Regensburg 2019 – wissenschaftliches Programm
MM 22.4: Vortrag
Mittwoch, 3. April 2019, 11:00–11:15, H43
Applicability of MAX phases as diffusion barrier for hydrogen and chromium in SOFC — •Daniel F. Urban1,2, Dimitrios Satkas1, and Christian Elsässer1,2 — 1Fraunhofer IWM, Freiburg, Germany — 2University of Freiburg, FMF, Germany
Promising candidates in the search for corrosion protection coatings for high temperature energy-conversion devices such as solid oxide fuel cells (SOFC) are MAX phases which are ternary metal carbides and nitrides with multi-layered crystal structures. To assess the capability of MAX phases as diffusion barriers for hydrogen and chromium, we investigate the absorption and migration of H and Cr atoms in a variety of MAX-phase carbides and nitrides by means of first-principles calculations based on density functional theory. Based on the calculated formation and migration energies we discuss how MAX-phase coatings can act as efficient protective diffusion barriers for both hydrogen and chromium and explain the underlying migration mechanisms. While Cr atoms are found to diffuse via a vacancy mediated mechanism and substitute M- and A-atoms, H diffusion occurs on essentially decoupled bilayer dice-lattices of tetrahedrally and octahedrally coordinated interstitial sites. . We discuss the possibility to tailor specific material properties like lattice constants or thermal expansion coefficients for a given required diffusion barrier impact by making use of the flexibility of the MAX-crystal structure which allows for mixed (M1,M2)(A1A2)X phases.
 F. Colonna, C. Elsässer, RSC Advances 7, 37852 (2017).