Study On The Ti-Cr Based Thermal Compression Hydrogen Storage Alloys

The adoption of new energy power generation to promote the development of smart grids is a new direction for the development of energy science and technology in the world.However,the instability of wind power,solar energy and other power generation methods leads to grid connection difficulties.The development of large-capacity,long-life,high-power energy storage methods is conducive to maintaining the stability of the power grid system and solving the technical problems.Hydrogen energy is a clean and efficient form of energy.Hydrogen storage energy is used in new energy grid connection,which is strongly supported and developed in developed countries.China is also working on this area currently.The safe and efficient hydrogen storage technology is the bottleneck of the system.The solid-high pressure compound hydrogen storage method has the advantages of high volumetric hydrogen storage density,high safety factor,and good hydrogen absorb and desorb kinetics properties,and thus having good prospects.The development of hydrogen storage alloys with excellent overall performance is one of the key technologies.Hydrogen storage alloys for hydrogen storage systems in power grids need to have excellent hydrogen absorb and desorb kinetics properties,moderate plateau pressure that can be combined with the techniques of cylinders,which has the advantages of low-cost and convenience,and thus achieving large-scale applications.AB2 type titanium-chromium based hydrogen storage alloys have the advantages of high activation properties,low hysteresis coefficient and low cost.In this paper,the hydrogen storage performance is adjusted by alloying method on Ti-Cr based alloy.The hydrogen storage capacity of the alloy is improved by using zirconium to replace titanium.The amount of iron in the alloy is reduced to change the plateau pressure and the pression factor of the alloy.The substitution of manganese for chromium improves the plateau properties,and the addition of rare earth element Ce depresses the precipitation of the heterophase in the alloy to further improve the hydrogen storage properties of the alloy.It is found that after the substitution of titanium with zirconium,the alloy is a C14-type Laves phase,the lattice expands,and the unit cell volume increases.The results of hydrogen absorption and desorption tests show that the hydrogen storage capacity(HSC)increased with the increase of the x value of the titanium atom substitution of zirconium,but the plateau pressure decreased,and both the hysteresis coefficient and the slope coefficient increased.In this chapter,the alloy sample with x = 0.10 is selected as the basis for the next research.The HSC of the alloy is 1.503%by weight,and the hydrogen desporption pressure at 65? is 14.01 MPa,which is equivalent to the pressure of hydrogen storage in cylinders,while the plateau pressure at 25 ? is 4.63MPa.At the same time,it has a comparatively low hysteresis coefficient Hf = 0.109 and slope factor Sf = 1.623.In order to further reduce the plateau pressure at 25? of the alloy,and at the same time ensure that the hydrogen plateau pressure at 65 ? is equivalent to the pressure of the hydrogen storage in the cylinder,the compressibility of the alloy needs to be increased,and Fe used for chromium substitution is studied.Analytical tests show that as the content of iron to chromium decreases,the pression coefficient of alloys increases,the plateau pressure decreases,and the amount of hydrogen absorbed gradually increases.The sample of y = 0.30 serves as the basis for the next study.The hydrogen pressure of the alloy at room temperature is Pa(25?)= 3.47 MPa,the pression factor Rp(65?/25?)is 3.81,and the HSC is 1.562 wt.%,hysteresis coefficient Hf 0.117,slope factor Sf= 2.048.In the first two chapters research,it is found that a small amount of titanium-rich phase precipitates in the as-cast alloy except for the C14 Laves phase,which would result in the partial activation of the alloy after the first activation of the alloy,making the hydrogen storage capacity attenuated between the first and the second activation of the alloy.To improve this problem,rare earth element cerium is added to the alloys optimized by the earlier two chapter's studies.The results show that the precipitation of the heterophase in the alloy is suppressed when the Ce content is 2%by weight,and the hydrogen absorption amount of the alloy is kept stable for the three activation kinetic curves.The strong oxygen-absorbing ability of Ce suppresses the formation of TiOx.So that more titanium atoms resolves into the basement phase,resulting in a slight expansion of the lattice,and making the plateau pressure of the alloys slightly reduces.In order to improve the plateau characteristics of the alloy,manganese is further substituted for chromium.When the amount of manganese substituted for chromium(z)is less than 0.15,the improvement of the alloy plateau pressure is not significant,but the plateau characteristics of the alloy can be effectively improved.The plateau slope of the alloys are very low when Mn substituted Cr.The alloy of z=0.15 has excellent overall performance,with HSC = 1.709 wt.%,Pa(25?)= 3.42MPa,Pd(65?)= 11.91MPa,RP(65/25)= 3.49,Hf = 0.140,Sf = 1.49,and thus can be used in hydrogen energy storage systems of power grids combined with hydrogen storage technology of cylinders.