Glass Ceramic Fibers Research Articles

Effect of water conditioning on the fracture behavior of PA12 composites processed by selective laser sintering

This study aims to elucidate the combined effects of reinforcing particles and water on PA12 processed by selective laser sintering (SLS). PA12 is one of the toughest polyamides. However, PA12 processed by SLS is rather brittle due to the presence of voids and the relative low molecular weight of the polymers used in SLS. It is demonstrated that humidity impoverishes the mechanical properties of neat PA12, including ductility and toughness. A ductile/brittle transition was detected, which was attributed to the competition between the plasticizing effect and the hydrolization of PA12 molecules plus the increase in crystallinity which counteracted this mechanism. It has been found that addition of hard particles, such as glass spheres and ceramic fibers, prevents the ductile/brittle transition by water conditioning at high temperature to happen.

Er-doped and Er, Yb co-doped oxyfluoride glasses and glass–ceramics, structural and optical properties

The selected glasses and glass–ceramics pertinent to following chemical composition in mol%:48%SiO 2–11%Al 2O 3–7%Na 2O–10%CaO–10%PbO–11%PbF 2–3%ErF 3 and 48%SiO 2–11%Al 2O 3–7%Na 2O–10%CaO–10%PbO–10%PbF 2–1%ErF 3–3%YbF 3 have been manufactured from high purity components (Aldrich) at 1450 °C in normal atmosphere. Glass optical fibers were successfully drawn. Subsequently they were subject to the heat-treatment at 700 °C in various time periods. The preceding differential thermal analysis (DTA) studies allowed estimating both the fiber drawing temperature and the controlled crystallization temperature of glass fibers. It has been observed that the controlled heat-treatment of oxyfluoride glass fibers results in the creation of Pb 5Al 3F 19, Er 4F 2O 11Si 3 and Er 3FO 10Si 3 crystalline phases. The identified phases were characterized by X-ray powder diffraction (XRD) and confirmed by selected area electron diffraction (SAED). The fibers consist of mixed amorphous–crystalline microstructure with nano-crystals of size even below 10 nm distributed in the glassy host. Their morphology was investigated applying high-resolution transmission electron microscopy. Optical properties and excited state relaxation dynamics of optically active ions (Er 3+, Yb 3+) in glass and glass–ceramics have been studied. Based on absorption spectra the Judd–Ofelt analysis was carried out. The main attention was directed to NIR luminescence at. 1.6 μm related to 4I 13/2 → 4I 15/2 Er 3+ and less effective emission associated with 4I 11/2 → 4I 15/2 Er 3+ and 2F 5/2 → 2F 7/2 Yb 3+ transitions. The dissimilar spectroscopic properties have been revealed for glasses and glass–ceramic samples, respectively. The reduction of emission linewidth at 1.6 and 1.0 μm combined with substantial increase of 4I 13/2 lifetimes of erbium in glass–ceramics appear to be evidences that Er 3+ ions are accommodated in crystalline phases. The structural and optical characteristics of oxyfluoride glass–ceramic fibers indicate that these optical systems may be considered as promising materials for Er-doped optical amplifiers operating within third telecommunication window.

Porous ceramic fiber glass matrix composites for solid oxide fuel cell seals

Porous ceramic fiber glass matrix composites with porosities of 19–24% were prepared with mixtures of a glass and short alumino-silicate ceramic fibers for the sealing of solid oxide fuel cells. The sealing performance was evaluated by measuring leak rates at the seal operation temperature of 650 °C and by investigating adherence at seal–metal interfaces after the seal test. Composite seals prepared with 55 vol% glass in the mixture showed a leak rate of ∼105 sccm/cm and did not adhere to the metal tube. Leak rate could be reduced to ∼0.003 sccm/cm when using composite seals prepared with 65 vol% glass. The maximum size of the pores present at the seal interface was estimated from the standard leak rate by assuming a single leak hole.

Nickel-doped nanocrystalline glass-ceramic fiber

The spectroscopic properties of Ni(2+)- doped nanocrystalline glass-ceramic fibers are reported. The cerammed fibers show strong fluorescence with peak wavelength at 1250 nm, 3-dB bandwidth at ~250nm, measured lifetimes at >1ms, and low-fluorescence saturation powers (~35mW) for 980-nm diode pumping. Current diode-pumped output powers are ~100microW .

Efficient neodymium-doped glass-ceramic fiber laser and amplifier

We report an efficient glass-ceramic fiber laser and show that its slope efficiency (~30%) is not compromised by the presence of Nd-doped fluoride crystals embedded within the core of the single-mode optical fiber. In contrast, the spectroscopy (fluorescence and gain spectrum) of the Nd(3+) ions is dramatically changed by the ceramming process, an indication of strong partitioning of the rare-earth ions into the CdF(2):PbF(2):YF(3) crystal environment. The enormous potential for a new range of optical devices based on transparent glass-ceramic materials is highlighted.

INHIBITION OF CYTOKINESIS BY ASBESTOS AND SYNTHETIC FIBRES

Using high-resolution timelapse microscopy, we have followed individual phagocytized fibres through the later stages of division in MeT-5A human mesothelial cells and LLC-MK2monkey epithelial cells. The fibres used were crocidolite and chrysotile asbestos, fibrous glass (MMVF), and refractory ceramic fibres (RCF). Long fibres (15–80μm) trapped within the cleavage furrow can partially or completely block cytokinesis. Cells proceed in one of three ways: (1) eventual completion of cytokinesis; (2) incomplete cytokinesis, resulting in two cells joined by a fibre-containing intercellular channel; or (3) failure of cytokinesis, resulting in a binucleate or trinucleate cell. Two factors associated with fibre-induced bi/trinucleation are: (1) an initial association between the fibre and the forming daughter nuclei, which is sometimes lost over time, and (2) disintegration of the midbody. The studies suggest that delay of cytokinesis by interzonal fibres can result in bi/trinucleation through the loss of midbody/intercellular bridge proteins that are required for completion of cytokinesis.

High-T c superconducting Bi(Al)-Ca-Sr-Cu-O glass-ceramic fibres drawn from glass preforms

Bi(Al)-Ca-Sr Cu-O glass-ceramic fibres over 100 cm in length were successfully drawn from a glass preform above the crystallization temperature,T x. The diameters of the uniformly drawn fibres with circular cross-section could be controlled in the range from 25–200 μm and the drawing speed was as high as 200 cm min−1. In this work Al2O3 was used to modify the properties of the glass. It increased the glass transition and crystallization temperatures but did not significantly increase the glass working range. Shrinkage and increase of density during heat treatment of the glass fibres were observed. The annealed (825°C/12 h in air) Bi4Al0.1Ca3Sr3Cu4Oy glass-ceramic fibre showed aT c(onset) of 82 K and aT c(zero) of 71 K.

Characteristic Grain Orientations on Surface of Bi<sub>2</sub>Sr<sub>2</sub>CaCu<sub>2</sub>O<sub><i>x</i></sub> Superconducting Glass-Ceramics and Fibers

Bi2Sr2CaCu2Ox glass and glass fibers were prepared by a conventional melt-quenching method and fiber drawing from a glass plate respectively, and grain orientation behavior of superconducting glass-ceramics and fibers obtained by annealing was examined. At the surface and in the interior of the glass-ceramic fiber, all c-axes oriented parallel to the direction of fiber length. In the bulk glass-ceramics, the oriented grains grew from the surface to the interior of the bulk and the morphology and thickness of the oriented layer were very sensitive to the annealing atmosphere. It is concluded that the oriented layers at the surface were formed by precipitation of the Bi2Sr2CaCu2Ox phase with release of oxygen absorbed during heating.

Comparative investigations of the biodurability of mineral fibers in the rat lung.

The biodurability of various glass fibers, rockwool, and ceramic fibers was examined in rat lungs and compared with natural mineral fibers. Experiments were based on studies that have shown that the biodurability of fibers is one of the essential factors of the carcinogenic potency of these materials. Sized fractions of fibers were instilled intratracheally into Wistar rats. The evenness of distribution of fibers in the lung was checked by scanning electron microscopy (SEM) or careful examination of the fiber suspension before treatment. After serial sacrifices up to 24 months after treatment, the fibers were analyzed by SEM following low temperature ashing of the lungs. Parameters measured included number of fibers, diameter, and length distribution at the various sacrifice dates, so that analyses could be made of the elimination kinetics of fibers from the lung in relation to fiber length (FL). Size selective plots of the fiber elimination correlated with fiber diameters enables the mechanism of the fiber elimination (dissolution, fiber breakage, physical clearance) to be interpreted. The half-time of fiber elimination from the lung ranges from about 10 days for wollastonite to more than 300 days for crocidolite. The biodurability of man-made vitreous fibers (MMVF) is between these values and is dependent on the chemical composition of the fibers and the diameter and length distribution. Results indicate that the in vivo durability of glass fibers is considerably longer than expected from extrapolation of published data on their in vitro dissolution rates.

Biopersistence of man-made vitreous silicate fibers in the human lung.

There is now a substantial body of experimental data on the pulmonary biopersistence of man-made vitreous silicate fibers (MMVSF), but human data are seriously lacking. Our knowledge in this field is essentially limited to a few reports of measurements of fibers retained in lung tissue samples taken at autopsy from workers manufacturing these products. Three types of exposure were studied: fibrous glass, mineral wool, and refractory ceramic fibers. Overall, the available data do not provide evidence for substantial long-term retention of fibers in the human lung after occupational exposure to MMVSF dusts. A word of caution, however; the amount of data supporting the previous statement is much greater for fibrous glass than for either mineral wool or refractory ceramic fibers. There is no human data on the key question of the kinetics of pulmonary clearance of inhaled MMVSF.

Relationship between lung biopersistence and biological effects of man-made vitreous fibers after chronic inhalation in rats.

This article describes the relationship between fiber biopersistence and the chronic toxicity of different chemical compositions of man-made vitreous fibers (MMVF) in the lung. Rats were exposed in "nose-only" inhalation chambers, 6 hr/day, 5 days/week, for 24 months to aerosol concentrations of 30 mg/m3 containing comparable fiber numbers and similar dimensions of fibrous glass (FG) or refractory ceramic fiber (RCF). Interim sacrifices were performed periodically to monitor fiber number and dimensions in the lung and the progression of pulmonary alterations. At each interim sacrifice, three to six recovery animals were removed from each exposure group and held until two years to determine the biopersistence of fibers after different exposure times. Fibers were recovered from the ashed lungs, counted, and measured using optical and scanning electron microscopy (SEM). Fiber chemistry was assessed in 91-week recovery lungs using energy dispersive spectroscopy (EDS) analysis. RCF induced lung fibrosis and an elevation in lung tumors and pleural mesotheliomas. FG exposure resulted in no lung fibrosis, no statistically significant increase in the lung tumor incidence, and no mesotheliomas. After two years of continuous exposure, the number of World Health Organization fibers per milligram dry lung recovered from RCF and FG exposed lungs was comparable. EDS analysis of recovery lungs showed that most of the alkalis and alkaline earths had leached from the FG fibers over time. A slight change in RCF chemistry was observed. These findings indicate that the change in the chemical composition of fibers may be an important determinant of the chronic toxicity of MMVFs.

Mesothelial Cell Proliferation Induced by Intrapleural Instillation of Man-Made Fibers in Rats and Hamsters

Mesothelial Cell Proliferation Induced by Intrapleural Instillation of Man-Made Fibers in Rats and Hamsters. Rutten, A. A. J. J. L., Bermudez, E., Mangum, J. B., Wong, B. A., Moss, O. R., and Everitt, J. I. (1994). Fundam. Appl. Toxicol. 23, 107-116.Long-term inhalation exposure to a biopersistent man-made ceramic fiber (RCF 1) results in a high incidence of pleural mesotheliomas in Syrian golden hamsters but not in identically exposed rats. To understand better the mechanisms involved in the intraspecies pathobiology of fiber-exposed mesothelium, the ability of the two different man-made fibers to induce cell proliferation in hamster and rat pleural mesothelial cells was investigated. Three dose levels of either glass fibers (MMVF 10) or ceramic fibers (RCF 1) were instilled intrapleurally into male Fischer 344 rats and male Syrian Golden hamsters. Rats and hamsters were exposed to approximately equal numbers of long thin fibers per kilogram of body weight using a single intrapleural instillation. Bromodeoxyuridine (BrdU) was administered via an implanted osmotic pump, and mesothelial cell proliferation was assessed at 7 and 28 days postinstillation (PI) using immunocytochemical visualization of labeled S-phase cells. Both rats and hamsters exhibited dose-dependent increases in proliferation of pleural mesothelial cells following exposure to both fiber types. Interspecies differences in mesothelial cell proliferation were noted for fiber type and pleural site. At 28 days PI, RCF-induced mesothelial cell proliferation was found to be more pronounced in hamsters than in rats in the caudal visceral pleural. Comparing both fibers either by equal mass or by equal fiber numbers, mesothelial cell proliferation in RCF 1-treated animals was higher than in animals exposed to MMVF 10, especially in hamsters, and may be a factor in the difference in mesothelioma induced by the two fibers. The higher sustained (28 day) mesothelial cell proliferation in the visceral pleural of hamsters exposed to RCF may contribute to the species-specific differences in mesothelioma incidence found in long-term rodent inhalation studies.

High-modulus glass fibers for new transportation and infrastructure composites and new infrared uses

Calcium aluminate glass fibers offer major new opportunities in transportation, infrastructure composites and new infrared sensor applications. They possess a higher modulus than S-glass, an advantage that can yield major weight and energy savings in car, aircraft and aerospace composites, or stiffer composite parts in emerging bridge and construction markets. Their superior alkali resistance is an important advantage in cement composites. They also possess sapphire-like infrared transmission, a property that is obtained at a fraction of the cost of single crystal sapphire fibers. Quaternary non-silica calcium aluminates with 40–50% alumina have high melt viscosities ( ⪢10 Pa s). Experimental fibers were obtained by potentially commercial processes (up-drawing from supercooled melts and down-drawing from performs). Binary compositions with >50% alumina have low viscosities ( ⪡10 Pa s). Glass fibers were obtained by an experimental process (inviscid melt spinning) from melts with up to 81% alumina. Infrared optical aluminum tellurite fibers were obtained from supercooled melts. New glass theory is applied. Melt viscosity and glassy modulus are rheology controlled and their magnitude is due to differences in size, shape and orientation of nanocrystalline domains. Not surprisingly, the silicate and aluminate glass (or glass ceramic) fibers with the highest modulus (160–180 versus 69 GPa for E-glass) had the most pronounced nanocrystallinity.

Production and Use of Glass Fibers, Rock/Slag Wool and Ceramic Fibers

Production and Use of Glass Fibers, Rock/Slag Wool and Ceramic Fibers

A thermoanalytical study on non-asbestos ring-lining materials for dental application

New non-asbestos papers composed of glass fibres and ceramic fibres were used as asbestossubstitute casting-ring liners in the dental field. The lining materials showed a softening temperature higher (above 800°C) than the furnace temperature. As far as the accuracy due to dimensional changes is concerned, new ring-lining materials such as glass fibre (paper and twill) and ceramic fibre have an effect similar to that of a conventional asbestos paper, indicating that non-asbestos liners could be advantageous.

An application of non-asbestos papers to the dental field: mechanical properties and structural change

New non-asbestos papers composed of glass fibres and ceramic fibres were examined for dental application. The fibre liners showed a larger deformation ability than conventional asbestos paper, and had a smaller water uptake than the conventional liner. In addition, the setting expansion in new non-asbestos papers was increased at 60 min after investing, similarly to the setting expansion behaviour in a conventional liner. After casting a silver alloy using the new fibre liners, a microstructure mainly of primary solid formed, with a smaller amount of complex phases. The microstructures formed were similar to those in the conventional asbestos liner.

Viscosity and crystallization of quenched Bi-Ca-Sr-Cu-O glasses as high-T c superconductor precursors

The possible procedure for the fabrication of high- T c superconductor glass-ceramic fibers is proposed on the ground of the transition-range viscosity studies of the Bi-Ca-Sr-Cu-O glasses. The possibility of fiber drawing in the glasses is discussed on the basis of the composition dependence of viscous and thermal properties of the glasses.

Preparation of Ag-coated superconducting Bi2Sr2CaCu2Ox glass-ceramic fibers

The Ag-coated superconducting Bi2 Sr2 CaCu2 Ox glass-ceramic fibers were successfully prepared. The glass fibers with a length of 50 cm, a width of 100–200 μm, and a thickness of about 20 μm were first drawn from glass plates with a thickness of 1 mm and then silver pastes were coated on the smooth surface of glass fibers. The Ag-coated glass fibers were converted into superconductors after annealing at temperatures of 820–860 °C. The main crystalline phase in the glass-ceramic fibers was the superconducting low Tc phase. The Ag-coated glass-ceramic fibers obtained by annealing at 840 °C for 5 h in air exhibited superconductivity with a Tc (zero)=70 K and a critical current density (60 K, zero magnetic field) of more than 40 A/cm2 .

Crystallization and properties of Li-Al-B-Ti-Zn-silicate system glass-ceramic fibres

Phase separation, nucleation, crystallization and micro-crack extension and their affects on the tensile strength and alkaline resistance of TiO2 nucleating Li2O-Al2O3-B2O3-ZnO-SiO2 system glass-ceramic fibres are studied by DTA, XRD, TEM and SEM. Phase separation, temperature range of nucleation, Tg, sequence and kinetics of crystallization, sizes of microstructure and surface microcracks, tensile strength and weight loss of alkali corrosion of glass-ceramic fibres are also studied. The mechanism of crystallization and the process of microcrack extension during the preparation of glass-ceramic fibres are discussed in detail. The glass prepared for glass-ceramic fibres should be characterized by the temperature of phase separation, nucleation and crystallization of the glass ought to be low, as near Tg as possible, corresponding to its basic properties and the rate of dense bulk crystallization must be closely controlled. The microstructure of small and concentrated crystallites, about, 25 nm in size while the diameter of the glass-ceramic fibres is 16 μm, produced in the glass-ceramic fibres increases its tensile strength and alkaline resistance. A suitable coupling agent covering the surface of the glass-ceramic fibres and tensile stress exerted on them during heat treatment benefit its mechanical and chemical properties.

最近の無機繊維質断熱材料

Recently the requirements for the performance and applicability of the thermal insulation materials have become intensified. Responding to these requirements, many kinds of insulation materials are being developed excellent in heat resistance, thermal shock resistance, insulating property, strength, applicability, etc. Synthetic inorganic fiber is one of the representative insulation materials among the porous materials excellent in insulating properties and its application becomes much wider.Here I would like to introduce the outlines and new applications of glass fibers, rockwool fibers, ceramic fibers and alumina fibers which are now widely used. Among these fibers, I can select the following three fibers which are having the novelties and newness.1. Light weight and high strength molded shapes of ceramic fibers.2. Fire resistant refractory board of alumina fibers up to 1, 800°C.3. Reusable thermal insulation tiles for the space orbitor.