Mechanical alloying, mechanochemical

New Routes to Nanomaterials Mechanical Alloying and Mechanochemical Activation... 

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). 

Kojima Y., Isobe T., Senna M., et al. Mechanochemical synthesis of AlsTiOj J. Mechanochemistry and Mechanical Alloying 1994 1 34-39. 

The use of mechanical milling is also a suitable method for powder preparation. The feature of this procedure is to obtain powders of small crystallite size of a few nanometers with a high concentration of lattice defects. There are many mechanochemical studies on the synthesis of alloys, solid solutions, nanophasc materials, and intermetallic compounds. Of course, the mechanical alloying also has been applied to prepare mixed oxides containing cerium oxide to enhance catalysis, such as CeOj-TbO, CeOj-HfOj, Ce02 Zr02-Mn0, and CeOt ... 

This review attempts to give a short account of the main aspects of mechanochemical treatment such as (a) mechanical alloying (b) commonly used milling units, herewith the influence of milling parameters on the rate and products of mechanochemical treatment (c) stmctural changes (d) mechanochemical reactions (e) subsequent heat treatment and (f) powder contamination. 

Mechanochemical treatment, as already emphasized, produces nanocrystalline/amorphous phases. Such pronounced metastable states readily react at elevated temperatures, thereby related equilibrium phases can be obtained relatively easily. For instance, high-temperature intermetallic compound AlgMos (melting point 2123 K), which, due to significantly different melting points of A1 and Mo is otherwise difficult to prepare from liquid phase, was obtained by continuous heating up to 1400 K of the mechanically alloyed Al-27 at.% Mo powder [46]. 

Mechanochemical combustion reactions 55 5. Applications of mechanically alloyed ... 

Mechanical alloying and mechanochemical processing refer to the use of mechanical energy to activate chemical reactions and structural changes. The use of mechanically activated processes dates back to the early history of mankind. The first and today still the most common use of mechanical activation is the use of flints to initiate fires. The term mechanochemical was coined by Ostwald in 1911 (Ostwald 1919),... 

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