A facile solution-immersion process for the fabrication of superhydrophobic gibbsite films with a binary micro-nano structure: Effective factors optimization via Taguchi method

Abstract A superhydrophobic gibbsite film composed of a binary micro-nano hierarchical structure has been fabricated on the aluminum foil via the solution-immersion method as a facile route. The gibbsite film was formed based on the reaction of ammonia and aluminum nitrate as the precursor. Taguchi L16 experimental design was used to evaluate and optimize the effective factors, such as the ammonia/Al3+ molar ratio, concentration and type of the surface modifiers, reaction time and solution. Morphology features, phase analysis, chemical composition, topography and static water contact angle (WCA) were evaluated by means of FESEM, XRD, FTIR and AFM. Results showed that the ammonia/Al3+ molar ratio was the most effective parameter to achieve higher values of WCA and superhydrophobic property. Effect of the surface modifier was studied and two different fatty acids (stearic and palmitic) were compared. ANOVA showed that stearic acid is more effective for hydrophobization. Finally, a superhydrophobic thin film of aluminum hydroxide with WCA of 164.4 ± 0.44° and contact angle hysteresis of about 3.05° was obtained. Results indicated that a binary micro-nano structured gibbsite composed of nano plates of about 30 nm thickness has been formed.