In the pulsed wire discharge method, a coating technique to prepare metal nanoparticles covered with organic matter has Men investigated. Copper nanoparticles covered with organic matter have been successfully prepared by evaporation of a copper wire in an oleic acid vapor/mist. The thickness of the coating layer was a few nanometres. The median diameter of the powder was 25 nm, and became 10 nm smaller than that without the coating because of the inhibition of particle growth by the formation of the coating. From phase identification by transmission electron microscopy and X-ray diffraction analysis, it was found that the copper nanoparticles have been passivated and have not been oxidized in over 2 months.

Keywords: nanoparticles; pulsed wire discharge; copper; passivation