Abstract
The hydrogen absorption and desorption characteristics of Ti1-xLaxCo(x=0.05∼0.5) alloys were investigated. The alloys can easily be activated and they react readily with hydrogen to form the hydrides Ti0.95La0.05CoH1..4, Ti0.9, La0.1, CoH01.3, Ti0.75La0.25CoH0.8 and Ti0.5La0.5CoH0.4(the hydrogen contents: 1.3, 1.1, 0.6 and 0.3 wt%, respectively) under the hydrogen pressure of 30 atm at 80°C. The dissociation pressure of these hydrides, P is dependent on the lanthanum content x by which the titanium is substituted. The value of log P increases gradually with increasing x.
The standard enthalpy change for the Ti0.9, La0.1, , Co-H2, reaction, -14.3 kcal/mol H2 is determined on the basis of the dissociation isotherms (Fig.5); this value is nearly the same as that for the TiCo-H2, reaction. The temperature required to generate the dissociation pressure of 1 atm for Ti0.9, La0.1, CoH1.3, (tetragonal structure) is 115°C, lower than 130°C for TiCoH1.4. For Ti0.9La0.1, Co, only two hydrogen absorption-desorption cycles under the mild conditions perm it the alloy to be fully activated. The cycle is repeated 30 times but no variation in the hydrogen absorption-desorption capacity is observed.
