Filtern
Erscheinungsjahr
Dokumenttyp
- Zeitschriftenartikel (60)
Referierte Publikation
- ja (60) (entfernen)
Schlagworte
- Glass (10)
- Sintering (8)
- Crystallization (7)
- Viscosity (6)
- EBSD (4)
- Vickers indentation (4)
- Water content (4)
- Crystal growth (3)
- Internal friction (3)
- LTCC (3)
- Soda-lime-silica (3)
- Bioactive glass (2)
- Crack healing (2)
- Diopsid (2)
- Foaming (2)
- Glass ceramic composites (2)
- Glass ceramics (2)
- Glass transition (2)
- Glasses (2)
- Incinerator ash (2)
- Infrared spectroscopy (2)
- Mechanical properties (2)
- NMR spectroscopy (2)
- Oxide glasses (2)
- Permeability (2)
- Sewage sludge ash (2)
- Silicates (2)
- Stress intensity factor (2)
- Viskosität (2)
- Water in glass (2)
- Water speciation (2)
- 3D etching (1)
- Additive manufacturing (1)
- Al2O3-inclusions (1)
- Alkali aluminosilicate glasses (1)
- Alkali and alkaline earth silicate and borate glass (1)
- Alkali silicates (1)
- Alumina dissolution (1)
- Aluminium phosphate (1)
- Aluminoborosilicate glass (1)
- Aluminosilicate glasses (1)
- Aluminum phosphate (1)
- Analytical scanning electron microscopy (1)
- Ash (1)
- Automated analysis (1)
- Batch reactions (1)
- Bioactive Glass (1)
- Borate (1)
- Borate glasses (1)
- Boratgläser (1)
- Borosilicate glass (1)
- Brittle fracture (1)
- Bubble formation (1)
- Calculated intrinsic fracture toughness (1)
- Carrier gas analysis (1)
- Chemical durability (1)
- Chemical properties (1)
- Chemical stabilization of high-temperature forms (1)
- Coating (1)
- Corrosion (1)
- Crack growth (1)
- Crack growth in air (1)
- Cristobalite form (1)
- Crystal morphology (1)
- Crystal orientation (1)
- DCB (1)
- DCB geometry (1)
- DTA (1)
- Debindering (1)
- Densification (1)
- Diffusivity (1)
- Effective Viscosity (1)
- Efficiency (1)
- Elastic constants (1)
- Epoxy resin (1)
- Fluorescence properties (1)
- Fly ash (1)
- Fracture surface energy (1)
- Fragility (1)
- Fresnoite (1)
- Gas calibration (1)
- Glass Ceramic (1)
- Glass Matrix Composites (1)
- Glass capillaries (1)
- Glass ceramic (1)
- Glass crystallization stress (1)
- Glass forming melts (1)
- Glass manufacturing (1)
- Glass matrix composites (1)
- Glass powder (1)
- Glass-ceramic (1)
- Glass-ceramics definition (1)
- Hardness (1)
- High pressure (1)
- Hydrogen (1)
- Hydrogen diffusivity (1)
- Hydrogen gas (1)
- Hydrogen storage (1)
- Hydrous glass (1)
- Inclusions (1)
- Indentation (1)
- Indentation fracture toughness (1)
- Ion beam erosion Sectioning (1)
- Ionic porosity (1)
- Kinetic Modelling (1)
- Kinetik (1)
- Kristallisation (1)
- Kristallwachstumsgeschwindigkeit (1)
- Lithiumionen-Batterie (1)
- Long-term calculation (1)
- Luminescence (1)
- Mass spectroscopy (1)
- Master curve (1)
- Microhardness (1)
- Microindentation (1)
- Microscopy (1)
- Milling (1)
- Mixing (1)
- Modeling (1)
- Modelling (1)
- Nanoparticles (1)
- Nucleation (1)
- Nydrogen melting (1)
- Optical microscopy (1)
- Optical properties (1)
- Optical solids (1)
- Optical spectroscopy (1)
- Orientation (1)
- Phasenentwicklung (1)
- Phosphate (1)
- Photovoltaic modules (1)
- Porosity (1)
- Powder preparation (1)
- Powders (1)
- Precursor chemistry (1)
- Raman spectroscopy (1)
- Relaxation (1)
- Rheology (1)
- Rietveld analysis (1)
- Rigid Inclusion (1)
- Roughness (1)
- SEM (1)
- SOFC (1)
- Sample preparation (1)
- Sand blasting (1)
- Scaffolds (1)
- Scanning electron microscopy (1)
- Shaping (1)
- Shear thinning (1)
- Silicate glass (1)
- Silicatgläser (1)
- Silicoborate glasses (1)
- Silikatgläser (1)
- Silver metallization paste (1)
- Sintering glass composit bio material (1)
- Sintering kinetics (1)
- Slow crack growth (1)
- Soda lime silicate glass (1)
- Soda-lime silicate glass (1)
- Soda-lime-silica glass (1)
- Sodium ion batteries (1)
- Sol-gel (1)
- Solid-state reaction (1)
- Solubility (1)
- Stable crack growth (1)
- Stacking disorder (1)
- Steel (1)
- Strength (1)
- Stress intensity (1)
- Stress-corrosion (1)
- Structural relaxation (1)
- Subcritical crack growth (1)
- Surface crystallization (1)
- Surface energy (1)
- Surface nucleation (1)
- Surface plasmon resonance (1)
- Surfaces and interfaces (1)
- Synchrotron radiation (1)
- Thermal analysis (1)
- Thermische Analyse (1)
- Thermo gravimetry (1)
- Titanium hydride (1)
- Toughness (1)
- Transmittance (1)
- Tridymite form (1)
- Ultrasonic relaxation (1)
- Unterschiedliche Atmosphären (1)
- Vacuum hot extraction (1)
- Wassergehalt (1)
- Wasserhaltige Gläser (1)
- Water (1)
- Water-bearing glasses (1)
- X-ray lithography (1)
Organisationseinheit der BAM
Theory of nucleation in viscoelastic media: application to phase formation in glassforming melts
(2003)
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.
Thermo Analytic Investigation of Hydrogen Effusion Behavior - Sensor Evaluation and Calibration
(2011)
The well established carrier gas analysis (CGA) method was used to test different hydrogen detectors comprising a thermal conductivity detector (TCD) and a metal oxide semiconducting (MOx) sensor. The MOx sensor provides high hydrogen sensitivity and selectivity, whereas the TCD exhibits a much shorter response time and a linear hydrogen concentration dependency. Therefore, the TCD was used for quantitative hydrogen concentration measurements above 50?µmol/mol. The respective calibration was made using N2/H2 gas mixtures. Furthermore, the hydrogen content and degassing behaviour of titanium hydride (TiH2-x) was studied. This material turned out to be a potential candidate for a solid sample calibration. Vacuum hot extraction (VHE) coupled with a mass spectrometer (MS) was then calibrated with TiH2-x as transfer standard. The calibration was applied for the evaluation of the hydrogen content of austenitic steel samples (1.4301) and the comparison of CGA-TCD and VHE-MS.
Glass-ceramics are noted for their unusual combination of properties and manifold commercialized products for consumer and specialized markets. Evolution of novel glass and ceramic processing routes, a plethora of new compositions, and unique exotic nano- and microstructures over the past 60 years led us to review the Definition of glass-ceramics. Well-established and emerging processing methods, such as co-firing, additive manufacturing, and laser patterning are analyzed concerning the core requirements of processing glass-ceramics and the Performance of the final products. In this communication, we propose a revised, updated definition of glass-ceramics, which reads “Glass-ceramics are inorganic, non-metallic materials prepared by controlled crystallization of glasses via different processing methods. They contain at least one type of functional crystalline phase and a residual glass. The volume fraction crystallized may vary from ppm to almost 100%”.
Crack growth velocity in alkali silicate glasses was measured in vacuum across 10 orders of magnitude with double cantilever beam technique. Measured and literature crack growth data were compared with calculated intrinsic fracture toughness data obtained from Young´s moduli and the theoretical fracture surface energy estimated from chemical bond energies. Data analysis reveals significant deviations from this intrinsic brittle fracture behavior. These deviations do not follow simple compositional trends. Two opposing processes may explain this finding: a decrease in the apparent fracture surface energy due to stress-induced chemical changes at the crack tip and its increase due to energy dissipation during fracture.
AbstractViscous healing of cracks induced by the Vickers indentation in a soda lime magnesium silicate, a soda borosilicate, and a soda aluminosilicate glass (NAS) was studied by laser scanning microscopy. Plots of the crack length, width, and depth normalized to the initial crack length versus time over viscosity merge into single master curves of each of these quantities for each glass. Despite glass properties do not differ strikingly from each other, however, these master curves strongly differ among the glasses. This finding was attributed to a different interplay of various crack healing phenomena. Lateral cracks were found to be responsible for the bulging of the sample surface around the Vickers imprint, which in turn promotes radial crack widening as the main cause of healing delay. The most rapid healing of lateral cracks was observed in NAS in which bulging and crack widening were least pronounced.
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.
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.
In the present study we have investigated whether the effect of water on properties of borate glasses resembles that of alkali oxide. Soda-lime-borate glasses with nominal compositions of x Na2O, 10 CaO, (90-x) B2O3 (x = 5, 15 and 25 mol%) were doped with up to 8 wt.% H2O by processing glass powder + distilled water in platinum capsules in an internally heated gas pressure vessel at 1523 K and 500 MPa. The water content of hydrous glasses was determined by Karl-Fischer titration and near-infrared spectroscopy. The glass transition temperature T-g. was derived from DTA and micropenetration experiments for which the effect of water loss at the surface of the hydrous glasses was studied. Heating glass samples at 10 K min(-1) in the DTA resulted in T-g values which are close to T-12 isokom temperatures confirming the equivalence of enthalpy relaxation and viscous relaxation for borate glasses. For all three glass series it is shown that T-g strongly decreases whereas the liquid fragility strongly increases upon the addition of water. These findings reveal that H2O primarily causes breaking of B-O-B bonds rather than supporting 4-fold coordinated boron as it is well-known for alkali oxides in this concentration range. (C) 2015 Elsevier B.V. All rights reserved.