A highly transparent and photothermal composite coating for effective anti-/de-icing of glass surfaces

Abstract

Anti-/de-icing of glass surfaces is of great importance in present daily life. The long-standing challenge in this field is largely due to the lack of stable multifunctional coatings that can be conveniently and economically constructed on the glass surface, and more importantly, are capable of retaining the original transparency of glass ranging from the visible to the near infrared spectrum. Herein, a direct spraying sol method on the glass surface to prepare a highly transparent and photothermal composite coating is reported. Such multifunctional coating of Cu₇S₄ nanoparticles/organo-silicone sols has displayed a good photothermal conversion property and hydrophobic property and therefore yields excellent anti-icing and self-melting ice properties. The condensation time of water droplets can be extended to 86 s even at -10 °C, which is 3.42 times delayed relative to ordinary blank glass. And the adhesion strength of ice is largely reduced to 72 KPa, which is as low as ∼1/3 that of ordinary glass. Meanwhile, the subcooling of adhering droplets is reduced to -12 °C under one solar illumination condition and exhibits a rapid de-icing capability. More impressively, the prepared functional coating glass shows an outstanding transmittance of more than 75% in the visible region, while it is over the minimum glass transmittance limit allowed by Safety Standards for Glass (GB9656-2016, China). In addition, the multifunctional photothermal glass coating exhibits good physical/chemical stability, which facilitates the long-term application of the coating in different environments.

Fig. 1. (A) Schematic diagram of the preparation process of the transparent, hydrophobic and photothermal coating. (B) Diagram of the anti-/de-icing process of ordinary glass and photothermal glass. (C) Schematic diagram of the principle of photothermal glass de-icing.

Fig. 2. (A) SEM image of the water-dispersed Cu₇S₄. (B) Uniform beams can be observed with laser irradiation of aqueous modified Cu₇S₄/organo-silicone sol solution. (C) Pictures of blank glass and coated glass. (D) Transmittance of photothermal glass with different nanoparticle doping concentrations. (E) and (F) SEM images of photothermal coating with 0.2 wt% doping concentration of Cu₇S₄ photothermal nanoparticles.

Fig. 3. (A) The effect of different hydrolysis times on CA and SA. (B) CA of blank glass and coated glass. (C) The surface temperature change of blank glass and coated glass as a function of time under solar illumination conditions. (D) The surface temperature change of the coating as a function of time under different light power conditions.

Fig. 4. (A) The freezing time of 5 μL droplets under different ambient temperature conditions. (B) The process of 5 μL droplets freezing on the surface of coated glass and blank glass at −10 °C. (C) Ice adhesion strength of blank glass and photothermal coating. (D) The process of 5 μL droplet freezing under light conditions at an ambient temperature of −14 °C. (E) Time taken for droplets to freeze completely under different room temperature conditions at one solar illumination.

Fig. 5. (A) Top-view image sequences showing the de-icing process under 1-sun illumination on the surface of blank glass and coated glass. (B) Schematic of the experimental setup where the samples are mounted with a tilt angle of 30° from the horizontal and illustration of distinct deicing phenomena on the surfaces of blank glass and coated glass. (C) Comparison of the de-icing time between blank glass and coated glass.

Fig. 6. Photothermal conversion and CA of the coating treated with (A) different pH solutions, (B) aging test, (C) −30–30 °C cycles, (D) sand impact cycles, respectively.