Hydrogen Storage Properties of Mg and Mg-Ni Films Prepared by Thermal Evaporation
热蒸发法制备Mg和Mg-Ni薄膜及其氢化性能

Microstructure and hydrogenation properties of Mg and Mg-Ni films fabricated by thermal evaporation method were investigated. The as deposited Mg film exhibits a preferred orientation and a typical columnar crystalline structure. The as deposited Mg-Ni film with a composition of Mg_(78)Ni_(22) is composed of nanocrystalline Mg_2Ni, Mg and a small amount of amorphous phase. Besides, the Mg_2Ni crystallites grow with their (001) crystalline plane parallel to the substrate surface. The hydrogen absorption and desorption temperatures of pure Mg film are 593 K and 653 K, respectively and its hydriding reaction follows a nucleation and growth mechanism. Pressure-composition isotherms of Mg_(78)Ni_(22) film show that its maximum hydrogen absorption capacity (mass fraction) reaches to 5.7% and there are the lower and higher pressure plateaus corresponding to the hydriding reactions of Mg and Mg_2Ni, respectively. The hydriding/dehydriding temperatures of Mg in Mg_(78)Ni_(22) film decreased down to 473 K and 503 K, respectively. The improvement on the hydrogenation properties of Mg is related to the catalytic role of nanocrystalline Mg_2Ni and amorphous phase.