Glastechnische Berichte : Zeitschrift für Glaskunde
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- Item11B MAS NMR spectra of BO3/2-TeO2 glasses(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1993) Sekiya, Takao; Mochida, Norio; Ohtsuka, Atsushi; Soejima, Ayako; Yasumori, Atsuo; Yamane, Masayuki11B Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) spectra of BO3/2-TeO2 glasses have been used to determine the compositional dependence of the fraction of 4-coordinated boron atoms, N4 = BO4/(BO3+BO4). In 1 BO3/2 ∙ 99 TeO2 (mol%) glass, almost all boron atoms form BO4 tetrahedra. The fraction N4 decreases with increase of BO3/2 content. The authors propose a glass structural model in which the TeO3 trigonal pyramids formed by a part of the tellurium atoms are connected with the BO4 tetrahedra by vertex-sharing. An excess and a deficiency of local charges of a TeO3 trigonal pyramid and a BO4 tetrahedron compensate each other. The conversion of a BO3 triangle to a BO4 tetrahedron is concurrent with the formation of a TeO3 trigonal pyramid.
- ItemAdvanced layer systems and coating techniques for large-area glass coatings by means of high-rate sputtering(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1993) Beister, Günter; Beißwenger, Siegfried; Bräuer, Günter; Dietrich, Eckhard; Kukla, Reiner; Szczyrbowski, Joachim; Teschner, GötzThe application of high-rate sputtering for large-area glass coating aims at the improvement of the glass properties by antisolar and low-emissivity coatings. The first part of the present paper deals with a new low-emissivity coating, which is based on a so-called double-blocking layer arrangement for protection of the infrared-reflecting silver layer. Compared to conventional layer stacks an improved resistance against environmental attacks (humidity, salt, sulphur dioxide) is found. A new application of high-rate sputtering for glass coating is the manufacturing of conductive and semitransparent antireflective thin film systems for data display screens. A system based upon TiN layers is discussed. Layer stacks on glass mostly include dielectric films, which have to be deposited by reactive sputter processes. Process stability and layer quality may suffer from arc discharges. The second part of the paper deals with new developments for the improvement of process long-term stability. The operation principle of an arc suppressor interface for DC-reactive sputtering is explained. Finally a mid-frequency-powered twin magnetron for reactive sputter deposition of highly insulating films (SiO2, Si3N4, AI2O3) is presented, which enables long-term stable processes at very high deposition rates.
- ItemAlternating bending load behaviour of unidirectionally fibre-reinforced glasses(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1992) Klug, Thomas; Bornhöft, Hansjörg; Brückner, RolfAlternating bending load experiments are described and applied on SiC- and carbon-fibre-reinforced alkaline earth borosilicate glass samples. The mechanical properties (strength, bendover stress, Young's modulus) were determined by the three point bending method after 1000 strain-controlled alternations of load and compared with those of non-pretreated samples. It could be shown that all composites can be treated by an alternating bending load up to their elastic proportionahty limit (bendover stress) without failure or without any loss of their mechanical properties. Alternating bending loads above the bendover stress lead to a rapid fatigue of the SiC-fibre-reinforced glass composites while the carbon-fibre-reinforced composites show a great toleration of damage under the applied experimental conditions. In the case of the carbon-fibre-reinforced glass the homogeneity of the fibre distribution is of special importance for high bendover stresses and strengths during cyclic bending load experiments.
- ItemAlternativen der Abwärmenutzung und Emissionsminderung an Glasschmelzöfen mit rekuperativer Luftvorwärmung(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1993) Pörtner, Dirk[no abstract available]
- ItemAluminium release of pharmaceutical glass containers: Determination by GFAAS in the extract solutions and study of the inner surfaces by XPS and SIMS(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1991) Guadagnino, Emanuel; Verità, Marco; Furlani, Claudio; Polzonetti, GiovanniIt is well-known that aluminium accumulation in the body is responsible for severe neurological diseases to which patients receiving haemodialysis are particularly exposed. This problem, which could arise for any kind of solutions for hypodermoclysis, seems to be overcome if the aluminium content of the injectable preparations is less than 10 µg/l. In the present paper the aluminium release has been determined for different glass containers for pharmaceutical use after autoclave treatment with distilled water for 60 min at 121 °C. The determinations have been carried out by Graphite Furnace Atomic Absorption Spectrometry in the extracts: The best result was obtained for the glass of type II whose release was lower than 2 μg/l for any capacity. An explanation of the aluminium release mechanism from these glasses is attempted an the basis of XPS and SIMS data obtained for the inner surface of the containers. The sulphur treatment depletes the surface almost completely of calcium and sodium ions, thus forming a highly durable SiO2-rich layer. After autoclaving the pH value of the solution remains in the range of neutral values and the dissolution process is limited to about 5 nm. No preferential extraction of aluminium has been detected in the bloom.
- ItemAnalysis of gases evolved by AZS refractories and by refractory/glass melt reactions. Techniques and results. Contribution to the bubble-forming mechanism of AZS material(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1992) Krämer, Fritz W.To understand the bubble-forming mechanism at the interface AZS material/glass melt, gas-analyzing techniques are necessary. Α review on gas bubble analysis techniques - gas chromatographic and mass spectrometric - as well as on hot extraction techniques is given. Pore gas analyses of pristine, of sustained- and cyclically-heated AZS material without glass contact, analyses of bubbles of the exudation layer, analyses of bubbles in glass melts near the AZS material and hot extraction measurements show that at least two bubble-forming mechanisms take place at the interface refractory/glass melt. The first process is the opening of closed pores of the AZS material filled with nitrogen, oxygen and carbon dioxide due to the normal corrosion of the AZS blocks by the glass melt. The second mechanism is the oxygen release due to a redox process of multivalent ingredients of the refractory material when temperature is increased, which forms additional oxygen bubbles and knots in the glass melt. Both processes generate bubbles whose gas content is almost the same in the glass product.
- ItemApplication of ultrasonic measuring techniques in industrial glass melting(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1991) Faber, Anne J.; Simonis, Frank; Breeuwer, René; Waal, Henk deThe potential applications of ultrasonic measurements in glass melts have been studied, using a measuring system comprising ultrasonic waveguides of polycrystalline translucent Al2O3. These high-temperature buffer rods serve to transport ultrasonic signals into the glass melt and to receive acoustic echoes generated in the melt, respectively. The fundamental acoustic properties of a soda-lime-silica glass composition as a function of temperature have been obtained experimentally: The observed sound velocity varies from 2.86 km/s at 1150 °C to 2.70 km/s at 1300 °C. The observed attenuation of 1 MHz waves has a minimum at 1300 °C of 840 dB/m. For 100 kHz waves the attenuation is a factor 100 lower. It is concluded that 100 kHz ultrasonic signals can be utilized for detection of bubbles with critical radii (≥ 0.2 mm) in a feeder, for measurement of glass flow velocities and for measurements of glass temperature. For measurement of the residual thickness of refractory bricks of a glass tank, application of echo acoustic sensors an the outer surface of the wall probably is more practical.
- ItemBehaviour of rf sputter deposited SiO2 and AI2O3 diffusion barriers on float glass at 300 °C in air(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1993) Chaissac, Martine; Claus, Jürgen; Borchardt, Günter; Slowik, Jacek; Frischat, Günther Heinz; Scherrer, Stanislas; Weber, SylvainIn order to study the resistance of high-frequency sputtered thin SiO2 and AI2O3 coatings on float glass to sodium diffusion, coated glasses were submitted to heat treatments in air. The element distribution in the coatings and in the substrates was measured with neutral primary beam-secondary ion mass spectrometry.
- ItemBoussinesq approximation to compute the temperature and velocity distributions in glass melts(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1992) Hofmann, Otto R.The objective of the paper is to discuss the basis of glass melt modelling. For the governing equations to compute the Joule heat, temperatures and velocities in glass melts, conditions and criteria have been derived which enable the use of simplified equations and material properties. The computed examples base on the properties of the typical mass glasses: float glass, green container glass, fibre glass (E-glass) and Pyrex-type borosilicate glass. The computations show that in future it will be necessary to get more knowledge about the cubic and temperature-dependent expansion coefficient of glass melts. The per volume element constant viscosity, thermal and electric conductivity cause inaccuracies of more than 5 % in numerical modelling. The proposal is made to name a similarity number of direct Joule heat production Staněk number.
- ItemBrief overview on glass industry and glass research in Spain(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1993) Fernández Navarro, José MariaThe Spanish glass industry consists of about 60 production centres and more than 650 manufacturing and processing factories and workshops, with a total of 50 000 employees. The overall annual turnover amounts to around 400 billion Pta. The most important sector is the hollow glass industry. It represents 67.2% of the total glass production (more than 1.4 mill. t, and 69 billion Pta in 1991). The flat glass production is shared among two big companies. They have three float glass production lines (a fourth line is currently being built) and two cast-glass lines. In 1990 flat glass producdon was divided between 450 000 t of float glass and 76 000 t of cast glass. Sales amounted to 66 000 mill. Pta. Furthermore, there are three factories for glass fibres and one factory for glass tubes. The percentage distribudon of the different glass products is very similar to that of the European Community countries. The Spanish quota on the total European Community glass producdon is 9 %. The glass research in the state-owned sector is carried out by some scientists groups at different Spanish Universities and at the Ceramics and Glass Institute. Within the private industrial field of research there are two Research and Development centres which belong to Saint-Gobain group.
- ItemBubble generation at glass/refractory interfaces: Α review of fundamental mechanisms and practical considerations(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1992) Swarts, E. LowellFewer point defects, especially fewer bubbles, have become a principal requirement in meeting improved quality standards for many commercial glass products. Many of these defects may be bubbles generated from the interaction of refractories with the molten soda-lime-silica glass. Porosity of the refractories is an obviously important factor: under some conditions thermal transpiration may become a mechanism. In fused-cast refractories, exudation of vitreous phases likely leads to bubble formation, and ZrO2-containing bodies have the potential for supporting electrolytic mechanisms. Specific refractory impurities, e.g., nitrides and iron species, also generate bubbles in contact with the melt. Interactions between molten glass and refractories are best characterized by tests that use a covering atmosphere typical of actual service. Long enough equilibration times are necessary to document transient behavior and steady-state conditions.
- ItemCalibration of Littleton measuring instruments using test specimens of reference glass(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1992) Broeke, HerbertThe determination of the softening point of glass according to Littleton (Littleton point) is carried out by a conventional method of measurement. The measuring device and the method of measurement are standardized. The calibration of Littleton measuring instruments is performed with the aid of test specimens manufactured in the laboratories of the glass industry from standard glass with a known Littleton point using various technologies. Owing to the availability of test specimens which are machine-made and traced back to a standard measuring device and whose Littleton point is certified, deficiencies of the usual calibration procedure are avoided and the comparability of the measurement results is improved.
- ItemChemical and physical characterization of porous materials prepared by leaching glasses in the system Na2O-Al2O3-B2O3-F(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1991) Elmer, Thomas H.; Seward III, Thomas P.The leachability of glasses in the system Na2O-Al2O3-B2O3-F with Al2O3 contents of about 50 wt% was investigated. It was found necessary to heat-treat the glasses at temperatures that assure not only phase separation but also formation of microcrystalline phases to prevent crumbling, swelling, and excessive restructuring of the glasses on leaching in hot dilute acetic acid solutions or hot distilled water. Chemical analysis showed that the leached glasses contain up to 96 wt% Al2O3 , based on ignited weight. Leaching rate studies show that the removal of the nonaluminous constituents by the hot leachant is diffusion-controlled. The surface areas and pore sizes of the alumina-rich porous skeleton that results on leaching are from ≈ 80 to ≈ 250 m2/g and from ≈ 6 to ≈ 15 nm, depending on heat treatment and leaching conditions. Visual examination and x-ray diffraction studies show that the heat treatment of the base glass induces phase separation and leads to the formation of crystalline phases such as Na3AlF6 and Na2Al2B2O7. The increases in density and thermal expansion of the base glasses with fluoride content on subsequent heat treatment are chiefly due to the formation of such crystalline phases.
- ItemChloride emission from glass melting furnaces(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1992) ter Beek, Arno F. M.; Thole, Eric J. M. C.By means of chloride measurements in input and output flows of glass melting furnaces, chloride balances have been established. The measurements were carried out on industrial container and flat glass furnaces. The balances show a good consistence. It has been found that from the chloride in the feed of the furnace roughly the first 110 mg Cl-/kg molten glass wih be incorporated into the glass. The rest will be divided between flue gas and glass (50 %/50 %), however, this depends slightly on the concentration of chloride in the feed, the amount of recycled cullet and the Na2O content in the glass composition. By formulating a model with the three mentioned factors the amount of incorporated chloride can be accurately predicted. The model presented is an empirical one and is applicable to soda-lime-silica glasses. It is valid between the limits: chloride in the feed 160 to 560 mg Cl-/kg molten glass, 0.15 to 0.80 kg cullet/kg molten glass and 0.11 to 0.16 kg Na2O/kg molten glass. The chloride concentration in the flue gas is given by the difference between the chloride content in the feed and in the glass divided by the gas volume per quantity of molten glass. This volume depends on the energy economy of the furnace, the raw materials and the amount of recycled glass used. European emission standards for HCl are expressed per volume of flue gas and, therefore, do not stimulate a more efficient use of energy and of recycled raw materials. This can be changed by providing emission standards which are basded on the quantity of molten glass rather than on the released flue gas volume.
- ItemComparative study on energy-saving technologies for glass furnaces(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1992) Beerkens, Ruud G. C.; Muysenberg, Hendrikus P. H.Different new technologies for increasing the energy efficiency of glass furnaces have been compared. The most important technologies are: - batch and cullet preheating, using a fluidized bed for batch preheating and dust filtration; - thermochemical recuperators using a water/methane reformer; - oxygen burners; - advanced air preheat systems like ceramic recuperators; - twin-bed burners; - new combustion technologies. The energy savings of these different measures for an industrial glass furnace have been calculated by using an energy-balance model. Α soda-lime glass furnace with a production rate of 250 t glass/d has been chosen as an example for making these comparisons. The economics of all these different technologies have not been compared here. Melting of batches with up to 100 % cullet may have additional advantages for the energy consumption because of the possible lower melting temperatures needed to remelt pure cullet without other raw materials. Batch and cullet preheaters are the most important systems for the near future. Besides the improvement of the energy efficiency, the impact of some of the mentioned energy-saving technologies on the reduction of the emissions of air pollutants like dust, nitrogen oxides, sulfur oxides, chlorides and fluorides seems to be promising.
- ItemComposition fluctuation in an alkali silicate glass(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1993) Boksay, Zoltán; Bonquet, Gusztáv; Hári, Erzsébet; Rohonczy, JánosInclination toward composition fluctuation was assumed to be an inherent property of silicate glasses. An alkali silicate glass of the system Li2O-Na2O-SiO2 chosen for investigation was broken into small grain sizes from 10^-5 to 10^-2 g and then separated into various fractions by sieving. A certain number of grains of different mass were analyzed with respect to the oxide composition. The analytical investigations proved that the lithium and sodium ions were mixed to a high extent and that the scattering of the mole fractions of the alkali ions obeys the Gaussian distribution. Clear evidence was found for partial segregation of the silica and the alkali oxides. No grain was found with relatively high mass and relatively low silica content. On the basis of the scattering of the mole fractions of the silica and the alkali ions in the grains the relative frequency (distribution density) was calculated and presented by contour and perspective diagrams in dependence on the mass of the grains.The influence of the melting procedure on the fluctuations of the glass composition was not investigated.A correlation between the inhomogeneity of the glass and its fragility is assumed.
- ItemConstruction of an experimental unit for the mechanical colour sorting of non-crushed recycled container glass(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1991) Gitzhofer, Karl-HeinzThe continuous growth of container glass recycling requires additional measures for the colour separation of waste glass. This paper presents the results of a research programme partly financed by the Umweltbundesamt (Federal Office for the Environment), Berlin, which deals with the mechanical colour separation of recycled container glass. It was the task of this research programme to develop and build a pilot unit which would function under operational conditions. For economic reasons and in order to limit the technological input, the process is designed for the sorting of whole bottles and large pieces of cullet. Before starting colour sorting, small pieces of glass are screened off. The larger material is aligned in the conveyor direction and is fed in single file to the colour recognition and ejector systems. After colour recognition by a light transmission measurement, the bottles or glass pieces are separated according to colour, in free fall, by mechanical ejection of the samples. The colours flint, amber, green and opaque are differentiated.
- ItemContribution to basicity of technical glass melts in relation to redox equilibria and gas solubilities(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1991) Krämer, Fritz W.To use the gas solubilities reported in the literature for binary or ternary silicate or borate melts to predict values for industrial glass melts, a basicity number concept was developed. Acidic values derived by cation-oxygen bond strengths multiplied by the mole fractions of the glass oxides were used to form a scale of basicity numbers for glass melts. The origin of this scale is the basicity number of boron oxide. This basicity number concept was successfully applied to gas solubility values for H2O, CO2, and SO2 in binary and ternary glass melts and to the solubility of oxygen in glass melts with multivalent ions, such as iron, arsenic, antimony, cerium, chromium and manganese.
- ItemContribution to comparability of in-vitro and in-vivo man-made mineral fibre (MMMF) durability experiments(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1993) Förster, Hansgeorg; Tiesler, HartmutToxicologists discuss three major conditions which must be met in order to prevent adverse health effects of dust with regard to three necessary fibre properties: the fibre has to be thin, long, and durable. First definitions concerning the geometric properties thin and long were made already in 1972; however, the criterion durability has not yet been defined. The durability of man-made siliceous fibres has been tested with experimental animals (in-vivo) as well as with purely chemical methods (in-vitro). A reaction of first order was deduced from in-vivo experiments. On the other hand, in-vitro experiments in different setups proved all to follow zeroth-order kinetics. From that, it was postulated sometimes that in-vitro experiments are unsuited to determine the persistence of man-made siliceous fibres. The present study will show that correct mathematical treatment of in-vivo data leads to the same results as obtained from in-vitro experiments. The lg-normal distribution in fine fibrous dust is responsible for the seemingly first-order pattern for mass and fibre number. If the time intervals are chosen to be rather long - as in published in-vivo studies - it is impossible to demonstrate the deviation from the dissolution process at the beginning and at the end. This means the solution of the apparent discrepancy between in-vivo and in-vitro experiments. The mathematical model allows to estimate the lifetime of inhaled fibrous particles from known dissolution velocity and fibre size distribution for the worst case, since the chemical process of dissolution of siliceous fibres is superimposed by accelerating effects as fragmentation or clearance. The validity of the model is shown by comparison with data from an inhalation study [1 to 3]. Also, the model allows the calculation of the accumulated fibre number from dose and duration of exposure.
- ItemCorrection of the Short Communication: Effect of PbO on some properties, especially light scattering, of glasses with mixed alkalis(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1993) Dietzel, Adolf[no abstract available]