Thermal properties of superhydrophobic films applied in ceramic tiles

Abstract

Improving heat transfer on superhydrophobic surfaces is one of the most important wettability challenges due to its wide application. In this study a superhydrophobic coating, with enhanced thermal properties and excellent water drops impact resistance, was performed by the sol-gel process and spray coating technique with different alumina (Al2O3) solution concentrations, heat-treatment temperatures, and heat treatment temperature times. The results of variance analysis (ANOVA) showed that the heat-treatment temperature was the factor that significantly affected the superhydrophobic properties of samples. Furthermore, in this research, the best formulation for superhydrophobicity was obtained with an alumina solution concentration of 0.20 M, heat-treatment temperature of 475 °C and heat-treatment time at 20 min, under these conditions, films with 1.29 ± 0.05 μm roughness and 159.80 ± 0.50° static contact angle were obtained. Thus, superhydrophobic coatings displayed good thermal stability up to 475 °C. The results showed differences in thermal properties of films, indicating a good enhancement in thermal insulation. SEM and AFM micrographs studies have shown a binary surface topography composed of micro/nano scale granules. This method is simple and low cost and can be applied to different kinds of building materials as concrete, steel, and glass.