Synthesis and characterization of metallic nanoparticles of Cu, Co and Cu-Co by reactive milling

Nanoparticles have been produced by reactive ball milling. Cu, Co and alloyed Cu- 10 at. % Co particles have been obtained by milling metallic chlorides with pure sodium having NaCl in excess. Sodium chloride is also a product of the reduction reaction and it is used both to protect particles from oxidation and to prevent particle coalescence. A volume fraction of approximately 3 % is obtained in 3 or 8 h of milling. Characterization of the produced nanoparticles is made by electron microscopy, X-ray diffraction and calorimetry. Particles in all cases have sizes around 7 nm. A mixture of Co and Cu chlorides reacting with Na gives rise to alloyed Cu-Co nanoparticles. Such particles have spherical shapes and consist of a non equilibrium solid solution which can be decomposed into Cu and Co by thermal treatment as expected from the corresponding equilibrium phase diagram.