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- ItemDevelopment of a simulation model for the expansion of perlite(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2001) Zähringer, Katharina; Martin, Jean-Pierre; Petit, Jean-PierreNew applications of expanded perlite in the building industry lead to a growing demand for process optimization for the expansion of periite. Periite expanders aim to adapt their furnaces and/or furnace operation conditions in order to attain more flexibility to produce different expanded periite qualities. Α way to examine the possibilities of an existing installation is the numerical simulation of the periite expansion process in that installation. The two-phase flow field and combustion in the furnace can be modelled by using currently available Computational Fluid Dynamics (CFD) codes. The only problem is the modelling of the expansion process, which changes the particle size and thus influences the two-phase flow calculations. In this paper the authors propose a physical model for the simulation of the expansion of periite. This model is based on the results of fundamental studies concerning the expansion phenomenon. It relies on the calculation of particle temperature and viscosity and thus takes into account the most influential parameters for perlite expansion. It allows the calculation of the perlite particle size as a funedon of time or of the particle's trajectory inside a furnace. Particle size statistics of the expanded product can be determined in that way. The model has been validated by comparison with experimental results from laboratory and industrial measurements.
- ItemEURIMA test guideline: In-vitro acellular dissolution of man-made vitreous silicate fibres(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2002) Sebastian, Klaus; Fellman, Jacob; Potter, Russell; Bauer, Jon; Searl, Alison; Meringo, Alain de; Maquin, Bertrand; Reydellet, Aymon de; Jubb, Gary; Moore, Martin; Preininger, Reinhard; Zoitos, Bruce; Boymel, Paul; Steenberg, Thomas; Madsen, Anders Lie; Guldberg, Marianne[no abstract available]
- ItemEvolution of the compositions of commercial glasses 1830 to 1990. Part III. Pressed glass(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2005) Smrček, AntonínThis paper considers the evolution of glasses used for pressed wares in the way already used for flat and container glass. About 160 samples of common pressed soda-lime-silica glass used for utilitarian and technical purposes are considered. The composition of pressed glass is related to flint container glass, it differs mainly in higher alkali content, low iron content and, from time to time, in addidons of K2O and BaO. Development of the compositions of flat, container, and pressed glasses is then compared and notable features such as the introductions of magnesia and alumina discussed, as is the use of high-alumina low-alkali container glasses. How future constraints may affect further developments is also considered.
- 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.
- ItemIon refraction and stress optical coefficients for di- and metasilicate glasses(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2002) Noll, Claudius; Habeck, Andreas; Brückner, RolfGlasses of the di- and metasilicate stoichiometric composition were melted, with lithium, sodium and potassium being replaced for each other. Additionally, SiO2 and B2O3 glass samples, the DGG standard glass, a float glass and a metaphosphate glass were examined. Molar mass, molar volume and oxygen partial volume were measured and found to increase in the sequence Li < Na < K. While potassium expands the glass network, the lithium ions show a counteracting behavior. The metaphosphate and the pure B2O3 glass are those with the most compact structure (related to one structure unit) and therefore with the lowest values of the studied properties. It was shown quantitatively that the polarizabilities of the nonbridging oxygen atoms are much higher than those of the bridging oxygen atoms. The influence of the cations was usually small. The origin of the small polarizability values of the B2O3 glass may be interpreted in terms of the lack of the nonbridging oxygen atoms and in terms of the denser structure of the oxygen polyhedra as compared with those in the SiO2 glass. The values of the stress-optical coefficients increase from lithium- to sodium- to potassium-dominated glasses, presumably resulting from increasing ion refraction of the nonbridging oxygen atoms. All preloaded samples of the di- and possibly also of the metasilicate composition showed an increase of the stress-optical coefficients with increasing preload at temperatures higher than the glass transformation temperature Tg. The reason is that a certain flow condition of the glass melts is frozen-in.
- ItemApplication of steam in the glass forming process(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2003) Kropp, Andreas[no abstract available]
- ItemDerivation of the temperature dependent constants for KAIO2 and NaAIO2 in a viscosity predictive model for high aluminosilicate melts(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2003) Korsgaard, Martin; Pind, Martin; Sørensen, Peter Møller; Woldum, Henriette Sie; Solvang, MetteThe compositional dependence of the viscosity was studied for two high aluminosilicate melt series: Na2O-CaO-Al2O3-SiO2 (NCAS) and K2O-Na2O-CaO-Al2O3-SiO2 (KNCAS). The viscosity and the glass transition temperature were measured by concentric cylinder viscometry and differential scanning calorimetry, respectively. This work discusses the viscosity predictive model set up by Bottinga and Weill. The temperature dependent constant, D, defining the relative impact of each component on the viscosity, was derived for the compositional range from 35 to 45 mol% SiO2 for KAIO2 and NaAlO2, respectively. With the newly derived D-values, a good agreement was achieved between measured and predicted values.
- ItemForming of noncircular cross-section SiO2 glass fibers(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2005) Wegmann, Markus; Heiber, Juliane; Clemens, Frank; Graule, Thomas; Hülsenberg, Dagmar; Schuster, KaySilica glass fibers with triangular and rectangular cross-sections have been produced by two different means, namely preform drawing and powder extrusion. For the preform drawing method, silica glass rods were machined and polished to yield preforms with the desired cross-sections. These were then heated to temperatures in excess of 1600°C and drawn to fibers with approximately 265 μm × 265 μm × 265 μm triangular and 275 μm × 100 μm rectangular cross-sections exhibiting tensile strengths between 300 and 400 MPa and bending radii smaller than 50 mm. For the extrusion route, a silica nanopowder was compounded at ≈ 150°C with a polyethylene-based binder and extruded at similar temperatures through dies with the desired exit cross-section. The fibers were debound by thermally decomposing the binder and sintered at 1100°C to yield amorphous glass fibers with approximately 205 μm × 205 μm × 205 μm triangular and 275 μm × 90 μm rectangular cross-sections. Although the two manufacturing processes are radically different, both involve flow of a fluid with a temperature-dependent viscosity and this dictates that shape trueness (i.e. flat faces and sharp corners) is a function of the drawing and extrusion rates and the temperature during drawing and sintering.
- ItemInitial practical experience in monitoring refractory material in the glass industry using the SAVEWAY system(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2000) Löhlein, AndreasBy means of the SAVEWAY system it is possible to continuously control the refractory material. The measurement of the lining wear is based on the characteristic temperature dependence of the specific electrical resistance of the refractory materials. The advantage of the SAVEWAY system in comparison with other known procedures lies in the areal monitoring of a refractory material. Trough construction areas which are difficult to overlook from the exterior can also be reliably monitored using SAVEWAY. When this system was used in the mineral wool industry it was possible to confirm the remaining wall thickness measurements by means of the SAVEWAY system when breaking out the lining. The results achieved by the glass industry up to now reflect the fact that it is possible to monitor the refractory material by means of SAVEWAY. Modified melting conditions are included in the respective calculations of the remaining wall thickness.
- ItemIR and Raman study of calcium aluminosilicate glasses of the composition xCaO ∙ xAI2O3 ∙ (100 - 2x)SiO2(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2002) Peuker, Christel; Bessau, Waltraud; Brzezinka, Klaus-Werner; Kohl, Anka; Reinholz, Uwe; Geißler, HeinzVibrational spectra are measured for calcium aluminosilicate glasses with the composition (in mol%) xCaO ∙ xAI2O3 ∙ (100 - 2x)SiO2. The OH bands show a systematic change with x in both MIR and NIR regions. The strongly asymmetric band at about 3550 cm-1 shifts to lower wave numbers with increasing x. In the same way the OH combination band at about 4500 cm-1 shifts to lower wave numbers. For the 3550 cm-1 band an extinction coefficient of about 60 1 ∙ mol-1 ∙ cm-1 is suggested for all the samples with x from 15 to 32. For the 4500 cm-1 band the extinction coefficient decreases from 1.0 to 0.49 1 ∙ mol-1 ∙ cm-1 with increasing x from 15 to 32. Systematic changes in the Raman and IR reflectance spectra reflect the substitution of Al3+ for Si4+ and a corresponding increase of Ca2+ in the network. Thus, the vibrational spectra can be related to a fully polymerized network without or with a small amount of nonbridging oxygens also for glasses with x ≥ 25.