Study On Hydrogen Absorption/Desorption Characteristics Of Ti-V-based Solid Solution Type Hydrogen Storage Alloys

Ti-V-based solid solution type hydrogen storage alloys are considered as one of the promising candidates for fuel-cell automobiles due to their large hydrogen storage capacities and good hydrogen sorption kinetics characteristics. Commonly, the hydrogen desorption plateau pressure of Ti-V-based hydrogen storage alloys with high V content is below atmospheric pressure. In this thesis, the effective hydrogen desorption capacity is defined as the difference between maximum hydrogen storage capacity and the remaining hydrogen storage capacity when the alloy releases hydrogen to atmospheric pressure. According to the definition, effective hydrogen desorption capacites of Ti-V-based hydrogen storage alloys with high V content are relatively low while their costs are high, which limits their practical application. This work aims to improve performance of Ti-V-based alloys and lower their cost mainly through optimizing composition, substituting partial elements and annealing heat treatment. XRD (X-ray diffraction), SEM (scanning electron spectroscopy) and PCT (Pressure Component Temperature) techniques were used to study the hydrogen absorption/desorption properties of Ti-V-based solid solution type hydrogen storage alloys.InthecaseofxTi-18Mn-(50-x)Cr-32V (x=36, 34, 32, 30, 28) alloys, adjusting Ti/Cr ratio does not change their BCC structure. However, with the decrease of Ti/Cr ratio, the lattice parameters, cell volumes and maximum hydrogen absoiption capacities decrease and desorption plateau pressure increase, resulting from the smaller radius of Cr compared with that of Ti. In addition, the effective hydrogen desorption capacities increase on the whole and hysteresis of PCT curves decreases, which shows improvement of alloys' performance.Substituting V₄Fe for V in 34Ti-18Mn-16Cr-32V alloy is effective in reducing the cost and improving the properties. It was found that the the addition of V₄Fe alloy resulted in the formation of C14 Laves phase in the alloy. The maximum hydrogen absorption capacities decrease and desorption plateau pressure increases gradually due to...