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 DO - 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 - Eckhardt, B. A1 - Ortel, Erik A1 - Bernsmeier, D. A1 - Polte, J. A1 - Strasser, P. A1 - Vainio, U. A1 - Emmerling, Franziska A1 - Kraehnert, R. T1 - Micelle-templated oxides and carbonates of zinc, cobalt, and aluminium and a generalized strategy for their synthesis N2 - Catalysis, energy storage, and light harvesting require functional materials with tailored porosity and nanostructure. However, common synthesis methods that employ polymer micelles as structure-directing agents fail for zinc oxide, for cobalt oxide, and for metal carbonates in general. We report the synthesis of the oxides and carbonates of zinc, cobalt, and aluminum with micelle-templated structure. The synthesis relies on poly(ethylene oxide)-block-poly(butadiene)-block-poly(ethylene oxide) triblock copolymers and a new type of precursor formed by chemical complexation of a metal nitrate with citric acid. A general synthesis mechanism is deduced. Mechanistic insights allow for the prediction of optimal processing conditions for different oxides and carbonates based on simple thermogravimetric analysis. Employing this synthesis, films of ZnO and Co3O4 with micelle-controlled mesoporosity become accessible for the first time. It is the only soft-templating method reported so far that also yields mesoporous metal carbonates. The developed synthesis is generic in nature and can be applied to many other metal oxides and carbonates. KW - EISA KW - Pore templating KW - Metal oxide KW - Metal carbonate KW - Zinc oxide KW - Cobalt oxide PY - 2013 DO - https://doi.org/10.1021/cm400535d SN - 0897-4756 SN - 1520-5002 VL - 25 IS - 14 SP - 2749 EP - 2758 PB - American Chemical Society CY - Washington, DC AN - OPUS4-29113 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Polte, J. A1 - Polte, M. A1 - Lorenz, D. A1 - Oberschmidt, D. A1 - Sturm, Heinz A1 - Uhlmann, E. T1 - Binderless-cBN as cutting material for ultra-precision machining of stainless steel N2 - The ultra–precision cutting of steel materials is possible but needs modifications of machine tools or the workpiece material. One approach of actual research is the development of cutting materials that gives the opportunity for direct cutting of surfaces with ultra–precision quality. Binderless–cBN is here one of the most promising materials. The paper shows results of experimental studies with binderless–cBN as cutting material while turning stainless steel. Various investigations were carried out to determine the wear mechanisms. Furthermore, measurements are shown regarding the surface quality. The achieved results show the high potential ofbinderless–cBN as cutting material for the machining of steel. KW - Cubic boron nitride KW - Stainless steel KW - Ultra-precision PY - 2014 DO - https://doi.org/10.4028/www.scientific.net/AMR.1018.107 SN - 1022-6680 SN - 1662-8985 VL - 1018 SP - 107 EP - 114 PB - Trans Tech Publ. CY - Zurich AN - OPUS4-32377 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wuithschick, M. A1 - Paul, B. A1 - Bienert, Ralf A1 - Sarfraz, A. A1 - Vainio, U. A1 - Sztucki, M. A1 - Kraehnert, R. A1 - Strasser, P. A1 - Rademann, K. A1 - Emmerling, Franziska A1 - Polte, J. T1 - Size-controlled synthesis of colloidal silver nanoparticles based on mechanistic understanding N2 - Metal nanoparticles have attracted much attention due to their unique properties. Size control provides an effective key to an accurate adjustment of colloidal properties. The common approach to size control is testing different sets of parameters via trial and error. The actual particle growth mechanisms, and in particular the influences of synthesis parameters on the growth process, remain a black box. As a result, precise size control is rarely achieved for most metal nanoparticles. This contribution presents an approach to size control that is based on mechanistic knowledge. It is exemplified for a common silver nanoparticle synthesis, namely, the reduction of AgClO4 with NaBH4. Conducting this approach allowed a well-directed modification of this synthesis that enables, for the first time, the size-controlled production of silver nanoparticles 4–8 nm in radius without addition of any stabilization agent. KW - Silver nanoparticles KW - Growth mechanism KW - SAXS KW - Size control KW - Sodium borohydride PY - 2013 DO - https://doi.org/10.1021/cm401851g SN - 0897-4756 SN - 1520-5002 VL - 25 IS - 23 SP - 4679 EP - 4689 PB - American Chemical Society CY - Washington, DC AN - OPUS4-30194 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bernsmeier, D. A1 - Bernicke, M. A1 - Ortel, Erik A1 - Bergmann, A. A1 - Lippitz, Andreas A1 - Nissen, J. A1 - Schmack, R. A1 - Strasser, P. A1 - Polte, J. A1 - Kraehnert, R. T1 - Nafion-free carbon-supported electrocatalysts with superior hydrogen evolution reaction performance by soft templating N2 - Efficient water electrolysis requires electrode coatings with high catalytic activity. Platinum efficiently catalyzes the hydrogen evolution reaction in acidic environments, but is a rare and expensive metal. The activity achieved per metal atom can be increased if small Pt particles are dispersed onto electrically conductive, highly accessible and stable support materials. However, the addition of Nafion, a typical binder material used in the manufacture of electrode coatings, can decrease catalytic activity by the blocking of pores and active surface sites. A new approach is reported for the direct synthesis of highly active Nafion-free Pt/C catalyst films consisting of small Pt nanoparticles supported in size-controlled mesopores of a conductive carbon film. The synthesis relies on the co-deposition of suitable Pt and C precursors in the presence of polymer micelles, which act as pore templates. Subsequent carbonization in an inert atmosphere produces porous catalyst films with controlled film thickness, pore size and particle size. The catalysts clearly outperform all Nafion-based Pt/C catalysts reported in the literature, particularly at high current densities. KW - XPS KW - SEM KW - TEM KW - SAXS KW - Catalysis KW - Electrochemistry PY - 2017 DO - https://doi.org/10.1002/celc.201600444 SN - 2196-0216 VL - 4 IS - 1 SP - 221 EP - 229 PB - Wiley Online Library CY - Weinheim AN - OPUS4-39733 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Scheuschner, Nils A1 - Heinrichsdorff, F. A1 - Oster, Simon A1 - Uhlmann, E. A1 - Polte, J. A1 - Gordei, A. A1 - Hilgenberg, Kai T1 - In-situ monitoring of the laser powder bed fusion process by thermography, optical tomography and melt pool monitoring for defect detection N2 - For the wide acceptance of the use of additive manufacturing (AM), it is required to provide reliable testing methods to ensure the safety of the additively manufactured parts. A possible solution could be the deployment of in-situ monitoring during the build process. However, for laser powder bed fusion using metal powders (PBF-LB/M) only a few in-situ monitoring techniques are commercially available (optical tomography, melt pool monitoring), which have not been researched to an extent that allows to guarantee the adherence to strict quality and safety standards. In this contribution, we present results of a study of PBF-LB/M printed parts made of the nickel-based superalloy Haynes 282. The formation of defects was provoked by local variations of the process parameters and monitored by thermography, optical tomography and melt pool monitoring. Afterwards, the defects were characterized by computed tomography (CT) to identify the detection limits of the used in-situ techniques. T2 - Lasers in Manufacturing Conference 2023 CY - Munich, Germany DA - 26.06.2023 KW - Thermography KW - Optical tomography KW - Melt-pool-monitoring KW - Laser powder bed fusion KW - Haynes 282 KW - Additive Manufacturing PY - 2023 UR - https://www.wlt.de/lim2023-proceedings/system-engineering-and-process-control SP - 1 EP - 10 AN - OPUS4-58466 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -