Continuous Hydrothermal Synthesis of Nano Copper Particles

摘要

In this study the formation of copper particles by reacting Cu(NO_3)_2 and CuSO_4 with C_6H_(13)SH was conducted in a continuous hydrothermal reactor. The investigated pressure was 200 and 250 bar, and the temperature ranged from 310～385°C. It is found that the reaction rate constant for CuSO_4 is higher than that of Cu(NO_3)_2. Also, the activation energy at compressed liquid is much lower than that at compressed gas. For CuSO_4, three different morphology of metal particles are obtained; nanoparticles, agglomerated nanoparticles, and dendritic particles. However, no dendritic structure is obtained if Cu(NO_3)_2 is used. It is found that samples with dendritic structure are observed in the conditions of compressed liquid and high concentration of the precursor's solution. It is presumed that the formation of dendrite is due to the fast crystal growth. This need fast decomposition of the precursor and moderately rapid crystal growth. However, the organic alkanethiol ion can cap on the surface of growing particles and provide diffusion barrier to the hydrogen ion in the supercritical state. This would reduce the crystal growth rate. The mechanism for producing dendritic particles in the hydrothermal condition is proposed, and the effects of temperature and pressure and the precursor's concentration on the particle size are also discussed in this paper.