@inproceedings{StehlikovaDoehringSchaeferetal.2019, author = {Stehlikova, Veronika and D{\"o}hring, Thorsten and Sch{\"a}fer, Tobias and Stollenwerk, Manfred and Friedrich, Peter and Burwitz, Vadim and Hartner, Gisela and Bradshaw, Miranda and Liao, Yingyu and Pelliciari, Carlo}, title = {X-ray reflectivity measurements at chromium-iridium tri-layer coatings}, series = {Proceedings of SPIE}, volume = {2019}, booktitle = {Proceedings of SPIE}, number = {11119}, organization = {Max-Planck-Institut f{\"u}r Extraterrestrische Physik}, doi = {http://dx.doi.org/10.1117/12.2530439}, pages = {111191L-1 -- 111191L-6}, year = {2019}, abstract = {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.}, subject = {R{\"o}ntgenastronomie}, language = {en} } @article{StollenwerkDoehringFreudenmannetal.2021, author = {Stollenwerk, Manfred and D{\"o}hring, Thorsten and Freudenmann, Dominic and Sch{\"a}fer, Tobias and Stadtm{\"u}ller, Johannes and R{\"o}cke, Nicole}, title = {Sputtered highly effective iridium catalysts: a new approach for green satellite propulsion}, series = {Journal of Materials Science}, volume = {2021}, journal = {Journal of Materials Science}, number = {2021}, doi = {https://doi.org/10.1007/s10853-021-05897-z}, pages = {1 -- 11}, year = {2021}, abstract = {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.}, subject = {Iridium}, language = {en} }