title: Air Cushion Convection Inhibiting Icing of Self-Cleaning Surfaces.
abstract: Anti-icing surfaces/interfaces are of considerable importance in various engineering fields under natural freezing environment. Although superhydrophobic self-cleaning surfaces show good anti-icing potentials, promotion of these surfaces in engineering applications seems to enter a "bottleneck" stage. One of the key issues is the intrinsic relationship between superhydrophobicity and icephobicity is unclear, and the dynamic action mechanism of "air cushion" (a key internal factor for superhydrophobicity) on icing suppression was largely ignored. Here we report that icing inhibition (i.e., icing-delay) of self-cleaning surfaces is mainly ascribed to air cushion and its convection. We experimentally found air cushion on the porous self-cleaning coating under vacuum environments and on the water/ice-coating interface at low temperatures. The icing-delay performances of porous self-cleaning surfaces compared with bare substrate, up to 10-40 min under 0 to ∼-4 °C environments close to freezing rain, have been accurately real-time recorded by a novel synergy method including high-speed photography and strain sensing voltage. Based on the experimental results, we innovatively propose a physical model of "air cushion convection inhibiting icing", which envisages both the static action of trapped air pocket without air flow and dynamic action of air cushion convection. Gibbs free energy of water droplets increased with the entropy of air derived from heat and mass transfer between warmer air underneath water droplets and colder surrounding air, resulting in remarkable ice nucleation delay. Only when air cushion convection disappears can ice nucleation be triggered on suitable Gibbs free energy conditions. The fundamental understanding of air cushion on anti-icing is an important step toward designing optimal anti-icing surfaces for practical engineering application.
authors.affiliation: Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences , Chongqing 400714, P. R. China.|University of Chinese Academy of Sciences , Beijing 100049, P. R. China.
authors.forename: Qin
authors.initials: Q
authors.lastname: Yang
authors.affiliation: Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences , Chongqing 400714, P. R. China.
authors.forename: Zhuangzhu
authors.initials: Z
authors.lastname: Luo
authors.affiliation: Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences , Chongqing 400714, P. R. China.|University of Chinese Academy of Sciences , Beijing 100049, P. R. China.
authors.forename: Faming
authors.initials: F
authors.lastname: Jiang
authors.affiliation: Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences , Chongqing 400714, P. R. China.
authors.forename: Yimin
authors.initials: Y
authors.lastname: Luo
authors.affiliation: Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences , Chongqing 400714, P. R. China.
authors.forename: Sheng
authors.initials: S
authors.lastname: Tan
authors.affiliation: Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences , Lanzhou 730000, P. R. China.
authors.forename: Zhibin
authors.initials: Z
authors.lastname: Lu
authors.affiliation: Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences , Lanzhou 730000, P. R. China.
authors.forename: Zhaozhu
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences , Lanzhou 730000, P. R. China.
authors.forename: Weimin
authors.initials: W
authors.lastname: Liu
keywords: air cushion convection; heat and mass transfer; icing-delay; porous structure; superhydrophobic surfaces