Investigation On The Microstructure And Gaseous Hydrogen Absorbing/Desorbing Properties Of Mg_23-xLa_xNi₁₀ Hydrogen Storage Alloys

Mg-based hydrogen storage have been considered the one of the most promising hydrogen storage because of high hydrogen storage capacity, abundant resources,light weight and low price. It is excellent representative of Mg2Ni. However, because of their harsh conditions of absorption and desorption of hydrogen (hydrogen absorption and desorption temperature is high, the slow rate of hydrogen absorption and desorption) severely hindered its practical application. Scientists how to solve the problem in this area is a priority. The purpose of this project is the result of optimal adjustment of the alloy composition, while the use of proper milling process to improve hydrogen storage properties of magnesium-based hydrogen storage alloys.In this article, on the basis of research and development at home and abroad on Mg2Ni, we decided to use components of the hydrogen storage alloy Mg23Ni10as experimental subjects. Diverse Mg23Ni10hydrogen storage alloy is melted by vacuum medium frequency induction furnace, composition of the alloy is: Mg23-xLaxNi10(x=0,1,2,3,4,5). To prevent evaporation during the preparation of Mg, in the preparation we used high-purity helium gas as a protective, the alloys were milled processing by mechanical milling method. We used x-ray diffraction (XRD), scanning electron microscopy (SEM) to study the phase and the microstructure morphology structure of the as-cast alloys and milling. The gaseous hydrogen absorbing/desorbing kinetic performances of experimental alloys were measured by PCT equipment provided by Beijing non-ferrous metal research institute. The obtained results are as follows:The addition of rear earth element La into the alloys can greatly increase the formation capability of the amorphous phase in Mg23-xLaxNi10(x=0,1,2,3,4,5) the alloys. The phase structure changes obviously with the addition of La, and the main Mg2Ni phase changes toLaNi3phase and LaMg3phase with the increasing La content. The La addition changed the microstructure and the grains were refined obviously.We have found that the amount of hydrogen absorption of as-cast Mg23-xLaxNi10(x=0,1,2,3,4,5) alloys increased as the pressure raised. The amount of hydrogen absorption and desorption alloy has improved significantly with increasing temperature. Under the same pressure conditions, elevating temperature also can improve the kinetics of hydriding, because the higher the temperature is, the bigger the hydrogen atom diffusion coefficient will be；It is favourable for the hydrogen atoms spreading and dissolving. It helps to improve the amount of hydrogen absorbing alloy by La adding, while improving the alloy hydrogen absorption and desorption kinetics performance.The milled of Mg23-xLaxNi10(x=0,1,2,3,4,5) alloys have a more favorable activation properties and hydrogen storage properties. Amorphous formation is associated with milling time, the more the ball-milling time, the more amorphous quantity. Therefore, the amount of hydrogen storage alloys getting lower and lower.