249 results
Search Results
Now showing 1 - 10 of 249
- ItemMulti-method characterization of soda-lime glass corrosion : Part 2. Corrosion in humidity Report of the International Commissionon Glass (ICG) Subcommittee of Technical Committee 19 "Glass Surface Diagnostics"(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2002) Bange, Klaus; Anderson, Olaf; Rauch, Friedrich; Lehuédé, Patrice; Rädlein, Edda; Tadokoro, Nobuyuki; Mazzoldi, Paolo; Rigato, Valentino; Matsumoto, Kiyoshi; Farnworth, MarkAs-received and cleaned soda-lime glass surfaces corroded in high relative humidity of 95 % at a temperature of 60 °C for times up to one week are investigated by means of TOF-SIMS, SNMS, XPS, NRA, ERD, RBS, GIXR, AFM, SEM and optical microscopy. Distinct differences in the corrosion behavior are observed for as-received and cleaned glass surfaces. Changes in element concentration in the glass interface and in the topography of the glass surfaces are described for different exposure times in humidity. They are combined with variations in density of the modified surface layer. Cleaning before the corrosion treatment drastically reduces degradation; cleaning after the corrosion treatment can restore the surface.
- ItemFabrication of SiO2 glass fibres by thermoplastic extrusion(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2004) Heiber, Juliane; Clemens, Frank; Graule, Thomas; Hülsenberg, DagmarThe fabrication of silica glass fibres by thermoplastie extrusion of nanosize and micron SiO2 powders has been investigated. The powders were mixed with a binder system, compounded for 3 h at 150 °C, and finally extruded through a die with a 500 μm-diameter die land. After debinding the green fibres at 500 °C, these were sintered for 1 h at 1100°C under air to yield glassy and crack-free silica fibres with a final diameter of 400 μm. The effect of the two different particle size distributions as well as the influence of varying powder loading (between 38 and 58 vol.%) on the rheological properties of the feedstocks were analysed using capillary rheometry. The debinding and sintering behaviour was also investigated using mercury intrusion porosimetry, thermal gravimetrie analysis and dilatometry.
- ItemMechanisms of the formation of gas bubbles in heat treatment of glass-silicate tiles(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2002) Linhart, JurijTheoretical research has been done into the mechanisms of the formation of gas bubbles which takes place during the sintering of the glass granulation product under the conditions of heating its upper layer. It is shown that in the bubble, there is a possibility of an inverse thermal distribution which will lead to a thermal jump on its boundary. At the thermal processing temperatures, the presence of CO2 increases the effect of absorption of the radiation conditioned by the spectral zones. Experimentally, it has been proved that a thermal field inversion takes place in the presence of an inner diffusing layer joined to a clearly transparent one for the thermal radiation of the material.
- ItemOrigins of anomalous mixed-alkali effects in ion-exchanged glasses(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2000) Ingram, Malcolm D.; Davidson, Jill E.; Coats, Alison M.; Kamitsos, Efstratios I.; Kapoutsis, Jannis Α.Ion transport properties in ion-exchanged glasses are re-examined by a.c. impedance and infrared spectroscopies. In typical soda - lime-silica (float) glass it is shown that when Na+ ions are replaced by K+ ions, the region of highest resistivity resides in the surface, confirming the earlier result of Tomandl and Schaeffer. The existence of this anomalous impedance is correlated with cationinduced relaxations of the network (CIRON). This process enables the glass to accommodate larger ions at the expense of empty Κ sites (which in melt-grown glasses provide the stepping stones for ion migration). As a consequence of the structural relaxations, the compressive stresses stored within the surface of the glass may be smaller than expected, even when ion exchange occurs far below Tg and the effects of viscous flow can be neglected.
- ItemStudies on viscosity of dried sodium water glasses by extrusion(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2003) Maia, Luciana; Dontal, Patricia Trindade; Rakus, Sigrun; Rüssel, ChristianΑ study on viscosity and flow behavior of dried water glasses using an extrusion method is first reported. The rheological properties of water glass samples with water concentrations in the range from 22.2 to 36.4 wt% and also some glycerin-containing samples were studied. The extrusion method used enables the determination of viscosities in the range from 10^7 to 10^10 dPa s. By comparison to glass melts, relatively low temperatures in the range from 50 to 85 °C are used. During extrusion of dried water glasses, the viscosity decreases significantly with increasing shear rate. Lower water concentrations lead to a more pronounced deviation from Newtonian flow behavior. This is attributed to nonlinear flow behavior rather than to localized viscous heating effects by mechanical deformation work. Furthermore, the effect of composition on the viscosity-temperature dependence is studied. The higher the water concentration, the lower is the viscosity. Glycerin additions intensify this effect. Generally, the viscosity decreases with increasing temperature. Vogel-Fulcher-Tammann parameters are obtained by ftting the data of extrusion experiments and the corresponding Tg values.
- ItemLocal clouding of glass after machine dishwashing(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2005) Martinek, Klaus-Peter; Wang, Chun; Krausch, Georg; Rädlein, EddaThe local clouding of glasses after dishwashing near the mouth rims on a coffee pot made from borosilicate glass, on a wine cup made from lead crystal glass and near the stem base on a wine cup made from barium Silicate glass has been found to be due to damage during manufacture. The examined clouding is different from the two well known types of filming and etching cloudiness related to the reactions of glass with water and detergent in the dishwasher. The intensive study on the wine cup of lead crystal glass shows that a phase Separation was induced during the flame treatment on the sharp rim and base. The aggregates of Pb-rich spheres scaled off when the thin covering of SiO2 rich skin was eroded away and consequently holes were formed on the glass surface on the micrometre scale, which resulted in light scattering and the clouding of the glassware. Evaporation species from warmer regions onto the colder areas of the glass surface could be observed, but they are not the reason for the local clouding in this study. Dendritic thin corrosion products caused by air exposure could be detected on the undisturbed glass surface as well.
- ItemSupervisory advanced control of glass melters and forehearths by the GS expert system(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2000) Chmelar, Josef; Bodi, Robert; Muysenberg, ErikAdvanced control is one of the most important tools to increase glass quality and production in existing furnaces. This paper describes a method of how advanced control has been applied in glass industry. Practical experience of an advanced control system called EXPERTSystem II is shown and explained. The present state of control in the glass industry is relatively poor compared to other chemical industries, therefore the potential increase in benefits by advanced control systems is very high for the glass production system.
- ItemInvestigation of selenium retention in high redox glasses(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2005) Shelestak, Larry J.; Arbab, MehranLaboratory glass melting experiments were made to study the effect of glass redox on selenium retention. Initially, it was found that as expected selenium retention decreases as glass redox ratio increases. But, unexpectedly, selenium retention then levels off and reaches a minimum upon further increases in glass redox, before once again increasing for very high redox ratios of more than 0.60. Selenium concentrations in the furnace atmosphere at different locations in a commercial float glass furnace were also measured as an indicator of selenium volatility at different stages of glass melting. Α study of the effect of glass redox ratio on the spectral absorption of the major selenium containing coloring centers in float glass was also made.
- ItemDissolution of heat-treated magnesium-rich amorphous silicate fibers in a simple amino acid solution - An appendix(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2005) Ohsawa, MasatoThis study provides the data of the concentration of released elements for the dissolution, in a glycine solution, of Mg-rich amorphous alkaline earth silicate (AES) fibers heat-treated at the temperature of 700°C. It is shown that: a) the heat treatment at 700°C facilitates the glass network dissolution of the fibers, b) the heat treatment also facilitates significantly the alkaline earth elements leaching in the fibers, c) the (Mg+Ca+Sr)/Si molar ratio of the released elements for the dissolution, in the glycine solution, of the fibers heat-treated at 700°C is within the molar ratio range for the dissolution of diopside in a buffer solution. This suggests that Mg-rich AES fibers are phase separated and form diopside-like glassy phase as the chemically less durable phase resulting from the heat treatment around 700°C.
- ItemIndustrial processing of TiO2 thin films from soluble precursor powders(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2003) Löbmann, Peer; Röhlen, PeterSoluble, amorphous powders were prepared as precursors for the sol-gel processing of TiO2 films. Layers of up to 800 nm and 2.0 μm were prepared on borosilicate glass and Ni-alloy by multiple coating, respectively. Α refractive index of 2.3 was achieved. The interdependency of parameters such as solvent composition, withdrawal rate, thermal treatment with film quality, thickness and optical properties was investigated. The conditions were optimized for large-area coatings on an industrial scale. The overall process is highly advantageous for industrial production of optical interference filters due to the long-time stability of precursor powders and sols, high optical quality of the resulting films, excellent substrate adhesion and good compatibility with other sol-gel films.