Multiscale superhydrophobic zeolitic imidazolate framework coating for static and dynamic anti-icing purposes

Official URL: https://dx.doi.org/10.1002/admi.202202510

Ice formation is a major challenge for engineering systems. Superhydrophobic surfaces constitute an effective approach to address this challenge. However, in addition to complex preparation methods, surface texture- and chemistry-related shortcomings reduce their effectiveness. In this study, a functionalized metal–organic framework (ZIF-8) based micro-nano-subnano scale coating (SuperHydrophobic Multiscale Coating – SHMC) with CA (contact angle) > 172°, rolling angle < 5°, and CAH (contact angle hysteresis) < 3° is developed and applied to metallic surfaces by spray coating. A fractal theory-based model of contact angle is adapted to reveal its non-wetting mechanism. SHMC extends the icing time by at least 300% and maintains its superhydrophobicity for > 30 icing/deicing cycles. The generated capillary pressure ranges within the multiscale coating are studied. The three-phase contact line characteristics including contact times, contact diameters, and interfacial heat transfer during droplet impact are assessed. A numerical model is developed using dynamic contact angle physics for transient heat transfer during the impact. Compared to the plain surface, which leads to instant icing at 60 ms after impact, no icing is observed on the developed coating. At least an order of magnitude reduction in heat transfer rate during the droplet contact time is obtained with SHMC.