Investigation On The Microstructure And Hydrogen Storage Performance Of Ti-Cr-Mn-Fe Based Alloys With High Desorption Pressure

In recent years, solid-high pressure hybrid hydrogen storage technology, which combines the method of metal hydride solid hydrogen storage with high pressure gaseous hydrogen storage, has been an important research direction of high efficient hydrogen storage system used in hydrogen refueling station. Among solid hydrogen storage alloys, AB2-type Ti-Cr based alloys are supposed to be the most promising alloys used in solid-high pressure hybrid hydrogen storage vessel application because of their high dehydrogenation pressures and high hydrogen storage capacities. Based on an overall review of the research and development of AB2-type Ti-Cr based alloys, Ti-Cr-Mn-Fe based alloys with high hydrogen desorption pressures have been developed for hybrid hydrogen storage vessel application in this thesis, and the microstructure and hydrogen storage properties of four series multicomponent alloys were systematically investigated.The effects of partial substitution of Cr with Fe on the microstructure and hydrogen storage properties of TiCr1.9-xMno.1Fex(x=0.4-0.6) alloys have been systematically investigated. The results show that all of the alloys were determined as a single phase of C14-type Laves structure. The increase of Fe content in the TiCr1.9-xMno.1Fex(x=0.4-0.6) alloys leads to the decrease of unit cell volume. It is found that with the Fe content in the alloys increases, the hydrogen absorption and desorption plateau pressures increase, for example, as Fe content increases from0.4to0.6, the hydrogen desorption plateau pressure increases from21.06MPa to40.77MPa at318K, but the hydrogen storage capacity decreases. The dissociation enthalpies of TiCr1.9-xMn0.1Fex(x=0.4-0.6) alloys are all between14.18-18.54kJ/mol H2.The influence of partial substitution of Mn for Cr on the microstructure and hydrogen storage properties of TiCr1.4-xMnxFeo.6(x=0.1-0.3) alloys also have been systematically investigated. The results show that all of the alloys were determined as a single phase of C14-type Laves structure. The increase of Fe content in the TiCr1.9-xMno.iFex(x=0.4-0.6) alloys leads to the decrease of unit cell volume. It is found that with the Mn content in the alloys increases, the hydrogen absorption and desorption plateau pressures increase, for example, as Mn content increases from0.1to0.3, the hydrogen desorption plateau pressure increases from40.77MPa to59.08MPa at318K, but the hydrogen storage capacity decreases. The dissociation enthalpies of TiCr1.4-xMnxFeo.6(x=0.1-0.3) alloys are all around14.25kJ/mol H2.In order to develop alloys with high hydrogen desorption pressures and large hydrogen storage capacities, some extra amount of Ti was added to form titanium super-stoichiometric alloys, and the microstructure and hydrogen storage properties of Ti1+xCr1.2Mno.2Feo.6(x=0-0.1) as well as Ti1+yCr1.1Mno.3Feo.6(y=0-0.04) have been systematically investigated. The results show that all of the alloys were determined as a single phase of C14-type Laves structure. And the increase of Ti content in the alloys leads to the decrease of the unit cell volume. It is found that the titanium super-stoichiometric alloys have larger hydrogen storage capacities compared with the stoichiometric alloy, for example, as Ti content increases from1to1.1in Ti1+xCr1.2Mn0.2Feo.6(x=0-0.1) alloys, the hydrogen storage capacity increases from1.39wt.%to1.72wt.%, as Ti content increases from1to1.04in Ti1+yCr1.1Mno.3Feo.6(y=0-0.04) alloys, the hydrogen storage capacity increases from1.26wt.%to1.80wt.%, But titanium super-stoichiometric decreases hydrogen absorption and desorption plateau pressures. The dissociation enthalpies of these super-stoichiometric alloys are all between13.70-17.46kJ/mol H2.Among the studied alloys, Ti1.02Cr1.1Mno.3Feo.6has the best overall performance for hybrid hydrogen storage application. Its hydrogen desorption pressure at318K is41.28MPa, its hydrogen storage capacity is1.78wt.%and its dissociation enthalpy (ΔHd) is16.24kJ/mol H2. It has been applied to the production of solid-high pressure hybrid hydrogen storage vessel application in hydrogen refueling station.