Robust and durable transparent superhydrophobic boehmite (γ-AlOOH) film by a simple hydrothermal method

Transparent superhydrophobic films are attractive for applications in a wide range of fields, such as electronics, windshields and displays. However, it is especially challenging to manufacture a superhydrophobic film with high transparency and mechanical robustness because the high transparency and superhydrophobicity are generally competitive surface properties while the robustness and water repellency are also mutually exclusive. In this paper, transparent superhydrophobic boehmite (γ-AlOOH) films modified by perfluorodecyltrisethoxysilane (C16H19F17O3Si) with different morphology were prepared via a simple hydrothermal method in a solution of Al(NO3)3·9H2O and CH3COONa. The results showed that morphology impacted the wettability, transparency and mechanical durability of the film. The superhydrophobic boehmite film synthesized at the proportion of 40: 1 (Al(NO3)3·9H2O: CH3COONa) consisted of nano scale flaky boehmite clusters perpendicular to the glass surface and micro-nano scale pores between the crystals and achieved a high wear resistance, good chemical stability and appropriate transparency. The formation mechanism of this film and the reason for its mechanical robustness was explored in this paper. It was proposed that the excellent wear resistance benefited from the frame microstructure formed by interconnected flaky crystal clusters as well as the chemical bonding between the boehmite grain and the glass substrate. The nanostructure boehmite film prepared by the simple hydrothermal method in this paper not only could reach a proper balance between superhydrophobicity and transparency, but also exhibited an excellent mechanical durability, which demonstrated a potential application prospect in the field of transparent superhydrophobicity.