Aging Effects in Stored MgH2 Powders

In the already briefly mentioned paper, Friedrichs et al. [26] carried out very elegant HRTEM (high-resolution transmission electron microscopy) and XPS (X-ray photoelectron spectroscopy) studies of the initial stages of the formation of MgO/ Mg(OII) on the ball-milled nanocrystalline MgH2 (BM-MgH2) and Mg (BM-Mg) powders, the latter obtained after hydrogen desorption of the former with particle 

As also mentioned in Sect. 2.1.2, Varin et al. [27] showed that a long-term air exposure of nanocrystaUine MgII2 for a few months led to a massive formation of crystalline Mg(OH)2 not only on the surface but also in the bulk by conversion of the entire MgII2 particles into Mg(OH)2. Apparently, the initial amorphous hydroxide layer Mg(OH)x grows and transforms into a crystalline-phase Mg(OH)2 (the reaction of (2.3)). 

6 Other Methods of Synthesis of Nanostructured MgH2 than Ball Milling 

Two methods of producing nanostructured MgH2 were already briefly mentioned in Sect. 2.1.3.3 and 2.1.5. Shao et al. [44] used the hydrogen plasma-metal reaction to obtain ultrafine magnesium with an average size of about 300 nm. The activation of 

Saita et al. [80] applied hydriding chemical vapor deposition (HCVD) for preparing MgH2. They used commercial Mg, which was heated to 600°C and vaporized in a hydrogen atmosphere at a pressure of 4 MPa. The reaction product was deposited on a cooled Inconel substrate and subsequently collected for further investigation. Quite remarkably, the obtained morphology was nanofibrous, as shown in Fig. 2.47, and is very similar to the one fabricated by Zlotea et al. [79], Each fiber was less than 1 pm in diameter and 10 or more micrometers in length. 

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