Study On Magnesium-Based Hydrogen Storage Material Of Mechanical Alloying

In the first of the paper the importance and development of hydrogen energy, various means and mechanisms of hydrogen storage, especially the application of metallic hydrides are reviewed generally, then hydrogen storage performance, the mechanism of activation characteristics and important modification methods for improvement of hydrogen storage ability of Mg-based materials such as alloying, chemical treatment of surface are discussed in details. Since alloying with other elements is one of the most effective and economical methods to improve the activation characteristics and hydrogen storagecapabilities of Mg-Ni alloys. The effects of mechanical alloying and the hydrogen storage performance of Mg-Ni alloys are studied; partial substitution of Ni by Cu is also investigated. Then spontaneous monolayer dispersion of magnesium compounds on mordenie was evaluated systematically.The results of study of XRD analysis indicate that diffraction figures of Mg2Ni alloys turn up in 20h with increasing of milling time. Up to 80h milling time, these alloys have been amophized completely. These alloys show high activities for hydriding for longer milling time. Magnesium-based alloy for 100h milling time can be hydrogenated at the temperature of 250C and the pressure of 5.0MPa after a short period of incubation, which only 0.5 minutes. But after activation, the hydrogen storage capacity and hydriding rates of these alloys have not distinction among all alloys. The dehydiding properties of these alloys at the temperature of 275,300,325,350C are investigated. With increasing milling time, dehydriding rates rise first, and then decrease. Dehydridng rate of alloy for 80h milling time is fastest,then that is slower for 100h milling time again. After ten hydrogen absorption-desorption cycles, metal hydride transformed from amorphous to crystalline. The composites particles size changed more little. The thermodynamatics parameters of alloys such as H0 S0 ,are calculated according to Van't Hoff equation.XRD indicates that alloy with Cu transform to amorphous quickly during mechanical grinding. MgNiCu hydrogen capacities decrease due to addition of Copper, however, hydride stability abates. At the room temperature, alloy can go on hydrogen desorption, The thermodynamatics parameters of alloys show that MgNiCu have relative small enthalpy values.Mechanical milling spontaneous monolayer dispersion for magnesium compounds on mordenite is investigated using XRD. The results show partial magnesium compounds disperse on mordenie at room temperature. After calcined 3h at 400C, magnesium chloride transform to magnesium oxide.