| The preparation, structure and the influences of each other of 20 gram 95Mg-Ni-MnO2 nanocrystalline hydrogen storage materials, which was added into 0.4 gram. 0.6 gram and 0.8 gram of CNTs separately, were systematically investigated in the paper. The CNTs is prepared by mechanical milling under hydrogen protection. The results show that mechanical milling under hydrogen protection is a useful and effective method for the preparation of the magnesium based hydrogen storage material. Mechanical milling the specimen with different amount of carbon nanometer tubes under different preparation time, It was found that more than 20 hours ball-milling time did not remarkably improve the hydrogen storage properties of 95Mg-3Ni-2MnO2-nCNTs. But longer ball-milling time would increase the crystal lattice aberrance and decrease the average diameter of grains, meanwhile, the surface energy and crystal boundary would be increased, which would raise the diffusion velocity, thus the hydriding-dehydriding characteristic of 95Mg-3Ni-2MnO2-nCNTs would be improved. During the process of hydriding,adding carbon nano tubes would decrease the minimum temperature of hydriding and the maximum temperature of ignition point. However, the hydriding speed was not lowered down because of the well catalysis of carbon nanometer tubes. nanocomposite has very high absorption hydrogen capacity and remarkable kinetic properties in hydriding/dehydriding process. for example the nanocomposite can absorb 6 .0% hydrogen in 100 s at 200 0C under of hydrogen pressure of 1 .5 MPa. The grain of Mg-based hydrogen storage materials with CNTs is much smaller in ball milling process than that of the materials without CNTs .Hydrogen storage materials showed steady hydrogen storage properties after six cycles of hydriding and dehydriding.
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