Comparing the hydrogen storage alloys-TiCrV and vanadium-rich TiCrMnV

Two hydrogen storage alloys: (A) 33.5 mass% Ti-34.7 mass% Cr-V; (B) 9.5 mass% Ti-14.7 mass% Cr-2 mass% Mn-V are investigated. X-ray diffraction results indicate both alloys are bcc phase, and only slightly different in lattice parameters. TEM analysis on alloy A determined that it is homogeneously bcc structured with a lattice constant of 0.306 nm. The alloy B displayed a second phase in plate shape, which is identified as Ti-5% V. One of its lattice constants is determined to be 0.76 nm from several sets of diffraction pattern. The hydrogen storing capability showed that alloy A could absorb 3.6% hydrogen in the first cycle, when breathing in H₂ at 25 ^{{ring operator}} C and releasing out at 400 and 500 ^{{ring operator}} C. The absorbing ability decreased progressively in the successive cycles, down to 3.0% at the fourth round. Hydrogen storage ability of alloy B is much markedly inferior to that of alloy A, possibly due to the plate shape, functionless Ti-5 mass% V.