Facile Synthesis of Fluorinated Polysilazanes and Their Durable Icephobicity on Rough Al Surfaces
Tien Nu Hoang Lo, Sung Woo Hong, Ha Soo Hwang, In Park
Abstract
Superhydrophobic Al surfaces with excellent durability and anti-icing properties were fabricated by coating dual-scale rough Al substrates with fluorinated polysilazane (FPSZ). Flat Al plates were etched using an acidic solution, followed by immersion in boiling water to generate hierarchical micro-nano structures on their surfaces. The FPSZ coatings were synthesized by grafting 1H,1H,2H,2H-perfluorodecyltrimethoxysilane (FAS-17), a fluoroalkyl silane), onto methylpolysilazane, an organopolysilazane (OPSZ) backbone. The high water contact angle (175°) and low sliding angle (1.6°) of the FPSZ-coated sample with an FAS-17 content of 17.3 wt% promoted the efficient removal of a frozen ice column with a low ice adhesion strength of 78 kPa at -20.0 °C (70% relative humidity), which was 4.3 times smaller than that of an OPSZ-coated surface. The FPSZ-coated Al surface suppressed ice nucleation, leading to a decrease in ice nucleation temperature from -19.5 to -21.9 °C and a delay in freezing time from 334 to 4914 s at -19.0 °C compared with the OPSZ-coated Al surface. Moreover, after 40 icing-melting cycles the freezing temperature of a water droplet on the FPSZ-coated Al surface remained unchanged, whereas that on the FAS-17-coated Al surface increased from -22.3 to -20.7 °C. Therefore, the durability of the polymeric FPSZ coating was superior to that of the FAS-17 monolayer coating.