Research On Modification Of Zr-Fe Based High Pressure Hydrogen Storage Alloys

With the high hydrogen desorption plateau pressures, low platform slopes and low residual amount of hydrogen, the Zr-Fe-based hydrogen storage alloys were chosen as the objects in this thesis. The crystal structures, the absorption/desorption PCT isotherms and the hydrogen absorption kinetics of the Zr-Fe-based hydrogen storage alloys with Fe partially replaced by V and Mn and Zr partially replaced by Ti were investigated systematically by X-ray diffraction (XRD), Electron Probe Micro Analysis (EPMA), scanning electronic microscope (SEM) and Sie vert’s volumetric method. And the new high plateau pressures alloys may be used in the solid/hydrogen storage system.In order to maintain a single-phase, study was focused on microscopic structure of as-cast ZrFex (x=1.9,1.95,2,2.05,2.1) alloys. It was found that the alloys had a single-phase when x≥2.05and ZrFe2.05was chosen to be the basic substrational binary alloy.To ease the activation and reduce the hysteresis factor, the microstructure and hydrogen storage properties of the as-cast ZrFe2.05-xVx (x=0.05,0.1,015,0.2) alloys were studied systematically. XRD patterns reveales that all samples have C15type Laves phase cubic structure and their lattice constants increase with the increase of V content while ZrFe1.9V0.15and ZrFe1.85V0.2possesses a second phase with C14type Laves hexagonal structure. With the increase of V content, the activation time is reduced and the hysteresis alleviates. The hydrogen absorption rate enhances and the pulverization resistance is improved while the effective hydrogen intake capacity first increases and then decreases. On the other hand, the desorption plateau pressure decreases while the plateau slopes and ΔH increase.It can be seen from the annealing ZrFe1.9V0.15alloys that the high temperature annealing can homogenize the alloys and reduce the abundance of C14-type Laves phase effectively. The activation can be easied greatly while the hysteresis alleviates and the plateau slopes decrease. The max and effective hydrogen intake capacity increases and the ΔH decreases. On the other hand, the equilibrium desorption plateau pressures decrease slightly while the hydrogen absorption rates ramain unchanged. Considering the energy consumption and the degree of improvement of hydrogen storage properties, the appropriate annealing temperature is1173K.The microstructure and hydrogen storage properties of of the ZrFe2.05-x-yMnyVx(y=0,0.05,0.1,0.15; x=0.1,0.15) alloys were also investigated systematically. XRD patterns reveals that all samples have single C15type Laves phase and the lattice constants increase with the increase of Mn content when y≤0.1in ZrFe1.95-yMnyV0.1(y=0,0.05,0.1,0.15) alloys. ZrFe1.8Mn0.15V0.1alloy possesses a second new phase with C14type hexagonal structure and its lattice constant is less than that of ZrFe1.85Mn0.iV0.1alloy. With the increase of Mn content, the hysteresis alleviates and the activation time is reduced while the plateau slopes increase slightly and the equilibrium desorption plateau pressures decrease. On the other hand, the hydrogen intake capacity increases first and then decreases. The ZrFe1.85Mn0.1V0.1alloy has the maximum hydrogen intake capacity of1.69wt.%and the highest absorption rates t0.9=46s among these alloys at243K. The precipitation of the C14type Laves phase may be inhibited when y≤0.1in ZrFe1.9-yMnyV0.15(y=0,0.05,0.1,0.15) alloys, thereby expanding the range of ingredients to maintain a single C15type Laves phase structure.To further raise the hydrogen desorption plateau pressure, the effects of hydrogen storage properties of TixZr1-xFe1.95V0.1Mmy (x=0.05,0.1,0.15; y=0,0.015) alloys were also investigated. With the adding of the Mm content in the TixZr1-xFe1.95V0.1Mmy,(y=0,0.015) alloys, the incubation time is shortened and hydrogen absorption speed is accelerated while Hf and the plateau slopes increase. Meanwhile, ΔH increases and the hydrogen desorption plateau pressurses decrease. With the adding of Ti content in the TixZr1-xFe1.95V0.1Mm0.015(x=0.05,0.1,0.15) alloys, there exists a second phase in all the alloys and the incubation time is lengthened while the hydrogen absorption speed is decelerated. Meanwhile,Hfgets smaller and the plateau slopes and ΔH both decrease while the effective hydrogen storage capacity and the hydrogen desorption plateau pressure both increase. On the other hand, the hydrogen absorption rate reduces slightly.