Microstructure of ball milled MgH2 powders upon hydrogen cycling: An electron microscopy study

Catalysis and evolution on cycling of nano-structured magnesium multilayer thin films

“…[21] observe an increase from 11 to 200 nm for a Nb 2 O 5 -catalysed magnesium hydride sample at temperatures above 300 • C. Similarly, grain growth in non-catalysed, ballmilled magnesium hydride has been observed by Paik et al [22] from 32 nm to 422 nm, consistent with the observations that were made for the Mg control sample.…”

The effect of chromium (III) oxide (Cr2O3) nanopowder on the microstructure and cyclic hydrogen storage behavior of magnesium hydride (MgH2)

“…For example, Varin et al [7] reported an increase of grain size of MgH 2 from ∼30 nm recorded after ball milling to 90 ± 10 nm after barely 5 cycles at 300 • C for MgH 2 originally doped with a nanometric Ni catalyst which was eventually transformed into an intermetallic/hydride Mg 2 Ni/Mg 2 NiH 4 as a result of cycling. Paik et al [8] reported an increase of grain size of MgH 2 from ∼60-70 nm recorded after ball milling to over 200 nm after only 6 cycles at 300 • C. However, in contrast to the results in the present work and those reported in [8], Dehouche et al [9] reported that for the MgH 2 + 0.2 mol.% Cr 2 O 3 the grains/crystallites of MgH 2 grew from initially from 21 nm for ball milled material to barely 84 nm after 1000 cycles at 300 • C. It is hard to explain such a low nanograin growth rate during so many thermal cycles at such a high temperature. However, it must be pointed out that in contrast to our experiments the cyclic loading carried out by Dehouche et al [9] was performed at 300 • C under continues hydrogen pressure, i.e., the desorption pressure of 0.25 bar and absorption pressure of 10 bars.…”

The influence of ball-milling time on the dehydrogenation properties of the NaAlH4–MgH2 composite

“…This effect may be associated with the impact of high energy ball-milling on the grinded samples. Prolonged milling of hydrides such as MgH 2 leads to decreased crystallite and particle sizes, and of the introduction of various defects, which enable a faster hydrogen diffusion process in the bulk of the ball-milled materials [20,21]. A significant temperature decrease of 60e80 C, depending on the sample, is also more clearly observed during the completed first dehydrogenation step in Fig.…”