Faserlaserbasierte Direktanalyse von Metall-Legierungen

At a time when resources are becoming increasingly scarce mobile chemical analysis gains in importance for recycling issues. Conventional procedures like spark discharge optical emission spectrometry or x-ray fluorescence are subject to limitations concerning sensitivity or sample preparation that can be overcome by laser-induced breakdown spectroscopy (LIBS). To realise a hand-held spectroscopy system laser source and measuring probe should both be connected via an optical fibre. A fibre laser is particularly suited for this purpose since, this way, the extensive and error-prone coupling of the laser light into a transport fibre is dropped. In this thesis a fibre laser based LIBS procedure is developed and evaluated. For this purpose, issues like ablation, single pulse behaviour or effects of the repetition rate on the results of the analysis are being investigated. A comparison of the analytical capabilities performed with commercial hand-held analysers for aluminium and steel shows that similar values can be achieved in much shorter measuring times of less than 10 s compared to 25-150 s. By improving the optical setup even measuring times of less than 1 s are possible. With the help of the LIBS method relative root mean square errors of 5.6% (Cr) to 13.7% (Ni) for high alloyed steel and 7.6% (Si) to 21.7% (Zn) for aluminium can be achieved. Finally, based on the elaborated method a demonstrator is set up and evaluated in field tests at the sites of recycling companies