Statistically understanding the roles of nanostructure features in interfacial ice nucleation for enhancing icing delay performance

Freezing is a spontaneous phase transformation process, which is mainly governed by the heterogeneous ice nucleation. This work aims at the discussion of roles of nanostructure geometrical features in interfacial ice nucleation. The two kinds of superhydrophobic nanostructures with the sealed layered porous and open cone features were designed and fabricated by means of the wet-chemical processing methods. The resultant surfaces both exhibited a larger extent of improvement of non-wettability, especially in the aspect of droplet movement. Comparing with the sealed layered nanoporous structures, the open nanocone structures only induced a sliding angle of 1°. During the freezing process, the solid-liquid contact type highly determined the macroscopic freezing process, and resulted in a difference of icing delay time of ~170 s (and freezing temperature of ~3.7 °C) between the both superhydrophobic nanostructures. Also, the precooling time, the period before the moment of droplet instantaneously becoming turbid, occupied a dominant role (~90%) in the entire freezing time. The ice nucleation behavior was analyzed in details according to the statistical results of 500-cycle freezing temperatures, demonstrating the relation in ice nucleation probability of nanocone structures less than layered nanoporous structures. This is in a line with the ice nucleation temperatures between the both as-prepared superhydrophobic nanostructures. As a consequence, there was a greater distinction in the ice nucleation rate, especially in the solid-liquid interface nucleation rate with two orders of magnitude.