Reactive mechanical milling

Table 2.15 Composition of powders and processing parameters for reactive mechanical milling of Mg-H powders [63]... 

For the sake of clarity, it must be mentioned that Huot et al. [24, 35] reported that at 350°C the absorption/desorption PCT plateau pressure hysteresis of the unmilled MgH was quite substantial, while the hysteresis of the same material milled for 20 h was very small. They argued that the plateau pressure difference observed for the uiimilled material was due to a very slow desorption kinetics which did not allow reaching equilibrium. In turn, ball milling increased desorption kinetics, which allowed reaching equilibrium and eliminated hysteresis. However, it must be noticed that the situation reported by Huot et al. is completely opposite to what is observed in Fig. 2.43, in which MgH synthesized by reactive mechanical milling shows a pressure hysteresis. 

Elansari et al. [201] developed a novel method of synthesizing alkali metal hydrides Na, KH, RbH, and CsH by reactive mechanical milling of pure alkaline metals under hydrogen pressure up to 30 bars in a planetary mill (Retsch PM 400). The reaction proceeds in 16 h and gives 3-15 g of very pure alkali metal hydride with FCC crystal structure (space group Fm3m). 

R.A. Varin, S. Li, A. Calka, Environmental degradation by hydrolysis of nanostructured P-MgHj hydride synthesized by controlled reactive mechanical milling, J. Alloys Compd. 376 (2004) 222-231. 

It is relevant to point out that we have recently reported [203] a similar destabilization of MgHj in a nanocomposite with NaBH synthesized by reactive mechanical milling of (Mg -i- Awt%NaBH ) where X = 2, 10 and 20. In this nanocomposite... 

R.A. Varin, T. Czujko, E.B. Wasmund, Z. Wronski, Catalytic effects of various forms of nickel on the synthesis rate and hydrogen desorption properties of nanocrystalline magnesium hydride (MgH2) synthesized by controlled reactive mechanical milling (CRMM), . /. Alloys Compd. 432 (2007) 217-231. 

I.G. Fernandez, G.O. Meyer, F.C. Gennari, Hydriding/dehydriding behavior of Mg2CoH5 produced by reactive mechanical milling , J. Alloys Compd. 464 (2008) 111-117. 

Bobet, J. L., Chevalier, B., Song, M. Y. and Darriet, B. (2003a) Improvements of hydrogen storage properties of Mg-based mixtures elaborated by reactive mechanical milling. Journal of Alloys and Compounds, 356, 570-574. 

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