Mechanochemical Synthesis Of Alkaline Earth Carbides And Intercalation Compounds

Abstract

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 2C 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. © 2009 American Chemical Society