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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. 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.

  13. 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.

  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. 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.

  3. 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)

  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

    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

  7. 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.

  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. 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.

  11. 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

  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. 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.

  4. 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.

  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. 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%.

  9. 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.

  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. 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.

  8. 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.

  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. 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.

  14. 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.

  15. 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.

  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. 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.

  10. 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.

  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. 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

  6. 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.

  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. 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.