形成可逆氢化物的Sm2MnxNi7-x（0<x<0.5）金属间化合物的吸氢和腐蚀性能研究
Investigation of H Sorption and Corrosion Properties of Sm2MnxNi7-x (0<x<0.5) Intermetallic Compounds Forming Reversible Hydrides
摘要：
金属间化合物是能量转换的关键材料，因为它们形成可用于固态储氢或用作电池阳极的可逆金属间化合物。ABy化合物（A =稀土（RE）; B =过渡金属; 2 < y < 5）是满足实际应用所需性质的良好候选物。它们可以被描述为AB 5和AB 2亚基沿着c晶轴的堆叠。后者子单元带来了更大的容量，而前者提供了更好的循环稳定性。然而，ABy二进制文件没有显示出足够好的应用程序属性。氢化后，它们表现出多平台行为和不良的可逆性，归因于H诱导的非晶化。这些缺点可以通过在A和/或B位点上的化学取代来克服，从而导致稳定的可逆的双链反应。本文研究了Sm_2Mn_xNi_（7-x）（0 <= x < 0.5）赝二元体系。通过X射线衍射、化学分析、扫描电子显微镜、热重分析和磁性测量等手段对合金的结构、热力学和腐蚀性能进行了分析和解释。意外的电池参数变化的报告和解释可能形成的结构缺陷和不均匀的Mn分布在Ni亚晶格。对于x > 0.3，可逆容量得到改善，导致更大和更平坦的等温曲线，允许可逆容量>1.4重量%。在腐蚀方面，该二元化合物在碱性介质中发生腐蚀，生成稀土氢氧化物和纳米多孔镍。对于Mn取代的化合物，除了上述那些之外，还形成了新的腐蚀产物，因为锰在腐蚀早期阶段启动了发生的牺牲阳极机制。
英文摘要：
Intermetallic compounds are key materials for energy transition as they form reversible hydrides that can be used for solid state hydrogen storage or as anodes in batteries. ABy compounds (A = Rare Earth (RE); B = transition metal; 2 < y < 5) are good candidates to fulfill the required properties for practical applications. They can be described as stacking of AB5 and AB2 sub-units along the c crystallographic axis. The latter sub-unit brings a larger capacity, while the former one provides a better cycling stability. However, ABy binaries do not show good enough properties for applications. Upon hydrogenation, they exhibit multiplateau behavior and poor reversibility, attributed to H induced amorphization. These drawbacks can be overcome by chemical substitutions on the A and/or the B sites leading to stabilized reversible hydrides. The present work focuses on the pseudo-binary Sm2MnxNi7-x system (0 <= x < 0.5). The structural, thermodynamic and corrosion properties are analyzed and interpreted by means of X-ray diffraction, chemical analysis, scanning electron microscopy, thermogravimetric analysis and magnetic measurements. Unexpected cell parameter variations are reported and interpreted regarding possible formation of structural defects and uneven Mn distribution within the Ni sublattice. Reversible capacity is improved for x > 0.3 leading to larger and flatter isotherm curves, allowing for reversible capacity >1.4 wt %. Regarding corrosion, the binary compound corrodes in alkaline medium to form rare earth hydroxide and nanoporous nickel. As for the Mn-substituted compounds, a new corrosion product is formed in addition to those above mentioned, as manganese initiates a sacrificial anode mechanism taking place at the early corrosion stage.
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