A study on superhydrophobic coating in anti-icing of glass/porcelain insulator

This paper focuses on the preparation of a superhydrophobic coating on glass/porcelain insulators which possess anti-icing property below freezing temperature. Inspired by lotus-effect, the fabrication of a superhydrophobic coating has two steps: the first step is to construct a hierarchical SiO2 coating on the substrate surface, and the second step is the chemical modification of the SiO2 coating with 1H,1H,2H,2H-Perfluorodecyltriethoxysilane (PDTS). The precursor for the hierarchical SiO2 coating is a suspension of SiO2 sol particles and dispersible SiO2 powder particles. According to the TEM testing, SiO2 sol particles prepared by sol-gel method has an average particle size about 2-5 nm, while the size of the dispersible SiO2 particles is ca. 20 nm. The precursor was sprayed on glass/porcelain insulators, and then dried at ambient condition, finally heat-treated at 773 K for 2 h. The morphology of the superhydrophobic coating was characterized by TEM and AFM, and experimental results indicated that the coating featured [hierarchical structure consisting of both large bumps with micron-sized height (0.8 mu m) and tiny papillae with the size about 30 nm] micron-sized roughness (0.8 mu m) combined with nano-sized roughness (about 2 nm). Moreover, the scratch test showed that the coating tightly adhered to the surface of the glass/porcelain insulators. The superhydrophobic property of the coating was examined by a contact angle measurement, and the results demonstrated that the static water contact angle is high up to 163.6A degrees, and the sliding angle is 1.4A degrees. The superhydrophobic property of the coating was also confirmed by the outdoor tests in winter, and it was found that the superhydrophobic coating had the function in anti-icing, based on which the anti-icing mechanism underlying was discussed in terms of the interaction between impacting droplets and superhydrophobic surface.