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 - Khropost, Diana A1 - Riethmüller, Franziska A1 - Stanik, Eva A1 - Döhring, Thorsten A1 - Hertwig, Andreas A1 - Huelague, Deniz T1 - Polydopamine – a bionic material and its potential applications for batteries T2 - MaterialsWeek 2025 – Book of Abstracts N2 - Polydopamine (PDA) recently came into focus as an innovative material for applications in various technical fields, especially in the energy field it is considered for batteries as well as for supercapacitors. It is a very strong glue that sticks on almost everything, even under water: In nature, PDA is found in the byssal thread cuticles of mussels. The wet-resistant adhesion ability of PDA can be used in the treatment of separator membranes in batteries, but furthermore PDA is also considered as an electrode material for batteries. We have investigated thin layers of poly-dopamine with different methods including ellipsometry, tactile measurements of the layer thickness and in situ absorption measurements during the polymerization process. KW - polydopamine KW - PDA KW - bionic material KW - adhesion KW - absorption KW - Iridium KW - Katalysator KW - Wasserstoffenergietechnik Y1 - 2025 SN - 978-3-88355-446-4 SP - 67 EP - 67 PB - Deutsche Gesellschaft für Materialkunde e.V. (DGM) CY - Sankt Augustin 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 - 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 - Döhring, Thorsten A1 - Stieglitz, Veronika A1 - Hudec, Rene A1 - Sapsai, Iryna A1 - Friedrich, Peter A1 - Burwitz, Vadim T1 - Characterization of a lobster-eye type X-ray telescope T2 - EOSAM-Conference N2 - Lobster-eye type X-ray telescopes use reflecting plano mirrors under grazing incidence and can observe a large field of view. As part of a Bavarian-Czech cooperation, two telescopes were build, equipped with mirrors coated with gold and iridium. Their X-ray characterization was carried out at the PANTER test facility, which simulates parallel starlight incident on the telescopes. The telescopes have an angular resolution of about 4 arc minutes in X-rays and a focal length of about 2 meters. The used X-ray mirrors reflect and focus visible light as well; their functionality in the optical regime was checked in laboratory tests. Now another test campaign will be carried out to examine the telescope resolution for real objects of the visible night sky and the imaging properties for star constellations. KW - Lobster-Eye KW - X-ray KW - telescope KW - iridium KW - mirror KW - Röntgenteleskop KW - Iridium KW - Röntgenspiegel Y1 - 2022 UR - https://www.europeanoptics.org/events/eos/eosam2022.html VL - 2022 SP - 1 EP - 1 ER - TY - CHAP A1 - Döhring, Thorsten A1 - Stollenwerk, Manfred A1 - Schmitt, Paul A1 - Szeghalmi, Andrea T1 - Umweltbeständige Spiegelbeschichtungen aus Iridium für den infraroten Spektralbereich T2 - DGaO Proceedings N2 - Das Edelmetall Iridium ist hart; extrem dicht; thermisch, mechanisch und chemisch stabil; weist eine hohe Reflektivität im mittleren und fernen Infrarot auf und hat eine hohe Beständigkeit gegenüber Umwelteinflüssen - auch ohne weitere Schutzschichten. Es wurden die komplexen Brechungsindizes für Iridium-Spiegelbeschichtungen bestimmt, welche vorhandene Literaturwerte ergänzen. KW - Iridium KW - Spiegel KW - Reflektivität KW - Brechungsindex KW - ALD KW - Iridium KW - Beschichtung Y1 - 2022 UR - https://www.dgao-proceedings.de/download/123/123_p13.pdf SN - 1614-8436 VL - 2022 IS - 123 SP - 1 EP - 2 PB - DGaO ER - TY - CHAP A1 - Döhring, Thorsten A1 - Zeising, Sebastian A1 - Stieglitz, Veronika A1 - Burwitz, Vadim A1 - Rukdee, Surangkhana A1 - Friedrich, Peter A1 - Jelinek, Martin A1 - Hudec, Rene T1 - Röntgenteleskop-Funktionstests durch Beobachtung astronomischer Objekte am sichtbaren Nachthimmel T2 - DGaO Proceedings N2 - Lobster-Eye-Röntgenteleskope nutzen reflektierende Planspiegel unter streifendem Einfall und zeichnen sich durch ein großes Beobachtungsfeld aus. Die Spiegel reflektieren auch sichtbare Strahlung hervorragend. Nach Röntgen-messungen im Labor wurden nun weitere Tests durchgeführt, um die Abbildungs-eigenschaften mit realen Objekten des sichtbaren Himmels zu untersuchen. KW - Röntgenstrahlung KW - Teleskop KW - Lobster-Eye KW - Iridium KW - Astronomie KW - Röntgenteleskop KW - Spiegelteleskop Y1 - 2022 UR - https://www.dgao-proceedings.de/download/123/123_a35.pdf SN - 1614-8436 VL - 2022 SP - 1 EP - 2 PB - DGaO ER - TY - CHAP A1 - Döhring, Thorsten A1 - Stollenwerk, Manfred A1 - Schmitt, Paul A1 - Szeghalmi, Adriana T1 - Environmentally stable iridium mirror coatings for the infrared spectral range T2 - Proceedings of SPIE N2 - Highly reflective metal coatings are essential for numerous optical elements. Established mirror coatings made of silver (Ag) and gold (Au) offer high and broadband self-reflection in the infrared (IR) spectral range but are susceptible to environmental influences and mechanical stress without suitable protective layers. In the long-wavelength spectral range, in particular, the absorption bands of these protective layers partially reduce the high mirror reflectivity again. However, the noble metal iridium (Ir) is hard, extremely dense, and thermally, mechanically, and chemically stable. Iridium provides a similarly high reflectivity in the mid (MIR) and far-infrared (FIR) spectral range, as silver and gold, and high resistance to environmental influences - even without protective layers. In this paper, the different deposition processes, as well as the optical and structural properties of iridium mirror coatings fabricated by atomic layer deposition (ALD) and by magnetron sputtering (MS), are presented and compared with each other. The complex refractive indices for ALD and MS deposited iridium mirror coatings were determined for wavelengths from 200 nm to 20 μm, complementing the existing literature values. We demonstrate that iridium mirror coatings offer a high and broadband reflectivity from the mid to far-infrared spectral range. In contrast to established – protected – silver and gold mirror coatings, the iridium coatings are environmentally durable and thermally stable up to 600 °C, even without protective layers. Therefore, as an interesting mirror coating material, iridium has the potential for special applications in infrared astronomy and probably also for industrial instruments. KW - iridium KW - coating KW - magnetron sputtering KW - atamic layer deposition KW - reflectivity KW - Iridium KW - Beschichtung Y1 - 2022 U6 - https://doi.org/https://doi.org/10.1117/12.2632057 VL - 2022 IS - 12298 SP - 122980A-1 EP - 122980A-08 PB - SPIE ER - TY - GEN A1 - Döhring, Thorsten A1 - Stollenwerk, Manfred A1 - Schmitt, Paul A1 - Szeghalmi, Adriana T1 - Umweltbeständige Spiegelbeschichtungen aus Iridium für den infraroten Spektralbereich N2 - Hochreflektierende Metallbeschichtungen sind essenziell für zahlreiche optische Elemente. Bewährte Spiegelbeschichtungen aus Silber und Gold bieten eine hohe und breitbandige Eigenreflexion im infraroten Spektralbereich, sind ohne geeignete Schutzschichten jedoch anfällig gegenüber Umwelteinflüssen und mechanischer Beanspruchung. Insbesondere im langwelligen Spektralbereich verringern die Absorptionsbanden dieser Schutzschichten teilweise die hohe Spiegelreflektivität wieder. Das Edelmetall Iridium (Ir) ist hart; extrem dicht; thermisch, mechanisch und chemisch stabil; weist eine ähnlich hohe Reflektivität im mittleren und fernen Infrarot, wie Silber und Gold, auf und hat zusätzlich eine hohe Beständigkeit gegenüber Umwelteinflüssen - auch ohne Schutzschichten. In diesem Beitrag werden die optischen und strukturellen Eigenschaften von Iridium-Spiegelbeschichtungen, welche mittels Atomlagenabscheidung (ALD) und DC-Magnetron-Sputtern hergestellt wurden, vorgestellt und miteinander verglichen. Die komplexen Brechungsindizes für ALD-erzeugte und gesputterte Iridium-Spiegelbeschichtungen wurden für Wellenlängen von 200 nm bis 20 μm bestimmt, welche nun bereits vorhandene Literaturwerte ergänzen. N2 - Poster KW - Iridium KW - Brechungsindex KW - infrarot KW - Spiegel KW - Beschichtung KW - Iridium KW - Beschichtung Y1 - 2022 SP - 1 EP - 1 PB - DGaO ER - TY - JOUR A1 - Schmitt, Paul A1 - Felde, Nadja A1 - Döhring, Thorsten A1 - Stollenwerk, Manfred A1 - Uschmann, Ingo A1 - Hanemann, Kevin A1 - Siegler, Marie A1 - Klemm, Georg A1 - Gratzke, Nancy A1 - Tünnermann, Andreas A1 - Schwinde, Stefan A1 - Schröder, Sven A1 - Szeghalmi, Adriana T1 - Optical, structural, and functional properties of highly reflective and stable iridium mirrorcoatings for infrared applications: supplement JF - Optical Materials Express N2 - Metallic coatings are essential for numerous optical systems due to their high and broadband refl ectivity in the infrared spectral range. In contrast to well-established (protected)silver and gold mirror coatings, iridium is environmentally durable, referring to ISO 9211-3 and thermally stable up to 600 °C even without protective layers, as demonstrated. Additionally,the optical and related structural properties of atomic layer deposited (ALD) and magnetron sputtered (MS) Ir coatings were investigated using spectrophotometry, FTIR, ellipsometry, WLI, AFM, XRR, XRD, SEM, and electrical resistivity measurements. The properties of Ir ALD and Ir MS coatings diff er due to their topography and microstructure. KW - Iridium KW - mirror KW - ALD KW - Sputter KW - Iridium KW - Beschichtung Y1 - 2022 U6 - https://doi.org/10.6084/m9.figshare.17121509 VL - 2022 IS - 12/2 SP - 545 EP - 559 ER - TY - JOUR A1 - Schmitt, Paul A1 - Felde, Nadja A1 - Döhring, Thorsten A1 - Stollenwerk, Manfred A1 - Uschmann, Ingo A1 - Hanemann, Kevin A1 - Siegler, Marie A1 - Klemm, Georg A1 - Gratzke, Nancy A1 - Tünnermann, Andreas A1 - Schwinde, Stefan A1 - Schröder, Sven A1 - Szeghalmi, Adriana T1 - Optical, structural, and functional properties of highly reflective and stable iridium mirror coatings for infrared applications JF - Optical Materials Express N2 - Metallic coatings are essential for numerous optical systems due to their high and broadband refl ectivity in the infrared spectral range. In contrast to well-established (protected)silver and gold mirror coatings, iridium is environmentally durable, referring to ISO 9211-3 and thermally stable up to 600 °C even without protective layers, as demonstrated. Additionally,the optical and related structural properties of atomic layer deposited (ALD) and magnetron sputtered (MS) Ir coatings were investigated using spectrophotometry, FTIR, ellipsometry, WLI,AFM, XRR, XRD, SEM, and electrical resistivity measurements. The properties of Ir ALD and Ir MS coatings diff er due to their topography and microstructure. KW - Iridium KW - mirror KW - Sputter KW - ALD KW - Iridium KW - Beschichtung Y1 - 2022 U6 - https://doi.org/10.1364/OME.447306 VL - 2022 IS - 12 / 2 SP - 545 EP - 559 ER - TY - CHAP A1 - Döhring, Thorsten A1 - Rödling, Claudius A1 - Kimmel, Kevin A1 - Zeising, Sebastian A1 - Stadtmüller, Johannes A1 - Stollenwerk, Manfred A1 - Verma, Shruti A1 - Rees, Paul T1 - Optical characterization of reflective coatings for astronomical telescope mirrors T2 - DGaO Proceedings N2 - Aluminium evaporation is still the standard solution for reflective coatings of large astronomical mirrors. Silver and gold are also used in specific cases depending on the targeted wavelength. This study characterized different metallic coatings - including unusual ones like sputtered iridium - to identify the most suitable mirror coating for the spectral range from ultraviolet to infrared wavelengths. KW - Iridium KW - mirror KW - coating KW - reflectivity KW - telescope KW - Spiegelteleskop Y1 - 2021 UR - https://www.dgao-proceedings.de/download/122/122_p4.pdf SN - 1614-8436 VL - 2021 IS - 122 SP - 1 EP - 1 PB - DGaO ER - TY - CHAP A1 - Döhring, Thorsten A1 - Stadtmüller, Johannes A1 - Stollenwerk, Manfred A1 - Cotroneo, Vincenzo A1 - Pareschi, Giovanni A1 - Gibertini, Eugenio A1 - Magagnin, Luca T1 - Low-density coatings for enhanced X-ray reflectivity of astronomical telescope mirrors T2 - DGaO Proceedings N2 - High reflectivity grazing incidence mirrors of astronomical X-ray telescopes are usually coated with thin layers of iridium, gold, or platinum. Due to a series of absorption edges, these noble metals have low reflectivity in the 2 - 4 keV band. We present the development of innovative material combinations using chromium and an additional layer of polydopamine for enhanced reflectivity X-ray coatings. KW - Dopamin KW - Iridium KW - mirror KW - coating KW - X-ray KW - Röntgenteleskop Y1 - 2021 UR - https://www.dgao-proceedings.de/download/122/122_p3.pdf SN - 1614-8436 VL - 2021 IS - 122 SP - 1 EP - 2 PB - DGaO ER - TY - CHAP A1 - Döhring, Thorsten A1 - Stieglitz, Veronika A1 - Burwitz, Vadim A1 - Hartner, Gisela A1 - Müller, Thomas A1 - Schmidt, Thomas A1 - Rukdee, Surangkhana A1 - Friedrich, Peter A1 - Sahin, Fatih A1 - Hudec, Rene T1 - Charakterisierung von Weitwinkel-Röntgenteleskopen in der Testanlage PANTER T2 - DGaO Proceedings N2 - Im Rahmen einer bayerisch-tschechischen Kooperation entstanden zwei Röntgenteleskope, bestückt mit Gold- und Iridium-beschichteten Planspiegeln. Deren Charakterisierung erfolgte an der Röntgentestanlage PANTER, welche parallel auf die Teleskope einfallendes Sternenlicht simuliert. Die Teleskope haben eine Winkelauflösung von ca. 4 Bogenminuten und eine Brennweite von rund 2 Metern. KW - Röntgenstrahlung KW - Teleskop KW - Iridium KW - Beschichtung KW - Astronomie KW - Röntgenteleskop KW - Iridium KW - Spiegelteleskop Y1 - 2021 UR - https://www.dgao-proceedings.de/download/122/122_p2.pdf SN - 1614-8436 VL - 2021 IS - 122 SP - 1 EP - 2 PB - DGaO ER - TY - CHAP A1 - Freudenmann, Dominic A1 - Stollenwerk, Manfred A1 - Döhring, Thorsten A1 - Stadtmüller, Johannes A1 - Negri, Michele A1 - Lauck, Felix T1 - Combustion efficiency of iridium coated pellets for environmentally friendly space propulsion T2 - 14th Pico- and Nanosatellite Workshop, Würzburg, Germany N2 - Most of the satellite engines still uses critical fuels such as hydrazine, which is chemically aggressive, toxic and carcinogenic. New developments for satellite engines try to avoid such critical propellants. One promising approach is the usage of rocket-grade hydrogen peroxide [H2O2] in mono- and bipropellant driven rocket engines. Catalysts in the rocket engines convert the hydrogen peroxide by an exothermic catalytic reaction; the resulting hot gases oxygen and water vapor provide the thrust. Currently used catalysts are, for example, Al2O3 pellets impregnated with platinum. Within a joint research project of Aschaffenburg University and the German Aerospace Center new catalysts are developed. They consist of ceramic pellets coated with iridium using the magnetron sputtering process. Thereby the surface structure of the iridium layers strongly depends on the used sputtering process conditions [1]. After optimization of the sputtering parameters, it was demonstrated in laboratory experiments that the catalytic effect (measured by the volume of released gas) can be increased by a factor of four compared to platinum impregnated pellets [2]. In first hot firing tests at the test bench complex M11 at the DLR- Institute of Space Propulsion, these new, iridium-based catalysts have been used in a model combustion chamber for hydrogen peroxide decomposition. For this purpose, the reaction chamber was filled with iridium pellets in the high-altitude simulation chamber of the M11.2 test bench. The model chamber was equipped with numerous measuring devices like temperature and pressure sensors (e.g. Tcat, pcat). With the help of the mass flow and the herein obtained data, performance characteristics of the propellant system were accessible. High-concentrated hydrogen peroxide was used in the experiments as monopropellant (~ 87-wt.% H2O2). During the experiments, the combustion chamber was operated in pulse mode and in continuous mode. Aim of this campaign called MoCa (“Monopropellant Catalytic Demonstrator”) is the demonstration of functionality and the performance evaluation of this iridium-based monopropellant system. Recent experimental results will be presented. References: [1] A. Büttner et al., Thin Solid Films 2018, 662: 41–46 [2] M. Stollenwerk et al., Journal of Materials Science 2021, 56(16), 9974-9984 KW - Satellitentechnik KW - Katalysator KW - Iridium Y1 - 2021 ER - TY - GEN A1 - Döhring, Thorsten A1 - Stieglitz, Veronika A1 - Burwitz, Vadim A1 - Hartner, Gisela A1 - Müller, Thomas A1 - Schmidt, Thomas A1 - Rukdee, Surangkhana A1 - Friedrich, Peter A1 - Sahin, Fatih A1 - HUdec, Rene T1 - Charakterisierung von Weitwinkel-Röntgenteleskopen in der Testanlage PANTER T2 - DGaO Jahrestagung N2 - Im Rahmen einer bayerisch-tschechischen Kooperation entstanden zwei mechanisch baugleiche Röntgenteleskope, bestückt mit Gold- und Iridium-beschichteten Planspiegeln. Die Charakterisierung der nach dem ägyptischen Gott HORUS benannten Teleskope erfolgte an der Röntgentestanlage PANTER des Max-Plack-Instituts für extraterrestrische Physik. Diese Vakuum-Testanlage simuliert parallel auf die Teleskope einfallendes Sternenlicht, wobei hier die Strahlung aus einer Röntgenquelle in 120 Metern Abstand stammt. Die Messungen selbst fanden in einer daran angebauten 12 Meter langen Testkammer von 3,5 Metern Durchmesser statt. Im März 2021 sahen die HORUS-Teleskope zum erstem Mal Röntgenlicht. Während der Testkampagne von ca. 54 Stunden Dauer wurden 536 Einzelmessungen an den beiden Teleskopen durchgeführt, bei denen Photonenenergien und Einfallswinkel variiert wurden. Von einer empfindlichen CCD-Kamera, einem Prototyp der eROSITA-Satellitenkamera, wurden hierbei insgesamt 11.153.574 Röntgenphotonen individuell detektiert, analysiert und digital verarbeitet. Die beiden Weitwinkel-Röntgenteleskope haben eine Winkelauflösung von circa 4 Bogenminuten und eine Brennweite von rund zwei Metern. N2 - Poster KW - Röntgenstrahlung KW - Spiegel KW - Teleskop KW - Satellit KW - Iridium KW - Röntgenstrahlung KW - Spiegelteleskop Y1 - 2021 UR - https://dgao.de/jahrestagung/ VL - 2021 SP - 1 EP - 1 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 - TY - GEN A1 - Döhring, Thorsten T1 - Advanced Materials and Manufacturing Technologies for Space Applications T2 - Proceedings of International Research Days N2 - The goal of this project is to develop satellite components for space-based astronomical satellite payloads. Thereby advanced materials like iridium and innovative manufacturing technologies will be applied. After environmental testing and space qualifications tests it is planned to do an astronomical experiment with a stratospheric balloon or a sounding rocket. The work is embedded in ACCASI („Aschaffenburg Competence Center for Astronomical and Space Instumentation“) N2 - Poster KW - satellite KW - iridium KW - telescope KW - mirror KW - Satellitentechnik KW - Iridium KW - Spiegelteleskop Y1 - 2021 VL - 2021 ER - TY - GEN A1 - Döhring, Thorsten A1 - Stollenwerk, Manfred A1 - Stadtmüller, Johannes A1 - Freudenmann, Dominic A1 - Röcke, Nicole T1 - Nanostructured iridium catalysts for effective hydrogen peroxide decomposition T2 - EuroNanoForum N2 - The EU intends to restrict the use of critical fuels in space propulsion systems. These propellants like hydrazine are chemically aggressive, toxic and carcinogenic. Space propulsion of the future should be environmentally friendly, inexpensive, and easy to handle. Aschaffenburg University and DLR are currently developing environmentally friendly technologies for future satellite engines. Thereby rocket-grade hydrogen peroxide, which is foreseen as a substitute, is converted to uncritical water vapour and oxygen by an exothermic catalytic reaction on nanostructured iridium layers. The resulting hot gases provide the required amount of thrust. The iridium catalyst layers are coated onto ceramic pellets, using RF magnetron sputtering technology. The catalytic functionality was tested afterwards at the chemical laboratories of DLR. First experimental results show a significantly higher catalytic activity for nanostructured iridium surfaces than for smoother crystalline layers. N2 - Poster KW - satellite KW - propulsion KW - catalyst KW - iridium KW - hydrogen peroxide KW - Iridium KW - Katalysator KW - Satellitentechnik Y1 - 2021 VL - 2021 ER - TY - JOUR A1 - Döhring, Thorsten ED - IHK Aschaffenburg, T1 - Forscher entwickeln umweltfreundliche Satellitenantriebe JF - Wirtschaft am Bayerischen Untermain N2 - In der aktuellen Förderrunde des vom Bayerischen Staatsministeriums für Wissenschaft und Kunst aufgesetzten „Programms zur Förderung der angewandten Forschung und Entwicklung an Hochschulen für angewandte Wissenschaften – Fachhochschulen“ war die Technische Hochschule Aschaffenburg sehr erfolgreich. Für das Technologieprojekt ACCASI („Aschaffenburg Competence Center for Astronomical and Space Instrumentation“) erhält sie über eine Laufzeit von drei Jahren insgesamt 250.000 Euro. KW - Satellit KW - Triebwerk KW - Iridium KW - Katalysator KW - Satellitentechnik Y1 - 2021 UR - https://www.aschaffenburg.ihk.de/share/flipping-book/5064860/flippingbook.pdf VL - 2021 IS - März SP - 12 EP - 13 ER - TY - JOUR A1 - Stollenwerk, Manfred A1 - Döhring, Thorsten A1 - Freudenmann, Dominic A1 - Schäfer, Tobias A1 - Stadtmüller, Johannes A1 - Röcke, Nicole T1 - Sputtered highly effective iridium catalysts: a new approach for green satellite propulsion JF - Journal of Materials Science N2 - This work demonstrated the large potential of sputtered iridium metal for catalytic reactions shown by the example of decomposition of hydrogen peroxide (H2O2) for space propulsion systems. For this purpose, iridium was coated onto Al2O3 pellets by a sputter process under varied process parameters. Depending on previously selected parameters, the obtained metal-loaded pellets offer closed- and/or open-shell structures. Catalytic productivity of these first-generation iridium-sputtered catalysts was estimated in laboratory experiments and compared to platinum-loaded pellets. Under optimized sputter-process conditions, the reactivity is significantly improved compared to the platinum-impregnated pellets. The better catalytic productivity can be explained by the increased active surface area of the iridium layers on the pellets. The surface morphology and the microstructure of the iridium coating can be actively controlled by the sputter pressure. The results are in accordance with the sputtering process pressure tendency described by the Thornton Structure–Zone Model. KW - Iridium KW - Katalysator KW - Satellitentechnik Y1 - 2021 U6 - https://doi.org/https://doi.org/10.1007/s10853-021-05897-z VL - 2021 IS - 2021 SP - 1 EP - 11 ER - TY - JOUR A1 - Probst, Anne-Catherine A1 - Begou, Thomas A1 - Döhring, Thorsten A1 - Zeising, Sebastian A1 - Stollenwerk, Manfred A1 - Stadtmüller, Johannes A1 - Emmerich, Florian A1 - Lumeau, Julien ED - Publishing OSA, T1 - Coating stress analysis and compensation for iridium-based x-ray mirrors JF - Applied Optics N2 - Iridium-based coatings for mirrors of x-ray telescopes are studied. In particular, stress-induced deformation is characterized and shown to be compressive and equal to −1786  MPa. Two methods for stress compensation are then studied. One relies on the deposition of silica on the back surface of the substrate and a second one relies on the deposition of a chromium sublayer. Advantages and drawbacks of each of these techniques are presented. KW - iridium KW - coating stress KW - X-ray KW - mirror KW - astronomy KW - Röntgenteleskop KW - Iridium KW - Spiegelteleskop Y1 - 2018 UR - https://doi.org/10.1364/AO.57.008775 VL - 2018 IS - 57 (29) SP - 8775 EP - 8779 ER - TY - JOUR A1 - Probst, Anne-Catherine A1 - Stollenwerk, Manfred A1 - Emmerich, Florian A1 - Büttner, Andre A1 - Zeising, Sebastian A1 - Stadtmüller, Johannes A1 - Riethmüller, Franziska A1 - Stehlikova, Veronika A1 - Mingwu, Wen A1 - Proserpio, Laura A1 - Damm, Christine A1 - Rellinghaus, Bernd A1 - Döhring, Thorsten T1 - Influence of sputtering pressure on the nanostructure and the X-ray reflectivity of iridium coatings JF - Surface and Coatings Technology N2 - Reflective mirror coatings made of iridium are used in X-ray telescopes of the Chandra X-ray Observatory (CXO) launched in 1999 by the National Aeronautics and Space Administration (NASA) to investigate astronomical sources at photon energies below 10. keV. These coatings were produced in a DC magnetron sputtering process and have so far proven their suitability for space-based applications. We are considering in the present paper the processing of thin iridium films for lightweight telescopes using the radio frequency magnetron sputtering technique with an oblique angle deposition. The coating development presented here is focused on the influence of total sputtering pressure on film properties as well as on its impact on the mirror's performance. Characterisation methods such as X-ray diffractometry, X-ray reflectometry, atomic force microscopy and transmission electron microscopy have been used. Correlations between morphology, density, surface micro-roughness, crystal structure of the iridium layer and the expected reflectivity of the X-ray mirror are described and discussed. KW - Iridium KW - sputtering KW - microstructure KW - coating KW - X-ray KW - Iridium KW - Röntgenteleskop Y1 - 2017 UR - https://doi.org/10.1016/j.surfcoat.2017.10.062 SN - 0257-8972 VL - 2017 IS - 343 SP - 101 EP - 107 ER - TY - JOUR A1 - Büttner, Andre A1 - Probst, Anne-Catherine A1 - Emmerich, Florian A1 - Damm, Christine A1 - Rellinghaus, Bernd A1 - Döhring, Thorsten A1 - Stollenwerk, Manfred T1 - Influence of Sputtering Pressure on the Microstructure and Layer Properties of Iridium Thin Films JF - Thin Solid Films N2 - Iridium layers with low stress, high density, and low surface roughness find widespread use in different high-technology applications. This paper presents a study of the influence of the sputtering pressure on the properties of iridium thin films and of its effect on the substrate surface microstructure. We analysed the dependence of the microstructure, crystalline structure, electrical resistivity, and deposition rate on the sputtering pressure and surface defects of the substrate. For the latter, plasma etching of the substrate was performed for different processing times and its effect on the surface roughness of substrates and, subsequently, on the grown iridium films, was examined. The sputtering pressure and the substrate plasma etching time both had a strong influence on the microstructure and surface roughness. These microstructural changes are in good agreement with the tendency described in the Thornton Structure-Zone Model for different sputtering pressures and the microstructure phase map of Alvarez. The electrical resistivity, deposition rate, and crystalline structure were highly dependent on the sputtering pressure. KW - Iridium KW - microstructure KW - TEM KW - sputtering KW - thin films KW - Iridium KW - Dünne Schicht Y1 - 2018 UR - https://doi.org/10.1016/j.tsf.2018.06.056 SN - 0040-6090 VL - 2018 IS - 662 SP - 41 EP - 46 ER - TY - JOUR A1 - Stehlikova, Veronika A1 - Probst, Anne-Catherine A1 - Nentvich, Ondrej A1 - Urban, Martin A1 - Sieger, Ladislav A1 - Döhring, Thorsten A1 - Hudec, René ED - Skopal, Augustín T1 - Study of multiple layers coatings for X–ray mirrors JF - Contributions of the Astronomical Observatory Skalnaté Pleso N2 - This paper focuses on a theoretical background that motivated the experimental campaign of multiple layer coatings of X-ray mirrors, and the first results of the testing of the prepared samples. Simulations of the use of different overcoats were performed in order to improve the reflectivity of thin iridium coatings designed for X-ray optics effective in the energy up to 10 keV. Samples based on these simulations were prepared and are being tested for the properties that influence the X-ray optical performance, such as layer homogeneity, density and surface micro-roughness. Further the topic of the coating stress was addressed, as it is an issue in case of thin, lightweight X-ray mirrors and affects the time stability of layers. The discussion and preliminary results conclude our contribution. KW - X-ray KW - optics KW - coating KW - reflectivity KW - iridium KW - Röntgenspiegel KW - Iridium Y1 - 3018 UR - https://www.ta3.sk/caosp/Eedition/Abstracts/2018/Vol_48/No_3/pp488-497_abstract.html VL - 2018 IS - 48 SP - 488 EP - 497 ER - TY - JOUR A1 - Döhring, Thorsten A1 - Hudec, Rene ED - Skopal, Augustín T1 - JEUMICO and TRILAMICO: Dimensions of successful Bavarian-Czech cooperation JF - Contributions of the Astronomical Observatory Skalnaté Pleso N2 - In December 2017 the two projects JEUMICO (an acronym for Joint European Mirror Cooperation) and TRILAMICO (standing for Trilateral Mirror Collaboration) are ending. Different aspects of this Bavarian-Czech collaboration between Aschaffenburg University and the Czech Technical University in Prague are discussed. The multiple dimensions of this cooperation are scientific achievements, public relation measures, internationalization of education, financial aspects, inter-cultural communication, and also the actual political situation within Europe. KW - JEUMICO KW - TRILAMICO KW - BTHA KW - Iridium KW - astronomy KW - Röntgenspiegel KW - Spiegelteleskop Y1 - 2018 UR - https://www.astro.sk/caosp/Eedition/Abstracts/2018/Vol_48/No_3/pp430-436_abstract.html VL - 2018 IS - Vol. 48 / 3 SP - 430 EP - 436 ER - TY - CHAP A1 - Probst, Anne-Catherine A1 - Döhring, Thorsten A1 - Stollenwerk, Manfred A1 - Mingwu, Wen A1 - Proserpio, Laura ED - Cugny, Bruno ED - Karafolas, Nikos ED - Sodnik, Zoran T1 - Iridium coatings for space based x-ray optics T2 - Proceedings of SPIE N2 - Future investigations of astronomical X-ray sources require light weight telescope systems with large collecting areas and good angular resolution. The Wolter I type telescope design offers a suitable possibility for obtaining performant X-ray mirrors with high collecting areas. The technology based on replicated slumped glass optics using thin glasses thereby provides the opportunity to fulfil the light weight and mass production requirements. In NASA's telescope NuSTAR this technology has been proven as advantageous compared to previous systems. Coating thin glasses with iridium, gold or platinum enhances the reflectivity of X-ray mirrors. KW - Iridium KW - coating KW - X-ray KW - astronomy KW - mirror KW - Iridium KW - Spiegelteleskop KW - Röntgenastronomie Y1 - 2017 U6 - https://doi.org/10.1117/12.2296167 VL - 2017 IS - 10562 SP - 105621E-01 EP - 105621E-09 ER - TY - CHAP A1 - Döhring, Thorsten A1 - Probst, Anne-Catherine A1 - Zeising, Sebastian T1 - Analyse der Schichtspannungen von Röntgenspiegeln mit einem Weißlichtinterferometer T2 - DGaO-Proceedings N2 - An der Hochschule Aschaffenburg werden iridiumbasierte Schichtsysteme für röntgenastronomische Anwendungen hergestellt. Unter Nutzung eines Weißlichtinterferometers wurde hierfür ein Verfahren zur Vermessung der inhärenten Schichtspannungen entwickelt. Erste vielversprechende Ergebnisse von spannungsarmen Röntgenreflexionsbeschichtungen werden vorgestellt. KW - Röntgenspiegel KW - Interferometer KW - Iridium KW - Schichtspannung Y1 - 2018 UR - https://www.dgao-proceedings.de/download/119/119_p10.pdf SN - 1614-8436 VL - 2018 IS - 2018 SP - P10-1 EP - P10-2 PB - Deutsche Gesellschaft für angewandte Optik e.V. CY - Erlangen ER - TY - CHAP A1 - Stehlikova, Veronika A1 - Probst, Anne-Catherine A1 - Nentvich, Ondrej A1 - Urban, Martin A1 - Inneman, Adolf A1 - Sieger, Ladislav A1 - Marsikova, Veronika A1 - Döhring, Thorsten T1 - Development of iridium coated silicon X-ray mirrors for Lobster Eye astronomical telescopes T2 - Proceedings of EOSMOS 2017 N2 - In the field of X-ray astronomy different types of telescope optics based on grazing incidence mirrors can be used. This contribution presents a special design of a Lobster Eye wide-field telescope with mirrors based on flat silicon wafers and the task of coating such mirror substrates with reflective iridium layers. KW - X-ray KW - mirror KW - telescope KW - Lobster Eye KW - iridium KW - Iridium KW - Röntgenteleskop Y1 - 2017 VL - 2017 IS - EOSMOS 2017 SP - 1 EP - 2 PB - European Optical Society ER - TY - CHAP A1 - Stehlikova, Veronika A1 - Proserpio, Laura A1 - Friedrich, Peter A1 - Madarasz, Emanuel A1 - Breunig, Elias A1 - Burwitz, Vadim A1 - Döhring, Thorsten A1 - Probst, Anne-Catherine T1 - Indirect glass slumping of grazing incidence mirror segments for lightweight x-ray telescopes T2 - Proceedings of the International Society for Optics and Photonics (SPIE) N2 - The paper provides a description of recent progress in the development of lightweight, precision and highthroughput grazing-incidence mirrors for X-ray astronomy made of glass. In particular, the indirect slumping technology under investigation at the Max Planck Institute for Extraterrestrial Physics (MPE) is reviewed and recent activities are presented together with the research approach. The glass slumping technique foresees several steps: a thermal forming process using a suitable mould; a re ective layer application; the alignment and integration of mirror segments into a supporting structure; and the � nal veri� cation of prototype modules using X-rays. Each step is considered at MPE, with the involvement of partner institutes and universities. The last year of activities was mainly dedicated to the procurement of new moulds and to the application of Iridium coating. The main results will be presented. KW - X-ray KW - iridium KW - telescope KW - slumping KW - glass KW - Iridium KW - Röntgenteleskop Y1 - 2017 U6 - https://doi.org/10.1117/12.2272671 VL - 2017 IS - 10399 SP - 103991Z-1 EP - 103991Z-7 PB - SPIE ER - TY - CHAP A1 - Döhring, Thorsten A1 - Probst, Anne-Catherine A1 - Emmerich, Florian A1 - Stollenwerk, Manfred A1 - Stehlikova, Veronika A1 - Friedrich, Peter A1 - Damm, Christine T1 - Development of iridium coated X-ray mirrors for astronomical applications T2 - Proceedings of the International Society for Optics and Photonics (SPIE) N2 - Future space-based X-ray observatories need to be very lightweight for launcher mass constraints. Therefore they will use a reduced mirror thickness, which results in the additional requirement of low coating stress to avoid deformation of the initial precisely shaped mirror substrates. Due to their excellent reflection properties iridium coatings are sometimes applied for grazing incidence mirrors in astronomical X-ray telescopes. At Aschaffenburg University of Applied Sciences the coating of thin iridium films by an RF-magnetron sputtering technique is under development. The work is embedded in collaborations with the Max-Planck-Institute for Extraterrestrial Physics in Germany, the Czech Technical University in Prague, the Osservatorio Astronomico di Brera in Italy, the German Leibniz Institute for Solid State and Materials Research in Dresden, and the French Institute Fresnel. Sputtering with different parameters leads to iridium films with different properties. The current work is focused on the microstructure of the iridium coatings to study the influence of the substrate and of the argon gas pressure on the thin film growing process. Correlations between coating density, surface micro-roughness, the crystalline structure of the iridium layers, and the expected reflectivity of the X-ray mirror as well as coating stress effects are presented and discussed. The final goal of the project is to integrate the produced prototype mirrors into an X-ray telescope module. On a longer timescale measurements of the mirror modules optical performance are planned at the X-ray test facility PANTER. KW - X-ray KW - telescope KW - mirror KW - iridium KW - coating KW - Iridium KW - Röntgenteleskop Y1 - 2017 U6 - https://doi.org/10.1117/12.2273988 VL - 2017 IS - 10399 SP - 103991C-1 EP - 103991C-8 PB - SPIE ER - TY - JOUR A1 - Hudec, Rene A1 - Döhring, Thorsten ED - Slovak Academy of Sciences Astronomical Institute, T1 - JEUMICO: Czech-Bavarian astronomical X-ray optics project JF - Contributions of the Astronomical Observatory Skalnaté Pleso N2 - Within the project JEUMICO, an acronym for Joint European Mirror Competence, the Aschaffenburg University of Applied Sciences and the Czech Technical University in Prague started a collaboration to develop mirrors for X-ray telescopes. Corresponding mirror segments use substrates of at silicon wafers which are coated with thin iridium � lms, as this material is promising high re ectivity in the X-ray range of interest. The sputtering parameters are optimized in the context of the expected re ectivity of the coated X-ray mirrors. In near future measurements of the assembled mirror modules optical performances are planned at an X-ray test facility. KW - JEUMICO KW - astronomy KW - mirror KW - iridium KW - Iridium KW - Spiegelteleskop Y1 - 2017 UR - https://www.ta3.sk/caosp/Eedition/Abstracts/2017/Vol_47/No_2/pp170-177_abstract.html VL - 2017 IS - 47 SP - 170 EP - 177 ER - TY - CHAP A1 - Stehlikova, Veronika A1 - Urban, Martin A1 - Nentvich, Ondrej A1 - Inneman, Adolf A1 - Döhring, Thorsten A1 - Probst, Anne-Catherine ED - Hudec, Rene T1 - Study of lobster eye optics with iridium coated X-ray mirrors for a rocket experiment T2 - Proceedings of the International Society for Optics and Photonics (SPIE) N2 - In the field of astronomical X-ray telescopes, different types of optics based on grazing incidence mirrors can be used. This contribution describes the special design of a lobster-eye optics in Schmidt's arrangement, which uses dual reflection to increase the collecting area. The individual mirrors of this wide-field telescope are made of at silicon wafers coated with reflecting iridium layers. This iridium coatings have some advantages compared to more common gold layers as is shown in corresponding simulations. The iridium coating process for the X-ray mirrors was developed within a cooperation of the Aschaffenburg University of Applied Sciences and the Czech Technical University in Prague. Different mirror parameters essential for a proper function of the X-ray optics, like the surface microroughness and the problematic of a good adhesion quality of the coatings were studied. After integration of the individual mirrors into the final lobster-eye optics and the corresponding space qualification testing it is planned to fly the telescope in a recently proposed NASA rocket experiment. KW - Lobster Eye KW - Iridium KW - mirror KW - coating KW - Iridium KW - Spiegelteleskop KW - optische Schicht Y1 - 2017 U6 - https://doi.org/10.1117/12.2265769 VL - 2017 IS - 10235 SP - 1023505-1 EP - 1023505-7 PB - SPIE International Society for Optics and Photonics CY - Bellingham WA ER - TY - CHAP A1 - Döhring, Thorsten A1 - Probst, Anne-Catherine A1 - Stollenwerk, Manfred A1 - Emmerich, Florian A1 - Stehlíková, Veronika A1 - Inneman, Adolf ED - Hudec, René ED - Pina, Ladislav T1 - Prototyping iridium coated mirrors for X-ray astronomy T2 - Proceedings of the International Society for Optics and Photonics N2 - X-ray astronomy uses space-based telescopes to overcome the disturbing absorption of the Earth´s atmosphere. The telescope mirrors are operating at grazing incidence angles and are coated with thin metal films of high-Z materials to get sufficient reflectivity for the high-energy radiation to be observed. In addition the optical payload needs to be light-weighted for launcher mass constrains. Within the project JEUMICO, an acronym for “Joint European Mirror Competence”, the Aschaffenburg University of Applied Sciences and the Czech Technical University in Prague started a collaboration to develop mirrors for X-ray telescopes. The X-ray telescopes currently developed within this Bavarian- Czech project are of Lobster eye type optical design. Corresponding mirror segments use substrates of flat silicon wafers which are coated with thin iridium films, as this material is promising high reflectivity in the X-ray range of interest. The deposition of the iridium films is based on a magnetron sputtering process. Sputtering with different parameters, especially by variation of the argon gas pressure, leads to iridium films with different properties. In addition to investigations of the uncoated mirror substrates the achieved surface roughness has been studied. Occasional delamination of the iridium films due to high stress levels is prevented by chromium sublayers. Thereby the sputtering parameters are optimized in the context of the expected reflectivity of the coated X-ray mirrors. In near future measurements of the assembled mirror modules optical performances are planned at an X-ray test facility. KW - X-ray KW - iridium KW - mirror KW - lightweight optic KW - Lobster Eye KW - Iridium KW - Röntgenastronomie KW - Spiegelteleskop Y1 - 2017 U6 - https://doi.org/10.1117/12.2265931 VL - 2017 IS - 10235 SP - 1023504-1 EP - 1023504-8 PB - SPIE International Society for Optics and Photonics CY - Bellingham WA ER - TY - CHAP A1 - Döhring, Thorsten A1 - Probst, Anne-Catherine A1 - Stollenwerk, Manfred A1 - Wen, Mingwu A1 - Proserpio, Laura ED - den Herder, Jan-Willem A. ED - Takahashi, Tadayuki ED - Bautz, Marshall T1 - Development of low-stress Iridium coatings for astronomical x-ray mirrors T2 - Proceedings of SPIE 9905, Space Telescopes and Instrumentation 2016: Ultraviolet to Gamma Ray N2 - Previously used mirror technologies are not suitable for the challenging needs of future X-ray telescopes. This is why the required high precision mirror manufacturing triggers new technical developments around the world. Some aspects of X-ray mirrors production are studied within the interdisciplinary project INTRAAST, a German acronym for "industry transfer of astronomical mirror technologies". The project is embedded in a cooperation of Aschaffenburg University of Applied Sciences and the Max-Planck-Institute for extraterrestrial Physics. One important task is the development of low-stress Iridium coatings for X-ray mirrors based on slumped thin glass substrates. The surface figure of the glass substrates is measured before and after the coating process by optical methods. Correlating the surface shape deformation to the parameters of coating deposition, here especially to the Argon sputtering pressure, allows for an optimization of the process. The sputtering parameters also have an influence on the coating layer density and on the micro-roughness of the coatings, influencing their X-ray reflection properties. Unfortunately the optimum coating process parameters seem to be contrarious: low Argon pressure resulted in better micro-roughness and higher density, whereas higher pressure leads to lower coating stress. Therefore additional measures like intermediate coating layers and temperature treatment will be considered for further optimization. The technical approach for the low-stress Iridium coating development, the experimental equipment, and the obtained first experimental results are presented within this paper. KW - telescope KW - mirror KW - coating KW - iridium KW - astronomy KW - Röntgenspiegel KW - Iridium KW - Beschichtung Y1 - 2016 U6 - https://doi.org/10.1117/12.2232074 VL - 2016 IS - 9905 SP - 99056S-1 EP - 99056S-7 ER -