Mechanochemical Synthesis Mechanosynthesis of Nanohydrides

A primary method of mechanochemical synthesis of nanostructured hydrides (nanohydrides) is processing by mechanical (ball) milling. Processes of manufacturing of nanocrystalline/nanostructured hydrides by ball milling are shown in Fig. 1.21. 

There are three major processes all of which start from raw metallic/nonmetallic elements [157]. 

As seen from the change in valency of metal and hydrogen, this is a redox reaction because the metal is oxidized (loses n electrons) by the hydrogen, while the valence of hydrogen becomes, formally, -1. Magnesium dihydride, MgH, can be manufactured in ball mills in such a manner, with the reaction yield close to 90%. The reaction of 

In a variant of the second method described earlier the premixed metallic powders (or pulverized ingots) are milled under hydrogen atmosphere to directly form an intermetallic hydride. It can be also viewed as hydrogen alloying of metal powders and powder mixtures in hydrogen alloying mills. This method is called a reactive mechanical alloying (RMA) or mechanochemical synthesis (MCS). 

MCS-type reactions can occur while milling a simple metal hydride with a metallic element M, 

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