Effects of Protide Structures on Hysteresis in Ti-Cr-V Protium Absorption Alloys

Ti–Cr–V alloys have a higher protium (hydrogen atom) desorption capacity, but a larger hysteresis in the absorption and desorption processes than AB2 and AB5 type protium absorption alloys. It is desirable that the alloys have a smaller hysteresis for the use of hydrogen storage tanks. This paper aims to clarify the effects of protide (hydride) structures on the hysteresis in Ti–Cr–V protium absorption alloys. It was found that the β phases observed after desorbing at the desorption plateau region had the BCC structure for the alloys (Ti:Cr=2:3) containing less than 70 at%V, but the BCT structure for the alloys (Ti:Cr=2:3) containing more than 70 at%V . A major reason for the large hysteresis in the Ti–Cr–V alloys appears to be the a-axial contraction in the absorbing process and the a-axial expansion in the desorbing process as opposed to the c-axial changes.