Borosilicate Glass Fiber Research Articles

Polarization mode coupling in circularly birefringent gratings.

Polarization mode coupling in circularly birefringent gratings is analyzed. It is numerically found that efficient LP01x-LP02y mode coupling (where LP is linear polarization) is possible in a 50-cm-long circularly birefringent fiber grating formed in a terbium-doped borosilicate glass fiber and that complete LP01x-LP02y and LP01x-LP03y mode couplings result after a few-centimeter-long circularly birefringent grating that is formed in a bismuth-substitute iron garnet waveguide. Various parameters of polarization mode coupling in a number of circularly birefringent gratings are also computed.

Sintering behaviour of composite materials borosilicate glass-ZrO2 fibre composite materials

The characteristics and properties of mixtures of a borosilicate glass and ZrO2 fibres obtained from compacts isothermally sintered are presented. Three different particle sizes of glass powder and different sintering temperatures and times have been used to reveal the influence of the specific surface area and the glass matrix viscosity on sintering. The fundamental developed aspects are the sintering kinetics, the dense material characterisation and the study of the sintering mechanisms. The composite materials are suitable for sealing molten carbonate fuel cells (MCFC). # 2002 Elsevier Science Ltd. All rights reserved.

ESTIMATING ROCK AND SLAG WOOL FIBER DISSOLUTION RATE FROM COMPOSITION

A method was tested for calculating the dissolution rate constant in the lung for a wide variety of synthetic vitreous silicate fibers from the oxide composition in weight percent. It is based upon expressing the logarithm of the dissolution rate as a linear function of the composition and using a different set of coefficients for different types of fibers. The method was applied to 29 fiber compositions including rock and slag fibers as well as refractory ceramic and special-purpose, thin E-glass fibers and borosilicate glass fibers for which in vivo measurements have been carried out. These fibers had dissolution rates that ranged over a factor of about 400, and the calculated dissolution rates agreed with the in vivo values typically within a factor of 4. The method presented here is similar to one developed previously for borosilicate glass fibers that was accurate to a factor of 1.25. The present coefficients work over a much broader range of composition than the borosilicate ones but with less accuracy. The dissolution rate constant of a fiber may be used to estimate whether disease would occur in animal inhalation or intraperitoneal injection studies of that fiber.

ESTIMATING IN VITRO GLASS FIBER DISSOLUTION RATE FROM COMPOSITION

A method is presented for calculating the dissolution rate constant of a borosilicate glass fiber in the lung, as measured in vitro, from the oxide composition in weight percent. It is based upon expressing the logarithm of the dissolution rate as a linear function of the composition. It was found that the calculated dissolution rate constant agreed with the measured value within the variation of the measured data in a set of compositions in which the dissolution rate constant ranged over a factor of 100. The method was shown to provide a reasonable estimate of dissolution over a considerably wider range of composition than what was used to determine the parameters, such as a set of data in which the dissolution rate constant varied over a factor of 100,000. The dissolution rate constant may be used to estimate whether disease would ensue following animal inhalation or intraperitoneal studies.

Dissolution mechanisms of boro-silicate glass fibres in saline solution with added dissolved silica

Experiments of dissolution of a soluble boro-silica glass were performed at 37°C in a saline solution without and with 50, 75 and 100 ppm of added silica. After reaction silica concentration was measured by AAS and colorimetry and fibers were investigated by SEM-EDS and XPS. The results give informations on the dissolution velocity of the glass and the factors controlling the formation rate of the gel layer and its composition. The dissolution velocity measured at the unaltered glass-gel interface is not significantly decreased by the silica concentration in solution whatever its origin (leaching of the glass fibres or initial addition). Accordingly, gel formation is controlled by the chemical reactions rate at, or near, the boundary of the unaltered core. The composition and the stucture of the gel layer are depending on the silica concentration in solution above a threshold of about 50 ppm. The framework of the gel appears to play the more important role in the dissolution velocity of the glass.

Optimisation of Hollow Glass Fibres and their Composites

Hollow glass fibre reinforced plastics have a structural performance niche in a class of their own. They offer increased flexural rigidity compared to solid glass fibre reinforced plastics, they offset the need for thin sandwich construction which is both difficult and expensive, and they provide an opportunity to develop laminates with improved or tailored characteristics. An experimental hollow glass fibre manufacturing facility is in operation at the University of Bristol. The facility is capable of drawing precision hollow glass fibres of various diameters with varying degrees of hollowness under precise parameter control. Hollow borosilicate glass fibres have been manufactured from tubular preforms with a variety of internal and external diameters, which correspond to a range of hollowness values. In all cases, the resulting hollowness was reduced from that present in the preform state, regardless of drawing rate or furnace temperature. In fact, temperature has been demonstrated to be of paramount importance in controlling fibre hollowness due to the interaction between glass viscosity and surface tension effects. These results suggest that for a given temperature and draw rate there is a single condition where fibre hollowness is maximised and external diameter minimised.

Measurement of the refractive index of glass fibers by the Christiansen-Shelyubskii method

The Christiansen principle was employed to measure the refractive index of borosilicate glass fibers (13–41 μm diameter) over the visible range. The refractive index for glass fibers at 589.3 nm was measured by temperature and wavelength scan and values obtained were in close agreement. The refractive index for glass fibers as a function of wavelength was measured to an accuracy of < 10 −4. The uniformity of the refractive index for a bundle of fibers of slightly different diameter was calculated using the modified Shelyubskii method and compared to experimental values. Theoretical calculations of the transmission by the present work suggest that, for high optical clarity and transmission of Christiansen cell (or transparent composite consisting of glass fiber and polymer), the refractive index must be controlled to the fifth decimal place. For example, the maximum transmission of a fiber/liquid mixture cell at 25°C can increase from 89 to 97% when the standard deviation is reduced from 13 × 10 −5 to 9 × 10 −5.

Change in Refractive Index of a Borosilicate Glass Fiber Annealed Below the Glass Transformation Temperature

Glass fibers pulled from multihole bushings can have a slight difference in thermal history that causes a distribution in the refractive index that can be narrowed by annealing the fibers. The kinetics for the initial stage change in refractive index for fiber annealed between 300° and 500°C are best described by a second‐order reaction with an activation energy of 120° 17 kj/mol. The improved uniformity in refractive index for annealed fibers is indicated by a decrease in the half‐height width of the optical transmission versus temperature curve for glass fiber immersed in a liquid. The standard deviation in the refractive index of glass fibers with a bimodal distribution in diameter decreases from 8 × 10‐4≤0.0002 to 4 × 10‐4 0.0002 after the fibers are annealed at 400°C for 1 h.

Recovery of Bromine from Waste Gas‐Phase Hydrogen Bromide Streams Using an Electrolytic Membrane

An electrochemical cell is used to demonstrate a significant improvement in the recovery of bromine from waste gas‐phase hydrogen bromide (HBr) streams. The continuous process operates at 300°C and utilizes reticulated vitreous carbon gas‐diffusion electrodes, a molten Br electrolyte, and borosilicate glass fiber membrane. HBr is simultaneously electrolytically decomposed and separated into a hydrogen enriched waste stream and pure anhydrous product stream. Simulated industrial waste streams containing HBr, nitrogen, water vapor, and organic compounds have been tested. These results include removals of greater than 90% and current densities approaching 1.0 A/cm2.

Dissolution kinetics of glass fibres in saline solution: in vitro persistence of a sparingly soluble aluminium-rich leached layer

The dissolution of boro-silicate glass fibres in physiological saline solution was studied at 37°C either in a non-refilled or in a periodically refilled reactor. Large variations of the weight losses were observed with time and refilling frequencies. The weight losses were found to increase with the refilling frequency. Sections of altered fibres, studied using scanning electron microscopy, show an outer hydrated layer surrounding an unaltered glass core. The residual silicon- and aluminium-rich hydrated layer (Al/Si=0.2, H2O/Al=16–19) was characterized by X-ray photoelectron spectrometry, energy dispersive spectrometry and thermogravimetric analysis. The thickness of the hydrated layer may be theoretically calculated from the degree of reaction progression. Under unsteady state conditions, most of the dissolution occurs at the fresh glass-hydrated layer boundary, through selective processes. The proposed model explains the persistence of the aluminium-rich residue when dissolution proceeds in non-replenished systems.

Pyrolysis of arylglycol-β-propylphenyl ether lignin model in the presence of borosilicate glass fibers.: I. Pyrolysis reactions of β-ether compounds

Two β-aryl ether type model compounds, guaiacylglycol- and veratrylglycol-β-propylphenyl ethers, were copyrolyzed with borosilicate glass fibers. The results provided a better understanding of the effect of copyrolysis with the fibers on the yields of lignin-derived products from lignocellulosics. The observed products indicated the following reactions occurring in the models; (1) cleavage of the Cα-aromatic ring bond, (2) cleavage of the β-ether bond, (3) cleavage of the Cα-Cβ bond, (4) α,β-dehydration, and (5) demethylation, and others. Of these reactions, reactions (1), (2) and (4) were the main pyrolysis reactions and fully explained the increase in the total yield of lignin-derived pyrolysis products from Japanese red pine ( Pinus densiflora Sieb. et Zucc.) in the presence of borosilicate glass fibers. Reaction (1) was a particularly characteristic reaction in copyrolysis with the fibers. Important reactions relating to the increase in the total yield of lignin-derived pyrolysis products were reproduced on the models used.

Microstructure of glass fibre reinforced water resistant gypsum binder composites

The microstructure at the interface was studied in case of glass fibre reinforced gypsum binder composites exposed to water, accelerated ageing, i.e. alternate wetting and drying cycles at 27° to 60°C and to natural weathering. After 50 wetting and drying cycles at 60°C, deposition of gypsum binder products was observed in an irregular manner at the surface and in between glass fibre strands. Durability of E-type glass (borosilicate glass) fibres used as reinforcement in the water resistant gypsum binder composites has been assessed after exposure to aqueous extract of gypsum binder at temperature 27° to 60°C. The extracted glass fibres were characterized by scanning electron microscope and weight loss. Up to 40°C, no damage to glass fibres was noticed but at 50°C and 60°C, the glass fibres are attacked and erosion of glass surface takes place leading to the weakening of the interfacial bond at the matrix and fibre interface. A correlation between the durability of glass fibre and its weight loss was established. The loss in durability of glass fibre governs the flexural strength of gypsum binder composites tested under accelerated ageing.

Fabrication and Mechanical Properties of an Optically Transparent Glass Fiber/Polymer Matrix Composite

A composite with substantial optical transparency was produced by rein forcing poly(methyl methacrylate) (PMMA) with unidirectional borosilicate glass fibers. Optical transparency of the composite was achieved by matching the refractive index ( n D) of the glass fiber and polymer matrix to within ±0.002. The optical transmission of the composite decreased with increasing volume percentage of glass fibers. Composites con taining 30 volume percent of unidirectional 12 μm diameter fibers had a transmission at 589.3 nm of 20 percent measured through a 10 mm thickness. Composites containing 30 volume percent of 56 μm diameter fibers had an optical transmission of 45 percent. Type written text could be clearly read through the composite when it was laid directly on a printed page. Composites with 40 volume percent fiber had a flexural strength of 600 MPa which is six times greater than that of pure PMMA. The flexural modulus for the same composite was 18 MPa which is nine times greater than the 2 MPa measured for pure PMMA. The work of fracture was 110 kJ/m 2 or more than double the 45 kJ/m2 for pure PMMA. Suggestions are made for further improvements in the optical properties.

Study of the high purity and ultrafine silica fibre

The effects of leaching time, temperature and the concentration of the acid solution on the purity of the drawn sodium borosilicate glass fibres were systematically studied. The high purity and ultrafine silica fibres were obtained by acid leaching method. The law of leaching non-siliceous constituents was found. Furthermore, leaching mechanism is discussed, which can be considered as a process of ion exchange and diffusion.

Analysis of lignin by pyrolysis-gas chromatography. I. Effect of inorganic substances on guaiacol-derivative yield from softwoods and their lignins

To obtain lignin-derived pyrolysis products in larger yields, Curie-point pyrolysis was performed on the softwood species Japanese red pine ( Pinus densiflora Sieb. et Zucc.), Japanese cedar ( Cryptomeria japonica D. Don) and Japanese cypress ( Chamaecyparis obtusa Endl.), and their dioxane lignins treated with various inorganic substances, over the temperature range 358–764°C. The resulting guaiacol derivatives (guaiacol, 4-methyl-, 4-ethyl- and 4-vinylguaiacols, eugenol, vanillin, cis- and trans-isoeugenol, and acetovanillone) were determined by gas chromatography. The softwood samples sandwiched between two sheets of heat-resistant filter paper made of borosilicate glass fibers yielded from 1.56 to 1.64 times more guaiacol derivatives than unsandwiched samples. Sandwiching the dioxane lignins between heat-resistant papers also increased the guaiacol-derivative yield, by 13 to 27%. The sandwich-2 method developed in this study is widely applicable as a sample preparation method for increasing the yield of lignin-derived products on Curie-point pyrolysis.

Performance of High-Strength Borosilicate Glass Fiber Versus Graphite Fiber in Nylon

Abstract The advantages of using graphite fibers in reinforcing nylon over “E”-type glass fibers include differences in properties such as reduced shrinkage, increased Rockwell hardness at lower reinforcement levels of 10 and 20%, tensile strength increase of 30 to 40%, flexural strength increase of 25 to 30%, and an increase in modulus that is double to triple that of conventional “E”-type glass fiber reinforcements. Graphite fibers also provide some additional advantages such as static dissipation, low specific gravity, low thermal expansion, high fatigue resistance, and thermal conductivity.

Sieving Techniques in Palynological Sample Processing with Special Reference to the MRA System

Sieving Techniques in Palynological Sample Processing with Special Reference to the MRA System

Boron Coordination in Rapidly Cooled and in Annealed Aluminum Borosilicate Glass Fibers

The fraction of four‐coordinated boron was observed to increase from 10% in a rapidly cooled aluminum borosilicate glass fiber to 16% in the same fiber after it was annealed; the refractive index also increased. The index of the annealed fiber agreed with that of the bulk glass. Crystallization was not observed in the annealed fiber. It is concluded that boron coordination is temperature dependent and associated with structural relaxation.

Investigation of the state of polarization of light in a single-mode fiber waveguide

An analysis is made of the polarization anisotropy of a single-mode fiber with a twisted elliptic core. The Jones matrix is obtained and the complex function of the state of polarization of light in a fiber is investigated. The results are reported of measurements of the linear and circular birefringence of a borosilicate single-mode glass fiber.

Birefringence caused by thermal stress in elliptically deformed core optical fibers

Birefringence and polarization dispersion introduced by thermal stress in single-mode fibers with elliptical core are formulated here in terms of fiber structure parameters, thermal expansion coefficients, and thermoelastic constants. Thermal stress distribution and birefringence characteristics are estimated within first-order perturbation with respect to fiber core ellipticity. Normalized frequency dependence of birefringence and polarization dispersion is also derived in this paper. Birefringence and polarization dispersion in elliptical core fiber are seen to depend on thermal stress rather than geometrical anisotropy for relatively small relative index differences. Numerical examples are presented for germanosilicate, borosilicate, and phosphosilicate glass fibers.