5 Werkstofftechnik
Filtern
Dokumenttyp
- Zeitschriftenartikel (51)
- Vortrag (50)
- Posterpräsentation (24)
- Buchkapitel (1)
- Beitrag zu einem Tagungsband (1)
- Sonstiges (1)
Sprache
- Englisch (112)
- Deutsch (15)
- Mehrsprachig (1)
Schlagworte
- Glass (33)
- Crystallization (16)
- Sintering (16)
- Crack growth (12)
- DCB (9)
- Water speciation (9)
- Soda-lime silicate glass (7)
- Vickers (7)
- Water content (7)
- Foaming (6)
- Glas (6)
- EBSD (5)
- Vickers indentation (5)
- Viscosity (5)
- Alkali ions (4)
- Alkali zinc borate glasses (4)
- Bildanalyse (4)
- Bioactive glass (4)
- Internal friction (4)
- Ontologie (4)
- Orientation (4)
- Oxidglas (4)
- Surface energy (4)
- Coating (3)
- Corrosion (3)
- Crack healing (3)
- Crystal orientation (3)
- Digitaler Zwilling (3)
- Diopside (3)
- Fracture Toughness (3)
- Glass ceramic (3)
- Glass powder (3)
- ML (3)
- NMR spectroscopy (3)
- Oxide Glasses (3)
- Silicate Glasses (3)
- Surface crystallization (3)
- Wasser (3)
- Al2O3 (2)
- Aluminosilicate glasses (2)
- Bioactive Glass (2)
- Bond energy (2)
- Diffusion (2)
- Diffusion coefficient (2)
- Diopsid (2)
- Elastic constants (2)
- Fracture surface energy (2)
- Geothermal (2)
- GlasDigital (2)
- Glass composition (2)
- Glass transition (2)
- Glass-ceramic (2)
- Hydrogen permeation (2)
- IR (2)
- Infrared spectroscopy (2)
- Ionic porosity (2)
- Lead borate glasses (2)
- Martensitic steel (2)
- Material Digital (2)
- Mechanical properties (2)
- Microhardness (2)
- Microstructure (2)
- Oriented surface crystallization (2)
- Permeability (2)
- Powder (2)
- Raman spectroscopy (2)
- Relaxation (2)
- Risswachstum (2)
- Robotische Glasschmelzanlage (2)
- SEM (2)
- Silver diffusion (2)
- Silver metallization paste (2)
- Silver-glass-metallization-paste (2)
- Sintern (2)
- Soda-lime-silica glass (2)
- Sol-gel coating (2)
- Solubility (2)
- Stress intensity factor (2)
- Superconducting magnet (2)
- Surface (2)
- Surface Energy (2)
- Surface nucleation (2)
- robotische Glasschmelzanlage (2)
- 3D REM (1)
- 3D etching (1)
- 3D glass structure model (1)
- 3D printing (1)
- Acid-leaching (1)
- Alkali aluminosilicate glasses (1)
- Alkali and alkaline earth silicate and borate glass (1)
- Alkali zinc borate glass (1)
- Alumina coatings (1)
- Analytical scanning electron microscopy (1)
- Artificial weathering (1)
- Atomic packing factor (1)
- Automated analysis (1)
- BCS (1)
- BTS (1)
- Batch reactions (1)
- Behmite (1)
- Bioactive (1)
- Blähen (1)
- Borate (1)
- Borate glasses (1)
- Borosilicate glass (1)
- Brittle fracture (1)
- Bruchflächen (1)
- Bubble formation (1)
- Calculated intrinsic fracture toughness (1)
- Cement (1)
- Ceramic multilayers (1)
- Co-firings (1)
- Coefficient of thermal expansion (1)
- Concrete (1)
- Crack growth in air (1)
- Crosslinking (1)
- Crystal growth (1)
- Crystal growth velocity (1)
- Crystal lattice (1)
- Crystal morphology (1)
- Cytocompatibility (1)
- DCB geometry (1)
- Data space (1)
- Degradation (1)
- Density (1)
- Differential scanning calorimetry (1)
- Diffusivity (1)
- Digitalisierung (1)
- Dissolved water (1)
- Dynamic mechanical analysis (1)
- Dynamisch Mechanische Analyse (1)
- Efficiency (1)
- Epoxy resin (1)
- Exposed metal sites (1)
- Facilitated activation (1)
- Ferrous phosphate hydrate (1)
- Flow Coefficient (1)
- Fluorescence spectroscopy (1)
- Formerkennung (1)
- Fracture Mechanics (1)
- Fracture surface (1)
- Fracture toughness (1)
- Fragility (1)
- Fraktographie (1)
- Fresnoit (1)
- Fresnoite (1)
- Gasabgabe (1)
- Gasgehalt (1)
- Gefüge (1)
- General Chemistry (1)
- Glasmatrixkomposit (1)
- Glass Ceramic (1)
- Glass capillaries (1)
- Glass crystallization stress (1)
- Glass forming melts (1)
- Glass liner (1)
- Glass manufacturing (1)
- Glass matrix composite (1)
- Glass melt (1)
- Glass melting (1)
- Glass screening device (1)
- Glass structure (1)
- Glass transformation temperature (1)
- Glass-ceramics definition (1)
- Grenzflächenenergie (1)
- Growth kinetics (1)
- Growth rate (1)
- Heißgasextraktion (1)
- High pressure (1)
- High temperature (1)
- High temperature corrosion (1)
- High-temperature corrosion (1)
- High-temperature oxidation (1)
- Hochtemperatur (1)
- Hochtemperaturbrennstoffzelle (1)
- Hot stage microscopy (1)
- Hydrogen diffusivity (1)
- Hydrogen permeability (1)
- Hydrogen storage (1)
- Hydrogen storage tank (1)
- Hydrous glass (1)
- IR spectroscopy (1)
- Inconel 625 (1)
- Indentation fracture toughness (1)
- Internal stresses (1)
- Ion beam erosion Sectioning (1)
- JMAK model (1)
- Kristallisation (1)
- Kristallorientierung (1)
- Limestone Filler (1)
- Long-term calculation (1)
- Low expansion (1)
- MOF-74 (1)
- Martensitic steels (1)
- Master curve (1)
- Materials Chemistry (1)
- Mechanical Engineering (1)
- Mechanics of Materials (1)
- Metallic silver precipitates (1)
- Metals and Alloys (1)
- Metformin (1)
- Milling (1)
- Mixed-linkers (1)
- Modeling (1)
- Moisture (1)
- NMR (1)
- Nb3Sn (1)
- Non-desired foaming (1)
- Nucleation (1)
- Nucleation mode (1)
- Nucleation tendency (1)
- Nydrogen melting (1)
- Oberflächenkeimbildung (1)
- Ontology (1)
- Oxidation protection (1)
- Oxide coatings (1)
- Oxide glass (1)
- Oxyfuel (1)
- Particle Size Distribution (1)
- Peem (1)
- Phase Separation (1)
- Phase separation (1)
- Phase transformations (1)
- Phosphate (1)
- Photocatalysis (1)
- Photovoltaic modules (1)
- Physical properties (1)
- Polymer (1)
- Polyurethane (1)
- Precipitation (1)
- Property simulation (1)
- Protective coating (1)
- Reference Material (1)
- Relaxationsphänomene (1)
- Resonance testing (1)
- Rheology (1)
- Rissheilung (1)
- Robot-assisted galss melting (1)
- Roboter (1)
- Roughness (1)
- Sample preparation (1)
- Sand blasting (1)
- Scaffolds (1)
- Shear thinning (1)
- Silber (1)
- Silicate glass (1)
- Silicatglas (1)
- Silicoborate glasses (1)
- Silver (1)
- Silver cluster (1)
- Silver glass paste (1)
- Silver precipitates (1)
- Silver-glass metallization paste (1)
- Simulation (1)
- Sinter retardation (1)
- Sintering atmosphere (1)
- Sinterung (1)
- Slow crack growth (1)
- Soda lime silicate glass (1)
- Soda-lime-silica (1)
- Sodium ion batteries (1)
- Sodium zinc borate glass (1)
- Sodiumborosilicate glasses (1)
- Stable crack growth (1)
- Steel (1)
- Steel P92 (1)
- Stress intensity (1)
- Stress-corrosion (1)
- Stress-strain behavior (1)
- Stress-strain-behavior (1)
- Structural defects (1)
- Structure (1)
- Struktur (1)
- Subcritical crack growth (1)
- Supersaturation (1)
- Surface Nucleation (1)
- Surface roughness (1)
- Synchrotron (1)
- Synchrotron micro-tomography (1)
- TEM (1)
- Thermal expansion (1)
- Thermo-optical measurement (1)
- Thermoanalytical Methods (1)
- Toughness (1)
- Transmission electron microscopy (1)
- Transmittance (1)
- Vacuum hot extraction (1)
- Viscose sintering (1)
- Viscous sintering (1)
- Vivianite (1)
- Volume Fraction (1)
- Volume changes (1)
- Water (1)
- Water in glass (1)
- X-ray diffraction (1)
- XRM (1)
- Young`s modulus (1)
- Young´s Modulus (1)
- Young´s modulus (1)
- Young’s Modulus (1)
- high pressure (1)
- hydrogen storage (1)
- infrared spectroscopy (1)
- phosphate glasses (1)
- water speciation (1)
Organisationseinheit der BAM
- 5.6 Glas (128) (entfernen)
Premature failure of glass under load is caused by sub-critical crack growth (SCCG) originate from microscopic flaws at the surface. While SCCG is related to the humidity of the ambient atmosphere, leading to stress corrosion phenomena at the crack tip, the detailed mechanism and the effect of different network formers are still not fully understood. For more clarity, various soda silicate glasses with a second network former were investigated by double cantilever beam technique: Na2O*Al2O3*SiO2 (NAS), Na2O*B2O3*SiO2 (NBS), Na2O*PbO*SiO2 (NPbS).
Three effects on the crack growth velocity, v, versus stress intensity, KI, curves were found out. The slope in region I, which is limited by corrosion, increases in the order NAS < NBS ≲ NPbS. The velocity range of region II reflecting the transition between corrosion effected and inert crack growth (region III), varies within one order of magnitude between the glasses. The KI region of inert crack growth strongly scatters between 0.4 and 0.9 MPam1/2. For comparison, crack growth at different humidity in commercial soda lime silicate glass (NCS) was measured.
Die Festigkeit von Gläsern wird durch die Oberflächenqualität beeinflusst. Kommt es neben dem Auftreten von Defekten zusätzlich zum Risswachstum ausgehend hiervon, wird die Festigkeit minimiert. Das Wachstum hängt dabei maßgeblich von der Luftfeuchtigkeit ab. Dieses Ermüdungsverhalten von Gläsern besser zu verstehen und dabei die Mechanismen und den Einfluss von im Volumen eingebauten Wasser auf das unterkritische Risswachstum zu untersuchen, ist Ziel der Arbeiten. Als Teilprojekt im Rahmen des DFG Schwerpunktprogramms SPP 1594 „Ultrastrong glasses“ soll der Einfluss des im Volumen eingebauten Wassers auf die Rissspitze untersucht werden. Zusammen mit der Leibniz Universität Hannover und der TU Clausthal werden hierfür hochwasserhaltige Gläser (bis zu 8 Gew%) bei 8 kbar über die Flüssigphase synthetisiert, die makroskopisch den hohen Wasseranteil nachstellen. Die Charakterisierung erfolgt hinsichtlich des Wassereinbaus, der mechanischen Eigenschaften und des Risswachstums. Die Arbeiten in Berlin beziehen sich hierbei auf die Messungen des unterkritischen Risswachstums in Luft und Vakuum, sowie Verlustwinkelmessungen.
Erste Ergebnisse zeigen Unterschiede im korrosionsbeeinflussten (langsames) und inerten (schnelles und im Vakuum stattfindendes) Risswachstumsverhalten der untersuchten Gläsern. Die Rissgeschwindigkeit beim Übergang vom korrosionsbeeinflussten zum inerten Risswachstum ist hin¬gegen für alle Gläser ähnlich und folglich ein kinetisch durch den äußeren Wassertransport an die Rissspitze bestimmter Prozess. Der Widerstand gegen Risswachstum steigt mit Tg und zusätzlich kann anhand der Verlustwinkelmessungen ein Zusammenhang zwischen der Netzwerk- und der β-Relaxation ermittelt werden. Je höher der Wassergehalt im Glas ist, desto niedriger wird Tg und einfacher das Risswachstum, welches sich durch längere Risse kennzeichnet. Besonders stark tritt dieser Effekt bei einem Überschuss an molekularem Wasser auf.
Dissolved water decisively influences numerous thermally activated relaxation phenomena in glasses like stress relaxation, sub-critical crack growth, internal friction, viscosity, sintering, and crystallization. Thermoanalytical methods can essentially help for better understanding of these phenomena. The lecture introduces the Vacuum Hot Extraction method (VHE) and illustrates its possibilities for measuring water content, degassing and mobility. As another thermoanalytical method, the Dynamic Mechanical Themoanalysis (DMA), allowing to study the effect of dissolved water on the internal friction in glasses, is introduced.
Glass powders are promising candidates for manufacturing a broad diversity of sintered materials like sintered glass-ceramics, glass matrix composites or glass bonded ceramics with tailored mechanical, thermal, electrical and optical properties and complex shape. Its wide and precise adjustability makes this class of materials a key component for advanced technologies. Processing of glass or composite powders often allow even more flexibility in materials design. At the same time, however, processing can have substantial effects on the glass powder surface and sinterability. Thus, mechanical damage and surface contamination can strongly enhance surface crystallization, which may retard or even fully prevent densification. Whereas sintering and concurrent crystallization have been widely studied, partially as cooperative effort of the TC7 of the ICG, and although glass powder sintering is predominantly applied for glasses of low crystallization tendency, sintering is also limited by gas bubble formation or foaming. The latter phenomenon is much less understood and can occur even for slow crystallizing glass powders. The lecture illustrates possible consequences of glass powder processing on glass sintering, crystallization and foaming.
Wasser in Silicatglas
(2018)
Der Vortrag gibt eine Einführung in die Methode der Vakuumheißextraktion und beschreibt die Anwendungsmöglichkeiten der an der BAMN betriebenen Anlage.
Borosilicate glasses (16Na2O–10B2O3–74SiO2, NBS) with water contents up to 22 mol% H2O were prepared to study the effect of water on structural relaxation using DTA, viscometry and internal friction measurements. The results show that the glass transition temperature Tg of DTA and the isokom temperature T12, of viscometry are in excellent agreement, confirming the equivalence of enthalpy and viscous relaxation for NBS glass. Combining Tg data with water speciation data demonstrates that OH groups are mainly responsible for the decrease of Tg with increasing hydration, while molecular water plays only a minor role. Internal friction spectra at 7.125 Hz confirm the decisive influence of water on mechanical relaxation. The temperature range of α-relaxation (glass transition) strongly decreases while two β-relaxation peaks (sub-Tg) progressively appear with increasing water content. A high temperature β-relaxation peak, attributed to the presence of OH groups, shifts from 670 to 450 K as total water content increases from 0.01 to 5 wt%. A low temperature β-relaxation peak, attributed to molecular water, appears at 380 K and 330 K in glasses containing 3 and 5 wt% H2O, respectively. These findings suggest that relaxation mechanism of different hydrous species at low temperature may contribute to fatigue of stressed glasses.
Up to now, the mechanisms of surface nucleation and surface-induced texture formation are far from being understood. Corresponding phenomena are discussed hypothetically or even controversial, and related studies are restricted to very few glasses. In this talk the state of the art on mechanisms of surface nucleation are summarized. On one hand, mechanical damaged surfaces show high nucleation activity, at which the nucleation occurs at convex tips and edges preferentially. On the other hand, solid foreign particles are dominant nucleation sites at low damaged surfaces. They enable nucleation at temperatures even far above Tg. The nucleation activity of the particles is substantially controlled by their thermal and chemical durability. But no systematic studies on initially oriented crystal growth or nucleation from defined active nucleation sites have been pursued, so far. Therefore, the main objective of a just started project is to advance the basic understanding of the mechanisms of surface-induced microstructure formation in glass ceramics. We shall answer the question whether preferred orientation of surface crystals is the result of oriented nucleation or caused by other orientation selection mechanisms acting during early crystal growth. In both cases, crystal orientation may be caused by the orientation of the glass surface itself or the anisotropy and orientation of active surface nucleation defects. As a first attempt we focused on possible reorientation of separately growing surface crystals during early crystal growth. First results show clear evidence that separately growing crystals can reorient themselves as they are going to impinge each other.
Sintered bioactive glass scaffolds of defined shape and porosity, e.g. made via additive manufacturing, must provide sufficient bioactivity and sinterability. As higher bioactivity is often linked to high corrosion and crystallization tendency, a certain compromise between sintering ability and bioactivity is therefore required. Groh et al. developed a fluoride-containing bioactive glass (F3), which allows fiber drawing and shows a bioactivity well comparable to that of Bioglass®45S5.
To study whether and to what extent the sinterability of F3 glass powder is controlled by particle size, coarse and fine F3 glass powders (300-310µm and 0-32µm) were prepared by crushing, sieving and milling. Sintering, degassing and phase transformation during heating were studied with heating microscopy, vacuum hot extraction (VHE), DTA, XRD, and SEM.
For the coarse glass powder, sintering proceeds slowly and is limited by surface crystallization of primary Na2CaSi2O6 crystals. Although the crystallization onset of Na2CaSi2O6 is shifted to lower temperature, full densification is attained for the fine powder. This finding indicate that certain porosity might be tuned via particle size variation. Above 900°C, intensive foaming is evident for the fine powder. VHE studies revealed that carbon species are the main foaming source.