Study on Morphology and Hydrophobicity of CaCO3/SiO2 Composite Surface Coating

A superhydrophobic CaCO3/SiO2 composite surface coating, with a very high water contact angle (WCA) of 169 nd a small sliding angle (SA) of 2 was prepared by means of self-assembly function of polydimethylsilioxane (PDMS). Dual-size surface roughness, which mimicked the surface topology of the lotus leaf, was originated from well-defined CaCO3/SiO2 raspberry-like particles which were prepared by violent stirring and surface modification. The coating surface morphologies were observed with scanning electron microscope. Roughness and WCA were measured with atom force microscope and WCA tester, respectively. It is found that there are many microconvexities with binary structure uniformly distributed on the surface lower of the film with diameter of about 2 to 3| and nanoconvexities or submicroconvexities on the atop surface layer of the coating with diameter of about 200nm, and the surface microstructure is similar to that of lotus surface. Relationships between the surface microstructure, roughness and the wettability of the surface coating are discussed. The possible reason for the excellent superhydrophobic properties on the coating surface is due to co-effect of forming an appropriate surface roughness with well-defined composite particles and the low surface energy of PDMS.a¤