Synthesis and characterization of bimetallic Ni-Cu particles

Bimetallic Ni-Cu particles were synthesized from either suspensions of nickel carbonate and copper carbonate, and solutions of nickel nitrate and copper nitrate in ethylene glycol which acts both as solvent and reducing agent. The nature and composition of the powders depend on both the reaction temperature and time, and the reactants. Using the carbonates, bimetallic Ni-Cu powders composed of a nickel-rich and a copper-rich solid solution were obtained after 39 h at 140degreesC. Increasing the reaction temperature to 190degreesC gives a Ni-Cu powder composed of a copper-rich solid solution and nickel. Particles obtained under these conditions, however, are polydisperse. The nitrate solution gave bimetallic Ni-Cu particles with a narrow size distribution of about 140 nm after 4 h of reaction at 196degreesC. These particles are made of a copper core and a nickel shell. The mechanism of bimetallic particle formation is controlled by the solubility of the reactants, the formation of intermediate metal glycolates and Cu2O, and the required reduction temperature. (C) 2003 Elsevier Science (USA). All rights reserved.