Study On Co Free And Over Stoichiometric AB₅ Type Hydrogen Storage's High Rate Discharge Performance

In this thesis, the La_1-xCe_xNi_4.37Al_0.3Mn_0.39(x=0.3,0.4) and La_0.7Ce_0.3Ni_4.17Fe_0.4Al_0.1Mn_0.93(x=0.3,0.4) Co-free nonstoichiometric rapidly quenching hydrogen storage alloys were studied. By means of XRD analysis, SEM investigation ,TEM investigation and electrochemical measurements.The effects of chemical composition,annealing in 400℃,surface treatment and MA on high rate discharge performance were studied systemically.It is found that there are non-crystal on the surface of alloys prepared with rapidly quenching.The non-crystal on the surface is advantaged for the cycling life of the alloys.But it is baleful for the high rate discharge performance of the alloys.It is proved that can improve the high rate dischatgeability of the alloys through adjust the chemical composition of alloys, annealing in 400℃,surface treatment and MA .But there are different in the hypostasis for the methods.Adjust chemical composition can change the thermodynamics of alloys , the size of crystal lattice,the pressure of PCT curve and disfigurements.The high rate dischatgeability can improved throu the changes.For example ,with the increase of content of Ce or Al,the high rate dischatge performance can be improved .Because non-crystal on surface of the alloys is baleful for the high rate discharge performance,so we must eliminate it.We found annealing in 400°C can clear up the non-crystal effectual,and at the same time ,the phase structure of the alloys is not changed.The surface characteristics of alloys affect critically its bulk characteristics. Therefore, scientists take many measures to improve the surface characteristics of alloys. The purpose of these measures is to improve dynamic property and give free rein to intrinsic characteristics of alloys.Through the sueface treatement, the alloy coated with nickel was effectively improved the high rate discharge performance.The avtivation of alloys is improved remarkably because non-crystal on the surface of alloys was destroyed through MA.At one time,the size of crystal lattice rduced,this is very favorable for the pervasion of hydrogen in the alloys.So MA can improve the high rate dischargeability without question.We found that we can improve high rate discharge perforce of the alloys,but at thesame time ,the cycling life of alloys is reduce.So we must control the cycling life when we tried to improve the high rate discharge performance of the alloys.