Controlled nucleation and growth of micrometre-size copper particles prepared by the polyol process

Abstract

Fine, equiaxed copper particles have been obtained by reduction of CuO in ethylene glycol. Cu₂O always exists as an intermediate solid phase. Copper particles with a narrow size distribution within the micrometee range can be obtained if the nucleation and growth steps are completely separated and if agglomeration is avoided. Addition of D-sorbitol, which acts as a protective agent, prevents particle sintering. Addition of a strong base, e.g. NaOH, enhances the solubility of the precursor CuO and of the intermediate Cu₂O. Under these conditions the overall reaction appears to be controlled by the nucleation and growth steps of the metallic particles. Their mean size can be largely controlled by varying the NaOH concentration. The synthesis of copper particles in liquid polyols, which act as both solvent and reducing agent, is a simple method for producing highly pure, equiaxed, non-agglomerated monodisperse particles.