Ingenieurwissenschaften
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- Age hardening (1)
- Al‐Cu‐Li‐alloy (1)
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Eingeladener Vortrag
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Bacterial infections are a global threat to human health1. Especially nosocomial infections with multidrug-resistant Gram-negative bacteria challenge public health systems and endanger successful treatment of patients in many modern medicine applications as e.g. organ transplant. In the last three decades classical approaches failed to find novel chemical scaffolds suitable for the development of antibiotics that reach the market and caused the modern antibiotics crisis1.
Insect microbiomes produce potent antibiotics with low toxicity to eukaryotic cells to defend their hosts against entomopathogenic microorganisms2. In order to exploit insect microbiomes efficiently and to identify novel antibiotics producing bacteria, we implemented an ultra-high throughput Microfluidics/FACS (fluorescence-associated cell sorting) cultivation and screening pipeline. Here we present the technical aspects of our pipeline including downstream processing of identified producer strains and its suitability for antibiotics discovery.
Fundamental understanding of crack healing in glassy crystalline materials is very important for many applications, especially for sealing solid oxide fuel cells (SOFC) since cracks caused by sealing or thermal cycling still remain a substantial bottleneck in developing durable SOFC.
Previous studies on soda lime silicate glass [Sin14] showed that crack healing is driven by viscous flow and that healing progress is proportional to time t and inverse viscosity η. This finding would allow to present healing data of a given glass for different temperatures in a master curve healing progress versus t/η. Such master curves would be a helpful tool in understanding crack healing kinetics.
Against this background, crack healing in non-crystallizing sodium calcium silicate (NCS) and sodium borosilicate glasses (NBS) have been studied. Moreover, to evaluate the influence of micros structure in crystallized glass on crack healing process, glass matrix composites (GMC) where prepared out of NCS and zirconia as inert ceramic filler material mimicking a partially crystalline micro structure. Cracks were generated by Vickers indention and healed isothermally at different temperatures. Crack healing progress was monitored by optical and electron microscopy. Results show that the above mentioned proportionality actually applies for the studied glasses for which such a master curve could be obtained. In comparison to a non-crystallized glass, the effective viscosity of GMC is increased by rigid filler content. This effect substantially retards crack broadening during later healing stages, which often ends up in large pores. On the other hand, local viscous crack healing is still possible in larger glassy regions. This behavior seems to be very interesting for crack healing optimized sealants.
Experimental and phase field studies of age hardening response of a high purity Al‐4Cu‐1Li‐0.25Mn‐alloy (mass %) during isothermal aging are conducted. In the experiments, two hardening phases are identified: the tetragonal θ′ (Al₂Cu) phase and the hexagonal T1 (Al₂CuLi) phase. Both are plate shaped and of nm size. They are analyzed with respect to the development of their size, number density and volume fraction during aging by applying different analysis techniques in TEM in combination with quantitative microstructural analysis. 3D phase‐field simulations of formation and growth of θ′ phase are performed in which the full interfacial, chemical and elastic energy contributions are taken into account. 2D simulations of T1 phase are also investigated using multi‐component diffusion without elasticity. This is a first step toward a complex phase‐field study of T1 phase in the ternary alloy. The comparison between experimental and simulated data shows similar trends. The still unsaturated volume fraction indicates that the precipitates are in the growth stage and that the coarsening/ripening stage has not yet been reached.