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Silica Glass (silica + glass)
Selected AbstractsStructural Changes in Silica Glass by Continuous-Wave Laser Backside IrradiationJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2010Hirofumi Hidai We report on a permanent change in the physical properties inside silica glass by rapid heating and quenching using a continuous-wave laser beam. The absorption of the glass was enhanced by laser heating, and the heated spot moved as a result of thermal radiation and conduction. To trigger heating, an absorbent material was placed on the backside of a glass plate and irradiated through the glass. Laser illumination with a power of 11 W focused on the absorbent material induced a cylindrical modified zone along the laser beam with a length of up to 5.5 mm that was modified at a rate of ,130 mm/s. The characteristics of the modified silica glass were studied. The modified area consists of two layers, and the diameters of the inner and outer zones are ,40 and ,55 ,m, respectively. The inner zone was modified by laser heating. The fictive temperature is estimated to be ,1900 K. The etch rate and hardness of the modified glass increased owing to the increment of the fictive temperature. The outer zone was modified by tensile stress due to the densification of the inner zone. In the outer zone, the etch rate is increased and hardness is decreased. [source] Photonic Crystal Fibers and Their ApplicationsIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 6 2009Osamu Tohyama Member Abstract Dramatic advances in research and development on photonic crystal fibers (PCF) have created new properties that had not been achievable using conventional fibers. PCFs have many fascinating features. The very high relative refractive index between the fiber core and air-hole cladding enables several prominent properties, notably endlessly single-mode (ESM) operation, high nonlinearity, wide-ranging dispersion management, and the ability to maintain high polarization. The processes involved in manufacturing PCFs are quite different from those used to manufacture conventional fibers, and this is largely because of the profusion of air holes in the silica glass that comprises PCFs. The authors have optimized the technology to manufacture photonic crystals with the required optical characteristics. This paper describes the properties and application of large-mode and ESM guidance, nonlinearity, and double cladding. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Fabrication and Application of an Oxide Thermoelectric SystemINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 4 2007Ryoji Funahashi A plate-shaped thermoelectric module was prepared using 140 pairs of p -type Ca3Co4O9 (Co-349) and n -type LaNiO3 (Ni-113) bulks. The hot-pressed thermoelectric oxide bulks were connected with an Ag paste, incorporating oxide powder, and Ag sheets. The module's open-circuit voltage increases with increasing hot-side temperature (TH) and reaches 4.5 V at a TH of 1072 K in air. No deterioration in output power was seen when power generation was carried out 10 times at a TH of 723 K with intermediate cooling to room temperature. The module was successfully used to charge a lithium-ion battery in a mobile phone. Thermoelectric modules composed of p -type Co-349 and n -type CaMnO3 (Mn-113) bulks, which have a pipe shape, were constructed using Ag electrodes and stainless-steel tubes. The devices were connected with the stainless-steel tube coated with ZrO2 by thermal spray using a dielectric paste composed of silica glass and iron oxide. Power generation was carried out in flame by combustion of natural gas. Water flowed inside the stainless-steel tube for cooling. One module consisting of 54 pairs of legs can generate 1.5 V, 0.28 W, and steam simultaneously by installing in an instantaneous water heater. Power generation was carried out four times with intermediate cooling. Deterioration in the open-circuit voltage of the module was not observed after the fourth combustion. [source] One-Pot Homogeneous and Heterogeneous Oxidation of Glycerol to Ketomalonic Acid Mediated by TEMPOADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 3 2003Rosaria Ciriminna Abstract Glycerol, an increasingly abundant by-product of biodiesel production, is selectively converted to ketomalonic acid in one pot at pH 10 using NaOCl as regenerating oxidant in water at 2,°C in the presence of catalytic Br, along with the radical TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl). The reaction can also be conducted at completion over a sol-gel silica glass doped with the nitroxyl radical. Considering the stability and versatility of such doped glasses, these materials show real promise as reusable metal-free catalysts for the conversion of a readily available and renewable biofeedstock into a highly valued compound. [source] Low-wavenumber Raman scattering spectroscopy in studies of new gallium-doped silica glass-based transparent vitroceramic mediumJOURNAL OF RAMAN SPECTROSCOPY, Issue 8 2001R. Ceccato Optically transparent, silica glass-based vitroceramic material doped with gallium oxide was obtained by standard glass fusion and appropriate thermal treatments. Low-wavenumber Raman scattering spectroscopy allowed the determination of the microstructure and in particular the size distribution of nanoparticles embedded in the amorphous matrix. The nanocrystal growth was accurately controlled by heat treatment conditions. Transmission electron microscopy and X-ray diffraction measurements revealed the presence of a single crystalline phase, spherical-shaped nanoaggregates, homogeneously distributed in the transparent composite medium. Copyright © 2001 John Wiley & Sons, Ltd. [source] Structural Changes in Silica Glass by Continuous-Wave Laser Backside IrradiationJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2010Hirofumi Hidai We report on a permanent change in the physical properties inside silica glass by rapid heating and quenching using a continuous-wave laser beam. The absorption of the glass was enhanced by laser heating, and the heated spot moved as a result of thermal radiation and conduction. To trigger heating, an absorbent material was placed on the backside of a glass plate and irradiated through the glass. Laser illumination with a power of 11 W focused on the absorbent material induced a cylindrical modified zone along the laser beam with a length of up to 5.5 mm that was modified at a rate of ,130 mm/s. The characteristics of the modified silica glass were studied. The modified area consists of two layers, and the diameters of the inner and outer zones are ,40 and ,55 ,m, respectively. The inner zone was modified by laser heating. The fictive temperature is estimated to be ,1900 K. The etch rate and hardness of the modified glass increased owing to the increment of the fictive temperature. The outer zone was modified by tensile stress due to the densification of the inner zone. In the outer zone, the etch rate is increased and hardness is decreased. [source] Toward Deterministic Material Removal and Surface Figure During Fused Silica Pad PolishingJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2010Tayyab I. Suratwala The material removal and surface figure after ceria pad polishing of fused silica glass have been measured and analyzed as a function of kinematics, loading conditions, and polishing time. Also, the friction at the workpiece/lap interface, the slope of the workpiece relative to the lap plane, and lap viscoelastic properties have been measured and correlated to material removal. The results show that the relative velocity between the workpiece and the lap (i.e., the kinematics) and the pressure distribution determine the spatial and temporal material removal, and hence the final surface figure of the workpiece. In cases where the applied loading and relative velocity distribution over the workpiece are spatially uniform, a significant nonuniformity in material removal, and thus surface figure, is observed. This is due to a nonuniform pressure distribution resulting from: (1) a moment caused by a pivot point and interface friction forces; (2) viscoelastic relaxation of the polyurethane lap; and (3) a physical workpiece/lap interface mismatch. Both the kinematics and these nonuniformities in the pressure distribution are quantitatively described, and have been combined to develop a spatial and temporal model, based on Preston's equation, called Surface Figure or SurF. The surface figure simulations are consistent with the experiment for a wide variety of polishing conditions. This study is an important step toward deterministic full-aperture polishing, allowing optical glass fabrication to be performed in a more repeatable, less iterative, and hence more economical manner. [source] Crack Tip Morphology of Slowly Growing Cracks in GlassJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2000Stéphane Hénaux We present atomic force microscopy (AFM) observations of crack tips in glass during subcritical propagation. These have been obtained by means of an AFM sample holder which has been specially designed to propagate indentation cracks in glass plates. Crack tips in soda,lime,silica glass are always preceded by a few nanometers deep deformation. In vitreous silica, no other surface deformation than the crack itself could be detected. For both materials, the crack opening is found to largely exceed the elastic solution. [source] Silica as a shock index in shergottites: A cathodoluminescence studyMETEORITICS & PLANETARY SCIENCE, Issue 7 2005Hasnaa CHENNAOUI AOUDJEHANE Determining its structural state as either silica glass, quartz, cristobalite, tridymite, coesite, stishovite, or post-stishovite could provide informations about their shock history. The purpose of this work is to assess the shock intensity in shergottites using two spectroscopic methods. On a conventional polished section, a scanning electron microscope (SEM) enables us to study the cathodoluminescence (CL) of silica at variable magnification. The results were crosschecked by systematic Raman spectroscopy of the selected areas. CL spectra differ substantially from one another and enable separating stishovite, high and low pressure silica glass, quartz, and cristobalite. We studied a set of five shergottites: Northwest Africa (NWA) 480, NWA 856, Zagami, Shergotty, and Los Angeles. Stishovite is common in Shergotty, Zagami, NWA 856, and NWA 480 and absent in the studied section of Los Angeles. High-pressure glass is very common, particularly in close association with stishovite. According to the textural relationship, it may be a product of the retromorphosis (amorphization during decompression) of stishovite. Large stishovite areas result from the transformation of preexisting low-pressure silica crystals, while needles result from the high-pressure transformation of pyroxene to glass (melt) and silica. In the latter case, they are found in melt pockets and represent a small fraction of areas of overall pyroxene composition. Needles exhibit square sections of about 1 ,m. Silica spots identical to those described previously as post-stishovite are found in Shergotty, Zagami, NWA 480, and NWA 856. At present, the spectroscopic distinction of post-stishovite from stishovite is difficult. Post-stishovite is destroyed under the Raman beam, and CL spectra are possible mixtures of several phases (e.g., glass and post-stishovite). It is concluded that the shock intensity is highly heterogeneous, and the pressure probably exceeded 60 GPa in all shergottites studied here. [source] Multi-generational carbonate assemblages in martian meteorite Allan Hills 84001: Implications for nucleation, growth, and alterationMETEORITICS & PLANETARY SCIENCE, Issue 1 2004Catherine M. CORRIGAN These regions contain familiar forms of carbonate, as well as textural forms previously unreported including carbonate rosettes, planiform "slab" carbonates, distinct "post-slab" magnesites, and carbonates interstitial to feldspathic glass and orthopyroxene. Slab carbonates reveal portions of the carbonate growth sequence not seen in the rosettes and suggest that initial nucleating compositions were calcite-rich. The kinetically controlled growth of rosettes and slab carbonates was followed by an alteration event that formed the magnesite-siderite layers on the exterior surfaces of the carbonate. Post-slab magnesite, intimately associated with silica glass, is compositionally similar to the magnesite in these exterior layers but represents a later generation of carbonate growth. Feldspathic glasses had little or no thermal effect on carbonates, as indicated by the lack of thermal decomposition or any compositional changes associated with glass/carbonate contacts. [source] | |||||||||||||