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Author: Frischat, Günther Heinz × End date: 2023 × Start date: 2023 × End date: 2009 × Start date: 2000 × Has files: Yes ×

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    Preparation and properties of model glasses of historic enamels of the Green Vault Museum, Dresden
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2005) Wagner, Marcel; Frischat, Günther Heinz; Hellmold, Peter
    Many enamelled art objects of the Green Vauk Museum, Dresden, have been suffering a severe deterioration of the enamel layers during the last 20 to 30 years. The authors obtained three splinters of about 200 mg weight each of green, blue, and opaque turquoise enamel of the Aurangzeb ensemble. Model glasses of these originals were prepared which should match them as closely as possible. The investigations showed that the simple degree of network polymerization related to the SiO2/Na2O ratio is insufficient to understand their chemical properties even if one takes components such as MgO, CaO or AI2O3 also into consideration. To understand further structural influences IR, UV/VIS, and EPR spectroscopy studies were performed on the enamels, and it could be evidenced that components such as MnO, Fe2O3, CuO, CoO, PbO and SnO2 not only act as colorants or opacifiers but also as stabilizers of these materials. Taking this into account the chemical and physical behavior of the respective enamels in the museum can be elucidated.
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    Preparation and characterization of Na2O-Al2O3-B2O3 sol-gel glasses with aluminum lactate and formiate as precursors
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2005) Hoyer, Lars P.; Helsch, Gundula; Frischat, Günther Heinz; Zhang, Long; Eckert, Hellmut
    In this work aluminum lactate and aluminum formiate have been used as precursors to obtain room temperature stable sols and gels and after annealing homogeneous glasses in the System Na2O-Al2O3-B2O3. The local environments and connectivities of boron and aluminum have been investigated by 11B and 27Al solid-state nuclear magnetic resonance (NMR). It was found that the local atomic structures of the sol-gel glasses markedly depend on the precursors and the preparation routes and are also dissimilar to those of melt quenched glasses of the same compositions. Thus, for example, the fractions of BO3/2 and BO4/2 units differ and it is interesting to note that there are no asymmetric ΒO2/2(O-) units present in the sol-gel materials. The 27Al spectra show AI in four-, five- and sixfold coordination, whose relative abundance in a given glass composition is also dependent on the preparadon route. Rotational echo double resonance (REDOR) 11B {27Al} and 27Al {11B} resuhs indicate that the extent of B-O-Al connectivity is diminished in the gel prepared glasses when compared to the melt cooled glasses. Element distributions are reported on the basis of secondary neutral mass spectrometry (SNMS) data, and the nanostructures of surfaces have been characterized by atomic force microscopy (AFM).