Diffusion And Elastoplastic Analyses Of Polycrystalline Magnesium For Solid State Hydrogen Storage Application

Abstract

Solid state hydrogen storage can be an effective way of storing hydrogen as an energy source for mobile applications. The advantage includes high energy density, low setup cost, safe operation, abundance of metal hydrides, low maintenance, etc. Magnesium is one of the potential metals for the application. However, sluggish desorption kinetics of magnesium requiring relatively high operation temperature has hindered its practical realization. In the present study, an attempt is made to analyze effects of grain boundary on diffusion and diffusion induced stresses in polycrystalline magnesium. Grain boundaries in nanostructured magnesium can undergo severe plastic deformations during the hydrogen insertion and desertion processes. Such boundaries are characterized by excess grain boundary energy, presence of long range elastic stresses and enhanced pathways for hydrogen transport. Finite element models have been developed for the analyses by realizing the different physical and chemical parameters of magnesium grains and grain boundaries. The study provides convincing evidence of the importance of the presence of grain boundaries. The results may help find ways to improve hydrogen charging/discharging efficiency by means of plastic deformations in grain boundaries while maintaining the overall structural integrity of host magnesium.