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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. Study on Tb3+ containing high silica and low silica calcium aluminate glasses: Impact of optical basicity.

    PubMed

    Sontakke, Atul D; Annapurna, K

    2012-08-01

    Two series of glasses based on high silica (CAS) and low silica calcium aluminates (LSCA) have been investigated for their structural, optical and Tb(3+) luminescence properties. The compositional modification reduces host phonon energy in LSCA glasses. Still, LSCA glasses exhibit Tb(3+) green luminescence quenching, whereas no quenching observed in CAS glasses. Material property influence on this behaviour has been discussed with an insight into the redox state of active ions. Copyright © 2012 Elsevier B.V. All rights reserved.

  3. High-performance geometric phase elements in silica glass

    NASA Astrophysics Data System (ADS)

    Drevinskas, Rokas; Kazansky, Peter G.

    2017-06-01

    High-precision three-dimensional ultrafast laser direct nanostructuring of silica glass resulting in multi-layered space-variant dielectric metasurfaces embedded in volume is demonstrated. Continuous phase profiles of nearly any optical component are achieved solely by the means of geometric phase. Complex designs of half-wave retarders with 90% transmission at 532 nm and >95% transmission at >1 μm, including polarization gratings with efficiency nearing 90% and computer generated holograms with a phase gradient of ˜0.8π rad/μm, were fabricated. A vortex half-wave retarder generating a single beam optical vortex with a tunable orbital angular momentum of up to ±100ℏ is shown. The high damage threshold of silica elements enables the simultaneous optical manipulation of a large number of micro-objects using high-power laser beams. Thus, the continuous control of torque without altering the intensity distribution was implemented in optical trapping demonstration with a total of 5 W average power, which is otherwise impossible with alternate beam shaping devices. In principle, the direct-write technique can be extended to any transparent material that supports laser assisted nanostructuring and can be effectively exploited for the integration of printed optics into multi-functional optoelectronic systems.

  4. Green and red high-silica luminous glass suitable for near-ultraviolet excitation.

    PubMed

    Yang, Luyun; Yamashita, Masaru; Akai, Tomoko

    2009-04-13

    We report on the preparation of transparent and colorless green-and red-emitting luminous glasses by sintering high-silica porous glass impregnated with rare-earth ions. These kinds of glasses can be efficiently excited by near-UV sources. The fluorescence of the glasses under near-UV excitation is dependent on energy transfer processes. In order to obtain strong visible emission, it is necessary to co-dope some optically inert rare-earth ions into the glasses. The roles of the optically inert rare-earth ions are discussed.

  5. Lead recovery and high silica glass powder synthesis from waste CRT funnel glasses through carbon thermal reduction enhanced glass phase separation process.

    PubMed

    Xing, Mingfei; Fu, Zegang; Wang, Yaping; Wang, Jingyu; Zhang, Zhiyuan

    2017-01-15

    In this study, a novel process for the removal of toxic lead from the CRT funnel glass and synchronous preparation of high silica glass powder was developed by a carbon-thermal reduction enhanced glass phase separation process. CRT funnel glass was remelted with B2O3 in reducing atmosphere. In the thermal process, a part of PbO contained in the funnel glass was reduced into metallic Pb and detached from the glass phase. The rest of PbO and other metal oxides (including Na2O, K2O, Al2O3, BaO and CaO) were mainly concentrated in the boric oxide phase. The metallic Pb phase and boric oxide phase were completely leached out by 5mol/L HNO3. The lead removal rate was 99.80% and high silica glass powder (SiO2 purity >95wt%) was obtained by setting the temperature, B2O3 added amount and holding time at 1000°C, 20% and 30mins, respectively. The prepared high silicate glass powders can be used as catalyst carrier, semipermeable membranes, adsorbents or be remelted into high silicate glass as an ideal substitute for quartz glass. Thus this study proposed an eco-friendly and economical process for recycling Pb-rich electronic glass waste.

  6. Structure and spectral properties of the silver-containing high-silica glasses

    NASA Astrophysics Data System (ADS)

    Girsova, M. A.; Golovina, G. F.; Anfimova, I. N.; Arsent'ev, M. Yu; Antropova, T. V.

    2016-08-01

    Silver-containing high-silica glasses were synthesized by an impregnation of the silica porous glasses (PGs) first with AgNO3 aqueous solution (with or without the presence of the sensitizers, such as Cu(NO3)2 or Ce(NO3)3), next in the mixed halide salt (NH4Cl, KBr, KI) solution. Then some part of the samples was sintered at the temperatures from 850 to 900°C up to closing of the pores. The structure of glasses was studied by UV-VIS-NIR and IR spectroscopy and X-ray diffraction (XRD) techniques. According to XRD data the silver-containing high-silica glasses contain the AgBr, AgI, Ag3PO4, (CuBr)0.75(CuI)0.25 phases. IR spectra confirmed B-O-B, Si- O-Si, P-O-P, O-P-O, O-B-O bonds, (PO4)3- and P-O- groups in glasses.

  7. Silica and Germanate Glass High Power Fiber Laser Sources

    DTIC Science & Technology

    2014-01-01

    with bismuth germanate glasses. The lower phonon energy offers negligible nonradiative multiphonon relaxation of rare earth transitions up to 2.5µm...of the various emission transitions. [1] J.M.F. van Dijk, M.F.H. Schuurmans, “On the nonradiative and radiative decay rates and a modified

  8. Adsorption of ions onto high silica volcanic glass.

    PubMed

    Steinhauser, Georg; Bichler, Max

    2008-01-01

    Chemical fingerprint techniques are frequently applied to airborne volcanic eruption products, so-called tephra, such as ash and pumice for archeological and geoscientific purposes. However, in some cases, a meaningful interpretation of the results is complicated by superficial contaminations. Therefore, this situation was simulated by the use of powdered rhyolitic pumice to investigate its capability to adsorb several ions from aqueous solutions. Using neutron activation analysis, adsorption could be proven for Cr(3+), Cr(2)O(7)(2-) (dichromate), Fe(3+), Co(2+), HAsO(4)(2-) (hydrogen arsenate), Rb(+), Sr(2+), Cs(+), Ba(2+), La(3+), Ce(3+), Ce(4+), Sm(3+), Th(4+) and UO(2)(2+), which is a clear evidence for the interaction of those ions with the volcanic glass. In our experiments, pumice powder showed the ability to adsorb ions in the range from 1.8 mg kg(-1) (in case of HAsO(4)(2-)) to 5.8 wt% (in case of Fe(3+)). Adsorption is probably due to ion-exchange reactions. It could also be shown that a few ions are not adsorbed in detectable quantities: Na(+), K(+), Fe(2+), Zn(2+) and Nd(3+). The knowledge about adsorption of ions enables us not only to examine the possible influence of contaminations where chemical fingerprinting methods are applied to volcanic material for archaeometry, but it also suggests the technical application of pumiceous materials for technical purposes, like water purification or as an adsorbent in the final storage of nuclear waste. In another series of INAA supported experiments, the influence of chemicals like ascorbic acid, acetic acid, HCl, HF, HNO(3), H(2)O, H(2)O(2), H(3)PO(4), H(2)SO(4), NaOH and NH(3) on the bulk composition of pumice powder was investigated-resulting in no detectable change. We conclude that superficially contaminated tephra can be washed in diluted HF to remove contaminations without influencing the chemical fingerprint.

  9. Highly Efficient Optical Second Harmonic Generation in Poled Ti-Doped Silica Glasses

    NASA Astrophysics Data System (ADS)

    Tanaka, Katsuhisa; Kashima, Kenichi; Hirao, Kazuyuki; Soga, Naohiro; Yamagata, Shigeru; Mito, Akihiro; Nasu, Hiroyuki

    1995-01-01

    Optical second harmonic intensity of poled Ti-doped silica glasses prepared by the Verneuil method has been measured. The second-order nonlinear coefficient, d33, of the glasses prepared from starting materials of TiO2 and SiO2 powders ranges from 0.2 to 0.5 pm/V. These values are one order of magnitude larger than that for silica glass without intentional dopants.

  10. Phosphate glass core/silica clad fibres with a high concentration of active rare-earth ions

    NASA Astrophysics Data System (ADS)

    Egorova, O. N.; Galagan, B. I.; Denker, B. I.; Sverchkov, S. E.; Semjonov, S. L.

    2016-12-01

    We report a study of silica-clad composite optical fibres having a phosphate glass core doped with active rare-earth elements. The phosphate glass core allows a high concentration of active rare-earth ions to be obtained, and the silica cladding ensures high mechanical strength and facilitates fusion splicing of such fibres to silica fibres. Owing to the high concentration of active rare-earth ions, this type of fibre is potentially attractive for applications where a small cavity length and high lasing efficiency are needed.

  11. 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.

  12. Ytterbium-doped all glass leakage channel fibers with highly fluorine-doped silica pump cladding.

    PubMed

    Dong, Liang; McKay, Hugh A; Fu, Libin; Ohta, Michiharu; Marcinkevicius, Andrius; Suzuki, Shigeru; Fermann, Martin E

    2009-05-25

    All glass leakage channel fibers have been demonstrated to be a potential practical solution for power scaling in fiber lasers beyond the nonlinear limits in conventional large mode area fibers. The all glass nature with absence of any air holes is especially useful for allowing the fibers to be used and fabricated much like conventional fibers. Previously, double clad active all glass leakage channel fibers used low index polymer as a pump guide with the drawbacks of being less reliable at high pump powers and not being able to change fiber outer diameter independent of pump guide dimension. In this work, we demonstrate, for the first time, ytterbium-doped double clad all glass leakage channel fibers with highly fluorine-doped silica as pump cladding. The new all glass leakage channel fibers have no polymer in the pump path and have independent control of fiber outer diameters and pump cladding dimension, and, therefore, enable designs with smaller pump guide for high pump absorption and, at the same time, with large fiber diameters to minimize micro and macro bending effects, a much desired features for large core fibers where intermodal coupling can be an issue due to a much increased mode density. An ytterbium-doped double clad PM fiber with core diameter of 80 microm is also reported, which can be coiled in 76 cm diameter coils.

  13. Mechanism of mechanical fatigue of silica glass. Progress report

    SciTech Connect

    Tomozawa, M.

    1993-11-01

    Results are summarized on: blunt crack tip existence, mechanical behavior of glasses with blunt cracks, water entry into glass under stress, water diffusion into SiO{sub 2} glass at low temperature, mechanical properties of glasses with high water content, cyclic fatigue, fatigue resistance improvement by coating, IR peaks of silica-water, water diffusion and structural changes in silica glasses, water diffusion and time dependent mechanical properties, effects of N and C implantation on devitrification of silica glasses.

  14. 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.

  15. 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.

  16. 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.

  17. Zinc-embedded silica nanoparticle layer in a multilayer coating on a glass substrate achieves broadband antireflection and high transparency

    NASA Astrophysics Data System (ADS)

    Kim, Sang Woo; Bae, Dong-Sik; Shin, Hyunho

    2004-12-01

    A zinc-embedded silica (Zn-SiO2) nanoparticle layer has been applied as the outermost layer over the three-layer coating system, Zn-SiO2/SiO2/ITO (indium tin oxide), coated on a soda-lime glass substrate. The additional coating of the zinc-embedded nanoparticle layer over the 2-layer/glass, i.e., SiO2/ITO /glass system, yielded a significant diminution in reflectance, as well as an improved transmittance as compared to the 2-layer/glass system. Plausible mechanisms responsible for such phenomena are discussed. The application of the zinc-embedded silica nanoparticle layer to the multilayer coating system is shown to provide a flexible way to achieve a broadband antireflection and a high transmission.

  18. Three-dimensional printing of transparent fused silica glass

    NASA Astrophysics Data System (ADS)

    Kotz, Frederik; Arnold, Karl; Bauer, Werner; Schild, Dieter; Keller, Nico; Sachsenheimer, Kai; Nargang, Tobias M.; Richter, Christiane; Helmer, Dorothea; Rapp, Bastian E.

    2017-04-01

    Glass is one of the most important high-performance materials used for scientific research, in industry and in society, mainly owing to its unmatched optical transparency, outstanding mechanical, chemical and thermal resistance as well as its thermal and electrical insulating properties. However, glasses and especially high-purity glasses such as fused silica glass are notoriously difficult to shape, requiring high-temperature melting and casting processes for macroscopic objects or hazardous chemicals for microscopic features. These drawbacks have made glasses inaccessible to modern manufacturing technologies such as three-dimensional printing (3D printing). Using a casting nanocomposite, here we create transparent fused silica glass components using stereolithography 3D printers at resolutions of a few tens of micrometres. The process uses a photocurable silica nanocomposite that is 3D printed and converted to high-quality fused silica glass via heat treatment. The printed fused silica glass is non-porous, with the optical transparency of commercial fused silica glass, and has a smooth surface with a roughness of a few nanometres. By doping with metal salts, coloured glasses can be created. This work widens the choice of materials for 3D printing, enabling the creation of arbitrary macro- and microstructures in fused silica glass for many applications in both industry and academia.

  19. 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.

  20. The effect of composition on spinel crystals equilibrium in low-silica high-level waste glasses

    SciTech Connect

    Jiricka, M.; Hrma, P.; Vienna, J. D.

    2003-05-01

    The liquidus temperature (TL) and the equilibrium mass fraction of spinel were measured in the regions of low-silica (less than 42 mass% SiO2) high-level waste borosilicate glasses within the spinel primary phase field as functions of glass composition. The components that varied, one at a time, were Al2O3, B2O3, Cr2O3, Fe2O3, Li2O, MnO, Na2O, NiO, SiO2, and ZrO2. The effects of Al2O3, B2O3, Fe2O3, NiO, SiO2, and ZrO2 on the TL in this region and in glasses with 42 to 56 mass% SiO2 were similar. However, in the low-silica region, Cr2O3 increased the TL substantially less, and Li2O and Na2O decreased the TL significantly less than in the region with 42 to 56 mass% SiO2. The effect of MnO on the TL of the higher SiO2 glasses is not yet understood with sufficient accuracy. The temperature at which the equilibrium mass fraction of spinel was 1 mass% was 25?C to 64?C below the TL.

  1. The Effect of Composition on Spinel Crystals Equilibrium in Low-Silica High-Level Waste Glasses

    SciTech Connect

    Jiricka, Milos; Hrma, Pavel R.; Vienna, John D.

    2003-05-15

    The liquidus temperature (TL) and the equilibrium mass fraction of spinel were measured in the regions of low-silica (less than 42 mass% SiO2) high-level waste borosilicate glasses within the spinel primary phase field as functions of glass composition. The components that varied, one at a time, were Al2O3, B2O3, Cr2O3, Fe2O3, Li2O, MnO, Na2O, NiO, SiO2, and ZrO2. The effects of Al2O3, B2O3, Fe2O3, NiO, SiO2, and ZrO2 on the TL in this region and in glasses with 42 to 56 mass% SiO2 were similar. However, in the low-silica region, Cr2O3 increased the TL substantially less, and Li2O and Na2O decreased the TL significantly less than in the region with 42 to 56 mass% SiO2. The effect of MnO on the TL of the higher SiO2 glasses is not yet understood with sufficient accuracy. The temperature at which the equilibrium mass fraction of spinel was 1 mass% was 25C to 64C below the TL.

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

    SciTech Connect

    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 of 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.

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

    DOE PAGES

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

    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

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

    SciTech Connect

    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 of 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.

  5. 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.

  6. Modelling of fluorine based high density plasma for the etching of silica glasses

    SciTech Connect

    Lallement, Ludovic; Rhallabi, Ahmed; Cardinaud, Christophe; Peignon Fernandez, Marie Claude

    2011-09-15

    An etching simulator has been developed to study the etching of commercial silica glass (Pyrex, D263, AF45, and Vycor) in a SF{sub 6}/Ar inductively coupled plasma (ICP) discharge. The etching model is based on the development of the plasma kinetic model coupled to a two dimensional (2D) Monte Carlo cellular surface model to predict the etched surface morphology as a function of the operating conditions. The SF{sub 6}/Ar plasma model allows us to predict the neutral and ion species fluxes, as well as the density and the temperature of electrons, as a function of the reactor operating conditions. Such output parameters are used as input parameters in both the sheath and etching models. The 2D Monte Carlo cellular model is based on the representation of both the substrate and the mask by uniform cells, which each represents a real number of sites. The preferential redeposition mechanism of the etched products on the metallic sites seems to play an important role on the formation and the propagation of the etched surface roughness. The results obtained by the model are compared with the experimental results for etching rate and roughness. A satisfactory agreement between the experimental results and the model concerning the etching rate and the etched surface morphology has been obtained for different glasses.

  7. Ultrafast laser-induced birefringence in various porosity silica glasses: from fused silica to aerogel.

    PubMed

    Cerkauskaite, Ausra; Drevinskas, Rokas; Rybaltovskii, Alexey O; Kazansky, Peter G

    2017-04-03

    We compare a femtosecond laser induced modification in silica matrices with three different degrees of porosity. In single pulse regime, the decrease of substrate density from fused silica to high-silica porous glass and to silica aerogel glass results in tenfold increase of laser affected region with the formation of a symmetric cavity surrounded by the compressed silica shell with pearl like structures. In multi-pulse regime, if the cavity produced by the first pulse is relatively large, the subsequent pulses do not cause further modifications. If not, the transition from void to the anisotropic structure with the optical axis oriented parallel to the incident polarization is observed. The maximum retardance value achieved in porous glass is twofold higher than in fused silica, and tenfold greater than in aerogel. The polarization sensitive structuring in porous glass by two pulses of ultrafast laser irradiation is demonstrated, as well as no observable stress is generated at any conditions.

  8. Evidence of a green luminescence band related to surface flaws in high purity silica glass.

    PubMed

    Fournier, J; Néauport, J; Grua, P; Fargin, E; Jubera, V; Talaga, D; Jouannigot, S

    2010-10-11

    Using luminescence confocal microscopy under 325 nm laser excitation, we explore the populations of defects existing in or at the vicinity of macroscopic surface flaws in fused silica. We report our luminescence results on two types of surface flaws: laser damage and indentation on fused silica polished surfaces. Luminescence cartographies are made to show the spatial distribution of each kind of defect. Three bands, centered at 1.89 eV, 2.75 eV and 2.25 eV are evidenced on laser damage and indentations. The band centered at 2.25 eV was not previously reported in photo luminescence experiments on indentations and pristine silica, for excitation wavelengths of 325 nm or larger. The luminescent objects, expected to be trapped in sub-surface micro-cracks, are possibly involved in the first step of the laser damage mechanism when fused silica is enlightened at 351 nm laser in nanosecond regime.

  9. Mechanism of mechanical fatigue of silica glass

    SciTech Connect

    Tomozawa, Minoru.

    1990-01-01

    Research continued on the mechanism of mechanical fatigue of silica glass. Significant accomplishments this quarter include: strength increase of abraded glasses by thermal and chemical treatments was found best explained by crack tip blunting; fatigue was found to involve crack initiation in addition to crack propagation, and only water and ammonia were found capable of causing crack initiation from blunt crack tips at sub-critical stresses; water was found to enter into silica glass during microhardness indentation as well as during slow crack growth in water-containing atmospheres at room temperature; water diffusion at low temperature showed anomalous phenomena including initial time dependences of solubility and apparent diffusion coefficient; glass containing water showed greater fatigue susceptibility and lower crack initiation stress than dry glass; fatigue of abraded silica glass showed effects of cyclic stress when tested by the rotation bending method while no cyclic stress effect was observed in reciprocal bending; and a new coating which can reduce fatigue of silica glass was developed.

  10. Temperature dependences of optical path length in fluorine-doped silica glass and bismuthate glass

    NASA Astrophysics Data System (ADS)

    Koike, Akio; Sugimoto, Naoki

    2006-02-01

    Temperature dependences of optical path length (dS/dT; calculated using the equation, dS/dT = dn/dT + na, where a is coefficient of thermal expansion, n is refractive index and dn/dT is temperature coefficient of refractive index) in various oxide glasses were investigated. The dS/dT is generally difficult to adjust by change of glass composition because dn/dT and a are interrelated. However, low dS/dT materials are desired for optical applications such as athermal devices, and high dS/dT materials can be used for thermo-optic devices. Pure silica glass is well-known as a typical low dS/dT material but still not sufficient. Fluorine-doped silica glass showed a lower dS/dT than that of pure silica glass. By fluorine-doping in silica glass, refractive index and dn/dT decreased but a near room temperature stayed at the same level. As a result, the dS/dT decreased with increasing fluorine concentration. On the other hand, bismuthate glass showed the highest dS/dT in this study. Most glasses having high a such as tellurite glass showed negative dn/dT. However, bismuthate glasses showed positive dn/dT in spite of high a. As a result, bismuthate glasses showed quite high dS/dT. These results indicate that dS/dT of the glass can be controllable and that fluorine doped silica glass and bismuthate glass are appropriate candidate materials for optical applications.

  11. F/Yb-codoped sol-gel silica glasses: toward tailoring the refractive index for the achievement of high-power fiber lasers.

    PubMed

    El Hamzaoui, Hicham; Bouwmans, Geraud; Cassez, Andy; Bigot, Laurent; Capoen, Bruno; Bouazaoui, Mohamed; Vanvincq, Olivier; Douay, Marc

    2017-04-01

    Accurate control of both the doping distribution inside the fiber core and the low refractive index contrast between the fiber core and cladding materials is essential for the development of high-power fiber lasers based on the use of single-mode large-mode-area (LMA) optical fibers. Herein, sol-gel monolithic F/Yb3+-codoped silica glasses were prepared from porous large silica xerogels doped with ytterbium salt solution, which had been subjected to fluorination with hexafluoroethane gas, before subsequent sintering. The fluorine content inside the doped glass has been varied by adjusting the fluorination duration. The space homogeneity of fluorine and ytterbium concentrations in the cylindrical preforms has been checked by chemical analysis and Raman spectroscopy. Moreover, the glass with the lowest fluorine content has been successfully integrated as a core material in a microstructured optical fiber made using the stack-and-draw method. This fiber was tested in an all-fiber cavity laser architecture to evaluate potential lasing performances of the F/Yb3+-codoped silica glass. It presents a maximum efficiency of 70.4%, achieved at 1031 nm from a 1.16 m length fiber. These results confirm the potentialities of the obtained F/Yb3+-codoped glasses for the fabrication of LMA optical fiber lasers.

  12. Relaxation processes of densified silica glass

    NASA Astrophysics Data System (ADS)

    Cornet, Antoine; Martinez, Valérie; de Ligny, Dominique; Champagnon, Bernard; Martinet, Christine

    2017-03-01

    Densified SiO2 glasses, obtained from different pressure and temperature routes, have been annealed over a wide range of temperatures far below the glass transition temperature (500 °C-900 °C). Hot and cold compressions were useful to separate the effects of pressure and the compression temperature. In situ micro-Raman spectroscopy was used to follow the structural evolution during the thermal relaxation. A similar glass structure between the non-densified silica and the recovered densified silica after the temperature annealing demonstrates a perfect recovery of the non-densified silica glass structure. While the density decreases monotonically, the structural relaxation takes place through a more complex mechanism, which shows that density is not a sufficient parameter to fully characterize the structure of densified silica glass. The relaxation takes place through a transitory state, consisting in an increase of the network inhomogeneity, shown by an increase in the intensity of the D2 band which is associated with 3 membered rings. The activation energy of these processes is 255 ± 45 kJ/mol for the hot compressed samples. The kinetic is overall faster for the cold compressed samples. In that last case, the relaxation is partially activated by internal stresses release.

  13. Structure and Properties of Dense Silica Glass

    PubMed Central

    Wu, Min; Liang, Yunfeng; Jiang, Jian-Zhong; Tse, John S.

    2012-01-01

    The O K-edge x-ray Raman scattering (XRS), Brillouin scattering and diffraction studies on silica glass at high pressure have been elucidated in a unified manner using model structures obtained from First-Principles molecular dynamics calculations. This study provides a comprehensive understanding on how the structure is related to the physical and electronic properties. The origin of the “two peak” pattern in the XRS is found to be the result of increased packing of oxygen near the Si and is not a specific sign for sixfold coordination. The compression mechanism involving the presence of 5- and 6-fold coordinated silicon is confirmed. A slight increase in the silicon-oxygen coordination higher than six was found to accompany the increase in the acoustic wave velocity near 140 GPa. PMID:22570763

  14. 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.

  15. A New Model for the Structure of Silica Glass

    DTIC Science & Technology

    1989-09-20

    of Hosemann [61 suggests that really silica glass consists of a material with the connectivity of one of the SiO2 polymorphs, such as cristobalite but...Figure 1: Six-rings Both cristobalite and tridymite, two high temperature silica polymorphs contain s,1ch rings. They differ only in the stacking sequence...of sheets of tetrahedra, ABC for (cubic) cristobalite and AB for (hexagonal) tridymite. Importantly the linkages between the sheets in these dimorphs

  16. 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.

  17. High Q silica microbubble resonators fabricated by heating a pressurized glass capillary

    NASA Astrophysics Data System (ADS)

    Yu, Zhe; Liu, Tiegen; Jiang, Junfeng; Liu, Kun; Chen, Wenjie; Zhang, Xuezhi; Lin, Xujun; Liu, Wenhui

    2014-11-01

    Microbubble resonators combine the unique properties of whispering gallery mode resonators with the capability of integrated microfluidics. The microbubble resonator is fabricated by heating the tapered tip of a pressurized glass capillary with oxyhydrogen flame. Firstly, a microtube with a diameter of 250um is stretched under heating of oxyhydrogen flame, the heating zone length is set to be 20mm and the length of stretch is set to be 7000um.Then nitrogen will be pumped in to the tapered microtube with the pressure of 0.1Mpa, the tapered tip will be heated by the oxyhydrogen flame continuously until a microbubble forms. An optical fiber taper with a diameter of 2 um, fabricated by stretching a single-mode optical fiber under flame was brought in contact with the microbubble to couple the light from a 1550nm tunable diode laser into the whispering gallery mode. The microbubble resonator has a Q factors up to 1.5 × 107 around 1550nm. Different concentrations of ethanol solution (from 5% to 30%) are filled into it in order to test the refractive index sensing capabilities of such resonator, which shows a sensitivity of 82nm/RIU.

  18. The sensitivity of physical and spectral properties of silica glass to variations of interatomic potentials under high pressure

    NASA Astrophysics Data System (ADS)

    Rustad, James R.; Yuen, David A.; Spera, Frank J.

    We have investigated with molecular dynamics various aspects of the structure and vibrational properties of silica glass at a temperature near 330 K to pressures of 40 GPa for three sets of interatomic potentials using 1500 atoms. The potentials were chosen from previous works. Only one of these potentials shows a transition from tetrahedral silicon coordination to octahedral silicon coordination. For this potential the percentage of five-fold coordinated silicon increases from 12% at 10 GPa to 35% at 15 GPa. The geometry of the five-coordinated complexes is that of a distorted pyramid with the silicon situated at the base, or, equivalently, it is an octahedron with one vertex missing. The shape of the OSiO distribution for the five-fold-coordinated complex is similar for all three potentials, but they are present in lesser amounts in the two which do not show the tetrahedral to octahedral transition. In the potential that shows the transition the distribution of SiOSi angles is bimodal at pressures above 30 GPa, coinciding with large populations of two-silicon rings. Analysis of the density of states reveals that two of the potentials give enhanced contributions from the frequencies in the 800-900 cm -1 range which agrees with in situ infrared spectroscopic studies of silica glass. The major effect of pressure on the velocity autocorrelation function is to increase the amount of negatively correlated motion for silicon atoms during the approach to the first maximum.

  19. High thermal behavior of a new glass ceramic developed from silica xerogel/SnO{sub 2} composite

    SciTech Connect

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

    2016-02-08

    In this investigation, a new glass ceramics have been produced by mixing SnO{sub 2} and amorphous silica xerogel (ASX) extracted from sago waste ash. The composition has been prepared by adding 10 mol% of SnO{sub 2} 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 SnO{sub 2} and their relationship to bulk density have been studied. The crystallization process of the silica xerogel/SnO{sub 2} 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 SnO{sub 2} 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 SnO{sub 2} in the composite.

  20. 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.

  1. 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.

  2. 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.

  3. The ultimate strength of glass silica nanowires.

    PubMed

    Brambilla, Gilberto; Payne, David N

    2009-02-01

    In the past decade nanowires have attracted an increase interest because of their extraordinary mechanical strength. In fact, material properties in the nanoregime are extremely different from those found in macroscopic samples: few crystalline materials have shown a tensile strength in excess of 10 GPa in the form of nanowires. Still the length of defect-free crystalline nanowires is limited to a few millimeters and the strength of long nanowires is compromised by defects. The strength of glass nanowires is less affected by single defects. In this paper we present the ultimate strength of glass silica nanowires manufactured by a top-down fabrication technique; this is the highest value reported for glass materials. The measured ultimate strength is in excess of 10 GPa and increases for decreasing nanowire diameters. Scanning electron micrographs of the broken fragments showed a fragile rupture.

  4. Tensile bond strength of resin-modified glass-ionomer cement to microabraded and silica-coated or tin-plated high noble ceramic alloy.

    PubMed

    Swartz, J M; Davis, R D; Overton, J D

    2000-12-01

    The purpose of this study was to evaluate the influence of alloy surface microabrasion, silica coating, or microabrasion plus tin plating on the tensile bond strengths between a resin-modified glass-ionomer luting cement and a high-noble alloy. Bond strength between the microabraded alloy specimens and conventional glass-ionomer cement or resin cement were included for comparison. One hundred twenty uniform size, disk-shaped specimens were cast in a noble metal alloy and divided into 6 groups (n = 10 pairs/group). The metal surfaces of the specimens in each group were treated and cemented as follows. Group 1: No surface treatment (as cast, control), cemented with a resin-modified glass-ionomer cement. Group 2: Microabrasion with 50-microm aluminum oxide particles, resin-modified glass-ionomer cement. Group 3: A laboratory microabrasion and silica coating system, resin-modified glass-ionomer cement. Group 4: Microabrasion and tin-plating, resin-modified glass-ionomer cement. Group 5: Microabrasion only, conventional glass-ionomer cement. Group 6: Microabrasion and tin-plating, conventional resin cement. The uniaxial tensile bond strength for each specimen pair was determined using an Instron Universal Testing Machine (Instron Corp, Canton, MA). Results were analyzed using a one-way analysis of variance (alpha = 0.05) and a Tukey post-hoc analysis. Mean bond strength: Group 1: 3.6 (+/- 1.5) MPa. Group 2: 4.2 (+/-0.5) MPa. Group 3: 6.7 (+/- 0.9) MPa. Group 4: 10.6 (+/- 1.8) MPa. Group 5: 1.1 (+/- 0.4) MPa. Group 6: 14.6 (+/- 2.3) MPa. Group 6 was significantly stronger than Group 4. The bond strength of specimens cemented with the resin-modified glass-ionomer cement using microabrasion and tin-plating (Group 4) was significantly stronger than all other groups except the resin cement with microabrasion and tin-plating (Group 6). Microabraded and tin-plated alloy specimens luted with the resin-modified glass-ionomer cement resulted in the greatest mean tensile strengths

  5. 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.

  6. 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.

  7. Temperature dependence of nonlinear optical phenomena in silica glasses

    NASA Astrophysics Data System (ADS)

    Mikami, K.; Motokoshi, S.; Fujita, M.; Jitsuno, T.; Murakami, M.

    2010-11-01

    A linear increase of the laser-induced damage thresholds in silica glasses with decreasing the temperature was reported in this conference at last year. Various nonlinear phenomena should be generated in silica glasses besides the damage in high intensity. Temperature dependences of the nonlinear refractive indices and the SBS (stimulated Brillouin scattering) thresholds in silica glasses at temperature 173 K to 473 K were measured with single-mode Q-switched Nd:YAG laser at fundamental wavelength. As the result, the nonlinear refractive indices increased with decreasing temperature. Because the change was not enough to explain the temperature dependence of laser-induced damage thresholds, the temperature dependence of nonlinear refractive indices would be negligible on laser-induced damage thresholds. On the other hand, the SBS thresholds also increased with decreasing temperature. This result means that acoustic phonons arise easily at high temperature. Probably, the SBS phenomenon is one of reasons for temperature dependence of laser-induced damage thresholds.

  8. Laser-induced bulk damage of silica glass at 355nm and 266nm

    NASA Astrophysics Data System (ADS)

    Kashiwagi, R.; Aramomi, S.

    2016-12-01

    Laser processing machines using Nd:YAG 3rd harmonic wave (355 nm) and 4th harmonic wave (266 nm) have been developed and put into practical use lately. Due to this, optical elements with high laser durability to 355 nm and 266 nm are required. Silica glass is the optical element which has high UV transmission and high laser durability. Laser-induced surface damage of the silica glass has been studied in detail, but we hardly have the significant knowledge of laserinduced bulk damage. This knowledge is required in order to evaluate the silica glass itself. That is because cracks and scratches on the surface give rise to a higher possibility of damage. Therefore, we studied the laser durability of a variety of the silica glass samples by 1-on-1 and S-on-1 laser-induced bulk damage threshold (LIDT) at 355 nm and 266 nm. In this study, we gained knowledge in three areas about bulk damage to the silica glass. First, the LIDT became lower as shot counts increased. Second, the LIDT decreased as the hydroxyl content in the silica glass increased. Last, the LIDT became higher as the hydrogen concentration in the silica glass increased. Under the UV irradiation, impurities are generated and the silica glass absorbs more light. Therefore, the LIDT decreased as shot counts increased. Also, the hydroxyl in particular generates more impurities, so damage easily occurs. On the other hand, the hydrogen reacts with impurities and absorption is suppressed. Based on these results, we can improve laser durability at 355 nm and 266 nm by reducing the hydroxyl content and increasing the hydrogen concentration in the silica glass.

  9. Photosensitivity of germanium-doped silica glass and fibers

    NASA Astrophysics Data System (ADS)

    Grubsky, Victor

    Germanium-doped silica glass changes its refractive index when it is exposed with UV light. This effect is caused by intrinsic defects of germanosilicate glass called germanium oxygen-deficient centers (GODC). The photosensitivity of glass allows fabrication of various refractive-index gratings in germanosilicate optical fibers. These gratings are basic elements used by the telecommunication industry. Nevertheless, the physical mechanisms causing the index change in glass are still unclear. In this thesis we discuss some aspects of the photosensitivity of germanium-doped glass and optical fibers. First, we present a historic overview of the previous work on defects in glass and their role for photosensitivity. The photoionization and densification theories of photosensitivity are reviewed. We then consider the transformations of defects in glass caused by UV radiation. We show that an index change can be produced by exciting either 240-nm or 330-nm absorption bands of GODC. We prove that the excitation of GODC to their triplet state is essential to produce a change in the glass structure. We also show that UV radiation forms a new defect with a luminescence band at 650 nm. We study the nature of the increase in glass photosensitivity caused by saturating glass with molecular hydrogen before exposing it to UV light. Hydrogen-loading the glass increases the saturated value of its index change by at least an order of magnitude and allows the use of high-coherence lasers at 275-305 nm for efficient and high-precision fiber grating fabrication. We also show that the stability of the refractive index change in hydrogen-loaded fibers is correlated with the water content of the glass. The difference between the spectral dependencies of photosensitivity in hydrogen-loaded and hydrogen-free glass suggests that different mechanisms are responsible for the index change in these two cases. We propose possible photoinduced reactions of hydrogen with germanium-doped glass

  10. Preparation of antibacterial silver-doped silica glass microspheres.

    PubMed

    Kawashita, Masakazu; Toda, Shogo; Kim, Hyun-Min; Kokubo, Tadashi; Masuda, Noriaki

    2003-08-01

    Various types of inorganic substances doped with silver ions have been developed as antibacterial materials, and some have already been commercialized. Colorless and chemically durable materials that slowly release silver ions are, however, still need to be developed. The present authors have previously shown that when a silica glass doped with silver and aluminium ions is prepared using the sol-gel method, the resultant product is colorless, chemically durable, and slowly releases silver ions into water over a long period. The doped silica glass takes a form of microspheres <1 microm in diameter, it is easily mixed with organic polymers, and the mixture can be formed into a thin film or fine fibers, etc. We report on the preparation of silver doped silica glass microspheres having a diameter =1 microm, using the sol-gel method. Initially, tetraethoxysilane was partially prehydrolyzed by water in ethanol, and then aluminium triisopropoxide was added to the solution to form Si-O-Al bonds. Finally, an ammonia solution containing silver nitrate was added to form silica microspheres doped with silver ion together with aluminium ions. The results show monodispersed microspheres 0.4-0.6 microm in diameter were obtained with nominal compositions of Si/Al/Ag = 1/0.01-0.03/0.003-0.03, with a molar ratio of Al/Ag = 1-3.3. The microspheres were colorless, showed a high chemical durability, and slowly released silver ions into water at 37 degrees C. Microspheres with the composition Si/Al/Ag = 1/0.01/0.01 showed excellent antibacterial activity against Escherichia coli. The minimum inhibitory concentration (MIC) of the microspheres was 400, which is less than the MIC value (800) of commercial antibacterial materials.

  11. Nanoporous silica glass for the immobilization of interactive enzyme systems.

    PubMed

    Buthe, Andreas; Wu, Songtao; Wang, Ping

    2011-01-01

    Recent pursuit on utilization of nanoscale materials has manifested a variety of configurations of highly efficient enzymic biocatalyst systems for biotechnological applications. Nanoscale structures are particularly powerful in effecting multienzyme biocatalysis. Inherent properties of nanomaterials--primarily, the high surface area to volume ratio and atomic scale 3D configurations--enable higher enzyme loadings, microenvironment control surrounding enzyme molecules, regulation on mass transfer, and protein structural stabilization of the biocatalyst as compared to traditional immobilization systems. This chapter introduces one versatile nanoscale immobilization method via details demonstrated using the case of nanoporous silica glass (30 nm diameter) for the concomitant incorporation of lactate dehydrogenase (LDH), glucose dehydrogenase (GDH), and the cofactor (NADH).

  12. 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.

  13. Ultrasonic Microspectroscopy Measurement of Fictive Temperature for Synthetic Silica Glass

    NASA Astrophysics Data System (ADS)

    Kushibiki, Jun-ichi; Arakawa, Mototaka; Ohashi, Yuji; Maruyama, Yuko

    2011-05-01

    Experimental procedures to evaluate the fictive temperature (TF) of synthetic silica glass were developed using ultrasonic microspectroscopy (UMS) technology by measuring longitudinal-wave velocity (Vl). Two kinds of commercial synthetic silica glass (without and with water) were demonstrated, resulting in the establishment of calibration lines between Vl and TF with a resolution within 1 °C and clear observation of their hydroxyl (OH) dependences. This ultrasonic method and system will be extremely useful and effective for improving mass-production conditions of glass ingots as well as for conducting basic studies on glass science.

  14. Dependence of flame characteristics on the bubble generation and hydroxyl content in silica glass

    NASA Astrophysics Data System (ADS)

    Sekiya, E. H.; Torikai, D.; Suzuki, C. K.

    High quality silica glass was prepared by flame fusion Verneuil technique using two types of silica powders: purified natural quartz and synthetic sol-gel silica. Two different types of flames, GC2/O2 and LPG/O2, with various conditions of mixture ratios were used. Bubble generation and hydroxyl incorporation were analyzed in these as-fused materials. Silica glass prepared with purified natural quartz powder showed large concentration of bubbles in the most recently fused region. The bubbles were generated from the fluid and depending on the fusion condition it was possible to obtain bubble-free silica glass. A strong dependence of hydroxyl concentration on the flame mixture ratio was also observed.

  15. Structure and Properties of Silica Glass Densified in Cold Compression and Hot Compression

    NASA Astrophysics Data System (ADS)

    Guerette, Michael; Ackerson, Michael R.; Thomas, Jay; Yuan, Fenglin; Bruce Watson, E.; Walker, David; Huang, Liping

    2015-10-01

    Silica glass has been shown in numerous studies to possess significant capacity for permanent densification under pressure at different temperatures to form high density amorphous (HDA) silica. However, it is unknown to what extent the processes leading to irreversible densification of silica glass in cold-compression at room temperature and in hot-compression (e.g., near glass transition temperature) are common in nature. In this work, a hot-compression technique was used to quench silica glass from high temperature (1100 °C) and high pressure (up to 8 GPa) conditions, which leads to density increase of ~25% and Young’s modulus increase of ~71% relative to that of pristine silica glass at ambient conditions. Our experiments and molecular dynamics (MD) simulations provide solid evidences that the intermediate-range order of the hot-compressed HDA silica is distinct from that of the counterpart cold-compressed at room temperature. This explains the much higher thermal and mechanical stability of the former than the latter upon heating and compression as revealed in our in-situ Brillouin light scattering (BLS) experiments. Our studies demonstrate the limitation of the resulting density as a structural indicator of polyamorphism, and point out the importance of temperature during compression in order to fundamentally understand HDA silica.

  16. Structure and Properties of Silica Glass Densified in Cold Compression and Hot Compression.

    PubMed

    Guerette, Michael; Ackerson, Michael R; Thomas, Jay; Yuan, Fenglin; Bruce Watson, E; Walker, David; Huang, Liping

    2015-10-15

    Silica glass has been shown in numerous studies to possess significant capacity for permanent densification under pressure at different temperatures to form high density amorphous (HDA) silica. However, it is unknown to what extent the processes leading to irreversible densification of silica glass in cold-compression at room temperature and in hot-compression (e.g., near glass transition temperature) are common in nature. In this work, a hot-compression technique was used to quench silica glass from high temperature (1100 °C) and high pressure (up to 8 GPa) conditions, which leads to density increase of ~25% and Young's modulus increase of ~71% relative to that of pristine silica glass at ambient conditions. Our experiments and molecular dynamics (MD) simulations provide solid evidences that the intermediate-range order of the hot-compressed HDA silica is distinct from that of the counterpart cold-compressed at room temperature. This explains the much higher thermal and mechanical stability of the former than the latter upon heating and compression as revealed in our in-situ Brillouin light scattering (BLS) experiments. Our studies demonstrate the limitation of the resulting density as a structural indicator of polyamorphism, and point out the importance of temperature during compression in order to fundamentally understand HDA silica.

  17. XPS study on silica bismuthate glasses and glass ceramics

    NASA Astrophysics Data System (ADS)

    Simon, V.; Todea, M.; Takács, A. F.; Neumann, M.; Simon, S.

    2007-01-01

    X-ray photoelectron spectroscopy (XPS) was used to evidence the effect of the Bi 2O 3 to SiO 2 ratio and of partial crystallisation on the electronic charge density around the atoms entering silica-bismuthate glasses of nominal composition 0.01Fe 2O 3ṡ0.99[ xSiO 2ṡ(100- x)Bi 2O 3] with 10≤x≤60 mol%. The core level spectra show significant composition dependent changes in binding energy, and the full width at half maximum of photoelectron peaks both of cations and of oxygen atoms. The analysis reveals changes in electron density correlated with the ionic and covalent character of the samples. The shift in binding energy suggests charge transfer from silicon and oxygen atoms to bismuth atoms. Contrary to the expected behaviour in conventional silicate oxide systems, the results indicate an increase of ionicity for silicon and of covalency for bismuth atoms. The same evolution of ionicity/covalency is observed after partial crystallisation.

  18. Femtosecond laser fabrication of nanostructures in silica glass.

    PubMed

    Taylor, R S; Hnatovsky, C; Simova, E; Rayner, D M; Bhardwaj, V R; Corkum, P B

    2003-06-15

    A femtosecond laser beam focused inside fused silica and other glasses can modify the refractive index of the glass. Chemical etching and atomic-force microscope studies show that the modified region can have a sharp-tipped cone-shaped structure with a tip diameter as small as 100 nm. Placing the structure near the bottom surface of a silica glass sample and applying a selective chemical etch to the bottom surface produces clean, circular, submicrometer-diameter holes. Holes spaced as close to one another as 1.4 microm are demonstrated.

  19. Photoluminescence decay dynamics of transparent silica glass prepared from nanometer-sized silica particles

    SciTech Connect

    Yamada, Tomoko; Uchino, Takashi

    2005-08-22

    The time-resolved photoluminescence (PL) decays are measured for transparent amorphous silica prepared from solid-phase sintering of nanometer-sized silica particles, which has recently been shown to exhibit a unique white PL emission under ultraviolet excitation [T. Uchino and T. Yamada, Appl. Phys. Lett. 85, 1164 (2004)]. Unlike usual PL processes observed in normal silica glass, it is shown that the present PL results from trapping-controlled migration of photoexcited carriers and their radiative recombination.

  20. Photoluminescence decay dynamics of transparent silica glass prepared from nanometer-sized silica particles

    NASA Astrophysics Data System (ADS)

    Yamada, Tomoko; Uchino, Takashi

    2005-08-01

    The time-resolved photoluminescence (PL) decays are measured for transparent amorphous silica prepared from solid-phase sintering of nanometer-sized silica particles, which has recently been shown to exhibit a unique white PL emission under ultraviolet excitation [T. Uchino and T. Yamada, Appl. Phys. Lett. 85, 1164 (2004)]. Unlike usual PL processes observed in normal silica glass, it is shown that the present PL results from trapping-controlled migration of photoexcited carriers and their radiative recombination.

  1. Fabrication of transparent superhydrophobic glass with fibered-silica network

    NASA Astrophysics Data System (ADS)

    Zhang, Feng; Shi, Zhenwu; Jiang, Yingjie; Xu, Chengyun; Wu, Zhuhui; Wang, Yanyan; Peng, Changsi

    2017-06-01

    In this paper, silica was deposited on the soot film pre-coated glass via chemical vapor deposition. Through calcination at 500 °C with the assistance of O2 airflow, the soot film was removed and a novel robust fibered-silica network film was then decorated onto the glass substrate. After modification with fluorosilane, the surface water contact angle (WCA) was 166° and sliding angle (SA) was 1° which behaves a good self-cleaning for the as-prepared glass. And its average transmittance was still over 88% in visible wavelength. Moreover, this fibered-silica coating showed a strong tolerance for heavy water droplets, acid/alkali corrosion, salt solution immersion and thermal treatment.

  2. Time-resolved dynamics of plasma self-channeling and bulk modification in silica glasses induced by a high-intensity femtosecond laser

    NASA Astrophysics Data System (ADS)

    Cho, Sung-Hak; Kumagai, Hiroshi; Midorikawa, Katsumi; Obara, Minoru

    2000-11-01

    The time-resolved dynamics of plasma self-channeling and refractive index bulk modification in the silica glasses are first observed using a high-intensity femtosecond (110 fs) Ti: sapphire laser ((Lambda) pequals790 nm) We propose the new pump-probe measurement to observe the lifetime of both plasma self-channeling and induced refractive index bulk modification. The energy variation of transmitted probe beam, which propagates transversely through the plasma self- channeling is measured. At the pre-breakdown domain, the lifetime of induced plasma self-channeling is 20 ps and structural transition time for reforming the refractive index change is 10 ps. At the breakdown domain, however, the lifetime of induced plasma formation is 30 ps and structural transition time for forming the optical damage is 40 ps. We find that the process of refractive index bulk modification is significantly different from those of optical damage. We also measure a wavelength shift (blueshift) of reflected probe beam from the surface of the plasma self-channeling induced by the pump beam. A maximum value of blue wavelength shift is 3 nm when the time delay of probe beam is 2 ps. The expanding velocity of the plasma ionization is calculated from the wavelength shirt (blueshift) using the Doppler formula. A maximum velocity of the plasma ionization is calculated to be approximately 6x105 m/s at the delay time of 2 ps.

  3. 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.

  4. Indirect slumping of D263 glass on Fused Silica mould

    NASA Astrophysics Data System (ADS)

    Proserpio, Laura; Wen, Mingwu; Breunig, Elias; Burwitz, Vadim; Friedrich, Peter; Madarasz, Emanuel

    2016-07-01

    The Slumped Glass Optic (SGO) group of the Max Planck Institute for Extraterrestrial physics (MPE) is studying the indirect slumping technology for its application to X-ray telescope manufacturing. Several aspects of the technology have been analyzed in the past. During the last months, we concentrated our activities on the slumping of Schott D263 glass on a precise machined Fused Silica mould: The concave mould was produced by the Italian company Media Lario Technologies with the parabola and hyperbola side of the typical Wolter I design in one single piece. Its shape quality was estimated by optical metrology to be around 6 arcsec Half Energy Width (HEW) in double reflection. The application of an anti-sticking Boron Nitride layer was necessary to avoid the adhesion of the glass on the mould during the forming process at high temperatures. The mould has been used for the slumping of seven mirror segments 200 mm long, 100 mm wide, and with thickness of 200 μm or 400 μm. The influence of the holding time at maximum temperature was explored in this first run of tests. The current results of the activities are described in the paper and plans for further investigations are outlined.

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

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

    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-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.

  6. 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.

  7. Damages to optical silica glass: processes and mechanisms

    NASA Astrophysics Data System (ADS)

    Luo, Sheng-Nian; Zheng, Lianqing; An, Qi; Wu, Heng-An; Xia, Kaiwen; Ni, Sidao

    2007-01-01

    We present recent results of molecular dynamics simulations to illustrate the processes and mechanisms in damages to silica glass, including densification, cavitation, fragmentation and agglomeration via photon, electron, ion and neutron radiations and stresses. Radiation of glass creates point defects (vacancies and interstitials), and subsequent structure relaxation induces densification. Nanovoid below a certain size and rapid-quenching of silica liquid can also densify a glass. Hot spots due to photon-absorbing impurities in glass may cause local densification and cavitation as well. Densification can also be induced by compressional stress, and spall, by tensile stress. The densified glasses, regardless of the exact processes, share similar structural and vibrational properties, for example, the five-fold coordinated Si atoms. Densification is essentially a kinetic frustration during structure relaxation driven by excessive free energy, e.g., due to defects or stresses. The point-defect mechanism is dominant for densification without compression and complemented by thermal spike mechanism in thermal processes. Defects, thermal effects and stresses may interplay in a general damage process in silica glass.

  8. 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.

  9. Low-power continuous-wave nonlinear optics in doped silica glass integrated waveguide structures

    NASA Astrophysics Data System (ADS)

    Ferrera, M.; Razzari, L.; Duchesne, D.; Morandotti, R.; Yang, Z.; Liscidini, M.; Sipe, J. E.; Chu, S.; Little, B. E.; Moss, D. J.

    2008-12-01

    Photonic integrated circuits are a key component of future telecommunication networks, where demands for greater bandwidth, network flexibility, and low energy consumption and cost must all be met. The quest for all-optical components has naturally targeted materials with extremely large nonlinearity, including chalcogenide glasses and semiconductors, such as silicon and AlGaAs (ref. 4). However, issues such as immature fabrication technology for chalcogenide glass and high linear and nonlinear losses for semiconductors motivate the search for other materials. Here we present the first demonstration of nonlinear optics in integrated silica-based glass waveguides using continuous-wave light. We demonstrate four-wave mixing, with low (5 mW) continuous-wave pump power at λ = 1,550 nm, in high-index, doped silica glass ring resonators. The low loss, design flexibility and manufacturability of our device are important attributes for low-cost, high-performance, nonlinear all-optical photonic integrated circuits.

  10. Proton therapy dosimetry by using silica glass optical fiber microprobes

    NASA Astrophysics Data System (ADS)

    Darafsheh, Arash; Taleei, Reza; Kassaee, Alireza; Finlay, Jarod C.

    2017-02-01

    We investigated the feasibility of proton therapy dosimetry by using bare silica glass optical fibers. A silica glass fiber, with 400μm core diameter, was placed in proton radiation fields generated by a proton therapy cyclotron and simultaneously luminescence spectroscopy was performed to analyze the emission spectrum of the fiber tip. In order to measure the radiation absorbed dose at various depths in tissue-mimicking media, the fiber tip was embedded in a plastic slab and additional slabs of phantom were added sequentially. The spectrum of the irradiated fiber over the 400-700 nm sensitivity range of the spectrometer shows two distinct peaks at 460 and 650 nm, whose spectral shape is different from that of Čerenkov radiation. We found that the emission peak at 650 nm shows correlation with the radiation absorbed dose measured by a standard ion chamber device indicating the feasibility of proton dose measurement by using a bare silica fiber.

  11. Surface microstructures of silica glass by laser-induced backside wet etching

    NASA Astrophysics Data System (ADS)

    Niino, H.; Kawaguchi, Y.; Sato, T.; Narazaki, A.; Kurosaki, R.

    2008-02-01

    We have investigated a one-step method to fabricate a microstructure on a silica glass plate using laser-induced backside wet etching (LIBWE) upon irradiation with DPSS (diode-pumped solid state) lasers. Well-defined deep microtrenches without crack formations on a fused silica glass plate were fabricated by LIBWE method. As the laser beam of DPSS UV laser at a high repetition rate up to 5 - 100 kHz is scanned on the sample surface with the galvanometer controlled by a computer for flexible operations, galvanometer-based point scanning system is suitable for a rapid prototyping process according to electronic design data in the computer. The behavior of liquid ablation (explosive vaporization) was monitored by impulse pressure detection with a fast-response piezoelectric pressure gauge. LIBWE method is suitable for rapid prototyping and rapid manufacturing of surface microstructuing of silica glass as mask-less exposure system in a conventional atmospheric environment.

  12. Tellurite glass thin films on silica and polymer using UV (193 nm) pulsed laser ablation

    NASA Astrophysics Data System (ADS)

    Zhao, Zhanxiang; Jose, Gin; Steenson, Paul; Bamiedakis, Nikos; Penty, Richard V.; White, Ian H.; Jha, Animesh

    2011-03-01

    Erbium-doped tellurite glass thin films were deposited using excimer (193 nm) laser ablation onto two different types of substrates: silica and polymer-coated silica for engineering optical integrated active-passive devices. The deposition conditions were optimized for both substrates in order to produce high-quality rare-earth (Er3+) ion-doped glass thin films with low propagation loss. The optical and spectroscopic properties of the deposited films, namely transmittance, fluorescence, lifetime as well as refractive indices at 633 nm were measured and analysed in detail.

  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. 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.

  16. 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.

  17. 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.

  18. Low Pressure Origin of High-Silica Rhyolites

    NASA Astrophysics Data System (ADS)

    Gualda, G. A.; Ghiorso, M. S.

    2011-12-01

    High-silica rhyolites and granites are common components of the continental crust. High-silica rhyolites appear as whole-rocks, glass inclusions and matrix glass; in homogeneous crystal-rich dacites, matrix glass is usually high-silica rhyolite (Fish Canyon Tuff), while in more evolved systems both whole-rocks and glass are high-silica rhyolite (Bishop Tuff). High-silica granites are typically aplites (Tuolomne Intrusive Suite), but also appear as larger discrete units in plutons (Spirit Mountain Batholith). Geobarometric evidence suggests low pressure (<300 MPa) crystallization of high-silica melts. But recent works (Thomas et al. 2010 - CMP 160:743-759) have appealed to quartz crystallization at high pressures (>500 MPa), suggesting a polybaric evolution. We use a combination of phase equilibria considerations, literature and database data to constrain the pressure under which high-silica rhyolite melts form and crystallize. Phase relations in the haplogranitic (Qz-Ab-Or) system are well-known from experiments. A first order feature is that the stability field of sanidine increases while that of quartz decreases - causing the quartz-sanidine cotectic to migrate towards the quartz apex - with decreasing pressure. The effect is that compositions of cotectic melts become more quartz-normative with decreasing pressure. Experiments suggest that the pressure effect is persistent in An and CO2-bearing systems. We retrieved from EarthChem 627 analyses of strictly metaluminous rhyolitic (in TAS classification diagram) glass. Compositions (anhydrous basis) binned in 1 wt. % SiO2 increments were projected onto the ternary (following Blundy & Cashman 2001 - CMP 140:631-650) and parallel the experimental cotectics. At low silica (70%), glass compositions cluster around the 1000 MPa eutectic; at high silica (76%), compositions are distributed between 200 and 300 MPa cotectics; at higher silica (78%), compositions are distributed along the 100 MPa cotectic. The correlation

  19. 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.

  20. 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.

  1. Ab initio simulation of permanent densification in silica glass

    NASA Astrophysics Data System (ADS)

    Ryuo, Emina; Wakabayashi, Daisuke; Koura, Akihide; Shimojo, Fuyuki

    2017-08-01

    To clarify the microscopic structure of densified Si O2 glass, we have conducted ab initio molecular-dynamics simulations on the decompression process of Si O2 glass in its relaxed state from high pressures up to 40 GPa. When decompressed from high pressures above at least 15 GPa, the density and structure always converge to those of densified glass, while the coordination number of silicon decreases to four rapidly. This is in good agreement with previous experimental studies and strongly suggests that densified glass behaves as a high-pressure polymorph of Si O2 glass. In comparison to ordinary glass, although the coordination number of densified glass is almost the same, the size of an intermediate-range network consisting of Si O4 tetrahedra is smaller. Detailed analyses clarify that Si O4 tetrahedra in densified glass are deformed and the Si-O bonds are less covalent.

  2. 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.

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

    SciTech Connect

    Mann, Sarita; Rani, Pooja

    2016-05-06

    Silica is one of the most commonly encountered substances in daily life and in electronics industry. Crystalline SiO{sub 2} (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 SiO{sub 2} 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.

  4. 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.

  5. Chiroptical properties photo-induced by femtosecond laser irradiation in silica glass

    NASA Astrophysics Data System (ADS)

    Desmarchelier, R.; Lancry, M.; Tian, J.; Poumellec, B.

    2017-01-01

    We confirm that the irradiation of silica glass (achiral material) with a linear polarized Gaussian beam (achiral light) from a femtosecond laser can create chiroptical properties such as UV-Vis circular dichroism. This last result is surprising because crystalline silica exhibits optical rotation but no circular dichroism in the UV-Vis range. In this paper we show that ellipticity can be as high as 1400 mdeg at 400 nm, by controlling the laser irradiation configuration. In addition, we show that the non-reversible sample circular dichroism measurements are due to the fact that linear and circular optical properties do not have the same distribution in depth.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. Investigation on femtosecond laser-assisted microfabrication in silica glasses

    NASA Astrophysics Data System (ADS)

    Liu, Hewei; Chen, Feng; Yang, Qing; Si, Jinhai; Hou, Xun

    2010-11-01

    Fabrication of microstructures embedded in silica glasses using a femtosecond (fs)-laser-assisted chemical etching technique is systematically studied in this work. By scanning the laser pulses inside samples followed by the treatment of 5%-diluted hydrofluoric (HF) acid, groups of straight channels are fabricated and the relationship between the etching rate and processing parameters, including laser power, scanning speed, scanning time and laser polarization, is demonstrated. Based on the optimization of these parameters, complicated microstructures such as channels, cavities and their combinations are manufactured. The work has great potential applications in microelectromechanical systems, biomedical detection and chemical analysis.

  11. Silica nanoparticles on front glass for efficiency enhancement in superstrate-type amorphous silicon solar cells

    NASA Astrophysics Data System (ADS)

    Das, Sonali; Banerjee, Chandan; Kundu, Avra; Dey, Prasenjit; Saha, Hiranmay; Datta, Swapan K.

    2013-10-01

    Antireflective coating on front glass of superstrate-type single junction amorphous silicon solar cells (SCs) has been applied using highly monodispersed and stable silica nanoparticles (NPs). The silica NPs having 300 nm diameter were synthesized by Stober technique where the size of the NPs was controlled by varying the alcohol medium. The synthesized silica NPs were analysed by dynamic light scattering technique and Fourier transform infrared spectroscopy. The NPs were spin coated on glass side of fluorinated tin oxide (SnO2: F) coated glass superstrate and optimization of the concentration of the colloidal solution, spin speed and number of coated layers was done to achieve minimum reflection characteristics. An estimation of the distribution of the NPs for different optimization parameters has been done using field-emission scanning electron microscopy. Subsequently, the transparent conducting oxide coated glass with the layer having the minimum reflectance is used for fabrication of amorphous silicon SC. Electrical analysis of the fabricated cell indicates an improvement of 6.5% in short-circuit current density from a reference of 12.40 mA cm-2 while the open circuit voltage and the fill factor remains unaltered. A realistic optical model has also been proposed to gain an insight into the system.

  12. High-Silica Lamoose Rock

    NASA Image and Video Library

    2015-07-23

    A rock fragment dubbed "Lamoose" is shown in this picture taken by the Mars Hand Lens Imager (MAHLI) on NASA's Curiosity rover. Like other nearby rocks in a portion of the "Marias Pass" area of Mt. Sharp, Mars, it has unusually high concentrations of silica. The high silica was first detected in the area by the Chemistry & Camera (ChemCam) laser spectrometer. This rock was targeted for follow-up study by the MAHLI and the arm-mounted Alpha Particle X-ray Spectrometer (APXS). Silica is a rock-forming compound containing silicon and oxygen, commonly found on Earth as quartz. High levels of silica could indicate ideal conditions for preserving ancient organic material, if present, so the science team wants to take a closer look. The rock is about 4 inches (10 centimeters) across. It is fine-grained, perhaps finely layered, and etched by the wind. The image was taken on the 1,041st Martian day, or sol, of the mission (July 11, 2015). MAHLI was built by Malin Space Science Systems, San Diego. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Science Laboratory Project for the NASA Science Mission Directorate, Washington. JPL designed and built the project's Curiosity rover. http://photojournal.jpl.nasa.gov/catalog/PIA19828

  13. 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. © The Author(s) 2015.

  14. Sealing of Al-containing stainless steel to lithia-alumina-silica glass-ceramic

    SciTech Connect

    Cassidy, R.T.; Moddeman, W.E.

    1989-12-31

    Recent work on a new glass-ceramic/alloy for pyrotechnic components is discussed. A newly developed family of austenitic stainless steels has been hermetically sealed to a widely used lithia-alumina-silica (LAS) glass-ceramic. These alloys, originally developed for high oxidation resistance, contain 4-5 wt% Al. The presence of Al offers several advantages from a glass or glass/ceramic sealing point of view: presence of a tenacious, stable oxide (Al{sub 2}O{sub 3}) on the alloys` surface as well as the fact that they can be strengthened during sealing via precipitation of a secondary phase, NiAl. In addition these new alloys offer lower material and machining costs and improved weldability compared to the widely used Ni-base superalloys.

  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. Fabrication of an octadecylated silica monolith inside a glass microchip for protein enrichment.

    PubMed

    Alzahrani, Eman; Welham, Kevin

    2012-10-21

    Silica-based monolithic materials have shown great promise for use as sorbent materials due to their large surface area and bimodal pore size distribution. In this paper, a new process for the fabrication of a silica-based monolith inside a glass microchip and its modification with octadecylsilyl ligands was successfully developed for use in the microchip-based solid phase extraction of proteins. Monolithic porous silica without cracks was prepared by a sol-gel process, followed by placement of the monolithic silica disk inside the extraction chamber in the base plate of the microchip. The two plates of the glass microchip were then thermally bonded at 575 °C for 3 hours. The silica-based monolith was not affected by the thermal bonding of the two plates of the microchip. This process completely avoids the problem of shrinkage in the silica skeleton during preparation. The monolithic silica disk inside the glass microchip was subsequently modified with octadecylsilyl (C(18)) moieties for increased protein binding capacity. The performance of the microchip was evaluated using the extraction of six proteins varying in molecular weight and isoelectric point, namely insulin, cytochrome C, lysozyme, myoglobin, β-lactoglobulin, and hemoglobin at a concentration of 60 μM. The standard protein was mixed with a double concentration of the detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS). The results show that the octadecylated silica monolith was permeable, has the ability to remove impurities, and achieved a high extraction recovery of the proteins (94.8-99.7%) compared with conventional octadecylated silica particles (48.3-91.3%). The chip-to-chip reproducibility was assessed by calculating the relative standard deviations (RSDs) for the six proteins during extraction. The intra-batch and inter-batch RSDs were in the range of 2.0-4.5% and 2.9-6.4%, respectively. This new microfluidic device for protein extraction may find an application in

  17. Silica glass structure generation for ab initio calculations using small samples of amorphous silica

    NASA Astrophysics Data System (ADS)

    van Ginhoven, Renée M.; Jónsson, Hannes; Corrales, L. René

    2005-01-01

    Multiple small samples of amorphous silica have been generated and optimized using classical dynamics and the van Beest-Kramer-van Santen (BKS) empirical potential function. The samples were subsequently optimized and annealed using density functional theory (DFT) with both the local density and the generalized gradient approximations. A thorough analysis of the local and medium-range structure of the optimized samples obtained from the different methods was carried out. The structural characteristics obtained for the average of small systems each containing ca. 100 ions are compared for each of the different methods, and to the BKS simulation of a larger system. The differences found between the DFT and BKS simulations and the effects of volume relaxation on the structures are discussed. Fixed-volume samples are compared to neutron scattering data, with good agreement to 5Å , the length limit of the sample sizes used here. It is shown that by creating multiple small samples, it is possible to achieve a good statistical sampling of structural features consistent with larger simulated glass systems. This study also shows that multiple small samples are necessary to capture the structural distribution of silica glass, and therefore to study more complex processes in glass, such as reactions.

  18. 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.

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

    DOE PAGES

    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

    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.

  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. Luminescence of Yb3+ ions in silica-based glasses synthesized by SPCVD

    NASA Astrophysics Data System (ADS)

    Savel'ev, E. A.; Krivovichev, A. V.; Yapaskurt, V. O.; Golant, K. M.

    2017-02-01

    The spectra and decay kinetics of Yb3+ single-ion and cooperative luminescence in silica-based optical slab waveguides are investigated. The slab waveguides with a high content of Yb and various amounts of P and Al additives to the light-guiding core glass were fabricated on the basis of fused and unfused glassy layers synthesized via surface-plasma chemical vapor deposition (SPCVD). Luminescence was pumped by laser diodes at ∼904 nm and ∼967 nm wavelengths and recorded in the 450-1175 nm spectral band. For the pure silica host doped with Yb, only the influence of cluster sizes on the luminescence decay kinetics is determined. It is found that the profusion of deposited glass with increased Al content favors separation by geometry of the Yb3+ and Tm3+ ions; the latter are present in the glass as an uncontrollable contamination. Evidence was found that at least two different types of Yb clusters were formed in P doped silica as a result of profusion.

  3. 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.

  4. Distributions of self-trapped hole continuums in silica glass

    SciTech Connect

    Wang, R. P.; Saito, K.; Ikushima, A. J.

    2006-07-01

    Photobleaching of self-trapped holes (STH) in low temperature UV-irradiated silica glass has been investigated by the electron spin resonance method. The bleaching time dependence of the decay of two kinds of STH, STH{sub 1}, and STH{sub 2}, could be well fitted by the stretched exponential function, and STH{sub 2} has a quicker decay than STH{sub 1}. On the other hand, the decay becomes significant large when the photon energy increases from 1.5 to 2.0 eV, and then keeps constant with a further increase of photon energy. The distributions of the STH continuums are estimated at the positions on top of the valence band, being 1.66{+-}0.27 eV for STH{sub 1} and 1.63{+-}0.33 eV for STH{sub 2}. A possible recombination mechanism is proposed to explain the decay of STH signals.

  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. Encapsulation of cobalt porphyrins in organically modified silica gel glasses and their nonlinear optical properties

    NASA Astrophysics Data System (ADS)

    Zheng, Chan; Huang, Li; Li, Wei; Chen, Wenzhe

    2017-01-01

    2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin Cobalt(II) (CoPor) was introduced into nanostructured organically modified silica (ORMOSIL) using a sol-gel technique. Scanning electron microscopy, Fourier transform infrared (FT-IR), thermogravimetric analysis, and UV-Vis spectroscopy were performed to investigate the morphology, structure, thermal stability, and linear optical properties of the resulting gel glasses. The FT-IR spectrum and UV-Vis spectra strongly indicated the formation of a silica gel glass network and the successful encapsulation of CoPor in ORMOSIL silica gel glasses, respectively. The introduction of guest CoPor molecules induces silica to form more condensed surface characteristics, owing to the fact that CoPor can promote the hydrolysis and polycondensation procedure, and hence have better thermal stability as compared to blank silica gel glasses. Meanwhile, the dimerization phenomenon in a liquid matrix can be effectively suppressed in a silica solid-state matrix and is attributed to the `cage protection effect.' The nonlinear optical (NLO) properties of CoPor gel glasses were investigated using the open-aperture Z-scan technique at 532 nm. The NLO performance of CoPor-incorporated solid-state silica gel glasses has been improved in comparison with those dispersed in dimethylformamide solution. More significantly, the NLO properties of CoPor-doped ORMOSIL gel glasses can be controlled by adjusting the concentration of the CoPor molecules.

  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. 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.

  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

    2012-02-08

    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.

  10. 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.

  11. 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.

  12. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-07-01

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

  15. 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.

  16. 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.

  17. Dynamics of Methyl Methacrylate Nanoconfined in Silica Sol Glasses Studied by Optical Kerr Effect Spectroscopy

    NASA Astrophysics Data System (ADS)

    Meng, Dujuan; Xue, Lianjie; Tamas, George; Quitevis, Edward; Simon, Sindee

    2014-03-01

    Nanoconfinement has been found to have an effect on polymerization processes [1,2] and on the glass transition temperature Tg [3]. Here we report studies of the nanoconfinement effect on the dynamics of monomers in the pores of silica sol-gel glass. The samples were prepared under a vacuum and studied by using optical Kerr effect (OKE) spectroscopy. The reorientational dynamics of methyl methacrylate (MMA) confined in silica sol-gel glasses with pore diameters of 32, 41, and 82 Å was studied. The decays of the reorientational correlation function C(t) became longer as the pore size decreased. Based on the analysis of the reorientational correlation functions using a two-state model [4], the nanoconfinement effect is due to the interaction of molecules with the surface of the silica-gel glass. In a study of the effect of nanoconfinement in modified silica sol-gel glasses, which were obtained by refluxing the sol-gel glasses in methanol to give hydrophobic pore surfaces, the decay is faster in the modified silica gel glass than in the unmodified sol-gel glass. This work is supported by NSF Grant CMMI-1235346.

  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. Helium penetrates into silica glass and reduces its compressibility.

    PubMed

    Sato, Tomoko; Funamori, Nobumasa; Yagi, Takehiko

    2011-06-14

    SiO(2) glass has a network structure with a significant amount of interstitial voids. Gas solubilities in silicates are expected to become small under high pressure due to compaction of voids. Here we show anomalous behaviour of SiO(2) glass in helium. Volume measurements clarify that SiO(2) glass is much less compressible than normal when compressed in helium, and the volume in helium at 10 GPa is close to the normal volume at 2 GPa. X-ray diffraction and Raman scattering measurements suggest that voids are prevented from contracting when compressed in helium because helium penetrates into them. The estimated helium solubility is very high and is between 1.0 and 2.3 mol per mole of SiO(2) glass at 10 GPa, which shows marked contrast with previous models. These results may have implications for discussions of the Earth's evolution as well as interpretations of various high-pressure experiments, and also lead to the creation of new materials.

  20. Permanent computer-generated holograms embedded in silica glass by femtosecond laser pulses.

    PubMed

    Li, Yan; Dou, Yanping; An, Ran; Yang, Hong; Gong, Qihuang

    2005-04-04

    We present a novel technique to directly fabricate permanent computer-generated holograms inside silica glass with femtosecond laser pulses. The Fourier transform of an object is performed using a computer and the complex amplitude distribution is encoded by the detour phase method. The resulted cell-oriented hologram is directly written inside a bulk of silica glass by femtosecond laser-induced microexplosion. The image is then reconstructed with a collimated He-Ne laser beam.

  1. 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.

  2. 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.

  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. Structural and Microwave Properties of Silica Xerogel Glass-Ceramic Sintered by Sub-millimeter Wave Heating using a Gyrotron

    NASA Astrophysics Data System (ADS)

    Aripin, H.; Mitsudo, S.; Prima, E. S.; Sudiana, I. N.; Tani, S.; Sako, K.; Fujii, Y.; Saito, T.; Idehara, T.; Sano, S.; Sunendar, B.; Sabchevski, S.

    2012-11-01

    In this paper, we present and discuss experimental results from a microwave sintering of silica glass-ceramics, produced from amorphous silica xerogel extracted from sago waste ash. As a radiation source for a microwave heating a sub-millimeter wave gyrotron (Gyrotron FU CW I) with an output frequency of 300 GHz has been used. The powders of the amorphous silica xerogel have been dry pressed and then sintered at temperatures ranging from 300 °C to 1200 °C. Microwave absorbing properties of the sintered samples were investigated by measuring the dielectric constant, the dielectric loss, and the reflection loss at different frequencies in the interval from 8.2 to 12.4 GHz. Furthermore, the characteristics of the formation process for producing silica glass-ceramics were studied using a Raman Spectroscopy and a Scanning Electron Microscopy (SEM). The results indicate that the samples sintered at 1200 °C are characterized by lower reflection losses and a better transparency due to the formation of a fully crystallized silica glass- ceramic at sufficiently high temperature.

  5. Enhanced 2.0 μm emission in Ho3+/Yb3+ co-doped silica-germanate glass

    NASA Astrophysics Data System (ADS)

    Xia, Jienan; Tian, Ying; Li, Bingpeng; Zheng, Lixia; Jing, Xufeng; Zhang, Junjie; Xu, Shiqing

    2017-03-01

    A detailed investigation on thermal and spectroscopic properties of different Ho3+/Yb3+ concentration ratios in silica-germanate glasses is displayed. According to the measurement of thermal properties, the host glass possesses high transition temperature (585 °C) as well as the large ΔT(155 °C). The 2.0 μm fluorescence can be obtained from all the samples. Maximum stimulated emission cross-section of around 2.0 μm is 0.56 × 10-20 cm2 of Ho3+ as calculated by McCumber theory. Besides, the underlying mechanism is analyzed by means of fluorescence spectra. Thus, desirable thermal properties and spectroscopic characteristics of Ho3+/Yb3+ co-doped silica-germanate glass is a promising material in 2.0 μm emission.

  6. Effects of F- on the optical and spectroscopic properties of Yb3+/Al3+-co-doped silica glass

    NASA Astrophysics Data System (ADS)

    Xu, Wenbin; Yu, Chunlei; Wang, Shikai; Lou, Fengguang; Feng, Suya; Wang, Meng; Zhou, Qinling; Chen, Danping; Hu, Lili; Guzik, Malgorzata; Boulon, Georges

    2015-04-01

    Yb3+/Al3+-co-doped silica glasses with different F- content were prepared in this work by sol-gel method combined with high temperature sintering. XRF, FTIR and XPS methods were used to confirm the presence of F-. The effects of F- on the optical and spectroscopic properties of these glasses have been investigated. It is worth to notice that the F-/Si4+ mass ratio equal to 9% is a significant value showing a real change in the variation trends of numerous following parameters: refractive index, UV absorption edge, absorption and emission cross sections, scalar crystal-field NJ and fluorescent lifetimes. Furthermore, introduction of F- can adjust the refractive index of Yb3+/Al3+-co-doped silica glass and it is useful for large mode area (LMA) fibers.

  7. Light-controlled gas permeability of mesoporous silica glass bearing photochromic spironaphthoxazine on its surface.

    PubMed

    Yagi, Shigeyuki; Minami, Naemi; Fujita, Junpei; Hyodo, Yutaka; Nakazumi, Hiroyuki; Yazawa, Tetsuo; Kami, Tetsuro; Ali, Aliyar Hyder

    2002-10-21

    N2 and CO2 gas permeability of mesoporous silica glass bearing photochromic indolinospironaphth[2,1-b][1,4]oxazine through a covalent linkage was controlled by photo-irradiation: the photo-isomerization of the spironaphthoxazine to the photomerocyanine form suppressed the gas permeation of the glass.

  8. Deposition of thin mesoporous silica films on glass substrates from basic solution.

    PubMed

    Shimura, Naoki; Ogawa, Makoto

    2006-11-01

    Transparent thin (ca. 100 nm) films of silica-surfactant mesostructured materials were deposited on borosilicate glass plates and soda-lime glass tubes from aqueous solutions containing tetraethoxysilane, alkyltrimethylammonium chloride, ammonia, and methanol. By calcination in air, the films became mesoporous (BET surface area of 700-900 m2 g-1) with pore diameter 2.0-2.8 nm.

  9. Cross Section Morphology of the Scratch Induced Cracks in Soda-Lime-Silica Glass

    NASA Astrophysics Data System (ADS)

    Matsuoka, Jun; Guo, Danwei; Yoshida, Satoshi

    2017-03-01

    Scratch-induced cracking is a serious problem for the use of glass products. At the scratch process, both median (vertical to the glass surface) and lateral (horizontal to the glass surface) cracks are formed. In this study, morphology of the scratch-induced cracks in a commercial soda-lime-silica glass was investigated by the scanning electron microscopy for the specimen broken across the scratch groove. Scratch test was carried out using a Knoop indenter in water and in dehydrated heptane. When scratch speed was 70 x 10-6 ms-1, length of both vertical and horizontal cracks was proportional to the normal load at scratching, and environmental dependence was not observed. When scratch speed was increased with the constant normal load of 200g, length of both cracks was decreased. In the case of horizontal crack, no environmental effect was observed. On the other hand, length of the vertical crack scratched in water was much longer than that in heptane. At very high scratch speed as high as 1000 x 10-6 ms-1, no vertical crack was formed in the heptane. These differences between horizontal and vertical cracks should be due to the differences of crack initiation position and the influence of subcritical crack growth to these cracks.

  10. Optical properties of green-emitting β-sialon:Eu phosphor-containing silica glasses and their deterioration mechanism

    NASA Astrophysics Data System (ADS)

    Yoshimura, Kenichi; Fukunaga, Hiroshi; Izumi, Makoto; Harada, Masamichi; Takahashi, Kohsei; Segawa, Hiroyo; Xie, Rong-Jun; Hirosaki, Naoto

    2017-06-01

    β-sialon:Eu phosphor-containing silica glass was synthesized as a wavelength converter in solid-state lighting. The optical properties and pore density of the sample strongly depended on the sintering temperature. Sintering at a high temperature of 1050 °C led to a severe deterioration of β-sialon:Eu phosphor owing to N2 evaporation, whereas a high conversion efficiency could be achieved by lowering the sintering temperature down to 600 °C. The β-sialon:Eu phosphor-containing silica glass sintered at 600 °C showed a high durability against high-power excitation, making it possible to be used in high-luminosity and high-power solid-state laser lighting.

  11. 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.

  12. 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.

  13. 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.

  14. Three-dimensional hole drilling of silica glass from the rear surface with femtosecond laser pulses.

    PubMed

    Li, Y; Itoh, K; Watanabe, W; Yamada, K; Kuroda, D; Nishii, J; Jiang, Y

    2001-12-01

    By moving silica glass in a preprogrammed structure, we directly produced three-dimensional holes with femtosecond laser pulses in single step. When distilled water was introduced into a hole drilled from the rear surface of the glass, the effects of blocking and redeposition of ablated material were greatly reduced and the aspect ratio of the depth of the hole was increased. Straight holes of 4-mu;m diameter were more than 200 microm deep. Three-dimensional channels can be micromachined inside transparent materials by use of this method, as we have demonstrated by drilling a square-wave-shaped hole inside silica glass.

  15. High-power laser damage in fused silica

    NASA Astrophysics Data System (ADS)

    Salleo, Alberto

    Laser-induced damage (LID) at the surface of transparent materials is widely considered the main obstacle in the development of inertial confinement fusion (ICF) facilities. This dissertation is a study, both theoretical and experimental, of LID initiation and propagation at fused silica surfaces. Numerical simulation of light propagation shows that micro-cracks due to polishing amplify light intensity in their vicinity at the air/glass boundary. The mechanism of light amplification is a combination of partial reflection at air/glass boundaries and constructive interference of the reflected waves. The maximum amplification factor for a single crack is 10.7. Multiple cracks interact cooperatively and generate higher amplification factors. Conical cracks generate amplification factors of 20. The electric field intensity profile at the glass surface due to underlying conical cracks correlates well with observed LID morphology. Light amplification at micro-cracks may also play a role in LID propagation. LID propagation rates under repetitive illumination are measured. Rear-surface LID propagates from pre-existing damage sites at sub-threshold fluence. Rear-surface propagation rates depend linearly on laser fluence and are independent of environment or beam size. Rear-surface LID propagates faster in the UV than in the IR. Front-surface LID propagation is two orders of magnitude slower than rear-surface propagation. Pump and probe experiments of LID confirm that this difference is due to laser-plasma interactions. At the front-surface, up to 60% of the laser energy is dispersed outside the glass. At the rear-surface, 35% of the laser energy is dispersed outside the glass, thus more energy is available for damage propagation. Based on these observations, a model of LID propagation is developed based on the physics of impact cratering. Laser-induced transformations of glass are studied. High pressures associated with LID permanently densify fused silica by as much as 20

  16. Micro Fluidic Channel Machining on Fused Silica Glass Using Powder Blasting.

    PubMed

    Jang, Ho-Su; Cho, Myeong-Woo; Park, Dong-Sam

    2008-02-06

    In this study, micro fluid channels are machined on fused silica glass via powder blasting, a mechanical etching process, and the machining characteristics of the channels are experimentally evaluated. In the process, material removal is performed by the collision of micro abrasives injected by highly compressed air on to the target surface. This approach can be characterized as an integration of brittle mode machining based on micro crack propagation. Fused silica glass, a high purity synthetic amorphous silicon dioxide, is selected as a workpiece material. It has a very low thermal expansion coefficient and excellent optical qualities and exceptional transmittance over a wide spectral range, especially in the ultraviolet range. The powder blasting process parameters affecting the machined results are injection pressure, abrasive particle size and density, stand-off distance, number of nozzle scanning, and shape/size of the required patterns. In this study, the influence of the number of nozzle scanning, abrasive particle size, and pattern size on the formation of micro channels is investigated. Machined shapes and surface roughness are measured using a 3-dimensional vision profiler and the results are discussed.

  17. Micro Fluidic Channel Machining on Fused Silica Glass Using Powder Blasting

    PubMed Central

    Jang, Ho-Su; Cho, Myeong-Woo; Park, Dong-Sam

    2008-01-01

    In this study, micro fluid channels are machined on fused silica glass via powder blasting, a mechanical etching process, and the machining characteristics of the channels are experimentally evaluated. In the process, material removal is performed by the collision of micro abrasives injected by highly compressed air on to the target surface. This approach can be characterized as an integration of brittle mode machining based on micro crack propagation. Fused silica glass, a high purity synthetic amorphous silicon dioxide, is selected as a workpiece material. It has a very low thermal expansion coefficient and excellent optical qualities and exceptional transmittance over a wide spectral range, especially in the ultraviolet range. The powder blasting process parameters affecting the machined results are injection pressure, abrasive particle size and density, stand-off distance, number of nozzle scanning, and shape/size of the required patterns. In this study, the influence of the number of nozzle scanning, abrasive particle size, and pattern size on the formation of micro channels is investigated. Machined shapes and surface roughness are measured using a 3-dimensional vision profiler and the results are discussed. PMID:27879730

  18. Enhanced ultraviolet emission and its irreversible temperature antiquenching behavior of twofold coordinated silicon centers in silica glass

    NASA Astrophysics Data System (ADS)

    Nagayoshi, Yu; Uchino, Takashi

    2016-10-01

    It has been well documented that an oxygen divacancy center, or a twofold-coordinated Si center, in silica glass yields a singlet-to-singlet photoluminescence (PL) emission at 4.4 eV with a decay time of ˜4 ns. Although the 4.4-eV PL band is interesting in terms of a deep-ultraviolet light emitter, the emission efficiency has been too low to be considered for a practical application. In this work, we show that a highly luminescent silica glass, with an internal quantum yield of 68% for the 4.4-eV PL band at room temperature, can be prepared when micrometer-sized silica powders are heat treated at ˜1900 °C under inert gas atmosphere by using a high-frequency induction heating unit equipped with a graphite crucible. We also show that the intensity of the 4.4-eV emission in the thus prepared silica glass exhibits an irreversible temperature antiquenching behavior in the temperature region below ˜320 K during heating-cooling cycles. The anomalous temperature dependencies of the 4.4-eV emission can be interpreted in terms of thermally activated trapping-detrapping processes of photoexcited electrons associated with deep trap states.

  19. 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

    2015-09-15

    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.

  20. 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

  1. 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.

  2. 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.

  3. 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.

  4. Formation of cylindrical micro-lens array in fused silica glass using laser irradiations

    NASA Astrophysics Data System (ADS)

    Choi, Hun-Kook; Ahsan, Md. Shamim; Yoo, Dongyoon; Sohn, Ik-Bu; Noh, Young-Chul; Kim, Jin Tae; Jung, Deok; Kim, Jin Hyeok

    2013-12-01

    In this article, we report the development of plano-convex cylindrical micro-lens array on the surface of fused silica glass using laser processing technology. Initially, femtosecond laser pulses are irradiated on the target fused silica glass substrate to pattern periodic micro-grooves. Afterwards, laser beam from CO2 laser source is applied several times on the previously micro-patterned fused silica glass surface, the purpose of which is to polish the micro-patterned glass surface. As a consequence, periodic plano-convex cylindrical micro-lens array is evolved on the glass surface. The micro-lens array shows great consistency in size and shape throughout the sample area. We also investigate various optical properties of the micro-lenses evolved glass substrates including the diffraction pattern and diffraction efficiency of light. The glass sample comprising cylindrical micro-lens array can diffract light with moderate diffraction efficiency. We strongly believe that, it is possible to engineer cylindrical micro-lens array on the surface of a variety of transparent materials including glasses and polymers over a large area.

  5. 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.

  6. 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.

  7. 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.

  8. Fabrication of silica glass containing yellow oxynitride phosphor by the sol–gel process

    PubMed Central

    Segawa, Hiroyo; Yoshimizu, Hisato; Hirosaki, Naoto; Inoue, Satoru

    2011-01-01

    We have prepared silica glass by the sol–gel method and studied its ability to disperse the Ca-α-SiAlON:Eu2+ phosphor for application in white light emitting diodes (LEDs). The emission color generated by irradiating doped glass with a blue LED at 450 nm depended on the concentration of SiAlON and the glass thickness, resulting in nearly white light. The luminescence efficiency of 1-mm-thick glass depended on the SiAlON concentration, and was highest at 4 wt% SiAlON. PMID:27877398

  9. 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.

  10. 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.

  11. 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. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. 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.

  13. Autonomous movement of silica and glass micro-objects based on a catalytic molecular propulsion system.

    PubMed

    Stock, Christoph; Heureux, Nicolas; Browne, Wesley R; Feringa, Ben L

    2008-01-01

    A general approach for the easy functionalization of bare silica and glass surfaces with a synthetic manganese catalyst is reported. Decomposition of H(2)O(2) by this dinuclear metallic center into H(2)O and O(2) induced autonomous movement of silica microparticles and glass micro-sized fibers. Although several mechanisms have been proposed to rationalise movement of particles driven by H(2)O(2) decomposition to O(2) and water (recoil from O(2) bubbles, ([36,45]) interfacial tension gradient([37-42]), it is apparent in the present system that ballistic movement is due to the growth of O(2) bubbles.

  14. 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.

  15. In situ diagnostics of pulse laser-induced defects in DUV transparent fused silica glasses

    NASA Astrophysics Data System (ADS)

    Mühlig, Ch.; Triebel, W.; Bark-Zollmann, S.; Grebner, D.

    2000-05-01

    Excimer laser pulses (λ=248 or 193 nm) induce transient and permanent defects in optical glasses of high UV transparency. Such defects are causing additional absorption and changes of density and refractive index, respectively (compaction). The interaction of each laser pulse with different OH-rich fused silica samples was investigated by real time measurements of laser-induced fluorescence (LIF) and of Raman spectra excited by the 248 nm KrF-excimer laser. The irradiation of the glasses with energy densities of about 10 mJ/cm2 and more induces E‧ and NBOH defects simultaneously. The laser-induced fluorescence of NBOH defect centres at 650 nm characterises the kinetics of defect generation and relaxation. The primary absorption process is the two-photon absorption of KrF laser pulses. The relaxation of defects in the time interval between the laser pulses is mainly influenced by diffusion limited processes. Locally resolved LIF and Raman spectra allow the investigation of homogeneity and laser damage stability in large area substrates (e.g. for mask blanks). Raman spectra excited by KrF laser pulses are measured to detect precursors and intermediates of laser-induced defects and molecular hydrogen in the glass matrix. The detection limit of H2 molecules is in the range of 1017 cm-3. A correlation between LIF intensities and H2 concentrations is found.

  16. 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.

  17. Structural and thermal studies of modified silica-strontium-barium glass from CRT

    NASA Astrophysics Data System (ADS)

    Grelowska, I.; Kosmal, M.; Reben, M.; Pichniarczyk, P.; Sitarz, M.; Olejniczak, Z.

    2016-12-01

    Glasses were prepared by conventional melting method from 100 g batches. The influence of alumina and calcium oxide on the crystallization process of silica-strontium-barium glass from Cathode Ray Tube (CRT) were studied by means of 27Al MAS NMR and FTIR spectroscopy. This made possible to determine the influence of additives, e.g. blast furnace slag and cement dust on the structural changes of glasses (changes in the spectra shapes). The introduction of waste modifiers into the glass structure leads to the breaking of Al-O-Si and Si-O-Si bonds what causes the depolymerization of the glass network. From the FTIR spectra the narrowing of the bands at 1022 and 1027 cm-1 was observed, which may indicate on the ordering of glass network. Appearance of alumina in coordination 4 was confirmed by NMR investigations. The effects of compositional variation, thermal treatment on the nature, type and stability field of crystallizing phases and microstructure formed in CaO and/or Al2O3 silica-strontium-barium glasses were described using DTA/DSC method. Thermal characteristics of glasses like the transition temperature Tg, the temperature for the crystallization Tc, thermal stability parameter were determined. The crystalline phase was determined by the X-ray diffractometry. The microstructure of the samples was studied by SEM technique. Analysis of the local atomic interactions in the structure of glasses has been used to explain the course of the crystallization.

  18. UV-curable low index hybrid glass as hard cladding for silica fibers

    NASA Astrophysics Data System (ADS)

    Wojcik, Anna B.; Wojcik, Jan

    2005-09-01

    UV-curable hybrid glass materials, when applied as thin coatings on optical fibers are already known to result in fibers enhanced mechanical strength as well as thermal and environmental stability [1]. These materials, when fully cured offer refractive index in the range 1.470-1.50 measured at 1300 nm. In search for low optical loss and lower refractive index claddings the hybrid glass composition was altered to result in UV curable two component formulation HG-LI (1+2) of refractive index 1. 380 The goal of this study was fabrication and valuation of the optical, mechanical and thermal properties of the silica fibers cladded with this novel hybrid glass material. The silica fibers were drawn and cladded by HG-LI-(1+2) and HG-LI-2. For control fibers, soft silicone resin and hard silicone resin were used as cladding for the same silica preform rod. The basic optical (spectral attenuation) and mechanical characteristics (tensile strength, n parameter) for hybrid glass cladded fibers were performed. Thermo Gravimetric Analysis (TGA) was performed as well. The results showed that hybrid glass cladding has the onset decomposition temperature exceeding 300 °C, whereas the NA values of the silica fiber cladded by HG-LI-(1+2) and HG-Li-2 were 0.31 and 0.33, respectively.

  19. 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.

  20. 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 Yb(3+)-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 Yb(3+) concentration of 9811 ppm by weight, a low background attenuation of 0.02 dB/m, and absorption from Yb(3+) 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.

  1. 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

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

    PubMed

    Schibille, Nadine

    2011-04-19

    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.

  3. Microsecond molecular dynamics simulations of stress relaxation and slow quench in silica melts and glasses

    NASA Astrophysics Data System (ADS)

    Lane, J. Matthew D.

    2014-03-01

    Quench rates and stress relaxation in molecular dynamics simulations of glasses are usually studied on time-scales which are many orders of magnitude faster that those in experiment. We present results from relaxation of hydrostatic compressive stress in silica glass using classical molecular dynamics simulations. Structural variation will be discussed as a function of quench rate for glasses quenched 2 to 3 orders of magnitude slower than previously reported. Stress relaxation curves plotted in log t show time-temperature superposition holds over a wide-range of temperatures for 3% initial volume compression. Silica melts and glasses were modeled with the BKS interatomic potential and were produced through a melt-quench process. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  4. A novel approach for preparation and in situ tensile testing of silica glass membranes in the TEM

    NASA Astrophysics Data System (ADS)

    Mačković, Mirza; Przybilla, Thomas; Dieker, Christel; Herre, Patrick; Romeis, Stefan; Stara, Hana; Schrenker, Nadine; Peukert, Wolfgang; Spiecker, Erdmann

    2017-04-01

    The mechanical behavior of glasses in the micro- and/or nanometer regime increasingly gains importance in nowadays modern technology. However, suitable small scale preparation and mechanical testing approaches for a reliable assessment of the mechanical properties of glasses still remain a big challenge. In the present work, a novel approach for site-specific preparation and quantitative in situ tensile testing of thin silica glass membranes in the transmission electron microscope is presented. Thereby, advanced focused ion beam techniques are used for the preparation of nanoscale dog bone shaped silica glass specimens suitable for in situ tensile testing. Small amounts of gallium are detected on the surface of the membranes resulting from redeposition effects during the focused ion beam preparation procedure. Possible structural changes of silica glass upon irradiation with electrons and gallium ions are investigated by controlled irradiation experiments, followed by a structural analysis using Raman spectroscopy. While moderate electron beam irradiation does not alter the structure of silica glass, ion beam irradiation results in minor densification of the silica glass membranes. In situ tensile testing of membranes under electron beam irradiation results in distinctive elongations without fracture confirming the phenomenon of superplasticity. In contrast, in situ tensile testing in the absence of the electron beam reveals an elastic/plastic deformation behavior, and finally leads to fracture of the membranes. The Young’s moduli of the glass membranes pulled at beam off conditions in the TEM are comparable with values known for bulk fused silica, while the tensile strength is in the range of values reported for silica glass fibers with comparable dimensions. The impact of electron beam irradiation on the mechanical properties of silica glass membranes is further discussed. The results of the present work open new avenues for dedicated preparation and

  5. 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.

  6. 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.

  7. Simulation of a silica glass from combined classical and ab initio molecular-dynamics

    NASA Astrophysics Data System (ADS)

    Benoit, Magali; Ispas, Simona; Jund, Philippe; Jullien, Rémi

    1999-11-01

    We present structural and electronic characteristics of a vitreous silica glass obtained from combined classical and Car-Parrinello (CP) molecular-dynamics (MD) simulations. The equilibration of the liquid, quench and relaxation of the glass are performed classically using the van Beest et al. (BKS) potential and the resulting configuration is used as input for the CP simulation. A remarkable stability of the CP dynamics is observed justifying this procedure and validating the BKS potential.

  8. Deformation and strength of silica fibers in three-point bending in consideration of nonlinear elasticity of glass

    NASA Astrophysics Data System (ADS)

    Baikova, L. G.; Pesina, T. I.; Mansyrev, E. I.; Kireenko, M. F.; Tikhonova, L. V.

    2017-01-01

    We consider the problem of asymmetric strain and stress distribution in silica fiber under threepoint bending. The parameters of nonlinear elasticity of silica glass under tension and compression are estimated using available data from the literature. It has been found that consideration of the nonlinear elasticity of silica glass leads to a slight increase in the calculated values of strength compared to the data obtained from estimates based on the linear theory of elasticity.

  9. 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. Copyright © 2014 Elsevier Inc. All rights reserved.

  10. 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

  11. Effects of various calcined ash and sludge waste loadings on the durability of a soda-lime-silica glass

    SciTech Connect

    Kramer, D.P.; Lewis, E.L.; Armstrong, K.M.; Doty, J.W.

    1982-01-01

    A commercially available joule-heated glass furnace system is currently being evaluated at Mound as a means of reducing the volume of low-level radioactive waste similar to that found in light water reactor facilities. The furnace utilizes molten soda-lime-silica to initiate and support combustion of the waste feed and to serve as an immobilization matrix. First, corrosion studies were performed to determine the result that various waste loadings of glass would have on the refractory lining the furnace. Second, the chemical durability of soda-lime-silica under various waste loadings was assessed to determine its resistance to leaching under conditions similar to those encountered at waste disposal sites. Results proved that, although corrosion was quite significant for pure soda-lime-silica and a 10% waste loading, by the time a waste loading of 40% was achieved, the effects of corrosion were virtually nil. The temperature dependence of the corrosion caused by a 0% waste loading of soda-lime-silica on the refractory was also investigated. With an increase in temperature to 2650/sup 0/F, corrosion more than tripled. As a result, incineration and idle temperature is being maintained at, or below, 2400/sup 0/F. In conclusion, from the fact that the higher waste loading of soda-lime glass produced both increased chemical durability and increased refractory life, waste loadings in excess of 40%, and as high as 80%, may be achieved without adverse effect to the glass furnace system or its effectiveness for immobilizing radioactive waste.

  12. Mechanisms of silica refractory corrosion in glass-melting furnaces: Equilibrium predictions

    SciTech Connect

    Mark D. Allendorf, SNL Karl E. Spear, Penn State University

    1999-10-17

    Corrosion of refractory silica brick used to line the roof or crown of many-glass-melting furnaces is a serious problem in furnaces using oxygen-fuel rather than air-fuel. In this work, the authors report equilibrium calculations for the Na{sub 2}O-SiO{sub 2} system that predict the formation of a variable-composition liquid-solution phase as a function of key furnace variables. Since thermodynamic data for the relevant liquid phases are unavailable in standard compilations, new data generated using the associate species model are included in the calculations. The calculations indicate that gas-phase NaOH concentrations less than {approximately}15 ppm will not react with the silica refractory under either air-fired or oxy-fired conditions, since this is the smallest equilibrium NaOH partial pressure in a system containing crystalline SiO{sub 2} (either cristobalite or tridymite) in equilibrium with a variable-composition sodium-silicate liquid phase at refractory temperatures in the range 1,400--1,700 C. The high water content ({approximately}65%) of oxygen-fired furnaces results in measured NaOH(g) concentrations as high as 300 ppm, which greatly exceeds the 1,600 C maximum of 68 ppm NaOH(g) for oxy-fired equilibrium with a liquid-SiO{sub 2} (crystalline) system. This indicates that there is a thermodynamic driving force for NaOH(g) to react with silica refractories in oxy-fired furnaces. The results of the calculations are used to define a critical temperature, above which corrosion is not expected to occur for a given NaOH(g) partial pressure.

  13. 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.

  14. 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.

  15. Organoaluminophosphate sol-gel silica glass thin films for integrated optics

    NASA Astrophysics Data System (ADS)

    Touam, Tahar; Milova, Galina; Saddiki, Z.; Fardad, M. A.; Andrews, Mark P.; Juma, Salim K.; Chrostowski, Jacek; Najafi, S. Iraj

    1997-01-01

    We report on the fabrication and characterization of waveguide thin films on silicon by ultraviolet light imprinting in a new photosensitive, organically modified aluminophosphate sol-gel silica glass prepared by a one-step dip-coating process. Appropriate combinations of ultraviolet light exposure time, sol-gel film thickness and postbake parameters produce waveguides suitable for optical telecommunication applications.

  16. Clustering of Yb in silica-based glasses synthesized by SPCVD

    NASA Astrophysics Data System (ADS)

    Savel'ev, E. A.; Krivovichev, A. V.; Golant, K. M.

    2016-12-01

    Light absorption and scattering are studied in silica-based slab lightguides with different contents of aluminum, ytterbium and phosphorous in the silica core. The slab lightguides used in the experiments were fabricated from the structures of doped silica deposited on the inner surface of a substrate silica tube via surface-plasma chemical vapor deposition (SPCVD). The synthesized glasses contained 0.004-0.4 at. % of Yb, as well as various contents of Al and P ranging from 0 to 1 at. %. Loss spectra of the slab lightguides are measured in the 300-1050 nm wavelength band, with the influence of the profusion of deposited glass on the loss spectra investigated by means of substrate tube external processing at a temperature of ∼1600 °C in the flame of a hydrogen-oxygen burner. We found that a combination of the temperature of the inner surface of the substrate tube during the deposition process and the subsequent profusion of the deposited structure essentially influence the distribution uniformity of ytterbium ions in the glass volume. If aluminum and phosphorous are present in the glass, such profusion can influence the formation of ytterbium clusters in opposite ways.

  17. Refractive index and density in F- and Cl-doped silica glasses

    SciTech Connect

    Kakiuchida, Hiroshi; Shimodaira, Noriaki; Sekiya, Edson H.; Saito, Kazuya; Ikushima, Akira J.

    2005-04-18

    The refractive index and density of fluorine- and chlorine-doped silica glasses were measured as functions of fictive temperature. The halogen concentrations were observed to have a refractive index or density that is independent of the fictive temperature were found. This implies that these properties are not affected by any heat-treatment conditions.

  18. Fabrication of Silica Glass from Rice Husk Ash with Spodumene Additions

    NASA Astrophysics Data System (ADS)

    Wasanapiarnpong, T.; Vorajesdarom, B.; Rujirakamort, E.; Nilpairach, S.; Mongkolkachit, C.

    2011-10-01

    Silica glass is an interesting material due to its low thermal expansion coefficient, high chemical inertness, and transparency. In this study, low cost rice husk ash waste containing mainly amorphous silica phase was used as a starting raw material. Formation of cristrobalite caused product damage during cooling down was suppressed by an addition of some sintering aids. Spodumene was selected to use as the sintering aid due to its ability to promote the sinterability of the rice husk ash by liquid phase forming. Lithium carbonate and aluminum nitrate were mixed with the rice husk ash as starting chemicals for spodumene forming. To investigate the effects of spodumene addition on densification, physical properties and thermal expansion coefficient, 25 and 50 mass% of spdumene were added to the mixture. Mixed powders were dry pressed into pellet shapes and sintered at 1000-1250 °C for 30 min in an electric furnace. It was found that 50 mass% addition of spodumene enhanced the densification of the specimens sintered at the temperature higher than 1250 °C. Water absorption was reduced to 1.11 % with bulk density of 2.12 g/cm3. Low thermal expansion coefficient of 2.70×10-6 /°C was achieved with only the petalite phase detection.

  19. 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.

  20. 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.

  1. 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.

  2. Sol-Gel Synthesis of Rare-Earth and Phosphorus Codoped Monolithic Silica Glasses from a Cosolvent-Free Phase-Separating System

    NASA Astrophysics Data System (ADS)

    Kajihara, Koichi; Kuwatani, Shungo; Kanamura, Kiyoshi

    2012-01-01

    A cosolvent-free sol-gel method to prepare monolithic transparent silica glasses doped by rare-earth ions at high concentrations has been developed. Despite the simple solution composition, the reaction mixture undergoes a macroscopic phase separation in parallel with the gelation, and the resultant macropores make it possible to considerably shorten the processing time by facilitating the drying and sintering of gels. The addition of a small amount of phosphorus significantly enhances the dissolution of rare-earth ions, demonstrating a notable effect of phosphorus on the solvation of rare-earth ions in silica glasses.

  3. 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.

  4. Development of a tuned interfacial force field parameter set for the simulation of protein adsorption to silica glass.

    PubMed

    Snyder, James A; Abramyan, Tigran; Yancey, Jeremy A; Thyparambil, Aby A; Wei, Yang; Stuart, Steven J; Latour, Robert A

    2012-12-01

    Adsorption free energies for eight host-guest peptides (TGTG-X-GTGT, with X = N, D, G, K, F, T, W, and V) on two different silica surfaces [quartz (100) and silica glass] were calculated using umbrella sampling and replica exchange molecular dynamics and compared with experimental values determined by atomic force microscopy. Using the CHARMM force field, adsorption free energies were found to be overestimated (i.e., too strongly adsorbing) by about 5-9 kcal/mol compared to the experimental data for both types of silica surfaces. Peptide adsorption behavior for the silica glass surface was then adjusted using a modified version of the CHARMM program, which we call dual force-field CHARMM, which allows separate sets of nonbonded parameters (i.e., partial charge and Lennard-Jones parameters) to be used to represent intra-phase and inter-phase interactions within a given molecular system. Using this program, interfacial force field (IFF) parameters for the peptide-silica glass systems were corrected to obtain adsorption free energies within about 0.5 kcal/mol of their respective experimental values, while IFF tuning for the quartz (100) surface remains for future work. The tuned IFF parameter set for silica glass will subsequently be used for simulations of protein adsorption behavior on silica glass with greater confidence in the balance between relative adsorption affinities of amino acid residues and the aqueous solution for the silica glass surface.

  5. 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.

  6. High density fluoride glass calorimeter

    NASA Astrophysics Data System (ADS)

    Xie, Q.; Scheltzbaum, J.; Akgun, U.

    2014-04-01

    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. Quartz plates to replace the plastic scintillators in current LHC calorimeters have been proposed in recent reports. Quartz based Cherenkov calorimeters can solve the radiation damage problem, however light production and transfer have proven to be challenging. This report summarizes the results from a computational study on the performance of a high-density glass calorimeter. High-density, scintillating, fluoride glass, CHG3, was used as the active material. This glass has been developed specifically for hadron collider experiments, and is known for fast response time, in addition to high light yield. Here, the details of a Geant4 model for a sampling calorimeter prototype with 20 layers, and its hadronic as well as electromagnetic performances are reported.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. White light emission from transparent SiO2 glass prepared from nanometer-sized silica particles

    NASA Astrophysics Data System (ADS)

    Uchino, Takashi; Yamada, Tomoko

    2004-08-01

    We report that nanometer-sized silicon-dioxide particles are sintered to optical transparency at temperatures even below 1000°C, forming nonporous bulk silica glass. The resultant silica glass exhibits visible emission, which appears white to the naked eye, in the wavelength range from ˜400to˜700nm at room temperature under ultraviolet excitation. The observed emission is quite stable after prolonged exposure to the atmosphere and shows no appreciable light-induced degradation. The present photoluminescence characteristics are found to be basically different from those reported previously for silica nanoparticles and silica-based porous materials.

  12. 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.

  13. Experimental Investigation on Cutting Characteristics in Nanometric Plunge-Cutting of BK7 and Fused Silica Glasses

    PubMed Central

    An, Qinglong; Ming, Weiwei; Chen, Ming

    2015-01-01

    Ductile cutting are most widely used in fabricating high-quality optical glass components to achieve crack-free surfaces. For ultra-precision machining of brittle glass materials, critical undeformed chip thickness (CUCT) commonly plays a pivotal role in determining the transition point from ductile cutting to brittle cutting. In this research, cutting characteristics in nanometric cutting of BK7 and fused silica glasses, including machined surface morphology, surface roughness, cutting force and specific cutting energy, were investigated with nanometric plunge-cutting experiments. The same cutting speed of 300 mm/min was used in the experiments with single-crystal diamond tool. CUCT was determined according to the mentioned cutting characteristics. The results revealed that 320 nm was found as the CUCT in BK7 cutting and 50 nm was determined as the size effect of undeformed chip thickness. A high-quality machined surface could be obtained with the undeformed chip thickness between 50 and 320 nm at ductile cutting stage. Moreover, no CUCT was identified in fused silica cutting with the current cutting conditions, and brittle-fracture mechanism was confirmed as the predominant chip-separation mode throughout the nanometric cutting operation. PMID:28788010

  14. Size-Dependent Brittle-to-Ductile Transition in Silica Glass Nanofibers.

    PubMed

    Luo, Junhang; Wang, Jiangwei; Bitzek, Erik; Huang, Jian Yu; Zheng, He; Tong, Limin; Yang, Qing; Li, Ju; Mao, Scott X

    2016-01-13

    Silica (SiO2) glass, an essential material in human civilization, possesses excellent formability near its glass-transition temperature (Tg > 1100 °C). However, bulk SiO2 glass is very brittle at room temperature. Here we show a surprising brittle-to-ductile transition of SiO2 glass nanofibers at room temperature as its diameter reduces below 18 nm, accompanied by ultrahigh fracture strength. Large tensile plastic elongation up to 18% can be achieved at low strain rate. The unexpected ductility is due to a free surface affected zone in the nanofibers, with enhanced ionic mobility compared to the bulk that improves ductility by producing more bond-switching events per irreversible bond loss under tensile stress. Our discovery is fundamentally important for understanding the damage tolerance of small-scale amorphous structures.

  15. Thermal characterization of semi-transparent media: measurement of phononic diffusivity of glass and silica

    NASA Astrophysics Data System (ADS)

    Lazard, M.; André, S.; Maillet, D.

    2003-09-01

    Materials such as glasses, insulated foams, polymers are semi-transparent. In order to measure the phononic diffusivity of such media in which the heat transfer is both conductive and radiative it is necessary to develop a complete methodology. The technique, we propose here, is an extension of the Flash method with the use of a semi-analytical combined model. It permits to determine the diffusivity of materials such as glass and silica for a large range of temperature (from 300K to 700K).

  16. 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.

  17. Surface microfabrication of silica glass by LIBWE using DPSS-UV laser

    NASA Astrophysics Data System (ADS)

    Niino, H.; Kawaguchi, Y.; Sato, T.; Narazaki, A.; Kurosaki, R.

    2006-02-01

    Surface micro-structuring of silica glass plates was performed by using laser-induced backside wet etching (LIBWE) upon irradiation with a single-mode laser beam from a diode-pumped solid-state UV laser at 266 nm. We have succeeded in a well-defined micro-pattern formation without debris and microcrack formations around the etched area on the basis of galvanometer-based point scanning system with the laser beam. The behavior of liquid ablation (explosive vaporization) was monitored by impulse pressure detection with a fast-response piezoelectric pressure gauge. LIBWE method is suitable for rapid prototyping and rapid manufacturing of surface microstructuing of silica glass as mask-less exposure system in a conventional atmospheric environment.

  18. On the nature of photoluminescence in Bismuth-doped silica glass.

    PubMed

    Laguta, Oleksii V; Hamzaoui, Hicham El; Bouazaoui, Mohamed; Arion, Vladimir B; Razdobreev, Igor M

    2017-06-09

    We report on the investigation of Bismuth-doped pure silica glass without other co-dopant by the tech- nique of magnetic circular dichroism (MCD), which allows the direct probing of the ground state of optical centres. Taking into account the results of conventional optical spectroscopy, we show that the observed MCD bands belong to the centre responsible for the red photoluminescence in this material. Measurements of the temperature and field dependences indicate that the MCD effect is caused by the even-electron system. This, however, opposes the widespread opinion that Bi(2+) ions are the origin of red photoluminescence in Bismuth-doped silica glasses. On the other hand, the lasing centre responsi- ble for the near infrared photoluminescence does not exhibit any magnetic optical activity connected to its ground state. As a consequence, we conclude that the ground state of lasing centre is a magnetic singlet with the effective spin S = 0.

  19. Chalcogenide microresonators tailored to distinct morphologies by the shaping of glasses on silica tapers.

    PubMed

    Aktaş, Ozan

    2017-03-01

    Production of chalcogenide (As2Se3) microresonators in sphere, loop, and bottle morphologies by the shaping of glasses at appropriate temperatures between cleaved silica tapers is reported. The quality factors exceed QS=6.2×105, QB=6.7×105, and QL=1.6×104 for the sphere, bottle, and loop microresonators, respectively. All-optical thermally assisted tuning with a rate of 0.61 nm/mW is demonstrated for a bottle microcavity pumped via a silica taper at a wavelength of 670 nm. This technique enables practical and robust in situ production of chalcogenide microresonators thermally spliced to silica fibers in several morphologies with a wide tuning range of size.

  20. Broadband, ultralow reflectance surface structures on silica windows for high-energy laser applications (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Busse, Lynda E.; Frantz, Jesse A.; Shaw, L. Brandon; Poutous, Menelaos K.; Aggarwal, Ishwar D.; Sanghera, Jasbinder S.

    2017-05-01

    The characteristics of broadband transmission, environmental durability, and laser damage resistance are critical for silica glass exit aperture windows for their use in kW-level, high energy laser systems. The use of conventional antireflective (AR) coatings on windows for high energy lasers operating in the near infrared is impacted by laser induced damage that occurs under high power irradiation as well as the potential for delamination in operational environments. Novel methods for fabricating antireflective surface structures (ARSS) directly on optics have resulted not only in reduced reflection loss, but also in other advantages to AR coatings as well. The ARSS approach involves sub-wavelength surface structures fabricated directly into the actual surface of the window, eliminating the need for a coating of extraneous materials. We will report on results for ARSS fabricated on silica glass windows. Recently we have reported broadband, low reflectance (< 0.02% at 1 µm) for silica glass windows with random ARSS, fabricated using reactive ion etching. These windows have shown remarkably high laser damage thresholds of 100 J/cm2 at 1.06 µm, which is 5x the threshold measured for a conventional AR coating. We will also present results for MILSPEC durability tests on silica windows, both with and without ARSS, for rain and sand erosion as well as salt fog testing, conducted at a government facility. We will also report on scale up of ARSS on silica windows of large sizes (33 cm), making them practical for system implementation.

  1. The Formation of the Second-Order Nonlinearity in Thermally Poled Fused Silica Glass

    DTIC Science & Technology

    2007-11-02

    NONIINEARITY IN THERMALLY POLED FUSED SILICA GLASS 6. AUTHOR(S) THOMAS GUSTAVE ALLEY 5. FUNDING NUMBERS 7. PERFORMING ORGANIZATION NAME(S) AND...ADDRESS(ES) The University of New Mexico 8. PERFORMING ORGANIZATION REPORT NUMBER 98-020D 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES...self- organized , photoinduced, second-order nonlinearity. The most widely accepted explanation attributes the nonlinearity to an asymmetric

  2. 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.

  3. Physicochemical evaluation of silica-glass fiber reinforced polymers for prosthodontic applications.

    PubMed

    Meriç, Gökçe; Dahl, Jon E; Ruyter, I Eystein

    2005-06-01

    This investigation was designed to formulate silica-glass fiber reinforced polymeric materials. Fused silica-glass fibers were chosen for the study. They were heat-treated at various temperatures (500 degrees C, 800 degrees C and 1100 degrees C), silanized, sized and incorporated in two modified resin mixtures (A and B). The flexural properties in dry and wet conditions were tested and statistically analyzed, and the content of residual methyl methacrylate (MMA) monomer, dimensional changes with temperature, water sorption and solubility were determined. Woven fibers [36.9% (wt/wt)], heat-treated at 500 degrees C, gave the highest strength values for the polymeric composites (an ultimate transverse strength of 200 Mpa and a flexural modulus of 10 GPa) compared with the fibers heat-treated at other temperatures. There was no statistically significant difference in the measured flexural properties between resins A and B regarding fiber treatment and water storage time. These fiber composites had a small quantity of residual MMA content [0.37 +/- 0.007% (wt/wt)] and very low water solubility, indicating good biocompatibility. It was suggested that silica-glass fibers could be used for reinforcement as a result of their anticipated good qualities in aqueous environments, such as the oral environment.

  4. 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.

  5. 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.

  6. Transparent silica glasses containing single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    DiMaio, Jeffrey R.; Rhyne, Suzette L.; Ballato, John M.; Czerw, Richard; Xu, Jianfeng; Webster, Scott; Carroll, David L.; Fu, Kefu; Sun, Ya-Ping

    2001-11-01

    Organic - Inorganic matrix nano composites have been created using an acid catalyzed, tetraethyl orthosilicate-based sol- gel technique with SWNTs. By utilizing nanotubes functionalized with the dendron methyl 3,5- di(methyltrigycoloxy)benzylic alcohol, ultrasonication blending in the sol phase prior to gelation yields excellent dispersion characteristics of the nanotube phase. Further, glasses could easily be dried by heating to 600 degrees C yielding 80 percent of theoretical density wit little change in the nanotube content. These materials exhibited intrinsic Rayleigh scattering, suggesting near ideal dispersion. Nonlinear optical transmissivity was observed for 1064 and 532 nm light suggesting that the matrix has a strong broad band coupling to the optical field. Such composites allow for a host of applications based on the novel confinement properties of carbon nanotubes in a robust host.

  7. Transparent Superhydrophobic silica coatings on glass by sol-gel method

    NASA Astrophysics Data System (ADS)

    Mahadik, Satish A.; Kavale, Mahendra S.; Mukherjee, S. K.; Rao, A. Venkateswara

    2010-11-01

    Wetting behavior of solid surfaces is a key concern in our daily life as well as in engineering and science. In the present study, we demonstrate a simple dip coating method for the preparation of Thermally stable, transparent superhydrophobic silica films on glass substrates at room temperature by sol-gel process. The coating alcosol was prepared by keeping the molar ratio of methyltriethoxysilane (MTES), trimethylmethoxysilane (TMMS), methanol (MeOH), water (H2O) constant at 1:0.09:12.71:3.58, respectively with 13 M NH4OH throughout the experiments and the films were prepared with different deposition time varied from 5 to 25 h. In order to improve the hydrophobicity of as deposited silica films, the films were derivatized with 10% trimethylchlorosilane (TMCS) as a silylating agent in hexane solvent for 24 h. Enhancement in wetting behavior was observed for surface derivatized silica films which showed a maximum static water contact angle (172°) and minimum sliding angle (2°) for 25 h of deposition time. The superhydrophobic silica films retained their superhydrophobicity up to a temperature of 550 °C. The silica films were characterized by field emission scanning electron microscopy (FE-SEM), surface profilometer, Fourier transform infrared (FT-IR) spectroscopy, thermo-gravimetric and differential thermal analysis (TG-DTA), percentage of optical transmission, water contact angle measurements. The imperviousness behavior of the films was tested with various acids.

  8. Silica containing highly porous alumina ceramic

    NASA Astrophysics Data System (ADS)

    Svinka, R.; Svinka, V.; Zake, I.

    2011-04-01

    Porous alumina ceramic were produced by slip casting of aqueous alumina slurry with added small amount of metallic aluminium powder. Pores form in result of chemical reaction of aluminum with water by hydrogen gas evolution reaction and solidification of suspension. Porosity of such materials sintered at a temperature of 1600 - 1750°C varies from 60 to 90%. Pore size distribution and mechanical strength of these materials depend largely on the grain size of used raw materials. The major part of pores in the materials produced without additive of silica are larger than 10 ±m, but with 5 - 10 wt.% additive of silica in the raw mix pore size decreases considerably. The sintering shrinkage decreases to 2.5%. Coefficient of thermal expansion equally decreases from 8.9-10-6 K-1 to 7.1 10-6 K-1 and classification temperature increases to 1600°C, while deformation at high temperature decreases considerably.

  9. Ion-implantation-induced phase separation and crystallization in lithia-silica glasses

    SciTech Connect

    Arnold, G. W.; Peercy, P. S.; Doyle, B. L.

    1980-01-01

    Crystallization of annealed Li/sub 2/O.2SiO/sub 2/ glasses implanted with inert ions and fused SiO/sub 2/ glass implanted with Li ions was monitored using infrared reflection spectroscopy. Elastic recoil detection analysis was used to study changes in the Li and H concentration induced in these glasses by implantation and annealing. Implantation of Li/sub 2/O.2SiO/sub 2/ with inert ions results in Li depletion, accompanied by H indiffusion, in the implanted region. For Li-implanted SiO/sub 2/, crystallization of ..cap alpha..-quartz is accompanied by appreciable Li diffusion to the surface and attendant H migration to the Li-depleted region. The crystallization mechanisms are discussed in terms of phase separation in the lithia-silica system.

  10. Structural and optical properties of Eu3+ activated low cost zinc soda lime silica glasses

    NASA Astrophysics Data System (ADS)

    Omar, Nur Alia Sheh; Fen, Yap Wing; Matori, Khamirul Amin; Zaid, Mohd Hafiz Mohd; Samsudin, Nur Farhana

    A low cost method was employed to synthesize ZnO-SLS:xEu3+ phosphors using recyclable bottle glass as silica source. The structural and optical properties of ZnO-SLS:xEu3+ (x = 0, 1, 2, 3, 4 and 5 wt.%) glasses were determined using X-ray diffraction (XRD), Fourier transform infrared reflectance (FTIR), UV-visible (Uv-Vis) and photoluminescence (PL) spectroscopy. Structural investigation using XRD measurement had broadened the halo peak with the doping of dopants. FTIR spectra showed the glass system consists of -OH and SiO4 bands. Meanwhile, the optical measurement using UV-Vis absorption has been induced a blue shift of the electronic absorption edge. The emission peak intensity of ZnO-SLS:xEu3+ phosphors was enhanced with the progression of doping concentration and thus, revealed their potential as red emitting phosphors under 400 nm excitation.

  11. 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).

  12. 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.

  13. High-Intensity Plasma Glass Melter

    SciTech Connect

    2004-01-01

    Modular high-intensity plasma melter promises improved performance, reduced energy use, and lower emissions. The glass industry has used the same basic equipment for melting glass for the past 100 years.

  14. 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.

  15. Atomic-scale simulations of vitreous silica under high pressure: Structure and properties

    NASA Astrophysics Data System (ADS)

    Davila, Lilian P.

    The work presented in this thesis consists of using computational methods to understand the nature of vitreous silica at high pressure, predict the possible atomistic processes that lead to the densification in this glass, and examine the implications these structural modification have on selected useful properties. These simulations are part of an effort required to develop realistic models of this technologically important glass. Vitreous silica is simulated on the atomic-scale at elevated pressures using two computational tools. First, we reproduce realistic models of pure vitreous silica. Next, we monitor the behavior of this glass under shock pressures using molecular dynamics (MD) simulations. The simulations reproduce the experimental equation of state (EOS) of this material and explain its characteristic dependence on pressure. It is found that shock pressures modify the medium-range order of this amorphous system, producing changes that are revealed by its ring size distribution. The ring size distribution remains unchanged during elastic compression but varies continuously after the transition to the plastic regime. A detailed analysis of key structural parameters indicates the mechanisms that lead to such transformations in vitreous silica. Finally, we perform first-principles calculations to investigate the role of selected defects in the degradation of the optical properties in densified vitreous silica.

  16. Silica with high resistance to excimer laser

    SciTech Connect

    Fujinoki, Akira

    1995-12-31

    Optical properties change of newly developed silica by the both KrF add ArF excimer laser irradiation will be reported. X-2-01 has been provided for high power laser application for several years and has proved its high performance against KrF laser irradiation. The new material X-1-04 shows superior optical stability in transmittance and refractive index change by KrF and ArF laser irradiation. The application of these material will be discussed considering their properties of geometry, homogeneity and laser resistance.

  17. 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.

  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. 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.

  20. Melting behavior of water in cylindrical pores: carbon nanotubes and silica glasses.

    PubMed

    Sliwinska-Bartkowiak, M; Jazdzewska, M; Huang, L L; Gubbins, K E

    2008-08-28

    We report a study of the effects of confinement in multi-walled carbon nanotubes and mesoporous silica glasses (SBA-15) on the solid structure and melting of both H(2)O and D(2)O ice, using differential scanning calorimetry, dielectric relaxation spectroscopy, and neutron diffraction. Multi-walled nanotubes of 2.4, 3.9 and 10 nm are studied, and the SBA-15 studied has pores of mean diameter 3.9 nm; temperatures ranging from approximately 110 to 290 K were studied. We find that the melting point is depressed relative to the bulk water for all systems studied, with the depression being greater in the case of the silica mesopores. These results are shown to be consistent with molecular simulation studies of freezing in silica and carbon materials. The neutron diffraction data show that the cubic phase of ice is stabilized by the confinement in carbon nanotubes, as well as in silica mesopores, and persists up to temperatures of about 240 K, above which there is a transition to the hexagonal ice structure.

  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. 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.

  4. In situ growth of luminescent silver nanoclusters inside bulk sol-gel silica glasses

    NASA Astrophysics Data System (ADS)

    El Hamzaoui, Hicham; Capoen, Bruno; Razdobreev, Igor; Bouazaoui, Mohamed

    2017-07-01

    Silver nanocluster-doped glasses are attractive materials for various photonic applications. In this paper, bulk silica glasses doped with luminescent silver nanoclusters have been prepared using the sol-gel technique. As a first step, dense silica glasses doped with ionic silver have been loaded with hydrogen. Thereafter, a heat-treatment in air atmosphere was performed to enable the growth of silver nanoclusters at different temperatures in the range 100-600 °C. The optical properties of the obtained nanocomposites have been studied, as a function of the post-annealing temperature, using optical absorption and photoluminescence spectroscopies. It has been shown that, under UV photoexcitation, the hydrogenated samples, heat-treated between 200 and 500 °C present visible luminescence due to cationic and neutral molecular-like silver clusters, consisting of a small number of Ag atoms or ions. After annealing at 600 °C, further Ag aggregation led to 2 nm-size silver nanoparticles, resulting in a quenching of the visible luminescence.

  5. 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.

  6. The research progress of large-aperture fused silica for high power laser

    NASA Astrophysics Data System (ADS)

    Shao, Zhufeng; Wang, Yufen; Xiang, Zaikui; Rao, Chuandong

    2016-03-01

    Because of its excellent optical performance, the fused silica is widely used in laser industry. In addition, the fused silica can withstand high power laser, due to its pure component, and the performance is most outstanding within all types of glasses. So fused silica can be used for optical lens in high power laser field. From the manufacturing process stand point, the fused silica can be categorized to four types: type Ⅰ, type Ⅱ, type Ⅲ, and type Ⅳ. The fused silica of type Ⅰand type Ⅱ is made through melting silica sand in graphite furnace or oxyhydrogen flame. There are many defects in these types of fused silica, for example, the air bubbles, inclusions and metallic impurity. The other two types are made by synthetic reaction of SiCl4 with water in oxyhydrogen or plasma flame. Both type Ⅲ and Ⅳ have excellent performance in transmittance and internal quality. However, type Ⅳof fused silica has disadvantage in small aperture and overall high manufacturing cost. Take the transmittance and internal quality into consideration, the type Ⅲ fused silica is the most suitable for large-aperture lens, and can withstand high power laser. The systemic studies of manufacturing process were done to improve the performance of type Ⅲ fused silica in various areas, for instance, the optical homogeneity, the stress birefringence, the absorption coefficient and the damage threshold. There are four steps in manufacturing process of type Ⅲ fused silica, ingot production, reshaping, annealing and cold-working. The critical factors of ingot production, like the flame of burner and the structure of furnace, were deeply studied in this paper to improve the performance of fused silica. On the basis of the above research, the performance and quality of the fused silica measured up to advanced world levels. For instance, the result of optical homogeneity can be controlled to 2~5 ppm, the stress birefringence is better than 4 nm/cm, the absorption coefficient

  7. The ubiquitous presence of silica-rich glass inclusions in mafic minerals: Examples from Earth, Mars, Moon and the aubrite parent body

    NASA Astrophysics Data System (ADS)

    Varela, M. E.; Kurat, G.; Clocchiatti, R.; Schiano, P.

    1998-09-01

    Highly silicic glass inclusions are commonly present in mafic minerals of xenolithic terrestrial upper mantle rocks (Schiano and Clocchiatti, 1994). They are believed to be the products of volatile-rich silicic melts for which several sources have been proposed (Francis, 1976 ; Frey and Green, 1974 ; Schiano et al., 1995) but their origin(s) and, consequently, that of the glasses, remains unknown. However, in situ formation by very low degree partial melting seems to be possible as has been shown by experiments (e.g., Baker et al., 1995 ; Draper and Green, 1997). Glass inclusions of silicic chemical composition are also present in some mafic minerals of achondritic meteorites (e.g., Fuchs, 1974 ; Okada et al., 1988 ; Johnson et al.,1991 ). The enstatite achondrites (aubrites) Aubres and Norton County, which record early planetesimal and planet formation in the solar nebula, and the olivine achondrite (chassignite) Chassigny, a rock believed to originate from Mars, contain abundant glass inclusions in their main minerals enstatite and olivine, respectively. Glasses of glass-bearing inclusions have a highly silicic and volatile-rich chemical composition similar, but not identical, to that of glass inclusions in terrestrial upper mantle peridotite minerals. Furthermore, glass inclusions in olivines from the Moon (e.g., Roedder and Weiblen, 1977) are also silica- rich. Since different physico-chemical conditions prevails in the source regions of these rocks, the process of melting is, perhaps, not generally applicable for the generation of silica-rich glasses. Alternatively, the glasses could have been formed via precipitation from silicate-loaded fluids (Schneider and Eggler, 1986) or vapors. Another possible mechanism, not previously identified, could be dehydrogenation of nominally non-hydrous mafic minerals by heating or depressurization which should be accompanied by expulsion of excess silica and incompatible elements. This process will mimic low temperature

  8. Exposure and compositional factors that influence polarization induced birefringence in silica glass

    NASA Astrophysics Data System (ADS)

    Allan, Douglas C.; Mlejnek, Michal; Neukirch, Ulrich; Smith, Charlene M.; Smith, Frances M.

    2007-03-01

    Silica glass exhibits a permanent anisotropic response, referred to as polarization induced birefringence (PIB), when exposed to short wavelength, polarized light. The magnitude of the PIB has been empirically correlated with the OH content of the glass. Our recent studies pertaining to PIB have focused on careful characterization of PIB, with particular emphasis on understanding all of the contributions to the measured birefringence signal and finally extracting only that signal associated with birefringence arising from exposure to a polarized light beam. We will demonstrate that a critical contributor to the total birefringence signal is birefringence that comes from exposure beam inhomogeneities. After subtracting beam profile effects we are able to show that PIB is proportional to the OH content of the glass. Polarized infrared (IR) measurements were performed on glasses that developed PIB as a consequence of exposure to polarized 157-nm light. These studies reveal that there is preferential bleaching of a specific hydroxyl (OH) species in the glass with OH aligned parallel to the incident polarization undergoing more bleaching than those perpendicular. Further, we observe a very strong correlation between the measured PIB of these samples and the anisotropic bleaching. From these studies we propose a mechanism that can explain the role of hydroxyl in PIB.

  9. Phase equilibrium and preparation, crystallization and viscous sintering of glass in the alumina-silica-lanthanum phosphate system

    NASA Astrophysics Data System (ADS)

    He, Feng

    The phase equilibrium, viscosity of melt-quenched glasses, and processing of sol-gel glasses of the alumina-silica-lanthanum phosphate system were studied. These investigations were directed towards serving the objective of synthesizing nano-structured ceramic-matrix-composites via controlled crystallization of glass precursors. The thermal stability, phase equilibrium, and liquidus temperatures of the alumina- and mullite-lanthanum phosphate systems are determined. An iridium wire heater was constructed to anneal samples up to 2200°C. Phosphorus evaporation losses were significant at high temperatures, especially over 1800°C. The tentative phase diagrams of the two quasi-binary systems were presented. The viscosity of the melt-quenched mullite-lanthanum phosphate glasses was measured by three different methods, including viscous sintering of glass powder compacts, neck formation between two Frenkel glass beads, and thermal analysis of the glass transition. Improved methodologies were developed for applying the interpretative mathematical models to the results of the sintered powder and thermal analytical experiments. Good agreement was found between all three methods for both absolute values and temperature dependence. A sol-gel process was developed as a low temperature route to producing glasses. A unique, single phase mullite gel capable of low temperature (575°C) mullitization was made from tetraethoxysilane and aluminum isopropoxide at room temperature in three days. Low temperature crystallization was attributed to the avoidance of phase segregation during gel formation and annealing. This was greatly enhanced by a combination of low temperature preheating in the amorphous state, a high heating rate during crystallization and low water content. The Al2O3 content in mullite (61-68 mol%) depended on the highest annealing temperature. Two mullite-lanthanum phosphate gels were made based upon modifying the chemical procedures used for the homogeneous single

  10. Origin of high-silica liquids at Stromboli volcano (Aeolian Islands, Italy) inferred from crustal xenoliths

    NASA Astrophysics Data System (ADS)

    Renzulli, A.; Serri, G.; Santi, P.; Mattioli, M.; Holm, P. M.

    High-silica igneous xenoliths (granophyre and obsidian fragments with SiO2 ca. 75 wt.%) and high-silica glass (SiO2 between ca. 64 and 75 wt.%) within glass-bearing tonalitic and dioritic xenoliths have been discovered at Stromboli. They are well beyond the silica range of the volcanic rocks erupted during the subaerial activity of the volcano. The granophyre and the obsidian fragments occur within the Petrazza pyroclastics (high-K andesite pumiceous scoriae) of the Paleostromboli I period (� to >61 ka), whereas the glass-bearing tonalites and diorites are hosted in the Omo basaltic-andesite lava flows of the Paleostromboli II period (64-55 ka). The obsidian represents an extremely evolved liquid derived from low-pressure fractional crystallization of high-K calc-alkaline magmas of Stromboli, coupled with minor assimilation of upper crust or terrigenous sediments. The other studied high-silica products have an anatectic origin. The granophyre composition is compatible with a genesis by low-degree melting of leucotonalites similar to some Calabrian Arc lithotypes. Partial melting of crustal rocks from the Stromboli basement is also demonstrated by interstitial glass in the tonalite and diorite xenoliths. Textural evidence and the presence of variable glass compositions suggest that in these plutonic xenoliths the melt chemistry was controlled by dehydration melting of biotite and non-modal melting of local mineralogy. High-degree undercooling of granophyre melt and of the partially melted xenoliths is consistent with rapid rise of the host magmas leading to eruption. Whether partial melting was initiated during stoping and transport of xenoliths within the rising magma or in situ during magma storage within the crust has not been unequivocally established.

  11. Surface modification of glass plates and silica particles by phospholipid adsorption.

    PubMed

    Chibowski, Emil; Delgado, Angel V; Rudzka, Katarzyna; Szcześ, Aleksandra; Hołysz, Lucyna

    2011-01-01

    The effect of phospholipid adsorption on the hydrophobicity of glass plates and on the surface charge of silica particles using contact angle and electrophoretic mobility measurements, respectively, was investigated. Deposition of successive statistical monolayers of dipalmitoylphosphatidylcholine (DPPC) on the glass surface showed zig-zag changes of water contact angle, especially on the first few monolayers. This behavior is qualitatively coherent with the oscillations observed in zeta potential values for increasing DPPC concentration. The results indicate that the phospholipid is adsorbed vertically on the plates, exposing alternately its polar head and non-polar hydrocarbon chains in successive layers. On the other hand, experiments conducted on glass plates prior hydrophobized by contact with n-tetradecane suggest that DPPC molecules may to some extent dissolve in the relatively thick n-alkane film and then expose their polar heads over the film surface thus producing polar electron-donor interactions. The effect of both DPPC and dioleoylphosphatidylcholine (DOPC) on the electrokinetic potential of silica spheres confirms adsorption of the phospholipids, leading to a decrease in the (originally negative) zeta potential of silica and even reversal of its sign to positive at acidic pH. Hydrophobic interactions between phospholipid molecules in the medium and those already adsorbed may explain the overcharging. The adsorption of neutral phospholipids may reduce the zeta potential as a consequence of the shift of the electrokinetic or slip plane. The effect is more evident in the case of DOPC, suggesting a less efficient packing of this phospholipid because of the presence of double bonds in its molecule, which in fact is well known.

  12. 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.

  13. 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%.

  14. 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.

  15. Fabrication of highly transparent superhydrophobic coatings from hollow silica nanoparticles.

    PubMed

    Xu, Ligang; He, Junhui

    2012-05-15

    We herein report a simple and effective method to fabricate excellent transparent superhydrophobic coatings. 3-Aminopropytriethoxysilane (APTS)-modified hollow silica nanoparticle sols were dip-coated on slide glasses, followed by thermal annealing and chemical vapor deposition with 1H,1H,2H,2H-perfluorooctyltrimethoxysilane (POTS). The largest water contact angle (WCA) of coating reached as high as 156° with a sliding angle (SA) of ≤2° and a maximum transmittance of 83.7%. The highest transmittance of coated slide glass reached as high as 92% with a WCA of 146° and an SA of ≤6°. A coating simultaneously showing both good transparency (90.2%) and superhydrophobicity (WCA: 150°, SA: 4°) was achieved through regulating the concentration of APTS and the withdrawing speed of dip-coating. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) were used to observe the morphology and structure of nanoparticles and coating surfaces. Optical properties were characterized by a UV-visible spectrophotometer. Surface wettability was studied by a contact angle/interface system. The effects of APTS concentration and the withdrawing speed of dip-coating were also discussed on the basis of experimental observations.

  16. 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.

  17. 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.

  18. High-Entropy Metallic Glasses

    NASA Astrophysics Data System (ADS)

    Wang, W. H.

    2014-10-01

    The high-entropy alloys are defined as solid-solution alloys containing five or more than five principal elements in equal or near-equal atomic percent. The concept of high mixing entropy introduces a new way for developing advanced metallic materials with unique physical and mechanical properties that cannot be achieved by the conventional microalloying approach based on only a single base element. The metallic glass (MG) is the metallic alloy rapidly quenched from the liquid state, and at room temperature it still shows an amorphous liquid-like structure. Bulk MGs represent a particular class of amorphous alloys usually with three or more than three components but based on a single principal element such as Zr, Cu, Ce, and Fe. These materials are very attractive for applications because of their excellent mechanical properties such as ultrahigh (near theoretical) strength, wear resistance, and hardness, and physical properties such as soft magnetic properties. In this article, we review the formation and properties of a series of high-mixing-entropy bulk MGs based on multiple major elements. It is found that the strategy and route for development of the high-entropy alloys can be applied to the development of the MGs with excellent glass-forming ability. The high-mixing-entropy bulk MGs are then loosely defined as metallic glassy alloys containing five or more than five elements in equal or near-equal atomic percent, which have relatively high mixing entropy compared with the conventional MGs based on a single principal element. The formation mechanism, especially the role of the mixing entropy in the formation of the high-entropy MGs, is discussed. The unique physical, mechanical, chemical, and biomedical properties of the high-entropy MGs in comparison with the conventional metallic alloys are introduced. We show that the high-mixing-entropy MGs, along the formation idea and strategy of the high-entropy alloys and based on multiple major elements, might provide

  19. Sol gel synthesis and photoluminescence of AlP nanocrystals embedded in silica glasses

    NASA Astrophysics Data System (ADS)

    Yang, Heqing; Yao, Xi; Huang, Daming

    2007-03-01

    AlP nanocrystals embedded in silica glasses were prepared via an easy sol-gel process. The gels synthesized by the hydrolysis of a complex solution of Si(OC2H5)4, Al(NO3)3 · 9H2O and PO(OC2H5)3 were heated at 600 °C for 10 h in an air atmosphere to form an Al2O3-P2O5-SiO2 gel glass. The gel glasses were then heated in the presence of H2-N2 mixed gas, in which the P(V) are reduced by the H2 gas, and react with Al(III) to form fine cubic AlP crystallites embedded in silica glasses. The X-ray diffraction patterns showed (1 1 1), (2 2 0), and (3 1 1) diffraction lines from cubic AlP crystals. The AlP (2 2 0), (3 1 1), (4 2 2), and (4 4 0) diffraction lines were observed in the electron diffraction pattern. The size of AlP nanocrystals was found to be from 5 to 10 nm in diameter by transmission electron microscopy. A strong room temperature photoluminescence (PL) with peaks at 533, 582, 649, and 688 nm was observed from AlP/SiO2 nanocomposites. The PL is suggested to originate from the hydrogen-related species (PL band at 533 nm), the small "peroxy radical" (PL band at 582 nm), and the nonbridging oxygens (PL bands at 649 and 688 nm), respectively.

  20. In vitro apatite forming ability of type I collagen hydrogels containing bioactive glass and silica sol-gel particles.

    PubMed

    Eglin, David; Maalheem, Sonia; Livage, Jacques; Coradin, Thibaud

    2006-02-01

    Type I collagen hydrogel containing bioactive glass (CaO-P2O5-SiO2) and silica sol-gel micrometric particles were prepared and their in vitroapatite-forming ability in simulated body fluid assessed. X-ray diffraction and scanning electron microscopy analysis showed that bioactive glass particles entrapment in collagen matrix did not inhibit calcium phosphate formation and induced morphology variations on the crystalline phase precipitated on the hydrogel surface. The silica--collagen hydrogel composite precipitated calcium phosphate whereas silica particles and collagen hydrogel alone did not, indicating a possible synergetic effect between collagen and silica on the apatite-forming ability. Mechanisms of calcium phosphate precipitation and its relevance to biomaterial development are discussed.

  1. Free energy profiles of Al3+ and La3+ cation distribution in silica and soda silicate glasses

    SciTech Connect

    Corrales, Louis R.

    2005-03-01

    The factors that control the distribution of Al3+ and La3+ cations in silica and soda silicate glasses is examined by using molecular dynamics (MD) simulations. In particular, the response of the glass network to the presence of metal oxide is probed using liquid state theory that treats the glass network as a solvent and the metal cation as a solute. MD simulations are used to obtain the mean force of the solvent-solute and solute-solute interactions along a trajectory that is then used to obtain the potential of mean force. The resulting free energy is analyzed along the trajectory to determine the stable configurations of the cation pair. Details of determining the PMF for an Al cation pair in silica and silicate glass is presented. A comparison of these results with those previously calculated for a La cation pair in the same glass systems is given. The results reveal that there are distinct differences on how the network accommodates the two different size cations. It is found that the network wraps itself around the larger La cation very much like a solvent shell, whereas, the smaller Al cation is incorporated into the network backbone. In silica and soda silicate glasses clustering of the La ion pair to form La-O-La linkages is favored, in contrast, the glasses favor a separated state of the Al ion pair.

  2. 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.

  3. Femtosecond versus picosecond laser machining of nano-gratings and micro-channels in silica glass.

    PubMed

    Corbari, Costantino; Champion, Audrey; Gecevičius, Mindaugas; Beresna, Martynas; Bellouard, Yves; Kazansky, Peter G

    2013-02-25

    The ability of 8 picosecond pulse lasers for three dimensional direct-writing in the bulk of transparent dielectrics is assessed through a comparative study with a femtosecond laser delivering 600 fs pulses. The comparison addresses two main applications: the fabrication of birefringent optical elements and two-step machining by laser exposure and post-processing by chemical etching. Formation of self-organized nano-gratings in glass by ps-pulses is demonstrated. Differential etching between ps-laser exposed regions and unexposed silica is observed. Despite attaining values of retardance (>100 nm) and etching rate (2 μm/min) similar to fs pulses, ps pulses are found unsuitable for bulk machining in silica glass primarily due to the build-up of a stress field causing scattering, cracks and non-homogeneous etching. Additionally, we show that the so-called "quill-effect", that is the dependence of the laser damage from the direction of writing, occurs also for ps-pulse laser machining. Finally, an opposite dependence of the retardance from the intra-pulse distance is observed for fs- and ps-laser direct writing.

  4. 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.

  5. Single and multiple molecular beacon probes for DNA hybridization studies on a silica glass surface

    NASA Astrophysics Data System (ADS)

    Fang, Xiaohong; Liu, Xiaojing; Tan, Weihong

    1999-05-01

    Surface immobilizable molecular beacons have been developed for DNA hybridization studies on a silica glass plate. Molecular beacons are a new class of oligonucleotide probes that have a loop-and-stem structure with a fluorophore and a quencher attached to the two ends of the stem. They only emit intense fluorescence when hybridize to their target molecules. This provides an excellent selectivity for the detection of DNA molecules. We have designed biotinylated molecular beacons which can be immobilized onto a solid surface. The molecular beacon is synthesized using DABCYL as the quencher and an optical stable dye, tetramethylrhodamine, as the fluorophore. Mass spectrometry is used to confirm the synthesized molecular beacon. The molecular beacons have been immobilized onto a silica surface through biotin-avidin binding. The surface immobilized molecular beacons have been used for the detection of target DNA with subnanomolar analytical sensitivity. have also immobilized two different molecular beacons on a silica surface in spatially resolved microscopic regions. The hybridization study of these two different molecular beacon probes has shown excellent selectivity for their target sequences. The newly designed molecular beacons are intended for DNA molecular interaction studies at an interface and for the development of ultrasensitive DNA sensors for a variety of applications including disease diagnosis, disease mechanism studies, new drug development, and in the investigation of molecular interactions between DNA molecules and other interesting biomolecules.

  6. Hybrid glass coatings for optical fibers: effect of coating thickness on strength and dynamic fatigue characteristics of silica fibers

    NASA Astrophysics Data System (ADS)

    Wojcik, A. B.; Matthewson, M. J.; Castelino, K. T.; Wojcik, J.; Walewski, A.

    2006-04-01

    Specialty optical fibers operating in harsh aerospace environments are typically exposed to high temperatures and elevated humidity. This calls for better performing protective coatings. Recently developed sol-gel derived inorganicorganic hybrid materials called hybrid glass offered improved protective performance as compared to standard dual polymer coated fibers [1]. In this paper we examine the effectiveness of online UV curing for the protective ability of hybrid glass coatings. For this purpose two types of UV-curable hybrid glass candidates representing two different concentrations of acrylate groups were applied online to silica fibers as single and dual coats. Samples of fibers were collected and subjected to dynamic fatigue testing by two-point bending. The stress corrosion parameter, n, as well as the strength of the fibers were determined. Both the strength and n were higher for fibers with two layers of coating as compared to single coatings even when the thickness of both one and two layer coatings was the same. This may be caused by the greater degree of cross linking of the inorganic component when the coating is exposed twice to the heat generated in the UV chamber. Coating materials with reduced acrylate group content had higher values of the fatigue parameter n but at the same time reduced strength.

  7. Chemical interaction between nitrogen and iron in silica glasses via sequential ion-implantation

    SciTech Connect

    Isobe, T.; Toriyama, T.; Weeks, R.A.; Zuhr, R.A.

    1998-08-01

    Silica glass plates (Corning 7940 excimer grade) were implanted sequentially with N{sup +} at 52 keV to different doses, ranging from 0 to 1.2{times}10{sup 17}thinspionsthinspcm{sup {minus}2}, and then with Fe{sup +} at 160 keV to 6{times}10{sup 16}thinspionsthinspcm{sup {minus}2} at room temperature and 4 {mu}Athinspcm{sup {minus}2}. The intensity of ferromagnetic magnetic resonance (FMR) absorption and the magnetization calculated by the angular dependence of the FMR field reach maxima at an N/Fe atomic ratio {approximately}0.2. Two peaks due to Fe 2p{sub 3/2} electron are observed at 707.2{plus_minus}0.2 and 710.9{plus_minus}0.2thinspeV in the x-ray photoelectron spectra. The intensity of the former relative to the latter decreases with increasing the N dose. The conversion electron M{umlt o}ssbauer spectrum reveals the formation of superparamagnetic iron nitride as well as the existence of Fe{sup 2+} and Fe{sup 3+} in silica when implanting N{sup +} to 7.5{times}10{sup 15}thinspionsthinspcm{sup {minus}2} and then {sup 57}Fe{sup +} to 6{times}10{sup 16}thinspionsthinspcm{sup {minus}2} at N/Fe=0.125. These results suggest that sequential ion-implantation of N{sup +} and Fe{sup +} produces iron nitride in silica glasses. {copyright} {ital 1998 Materials Research Society.}

  8. Positively charged mini-protein Zbasic2 as a highly efficient silica binding module: opportunities for enzyme immobilization on unmodified silica supports.

    PubMed

    Bolivar, Juan M; Nidetzky, Bernd

    2012-07-03

    Silica is a highly attractive support material for protein immobilization in a wide range of biotechnological and biomedical-analytical applications. Without suitable derivatization, however, the silica surface is not generally usable for attachment of proteins. We show here that Z(basic2) (a three α-helix bundle mini-protein of 7 kDa size that exposes clustered positive charges from multiple arginine residues on one side) functions as highly efficient silica binding module (SBM), allowing chimeras of target protein with SBM to become very tightly attached to underivatized glass at physiological pH conditions. We used two enzymes, d-amino acid oxidase and sucrose phosphorylase, to demonstrate direct immobilization of Z(basic2) protein from complex biological samples with extremely high selectivity. Immobilized enzymes displayed full biological activity, suggesting that their binding to the glass surface had occurred in a preferred orientation via the SBM. We also show that charge complementarity was the main principle of affinity between SBM and glass surface, and Z(basic2) proteins were bound in a very strong, yet fully reversible manner, presumably through multipoint noncovalent interactions. Z(basic2) proteins were immobilized on porous glass in a loading of 30 mg protein/g support or higher, showing that attachment via the SBM combines excellent binding selectivity with a technically useful binding capacity. Therefore, Z(basic2) and silica constitute a fully orthogonal pair of binding module and insoluble support for oriented protein immobilization, and this opens up new opportunities for the application of silica-based materials in the development of supported heterogeneous biocatalysts.

  9. Formation of a plano-convex micro-lens array in fused silica glass by using a CO2 laser-assisted reshaping technique

    NASA Astrophysics Data System (ADS)

    Sohn, Ik-Bu; Yoo, Dongyoon; Noh, Young-Chul; Sung, Jae-Hee; Lee, Seong-Ku; Choi, Hun-Kook; Ahsan, Md. Shamim

    2016-08-01

    We report on fabricating high-fill-factor plano-convex spherical and square micro-lens arrays on fused silica glass surface by using a CO2 laser-assisted reshaping technique. Initially, periodic micro-pillars are encoded on glass surfaces by means of a femtosecond laser beam, afterwards, the micro-pillars are polished several times by irradiating a CO2 laser beam on top of the micro-pillars. Consequently, a spherical micro-lens array with micro-lens size of 50 μm × 50 μm and a square micro-lens array with micro-lens size of 100 μm × 100 μm are formed on the surface of the fused silica glass. We also study the intensity distribution of light passing through the glass sample engraved with a spherical micro-lens array. The simulation result shows that the focal length of the spherical micro-lens array is 35 μm. Furthermore, we investigate the optical properties of glass samples with engraved micro-lens arrays. The proposed CO2-laser-based reshaping technique is simple and fast and shows promises for fabricating arrays of smooth micro-lenses in various transparent materials.

  10. 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

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

    PubMed

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

    2014-01-23

    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%.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

    2016-10-01

    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.

  18. 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.

  19. High-quality substrate for fluorescence enhancement using agarose-coated silica opal film.

    PubMed

    Xu, Ming; Li, Juan; Sun, Liguo; Zhao, Yuanjin; Xie, Zhuoying; Lv, Linli; Zhao, Xiangwei; Xiao, Pengfeng; Hu, Jing; Lv, Mei; Gu, Zhongze

    2010-08-01

    To improve the sensitivity of fluorescence detection in biochip, a new kind of substrates was developed by agarose coating on silica opal film. In this study, silica opal film was fabricated on glass substrate using the vertical deposition technique. It can provide stronger fluorescence signals and thus improve the detection sensitivity. After coating with agarose, the hybrid film could provide a 3D support for immobilizing sample. Comparing with agarose-coated glass substrate, the agarose-coated opal substrates could selectively enhance particular fluorescence signals with high sensitivity when the stop band of the silica opal film in the agarose-coated opal substrate overlapped the fluorescence emission wavelength. A DNA hybridization experiment demonstrated that fluorescence intensity of special type of agarose-coated opal substrates was about four times that of agarose-coated glass substrate. These results indicate that the optimized agarose-coated opal substrate can be used for improving the sensitivity of fluorescence detection with high quality and selectivity.

  20. 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

  1. Visible luminescence of Al2O3 nanoparticles embedded in silica glass host matrix

    NASA Astrophysics Data System (ADS)

    El Mir, L.; Amlouk, A.; Barthou, C.

    2006-11-01

    This paper deals with the sol gel elaboration and defects photoluminescence (PL) examination of Al2O3 nanocrystallites (size ˜30 nm) confined in glass based on silica aerogel. Aluminium oxide aerogels were synthesized using esterification reaction for hydrolysis of the precursor and supercritical conditions of ethyl alcohol for drying. The obtained nanopowder was incorporated in SiO2 host matrix. After heating under natural atmosphere at 1150 °C for 2 h, the composite Al2O3/SiO2 (AS) exhibited a strong PL bands at 400 600 and 700 900 nm in 78 300 K temperature range. PL excitation (PLE) measurements show different origins of the emission. It was suggested that OH-related radiative centres and non-bridging oxygen hole centres (NBOHCs) were responsible for the bands at 400 600 and 700 900 nm, respectively.

  2. Synthesis and photoluminescence property of nanostructured sol-gel antimony tin oxide film on silica glass

    NASA Astrophysics Data System (ADS)

    Dua, Laxmikanta; Biswas, Prasanta K.

    2013-05-01

    Sol-gel based spin coated nanostructured films of tetragonal phase of antimony (10 at%) doped tin oxide (ATO) were prepared on silica glass. XRD and TEM images identify the crystallite size lying in the range, ∼3.4-9.8 nm. Quantum confinement was observed in the nanoclusters. Evaluated band gaps at 3.62 eV correspond to the transition for bulk ATO and 4.51 eV, 5.26 eV for excitons and oxygen deficiency. Schemes have been proposed for absorption and photoluminescence excitation (PLE). Two excitonic transitions were observed at 275 nm and 310 nm for different nanocluster sizes. Evaluation of mean free path and Fermi energy correspond to ionized scattering and degeneracy of the ATO films.

  3. Three-dimensional optical sensing network written in fused silica glass with femtosecond laser.

    PubMed

    Zhang, Haibin; Ho, Stephen; Eaton, Shane M; Li, Jianzhao; Herman, Peter R

    2008-09-01

    A single-step fast-writing method of burst ultrafast laser modification was applied to form a mesh network of multi-wavelength Bragg grating waveguides in bulk fused silica glass. Strain-optic and thermo-optic responses of the laser-written internal sensors are reported for the first time. A dual planar layout provided independent temperature- and strain-compensated characterization of temperature and strain distribution with coarse spatial resolution. The grating responses were thermally stable to 500 masculineC. To our best knowledge, the grating network represents the first demonstration of 3D distributed optical sensing network in a bulk transparent medium. Such 3D grating networks open new directions for strain and temperature sensing in optical circuits, optofluidic, MEMS or lab-on-a-chip microsystems, actuators, and windows and other large display or civil structures.

  4. 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.

  5. Surface-dependent transitions during self-assembly of phospholipid membranes on mica, silica, and glass.

    PubMed

    Benes, Martin; Billy, Didier; Benda, Ales; Speijer, Han; Hof, Martin; Hermens, Wim Th

    2004-11-09

    Formation of supported membranes by exposure of solid surfaces to phospholipid vesicles is a much-used technique in membrane research. Freshly cleaved mica, because of its superior flatness, is a preferred support, and we used ellipsometry to study membrane formation kinetics on mica. Neutral dioleoyl-phosphatidylcholine (DOPC) and negatively charged dioleoyl-phosphatidylserine/dioleoyl-phosphatidylcholine (20% DOPS/80% DOPC) vesicles were prepared by sonication. Results were compared with membrane formation on silica and glass, and the influence of stirring, buffer, and calcium was assessed. Without calcium, DOPC vesicles had a low affinity (Kd approximately 30 microM) for mica, and DOPS/DOPC vesicles hardly adsorbed. Addition of calcium promptly caused condensation of the adhering vesicles, with either loss of excess lipid or rapid additional lipid adsorption up to full surface coverage. Vesicle-mica interactions dominate the adsorption process, but vesicle-vesicle interactions also seem to be required for the condensation process. Membranes on mica proved unstable in Tris-HCl buffer. For glass, transport-limited adsorption of DOPC and DOPS/DOPC vesicles with immediate condensation into bilayers was observed, with and without calcium. For silica, vesicle adsorption was also rapid, even in the absence of calcium, but the transition to condensed layers required a critical surface coverage of about 50% of bilayer mass, indicating vesicle-vesicle interaction. For all three surfaces, additional adsorption of DOPC (but not DOPS/DOPC) vesicles to condensed membranes was observed. DOPC membranes on mica were rapidly degraded by phospholipase A2 (PLA2), which pleads against the role of membrane defects as initial PLA2 targets. During degradation, layer thickness remained unchanged while layer density decreased, in accordance with recent atomic force microscopy measurements of gel-phase phospholipid degradation by PLA2.

  6. In Vitro Cytotoxicity Evaluation of Novel Nano-Hydroxyapatite-Silica Incorporated Glass Ionomer Cement

    PubMed Central

    Noorani, Tahir Yusuf; Rahman, Ismail Ab.; Masudi, Saman Malik

    2017-01-01

    Introduction Glass Ionomer Cements (GIC) are among the most popular restorative materials, but their use in dentistry is limited due to their physical properties. The hardness of GIC was improved by incorporation of nano-hydroxyapatite-silica into GIC, to expand its applicability. Aim To evaluate the cytotoxic effects of nano-hydroxyapatite-silica incorporated glass ionomer cement (HA-SiO2-GIC) on human Dental Pulp Stem Cells (DPSC) and compare it with conventional GIC and resin modified GIC. Materials and Methods Material extracts of Fuji IX, Fuji II LC and HA-SiO2-GIC were prepared into seven serial concentrations and applied to 96-well-plates seeded with DPSC. The 96-well-plates were incubated for 24 and 72 hours. The morphology of DPSC was observed under the inverted phase contrast microscope, and the cell viability was determined using MTT assay at both time intervals. Kruskal-Wallis test was performed for statistical analysis. Results At maximum concentration, DPSC appeared fewer in number, but the normal spindle morphology was maintained in all groups except for Fuji II LC. At lower concentrations, DPSC appeared normal and more confluent in all groups. The cytotoxic effects of all groups were dose dependent. Fuji IX demonstrated the lowest cytotoxicity, followed by HA-SiO2-GIC. Fuji II LC demonstrated the highest cytotoxicity. The difference was significant between all groups at 200 mg/ml concentration (p<0.05). At concentration <100 mg/ml, cytotoxicity of HA-SiO2-GIC was comparable to that of Fuji IX and lower than that of Fuji II LC. Conclusion HA-SiO2-GIC showed a favourable cytotoxicity response and thus holds promise as a future potential restorative material in clinical dentistry. PMID:28571275

  7. 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).

  8. 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.

  9. Fabrication of curved PDMS microstructures on silica glass by proton beam writing aimed for micro-lens arrays on transparent substrates

    NASA Astrophysics Data System (ADS)

    Saito, Keisuke; Hayashi, Hidetaka; Nishikawa, Hiroyuki

    2013-07-01

    Polydimethylsiloxane (PDMS), a type of silicone rubber, has excellent material properties such as flexibility, optical transparency and biocompatibility. Therefore, it can offer possible applications in the field of microfluidics as flexible micro-optical components, when they can be formed on transparent materials such as silica glass. We performed proton beam writing (PBW) (with 1.0 MeV beam) on PDMS microstructures with curved surface on silica glass. We found that 13-μm thick PDMS films on silica glass are sensitive only for proton fluences above 600 nC/mm2 in contrast with the sensitivity of 4.0 nC/mm2 when using a silicon substrate. Based on the hypothesis that the effective sensitivity was lower due to the electric charging of silica glass surface during PBW, we coated the silica glass surface by Au sputtering. As a result, we were able to observe the formation of PDMS on the Au-coated silica glass at a much lower fluence of 2.0 nC/mm2. Arrays of curved PDMS structures with a height of 13 μm and diameter of 40 μm have been fabricated on a semi-transparent Au-coated silica glass.

  10. Structure and IRR spectra of copper-exchanged soda-lime silica glass

    NASA Astrophysics Data System (ADS)

    Suszynska, M.; Maczka, M.; Bukowska, E.; Berg, K. J.

    2010-11-01

    Multi-component soda lime silica glass (SLSG) specimens, with composition from the miscibility gap in the SiO2-Na2O system, were investigated after the substitution of copper for sodium and after thermal treatment of the exchanged samples in gaseous hydrogen. The behaviour of the obtained composite materials was studied by infrared reflection spectroscopy (IRRS). Some optical absorption micro-spectrophotometry (OAMS) measurements and X-ray-diffraction (XRD) analyses complemented these investigations. It has been stated that after exchange in the CuCl molten bath, the dopant was present in the glassy matrix in the form of cuprous and cupric ions. The cuprous ions participate in the formation of semiconducting Cu2O nanoparticles. Hydrogenation of the exchanged specimens leads to the formation of metallic copper atoms which due to the van der Waals interactions precipitate in the form of colloidal copper nanoparticles. Changes of the matrix morphology are mainly related with the presence of cupric ions which behave as glass forming cations and such as these participate in the formation of mixed copper-sodium silicates. The effectiveness of these processes is substantially dependent on the exchange and hydrogenation parameters.

  11. 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.

  12. Silica removal in industrial effluents with high silica content and low hardness.

    PubMed

    Latour, Isabel; Miranda, Ruben; Blanco, Angeles

    2014-01-01

    High silica content of de-inked paper mill effluents is limiting their regeneration and reuse after membrane treatments such as reverse osmosis (RO). Silica removal during softening processes is a common treatment; however, the effluent from the paper mill studied has a low hardness content, which makes the addition of magnesium compounds necessary to increase silica removal. Two soluble magnesium compounds (MgCl₂∙6H₂O and MgSO₄∙7H₂O) were tested at five dosages (250-1,500 mg/L) and different initial pH values. High removal rates (80-90%) were obtained with both products at the highest pH tested (11.5). With these removal efficiencies, it is possible to work at high RO recoveries (75-85%) without silica scaling. Although pH regulation significantly increased the conductivity of the waters (at pH 11.5 from 2.1 to 3.7-4.0 mS/cm), this could be partially solved by using Ca(OH)₂ instead of NaOH as pH regulator (final conductivity around 3.0 mS/cm). Maximum chemical oxygen demand (COD) removal obtained with caustic soda was lower than with lime (15 vs. 30%). Additionally, the combined use of a polyaluminum coagulant during the softening process was studied; the coagulant, however, did not significantly improve silica removal, obtaining a maximum increase of only 10%.

  13. Dopant distribution in a Tm(3+)-Yb(3+) codoped silica based glass ceramic: an infrared-laser induced upconversion study.

    PubMed

    Lahoz, F; Martin, I R; Mendez-Ramos, J; Nunez, P

    2004-04-01

    The optically active dopant distribution in a Tm(3+)-Yb(3+) doped silica based glass ceramic sample has been investigated. A systematic analysis of the upconversion fluorescence of the Tm(3+)-Yb(3+) codoped glass and glass ceramic has been performed at room temperature. Tm(3+) and Yb(3+) single doped glass and glass ceramics have also been included in the study. Upon infrared excitation at 790 nm into the (3)H(4) level of the Tm(3+) ions a blue upconversion emission is observed, which is drastically increased in the Yb(3+) codoped samples. A rate equation model confirmed the energy transfer upconversion mechanism. Based on these results, the temporal dynamic curves of the levels involved in the upconversion process, (3)H(4), (2)F(5/2), and (1)G(4) were interpreted in the glass ceramic samples. The contribution of the optically active Tm(3+) and Yb(3+) ions in the crystalline and in the vitreous phase of the glass ceramic was distinguished and the ratio of Tm(3+) ions in the crystalline phase could be quantified for the 1 mol % Tm(3+)-2.5 mol % Yb(3+) glass ceramic. A surprising result was obtained for that concentration: the main contribution to the upconversion emission of the glass ceramic is due to Tm(3+)-Yb(3+) ions in the vitreous phase.

  14. 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.

  15. Formation of cylindrical micro-lens array on fused silica glass surface using CO2 laser assisted reshaping technique

    NASA Astrophysics Data System (ADS)

    Choi, Hun-Kook; Ahsan, Md. Shamim; Yoo, Dongyoon; Sohn, Ik-Bu; Noh, Young-Chul; Kim, Jin-Tae; Jung, Deok; Kim, Jin-Hyeok; Kang, Ho-Min

    2015-12-01

    This paper demonstrates the laser assisted formation of plano-convex cylindrical and flat-top curved micro-lens array on fused silica glass surface. Initially, femtosecond laser pulses are irradiated on the sample glass to fabricate periodic linear micro-gratings on the glass surface. Afterwards, we reshape the micro-gratings by several times irradiation of a CO2 laser beam by focusing the laser beam on top of the micro-gratings. As a consequence, plano-convex cylindrical micro-lens array with a period varying from 20 to 40 μm are formed on fused silica glass surface. However, flat-top curved gratings' array is observed on the glass surface for a gratings' period of 50 μm. The fabricated micro-lenses show great consistency in size and shape throughout the sample area. Furthermore, we analyze the formation mechanism of micro-lens array on glass surface using the CO2 laser assisted reshaping technique. The proposed reshaping technique exhibits great potential for forming a large variety of micro-lens arrays on the surface of various transparent materials.

  16. 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.

  17. Study on Au nanoparticles, TiO2 nanoclusters, and SiO2 nanoshells coated multi-wall carbon nanotubes/silica gel-glass

    NASA Astrophysics Data System (ADS)

    Zheng, Chan; Chen, Wenzhe; Ye, Xiaoyun

    2012-05-01

    Multi-wall carbon nanotubes (MWCNTs) coated with crystalline Au nanoparticles, TiO2 nanoclusters, and amorphous SiO2 nanoshells, to represent conductors, semiconductors, and insulators, respectively, were embedded in transparent silica gel-glass. The coated MWCNT/silica gel-glasses were prepared by the sol-gel technique. Scanning electron microscopy (SEM), X-ray diffraction (XRD), UV/Vis spectroscopy, Fourier Transform Infrared (FT-IR) spectroscopy and pore structure measurements were used to investigate the morphology, structure, and texture properties of the coated MWCNT/silica gel-glasses. The hardness and elastic modulus of the silica gel-glasses were characterized using a Nanoindenter and found to depend on the coating materials. Coating the MWCNTs with crystalline Au nanoparticles, TiO2 nanoclusters, and amorphous SiO2 nanoshells leads to an increase in the hardness and elastic modulus, despite the higher specific surface area and pore volume of the coated MWCNT/silica gel-glasses. Consequently, we can conclude that the mechanical properties of coated MWCNT/silica gel-glass might be greatly dependent on the guest MWCNTs rather than the silica gel matrix.

  18. 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).

  19. Pyroxene-high silica rhyolite trace element partition coefficients measured by ion microprobe

    NASA Astrophysics Data System (ADS)

    Sisson, T. W.

    1991-06-01

    Pyroxene-liquid trace element partition coefficients have been measured in situ by ion microprobe in high silica rhyolites. Partition coefficients are reported for La, Ce, Nd, Sm, Dy, Er, Yb, Sc, Ti, V, Cr, Sr, Y, and Zr. The in situ analyses avoid the problem of contamination of the pyroxene phase by trace element-rich accessory mineral inclusions encountered in traditional bulk phenocryst-glass partitioning studies. Pyroxenes and glasses which have been analyzed are typical of high silica rhyolites worldwide. The samples analyzed are Bishop Tuff, California (augite, hypersthene); Sierra La Primavera, Mexico (ferrohedenbergite); and two samples of the Huckleberry Ridge Tuff, Wyoming (ferroaugite). Rare earth element (REE) partition coefficient patterns are convex-upward and resemble patterns determined in less silicic bulk compositions. Partition coefficients for the REEs Sr, Zr, and Cr show correlations with the Mg# of clinopyroxene, suggesting that crystal composition influences the fine structure of partitioning patterns. The overall similarity of partitioning patterns between samples indicates that the partition coefficients determined in this study can be generally applied in the geochemical modeling of high silica rhyolites.

  20. 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.'

  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. Tailoring the size and distribution of Ag nanoparticles in silica glass by defects

    NASA Astrophysics Data System (ADS)

    Yang, Yitao; Zhang, Chonghong; Song, Yin; Gou, Jie; Zhang, Liqing; Zhang, Hengqing; Liu, Juan; Xian, Yongqiang; Ma, Yizhun

    2014-02-01

    The composites embedded with metallic nanoparticles show large nonlinear optical susceptibility and strong surface plasmon resonance absorption, which enable potential application in opto-electronics. Ion implantation has been proven to be a powerful technique of synthesis of metallic nanoparticles due to its versatility and compatibility. However, the synthesis of nanoparticles by ion implantation inevitably leads to a broad size distribution due to Ostwald ripening process. The broad size distribution has a negative effect on improving the figure of merits for nonlinear optics. In this paper, we tried to introduce defects in silica glass to act as pre-nucleation centers to mediate the size and distribution of Ag nanoparticles. In experiment, the silica glass samples were pre-irradiated by 200 keV Ar ions to fluences of 0.8, 2.0 and 5.0 × 1016 ions/cm2, and then 200 keV Ag ions were implanted into the pre-irradiated samples to fluence of 2.0 × 1016 ions/cm2. UV-VIS results show that the absorbance intensity of Ag SPR peak initially increases and then decreases with pre-irradiation fluence, which implies the change in size and density of Ag nanoparticles in samples. TEM results verify that Ag nanoparticles in the sample pre-irradiated to the fluence of 0.8 × 1016 ions/cm2 grow bigger and distribute in a relatively narrow region comparing with that without pre-irradiation. With further increase of pre-irradiation fluence, the size of Ag nanoparticles shows a depth dependent distribution. A boundary can be clear seen at the depth of 110 nm, larger Ag nanoparticles disperse in region shallower than 110 nm, and smaller Ag nanoparticles disperse in the region deeper than 110 nm. The average size of Ag nanoparticles initially increases and then decreases with pre-irradiation fluence. Therefore, the introduction of defects by pre-irradiation could be an effective way to tailor the size and distribution of metallic nanoparticles in matrix.

  3. Direct measurement of the nonlinear refractive-index coefficient gamma at 355 nm in fused silica and in BK-10 glass.

    PubMed

    Iii, W T; Smith, W L; Milam, D

    1984-01-01

    We have measured the nonlinear refractive-index coefficient gamma interferometrically at 355 nm in fused silica and in BK-10, a borosilicate crown glass. These measurements are the first reported direct ultraviolet measurements of the nonlinear index of refraction in any transparent glass. Our results are gamma = (2.5 +/- 1.2) x 10(-16) cm(2)/W and gamma = (1.7 +/- 0.8) x 10(-16) cm(2)/W, respectively, for fused silica and BK-10.

  4. Suppression mechanism of radiation-induced darkening by Ce doping in Al/Yb/Ce-doped silica glasses: Evidence from optical spectroscopy, EPR and XPS analyses

    NASA Astrophysics Data System (ADS)

    Shao, Chongyun; Xu, Wenbin; Ollier, Nadege; Guzik, Malgorzata; Boulon, Georges; Yu, Lu; Zhang, Lei; Yu, Chunlei; Wang, Shikai; Hu, Lili

    2016-10-01

    Yb3+/Al3+ co-doped silica glasses with different Ce2O3 contents were prepared using the sol-gel method combined with high-temperature sintering. Changes in refractive index, absorption, emission and fluorescence lifetime of these glasses caused by X-ray irradiation were recorded and analyzed systematically. It is found that co-doping with certain amount of Ce could greatly improve the radiation resistance without evident negative effects on the basic optical properties of the Yb3+ ions in the near-infrared region. The nature of the radiation-induced color centres and the mechanism by which Ce prevented the formation of these centres were studied using optical absorption, electron paramagnetic resonance (EPR), and X-ray photoelectron spectroscopy (XPS) methods. Direct evidence confirmed that trapped electron centres (Yb2+/Si-E'/Al-E') and trapped hole centres (Al-OHCs) were effectively inhibited by Ce doping, which was correlated to the coexistence of the redox couple Ce3+/Ce4+ in the glasses. These results are helpful to understand the micro-structural origin and the suppression mechanism by Ce co-doping of the photodarkening effect in Yb3+-doped silica fibers.

  5. 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.

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

    PubMed

    Feng, Miao; Zhan, Hongbing

    2014-04-21

    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.

  7. High chloride content calcium silicate glasses.

    PubMed

    Chen, Xiaojing; Karpukhina, Natalia; Brauer, Delia S; Hill, Robert G

    2017-03-08

    Chloride is known to volatilize from silicate glass melts and until now, only a limited number of studies on oxychloride silicate glasses have been reported. In this paper we have synthesized silicate glasses that retain large amounts of CaCl2. The CaCl2 has been added to the calcium metasilicate composition (CaO·SiO2). Glasses were produced via a melt quench route and an average of 70% of the chloride was retained after melting. Up to 31.6 mol% CaCl2 has been successfully incorporated into these silicate glasses without the occurrence of crystallization. (29)Si MAS-NMR spectra showed the silicon being present mainly as a Q(2) silicate species. This suggests that chloride formed Cl-Ca(n) species, rather than Si-Cl bonds. Upon increasing the CaCl2 content, the Tg reduced markedly from 782 °C to 370 °C. Glass density and glass crystallization temperature decreased linearly with an increase in the CaCl2 content. However, both linear regressions revealed a breakpoint at a CaCl2 content just below 20 mol%. This might be attributed to a significant change in the structure and is also correlated with the nature of the crystallizing phases formed upon heat treatment. The glasses with less than 19.2 mol% CaCl2 crystallized to wollastonite, whilst the compositions with CaCl2 content equal to or greater than 19.2 mol% are thought to crystallize to CaCl2. In practice, the crystallization of CaCl2 could not occur until the crystallization temperature fell below the melting point of CaCl2. The implications of the results along with the high chloride retention are discussed.

  8. Laser-driven formation of a high-pressure phase in amorphous silica

    SciTech Connect

    Salleo, Alberto; Taylor, Seth T.; Martin, Michael C.; Panero, Wendy R.; Jeanloz, Raymond; Genin, Francois Y.; Sands, Timothy

    2002-05-31

    A combination of electron diffraction and infrared reflectance measurements shows that synthetic silica transforms partially into stishovite under high-intensity (GW/cm2) laser irradiation, probably by the formation of a dense ionized plasma above the silica surface. During the transformation the silicon coordination changes from four-fold to six-fold and the silicon-oxygen bond changes from mostly covalent to mostly ionic, such that optical properties of the transformed material differ significantly from those of the original glass. This phase transformation offers one suitable mechanism by which laser-induced damage grows catastrophically once initiated, thereby dramatically shortening the service lifetime of optics used for high-power photonics applications such as inertial confinement fusion.

  9. Characteristic coordination structure around Nd Ions in sol-gel-derived Nd-Al-codoped silica glasses.

    PubMed

    Funabiki, Fuji; Kajihara, Koichi; Kaneko, Ken; Kanamura, Kiyoshi; Hosono, Hideo

    2014-07-24

    Al codoping can improve the poor solubility of rare-earth ions in silica glasses. However, the mechanism is not well understood. The coordination structure around Nd ions in sol-gel-derived Nd-Al-codoped silica glasses with different Al content was investigated by optical and pulsed electron paramagnetic resonance spectroscopies. Both tetrahedral AlO4 and octahedral AlO6 units were observed around Nd ions as ligands. The average total number of these two types of ligands for each Nd(3+) ion was ∼ 2 irrespective of Al content and was larger by 1-2 orders of magnitude than that calculated for a uniform distribution of codopant ions (∼ 0.08-0.25). With increasing Al content, AlO4 units disappeared and AlO6 units became dominant. The preferential coordination of AlOx (x = 4, 6) units to Nd ions enabled the amount of Al necessary to dissolve Nd ions uniformly in silica glass at a relatively low temperature of 1150-1200 °C to be minimized, and the conversion of AlO4 units to AlO6 units around Nd ions caused the asymmetry of the crystal field at the Nd sites to increase and the site-to-site distribution to decrease.

  10. Synthesis of Hollow Silica Microspheres with High-Developed Surface Area

    NASA Astrophysics Data System (ADS)

    Bei, I.; Tolstov, A.; Ishchenko, A.

    Hollow silica microspheres (HSM), as efficient drug delivery carriers, were successfully prepared via a facile water-in-oil emulsion method using water glass precursor. The kinetics of drug release in aqueous medium was simulated using water-soluble erythrosine. Hollow silica microspheres show intensive release of active component at the beginning stages of introduction into aqueous (organism-imitating) conditions. Release rate of the model compound decreased and desorption time increased in the follow range: hollow silica microspheres > porous silica microparticles > silica nanoparticles.

  11. 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.

  12. Computational approaches for investigating interfacial adhesion phenomena of polyimide on silica glass.

    PubMed

    Min, Kyoungmin; Rammohan, Aravind R; Lee, Hyo Sug; Shin, Jaikwang; Lee, Sung Hoon; Goyal, Sushmit; Park, Hyunhang; Mauro, John C; Stewart, Ross; Botu, Venkatesh; Kim, Hyunbin; Cho, Eunseog

    2017-09-05

    This manuscript provides a comprehensive study of adhesion behavior and its governing mechanisms when polyimide undergoes various modes of detachment from silica glass. Within the framework of steered molecular dynamics, we develop three different adhesion measurement techniques: pulling, peeling, and sliding. Such computational methodologies can be applied to investigate heterogeneous materials with differing interfacial adhesion modes. Here, a novel hybrid potential involving a combination of the INTERFACE force field in conjunction with ReaxFF and including Coulombic and Lennard-Jones interactions is employed to study such interfaces. The studies indicate that the pulling test requires the largest force and the shortest distance to detachment as the interfacial area is separated instantaneously, while the peeling test is observed to exhibit the largest distance for detachment because it separates via line-by-line adhesion. Two kinds of polyimides, aromatic and aliphatic type, are considered to demonstrate the rigidity dependent adhesion properties. The aromatic polyimide, which is more rigid due to the stronger charge transfer complex between chains, requires a greater force but a smaller distance at detachment than the aliphatic polyimide for all of the three methodologies.

  13. Electroless porous silicon formation applied to fabrication of boron-silica-glass cantilevers

    NASA Astrophysics Data System (ADS)

    Teva, J.; Davis, Z. J.; Hansen, O.

    2010-01-01

    This work describes the characterization and optimization of anisotropic formation of porous silicon in large volumes (0.5-1 mm3) of silicon by an electroless wet etching technique. The main goal is to use porous silicon as a sacrificial volume for bulk micromachining processes, especially in cases where etching of the full wafer thickness is needed. The porous silicon volume is formed by a metal-assisted etching in a wet chemical solution composed of hydrogen peroxide (30%), hydrofluoric acid (40%) and ethanol. This paper focuses on optimizing the etching conditions in terms of maximizing the etching rate and reproducibility of the etching. In addition to that, a study of the morphology of the pore that is obtained by this technique is presented. The results from the characterization of the process are applied to the fabrication of boron-silica-glass cantilevers that serve as a platform for bio-chemical sensors. The porous silicon volume is formed in an early step of the fabrication process, allowing easy handling of the wafer during all of the micromachining processes in the process flow. In the final process step, the porous silicon is quickly etched by immersing the wafer in a KOH solution.

  14. 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.

  15. In-situ observation of bubble formation at silicon melt-silica glass interface

    NASA Astrophysics Data System (ADS)

    Minami, Toshiro; Maeda, Susumu; Higasa, Mitsuo; Kashima, Kazuhiko

    2011-03-01

    The generation mechanism of pinhole defects in the Czochralski (CZ)-grown silicon (Si) single crystals was clarified by in-situ observations of bubble formation at the interface between Si melt and a silica glass crucible in a small experimental apparatus. The nucleation and growth of bubbles were facilitated by creating small cavities on the inner wall of the crucible. Si melting was conducted in an argon (Ar) atmosphere, and the pressure was maintained at either 100 Torr or close to a vacuum (no Ar-gas flow). It was found that in the presence of Ar, bubbles formed in the cavities immediately after the cavities came in contact with the melt. However, no bubbles formed in a vacuum in the experimental apparatus. These results indicate that the bubbles formed in the cavities are largely filled with Ar, and the initial bubble volumes are nearly comparable with those of the cavities. In an initial stage of expansion of a bubble, estimated volumes changed nearly in accordance with the Boyle-Charles law. Further, participation of SiO gas in bubble growth may explain the deviation of the bubble volume from the theoretical value anticipated if only Ar gas was involved in the bubble growth.

  16. 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.

  17. 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.

  18. 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.

  19. A magmatic origin for silica-rich glass inclusions hosted in porphyritic magnesian olivines in chondrules: An experimental study

    NASA Astrophysics Data System (ADS)

    Faure, François; Tissandier, Laurent; Florentin, Léa; Devineau, Karine

    2017-05-01

    Rare silica-rich glass inclusions (69 < SiO2 < 82 wt.%) are described within magnesian olivines of porphyritic Type IA chondrules. These glass inclusion compositions are clearly out of equilibrium with their host Mg-olivines and their presence within the olivines is generally attributed to an unclear secondary process such as a late interaction with nebular gases. We performed dynamic crystallisation experiments that demonstrate that these Si-rich glass inclusions are actually magmatic in origin and were trapped inside olivines that crystallized slowly from a magma with a CI, i.e. solar, composition. Their silica-rich compositions are the consequence of the small volumes of inclusions, which inhibit the nucleation of secondary crystalline phase (Ca-poor pyroxene) but allow olivine to continue to crystallize metastably on the walls of the inclusions. We suggest that Si-rich glass inclusions could be the only reliable relicts of what were the first magmas of the solar system, exhibiting a CI, i.e. non-fractionated, composition.

  20. 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.

  1. In situ measurements of density fluctuations and compressibility in silica glasses as a function of temperature and thermal history

    SciTech Connect

    Levelut, C.; Faivre, A; Le Parc, R.; Champagnon, B.; Hazemann, J.-L.; Simon, J.-P.

    2005-12-01

    In this paper, small-angle x-ray scattering measurements are used to determine the different compressibility contributions, as well as the isothermal compressibility {chi}{sub T}{sup 0} in thermal equilibrium in silica glasses having different thermal histories. Using two different methods of analysis, in the supercooled liquid and in the glassy state, we obtain, respectively, the temperature and fictive temperature dependences of {chi}{sub T}{sup 0}. The values obtained in the glass and supercooled liquid states are very close to each other. They agree with previous determinations of the literature. The compressibility in the glass state slightly decreases with increasing fictive temperature. The relaxational part of the compressibility is also calculated and compared to previous determinations. We discussed the small differences between the different determinations.

  2. 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.”

  3. Curiosity ChemCam Finds High-Silica Mars Rocks

    ScienceCinema

    Frydenvang, Jens

    2016-07-12

    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.”

  4. Effect of water storage on the flexural properties of E-glass and silica fiber acrylic resin composite.

    PubMed

    Vallittu, P K; Ruyter, I E; Ekstrand, K

    1998-01-01

    The aim of this study was to determine the effect of water on the flexural properties of fiber-reinforced denture base polymers. Continuous woven silanized electrical glass, or E-glass, fibers and woven silica fibers were used to reinforce heat-cured and autopolymerized denture base polymers. Fibers were oriented at a 45-degree angle to the long axis of the test specimens. Control specimens were unreinforced. Dry test specimens and those stored in water for up to 48 weeks were tested with a three-point loading apparatus. The surfaces of the fibers of the test specimens stored dry or 48 weeks in water were analyzed with a scanning electron microscope to evaluate the degree of adhesion between fibers and polymer matrix. The ultimate transverse strength of unreinforced and reinforced denture base polymers decreased during 48 weeks' storage in water (P < 0.05, one-way analysis of variance, n = 5), and most of this reduction occurred during the first 4 weeks of storage in water. The flexural modulus of the unreinforced test specimens decreased significantly (P < 0.001), whereas there was less, if any, change in the flexural modulus of the fiber-reinforced test specimens. Scanning electron microscopic examination revealed no differences in adhesion of E-glass fibers to the polymer matrix when the specimens stored in water were compared with those stored by. Reduced adhesion between the silica fibers and matrix was observed after 48 weeks' storage in water. The results of this study suggest that the ultimate transverse strength of the E-glass fiber-reinforced test specimens decreased 14% and that of the silica fiber-reinforced test specimens decreased 36% after 48 weeks of storage in water.

  5. 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

  6. 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.

  7. Shock sensitivity of energetic material and nanometric damage mechanisms in silica glass

    NASA Astrophysics Data System (ADS)

    Nomura, Ken-Ichi

    This dissertation focuses on molecular dynamics (MD) simulations of shock sensitivity of energetic material (EM) and nanometric damage mechanisms in amorphous SiO2 (a-SiO2). A scalable parallel MD algorithm incorporating first principles-based reactive force fields (ReaxFF) has been implemented to perform multimillion-to-billion atom chemically reactive MD simulations. Mechanical stimuli in energetic materials initiate chemical reactions at shock fronts prior to detonation. Multimillion-atom ReaxFF-MD simulations are performed to investigate atomistic mechanisms of shock-induced reaction initiation in 1,3,5-trinitro-1,3,5-triazine (RDX) crystal. The simulation reveals a bi-modal molecular response against a planar shock loading, which creates a nanoscale layered-structure of molecular dipole behind a shock front. The sensitivity of energetic crystals changes with defects such as voids, grain boundaries and cracks. By performing million-atom ReaxFF-MD simulations, the effects of microstructures in crystal on shock sensitivity have been investigated. MD simulation reveals the formation of a nanojet which focuses into a narrow beam as the void collapses. By increasing particle velocity, a pinning-depinning transition of the shock wave front at the void occurs. Shock loading simulation in a nanophase RDX crystal reveals a deformation mechanism that is mediated by molecular reorientation and conformation changes. Molecular rotation and deformation significantly reduce the energy barrier for the onset of slip. In contrast to crystalline solids, damage, flow and fracture in glass are still controversial areas. We have performed multimillion-atom MD simulations to investigate initiation and growth of wing cracks in confined silica glass. Under dynamic compression, frictional sliding of precrack surfaces nucleates nanovoids which evolve into nanocrack columns at the precrack tip. Nanocrack columns merge to form a wing crack, which grows via coalescence with nanovoids in the

  8. Sodium-sulfur cells with high conductivity glass electrolytes

    NASA Astrophysics Data System (ADS)

    Nelson, P. A.; Bloom, I.; Bradley, J.; Roche, M. F.

    1985-05-01

    A study is under way to develop glasses in the soda-alumina-zirconia-silica system that have high conductivity for sodium ions. Sodium-conductivity and corrosion experiments indicate that the target resistivity of 100 ohm-cm at 300(0)C can be achieved for glasses having satisfactory corrosion resistance for use in sodium-sulfur cells. The low resistivity makes possible a unique approach to cell design. Cells of 150 A-hr capacity were designed having 6-mm dia electrolytes and are expected to achieve a specific energy of up to 270 W-hr/kg. Others having 1.5-mm dia electrolytes are expected to attain a specific power of up to 2 or 3 kW/kg. Excellent heat removal can be provided for high-specific-power cells by short metallic paths from the center of the cell to the cooled cell wall. Reliability of the cell may be achieved by: (1) use of a protective tube around each electrolyte tube to protect against failure propagation, and (2) the provision for automatic disconnection of a failed element by burnout of its current collector wire.

  9. 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

  10. 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

  11. 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.

  12. 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.

  13. Highly Aminated Mesoporous Silica Nanoparticles with Cubic Pore Structure

    PubMed Central

    Suteewong, Teeraporn; Sai, Hiroaki; Cohen, Roy; Wang, Suntao; Bradbury, Michelle; Baird, Barbara; Gruner, Sol M.; Wiesner, Ulrich

    2010-01-01

    Mesoporous silica with cubic symmetry has attracted interest from researchers for some times. Here we present the room temperature synthesis of mesoporous silica nanoparticles possessing cubic Pm3̄n symmetry with very high molar ratios (>50%) of 3-aminopropyl triethoxysilane. The synthesis is robust allowing, e.g. for co-condensation of organic dyes without loss of structure. By means of pore expander molecules, the pore size can be enlarged from 2.7 to 5 nm, while particle size decreases. Adding pore expander and co-condensing fluorescent dyes in the same synthesis reduces average particle size further down to 100 nm. After PEGylation, such fluorescent aminated mesoporous silica nanoparticles are spontaneously uptaken by cells as demonstrated by fluorescence microscopy. PMID:21158438

  14. 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.

  15. On the strength of glasses

    PubMed Central

    Wisitsorasak, Apiwat; Wolynes, Peter G.

    2012-01-01

    The remarkable strength of glasses is examined using the random first order transition theory of the glass transition. The theory predicts that strength depends on elastic modulus but also on the configurational energy frozen in when the glass is prepared. The stress catalysis of cooperative rearrangements of the type responsible for the supercooled liquid’s high viscosity account quantitatively for the measured strength of a range of metallic glasses, silica, and a polymer glass. PMID:22988070

  16. Bioinspired Strong and Highly Porous Glass Scaffolds.

    PubMed

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

    2011-03-22

    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.

  17. 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

  18. 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.

  19. Effect of sintering temperature on physical, structural and optical properties of wollastonite based glass-ceramic derived from waste soda lime silica glasses

    NASA Astrophysics Data System (ADS)

    Almasri, Karima Amer; Sidek, Hj. Ab Aziz; Matori, Khamirul Amin; Zaid, Mohd Hafiz Mohd

    The impact of different sintering temperatures on physical, optical and structural properties of wollastonite (CaSiO3) based glass-ceramics were investigated for its potential application as a building material. Wollastonite based glass-ceramics was provided by a conventional melt-quenching method and followed by a controlled sintering process. In this work, soda lime silica glass waste was utilized as a source of silicon. The chemical composition and physical properties of glass were characterized by using Energy Dispersive X-ray Fluorescence (EDXRF) and Archimedes principle. The Archimedes measurement results show that the density increased with the increasing of sintering temperature. The generation of CaSiO3, morphology, size and crystal phase with increasing the heat-treatment temperature were examined by field emission scanning electron microscopy (FESEM), Fourier transforms infrared reflection spectroscopy (FTIR), and X-ray diffraction (XRD). The average calculated crystal size gained from XRD was found to be in the range 60 nm. The FESEM results show a uniform distribution of particles and the morphology of the wollastonite crystal is in relict shapes. The appearance of CaO, SiO2, and Ca-O-Si bands disclosed from FTIR which showed the formation of CaSiO3 crystal phase. In addition to the calculation of the energy band gap which found to be increased with increasing sintering temperature.

  20. Thermo-optic characterization of neodymium/nickel doped silica glasses prepared via sol-gel route.

    PubMed

    Manuel, Ancy; Kumar, B Rajesh; Basheer, N Shemeena; Kumari, B Syamala; Paulose, P I; Kurian, Achamma; George, Sajan D

    2012-12-01

    Intrinsic as well as rare earth (Neodymium) doped silica glasses with various molar ratio of dopant and a metallic (Nickel) co-dopant is prepared via sol-gel route. The structural characterization of the sample is carried out using X-ray diffraction and Fourier Transform Infrared Spectroscopy. The influence of dopant and doping concentration on the optical properties of silica matrix is investigated via UV-VIS absorption spectroscopy. Effect of dopant on thermal effusivity value of the host matrix is carried out by laser induced open cell photoacoustic technique. Analysis of the results showed that doping affect the thermal effusivity value and results are interpreted in terms of structural modification of the lattice and phonon assisted heat transport mechanism.

  1. Preparation and characterization of a BisGMA-resin dental restorative composites with glass, silica and titania fillers.

    PubMed

    Thorat, Sanjay; Patra, Niranjan; Ruffilli, Roberta; Diaspro, Alberto; Salerno, Marco

    2012-01-01

    A photo-polymerizable Bisphenol-A diglycidylether methacrylate resin was characterized by Fourier transform infrared spectroscopy after its irradiation under different conditions to identify the best curing. Bonding-agent free composites with particles of ball-milled glass, silica and titania at loading of 10 and 50%wt were prepared, and their viscoelastic properties investigated by dynamic mechanical analysis, in experimental conditions close to the working environment in the mouth. All composites showed good stability at the considered conditions. The stiffest composite was the silica one, which was based on the smallest primary particles. The storage moduli close to room temperature (25°C) and mastication frequency (1 Hz) were extracted as reference bending moduli for the materials, and compared to static compressive moduli measured by nanoindentation performed by atomic force microscopy.Nanoindentation showed qualitative results in agreement with dynamic mechanical analysis as to the ranking of different materials, while resulting in approximately two-fold elastic modulus.

  2. Silica sol-gel glasses incorporating dual-luminescent Yb quinolinolato complex: processing, emission and photosensitising properties of the 'antenna' ligand.

    PubMed

    Artizzu, Flavia; Quochi, Francesco; Saba, Michele; Loche, Danilo; Mercuri, Maria Laura; Serpe, Angela; Mura, Andrea; Bongiovanni, Giovanni; Deplano, Paola

    2012-11-14

    The [Yb(5,7ClQ)(2)(H5,7ClQ)(2)Cl] (1) complex, that exhibits dual-luminescence in the visible (ligand-centered) and in the NIR (Yb-centered), has been incorporated into a silica sol-gel glass obtaining 1-doped glassy material which is optically transparent and homogeneous and with good mechanical properties. The doped sol-gel glass can be considered a "solid state solution" and photophysical studies demonstrate that the emissive properties of the dopant complex are preserved in the silica matrix. Observed NIR decay times fall in the μs range and are likely limited by "second-sphere" matrix interactions. The ligand-to-metal energy transfer mechanism occurs on ultrafast timescale and involves ligand triplet states. The sensitization efficiency of the antenna quinolinolato ligand toward Yb(3+) is estimated to be as high as ~80%. The Yb natural radiative lifetime observed for 1 in MeCN-EtOH solution (τ(rad) = 438 μs) is the shortest reported so far for ytterbium complexes.

  3. Controlling the stimulated Brillouin scattering of self-focusing nanosecond laser pulses in silica glasses

    SciTech Connect

    Mauger, Sarah; Berge, Luc; Skupin, Stefan

    2011-06-15

    We numerically investigate the interplay between Kerr self-focusing (SF) and transient stimulated Brillouin scattering (SBS) for nanosecond pulses in bulk silica. The influences of the input power, phase, or amplitude modulations in the pump pulse together with the incident beam shape on the filamentation dynamics are discussed. We show that appropriate amplitude modulations dividing nanosecond laser pumps into picosecond-long pulse trains inhibit SBS at any power. In contrast, phase-modulated pulses with comparable spectral width undergo multiple filamentation and earlier beam collapse due to modulational instabilities. We demonstrate, however, the existence of a critical pump bandwidth above which SBS can be efficiently suppressed by phase modulations even at high powers. This observation also holds for squared beam shapes with much broader spatial spectra, which decay more easily into multiple filaments over short distances. Intensity profiles of the reflected Stokes waves for such broad pumps are finally discussed.

  4. Structural and plasmonic studies of Ag nanoparticles in silica glass hosts

    NASA Astrophysics Data System (ADS)

    R, Rejikumar P.; Thomas, Vinoy; George, Jacob; Joseph, Cyriac; R, Biju P.; V, Unnikrishnan N.

    2013-05-01

    Silica glassy materials doped with Ag were prepared through sol gel route. The structural studies of the prepared samples showed an icosahedral morphology of the nanocrystals formed along with spherical morphology. The XRD and TEM data confirmed the formation of silver nanoparticles of size between 20 and 22nm. The surface plasmon resonance (SPR) of silver nanoparticles with spherical morphology was studied with the discrete dipole approximation . The shape and size effects of the nanoparticles can induce distinctive features of the SPR spectrum. It has been shown that such effects can induce peak intensity enhancement, wavelength shift and spectral broadening of the SPR spectra of the nanoparticles. The results obtained depend on the existence of highly localized plasmonic oscillations. An attempt has also been made to calculate the van der Waals force between nanoparticles.

  5. Vibrational properties of silica species in MgO-SiO2 glasses from ab initio molecular dynamics

    NASA Astrophysics Data System (ADS)

    Spiekermann, G.; Steele-MacInnis, M.; Kowalski, P. M.; Schmidt, C.; Jahn, S.

    2012-04-01

    Glasses and melts in the system MgO-SiO2 are analogs for magmas of the Earth's mantle. Therefore knowledge of the structure of these glasses and melts is important for understanding numerous geological processes. Raman spectroscopy is useful for probing the atomic-scale structure of glasses and melts. However, correct assignment of observed vibrational bands to specific structural and modal origins is challenging. We present the mode-projection technique to calculate vibrational subspectra for specific modal vibrations of several fundamental silica structures in silicate glasses. Structural subunits that we have studied include Q0 to Q4 tetrahedra, Si-O-Si bridging oxygen atoms for any degree of polymerization of the adjacent tetrahedra, the ethane-like symmetry of the dimer, and three- and four-fold rings. We apply this technique to ab initio molecular dynamics (MD) trajectories of MgO-SiO2 glasses at 1000 K. We found the tetrahedral symmetric stretch at 863 cm-1 for Q0, 885 cm-1 for Q1, a double peak of 960 cm-1 and 1037 cm-1 for Q2, 1032 cm-1 for Q3 and 1080 cm-1 for Q4. The bridging oxygen asymmetric stretch is at about 980 cm-1 for Q1-Q1, and it shifts to about 1100 cm-1 with increasing polymerization. This analysis has applications especially for understanding the structure of silica-poor glasses. For instance, two contradicting Raman spectroscopy studies of Mg2SiO4 glasses reported the most polymerized SiO4 tetrahedra in the glass structure to be either Q0 [1] or Q3 [2]. Our results indicate that the degree of polymerization is overestimated, if the Si-O-Si stretching modes are not considered in the interpretation of the measured Raman spectra. [1] Nasikas, N. K. and Chrissanthopoulos, A. and Bouropoulos, N. and Sen, S. and Papatheodorou, G. N., 2011, Chemistry of Materials 23, 3692-3697. [2] Kalampounias, A. G. and Nasikas, N. K. and Papatheodorou, G. N., 2009, Journal of Chemical Physics 131, 114513.

  6. 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.

  7. 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.

  8. 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.

  9. High Strength, Large Core Pure Silica Fibers For Laser Surgery

    NASA Astrophysics Data System (ADS)

    Skutnik, B. J.; Hodge, M. H.; Clarkin, J. P.

    1988-06-01

    Recently many researchers, doctors and instrument companies have begun developing fiber optic laser power delivery systems to accomplish less traumatic surgery or localized irradiation treatment(1). With high power levels, particularly in short bursts, large core fibers are needed to keep the power densities from approaching the damage threshold of silica. Among the many advantages of using optical fibers in laser surgery are the following: microsurgery can be employed, trauma is reduced, access to interior through catheter introduction into vascular, gastrointestinal or respiratory tracts, accurate application of laser power through a flexible lightweight medium to provide localized irradiation as well as surgical removal, and the devices are sterilizable and of moderate cost permitting one-time use (disposable) probes. To achieve these wonderful gains in surgical procedures, the optical fibers must satisfy many optical and mechanical requirements. In use the optical fibers are often required to bend around curves or obstructions to reach the desired application area. Large tensile stresses can occur on the outer radius of the bent fiber, especially with large core fibers, thus high strength fibers are needed. Furthermore, since body fluids are primarily water, stress corrosion and fatigue(2-6) will occur. Therefore, the fibers should have excellent fatigue resistance as well as high strength. This paper further describes these requirements and presents details about an optical fiber which meets these requirements and provides additional very useful properties. These fibers with pure silica cores are called Hard Clad Silica, HCS*, fibers because of their hard bonded cladding over silica structure.

  10. Compositional zoning in high-silica rhyolite tuffs

    NASA Astrophysics Data System (ADS)

    Wolff, J. A.; Ramos, F. C.; Olin, P. H.

    2012-12-01

    The mush model for silicic magma systems predicts the development of a supernatant crystal-poor melt lens overlying rheologically static crystal mush following roughly 50% crystallization of an initially well-stirred magma body. It does not immediately explain the origin of strong chemical zonation in large bodies of crystal-poor high-silica rhyolite magma exemplified by the Bishop Tuff and Bandelier Tuff. Concentrations of incompatible trace elements in pumice clasts from the first-erupted portion of the 1.60 Ma Otowi Member of the Bandelier Tuff, Valles Caldera, NM, are up 4 times those in late-erupted pumice, seemingly requiring 75% crystallization. Early/late element enrichments and depletions in the Otowi are indeed predicted by fractionation of the observed phenocryst assemblage. However, the Otowi Member also exhibits a strong gradient in Sr isotopes and, in late-erupted pumices, reverse zoning of sanidine and feldspar phenocrysts and micro-scale variations in glass chemistry that lie off the trend for the whole tuff. Zoning is not simply the result of recharge and mixing with more mafic magma because Sr concentrations are typically very low (<5 ppm) throughout the the zoned sequence and not all element pairs exhibit linear co-variation. These apparently conflicting observations are reconciled by a model in which the static mush layer beneath the crystal-poor melt lens is repeatedly partially melted by recharging magma. The regenerated melt is indistinguishable in major element composition from the intial melt lens but is depleted in incompatible trace elements. It is also more dense than the original melt lens because it has been produced by melting of anhydrous phases (sanidine + quartz). Consequently, the new melt pools at the interface of the non-eruptible mush pile and the original melt lens to produce an eruptible, compositionally zoned crystal-poor rhyolitic liquid. The whole compositional range of original melt + remelted crystal residue duplicates

  11. 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

  12. Immobilization of trypsin on silica-coated fiberglass core in microchip for highly efficient proteolysis.

    PubMed

    Liu, Ting; Wang, Sheng; Chen, Gang

    2009-03-15

    In this report, trypsin was immobilized on silica-coated fiberglass core in microchip to form a core-changeable bioreactor for highly efficient proteolysis. To prepare the fiber core, a layer of organic-inorganic hybrid silica coating was prepared on the surface of a piece of glass fiber by a sol-gel method with tetraethoxysilane (TEOS) and 3-aminopropyltriethoxysilane (APTES) as precursors. Subsequently, trypsin was immobilized on the coating with the aid of glutaraldehyde. Prior to use, the enzyme-immobilized fiber was inserted into the channel of a microchip to form an in-channel fiber bioreactor. The novel bioreactor can be regenerated by changing its fiber core. The scanning electron microscopy images of the cross-section of a trypsin-immobilized fiber indicated that a layer of approximately 1mum thick film formed on the glass substrate. The feasibility and performance of the unique bioreactor were demonstrated by the tryptic digestion of bovine serum albumin (BSA) and cytochrome c (Cyt-c) and the digestion time was significantly reduced to less than 10s. The digests were identified by MALDI-TOF MS with sequence coverages of 45% (BSA) and 77% (Cyt-c) that were comparable to those obtained by 12-h conventional in-solution tryptic digestion. The fiber-based microchip bioreactor provides a promising platform for the high-throughput protein identification.

  13. Development of new composite materials for hydrogen storage. The AB5 type hydride alloy with silica glass support

    NASA Astrophysics Data System (ADS)

    Grinberga, L.; Kleperis, J.

    2007-12-01

    Use of the spill-over effect to enhance catalytic activity and the amount of absorbed hydrogen in a new composite material is reported. An AB5 lanthanum nickel alloy with a small number of additives serves as the catalyst and the bulk material for hydrogen storage and a silica glass powder with a developed surface serves as the support material. The amount of absorbed hydrogen in the alloy and composite is determined from thermo-gravimetric data. Structural changes in the developed composite during hydrogenation are found to confirm the synergy between the alloy and the support material.

  14. Remote Near Infrared Spectrometry In The Food Industry With The Use Of Silica And Fluoride Glasses Fibers

    NASA Astrophysics Data System (ADS)

    Bellon-Maurel, Veronique; Boisde, Gilbert

    1989-07-01

    In order to respond to the food industry and agriculture needs of on-line control, a NIR spectrometer was developed and coupled with optical fibers. Silica and fluoride glasses were tested. Different geometrical configurations of the optodes were used and compared. The aim was to measure non-destructively the sugar of the fruit (apples and nectarines) and the humidity of the flour. Good results were obtained on the nectarines (sugar) and on the flour (humidity) but the determination of the sugar content of the apples was not satisfying. The depth of penetration of the light and the influence of fruit firmness on spectral characteristics are also discussed.

  15. 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.

  16. 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.

  17. 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

  18. 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.

  19. [Kinetic study on the in situ synthesis of nickle phthalocyanine in silica gel glass matrix by UV/Vis absorption spectra].

    PubMed

    Huang, Juan; Zheng, Chan; Feng, Miao; Zhan, Hong-Bing

    2009-01-01

    In decades, metallo-phthalocyanines (MPcs) have undergone a renaissance because of their singular and unconventional physical properties. However, for the successful application of MPcs in practical devices, it is important to disperse MPc molecules into solid state matrix to fabricate MPc doped composite with desired properties. Inorganic glass is an ideal matrix because of its transparency and high environmental stability. One attractive approach to fabricating MPc/inorganic composite is sol-gel technique. In the present paper, silica gel glass matrix was prepared by hydrolysis and poly-condensation of tetraethyloxysilane. 1,2-dicyanobenzene and analytically pure soluble nickle salt were used as the nickle phthalocyanine (NiPc) reactants and chemical synthesis technique was used to prepare NiPc doped sol-gel materials at several temperatures. During the heat treatment, four 1, 2-dicyanobenzene molecules and one nickle ion collide to form a NiPc molecule. In-situ synthesizing process of NiPc in the pores of silica gel glass matrix was traced by UV/Vis absorption spectra. Owing to the remarkable absorption band of NiPc in visible region, quantity of in-situ synthesized NiPc was calculated by the absorbance at certain wavelength of 670 nm, using composites with physically doped NiPc as a reference. The in-situ synthesized kinetics was studied in detail and found to be consistent with Avrami-Erofeev equation The reaction grades were deduced to be 4.5, 4.5, 3.7, 3.2 and 1.9 respectively at temperatures of 180 degrees C, 185 degrees C, 190 degrees C, 195 degrees C and 200 degrees C, respectively.

  20. Reduced-mobility layers with high internal mobility in poly(ethylene oxide)-silica nanocomposites

    NASA Astrophysics Data System (ADS)

    Golitsyn, Yury; Schneider, Gerald J.; Saalwächter, Kay

    2017-05-01

    A series of poly(ethylene oxide) nanocomposites with spherical silica was studied by proton NMR spectroscopy, identifying and characterizing reduced-mobility components arising from either room-temperature lateral adsorption or possibly end-group mediated high-temperature bonding to the silica surface. The study complements earlier neutron-scattering results for some of the samples. The estimated thickness of a layer characterized by significant internal mobility resembling backbone rotation ranges from 2 nm for longer (20 k) chains adsorbed on 42 nm diameter particles to 0.5 nm and below for shorter (2 k) chains on 13 nm particles. In the latter case, even lower adsorbed amounts are found when hydroxy endgroups are replaced by methyl endgroups. Both heating and water addition do not lead to significant changes of the observables, in contrast to other systems such as acrylate polymers adsorbed to silica, where temperature- and solvent-induced softening associated with a glass transition temperature gradient was evidenced. We highlight the actual agreement and complementarity of NMR and neutron scattering results, with the earlier ambiguities mainly arising from different sensitivities to the component fractions and the details of their mobility.

  1. 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

  2. Synthesis of organic-inorganic hybrid sols with nano silica particles and organoalkoxysilanes for transparent and high-thermal-resistance coating films using sol-gel reaction.

    PubMed

    Na, Moonkyong; Park, Hoyyul; Ahn, Myeongsang; Lee, Hyeonhwa; Chung, Ildoo

    2010-10-01

    Organic-inorganic hybrid sols were synthesized from nano silica particles dispersed in water and from organoalkoxysilanes, using the sol-gel reaction. This work focuses on the effects of the three multifunctional organoalkoxysilanes dimethyldimethoxysilane (DMDMS), methyltrimethoxysilane (MTMS), and tetramethoxysilane (TMOS) to form a transparent and high-thermal-resistance coating film. The stability of the hybrid sol was evaluated as a function of the reaction time for 10 d through the variation of the viscosity. The viscosity of the silica/DMDMS and silica/MTMS sol was slightly increased for 10 d. The multifunctional organoalkoxysilanes formed dense silica networks through hydrolysis and condensation reaction, which enhanced the thermal resistance of the coating films. No thermal degradation of the silica/DMDMS sample occurred up to 600 degrees C, and none of the silica/MTMS and silica/TMOS samples occurred either up to 700 degrees C. The organic-inorganic hybrid sols were coated on the glass substrate using a spin-coating procedure. The organic-inorganic hybrid sols formed flat coating films without cracks. The transmittance of the hybrid sol coating films using MTMS and DMDMS was shown to be over 90%. The transmittance of the silica/TMOS sol coating film reacted for 10 d abruptly decreased due to faster gelation. The silica/DMDMS and silica/MTMS hybrid sols formed smooth coating films while the surface roughness of the silica/TMOS coating film markedly increased when the hybrid sol reacted for 10 d. The increase of the surface roughness of the silica/TMOS coating film can be attributed to the degradation of the stability of the hybrid sol and to the loss of transmittance of the coating film. It was confirmed in this study that the use of organic-inorganic hybrid sol can yield transparent and high-thermal-resistance coating films.

  3. 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.

  4. Synthesis of silica gel from waste glass bottles and its application for the reduction of free fatty acid (FFA) on waste cooking oil

    NASA Astrophysics Data System (ADS)

    Sudjarwo, Wisnu Arfian A.; Bee, Mei Magdayanti F.

    2017-06-01

    Synthesis of silica gel from waste glass bottles was conducted with aims to characterize the product and to analyze its application forthe reduction of free fatty acid (FFA) on waste cooking oil. Silica source taken from waste glass bottles was synthesized into silica gel by using the sol-gel method. Several types of silica gel were produced with three different weight ratios of waste glass and sodium hydroxide as an extractor. They were: 1:1, 1:2, and 1:3. The results indicated that synthesized silica possessed morphology innano-sizedranging from 85 nm to 459 nm. Adsorption performance was investigated by a batch system atthe temperature between 70°C and 110°C by a range of 10°C in an hour. Analysis of the adsorption characteristic showed that the highest efficiency value of FFA reduction of 91% was obtained by silica gel with ratiosof 1:1 (SG 1) and 1:3 (SG 3). Their performances were also followed by the decline of the refractive index and the density of waste cooking oil.

  5. 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.

  6. The transformation balance between two types of structural defects in silica glass in ion-irradiation processes

    SciTech Connect

    Yang, Tengfei; Gao, Yuan; Huang, Xuejun; Zhang, Yanwen; Toulemonde, Marcel; Xue, Jianming; Yan, Sha; Wang, Yugang

    2011-01-01

    Structural modification in silica glass irradiated by Au ions was investigated by ultraviolet (UV), photoluminescence and Raman spectrum at the energies from 0.5 to 8 MeV with a fluence of 5 1013 cm 2. In this transit energy region, both nuclear energy loss and electronic energy loss are not negligible. It was found that both the formation of irradiation-induced intrinsic defects and structural transformation from irregular large ring structure (LRS) to small three- and four-member ring structures (SRS) are dominated by the nuclear energy loss. Furthermore, unlike the case of irradiation with , or proton, the concentration of non-bridging oxygen hole center is much enhanced followed with a distinct peak appearing at 5.05 eV in the UV absorption spectra that is attributed to divalent Si. The results suggest that the structural modification in silica glass in the transit energy region is dominated by nuclear energy loss. A mutual transformation balance model among irradiation-induced intrinsic defects, LRS and SRS is established to interpret the identical variation tendencies of intrinsic defects and structural transformation with ion energy.

  7. Etching studies of silica glasses in SF{sub 6}/Ar inductively coupled plasmas: Implications for microfluidic devices fabrication

    SciTech Connect

    Lallement, L.; Gosse, C.; Cardinaud, C.; Peignon-Fernandez, M.-C.; Rhallabi, A.

    2010-03-15

    To fabricate microlaboratories, commercially available silica glasses represent a good alternative to the expensive quartz or fused silica substrates. Therefore, the authors have here investigated the behavior of four of them--Vycor, Pyrex, D263, and AF45--in SF{sub 6} and SF{sub 6}/Ar inductively coupled plasmas. Using Vycor, a material close to pure SiO{sub 2}, as a reference, they demonstrated that the etch rate negatively correlates with the global content in metallic oxides. However, no such clear trend was found for the surface roughness and they hypothesize that the large asperities (>500 nm) sometimes observed might be due to local variation in the glass surface composition. Furthermore, investigations on the influence of the plasma conditions (i.e., source power, dc self-bias, gas mixture, and pressure) on the etch rate, surface chemistry, and surface morphology, as well as positive ion current and fluorine concentration measurements, enable them to unravel an ion enhanced chemical etching mechanism, where stronger ion assistance is needed when more metallic oxides are present. By increasing the ion to neutral flux ratio, they consequently could, for all the materials, reduce the surface roughness to less than 5 nm while maintaining etch rates around 150 nm/min. These conditions have further been used to optimize pattern transfer experiments.

  8. High density scintillating glass proton imaging detector

    NASA Astrophysics Data System (ADS)

    Wilkinson, C. J.; Goranson, K.; Turney, A.; Xie, Q.; Tillman, I. J.; Thune, Z. L.; Dong, A.; Pritchett, D.; McInally, W.; Potter, A.; Wang, D.; Akgun, U.

    2017-03-01

    In recent years, proton therapy has achieved remarkable precision in delivering doses to cancerous cells while avoiding healthy tissue. However, in order to utilize this high precision treatment, greater accuracy in patient positioning is needed. An accepted approximate uncertainty of +/-3% exists in the current practice of proton therapy due to conversions between x-ray and proton stopping power. The use of protons in imaging would eliminate this source of error and lessen the radiation exposure of the patient. To this end, this study focuses on developing a novel proton-imaging detector built with high-density glass scintillator. The model described herein contains a compact homogeneous proton calorimeter composed of scintillating, high density glass as the active medium. The unique geometry of this detector allows for the measurement of both the position and residual energy of protons, eliminating the need for a separate set of position trackers in the system. Average position and energy of a pencil beam of 106 protons is used to reconstruct the image rather than by analyzing individual proton data. Simplicity and efficiency were major objectives in this model in order to present an imaging technique that is compact, cost-effective, and precise, as well as practical for a clinical setting with pencil-beam scanning proton therapy equipment. In this work, the development of novel high-density glass scintillator and the unique conceptual design of the imager are discussed; a proof-of-principle Monte Carlo simulation study is performed; preliminary two-dimensional images reconstructed from the Geant4 simulation are presented.

  9. High purity silica reflective heat shield development

    NASA Technical Reports Server (NTRS)

    Blome, J.

    1974-01-01

    Progress is reported on the development of a high purity reflective heat shield material. Silicon dioxide was selected as the material because it is highly reflective in the correct wavelength band, has good ablation characteristics, is thermal shock resistant, and is readily fabricated to full size at reasonable cost. Conclusions indicate that: reflectance is affected by purity and morphology; the pure material is readily available; required purity and morphology can be maintained with reasonable care; high reflectances are determined (0.99 from 0.4 to 1.2 microns); major processing steps are defined; and the material appears to be cost effective. It is indicated that the materials are developed to the point of readiness for full scale fabrication and characterization.

  10. SCOPING MELTING STUDIES OF HIGH ALUMINA WASTE GLASS COMPOSITIONS

    SciTech Connect

    Kroll, Jared O.; Schweiger, Michael J.; Vienna, John D.

    2015-09-04

    Glass property models will be used at the Hanford Tank Waste Treatment and Immobilization Plant to formulate durable high-level waste glasses for disposal. A major effort is focused on expanding glass property models to cover a broader range of wastes and higher waste-loaded glasses. As a part of this effort, a statistically designed matrix of high-alumina glass compositions was developed. Forty five compositions were selected from the matrix to evaluate glass properties. Of these compositions, thirty three produced homogeneous glasses. The other twelve compositions contained segregated phases and high crystallinity; these were iteratively modified in an attempt to produce homogeneous glass samples while altering the original composition as little as possible. This paper focuses on the characterization of the twelve inhomogeneous compositions and their modifications using X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy.

  11. Factors Influencing Material Removal And Surface Finish Of The Polishing Of Silica Glasses

    DTIC Science & Technology

    2006-01-01

    Mechanical Properties of Quartz and Zerodur ® ..................................... 48 TABLE 4.2: Results from variable load and lap velocity experiments...of glass and glass-ceramic substrates which are used in a vast amount of applications, from optics for lithographic machines to mirrors and lenses...SiO2) glass polishing with metal oxide abrasive particles. This scheme will mirror the experimentation in this thesis, and hopefully provide a better

  12. LED collimation using high-index glass

    NASA Astrophysics Data System (ADS)

    Biertümpfel, Ralf; Reichel, Steffen

    2011-10-01

    LEDs emit light over a broad range of angles. Additionally, a narrow collimation of LED light is difficult because of the broad emission area of the LED. In order to implement an efficient beam shaping with small optics we propose to use a glass lens design with a refractive index (nd) greater than 1.7. Our design is characterized by a very small size and a high efficiency. This enables us to design optical arrays with an extremely high packing density of LEDs. Additional advantages are the high temperature resistance, the climate resistance and the stability against solarization. For many applications the footprint of the light beam should not only be collimated but also formed into a specific shape. Design results for a rectangular or oval beam shaping using high refractive index glass are presented. The designs collimate the broad emitted LED light and are optimized to incorporate also the manufacturability of the lens. Our proposed lens designs can easily be manufactured by modern pressing techniques, thus, these solutions are suitable for mass production.

  13. Structural transformation in densified silica glass: A molecular-dynamics study

    SciTech Connect

    Jin, W.; Kalia, R.K.; Vashishta, P. ); Rino, J.P. )

    1994-07-01

    Pressure-induced structural transformation and the concomitant loss of intermediate-range order (IRO) in high-density SiO[sub 2] glass are investigated with the molecular-dynamics (MD) approach. The MD simulations cover a wide range of mass densities---from normal density (2.20 g/cm[sup 3]) to the density corresponding to stishovite (4.28 g/cm[sup 3]). This twofold increase in the density produces significant changes in the short-range order and intermediate-range order. As the density increases from 2.20 to 4.28 g/cm[sup 3], the Si-O bond length increases from 1.61 to 1.67 A, the Si-O and O-O coordinations change from 4 to 5.8 and from 6 to 12, respectively, and the O-Si-O bond angle changes from 109[degree] to 90[degree]. These results provide firm evidence of structural transition from a corner-sharing Si(O[sub 1/2])[sub 4] tetrahedral network to a network of Si(O[sub 1/3])[sub 6] octahedra jointed at corners and edges. At normal density, the first sharp diffraction peak (FSDP) in the static structure factor [ital S]([ital q]) is at 1.6 A[sup [minus]1] whereas under pressure the height of the FSDP is considerably diminished and its position shifts to larger [ital q] values. At a density of 2.64 g/cm[sup 3], a peak in [ital S]([ital q]) appears at 2.85 A[sup [minus]1]. The height of this peak grows as the density increases. All of these results are in agreement with the recent high-pressure x-ray measurements on SiO[sub 2] glass.

  14. Using fume silica as heavy metals' stabilizer for high alkali and porous MSWI baghouse ash.

    PubMed

    Huang, Wu-Jang; Huang, Hung-Shao

    2008-03-21

    In this study, we have proved that heavy metals in high porous and alkali baghouse ash could be fixed effectively by fume silica powder alone, or with the incorporation of colloidal aluminum oxide (CAO). The optimum amount is about 100g of fume silica per kilogram of baghouse ash. Results have indicated that fume silica has a better fixation efficiency of lead in high porous baghouse ash. In addition, the reaction mechanism of fume silica is also discussed.

  15. Sorption and pore condensation behavior of pure fluids in mesoporous MCM-48 silica, MCM-41 silica, SBA-15 silica and controlled-pore glass at temperatures above and below the bulk triple point

    NASA Astrophysics Data System (ADS)

    Thommes, Matthias; Köhn, Ralf; Fröba, Michael

    2002-08-01

    The pore condensation and hysteresis behavior of nitrogen and argon was studied on well-defined, ordered porous materials like MCM-48, MCM-41 silica (mode pore diameters, 2-5 nm) and SBA-15 (6.7 nm) at 87 and 77 K. A comparison with the results of similar sorption experiments carried out using more disordered adsorbents like controlled-pore glasses (CPG) (mode pore diameters, 11 and 16 nm) is made. The results show clearly that the shape of sorption isotherms (in particular the shape and the width of sorption hysteresis loops) depend both on temperature and pore diameter, i.e. the thermodynamic states of pore fluid and bulk fluid, but—in particular at temperatures below the bulk triple point—also strongly on the texture (and degree of disorder) of the porous material. Analyses of nitrogen (at 77 K) and argon (at 87 K) adsorption-desorption isotherms in MCM-48 silica lead to the conclusion that in this well-defined, interconnected pore network the desorption branch of the hysteresis loop represents the equilibrium transition. In addition, pore condensation of argon can still be observed at 77 K, i.e. ca. 6.5 K below the bulk triple point in MCM-48/41 and SBA-15 silica materials with pore diameters<8 nm. However, pore condensation of argon at 77 K vanishes in case the pore diameter exceeds ca. 12 nm (based on BJH method), which limits the range for mesopore-size analysis of silica materials using argon sorption at 77 K.

  16. 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.

  17. Germanate Glass Fiber Lasers for High Power

    DTIC Science & Technology

    2016-01-04

    germanate based glasses with a specific focus on glass stability during thermal- cycling which is representative of the steps required to fabricate a doped...evidence of crystallisation after thermal cycling , and is of a low enough loss to realize a fiber laser. The glass stability is demonstrated by...specific focus on glass stability during thermal- cycling which is representative of the steps required to fabricate a doped micro-structured germanate

  18. High strength fused silica flexures manufactured by femtosecond laser

    NASA Astrophysics Data System (ADS)

    Bellouard, Yves; Said, Ali A.; Dugan, Mark; Bado, Philippe

    2009-02-01

    Flexures are mechanical elements used in micro- and precision-engineering to precisely guide the motion of micro-parts. They consist of slender bodies that deform elastically upon the application of a force. Although counter-intuitive at first, fused silica is an attractive material for flexure. Pending that the machining process does not introduce surface flaws that would lead to catastrophic failure, the material has a theoretically high ultimate tensile strength of several GPa. We report on high-aspect ratio fused silica flexures manufactured by femtosecond laser combined with chemical etching. Notch-hinges with thickness as small as twenty microns and aspect ratios comparable to aspect ratios obtained by Deep- Reactive-Ion-Etching (DRIE) were fabricated and tested under different loading conditions. Multiple fracture tests were performed for various loading conditions and the cracks morphologies were analyzed using Scanning Electron Microscopy. The manufactured elements show outstanding mechanical properties with flexural strengths largely exceeding those obtained with other technologies and materials. Fused silica flexures offer a mean to combine integrated optics with micro-mechanics in a single monolithic substrate. Waveguides and mechanical elements can be combined in a monolithic devices opening new opportunities for integrated opto-mechatronics devices.

  19. Monolithic Cylindrical Fused Silica Resonators with High Q Factors

    PubMed Central

    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

  20. 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.

  1. Optical decoherence and spectral diffusion in an erbium-doped silica glass fiber featuring long-lived spin sublevels

    NASA Astrophysics Data System (ADS)

    Veissier, Lucile; Falamarzi, Mohsen; Lutz, Thomas; Saglamyurek, Erhan; Thiel, Charles W.; Cone, Rufus L.; Tittel, Wolfgang

    2016-11-01

    Understanding decoherence in cryogenically cooled rare-earth-ion doped glass fibers is of fundamental interest and a prerequisite for applications of these material in quantum information applications. Here we study the coherence properties in a weakly doped erbium silica glass fiber motivated by our recent observation of efficient and long-lived Zeeman sublevel storage in this material and by its potential for applications at telecommunication wavelengths. We analyze photon echo decays as well as the potential mechanisms of spectral diffusion that can be caused by coupling with dynamic disorder modes that are characteristic for glassy hosts, and by the magnetic dipole-dipole interactions between Er3 + ions. We also investigate the effective linewidth as a function of magnetic field, temperature, and time, and then present a model that describes these experimental observations. We highlight that the operating conditions (0.6 K and 0.05 T) at which we previously observed efficient spectral hole burning coincide with those for narrow linewidths (1 MHz)—an important property for applications that has not been reported before for a rare-earth-ion doped glass.

  2. Effect of different glasses in glass bonded zeolite

    SciTech Connect

    Lewis, M.A.; Ackerman, J.P.; Verma, S.

    1995-05-01

    A mineral waste form has been developed for chloride waste salt generated during the pyrochemical treatment of spent nuclear fuel. The waste form consists of salt-occluded zeolite powders bound within a glass matrix. The zeolite contains the salt and immobilizes the fission products. The zeolite powders are hot pressed to form a mechanically stable, durable glass bonded zeolite. Further development of glass bonded zeolite as a waste form requires an understanding of the interaction between the glass and the zeolite. Properties of the glass that enhance binding and durability of the glass bonded zeolite need to be identified. Three types of glass, boroaluminosilicate, soda-lime silicate, and high silica glasses, have a range of properties and are now being investigated. Each glass was hot pressed by itself and with an equal amount of zeolite. MCC-1 leach tests were run on both. Soda-lime silicate and high silica glasses did not give a durable glass bonded zeolite. Boroaluminosilicate glasses rich in alkaline earths did bind the zeolite and gave a durable glass bonded zeolite. Scanning electron micrographs suggest that the boroaluminosilicate glasses wetted the zeolite powders better than the other glasses. Development of the glass bonded zeolite as a waste form for chloride waste salt is continuing.

  3. 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.

  4. 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.

  5. 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)

  6. Mechanism of mechanical fatigue of fused silica

    SciTech Connect

    Tomozawa, M.

    1992-01-01

    This report discusses work on the fatigue of fused silica. Topics covered include: the effect of residual water in silica glass on static fatigue; strengthening of abraded silica glass by hydrothermal treatment; fatigue-resistant coating of silicon oxide glass; and water entry into silica glass during slow crack growth.

  7. 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.

  8. Yb3+ borate laser glasses containing high-valency cations

    NASA Astrophysics Data System (ADS)

    Izumitani, Tetsuro; Hu, Lili; Dai, Shixun; Jiang, Zhonghong

    1999-07-01

    A new kind of Yb3+ borate laser glass containing high valency cations was reported in this work. B2O3-ZnO and B2O3-BaO glasses were chosen as the base glasses of Yb$3+)-BaO glasses were chosen as the base glasses of Yb3+ ions. Yb3+ ion has a large integrated absorption area in the former and longer fluorescent lifetime in the latter. The effect of Al3+, La3+, Ti3+, Zr4+, Nb4+ Ta5+, W6+ high valency cations on the absorption and fluorescent behaviors of Ba2O3-ZnO- RmOn-Yb2O3 and B2O3-BaO-RmOn-Yb2O3 glasses was examined. Some Yb3+ borate laser glasses with high cross section for stimulated emissions, good stability, good stability against devitrification and lower non-linear refractive index were presented.

  9. Partition coefficients for rare earth elements in mafic minerals of high silica rhyolites: The importance of accessory mineral inclusions

    NASA Astrophysics Data System (ADS)

    Michael, Peter J.

    1988-02-01

    REE concentrations of mafic mineral separates from high-silica rhyolites measured by INAA are high and variable compared to electron microprobe analyses of the minerals themselves. The mafic phases commonly contain inclusions or have adhering grains of accessory rare earth element (REE)-rich minerals. Optical and electron microscopic observation revealed discrete grains of chevkinite (rare earth titano-silicate) included within clinopyroxenes from the Sierra La Primavera (Mexico) rhyolite, and monazite grains adhering to ortho- and clinopyroxenes from the Bishop Tuff (California). During hand-picking of mineral separates, inclusions are only partly removed. As a result, the magnitude and variability of true mineral-melt partition coefficients for light REE have been overestimated. The true REE partition coefficients of La Primavera and Bishop Tuff pyroxenes obtained by microprobe are only slightly higher than they are in lower-silica rhyolites, and are not as variable as previously thought. The partitioning slope is positive, as in less silicic systems. The relative partitioning behavior of REE in high-silica rhyolites is dominated by crystal-chemical controls and not by liquid structural effects. When a partition coefficient is used for crystallization calculations, adhering phases and inclusions should be retained or the minor phases must be accounted for separately. Alternatively, a bulk distribution coefficient can be calculated using whole rock and glass compositions and the glass mode.

  10. Self-Cleaning Anticondensing Glass via Supersonic Spraying of Silver Nanowires, Silica, and Polystyrene Nanoparticles.

    PubMed

    Lee, Jong-Gun; An, Seongpil; Kim, Tae-Gun; Kim, Min-Woo; Jo, Hong-Seok; Swihart, Mark T; Yarin, Alexander L; Yoon, Sam S

    2017-10-11

    We have sequentially deposited layers of silver nanowires (AgNWs), silicon dioxide (SiO2) nanoparticles, and polystyrene (PS) nanoparticles on uncoated glass by a rapid low-cost supersonic spraying method to create antifrosting, anticondensation, and self-cleaning glass. The conductive silver nanowire network embedded in the coating allows electrical heating of the glass surface. Supersonic spraying is a single-step coating technique that does not require vacuum. The fabricated multifunctional glass was characterized by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), ultraviolet-visible spectroscopy, and transmission electron microscopy (TEM). The thermal insulation and antifrosting performance were demonstrated using infrared thermal imaging. The reliability of the electrical heating function was tested through extensive cycling. This transparent multifunctional coating holds great promise for use in various smart window designs.

  11. 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.

  12. Evaluation of the water-treatment ability of silica-doped titanium dioxide-coated glass plates using a cationic coupling reagent based on a flow analytical system.

    PubMed

    Sugita, Tsuyoshi; Mori, Masanobu; Mase, Akinori; Noguchi, Shin-nosuke; Tokutome, Toru; Fujii, Kengo; Hara, Chisato; Katayama, Kenji; Iwamoto, Shinji; Itabashi, Hideyuki

    2015-01-01

    In this study, a photocatalytic plate bound to highly dispersible silica-doped titanium dioxide (SiT) on a trimethoxysilyl-propyldiethylenetriamine (dien)-coated glass plate (dien-plate) was newly synthesized, and was evaluated by a flow analytical (FA) system, which consists of a photocatalytic reactor and a spectrophotometer, to continuously monitor the absorbance of tested chemicals. The method was not required to collect any sample solution at a constant period. The SiT-dien-plate facilitated the photodecomposition of methylene blue (MB) and indigo carmine (InC) in aqueous solutions. Notably, MB was quantitatively photo-decomposed following 18 h of UV-light irradiation, related to the electrostatic adsorption of surface-bound particles. A water-treatment ability of visible-light-responsive vanadium-modified nitrogen/silica co-doped titanium dioxide fixed on the dien-plate was also evaluated by the FA system. It clarified to decompose MB and InC under visible-light irradiation. Finally, the decomposition of a humic substance dissolved from Middle West China peaty soils by the SiT-dien-plate under UV-irradiation was assessed as applying the FA system with a photocatalytic plate.

  13. Silica glasses with nanoparticles of copper compounds: spectroscopy properties and laser passive shutter application

    NASA Astrophysics Data System (ADS)

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

    2003-11-01

    Sol-gel glasses containing copper selenide nanoparticles and having absorption band at 1.1?2.2 ?m can be used as saturable absorber passive shutter for Q-switching and mode-locking of the solid-state lasers operating in the wavelength range of 1.0?1.5 ?m. The bleaching relaxation time of the glasses was measured to be 0.46?1.4 ns in dependence on copper selenide stoichiometry.

  14. 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.

  15. Dansylated aminopropyl controlled pore glass: a model for silica-liquid solvation.

    PubMed

    Page, Phillip M; Munson, Chase A; Bright, Frank V

    2004-11-23

    We have prepared a series of aminopropyl controlled pore glass (CPG) particles that have been labeled with a solvatochromic fluorescent probe molecule (dansyl). We report on the behavior of the attached dansyl reporter as a function of dansyl-to-amine molar ratio (i.e., dansyl loading), solvent dipolarity, and surface-residue end capping. In these experiments, we systematically adjust the dansyl loading by 10(5); a range much larger than ever explored. The dansylated CPG particles were also end capped with trimethylchlorosilane to derivatize most of the residual silanol and/or aminopropyl groups. The attached dansyl molecules can be surrounded by other dansyl molecules; they can be distributed within an ensemble of sites with differing physicochemical properties, and/or they can be distributed in sites that are restrictive to dansyl motion and/or solvent inaccessible. At high dansyl loadings, the majority of the dansyl groups are solvated by other dansyl moieties and solvent does not significantly alter the local microenvironment surrounding the average dansyl molecule (i.e., the cybotactic region) to any significant level. At intermediate dansyl loadings, the average distance between the dansyl groups increases and solvent is able to access/solvate/wet the dansyl groups and alter their cybotactic region to a greater extent. At the lowest dansyl loadings studied, the results suggest that these dansyl moieties are localized within solvent inaccessible/restrictive SiO2 sites (e.g., small pores).

  16. 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.

  17. Metallization of Silica Analogue: High pressure study of Barium Iodide

    NASA Astrophysics Data System (ADS)

    Smart, T. J.; Harrison, L. M.; O'Bannon, E. F., III; Stackhouse, S.; Godwal, B. K.; Williams, Q. C.; Jeanloz, R.

    2016-12-01

    In this study we observed the transition from an insulating to metallic bonding type of BaI2. To document the metallization of this compound, we use an absorption edge infrared spectroscopy technique to observe the closure of bandgap with increasing pressure. BaI2 is expected to become fully metallic under 100 GPa, which would be the lowest metallization pressure of the AX2compound group. Band gap measured as a function of pressure will be compared with results from first principles quantum mechanical calculations. The Chemical bonding properties of materials of large Exo-planets are difficult to study directly; the bulk of the rocky material is believed to be siliceous, but the physical properties of silica are not well understood at high pressures and temperatures.Rrecent studies suggest that silica transforms from an insulating to a metallic state at high pressures. With the distinction between a planetary core and its mantle characterized by the type of chemical bonding as well as composition, this change in chemical bonding type is profound in planetary sciences. Although the high-pressure structures of SiO2 are not well known past the stishovite phase, the AX2 analogs like BaI2 have been observed to follow a systematic sequence of high-pressure transformations with a succession of coordination changes. The sequence is well- established up to the cotunnite phase (orthorhombic structure, space group: Pnma), the highest-coordination structure observed in AX2 compounds at ambient pressure (predicted to be acquired in SiO2 by 750 GPa). This makes materials that possess the cotunnite structure, as BaI2 does at ambient conditions useful as structural analogs to silica.

  18. Broadband near-infrared emission property in Er3+/Ce3+ co-doped silica-germanate glass for fiber amplifier

    NASA Astrophysics Data System (ADS)

    Wei, Tao; Chen, Fangze; Tian, Ying; Xu, Shiqing

    Er3+ doped and Er3+/Ce3+ co-doped silica-germanate glasses were synthesized by high-temperature melt-quenching technique. A detailed study of the 1.53 μm spectroscopic properties and thermal stability was presented in this work. The absorption spectra, 1.53 μm emission spectra and fluorescence lifetimes were measured and investigated, along with the quantitative calculations and analyses of Judd-Ofelt intensity parameters, stimulated absorption and emission cross-sections and the product of FWHM×σemp. It was found that the prepared samples have outstanding thermal stability (Tg = 585 °C), large FWHM (77 nm and 108 nm) and high stimulated emission cross-sections (9.55 × 10-28 cm3 and 8.72 × 10-28 cm3) of Er3+. The 1.53 μm fluorescence intensity improved significantly with the introduction of Ce3+. Furthermore, the wavelength dependent gain coefficient G(λ) of 4I13/2 → 4I15/2 transition of Er3+ was determined by means of the absorption and emission cross-sections. The results indicate that the developed glass co-doped with Er3+/Ce3+ is a promising gain medium applied for broadband amplifier pumped with a 980 nm laser diode.

  19. Broadband near-infrared emission property in Er3+/Ce3+ co-doped silica-germanate glass for fiber amplifier.

    PubMed

    Wei, Tao; Chen, Fangze; Tian, Ying; Xu, Shiqing

    2014-05-21

    Er(3+) doped and Er(3+)/Ce(3+) co-doped silica-germanate glasses were synthesized by high-temperature melt-quenching technique. A detailed study of the 1.53μm spectroscopic properties and thermal stability was presented in this work. The absorption spectra, 1.53μm emission spectra and fluorescence lifetimes were measured and investigated, along with the quantitative calculations and analyses of Judd-Ofelt intensity parameters, stimulated absorption and emission cross-sections and the product of FWHM×σem(p). It was found that the prepared samples have outstanding thermal stability (Tg=585°C), large FWHM (77nm and 108nm) and high stimulated emission cross-sections (9.55×10(-28)cm(3) and 8.72×10(-28)cm(3)) of Er(3+). The 1.53μm fluorescence intensity improved significantly with the introduction of Ce(3+). Furthermore, the wavelength dependent gain coefficient G(λ) of (4)I13/2→(4)I15/2 transition of Er(3+) was determined by means of the absorption and emission cross-sections. The results indicate that the developed glass co-doped with Er(3+)/Ce(3+) is a promising gain medium applied for broadband amplifier pumped with a 980nm laser diode.

  20. Damage behavior of Nd:glass of high-power disk amplifier medium in ICF Facility

    NASA Astrophysics Data System (ADS)

    He, Shaobo; Chen, Lin; Yuan, Xiaodong; Chen, Yuanbin; Cheng, Xiaofeng; Xie, Xudong; Wang, Wenyi; Zu, Xiaotao

    2016-12-01

    Large aperture Nd:glass disk is often used as the amplifier medium in the inertial confinement fusion (ICF) facilities. The typical size of Nd:glass is up to 810mm×460mm×40mm and more than 3,000 Nd:glass components are needed in the ICF facility. At present, the 3ω fused silica glass and DKDP crystal are mainly responsible for the damage of driver used for ICF. However, with the enlargement of the facility and increase of laser shot number, the laser damage of Nd:glass at 1ω waveband is still an important problem to limit the stable operation of facility and improvement of laser beam quality. In this work, the influence of Nd:glass material itself, mechanical processing, service environment, and laser beam quality on its damage behavior is investigated experimentally and theoretically. The results and conclusions can be summarized as follows: (1) It is very important to control the concentration of platinum impurity particles during melting and the sputtering effect of the cladding materials. (2) The number and length of fractural and brittle scratches should be strictly suppressed during mechanical processing of Nd:glass. (3) The B-integral of high power laser beam should be rigorously controlled. Particularly, the top shape of pulses must be well controlled when operating at high peak laser power. (4) The service environment should be well managed to make sure the cleanness of the surface of Nd:glass better than 100/A level during mounting and running. (5) The service environment and beam quality should be monitored during operation.

  1. Electrochemical cell with high conductivity glass electrolyte

    DOEpatents

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

    1987-04-21

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

  2. Electrochemical cell with high conductivity glass electrolyte

    DOEpatents

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

    1986-04-17

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

  3. Electrochemical cell with high conductivity glass electrolyte

    DOEpatents

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

    1987-01-01

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

  4. Comparison on pulse propagation and plasma generation in contact and noncontact geometries for femtosecond micromachining of silica glass

    NASA Astrophysics Data System (ADS)

    Arabanian, Atoosa Sadat; Massudi, Reza

    2013-02-01

    The nonlinear Schrödinger equation and Drude equation are simultaneously solved taking into account diffraction, group velocity dispersion, self-focusing, multiphoton ionization and plasma creation, and plasma absorption inside a transparent material, i.e., silica. Contact and noncontact geometries, where the focusing lens is, respectively, in contact with the sample or at a specified distance from it, are studied. It is observed that for noncontact geometry, maximum electron density in the vicinity of the focal point inside silica is lower than that in contact geometry. Furthermore, it is observed that locations for initiation of pulse splitting for two geometries are different. The effect of the variations of the peak power of the incident pulse, its beam waist, the focal length of the focusing lens, and the air gap length on the maximum electron density is also investigated in noncontact geometry. Calculation reveals that for higher peak powers and larger beam waists, maximum electron density increases and occurs at closer distance relative to linear focus point inside glass. Simulations are performed in time domain by operator-split technique and alternating-direction implicit algorithm to reduce execution time of the program.

  5. New generation high-power rare-earth-doped phosphate glass fiber and fiber laser

    NASA Astrophysics Data System (ADS)

    Wu, Ruikun; Myers, John D.; Myers, Michael J.

    2001-04-01

    High power, high brightness fiber lasers have numerous potential commercial and military applications. Fiber lasers with cladding pump designs represent a new generation of diode pumped configurations that are extremely efficient, have single mode output and may be operated with or without active cooling. Kigre has invented a new family of Er/Yb/Nd phosphate laser glass materials (designated QX) that promise to facilitate a quantum leap in fiber laser technology of this field. The new phosphate glass Rare-Earth doped fiber exhibit many advantages than Silica or Fluoride base fiber, see table.1. Instead of 30 to 50 meters of fused silica with a 50 mm bend radii; Kigre's phosphate glass fiber amplifiers may be designed to be less than 4 meters long .Laser performance and various design parameters, such as the fiber core diameter, NA, inner cladding shape and doping concentration are evaluated. Laser performances was demonstrated for an experimental QX/Er doubled clading fiber commissioned by MIT having 8 micron core, a 240 X 300 micron rectangle shaped inner cladding with 0.4 NA and 500 micron outer clading.. Kigre obtained approximately 2 dB/cm gain from 15cm long fiber under 940nm pumping The same fiber was evaluated by researcher at MIT. They used 975nm pump source. Maximum 270mW output was demonstrated by 30 cm long fiber with Fresnel reflection resonator mirrors. The slope efficiency of absorbed pump power s 47%.

  6. High strength E-glass/CNF fibers nanocomposite

    NASA Astrophysics Data System (ADS)

    Abu-Zahra, Esam H.

    Glass fibers are among the most versatile industrial materials known today, where 4 billion pounds of glass are used every year. They are readily produced from raw materials, which are available in virtually unlimited supply. Reinforced glass composites still suffer from different weaknesses; such as: poor dispersion, poor alignment and orientation of reinforcing materials, in addition to the difficulties associated with handling randomly oriented nanofibers and nanotubes in an industrial setting. The aim of this work is to study the feasibility of a manufacturing methodology to align the imbedded CNFs in the glass fibers and to quantify the potential gains in the mechanical strength of the nanocomposite glass fibers. The method makes use of the high aspect ratio of the CNFs along with the glass filament drawing process to imbed, disperse and align the CNFs in glass fibers. E-glass frit was prepared and mixed with 5% vol. CNFs. The mix was fed to the glass fibers drawing machine using a special feeding mechanism. Hybrid glass fibers were drawn on 12 runs and tested for their tensile strength properties. A 300% increase on the tensile strength of the E-glass/CNFs fibers was successfully demonstrated. Structural analysis using SEM testing revealed that the CNFs survived the high temperature in the premelter (2400°F), in addition to that for being well dispersed and aligned.

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

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

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

  8. Low melting high lithia glass compositions and methods

    DOEpatents

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

    2003-09-23

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  10. Phosphate glass useful in high energy lasers

    DOEpatents

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

    1996-06-11

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

  11. Phosphate glass useful in high energy lasers

    DOEpatents

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

    1996-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

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

  14. Blue light emission from trivalent cerium doped in sol-gel silica glass

    NASA Astrophysics Data System (ADS)

    Tokumitsu, Seika; Murakami, Yukon; Oda, Hisaya; Kawabe, Yutaka

    2017-02-01

    Rare earths in glass matrices are promising for active optical devices as amplifiers and lasers. Emission originating from d-f transitions in sol-gel glass has not been studied very often, while those based on f-f transitions were widely utilized. However, d-f emission in rare earths is very important because of their strong oscillator strength and broad emission widths suitable for the application to scintillators and solid-state lasers. Co-doping of aluminum in sol-gel synthesis was known to be effective for the emission enhancement of trivalent terbium and europium. Recently, we applied aluminum co-doping to cerium and europium systems in sol-gel glass to succeed in the observation of strong blue light emission originating from d-f transitions. Glass samples were prepared with conventional sol-gel process where tetramethylorthosilicate was hydrolyzed in the mixture of water, ethanol and dimethylformamide with nitric acid catalyst. After adding cerium nitrate and aluminum nitrate, the solution experienced drying followed by calcination at 1,050°C under air environment. When molar ratio of cerium to silicon was adjusted at 0.1% and Al concentration was varied in 0.1 2.0%, transparent glass products showed bright and broad blue photoluminescence under UV illumination. The fluorescence lifetimes were found to be about 50 90 ns, indicating that the emission was due to d-f transitions. Considering the simplicity of the process, blue phosphors based on sol-gel glass will be very promising for future applications.

  15. Modifications under irradiation of a self-assembled monolayer grafted on a nano-porous silica glass: a solid-state NMR characterization

    SciTech Connect

    Le Caer, S.; Chatelain, C.; Renault, J.Ph.; Brunet, F.; Charpentier, T.; Durand, D.; Dauvois, V.

    2012-02-15

    Controlled pore glasses with a pore size of 8 nm are grafted with chlorodimethylsilane (ClSi(CH{sub 3}){sub 2}H). The surface of the glass is carefully characterized before and after irradiation with 10 MeV electrons by solid-state NMR measurements. {sup 1}H MAS NMR experiments in one and two dimensions (2D double quantum and 2D exchange) have been used to reveal the grafting of the chlorodimethylsilane at the silica surface and evidence the formation of a homogeneous layer on the surface. Irradiation leads to a high H{sub 2} yield (3.3 * 10{sup -7} mol/J) due to the efficient cleavage of the Si H bond. Methane is detected in smaller quantities (5.5 * 10{sup -8} mol/J), indicating that the Si-H bond is preferentially cleaved over the Si-C bond. The H{sub 2} production arising from OH groups on the surface is very minor in comparison to the S- H and Si-C radiolysis. (authors)

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

    SciTech Connect

    Patricia M. Dove

    2000-12-13

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

  17. High-density scintillating glasses for a proton imaging detector

    NASA Astrophysics Data System (ADS)

    Tillman, I. J.; Dettmann, M. A.; Herrig, V.; Thune, Z. L.; Zieser, A. J.; Michalek, S. F.; Been, M. O.; Martinez-Szewczyk, M. M.; Koster, H. J.; Wilkinson, C. J.; Kielty, M. W.; Jacobsohn, L. G.; Akgun, U.

    2017-06-01

    High-density scintillating glasses are proposed for a novel proton-imaging device that can improve the accuracy of the hadron therapy. High-density scintillating glasses are needed to build a cost effective, compact calorimeter that can be attached to a gantry. This report summarizes the study on Europium, Terbium, and Cerium-doped scintillating glasses that were developed containing heavy elements such as Lanthanum, Gadolinium, and Tungsten. The density of the samples reach up to 5.9 g/cm3, and their 300-600 nm emission overlaps perfectly with the peak cathode sensitivity of the commercial photo detectors. The developed glasses do not require any special quenching and can be poured easily, which makes them a good candidate for production in various geometries. Here, the glass making conditions, preliminary tests on optical and physical properties of these scintillating, high-density, oxide glasses developed for a novel medical imaging application are reported.

  18. Effect of 180-week water storage on the flexural properties of E-glass and silica fiber acrylic resin composite.

    PubMed

    Vallittu, P K

    2000-01-01

    The aim of this study was to determine the effect of long-term water immersion on the flexural properties of fiber-reinforced composite. Continuous, woven, silanized E-glass fibers and woven silica fibers were used to reinforce heat-cured and autopolymerized denture base polymers. Fibers were oriented at a 45-degree angle to the long axis of the test specimens. Control specimens were unreinforced. Dry test specimens and those stored in water for up to 180 weeks were tested with a 3-point loading apparatus. Ultimate transverse strength and flexural modulus of unreinforced and fiber-reinforced composite test specimens decreased during water storage (P < 0.001, analysis of variance). Post hoc analysis revealed that after the storage of 4 weeks no statistically significant reduction occurred. The results of this study suggest that the ultimate transverse strength of the fiber-reinforced composite made from E-glass fibers is reduced by approximately 27% compared to the dry fiber-reinforced composite. The majority of the reduction occurred during 4 weeks of storage in water and remained approximately at that level for 180 weeks.

  19. Inelastic ultraviolet scattering from high frequency acoustic modes in glasses.

    PubMed

    Masciovecchio, C; Gessini, A; Di Fonzo, S; Comez, L; Santucci, S C; Fioretto, D

    2004-06-18

    The dynamic structure factor of vitreous silica and glycerol has been measured as a function of temperature and of the momentum transfer up to Q=0.105 nm(-1) using a novel experimental technique, the inelastic ultraviolet scattering. As in the case of Brillouin light scattering and ultrasonic measurements, the temperature dependence of the acoustic attenuation shows a plateau below the glass transition whose amplitude scales as Q2. Moreover, a slight temperature dependence of attenuation has been found in vitreous silica at about 130 K, which seems to be reminiscent of the peak measured at lower Qs. These two findings strongly support the idea that anharmonicity is responsible for sound attenuation at ultrasonic and hypersonic frequencies. Finally, we demonstrate that the attenuation mechanism should show a change of regime between 0.105 and 1 nm(-1).

  20. 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.

  1. Semiconductor/porous silica glass nanocomposites via the single-source precursor approach

    SciTech Connect

    Romano, Ricardo . E-mail: rromano@iqm.unicamp.br; Alves, Oswaldo L.

    2006-02-02

    The utilization of single-source molecular precursor approach to obtain II-VI and IV-VI semiconductors encapsulated in porous Vycor glass (PVG) is described. The procedure is based on the impregnation of cadmium and lead(II) diethyl-dithiocarbamate complexes, Cd(S{sub 2}CNEt{sub 2}){sub 2} and Pb(S{sub 2}CNEt{sub 2}){sub 2}, inside the porous environment of PVG followed by a thermal treatment of the glass. The pyrolysis of the impregnated precursor gives rise to binary semiconductors CdS and PbS, respectively. The impregnation step is driven by interactions between the precursors and active sites located at glass pore surfaces. After completing the impregnation-decomposition cycle, it was found that the active glass sites were regenerated, making new cycles possible. The amount of encapsulated semiconductor increases linearly as a function of the number of cycles. Nanocomposites obtained after 1-10 cycles were prepared and characterized by optical spectroscopy, X-ray diffraction powder and transmission electron microscopy.

  2. Ultrafast laser photoinscription of polarization sensitive devices in bulk silica glass.

    PubMed

    Cheng, G; Mishchik, K; Mauclair, C; Audouard, E; Stoian, R

    2009-06-08

    Ultrashort pulsed laser irradiation of bulk fused silica may result under specific energetic conditions in the self-organization of subwavelength material redistribution regions within the laser trace. The modulated structures have birefringent properties and show unusual anisotropic light scattering and reflection characteristics. We report here on the formation of waveguiding structures with remarkable polarization effects for infrared light. The photoinscription process using 800 nm femtosecond laser pulses is accompanied by third harmonic generation and polarization dependent anisotropic scattering of UV photons. The photowritten structures can be arranged in three-dimensional patterns generating complex propagation and polarization effects due to the anisotropic optical properties.

  3. High-Intensity Plasma Glass Melter Final Technical Report

    SciTech Connect

    Gonterman, J. Ronald; Weinstein, Michael A.

    2006-10-27

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

  4. Optical and electrical properties of boron doped diamond thin conductive films deposited on fused silica glass substrates

    NASA Astrophysics Data System (ADS)

    Ficek, M.; Sobaszek, M.; Gnyba, M.; Ryl, J.; Gołuński, Ł.; Smietana, M.; Jasiński, J.; Caban, P.; Bogdanowicz, R.

    2016-11-01

    This paper presents boron-doped diamond (BDD) film as a conductive coating for optical and electronic purposes. Seeding and growth processes of thin diamond films on fused silica have been investigated. Growth processes of thin diamond films on fused silica were investigated at various boron doping level and methane admixture. Two step pre-treatment procedure of fused silica substrate was applied to achieve high seeding density. First, the substrates undergo the hydrogen plasma treatment then spin-coating seeding using a dispersion consisting of detonation nanodiamond in dimethyl sulfoxide with polyvinyl alcohol was applied. Such an approach results in seeding density of 2 × 1010 cm-2. The scanning electron microscopy images showed homogenous, continuous and polycrystalline surface morphology with minimal grain size of 200 nm for highly boron doped films. The sp3/sp2 ratio was calculated using Raman spectra deconvolution method. A high refractive index (range of 2.0-2.4 @550 nm) was achieved for BDD films deposited at 500 °C. The values of extinction coefficient were below 0.1 at λ = 550 nm, indicating low absorption of the film. The fabricated BDD thin films displayed resistivity below 48 Ohm cm and transmittance over 60% in the visible wavelength range.

  5. Recent advances in phosphate laser glasses for high power applications

    SciTech Connect

    Campbell, J.H.

    1996-05-14

    Recent advances in Nd-doped phosphate laser glasses for high-peak-power and high-average-power applications are reviewed. Compositional studies have progressed to the point that glasses can be tailored to have specific properties for specific applications. Non-radiative relaxation effects can be accurately modeled and empirical expressions have been developed to evaluate both intrinsic (structural) and extrinsic (contamination induced) relaxation effects. Losses due to surface scattering and bulk glass absorption have been carefully measured and can be accurately predicted. Improvements in processing have lead to high damage threshold (e.g. Pt inclusion free) and high thermal shock resistant glasses with improved edge claddings. High optical quality pieces up to 79 x 45 x 4cm{sup 3} have been made and methods for continuous melting laser glass are under development.

  6. High expansion, lithium corrosion resistant sealing glasses

    DOEpatents

    Brow, Richard K.; Watkins, Randall D.

    1991-01-01

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

  7. High expansion, lithium corrosion resistant sealing glasses

    DOEpatents

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

    1991-06-04

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

  8. The ion beam mixing of Ti and Cr films on silica glass

    NASA Astrophysics Data System (ADS)

    Lane, D. W.

    1992-06-01

    The effects of ion implantation dose Φ and substrate temperature have been examined for the 75 keV Ar + ion beam mixing of thin Ti and Cr films on silica. The dose dependence could be described in three distinct regions: (1) at low doses the amount of metal mixed into the silica was approximately proportional to φ {1}/{2} indicating the isotropic cascade mixing was dominant; (2) above a dose of ˜5×10 16 Ar + cm -2 this changed to a Φ2 dependence; (3) at ˜2×10 17 Ar + cm -2 surface erosion by sputtering became important adn reduced the concentration of metal mixed in to the substrate. Optical measurements were performed on the etched surfaces of the specimens and indicated that chemical reactions may have occured at the mixed interfaces. The ion beam mixing of Ti was found to be independent of temperature throughout the experimental temperature range of 300 to 600 K, whereas the mixing of Cr was temperature dependent above 440 K. It exhibited an activation energy of ˜ 0.2 eV, due to radiation enhanced diffusion.

  9. Synthesis of monodisperse high-aspect-ratio colloidal silicon and silica rods.

    PubMed

    van Kats, Carlos M; Johnson, Patrick M; van den Meerakker, Jan E A M; van Blaaderen, Alfons

    2004-12-07

    We describe the synthesis and the physical properties of suspensions of colloidal silicon and silica rodlike particles. In addition to pure silicon and pure silica rods, we have also synthesized silicon rods with a silica shell and silica rods with a fluorescent silica layer. Pre-patterned p-type (100) silicon wafers were electrochemically etched in electrolyte solutions containing hydrogen fluoride. By the current density being varied while etching, macropores were etched with controllable modulated pore diameters. These silicon structures were transformed into rods with indentations 5.5 mum apart and with lengths up to 100 mum using iterative oxidation in air and dissolution of the silica by HF. Complete oxidation of these rods was also achieved. Sonication of the modulated rods resulted in monodisperse particles of 5.5 mum length and 300 nm width. A high yield of 10(12) particles, or more, is possible with this method. At high concentrations, these particles show nematic ordering in charge-stabilized suspensions. The oxidized silica outer layer of the silicon rods makes the further growth of silica in solution or on a wafer possible. This allows for control of the particles' interaction potential. Labeling with a fluorescent dye and index matching of the complete silica rods enable the study of concentrated dispersions quantitatively, on a single particle level, with confocal microscopy. Because of their high refractive index in the near-IR, the nematic phases of rods with a silica core are also interesting for photonic applications.

  10. [Preparation of porous silica microspheres with high porosity using base-dissolving method].

    PubMed

    Zhao, Rui; Li, Xinhui; Liu, Guoquan

    2005-11-01

    A novel method was proposed and studied for the preparation of porous silica with high porosity using base-dissolving technology. The relationships between the removal of silica and the base concentration, the reaction temperature as well as the reaction time were evaluated. The amount of silica removed from silica spheres was increased and silica-dissolving rate was also accelerated along with the increase of NaOH concentration. This was due to the damage of some inner walls of the porous silica and the dissolution of small fragments into the base solution. The amount of silica removed was in direct proportion to the reaction temperature and reaction time. Moreover, the specific pore volumes were linearly increased along with the increase of the amount of silica removed. The treated silica particles remained as homogeneous spheres and the changes of the particle diameter were not observed. Under the optimized conditions with the NaOH solution of 1.25 mol/L, the reaction temperature of 25 degrees C and the reaction time of 3.0 h, the original silica spheres with the diameter of 4 - 5 microm, the pore size of 8 nm and the specific pore volume (V(p)) of 1.4 cm3/g were modified to the high-porosity silica with the diameter of 4 - 5 microm, the pore size of 14 nm and the V(p) of 3.2 cm3/g. The porosity of the silica microspheres was changed from 75% to 88%. This high-porosity silica was suitable for the preparation of high performance gel filtration packings.

  11. High quality factor silica microspheres functionalized with self-assembled nanomaterials.

    PubMed

    Kandas, Ishac; Zhang, Baigang; Daengngam, Chalongrat; Ashry, Islam; Jao, Chih-Yu; Peng, Bo; Ozdemir, Sahin K; Robinson, Hans D; Heflin, James R; Yang, Lan; Xu, Yong

    2013-09-09

    With extremely low material absorption and exceptional surface smoothness, silica-based optical resonators can achieve extremely high cavity quality (Q) factors. However, the intrinsic material limitations of silica (e.g., lack of second order nonlinearity) may limit the potential applications of silica-based high Q resonators. Here we report some results in utilizing layer-by-layer self-assembly to functionalize silica microspheres with nonlinear and plasmonic nanomaterials while maintaining Q factors as high as 10(7). We compare experimentally measured Q factors with theoretical estimates, and find good agreement.

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

    SciTech Connect

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

    2009-04-13

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

  13. High Numerical Aperture Silica Core Fibers For Biosensor Applications

    NASA Astrophysics Data System (ADS)

    Skutnik, B. J.; Brucker, C. T.; Clarkin, J. P.

    1988-06-01

    The whole field of biosensing has been enhanced by the development of optical fibers(l). They provide a means of activating the sensors and of carrying the sensor's signal back to the detector. The small dimensions and flexibility of the fibers allow the development of miniaturized sensor packages capable of introduction into a patient's vascular system. Several in vitro systems are already competing in high risk operations with standard laboratory procedures to provide more timely and accurate analysis of the patient's condition. During the next decade real time sensing in vivo together with various endoscopic and developing laser surgery techniques will provide doctors and patients with many new and delicate alternative procedures to common surgery. Not only will trauma be minimized, but with better and quicker knowledge of the patient's blood gas levels and other body conditions, doctors will be able to efficiently correct for unforeseen difficulties while controlling the known problems effectively. To achieve these wonders extremely small sensing areas will be available so that the sensor systems must be highly efficient. The optical fibers must activate all or at least most of the sensor's area and must be able to gather as much of the return signal from the sensor as possible. This places some strong requirements on the optical properties of the fibers. The need for flexible, yet sturdy, devices places requirements on the mechanical properties of the fibers. For the preferred silica based fibers, the fact that body fluids are primarily water place additional demands on the fibers' mechanical properties. Obviously the sensing system being in contact or close proximity with the body or its fluids must satisfy certain biocompatibility and sterilization requirements. This paper further describes these requirements and presents details about a new optical fiber which meets these requirements and provides some additional very useful properties. This new fiber which

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

    PubMed

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

    2004-03-15

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

  15. In-depth survey report of silica flour dust during packing, transfer, and shipping at Pennsylvania Glass Sand Corporation, Berkeley Springs, West Virginia

    SciTech Connect

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

    1981-09-01

    A visit was made to Pennsylvania Glass Sand Corporation, Berkeley Springs, West Virginia to evaluate control measures in place to protect workers from silica dust exposures. Two dust suppressant techniques were in use. The first used an agglomerating/foaming agent, Deter(R), sprayed into whole grain sand during its transfer through the old screen tower building. The second used exhaust ventilation during the bulk loading of silica-flour into enclosed hopper cars. Exhaust-ventilation systems were used to capture point source emissions from the six pebble mills, the three packer stations and the bulk loading stations. An exhaust-ventilation system was also used to control dust emissions during the bulk loading of silica-flour into closed hopper trucks and railroad cars. The injection of the agglomerating agent reduced dust emissions by 20 to 67%. The bulk loading of silica-flour under local exhaust ventilation reduced dust levels from 90 micrograms/cubic meter total dust and 80 micrograms/cubic meter silica dust. The local exhaust ventilation systems at the three silica-flour packing stations showed varying degrees of effectiveness as a result of the design, total air-movement control, and housekeeping practices. Other existing and planned control strategies were briefly discussed.

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

    PubMed

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

    2013-07-30

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

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

    SciTech Connect

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

    2010-01-01

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

  18. High stored energy of metallic glasses induced by high pressure

    NASA Astrophysics Data System (ADS)

    Wang, C.; Yang, Z. Z.; Ma, T.; Sun, Y. T.; Yin, Y. Y.; Gong, Y.; Gu, L.; Wen, P.; Zhu, P. W.; Long, Y. W.; Yu, X. H.; Jin, C. Q.; Wang, W. H.; Bai, H. Y.

    2017-03-01

    Modulating energy states of metallic glasses (MGs) is significant in understanding the nature of glasses and controlling their properties. In this study, we show that high stored energy can be achieved and preserved in bulk MGs by high pressure (HP) annealing, which is a controllable method to continuously alter the energy states of MGs. Contrary to the decrease in enthalpy by conventional annealing at ambient pressure, high stored energy can occur and be enhanced by increasing both annealing temperature and pressure. By using double aberration corrected scanning transmission electron microscopy, it is revealed that the preserved high energy, which is attributed to the coupling effect of high pressure and high temperature, originates from the microstructural change that involves "negative flow units" with a higher atomic packing density compared to that of the elastic matrix of MGs. The results demonstrate that HP-annealing is an effective way to activate MGs into higher energy states, and it may assist in understanding the microstructural origin of high energy states in MGs.

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

    NASA Technical Reports Server (NTRS)

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

    1970-01-01

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

  20. High temperature glass coatings for superalloys and refractory metals

    NASA Technical Reports Server (NTRS)

    Chapman, J. W.; Grekila, R. B.; Hirayama, C.; Mattox, D. M.

    1970-01-01

    New glasses are used as protective coatings on metals and alloys susceptible to oxidation at high temperatures in oxidizing atmospheres. Glasses are stable and solid at temperatures up to 1000 deg C, adhere well to metal surfaces, and are usable for metals with broad range of expansion coefficients.

  1. Compact silica-on-silicon planar lightwave circuits for high speed optical signal processing

    NASA Astrophysics Data System (ADS)

    Callender, C. L.; Dumais, P.; Blanchetiere, C.; Jacob, S.; Ledderhof, C.; Smelser, C. W.; Yadav, K.; Albert, J.

    2012-02-01

    Silica-on-silicon planar lightwave circuit (PLC) technology is well established and provides a low loss and stable photonic device platform. However, limitations in size and integration of active components remain. Engineering of the layer structure in silica PLCs to achieve high-index contrast, compact device architectures and monolithically integrated optical nonlinearities is described. Modeling of properties of doped-silica layers provides a design strategy for optimization of waveguide loss and birefringence. Optical nonlinearities in poled silica layers have been demonstrated, and recent work to incorporate these into functional device structures and exploit them for high speed modulation is reported.

  2. Sodium hydroxide catalyzed monodispersed high surface area silica nanoparticles

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  3. Sodium hydroxide catalyzed monodispersed high surface area silica nanoparticles

    PubMed Central

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

    2016-01-01

    Understanding of the synthesis kinetics and our ability to modulate medium conditions allowed us to generate nanoparticles via an ultra-fast process. The synthesis medium is kept quite simple with tetraethyl orthosilicate (TEOS) as precursor and 50% ethanol and sodium hydroxide catalyst. Synthesis is performed under gentle conditions at 20 °C for 20 min Long synthesis time and catalyst-associated drawbacks are most crucial in silica nanoparticle synthesis. We have addressed both these bottlenecks by replacing the conventional Stober catalyst, ammonium hydroxide, with sodium hydroxide. We have reduced the overall synthesis time from 20 to 1/3 h, ~60-fold decrease, and obtained highly monodispersed nanoparticles with 5-fold higher surface area than Stober particles. We have demonstrated that the developed NPs with ~3-fold higher silane can be used as efficient probes for biosensor applications. PMID:27606068

  4. Optical Basicity and Nepheline Crystallization in High Alumina Glasses

    SciTech Connect

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

    2011-02-25

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

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

    NASA Technical Reports Server (NTRS)

    Tucker, Dennis S.

    1990-01-01

    A dynamic fatigue study was performed on a Li2O-Al2O3-SiO2 glass-ceramic in order to assess its susceptibility to delayed failure. Fracture mechanics techniques were used to analyze the results for the purpose of making lifetime predictions for optical elements made from this material. The material has reasonably good resistance (N = 20) to stress corrosion in ambient conditions. Analysis also indicated the elements should survive applied stresses incurred during grinding and polishing operations.

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

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

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

  7. Development of high efficiency q-switched glass laser via sol-gel processing

    NASA Astrophysics Data System (ADS)

    Moreshead, William V.

    1988-02-01

    The sol-gel process is a logical choice for silica-based laser glasses, since it requires lower processing temperatures than traditional melt glass techniques, and allows good control of purity. This report describes attempts to prepare silica glasses containing neodymium or neodymium and erbium using sol-gel technology. A description of two different doping procedures is given, along with results. The materials produced were characterized and the spectral, thermal, and physical properties are reported. Fluorescence spectra and fluorescence lifetimes are given for three different materials prepared.

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

    PubMed Central

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  10. Formation Process of High-Pressure Silica Polymorphs in Lunar Meteorites of the NWA 773 Clan

    NASA Astrophysics Data System (ADS)

    Kayama, M.; Tomioka, N.; Seto, Y.; Ohtani, E.; Nagaoka, H.; Fagan, T. J.; Ozawa, S.; Sekine, T.; Miyahara, M.; Miyake, A.; Tomeoka, K.

    2016-08-01

    Recent studies of lunar samples discovered high-pressure phases of silica in Asuka-881757, NWA 4734 and Apollo 15299. Here, we first discovered high-pressure silica from lunar meteorite NWA 773 clan, constraining the shock-pressure and temperature.

  11. High export of dissolved silica from the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Meire, L.; Meire, P.; Struyf, E.; Krawczyk, D. W.; Arendt, K. E.; Yde, J. C.; Juul Pedersen, T.; Hopwood, M. J.; Rysgaard, S.; Meysman, F. J. R.

    2016-09-01

    Silica is an essential element for marine life and plays a key role in the biogeochemistry of the ocean. Glacial activity stimulates rock weathering, generating dissolved silica that is exported to coastal areas along with meltwater. The magnitude of the dissolved silica export from large glacial areas such as the Greenland Ice Sheet is presently poorly quantified and not accounted for in global budgets. Here we present data from two fjord systems adjacent to the Greenland Ice Sheet which reveal a large export of dissolved silica by glacial meltwater relative to other macronutrients. Upscaled to the entire Greenland Ice Sheet, the export of dissolved silica equals 22 ± 10 Gmol Si yr-1. When the silicate-rich meltwater mixes with upwelled deep water, either inside or outside Greenland's fjords, primary production takes place at increased silicate to nitrate ratios. This likely stimulates the growth of diatoms relative to other phytoplankton groups.

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

    SciTech Connect

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

    1981-09-01

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

  13. A Versatile Glass Processor for High Performance Photonic Platforms

    DTIC Science & Technology

    2015-12-08

    SECURITY CLASSIFICATION OF: With the DURIP fund, we acquire a glass processing station to enhance our capabilities to achieve ultra-high performance...funded by PECASE (supported by DoD-ARO under the contract/grant number W911NF-12-1-0026) on high performance optical sensors. The multipurpose glass ...Distribution Unlimited UU UU UU UU 08-12-2016 1-Aug-2014 31-Jul-2015 Final Report: A Versatile Glass Processor for High-Performance Photonic Platforms The views

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

    NASA Astrophysics Data System (ADS)

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

    1981-09-01

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

  15. HIGH STRENGTH GLASS FIBERS DEVELOPMENT PROGRAM

    DTIC Science & Technology

    Contents: Status of information relative to commercial fiberglass Intrinsic strength of the glass fiber Degree of surface damage existing in...the fibers after processing into the filament wound structure Failure mechanisms in a filament wound structure Need for understanding in two distinct problem areas

  16. High level radioactive waste glass production and product description

    SciTech Connect

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

    1993-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

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

    PubMed

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

    2008-01-01

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

  19. The electronic structure of iron in rhyolitic glass at high pressure

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    The physical properties of silicate melts within the Earth's mantle affect the chemical and thermal evolution of the Earth's interior. The behavior of iron in mantle melts is poorly understood, but can be experimentally approximated by iron-bearing silicate glasses. Previous studies have conflicting conclusions on whether iron in lower mantle silicate melts goes through a high-spin to low-spin transition [1-3]. Additionally, the average coordination environment of iron in glasses is poorly constrained. XANES experiments on MORB glasses have demonstrated that both four and six-fold coordinated iron may exist in significant amounts regardless of oxidation state [4] while conventional Mossbauer experiments have observed five-fold coordinated Fe2+ with small amounts of four and six-fold coordinated Fe2+[5]. In an attempt to resolve these discrepancies, we have measured the hyperfine parameters of iron-bearing rhyolitic glass up to ~115 GPa in a neon pressure medium using time-resolved synchrotron Mössbauer spectroscopy at the Advanced Photon Source (Argonne National Laboratory, IL). Our spectra are well explained with a three-doublet model: two high-spin Fe2+-like sites with distinct quadrupole splittings and similar isomer shifts and one high-spin Fe3+-like site. Our results indicate that iron experiences changes in coordination with increasing pressure without undergoing a high-spin to low-spin transition. With the assumption that silicate glasses can be used to model structural behavior in silicate melts, our study predicts that iron in chemically-complex silica-rich melts in the lower mantle likely exists in a high-spin state. References: [1] Nomura, R. et al., Nature 473 (2011). [2] Gu, C. et al., Geophys. Res. Lett. 39 (2012). [3] Mao, Z. et al., Am. Mineral. 99 (2014). [4] Wilke, M. et al., Chem. Geology 220 (2005). [5] Cottrell, E. and Kelley, A.K., Earth Planet. Sci. Lett. 305 (2011).

  20. High-temperature study of defects and homogeneity in glass

    NASA Astrophysics Data System (ADS)

    Yoon, Chang Hyun

    Glass frit has many useful applications in the glass and ceramic industries. Several attempts were made in this study to understand the origin of problems that generally occur when using glass frit. The effect of water/glass interactions on the rheology of glass suspension and the final properties of glass and glaze were studied. The dissolution of refractory inclusions and its influence on the bubble evolution, glass structure, and homogeneity of the resulting melt were also studied. The effects of long-term interaction of water with various frit suspensions were considered. The change in suspension rheology is associated with the ion concentration of the frit suspension, which strongly depends on the frit composition, additives, and solid content of frit suspension. Physical property and compositional variations resulted from dealkalization reactions between the frit particles and water. New investigative techniques for continuous monitoring and quantitative analysis of the dissolution of refractory inclusions in glass have been developed utilizing high-temperature microscopy with computer image analysis. The dissolution rates of refractory oxides in glass frit were measured utilizing hot-stage microscopy in the temperature range from 1050°C to 1400°C. The effects of dissolution on the structure of the final glass, were monitored by infrared spectroscopy. Homogenization of the resulting melts was studied using a Christiansen filter. It was found that melting temperature and time strongly influence the dissolution of refractory batch materials and subsequent homogenization rates, leading to large differences in final structures for glass melts and glazes which have not attained equilibrium.

  1. In vitro osteogenesis on a highly bioactive glass-ceramic (Biosilicate).

    PubMed

    Moura, João; Teixeira, Lucas Novaes; Ravagnani, Christian; Peitl, Oscar; Zanotto, Edgar Dutra; Beloti, Márcio Mateus; Panzeri, Heitor; Rosa, Adalberto Luiz; de Oliveira, Paulo Tambasco

    2007-09-01

    One of the strategies to improve the mechanical performance of bioactive glasses for load-bearing implant devices has been the development of glass-ceramic materials. The present study aimed to evaluate the effect of a highly bioactive, fully-crystallized glass-ceramic (Biosilicate) of the system P(2)O(5)-Na(2)O-CaO-SiO(2) on various key parameters of in vitro osteogenesis. Surface characterization was carried out by scanning electron microscopy and Fourier transform infrared spectroscopy. Osteogenic cells were obtained by enzymatic digestion of newborn rat calvarial bone and by growing on Biosilicate discs and on control bioactive glass surfaces (Biosilicate) parent glass and Bioglass(R) 45S5) for periods of up to 17 days. All materials developed an apatite layer in simulated body fluid for 24h. Additionally, as early as 12 h under culture conditions and in the absence of cells, all surfaces developed a layer of silica-gel that was gradually covered by amorphous calcium phosphate deposits, which remained amorphous up to 72 h. During the proliferative phase of osteogenic cultures, the majority of cells exhibited disassembly of the actin cytoskeleton, whereas reassembly of actin stress fibers took place only in areas of cell multilayering by day 5. Although no significant differences were detected in terms of total protein content and alkaline phosphatase activity at days 11 and 17, Biosilicate supported significantly larger areas of calcified matrix at day 17. The results indicate that full crystallization of bioactive glasses in a range of compositions of the system P(2)O(5)-Na(2)O-CaO-SiO(2) may promote enhancement of in vitro bone-like tissue formation in an osteogenic cell culture system.

  2. Glass precursor approach to high-temperature superconductors

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.

    1992-01-01

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

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

    SciTech Connect

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

    2012-10-15

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

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

    PubMed

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

    2014-01-01

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

  5. Preliminary analysis of DHLW (Defense High-Level Waste) glass performance as related to the NRC 10CFR60 slow release limit criterion

    SciTech Connect

    McGrail, B.P.

    1988-07-01

    A preliminary analysis was performed to determine if the dissolution resistance of Defense High-Level Waste (DHLW) glass in silicia-saturated brine is sufficient to meet the Nuclear Regulatory Commission (NRC) fractional release rate requirement for nuclear waste repositories. The sensitivities of fractional release to variations in temperature, surface area, and matrix solubility were also examined. Results indicate that a waste form dissolution resistance strategy is potentially viable for demonstrating compliance with the NRC regulatory requirement. However, major uncertainties exist in two areas: demonstrating that the brine contacting the glass is saturated in silica, and predicting the exposed glass surface area. 12 refs., 4 figs.

  6. Iron oxide nanoparticles stabilized inside highly ordered mesoporous silica

    NASA Astrophysics Data System (ADS)

    Bhaumik, A.; Samanta, S.; Mal, N. K.

    2005-11-01

    Nanosized iron oxide, a moderately large band-gap semiconductor and an essential component of optoelectrical and magnetic devices, has been prepared successfully inside the restricted internal pores of mesoporous silica material through in-situ reduction during impregnation. The samples were characterized by powder XRD, TEM, SEM/EDS, N_{2} adsorption, FT-IR and UV-visible spectroscopies. Characterization data indicated well-dispersed isolated nanoclusters of (Fe_{2}O_{3})_{n}, within the internal surface of 2D-hexagonal mesoporous silica structure. No occluded Fe/Fe_{2}O_{3} crystallites were observed at the external surface of the mesoporous silica nanocomposites. Inorganic mesoporous host, such as hydrophilic silica in the pore walls, directs a physical constraint necessary to prevent the creation of large Fe_{2}O_{3} agglomerates and enables the formation of nanosized Fe_{2}O_{3} particles inside the mesopore.

  7. Favorable Influence of Hydrophobic Surfaces on Protein Structure in Porous Organically-modified Silica Glasses

    PubMed Central

    Menaa, Bouzid; Herrero, Mar; Rives, Vicente; Lavrenko, Mayya; Eggers, Daryl K.

    2008-01-01

    Organically-modified siloxanes were used as host materials to examine the influence of surface chemistry on protein conformation in a crowded environment. The sol-gel materials were prepared from tetramethoxysilane and a series of monosubstituted alkoxysilanes, RSi(OR′)3, featuring alkyl groups of increasing chain length in the R-position. Using circular dichroism spectroscopy in the far-UV region, apomyoglobin was found to transit from an unfolded state to a native-like helical state as the content of the hydrophobic precursor increased from 0–15%. At a fixed molar content of 5% RSi(OR’)3, the helical structure of apomyoglobin increased with the chain length of the R-group, i.e. methyl < ethyl < n-propyl < n-butyl < n-hexyl. This trend also was observed for the tertiary structure of ribonuclease A, suggesting that protein folding and biological activity are sensitive to the hydrophilic/hydrophobic balance of neighboring surfaces. The observed changes in protein structure did not correlate with total surface area or the average pore size of the modified glasses, but scanning electron microscopy images revealed an interesting relationship between surface morphology and alkyl chain length. The unexpected benefit of incorporating a low content of hydrophobic groups into a hydrophilic surface may lead to materials with improved biocompatibility for use in biosensors and implanted devices. PMID:18359512

  8. Fabrication of transparent superhydrophobic silica-based film on a glass substrate

    NASA Astrophysics Data System (ADS)

    Wang, Shing-Dar; Luo, Shih-Shiang

    2012-05-01

    Tetraethoxysilane (TEOS) was hydrolyzed in an acidic environment and then reacted with hexamethyldisilazane (HMDS) to obtain a superhydrophobic transparent film on a glass substrate. The molar ratios of water and ethanol to TEOS, the pH value of the acidic (or basic) water that is used to hydrolyze TEOS, the heat treatment conditions and other factors were investigated systematically to optimize the transmission through, and the contact angle of water on the film. HMDS (total amount of HMDS/TEOS = 2) was divided into 20 parts, which were added into the sol successively to prevent the sudden production of a large quantity of NH3 in a small area of the sol. The optical and hydrophobic properties of the sol gel continued to change after it had been prepared. The conditions that TEOS was hydrolyzed with acidic water at pH 1.2 at 70 °C and the sol gel was aged at 20 °C for 48 h realized transmission of 90.9% and a water contact angle of 154.3°. No additional surface chemistry modification was needed.

  9. Germanate glass as a window for high energy laser systems

    NASA Astrophysics Data System (ADS)

    Bayya, Shyam S.; Chin, Geoffrey D.; Sanghera, Jasbinder S.; Aggarwal, Ishwar D.

    2006-11-01

    A modified Barium Gallo-Germanate glass has been developed as an exit window for high energy lasers operating in the mid-infrared wavelength region. All the physical properties, for application as a window for high energy laser systems have been measured. Absorption loss and thermo-optic coefficient were identified as key in developing the Barium Gallo-Germanate glass for high energy laser applications. A purification method was developed to reduce the absorption loss of the glass from 6x10-2 cm-1 to 2x10-3 cm-1 at 3.8 μm. Manufacturability in large size windows has been demonstrated with the fabrication of an 18” diameter prototype window. Modified Barium Gallo-Germanate glasses have also been developed with lower thermo-optic coefficient resulting in lower optical path distortion.

  10. The glass transition in high-density amorphous ice

    PubMed Central

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

    2015-01-01

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

  11. High strain rate fracture behaviour of fused silica

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

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

    PubMed

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

    2015-08-15

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

  13. High-temperature chlorination-reduction sequence for the preparation of silicon hydride modified silica surfaces.

    PubMed

    Plumeré, Nicolas; Speiser, Bernd; Mayer, Hermann A; Joosten, Dominik; Wesemann, Lars

    2009-01-01

    A general method for the functionalization of silica surfaces with silicon hydride (Si-H) groups is described for four different preparations of silica. The silica surface is reduced in a two-step chlorination-reduction procedure within a simple gas-flow system at high temperatures. After initial dehydroxylation of the silica surface, silicon chloride groups are formed by the reaction with thionyl chloride. The chlorination activates otherwise inaccessible surface siloxane moieties. A high silicon-hydride surface concentration results from the subsequent reduction of the chlorinated surface with hydrogen. The physical properties of the resulting silica are analyzed using scanning electron microscopy, as well as dynamic light scattering and Brunauer-Emmet-Teller measurements. The chlorination-reduction sequence has no significant impact on the structure, surface area and mesopore size of the silica materials used. The surface of the materials is characterized by diffuse reflectance infrared Fourier transform (DRIFT) and (29)Si CP/MAS NMR spectroscopy. The silicon-hydride groups are mostly of the ${{\\rm T}{{3\\hfill \\atop {\\rm H}\\hfill}}}$-type. The use of high temperatures (>800 degrees C) results in the condensation of internal and surface silanol groups. Therefore, materials with both a fully condensed silica matrix as well as a surface free of silanol groups are obtained. The materials are ideal precursors for further molecular silica surface modification, as demonstrated with a ferrocene derivative.

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

    SciTech Connect

    Felmy, Andrew R.

    2004-06-01

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

  15. Elastocapillary bundling of high aspect-ratio metallic glass nanowires

    NASA Astrophysics Data System (ADS)

    Hu, Zhonglue; Uzun, Ceren; Dong, Ziye; Li, Wei; Bernussi, Ayrton A.; Kumar, Golden

    2017-07-01

    Collapsing and bundling of wet nanostructures can be a desirable or an unwanted phenomenon depending on the target application. We study the effect of the aspect-ratio and solvent surface tension on bundling of Pt-based metallic glass nanowires prepared by thermoplastic molding. The results show that the bundling can be quantitatively described by the competition between the Laplacian capillary force and the elastic restoring force. Supercritical CO2 drying can prevent bundling to form vertically aligned metallic glass nanowires with high aspect-ratios (>15). Optical measurements and simulations reveal that the diffuse reflectance of metallic glass nanowires strongly depends on their profile (vertical or bundled).

  16. Study of the glass formation of high temperature superconductors

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

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

    SciTech Connect

    Marra, J.C.

    1995-02-01

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

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

    SciTech Connect

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

    2004-03-29

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

  19. RETENTION OF SULFATE IN HIGH LEVEL RADIOACTIVE WASTE GLASS

    SciTech Connect

    Fox, K.

    2010-09-07

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

  20. Equation of State for a High-Density Glass

    NASA Astrophysics Data System (ADS)

    Mattsson, A. E.

    2004-07-01

    Properties of relevance for the equation of state for a high-density glass are discussed. We review the effects of failure waves, comminuted phase, and compaction on the validity of the Mie-Grüneisen EOS. The specific heat and the Grüneisen parameter at standard conditions for a ρ0 = 5.085 g/cm3 glass ("Glass A") is then estimated to be 522 mJ/g/K and 0.1 - 0.3, respectively. The latter value is substantially smaller than the value of 2.1751 given in the SESAME tables for a high-density glass with ρ0 = 5.46 g/cm3. The present unusual value of the Grüneisen parameter is confirmed from the volume dependence determined from fitting the Mie-Grüneisen EOS to shock data in Ref. [2].

  1. Equation of state for a high-density glass.

    SciTech Connect

    Mattsson, Ann Elisabet

    2003-07-01

    Properties of relevance for the equation of state for a high-density glass are discussed. We review the effects of failure waves, comminuted phase, and compaction on the validity of the Mie-Grueneisen EOS. The specific heat and the Grueneisen parameter at standard conditions for a {rho}{sub 0} = 5.085 g/cm{sup 3} glass ('Glass A') is then estimated to be 522 mJ/g/K and 0.1-0.3, respectively. The latter value is substantially smaller than the value of 2.1751 given in the SESAME tables for a high-density glass with {rho}{sub 0} = 5.46 g/cm{sup 3}. The present unusual value of the Grueneisen parameter is confirmed from the volume dependence determined from fitting the Mie-Grueneisen EOS to shock data in Ref. [2].

  2. Low melting high lithia glass compositions and methods

    DOEpatents

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

    2000-01-01

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

  3. Low melting high lithia glass compositions and methods

    DOEpatents

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

    2003-10-07

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

  4. Low melting high lithia glass compositions and methods

    DOEpatents

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

    2004-11-02

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

  5. A hydrothermal peroxo method for preparation of highly crystalline silica-titania photocatalysts.

    PubMed

    Krivtsov, Igor; Ilkaeva, Marina; Avdin, Viacheslav; Khainakov, Sergei; Garcìa, Jose R; Ordòñez, Salvador; Dìaz, Eva; Faba, Laura

    2015-04-15

    A new completely inorganic method of preparation of silica-titania photocatalyst has been described. It has been established that the addition of silica promotes crystallinity of TiO2 anatase phase. Relative crystallinity and TiO2 crystal size in the silica-titania particles increase with the silica content until SiO2/TiO2 molar ratio of 0.9, but at higher molar ratios they start to decrease. The single-source precursor containing peroxo titanic (PTA) and silicic acids has been proved to be responsible for high crystallinity of TiO2 encapsulated into amorphous silica. It has been proposed that peroxo groups enhance rapid formation of crystalline titania seeds, while silica controls their growth. It has been concluded from the TEM that the most morphologically uniform anatase crystallites covered with SiO2 particles are prepared at SiO2/TiO2 molar ratio of 0.4. This sample, according to (29)Si NMR, also shows the high content of hydroxylated silica Q(3) and Q(2) groups, and it is the most photocatalytically active in UV-assisted decomposition of methylene blue among the tested materials. It has been determined that the increase in the amount of the condensed Q(4) silica in the mixed oxides leads to the decrease in photocatalytic performance of the material, despite its better crystallinity. High crystallinity, low degree of incorporation of Ti atoms in SiO2 in the mixed oxide and adsorption of methylene blue in the vicinity of photoactive sites on the hydroxylated silica have been considered as the main factors determining the high degradation degree of methylene blue in the presence of silica-titania. Copyright © 2014 Elsevier Inc. All rights reserved.

  6. High-pressure structural changes in liquid silica

    NASA Astrophysics Data System (ADS)

    Denoeud, A.; Mazevet, S.; Guyot, F.; Dorchies, F.; Gaudin, J.; Ravasio, A.; Brambrink, E.; Benuzzi-Mounaix, A.

    2016-09-01

    The structural properties of liquid silica at high pressure and moderate temperature conditions, also referred to as the warm dense matter regime, were investigated using time-resolved K -edge x-ray absorption spectroscopy and ab initio calculations. We used a nanosecond laser beam to compress uniformly a solid Si O2 target and a picosecond laser beam to generate a broadband x-ray source. We obtained x-ray absorption spectra at the Si K edge over a large pressure-temperature domain to probe the liquid phase up to 3.6 times the normal solid density. Using ab initio simulations, we are able to interpret the changes in the x-ray absorption near-edge structure with increasing densities as an increase in the coordination number of silicon by oxygen atoms from 4 to 9. This indicates that, up to significant temperatures, the liquid structure becomes akin to what is found in the solid Si O2 phases.

  7. Preparation and characterization of the As40Se60 and As38.8Se61.2 glasses with high quality for the single mode IR glass fiber

    NASA Astrophysics Data System (ADS)

    Oh, Min-Suk; Seo, Inseok

    2015-01-01

    In this paper, high quality chalcogenide infrared-transmitting As40Se60 and As38.8Se61.2 glasses were prepared and characterized for single mode glass fibers. In order to obtain high purity glasses, the starting materials, As and Se (99.9999%), were purified using a distillation method, which required heat treatment under vacuum using silica tubes and a liquid N2 trap system. As40Se60 and As38.8Se61.2 glasses are chosen as core and cladding, respectively. From the differential scanning calorimetry (DSC) results, the glass transition temperature (Tg) of the As40Se60 and As38.8Se61.2 glasses was 183 °C and 173 °C, respectively. Infrared transmission of the two glasses shows good transmittance over the range of 1-12 μm. There is a slight absorption in both glasses at ∼4.4 μm which is related to Se-H bonds. In order to measure the refractive index over the range of ∼2 -12 μm, prisms of 40 mm × 40 mm × 15 mm with 20° angles were made and were carefully polished. It was found that the refractive indices of As40Se60 were slightly higher than those of the As38.8Se61.2.

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

    NASA Astrophysics Data System (ADS)

    Mahood, Gail; Hildreth, Wes

    1983-01-01

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

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

    USGS Publications Warehouse

    Mahood, G.; Hildreth, W.

    1983-01-01

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

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

    PubMed

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

    2014-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

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

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

    SciTech Connect

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

    2010-07-28

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

  13. Formation mechanism of highly luminescent silica capsules incorporating multiple hydrophobic quantum dots with various emission wavelengths.

    PubMed

    Li, Chunliang; Murase, Norio

    2013-12-01

    A synthesis process was reconsidered for encapsulating hydrophobic quantum dots (QDs) into silica capsules with high photoluminescent (PL) efficiency. The process comprises three steps: silanization of QD surfaces, seed formation by assembly of the QDs, and coating of the QD seeds with a silica shell. Analysis of the encapsulation mechanism enabled this process to be adapted for application to CdSe-based core-shell QDs with various organic ligands such as oleic acid and with various emission wavelengths. Formation of the seeds is the key step in synthesizing the silica capsules, so that they have high PL efficiency. Due to the differences in QD size and in the affinity of the ligands on their surfaces, the concentration of QDs used in the synthesis must be optimized to maximize emission efficiency. Contrary to an initial assumption, several ligands remained on the QD surfaces even after the QDs were transferred from organic solution to water. This greatly affected the size and PL efficiency of the seeds. Judicious selection of the conditions for seed and silica capsule synthesis resulted in seeds with PL efficiency greater than 70% and in silica capsules encapsulating multiple CdSe/CdZnS QDs with PL efficiency as high as 41%. Silica capsules incorporating QDs with various emission peak wavelengths from green to red were also prepared. The process presented serves as a guideline for encapsulating various types of hydrophobic QDs into silica capsules for biological tagging applications.

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

    SciTech Connect

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

    1999-03-01

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

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

    DOE PAGES

    Pierce, Eric M.; Kerisit, Sebastien N.; Charpentier, Thibault; ...

    2016-02-27

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

  16. A Silica Long Base Tiltmeter with high Stability and Resolution

    NASA Astrophysics Data System (ADS)

    Boudin, F.; Bernard, P.; Longuevergne, L.; Florsch, N.; Bour, O.; Esnoult, M.; Courteille, C.; Caudal, J.

    2006-12-01

    Two 100 m long silica water tube tiltmeters (based on the communicating vessels' principle) were installed in the French Vosges Massif one along the 37°E direction and the other one along the 127°E direction. This experiment was part of a hydrology research project which started at the end of the year 2004 to study the effect of the hydrological load of an aquifer in the Rhin Valley and the associated crustal flexure. In order to gather relevant data, we need to be able to measure the strain or tilt with high resolution and stability for periods ranging from few minutes to few years. The site is a mine located at 35 km eastward from the large Rhin aquifer. Our instruments have shown a remarkably good stability and resolution (6.5x10-9rad/month) and were even able to detect the toroidal and spheroidal free oscillations of the Earth excited by the two last major earthquakes of Sumatra. Long base Tiltmeters will be a part of future multi-parameters survey projects if they can be installed in a larger variety of sites. After this first hydrological experiment we set up a new pair of long base tiltmeters to observe the influence of a underground aquifer exploited by the town of Ploemeur (Morbihan). Water pumping has been stopped during 41 hours to prompt a variation of volume between 2000 and 4000 m3 inducing a variation of pressure in the cavity. In this multi-parameters survey which included GPS, absolute and relative gravimetric and tiltmetric measurements only the long base tiltmeters have a sufficient resolution to detect the vertical rock deformation of 0.1 to 1 mm over a base of 1000m.

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

    SciTech Connect

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

    1994-12-31

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

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

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

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

  20. High temperature thermographic measurements of laser heated silica

    SciTech Connect

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

    2009-11-02

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

  1. High temperature thermographic measurements of laser heated silica

    NASA Astrophysics Data System (ADS)

    Elhadj, Selim; Yang, Steven T.; Matthews, Manyalibo J.; Cooke, Diane J.; Bude, Jeffrey D.; Johnson, Michael; Feit, Michael; Draggoo, Vaughn; Bisson, Scott E.

    2009-10-01

    In situ spatial and temporal surface temperature profiles of CO2 laser-heated silica were obtained using a long wave infrared (LWIR) HgCdTe camera. Solutions to the linear diffusion equation with volumetric and surface heating are shown to describe the temperature evolution for a range of beam powers, over which the peak surface temperature scales linearly with power. These solutions were used with on-axis steady state and transient experimental temperatures to extract thermal diffusivity and conductivity for a variety of materials, including silica, spinel, sapphire, and lithium fluoride. Experimentally-derived thermal properties agreed well with reported values and, for silica, thermal conductivity and diffusivity are shown to be approximately independent of temperature between 300 and 2800K. While for silica our analysis based on a temperature independent thermal conductivity is shown to be accurate, for other materials studied this treatment yields effective thermal properties that represent reasonable approximations for laser heating. Implementation of a single-wavelength radiation measurement in the semi-transparent regime is generally discussed, and estimates of the apparent temperature deviation from the actual outer surface temperature are also presented. The experimental approach and the simple analysis presented yield surface temperature measurements that can be used to validate more complex physical models, help discriminate dominant heat transport mechanisms, and to predict temperature distribution and evolution during laser-based material processing.

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  3. Highly ytterbium-doped silica fibers with low photo-darkening.

    PubMed

    Suzuki, Shigeru; McKay, Hugh A; Peng, Xiang; Fu, Libin; Dong, Liang

    2009-06-08

    Phosphorus co-doping is known to reduce clustering levels of rare earth ions in silica hosts. In this paper, ytterbium-doped silica fibers with approximately 8.9 wt% Yb(2)O(3), up to approximately 4700 dB/m peak core absorption at 976 nm, and low photo-darkening are demonstrated using high phosphorus co-doping. Measured gain as high as approximately 7 dB/cm is demonstrated in the fiber.

  4. Inexpensive approach for production of high-surface-area silica nanoparticles from rice hulls biomass.

    PubMed

    Palanivelu, Rajagounder; Padmanaban, Periasamy; Sutha, Sadhasivam; Rajendran, Venkatachalam

    2014-12-01

    In this study, we prepared amorphous and crystalline silica nanoparticles from rice hulls biomass using pyrolysis technique at different processing temperatures such as 923, 973, 1023, 1073, 1123 and 1173 K. X-ray fluorescence studies show that the purity of all the synthesised silica nanoparticles is in the range of 98-99.7%. X-ray diffraction studies reveal that amorphous silica nanoparticles are formed at 923-1023 K, whereas crystalline particles at 1073-1173 K. Morphology and microstructure of silica nanoparticles are studied by scanning electron and transmission electron microscopes. Silica nanoparticles obtained at different processing temperatures yield particle size in the range of 6-100 nm. Chemical composition and surface functionalities of the particles are examined by energy-dispersive X-ray diffraction and Fourier transform infrared spectroscopic studies. The developed method effectively uses rice hulls biomass as a green natural source in the synthesis of amorphous and crystalline silica nanoparticles with high-specific surface area. The optimised processing temperature (1023 K) enables amorphous silica nanoparticles to have high-specific surface area of 538 m(2)g(-1).

  5. Nanostructures synthesis by femtosecond laser ablation of glasses

    NASA Astrophysics Data System (ADS)

    Vipparty, D.; Tan, B.; Venkatakrishnan, K.

    2012-10-01

    In this article, we investigate the variations in ablation dynamics that result in diverse nanostructures on SiO2 based glass samples. A three-dimensional fibrous nanoparticle agglomerate was observed on sodalime glass when exposed to femtosecond laser irradiation. The fused nanoparticles have diameters ranging from 30 nm to 70 nm. Long continuous nanofibers of extremely high aspect ratio (certain fibers up to 100 000:1) were obtained by exposing silica glass surface to femtosecond laser irradiation at MHz repetition rate in air. A nanostructure assembly comprising of nanofiber and nanoparticle agglomerates was also observed by ablating silica glass. From our experimental analysis, it was determined that variation in bandgap and material composition alters ablation dynamics and dictates the response of glass to femtosecond laser irradiation, ultimately leading to the formation of structures with varying morphology on silica and sodalime glass. The possible underlying mechanisms that produce such nanostructures on glass specimens have also been explored.

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

    SciTech Connect

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

    2001-06-01

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

  7. High-power 83 W holmium-doped silica fiber laser operating with high beam quality.

    PubMed

    Jackson, Stuart D; Sabella, Alex; Hemming, Alex; Bennetts, Shayne; Lancaster, David G

    2007-02-01

    A high-power 83 W cladding-pumped Tm3+-Ho3+-doped silica fiber laser is reported. Using bidirectional 793 nm diode pumping, a maximum slope efficiency of 42% was produced after a threshold launched pump power of 12 W was exceeded. The laser operated at wavelengths near 2105 nm with moderate beam quality, i.e., M2 approximately 1.5. Further power scaling of the fiber laser was limited by thermal failure of the fiber ends.

  8. High-power 83 W holmium-doped silica fiber laser operating with high beam quality

    NASA Astrophysics Data System (ADS)

    Jackson, Stuart D.; Sabella, Alex; Hemming, Alex; Bennetts, Shayne; Lancaster, David G.

    2007-02-01

    A high-power 83W cladding-pumped Tm3+-Ho3+-doped silica fiber laser is reported. Using bidirectional 793nm diode pumping, a maximum slope efficiency of 42% was produced after a threshold launched pump power of 12W was exceeded. The laser operated at wavelengths near 2105nm with moderate beam quality, i.e., M2˜1.5. Further power scaling of the fiber laser was limited by thermal failure of the fiber ends.

  9. High-power and highly efficient diode-cladding-pumped Ho3+-doped silica fiber lasers.

    PubMed

    Jackson, Stuart D; Bugge, Frank; Erbert, Götz

    2007-11-15

    We demonstrate high-power operation from a singly Ho3+-doped silica fiber laser that is cladding pumped directly with diode lasers operating at 1150 nm. Internal slope efficiencies approaching the Stokes limit were produced, and the maximum output power was 2.2W. This result was achieved using a low Ho3+-ion concentration and La3+-ion codoping, which together limit the transfer of energy between excited Ho3+ ions.

  10. Impurity removal process for high-purity silica production by acid leaching

    NASA Astrophysics Data System (ADS)

    Khalifa, M.; Hajji, M.; Ezzaouia, H.

    2012-06-01

    In our days obtaining silica sand with very high purity is a primordial stage in photovoltaic industry. The effects of acids on the removal of impurity from silica sand have been studied using leaching acids: mixture composed of HF/HCl/H2O with a volume composition of (1:7:24).The obtained material was characterized using Ultraviolet-Visible absorbance (UV-Vis) and Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). Results of the application of this technique show a significant reduction of the amounts of undesirable impurities present in natural silica (such as Co, Fe, Ca, Al, Mg …).

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

    NASA Technical Reports Server (NTRS)

    Drummond, Charles H., III

    1991-01-01

    The softening of glassy grain boundaries in ceramic matrix composites and Si3N4 at high temperatures reduces mechanical strength and the upper-use temperature. By crystallizing this glass to a more refractory crystalline phase, a material which performs at higher temperatures may result. Three systems were examined: a cordierite composition with ZrO2 as a nucleating agent; celsian compositions; and yttrium silicate glasses both in bulk and intergranular in Si3N4. For the cordierite compositions, a series of metastable phases was obtained. The crystallization of these compositions was summarized in terms of metastable ternary isothermal sections. Zircon formed at the expense of ZrO2 and spinel. In SiC composites, the transformations were slower. In celsian, two polymorphs were crystallized. One phase, hexacelsian, which always crystallized, even when metastable, had an undesirable volume change. The other phase, celsian, was very difficult to crystallize. In yttrium silicate bulk glasses, similar in composition to the intergranular glass in Si3N4, a number of polymorphs of Y2Si2O7 were crystallized. The conditions under which these polymorphs formed are compared with crystallization in Si3N4.

  12. Fluorinated epoxy resins with high glass transition temperatures

    NASA Technical Reports Server (NTRS)

    Griffith, James R.

    1991-01-01

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

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

    SciTech Connect

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

    2015-07-01

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

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

    SciTech Connect

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

    2014-04-01

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

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

    PubMed Central

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

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

  17. High-throughput drawing and testing of metallic glass nanostructures.

    PubMed

    Hasan, Molla; Kumar, Golden

    2017-03-02

    Thermoplastic embossing of metallic glasses promises direct imprinting of metal nanostructures using templates. However, embossing high-aspect-ratio nanostructures faces unworkable flow resistance due to friction and non-wetting conditions at the template interface. Herein, we show that these inherent challenges of embossing can be reversed by thermoplastic drawing using templates. The flow resistance not only remains independent of wetting but also decreases with increasing feature aspect-ratio. Arrays of assembled nanotips, nanowires, and nanotubes with aspect-ratios exceeding 1000 can be produced through controlled elongation and fracture of metallic glass structures. In contrast to embossing, the drawing approach generates two sets of nanostructures upon final fracture; one set remains anchored to the metallic glass substrate while the second set is assembled on the template. This method can be readily adapted for high-throughput fabrication and testing of nanoscale tensile specimens, enabling rapid screening of size-effects in mechanical behavior.

  18. Highly evolved rhyolitic glass compositions from the Toba Caldera, Sumatra

    SciTech Connect

    Chesner, C.A.

    1985-01-01

    The quartz latite to rhyolitic ash flow tuffs erupted form the Toba Caldera, perhaps the largest caldera on earth (100 by 30 kms), provide the unique opportunity to study a highly differentiated liquid in equilibrium with numerous mineral phases. Not only are the rocks very crystal rich (30-50%), but at present a minimum of 15 co-existing mineral phases have been identified. Both whole-rock and glass analyses were made by XRF techniques providing data on both major and trace elements. Whole rock chemistry of individual pumices from the youngest eruption at Toba (75,000 years ago), are suggestive of the eruption of two magma compositions across a boundary layer in the magma chamber. Glass chemistry of the pumices also show two distinct liquid compositions. The more silicic pumices, which have the most evolved glass compositions, are similar to the whole rock chemistry of the few aplitic pumices and cognate granitic xenoliths that were collected. This highly evolved composition resulted from the removal of up to 15 mineral phases and may be a fractionation buffered, univariant composition. The glasses from the less silicic pumices are similar to the whole rock chemistry of the more silicic pumice, thus falling nicely on a fractionation trend towards the univariant composition for these rocks. This set of glass compositions allows an independent test for the origin of distal ashes thought to have erupted from Toba and deposited in Malaysia, the Indian Ocean, and as far away as India.

  19. HIGH-LEVEL WASTE GLASS FORMULATION MODEL SENSITIVITY STUDY 2009 GLASS FORMULATION MODEL VERSUS 1996 GLASS FORMULATION MODEL

    SciTech Connect

    BELSHER JD; MEINERT FL

    2009-12-07

    This document presents the differences between two HLW glass formulation models (GFM): The 1996 GFM and 2009 GFM. A glass formulation model is a collection of glass property correlations and associated limits, as well as model validity and solubility constraints; it uses the pretreated HLW feed composition to predict the amount and composition of glass forming additives necessary to produce acceptable HLW glass. The 2009 GFM presented in this report was constructed as a nonlinear optimization calculation based on updated glass property data and solubility limits described in PNNL-18501 (2009). Key mission drivers such as the total mass of HLW glass and waste oxide loading are compared between the two glass formulation models. In addition, a sensitivity study was performed within the 2009 GFM to determine the effect of relaxing various constraints on the predicted mass of the HLW glass.

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

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

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