Korrelierte Anwendung von Präzessionselektronenbeugung und Atomsondentomographie zur kristallographischen und chemischen Untersuchung von Nanomaterialien in 3D
Experimentelle Physik der kondensierten Materie
Zusammenfassung der Projektergebnisse
In this project, we developed innovative methods to better understand how atoms behave at grain boundaries in nanocrystalline materials such as iron-carbon, nickel-tungsten, and iron-tungsten alloys. Grain boundaries are the interfaces where different crystalline regions meet within a material, and they play a crucial role in determining the overall properties of materials. By combining two advanced imaging techniques — four-dimensional scanning transmission electron microscopy (4D-STEM) and atom probe tomography (APT) — we achieved a three-dimensional characterization of both the microstructure and chemical composition of these materials. The 4D-STEM technique allowed us to map the arrangement and orientation of grains and their boundaries in three dimensions with 3-4 nm spatial resolution. APT provided detailed chemical analysis at the near atomic level, enabling us to identify the types and quantity of atoms within the material. We developed new experimental procedures and software to couple 3D scanning precession electron diffraction (3D-SPED) reconstruction with APT data. This allowed us to simultaneously acquire three-dimensional structural and compositional information at the nanometer scale. The ability to study complex interfacial networks in polycrystalline nanomaterials with such high resolution opens up new possibilities for analyzing the physical mechanisms that govern material properties. The integration of these techniques was a significant advancement. It enabled us to correlate structural and chemical information within the same three-dimensional reference frame. This combined approach allowed us to observe how atoms segregate at different types of grain boundaries. For example, in a nickel alloy subjected to heat treatment, we observed that copper atoms preferentially segregated at certain grain boundaries. We found that grain boundaries with higher symmetry, such as twin boundaries, had significantly fewer segregated atoms compared to more disordered boundaries. This indicates that the atomic structure and symmetry of grain boundaries play a critical role in how atoms distribute themselves within the material. One surprising finding was the significant impact of grain boundary defects, such as dislocations, on atomic segregation. In body-centered cubic (BCC) iron systems, our experiments revealed that dislocations at grain boundaries introduce additional elastic energy, which can vary by up to 4,000 J/mole. This extra energy causes a heterogeneous distribution of tungsten atoms at the boundaries, a phenomenon not fully accounted for in existing models such as the Langmuir-McLean isotherm. This discovery highlights the importance of considering the elastic strain fields introduced by defects when predicting segregation behavior. During the course of the project, we encountered some unexpected challenges and discoveries. The significant effect of secondary grain boundary dislocations on atomic segregation was a surprise, as was the extent to which elastic energy influences segregation behavior. These findings suggest that more complex models are needed to accurately predict material behavior at the atomic level. By combining advanced imaging techniques and developing new analytical methods, we have provided a powerful toolset for investigating and quantifying solute-grain boundary interactions in three dimensions. This not only enhances our fundamental understanding of material behavior but also contributes to the development of next-generation materials with improved performance and reliability.
Projektbezogene Publikationen (Auswahl)
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Reconstructing dual-phase nanometer scale grains within a pearlitic steel tip in 3D through 4D-scanning precession electron diffraction tomography and automated crystal orientation mapping. Ultramicroscopy, 238, 113536.
Harrison, Patrick; Zhou, Xuyang; Das, Saurabh Mohan; Lhuissier, Pierre; Liebscher, Christian H.; Herbig, Michael; Ludwig, Wolfgang & Rauch, Edgar F.
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Atomic motifs govern the decoration of grain boundaries by interstitial solutes. Nature Communications, 14(1).
Zhou, Xuyang; Ahmadian, Ali; Gault, Baptiste; Ophus, Colin; Liebscher, Christian H.; Dehm, Gerhard & Raabe, Dierk
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Effect of Pore Formation on Redox-Driven Phase Transformation. Physical Review Letters, 130(16).
Zhou, Xuyang; Bai, Yang; El-Zoka, Ayman A.; Kim, Se-Ho; Ma, Yan; Liebscher, Christian H.; Gault, Baptiste; Mianroodi, Jaber R.; Dehm, Gerhard & Raabe, Dierk
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Determination of five-parameter grain boundary characteristics in nanocrystalline Ni-W by scanning precession electron diffraction tomography. Ultramicroscopy, 267, 114038.
Harrison, Patrick; Das, Saurabh Mohan; Goncalves, William; da Silva, Alessandra; Chen, Xinren; Viganò, Nicola; Liebscher, Christian H.; Ludwig, Wolfgang; Zhou, Xuyang & Rauch, Edgar F.
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Quasi‐“In Situ” Analysis of the Reactive Liquid‐Solid Interface during Magnesium Corrosion Using Cryo‐Atom Probe Tomography. Advanced Materials, 36(32).
Schwarz, Tim M.; Yang, Jing; Aota, Leonardo S.; Woods, Eric; Zhou, Xuyang; Neugebauer, Jörg; Todorova, Mira; McCarroll, Ingrid & Gault, Baptiste
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Correlating Grain Boundary Character and Composition in 3‐Dimensions Using 4D‐Scanning Precession Electron Diffraction and Atom Probe Tomography. Small Methods, 9(5).
Das, Saurabh M.; Harrison, Patrick; Kiranbabu, Srikakulapu; Zhou, Xuyang; Ludwig, Wolfgang; Rauch, Edgar F.; Herbig, Michael & Liebscher, Christian H.
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Secondary grain boundary dislocations alter segregation energy spectra. Nature Communications, 16(1).
Chen, Xinren; Gonçalves, William; Hu, Yi; Gao, Yipeng; Harrison, Patrick; Dehm, Gerhard; Gault, Baptiste; Ludwig, Wolfgang; Rauch, Edgar; Zhou, Xuyang & Raabe, Dierk
