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5 Werkstofftechnik

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

  • Häusler, Ines (6) (entfernen)

Erscheinungsjahr

  • 2017 (6) (entfernen)

Sprache

  • Englisch (5)
  • Mehrsprachig (1)

Referierte Publikation

  • ja (5)
  • nein (1)

Schlagworte

  • Nanoparticles (2)
  • TEM (2)
  • (Mn,Ga)As crystallites (1)
  • Age hardening (1)
  • Al-Cu-Li-Legierung (1)
  • Al‐Cu‐Li‐alloy (1)
  • Ausscheidungen (1)
  • Crystal phase determination (1)
  • DSSC (1)
  • Elasticity (1)
  • Focused ion beam tomography (1)
  • Growth kinetics (1)
  • Material (1)
  • Measurement uncertainty (1)
  • Microstructure (1)
  • Multi‐component diffusion (1)
  • Number density (1)
  • Orientation mapping (1)
  • Particle size (1)
  • Particle size distribution (1)
  • Phase‐field modeling (1)
  • Porosity (1)
  • Porous film (1)
  • Precipitates (1)
  • STEM/TEM imaging (1)
  • Scanning nano beam electron diffraction (1)
  • Shape distribution (1)
  • Size distribution (1)
  • TKD (1)
  • TiO2 (1)
  • Titania (1)
  • Titanium dioxide (1)
  • Transmission Kikuchi diffraction (1)
  • Volume fraction (1)
  • Volumenbruchteil (1)
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Organisationseinheit der BAM

  • 5 Werkstofftechnik (6)
  • 5.1 Materialographie, Fraktographie und Alterung technischer Werkstoffe (3)
  • 5.2 Experimentelle und modellbasierte Werkstoffmechanik (3)
  • 6 Materialschutz und Oberflächentechnik (3)
  • 6.1 Oberflächenanalytik und Grenzflächenchemie (3)

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Characterization of the inner structure of porous TiO2 nanoparticle films in dye sensitive solar cells (DSSC) by focused ion beam (FIB) tomography and transmission Kikuchi diffraction (TKD) in the scanning electron microscope (SEM) (2017)
Wollschläger, Nicole ; Palasse, L. ; Häusler, Ines ; Dirscherl, K. ; Oswald, F. ; Narbey, S. ; Ortel, Erik ; Hodoroaba, Vasile-Dan
A combined methodical approach is tested for the first time with respect to the characterization of the inner structure of porous TiO2 layers infiltrated with ruthenium molecular sensitizer as typically used in modern dye sensitized solar cells (DSSC). Their performance is directly linked to the surface area ‘offered’ by the pore Network to the dye. The micrometer thick layer employed was manufactured by screen-printing of a starting TiO2 powder constituted of shape-controlled, bipyramidal anatase nanoparticles (NPs) on FTO/glass substrates. The analytical methods exploited in our study are Focused Ion Beam (FIB) slicing followed by 3D reconstruction as well as the new approach transmission Kikuchi diffraction (TKD) technology in the scanning electron microscope (SEM). While the first method results in the visualization of the 3D pore network within the TiO2 layer, the second one can be successfully applied to analyze the crystal orientation of grains (i.e. NPs in our case) in nanometer resolution. Moreover, size and shape distribution of the TiO2 NPs within the layer can be extracted. SEM in transmission mode and atomic force microscopy (AFM) have been used to verify the dimensional data obtained by the new combined methodical approach. Its analytical benefits but also the challenges and limitations are highlighted.
Characterization of porous, TiO2 nanoparticle films using on-axis TKD in SEM – a new nano-analysis tool for a large-scale application (2017)
Wollschläger, Nicole ; Häusler, Ines ; Ortel, Erik ; Hodoroaba, Vasile-Dan ; Palasse, L. ; Dirscherl, K.
A combined methodical approach is tested with respect to the characterization of the inner structure of porous TiO2 layers as typically used in modern dye sensitized solar cells (DSSC). Their performance is directly linked to the surface area of the pore network. The micrometer thick layer employed was manufactured by screen-printing of a starting TiO2 powder constituted of shape-controlled, bipyramidal anatase nanoparticles on FTO/glass substrates. The analytical methods exploited in our study are Focused Ion Beam (FIB) slicing followed by 3D reconstruction as well as the new approach transmission Kikuchi diffraction (TKD) technology in the scanning electron microscope (SEM). Size and shape distribution of the TiO2 NPs within the layer can be extracted. SEM in transmission mode and atomic force microscopy (AFM) have been used to verify the dimensional data obtained by the new combined methodical approach. Its analytical benefits but also the challenges and limitations are highlighted.
Precipitation of T1 and theta′ Phase in Al‐4Cu‐1Li‐0.25Mn During Age Hardening: Microstructural Investigation and Phase‐Field Simulation (2017)
Häusler, Ines ; Schwarze, C. ; Umer Bilal, M. ; Valencia Ramirez, D. ; Hetaba, W. ; Darvishi Kamachali, R. ; Skrotzki, Birgit
Experimental and phase field studies of age hardening response of a high purity Al‐4Cu‐1Li‐0.25Mn‐alloy (mass %) during isothermal aging are conducted. In the experiments, two hardening phases are identified: the tetragonal θ′ (Al₂Cu) phase and the hexagonal T1 (Al₂CuLi) phase. Both are plate shaped and of nm size. They are analyzed with respect to the development of their size, number density and volume fraction during aging by applying different analysis techniques in TEM in combination with quantitative microstructural analysis. 3D phase‐field simulations of formation and growth of θ′ phase are performed in which the full interfacial, chemical and elastic energy contributions are taken into account. 2D simulations of T1 phase are also investigated using multi‐component diffusion without elasticity. This is a first step toward a complex phase‐field study of T1 phase in the ternary alloy. The comparison between experimental and simulated data shows similar trends. The still unsaturated volume fraction indicates that the precipitates are in the growth stage and that the coarsening/ripening stage has not yet been reached.
Orientation relationships of Mn0.75Ga0.25As crystallites on and within GaAs determined by scanning nano beam electron diffraction (2017)
Häusler, Ines ; Moeck, P. ; Volz, K. ; Neumann, W.
Mn0.75Ga0.25As crystallites, partially embedded on and fully embedded within a single crystalline matrix of GaAs formed during metal organic vapor phase epitaxy (MOVPE) of Mn-rich (Mn,Ga)As on (001) oriented GaAs wafers. Phase and orientation analysis of these crystallites were performed with scanning nano beam electron diffraction (SNBED). The investigation of plan-view specimens using a liquid nitrogen cooling stage enabled the phase and orientation analysis of partially embedded ferromagnetic a-phase particles. In all specimens the following two orientation relationships (O) between the a-phase particles and the GaAs matrix were determined: O1: [1-2.0] Mn0.75Ga0.25As || [110] GaAs and [10.2] Mn0.75Ga0.25As || [-110] GaAs O2: [10.2] Mn0.75Ga0.25As || [110] GaAs and [1-2.0] Mn0.75Ga0.25As || [-110] GaAs. The study of cross-sectional specimens enabled the analysis of fully embedded crystallites. It could be unambiguously detected that a fully embedded crystallite has the structure of the atomically ordered monoclinic β' phase. The β' phase crystallite consists of two domains which are related in twin positions to each other. The orientation relations of the different particles are illustrated by color coded stereographic projections.
Volume fraction determination of discretely oriented disc-shaped precipitates in transmission mode (2017)
Häusler, Ines
In der vorliegenden Arbeit wurde eine Formel zur Berechnung des Volumenantei ls dis­ kret orientierter scheibenförmiger Phasen für die Untersuchung im Transmissionsmodus hergeleitet, validiert und mit bereits veröffent­ lichen Formeln verglichen. Bei diesem Ver­ gleich konnte gezeigt werden,dass die in zahl­ reichen Veröffentlichungen benutzte Formel von E. E. Underwood für die Volumenanteils­ bestimmungbeidiskret orientierten Ausschei­ dungsphasen nicht benutzt werden sollte, da sie den Volumenanteil deutlich unterschätzt. Die Ursache liegt in der von E.E. Underwood getroffenen Annahme, dass die kreisförmigen Scheiben regellos angeordnet und nicht aus­ gerichtet sind, was in Al-Legierungen in der Regel nicht der Fall ist.
Size and shape distributions of primary crystallites in titania aggregates (2017)
Grulke, E. A. ; Yamamoto, K. ; Kumagai, K. ; Häusler, Ines ; Österle, Werner ; Ortel, Erik ; Hodoroaba, Vasile-Dan ; Brown, S. C. ; Chan, C. ; Zheng, J. ; Yamamoto, K. ; Yashiki, K. ; Song, N. W. ; Kim, Y. H. ; Stefaniak, A. B. ; Schwegler-Berry, D. ; Coleman, V. A. ; Jämting, Å. K. ; Herrmann, J. ; Arakawa, T. ; Burchett, W. W. ; Lambert, J. W. ; Stromberg, A. J.
The primary crystallite size of titania powder relates to its properties in a number of applications. Transmission electron microscopy was used in this interlaboratory comparison (ILC) to measure primary crystallite size and shape distributions for a commercial aggregated titania powder. Data of four size descriptors and two shape descriptors were evaluated across nine laboratories. Data repeatability and reproducibility was evaluated by analysis of variance. One-third of the laboratory pairs had similar size descriptor data, but 83% of the pairs had similar aspect ratio data. Scale descriptor distributions were generally unimodal and were well-described by lognormal reference models. Shape descriptor distributions were multi-modal but data visualization plots demonstrated that the Weibull distribution was preferred to the normal distribution. For the equivalent circular diameter size descriptor, measurement uncertainties of the lognormal distribution scale and width parameters were 9.5% and 22%, respectively. For the aspect ratio shape descriptor, the measurement uncertainties of the Weibull distribution scale and width parameters were 7.0% and 26%, respectively. Both measurement uncertainty estimates and data visualizations should be used to analyze size and shape distributions of particles on the nanoscale.
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