Investigations On The Preparation And Modification Of Ti-Cr-V Based Hydrogen Storage Alloys

Hydrogen is a kind of new energy because of its inexhaustible,efficient and zero emission characteristics.Although the hydrogen energy application prospect is promising,the problems of its preparation,storage and transportation are the main reasons for constraining its commercial development.Ti-Cr-V solid solution alloys have high hydrogen storage capacity,which have been found to absorb more hydrogen than the conventional AB5,AB2 and TiFe type hydrogen storage alloys at room temperature,and therefor are regard as promising third-generation hydrogen storage materials.In this paper,the research and development of Ti-Cr-V BCC solid solution hydrogen storage alloys at home and abroad were reviewed first.On this basis,Ti_0.32Cr_0.345V_0.25Fe_0.03Mn_0.055 hydrogen storage alloy was chosen as the object of this study.By means of XRD,SEM,EDS,TG/DTA and PCT hydriding/dehydriding measurement,the effects of multi-component alloying and the alloy preparation method on the microstructure and hydrogen storage properties of the alloys have been studied.The purpose of such investigation that adding alloy element and rapidly quenching is to further improve the overallproperties of hydrogen storage alloy.The results are as follows:The Zr element partially substitutes Ti of Ti_0.32Cr_0.345V_0.25Fe_0.03Mn_0.055 alloys.The results show that the alloys are still composed of BCC phase and Laves phase,which indicates the partial substitution of Zr does not change the original two-phase structure.With the increase of Zr content,the Laves phase in the alloy increased,and Zr was mainly present in the Laves second phase.Under the condition of 298 K,the hydrogen absorption kinetics of the alloy is still good.With the partial substitution of Zr,the hydrogen absorption and desorption plateau pressure increase,its slope increases,hysteresis decreases.The effects of rapid solidification on the microstructures and hydrogen storage characteristics of the Ti_0.32-xZr_xCr_0.345V_0.25Fe_0.03Mn_0.055（x=0）alloy have been investigated.It is found that the grain of the alloy has been fined,the lattice constant of BCC main phase decreases from 0.3141 nm to 0.2984 nm,hydrogen absorption kinetics declined compared with the as cast alloy.Rapid solidification has a significant effect on the kinetics of hydrogen absorption behavior,which is described by chemical reaction mechanism for as-cast alloy and formation and growth of crystal nucleus in new phase mechanism for rapidly solidified alloy.The results of PCT test show that absorption and desorption plateau pressure increases,and the hydrogen hysteresis increases.The TG/DTA curves show that rapid solidification does not change the residual hydrogen content of the alloy,but increases the dehydriding temperature.On the basis of previous research,Ti_0.32-xZr_xCr_0.345V_0.25Fe_0.03Mn_0.055（x=2）alloy was chosen to be further researched.It can been found that Laves phase reduced when compared to the cast alloy,the grain has been obviously fined,but the activation process becomes difficult,the hydrogen absorption and desorption plateau pressure increased significantly,hydrogen hysteresis becomes smaller.It can been seen that the effect of Zr substitution and rapid solidification simultaneously is beneficial to the improvement of desorption capacity and hydrogen hysteresis,which needs further research.