Synthesis of nanocrystalline cubic substoichiometric WC1-z powders by mechanochemical technology

Nanocrystalline cubic substoichiometric WC1-z powders were synthesized by a mechanochemical method at room temperature, a process of highly reactive e nergetic ball milling of WO3 + 3Mg mixtures containing excessive graphite a s a source of carbon for W phase. The excessive graphite plays a very impor tant role in the formation of cubic phase, otherwise the h.c.p. phase is fo rmed. The entropy evaluation shows that the reduction reaction is a self-pr opagating process. After millimg for 90 hours and excluding MgO from the pr oduct by using HCl solution, the cubic substoichiometric WC1-z powders cont aining a little excessive graphite with the grain size in the range of 4 to 20 nm were obtained. (C) 2000 Kluwer Academic Publishers.