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The role of Cr atom in the early steam oxidation of Fe‐based alloys: An atomistic simulation
Materials and Corrosion ( IF 1.6 ) Pub Date : 2020-09-01 , DOI: 10.1002/maco.202011774 Jing Qi 1 , Hong Xu 1 , Zhiyuan Liang 2 , Ping Lu 1 , Changsong Zhou 1
Materials and Corrosion ( IF 1.6 ) Pub Date : 2020-09-01 , DOI: 10.1002/maco.202011774 Jing Qi 1 , Hong Xu 1 , Zhiyuan Liang 2 , Ping Lu 1 , Changsong Zhou 1
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This study employed the density functional theory to capture the atomic‐level dissociation processes of steam and investigate the ions migration on Fe(001) and FeCr(001) surfaces, revealing the role of Cr atom in the early oxidation. Various coadsorption structures with different steam‐derived species have been systematically examined to find the most energetically favored surface site. The results showed that the steam dissociation on the alloy surface underwent two steps. First, H2O molecule on the top site was dissociated into OH group and H atom, which further combined with metal atoms on the bridge site and hollow site. Second, the OH group was decomposed into O and H atoms, which moved to two adjacent hollow sites and generated an oxide. On further oxidation, the Fe atom migrated outward and formed an outer Fe oxide, whereas the Cr oxide could only grow inward as O atom passed through oxide. It was found that the presence of Cr atom on the surface was thermodynamically beneficial, which could promote steam oxidation. The Cr atom could effectively block ion diffusion across the oxide scale and protect the underlying substrate from further oxidation. These results were in good agreement with experimental observation.
中文翻译：
Cr原子在铁基合金的早期蒸汽氧化中的作用：原子模拟
这项研究采用密度泛函理论来捕获蒸汽的原子级解离过程，并研究离子在Fe（001）和FeCr（001）表面上的迁移，揭示了Cr原子在早期氧化中的作用。系统地检查了具有不同蒸汽来源物种的各种共吸附结构，以找到最受能量支持的表面位置。结果表明，合金表面的蒸汽离解经历了两个步骤。首先，H 2顶部位点的O分子解离成OH基和H原子，它们进一步与桥位点和空心位点上的金属原子结合。其次，OH基团被分解为O和H原子，它们移至两个相邻的中空部位并生成氧化物。进一步氧化时，Fe原子向外迁移并形成外部Fe氧化物，而Cr氧化物只能在O原子穿过氧化物时向内生长。发现表面上Cr原子的存在在热力学上是有利的，其可以促进蒸汽氧化。Cr原子可以有效地阻止离子在整个氧化皮上扩散，并保护下面的基材免受进一步氧化。这些结果与实验观察非常吻合。
更新日期：2020-09-01
中文翻译：
Cr原子在铁基合金的早期蒸汽氧化中的作用：原子模拟
这项研究采用密度泛函理论来捕获蒸汽的原子级解离过程，并研究离子在Fe（001）和FeCr（001）表面上的迁移，揭示了Cr原子在早期氧化中的作用。系统地检查了具有不同蒸汽来源物种的各种共吸附结构，以找到最受能量支持的表面位置。结果表明，合金表面的蒸汽离解经历了两个步骤。首先，H 2顶部位点的O分子解离成OH基和H原子，它们进一步与桥位点和空心位点上的金属原子结合。其次，OH基团被分解为O和H原子，它们移至两个相邻的中空部位并生成氧化物。进一步氧化时，Fe原子向外迁移并形成外部Fe氧化物，而Cr氧化物只能在O原子穿过氧化物时向内生长。发现表面上Cr原子的存在在热力学上是有利的，其可以促进蒸汽氧化。Cr原子可以有效地阻止离子在整个氧化皮上扩散，并保护下面的基材免受进一步氧化。这些结果与实验观察非常吻合。
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