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Development of a simulation model for the expansion of perlite
New 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.
Chemical surface and thin film analysis in glass coating
After a short overview of recent analytical techniques for compositional surface analysis and the determination of concentration depth profiles, the principle, the Instrumentation and the Performance of the routinely used electron spectroscopic and mass spectrometric methods, namely photo- and Auger electron spectroscopy as well as secondary ion and secondary neutral mass spectrometry, are described. The application of these techniques to electrically insulating surfaces and layer structures is particularly emphasized by corresponding practical examples. Secondary neutral mass spectrometry is specifically addressed with regard to the potentialities of the novel high-frequency mo d e of electron-gas secondary neutral mass spectrometry for quantitative composition analysis and high-resolution depth profiling of electrically nonconducting sample structures.
Weathering of tin oxide coated glass with low IR emissivity
The 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.
Öfen zur vollelektrischen Schmelze von Glas in Deutschland
Die HVG verschickte im November 1993 einen Fragebogen an alle Betreiber von vollelektrischen Wannen in Deutschland mit einem Durchsatz von mehr als 10 t/d. 24 ausgefüllte Fragebögen wurden der HVG bis zum April 1994 zurückgesandt. Auch 6 vollelektrische Öfen von Nichtmitgliedern sind in die Auswertung mit aufgenommen. Ausgewertet wurden die Wannengröße (Durchmesser und Badtiefe), Art und Material der Heizelektroden, Gemengeeinlage, Gesamtscherbenanteil, Glasart und gefertigtes Erzeugnis, Schmelzleistung und spezifischer Wärmeverbrauch. In 8 Wannen wird Borosilicatglas erschmolzen, in 6 Kalk-Natronsilicatglas, in 4 Bleikristall- und in 2 Kristallglas, in 2 weiteren C-Glas und in einer Opalglas. Gefertigt werden Glasbehälter, Rohre, Wirtschaftsglas, Fasern, Streuscheiben und Beleuchtungsglas. Sowohl bei der Wannenfläche als auch bei der Badtiefe läßt sich in Abhängigkeit von der maximalen Tagestonnage eine gemeinsame Tendenz bei fast allen Öfen erkennen. Der spezifische Wärmeverbrauch sinkt mit steigendem Durchsatz bzw. größerem Wannenvolumen, da das Verhältnis von Oberfläche zu Wanneninhalt besser wird damit die Wandverluste anteilmäßig geringer werden. An 20 Wannen werden Molybdänelektroden und an 4 Wannen Zinnoxidelektroden eingesetzt. Diese Heizelektroden sind an 9 Wannen als Seiten- und Bodenelektroden eingebaut, an 7 Wannen als Seitenelektroden, an 5 Wannen als Bodenelektroden und an 3 Wannen als Topelektroden.
study of structural modification in extruded and heat-treated lithium disilicate glasses by the method of radiation color centers chronospectroscopy
Samples of extruded and non-extruded lithium disilicate glasses were studied. Extruded glass samples were cut out along and across the extrusion axis of fmished cylindrical rods. For all the samples, spectra of radiation-induced absorption, Δα(E), were measured for various time instants after the cessation of X-irradiation. On the data basis obtained, kinetic dependences. Δα = f(t), were plotted and analyzed. In the diagram "Δα versus lgt", they are represented by straight hnes. Each of them is falling down with its own constant slope a. These a's are rate parameters of the decay of radiation color centers (CCs). They appear to be functions of average distances between recombinating electron and hole CCs. The above α-parameter decreases when passing from the longitudinal cut extruded glass sample to the sample of the non-extruded glass and finally to the transversely cut extruded glass sample. These data mean that, in the course of extrusion, the glass structure becomes less dense in the axial direction of extruded glass rods and more dense in the radial one. Α 4-hour heat treatment at 465 °C (≈5°C above the glass transformation temperature, Tg) eliminated the above anisotropy of radiation properties in extruded glasses and forced their anisometric structures to return to the isometric State characteristic of the non-extruded glass.
EURIMA test guideline: In-vitro acellular dissolution of man-made vitreous silicate fibres
[no abstract available]
Chemical composition of medieval glass from excavations in West Germany
Investigations of excavated glass fragments from the Roman-Frankish cemetery at Krefeld-Gellep, the Carolingian imperial palace with glassworks at Paderborn, the monasteries and towns of Corvey, Höxter and Brunshausen-Gandersheim and several glassworks in the Bramwald, Hils, Spessart and Eichsfeld areas allow conclusions on the sequence of major medieval glass types. Exhaustion of Imports of trona-soda or soda raw glass and increased needs caused the introduction of woodash as domestic alkali and earth alkali source for glass manufacture at about 800 AC. Early woodash glass from 800 to 1000, woodash glass from about 1000 to 1400 and woodash-lime glass from about 1400 to post-medieval times were the major glass types. They were accompanied by minor Imports of soda-lime and soda-ash glass objects, the latter since about 1300. From about 1100 to 1400 woodash-lead and lead glass have been produced from the P bO byproducts of the silver metallurgy. Galena from the Harz Mountains was a major source of lead for lead glass in northwestern Europe. The average production of a medieval glassworks was in the order of 15 t glass per year and its requirements for ash and fuel about 30001 wood. The number of glassworks in Germany during the late medieval period (moving after 5 to 30 years from one to another location) is tentatively estimated to be in the order of 40. Their main furnaces were constructed for about 1400 C working temperature. The occurrence of the medieval chemical glass types in a sequence allows some rough dating of glass fragments.
Laser glass level measurement - Possibilities and perspectives using the Horn System
[no abstract available]
Evolution of the compositions of commercial glasses 1830 to 1990. Part III. Pressed glass
This 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.
Ion refraction and stress optical coefficients for di- and metasilicate glasses
Glasses 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.