TY - JOUR A1 - Mielke, Johannes A1 - Rades, Steffi A1 - Ortel, Erik A1 - Salge, T. A1 - Hodoroaba, Vasile-Dan T1 - Improved spatial resolution of EDX/SEM for the elemental analysis of nanoparticles N2 - The interest in nanoparticles remains at a high level in fundamental research since many years and increasingly, nanoparticles are incorporated into consumer products to enhance their performance. Consequently, the accurate and rapid characterization of nanoparticles is more and more demanded. Electron microscopy (SEM, TSEM and TEM) is one of the few techniques which are able to image individual nanoparticles. It was demonstrated recently that the transmission electron microscopy at a SEM can successfully be applied as a standard method to characterize accurately the size (distribution) and shape of nanoparticles down to less than 10 nm. PY - 2015 U6 - https://doi.org/10.1017/S1431927615009344 SN - 1431-9276 SN - 1435-8115 VL - 21 IS - Suppl. 3 SP - Paper 0855, 1713 EP - 1714 PB - Cambridge University Press CY - New York, NY AN - OPUS4-34923 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ortel, Erik A1 - Kraehnert, R. A1 - Galbert, F. A1 - Hodoroaba, Vasile-Dan T1 - Thin film porosity determined by X-rays at SEM N2 - Various applications such as automotive catalysts, photocatalysis and sensors rely on thin coatings with high active surface area. The development of new and improved coatings requires in-depth understanding of the film morphology and texture. Especially the film porosity is a key parameter to identify structure-property relationships in applications. However, an accurate porosity determination of thin porous coatings is a challenging. In this contribution we present and discuss a new approach for determining the porosity of films by x-rays at SEM. KW - Thin film KW - Porosity KW - EDX KW - SEM KW - Stratagem KW - WDX PY - 2015 U6 - https://doi.org/10.1017/S1431927615009319 SN - 1431-9276 SN - 1435-8115 VL - 21 IS - Suppl. 3 SP - Paper 0852, 1707 EP - 1708 PB - Cambridge University Press CY - New York, NY AN - OPUS4-34162 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hodoroaba, Vasile-Dan A1 - Rades, Steffi A1 - Salge, T. A1 - Mielke, Johannes A1 - Ortel, Erik A1 - Schmidt, R. T1 - Characterisation of nanoparticles by means of high-resolution SEM/EDS N2 - Advances in scanning electron microscopy (SEM) enable the high-resolution imaging of single nanoparticles (NPs) with sizes well below 10 nm. The SEM analysis in transmission mode (T-SEM) of NPs on thin film supports has many benefits when compared to the analysis of NPs on bulk substrates. The enhanced material (mass - thickness) contrast of the T-SEM imaging mode is well suited for in-depth and, particularly valuable, to very accurate, traceable, lateral dimensional measurements of NPs. Compared to samples prepared on bulk substrates, T-SEM with energy dispersive X-ray spectroscopy (EDS) achieves a drastically improved spatial resolution of the emitted X-rays. The poor signal-to-noise ratio of the X-ray spectra emitted by a single nanoparticle (NP) can be improved by the use of high-sensitivity (high collection solid angle) silicon drift (SDD), energy-dispersive X-ray spectrometers (EDS). The EDS spectral imaging of a single NP with a spatial resolution below 10 nm has become possible. This is demonstrated by means of various examples of nanostructures. Advanced data processing of T-SEM/EDS results sets the stage for the automated classification of NPs by feature analysis. This method combines the detection of morphological structures of interest by image processing of T-SEM micrographs with the chemical classification by EDS. T2 - EMAS 2015 - 14th European workshop on modern developments and applications in microbeam analysis CY - Portoroz, Slovenia DA - 03.05.2015 KW - SEM KW - T-SEM KW - EDX KW - Nanoparticles KW - High-resolution PY - 2015 SN - 978-90-8227-691-6 U6 - https://doi.org/10.1088/1757-899X/109/1/012006 SP - NUR code:972 - Materials Science, 187-199 AN - OPUS4-33258 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ortel, Erik A1 - Polte, J. A1 - Bernsmeier, D. A1 - Eckhardt, B. A1 - Paul, B. A1 - Bergmann, A. A1 - Strasser, P. A1 - Emmerling, Franziska A1 - Kraehnert, R. T1 - Pd/TiO2 coatings with template-controlled mesopore structure as highly active hydrogenation catalyst N2 - Micro-structured reactors offer excellent mass and heat transport capabilities and can therefore sustain very high reaction rates and space–time-yields also for highly exothermic catalytic reactions. However, such high rates cannot be reached when the reactors are coated or filled with conventional catalysts powders. We present a strategy for the direct synthesis of highly active wall-coated supported catalysts via co-deposition of a pore template (here micelles formed from PEO-b-PPO-b-PEO) and a precursors for the metal oxide (TiCl4) along with a compatible precursor for the active metal (PdCl2). The obtained catalytic coatings possess a template-controlled open pore structure and excellent mechanical stability. Moreover, the active metal is highly dispersed and well-distributed across the coating also at high Pd loadings. The corresponding high activity along with rapid mass transfer enabled by the open pore system results in the best space–time-yields in the gas-phase hydrogenation of butadiene reported so far in literature for a supported catalyst. KW - Titanium oxide films KW - Palladium nanoparticle KW - Wall-coated supported catalysts KW - Template-controlled mesoporous materials KW - Hydrogenation of 1,3-butadiene PY - 2015 U6 - https://doi.org/10.1016/j.apcata.2014.12.044 SN - 0926-860X SN - 1873-3875 VL - 493 SP - 25 EP - 32 PB - Elsevier CY - Amsterdam AN - OPUS4-32465 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bernicke, M. A1 - Ortel, Erik A1 - Reier, T. A1 - Bergmann, A. A1 - De Araujo, J.F. A1 - Strasser, P. A1 - Kraehnert, R. T1 - Iridium oxide coatings with templated porosity as highly active oxygen evolution catalysts: Structure-activity relationships N2 - Iridium oxide is the catalytic material with the highest stability in the oxygen evolution reaction (OER) performed under acidic conditions. However, its high cost and limited availability demand that IrO2 is utilized as efficiently as possible. We report the synthesis and OER performance of highly active mesoporous IrO2 catalysts with optimized surface area, intrinsic activity, and pore accessibility. Catalytic layers with controlled pore size were obtained by soft-templating with micelles formed from amphiphilic block copolymers poly(ethylene oxide)-b-poly(butadiene)-b-poly(ethylene oxide). A systematic study on the influence of the calcination temperature and film thickness on the morphology, phase composition, accessible surface area, and OER activity reveals that the catalytic performance is controlled by at least two independent factors, that is, accessible surface area and intrinsic activity per accessible site. Catalysts with lower crystallinity show higher intrinsic activity. The catalyst surface area increases linearly with film thickness. As a result of the templated mesopores, the pore surface remains fully active and accessible even for thick IrO2 films. Even the most active multilayer catalyst does not show signs of transport limitations at current densities as high as 75 mA cm-2. KW - Electrochemistry KW - Iridium KW - Structure–activity relationships KW - Template synthesis KW - Water splitting PY - 2015 U6 - https://doi.org/10.1002/cssc.201402988 SN - 1864-5631 SN - 1864-564X VL - 8 IS - 11 SP - 1908 EP - 1915 PB - Wiley-VCH CY - Weinheim AN - OPUS4-33503 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kraehnert, R. A1 - Ortel, Erik A1 - Paul, B. A1 - Eckhardt, B. A1 - Kanis, M. A1 - Liu, R. A1 - Antoniou, A. T1 - Electrochemically dealloyed platinum with hierarchical pore structure as highly active catalytic coating N2 - Micro structured reactors are attractive candidates for further process intensification in heterogeneous catalysis. However, they require catalytic coatings with significantly improved space-time yields compared to traditional supported catalysts. We report the facile synthesis of homogeneous nanocrystalline Pt coatings with hierarchical pore structure by electrochemical dealloying of amorphous sputter-deposited platinum silicide layers. Thickness, porosity and surface composition of the catalysts can be controlled by the dealloying procedure. XPS analysis indicates that the catalyst surface is primarily composed of metallic Pt. Catalytic tests in gas-phase hydrogenation of butadiene reveal the typical activity, selectivity and activation energy of nanocrystalline platinum. However, space time yields are about 13 to 200 times higher than values reported for Pt-based catalysts in literature. The highly open metallic pore structure prevents heat and mass transport limitations allowing for very fast reactions and reasonable stability at elevated temperatures. KW - Pt catalysts KW - Pt–Si layers KW - Scanning Electron Microscopy (SEM) KW - Transmission Electron Microscopy (TEM) KW - pore structure KW - electrochemical dealloying PY - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-351393 SN - 2044-4753 SN - 2044-4761 VL - 5 IS - 1 SP - 206 EP - 216 PB - RSC Publ. CY - Cambridge AN - OPUS4-35139 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -