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

Abstract

Ti-Cr-V alloys have a higher protium (hydrogen atom) desorption capacity, but a larger hysteresis in the absorption and desorption processes than AB 2 and AB 5 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.

Hydrogen Isotope Effects on Absorption Properties of Ti-Cr-V Alloys

“…23) Vanadium is known to have large hydrogen isotope effects. 19,24) However, no hydrogen isotope effects of the Ti-Cr-V alloys were reported except for the works by Cho. 25,26) Therefore, the purpose of this study is to clarify the hydrogen isotope effects on the absorption properties of the Ti-Cr-V alloys in a composition range near the boundary between the appearance regions of the mono-and di-protides.…”

“…This phenomenon was considered in our previous work. 19) The absorption plateau pressure for deuterium is lower than that for protium. Figure 5 shows PCT curves for protium and deuterium at 244 K for the Ti-62Cr-20V alloy.…”

“…Ti-Cr-V alloys with a BCC structure are regarded as one of the candidates for hydrogen storage tanks. 1) Since the Ti-Cr-V alloys show the capacity of nearly 3 mass%at 373 K, a lot of works, such as the additions of other elements, 2-7) the effects of heat-treatment and composition, [8][9][10][11][12] V free alloys, [13][14][15][16] cyclic properties 17,18) and the effects on hysteresis, 19) have been reported for improving the properties. Ti-Cr-V alloys absorb protium up to H/M = 2 (about 3.7 mass% of protium), but desorb about 2.4 mass% from the viewpoint of protium desorption capacity (9-0.01 MPa) by forming stable protides in low hydrogen pressure regions.…”

Isotope Effects on Protium and Deuterium Absorption Properties in Ti-56 at%Cr-20 at%V Alloy

“…Ti-Cr-V alloys with a BCC structure are regarded as one of the candidates for hydrogen storage tanks. 1) Since the Ti-Cr-V alloys show the capacity of nearly 3 mass% at 373 K, a lot of works, such as the additions of other elements, 2-7) the effects of heat-treatment and composition, [8][9][10][11][12] V free Ti-Cr alloys, [13][14][15][16] cyclic properties [17][18][19] and the effects on hysteresis, 20) have been reported in improving the properties. Ti-Cr-V alloys absorb protium up to H/M = 2 (about 3.7 mass% of protium), but desorb about 2.4 mass% from the viewpoint of protium desorption capacity (9-0.01 MPa) through forming stable protides in low hydrogen pressure regions.…”

Effects of Absorption-Desorption Cycles on Protium Absorption Properties in Ti-Cr-M Alloys (M = V, Mo, Al)

“…Ti-Cr-V alloys with a BCC structure, which are known to have about 3 mass% effective protium desorbing capacity at 373 K, are regarded as one of the candidates for the media of hydrogen storage tanks. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] In considering practical use of the alloys, it is important to know the absorption-desorption cyclic properties of the alloys.…”