Mechanochemical synthesis of alkaline Earth carbides and intercalation compounds.

High-energy ball milling has been successfully employed to produce alkaline earth carbides from the elements. In particular, CaC(2) yields of up to 98% can be realized in as little as 12 h. Similarly, the carbides of Mg (39% yield), Sr (87% yield), and Ba (82% yield) have been prepared. An intermediate in the synthesis of CaC(2) is the newly discovered gold-colored Ca-graphite intercalation compound CaC(6). Sr and Ba also go through initial intercalation phases (SrC(6) and BaC(6)) before ultimately producing the carbides. The magnesium product consisted of Mg(2)C(3) with no MgC(2) observed. The addition of sulfur to CaC(2) forming reactions did not adversely affect the overall synthesis; this suggests that this method may be utilized to sequester sulfur from high-sulfur coal. The preparation of these compounds by high-energy ball milling represents a novel method for producing pure carbides, as well as a convenient route to isotopically enriched ethyne.