5 Werkstofftechnik
Filtern
Erscheinungsjahr
- 2019 (187) (entfernen)
Dokumenttyp
- Vortrag (73)
- Zeitschriftenartikel (55)
- Posterpräsentation (31)
- Beitrag zu einem Tagungsband (19)
- Buchkapitel (2)
- Sonstiges (2)
- Forschungsbericht (2)
- Monografie (1)
- Dissertation (1)
- Forschungsdatensatz (1)
Sprache
- Englisch (156)
- Deutsch (30)
- Mehrsprachig (1)
Schlagworte
- Corrosion (17)
- Additive Manufacturing (14)
- Glass (12)
- Carbon steel (8)
- Low Cycle Fatigue (8)
- Microstructure (7)
- CO2 (6)
- Degradation (6)
- Fatigue (6)
- Water content (6)
- Additive manufacturing (5)
- CCS (5)
- Ceramic (5)
- Crack growth (5)
- Crystallization (5)
- EBSD (5)
- Oxidation (5)
- 3D printing (4)
- LCF (4)
- Mikrostruktur (4)
- P92 (4)
- Ti-6Al-4V (4)
- Transmission electron microscopy (4)
- 316L (3)
- Alloy 2618A (3)
- Anisotropy (3)
- Carbon capture (3)
- Ceramic spring (3)
- Ceramics (3)
- DCB (3)
- Diesel (3)
- Diffraction (3)
- Diopside (3)
- Full-Notch Creep Test (FNCT) (3)
- High temperature corrosion (3)
- In situ (3)
- Modeling (3)
- Orientation (3)
- Pitting (3)
- Polymer (3)
- Sandwich (3)
- Simulation (3)
- Sintering (3)
- Slurry (3)
- Steel (3)
- Sulfidation (3)
- Tempered Martensite Ferritic Steels (3)
- Thermo-Mechanical Fatigue (3)
- Utilization (3)
- Water speciation (3)
- µ-gravity (3)
- 3D (2)
- AISI 316L (2)
- Additive Fertigung (2)
- Al-Cu-Li alloys (2)
- Alterung (2)
- Aluminium (2)
- Betriebsfestigkeit (2)
- Bioactive glass (2)
- Bioceramics (2)
- CCU (2)
- CCUS (2)
- CT (2)
- Capture (2)
- Carbon (2)
- Coarsening (2)
- Composite (2)
- Computed Tomography (2)
- Condensate (2)
- Condensation (2)
- Corrosion Fatigue (2)
- Crack Propagation (2)
- Crack propagation (2)
- Creep-Fatigue (2)
- Crevice corrosion (2)
- Crystal plasticity (2)
- Dehnungsfehler (2)
- Digital material representation (2)
- Distribution function (2)
- Ductile iron (2)
- Early oxidation (2)
- Elastic constants (2)
- Electron energy (2)
- Energy distribution (2)
- Extensometer (2)
- FeCr- alloys (2)
- Fiber reinforced polymer (2)
- Fracture surface analysis (2)
- Fraktografie (2)
- Geothermal (2)
- Glas (2)
- Glass fiber reinforced polymers (2)
- Glass-ceramic (2)
- High Alloyed Steel (2)
- High Temperature Testing (2)
- High temperature (2)
- IN 718 (2)
- IR (2)
- Impurities (2)
- Internal friction (2)
- Kavitation (2)
- Kikuchi pattern (2)
- Kleinprobenprüfung (2)
- Laminography (2)
- Layerwise (2)
- Layerwise slurry deposition (2)
- Lightweight materials (2)
- Material degradation (2)
- Microhardness (2)
- Mixed Ca-K-Na phosphates (2)
- Monte-Carlo Simulation (2)
- NMR spectroscopy (2)
- Na and K rhenanites (2)
- Niobium alloying (2)
- Non-destructive testing (2)
- Phase diagram (2)
- Phase transformations (2)
- Photon counting detector (2)
- Pipelines (2)
- Polyethylene, PE-HD (2)
- Polymer matrix composites (2)
- Pores (2)
- Powder (2)
- Probengrößeneffekt (2)
- Roughness (2)
- Röntgenbeugung (2)
- Röntgenrefraktion (2)
- Scale-bridging (2)
- Schadensanalyse (2)
- Schädigung (2)
- Selective laser melting (2)
- Silicon Carbide (2)
- Soda-lime silicate glass (2)
- Soda-lime-silica glass (2)
- Storage (2)
- Surface (2)
- Surface crystallization (2)
- Synthetic air (2)
- TMF (2)
- Temperaturschwankungen (2)
- Tensile Properties (2)
- Ti64 (2)
- TiAl5V4 (2)
- Titan (2)
- Titanium (2)
- Topografie (2)
- Utilization, and storage (CCUS) technology (2)
- VSSA (2)
- Vickers indentation (2)
- Virtual experiments (2)
- Weibull Distribution (2)
- Werkstoffprüfung (2)
- Wind energy (2)
- Wind turbine blades (2)
- Zero-g (2)
- Zugeigenschaften (2)
- Zugversuch (2)
- 3D imaging (1)
- 5G (1)
- AFM based test methods (1)
- AISI 304L (1)
- AM (1)
- Abrasion (1)
- Aggressive environment (1)
- Alkali-activated materials (1)
- Alumina (1)
- Aluminosilicate glasses (1)
- Analytische Zentrifuge (1)
- Anwendungen (1)
- Aquifer (1)
- Artificial weathering (1)
- Atomization (1)
- Aufbau von Festkörpern (1)
- Aussonderugnsrate (1)
- BTS (1)
- Berstdruck (1)
- Biodiesel (1)
- Biogeochemical cycling (1)
- Biomineralisation (1)
- Biopolymer (1)
- Blähen (1)
- Breakdown strength (1)
- Brittle fracture (1)
- Bruchflächenanalyse (1)
- Bubble formation (1)
- C. lap-shear (1)
- CALPHAD (1)
- CALPHAD databases analysis (1)
- CFRP (1)
- CO2 Corrosion (1)
- CO2 separation membranes (1)
- CO2-Speicherung (1)
- CO2-storage (1)
- Calcination (1)
- Calcium cobaltite (1)
- Calibration (1)
- Carbidic austempered ductile iron (1)
- Carbon Capture, Utilization and Storage (CCUS) (1)
- Carbon capture, utilization and storage technology (1)
- Carbon fibres (1)
- Carbon storage (1)
- Cavitation (1)
- Cellulose (1)
- Cement (1)
- Certification Standard 22 (1)
- Chalcogenides (1)
- Characterisation (1)
- Chemically Complex Alloy (1)
- Chemische Analyse (1)
- Chemo-mechanical coupling (1)
- Co-axial monitoring (1)
- Coefficient of thermal expansion (1)
- Complex concentrated alloy (CCA) (1)
- Contact angle (1)
- Contact fatigue (1)
- Copper vacancies (1)
- Corrosion and storage (CCUS) technology (1)
- Corrosion pits (1)
- Corrosion resistance (1)
- Crack arrest (1)
- Crack healing (1)
- Creep (1)
- Crosslinking (1)
- Crystal Plasticity Modelling (1)
- Crystal Texture (1)
- Crystal orientation (1)
- Cyclic softening (1)
- D. aging (1)
- D. creep D. viscoelasticity (1)
- DED-L (1)
- Damage (1)
- Dark-field transmission electron microscopy (DFTEM) (1)
- Data storage (1)
- Defects (1)
- Deformation behavior (1)
- Dense phase (1)
- Destabilization (1)
- Deuterium (1)
- Dielectric breakdown (1)
- Dielectric strength (1)
- Diesel Fuel (1)
- Dislocation (1)
- Dislocations (1)
- Distributed fiber optic sensing (1)
- Distributed fiber optic sensors (1)
- Droplet (1)
- Droplet corrosion (1)
- Druckgasspeicher (1)
- Dual-energy (1)
- Dynamic mechanical analysis (1)
- Dynamisch Mechanische Analyse (1)
- EASA (1)
- EIS (1)
- Early sulfidation (1)
- Eigenschaften (1)
- Electrochemical characterisation (1)
- Electrochemical deposition (1)
- Electrochemical dressing (1)
- Electrochemical impedance spectroscopy (1)
- Electromicroscopy (1)
- Electron backscattered diffraction (EBSD) (1)
- Electron microscopy (1)
- Electropolishing (1)
- Endurance Limit (1)
- Energiespeicherung (1)
- Environment (1)
- Environmental Stress Cracking (ESC) (1)
- Environmental stress cracking (1)
- Environmental stress cracking (ESC) (1)
- Environmentally assisted cracking (1)
- Ermüdung (1)
- Erneuerbare Energien (1)
- Explosionsschutz (1)
- Exposed metal sites (1)
- FSDC (1)
- Fabrication (1)
- Facilitated activation (1)
- Failure test (1)
- Faser-Kunststoff-Verbunde (1)
- Faserkunststoffverbunde (1)
- Fatigue Life Evaluation (1)
- Fatigue Testing (1)
- Fatigue crack propagation stages (1)
- Ferritic steels (1)
- Ferritic–martensitic steel (1)
- Fiber reinforced polymers (1)
- Fine Powder (1)
- Finite element analysis (1)
- Flowability (1)
- Foaming (1)
- Focused Ion Beam (1)
- Force-distance diagram (1)
- Four-point bending test (1)
- Fracture (1)
- Fracture mechanics (1)
- Freeze Drying (1)
- Freeze casting (1)
- Fresnoit (1)
- Friction Stir Welding (1)
- Frozen state photopolymerization (1)
- GFRP (1)
- Gasdetektion (1)
- Gassensorik (1)
- Gefügeuntersuchung (1)
- Glass ceramic (1)
- Glass matrix composite (1)
- Glass powder (1)
- Glass screening device (1)
- Glasspeicher (1)
- Gleichgewicht (1)
- Gold (1)
- Grain boundary (1)
- Grünfolieneigenschaften (1)
- HDPE Soprption (1)
- HDPE Sorption (1)
- Hard machining (1)
- Hardness (1)
- Heat treatment (1)
- Heißgasextraktion (1)
- Heißgaskorrosion (1)
- Hierarchical porosities (1)
- High alloyed steel (1)
- High entropy alloys (1)
- High pressure (1)
- High-entropy alloys (1)
- High-temperature corrosion (1)
- High-temperature oxidation (1)
- High-temperature properties (1)
- High-voltage testing (1)
- Hochentropielegierungen (1)
- Hochtemperaturermüdung (1)
- Honing (1)
- Honing Stone (1)
- Hydrogel (1)
- Hydrogen (1)
- Hydrogen diffusivity (1)
- Hygrothermal (1)
- Impact damage (1)
- In-situ Process Monitoring (1)
- Inclusion cluster (1)
- Inclusion size (1)
- Inconel 625 (1)
- Inconel 686 (1)
- Incremental lifetime models (1)
- Infrared nano AFM (1)
- Infrared spectroscopy (1)
- Intermodulation AFM (1)
- Internal Surfaces (1)
- Internal oxidation (1)
- Interphase (1)
- Ionic porosity (1)
- Iron meteorite (1)
- Irregular topography (1)
- Keramikfeder (1)
- Keramische Folien (1)
- Korrosion (1)
- Kreislaufwirtschaft (1)
- Kriechen (1)
- Kristallisation (1)
- Kristallsystem (1)
- Kurzfaser-verstärkte Thermoplaste (1)
- LMD (1)
- LSD print (1)
- LTCC multilayer (1)
- Langzeitstabilität (1)
- Laser Beam Melting (1)
- Laser Scanning Microscopy (1)
- Laser Scanning Microscopy (LSM) (1)
- Laser beam melting (1)
- Laser cladding (1)
- Laser-induced slip casting (1)
- Laserbearbeitung (1)
- Laserscanningmikroskopie (LSM) (1)
- Layer system (1)
- Layerwise Slurry Deposition (1)
- Lebensdauer (1)
- Long-term storage (1)
- Low cycle fatigue (1)
- MOF-74 (1)
- Machine Learning (1)
- Magmatic and hydrothermal processes (1)
- Magnetic domains (1)
- Magnetische Domänen (1)
- Magnetoelastic effect (1)
- Magnetoelastischer Effekt (1)
- Martensite (1)
- Mass transport (1)
- Materialkreislauf (1)
- Materialprüfung (1)
- Materials science (1)
- Mechanical behavior (1)
- Mechanical properties (1)
- Mehrachsige Verformung (1)
- Metal powder characterization (1)
- Metrology (1)
- Micro-shrinkages (1)
- Micromechanical model (1)
- Microstructure analysis (1)
- Microstructure characterisation (1)
- Microstructure evolution (1)
- Microstructure modification (1)
- Mikrostrukturuntersuchung (1)
- Mindedestberstdruck (1)
- Mini-UAV (1)
- Mis-match (1)
- Mixed-linkers (1)
- Modell (1)
- Moisture (1)
- Mortel (1)
- Multiaxial deformation (1)
- Multiple cracks (1)
- NDT (1)
- NMR (1)
- Nano particle (1)
- Nano screening (1)
- Nanocomposites (1)
- Nanomaterial (1)
- Nanoparticles (1)
- Natural (1)
- Neutron diffraction (1)
- New standards (1)
- Ni-Resist (1)
- Nitride (1)
- Non-destructive Materials (1)
- Non-metallic inclusions (1)
- Nondestructive testing (1)
- Normung (1)
- Ooxidation (1)
- Optical criterion (1)
- Orientation relationship (1)
- Oxidation protection (1)
- PE-HD Sorption (1)
- Parabolic flight (1)
- Particle size (1)
- Partikelgrößenverteilung (1)
- Permeability (1)
- Phase transformation (1)
- Phase-field (1)
- Phase-field simulation (1)
- Phosphate (1)
- Physically based material model (1)
- Pipeline (1)
- Pitting corrosion (1)
- Plastic deformation (1)
- Platinum-group-metals (1)
- Polyaniline (1)
- Polyethylen hoher Dichte (1)
- Polyurethane (1)
- Power plant (1)
- Power-to-Gas (1)
- Preceramic polymer (1)
- Pressure-assisted sintering (1)
- Process Monitoring (1)
- Process development (1)
- Process monitoring (1)
- Processing window (1)
- Pultruded fiber rods (1)
- REM (1)
- Referenzmaterial (1)
- Referenzorganismus (1)
- Referenzverfahren (1)
- Relaxation fatigue (1)
- Repair patch (1)
- Residual stress (1)
- Resonance testing (1)
- Restberstfestigkeit (1)
- Risikoanalyse (1)
- Rohrprobekörper (1)
- SDC (1)
- STEM (1)
- Safety (1)
- Sailplane Development Panel (1)
- Salt melt (1)
- Samarium doped ceria (1)
- Sample preparation (1)
- Sandwich structures (1)
- Scaffolds (1)
- Scanning Electron Microscopy (SEM) (1)
- Scanning electron microscopy (1)
- Scavenging effect of iron (1)
- Scratches (1)
- Semiconductor materials (1)
- Sensor (1)
- Sensorik (1)
- Silicoborate glasses (1)
- Silver glass paste (1)
- Sintern (1)
- Slip-rolling (1)
- Slow Crack Growth (SCG) (1)
- Slow crack growth (1)
- Soda-lime-silica (1)
- Sodium ion batteries (1)
- Sol-gel coating (1)
- Sorption (1)
- Spannungs-Dehnungs-Verhalten (1)
- Spannungsriss (1)
- Spar cap design (1)
- Spectroscopy (1)
- Spring constant (1)
- Spring constant (1)
- Standardisation (1)
- Stanzen (1)
- Statistics (1)
- Stress intensity factor (1)
- Stress-strain behavior (1)
- Streuung (1)
- Structural composites (1)
- Structural defects (1)
- Structural health monitoring (1)
- Structural steel (1)
- Struktur (1)
- Subcritical crack growth (1)
- Superalloy (1)
- Superconducting magnet (1)
- Supercritical CO2 (1)
- Supercritical/dense phase CO2 (1)
- Surface treatments (1)
- Swept wavelength interferometry (1)
- Synthesis (1)
- TEM (1)
- Tempered martensite ferritic steel (1)
- Tempered martensite ferritic steels (1)
- Tensile testing (1)
- Thermodynamic analysis (1)
- Thermoelectric properties (1)
- Thermomechanics (1)
- Thermomechanik (1)
- Thiol-ene click chemistry (1)
- ToF-SIMS (1)
- Transmission electron microscopy (TEM) (1)
- Tribologie (1)
- Tungsten-Rhenium (1)
- Ultrasound (1)
- Ungleichgewicht (1)
- Unlegierter Baustahl (1)
- VM12 SHC (1)
- Vacuum hot extraction (1)
- Vickers (1)
- Viscoelastic model (1)
- Viscous sintering (1)
- Viskoplastisch (1)
- WAXS (1)
- Wasserstoff (1)
- Wasserstofferzeugung (1)
- Werkstoffmechanische Prüfung (1)
- Wetting (1)
- Wind turbine blade shells (1)
- Windenergie (1)
- X-ray absorption spectroscopy (1)
- X-ray refraction (1)
- XRD (1)
- Young´s modulus (1)
- Zerstörungsfreie Prüfung (1)
- ZnO (1)
- Zug-Druck-Schubprüfung (1)
- alumina (1)
- arbidic austempered ductile iron (1)
- arbon capture (1)
- ausfgallfreie Lastwechsel (1)
- bioactive (1)
- biomaterials (1)
- bone (1)
- carbon steel (1)
- ceramics (1)
- coarsening (1)
- condensate (1)
- corrosion (1)
- electrochemical characterization (1)
- hardness (1)
- high pressure (1)
- impurities (1)
- infrared spectroscopy (1)
- microstructure analysis (1)
- phosphate glasses (1)
- pitting corrosion (1)
- selective laser melting (1)
- statistische Auswertung (1)
- utilization, and storage (CCUS) technology (1)
- volume resistivity (1)
- water speciation (1)
Organisationseinheit der BAM
- 5 Werkstofftechnik (187)
- 5.1 Mikrostruktur Design und Degradation (56)
- 5.4 Multimateriale Fertigungsprozesse (37)
- 5.2 Metallische Hochtemperaturwerkstoffe (35)
- 5.6 Glas (30)
- 5.3 Polymere Verbundwerkstoffe (28)
- 7 Bauwerkssicherheit (25)
- 5.5 Materialmodellierung (17)
- 8 Zerstörungsfreie Prüfung (17)
- 9 Komponentensicherheit (16)
Eingeladener Vortrag
- nein (73)
Efficient studies of scarce or expensive materials require material saving processes. Therefore, a high yield concept for small batch preparation of ready-to-press powder is exemplarily presented for yttria stabilized nano-zirconia (d50 < 50 nm).
The concept involves small batch preparation in an ultrasound resonator, dispersant selection based on zeta potential measurements, evaluation of slurry stability using an analytical centrifuge, and preparation of ready-to-press powder by freeze drying.
Freeze drying offers key advantages. Process efficiency and high yield above 95 % are independent of sample size. The dried product does not require further mechanical treatment like milling or grinding. Side effects like migration of additives are avoided.
An optimized freeze drying process tolerates slurries with moderate stability. Thus, efforts for slurry development can be reduced. Generally, identifying a suitable dispersing agent requires only 3-5 zeta potential measurements. Slurry stability is rechecked using an analytical centrifuge, which also accounts for steric stabilization. An ultrasound resonator is used to disperse the powder without contamination, which becomes critical for small batches.
The described route is exemplarily presented for the development of an additive recipe for nano-sized zirconia powder, targeting for good pressing behavior and high green density. Therefore, a variety of binding and lubricating agents were tested.
Following the presented route, 80 g zirconia powder were sufficient to conduct a study including slurry development and five sample sets with varying composition, each set comprising five discs (d = 20 mm and h = 2 mm).
Due to the stochastic nature of crack nucleation by Vickers indentation, a statistical analysis of propagation rates of 185 radial cracks was performed. Crack growth was observed directly using a video camera with high Image acquisition rate. It is found that propagation rates are controlled by the environmental reactions at the crack-tip shortly after their initiation (< 1 s). Calibration of the stress intensity KI showed that the residual stress factor χ and the exponent n of the equation KI==χPc−n (with P==load and c==crack length) are broadly distributed among the 185 analyzed cracks, ranging from 10−16 to 104 and from 0.1 to 5, respectively. For the most frequent crack, the equation KI==0.052Pc−1.47 holds. The results show that correlations of indentation-induced crack length to stress intensity necessitate the use of statistical significant data that are calibrated by the environmental reactions at the crack-tip.
Dissolved water has major impact on the physical and chemical properties of phosphate glasses. In the present study we have investigated the structural response to water incorporation for glasses in the system Li2O–MgO–Al2O3–P2O5.
Glasses containing 0–8 wt% H2O were synthesised at 500 MPa confining pressure in internally heated gas pressure vessels at 1323 K (LMP, Al-poor glass) and 1423 K (LMAP, Al-enriched glass). Water contents of glasses were determined by pyrolysis and subsequent Karl-Fischer titration (KFT) and/or by infrared spectroscopy. Density varies nonlinearly with water content implying large structural changes when adding up to 2 wt% H2O to the dry glass. Glass Transition temperatures measured by differential thermal analysis (DTA) continuously decrease with water content. The trend can be explained by depolymerisation of the phosphate network. Near-infrared spectroscopy shows that even in Al poor glasses only a minority of dissolved water is present as H2O molecules, but the largest amount is present as OH Groups formed by hydrolysis of P–O–P bonds. The network is stabilised by aluminium which is predominantly six-coordinated in these glasses as shown by 27Al MAS NMR spectroscopy. With increase of Al in the glasses, breaking up of the Phosphate network through hydrolysis is depressed, i.e. much lower OH Contents are formed at same total water content.
Network depolymerisation upon addition of H2O is evident also from 31P MAS NMR spectroscopy. While Phosphate tetraheda are crosslinked by two to three bridging oxygen in dry glasses, diphosphate Groups are dominant in glasses containing 8 wt% H2O.
Environmental conditions are known to influence sub-critical crack growth (SCCG) that starts from microscopic flaws at the glass surface, leading to stress corrosion phenomena at the crack tip. The processes at the crack tip are complex and water has been identified as a key component governing SCCG at low crack velocities (region I). In particular, the influence of humidity accelerating crack propagation is well studied for dry industrial soda-lime silicate glasses (< 1000 ppm water). To shed light on this influence, the effect of water is mimicked by studying SCCG in water-bearing glasses. For this purpose, water-bearing silicate glasses of up to 8 wt% total water were synthesized in an internally heated pressure vessel at 0.5 GPa and compared to dry glasses. SCCG was measured using the double cantilever beam technique. For dry glasses, three trends in the crack growth velocity versus stress intensity, KI, curve were found. The slope in region I, limited by environmental corrosion, increases in the order soda-lime silicate < sodium borosilicate < barium calcium silicate < sodium zinc silicate < sodium aluminosilicate glass. The velocity range of region II, reflecting the transition between corrosion affected and inert crack growth (region III), varies within one order of magnitude among these glasses. The KI region of inert crack growth strongly scatters between 0.4 and 0.9 MPam1/2. For hydrous glasses, it is found that water strongly decreases Tg, form a new sub-Tg relaxation peak caused by molecular water, and makes the glasses more prone to SCCG. The observed trends will be discussed in terms of the effects of Youngs Modulus on strain energy release rate and energy dissipation related to glass relaxation phenomena.
Ambient water influences sub-critical crack growth (SCCG) from microscopic surface flaws, leading to stress corrosion at the crack tip. The complex influence of humidity accelerating slow crack propagation (region I) is well studied only for dry commercial NCS glass (< 1000 ppm water). To shed light on this influence, the effect of water is mimicked by studying SCCG water-bearing glasses. For this purpose, water-bearing silicate glasses of 8 wt% total water were synthesized at 0.5 GPa and compared to dry glasses. SCCG was measured in double cantilever beam geometry. For dry glasses, 3 trends in crack velocity vs. stress intensity, KI, curve were found. The slope in region I increases in the order NCS < NBS < BaCS < NZnS < NAS glass. The velocity range of region II, reflecting the transition between corrosion affected and inert crack growth (region III), varies within one order of magnitude among these glasses. The KI region of inert crack growth strongly scatters between 0.4 and 0.9 MPam0.5. For hydrous glasses, it is found that water strongly decreases Tg, form a new sub-Tg internal friction peak caused by molecular water, and makes the glasses more prone to SCCG. The observed trends will be discussed in terms of the effects of Youngs Modulus on the strain energy release rate and energy dissipation related to mechanical glass relaxation phenomena.
Glass strength and fatigue is limited by surface cracks. As subcritical crack growth (SCCG) is governed by ambient humidity, stress corrosion at the crack tip is widely accepted to be the underlying mechanism. However, as water is known to have decisive effect on glass properties and can rapidly enter the crack tip near glass region, SCCG could be affected by such water related phenomena. We tried to mimic these effects studying water dissolution and speciation, mechanical properties, and SCCG in water-bearing glasses. For this purpose, glasses up to 8 wt% water have been prepared by means of high-pressure melting of glass powder - water mixtures.
As part of this effort, SCCG in dry and hydrous commercial micros¬cope slide glass (CW = 6 wt%) was studied in double cantilever beam (DCB) geometry and sub-Tg relaxation was measured by Dynamic Mechanical Analysis (DMA).
For SCCG in ambient air (24% r.h.), SCCG was promoted by the presence of 6wt% bulk water with respect to the dry glass. On the other hand, stress intensity values, KI, required to cause slow crack growth (v < 10-6 ms-1) resemble literature findings for float glass of similar composition in liquid water, which might represent the maximum possible promoting effect of ambient water on SCCG.
For SCCG in vacuum (10-3 mbar), dissolved bulk water causes even more pronounced effects. Most strikingly, it strongly decreases the slope of the log v(KI)-curve, which is a measure of dissipated energy during fracture. A strong increase of sub-Tg relaxation with increasing water content was confirmed by DMA. As a consequence, slow crack growth occurs at KI values as measured in the dry glass whereas fast crack growth occurs at much larger KI than that of the dry glass. Kinks and shoulders shown by the inert log v(KI)-curve indicate that bulk water does not simply affect bulk mechanical properties.
Homogeneous introduction of organic additives is a key of ceramic powder processing. Addition of organics to ceramic slurries holds advantages compared to dry processing like organic content reduction and a more homogeneous additive distribution on the particle surface.
Investigations of the alumina slurries were primarily based on zeta potential measurements and sedimentation analysis by optical centrifugation. Both methods were combined to determine a suitable additive type, amount and composition, whereas the spray drying suitability has been ensured by viscosity measurements. Granules, yielded by spray drying of such ideally dispersed alumina slurries, are mostly hollow and possess a hard shell. Those granules cannot easily be processed and can only hardly be destroyed in the following shaping step, leading to sinter bodies with many defects and poor strength and density.
The precise slurry destabilization, carried out after ideally dispersing the ceramic powder, shows a strong influence on the drying behavior of the granules and hence on the granule properties. A promising degree of destabilization and partial flocculation was quantified by optical centrifugation and resulted in improved granule properties. Spray drying the destabilized alumina slurries yielded homogeneous “non-hollow” granules without the above mentioned hard shell. Sample bodies produced of these granules exhibited a reduction of defect size and number, leading to better results for sinter body density and strength.
The positive effect of the slurry destabilization has been further improved, by exchanging the atomizing unit from a two-fluid one to an ultrasound atomizer with only minor slurry adjustments necessary. The controlled destabilization and ultrasound atomization of the ceramic slurry show excellent transferability for zirconia and even ZTA (zirconia toughened alumina) composite materials.
The crystallization behavior of sodium ion conductive Na2MnP2O7 glass was examined to clarify the crystallization mechanism. The formation of thermodynamically metastable phase, layered Na2MnP2O7, at the surface of the glass occurred. Heat treatment at 430 °C for 3 h lead to surface crystals of Na2MnP2O7 oriented with the (101) direction perpendicular to the sample surface. As the heat treatment temperature increased, the glass-ceramic samples deformed, and the presence numerous micro bubbles due to dissolved water was detected.
Fresnoite glass with excess SiO2 exhibits oriented surface crystallization, in contrast to the stoichiometric glass composition. Recent EBSD studies documented that the crystals in BTS (2BaO-TiO2-xSiO2, x=0-3) can occur in a distinct [101]-orientation perpendicular to the surface and claimed that this orientation is not a result of growth selection. During these previous studies, however, the effect of surface preparation and surrounding atmosphere during the crystallization experiments were not considered. As these parameters may influence crystal orientation, we studied the surface crystallization of a BTS glass (2BaO-TiO2–2.75SiO2) under controlled conditions with the help of light, electron and polarisation microscopy as well as EBSD. Heat treatments for one hour at 840°C of fractured BTS glass surfaces in air resulted in a large number of not-separable surface crystals. This large number of crystals can be caused by dust particles, which act as nucleation agents. As crystal growth velocity could further be influenced by humidity, our experiments are performed in a filtered and dried air atmosphere. The crystal morphology and orientation will be analysed in dependence of the sample preparation and a differing surrounding atmosphere.