Photothermal Study of the Formation Dynamics of Fumed Silica Thin Films

Abstract

In this work the formation of thin films by evaporation of liquid mixtures of agglomerated amorphous untreated fumed silicon dioxide nanoparticles is analyzed. Fumed silica is a material that has been used as a thickening agent due to the fact that it has chain-like particle morphology. When mixed with a liquid, the chains bond together and increase the viscosity. The experiments were performed on samples deposited on a metallic substrate. Thermal waves were generated by sending a modulated laser beam at constant frequency onto the substrate. These waves are propagated to the evaporating solution allowing the monitoring of the film formation. It is shown that the last stage of the film formation is strongly affected by the formation of cracks and migration of the material to the lateral surface of the container. The experimental data are compared with predictions of effective thermal property models.