250 results
Search Results
Now showing 1 - 10 of 250
- ItemAdvanced batch house technology for float glass - the new plant of SAINT-GOBAIN GLASS DEUTSCHLAND in Cologne/Porz(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2002) Drescher, Holger[no abstract available]
- ItemEstimation of liquidus temperatures in silicate glasses(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2001) Karlsson, Kaj H.; Backman, Rainer; Cable, Michael; Peelen, Jan; Hermans, JanTwo models for estimating liquidus temperature from composition are presented and compared with thermodynamically calculated temperature as well as primary phase. Α simple polynomial model is given for high silica glasses, while a model covering a wide composition range and several primary phase fields is more complex. Thermodynamic calculations generally give too high liquidus temperatures in the devitrite field and too low in the primary field for Na2O · 2 CaO · 3 SiO2. In the wollastonite field the values are scattered, but in general too high.
- ItemUV light induced photoreduction in phosphate and fluoridephosphate glasses doped with Ni2+, Ta5+, Pb2+, and Ag+ compounds(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2004) Möncke, Doris; Ehrt, DorisThe photoreduction of polyvalent ions was studied in high purity fluoride-phosphate and metaphosphate glasses doped with Ni2+ (3d8), Ta5+ (5d0), Pb2+ (6d2), and Ag+ (3d10). Compared to the undoped base glasses all doped samples display different electronic transitions in the UV at the irradiation wavelength. Glass samples containing 50 to 5000 ppm dopants were irradiated with excimer lasers at 193 and 248 nm, respectively. The subsequent defect centers, formed at ppm levels, were characterized by EPR and optical UV-VIS spectroscopy. The observed laser induced transmission losses in the UV and visible range increased in the order Ni, Ta, Pb to Ag. Extrinsic electron centers are formed by photoreduction of the dopants. (Ni2+)- is characterized by an optical transition with a maximum at 355 nm and an EPR signal around g ≈ 2.07. The maxima of the optical transitions of the (Pb2+)- -EC are positioned at 395 and 500 nm, of the (Ta5+)- -EC at 465 nm. The photoionization products of silver depend strongly on the silver concentration. At a silver content of 50 ppm only the (Ag+)- -EC is formed, visible in the optical spectra with a maximum around 450 nm. Α second silver species, (Ag+)2 -, which absorbs at 305 nm, is additionally observed in the sample doped with a silver concentration of 500 ppm. In the sample doped with 5000 ppm silver a third defect, the photooxidized (Ag+)+ -HC, with an optical band maximum at 405 nm and an EPR signal around g ≈ 2.3 is observed as well. The formation of extrinsic electron centers causes in all glasses an increase in the formation of intrinsic hole centers and often a decrease in the formation of intrinsic electron centers. Defect generation curves show that a very rapid darkening in the glasses is initiated by the addition of any of these dopants. The recovery rates of the defeets formed depend strongly on the dopant, not on the glass matrix.
- ItemWeathering of tin oxide coated glass with low IR emissivity(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2002) Rädlein, Edda; Buksak, Anna; Heide, Gerhard; Gläser, Hans Joachim; Frischat, Günther HeinzThe weathering of K-glass has been studied by measuring transmission and reflection in the visible (VIS), near infrared (NIR) and infrared (IR) wavelength ranges, by chemical depth profiling with secondary neutral mass spectrometry (SNMS) and by atomic force microscopy (AFM) imaging. K-glass is a commercial tin oxide coated glass with low IR emissivity. The SnO2:F-coated side has been exposed to atmospheric conditions for up to 32 weeks and for up to two years. It could be shown that the optical properties are only affected in the VIS range, but the visible contamination does not influence the high IR reflection. This means that the heat-insulating properties of window glazings with the K-glass coating on the surface do not degrade under atmospheric conditions. Chemical depth profiles did not reveal major changes, except for an increase in the signals of minor elements on the surface, namely sodium, carbon and silicon. AFM showed that after 32 weeks the deep valleys of the rather rough crystalline SnO2:F are partially filled up. The high transmission of new K-glass can be regained since contamination or corrosion products can be removed by washing. The coating itself is chemically stable.
- ItemAlkali ion migration control from flat glass substrates(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2000) Janke, Nikolas; Grassmé, Oliver; Weißmann, RudolfSodium diffusion from flat glass substrates during annealing changes properties of refined flat glass. In the ease of the development of the CuInSe2 thin film solar eell, annealing at 550 °C is necessary for the formation of suitable crystalline phases. Sodium diffusing from the soda-lime-silica glass substrate influences crystal growth and the main electrical parameters of the solar cell. Different possibilities in sodium ion migration control are presented, considering the influence of glass composition on sodium diffusion and its chemical potential as well as passivation of sodium-containing glasses by diffusion barriers. Experimental results in connection with the thin film solar cell show that sodium-free substrates or glass compositions which immobilise sodium at tetrahedral sites of boron oxide or alumina can be used without further surface treatment. Soda-lime-silica glass with sputter-deposited AI2O3 and BiOx thin films or CVD coatings (SiNx: H, SiOx) as diffusion barrier coatings shows promise as a cheap substrate material. Alternatively, dealkalisation of soda-lime-silica glass in HCl atmosphere leads to silica-rich surfaces with excellent barrier properties. The investigations are carried out using various surface analytical tools like Auger Electron Spectroscopy (AES), X-Ray Diffractommetry under Grazing Incidence (GI-XRD), high-resolution Scanning Electron Microscopy (SEM), and Fourier Transform Infrared spectroscopy (FTIR).
- ItemDevelopment of high-permittivity glasses for microwave LTCC tapes(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2003) Eberstein, Markus; Schiller Wolfgang A.One of today's leading packaging concepts in microelectronics and microsystems is the technology of Low Temperature Cofiring Ceramics (LTCC). It is based on ceramic tapes that sinter at low temperatures (< 950 °C) and are capable of fine-line wiring by use of high-conductivity metals, preferably silver ( ϑm = 961 °C). To lower sintering temperatures of crystalline powders, glass powder is added. Depending on the amount of glass added, two mechanisms of sintering are possible: reactive or nonreactive liquid phase sintering. Reactive sintering requires small amounts (< 10 vol.%) of a very low softening glass (ϑsoft < 400°C). If the glass amount is increased to more than 50 vol.%, nonreactive sintering occurs in the glass softening range. According to the microstructure observed for each case, the respective types of materials are called Glass Bonded Ceramics (GBC) and Glass Ceramic Composites (GCC). Integration of microwave filters in LTCC multilayers requires inner dielectric layers with medium, temperature-stable permittivities (εr = 30 to 60) and low dielectric loss (tan δ < 2 ∙ 10^-3). Up to now, appropriate materials have been realized only by GBC sintering at 900 °C and above. Hence, pure silver metallization is not possible. To overcome this limitation, GCC are a promising way. Therefore, crystalline substances possessing εr of about 100 and low dielectric loss - for example Ba(La, Nd)2Ti4O12 - were combined with special high-permittivity glasses. Α development of such glasses is presented in this work. Addition of oxides of easily polarizable elements (e. g. Nb2O5, La2O3 , TiO2 ) effects an increase in permittivity of selected basis compositions from the systems BaO-Al2O3-B2O3-SiO2 (εr up to 15) and La2O3-Ba2O3-TiO2 (εr up to 20). GCC mixtures made of 65 vol.% of these glasses and 35 vol.% BaLa2Ti4O12 showing microwave properties and sintering temperatures below 900 °C are introduced.
- ItemKinetics of phase separation in a 6.5 Na2O ∙ 33.5 B2O3 ∙ 60 SiO2 glass(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2000) Flügel, Alexander; Rüssel, ChristianIndustrially melted glasses with the composition (in mol%) 6.5 Na2O ∙ 33.5 B2O3 ∙ 60 SiO2 were thermally treated at temperatures in the range of 660 to 750 °C. This resulted in phase separation, i.e. in the formation of a silica- and a sodium borate-rich phase with an interconnected microstructure. Both, the volume content of the borate-rich phase and the mean structure thickness (the correlation length) increased with time as well as with temperature. The volume content approached to a limiting value at constant temperature. The correlation length increased with time according to a power law (~ t^1/n). By contrast to previous studies, n was in the range of 1 to 1.2 within the temperature range and time scale studied. The correlation lengths were much larger (up to 12 µm) and the viscosities much lower than in most previous studies. The kinetic law was explained as controlled by visous flow.
- ItemCrystallization, microstructure and properties of selected glasses and glass-ceramics in the SiO2-Li2O-ZnO-K2O-P2O5 system(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2002) Clausbruch, Sascha Cramer von; Schweiger, Marcel; Höland, Wolfram; Rheinberger, VolkerThe crystallization behavior of selected glasses in the multicomponent SiO2-Li2O-ZnO-K2O-P2O5 system was investigated using high-temperature X-ray diffraction and differential scanning calorimetry. Proceeding from a dental model glass with the molar composition 63.2 SiO2, 29.1 Li2O, 3.3 ZnO, 2.9 K2O and 1.5 P2O5, 20 glasses were melted, varying the concentrations of the single components systematically. Glass compositions mainly influenced the formations and dissolutions of metastable and stable phases in the temperature range of 480 to 1100 °C. In the majority of the glasses hthium disilicate (Li2Si2O5) precipitated as the main crystal phase during heating, while lithium metasilicate, lithium orthophosphate, cristobalite and quartz crystallized as secondary phases. After a one-step heat treatment microstructures of glass-ceramics and morphologies of Li2Si2O5 crystals were characterized by scanning electron microscopy. With few exceptions glass-ceramics showed a finegrained microstructure with interlocking, rodshaped Li2Si2O5 crystals with 0.5 to 10 µm in length. The corresponding glass-ceramics were processed by a hot-pressing technique to test samples for mechanical and optical measurements. Concentration variations of the base glasses caused bending strengths between 224 and 675 MPa. Within a comparison of translucency according to dental standard BS 5612 contrast ratios between 0.3 and 0.8 were determined.
- 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.
- ItemAtomistic simulation of glasses - Strategic considerations and review of selective results(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2005) Fotheringham, Ulrich; Binder, Kurt; Horbach, Jürgen; Kob, WalterWithin the seope of a ten year cooperation between SCHOTT AG and Mainz University, important contributions to the atomistic simulation of multicomponent glasses have been developed. They have made the state of the art come closer to the visionary goal of determining the properties of unknown glasses a priori by theoretical means.