Nanostructure-induced icephobic sol–gel coating for glass application

We present a study on materials formulation, self-assembled surface structure, and the correlation between room temperature water contact angle and contact angle hysteresis (CAH) and the icephobic property at −20 °C. Coating materials are based on TiO₂-modified polysiloxane (PDMS) incorporated in the inorganic–organic hybrid (sol–gel) materials with a self-assembled surface structure induced by fluoroalkylsilane (FAS) additive and nanoparticle dispersion. A home-made single-drop ice tester is used to record the ice formation and ice sliding process on the tilted surfaces with adjustable chamber temperatures below 0 °C. It is found that a CAH less than 10°, surface roughness in the range of 10–80 nm, and a two-scale surface structure with nanospikes are the essential features for automatic ice sliding at −20 °C at a tilting angle of 30°. We achieve such features by a proper formulation of sol–gel matrix containing PDMS and 2 % FAS, with incorporation of 0.5–1 wt% alumina nanoparticle dispersion in water/solvent 1:1 ratio. Preferred particle size is about 100 nm with single peak distribution as measured by a Marvin Zetasizer. Surface morphologies of coatings are measured by atomic force microscopy technique. Coatings are applied by an air atomizing spraying process and thermally cured. Chemical analyses by XPS, FTIR, and SEM–EDX evidenced the designed composition with PDMS and fluoro-group on the coated surface. Accelerated weathering test proved the stability of the coating for at least 1000 h.

Home-made single-drop ice tester (a) and the video-captured image of ice droplets on uncoated glass (b) and icephobic-coated glass during ice sliding down (c) at −20 °C.