Fabrication of a hierarchical aluminum oxide surface with micro/nanostructures via a single process and its application as a superhydrophobic surface: Simple sintering method with an aluminum microsized powder

Abstract

In this study, a hierarchical aluminum oxide surface with micro/nanostructures was fabricated via a single pressureless sintering method. About 70-μm-thickness pile of aluminum powder (i.e., sub-10-μm) was laid on a sapphire substrate with an area of 10×10mm2, and the substrate was placed in the middle of the furnace. Using a working temperature of 900°C, 1-, 2-, 4-, 6-, and 8-h sintering processes were performed. After this process, a plate with a micro-spherical shape similar to the initial morphology of the laid aluminum powder was formed via adhesion between the aluminum powders. In addition, needle-like nanorods were formed at the surface of the plate. Therefore, an aluminum oxide surface with hierarchical micro/nanostructures was fabricated. In addition, a mechanism was proposed to explain the fabrication process. Several types of experiments with varying temperatures, atmospheres, purging times, and substrates were performed to confirm the proposed mechanism. Finally, with the aid of a simple hydrophobic surface treatment, a superhydrophobic surface with low hysteresis was fabricated.