Design of TiVNb-(Cr, Ni or Co) multicomponent alloys with the same valence electron concentration for hydrogen storage
Design of TiVNb-(Cr, Ni or Co) multicomponent alloys with the same valence electron concentration for hydrogen storage
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DOI：
10.1016/j.jallcom.2021.158767
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发表时间：
2021-02-03
影响因子：
6.2
通讯作者：
Zepon, Guilherme
中科院分区：
文献类型：
--
作者：
Silva, Bruno Hessel;Zlotea, Claudia;Zepon, Guilherme
最近，有人假设体心立方（BCC）多元合金的氢吸附特性可能与合金的价电子浓度（VEC）有关。在这项工作中，我们采用 CALPHAD 方法设计了三种具有相同 VEC 的 BCC 合金来评估这一假设。采用电弧熔炼方法制备了 VEC = 4.87 的 (TiVNb)(85)Cr-15、(TiVNb)(95)Co-.(3)4(.7) 和 (TiVNb)(96)Ni-.(2)3(.8) 多元合金。尽管无法避免一定程度的偏析，但铸态显微组织由具有高度均匀化学成分的 BCC 相组成。该合金在室温下快速吸收氢并形成容量高达 2 H/M (3.1-3.2 wt%) 的 FCC 氢化物。对于这三种合金，观察到两步氢化顺序，表明在形成 FCC 二氢化物之前形成中间体 BCC 一氢化物。此外，这三种合金呈现出非常相似的氢化焓和熵值，表明最初的假设似乎适用于热力学性质。还评估了合金的加氢/脱氢循环行为。 (TiVNb)(85)Cr-15 在循环过程中容量出现小幅持续下降，这是由于 BCC 一氢化物不完全转化为 FCC 二氢化物所致，而 (TiVNb)(95)Co-.3(4.7) 和 (TiVNb)(96)Ni-.2(3.8) 显示出更稳定的行为，实现了 1.76 H/M 的可逆容量 20 个循环后 (2.77 wt%)。正如热解吸光谱 (TDS) 所示，所有合金的解吸都受到吸收/解吸循环的强烈影响。解吸的起始温度取决于合金的成分以及加氢/脱氢循环的次数。结果表明，合金的循环和解吸性能与其 VEC 相关性较小。 (C) 2021 Elsevier B.V. 保留所有权利。
Recently, it has been hypothesized that the hydrogen sorption properties of body-centered cubic (BCC) multicomponent alloys might be related to the alloy's valence electron concentration (VEC). In this work, we employed CALPHAD method to design three BCC alloys with the same VEC to evaluate this hypothesis. The (TiVNb)(85)Cr-15, (TiVNb)(95)Co-.(3)4(.7) and (TiVNb)(96)Ni-.(2)3(.8) multicomponent alloys with VEC = 4.87 were produced by arc melting. Although some amount of segregation could not be avoided, the as-cast microstructures were composed of a BCC phase with highly homogeneous chemical composition. The alloys quickly absorb hydrogen at room temperature and formed FCC hydrides with high capacities of 2 H/M (3.1-3.2 wt%). For the three alloys, it was observed a two-step hydrogenation sequence indicating the formation of an intermediate BCC monohydride prior to the formation of the FCC dihydride. Moreover, the three alloys presented very similar values of enthalpy and entropy of hydrogenation, showing that the initial hypothesis seems to hold for the thermodynamic properties. The alloys hydrogenation/dehydrogenation cycling behavior were also evaluated. (TiVNb)(85)Cr-15 had a small and continuous drop in capacity over cycling that was addressed to incomplete transformation of the BCC monohydride to the FCC dihydride, whereas (TiVNb)(95)Co-.3(4.7) and (TiVNb)(96)Ni-.2(3.8) showed a more stable behavior achieving a reversible capacity of 1.76 H/M (2.77 wt%) after 20 cycles. The desorption is strongly affected by absorption/desorption cycling for all alloys, as revealed by thermo desorption spectroscopy (TDS). The onset temperature of desorption depends on the alloys' composition as well as the number of hydrogenation/dehydrogenation cycles. The results suggest that cycling and desorption properties of the alloys are less related to their VEC. (C) 2021 Elsevier B.V. All rights reserved.