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Author: Hornberger, Helga ×

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    Machining of silica glasses using excimer laser radiation
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1996) Hornberger, Helga; Weißmann, Rudolf; Lutz, Norbert
    Various silica glasses were engraved deliberately by excimer laser radiation using wavelengths of 308 and 248 nm. The ablation of different samples was investigated by systematic Variation of the processing parameters. The ablation rates were determined using profilometry and gravimetric measurements by evaluating the processing quaUty and the morphology of the processed surfaces was considered. The phenomenon of ablation is explained as a non-linear interaction of the laser beam and the glass. The experimental results show that the ablation behaviour of silica glass depends on the wavelength and the intensity of the laser radiation, on the surface quahty and the degree of purity of the glass. Although high ablation rates were obtained, the suitability of excimer lasers for micromachining is restricted due to the rough surface morphology and poorly defmed edges.
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    Mechanical properties and microstructure of In-Ceram, a ceramic-glass composite for dental crowns
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1995) Hornberger, Helga; Marquis, Peter M.
    The mechanical properties and microstructure of In-Ceram have been investigated. In-Ceram is an alumina-glass composite used for the core of dental crowns produced by infiltrating a glass through a porous alumina skeleton framework. A key property of dental cores besides aesthetic is mechanical strength. The factors affecting strength and microstructure of In-Ceram are discussed in comparison with conventional dental core porcelain. The mean strength of In-Ceram has been found to exceed 600 MPa (ballon- ring tests), but the variance of the measurements is high, demonstrating the importance of the precise preparation of the composite. The influence of aqueous and acidic environment on strength was also studied. The results indicate that In-Ceram, although sensitive to acetic and aqueous environments, combines a level of strength and toughness which should result in an improved clinical performance. EDX-analysis and dilatometry showed that the composition and thermal expansion of the composite phases, glass phase and alumina particles, contribute to the fracture resistance and strength of the composite.