The intrinsic degradation of ($V_0.53Ti_0.47)_0.925Fe_0.075$ by thermally induced hydrogen absorption-desorption cycling at 600℃ was investigated using the P-C-Isothermal curves, the X-ray diffraction, thermal desorption analysis, SEM and TEM.
After 400 thermal cycles, the hydrogen absorption capacity was decreased by about 25% of the value of the beginning of the cycling, This alloy showed different degradation behaviors of higher plateau region and lower plateau region. The hydrogen storage capacity was gradurally decreased at higher plateau region and abruptly decreased at lower plateau region.
From the result of the thermal hydrogen desorption, X-ray diffraction and TEM, it is suggested that the intrinsic degradation of the lower plateau region is caused by the phase transformation from B.C.C to B.C.T and that of the higher plateau region is caused by the formation of amophous phase, From the result, phase transformation (from b.c.c to b.c.t) and amorphization must be prevented. Phase transeformation can be prevented by b.c.c stabilizer and amorphization with trasition metal of larger atomic radius. So, the decrease of storage capacity can be reduced by substitution of Fe with Cr which is effective to prevent V-Ti-Fe based alloy from phase-transforming and from forming of amorphous phase.
