Improving the crystallinity and purity of monodisperse Ag fine particles

What is it about?

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 is maintained. 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.

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Why is it important?

A single route based on an aerosol technique comprising rapid high-temperature spray drying (termed the rapid spray heating method in this paper) was examined as a means of producing a high purity, high crystallinity isolated, and monodisperse fine metal particles from a colloidal metal suspension. When particles prepared using a conventional liquid phase method are intended for industrial applications, heat treatment is necessary to increase the quality of the material. Conventionally, this treatment requires in excess of several hours in a high-temperature box furnace. Compared with this standard process, the method proposed in this paper is much more rapid (requiring only several seconds) and, as a result, the sintering of the particles and concurrent significant size increases are avoided. Ag particles were selected as a test material because Ag has many applications, such as in conductors, electrical contacts, catalysts, and wound dressing. In particular, correlations between the heating temperature and particle characteristics (including crystallinity, morphology, size, distribution, purity, and volume resistivity) were investigated in detail. A possible mechanism for producing isolated fine metal particles is suggested, based on the experimental results and available theory.

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