Superhydrophobic Coating Bioinspired on Rice Leaf: A First Attempt to Enhance Erosion Resistance Properties at Environmental Conditions with Ceramic Particles

Abstract

This study develops a new, facile and rapid process bioinspired on rice leaf with the aim of producing a hybrid composite coating in a first attempt to obtain a superhydrophobic coating with enhanced erosion resistance properties. Rice leaves (Oryza sativa L.) are made of hierarchical structures consisting of micropapillae and waxy nanobumps which confer to the surface a contact angle of 164° as Lotus leaf does. In particular, rice leaves accumulate amorphous silica inside and on the surface with various morphologies. This kind of silica is produced by absorbing silicates from the soil under specific conditions of temperature and pressure. The presence of biosilica in rice leaves is useful for preventing diseases or improves mechanical properties of the leaves. Single-step and two-step processes are the two strategies applied for generating a superhydrophobic coating by electrochemical deposition of ZnCl2, α-Al2O3 and lauric acid (C11H23COOH) onto commercial pure aluminum substrate. The static contact angle measured on the coating gives values of 170° and 1° for the sliding angle conducing to a coating with superhydrophobic and self-cleaning properties. Various characterization techniques are used to determine chemical and morphological structure such as FESEM, XPS or FTIR. On one hand, in morphological analysis, flower-like structure is obtained with petals thickness of 70nm corresponding to the nanostructured contribution to the system. On the other hand, chemical analysis concludes the generation of zinc laurate (Zn (C11H23COO)2) as a major compound contributing to the reduction of surface tension and increasing the superhydrophobic character of the coating as well.