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Author: Brückner, Rolf × Author: Murach, Jürgen × End date: 2024 × Start date: 2020 × End date: 1999 × Start date: 1990 ×

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    structure-sensitive investigations on glass fibers from the system SiO₂-Al₂O₃-GaO
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1998) Murach, Jürgen; Makat, Andreas; Brückner, Rolf
    Glass fibers of the system SiO₂-Al₂O₃-CaO were prepared with respect to defined drawing conditions and investigated with structure-sensitive methods (birefringence, radial and axial alterations by thermal treatment at Tg). These glass fibers, which lie in a compositional sense roughly between the disilicate and silica glasses concerning the ratio network modifiers to network formers, exhibit similar optical anisotropies. On the other hand, they show remarkably lower axial and radial alterations which are exclusively contracdons on annealing for all applied drawing conditions in contrast to the silica or the alkali disilicate glass fibers. Obviously, the filling of free volume hollows with and the reinforcement of them by the Ca²⁺ ions and the smaller polarizability of the latter as compared to alkali ions are responsible for the relatively low structural anisotropy. An increase of the optical anisotropy with increasing CaO concentration is observed at comparable viscosities. This is a consequence of the increasing incorporation of the network modifier oxide which produces a weaker network strength and a larger polarizability.
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    Properties of textile glass fibers based on alkali- and boron oxide-free aluminosilicate glasses
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1998) Kim, Young Keun; Brückner, Rolf; Murach, Jürgen
    The goal of this paper is to examine the possibihty of producing fibers from alkah- and boron oxide-free glasses with properties comparable to those of commercially available glass fibers. Various compositions from the Systems SiO₂ - Al₂O₃ - CaO - RO are investigated with RO = MgO, ZnO, MnO, BaO between 0 and 10 wt%. The fibers are suitable for application as textile fibers and as reinforcement component for composites. The mechanical properties (tensile strength, Young's and shear modulus and Poisson ratio) are comparable to and/or partly better than those of commercially produced glass fibers. The chemical resistivity in 2 mol/1 NaOH is better than that of E-glass fibers. Although the diameter of glass fibers is not the only parameter which determines fiber properties and structure, it is a very important one because it influences both the mechanical and the thermal history of the fibers. For this reason, and in order to approximate commercial fiber drawing conditions, fibers were prepared with roughly the same fiber diameters. Despite this restriction the results provide information for qualitative ratings and for relative comparison of properties and structural interpretations. Of special interest is the opposite dependence of strength and elastic moduli on the fiber diameter. This is explained by means of frozen-in orientation and deformation effects of microcracks and network anisometries due to the mechanical and thermal history of the fibers produced by the fiber drawing process.