Gray bimetallic copper-nickel powders were synthesized with hydrothermal-reduction method. Formic acid and glutin were employed as hydrothermal-reduction agent and dispersion agent, respectively. Nickelous carbonate, copper carbonate and sodium formate were carried out in a titanium material autoclave at 230 degrees C to obtain gray-black powders for 20 h. Scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersion X-ray (EDX), thermal analyzer and laser size distribution analyzer were applied to analyze particle behavior. Bimetallic copper-nickel particles with polyhedral shape and uniform size in the range of 0.5 +/- 0.2 mu m were formed in an optimal reaction condition. Influences of dispersing agent on size and shape of particles were obvious. The size of particles decreases as an increasing dosage of formic acid. Microanalysis and thermal behavior of nickel-rich Ni-Cu solid solution suggest that copper-nickel powder particle has a core-shell structure. (c) 2007 Elsevier B.V. All rights reserved.