Highly thermally conductive Ag/SiO2 superhydrophobic coating for accelerated dropwise condensation

Abstract

Due to the ability to promote dropwise condensation, superhydrophobic coatings are widely used to increase the heat transfer performance of functional surfaces. A higher thermal conductive coating is always required for maximum heat transfer. However, the traditional polymer or ceramic based coatings have poor thermal conductivity and weak adhesion, which will hinder the heat flow across the surface. As a candid attempt to improve the heat transfer, here we propose a smart method to fabricate a highly thermally conductive Ag/SiO2 superhydrophobic coating. The coating is obtained through screen printing Ag paste on Al surface followed by spray coating hydrophobic SiO2 nanoparticles and sintering at 600 degrees C. The Ag paste acted as a binder to hold the SiO2 particles and increased the thermal conductivity of the Ag/SiO2 coating up to 83.32 W/m.K, which was 40 times higher than that of the polyurethane/silica (PU/SiO2) coating. Because of the higher thermal conductivity, Ag/ SiO2 coating showed quicker dropwise condensation compared to PU/SiO2 coating. Dropwise condensation of Ag/SiO2 coatings was also confirmed and compared with other metals, Al, Ag, Cu, and SUS. This work would give a solution to the existing design limitation of a coating when it is applied for heat transfer applications.