• - 



' 





Magoe3iua-co?per Hydride. The magnesiua-copper hydride, also 

 investigated by Drs. Reilly and Wiswall [56], has many characteristics 

 similar to the cagcesiua-nickel hydride. It can hold 6.62 percent of 

 weight of hydrogen and appears to have satisfactory kinetics at 600 F. 

 Similar to the nagnesiua-nlckel hydride, the magnesium-copper hydride 

 has a large dissociation enthalpy. Generally, magnesium-copper hydride 

 is a second choice to the magnesia-nickel hydrides and, as such, would 

 only be used in cases when nickel was in short supply. As ia the case 

 of the magnesium-nickel hydride, data concerning the absorption and 

 generation rates is lacking. 



Iron-tit 3 "* 1 "" Hydride. If a hydride which operates well at tespera- 

 tures slightly above room temperature is needed, then iron-titaniua 

 hydride is probably the best that will be found. The price that is paid 

 is in the weight. About 3.3 pounds of iron titanium must be used to 

 store the same amount of hydrogen as can be stored in 1 pound of magnesium- 

 nickel hydride. About half as much heat is required to release that 

 hydrogen, though; and the heat that is required can be of a lower quality. 



Investigated by Drs. Reilly and Wiswall [57] in the early 1970*s, 

 iron titanium has proven to be a promising hydride for hydrogen storage. 

 It is about 3.6 times denser than magnesium-nickel hydride so it would 

 take 3 cubic feet and 1,060 pounds of iron-titanium to store 21.2 pounds of 

 hydrogen. The combination of this extra weight and an estimated cost of 

 about twice that of magnesium nickel makes the cost of an iron-titanium 

 system about six times that of magnesium nickel. These costs are esti- 

 mates; and, due to the great availability of the constituent cetals, the 

 costs should not rise due to shortages. In fact if new and cheaper 

 processes are developed for refining the metals, then the price should 

 drop. 



Lanthanua-pentanickel Hydride. Lanthanum-pentanickel (La Nij) 

 hydride was investigated in the 1960's by J. H. N. Van Vucht, F. A. 

 Kuijpers and H. C. A. M. Bruning of the Phillips Research Laboratory in 

 Eindhoven, Netherlands [58]. This hydride delivers a desirable pressure 

 at room temperature, though the reaction rate at this temperature is 

 slow. The reaction rate can be greatly improved by increasing the tempera- 

 ture. Reference 58 indicates that at a temperature of 120 F (49 C) the 

 hydrogen can be 952 desorbed in just 3 minutes, whereas at a temperature 

 of 64°F (18°C) the hydride is only 80% desorbed after 40 minutes. Thus, 

 the desorption rate of the hydride can be controlled by controlling iLs 

 temperature. This was the only hydride on which this type of data was 

 available. 



A look at Table 3 will show that the dissociation enthalpy is net a 

 firmly known v«Jut. Phillips Research Laboratory has indicated the 

 upper and lover values of this range; the actual dissociation enthalpy 

 is unclear [581. 



There are also tvo values listed in Table 3 for the density of 

 lanthanum-pentanickel hydride. Reference 35 states that the lattice 

 structure of this hydri.de changes with the addition of hydrogen to take 



24 



