Effect of reactive mechanical grinding on chemical and hydrogen sorption properties of the Mg+10 wt.% Co mixture

Abstract

:Reactive mechanical grinding (MG under H 2 ) of magnesium powder improves the hydrogen sorption properties. The hydrogenation of Mg starts in situ during the milling process that allows suppressing the activation procedure generally requested for Mg. The addition of Co, which acts as a catalyst for the dissociation of H 2 , also leads to an improvement of the hydrogen sorption properties (but a strong dependence upon the milling time is reported). The hydriding is determined to be a two-step process: nucleation and diffusion. A direct relationship exists between the nucleation duration and the specific surface. A critical milling time exists below which the diffusion process is improved and above which no more improvement is observed (the maximum internal stress in the powder is also reached at this critical time). The diffusion is controlled by the number of crystallites per particle which can be decreased by increasing the milling time up to 10 h. However, the sorption properties of Mg-Co mixtures are a little under those reported for MgH 2 -metal mixtures.

Atomic Hydrogen Diffusion in Novel Magnesium Nanostructures: The Impact of Incorporated Subsurface Carbon Atoms

“…Unfortunately, the application is primarily limited by the high hydrogenation reaction temperature and slow kinetics [4][5]. Experimentally, a number of studies have been devoted to the catalytic effect on hydrogen adsorption of mixing transition metals into the Mg powder by mechanical milling [6][7][8]. Apart from metallic alloying, some non-metallic elements such as graphitic carbon have been noted to facilitate the activation process of Mg and improve the absorption kinetics of H 2 [9][10][11][12][13].…”

Advances in the application of nanotechnology in enabling a ‘hydrogen economy’

“…Reactive mechanical milling of Mg and 10 wt.% Co has been shown to result in improvement of hydrogen sorption properties [82]. The rate of formation of MgH 2 at 350°C was fairly constant in the initial stages and decreased in the later stages (Fig.…”

“…For example, Bobet et al [82,[122][123][124] synthesized MgH 2 via RMA at room temperature and studied the influence of addition of 3d-metals on the synthesis. It was observed that addition of 10 wt.% Co as a catalyst increased the yield of MgH 2 to 71% after 10 h of milling.…”

The Preparation and Hydrogen Storage Performances of Nanocrystalline and Amorphous Mg2Ni-Type Alloys

“…This inhomogeneity is directly associated with the chemisorption of hydrogen and hence facilitates the hydriding reaction. The catalytic effect of Co has been well elaborated by Bobet et al [27]. Ni is a largely known catalyst, which is utilized for the hydriding reactions.…”