Structural characteristics and desorption properties of nanostructured MgH₂ synthesised by high energy mechanical milling

Abstract

The effect of particle size, lattice strain and crystallite size on the hydrogen desorption properties of nanocrystalline magnesium hydride powder was investigated. Commercial MgH₂ powder was milled in a Spex 8000M up to 16 h and its structural evolution and desorption characteristics at different time intervals were examined using various analytical techniques. At the early stage of milling, the formation of metastable γ-MgH₂ phase was noticed. While the crystallite size gradually decreased to 12 nm with increasing the milling time, the accumulated lattice strain gained a maximum value of 0·9% after 4 h milling. The highest drop in the desorption temperature (∼100°C) was attained at the peak strain with the average grain size of 20 nm. The particle size of MgH₂ varied in the range of 20–50 μm without profound effect of the desorption properties.

Keywords:

• Hydrogen storage materials
• Mechanical milling
• Grain size
• Lattice strain