TY - CHAP A1 - Mann, Michael A1 - Döhring, Thorsten A1 - Stollenwerk, Manfred A1 - Wenzler, Sebastian A1 - Pribulla, Theodor A1 - Komžík, Richard M. A1 - Sivanic, Peter ED - Benn, Chris R. ED - Seaman, Robert L. ED - Adler, David S. T1 - On the importance of the electrical grid power quality for astronomical observatories T2 - Proceedings of SPIE: Observatory Operations: Strategies, Processes, and Systems IX KW - Elektrizitätsversorgung KW - Sternwarte Y1 - 2022 U6 - https://doi.org/http://dx.doi.org/10.1117/12.2627227 PB - SPIE ER - TY - CHAP A1 - Döhring, Thorsten A1 - Stanik, Eva A1 - Pregler, Jan A1 - Stollenwerk, Manfred A1 - Hildenbrand, Georg T1 - Forschung zu Strahlenschäden mit dem Stratosphärenballon-Experiment ASTRABAX T2 - DGaO-Proceedings N2 - Das Stratosphärenballon-Experiment ASTRABAX ist als multimodale Plattform der Material- und Biowissenschaften für Untersuchungen bei extremen Strahlenbelastungen konzipiert, mit Fokus auf dem UV-C-Spektralbereich und der kosmischen Höhenstrahlung. Auswirkungen von Kombinationen aus hoch- und niederenergetischer Strahlung sind relevant, jedoch nicht ausreichend erforscht. KW - Stratosphärenballon KW - Dosimetrie KW - UV-Spektroskopie KW - kosmische Strahlung KW - Strahlenschäden KW - Stratosphären-Ballon KW - Strahlenbelastung Y1 - 2024 UR - https://www.dgao-proceedings.de/download/125/125_p21.pdf VL - 2024 IS - 125 SP - 1 EP - 2 ER - TY - JOUR A1 - Amorim, Isilda A1 - Spera, Natalia C.M. A1 - Nicoara, Nicoleta A1 - Ramasamy, Devaraj A1 - Alves, Diana F. A1 - Stollenwerk, Manfred A1 - Stadtmüller, Johannes A1 - Döhring, Thorsten A1 - Sadewasser, Sascha A1 - Kolen'ko, Yury V. A1 - Sousa, Juliana P.S. T1 - Overall alkaline water electrolysis over active, stable, low loading iridium catalysts sputtered on nickel foam JF - International Journal of Hydrogen Energy KW - Iridium KW - Katalysator KW - Wasserstoffelektrolyse KW - Wasser KW - Elektrolyse KW - Wasserstofferzeugung Y1 - 2024 U6 - https://doi.org/10.1016/j.ijhydene.2024.10.306 SN - 0360-3199 VL - 92 SP - 852 EP - 864 PB - Elsevier BV ER - TY - CHAP A1 - Wissel, Julian A1 - Freudenmann, Dominic A1 - Perez, Nicolas A1 - Döhring, Thorsten A1 - Stadtmüller, Johannes A1 - Stollenwerk, Manfred T1 - Various highly effective sputtered layer structures as catalysts for H2O2 decomposition for use in satellite engines T2 - MaterialsWeek 2025 – Book of Abstracts N2 - Catalysts are frequently employed in both research and industrial applications to facilitate or accelerate chemical reactions. One such application is in monopropellant thrusters for space propulsion systems, where hydrogen peroxide (H2O2) is used as a liquid propellant. The decomposition of liquid hydrogen peroxide into water and oxygen gas, which ultimately generates thrust, can be achieved using noble metal catalysts from the platinoid group, such as platinum and iridium. This promotes the use of more environmentally friendly and less toxic propellants, such as H2O2, instead of hydrazine and nitrogen tetroxide (NTO). The optimization of coating structures with these catalytic materials is essential for future space applications, as it aims to extend the lifespan of catalyst materials and results in a better utilization of H2O2 in satellite engines. Therefore, different layer structures were deposited onto Duranit D99 pellets using a controlled magnetron sputtering process. Previous studies have shown that the used sputtering pressure has a strong influence on the structure of the deposited coatings [2][3]. Certain parameter combinations produce catalytic layers with rough textures and a highly porous microstructure, see figure 1 [1]. To improve the thermal and mechanical stability of the sputtered layers, thin adhesive layers of Titanium and Zirconium were applied beneath the catalytic layer. The pellets were then heated in an oven at 640°C for one minute to simulate the thermal effects experienced in a satellite engine during ignition. Following this, the catalytic performance of the pellets was tested in laboratory experiments using 30% H2O2. Pellets with sputtered platinum as the catalytic coating delivered the best results. These coatings will be further evaluated in an engine test conducted at the German Aerospace Centre (DLR). Hydrogen peroxide is also expected to play a crucial role in future lunar and Martian colonization efforts. In this context, catalytic coatings would be used to decompose H2O2 to supply astronauts with water and oxygen, rather than to generate thrust in satellite engines. KW - catalyst KW - satellite propulsion KW - sputtered layers KW - iridium KW - platinum KW - Satellitentechnik KW - Katalysator Y1 - 2025 SN - 978-3-88355-446-4 SP - 53 EP - 53 PB - Deutsche Gesellschaft für Materialkunde e.V. (DGM) CY - Sankt Augustin ER - TY - GEN A1 - Licciardello, Nadia A1 - Döhring, Thorsten A1 - Stollenwerk, Manfred A1 - Kolen'ko, Yury V. A1 - Petrovykh, Dmitri Y. T1 - Innovative nanocomposite coatings for radiation shielding on satellites T2 - EuroNanoForum N2 - The current trend in development of low-cost satellites is based on small dimensions combined with advanced electronics. Traditionally, radiation-sensitive electronics on satellites are protected by tungsten or lead foils, which are high-density materials and contribute significantly to the overall mass of the satellite. Here, we design and investigate temperature-gradient-resistant lightweight silane-based composites containing micro- or nano-particles of W or WO3, taking inspiration from similar approaches in the medical field. While the polymeric matrix provides flexibility under thermal gradients (such as those occurring in satellites during their orbits) and low density, the particles enable shielding from soft X-rays and other radiation. For reference, thin tungsten films were deposited by magnetron sputtering. The properties of the two kinds of coatings were compared and the X-ray protective properties were investigated using both a custom-designed measurement setup and conventional X-ray absorption. The best performing radiation-protective coatings will be launched in a payload experiment on the INFANTE satellite. N2 - Poster KW - satellite KW - polymeric matrix KW - nanocomposite KW - radiation protection KW - Satellitentechnik KW - Strahlung Y1 - 2021 UR - https://euronanoforum2021.eu/ VL - 2021 ER - TY - CHAP A1 - Rivolta, Giacomo A1 - Basso, Stefano A1 - Civitani, Marta Maria A1 - Cotroneo, Vincenzo A1 - Döhring, Thorsten A1 - Michler, Willy-Leopold A1 - Pareschi, Giovanni A1 - Spiga, Daniele A1 - Stollenwerk, Manfred T1 - Upgrade of a laboratory X-ray diffractometer to extend its operating range towards soft energies T2 - Proceedings of SPIE N2 - The optical properties of X-ray mirror samples are commonly measured using diffractometers based on laboratory sources; like the Bede D1 diffractometer operating at INAF-OAB. This instrument can generate a collimated X-ray beam up to 60 keV, even though the most interesting energy region for x-ray astronomy applications is usually below 10 keV. In the softest part of this range (below 6 keV), high X-ray absorption in air hinders a full and precise characterization of optical components. In this work, we present an upgrade of the Bede D1 diffractometer that extends the operative range of the instrument below 6 keV; this is done by maximizing the flux at lowest energies and by reducing absorption by means of a helium-rich atmosphere. The upgraded instrument will be used for the tests of X-ray mirrors with innovative soft X-ray coatings, with potential application to the next generation X-ray telescopes (such as ATHENA and eXTP). KW - X-ray KW - mirror KW - reflectivity KW - refractometer KW - ATHENA KW - Röntgenspiegel KW - Diffraktometer Y1 - 2022 UR - https://www.spiedigitallibrary.org/conference-proceedings-of-spie/12181/121814S/Upgrade-of-a-laboratory-x-ray-diffractometer-to-extend-its/10.1117/12.2629940.short U6 - https://doi.org/doi: 10.1117/12.2629940 SN - 0277-786X VL - 2022 IS - 12181 SP - 121814S-1 EP - 121814s-7 PB - SPIE ER - TY - JOUR A1 - Wissel, Julian A1 - Freudenmann, Dominic A1 - Cichocka, Magdalena Ola A1 - Pöhl, Almut A1 - Stephan-Hofmann, Iris A1 - Röcke, Nicole A1 - Pérez, Nicolás A1 - Döhring, Thorsten A1 - Stadtmüller, Johannes A1 - Stollenwerk, Manfred T1 - Microstructure of highly effective platinum–iridium alloys as catalysts for hydrogen peroxide decomposition JF - Research on Chemical Intermediates KW - Iridium KW - Katalysator KW - Raumfahrttechnik KW - Antrieb, Technik KW - Wasserstoffperoxyd Y1 - 2024 U6 - https://doi.org/10.1007/s11164-024-05412-4 SN - 0922-6168 VL - 50 IS - 11 SP - 5385 EP - 5397 PB - Springer Science and Business Media LLC ER - TY - CHAP A1 - Stanik, Eva A1 - Stollenwerk, Manfred A1 - Hübner, Sophie A1 - Stadtmüller, Johannes A1 - Döhring, Thorsten T1 - Experimental studies on iridium catalysts for water PEM electrolysis T2 - MaterialsWeek 2025 – Book of Abstracts N2 - The enhanced use of sustainable energy sources entails strong fluctuations in the availability of electric power. As we need new approaches for energy distribution and energy storage systems, hydrogen is often discussed as a promising energy carrier. PEM electrolysis can be used to transform electrical energy from renewable sources into hydrogen. One challenge in this context is the need for catalysts, as these contribute significantly to the performance of the electrolysis cell. The commonly used platinum group metal (PGM) catalysts like Iridium are quite scarce and therefore expensive. A possible approach to reduce the Ir content is the application of magnetron sputtering for catalyst generation. By selecting the right process parameters, the desired layer properties can be set very precisely during sputtering. This ensures a large surface area with reduced material usage. The introduction of carbon can increase the surface area of the catalyst further and enhance its effectiveness. First results of investigations on the catalytic effect of sputtered Ir catalyst layers will be presented. KW - catalyst KW - iridium KW - PEM electrolysis KW - hydrogen KW - magnetron sputtering KW - Iridium KW - Katalysator KW - Wasserstoffenergietechnik Y1 - 2025 SN - 978-3-88355-446-4 SP - 62 EP - 62 PB - Deutsche Gesellschaft für Materialkunde e.V. (DGM) CY - Sankt Augustin ER - TY - CHAP A1 - Stehlikova, Veronika A1 - Döhring, Thorsten A1 - Stollenwerk, Manfred A1 - Stadtmüller, Johannes A1 - Marsikova, Veronika A1 - Hudec, Rene A1 - Flachs, Dennis A1 - Burwitz, Vadim A1 - Hartner, Gisela A1 - Rukdee, Surangkhana A1 - Müller, Thomas A1 - Schmidt, Thomas A1 - Inneman, Adolf A1 - Klementova, Mariana A1 - Zeising, Sebastian A1 - Langmeier, Andreas T1 - Lobster eye type X-ray telescope with chromium-iridium coated tri-layer mirrors T2 - Proceedings of SPIE N2 - For space-born astronomical X-ray telescopes, iridium-based reflective layer systems are known as highly effective mirrors coatings. During the recent years, Aschaffenburg University of Applied Sciences and the Czech Technical University in Prague jointly developed stress compensated chromium-iridium coatings for this application. To overcome the disturbing reflectivity reduction of the iridium absorption edge around 2 keV photon energy, thin overcoat layers of chromium were applied in addition. Now a prototype of a wide-field, imaging X-ray telescope of Lobster Eye type is assembled at the company RIGAKU. For this purpose a small series of 34 mirrors based on 100 x 50 mm semiconductor grade silicon substrates has been coated at Aschaffenburg University. The applied tri-layer system consists of a stack of 40 nm chromium, which act as adhesive layer and compensates layer stress, a 30 nm iridium thick reflective layer, and an additional overcoat layer of 6 nm chromium. This layer system have been analysed by AFM and TEM images. The mirrors are assembled into an aluminium frame to build a 2D Lobster Eye type telescope. The designed focal length of this wide field X-ray telescope is two meter. To study the performance of the tri-layer coating system, a twin LE telescope with convenient gold coatings was manufactured also. Performance measurements of both telescopes and under same conditions are planned at the PANTER test facility at the Max-Planck Institute for Extraterrestrial Physics. First experimental results, their comparison with theoretical simulations and the comparison between both models will be presented in this contribution. KW - telescope KW - Lobster Eye KW - X-ray KW - mirror KW - iridium KW - Röntgenteleskop KW - Röntgenspiegel Y1 - 2021 U6 - https://doi.org/https://doi.org/10.1117/12.2589266 VL - 2021 IS - 11776 SP - 1177605-1 EP - 1177605-8 PB - SPIE ER - TY - CHAP A1 - Döhring, Thorsten A1 - Stollenwerk, Manfred A1 - Stadtmüller, Johannes A1 - Zeising, Sebastian A1 - Flachs, Dennis A1 - Stehlikova, Veronika A1 - Burwitz, Vadim A1 - Krumrey, Michael K. A1 - Cotroneo, Vincenzo A1 - Klementova, Mariana T1 - Characterisation of X-ray mirrors based on chromium-iridium tri-layer coatings T2 - Proceedings of SPIE N2 - Iridium-based layer systems are highly effective mirror coatings for space-born X-ray telescopes. During the recent years, Aschaffenburg University of Applied Sciences and its partners developed stress compensated chromium-iridium coatings for such astronomical applications, using chromium as an adhesive layer between iridium reflective layer and mirror substrate. However, there was room for improvement: To overcome the disturbing reflectivity reduction of the iridium absorption edge around 2 keV photon energy, thin overcoat layers of chromium are applied in addition now. This layer system has been analyzed by atomic force microscopy and transmission electron microscopy images. Furthermore, the reflectivity of such innovative X-ray mirrors based on chromium-iridium tri-layer coatings was recently measured at PTB's four-crystal monochromator beamline at the synchrotron radiation facility BESSY II. The experimental results, obtained for photon energies between 1.9 keV and 11 keV at two grazing incidence angles (0.6 degree and 0.9 degree) and their comparison with corresponding simulations are presented in this contribution. When compared to simulations of pure iridium coatings, a significantly higher reflectivity was achieved especially in the soft X-ray regime between 2 keV and 4 keV. Such chromium-iridium tri-layer coatings have high potential to increase the effective area for X-ray telescopes in Lobster Eye Design, for Wolter-I type X-ray optics, and for silicon pore optics as considered for the ATHENA telescope of the European Space Agency. KW - iridium KW - mirror KW - X-ray KW - coating KW - telescope KW - Röntgenspiegel KW - Röntgenteleskop KW - Iridium Y1 - 2021 U6 - https://doi.org/https://doi.org/10.1117/12.2592551 VL - 2021 IS - 11776 SP - 1177607-1 EP - 11776076 PB - SPIE ER -