TY - GEN A1 - Döhring, Thorsten A1 - Stollenwerk, Manfred A1 - Proserpio, Laura A1 - Winter, Anita T1 - Transfer of astronomical mirror technologies – Project INTRAAST N2 - Poster KW - Optisches Glas KW - Raumfahrt Y1 - 2015 ER - TY - CHAP A1 - Döhring, Thorsten A1 - Stollenwerk, Manfred A1 - Gong, Qingqing A1 - Proserpio, Laura A1 - Winter, Anita A1 - Friedrich, Peter T1 - The challenge of developing thin mirror shells for future X-ray telescopes T2 - Proceedings of SPIE N2 - Previously used mirror technologies are not able to fulfil the requirements of future X-ray telescopes due to challenging requests from the scientific community. Consequently new technical approaches for X-ray mirror production are under development. In Europe the technical baseline for the planned X-ray observatory ATHENA is the radical new approach of silicon pore optics. NASA´s recently launched NuSTAR mission uses segmented mirrors shells made from thin bended glasses, successfully demonstrating the feasibility of the glass forming technology for X-ray mirrors. For risk mitigation also in Europe the hot slumping of thin glasses is being developed as an alternative technology for lightweight X-ray telescopes. The high precision mirror manufacturing requires challenging technical developments; several design trades and trend-setting decisions need to be made and are discussed within this paper. Some new technical and economic aspects of the intended glass mirror serial production are also studied within the recently started interdisciplinary project INTRAAST, an acronym for “industry transfer of astronomical mirror technologies”. The goal of the project, embedded in a cooperation of the Max-Planck-Institute for extraterrestrial Physics and the University of Applied Sciences Aschaffenburg, is to master the challenge of producing thin mirror shells for future X-ray telescopes. As a first project task the development of low stress coatings for thin glass mirror substrates have been started, the corresponding technical approach and first results are presented. KW - x-ray KW - telescope KW - astronomy KW - glass KW - Astronomie KW - Fernrohr KW - Optisches Glas Y1 - 2015 VL - 2015 IS - 9628 SP - 962809-1 EP - 962809-8 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 - TY - CHAP A1 - Döhring, Thorsten A1 - Stollenwerk, Manfred A1 - Proserpio, Laura A1 - Breunig, Elias A1 - Friedrich, Peter T1 - The challenging development of lightweight glass mirrors for future X-ray telescopes T2 - DGaO Proceedings N2 - Previously used mirror technologies are not able to fulfill the challenging requirements of future X-ray telescopes. A promising new technology under development is the hot slumping of thin glasses. Challenges, design trades and first results are presented, including the thermal shaping process, the development of low stress coatings and the mirror segments integration concept. KW - astronomy KW - telescope KW - mirror KW - X-ray KW - glass KW - Röntgenteleskop KW - Röntgenspiegel Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?nbn:de:0287-2016-B018-0 SN - 1614-8436 VL - 2016 PB - Deutsche Gesellschaft für angewandte Optik CY - Erlangen 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 - 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 - 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 - Probst, Anne-Catherine A1 - Döhring, Thorsten A1 - Zeising, Sebastian A1 - Salmaso, Bianca A1 - Stollenwerk, Manfred A1 - Proserpio, Laura T1 - Challenges in metrology of mirror segments for X-ray telescopes T2 - Proceedings of the 8th High Level Expert Meeting Asphere Metrology N2 - High angular resolution, large collecting area and reduced weight per unit area are required for astronomical X-ray telescopes of the next generation observatories. New technologies for processing X-ray mirrors are under development to fulfill these needs. One option is to realize a Wolter I type telescope constituted of several hundred nested thin and light-weight X-ray mirror segments. The individual mirror segments need to be coated with an about 100 nm thick film of a high-reflective material to enhance the reflectivity for X-rays. Thereby an accurate shape metrology of the segments is necessary to predict the angular resolution of the astronomical telescope as well as to control the development process of X-ray mirrors. We present the challenges in shape measurements of thin glasses used to control the coating process and first experimental results about the repeatability of the measurements. KW - metrology KW - mirror KW - telescope KW - Spiegelteleskop Y1 - 2017 UR - http://www.upob.de/index.php?option=com_phocadownload&view=category&download=198:8th-high-level-expert-meeting-2017-detailed-programme&id=21:upob-high-level-expert-meetings&Itemid=70 VL - 2017 IS - 8 PB - UTOB e.V. CY - Braunschweig 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 - 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 - GEN A1 - Döhring, Thorsten A1 - Probulla, Theodor A1 - Komzik, Richard A1 - Mann, Michael A1 - Sivanic, Peter A1 - Stollenwerk, Manfred ED - Hambalek, Lubomir T1 - Slovak-Bavarian collaboration on the development of telescope instrumentation N2 - Within the project SLOBATCO (Slovak-Bavarian Telescope Collaboration) the Astronomical Institute of the Slovak Academy of Sciences and Aschaffenburg University of Applied Sciences collaborate in the development and commissioning of the new Ø1.3 m astronomical telescope and the corresponding scientific instrumentation. The project is funded by the Bavarian Academic Center for Central, Eastern and Southeastern Europe (BAYHOST). Technical work packages are targeting filter wheel software for the VIS camera, additional IR filters, and an upgrade of the mirror coating facility by additional sputtering equipment. N2 - Poster KW - telescope KW - astronomy KW - instrumentation KW - Spiegelteleskop Y1 - 2018 UR - https://www.ta3.sk/conferences/75AI2018/posters/AP06.pdf 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 - 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 - 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 - 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 - 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 - 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 - 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 Jahrestagung N2 - With ground based optical telescopes astronomers observe celestial objects over a wide spectral range. As usually three or even more reflections at telescope mirrors are involved, good reflection properties of the mirror coatings are important. The aluminum evaporation technique has been - and is still - the standard solution for the reflective coatings of large astronomical mirrors. Such coatings have excellent reflectivity in the ultraviolet and in the visible, but perform poorly in the infrared. Silver is the metal having highest reflectivity for wavelengths longward of 400 nm, but isn´t the best choice for reflectivity in the ultraviolet and for blue light. To avoid degradation by oxidation, durable silver coatings need to be protected by transmitting overcoating layers. In the presented study, different metallic coatings – including unusual ones like sputtered iridium - are characterized to identify a coating that is most suitable for the spectral range from ultraviolet to infrared. Experimental results are compared to simulations based on the complex refractive indices of these materials. Thereby dependence of incidence angle and polarization is also considered. N2 - Poster KW - mirror KW - coating KW - iridium KW - astronomy KW - telescope KW - Spiegelteleskop Y1 - 2021 UR - https://dgao.de/jahrestagung/ VL - 2021 SP - 1 EP - 1 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 - 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 - 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 - GEN 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 Jahrestagung N2 - X-ray telescopes usually operate in space and are quite different from astronomical telescopes for visible light. For normal angles of incidence, optical light is reflected on the mirror surface, whereas X-rays are either transmitted or absorbed. However, also high reflectivity X-rays mirrors are possible, when the incident rays direction is almost parallel to the mirror surface. Such grazing incidence mirrors are usually coated with thin layers of precious metals like iridium, gold or platinum, as this result in high X-ray reflectivity. These noble metals offer a wide range of reflection up to high photon energies, but, due to a series of absorption edges, have low reflectivity in the 2 - 4 keV band and below. This contribution presents the development of innovative material combinations based on thin layers of iridium and chromium, followed by an additional layer of carbon-based materials. We also discuss corresponding production methods (like dip coating) for enhanced reflectivity mirror coatings of future X-ray telescopes. N2 - Poster KW - X-ray KW - mirror KW - coating KW - iridium KW - satellite KW - Röntgenstrahlung KW - Spiegelteleskop Y1 - 2021 UR - https://dgao.de/jahrestagung/ VL - 2021 SP - 1 EP - 1 ER - TY - CHAP A1 - Stehlikova, Veronika A1 - Döhring, Thorsten A1 - Schäfer, Tobias A1 - Stollenwerk, Manfred A1 - Friedrich, Peter A1 - Burwitz, Vadim A1 - Hartner, Gisela A1 - Bradshaw, Miranda A1 - Liao, Yingyu A1 - Pelliciari, Carlo T1 - X-ray reflectivity measurements at chromium-iridium tri-layer coatings T2 - Proceedings of SPIE N2 - Studying astronomical objects in the X-ray regime, iridium-based layer systems are highly effective reflective materials for telescopes mirrors. Aschaffenburg University and the Czech Technical University in Prague jointly developed stress compensated chromium-iridium coatings. To overcome the disturbing reflectivity reduction of the iridium absorption edge around 2 keV photon energy and improve general reflectivity at lower incident energies, thin overcoat layers of chromium have been applied in addition. Corresponding measurements at several X-ray lines have been performed on these samples at the PANTER test facility of the Max-Planck Institute for extraterrestrial Physics. A part of the experimental results and their comparison with theoretical simulations are presented in this contribution. KW - iridium KW - mirror KW - coating KW - reflectivity KW - X-ray KW - Röntgenastronomie KW - Röntgenteleskop Y1 - 2019 U6 - https://doi.org/http://dx.doi.org/10.1117/12.2530439 VL - 2019 IS - 11119 SP - 111191L-1 EP - 111191L-6 ER - TY - CHAP A1 - Witte, Gerd A1 - Stollenwerk, Manfred T1 - Energy saving of cooling water pumps for power plants using adjustable propeller blades T2 - International Rotating Equipment Conference 2008, Düsseldorf KW - Kühlwasseranlage KW - Energieeinsparung Y1 - 2008 ER - TY - CHAP A1 - Stollenwerk, Manfred T1 - DVD/R 16x high quality mass production - Vortrag auf der Conference Replication Expo, September 2005, Shanghai, China N2 - Vortrag auf der Conference Replication Expo September 2005, Shanghai, China KW - DVD-R Y1 - 2005 ER - TY - JOUR A1 - Mustorph, Heinz A1 - Stollenwerk, Manfred A1 - Bressau, Volker T1 - Current Developments in Optical Data Storage with Organic Dyes JF - Angewandte Chemie N2 - The main motivation for the development of digital data storage has been the improvement in play‐back quality and the increase in storage capacity. In 1982 Philips and Sony introduced the first technically and economically successful system based on this—the compact disc (CD) and a compatible player. A very broad diversity of optical data recording formats are available today, and a difference is drawn between prerecorded, recordable, and rewritable media. This Review gives an overview of the systems used, the main features of production, and then concentrates on the properties of the organic dyes that are used in recordable systems. Dyestuffs chemistry has gained the reputation of having become a mature field of activity. Is this prejudice or a justified swan song for dyestuffs chemistry? When applications in optical data storage are considered, it is evident that even today progresses such as CD‐R and DVD/R would not be feasible without functional dyes. KW - Optischer Speicher Y1 - 2006 VL - 45 IS - 13 SP - 2016 EP - 2035 ER - TY - JOUR A1 - Döhring, Thorsten A1 - Pribulla, Theodor A1 - Komzik, Richard A1 - Mann, Michael A1 - Sivanic, Peter A1 - Stollenwerk, Manfred T1 - Slovak-Bavarian collaboration on the development of telescope instrumentation JF - Contributions of the Astronomical Observatory Skalnate Pleso N2 - Within the project SLOBATCO (Slovak-Bavarian Telescope Collaboration) the Astronomical Institute of the Slovak Academy of Sciences and Aschaffenburg University of Applied Sciences collaborate in the development and commissioning of scientific instrumentation for the new Ø1.3 m astronomical telescope at the Skalnaté Pleso observatory. The joint project is funded by the Bavarian Academic Center for Central, Eastern and Southeastern Europe (BAYHOST). Planned technical work packages are targeting the filter wheel software for the VIS camera, additional IR filters, and an upgrade of the mirror coating facility by additional sputtering equipment. KW - telescope KW - instrumentation KW - filter KW - camera KW - coating KW - Spiegelteleskop Y1 - 2019 UR - https://www.ta3.sk/caosp/Eedition/FullTexts/vol49no2/pp154-158.pdf VL - 2019 IS - 49 / 2 SP - 154 EP - 158 ER - TY - GEN A1 - Mann, Michael A1 - Döhring, Thorsten A1 - Pribulla, Theodor A1 - Komzik, Richard A1 - Sivanic, Peter A1 - Stollenwerk, Manfred ED - Skopal, Augustin T1 - Power quality evaluation for observatories N2 - Within the project SLOBATCO the question did arise, to what extend observatories have to rely on adequate power quality, e.g. the perfect sinusoidal shape of supply voltage and current, in order to ensure safe operation and accurate measurement results. International power quality standards are put in perspective with requirement specifications. Telescope operators indicate partial or total loss of function of measurement instruments. Measurements conducted during SLOBATCO project substantiate the need for power quality measurement campaigns. N2 - Poster KW - instrumentation KW - site testing KW - telescope KW - Sternwarte KW - Elektrizitätsversorgung Y1 - 2019 ER - TY - CHAP A1 - Stollenwerk, Manfred T1 - The Energy Market within the next 20 years T2 - 6 MEAI, Wien KW - Energiemarkt Y1 - 2006 ER - TY - JOUR A1 - Stollenwerk, Manfred A1 - Gattinger, P. T1 - Process challenges of high Speed DVD/R manufacturing JF - One to One magazine KW - DVD-R KW - Herstellung Y1 - 2005 VL - 2005 IS - March SP - 55 EP - 58 ER - TY - CHAP A1 - Stollenwerk, Manfred T1 - Efficient DVD/R Production T2 - Optical Disc Seminar Asia ODSA, Teipei KW - DVD-R KW - Produktion Y1 - 2005 ER - TY - GEN A1 - Stollenwerk, Manfred T1 - Die optische Datenspeicherung auf CD und DVD T2 - Übersichtsvortrag auf der Fachtagung „Die Kunststoffoberfläche“ des Süddeutschen Kunststoffzentrums Würzburg N2 - Vortrag KW - Optischer Speicher Y1 - 2005 ER - TY - GEN A1 - Stollenwerk, Manfred T1 - Basics of Recordable Media Production T2 - Vortrag auf dem “International Recordable Media Technology Seminar”, Dubai N2 - Vortrag KW - CD-R KW - DVD-R Y1 - 2003 ER - TY - GEN A1 - Stollenwerk, Manfred T1 - Correlation of DVD-Recordable Disc Performance and Process Parameters T2 - Vortrag auf der „Replication EXPO 2003“, Shanghai, China N2 - Vortrag KW - DVD-R Y1 - 2003 ER - TY - GEN A1 - Stollenwerk, Manfred T1 - CD-Recordable CD-Rewriteable T2 - Vortrag auf der REPLItech Summit (Conference) São Paulo, Brazil N2 - Vortrag KW - CD-R Y1 - 1998 ER - TY - JOUR A1 - Stollenwerk, Manfred A1 - Alexander, Morgan A1 - Short, Robert A1 - Jones, Frank A1 - Zabold, Jochen A1 - Michaeli, Walter T1 - An X-ray photoelectron spectroscopic investigation into the chemical structure of deposits formed from hexamethyldisiloxane/ oxygen plasmas JF - Journal of Materials Science N2 - The effect of oxygen addition to microwave-sustained plasmas of hexamethyldisiloxane (HMDSO) has been investigated. Attention was directed to the solid products formed on aluminium substrates (plasma deposits). To enable a quantitative analysis of these, X-ray photoelectron spectroscopy (XPS) of standard silicon-containing materials was carried out. When suitable charge correction is applied to the XP spectra of HMDSO/O2 plasma deposits, a number of very clear trends emerge. From changes in elemental composition, core line binding energies (Si2p, C 1s, and O 1s) and widths, we show how oxygen addition to the plasma affects the chemical nature of the plasma deposit. The data reported also provide (some limited) information on the reactions taking place in the plasma. KW - Photoelektronenspektroskopie Y1 - 1996 VL - 31 IS - 7 SP - 1879 EP - 1885 ER - TY - JOUR A1 - Alexander, Morgan A1 - Short, Robert A1 - Jones, Frank A1 - Stollenwerk, Manfred A1 - Mathar, Gerd A1 - Zabold, Jochen A1 - Michaeli, Walter T1 - The heterogeneous nature of deposits from hexamethyldisiloxane/oxygen plasmas JF - Ceramic films and coatings KW - Hexamethyldisiloxan KW - Sauerstoff KW - Plasma Y1 - 1995 VL - 1995 IS - 54 SP - 87 EP - 99 ER - TY - BOOK A1 - Wolters, Leo A1 - Stollenwerk, Manfred A1 - Berthold, J. T1 - Die Plasmatechnologie und ihre Einsatzmöglichkeiten KW - Plasmatechnik Y1 - 1994 N1 - Lehrbuch des Technologie-Transfer-Rings Handwerk Nordrhein-Westfalen CY - Aachen ER - TY - GEN A1 - Michaeli, Walter A1 - Stollenwerk, Manfred A1 - Zell, Harald T1 - Variation der Oberflächenspannung bei flächigen Substraten und Verstärkungsfasern sowie der Einfluß auf die Faser/Matrix-Haftung bei faserverstärkten Kunststoffen KW - Faserverstärkter Kunststoff Y1 - 1994 N1 - Beitrag zum Seminar “Ausgewählte Anwendungen der Plasmapolymerisation“ der Plasmatechnologieinitiative NRW, Aachen, Oktober 1994 ER - TY - CHAP A1 - Michaeli, Walter A1 - Stollenwerk, Manfred A1 - Steinkamp, F. A1 - Zell, Harald T1 - Plasmabehandlung von Glasfasern für faserverstärkte Kunststoffe T2 - 6. Bundesdeutsche Fachtagung Plasmatechnologie, Wuppertal KW - Faserverstärkter Kunststoff KW - Glasfaserverstärkter Kunststoff Y1 - 1994 ER - TY - GEN A1 - Stollenwerk, Manfred A1 - Zell, Harald T1 - Veredeln von Kunststoffoberflächen mittels Mikrowellenplasmapolymerisation KW - Plasmapolymerisation KW - Mikrowellentechnik Y1 - 1994 N1 - Seminar zur FAKUMA der Firma Schall Kongress GmbH, Friedrichshafen, Oktober 1994 ER - TY - JOUR A1 - Michaeli, Walter A1 - Telgenbüscher, Klaus A1 - Stollenwerk, Manfred A1 - Mathar, Gerd A1 - Zell, Harald T1 - Plasmapolymerisierte Schichten: Neue Vielfalt der Funktionen JF - Schweizer Maschinenbau KW - Plasmapolymerisation Y1 - 1994 VL - 1994 IS - 41 SP - 90 EP - 93 ER - TY - GEN A1 - Stollenwerk, Manfred T1 - Das Abscheiden von kratzfesten, hydrophilen und hydrophoben Schichten mittels Plasmapolymerisation KW - Plasmapolymerisation Y1 - 1993 N1 - Beitrag zum Seminar “Plasmapolymerisation“ der Firma CP-Tec, München, November 1993 ER - TY - JOUR A1 - Leiber, Jörn A1 - Michaeli, Walter A1 - Telgenbüscher, Klaus A1 - Stollenwerk, Manfred T1 - UV protecting layers on PVC made by plasma polymerization JF - Journal of Vinyl Technology KW - Plasmapolymerisation Y1 - 1993 VL - 15 IS - 2 SP - 57 EP - 61 ER - TY - JOUR A1 - Michaeli, Walter A1 - Stollenwerk, Manfred A1 - Telgenbüscher, Klaus T1 - Plasmabehandlung - Ein umweltfreundliches Verfahren zur Oberflächenvorbehandlung und -reinigung JF - Scope-Journal Special KW - Plasmatechnik KW - Oberflächenbehandlung Y1 - 1993 VL - 1993 IS - 16 SP - 21 EP - 23 ER - TY - GEN A1 - Zell, Harald A1 - Telgenbüscher, Klaus A1 - Stollenwerk, Manfred T1 - Kratzfeste Beschichtungen von Kunststoffen mittels Plasmapolymerisation KW - Plasmapolymerisation Y1 - 1993 N1 - Seminar “Hartstoffbeschichtungen“, Haus der Technik, Essen, 28./29. September 1993 ER - TY - CHAP A1 - Michaeli, Walter A1 - Leiber, Jörn A1 - Telgenbüscher, Klaus A1 - Stollenwerk, Manfred T1 - Plasma polymerization in automotive industries - A possibility for the reduction of permeation in plastic fuel tanks T2 - 26th intern. Symposium on Automotive Technology and Automation, Aachen Tagungsband KW - Plasmapolymerisation KW - Kraftfahrzeugindustrie Y1 - 1993 SP - 469 EP - 476 ER - TY - GEN A1 - Stollenwerk, Manfred T1 - Oberflächenmodifikation mittels Plasmatechnik KW - Plasmatechnik KW - Oberflächenbehandlung Y1 - 1993 N1 - VDI-Werkstoff-Forum auf der Hannovermesse, April 1993 ER - TY - JOUR A1 - Meyer, R. A1 - Hardtdegen, Hilde A1 - Grützmacher, Detlev A1 - Carius, R. A1 - Stollenwerk, Manfred A1 - Balk, Peter T1 - Optical and structural properties of MOVPE grown GaxIn1-xAs/InP strained multiple quantum well structures JF - Journal of Electronic Materials N2 - This paper presents a study of the structural and optical properties of strained GaInAs/ InP multiple quantum well (MQW) structures fabricated by LP-MOVPE. The composition of the Ga x In1−x As films ranged fromx = 0.17 tox = 1.0 and was determined by sputtered neutral mass spectrometry (SNMS) on thick layers. The structures of the MQW samples with well widths from 1.5 to 5 nm were investigated by high resolution x-ray diffraction (HR-XRD). Simulations of the diffraction patterns showed that transition layers of approximately 2 monolayer (ML) thickness with high lattice mismatch exist at the interfaces. Photoluminescence (PL) measurements indicate well widths of a multiple of a monolayer with local variations of one monolayer. The PL peak energies vary smoothly with the Ga concentration. These results were confirmed by optical absorption measurements. KW - Galliumarsenid KW - Indiumarsenid KW - Indiumphosphid Y1 - 1992 VL - 21 IS - 3 SP - 293 EP - 298 ER - TY - JOUR A1 - Oschinowo, John A1 - Forchel, Alfred A1 - Dreybrodt, Jörg A1 - Emmerling, Monika A1 - Gyuro, Imre A1 - Speier, Peter A1 - Grützmacher, Detlev A1 - Stollenwerk, Manfred T1 - Lateral thermal stability modulation for the definition of InGaAs/InP wires JF - Microelectronic Engineering N2 - We have investigated a novel technique for the definition of semiconductor wires. By the selective local removal of the InP top barrier layer wire patterns in which the top material varies between InP and InGaAs are formed from an InGaAs/InP quantum well. In a subsequent annealing step the top InGaAs layer shows substantially stronger interdiffusion than the InP covered regions (wires). By using luminescence spectroscopy we show that this defectfree enhanced interdiffusion can be used to obtain a lateral energy barrier. KW - Indiumarsenid KW - Galliumarsenid Y1 - 1992 VL - 17 IS - 1–4 SP - 505 EP - 508 ER - TY - JOUR A1 - Wolter, Karl A1 - Schwedler, Ralf A1 - Gallmann, B. A1 - Jaekel, Christian A1 - Stollenwerk, Manfred A1 - Camassel, Jean A1 - Laurenti, Jean Pierre T1 - Optical characterization of strained InGaAs/InP quantum well structures JF - Microelectronic Engineering N2 - The effects of strain on the optical properties ofmultiple-quantum well structures grown by low pressure metal organic vapor phase epitaxy have been investigated by photoluminescence spectroscopy. The investigated composition range is varied between 0.17 ≤ xGa ≤ 1.00. Sputtered neutrals mass spectroscopy has been used to calibrate the growth interpolated nominal compositions. Distinct peaks from monolayer variations of well thickness are observed from all samples. The analysis of the PL-spectra leads to the assumption of an intermediate layer of InAs0.65P0.35 at the InP to In1−ϰGaχAs(lower) interface. KW - Indiumarsenid KW - Galliumarsenid Y1 - 1991 VL - 15 IS - 1–4 SP - 593 EP - 596 ER - TY - JOUR A1 - Schwedler, Ralf A1 - Wolter, Karl A1 - Gallmann, B. A1 - Grützmacher, Detlev A1 - Stollenwerk, Manfred A1 - Kurz, H. T1 - Optical characterization of In-rich strained In1-xGaxAs/InP single- and multiple-quantum-wells JF - Materials Science and Engineering: B N2 - We report on the photoluminescence spectroscopy of a large set of strained In1−xGaxAs/InP quantum well structures grown by low pressure metallo-organic vapour phase epitaxy. Distinct peaks from monolayer steps are observed in all samples. For the first time, data on indium-rich In1−xGaxAs/InP structures with complementary gallium contents as low as xGa = 0.07 and xGa = 0.11 are reported. The sample quality appears independent of the number of quantum wells stacked in the structure. With decreasing gallium content, a decrease in luminescence intensity is observed, which is related to an increase in the number of non-radiative recombination centres with respect to lattice-matched samples. KW - Photolumineszenzspektroskopie KW - Indiumarsenid KW - Galliumarsenid KW - Indiumphosphid Y1 - 1991 VL - 9 IS - 1–3 SP - 297 EP - 300 ER - TY - CHAP A1 - Mahlzahn, Erik A1 - Heuken, Michael A1 - Grützmacher, Detlev A1 - Stollenwerk, Manfred A1 - Heime, Klaus T1 - Advanced InGaAs/InP p-type sydomorphic MODFET T2 - Proceedings of the SPIE KW - Indiumarsenid KW - Galliumarsenid KW - Indiumphosphid Y1 - 1991 VL - 1362 SP - 199 EP - 204 ER - TY - CHAP A1 - Glade, M. A1 - Hergeth, J. A1 - Stollenwerk, Manfred A1 - Grützmacher, Detlev A1 - Balk, Peter T1 - Effects of zinc diffusion during MOPVE on performance of InP/InGaAsP double heterostructure lasers T2 - Proceedings of the 17th International Symposium of GaAs and related Compounds, Jersey, UK KW - Indiumphosphid KW - Indiumarsenid KW - Galliumarsenid Y1 - 1990 SP - 579 EP - 584 ER - TY - CHAP A1 - Mahlzahn, Erik A1 - Heuken, Michael A1 - Grützmacher, Detlev A1 - Stollenwerk, Manfred A1 - Heime, Klaus T1 - High mobility and high sheet density p-type pseudomorphic MODFET T2 - Proceedings of the 17th International Symposium of GaAs and related Compounds, Jersey, UK KW - HEMT Y1 - 1990 SP - 579 EP - 584 ER - TY - JOUR A1 - Alexander, Morgan A1 - Short, Robert A1 - Jones, Frank A1 - Stollenwerk, Manfred A1 - Mathar, Gerd A1 - Zabold, Jochen A1 - Michaeli, Walter T1 - An XPS investigation into the chemical structure of deposits formed from hexamethyldisiloxane/oxgen plasmas JF - Journal of Materials Science KW - Hexamethyldisiloxan KW - Plasma Y1 - 1996 VL - 31 SP - 1879 EP - 1885 ER - TY - JOUR A1 - Michaeli, Walter A1 - Stollenwerk, Manfred A1 - Telgenbüscher, Klaus A1 - Leiber, Jörn T1 - Vorbehandeln und Beschichten von Kunststoffteilen in PE-CVD-Anlagen JF - Maschinenmarkt KW - Kunststoffprodukt KW - Oberflächenbehandlung Y1 - 1993 VL - 99 IS - 29 SP - 42 EP - 48 ER - TY - JOUR A1 - Michaeli, Walter A1 - Telgenbüscher, Klaus A1 - Leiber, Jörn A1 - Stollenwerk, Manfred T1 - Plasmapolymerisation zur Veredelung von Kunststoffoberflächen JF - Dünne Schichten KW - Plasmapolymerisation KW - Kunststoffprodukt KW - Oberflächenbehandlung Y1 - 1992 VL - 1992 IS - 3 SP - 34 EP - 38 ER - TY - JOUR A1 - Michaeli, Walter A1 - Leiber, Jörn A1 - Telgenbüscher, Klaus A1 - Stollenwerk, Manfred T1 - Plasmapolymerisation: Kunststoffe beschichten JF - Industrieanzeiger KW - Plasmapolymerisation Y1 - 1992 VL - 1992 IS - 43 SP - 58 EP - 60 ER - TY - CHAP A1 - Stollenwerk, Manfred A1 - Michaeli, Walter A1 - Telgenbüscher, Klaus A1 - Leiber, Jörn A1 - Londschein, Martin T1 - Verbesserung von Verbundwerkstoffen durch Plasmabehandlung der Verstärkungsfasern KW - Faserverstärkter Kunststoff Y1 - 1992 N1 - 31. Internationale Chemiefasertagung Dornbirn, Österreich, September 1992 ER - TY - JOUR A1 - Stollenwerk, Manfred A1 - Grützmacher, Detlev T1 - GaInAs/GaInAsP SC-MQW-laser emitting at 1.35 µm grown by LP-MOVPE JF - Microelectronic Engineering KW - Quantenwell-Laser KW - Galliumarsenid KW - Indiumarsenid Y1 - 1991 VL - 1991 IS - 15 SP - 263 EP - 266 ER - TY - CHAP A1 - Stollenwerk, Manfred A1 - Grützmacher, Detlev A1 - Heime, Klaus A1 - Möhrle, Martin A1 - Fidorra, Frank T1 - GaInAs/GaInAsP SC-MQW Laser mit einer Emissionswellenlänge von 1,35 µm deponiert mit Hilfe der LP-MOVPE KW - Quantenwell-Laser KW - Galliumarsenid KW - Indiumarsenid Y1 - 1991 N1 - Beitrag zum Kolloquium “Photonische Komponenten“, Universität Ulm, April 1991 ER - TY - CHAP A1 - Stollenwerk, Manfred A1 - Grützmacher, Detlev A1 - Schwedler, Ralf A1 - Meyer, R. A1 - Hardtdegen, Hilde A1 - Kux, A. A1 - Heime, Klaus T1 - Systematic study of strained GaInAs/InP grown by MOVPE KW - Galliumarsenid KW - Indiumarsenid Y1 - 1991 N1 - 4th European workshop on metallorganic vapour phase epitaxy, Nijmegen, NL, 1991 ER - TY - JOUR A1 - Oschinowo, John A1 - Forchel, Alfred A1 - Grützmacher, Detlev A1 - Stollenwerk, Manfred A1 - Heuken, Michael A1 - Heime, Klaus T1 - Photoluminescence study of interdiffusion in In0,53Ga0,47/As/InP surface quantum wells JF - Applied Physics Letters N2 - We have investigated the thermal stability and interdiffusion of In0.53Ga0.47As/InP surface quantum wells. In these structures the optically active InGaAs layer is bounded on one side by vacuum and on the other side by InP. We obtain well‐defined photoluminescence emission spectra with high intensity. After rapid thermal annealing at temperatures between 500 and 900 °C (annealing time 1 min) we observe strong emission energy shifts of up to 316 meV. By using a simple model of ion intermixing we estimate large interdiffusion coefficients (e.g., 1.7×10−14 cm2 s−1 for T=900 °C) and an activation energy of 1.3 eV for the surface quantum wells. KW - Photolumineszenz Y1 - 1992 VL - 60 IS - 21 SP - 2660 EP - 2662 ER - TY - CHAP A1 - Oschinowo, John A1 - Forchel, Alfred A1 - Grützmacher, Detlev A1 - Stollenwerk, Manfred T1 - RTA study of thermal stability and interdiffusion of InGaAs/InP quantum wells - the influence of InGaAs cap layers T2 - Third International Conference Indium Phosphide and Related Materials Cardiff/Wales N2 - A study of the thermal stability of InGaAs/InP quantum wells with different top barrier compositions that used rapid thermal annealing at temperatures between 600 degrees C and 950 degrees C (annealing time 1 min) is discussed. The thermal interdiffusion effects were evaluated by photoluminescence spectroscopy. From the temperature dependence of the luminescence energy shifts the interdiffusion coefficients and activation energies are determined. KW - Photolumineszenzspektroskopie KW - Indiumarsenid KW - Galliumarsenid KW - Indiumphosphid Y1 - 1991 SP - 606 EP - 609 ER - TY - JOUR A1 - Shi, Chang-Xin A1 - Grützmacher, Detlev A1 - Stollenwerk, Manfred A1 - Wang, Qing-Kang A1 - Heime, Klaus T1 - High-performance undoped InP/n-InP/GaAs MSM photodetectors grown by LP-MOVPE JF - IEEE Transactions on Electron Devices KW - Indiumarsenid KW - Galliumarsenid Y1 - 1992 VL - 39 IS - 5 SP - 1028 EP - 1031 PB - IEEE 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 - 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 - CHAP A1 - Stanik, Eva A1 - Döhring, Thorsten A1 - Pregler, Jan A1 - Stollenwerk, Manfred A1 - Hildenbrand, Georg T1 - Spectral measurements and life science experiments using extreme radiation exposures at high altitude T2 - Proceedings of SPIE N2 - The ASTRABAX project ("Aschaffenburg Stratospheric Balloon Experiment"), being funded for the years 2024 to 2026, is designed as a multimodal platform for the investigation of radiation exposures at high altitude. The UV-C spectral region is of special interest. Spectral measurements observe this region of interest using miniature UV-VIS spectrometers. The platform also contains a radiation dosimetry, a power source for on-board electronics, and common shielding setups for multiple spectral combinations. Human cells are exposed simultaneously to radiation of different compositions as particle, X-ray and UV radiation. After the flight, possible changes in the spatial chromatin organization are examined. Material samples intended for the development of satellite components are irradiated also. Investigations under such conditions are realistic and crucial for high altitude flights in the atmosphere, for space flights as well as for comparable exposures on other objects of the solar system, and even for exoplanet habitats to some extent. KW - Ultraviolet radiation KW - Balloons KW - Solar radiation KW - Spectrometers KW - Diffusers KW - Spektroskopie KW - Messung KW - Ultraviolett KW - Sonnenstrahlung Y1 - 2024 UR - https://doi.org/10.1117/12.3028519 U6 - https://doi.org/10.1117/12.3028519 VL - 2024 IS - 13024 SP - 130240M EP - 130240M ER - TY - GEN A1 - Döhring, Thorsten A1 - Stanik, Eva A1 - Pregler, Jan A1 - Stollenwerk, Manfred A1 - Hildenbrand, Georg T1 - Forschung zu Strahlenschäden mit dem Stratosphärenballon-Experiment ASTRABAX N2 - Das für die Jahre 2024 bis 2026 geförderte Projekt ASTRABAX („Aschaffenburger Stratosphärenballon- Experiment“) ist als multimodale Plattform der Material- und Biowissenschaften für Untersuchungen bei extremen Strahlenbelastungen in großer Höhe konzipiert. Dabei ist der UV-C-Spektralbereich von besonderem Interesse und wird mit Miniatur-UV-Spektrometern untersucht. Die Plattform des Ballonexperimentes umfasst eine gemeinsame Strahlungsdosimetrie, eine Stromquelle für die Bordelektronik und Abschirmungen für mehrere Bestrahlungskombinationen. Biologische Zellen werden Kombinationen aus Partikel-, Röntgen- und UV-Strahlung ausgesetzt. Nach dem Flug werden mögliche Veränderungen in der räumlichen Chromatinorganisation mittels hochauflösender Mikroskopie untersucht. Auswirkungen von Kombinationen aus hoch- und niederenergetischer Strahlung sind bisher nicht ausreichend erforscht und beschrieben. Zusätzlich werden auch für Satelliten relevante Materialproben bestrahlt. Untersuchungen unter solchen Bedingungen sind realistisch und relevant für Flüge in der Stratosphäre, für Raumflüge sowie für vergleichbare Expositionen bei anderen Objekten des Sonnensystems oder Exoplaneten-Habitaten. N2 - Poster KW - Weltraumtechnik KW - Radiometrie KW - Biomedizin KW - Stratosphären-Ballon KW - Strahlenbelastung Y1 - 2024 UR - https://www.dgao-proceedings.de/abstract/abstract_only.php?id=3018 SP - 1 EP - 1 ER - TY - CHAP A1 - Mann, Michael A1 - Wenzler, Sebastian A1 - Döhring, Thorsten A1 - Stollenwerk, Manfred A1 - Pribulla, Theodor A1 - Sivanič, Peter A1 - Komžík, Richard ED - Karl Friedrich, Zieghahn T1 - Stromversorgung als Umweltfaktor: Analyse der elektrischen Netzqualität in astronomischen Observatorien T2 - Umwelteinflüsse erfassen, simulieren, bewerten KW - Netzqualität KW - Astronomische Observatorien KW - EMV KW - Erdung KW - Sternwarte KW - Elektrizitätsversorgung Y1 - 2022 SN - 978-3-9818507-7-2 VL - 2022 SP - 193 EP - 207 PB - Gesellschaft für Umweltsimulation e.V. ER - TY - GEN A1 - Stanik, Eva A1 - Döhring, Thorsten A1 - Pregler, Jan A1 - Stollenwerk, Manfred A1 - Hildenbrand, Georg T1 - Spectral measurements and life science experiments using extreme radiation exposures at high altitude N2 - The ASTRABAX project ("Aschaffenburg Stratospheric Balloon Experiment"), being funded for the years 2024 to 2026, is designed as a multimodal platform for the investigation of radiation exposures at high altitude. Miniature UV-VIS spectrometers observe the UV-C spectral region. The platform also contains a radiation dosimetry, a power source for on-board electronics, and common shielding setups for multiple spectral combinations. The effects of combinations of high- and low-energy rays on human cells haven´t been sufficiently investigated and described so far. Investigations under such conditions are realistic and crucial for high altitude flights in the atmosphere, for space flights as well as for comparable exposures on other objects of the solar system, and even for exoplanet habitats to some extent. N2 - Poster KW - Balloons KW - Diffusers KW - Solar radiation KW - Spectrometers KW - Ultraviolet radiation KW - Stahlenbelastung KW - Stratosphären-Ballon Y1 - 2024 ER - TY - CHAP A1 - Mann, Michael A1 - Döhring, Thorsten A1 - Stollenwerk, Manfred A1 - Priebsch, Alessandro A1 - Pribulla, Theodor A1 - Komžík, Richard M. A1 - Sivanic, Peter ED - Storrie-Lombardi, Lisa J. ED - Benn, Chris R. ED - Chrysostomou, Antonio T1 - Advanced power quality measurement techniques at the electric power grid of astronomical observatories T2 - Observatory Operations: Strategies, Processes, and Systems X, Conference of SPIE 13098, 17 - 20 June 2024 KW - Sternwarte KW - Elektrizitätsversorgung Y1 - 2024 U6 - https://doi.org/10.1117/12.3016562 PB - SPIE ER - 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 -