Løvvik Ole Martin, Zhao Dongdong, Li Yanjun, Bredesen Rune, Peters Thijs
SINTEF Industry, N-0314 Oslo, Norway.
Department of Materials Science and Engineering, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway.
Membranes (Basel). 2018 Sep 12;8(3):81. doi: 10.3390/membranes8030081.
Dense metal membranes that are based on palladium (Pd) are promising for hydrogen separation and production due to their high selectivity and permeability. Optimization of alloy composition has normally focused on bulk properties, but there is growing evidence that grain boundaries (GBs) play a crucial role in the overall performance of membranes. The present study provides parameters and analyses of GBs in the ternary Pd-Ag-Cu system, based on first-principles electronic structure calculations. The segregation tendency of Cu, Ag, and vacancies towards 12 different coherent ∑ GBs in Pd was quantified using three different procedures for relaxation of supercell lattice constants, representing the outer bounds of infinitely elastic and stiff lattice around the GBs. This demonstrated a clear linear correlation between the excess volume and the GB energy when volume relaxation was allowed for. The point defects were attracted by most of the GBs that were investigated. Realistic atomic-scale models of binary Pd-Cu and ternary Pd-Cu-Ag alloys were created for the ∑5(210) boundary, in which the strong GB segregation tendency was affirmed. This is a starting point for more targeted engineering of alloys and grain structure in dense metal membranes and related systems.
基于钯（Pd）的致密金属膜因其高选择性和渗透性，在氢气分离与生产方面颇具前景。合金成分的优化通常聚焦于整体性能，但越来越多的证据表明，晶界（GBs）在膜的整体性能中起着关键作用。本研究基于第一性原理电子结构计算，给出了三元Pd-Ag-Cu体系中晶界的参数及分析。使用三种不同的超胞晶格常数弛豫程序，对Cu、Ag和空位在Pd中12种不同的共格∑晶界处的偏析倾向进行了量化，这三种程序代表了晶界周围无限弹性和刚性晶格的外部边界。当允许体积弛豫时，这表明过量体积与晶界能量之间存在明显的线性相关性。大多数被研究的晶界会吸引点缺陷。针对∑5(210)边界创建了二元Pd-Cu和三元Pd-Cu-Ag合金的实际原子尺度模型，其中确认了强烈的晶界偏析倾向。这是对致密金属膜及相关系统中的合金和晶粒结构进行更具针对性设计的起点。
