Kinetics and mechanisms of nanoparticle formation and growth in vapor phase condensation process

Design of nanoparticle synthesis by inert-gas condensation process was studied according to the mechanisms and kinetics of nucleation and growth in the vapor phase. The effect of process parameters, e.g., source temperature, evaporation rate, and the inert-gas pressure, on the particle size and particle shape was examined at the example for silver and copper–tin alloy. The synthesized nanopowders had near spherical shape with particle size range from 10 to 60 nm dependent on the processing condition. Scanning and transmission electron microscopy (SEM and TEM) analyses showed that the crystallites are subunits of larger agglomerate particles, and relatively large particles display crystal habit. Based on the experimental results and theoretical principles, nucleation, growth, coagulation and coalescence of the particles were analyzed. Accordingly, the kinetics and mechanisms of nanoparticle synthesis in low-pressure gas phase was determined. A simple operating map for nanoparticle synthesis was presented. The results may serve as a guide for design of experimental studies on the effect of process parameters on nanoparticle characteristics.