Microstructure and hydrogen absorption properties of nano-phase composite prepared by mechanical alloying of MmNi5-x(CoAlMn)x and Mg

In this work high energy ball milling was used to prepare composite hydrogen storage alloy in the MmNi(5-x)M(x)-Mg system. X-ray diffraction and TEM analysis were used to characterise the microstructure of the composite alloy obtained by ball milling. It has been shown that the grain size of MmNi(5-x)M(x) and Mg components were reduced to nanometre range after about 20 h of milling. Besides, a Mm(2)Mg(17) phase of nanometre size was also formed in the milling process. Thus, a composite alloy, referred to as nano-phase composite here, composed of MmNi(5-x)M(x), Mg and Mm(2)Mg(17) phase of nanometre size was obtained. Hydrogen storage behaviour of the nano-phase composite was compared with that of conventional MmNi(5-x)M(x) alloy by measuring PCT and kinetics. It showed that the hydrogen absorption properties were improved. (C) 1999 Elsevier Science S.A. All rights reserved.