Superhydrophobic tin oxide nanostructures coated on copper plates: Wettability tuning by the etching medium

In the current work, the chemical etching process and hydrothermal method were used to create bio-inspired superhydrophobic fluorine-free tin oxide nanostructures on copper plates. Taguchi's experimental design was also used in investigating coating wettability characteristics based on fabrication parameters. Statistical analysis results demonstrated that the optimal superhydrophobic sample with a water contact angle of 163.40 degrees +/- 1.42 degrees and contact angle hysteresis of 3.00 degrees +/- 0.80 degrees could be fabricated under the following conditions: sodium hydroxide (2.00 M) as an etching solution, urea-to-tin chloride ratio 2.5:1, and 2.00 h reaction times. The effects of each synthesis parameter on the obtained sample's superhydrophobicity were evaluated through multiple one-variable-at-a-time experiments. Testing the chemical stability of the optimal sample revealed that it was more resistant to deterioration in an alkaline environment (8-10) than in an acidic environment (4-6). The resulting superhydrophobic sample was analyzed by a delay test for water droplets freezing on its surface to determine whether ice formed and accumulated. The created bio-inspired honeycomb-like nanocoating demonstrated exceptional mechanical robustness and good anti-icing performance after 10 consecutive icing cycles. These results indicated that superhydrophobic coatings could be easily and economically produced without using fluoropolymers and silanes on aluminum substrates.