Study On Hydrogen Storage Alloys Applied In High-pressure Hydrogen Storage Vessel And Metal Hydride Compressor

In this thesis, the recent research and development on hydrogen storage alloys for high-pressure metal hydride hybrid hydrogen storage vessel and high-pressure metal hydride compressor were exhaustively reviewed. AB2 type Ti-Cr-Mn(Fe)-based multi-component alloys with high hydrogen absorption/desoprtion plateau pressure was selected as the study object of this work, and the microstructures, hydrogen storage properties and compression properties were studied systematically. By means of hydrogen storage properties measurements and XRD analysis, the effect of alloy composition (including Cr/Mn ratio, Cr/Fe ratio, partial substitution of Cr and/or Mn by Fe, V and Cu) and averaged number of outer electrons (e/a) on the phase structure and the hydrogen storage characteristics were investigated. Alloys with good hydrogen storage properties were developed for metal hydride hybrid high-pressure hydrogen storage vessel and high-pressure hydrogen compressor. With the developed hydrogen storage alloys, we have built a metal hydride hybrid high-pressure hydrogen storage vessel with working pressure of 40MPa and a high-pressure metal hydride hydrogen compressor which can supply 70MPa high-pressure hydrogen.For Ti0.9Zr0.15CrxMn1.8-xV0.2 (x=1.4,0.9,0.5,0.2) and Ti0.95Zr0.05CrxMn1.75-xV0.2Fe0.05 (x=1.1,0.9,0.7,0.5,0.3) multi-component alloys, the experimental results show that all alloys consist of C14 Laves phase, and the lattice constants and cell volume of the alloys decrease as Cr/Mn ratio decreases. For Ti0.9Zr0.15CrxMn1.8-xV0.2 alloys, as Mn content increases, the hydrogen absorption/desorption plateau pressure increases and the slope factor decreases, but the hysteresis factor increases.Ti0.95Zr0.05CrxMn1.75-xV0.2Fe0.05 alloys have flatter and wider p-c-T plateau region, as well as larger hydrogen storage capacity and higher hydrogen desorption rate. It is found that as Cr/Mn ratio decreases and e/a increases, the hydrogen absorption/desorption plateau pressure and the hysteresis factor increases, the slope factor decreases remarkably. Ti0.95Zr0.05Cr0.7Mn1.05V0.2Fe0.05 alloy demonstrates fairly ideal properties with hydrogen absorption capacity of 2.09 wt.% at 273K and hydrogen absorption and desorption plateau pressure of 2.13MPa and 1.17MPa, respectively. Combined this alloy with a lightweight high-pressure hydrogen storage vessel, a metal hydride hybrid high-pressure hydrogen storage vessel with working pressure of 40MPa was made. Its volumetric hydrogen storage density and gravimetric hydrogen storage density reached 29.7kg·m-3 and 2.4 wt%, respectively. For Ti0.8Zr0.2Cr(2-x)/2Fe(2-x)/2Vx (x=0,0.1,0.2) and Ti0.8Zr0.2Cr1.9-xFexV0.1 (x=0.5,0.7, 0.95,1.1,1.2) alloys, the experimental results show that all of these alloys have a main phase of C14 type Laves phase, and the cell volume decrease with the decrease of Cr/Fe ratio. Ti0.8Zr0.2Cr(2-x)/2Fe(2-x)/2Vx possess flat plateau region and high plateau pressure, after adding small amounts of V and Cu, their hydrogen storage capacity and hydrogen absorption rate are improved. When adding a small amount of V, the hydrogen storage capacity increases and the plateau properties are improved. But when small amounts of Cu is added, the hysteresis factor and slope factor increase even though a little increment in hydrogen storage capacity. Partial substitution of Ti by Zr can improve the plateau properties but increase the hysteresis. Ti0.8Zr0.2Cr0.95Fe0.95V0.1 alloy show admirable performance with hydrogen absorption capacity of 1.72wt.% at 258K, and its hydrogen absorption and desorption plateau pressure are 2.54MPa and 2.32MPa, respectively, its hydrogen absorption and desorption enthalpy are -19.6kJ/molH2 and -20.5J/molH2, respectively. With La0.35Ce0.45Ca0.2Ni4.95Al0.05 as the first stage hydrogen compression alloy and Ti0.8Zr0.2Cr0.95Fe0.95V0.1 as the second stage hydrogen compression alloy, a double-stage hydride hydrogen compressor was designed and built. When the temperature of the hydride beds is increased to 423K, the metal hydride compressor can supply hydrogen with pressure of over 70MPa.