Browsing by Author "Heiber, Juliane"

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    Fabrication of SiO2 glass fibres by thermoplastic extrusion
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2004) Heiber, Juliane; Clemens, Frank; Graule, Thomas; Hülsenberg, Dagmar
    The fabrication of silica glass fibres by thermoplastie extrusion of nanosize and micron SiO2 powders has been investigated. The powders were mixed with a binder system, compounded for 3 h at 150 °C, and finally extruded through a die with a 500 μm-diameter die land. After debinding the green fibres at 500 °C, these were sintered for 1 h at 1100°C under air to yield glassy and crack-free silica fibres with a final diameter of 400 μm. The effect of the two different particle size distributions as well as the influence of varying powder loading (between 38 and 58 vol.%) on the rheological properties of the feedstocks were analysed using capillary rheometry. The debinding and sintering behaviour was also investigated using mercury intrusion porosimetry, thermal gravimetrie analysis and dilatometry.
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    Forming of noncircular cross-section SiO2 glass fibers
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2005) Wegmann, Markus; Heiber, Juliane; Clemens, Frank; Graule, Thomas; Hülsenberg, Dagmar; Schuster, Kay
    Silica glass fibers with triangular and rectangular cross-sections have been produced by two different means, namely preform drawing and powder extrusion. For the preform drawing method, silica glass rods were machined and polished to yield preforms with the desired cross-sections. These were then heated to temperatures in excess of 1600°C and drawn to fibers with approximately 265 μm × 265 μm × 265 μm triangular and 275 μm × 100 μm rectangular cross-sections exhibiting tensile strengths between 300 and 400 MPa and bending radii smaller than 50 mm. For the extrusion route, a silica nanopowder was compounded at ≈ 150°C with a polyethylene-based binder and extruded at similar temperatures through dies with the desired exit cross-section. The fibers were debound by thermally decomposing the binder and sintered at 1100°C to yield amorphous glass fibers with approximately 205 μm × 205 μm × 205 μm triangular and 275 μm × 90 μm rectangular cross-sections. Although the two manufacturing processes are radically different, both involve flow of a fluid with a temperature-dependent viscosity and this dictates that shape trueness (i.e. flat faces and sharp corners) is a function of the drawing and extrusion rates and the temperature during drawing and sintering.