Study On The Improvement Of Hydrogen Storage Performance Of Ti-Cr Based Alloys With High Desorption Pressure

In recent years, in order to meet the requirements of high efficient hydrogen storage system used in hydrogen refueling station, solid-high pressure hybrid hydrogen storage technology, which combines the method of metal hydride solid hydrogen storage with high pressure gaseous hydrogen storage, has attracted widespread attention and some important research have been underway. Developing hydrogen storage alloy with high desorption pressure is one of the key technics of the solid-high pressure hybrid hydrogen storage system. Based on an overall review of the research and development of alloys with high plateau pressure, Ti1.02(Cr-Mn-Fe)2based alloys were chosen as the research subjects, and the microstructure and hydrogen storage properties of the Ti1.02(Cr-Mn-Fe)2 based alloys with different Cr/Mn ratios and Fe/Mn ratios were systematically investigated. Based on the above research, The influence of RE additions(La, Ce, Ho), different annealing crafts on the microstructure and hydrogen storage properties of Ti1.02Cr1.1Mn0.3Fe0.6 alloy were further investigated.The effects of Cr/Mn ratios and Fe/Mn ratios on the microstructure and hydrogen storage properties of Ti1.02(Cr-Mn-Fe)2 based alloys have been systematically investigated. The results show that both of Ti1.02CrxMn1.4-xFe0.6(x=1,1.5,1.1) and Ti1.02Cr1.1Mn0.9-yFey(y=0.6,0.65) based alloys were determined as a single phase of C14-type Laves structure. The increase of Cr/Mn ratio content and the decrease of Fe/Mn ratio content in the Ti1.02(Cr-Mn-Fe)2 based alloys lead to the expansion of unit cell volume. It is found that with the Cr/Mn ratio content in the alloys increases, the hydrogen capacity increases and hydrogen absorption/desorption plateau pressures decreases, so does the decrease of the Fe/Mn ratio content. Ti1.02Cr1.1Mn0.3Fe0.6 has the best overall performance. Its hydrogen capacity is 1.621 wt.%, its desorption pressure at 318 K is 51.80 MPa, its desorption slope and hysteresis factor are 0.129 and 0.57 respectively and its dissociation enthalpy is 16.47 kJ/mol H2.Based on above research, to improve the activation under room temperature, the microstructure and hydrogen storage properties of Ti1.02Cr1.1Mn0.3Fe0.6REx (RE=La, Ce, Ho; x=0,0.01,0.03,0.05) based alloys were further investigated. The results show that all alloys contain a C14-type Laves main phase and the addition of RE increases the unit cell volume. As the doping content increases, there appears some RE oxide phase. It is found that adding of RE can improve activation property of alloys. All alloys can be activated completely under room temperature rather high temperature. The absorption and desorption pressure decrease after the La and Ce doping. The storage capacity increases with La additive while the storage capacity changes little with Ce additive. When the doping content is x=0.03, Ti1.02Cr1.1Mn0.3Fe0.6RE0.03 (RE=La, Ce, Ho) based alloys were investigated. It is found that the hydrogen absorption and desorption pressure decrease, the hysteresis of P-C-T curves decrease, the plateau slope increases and the dissociation enthalpy increase as the atomic number increases.The as-cast Ti1.02Cr1.1Mn0.3Fe0.6 alloy was mass prepared by vacuum induction melting under argon atomosphere. Hereafter the effects of annealing treatment on the microstructure and hydrogen storage performance of Ti1.02Cr1.1Mn0.3Fe0.6 alloy were investigated. The results show that after annealing a small amount of a secondary phase appears and the unit cell volume of C14-type Laves main phase expands. It is found that absorption plateau pressure at 298 K and desorption plateau pressure at 318 K decrease, meanwhile the plateau slope improved. At the annealing temperature of 1123 K, as the treat time extends, the hydrogen capacity increase first and then decrease, which reaches the highest of 1.721 wt.% at the annealing time of 5 h, meanwhile the hydrogen absorption and desorption plateau increase. Among the studied alloys, the alloy annealed at 1123 K for 5 h has the best overall properties for solid-high pressure hybrid hydrogen storage system. Its hydrogen absorption plateau at 298 K is 29.09 MPa and desortption plateau at 318 K is 45.12 MPa, its hydrogen storage capacity is 1.721 wt.% and its dissociation enthalpy is 17.76 kJ/mol H2.