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- 2012 (2) (entfernen)
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An intercomparison study of analytical methods for the determination of magnesium in low alloy steel
(2012)
In an intercomparison study three low alloy steel materials were analyzed on their content of the trace element Mg, and five different analytical techniques were used, namely spark-OES, inductively coupled plasma optical emission spectrometry (ICP-OES), inductively coupled plasma time of flight mass spectrometry (ICP-TOFMS), inductively coupled plasma quadrupole mass spectrometry (ICP-QMS), and glow discharge mass spectrometry (GD-MS). Solid steel discs were used for analysis with spark-OES and GD-MS. For the analyses with ICP-OES, ICP-TOFMS, and ICP-QMS steel chips were wet-digested in aqua regia, and the wet-digestion was performed either in polypropylene tubes placed in a heating block or in Teflon pressure vessels using a microwave assisted system. The Mg concentrations obtained for the three steel materials were: 2.0, 2.8, and 10.3 µg g-1, respectively, and the spread in results was acceptable, giving RSD values in the range of 2030%.
We have developed a very fast and entirely gas-phase based purification technique for carbon nanotubes (CNT) that allows removing metal and metal oxide impurities with high effectiveness. CNT agglomerates from chemical vapor deposition (CVD) synthesis which contained carbon encapsulated catalysts were injected into an atmospheric plasma torch. Very high heating rates allow for quasi-instantaneous vaporization of catalyst particles. This way, metal vapors are hyposized to break mechanically instable encapsulations and effuse from incomplete ones faster than thermally induced graphitization stabilizes such particle encapsulations. The ash content of multi-walled (MW) CNT samples was reduced to less than 15% of the initial value within a few milliseconds. Also the metal content of single-walled (SW) CNT agglomerates was significantly reduced. Repeated injection of CNT agglomerates into the plasma torch resulted in higher-purity products of improved structural integrity and increased oxidation resistance.