Browsing by Author "Bürger, Herbert"
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- ItemInvestigations 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, GünterOptical 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.
- ItemPhotochromic materials via sol-gel process(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1998) Fachet, Regina; Müller, Matthias; Bürger, Herbert; Kriltz, AntjePowders and thin films of photochromic glasses containing AgBr or AgCl microcrystals were synthesized via sol-gel process. Up to 10 wt%, of Ag⁺, bonded with suitable complexing agents, were introduced into the matrix system consisting of xSiO₂-(1 - x)Al₂O₃ (x = 0.7... 1). After drying and heat treatment the AgX microcrystals (X = Cl, Br) were characterized by X-ray diffraction and high-resolution TEM. The photochromic properties were measured using a diode array UV-VIS spectrometer.
- ItemSol-gel derived coatings with completely reversible photochromism(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2000) Fachet, Regina; Müller, Matthias; Bürger, Herbert; Kriltz, AntjeBesides the photochromic glasses based on silver halides especially the cuprous halide containing materials are of practical importance. Due to their high absorption coefficient the cuprous halides are particularly suited for the preparation of thin photochromic films. Using the sol-gel technique silicon alkoxide based coating solutions with continuously distributed photoactive components were prepared. From these sols single or multilayer coatings were produced by dipping. The precipitation of the cuprous halide microcrystals as carriers of the photochromic properties of the coatings proceeded during a subsequent heat treatment (temperature range of 100 to 800 °C). Thus it was possible for the first time to produee photochromic coatings with a pronounced darkening and with complete reversibility of the photochromic reactions at room temperature.