Study On Preparation For Mg-N-H Hydrogen Storage Material

Hydrogen storage material is the new type functional material along with hydrogen energy utilization in recent thirty years. It is an important material as hydrogen storage and deliver carrier in the hydrogen energy system. The combination of hydrogen storage and transportation will be optimal partner of hydrogen energy development and utilization in the 21st century. Hydrogen storage material takes an important part in the field of high technology. Therefore, study and development of hydrogen storage become a pop topic in the world.As development of varied alloy hydrogen storage material become riper day by day, development of higher quality/volume percentage in the proper temperature hydrogen storage material becomes the new subject. For its hydrogen density, much attention has paid to metal complex and some new type inorganic compound materials in recent years. Li-N-H series material has a theory hydrogen density of10.4wt%, but its reacting temperature is higher, thus, Mg-Li-N-H and other resemble series are researched, it is one of the research hotspot about the hydrogen storage field in the world at present.Magnesium amide is an important material in the Mg-Li-N-H series, but there is no sale in the world market, so it is required to be synthesized in the laboratory. The article synthesizes magnesium amide with the method of mechanical alloying and heating. In the way of mechanical alloying, amorphous state because of long time milling just changes into crystalline under 300℃, 5.5atm, and 6h. The result of heating using orthogonal experiments is that pressure is the major effect factor in the synthesis reaction, primal power milling time and temperature are followed, heating time is the smallest. The optimal condition from orthogonal experiments is that pressure is 5.5 atm, temperature is 310℃, primal power milling time is 1h, and heating time is 28h. Further searching temperature and pressure, the conclusion is that the proper temperature is 300℃-310℃; it is not apt to generate magnesium amide under 4.5 atm. Moreover, synthesis rate increases with higher pressure. The purer magnesium amide is synthesized under 7.0atm, 310℃, heating for 24h. Compared the two ways, decomposition temperature of magnesium amide synthesized in the mechanical alloying is lower nearly 26℃than its in the heating. It explains that the synthesized method has a great effect on thermal performances. It studies the mixture of magnesium amide and lithium hydride. With milling time increasing, its reacting temperature reduces. It explains that longer time milling makes close the mixture, thus temperature reduces.