TY - JOUR A1 - Müller, Ralf A1 - Prado, M. O. A1 - Zanotto, E. D. T1 - Model for sintering polydispersed glass particles N2 - We propose a model to describe the sintering kinetics of polydispersed glass particles, having no adjustable parameter. The model is based on three sintering stages: a pure ‘Frenkel' (F) first step, a mixed ‘Frenkel/Mackenzie–Shuttleworth' stage, and a third, pure ‘Mackenzie–Shuttleworth' (MS) step. The model considers sample shrinkage as the sum of the partial shrinkage of several clusters, each consisting of equally sized particles and each showing independent F or MS behavior. The overall set of clusters mimics the specimen's real particle size distribution. We then introduce the concept of neck forming ability, which allows the formation of necks among particles of different sizes, relaxing the clustering condition. Using experimental physical parameters: particle size distribution, viscosity, surface energy, and the theoretical neck forming ability, the model describes well the sintering kinetics of an alumino-borosilicate glass powder having polydispersed, irregular shaped particles in a variety of temperatures. The sintering kinetics of the real powder is slower, but not far from the calculated kinetics of a monodispersed distribution containing only particles of average size. Thus the model provides a tool for estimating the sintering kinetics of real glass powders, for any size distribution and temperature, thus minimizing the number of laboratory experiments. PY - 2001 DO - https://doi.org/10.1016/S0022-3093(00)00399-9 SN - 0022-3093 VL - 279 IS - 2-3 SP - 169 EP - 178 PB - North-Holland Publ. Co. CY - Amsterdam AN - OPUS4-935 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Deubener, Joachim A1 - Müller, Ralf A1 - Behrens, H. A1 - Heide, G. T1 - Water and the glass transition temperature of silicate melts N2 - Literature data on the effect of water on the glass transition in silicate melts are gathered for a broad range of total water content cw from 3 × 10-4 to 27 wt%. In terms of a reduced glass transition temperature Tg*=Tg/TgGN, where TgGN is Tg of the melt containing cw?0.02 wt% total water, a uniform dependence of Tg* on total water content (cw) is evident for silicate melts. Tg* decreases steadily with increasing water content, most strongly at the lowest water content where H2O is dominantly dissolved as OH. For water-rich melts, the variation of Tg* is less pronounced, but it does not vanish even at the largest water contents reported (?27 wt%). Tg* vs. cw is fitted by a three-component model. This approach accounts for different transition temperatures of the dry glass, hydroxyl and molecular water predicting Tg* as a weighted linear combination of these temperatures. The required but mostly unknown water speciation in the glasses was estimated using IR-spectroscopy data for hydrous sodium trisilicate and rhyolite. PY - 2003 DO - https://doi.org/10.1016/S0022-3093(03)00472-1 SN - 0022-3093 VL - 330 SP - 268 EP - 273 PB - North-Holland Publ. Co. CY - Amsterdam AN - OPUS4-3120 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schmelzer, J.W.P. A1 - Müller, Ralf A1 - Möller, J. A1 - Gutzow, I.S. T1 - Theory of nucleation in viscoelastic media: application to phase formation in glassforming melts N2 - Glassforming melts behave, in the vicinity of the temperature of vitrification Tg, as viscoelastic bodies. A general theory of nucleation in a viscoelastic body developed elsewhere is applicable to the description of phase formation processes in such systems. The present contribution is directed to the demonstration of the relevance of this proposed general theory to describing phase transformation processes in glassforming melts. The application of the theory is shown to explain a number of experimental results on crystallization of glassforming melts, which have not found a satisfactory interpretation so far. PY - 2003 DO - https://doi.org/10.1016/S0022-3093(02)01428-X SN - 0022-3093 VL - 315 SP - 144 EP - 160 PB - North-Holland Publ. Co. CY - Amsterdam AN - OPUS4-2078 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Unger, Brita A1 - Rurack, Knut A1 - Müller, Ralf A1 - Resch-Genger, Ute A1 - Buttke, K. T1 - Effects of the Sol-Gel Processing on the Fluorescence Properties of Laser Dyes in Tetraethoxysilane Derived Matrices N2 - Two fluorescent dyes were incorporated into sol-gel derived SiO2 matrices. The dye was added to SiO2 precursors of different degrees of pre-condensation and the spectroscopic properties of the immobilized dye were measured at various aging and drying stages of the resulting gels. The significant influence of the processing parameters on the spectroscopic properties is manifested in the relative intensity of a second red shifted emission band (550–560 nm), which was observed besides the typical coumarin emission band (495 nm). The appearance of this long wavelength emission might be attributed to dye aggregation or to other reactions with the ambient matrix forced by micro porosity phenomena. KW - Sol-gel KW - Precursor chemistry KW - Fluorescence properties KW - Optical solids PY - 2000 DO - https://doi.org/10.1023/A:1008768318418 SN - 0928-0707 SN - 1573-4846 VL - 19 SP - 799 EP - 802 PB - Kluwer Academic Publ. CY - Dordrecht AN - OPUS4-1080 LA - eng 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 - JOUR A1 - Schmelzer, J.W.P. A1 - Potapov, O. V. A1 - Fokin, V. M. A1 - Müller, Ralf A1 - Reinsch, Stefan T1 - The effect of elastic stress and relaxation on crystal nucleation in lithium disilicate glass N2 - In the framework of a general theoretical approach recently developed, the effect of elastic stresses on the rate of nucleation of crystallites of critical sizes in the process of crystallization of lithium disilicate glasses is studied. Hereby both the evolution of elastic stresses – due to changes in the specific volume of the crystallizing system (i.e., differences in the densities of the melt and the crystal) – and their relaxation – connected with viscous flow – are taken into consideration. If the classical theory of nucleation is employed for the determination of the nucleation rates (modified by taking into account elastic stresses), elastic stresses may lead, for the system under consideration, to a decrease of the nucleation rate by up to two orders of magnitude. As shown, the theory allows an at least qualitatively correct incorporation of the effect of elastic stresses and stress relaxation into the description of nucleation phenomena in glass-forming melts. PY - 2004 DO - https://doi.org/10.1016/j.jnoncrysol.2003.10.002 SN - 0022-3093 VL - 333 IS - 2 SP - 150 EP - 160 PB - North-Holland Publ. Co. CY - Amsterdam AN - OPUS4-6236 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Müller, Ralf A1 - Gaber, Martin A1 - Gottschling, Peter T1 - Water release and crystallisation of glass powders T2 - Physics and Chemistry of Glasses / VII Symposium on Crystallization in Glasses in Liquids CY - Sheffield, England, UK DA - 2004-07-06 PY - 2004 SN - 1753-3562 SN - 0017-1050 SN - 0031-9090 SN - 1750-6697 VL - 45 IS - 2 SP - 1 EP - 5 PB - Society of Glass Technology CY - Sheffield AN - OPUS4-6237 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Marzok, Ulrich A1 - Müller, Ralf A1 - Schadrack, Reinhard A1 - Krauhausen, M. A1 - Burgstedt, F. A1 - Brode, W. A1 - Reetz, R. T1 - High-temperature laser profilometry for ceramic tapes N2 - Advanced ceramics are promising key components for microsystems engineering, communication Technology and medical engineering. Driven by steadiiy increasing demands on dimensional accuracy of components and Integration density, sintering has to be controlled at an unprecedented degree of precision. Being most crucial for components of complex shape, graded or heterogeneous-composed parts like LTCC multilayers for microsystems, precise control of sintering has a decisive influence on the dimensional accuracy, mechanical integrity and reliability of sintered components. Thus, permanent or temporary shape distortions or warping during sintering may result from spatially heterogeneous microstructure and temperature distribution, e.g. during the co-firing process of green multilayer Stacks printed with metallization and other functional pastes. Whereas permanent warping can be easily measured after sintering, temporary warping during firing is more difficult to measure. Nonetheless, this effect may cause latent failures later, which often limit the applicability of ceramic components. PY - 2013 SN - 0173-9913 SN - 0196-6219 VL - 90 IS - 4 SP - E35 EP - E40 PB - Göller CY - Baden-Baden AN - OPUS4-28500 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Marzok, Ulrich A1 - Müller, Ralf A1 - Schadrack, Reinhard A1 - Krauhausen, M. A1 - Burgstedt, F. A1 - Brode, W. A1 - Reetz, R. T1 - Hochtemperatur-Laserprofilometrie an keramischen Bauteilen N2 - Hochleistungssinterwerkstoffe spielen eine wachsende Rolle in derzeitigen Schlüsseltechnologien wie der Mikrosystem-, Informations-, Kommunikations- und Medizintechnik. Dabei steigen die Anforderungen an die präzise Steuerung der Sinterung. Besonders für komplexe, gradierte oder heterogen zusammengesetzte Formkörper wie zum Beispiel keramische LTCC-Multilayer für die Mikrosystemtechnik hat die exakte Beherrschung dieses Prozessschrittes wesentlichen Einfluss auf die Maßhaltigkeit, mechanische Integrität und Zuverlässigkeit der gesinterten Bauteile. Bedingt durch die Heterogenität der mehrlagigen und mit Leit- und anderen Funktionspasten bedruckten Sinterkörper hinsichtlich ihrer sinterphysikalischen oder thermischen Eigenschaften können bleibende oder temporäre Verwerfungen beim Schrumpfungsprozess auftreten, wobei letztere unter Umständen Ursache latenter Fehler im späteren Bauteil sind. PY - 2013 SN - 0173-9913 SN - 0196-6219 VL - 90 IS - 3 SP - D19 EP - D24 PB - Göller CY - Baden-Baden AN - OPUS4-28013 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zocca, Andrea A1 - Wirth, Cynthia A1 - Bernardo, E. A1 - Müller, Ralf A1 - Günster, Jens A1 - Colombo, P. T1 - LAS glass-ceramic scaffolds by three-dimensional printing N2 - Highly porous (>60% open porosity) glass–ceramic scaffolds with remarkable mechanical properties (compression strength of ~15 MPa) were produced by indirect 3D printing. Precursor glass powders were printed into 3D ordered structures and then heat treated to sinter and develop crystalline phases. The final glass–ceramic contained a β-spodumene solid solution together with a secondary phase of lithium disilicate. The precision of the printed geometry and the density of the struts in the scaffold depended on several processing parameters (e.g. powder size and flowability, layer thickness) and were improved by increasing the binder saturation and drying time. Two types of powders with different particle size distribution (PSD) and flowability were used. Powders with a larger PSD, could be processed within a wider range of printing parameters due to their good flowability; however, the printing precision and the struts density were lower compared to the scaffolds printed using the powder in a smaller average PSD. KW - Glass ceramics KW - Porosity KW - Shaping KW - Strength KW - Additive manufacturing PY - 2013 DO - https://doi.org/10.1016/j.jeurceramsoc.2012.12.012 SN - 0955-2219 SN - 1873-619X N1 - Geburtsname von Wirth, Cynthia: Gomes, C. M. - Birth name of Wirth, Cynthia: Gomes, C. M. VL - 33 IS - 9 SP - 1525 EP - 1533 PB - Elsevier CY - Oxford AN - OPUS4-28284 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nagamine, K. A1 - Reinsch, Stefan A1 - Müller, Ralf A1 - Honma, T. A1 - Komatsu, T. T1 - Crystallization behavior of lithium iron phosphate glass powders in different atmospheres N2 - Crystallization behavior in different atmospheres (air, Ar, and 7% H2/Ar) of lithium iron phosphate glass (33Li2O–33Fe2O3–1Nb2O5–33P2O5 (LFNP)) powders with different sizes of 2–1000 µm was examined. The crystallization peak temperature (Tp) in Ar and 7% H2/Ar decreased with decreasing the particle size of glass powders, but the value of Tp in air was independent of particle size. The crystallized glass obtained by heating to Tp showed the formation of the α-Li3Fe2(PO4)3 and LiFePO4 crystalline phases. Fe2O3 crystals were formed only in the inside of crystallized glass plates in the heating in air. The crystallization of LiFePO4 was largely enhanced in the particle size of <2 µm during the heating in Ar and 7% H2/Ar atmospheres. The main crystallization mechanism in LFNP glass was found to be surface crystallization. Significant shrinkages were observed for glass compacts (pellets) in the heating in 7% H2/Ar. These results suggest that controlling particle sizes and atmospheres enables the design the morphology of LiFePO4 crystals in LFNP glass. KW - DTA KW - Kristallisation KW - Phasenentwicklung KW - Unterschiedliche Atmosphären KW - Lithiumionen-Batterie PY - 2011 DO - https://doi.org/10.1111/j.1551-2916.2011.04579.x SN - 0002-7820 SN - 1551-2916 VL - 94 IS - 9 SP - 2890 EP - 2895 PB - Blackwell Publishing CY - Malden AN - OPUS4-24914 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Apel, E. A1 - Deubener, J. A1 - Bernard, A. A1 - Müller, Ralf A1 - Kappert, H. A1 - Rheinberger, V. A1 - Höland, W. T1 - Phenomena and mechanisms of crack propagation in glass-ceramics N2 - Lithium disilicate, leucite and apatite glass-ceramics have become state-of-the-art framework materials in the fabrication of all-ceramic dental restorative materials. The goal of this study was to examine the crack propagation behaviour of these three known glass-ceramic materials after they have been subjected to Vickers indentation and to characterize their crack opening profiles (δmeas vs. (a-r)). For this purpose, various methods of optical examination were employed. Optical microscopy investigations were performed to examine the crack phenomena at a macroscopic level, while high-resolution techniques, such as scanning electron microscopy (SEM) and atomic force microscopy (AFM), were employed to investigate the crack phenomena at a microscopic level. The crack patterns of the three glass-ceramics vary from fairly straightforward to more complex, depending on the amount of residual glass matrix present in the material. The high-strength lithium disilicate crystals feature a high degree of crosslinking, thereby preventing crack propagation. In this material, the crack propagates only through the residual glass phase, which constitutes 30%–40% by volume. Having a high glass content of more than 65% by volume, the leucite and apatite glass-ceramics show far more complex crack patterns. Cracks in the leucite glass-ceramic propagate through both the glass and crystal phase. The apatite glass-ceramic shows a similar crack behaviour as an inorganic–organic composite material containing nanoscale fillers, which are pulled out in the surroundings of the crack tip. The observed crack behaviour and the calculated View the MathML source values of the three types of glass-ceramics were compared to the Kkic values determined according to the SEVNB method. KW - Glass KW - Viscosity KW - Water content PY - 2008 DO - https://doi.org/10.1016/j.jmbbm.2007.11.005 SN - 1751-6161 VL - 1 IS - 4 SP - 313 EP - 325 PB - Elsevier CY - Amsterdam AN - OPUS4-18308 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Müller, Ralf A1 - Reinsch, Stefan A1 - Eberstein, Markus A1 - Deubener, J. A1 - Thiel, A. A1 - Schiller, Wolfgang Arno T1 - Effects of dispersed Al2O3 particles on sintering of LTCC N2 - The sintering of Low Temperature Co-fired Ceramics prepared from alumoborosilicate glass- and Al2O3 powders of similar small particle size was studied by dilatometry, heating microscopy, microstructure analysis, glass- and effective viscosity measurements. The steric effect of Al3O3 inclusions was studied using a gnon-reactiveh model composite. With increasing Al3O3 volume fraction (Φ ≤ 0.45), sintering decelerates and its final stage shifts to higher temperature. The attainable shrinkage is reduced as Al2O3 particle clusters bearing residual pores become more frequent. The kinetics of sintering could be described formally superposing the weighed contributions of differentially sized and randomly composed glass-crystal particle clusters and assuming a sintering rate controlled by the effective matrix viscosity, which increases with Φ and with progressive wetting of Al2O3 particles during densification. The "reactive" model composite shows significant dissolution of Al2O3 into the glass, which has two opposed effects on sintering: reducing Φ and increasing glass viscosity. For the present case (Φ = 0.25), the latter effect dominates and sintering is retarded by Al2O3 dissolution. Crystallization of wollastonite starts after full densification. Dissolution of Al2O3 was found to promote the subsequent growth of anorthite. KW - LTCC KW - Glass matrix composites KW - Al2O3-inclusions KW - Sintering kinetics PY - 2005 SN - 1022-6680 SN - 1662-8985 VL - 39-40 SP - 375 EP - 380 PB - Trans Tech Publ. CY - Zurich AN - OPUS4-18441 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zietka, S. A1 - Deubener, J. A1 - Behrens, H. A1 - Müller, Ralf T1 - Glass transition and viscosity of hydrated silica glasses N2 - The viscosity of silica glasses with different water contents was measured by penetration of sapphire microspheres in the range from 1012-1014·7 Pas at ambient pressure. Commercial silica glasses were used together with hydrous silica glasses, which were prepared by melting glass powder plus water in an internally heated pressure vessel at 2-3 kbar and 1350-1450°C. The temperature dependence of the viscosity of silica glasses with total water contents Cw of 5·4×10-4, 7·0×10-4, 1·00×10-2, and 1·55×10-2(Cw in mass fractions) can be described by Arrhenius equations. From the results, the linear dependence of the T12 isokom (K) with the logarithm of the water content was determined as T12=192-409 logCw. The analysis of the compositional dependence of the T12 isokom in the H2O-Na2O-SiO2 system reveals a temperature depression of up to 200 K for mixed water- and sodium-bearing glasses compared to H2O-SiO2 and Na2O-SiO2 glasses with same molar silica content. From these findings we conclude that protons may contribute significantly to the mixed alkali effect in glasses. KW - Wassergehalt KW - Silicatgläser KW - Viskosität PY - 2007 SN - 1753-3562 SN - 0017-1050 SN - 0031-9090 SN - 1750-6697 VL - 48 IS - 6 SP - 380 EP - 387 PB - Society of Glass Technology CY - Sheffield AN - OPUS4-18396 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Reinsch, Stefan A1 - Nascimento, M.L.F. A1 - Müller, Ralf A1 - Zanotto, E. D. T1 - Crystal growth kinetics in cordierite and diopside glasses in wide temperature ranges N2 - We measured and collected literature data for the crystal growth rate, u(T), of µ-cordierite (2MgO · 2Al2O3 · 5SiO2) and diopside (CaO · MgO · 2SiO2) in their isochemical glass forming melts. The data cover exceptionally wide temperature ranges, i.e. 800–1350 °C for cordierite and 750–1378 °C for diopside. The maximum of u(T) occurs at about 1250 °C for both systems. A smooth shoulder is observed around 970 °C for µ-cordierite. Based on measured and collected viscosity data, we fitted u(T) using standard crystal growth models. For diopside, the experimental u(T) fits well to the 2D surface nucleation model and also to the screw dislocation growth mechanism. However, the screw dislocation model yields parameters of more significant physical meaning. For cordierite, these two models also describe the experimental growth rates. However, the best fittings of u(T) including the observed shoulder, were attained for a combined mechanism, assuming that the melt/crystal interface growing from screw dislocations is additionally roughened by superimposed 2D surface nucleation at large undercoolings, starting at a temperature around the shoulder. The good fittings indicate that viscosity can be used to assess the transport mechanism that determines crystal growth in these two systems, from the melting point Tm down to about Tg, with no sign of a breakdown of the Stokes–Einstein/Eyring equation. KW - Crystal growth KW - Oxide glasses KW - Silicates KW - Kristallwachstumsgeschwindigkeit KW - Kinetik KW - Silikatgläser PY - 2008 DO - https://doi.org/10.1016/j.jnoncrysol.2008.09.007 SN - 0022-3093 VL - 354 IS - 52-54 SP - 5386 EP - 5394 PB - North-Holland Publ. Co. CY - Amsterdam AN - OPUS4-18383 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Müller, Ralf A1 - Eberstein, Markus A1 - Reinsch, Stefan A1 - Schiller, Wolfgang Arno A1 - Deubener, J. A1 - Thiel, A. T1 - Effect of rigid inclusions on sintering of low temperature co-fired ceramics KW - Sintering KW - Glass Matrix Composites KW - Rigid Inclusion KW - Effective Viscosity KW - Kinetic Modelling KW - LTCC PY - 2007 SN - 1753-3562 SN - 0017-1050 SN - 0031-9090 SN - 1750-6697 VL - 48 IS - 4 SP - 259 EP - 266 PB - Society of Glass Technology CY - Sheffield AN - OPUS4-16211 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - de Moraes, Flavia A1 - Müller, Wolfgang A1 - Frischat, G.H. A1 - Müller, Ralf T1 - Corrosion and crystallization at the inner surfaces of glass bricks N2 - Glass bricks are important transparent building materials. They are produced by joining two halves of glass pressings at 600–700 °C. During this production process alkali oxides evaporate and are redeposited at the cooler inner front surfaces of the bricks. This surface layer reacts with H2O and CO2 from the residual brick atmosphere, leading to the formation of an alkali-rich silicate-hydrate layer of ≥50 nm thickness, which could be evidenced leading to a reduced nano-hardness of similar thickness, and from which NaHCO3 crystals can finally grow. Climate chamber experiments (repeated cooling between at -8 and -14 °C and reheating to 0 to 15 °C) resulted in reversible NaHCO3 crystallization and redissolution, presumably influenced by water evaporation or condensation and driven by the NaHCO3 supersaturation of the silicate-hydrate layer. Depending on the time–temperature schedule, different crystal morphologies became visible in this closed system, e.g. isolated spherical crystals, crystals arranged in chains and in double-chains, respectively, which can limit already the transmittance of the glass bricks. When a crack occurs or the brick is opened, the hygroscopic NaHCO3 crystals take up more H2O from the ambient, react irreversibly with the glass surface, finally leading to a total loss of transmittance. KW - Chemical properties KW - Chemical durability KW - Corrosion KW - Crystallization KW - Crystal growth KW - Nucleation KW - Glasses KW - Mass spectroscopy KW - Mechanical properties KW - Hardness KW - Indentation KW - Microindentation KW - Microscopy KW - Optical microscopy KW - Scanning electron microscopy KW - Optical properties KW - Optical spectroscopy KW - Oxide glasses KW - Alkali silicates KW - Soda-lime-silica KW - Surfaces and interfaces PY - 2008 DO - https://doi.org/10.1016/j.jnoncrysol.2007.07.086 SN - 0022-3093 VL - 354 IS - 2-9 SP - 284 EP - 289 PB - North-Holland Publ. Co. CY - Amsterdam AN - OPUS4-16433 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Reinsch, Stefan A1 - Gaber, Martin A1 - Müller, Ralf A1 - Schiller, Wolfgang Arno T1 - Rate controlled debindering of glass ceramic composites N2 - Green compacts of ceramics, glass ceramic composites and sinter glass ceramics contain different amounts of organic materials added as pressing aids or binders. Before sintering, these organics have to burn out completely. In oxidising atmospheres, the debindering process is mostly exothermic and therefore difficult to control. This uncontrolled heat production due to locally enhanced debindering and respective gas release may cause damages in the green compact microstructure. Therefore, debindering is usually operated with very low heating rates (< 3 K/min) which requires long processing times of many hours. In this paper, we will show that it is possible to reduce the processing time for debindering dramatically by using the decomposition rate of the organic binder, detected by the weight loss of the sample, as a control factor of the furnace. T2 - 9th ESG (European Society of Glass) Conference with the Annual Meeting of the ICG Glass - "The challenge for the 21st century" CY - Trencin, Slovakia DA - 2008-06-22 KW - Debindering KW - Thermo gravimetry KW - Glass ceramic composites PY - 2005 SN - 1022-6680 SN - 1662-8985 VL - 39-40 SP - 583 EP - 586 PB - Trans Tech Publ. CY - Zurich AN - OPUS4-17840 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Deubener, J. A1 - Behrens, H. A1 - Müller, Ralf A1 - Zietka, S. A1 - Reinsch, Stefan T1 - Kinetic fragility of hydrous soda-lime-silica glasses N2 - The effect of hydration on the kinetic fragility of soda-lime-silica glasses was investigated by viscometry in the glass transition range. Water-bearing glasses were prepared from industrial float glass (FG) and a ternary model glass (NCS = 16Na2O 10CaO 74SiO2 in mol%) by bubbling steam through the melt at 1480 °C and up to 7 bar. Additionally, a sodium borosilicate glass (NBS = 16Na2O 10B2O3 74SiO2 in mol%) was hydrated under equal conditions. As detected by infrared spectroscopy water dissolves in the glasses exclusively as OH-groups. The hydration resulted in a total water content CW up to ~ 0.2 wt% for FG, NCS and NBS glasses. Kinetic fragility, expressed by the steepness index m, was determined from the temperature dependence of η at the glass transition. Viscosity data from previous studies on hydrous float glasses (CW > 1 wt%) were surveyed together with literature data on the (H2O)–Na2O–CaO–SiO2, (H2O)–Na2O–SiO2 and (H2O)–SiO2 systems to expand the range of water concentration and bulk composition. We could demonstrate that m decreases for all glasses although water is dissolved as OH and should depolymerize the network. An empirical equation of the general type m = a - b logCW where a, b are fitting parameters, enables m to be predicted, for each glass series as function of the water content CW. The enlarged data base shows that the parameter B of the Arrhenius viscosity-temperature relation decreases much stronger than the isokom temperature at the glass transition. KW - Soda-lime-silica KW - Fragility KW - Viscosity KW - Water in glass PY - 2008 DO - https://doi.org/10.1016/j.jnoncrysol.2008.04.021 SN - 0022-3093 VL - 354 IS - 42-44 SP - 4713 EP - 4718 PB - North-Holland Publ. Co. CY - Amsterdam AN - OPUS4-18187 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Müller, Ralf A1 - Meszaros, Robert A1 - Peplinski, Burkhard A1 - Reinsch, Stefan A1 - Eberstein, Markus A1 - Schiller, Wolfgang Arno A1 - Deubener, J. T1 - Dissolution of alumina, sintering, and crystallization in glass ceramic composites for LTCC KW - LTCC KW - Sintering KW - Crystallization KW - Alumina dissolution KW - Rietveld analysis PY - 2009 DO - https://doi.org/10.1111/j.1551-2916.2009.03089.x SN - 0002-7820 SN - 1551-2916 VL - 92 IS - 8 SP - 1703 EP - 1708 PB - Blackwell Publishing CY - Malden AN - OPUS4-20676 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -