Facile spraying fabrication of highly flexible and mechanically robust superhydrophobic F-SiO₂@PDMS coatings for self-cleaning and drag-reduction applications

Abstract

Superhydrophobic coatings treated as surface functional materials are endowed with great application potential with respect to self-cleaning, drag-reduction, anti-icing, etc.

Prospects of Low-Pressure Cold Spray for Superhydrophobic Coatings

“…For the investigated amounts of FOTS, the obtained CA are from the range of 149 • and 154 • . Similar saturation of CA was observed by Wu et al [51]. In this paper, the excess of the functionalized agent may facilitate filling the cavities for air entrapping what lead to loosing of the complex internal structure and hence CA decreases slightly.…”

“…This powder form and the degree of dispersity originates from the application of base catalyst, ammonia [49,50] while the repeatable architecture of cauliflower-like sheathed SiO 2 -F particles-the individual steps of synthesis. The macroscopic analysis ensured that the FOTS-covered SiO 2 spheres (Figure 1a,b) are characterized by the high level of size and shape uniformity in submicron scale which is typical for sol-gel synthesized products [21,39,[46][47][48][49][50][51]. Furthermore, the size distribution analysis ( Figure 1c) illustrates average SiO 2 -F spheres diameter of 670 nm with the shape deviation ±50 nm which is rather common for silica formed in the Stöber process [22,47,48,59].…”

“…Each continuous soaking of samples (90 h of immersion or 100 min in an ultrasonic bath) was interrupted only for short periods of drying and taking readings. Finally, manually operated abrasive wear measurements were conducted similarly to [16,51,62] by sliding sample surface on the surface of 800-grit sandpaper. The specimen, under exerted gravitational pressure 2.4 kPa (taking into account the 100 g weight and the surface size being 20 mm × 20 mm), was slid in 150 mm cycles followed always by 90-degree turn.…”

“…The difference in the type of FOTS sheath originates from the chemistry of the functionalization on the sol-gel route ( Figure S1) because the incorporated long fluorocarbon chains, oriented outwardly with respect to the silica cores, are bonded covalently to the silica particles (replacing -OH groups) [38,51,65] they form the inner sheath. Subsequently, the sphericity of silica particles and the chained structure of FOTS form a steric barrier, which means that three-dimensionality of FOTS chains hinder binding of other fluorocarbon groups by shielding the active sites (-OH groups) on the silica surface [30].…”

“…First of all, the functionality of feedstock powder may be easily achieved on the sol-gel route, because carefully planned synthesis may provide the set of new, programmable features. Unlike the utilization of ready-made powders with properties ensured by the manufacturer, simple SiO 2 -chemistry design [21,30,39,[46][47][48][49][50][51][52] enables for adding functionalities with hydrophobicity as a leading example in this paper. Secondly, the hydrophobic surface must have two important parameters: adequate roughness and low free surface energy [6].…”