Evolution of microstructure in MgH2 powder particles during high energy ball milling and hydrogen cycling

We investigated in details the evolution of microstructure by electron microscopy when powder MgH2 particles were ball milled up to 60 h. The average particle size reduced to less than 5 mu m within 5 h of milling from an average size of 38 mu m measured before milling. The grain size reduced from an average of similar to 750 nm in the un-milled powder to below 100 nm after milling. Particle size, as well as the grain size of milled powders followed log-normal distribution. Lattice strain was introduced significantly in the milled powder as a result of milling. Upon hydrogen cycling, this strain was reduced and the grain size was increased. (C) 2009 Elsevier B.V. All rights reserved.