Browsing by Author "Völksch, Günter"

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    Crystalization in High Iron Containing Silicate Glasses - Electron Microscopy Investigation
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2004) Völksch, Günter; Harizanova, Ruzha; Rüssel, Christian; Mitsche, Stefan; Pölt, Peter
    [no abstract available]
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    Investigations into structure and composition of gel layers on medieval window glasses of the Katharinenkirche, Oppenheim (Germany), and the Cathedral St. Gatien, Tours (France)
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1995) Bräutigam, Uwe; Bürger, Herbert; Völksch, Günter
    Optical microscopy, Scanning Electron Microscopy (SEM), X-Ray Diffraction analysis (XRD) and Energy dispersive electron Probe Micro Analysis (EPMA) were used to characterize surface and subsurface layers and areas on medieval church window glasses generated by weathering and contamination, respectively. Investigations were carried out at surfaces and at existing or at artificially created cross-sections as well. Altogether 30 samples (22 from the Katharinenkirche, Oppenheim (Germany), and eight from the Cathedral St. Gatien, Tours (France)) were at disposal for the investigations. Depending on possibilities, conceded by the decisions of the responsible curators of the named historical monuments, investigations were carried out to get as much information as possible about chemical and structural characteristics of defects of the authentic glasses caused by weathering processes. In case of their appearance and detectability so-called gel layers or gel areas were of special interest. With attention to the specific conditions, samples were characterized with respect to the documentation of topographic changes of their surfaces (SEM), the detection and characterization of crystalline phases (XDA), the determination of compositions of the genuine glasses as well as material areas caused by weathering (EPMA). Using records of element-specific mappings, information about depth-dependent element distribution profiles was accessible.
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    Resistance of natural glass
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2003) Heide, Klaus; Kletti, Holger; Völksch, Günter
    Natural glass is a well-known phenomenon found in different geological formations on both the earth and the lunar surface. This demonstrates that the vitreous state has been resistant to change on these surfaces for more than a hundred million years. Glass formation is determined by magmatic, metamorphic and sedimentary processes. The quantities of naturally produced glass vary between 10^-6 and 10^9 g, and the occurrence is given in microscopie glassy inclusions as well as in 'glassy mountains'. The chemical composition of natural glass is mainly rhyolitic and peraluminous. Industrially produced glass usually contains less AI2O3 (< 10 wt%) than glass found in its natural state. The transformation of the glassy state occurs in different processes (in many cases at constant volume): crystallization ('devitrification'), solution (corrosion), or hydratization and pallagonitization. By these processes, glass is transformed into sheet silicates, zeolithes, feldspars etc. and amorphous gels of silicon, iron, manganese etc. Natural glass has been under consideration for use as a suitable material for isolating complex and dangerous wastes. To help solve problems of waste management particular to industrial production, and to achieve a greater productive use of natural glass resources, glass scientists and engineers as well as geoscientists will have to cooperate in the future.