Dokument-ID Dokumenttyp Autoren/innen Persönliche Herausgeber/innen Haupttitel Abstract Auflage Verlagsort Verlag Herausgeber (Institution) Erscheinungsjahr Titel des übergeordneten Werkes Jahrgang/Band ISBN Veranstaltung Veranstaltungsort Beginndatum der Veranstaltung Enddatum der Veranstaltung Ausgabe/Heft Erste Seite Letzte Seite URN DOI Lizenz Datum der Freischaltung OPUS4-50949 Zeitschriftenartikel Balzer, R.; Behrens, H.; Waurischk, Tina; Reinsch, Stefan; Müller, Ralf; Kiefer, P.; Deubener, J.; Fechtelkord, M. Water in Alkali Aluminosilicate Glasses To understand the influence of water and alkalis on aluminosilicate glasses, three polymerized glasses with varying ratios of Na/K were synthesized [(22. 5-x)Na2O-xK2O-22.5 Al2O3-55 SiO2 with x = 0, 7.5, and 11.25]. Subsequently, these glasses were hydrated (up to 8 wt% H2O) in an internally heated gas pressure vessel. The density of hydrous glasses linearly decreased with water content above 1 wt%, consistent with the partial molar volume of H2O of 12 cm3/mol. Near-infrared spectroscopy revealed that hydroxyl groups are the dominant species at water content of <4 wt%, and molecular water becomes dominating at water content of >5 wt%. The fraction of OH is particularly high in the pure Na-bearing glass compared to the mixed alkali glasses. 27Al magic angle spinning-NMR spectroscopy shows that aluminum is exclusively fourfold coordinated with some variations in the local geometry. It appears that the local structure around Al becomes more ordered with increasing K/Na ratio. The incorporation of H2O reinforces this effect. The differential thermal analysis of hydrous glasses shows a significant mass loss in the range of glass transition already during the first upscan, implying the high mobility of water in the glasses. This observation can be explained by the open structure of the aluminosilicate network and by the low dissociation enthalpy of H2O in the glasses (≈ 8 kJ/mol). The effect of the dissolved H2O on the glass transition temperature is less pronounced than for other aluminosilicate glasses, probably because of the large fraction of Al in the glasses. 2020 frontiers in Materials 7 85 urn:nbn:de:kobv:b43-509497 10.3389/fmats.2020.00085 https://creativecommons.org/licenses/by/4.0/deed.de 2020-06-29 OPUS4-45704 Posterpräsentation Kiefer, P. Subcritical crack growth in water bearing soda-lime silicate glasses The presence of water in the surrounding atmosphere of a propagating crack has a major influence on the subcritical crack growth. While these external phenomena are well understood, there is still a lack of knowledge on the influence of structurally bound water on crack propagation. Thus, our recent study aims on the analysis of crack propagation in water bearing soda-lime silicate glasses with up to 8 wt.% water. The samples were synthesized in an internally heated pressure vessel at 0.5 GPa. Since this preparation route limits the sample sizes, standard test geometries allowing for the determination of stress intensity factors, such as double cantilever beam, are not feasible. Thus, radial cracks in the hydrous glasses were initiated by Vickers indentation and crack growth was simultaneously captured with a camera system. An automated image analysis algorithm was used for the analysis of the crack length of each single video frame. To minimize influences by atmospheric water, all experiments were conducted in a glovebox purged with dry N2. About 150 cracks per glass composition were analyzed to provide statistical significance of the Vickers-induced SCCG. The results show that structurally bound water has a major influence on SCCG by means of crack lengths, growth rates and time of crack initiation. 2018 92nd Annual Meeting of the German Society of Glass Technology in Conjunction with the Annual Meetings of the Czech Glass Society & the Slovak Glass Society Bayreuth, Germany 28.05.2018 30.05.2018 2018-08-15 OPUS4-48343 Posterpräsentation Kiefer, P. Subcritical crack growth in water bearing soda-aluminosilicate glasses The subcritical crack growth in water bearing soda-aluminosilicate glasses is compared to the crack growth in a commercial soda-lime silicate glass. The water speciation is shown for comparison of water species in the material. Differences will be discussed in the poster session. 2019 Glastechnische Tagung 2019 Nürnberg, Germany 13.05.2019 15.05.2019 2019-07-02 OPUS4-45707 Vortrag Kiefer, P. Statistical analysis of subcritical crack growth in water bearing soda-lime silicate glasses The talk was given at the PNCS-ESG 2018 in Saint Malo and summarizes the actual findings about Vickers induced crack growth in water bearing soda-lime silicate glasses. 2018 15th International Conference on the Physics of Non-Crystalline Solids & 14th European Society of Glass Conference Saint Malo, France 09.07.2018 13.07.2018 2018-08-15