The solid-state displacement reaction of CuCl2 + 2Na = Cu + 2NaCl indu
ced by mechanical milling has been studied. Ultrafine Cu particles hav
e been produced after removing the by-product NaCl from the as-milled
mixture in a washing process. Two different morphologies of Cu particl
es were observed by transmission electron microscopic examinations. Cu
particles of uniform size in the range of 20-50 nm were found after a
steady-state reaction during mechanical milling, whereas larger parti
cles were observed when combustion had occurred.