Publications

PhD Yindong Fang honored with poster prize at LI CALPHAD conference in 2024 for his work on „Phase equilibria, microsegregations and mechanical properties of Inconel 718 alloy samples processed in electromagnetic levitation facility”

Image: L. Tkotz
PhD Yindong Fang honored with poster prize at LI CALPHAD conference in 2024 for his work on „Phase equilibria, microsegregations and mechanical properties of Inconel 718 alloy samples processed in electromagnetic levitation facility” watermark —

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  1. Near-Surface Microstructure and Properties of High-Carbon Metastable Austenitic Steels Subjected to Abrasive Wear

    Authors
    J. Ingber, J. Maier, S. Lippmann, K. Freiberg, T. Studecky, M. Kunert
    Year of publication
    Published in:
    Metallography, microstructure, and analysis: application and innovation for metals, alloys, and engineered materials
    The microstructure and properties in the near-surface region of two high-carbon metastable austenitic steels after two-body abrasive wear were studied. The samples were subjected to wear loads in a range of 8–32 N (corresponding to approximately 0.1–0.4 MPa). Vickers hardness measurements on the worn surface as well as nanoindentation measurements on the cross section present a significant hardness increase from the bulk toward the surface of up to 400%. Electron channeling contrast imaging was utilized to assign the indents from the nanoindentation measurements to the martensitic or austenitic phase. Within a subsurface layer with a thickness of a few microns, it was impossible to distinguish a phase via these images. Magnetic force microscopy revealed a few microns thick martensitic layer, which is the main cause of the significant hardness increase in the near-surface region. No considerable influence of the wear load (within the tested load range) on the resulting microstructure and mechanical properties was found. Transmission electron microscopy images reveal a grain size of several nanometers within the martensitic subsurface layer, which accounts for the observed ductility on the worn surfaces, despite the inherent brittleness typically associated with high-carbon martensite.
    University Bibliography Jena:
    fsu_mods_00036070External link

  2. Advancing thermal property measurements with a calibrated temperature gradient method on the example of Ag-35 wt% Zn Alloy

    Authors
    J. Zhuo, A. Walnsch, M. Kriegel, S. Lippmann
    Year of publication
    Published in:
    Journal of alloys and compounds : JAL
    The thermal transport properties of an Ag–35 wt% Zn alloy were systematically investigated over a large temperature range from 350 K to 800 K. Thermal conductivity, thermal diffusivity, and specific heat capacity were determined using a combination of laser flash analysis (LFA), the steady-state Temperature Gradient (TG) method, and differential scanning calorimetry (DSC). The thermal conductivity values ranged from 65 W m⁻¹ K⁻¹ to 75 W m⁻¹ K⁻¹. After applying heat-loss corrections to the TG method, the results exhibited close agreement with the thermal conductivities derived from LFA and CALPHAD data. Also, the specific heat capacity values obtained from combining the calibrated TG method and thermal diffusivity values from commercial LFA were consistent with the DSC measurements. In addition, since the TG method operates with a continuous measurement principle, unlike the stepwise approach used in LFA, it successfully detected the ζ→β phase transformation near 540 K, which aligns excellently with DSC and CALPHAD data. This study demonstrates the feasibility and enhanced accuracy of the corrected steady-state TG method for a reliable and comprehensive thermal characterization of alloys.
    University Bibliography Jena:
    fsu_mods_00044135External link

  4. Soft X-ray imaging with coherence tomography in the water window spectral range using high-harmonic generation

    Authors
    J. Reinhard, F. Wiesner, M. Hennecke, T. Sidiropoulos, S. Kaleta, J. Späthe, J. Abel, M. Wünsche, G. Schmidl, J. Plentz, U. Hübner, K. Freiberg, J. Apell, S. Lippmann, M. Schnürer, S. Eisebitt, G. Paulus, S. Fuchs
    Year of publication
    Published in:
    Light: Science and Applications
    High-harmonic generation (HHG) is used as a source for various imaging applications in the extreme ultraviolet spectral range. It offers spatially coherent radiation and unique elemental contrast with the potential for attosecond time resolution. The unfavorable efficiency scaling to higher photon energies prevented the imaging application in the soft X-ray range so far. In this work we demonstrate the feasibility of using harmonics for imaging in the water window spectral region (284 eV to 532 eV). We achieve nondestructive depth profile imaging in a heterostructure by utilizing a broadband and noise-resistant technique called soft X-ray Coherence Tomography (SXCT) at a high-flux lab-scale HHG source. SXCT is derived from Optical Coherence Tomography, a Fourier based technique that can use the full bandwidth of the source to reach an axial resolution of 12 nm in this demonstration. The employed source covers the entire water window, with a photon flux exceeding 10 ⁶ photons/eV/s at a photon energy of 500 eV. We show local cross sections of a sample consisting of Aluminium oxide and Platinum layers of varying thickness on a Zinc oxide substrate. We validate the findings with scanning and transmission electron microscopy after preparation with focused ion beam milling.
    University Bibliography Jena:
    fsu_mods_00030098External link

  5. Nanostructured Ti–6Al–4V Reduces Adhesion of Several Bacterial Species: An In Vitro Study

    Authors
    S. Khalatbarizamanpoor, A. Nowotnick, S. Lippmann, A. Häder, F. Otto, L. Raupach, T. Fritz, Y. Reisser, J. Bossert, B. Löffler, K. Jandt
    Year of publication
    Published in:
    Small science
    Biomaterial-associated infections (BAIs) and insufficient early cellular response remain critical challenges for orthopedic implants. We introduce a comprehensive study that bridges current knowledge gaps by examining an early-stage antimicrobial effect on the clinically relevant alloy Ti–6Al–4V. It combines pathogenic strains with parallel osteoblast assays and tilted-view SEM analysis to obtain a qualitative understanding of the adhesion mechanisms. Detailed physicochemical characterization revealed a progressive increase in nanoscale roughness and oxide layer thickness, accompanied by selective Al/V depletion and pronounced hydrophilization. To evaluate biological responses, we used standardized in vitro models with Staphylococcus aureus, Staphylococcus epidermidis, and Escherichia coli. Bacterial adhesion was quantified by SYTO9 staining, a GFP-expressing strain as a viability control, and SEM imaging. Nanostructured (R q ≤ 40 nm) surfaces significantly reduced early bacterial attachment compared to polished nanoflat controls. In parallel, osteoblast-like SaOs-2 cells showed stable adhesion and spreading, confirmed by phalloidin/DAPI staining and LDH cytotoxicity assay. Together, these results demonstrate that NaOH-etched Ti–6Al–4V surfaces can impair early microbial adhesion based on physical action and preserve osteoblast compatibility. By integrating advanced materials characterization with microbiological and cell biological assays, we provide a framework for topography-driven surface design toward infection-resistant orthopedic implants that support favorable early osteoblast–surface interactions.
    University Bibliography Jena:
    fsu_mods_00038516External link

  6. Reassessment of Al-Cu System Considering Metastable Extensions of Solid/Liquid Phase Equilibria

    Authors
    Y. Fang, K. Hack, S. Lippmann
    Year of publication
    Published in:
    Journal of phase equilibria and diffusion
    The thermodynamic description of the Al-Cu system is reassessed considering metastable states of Al based alloys in rapid solidification. In previous work, only an improved thermodynamic description of the FCC phase was presented based on experimental results from electromagnetic levitation and simulation results for free dendritic growth to be in accordance with existing thermodynamic descriptions of the liquid phase. The phase diagram thus obtained enabled the correction of the artificial miscibility gap when calculating metastable extensions of the FCC/liquid phase equilibria, the unphysical change of the slope of the solidus line on the Al-rich side and the artificial maximum on the Cu-rich side. However, the description did not well align with the most recent experimental results on the Cu-rich side. The new description reassessing FCC, liquid and the α′-phase demonstrates high consistency with these recent experimental results, reproducing all invariant reactions (temperatures) with an accuracy of ± 4 K and the experimental liquidus line with an accuracy of ± 10 K, all well within the experimental error. The results provide a robust framework for predicting phase behavior under metastable conditions, as confirmed by our experimental data.
    University Bibliography Jena:
    fsu_mods_00027653External link

  7. Experimentelle Untersuchungen zur Identifikation einer Lotlegierung auf Cu-Basis zum Hartlöten mit Schmelztemperaturen unter 800°C

    Author
    M. Salge
    Year of publication
    Die Kombination von unterschiedlichen Materialien mit deutlich voneinander abweichenden physikalischen Eigenschaften, wie Metall-Metall (z. B. Stahl-Aluminium), Metall-Keramik oder Metall-Glas, kann Verbessungen in bestehenden Anwendungen ermöglichen oder sogar vollkommen neue Einsatzgebiete erschließen. Ein wichtiges Verfahren zur Herstellung solcher Verbindungen ist das Hartlöten. Diese Technik ermöglicht stoffschlüssige, widerstandsfähige Fügeverbindungen zwischen verschiedenen Grundmaterialien ohne deren Eigenschaften nennenswert zu beeinträchtigen. Innerhalb des Legierungssystems Ag-Cu-Zn-Sn wurde über die Jahre eine Reihe von Lotlegierungen entwickelt, welche heute kommerziell zum Fügen verschiedenster Materialien verwendet werden und deren Eigenschaften bereits intensiv untersucht worden sind. Wesentliche Verbesserungen hinsichtlich Schmelztemperatur, Benetzung- bzw. Fließverhalten oder mechanischer Eigenschaften dieser Legierungen sind innerhalb des quaternären Ag-Cu-Zn-Sn-Systems nicht mehr möglich. In der vorliegenden Arbeit werden verschiedene Legierungssysteme mit zu herkömmlichen Ag-Cu-Zn-Sn-Legierungen vergleichbaren Eigenschaften hinsichtlich ihrer Phasenbildung untersucht und bewertet, inwieweit sich diese als Alternative zu standardisierten Hartloten eignen. Es werden Cu-Basislegierungen sowohl mit als auch ohne Ag hergestellt und die Auswirkung zusätzlicher Legierungselemente, insbesondere Lithium, auf Gefüge und Eigenschaften wie Schmelztemperatur, Verformbarkeit und Fließverhalten untersucht. Mit dem Ziel, die Entwicklungszeit zu verkürzen, werden für die Untersuchung der Cu-reichen Ecke des Cu-Ga-Sn-Systems Methoden der gerichteten Erstarrung genutzt. So können mit Hilfe von Temperaturgradienten hergestellten Proben in einem großen Zusammensetzungsbereich hinsichtlich des vorliegenden Gefüges, der Härte und des Schmelzbereiches untersucht werden. Zusätzlich werden mit Hilfe der CALPHAD-Methode Solidus- und Liquidusprojektionen optimiert.
    University Bibliography Jena:
    fsu_mods_00025462External link

  9. Comparative Study of Experimental Methods for Measuring Thermal Properties of 100Cr6 Steel Powders

    Authors
    J. Zhuo, H. Kohl, D. Liu, L. Matthäus, A. Bochmann, A. Berger, S. Weber, S. Nolte, S. Lippmann
    Year of publication
    Published in:
    Advanced Engineering Materials
    University Bibliography Jena:
    fsu_mods_00025275External link

  10. Fabrication of shallow EUV gratings on silicon by irradiation with helium ions

    Authors
    J. Kaufmann, R. Ciesielski, K. Freiberg, M. Walther, A. Fernández Herrero, S. Lippmann, V. Soltwisch, T. Siefke, U. Zeitner
    Year of publication
    Published in:
    Nanotechnology
    To accurately achieve structure height differences in the range of single digit nanometres is of great importance for the fabrication of diffraction gratings for the extreme ultraviolet range (EUV). Here, structuring of silicon irradiated through a mask by a broad beam of helium ions with an energy of 30 keV was investigated as an alternative to conventional etching, which offers only limited controllability for shallow structures due to the higher rate of material removal. Utilising a broad ion beam allows for quick and cost effective fabrication. Ion fluence of the irradiations was varied in the range of 10¹⁶ ... 10¹⁷ ions · cm⁻². This enabled a fine tuning of structure height in the range of 1.00 ± 0.05 to 20 ± 1 nm, which is suitable for shallow gratings used in EUV applications. According to transmission electron microscopy investigations the observed structure shape is attributed to the formation of point defects and bubbles/cavities within the silicon. Diffraction capabilities of fabricated elements are experimentally shown at the SX700 beamline of BESSY II. Rigorous Maxwell solver simulation based on the finite-element method and rigorous coupled wave analysis are utilised to describe the experimental obtained diffraction pattern.
    University Bibliography Jena:
    fsu_mods_00023928External link

  11. Ultra shallow silicon EUV gratings fabricated via ion irradiation

    Authors
    J. Kaufmann, R. Ciesielski, K. Freiberg, M. Walther, A. Fernández Herrero, S. Lippmann, V. Soltwisch, T. Siefke, U. Zeitner
    Year of publication
    Published in:
    EUV and X-Ray Optics: Synergy between Laboratory and Space IX: 7-8 April 2025, Prague, Czech Republic
    University Bibliography Jena:
    fsu_mods_00026647External link

  12. Fabrication of ultra-shallow EUV gratings in silicon via ion irradiation

    Authors
    J. Kaufmann, R. Ciesielski, K. Freiberg, M. Walther, A. Herrero, S. Lippmann, V. Soltwisch, T. Siefke, U. Zeitner
    Year of publication
    Published in:
    Advances in X-ray/EUV sources, optics, and components XX
    University Bibliography Jena:
    fsu_mods_00029436External link
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