Microstructure and Transparent Super-Hydrophobic Performance of Vacuum Cold-Sprayed Al₂O₃ and SiO₂ Aerogel Composite Coating

In this study, vacuum cold spraying was used as a simple and fast way to prepare transparent super-hydrophobic coatings. Submicrometer-sized Al₂O₃ powder modified by 1,1,2,2-tetrahydroperfluorodecyltriethoxysilane and mixed with hydrophobic SiO₂ aerogel was employed for the coating deposition. The deposition mechanisms of pure Al₂O₃ powder and Al₂O₃-SiO₂ mixed powder were examined, and the effects of powder structure on the hydrophobicity and light transmittance of the coatings were evaluated. The results showed that appropriate contents of SiO₂ aerogel in the mixed powder could provide sufficient cushioning to the deposition of submicrometer Al₂O₃ powder during spraying. The prepared composite coating surface showed rough structures with a large number of submicrometer convex deposited particles, characterized by being super-hydrophobic. Also, the transmittance of the obtained coating was higher than 80% in the range of visible light.