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Title: Size-dependent mechanical properties of Mg nanoparticles used for hydrogen storage

Magnesium (Mg) hydride is a promising hydrogen storage material, yet its application has been limited by the slow hydrogen sorption kinetics. Recently, Mg nanoparticles have shown significant improvement of hydrogen storage properties in terms of dimensional stability upon cycling with the trend that the smaller the particle, the better the sorption kinetics. Since the volume change during sorption generates stress, leading to plastic deformation, the fundamentals of the mechanical deformation of the Mg particles are a significant issue. By using in situ transmission electron microscope compression tests and atomistic simulations on Mg nanoparticles, it was observed that deformation in the larger particles was dominated by the nucleation of 〈a〉-type dislocations from stress concentrations at the contact surface, while the smaller particles deformed more homogeneously with greater distribution of multiple types of dislocation sources. Importantly, this improvement of plastic deformation with decrease in size is orientation-independent. First-principles calculations suggest that this improved plasticity can be explained by the nearly-isotropic ideal shear strength for Mg, which becomes more important in smaller nanoparticles. As a result, the smaller Mg nanoparticles demonstrated better plastic stability to accommodate volume change upon hydrogen storage cycling.
Authors:
 [1] ;  [2] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [2]
  1. Center of Electron Microscopy and State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China)
  2. (United States)
  3. Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109 (United States)
  4. General Motors Research and Development Center, Warren, Michigan 48090 (United States)
  5. Department of Materials Science and Engineering, Shanghai Jiaotong University, Shanghai 200240 (China)
  6. Department of Materials Science and Engineering, University of California, Berkeley, California 94720 (United States)
Publication Date:
OSTI Identifier:
22482016
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 106; Journal Issue: 26; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; DISLOCATIONS; HYDRIDES; HYDROGEN; HYDROGEN STORAGE; MAGNESIUM; NANOPARTICLES; NUCLEATION; ORIENTATION; PLASTICITY; SHEAR PROPERTIES; SIMULATION; SORPTION; STABILITY; STRESSES; SURFACES; TRANSMISSION ELECTRON MICROSCOPY