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- ItemNonlinear Maxwell behavior of sodium silicate glass in the surroundings of glass transition temperature(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2005) Fränzel, Wolfgang; Grau, PeterPresented are results from uniaxial cylinder upsetting tests of sodium silicate glass at different constant deformation rates each combined with relaxation experiments in the temperature range 480 to 580°C. Due to the complete stress relaxation to final load zero (vanished carrying capacity) also below glass transition temperature Tg, it follows Maxwell behavior in principle. But the rheological analyses of loading and unloading experiments together show that only nonlinear Maxwell model approaches can adequately describe the deformation behavior of the glass in the surroundings of Tg.
- ItemNoncontact measurement of central lens thickness(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2005) Kunkel, Matthias; Schulze, Jochen[no abstract available]
- ItemWater concentration and diffusivity in Silicates obtained by vacuum extraction(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2005) Müller, Ralf; Gottschling, Peter; Gaber, MartinWater concentration, Cw, and the mean effective diffusion coefficient of water, Dw, were measured by vacuum hot extraction coupled with mass spectrometer evolved gas analysis (VHE). The study includes silica, soda- and potassium-lime-silica, cordierite, and lamp bulb glasses of water concentrations between 0.017 and 0.17 mol H2O/l (122 and 1159 wt. ppm) as well as cordierite single crystals. Cw was obtained by integration of the VHE water degassing rate dQw/dt. For powdered samples (≈ 50 to 150 mg) of silica, soda-lime-silica and cordierite glass with water concentrations between 0.033 and 0.15 mol/1, VHE results well confirm IR spectroscopy within 5 to 15 % accuracy. Dw could be obtained by two methods: dQw/dt of powdered samples was measured during isothermal VHE experiments and dQw/dt fitted versus time with the appropriate diffusion models. Alternatively, powdered samples were pre-annealed in vacuum before measuring their residual water concentradon by VHE as described above. Cw was then analogously fitted versus the vacuum pre-annealing time. The applied methods and samples allowed the measuring of Dw within 10-9 and 10-13 cm2 s-1. Calculated values of Dw for soda-lime-silica glasses agree with literature data and values obtained by IR spectroscopy within a factor of 2 to 4.
- ItemProcessing of molten solid residues(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2005) Bieniarz, Piotr; Höhne, Diethard; Hessenkemper, Heiko; Zawada, AnnaAn alternative way of recovery, recycling and re-integration of solid wastes on a laboratory scale is demonstrated. The analysed synthetic slags belong to the System SiO2-Al2O3-CaO-MgO-Fe2O3-K2O-Na2O. Α polynomial model has been developed by means of a computing program in order to calculate some important technological features directly from a variable oxide concentration and to determine a processable composition. Furthermore, a concept of maximum application of the residues is suggested for slags from waste incineration and other industrial processes with relative low volatile components. Rolling has been chosen as the most suitable forming technique, because recycling melts show a short forming interval and an aggressive behaviour towards refractory materials. It is possible to form plates or tiles which afterwards can additionally be shaped e.g. to create profiles or breaking points. Because of their affmity to crystallization the glassy end-products can be devitrified at the surface (into semicrystalline products, i.e. glass-ceramics) to receive a better resistance. The present results show the possibility of using well known forming and treating processes to make high value products from low-value by-products, with a considerable economical advantage.
- 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.
- ItemRedox behaviour of iron bearing glass fibres during heat treatment under atmospheric conditions(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2005) Kirkegaard, Lisa Frank; Korsgaard, Martin; Yuanzheng, Yue; Mørup, StehenSystematic pre-oxidation experiments in the glass transition region have been carried out on iron bearing aluminosihcate glass fibres in air. The pre-oxidized fibres are up-scanned in a simultaneous thermal analyser to a temperature of 1273 Κ under atmospheric conditions in order to measure the increase in mass, which is a consequence of the oxidation of ferrous iron to ferric iron. Based on the Mössbauer spectroscopic measurements, an approach has been proposed to calculate the redox State of the iron from the increase in mass of the fibres. The quantitative relationships have been found between the redox State of the fibres and both the pre-oxidation temperature and the pre-oxidation duration. These relationships can be used to predict the degree of oxidation of the fibres by knowing the heat treatment conditions and vice versa.
- ItemIn-vitro dissolution rate of mineral fibres at pH 4.5 and 7.4 - A new mathematical tool to evaluate the dependency on composition(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2005) Knudsen, Torben; Guldberg, MarianneUseful mathematical models for the compositional dependency of the dissolution rate in flow-through measurements are presented. The rate of dissolution Kdis(Si) was determined for 81 different compositions at pH 4.5 and 7.4, respectively. Α high degree of correlation to composition was found at both pH regimes. In this work, the commonly used regression equation: Kdis= K0 exp(S) or In Kdis = In K0 + S has been replaced by: Kdis = K∞ exp(S)/(exp(S)+l) , where S = ∑CiXi is a linear combination ("index") of oxide contents. K0 and K∞ are constants, the latter is a limiting dissolution rate for S → ∞. At the other extreme S → -∞ is tends to zero. This feature of the new regression equation improves the correlation for the data sets applied and allows it to cover wider ranges of compositions. The coefficients in ∑CiXi are clearly different in the two regimes (pH 4.5 and 7.4). The most important difference is between the coefficients of alumina. At pH 4.5, it is highly positive, and at pH 7.4, it is highly negative.
- ItemEffects of redox State and atmosphere on the surface tension of ironcontaining soda-lime-silica melts(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2005) Wing, Douglas R.; Clare, Alexis G.; Jones, Linda E.The density and surface tension of 15Na2O 11CaO 74SiO2 glass melts (composition in mol%) containing additions of 0.5 and 1.0 mol% Fe2O3 were measured using the sessile and pendant drop techniques at various temperatures between 1200 and 1400°C. Melts of each composition were prepared under oxidizing and reducing conditions in order to study the effect of iron redox state on the surface tension. Surface tension measurements were carried out in reducing (96 %Ar/4 %Η2), inert (Ar) and oxidizing (dry air) atmospheres. The density of the melts increased with increasing iron content and decreasing melt temperature. The surface tension of the iron containing melts was found to be influenced by the atmosphere and its effect on iron coordination. It was determined that melts with high concentrations of Fe3+ are most susceptible to changes in the atmosphere, since Fe3+ can have either tetrahedral or octahedral coordination. Α minimum in melt surface tension was detected between 1300 and 1350°C for the iron containing melts.
- ItemLong-range granular feature of silicate glasses and its relation to glass properties(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2005) Wang, ChunNumerous experimental results show that silica and silicate glasses consist of higher density granules about 20 to 50 nm sized and lower density linkages. Such long-range feature should originate from the long-range density fluctuation of the glass-forming liquid. Due to the highly coordinated network structure of glass the lower density regions may be under strain. Following this assumption many phenomena of glass observed here and reported in the literature can be explained well, e.g. anomalous conductivity, brittleness, granular boundary contour of crack, high conductivity on the fracture surface, cloudy damage after dishwashing, corrosion products on glass surface, distribution pattern of Ag colloidal particles in float glass bath side, disproportional large influence of water on glass properties, the unusual increase in expansion coefficient with increasing modifier content, etc.
- ItemTime resolved fluorescence measurements on Tb3+ and Mn2+ doped glasses(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2005) Herrmann, Andreas; Ehrt, DorisTb3+ (4f8) and Mn2+ (3d5) ions, known as active luminescent centres for blue, green and red fluorescence, were doped in various fluoride, phosphate and Silicate glasses with well known structure. Narrow bands of f-f transitions with strong emission of Tb3+ in the blue, green and red and broad bands of d-d transitions of Mn2+ were measured with green emission in high optical basicity glasses with tetrahedrally coordinated Mn2+. Orange to red Mn2+ emission was found in glasses with low optical basicity where Mn2+ is octahedrally coordinated. Lifetimes, τe, in the range of milliseconds were recorded in dependence of glass composition and dopant concentration for both Tb3+ and Mn2+ doped glasses. Fluorescence lifetimes are as well shortened by higher basicity of the glasses as by increasing dopant concentration.