Morphology and nanostructure of granular materials built from nanoparticles

Abstract

Nanopowders or nanoparticles can be used as building blocks for the preparation of new materials with a prescribed structure. Monte Carlo simulations have shown that the morphological properties (bulk porosity and surface roughness) of a granular deposit can be tailored by properly adjusting the velocity of the particles approaching the deposit. Based on these theoretical predictions, experiments have been conducted to prepare nanostructured materials from carbon nanoparticles. By electrohydrodynamic atomization of a liquid suspension (carbon nanoparticles dispersed in ethanol), an electrospray of small droplets is generated. The charged droplets are driven by the electric field with the ethanol evaporating along the droplet path, leaving dry nanoparticles that deposit on the collecting surface. The surface roughness of the resulting material has been characterized as a function of the voltage drop. Moreover, catalytic suspensions of platinum supported on carbon nanoparticles (Pt/C) in Nafion®- alcohol solutions have been electrosprayed over carbon paper to prepare electrodes for proton exchange membrane fuel cells (PEMFC). The fuel cell power density was measured as a function of the platinum loading and the range of parameters leading to optimal platinum utilization was obtained. ©2014 Hosokawa Powder Technology Foundation.