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Secondary fluorescence is an inevitable effect that has to be taken into account in any algorithm for quantitative electron probe microanalysis (EPMA) as an additional correction. Moreover, secondary fluorescence worsens spatial resolution of EPMA. Secondary fluorescence is excited both by characteristic radiation and by the X-ray continuum. In most cases the correction is small. There are, however, cases, e.g. the determination of low heavy metal concentration in a light matrix, where the contribution of secondary fluorescence exceeds 10% of the measured X-ray line intensity.
For secondary fluorescence correction the measured X-ray line intensity has to be divided by the correction factor (1+I_flchar/I_p +I_flcont/I_p )≈(1+I_flchar/I_p )(1+I_flcont/I_p ) in order to get those intensity I_p, which is excited only by the primary electrons. I_flchar and I_flcont mean the calculated characteristic and continuums fluorescence intensities. In order to get the intensity of fluorescence radiation, the absorption of the exciting radiation in the specimen, the photoionization probability and the self-absorption of the emitted line must be calculated. The critical quantity is the X-ray yield of the exciting atoms in case of fluorescence by characteristic radiation and the bremsstrahlung yield of the specimen in case of continuum fluorescence. In the former case it is reasonable to apply the same physical model to calculate I_flchar and I_p.
A microfocus X-ray source mounted on the analysis chamber of an SEM was used to excite X-ray fluorescence spectra and to detect chemical elements with concentrations below the detection limit of the electron-excited X-ray spectra conventionally measured with SEM/EDS. An aluminium alloy and a hard material ceramics were analysed as representative examples. It is demonstrated that the combination of the three analytical methods: (1) SEM imaging for surface morphology characterisation; (2) electron-excited X-ray spectroscopy with its high spatial resolution for element analysis of inclusions or precipitates; and (3) X-ray fluorescence for the detection of elements with concentrations below 0.1 mass% considerably improves the performance of SEM/EDX analyses.
The results of an interlaboratory comparison of energy dispersive X-ray microanalysis of TiN0.84 and ZrN were presented. The microprobe group of the German Physical Society (DPG) and the Federal Institute for Materials Research and Testing (BAM) had initiated the interlaboratory comparison. The primary aim was to test modern EDX systems equipped with ultrathin windows concerning the accuracy and reliability of the analysis of compounds containing light elements. The participants from 23 laboratories performed the analysis at different primary energies, in the standard-less mode as well as on the base of own standards, and considering Ti-K or Ti-L in case of TiN0.84. The results show a slight overestimation of the nitrogen content and a large standard deviation from the mean value. Reasons for the scattering of the results are discussed.
The paper 'The constituents of the ink from a Qumran inkwell: New prospects for provenancing the ink on the Dead Sea Scrolls' by Rasmussen et al. (2012) presents an account of the analysis of a residue from an unprovenanced inkwell. In this comment, I reassess their study and offer alternative interpretations of their experimental results.
Single-pass solid-state laser welding of plates in the thickness range of 10 to 20 mm became possible with the invention of the fibre laser. This new technique provides excellent beam quality at powers as high as 20 kW or more, and has proved applicable in several industrial applications. By replacing conventional methods with the fibre laser, it is possible to avoid multiple-pass welding that requires time-consuming bevelling. The high energy density of the fibre laser beam also reduces the heat input and consequently the distortion. However, the rapid solidification and cooling associated with laser welding can cause imbalance of the microstructure of duplex stainless steel weldments, where excessively high ferrite contents may reduce the corrosion resistance and the ductility of the material. The solution is normally to add nickel-based filler wire and to increase the heat input. By using a hybrid welding process where the laser beam and the gas metal arc (GMA) process act in a common process zone, filler metal can be added to the molten pool at higher heat input and at the same time, higher welding speed and deeper penetration can be achieved. In this work, 13.5 mm thick 2205 (EN 1.4462, UNS S31803) was fibre laser-GMA hybrid welded in a single-pass using 14 kW of laser power and ISO 22 9 3 N L as filler wire for the GMA process. The resulting welds were free from defects, with smooth surfaces and full penetration. The investigation examines the weld metal microstructure and the effect on corrosion resistance and mechanical properties. The option to add nickel foil, when hybrid welding, was also investigated, as comparison, and the effect on austenite formation was evaluated.
To test whether the silicate reference glasses BAM-S005-A and BAM-S005-B from BAM (The Federal Institute for Materials Research and Testing, Germany) are suitable materials for microanalysis, we investigated the homogeneity of these reference glasses using the microanalytical techniques EPMA, LA-ICP-MS and SIMS. Our study indicated that all major and most trace elements are homogeneously distributed at micrometre sampling scale in both types of glass. However, some trace elements (e.g., Cs, Cl, Cr, Mo and Ni) seem to be inhomogeneously distributed. We also determined the composition of BAM-S005-A and BAM-S005-B. The EPMA data of major elements confirmed the information values specified by the certificate. With the exception of Sr, Ba, Ce and Pb, our trace element data by LA-ICP-MS were also in agreement with the certified values within the stated uncertainty limits. The reasons for the discrepancy in these four elements are still unclear. In addition, we report new data for twenty-two further trace elements, for which the concentrations were not certified. Based on our investigation, we suggest that both of these materials are suitable for many microanalytical applications.