Study On Hydrogen Storage Property Of LiAlH₄+MgH₂Compounds

This thesis studied the subject of LiAlH4+MgH2.Samples were maded by the means of machannical ball-milling. By utilizing the testing means of XRD, DTA, PCT; it explored how ball milling process, milling time, Ti base compounds and oxyde doped impact the functions of the hydrogen storage properties of LiAlH4+MgH2.Studies showed that LiAlH4decomposes exothermically to Li3AlH6、LiH and Al in the process of the High speed vibrating ball mill. The LiAlH44+MgH2samples which were maded after3h milling have better hydrogen absorption properties at300℃. Their total absorption capacity reached4.66wt.%,90%of which had achieved in345s.On the basis of the experiment above, it was investigated what the hydrogen absorption/desorption properties of LiAlH4+MgH2which were doped with5wt.%V2O5,5wt.%Cr2O3,5wt.%La2O3-2TiO2,5wt.%Nb2O5and5wt.%ZrO2are after3h high speed vibrating ball milling.The research showed that hydrogen absorption or desorption properties of the milled LiAlH4+MgH2+5wt.%ZrO2are better than the others:the onset hydrogen desorption temperature was80.9℃, which was15℃lower than undoped LiAlH4+MgH2; About5.32wt.%H2can be released from milled LiAlH4+MgH2+5wt.%ZrO2in the first time dehydrogenation; and the second time desorption capacity reached2.53wt.%H2; the non-isothermal absorption capacity reached5.90wt.%H2. At300℃, the LiAlH4+MgH2+5wt.%ZrO2samples can absorb5.45wt%H2,90%of which has achieved in81s. However, undoped LiAlH4+MgH2which absorbed the same amount of hydrogen needed380s.The LiAlH4+MgH2samples were prepared after horizontal-type planetary ball16h milling have better hydrogen absorption/desorption properties, the onset hydrogen desorption temperature was105.4℃, maximum desorption capacity reached 7.14wt.%H2;the first time absorption was finished at267.5℃, absorption capacity reached3.93wt.%H2; the onset temperature of the second time hydrogen desorption was271.4℃,and the second time desorption capacity reached2.95wt.%H2; At300℃, the LiAlH4+MgH2samples can absorb2.71wt%H2,90%of which has achieved in200s.At the base of experiment above, we added Ti base compounds and oxide catalyst. Result showed that5wt.%V2O5-added LiAlH4+MgH2have a better hydrogen absorption properties. It speeded up the rate of hydrogen absorption, increaed the mount of hydrogen absorption.5wt.%V2O5doped to LiAlH4+MgH2slightly improve the second desorption properties. The initial decomposition temperature dropped17.5℃, dehydrogenation processes temperature decreased10℃.3wt.%TiF3doped to LiAlH4+MgH2greatly improved the composite hydrogen absorption/desorption properties. The initial decomposition temperature of LiAlH4+MgH2dropped50.5℃, The initial dehydrogenation temperature decreased56.2℃the second time desorption, the non-isothermal absorption capacity increased0.52wt.%H2, At300℃, absorption capacity increased0.53wt.%H2. Which improve the hydrogen absorption/desorption kinetics of LiAlH4+MgH2composites.