Preparation And Thermal Analysis Of Hydrogen Storage Materials

This thesis focuses on the preparation and thermal analysis of new light weight hydrogenstorage materials. Doped additives composite systems were successfully prepared bymechanical milling under an argon atmosphere. The dehydrogenation performances of thecomposite systems were investigated by thermogravimetry (TG), differential scanningcalorimetry (DSC), and X-ray diffraction (XRD). Meanwhile, the dehydrogenationmechanisms of the doped additives composites were studied.The hydrogen storage material of AlCl3doped MgH2-Li3AlH6was successfully preparedby mechanical ball milling. The result showed that AlCl3as additive effectively increased thedehydrogenation activity, reduced the dehydrogenation temperature and enhanced thedehydrogenate capacity of MgH2-Li3AlH6. When4mol%AlCl3was doped into4MgH2-Li3AlH6, initial dehydrogenation temperature of this4MgH2-Li3AlH6-AlCl3composite was about130oC which was lower43oC than4MgH2-Li3AlH6’s and the totalamount of dehydrogenation increased from5.5wt.%to6.3wt.%(up to400oC). XRDanalysis showed that: LiH and active Al, which from the decomposition of Li3AlH6and thereaction AlCl3with Li3AlH6, can promote the decomposition of MgH2. Here, MgH2had thelower temperature of dehydrogenation and the apparent activation energy of itsdehydrogenation reduced to144kJ mol-1.For Nb2O5doped MgH2-Li3AlH6, the result showed when1mol%Nb2O5was doped into4MgH2-Li3AlH6, initial dehydrogenation temperature of the4MgH2-Li3AlH6-Nb2O5composite was about130oC which was lower59oC than4MgH2-Li3AlH6’s and the totalamount of dehydrogenation increased from5.5wt.%to6.5wt%(up to400oC). XRD analysisshowed that: Nb2O5was not involved in the decomposition of the composite, only acted as acatalyst. Doping Nb2O5maked the apparent activation energy of MgH2dehydrogenationdecrease from147kJ mol-1to127kJ mol-1.4MgH2-Li3AlH6-AlCl3-Ti quaternary system was successfully prepared by mechanicalball milling. The result showed when the amount of AlCl3and Ti doped respectively were14wt.%and6wt.%, initial dehydrogenation temperature of this quaternary system was about58oC which was lower120oC than4MgH2-Li3AlH6’s and the total amount ofdehydrogenation increased from5.5wt.%to7.6wt.%(up to400oC). The results of themechanism revealed that doping Ti in the4MgH2-Li3AlH6-AlCl3system produced Al3Ti. Onthe one hand, it could reduce the Li3AlH6’s decomposition temperature; on the other hand, it could weaken the interaction between Mg and H. It caused the apparent activation energy ofMgH2dehydrogenation obviously decreased, which from144kJ mol-1to113.9kJ mol-1.