Superhydrophobic and anti-icing properties of sol-gel prepared alumina coatings

Sol-gel is a convenient method to fabricate micro-nano structures on various surfaces. In the present study, rough alumina surfaces were prepared from aluminum isopropoxide and ethyl acetoacetate and modified with low-concentration lauric acid (LA) dissolved in ethanol. The sample hydrophobicity and antiicing property were optimized by changing the rotation speed, rotation time, and coating thickness during spin-coating, and the type and concentration of surface modifier used during surface hydrophobization. Superhydrophobic surfaces were achieved with contact angle values as high as 157.6A degrees, when 0.4-mm-thick coatings were modified with 0.4% LA dissolved in ethanol. The surface morphology of the superhydrophobic samples was shown to be rough at micro/nano-scale, which allowed them to demonstrate excellent anti-icing properties. Specifically, the optimized sample could delay the icing time and reduce the freezing temperature from 15 min and-4.1A degrees C (for uncoated aluminum) to 65 min and-8.3A degrees C, respectively, while also reducing the ice adhesion strength twice.