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 OPUS4-54881 Zeitschriftenartikel Tielemann, Christopher; Reinsch, Stefan; Maaß, Robert; Deubener, J.; Müller, Ralf Internal nucleation tendency and crystal surface energy obtained from bond energies and crystal lattice data We present an easy-to-apply method to predict structural trends in the internal nucleation tendency of oxide glasses. The approach is based on calculated crystal fracture surface energies derived from easily accessible diatomic bond energy and crystal lattice data. The applicability of the method is demonstrated on literature nucleation data for isochemically crystallizing oxide glasses. Elsevier B.V. 2022 Journal of Non-Crystalline Solids: X 14 1 5 urn:nbn:de:kobv:b43-548814 10.1016/j.nocx.2022.100093 https://creativecommons.org/licenses/by/4.0/deed.de 2022-05-23 OPUS4-56074 Posterpräsentation Tielemann, Christopher Oriented Surface Crystallization Up to now, oriented surface crystallization phenomena are discussed controversially, and related studies are restricted to few glasses. For silicate glasses we found a good correlation between the calculated surface energy of crystal faces and oriented surface nucleation. Surface energies were estimated assuming that crystal surfaces resemble minimum energy crack paths along the given crystal plane. This concept was successfully applied by Rouxel in calculating fracture surface energies of glasses. Several oriented nucleation phenomena can be herby explained assuming that high energy crystal surfaces tend to be wetted by the melt. This would minimize the total interfacial energy of the nucleus. Furthermore, we will discuss the evolution of the microstructure and its effect on the preferred crystal orientation. 2022 26th International Congress on Glass Berlin, Germany 03.07.2022 08.07.2022 2022-10-24 OPUS4-53073 Zeitschriftenartikel Tielemann, Christopher; Busch, R.; Reinsch, Stefan; Patzig, C.; Höche, T.; Avramov, I.; Müller, Ralf Oriented surface nucleation in diopside glass Es wird die Texturbildung in kristallisierendem Diopsidglas im Zusammenhang mit der Oberflächenbeschaffenheit der unbehandelten Probe untersucht. Zudem wird der diskutiert, dass es sich bei der Texturbildung in Gläsern höchstwahrscheinlich um ein Nukleationsphänomen handelt welches auf die richtungsabhängige Grenzflächenenergie der kristallisierenden Phase zurückzuführen ist. Elsevier B.V. 2021 Journal of Non-Crystalline Solids 562 10.1016/j.jnoncrysol.2021.120661 2021-08-09 OPUS4-53075 Zeitschriftenartikel Busch, R.; Tielemann, Christopher; Reinsch, Stefan; Müller, Ralf; Patzig, C.; Krause, M.; Höche, T. Sample preparation for analytical scanning electron microscopy using initial notch sectioning A novel method for broad ion beam based sample sectioning using the concept of initial notches is presented. An adapted sample geometry is utilized in order to create terraces with a well-define d step in erosion depth from the surface. The method consists of milling a notch into the surface, followed by glancing-angle ion beam erosion, which leads to preferential erosion at the notch due to increased local surface elevation. The process of terrace formation can be utilized in sample preparation for analytical scanning electron microscopy in order to get efficient access to the depth-dependent microstructure of a material. It is demonstrated that the method can be applied to both conducting and non-conducting specimens. Furthermore, experimental parameters influencing the preparation success are determined. Finally, as a proof-of-concept, an electron backscatter diffraction study on a surface crystallized diopside glass ceramic is performed, where the method is used to analyze orientation dependent crystal growth phenomena occurring during growth of surface crystals into the bulk. Elsevier B.V. 2021 Micron 150 10.1016/j.micron.2021.103090 2021-08-09 OPUS4-51336 Posterpräsentation Scheffler, F.; Tielemann, Christopher Crystallization of glasses studied with PEEM A heat treated glass that formed crystals under controlled conditions can be a glass ceramic. A proper understanding of crystallization in glassy melts is needed yet still lacking. Involved processes include the mobility of Elements within the glass during heat treatment and the reorganization of atomic bonds during crystallization. This change in coordination number of certain elements is easily observable in bulk glass samples during heat treatment with XAS. Our plan was to monitor these reorganization processes in situ at the immediate surface during heat treatment with PEEM to get time and spatial resolved data. 2020 Joint Meeting of the Polish Synchrotron Radiation Society and SOLARIS Users Online meeting 09.09.2020 11.09.2020 2020-09-30 OPUS4-47536 Posterpräsentation Tielemann, Christopher First hints on reorientation of surface crystals Up to now, the mechanisms of surface nucleation and surface-induced texture formation are far from being understood. Very few observations of crystal orientation were focused on separately growing surface crystals. In conclusion, no systematic studies on initially oriented crystal growth or nucleation from defined active surface nucleation sites exists. Therefore, the main objective of this just is to advance the basic understanding of the mechanisms of surface-induced microstructure formation in glass ceramics. As a first attempt, we focus on reorientation of separately growing surface crystals during their early growth. 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. Mai 2018 30. Mai 2018 2019-03-15 OPUS4-47537 Vortrag Tielemann, Christopher Surface Initiated Microstructure Formation in Glass -Ceramics Übersicht zur Oberflächeninitiierten Mikrostrukturbildung in Glasoberflächen. Dabei wird auf die Kristallvorzugsorientierung senkrecht zur Oberfläche der sich unter Temperatureinfluss behandelten Glasproben eingegangen. Zudem werden die ersten Experimente zur Eingrenzung des Ursprungs dieser Orientierung vorgestellt. 2019 AK Glasig-kristalline Multifunktionswerkstoffe 2019 TU Clausthal, Germany 21.02.2019 22.02.2019 2019-03-18 OPUS4-58723 Zeitschriftenartikel Scheffler, Franziska; Fleck, Mirjam; Busch, Richard; Casado, Santiago; Gnecco, Enrico; Tielemann, Christopher; Brauer, Delia S.; Müller, Ralf Surface Crystallization of Barium Fresnoite Glass: Annealing Atmosphere, Crystal Morphology and Orientation Controlled oriented crystallization of glass surfaces is desired for high precision applications, since the uppermost crystal layer significantly influences the properties of the material. In contrast to previous studies, the data presented here deal with separated crystals growing at defect-free surfaces in four atmospheres with different degrees of humidity (ambient/dry air, argon and vacuum). A glass with the composition 2 BaO-TiO2-2.75 SiO2 was heat-treated at 825 °C until fresnoite (Ba2TiSi2O8) grew to a significant size. The crystal growth rate is found to increase with increasing humidity. The morphology of the crystals changes from highly distorted dendrites in the driest atmosphere (vacuum) to circular/spear-head-shaped crystals in the wettest atmosphere (ambient air), which we attribute to a decrease in viscosity of the glass surface due to water uptake. The least distorted crystals appear in the form of depressions of up to 6 µm. This has an influence on the observed crystal orientation, as measured by electron backscatter diffraction (EBSD). The pulled-in crystals change the orientation during growth relative to the flat glass surface due to an enrichment in SiO2 at the crystal fronts. This confirms that the orientation of crystals is not fixed following nucleation. Basel MDPI AG 2023 Crystals 13 3 1 17 urn:nbn:de:kobv:b43-587230 10.3390/cryst13030475 https://creativecommons.org/licenses/by/4.0/deed.de 2023-11-02 OPUS4-58170 Zeitschriftenartikel Ivanov, V.V.; Tielemann, Christopher; Avramova, K.; Reinsch, Stefan; Tonchev, V. Modelling crystallization: When the normal growth velocity depends on the supersaturation The crystallization proceeds by the advance of the crystal faces into the disordered phase at the expense of the material excess, the supersaturation. Using a conservation constraint for the transformation ratio α∈[0,1] as complementing the rescaled supersaturation to 1 and a kinetic law for the normal growth velocity as function of the supersaturation raised to power g, the growth order, we derive an equation for the rate of transformation dα/dt. We integrate it for the six combinations of the three spatial dimensions D = 1, 2, 3 and the two canonical values of g = 1, 2 towards obtaining expressions for αDg. The same equation, with g = 1 and D = n (n is the so called Avrami exponent) is obtained when taking only the linear in α term from the Taylor's expansion around α = 0 of the model equation of Johnson-Mehl-Avrami-Kolmogorov (JMAK). We verify our model by fitting datasets of α21 and α31 (from α = 0 to αupper = 0.999) with JMAK to obtain from the fit n = 1.725, 2.43, resp. We show further how the values of n depend on the value of αupper to which the fit is performed starting always from 0. Towards building a validation protocol, we start with validating α21 with published results. Elsevier Ltd. 2023 Journal of Physics and Chemistry of Solids 181 1 10 urn:nbn:de:kobv:b43-581706 10.1016/j.jpcs.2023.111542 https://creativecommons.org/licenses/by-nc-nd/4.0/deed.de 2023-09-06