TY - JOUR A1 - Manzoni, Anna Maria A1 - Mohring, Wencke A1 - Schneider, Mike A1 - Laplanche, Guillaume A1 - Hagen, Sebastian Peter A1 - Stephan‐Scherb, Christiane T1 - High‐Temperature Oxidation of the CrFeNi Medium‐Entropy Alloy N2 - The isothermal high‐temperature oxidation behavior of the equiatomic CrFeNi medium‐entropy alloy is a key issue that determines whether this material is suited for high‐temperature application. In this view, the understanding of the long‐term behavior is even more crucial than short‐term corrosion effects. Herein, a single‐phase CrFeNi alloy of the face‐centered‐cubic structure is exposed to synthetic air at 1000, 1050, and 1100 °C for 24, 100, and 1000 h and its oxidation behavior is systematically compared to that of 316L steel, which shows a surprising initial oxidation stabilization during early stages. The oxidation rate of CrFeNi is parabolic at 1000 °C (with a parabolic constant kp = 1.4·10−5 mg−2 cm−4 s−1) and 1050 °C (kp = 2.7·10−5 mg−2 cm−4 s−1), but breakaway oxidation occurs at 1100 °C after 4 h of exposure. In all cases, the oxide scales are found to (at least) partially spall off. Chromium diffuses outward to form a Cr2O3 layer at the gas/oxide interface, and a thin layer of (Cr, Fe, Ni)3O4 is identified at the oxide/alloy interface. Unlike the 316L alloy, which contains more Mn and Fe, the CrFeNi alloy does not show any catastrophic oxidation behavior at the investigated conditions. KW - Corrosion KW - Medium-entropy alloy KW - Scanning electron microscopy PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-636672 DO - https://doi.org/10.1002/adem.202500400 SN - 1438-1656 SP - 1 EP - 14 PB - Wiley VHC-Verlag AN - OPUS4-63667 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Serrano-Munoz, Itziar A1 - Agudo Jácome, Leonardo A1 - Thompsom, Sean A1 - Schneider, Judy T1 - On the transferability of post-processing heat treatments designed for PBF-LB IN718 alloys to directed energy deposition specimens N2 - Many processes are being developed for metal additive manufacturing (AM) which vary by their heat source and feedstock. The use of directed energy deposition (DED) is growing due to its ability to build larger structures outside of a contained powder bed chamber. However, the only standard exclusively for post-build heat treatment of AM IN718 is ASTM standard F3055-14a, developed for powder bed fusion (PBF). This study evaluates the applicability of this current heat treatment standard to AM IN718 specimens produced using two methods of DED: laser-blown powder (LP)-DED and arc-wire (AW)-DED. Electron microscopy and X-ray diffraction techniques were used to characterize the specimens in the as-built condition and after the full heat treatment (FHT) specified in F3055. No evidence of remaining Laves phase was observed in the two DED specimens after the FHT. Yield strengths for the DED specimens were 1049 MPa for FHT AW-DED and 1096 MPa for LP-DED, higher than the minimum stated for PBF-LB IN718 of 920 MPa. The size, morphology, inter-spacing, and diffraction patterns of the γ´ and γ´´ strengthening precipitates are found to be similar for both DED processes. Differences were observed in the microstructure evolution where the F3055 heat treatments resulted in partial recrystallization of the grain structure, with a higher content of annealing twins observed in the AW-DED. These microstructural differences correlate with differences in the resulting elongation to failure. Thus, it is proposed that variations in heat treatments are needed for optimizing IN718 produced by different AM processes. KW - Additive manufacturing variants KW - Directed energy deposition (DED) KW - Post-process heat treatments KW - SEM-EBSD and TEM microscopy KW - XRD phase analysis PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-628165 DO - https://doi.org/10.1007/s00170-025-15386-1 SN - 1433-3015 VL - 137 IS - 7-8 SP - 3949 EP - 3965 PB - Springer Science and Business Media LLC AN - OPUS4-62816 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Weinel, Kristina A1 - Hahn, Marc Benjamin A1 - Lubk, Axel A1 - González Martínez, Ignacio Guillermo A1 - Büchner, Bernd A1 - Agudo Jácome, Leonardo T1 - Nanoparticle Synthesis by Precursor Irradiation with Low-Energy Electrons N2 - Nanoparticles (NPs) and their fabrication routes are intensely studied for their wide range of application in optics, chemistry, and medicine. Γ-ray and ion irradiation of precursor matter are established methods that facilitate tailored NP synthesis without complicated chemistry. Here, we develop and explore NP synthesis based on irradiating precursor microparticles with low-energy electron beams. We specifically demonstrate the fabrication of plasmonic gold nanoparticles of sizes between 3 and 350 nm on an amorphous SiOx substrate using a 30 kV electron beam. By detailed comparison with electron scattering simulations and thermodynamic modeling, we reveal the dominant role of inelastic electron–matter interaction and subsequent localized heating for the observed vaporization of the precursor gold microparticles. This general principle suggests the suitability of electron-beam irradiation for synthesizing NPs of a wide class of materials. KW - Gold Nanoparticle KW - Scanning Electron Microscopy KW - In situ irradiation KW - Thermodynamic modelling KW - Heat Transfer PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-627609 DO - https://doi.org/10.1021/acsanm.4c06033 SN - 2574-0970 VL - 8 IS - 10 SP - 4980 EP - 4988 PB - ACS Publications CY - Washington, DC AN - OPUS4-62760 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Feng, Wen A1 - Schulz, Johannes A1 - Wolf, Daniel A1 - Pylypenko, Sergii A1 - Gemming, Thomas A1 - Weinel, Kristina A1 - Agudo Jácome, Leonardo A1 - Büchner, Bernd A1 - Lubk, Axel T1 - Secondary electron emission from gold microparticles in a transmission electron microscope: comparison of Monte Carlo simulations with experimental results N2 - We measure the electron beam-induced current to analyze the electron-induced secondary electron (SE) emission from micron-sized gold particles illuminated by 80 and 300 keV electrons in a transmission electron microscope. A direct comparison of the experimental and simulated SE emission (SEE) employing Monte Carlo scattering simulations based on the GEANT4 toolkit yields overall good agreement with a noticeable discrepancy arising from the shortcoming of the GEANT4 scattering cross sections in the low-loss regime. Thus, the electron beam-induced current analysis allows to quantify the inelastic scattering including SEE in the transmission electron microscope and provides further insight into the charging mechanisms. KW - Electron beam-induced current KW - Transmission electron microscopy KW - Secondary electron emission KW - Secondary electron yield KW - Gold micronoparticle PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-622557 DO - https://doi.org/10.1088/1361-6463/ad9840 VL - 58 IS - 8 SP - 1 EP - 7 PB - IOP Publishing CY - Bristol, GB AN - OPUS4-62255 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Weinel, Kristina A1 - Schultz, Johannes A1 - Kalady, Mohammed Fayis A1 - Wolf, Daniel A1 - Agudo Jácome, Leonardo A1 - Lubk, Axel T1 - Fabrication of 2-dimensional disordered assemblies of gold nanoparticles and investigation of localized surface plasmon resonances N2 - Interaction of electromagnetic waves, such as electron beams or light, with conductive material can lead to localized surface plasmon resonances (LSPRs) where the incoming energy can be deposited in a collective excitation of electrons of the conduction band, which in turn can result in coherent localized plasmon oscillations. LSPR in metallic nanostructures, such as nanoparticles (NPs), which are sensitive to geometry, material composition and environment, are currently utilized in a wide range of applications, such as surface-enhanced Raman spectroscopy, plasmonic wave guides, improved solar cells, on-chip particle accelerators and nanoantennas. A host of studies that focus on plasmonic NPs ranging from single NPs with several shapes (cubic, spherical, tetrahedral) over 1D assemblies of NPs such as chains, to ordered 2D assemblies of NPs show an increase of the complexity regarding the hybridization behavior of LSPRs eventually lead to delocalized Surface Plasmons. Furthermore, Anderson predicted in 1977 the absence of diffusion or delocalization of waves in disordered systems, which has been discussed as the underlying mechanism for LSPRs localization in disordered metallic thin films and ultrathin 2D networks. Our aim is to further develop these studies on the surface plasmon localization in disordered structures by (1) developing a novel NPs assembly fabrication method that allows fabricating disordered assemblies of NPs of a wide range of NPs sizes, and (2) probing the LSPR with high-resolution electron energy-loss spectroscopy (EELS). Moreover, the dominant dipolar interaction between the NPs, also facilitates an efficient numerical modeling of these systems, which in comparison with the experiments allows for an in-depth study of the impact of various geometric parameters as well as retardation and life-time damping on the observed localization behavior. To synthesize 2D disordered assemblies of gold NPs on a TEM transparent silicon oxide substrate, a new synthesis routine was developed. This procedure is based on sublimation and redeposition of a gold microparticle precursor induced by an electron beam in a scanning electron microscope (SEM) operated at 30 kV. To characterize the assembly of synthesized NPs in terms of size, shape and spreading over the substrate, TEM measurements were conducted subsequently. To study LSPRs experimentally, EELS in scanning transmission electron microscopy (STEM) mode was carried out. The numerical modelling of LSPRs was performed using a self-consistent dipole model. The synthesized 2D disordered gold NPs assemblies exhibit a gradient in the NPs mean size, which ranges from 100 nm close to the precursor location down to 2 nm at a distance of more than 20 µm from the precursor location. Additionally, the interparticle distance between the gold NPs increases with increasing distance to the precursor location. The experimental investigation as well as the numerical simulation of the LSPRs demonstrate a localization behavior that decreases toward larger energies, which is driven by the disorder of the NPs assembly (mainly the random particle distance). That localization behavior stays in contrast to what was found in ultrathin 2D gold networks showing increasing of localization towards higher LSPRs energies. By varying the geometric parameters of the NPs assembly in the simulation, we could identify the NPs thickness as the parameter, that determines the energy-dependence of the localization. Specifically, a critical thickness of approx. 10 nm separates the two localization regimes, which correlates to the energy of the dipole mode resonance crucially depending on the thickness of the NPs. 2D disordered assemblies of gold NPs of a wide range of NPs sizes and distances can be synthesized directly on thin substrates facilitating structural characterization and EELS measurements in a TEM. It could be shown that such assemblies exhibit LSPRs with a localization behavior that may be tuned by the NPs sizes (including thickness) and interparticle distances. The proposed synthesis of random NPs assemblies opens new avenues for fundamental studies on Anderson localization in disordered plasmonic structures as well as its applications such as surface-enhanced Raman spectroscopy where localization behavior must be tuned to specific wave lengths. T2 - 17th European Microscopy Congress (EMC 2024) CY - Copenhagen, Denmark DA - 26.08.2024 KW - Scanning electron microscopy KW - Gold nanoparticle synthesis KW - Disordered assemblies KW - Localized surface plasmon resonances KW - Transmission electron microscopy PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-618330 DO - https://doi.org/10.1051/bioconf/202412932007 VL - 129 SP - 1 EP - 2 PB - EDP Sciences CY - Les Ulis AN - OPUS4-61833 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Suárez Ocaño, Patricia A1 - Agudo Jácome, Leonardo T1 - Creep degradation of the high entropy superalloy AlMo0.5NbTa0.5TiZr N2 - The refractory high entropy superalloy (RSA) AlMo0.5NbTa0.5TiZr was the first of a class, with a dual-phase microstructure that resembles that of γ/γ’ in Ni-base superalloys), and the open question whether it performs better as structural alloy under high temperature (HT) applications. Here, we address the HT creep behavior and its associated microstructural degradation of this RSA. The material was produced by arc-melting, heat treatment in argon (24 h @ 1400 °C + 4 h hot isostatic pressure @ 1370 °C & 170 MPa). Interrupted vacuum creep tests were performed at 900-1100 °C and 30-120 MPa. Scanning (S) and transmission (T) electron microscopy (EM) were used to reveal degradation mechanisms. At 1100 °C (Fig.1, middle), the dual A2/B2 microstructure coarsens and partially transforms into a Zr-Al-rich phase (red arrow). An additional external load pronounces directional coarsening. Results are further discussed on the base dislocation and additional damage mechanisms. T2 - International Conferende on Strength of Materials (ICSMA) 2022 CY - Metz, France DA - 26.06.2022 KW - High entropy superalloy KW - Rrafting KW - Dislocation creep KW - Phase transformation PY - 2022 AN - OPUS4-63856 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Paulisch-Rinke, M. C. A1 - Manzoni, Anna Maria A1 - Agudo Jácome, Leonardo A1 - Vogel, F. A1 - Reimers, W. T1 - Influence of chemical composition on microstructure and mechanical properties in the extruded aluminum alloys 7021B and 7175 N2 - The aim of this study is to improve the mechanical properties of Al 7xxx series alloys by achieving the strengthening benefits typically provided by Cu while avoiding the formation of low-melting eutectic phases associated with excessive Cu content. This is accomplished through a tailored combination of alloying elements and optimized thermomechanical treatments. Alloys 7021B (high Zn content) and 7175 (high Cu and Mg content) are analyzed and optimized threefold in this study: the heat treatment, the microstructural evolution and the mechanical properties are investigated by several methods and compared with the aim of improving the process parameters for subsequent application. The peak-aging process is optimized via compression tests to overcome the strength-ductility trade-off. Microstructure and phase chemistry analyses by transmission electron microscopy and atom probe tomography enable a better understanding of the underlying morphological features such as the spatial distribution, and the chemical composition of the hardening phases. The mechanical properties of the peak-aged alloys are determined by compression and tensile tests. Both alloys exhibit very high strength – even by 7xxx series standards. It can be traced back to the dislocation movement: it is impeded both by homogeneously distributed cuttable Guinier–Preston zones in both alloys and by non-cuttable η’ precipitates. As a result, we demonstrate that alloy 7021B offers novel possibilities for processing and industrial application: high strength, typically associated with Cu containing alloys, can also be obtained in Cu free alloys, if the Zn content is sufficiently high. We can thus suggest new opportunities for processing and industrial applications by reducing the risk of forming low-melting eutectic phases. KW - Aluminium alloys KW - Transmission electron microscopy KW - Atom probe tomography KW - Extrusion KW - Mechanical properties PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-640338 DO - https://doi.org/10.1016/j.matdes.2025.114649 SN - 0264-1275 VL - 258 SP - 1 EP - 11 PB - Elsevier Ltd. AN - OPUS4-64033 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Müller-Elmau, Johanna A1 - Göbel, Artur A1 - Junge, Paul A1 - Müller, Julian A1 - Rousseau, Tom A1 - Görke, Oliver A1 - Nikasch, Christian A1 - Kiliani, Stefan T1 - Thermal cycling of YAG infiltration and plasma sprayed coatings as environmental barrier coating on ceramic heat shields for use in hydrogen operating gas turbines N2 - Environmental barrier coatings (EBC) are intended to protect alumina ceramic tiles in hot water vapor conditions, enabling gas turbines to operate with higher hydrogen content or even pure hydrogen. For these operating conditions, yttrium aluminum garnet (YAG) promises the highest protection against hydrolysis, which can be applied via atmospheric plasmaspraying (APS). To enhance the protection efficiency, the coating is combined with a prior infiltration of the base material. The obtained design acts as in-depth protection even if the coating exhibits cracks. KW - Thermal shock KW - Thermal cycles KW - Environmental barrier coating (EBC) KW - Water vapor corrosion PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-639829 DO - https://doi.org/10.1016/j.oceram.2025.100837 VL - 23 SP - 1 EP - 7 PB - Elsevier Ltd. AN - OPUS4-63982 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Agudo Jácome, Leonardo T1 - In situ electron-beam 'melting' (sublimation) of gold microparticles in the SEM N2 - Gold micro particles have been modified in the past using the high power density of a localized electron beam of acceleration voltages above 100 kV as an energy source to transform matter at the sub-micron scale in a transmission electron microscope uses. Here, the e-beam-induced transformation of precursor microparticles employing a low-energy e-beam with an acceleration voltage of 30 kV in a scanning electron microscope is implemented. Under these conditions, the technique can be classified between e-beam lithography, where the e-beam is used to mill holes in or grow some different material onto a substrate, and e-beam welding, where matter can be welded together when overcoming the melting phase. Modifying gold microparticles on an amorphous SiOx substrate reveals the dominant role of inelastic electron-matter interaction and subsequent localized heating for the observed melting and vaporization of the precursor microparticles under the electron beam. Monte-Carlo scattering simulations and thermodynamic modeling further support the findings. T2 - IKZ International Fellowship Award & Summer School 2025 from May 5 to 7, 2025 CY - Berlin, Germany DA - 05.05.2025 KW - Gold Nanoparticle KW - Scanning Electron Microscopy KW - In situ irradiation KW - Thermodynamic modelling KW - Heat Transfer PY - 2025 AN - OPUS4-63256 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Agudo Jácome, Leonardo A1 - Manzoni, Anna Maria T1 - Elementverteilung in Hochentropiewürfelchen N2 - Seit Beginn der Luftfahrt Anfang des letzten Jahrhunderts ist die Menschheit auf der Suche nach neuen Materialien, die das Abenteuer Fliegen sicherer, angenehmer, schneller und rentabler gestalten. Hochentropielegierungen sind solche vielversprechenden Materialien. Die richtige Analytik hilft dabei, besser zu verstehen, wie deren Zusammensetzung und atomare Anordnung die makroskopischen Eigenschaften beeinflusst. KW - Chemically complex alloy KW - Transmissionselektronenmikroskopie KW - Energiedisersive Röntgenspektroskopie PY - 2022 UR - https://www.gdch.de/fileadmin/downloads/Netzwerk_und_Strukturen/Fachgruppen/Analytische_Chemie/Mitteilungsblatt/Internet_AC04-2022.pdf SN - 0939-0065 IS - 4 SP - 12 EP - 14 PB - Gesellschaft Deutscher Chemiker CY - Frankfurt, Main AN - OPUS4-56699 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -