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. 2022 Mar 25;12(16):9501-9511.
doi: 10.1039/d1ra09329k.

Molecular dynamics simulations of the initial oxidation process on ferritic Fe-Cr alloy surfaces

Yuan-Shuo Zhang  1 , Bao-Shuai Chu  1   2 , Hong-Li Yu  1 , Kun Li  1 , Wei-Hua Wang  3 , Wen Yang  1
Affiliations

Molecular dynamics simulations of the initial oxidation process on ferritic Fe-Cr alloy surfaces

Yuan-Shuo Zhang et al. RSC Adv. .

Abstract

Oxidation processes of metallic interconnects are crucial to the operation of solid oxide fuel cells (SOFCs), and ferritic Fe-Cr alloy is one of the most important metallic interconnect materials. Based on the ReaxFF reactive potential, the interaction of O2 molecules with three types of surfaces (100, 110, 111) of ferritic Fe-Cr alloy has been studied by classical molecular dynamics at constant O2 concentrations and temperatures. The initial oxidation process is systematically studied according to the analysis of O2 absorption rate, charge variations, charge distributions, mean squared distributions, and oxidation rate. The results reveal that it is easier and faster for the Cr atoms to lose electrons than for the Fe atoms during the oxidation process. The obtained oxidation rate of Cr atoms is larger and the formation of Cr2O3 takes precedence over that of FeO. And the thickness of oxidation layers of different surfaces could be determined quantitatively. We also find that the high O2 concentration accelerates the oxidation process and obviously increases the thickness of oxidation layers, while the temperature has a weaker effect on the oxidation process than the O2 concentration. Moreover, the (110) surface presents the best oxidation resistance compared to the other two surfaces. And the (110) surface is efficient in preventing Fe atoms from being oxidized. Here we explore the initial oxidation process of Fe-Cr alloy and the corresponding results could provide theoretical guides to the related experiments and applications as metallic interconnects.

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Conflict of interest statement

There are no conflicts to declare.

Figures

Fig. 1
Fig. 1. MD model of Fe–Cr alloy (100) surface with O2 molecular layers.
Fig. 2
Fig. 2. Dissociation of an O2 molecule. (a) An incident O2 molecule above the surface. (b) An O2 molecule beginning to dissociate. (c) Dissociated into two O ions. (d) Charge variation of O atom versus time.
Fig. 3
Fig. 3. Average charge variation of Fe and Cr atoms versus time in the three types of surfaces at 1000 K and two levels of O2 concentration.
Fig. 4
Fig. 4. Left axis: atomic charge distribution in the z direction of the three types of surfaces at 200 ps with T = 1000 K and two levels of O2 concentration. Right axis: corresponding number distribution of O atoms in the z direction.
Fig. 5
Fig. 5. RDF of Fe–O and Cr–O in the three types of surfaces at 1000 K and two levels of O2 concentration.
Fig. 6
Fig. 6. RDF of Fe oxides and Cr2O3 phases: (a) Cr2O3, (b) FeO, (c) Fe2O3, (d) Fe3O4.
Fig. 7
Fig. 7. Time dependence of ORFe and ORCr in the three different surfaces at 1000 K and high O2 concentration.
Fig. 8
Fig. 8. Oxygen absorption rate (OAR) versus time in the three types of surfaces at 1000 K and two levels of O2 concentration.
Fig. 9
Fig. 9. Average charge variations of Fe and Cr atoms over time at 1000 K and two levels of O2 concentration.
Fig. 10
Fig. 10. MSD of Fe and Cr atoms in the top 5 layers at 1000 K and two levels of O2 concentration.
See this image and copyright information in PMC

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