Anti-frosting and defrosting on photothermal superhydrophobic coatings based on silane hydrolysis and carbon nanotube doping

Condensation frosting on solid surfaces is a common phenomenon in nature and industry, and the covered frost layer is harmful to many applications, so it is necessary to take appropriate measures to anti-frosting and defrosting. Here, based on the hydrolytic condensation reaction of organosilane derivative octadecyltrichlorosilane (OTS), by doping carbon nanotubes (CNTs), a photothermal superhydrophobic coating solution was prepared and then sprayed on a copper substrate to obtain a photothermal superhydrophobic coating, labeled as Cu-OTS + CNT. The light absorptivity in the full spectral range of Cu-OTS + CNT can reach 96.3%, which exhibits excellent photothermal conversion properties. The effects of Cu-OTS + CNT in delaying frosting and promoting melting are also explored by experiments. During the condensation frosting stage, Cu-OTS + CNT can not only detach the droplets from the surface by spontaneous droplet jumping, but also increase the surface temperature, resulting in slower droplet growth, which further reduces the area covered by the droplets and inhibits the propagation of the frost front, thereby retarding the formation of the frost layer. In the frost melting stage, Cu-OTS + CNT can effectively shorten the time of frost melting and significantly reduce the coverage of melting droplets. The proposed photothermal superhydrophobic coating preparation method is convenient and efficient, without fluorination modification, and has prominent effects on both delaying frost formation and promoting frost melting, which shall provide inspirations for advanced anti-frosting technology.