Advanced Characterization

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Advanced Characterization

Advanced Characterization

Advanced Characterization

 Atom Probe Tomography

  Application of state-of-the-art characterization techniques will be a central part of our research. We particularly apply Atom Probe Tomography (APT) as a powerful nano-analytical tool for characterizing complex materials. The principle of APT is based on the controlled field evaporation and ionization of surface atoms from a fine needle-shaped emitter (radius of curvature typically below 100 nm). The field evaporated ions are accelerated towards a position-sensitive detector that records their time-of-flight and impact positions. A three-dimensional elemental map is reconstructed from the raw data, using a back projection algorithm. The great advantage of APT is its high spatial resolution (near-atomic) and high chemical sensitivity (ppm level), making it an ideal tool for studying local phase transformations and nano-scale chemical fluctuations in complex engineering alloys.

 Correlative microscopy

  Although APT even yields structural information for specific materials such as pure metals, dilute solid solutions, and highly ordered inter metallic phases, structural information cannot alway be accessed with this technique. To acquire both chemical and structural information, other methods need to be applied in conjunction with APT. Experimental techniques, which are particularly powerful in this respect, are transmission (TEM) and scanning electron microscopy (SEM), electron back scatter diffraction (EBSD) and electron channeling contrast imaging (ECCI). In combination with focused-ion-beam (FIB) milling it is nowadays possible to select and jointly analyze specific regions of interest of the sample (such as grain and phase boundaries) with these techniques. 

(C. Jung, K. Kang, A. Marshal, K. G. Pradeep, J. Seol, H. M. Lee, P. Choi, Acta Materialia, 171 (2019) 1)

The figures above show an example of correlative EBSD, TKD, and APT analyses of a softmagnetic high-entropy alloy. Distinct elemental partitioning at existing phase boundaries can be resolved, which significantly affects the saturation magnetization and coercivity of this system.



Department of Materials Science and Engineering, KAIST
291 Daehak-ro, Yuseong-gu, Daejeon 305-701 Republic of Korea

TEL : +82-42-350-3321 (Office), +82-42-350-3361 (Lab)
Location : W1 Applied Engineering Building #2432

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