Filtern
Erscheinungsjahr
- 2017 (49) (entfernen)
Dokumenttyp
Schlagworte
Eingeladener Vortrag
- nein (5)
Structural relaxation phenomena in binary and multicomponent lithium silicate glasses were studied upon irradiation with femtosecond (fs) laser pulses (800 nm central wavelength, 130 fs pulse duration) and subsequent thermal annealing experiments. Depending on the annealing temperature, micro-Raman spectroscopy analyses evidenced different relaxation behaviours, associated to bridging and non-bridging oxygen structures present in the glass network. The results indicate that the mobility of lithium ions is an important factor during the glass modification with fs-laser pulses. Quantitative phase contrast imaging (spatial light interference microscopy) revealed that these fs-laser induced structural modifications are closely related to local changes in the refractive index of the material. The results establish a promising strategy for tailoring fs-laser sensitivity of glasses through structural mobility.
Variations in the isotope amount composition of some elements like lithium, boron, magnesium, calcium, copper and strontium have been used as proof of provenance of a sample and to describe geological processes. Routinely, isotope compositions are determinate by mass spectrometry; the working horse of the isotope analysis. However, mass spectrometric methods are expensive, time consuming and they require a high qualified analysist.
Here an alternative faster and low cost optical method for isotope ratio determination is proposed: high-resolution continuum source molecular absorption spectrometry (HR-CS-MAS). Stable isotope amount composition of X= Li, B, Mg, Ca, Cu and Sr have been determined by monitoring the absorption spectrum of their monohydride (XH) in graphite furnace HR-CS-MAS. For example, for the three Mg isotopes (24Mg, 25Mg and 26Mg) band (0→0) for the electronic transition X1Σ+ → A1Π was evaluated around wavelength 513.4 nm (Fig. 1). Partial least square regression (PLS) for analysis of samples and reference materials were applied. For this, a spectral library with different isotopes ratios for PLS regression were built. Results are metrological compatible with those reported by mass spectrometric methods.
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.
Monitoring chemical reactions is the key to chemical process control. Today, mainly optical online methods are applied, which require excessive calibration effort. NMR spectroscopy has a high potential for direct loop process control while exhibiting short set-up times. Compact NMR instruments make NMR spectroscopy accessible in industrial and harsh environments for advanced process Monitoring and control, as demonstrated within the European Union’s Horizon 2020 project CONSENS.
We present a range of approaches for the automated spectra analysis moving from conventional multivariate statistical approach, (i.e., Partial Least Squares Regression) to physically motivated spectral models (i.e., Indirect Hard Modelling and Quantum Mechanical calculations). By using the benefits of traditional qNMR experiments data analysis models can meet the demands of the PAT community (Process Analytical Technology) regarding low calibration effort/calibration free methods, fast adaptions for new reactants or derivatives and robust automation schemes.
The joint research project AERIUS (BMBF), is working to determine the effectiveness and efficiency of CAF in comparison to pure water, water with foaming agents and nozzle-aspirated foams in an extensive series of firefighting experiments. The poster deals with a series of extinguishing tests with mixed-material burning cribs.