Dokument-ID Dokumenttyp Autoren/innen Persönliche Herausgeber/innen Haupttitel Abstract Auflage Verlagsort Verlag Herausgeber (Institution) Erscheinungsjahr Titel des übergeordneten Werkes Jahrgang/Band ISBN Veranstaltung Veranstaltungsort Beginndatum der Veranstaltung Enddatum der Veranstaltung Ausgabe/Heft Erste Seite Letzte Seite URN DOI Lizenz Datum der Freischaltung OPUS4-577 Zeitschriftenartikel Dörfel, Ilona; Wäsche, Rolf; Rabe, Torsten; Steinborn, Gabriele Tribological Induced Microstructural Changes in Subsurface Layers of Si3N4-Based Materials Aedermannsdorf Trans Tech Publ. 1994 Key engineering materials 89-91 763 767 2016-02-19 OPUS4-651 Zeitschriftenartikel Dörfel, Ilona; Urban, Ingrid TEM-Untersuchungen der Randzonenschädigung von Aluminiumoxidkeramiken nach Schleifbearbeitung Es werden elektronenmikroskopische Untersuchungsergebnisse an Al2O3-Keramiken, die verschiedenen Oberflächenbearbeitungsverfahren unterworfen wurden, vorgestellt. Die Untersuchungen dienen dem Ziel der Optimierung der Oberflächenbearbeitung von keramischen Werkstoffen, wobei der Einfluß leistungsfähiger Bearbeitungsverfahren auf die Ausbildung möglichst schädigungsarmer Oberflächenschichten, die keinen negativen Einfluß auf Festigkeitskennwerte aufweisen, betrachtet wird. Die Wirkung verschiedener Schleif- und Polierprozesse auf Oberflächenveränderungen bearbeiteter Werkstücke wird dargestellt. Es wurde sowohl die Mikrostruktur der geschädigten Randzonenschicht als auch die des unbeeinflußten Grundmaterials mit elektronenmikroskopischen Methoden charakterisiert. Die verschiedenen Schädigungsstadien gestatten eine Einschätzung der Stärke des Störungseintrages in das Material durch verschiedene Schleif- und Polierprozesse. Weinheim Wiley-VCH Verl. 1996 Materialwissenschaft und Werkstofftechnik = Materials science and engineering technology 27 6 307 312 10.1002/mawe.19960270609 2016-02-19 OPUS4-3496 Zeitschriftenartikel Österle, Werner; Dörfel, Ilona; Gesatzke, Wolfgang; Rooch, Heidemarie; Urban, Ingrid Charakterisierung tribologischer Kontakte mit FIB und TEM München Hanser 2004 Praktische Metallographie = Practical metallography 41 4 166 179 2016-02-19 OPUS4-2514 Zeitschriftenartikel Ressel, P.; Österle, Werner; Urban, Ingrid; Dörfel, Ilona; Klein, A.; Vogel, K.; Kräutle, H. Transmission electron microscopy study of rapid thermally annealed Pd/Ge contacts on IN0.53Ga0.47As Melville, NY American Institute of Physics 1996 Journal of applied physics 88 3910 3914 2016-02-19 OPUS4-2516 Zeitschriftenartikel Gajewski, Sven; Maneck, Heinz-Eberhard; Knoll, Uta; Neubert, Dietmar; Dörfel, Ilona; Mach, Reinhard; Strauß, Birgid; Friedrich, Jörg Florian Purification of single walled carbon nanotubes by thermal gas phase oxidation Single walled carbon nanotubes (SWNT) have been produced in an electric arc discharge by using a graphite rod as anode which is filled with a powder mixture of graphite and metallic catalysts like nickel and yttrium. The soot material containing approximately a third of SWNT was collected from the cathode region as a soft, voluminous material. The main by-products in this process are amorphous carbon and graphitic nanoparticles which have to be removed by an appropriate purification process. The as-produced soot material was purified by gas phase oxidation in air at 355 °C. The oxidation of amorphous carbon in air is advantageous against wet chemical methods because it is better controllable. Thermogravimetric analysis and electron microscopy were used to investigate the oxidation behavior of the different kinds of carbon. Oxidation of SWNT and amorphous carbon occurs simultaneously even at moderate temperatures, whereas amorphous carbon is more rapidly oxidized than SWNT. For optimizing the purification procedure by gas phase oxidation, kinetic studies were used to determine the oxidation time for each component in the soot at a given temperature. So it is possible to remove the amorphous carbon quantitatively with minimal losses of SWNT. But it was found that graphitic nanoparticles have the highest stability against oxidation and could therefore not be quantitatively removed by this method without the complete destruction of SWNT. Therefore, the electric arc discharge process has to be a controlled process for minimum production of graphitic nanoparticles to obtain a material with a high content of SWNT. New York, NY Elsevier 2003 Diamond and related materials 12 3-7 816 820 10.1016/S0925-9635(02)00362-X 2016-02-19 OPUS4-2545 Beitrag zu einem Sammelband Urban, Ingrid; Dörfel, Ilona; Österle, Werner; Schierhorn, Eike Interfaces between hard coating systems and substrates Brussels CESM, Committee of European Societies of Microscopy 1996 Electron microscopy 96 2-9600163-0-0 11th European Conference on Electron Microscopy (EUREM-11) Dublin, Ireland 1996-08-26 1996-08-30 2016-02-19 OPUS4-711 Zeitschriftenartikel Woydt, Mathias; Skopp, André; Dörfel, Ilona; Witke, Klaus Wear Engineering Oxides / Antiwear Oxides Philadelphia, Pa. Taylor & Francis Society of Tribologists and Lubrication Engineers 1999 Tribology transactions 42,1 21 31 2016-02-19 OPUS4-2074 Zeitschriftenartikel Rudolf, A.; Kaiser, W.-D.; Dörfel, Ilona; Engelhardt, Monika; Österle, Werner Zum Zusammenhang von Filiformkorrosion und Gefüge von Aluminiumlegierungen, Teil I Isernhagen Giesel 2002 Aluminium 78 7/8 596 601 2016-02-19 OPUS4-2075 Zeitschriftenartikel Rudolf, A.; Kaiser, W.-D.; Dörfel, Ilona; Engelhardt, Monika; Österle, Werner Zum Zusammenhang von Filiformkorrosion und Gefüge von Aluminiumlegierungen, Teil II Isernhagen Giesel 2002 Aluminium 78 11 994 1000 2016-02-19 OPUS4-2635 Beitrag zu einem Sammelband Dörfel, Ilona; Effner, Ute; Glaubitz, Steffen; Österle, Werner; Rudolph, Edith Ziegler, G. Charakterisierung hochfester ZrO2-Werkstoffe Frankfurt DGM Informationsges. Deutsche Gesellschaft für Materialkunde 1997 Werkstoff- und Verfahrenstechnik (Werkstoffwoche '96 Symposium 6) 6 3-88355-234-8 Werkstoffwoche '96 (WW) Stuttgart, Deutschland 1996-05-28 1996-05-31 691 702 2016-02-19 OPUS4-2363 Zeitschriftenartikel Österle, Werner; Dörfel, Ilona; Urban, Ingrid; Reier, T.; Schultze, J. XPS and XTEM study of AlN formation by N+2 implantation of aluminium X-ray photoelectron spectroscopy (XPS) and cross-sectional transmission electron microscopy (XTEM) were used to study the formation of AlN films by N+2 ion implantation of aluminium at energies of 3 keV and 100 keV. In both cases, a two-stage mechanism was found, comprising first the oriented precipitation of small particles of the hexagonal AlN-phase, followed by growth and coalescence finally forming a continuous AlN-layer while increasing the implantation dose from 1×1017 cm-2 to 2×1017 cm-2. The results of both methods are in excellent agreement and furthermore provide complementary information concerning chemical composition and binding energies as well as microstructural details. Lausanne Elsevier Science 1998 Surface and coatings technology 102 1-2 168 174 10.1016/S0257-8972(98)00355-7 2016-02-19 OPUS4-2364 Zeitschriftenartikel Dörfel, Ilona; Österle, Werner; Urban, Ingrid; Bouzy, E. Microstructural characterization of binary and ternary hard coating systems for wear protection - Part I: PVD coatings Different wear-resistant coatings produced by physical vapour deposition (PVD) were characterized with the aid of cross-sectional transmission electron microscopy (XTEM). All coating systems were optimized by the producers and exhibited good properties with respect to their special applications. The microstructure, texture and chemical composition of binary and ternary systems produced by the arc process [TiN, CrN, Cr2N (Ti, Cr)N on steel substrates] and magnetron sputtering process [TiN, CrN on steel substrates, (Ti, Al)N on Si-substrate] were investigated. All coatings had a more or less columnar microstructure, which was interrupted by interlayers in some cases. Whereas arc coatings always did show some kind of substrate modification, the latter was not observed after magnetron sputtering. Electron diffraction normally revealed a mono-phase fcc structure, except at sites very near to the interface. Only for the systems Cr–N and (Ti, Cr)–N were different additional phases observed at low nitrogen partial pressures. Lausanne Elsevier Science 1999 Surface and coatings technology 111 2-3 199 209 10.1016/S0257-8972(98)00735-X 2016-02-19 OPUS4-2365 Zeitschriftenartikel Dörfel, Ilona; Österle, Werner; Urban, Ingrid; Bouzy, E.; Morlok, O. Microstructural characterization of binary and ternary hard coating sytems for wear protection - Part II: Ti(CN) PACVD coatings Lausanne Elsevier Science 1999 Surface and coatings technology 116-119 898 905 2016-02-19 OPUS4-2413 Zeitschriftenartikel Dörfel, Ilona; Gesatzke, Wolfgang; Österle, Werner; Skopp, André Characterization of defects in dry-pressed green bodies Aedermannsdorf Trans Tech Publ. 1994 Key engineering materials 89-91 763 767 2016-02-19 OPUS4-7455 Zeitschriftenartikel Nofz, Marianne; Stösser, R.; Scholz, G.; Dörfel, Ilona; Schultze, Dietrich The thermally induced transformation of pseudoboehmite gels - a comparison of the effects of corundum seeding and iron doping The transformation of doped or seeded pseudoboehmite to corundum was studied by combining thermal analysis, X-ray diffraction, transmission electron microscopy, and electron paramagnetic resonance spectroscopy. The temperature of phase transformation to corundum was lowered by about 130 °C when Fe3+ or corundum seeds were added to the sols. Action of Fe3+ ions depends on the actual degree of thermally induced transformation of pseudoboehmite via transition aluminas to corundum and the ability of these alumina phases to incorporate Fe3+ ions. These ions tend to aggregate with increasing iron concentration of the alumina phases and can work as nucleation centers. Small (not, vert, similar20 nm) corundum particles act as active nucleation sites whereas larger grains (200–400 nm) also present in the samples are less effective. For the first time trapping and stabilization of NO2 molecules in transition aluminas formed by a sol–gel route was shown. Oxford Elsevier European Ceramic Society 2005 Journal of the European Ceramic Society 25 7 1095 1107 10.1016/j.jeurceramsoc.2004.04.014 2016-02-19 OPUS4-12051 Beitrag zu einem Tagungsband Wäsche, Rolf; Klaffke, Dieter; Woydt, Mathias; Dörfel, Ilona Interface formation by tribo-oxidation in SiC based ceramics BAM 2003 AIST-BAM Symposium on Materials Surface Technology in Twin Institute Programme AIST-BAM Symposium on Materials Surface Technology in Twin Institute Programme Tsukuba, Japan 2003-02-18 1 4 2016-02-19 OPUS4-12053 Zeitschriftenartikel Wäsche, Rolf; Klaffke, Dieter; Woydt, Mathias; Dörfel, Ilona Structure of the interface in SiC-based ceramic composites formed by tribo-oxidation under dry sliding conditions Westerville, Ohio American Ceramic Society 2004 Ceramic transactions 146 401 407 2016-02-19 OPUS4-12057 Beitrag zu einem Tagungsband Yarim, Rasim; Wäsche, Rolf; Woydt, Mathias; Dörfel, Ilona Analysis of wear protecting oxide layers in the system SiC-TiC-TiB2 formed in-situ at high temperatures BAM 2003 AIST-BAM Symposium on Materials Surface Technology in Twin Institute Programme AIST-BAM Symposium on Materials Surface Technology in Twin Institute Programme Tsukuba, Japan 2003-02-18 5 8 2016-02-19 OPUS4-25657 Zeitschriftenartikel Dörfel, Ilona; Rooch, Heidemarie; Österle, Werner Microstructural differences between two Zr(C,N) coatings revealed by analytical transmission electron microscopy The microstructures of two samples of a Zr(C,N) coating on steel, which unexpectedly differed in their tribological properties, were investigated by analytical transmission electron microscopy. The samples were produced by a cathodic arc evaporation process in two commercial coating devices under similar coating conditions with the exception of the number of Zr targets. The source of the differing tribological properties of the samples was detected by analytical transmission electron microscopy (TEM) methods energy-dispersive X-ray spectroscopy (EDX), energy filtering TEM (EFTEM), electron diffraction, high resolution electron microscopy, and high angel annular dark field. The TEM preparation and the results of the TEM investigations are shown in detail. The origin of the unexpected behavior was determined to be a nano-scale multilayer structure that existed only in the tribologically superior specimen. EDX and EFTEM investigations indicated enrichment in oxygen at the interface between coating and steel substrate in the tribologically inferior sample. Findings of the microstructural configuration were obtained by taking a closer look at the structure and comparing the results of the several analytical TEM techniques. This allows the allocation of the concentration fluctuations in N, C, and Zr to the two thickness fractions of the nano multilayers and a local correlation of the identified minority phase Zr3(C,N)4 to the higher N content in the narrower type of the multilayer fraction of the sample with the excellent tribological properties. The minority phase Zr3(C,N)4 is randomly distributed in the sample with the defective tribological properties. Coating conditions are not topic of this work, but after discussion of the TEM results, the fact that one of the coating devices worked with one Zr target and the other one with two, could be identified as cause for the formation of the nano multilayer structure in the sample with the superior tribological properties. Amsterdam Elsevier 2012 Thin solid films 520 13 4275 4281 10.1016/j.tsf.2012.02.051 2016-02-19 OPUS4-25986 Zeitschriftenartikel Meyer-Plath, Asmus; Orts Gil, Guillermo; Petrov, Sergej; Oleszak, Franz; Maneck, Heinz-Eberhard; Dörfel, Ilona; Haase, Oskar; Richter, Silke; Mach, Reinhard Plasma-thermal purification and annealing of carbon nanotubes We have developed a very fast and entirely gas-phase based purification technique for carbon nanotubes (CNT) that allows removing metal and metal oxide impurities with high effectiveness. CNT agglomerates from chemical vapor deposition (CVD) synthesis which contained carbon encapsulated catalysts were injected into an atmospheric plasma torch. Very high heating rates allow for quasi-instantaneous vaporization of catalyst particles. This way, metal vapors are hyposized to break mechanically instable encapsulations and effuse from incomplete ones faster than thermally induced graphitization stabilizes such particle encapsulations. The ash content of multi-walled (MW) CNT samples was reduced to less than 15% of the initial value within a few milliseconds. Also the metal content of single-walled (SW) CNT agglomerates was significantly reduced. Repeated injection of CNT agglomerates into the plasma torch resulted in higher-purity products of improved structural integrity and increased oxidation resistance. New York, NY Pergamon Press 2012 Carbon 50 10 3934 3942 10.1016/j.carbon.2012.04.049 2016-02-19 OPUS4-24413 Posterpräsentation Dörfel, Ilona V-Cr containing precipitates in the steel T92 before and after tests under oxyfuel steam power plant conditions 2011 Microscopy Conference 2011 Microscopy Conference 2011 Kiel, Germany 2011-08-28 2011-09-02 2016-02-19 OPUS4-27636 Zeitschriftenartikel Schulz, Wencke; Nofz, Marianne; Feigl, Michael; Dörfel, Ilona; Saliwan Neumann, Romeo; Kranzmann, Axel Corrosion of uncoated and alumina coated steel X20CrMoV12-1 in H2O-CO2-O2 and air at 600 °C Future coal power plants will in case of oxyfuel combustion be operated with altered atmospheres. Hence, corrosion attack might become more severe and steels have to be protected. An alumina-sol was used to coat X20CrMoV12-1 (X20) with alumina to test the protection. Testing was performed at 600 °C in flowing H2O-CO2-O2 and static laboratory air for 1000 h. Oxidation under air is minor compared to exposure in oxyfuel atmosphere. In both cases a multilayered oxide (hematite, magnetite, spinel) was formed on uncoated steels. Carburization appeared on uncoated X20 in H2O-CO2-O2. The coating demonstrates a high protection. Orlando, Fla. Elsevier Ltd. 2013 Corrosion science 68 44 50 10.1016/j.corsci.2012.10.031 2016-02-20 OPUS4-15016 Zeitschriftenartikel Nofz, Marianne; Dörfel, Ilona; Sojref, Regine Microstructure of sol-gel derived corundum containing coatings Up to ~ 3 µm thick alumina coatings on corundum ceramic, soda–lime–silica glass and Inconel718™ were produced from mixtures of boehmite sols and corundum suspensions. Transmission electron micrographs in combination with electron diffraction and energy dispersive X-ray spectroscopy served to identify crystallographic phases and to characterize the microstructure of the coatings. Using corundum ceramic as substrate the initially deposited boehmite transforms via transition aluminas to corundum while heating to 1200 °C. In the cases of glass and Inconel718™ thermal treatments up to 520 °C and 1100 °C, respectively, cause diffusion of ions from the substrates into the coatings. Thus additional oxide phases were formed. All coatings are free of cracks or delaminations and do not show any directed crystal growth. Amsterdam Elsevier 2007 Thin solid films 515 18 7145 7154 2016-02-19 OPUS4-18263 Zeitschriftenartikel Dreßler, Martin; Nofz, Marianne; Saliwan Neumann, Romeo; Dörfel, Ilona; Griepentrog, Michael Sol-gel derived alumina layers on nickel-base superalloy Inconel-718 (IN-718) Modified Yoldas sols can be used to prepare crack-free well adherent layers on different substrate materials such as soda–lime glass, corundum and metal (IN-718). These layers having thicknesses of 0.6 µm are strain tolerant and withstand thermal cycling between 810 °C and room temperature. Introducing alpha-Al2O3 filler particles into modified Yoldas sols allows the preparation of thicker layers of 1.6 µm, which as well can be thermally cycled without noticeable delaminations. Chemical bonding seems to be the predominant layer bonding mechanism. Amsterdam Elsevier 2008 Thin solid films 517 2 786 792 10.1016/j.tsf.2008.08.124 2016-02-19 OPUS4-15490 Posterpräsentation Dörfel, Ilona Al2O3-coatings after long-term heat treatment - a TEM study 2007 Microscopy Conference 2007 (33. Conference of DGE) Microscopy Conference 2007 (33. Conference of DGE) Saarbrücken, Germany 2007-09-02 2007-09-07 2016-02-19 OPUS4-7522 Beitrag zu einem Tagungsband Nofz, Marianne; Sojref, Regine; Dreßler, Martin; Dörfel, Ilona; Reinsch, Stefan; Saliwan Neumann, Romeo Korundhaltige Aluminiumoxidschichten Kassel DGM 2005 Tagungsband des 15. Symposium: Verbundwerkstoffe und Werkstoffverbunde 15. Symposium: Verbundwerkstoffe und Werkstoffverbunde Kassel, Germany 2005-04-06 2005-04-08 5 Seiten 2016-02-19 OPUS4-17857 Zeitschriftenartikel Dreßler, Martin; Nofz, Marianne; Dörfel, Ilona; Saliwan Neumann, Romeo Influence of sol-gel derived alumina coatings on oxide scale growth of nickel-base superalloy Inconel-718 Alumina coatings with differing phase compositions were deposited on Inconel-718 (IN-718) Ni-base superalloy substrates using sol–gel processing. Mass gain measurements served for studying the oxidation behavior of coated metal surfaces if exposed to 800°C and 900°C for up to 4000 h in static air. Itwas found, that alumina coatings significantly reduce the oxidation related mass gain of IN-718 even after heating to 900°C for 4000 h. Transmission electron microscopy (TEM) studies revealed diffusion of elements from the metal substrate (IN-718) into the alumina coatings and — to a much lower degree — from the coating into the substrate. These diffusion processes are greatly influenced by the phase composition of the coatings, especially by the presence of alpha-alumina. Lausanne Elsevier Science 2008 Surface and coatings technology 202 6095 6102 10.1016/surfcoat.2008.07.018 2016-02-19 OPUS4-19726 Zeitschriftenartikel Nofz, Marianne; Sojref, Regine; Dreßler, Martin; Hünert, Daniela; Dörfel, Ilona; Saliwan Neumann, Romeo Sol-gel alumina coatings for high-temperature corrosion protection of Ni-base alloy SC16 in water vapour containing atmosphere Alumosols in combination with well dispersed corundum were successfully used to form up to 2.5 ìm thick coatings on the Ni-base alloy SC16. These coatings withstood heat treatments at 700 °C in a water vapour containing atmosphere. The heat treatment caused formation of delta-alumina in the coating and diffusion of chromium and titanium into the coating. Düsseldorf DVS-Verl. 2009 Interceram 58 4 192 195 2016-02-19 OPUS4-20625 Zeitschriftenartikel Coniglio, N.; Cross, Carl Edward; Dörfel, Ilona; Österle, Werner Phase formation in 6060/4043 aluminium weld solidification Weld metal microstructure for alloy 6060 aluminum welds, made using the gas-tungsten arc process and alloy 4043 filler metal, has been characterized using optical metallography, EPMA microprobe analysis, SEM/EBSD and STEM/EDX electron microscopy, and single-sensor differential thermal analysis (SS-DTA). In addition, alloy 6060 castings were solidified at variable cooling rates approaching that of welding, to provide a reference for comparison with weld microstructure. It was found that a major change in cast microstructure occurs at cooling rates higher than 27 K/s resulting in a structure similar to that observed in weld metal. Rapid cooling is believed to favor low temperature solidification reactions that normally would be achieved only at higher silicon content. Accordingly, additions of 4043 filler metal that increase the weld metal silicon content have only limited affect on weld solidification range and microstructure. This has direct implications regarding how 4043 filler additions improve weldability and weld quality. Amsterdam Elsevier 2009 Materials science and engineering A 517 1-2 321 327 10.1016/j.msea.2009.03.087 2016-02-19 OPUS4-26823 Beitrag zu einem Tagungsband Österle, Werner; Deutsch, Cornelius; Rooch, Heidemarie; Dörfel, Ilona Friction films on C-SiC discs after dynamometer tests with different commercial brake pads 2012 EuroBrake 2012 (Proceedings) EuroBrake 2012 Dresden, Germany 2012-04-16 2012-04-18 EB2012-FM-01 1 9 2016-02-19 OPUS4-25830 Zeitschriftenartikel Dreßler, Martin; Nofz, Marianne; Dörfel, Ilona; Saliwan Neumann, Romeo Diffusion of Cr, Fe, and Ti ions from Ni-base alloy inconel-718 into a transition alumina coating Heat treating metals at high temperatures trigger diffusion processes which may lead to the formation of oxide layers. In this work the diffusion of Cr, Fe and Ti into an alumina coating applied to Inconel-718 is being investigated. Mass gain measurements, UV-vis spectroscopy and transmission electron microscopy were applied in order to study the evolution of the diffusion process. It was found that mainly Cr as well as minor amounts of Fe and Ti are being incorporated into the alumina coating upon prolonged heat treatment at 700 °C. It could be shown that alumina coatings being void of Cr have the same oxidation related mass gain as uncoated samples. However, incorporation of Cr into the alumina coating decreased their mass gain below that of uncoated substrates forming a Cr oxide scale only. Amsterdam Elsevier 2012 Thin solid films 520 13 4344 4349 10.1016/j.tsf.2012.02.006 2016-02-19 OPUS4-27322 Forschungsbericht Bresch, Harald; Dörfel, Ilona; Steinborn, Gabriele; Krietsch, Arne; Langner, Jeanette; Schmidt, Martin; Österle, Werner; Seeger, Stefan Physical-chemical characterization of NM105(P25) NM 105, Ti02 (P25) could not be ignited as dust layer and dispersed in air as dust/air-mixture as well. This dust is not dust explosible and the burning behaviour corresponds to Burning Class 1 (no Ignition). The results have shown that the tested sample is thus not combustible at all, because it is already oxidized completely. Berlin Bundesanstalt für Materialforschung und -prüfung (BAM) 2012 1 18 2016-02-20 OPUS4-29169 Posterpräsentation Dörfel, Ilona TEM Investigations of Alumina Coatings after Corrosion Experiments 2013 MC2013 MC2013 Regensburg, Germany 25.08.2013 30.08.2013 2016-02-20 OPUS4-29162 Zeitschriftenartikel Schulz, Wencke; Feigl, Michael; Dörfel, Ilona; Nofz, Marianne; Kranzmann, Axel Influence of a sol-gel alumina coating on oxidation of X20CrMoV12-1 in air up to 650 °C The need for a more efficient coal power plant generation (e.g. oxyfuel technology) results in modified process parameters and enhanced corrosion. To reach the necessary service life of high temperature parts protective coatings may be a sufficient technical solution. A modified Yoldas sol (Al2O3 based) was used to coat X20CrMoV12-1 by spin coating. After appropriate heat treatments transition alumina coatings being about 400 nm thick were obtained. Oxidation studies were carried out in laboratory air at temperatures up to 650 °C for up to 500 h exposure time. In case of the uncoated sample a rough oxide layer formed on the surface and a remarkable weight gain (2.62 mg/cm²) were detected. The sol-gel alumina layer (mainly δ-Al2O3) demonstrated a high protection, i.e. a very low weight gain (0.05 mg/cm²). Diffusion of alloying elements into the coating was observed. No indication of spallation of the coating occurred. Local defects (2 µm-30 µm) in the coating led to the formation of iron-oxide islands. Amsterdam Elsevier B.V. 2013 Thin solid films 539 29 34 10.1016/j.tsf.2013.04.132 2016-02-20 OPUS4-37306 Posterpräsentation Dörfel, Ilona Interface formation between steels and alumina coating in corrosive atmospheres A way to increase the application range and the lifetime of metallic substrates is their protection by coatings. Here the effect of alumina coatings on common steel substrates having different Chromium content is examined. The background of the investigations is to expand the application possibilities of mechanically good steels to higher temperatures and corrosive atmospheres in the framework of the European project POEMA ("Production of Coatings for New Efficient and Clean Coal Power Plant Materials") which was introduced to identify materials that can withstand the aggressive conditions arising during the oxyfuel process in modern coal power plants. This process is one possibility to reduce the CO2 emission by firing the coal in oxygen and recirculated flue gas. Substrate materials were P92 (9% Cr), K44X (19% Cr), and HR3C (25% Cr). The alumina coatings were deposited by a sol-gel-process using boehmite, this is relatively simple and offers application possibilities for a wide technical range without special surface preparations. All samples were dried for 30 minutes at 650° C to remove the organic components and to start the crystallization process of the alumina. For P92 and HR3C the following conditions simulated the oxyfuel process: 650°C in wet flue gas for 300h for the steel P92, the same conditions for 2000 hours for the steel HR3C. K44X was tested at 900°C in laboratory air for 500 hours. As well after drying as after testing TEM characterizations were performed, where the interfaces between steel and coating are of special interest to characterize the microstructure, detect failure mechanisms, and identify diffusion and crystallization processes and so to understand the mode of action of the alumina coating. The TEM samples were prepared by the lift-out-technique using a FIB Quanta 3D and were investigated in a STEM JEM2200FS at 200kV. After the coating and drying process all steels show chromium oxide layers directly at the steel surface, they vary in thickness and are island shaped in the case of the steel K44X. Chromium depletion arose more or less in the superficial zones of all samples. After the long term tests K44X showed breakaway oxidation while P92 and HR3C presented intact interfaces. This reveals: Beside the positive impact of the coating not only the Chromium content of a substrate is essential for the formation and self-healing of protective chromium oxide layers during the service time of steels. One has to consider the possibility of the steel to allow a continuously Cr diffusion to the interface and so e renewal of the Cr-oxide layer. 2016 EMC2016 Lyon, France 28.08.2016 02.09.2016 2016-09-09 OPUS4-31453 Beitrag zu einem Tagungsband Davydenko, L.; Nazarchuk, M.; Nasiedkin, D.; Plyuto, Y.; Mosquera Feijoo, Maria; Nofz, Marianne; Sojref, Regine; Dörfel, Ilona; Saliwan Neumann, Romeo; Kranzmann, Axel; Pérez, F.J. Anticorrosion hybrid AlPO4/Al2O3 coatings on the surface of P92 steel for oxy-fuel power plant application 2014 XtremeCOAT 2014 - Surface engineering for functional applications under extreme conditions XtremeCOAT 2014 - Surface engineering for functional applications under extreme conditions Madrid, Spain 2014-10-20 2014-10-21 P 5, 1 2 2016-02-20 OPUS4-19574 Beitrag zu einem Sammelband Österle, Werner; Bresch, Harald; Dörfel, Ilona; Prietzel, Claudia; Seeger, Stefan; Fink, C.; Giese, A.; Walter, J. Surface film formation and dust generation during brake performance tests Woodhead Publishing Ltd The Institution of Mechanical Engineers 2009 Braking 2009 978-1-84334-559-6 Braking 2009 York, UK 2009-06-09 2009-06-10 C672/028/09 29 38 2016-02-19 OPUS4-19345 Zeitschriftenartikel Gemeinert, Marion; Dörfel, Ilona; Griepentrog, Michael; Gross, U.; Klaffke, Dieter; Knabe, C.; Kranz, I.; Österle, Werner Biological response to micron- and nanometer-sized particles known as potential wear products from artificial hip joints: Part I: Selection and characterization of model particles Hoboken, NJ Wiley 2009 Journal of biomedical materials research / A 89A 2 379 389 10.1002/jbm.a.31952 2016-02-19 OPUS4-19346 Zeitschriftenartikel Kranz, I.; Gonzalez, J.B.; Dörfel, Ilona; Gemeinert, Marion; Griepentrog, Michael; Klaffke, Dieter; Knabe, C.; Österle, Werner; Gross, U. Biological response to micron- and nanometer-sized particles known as potential wear products from artificial hip joints: Part II: Reaction of murine macrophages to corundum particles of different size distributions Hoboken, NJ Wiley 2009 Journal of biomedical materials research / A 89A 2 390 401 10.1002/jbm.a.32121 2016-02-19 OPUS4-20133 Zeitschriftenartikel Naghib Zadeh, Hamid; Glitzky, Carsten; Dörfel, Ilona; Rabe, Torsten Low temperature sintering of barium titanate ceramics assisted by addition of lithium fluoride-containing sintering additives By addition of LiF-containing sintering additives to commercial BaTiO3 powder, more than 98% of the theoretical density was reached at a sintering temperature of 900 °C both on powder compacts and laminates. Dielectric measurements were performed on ceramic samples in the temperature and frequency ranges from -20 °C to 125 °C and from 103 to 106 Hz, respectively. High relative permittivity (εr ~ 3160) and low dielectric loss (tan δ ~ 0.014) were measured for tapes of the favoured material. The breakdown strength for tapes with a thickness of about 80 µm is 30 kV/mm. The microprobe analysis showed, that no interfacial reaction between the dielectric layer and the Ag-electrode had occurred. The newly developed barium titanate ceramics completely densifying at 900 °C turned out to be promising for integration of buried capacitors in LTCC multilayers. Oxford Elsevier European Ceramic Society 2010 Journal of the European Ceramic Society 30 1 81 86 10.1016/j.jeurceramsoc.2009.07.005 2016-02-19 OPUS4-22655 Beitrag zu einem Tagungsband Österle, Werner; Bresch, Harald; Dörfel, Ilona; Fink, C.; Giese, A.; Prietzel, Claudia; Seeger, Stefan; Walter, J. Examination of airborne brake dust GRRT, France 2010 JEF 2010 - 6th European conference on braking (Proceedings) JEF 2010 - 6th European conference on braking Lille, France 2010-11-24 2010-11-25 1 6(?) 2016-02-19 OPUS4-22678 Posterpräsentation Dörfel, Ilona Vanadium and chromium containing precipitates in heat resistant steel T92 2011 "Current Developments in TEM" (JEOL user meeting) "Current Developments in TEM" (JEOL user meeting) Freiberg, Germany 10.03.2011 11.03.2011 2016-02-19 OPUS4-22606 Zeitschriftenartikel Dreßler, Martin; Nofz, Marianne; Klobes, Peter; Dörfel, Ilona; Reinsch, Stefan Differences between films and monoliths of sol-gel derived aluminas This work compares thin layers (films) and monoliths prepared from alumina sols with respect to their microstructure, thermal evolution, porosity and specific surface area. After heat treatment at similar temperatures, films and monoliths showed the same qualitative changes in porosity and specific surface area. However, some marked quantitative differences were detected. Film fragments had a lower open porosity, a lower specific surface area and a narrower pore size distribution. Furthermore, the thermal evolution showed a markedly different burnout of organic components between films and monoliths. The observed differences between films and monolith can be explained by the ageing history of the sols during sample preparation. Amsterdam Elsevier 2010 Thin solid films 519 1 42 51 10.1016/j.tsf.2010.07.057 2016-02-19 OPUS4-24179 Beitrag zu einem Tagungsband Schulz, Wencke; Feigl, Michael; Dörfel, Ilona; Saliwan Neumann, Romeo; Nofz, Marianne; Kranzmann, Axel Alumina coatings against carburization and oxidation under oxyfuel conditions DECHEMA e.V. 2010 1st International conference on materials for energy 978-3-89746-117-8 1st International conference on materials for energy Karlsruhe, Germany 2010-07-04 2010-07-08 1012 2016-02-19 OPUS4-23482 Zeitschriftenartikel Merk, Virginia; Schulte, Franziska; Rooch, Heidemarie; Feldmann, Ines; Dörfel, Ilona; Österle, Werner; Panne, Ulrich; Kneipp, Janina Surface-enhanced Raman scattering with silver nanostructures generated in situ in a sporopollenin biopolymer matrix Silver nanoparticles were generated based on citrate reduction in the ultrastructure of the sporopollenin biopolymer of Ambrosia artemisiifolia (ragweed) and Secale cereale (rye). The nanoparticles enable the acquisition of SERS spectra and thereby a vibrational characterization of the local molecular structure of sporopollenin. Cambridge Royal Society of Chemistry Chemical Society 2011 Chemical communications 47 11 3236 3238 10.1039/c0cc05326k 2016-02-19 OPUS4-19450 Zeitschriftenartikel Österle, Werner; Dörfel, Ilona; Prietzel, Claudia; Rooch, Heidemarie; Cristol-Bulthé, A.-L.; Defallaix, G.; Desplanques, Y. A comprehensive microscopic study of third body formation at the interface between a brake pad and brake disc during the final stage of a pin-on-disc test Amsterdam Elsevier 2009 Wear 267 5-8 781 788 10.1016/j.wear.2008.11.023 2016-02-19 OPUS4-20263 Zeitschriftenartikel Nofz, Marianne; Sojref, Regine; Feigl, Michael; Dreßler, Martin; Dörfel, Ilona Sol-Gel-Aluminiumoxidschichten für den Oxidationsschutz von Hochtemperaturlegierungen, Teil 2 Düsseldorf DVS-Verl. 2009 Keramische Zeitschrift 61 5 272 277 2016-02-19 OPUS4-20264 Zeitschriftenartikel Nofz, Marianne; Sojref, Regine; Feigl, Michael; Dreßler, Martin; Dörfel, Ilona Sol-Gel-Aluminiumoxidschichten für den Oxidationsschutz von Hochtemperaturlegierungen, Teil 1 Düsseldorf DVS-Verl. 2009 Keramische Zeitschrift 61 2-3 82 86 2016-02-19 OPUS4-20561 Zeitschriftenartikel Peplinski, Burkhard; Fitch, A.N.; Evans, A.; Ibberson, R.M.; Többens, D.M.; Cranswick, L.M.D.; Dörfel, Ilona; Emmerling, Franziska; Matschat, Ralf Structural characterization of a coarse-grained transparent silicon carbide powder by a combination of powder diffraction techniques Diffraction of hard synchrotron radiation as well as constant-wavelength and time-of-flight neutron diffraction were used for the structural characterization of a silicon carbide powder having extremely low levels of chemical impurities, high perfection of the crystalline lattice and a grain size of up to 150 µm. The presence of three polytypes was ascertained and the ratios of their mass fractions were determined to be w15R : w6H = 0.002,3(8) and w4H : w6H = 0.000,6(2). München Oldenbourg Deutsche Gesellschaft für Kristallographie 2009 Zeitschrift für Kristallographie / Supplement issue 30 EPDIC 2008 61 66 10.1524/zksu.2009.0009 2016-02-19 OPUS4-38148 Zeitschriftenartikel Schulz, Wencke; Nofz, Marianne; Dörfel, Ilona; Saliwan Neumann, Romeo; Kranzmann, Axel Aluminiumoxid als Schutzschicht für kommerzielle Kraftwerksstähle (Teil 1) In Kohlekraftwerken mit Oxyfuel-Technologie erfolgt die Verbrennung unter Zufuhr von reinem Sauerstoff. Damit steht für die Abscheidung und Speicherung von CO2 ein Rauchgas mit hohem CO2-Anteil zur Verfügung (CCS-Technologie). Aufgrund dieses Verbrennungsprozesses ändert sich im Wesentlichen die Rauchgaszusammensetzung hin zu hohem H2O- und SO2 -Anteil. Deshalb wurden in verschiedenen Laboratorien kommerzielle Kraftwerksstähle unter den entsprechenden korrosiven Bedingungen getestet. Im Vergleich zur herkömmlichen Verbrennungsmethode zeigten die ferritisch-martensitischen Stähle schon nach 1000 h Auslagerungszeit unter Oxyfuel-Bedingungen eine durch einen deutlich erhöhten Materialverlust gekennzeichnete Korrosion. Eine Möglichkeit um dennoch die Lebensdauer dieser Stähle zu gewährleisten, besteht im Aufbringen geeigneter Schutzschichten auf die Stahloberfläche. Die vorliegende Arbeit befasst sich mit der Herstellung und Bewertung von Sol-Gel-Aluminiumoxidschichten als Schutz vor Korrosion in Oxyfuel-Rauchgas-Atmosphäre. Diese wurden auf den warmfesten Stahl X20CrMoV12-1 (X20) mittels der Tauchmethode aufgebracht. Anschließend erfolgte eine Auslagerung der beschichteten Proben für 1000 h bei 600 °C in einer H2O-CO2-O2-SO2 -Atmosphäre. Im Vergleich zum unbeschichteten Stahl X20 war der Materialverlust des beschichteten Stahls deutlich geringer. Insbesondere konnte durch die Aluminiumoxidschicht der Transport von CO2 und SO2 zur Stahloberfläche verhindert werden. Bad Saulgau Leuze Verlag 2016 Galvanotechnik 107 9 1900 1903 2016-11-08 OPUS4-38149 Zeitschriftenartikel Schulz, Wencke; Nofz, Marianne; Dörfel, Ilona; Saliwan Neumann, Romeo; Kranzmann, Axel Leuze-Reichert, Sylvia Aluminiumoxid als Schutzschicht für kommerzielle Kraftwerksstähle (Teil 2) In Kohlekraftwerken mit Oxyfuel-Technologie erfolgt die Verbrennung unter Zufuhr von reinem Sauerstoff. Damit steht für die Abscheidung und Speicherung von CO2 ein Rauchgas mit hohem CO2-Anteil zur Verfügung (CCS-Technologie). Aufgrund dieses Verbrennungsprozesses ändert sich im Wesentlichen die Rauchgaszusammensetzung hin zu hohem H2O- und SO2 -Anteil. Deshalb wurden in verschiedenen Laboratorien kommerzielle Kraftwerksstähle unter den entsprechenden korrosiven Bedingungen getestet. Im Vergleich zur herkömmlichen Verbrennungsmethode zeigten die ferritisch-martensitischen Stähle schon nach 1000 h Auslagerungszeit unter Oxyfuel-Bedingungen eine durch einen deutlich erhöhten Materialverlust gekennzeichnete Korrosion. Eine Möglichkeit um dennoch die Lebensdauer dieser Stähle zu gewährleisten, besteht im Aufbringen geeigneter Schutzschichten auf die Stahloberfläche. Die vorliegende Arbeit befasst sich mit der Herstellung und Bewertung von Sol-Gel-Aluminiumoxidschichten als Schutz vor Korrosion in Oxyfuel-Rauchgas-Atmosphäre. Diese wurden auf den warmfesten Stahl X20CrMoV12-1 (X20) mittels der Tauchmethode aufgebracht. Anschließend erfolgte eine Auslagerung der beschichteten Proben für 1000 h bei 600 °C in einer H2O-CO2-O2-SO2 -Atmosphäre. Im Vergleich zum unbeschichteten Stahl X20 war der Materialverlust des beschichteten Stahls deutlich geringer. Insbesondere konnte durch die Aluminiumoxidschicht der Transport von CO2 und SO2 zur Stahloberfläche verhindert werden. Bad Saulgau Leuze-Verlag 2016 Galvanotechnik 107 10 2098 2102 2016-11-08 OPUS4-34518 Posterpräsentation Dörfel, Ilona Microstructure of a steel-alumo-sol-coating-system after heat treatment in an oxyfuel atmosphere 2015 Microscopy Conference 2015 Microscopy Conference 2015 Göttingen, Germany 2015-09-06 2015-09-11 2016-02-20 OPUS4-35039 Beitrag zu einem Tagungsband Österle, Werner; Deutsch, Cornelius; Dörfel, Ilona; Gradt, Thomas; Häusler, Ines; Orts-Gil, G.; Prietzel, C.; Schneider, Thomas Final outcome of a fundamental research project on tribofilms formed during automotive braking, Part 1: Experimental studies In order to obtain a better understanding of the role of tribofilms during automotive braking, their structures were investigated and the essential features identified. Next, different ingredient combinations were studied by preparing some model materials with simpler compositions than real tribofilms. A test method was developed for verifying the tribological properties of the model materials and for comparison with results obtained with numerical sliding simulations of such structures. Prerequisites of good brake Performance properties were identified. Although the coefficient of friction could be varied in a wide ränge, smooth sliding conditions could only be achieved with values smaller than 0.4. Tests with artificial third body powders turned out to be useful as screening method for the selection of raw materials for brake pad formulations. London FISITA International Federation of Automotive Engineering Societies 2014 EuroBrake 2014 (Proceedings) 978-0-9572076-4-6 EuroBrake 2014 Lille, France 13.05.2014 15.05.2014 1 8 2016-02-20 OPUS4-38351 Zeitschriftenartikel Radziszewska, Agnieszka; Kranzmann, Axel; Dörfel, Ilona; Mosquera Feijoo, Maria; Solecka, M. Microstructure and chemical composition of Fe-Cr alloy tempered in high temperature and atmosphere containing Ar-SO2 The paper presents the microstructure, chemical and phase composition of thin scale, obtained as a result of high temperature corrosion of X20Cr13 stainless steel. Samples were exposed to gas atmosphere of the following composition: 0.25 vol.% of SO2 and 99.75 vol.% of Ar at 600 °C for 5 h. As a consequence, thin compact scale was formed on steel surface. This scale consisted of three different zones. An amorphous zone was formed close to steel surface. Then, nanocrystalline Zone could be observed. Finally, larger grains were formed during the corrosion process. The analysis of the chemical composition revealed higher concentration of chromium near steel surface. In contrast, to chromium, the content of iron, increased near the scale surface. It was found out that the (Cr, Mn, Fe)5O12 phase appeared in the thin scale. Berlin De Gruyter De Gruyter Stiftung 2016 Archives of metallurgy and materials 61 3 1607 1612 10.1515/amm-2016-0262 2016-11-18 OPUS4-44560 Zeitschriftenartikel Kirner, Sabrina V.; Slachciak, Nadine; Elert, Anna Maria; Griepentrog, Michael; Fischer, Daniel; Hertwig, Andreas; Sahre, Mario; Dörfel, Ilona; Sturm, Heinz; Pentzien, Simone; Koter, Robert; Spaltmann, Dirk; Krüger, Jörg; Bonse, Jörn Tribological performance of titanium samples oxidized by fs-laser radiation, thermal heating, or electrochemical anodization Commercial grade-1 titanium samples (Ti, 99.6%) were treated using three alternative methods, (i) femtosecond laser processing, (ii) thermal heat treatment, and (iii) electrochemical anodization, respectively, resulting in the formation of differently conditioned superficial titanium oxide layers. The laser processing (i) was carried out by a Ti:sapphire laser (pulse duration 30 fs, central wavelength 790 nm, pulse repetition rate 1 kHz) in a regime of generating laser-induced periodic surface structures (LIPSS). The experimental conditions (laser fluence, spatial spot overlap) were optimized in a sample-scanning setup for the processing of several square-millimeters large surface areas covered homogeneously by these nanostructures. The differently oxidized titanium surfaces were characterized by optical microscopy, micro Raman spectroscopy, variable angle spectroscopic ellipsometry, and instrumented indentation testing. The tribological performance was characterized in the regime of mixed friction by reciprocating sliding tests against a sphere of hardened steel in fully formulated engine oil as lubricant. The specific tribological performance of the differently treated surfaces is discussed with respect to possible physical and chemical mechanisms. Springer-Verlag 2018 Applied Physics A 124 4 326, 1 10 urn:nbn:de:kobv:b43-445609 10.1007/s00339-018-1745-8 https://creativecommons.org/licenses/by/4.0/deed.de 2018-03-23 OPUS4-45300 Zeitschriftenartikel Wollschläger, Nicole; Nofz, Marianne; Dörfel, Ilona; Schulz, Wencke; Sojref, Regine; Kranzmann, Axel Exposition of sol-gel alumina-coated P92 steel to flue gas: Time-resolved microstructure evolution, defect tolerance, and repairing of the coating Technically relevant P92 steel (9% Cr) was coated with a micron-thick porous alumina layer prepared by sol-gel technique and treated with flue gas (60 CO2-30 H2O-2 O2-1 SO2-7 N2 (mole fraction in %)) at 650 ° to mimic an oxyfuelcombustion process. Local defects in the coating were marked using focused ion beam (FIB) technique and were inspected after exposition to hot flue gas atmosphere at 300, 800, and 1300 h, respectively. Local defects like agglomerated alumina sol particles tend to spall off from the coating uncovering the underlying dense chromia scale. Re-coating was found to restore the protection ability from oxidation when repeatedly treated with hot flue gas. Cracks and voids did not promote the local oxidation due to the formation of crystalline Mn/S/O species within and on top of the coating. The protective character of the steel-coating system is a result of (i) the fast formation of a dense chromia scale at the surface of sol-gel alumina-coated P92 steel bars in combination with (ii) the porous alumina coating acting as diffusion barrier, but also as diffusion partner in addition with (iii) fast Mn outward diffusion capturing the S species from flue gas. Weinheim Wiley-VCH Verlag GmbH&Co. KGaA 2018 Materials and Corrosion 69 4 492 502 10.1002/maco.201709712 2018-06-26 OPUS4-44468 Zeitschriftenartikel Österle, Werner; Dörfel, Ilona; Wollenschläger, Nicole; Gradt, Thomas; Wolter, Christian; Reinstädt, Philipp; Zeigmeister, U.; Dmitriev, A. I.; Nikonov, A. Y. Potential of different nickel coatings for optimizing the sliding behavior of electrical connectors The potential of several nickel coatings was investigated by reciprocating sliding tests against copper thus simulating the plug-socket system of an electrical connector. Elsevier Ltd. 2018 Tribology International 120 491 501 10.1016/j.triboint.2018.01.006 2018-03-15 OPUS4-44472 Zeitschriftenartikel Nofz, Marianne; Dörfel, Ilona; Sojref, Regine; Wollschläger, Nicole; Mosquera Feijoo, Maria; Schulz, Wencke; Kranzmann, Axel Thin Sol-Gel Alumina Coating as Protection of a 9% Cr Steel Against Flue Gas Corrosion at 650 °C Samples of sol-gel alumina coated and uncoated P92 steel were exposed to flue gas at 650 °C for 300 h. As result of this treatment a 50 µm thick bi-layered oxide scale had formed on the surface of the uncoated sample. Below the scale a 40 µm thick inner oxidation zone was detected. In contrast, the porous, micron thick alumina coating enabled the formation of a chromium oxide scale with a thickness of some nanometers at the interface between steel substrate and coating. In this case high temperature corrosion of the steel was prevented so far. Springer 2018 Oxidation of Metals 89 3-4 453 470 10.1007/s11085-017-9799-0 2018-03-15 OPUS4-44678 Zeitschriftenartikel Donėlienė, J.; Rudzikas, M.; Rades, Steffi; Dörfel, Ilona; Peplinski, Burkhard; Sahre, Mario; Pellegrino, F.; Maurino, V.; Ulbikas, J.; Galdikas, A.; Hodoroaba, Vasile-Dan Morphology and structure of TixOy nanoparticles generated by femtosecond laser ablation in water In this work femto-second pulsed laser ablation in liquid (PLAL) procedure for the generation of titanium oxide nanoparticles (NP) is reported with the purpose of understanding morphology and structure of the newly generated NPs. Ablation duration was varied for optimization of NP generation processes between 10 and 90 min. Surface morphology of NPs as well as their size and shape (distribution) were analysed by various complementary electron microscopy techniques, i.e. SEM, TSEM and TEM. The crystalline structure of titanium oxide particles was investigated byXRD(two instruments operated in different geometries) and HR-TEM. Concentration of generated titanium oxide NPs in liquid was analysed by ICP-MS. A mix of crystalline (mainly anatase), partly crystalline and amorphous spherical titanium oxide NPs can be reported having a mean size between 10 and 20 nm, which is rather independent of the laser ablation (LA) duration. A second component consisting of irregularly shaped, but crystalline titanium oxide nanostructures is co-generated in the LA water, with more pronounced occurrence at longer LA times. The provenance of this component is assigned to those spherical particles generated in suspension and passing through the converging laser beam, being hence subject to secondary irradiation effects, e. g. fragmentation. London, UK IOP Publishing 2018 Materials Research Express 5 4 045015-1 045015-12 10.1088/2053-1591/aaba56 2018-04-12 OPUS4-33338 Zeitschriftenartikel Nofz, Marianne; Zietelmann, Christina; Feigl, Michael; Dörfel, Ilona; Saliwan Neumann, Romeo Microstructural origin of time-dependent changes in alumina sol-gel-coated Inconel 718 exposed to NaCl solution Inconel 718 was spin coated twice and fourfold with a sol to obtain 200- and 400-nm-thick transition alumina films on the surface. Bare and sol–gel alumina-coated Inconel 718 samples were exposed to NaCl solution to study their corrosion behavior by means of electrochemical impedance spectroscopy. In combination with scanning electron microscopy, it was shown that bare Inconel 718 is after initial passivation prone to pitting corrosion. For the coated Inconel 718 samples, an improvement in the protective effect of the coatings with time was observed. This observation is in contradiction to the results of other authors who observed degradation of alumina coatings exposed to NaCl solution with time. Transmission electron microscopy revealed a formation of (1) a compacted region at the coating surface as well as (2) a chromium-rich region at the interface between coating and alloy during the contact with a NaCl solution. The last one mainly contributes to the observed chronological sequence of electrochemical characteristics of the samples. Dordrecht Kluwer Academic Publ. 2015 Journal of sol gel science and technology 75 1 6 16 10.1007/s10971-015-3668-6 2016-02-20 OPUS4-35051 Zeitschriftenartikel Häusler, Ines; Dörfel, Ilona; Peplinski, Burkhard; Dietrich, Paul; Unger, Wolfgang; Österle, Werner Comprehensive characterization of ball-milled powders simulating a tribofilm system A model system was used to simulate the properties of tribofilms which form during automotive braking. The model system was prepared by ball milling of a blend of 70 vol.% iron oxides, 15 vol.% molybdenum disulfide and 15 vol.% graphite. The resulting mixture was characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and various transmission electron microscopic (TEM) methods, including energy dispersive X-ray spectroscopy (EDXS), high resolution investigations (HRTEM) with corresponding simulation of the HRTEM images, diffraction methods such as scanning nano-beam electron diffraction (SNBED) and selected area electron diffraction (SAED). It could be shown that the ball milling caused a reduction of the grain size of the initial components to the nanometer range. Sometimes even amorphization or partial break-down of the crystal structure was observed for MoS2 and graphite. Moreover, chemical reactions lead to a formation of surface coverings of the nanoparticles by amorphous material, molybdenum oxides, and iron sulfates as derived from XPS. New York, NY Elsevier International Metallographic Society 2016 Materials characterization 111 183 192 10.1016/j.matchar.2015.11.024 2016-02-20 OPUS4-30413 Zeitschriftenartikel Schempp, Philipp; Cross, C.E.; Pittner, Andreas; Oder, Gabriele; Neumann, R.S.; Rooch, Heidemarie; Dörfel, Ilona; Österle, Werner; Rethmeier, Michael Solidification of GTA aluminium weld metal: Part I - Grain morphology dependent upon alloy composition and grain refiner content New York, NY American Welding Society Welding Research Council 2014 Welding journal 93 53-s - 59-s 2016-02-20 OPUS4-40044 Zeitschriftenartikel Nofz, Marianne; Dörfel, Ilona; Sojref, Regine; Wollschläger, Nicole; Mosquera Feijoo, Maria; Kranzmann, Axel Microstructure, smoothening effect, and local defects of alumina sol-gel coatings on ground steel Porous alumina films with thicknesses of a few microns were prepared via a dip-coating technique on steel P92. The coating is shown to protect the steel against massive corrosion, which is typical in the hot reactive environment of coal fired power plants. To mimic real conditions ground steel plates were coated with a boehmite-sol. This leads to an overall smoothing of the formerly rough surface. In the following short annealing step the inner porous construction with worm-like particles consisting of nano-crystallites and amorphous alumina is formed. Due to the simultaneous diffusion of chromium and iron ions out of the bulk steel material into the porous alumina coating, a dense interface with satisfactory adhesion is formed. However, the film exhibits few local defects like cracks or dense alumina nodules caused by steep edges in the ground surface or agglomeration of boehmite-sol components, respectively. Cracks especially have to be avoided. This problem can be overcome so far by slight modifications in the sol preparation process and surface treatment of the substrates. Nevertheless the results demonstrate the potential of sol-gel based alumina coatings as a time- and cost-saving protection type for commercial steel P92. New York Springer 2017 Journal of Sol-Gel Science and Technology 81 1 185 194 10.1007/s10971-016-4188-8 2017-05-03 OPUS4-47423 Zeitschriftenartikel Chandra, K.; Dörfel, Ilona; Wollschläger, N.; Kranzmann, Axel Microstructural investigation using advanced TEM techniques of inner ocide layers formed on T92 steel in oxyfuel environment T92 steel was oxidized at 650 °C for 1000 h in dry and wet oxyfuel gases. The microstructure of inner oxide layer was investigated using scanning transmission electron microscopy and energy dispersive spectroscopy on thin lamellas of oxide cross-sections. The oxides were composed of fine equiaxed grains and separated into Fe-rich and Cr-rich regions. Fe-rich regions were wustite and iron sulphide while Cr-rich regions consisted of Fe-Cr spinel with different stoichiometries. Precipitates of (W,Mo)-rich oxides were formed within the oxide scale and beneath the oxide/alloy interface. Often iron sulphide and (W,Mo)-rich oxide were surrounded by Cr-rich spinel. Elsevier 2019 Corrosion Science 148 94 109 10.1016/j.corsci.2018.12.008 2019-02-22 OPUS4-41724 Posterpräsentation Dörfel, Ilona Microstructure of alumina coating on steel P92 after thermal cycling 1. Introduction Alumina coatings are one possibility to increase the corrosion resistance, lifetime and application range of thermally loaded steel components, e.g. in modern power plants where the use of the Oxy-fuel technology corrosive fuel gas (H2O-CO2-O2-SO2 at 650 °C) affects the steel parts. In previous investigations the efficacy of protective alumina coatings on steel P 92 under those conditions was demonstrated. A shutdown and re-start of power plants or parts of them causes thermal stresses of the components which can cause detrimental effects like microstructural changes in the steel itself, changes in its oxidation behavior, delamination or microstructural changes in the coating. All those effects can lead to failure of the components, resulting in lifetime reduction. 2. Objectives As a first step, we concentrate on the influence of thermal cycling tests and observe the impact on the microstructure of the coating and the interface in laboratory air. These investigations will help understanding the processes which occur, show directions of potentially necessary changes of the coating due to improved thermal stress behaviour. 3. Materials & methods P 92 is a ferritic-martensitic steel, containing 9% Cr which forms protective Cr-oxide-rich scales in dry environments and non-protective ones in water-containing environments. Coupons of P 92, having ground surfaces, were dip-coated via a sol-gel process and subjected to thermal cycling for 500 h (1000 cycles) in laboratory air in a temperature range between room temperature and 660° C. The resulting mass loss was determined by weighing. Samples for TEM investigations were produced as cross sections normal to the sample surface by FIB preparation (Quanta 3D, (FEI)). The TEM/STEM investigations were performed using a JEM2200FS (JEOL) operated at 200 kV. The microstructure of the coating and the interface after cycling tests was characterized via TEM, HREM, and STEM images, electron diffraction as well as EDX and EFTEM methods. 4. Results At steep edges in the surface profile the coating was imperfect and cracks have formed during the thermal cycling. Flat surface regions are well-covered. The whole interface region between the steel and the coating shows a dense Cr-oxide-rich zone, which can form protective regions in case of local failure. The Cr-oxide zone is followed by a region of mixed oxides, containing Cr, Mn, Fe, and Al in variable composition, to which a porous δ-Al2O3 zone is joined. 5. Conclusions • Alumina coatings promote the formation of dense, Cr-rich zones at the interface, which makes the system self-healing. • These zones are stable during thermal stresses, even in regions with cracked coatings. • They cause reduction of outward diffusion and mass loss during thermal cycling. 2017 MC2017 Lausanne, Switzerland 21.08.2017 25.08.2017 2017-08-29 OPUS4-45949 Zeitschriftenartikel Donėlienė, J.; Rudzikas, M.; Rades, Steffi; Dörfel, Ilona; Peplinski, Burkhard; Sahre, Mario; Pellegrino, F.; Maurino, V.; Ulbikas, J.; Galdikas, A.; Hodoroaba, Vasile-Dan Electron Microscopy and X-Ray Diffraction Analysis of Titanium Oxide Nanoparticles Synthesized by Pulsed Laser Ablation in Liquid A femto-second pulsed laser ablation in liquid (PLAL) procedure for the generation of titanium oxide nanoparticles (NP) is reported with the purpose of understanding morphology and structure of the newly generated NPs. Ablation duration was varied for optimization of NP generation processes between 10 and 90 min. Surface morphology of NPs as well as their size and shape (distribution) were analysed by various complementary electron microscopy techniques, i.e. SEM, TSEM and TEM. The crystalline structure of titanium oxide particles was investigated by XRD(two instruments operated in different geometries) and HR-TEM. Concentration of generated titanium oxide NPs in liquid was analysed by ICP-MS. A mix of crystalline (mainly anatase), partly crystalline and amorphous spherical titanium oxide NPs can be reported having a mean size between 10 and 20 nm, which is rather independent of the laser ablation (LA) duration. A second component consisting of irregularly shaped, but crystalline titanium oxide nanostructures is co-generated in the LA water, with more pronounced occurrence at longer LA times. The provenance of this component is assigned to those spherical particles generated in suspension and passing through the converging laser beam, being hence subject to secondary irradiation effects, e. g. fragmentation. New York, NY, U.S.A. Cambridge University Press 2018 Microscopy and Microanalysis 24 S1 (August) 1710 1711 10.1017/S1431927618009030 2018-09-17 OPUS4-47665 Zeitschriftenartikel Nofz, Marianne; Dörfel, Ilona; Sojref, Regine; Saliwan Neumann, Romeo Microstructure of bare and sol-gel alumina-coated nickel-base alloy Inconel 625 after long-term oxidation at 900 °C Though Ni-base superalloys show a high oxidation and corrosion resistance, coatings could still improve these properties, especially if used at temperatures up to 1000 °C. Here, a coating was prepared by applying a boehmite-sol via dip-coating and a subsequent heat treatment at 600 °C for 30 minutes. To evaluate the coating, the oxidation behavior of bare and alumina coated Ni-base alloy Inconel 625 in air at 900 °C was studied for up to 2000 h. Electron microscopic studies of sample surfaces and cross-sections showed that (i) in the 3.5 µm - 6.3 mm thick scale formed on the bare alloy, Fe and Ni are located as fine precipitates at the grain boundaries of the chromia-rich scale, (ii) Ni and Ti are concentrated to a minor degree at the grain boundaries of the scale, too; and for the coated sample: (iii) the only 1.8 µm thick sol-gel alumina coating slows down the formation of chromia on the alloy surface and reduces the outward diffusion of the alloy constituents. The protective effect of the coating was evidenced by (i) diminished chromium diffusion at grain boundaries resulting in less pronounced string-like protrusions at the outer surface of the coated IN 625, (ii) formation of a Cr-enriched zone above the alloy surface which was thinner than the scale on the uncoated sample, (iii) no detectable Cr-depleted zone at the alloy surface, and (iv) a narrower zone of formation of Kirkendall pores. Springer Science+Business Media 2019 Oxidation of Metals 91 3-4 395 416 10.1007/s11085-019-09888-z 2019-03-29