Development of new materials for hydrogen storage

Abstract

Hydrogen could be one the most efficient source of energy in the future. The problem which is remaining about this energy is storage. Indeed, it is still very hard to store hydrogen due to the volume that it takes in its liquid and gaseous. The solution could be solid storage of hydrogen using metal hybrids which are able to absorb it. By storing hydrogen with this method, the gains of volume and safety are very high. One of the metals which could be used is Magnesium, but it is necessary to create alloys in order to have even better properties. In this project, different magnesium alloys have been tested (Mg, MgTi and MgTiFe). These materials, in powder form, were milled for different times thanks to a planetary milling process in order to improve some of their properties (mainly remove oxide layer, specific surface area, particle size distribution). After that, these materials were tested on a system created by the PROCOMAME group in order to obtain results about hydrogen absorption. The morphology, the particle size distribution and the specific surface area of the milled powders were characterized by different techniques. In addition, X-ray diffraction patterns were obtained to check if mixing in solid solution was achieved during milling. There is a very large increase of the specific surface of powders, although the average particle size remains nearly the same due to the agglomeration of the small milled particles. On the other hand, neither a solid solution or intermetallics were found which means more milling time is required to get the total mixing. Regarding hydrogen absorption tests, indeed milling these materials help to destroy the oxide layer which unable the hydrogen absorbance. The absorption percentages are significant but not very large, and it was found that the hydrogen absorption of the powders seems to be related to the specific surface area and the particle size distribution and that there is no effect of Ti and Fe additions to Mg in the absorption starting temperature, at least in the tested milling conditions.