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Author: Frischat, Günther Heinz × End date: 1999 × Start date: 1999 ×

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Now showing 1 - 4 of 4
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    Sol-gel preparation of scratch-resistant AI₂O₃ coatings on float glass
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1999) Hauk, Rainer; Frischat, Günther Heinz; Ruppert, Karl
    Glass surfaces including those of automotive glazing show insufficient Scratch resistance. In order to improve this, a sol-gel process has been developed by means of which scratch-resistant and transparent corundum coatings (α-Αl₂O₃) may be deposited on glass surfaces. Coatings which were produced by using commercial boehmite(AlOOH) dispersions could also be completely transformed into α-Αl₂O₃, but they were not dense enough at about 500 nm thickness. Coatings produced by an alkoxide-gel process from aluminium butoxide were dense at a thickness of maximal 100 nm and adhered very well to the glass surface which had been slightly roughened by HF etching. Α Scratch test with a quartz grain showed that the damage of the glass surfaces coated in this way was less than 2 % compared to that of uncoated surfaces. Transmission of these coated glasses was about 90 % in the visible wavelength ränge.
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    Morphology of silica and borosilicate glass fracture surfaces by atomic force microscopy
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1999) Wünsche, Christine; Rädlein, Edda; Frischat, Günther Heinz
    Fracture surfaces of Herasil (silica) and Duran (borosilicate) glass rods were examined with an atomic force microscope. Generally the roughness in the fracture surface increases with growing distance from the origin of fracture. The morphology displays a variety of features. In the smooth fracture mirror near the origin of fracture the surface consists of small hillocks ≈25 nm in diameter and ≤ 1 nm high. With growing distance these hillocks increase in size and height. In the mist zone bigger outcrops occur with steep flanks. Steps can also be discovered in the fracture surface. Parts of the surface are covered by ripples, which are proposed to result from a local melting of the glass near the crack tip during fracture.
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    Analysis of as-prepared and corroded glass fibers by secondary neutral mass spectrometry
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1999) Müller-Fildebrandt, Constanze; Priller, Stefan; Frischat, Günther Heinz
    Three types of glass fibers, differing mainly in their alumina, alkaline earth and alkali oxide contents, were investigated by secondary neutral mass spectrometry. The investigation was carried out on fibers as-prepared and after exposure to humidity and to attack in distilled water. Concentration-depth profiles of the fibers obtained by secondary neutral mass spectrometry showed that the asprepared fibers were already pre-experimentally weathered in a ≤50nm deep surface zone. The pattern of chemical change and leaching was found for each fiber to be similar after exposure to humidity and short-term attack by water, respectively, however with enhanced leaching observed in water, where the leached elements are removed from the fiber surfaces. Different leach mechanisms could be established for the different fiber types and changes of leach mechanisms with time could be observed. Altogether, the depth profiling method proved to be a powerful tool to elucidate the comphcated leach mechanisms also in the case of glass fibers.
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    Optimizing the Christiansen-Shelyubskii method and its comparison with industrial control methods for homogeneity determination of glasses
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1999) Heidrich, Roland Paul; Frischat, Günther Heinz
    The Christiansen-Shelyubskii method used in this work was optimized experimentally. Different tests were performed with two grain fractions of standardized crushed sheet glass. Maximum transmissions, half-widths and their Standard deviations were optimized, and it was further shown that sampling, an appropriate cleaning of the granulated glass and the quality of the optical cells used are of great importance, too. Α variety of industrial glasses was investigated and the Christiansen-Shelyubskii homogeneity numbers were compared with the homogeneity data provided by the glass manufacturers using industrial homogeneity control methods for Container, tube and flat glasses, respectively. Although the physical principles of the homogeneity methods compared were dissimilar, mostly qualitatively similar trends were found. Only in the case of the Mach-Zehnder interferometry method, which is based on a similar principle as the Christiansen-Shelyubskii method, a quantitative correlation analysis was possible. Reasonable agreement between the homogeneity values from both methods was achieved. It was further shown that the Christiansen-Shelyubskii method can monitor the homogeneity during glass melting with external cullet, both in freshly prepared and in composted states.