SYNTHESIS AND CHARACTERIZATION OF NANOCRYSTALLINE POWDERS OF PURE NICKEL AND COPPER

Nanocrystalline particles of pure copper and nickel with a diameter of less than 0.1 mum have been produced by evaporating these metals into an inert gas atmosphere. A specific gas-evaporator apparatus was buil t to control the size of the nanocrystalline particles by adjusting th e following factors: the evaporation rate of metals, the distance betw een the evaporation crucible and the collection cold trap (LN2), the p ressure, and the type of carrier gas. The results indicated that the m ean particle size of Cu varied from 13 to 104 nm and that of Ni varied from 7 to 53 nm, with the absolute He pressure varying from 10 to 500 mbar. When the evaporation temperature increases, the evaporation rat es rises and the particle size distribution becomes broader. Also, und er a constant evaporation rate and absolute He pressure, varying the p article collection distance causes a change in the mean particle size. In the flowing helium process, the particles are more homogeneous and finer than those produced in the static process.