Study On Effect Of Hydrogen Storage Properties Of Magnesium

Magnesium is believed to be one of the most promising solid hydrogen storage materials because of its advantages such as large hydrogen capacity, low cost, natural abundance, et al. In order to get the best preparation parameters and high-performance hydrogen storage materials, this paper studied the effect of preparing magnesium based hydrogen storage materials by reactive ball milling method, including the parameters of ball milling and the addition of different dosage of carbon materials and metal.The main preparation parameters of reaction ball milling were studied. Pressure and ratio of ball to material would significantly affect the material dispersivity and hydrogen storage density. In the experiment, 1MPa H2 pressure and 45:1 ratio of ball to material were adopted. Under such conditions, hydrogen storage materials had a high hydrogen storage density and good dispersivity. Effect of ball milling time on particle size and hydrogen storage density had a critical range. Below the critical time range, extending the milling time was helpful to improve the hydrogen storage density. While exceeding the critical time range, it was easy to generate particle agglomeration and the hydrogen storage density and hydrogen desorption temperature would be lowered. According to the results,3h to 4h was the critical time range. It would do no good to improve material properties under longer or shorter milling time. Hydrogen charging times and hydrogen charging interval had less effect on the material properties.When pure magnesium powder was milled, almost all the powder adhered to the tank wall and balls, resulted in a low hydrogen storage density. The addition of carbon materials could significantly decrease the agglomeration, which helped refine magnesium particles. As different carbon materials had different structure and nature, the role of each carbon material was also different. In this paper, the structure and their function in improving magnesium based hydrogen storage material of five kinds of carbon materials, the carbonized anthracite, deposited carbon, graphite, needle coke and active carbon, were studied. Carbon materials were listed by their capability in improving the dispersivity of magnesium powder as follows: graphite> activated carbon> deposited carbon> needle coke> anthracite. The dispersivity was increased with the increased addition of carbon materials. Carbonized anthracite could significantly increase the magnesium hydrogen storage density. The addition of anthracite and needle coke simultaneously could significantly improve the dispersivity of magnesium powder and increase the hydrogen storage density. Carbon materials could reduce the hydrogen desorption temperature of magnesium hydride. And the downscale of the hydrogen desorption temperature would be extended with the increased addition of carbon materials.The addition of metal catalysts could improve the hydrogen storage performance of . magnesium based hydrogen storage materials. When the total quantity of added metal catalyst was more than lwt%, it was not helpful to improve the hydrogen storage density. The added four kinds of metal catalysts, Ni, Al, Mo, Co, had the effect of grinding aid and catalysis and did not form metal alloys or metal hydrides. With the addition of metal catalysts, the hydrogen desorption temperature of the hydrogen storage materials could be reduced. The more catalyzed metal were added, the lower the hydrogen desorption temperature was.