5 Werkstofftechnik
Filtern
Dokumenttyp
- Vortrag (36) (entfernen)
Sprache
- Englisch (36) (entfernen)
Referierte Publikation
- nein (36)
Schlagworte
- Glass (13)
- Sintering (9)
- Crack growth (7)
- DCB (5)
- Water speciation (5)
- Crystallization (4)
- Alkali ions (3)
- Foaming (3)
- Silicate Glasses (3)
- Soda-lime silicate glass (3)
- Vickers (3)
- Water content (3)
- Alkali zinc borate glasses (2)
- Diopside (2)
- Fracture Toughness (2)
- Glas (2)
- Orientation (2)
- Oxide Glasses (2)
- Powder (2)
- Silver diffusion (2)
- Silver-glass-metallization-paste (2)
- Viscosity (2)
- 3D glass structure model (1)
- 3D printing (1)
- Alkali zinc borate glass (1)
- Bioactive Glass (1)
- Blähen (1)
- Bond energy (1)
- Data space (1)
- Diffusion (1)
- Diffusion coefficient (1)
- Dissolved water (1)
- Dynamic mechanical analysis (1)
- Dynamisch Mechanische Analyse (1)
- Elastic constants (1)
- Fluorescence spectroscopy (1)
- Fracture Mechanics (1)
- Fracture surface (1)
- Fracture toughness (1)
- Gasabgabe (1)
- Gasgehalt (1)
- Glass composition (1)
- Glass melting (1)
- Glass powder (1)
- Glass screening device (1)
- Heißgasextraktion (1)
- Hydrogen permeation (1)
- IR (1)
- Internal friction (1)
- Kristallisation (1)
- Material Digital (1)
- Mechanical properties (1)
- Metallic silver precipitates (1)
- Microhardness (1)
- Non-desired foaming (1)
- Nucleation mode (1)
- Ontology (1)
- Oriented surface crystallization (1)
- Oxide glass (1)
- Phase Separation (1)
- Phase separation (1)
- Relaxation (1)
- Relaxationsphänomene (1)
- Silicatglas (1)
- Silver cluster (1)
- Silver metallization paste (1)
- Silver precipitates (1)
- Silver-glass metallization paste (1)
- Sintering atmosphere (1)
- Sintern (1)
- Soda-lime-silica glass (1)
- Structure (1)
- Surface Energy (1)
- Surface Nucleation (1)
- Surface crystallization (1)
- Surface energy (1)
- Thermo-optical measurement (1)
- Thermoanalytical Methods (1)
- Transmission electron microscopy (1)
- Vacuum hot extraction (1)
- Wasser (1)
Organisationseinheit der BAM
- 5.6 Glas (36) (entfernen)
Eingeladener Vortrag
- nein (36)
Artificial bone replacement by individual customized three-dimensional resorbable bioactive glass has not yet been widely established in the clinical use. This is mainly due to the antagonism of sintering ability and suitable bioactivity. Competitive crystallization often prevents the generation of dense sintered bodies, especially for additive manufactured 3D structures. Previous studies of the fluoride-containing glass F3 have shown its potential to combine both sintering ability and suitable bioactivity. Furthermore, the occurring sintering blockade by surface crystallization of Na2CaSi2O6 was tunable by glass particle size.
In this study the glasses F3, F3-Cu with 1 mol% CuO added at the expense of CaO and the well-known 13-93 were chosen to determine the influence of surface crystallization on 3D printed sinter bodies. For this purpose, grain size fractions in range of smaller 32 µm to 315 µm in fraction size of 6-20 µm were sieved from jaw crushed glass frit as well as glass cubes were cut from casted blocks for all glasses. Sintering behavior of both pressed and printed powder compacts was observed via heating microscopy. Crystallization was determined by DTA and crystallization progress was monitored on fractured sinter bodies and polished cubes via electron and laser scanning microscopy as well as with diffractometry.
Depending on grain size the formation of crystalline support framework along former grain boundaries shows the capability to stabilize fully densified sinter bodies before softening. Beside of this, the generation of complex hierarchic porosity was possible as well.
The search for strong and tough oxide glasses is important for making safer, more environmentally friendly, thinner glass products. However, this task remains generally difficult due to the material’s inherent brittleness. In search for tougher glasses, fracture toughness (KIC) prediction models are helpful tools to screen for promising candidates.
In this work, a novel model to predict KIC via the fracture surface energy, γ, is presented. Our approach uses readily available crystallographic structure data of the glass’s isochemical crystal and tabled diatomic chemical bond energies, D0. The method assumes that γ of a glass equals the fracture surface energy of the most likely cleavage plane of the crystal. Calculated values were not only in excellent agreement with those calculated with a former well-working model, but also demonstrates a remarkable equivalence between crystal cleavage planes and glass fracture surfaces.
Finally, the effectiveness of fracture toughness enhancement by chemical substitution is discussed based on our results and alternative toughening strategies will be suggested.
The search for strong and tough oxide glasses is important for making safer, environment-friendlier, thinner glasses. As fracture toughness experiments in brittle materials are complicated and time-consuming , modelling glass fracture surface energy, G, and fracture toughness, KIc, is of interest for screening promising candidates. Inspired by Rouxel´s idea of preferred crack growth along cutting weakest bonds within a glass structure and a study by Tielemann et al. , which indicates a correlation between crystal fracture surface and glass-crys¬tal interfacial energies, we present a new approach for predicting G. Combining both ideas, we used diatomic bond energies and readily available crystallographic structure data for estimating G. The proposed method assumes that G of the glass equals the surface fracture energy of the cleavage plane in its respective isochemical crystal. We calculated G- values for more than 25 iso-chemical silicate systems and compared them to calculated values from Rouxel’s widely used procedure, which is well working and based on glass densities and chemical bond energies. Not only does our model yields good agreement with [3], but it also enables an estimation for glasses with unknown density and can therefore contribute to broaden the data basis for glass property modelling tools. Most interestingly, however, this agreement indicates an interesting similarity between cleavage planes in a crystal and its corresponding glass state in terms of fracture processes.
Glass
(2019)
Overview about the key activities of division 5.6 glass and the diversity of the material glass. For the vacuum hot extraction method (VHE-MS) some examples are presented e. g. for the measurement of water content or the determination of diffusion coefficient of hydrogen in glasses. Finally, an outlook is shown on the robot controlled glass screening device which will be available next year.
Die technischen Möglichkeiten der robotischen Glasschmelzanlage der BAM werden vorgestellt.
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.
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.
Liquid phase sintering of glass bearing silver pastes used in photovoltaics and microelectronics is poorly understood. In particular, the role of different network modifiers acting in the glass component and the question of the most suitable atmospheric oxygen level during sintering are still under considerable debate. To tackle these issues, low-melting and lead-free X2O-ZnO-B2O3 glasses with X = Li, Na, K and Rb (LZB, NZB, KZB and RZB) were prepared. Infrared spectroscopy showed that the glass structure was similar to each other, while an increase of tetrahedrally coordinated boron with increasing field strength of the alkali was evident. In turn, the glass transition temperature (from differential thermal analysis) increased in the order: RZB (449 °C) < KZB (460 °C) < NZB (465 °C) < LZB (472 °C). Powders of each glass were mixed with organics to receive silver-glass-pastes containing 30 vol% glass and these were subjected to heating microscopy in air. Although similar onset temperatures of sintering were recorded for Ag-NZB and Ag-LZB glass pastes, and for Ag-RZB paste and KZB-Ag-paste, respectively, differences in the crystallization behavior and final densification were observed between the former and the latter group. These were translated in terms of differences in silver dissolution and reprecipitation among the two groups. Further, running the experiments in nitrogen gas showed that sintering of all pastes was considerably hampered. The slow-down of the sinter kinetics was found to be in line with the assumed lower oxidation and dissolution of silver ions into the glass-forming liquid.