    1993-01-01

    High-pressure infrared absorption spectra of alpha-quatz, coesite, stishovite, and SiO2 glass are consistent with the primary compression mechanism of the initially tetrahedrally bonded phases being the bending of the Si-O-Si angle at pressures less than 10-20 GPa. At higher pressures, up to 40 GPa, we observe a decline in the intensity of the infrared SiO4 asymmetric-stretching vibrations of all three phases, with an increase in the relative amplitude between 700 and 900/cm. This change in intensities is attributed to an increase in the average coordination number of silicon through extreme distortion of tetrahedra. At pressures above approximately 20 GPa, the low-pressure crystalline polymorphs gradually become amorphous, and the infrared spectra provide evidence for an increase in silicon coordination in these high-density amorphous phases. The pressure-amorphized samples prepared from quartz and coesite differ structurally both from each other and from silica glass that has been compressed, and the high pressure spectra indicate that these materials are considerably more disordered than stishovite under comparable pressure conditions. Average mode Grueneisen parameters calculated for quartz, stishovite and fused silica from both infrared and Raman spectra are compatible with the corresponding thermodynamic value of the Grueneisen parameter, however, that of coesite is significantly discrepant.

  7. Nanoscale plasticity in silica glass

    SciTech Connect

    Glosli, J.N.; Boercker, D.B.; Tesar, A.; Belak, J.

    1993-10-01

    Mechanisms of nano-scale plasticity and damage initiation in silica glass is examined using molecular dynamics simulation. Computer experiments are carried out by indenting a sharp diamond-like tool, containing 4496 atoms, into a silica slab consisting of 12288 atoms. Both elastic and plastic deformation of silica is observed during nanoindentation simulation; this transition occurs at an indentation of 1.25 nm, and the calculated hardness (15GPa for 1.5 nm indentation) agrees with experiment.

  8. Thermal diffusivity of pyroxene, feldspar, and silica melts, glasses, and single-crystals at high temperature

    NASA Astrophysics Data System (ADS)

    Pertermann, M.; Branlund, J.; Whittington, A.; Hofmeister, A.

    2007-12-01

    Thermal diffusivity (D) due to phonon transport (the lattice component) was measured using laser-flash analysis from oriented single-crystals and of glasses above the glass transition, which proxy as melts. Compositions include SiO2, CaMgSi2O6, LiAlSi2O6, NaAlSi3O8, and CaAl2Si2O8. KAlSi3O8 was studied previously. Viscosity measurements of the supercooled liquids, in the range 106.8 to 1012.3 Pas, confirm near-Arrhenian behavior. For all compositions and for crystal and glass, D decreases with T, approaching a constant generally near 1000 K: Dsat, which is larger in the crystal than in the glass. A rapid decrease in D as T is increased further (ca 1400 K for orthoclase) is consistent with crossing the glass transition, verified from our viscosity data on these systems. The amount of the decrease depends on the chemical composition and similar to the relative decrease observed in heat capacity. Orthoclase values for Dsat are 0.65± 0.3 mm2/s for bulk crystal and 0.53+/-0.03 mm2/s for the glass. Constant D = 0.475+/-.01 mm2/s represents melt. Thermal conductivity (klat) of orthoclase glass, calculated using previous results for heat capacity (CP) and our density data, increases with T due to CP strongly increasing with T, reaching a plateau near 1.45 W/m-K for melt, but is always below klat of the crystal. Similar results were obtained from the other systems studied. Melting of silica, pyroxene, and feldspars impedes heat transport, providing positive thermal feedback that may promote further melting in the continental crust. The consistency of the behavior for these different compositions and structures suggests that our results are universal, holding for oceanic lithosphere as well. Melts, due to being disordered, are poor transporters of heat via vibrations. However, d(ln klat)/dP depends inversely on bulk modulus, suggesting that at some high pressure, the thermal conductivity of the melt and corresponding crystal become equal so that retention of heat by melts

  9. Rapid micromachining of high aspect ratio holes in fused silica glass by high repetition rate picosecond laser

    NASA Astrophysics Data System (ADS)

    Karimelahi, Samira; Abolghasemi, Ladan; Herman, Peter R.

    2014-01-01

    We present multiple methods of high aspect ratio hole drilling in fused silica glass, taking advantage of high power and high repetition rate picosecond lasers and flexible beam delivery methods to excise deep holes with minimal collateral damage. Combinations of static and synchronous scanning of laser focus were explored over a range of laser repetition rates and burst-train profiles that dramatically vary laser plume interaction dynamics, heat-affected zone, and heat accumulation physics. Chemically assisted etching of picosecond laser modification tracks are also presented as an extension from femtosecond laser writing of volume nanograting to form high aspect ratio (77) channels. Processing windows are identified for the various beam delivery methods that optimize the laser exposure over energy, wavelength, and repetition rate to reduce microcracking and deleterious heating effects. The results show the benefits of femtosecond laser interactions in glass extend into the picosecond domain, where the attributes of higher power further yield wide processing windows and significantly faster fabrication speed. High aspect ratio holes of 400 μm depth were formed over widely varying rates of 333 holes per second for mildly cracked holes in static-focal positioning through to one hole per second for low-damage and taper free holes in synchronous scanning.

  10. Sub-micron fracture mechanism in silica-based glass activated by permanent densification from high-strain loading

    DOE PAGESBeta

    Wereszczak, Andrew A.; Waters, Shirley B.; Parten, Randy J.; Pye, L. David

    2016-04-26

    Several silica-based glasses were fractured at high strain energy via drop-weight testing on small specimens. A cylindrical specimen geometry was chosen to promote initially simple, axisymmetric, and uniform compressive loading. The imposed uniaxial compressive strain at impact was sufficiently high to qualitatively cause permanent densification. Produced fragments were collected for postmortem and a fraction of them, for all the silica-based glasses, consistently had distinct sub-micron-sized fractures (~ 300–1000 nm), designated here as “microkernels”, on their surfaces. They would most often appear as a sub-micron pore on the fragment - apparently if the microkernel had popped out as a consequence ofmore » the local crack plane running through it, tensile-strain release, and the associated formation of the fragment it was on. No fractographic evidence was found to show the microkernels were associated with local failure initiation. However, their positioning and habit sometimes suggested they were associated with localized crack branching and that they could have influenced secondary fracturing that occurred during overall crushing and comminution and associated fragment size and shape creation. Furthermore, the size range of these microkernels is much too small to affect structural flexure strength of these glasses for most applications but are of a size and concentration that may affect their ballistic, shock, crush, and comminution responses when permanent densification is concomitantly occurring.« less

  11. Inert strength of pristine silica glass fibers

    SciTech Connect

    Smith, W.L.; Michalske, T.A.

    1993-11-01

    Silica glass fibers have been produced and tested under ultra high vacuum (UHV) conditions to investigate the inert strength of pristine fibers in absence of reactive agents. Analysis of the coefficient of variation in diameter ({upsilon}{sub d}) vs the coefficient of variation of breaking strength ({upsilon}{sub {sigma}}) does not adequately explain the variation of breaking stress. Distribution of fiber tensile strength data suggests that the inert strength of such fibers is not single valued and that the intrinsic strength is controlled by defects in the glass. Furthermore, comparison of room temperature UHV data with LN{sub 2} data indicates that these intrinsic strengths are not temperature dependent.

  12. Electrochemical strain microscopy of silica glasses

    NASA Astrophysics Data System (ADS)

    Proksch, R.

    2014-08-01

    Piezoresponse Force Microscopy and Electrochemical Strain Microscopy (ESM) are two related techniques that have had considerable success in nano-scale probing of functional material properties. Both measure the strain of the sample in response to a localized electric field beneath a sharp conductive tip. In this work, a collection of commercially available glass samples were measured with a variety of Si cantilevers coated with different conductive metals. In some cases, these glasses showed significant hysteresis loops, similar in appearance to those measured on ferroelectric materials with spontaneous permanent electric dipoles. The magnitude of the electrochemical strain and hysteresis correlated well with the molar percentage of sodium in the glass material, with high sodium (soda-lime) glass showing large hysteresis and fused silica (pure SiO2) showing essentially no hysteresis. The "elephant-ear" shape of the hysteresis loops correlated well with it originating from relaxation behavior—an interpretation verified by observing the temperature dependent relaxation of the ESM response. Cation mobility in a disordered glass should have a low diffusion constant. To evaluate this diffusion constant, the temperature of the glass was varied between room temperature to ˜200 °C. Vanishing hysteresis as the temperature increased was associated with a decrease in the relaxation time of the electrochemical response. The hysteretic behavior changed drastically in this temperature range, consistent with bound surface water playing a large role in the relaxation. This demonstrates the ability of ESM to differentiate cationic concentrations in a range of silica glasses. In addition, since glass is a common sample substrate for, this provides some clear guidance for avoiding unwanted substrate crosstalk effects in piezoresponse and electrochemical strain response measurements.

  13. Patterning of silica MCM-41 high-order material on a glass surface by XeCl laser irradiation

    NASA Astrophysics Data System (ADS)

    Panahibakhsh, Somayeh; Hadi Maleki, Mohammad; Jelvani, Saeid

    2015-08-01

    Silica glass samples (with the compositions of SiO2 96.66, Na2O 0.62, MgO 0.80, Al2O3 1.66 and CaO 0.26 in wt%) were irradiated with 5 pulses of a nanosecond XeCl excimer laser at a fluence of 300mJ/cm2 and 1Hz repetition rate. Scanning electron microscopy images of the irradiated area showed that micro and nanostructures were developed on the glass surface by the XeCl laser irradiation. It is found from energy dispersive X-ray analysis, X-ray diffraction analysis and micro-Raman spectroscopy that the structures are fine crystalline patterns of silica MCM-41 materials. It is supposed that crystallization of the glass is induced through the absorption of 308nm wavelength XeCl laser irradiation by silicon ions. Therefore, it is proposed that this method of spatially selective crystallization of glass could be applicable to other glass materials for potential optics and photonics applications.

  14. Measuring nonlinear reflectance of laser radiation with a wavelength of 2940 nm from silica glass – water and silica glass – ethanol interfaces

    NASA Astrophysics Data System (ADS)

    Gulyamova, E. S.; Il'ichev, N. N.; Pashinin, P. P.; Polyanskii, V. I.; Sidorin, A. V.

    2016-07-01

    We have measured the reflectance of an Er3+ : YAG laser pulse from silica glass – water and silica glass – ethanol interfaces at high (0.9 J cm-2) and low (5 mJ cm-2) energy densities of incident radiation. The nonlinearity of reflectance dynamics is found for high-power radiation during the laser pulse action.

  15. Diffusive Gas Loss from Silica Glass Ampoules at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Palosz, W.

    1998-01-01

    Changes in the pressure of hydrogen, helium and neon due to diffusion through the wall of silica crystal growth ampoules at elevated temperatures were determined experimentally. We show that, while both He- and Ne-losses closely follow conventional model of diffusive gas permeation through the wall, hydrogen losses, in particular at low fill pressures, can be much larger. This is interpreted in terms of the high solubility of hydrogen in silica glasses.

  16. Study on laser damage of high transmission single layer optical thin film for fused silica glass induced by inclusion

    NASA Astrophysics Data System (ADS)

    Hao, Ming-ming; Lu, Guo-guang; Zhu, Hong-bo; Wang, Li-na

    2015-08-01

    In order to research the laser damage mechanism of high transmission single layer optical thin film for fused silica glass, finite element method was used to calculate laser induced damage threshold (LIDT) and an optical test system with a nanosecond solid-state lasers was set up to determine the LIDT according to standard of ISO 11254. Firstly, finite element model was created at COMSOL multi-physics software and the temperature of inclusion in the optical thin film was calculated with different physical parameter. It is found that temperature at center of the inclusion firstly decreases and then increase with the increasing of inclusion depth. It is also found that the temperature constantly increase with the radius increasing from 20nm to 100nm. Moreover, the inclusion temperature for MgF2 thin film is higher than that of CaF2 thin film. Lastly, LIDT were measured by the optical test system, and the average value of LIDT is 3.7J/cm2 for MgF2 thin film and 4.6J/cm2 for CaF2 thin film, which is well fit with the value calculated by COMSOL software. The study shows that finite element method is an effective method to calculate LIDT for optical thin film and impurity has significant impact on the LIDT of optical thin film and therefore decreasing the density of the impurity would increase the LIDT of the thin film.

  17. Properties Of Soda/Yttria/Silica Glasses

    NASA Technical Reports Server (NTRS)

    Angel, Paul W.; Hann, Raiford E.

    1994-01-01

    Experimental study of glass-formation compositional region of soda/ yttria/silicate system and of selected physical properties of glasses within compositional region part of continuing effort to identify glasses with high coefficients of thermal expansion and high softening temperatures, for use as coatings on superalloys and as glass-to-metal seals.

  18. High thermal behavior of a new glass ceramic developed from silica xerogel/SnO2 composite

    NASA Astrophysics Data System (ADS)

    Aripin, H.; Mitsudo, Seitaro; Sudiana, I. Nyoman; Priatna, Edvin; Sabchevski, Svilen

    2016-02-01

    In this investigation, a new glass ceramics have been produced by mixing SnO2 and amorphous silica xerogel (ASX) extracted from sago waste ash. The composition has been prepared by adding 10 mol% of SnO2 into SX. The samples have been dry pressed and sintered in the temperature range between 800 °C and 1500 °C. The effects of temperature on the crystallization of silica xerogel after adding SnO2 and their relationship to bulk density have been studied. The crystallization process of the silica xerogel/SnO2 composite has been examined by an X-ray diffraction (XRD) and the bulk density has been characterized on the basis of the experimental data obtained using Archimedes' principle. It has been found that an addition of SnO2 confers an appreciable effect on the grain and from the interpretation of XRD patterns allow one to explain the increase in the density by an increased crystallite size of SnO2 in the composite.

  19. Inhomogeneous Elastic Response of Silica Glass

    NASA Astrophysics Data System (ADS)

    Léonforte, F.; Tanguy, A.; Wittmer, J. P.; Barrat, J.-L.

    2006-08-01

    Using large scale molecular dynamics simulations we investigate the properties of the nonaffine displacement field induced by macroscopic uniaxial deformation of amorphous silica, a strong glass according to Angell’s classification. We demonstrate the existence of a length scale ξ characterizing the correlations of this field (corresponding to a volume of about 1000 atoms), and compare its structure to the one observed in a standard fragile model glass. The “boson-peak” anomaly of the density of states can be traced back in both cases to elastic inhomogeneities on wavelengths smaller than ξ where classical continuum elasticity becomes simply unapplicable.

  20. Crystallization of baria-titania-silica glasses

    NASA Technical Reports Server (NTRS)

    Ray, Chandra S.; Day, Delbert E.

    1986-01-01

    The critical cooling rate for glass formation, Rc, and the crystallization kinetics of the compositions (1/2)(100-x)BaO-(1/2)(100-x)TiO2-(x)SiO2 with x = 20, 25, 30, 33.3, and 40 mol pct were studied using a thermal image furnace. Crystallization was studied under nonisothermal conditions, and the data were analyzed using the Johnson-Mehl-Avrami equation. The Rc and activation energy for crystallization both decrease with increasing silica content. Fresnoite, Ba2TiSi2O8, crystallized from all of the glasses when they were reheated. The infrared absorption spectra of the glasses and crystals show that they both contain (Si2O7) and square pyramidal (TiO5) groups.

  1. Crystallization of calcia-gallia-silica glasses

    NASA Technical Reports Server (NTRS)

    Ray, C. S.; Day, D. E.

    1984-01-01

    A thermal image furance is presently used to study the critical cooling rate for glass formation, and the kinetics of crystallization, of the compositions 18.4CaO-(81.6-X)Ga2O3-XSiO2, where X = 3, 6, 9, and 13.8. Crystallization was studied nonisothermally, and the data were analyzed in light of the Avrami (1939) equation. Critical cooling rate and crystallization activation energy are both found to decrease with increasing silica content, and the results obtained by the present technique are noted to agree with those obtained on the basis of differential thermal analysis measurements.

  2. Hollow microspheres of silica glass and method of manufacture

    DOEpatents

    Downs, Raymond L.; Miller, Wayne J.

    1982-01-01

    A method of manufacturing gel powder suitable for use as a starting material in the manufacture of hollow glass microspheres having a high concentration of silica. The powder is manufactured from a gel containing boron in the amount of about 1% to 20% (oxide equivalent mole percent), alkali metals, specifically potassium and sodium, in an amount exceeding 8% total, and the remainder silicon. Preferably, the ratio of potassium to sodium is greater than 1.5.

  3. Fabricating silver nanoplate/hybrid silica gel glasses and investigating their nonlinear optical absorption behavior

    NASA Astrophysics Data System (ADS)

    Zheng, Chan; Wenzhe, Chen; Xiaoyun, Ye; Cai, Shuguang; Xiao, Xueqing

    2014-03-01

    Silver nanoplate/hybrid silica gel glasses were prepared via the sol-gel technique. Analysis of ultraviolet-visible spectroscopy extinction spectra confirmed the successful incorporation of silver nanoplates into the hybrid silica gel glasses. The silver nanoplate/hybrid silica gel glass composites are completely noncrystalline because of their low doping level compared with that of the silica matrix. The nonlinear optical absorption behavior of the silver nanoplate/hybrid silica gel glass composites was studied via open-aperture Z-scan technique with 4 ns pulse durations at 532 nm and 1064 nm. The nonlinear optical properties of silver nanoplates are maintained after they were introduced into silica gel glasses. Furthermore, the silver nanoplate/hybrid silica gel glasses exhibit intensity-dependent transformation from saturable absorption (SA) to reverse saturable absorption (RSA). The SA behavior at low excitation intensity can be attributed to the bleaching of ground-state surface plasmon resonance absorption induced by the retarded electronic relaxation process in solid-state gel glasses. By contrast, the RSA at high incident influence may have resulted from excited-state absorption and two-photon absorption.

  4. Brittle to Ductile Transition in Densified Silica Glass

    PubMed Central

    Yuan, Fenglin; Huang, Liping

    2014-01-01

    Current understanding of the brittleness of glass is limited by our poor understanding and control over the microscopic structure. In this study, we used a pressure quenching route to tune the structure of silica glass in a controllable manner, and observed a systematic increase in ductility in samples quenched under increasingly higher pressure. The brittle to ductile transition in densified silica glass can be attributed to the critical role of 5-fold Si coordination defects (bonded to 5 O neighbors) in facilitating shear deformation and in dissipating energy by converting back to the 4-fold coordination state during deformation. As an archetypal glass former and one of the most abundant minerals in the Earth's crest, a fundamental understanding of the microscopic structure underpinning the ductility of silica glass will not only pave the way toward rational design of strong glasses, but also advance our knowledge of the geological processes in the Earth's interior. PMID:24849328

  5. Structural and topological changes in silica glass at pressure.

    SciTech Connect

    Benmore, C. J.; Soignard, E.; Amin, S. A.; Guthrie, M.; Shastri, S. D.; Lee, P. L.; Yarger, J. L.; X-Ray Science Division; Arizona State Univ.; Carnegie Inst. of Science

    2010-01-01

    The effects of high pressures on the structure of silica glass have been elucidated using high-energy x-ray diffraction up to 43.5 GPa. A decrease in the first two peak positions in the real-space pair-distribution functions up to 15 GPa indicates an initial shrinkage of the tetrahedral units. Above this threshold pressure the Si-O bond peak shape becomes asymmetric and the average Si-O bond length and coordination number both increase linearly with pressure. Also, strained geometries in the O-O correlations lead a pronounced topological rearrangement of the second and third nearest neighbors.

  6. Superhydrophobic and highly luminescent polyfluorene/silica hybrid coatings deposited onto glass and cellulose-based substrates.

    PubMed

    de Francisco, Raquel; Hoyos, Mario; García, Nuria; Tiemblo, Pilar

    2015-03-31

    Neat poly(9,9-dioctyl-9H-fluorene) (PFO) and composites of PFO and a modified organonanosilica P(7) at weight ratios 90/10, 70/30, and 50/50 have been employed to prepare fluorescent and superhydrophobic coatings by spraying onto three different substrates: glass, Whatman paper, and a filtration membrane of mixed cellulose esters. The water repellency of the coatings and their photophysical properties are therein studied. It is found that, irrespective of the substrate and the composite composition, all coatings remain fluorescent. In some of the coatings prepared, confined morphologies are created, which fluoresce with a wavelength distribution resembling that of an ordered planar β-phase. Among the coatings prepared in this work, those with a ratio PFO/P(7) of 50/50 are the ones with the strongest chain confinement and the highest surface roughness, being highly emissive at the β-phase wavelengths and also superhydrophobic. Depending on the substrate these materials are also tough and flexible (cellulose based substrates) or display a remarkable light transmittance (glass). A final merit of these multifunctional materials is the simplicity of the preparation procedure, adequate for large surfaces and industrial applications. PMID:25747277

  7. Dissolution retardation of solid silica during glass batch-melting

    SciTech Connect

    Hrma, Pavel R.; Marcial, Jose

    2011-07-15

    During glass-batch melting, solid silica (quartz) usually dissolves last. A retardation function was defined as a measure of the progressive inhibition of silica dissolution that occurs during batch melting. This function is based on the comparison of the measured rate of dissolution of silica particles with the hypothetical diffusion-controlled volume flux from regularly distributed particles with uniform concentration layers around them. The severe inhibition of silica dissolution has been attributed to the irregular spatial distribution of silica particles that is associated with the formation of nearly saturated melt at a portion of their surfaces. Irregular shapes and unequal sizes of particles also contribute to their extended lifetime.

  8. White luminescence from silica glass containing red/green/blue luminescent nanocrystalline silicon particles

    SciTech Connect

    Sato, Keisuke; Kishimoto, Naoki; Hirakuri, Kenji

    2007-11-15

    Silica glasses containing blue/green/red luminescent nanocrystalline silicon (nc-Si) particles that consist of monolayer and/or three-layer structures were fabricated by a radio-frequency sputtering technique and postannealing treatment. These silica glasses showed very broad luminescence spectra with a peak at 460 nm (blue light), 550 nm (green light), and 800 nm (red light). When these samples were irradiated by using a xenon lamp with an optical bandpass filter of 313 nm, the luminescence colors from these silica glasses were a white light. The white luminescence of the sample with the three-layer structure exhibited the high luminance value of 1.5 cd/m{sup 2}. This value was ascribed to the adjustment of sizes and densities of blue/green/red luminescent nc-Si particles, and the lowering of densities of P{sub b} centers (nonradiative recombination centers) at the nc-Si particle/silica glass interface layer.

  9. Taper array in silica glass for beam splitting

    NASA Astrophysics Data System (ADS)

    Xia, Zehua; Li, Yan; Han, Yanhua; Ge, Meng; Ye, Jingfu; Deng, Duo; Wang, Benyang; Gao, Jianmin; Qu, Shiliang

    2016-03-01

    We proposed taper array in silica glass for beam splitting which was fabricated by water-assisted femtosecond laser direct writing technology and the subsequent heat treatment. We divided the array into many fabricating cells which were executed automatically in sequences as specified by the program that contained the information for the three-dimensional stage movements. Each cell could fabricated a rectangular cylinder. The size and distribution of the rectangular cylinder could be controlled by adjusting the position of the fabricating cells. Then the heat treatment should be used to reshape the rectangular cylinders into taper array. The experimental results show that the taper periodic microstructures in silica glass are uniform and smooth, and the tapers can divide the incident light into beam array. The results demonstrated that the combination of the water-assisted femtosecond laser direct writing technology and the heat treatment is accessible and practical for the high quality micro-optical elements. These micro-optical elements will have potential applications in fluorescence detection and beam splitter.

  10. Surface characterization of silica glass substrates treated by atomic hydrogen

    SciTech Connect

    Inoue, Hiroyuki; Masuno, Atsunobu; Ishibashi, Keiji; Tawarayama, Hiromasa; Zhang, Yingjiu; Utsuno, Futoshi; Koya, Kazuo; Fujinoki, Akira; Kawazoe, Hiroshi

    2013-12-15

    Silica glass substrates with very flat surfaces were exposed to atomic hydrogen at different temperatures and durations. An atomic force microscope was used to measure root-mean-square (RMS) roughness and two-dimensional power spectral density (PSD). In the treatment with atomic hydrogen up to 900 °C, there was no significant change in the surface. By the treatment at 1000 °C, the changes in the RMS roughness and the PSD curves were observed. It was suggested that these changes were caused by etching due to reactions of atomic hydrogen with surface silica. By analysis based on the k-correlation model, it was found that the spatial frequency of the asperities became higher with an increase of the treatment time. Furthermore, the data showed that atomic hydrogen can flatten silica glass surfaces by controlling heat-treatment conditions. - Highlights: • Silica glass surface was treated by atomic hydrogen at various temperatures. • Surface roughness was measured by an atomic force microscope. • Roughness data were analyzed by two-dimensional power spectral density. • Atomic hydrogen can flatten silica glass surfaces.

  11. Sulfate Fining Chemistry in Oxidized and Reduced Soda-Lime-Silica Glasses

    SciTech Connect

    Matyas, Josef; Hrma, Pavel R.

    2005-05-13

    Various reducing agents were used and their additions were varied to (1) increase glass quality through eliminating defects from silica scum, (2) decrease SOx emissions through changing the kind and quantity of reducing agents, and (3) improve production efficiency through increased flexibility of glass redox control during continuous processing. The work included measuring silica sand dissolution and sulfate decomposition in melts from glass batches. Glass batches were heated at a temperature-increase rate deemed similar to that experienced in the melting furnace. The sulfate decomposition kinetics was investigated with thermogravimetric analysis-differential thermal analysis and evolved gas analysis. Sulfur concentrations in glasses quenched at different temperatures were determined using X-ray fluorescence spectroscopy. The distribution of residual sand (that which was not dissolved during the initial batch reactions) in the glass was obtained as a function of temperature with optical microscopy in thin-sections of melts. The fraction of undissolved sand was measured with X-ray diffraction. The results of the present study helped Visteon Inc. reduce the energy consumption and establish the batch containing 0.118 mass% of graphite as the best candidate for Visteon glass production. The improved glass batch has a lower potential for silica scum formation and for brown fault occurrence in the final glass product. It was established that bubbles trapped in the melt even at 1450 C have a high probability to be refined when reaching the hot zone in the glass furnace. Furthermore, silica sand does not accumulate at the glass surface and dissolves faster in the batch with graphite than in the batch with carbocite.

  12. 3D laser-written silica glass step-index high-contrast waveguides for the 3.5 μm mid-infrared range.

    PubMed

    Martínez, Javier; Ródenas, Airán; Fernandez, Toney; Vázquez de Aldana, Javier R; Thomson, Robert R; Aguiló, Magdalena; Kar, Ajoy K; Solis, Javier; Díaz, Francesc

    2015-12-15

    We report on the direct laser fabrication of step-index waveguides in fused silica substrates for operation in the 3.5 μm mid-infrared wavelength range. We demonstrate core-cladding index contrasts of 0.7% at 3.39 μm and propagation losses of 1.3 (6.5) dB/cm at 3.39 (3.68) μm, close to the intrinsic losses of the glass. We also report on the existence of three different laser modified SiO₂ glass volumes, their different micro-Raman spectra, and their different temperature-dependent populations of color centers, tentatively clarifying the SiO₂ lattice changes that are related to the large index changes. PMID:26670520

  13. Poisson's Ratio and the Densification of Glass under High Pressure

    SciTech Connect

    Rouxel, T.; Ji, H.; Hammouda, T.; Moreac, A.

    2008-06-06

    Because of a relatively low atomic packing density, (C{sub g}) glasses experience significant densification under high hydrostatic pressure. Poisson's ratio ({nu}) is correlated to C{sub g} and typically varies from 0.15 for glasses with low C{sub g} such as amorphous silica to 0.38 for close-packed atomic networks such as in bulk metallic glasses. Pressure experiments were conducted up to 25 GPa at 293 K on silica, soda-lime-silica, chalcogenide, and bulk metallic glasses. We show from these high-pressure data that there is a direct correlation between {nu} and the maximum post-decompression density change.

  14. Photonic bandgap single-mode optical fibre with ytterbium-doped silica glass core

    SciTech Connect

    Egorova, O N; Semenov, S L; Vel'miskin, V V; Dianov, Evgenii M; Salganskii, M Yu; Yashkov, M V; Gur'yanov, Aleksei N

    2011-01-24

    A photonic bandgap fibre with an ytterbium-doped silica glass core is fabricated and investigated. The possibility of implementing single-mode operation of such fibres in a wide spectral range at a large (above 20 {mu}m) mode field diameter makes them promising for fibre lasers and amplifiers. To ensure a high quality of the beam emerging from the fibre, particular attention is paid to increasing the optical homogeneity of the ytterbium-doped core glass. (optical fibres)

  15. Photonic bandgap guiding into a composite AgPO3-glass/silica microstructured optical fibre

    NASA Astrophysics Data System (ADS)

    Konidakis, Ioannis; Zito, Gianluigi; Pissadakis, Stavros

    2012-04-01

    Infiltration of glass matrices inside Photonic Crystals Fibres (PCFs) for achieving photonic bandgap (PBG) guidance and expand devices development capabilities has been recently demonstrated. Herein, we report the fabrication of an all-solid PBG guiding PCF by suction-assisted infiltration of molten silver-metaphosphate (AgPO3) glass into the air capillaries of a commercial solid core PCF. The relatively low viscosity of the AgPO3 glass melt permitted infiltration at ~ 700 °C inside an annealing oven apparatus by applying suction with the use of a standard mechanical vacuum pump, while its low glass transition temperature of ~ 190 °C allows structural relaxations at temperatures close to ambient and the formation of high quality glass strands inside the silica structure of the PCF. The AgPO3/silica PCF was characterized by means of its transmission spectrum that showed PBG guidance over the measurement range (350-1650nm). The effect of the AgPO3 glass photosensitivity on the guiding properties of the AgPO3/silica PCF was explored by employing a 355nm, 150 ps laser irradiation. The exposure gave rise to a photo-induced enhancement of the transmission-to-stop-band extinction ratio by ~60 dB/cm as well as bandwidth tuning. Numerical calculations of the transmission spectra of the AgPO3/silica PCF have been performed for confirming the experimental results and modelling the photo-induced variation of the two-glass fibre transmission. We believe that the fabrication of the AgPO3/silica PBG fibre constitutes a strong base for the development of new in-fibre sensing and scattering-based devices, by exploiting the high photosensitivity of silver and its specific plasmon absorption properties.

  16. Magnetic pinch compression of silica glass

    NASA Technical Reports Server (NTRS)

    Bless, S. J.

    1974-01-01

    SiO2 glass has been irreversibly densified by pressures up to 250 kbar produced in a magnetic pinch apparatus. The threshold for significant densification was about 60 kbar. The recovered densities agree better with published shock wave results than with static results.

  17. Formation of plasma induced surface damage in silica glass etching for optical waveguides

    NASA Astrophysics Data System (ADS)

    Choi, D. Y.; Lee, J. H.; Kim, D. S.; Jung, S. T.

    2004-06-01

    Ge, B, P-doped silica glass films are widely used as optical waveguides because of their low losses and inherent compatibility with silica optical fibers. These films were etched by ICP (inductively coupled plasma) with chrome etch masks, which were patterned by reactive ion etching (RIE) using chlorine-based gases. In some cases, the etched surfaces of silica glass were very rough (root-mean square roughness greater than 100 nm) and we call this phenomenon plasma induced surface damage (PISD). Rough surface cannot be used as a platform for hybrid integration because of difficulty in alignment and bonding of active devices. PISD reduces the etch rate of glass and it is very difficult to remove residues on a rough surface. The objective of this study is to elucidate the mechanism of PISD formation. To achieve this goal, PISD formation during different etching conditions of chrome etch mask and silica glass was investigated. In most cases, PISD sources are formed on a glass surface after chrome etching, and metal compounds are identified in theses sources. Water rinse after chrome etching reduces the PISD, due to the water solubility of metal chlorides. PISD is decreased or even disappeared at high power and/or low pressure in glass etching, even if PISD sources were present on the glass surface before etching. In conclusion, PISD sources come from the chrome etching process, and polymer deposition on these sources during the silica etching cause the PISD sources to grow. In the area close to the PISD source there is a higher ion flux, which causes an increase in the etch rate, and results in the formation of a pit.

  18. Photosensitivity in a silica-based sol-gel glass

    SciTech Connect

    Korwin, D.M.; Pye, L.D.

    1996-12-31

    Photosensitivity in glasses containing Au and Ce was first reported by Dalton in 1943 and later reaffirmed by Stookey. The photothermal reduction of Au ions to form metallic colloids was determined to be responsible for the {open_quotes}ruby{close_quotes} color produced in these glasses. In this work, the photosensitive effect has been confirmed for the first time in a silica sol-gel glass containing Au and Ce. Two methods of producing Au colloids in this glass were investigated, one involved a short ultraviolet (UV) exposure followed by a thermal treatment, the other a simultaneous UV irradiation and thermal treatment. Colloid formation was studied using optical absorption spectroscopy, whereas the role of Ce in the photosensitive process was elucidated using optical absorption and fluorescence spectroscopic techniques.

  19. Three dimensional multilayer solenoid microcoils inside silica glass

    NASA Astrophysics Data System (ADS)

    Meng, Xiangwei; Yang, Qing; Chen, Feng; Shan, Chao; Liu, Keyin; Li, Yanyang; Bian, Hao; Si, Jinhai; Hou, Xun

    2016-01-01

    Three dimensional (3D) solenoid microcoils could generate uniform magnetic field. Multilayer solenoid microcoils are highly pursued for strong magnetic field and high inductance in advanced magnetic microsystems. However, the fabrication of the 3D multilayer solenoid microcoils is still a challenging task. In this paper, 3D multilayer solenoid microcoils with uniform diameters and high aspect ratio were fabricated in silica glass. An alloy (Bi/In/Sn/Pb) with high melting point was chosen as the conductive metal to overcome the limitation of working temperature and improve the electrical property. The inductance of the three layers microcoils was measured, and the value is 77.71 nH at 100 kHz and 17.39 nH at 120 MHz. The quality factor was calculated, and it has a value of 5.02 at 120 MHz. This approach shows an improvement method to achieve complex 3D metal microstructures and electronic components, which could be widely integrated in advanced magnetic microsystems.

  20. Improvement in hardness of soda-lime-silica glass

    SciTech Connect

    Chakraborty, Riya; De, Moumita; Roy, Sudakshina; Dey, Arjun; Biswas, Sampad K.; Middya, Tapas Ranjan; Mukhopadhyay, Anoop K.

    2012-06-05

    Hardness is a key design parameter for structural application of brittle solids like glass. Here we report for the first time the significant improvement of about 10% in Vicker's hardness of a soda-lime-silica glass with loading rate in the range of 0.1-10 N.s{sup -1}. Corroborative dark field optical and scanning electron microscopy provided clue to this improvement through evidence of variations in spatial density of shear deformation band formation as a function of loading rate.

  1. Hypervelocity impact damage tolerance of fused silica glass

    NASA Technical Reports Server (NTRS)

    Edelstein, K. S.

    1992-01-01

    A test program was conducted at the NASA/Johnson Space Center (JSC) concerning hypervelocity impact damage in fused silica glass. The objectives of this test program were: to expand the penetration equation data base in the velocity range between 2 and 8 km/s; to determine how much strength remains in a glass pane that has sustained known impact damage; and to develop a relationship between crater measurements and residual strength predictions that can be utilized in the Space Shuttle and Space Station programs. The results and conclusions of the residual strength testing are discussed below. Detailed discussion of the penetration equation studies will follow in future presentations.

  2. Luminescence properties of Cr-doped silica sol gel glasses

    NASA Astrophysics Data System (ADS)

    Strek, Wieslaw; Lukowiak, Edward; Deren, Przemyslaw J.; Maruszewski, K.; Trabjerg, Ib; Koepke, Czeslaw; Malashkevich, G. E.; Gaishun, Vladimir E.

    1997-11-01

    The emission of Cr-doped silica glass obtained by the sol- gel method is characterized by an orange broad band with a maximum at 610 nm. Its nature is examined by the absorption, excited state absorption, emission, excitation and lifetime measurements over a wide range of temperature and for different concentration of Cr ions. Our measurement show that in spite of fact that the absorption properties of Cr- doped silica sol-gel glass are predominantly associated with Cr4+ centers, the observed in visible range emission can be assigned neither to Cr3+ nor to Cr4+ ions. The discussion of the nature of observed emission was carried out for all possible valencies of the Cr ions. In conclusion is suggested that it may be ascribed to the transitions on the monovalent Cr1+ ion. The reducing agents occurring during the sol-gel process and leading to lowering the Cr valency are discussed.

  3. Imaging atomic rearrangements in two-dimensional silica glass: watching silica's dance.

    PubMed

    Huang, Pinshane Y; Kurasch, Simon; Alden, Jonathan S; Shekhawat, Ashivni; Alemi, Alexander A; McEuen, Paul L; Sethna, James P; Kaiser, Ute; Muller, David A

    2013-10-11

    Structural rearrangements control a wide range of behavior in amorphous materials, and visualizing these atomic-scale rearrangements is critical for developing and refining models for how glasses bend, break, and melt. It is difficult, however, to directly image atomic motion in disordered solids. We demonstrate that using aberration-corrected transmission electron microscopy, we can excite and image atomic rearrangements in a two-dimensional silica glass-revealing a complex dance of elastic and plastic deformations, phase transitions, and their interplay. We identified the strain associated with individual ring rearrangements, observed the role of vacancies in shear deformation, and quantified fluctuations at a glass/liquid interface. These examples illustrate the wide-ranging and fundamental materials physics that can now be studied at atomic-resolution via transmission electron microscopy of two-dimensional glasses. PMID:24115436

  4. Silver metaphosphate glass wires inside silica fibers--a new approach for hybrid optical fibers.

    PubMed

    Jain, Chhavi; Rodrigues, Bruno P; Wieduwilt, Torsten; Kobelke, Jens; Wondraczek, Lothar; Schmidt, Markus A

    2016-02-22

    Phosphate glasses represent promising candidates for next-generation photonic devices due to their unique characteristics, such as vastly tunable optical properties, and high rare earth solubility. Here we show that silver metaphosphate wires with bulk optical properties and diameters as small as 2 µm can be integrated into silica fibers using pressure-assisted melt filling. By analyzing two types of hybrid metaphosphate-silica fibers, we show that the filled metaphosphate glass has only negligible higher attenuation and a refractive index that is identical to the bulk material. The presented results pave the way towards new fiber-type optical devices relying on metaphosphate glasses, which are promising materials for applications in nonlinear optics, sensing and spectral filtering. PMID:26906989

  5. The deposition of boron nitride and carbon films on silica glass fibers

    SciTech Connect

    Smith, W.L.; Michalske, T.A.; Rye, R.R.

    1993-11-01

    A chemical vapor deposition technique is used to produce amorphous boron nitride and carbon thin films on high strength silica glass fibers. In this method, the fiber is drawn under ultra high vacuum conditions and low pressure process gases, in the presence of a hot tungsten filament, are used to grow films at low substrate temperatures. Films deposited with this technique do not degrade the intrinsic pristine strength of the silica fibers under dry conditions and, when stressed in chemically aggressive environments, act as effective barrier coatings.

  6. Spectroscopic evidence for new denser structure of silica glass under ultrahigh pressure (Invited)

    NASA Astrophysics Data System (ADS)

    Murakami, M.

    2013-12-01

    Silica glass is a prototype network-forming glass serving as the basic framework of a variety of glasses, which widely used as a technologically useful material. Polyamorphism in silica glass is thus one of the most fascinating and puzzling topics in condensed matter physics. Silica glass can be also considered as the major and simplest analogue for all geophysically relevant silicate melts/magmas. Therefore, knowledge of the structural changes and the densification mechanisms of the silica glass under high-pressure is particularly important to provide the fundamental constraints on the thermal, chemical, and dynamical states of the Earth's interior. Previous experimental investigations of the highpressure structure of silicate glasses up to a pressure of ~40 GPa strongly suggest that changes in the Si-O coordination number are a key component of the densification mechanism. However, little is known about further densification above ~40 GPa due to experimental challenges and the lack of suitable in-situ structural probes. Acoustic wave velocity measurement is one of the most promising approaches for detecting structural changes of glasses and melts, inasmuch as the sound velocity directly reflects the density and elasticity, regardless of whether a sample is crystalline or amorphous. Our newly developed in-situ high-pressure Brillouin scattering spectroscopic system has recently proven to be highly suitable for exploring the acoustic velocities under ultrahigh-pressure conditions approaching to 200 GPa. Our recent in-situ high-pressure Brillouin scattering results for several silicate glasses at pressures above 200 GPa have revealed an anomalous increase in the effect of pressure on velocity at ~130-140 GPa. We infer this to be a new transition to a denser structure that is likely associated with the onset of a change in Si-O coordination number to higher than sixfold. However, the change in acoustic wave velocity profile as a function of pressure only indicates

  7. Study of interaction in silica glass via model potential approach

    NASA Astrophysics Data System (ADS)

    Mann, Sarita; Rani, Pooja

    2016-05-01

    Silica is one of the most commonly encountered substances in daily life and in electronics industry. Crystalline SiO2 (in several forms: quartz, cristobalite, tridymite) is an important constituent of many minerals and gemstones, both in pure form and mixed with related oxides. Cohesive energy of amorphous SiO2 has been investigated via intermolecular potentials i.e weak Van der Waals interaction and Morse type short-range interaction. We suggest a simple atom-atom based Van der Waals as well as Morse potential to find cohesive energy of glass. It has been found that the study of silica structure using two different model potentials is significantly different. Van der Waals potential is too weak (P.E =0.142eV/molecule) to describe the interaction between silica molecules. Morse potential is a strong potential, earlier given for intramolecular bonding, but if applied for intermolecular bonding, it gives a value of P.E (=-21.92eV/molecule) to appropriately describe the structure of silica.

  8. Chemical treatment for silica-containing glass surfaces

    DOEpatents

    Grabbe, A.; Michalske, T.A.; Smith, W.L.

    1998-04-07

    Dehydroxylated, silica-containing, glass surfaces are known to be at least partially terminated by strained siloxane rings. According to the invention, a surface of this kind is exposed to a selected silane compound or mixture of silane compounds under reaction-promoting conditions. The ensuing reaction results in opening of the strained siloxane rings, and termination of surface atoms by chemical species, such as organic or organosilicon species, having desirable properties. These species can be chosen to provide qualities such as hydrophobicity, or improved coupling to a polymeric coating. 11 figs.

  9. Chemical treatment for silica-containing glass surfaces

    DOEpatents

    Grabbe, Alexis; Michalske, Terry Arthur; Smith, William Larry

    1999-01-01

    Dehydroxylated, silica-containing, glass surfaces are known to be at least partially terminated by strained siloxane rings. According to the invention, a surface of this kind is exposed to a selected silane compound or mixture of silane compounds under reaction-promoting conditons. The ensuing reaction results in opening of the strained siloxane rings, and termination of surface atoms by chemical species, such as organic or organosilicon species, having desirable properties. These species can be chosen to provide qualities such as hydrophobicity, or improved coupling to a polymeric coating.

  10. Chemical treatment for silica-containing glass surfaces

    DOEpatents

    Grabbe, Alexis; Michalske, Terry Arthur; Smith, William Larry

    1999-01-01

    Dehydroxylated, silica-containing, glass surfaces are known to be at least partially terminated by strained siloxane rings. According to the invention, a surface of this kind is exposed to a selected silane compound or mixture of silane compounds under reaction-promoting conditions. The ensuing reaction results in opening of the strained siloxane rings, and termination of surface atoms by chemical species, such as organic or organosilicon species, having desirable properties. These species can be chosen to provide qualities such as hydrophobicity, or improved coupling to a polymeric coating.

  11. Chemical treatment for silica-containing glass surfaces

    DOEpatents

    Grabbe, Alexis; Michalske, Terry Arthur; Smith, William Larry

    1998-01-01

    Dehydroxylated, silica-containing, glass surfaces are known to be at least partially terminated by strained siloxane rings. According to the invention, a surface of this kind is exposed to a selected silane compound or mixture of silane compounds under reaction-promoting conditions. The ensuing reaction results in opening of the strained siloxane rings, and termination of surface atoms by chemical species, such as organic or organosilicon species, having desirable properties. These species can be chosen to provide qualities such as hydrophobicity, or improved coupling to a polymeric coating.

  12. Chemical treatment for silica-containing glass surfaces

    SciTech Connect

    Grabbe, A.; Michalske, T.A.; Smith, W.L.

    1999-12-07

    Dehydroxylated, silica-containing, glass surfaces are known to be at least partially terminated by strained siloxane rings. According to the invention, a surface of this kind is exposed to a selected silane compound or mixture of silane compounds under reaction-promoting conditions. The ensuing reaction results in opening of the strained siloxane rings, and termination of surface atoms by chemical species, such as organic or organosilicon species, having desirable properties. These species can be chosen to provide qualities such as hydrophobicity, or improved coupling to a polymeric coating.

  13. Chemical treatment for silica-containing glass surfaces

    SciTech Connect

    Grabbe, A.; Michalske, T.A.; Smith, W.L.

    1999-10-12

    Dehydroxylated, silica-containing, glass surfaces are known to be at least partially terminated by strained siloxane rings. According to the invention, a surface of this kind is exposed to a selected silane compound or mixture of silane compounds under reaction-promoting conditions. The ensuing reaction results in opening of the strained siloxane rings, and termination of surface atoms by chemical species, such as organic or organosilicon species, having desirable properties. These species can be chosen to provide qualities such as hydrophobicity, or improved coupling to a polymeric coating.

  14. Chemical treatment for silica-containing glass surfaces

    SciTech Connect

    Grabbe, A.; Michalske, T.A.; Smith, W.L.

    1999-11-16

    Dehydroxylated, silica-containing, glass surfaces are known to be at least partially terminated by strained siloxane rings. According to the invention, a surface of this kind is exposed to a selected silane compound or mixture of silane compounds under reaction-promoting conditions. The ensuing reaction results in opening of the strained siloxane rings, and termination of surface atoms by chemical species, such as organic or organosilicon species, having desirable properties. These species can be chosen to provide qualities such as hydrophobicity, or improved coupling to a polymeric coating.

  15. Atmospheric Pressure Chemical Vapor Deposition of High Silica SiO2-TiO2 Antireflective Thin Films for Glass Based Solar Panels

    SciTech Connect

    Klobukowski, Erik R; Tenhaeff, Wyatt E; McCamy, James; Harris, Caroline; Narula, Chaitanya Kumar

    2013-08-30

    The atmospheric pressure chemical vapor deposition (APCVD) of SiO2-TiO2 thin films employing [[(tBuO)3Si]2O-Ti(OiPr)2], which can be prepared from commercially available materials, results in antireflective thin films on float glass under industrially relevant manufacturing conditions. It was found that while the deposition temperature had an effect on the SiO2:TiO2 ratio, the thickness was dependent on the time of deposition. This study shows that it is possible to use APCVD employing a single source precursor containing titanium and silicon to produce thin films on float glass with high SiO2:TiO2 ratios.

  16. Characteristics of waste automotive glasses as silica resource in ferrosilicon synthesis.

    PubMed

    Farzana, Rifat; Rajarao, Ravindra; Sahajwalla, Veena

    2016-02-01

    This fundamental research on end-of-life automotive glasses, which are difficult to recycle, is aimed at understanding the chemical and physical characteristics of waste glasses as a resource of silica to produce ferrosilicon. Laboratory experiments at 1550°C were carried out using different automotive glasses and the results compared with those obtained with pure silica. In situ images of slag-metal separation showed similar behaviour for waste glasses and silica-bearing pellets. Though X-ray diffraction (XRD) showed different slag compositions for glass and silica-bearing pellets, formation of ferrosilicon was confirmed. Synthesized ferrosilicon alloy from waste glasses and silica were compared by Raman, X-ray photoelectron spectroscopy and scanning electron microscopy (SEM) analysis. Silicon concentration in the synthesized alloys showed almost 92% silicon recovery from the silica-bearing pellet and 74-92% silicon recoveries from various waste glass pellets. The polyvinyl butyral (PVB) plastic layer in the windshield glass decomposed at low temperature and did not show any detrimental effect on ferrosilicon synthesis. This innovative approach of using waste automotive glasses as a silica source for ferrosilicon production has the potential to create sustainable pathways, which will reduce specialty glass waste in landfill. PMID:26628051

  17. Mechanical Properties of a High Lead Glass Used in the Mars Organic Molecule Analyzer

    NASA Technical Reports Server (NTRS)

    Salem, Jonathan A.; Smith, Nathan A.; Ersahin, Akif

    2015-01-01

    The elastic constants, strength, fracture toughness, slow crack growth parameters, and mirror constant of a high lead glass supplied as tubes and funnels were measured using ASTM International (formerly ASTM, American Society for Testing and Materials) methods and modifications thereof. The material exhibits lower Young's modulus and slow crack growth exponent as compared to soda-lime silica glass. Highly modified glasses exhibit lower fracture toughness and slow crack growth exponent than high purity glasses such as fused silica.

  18. High-temperature glass and glass coatings

    NASA Technical Reports Server (NTRS)

    Goldstein, H. E.; Katvala, V. E.; Leiser, D. B.

    1977-01-01

    Reaction-cured glasses resist thermal shock and maintain properties over range of -100 degrees Centrigrade to +1,480 degrees Centigrade. Stability makes these excellent materials for high-temperature glassware and tubing or as coatings for porous materials.

  19. Cooling rate and stress relaxation in silica melts and glasses via microsecond molecular dyanmics

    SciTech Connect

    Lane, J. Matthew D.

    2015-07-22

    We have conducted extremely long molecular dynamics simulations of glasses to microsecond times, which close the gap between experimental and atomistic simulation time scales by two to three orders of magnitude. The static, thermal, and structural properties of silica glass are reported for glass cooling rates down to 5×109 K/s and viscoelastic response in silica melts and glasses are studied over nine decades of time. We finally present results from relaxation of hydrostatic compressive stress in silica and show that time-temperature superposition holds in these systems for temperatures from 3500 to 1000 K.

  20. Cooling rate and stress relaxation in silica melts and glasses via microsecond molecular dyanmics

    DOE PAGESBeta

    Lane, J. Matthew D.

    2015-07-22

    We have conducted extremely long molecular dynamics simulations of glasses to microsecond times, which close the gap between experimental and atomistic simulation time scales by two to three orders of magnitude. The static, thermal, and structural properties of silica glass are reported for glass cooling rates down to 5×109 K/s and viscoelastic response in silica melts and glasses are studied over nine decades of time. We finally present results from relaxation of hydrostatic compressive stress in silica and show that time-temperature superposition holds in these systems for temperatures from 3500 to 1000 K.

  1. Synthesis of thiazole silica hybrid from waste glass for adsorption of cadmium(II)

    NASA Astrophysics Data System (ADS)

    Azmiyawati, C.; TaslimahVirkyanov

    2016-02-01

    Synthesis of thiazole silica hybrid from waste glass to adsorption of cadmium (II) metal ion has been performed. The synthesis was done by attaching thiazole group through liaison compound γ- glycidoxy propyl tri-methoxy silane with silica gel obtained from waste glass. In this study, the effect of adsorption contact time and the concentration of cadmium (II) was studied to determine the reaction rate and the amount of adsorption thermodynamics. The existence of the cluster thiazole on silica gel indicated by IR spectra at wavelengths around 2576 cm-1 of mercaptan groups that previously did not appear on silica gel without modification. The synthesized TSH showed a high adsorption capacity of 9.363 mmol/g of Cd(II). The adsorption isotherm obtained with Langmuir isotherm model gives the negative values of ΔG°, i.e. -15.488 kJ/mol for Cd(II), indicating the spontaneous process of adsorption. Kinetic studies showed that the adsorption of Cd(II) ion into TSH follows the pseudo-second-order kinetics.

  2. The Urbach tail in silica glass from first principles

    SciTech Connect

    Sadigh, B; Erhart, P; Aberg, D; Trave, A; Schwegler, E; Bude, J

    2010-06-15

    We present density-functional theory calculations of the optical absorption spectra of silica glass for temperatures up to 2400K. The calculated spectra exhibit exponential tails near the fundamental absorption edge that follow the Urbach rule, in quantitative agreement with experiments. We discuss the accuracy of our results by comparing to hybrid exchange correlation functionals. We derive a simple relationship between the exponential tails of the absorption coefficient and the electronic density-of-states, and thereby establish a direct link between the photoemission and the absorption spectra near the absorption edge. We use this relationship to determine the lower bound to the Urbach frequency regime. We show that in this frequency interval, the optical absorption is Poisson distributed with very large statistical fluctuations. We determine the upper bound to the Urbach frequency regime by identifying the frequency at which transition to Poisson distribution takes place.

  3. The Glass Transition at Silica/PMMA Nanocomposite Interfaces

    NASA Astrophysics Data System (ADS)

    Ozisik, Rahmi; Parker, Katelyn; Schneider, Ryan T.; Siegel, Richard W.; Cabanelas, Juan Carlos; Serrano, Berna; Antonelli, Claire; Baselga, Juan

    2011-03-01

    Local glass transition temperatures (Tg) have been measured in the interfaces of solution blended silica/poly(methyl methacrylate) (PMMA) nanocomposites using florescence spectroscopy and compared with Tg measured by differential scanning calorimetry (DSC). It was found that the two types of measurements yielded significantly different information. Combinations of silanes and poly(propylene glycol)- based molecular spacers bound to fluorophores were covalently linked to the surface of the nanoparticles, allowing for variation of the fluorophore response with respect to the distance from the nanofiller surface. Increases in the bulk Tg from the neat PMMA value were found upon the addition of nanofillers, but were independent of the nanofiller concentration when the filler concentration was above 2% by weight. Furthermore, as the size of the grafted molecular spacer was increased, Tg values were found to decrease and approach Tg of the neat PMMA. Owing to variable conformations of the spacers, an effective distribution of fluorophore-silica distances exists, which influences the fluorophores' response to the transition. Supported by NSF (CMMI-0500324) and CICYT (MAT 2007-63722).

  4. Effect of fictive temperature on dynamic fatigue behavior of silica and soda-lime glasses

    SciTech Connect

    Li, H.; Agarwal, A.; Tomozawa, Minoru

    1995-05-01

    The dynamic fatigue characteristics of silica glasses with fictive temperatures of 1,000, 1,100, and 1,300 C and soda-lime glasses with fictive temperatures of 470 and 530 C were measured in air. For both glasses, samples with higher fictive temperatures had a greater fatigue resistance. Inert strength of silica glasses with fictive temperatures of 1,000 and 1,300 C was also measured at liquid nitrogen temperature. Glass with higher fictive temperature had a greater inert strength.

  5. Observation of voids and optical seizing of voids in silica glass with infrared femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Watanabe, Wataru; Toma, Tadamasa; Yamada, Kazuhiro; Nishii, Junji; Hayashi, Ken-ichi; Itoh, Kazuyoshi

    2000-11-01

    Many researchers have investigated the interaction of femtosecond laser pulses with a wide variety of materials. The structural modifications both on the surface and inside the bulk of transparent materials have been demonstrated. When femtosecond laser pulses are focused into glasses with a high numerical-aperture objective, voids are formed. We demonstrate that one can seize and move voids formed by femtosecond laser pulses inside silica glass and also merge two voids into one. We also present clear evidence that a void is a cavity by showing a scanning-electron-microscope image of cleft voids: we clove through the glass along a plane that includes the laser-ablated thin line on the surface and the voids formed inside. The optical seizing and merging of voids are important basic techniques for fabricate micro-optical dynamic devices, such as the rewritable 3-D optical storage.

  6. Change in silica sources in Roman and post-Roman glass

    NASA Astrophysics Data System (ADS)

    Aerts, A.; Velde, B.; Janssens, K.; Dijkman, W.

    2003-04-01

    Although Roman and post-Empire glasses found in Europe are reputed to have a very constant composition and hence source of components, it appears that some 4-5th century and later specimens show evidence of a different source of silica (sand) component. Zirconium and titanium are the discriminating elements. Data presented here for 278 specimens from 1st to 4th century German and Belgian samples indicate a strongly homogeneous Zr and Ti content; N: number of analyzed samples while 62 samples from Maastricht show low Zr-Ti contents from 1st to 3rd century samples while 4-5th century samples show a strong trend of concomitant Ti and Zr increase. If the high values of Zr-Ti represent a new source of silica (sand) the trend from low to high content suggests that a significant amount of low Zr-Ti glass was recycled to form these glass objects. Similar high Ti content can be seen in analysis results reported for other but not all 4-5th century samples found in northern Europe while earlier productions show typical low Ti contents. Although the fusing agent for these glasses seems to have always been natron (a mineral deposit in the Nile delta) from Hellenistic times to the 9th century, a change in the silica source, indicated by variation of the Ti and Zr content, could very well reflect the results of political instability of the 4-5th century exemplified by the fragmentation of the Roman Empire into two parts.

  7. Waste vitrification: prediction of acceptable compositions in a lime-soda-silica glass-forming system

    SciTech Connect

    Gilliam, T.M.; Jantzen, C.M.

    1996-10-01

    A model is presented based upon calculated bridging oxygens which allows the prediction of the region of acceptable glass compositions for a lime-soda-silica glass-forming system containing mixed waste. The model can be used to guide glass formulation studies (e.g., treatability studies) or assess the applicability of vitrification to candidate waste streams.

  8. Phosphate glass useful in high power lasers

    DOEpatents

    Hayden, Joseph S.; Sapak, David L.; Ward, Julia M.

    1990-01-01

    A low- or no-silica phosphate glass useful as a laser medium and having a high thermal conductivity, K.sub.90.degree. C. >0.8 W/mK, and a low coefficient of thermal expansion, .alpha..sub.20.degree.-40.degree. C. <80.times.10.sup.-7 /.degree.C., consists essentially of (on a batch composition basis): the amounts of Li.sub.2 O and Na.sub.2 O providing an average alkali metal ionic radius sufficiently low whereby said glass has K.sub.90.degree. C. >0.8 W/mK and .alpha..sub.20.degree.-40.degree. C. <80.times.10.sup.-7 /.degree.C., and wherein, when the batch composition is melted in contact with a silica-containing surface, the final glass composition contains at most about 3.5 mole % of additional silica derived from such contact during melting. The Nd.sub.2 O.sub.3 can be replaced by other lasing species.

  9. Direct imaging of a two-dimensional silica glass on graphene.

    PubMed

    Huang, Pinshane Y; Kurasch, Simon; Srivastava, Anchal; Skakalova, Viera; Kotakoski, Jani; Krasheninnikov, Arkady V; Hovden, Robert; Mao, Qingyun; Meyer, Jannik C; Smet, Jurgen; Muller, David A; Kaiser, Ute

    2012-02-01

    Large-area graphene substrates provide a promising lab bench for synthesizing, manipulating, and characterizing low-dimensional materials, opening the door to high-resolution analyses of novel structures, such as two-dimensional (2D) glasses, that cannot be exfoliated and may not occur naturally. Here, we report the accidental discovery of a 2D silica glass supported on graphene. The 2D nature of this material enables the first atomic resolution transmission electron microscopy of a glass, producing images that strikingly resemble Zachariasen's original 1932 cartoon models of 2D continuous random network glasses. Atomic-resolution electron spectroscopy identifies the glass as SiO(2) formed from a bilayer of (SiO(4))(2-) tetrahedra and without detectable covalent bonding to the graphene. From these images, we directly obtain ring statistics and pair distribution functions that span short-, medium-, and long-range order. Ab initio calculations indicate that van der Waals interactions with graphene energetically stabilizes the 2D structure with respect to bulk SiO(2). These results demonstrate a new class of 2D glasses that can be applied in layered graphene devices and studied at the atomic scale. PMID:22268818

  10. Incorporation, oxidation and pyrolysis of ferrocene into porous silica glass: a route to different silica/carbon and silica/iron oxide nanocomposites.

    PubMed

    Schnitzler, Mariane C; Mangrich, Antônio S; Macedo, Waldemar A A; Ardisson, José D; Zarbin, Aldo J G

    2006-12-25

    This work reports the incorporation of ferrocene into a porous silica glass under ambient temperature and atmosphere. After or during the ferrocene incorporation, the spontaneous formation of ferricinium ions was observed by electron paramagnetic resonance (EPR), UV-visible, X-ray absorption near-edge structure (XANES), and 57Fe Mössbauer measurements. It was shown that the oxidation of ferrocene molecules to ferricinium ions was promoted by air and that the Si-O- groups on the surface of the pores act as counteranions. Pyrolysis of the porous glass/ferricinium material under argon atmosphere and variable temperature yields different glass/carbon nanocomposites, which were subsequently treated with an HF solution in order to remove the glassy fraction. The resulting insoluble carbon materials were characterized by transmission electron microscopy (TEM), Raman, and EPR spectroscopy and consisted of amorphous carbon when the pyrolysis was carried out at 900 or 1000 degrees C and of a mixture of carbon nanotubes and carbonaceous materials at a pyrolysis temperature of 1100 degrees C. When the pyrolysis was conducted under air, the incorporated ferricinium forms alpha-Fe2O3, and the resulting material is a transparent and highly homogeneous glass/iron oxide nanocomposite. PMID:17173419

  11. Fabrication and characterization of bioactive glass-ceramic using soda-lime-silica waste glass.

    PubMed

    Abbasi, Mojtaba; Hashemi, Babak

    2014-04-01

    Soda-lime-silica waste glass was used to synthesize a bioactive glass-ceramic through solid-state reactions. In comparison with the conventional route, that is, the melt-quenching and subsequent heat treatment, the present work is an economical technique. Structural and thermal properties of the samples were examined by X-ray diffraction (XRD) and differential thermal analysis (DTA). The in vitro test was utilized to assess the bioactivity level of the samples by Hanks' solution as simulated body fluid (SBF). Bioactivity assessment by atomic absorption spectroscopy (AAS) and scanning electron microscopy (SEM) was revealed that the samples with smaller amount of crystalline phase had a higher level of bioactivity. PMID:24582266

  12. Wettability of modified silica layers deposited on glass support activated by plasma

    NASA Astrophysics Data System (ADS)

    Terpiłowski, Konrad; Rymuszka, Diana; Goncharuk, Olena V.; Sulym, Iryna Ya.; Gun'ko, Vladimir M.

    2015-10-01

    Fumed silica modified by hexamethyldisilazane [HDMS] and polydimethylsiloxane [PDMS] was dispersed in a polystyrene/chloroform solution. To increase adhesion between deposited silica layers and a glass surface, the latter was pretreated with air plasma for 30 s. The silica/polystyrene dispersion was deposited on the glass support using a spin coater. After deposition, the plates were dried in a desiccator for 24 h. Water advancing and receding contact angles were measured using the tilted plate method. The apparent surface free energy (γS) was evaluated using the contact angle hysteresis approach. The surface topography was determined using the optical profilometry method. Contact angles changed from 59.7° ± 4.4 (at surface coverage with trimethylsilyl groups Θ = 0.14) to 155° ± 3.1 at Θ = 1. The value of γS decreased from 51.3 ± 2.8 mJ/m2 (for the sample at the lowest value of Θ) to 1.0 ± 0.4 mJ/m2 for the most hydrophobic sample. Thus, some systems with a high degree of modification by HDMS showed superhydrophobicity, and the sliding angle amounted to about 16° ± 2.1.

  13. Heat accumulation regime of femtosecond laser writing in fused silica and Nd:phosphate glass

    NASA Astrophysics Data System (ADS)

    Bukharin, M. A.; Khudyakov, D. V.; Vartapetov, S. K.

    2015-04-01

    We investigated refractive index induced by direct femtosecond laser writing inside fused silica and Nd:phosphate glass in heat accumulation regime. Spatial profile and magnitude of induced refractive index were investigated at various pulse repetition rates and translation velocities. It was shown that the magnitude of induced refractive index significantly rises with decreasing in time interval between successive laser pulses below the time for thermal diffusion. Going from nonthermal regime to heat accumulation regime, we achieved induced refractive index growth from 4 × 10-3 up to 6.5 × 10-3 in fused silica and from -6 × 10-3 to -9 × 10-3 in Nd:phosphate glass. Aspect ratio of treated area decreased from 2.1 down to less than 1.5 without correcting optical elements. It was shown that in heat accumulation regime, the treated area was surrounded by region of alternatively changed refractive index with significant magnitude up to -2 × 10-3. Wide regions of decreased refractive index enable fabrication of depressed cladding waveguides. We demonstrated low-loss (0.3 dB/cm) tubular waveguide inside fused silica. For orthogonal polarizations of guiding light, we achieved a small difference between losses as 0.1 dB/cm using highly symmetric written tracks forming the cladding. The desired structure was simulated with the beam propagation method, and the results were in good agreement with experiment data.

  14. Silica through the eyes of colloidal models—when glass is a gel

    NASA Astrophysics Data System (ADS)

    Saika-Voivod, Ivan; King, Heather Marie; Tartaglia, Piero; Sciortino, Francesco; Zaccarelli, Emanuela

    2011-07-01

    We perform molecular dynamics simulations of 'floating bond' (FB) models of network-forming liquids and compare the structure and dynamics against the BKS model of silica (van Beest et al 1990 Phys. Rev. Lett. 64 1955), with the aim of gaining a better understanding of glassy silica in terms of the variety of non-ergodic states seen in colloids. At low densities, all the models form tetrahedral networks. At higher densities, tailoring the FB model to allow a higher number of bonds does not capture the structure seen in BKS. Upon rescaling the time and length in order to compare mean squared displacements between models, we find that there are significant differences in the temperature dependence of the diffusion coefficient at high density. Additionally, the FB models show a greater range in variability in the behavior of the non-ergodicity parameter and caging length, quantities used to distinguish colloidal gels and glasses. Hence, we find that the glassy behavior of BKS silica can be interpreted as a 'gel' at low densities, with only a marginal gel-to-glass crossover at higher densities.

  15. Mechanism of mechanical fatigue of silica glass. Final technical report, July 1985--June 1995

    SciTech Connect

    Tomozawa, M.

    1995-08-01

    Objective is to study the static fatigue mechanism of silica glasses such as optical communication fibers. It is shown that the strength increase by thermal or hydrothermal treatment can be explained by formation of blunt crack tips. Specimens with blunt cracks exhibited fatigue only in water and NH3. While fatigue of glasses with sharp cracks involves only crack propagation, that of glasses with blunt cracks involves both crack initiation and propagation. Nonaqueous liquids can be adsorbed on the glass surface only, thus can aid crack propagation only. Water/NH3 can exhibit both adsorption and diffusion, and the ability of water to initiate a crack appears related to its diffusion into the glass. Mechanical fatigue of pristine silica fibers takes place in water but is not expected in nonaqueous liquids. Water entry into silica glass is accelerated by applied stress. Water entry (diffusion) into silica glasses at low temperatures was found closely coupled with structural relaxation of the glass, which lowers the fictive temperature. The relaxation can be monitored by simple IR spectroscopy; IR absorbance measures the fictive temperature over the entire thickness while IR reflection measures that of the surface. By combining IR reflection peak position measurement and successive etching, the depth profile of the fictive temperature can be determined. This was done in a communication fiber and in a specimen heat treated below the glass transition temperature. Glasses with higher fictive temperatures exhibit greater fatigue resistance.

  16. High-performance liquid chromatographic determination of mitoxantrone in plasma utilizing non-bonded silica gel for solid-phase isolation to reduce adsorptive losses on glass during sample preparation.

    PubMed

    Lin, K T; Rivard, G E; Leclerc, J M

    1989-03-10

    Mitoxantrone, a highly active antineoplastic agent, was found to bind strongly to non-bonded silica gel and glassware. When a Hamilton syringe was used to load and inject a mitoxantrone solution (0.4 microgram/ml in water) on to a high-performance liquid chromatographic (HPLC) system, about 95% of the loaded compound was found to bind to the glass surface of the syringe barrel and could not be removed by rinsing with water. It could, however, be removed slowly with an acidic solution and thus a small peak of mitoxantrone was present on the chromatogram whenever a blank acidic solution was injected with the syringe. The bound mitoxantrone could be removed effectively from the syringe surface with a solution of tetramethylammonium chloride, citric acid, methanol and water (elution solvent). This binding introduces a large error in assay results and might be one of the major factors responsible for contradictory pharmacokinetic data that have been reported. A new plasma preparation scheme and an HPLC method for mitoxantrone were developed to address this binding problem. Mitoxantrone was extracted directly from plasma samples with a plastic mini-column packed with non-bonded silica gel and eluted with the above elution solvent. The eluent was analysed by HPLC on an ODS column with an absorbance detector at 658 nm. The mobile phase was 0.1 M triethylamine phosphate (pH 3.0) in water-tetrahydrofuran-methanol (69:1:30) containing 0.02 M tetramethylammonium chloride. Methylene blue was added as an internal standard. Preliminary results showed that mitoxantrone levels in human plasma followed a triphasic decay curve after an intravenous bolus injection. The terminal elimination half-lives measured in three patients (mean t1/2 gamma = 25 min) were all shorter than the published values which ranged from 56 min to 9 days. PMID:2540217

  17. Optical fibers from sol-gel-derived germania-silica glasses

    NASA Astrophysics Data System (ADS)

    Kirkbir, Fikret; Chaudhuri, S. R.

    1992-12-01

    Step index multimode optical fibers were successfully drawn from germania doped silica rods prepared by sol-gel process. The fiber, drawn using rod-in-tube technique, had a 100 micron core with a pure silica cladding of 140 micron. The numerical aperture of the fiber was 0.21. Initial experimental results indicate an attenuation of 20 dB/km at 850 nm wavelength. Precursors used for sol preparation were tetraethyl orthosilicate, Si(OC2H5)4 and tetraethyl orthogermanate, Ge(OC2H5)4. Clear wet gels were routinely produced without any problem of premature precipitation of germanium dioxide even at high dopant concentration levels. The gels were dried by supercritical drying technique. Dry gels were consolidated to clear glass samples routinely at a temperature of 1300 degree(s)C. Fiber was drawn from these rods at a temperature of 1800 degree(s)C. The sintering parameters, i.e., type of gas flow at different steps of the sintering operation, duration of such steps and temperature were optimized to eliminate reboil of the glass above 1800 degree(s)C, resulting in bubble-free glass fibers.

  18. Glass formation, properties and structure of soda-yttria-silica glasses

    NASA Technical Reports Server (NTRS)

    Angel, Paul W.; Hann, Raiford E.

    1992-01-01

    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.

  19. Cerium-activated sol–gel silica glasses for radiation dosimetry in harsh environment

    NASA Astrophysics Data System (ADS)

    El Hamzaoui, Hicham; Capoen, Bruno; Helou, Nissrine Al; Bouwmans, Géraud; Ouerdane, Youcef; Boukenter, Aziz; Girard, Sylvain; Marcandella, Claude; Duhamel, Olivier; Chadeyron, Geneviève; Mahiou, Rachid; Bouazaoui, Mohamed

    2016-04-01

    Cerium-doped silica glass has been prepared for ionizing radiation dosimetry applications, using the sol–gel route and densification under different atmospheres. In comparison with the glass densified under air atmosphere, the one obtained after sintering the xerogel under helium gas presents improved optical properties, with an enhancement of the photoluminescence quantum yield up to 33%, which is attributed to a higher Ce3+ ions concentration. Such a glassy rod has been jacketed in a quartz tube and then drawn at high temperature to a cane, which has been used as active material in a fibered remote x-ray radiation dosimeter. The sample exhibited a reversible linear radioluminescence intensity response versus the dose rate up to 30 Gy s‑1. These results confirm the potentialities of this material for in vivo or high rate dose remote dosimetry measurements.

  20. Radiation hardening in sol-gel derived Er{sup 3+}-doped silica glasses

    SciTech Connect

    Hari Babu, B. E-mail: matthieu.lancry@u-psud.fr; León Pichel, Mónica; Ollier, Nadège; El Hamzaoui, Hicham; Bigot, Laurent; Savelii, Inna; Bouazaoui, Mohamed; Poumellec, Bertrand; Lancry, Matthieu E-mail: matthieu.lancry@u-psud.fr; Ibarra, Angel

    2015-09-28

    The aim of the present paper is to report the effect of radiation on the Er{sup 3+}-doped sol-gel silica glasses. A possible application of these sol-gel glasses could be their use in harsh radiation environments. The sol-gel glasses are fabricated by densification of erbium salt-soaked nanoporous silica xerogels through polymeric sol-gel technique. The radiation-induced attenuation of Er{sup 3+}-doped sol-gel silica is found to increase with erbium content. Electron paramagnetic resonance studies reveal the presence of E′{sub δ} point defects. This happens in the sol-gel aluminum-silica glass after an exposure to γ-rays (kGy) and in sol-gel silica glass after an exposure to electrons (MGy). The concentration levels of these point defects are much lower in γ-ray irradiated sol-gel silica glasses. When the samples are co-doped with Al, the exposure to γ-ray radiation causes a possible reduction of the erbium valence from Er{sup 3+} to Er{sup 2+} ions. This process occurs in association with the formation of aluminum oxygen hole centers and different intrinsic point defects.

  1. Colloid formation in copper-implanted fused silica and silicate glasses

    SciTech Connect

    Mazzoldi, P.; Caccavale, F.; Cattaruzza, E.

    1993-12-31

    Copper implantations (90 keV, 5{times}10{sup 16} ions/cm{sup 2}) were made into fused silica, borosilicate glasses and soda-lime glass. The copper distribution has been found to vary according to glass type. The optical absorption band characteristic of the implanted metal optical properties was observed only for copper-implanted fused silica. Absorption for all the other samples was either not observable or was negligibly small, however very small metallic particles are present also in soda-lime glass. Subsequent nitrogen implantation (100 keV, 1.5{times}10{sup 17} ions/cm{sup 2}) completely eliminated the copper-colloid induced absorption in the copper-implanted fused silica, while it facilitated formation of copper-colloids in soda-lime glass.

  2. Raman measurements in silica glasses irradiated with energetic ions

    SciTech Connect

    Saavedra, R. Martin, P.; Vila, R.; León, M.; Jiménez-Rey, D.; Girard, S.; Boukenter, A.; Ouerdane, Y.

    2014-10-21

    Ion irradiation with energetic He{sup +} (2.5 MeV), O{sup 4+} (13.5 MeV), Si{sup 4+} (24.4 MeV) and Cu{sup 7+} (32.6 MeV) species at several fluences (from 5 × 10{sup 12} to 1.65 × 10{sup 15} ion/cm{sup 2}) were performed in three types of SiO{sub 2} glasses with different OH content (KU1, KS-4V and Infrasil 301). After ion implantation the Raman spectra were measured and compared with the spectra of unirradiated samples. Irradiated samples of the three fused silica grades exhibit changes in the broad and asymmetric R-band (ω{sub 1} around 445 cm{sup −1}), in D{sub 1} (490 cm−1) and D{sub 2} (605 cm{sup −1}) bands associated to small-membered rings. The D{sub 2} band shows an increase with increasing fluences for different ions, indicating structural changes. Raman spectra of ion-irradiated samples were compared with the spectra of neutron irradiated samples at fluences 10{sup 17} n/cm{sup 2} and 1018 n/cm{sup 2}. Macroscopic surface cracking was detected, mainly at fluences corresponding to deposited energies between 10{sup 23} eV/cm{sup 3} and 10{sup 24} eV/cm{sup 3} (after ion beam shutdown)

  3. High purity silica reflecting heat shield development

    NASA Technical Reports Server (NTRS)

    Congdon, W.

    1974-01-01

    A reflecting heat shield composed of fused silica in which the scattering results from the refractive index mismatch between silica particles and the voids introduced during the fabrication process is developed. Major considerations and conclusions of the development are: the best material to use is Type A, which is capable of ultra-high-purity and which does not show the 0.243 micrometer absorption band; the reflection efficiency of fused silica is decreased at higher temperatures due to the bathochromic shift of the ultraviolet cut-off; for a given silica material, over the wavelength region and particle sizes tested, the monodisperse particle size configurations produce higher reflectances than continuous particle size configurations; and the smaller monodisperse particle size configurations give higher reflectance than the larger ones. A reflecting silica configuration that is an efficient reflector of shock layer radiation at high ablation temperatures is achieved by tailoring the matrix for optimum scattering and using an ultra-high-purity material.

  4. Computer Models of Micrometeoroid Impact on Fused Silica Glass Mirrors

    NASA Technical Reports Server (NTRS)

    Davison, David; Cour-Palais, Burton; Quan, X.; Holmquist, T. J.; Cohen, Lester; Ramsey, Ron; Cummings, Ramona; Hadaway, James (Technical Monitor)

    2002-01-01

    For the first (low energy) calculation both the particle and crater parameters (from tests at AU/HIF) were known, For the second (high energy) calculation, only the particle parameters were known. In both cases the computed craters agreed with historical data of impact on glass. Additional tests at AU/HIF are expected to confirm the results of the second calculation and to validate the technique for use at higher velocities.

  5. Target dependent femtosecond laser plasma implantation dynamics in enabling silica for high density erbium doping.

    PubMed

    Chandrappan, Jayakrishnan; Murray, Matthew; Kakkar, Tarun; Petrik, Peter; Agocs, Emil; Zolnai, Zsolt; Steenson, D P; Jha, Animesh; Jose, Gin

    2015-01-01

    Chemical dissimilarity of tellurium oxide with silica glass increases phase separation and crystallization tendency when mixed and melted for making a glass. We report a novel technique for incorporating an Er(3+)-doped tellurite glass composition into silica substrates through a femtosecond (fs) laser generated plasma assisted process. The engineered material consequently exhibits the spectroscopic properties of Er(3+)-ions, which are unachievable in pure silica and implies this as an ideal material for integrated photonics platforms. Formation of a well-defined metastable and homogeneous glass structure with Er(3+)-ions in a silica network, modified with tellurite has been characterized using high-resolution cross-sectional transmission electron microscopy (HRTEM). The chemical and structural analyses using HRTEM, Rutherford backscattering spectrometry (RBS) and laser excitation techniques, confirm that such fs-laser plasma implanted glasses may be engineered for significantly higher concentration of Er(3+)-ions without clustering, validated by the record high lifetime-density product 0.96 × 10(19) s.cm(-3). Characterization of planar optical layers and photoluminescence emission spectra were undertaken to determine their thickness, refractive indices and photoluminescence properties, as a function of Er(3+) concentration via different target glasses. The increased Er(3+) content in the target glass enhance the refractive index and photoluminescence intensity of the modified silica layer whilst the lifetime and thickness decrease. PMID:26370060

  6. Target dependent femtosecond laser plasma implantation dynamics in enabling silica for high density erbium doping

    NASA Astrophysics Data System (ADS)

    Chandrappan, Jayakrishnan; Murray, Matthew; Kakkar, Tarun; Petrik, Peter; Agocs, Emil; Zolnai, Zsolt; Steenson, D. P.; Jha, Animesh; Jose, Gin

    2015-09-01

    Chemical dissimilarity of tellurium oxide with silica glass increases phase separation and crystallization tendency when mixed and melted for making a glass. We report a novel technique for incorporating an Er3+-doped tellurite glass composition into silica substrates through a femtosecond (fs) laser generated plasma assisted process. The engineered material consequently exhibits the spectroscopic properties of Er3+-ions, which are unachievable in pure silica and implies this as an ideal material for integrated photonics platforms. Formation of a well-defined metastable and homogeneous glass structure with Er3+-ions in a silica network, modified with tellurite has been characterized using high-resolution cross-sectional transmission electron microscopy (HRTEM). The chemical and structural analyses using HRTEM, Rutherford backscattering spectrometry (RBS) and laser excitation techniques, confirm that such fs-laser plasma implanted glasses may be engineered for significantly higher concentration of Er3+-ions without clustering, validated by the record high lifetime-density product 0.96 × 1019 s.cm-3. Characterization of planar optical layers and photoluminescence emission spectra were undertaken to determine their thickness, refractive indices and photoluminescence properties, as a function of Er3+ concentration via different target glasses. The increased Er3+ content in the target glass enhance the refractive index and photoluminescence intensity of the modified silica layer whilst the lifetime and thickness decrease.

  7. Target dependent femtosecond laser plasma implantation dynamics in enabling silica for high density erbium doping

    PubMed Central

    Chandrappan, Jayakrishnan; Murray, Matthew; Kakkar, Tarun; Petrik, Peter; Agocs, Emil; Zolnai, Zsolt; Steenson, D.P.; Jha, Animesh; Jose, Gin

    2015-01-01

    Chemical dissimilarity of tellurium oxide with silica glass increases phase separation and crystallization tendency when mixed and melted for making a glass. We report a novel technique for incorporating an Er3+-doped tellurite glass composition into silica substrates through a femtosecond (fs) laser generated plasma assisted process. The engineered material consequently exhibits the spectroscopic properties of Er3+-ions, which are unachievable in pure silica and implies this as an ideal material for integrated photonics platforms. Formation of a well-defined metastable and homogeneous glass structure with Er3+-ions in a silica network, modified with tellurite has been characterized using high-resolution cross-sectional transmission electron microscopy (HRTEM). The chemical and structural analyses using HRTEM, Rutherford backscattering spectrometry (RBS) and laser excitation techniques, confirm that such fs-laser plasma implanted glasses may be engineered for significantly higher concentration of Er3+-ions without clustering, validated by the record high lifetime-density product 0.96 × 1019 s.cm−3. Characterization of planar optical layers and photoluminescence emission spectra were undertaken to determine their thickness, refractive indices and photoluminescence properties, as a function of Er3+ concentration via different target glasses. The increased Er3+ content in the target glass enhance the refractive index and photoluminescence intensity of the modified silica layer whilst the lifetime and thickness decrease. PMID:26370060

  8. Lattice dynamics of α-cristobalite and the Boson peak in silica glass

    NASA Astrophysics Data System (ADS)

    Wehinger, Björn; Bosak, Alexeï; Refson, Keith; Mirone, Alessandro; Chumakov, Aleksandr; Krisch, Michael

    2015-08-01

    The lattice dynamics of the silica polymorph α -cristobalite has been investigated by a combination of diffuse and inelastic x-ray scattering and ab initio lattice dynamics calculations. Phonon dispersion relations and vibrational density of states are reported and the phonon eigenvectors analyzed by a detailed comparison of scattering intensities. The experimentally validated calculation is used to identify the vibration contributing most to the first peak in the density of vibrational states. The comparison of its displacement pattern to the silica polymorphs α -quartz and coesite and to vitreous silica reveals a distinct similarity and allows for decisive conclusions on the vibrations causing the so-called Boson peak in silica glass.

  9. In-depth survey report of silica flour dust during packing, transfer, and shipping at the Central Silica Company, Glass Rock Plant, Glass Rock, Ohio

    SciTech Connect

    Caplan, P.E.; Reed, L.D.; Amendola, A.A.; Cooper, T.C.

    1981-12-01

    A visit was made to the Central Silica Company, Glass Rock, Ohio to evaluate methods used to control employee exposure to silica dust. The control methods at this company included careful handling and transfer of damp materials, exhaust ventilation, good housekeeping procedures, and the use of respiratory protection. Evaluations were made of the packing area, transfer point, inside loading trucks, and ambient air at sections of the flour building. Control systems included a good exhaust-ventilation system and four ventilation hoods. Evaluations were made of samples collected by an MSA gravimeter dust sampler, the Del High volume electrostatic precipitation, and bulk and rafter samples. Dust control methods appeared to be effective due to the existence of good engineering controls, good work practices, and an effective respiratory protection program. Additional control measures included the handling of the ore as a damp material, thus reducing the generation of dust particles. Outside dust sources were being reduced. Most of the product was shipped in bulk. Plastic wrapping was used around pallet loads to reduce bag breakage and dust dispersion. A filtered air system controlled low dust levels in the Pebble Mill control room. Enclosed screens operated under negative pressure separated fine from coarse product at the process building.

  10. High modulus high temperature glass fibers

    NASA Technical Reports Server (NTRS)

    Bacon, J. F.

    1973-01-01

    The search for a new high-modulus, high-temperature glass fiber involved the preparation of 500 glass compositions lying in 12 glass fields. These systems consisted primarily of low atomic number oxides and rare-earth oxides. Direct optical measurements of the kinetics of crystallization of the cordierite-rare earth system, for example, showed that the addition of rare-earth oxides decreased the rate of formation of cordierite crystals. Glass samples prepared from these systems proved that the rare-earth oxides made large specific contributions to the Young's modulus of the glasses. The best glasses have moduli greater than 21 million psi, the best glass fibers have moduli greater than 18 million psi, and the best glass fiber-epoxy resin composites have tensile strengths of 298,000 psi, compressive strengths of at least 220,000 psi, flexural strengths of 290,000 psi, and short-beam shear strengths of almost 17,000 psi.

  11. Diffusion of hydroxyl groups in silica glass through the binding interface

    NASA Astrophysics Data System (ADS)

    Sato, Naoya; Yamamoto, Takaki; Kuzuu, Nobu; Horikoshi, Hideharu; Niwa, Shohei

    2016-02-01

    Diffusion of hydroxyl groups in silica glass through an interface formed by binding between high-hydroxyl (ca. 1200 wt.ppm) and low-hydroxyl (ca. 130 wt.ppm)-containing silica glasses in the temperature range of 900-1150 °C was investigated. Although the theoretical curve with a hydroxyl-concentration-independent diffusion coefficient deviates from the experimental curve, the diffusion coefficients obtained by fitting to the experimental results by the least squares method coincided with the “effective diffusion coefficients” in the literature, which were obtained from the total absorption change in the IR absorption peak for the hydroxyl group using thin samples. By the analysis considering the hydroxyl concentration dependence of the diffusion coefficient, we showed that the diffusion coefficient is proportional to hydroxyl concentration at each temperature, which is consistent with the model of the diffusion: SiOSi + H2O = 2SiOH. On the basis of this scheme, we tried to evaluate the diffusion coefficients of molecular water using equilibrium constant in the literature.

  12. Phosphate glass useful in high power lasers

    DOEpatents

    Hayden, J.S.; Sapak, D.L.; Ward, J.M.

    1990-05-29

    A low- or no-silica phosphate glass useful as a laser medium and having a high thermal conductivity, K[sub 90 C] > 0.8 W/mK, and a low coefficient of thermal expansion, [alpha][sub 20--40 C] < 80[times]10[sup [minus]7]/C, consists essentially of (on a batch composition basis Mole %): P[sub 2]O[sub 5], 45-70; Li[sub 2]O, 15-35; Na[sub 2]O, 0-10; Al[sub 2]O[sub 3], 10-15; Nd[sub 2]O[sub 3], 0.01-6; La[sub 2]O[sub 3], 0-6; SiO[sub 2], 0-8; B[sub 2]O[sub 3], 0-8; MgO, 0-18; CaO, 0-15; SrO, 0-9; BaO, 0-9; ZnO, 0-15; the amounts of Li[sub 2]O and Na[sub 2]O providing an average alkali metal ionic radius sufficiently low whereby said glass has K[sub 90 C] > 0.8 W/mK and [alpha][sub 20--40 C] < 80[times]10[sup [minus]7]/C, and wherein, when the batch composition is melted in contact with a silica-containing surface, the final glass composition contains at most about 3.5 mole % of additional silica derived from such contact during melting. The Nd[sub 2]O[sub 3] can be replaced by other lasing species. 3 figs.

  13. Adhesion and removal of glass, silica and PSL particles from silicon dioxide substrates

    NASA Astrophysics Data System (ADS)

    Feng, Jiangwei

    As circuit minimum feature size continues to shrink, surface cleanliness requirements become more stringent, making surface cleaning more challenging. To develop effective cleaning techniques, it is important to understand particle adhesion and removal mechanisms. Although many studies have been conducted in particle adhesion, the effects of humidity and aging, hydrogen and covalent bonds, and particle's submicron size on adhesion are not well understood. It is necessary to study and understand how the adhesion force changes with time under different conditions in order to develop effective cleaning techniques. The humidity and aging effects on the adhesion and removal of glass particles on flat panel display glass surface, silica particles on thermal oxide silicon wafers and PSL (Polystyrene Latex) particles on silicon wafers are investigated. The results show that silica particles' contact area increases dramatically in high humidity environment over time. This is due to the water reacting with the silica and forming a covalent bond. The results show that silica particles' adhesion force is found to depend on the aging time. After six weeks 95%RH aging, the adhesion force is larger than MP model (for plastic deformation) predicted adhesion force. This is due to the formation of hydrogen bonds and covalent bonds. Removal of glass particles on Flat Panel Display aged in a humid environment using megasonic cleaning is also investigated. The effect of temperature, cleaning time and megasonic power on particle removal is shown. The time and humidity effect on submicron PSL particles' adhesion is also investigated. The combined effect of time and humidity results in increased particle deformation and consequently the increased adhesion force. An empirical model is proposed to describe the relationship between the contact diameter, particle diameter and aging time. The proposed model is in good agreement with the experimental data. The results suggest that a greater

  14. Preparation and photoluminescence of monolithic silica glass doped with Tb3+ ions using SiO2-PVA nanocomposite

    NASA Astrophysics Data System (ADS)

    Ikeda, Hiroshi; Murata, Takahiro; Fujino, Shigeru

    2014-05-01

    The monolithic silica glass doped with Tb3+ ions was fabricated using the SiO2-PVA nanocomposite as the glass precursor. In order to dope Tb3+ ions in the monolithic silica glass, the mesoporous SiO2-PVA nanocomposite was immersed in the Tb3+ ions contained solution and subsequently sintered at 1100 °C in air. Consequently the monolithic transparent silica glass was obtained, exhibiting green fluorescence attributed to 5D4 → 7F5 main transitions under UV excitation. The Tb concentration in the sintered glass could be controlled by immersion time of the nanocomposite in the solution.

  15. At the interface of silica glass and compressed silica aerogel in Stardust track 10: Comet Wild 2 is not a goldmine

    NASA Astrophysics Data System (ADS)

    Rietmeijer, Frans J. M.

    2016-03-01

    In Stardust tracks C2044,0,38, C2044,0,39, and C2044,0,42 (Brennan et al.) and Stardust track 10 (this work) gold is present in excess of its cosmochemical abundance. Ultra-thin sections of allocation FC6,0,10,0,26 (track 10) show a somewhat wavy, compressed silica aerogel/silica glass interface which challenges exact location identification, i.e., silica glass, compressed silica aerogel, or areas of overlap. In addition to domains of pure silica ranging from SiO2 to SiO3 glass, there is MgO-rich silica glass with a deep metastable composition, MgO = 14 ± 6 wt%, due to assimilation of Wild 2 Mg-silicate matter in silica melt. This magnesiosilica composition formed when temperatures during hypervelocity capture reached >2000 °C followed by ultrafast quenching of the magnesiosilica melt when it came into contact with compressed aerogel at ~155 °C. The compressed silica aerogel in track 10 has a continuous Au background as result of the melting point depression of gold particles <5 nm that showed liquid-like behavior. Larger gold particles are scattered found throughout the silica aerogel matrix and in aggregates up to ~50 nm in size. No gold is found in MgO-rich silica glass. Gold in track 10 is present at the silica aerogel/silica glass interface. In the other tracks gold was likely near-surface contamination possibly from an autoclave used in processing of these particular aerogel tiles. So far gold contamination is documented in these four different tracks. Whether they are the only tiles with gold present in excess of its cosmochemical abundance or whether more tiles will show excess gold abundances is unknown.

  16. Novel cost-effective process for the replication of hybrid diffractive/refractive optical elements in silica glass

    SciTech Connect

    Maxey, L.C.; Nogues, J.L.; Moreshead, B.

    1998-08-01

    This CRADA between Martin Marietta Energy Systems, Inc. (Contractor) and GELTECH, Inc. (Participant) has demonstrated the feasibility of producing hybrid diffractive/refractive optics by a replication process which lends itself to high-volume, low-cost production. The program has built unpon unique capabilities of the Contractor and the Participant to achieve this demonstration. The Contractor has extensive experience and unique capabilities in the technology of single point diamong turning for optical components. The Participant has achieved unique success in the development of manufacturing processes for high-quality silica optical components using sol-gel technology. The merging of these two leading technologies has provided a synergism resulting in the demonstration of a manufacturing technology for cost-effective, high-volume production of silica glass precision hybrid optical components. Hybrid optical components are systems that integrate diffractive optical surfaces into lenses, resulting in designs that minimize the aberrations that degrade image quality without the need for additional glass elements. This reduces the cost, weight, and complexity of the system, while improving the overall optical efficiency. Previous applications of hybrid optical components have been primarily for infra-red applications, where diamond-turned germanium or silicon optics have been used. Hybrid optics for use in the visible have been limited to laboratory curiosities that were directly turned into plastic substrates. Through this CRADA the authors have achieved a manufacturing process for producing high quality silica glass hybrid lenses in an way that lends itself to mass production.

  17. Anisotropic surroundings effects on photo absorption of partially embedded Au nanospheroids in silica glass substrate

    SciTech Connect

    Meng, Xuan; Shibayama, Tamaki Watanabe, Seiichi; Yu, Ruixuan; Ishioka, Junya

    2015-02-15

    The influence of a directly adjacent or an anisotropic surrounding medium alters the plasmonic properties of a nanoparticle because it provides a mechanism for symmetry breaking of the scattering. Given the success of ion irradiation induced embedment of rigid metallic nanospheroids into amorphous substrate, it is possible to examine the effect of the silica glass substrate on the plasmonic properties of these embedded nanospheroids. In this work presented here, discrete dipole approximation (DDA) calculations for the Au nanospheroids’ optical properties were performed based on 3–dimensional (3D) configuration extracted from planar SEM micrographs and cross–sectional TEM micrographs of the Au nanospheroids partially embedded in the silica glass, and the well–matched simulations with respect to the experimental measurements could demonstrate the dielectric constant at the near surface of silica glass decreased after Ar–ion irradiation.

  18. Manganese modified structural and optical properties of zinc soda lime silica glasses.

    PubMed

    Samsudin, Nur Farhana; Matori, Khamirul Amin; Wahab, Zaidan Abdul; Fen, Yap Wing; Liew, Josephine Ying Chi; Lim, Way Foong; Mohd Zaid, Mohd Hafiz; Omar, Nur Alia Sheh

    2016-03-20

    A series of MnO-doped zinc soda lime silica glass systems was prepared by a conventional melt and quenching technique. In this study, the x-ray diffraction analysis was applied to confirm the amorphous nature of the glasses. Fourier transform infrared spectroscopy shows the glass network consists of MnO4, SiO4, and ZnO4 units as basic structural units. The glass samples under field emission scanning electron microscopy observation demonstrated irregularity in shape and size with glassy phase-like structure. The optical absorption studies revealed that the optical bandgap (Eopt) values decrease with an increase of MnO content. Through the results of various measurements, the doping of MnO in the glass matrix had effects on the performance of the glasses and significantly improved the properties of the glass sample as a potential host for phosphor material. PMID:27140551

  19. Time-resolved measurement of photon emission during fast crack propagation in three-point bending fracture of silica glass and soda lime glass

    SciTech Connect

    Shiota, Tadashi Sato, Yoshitaka; Yasuda, Kouichi

    2014-03-10

    Simultaneous time-resolved measurements of photon emission (PE) and fast crack propagation upon bending fracture were conducted in silica glass and soda lime glass. Observation of fracture surfaces revealed that macroscopic crack propagation behavior was similar between the silica glass and soda lime glass when fracture loads for these specimens were comparable and cracks propagated without branching. However, a large difference in the PE characteristics was found between the two glasses. In silica glass, PE (645–655 nm) was observed during the entire crack propagation process, whereas intense PE (430–490 nm and 500–600 nm) was observed during the initial stages of propagation. In contrast, only weak PE was detected in soda lime glass. These results show that there is a large difference in the atomic processes involved in fast crack propagation between these glasses, and that PE can be used to study brittle fracture on the atomic scale.

  20. Ultrathin silica films: the atomic structure of two-dimensional crystals and glasses.

    PubMed

    Büchner, Christin; Lichtenstein, Leonid; Yu, Xin; Boscoboinik, J Anibal; Yang, Bing; Kaden, William E; Heyde, Markus; Shaikhutdinov, Shamil K; Włodarczyk, Radosław; Sierka, Marek; Sauer, Joachim; Freund, Hans-Joachim

    2014-07-21

    For the last 15 years, we have been studying the preparation and characterization of ordered silica films on metal supports. We review the efforts so far, and then discuss the specific case of a silica bilayer, which exists in a crystalline and a vitreous variety, and puts us into a position to investigate, for the first time, the real space structure (AFM/STM) of a two-dimensional glass and its properties. We show that pair correlation functions determined from the images of this two-dimensional glass are similar to those determined by X-ray and neutron scattering from three-dimensional glasses, if the appropriate sensitivity factors are taken into account. We are in a position, to verify, for the first time, a model of the vitreous silica structure proposed by William Zachariasen in 1932. Beyond this, the possibility to prepare the crystalline and the glassy structure on the same support allows us to study the crystal-glass phase transition in real space. We, finally, discuss possibilities to use silica films to start investigating related systems such as zeolites and clay films. We also mention hydroxylation of the silica films in order to adsorb metal atoms modeling heterogenized homogeneous catalysts. PMID:24990633

  1. Fabrication of 3D solenoid microcoils in silica glass by femtosecond laser wet etch and microsolidics

    NASA Astrophysics Data System (ADS)

    Meng, Xiangwei; Yang, Qing; Chen, Feng; Shan, Chao; Liu, Keyin; Li, Yanyang; Bian, Hao; Du, Guangqing; Hou, Xun

    2015-02-01

    This paper reports a flexible fabrication method for 3D solenoid microcoils in silica glass. The method consists of femtosecond laser wet etching (FLWE) and microsolidics process. The 3D microchannel with high aspect ratio is fabricated by an improved FLWE method. In the microsolidics process, an alloy was chosen as the conductive metal. The microwires are achieved by injecting liquid alloy into the microchannel, and allowing the alloy to cool and solidify. The alloy microwires with high melting point can overcome the limitation of working temperature and improve the electrical property. The geometry, the height and diameter of microcoils were flexibly fabricated by the pre-designed laser writing path, the laser power and etching time. The 3D microcoils can provide uniform magnetic field and be widely integrated in many magnetic microsystems.

  2. Shape dependence of nonlinear optical behaviors of nanostructured silver and their silica gel glass composites

    SciTech Connect

    Zheng Chan; Du Yuhong; Feng Miao; Zhan Hongbing

    2008-10-06

    Nanostructured Ag in shapes of nanoplate, nanowire, and nanoparticle, as well as their silica gel glass composites have been prepared and characterized. Nonlinear optical (NLO) properties were measured at 532 and 1064 nm using open aperture z-scan technique and studied from the view of shape effect. NLO behaviors of the nanostructured Ag are found to be shape dependent in suspensions at both the investigated wavelengths, although they originate differently. Comparing to the mother suspensions, the Ag/silica gel glass nanocomposites present rather dissimilar NLO behaviors, which is quite interesting for further studies.

  3. Porous Silica Sol-Gel Glasses Containing Reactive V2O5 Groups

    NASA Technical Reports Server (NTRS)

    Stiegman, Albert E.

    1995-01-01

    Porous silica sol-gel glasses into which reactive vanadium oxide functional groups incorporated exhibit number of unique characteristics. Because they bind molecules of some species both reversibly and selectively, useful as chemical sensors or indicators or as scrubbers to remove toxic or hazardous contaminants. Materials also oxidize methane gas photochemically: suggests they're useful as catalysts for conversion of methane to alcohol and for oxidation of hydrocarbons in general. By incorporating various amounts of other metals into silica sol-gel glasses, possible to synthesize new materials with broad range of new characteristics.

  4. Colloidal silica films for high-capacity DNA arrays

    NASA Astrophysics Data System (ADS)

    Glazer, Marc Irving

    The human genome project has greatly expanded the amount of genetic information available to researchers, but before this vast new source of data can be fully utilized, techniques for rapid, large-scale analysis of DNA and RNA must continue to develop. DNA arrays have emerged as a powerful new technology for analyzing genomic samples in a highly parallel format. The detection sensitivity of these arrays is dependent on the quantity and density of immobilized probe molecules. We have investigated substrates with a porous, "three-dimensional" surface layer as a means of increasing the surface area available for the synthesis of oligonucleotide probes, thereby increasing the number of available probes and the amount of detectable bound target. Porous colloidal silica films were created by two techniques. In the first approach, films were deposited by spin-coating silica colloid suspensions onto flat glass substrates, with the pores being formed by the natural voids between the solid particles (typically 23nm pores, 35% porosity). In the second approach, latex particles were co-deposited with the silica and then pyrolyzed, creating films with larger pores (36 nm), higher porosity (65%), and higher surface area. For 0.3 mum films, enhancements of eight to ten-fold and 12- to 14-fold were achieved with the pure silica films and the films "templated" with polymer latex, respectively. In gene expression assays for up to 7,000 genes using complex biological samples, the high-capacity films provided enhanced signals and performed equivalently or better than planar glass on all other functional measures, confirming that colloidal silica films are a promising platform for high-capacity DNA arrays. We have also investigated the kinetics of hybridization on planar glass and high-capacity substrates. Adsorption on planar arrays is similar to ideal Langmuir-type adsorption, although with an "overshoot" at high solution concentration. Hybridization on high-capacity films is

  5. Shock temperatures in silica glass - Implications for modes of shock-induced deformation, phase transformation, and melting with pressure

    NASA Technical Reports Server (NTRS)

    Schmitt, Douglas R.; Ahrens, Thomas J.

    1989-01-01

    Observations of shock-induced radiative thermal emissions are used to determine the gray body temperatures and emittances of silica glass under shock compression between 10 and 30 GPa. The results suggest that fused quartz deforms heterogeneously in this shock pressure range. It is shown that the 10-16 GPa range coincides with the permanent densification region, while the 16-30 GPa range coincides with the inferred mixed phase region along the silica glass Hugoniot. Low emittances in the mixed phase region are thought to represent the melting temperature of the high-pressure phase, stishovite. Also, consideration is given to the effects of pressure on melting relations for the system SiO2-Mg2SiO4.

  6. Late Byzantine mineral soda high alumina glasses from Asia Minor: a new primary glass production group.

    PubMed

    Schibille, Nadine

    2011-01-01

    The chemical characterisation of archaeological glass allows the discrimination between different glass groups and the identification of raw materials and technological traditions of their production. Several lines of evidence point towards the large-scale production of first millennium CE glass in a limited number of glass making factories from a mixture of Egyptian mineral soda and a locally available silica source. Fundamental changes in the manufacturing processes occurred from the eight/ninth century CE onwards, when Egyptian mineral soda was gradually replaced by soda-rich plant ash in Egypt as well as the Islamic Middle East. In order to elucidate the supply and consumption of glass during this transitional period, 31 glass samples from the assemblage found at Pergamon (Turkey) that date to the fourth to fourteenth centuries CE were analysed by electron microprobe analysis (EPMA) and by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The statistical evaluation of the data revealed that the Byzantine glasses from Pergamon represent at least three different glass production technologies, one of which had not previously been recognised in the glass making traditions of the Mediterranean. While the chemical characteristics of the late antique and early medieval fragments confirm the current model of glass production and distribution at the time, the elemental make-up of the majority of the eighth- to fourteenth-century glasses from Pergamon indicate the existence of a late Byzantine glass type that is characterised by high alumina levels. Judging from the trace element patterns and elevated boron and lithium concentrations, these glasses were produced with a mineral soda different to the Egyptian natron from the Wadi Natrun, suggesting a possible regional Byzantine primary glass production in Asia Minor. PMID:21526144

  7. Late Byzantine Mineral Soda High Alumina Glasses from Asia Minor: A New Primary Glass Production Group

    PubMed Central

    Schibille, Nadine

    2011-01-01

    The chemical characterisation of archaeological glass allows the discrimination between different glass groups and the identification of raw materials and technological traditions of their production. Several lines of evidence point towards the large-scale production of first millennium CE glass in a limited number of glass making factories from a mixture of Egyptian mineral soda and a locally available silica source. Fundamental changes in the manufacturing processes occurred from the eight/ninth century CE onwards, when Egyptian mineral soda was gradually replaced by soda-rich plant ash in Egypt as well as the Islamic Middle East. In order to elucidate the supply and consumption of glass during this transitional period, 31 glass samples from the assemblage found at Pergamon (Turkey) that date to the fourth to fourteenth centuries CE were analysed by electron microprobe analysis (EPMA) and by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The statistical evaluation of the data revealed that the Byzantine glasses from Pergamon represent at least three different glass production technologies, one of which had not previously been recognised in the glass making traditions of the Mediterranean. While the chemical characteristics of the late antique and early medieval fragments confirm the current model of glass production and distribution at the time, the elemental make-up of the majority of the eighth- to fourteenth-century glasses from Pergamon indicate the existence of a late Byzantine glass type that is characterised by high alumina levels. Judging from the trace element patterns and elevated boron and lithium concentrations, these glasses were produced with a mineral soda different to the Egyptian natron from the Wadi Natrun, suggesting a possible regional Byzantine primary glass production in Asia Minor. PMID:21526144

  8. Effect of OH content on phase separation behavior of soda-silica glasses

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

    The kinetics of phase separation in a gel and ordinary soda-silica glass are followed by use of small angle X-ray scattering. Also, the influence of OH on the phase separation behavior is studied. It is found that OH accelerates the growth of the secondary phase, and that gel and ordinary glasses of similar composition and OH concentration exhibit similar phase separation characteristics.

  9. Silane Modification of Glass and Silica Surfaces to Obtain Equally Oil-Wet Surfaces in Glass-Covered Silicon Micromodel Applications

    SciTech Connect

    Grate, Jay W.; Warner, Marvin G.; Pittman, Jonathan W.; Dehoff, Karl J.; Wietsma, Thomas W.; Zhang, Changyong; Oostrom, Martinus

    2013-08-05

    The wettability of silicon and glass surfaces can be modified by silanization. However, similar treatments of glass and silica surfaces using the same silane do not necessarily yield the same wettability as determined by the oil-water contact angle. In this technical note, surface cleaning pretreatments were investigated to determine conditions that would yield oil-wet surfaces on glass with similar wettability to silica surfaces treated with the same silane, and both air-water and oil-water contact angles were determined. Air-water contact angles were less sensitive to differences between silanized silica and glass surfaces, often yielding similar values while the oil-water contact angles were quite different. Borosilicate glass surfaces cleaned with standard cleaning solution 1 (SC1) yield intermediate-wet surfaces when silanized with hexamethyldisilazane, while the same cleaning and silanization yields oil-wet surfaces on silica. However, cleaning glass in boiling concentrated nitric acid creates a surface that can be silanized to obtain oil-wet surfaces using HDMS. Moreover, this method is effective on glass with prior thermal treatment at an elevated temperature of 400oC. In this way, silica and glass can be silanized to obtain equally oil-wet surfaces using HMDS. It is demonstrated that pretreatment and silanization is feasible in silicon-silica/glass micromodels previously assembled by anodic bonding, and that the change in wettability has a significant observable effect on immiscisble fluid displacements in the pore network.

  10. Controlling surface energy of glass substrates to prepare superhydrophobic and transparent films from silica nanoparticle suspensions.

    PubMed

    Ogihara, Hitoshi; Xie, Jing; Saji, Tetsuo

    2015-01-01

    We fabricated superhydrophobic and transparent silica nanoparticle (SNP) films on glass plates via spray-coating technique. When suspensions containing 1-propanol and hydrophobic SNPs were sprayed over glass plates that were modified with dodecyl groups, superhydrophobic and transparent SNP films were formed on the substrates. Surface energy of the glass plates had a significant role to obtain superhydrophobic and transparent SNP films. SNP films did not show superhydrophobicity when bare glass plates were used as substrates, because water droplets tend to adhere the exposed part of the hydrophilic glass plate. Glass plates having extreme low surface energy were not also suitable because suspension solution was repelled from the substrates, which resulted in forming non-uniform SNP films. PMID:25310579

  11. High purity silica reflective heat shield development

    NASA Technical Reports Server (NTRS)

    Nachtscheim, P. R.; Blome, J. C.

    1976-01-01

    A hyperpure vitreous silica material is being developed for use as a reflective and ablative heat shield for planetary entry. Various purity grades and forms of raw materials were evaluated along with various processing methods. Slip casting of high purity grain was selected as the best processing method, resulting in a highly reflective material in the wavelength bands of interest (the visible and ultraviolet regions). The selected material was characterized with respect to optical, mechanical and physical properties using a limited number of specimens. The process has been scaled up to produce a one-half scale heat shield (18 in. dia.) (45.72 cm) for a Jupiter entry vehicle. This work is now being extended to improve the structural safety factor of the heat shield by making hyperpure silica material tougher through the addition of silica fibers.

  12. Surface spin-glass in cobalt ferrite nanoparticles dispersed in silica matrix

    NASA Astrophysics Data System (ADS)

    Zeb, F.; Sarwer, W.; Nadeem, K.; Kamran, M.; Mumtaz, M.; Krenn, H.; Letofsky-Papst, I.

    2016-06-01

    Surface effects in cobalt ferrite (CoFe2O4) nanoparticles dispersed in a silica (SiO2) matrix were studied by using AC and DC magnetization. Nanoparticles with different concentration of SiO2 were synthesized by using sol-gel method. Average crystallite size lies in the range 25-34 nm for different SiO2 concentration. TEM image showed that particles are spherical and elongated in shape. Nanoparticles with higher concentration of SiO2 exhibit two peaks in the out-of-phase ac-susceptibility. First peak lies in the high temperature regime and corresponds to average blocking temperature of the nanoparticles. Second peak lies in the low temperature regime and is attributed to surface spin-glass freezing in these nanoparticles. Low temperature peak showed SiO2 concentration dependence and was vanished for large uncoated nanoparticles. The frequency dependence of the AC-susceptibility of low temperature peak was fitted with dynamic scaling law which ensures the presence of spin-glass behavior. With increasing applied DC field, the low temperature peak showed less shift as compared to blocking peak, broaden, and decreased in magnitude which also signifies its identity as spin-glass peak for smaller nanoparticles. M-H loops showed the presence of more surface disorder in nanoparticles dispersed in 60% SiO2 matrix. All these measurements revealed that surface effects become strengthen with increasing SiO2 matrix concentration and surface spins freeze in to spin-glass state at low temperatures.

  13. Planar gas chromatography column on glass plate with nanodispersed silica as the stationary phase

    NASA Astrophysics Data System (ADS)

    Platonov, I. A.; Platonov, V. I.; Pavelyev, V. S.; Agafonov, A. N.

    2016-04-01

    The paper presents the GC column in the plane of the glass plate with the adsorption layer nanodispersed silica. Created gas chromatographic column allows to separate a mixture of five alkanes from pentane to nonane in isothermal (90 ° C) mode less than one minute.

  14. High resolution patterning of silica aerogels

    SciTech Connect

    Bertino, M.F.; Hund, J.F.; Sosa, J.; Zhang, G.; Sotiriou-Leventis, C.; Leventis, N.; Tokuhiro, A.T.; Terry, J.

    2008-10-30

    Three-dimensional metallic structures are fabricated with high spatial resolution in silica aerogels. In our method, silica hydrogels are prepared with a standard base-catalyzed route, and exchanged with an aqueous solution typically containing Ag{sup +} ions (1 M) and 2-propanol (0.2 M). The metal ions are reduced photolytically with a table-top ultraviolet lamp, or radiolytically, with a focused X-ray beam. We fabricated dots and lines as small as 30 x 70 {micro}m, protruding for several mm into the bulk of the materials. The hydrogels are eventually supercritically dried to yield aerogels, without any measurable change in the shape and spatial resolution of the lithographed structures. Transmission electron microscopy shows that illuminated regions are composed by Ag clusters with a size of several {micro}m, separated by thin layers of silica.

  15. Glass formation and properties in the system calcia-gallia-silica

    NASA Technical Reports Server (NTRS)

    Angel, Paul W.; Ray, Chandra S.; Day, Delbert E.

    1990-01-01

    The glass-forming region in the calcia-gallia-silica system is studied and found to be fairly large, with a density of 3-4 g/cu cm, a refractive index of 1.6-1.73, an Abbe number of 35-58, a thermal expansion coefficient of 6.5-11.5 x 10 to the -7th/deg C, and a Vickers microhardness of 5.2-7.3 GPa. Crystalline phases are identified at the boundary of the glass-forming region. The structural groups in the glass-forming compositions are analyzed by infrared absorption spectroscopy.

  16. An optical amplifier having 5 cm long silica-clad erbium doped phosphate glass fiber fabricated by "core-suction" technique

    NASA Astrophysics Data System (ADS)

    Goel, Nitin K.; Pickrell, Gary; Stolen, Roger

    2014-08-01

    We have fabricated an erbium-doped phosphate glass fiber with a silica cladding and used 5 cm length of it to form an optical amplifier. A bulk erbium phosphate glass called MM2 was used as a core glass in a silica cladding tube to prepare a preform using "core-suction" technique. This MM2 glass preform was drawn to a fiber and the resultant fiber was of good optical quality, free from air bubbles and major defects. The fiber was mechanically strong enough to allow for ease of handling and could be spliced to conventional silica fiber using commercial fusion splicer. This fiber was then used to setup an EDFA. Our work demonstrates the potential to form silica clad optical fibers with phosphate cores doped with very high levels of rare-earth ions. It is demonstrated that the core suction technique can be used to make a high-gain erbium phosphate fiber amplifier that is compatible with conventional silica fibers.

  17. A Pd/silica composite with highly uniform Pd nanoparticles on silica lamella via layered silicate

    NASA Astrophysics Data System (ADS)

    Hao, Jing; Cui, Zhi-Min; Cao, Chang-Yan; Song, Weiguo

    2016-08-01

    Pd nanoparticles was loaded on silica lamella via layered silicate through a simple ion-exchange and in situ reduction method. The obtained Pd/silica composite has Pd nanoparticles with highly uniform size dispersed well on the silica lamella. The Pd/silica composite is active and recoverable catalyst for the hydrogenation reaction and the reaction can be completed in a short time of 2 h at room temperature and 1 atm H2 pressure.

  18. Lattice dynamics of α-cristobalite and the Boson peak in silica glass.

    PubMed

    Wehinger, Björn; Bosak, Alexeï; Refson, Keith; Mirone, Alessandro; Chumakov, Aleksandr; Krisch, Michael

    2015-08-01

    The lattice dynamics of the silica polymorph [Formula: see text]-cristobalite has been investigated by a combination of diffuse and inelastic x-ray scattering and ab initio lattice dynamics calculations. Phonon dispersion relations and vibrational density of states are reported and the phonon eigenvectors analyzed by a detailed comparison of scattering intensities. The experimentally validated calculation is used to identify the vibration contributing most to the first peak in the density of vibrational states. The comparison of its displacement pattern to the silica polymorphs [Formula: see text]-quartz and coesite and to vitreous silica reveals a distinct similarity and allows for decisive conclusions on the vibrations causing the so-called Boson peak in silica glass. PMID:26173206

  19. Superhydrophobic films on glass surface derived from trimethylsilanized silica gel nanoparticles.

    PubMed

    Goswami, Debmita; Medda, Samar Kumar; De, Goutam

    2011-09-01

    The paper deals with the fabrication of sol-gel-derived superhydrophobic films on glass based on the macroscopic silica network with surface modification. The fabricated transparent films were composed of a hybrid -Si(CH(3))(3)-functionalized SiO(2) nanospheres exhibiting the desired micro/nanostructure, water repellency, and antireflection (AR) property. The wavelength selective AR property can be tuned by controlling the physical thickness of the films. Small-angle X-ray scattering (SAXS) studies revealed the existence of SiO(2) nanoparticles of average size ∼9.4 nm in the sols. TEM studies showed presence of interconnected SiO(2) NPs of ∼10 nm in size. The films were formed with uniformly packed SiO(2) aggregates as observed by FESEM of film surface. FTIR of the films confirmed presence of glasslike Si-O-Si bonding and methyl functionalization. The hydrophobicity of the surface was depended on the thickness of the deposited films. A critical film thickness (>115 nm) was necessary to obtain the air push effect for superhydrophobicity. Trimethylsilyl functionalization of SiO(2) and the surface roughness (rms ≈30 nm as observed by AFM) of the films were also contributed toward the high water contact angle (WCA). The coated glass surface showed WCA value of the droplet as high as 168 ± 3° with 6 μL of water. These superhydrophobic films were found to be stable up to about 230-240 °C as confirmed by TG/DTA studies, and WCA measurements of the films with respect to the heat-treatment temperatures. These high water repellant films can be deposited on relatively large glass surfaces to remove water droplets immediately without any mechanical assistance. PMID:21823656

  20. Silane modification of glass and silica surfaces to obtain equally oil-wet surfaces in glass-covered silicon micromodel applications

    NASA Astrophysics Data System (ADS)

    Grate, Jay W.; Warner, Marvin G.; Pittman, Jonathan W.; Dehoff, Karl J.; Wietsma, Thomas W.; Zhang, Changyong; Oostrom, Mart

    2013-08-01

    Wettability is a key parameter influencing capillary pressures, permeabilities, fingering mechanisms, and saturations in multiphase flow processes within porous media. Glass-covered silicon micromodels provide precise structures in which pore-scale displacement processes can be visualized. The wettability of silicon and glass surfaces can be modified by silanization. However, similar treatments of glass and silica surfaces using the same silane do not necessarily yield the same wettability as determined by the oil-water contact angle. In this study, surface cleaning pretreatments were investigated to determine conditions that yield oil-wet surfaces on glass with similar wettability to silica surfaces treated with the same silane, and both air-water and oil-water contact angles were determined. Borosilicate glass surfaces cleaned with standard cleaning solution 1 (SC1) yield intermediate-wet surfaces when silanized with hexamethyldisilazane (HMDS), while the same cleaning and silanization yields oil-wet surfaces on silica. However, cleaning glass in boiling concentrated nitric acid creates a surface that can be silanized to obtain oil-wet surfaces using HMDS. Moreover, this method is effective on glass with prior thermal treatment at an elevated temperature of 400°C. In this way, silica and glass can be silanized to obtain equally oil-wet surfaces using HMDS. It is demonstrated that pretreatment and silanization is feasible in silicon-silica/glass micromodels previously assembled by anodic bonding, and that the change in wettability has a significant observable effect on immiscible fluid displacements in the pore network.

  1. Polarized IR studies of silica glasses exposed to polarized excimer radiation

    SciTech Connect

    Smith, Charlene M.; Borrelli, Nicholas F.; Tingley, James E.

    2006-12-15

    Silica glass exhibits a permanent anisotropic response, polarization-induced birefringence (PIB), when exposed to short-wavelength polarized light. This behavior has been correlated with the OH content of the glass. In this paper we describe polarized infrared studies of silica glasses of different OH content exposed with polarized 157 nm laser light. Changes in the fundamental OH band as a consequence of exposure are shown. We find differential bleaching of a particular OH band where OH species that are oriented parallel to the incident exposing polarization undergo greater bleaching than those oriented perpendicular. The preferential bleaching as a function of exposure time correlates strongly with the evolution of PIB, leading to a bleaching model of OH that is causally linked to PIB.

  2. Thermomechanical Modeling of Laser-Induced Structural Relaxation and Deformation of Glass: Volume Changes in Fused Silica at High Temperatures [Thermo-mechanical modeling of laser-induced structural relaxation and deformation of SiO2 glass

    SciTech Connect

    Vignes, Ryan M.; Soules, Thomas F.; Stolken, James S.; Settgast, Randolph R.; Elhadj, Selim; Matthews, Manyalibo J.; Mauro, J.

    2012-12-17

    In a fully coupled thermomechanical model of the nanoscale deformation in amorphous SiO2 due to laser heating is presented. Direct measurement of the transient, nonuniform temperature profiles was used to first validate a nonlinear thermal transport model. Densification due to structural relaxation above the glass transition point was modeled using the Tool-Narayanaswamy (TN) formulation for the evolution of structural relaxation times and fictive temperature. TN relaxation parameters were derived from spatially resolved confocal Raman scattering measurements of Si–O–Si stretching mode frequencies. These thermal and microstructural data were used to simulate fictive temperatures which are shown to scale nearly linearly with density, consistent with previous measurements from Shelby et al. Volumetric relaxation coupled with thermal expansion occurring in the liquid-like and solid-like glassy states lead to residual stresses and permanent deformation which could be quantified. But, experimental surface deformation profiles between 1700 and 2000 K could only be reconciled with our simulation by assuming a roughly 2 × larger liquid thermal expansion for a-SiO2 with a temperature of maximum density ~150 K higher than previously estimated by Bruckner et al. Calculated stress fields agreed well with recent laser-induced critical fracture measurements, demonstrating accurate material response prediction under processing conditions of practical interest.

  3. Silica Integrated Optical Circuits Based on Glass Photosensitivity

    NASA Technical Reports Server (NTRS)

    Abushagur, Mustafa A. G.

    1999-01-01

    Integrated optical circuits play a major rule in the new photonics technology both in communication and sensing due to their small size and compatibility with integrated circuits. Currently integrated optical circuits (IOCs) are fabricated using similar manufacturing to those used in the semiconductor industry. In this study we are considering a new technique to fabricate IOCs which does not require layers of photolithography, depositing and etching. This method is based on the photosensitivity of germanosilicate glasses. Waveguides and other IOC devises can be patterned in these glasses by exposing them using UV lasers. This exposure by UV light changes the index of refraction of the germanosilicate glass. This technique enjoys both the simplicity and flexibility of design and fabrication with also the potential of being fast and low cost.

  4. Optical constants of silica glass from extreme ultraviolet to far infrared at near room temperature.

    PubMed

    Kitamura, Rei; Pilon, Laurent; Jonasz, Miroslaw

    2007-11-20

    We thoroughly and critically review studies reporting the real (refractive index) and imaginary (absorption index) parts of the complex refractive index of silica glass over the spectral range from 30 nm to 1000 microm. The general features of the optical constants over the electromagnetic spectrum are relatively consistent throughout the literature. In particular, silica glass is effectively opaque for wavelengths shorter than 200 nm and larger than 3.5-4.0 microm. Strong absorption bands are observed (i) below 160 nm due to the interaction with electrons, absorption by impurities, and the presence of OH groups and point defects; (ii) at aproximately 2.73-2.85, 3.5, and 4.3 microm also caused by OH groups; and (iii) at aproximately 9-9.5, 12.5, and 21-23 microm due to Si-O-Si resonance modes of vibration. However, the actual values of the refractive and absorption indices can vary significantly due to the glass manufacturing process, crystallinity, wavelength, and temperature and to the presence of impurities, point defects, inclusions, and bubbles, as well as to the experimental uncertainties and approximations in the retrieval methods. Moreover, new formulas providing comprehensive approximations of the optical properties of silica glass are proposed between 7 and 50 microm. These formulas are consistent with experimental data and substantially extend the spectral range of 0.21-7 microm covered by existing formulas and can be used in various engineering applications. PMID:18026551

  5. Comparisons of Aluminum and Silica Elution from Various Glass Vials.

    PubMed

    Ogawa, Toru; Miyajima, Makoto; Nishimoto, Norihiro; Minami, Hidemi; Terada, Katsuhide

    2016-01-01

    To understand the risk of particle formation in glass vials, we investigated the correlation between vial surface condition and alminum (Al) or silicon (Si) elution using various suppliers' vials with or without surface treatment. The elution of Si, which can also be an indicator of Al elution, consists of two phases; the first phase is influenced by roughness of the glass surface at the time of filling, and the second phase is dependent on the fundamental elution rate from the glass tube. When vials were filled with citrate buffer at pH 7, vials with varied surface conditions showed the most obvious differences in Al and Si elution. Sulfur-treated vials showed slightly lower Al and Si elution than the non-treated vials. It is considered that this effect of the sulfur treatment on elution is due to the surface being smoothed during heat treatment after the washing process. Different from the sulfur treatment, silicon dioxide (SiO2)-coated vials hardly showed any Al elution as long as the surface was fully coated with the SiO2 layer. It was found that the protective effect of the SiO2 layer against Al elution is more effective in a vial filled with a solution having a lower pH, due to the lower Si dissolving rate occurring at a lower pH. As shown above, pre-measuring the Si and Al present in a citrate buffer at pH 7 placed within a glass container can be a useful tool for selecting the appropriate container for liquid drugs. PMID:26656229

  6. Vibrational Sum Frequency Generation Spectroscopy Study of Hydrous Species in Soda Lime Silica Float Glass.

    PubMed

    Luo, Jiawei; Banerjee, Joy; Pantano, Carlo G; Kim, Seong H

    2016-06-21

    It is generally accepted that the mechanical properties of soda lime silica (SLS) glass can be affected by the interaction between sodium ions and hydrous species (silanol groups and water molecules) in its surface region. While the amount of these hydrous species can be estimated from hydrogen profiles and infrared spectroscopy, their chemical environment in the glass network is still not well understood. This work employed vibrational sum frequency generation (SFG) spectroscopy to investigate the chemical environment of hydrous species in the surface region of SLS float glass. SLS float glass shows sharp peaks in the OH stretching vibration region in SFG spectra, while the OH stretch peaks of glasses that do not have leachable sodium ions and the OH peaks of water molecules in condensed phases are normally broad due to fast hydrogen bonding dynamics. The hydrous species responsible for the sharp SFG peaks for the SLS float glass were found to be thermodynamically more stable than physisorbed water molecules, did not exchange with D2O, and were associated with the sodium concentration gradient in the dealkalized subsurface region. These results suggested that the hydrous species reside in static solvation shells defined by the silicate network with relatively slow hydrogen bonding dynamics, compared to physisorbed water layers on top of the glass surface. A putative radial distribution of the hydrous species within the SLS glass network was estimated based on the OH SFG spectral features, which could be compared with theoretical distributions calculated from computational simulations. PMID:27254814

  7. Photoinduced transformations of oxygen-deficient centers in Silica and Germanosilicate glasses

    SciTech Connect

    Marchenko, V.M.

    1995-07-01

    The methods for producing the oxygen-deficient centers and the experimental findings on the photoinduced processes in silica and germanosilicate glasses as well as in such optical waveguides manufactured from these glasses that underlie the development of promising integrated-optical and optical fiber devices and instruments are considered. the discrepancy in the photochromic process interpretation made on the ground of the structural models proposed for the oxygen-deficient centers in the glasses under consideration is discussed. The observable photoinduced transformations of the oxygen-deficient centers and associated changes in the physical properties of the glasses are explained on the assumption that photoexcitation initiates not internal ionization, but solid-phase chemical reactions accompanied by the breaking and switching of valence bonds.

  8. 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.

  9. Deep-UV Raman spectroscopic analysis of structure and dissolution rates of silica-rich sodium borosilicate glasses

    SciTech Connect

    Windisch, Charles F.; Pierce, Eric M.; Burton, Sarah D.; Bovaird, Chase C.

    2011-03-24

    As part of ongoing studies to evaluate the relationships between structural variations in silicate glasses and rates of glass dissolution in aqueous media, molecular structures present in sodium borosilicate glasses of composition Na2O.xB2O3.(3-x)SiO2, with x 1 (Na2O/B2O3 ratio 1), were analyzed using deep-UV Raman spectroscopy. The results were quantified in terms of the fraction of SiO4 tetrahedra with one non-bridging oxygen (Q3) and then correlated with Na2O and B2O3 content. Increasing Na2O was found to raise the fraction of Q3 units in the glasses systematically, in agreement with studies on related glasses, and, as long as the value of x was not too high, contribute to higher rates of dissolution in single pass flow-through testing. The finding was obtained across more than one series of silica-rich glasses prepared for independent dissolution studies. In contrast, dissolution rates were less strongly determined by the Q3 fraction when the value of x was near unity and appeared to grow larger upon further reduction of the Q3 fraction. The results were interpreted to indicate the increasingly important role of network hydrolysis in the glass dissolution mechanism as the BO4 tetrahedron replaces the Q3 unit as the charge-compensating structure for Na+ ions. Finally, the use of deep-UV Raman spectroscopy was found to be advantageous in studying finely powdered glasses in cases where visible Raman spectroscopy suffered from weak Raman scattering and fluorescence interference.

  10. High-Strength Glass Fibers and Markets

    NASA Astrophysics Data System (ADS)

    Hausrath, Robert L.; Longobardo, Anthony V.

    High-strength glass fibers play a crucial role in composite applications requiring combinations of strength, modulus, and high-temperature stability. Compositions in the high-strength glass group include S-glass and R-glass, which are used for applications requiring physical properties that cannot be satisfied by conventional E-glass. Additional compositions are also available for specialized applications requiring extreme performance in any one area. The main competition for high-strength glasses in the marketplace comes from carbon and polymer fibers. Ultimately, the product of choice is based on a compromise between cost and performance and will vary depending on the application.

  11. The effect of heat treatment on the magnitude and composition of residual gas in sealed silica glass ampoules

    NASA Technical Reports Server (NTRS)

    Palosz, W.; Szofran, F. R.; Lehoczky, S. L.

    1994-01-01

    The residual gas pressure and composition in sealed silica glass ampoules as a function of different treatment procedures has been investigated. The dependence of the residual gas on the outgassing and annealing parameters has been determined. The effects of the fused silica brand, of the ampoule fabrication, and of post-outgassing procedures have been evaluated.

  12. Multimillion-to-billion atom molecular dynamics simulations of deformation, damage, nanoindentation, and fracture in silica glass and energetic materials

    NASA Astrophysics Data System (ADS)

    Chen, Yi-Chun

    Multimillion-to-billion molecular dynamics (MD) simulations are carried out to study atomistic mechanisms of deformation, damage and failure in silica glass and energetic materials. The simulations are based on experimentally validated interatomic potentials and employ highly efficiently algorithms for parallel architectures. The onset of void-void interaction is investigated by performing MD simulations of amorphous silica under hydrostatic tension. The simulations reveal that nanocavities in amorphous silica (a-SiO2), which are linked to Si-O rings, play an important role in void-void coalescence and inter-void ligament failure. Nanocracks nucleated by the migration of three-fold coordinated Si and nonbridging O on ---Si-O-Si-O--- rings are observed in the multimillion MD simulations of a single void in amorphous silica subjected to a high shear rate. With the increase in shear strain, nanocracks appear on void surfaces and the voids deform into a threadlike structure. At a strain of 40%, the voids break into fragments. The results are similar to experimental and theoretical studies of bubble deformation and breakup under shear. Defects such as voids are known to be important in the detonation of energetic materials. To investigate deformation of a void in an RDX crystal under high shear rate, we have performed million-atom reactive force field (ReaxFF) MD simulations. Simulations reveal that without breaking a bond, the excess strain energy leads to translational and rotational motion of RDX molecules. At a strain of 13%, molecules with high kinetic energy collapse inward without affecting the rest of the system. MD simulations of nanoindentation in amorphous silica reveal migration of defects and their recombination in the densified plastic region under and the material pileup region around the indenter. The plastic flow of silica glass is related to the defect transport mechanism where a defect migrates a considerable distance via a chain of bond

  13. Damage Resistant Optical Glasses for High Power Lasers: A Continuing Glass Science and Technology Challenge

    SciTech Connect

    Campbell, J H

    2002-08-28

    A major challenge in the development of optical glasses for high-power lasers is reducing or eliminating laser-induced damage to the interior (bulk) and the polished surface of the glass. Bulk laser damage in glass generally originates from inclusions. With the development of novel glass melting and forming processes it is now possible to make both fused silica and a suit of meta-phosphate laser glasses in large sizes ({approx}>0.5-lm diameter), free of inclusions and with high optical homogeneity ({approx} 10{sup -6}). Considerable attention also has been focused on improving the laser damage resistance to polished optical glass surfaces. Studies have shown that laser-induced damage to surfaces grows exponentially with the number of shots when illuminated with nano-second pulses at 351-nm above a given fluence threshold. A new approach for reducing and eliminating laser-induced surface damage relies on a series of post-polishing treatment steps. This damage improvement method is briefly reviewed.

  14. Deep drilling of silica glass by continuous-wave laser backside irradiation

    NASA Astrophysics Data System (ADS)

    Hidai, Hirofumi; Saito, Namiko; Matsusaka, Souta; Chiba, Akira; Morita, Noboru

    2016-04-01

    We propose a novel method for drilling of silica glass based on the continuous-wave laser backside irradiation (CW-LBI) phenomenon. The method allows drilling to be performed by single-shot irradiation using a CW laser. A spindle-shaped emission is generated in the bulk glass and is then guided to the glass surface, and at the instant that the beam reaches the surface, the glass material is ejected. The glass ejection process occurs for a time of ~250 μs. A hole that is similar in shape to that of the spindle-shaped emission is left. The hole length tended to increase linearly with increasing laser power. The laser power dependence of the spindle-shaped emission propagation velocity is also linear, and the velocity increases with increasing laser power. The hole diameters were smaller in the case where the laser focus position was set on the glass surface, and these diameters increased with increasing defocusing. The maximum hole depth reached more than 5 mm. Through-hole drilling was demonstrated using a 3-mm-thick glass substrate.

  15. Luminescence of silicon dioxide different polymorph modification: Silica glass, α-quartz, stishovite, coesite

    SciTech Connect

    Trukhin, A. N.

    2014-10-21

    Stishovite, coesite, oxygen deficient silica glass as well as irradiated α-quartz, exhibit two luminescence bands: a blue one and an UV one both excitable in the range within optical gap. There are similarities in spectral position and in luminescence decay kinetics among centers in these materials. The interpretation was done on the model of Oxygen Deficient Centers (ODC) [1]. The ODC(II) or twofold coordinated silicon and ODC(I) are distinguished. ODC(I) is object of controversial interpretation. The Si-Si oxygen vacancy [2] and complex defect including latent twofold coordinated silicon [3] are proposed. Remarkably, this luminescence center does not exist in as grown crystalline α-quartz. However, destructive irradiation of α-quartz crystals with fast neutrons, γ rays, or dense electron beams [4–6] creates ODC(I) like defect. In tetrahedron structured coesite the self trapped exciton (STE) luminescence observed with high energetic yield (∼30%) like in α-quartz crystals. STE in coesite coexists with oxygen deficient-like center. In octahedron structured stishovite STE was not found and only ODC exists.

  16. Direct Imaging of a Two-Dimensional Silica Glass on Graphene

    NASA Astrophysics Data System (ADS)

    Huang, P. Y.; Kurasch, S.; Srivastava, A.; Skakalova, V.; Kotakoski, J.; Krasheninnikov, A. V.; Hovden, R. M.; Mao, Q.; Meyer, J. C.; Smet, J.; Muller, D. A.; Kaiser, U.

    2012-02-01

    Large-area graphene substrates [1] are a promising lab bench for synthesizing and characterizing novel low-dimensional materials such as two-dimensional (2D) glasses. Unlike 2D crystals such as graphene, 2D glasses are almost entirely unexplored--yet they have enormous applicability for understanding amorphous structures, which are difficult to probe in 3D. We report direct observations of the structure of an amorphous 2D silica supported on graphene. To our knowledge, these results represent the first discovery of an extended 2D glass. The 2D glass enables aberration-corrected scanning transmission electron microscopy and spectroscopy, producing the first atomically-resolved experimental images of a glass. The images strikingly resemble Zachariasen's seminal 1932 cartoons of a 2D continuous random network glass [2] and allow direct structural analyses not possible in 3D glassy materials. DFT calculations indicate that van der Waals interactions with graphene energetically favor the 2D structure over bulk SiO2, suggesting that graphene can be instrumental in stabilizing new 2D materials. [1] J. C. Meyer et al., Nature 454, 319--322 (2008). [2] W. H. Zachariasen, J. Am. Chem. Soc. 54, 3841--3851 (1932).

  17. Alkali-silica reactivity of expanded glass granules in structure of lightweight concrete

    NASA Astrophysics Data System (ADS)

    Bumanis, G.; Bajare, D.; Locs, J.; Korjakins, A.

    2013-12-01

    Main component in the lightweight concrete, which provides its properties, is aggregate. A lot of investigations on alkali silica reaction (ASR) between cement and lightweight aggregates have been done with their results published in the academic literature. Whereas expanded glass granules, which is relatively new product in the market of building materials, has not been a frequent research object. Therefore lightweight granules made from waste glass and eight types of cement with different chemical and mineralogical composition were examined in this research. Expanded glass granules used in this research is commercially available material produced by Penostek. Lightweight concrete mixtures were prepared by using commercial chemical additives to improve workability of concrete. The aim of the study is to identify effect of cement composition to the ASR reaction which occurs between expanded glass granules and binder. Expanded glass granules mechanical and physical properties were determined. In addition, properties of fresh and hardened concrete were determined. The ASR test was processed according to RILEM AAR-2 testing recommendation. Tests with scanning electron microscope and microstructural investigations were performed for expanded glass granules and hardened concrete specimens before and after exposing them in alkali solution.

  18. Phosphate glass useful in high energy lasers

    DOEpatents

    Hayden, Yuiko T.; Guesto-Barnak, Donna

    1992-01-01

    A low-or no-silica, low- or no-alkali phosphate glass useful as a laser amplifier in a multiple pass, high energy laser system having a high thermal conductivity, K.sub.90.degree. C. >0.85 W/mK, a low coefficient of thermal expansion, .alpha..sub.20.degree.-300.degree. C. <80.times.10.sup.-7 /.degree.C., low emission cross section, .sigma.<2.5.times.10.sup.-20 cm.sup.2, and a high fluorescence lifetime, .tau.>325 .mu.secs at 3 wt. % Nd doping, consisting essentially of (on an oxide composition basis): wherein Ln.sub.2 O.sub.3 is the sum of lanthanide oxides; .SIGMA.R.sub.2 O is <5, R being Li, Na, K, Cs, and Rb; the sum of Al.sub.2 O.sub.3 and MgO is <24 unless .SIGMA.R.sub.2 O is 0, then the sum of Al.sub.2 O.sub.3 and MgO is <42; and the ratio of MgO to B.sub.2 O.sub.3 is 0.48-4.20.

  19. Interstitial BiO molecule as a broadband IR luminescence centre in bismuth-doped silica glass

    SciTech Connect

    Sokolov, V O; Plotnichenko, V G; Dianov, Evgenii M

    2011-12-31

    Experimental data on absorption and luminescence in optical fibres with a Bi : SiO{sub 2} glass core are compared to experimentally determined and calculated spectroscopic properties of the BiO molecule. The results suggest that the IR luminescence of Bi : SiO{sub 2} glass is due to interstitial BiO molecules. This assumption is supported by quantum-chemical simulation results for a BiO molecule in a ring interstice of the silica glass network.

  20. Readily fiberizable glasses having a high modulus of elasticity

    NASA Technical Reports Server (NTRS)

    Bacon, J. F.

    1970-01-01

    New glass compositions yield composites having higher moduli of elasticity and specific moduli of elasticity than commercially available glasses. Over a reasonable temperature range the glasses have a viscosity of about 20,000 poises. They consist of silica, alumina, magnesia, and beryllia, plus at least one uncommon oxide.

  1. Effects of adding silica particles on certain properties of resin-modified glass-ionomer cement

    PubMed Central

    Felemban, Nayef H.; Ebrahim, Mohamed I.

    2016-01-01

    Objective: This study was conducted to evaluate the effect of incorporation of silica particles with different concentrations on some properties of resin-modified glass ionomer cement (RMGIC): Microleakage, compressive strength, tensile strength, water sorption, and solubility. Materials and Methods: Silica particle was incorporated into RMGIC powder to study its effects, one type of RMGIC (Type II visible light-cured) and three concentrations of silica particles (0.06, 0.08, and 0.1% weight) were used. One hundred and twenty specimens were fabricated for measuring microleakage, compressive strength, tensile strength, water sorption, and solubility. Statistical Analysis: One-way analysis of variance and Tukey's tests were used for measuring significance between means where P ≤ 0.05. Results: RMGIC specimens without any additives showed significantly highest microleakage and lowest compressive and tensile strengths. Conclusion: Silica particles added to RMGIC have the potential as a reliable restorative material with increased compressive strength, tensile strength, and water sorption but decreased microleakage and water solubility. PMID:27095901

  2. Making Highly Pure Glass Rods

    NASA Technical Reports Server (NTRS)

    Naumann, R. J.

    1986-01-01

    Proposed quasi-containerless method for making glass rods or fibers minimizes contact between processing equipment and product. Method allows greater range of product sizes and shapes than achieved in experiments on containerless processing. Molten zone established in polycrystalline rod. Furnace sections separated, and glass rod solidifies between them. Clamp supports solid glass as it grows in length. Pulling clamp rapidly away from melt draws glass fiber. Fiber diameter controlled by adjustment of pulling rate.

  3. Smoothing of surface of silica glass by heat treatment in wet atmosphere

    SciTech Connect

    Osawa, Kenta; Katayama, Keiichi; Inoue, Hiroyuki; Masuno, Atsunobu; Zhang Yingjiu; Utsuno, Futoshi; Sugahara, Yoshiyuki; Koya, Kazuo; Fujinoki, Akira; Tawarayama, Hiromasa; Kawazoe, Hiroshi

    2011-05-15

    The effect of heat treatment on the surface morphology of fused silica glass substrates was investigated. It was found that the water vapor pressure during heat treatment had a strong influence on the flattening of the silica glass surface. The surface of the frosted glass changed into a transparent and lustrous surface after heat treatment with water vapor at 1200 deg. C for 48 h, whereas surface irregularities remained for heat treatment under a dry atmosphere. It was suggested that the difference in surface flattening was caused by changes in surface viscosity that depended on the concentration of OH groups on the surface. In order to quantitatively understand the effect of the heat treatment atmosphere, power spectral density (PSD) analysis and a novel peak and valley method were applied to the experimental results. From the PSD analysis, it was found that the Mullins' model could not explain the smoothing behavior by heat treatment. The peak and valley method, which could separate the surface morphology into the surface irregularities and the background undulation, revealed that the Mullins' model limitation was mainly for the surface and the background undulation could be understood within the model. These results indicate that there are different mechanisms between for the surface smoothing and for the relaxation of the background undulation.

  4. Effects of fictive temperature and halogen doping on the boson peak in silica glass

    NASA Astrophysics Data System (ADS)

    Shimodaira, N.; Saito, K.; Hiramitsu, N.; Matsushita, S.; Ikushima, A. J.

    2005-01-01

    We have investigated the effect of structural disorder on the boson peak in the Raman scattering of silica glass. The structural disorder was controlled in two ways: fictive temperature (Tf) and concentration of doped halogen element (F or Cl). As results, it has been simply demonstrated from nonreduced Raman spectra that (1) the peak position and full width at half maximum of the boson peak linearly increase with increasing Tf irrespective of the halogen concentrations, and in contrast, (2) the intensity is rather strongly dependent on the halogen concentrations than Tf . Since the result in (1) is much similar to the dependence on Tf and fluorine concentration for the IR absorption around 2260cm-1 , it has been concluded that the boson peak in silica glass is microscopically related to the average magnitude and distribution of Si-O-Si bond angles in glass network. The intensity enhancement in (2) has suggested two possibilities about the contribution of the doped halogen element to the boson peak: One is a direct contribution of F or Cl atoms due to diffusive motions falling within the range of the boson peak. The other is an indirect contribution introduced by the termination of Si-O-Si bridges to some sort of vibrational motions, which may be related to the boson peak.

  5. Etching of fused silica and glass with excimer laser at 351 nm

    NASA Astrophysics Data System (ADS)

    Zimmer, K.; Braun, A.; Böhme, R.

    2003-03-01

    The etching of solid surfaces at the interface to liquids is a new promising method for micro-machining of transparent materials. To extend the method to additional materials the pulsed radiation of a XeF-excimer laser (351 nm) was used for etching different types of glass (Corning Inc.: Pyrex, 7059 and Schott Group: D263, AF45) and fused silica for comparison. The etch rates of the investigated materials increase almost linear at low laser fluences. Threshold fluences for glass as low as 0.5 J/cm 2 and etch rates from 6 to 10 nm per pulse at 1 J/cm 2 have been determined. The etch rate and the threshold fluence depend also on the used liquid, consisting of a solvent (acetone, toluene) and a certain concentration of dissolved pyrene, but only little on the glass type. Due to the low etch rate typically very smooth surfaces are achieved. The surface roughness measured by AFM on Corning 7059-glass at an etch depth of 3.7 μm is as low as 4 nm. Contrary to the other glasses the surface roughness of Pyrex is much higher and dominated by typical arbitrary etch pits with micron dimensions. Comparing the etching of fused silica at a wavelength of 248 and 351 nm the used solution influences both the etch threshold and the etch rate. In accordance to earlier investigations at 248 nm also XeF-laser etching at the interface to an absorbing liquid results in a good surface quality, well defined patterns and almost no debris deposition. Thus, this technique is a good candidate for precise micro-machining applications.

  6. Effects of secondary electrons emitted from surroundings on defect formation in silica glass under γ-ray irradiation

    NASA Astrophysics Data System (ADS)

    Obata, S.; Yoshida, T.; Tanabe, T.; Allen, C.; Okada, M.; Xu, Qiu

    2006-09-01

    We have investigated the effects of secondary electrons and photons emitted from surrounding materials on defect formation in silica glass under γ-ray irradiation. SiO 2 (silica) glass plates and those sandwiched in a pair of various material disks (carbon, stainless steel or lead) were irradiated by γ-ray, and the optical absorption spectra (UV-vis spectra) of the silica glass plates before and after the irradiation were examined. UV-vis spectra of the glass plates after the irradiation showed three absorption bands peaked around 2 eV, 4 eV and 5.8 eV being assigned to color centers relate metal impurities (Al and Ge) and oxygen-deficient centers like E' center, respectively. All three bands were found to grow with γ-ray irradiation dose and saturated at higher doses, and absorbance of the bands at the saturation for the sandwiched glass plates was higher than that for the bare glass plate. Moreover, the saturated absorbance was higher for the glass plate sandwiched with heavier materials. Employing Monte Carlo N-Particle (MCNP) code for the simulation of the photon-electron transport process, enhanced energy deposition and numbers of secondary electrons and photons emitted from sandwiching material disks to a silica glass plate were calculated. The higher deposition energy correlates well to the higher saturated absorbance, indicating that the secondary electrons and photons emitted from the disks clearly enhanced the defect formation in the sandwiched silica glass plates. This suggests the existence of the dose effect above a critical does, i.e. the irradiation with higher dose will result in higher saturated absorbance.

  7. Short and medium range order in two-component silica glasses by positron annihilation spectroscopy

    SciTech Connect

    Inoue, K.; Kataoka, H.; Nagai, Y.; Hasegawa, M.; Kobayashi, Y.

    2014-05-28

    The dependence of chemical composition on the average sizes of subnanometer-scale intrinsic structural open spaces surrounded by glass random networks in two-component silica-based glasses was investigated systematically using positronium (Ps) confined in the open spaces. The average sizes of the open spaces for SiO{sub 2}-B{sub 2}O{sub 3} and SiO{sub 2}-GeO{sub 2} glasses are only slightly dependent on the chemical compositions because the B{sub 2}O{sub 3} and GeO{sub 2} are glass network formers that are incorporated into the glass network of the base SiO{sub 2}. However, the open space sizes for all SiO{sub 2}-R{sub 2}O (R = Li, Na, K) glasses, where R{sub 2}O is a glass network modifier that occupies the open spaces, decrease rapidly with an increase in the R{sub 2}O concentration. Despite the large difference in the ionic radii of the alkali metal (R) atoms, the open space sizes decrease similarly for all the alkali metal atoms studied. This dependence of the chemical composition on the open space sizes in SiO{sub 2}-R{sub 2}O observed by Ps shows that the alkali metal atoms do not randomly occupy the structural open spaces, but filling of the open spaces by R{sub 2}O proceeds selectively from the larger to the smaller open spaces as the R{sub 2}O concentrations are increased.

  8. Subsurface mechanical damage during bound abrasive grinding of fused silica glass

    NASA Astrophysics Data System (ADS)

    Blaineau, P.; André, D.; Laheurte, R.; Darnis, P.; Darbois, N.; Cahuc, O.; Neauport, J.

    2015-10-01

    The subsurface damage (SSD) introduced during bound abrasive grinding of fused silica glass was measured using a wet etch technique. Various process parameters and grinding configurations were studied. The relation between the SSD depth, the process parameters and forces applied by the grinding wheel on the sample was investigated and compared to a simulation using a discrete element method to model the grinding interface. The results reveal a relation between the SSD depth and the grinding forces normalized by the abrasive concentration. Regarding the creation of the SSD, numerical simulations indicate that only a small fraction of the largest particles in the diamond wheel are responsible for the depth of the damaged layer.

  9. Yb-doped silica glass and photonic crystal fiber based on laser sintering technology

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Wu, Jiale; Zhou, Guiyao; Xia, Changming; Liu, Jiantao; Tian, Hongchun; Liang, Wanting; Hou, Zhiyun

    2016-03-01

    We demonstrate the fabricating method for Yb3+-doped silica glass and double-cladding large mode area photonic crystal fiber (LMA PCF) based on laser sintering technology combined with a liquid phase doping method. The doped material prepared shows the amorphous property and the hydroxyl content is approximately 40 ppm. The attenuation of the fabricated LMA PCF is 14.2 dB m-1 at 976 nm, and the lowest value is 0.25 dB m-1 at 1200 nm. The laser slope efficiency is up to 70.2%.

  10. KrF- and ArF-excimer-laser-induced absorption in silica glasses produced by melting synthetic silica powder

    SciTech Connect

    Kuzuu, Nobu; Sasaki, Toshiya; Kojima, Tatsuya; Tanaka, Jun-ichiro; Nakamura, Takayuki; Horikoshi, Hideharu

    2013-07-07

    KrF- and ArF-excimer-laser-induced absorption of silica glasses produced by electric melting and flame fusion of synthetic silica powder were investigated. The growth of KrF-laser-induced absorption was more gradual than that of ArF-laser-induced absorption. Induced absorption spectra exhibited a peak at about 5.8 eV, of which the position and width differed slightly among samples and laser species. Widths of ArF-laser-induced absorption spectra were wider than those of KrF-laser-induced spectra. KrF-laser-induced absorption is reproducible by two Gaussian absorption bands peaking at 5.80 eV with full width at half maximum (FWHM) of 0.62 eV and at 6.50 eV with FWHM of 0.74 eV. For reproduction of ArF-laser-induced absorption, Gaussian bands at 5.41 eV with FWHM of 0.62 eV was necessary in addition to components used for reproducing KrF-laser-induced absorption. Based on the discussion of the change of defect structures evaluated from change of absorption components, we proposed that the precursor of the 5.8-eV band ascribed to E Prime center ({identical_to}Si{center_dot}) is {identical_to}Si-H HO-Si{identical_to} structures formed by the reaction between strained Si-O-Si bonds and interstitial H{sub 2} molecules during the irradiation.

  11. Fabrication of 250-nm-hole arrays in glass and fused silica by UV laser ablation

    NASA Astrophysics Data System (ADS)

    Karstens, R.; Gödecke, A.; Prießner, A.; Ihlemann, J.

    2016-09-01

    Parallel nanohole drilling in glass using an ArF excimer laser (193 nm) is demonstrated. For the first time, hole arrays with 500 nm pitch and individual holes with 250 nm diameter and more than 100 nm depth are fabricated by phase mask imaging using a Schwarzschild objective. Holes in soda lime glass are drilled by direct ablation; fused silica is processed by depositing a SiOx-film on SiO2, patterning the SiOx by ablation, and finally oxidizing the remaining SiOx to SiO2. Thermally induced ordered dewetting of noble metal films deposited on such templates may be used for the fabrication of plasmonic devices.

  12. Electron, hole and exciton self-trapping in germanium doped silica glass from DFT calculations with self-interactions correction

    SciTech Connect

    Du, Jincheng; Corrales, Louis R.; Tsemekhman, Kiril L.; Bylaska, Eric J.

    2007-02-01

    We performed density functional theory (DFT) calculations of electron, hole and exciton self-trapping in germanium doped silica glass to understand the refractive index change in these glasses induced by UV irradiation. The local structure relaxation and excess electron density distribution upon trapping of the above species were calculated. The results show that both trapped exciton and electron are highly localized on germanium ion and, to some extent, on its oxygen neighbors. Exciton self-trapping is found to lead to the formation of Ge E’ center and non-bridging hole center. Electron trapping changes the GeO4 tetrahedron structure into trigonal bi-pyramid with the majority of the excess electron density located along the equatorial line. Self-trapped hole is localized on bridging oxygen ions that are not coordinated to germanium atoms and leads to elongation of the Si-O bonds and change of the Si-O-Si bond angles. We did comparative study of standard DFT vs. DFT with a hybrid PBE0 exchange and correlation functional. The results show that the two methods give qualitatively similar relaxed structure and charge distribution for the electron and exciton trapping in germanium doped silica glass; however, only using the PBE0 functional reproduces the hole self-trapping. This research is supported by the Divisions of Chemical Science, Office of Basic Energy Sciences, US Department of Energy. This research was performed in part using the Molecular Science Computing Facility in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL) at the Pacific Northwest National Laboratory (PNNL). The EMSL is funded by DOE’s Office of Biological and Environmental Research. The pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

  13. Evaluation of Respirable Crystalline Silica in High School Ceramics Classrooms

    PubMed Central

    Fechser, Matthew; Alaves, Victor; Larson, Rodney; Sleeth, Darrah

    2014-01-01

    Air concentrations of respirable crystalline silica were measured in eleven (11) high school ceramics classrooms located in Salt Lake County, UT, USA. Respirable dust was collected on PVC filters using precision flow pumps and cyclone samplers (n = 44). Filters were subsequently analyzed for respirable dust and percent crystalline silica content. The geometric mean of the silica concentrations was 0.009 mg/m3 near the teacher’s work station and 0.008 mg/m3 near the kilns. The number of students in the classroom was correlated to the silica concentration in the ceramics classroom, but no correlation was found between the silica concentrations and either the size of the classroom or the age of the building. Results from this study indicate that ceramics teachers may be at an increased risk of exposure to crystalline silica based on the ACGIH TLV of 0.025 mg/m3, with an exceedance of 21%. PMID:24464235

  14. Evaluation of respirable crystalline silica in high school ceramics classrooms.

    PubMed

    Fechser, Matthew; Alaves, Victor; Larson, Rodney; Sleeth, Darrah

    2014-02-01

    Air concentrations of respirable crystalline silica were measured in eleven (11) high school ceramics classrooms located in Salt Lake County, UT, USA. Respirable dust was collected on PVC filters using precision flow pumps and cyclone samplers (n = 44). Filters were subsequently analyzed for respirable dust and percent crystalline silica content. The geometric mean of the silica concentrations was 0.009 mg/m3 near the teacher's work station and 0.008 mg/m3 near the kilns. The number of students in the classroom was correlated to the silica concentration in the ceramics classroom, but no correlation was found between the silica concentrations and either the size of the classroom or the age of the building. Results from this study indicate that ceramics teachers may be at an increased risk of exposure to crystalline silica based on the ACGIH TLV of 0.025 mg/m3, with an excess of 21%. PMID:24464235

  15. High-Strength Glass for Solar Applications

    NASA Technical Reports Server (NTRS)

    Bouquet, F. L.

    1987-01-01

    Technology for strengthening thin sections reviewed. Report reviews technology of high-strength glass for such solar applications as heat collectors, reflectors, and photovoltaic arrays. Discusses most feasible methods - heat strengthening and chemical strengthening of increasing strength of glass for solar-energy use. Also estimates cost and availability of high-strength glass and considers physical characteristics, amenability to back-silvering, and effects of atmospheric contamination.

  16. Non-textured laser modification of silica glass surface: Wettability control and flow channel formation

    NASA Astrophysics Data System (ADS)

    Aono, Yuko; Hirata, Atsushi; Tokura, Hitoshi

    2016-05-01

    Local wettability of silica glass surface is modified by infrared laser irradiation. The silica glass surface exhibits hydrophobic property in the presence of sbnd CF3 or sbnd (CH3)2 terminal functional groups, which are decomposed by thermal treatment, and degree of the decomposition depends on the applied heat. Laser irradiation can control the number of remaining functional groups according to the irradiation conditions; the contact angle of deionized water on the laser modified surfaces range from 100° to 40°. XPS analysis confirms that the variation in wettability corresponds to the number of remaining sbnd CF3 groups. The laser irradiation achieves surface modification without causing any cracks or damages to the surface, as observed by SEM and AFM; moreover, surface transparency to visible light and surface roughness remains unaffected. The proposed method is applied to plane flow channel systems. Dropped water spreads only on the hydrophilic and invisible line modified by the laser irradiation without formation of any grooves. This indicates that the modified line can act as a surface channel. Furthermore, self-transportation of liquid is also demonstrated on a channel with gradually-varied wettability along its length. A water droplet on a hydrophobic side is self-transported to a hydrophilic side due to contact-angle hysteresis force without any actuators or external forces.

  17. Ultradeep fused silica glass etching with an HF-resistant photosensitive resist for optical imaging applications

    NASA Astrophysics Data System (ADS)

    Nagarah, John M.; Wagenaar, Daniel A.

    2012-03-01

    Microfluidic and optical sensing platforms are commonly fabricated in glass and fused silica (quartz) because of their optical transparency and chemical inertness. Hydrofluoric acid (HF) solutions are the etching media of choice for deep etching into silicon dioxide substrates, but processing schemes become complicated and expensive for etching times greater than 1 h due to the aggressiveness of HF migration through most masking materials. We present here etching into fused silica more than 600 µm deep while keeping the substrate free of pits and maintaining a polished etched surface suitable for biological imaging. We utilize an HF-resistant photosensitive resist (HFPR) which is not attacked in 49% HF solution. Etching characteristics are compared for substrates masked with the HFPR alone and the HFPR patterned on top of Cr/Au and polysilicon masks. We used this etching process to fabricate suspended fused silica membranes, 8-16 µm thick, and show that imaging through the membranes does not negatively affect image quality of fluorescence microscopy of biological tissue. Finally, we realize small through-pore arrays in the suspended membranes. Such devices will have applications in planar electrophysiology platforms, especially where optical imaging is required.

  18. Yb3+-doped large core silica fiber for fiber laser prepared by glass phase-separation technology.

    PubMed

    Chu, Yingbo; Ma, Yunxiu; Yang, Yu; Liao, Lei; Wang, Yibo; Hu, Xiongwei; Peng, Jinggang; Li, Haiqing; Dai, Nengli; Li, Jinyan; Yang, Luyun

    2016-03-15

    We report on the preparation and optical characteristics of an Yb3+-doped large core silica fiber with the active core prepared from nanoporous silica rod by the glass phase-separation technology. The measurements show that the fiber has an Yb3+ concentration of 9811 ppm by weight, a low background attenuation of 0.02 dB/m, and absorption from Yb3+ about 5.5 dB/m at 976 nm. The laser performance presents a high slope efficiency of 72.8% for laser emission at 1071 nm and a low laser threshold of 3 W within only 2.3 m fiber length. It is suggested that the glass phase-separation technology shows great potential for realizing active fibers with larger core and complex fiber designs. PMID:26977675

  19. High-Density, Scintillating, Fluoride Glass Calorimeters

    NASA Astrophysics Data System (ADS)

    Akgun, Ugur; Xie, Qiuchen

    2014-03-01

    The unprecedented radiation levels in current Large Hadron Collider runs, and plans to even increase the luminosity creates a need for new detector technologies to be investigated. Here, we propose to use high density, scintillating, fluoride glasses as active media in calorimeters. CHG3 is a special example of this glass family, which has been developed specifically for hadron collider experiments, and is known for fast response time, in addition to high light yield. In this presentation, the results from a computational study on the performances of the two different designs of CHG3 glass calorimeters are reported. First design reads the signal directly from the edge of the glass plate; the second design utilizes wavelength-shifting fibers to carry the signal out of the glass plate. Each simulation model is a sampling calorimeter with 20 alternating layers of glass and iron absorber. By changing the absorber thickness we tested hadronic as well as electromagnetic capabilities of the calorimeter models.

  20. High power operation of cladding pumped holmium-doped silica fibre lasers.

    PubMed

    Hemming, Alexander; Bennetts, Shayne; Simakov, Nikita; Davidson, Alan; Haub, John; Carter, Adrian

    2013-02-25

    We report the highest power operation of a resonantly cladding-pumped, holmium-doped silica fibre laser. The cladding pumped all-glass fibre utilises a fluorine doped glass layer to provide low loss cladding guidance of the 1.95 µm pump radiation. The operation of both single mode and large-mode area fibre lasers was demonstrated, with up to 140 W of output power achieved. A slope efficiency of 59% versus launched pump power was demonstrated. The free running emission was measured to be 2.12-2.15 µm demonstrating the potential of this architecture to address the long wavelength operation of silica based fibre lasers with high efficiency. PMID:23481989

  1. High Tech Art: Chameleon Glass

    NASA Technical Reports Server (NTRS)

    1993-01-01

    Dichroic Glass is a technology wherein extremely thin films of metal are vacuum deposited on a glass surface. The coated glass shields spacecraft instruments from cosmic radiation and protects human vision from unfiltered sunlight in space. Because the coating process allows some wavelengths of light and color to reflect and others to pass through, a chameleon effect is produced. Murray Schwartz, a former aerospace engineer, has based his business KROMA on this NASA optical technology. He produces dichroic stained glass windows, mobiles and jewelry. The technique involves deposition of super thin layers of metal oxides applied one layer at a time in a specific order and thickness for the desired effect. His product line is unique and has been very successful.

  2. Quasi-Resonant Nonlinear Absorption for Optical Power Limiting: solgel-Processed Er(3+)-Doped Multicomponent Silica Glass.

    PubMed

    Maciel, G S; Biswas, A; Friend, C S; Prasad, P N

    2000-05-20

    We demonstrate optical power limiting by what we believe to be a new mechanism of nonlinear absorption, which involves a quasi-resonant ground-state absorption that is either phonon assisted or assisted by the presence of defect sites (tail absorption). Such a mechanism provides high transmittance at low intensity yet optical limiting under cw conditions. The sample used was a novel solgel-processed Er(3+)-doped multicomponent silica glass. In this system the nonlinear absorption process is achieved because the resonant excited-state ((4)I(13/2) ? (4)S(3/2)) absorption cross section is larger than the quasi-resonant ground-state ((4)I(15/2) ? (4)I(9/2)) absorption cross section. PMID:18345156

  3. Formation, structural and optical characterization of neodymium doped-zinc soda lime silica based glass

    NASA Astrophysics Data System (ADS)

    Zamratul, M. I. M.; Zaidan, A. W.; Khamirul, A. M.; Nurzilla, M.; Halim, S. A.

    New glass system of neodymium - doped zinc soda lime silica glass has been synthesized for the first time by melt-quenching of glass waste soda lime silica (SLS) with zinc oxide (ZnO) as precursor glass and Nd2O3 as dopant. In order to examine the effect of Nd3+ on the structural and optical properties, the prepared sample of structure [(ZnO)0.5(SLS)0.5](Nd2O3)x (x = 0, 1, 2, 3, 4 and 5 wt%) was characterized through X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, UV-Vis spectroscopy (UV-Vis) and the photoluminescence (PL). XRD pattern justifies the amorphous nature of synthesized glasses. FTIR spectroscopy has been used to observe the structural evolution of ZnO4 and SiO4 groups. The UV-Vis-NIR absorption spectra reveals seven peaks centered at excitation of electron from ground state 4I9/2 to 4D3/2 + 4D5/2 (∼360 nm), 2G9/2 + 2D3/2 + 2P3/2(∼470 nm), 2K13/2 + 4G7/2 + 4G9/2 (∼523 nm), 4G5/2 + 2G7/2 (∼583 nm), 4F9/2 (∼678 nm), 4S3/2 + 4F7/2 (∼748 nm) and 4F5/2 + 2H9/2 (∼801 nm). PL spectra under the excitation of 800 nm display four emission bands centered at 531 nm, 598 nm, 637 nm and 671 nm corresponding to 4G7/2 → 4I9/2, (4G7/2 → 4I11/2, 4G5/2 → 4I9/2), (4G5/2 → 4I11/2) and (4G7/2 → 4I13/2, 4G5/2 → 4I11/2) respectively.

  4. High thermal expansion, sealing glass

    DOEpatents

    Brow, R.K.; Kovacic, L.

    1993-11-16

    A glass composition is described for hermetically sealing to high thermal expansion materials such as aluminum alloys, stainless steels, copper, and copper/beryllium alloys, which includes between about 10 and about 25 mole percent Na[sub 2]O, between about 10 and about 25 mole percent K[sub 2]O, between about 5 and about 15 mole percent Al[sub 2]O[sub 3], between about 35 and about 50 mole percent P[sub 2]O[sub 5] and between about 5 and about 15 mole percent of one of PbO, BaO, and mixtures thereof. The composition, which may also include between 0 and about 5 mole percent Fe[sub 2]O[sub 3] and between 0 and about 10 mole percent B[sub 2]O[sub 3], has a thermal expansion coefficient in a range of between about 160 and 210[times]10[sup [minus]7]/C and a dissolution rate in a range of between about 2[times]10[sup [minus]7] and 2[times]10[sup [minus]9]g/cm[sup 2]-min. This composition is suitable to hermetically seal to metallic electrical components which will be subjected to humid environments over an extended period of time.

  5. High thermal expansion, sealing glass

    DOEpatents

    Brow, Richard K.; Kovacic, Larry

    1993-01-01

    A glass composition for hermetically sealing to high thermal expansion materials such as aluminum alloys, stainless steels, copper, and copper/beryllium alloys, which includes between about 10 and about 25 mole percent Na.sub.2 O, between about 10 and about 25 mole percent K.sub.2 O, between about 5 and about 15 mole percent Al.sub.2 O.sub.3, between about 35 and about 50 mole percent P.sub.2 O.sub.5 and between about 5 and about 15 mole percent of one of PbO, BaO, and mixtures thereof. The composition, which may also include between 0 and about 5 mole percent Fe.sub.2 O.sub.3 and between 0 and about 10 mole percent B.sub.2 O.sub.3, has a thermal expansion coefficient in a range of between about 160 and 210.times.10-7/.degree.C. and a dissolution rate in a range of between about 2.times.10.sup.- 7 and 2.times.10.sup.-9 g/cm.sup.2 -min. This composition is suitable to hermetically seal to metallic electrical components which will be subjected to humid environments over an extended period of time.

  6. Compositional dependent response of silica-based glasses to femtosecond laser pulse irradiation

    NASA Astrophysics Data System (ADS)

    Seuthe, Thomas; Grehn, Moritz; Mermillod-Blondin, Alexandre; Bonse, Jörn; Eberstein, Markus

    2013-11-01

    Femtosecond laser pulse irradiation of inorganic glasses allows a selective modification of the optical properties with very high precision. This results in the possibility for the production of three-dimensional functional optical elements in the interior of glass materials, such as optical data storage, waveguide writing, etc. The influence of the chemical glass composition to the response upon ultrashort laser irradiation has not been studied systematically. For that, simple silicabased model glasses composed of systematically varying alkaline- and earth-alkaline components were prepared, irradiated on the surface and in the volume with single fs-laser pulses (~130 fs, 800 nm), and were subsequently analyzed by means of micro-Raman spectroscopy and quantitative phase contrast microscopy in order to account for changes in the glass structure and for alterations of the optical refractive index, respectively. The Raman spectroscopic studies of the laser-irradiated spots revealed no change in the average binding configuration (the so called Q-structure), but local changes of bond-angles and bond-lengths within the glass structure structure. Those changes are explained by structural relaxation of the glass network due to densification caused by a transient laser-induced plasma generation and the following shock wave and other thermal phenomena. Glasses with a low amount of network modifiers show changes in the Si-O network while glasses with a high amount of network modifiers react primarily via variation of the nonbridging oxygen ions. The results are discussed in terms of possible structural response mechanisms and conclusions are outlined regarding glass compositions with technical suitability for fs-laser modifications.

  7. Nanostructuring an erbium local environment inside sol-gel silica glasses: toward efficient erbium optical fiber lasers

    NASA Astrophysics Data System (ADS)

    Savelii, Inna; El Hamzaoui, Hicham; Bigot, Laurent; Bouwmans, Géraud; Fsaifes, Ihsan; Capoen, Bruno; Bouazaoui, Mohamed

    2016-02-01

    To extend the use of erbium- (Er-)/aluminum- (Al-) codoped optical fibers in hostile environments, the reduction of the Al amount has been identified as a serious way to harden them against harsh radiation. In this work, sol-gel monolithic Er3+-doped and Er3+/Al3+-codoped silica glasses were prepared from nanoporous silica xerogels soaked in a solution containing an Er salt together or not with an Al salt. After sintering, these glasses were used as the core material of microstructured optical fibers made by the stack-and-draw method. The influence of Al incorporation on the optical properties of Er3+-doped silica glasses and fibers is investigated. This approach enabled the preparation of silica glasses containing dispersed Er3+ ions with low Al content. The obtained fibers have been tested in an all-fibered cavity laser architecture. The Er3+/Al3+-codoped fiber laser presents a maximum efficiency of 27% at 1530 nm. We show that without Al doping, the laser exhibits lower performances that depend on Er content inside the doped fiber core. The effect of Er pair-induced quenching also has been investigated through nonsaturable absorption experiments, which clearly indicate that the fraction of Er ion pairs is significantly reduced in the Al-codoped fiber.

  8. Enhanced Si-O Bond Breaking in Silica Glass by Water Dimer: A Hybrid Quantum-Classical Simulation Study

    NASA Astrophysics Data System (ADS)

    Kouno, Takahisa; Ogata, Shuji; Shimada, Takaaki; Tamura, Tomoyuki; Kobayashi, Ryo

    2016-05-01

    A hybrid quantum-classical simulation of a 4,608-atom silica glass is performed at a temperature of 400 K with either a water monomer or dimer inserted in a void. The quantum region that includes the water and the surrounding atoms is treated by the density-functional theory (DFT). During a simulation, the silica glass is gradually compressed or expanded. No Si-O bond breaking occurs with a water monomer until the silica glass collapses. With a water dimer, we find that Si-O bond breaking occurs through three steps in 3 out of 24 compression cases: (i) H-transfer as 2H2O → OH- + H3O+ accompanied by the adsorption of OH- at a strained Si to make it five-coordinated, (ii) breaking of a Si-O bond that originates from the five-coordinated Si, and (iii) H-transfer from H3O+ to the O of the broken Si-O bond. A separate DFT calculation confirms that the barrier energy of the bond breaking with a water dimer under compression is smaller than that with a water monomer and that the barrier energy decreases significantly when the silica glass is compressed further.

  9. Energy dissipation at the silica glass/compressed aerogel interface: The fate of Wild 2 mineral grains and fragments smaller than ~100 nm

    NASA Astrophysics Data System (ADS)

    Rietmeijer, Frans J. M.

    2016-07-01

    Allocation FC6,0,10,0,26 from Stardust track 10 shows a slightly wavy silica glass/compressed silica aerogel interface exposing a patchwork of compressed silica aerogel domains and domains of silica glass with embedded Wild 2 materials in ultra-thin TEM sections. This interface is where molten silica encountered compressed silica aerogel at temperatures <100 °C, and probably near room temperature, causing steep thermal gradients. An Mg, Fe-olivine grain, and a plagioclase-leucite intergrowth survived without melting in silica glass. A Mg-, Al-, Ca-, K-bearing silica globule moved independently as a single object. Two clusters of pure iron, low-Ni iron, and low-Ni, low-sulfur Fe-Ni-S grains also survived intact and came to rest right at the interface between silica glass/compressed silica aerogel. There are numerous Fe-Ni-S nanograins scattered throughout MgO-rich magnesiosilica glass, but compositionally similar Fe-Ni-S are also found in the compressed silica aerogel, where they are not supposed to be. This work could not establish how deep they had penetrated the aerogel. Iron nanograins in this allocation form core-ring grains with a gap between the iron core and a surrounding ring of thermally modified aerogel. This structure was caused when rapid, thermal expansion of the core heated the surrounding compressed aerogel that upon rapid cooling remained fixed in place while the iron core shrank back to its original size. The well-known volume expansion of pure iron allowed reconstruction of the quench temperature for individual core-ring grains. These temperatures showed the small scale of thermal energy loss at the silica glass/compressed silica aerogel interface. The data support fragmentation of olivine, plagioclase, and iron and Fe ± low-Ni grains from comet 81P/Wild 2 during hypervelocity capture.

  10. Osseointegration properties of titanium dental implants modified with a nanostructured coating based on ordered porous silica and bioactive glass nanoparticles

    NASA Astrophysics Data System (ADS)

    Covarrubias, Cristian; Mattmann, Matías; Von Marttens, Alfredo; Caviedes, Pablo; Arriagada, Cristián; Valenzuela, Francisco; Rodríguez, Juan Pablo; Corral, Camila

    2016-02-01

    The fabrication of a nanoporous silica coating loaded with bioactive glass nanoparticles (nBG/NSC) on titanium dental implant surface and its in vitro and in vivo evaluation is presented. The coating was produced by a combined sol-gel and evaporation induced self-assembly process. In vitro bioactivity was assessed in simulated body fluid (SBF) and investigating the osteogenic differentiation of human bone marrow mesenchymal stem cells (hBMSCs). A rat tibial model was employed to analyze the bone response to nBG/NSC-modified titanium implant surface in vivo. The nBG/NSC coating was confirmed at nano level to be constituted by a highly ordered nanoporous silica structure. The coating nanotopography in conjunction with the bioactivity of the BG particles accelerate the in vitro apatite formation and promote the osteogenic differentiation of hBMSCs in absence of osteogenic supplements. These properties accelerate the formation of bone tissue in the periphery of the implant after 3 weeks of implantation. Backscattered scanning electron microscopy images revealed the presence of gaps and soft tissue in the unmodified implant after 6 weeks, whereas the nBG/NSC-modified implant showed mature bone in intimate contact with the implant surface. The nBG/NSC coating appears promising for accelerating the osseointegration of dental implants.

  11. High-throughput planer glass coating using Laser Reactive Deposition (LRD)

    NASA Astrophysics Data System (ADS)

    Bi, Xiangxin; Mosso, Ronald; Chiruvolu, Shiv; Euvrard, Eric; Bryan, Michael A.; Jenks, Tim

    2001-10-01

    Planar Lightwave Circuit (PLC) technology has been considered as a promising route to integrate a greater number of channels and more optical functionalities onto a small foot print, enabling smaller device sizes and lower costs of manufacturing by using existing semiconductor process technologies. Among several planar technology platforms, silica-on-silicon technology comprised of a silica higher index core and lower index clad has taken the lead in this direction. One of the major advantages of silica based PLC technology is its relative ease to couple to a single mode silica fiber because of a close match of the index and dimensions of the waveguide core of planar chip and fiber. In this structure, to completely confine and guide light signals, the silica layer stack, including lower clad, core and top clad can be as thick as 20 - 40 microns, in which the core layer thickness is around 6 - 8 micron. This has presented a major challenge to several major silica film deposition technologies including CVD, FHD, PVD, and Sol-Gel processes. In addition to basic requirements for optical quality of the glass film, low cost manufacture also demands a high deposition rate to reduce process costs in the fabrication of these planar chips. In this paper, we present a high throughput and planar glass coating technology to lay down doped and undoped glass films at unprecedented rates. The technology is comprised of a laser reactive deposition (LRDTM) process developed based on our nanoscale particle manufacture (NPMTM) methods pioneered by NanoGram Corporation. We report results on planar glass films deposited using this technology and describe the concepts employed using this technology in manufacturing. Furthermore, we will compare it with various existing glass film deposition technologies.

  12. DEFENSE HIGH LEVEL WASTE GLASS DEGRADATION

    SciTech Connect

    W. Ebert

    2001-09-20

    The purpose of this Analysis/Model Report (AMR) is to document the analyses that were done to develop models for radionuclide release from high-level waste (HLW) glass dissolution that can be integrated into performance assessment (PA) calculations conducted to support site recommendation and license application for the Yucca Mountain site. This report was developed in accordance with the ''Technical Work Plan for Waste Form Degradation Process Model Report for SR'' (CRWMS M&O 2000a). It specifically addresses the item, ''Defense High Level Waste Glass Degradation'', of the product technical work plan. The AP-3.15Q Attachment 1 screening criteria determines the importance for its intended use of the HLW glass model derived herein to be in the category ''Other Factors for the Postclosure Safety Case-Waste Form Performance'', and thus indicates that this factor does not contribute significantly to the postclosure safety strategy. Because the release of radionuclides from the glass will depend on the prior dissolution of the glass, the dissolution rate of the glass imposes an upper bound on the radionuclide release rate. The approach taken to provide a bound for the radionuclide release is to develop models that can be used to calculate the dissolution rate of waste glass when contacted by water in the disposal site. The release rate of a particular radionuclide can then be calculated by multiplying the glass dissolution rate by the mass fraction of that radionuclide in the glass and by the surface area of glass contacted by water. The scope includes consideration of the three modes by which water may contact waste glass in the disposal system: contact by humid air, dripping water, and immersion. The models for glass dissolution under these contact modes are all based on the rate expression for aqueous dissolution of borosilicate glasses. The mechanism and rate expression for aqueous dissolution are adequately understood; the analyses in this AMR were conducted to

  13. Particle size and surfactant effects on chemical mechanical polishing of glass using silica-based slurry

    SciTech Connect

    Zhang Zefang; Liu Weili; Song Zhitang

    2010-10-01

    This study explores the effect of particle size and surfactant on the chemical mechanical polishing (CMP) of glass using colloidal silica-based slurry. It was found that the material removal rate strongly depends on the particle size and the types of surfactants and that the rms roughness was independent of particle size and correlated to surfactants. On the basis of polishing results, it was concluded that the main polishing mechanism was changed from indentation mechanism to surface-area mechanism, with the variation of particle size. In addition, the molecular structure, charge type, and lubricating effect of the surfactants play an important role in the dispersion of abrasive particles and in the CMP performance.

  14. Influence of silver on the Sm3+ luminescence in ``Aerosil'' silica glasses

    NASA Astrophysics Data System (ADS)

    Malashkevich, G. E.; Semchenko, A. V.; Sukhodola, A. A.; Stupak, A. P.; Sukhodolov, A. V.; Plyushch, B. V.; Sidskiĭ, V. V.; Denisenko, G. A.

    2008-08-01

    The introduction of silver into the samarium-containing silica glasses prepared by the original solgel method leads to the formation of complex optical centers involving samarium ions and simple and/or complex silver ions. These centers are characterized by the effective sensitization of Sm3+ luminescence by Ag+, (Ag2)+, and (Ag+)2 ions according to the exchange mechanism for, at least, Sm3+-Ag+ centers. The formation of Sm-Ag centers is accompanied by an increase in the concentration of nonbridging oxygen ions, which prevent the reduction of silver ions by hydrogen. Silver nanoparticles formed in small amounts upon this reduction are effective quenchers of luminescence from the corresponding excited states of Sm3+ ions.

  15. ESR study of the heterogeneous radical decomposition of hydrogen peroxide vapor on glass and silica

    SciTech Connect

    Arutyunyan, A.Z.; Grigoryan, G.L.; Nalbandyan, A.B.

    1986-01-01

    This paper presents the results of a study carried out on the laws governing the accumulation of HO/sub 2/ radicals in the gas phase during the heterogeneous decomposition of hydrogen peroxide vapor on surfaces of Pyrex glass and silica tablets. It was found that for short contact times (10/sup -2/ sec) and low mixture pressures (of the order of several hundred Pa) the decomposition of H/sub 2/O/sub 2/ occurs mainly on the external surface of the tablets. Rates and activation energies were determined for the generation and heterogeneous decay of HO/sub 2/ radicals on these surfaces at 473-623 K. A low activation energy of 4.6 kJ/mole was obtained for the radical decay process.

  16. The vibrational behavior of silica clusters at the glass transition: Ab initio calculations and thermodynamic implications.

    PubMed

    Ottonello, G; Zuccolini, M Vetuschi; Belmonte, D

    2010-09-14

    We present the results of a computational investigation with ab initio procedures of the structure-energy and vibrational properties of silica clusters in a dielectric continuum with dielectric constant ε=3.8, through density functional theory/B3LYP gas phase calculations coupled with a polarized continuum model approach [integral equation formalism applied to a polarized continuum (IEFPCM)] and those of the periodical structure D(6h) which leads to the α-cristobalite polymorph of silica when subjected to symmetry operations with the same functional within the linear combination of atomic orbitals (LCAO) approximation and in the framework of Bloch's theorem. Based on the computed energies and vibrational features, an aggregate of the D(6h) network and the monomer locally ordered in the short-medium range and both present in the glass in a mutual arrangement lacking of spatial continuity reproduces satisfactorily the experimentally observed low T heat capacity and the deviation from the Debye T(3) law. Above T(g), the experimental heat capacity of the liquid is perfectly reproduced summing to the internal modes the translational and rotational contributions to the bulk heat capacity and subtracting the (acoustic) terms arising from coherent motion (no longer existent). PMID:20849179

  17. Glass-ceramic hermetic seals to high thermal expansion metals

    DOEpatents

    Kramer, D.P.; Massey, R.T.

    1987-04-28

    A process for forming glass-ceramic materials from an alkaline silica-lithia glass composition comprising 60-72 mole-% SiO/sub 2/, 18-27 mole-% Li/sub 2/O, 0-5 mole-% Al/sub 2/O/sub 3/, 0-6 mole-% K/sub 2/O, 0-3 mole-% B/sub 2/O/sub 3/, and 0.5-2.5 mole-% P/sub 2/O/sub 5/, which comprises heating said glass composition at a first temperature within the 950-1050/degree/C range for 5-60 minutes, and then at a devitrification temperature within the 700-900/degree/C range for about 5-300 minutes to obtain a glass-ceramic having a thermal expansion coefficient of up to 210 x 10/sup /minus/7///degree/C. These ceramics form strong, hermetic seals with high expansion metals such as stainless steel alloys. An intermediate nucleation heating step conducted at a temperature within the range of 675-750/degree/C for 10-120 minutes may be employed between the first stage and the devitrification stage. 1 fig., 2 tabs.

  18. Phosphate glass useful in high energy lasers

    DOEpatents

    Hayden, Y.T.; Guesto-Barnak, D.

    1992-12-22

    Disclosed is a low-or no-silica, low- or no-alkali phosphate glass useful as a laser amplifier in a multiple pass, high energy laser system having a high thermal conductivity, K[sub 90 C] >0.85 W/mK, a low coefficient of thermal expansion, [alpha][sub 20-300 C] <80[times]10[sup [minus]7]/C, low emission cross section, [sigma]<2.5[times]10[sup [minus]20] cm[sup 2], and a high fluorescence lifetime, [tau]>325 [mu]secs at 3 wt. % Nd doping, consisting essentially of (on an oxide composition basis): (Mole %) P[sub 2]O[sub 5], (52-72); Al[sub 2]O[sub 3], (0-<20); B[sub 2]O[sub 3], (>0-25); ZnO, (0-31); Li[sub 2]O, (0-5); K[sub 2]O, (0-5); Na[sub 2]O, (0-5); Cs[sub 2]O, (0-5); Rb[sub 2]O, (0-5); MgO, (>0-<30); CaO, (0-20); BaO, (0-20); SrO, (0-<20); Sb[sub 2]O[sub 3], (0-<1); As[sub 2]O[sub 3], (0-<1); Nb[sub 2]O[sub 5], (0-<1); Ln[sub 2]O[sub 3], (up to 6.5); PbO, (0-<5); and SiO[sub 2], (0-3); wherein Ln[sub 2]O[sub 3] is the sum of lanthanide oxides; [Sigma]R[sub 2]O is <5, R being Li, Na, K, Cs, and Rb; the sum of Al[sub 2]O[sub 3] and MgO is <24 unless [Sigma]R[sub 2]O is 0, then the sum of Al[sub 2]O[sub 3] and MgO is <42; and the ratio of MgO to B[sub 2]O[sub 3] is 0.48-4.20. 7 figs.

  19. 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.

  20. A highly ordered cubic mesoporous silica/graphene nanocomposite.

    PubMed

    Lee, Chang-Wook; Roh, Kwang Chul; Kim, Kwang-Bum

    2013-10-21

    A highly ordered cubic mesoporous silica (KIT-6)/graphene nanocomposite and 2D KIT-6 nanoflakes were synthesized using a novel synthesis methodology. The non-ionic triblock copolymer, P123, played a dual role as a structure-directing agent in the formation of the cubic mesoporous structure and as a cross-linking agent between mesoporous silica and graphene. The prepared (KIT-6)/graphene nanocomposite could act as a template for the preparation of mesoporous material/graphene nanocomposites. PMID:24057016

  1. High purity silica reflective heat shield development

    NASA Technical Reports Server (NTRS)

    Blome, J. C.; Drennan, D. N.; Schmitt, R. J.

    1974-01-01

    Measurements were made of reflectance in the vacuum ultraviolet down to 0.15 micron. Scattering coefficients (S) and absorption coefficients (K) were also measured. These coefficients express the optical properties and are used directly in a thermodynamic analysis for sizing a heat shield. The effect of the thin silica melt layer formed during entry was also studied from the standpoint of trapped radiant energy.

  2. Strength of inorganic glass

    SciTech Connect

    Kurkjian, C.R.

    1985-01-01

    This book presents information on the following topics: a look at the history of glass strength; atomistic theory of fracture; surface chemistry in relation to the strength and fracture of silicate glasses; high-speed photographic investigations of the dynamic localized loading of some oxide glasses; a correction for measurements of contact area using Newton's rings; envionmentally enhanced crack growth; fatigue in glass; behavior of flaws in fused silica fibers; fracture toughness of chalcogenide glasses and glass-ceramics; fracture analysis of glass surfaces; and fracture mechanics parameters for glasses - a compilation and correlation.

  3. Quantifying silica reactivity in subsurface environments: Reaction affinity and solute matrix controls on quartz and SiO{sub 2} glass. 1997 annual progress report

    SciTech Connect

    Dove, P.M.

    1997-10-15

    'The author reports the preliminary results of the experiments on the dissolution behavior of vitreous silica (v-SiO{sub 2}) into aqueous solutions of variable pH and ionic strength. The experiments are being conducted in mixed flow reactors with a high circulation rate that simulates constant-stirred conditions, the efficacy of which the authors discuss below. The preliminary results indicate that v-SiO{sub 2} dissolves into aqueous solutions approximately two orders of magnitude more quickly than crystalline silica (e.g., quartz). With additional experiments, they will utilize the dissolution rate data as a framework for understanding the behavior of waste glass compositions in the subsurface. In other work related to the studies of glass reactivity, the author has written one book chapter that will be published as part of a proceedings for the CEA/VALRHO international nuclear waste disposal conference held in Mejannes le Clap, France. In separate work, she is presently writing a second book chapter for the volume entitled Adsorption on Silica Surfaces.'

  4. Reaction cured glass and glass coatings

    NASA Technical Reports Server (NTRS)

    Goldstein, H. E.; Leiser, D. B.; Katvala, V. W. (Inventor)

    1978-01-01

    The invention relates to reaction cured glass and glass coatings prepared by reacting a compound selected from the group consisting of silicon tetraboride, silicon hexaboride, other boron silicides, boron and mixtures with a reactive glass frit composed of a porous high silica borosilicate glass and boron oxide. The glassy composites of the present invention are useful as coatings on low density fibrous porous silica insulations used as heat shields and for articles such as reaction vessels that are subjected to high temperatures with rapid heating and cooling and that require resistance to temperature and repeated thermal shock at temperatures up to about 1482C (2700PF).

  5. Influence of amorphous silica on the hydration in ultra-high performance concrete

    SciTech Connect

    Oertel, Tina; Helbig, Uta; Hutter, Frank; Kletti, Holger; Sextl, Gerhard

    2014-04-01

    Amorphous silica particles (silica) are used in ultra-high performance concretes to densify the microstructure and accelerate the clinker hydration. It is still unclear whether silica predominantly increases the surface for the nucleation of C–S–H phases or dissolves and reacts pozzolanically. Furthermore, varying types of silica may have different and time dependent effects on the clinker hydration. The effects of different silica types were compared in this study by calorimetric analysis, scanning and transmission electron microscopy, in situ X-ray diffraction and compressive strength measurements. The silica component was silica fume, pyrogenic silica or silica synthesized by a wet-chemical route (Stoeber particles). Water-to-cement ratios were 0.23. Differences are observed between the silica for short reaction times (up to 3 days). Results indicate that silica fume and pyrogenic silica accelerate alite hydration by increasing the surface for nucleation of C–S–H phases whereas Stoeber particles show no accelerating effect.

  6. Dissociation of silica at high pressure

    NASA Astrophysics Data System (ADS)

    Hicks, Damien; Boehly, Tom

    2005-07-01

    Measurements of the temperature and optical reflectivity of quartz and fused silica under shock loading from 100 to 1000 GPa have revealed evidence for dissociation of silica between ˜150 and 400 GPa. Using attenuating laser-driven shock waves a continuous record of the temperature and reflectivity dependence on pressure has been obtained in both materials allowing the specific heat capacity and electronic conductivity to be deduced. Results show that between 150 and 400 GPa the specific heat rises significantly above that expected from the Dulong-Petit law, indicating the presence of a latent energy. Coincident with this anomalous specific heat is a rapid rise in electronic conductivity. Both these observables suggest that dissociation is occurring in the dense fluid. In addition temperature measurements near 5000 K detect a discontinuity at the melt transition, as measured earlier on gas gun experiments. This work was performed under the auspices of the US DOE by LLNL under Contract No. W-7405-ENG-48 and by the University of Rochester under Cooperative Agreement No. DE-FC03-92SF19460.

  7. Time-resolved shadowgraphs of transient plasma induced by spatiotemporally focused femtosecond laser pulses in fused silica glass.

    PubMed

    Wang, Zhaohui; Zeng, Bin; Li, Guihua; Xie, Hongqiang; Chu, Wei; He, Fei; Liao, Yang; Liu, Weiwei; Gao, Hui; Cheng, Ya

    2015-12-15

    We report on experimental observations of formation and evolution of transient plasma produced in fused silica glass with spatiotemporally focused (STF) femtosecond laser pulses using a pump-probe shadow imaging technique. Surprisingly, the observation shows that the track of the plasma is significantly curved, which is attributed to an asymmetric density distribution of the transient plasma produced in the focal volume caused by the pulse front tilt of the STF laser field. PMID:26670497

  8. Facile preparation of transparent and dense CdS-silica gel glass nanocomposites for optical limiting applications

    NASA Astrophysics Data System (ADS)

    Feng, Miao; Zhan, Hongbing

    2014-03-01

    To realize their practical and operable applications as a potential optical limiting (OL) material, quantum dots (QDs) need to have good processability by incorporating them into optical-quality matrices. This work reports a facile route for the room-temperature preparation of large, stable transparent monolithic CdS nanocomposites which can be easily extended to allow the introduction of acid-sensitive functional molecules/nanoparticles into a silica network by sol-gel chemistry. Our strategy involves a two-step sol-gel process (acid-catalyst hydrolysis and basic-catalyst condensation) and the co-condensation of the resulting alkoxysilane-capped CdS QDs with other alkoxysilanes, which allows the CdS QDs to become part of the silica covalent network. The degradation and agglomeration of CdS QDs were thereby effectively restrained, and large monolithic transparent CdS-silica gel glass was obtained. Using Z-scan theory and the resulting open-aperture Z-scan curves, the nonlinear extinction coefficient of the CdS-silica nanocomposite gel glass was calculated to be 1.02 × 10-14 cm W-1, comparable to that of the parent CdS QD dispersion, indicating their promise for OL applications.

  9. Liquid-liquid phase separation on melts and glasses in ferric ferrous oxide-silica system

    SciTech Connect

    Yasumori, A.; Koike, A.; Kameshima, Y.; Okada, K.; Yano, T.; Yamane, M.; Inoue, S.

    1997-12-31

    The existence of liquid-liquid miscibility gap in ferric ferrous oxide-silica system has been reported, however, the phase separation phenomena and the derived morphology of the phase separated glasses are uncertain. In this study, the melt-quenched samples of 5 Fe{sub 3}O{sub 4}-95 SiO{sub 2} and 15 Fe{sub 3}O{sub 4}-085 SiO{sub 2} (mol%) were prepared by melting at 2,300 C or 2,200 C (expected to be above miscibility gap), and subsequently at 1,800 C or 1,750 C (in immiscible region) by use of infrared image furnace and quenching at the rate of {approx}10{sup 2} K/sec. The glassy materials exhibited phase separation having discrete spherical particles or interconnected structure due to the composition, melting temperature and time. Also, the segregation of Fe component occurred during melting, which was caused by the difference of specific gravity of components in the melt.

  10. Comprehensive modeling of structural modification induced by a femtosecond laser pulse inside fused silica glass

    NASA Astrophysics Data System (ADS)

    Najafi, Somayeh; Sadat Arabanian, Atoosa; Massudi, Reza

    2016-06-01

    A comprehensive theoretical model is proposed based on equations describing the nonlinear propagation of an ultrashort pulse inside transparent material, electron density evolution, non-Fourier heat conduction, and thermo-elasto plastic displacement which are respectively solved by various methods. These methods include the split-step finite difference technique and alternating-direction implicit algorithm, fourth-order Range–Kutta algorithm, hybrid finite-element method/finite-difference method, and finite-element method in both space and time to achieve refractive index changes. The whole chain of processes occurring in the interaction of a focused ultrashort laser pulse with fused silica glass in prevalent conditions of micromachining applications is numerically investigated. By optimizing the numerical method and by using an adaptive mesh approach, the execution time of the program is significantly reduced so that the calculations are done at each time step in a fraction of a second. Simulation results show that the energy and duration of the input pulse are very important parameters in induced changes, but the chirp of the input pulse is not an effective parameter. Consequently, by appropriate setting of those parameters one can design a desired refractive index profile.

  11. Effect of sintering temperature variations on fabrication of 45S5 bioactive glass-ceramics using rice husk as a source for silica.

    PubMed

    Leenakul, Wilaiwan; Tunkasiri, Tawee; Tongsiri, Natee; Pengpat, Kamonpan; Ruangsuriya, Jetsada

    2016-04-01

    45S5 bioactive glass is a highly bioactive substance that has the ability to promote stem cell differentiation into osteoblasts--the cells that create bone matrix. The aim of this work is to analyze physical and mechanical properties of 45S5 bioactive glass fabricated by using rice husk ash as its silica source. The 45S5 bioactive glass was prepared by melting the batch at 1300 °C for 3h. The samples were sintered at different temperatures ranging from 900 to 1050 °C with a fixed dwell-time of 2h. The phase transitions, density, porosity and microhardness values were investigated and reported. DTA analysis was used to examine the crystallization temperatures of the glasses prepared. We found that the sintering temperature had a significant effect on the mechanical and physical properties of the bioactive glass. The XRD showed that when the sintering temperature was above 650 °C, crystallization occurred and bioactive glass-ceramics with Na2Ca2Si3O9, Na2Ca4(PO4)2SiO4 and Ca3Si2O7 were formed. The optimum sintering temperature resulting in maximum mechanical values was around 1050 °C, with a high density of 2.27 g/cm(3), 16.96% porosity and the vicker microhardness value of 364HV. Additionally, in vitro assay was used to examine biological activities in stimulated body fluid (SBF). After incubation in SBF for 7 days, all of the samples showed formations of apatite layers indicating that the 45S5 bioactive glasses using rice husk as a raw material were also bioactive. PMID:26838899

  12. Development of Silica Glass Coatings on 316L SS and Evaluation of its Corrosion Resistance Behavior in Ringer's Solution

    NASA Astrophysics Data System (ADS)

    Vijayalakshmi, U.; Rajeswari, S.

    2012-12-01

    Sol-gel derived silica glasses have many promising features, including low-temperature preparation as well as chemical and physical stability. Two silica glasses with Si100 and Si80 composition were prepared to understand the factors contributing to the rate of bioactivity. The effects of pH, solution aging temperature, and molar ratio of H2O/tetraethyl orthosilicate (TEOS) were studied, and the obtained powder sample was characterized by Fourier transform infrared spectroscopy, X-ray diffraction studies, and scanning electron microscopy. The synthesized silica glasses were deposited on 316L SS by the spin coating method at the optimized speed of 2000 revolutions per minute. The corrosion resistance behavior of the coatings was determined by (1) open-circuit potential vs time of exposure, (2) electrochemical impedance spectroscopy, and (3) cyclic polarization in Ringer's solution. A higher breakdown potential ( E b) and repassivation potential ( E p) value with lower current density was obtained from cyclic polarization. Similar results were observed from impedance analysis with higher charge transfer resistance ( R ct) and lower double layer capacitance ( C dl) indicating the corrosion resistance behavior of the coatings compared with the uncoated 316L stainless steel. From the results, it was observed that both Si100 and Si80 glass coatings had a positive effect on the corrosion resistance behavior. An adhesive strength of 46 MPa and 45 MPa was obtained for the Si100 and Si80 coatings, respectively. An accelerated leach out study was carried out by impressing the potential at their breakdown potential to determine the effect of glass coating for long-term contact between the implant and a normal biological medium.

  13. Sol-gel derived copper-doped silica glass as a sensitive material for X-ray beam dosimetry

    NASA Astrophysics Data System (ADS)

    Capoen, Bruno; Hamzaoui, Hicham El; Bouazaoui, Mohamed; Ouerdane, Youcef; Boukenter, Aziz; Girard, Sylvain; Marcandella, Claude; Duhamel, Olivier

    2016-01-01

    The light emission from a sol-gel-derived Cu-doped silica glass was studied under 10 keV X-ray irradiation using a fibered setup. Both radioluminescence (RL) and optically stimulated luminescence (OSL) were analyzed at different high dose rates up to 50 Gy/s and for different exposure times, yielding accumulated doses up to 50 kGy (in SiO2). Even if a darkening effect appears at this dose level, the material remains X-sensitive after exposure to several kGy. At low dose rate, the scintillation mechanisms are similar to photoluminescence, involving the Cu+ ions electronic levels, contrary to the nonlinear domain (for dose rates higher than 30 Gy/s). This RL, as well as the OSL, could be exploited in their linear domain to measure doses as high as 3 kGy. A thorough study of the OSL signal has shown that it must be employed with caution in order to take the fading phenomenon and the response dependency on stimulation source intensity into consideration.

  14. Optical Degradation of Colloidal Eu-Complex Embedded in Silica Glass Film Using Reprecipitation and Sol-Gel Methods.

    PubMed

    Fukuda, Takeshi; Kurabayashi, Tomokazu; Yamaki, Tatsuki

    2016-04-01

    A reprecipitation method has been investigated for fabricating colloidal nanoparticles using Eu-complex. Herein, we investigated optical degradation characteristics of (1,10-phenanthroline)tris [4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedionato]europium(III) colloidal nanoparticles, which were embedded into a silica glass film fabricated by a conventional sol-gel process. At first, we tried several types of good solvents for the reprecipitation method, and dimethyl sulfoxide (DMSO) is found to be a suitable solvent for realizing the small diameter and the high long-term stability against the ultraviolet irradiation even though the boing point of DMSO is higher than that of water used as a poor solvent. By optimizing the good solvent and the concentration of Eu-complex, the relative photoluminescence intensity of 0.96 was achieved even though the ultraviolet light was continuously irradiated for 90 min. In addition, the average diameter of 106 nm was achieved when DMSO was used as a good solvent, resulting in the high transmittance at a visible wavelength region. Therefore, we can achieve the transparent emissive thin film with a center wavelength of 612 nm, and the optical degradation was drastically reduced by forming nanoparticles. PMID:27451610

  15. Curiosity ChemCam Finds High-Silica Mars Rocks

    SciTech Connect

    Frydenvang, Jens

    2015-12-17

    A team of scientists, including one from Los Alamos National Laboratory, has found much higher concentrations of silica at some sites the Curiosity rover has investigated in the past seven months than anywhere else it has visited since landing on Mars 40 months ago. The first discovery was as Curiosity approached the area “Marias Pass,” where a lower geological unit contacts an overlying one. ChemCam, the rover’s laser-firing instrument for checking rock composition from a distance, detected bountiful silica in some targets the rover passed along the way to the contact zone. The ChemCam instrument was developed at Los Alamos in partnership with the French IRAP laboratory in Toulouse and the French Space Agency. “The high silica was a surprise,” said Jens Frydenvang of Los Alamos National Laboratory and the University of Copenhagen, also a Curiosity science team member. “While we’re still working with multiple hypotheses on how the silica got so enriched, these hypotheses all require considerable water activity, and on Earth high silica deposits are often associated with environments that provide excellent support for microbial life. Because of this, the science team agreed to make a rare backtrack to investigate it more.”

  16. A High Temperature Capacitive Humidity Sensor Based on Mesoporous Silica

    PubMed Central

    Wagner, Thorsten; Krotzky, Sören; Weiß, Alexander; Sauerwald, Tilman; Kohl, Claus-Dieter; Roggenbuck, Jan; Tiemann, Michael

    2011-01-01

    Capacitive sensors are the most commonly used devices for the detection of humidity because they are inexpensive and the detection mechanism is very specific for humidity. However, especially for industrial processes, there is a lack of dielectrics that are stable at high temperature (>200 °C) and under harsh conditions. We present a capacitive sensor based on mesoporous silica as the dielectric in a simple sensor design based on pressed silica pellets. Investigation of the structural stability of the porous silica under simulated operating conditions as well as the influence of the pellet production will be shown. Impedance measurements demonstrate the utility of the sensor at both low (90 °C) and high (up to 210 °C) operating temperatures. PMID:22163790

  17. Kinetics of Oligonucleotide Hybridization to DNA Probe Arrays on High-Capacity Porous Silica Substrates

    PubMed Central

    Glazer, Marc I.; Fidanza, Jacqueline A.; McGall, Glenn H.; Trulson, Mark O.; Forman, Jonathan E.; Frank, Curtis W.

    2007-01-01

    We have investigated the kinetics of DNA hybridization to oligonucleotide arrays on high-capacity porous silica films that were deposited by two techniques. Films created by spin coating pure colloidal silica suspensions onto a substrate had pores of ∼23 nm, relatively low porosity (35%), and a surface area of 17 times flat glass (for a 0.3-μm film). In the second method, latex particles were codeposited with the silica by spin coating and then pyrolyzed, which resulted in larger pores (36 nm), higher porosity (65%), and higher surface area (26 times flat glass for a 0.3-μm film). As a result of these favorable properties, the templated silica hybridized more quickly and reached a higher adsorbed target density (11 vs. 8 times flat glass at 22°C) than the pure silica. Adsorption of DNA onto the high-capacity films is controlled by traditional adsorption and desorption coefficients, as well as by morphology factors and transient binding interactions between the target and the probes. To describe these effects, we have developed a model based on the analogy to diffusion of a reactant in a porous catalyst. Adsorption values (ka, kd, and K) measured on planar arrays for the same probe/target system provide the parameters for the model and also provide an internally consistent comparison for the stability of the transient complexes. The interpretation of the model takes into account factors not previously considered for hybridization in three-dimensional films, including the potential effects of heterogeneous probe populations, partial probe/target complexes during diffusion, and non-1:1 binding structures. The transient complexes are much less stable than full duplexes (binding constants for full duplexes higher by three orders of magnitude or more), which may be a result of the unique probe density and distribution that is characteristic of the photolithographically patterned arrays. The behavior at 22°C is described well by the predictive equations for

  18. Nonlinear optical properties and Q-switch performance of silica glasses doped with CuxSe nanoparticles

    NASA Astrophysics Data System (ADS)

    Zolotovskaya, Svetlana A.; Savitski, Vasily G.; Prokoshin, Pavel V.; Yumashev, Konstantin V.; Gurin, Valerij S.; Alexeenko, Alexander A.

    2006-07-01

    Glasses containing copper selenide nanoparticles (CuxSe) reveal an intense absorption band peaking at 1 μm (1.24 eV). The transient bleaching and intensity-dependent transmission of silica glasses with CuxSe nanoparticles of different stoichiometry are studied with 1.08 μm (1.15 eV) picosecond pulses. The bleaching relaxation time decreases with a shift in the absorption band maximum to the lower photon energies. The dependence of absorption on the input energy of the pulses is saturationlike at the beginning of the plateau at ~40 mJ/cm2. Passive Q-switching of the Nd3+:KGd(WO4)2 laser at 1.067 μm is realized with the CuxSe-doped glasses for different x.

  19. Properties Of Low Cost, High Volume Glasses

    NASA Astrophysics Data System (ADS)

    Lind, M. A.; Hartman, J. S.; Buckwalter, C. Q.

    1980-02-01

    The properties of new and weathered samples of low cost, high volume glasses have been studied to determine their usefulness for solar energy applications. Glasses of varying compositions produced by float, drawn, rolled, fusion, and twin ground techniques were examined. Spectral transmittance and reflectance were measured and solar weighted values calculated. Laser raytrace techniques were used to evaluate surface parallelism and bulk homogeneity. Compositional changes were examined with scanning electron microscopy, X-ray fluorescence, and Auger electron spectroscopy. These techniques were used in conjunction with ellipsometry to study the surface effects associated with weathering.

  20. The dissociation of liquid silica at high pressure and temperature

    SciTech Connect

    Hicks, D; Boehly, T; Eggert, J; Miller, J; Celliers, P; Collins, G

    2005-11-17

    Liquid silica at high pressure and temperature is shown to undergo significant structural modifications and profound changes in its electronic properties. Temperature measurements on shock waves in silica at 70-1000 GPa indicate that the specific heat of liquid SiO{sub 2} rises well above the Dulong-Petit limit, exhibiting a broad peak with temperature that is attributable to the growing structural disorder caused by bond-breaking in the melt. The simultaneous sharp rise in optical reflectivity of liquid SiO{sub 2} indicates that dissociation causes the electrical and therefore thermal conductivities of silica to attain metallic-like values of 1-5 x 10{sup 5} S/m and 24-600 W/m.K respectively.

  1. High Resolution, Single-Step Patterning of Silica Aerogels

    NASA Technical Reports Server (NTRS)

    Bertino, M. F.; Hund, J. F.; Sosa, J.; Zhang, G.; Sotiriou-Leventis, C.; Leventis, N.; Tokuhiro, A. T.; Terry, J.

    2003-01-01

    Three-dimensional metallic structures are fabricated with high spatial resolution in silica aerogels. In our method, silica hydrogels are prepared with a standard base-catalyzed route, and exchanged with an aqueous solution typically containing Ag' ions (1 M) and 2-propanol (0.2 M). The metal ions are reduced photolytically with a table-top ultraviolet lamp, or radiolytically, with a focused X-ray beam. We fabricated dots and lines as small as 30 x 70 km, protruding for several mm into the bulk of the materials. The hydrogels are eventually supercritically dried to yield aerogels, without any measurable change in the shape and spatial resolution of the lithographed structures. Transmission electron microscopy shows that illuminated regions are composed of Ag clusters with a size of several pm, separated by thin layers of silica.

  2. Deep wet etching of borosilicate glass and fused silica with dehydrated AZ4330 and a Cr/Au mask

    NASA Astrophysics Data System (ADS)

    Jin, Joo-Young; Yoo, Sunghyun; Bae, Jae-Sung; Kim, Yong-Kweon

    2014-01-01

    This research highlights a superior glass-wet-etch technique which enables a glass wafer to be etched for more than 20 h in 49 wt% hydrofluoric acid (HF) only with Cr/Au film and a common positive photoresist, AZ4330. We demonstrated that pits on the wet-etched glass wafer were generated not only due to HF diffusion through the Cr/Au film but also due to pinholes on the Cr/Au films created by the diffusion of the Cr/Au etchant through a photoresist etching-mask during the Cr/Au wet etching process. These two types of diffusion, HF diffusion and Cr/Au etchant diffusion, were eliminated by the thermal curing of a photoresist (PR), AZ4330, before the Cr/Au wet etching process. The curing process allowed the PR to dehydrate, increased the hydrophobicity, and prevented the diffusion of the hydrophilic HF and Cr/Au etchant. Optimization of the curing process was performed, showing that curing at 130 °C for 20 min was the proper condition. With the optimized process, a 525 µm thick borosilicate glass wafer was penetrated with 49%wt HF. A fused silica wafer 525 µm thick was also wet-etched and penetrated with 49 wt% HF at 10 h. Moreover, no pits were found in wet etching of the fused silica for 20 h in 49 wt% HF. These findings demonstrate that the proposed technique allows the wet etching of a glass wafer for more than 20 h in 49%wt HF, the best result thus far. We fabricated a glass substrate with a 217.0 µm deep cavity and a penetrating through-via using the proposed technique, proving the feasibility of the product as an optical component with a surface roughness of 45.5 Å in the cavity.

  3. Growth of silver nanoparticles of variable and controlled diameter in silica-based and soda-lime glasses by simultaneous continuous ultraviolet irradiation and heat treatment

    SciTech Connect

    Goutaland, F.; Marin, E.; Michalon, J. Y.; Boukenter, A.

    2009-05-04

    We report on the space-selective precipitation of silver nanoparticles in silica-based and silver-exchanged soda-lime glasses by simultaneous continuous wave ultraviolet exposure and heat treatment. In silica-based glasses, we explain that simultaneous treatments lead to much higher silver nanoparticles concentration than similar treatments performed into two separated steps by minimizing the detrimental influence of oxidation on the nanoparticles' growth. In the case of silver-exchanged soda-lime glasses, nanoparticles are observed with both small and larger diameters of about 1 and 7 nm, whose concentrations depend both on the laser power density and on the heating temperature.

  4. The effect of high-pressure devitrification and densification on ballistic-penetration resistance of fused silica

    NASA Astrophysics Data System (ADS)

    Avuthu, Vasudeva Reddy

    Despite the clear benefits offered by more advanced transparent materials, (e.g. transparent ceramics offer a very attractive combination of high stiffness and high hardness levels, highly-ductile transparent polymers provide superior fragment-containing capabilities, etc.), ballistic ceramic-glass like fused-silica remains an important constituent material in a majority of transparent impact-resistant structures (e.g. windshields and windows of military vehicles, portholes in ships, ground vehicles and spacecraft) used today. Among the main reasons for the wide-scale use of glass, the following three are most frequently cited: (i) glass-structure fabrication technologies enable the production of curved, large surface-area, transparent structures with thickness approaching several inches; (ii) relatively low material and manufacturing costs; and (iii) compositional modifications, chemical strengthening, and controlled crystallization have been demonstrated to be capable of significantly improving the ballistic properties of glass. In the present work, the potential of high-pressure devitrification and densification of fused-silica as a ballistic-resistance-enhancement mechanism is investigated computationally. In the first part of the present work, all-atom molecular-level computations are carried out to infer the dynamic response and material microstructure/topology changes of fused silica subjected to ballistic impact by a nanometer-sized hard projectile. The analysis was focused on the investigation of specific aspects of the dynamic response and of the microstructural changes such as the deformation of highly sheared and densified regions, and the conversion of amorphous fused silica to SiO2 crystalline allotropic modifications (in particular, alpha-quartz and stishovite). The microstructural changes in question were determined by carrying out a post-processing atom-coordination procedure. This procedure suggested the formation of high-density stishovite (and

  5. Recent Progress in Monolithic Silica Columns for High-Speed and High-Selectivity Separations

    NASA Astrophysics Data System (ADS)

    Ikegami, Tohru; Tanaka, Nobuo

    2016-06-01

    Monolithic silica columns have greater (through-pore size)/(skeleton size) ratios than particulate columns and fixed support structures in a column for chemical modification, resulting in high-efficiency columns and stationary phases. This review looks at how the size range of monolithic silica columns has been expanded, how high-efficiency monolithic silica columns have been realized, and how various methods of silica surface functionalization, leading to selective stationary phases, have been developed on monolithic silica supports, and provides information on the current status of these columns. Also discussed are the practical aspects of monolithic silica columns, including how their versatility can be improved by the preparation of small-sized structural features (sub-micron) and columns (1 mm ID or smaller) and by optimizing reaction conditions for in situ chemical modification with various restrictions, with an emphasis on recent research results for both topics.

  6. Recent Progress in Monolithic Silica Columns for High-Speed and High-Selectivity Separations.

    PubMed

    Ikegami, Tohru; Tanaka, Nobuo

    2016-06-12

    Monolithic silica columns have greater (through-pore size)/(skeleton size) ratios than particulate columns and fixed support structures in a column for chemical modification, resulting in high-efficiency columns and stationary phases. This review looks at how the size range of monolithic silica columns has been expanded, how high-efficiency monolithic silica columns have been realized, and how various methods of silica surface functionalization, leading to selective stationary phases, have been developed on monolithic silica supports, and provides information on the current status of these columns. Also discussed are the practical aspects of monolithic silica columns, including how their versatility can be improved by the preparation of small-sized structural features (sub-micron) and columns (1 mm ID or smaller) and by optimizing reaction conditions for in situ chemical modification with various restrictions, with an emphasis on recent research results for both topics. PMID:27306311

  7. Nanoscale confinement and interfacial effects on the dynamics and glass transition/crystallinity of thin adsorbed films on silica nanoparticles

    NASA Astrophysics Data System (ADS)

    Madathingal, Rajesh Raman

    The research investigated in this dissertation has focused on understanding the structure-property-function relationships of polymer nanocomposites. The properties of composite systems are dictated by the properties of their components, typically fillers in a polymer matrix. In nanocomposites, the polymer near an interface has significantly different properties compared with the bulk polymer, and the contribution of the adsorbed polymer to composite properties becomes increasingly important as the filler size decreases. Despite many reports of highly favorable properties, the behavior of polymer nanocomposites is not generally predictable, and thus requires a better understanding of the interfacial region. The ability to tailor the filler/matrix interaction and an understanding of the impact of the interface on macroscopic properties are keys in the design of nanocomposite properties. In this original work the surface of silica nanoparticles was tailored by: (a) Changing the number of sites for polymer attachment by varying the surface silanols and, (b) By varying the size/curvature of nanoparticles. The effect of surface tailoring on the dynamic properties after the adsorption of two model polymers, amorphous polymethyl methacrylate (PMMA) and semicrystalline polyethylene oxide (PEO) was observed. The interphase layer of polymers adsorbed to silica surfaces is affected by the surface silanol density as well as the relative size of the polymer compared with the size of the adsorbing substrate. The non-equilibrium adsorption of PMMA onto individual colloidal Stober silica (SiO2) particles, where Rparticle (100nm) > RPMMA (˜6.5nm) was compared with the adsorption onto fumed silica, where Rparticle (7nm) ˜ RPMMA (6.5nm) < Raggregate (˜1000nm), both as a function of silanol density [SiOH] and hydrophobility. In the former case, TEM images showed that the PMMA adsorbed onto individual nanoparticles, so that the number of PMMA chains/bead could be calculated, whereas

  8. HIGH ALUMINUM HLW GLASSES FOR HANFORDS WTP

    SciTech Connect

    KRUGER AA; JOSEPH I; BOWMAN BW; GAN H; KOT W; MATLACK KS; PEGG IL

    2009-08-19

    The world's largest radioactive waste vitrification facility is now under construction at the United State Department of Energy's (DOE's) Hanford site. The Hanford Tank Waste Treatment and Immobilization Plant (WTP) is designed to treat nearly 53 million gallons of mixed hazardous and radioactive waste now residing in 177 underground storage tanks. This multi-decade processing campaign will be one of the most complex ever undertaken because of the wide chemical and physical variability of the waste compositions generated during the cold war era that are stored at Hanford. The DOE Office of River Protection (ORP) has initiated a program to improve the long-term operating efficiency of the WTP vitrification plants with the objective of reducing the overall cost of tank waste treatment and disposal and shortening the duration of plant operations. Due to the size, complexity and duration of the WTP mission, the lifecycle operating and waste disposal costs are substantial. As a result, gains in High Level Waste (HLW) and Low Activity Waste (LAW) waste loadings, as well as increases in glass production rate, which can reduce mission duration and glass volumes for disposal, can yield substantial overall cost savings. EnergySolutions and its long-term research partner, the Vitreous State Laboratory (VSL) of the Catholic University of America, have been involved in a multi-year ORP program directed at optimizing various aspects of the HLW and LAW vitrification flow sheets. A number of Hanford HLW streams contain high concentrations of aluminum, which is challenging with respect to both waste loading and processing rate. Therefore, a key focus area of the ORP vitrification process optimization program at EnergySolutions and VSL has been development of HLW glass compositions that can accommodate high Al{sub 2}O{sub 3} concentrations while maintaining high processing rates in the Joule Heated Ceramic Melters (JHCMs) used for waste vitrification at the WTP. This paper, reviews

  9. Preparation of high purity glasses in the Ga-Ge-As-Se system

    NASA Astrophysics Data System (ADS)

    Shiryaev, V. S.; Velmuzhov, A. P.; Tang, Z. Q.; Churbanov, M. F.; Seddon, A. B.

    2014-11-01

    Small additions of Ga to Ge-As-Se glasses are known to enhance rare earth ion solubility in Ge-As-Se chalcogenide glasses designed for active optical applications. The effect of variants and conditions for producing samples of an exemplar Ge16As17Se64Ga3 (atomic%) glass on optical transmission, and the content of limiting impurities, is investigated. To prepare the high-purity glass samples, chemical distillation for purification of the Ge-As-Se base-glass is used. Next, a new vapor phase transport approach of metallic Ga transfer in a GaI3 flow is developed to purify and add the batch of metallic gallium into the silica-glass reactor for the Ge-As-Se-Ga glass synthesis. A thermodynamic equilibrium based vapor phase transport model is discussed. In the best examples of these glasses, the content of residual impurities is: hydrogen - 0.15 ppm, oxygen - <1 ppm, and transition metals - less than 0.1 ppm.

  10. Bioinspired Strong and Highly Porous Glass Scaffolds

    PubMed Central

    Saiz, Eduardo; Tomsia, Antoni P.

    2011-01-01

    The quest for more efficient energy-related technologies is driving the development of porous and high-performance structural materials with exceptional mechanical strength. Natural materials achieve their strength through complex hierarchical designs and anisotropic structures that are extremely difficult to replicate synthetically. We emulate nature’s design by direct-ink-write assembling of glass scaffolds with a periodic pattern, and controlled sintering of the filaments into anisotropic constructs similar to biological materials. The final product is a porous glass scaffold with a compressive strength (136 MPa) comparable to that of cortical bone and a porosity (60%) comparable to that of trabecular bone. The strength of this porous glass scaffold is ~100 times that of polymer scaffolds and 4–5 times that of ceramic and glass scaffolds with comparable porosities reported elsewhere. The ability to create both porous and strong structures opens a new avenue for fabricating scaffolds for a broad array of applications, including tissue engineering, filtration, lightweight composites, and catalyst support. PMID:21544222

  11. Size saturation in low energy ion beam synthesized nanoparticles in silica glass: 50 keV Ag{sup -} ions implantation, a case study

    SciTech Connect

    Kuiri, P. K.

    2010-09-15

    Fluence-dependent formation of Ag nanoparticles (NPs) in silica glass by 50 keV Ag{sup -} ions implantation has been studied. Samples implanted with fluences of 2x10{sup 16} ions cm{sup -2} and above are found to show an absorption band at around 410 nm, corresponding to the surface plasmon resonance (SPR) of the Ag NPs in silica glass. An increase in SPR peak intensity with increase in fluence has been observed up to a fluence of 7x10{sup 16} ions cm{sup -2} (F7), after which the absorption intensity shows a saturation. Simulations of the optical absorption spectra also indicated an increase in the absorption intensity and hence the size of the NPs with increase in fluence up to F7, beyond which NP size is seen to saturate. The saturation of fluence and the SPR intensity (or NP size) have been explained as coming due to a break up of larger Ag NPs formed near the surface by displacement spikes induced by subsequently incident Ag ions against their regrowth from the movement of Ag atoms toward the surface and their sputtering loss. Further, we have compared our observations with the earlier data on saturation of fluence and size of NPs in cases of Au and Zn, and concluded that the saturation of both fluence and NP size are general phenomena for low energy high fluence metal ion implantation.

  12. A compliant, high failure strain, fibre-reinforced glass-matrix composite

    NASA Technical Reports Server (NTRS)

    Prewo, K. M.

    1982-01-01

    A glass-matrix composite reinforced by discontinuous graphite fibers was produced by hot pressing glass-powder-impregnated two-dimensional arrays of in-plane randomly oriented graphite fibers held together by approximately 5-10% by weight of organic binder (generally polyester). The composite tensile behavior is characterized by a highly nonlinear stress-strain curve which differs markedly from that of either unreinforced glass or a similarly reinforced epoxy-matrix composite. By virtue of this nonlinearity, the composite is able to redistribute applied stresses to achieve a high load-carrying capacity. The fibrous microstructure and the low fiber-matrix bond provide a mechanism for achieving high fracture toughness and unusually high compliance. For a 96%-silica-matrix composite, the strength is retained to over 1000 C.

  13. Investigating in vitro bioactivity and magnetic properties of the ferrimagnetic bioactive glass-ceramic fabricated using soda-lime-silica waste glass

    NASA Astrophysics Data System (ADS)

    Abbasi, M.; Hashemi, B.; Shokrollahi, H.

    2014-04-01

    The main purpose of the current research is the production and characterization of a ferrimagnetic bioactive glass-ceramic prepared through the solid-state reaction method using soda-lime-silica waste glass as the main raw material. In comparison with the conventional route, that is, the melt-quenching and subsequent heat treatment, the present work is an economical technique. Structural, thermal and magnetic properties of the samples were examined by X-ray diffraction (XRD), differential thermal analysis (DTA) and vibrating sample magnetometer (VSM). The in vitro test was utilized to assess the bioactivity level of the samples by Hanks' solution as simulated body fluid (SBF). The apatite surface layer formation was examined by the scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS). The calcium ion concentration in the solutions was measured by atomic absorption spectroscopy (AAS). VSM results revealed that with the addition of 5-20 wt% strontium hexaferrite to bioactive glass-ceramics, the ferrimagnetic bioactive glass-ceramics with hysteresis losses between 7024 and 75,852 erg/g were obtained. The in vitro test showed that the onset formation time of hydroxyapatite layer on the surface of the samples was 14 days and after 30 days, this layer was completed.

  14. High-purity silica reflecting heat shield development

    NASA Technical Reports Server (NTRS)

    Congdon, W. M.

    1974-01-01

    A high-purity, fused-silica reflecting heat shield for the thermal protection of outer-planet probes was developed. Factors that strongly influence the performance of a silica heat shield were studied. Silica-bonded silica configurations, each prepared by a different technique, were investigated and rated according to its relative merits. Slip-casting was selected as the preferred fabrication method because it produced good reflectivity and good strength, and is relatively easy to scale up for a full-size outer-planet probe. The slips were cast using a variety of different particle sizes: continuous particle-size slips; monodisperse particle-size slips; and blends of monodisperse particle-size slips were studied. In general, smaller particles gave the highest reflectance. The monodisperse slips as well as the blend slips gave a higher reflectance than the continuous particle-size slips. An upgraded and fused natural quartz was used to study the effects of microstructure on reflectance and as the baseline to ascertain the increase in reflectance obtained from using a higher-purity synthetic material.

  15. A highly ordered cubic mesoporous silica/graphene nanocomposite

    NASA Astrophysics Data System (ADS)

    Lee, Chang-Wook; Roh, Kwang Chul; Kim, Kwang-Bum

    2013-09-01

    A highly ordered cubic mesoporous silica (KIT-6)/graphene nanocomposite and 2D KIT-6 nanoflakes were synthesized using a novel synthesis methodology. The non-ionic triblock copolymer, P123, played a dual role as a structure-directing agent in the formation of the cubic mesoporous structure and as a cross-linking agent between mesoporous silica and graphene. The prepared (KIT-6)/graphene nanocomposite could act as a template for the preparation of mesoporous material/graphene nanocomposites.A highly ordered cubic mesoporous silica (KIT-6)/graphene nanocomposite and 2D KIT-6 nanoflakes were synthesized using a novel synthesis methodology. The non-ionic triblock copolymer, P123, played a dual role as a structure-directing agent in the formation of the cubic mesoporous structure and as a cross-linking agent between mesoporous silica and graphene. The prepared (KIT-6)/graphene nanocomposite could act as a template for the preparation of mesoporous material/graphene nanocomposites. Electronic supplementary information (ESI) available: S1: TEM images of disordered mesoporous silica/graphene nanocomposite; S2: TEM images of KIT-6/GO nanocomposite; S3: Thermogravimetric analysis of KIT-6/GO and KG-400-700; S4: SEM and TEM images of KIT-6; S5: Low angle XRD, Raman spectra, N2 adsorption isotherms, pore size distribution and photographic images of the prepared samples; S6: TEM image and N2 adsorption isotherms of mesoporous carbon/graphene nanocomposite; S7: XPS C1s spectra of the prepared samples. See DOI: 10.1039/c3nr03108j

  16. Sealed glass coating of high temperature ceramic superconductors

    DOEpatents

    Wu, Weite; Chu, Cha Y.; Goretta, Kenneth C.; Routbort, Jules L.

    1995-01-01

    A method and article of manufacture of a lead oxide based glass coating on a high temperature superconductor. The method includes preparing a dispersion of glass powders in a solution, applying the dispersion to the superconductor, drying the dispersion before applying another coating and heating the glass powder dispersion at temperatures below oxygen diffusion onset and above the glass melting point to form a continuous glass coating on the superconductor to establish compressive stresses which enhance the fracture strength of the superconductor.

  17. High-performance light-emitting diodes encapsulated with silica-filled epoxy materials.

    PubMed

    Li, Tian; Zhang, Jie; Wang, Huiping; Hu, Zhongnan; Yu, Yingfeng

    2013-09-25

    Packaging materials have a great impact on the performance and reliability of light-emitting diodes (LEDs). In this study, we have prepared high performance LED devices through encapsulating LEDs by epoxy materials incorporated with filler powders. A set of evaluation methods have also been established to characterize the reliability of LED devices. No delamination or internal cracking between packaging materials and lead frames has been found for the encapsulated high performance LED devices after the package saturation with moisture and subsequent exposure to high-temperature solder reflow and thermal cycling. Four kinds of inorganic silica fillers, namely, quartz, fused silica, cristobalite, and spherical silica, and one kind of organic filler, that is, spherical silicone powder, were incorporated into the epoxy packaging materials to compare their effects on performance of LED devices. The properties of epoxy packaging materials and LED devices were studied by differential scanning calorimetry (DSC), thermogravimetric analyses (TGA), dynamic mechanical analysis (DMA), thermomechanical analyzer (TMA), ultravioletvisible spectrophotometer (UV-vis), scanning acoustic microscopy (SAM), and scanning electron microscopy (SEM). Except the spherical silicone powder filled epoxy materials, all the other filled systems showed lower equilibrium water sorption content and smaller water diffusion coefficient in both water sorption and moisture sorption tests. The coefficient of thermal expansion (CTE) values were also decreased with the addition of fillers, and the systems filled with quartz, fused, and filled with spherical silica gave the best performance, which exhibited the reduced CTE values both below and above Tg. The results of TGA essentially showed no difference between filled and unfilled systems. The glass transition temperature changed little for all the filled systems, except the one incorporated with spherical silicone. The modulus at room temperature

  18. Role of Accessory Phase Crystallization Within the High-Silica Magma Batches of the Rainier Mesa Tuff, Southwest Nevada Volcanic Field

    NASA Astrophysics Data System (ADS)

    Tefend, K. S.; Vogel, T. A.; Patino, L. C.

    2004-05-01

    Compositionally zoned ignimbrites from the Timber Mountain/Oasis Valley magmatic system, Southwest Nevada Volcanic Field (SWNVF), represent open system processes as opposed to in situ differentiation within a single magma chamber. The large chemical variation of the pumice fragments in the ash-flow sheets are due to emplacement of different magma batches into the magma chamber prior to eruption1,2. The 11.6 Ma Rainier Mesa tuff is a large (1200 km3) ignimbrite containing low-silica pumice fragments, and two distinct high-silica rhyolitic pumice fragments, distinguished by the Th/Nb ratios1. Based on trace element modeling, Mills et al. (1997) concluded that these were three separate magma batches. Recent δ 18O data from minerals separated from pumice fragments are consistent with this interpretation for the independent origin of the high- and low-silica magmas, and that these represent distinct magma types that erupted coevally1,3. However, chemical data from melt inclusions and glass matrix from the two high-silica magma types do not support the model that these are unrelated. Melt inclusion and glass matrix compositions were obtained from the high-Th/Nb, high-silica and low-Th/Nb, high-silica pumice fragments. The two groups of pumice fragments have identical glass matrix major and trace element compositions, and both high-silica groups have identical melt inclusion compositions. In both high-silica groups, Th and Th/Nb increase with increasing La within the melt inclusions. The two high-silica magma types have identical major phase minerals of similar compositions, indicating that the trace element signature of the whole pumice is controlled by accessory phase fractionation. Analyses of monazite, apatite, and zircon from both high-silica pumice groups show similar compositions, with La and Th concentrated in the monazite. Our interpretation is that the high-Th/Nb, high-silica magma represents accessory phase (monazite) accumulation, resulting in a compositional

  19. Densification of silica glass induced by 0.8 and 1.5 {mu}m intense femtosecond laser pulses

    SciTech Connect

    Saliminia, A.; Nguyen, N.T.; Chin, S.L.; Vallee, R.

    2006-05-01

    We investigate the physical mechanisms responsible for waveguide formation in silica glass induced by 1 kHz intense femtosecond laser pulses from a Ti-sapphire laser at 0.8 {mu}m as well as from a femtosecond optical parametric amplifier at 1.5 {mu}m. It is demonstrated that the densification taking place at the irradiated region is the principal cause for refractive index change in the waveguides written with both 0.8 and 1.5 {mu}m pulses. The birefringence induced by the stress arising from such densification and its behavior against thermal annealing are also studied.

  20. The role of natural glasses as analogues in projecting the long-term alteration of high-level nuclear waste glasses: Part 1

    SciTech Connect

    Mazer, J.J.

    1993-12-31

    The common observation of glasses persisting in natural environments for long periods of time (up to tens of millions of years) provides compelling evidence that these materials can be kinetically stable in a variety of subsurface environments. This paper reviews how natural and historical synthesized glasses can be employed as natural analogues for understanding and projecting the long-term alteration of high-level nuclear waste glasses. The corrosion of basaltic glass results in many of the same alteration features found in laboratory testing of the corrosion of high-level radioactive waste glasses. Evidence has also been found indicating similarities in the rate controlling processes, such as the effects of silica concentration on corrosion in groundwater and in laboratory leachates. Naturally altered rhyolitic glasses and tektites provide additional evidence that can be used to constrain estimates of long-term waste glass alteration. When reacted under conditions where water is plentiful, the corrosion for these glasses is dominated by network hydrolysis, while the corrosion is dominated by molecular water diffusion and secondary mineral formation under conditions where water contact is intermittent or where water is relatively scarce. Synthesized glasses that have been naturally altered result in alkali-depleted alteration features that are similar to those found for natural glasses and for nuclear waste glasses. The characteristics of these alteration features appear to be dependent on the alteration conditions which affect the dominant reaction processes during weathering. In all cases, care must be taken to ensure that the information being provided by natural analogues is related to nuclear waste glass corrosion in a clear and meaningful way.

  1. High strength, low dielectric constant fluorinated silica xerogel films

    NASA Astrophysics Data System (ADS)

    Gorman, B. P.; Orozco-Teran, Rosa A.; Roepsch, Jodi A.; Dong, Hanjiang; Reidy, Richard F.; Mueller, D. W.

    2001-12-01

    The mechanical, electrical, and microstructural properties of low-k fluorinated silica xerogels produced using a one step spin-on process are reported. Derived from a fluorinated silane monomer, these films are easily processed and exhibit very low dielectric constants (2.1 as processed and 2.3 after heat treating at 450 °C in air). Structural determination by Fourier transform infrared spectrophotometry indicates a fluorinated silica structure with shortened Si-O bonds; however, some of the fluorine is lost during annealing. Nanoindentation studies show high elastic moduli (12 GPa) and hardness (1 GPa). Microstructural analyses by transmission and scanning electron microscopy indicate an unusual morphology with highly linked features and pore sizes in the 20-30 nm range. We believe the low dielectric constants and robust mechanical properties are due to the unusual microstructure of these films.

  2. Watching Silica's Dance: Imaging the Structure and Dynamics of the Atomic (Re-) Arrangements in 2D Glass

    NASA Astrophysics Data System (ADS)

    Muller, David

    2014-03-01

    Even though glasses are almost ubiquitous--in our windows, on our iPhones, even on our faces--they are also mysterious. Because glasses are notoriously difficult to study, basic questions like: ``How are the atoms arranged? Where and how do glasses break?'' are still under contention. We use aberration corrected transmission electron microscopy (TEM) to image the atoms in a new two-dimensional phase of silica glass - freestanding it becomes the world's thinnest pane of glass at only 3-atoms thick, and take a unique look into these questions. Using atom-by-atom imaging and spectroscopy, we are able to reconstruct the full structure and bonding of this 2D glass and identify it as a bi-tetrahedral layer of SiO2. Our images also strikingly resemble Zachariasen's original cartoon models of glasses, drawn in 1932. As such, our work realizes an 80-year-old vision for easily understandable glassy systems and introduces promising methods to test theoretical predictions against experimental data. We image atoms in the disordered solid and track their motions in response to local strain. We directly obtain ring statistics and pair distribution functions that span short-, medium-, and long-range order, and test these against long-standing theoretical predictions of glass structure and dynamics. We use the electron beam to excite atomic rearrangements, producing surprisingly rich and beautiful videos of how a glass bends and breaks, as well as the exchange of atoms at a solid/liquid interface. Detailed analyses of these videos reveal a complex dance of elastic and plastic deformations, phase transitions, and their interplay. These examples illustrate the wide-ranging and fundamental materials physics that can now be studied at atomic-resolution via transmission electron microscopy of two-dimensional glasses. Work in collaboration with: S. Kurasch, U. Kaiser, R. Hovden, Q. Mao, J. Kotakoski, J. S. Alden, A. Shekhawat, A. A. Alemi, J. P. Sethna, P. L. McEuen, A.V. Krasheninnikov

  3. Glass Property Data and Models for Estimating High-Level Waste Glass Volume

    SciTech Connect

    Vienna, John D.; Fluegel, Alexander; Kim, Dong-Sang; Hrma, Pavel R.

    2009-10-05

    This report describes recent efforts to develop glass property models that can be used to help estimate the volume of high-level waste (HLW) glass that will result from vitrification of Hanford tank waste. The compositions of acceptable and processable HLW glasses need to be optimized to minimize the waste-form volume and, hence, to save cost. A database of properties and associated compositions for simulated waste glasses was collected for developing property-composition models. This database, although not comprehensive, represents a large fraction of data on waste-glass compositions and properties that were available at the time of this report. Glass property-composition models were fit to subsets of the database for several key glass properties. These models apply to a significantly broader composition space than those previously publised. These models should be considered for interim use in calculating properties of Hanford waste glasses.

  4. Secondary emission conductivity of high purity silica fabric

    NASA Technical Reports Server (NTRS)

    Belanger, V. J.; Eagles, A. E.

    1977-01-01

    High purity silica fabrics were proposed for use as a material to control the effects of electrostatic charging of satellites at synchronous altitudes. These materials exhibited very quiet behavior when placed in simulated charging environments as opposed to other dielectrics used for passive thermal control which exhibit varying degrees of electrical arcing. Secondary emission conductivity is proposed as a mechanism for this superior behavior. Design of experiments to measure this phenomena and data taken on silica fabrics are discussed as they relate to electrostatic discharge (ESD) control on geosynchronous orbit spacecraft. Studies include the apparent change in resistivity of the material as a function of the electron beam energy, flux intensity, and the effect of varying electric fields impressed across the material under test.

  5. Monolithic Cylindrical Fused Silica Resonators with High Q Factors.

    PubMed

    Pan, Yao; Wang, Dongya; Wang, Yanyan; Liu, Jianping; Wu, Suyong; Qu, Tianliang; Yang, Kaiyong; Luo, Hui

    2016-01-01

    The cylindrical resonator gyroscope (CRG) is a typical Coriolis vibratory gyroscope whose performance is determined by the Q factor and frequency mismatch of the cylindrical resonator. Enhancing the Q factor is crucial for improving the rate sensitivity and noise performance of the CRG. In this paper, for the first time, a monolithic cylindrical fused silica resonator with a Q factor approaching 8 × 10⁵ (ring-down time over 1 min) is reported. The resonator is made of fused silica with low internal friction and high isotropy, with a diameter of 25 mm and a center frequency of 3974.35 Hz. The structure of the resonator is first briefly introduced, and then the experimental non-contact characterization method is presented. In addition, the post-fabrication experimental procedure of Q factor improvement, including chemical and thermal treatment, is demonstrated. The Q factor improvement by both treatments is compared and the primary loss mechanism is analyzed. To the best of our knowledge, the work presented in this paper represents the highest reported Q factor for a cylindrical resonator. The proposed monolithic cylindrical fused silica resonator may enable high performance inertial sensing with standard manufacturing process and simple post-fabrication treatment. PMID:27483263

  6. Reaction of positronium with doped ions in silica-based glasses in the size determination of subnanometer structural open spaces

    NASA Astrophysics Data System (ADS)

    Inoue, K.; Kataoka, H.; Nagai, Y.; Hasegawa, M.; Kobayashi, Y.

    2013-10-01

    Positron annihilation spectroscopy is employed to estimate the size of subnanometer-scale open spaces in insulating materials. In most cases, the size is estimated from the lifetime of long-lived ortho-positronium (o-Ps) by pickoff annihilation using a simplified model. However, reactions of Ps with surrounding electrons other than the pickoff reaction, such as spin conversion or chemical reaction, could give a substantially underestimated size using the simplified model. In the present paper, we report that the size of the open spaces can be evaluated correctly by the angular correlation of positron annihilation radiation (ACAR) with a magnetic field using the spin-polarization effect on Ps formation, even if such reactions of Ps occur in the material. This method is applied to the subnanometer-scale structural open spaces of silica-based glass doped with Fe. We demonstrate the influence of the Ps reaction on size-estimation of the open spaces from the o-Ps lifetime. Furthermore, the type of reaction, whether spin conversion or chemical, is distinguished from the magnetic field dependence of the Ps self-annihilation component intensity in the ACAR spectra. The Ps reaction in silica-based glass doped with Fe is a chemical reaction (most likely oxidation) rather than spin conversion, with Fe ions. The chemical quenching rate with Fe ions is determined from the dependence of the o-Ps lifetime on the Fe content.

  7. Application of atomic force microscopy in determining the fractal dimension of the mirror, mist, and hackle region of silica glass

    SciTech Connect

    Smith, R.L. Mecholsky, J.J.

    2011-05-15

    Fractal analysis has been used as a method to study fracture surfaces of brittle materials. However, it has not been determined if the fractal characteristics of brittle materials is consistent throughout the fracture surface. Therefore, the fractal dimensional increment of the mirror, mist, and hackle regions of the fracture surface of silica glass was determined using atomic force microscopy. The fractal dimensional increment of the mirror region (0.17-0.26) was determined to be statistically greater than that for the mist (0.08-0.12) and hackle (0.08-0.13) regions. It is thought that the increase in the fractal dimensional increment is caused by a greater tortuosity in the mirror region due to, most likely, the slower crack velocity of the propagating crack in that region and that there is a point between the mirror and mist region at which the fractal dimension decreases and becomes constant. - Research Highlights: {yields} The fracture surface of silica glass does not have a constant fractal dimension. {yields} Mirror region has greater fractal dimension than mist or hackle region. {yields} Fractal dimension decreases between mirror and mist region. {yields} Greater fractal dimension could be due to slower crack velocity in mirror region.

  8. Chromium doped nano-phase separated yttria-alumina-silica glass based optical fiber preform: fabrication and characterization

    NASA Astrophysics Data System (ADS)

    Dutta, Debjit; Dhar, Anirban; Das, Shyamal; Bysakh, Sandip; Kir'yanov, Alexandar; Paul, Mukul Chandra

    2015-06-01

    Transition metal (TM) doping in silica core optical fiber is one of the research area which has been studied for long time and Chromium (Cr) doping specially attracts a lot of research interest due to their broad emission band covering U, C and L band with many potential application such as saturable absorber or broadband amplifier etc. This paper present fabrication of Cr doped nano-phase separated silica fiber within yttria-alumina-silica core glass through conventional Modified Chemical Vapor Deposition (MCVD) process coupled with solution doping technique along with different material and optical characterization. For the first time scanning electron microscope (SEM) / energy dispersive X-ray (EDX) analysis of porous soot sample and final preform has been utilized to investigate incorporation mechanism of Crions with special emphasis on Cr-species evaporation at different stages of fabrication. We also report that optimized annealing condition of our fabricated preform exhibited enhanced fluorescence emission and a broad band within 550- 800 nm wavelength region under pumping at 532 nm wavelength due to nano-phase restructuration.

  9. Tb3+/Yb3+ codoped silica-hafnia glass and glass-ceramic waveguides to improve the efficiency of photovoltaic solar cells

    NASA Astrophysics Data System (ADS)

    Bouajaj, A.; Belmokhtar, S.; Britel, M. R.; Armellini, C.; Boulard, B.; Belluomo, F.; Di Stefano, A.; Polizzi, S.; Lukowiak, A.; Ferrari, M.; Enrichi, F.

    2016-02-01

    In this paper we present the investigation of the energy transfer efficiency between Tb3+ and Yb3+ ions in silica-hafnia waveguides. Cooperative energy transfer between these two ions allows to cut one 488 nm photon in two 980 nm photons and could have important applications in improving the performance of photovoltaic solar cells. Previous works revealed that for a given concentration of donors (Tb3+), increasing the number of acceptors (Yb3+) located near to the Tb3+ ion can increase the Tb-Yb transfer probability. However, when increasing the density of active ions, some detrimental effects due to cross-relaxation mechanisms become relevant. On the basis of this observation the sample doping was chosen keeping constant the molar ratio [Yb]/[Tb] = 4 and the total rare earths contents were [Tb + Yb]/[Si + Hf] = 5%, 7%, 9%. The choice of the matrix is another crucial point to obtain an efficient down conversion processes with rare earth ions. To this respect a 70SiO2-30HfO2 waveguide composition was chosen. The comparison between the glass and the glass-ceramic structures demonstrated that the latter is more efficient since it combines the good optical properties of glasses with the optimal spectroscopic properties of crystals activated by luminescent species. A maximum transfer efficiency of 55% was found for the highest rare earth doping concentration.

  10. Fabrication of silica ultra high quality factor microresonators.

    PubMed

    Maker, Ashley J; Armani, Andrea M

    2012-01-01

    Whispering gallery resonant cavities confine light in circular orbits at their periphery. The photon storage lifetime in the cavity, quantified by the quality factor (Q) of the cavity, can be in excess of 500ns for cavities with Q factors above 100 million. As a result of their low material losses, silica microcavities have demonstrated some of the longest photon lifetimes to date. Since a portion of the circulating light extends outside the resonator, these devices can also be used to probe the surroundings. This interaction has enabled numerous experiments in biology, such as single molecule biodetection and antibody-antigen kinetics, as well as discoveries in other fields, such as development of ultra-low-threshold microlasers, characterization of thin films, and cavity quantum electrodynamics studies.(3-7) The two primary silica resonant cavity geometries are the microsphere and the microtoroid. Both devices rely on a carbon dioxide laser reflow step to achieve their ultra-high-Q factors (Q>100 million). However, there are several notable differences between the two structures. Silica microspheres are free-standing, supported by a single optical fiber, whereas silica microtoroids can be fabricated on a silicon wafer in large arrays using a combination of lithography and etching steps. These differences influence which device is optimal for a given experiment. Here, we present detailed fabrication protocols for both types of resonant cavities. While the fabrication of microsphere resonant cavities is fairly straightforward, the fabrication of microtoroid resonant cavities requires additional specialized equipment and facilities (cleanroom). Therefore, this additional requirement may also influence which device is selected for a given experiment. PMID:22805153

  11. Fundamental-frequency-absorbed oxyfluoride glass in a high-power laser.

    PubMed

    Hou, Chaoqi; Li, Weinan; Wang, Pengfei; Lu, Min; Peng, Bo; Guo, Haitao; Gao, Fei; Cui, Xiaoxia

    2016-04-01

    A high-power third-harmonic laser faces challenges in the filtering remnant unconverted fundamental frequency, which is from the frequency converting crystal. In this work, a novel fundamental-frequency-absorbed oxyfluoride glass has been prepared, which provides a possible option to solve the problem. By being doped with Fe2+ ion, the glass shows strong absorption property at 1053 nm, and the glass's transmittances at 351 and 1053 nm are stable with changing the laser power or increasing the irradiation times under high-power laser irradiation. Meanwhile, the laser-induced damage threshold of the glass is 12.5  J/cm2 at 351 nm, which is two times higher than that of fused silica whose threshold is 6.2  J/cm2 in the same testing condition. The glass also exhibits a higher laser-induced damage threshold as well as 36.6  J/cm2 at its absorption wavelength of 1053 nm. The results indicate that this glass is promising as a color-separation optic, thus allowing a novel design for the final optics assembly in an inertial confinement fusion laser system. PMID:27139668

  12. Decomposition of trichloroethene on ozone-adsorbed high silica zeolites.

    PubMed

    Fujita, Hirotaka; Izumi, Jun; Sagehashi, Masaki; Fujii, Takao; Sakoda, Akiyoshi

    2004-01-01

    We developed a novel ozonation process for water treatment using high silica zeolites as an adsorptive concentrator of water-dissolved ozone and organic pollutants, resulting in a significant increase in reaction rate. In experiments involving trichloroethene (TCE) decomposition using a tubular flow reactor, TCE decomposition was much greater in the presence of ZSM-5 (SiO(2)/Al(2)O(3) ratio=3000) than in its absence, possibly due to the high concentrations of ozone and TCE inside the adsorbent. The TCE conversion obtained in our experiments was found to reach its theoretically maximum limit. PMID:14630114

  13. High-Temperature Viscosity of Commercial Glasses

    SciTech Connect

    Hrma, Pavel R.

    2006-08-31

    Arrhenius models were developed for glass viscosity within the processing temperature of six types of commercial glasses: low-expansion-borosilicate glasses, E glasses, fiberglass wool glasses, TV panel glasses, container glasses, and float glasses. Both local models (for each of the six glass types) and a global model (for the composition region of commercial glasses, i.e., the six glass types taken together) are presented. The models are based on viscosity data previously obtained with rotating spindle viscometers within the temperature range between 900 C and 1550 C; the viscosity varied from 1 Pa?s to 750 Pa?s. First-order models were applied to relate Arrhenius coefficients to the mass fractions of 15 components: SiO2, TiO2, ZrO2, Al2O3, Fe2O3, B2O3, MgO, CaO, SrO, BaO, PbO, ZnO, Li2O, Na2O, K2O. The R2 is 0.98 for the global model and ranges from .097 to 0.99 for the six local models. The models are recommended for glasses containing 42 to 84 mass% SiO2 to estimate viscosities or temperatures at a constant viscosity for melts within both the temperature range from 1100 C to 1550 C and viscosity range from 5 to 400 Pa?s.

  14. Characteristic strength, Weibull modulus, and failure probability of fused silica glass

    NASA Astrophysics Data System (ADS)

    Klein, Claude A.

    2009-11-01

    The development of high-energy lasers has focused attention on the requirement to assess the mechanical strength of optical components made of fused silica or fused quartz (SiO2). The strength of this material is known to be highly dependent on the stressed area and the surface finish, but has not yet been properly characterized in the published literature. Recently, Detrio and collaborators at the University of Dayton Research Institute (UDRI) performed extensive ring-on-ring flexural strength measurements on fused SiO2 specimens ranging in size from 1 to 9 in. in diameter and of widely differing surface qualities. We report on a Weibull statistical analysis of the UDRI data-an analysis based on the procedure outlined in Proc. SPIE 4375, 241 (2001). We demonstrate that (1) a two-parameter Weibull model, including the area-scaling principle, applies; (2) the shape parameter (m~=10) is essentially independent of the stressed area as well as the surface finish; and (3) the characteristic strength (1-cm2 uniformly stressed area) obeys a linear law, σC (in megapascals) ~=160-2.83×PBS (in parts per million per steradian), where PBS characterizes the surface/subsurface ``damage'' of an appropriate set of test specimens. In this light, we evaluate the cumulative failure probability and the failure probability density of polished and superpolished fused SiO2 windows as a function of the biaxial tensile stress, for stressed areas ranging from 0.3 to 100 cm2.

  15. The Effect of Foaming and Silica Dissolution on Melter Feed Rheology during Conversion to Glass

    SciTech Connect

    Marcial, Jose; Chun, Jaehun; Hrma, Pavel R.; Schweiger, Michael J.

    2014-11-23

    As the nuclear waste glass melter feed is converted to molten glass, the feed eventually becomes a continuous glass-forming melt in which dissolving refractory constituents are suspended together with numerous gas bubbles. Knowledge of mechanical properties of the melter feed is crucial for understanding the feed-to-glass conversion as it occurs in the cold cap. We measured the viscosity during heating of the feed and correlated it with the independently determined volume fractions of dissolving quartz particles and the gas phase. The measurement was performed with a rotating spindle rheometer on the melter feed heated at 5 K/min starting at several different temperatures. The effect of quartz particles, gas bubbles, and compositional inhomogeneity on the glass-forming melt viscosity was determined by fitting a linear relationship between log viscosity and volume fractions of suspended phases to data.

  16. New high-strength neodymium phosphate laser glass

    SciTech Connect

    Galagan, B I; Glushchenko, I N; Denker, B I; Kalachev, Yu L; Mikhailov, Viktor A; Sverchkov, S E; Shcherbakov, Ivan A; Kuleshov, N V

    2009-12-31

    A high-strength neodymium laser glass (SNLG) based on an alumoborophosphate composition is developed and synthesised; its physicochemical, spectral, luminescent, and lasing characteristics are studied. It is found that the chemical stability and thermal resistance of the new glass are considerably higher than the corresponding characteristics of known neodymium-doped phosphate laser glasses. Investigations of lasing upon longitudinal diode pumping showed that, due to the higher thermal resistance, the new glass allows one to obtain output powers twice as high as those of industrial GLS22 glass. (active media)

  17. High-Strength / High Alkaline Resistant Fe-Phosphate Glass Fibers as Concrete Reinforcement

    SciTech Connect

    Mariano Velez

    2008-03-31

    Calcium-iron-phosphate glasses were developed whose chemical durabilities in alkaline solutions (pH 13) were comparable or superior to those of commercial alkaline-resistant (AR) silica-based glasses. However, the tensile strength of Ca-Fe-phosphate fibers, after being exposed to alkaline environments, including wet Portland cement pastes, is lower than that of current AR silicate fibers. Another series of Ca-Fe-phosphate glasses were developed with excellent chemical durability in strong acidic solutions (H2SO4, HF), indicating potential applications where silica-based fibers degrade very quickly, including E-glass. The new Ca-Fe-phosphate glasses can be melted and processed 300 to 500°C lower than silica-based glasses. This offers the possibility of manufacturing glass fibers with lower energy costs by 40-60% and the potential to reduce manufacturing waste and lower gas emissions. It was found that Ca-Fe-phosphate melts can be continuously pulled into fibers depending on the slope of the viscosity-temperature curve and with viscosity ~100 poise, using multi-hole Pt/Rh bushings.

  18. Crystallization in high-level waste glass: A review of glass theory and noteworthy literature

    SciTech Connect

    Christian, J. H.

    2015-08-18

    There is a fundamental need to continue research aimed at understanding nepheline and spinel crystal formation in high-level waste (HLW) glass. Specifically, the formation of nepheline solids (K/NaAlSiO4) during slow cooling of HLW glass can reduce the chemical durability of the glass, which can cause a decrease in the overall durability of the glass waste form. The accumulation of spinel solids ((Fe, Ni, Mn, Zn)(Fe, Cr)2O4), while not detrimental to glass durability, can cause an array of processing problems inside HLW glass melters. In this review, the fundamental differences between glass and solid-crystals are explained using kinetic, thermodynamic, and viscosity arguments, and several highlights of glass-crystallization research, as it pertains to high-level waste vitrification, are described. In terms of mitigating spinel in the melter and both spinel and nepheline formation in the canister, the complexity of HLW glass and the intricate interplay between thermal, chemical, and kinetic factors further complicates this understanding. However, new experiments seeking to elucidate the contributing factors of crystal nucleation and growth in waste glass, and the compilation of data from older experiments, may go a long way towards helping to achieve higher waste loadings while developing more efficient processing strategies. Higher waste loadings and more efficient processing strategies will reduce the overall HLW Hanford Tank Waste Treatment and Immobilization Plant (WTP) vitrification facilities mission life.

  19. Crystallization in high-level waste glass: A review of glass theory and noteworthy literature

    SciTech Connect

    Christian, J. H.

    2015-08-01

    There is a fundamental need to continue research aimed at understanding nepheline and spinel crystal formation in high-level waste (HLW) glass. Specifically, the formation of nepheline solids (K/NaAlSiO₄) during slow cooling of HLW glass can reduce the chemical durability of the glass, which can cause a decrease in the overall durability of the glass waste form. The accumulation of spinel solids ((Fe, Ni, Mn, Zn)(Fe,Cr)₂O₄), while not detrimental to glass durability, can cause an array of processing problems inside of HLW glass melters. In this review, the fundamental differences between glass and solid-crystals are explained using kinetic, thermodynamic, and viscosity arguments, and several highlights of glass-crystallization research, as it pertains to high-level waste vitrification, are described. In terms of mitigating spinel in the melter and both spinel and nepheline formation in the canister, the complexity of HLW glass and the intricate interplay between thermal, chemical, and kinetic factors further complicates this understanding. However, new experiments seeking to elucidate the contributing factors of crystal nucleation and growth in waste glass, and the compilation of data from older experiments, may go a long way towards helping to achieve higher waste loadings while developing more efficient processing strategies.

  20. A Compaction Model for Highly Porous Silica Powder.

    NASA Astrophysics Data System (ADS)

    Church, P. D.; Tsembelis, K.

    2005-07-01

    This paper describes research to develop an equation of state to describe the behaviour of a highly porous silica powder. It shows that whilst molecular modelling techniques can be readily applied to develop a description of a compact material the description of the compaction process is more problematic. An empirical model, based upon the Lennard-Jones potential, has been shown to be capable of describing the compaction process observed in simple experiments. This development and application of the model in the Eulerian hydrocode GRIM to reproduce experimental plate impact data over a wide range of impact velocities is described and the results compared with experimental data.

  1. High energy ion irradiation induced surface patterning on a SiO2 glass substrate

    NASA Astrophysics Data System (ADS)

    Srivastava, S. K.; Ganesan, K.; Gangopadhyay, P.; Panigrahi, B. K.; Nair, K. G. M.; Tyagi, A. K.

    2014-11-01

    Experimental results about formation of self-organized surface patterns on a silica glass substrate due to irradiations with high energy Au ions at various angles of incidences have been reported in this paper. Pattern formations are found to vary significantly from theoretical predictions. Orientation, growth of ripples and ripple characteristics observed here do not conform to established results of low energy heavy-ion irradiation studies. High energy Au ion-induced effects (e.g., surface stress, mass redistribution and surface current) have been suitably invoked to explain observed phenomena.

  2. Effect of Bubbles and Silica Dissolution on Melter Feed Rheology during Conversion to Glass

    SciTech Connect

    Marcial, Jose; Chun, Jaehun; Hrma, Pavel R.; Schweiger, Michael J.

    2014-10-21

    As the nuclear waste glass melter feed is converted to molten glass, the feed becomes a continuous glass-forming melt where dissolving refractory constituents are suspended together with numerous gas bubbles. Knowledge of mechanical properties of the reacting melter feed is crucial for understanding the feed-to-glass conversion as it occurs during melting. We studied the melter feed viscosity during heating and correlated it with volume fractions of dissolving quartz particles and gas phase. The measurements were performed with a rotating spindle rheometer on the melter feed heated at 5 K/min, starting at several different temperatures. The effects of undissolved quartz particles, gas bubbles, and compositional inhomogeneity on the melter feed viscosity were determined by fitting a linear relationship between log viscosity and volume fractions of suspended phases.

  3. Sealed glass coating of high temperature ceramic superconductors

    DOEpatents

    Wu, W.; Chu, C.Y.; Goretta, K.C.; Routbort, J.L.

    1995-05-02

    A method and article of manufacture of a lead oxide based glass coating on a high temperature superconductor is disclosed. The method includes preparing a dispersion of glass powders in a solution, applying the dispersion to the superconductor, drying the dispersion before applying another coating and heating the glass powder dispersion at temperatures below oxygen diffusion onset and above the glass melting point to form a continuous glass coating on the superconductor to establish compressive stresses which enhance the fracture strength of the superconductor. 8 figs.

  4. Effect of bubbles and silica dissolution on melter feed rheology during conversion to glass.

    PubMed

    Marcial, José; Chun, Jaehun; Hrma, Pavel; Schweiger, Michael

    2014-10-21

    Nuclear-waste melter feeds are slurry mixtures of wastes with glass-forming and glass-modifying additives (unless prefabricated frits are used), which are converted to molten glass in a continuous electrical glass-melting furnace. The feeds gradually become continuous glass-forming melts. Initially, the melts contain dissolving refractory feed constituents that are suspended together with numerous gas bubbles. Eventually, the bubbles escape, and the melts homogenize and equilibrate. Knowledge of various physicochemical properties of the reacting melter feed is crucial for understanding the feed-to-glass conversion that occurs during melting. We studied the melter feed viscosity during heating and correlated it with the volume fractions of dissolving quartz (SiO2) particles and the gas phase. The measurements were performed with a rotating spindle rheometer on the melter feed heated at 5 K/min, starting at several different temperatures. The effects of undissolved quartz particles, gas bubbles, and compositional inhomogeneity on the melter feed viscosity were determined by fitting a linear relationship between the logarithm of viscosity and the volume fractions of suspended phases. PMID:25229521

  5. Analysis of adhesive elastic contact between a silica glass lens and silicone rubber using the JKR theory

    NASA Astrophysics Data System (ADS)

    Baek, Dooyoung; Hemthavy, Pasomphone; Takahashi, Kunio

    2014-08-01

    Contact between a silica glass lens and silicone rubber is experimentally investigated by simultaneously measuring displacement, force and contact radius. The relationship between these three parameters is derived using elastic theory. The discrepancy between the theoretical relationship and the experimental results is observed to increase as the deformation of the silicone rubber increases. Under smaller deformation conditions, the elastic theory shows good agreement with the experimental results, although infinite stress on the edge of the contact area is predicted in the theory, and time dependence and adhesion hysteresis are observed in all experiments. It is suggested that time dependence and adhesion hysteresis in contact are not induced by the deformation of the bulk of the silicone rubber, but are induced by surface effects. The result suggests that the applicability limit of the elastic theory must be carefully considered in the JKR analysis of point contact for polymers.

  6. Monolayer sorption of neon in mesoporous silica glass as monitored by wide-angle x-ray scattering.

    PubMed

    Kilburn, Duncan; Sokol, Paul E

    2008-02-01

    We report measurements of the x-ray scattering intensity as mesoporous silica glasses are filled with neon. The intensity of the first peak in the liquidlike diffraction pattern increases nonlinearly with mass adsorbed. We outline a simple model assuming that the major coherent contribution to the first peak in the scattering function S(Q) is due to interference from nearest-neighbor scatterers. This allows us to demonstrate an approach for surface area determination which does not rely on thermodynamic models -- and is therefore complementary to existing methods. We also suggest that the overestimation of surface area by the traditional Brunauer-Emmett-Teller method may be resolved by using the capillary, and not the bulk, condensation pressure as the reference pressure p(0). Furthermore, the alternative analysis offers an insight into the atomic structure of monatomic sorption, which may be of use for further studies on materials with different surface properties. PMID:18352035

  7. Electronic structure and photoluminescence properties of Zn-ion implanted silica glass before and after thermal annealing

    NASA Astrophysics Data System (ADS)

    Zatsepin, D. A.; Zatsepin, A. F.; Boukhvalov, D. W.; Kurmaev, E. Z.; Pchelkina, Z. V.; Gavrilov, N. V.

    2016-01-01

    The results of XPS core-level and valence band measurements, photoluminescence spectra of a-SiO2 implanted by Zn-ions (E=30 keV, D=1*1017 cm^-2) and Density Functional Theory calculations of electronic structure as well as formation energies of structural defects in silica glass induced by Zn-ion implantation are presented. Both theory and experiment show that it is energetically more favorable for implanted zinc ions to occupy the interstitial positions instead of cation substitution. As a result, the Zn-ions embedded to interstitials, form chemical bonds with the surrounding oxygen atoms, formation ZnO-like nanoparticles and oxygen-deficient SiOx matrix. The subsequent thermal annealing at 900 0C (1 hr) strongly reduces the amount of ZnO nanoparticles and induces the formation of {\\alpha}-Zn2SiO4 phase which markedly enhances the green emission.

  8. High strain rate fracture behavior of fused silica

    NASA Astrophysics Data System (ADS)

    Ruggiero, Andrew; Iannitti, Gianluca; Testa, Gabriel; Limido, Jerome; Lacome, Jean; Olovsson, Lars; Ferraro, Mario; Bonora, Nicola

    2013-06-01

    Fused silica is a high purity synthetic amorphous silicon dioxide characterized by low thermal expansion coefficient, excellent optical qualities and exceptional transmittance over a wide spectral range. Because of its wide use in the military industry as window material, it may be subjected to high-energy ballistic impacts. Under such dynamic conditions, post-yield response of the ceramic as well as the strain rate related effects become significant and should be accounted for in the constitutive modeling. In this study, the procedure for constitutive model validation and model parameters identification, is presented. Taylor impact tests and drop weight tests were designed and performed at different impact velocities, from 1 to 100 m/s, and strain rates, from 102 up to 104 s-1. Numerical simulation of both tests was performed with IMPETUS-FEA, a general non-linear finite element software which offers NURBS finite element technology for the simulation of large deformation and fracture in materials. Model parameters were identified by optimization using multiple validation metrics. The validity of the parameters set determined with the proposed procedure was verified comparing numerical predictions and experimental results for an independent designed test consisting in a fused silica tile impacted at prescribed velocity by a steel sphere.

  9. Highly Loaded Mesoporous Silica/Nanoparticle Composites and Patterned Mesoporous Silica Films

    NASA Astrophysics Data System (ADS)

    Kothari, Rohit; Hendricks, Nicholas R.; Wang, Xinyu; Watkins, James J.

    2014-03-01

    Novel approaches for the preparation of highly filled mesoporous silica/nanoparticle (MS/NP) composites and for the fabrication of patterned MS films are described. The incorporation of iron platinum NPs within the walls of MS is achieved at high NP loadings by doping amphiphilic poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) (Pluronic®) copolymer templates via selective hydrogen bonding between the pre-synthesized NPs and the hydrophilic portion of the block copolymer. The MS is then synthesized by means of phase selective condensation of tetraethylorthosilicate (TEOS) within the NP loaded block copolymer templates dilated with supercritical carbon dioxide (scCO2) followed by calcination. For patterned films, microphase separated block copolymer/small molecule additive blends are patterned using UV-assisted nanoimprint lithography. Infusion and condensation of a TEOS within template films using ScCO2 as a processing medium followed by calcination yields the patterned MS films. Scanning electron microscopy is used characterize pattern fidelity and transmission electron microscopy analysis confirms the presence of the mesopores. Long range order in nanocomposites is confirmed by low angle x-ray diffraction.

  10. Electrochemical cell with high conductivity glass electrolyte

    DOEpatents

    Nelson, Paul A.; Bloom, Ira D.; Roche, Michael F.

    1987-01-01

    A secondary electrochemical cell with sodium-sulfur or other molten reactants is provided with a ionically conductive glass electrolyte. The cell is contained within an electrically conductive housing with a first portion at negative potential and a second portion insulated therefrom at positive electrode potential. The glass electrolyte is formed into a plurality of elongated tubes and placed lengthwise within the housing. The positive electrode material, for instance sulfur, is sealed into the glass electrolyte tubes and is provided with an elongated axial current collector. The glass electrolyte tubes are protected by shield tubes or sheets that also define narrow annuli for wicking of the molten negative electrode material.

  11. Electrochemical cell with high conductivity glass electrolyte

    DOEpatents

    Nelson, P.A.; Bloom, I.D.; Roche, M.F.

    1986-04-17

    A secondary electrochemical cell with sodium-sulfur or other molten reactants is provided with an ionically conductive glass electrolyte. The cell is contained within an electrically conductive housing with a first portion at negative potential and a second portion insulated therefrom at positive electrode potential. The glass electrolyte is formed into a plurality of elongated tubes and placed lengthwise within the housing. The positive electrode material, for instance sulfur, is sealed into the glass electrolyte tubes and is provided with an elongated axial current collector. The glass electrolyte tubes are protected by shield tubes or sheets that also define narrow annuli for wicking of the molten negative electrode material.

  12. Electrochemical cell with high conductivity glass electrolyte

    DOEpatents

    Nelson, P.A.; Bloom, I.D.; Roche, M.F.

    1987-04-21

    A secondary electrochemical cell with sodium-sulfur or other molten reactants is provided with a ionically conductive glass electrolyte. The cell is contained within an electrically conductive housing with a first portion at negative potential and a second portion insulated therefrom at positive electrode potential. The glass electrolyte is formed into a plurality of elongated tubes and placed lengthwise within the housing. The positive electrode material, for instance sulfur, is sealed into the glass electrolyte tubes and is provided with an elongated axial current collector. The glass electrolyte tubes are protected by shield tubes or sheets that also define narrow annuli for wicking of the molten negative electrode material. 6 figs.

  13. High-Temperature Viscosity Of Commercial Glasses

    SciTech Connect

    Hrma, Pavel R; See, Clem A; Lam, Oanh P; Minister, Kevin B

    2005-01-01

    Viscosity was measured for six types of commercial glasses: low-expansion-borosilicate glasses, E glasses, fiberglass wool glasses, TV panel glasses, container glasses, and float glasses. Viscosity data were obtained with rotating spindle viscometers within the temperature range between 900°C and 1550°C; the viscosity varied from 1 Pa∙s to 750 Pa∙s. Arrhenius coefficients were calculated for individual glasses and linear models were applied to relate them to the mass fractions of 11 major components (SiO2, CaO, Na2O, Al2O3, B2O3, BaO, SrO, K2O, MgO, PbO, and ZrO2) and 12 minor components (Fe2O3, ZnO, Li2O, TiO2, CeO2, F, Sb2O3, Cr2O3, As2O3, MnO2, SO3, and Co3O4). The models are recommended for glasses containing 42 to 84 mass% SiO2 to estimate viscosities or temperatures at a constant viscosity for melts within both the temperature range from 1100°C to 1550°C and viscosity range from 10 to 400 Pas.

  14. Fiber reinforced glasses and glass-ceramics for high performance applications

    NASA Technical Reports Server (NTRS)

    Prewo, K. M.; Brennan, J. J.; Layden, G. K.

    1986-01-01

    The development of fiber reinforced glass and glass-ceramic matrix composites is described. The general concepts involved in composite fabrication and resultant composite properties are given for a broad range of fiber and matrix combinations. It is shown that composite materials can be tailored to achieve high levels of toughness, strength, and elastic stiffness, as well as wear resistance and dimensional stability.

  15. Low melting high lithia glass compositions and methods

    DOEpatents

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

    2003-09-23

    The invention relates to methods of vitrifying waste and for lowering the melting point of glass forming systems by including lithia formers in the glass forming composition in significant amounts, typically from about 0.16 wt % to about 11 wt %, based on the total glass forming oxides. The lithia is typically included as a replacement for alkali oxide glass formers that would normally be present in a particular glass forming system. Replacement can occur on a mole percent or weight percent basis, and typically results in a composition wherein lithia forms about 10 wt % to about 100 wt % of the alkali oxide glass formers present in the composition. The present invention also relates to the high lithia glass compositions formed by these methods. The invention is useful for stabilization of numerous types of waste materials, including aqueous waste uranium oxides The decrease in melting point achieved by the present invention desirably prevents volatilization of hazardous or radioactive species during vitrification.

  16. Rotational and Translational Diffusion of Glass-Forming Ionic Liquids Confined in Nanoporous Silica

    NASA Astrophysics Data System (ADS)

    Iacob, Ciprian; Sangoro, Joshua; Runt, James; Kremer, Friedrich

    2014-03-01

    Charge transport and glassy dynamics of several classes of ionic liquids confined in uni-directional nanoporous silica membranes are investigated in a wide frequency and temperature range by a combination of Broadband Dielectric Spectroscopy (BDS), Pulsed Field Gradient Nuclear Magnetic Resonance (PFG NMR) and Fourier Transform Infrared spectroscopy (FTIR). Two opposite effects are observed: (i) surface effects - resulting from strong interactions between the host system (nanoporous silica membrane) and the guest molecules (ILs) lead to slower dynamics - which are significantly reduced upon pore surface modification through silanization of the pores, and (ii) confinement effects - arising from spatial restriction of the molecules in nanometric length-scales - leading to enhancement of molecular dynamics. A model assuming a reduced mobility of the adsorbed layer at the pore wall/IL interface is shown to provide a quantitative explanation for the remarkable decrease of effective transport quantities (such as diffusion coefficient, dc conductivity and consequently, the dielectric loss) of the ILs in non-silanized porous silica membranes.

  17. Phosphate glass useful in high energy lasers

    DOEpatents

    Hayden, Y.T.; Payne, S.A.; Hayden, J.S.; Campbell, J.H.; Aston, M.K.; Elder, M.L.

    1996-06-11

    In a high energy laser system utilizing phosphate laser glass components to amplify the laser beam, the laser system requires a generated laser beam having an emission bandwidth of less than 26 nm and the laser glass components consist essentially of (on an oxide composition basis) in mole percent: P{sub 2}O{sub 5}, 50--75; Al{sub 2}O{sub 3}, {gt}0--10; K{sub 2}O, {gt}0--30; MgO, 0--30; CaO, 0--30; Li{sub 2}O, 0--20; Na{sub 2}O, 0--20; Rb{sub 2}O, 0--20; Cs{sub 2}O, 0--20; BeO, 0--20; SrO, 0--20; BaO, 0--20; ZnO, 0--20; PbO, 0--20; B{sub 2}O{sub 3}, 0--10; Y{sub 2}O{sub 3}, 0--10; La{sub 2}O{sub 3}, 0--8; Ln{sub 2}O{sub 3}, 0.01--8; wherein the sum of MgO and CaO is >0--30; the sum of Li{sub 2}O, Na{sub 2}O, Rb{sub 2}O, and Cs{sub 2}O is 0--20; the sum of BeO, SrO, BaO, ZnO, and PbO is 0--20; the sum of B{sub 2}O{sub 3} and Y{sub 2}O{sub 3} is 0--10; and Ln{sub 2}O{sub 3} represents the sum of the oxides of active lasing lanthanides of atomic number 58--71. 21 figs.

  18. Phosphate glass useful in high energy lasers

    DOEpatents

    Hayden, Yuiko T.; Payne, Stephen A.; Hayden, Joseph S.; Campbell, John H.; Aston, Mary Kay; Elder, Melanie L.

    1996-01-01

    In a high energy laser system utilizing phosphate laser glass components to amplify the laser beam, the laser system requires a generated laser beam having an emission bandwidth of less than 26 nm and the laser glass components consist essentially of (on an oxide composition basis) in mole percent: P{sub 2}O{sub 5}, 50--75; Al{sub 2}O{sub 3}, {gt}0--10; K{sub 2}O, {gt}0--30; MgO, 0--30; CaO, 0--30; Li{sub 2}O, 0--20; Na{sub 2}O, 0--20; Rb{sub 2}O, 0--20; Cs{sub 2}O, 0--20; BeO, 0--20; SrO, 0--20; BaO, 0--20; ZnO, 0--20; PbO, 0--20; B{sub 2}O{sub 3}, 0--10; Y{sub 2}O{sub 3}, 0--10; La{sub 2}O{sub 3}, 0--8; Ln{sub 2}O{sub 3}, 0.01--8; wherein the sum of MgO and CaO is >0--30; the sum of Li{sub 2}O, Na{sub 2}O, Rb{sub 2}O, and Cs{sub 2}O is 0--20; the sum of BeO, SrO, BaO, ZnO, and PbO is 0--20; the sum of B{sub 2}O{sub 3} and Y{sub 2}O{sub 3} is 0--10; and Ln{sub 2}O{sub 3} represents the sum of the oxides of active lasing lanthanides of atomic number 58--71. 21 figs.

  19. Quantifying Silica Reactivity in Subsurface Environments: Reaction Affinity and Solute Matrix Controls on Quartz and SiO2 Glass Dissolution Kinetics

    SciTech Connect

    Patricia M. Dove

    2000-12-13

    the Icenhower move from postdoc in the Dove lab to a senior scientist position at PNNL, we directly facilitated information transfer from the ''university to user'' environment. Icenhower brought experience in silica-water reactivity and the experimental expertise in high-quality methods of mineral-water reaction kinetics to the PNNL waste clean-up effort. In a further interaction, M.S. student Troy Lorier was hired at the Savannah River Laboratory for a staff position with the Bill Holtzcheiter glass group. His research meshed well with on-going efforts at SRL. In short, our EMSP project went well beyond the academic goals of producing high quality scientific knowledge to establish connections with on-site users to solve problems in TFA. This project also produced new talent for the waste immobilization effort. This EMSP project was highly successful and we thank our sponsors for the opportunity to advance scientific knowledge in this important area of research.

  20. Anomalous phase separation behavior of gel-derived soda-silica glasses

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

    The effects of retained bound hydroxyl groups on amorphous immiscibility behavior and on the kinetics of phase separation were studied in glasses containing from 10 to 19 percent sodium oxide preparaed by the gel process. Differences in behavior as functions of preliminary thermal treatment of the gel precursor and of melting conditions were studied, employing IR spectroscopy, SAXS and WAXD to monitor the variation in glass microstructure. Both the initial gel treatment and the OH concentration in the prepared glasses were found to affect the immiscibility temperatures, and the magnitude of the maximum temperature increase was also a function of the sodium oxide concentration. It is suggested that the variation in thermodynamic behavior may be caused by the structural arrangement attained by the OH groups during the gel condensation process, which in turn affects the extent of hydrogen bonding to nonbridging oxygen ions.

  1. High-Intensity Plasma Glass Melter Final Technical Report

    SciTech Connect

    Gonterman, J. Ronald; Weinstein, Michael A.

    2006-10-27

    frits. Exploratory melts of non-glassy materials, such as wollastonite, zirconium silicate, and alumino-silicate melts were successfully done indicating that plasma melting has potential application beyond glass. Experimental results were generated that show the high quality of plasma-melted fiberglass compositions, such as E-glass, can result in good fiberizing performance. Fiberizing performance and tensile strength data were achieved during the project to support this conclusion. High seed counts are a feature of the current lab scale melter and must be dealt with via other means, since fining work was outside the scope of this project.

  2. Sodium hydroxide catalyzed monodispersed high surface area silica nanoparticles

    NASA Astrophysics Data System (ADS)

    Bhakta, Snehasis; Dixit, Chandra K.; Bist, Itti; Abdel Jalil, Karim; Suib, Steven L.; Rusling, James F.

    2016-07-01

    Understanding of the synthesis kinetics and our ability to modulate medium conditions allowed us to generate nanoparticles via an ultra-fast process. The synthesis medium is kept quite simple with tetraethyl orthosilicate (TEOS) as precursor and 50% ethanol and sodium hydroxide catalyst. Synthesis is performed under gentle conditions at 20 °C for 20 min Long synthesis time and catalyst-associated drawbacks are most crucial in silica nanoparticle synthesis. We have addressed both these bottlenecks by replacing the conventional Stober catalyst, ammonium hydroxide, with sodium hydroxide. We have reduced the overall synthesis time from 20 to 1/3 h, ∼60-fold decrease, and obtained highly monodispersed nanoparticles with 5-fold higher surface area than Stober particles. We have demonstrated that the developed NPs with ∼3-fold higher silane can be used as efficient probes for biosensor applications.

  3. Vertically integrated high-silica channel waveguides on Si

    NASA Astrophysics Data System (ADS)

    Barbarossa, G.; Laybourn, P. J. R.

    1992-02-01

    For the first time the vertical integration of high-silica content low-loss channel waveguides on an Si substrate is reported. The fabrication process, which has made the vertical integration feasible, consists of a practical multistep combination of flame hydrolysis deposition (FHD), photolithographic patterning, and reactive ion etching. The successful application to a double integration of single-mode waveguides at 1.55 micron is also reported. This result, which has been possible thanks to the FHD peculiarities, by extending the optical interaction to a third dimension, opens a wide range of original and promising applications, such as vertically coupled devices or parallel optical signal processes, and it effectively increases the density of optical guided-wave functions available on the same substrate.

  4. High expansion, lithium corrosion resistant sealing glasses

    DOEpatents

    Brow, Richard K.; Watkins, Randall D.

    1991-01-01

    Glass compositions containing CaO, Al.sub.2 O.sub.3, B.sub.2 O.sub.3, SrO and BaO in various combinations of mole % are provided. These compositions are capable of forming stable glass-to-metal seals with pin materials of 446 Stainless Steel and Alloy-52 rather than molybdenum, for use in harsh chemical environments, specifically in lithium batteries.

  5. High expansion, lithium corrosion resistant sealing glasses

    DOEpatents

    Brow, R.K.; Watkins, R.D.

    1991-06-04

    Glass compositions containing CaO, Al[sub 2]O[sub 3], B[sub 2]O[sub 3], SrO and BaO in various combinations of mole % are provided. These compositions are capable of forming stable glass-to-metal seals with pin materials of 446 Stainless Steel and Alloy-52 rather than molybdenum, for use in harsh chemical environments, specifically in lithium batteries.

  6. Preparation and Characterization of Single Ion Conductors from High Surface Area Fumed Silica

    NASA Technical Reports Server (NTRS)

    Zhang, H.; Maitra, P.; Liu, B.; Wunder, S. L.; Lin, H.-P.; Salomon, M.; Hagedorn, Norman H. (Technical Monitor)

    2002-01-01

    Anions that can form dissociative salts with Li(+) have been prepared and covalently attached to high surface area fumed silica. When blended with polyethylene oxide (PEO), the functionalized fumed silica suppresses the crystallization of the PEO, provides dimensional stability, and serves as a single ion conductor. Since functionalized fumed silica is easily dispersed in common polar solvents, it can be incorporated in both the polymer electrolyte and the electrodes.

  7. Highly ordered mesoporous silica nanoparticles and their application to DNA separation

    NASA Astrophysics Data System (ADS)

    Lee, Hye Sun; Chang, Jeong Ho

    2008-12-01

    This work describes the innovative development of high throughput human DNA purification process using the molecular self-assembled mesoporous silica nanoparticles. The mesoporous silica nanoparticles were prepared by sol-gel method and the formation of molecular self-assembled monolayers with functional groups was chemically demonstrated. The surface modification of functional groups was performed with aminofunctionallized organic silanes on mesoporous silica nanoparticles and the results of DNA separation was represented with electrophoresis images.

  8. ZERODUR® glass ceramics for high stress applications

    NASA Astrophysics Data System (ADS)

    Hartmann, Peter; Nattermann, Kurt; Döhring, Thorsten; Jedamzik, Ralf; Kuhr, Markus; Thomas, Peter; Kling, Guenther; Lucarelli, Stefano

    2009-08-01

    Recently SCHOTT has shown in a series of investigations the suitability of the zero expansion glass ceramic material ZERODUR® for applications like mirrors and support structures of complicated design used at high mechanical loads. Examples are vibrations during rocket launches, bonded elements to support single mirrors or mirrors of a large array, or controlled deformations for optical image correction, i.e. adaptive mirrors. Additional measurements have been performed on the behavior of ZERODUR® with respect to the etching process, which is capable of increasing strength significantly. It has been determined, which minimum layer thickness has to be removed in order to achieve the strength increase reliably. New data for the strength of the material variant ZERODUR K20® prepared with a diamond grain tool D151 are available and compared with the data of ZERODUR® specimens prepared in the same way. Data for the stress corrosion coefficient n of ZERODUR® for dry and normal humid environment have been measured already in the 1980s. It has been remeasured with the alternative double cleavage drilled compression (DCDC) method.

  9. Fabrication of anatase precipitated glass-ceramics possessing high transparency

    SciTech Connect

    Masai, Hirokazu; Toda, Tatsuya; Takahashi, Yoshihiro; Fujiwara, Takumi

    2009-04-13

    Transparent anatase precipitated glass-ceramics were fabricated using ZnO as a component. The particle size of precipitated anatase is several nanometers enough to possess high transparency. The preparation of the Bi-free transparent TiO{sub 2} glass-ceramic was attained by substitution of two different kinds of oxides for bismuth oxide. It is also noteworthy that we have demonstrated the crystallization of metastable anatase in the glass-ceramics as a main phase. The present bulk anatase glass-ceramics will open up an application field for a TiO{sub 2}-containing photocatalyst.

  10. High expansion coefficient glasses can be sealed to common metals

    NASA Technical Reports Server (NTRS)

    Camp, F. E.; Champman, J. W.; Hirayama, C.

    1970-01-01

    New series of high expansion coefficient glasses can be sealed by fusion onto hot surfaces of metals and alloys. Glasses have relatively low working temperatures, good chemical durability, and can be used in electrical insulators and feedthroughs to fluid or vacuum systems.

  11. Deep-UV Raman spectroscopic analysis of structure and dissolution rates of silica-rich sodium borosilicate glasses

    SciTech Connect

    Pierce, Eric M; WindischJr., Charles F.; Burton, Sarah D.; Bovaird, Chase C.

    2010-01-01

    As part of ongoing studies to evaluate relationships between structure and rates of dissolution of silicate glasses in aqueous media, sodium borosilicate glasses of composition Na2O xB2O3 (3 x)SiO2, with x 1 (Na2O/B2O3 ratio 1), were analyzed using deep-UV Raman spectroscopy. Results were quantified in terms of the fraction of SiO4 tetrahedra with one non-bridging oxygen (Q3) and then correlated with Na2O and B2O3 content. The Q3 fractionwas found to increase with increasing Na2O content, in agreement with studies on related glasses, and, as long as the value of x was not too high, this contributed to higher rates of dissolution in single pass flow-through testing. In contrast, dissolution rates were less strongly determined by the Q3 fraction when the value of x was near unity, and appeared to grow larger upon further reduction of the Q3 fraction. Results were interpreted to indicate the increasingly important role of network hydrolysis in the glass dissolution mechanism as the BO4 tetrahedron replaces the Q3 unit as the charge-compensating structure for Na+ ions. Finally, the use of deep-UV Raman spectroscopy was found to be advantageous in studying finely powdered glasses in cases where visible Raman spectroscopy suffered from weak Raman scattering and fluorescence interference.

  12. Effects of soda-lime-silica waste glass on mullite formation kinetics and micro-structures development in vitreous ceramics.

    PubMed

    Marinoni, Nicoletta; D'Alessio, Daniela; Diella, Valeria; Pavese, Alessandro; Francescon, Ferdinando

    2013-07-30

    The effects of soda-lime waste glass, from the recovery of bottle glass cullet, in partial replacement of Na-feldspar for sanitary-ware ceramic production are discussed. Attention is paid to the mullite growth kinetics and to the macroscopic properties of the final output, the latter ones depending on the developed micro-structures and vitrification grade. Measurements have been performed by in situ high temperature X-ray powder diffraction, scanning electron microscopy, thermal dilatometry, water absorption and mechanical testing. Glass substituting feldspar from 30 to 50 wt% allows one (i) to accelerate the mullite growth reaction kinetics, and (ii) to achieve macroscopic features of the ceramic output that comply with the latest technical requirements. The introduction of waste glass leads to (i) a general saving of fuel and reduction of the CO2-emissions during the firing stage, (ii) a preservation of mineral resources in terms of feldspars, and (iii) an efficient management of the bottle glass refuse by readdressing a part of it in the sanitary-ware manufacturing. PMID:23624427

  13. Void-nanograting transition by ultrashort laser pulse irradiation in silica glass.

    PubMed

    Dai, Ye; Patel, Aabid; Song, Juan; Beresna, Martynas; Kazansky, Peter G

    2016-08-22

    The structural evolution from void modification to self-assembled nanogratings in fused silica is observed for moderate (NA > 0.4) focusing conditions. Void formation, appears before the geometrical focus after the initial few pulses and after subsequent irradiation, nanogratings gradually occur at the top of the induced structures. Nonlinear Schrödinger equation based simulations are conducted to simulate the laser fluence, intensity and electron density in the regions of modification. Comparing the experiment with simulations, the voids form due to cavitation in the regions where electron density exceeds 1020 cm-3 but is below critical. In this scenario, the energy absorption is insufficient to reach the critical electron density that was once assumed to occur in the regime of void formation and nanogratings, shedding light on the potential formation mechanism of nanogratings. PMID:27557213

  14. Chromatic dispersions in highly nonlinear glass nanofibers

    NASA Astrophysics Data System (ADS)

    Chaudhari, Chitrarekha; Suzuki, Takenobu; Ohishi, Yasutake

    2008-08-01

    We design air cladding tellurite (TeO2), bismuth oxide (Bi2O3) based, and chalcogenide (As2S3) nanofibers, and calculate the chromatic dispersions. For each material, wavelength dependent propagation constants of the nanofiber are obtained from the exact solutions of the Maxwell's equations, and from the propagation constants the chromatic dispersion is calculated. We tailor the dispersion to zero at the communication wavelength, 1.5 μm, by proper selection of the core diameter of the nanofiber for all the above materials. We further explain the technique for flattening the zero dispersion in telecommunication window, using glass instead of air, as the cladding of the nanofiber structure. Using the glass cladding has the advantage of easy handling, specially, for the communication purposes. Further, the glass cladding causes larger effective index difference between various modes of the nanofiber, thus reducing the mode coupling. We present the numerical results of the dispersion flattening technique by assuming the borosilicate glass cladding to the chalcogenide As2S3 glass core nanofiber. With the borosilicate cladding the dispersion characteristics of the nanofiber change drastically and flattening of the zero dispersion is achieved at 1.408 μm wavelength, when the core diameter is 724 nm.

  15. Optical Basicity and Nepheline Crystallization in High Alumina Glasses

    SciTech Connect

    Rodriguez, Carmen P.; McCloy, John S.; Schweiger, M. J.; Crum, Jarrod V.; Winschell, Abigail E.

    2011-02-25

    The purpose of this study was to find compositions that increase waste loading of high-alumina wastes beyond what is currently acceptable while avoiding crystallization of nepheline (NaAlSiO4) on slow cooling. Nepheline crystallization has been shown to have a large impact on the chemical durability of high-level waste glasses. It was hypothesized that there would be some composition regions where high-alumina would not result in nepheline crystal production, compositions not currently allowed by the nepheline discriminator. Optical basicity (OB) and the nepheline discriminator (ND) are two ways of describing a given complex glass composition. This report presents the theoretical and experimental basis for these models. They are being studied together in a quadrant system as metrics to explore nepheline crystallization and chemical durability as a function of waste glass composition. These metrics were calculated for glasses with existing data and also for theoretical glasses to explore nepheline formation in Quadrant IV (passes OB metric but fails ND metric), where glasses are presumed to have good chemical durability. Several of these compositions were chosen, and glasses were made to fill poorly represented regions in Quadrant IV. To evaluate nepheline formation and chemical durability of these glasses, quantitative X-ray diffraction (XRD) analysis and the Product Consistency Test were conducted. A large amount of quantitative XRD data is collected here, both from new glasses and from glasses of previous studies that had not previously performed quantitative XRD on the phase assemblage. Appendix A critically discusses a large dataset to be considered for future quantitative studies on nepheline formation in glass. Appendix B provides a theoretical justification for choice of the oxide coefficients used to compute the OB criterion for nepheline formation.

  16. Dynamic fatigue of a lithia-alumina-silica glass-ceramic

    NASA Technical Reports Server (NTRS)

    Tucker, Dennis S.

    1990-01-01

    A dynamic fatigue study was performed on a Li2O-Al2O3-SiO2 glass-ceramic 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 = 20) to stress corrosion in ambient conditions. Analysis also indicated the elements should survive applied stresses incurred during grinding and polishing operations.

  17. Thermal lens effects on highly pumped Yb:glass

    NASA Astrophysics Data System (ADS)

    Nishimura, Akihiko; Akaoka, Katsuaki; Ohzu, Akira; Sugiyama, Akira; Usami, Tsutomu; Matoba, Tohru

    2000-04-01

    Thermal lens effects on highly pumped Yb doped phosphate glass was measured by a Shack-Hartmann wavefront sensor for the development of compact chirped pulse amplification systems. High energy pump pulses of 1 - 2 Joules were produced by a flashlamp pumped Ti-sapphire laser. The pumping intensity on the Yb:glass surface exceeded 800 kW/cm2. The pulse energy of 330 mJ from Yb:glass was obtained with 53% slope efficiency with 0.5 Hz reputation. The absorbed pump energy generated the thermal lens effects inside the Yb:glass. The wavefront distortion completely disappeared after 300 ms of pump pulse. Neither heat accumulation nor pumping damage was observed on the Yb:glass.

  18. Reference commercial high-level waste glass and canister definition.

    SciTech Connect

    Slate, S.C.; Ross, W.A.; Partain, W.L.

    1981-09-01

    This report presents technical data and performance characteristics of a high-level waste glass and canister intended for use in the design of a complete waste encapsulation package suitable for disposal in a geologic repository. The borosilicate glass contained in the stainless steel canister represents the probable type of high-level waste product that will be produced in a commercial nuclear-fuel reprocessing plant. Development history is summarized for high-level liquid waste compositions, waste glass composition and characteristics, and canister design. The decay histories of the fission products and actinides (plus daughters) calculated by the ORIGEN-II code are presented.

  19. Quantitative image analysis for evaluating the abrasion resistance of nanoporous silica films on glass

    NASA Astrophysics Data System (ADS)

    Nielsen, Karsten H.; Karlsson, Stefan; Limbach, Rene; Wondraczek, Lothar

    2015-12-01

    The abrasion resistance of coated glass surfaces is an important parameter for judging lifetime performance, but practical testing procedures remain overly simplistic and do often not allow for direct conclusions on real-world degradation. Here, we combine quantitative two-dimensional image analysis and mechanical abrasion into a facile tool for probing the abrasion resistance of anti-reflective (AR) coatings. We determine variations in the average coated area, during and after controlled abrasion. Through comparison with other experimental techniques, we show that this method provides a practical, rapid and versatile tool for the evaluation of the abrasion resistance of sol-gel-derived thin films on glass. The method yields informative data, which correlates with measurements of diffuse reflectance and is further supported by qualitative investigations through scanning electron microscopy. In particular, the method directly addresses degradation of coating performance, i.e., the gradual areal loss of antireflective functionality. As an exemplary subject, we studied the abrasion resistance of state-of-the-art nanoporous SiO2 thin films which were derived from 5-6 wt% aqueous solutions of potassium silicates, or from colloidal suspensions of SiO2 nanoparticles. It is shown how abrasion resistance is governed by coating density and film adhesion, defining the trade-off between optimal AR performance and acceptable mechanical performance.

  20. Quantitative image analysis for evaluating the abrasion resistance of nanoporous silica films on glass

    PubMed Central

    Nielsen, Karsten H.; Karlsson, Stefan; Limbach, Rene; Wondraczek, Lothar

    2015-01-01

    The abrasion resistance of coated glass surfaces is an important parameter for judging lifetime performance, but practical testing procedures remain overly simplistic and do often not allow for direct conclusions on real-world degradation. Here, we combine quantitative two-dimensional image analysis and mechanical abrasion into a facile tool for probing the abrasion resistance of anti-reflective (AR) coatings. We determine variations in the average coated area, during and after controlled abrasion. Through comparison with other experimental techniques, we show that this method provides a practical, rapid and versatile tool for the evaluation of the abrasion resistance of sol-gel-derived thin films on glass. The method yields informative data, which correlates with measurements of diffuse reflectance and is further supported by qualitative investigations through scanning electron microscopy. In particular, the method directly addresses degradation of coating performance, i.e., the gradual areal loss of antireflective functionality. As an exemplary subject, we studied the abrasion resistance of state-of-the-art nanoporous SiO2 thin films which were derived from 5–6 wt% aqueous solutions of potassium silicates, or from colloidal suspensions of SiO2 nanoparticles. It is shown how abrasion resistance is governed by coating density and film adhesion, defining the trade-off between optimal AR performance and acceptable mechanical performance. PMID:26656260

  1. Synthesis and new structure shaping mechanism of silica particles formed at high pH

    SciTech Connect

    Zhang, Henan; Zhao, Yu; Akins, Daniel L.

    2012-10-15

    For the sol-gel synthesis of silica particles under high pH catalytic conditions (pH>12) in water/ethanol solvent, we have deduced that the competing dynamics of chemical etching and sol-gel process can explain the types of silica particles formed and their morphologies. We have demonstrated that emulsion droplets that are generated by adding tetraethyl orthosilicate (TEOS) to a water-ethanol solution serve as soft templates for hollow spherical silica (1-2 {mu}m). And if the emulsion is converted by the sol-gel process, one finds that suspended solid silica spheres of diameter of {approx}900 nm are formed. Moreover, several other factors are found to play fundamental roles in determining the final morphologies of silica particles, such as by variation of the pH (in our case, using OH{sup -}) to a level where condensation dominates; by changing the volume ratios of water/ethanol; and using an emulsifier (specifically, CTAB) - Graphical abstract: 'Local chemical etching' and sol-gel process have been proposed to interpret the control of morphologies of silica particles through varying initial pHs in syntheses. Highlights: Black-Right-Pointing-Pointer Different initial pHs in our syntheses provides morphological control of silica particles. Black-Right-Pointing-Pointer 'Local chemical etching' and sol-gel process describes the formation of silica spheres. Black-Right-Pointing-Pointer The formation of emulsions generates hollow silica particles.

  2. Turning geothermal waste into glasses and glass ceramics

    SciTech Connect

    Diaz, C. ); Torres-Martinez, L.M.; Garza, L. ); Avalos-Borja, M. ); Rincon, J.M. )

    1993-10-01

    Researchers investigating the waste on the pipes at the Cerro Prieto geothermal plant in Mexico found that it contained high amounts of silica. Initial tests showed that this waste silica had a high specific surface area, contained salts that could easily be eliminated, and resisted high temperatures effectively. Further research was done to see if this waste material could be used as silica sand in the production of glass. Testing of the waste material included the following: X-ray diffraction with nickel filters; EDX spectroscopy with ultrathin window; Differential thermal analysis; IR spectroscopy analysis; Electron microscope analysis. The tests were done on the raw material itself and on four sets of glass formulated from the raw material. Two sets of glass were formulated from untreated waste material, and two sets were formulated from treated waste material. The raw material was tested for purity, and the glass was tested for hardness, toughness, and transparency. As the tests show, the silica material from the Cerro Prieto plant steam pipes is not merely useless industrial waste. It is a reproducible source of silica sand that producers can use in ceramic and glass production. The initial tests show that the properties of the raw material, and those of the glass formulated from the raw material, will meet industry requirements.

  3. New support for high-performance liquid chromatography based on silica coated with alumina particles.

    PubMed

    Silveira, José Leandro R; Dib, Samia R; Faria, Anizio M

    2014-01-01

    A new material based on silica coated with alumina nanoparticles was proposed for use as a chromatographic support for reversed-phase high-performance liquid chromatography. Alumina nanoparticles were synthesized by a sol-gel process in reversed micelles composed of sodium bis(2-ethylhexyl)sulfosuccinate, and the support material was formed by the self-assembly of alumina layers on silica spheres. Spectroscopic and (29)Si nuclear magnetic resonance results showed evidence of chemical bonds between the alumina nanoparticles and the silica spheres, while morphological characterizations showed that the aluminized silica maintained the morphological properties of silica desired for chromatographic purposes after alumina incorporation. Stability studies indicated that bare silica showed high dissolution (~83%), while the aluminized silica remained practically unchanged (99%) after passing one liter of the alkaline mobile phase, indicating high stability under alkaline conditions. The C18 bonded aluminized silica phase showed great potential for use in high-performance liquid chromatography to separate basic molecules in the reversed-phase mode. PMID:24521917

  4. High level radioactive waste glass production and product description

    SciTech Connect

    Sproull, J.F.; Marra, S.L.; Jantzen, C.M.

    1993-12-01

    This report examines borosilicate glass as a means of immobilizing high-level radioactive wastes. Borosilicate glass will encapsulate most of the defense and some of the commercial HLW in the US. The resulting waste forms must meet the requirements of the WA-SRD and the WAPS, which include a short term PCT durability test. The waste form producer must report the composition(s) of the borosilicate waste glass(es) produced but can choose the composition(s) to meet site-specific requirements. Although the waste form composition is the primary determinant of durability, the redox state of the glass; the existence, content, and composition of crystals; and the presence of glass-in-glass phase separation can affect durability. The waste glass should be formulated to avoid phase separation regions. The ultimate result of this effort will be a waste form which is much more stable and potentially less mobile than the liquid high level radioactive waste is currently.

  5. High strain rate fracture behaviour of fused silica

    NASA Astrophysics Data System (ADS)

    Ruggiero, A.; Iannitti, G.; Testa, G.; Limido, J.; Lacome, J. L.; Olovsson, L.; Ferraro, M.; Bonora, N.

    2014-05-01

    Fused silica is a high purity synthetic amorphous silicon dioxide characterized by low thermal expansion coefficient, excellent optical qualities and exceptional transmittance over a wide spectral range. Because of its wide use in the military industry as window material, it may be subjected to high-energy ballistic impacts. Under such dynamic conditions, post-yield response of the ceramic as well as the strain rate related effects become significant and should be accounted for in the constitutive modelling. In this study, the Johnson-Holmquist (J-H) model parameters have been identified by inverse calibration technique, on selected validation test configurations, according to the procedure described hereafter. Numerical simulations were performed with LS-DYNA and IMPETUS-FEA, a general non-linear finite element software which offers NURBS finite element technology for the simulation of large deformation and fracture in materials. In order to overcome numerical drawbacks associated with element erosion, a modified version of the J-H model is proposed.

  6. Alkali-silica reactions of mortars produced by using waste glass as fine aggregate and admixtures such as fly ash and Li2CO3.

    PubMed

    Topçu, Ilker Bekir; Boğa, Ahmet Raif; Bilir, Turhan

    2008-01-01

    Use of waste glass or glass cullet (GC) as concrete aggregate is becoming more widespread each day because of the increase in resource efficiency. Recycling of wastes is very important for sustainable development. When glass is used as aggregate in concrete or mortar, expansions and internal stresses occur due to an alkali-silica reaction (ASR). Furthermore, rapid loss in durability is generally observed due to extreme crack formation and an increase in permeability. It is necessary to use some kind of chemical or mineral admixture to reduce crack formation. In this study, mortar bars are produced by using three different colors of glass in four different quantities as fine aggregate by weight, and the effects of these glass aggregates on ASR are investigated, corresponding to ASTM C 1260. Additionally, in order to reduce the expansions of mortars, 10% and 20% fly ash (FA) as mineral admixture and 1% and 2% Li(2)CO(3) as chemical admixture are incorporated by weight in the cement and their effects on expansion are examined. It is observed that among white (WG), green (GG) and brown glass (BG) aggregates, WG aggregate causes the greatest expansion. In addition, expansion increases with an increase in amount of glass. According to the test results, it is seen that over 20% FA and 2% Li(2)CO(3) replacements are required to produce mortars which have expansion values below the 0.2% critical value when exposed to ASR. However, usages of these admixtures reduce expansions occurring because of ASR. PMID:17570652

  7. The Aqueous Thermodynamics and Complexation Reactions of Anionic Silica and Uranium Species to High Concentration

    SciTech Connect

    Felmy, Andrew R.

    2004-06-01

    Highly basic tank wastes contain several important radionuclides, including 90Sr, 99Tc, and 60Co, as well as actinide elements (i.e., isotopes of U, Pu, and Am). These highly basic tank wastes are known to have leaked into the vadose zone at the Hanford Site. Upon entering the sediments in the vadose zone, the highly basic solutions dissolve large concentrations of silica from the silica and aluminosilicate minerals present in the subsurface. These dissolution reactions alter the chemical composition of the leaking solutions, transforming them from a highly basic (as high 2M NaOH) solution into a pore solution with a very high concentration of dissolved silica and a significantly reduced pH. This moderately basic (pH 9 to 11), high-silica solution has the potential to complex radionuclides and move through the subsurface. Such strong radionuclide complexation is a currently unconsidered transport vector that has the potential to expedite radionuclide transport through the vad ose zone. These strong complexation effects have the ability to significantly alter current conceptual models of contaminant migration beneath leaking tanks. In this project, we are determining the aqueous thermodynamics and speciation of dissolved silica and silica-radionuclide complexes to high silica concentration. We are also initiating studies of U(VI) speciation under strongly basic conditions.

  8. Effect of aluminium on the silica compressibility and transition to the CaCl2-form at high- pressure and high-temperature up to 100 GPa

    NASA Astrophysics Data System (ADS)

    Bolfan-Casanova, N.; Andrault, D.; Guignot, N.; Amiguet, E.

    2008-12-01

    The recycling of oceanic crust into the deep Earth offers a way of enriching the mantle in silica. In such a subduction context, the high-pressure phase of silica, stishovite, present in the basaltic and the sedimentary portions of the slab, has been shown to contain significant amounts of aluminium. The incorporation of this element and its possible coupling with oxygen vacancies (Si4+ = Al3+ + " O) can influence significantly the density, compressibility and phase transitions of mantle phases. We investigated the effect of Al on stishovite properties up to ~100 GPa in a YAG or CO2-laser heated diamond anvil cell using in-situ X-ray diffraction at the ID30-ID27 beamline of ESRF. Using an Al-bearing silica glass as starting material, we performed more than 10 different experimental runs at various P and T conditions. Our first observation is that the transition from rutile to calcium chloride (CaCl2) phase of silica occurs at lower pressure, down to 23 GPa at 300 Kelvin, compared to 50 GPa in the pure SiO2 system. [1]. Also, we confirm that the stishovite room pressure volume is increased with increasing Al-content. Still, the volume difference of ~1% at 1 bar rapidly vanishes at higher pressures and the PV equation of state of Al-bearing stishovite at room pressure appears similar to that of Al-free stishovite at all pressures investigated to 100 GPa, within the experimental error. The CaCl2 distortion increases with pressure and decreases with temperature allowing to measure the clapeyron slope of the transition in-situ at high-pressure and high-temperature: dP/dT of 0.02 GPa/K. According to the phase diagram determined by in-situ X-ray diffraction, silica should be in the CaCl2 form in most of the transition and lower mantle. Also, aluminous silica, whether in the rutile or calcium chloride structure, is softer than pure silica. Our results show that the incorporation of ~2.3 weight % of alumina in silica decreases its bulk modulus of around 7-10% in case of the

  9. Novel broadband glass phosphors for high CRI WLEDs.

    PubMed

    Chen, Li-Yin; Cheng, Wei-Chih; Tsai, Chun-Chin; Chang, Jin-Kai; Huang, Yi-Chung; Huang, Jhih-Ci; Cheng, Wood-Hi

    2014-05-01

    New broadband glass phosphors with excellent thermal stability were proposed and experimentally demonstrated for white light-emitting-diodes (WLEDs). The novel glass phosphors were realized through dispersing multiple phosphors into SiO₂ based glass (SiO₂-Na₂O-Al₂O₃-CaO) at 680°C. Y₃Al₅O₁₂:Ce³⁺ (YAG), Lu₃Al₅O₁₂:Ce³⁺ (LuAG), and CaAlSiN₃: Eu²⁺ (nitride) phosphor crystals were chosen respectively as the yellow, green, and red emitters of the glass phosphors. The effect of sintering temperature on inter-diffusion reduction between phosphor crystals and amorphous SiO₂ in nitride-doped glass phosphors was studied and evidenced by the aid of high-resolution transmission electron microscopy (HRTEM). Broadband glass phosphors with high quantum-yield of 55.6% were thus successfully realized through the implementation of low sintering temperature. Proof-of-concept devices utilizing the novel broadband phosphors were developed to generate high-quality cool-white light with trisstimulus coordinates (x, y) = (0.358, 0.288), color-rending index (CRI) = 85, and correlated color temperature (CCT) = 3923K. The novel broadband glass phosphors with excellent thermal stability are essentially beneficial to the applications for next-generation solid-state indoor lighting, especially in the area where high power and absolute reliability are required. PMID:24922375

  10. High-beam quality, high-efficiency laser based on fiber with heavily Yb(3+)-doped phosphate core and silica cladding.

    PubMed

    Egorova, O N; Semjonov, S L; Medvedkov, O I; Astapovich, M S; Okhrimchuk, A G; Galagan, B I; Denker, B I; Sverchkov, S E; Dianov, E M

    2015-08-15

    We have fabricated and tested a composite fiber with an Yb(3+)-doped phosphate glass core and silica cladding. Oscillation with a slope efficiency of 74% was achieved using core pumping at 976 nm with fiber lengths of 48-90 mm in a simple laser configuration, where the cavity was formed by a high-reflectivity Bragg grating and the cleaved fiber end. The measured M(2) factors were as low as 1.05-1.22 even though the fiber was multimode at the lasing wavelength. PMID:26274654

  11. High-Silica Rock Coatings on Mars: Constraining Secondary Silicate Mineralogy and Chemical Weathering Processes on Mars.

    NASA Astrophysics Data System (ADS)

    Kraft, M. D.; Michalski, J. R.; Sharp, T. G.

    2003-12-01

    Thermal Emission Spectrometer (TES) data have been fundamental to understanding Martian surface mineralogy. These data, however, require careful modeling based on laboratory spectroscopic measurements, and modeling of some minerals for Mars has been equivocal. Due to high degrees of spectral similarity, it is difficult to distinguishing silicate glass, clay minerals, zeolites, palagonitized glass, and other secondary products such as amorphous silica as components of surface rock spectra. Deciphering the nature of secondary mineral products on Mars is of key importance to understanding the role of water at the Martian surface over time. It is of central interest to distinguish primary glass from secondary silicate minerals, and secondary minerals from one another to better constrain the degree and mechanisms of aqueous alteration. Observations of Martian surface materials indicate some degree of atmosphere-water-rock interaction. These include nanophase ferric-iron oxides from visible/near-infrared spectroscopy, concentrated hematite deposits identified with TES, high water contents of rocks measured by the Alpha Proton X-ray Spectrometer, sulfate and halide minerals inferred from lander geochemical measurements, and carbonate minerals identified in Martian dust with TES data. Mass balance suggests that if there are oxides, salts, and carbonates there must also be secondary silicate phases present on Mars, which may be identifiable with TES. Identifying the types, distribution, and abundance (or absence) of secondary silicates will enable better constrains to be placed on Martian chemical weathering processes and the role water has played at the Martian surface. We suggest that rock coatings dominated by amorphous silica are geologically reasonable for Mars and may be consistent with TES data. Laboratory measurements of silica-coated rocks show that thin, micrometer-scale silica coatings have a substantial impact on rock spectra. Consequently, if authegenic

  12. Glass precursor approach to high-temperature superconductors

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.

    1992-01-01

    The available studies on the synthesis of high T sub c superconductors (HTS) via the glass precursor approach were reviewed. Melts of the Bi-Sr-Ca-Cu-O system as well as those doped with oxides of some other elements (Pb, Al, V, Te, Nb, etc.) could be quenched into glasses which, on further heat treatments under appropriate conditions, crystallized into the superconducting phase(s). The nature of the HTS phase(s) formed depends on the annealing temperature, time, atmosphere, and the cooling rate and also on the glass composition. Long term annealing was needed to obtain a large fraction of the 110 K phase. The high T sub c phase did not crystallize out directly from the glass matrix, but was preceded by the precipitation of other phases. The 110 K HTS was produced at high temperatures by reaction between the phases formed at lower temperatures resulting in multiphase material. The presence of a glass former such as B2O3 was necessary for the Y-Ba-Cu-O melt to form a glass on fast cooling. A discontinuous YBa2Cu3O(7-delta) HTS phase crystallized out on heat treatment of this glass. Attempts to prepare Tl-Ba-Ca-Cu-O system in the glassy state were not successful.

  13. Synthesis, structure, and properties of glasses under extreme conditions

    NASA Astrophysics Data System (ADS)

    Guerette, Michael J.

    Anomalous mechanical properties of silica glass include stiffening upon heating, initially softening under pressure, and non-linear elastic response to strains. Through understanding structural changes in silica glass under a broad range of temperature, pressure, and strain conditions and how they influence the mechanical properties, insight was gained for how to change the silica glass network to better suit specific uses in extreme conditions. In this dissertation, pressure-quenching routes were used to effectively change the glass atomic packing and to make densified glass. Applied in the non-rigid state near the glass transition temperature, quench pressures up to 8 GPa have been used to achieve density increase of 25% in silica glass. The resulting structure and properties of as-quenched samples have been investigated using XRD, Raman and Brillouin spectroscopy. In-situ Raman and Brillouin light scattering techniques were developed to study the structure, elastic and dynamic properties of silica glass under high temperature, high pressure and high strain conditions. High temperature measurements were carried out in an optical furnace up to 1500°C, a diamond anvil cell was used to carry out high pressure experiments up to 25 GPa, and a two-point bender was used for measuring glasses in excess of 6% strain in both tensile and compressive regions. Pressure-quenching from the non-rigid state near the glass transition temperature imparts structural signatures to densified silica glass that cannot be accomplished through cold compression at room temperature. The unique structures of pressure-quenched silica glass are reflected in decreased anomalous response of silica glass to external stimuli of high temperature or high pressure, and therefore greater thermo-mechanical stability. The nonlinear elastic behavior of silica glass has been directly probed from the compressive to the tensile side of silica fibers in bend by using in-situ Brillouin light scattering. This

  14. High transmission glasses for solar applications

    SciTech Connect

    Johnson, L.K.; Thompson, D.A.

    1981-11-03

    The instant invention is directed to glasses manifesting solar transmissions (350-2100 nm) through a 2.54 mm thick sheet in excess of 90% which can be prepared from conventional glass batch materials containing up to 0.1% iron, expressed as Fe/sub 2/O/sub 3/, as impurities. The inventive glasses consist essentially, expressed in weight percent on the oxide basis as calculated from the batch, of -Al/sub 2/O/sub 3/ 7-13 -B/sub 2/O/sub 3/ 7-10 -Na/sub 2/O 6-11 -K/sub 2/O 2-7 -CaO 2-7 TiO/sub 2/ 0.1-1 -As/sub 2/O/sub 3/ 0-1 -Sb/sub 2/O/sub 3/ 0-1 -SiO/sub 2/. Balance part of the batch materials is added in the form of nitrates in a sufficient amount to virtually completely oxidize all the tramp iron present to the Fe/sup +3/ state.

  15. Thermal poling of alkaline earth boroaluminosilicate glasses with intrinsically high dielectric breakdown strength

    NASA Astrophysics Data System (ADS)

    Smith, Nicholas J.; Lanagan, Michael T.; Pantano, Carlo G.

    2012-04-01

    Per the rectification model of thermal poling, it has been proposed that intrinsic breakdown strength plays a strong limiting role in the internal DC fields supported by the glass from the poling process. One might therefore hypothesize proportionately larger second-order nonlinearity (SON) in glasses with intrinsically high dielectric breakdown strength. We test these ideas by thermal poling of two different commercial alkali-free alkaline-earth boroaluminosilicate display glasses—one with barium only (AF45 from Schott), and the other with a mixture of alkaline-earth ions (OA-10 G from NEG). Not only are such compositions relevant from a commercial standpoint, they are also interesting in that they have been recently shown to exhibit remarkably high intrinsic dielectric breakdown strengths of 11-14 MV/cm. Quantitative Maker fringe and stack Maker-fringe measurements provide an accurate evaluation of the poling-induced SON susceptibilities, and indicate maximum χ(2) values of 0.44 and 0.26 pm/V in these glasses. These values are comparable to those reported for silica and other multicomponent glasses. Thus, the hypothesis that higher χ(2) would be observed in high intrinsic breakdown strength glasses was not validated. Based on our application of the rectification model, internal fields of the order 2-4 MV/cm were calculated, which are well below the measured intrinsic breakdown strengths at room temperature. The most plausible explanation for these observations is nonlinear electronic conduction effects taking place within the depletion region at the poling temperature, limiting internal fields to a fraction of the breakdown field.

  16. Large partition coefficients for trace elements in high-silica rhyolites

    USGS Publications Warehouse

    Mahood, G.; Hildreth, W.

    1983-01-01

    The partitioning of 25 trace elements between high-silica rhyolitic glass and unzoned phenocrysts of potassic and sodic sanidine, biotite, augite, ferrohedenbergite, hypersthene, fayalite, titanomagnetite, ilmenite, zircon, and allanite has been determined by INAA on suites of samples from the mildly peralkaline lavas and tuff of the Sierra La Primavera, Mexico, and the metaluminous, compo. sitionally zoned, Bishop Tuff, California. The partition coefficients are much larger than published values for less silicic compositions; the range of values among Primavera samples that differ only slightly in temperature or bulk composition approaches that previously reported from basalts to rhyodacites. Intrinsic temperature dependence of the crystal/liquid partitioning is apparently small. The high values of partition coefficients reflect principally the strongly polymerized nature of the alkali-aluminosilicate liquid, whereas the marked variability of values for partition coefficients is attributed to differences in the concentrations of complexing ligands and/or different degrees of melt polymerization. Great variation in the values of partition coefficients that are potentially applicable to early stages in the partial melting of crustal rocks complicates assessment of 1. (1) source regions for granitic melts and 2. (2) contributions by crustal-melt increments to andesites. ?? 1983.

  17. The glass transition in high-density amorphous ice

    PubMed Central

    Loerting, Thomas; Fuentes-Landete, Violeta; Handle, Philip H.; Seidl, Markus; Amann-Winkel, Katrin; Gainaru, Catalin; Böhmer, Roland

    2015-01-01

    There has been a long controversy regarding the glass transition in low-density amorphous ice (LDA). The central question is whether or not it transforms to an ultraviscous liquid state above 136 K at ambient pressure prior to crystallization. Currently, the most widespread interpretation of the experimental findings is in terms of a transformation to a superstrong liquid above 136 K. In the last decade some work has also been devoted to the study of the glass transition in high-density amorphous ice (HDA) which is in the focus of the present review. At ambient pressure HDA is metastable against both ice I and LDA, whereas at > 0.2 GPa HDA is no longer metastable against LDA, but merely against high-pressure forms of crystalline ice. The first experimental observation interpreted as the glass transition of HDA was made using in situ methods by Mishima, who reported a glass transition temperature Tg of 160 K at 0.40 GPa. Soon thereafter Andersson and Inaba reported a much lower glass transition temperature of 122 K at 1.0 GPa. Based on the pressure dependence of HDA's Tg measured in Innsbruck, we suggest that they were in fact probing the distinct glass transition of very high-density amorphous ice (VHDA). Very recently the glass transition in HDA was also observed at ambient pressure at 116 K. That is, LDA and HDA show two distinct glass transitions, clearly separated by about 20 K at ambient pressure. In summary, this suggests that three glass transition lines can be defined in the p–T plane for LDA, HDA, and VHDA. PMID:25641986

  18. Enhancement of the glass corrosion in the presence of clay minerals: Testing experimental results with an integrated glass dissolution model

    SciTech Connect

    Curti, E.; Godon, N.; Vernaz, E.Y.

    1993-12-31

    Recent glass dissolution experiments, conducted at 90{degrees}C in the presence of potential backfill materials, indicate remarkably faster glass corrosion in the presence of clay, compared to tests where the glass is leached either alone or with alternative backfill materials. This effect correlates with the clay content in the backfill, and may be attributed to the removal of silica from solution. Sorption, or dissolution with reprecipitation of a silica-rich clay, have been proposed as possible mechanisms for the silica consumption. The results of some experiments have been tested against a glass dissolution model, in which a widely used kinetic equation for glass corrosion is coupled with diffusive silica transport through a single porosity, linearly sorbing medium, which represents the backfilling. Because the glass corrosion rates imposed by the kinetic equation are inversely proportional to the silicic acid concentration of the leachant contacting the glass, the model predicts enhanced glass dissolution if silica is sorbed by the porous medium. The experimental data proved to be consistent with the predicted enhancement of the glass dissolution. Moreover, the model-estimated distribution coefficients for silica sorption (K{sub d}) fall within the range of values extracted from available literature data, thus supporting the hypothesis that the observed high corrosion rates are due to sorption of silica on the clay mineral surfaces.

  19. Gold nanoparticle decorated graphene oxide/silica composite stationary phase for high-performance liquid chromatography.

    PubMed

    Liang, Xiaojing; Wang, Xusheng; Ren, Haixia; Jiang, Shengxiang; Wang, Licheng; Liu, Shujuan

    2014-06-01

    In the initial phase of this study, graphene oxide (GO)/silica was fabricated by assembling GO onto the silica particles, and then gold nanoparticles (GNPs) were used to modify the GO/silica to prepare a novel stationary phase for high-performance liquid chromatography. The new stationary phase could be used in both reversed-phase chromatography and hydrophilic interaction liquid chromatography modes. Good separations of alkylbenzenes, isomerides, amino acids, nucleosides, and nucleobases were achieved in both modes. Compared with the GO/silica phase and GNPs/silica phase, it is found that except for hydrophilicity, large π-electron systems, hydrophobicity, and coordination functions, this new stationary phase also exhibited special separation performance due to the combination of 2D GO with zero-dimensional GNPs. PMID:24723561

  20. Iron Phosphate Glasses for Vitrifying DOE High Priority Nuclear Wastes

    SciTech Connect

    Kim, C.W.; Day, D.E.

    2004-03-29

    Iron phosphate glasses have been studied as an alternative glass for vitrifying Department of Energy (DOE) high priority wastes. The high priority wastes were the Low Activity Waste (LAW) and the High Level Waste (HLW) with high chrome content stored at Hanford, WA, and the Sodium Bearing Waste (SBW) stored at the Idaho National Engineering and Environmental Laboratory. These wastes were recommended by Tanks Focus Area since they were expected to require special attention when vitrified in borosilicate glasses. All three of these wastes have been successfully vitrified in iron phosphate glasses at waste loadings ranging from a low of 32 wt% for the high sulfate LAW to 40 wt% for the SBW to a high of 75 wt% for the high chrome HLW. In addition to these desirable high waste loadings, the iron phosphate glasses were easily melted, typically between 950 and 1200 C, in less than 4 hours in commercial refractory oxide containers. It is noteworthy that the chemical durability of both glassy and deliberately crystallized iron phosphate wasteforms not only met, but significantly exceeded, all current DOE chemical durability requirements as measured by the Product Consistency Test (PCT) and Vapor Hydration Test (VHT). The high waste loading, low melting temperature, rapid furnace throughput (short melting time) and their outstanding chemical durability could significantly accelerate the clean up effort and reduce the time and cost of vitrifying these high priority wastes.

  1. Study of the glass formation of high temperature superconductors

    NASA Technical Reports Server (NTRS)

    Ethridge, Edwin C.; Kaukler, William F.; Rolin, Terry

    1992-01-01

    A number of compositions of ceramic oxide high T(sub c) superconductors were elevated for their glass formation ability by means of rapid thermal analysis during quenching, optical, and electron microscopy of the quenched samples, and with subsequent DSC measurements. Correlations between experimental measurements and the methodical composition changes identified the formulations of superconductors that can easily form glass. The superconducting material was first formed as a glass; then, with subsequent devitrification, it was formed into a bulk crystalline superconductor by a series of processing methods.

  2. Fabrication of high-efficiency diffraction gratings in glass

    NASA Astrophysics Data System (ADS)

    Takeshima, Nobuhito; Narita, Yoshihiro; Tanaka, Shuhei; Kuroiwa, Yutaka; Hirao, Kazuyuki

    2005-02-01

    We investigated a microfabrication process for optical gratings with periods of micrometer order that use ultrafast laser pulses in semiconductor-doped glass. ZnS- or PbS-doped SiO2 - Al2O3 - B2O3 - CaO - ZnO - Na2O - K2O glass was prepared by a melting method. Glass transmission diffraction gratings with a high refractive-index difference were fabricated with femtosecond laser pulses. The first-order diffraction efficiencies of these gratings were approximately 80%, and the first-order diffraction angles of these gratings were 8° at telecommunication wavelengths.

  3. Glass-to-metal seals comprising relatively high expansion metals

    NASA Technical Reports Server (NTRS)

    Hirayama, C. (Inventor)

    1974-01-01

    A glass suitable for glass-to-metal seals that has a resistance to attack by moisture and a high coefficient of linear thermal expansion is introduced. Linear expansion covers the range from 12 to 14 x 10 to the minus 6 C between room temperature and 500 C. The glass is essentially composed of, by molar percent, about 9% of K2O, about 10% of Na2O, about 70% of SiO2, about 6% Al2O3, and about 5% of MgO.

  4. Glass composition development for plasma processing of Hanford high sodium content low-level radioactive liquid waste

    SciTech Connect

    Marra, J.C.

    1995-02-01

    To assess the acceptability of prospective compositions, response criteria based on durability, homogeneity, viscosity and volatility were defined. Response variables were weighted: durability 35%, homogeneity 25%, viscosity 25%, volatility 15%. A Plackett-Burman experimental design was used to define the first twelve glass formulations. Glass former additives included Al2O3, B2O3, CaO, Li2O, ZrO2 and SiO2. Lithia was added to facilitate fritting of the additives. The additives were normalized to silica content to ease experimental matrix definition and glass formulation. Preset high and low values of these ratios were determined for the initial twelve melts. Based on rankings of initial compositions, new formulations for testing were developed based on a simplex algorithm. Rating and ranking of subsequent compositions continued until no apparent improvement in glass quality was achieved in newly developed formulations. An optimized composition was determined by averaging the additive component values of the final best performing compositions. The glass former contents to form the optimized glass were: 16.1 wt % Al2O3, 12.3 wt % B2O3, 5.5 wt % CaO, 1.7 wt % Li2O, 3.3 wt % ZrO2, 61.1 wt % SiO2. An optimized composition resulted after only 25 trials despite studying six glass additives. A vitrification campaign was completed using a small-scale Joule heated melter. 80 lbs of glass was produced over 96 hours of continuous operation. Several salt compounds formed and deposited on melter components during the run and likely caused the failure of several pour chamber heaters. In an attempt to minimize sodium volatility, several low or no boron glasses were formulated. One composition containing no boron produced a homogeneous glass worthy of additional testing.

  5. Laterally stacked glass substrates with high density electrical feedthroughs

    NASA Astrophysics Data System (ADS)

    Tanaka, Shuji; Fujimoto, Satoshi; Ito, Osamu; Choe, Seong-Hun; Esashi, Masayoshi

    2007-03-01

    This paper reports a novel method to produce high density feedthrough glass wafers with sufficient thickness for the packaging and interconnection of high density array micro electromechanical systems (MEMS). Pyrex glass wafers with thin film metal lines on the surface are stacked and bonded with each other using phenyl methyl siloxane-based adhesive. The stacked glass wafer block is then sliced using a wire saw as the slicing surfaces cross the adhesive bonding interfaces vertically. Prototyped feedthrough glass wafers were subjected to anodic bonding to a silicon wafer with diaphragms. The anodic bonding was successful, but hermetic sealing was not achieved. The bending of the bonded sample can be reduced by annealing the sample at 400 °C in a vacuum before anodic bonding.

  6. RETENTION OF SULFATE IN HIGH LEVEL RADIOACTIVE WASTE GLASS

    SciTech Connect

    Fox, K.

    2010-09-07

    High level radioactive wastes are being vitrified at the Savannah River Site for long term disposal. Many of the wastes contain sulfate at concentrations that can be difficult to retain in borosilicate glass. This study involves efforts to optimize the composition of a glass frit for combination with the waste to improve sulfate retention while meeting other process and product performance constraints. The fabrication and characterization of several series of simulated waste glasses are described. The experiments are detailed chronologically, to provide insight into part of the engineering studies used in developing frit compositions for an operating high level waste vitrification facility. The results lead to the recommendation of a specific frit composition and a concentration limit for sulfate in the glass for the next batch of sludge to be processed at Savannah River.

  7. High performance shear thickening fluid based on calcinated colloidal silica microspheres

    NASA Astrophysics Data System (ADS)

    Zheng, Sheng-Biao; Xuan, Shou-Hu; Jiang, Wan-Quan; Gong, Xing-Long

    2015-08-01

    Here, a novel method to prepare high performance shear thickening fluids (STFs) by dispersing calcinated silica microspheres into ethylene glycol is reported. The silica particles were prepared by hydrolyzing tetraethylorthosilicate (TEOS), and then they were treated under high temperature to remove the physically adsorbed water and the -OH groups on the surfaces. The influence of the temperature on the rheological properties of the final STFs was investigated and the STF prepared under the optimum temperature exhibited the best ST effects. A possible mechanism was proposed and it was found that a proper solvation layer adsorbed on the silica surface resulted in lower critical shear rate and higher shear thickening viscosity.

  8. Low melting high lithia glass compositions and methods

    DOEpatents

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

    2004-11-02

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

  9. Low melting high lithia glass compositions and methods

    DOEpatents

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

    2003-10-07

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

  10. Low melting high lithia glass compositions and methods

    DOEpatents

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

    2000-01-01

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

  11. The development of a high average power glass laser source

    NASA Astrophysics Data System (ADS)

    Myers, J. D.

    1984-05-01

    The subject contract has as its objective the development of a high average power glass laser by systematically improving the factors which influence the ability of a laser glass to handle large power levels. Based upon the availability of the thermal laser glass composition Q-100, the rationale used was toward the improvement of the efficiency of a glass laser by developing methods to increase the pumping efficiency and toward the improvement of the power handling capability of the glass laser rod itself. These incremental developments were broken down as follows: (1) Characterization of Q-100 Laser Glass: The measurement of its thermo-physical and thermo-optical properties to better define its engineering design parameters. (2) Improve Pumping Efficiency or Q-100: Primarily by cladding Q-100 with a matching cladding glass which would act as a lens and improve the transfer of pumping energy from the flashlamp. (3) Reduce thermal loading of Q-100 by Selective filtering of the flashlamp radiation and/or use energy transfer schemes to increase that portion of the flashlamp radiation corresponding to the neodymium pump bands. (4) Increase the rupture strength of Q-100 to directly increase its power-handling capability. (5) Investigate alternate pump sources to improve efficiency.

  12. Compressive Creep Performance and High Temperature Dimensional Stability of Conventional Silica Refractories

    SciTech Connect

    Karakus, M.; Kirkland, T.P.; Liu, K.C.; Moore, R.E.; Pint, B.A.; Wereszczak, A.A.

    1999-03-01

    Furnace designers and refractory engineers recognize that optimized furnace superstructure design and refractory selection are needed as glass production furnaces are continually striving toward greater output and efficiencies. Harsher operating conditions test refractories to the limit, while changing production technology (such as the conversion to oxy-fuel from traditional air-fuel firing) can alter the way the materials perform. Refractories for both oxy- and air-fuel fired furnace superstructures are subjected to high temperatures during service that may cause them to excessively creep or subside if the refractory material is not creep resistant, or if it is subjected to high stress, or both. Furnace designers can ensure that superstructure structural integrity is maintained if the creep behavior of the refractory material is well understood and well represented by appropriate engineering creep models. Several issues limit the abilities of furnace designers to (1) choose the optimum refractory for their applications, (2) optimize the engineering design, or (3) predict the service mechanical integrity of their furnace superstructures. Published engineering creep data are essentially non-existent for almost all commercially available refractories used for glass furnace superstructures. The limited data that do exist are supplied by the various refractory suppliers. Unfortunately, these suppliers generally have different ways of conducting their mechanical testing and they also interpret and report their data differently; this makes it hard for furnace designers to draw fair comparisons between competing grades of candidate refractories. Furthermore, the refractory supplier's data are often not available in a form that can be readily used for furnace design and for the prediction and design of long-term structural integrity of furnace superstructures. With the aim of providing such comparable data, the US DOE's Office of Industrial Technology and its Advanced

  13. Characterisation of the thermoluminescence (TL) properties of tailor-made Ge-doped silica glass fibre for applications in medical radiation therapy dosimetry

    NASA Astrophysics Data System (ADS)

    Zahaimi, N. A.; Zin, H.; Mahdiraji, G. A.; Rahman, A. L. Abdul; Bradley, D. A.; Rahman, A. T. Abdul

    2014-11-01

    We have investigated the characterisation of new fabricated material Ge doped silica glass thermoluminescence TL dosimeter (Photonic Research Centre, University of Malaya) for medical radiation dosimetry at therapy energy. Previously, the dosimeter has been studied to provide ideal dosimetry system, suitable to ensure an accurate delivery of radiation doses to tumour tissue while minimising the amount of radiation administrated to healthy tissue. Both energies of photon and electron were used in this experiment for a dose range of 1 to 5 Gy. The various sizes of core diameter Ge doped silica glass (120, 241, 362, 483 and 604 μm) were exposed by using linear accelerator at Pantai Medical Centre. For both energies, the optical fibres were found to produce a flat response to a fixed photon and electron doses to within 4% (S.D) of the mean of the TL distribution. In terms of dose response, the fibres provide linear response over the range investigated, from a fraction of 1-5 Gy. The finding shows 120 μm fibres have 1.82 greater dose response than 604 pm fibres irradiated at 6 MV photon with a fixed dose of 3 Gy. While for electron energy 12 MeV, the response shows 120 μm fibres have 1.58 greater dose response compared to 604 μm fibres. The good responses are suitable to make these tailor-made doped silica fibres a promising TL material for use as a dosimetric system in medical radiation therapy.

  14. Commercial and Experimental Glass Fibers

    NASA Astrophysics Data System (ADS)

    Wallenberger, Frederick T.

    Continuous glass fibers can be formed from melts with a wide range of compositions and viscosities. This chapter reviews pure silica fibers which are formed from highly viscous melts, silicate glass fibers with 50-70% SiO2 which are formed from moderately viscous melts, aluminate glass fibers with 50-80% Al2O3, as well as yttria-alumina-garnet (YAG) glass fibers which are formed from inviscid (literally non-viscous) melts. Commercial glass fibers are made for a variety of applications from pure silica rods and from silicate melts containing 50-70% SiO2 and 10-25% Al2O3. Boron-free, essentially boron-free, and borosilicate E-glass are general-purpose fibers. ERC-glass offers high corrosion resistance, HS-glass offers high-strength composites, D-glass offers a low dielectric constant, and A-glass offers the possibility of using waste container glass for less demanding applications.

  15. Comparative study of controlled pore glass, silica gel and poraver for the immobilization of urease to determine urea in a flow injection conductimetric biosensor system.

    PubMed

    Limbut, Warakorn; Thavarungkul, Panote; Kanatharana, Proespichaya; Asawatreratanakul, Punnee; Limsakul, Chusak; Wongkittisuksa, Booncharoen

    2004-03-15

    This study compared the responses of three enzyme reactors containing urease immobilized on three types of solid support, controlled pore glass (CPG), silica gel and Poraver. The evaluation of each enzyme reactor column was done in a flow injection conductimetric system. When urea in the sample solution passed though the enzyme reactor, urease catalysed the hydrolysis of urea into charged products. A lab-built conductivity meter was used to measure the increase in conductivity of the solution. The responses of the enzyme reactor column with urease immobilized on CPG and silica gel were similar and were much higher than that of Poraver. Both CPG and silica gel reactor columns gave the same limit of detection, 0.5 mM, and the response was still linear up to 150mM. The analysis time was 4-5 min per sample. The enzyme reactor column with urease immobilized on CPG gave a slightly better sensitivity, 4% higher than the reactor with silica gel. The life time of the immobilized urease on CPG and silica gel were more than 310h operation time (used intermittently over 7 months). Good agreement was obtained when urea concentrations of human serum samples determined by the flow injection conductimetric biosensor system was compared to the conventional methods (Fearon and Berthelot reactions). These were statistically shown using the regression line and Wilcoxon signed rank tests. The results showed that the reactor with urease immobilized on silica gel had the same efficiency as the reactor with urease immobilized on CPG. PMID:15128100

  16. High temperature thermographic measurements of laser heated silica

    SciTech Connect

    Elhadj, S; Yang, S T; Matthews, M J; Cooke, D J; Bude, J D; Johnson, M; Feit, M; Draggoo, V; Bisson, S E

    2009-11-02

    In situ spatial and temporal surface temperature profiles of CO{sub 2} laser-heated silica were obtained using a long wave infrared (LWIR) HgCdTe camera. Solutions to the linear diffusion equation with volumetric and surface heating are shown to describe the temperature evolution for a range of beam powers, over which the peak surface temperature scales linearly with power. These solutions were used with on-axis steady state and transient experimental temperatures to extract thermal diffusivity and conductivity for a variety of materials, including silica, spinel, sapphire, and lithium fluoride. Experimentally-derived thermal properties agreed well with reported values and, for silica, thermal conductivity and diffusivity are shown to be approximately independent of temperature between 300 and 2800K. While for silica our analysis based on a temperature independent thermal conductivity is shown to be accurate, for other materials studied this treatment yields effective thermal properties that represent reasonable approximations for laser heating. Implementation of a single-wavelength radiation measurement in the semi-transparent regime is generally discussed, and estimates of the apparent temperature deviation from the actual outer surface temperature are also presented. The experimental approach and the simple analysis presented yield surface temperature measurements that can be used to validate more complex physical models, help discriminate dominant heat transport mechanisms, and to predict temperature distribution and evolution during laser-based material processing.

  17. Diffusion between glass and metals for optical fiber preform extrusion

    NASA Astrophysics Data System (ADS)

    Yeo, Felicia Yan Xin; Zhang, Zhifeng; Kumar Chakkathara Janardhanan Nair, Dileep; Zhang, Yilei

    2015-07-01

    When silica is extruded, diffusion of metal atoms into silica results contamination to the silica being heated, and thus is a serious concern for the glass extrusion process, such as extrusion of glass fiber preform. This paper examines diffusion between fused silica and two high strength metals, the stainless steel SS410 and the superalloy Inconel 718, at 1000 °C and under the normal atmosphere condition by SEM and Electron Dispersion Spectrum. It is found that diffusion occurs between silica and SS410, and at the same time, SS410 is severely oxidized during diffusion experiment. On the contrary, the diffusion between Inconel 718 and silica is unnoticeable, suggesting excellent high temperature performance of Inconel 718 for glass extrusion.

  18. An Aqueous Thermodynamic Model for Polymerized Silica Species to High Ionic Strength

    SciTech Connect

    Felmy, Andrew R.; Cho, Herman M.; Rustad, James R.; Mason, Marvin J.

    2001-06-01

    The development of an aqueous thermodynamic model for polymerized silica species is presented which is valid to high ionic strengths and high dissolved silica concentration ({approx}0.1m) at low temperature (22-25 C). The model is based upon the equations of Pitzer and has been parameterized from solubility, electromotive force (emf), and nuclear magnetic resonance (NMR) data. The description of the silica speciation reactions at high dissolved silica and basic conditions (pH > 10) required the inclusion of monomeric, dimeric, trimeric (linear, cyclic and substituted), tetrameric (linear and cyclic) and hexameric (prismatic) species. The standard state equilibrium constants for the formation of these species, as well as the necessary Pitzer ion-interaction parameters to describe the ionic strength dependence of the formation reactions were determined.

  19. EFFECTS OF QUARTZ PARTICLE SIZE AND SUCROSE ADDITION ON MELTING BEHAVIOR OF A MELTER FEED FOR HIGH-LEVEL GLASS

    SciTech Connect

    MARCIAL J; KRUGER AA; HRMA PR; SCHWEIGER MJ; SWEARINGEN KJ; TEGROTENHUIS WE; HENAGER SH

    2010-07-28

    The behavior of melter feed (a mixture of nuclear waste and glass-forming additives) during waste-glass processing has a significant impact on the rate of the vitrification process. We studied the effects of silica particle size and sucrose addition on the volumetric expansion (foaming) of a high-alumina feed and the rate of dissolution of silica particles in feed samples heated at 5 C/min up to 1200 C. The initial size of quartz particles in feed ranged from 5 to 195 {micro}m. The fraction of the sucrose added ranged from 0 to 0.20 g per g glass. Extensive foaming occurred only in feeds with 5-{micro}m quartz particles; particles {ge}150 {micro}m formed clusters. Particles of 5 {micro}m completely dissolved by 900 C whereas particles {ge}150 {micro}m did not fully dissolve even when the temperature reached 1200 C. Sucrose addition had virtually zero impact on both foaming and the dissolution of silica particles. Over 100 sites in the United States are currently tasked with the storage of nuclear waste. The largest is the Hanford Site located in southeastern Washington State with 177 subterranean tanks containing over fifty-million gallons of nuclear waste from plutonium production from 1944 through 1987. This waste will be vitrified at the Hanford Tank Waste Treatment and Immobilization Plant. In the vitrification process, feed is charged into a melter and converted into glass to be ultimately stored in a permanent repository. The duration of waste-site cleanups by the vitrification process depends on the rate of melting, i.e., on the rate of the feed-to-glass conversion. Foaming associated with the melting process and the rate of dissolution of quartz particles (silica being the major glass-forming additive) are assumed to be important factors that influence the rate of melting. Previous studies on foaming of high-alumina feed demonstrated that varying the makeup of a melter feed has a significant impact on foaming. The volume of feeds that contained 5-{micro

  20. Thermal conductivity of Glycerol's liquid, glass, and crystal states, glass-liquid-glass transition, and crystallization at high pressures

    NASA Astrophysics Data System (ADS)

    Andersson, Ove; Johari, G. P.

    2016-02-01

    To investigate the effects of local density fluctuations on phonon propagation in a hydrogen bonded structure, we studied the thermal conductivity κ of the crystal, liquid, and glassy states of pure glycerol as a function of the temperature, T, and the pressure, p. We find that the following: (i) κcrystal is 3.6-times the κliquid value at 140 K at 0.1 MPa and 2.2-times at 290 K, and it varies with T according to 138 × T-0.95; (ii) the ratio κliquid (p)/κliquid (0.1 MPa) is 1.45 GPa-1 at 280 K, which, unexpectedly, is about the same as κcrystal (p)/κcrystal (0.1 MPa) of 1.42 GPa-1 at 298 K; (iii) κglass is relatively insensitive to T but sensitive to the applied p (1.38 GPa-1 at 150 K); (iv) κglass-T plots show an enhanced, pressure-dependent peak-like feature, which is due to the glass to liquid transition on heating; (v) continuous heating cold-crystallizes ultraviscous glycerol under pressure, at a higher T when p is high; and (vi) glycerol formed by cooling at a high p and then measured at a low p has a significantly higher κ than the glass formed by cooling at a low p. On heating at a fixed low p, its κ decreases before its glass-liquid transition range at that p is reached. We attribute this effect to thermally assisted loss of the configurational and vibrational instabilities of a glass formed at high p and recovered at low p, which is different from the usual glass-aging effect. While the heat capacity, entropy, and volume of glycerol crystal are less than those for its glass and liquid, κcrystal of glycerol, like its elastic modulus and refractive index, is higher. We discuss these findings in terms of the role of fluctuations in local density and structure, and the relations between κ and the thermodynamic quantities.

  1. Amorphous silica in ultra-high performance concrete: First hour of hydration

    SciTech Connect

    Oertel, Tina; Hutter, Frank; Helbig, Uta; Sextl, Gerhard

    2014-04-01

    Amorphous silica in the sub-micrometer size range is widely used to accelerate cement hydration. Investigations including properties of silica which differ from the specific surface area are rare. In this study, the reactivity of varying types of silica was evaluated based on their specific surface area, surface silanol group density, content of silanol groups and solubility in an alkaline suspension. Pyrogenic silica, silica fume and silica synthesized by hydrolysis and condensation of alkoxy silanes, so-called Stoeber particles, were employed. Influences of the silica within the first hour were further examined in pastes with water/cement ratios of 0.23 using in-situ X-ray diffraction, cryo scanning electron microscopy and pore solution analysis. It was shown that Stoeber particles change the composition of the pore solution. Na{sup +}, K{sup +}, Ca{sup 2+} and silicate ions seem to react to oligomers. The extent of this reaction might be highest for Stoeber particles due to their high reactivity.

  2. Mesoporous CLEAs-silica composite microparticles with high activity and enhanced stability

    PubMed Central

    Cui, Jiandong; Jia, Shiru; Liang, Longhao; Zhao, Yamin; Feng, Yuxiao

    2015-01-01

    A novel enzyme immobilization approach was used to generate mesoporous enzymes-silica composite microparticles by co-entrapping gelatinized starch and cross-linked phenylalanine ammonia lyase (PAL) aggregates (CLEAs) containing gelatinized starch into biomemitic silica and subsequently removing the starch by α-amylase treatment. During the preparation process, the gelatinzed starch served as a pore-forming agent to create pores in CLEAs and biomimetic silica. The resulting mesoporous CLEAs-silica composite microparticles exhibited higher activity and stability than native PAL, conventional CLEAs, and PAL encapsulated in biomimetic silica. Furthermore, the mesoporous CLEAs-silica composite microparticles displayed good reusability due to its suitable size and mechanical properties, and had excellent stability for storage. The superior catalytic performances were attributed to the combinational unique structure from the intra-cross-linking among enzyme aggregates and hard mesoporous silica shell, which not only decreased the enzyme-support negative interaction and mass-transfer limitations, but also improved the mechanical properties and monodispersity. This approach will be highly beneficial for preparing various bioactive mesoporous composites with excellent catalytic performance. PMID:26374188

  3. High-temperature testing of glass/ceramic matrix composites

    NASA Technical Reports Server (NTRS)

    Mandell, John F.; Grande, Dodd H.; Dannemann, Kathryn A.

    1989-01-01

    Recent advances in ceramic and other high-temperature composites have created a need for test methods that can be used at 1000 C and above. Present test methods usually require adhesively bonded tabs that cannot be used at high temperatures. This paper discusses some of the difficulties with high-temperature test development and describes several promising test methods. Stress-strain data are given for Nicalon ceramic fiber reinforced glass and glass-ceramic matrix composites tested in air at temperatures up to 1000 C.

  4. Bio-templated synthesis of highly ordered macro-mesoporous silica material for sustained drug delivery

    NASA Astrophysics Data System (ADS)

    Qu, Fengyu; Lin, Huiming; Wu, Xiang; Li, Xiaofeng; Qiu, Shilun; Zhu, Guangshan

    2010-05-01

    The bimodal porous structured silica materials consisting of macropores with the diameter of 5-20 μm and framework-like mesopores with the diameter of 4.7-6.0 nm were prepared using natural Manchurian ash and mango linin as macropored hard templates and P123 as mesopore soft templates, respectively. The macroporous structures of Manchurian ash and mango linin were replicated with the walls containing highly ordered mesoporous silica as well. As-synthesized dual porous silica was characterized by scanning electron microscope (SEM), powder X-ray diffraction (XRD), transmission electron microscope (TEM) and nitrogen adsorption/desorption, fourier transform IR (FTIR) spectroscopy, and thermo-gravimetric analyzer (TGA). Ibuprofen (Ibu) was employed as a model drug and the release profiles showed that the dual porous material had a sustained drug delivery capability. And such highly ordered dual pore silica materials may have potential applications for bimolecular adsorption/separation and tissue repairing.

  5. Glass-water interactions: Effect of high-valence cations on glass structure and chemical durability

    DOE PAGESBeta

    Pierce, Eric M.; Kerisit, Sebastien N.; Charpentier, Thibault; Angeli, Frederic; Icenhower, J. P.; McGrail, B. Pete; Charles F. Windisch; Burton, Sarah D.; Hopf, Juliane

    2016-02-27

    Spectroscopic measurements, dissolution experiments, and Monte Carlo simulations were performed to investigate the effect of high valence cations (HVC) on the mechanisms of glass dissolution under dilute and near-saturated conditions. Raman and NMR spectroscopy were used to determine the structural changes that occur in glass, specifically network formers (e.g., Al, Si, and B), with the addition of the HVC element hafnium in the Na2O Al2O3 B2O3 HfO2 SiO2 system (e.g., Na/(Al+B) = 1.0 and HfO2/SiO2 from 0.0 to 0.42). Spectroscopic measurements revealed that increasing hafnium content decreases N4 and increases the amount of Si–O–Hf moieties in the glass. Results frommore » flow through experiments conducted under dilute and near saturated conditions show a decrease of approximately 100 or more in the dissolution rate over the series from 0 to 20 mol% HfO2. Comparing the average steady-state rates obtained under dilute conditions to the rates obtained for near-saturated conditions reveal a divergence in the magnitude between the average steady state rates measured in these different conditions. The reason for this divergence was investigated more thoroughly using Monte Carlo simulations. Simulations indicate that the divergence in glass dissolution behavior under dilute and near-saturated conditions result from the formation of a low coordination Si sites when Si from the saturated solution adsorbs to Hf on the glass surface. The residence time of the newly formed low coordination Si sites is longer at the glass surface and increases the density of anchor sites from which altered layers with higher Si densities can form than in the absence of Hf. These results illustrate the importance of understanding solid water/solid-fluid interactions by linking macroscopic reaction kinetics to nanometer scale interfacial processes.« less

  6. Volcanic glass as a natural analog for borosilicate waste glass

    SciTech Connect

    Morgenstein, M.E.; Shettel, D.L.

    1994-12-31

    Obsidian and basaltic glass are opposite end-members of natural volcanic glass compositions. Syngenetic and diagenetic tensile failure in basaltic glass (low silica glass) is pervasive and provides abundant alteration fronts deep into the glass structure. Perlitic fracturing in obsidian (high silica glass) limits the alteration zones to an {open_quotes}onion skin{close_quotes} geometry. Borosilicate waste glass behaves similarly to the natural analog of basaltic glass (sideromelane). During geologic time, established and tensile fracture networks form glass cells (a three-dimensional reticulated pattern) where the production of new fracture surfaces increases through time by geometric progression. This suggests that borosilicate glass monoliths will eventually become rubble. Rates of reaction appear to double for every 12C{degrees} of temperature increase. Published leach rates suggest that the entire inventory of certain radionuclides may be released during the 10,000 year regulatory time period. Steam alteration prior to liquid attack combined with pervasive deep tensile failure behavior may suggest that the glass waste form is not license defensible without a metallic- and/or ceramic-type composite barrier as an overpack.

  7. Glass-water interaction: Effect of high-valence cations on glass structure and chemical durability

    NASA Astrophysics Data System (ADS)

    Hopf, J.; Kerisit, S. N.; Angeli, F.; Charpentier, T.; Icenhower, J. P.; McGrail, B. P.; Windisch, C. F.; Burton, S. D.; Pierce, E. M.

    2016-05-01

    Borosilicate glass is a durable solid, but it dissolves when in contact with aqueous fluids. The dissolution mechanism, which involves a variety of sequential reactions that occur at the solid-fluid interface, has important implications for the corrosion resistance of industrial and nuclear waste glasses. In this study, spectroscopic measurements, dissolution experiments, and Monte Carlo simulations were performed to investigate the effect of high-valence cations (HVC) on the mechanisms of glass dissolution under dilute and near-saturated conditions. Raman and NMR spectroscopy were used to determine the structural changes that occur in glass, specifically network formers (e.g., Al, Si, and B), with the addition of the HVC element hafnium in the Na2O-Al2O3-B2O3-HfO2-SiO2 system (e.g., Na/[Al + B] = 1.0 and HfO2/SiO2 from 0.0 to 0.42). Spectroscopic measurements revealed that increasing hafnium content decreases N4 (tetrahedral boron/total boron) and increases the amount of Si-O-Hf moieties in the glass. Results from flow-through experiments conducted under dilute and near-saturated conditions show a decrease of approximately 100× or more in the dissolution rate over the series from 0 to 20 mol% HfO2. Comparing the average steady-state rates obtained under dilute conditions to the rates obtained for near-saturated conditions reveals a divergence in the magnitude between the average steady state rates measured in these different conditions. The reason for this divergence was investigated more thoroughly using Monte Carlo simulations. Simulations indicate that the divergence in glass dissolution behavior under dilute and near-saturated conditions result from the stronger binding of Si sites that deposit on the surface from the influent when Hf is present in the glass. As a result, the residence time at the glass surface of these newly-formed Si sites is longer in the presence of Hf, which increases the density of anchor sites from which altered layers with higher Si

  8. Evaluation of Silica-based/Nickel and Borate-based/ Silver Glass Composites Seals for Solid Oxide Fuel Cells

    NASA Astrophysics Data System (ADS)

    Aguilar-Diaz, Yaneth

    The increasing demand for energy and the necessity to overcome the depletion of fossil fuel supplies requires that alternative energy sources be developed. Solid Oxide Fuel Cells (SOFCs) are one of the alternative technologies to minimise our dependence on fossil fuel due to their numerous advantages including high efficiency, long-term stability, fuel flexibility and low emissions. However, the development of reliable sealing techniques remains a crucial challenge to overcome to allow usable efficiency and facilitate commercialization. Sealing technology has been object of research for several years. Nevertheless, the optimal solution is yet to be found. The use of a glass composite approach is attractive as it allows the possibility of engineering the properties of the seal, by independently adjusting the particle size distribution and volume fraction of the additives. In the present work, the interaction between various SiO2 based glasses with nickel and B2O3 based glasses with silver were studied. Results as a function of additive particle size distribution (7-100 microns) and volume fraction (0-18%) will be presented. Micrographs, X-ray patterns and CTE measurements showed that the proposed systems have adequate characteristics for usage as seal for fuel cells due to the inertness of the additive particles with the respective glass matrix and predictable long-term chemical and thermal stability. The use of DTMA as a technique to calculate the onset of residual stresses, explores the influence of the additive and its interfacial interactions on the dissipation of energy during deformation. The multi-frequency test lead to an activation energy for stress relaxation between 400 and 600 kJ/mol depending on the different additive content. Furthermore, the temperature difference between de Tg and the onset of residual stresses was calculated showing that increments on the additive content results on a larger temperature range that allows stress relaxation. The

  9. Fluorinated epoxy resins with high glass transition temperatures

    NASA Technical Reports Server (NTRS)

    Griffith, James R.

    1991-01-01

    Easily processed liquid resins of low dielectric constants and high glass transition temperatures are useful for the manufacture of certain composite electronic boards. That combination of properties is difficult to acquire when dielectric constants are below 2.5, glass transition temperatures are above 200 C and processability is of conventional practicality. A recently issued patent (US 4,981,941 of 1 Jan. 1991) teaches practical materials and is the culmination of 23 years of research and effort and 15 patents owned by the Navy in the field of fluorinated resins of several classes. In addition to high fluorine content, practical utility was emphasized.

  10. High temperature glass thermal control structure and coating. [for application to spacecraft reusable heat shielding

    NASA Technical Reports Server (NTRS)

    Stewart, D. A.; Goldstein, H. E.; Leiser, D. B. (Inventor)

    1983-01-01

    A high temperature stable and solar radiation stable thermal control coating is described which is useful either as such, applied directly to a member to be protected, or applied as a coating on a re-usable surface insulation (RSI). It has a base coat layer and an overlay glass layer. The base coat layer has a high emittance, and the overlay layer is formed from discrete, but sintered together glass particles to give the overlay layer a high scattering coefficient. The resulting two-layer space and thermal control coating has an absorptivity-to-emissivity ratio of less than or equal to 0.4 at room temperature, with an emittance of 0.8 at 1200 F. It is capable of exposure to either solar radiation or temperatures as high as 2000 F without significant degradation. When used as a coating on a silica substrate to give an RSI structure, the coatings of this invention show significantly less reduction in emittance after long term convective heating and less residual strain than prior art coatings for RSI structures.

  11. Bifunctional hairy silica nanoparticles as high-performance additives for lubricant

    PubMed Central

    Sui, Tianyi; Song, Baoyu; Wen, Yu-ho; Zhang, Feng

    2016-01-01

    Bifunctional hairy silica nanoparticles (BHSNs), which are silica nanoparticles covered with alkyl and amino organic chains, were prepared as high-performance additives for lubricants. Compared with hairy silica nanoparticles covered by a single type of organic chain, binary hairy silica nanoparticles exhibit the advantages of both types of organic chains, which exhibit excellent compatibility with lubricants and adsorbability to metal surfaces. Nanoparticles with different ratios of amino and alkyl ligands were investigated. In comparison to an untreated lubricant, BHSNs reduce the friction coefficient and wear scar diameter by 40% and 60%, respectively. The wear mechanism of BHSNs was investigated, and the protective and filling effect of the nanoparticles improved because of collaboration of amino and alkyl ligands. PMID:26936117

  12. Bifunctional hairy silica nanoparticles as high-performance additives for lubricant.

    PubMed

    Sui, Tianyi; Song, Baoyu; Wen, Yu-Ho; Zhang, Feng

    2016-01-01

    Bifunctional hairy silica nanoparticles (BHSNs), which are silica nanoparticles covered with alkyl and amino organic chains, were prepared as high-performance additives for lubricants. Compared with hairy silica nanoparticles covered by a single type of organic chain, binary hairy silica nanoparticles exhibit the advantages of both types of organic chains, which exhibit excellent compatibility with lubricants and adsorbability to metal surfaces. Nanoparticles with different ratios of amino and alkyl ligands were investigated. In comparison to an untreated lubricant, BHSNs reduce the friction coefficient and wear scar diameter by 40% and 60%, respectively. The wear mechanism of BHSNs was investigated, and the protective and filling effect of the nanoparticles improved because of collaboration of amino and alkyl ligands. PMID:26936117

  13. Bifunctional hairy silica nanoparticles as high-performance additives for lubricant

    NASA Astrophysics Data System (ADS)

    Sui, Tianyi; Song, Baoyu; Wen, Yu-Ho; Zhang, Feng

    2016-03-01

    Bifunctional hairy silica nanoparticles (BHSNs), which are silica nanoparticles covered with alkyl and amino organic chains, were prepared as high-performance additives for lubricants. Compared with hairy silica nanoparticles covered by a single type of organic chain, binary hairy silica nanoparticles exhibit the advantages of both types of organic chains, which exhibit excellent compatibility with lubricants and adsorbability to metal surfaces. Nanoparticles with different ratios of amino and alkyl ligands were investigated. In comparison to an untreated lubricant, BHSNs reduce the friction coefficient and wear scar diameter by 40% and 60%, respectively. The wear mechanism of BHSNs was investigated, and the protective and filling effect of the nanoparticles improved because of collaboration of amino and alkyl ligands.

  14. Advanced High-Level Waste Glass Research and Development Plan

    SciTech Connect

    Peeler, David K.; Vienna, John D.; Schweiger, Michael J.; Fox, Kevin M.

    2015-07-01

    The U.S. Department of Energy Office of River Protection (ORP) has implemented an integrated program to increase the loading of Hanford tank wastes in glass while meeting melter lifetime expectancies and process, regulatory, and product quality requirements. The integrated ORP program is focused on providing a technical, science-based foundation from which key decisions can be made regarding the successful operation of the Hanford Tank Waste Treatment and Immobilization Plant (WTP) facilities. The fundamental data stemming from this program will support development of advanced glass formulations, key process control models, and tactical processing strategies to ensure safe and successful operations for both the low-activity waste (LAW) and high-level waste (HLW) vitrification facilities with an appreciation toward reducing overall mission life. The purpose of this advanced HLW glass research and development plan is to identify the near-, mid-, and longer-term research and development activities required to develop and validate advanced HLW glasses and their associated models to support facility operations at WTP, including both direct feed and full pretreatment flowsheets. This plan also integrates technical support of facility operations and waste qualification activities to show the interdependence of these activities with the advanced waste glass (AWG) program to support the full WTP mission. Figure ES-1 shows these key ORP programmatic activities and their interfaces with both WTP facility operations and qualification needs. The plan is a living document that will be updated to reflect key advancements and mission strategy changes. The research outlined here is motivated by the potential for substantial economic benefits (e.g., significant increases in waste throughput and reductions in glass volumes) that will be realized when advancements in glass formulation continue and models supporting facility operations are implemented. Developing and applying advanced

  15. 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.

  16. Glass formation and crystallization in high-temperature glass-ceramics and Si3N4

    NASA Astrophysics Data System (ADS)

    Drummond, Charles H., III

    1991-08-01

    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.

  17. Predicting Novel Bulk Metallic Glasses via High- Throughput Calculations

    NASA Astrophysics Data System (ADS)

    Perim, E.; Lee, D.; Liu, Y.; Toher, C.; Gong, P.; Li, Y.; Simmons, W. N.; Levy, O.; Vlassak, J.; Schroers, J.; Curtarolo, S.

    Bulk metallic glasses (BMGs) are materials which may combine key properties from crystalline metals, such as high hardness, with others typically presented by plastics, such as easy processability. However, the cost of the known BMGs poses a significant obstacle for the development of applications, which has lead to a long search for novel, economically viable, BMGs. The emergence of high-throughput DFT calculations, such as the library provided by the AFLOWLIB consortium, has provided new tools for materials discovery. We have used this data to develop a new glass forming descriptor combining structural factors with thermodynamics in order to quickly screen through a large number of alloy systems in the AFLOWLIB database, identifying the most promising systems and the optimal compositions for glass formation. National Science Foundation (DMR-1436151, DMR-1435820, DMR-1436268).

  18. Controllable formation of high density SERS-active silver nanoprism layers on hybrid silica-APTES coatings

    NASA Astrophysics Data System (ADS)

    Pilipavicius, J.; Kaleinikaite, R.; Pucetaite, M.; Velicka, M.; Kareiva, A.; Beganskiene, A.

    2016-07-01

    In this work sol-gel process for preparation of the uniform hybrid silica-3-aminopropyltriethoxysilane (APTES) coatings on glass surface is presented from mechanistic point of view. The suggested synthetic approach is straightforward, scalable and provides the means to tune the amount of amino groups on the surface simply by changing concentration of APTES in the initial sol. Deposition rate of different size silver nanoprisms (AgNPRs) on hybrid silica coatings of various amounts of APTES were studied and their performance as SERS materials were probed. The acquired data shows that the deposition rate of AgNPRs can be tuned by changing the amount of APTES. The optimal amount of APTES was found to be crucial for successful AgNPRs assembly and subsequent uniformity of the final SERS substrate-too high APTES content may result in rapid non-stable aggregation and non-uniform assembly process. SERS study revealed that SERS enhancement is the strongest at moderate AgNPRs aggregation level whereas it significantly drops at high aggregation levels.

  19. Highly evolved rhyolitic glass compositions from the Toba Caldera, Sumatra

    SciTech Connect

    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 of 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.

  20. Silica nephropathy.

    PubMed

    Ghahramani, N

    2010-07-01

    Occupational exposure to heavy metals, organic solvents and silica is associated with a variety of renal manifestations. Improved understanding of occupational renal disease provides insight into environmental renal disease, improving knowledge of disease pathogenesis. Silica (SiO2) is an abundant mineral found in sand, rock, and soil. Workers exposed to silica include sandblasters, miners, quarry workers, masons, ceramic workers and glass manufacturers. New cases of silicosis per year have been estimated in the US to be 3600-7300. Exposure to silica has been associated with tubulointerstitial disease, immune-mediated multisystem disease, chronic kidney disease and end-stage renal disease. A rare syndrome of painful, nodular skin lesions has been described in dialysis patients with excessive levels of silicon. Balkan endemic nephropathy is postulated to be due to chronic intoxication with drinking water polluted by silicates released during soil erosion. The mechanism of silica nephrotoxicity is thought to be through direct nephrotoxicity, as well as silica-induced autoimmune diseases such as scleroderma and systemic lupus erythematosus. The renal histopathology varies from focal to crescentic and necrotizing glomerulonephritis with aneurysm formation suggestive of polyarteritis nodosa. The treatment for silica nephrotoxicity is non-specific and depends on the mechanism and stage of the disease. It is quite clear that further research is needed, particularly to elucidate the pathogenesis of silica nephropathy. Considering the importance of diagnosing exposure-related renal disease at early stages, it is imperative to obtain a thorough occupational history in all patients with renal disease, with particular emphasis on exposure to silica, heavy metals, and solvents. PMID:23022796

  1. High performance of phosphonate-functionalized mesoporous silica for U(VI) sorption from aqueous solution.

    PubMed

    Yuan, Li-Yong; Liu, Ya-Lan; Shi, Wei-Qun; Lv, Yu-Long; Lan, Jian-Hui; Zhao, Yu-Liang; Chai, Zhi-Fang

    2011-07-28

    The renaissance of nuclear energy promotes increasing basic research on the separation and enrichment of nuclear fuel associated radionuclides. Herein, we report the first study for developing mesoporous silica functionalized with phosphonate (NP10) as a sorbent for U(VI) sorption from aqueous solution. The mesoporous silica was synthesized by co-condensation of diethylphosphatoethyltriethoxysilane (DPTS) and tetraethoxysilane (TEOS), using cationic surfactant cetyltrimethylammonium bromide (CTAB) as the template. The synthesized silica nanoparticles were observed to possess a mesoporous structure with a uniform pore diameter of 2.7 nm, and to have good stability and high efficiency for U(VI) sorption from aqueous solution. A maximum sorption capacity of 303 mg g(-1) and fast equilibrium time of 30 min were achieved under near neutral conditions at room temperature. The adsorbed U(VI) can be easily desorbed by using 0.1 mol L(-1) HNO(3), and the reclaimed mesoporous silica can be reused with no decrease of sorption capacity. In addition, the preconcentration of U(VI) from a 100 mL aqueous solution using the functionalized mesoporous silica was also studied. The preconcentration factor was found to be as high as 100, suggesting the vast opportunities of this kind of mesoporous silica for the solid-phase extraction and enrichment of U(VI). PMID:21681327

  2. Phenomenological study of the behavior of some silica formers in a high velocity jet fuel burner

    NASA Technical Reports Server (NTRS)

    Cawley, J. D.; Handschuh, R. F.

    1985-01-01

    Samples of four silica formers: single crystal SiC, sintered alpha-SiC, reaction sintered Si3N4 and polycrystalline MoSi2, were subjected to a Mach 1 jet fuel burner for 1 hr, at a sample temperature of 1375 deg C (2500 deg F). Two phenomena were identified which may be deleterious to a gas turbine application of these materials. The glass layer formed on the MoSi2 deformed appreciably under the aerodynamic load. A scale developed on the samples of the other materials which consisted of particular matter from the gas stream entrapped in a SiO2 matrix.

  3. HIGH-LEVEL WASTE GLASS FORMULATION MODEL SENSITIVITY STUDY 2009 GLASS FORMULATION MODEL VERSUS 1996 GLASS FORMULATION MODEL

    SciTech Connect

    BELSHER JD; MEINERT FL

    2009-12-07

    This document presents the differences between two HLW glass formulation models (GFM): The 1996 GFM and 2009 GFM. A glass formulation model is a collection of glass property correlations and associated limits, as well as model validity and solubility constraints; it uses the pretreated HLW feed composition to predict the amount and composition of glass forming additives necessary to produce acceptable HLW glass. The 2009 GFM presented in this report was constructed as a nonlinear optimization calculation based on updated glass property data and solubility limits described in PNNL-18501 (2009). Key mission drivers such as the total mass of HLW glass and waste oxide loading are compared between the two glass formulation models. In addition, a sensitivity study was performed within the 2009 GFM to determine the effect of relaxing various constraints on the predicted mass of the HLW glass.

  4. Speciation of Aqueous Silica at High pH Using Raman Spectroscopy

    NASA Astrophysics Data System (ADS)

    Hunt, J. D.; Kavner, A.; Schauble, E. A.; Doltsinis, N. L.; Manning, C. E.

    2008-12-01

    This study presents Raman spectra of silica solutions taken at ambient conditions with varying pH (11.4-14.2) and SiO2 concentrations (0.005-5.5 molal). These results are the foundation of a comprehensive set of hydrothermal diamond anvil cell experiments aimed at exploring the effects of temperature, pressure, and concentration on silica polymerization. Dissolved silica in basic aqueous solution plays an important role in the manufacture of detergents, adhesives, and the formation of zeolites. The nature of dissolved silica is also of central importance in understanding lithospheric fluid chemistry. At lower crustal to upper mantle temperatures and pressures, silica is one of the most soluble major rock-forming oxides, and will dominate the aqueous chemistry at these conditions, especially at conditions approaching the upper critical end point in the SiO2-H2O system. The concentration of dissolved silica will not be limited to the quartz saturation surface, however, and it would therefore be useful to understand what the independent effect of silica concentration is on polymerization. The pH of lithospheric fluids is not as high as in this study, but high pH solutions dissolve large amounts of silica, and thereby allow concentrated silica solutions to be studied at ambient conditions. The effect of pH on silica polymerization is therefore also important to characterize. We collected Raman spectra of silica solutions at ambient conditions with varying pH and silica concentrations, using first-principles calculations to interpret the spectra. Total silica concentration was varied from 0.1 to 5.5 molal while keeping the total K/Si ratio constant at three different K/Si ratios from 1 to 1.4. Raman spectra were also taken at a 1.6 K/Si ratio for silica concentrations ranging from 0.005 to 5.5 molal. The spectra show increasing polymerization with increasing silica concentration, and decreasing polymerization with increasing K/Si ratio. The polymer (475-650 cm-1) and

  5. High-Aluminum-Affinity Silica Is a Nanoparticle That Seeds Secondary Aluminosilicate Formation

    PubMed Central

    Jugdaohsingh, Ravin; Brown, Andy; Dietzel, Martin; Powell, Jonathan J.

    2013-01-01

    Despite the importance and abundance of aluminosilicates throughout our natural surroundings, their formation at neutral pH is, surprisingly, a matter of considerable debate. From our experiments in dilute aluminum and silica containing solutions (pH ~ 7) we previously identified a silica polymer with an extraordinarily high affinity for aluminium ions (high-aluminum-affinity silica polymer, HSP). Here, further characterization shows that HSP is a colloid of approximately 2.4 nm in diameter with a mean specific surface area of about 1,000 m2 g-1 and it competes effectively with transferrin for Al(III) binding. Aluminum binding to HSP strongly inhibited its decomposition whilst the reaction rate constant for the formation of the β-silicomolybdic acid complex indicated a diameter between 3.6 and 4.1 nm for these aluminum-containing nanoparticles. Similarly, high resolution microscopic analysis of the air dried aluminum-containing silica colloid solution revealed 3.9 ± 1.3 nm sized crystalline Al-rich silica nanoparticles (ASP) with an estimated Al:Si ratio of between 2 and 3 which is close to the range of secondary aluminosilicates such as imogolite. Thus the high-aluminum-affinity silica polymer is a nanoparticle that seeds early aluminosilicate formation through highly competitive binding of Al(III) ions. In niche environments, especially in vivo, this may serve as an alternative mechanism to polyhydroxy Al(III) species binding monomeric silica to form early phase, non-toxic aluminosilicates. PMID:24349573

  6. HIGH ALUMINUM HLW (HIGH LEVEL WASTE ) GLASSES FOR HANFORDS WTP (WASTE TREATMENT PROJECT)

    SciTech Connect

    KRUGER AA; BOWAN BW; JOSEPH I; GAN H; KOT WK; MATLACK KS; PEGG IL

    2010-01-04

    This paper presents the results of glass formulation development and melter testing to identify high waste loading glasses to treat high-Al high level waste (HLW) at Hanford. Previous glass formulations developed for this HLW had high waste loadings but their processing rates were lower that desired. The present work was aimed at improving the glass processing rate while maintaining high waste loadings. Glass formulations were designed, prepared at crucible-scale and characterized to determine their properties relevant to processing and product quality. Glass formulations that met these requirements were screened for melt rates using small-scale tests. The small-scale melt rate screening included vertical gradient furnace (VGF) and direct feed consumption (DFC) melter tests. Based on the results of these tests, modified glass formulations were developed and selected for larger scale melter tests to determine their processing rate. Melter tests were conducted on the DuraMelter 100 (DMIOO) with a melt surface area of 0.11 m{sup 2} and the DuraMelter 1200 (DMI200) HLW Pilot Melter with a melt surface area of 1.2 m{sup 2}. The newly developed glass formulations had waste loadings as high as 50 wt%, with corresponding Al{sub 2}O{sub 3} concentration in the glass of 26.63 wt%. The new glass formulations showed glass production rates as high as 1900 kg/(m{sup 2}.day) under nominal melter operating conditions. The demonstrated glass production rates are much higher than the current requirement of 800 kg/(m{sup 2}.day) and anticipated future enhanced Hanford Tank Waste Treatment and Immobilization Plant (WTP) requirement of 1000 kg/(m{sup 2}.day).

  7. Inverse melting in stressed fused silica

    NASA Astrophysics Data System (ADS)

    Bouchut, Philippe

    2012-12-01

    The emissive properties of proton implanted fused silica surfaces have been studied by laser beam annealing. When submitted to a high thermal step from a focused CO2 laser, an intense near infra-red thermoluminescence peak rises at a heating rate threshold. The in plane tensile stress relaxes and silica melts. We show that in the irreversible inverse melting of stressed fused silica, the protons exo-diffuse through internal modes coupling. The heat and mass transfer is one entropy flux whose dynamics are regulated by the mass transport. Inverse melting is the thermodynamic process that initiates the glass transition when heating.

  8. High Temperature Brillouin Scattering of Potassium Borate Glasses

    NASA Astrophysics Data System (ADS)

    Kawashima, Mitsuru; Matsuda, Yu; Aramomi, Syunsuke; Kojima, Seiji

    2010-07-01

    High temperature elastic properties of potassium borate glasses, xK2O·(100-x)B2O3 (x=4, 10, 14, 20, 28, and 34 mol %), have been investigated between 20 and 1100 °C by Brillouin scattering. Longitudinal sound velocity of the glasses changes only slightly up to the glass transition temperature (Tg), and, with further heating above Tg, it decreases markedly. This sudden decrease in sound velocity is caused by structural rearrangements that make glass networks soft above Tg. With an increase in K2O composition, the slope of sound velocity just above Tg increases. The composition dependence of the fragility of potassium borate glass is suggested on the basis of the slope. The activation energy of the relaxation process of 28K2O·72B2O3 measured by Brillouin scattering is estimated to be 6.84 kcal/mol, which is comparable to the energy of formation of a boroxol ring structure in a liquid phase.

  9. High Temperature Brillouin Scattering of Potassium Borate Glasses

    NASA Astrophysics Data System (ADS)

    Mitsuru Kawashima,; Yu Matsuda,; Syunsuke Aramomi,; Seiji Kojima,

    2010-07-01

    High temperature elastic properties of potassium borate glasses, xK2O\\cdot(100-x)B2O3 (x=4, 10, 14, 20, 28, and 34 mol %), have been investigated between 20 and 1100 °C by Brillouin scattering. Longitudinal sound velocity of the glasses changes only slightly up to the glass transition temperature (Tg), and, with further heating above Tg, it decreases markedly. This sudden decrease in sound velocity is caused by structural rearrangements that make glass networks soft above Tg. With an increase in K2O composition, the slope of sound velocity just above Tg increases. The composition dependence of the fragility of potassium borate glass is suggested on the basis of the slope. The activation energy of the relaxation process of 28K2O\\cdot72B2O3 measured by Brillouin scattering is estimated to be 6.84 kcal/mol, which is comparable to the energy of formation of a boroxol ring structure in a liquid phase.

  10. Non-toxic invert analog glass compositions of high modulus

    NASA Technical Reports Server (NTRS)

    Bacon, J. F. (Inventor)

    1974-01-01

    Glass compositions having a Young's modulus of at least 15 million psi are described. They and a specific modulus of at least 110 million inches consist essentially of, in mols, 15 to 40% SiO2, 6 to 15% Li2O, 24 to 45% of at least two bivalent oxides selected from the group consisting of Ca, NzO, MgO and CuO; 13 to 39% of at least two trivalent oxides selected from the group consisting of Al2O3, Fe2O3, B2O3, La2O3, and Y2O3 and up to 15% of one or more tetravelent oxides selected from the group consisting of ZrO2, TiO2 and CeO2. The high modulus, low density glass compositions contain no toxic elements. The composition, glass density, Young's modulus, and specific modulus for 28 representative glasses are presented. The fiber modulus of five glasses are given.

  11. One-pot synthesis of silica-coated copper nanoparticles with high chemical and thermal stability.

    PubMed

    Shiomi, Shohei; Kawamori, Makoto; Yagi, Shunsuke; Matsubara, Eiichiro

    2015-12-15

    With the recent development of nanotechnology, enhancement of the stability of nanomaterials is becoming ever more important for their practical applications. We studied the silica-coating of Cu nanoparticles and the enhanced stability of silica-coated Cu nanoparticles to oxidation. The metallic nanoparticles are easily oxidized and agglomerated compared with the bulk metals because the nanoparticles possess large specific surfaces. The Cu nanoparticle is one of the most difficult nanoparticles to be handled due to its absence of the oxidation stability. In the synthesis of silica-coated Cu nanoparticles via a sol-gel process using tetraethyl orthosilicate, the addition of NH3 as a catalyst of sol-gel reaction yielded homogeneous silica-coating. However, a large amount of Cu nanoparticles is instantly dissolved by forming complex ions in a NH3 solution during and before the silica-coating process. This is the difficulty in the silica-coating of Cu nanoparticles. In the present work, the dissolution behavior of Cu nanoparticles was electrochemically examined. This electrochemistry-based optimization of reducing power of a reaction bath enabled us to synthesize the silica-coated Cu nanoparticle via a consecutive liquid-phase reaction which requires only basic equipment and involves no separate centrifuging or extraction step. Cu nanoparticles coated by silica shells had the remarkable stability even in the presence of a strong oxidizing agent. Furthermore, we demonstrated that the highly stable Cu nanoparticles can be applied to a red pigment using a unique red color of Cu nanoparticles because of its surface plasmon resonance. PMID:26313712

  12. Optothermal nonlinearity of silica aerogel

    NASA Astrophysics Data System (ADS)

    Braidotti, Maria Chiara; Gentilini, Silvia; Fleming, Adam; Samuels, Michiel C.; Di Falco, Andrea; Conti, Claudio

    2016-07-01

    We report on the characterization of silica aerogel thermal optical nonlinearity, obtained by z-scan technique. The results show that typical silica aerogels have nonlinear optical coefficient similar to that of glass (≃10-12 m2/W), with negligible optical nonlinear absorption. The nonlinear coefficient can be increased to values in the range of 10-10 m2/W by embedding an absorbing dye in the aerogel. This value is one order of magnitude higher than that observed in the pure dye and in typical highly nonlinear materials like liquid crystals.

  13. Pure-silica optical waveguides, fiber couplers, and high-aspect ratio submicrometer channels for electrokinetic separation devices.

    PubMed

    Mogensen, Klaus B; Eriksson, Fredrik; Gustafsson, Omar; Nikolajsen, Rikke P H; Kutter, Jörg P

    2004-11-01

    A new fabrication procedure for integration of ultraviolet transparent pure-silica planar waveguides, fiber couplers and high-aspect ratio submicrometer channels is presented. Only a single photolithographic mask step is required. The channels are 80-90 microm deep and the width can be reduced to about 0.5 microm, corresponding to a height-to-width ratio of more than 150. The core of the waveguides consists of pure silicon dioxide, which is favorable over doped silica, due to the absence of absorption centers associated with the dopants. This furthermore improves the long-term stability of the waveguides, because of an increased radiation resistance of the glass. The propagation loss decreases from 1.0 dB/cm at 200 nm to 0.2 dB/cm at 800 nm, which, to our knowledge, is the lowest propagation loss reported for integrated planar waveguides in the ultraviolet wavelength region to date. The effective optical path length is 1.2 mm for an absorbance cell with a nominal length of 1.0 mm, indicating effective suppression of stray light. The limit of detection for paracetamol when present in the entire channel network was determined to 3 microg/mL. Finally, the applicability of the fabricated devices for capillary electrophoresis was evaluated by separation of caffein, paracetamol and ketoprofone using absorbance detection at 254 nm. PMID:15565688

  14. Development of Crystal-Tolerant High-Level Waste Glasses

    SciTech Connect

    Matyas, Josef; Vienna, John D.; Schaible, Micah J.; Rodriguez, Carmen P.; Crum, Jarrod V.; Arrigoni, Alyssa L.; Tate, Rachel M.

    2010-12-17

    Twenty five glasses were formulated. They were batched from HLW AZ-101 simulant or raw chemicals and melted and tested with a series of tests to elucidate the effect of spinel-forming components (Ni, Fe, Cr, Mn, and Zn), Al, and noble metals (Rh2O3 and RuO2) on the accumulation rate of spinel crystals in the glass discharge riser of the high-level waste (HLW) melter. In addition, the processing properties of glasses, such as the viscosity and TL, were measured as a function of temperature and composition. Furthermore, the settling of spinel crystals in transparent low-viscosity fluids was studied at room temperature to access the shape factor and hindered settling coefficient of spinel crystals in the Stokes equation. The experimental results suggest that Ni is the most troublesome component of all the studied spinel-forming components producing settling layers of up to 10.5 mm in just 20 days in Ni-rich glasses if noble metals or a higher concentration of Fe was not introduced in the glass. The layer of this thickness can potentially plug the bottom of the riser, preventing glass from being discharged from the melter. The noble metals, Fe, and Al were the components that significantly slowed down or stopped the accumulation of spinel at the bottom. Particles of Rh2O3 and RuO2, hematite and nepheline, acted as nucleation sites significantly increasing the number of crystals and therefore decreasing the average crystal size. The settling rate of ≤10-μm crystal size around the settling velocity of crystals was too low to produce thick layers. The experimental data for the thickness of settled layers in the glasses prepared from AZ-101 simulant were used to build a linear empirical model that can predict crystal accumulation in the riser of the melter as a function of concentration of spinel-forming components in glass. The developed model predicts the thicknesses of accumulated layers quite well, R2 = 0.985, and can be become an efficient tool for the formulation

  15. High temperature crystalline superconductors from crystallized glasses

    DOEpatents

    Shi, Donglu

    1992-01-01

    A method of preparing a high temperature superconductor from an amorphous phase. The method involves preparing a starting material of a composition of Bi.sub.2 Sr.sub.2 Ca.sub.3 Cu.sub.4 Ox or Bi.sub.2 Sr.sub.2 Ca.sub.4 Cu.sub.5 Ox, forming an amorphous phase of the composition and heat treating the amorphous phase for particular time and temperature ranges to achieve a single phase high temperature superconductor.

  16. Physicochemical and Biological Zonation of High Temperature Silica and Arsenic-Rich Streams at El Tatio Geyser Field, Chile

    NASA Astrophysics Data System (ADS)

    Myers, K. D.; Engel, A. S.; Omelon, C. R.; Bennett, P.

    2012-12-01

    El Tatio Geyser Field is a geothermal complex comprised of three main basins in the northern Atacama Desert (Region II), Chile. Located at 4400 m elevation in the Andes Mountains it experiences intense solar radiation and a UV flux 33% higher than at Yellowstone National Park (Wyoming). Local boiling point is 86°C, and geothermal waters are Na-Ca-Cl type with circumneutral pH, high dissolved silica, and high dissolved arsenic concentrations (30-50 ppm). Most thermal features contain scant dissolved inorganic carbon (DIC as CO2(aq) + HCO3- + CO3-2). There is a conspicuous lack of microbial mat development in temperature zones where thick mats are seen at other geothermal sites. This investigation focused on understanding the physicochemical controls on microbial diversity that lead to microbial mat colonization and development within specific thermal regions of the geothermal features. Temperature surveys were done at three geothermal features where microbial mats and water chemistry were sampled, and a high-resolution thermal survey was conducted at one geyser orifice through the discharge channel where chemistry and mineralogy have been characterized, and microbial diversity was evaluated from 16S rRNA gene sequences. At the main study geyser, the stream is 0.25 m wide near its source, and for the first 20 m, the discharge stream is constrained by a solid silica bank with a mineralized channel bottom and no obvious microbial mat development. Temperatures decrease from ~86°C to ~67°C. In this zone sparse filaments were observed on rare sediments below the water surface consisting of ~80% Thermus spp. with rare uncultured Chloroflexus spp. and Candidate Division OP1 sequences. At 12 m, visible red-orange mat development starts on the sides of the channel where bulk water temperature is 67°C. Photosynthetic Chloroflexus spp. dominate red-orange filaments that form the first conspicuous mats (between 43-88% of the 16S rRNA sequences from different samples), with

  17. Crystallization kinetics of a lithia-silica glass - Effect of sample characteristics and thermal analysis measurement techniques

    NASA Technical Reports Server (NTRS)

    Ray, Chandra S.; Huang, Wenhai; Day, Delbert E.

    1991-01-01

    DTA and both isothermal and nonisothermal DSC techniques are presently used to investigate the crystallization kinetics of a 40 (mol) percent Li2O-60 percent SiO2 glass as a function of glass powder particle size, the use of either alumina or Pt as the crucible material, the use of N, O, or Ar atmospheres, and surface pretreatments of the glass powder with deionized water, HCl, or HF. Neither the furnace atmosphere nor the crucible material had a significant effect on activation energy, frequency factor, or Avrami exponent. Washings of the glass with the three different fluids decreased the crystallization temperature by 25 to 30 C.

  18. High-temperature photoluminescence in sol-gel silica containing SiC/C nanostructures

    NASA Astrophysics Data System (ADS)

    Li, Guangming; Burggraf, Larry W.; Shoemaker, James R.; Eastwood, DeLyle; Stiegman, Albert E.

    2000-06-01

    Silicon carbide and carbon nanostructures were produced by pyrolysis of organosilane or aromatic compounds in nanoporous sol-gel silica glasses. Intense photoluminescence was observed in the visible and the near infrared regions, depending on material processing. Emission bands at 2.97, 2.67, 2.53, 2.41, 2.24, 2.09, 1.93, 1.13, 1.00, and 0.85 eV were observed in samples prepared at temperatures between 870 and 1220 K. Phosphorescence emission showed two lifetime components at 300 K: a 0.03 s component and a very long component of 0.5-4 s that depends on the precursors and sample processing. These lifetimes approximately doubled at 77 K. The visible emission increased significantly as the temperature was elevated from 77 to 950 K, suggesting thermally assisted light emission from sites in the silica glasses containing SiC/C nanostructures. Surface SiC vacancy defects modeled using integrated ab initio quantum mechanics/molecular mechanics calculations suggest phosphorescence may originate from C vacancy (Si-Si dimers) in the visible and Si vacancy in the near infrared.

  19. Highly hydrothermally stable microporous silica membranes for hydrogen separation.

    PubMed

    Wei, Qi; Wang, Fei; Nie, Zuo-Ren; Song, Chun-Lin; Wang, Yan-Li; Li, Qun-Yan

    2008-08-01

    Fluorocarbon-modified silica membranes were deposited on gamma-Al2O3/alpha-Al2O3 supports by the sol-gel technique for hydrogen separation. The hydrophobic property, pore structure, gas transport and separation performance, and hydrothermal stability of the modified membranes were investigated. It is observed that the water contact angle increases from 27.2+/-1.5 degrees for the pure silica membranes to 115.0+/-1.2 degrees for the modified ones with a (trifluoropropyl)triethoxysilane (TFPTES)/tetraethyl orthosilicate (TEOS) molar ratio of 0.6. The modified membranes preserve a microporous structure with a micropore volume of 0.14 cm3/g and a pore size of approximately 0.5 nm. A single gas permeation of H2 and CO2 through the modified membranes presents small positive apparent thermal activation energies, indicating a dominant microporous membrane transport. At 200 degrees C, a single H2 permeance of 3.1x10(-6) mol m(-2) s(-1) Pa(-1) and a H2/CO2 permselectivity of 15.2 were obtained after proper correction for the support resistance and the contribution from the defects. In the gas mixture measurement, the H2 permeance and the H2/CO2 separation factor almost remain constant at 200 degrees C with a water vapor pressure of 1.2x10(4) Pa for at least 220 h, indicating that the modified membranes are hydrothermally stable, benefiting from the integrity of the microporous structure due to the fluorocarbon modification. PMID:18613718

  20. Glass ceramics for sealing to high-thermal-expansion metals

    SciTech Connect

    Wilder, Jr., J. A.

    1980-10-01

    Glass ceramics were studied, formulated in the Na/sub 2/O CaO.P/sub 2/O/sub 5/, Na/sub 2/O.BaOP/sub 2/O/sub 5/, Na/sub 2/O.Al/sub 2/O/sub 3/.P/sub 2/O/sub 5/, and Li/sub 2/O.BaO.P/sub 2/O/sub 5/ systems to establish their suitability for sealing to high thermal expansion metals, e.g. aluminum, copper, and 300 series stainless steels. Glass ceramics in Na/sub 2/O.CaO.P/sub 2/O/sub 5/ and Na/sub 2/O.BaO.P/sub 2/O/sub 5/ systems have coefficients of thermal expansion in the range 140 x 10/sup -1/ per /sup 0/C less than or equal to ..cap alpha.. less than or equal to 225 x 10/sup -7/ per /sup 0/C and fracture toughness values generally greater than those of phosphate glasses; they are suitable for fabricating seals to high thermal expansion metals. Crystal phases include NaPo/sub 3/, (NaPO/sub 3/)/sub 3/, NaBa(PO/sub 3/)/sub 3/, and NaCa(PO/sub 3/)/sub 3/. Glass ceramics formed in the Na/sub 2/O.Al/sub 2/O/sub 3/.P/sub 2/O/sub 5/ systems have coefficients of thermal expansion greater than 240 x 10/sup -7/ per /sup 0/C, but they have extensive microcracking. Due to their low thermal expansion values (..cap alpha.. less than or equal to 120 x 10/sup -7/ per /sup 0/C), glass ceramics in the Li/sub 2/O.BaO.P/sub 2/O/sub 5/ system are unsuitable for sealing to high thermal expansion metals.

  1. Volumetric properties of magnesium silicate glasses and supercooled liquid at high pressure by X-ray microtomography

    NASA Astrophysics Data System (ADS)

    Lesher, Charles E.; Wang, Yanbin; Gaudio, Sarah; Clark, Alisha; Nishiyama, Nori; Rivers, Mark

    2009-05-01

    The volumetric properties of silicate glasses and supercooled liquid are examined at high pressures and temperatures using X-ray computed tomography (CT) and absorption. The high pressure X-ray microtomography (HPXMT) system at the Advanced Photon Source, Argonne National Laboratory (GeoSoilEnvironCARS 13-BM-D beamline) consists of two opposing anvils compressed within an X-ray-transparent containment ring supported by thrust bearings and loaded using a 250-ton hydraulic press. This system permits the pressure cell to rotate under the load, while collecting radiographs through at least 180° of rotation. The 13-BM-D beamline permits convenient switching between monochromatic radiation required for radiography and polychromatic radiation for pressure determination by energy dispersive diffraction. We report initial results on several refractory magnesium silicate glasses synthesized by levitation laser heating. Volume changes during room temperature compression of Mg-silicate glasses with 33 mol% and 38 mol% SiO 2 up to 11.5 GPa give an isothermal bulk moduli of 93-100 GPa for a K' of 1. These values are consistent with ultrasonic measurements of more silica-rich glasses. The volumetric properties of amorphous MgSiO 3 at 2 GPa were examined during annealing up to 1000 °C. We consider the consequences of heating through the glass transition and the implications for thermal expansivity of supercooled liquids at high pressure. Our results illustrate the capabilities of HPXMT for studies of refractory glasses and liquids at high pressure and offer strategies for future studies of liquid densities within the melting interval for magmas in planet interiors.

  2. Volumetric properties of magnesium silicate glasses and supercooled liquid at high pressure by X-ray microtomography

    SciTech Connect

    Lesher, Charles E.; Wang, Yanbin; Gaudio, Sarah; Clark, Alisha; Nishiyama, Nori; Rivers, Mark

    2009-06-01

    The volumetric properties of silicate glasses and supercooled liquid are examined at high pressures and temperatures using X-ray computed tomography (CT) and absorption. The high pressure X-ray microtomography (HPXMT) system at the Advanced Photon Source, Argonne National Laboratory (GeoSoilEnvironCARS 13-BM-D beamline) consists of two opposing anvils compressed within an X-ray-transparent containment ring supported by thrust bearings and loaded using a 250-ton hydraulic press. This system permits the pressure cell to rotate under the load, while collecting radiographs through at least 180{sup o} of rotation. The 13-BM-D beamline permits convenient switching between monochromatic radiation required for radiography and polychromatic radiation for pressure determination by energy dispersive diffraction. We report initial results on several refractory magnesium silicate glasses synthesized by levitation laser heating. Volume changes during room temperature compression of Mg-silicate glasses with 33 mol% and 38 mol% SiO2 up to 11.5 GPa give an isothermal bulk moduli of 93--100 GPa for a K' of 1. These values are consistent with ultrasonic measurements of more silica-rich glasses. The volumetric properties of amorphous MgSiO{sub 3} at 2 GPa were examined during annealing up to 1000 C. We consider the consequences of heating through the glass transition and the implications for thermal expansivity of supercooled liquids at high pressure. Our results illustrate the capabilities of HPXMT for studies of refractory glasses and liquids at high pressure and offer strategies for future studies of liquid densities within the melting interval for magmas in planet interiors.

  3. Vital roles of nano silica in synthetic based mud for high temperature drilling operation

    NASA Astrophysics Data System (ADS)

    Yusof, Muhammad Aslam Md; Hanafi, Nor Hazimastura

    2015-07-01

    At high temperature drilling, chemicals degradation occurs which reduce the effectiveness of the drilling fluid. There is a potential that by using nano sized particles which have thermal stability up to 2500°F to be used as a stabilizer to withstand the harsh condition. Therefore, this project aims to identify the performance of synthetic-based mud (SBM) with nano silica for high temperature drilling operation. A conventional SBM performance has been compared with additional percentages of nano silica. 20% and 40% of nano silica out of fluid loss weight has been added into the SBM and analyzed the rheological properties and other drilling fluid properties. The conventional SBM formulation has lost some amount of weighting material or solids in the mud and has been replaced by lighter and smaller size of nanoparticles. It has reduced the rheological properties of the mud but the gelation formed by nano silica material has given higher gel strength. Also, nano silica potentially plugs the porous media, resulted in lower filtration loss measurement and thinner mud cake ranged 20% to 50% respectively.

  4. Highly dense, optically inactive silica microbeads for the isolation and identification of circulating tumor cells.

    PubMed

    Yoo, Chang Eun; Moon, Hui-Sung; Kim, Yeon Jeong; Park, Jong-Myeon; Park, Donghyun; Han, Kyung-Yeon; Park, Keunchil; Sun, Jong-Mu; Park, Woong-Yang

    2016-01-01

    Efficient isolation of circulating tumor cells (CTCs) from whole blood is a major challenge for the clinical application of CTCs. Here, we report an efficient method to isolate CTCs from whole blood using highly dense and transparent silica microbeads. The surfaces of silica microbeads were fully covered with an antibody to capture CTCs, and blocked by zwitterionic moieties to prevent the non-specific adsorption of blood cells. Owing to the high density of the silica microbeads, the complexation of CTCs with silica microbeads resulted in the efficient sedimentation of CTC-microbead complexes, which enabled their discrimination from other blood cells in density gradient media. Model CTCs (MCF-7, HCC827, and SHP-77) with various levels of epithelial cell adhesion molecule (EpCAM) were isolated efficiently, especially those with low EpCAM expression (SHP-77). Moreover, the transparency of silica microbeads enabled CTCs to be clearly identified without interference caused by microbeads. The improved sensitivity resulted in increased CTC recovery from patient samples compared with the FDA-approved CellSearch system (14/15 using our method; 5/15 using the CellSearch system). These results indicate that the isolation method described in this report constitutes a powerful tool for the isolation of CTCs from whole blood, which has important applications in clinical practice. PMID:26513419

  5. Highly Efficient Elimination of Carbon Monoxide with Binary Copper-Manganese Oxide Contained Ordered Nanoporous Silicas

    NASA Astrophysics Data System (ADS)

    Lee, Jiho; Kim, Hwayoun; Lee, Hyesun; Jang, Seojun; Chang, Jeong Ho

    2016-01-01

    Ordered nanoporous silicas containing various binary copper-manganese oxides were prepared as catalytic systems for effective carbon monoxide elimination. The carbon monoxide elimination efficiency was demonstrated as a function of the [Mn]/[Cu] ratio and reaction time. The prepared catalysts were characterized by Brunauer-Emmett-Teller (BET) method, small- and wide-angle X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HR-TEM) for structural analysis. Moreover, quantitative analysis of the binary metal oxides within the nanoporous silica was achieved by inductively coupled plasma (ICP). The binary metal oxide-loaded nanoporous silica showed high room temperature catalytic efficiency with over 98 % elimination of carbon monoxide at higher concentration ratio of [Mn]/[Cu].

  6. Highly Efficient Elimination of Carbon Monoxide with Binary Copper-Manganese Oxide Contained Ordered Nanoporous Silicas.

    PubMed

    Lee, Jiho; Kim, Hwayoun; Lee, Hyesun; Jang, Seojun; Chang, Jeong Ho

    2016-12-01

    Ordered nanoporous silicas containing various binary copper-manganese oxides were prepared as catalytic systems for effective carbon monoxide elimination. The carbon monoxide elimination efficiency was demonstrated as a function of the [Mn]/[Cu] ratio and reaction time. The prepared catalysts were characterized by Brunauer-Emmett-Teller (BET) method, small- and wide-angle X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HR-TEM) for structural analysis. Moreover, quantitative analysis of the binary metal oxides within the nanoporous silica was achieved by inductively coupled plasma (ICP). The binary metal oxide-loaded nanoporous silica showed high room temperature catalytic efficiency with over 98 % elimination of carbon monoxide at higher concentration ratio of [Mn]/[Cu]. PMID:26744146

  7. Mimicking high-silica zeolites: highly stable germanium- and tin-rich zeolite-type chalcogenides.

    PubMed

    Lin, Qipu; Bu, Xianhui; Mao, Chengyu; Zhao, Xiang; Sasan, Koroush; Feng, Pingyun

    2015-05-20

    High-silica zeolites, as exemplified by ZSM-5, with excellent chemical and thermal stability, have generated a revolution in industrial catalysis. In contrast, prior to this work, high-silica-zeolite-like chalcogenides based on germanium/tin remained unknown, even after decades of research. Here six crystalline high-germanium or high-tin zeolite-type sulfides and selenides with four different topologies are reported. Their unprecedented framework compositions give these materials much improved thermal and chemical stability with high surface area (Langmuir surface area of 782 m(2)/g(-1)) comparable to or better than zeolites. Among them, highly stable CPM-120-ZnGeS allows for ion exchange with diverse metal or complex cations, resulting in fine-tuning in porosity, fast ion conductivity, and photoelectric response. Being among the most porous crystalline chalcogenides, CPM-120-ZnGeS (exchanged with Cs(+) ions) also shows reversible adsorption with high capacity and affinity for CO2 (98 and 73 cm(3) g(-1) at 273 and 298 K, respectively, isosteric heat of adsorption = 40.05 kJ mol(-1)). Moreover, CPM-120-ZnGeS could also function as a robust photocatalyst for water reduction to generate H2. The overall activity of H2 production from water, in the presence of Na2S-Na2SO3 as a hole scavenger, was 200 μmol h(-1)/(0.10 g). Such catalytic activity remained undiminished under illumination by UV light for as long as measured (200 h), demonstrating excellent resistance to photocorrosion even under intense UV radiation. PMID:25950820

  8. Fabrication and characterization of strontium incorporated 3-D bioactive glass scaffolds for bone tissue from biosilica.

    PubMed

    Özarslan, Ali Can; Yücel, Sevil

    2016-11-01

    Bioactive glass scaffolds that contain silica are high viable biomaterials as bone supporters for bone tissue engineering due to their bioactive behaviour in simulated body fluid (SBF). In the human body, these materials help inorganic bone structure formation due to a combination of the particular ratio of elements such as silicon (Si), calcium (Ca), sodium (Na) and phosphorus (P), and the doping of strontium (Sr) into the scaffold structure increases their bioactive behaviour. In this study, bioactive glass scaffolds were produced by using rice hull ash (RHA) silica and commercial silica based bioactive glasses. The structural properties of scaffolds such as pore size, porosity and also the bioactive behaviour were investigated. The results showed that undoped and Sr-doped RHA silica-based bioactive glass scaffolds have better bioactivity than that of commercial silica based bioactive glass scaffolds. Moreover, undoped and Sr-doped RHA silica-based bioactive glass scaffolds will be able to be used instead of undoped and Sr-doped commercial silica based bioactive glass scaffolds for bone regeneration applications. Scaffolds that are produced from undoped or Sr-doped RHA silica have high potential to form new bone for bone defects in tissue engineering. PMID:27524030

  9. Triconstituent co-assembly to ordered mesostructured polymer-silica and carbon-silica nanocomposites and large-pore mesoporous carbons with high surface areas.

    PubMed

    Liu, Ruili; Shi, Yifeng; Wan, Ying; Meng, Yan; Zhang, Fuqiang; Gu, Dong; Chen, Zhenxia; Tu, Bo; Zhao, Dongyuan

    2006-09-01

    Highly ordered mesoporous polymer-silica and carbon-silica nanocomposites with interpenetrating networks have been successfully synthesized by the evaporation-induced triconstituent co-assembly method, wherein soluble resol polymer is used as an organic precursor, prehydrolyzed TEOS is used as an inorganic precursor, and triblock copolymer F127 is used as a template. It is proposed for the first time that ordered mesoporous nanocomposites have "reinforced concrete"-structured frameworks. By adjusting the initial mass ratios of TEOS to resol, we determined the obtained nanocomposites possess continuous composition with the ratios ranging from zero to infinity for the two constituents that are "homogeneously" dispersed inside the pore walls. The presence of silicates in nanocomposites dramatically inhibits framework shrinkage during the calcination, resulting in highly ordered large-pore mesoporous carbon-silica nanocomposites. Combustion in air or etching in HF solution can remove carbon or silica from the carbon-silica nanocomposites and yield ordered mesoporous pure silica or carbon frameworks. The process generates plenty of small pores in carbon or/and silica pore walls. Ordered mesoporous carbons can then be obtained with large pore sizes of approximately 6.7 nm, pore volumes of approximately 2.0 cm(3)/g, and high surface areas of approximately 2470 m(2)/g. The pore structures and textures can be controlled by varying the sizes and polymerization degrees of two constituent precursors. Accordingly, by simply tuning the aging time of TEOS, ordered mesoporous carbons with evident bimodal pores at 2.6 and 5.8 nm can be synthesized. PMID:16939291

  10. Solidification of Acidic, High Nitrate Nuclear Wastes by Grouting or Absorption on Silica Gel

    SciTech Connect

    A. K. Herbst; S. V. Raman; R. J. Kirkham

    2004-01-01

    The use of grout and silica gel were explored for the solidification of four types of acidic, high nitrate radioactive wastes. Two methods of grouting were tested: direct grouting and pre-neutralization. Two methods of absorption on silica gel were also tested: direct absorption and rotary spray drying. The waste simulant acidity varied between 1 N and 12 N. The waste simulant was neutralized by pre-blending calcium hydroxide with Portland cement and blast furnace slag powders prior to mixing with the simulant for grout solidification. Liquid sodium hydroxide was used to partially neutralize the simulant to a pH above 2 and then it was absorbed for silica gel solidification. Formulations for each of these methods are presented along with waste form characteristics and properties. Compositional variation maps for grout formulations are presented which help determine the optimum "recipe" for a particular waste stream. These maps provide a method to determine the proportions of waste, calcium hydroxide, Portland cement, and blast furnace slag that provide a waste form that meets the disposal acceptance criteria. The maps guide researchers in selecting areas to study and provide an operational envelop that produces acceptable waste forms. The grouts both solidify and stabilize the wastes, while absorption on silica gel produces a solid waste that will not pass standard leaching procedures (TCLP) if required. Silica gel wastes can be made to pass most leach tests if heated to 600ºC.

  11. Highly efficient antibody immobilization with multimeric protein Gs coupled magnetic silica nanoparticles

    NASA Astrophysics Data System (ADS)

    Lee, J. H.; Choi, H. K.; Chang, J. H.

    2011-10-01

    This work reports the immobilization of monomeric, dimeric and trimer protein Gs onto silica magnetic nanoparticles for self-oriented antibody immobilization. To achieve this, we initially prepared the silica-coated magnetic nanoparticle having about 170 nm diameters. The surface of the silica coated magnetic nanoparticles was modified with 3- aminopropyl-trimethoxysilane (APTMS) to chemically link to multimeric protein Gs. The conjugation of amino groups on the SiO2-MNPs to cysteine tagged in multimeric protein Gs was performed using a sulfo-SMCC coupling procedure. The binding efficiencies of monomer, dimer and trimer were 77 %, 67 % and 55 % respectively. However, the efficiencies of antibody immobilization were 70 %, 83 % and 95 % for monomeric, dimeric and trimeric protein G, respectively. To prove the enhancement of accessibility by using multimeric protein G, FITC labeled goat-anti-mouse IgG was treated to mouse IgG immobilized magnetic silica nanoparticles through multimeric protein G. FITC labeled goat anti-mouse IgGs were more easily bound to mouse IgG immobilized by trimeric protein G than others. Finally protein G bound silica magnetic nanoparticles were utilized to develop highly sensitive immunoassay to detect hepatitis B antigen.

  12. Fracture strength of glass chips for high-pressure microfluidics

    NASA Astrophysics Data System (ADS)

    Andersson, Martin; Hjort, Klas; Klintberg, Lena

    2016-09-01

    High-pressure microfluidics exposes new areas in chemistry. In this paper, the reliability of transparent borosilicate glass chips is investigated. Two designs of circular cavities are used for fracture strength tests, either 1.6 mm wide with rounded corners to the fluid inlets, or 2.0 mm wide with sharp inlet corners. Two kinds of tests are done, either short-term, e.g. pressurization to fracture at room temperature, or long-term, with fracture at constant pressurization for up to one week, in the temperature region 11–125 °C. The speed of crack fronts is measured using a high-speed camera. Results show fracture stresses in the range of 129 and 254 MPa for short-term measurements. Long-term measurements conclude the presences of a temperature and stress dependent delayed fracture. For a reliability of one week at 11–38 °C, a pressure limit is found at the lower end of the short-term measurements, or 15% lower than the average. At 80 °C, this pressure limit is 45% lower. Crack speeds are measured to be 10‑5 m s‑1 during short-term fracture. These measurements are comparable with estimations based on slow crack growth and show that the growth affects the reliability of glass chips. This effect is strongly affected by high temperatures, thus lowers the operating window of high-pressure glass microfluidic devices.

  13. Carbon dioxide in silica-undersaturated melt Part II: Effect of CO2 on quenched glass structure

    NASA Astrophysics Data System (ADS)

    Morizet, Yann; Paris, Michael; Gaillard, Fabrice; Scaillet, Bruno

    2014-11-01

    Despite CO2 is the second most abundant volatile species implied in magmatic systems, its impact on the molecular structure of aluminosilicate glasses in complex systems is currently not well-constrained. Inasmuch, whether CO2 induces an increase in glass polymerization or not is yet not clear for complex glass compositions. Using the set of nephelinite glass samples investigated in Part I (Morizet et al., 2014), in which the CO2 solubility and speciation have been constrained as a function of the #K (molar K2O/K2O + Na2O), we have conducted a thorough investigation of the change in the silicate network structure associated to CO2 dissolution. The change in silicate structure has been studied as a function of volatiles solubility (CO2 up to 4.5 wt.%, H2O up to 3 wt.%) as well as a function of the #K (between 0 and 0.75) of the glasses. We used 29Si Solid-State NMR for probing the silicon local environment in the quenched glasses. We observe that in such depolymerized nephelinite compositions the exchange between Na and K in volatile-free glasses induces a change in the glass structure attributed to the Mixed Alkali Effect (MAE) invoked in previous works. The observed changes might be related to geometric changes in the glass structure (change in network species bond lengths or angles). The addition of H2O only produces a negligible change in the degree of polymerization being probed by the constant NBO/T (Non-Bridging Oxygen per Tetrahedron) as H2O is added to volatile-free glasses. In contrast, we observed that the addition of CO2 induces a strong change in the glass structure which might be interpreted as an increase in polymerization. Alternatively, considering the identified CO2 dissolution mechanism (mostly as non-bridging carbonates units), the glass structure changes might reflect an apparent glass polymerization through the creation of Si-O-C bonds rather a true polymerization through the creation of Si-O-Si bonds.

  14. High power nd:glass laser for fusion applications.

    PubMed

    Soures, J; Kumpan, S; Hoose, J

    1974-09-01

    Experiments on laser-induced thermonuclear fusion require high brightness lasers capable of producing subnanosecond pulses with total energy content of several kilojoules. Of existing laser media, Nd:glass appears to be the best choice for meeting these criteria. In this paper we discuss the problems of designing a high power Nd:glass laser system. A detailed description of an operating two-beam system producing subnanosecond pulses with a maximum energy of 350 J per beam is presented, along with an extensive description of beam diagnostic techniques. A four beam version of this system became operational on 3 April 1974 and is now producing energies in excess of a kilojoule in subnanosecond pulses. PMID:20134633

  15. Glass Strengthening via High-Intensity Plasma-Arc Heating

    SciTech Connect

    Wereszczak, Andrew A; Harper, David C; Duty, Chad E; Patel, P

    2010-01-01

    The use of a high-intensity plasma-arc lamp was used to irradiate the surface of soda-lime silicate glass tiles to determine if an increase in strength could be achieved. The lamp had a power density of 3500 W/cm2, a processing area of 1 cm x 10 cm, irradiated near-infrared heating at a wavelength between 0.2 1.4 m, and was controlled to unidirectionally sweep across 50-mm-square tiles at a constant speed of 8 mm/s. Ring-on-ring (RoR) equibiaxial flexure and 4 pt uni-directional flexure testings of entire tiles were used to measure and compare failure stress distributions of treated and untreated glass. Even with non-optimized processing conditions, RoR failure stress increased by approximately 25% and the 4 pt bend failure stress increased by approximately 65%. Strengthening was due to a fire-polishing-like mechanism. The arc-lamp heat-treatment caused the location of the strength-limiting flaws in the 4-pt-bend tiles to change; namely, failure initiation occurred on the gage section surface for the treated glass whereas it occurred at a gage section edge for the untreated. Arc-lamp heat-treatment is attractive not only because it provides strengthening, but because it can (non-contact) process large amounts of glass quickly and inexpensively, and is a process that either a glass manufacturer or end-user can readily employ.

  16. Status of Gr/glass composites technology at UTOS

    NASA Technical Reports Server (NTRS)

    Mayor, Ramon A.

    1988-01-01

    The TSC (Thermally Stable Composite) refers to a family of graphite reinforced glass matrix composite materials developed by UTOS. This fiber matrix combination exhibits low coefficients of thermal expansion (CTE), exceptional dimensional stability, high specific strength and stiffness, adequate fracture toughness, and space environment compatibility. The dimensional stability of a TSC mirror structure was experimentally characterized at the Steward Observatory. Preliminary results indicate that TSC is significantly more thermally stable than most current structural composite materials. In addition, the use of lower CTE glass matrix materials, such as 96 percent silica glass, have the potential for producing graphite/glass panels with expansion rates and stability comparable to that of fused silica.

  17. ETHANOL, ACETIC ACID, AND WATER ADSORPTION FROM BINARY AND TERNARY LIQUID MIXTURES ON HIGH-SILICA ZEOLITES

    EPA Science Inventory

    Adsorption isotherms were measured for ethanol, acetic acid, and water adsorbed on high-silica ZSM-5 zeolite powder from binary and ternary liquid mixtures at room temperature. Ethanol and water adsorption on two high-silica ZSM-5 zeolites with different aluminum contents and a h...

  18. Z method calculations to determine the melting curve of silica at high pressures

    NASA Astrophysics Data System (ADS)

    González-Cataldo, F.; Davis, S.; Gutiérrez, G.

    2016-05-01

    The Z method is a novel technique that allows to calculate the melting temperature of materials at different pressures from the microcanonical ensemble. In this work, we apply this method to study the melting behavior of silica at high pressures, determining melting temperatures and dynamical properties.

  19. Ionic liquid decorated mesoporous silica nanoparticles: a new high-performance hybrid electrolyte for lithium batteries.

    PubMed

    Li, Yang; Wong, Ka-Wai; Ng, Ka-Ming

    2016-03-10

    We report a novel hybrid electrolyte based on mesoporous silica nanoparticles decorated with an ionic liquid, which exhibits a superior lithium ion transference number of >0.8, and an excellent electrochemical window of >5 V with attractive ionic conductivity. The insights obtained pave a new way for the preparation of high-performance electrolytes with mesoporous structures. PMID:26926805

  20. Low-temperature Raman spectroscopy of copper and silver nanoparticles ion-synthesized in a silica glass and subjected to laser annealing

    NASA Astrophysics Data System (ADS)

    Kurbatova, N. V.; Galyautdinov, M. F.; Shtyrkov, E. I.; Nuzhdin, V. I.; Stepanov, A. L.

    2010-06-01

    The modification of the shape of ion-synthesized silver and copper nanoparticles in a silica glass during laser annealing has been studied for the first time by Raman spectroscopy at a temperature of 77 K. The laser annealing has been carried out for a wavelength of 694 nm at the edge of the plasmon absorption spectrum of nanoparticles. A comparison of the experimental spectra and the calculated modes of in-phase bending vibrations of the “harmonica” type in nanostrings of the corresponding metals has demonstrated their good agreement. The effects observed have been discussed from the standpoint of the size quantization of vibrations in metal nanowires. This methodical approach has made it possible to estimate the sizes of the Ag and Cu nanoparticles under the assumption that they have an elongated form; in this case, their average lengths are equal to 2.5 and 1.4 nm, respectively.

  1. Facilitated fabrication of high strength silica aerogels using cellulose nanofibrils as scaffold.

    PubMed

    Fu, Jingjing; Wang, Siqun; He, Chunxia; Lu, Zexiang; Huang, Jingda; Chen, Zhilin

    2016-08-20

    Monolithic cellulose nanofibrils (CNF)-silica composite aerogels were successfully prepared by immersing CNF aerogels into a silica solution in a two-step sol-gel process (initial hydrolysis of tetraethyl orthosilicate (TEOS) followed by condensation of silica particles). Aerogels were characterized by SEM, BET surface area test, bulk density and silica content analysis, FTIR spectroscopy, and compression test. The form of SiO2 existing in the composite aerogel was the spherical individual particles coated on CNF fibrils. The pH value of condensation solution was found to have great influence on the properties of the composite aerogels. By varying the pH value of condensation atmosphere from 8 to 12, the bulk densities of composite aerogels were able to be linearly increased from 0.059gcm(-3) to 0.29gcm(-3),and the silica content in the matrix sharply jumped from 3wt% to 79wt%. The porosities of the aerogels remained very high, between 85 and 96%, and the surface area of the composite aerogel reached up to 700.1m(2)g(-1). The compression properties of the composite aerogel improved greatly compared with those of the silica aerogel, about 8-30 times higher. Moreover, the compressive strength of the composite aerogel prepared in this work greatly exceeded the conventional insulation materials found in the recent commercial market, and without substantial increases in thermal conductivity. Hence, the findings of this research offer a promising application for composite aerogels and give a theoretical basis for developing new advanced materials. PMID:27178912

  2. High frequency ultrasound detection with ultra-high-Q silica microspheres

    NASA Astrophysics Data System (ADS)

    Chistiakova, Maria V.; Armani, Andrea M.

    2015-03-01

    Due to the nondestructive and noninvasive nature of ultrasound imaging, the technique has a variety of applications in many fields, most notably in healthcare and electronics. Ultrasound detection based on optical microcavities has emerged as one accurate and sensitive method. While previous research using polymer microring cavities showed detection based on device deformation, the approach presented here relied on the photoelastic effect. In this effect, the ultrasound wave induces a strain in the medium leading to a refractive index change. This effect was shown experimentally and in a COMSOL simulation with the use of ultra high quality factor silica microspheres. With an increase in quality factor and input power from previous research, the device response is increased and the noise equivalent pressure is decreased. The simulations presented use the finite element method and integrate acoustic and optics components of the system. The predictive accuracy of the simulation is also presented.

  3. Effects of Quartz Particle Size and Sucrose Addition on Melting Behavior of a Melter Feed for High-Level Waste Glass

    SciTech Connect

    Marcial, Jose; Hrma, Pavel R; Schweiger, Michael J; Swearingen, Kevin J; Tegrotenhuis, Nathan E; Henager, Samuel H

    2010-08-11

    The behavior of melter feed (a mixture of nuclear waste and glass-forming additives) during waste-glass processing has a significant impact on the rate of the vitrification process. We studied the effects of silica particle size and sucrose addition on the volumetric expansion (foaming) of a high-alumina feed and the rate of dissolution of silica particles in feed samples heated at 5°C/min up to 1200°C. The initial size of quartz particles in feed ranged from 5 to 195 µm. The fraction of the sucrose added ranged from 0 to 0.20 g per g glass. Extensive foaming occurred only in feeds with 5-μm quartz particles; particles >150 µm formed clusters. Particles of 5 µm completely dissolved by 900°C whereas particles >150 µm did not fully dissolve even when the temperature reached 1200°C. Sucrose addition had virtually zero impact on both foaming and the dissolution of silica particles.

  4. Effect of Feed Melting, Temperature History and Minor Component Addition on Spinel Crystallization in High-Level Waste Glass

    SciTech Connect

    Izak, Pavel; Hrma, Pavel R.; Arey, Bruce W.; Plaisted, Trevor J.

    2001-08-01

    This study was undertaken to help design mathematical models for high-level waste (HLW) glass melter that simulate spinel behavior in molten glass. Spinel, (Fe,Ni,Mn) (Fe,Cr)2O4, is the primary solid phase that precipitates from HLW glasses containing Fe and Ni in sufficient concentrations. Spinel crystallization affects the anticipated cost and risk of HLW vitrification. To study melting reactions, we used simulated HLW feed, prepared with co-precipitated Fe, Ni, Cr, and Mn hydroxides. Feed samples were heated up at a temperature-increase rate (4C/min) close to that which the feed experiences in the HLW glass melter. The decomposition, melting, and dissolution of feed components (such as nitrates, carbonates, and silica) and the formation of intermediate crystalline phases (spinel, sodalite [Na8(AlSiO4)6(NO2)2], and Zr-containing minerals) were characterized using evolved gas analysis, volume-expansion measurement, optical microscope, scanning electron microscope, thermogravimetric analysis, differential scanning calorimetry, and X-ray diffraction. Nitrates and quartz, the major feed components, converted to a glass-forming melt by 880C. A chromium-free spinel formed in the nitrate melt starting from 520C and Sodalite, a transient product of corundum dissolution, appeared above 600C and eventually dissolved in glass. To investigate the effects of temperature history and minor components (Ru,Ag, and Cu) on the dissolution and growth of spinel crystals, samples were heated up to temperatures above liquidus temperature (TL), then subjected to different temperature histories, and analyzed. The results show that spinel mass fraction, crystals composition, and crystal size depend on the chemical and physical makeup of the feed and temperature history.

  5. Enhanced high temperature oxidization resistance of silica coated γ-Ce2S3 red pigments

    NASA Astrophysics Data System (ADS)

    Liu, Shun-Guo; Li, Yue-Ming; Wang, Zhu-Mei; Shen, Zong-Yang; Xie, Zhi-Xiang

    2016-11-01

    Silica layer coated γ-Ce2S3 red pigments were successfully prepared based on a Stober method followed by a hydrogen-argon atmosphere heat treatment at 700 °C. The effect of water/ethanol volume ratio and tetraethoxysilane concentration on the microstructure of the coating layer and its high temperature oxidizing protection to pigments was investigated. A transparent silica coating layer with dense microstructure and about 60 nm thickness can provide a favorable protection for the red hue of the γ-Ce2S3 pigments. The oxidization resistant temperature was enhanced to 550 °C for the dense silica layer coated γ-Ce2S3 pigments as compared to ≤350 °C for the uncoated ones. A red color (L* = 29.59, a* = 27.53 and b* = 27.66) was still remained for such silica coated γ-Ce2S3 pigments after heated treated at 550 °C in air, indicating its potential for high temperature industrial applications.

  6. Bulk damage and absorption in fused silica due to high-power laser applications

    NASA Astrophysics Data System (ADS)

    Nürnberg, F.; Kühn, B.; Langner, A.; Altwein, M.; Schötz, G.; Takke, R.; Thomas, S.; Vydra, J.

    2015-11-01

    Laser fusion projects are heading for IR optics with high broadband transmission, high shock and temperature resistance, long laser durability, and best purity. For this application, fused silica is an excellent choice. The energy density threshold on IR laser optics is mainly influenced by the purity and homogeneity of the fused silica. The absorption behavior regarding the hydroxyl content was studied for various synthetic fused silica grades. The main absorption influenced by OH vibrational excitation leads to different IR attenuations for OH-rich and low-OH fused silica. Industrial laser systems aim for the maximum energy extraction possible. Heraeus Quarzglas developed an Yb-doped fused silica fiber to support this growing market. But the performance of laser welding and cutting systems is fundamentally limited by beam quality and stability of focus. Since absorption in the optical components of optical systems has a detrimental effect on the laser focus shift, the beam energy loss and the resulting heating has to be minimized both in the bulk materials and at the coated surfaces. In collaboration with a laser research institute, an optical finisher and end users, photo thermal absorption measurements on coated samples of different fused silica grades were performed to investigate the influence of basic material properties on the absorption level. High purity, synthetic fused silica is as well the material of choice for optical components designed for DUV applications (wavelength range 160 nm - 260 nm). For higher light intensities, e.g. provided by Excimer lasers, UV photons may generate defect centers that effect the optical properties during usage, resulting in an aging of the optical components (UV radiation damage). Powerful Excimer lasers require optical materials that can withstand photon energy close to the band gap and the high intensity of the short pulse length. The UV transmission loss is restricted to the DUV wavelength range below 300 nm and

  7. Thermal pretreatments of superficially porous silica particles for high-performance liquid chromatography: Surface control, structural characterization and chromatographic evaluation.

    PubMed

    Mignot, Mélanie; Sebban, Muriel; Tchapla, Alain; Mercier, Olivier; Cardinael, Pascal; Peulon-Agasse, Valérie

    2015-11-01

    This study reports the impact of thermal pretreatment between 400 and 1100°C on superficially porous silica particles (e.g. core-shell, fused-core; here abbreviated as SPP silica). The different thermally pretreated SPP silica (400°C, 900°C and 1100°C) were chemically bonded with an octadecyl chain under microwave irradiation. The bare SPP silica, thermally untreated and pretreated, as well as the chemically bonded phases (CBPs) were fully characterized by elemental analysis, diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), and solid state cross polarization magic angle spinning (CP-MAS) (29)Si NMR. The chromatographic properties of the overall set of C18-thermally pretreated SPP silica stationary phases were determined using the Tanaka test. Complementary, the simplified Veuthey test was used to deeply study the silanol activity, considering a set of 7 basic solutes with various physicochemical properties. Both tests were also performed on different commercial SPP silica columns and different types of bonding chemistry (C18, Phenyl-hexyl, RP-amide, C30, aQ). Multivariate data analyses (hierarchical cluster analysis and principal component analysis) were carried out to define groups of stationary phases with similar chromatographic properties and situate them in relation to those commercially available. These different C18-thermally pretreated SPP silicas represented a wide range of stationary phases as they were spread out along the score plot. Moreover, this study highlighted that the thermal pretreatment improved the chemical stability of the SPP silica compare to untreated SPP silica and untreated porous silica. Consequently, higher thermal pretreatment can be applied (up to 900°C) before functionalization without destruction of the silica matrix. Indeed, a significantly lower dissolution of the thermally pretreated SPP silica under aggressive conditions could allow the use of the corresponding functionalized stationary phases at high

  8. High Purity Zirconium Tetrafluoride For Fluoride Glass Applications

    NASA Astrophysics Data System (ADS)

    Withers, Howard P.; Monk, V. A.; Cooper, G. A.

    1989-06-01

    A totally anhydrous process has been developed for the preparation of high purity zirconium tetrafluoride for use in low loss fluoride glass applications. The ZrF4 purityis 99.99997% with respect to all transition elements (excluding HO based on analysis by spark source mass spectrometry (SSMS) and graphite furnace/atomic absorption spectroscopy (GF/AA). The only transition elements detected by these techniques were Fe, Ni and Cr, while Co and Cu were consistently below the detection limits. The anhydrous nature of the process, which is strictly maintained by the choice of reactants, affords product with very low oxide and hydroxide content. Total oxygen concentrations of less than 10 ppm have been measured by the inert gas fusion technique. A ZBLAN glass composition prepared using this ZrF4 showed extremely low UV absorption having an absorption constant of 1 cm-1 at 198 nm. ZrF4 from this process was also used in a ZBLAN glass fiber whose minimum optical loss was measured at 6.3 dB/km over 150 meters of fiber. The process is straightforward to scale up and has also been demonstrated to be useful for the preparation of HfF4, BaF2, A1F3 and LaF3.

  9. Temperature dependence and annealing effects of absorption edges for selenium quantum dots formed by ion implantation in silica glass

    SciTech Connect

    Ueda, A.; Wu, M.; Mu, R.

    1998-12-31

    The authors have fabricated Se nanoparticles in silica substrates by ion implantation followed by thermal annealing up to 1000 C, and studied the Se nanoparticle formation by optical absorption spectroscopy, Rutherford backscattering spectrometry, X-ray diffraction, and transmission electron microscopy. The sample with the highest dose (1 {times} 10{sup 17} ions/cm{sup 2}) showed the nanoparticle formation during the ion implantation, while the lower dose samples (1 and 3 {times} 10{sup 16} ions/cm{sup 2}) required thermal treatment to obtain nano-sized particles. The Se nanoparticles in silica were found to be amorphous. After thermal annealing, the particle doses approached the value of bulk after thermal annealing. The temperature dependent absorption spectra were also measured for this system in a temperature range from 15 to 300 K.

  10. A-thermal elastic behavior of silicate glasses

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    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 Si4+ ions by Al3+ 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.

  11. 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. PMID:26815634

  12. Highly fluorescent silver nanoclusters in alumina-silica composite optical fiber

    SciTech Connect

    Halder, A.; Chattopadhyay, R.; Majumder, S.; Paul, M. C.; Das, S.; Bhadra, S. K.; Bysakh, S.; Unnikrishnan, M.

    2015-01-05

    An efficient visible fluorescent optical fiber embedded with silver nanoclusters (Ag-NCs) having size ∼1 nm, uniformly distributed in alumina-silica composite core glass, is reported. Fibers are fabricated in a repetitive controlled way through modified chemical vapour deposition process associated with solution doping technique. Fibers are drawn from the transparent preforms by conventional fiber drawing process. Structural characteristics of the doped fibers are studied using transmission electron microscopy and electron probe micro analysis. The oxidation state of Ag within Ag-NCs is investigated by X-ray photo electron spectroscopy. The observed significant fluorescence of the metal clusters in fabricated fibers is correlated with electronic model. The experimentally observed size dependent absorption of the metal clusters in fabricated fibers is explained with the help of reported results calculated by ab-initio density functional theory. These optical fibers may open up an opportunity of realizing tunable wavelength fiber laser without the help of rare earth elements.

  13. High-Power Solid-State Lasers from a Laser Glass Perspective

    SciTech Connect

    Campbell, J H; Hayden, J S; Marker, A J

    2010-12-17

    Advances in laser glass compositions and manufacturing have enabled a new class of high-energy/high-power (HEHP), petawatt (PW) and high-average-power (HAP) laser systems that are being used for fusion energy ignition demonstration, fundamental physics research and materials processing, respectively. The requirements for these three laser systems are different necessitating different glasses or groups of glasses. The manufacturing technology is now mature for melting, annealing, fabricating and finishing of laser glasses for all three applications. The laser glass properties of major importance for HEHP, PW and HAP applications are briefly reviewed and the compositions and properties of the most widely used commercial laser glasses summarized. Proposed advances in these three laser systems will require new glasses and new melting methods which are briefly discussed. The challenges presented by these laser systems will likely dominate the field of laser glass development over the next several decades.

  14. The Effects of High Temperature and Nuclear Radiation on the Optical Transmission of Silica Optical Fibers

    NASA Astrophysics Data System (ADS)

    Hawn, David P.

    Distributed measurements made with fiber optic instrumentation have the potential to revolutionize data collection for facility monitoring and process control in industrial environments. Dozens of sensors etched into a single optical fiber can be used to instrument equipment and structures so that dozens of spatially distributed temperature measurements, for example, can be made quickly using one optical fiber. Optically based sensors are commercially available to measure temperature, strain, and other physical quantities that can be related to strain, such as pressure and acceleration. Other commercially available technology eliminates the need to etch discrete sensors into an optical fiber and allows temperature measurements to be made along the length of an ordinary silica fiber. Distributed sensing with optical instrumentation is commonly used in the petroleum industry to measure the temperature and pressure profiles in down hole applications. The U.S. Department of Energy is interested in extending the distributed sensing capabilities of optical instrumentation to high temperature reactor radiation environments. For this technology extension to be possible, the survivability of silica optical fibers needed to be determined in this environment. In this work the optical attenuation added to silica optical fiber exposed simultaneously to reactor radiation and temperatures to 1000°C was experimentally determined. Optical transmission measurements were made in-situ from 400nm-2300nm. For easy visualization, all of the results generated in this work were processed into movies that are available publicly [1]. In this investigation, silica optical fibers were shown to survive optically and mechanically in a reactor radiation environment to 1000°C. For the combined high temperature reactor irradiation experiments completed in this investigation, the maximum attenuation increase in the low-OH optical fibers was around 0.5db/m at 1550nm and 0.6dB/m at 1300nm. The

  15. Repairing cracked glass

    NASA Technical Reports Server (NTRS)

    Helman, D. D.; Holt, J. W.; Smiser, L. V.

    1979-01-01

    Filing procedure consisting of machined lightweight fused-silica tiles coated with thin-layer of borosilicate glass produces homogeneous seal in thin glass. Procedure is useful in repairing glass envelopes, X-ray tub windows, Dewar flasks, and similar thin glass objects.

  16. Impact testing of simulated high-level waste glass canisters

    SciTech Connect

    Peterson, M.E.; Alzheimer, J.M.; Slate, S.C.

    1985-01-01

    Three Savannah River Laboratory reference high-level waste canisters were subjected to impact tests at the Pacific Northwest Laboratory in Richland, Washington, in June 1983. The purpose of the test was to determine the integrity of the canister, nozzle, and final closure weld and to assess the effects of impacts on the glass. Two of the canisters were fabricated from 304L stainless steel and the third canister from titanium. The titanium canister was subjected to two drops. The first drop was vertical from 9.14 m onto an unyielding surface with the bottom corner of the canister receiving the impact. No failure occurred during this drop. The second drop was vertical from 9.14 m onto an unyielding surface with the corner of the fill nozzle receiving the impact. A large breach in the canister occurred in the region where the fill nozzle joins the dished head. The first stainless steel canister was dropped with the corner of the fill nozzle receiving the impact. The canister showed significant strain with no rupturing in the region where the fill nozzle joins the dished head. The second canister was dropped with the bottom corner receiving the impact and also, dropped horizontally onto an unyielding vertical solid steel cylinder in a puncture test. The bottom drop did not damage the weld and the puncture test did not rupture the canister body. The glass particles in the damaged zone of these canisters were sampled and analyzed for particle size. A comparison was made with control canister in which no impact had occurred. The particle size distribution for the control canisters and the zones of damaged glass were determined down to 1.5 ..mu..m. The quantity of glass fines, smaller than 10 ..mu..m, which must be determined for transportation safety studies, was found to be the largest in the bottom-damaged zone. The total amount of fines smaller than 10 ..mu..m after impact was less than 0.01 wt % of the total amount of glass in the canister.

  17. The Compressive Behavior of Isocyanate-crosslinked Silica Aerogel at High Strain Rates

    NASA Technical Reports Server (NTRS)

    Luo, H.; Lu, H.; Leventis, N.

    2006-01-01

    Aerogels are low-density, highly nano-porous materials. Their engineering applications are limited due to their brittleness and hydrophilicity. Recently, a strong lightweight crosslinked silica aerogel has been developed by encapsulating the skeletal framework of amine-modified silica aerogels with polyureas derived by isocyanate. The mesoporous structure of the underlying silica framework is preserved through conformal polymer coating, and the thermal conductivity remains low. Characterization has been conducted on the thermal, physical properties and the mechanical properties under quasi-static loading conditions. In this paper, we present results on the dynamic compressive behavior of the crosslinked silica aerogel (CSA) using a split Hopkinson pressure bar (SHPB). A new tubing pulse shaper was employed to help reach the dynamic stress equilibrium and constant strain rate. The stress-strain relationship was determined at high strain rates within 114-4386/s. The effects of strain rate, density, specimen thickness and water absorption on the dynamic behavior of the CSA were investigated through a series of dynamic experiments. The Young's moduli (or 0.2% offset compressive yield strengths) at a strain rate approx.350/s were determined as 10.96/2.08, 159.5/6.75, 192.2/7.68, 304.6/11.46, 407.0/20.91 and 640.5/30.47 MPa for CSA with densities 0.205, 0.454, 0.492, 0.551,0.628 and 0.731 g/cu cm, respectively. The deformation and failure behaviors of a native silica aerogel with density (0.472 g/cu cm ), approximately the same as a typical CSA sample were observed with a high speed digital camera. Digital image correlation technique was used to determine the surface strains through a series of images acquired using high speed photography. The relative uniform axial deformation indicated that localized compaction did not occur at a compressive strain level of approx.17%, suggesting most likely failure mechanism at high strain rate to be different from that under quasi

  18. The compressive behavior of isocyanate-crosslinked silica aerogel at high strain rates

    NASA Astrophysics Data System (ADS)

    Luo, H.; Lu, H.; Leventis, N.

    2006-06-01

    Aerogels are low-density, highly nano-porous materials. Their engineering applications are limited due to their brittleness and hydrophilicity. Recently, a strong lightweight crosslinked silica aerogel has been developed by encapsulating the skeletal framework of amine-modified silica aerogels with polyureas derived by isocyanate. The mesoporous structure of the underlying silica framework is preserved through conformal polymer coating, and the thermal conductivity remains low. Characterization has been conducted on the thermal, physical properties and the mechanical properties under quasi-static loading conditions. In this paper, we present results on the dynamic compressive behavior of the crosslinked silica aerogel (CSA) using a split Hopkinson pressure bar (SHPB). A new tubing pulse shaper was employed to help reach the dynamic stress equilibrium and constant strain rate. The stress-strain relationship was determined at high strain rates within 114-4386 s-1. The effects of strain rate, density, specimen thickness and water absorption on the dynamic behavior of the CSA were investigated through a series of dynamic experiments. The Young’s moduli (or 0.2% offset compressive yield strengths) at a strain rate ˜350 s-1 were determined as 10.96/2.08, 159.5/6.75, 192.2/7.68, 304.6/11.46, 407.0/20.91 and 640.5/30.47 MPa for CSA with densities 0.205, 0.454, 0.492, 0.551, 0.628 and 0.731 g cm-3, respectively. The deformation and failure behaviors of a native silica aerogel with density (0.472 g cm-3), approximately the same as a typical CSA sample were observed with a high speed digital camera. Digital image correlation technique was used to determine the surface strains through a series of images acquired using high speed photography. The relative uniform axial deformation indicated that localized compaction did not occur at a compressive strain level of ˜17%, suggesting most likely failure mechanism at high strain rate to be different from that under quasi

  19. Liquidus Temperature and Primary Crystallization Phases in High-Zirconia High-Level Waste Borosilicate Glasses

    SciTech Connect

    Plaisted, Trevor J.; Hrma, Pavel R.; Vienna, John D.; Jiricka, Antonin

    1999-12-09

    Liquidus temperature (TL) studies of high-Zr high-level waste (HLW) borosilicate glasses have identified three primary phases: baddelyite (ZrO2), zircon (ZrSiO4), and alkali-zirconium silicates, such as parakeldyshite (Na2ZrSi2O7). Using published TL data for HLW glasses with these primary phases, we have computed partial specific TLs for major glass components. On the Na2O-SiO2-ZrO2 submixture, we have determined approximate positions of the boundaries between the baddelyite, zircon, and parakeldyshite primary phase fields. The maximum that can dissolve at 1150?C in a borosilicate HLW glass subjected to common processability and acceptability constraints appears to be 16.5 mass% ZrO2.

  20. PLUTONIUM SOLUBILITY IN HIGH-LEVEL WASTE ALKALI BOROSILICATE GLASS

    SciTech Connect

    Marra, J.; Crawford, C.; Fox, K.; Bibler, N.

    2011-01-04

    The solubility of plutonium in a Sludge Batch 6 (SB6) reference glass and the effect of incorporation of Pu in the glass on specific glass properties were evaluated. A Pu loading of 1 wt % in glass was studied. Prior to actual plutonium glass testing, surrogate testing (using Hf as a surrogate for Pu) was conducted to evaluate the homogeneity of significant quantities of Hf (Pu) in the glass, determine the most appropriate methods to evaluate homogeneity for Pu glass testing, and to evaluate the impact of Hf loading in the glass on select glass properties. Surrogate testing was conducted using Hf to represent between 0 and 1 wt % Pu in glass on an equivalent molar basis. A Pu loading of 1 wt % in glass translated to {approx}18 kg Pu per Defense Waste Processing Facility (DWPF) canister, or about 10X the current allowed limit per the Waste Acceptance Product Specifications (2500 g/m{sup 3} of glass or about 1700 g/canister) and about 30X the current allowable concentration based on the fissile material concentration limit referenced in the Yucca Mountain Project License Application (897 g/m{sup 3}3 of glass or about 600 g Pu/canister). Based on historical process throughput data, this level was considered to represent a reasonable upper bound for Pu loading based on the ability to provide Pu containing feed to the DWPF. The task elements included evaluating the distribution of Pu in the glass (e.g. homogeneity), evaluating crystallization within the glass, evaluating select glass properties (with surrogates), and evaluating durability using the Product Consistency Test -- Method A (PCT-A). The behavior of Pu in the melter was evaluated using paper studies and corresponding analyses of DWPF melter pour samples.The results of the testing indicated that at 1 wt % Pu in the glass, the Pu was homogeneously distributed and did not result in any formation of plutonium-containing crystalline phases as long as the glass was prepared under 'well-mixed' conditions. The

  1. Fabrication of high specificity hollow mesoporous silica nanoparticles assisted by Eudragit for targeted drug delivery.

    PubMed

    She, Xiaodong; Chen, Lijue; Velleman, Leonora; Li, Chengpeng; Zhu, Haijin; He, Canzhong; Wang, Tao; Shigdar, Sarah; Duan, Wei; Kong, Lingxue

    2015-05-01

    Hollow mesoporous silica nanoparticles (HMSNs) are one of the most promising carriers for effective drug delivery due to their large surface area, high volume for drug loading and excellent biocompatibility. However, the non-ionic surfactant templated HMSNs often have a broad size distribution and a defective mesoporous structure because of the difficulties involved in controlling the formation and organization of micelles for the growth of silica framework. In this paper, a novel "Eudragit assisted" strategy has been developed to fabricate HMSNs by utilising the Eudragit nanoparticles as cores and to assist in the self-assembly of micelle organisation. Highly dispersed mesoporous silica spheres with intact hollow interiors and through pores on the shell were fabricated. The HMSNs have a high surface area (670 m(2)/g), small diameter (120 nm) and uniform pore size (2.5 nm) that facilitated the effective encapsulation of 5-fluorouracil within HMSNs, achieving a high loading capacity of 194.5 mg(5-FU)/g(HMSNs). The HMSNs were non-cytotoxic to colorectal cancer cells SW480 and can be bioconjugated with Epidermal Growth Factor (EGF) for efficient and specific cell internalization. The high specificity and excellent targeting performance of EGF grafted HMSNs have demonstrated that they can become potential intracellular drug delivery vehicles for colorectal cancers via EGF-EGFR interaction. PMID:25617610

  2. 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. PMID:24514181

  3. Studies on molten glass sealing in diffusion coefficient measurements using shear cell technique

    NASA Astrophysics Data System (ADS)

    Yu, Jianding; Natsuisaka, Makoto; Kato, Hirokazu; Matsumoto, Satoshi; Kinoshita, Kyoichi; Itami, Toshio; Yoda, Shinichi

    2000-05-01

    To develop a shear cell technique for measuring the diffusion coefficient of molten materials with high vapor pressure, molten silica glass was used to seal the vapor leak from the clearance between the cell and the rotating rod. An apparatus was designed to investigate the sealing ability of several molten silica glasses. Using Corning 0211, 7059, and 7740 silica glasses, Ar could be sealed under 150 kPa in the 1100-1500 K temperature range. The corresponding viscosities of the molten silica glasses in the sealing temperature range were 105.3-103.8 Pa s. Based on the results of Ar sealing experiments, the configuration of molten glass sealing was used to seal the As vapor leak in InxGa1-xAs diffusion coefficient measurement experiments. The As vapor leak was successfully sealed and excellent diffusion coefficient measurement data were obtained using the shear cell technique during microgravity experiments carried out on sounding rocket.

  4. High-Q silica zipper cavity for optical radiation pressure driven MOMS switch

    SciTech Connect

    Tetsumoto, Tomohiro; Tanabe, Takasumi

    2014-07-15

    We design a silica zipper cavity that has high optical and mechanical Q (quality factor) values and demonstrate numerically the feasibility of a radiation pressure driven micro opto-mechanical system (MOMS) directional switch. The silica zipper cavity has an optical Q of 4.0 × 10{sup 4} and an effective mode volume V{sub mode} of 0.67λ{sup 3} when the gap between two cavities is 34 nm. The mechanical Q (Q{sub m}) is determined by thermo-elastic damping and is 2.0 × 10{sup 6} in a vacuum at room temperature. The opto-mechanical coupling rate g{sub OM} is as high as 100 GHz/nm, which allows us to move the directional cavity-waveguide system and switch 1550-nm light with 770-nm light by controlling the radiation pressure.

  5. Highly Electrically Conducting Glass-Graphene Nanoplatelets Hybrid Coatings.

    PubMed

    Garcia, E; Nistal, A; Khalifa, A; Essa, Y; Martín de la Escalera, F; Osendi, M I; Miranzo, P

    2015-08-19

    Hybrid coatings consisting of a heat resistant Y2O3-Al2O3-SiO2 (YAS) glass containing 2.3 wt % of graphene nanoplatelets (GNPs) were developed by flame spraying homogeneous ceramic powders-GNP granules. Around 40% of the GNPs survived the high spraying temperatures and were distributed along the splat-interfaces, forming a percolated network. These YAS-GNP coatings are potentially interesting in thermal protection systems and electromagnetic interference shields for aerospace applications; therefore silicon carbide (SiC) materials at the forefront of those applications were employed as substrates. Whereas the YAS coatings are nonconductive, the YAS-GNP coatings showed in-plane electrical conductivity (∼10(2) S·m(-1)) for which a low percolation limit (below 3.6 vol %) is inferred. Indentation tests revealed the formation of a highly damaged indentation zone showing multiple shear displacements between adjacent splats probably favored by the graphene sheets location. The indentation radial cracks typically found in brittle glass coatings are not detected in the hybrid coatings that are also more compliant. PMID:26222837

  6. Atom-economical synthesis of a high silica CHA zeolite using a solvent-free route.

    PubMed

    Wang, Xiong; Wu, Qinming; Chen, Chunyu; Pan, Shuxiang; Zhang, Weiping; Meng, Xiangju; Maurer, Stefan; Feyen, Mathias; Müller, Ulrich; Xiao, Feng-Shou

    2015-12-11

    A high silica CHA zeolite is successfully synthesized in the presence of a small amount of N,N,N-dimethylethylcyclohexylammonium bromide under solvent-free conditions. Catalytic tests for the selective catalytic reduction of NOx with NH3 (NH3-SCR) and methanol-to-olefins (MTO) show that the sample from the solvent-free route exhibits comparable catalytic properties to that from the conventional route. PMID:26440601

  7. CO2 laser scribe of chemically strengthened glass with high surface compressive stress

    NASA Astrophysics Data System (ADS)

    Li, Xinghua; Vaddi, Butchi R.

    2011-03-01

    Chemically strengthened glass is finding increasing use in handheld, IT and TV cover glass applications. Chemically strengthened glass, particularly with high (>600MPa) compressive stress (CS) and deeper depth of layer (DOL), enable to retain higher strength after damage than non-strengthened glass when its surface is abraded. Corning Gorilla® Glass has particularly proven to be advantageous over competition in this attribute. However, due to high compressive stress (CS) and Central Tension (CT) cutting ion-exchanged glass is extremely difficult and often unmanageable where ever the applications require dicing the chemically strengthened mother glass into smaller parts. We at Corning have developed a CO2 laser scribe and break method (LSB) to separate a single chemically strengthened glass sheet into plurality of devices. Furthermore, CO2 laser scribe and break method enables debris-free separation of glass with high edge strength due to its mirror-like edge finish. We have investigated laser scribe and break of chemically strengthened glass with surface compressive stress greater than 600 MPa. In this paper we present the results of CO2 scribe and break method and underlying laser scribing mechanisms. We demonstrated cross-scribe repetitively on GEN 2 size chemically strengthened glass substrates. Specimens for edge strength measurements of different thickness and CS/DOL glass were prepared using the laser scribe and break technique. The specimens were tested using the standard 4-point bend method and the results are presented.

  8. The largest Bio-Silica Structure on Earth: The Giant Basal Spicule from the Deep-Sea Glass Sponge Monorhaphis chuni

    PubMed Central

    Wang, Xiaohong; Gan, Lu; Jochum, Klaus P.; Schröder, Heinz C.; Müller, Werner E. G.

    2011-01-01

    The depth of the ocean is plentifully populated with a highly diverse fauna and flora, from where the Challenger expedition (1873–1876) treasured up a rich collection of vitreous sponges [Hexactinellida]. They have 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. Later, 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 structures, the giant basal spicules (3 m × 10 mm). With such spicules as a model, basic knowledge on the morphology, formation, and development of the skeletal elements could be elaborated. Spicules are formed by a proteinaceous scaffold which mediates the formation of siliceous lamellae in which the proteins are encased. Up to eight hundred 5 to 10 μm thick lamellae can be concentrically arranged around an axial canal. The silica matrix is composed of almost pure silicon and oxygen, providing it with unusual optophysical properties that are superior to those of man-made waveguides. Experiments indicated 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 the hexactinellids synthesize their silica enzymatically, via the enzyme silicatein. All these basic insights will surely contribute also to a further applied utilization and exploration of bio-silica in material/medical science. PMID:21941585

  9. Direct and reversible immobilization and microcontact printing of functional proteins on glass using a genetically appended silica-binding tag.

    PubMed

    Coyle, Brandon L; Baneyx, François

    2016-05-19

    Fusion of disulfide-constrained or linear versions of the Car9 dodecapeptide to model fluorescent proteins support their on-contact and oriented immobilization onto unmodified glass. Bound proteins can be released and the surface regenerated by incubation with l-lysine. This noncovalent chemistry enables rapid and reversibe microcontact printing of tagged proteins and speeds up the production of bicontinuous protein patterns. PMID:27157272

  10. Insulation Blankets for High-Temperature Use

    NASA Technical Reports Server (NTRS)

    Goldstein, H.; Leiser, D.; Sawko, P. M.; Larson, H. K.; Estrella, C.; Smith, M.; Pitoniak, F. J.

    1986-01-01

    Insulating blanket resists temperatures up to 1,500 degrees F (815 degrees C). Useful where high-temperature resistance, flexibility, and ease of installation are important - for example, insulation for odd-shaped furnaces and high-temperature ducts, curtains for furnace openings and fire control, and conveyor belts in hot processes. Blanket is quilted composite consisting of two face sheets: outer one of silica, inner one of silica or other glass cloth with center filling of pure silica glass felt sewn together with silica glass threads.

  11. High speed, high strength microwelding of Si/glass using ps-laser pulses.

    PubMed

    Miyamoto, Isamu; Okamoto, Yasuhiro; Hansen, Assi; Vihinen, Joma; Amberla, Tiina; Kangastupa, Jarno

    2015-02-01

    A novel microwelding procedure to join Si-to-glass using ps-laser pulses with high repetition rates is presented. The procedure provides weld joint with mechanical strength as high as 85 MPa and 45 MPa in sample pairs of Si/aluminosilicate (Si/SW-Y) and Si/borosilicate (Si/Borofloat 33), respectively, which are higher than anodic bonding, at high spatial resolution (< 20 µm) and very high throughput without pre- and post-heating. Laser-matter interaction analysis indicates that excellent weld joint of Si/glass is obtained by avoiding violent evaporation of Si substrate using ps-laser pulses. Laser welded Si/glass samples can be singulated along the weld lines by standard blade dicer without defects, demonstrating welding by ps-laser pulses is applicable to wafer-level packaging. PMID:25836199

  12. Liquid Glass: A Facile Soft Replication Method for Structuring Glass.

    PubMed

    Kotz, Frederik; Plewa, Klaus; Bauer, Werner; Schneider, Norbert; Keller, Nico; Nargang, Tobias; Helmer, Dorothea; Sachsenheimer, Kai; Schäfer, Michael; Worgull, Matthias; Greiner, Christian; Richter, Christiane; Rapp, Bastian E

    2016-06-01

    Liquid glass is a photocurable amorphous silica nanocomposite that can be structured using soft replication molds and turned into glass via thermal debinding and sintering. Simple polymer bonding techniques allow the fabrication of complex microsystems in glass like microfluidic chips. Liquid glass is a step toward prototyping of glass microstructures at low cost without requiring cleanroom facilities or hazardous chemicals. PMID:27060964

  13. High-Silica Rocks and Soils at Gusev Crater, Mars: Distribution, Spectra, and Implications for Past Hydrothermal Activity

    NASA Astrophysics Data System (ADS)

    Rice, M. S.; Bell, J. F.; Wang, A.; Cloutis, E. A.

    2008-12-01

    The Mars Exploration Rover (MER) Spirit has discovered surprisingly high concentrations of amorphous silica in the Inner Basin of the Columbia Hills. As described by Squyres et al. (2008, Science, 320, 1063), within a topographic lowland called Eastern Valley, Spirit's Alpha Particle X-Ray Spectrometer (APXS) measured a composition of >90 wt.% silica at the soil feature "Gertrude Weise", a record high for Mars. The Mössbauer spectrum of this target is featureless. APXS measurements of light-toned nodular outcrops also show high silica concentrations (up to ~72 wt.%), which in some locations co-exist with sulfur-rich soils. Miniature Thermal Emission Spectrometer (Mini-TES) results from the soils and nodules are consistent with opal-A. These deposits have been found adjacent to "Home Plate", a layered plateau interpreted as the product of explosive volcanism. The silica-rich soils and nodules are consistent with sinters and/or residues formed in a hydrothermal system, and may be related to the same hydrovolcanic activity that produced Home Plate. We have begun to map the distribution of high-silica materials in Gusev Crater more extensively using remote sensing, in order to understand the regional extent of possible hydrothermal activity. Spirit's Pancam instrument has collected visible to near-infrared relative reflectance spectra of the region in 11 unique wavelengths. We find that a distinct absorption feature at the longest Pancam wavelength (1009 nm) appears to be characteristic of the high-silica soils and nodules. By mapping the occurrence of this feature with other spectral parameters in Pancam images, we can remotely identify potential amorphous silica deposits elsewhere in the Columbia Hills. Here we present a map with our proposed regional distribution of silica-rich materials within the rover's Gusev Crater traverse area. The mineralogic origin of the 1009nm feature is enigmatic; reflectance spectra of amorphous silica are typically featureless in near

  14. High-entropy bulk metallic glasses as promising magnetic refrigerants

    SciTech Connect

    Huo, Juntao; Huo, Lishan; Li, Jiawei; Men, He; Wang, Xinmin; Chang, Chuntao E-mail: jqwang@nimte.ac.cn; Wang, Jun-Qiang E-mail: jqwang@nimte.ac.cn; Li, Run-Wei; Inoue, Akihisa

    2015-02-21

    In this paper, the Ho{sub 20}Er{sub 20}Co{sub 20}Al{sub 20}RE{sub 20} (RE = Gd, Dy, and Tm) high-entropy bulk metallic glasses (HE-BMGs) with good magnetocaloric properties are fabricated successfully. The HE-BMGs exhibit a second-order magnetic phase transition. The peak of magnetic entropy change (ΔS{sub M}{sup pk}) and refrigerant capacity (RC) reaches 15.0 J kg{sup −1} K{sup −1} and 627 J kg{sup −1} at 5 T, respectively, which is larger than most rare earth based BMGs. The heterogeneous nature of glasses also contributes to the large ΔS{sub M}{sup pk} and RC. In addition, the magnetic ordering temperature, ΔS{sub M}{sup pk} and RC can be widely tuned by alloying different rare earth elements. These results suggest that the HE-BMGs are promising magnetic refrigerant at low temperatures.

  15. High thermal stability and sluggish crystallization kinetics of high-entropy bulk metallic glasses

    NASA Astrophysics Data System (ADS)

    Yang, M.; Liu, X. J.; Ruan, H. H.; Wu, Y.; Wang, H.; Lu, Z. P.

    2016-06-01

    Metallic glasses are metastable and their thermal stability is critical for practical applications, particularly at elevated temperatures. The conventional bulk metallic glasses (BMGs), though exhibiting high glass-forming ability (GFA), crystallize quickly when being heated to a temperature higher than their glass transition temperature. This problem may potentially be alleviated due to the recent developments of high-entropy (or multi-principle-element) bulk metallic glasses (HE-BMGs). In this work, we demonstrate that typical HE-BMGs, i.e., ZrTiHfCuNiBe and ZrTiCuNiBe, have higher kinetic stability, as compared with the benchmark glass Vitreoy1 (Zr41.2Ti13.8Cu12.5Ni10Be22.5) with a similar chemical composition. The measured activation energy for glass transition and crystallization of the HE-BMGs is nearly twice that of Vitreloy 1. Moreover, the sluggish crystallization region ΔTpl-pf, defined as the temperature span between the last exothermic crystallization peak temperature Tpl and the first crystallization exothermic peak temperature Tpf, of all the HE-BMGs is much wider than that of Vitreloy 1. In addition, high-resolution transmission electron microscopy characterization of the crystallized products at different temperatures and the continuous heating transformation diagram which is proposed to estimate the lifetime at any temperature below the melting point further confirm high thermal stability of the HE-BMGs. Surprisingly, all the HE-BMGs show a small fragility value, which contradicts with their low GFA, suggesting that the underlying diffusion mechanism in the liquid and the solid of HE-BMGs is different.

  16. High-power operation of silica-based Raman fiber amplifier at 2147 nm.

    PubMed

    Liu, Jiang; Tan, Fangzhou; Shi, Hongxing; Wang, Pu

    2014-11-17

    We demonstrated a 2147 nm silica-based Raman fiber amplifier with output power of 14.3 W directly pumped with a 1963 nm CW thulium-doped all-fiber MOPA. The 1963 nm thulium-doped all-fiber MOPA is seeded with a 2147 nm thulium-doped all-fiber laser at the same time. The Raman Stokes power shift from 1963 nm to 2147 nm is accomplished in a piece of 50 m silica-based highly nonlinear fiber (HNLF). The conversion efficiency was 38.5% from 1963 nm to 2147 nm in the HNLF. The output power achieved was only currently limited by available 1963 nm input power and the architecture has significant scaling potential. To the best of our knowledge, this is the highest power operation of a Raman fiber amplifier at >2 µm wavelength region. PMID:25402080

  17. Preparation of highly anisotropic cobalt ferrite/silica microellipsoids using an external magnetic field.

    PubMed

    Abramson, Sébastien; Dupuis, Vincent; Neveu, Sophie; Beaunier, Patricia; Montero, David

    2014-08-01

    Magnetic cobalt ferrite/silica microparticles having both an original morphology and an anisotropic nanostructure are synthesized through the use of an external magnetic field and nanoparticles characterized by a high magnetic anisotropy. The association of these two factors implies that the ESE (emulsion and solvent evaporation) sol-gel method employed here allows the preparation of silica microellipsoids containing magnetic nanoparticles aggregated in large chains. It is clearly shown that without this combination, microspheres characterized by an isotropic distribution of the magnetic nanoparticles are obtained. While the chaining of the cobalt ferrite nanoparticles inside the silica matrix is related to the increase of their magnetic dipolar interactions, the ellipsoidal shape of the microparticles may be explained by the elongation of the sol droplets in the direction of the external magnetic field during the synthesis. Because of their highly anisotropic structure, these microparticles exhibit permanent magnetic moments, which are responsible, at a larger scale, for the existence of strong magnetic dipolar interactions. Therefore, when they are dispersed in water, the microellipsoids self-assemble into large and irregular chains. These interactions can be reinforced by the use of external magnetic field, allowing the preparation of very large permanent chains. This research illustrates how nanostructured particles exhibiting complex architectures can be elaborated through simple, fast, and low-cost methods, such as the use of external fields in combination with soft chemistry. PMID:25029515

  18. Development, fabrication and test of a high purity silica heat shield

    NASA Technical Reports Server (NTRS)

    Rusert, E. L.; Drennan, D. N.; Biggs, M. S.

    1978-01-01

    A highly reflective hyperpure ( 25 ppm ion impurities) slip cast fused silica heat shield material developed for planetary entry probes was successfully scaled up. Process development activities for slip casting large parts included green strength improvements, casting slip preparation, aggregate casting, strength, reflectance, and subscale fabrication. Successful fabrication of a one-half scale Saturn probe (shape and size) heat shield was accomplished while maintaining the silica high purity and reflectance through the scale-up process. However, stress analysis of this original aggregate slip cast material indicated a small margin of safety (MS. = +4%) using a factor of safety of 1.25. An alternate hyperpure material formulation to increase the strength and toughness for a greater safety margin was evaluated. The alternate material incorporates short hyperpure silica fibers into the casting slip. The best formulation evaluated has a 50% by weight fiber addition resulting in an 80% increase in flexural strength and a 170% increase in toughness over the original aggregate slip cast materials with comparable reflectance.

  19. Dynamic High-Pressure Behavior of Quartz Silica Sand of Two Different Particle Sizes

    NASA Astrophysics Data System (ADS)

    Kennedy, Gregory; Thadhani, Naresh

    2015-06-01

    The dynamic high-pressure behavior of customized high purity quartz silica sand is presented. The silica was chosen to have rounded grains and controlled size, size distribution, and water content. The customized sand was selected with two narrow size ranges, approximately 100 μm and 500 μm, to provide a range of responses to compare with meso-scale simulations. The materials were pressed into a copper capsule ring connected to a copper driver plate and backed by a PMMA window. Experiments were performed in plate impact light gas gun and powder gun, using VISAR and PDV velocity measurement techniques, and PVDF piezoelectric pressure gauges. The compaction wave velocity was calculated from transit times measured by PVDF gauges placed on either side of the silica samples. Interface particle velocity profiles were recorded by VISAR and PDV at the rear surface of the sample in contact with a PMMA window. Analysis of the details of the shapes of the rise and plateaus in the VISAR and PDV measured velocities reveal a dependence on the size of the particles.

  20. Spherulites and lithophysae—200 years of investigation on high-temperature crystallization domains in silica-rich volcanic rocks

    NASA Astrophysics Data System (ADS)

    Breitkreuz, Christoph

    2013-04-01

    High-temperature crystallization domains (HTCDs) including spherulites and lithophysae form during cooling of silica-rich lava and welded ignimbrites. Spherulites grow in silicate melts or hot glass and they display a radiating or microcrystalline texture, typically consisting of cristobalite, tridymite, and sanidine. Lithophysae are HTCDs comprising one or more cavities. This contribution reviews the research and discussions on HTCDs carried out over the last 200 years. The emphasis, here, is on lithophysae and summarizes current knowledge of their formation. A number of parameters influence the initiation and growth of lithophysae, as well as, their shapes and internal textures. The most likely cause of cavity formation is transient tensional stress that produces a mechanical opening and widening at the interface between the crystallization front and the host melt (e.g., where T > T g ). Cavity growth and expansion forced by rising vapor pressure is considered less important. In some cases, further growth of HTCD cavities results from vapor phase corrosion and brecciation.

  1. Functionalized magnetic mesoporous silica nanoparticles for U removal from low and high pH groundwater.

    PubMed

    Li, Dien; Egodawatte, Shani; Kaplan, Daniel I; Larsen, Sarah C; Serkiz, Steven M; Seaman, John C

    2016-11-01

    U(VI) species display limited adsorption onto sediment minerals and synthetic sorbents in pH <4 or pH >8 groundwater. In this work, magnetic mesoporous silica nanoparticles (MMSNs) with magnetite nanoparticle cores were functionalized with various organic molecules using post-synthetic methods. The functionalized MMSNs were characterized using N2 adsorption-desorption isotherms, thermogravimetric analysis (TGA), transmission electron microscopy (TEM), (13)C cross polarization and magic angle spinning (CPMAS) nuclear magnetic resonance (NMR) spectroscopy, and powder X-ray diffraction (XRD), which indicated that mesoporous silica (MCM-41) particles of 100-200nm formed around a core of magnetic iron oxide, and the functional groups were primarily grafted into the mesopores of ∼3.0nm in size. The functionalized MMSNs were effective for U removal from pH 3.5 and 9.6 artificial groundwater (AGW). Functionalized MMSNs removed U from the pH 3.5 AGW by as much as 6 orders of magnitude more than unfunctionalized nanoparticles or silica and had adsorption capacities as high as 38mg/g. They removed U from the pH 9.6 AGW as much as 4 orders of magnitude greater than silica and 2 orders of magnitude greater than the unfunctionalized nanoparticles with adsorption capacities as high as 133mg/g. These results provide an applied solution for treating U contamination that occurs at extreme pH environments and a scientific foundation for solving critical industrial issues related to environmental stewardship and nuclear power production. PMID:27341378

  2. Optical and structural properties of polycrystalline CVD diamond films grown on fused silica optical fibres pre-treated by high-power sonication seeding

    NASA Astrophysics Data System (ADS)

    Bogdanowicz, R.; Śmietana, M.; Gnyba, M.; Gołunski, Ł.; Ryl, J.; Gardas, M.

    2014-09-01

    In this paper, the growth of polycrystalline chemical vapour deposition (CVD) diamond thin films on fused silica optical fibres has been investigated. The research results show that the effective substrate seeding process can lower defect nucleation, and it simultaneously increases surface encapsulation. However, the growth process on glass requires high seeding density. The effects of suspension type and ultrasonic power were the specific objects of investigation. In order to increase the diamond density, glass substrates were seeded using a high-power sonication process. The highest applied power of sonotrode reached 72 W during the performed experiments. The two, most common diamond seeding suspensions were used, i.e. detonation nanodiamond dispersed in (a) dimethyl sulfoxide and (b) deionised water. The CVD diamond nucleation and growth processes were performed using microwave plasma assisted chemical vapour deposition system. Next, the seeding efficiency was determined and compared using the numerical analysis of scanning electron microscopy images. The molecular composition of nucleated diamond was examined with micro-Raman spectroscopy. The sp3/sp2 band ratio was calculated using Raman spectra deconvolution method. Thickness, roughness, and optical properties of the nanodiamond films in UV-vis wavelength range were investigated by means of spectroscopic ellipsometry. It has been demonstrated that the high-power sonication process can improve the seeding efficiency on glass substrates. However, it can also cause significant erosion defects at the fibre surface. We believe that the proposed growth method can be effectively applied to manufacture the novel optical fibre sensors. Due to high chemical and mechanical resistance of CVD diamond films, deposition of such films on the sensors is highly desirable. This method enables omitting the deposition of an additional adhesion interlayer at the glass-nanocrystalline interface, and thus potentially increases

  3. Elasticity and structure of sodium disilicate glass at high pressures and high temperatures

    NASA Astrophysics Data System (ADS)

    Yu, T.; Kono, Y.; Sakamaki, T.; Jing, Z.; Wang, Y.; Shen, G.

    2012-12-01

    Studying the structures and physical properties of silicate melts under extreme conditions is essential for understanding the dynamics of the earth's interior. A complete understanding of physical and thermodynamic properties of melts at high pressures requires systematic studies from low temperature (super-cooled state - glass) to high temperature (liquid state - melt). In this study, we focus on the super-cooled liquid. Sodium disilicate (Na2Si2O5) glass is a good model material for studying basalt magma since they have similar ratios of non-bridging oxygen to tetrahedrally coordinated cations (NBO/T). Synthesized sodium disilicate glass was loaded into a Paris-Edinburgh (PE) cell and pressed up to 4.5GPa and heated up to 1000oC at the HPCAT beamline 16-BM-B of the Advanced Photon Source. Elastic wave travel times of the amorphous sample were collected using the ultrasonic pulse reflection method with a 10o Y-cut LiNbO3 transducer. X-ray radiographs were used to determine the elastic wave travel distance. Room temperature velocity results show minimum velocity values between 2-3 GPa for both the longitudinal wave velocity (Vp) and the transverse wave velocity (Vs), similar pressure dependence of elastic wave velocities at ambient temperature have also been observed in pure SiO2 from previous studies. Under high pressure (3 GPa), both Vp and Vs for sodium disilicate glass remain nearly constant with increasing temperature before the glass transition temperature (~700oC at ambient pressure). An 8.7% drop in Vp and a 11.9% drop in Vs were observed above the glass transition temperature. Structure information of the glass sample has recently been collected and the results will be presented in the context of observed velocity drops. We acknowledge the supports of COMPRES on facility development, of GSECARS for the Paris-Edinburgh press system, and of HPCAT for elastic wave velocity measurement developments.

  4. Silica-Ceria Hybrid Nanostructures

    SciTech Connect

    Munusamy, Prabhakaran; Sanghavi, Shail P.; Nachimuthu, Ponnusamy; Baer, Donald R.; Thevuthasan, Suntharampillai

    2012-04-25

    A new hybrid material system that consists of ceria attached silica nanoparticles has been developed. Because of the versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and antioxidant properties of ceria nanoparticles, this material system is ideally suited for biomedical applications. The silica particles of size ~50nm were synthesized by the Stöber synthesis method and ceria nanoparticles of size ~2-3nm was attached to the silica surface using a hetrocoagulation method. The presence of silanol groups on the surface of silica particles mediated homogenous nucleation of ceria which were attached to silica surface by Si-O-Ce bonding. The formations of silica-ceria hybrid nanostructures were characterized by X-photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM). The HRTEM image confirms the formation of individual crystallites of ceria nanoparticles attached to the silica surface. The XPS analysis indicates that ceria nanoparticles are chemically bonded to surface of silica and possess mixture of +3 and +4 chemical states.

  5. Silica fertilization and nano-MnO₂ amendment on bacterial community composition in high arsenic paddy soils.

    PubMed

    Shao, Jihai; He, Yaxian; Zhang, Huiling; Chen, Anwei; Lei, Ming; Chen, Junfeng; Peng, Liang; Gu, Ji-Dong

    2016-03-01

    Silica fertilization and nano-MnO2 amendment are reported as useful approaches in lowering the accumulation of arsenic in rice grains, but the effects of silica fertilization or nano-MnO2 amendment on microbial community in the paddy soils containing high concentration of arsenic are still unknown. In order to elucidate this question, the structures and composition of microbial community in the paddy soils, in response to silica fertilization and nano-MnO2 amendment, were investigated using pyrosequencing technique. The results indicated that Proteobacteria, Chloroflexi, and Acidobacteria were the main dominating phyla in these paddy soils. A decrease in the relative abundance of Chloroflexi and Cyanobacteria, but an increase in the relative abundance of Acidobacteria was observed after silica fertilization and nano-MnO2 amendment. The changes of Acidobacteria, Chloroflexi, and Cyanobacteria were strongly correlated with pH and the concentration of bioavailable arsenic in the paddy soils. The α-diversity of bacteria in the paddy soils increased in response to silica fertilization at low amendment level, but decreased under silica or nano-MnO2 amendment at high amendment level. Results of β-diversity analysis indicated that the microbial communities in the control treatment shared more similarity with that of those received low level of nano-MnO2 amendment, and the two silica fertilization treatments also shared more similarity with each other. PMID:26563550

  6. The Effect of High-Pressure Devitrification and Densification on Ballistic-Penetration Resistance of Fused Silica

    NASA Astrophysics Data System (ADS)

    Grujicic, M.; Avuthu, V.; Snipes, J. S.; Ramaswami, S.; Galgalikar, R.

    2015-12-01

    Recent experimental and molecular-level computational analyses have indicated that fused silica, when subjected to pressures of several tens of GPa, can experience irreversible devitrification and densification. Such changes in the fused-silica molecular-level structure are associated with absorption and/or dissipation of the strain energy acquired by fused silica during high-pressure compression. This finding may have important practical consequences in applications for fused silica such as windshields and windows of military vehicles, portholes in ships, ground vehicles, spacecraft, etc. In the present work, our prior molecular-level computational results pertaining to the response of fused silica to high pressures (and shear stresses) are used to enrich a continuum-type constitutive model (that is, the so-called Johnson-Holmquist-2, JH2, model) for this material. Since the aforementioned devitrification and permanent densification processes modify the response of fused silica to the pressure as well as to the deviatoric part of the stress, changes had to be made in both the JH2 equation of state and the strength model. To assess the potential improvements in respect to the ballistic-penetration resistance of this material brought about by the fused-silica devitrification and permanent densification processes, a series of transient non-linear dynamics finite-element analyses of the transverse impact of a fused-silica test plate with a solid right-circular cylindrical steel projectile were conducted. The results obtained revealed that, provided the projectile incident velocity and, hence, the attendant pressure, is sufficiently high, fused silica can undergo impact-induced devitrification, which improves its ballistic-penetration resistance.

  7. Yb{sup 3+},Er{sup 3+} codoped silica-based glasses for planar optical waveguide amplifiers

    SciTech Connect

    Hehlen, M.P.; Gosnell, T.R.; Cockroft, N.J.; Bruce, A.J.; Grodkiewicz, W.H.; Nykolak, G.; Shmulovich, J.; Gosh, R.; Barros, M.R.X.

    1996-04-01

    Spectroscopic properties of Er{sup 3+}-doped and Yb{sup 3+},Er{sup 3+}-codoped sodium- and alumino-silicate glasses, potential planar optical waveguide amplifier materials for 1.55 {mu}m, are investigated. With the exception of {sup 4}I{sub 1 3/2}, multiphonon relaxation is dominant for all Er{sup 3+} excited-state multiplets, allowing efficient population of the emitting {sup 4}I{sub 1 3/2} state by {sup 4}I{sub 1 1/2} excitation around 980 nm. In both glasses, multiphonon relaxation from {sup 4}I{sub 1 3/2} is negligible up to 678 K, and the respective 300 K absolute quantum yields are {similar_to}0.9 for 0.05 mol% Er{sup 3+}-doped samples under low- power {sup 4}I{sub 1 1/2} excitation. OH{sup {minus}} impurities are able to efficiently quench {sup 4}I{sub 1 3/2} excitation. Absolute {sup 4}I{sub 1 3/2} quantum yields are used to predict an optimum Yb{sup 3+},Er{sup 3+} concentration range for sensitization. Yb{sup 3+} codotation strongly enhances pump-light absorption and increases {sup 4}I{sub 1 3/2} population by almost two orders of magnitude in some samples. Relative {sup 2}H{sub 1 1/2}/{sup 4}S{sub 3/2} upconversion luminescence intensities are shown to be a sensitive measure for the substantial internal sample heating observed in Yb{sup 3+} codoped glasses.

  8. Glasses in ancient and young Apollo 16 regolith breccias - Populations and ultra Mg-prime glass

    NASA Technical Reports Server (NTRS)

    Wentworth, Susan J.; Mckay, David S.

    1988-01-01

    Electron microprobe analysis was used to determine the major element compositions of glass spheres and fragments in seven possibly ancient (about 4 Gyr) and three young (less than 4 Gyr) Apollo 16 regolith breccias. It is found that mare glasses are extremely rare in the ancient regolith breccias, and silica-poor gabbroic anorthosite and high-alumina silica-poor glasses are not present in ancient breccias. Ultra Mg-prime glasses are unique to the Apollo 16 regolith breccias and are most common in the ancient breccias. It is suggested that the presence of ultra Mg-prime glasses could indicate the presence of previously unsampled crustal or volcanic rock types on the moon.

  9. LIQUIDUS TEMPERATURE AND PRIMARY CRYSTALLIZATION PHASES IN HIGH-ZIRCONIA HIGH-LEVEL WASTE BOROSILICATE GLASSES

    EPA Science Inventory

    Liquidus temperature (TL) studies of high-Zr high-level waste (HLW) borosilicate glasseshave identified three primary phases: baddelyite (ZrO2), zircon (ZrSiO4), and alkali-zirconiumsilicates, such as parakeldyshite (Na2ZrSi2O7). Using published TL data for HLW glasses withthe...

  10. Mirror substrate fabrication techniques of low expansion glasses.

    NASA Astrophysics Data System (ADS)

    Spangenberg-Jolley, J.; Hobbs, T.

    1989-04-01

    Low expansion glasses offer many advantages as mirror blank materials due to their thermal and mechanical properties as well as the flexibility they offer in design and fabrication. Fused Silica, Corning Code 7940 and ULETM titanium silicate, Code 7971, produced by the flame hydrolysis process, are high purity and homogeneous glasses. The ability to fusion seal each of the glasses offers mirror manufacturing design freedom of shape, size and weight.

  11. High-level waste borosilicate glass: A compendium of corrosion characteristics. Volume 3

    SciTech Connect

    Cunnane, J.C.; Bates, J.K.; Bradley, C.R.

    1994-03-01

    The objective of this document is to summarize scientific information pertinent to evaluating the extent to which high-level waste borosilicate glass corrosion and the associated radionuclide release processes are understood for the range of environmental conditions to which waste glass may be exposed in service. Alteration processes occurring within the bulk of the glass (e.g., devitrification and radiation-induced changes) are discussed insofar as they affect glass corrosion. Volume III contains a bibliography of glass corrosion studies, including studies that are not cited in Volumes I and II.

  12. ANNUAL PROGRESS REPORT. THE AQUEOUS THERMODYNAMICS AND COMPLEXATION REACTIONS OF ANIONIC SILICA SPECIES TO HIGH CONCENTRATION: EFFECTS ON NEUTRALIZATION OF LEAKED TANK WASTES AND MIGRATION OF RADIONUC

    EPA Science Inventory

    In this project, we are determining the aqueous thermodynamics and speciation of dissolved silica and silica-radionuclide complexes to high silica concentration using a combination of 1) studies of chemical species structure and composition (via nuclear magnetic resonance and, wh...

  13. Synthesis, tailoring and characterization of silica nanoparticles containing a highly stable ruthenium complex

    NASA Astrophysics Data System (ADS)

    Wencel, D.; Dolan, C.; Barczak, M.; Keyes, T. E.; McDonagh, C.

    2013-09-01

    This paper describes the synthesis and characterization of sol-gel silica nanoparticles (NPs) derived from tetraethoxysilane (TEOS) and from tetraethoxysilane and methyltriethoxysilane (TEOS-MTEOS) in which is encapsulated, an in-house synthesized, stable oxygen-sensitive ruthenium complex, ruthenium (II) (bis-2,2-bipyridyl)-2(4-carboxylphenyl) imidazo[4,5-f][1,10]phenanthroline. These NPs were characterized using dynamic light scattering, transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy and Brunauer-Emmett-Teller analysis. The spherical, stable and monodispersed NPs have been prepared using the Stöber method. It was found that the addition of prehydrolyzed MTEOS-based sol prepared in an acidic environment to the reaction mixture containing TEOS NPs synthesized for 6 h produced material with increased porosity when compared to pure silica NPs. Oxygen sensitivity, stability, photobleaching and leaching have been characterized. The hybrid NPs exhibit enhanced O2 sensitivity but a high degree of leaching when compared to pure silica NPs, which have minimum O2 sensitivity and no leaching.

  14. Lead iron phosphate glass as a containment medium for disposal of high-level nuclear waste

    DOEpatents

    Boatner, Lynn A.; Sales, Brian C.

    1989-01-01

    Lead-iron phosphate glasses containing a high level of Fe.sub.2 O.sub.3 for use as a storage medium for high-level radioactive nuclear waste. By combining lead-iron phosphate glass with various types of simulated high-level nuclear waste, a highly corrosion resistant, homogeneous, easily processed glass can be formed. For corroding solutions at 90.degree. C., with solution pH values in the range between 5 and 9, the corrosion rate of the lead-iron phosphate nuclear waste glass is at least 10.sup.2 to 10.sup.3 times lower than the corrosion rate of a comparable borosilicate nuclear waste glass. The presence of Fe.sub.2 O.sub.3 in forming the lead-iron phosphate glass is critical. Lead-iron phosphate nuclear waste glass can be prepared at temperatures as low as 800.degree. C., since they exhibit very low melt viscosities in the 800.degree. to 1050.degree. C. temperature range. These waste-loaded glasses do not readily devitrify at temperatures as high as 550.degree. C. and are not adversely affected by large doses of gamma radiation in H.sub.2 O at 135.degree. C. The lead-iron phosphate waste glasses can be prepared with minimal modification of the technology developed for processing borosilicate glass nuclear wasteforms.

  15. Aptamer-Functionalized Fluorescent Silica Nanoparticles for Highly Sensitive Detection of Leukemia Cells

    NASA Astrophysics Data System (ADS)

    Tan, Juntao; Yang, Nuo; Hu, Zixi; Su, Jing; Zhong, Jianhong; Yang, Yang; Yu, Yating; Zhu, Jianmeng; Xue, Dabin; Huang, Yingying; Lai, Zongqiang; Huang, Yong; Lu, Xiaoling; Zhao, Yongxiang

    2016-06-01

    A simple, highly sensitive method to detect leukemia cells has been developed based on aptamer-modified fluorescent silica nanoparticles (FSNPs). In this strategy, the amine-labeled Sgc8 aptamer was conjugated to carboxyl-modified FSNPs via amide coupling between amino and carboxyl groups. Sensitivity and specificity of Sgc8-FSNPs were assessed using flow cytometry and fluorescence microscopy. These results showed that Sgc8-FSNPs detected leukemia cells with high sensitivity and specificity. Aptamer-modified FSNPs hold promise for sensitive and specific detection of leukemia cells. Changing the aptamer may allow the FSNPs to detect other types of cancer cells.

  16. Aptamer-Functionalized Fluorescent Silica Nanoparticles for Highly Sensitive Detection of Leukemia Cells.

    PubMed

    Tan, Juntao; Yang, Nuo; Hu, Zixi; Su, Jing; Zhong, Jianhong; Yang, Yang; Yu, Yating; Zhu, Jianmeng; Xue, Dabin; Huang, Yingying; Lai, Zongqiang; Huang, Yong; Lu, Xiaoling; Zhao, Yongxiang

    2016-12-01

    A simple, highly sensitive method to detect leukemia cells has been developed based on aptamer-modified fluorescent silica nanoparticles (FSNPs). In this strategy, the amine-labeled Sgc8 aptamer was conjugated to carboxyl-modified FSNPs via amide coupling between amino and carboxyl groups. Sensitivity and specificity of Sgc8-FSNPs were assessed using flow cytometry and fluorescence microscopy. These results showed that Sgc8-FSNPs detected leukemia cells with high sensitivity and specificity. Aptamer-modified FSNPs hold promise for sensitive and specific detection of leukemia cells. Changing the aptamer may allow the FSNPs to detect other types of cancer cells. PMID:27299653

  17. Mechanisms of optical losses in the 5D4 and 5D3 levels in Tb3+ doped low silica calcium aluminosilicate glasses

    NASA Astrophysics Data System (ADS)

    dos Santos, J. F. M.; Terra, I. A. A.; Astrath, N. G. C.; Guimarães, F. B.; Baesso, M. L.; Nunes, L. A. O.; Catunda, T.

    2015-02-01

    Trivalent Tb-doped materials exhibit strong emission in the green and weak emission in the UV-blue levels. Usually, this behavior is attributed to the cross relaxation (CR) process. In this paper, the luminescence properties of Tb3+-doped low silica calcium aluminosilicate glasses are analyzed for UV (λexc = 325 nm) and visible (488 nm) excitations. Under 325 nm excitation, the intensity of green luminescence increases proportionally to Tb3+ concentration. However, the blue luminescence intensity is strongly reduced with the increase of concentration from 0.5-15.0 wt. %. In the case of 488 nm excitation, a saturation behavior of the green emission is observed at intensities two orders of magnitude smaller than expected for bleaching of the ground state population. Using a rate equation model, we showed that this behavior can be explained by an excited state absorption cross section two orders of magnitude larger than the ground state absorption. The blue emission is much weaker than expected from our rate equations (325 nm and 488 nm excitation). We concluded that only the CR process cannot explain the overall feature of measured luminescence quenching in the wide range of Tb3+ concentrations. Cooperative upconversion from a pair of excited ions (5D3:5D3 or 5D3:5D4) and other mechanisms involving upper lying states (4f5d, charge transfer, host matrix, defects, etc.) may play a significant role.

  18. Sol-gel synthesis of nanocomposite materials based on lithium niobate nanocrystals dispersed in a silica glass matrix

    NASA Astrophysics Data System (ADS)

    Marenna, Elisa; Aruta, Carmela; Fanelli, Esther; Barra, Mario; Pernice, Pasquale; Aronne, Antonio

    2009-05-01

    With the final goal to obtain thin films containing stoichiometric lithium niobate nanocrystals embedded in an amorphous silica matrix, the synthesis strategy used to set a new inexpensive sol-gel route to prepare nanocomposite materials in the Li 2O-Nb 2O 5-SiO 2 system is reported. In this route, LiNO 3, NbCl 5 and Si(OC 2H 5) 4 were used as starting materials. The gels were annealed at different temperatures and nanocrystals of several phases were formed. Futhermore, by controlling the gel compositions and the synthesis parameters, it was possible to obtain LiNbO 3 as only crystallizing phase. LiNbO 3-SiO 2 nanocomposite thin films on Si-SiO 2 and Al 2O 3 substrates were grown. The LiNbO 3 average size, increasing with the annealing temperature, was 27 nm for a film of composition 10Li 2O-10Nb 2O 5-80SiO 2 heated 2 h at 800 °C. Electrical investigation revealed that the nanocrystals size strongly affects the film conductivity and the occurrence of hysteretic current-voltage curves.

  19. In situ high-temperature infrared emissivity spectroscopy of silicate glasses and glass-ceramics

    NASA Astrophysics Data System (ADS)

    Santos, Cristiane N.; de Sousa Meneses, Domingos; Montouillout, Valerie; Echegut, Patrick

    2011-03-01

    Glasses and glass-ceramics are materials of widespread application in industry, building, photonics, microelectronics and medicine. Glass-ceramics are obtained by controlled glass crystallization, and many efforts have been done in the last years to better understand the structural changes occurring in this process. Here we show that in situ infrared emissivity spectroscopy is also a suitable technique for this purpose and a wide spectral and temperature range could be accessed (25-16000 cm-1 and 400-1700 K, respectively). We use a home-made instrument composed of two spectrometers, and a CO2 laser for locally heat the glass samples up to the melt. A dielectric function model was applied to fit the experimental data and compute the materials optical properties. We show that using new decomposition procedure quantitative information on the distribution of the Qn tetrahedral units (n being the number of bridging oxygen) can be obtained. The results at room temperature are in good agreement with recent molecular dynamics simulations. The major changes occur during quartz crystallization, with a remarkable increase of Q4 units. Supported by ANR Postre.

  20. SETTLING OF SPINEL IN A HIGH-LEVEL WASTE GLASS MELTER

    SciTech Connect

    Pavel Hrma; Pert Schill; Lubomir Nemec

    2002-01-07

    High-level nuclear waste is being vitrified, i.e., converted to a durable glass that can be stored in a safe repository for hundreds of thousands of years. Waste vitrification is accomplished in reactors called melters to which the waste is charged together with glass-forming additives. The mixture is electrically heated to a temperature as high as 1150 decrees C to create a melt that becomes glass on cooling.

  1. Fabrication and characterization of a silicon cantilever probe with an integrated quartz-glass (fused-silica) tip for scanning near-field optical microscopy.

    PubMed

    Schürmann, G; Noell, W; Staufer, U; de Rooij, N F; Eckert, R; Freyland, J M; Heinzelmann, H

    2001-10-01

    A cantilever-based probe is introduced for use in scanning near-field optical microscopy (SNOM) combined with scanning atomic-force microscopy (AFM). The probes consist of silicon cantilevers with integrated 25-mum-high fused-silica tips. The probes are batch fabricated by microfabrication technology. Transmission electron microscopy reveals that the transparent quartz tips are completely covered with an opaque aluminum layer before the SNOM measurement. Static and dynamic AFM imaging was performed. SNOM imaging in transmission mode of single fluorescent molecules shows an optical resolution better than 32 nm. PMID:18364783

  2. Disposition of actinides released from high-level waste glass

    SciTech Connect

    Ebert, W.L.; Bates, J.K.; Buck, E.C.; Gong, M.; Wolf, S.F.

    1994-05-01

    A series of static leach tests was conducted using glasses developed for vitrifying tank wastes at the Savannah River Site to monitor the disposition of actinide elements upon corrosion of the glasses. In these tests, glasses produced from SRL 131 and SRL 202 frits were corroded at 90{degrees}C in a tuff groundwater. Tests were conducted using crushed glass at different glass surface area-to-solution volume (S/V) ratios to assess the effect of the S/V on the solution chemistry, the corrosion of the glass, and the disposition of actinide elements. Observations regarding the effects of the S/V on the solution chemistry and the corrosion of the glass matrix have been reported previously. This paper highlights the solution analyses performed to assess how the S/V used in a static leach test affects the disposition of actinide elements between fractions that are suspended or dissolved in the solution, and retained by the altered glass or other materials.

  3. Bulk metallic glass composite with good tensile ductility, high strength and large elastic strain limit

    PubMed Central

    Wu, Fu-Fa; Chan, K. C.; Jiang, Song-Shan; Chen, Shun-Hua; Wang, Gang

    2014-01-01

    Bulk metallic glasses exhibit high strength and large elastic strain limit but have no tensile ductility. However, bulk metallic glass composites reinforced by in-situ dendrites possess significantly improved toughness but at the expense of high strength and large elastic strain limit. Here, we report a bulk metallic glass composite with strong strain-hardening capability and large elastic strain limit. It was found that, by plastic predeformation, the bulk metallic glass composite can exhibit both a large elastic strain limit and high strength under tension. These unique elastic mechanical properties are attributed to the reversible B2↔B19′ phase transformation and the plastic-predeformation-induced complicated stress state in the metallic glass matrix and the second phase. These findings are significant for the design and application of bulk metallic glass composites with excellent mechanical properties. PMID:24931632

  4. PERFORMANCE OF A BURIED RADIOACTIVE HIGH LEVEL WASTE GLASS AFTER 24 YEARS

    SciTech Connect

    Jantzen, C; Daniel Kaplan, D; Ned Bibler, N; David Peeler, D; John Plodinec, J

    2008-05-05

    A radioactive high level waste glass was made in 1980 with Savannah River Site (SRS) Tank 15 waste. This glass was buried in the SRS burial ground for 24 years but lysimeter data was only available for the first 8 years. The glass was exhumed and analyzed in 2004. The glass was predicted to be very durable and laboratory tests confirmed the durability response. The laboratory results indicated that the glass was very durable as did analysis of the lysimeter data. Scanning electron microscopy of the glass burial surface showed no significant glass alteration consistent with the results of the laboratory and field tests. No detectable Pu, Am, Cm, Np, or Ru leached from the glass into the surrounding sediment. Leaching of {beta}/{delta} from {sup 90}Sr and {sup 137}Cs in the glass was diffusion controlled. Less than 0.5% of the Cs and Sr in the glass leached into the surrounding sediment, with >99% of the leached radionuclides remaining within 8 centimeters of the glass pellet.

  5. [INVITED] Laser welding of glasses at high repetition rates - Fundamentals and prospects

    NASA Astrophysics Data System (ADS)

    Richter, Sören; Zimmermann, Felix; Tünnermann, Andreas; Nolte, Stefan

    2016-09-01

    We report on the welding of various glasses with ultrashort laser pulses. Femtosecond laser pulses at repetition rates in the MHz range are focused at the interface between two substrates, resulting in multiphoton absorption and heat accumulation from successive pulses. This leads to local melting and subsequent resolidification which can be used to weld the glasses. The fundamental interaction process was studied using an in-situ micro Raman setup to measure the laser induced temperature distribution and its temporal decay. The induced network changes were analyzed by Raman spectrocopy identifying an increase of three and four membered silicon rings within the laser irradiated area. In order to determine the stability of the laser welded samples a three point bending test was used. Thereby, we identified that the maximal achievable breaking strength is limited by laser induced stress surrounding the modified material. To minimize the amount of stress bursts of laser pulses or an post processing annealing step can be applied. Besides fused silica, we welded borosilicate glasses and glasses with a low thermal expansion coefficient. Even the welding of different glass combinations is possible demonstrating the versatility of ultrashort pulse induced laser welding.

  6. High-Quality Hollow Closed-Pore Silica Antireflection Coatings Based on Styrene-Acrylate Emulsion @ Organic-Inorganic Silica Precursor.

    PubMed

    Guo, Zhaolong; Zhao, Haixin; Zhao, Wei; Wang, Tao; Kong, Depeng; Chen, Taojing; Zhang, Xiaoyan

    2016-05-11

    Making use of a facile and low-cost way for the preparation of a hierarchically organized novel hollow closed-pore silica antireflective coating (CHAR) with tailored optical properties and a mechanical reliability is of great interest in the field of solar photovoltaic technology. The process mainly contains two aspects: (1) a styrene-acrylate emulsion @ organic-inorganic silica precursor (SA@OISP) core/shell hierarchical nanostructure, consisting of a sacrificial styrene-acrylate (SA) primary template, was fabricated using a sol-gel method; (2) the self-assembly of the nanostructures leads to SA@OISP nanospheres forming the high-quality hollow closed-pore silica antireflection coating (CHAR) by a dip-coating process and a subsequent calcination treatment. The resulting SA@OISP nanospheres have a mean diameter of 65.2 nm and contained a SA soft core with a mean diameter of approximately 54.8 nm and an organic-inorganic silica precursor (OISP) shell with a thickness of approximately 6-10 nm. Furthermore, the prepared CHAR film exhibited a high transmittance and good ruggedness. An average transmittance (TAV) of 97.64% was obtained, and the value is close to the ideal single-layered antireflection coating (98.09%) over a broad range of wavelengths (from 380 to 1100 nm). The CHAR film showed a stable TAV, with attenuation values of less than 0.8% and 0.43% after the abrasion test and the damp heat test, respectively. The conversion efficiency of the CHAR coating cover solar modules tends to be increased by 3.75%. The promising results obtained in this study suggest that the CHAR film was considered as an essential component of the solar module and were expected to provide additional solar energy harvest under extreme outdoor climates. PMID:27104837

  7. Thermally Stable Nanocatalyst for High Temperature Reactions: Pt-Mesoporous Silica Core-Shell Nanoparticles

    SciTech Connect

    Joo, Sang Hoon; Park, J.Y.; Tsung, C.-K.; Yamada, Y.; Yang, P.; Somorjai, G.A.

    2008-10-25

    Recent advances in colloidal synthesis enabled the precise control of size, shape and composition of catalytic metal nanoparticles, allowing their use as model catalysts for systematic investigations of the atomic-scale properties affecting catalytic activity and selectivity. The organic capping agents stabilizing colloidal nanoparticles, however, often limit their application in high-temperature catalytic reactions. Here we report the design of a high-temperature stable model catalytic system that consists of Pt metal core coated with a mesoporous silica shell (Pt{at}mSiO{sub 2}). While inorganic silica shells encaged the Pt cores up to 750 C in air, the mesopores directly accessible to Pt cores made the Pt{at}mSiO{sub 2} nanoparticles as catalytically active as bare Pt metal for ethylene hydrogenation and CO oxidation. The high thermal stability of Pt{at}mSiO{sub 2} nanoparticles permitted high-temperature CO oxidation studies, including ignition behavior, which was not possible for bare Pt nanoparticles because of their deformation or aggregation. The results suggest that the Pt{at}mSiO{sub 2} nanoparticles are excellent nanocatalytic systems for high-temperature catalytic reactions or surface chemical processes, and the design concept employed in the Pt{at}mSiO{sub 2} core-shell catalyst can be extended to other metal-metal oxide compositions.

  8. Polyimide/Glass Composite High-Temperature Insulation

    NASA Technical Reports Server (NTRS)

    Pater, Ruth H.; Vasquez, Peter; Chatlin, Richard L.; Smith, Donald L.; Skalski, Thomas J.; Johnson, Gary S.; Chu, Sang-Hyon

    2009-01-01

    Lightweight composites of RP46 polyimide and glass fibers have been found to be useful as extraordinarily fire-resistant electrical-insulation materials. RP46 is a polyimide of the polymerization of monomeric reactants (PMR) type, developed by NASA Langley Research Center. RP46 has properties that make it attractive for use in electrical insulation at high temperatures. These properties include high-temperature resistance, low relative permittivity, low dissipation factor, outstanding mechanical properties, and excellent resistance to moisture and chemicals. Moreover, RP46 contains no halogen or other toxic materials and when burned it does not produce toxic fume or gaseous materials. The U. S. Navy has been seeking lightweight, high-temperature-resistant electrical-insulation materials in a program directed toward reducing fire hazards and weights in ship electrical systems. To satisfy the requirements of this program, an electrical-insulation material must withstand a 3-hour gas-flame test at 1,600 F (about 871 C). Prior to the development reported here, RP46 was rated for use at temperatures from -150 to +700 F (about -101 to 371 C), and no polymeric product - not even RP46 - was expected to withstand the Navy 3-hour gas-flame test.

  9. High pressure dielectric studies on the structural and orientational glass.

    PubMed

    Kaminska, E; Tarnacka, M; Jurkiewicz, K; Kaminski, K; Paluch, M

    2016-02-01

    High pressure dielectric studies on the H-bonded liquid D-glucose and Orientationally Disordered Crystal (ODIC) 1,6-anhydro-D-glucose (levoglucosan) were carried out. It was shown that in both compounds, the structural relaxation is weakly sensitive to compression. It is well reflected in the low pressure coefficient of the glass transition and orientational glass transition temperatures which is equal to 60 K/GPa for both D-glucose and 1,6-anhydro-D-glucose. Although it should be noted that ∂Tg(0)/∂p evaluated for the latter compound seems to be enormously high with respect to other systems forming ODIC phase. We also found that the shape of the α-loss peak stays constant for the given relaxation time independently on the thermodynamic condition. Consequently, the Time Temperature Pressure (TTP) rule is satisfied. This experimental finding seems to be quite intriguing since the TTP rule was shown to work well in the van der Waals liquids, while in the strongly associating compounds, it is very often violated. We have also demonstrated that the sensitivity of the structural relaxation process to the temperature change measured by the steepness index (mp) drops with pressure. Interestingly, this change is much more significant in the case of D-glucose with respect to levoglucosan, where the fragility changes only slightly with compression. Finally, kinetics of ODIC-crystal phase transition was studied at high compression. It is worth mentioning that in the recent paper, Tombari and Johari [J. Chem. Phys. 142, 104501 (2015)] have shown that ODIC phase in 1,6-anhydro-D-glucose is stable in the wide range of temperatures and there is no tendency to form more ordered phase at ambient pressure. On the other hand, our isochronal measurements performed at varying thermodynamic conditions indicated unquestionably that the application of pressure favors solid (ODIC)-solid (crystal) transition in 1,6-anhydro-D-glucose. This result mimics the impact of pressure on the

  10. High pressure dielectric studies on the structural and orientational glass

    NASA Astrophysics Data System (ADS)

    Kaminska, E.; Tarnacka, M.; Jurkiewicz, K.; Kaminski, K.; Paluch, M.

    2016-02-01

    High pressure dielectric studies on the H-bonded liquid d-glucose and Orientationally Disordered Crystal (ODIC) 1,6-anhydro-d-glucose (levoglucosan) were carried out. It was shown that in both compounds, the structural relaxation is weakly sensitive to compression. It is well reflected in the low pressure coefficient of the glass transition and orientational glass transition temperatures which is equal to 60 K/GPa for both d-glucose and 1,6-anhydro-d-glucose. Although it should be noted that ∂ Tg 0 / ∂ p evaluated for the latter compound seems to be enormously high with respect to other systems forming ODIC phase. We also found that the shape of the α-loss peak stays constant for the given relaxation time independently on the thermodynamic condition. Consequently, the Time Temperature Pressure (TTP) rule is satisfied. This experimental finding seems to be quite intriguing since the TTP rule was shown to work well in the van der Waals liquids, while in the strongly associating compounds, it is very often violated. We have also demonstrated that the sensitivity of the structural relaxation process to the temperature change measured by the steepness index (mp) drops with pressure. Interestingly, this change is much more significant in the case of d-glucose with respect to levoglucosan, where the fragility changes only slightly with compression. Finally, kinetics of ODIC-crystal phase transition was studied at high compression. It is worth mentioning that in the recent paper, Tombari and Johari [J. Chem. Phys. 142, 104501 (2015)] have shown that ODIC phase in 1,6-anhydro-d-glucose is stable in the wide range of temperatures and there is no tendency to form more ordered phase at ambient pressure. On the other hand, our isochronal measurements performed at varying thermodynamic conditions indicated unquestionably that the application of pressure favors solid (ODIC)-solid (crystal) transition in 1,6-anhydro-d-glucose. This result mimics the impact of pressure on the

  11. Fused silica windows for solar receiver applications

    NASA Astrophysics Data System (ADS)

    Hertel, Johannes; Uhlig, Ralf; Söhn, Matthias; Schenk, Christian; Helsch, Gundula; Bornhöft, Hansjörg

    2016-05-01

    A comprehensive study of optical and mechanical properties of quartz glass (fused silica) with regard to application in high temperature solar receivers is presented. The dependence of rupture strength on different surface conditions as well as high temperature is analyzed, focussing particularly on damage by devitrification and sandblasting. The influence of typical types of contamination in combination with thermal cycling on the optical properties of fused silica is determined. Cleaning methods are compared regarding effectiveness on contamination-induced degradation for samples with and without antireflective coating. The FEM-aided design of different types of receiver windows and their support structure is presented. A large-scale production process has been developed for producing fused silica dome shaped windows (pressurized window) up to a diameter of 816 mm. Prototypes were successfully pressure-tested in a test bench and certified according to the European Pressure Vessel Directive.

  12. Highly sensitive and stable relative humidity sensors based on WO3 modified mesoporous silica

    NASA Astrophysics Data System (ADS)

    Tomer, Vijay K.; Duhan, Surender

    2015-02-01

    This study investigates the effectiveness of using WO3 loaded mesoporous silica nanocomposite developed using one step hydrothermal method for measuring relative humidity (RH) at room temperature. On measuring the sensing response, the nanocomposite sensor exhibits excellent linearity, negligible hysteresis, swift response and recovery time, good repeatability, and outstanding stability in 11%-98% RH range. The complex impedance spectra of the sensor at different RHs were used to explore the humidity sensing mechanism. This work could encourage a right approach to blueprint practical humidity sensors with high sensitivity, long stability and fast response/recovery time.

  13. An XPS study of the optimum loading of barium on high-silica MFI zeolite

    NASA Astrophysics Data System (ADS)

    Mohamed, M. H.; Abdillahi, M. M.; Abbas, N. M.; Siddiqui, A. B.

    1995-12-01

    X-ray photoelectron spectroscopy (XPS) has been applied to the characterization of barium-impregnated MFI high-silica zeolites which are used for the conversion of methanol to light alkenes. X-ray photoelectron spectroscopy provided information about the degree of the dispersion of the various barium loadings on the silicalite structure, and this information helped in elucidating the observed relationship between the activity/selectivity of the catalysts and the barium loading. The XPS results also helped in predicting that the performance of the catalyst would be optimized at 4 wt% Ba loading which was found to agree with the catalytic conversion of methanol to light alkenes.

  14. Morphology evolution of fused silica surface during ion beam figuring of high-slope optical components.

    PubMed

    Liao, Wenlin; Dai, Yifan; Xie, Xuhui; Zhou, Lin

    2013-06-01

    Ultra-precision and ultra-smooth surfaces are vitally important for some high performance optical systems. Ion beam figuring (IBF) is a well-established, highly deterministic method for the final precision figuring of extremely high quality optical surfaces, whereas ion sputtering induced smoothing, or roughening for nanoscale surface morphology, strongly depends on the processing conditions. Usually, an improper machining method would arouse the production of nanoscale patterns leading to the coarsening of the optical surface. In this paper, the morphology evolution mechanism on a fused silica surface during IBF of high-slope optical components has been investigated by means of atomic force microscopy. Figuring experiments are implemented on two convex spherical surfaces by using different IBF methods. Both of their surface errors are rapidly reduced to 1.2 nm root mean square (RMS) after removing similar deep material, but their surfaces are characterized with obviously different nanoscale morphologies. The experimental results indicate that the ion incidence angle dominates the microscopic morphology during the IBF process. At near-normal incidence, fused silica achieves an ultra-smooth surface with an RMS roughness value R(q) down to 0.1 nm, whereas nanoscale ripple patterns are observed at a large incidence angle with an R(q) value increasing to more than 0.9 nm. Additionally, the difference of incidence angles on various machined areas would influence the uniformity of surface quality, resulting from the interplay between the smoothing and roughening effects induced by ion sputtering. PMID:23736325

  15. Highly sensitive and fast response gas sensor based on a light reflection at the glass-photonic crystal interface

    NASA Astrophysics Data System (ADS)

    Kuchyanov, A. S.; Chubakov, P. A.; Plekhanov, A. I.

    2015-09-01

    We develop a versatile gas sensor based on the condition for total internal reflection at the glass-photonic crystal interface and corresponding detection scheme for rapid and precise measurement of vapors. The sensor consists of a vapor sensitive photonic crystal film as a Fabry-Perot etalon coated on a solid substrate (e.g., large face of a glass prism or glass slide). Such scheme and specific physicochemical properties of submicron silica particles provide photonic crystal sensor selectivity due to the capillary condensation of ammonia vapor with a sensitivity of 1 ppm with a response time of 100 ms.

  16. Luminescence in the fluoride-containing phosphate-based glasses: a possible origin of their high resistance to nanosecond pulse laser-induced damage.

    PubMed

    Wang, Pengfei; Lu, Min; Gao, Fei; Guo, Haitao; Xu, Yantao; Hou, Chaoqi; Zhou, Zhiwei; Peng, Bo

    2015-01-01

    Fusion power offers the prospect of an almost inexhaustible source of energy for future generations. It was reported that fusion fuel gains exceeding unity on the National Ignition Facility (NIF) were achieved, but so far great deal of scientific and engineering challenges have to be overcome for realizing fusion power generation. There is a bottleneck for color-separation gratings in NIF and other similar inertial confinement fusion (ICF) lasers. Here we show a series of high performance phosphate-based glasses that can transmit the third harmonic frequency (3ω) laser light with high efficiency meanwhile filter the fundamental (1ω) and the second harmonic frequency (2ω) laser lights through direct absorption, and especially they exhibit excellent damage threshold induced by nanosecond pulse laser compared with that of the fused silica used in NIF. Yellowish-orange fluorescence emits during the laser-material interaction process, and it can be tailored through regulating the glass structure. Study on its structural origin suggests that the fluorescence emission is a key factor that conduces to the high laser-induced damage resistance of these glasses. The results also indicated the feasibility of utilizing these high performance glasses in novel color separation optics, allowing novel design for the final optics assembly in ICF lasers. PMID:25716328

  17. Luminescence in the fluoride-containing phosphate-based glasses: A possible origin of their high resistance to nanosecond pulse laser-induced damage

    NASA Astrophysics Data System (ADS)

    Wang, Pengfei; Lu, Min; Gao, Fei; Guo, Haitao; Xu, Yantao; Hou, Chaoqi; Zhou, Zhiwei; Peng, Bo

    2015-02-01

    Fusion power offers the prospect of an almost inexhaustible source of energy for future generations. It was reported that fusion fuel gains exceeding unity on the National Ignition Facility (NIF) were achieved, but so far great deal of scientific and engineering challenges have to be overcome for realizing fusion power generation. There is a bottleneck for color-separation gratings in NIF and other similar inertial confinement fusion (ICF) lasers. Here we show a series of high performance phosphate-based glasses that can transmit the third harmonic frequency (3ω) laser light with high efficiency meanwhile filter the fundamental (1ω) and the second harmonic frequency (2ω) laser lights through direct absorption, and especially they exhibit excellent damage threshold induced by nanosecond pulse laser compared with that of the fused silica used in NIF. Yellowish-orange fluorescence emits during the laser-material interaction process, and it can be tailored through regulating the glass structure. Study on its structural origin suggests that the fluorescence emission is a key factor that conduces to the high laser-induced damage resistance of these glasses. The results also indicated the feasibility of utilizing these high performance glasses in novel color separation optics, allowing novel design for the final optics assembly in ICF lasers.

  18. Characterization of high-level nuclear waste glass using magnetic measurements

    SciTech Connect

    Senftle, F.E.; Thorpe, A.N.; Grant, J.R.; Barkatt, A.

    1994-12-31

    Magnetic measurements constitute a promising method for the characterization of nuclear waste glasses in view of their simplicity and small sample weight requirements. Initial studies of simulated high-level waste glasses show that the Curie constant is generally a useful indicator of the Fe{sup 2+}:Fe{sup 3+} ratio. Glasses produced by air-cooling in large vessels show systematic deviations between experimental and calcined values, which are indicative of the presence of small amounts of crystalline iron-containing phases. Most of the iron in these phases becomes dissolved in the glass upon re-heating and more rapid quenching. The studies further show that upon leaching the glass in water some of the iron in the surface regions of the glass is converted to a form which has high temperature-independent magnetic susceptibility.

  19. Hydrothermal transformations in an aluminophosphate glass matrix containing simulators of high-level radioactive wastes

    NASA Astrophysics Data System (ADS)

    Yudintsev, S. V.; Mal'kovsky, V. I.; Mokhov, A. V.

    2016-05-01

    The interaction of aluminophosphate glass with water at 95°C for 35 days results in glass heterogenization and in the appearance of a gel layer and various phases. The leaching rate of elements is low owing to the formation of a protective layer on the glass surface. It is shown that over 80% of uranium leached from the glass matrix occurs as colloids below 450 nm in size characterized by high migration ability in the geological environment. To determine the composition of these colloids is a primary task for further studies. Water vapor is a crystallization factor for glasses. The conditions as such may appear even at early stages of glass storage because of the failure of seals on containers of high-level radioactive wastes. The examination of water resistance of crystallized matrices and determination of the fraction of radionuclide in colloids are also subjects for further studies.

  20. In-line silica capillary tube all-silica fiber-optic Fabry-Perot interferometric sensor for detecting high intensity focused ultrasound fields.

    PubMed

    Wang, D H; Wang, S J; Jia, P G

    2012-06-01

    Aiming at detecting high intensity focused ultrasound (HIFU) fields, this letter reports on a novel in-line silica capillary tube all-silica fiber-optic Fabry-Perot (ILSCT-ASFP) interferometric sensor fabricated by splicing a commercially available silica capillary tube to two single-mode fibers. The experimental results show that such a novel ILSCT-ASFP interferometric sensor with a cavity length of ∼60.76 μm has an excellent fringe visibility of up to ∼20 dB, and the fringe visibility is still good when the cavity length extends up to ∼1031.07 μm. The measured wavelength-temperature sensitivity of 0.000858 nm/°C shows that the wavelength drift of the fabricated ILSCT-ASFP interferometric sensor towards temperature is extremely low. Meanwhile, the measurement of HIFU fields by this novel sensor is demonstrated, and the experimental results indicate that the signal-to-noise ratio of the sensing system for sensing a 0.93 MHz HIFU field with a pressure of 2.69 MPa in the focus area can reach 42.8 dB. The corresponding noise equivalent pressure is 0.0194 MPa, and the calculated acoustic sensitivity is 65.4 mV/MPa over a 2.5 MHz measurement bandwidth. PMID:22660116

  1. High Glass Transition Temperature Renewable Polymers via Biginelli Multicomponent Polymerization.

    PubMed

    Boukis, Andreas C; Llevot, Audrey; Meier, Michael A R

    2016-04-01

    A novel and straightforward one-pot multicomponent polycondensation method was established in this work. The Biginelli reaction is a versatile multicomponent reaction of an aldehyde, a β-ketoester (acetoacetate) and urea, which can all be obtained from renewable resources, yielding diversely substituted 3,4-dihydropyrimidin-2(1H)-ones (DHMPs). In this study, renewable diacetoacetate monomers with different spacer chain lengths (C3, C6, C10, C20) were prepared via simple transesterification of renewable diols and commercial acetoacetates. The diacetoacetate monomers were then reacted with renewable dialdehydes, i.e., terephthalaldehyde and divanillin in a Biginelli type step-growth polymerization. The obtained DHMP polymers (polyDHMPs) displayed high molar masses, high glass transition temperatures (Tg) up to 203 °C and good thermal stability (Td5%) of 280 °C. The Tg of the polyDHMPs could be tuned by variation of the structure of the dialdehyde or the diacetoacetate component. PMID:26800511

  2. Self-concentrating buoyant glass microbubbles for high sensitivity immunoassays.

    PubMed

    Juang, Duane S; Hsu, Chia-Hsien

    2016-02-01

    Here, we report the novel application of a material with self-concentrating properties for enhancing the sensitivity of immunoassays. Termed as glass microbubbles, they are antibody functionalized buoyant hollow glass microspheres that simultaneously float and concentrate into a dense monolayer when dispensed in a liquid droplet. This self-concentrating charactaristic of the microbubbles allow for autonomous signal localization, which translates to a higher sensitivity compared to other microparticle-based immunoassays. We then demonstrated a "microbubble array" platform consisting of the glass microbubbles floating in a microfluidic liquid hemisphere array for performing multiplex immunoassays. PMID:26620967

  3. Microstructural Investigation of High Emittance Glass Coatings on Fibrous Ceramic Insulation

    NASA Technical Reports Server (NTRS)

    Ellerby, Don; Leiser, Dan; DiFiore, Robert; Figone, Jeff; Smith, Dane; Loehman, Ron; Kotula, Paul

    2001-01-01

    This viewgraph presentation provides an overview of the Space Shuttle Thermal Protection System (TPS) and the various products incorporated in the TPS. There are three tile systems which include pure silica, fibrous refractory composite insulation (FRCI), and alumina enhanced thermal barrier (AETB). Coating systems include reaction cured glass (RCG) and toughened uni-piece insulation (TUFI). The microstructures of these systems are explored as are the manufacturing processes associated with each. Microstructural investigation using methods such as automated X-ray spectral image analysis (AXSIA) is a crucial part of understanding the mechanical nature of these systems.

  4. Highly hydrophilic polyvinylidene fluoride (PVDF) ultrafiltration membranes via postfabrication grafting of surface-tailored silica nanoparticles.

    PubMed

    Liang, Shuai; Kang, Yan; Tiraferri, Alberto; Giannelis, Emmanuel P; Huang, Xia; Elimelech, Menachem

    2013-07-24

    Polyvinylidene fluoride (PVDF) has drawn much attention as a predominant ultrafiltration (UF) membrane material due to its outstanding mechanical and physicochemical properties. However, current applications suffer from the low fouling resistance of the PVDF membrane due to the intrinsic hydrophobic property of the membrane. The present study demonstrates a novel approach for the fabrication of a highly hydrophilic PVDF UF membrane via postfabrication tethering of superhydrophilic silica nanoparticles (NPs) to the membrane surface. The pristine PVDF membrane was grafted with poly(methacrylic acid) (PMAA) by plasma induced graft copolymerization, providing sufficient carboxyl groups as anchor sites for the binding of silica NPs, which were surface-tailored with amine-terminated cationic ligands. The NP binding was achieved through a remarkably simple and effective dip-coating technique in the presence or absence of the N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC)/N-hydroxysuccinimide (NHS) cross-linking process. The properties of the membrane prepared from the modification without EDC/NHS cross-linking were comparable to those for the membrane prepared with the EDC/NHS cross-linking. Both modifications almost doubled the surface energy of the functionalized membranes, which significantly improved the wettability of the membrane and converted the membrane surface from hydrophobic to highly hydrophilic. The irreversibly bound layer of superhydrophilic silica NPs endowed the membranes with strong antifouling performance as demonstrated by three sequential fouling filtration runs using bovine serum albumin (BSA) as a model organic foulant. The results suggest promising applications of the postfabrication surface modification technique in various membrane separation areas. PMID:23796125

  5. Quantum dots/silica/polymer nanocomposite films with high visible light transmission and UV shielding properties

    NASA Astrophysics Data System (ADS)

    Mumin, Md Abdul; Xu, William Z.; Charpentier, Paul A.

    2015-08-01

    The dispersion of light-absorbing inorganic nanomaterials in transparent plastics such as poly(ethylene-co-vinyl acetate) (PEVA) is of enormous current interest in emerging solar materials, including photovoltaic (PV) modules and commercial greenhouse films. Nanocrystalline semiconductor or quantum dots (QDs) have the potential to absorb UV light and selectively emit visible light, which can control plant growth in greenhouses or enhance PV panel efficiencies. This work provides a new and simple approach for loading mesoporous silica-encapsulated QDs into PEVA. Highly luminescent CdS and CdS-ZnS core-shell QDs with 5 nm size were synthesized using a modified facile approach based on pyrolysis of the single-molecule precursors and capping the CdS QDs with a thin layer of ZnS. To make both the bare and core-shell structure QDs more resistant against photochemical reactions, a mesoporous silica layer was grown on the QDs through a reverse microemulsion technique based on hydrophobic interactions. By careful experimental tuning, this encapsulation technique enhanced the quantum yield (˜65%) and photostability compared to the bare QDs. Both the encapsulated bare and core-shell QDs were then melt-mixed with EVA pellets using a mini twin-screw extruder and pressed into thin films with controlled thickness. The results demonstrated for the first time that mesoporous silica not only enhanced the quantum yield and photostability of the QDs but also improved the compatibility and dispersibility of QDs throughout the PEVA films. The novel light selective films show high visible light transmission (˜90%) and decreased UV transmission (˜75%).

  6. Hollow mesoporous silica as a high drug loading carrier for regulation insoluble drug release.

    PubMed

    Geng, Hongjian; Zhao, Yating; Liu, Jia; Cui, Yu; Wang, Ying; Zhao, Qinfu; Wang, Siling

    2016-08-20

    The purpose of this study was to develop a high drug loading hollow mesoporous silica nanoparticles (HMS) and apply for regulation insoluble drug release. HMS was synthesized using hard template phenolic resin nanoparticles with the aid of cetyltrimethyl ammonium bromide (CTAB), which was simple and inexpensive. To compare the difference between normal mesoporous silica (NMS) and hollow mesoporous silica in drug loading efficiency, drug release behavior and solid state, NMS was also prepared by soft template method. Transmission electron microscopy (TEM), specific surface area analysis, FT-IR and zeta potential were employed to characterize the morphology structure and physicochemical property of these carriers. The insoluble drugs, carvedilol and fenofibrate(Car and Fen), were chosen as the model drug to be loaded into HMS and NMS. We also chose methylene blue (MB) as a basic dye to estimate the adsorption ability of these carriers from macroscopic and microscopic view, and the drug-loaded carriers were systematically studied by differential scanning calorimetry (DSC), X-ray diffraction (XRD) and UV-vis spectrophotometry. What' more, the in vivo process of HMS was also study by confocal microscopy and in vivo fluorescence imaging. In order to confirm the gastrointestinal safety of HMS, the pathological examination of stomach and intestine also be evaluated. HMS allowed a higher drug loading than NMS and exhibited a relative sustained release curve, while NMS was immediate-release. And the effect of preventing drugs crystallization was weaker than NMS. As for in vivo process, HMS was cleared relatively rapidly from the mouse gastrointestinal and barely uptake by intestinal epithelial cell in this study due to its large particle size. And the damage of HMS to gastrointestinal could be ignored. This study provided a simple method to obtain high drug loading and regulation insoluble drug release, expanded the application of inorganic carriers in drug delivery system

  7. Quantum dots/silica/polymer nanocomposite films with high visible light transmission and UV shielding properties.

    PubMed

    Mumin, Md Abdul; Xu, William Z; Charpentier, Paul A

    2015-08-01

    The dispersion of light-absorbing inorganic nanomaterials in transparent plastics such as poly(ethylene-co-vinyl acetate) (PEVA) is of enormous current interest in emerging solar materials, including photovoltaic (PV) modules and commercial greenhouse films. Nanocrystalline semiconductor or quantum dots (QDs) have the potential to absorb UV light and selectively emit visible light, which can control plant growth in greenhouses or enhance PV panel efficiencies. This work provides a new and simple approach for loading mesoporous silica-encapsulated QDs into PEVA. Highly luminescent CdS and CdS-ZnS core-shell QDs with 5 nm size were synthesized using a modified facile approach based on pyrolysis of the single-molecule precursors and capping the CdS QDs with a thin layer of ZnS. To make both the bare and core-shell structure QDs more resistant against photochemical reactions, a mesoporous silica layer was grown on the QDs through a reverse microemulsion technique based on hydrophobic interactions. By careful experimental tuning, this encapsulation technique enhanced the quantum yield (∼65%) and photostability compared to the bare QDs. Both the encapsulated bare and core-shell QDs were then melt-mixed with EVA pellets using a mini twin-screw extruder and pressed into thin films with controlled thickness. The results demonstrated for the first time that mesoporous silica not only enhanced the quantum yield and photostability of the QDs but also improved the compatibility and dispersibility of QDs throughout the PEVA films. The novel light selective films show high visible light transmission (∼90%) and decreased UV transmission (∼75%). PMID:26177824

  8. Tailored hybrid hyperbranched polyglycidol-silica nanocomposites with high third-order nonlinearity

    NASA Astrophysics Data System (ADS)

    Postnova, Irina; Bezverbny, Alexander; Golik, Sergey; Kulchin, Yury; Li, Haiqing; Wang, Jing; Kim, Il; Ha, Chang-Sik; Shchipunov, Yury

    2012-07-01

    One of the most convenient techniques for optical material fabrication is the sol-gel processing. It can be performed at low temperature that enables one to entrap even relatively unstable organic substances into silica matrix at the nanometer scale, thus developing homogeneous hybrid organic-inorganic nanocomposite materials of various functionalities. Here, novel hybrid organic-inorganic nanocomposites with good optical transparency and high third-order nonlinearity were prepared biomimetically through the mineralization of dendritic macromolecules (hyperbranched polyglycidols) using a compatible ethylene glycol-containing silica precursor. The synthesis was performed at neutral pH media in aqueous solutions without addition of organic solvents at ambient conditions owing to the catalysis of processing. Polyglycidols provided also the formation of gold nanoparticles localized in their core. They served as reducing and stabilizing agents. It is shown that trace amounts of nanoparticles could regulate nonlinear properties of a nanocomposite. High nonlinearity manifests itself in a supercontinuum generation at remarkably short lengths ca. 1 mm. The phenomenon consists of filamentous intense white lighting due to the spectral broadening of initial ultrashort (femtosecond) laser pulses propagating through the material. The developed hybrid nanocomposites possessing large nonlinearity, high-speed optical response, stability under intense lighting, low-cost, and easy preparation are promising for a diverse range of applications as active components for all-optical signal processing from chemical sensing to biological cell imaging and lighting control in telecommunication.

  9. Recent advances in phosphate laser glasses for high power applications. Revision 1

    SciTech Connect

    Campbell, J.H.

    1996-05-01

    Recent advances in Nd-doped phosphate laser glasses for high-peak-power and high-average-power applications are reviewed. Compositional studies have progressed to the point that glasses can be tailored to have specific properties for specific applications. Non-radiative relaxation effects can be accurately modeled and empirical expressions have been developed to evaluate both intrinsic (structural) and extrinsic (contamination induced) relaxation effects. Losses due to surface scattering and bulk glass absorption have been carefully measured and can be accurately predicted. Improvements in processing have lead to high damage threshold (e.g. Pt inclusion free) and high thermal shock resistant glasses with improved edge claddings. High optical quality pieces up to 79 x 45 x 4 cm{sup 3} have been made and methods for continuous melting laser glass are under development.

  10. Study to determine and analyze the strength of high modulus glass in epoxy-matrix composites

    NASA Technical Reports Server (NTRS)

    Bacon, J. F.

    1974-01-01

    Glass composition research was conducted to produce a high modulus, high strength beryllium-free glass fiber. This program was built on the previous research for developing high modulus, high strength glass fibers which had a 5 weight percent beryllia content. The fibers resulting from the composition program were then used to produce fiber reinforced-epoxy resin composites which were compared with composites reinforced by commercial high modulus glass fibers, Thornel S graphite fiber, and hybrids where the external quarters were reinforced with Thornel S graphite fiber and the interior half with glass fiber as well as the reverse hybrid. The composites were given tensile strength, compressive strength, short-beam shear strength, creep and fatigue tests. Comments are included on the significance of the test data.

  11. Design and fabrication of high performance wafer-level vacuum packaging based on glass-silicon-glass bonding techniques

    NASA Astrophysics Data System (ADS)

    Zhang, Jinwen; Jiang, Wei; Wang, Xin; Zhou, Jilong; Yang, Huabing

    2012-12-01

    In this paper, a high performance wafer-level vacuum packaging technology based on GSG triple-layer sealing structure for encapsulating large mass inertial MEMS devices fabricated by silicon-on-glass bulk micromachining technology is presented. Roughness controlling strategy of bonding surfaces was proposed and described in detail. Silicon substrate was thinned and polished by CMP after the first bonding with the glass substrate and was then bonded with the glass micro-cap. Zr thin film was embedded into the concave of the micro-cap by a shadow-mask technique. The glass substrate was thinned to about 100 µm, wet etched through and metalized for realizing vertical feedthrough. During the fabrication, all patterning processes were operated carefully so as to reduce extrusive fragments to as little as possible. In addition, a high-performance micro-Pirani vacuum gauge was integrated into the package for monitoring the pressure and the leak rate further. The result shows that the pressure in the package is about 120 Pa and has no obvious change for more than one year indicating 10-13 stdcc s-1 leak rate.

  12. Silica and boron-containing ultraphosphate laser glass with low concentration quenching and improved thermal shock resistance

    DOEpatents

    Cook, Lee M.; Stokowski, Stanley E.

    1987-04-28

    Neodymium-doped phosphate glasses having a refractive index, nd>1.520; an Abbe number, Vd, <60; a density <3.0 g/cm.sup.3, a thermal expansion coefficient, .alpha., .ltoreq.110.times.10.sup.-7 .degree.C..sup.-1 ; a Young's Modulus, E, <70.times.10.sup.3 N/mm.sup.2 ; a Poisson's Ratio, .nu., <0.28; a thermal conductivity, K, >0.5 W/m.multidot.K, a thermal FOM=(1-.nu.).multidot.K/.alpha.E>0.7, consisting essentially of, in mol. %: P.sub.2 O.sub.5 : 40-70% SiO.sub.2 : 0-20% B.sub.2 O.sub.3 : 5-20% Sum SiO.sub.2 +B.sub.2 O.sub.3 : 5-35% Sum Li.sub.2 O+Na.sub.2 O+K.sub.2 O: 5-20% Sum La.sub.2 O.sub.3 +Nd.sub.2 O.sub.3 : 3-10% Sum MgO+CaO+SrO+BaO+ZnO: 0-10% and preferably containing an amount of Nd.sub.2 O.sub.3 effective for laser activity having an emission cross-section, .sigma., >3.5.times.10.sup.-20 cm.sup.2 ; a fluorescence linewidth (.DELTA..lambda..sub.f1)<23.5 nm; a first e-folding time of the Nd.sup.3+ fluorescence at 0.5 wt. % Nd.sub.2 O.sub.3 >375 .mu.sec, and a first e-folding time of the Nd.sup.3+ fluorescence at 10 wt. % >175 .mu.sec at 10 wt. %, have very low self-concentration quenching rates.

  13. High-temperature relaxation spectra of borate glasses

    SciTech Connect

    Lomovskoi, V.A.; Bartenev, G.M.

    1993-07-01

    A critical analysis of a method for calculating the spectrum characteristics of mechanical relaxation in glass melts is given. The analysis of changes in the spectrum characteristics (in the Kohlrausch function approximation) for B{sub 2}O{sub 3} and sodium borate glasses within a broad temperature and frequency range allows us to ascertain the specific features of these changes due to structural factors.

  14. Achieving high energy absorption capacity in cellular bulk metallic glasses

    PubMed Central

    Chen, S. H.; Chan, K. C.; Wu, F. F.; Xia, L.

    2015-01-01

    Cellular bulk metallic glasses (BMGs) have exhibited excellent energy-absorption performance by inheriting superior strength from the parent BMGs. However, how to achieve high energy absorption capacity in cellular BMGs is vital but mysterious. In this work, using step-by-step observations of the deformation evolution of a series of cellular BMGs, the underlying mechanisms for the remarkable energy absorption capacity have been investigated by studying two influencing key factors: the peak stress and the decay of the peak stress during the plastic-flow plateau stages. An analytical model of the peak stress has been proposed, and the predicted results agree well with the experimental data. The decay of the peak stress has been attributed to the geometry change of the macroscopic cells, the formation of shear bands in the middle of the struts, and the “work-softening” nature of BMGs. The influencing factors such as the effect of the strut thickness and the number of unit cells have also been investigated and discussed. Strategies for achieving higher energy absorption capacity in cellular BMGs have been proposed. PMID:25973781

  15. Achieving high energy absorption capacity in cellular bulk metallic glasses

    NASA Astrophysics Data System (ADS)

    Chen, S. H.; Chan, K. C.; Wu, F. F.; Xia, L.

    2015-05-01

    Cellular bulk metallic glasses (BMGs) have exhibited excellent energy-absorption performance by inheriting superior strength from the parent BMGs. However, how to achieve high energy absorption capacity in cellular BMGs is vital but mysterious. In this work, using step-by-step observations of the deformation evolution of a series of cellular BMGs, the underlying mechanisms for the remarkable energy absorption capacity have been investigated by studying two influencing key factors: the peak stress and the decay of the peak stress during the plastic-flow plateau stages. An analytical model of the peak stress has been proposed, and the predicted results agree well with the experimental data. The decay of the peak stress has been attributed to the geometry change of the macroscopic cells, the formation of shear bands in the middle of the struts, and the “work-softening” nature of BMGs. The influencing factors such as the effect of the strut thickness and the number of unit cells have also been investigated and discussed. Strategies for achieving higher energy absorption capacity in cellular BMGs have been proposed.

  16. Volcanic Glasses: Construction Materials

    NASA Astrophysics Data System (ADS)

    Moskowitz, Samuel E.

    1998-01-01

    Natural glass is the product of rapidly cooled molten rock. Two natural sources of the melt are volcanic eruption and meteoritic impact. Pure glass is an amorphous aggregate. Volcanic glass is a material that could be utilized in the construction of extraterrestrial outposts. Pumice and perlite are volcanic glasses currently used in the building industry. Samples of natural volcanic glass found in the lunar regolith were returned to Earth as part of the Apollo and Luna programs. An alpha proton X-ray spectrometer onboard the Pathfinder recently examined martian rocks located in the vicinity of the lander craft. Preliminary results of chemical composition by weight of SiO2 50-55%, Al203 11-13%, K20 1-2%, Na20 2-5%, CaO 4-6%, MgO 3-7%, FeO 12-14%, S03 2-5%, and MnO <1% were given for two rocks. Parenthetically, the values for K and Mn were perhaps too high, and the analysis was based on X-ray data only. The appreciable amount of silica already found on Mars and empirical evidence to support the hypothesis that the planet once had water sufficient to rapidly cool magma imply the possibility of discovering natural glass of volcanic origin in subsequent missions.

  17. Highly stabilized, polymer-lipid membranes prepared on silica microparticles as stationary phases for capillary chromatography

    PubMed Central

    Gallagher, Elyssia S.; Adem, Seid M.; Baker, Christopher A.; Ratnayaka, Saliya N.; Jones, Ian W.; Hall, Henry K.; Saavedra, S. Scott; Aspinwall, Craig A.

    2015-01-01

    The ability to rapidly screen complex libraries of pharmacological modulators is paramount to modern drug discovery efforts. This task is particularly challenging for agents that interact with lipid bilayers or membrane proteins due to the limited chemical, physical, and temporal stability of conventional lipid-based chromatographic stationary phases. Here, we describe the preparation and characterization of a novel stationary phase material composed of highly stable, polymeric-phospholipid bilayers self-assembled onto silica microparticles. Polymer lipid membranes were prepared by photochemical or redox initiated polymerization of 1,2-bis[10-(2′,4′-hexadieoyloxy)decanoyl]-sn-glycero-2-phosphocholine (bis-SorbPC), a synthetic, polymerizable lipid. The resulting polymerized bis-SorbPC (poly(bis-SorbPC)) stationary phases exhibited enhanced stability compared to particles coated with 1,2-dioleoyl-sn-glycero-phosphocholine (unpolymerized) phospholipid bilayers when exposed to chemical (50mM triton X-100 or 50% acetonitrile) and physical (15 min sonication) insults after 30 days of storage. Further, poly(bis-SorbPC)-coated particles survived slurry packing into fused silica capillaries, compared to unpolymerized lipid membranes, where the lipid bilayer was destroyed during packing. Frontal chromatographic analyses of the lipophilic small molecules acetylsalicylic acid, benzoic acid, and salicylic acid showed > 44% increase in retention times (P < 0.0001) for all analytes on poly(bis-SorbPC)-functionalized stationary phase compared to bare silica microspheres, suggesting a lipophilic retention mechanism. Phospholipid membrane-functionalized stationary phases that withstand the chemical and physical rigors of capillary LC conditions can substantially increase the efficacy of lipid membrane affinity chromatography, and represents a key advance towards the development of robust membrane protein-functionalized chromatographic stationary phases. PMID:25670414

  18. Accurate glass forming for high-temperature solar applications. Final report

    SciTech Connect

    1980-10-01

    Development work was undertaken to thermally form glass for solar concentrators. Sagging and pressing glass to parabolic shapes was investigated with goal of achieving slope errors less than 2.0 mr RMS and costs of $1.25/ft/sup 2/. In addition, a laminating process was investigated to overcome the problem of silvering of a curved surface and to reduce corrosion of the silver. Thermal sagging is a process in which glass is shaped by heating the glass until it is sufficiently soft to deform under its own weight and conform to a mold. For cylindrical parabolic shapes, a method for producing low cost high accuracy molds was developed using castable ceramics and a grinder. Thermal conditions were established for a commercial glass bending furnace to obtain good replication of the mold. The accuracy and cost goals were met for glass size up to 30 x 30 x 0.125 inches and for low iron and regular iron float and sheet glasses. Lamination of two curved pieces of glass using automotive technology was investigated. A silver film was placed between two layers of polyvinyl and butyral (PVB) and this was used to bond two sheets of glass. Economically, and technically, the process appears feasible. However, the non-uniform thickness of PBV cause distortion in the reflected image. More work is needed to assess accuracy of curved laminated composites. Thermal pressing of glass is accomplished by heating the glass until it is soft and mechanically stamping the shape. Equipment was built and operated to determine important parameters in pressing. Control of thermal stresses in the glass is critical to preventing cracks. No glass pieces were produced without cracks.

  19. Preparation and characterization of titania-deposited silica composite hollow fiber membranes with high hydrothermal stability.

    PubMed

    Kwon, Young-Nam; Kim, In-Chul

    2013-11-01

    Hydrothermal stability of a porous nickel-supported silica membrane was successfully improved by deposition of titania multilayers on colloidal silica particles embedded in the porous nickel fiber support. Porous nickel-supported silica membranes were prepared by means of a dipping-freezing-fast drying (DFF) method. The titania layers were deposited on colloidal silica particles by repeating hydrolysis and condensation reactions of titanium isopropoxide on the silica particle surfaces. The deposition of thin titania layers on the nickel-supported silica membrane was verified by various analytical tools. The water flux and the solute rejection of the porous Ni fiber-supported silica membranes did not change after titania layer deposition, indicating that thickness of titania layers deposited on silica surface is enough thin not to affect the membrane performance. Moreover, improvement of the hydrothermal stability in the titania-deposited silica membranes was confirmed by stability tests, indicating that thin titania layers deposited on silica surface played an important role as a diffusion barrier against 90 degrees C water into silica particles. PMID:24245310

  20. Hydro-oleophobic silica antireflective films with high laser-damage threshold

    NASA Astrophysics Data System (ADS)

    Yan, Lianghong; Lv, Haibing; Wang, Chengcheng; Yuan, Xiaodong

    2011-02-01

    A simple method of preparing hydro-oleophobic anitreflective films with high laser-damage threshold is reported in this article. By adding fluoroalkylsilanes (FAS) into reactant mixture as a co-precursor, FAS modified SiO 2 was obtained under base catalyzed hydrolysis and condensation of tetraethoxysilane. The dip-coating films were deposited on two sides of fused silica substrates. The experimental results on the effect of adding fluoroalkylsilanes (FAS) as a co-precursor on the hydro-oleophobicity and optical properties of tetraethoxysilane (TEOS) based silica AR films, are reported. The hydro-oleophobicity of the films was tested by the contact angle measurements and the highest water contact angle of 136° and oil (peanut) contact angle of 93° were obtained. The surface chemical modification of the hydro-oleophobic films was confirmed using Fourier transform infrared spectroscopy (FTIR). For the films based on FAS and TEOS, additional absorption bands at 1100 cm -1 corresponding to C-F bond presented, clearly indicating the organic modification of the films. The highest optical transmittance of the hydro-oleophobic films was found to be 99.5%. By a Nd:YAG lasers the laser-damage threshold of as-deposited films was measured at 351 nm wavelength (1 ns). The laser-damage threshold was as high as 22.6 J/cm 2.

  1. Silica colloidal crystals as emerging materials for high-throughput protein electrophoresis.

    PubMed

    Njoya, Nadine K; Birdsall, Robert E; Wirth, Mary J

    2013-10-01

    Silica colloidal crystals are a new type of media for protein electrophoresis, and they are assessed for their promise in rapidly measuring aggregation of monoclonal antibodies. The nature of silica colloidal crystals is described in the context of the need for a high-throughput separation tool for optimizing the formulations of protein drugs for minimal aggregation. The fundamental relations between molecular weight and mobility in electrophoresis are used to make a theoretical comparison of selectivity between gels and colloidal crystals. The results show that the selectivity is similar for these media, but slightly higher, 10%, for gels, and the velocity is inherently lower than that for gels due to the smaller free volume fraction. These factors are more than compensated for by lower broadening in colloidal crystals. These new media give plate heights of only 0.15 μm for the antibody monomer and 0.42 μm for the antibody dimer. The monoclonal antibody is separated from its dimer in 72 s over a distance of only 6.5 mm. This is five times faster than size-exclusion chromatography, with more than tenfold miniaturization, and amenable to parallel separations, all of which are promising for the design of high-throughput devices for optimizing protein drug formulations. PMID:23800834

  2. Dual aptamer-functionalized silica nanoparticles for the highly sensitive detection of breast cancer.

    PubMed

    Jo, Hunho; Her, Jin; Ban, Changill

    2015-09-15

    In this study, we synthesized dual aptamer-modified silica nanoparticles that simultaneously target two types of breast cancer cells: the mucin 1 (MUC1)(+) and human epidermal growth factor receptor 2 (HER2)(+) cell lines. Dual aptamer system enables a broad diagnosis for breast cancer in comparison with the single aptamer system. The dye-doped silica nanoparticles offer great stability with respect to photobleaching and enable the accurate quantification of breast cancer cells. The morphological and spectroscopic characteristics of the designed Dual-SiNPs were demonstrated via diverse methods such as DLS, zeta potential measurements, UV-vis spectroscopy, and fluorescence spectroscopy. Negatively charged Dual-SiNPs with a homogeneous size distribution showed robust and strong fluorescence. In addition, Dual-SiNPs did not affect cell viability, implying that this probe might be readily available for use in an in vivo system. Through ratio optimization of the MUC1 and HER2 aptamers, the binding capacities of the Dual-SiNPs to both cell lines were maximized. Based on Dual-SiNPs, a highly sensitive quantification of breast cancer cells was performed, resulting in a detection limit of 1 cell/100 μL, which is significantly lower compared with those reported in other studies. Moreover, the developed detection platform displayed high selectivity for only the MUC1(+) and HER2(+) cell lines. It is expected that this valuable diagnostic probe will be a noteworthy platform for the diagnosis and prognosis of breast cancer. PMID:25897882

  3. Porous Silica-Coated Gold Nanorods: A Highly Active Catalyst for the Reduction of 4-Nitrophenol.

    PubMed

    Mohanta, Jagdeep; Satapathy, Smithsagar; Si, Satyabrata

    2016-02-01

    The successful coating of thin porous silica layers of various thicknesses [(10±1), (12±1), and (14±1) nm] on cetyl trimethylammonium bromide (CTAB) capped gold nanorods was achieved through a modified Stöber procedure. The resulting material was applied as a novel catalyst for the reduction of 4-nitrophenol. The catalytic activities of the gold nanorods increased up to eight times after coating with a layer of porous silica and the reaction followed a zero-order kinetics, having a rate constant as high as 2.92×10(-1) mol L(-1) min(-1). The spectral changes during the reduction reaction of 4-nitrophenol were observed within a very short span of time and a complete conversion to 4-aminophenol occured within 5-6 mins, including the induction period of ≈2 mins. The reusability of the catalyst was studied by running the catalytic reaction during five consecutive cycles with good efficiency without destroying the nanostructure. The methodology can be effectively applied to the development of composite catalysts with highly enhanced catalytic activity. PMID:26663755

  4. High performance ErYb:Glass for eye-safe lasers

    NASA Astrophysics Data System (ADS)

    George, Simi

    2016-03-01

    Phosphate glasses are known to produce high gain for the Er3+ emission into 1540nm, especially when sensitized with Yb. Unfortunately, the phosphate glass matrix tends to be weaker than other available amorphous materials. Unlike crystalline materials, glass chemical structure around the active ion can be optimized for both material strength and laser output. Reported here is the result from a design of experiment that was completed in order to strengthen the glass structure of a commercially available phosphate laser glass without impacting its laser output efficiencies. Laser output performance results for the glass that met the targeted thermal and mechanical limits are presented. This effort concludes with a scalable material that is ultimately released to the commercial market.

  5. Operating Range for High Temperature Borosilicate Waste Glasses: (Simulated Hanford Enveloped)

    SciTech Connect

    Mohammad, J.; Ramsey, W. G.; Toghiani, R. K.

    2003-02-24

    The following results are a part of an independent thesis study conducted at Diagnostic Instrumentation and Analysis Laboratory-Mississippi State University. A series of small-scale borosilicate glass melts from high-level waste simulant were produced with waste loadings ranging from 20% to 55% (by mass). Crushed glass was allowed to react in an aqueous environment under static conditions for 7 days. The data obtained from the chemical analysis of the leachate solutions were used to test the durability of the resulting glasses. Studies were performed to determine the qualitative effects of increasing the B2O3 content on the overall waste glass leaching behavior. Structural changes in a glass arising due to B2O3 were detected indirectly by its chemical durability, which is a strong function of composition and structure. Modeling was performed to predict glass durability quantitatively in an aqueous environment as a direct function of oxide composition.

  6. Structured material combined HMO-silica fibers: preparation, optical and mechanical behavior

    NASA Astrophysics Data System (ADS)

    Schuster, K.; Kobelke, J.; Litzkendorf, D.; Schwuchow, A.; Lindner, F.; Kirchhof, J.; Bartelt, H.; Auguste, J.-L.; Humbert, G.; Blondy, J.-M.

    2011-03-01

    We report about preparation technique and characterization of structured fibers composed of HMO core glasses and silica cladding. Two processes as material preparation techniques have been developed based on glasses prepared by melting of SAL (e.g. 70SiO2-20Al2O3-10La2O3) glasses and the reactive powder sintering (REPUSIL) method. The melted glasses have been characterized by dilatometrical methods to find Tg values of 827-875°C and expansion coefficients between 4.3 and 7.0×10-6 K-1. The latter is one order of magnitude higher than the expansion coefficient of pure silica glass. Structured fibers (SAL core, silica cladding) were fabricated following the Rod-in-Tube (RIT) and Granulate-in-Tube (GIT) process. The HMO glasses were chosen due du their high lanthanum content and the expected high nonlinearity, suitable for nonlinear applications (e.g. supercontinuum sources). The partial substitution of lanthanum by other rare earth elements (e.g. Ytterbium) allows the preparation of fibers with extremely high rare earth concentration up to 5 mol% Yb2O3. The concentration of alumina in the HMO glasses as "solubilizer" for lanthanide was adjusted to about 20 mol%. So we overcame the concentration limits of rare earth doping of MCVD (maximum ca. 2 mol% RE2O3). Nevertheless, the investigated HMO glasses show their limits by integration in structured silica based fibers: Optical losses are typically in the dB/m range, best value of this work is about 600 dB/km. The mechanical stability of fibers is influenced by mechanical strain caused by the high thermal expansion of the core material and the lower network bonding stability of the HMO glasses, but partially compensated by the silica cladding.

  7. The ilmenite liquidus and depths of segregation for high-Ti picrite glasses

    NASA Technical Reports Server (NTRS)

    Hess, P. C.

    1993-01-01

    Lunar picrite glasses represent primitive and perhaps near primary liquids which have suffered only minor degrees of crystallization or near crustal modification. These glasses are multisaturated with olivine and orthopyroxene at pressures from 20-25 kb. I argue below that high TiO2 mare glasses were indeed equilibrated with orthopyroxene and were segregated from the lunar mantle at mean depths of 400-500 km. The glasses are typically modelled as products of relatively low degrees of melting of an hybridized source resulting from the overturn and mixing of the gravitationally unstable cumulate pile. But the models are neither unique nor, in some cases, correct.

  8. High-silica rhyolite magmatism in the Big Pine volcanic field, eastern California

    NASA Astrophysics Data System (ADS)

    Lidzbarski, M. I.; Vazquez, J. A.

    2007-12-01

    The Quaternary Big Pine volcanic field (BPVF) located in the Owens Valley of eastern California is dominated by basaltic cinder cones and associated lava flows, but contains a single rhyolite lava erupted at circa 1 Ma. Despite its uniqueness, the petrogenesis of this rhyolite is poorly known. At nearby Coso volcanic field, an abundance of rhyolite relative to basalt suggests crustal melting by mafic magmas stalled in mid to upper crustal reservoirs, whereas the paucity of rhyolite relative to basalt at BPVF suggests only brief crustal residence of ascending mafic magmas (Mordick and Glazner, 2006). In order to determine the origin of rhyolite magmatism at BPVF (e.g., crustal melting versus extreme fractionation), we have examined the geochemical and petrographic characteristics of the Fish Springs high-silica rhyolite. The Fish Springs rhyolite comprises a single thick coulee with a volume of at least 0.05 km3 (DRE) of highly evolved (~76 wt.% SiO2) magma. The outer portions of the coulee are composed of autobrecciated and felsitic rhyolite, and internal portions, as exposed by quarrying, are pumiceous perlite with local obsidian. Fish Springs rhyolite is crystal poor (~1%), with small (<0.5 mm) phenocrysts of generally euhedral to subhedral plagioclase, sanidine, quartz, orthopyroxene, clinopyroxene, biotite, hornblende, Fe-Ti oxides, apatite, pyrrhotite, and zircon, as well as apparent xenoliths and xenocrysts of metamorphic and igneous wallrocks. Orthopyroxene phenocrysts show compositional zoning, with rims that contain higher Mg and lower Fe concentrations than cores. Trace element concentrations in Fish Springs rhyolite are characterized by very low concentrations of typically compatible elements such as Ba (~15 ppm), Sr (~8 ppm), La (~10 ppm) and Zr (~80 pm), as well as a pronounced europium anomaly, comparable to other high-silica rhyolites elsewhere in the Owens Valley, and suggesting high degrees of feldspar and accessory mineral fractionation. Samples

  9. LIQUIDUS TEMPERATURE OF HIGH-LEVEL WASTE BOROSILICATE GLASSES WITH SPINEL PRIMARY PHASE

    EPA Science Inventory

    Liquidus temperatures (TL) were measured for high-level waste (HLW) borosilicate glasses covering a Savannah River composition region. The primary crystallization phase for most glasses was spinel, a solid solution of trevorite (NiFe2O4) with other oxides (FeO, MnO, and Cr2O3). T...

  10. FINAL REPORT. SETTLING OF SPINEL IN A HIGH-LEVEL WASTE GLASS MELTER

    EPA Science Inventory

    The research on spinel settling in the high-level waste (HLW) glass melter was conducted to assist HLW retrieval, glass formulation, feed preparation, and melter design and operation for minimum-risk and minimum-cost vitrification of HLW at Hanford and other DOE sites. The main r...

  11. A simple demonstration of the high-temperature electrical conductivity of glass

    NASA Astrophysics Data System (ADS)

    2014-01-01

    We usually think of glass as a good electrical insulator; this, however, is not always the case. There are several ways to show that glass becomes conducting at high temperatures, but the following approach, devised by Brown University demonstration manager Gerald Zani, may be one of the simplest to perform.

  12. A simple demonstration of the high-temperature electrical conductivity of glass

    NASA Astrophysics Data System (ADS)

    Chiaverina, Chris

    2014-01-01

    We usually think of glass as a good electrical insulator; this, however, is not always the case. There are several ways to show that glass becomes conducting at high temperatures,1,2 but the following approach, devised by Brown University demonstration manager Gerald Zani, may be one of the simplest to perform.

  13. A Simple Demonstration of the High-Temperature Electrical Conductivity of Glass

    ERIC Educational Resources Information Center

    Chiaverina, Chris

    2014-01-01

    We usually think of glass as a good electrical insulator; this, however, is not always the case. There are several ways to show that glass becomes conducting at high temperatures, but the following approach, devised by Brown University demonstration manager Gerald Zani, may be one of the simplest to perform.

  14. MILLIMETER-WAVE MEASUREMENTS OF HIGH LEVEL AND LOW ACTIVITY GLASS MELTS

    EPA Science Inventory

    The objectives of the proposed multi-organizational research are to develop new real-time sensors for characterizing glass melts in high level waste (HLW) and low activity waste (LAW) melters, and to understand the scientific basis and bridge the gap between glass melt model data...

  15. Size-dependent luminescence of Sm3+ doped SnO2 nano-particles dispersed in sol-gel silica glass

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

    Sol-gel glasses with composition (100- x)SiO2- xSnO2 doped with 0.4 mol% of Sm3+, with x ranging from 1 to 10, have been successfully synthesized. Transparent doped nano-glass-ceramics were prepared by thermal treatment of the precursor glasses at 900°C during 4 hours, leading to nanocomposites comprising SnO2 nanocrystals embedded into an amorphous SiO2 phase. A structural analysis in terms of X-ray Diffraction and High Resolution Transmission Electron Microscopy confirms the precipitation of SnO2 nanocrystals within the glassy matrix. The mean radius of the obtained SnO2 nanocrystals, ranging from 2.1 to 4.7 nm calculated by the Scherrer and Brus equations, similar to the Bohr's exciton radius, constitutes a wide band-gap semiconductor quantum-dot system. Energy transfer from SnO2 nanocrystal host to Sm3+ ions is confirmed by luminescence spectra and analyzed as a function of SnO2 concentration, showing an evolution that could be ascribed to selective excitation of nanocrystal sets with predetermined size. Besides, a study of the luminescence as a function of temperature helps to clarify the involved energy transfer mechanisms.

  16. High resolution transmission electron microscopy of melamine-formaldehyde aerogels and silica aerogels

    SciTech Connect

    Ruben, G.C. . Dept. of Biological Sciences)

    1991-09-01

    The goal of the high resolution transmission electron microscopy (HRTEM) was to image the structure of two tetramethyl orthosilicate (TMOS) and two melamine-formaldehyde (MF) aerogels at the single polymer chain level{sup 1,2}. With this level of structural resolution we hoped to interrelate each aerogel's structure with its physical properties and its method of synthesis. Conventional single-step base catalysed TMOS aerogels show strings of spheroidal particles linked together with minimal necking. The spheroidal particles range from 86--132 {Angstrom} and average 113{plus minus}10 {Angstrom} in diameter{sup 2}. In contrast the TMOS aerogels reported on here were made by a two step method. After extended silica chains are grown in solution under acidic conditions with a substoichiometric amount of water, the reaction is stopped and the methanol hydrolysed from TMOS is removed. Then base catalysis and additional water are added to cause gel formation is a nonalcoholic solvent. The MF aerogels were prepared for HRTEM by fracturing them on a stereo microscope stage with razor knife so that fractured pieces with smooth flat surfaces could be selected for platinum-carbon replication. The two silica (TMOS) aerogels were both transparent and difficult to see. These aerogels were fractured on a stereo microscope stage with tweezers. 6 refs., 4 figs.

  17. High power laser antireflection subwavelength grating on fused silica by colloidal lithography

    NASA Astrophysics Data System (ADS)

    Ye, Xin; Huang, Jin; Geng, Feng; Liu, Hongjie; Sun, Laixi; Yan, Lianghong; Jiang, Xiaodong; Wu, Weidong; Zheng, Wanguo

    2016-07-01

    In this study we report on an efficient and simple method to fabricate an antireflection subwavelength grating on a fused silica substrate using two-step reactive ion etching with monolayer polystyrene colloidal crystals as masks. We show that the period and spacing of the obtained subwavelength grating were determined by the initial diameter of polystyrene microspheres and the oxygen ion etching duration. The height of pillar arrays can be adjusted by tuning the second-step fluorine ion etching duration. These parameters are proved to be useful in tailoring the antireflection properties of subwavelength grating using a finite-difference time-domain (FDTD) method and effective medium theory. The subwavelength grating exhibits excellent antireflection properties. The near-field distribution of the SWG which is directly patterned into the substrate material is performed by a 3D-FDTD method. It is found that the near-field distribution is strongly dependent on the periodicity of surface structure, which has the potential to promote the ability of anti-laser-induced damage. For 10 ns pulse duration and 1064 nm wavelength, we experimentally determined their laser induced damage threshold to 32 J cm‑2, which is nearly as high as bulk fused silica with 31.5 J cm‑2.

  18. Metal-silica sol-gel materials

    NASA Technical Reports Server (NTRS)

    Stiegman, Albert E. (Inventor)

    2002-01-01

    The present invention relates to a single phase metal-silica sol-gel glass formed by the co-condensation of a transition metal with silicon atoms where the metal atoms are uniformly distributed within the sol-gel glass as individual metal centers. Any transition metal may be used in the sol-gel glasses. The present invention also relates to sensor materials where the sensor material is formed using the single phase metal-silica sol-gel glasses. The sensor materials may be in the form of a thin film or may be attached to an optical fiber. The present invention also relates to a method of sensing chemicals using the chemical sensors by monitoring the chromatic change of the metal-silica sol-gel glass when the chemical binds to the sensor. The present invention also relates to oxidation catalysts where a metal-silica sol-gel glass catalyzes the reaction. The present invention also relates to a method of performing oxidation reactions using the metal-silica sol-gel glasses. The present invention also relates to organopolymer metal-silica sol-gel composites where the pores of the metal-silica sol-gel glasses are filled with an organic polymer polymerized by the sol-gel glass.

  19. Structure and high temperature physical properties of glass seal materials in solid oxide electrolysis cell

    NASA Astrophysics Data System (ADS)

    Hao, Jie; Zan, Qingfeng; Ai, Desheng; Ma, Jingtao; Deng, Changsheng; Xu, Jingming

    2012-09-01

    Three series of BaO-CaO-SiO2-Al2O3, SrO-SiO2-Al2O3, and SrO-CaO-SiO2-Al2O3 glasses are prepared. Their basic physical properties are measured using dilatometry and differential scanning calorimetry from room temperature to the softening temperature. Their structures are characterized with infrared spectroscopy. The wetting characteristics of all glasses are examined by monitoring the change in shape of a cube specimen on crofer22 substrates from room temperature to flow temperature with a high temperature shape microscope. Five main absorption bands can be distinguished in the infrared absorption spectra of the three systems. The optimum ranges of sealing temperature of the glasses are determined. The 24SrO-16CaO-25SiO2-8Al2O3 glass is found to be the best sealant for the solid oxide electrolyzer/fuel cells under low loading without leakage. SrO improves the wetting ability of the glass by decreasing the contact angle between the glass and crofer22 substrates. The thermal properties of all the glasses fulfill the requirements for sealing solid oxide electrolysis/fuel cells. In terms of air tightness, the SrO-containing glass shows the best wetting ability among other glasses, and is the most suitable sealant for planar solid oxide electrolyzers/fuel cells.

  20. Influence of temperature on period of torsion pendulum with a high-Q fused silica fiber

    NASA Astrophysics Data System (ADS)

    Luo, Jie; Wu, Wei-Huang; Shao, Cheng-Gang; Li, Qing; Liu, Jian-Ping; Zhan, Wen-Ze; Wang, Dian-Hong

    2015-09-01

    Due to the high-Q fused silica fiber's extreme sensitivity to temperature change, the period estimation of torsion pendulum with high precision depends on the effective correction of the thermoelastic effect. In the measurement of G with the time-of-swing method, we analyze the complex relation between temperature and the pendulum's period and propose a developed method to find the shear thermoelasticity coefficient as well as isolate the influence of temperature on period alone. The result shows that the shear thermoelasticity coefficient is 101(2) × 10-6/∘C, the resultant correction to Δ(ω2) is 9.16(0.18) ppm, and the relative uncertainty to G is less than 1 ppm.