The Hydrogen Storage Properties Of Mg-Al-Ti Alloys

In this paper, we prepared Mg55-xAl10Ti15+x (x=0,5,10,15), Mg55Al10Ti15-xVx(x=2,4,6,8) and Mg55Al10Ti11TM4(TM=Zr, V, Cr, Ni) alloys by high temperature sintering and mechanical alloying method, and then investigated their phase structures, hydrogen storage properties and thermodynamic properties.Firstly, we prepared Mg55-xAl10Ti15+x (x=0,5,10,15) alloys and analyzed its property. Mg55-xAl10Ti15+x(x=0,5,10,15) alloys were prepared by mechanical alloying method under argon atmosphere after sintering. FCC structure and Al3.16Mg1.84phase were produced by160h ball milling. The kinetics and thermodynamic properties of alloy are improved prominently with on its hydrogen storage capacity reduction by addition of Al and Ti. Mg55AlioTii5alloy have a better hydrogen storage property, which reach to1.6wt.%on the hydrogen storage capacity by160h ball milling.Secondly, the performance of Mg55Al10Ti15was improved by adding V. The hydrogen storage of alloy could be improved by element substitution, element mixed and addition of catalyst, element substitution method was selected in our experiment. Mg55Al10Ti15-xVx (x=2,4,6,8) alloys were prepared by ball milling. The structure of samples are composed of Al3.16Mg1.84phase, Al18Ti2Mg3phase and FCC structure. The results show that the hydrogen storage content of Mg55Al10Ti11V4alloy increased with the increase of milling time. The main reasons are:(1) FCC structure and Mg3.16Mg1.g4phas are produced by ball milling;(2) V merged into alloy with the increase of milling time. The hydrogen storage capacity of Mg55Al10Ti11V4alloy reach to3.9wt.%by100h ball milling, which imporved that it has a better hydrogen storage property. Mg55Al10Ti11V4alloy takes100s to reach to2.0wt.%by160h ball milling on the hydrogen storage capacity under the condition of250℃and25atm hydrogen pressure, which imporved that it has a better kinetics property. Experimental results show that the usage of V to replace Ti in a certain proportion not only increases the alloy’s hydrogen absorption capacity, but also improve the alloy’s absorption kinetics performance.Thirdly, in order to improve the hydrogen storage performance of Mg55Al10Ti15alloy, we also study other transition metals with excellent hydrogen storage properties, such as Zr, Cr, Ni etc., and then use them to replace Ti in a certain proportion to improve the hydrogen storage performance of Mg55Al10Ti15alloy. The Mg55Al10Ti11TM4(TM=Zr, V, Cr, Ni) alloys were prepared by mechanical alloying method under the protection of hydrogen atmosphere. The results show that Al3.16Mg1.g4phase, MgH2phase and FCC structure emerged in the sample by160h ball milling. The hydrogen storage capacity of Mg55Al10Ti11V4reach to4.4wt.%after80h ball milling, which imporved that it has a better hydrogen storage performance. Mg55Al10Ti11Ni4takes80s to reach to2.0wt.%on the hydrogen storage capacity under the condition of250℃and25atm hydrogen pressure, which imporved that it has a better kinetics property. The dehydrogenation activation of Mg55Al10Ti11Ni4sample is equal to49.97kJ/mol according to the Kissinger equation, which is just1/2of those of other three samples. Experimental results show that the usage of Ni to replace Ti in a certain proportion could decrease the dehydrogenation activation performance of Mg55Al10Ti15alloy better.