Browsing by Author "Kaps, Christian"
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- ItemSodium/silver ion exchange between a non-bridging oxygen-free boroaluminosilicate glass and nitrate melts(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1991) Kaps, Christian; Fliegel, WolframA sodium boroaluminosilicate glass, in which no non-bridging oxygen could be detected, is contacted with AgNO3—NaNO3 melts at 375 °C. A diffusion-controlled Na+/Ag+ exchange has been observed in the bulk of the glass up to a degree of exchange of 70 % (Fickian behaviour). For a higher degree of exchange network-structure relaxation processes appear as a result of the viscosity-lowering effect of silver, causing a change of the diffusion conditions during the ion exchange in the glass (non-Fickian behaviour) . The time-independent equilibrium concentrations at the glass surface refer to a remarkable affinity of the glass for the highly polarisable Ag+ cations (degree of exchange: 98 %). This result can be explained by coordinative binding of silver on the basic bridging oxygen of the AlO4/2 tetrahedrons into the glass network.
- ItemSpecial glass for integrated and microoptics(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1991) Poßner, Torsten; Schreiter, Gerd; Müller, Rudolf; Kaps, Christian; Kahnt, HannoA special glass for integrated and microoptics, designed for Ag+ — Na+ ion exchange, is introduced. A maximum refractive-index increase of 12.2 ∙ 10^-2 (λ = 633 nm) is possible without any silver reduction. To match the numerical aperture to standard fibres, the dilution of AgNO3 is investigated. Profile burying at low temperatures is possible using an eutectic melt of KNO3 and NaNO3 . Diffusion coefficients and melt mobilities are determined from refractive-index profiles of slab waveguides. Field-assisted ion exchange in combination with profile burying enables the generation of matched refractive-index profiles of slab and strip waveguides. Planar microlenses expand the series of possible applications.
- ItemThermodynamic behaviour of the non-bridging oxygen-free glass system X Ag2O ∙ (2-X) Na2O ∙ 2 Al2O3 ∙ 3 SiO2 ∙ B2O3 in contact with nitrate melts(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1991) Kaps, ChristianEquilibrium data for the Na+/Ag+ ion exchange at 375 °C between the glass 2 Na2O ∙ 2 Al2O3 ∙ 3 SiO2 ∙ B2O3 (Tg = 560 °C), which is free of non-bridging oxygen, and AgNO3—NaNO3 salt melts are analyzed in two different ways (I and II). With the description of the glass as a regular solution (I) as well as with that as a mixed phase with a ñ-type behaviour (II), the high selectivity of the glass system for the Ag+ ions, having the larger crystalline ionic radius as compared to the Na+ ions, is reflected by model-owned parameters. However, the existence of mechanical compressive stress and its partial reduction by structure relaxation in consequence of the viscosity-lowering effect of a high silver content are considerably differently in the two models.