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Kang, ShinYoung

Kaufman, Jonas

Keilbart, Nathan

Rowberg, Andrew

Wood, Brandon

English

Engineering Conferences International

HYDROGEN PERMEATION THROUGH SURFACE OXIDES OF TITANIUM IRON ALLOYS  Andrew Rowberg, Lawrence Livermore National Laboratory Rowberg1@llnl.gov  ShinYoung Kang, Lawrence Livermore National Laboratory Nathan Keilbart, Lawrence Livermore National Laboratory Jonas Kaufman, Lawrence Livermore National Laboratory Brandon Wood, Lawrence Livermore National Laboratory   The complex and heterogenous native surface oxide that forms on titanium and titanium-iron alloys (TiFe) is acknowledged to be critical for determining rates of initial hydride formation in hydrogen-rich environments.1 However, the precise nature of its interactions with hydrogen, as well as the specific features that promote or inhibit hydrogen penetration into the underlying matrix, remain subjects of controversy, Here, we use ab initio simulations of diverse compositions and configurations of the surface oxide as the basis for multiscale modeling to study the hydrogen permeability of the oxide layer. We explicitly consider stoichiometries that have been observed experimentally, such as TiFeO3, Ti2FeO5, TiFe2O4, and Ti4Fe2O.2 Along with simulations of the bulk crystalline phases, we use ab initio molecular dynamics to construct disordered and highly defective structures to capture a wide variety of local environments for hydrogen. We take various effects, such as strain, oxygen deficiency, and the presence of such minority alloying elements as Mn and V, into consideration, and we identify how they impact the energetics and kinetics of hydrogen incorporation.  Our work provides a comprehensive analysis of the key factors governing hydrogen permeation through the surface oxide layer and, ultimately, metal hydride formation kinetics in TiFe with and without minority alloying elements. In addition, we demonstrate a fundamental change in the behavior of hydrogen as it passes through the oxide, from protonic character in higher atomic layers to hydridic character closer to the TiFe interface. By characterizing the role of the surface oxide from the atomic scale, we provide insights into the factors most important for dictating kinetics of hydriding of the underlying TiFe matrix.  This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.    E. M. Dematteis, D. M. Dreistadt, G. Capurso, J. Jepsen, F. Cuevas, and M. Latroche, J. Alloys Cmpnds. 874, 159925 (2021). V. Chuprina, I. Shalya, and I. Karpikov, Powder Metallurgy and Metal Ceramics 34, 663 (1996).  

Hydrogen permeation through surface oxides of titanium iron alloys

https://dc.engconfintl.org/cgi/viewcontent.cgi?filename=0&article=1078&context=hydrogen&type=additional

Hydrogen permeation through surface oxides of titanium iron alloys

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Engineering Conferences International