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Multi-component AB2 metal hydride alloys for nickel metal hydride battery applications.

机译：用于镍金属氢化物电池应用的多组分AB2金属氢化物合金。

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摘要

Compared to the mish metal-based AB5 MH alloy commonly used in Ni/MH batteries, the transition metal-based AB2 MH alloy not only reduces the rare earth dependency, it also has higher specific energy. In order to further improve the performance of AB2 MH alloy, it's crucial to full understand its multi-phase nature, which includes the main C14/C15 Laves phases and the secondary non-Laves phases.;In order to optimize the gaseous phase and electrochemical advantages of both the C14 and C15 Laves phases, a study was established to recognize the factors that affect the C14/C15 phase abundance. Average electron density (e/a) was proven to be an influential parameter in determining the C14/C15 phase abundance: as e/a increased, C14/C15 became less/more dominant, respectively. However, with different A-site composition, a shift in e/a was observed in the C14/C15 phase abundance vs. e/a relationship. The average chemical potential for electronic charge of A atoms (&phis;*A) was found to show a nearly perfect linear correlation to the C14/C15 threshold with various selections of A-site elements. The combination of e/a and &phis;*A can be used to predict the C14/C15 phase abundance and assist future AB2 MH alloy design process.;Four non-Laves phase alloys, Zr8Ni21, Zr7 Ni10, Zr9Ni11, and ZrNi, commonly seen in AB2 MH alloys were studied. Annealing treatment was adopted on each alloy to change the abundances of various phases. Annealing suppressed secondary phases except for the case of Zr9Ni11, where its secondary ZrNi phase increased. As the Zr/Ni ratio increased, the maximum gaseous phase hydrogen storage capacity increased but maximized at Zr : Ni = 9 : 11. Comparing the properties before and after annealing, it was clear that the natures of constituent phases influenced the gaseous phase storage. The highest full discharge capacity was obtained at Zr : Ni = 7 : 10, which is a compromise between the hydrogen desorption rate and the theoretical maximum gaseous phase hydrogen storage. As the Zr/Ni ratio increased, the amount of metallic Ni in the surface oxide decreased, therefore the high-rate dischargeablity decreased. Among all alloys, the unannealed Zr7Ni10 demonstrated the best gaseous phase hydrogen storage and electrochemical capacities, and the unannealed Zr8Ni21 showed excellent HRD and activation.;Zr8Ni21 alloy was then chosen based on its promising performance to be further modified for the purpose of developing alternative MH alloys for Ni/MH batteries. Zr8Ni19X 2 alloys (X = Ni, Mg, Al, Sc, V, Mn, Co, Sn, La, and Hf) were prepared and studied. The effect of annealing on these alloys was also investigated. Only the main phase of the annealed Sn-substitution remained Zr8Ni21-structured while those of other substitutions turned into Zr7Ni10 or Zr2Ni7. Annealing generally suppressed secondary phases except for the case of Zr 8Ni19Sn2, where the major phase transformed from Zr2Ni7 to Zr8Ni21. Both the maximum gaseous phase hydrogen storage and electrochemical full discharge capacities followed the increasing order of B/A ratio of the main phase. After annealing, all alloys except for the Sn-substituion showed degradation in full discharge capacity due to the reduction in number and abundance of the catalytic secondary phases. Among all alloys, the as-cast Hf-substituted Zr8Ni 21 alloy demonstrated the best overall gaseous phase hydrogen storage and electrochemical properties.
机译：与Ni / MH电池中常用的混合金属基AB5 MH合金相比，过渡金属基AB2 MH合金不仅降低了稀土依赖性，而且具有更高的比能。为了进一步改善AB2 MH合金的性能，至关重要的是充分了解其多相性质，包括主要的C14 / C15 Laves相和次要的非Laves相。;为了优化气相和电化学C14和C15 Laves相的优势，我们进行了一项研究以认识到影响C14 / C15相丰度的因素。事实证明，平均电子密度（e / a）是确定C14 / C15相丰度的重要参数：随着e / a的增加，C14 / C15的占主导地位分别降低。但是，使用不同的A位点组成，在C14 / C15相丰度与e / a关系中观察到e / a的变化。发现A原子的平均电子电荷化学势（φ* A）显示出与C 14 / C 15阈值几乎完美的线性相关性，其中选择了各种A位元素。 e / a和φ* A的组合可用于预测C14 / C15相的丰度并协助将来的AB2 MH合金设计过程。四种非Laves相合金Zr8Ni21，Zr7 Ni10，Zr9Ni11和ZrNi通常在AB2 MH合金中观察到了这种现象。每种合金均采用退火处理以改变各个相的丰度。退火抑制了第二相，但Zr9Ni11的次级ZrNi相增加了。随着Zr / Ni比的增加，最大气相储氢量增加，但在Zr：Ni = 9:11时达到最大值。比较退火前后的性能，很明显组成相的性质会影响气相储藏。在Zr：Ni = 7:10时可获得最高的全放电容量，这是氢气解吸速率与理论上最大气相气相氢气存储量之间的折衷。随着Zr / Ni比的增加，表面氧化物中金属Ni的量减少，因此高倍率放电性降低。在所有合金中，未退火的Zr7Ni10表现出最佳的气相储氢和电化学容量，未退火的Zr8Ni21表现出出色的HRD和活化性。用于Ni / MH电池的合金。制备和研究Zr8Ni19X 2合金（X = Ni，Mg，Al，Sc，V，Mn，Co，Sn，La和Hf）。还研究了退火对这些合金的影响。只有退火的Sn替代的主相保持Zr8Ni21结构，而其他替代的主相变为Zr7Ni10或Zr2Ni7。除了Zr 8Ni19Sn2的情况外，退火通常抑制了第二相，其中Zr8Ni19Sn2的主相从Zr2Ni7转变为Zr8Ni21。最大气相储氢量和电化学完全放电容量都遵循主相B / A比的增加顺序。退火后，由于减少了催化次级相的数量和数量，除Sn替代以外的所有合金均显示出完全放电容量的下降。在所有合金中，铸态的Hf取代Zr8Ni 21合金表现出最佳的整体气相储氢和电化学性能。

著录项

  • 作者

    Nei, Jean.;

  • 作者单位

    Wayne State University.;

  • 授予单位 Wayne State University.;
  • 学科 Alternative Energy.;Chemistry Inorganic.;Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2012
  • 页码 185 p.
  • 总页数 185
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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