MG COMPOSITES FOR HYDROGEN STORAGE - THE DEPENDENCE OF HYDRIDING PROPERTIES ON COMPOSITION

Magnesium alloys show great potential as materials for gaseous hydroge n storage. However, their practical use is limited by poor hydrogen ab sorption and desorption kinetics. This problem can be resolved by mixi ng Mg alloys with other materials to form composites. We present an in vestigation of composites formed by mechanically milling La2Mg17 with x wt.% LaNi5 (x=0, 10, 20, 30, 40, 50, 60 wt.%). The rate of hydrogen absorption and desorption was measured for all of these compositions o ver a wide range of temperatures. These composites were then character ized using a set of reaction rate equations. The composite La2Mg17+40 wt.% LaNi5 showed the best overall kinetics. At 250 degrees C it has a n average absorption rate of 8.2 (wt.% min(-1)) and a desorption rate of 1.0 (wt.% min(-1)) with a final capacity of 3.7 wt.%. This is appro ximately 50 times faster than purl La2Mg17 under the same conditions. (C) 1997 Elsevier Science S.A.