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5 Werkstofftechnik

  • 5.0 Abteilungsleitung und andere (119) RSS-Feed abonnieren
  • 5.1 Materialographie, Fraktographie und Alterung technischer Werkstoffe (336) RSS-Feed abonnieren
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Autor

  • Unger, Wolfgang (11) (entfernen)

Erscheinungsjahr

  • 2019 (1)
  • 2018 (1)
  • 2017 (2)
  • 2016 (3)
  • 2015 (2)
  • 2013 (2)

Dokumenttyp

  • Zeitschriftenartikel (7)
  • Posterpräsentation (2)
  • Beitrag zu einem Tagungsband (1)
  • Vortrag (1)

Sprache

  • Englisch (9)
  • Deutsch (2)

Referierte Publikation

  • ja (7)
  • nein (4)

Schlagworte

  • ToF-SIMS (5)
  • EBSD (3)
  • Hydrogen (3)
  • SEM (3)
  • AISI 304L (2)
  • Data fusion (2)
  • EDX (2)
  • AES (1)
  • Austenitic stainless steel (1)
  • BAM-L200 (1)
  • Ball milling (1)
  • CRM (1)
  • Certified reference material (1)
  • Crystallinity (1)
  • DSS steel (1)
  • Depth profiling (1)
  • Deuterium (1)
  • Electron backscatter diffraction (1)
  • FIB (1)
  • Hydrogen assisted cracking (1)
  • Hydrogen embrittlement (1)
  • Hydrogen-assisted cracking (1)
  • Imaging (1)
  • Imaging surface analysis (1)
  • Lateral resolution (1)
  • Lean duplex stainless steel (1)
  • Line scan (1)
  • Mapping (1)
  • Martensite (1)
  • NanoValid (1)
  • Nanoparticles (1)
  • Ru dye sensitizer (1)
  • STXM (1)
  • Sharpness (1)
  • Standardisation (1)
  • T-SEM (1)
  • TEM (1)
  • TiO2 films (1)
  • Time-of-flight secondary ion mass spectrometry (1)
  • ToF SIMS (1)
  • Transmission electron microscopy (1)
  • Tribofilm model system (1)
  • X-ray powder diffraction (1)
  • XPEEM (1)
  • XPS (1)
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Organisationseinheit der BAM

  • 5 Werkstofftechnik (11)
  • 5.1 Materialographie, Fraktographie und Alterung technischer Werkstoffe (11)
  • 6 Materialschutz und Oberflächentechnik (11)
  • 6.1 Oberflächenanalytik und Grenzflächenchemie (11)
  • 9 Komponentensicherheit (5)
  • 9.0 Abteilungsleitung und andere (5)
  • 1 Analytische Chemie; Referenzmaterialien (2)
  • 1.3 Strukturanalytik (2)
  • 5.2 Experimentelle und modellbasierte Werkstoffmechanik (2)

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Comprehensive characterization of ball-milled powders simulating a tribofilm system (2016)
Häusler, Ines ; Dörfel, Ilona ; Peplinski, Burkhard ; Dietrich, Paul ; Unger, Wolfgang ; Österle, Werner
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.
Comprehensive morphological and chemical characterization of thin engineered TiO2films (2015)
Unger, Wolfgang
Comprehensive study of deuterium-induced effects in in austenitic stainless steel AISI 304L (2019)
Röhsler, Andreas ; Sobol, Oded ; Unger, Wolfgang ; Böllinghaus, Thomas
The damaging impact of hydrogen on the austenitic stainless steel AISI 304 L was analysed. To this aim, samples were charged electrochemically with the hydrogen isotope deuterium (2H, D) and examined with time-of-flight secondary ion mass spectrometry (ToF-SIMS) and electron backscatter diffraction (EBSD). The fusion of the obtained chemical and structural information revealed local enrichment of deuterium in austenite, transformation into martensite, crack formation and severe roughening of the specimen surface. The results indicated that martensite was not only formed during charging but also during Desorption and ToF-SIMS examinations. Furthermore, cross-sections of deuterium-charged samples revealed that in preferred deformation bands a g/ε/a 0 evolution is taking place. By means of microscopic analyses and carrier gas hot extraction (CGHE), it was found that the use of NaAsO2 as recombination poison decreased the uptake of hydrogen significantly and resulted in severe precipitation on the specimen surfaces. This is in contrast to the popular presumption that NaAsO2 enhances the uptake of hydrogen (and deuterium) during electrochemical charging by hampering its recombination from Atoms to molecules.
In-depth structural and chemical characterization of engineered TiO2 films (2016)
Ortel, Erik ; Häusler, Ines ; Österle, Werner ; Narbey, S. ; Oswald, F. ; Andersen, I. H. ; Holzweber, Markus ; Unger, Wolfgang ; Hodoroaba, Vasile-Dan
Analytical routines for a comprehensive in-depth morphological, structural, and chemical characterization of functionalized TiO2 films by using different state-of-the-art analytical techniques are presented and discussed with the main objective to identify potential reference TiO2 coating parameters able to be certified at a later stage. TiO2 films fabricated by two different synthetic procedures as representative for two main large-scale applications were selected: (i) pulsed d.c. magnetron sputtering for photocatalytic applications and (ii) screen printing from preformed anatase nanoparticles. The screen-printed films were further loaded with a sensitizing dye for application as a dye-sensitized solar cell. Film properties such as microstructure and crystallographic texture of pulsed d.c. magnetron sputtering synthesized films were systematically studied by means of scanning nanobeam electron diffraction in a transmission electron microscope and the surface and inner morphology by scanning electron microscopy. The dye distribution over the depth of screen-printed TiO2 layers was analyzed before and after dye-loading by means of energy dispersive X-ray spectroscopy at scanning electronmicroscope, Auger electron spectroscopy and time-of-flight secondary ion mass spectrometry. The long-term goal of the present study is the improvement of quality of the TiO2 film parameters as measured by using different types of reference TiO2 coatings having specific parameters certified.
Lateral resolution of nanoscaled images delivered by surface-analytical instruments: application of the BAM-L200 certified reference material and related ISO standards (2015)
Senoner, Mathias ; Maaßdorf, A. ; Rooch, Heidemarie ; Österle, Werner ; Malcher, M. ; Schmidt, M. ; Kollmer, F. ; Paul, D. ; Hodoroaba, Vasile-Dan ; Rades, Steffi ; Unger, Wolfgang
The certified reference material BAM-L200, a nanoscale stripe pattern for length calibration and specification of lateral resolution, is described. BAM-L200 is prepared from a cross-sectioned epitaxially grown layer stack of AlxGa1–xAs and InxGa1–xAs on a GaAs substrate. The surface of BAM-L200 provides a flat pattern with stripe widths ranging down to 1 nm. Calibration distances, grating periods and stripe widths have been certified by TEM with traceability to the length unit. The combination of gratings, isolated narrow stripes and sharp edges of wide stripes offers plenty of options for the determination of lateral resolution, sharpness and calibration of length scale at selected settings of imaging surface-analytical instruments. The feasibility of the reference material for an analysis of the lateral resolution is demonstrated in detail by evaluation of ToF-SIMS, AES and EDX images. Other applications developed in the community are summarized, too. BAM-L200 fully supports the implementation of the revised International Standard ISO 18516 (in preparation) which is based on knowledge outlined in the Technical Report ISO/TR 19319:2013.
Morphology of nanoparticles - A characterization using high-resolution SEM (2013)
Hodoroaba, Vasile-Dan ; Rades, Steffi ; Natte, Kishore ; Orts Gil, Guillermo ; Unger, Wolfgang
Potential candidates of reference nano-materials are manufactured and systematically characterized in particular with respect to their morphology (shape, size and size distribution) in the frame of the running large European project NanoValid. By exploiting the transmission operation mode in a SEM, known as T-SEM, it is demonstrated by means of three representative examples of nanoparticles how a quick morphological inspection up to a complete, metrological characterization is feasible.
Novel approach to image hydrogen distribution and related phase transformation in duplex stainless steels at the sub-micron scale (2017)
Sobol, Oded ; Nolze, Gert ; Saliwan Neumann, Romeo ; Eliezer, D. ; Böllinghaus, Thomas ; Unger, Wolfgang
The effect of electrochemical charging of hydrogen on the structure of a lean duplex stainless steel LDX 2101® (EN 1.4162, UNS S32101) was examined by both Time-of-Flight secondary ion mass spectrometry and electron back-scatter diffraction. The goal is to correlate hydrogen concentration and induced structural changes. Chemical and structural characterizations were done for the same region at the sample's surface with sub-micron spatial resolution. Regions of interest were varying in size between 50 × 50 μm and 100 × 100 μm. The results show a phase transformation of austenite to mainly a defect-rich BCC and scarcely a HCP phase. The phase transformation occurred in deuterium rich regions in the austenite.
Time-of-Flight secondary ion mass spectrometry (ToF-SIMS) imaging of deuterium assisted cracking in a 2205 duplex stainless steel microstructure (2016)
Sobol, Oded ; Holzlechner, Gerald ; Nolze, Gert ; Wirth, Thomas ; Eliezer, D. ; Böllinghaus, Thomas ; Unger, Wolfgang
In the present work, the influence of deuterium on the microstructure of a duplex stainless steel type EN 1.4462 has been characterized by Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) supported by scanning electron microscopy (SEM), focused ion beam (FIB), electron back scattered diffraction(EBSD) and energy dispersive x-ray (EDX) investigations. Characterization has been carried out before and after electrochemical charging with deuterium which has been used as a tracer, due to its similar behavior to hydrogen in the steel microstructure. In a first approach, the distribution of the deuterium occurring at temperatures above 58 °C has been visualized. Further it turned out that sub-surface micro blisters are formed in the ferrite-austenite interface, followed by the formation of needle shaped plates and subsequent cracking at the ferrite surface. In the austenite phase, parallel cracking alongside twins and hexagonal close packed (martensitic) regions has been observed. In both phases and even in the apparent interface, cracking has been associated with high deuterium concentrations, as compared to the surrounding undamaged microstructure. Sub-surface blistering in the ferrite has to be attributed to the accumulation and recombination of deuterium at the ferrite-austenite interface underneath the respective ferrite grains and after fast diffusing through this phase. Generally, the present application of chemometric imaging and structural analyses allows characterization of hydrogen assisted degradation at a sub-micron lateral resolution.
Tof-SIMS imaging of Deuterium in DSS steel microstructures and data fusion with SEM topography data: Towards a better understanding of hydrogen assisted cracking in steel (2017)
Unger, Wolfgang
The use of duplex stainless steels (DSS) in energy related applications is well known. Nowadays, DSS steels become more favorable than austenitic steels due to the outstanding mechanical properties, the good corrosion resistance and the lower nickel content. However, the use of the duplex grade in acidic environments such as seawater often leads to severe degradation of the structural integrity of the steel by hydrogen-induced/assisted cracking (HAC) phenomena, which can eventually result in premature failure. Hydrogen assisted degradation and cracking of steels are active fields of research even though this topic is intensively studied for more than a century. A bottleneck is the analytical validation of the theoretical models proposed ion the literature at the sub-micron scale. Industrial and the research communities see a need for an accurate analytical method by which it is possible to image the distribution of hydrogen in the microstructure of a steels or and other alloys. Among the very few available methods hydrogen imaging methods, Time-of-Flight secondary ion mass spectrometry (ToF-SIMS) has the principal capability for mapping of hydrogen in a steel’s microstructure. The combination of ToF-SIMS with multivariate data analysis (MVA), electron microscopy (SEM) and electron-backscattered diffraction (EBSD) is a powerful approach for providing chemical and structural information. The use of data fusion techniques has been shown recently to enhance the better understanding of the hydrogen induced degradation processes in in a DSS steel.
Traceable Size Characterization of Nanoparticles at BAM with a Zeiss Supra 40 Scanning Electron Mircroscope and a Transmission Setup (2013)
Unger, Wolfgang
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