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.

Tunable Band‐Selective UV‐Photodetectors by 3D Self‐Assembly of Heterogeneous Nanoparticle Networks

“…In contrast, the Si atoms, strongly visible in the glass substrate, were randomly distributed within the ZnO layer (Figure g). This is in line with very rough top surface morphology of these aerosol‐deposited nanoparticle layers that can be easily penetrated and filled by deposition of sequential nanoparticle aerosols. This cross‐sectional composition is also in good agreement with the observed layer growth rates (Figure d and Figure S4, Supporting Information) and confirms the vertical stacking of the ZnO and TiO 2 nanoparticle layers.…”

Effect of crystallization kinetics on the properties of spray dried microparticles

“…t iC1 and t i are the time corresponding to droplet iC1 and i, respectively. Previous publications have demonstrated that the Peclet number, Pe, is an indicator of the morphology of the final dried particles (Belotti et al 2015;Castillo et al 2014;Nuzzo et al 2014). Larger Peclet numbers indicate low density particles, typically with a shell.…”

Liquid Flame Spray—A Hydrogen-Oxygen Flame Based Method for Nanoparticle Synthesis and Functional Nanocoatings

“…6e-f, has a strikingly similar structure to the one presented by Mädler et al (2006a), where also thermophoresis is the dominating deposition mechanism, but clearly differs from the more tree-like structure presented by Castillo et al (2014), where diffusion clearly is the dominating deposition mechanism.…”

“…deposition of the nanoparticles from the gas phase (Mädler et al, 2006a;Castillo et al, 2014;Liu et al, 2016). In our case, the nanoparticle deposition process from the flame onto the substrate is mainly a combination of thermophoresis and diffusion through the boundary layer above the surface:…”