Preparation Of Nano-and Micro-Calcium Carbonate Composite Coating And Study On Its Superhydrophobicity

The self-cleaning property of a superhydrophobic surface, on which the water contact angle (CA) is larger than 150°and the sliding angle is no more than 10°, has drawn tremendous interest recently because of its potential application in industrial areas and biological processes, such as self-cleaning materials, anti-adhesive coatings, corrosion-free coatings, and so on. The wettability of solid substrates is governed by their surface energy and surface morphology. Wenzel and Cassie-Baxter models reveal that both suitable surface roughness and low-surface-energy materials are critical to achieving the self-cleaning property. Commonly, there are two kinds of approaches to prepare superhydrophobic surfaces:enhancing the roughness on the hydrophobic substrate or modifying the rough surfaces with low-surface- energy materials.In this study, we have developed a facile and inexpensive method to fabricate a superhydrophobic surface with hierarchical nano- and microstructures. The superhydrophobic surface was prepared through spin coating of a mixture of nano- and microsized calcium carbonate suspensions on a substrate, followed by modification of a low-surface-energy monolayer of stearic acid. The key parameters of the fabrication of suitable surface morphologies, including the content of CaCO3 powder, the influence of hierarchical structure on superhydrophobicity and the percentage of nano- and microsized CaCO3 powder, were also investigated. FE-SEM,FT-IR and CA meter were used for surface characterizations and the effect of pH values on the CAs for the prepared coating was also discussed in this paper. Finally, Cassie model was employed for theoretic analysis of the coatings. Results showed that the optimum CaCO3 content was 40 wt% and the self-cleaning property of the film was achieved only by the addition of 2 wt% microsized CaCO3 powder and 38 wt% nanosized CaCO3 powder. After modification with a self-assembled monolayer of stearic acid, the as-prepared coating showed self-cleaning properties with a water contact angle as high as 152.8°and a sliding angle of 7.8°.