TY - CONF A1 - Unger, Brita A1 - Jancke, Harald A1 - Müller, Renate A1 - Peplinski, Burkhard A1 - Hähnert, Manfred ED - Rüssel, C. T1 - Sol-gel derived precursors for cordierite glass-ceramics T2 - 5th International Otto Schott Colloquium ; 5. Internationales Otto-Schott-Kolloquium CY - Jena, Germany DA - 1994-07-10 PY - 1994 SN - 0946-7475 N1 - Serientitel: Glass science and technology – Series title: Glass science and technology IS - 67 SP - 448 EP - 451 PB - Verl. Dt. Glastechn. Ges. CY - Frankfurt/Main AN - OPUS4-12598 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Unger, Brita A1 - Rurack, Knut A1 - Müller, Ralf A1 - Jancke, Harald T1 - Untersuchungen zur Alterung von Kieselsolen und -gelen T2 - 11. Arbeitstagung des AK Nichtkristalline und Partiellkristalline Strukturen CY - Wolfersdorf, Deutschland DA - 2003-09-08 PY - 2003 UR - http://www2.uni-jena.de/chemie/DGK-AK4/VOR_03/Unger.pdf SP - 1(?) EP - 10(?) AN - OPUS4-3119 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Unger, Brita A1 - Rurack, Knut A1 - Müller, Ralf A1 - Jancke, Harald A1 - Resch-Genger, Ute T1 - Microscopic vs. macroscopic structural evolution of SiO2 sols and gels employing a tailor-made fluorescent reporter dye N2 - The short- and long-term structural evolution and aging of sol–gel materials prepared under mild conditions are studied by fluorometry, dynamic light scattering (DLS), 29Si NMR and gravimetry. In combination with the first, a newly developed donor–acceptor-substituted fluorescent probe with two acidophilic sites of different strength and topology is introduced. Its performance in detecting changes in parameters such as polarity, proticity, and pore volume on the microscopic scale is compared to two other dyes and to the macroscopic changes revealed by DLS, NMR and gravimetry. At early stages of the sol–gel process, fluorometry, DLS and NMR reveal similar changes which are typical of the structural evolution of SiO2 sols having different synthesis parameters. During later times of sol aging, DLS and NMR reflect the growth of the network and indicate that all sols approach similar structural equilibria. Fluorometry supports these findings by signalling a gradual decrease in mobile species with high proton activity. The formation of the spanning cluster upon gelation is strongly evident only from DLS results while the local environment of the fluorophore remains largely unchanged. However, the fluorescent dye is able to report microscopic changes even during long-term aging. Drying of the gels with a pronounced contraction of solvated pores is readily observable by fluorometry and gravimetry. During the late reaction stages, the fluorescence properties of the tailor-made dye are still sensitive toward the environment. PY - 2005 DO - https://doi.org/10.1039/b501622c SN - 0959-9428 SN - 1364-5501 VL - 15 IS - 30 SP - 3069 EP - 3083 PB - Royal Society of Chemistry CY - Cambridge AN - OPUS4-10378 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rurack, Knut A1 - Unger, Brita A1 - Müller, Ralf A1 - Jancke, Harald A1 - Resch-Genger, Ute T1 - Die Strukturentwicklung von SiO2 Solen und Gelen im Vergleich mikroskopischer und makroskopischer Untersuchungsmethoden T2 - 77. Glastechnische Tagung CY - Leipzig, Deutschland DA - 2003-05-26 PY - 2003 VL - 77 SP - 101 EP - 104 PB - DGG CY - Offenbach AN - OPUS4-3121 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -