Titanium-Iron AB Compounds

Saita et al. [215] used hydriding combustion synthesis for a direct production of TiFe. In the experiments, an exothermic reaction of Ti with hydrogen (Ti + H2= TiH2 + 144 kJ) was utilized for HCS of TiFe because the adiabatic flame temperature of this reaction was estimated to be 2,000°C, which is sufficiently high for melting both iron and titanium. A 1 1 molar mixture of elemental Ti and Fe pow- 

The same alloy milled for 80 h did not absorb hydrogen. It seems that the presence of the FCC phase formed during milling somehow blocks the hydrogen intake but the exact explanation is lacking. 

Guenee and Yvon [217] synthesized LaNi MOj intermetallic with a YNi Alj-type crystal structure. However, its hydrogen storage properties are no better than those of LaNij-type because it could barely absorb -1.4 wt.%Hj forming LaNi MnjH and its equilibrium temperature at 1 bar H, is about 60°C. No attempt of nanostructuring the compound by ball milling was made. 

The Aoki group [218] has been developing intermetallic alloys based on a CaSi compound that is alloyed with Si, Al, Ge, Mg, and Sr. However, the alloys cannot compete with the LaNi -type or even TiFe because they absorb only slightly more than 2 wt.%H at 100°C and desorb at 200°C. 

Okamoto, Desk Handbook-Phase Diagrams for Binary AUoys, ASM International, Materials Park, OH, (2000), p.430. 

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