Improving the Crystallinity and Purity of Monodisperse Ag Fine Particles by Heating Colloidal Sprays In-Flight

This work demonstrated the production of highly crystalline, monodisperse fine metal particles with high density and purity using a simple, facile rapid spray heating process. In this technique, a starting solution including fine Ag particles, prepared using a liquid phase method, is sprayed into a horizontal furnace. After this spray heating step, the crystallinity and purity of the particles are greatly improved relative to those of the initial particles, while the morphology and size distribution are maintained. Consequently, the volume resistivity of the Ag particles is decreased from 6.4 × 10–3 Ω·cm (before spray heating) to 3.6 × 10–5 Ω·cm (after spray heating at 500 °C). Detailed analyses show that this significant increase in conductivity results from the improved crystallinity, purity, and density of the material. The rapid spray heating method proposed in this research could be applied to other metals with the potential to produce high-quality fine metal particles.