Fabrication of a hierarchical superhydrophobic surface based on candle soot and nano silica

A durable superhydrophobic coating was fabricated through the layered coating strategy. • Hierarchical roughness was constructed with the use of candle soot and nanosilica. • Water absorption of the coated cement mortar is reduced by approximately 74.93%. • The coating retains hydrophobicity under mechanical damage and UV exposure. • Ice adhesion force decreased by 69.75% with stable cyclic deicing performance. In this study, a durable superhydrophobic coating was fabricated on the surface of cement mortar via a layered coating strategy that integrates hierarchical rough structures with low surface energy modification. This coating consisted of a bottom protective coating layer, an intermediate candle soot coating layer and a top low surface energy nanoparticle coating layer, forming the hierarchical micro-nano roughness surface. Microscopic analyses confirmed the successful construction of multilevel roughness, which promoted stable air retention at the solid–liquid interface. The microstructure confirmed the successful construction of multilevel roughness, which ensured stable air retention at the solid–liquid interface. As a consequence, the coating exhibited a contact angle of 161.5°±1.9° and a slide angle of 6.6°±0.8°, indicating a stable Cassie-Baxter wetting state. Compared with the blank cement mortar, the water absorption rate was reduced by approximately 74.93%. The coating also showed good self-cleaning behavior and UV stability. Mechanical durability tests revealed that the hierarchical rough structures experienced progressive damage under several external mechanical actions, but still maintained hydrophobicity. In addition, the coating exhibited a 69.75% reduction in initial ice adhesion force, maintaining low ice adhesion after repeated deicing cycles. These results demonstrate the potential of the proposed coating for long-term outdoor applications of cement-based materials. Download: Download high-res image (148KB) Download: Download full-size image