TY - CONF A1 - Weinel, Kristina T1 - Electron-beam-induced synthesis and characterization of disordered plasmonic gold nanoparticle assemblies N2 - Several studies have been shown that the electron beam can be used to create nanomaterials from microparticle targets in situ in a transmission electron microscope (TEM). Here, we show how this method has to be modified in order to synthesize plasmonic gold nanoparticles (NPs) on insulating silicon oxide substrate by employing a scanning electron microscope with a comparatively low acceleration voltage of 30 kV. The synthesized NPs exhibit a random distribution around the initial microparticle target: Their average size reduces from 150 nm to 3 nm with growing distance to the initial Au microparticle target. Similarly, their average distance increases. The synthesized NP assemblies therefore show distinctly different plasmonic behaviour with growing distance to the target, which allows to study consequences of random hybridization of surface plasmon in disordered system, such as Anderson localization. To reveal the surface plasmons and their localization behaviour we apply electron energy loss spectroscopy in the TEM. T2 - DPG spring conference, condensed matter section CY - Berlin, Germany DA - 17.03.2024 KW - Scanning electron microscopy KW - Gold nanoparticle synthesis KW - Disordered assemblies KW - Localized plasmons PY - 2024 AN - OPUS4-59763 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Heuser, Lina T1 - Silver in low-melting alkali zinc borate glasses N2 - Ein aktuelles Forschungsziel ist die Substitution von Bleioxid in niedrig schmelzenden Gläsern z.B. zur Anwendung in Silber-Metallisationspasten. Im Fokus steht hier die Untersuchung der Silberdiffusion in Alkali-Zink-Boratgläsern (X2O-ZnO-B2O3, X = Li, Na, K, Rb). Zudem wird der Redoxzustand des Silbers (Ag) und somit die Art der diffundierenden Silberspezies bestimmt. Hierzu wurde eine metallische Silberschicht mittels Sputterns auf Glaswürfel aufgebracht. Die Wärmebehandlung erfolgte nahe der Glasübergangstemperatur bei 470 °C über 2 h unter Luft und Stickstoffatmosphäre. Die Schichtdicke der Silberbeschichtung betrug 1.8 µm nach der Wärmebehandlung, gemessen mittels Weißlicht-Interferometer. Die Silberdiffusionsprofile wurden mittels Sekundär-Neutral-Teilchen-Massenspektrometrie gemessen. Die Diffusionskoeffizienten des Silbers liegen in der Größenordnung von ~10-14 cm2/s und unterscheiden sich nur gering in Abhängigkeit des Alkali-Ions im Glas. Mittels Fluoreszenz-Spektroskopie ließen sich gelöste Ag+-Ionen und [Agm]n+-Cluster nach der Wärmebehandlung unterscheiden. Zusätzlich konnten ausgeschiedene metallische Silber-Partikel im Natrium-enthaltenden Glas mittels Transmissionselektronenmikroskopie beobachtet werden. Diese haben einen mittleren Durchmesser von ~6 nm. N2 - Substitution of lead oxide in low-melting glasses, e.g., for application in silver metallization pastes, is a current research goal. This work is focused on the investigation of silver diffusion in alkali zinc borate glasses (X2O-ZnO-B2O3, X = Li, Na, K, Rb). In addition, the redox state of silver (Ag) and thus the type of diffusing silver species were studied. For this purpose, a metallic silver coating was applied on glass cubes by means of sputtering. Heat treatment of the samples was performed close to the glass transition temperatures at 470 °C for 2 h under air and nitrogen atmosphere. Coating thickness was 1.8 µm after heat treatment, measured by a white light interferometer. Silver diffusion profiles were measured by means of secondary neutral mass spectrometry. The silver diffusion coefficients are in the range of ~10-14 cm2/s and indicate no significant differences depending on the type of alkali ions in the glass. Dissolved Ag+-ions and [Agm]n+-clusters in the glasses were differentiated using fluorescence spectroscopy. Precipitated metallic silver particles in the sodium containing glass were observed by means of transmission electron microcopy. Their mean particle diameter was ~6 nm. T2 - Living Glass Surfaces XI - Year of Glass CY - Ilmenau, Germany DA - 14.09.2022 KW - Alkali zinc borate glasses KW - Silver diffusion KW - Transmission electron microscopy KW - Fluorescence spectroscopy KW - Silver cluster PY - 2022 AN - OPUS4-55736 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Manzoni, Anna Maria T1 - High temperature oxidation of CrFeNi in synthetic air N2 - The surface corrosion behaviour is a key issue which determines whether the material is applicable at a given atmosphere. Medium-entropy alloy FeCrNi alloy was exposed to synthetic air at 1000°C, 1050°C, and 1100 °C for up to 1000 h using a thermobalance. The oxidation rate was parabolic at 1000 and 1050°C, but breakaway occurred at 1100°C after 5 h of aging time. The whole oxide scales formed under the isothermal oxidation tests spalled off and additional oxidation tests were carried out at 1000 °C and 1050°C for 24 h and up to 100 h at 1000°C in a tubular furnace. The corrosion behaviour of the MEA was analysed by scanning electron microscope, energy-dispersive X-ray spectroscopy, and X-ray diffraction and compared to the behaviour of 316 L. The experimental results showed that under all conditions chromium is the main diffusion element resulting in the formation of a Cr2O3 layer at the MEA surface. Spallation of the layer induces the formation of additional oxidation products under the surface of the (spalled off) chromia layer. T2 - Euromat 2023 CY - Frankfurt a. M., Germany DA - 03.09.2023 KW - Medium entopy alloy KW - Oxidation KW - Scanning electron microscopy KW - Thermogravimetric analysis PY - 2023 AN - OPUS4-58198 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Manzoni, Anna T1 - High-temperature in-situ investigation of refractory high entropy superalloys N2 - The spinodal decomposition in bcc structured refractory alloys can be used as a potential strengthening mechanism, as has been demonstrated over the last decade in research on high entropy alloys and compositionally complex alloys. Early work from the 1990s already showed the possibility of further enhancing this spinodal decomposition by adding the element Al, which in addition to spinodal decomposition also provides an ordering process in the otherwise disordered bcc phases of the alloy. Nevertheless, the knowledge of refractory high entropy (super)alloy systems, is still in its infancy and requires further research to fully exploit its potential for high temperature applications in the future. Two refractory alloys of the Al-Nb-Ta-Ti-Zr family are investigated via (high temperature in-situ) XRD, in the long run for understanding spinodal decomposition properties. Ex-situ XRD and TEM observations show the formation of at least one bcc phase and an ordered B2 phase. In addition, one or more Al-Zr rich phases are observed, which are not part of the spinodal phases and are unwanted. The high-temperature observations at 1000°C for 60 h show a remarkable increase in peak width up to 2° FWHM that does not disappear after cooling in the furnace. Ex-situ observations after 1000°C for hundreds of hours and subsequent quenching show narrow peaks (max 0,2° FWHM) at the same position. This and several other observations will be presented in this talk and possible explanations are presented. T2 - Euromat 2025 CY - Granada, Spain DA - 14.09.2025 KW - High-entropy alloys KW - Superalloys KW - X-ray diffraction KW - In-situ KW - Scanning electron microscopy PY - 2025 AN - OPUS4-64840 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Suárez Ocano, Patricia T1 - High temperature and low stress creep behavior of the refractory chemically complex alloy AlMo 0.5 NbTa 0.5 TiZr N2 - The refractory chemically complex alloy (rCCA) AlMo0.5NbTa0.5TiZr, with a density of 7.4 g/cm3, shows a compressive ultimate strength of 772 MPa at 1000 °C, comparatively surpassing Ni-base and other rCCAs. Its dual-phase microstructure, with a high volume fraction (≈ 62%) of cuboidal and plate-like particles coherently embedded in a continuous matrix, resembles the well-known pattern of the γ/γ" in Ni-base superalloys. Its developers have thus implied that it could stand as structural alloy for high temperature (HT) applications. Here, we report the HT creep properties and the underlying microstructural changes of the rCCA AlMo0.5NbTa0.5TiZr to propose deformation and degradation micromecanisms for this regime. The material was produced by arc-melting and subsequently heat treated in argon: at 1400 °C for 24 h plus a hot isostatic pressure treatment at 1370 °C and 170 MPa for 4 h, with a cooling rate of 10 K/min. Miniaturized tensile specimens (≈ 28 x 7 x 2 mm) were cut and polished to a quality of 1 μm. Creep tests were conducted in vacuum in the respective temperature and stress range 800-1200 °C and 30-120 MPa. For observation, thin slices were extracted from the gauge length, away from the fracture surface, grinded to a thickness of 100 μm, and electropolished to electron transparency. The microstructure was observed on the electropolished specimens using scanning (S) as well as transmission (T) electron microscopy (EM). The Norton plot gives Norton exponents of about 3.1 and 3.2 for temperatures of 1000 and 1100 °C, respectively. Curiously, creep rate minima are very close for a stress level of 30. The starting microstructure reflects a macroscopically lean coarse grain structure and a microscopically fine-meshed basketweave structure with coherency dislocations only around coarsened particles usually close to subgrain boundaries. Results are discussed on the base of variations of this starting microstructure after interrupted and ruptured creep tests. T2 - 15th International Conference on Creep and Fracture of Engineering Materials and Structures CY - Online meeting DA - 14.06.2021 KW - Creep behavior KW - Chemically complex alloy KW - Cow stress PY - 2021 AN - OPUS4-53388 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Suárez Ocano, Patricia T1 - Effect of the heat treatment in the microstructure of a refractory chemically complex alloy N2 - A set of some unexpected and interesting microstructures has put the so-called complex concentrated alloys (CCAs) in the eye of the scientific community. The AlMo0.5NbTa0.5TiZr refractory (r)CCA, aimed at substituting Ni-base superalloys in gas turbine applications, belongs to this alloy family. After a two-stage heat treatment, this rCCA morphologically resembles the typical a two-phase microstructure of the latter. The objective of this work consists in determining the effect of the two stages of the heat treatment on the microstructure of the AlMo0.5NbTa0.5TiZr alloy to eventually improve it in terms of homogeneity and porosity. T2 - Third International Conference on High Entropy Materials (2020) CY - Berlin, Germany DA - 27.09.2020 KW - Annealing KW - Hot isostatic pressing KW - Refractory chemically complex alloy KW - Microstructure PY - 2020 AN - OPUS4-53386 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Manzoni, Anna Maria T1 - Reliable welding of high-entropy alloys N2 - The importance of high-entropy alloy (HEAs) in the field of materials research is increasing continuously and numerous studies have been published, recently. These are mainly focused on manufacturing of different alloy systems having excellent structural properties from low to high temperatures. Therefore, HEAs are of high potential for many applications in very demanding conditions. However, this is so far limited by poor knowledge and experience regarding economic and reliable component manufacturing. The processability of HEAs has hardly been investigated so far, indicated by the small number of publications worldwide: welding <30 and machining <5. Hence, this contribution provides an overview about the current state of the art on processing of HEAs. Fundamental principles are shown for safe weld joints while ensuring high component integrity. For safe welding, the combined consideration of complex interactions of material, construction and process is necessary. Recent studies on different HEAs showed the influence of heat input by means of different welding processes on the microstructure and respective properties. Based on intensive literature survey and on our initial study, the main research objectives of processing HEAs are presented. T2 - ICHEM 2020 - Third International Conference on High Entropy Materials CY - Berlin, Germany DA - 27.09.2020 KW - High Entropy Alloy KW - Welding KW - Welding processing influences PY - 2020 AN - OPUS4-51591 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Cornelsen Sampaio Kling, I. A1 - Pauw, Brian Richard A1 - Agudo Jácome, Leonardo A1 - Archanjo, B. S. A1 - Simão, R. A. T1 - Development and characterization of starch film and the incorporation of silver nanoparticles N2 - Starch is one of the biopolymers being used for bioplastic synthesis. For production, starch can be combined with different plasticizers, starches from different plant sources and even with nanomaterials to improve or to add film properties. The challenge of adding these, e.g. in the form of silver nanoparticles (AgNp) is to determine the concentration so as to avoid impairing the properties of the film, agglomeration or altering the visual characteristics of the film. In this study, a starch film synthesis route and the incorporation of silver nanoparticles has been proposed in order not to alter the properties of the film while maintaining the transparency and a clear colour of the starch film. The results showed that the proposed synthesis route is promising, efficient, reproducible, fast and the film has good mechanical properties. T2 - Semana MetalMat & Painal PEMM 2020 CY - Online meeting DA - 23.11.2020 KW - Biofilm KW - Silver nanoparticle KW - Starch KW - Starch nanoparticle PY - 2020 SP - 1 EP - 2 AN - OPUS4-51940 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Manzoni, Anna Maria T1 - Tuning high entropy alloys towards superalloy applications N2 - The discovery of the high entropy concept at the beginning of the 3rd millennium lead to a worldwide increase in metallurgical research, as the possible element combinations seemed nearly endless and the range of applications wide. In the early years of research, one of the main goals was the discovery of a single-phase high entropy alloy. As research evolved, it was found that properties could be enhanced by opening the HE-concept towards multiphase alloys, and from the wide area of possibilities our group chose a tuning of the properties towards high temperature application. Compositionally complex Al10Co25Cr8Fe15Ni36Ti6 alloy, which is single-phase at high temperature, around 1200°C, shows a three phase morphology at intermediate temperatures, around 800°C. A high temperature homogenization procedure has to be applied in order to decrease the segregation induced by the dendritic growth. Subsequent annealing promotes the formation of the strengthening γ' precipitates. The alloy shows a positive lattice misfit between the γ and the γ' phase, which can be an indicator for good creep properties. The microstructure can be optimized by adding trace elements such as Mo and Hf, known as γ and γ' strengtheners in Ni-based superalloys, respectively. Atom probe measurements show that Mo segregates into the γ matrix, and Hf prefers the γ' precipitates, where it increases the lattice parameter and thus also the lattice misfit, by about 50%. The alloy family shows interesting mechanical properties, especially the Al9.5Co25Cr8Fe15Ni36Ti6Hf0,5 alloy – its tensile properties are better than those of commercial Alloy 800H and IN617 at temperatures up to 700°C. T2 - BAM Abteilungsseminar CY - Online meeting DA - 21.01.2021 KW - High entropy alloys KW - Compositionally complex alloys KW - Superalloys KW - Hochentropie-Legierung KW - Legierung mit komplexer Zusammensetzung KW - Superlegierung PY - 2021 AN - OPUS4-52442 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kling, I. C. S. T1 - Development and characterization of starch film and the incorporation of silver nanoparticles N2 - Starch is one of the biopolymers being used for bioplastic synthesis. For production, starch can be combined with different plasticizers, starches from different plant sources and even with nanomaterials to improve or to add film properties. The challenge of adding these, e.g. in the form of silver nanoparticles (AgNp) is to determine the concentration so as to avoid impairing the properties of the film, agglomeration or altering the visual characteristics of the film. In this study, a starch film synthesis route and the incorporation of silver nanoparticles has been proposed in order not to alter the properties of the film while maintaining the transparency and a clear colour of the starch film. The results showed that the proposed synthesis route is promising, efficient, reproducible, fast and the film has good mechanical properties. T2 - Semana MetalMat & Painal PEMM 2020 CY - Online meeting DA - 23.11.2020 KW - Biofilm KW - Starch KW - Starch nanoparticle KW - Silver nanoparticle PY - 2020 AN - OPUS4-51828 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -