999 publications from this institution
Electrodeposition is an increasingly important method to synthesize supported nanoparticles, yet the early stages of electrochemical nanoparticle formation are not perfectly understood. In this paper, the early stages of silver nanoparticle electrodeposition on carbon substrates have been studied by aberration-corrected TEM, using carbon-coated TEM grids as electrochemical electrodes. In this manner we have access to as-deposited nanoparticle size distribution and structural characterization at the atomic scale combined with electrochemical measurements, which represents a breakthrough in a full understanding of the nanoparticle electrodeposition mechanisms. Whereas classical models, based upon characterization at the nanoscale, assume that electrochemical growth is only driven by direct attachment, the results reported hereafter indicate that early nanoparticle growth is mostly driven by nanocluster surface movement and aggregation. Hence, we conclude that electrochemical nulceation and growth models should be revised and that an electrochemical aggregative growth mechanism should be considered in the early stages of nanoparticle electrodeposition.
The influence of heat transfer on anodic oxide growth during anodizing of high purity Al is studied on a laboratory scale in a wall-jet electrode reactor under different flow conditions. Local electrode temperatures are monitored by temperature measurements on the backside of the anode, whereas the effect of local temperature on film growth is evaluated by FE-SEM analyses. Quantitative information on the conditions of heat transfer is provided by numerical calculations of the flow field, and is applied during simulations of the anodizing process. The impact of the flow field, calculated by two different turbulence models, on the simulations is verified.
