Browsing by Author "Korsgaard, Martin"

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    Derivation 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, Mette
    The 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.
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    Redox 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, Stehen
    Systematic 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.