FEM simulation supported evaluation of a hydrogen grain boundary diffusion coefficient in MgH2
FEM simulation supported evaluation of a hydrogen grain boundary diffusion coefficient in MgH2
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DOI：
10.1016/j.ijhydene.2017.05.050
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发表时间：
2017-08
影响因子：
7.2
通讯作者：
M. Hamm;A. Pundt
中科院分区：
文献类型：
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作者：
M. Hamm;A. Pundt
氢在镁-氢系统中的扩散系数数据显示出很大的分散性，它们的趋势外推在室温下在10 - 12 m2/s和10 - 29 m2/s之间变化。在室温下的氢在MgH 2中的扩散系数，因此，不确定约17个数量级。这可能部分归因于晶界有助于测得的扩散系数。在本文中，我们使用有限元（FEM）模拟来评估的晶界扩散对测得的总扩散的影响取决于晶界（DGB）和体积（DV）扩散系数的差异，以及晶粒尺寸。将这些结果与Harrisson的解析解进行比较。当扩散系数相差大于DV < 10−3·DGB时，哈里森扩散区C成为描述总扩散的最佳方式。结果被用来重新解释文献数据氢扩散MgH 2从晶界贡献的角度来看。在300 K时，氢的晶界扩散系数从DGB = 10− 17 m2/s到DGB = 10− 20 m2/s，取决于MgH 2中样品的个别类型，由数据评估得出。
The diffusion coefficient data of hydrogen in the Magnesium-hydrogen system shows a large scatter, their trends extrapolations vary at room temperature between 10−12m2/s and 10−29m2/s. At room temperature the hydrogen diffusion coefficient in MgH2is, thus, uncertain by about 17 orders of magnitude. This may be partially attributed to grain boundaries contributing to the measured diffusion coefficient. In this paper we use finite-element (FEM) simulations to evaluate the influence of the grain boundary diffusion on the measured total diffusion depending on the difference of the grain boundary (DGB) and volume (DV) diffusion coefficients, as well as on the grain size. These results will be compared to Harrisson's analytical solutions. When the diffusion coefficients differ by more thanDV< 10−3·DGB, Harrison's diffusion regime C becomes the best way to describe the total diffusion. The results are used to re-interpret literature data on hydrogen diffusion in MgH2from this grain boundary contribution point of view. At 300 K, a hydrogen grain boundary diffusion coefficient ranging fromDGB= 10−17m2/s toDGB= 10−20m2/s, depending on the individual type of sample in MgH2, results from the data evaluation.