Increase of specific surface area of metal hydrides by lixiviation

In this paper, we present a new and powerful method to increase the specific surface area of nanocrystalline ball milled materials. The method consists of using a lixiviation technique to increase the surface area. The element to be lixiviated is ball milled with the hydrogen-absorbing alloy. After complete mixing, the lixiviated element is leached in an appropriate solution. The end product is a porous metal hydride with high specific surface area. The system magnesium-lithium is presented as an example. The results show that before lixiviation, the alloys absorb hydrogen slowly and the hydrogen capacity is reduced due to the presence of lithium. After lixiviation, the specific surface area shows a ten-fold increase and the hydrogen sorption kinetics are faster. (C) 1998 Elsevier Science S.A.