TY - JOUR A1 - Rackwitz, Vanessa A1 - Panne, Ulrich A1 - Hodoroaba, Vasile-Dan T1 - Calculation of X-ray tube spectra by means of photon generation yields and a modified Kramers background for side-window X-ray tubes N2 - Popular X-ray tube models available in the literature, i.e. 'Pella', 'Ebel', and 'Finkelshtein and Pavlova', are systematically evaluated with the focus on the estimation of the associated uncertainties. Also taken in consideration and compared is our recent semi-empirical own approach already employed in our lab. This has been working for the common target elements rhodium, molybdenum and tungsten and was further extended in the present work for the target elements copper, chromium and vanadium. By using a modern scanning electron microscope/energy dispersive spectroscopy (SEM/EDS) system this time, higher performances such as stability of the beam current and especially the better energy resolution of the EDS have enabled the reliable extension of our own X-ray tube spectrum approach into the low-energy range, due to increasing interest. Hence, also the more challenging X-ray lines of copper, chromium and vanadium L-series lying in the energy range below 1–2?keV are included into the model. Such low-energy L-lines or, e.g. M-lines of tungsten, are not treated explicitly by the other existing popular algorithms for the nowadays widely used geometries of side-window tubes, offering a unique virtue to our present, modern approach. With our own model, a measurement uncertainty of the X-ray tube spectra (considering the uncertainties associated with the SEM beam current, the detector acceptance solid angle and efficiency of the spectrometer) within 15% has been estimated. The validation of the approach is demonstrated with metrological measurements with a calibrated SEM/EDS system geometrically configured as a side-window X-ray tube. KW - X-ray tube spectra KW - Side-window X-ray tube KW - Reference-free XRF KW - Photon generation yield KW - Kramers background KW - Calibrated SEM/EDS PY - 2012 U6 - https://doi.org/10.1002/xrs.2391 SN - 0049-8246 VL - 41 IS - 4 SP - 264 EP - 272 PB - Wiley CY - Chichester AN - OPUS4-26239 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rackwitz, Vanessa A1 - Ostermann, Markus A1 - Panne, Ulrich A1 - Hodoroaba, Vasile-Dan T1 - Performance of mu-XRF with SEM/EDS for trace analysis on the example of RoHS relevant elements - measurement, optimisation and predivtion of the detection limits N2 - For ten years µ-XRF (micro-focus X-ray fluorescence) analysis has been performed with SEM/EDS (scanning electron microscope with an energy dispersive X-ray detector) so that non-destructive analysis of elements at trace level concentrations below 100 µg g-1 becomes possible. This can be considered as a valuable completion of the classical electron probe microanalysis by EDS, an analytical method 'suffering' from rather poor limits of detection in the range of one to two orders of magnitude higher than those of µ-XRF. Based on a representative actual application, namely analysis of RoHS relevant elements at trace concentration levels, the performance of the rather new analytical method with respect to its limits of detection is systematically evaluated. CRMs (certified reference materials) specially prepared to support the quantitative XRF analysis of RoHS relevant elements were employed. On the other side, based on calculations of µ-XRF spectra according to a recently developed physical model the optimization of the analytical performance is also successfully undertaken. KW - RoHS KW - XRF KW - muXRF KW - SEM/EDS KW - Detection limits KW - Trace elements KW - Modelling PY - 2013 U6 - https://doi.org/10.1039/c3ja50064k SN - 0267-9477 SN - 1364-5544 VL - 28 IS - 9 SP - 1466 EP - 1474 PB - Royal Society of Chemistry CY - London AN - OPUS4-29045 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rackwitz, Vanessa A1 - Warrikhoff, A. A1 - Panne, Ulrich A1 - Hodoroaba, Vasile-Dan T1 - Determination of the efficiency of an energy dispersive X-ray spectrometer up to 50 keV with a SEM N2 - Both electron and polychromatic photon excitations (micro-focus X-ray source) at a scanning electron microscope (SEM) are used to determine the efficiency of an energy dispersive X-ray spectrometer up to 50 keV by means of a calibrated X-ray spectrometer and reference materials (RM) specially selected for this purpose. KW - Detector efficiency KW - Calibration KW - XRF KW - EDS KW - SEM KW - EDS-TM001 KW - Scattering PY - 2009 U6 - https://doi.org/10.1039/b907815k SN - 0267-9477 SN - 1364-5544 VL - 24 SP - 1034 EP - 1036 PB - Royal Society of Chemistry CY - London AN - OPUS4-19714 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rackwitz, Vanessa A1 - Procop, M. A1 - Bjeoumikhova, S. A1 - Panne, Ulrich A1 - Hodoroaba, Vasile-Dan T1 - A routine procedure for the characterisation of polycapillary X-ray semi-lenses in prallelising mode with SEM/EDS N2 - The accurate knowledge of the properties of polycapillary X-ray semi-lenses has a significant influence on the quantitative results in a widespread field of applications involving microfocus X-ray beams. A routine procedure for the characterisation of a polycapillary X-ray semi-lens with a scanning electron microscope (SEM) having attached an energy dispersive spectrometer (EDS) is presented in this paper. A key issue of the procedure consists of fitting the semi-lens in front of the EDS for spectra acquisition. Relevant semi-lens parameters such as focal distance, full width at half maximum (FWHM) of the acceptance area, and transmission are determined in parallelising mode of the semi-lens. Special attention has been paid to the calculation of the transmission. KW - Polycapillary X-ray optics KW - Semi-lens KW - Parallelising mode KW - SEM KW - EDS KW - Acceptance area KW - FWHM KW - Transmission KW - Focal distance KW - XRF PY - 2011 U6 - https://doi.org/10.1039/c0ja00135j SN - 0267-9477 SN - 1364-5544 VL - 26 IS - 3 SP - 499 EP - 504 PB - Royal Society of Chemistry CY - London AN - OPUS4-23555 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nadejde, C. A1 - Neamtu, M. A1 - Hodoroaba, Vasile-Dan A1 - Schneider, Rudolf A1 - Ababei, G. A1 - Panne, Ulrich T1 - Hybrid iron-based core-shell magnetic catalysts for fast degradation of bisphenol A in aqueous systems N2 - Three types of hybrid modified magnetite (Fe₃O₄) nanoparticles, functionalized with either chitosan, chitosan/iron (II) oxalate or chitosan/iron (III) citrate, were synthesized by chemical precipitation method. The obtained nanomaterials were characterized by energy dispersive X-ray spectroscopy, X-ray diffraction, Brunauer–Emmett–Teller analysis, scanning and Transmission electron microscopy, Fourier transform infrared spectroscopy and vibrating sample magnetometry. The prepared composites were further tested as magnetic catalysts for the removal of bisphenol A (BPA) in aqueous media. The kinetic Degradation experiments were performed at laboratory scale, while the best operational parameters for all three materials were established: 1.00 g L⁻¹ of catalyst, 10 mmol L⁻¹ H₂O₂, under simulated solar light irradiation. After 15 min of UVA irradiation under the experimental conditions mentioned above, it was possible to decompose up to 99% of the micropollutant over all catalysts. Fe₃O₄/chitosan/iron oxalate catalyst showed the highest and fastest catalytic activity in BPA removal. Catalytic wet peroxide oxidation of non-biodegradable micropollutants on such iron-based hybrid nanoparticles can be a suitable pre-treatment method for wastewater decontamination, as an environment-friendly simplified Approach for water clean-up. KW - Katalysator KW - Bisphenol A KW - Nano KW - Fenton KW - Magnetische Nanopartikel PY - 2016 U6 - https://doi.org/10.1016/j.cej.2016.05.090 SN - 1385-8947 VL - 302 SP - 587 EP - 594 PB - Elsevier CY - Amsterdam AN - OPUS4-37126 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gusarova, Tamara A1 - Hodoroaba, Vasile-Dan A1 - Matschat, Ralf A1 - Kipphardt, Heinrich A1 - Panne, Ulrich T1 - Exploitation of the hollow cathode effect for sensitivity enhancement of Grimm-type DC glow discharge optical emission spectroscopy N2 - The hollow cathode (HC) effect was investigated in non-cooled 15 mm deep drilled flat metallic analytical samples that were easy to prepare. The deep cavity used ("complete HC" in contrast to "recessed HC" with 2-3 mm deep cavity) intensified the HC effect notably and therefore distinctly improved the detection power of the common GD-OES with planar cathodes. A signal enhancement of up to a factor of 150, not reported earlier, in comparison with flat conventional samples was achieved. A better separation of the analytical lines from spectral interferences was observed when the HC assembly was applied. Additionally, an effect of strongly enhanced intensities of atomic lines and somewhat decreased intensities of ionic lines was detected in the case of HC in comparison to usual planar cathodes. The investigations were carried out with samples of copper, steel and zinc matrices using both the same and individually optimised glow discharge (GD) electrical parameters. KW - Hollow cathode KW - Grimm type glow discharge KW - Emission spectroscopy KW - GD-OES KW - Sensitivity PY - 2009 U6 - https://doi.org/10.1039/b814977a SN - 0267-9477 SN - 1364-5544 VL - 24 SP - 680 EP - 684 PB - Royal Society of Chemistry CY - London AN - OPUS4-19600 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rackwitz, Vanessa A1 - Warrikhoff, A. A1 - Panne, Ulrich A1 - Hodoroaba, Vasile-Dan T1 - Determination of emitted X-ray tube spectra by means of a calibrated instrumental setup KW - X-ray tube spectrum KW - XRF KW - SEM KW - EDS KW - Spectrometer efficiency PY - 2010 U6 - https://doi.org/10.1017/S1431927610054292 SN - 1431-9276 SN - 1435-8115 VL - 16 IS - Supplement S2 SP - 930 EP - 931 PB - Cambridge University Press CY - New York, NY AN - OPUS4-22471 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nadejde, C. A1 - Neamtu, M. A1 - Hodoroaba, Vasile-Dan A1 - Schneider, Rudolf A1 - Paul, Andrea A1 - Ababei, G. A1 - Panne, Ulrich T1 - Green Fenton-like magnetic nanocatalysts: Synthesis, characterization and catalytic application N2 - Five iron oxalate core–shell magnetite nanoparticles catalysts are evaluated as magnetic heterogeneous materials. Simple and efficient procedures for the preparation of magnetic iron oxalate coated nanoparticles are presented. The catalysts are fully characterized using various investigation techniques. Additionally, the formation of photo-sensitized oxygen by spin-trapping using electron spin resonance is investigated. The catalytic activity of two model substrates (carbamazepine and bisphenol A) is also evaluated. The effect of operational parameters (catalyst and H2O2 concentration, UVA light) on the degradation performance of the oxidation process is investigated. The obtained reaction rates depend on the nature of the compound and increase with iron oxide shell thickness of the catalyst. Moreover, these materials show a significant activity during two consecutive tests. The optimum experimental parameters are found to be 1.0 g L-1 of catalysts, 10 mM H2O2, under UVA irradiation. More than 99% of both substrates are removed after 30 min of reaction time under the experimental conditions given above. The results obtained show that the catalysts are suitable candidates for the removal of pollutants in wastewaters by means of the Fenton heterogeneous reaction. KW - Magnetic core–shell nanocatalysts KW - Characterization KW - Fenton oxidation KW - Micropollutants KW - Water treatment PY - 2015 U6 - https://doi.org/10.1016/j.apcatb.2015.04.050 SN - 0926-3373 SN - 1873-3883 VL - 176-177 SP - 667 EP - 677 PB - Elsevier CY - Amsterdam AN - OPUS4-33820 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nadejde, C. A1 - Neamtu, M. A1 - Hodoroaba, Vasile-Dan A1 - Schneider, Rudolf A1 - Paul, Andrea A1 - Ababei, G. A1 - Panne, Ulrich T1 - Tannic acid- and natural organic matter-coated magnetite as green Fenton-like catalysts for the removal of water pollutants N2 - The use of magnetic materials as heterogeneous catalysts has attracted increasing attention in the last years since they proved to be promising candidates for water treatment. In the present study, two types of surface-modified magnetite (Fe3O4) nanoparticles, coated with non-hazardous naturally occurring agents—either tannic acid (TA) or dissolved natural organic matter—were evaluated as magnetic heterogeneous catalysts. Chemical synthesis (co-precipitation) was chosen to yield the nanocatalysts due to its well-established simplicity and efficiency. Subsequently, the properties of the final products were fully assessed by various characterization techniques. The catalytic activity in heterogeneous oxidation of aqueous solutions containing a model pollutant, Bisphenol A (BPA), was comparatively studied. The effect of operational parameters (catalyst loading, H2O2 dosage, and UV light irradiation) on the Degradation performance of the oxidation process was investigated. The optimum experimental parameters were found to be 1.0 g/L of catalysts and 10 mM H2O2, under UV irradiation. The highest mineralization rates were observed for Fe3O4-TA catalyst. More than 80 % of BPA was removed after 30 min of reaction time under the specified experimental conditions. The obtained results showed that the two catalysts studied here are suitable candidates for the removal of pollutants in wastewaters by means of heterogeneous reaction using a green sustainable treatment method. KW - Nanocatalysts KW - Photo-Fenton oxidation KW - Wastewater KW - Bisphenol A degradation KW - Environment KW - Mitigation PY - 2015 UR - http://link.springer.com/article/10.1007/s11051-015-3290-0 U6 - https://doi.org/10.1007/s11051-015-3290-0 VL - 17 IS - 12 SP - 476 (1) EP - 476 (10) PB - Springer AN - OPUS4-38758 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nadejde, C. A1 - Neamtu, M. A1 - Schneider, Rudolf A1 - Hodoroaba, Vasile-Dan A1 - Ababei, G. A1 - Panne, Ulrich T1 - Catalytical degradation of relevant pollutants from waters using magnetic nanocatalysts N2 - The catalytic efficiency of two magnetically responsive nanocatalysts was evaluated for the Degradation of Reactive Black 5 (RB5) and Reactive Yellow 84 (RY84) azo dyes using hydrogen peroxide as oxidant undervery mild conditions (atmospheric pressure, room temperature). In order to obtain the nanocatalysts, thesurface of magnetite (Fe3O4) nanoparticles, prepared by a co-precipitation method, was further modified with ferrous oxalate, a highly sensitive non-hazardous reducing agent. The sensitized nanomaterials were characterized by X-ray diffraction, scanning and transmission electron microscopy, energy-dispersive X-ray spectroscopy and vibrating sample magnetometry, and used in the catalytic wet hydrogen peroxideoxidation (CWHPO) of RB5 and RY84, in laboratory-scale experiments. The effect of important variables such as catalyst dosage, H2O2 concentration, and contact time was studied in the dye Degradation kinetics. The results showed that it was possible to remove up to 99.7% dye in the presence of 20 mM H2O2 after 240 min of oxidation for a catalyst concentration of 10 g L−1at 25◦C and initial pH value of 9.0.CWHPO of reactive dyes using sensitized magnetic nanocatalysts can be a suitable pre-treatment methodfor complete decolorization of effluents from textile dyeing and finishing processes, once the Optimum operating conditions are established. T2 - 10th International Conference On Physics Of Advanced Materials (ICPAM-10) CY - Iasi, Romania DA - 22.09.2014 KW - Sensitized magnetic nanocatalysts KW - Catalytic wet peroxide oxidation KW - Reactive azo dye degradation PY - 2015 UR - http://www.sciencedirect.com/science/article/pii/S0169433215000483 U6 - https://doi.org/10.1016/j.apsusc.2015.01.036 SN - 0169-4332 VL - 352 SP - 42 EP - 48 PB - Elsevier B.V. AN - OPUS4-38760 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -