Growth process of copper particles in the cuprous oxide-water system

Dispersed copper powder was prepared from cuprous oxide slurry by a wet chemical reduction technique with hydrazine. Palladium chloride (PdCl2) was used to produce palladium (Pd) seed with its stabilizer, polyvinyl pyrrolidone (PVP) and sodium pyrophosphate (Na4O7P2) was added as a dispersion agent. The formation and growth process of copper particles in the heterogeneous system were investigated in terms of reaction temperature and slurry concentration. As a general trend observed elsewhere, the average particle size of copper powder decreased from 420 nm to 150 nrn with an increase of temperature from 313 to 353 K, while the shape of its number particle size distribution changed from bimodal at low temperatures (313-323 K) to mono-modal at higher ones (333-353 K). Moreover, number size distributions of the powders produced at higher concentrations (2.5-40 g/L) all exhibit mono-modal shape while at 1.25 g/L it is bi-modal one. The explanation were based on the relationship between the number of Pd seed on the copper particles activated, which govern size and size distribution of final production in heterogeneous system, and the generation rate of Cu monomer at given conditions.