Top-down Cleaner Production of Nanoparticle Dispersions inLiquid Phase by Vibrating Granular Beds

A mechanosynthesis process aiming at producing stable particles dispersions embedded in a liquid phase is proposed, starting from spheres of a metal precursor subject to a progressive disaggregation carried out by a tribological process. The method consists in using a precursor in metal spheres of millimetric dimensions, placed in a suitable vessel together with a ceramic milling medium in a liquid phase. The vessel is subject to vertical oscillations at variable frequency, leading to a production of a micro- or nanometric dispersion of the pristine material in a liquid medium as a consequence of friction and impact between spheres. The process has been tested for Ag spheres at different operating conditions and the effect of frequency, hold-up fraction and capping agents dissolved in the liquid phase has been considered and related to the quality of the final product. The characterization of the solid phase has been carried out by dynamic scattering for particle diameter, giving distribution curves with average values at 11.7 and 16.9 nm using polyvinyl pyrrolidone as capping agent of two different molecular weights. The present indirect milling technique, as other analogous reagentless methods for the synthesis of nanodispersions, may represent a sustainable alternative to the standard wet chemical bottom-up schemes, owing to its cost-effectiveness and ease of realization.