Study Of Hydrogen Storage Alloys In Timn

Hydrogen as a new generation energy source is receiving increasing attention. However, the storage and transportation of hydrogen is an obstacle for it's wide application. Using hydrogen storage alloy to store and transport hydrogen is an effective and safe solution. Among the existing hydrogen storage alloys, Ti-Mn based alloy has been got much emphasis for its good performance, such as easy activation, high hydrogen storage content, and fast absorption and desorption characteristics under low pressure of hydrogen. However, Ti-Mn based alloy also has some disadvantages such as large hysteresis of absorption and desorption, requirement of high hydrogen pressure for initial activation. In this paper some approaches to decrease the hysteresis and the hydrogen pressure for initial activation have been proposed. The effects of partial substitution of vanadium and iron for manganese, nonstoichiometry and heat treatment on alloy performances were investigated.The results showed that the alloy's activation characteristics, hydrogen storage content, thermodynamic and mechanical characteristics had been improved significantly after manganese was partially substituted by vanadium and iron. For example, TiM^ .i(VFe)OJ alloy begins hydrogen absorption only after 5 minutes at 353K and under 2MPa of hydrogen pressure. The corresponding hydride can release hydrogen up to 220ml/g under standard condition if the alloy absorb hydrogen at 293K and 4MPa. The enthalpy and entropy of the hydride during absorption of hydrogen were calculated. The X-ray diffraction (XRD) showed that the phase constitution of TiMn1.5 alloy had transformed from single Y -TiMn1-2 to coexistence of Y -TiMn1-2 and 8 -MnV after manganese was partially substituted by vanadium and iron. Whereas, the phase constitution of TiMn2 alloy have changed from single of Y -TiMn1-2 to two phases of Y -TiMn1-2 and TiMn5.As to Ti-Fe based hydrogen storage alloys, the activation characteristics canbe greatly improved by partially substituting chromium or manganese for iron. Moreover, the alloy also shows large desorption hydrogen content (up to 200ml/g) with fast absorption and desorption performance.At last, the influences of heat treatment on hydrogen storage alloy behaviors were examined. The results showed that heat treatment could improve the alloy's absorption-desorption property, as well as the alloy's microstructure and thermodynamic characteristics.