# A thermal grooving study of relative grain boundary energies of nickel in polycrystalline Ni and in a Ni/YSZ anode measured by atomic force microscopy

Haremski, Patricia 1; Epple, Lars; Wieler, Matthias; Lupetin, Piero; Thelen, Richard 2; Hoffmann, Michael J. 1
1 Karlsruher Institut für Technologie (KIT)
2 Institut für Mikrostrukturtechnik (IMT), Karlsruher Institut für Technologie (KIT)

## Abstract:

Grain boundary grooves of nickel were studied in Ni polycrystals and in Ni/YSZ (nickel/yttria-stabilized zirconia) anode microstructures of an solid oxide fuel cell (SOFC) in order to determine the relative grain boundary energies of nickel. Reliable material parameters are necessary for realistic simulations to model the coarsening of nickel grains in SOFC anodes. However, the reported values in literature do not meet the requirements for accuracy and the experimental conditions differ strongly from the conditions within an anode. In this work, the measurement approach for atomic force microscopy was optimized to ensure the required accuracy in measuring grain boundary grooves; the thermal grooving experiments were performed at T=750 °C in dry and humid atmosphere. The resulting distributions of measured dihedral angles and relative grain boundary energies are identical in the polycrystal and the anode microstructure and are independent of annealing time and humidity. For the first time, precise values of the relative grain boundary energies of nickel are determined with high accuracy under operating conditions of an SOFC anode. The mean value of the relative grain boundary energies γ$_{GB}$ /γ$_{S}$ of nickel is 0.475 ± 0.013 for high-angle grain boundaries, 0.157 ± 0.013 for Σ3 low-angle grain boundaries, for grain boundaries and 0.019 ± 0.002 for twin boundaries.

 Zugehörige Institution(en) am KIT Institut für Mikrostrukturtechnik (IMT)Institut für Angewandte Materialien – Keramische Werkstoffe und Technologien (IAM-KWT) Publikationstyp Zeitschriftenaufsatz Publikationsdatum 01.08.2021 Sprache Englisch Identifikator ISSN: 1359-6454 KITopen-ID: 1000134531 HGF-Programm 43.35.01 (POF IV, LK 01) Platform for Correlative, In Situ & Operando Charakterizat. Erschienen in Acta materialia Verlag Elsevier Band 214 Seiten Art. Nr.: 116936 Schlagwörter Nickel, Grain boundaries (GBs), Grain boundary energy, Anisotropy, Atomic force microscopy (AFM) Nachgewiesen in ScopusDimensionsWeb of Science
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