Preparation of Superhydrophobic Surfaces Based on Rod-Shaped Micro-Structure Induced by Nanosecond Laser

Zhi Li,Gang Xue,Hengpei Pan,Xinghua Wang,Yanming Wu

doi:10.3390/cryst11111274

Abstract

Solid–liquid frictional resistance is mainly attributed to the adhesion caused by the boundary layer effect. Superhydrophobic surfaces are expected to be an effective method to reduce frictional resistance. In this paper, a rod-shaped micro-structure was prepared on surfaces of Al alloy (5083) and Ti alloy (TC4) by line-by-line scanning with nanosecond laser. The inherent properties of the metal materials—such as their coefficient of thermal conductivity (CTC) and specific heat capacity (SHC)—had a major influence on the surface morphology and shape size of the rod-shaped micro-structure. Both two metals showed apparent oxidation on their surfaces during laser ablation, however, the degree of surface oxidation of the Al alloy was greater than that of the Ti alloy due to its more fragmentary rod-shaped micro-structure. The laser-treated surfaces could turn from hydrophilic to hydrophobic or even superhydrophobic after being left in the air for 20 days, which might be caused by the adsorption of low-surface energy matter in the air. In addition, the contact angle of the Al alloy was larger than that of the Ti alloy, which is due to the larger ratio of height to width of the micro–nano composite rod-shaped micro-structure on the surface of the Al alloy.

Highlights

Underwater operation equipment, such as underwater robots, underwater unmanned vehicles, and towed sonar, would be subjected to great resistance in the process of navigation, resulting in a decrease in navigation efficiency and an increase in energy consumption. This is mainly attributed to the adhesion of water to the metal surface caused by the boundary layer effect [1,2]
This work visually demonstrates the difference between the effects of laser treatment on the morphology and wettability transition of aluminum alloys and titanium alloys, and has certain positive significance for the laser preparation of superhydrophobic metal surfaces
The rod-shaped micro-structure shows a certain hierarchy in the direction of height, and presents a distribution rule of ‘short-range disorder and long-range order’ due to a line-by-line scan path (Figure 1b,e)

Summary

Introduction

Underwater operation equipment, such as underwater robots, underwater unmanned vehicles, and towed sonar, would be subjected to great resistance in the process of navigation, resulting in a decrease in navigation efficiency and an increase in energy consumption This is mainly attributed to the adhesion of water to the metal surface caused by the boundary layer effect [1,2]. This work visually demonstrates the difference between the effects of laser treatment on the morphology and wettability transition of aluminum alloys and titanium alloys, and has certain positive significance for the laser preparation of superhydrophobic metal surfaces. The substrates were blow-dried with pure nitrogen for later use

Fabrication of Superhydrophobic Surface

Surface Characterization

Results and Discussions